The University of Maryland Graduate School Baltimore (UMGSB) offers 27 master's and doctoral programs in health, physical, biomedical, medical, and social sciences.

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  • Probiotic Use for the Primary Prevention of Clostridioides difficile infection

    Heil, Emily; Leekha, Surbhi; 0000-0002-6644-6684 (2020)
    Primary prevention of C. difficile infection (CDI) is a priority for hospitals and probiotics have the potential to interfere with colonization and/or infection with C. difficile offering an opportunity to enhance ongoing primary prevention strategies. The overall objective of this study was to evaluate the impact of a hospital-wide computerized clinical decision support system tool to prescribe probiotics to eligible adult patients receiving antibiotics for the primary prevention of CDI. After implementation of the tool, the odds of CDI was 1.41 in eligible patients compared to the pre-intervention time period (aOR 1.41, 95% CI 1.11, 1.79). A propensity score matched analysis showed that patients who received probiotics did not have lower rates of CDI compared to those who did not (OR 1.46, 95% CI 0.87, 2.45). Based on these findings, the use of probiotics for the primary prevention of CDI is not supported.
  • Discovery of a thalamic integrator for action reinforcement

    Cover, Kara; Mathur, Brian N. (Brian Neil); 0000-0003-3938-9669 (2020)
    The pursuit and acquisition of rewards is essential for survival. The input nucleus of the basal ganglia, the striatum, facilitates the selection, execution, and reinforcement of reward obtaining actions. The contributions of excitatory input from cortical regions and the influence of dopaminergic signaling on corticostriatal synapses to these vital functions has been studied extensively. A relative underappreciation for thalamic contributions to striatal signaling has consequently excluded this major excitatory input from basal ganglia models of action selection and reinforcement. I investigated the contributions of the rostral intralaminar thalamic nuclei to striatal-mediated action sequence performance using a combination of ex vivo physiological and in vivo behavioral assays. In the present dissertation, I characterize mechanisms by which this thalamic projection interacts with striatal neuronal populations and modulates dopaminergic signaling to sculpt output activity. I further identify that the rostral intralaminar nuclei causally contribute to action execution in the pursuit of rewards. This work serves to further understanding of how thalamic inputs participate in action selection and reinforcement.
  • Melanocyte stem cell subpopulations show distinct pigmentation and regenerative potential

    Tandukar, Bishal; Hornyak, Thomas; 0000-0002-9650-1664 (2020)
    Melanocyte stem cells (McSCs) are key components of the hair follicle (HF) stem cell system. They are derived from neural crest during embryogenesis and are responsible for regeneration of differentiated melanocytes during successive HF cycles. We have described McSC subsets that can be distinguished by CD34 expression. CD34+ McSCs are located within the bulge/lower permanent portion (LPP) while CD34- McSCs are in the secondary hair germ (SHG) during the resting stage (telogen). Whether these two cell subpopulations are maintained separately or exist in a developmental hierarchy is not yet known. The goal of my thesis is to explore whether (a) the two McSC subpopulations are functionally distinct, (b) if they are maintained independently throughout the HF cycle and (c) their role in generation of mature melanocytes. To study McSCs, we engineered the Dct-H2BGFP bitransgenic mouse. We confirm that this animal model accurately identifies melanoblasts, McSCs and mature melanocytes by constitutive GFP expression that can be regulated by doxycycline. Using our Dct-H2BGFP mouse, we compared the transcriptomes of bulge and SHG McSC subsets by genome-wide expression profiling (RNA-seq). This study, along with functional in vitro and in vivo assays, confirms that CD34+/bulge share characteristics of neural crest stem cells with multilineage potential while CD34-/SHG McSCs represent a stem cell population that is more committed to melanocyte differentiation. To further understand the relationship between two McSC subpopulations, we traced their proliferation throughout the HF cycle and found that proliferation of SHG McSCs gives rise to mature melanocytes. The analysis also surprisingly revealed quiescent CD34- melanocytes maintained outside of the HF bulge region throughout anagen retaining the stem cell phenotype, identifying a SHG McSC-like population outside telogen suggesting independent or quasi-independent maintenance of the two McSC subpopulations. Taken together, our study identifies heterogeneous McSC subpopulations with distinct pigmentation and regenerative potential for the first time. Strikingly, CD34+/bulge McSCs exhibited the ability to myelinate neurons in vivo, revealing a novel therapeutic possibility for demyelinating disorders and traumatic nerve injury.
  • Development and Usability Testing of a Mobile Health Game Application for Older Adults on Warfarin

    Opoku-Agyemang, Ernest; Johantgen, Mary E.; Nahm, Eun-Shim (2020)
    Background: Chronic disease management constitutes a special challenge in the United States due to deficiencies in the healthcare system. Chronic disease self-management (CDSM) using technology and gaming principles is a promising way to overcome these challenges. Yet, there are few disease-specific apps to benefit the populations likely to benefit from such innovations. Purpose: This proof of concept study evaluated the feasibility of a Warfarin game app for older adults. The aims were to: 1) Design and develop a mobile game app to educate patients on Warfarin; and 2) Conduct usability testing of the game app among patients on Warfarin receiving care at an anticoagulation clinic. Methods: Following the design and development of a Warfarin app called Coumadin Hero, the usability testing of the app was conducted with 25 participants. Heuristics and user testing were conducted. The Technology Acceptance Model (TAM) was the theory that informed the study design and implementation. An adaptation of the Perceived Health Web Site Usability Questionnaire (PHWSUQ) was used to assess the participant usability. Descriptive and correlational statistics were used to analyze game play data and responses to survey questionnaires. Results: The median percent correct of Vitamin K food identification was 79%. Generally, participants had higher knowledge of Vitamin K levels in green vegetables (92% - 96%). User technology experience and demographic characteristics were not associated with Vitamin K food knowledge or level of satisfaction. The overwhelming majority of users found the app easy to learn and use. The ease of reading and finding information were 68 – 72%, respectively. Conclusion: Because self-management is vital for people taking Warfarin, using a game app as a supplement to traditional teaching could have significant positive impact on their health. As apps are increasingly easy to develop and smartphone use increases, apps should be developed to help people manage chronic diseases. Findings from this study support people’s interest and ability to use apps.
  • Expanding Post-Stroke Telerehabilitation: A Qualitative Study of User Experience Piloting VA Secure Messaging Use in a Telerehabilitation Format

    Keldsen, Linda; Storr, Carla L.; 0000-0002-5395-1358 (2020)
    BACKGROUND: Stroke is the fourth leading cause of death and primary cause of long-term disability in the U.S. As many as 40% of stroke survivors are discharged home without any inpatient or outpatient comprehensive stroke rehabilitation leading to the need for continued care for basic activities of daily living (grooming, toileting and feeding). Barriers to post-discharge comprehensive stroke rehabilitation are distance to travel, lack of transportation and inadequate social support. Telerehabilitation has been suggested as a possible solution for the delivery of low cost, convenient, home-based rehabilitative care. OBJECTIVE: To understand the experience of researchers and stroke survivors piloting the use of the My HealtheVet personal health record and secure messaging for stroke telerehabilitation. METHODS: A retrospective qualitative study using semi-structured interviews with a convenience sample of five study participants from the intervention arm of VA funded stroke rehabilitation single-blinded randomized controlled trail was conducted in addition to a focus group of three of the research team members. A descriptive phenomenological approach was used to describe the study participants and selected research team members experience using the VA’s My HealtheVet personal health record and secure messaging in telerehabilitation research. RESULTS: Researchers and study participants reported benefits from using the My HealtheVet personal health record with secure messaging that included the ability to send and or respond to secure messages at a time and place of their choosing, flexibility in scheduling the time of their therapy, ability to use any internet-enable device to access their My HealtheVet account, and the ability to retrieve and reread or watch education provided by the therapist when needed. Barriers to use were outweighed by the increased flexibility in scheduling, feeling empowered and having caregiver support. CONCLUSIONS: This small feasibility pilot suggests My HealtheVet with secure messaging may be an appropriate telecommunication tool for telerehabilitation. The study researchers caution that this was a small pilot and consideration should be given to ensuring adequate resources to support a larger study panel if expanded.
  • The Contribution of TRPV1 S801 Phosphorylation to Nociception and Inflammatory Pain in Vivo

    Joseph, John; Chung, Man-Kyo (2020)
    Transient receptor potential vanilloid subtype 1 (TRPV1) is a nonselective cation permeable channel activated by painful stimuli, such as capsaicin and noxious heat, and enriched in many primary afferent neurons of the pain pathway. During inflammation, chemical mediators activate protein kinases (such as PKC) that phosphorylate TRPV1 and thereby enhance its function, which results in nociceptor sensitization. And this can result in a lower threshold for pain. However, the causal relationships between TRPV1 phosphorylation and pathological pain remain unexplored. To directly investigate the roles of one specific TRPV1 phosphorylation event in vivo, we genetically altered a major PKC phosphorylation site, mouse TRPV1 S801, to alanine. The TRPV1 expression pattern in sensory neurons of S801A knock-in (KI) mice was comparable to that in wildtype (WT) controls. In sensory neurons from KI mice, following the activation of PKC, the usual increase of capsaicin-induced currents was substantially impaired. Thermal hyperalgesia induced by PMA or burn injury in KI was identical to WT. Thermal hyperalgesia was only marginally attenuated in KI mice duirng inflammation. In contrast, PMA-evoked nocifensive responses and hyperalgesia to capsaicin were significantly attenuated in the hindpaws of KI mice. Ongoing pain from inflamed masseter muscle was also reduced in KI mice, and the pain was further inhibited by the TRPV1 antagonist AMG9810. These results suggest that PKC-mediated phosphorylation of TRPV1 S801 contributes to inflammation-mediated sensitization of TRPV1 to ligand, but not heat, in vivo. Further, this suggests that interference with TRPV1 S801 phosphorylation might represent a potential way to reduce inflammatory pain in the clinic, yet spare basal sensitivity and produce fewer side effects than with a more general TRPV1 inhibition.
  • Characterization of Ketamine’s (2,6)-Hydroxynorketamine Metabolites: Pharmacokinetic and Behavioral Considerations for Antidepressant Applications

    Highland, Jaclyn; Gould, Todd D.; 0000-0002-9600-2830 (2020)
    Despite numerous available treatments for depression, most are not only slow to take effect but also ineffective in many patients, highlighting the need for novel and effective antidepressant treatments. While (R,S)-ketamine (ketamine) has gained attention for its rapid-acting antidepressant effects in previously treatment-resistant patients, its widespread antidepressant use is limited by adverse effects and abuse potential. The ketamine metabolite (2R,6R;2S,6S)-hydroxynorketamine (HNK), and most potently the (2R,6R)-HNK stereoisomer, shares the antidepressant-like behavioral effectiveness, but lacks the adverse effect burden and abuse potential, of ketamine in rodents, suggesting that (2R,6R)-HNK, and possibly other HNKs (12 have been identified, but only (2R,6R)- and (2S,6S)-HNK were previously studied), may be favorable antidepressant drug candidates. However, several important considerations for the development of HNKs as antidepressants were not previously evaluated. Such considerations were addressed in the present study. First, the pharmacokinetic profiles of the 12 HNKs were characterized, revealing robust differences in plasma and brain concentrations among the various HNKs, despite similar brain-to-plasma ratios and rapid elimination profiles. Second, it was demonstrated that (2R,6R)-HNK has favorable oral bioavailability (45-52%) and orally administered (2R,6R)-HNK exerts antidepressant-relevant behavioral effects, but not overt adverse effects, in mice. Third, the sex-dependent differences in the metabolism of ketamine and (2R,6R)-HNK in mice were characterized. It was demonstrated that, following ketamine administration, female mice have lower levels of ketamine and higher levels of HNK than male mice. In addition, following direct dosing, female mice have higher levels of (2R,6R)-HNK than males. Male gonadal hormones at least partly mediate these differences. Further, the relative effectiveness of the four (2,6)-HNKs in the mouse forced swim test were compared, revealing that both (2R,6S)- and (2S,6R)-HNK exert effects at lower doses compared to either (2R,6R)- or (2S,6S)-HNK, and establishing a relative rank-order of effectiveness of (2R,6R)- > (2S,6R)- > (2R,6R)- > (2S,6S)-HNK. Finally, it was identified that the novel compound, (5R)-methyl-(2R,6R)-HNK recapitulates the antidepressant dose-response relationship of (2R,6S)-HNK, with which it shares a similar three-dimensional structure, suggesting a critical role of three-dimensional structure in mediating antidepressant-relevant effectiveness. Altogether, these studies represent several important insights which may support the development of (2,6)-HNKs as antidepressant treatments.
  • Impact of Colonic Inflammation During Chronic Experimental Traumatic Brain Injury in Mice on Long-Term Outcomes

    Hanscom, Marie; Shea-Donohue, Terez; Faden, A. I.; 0000-0001-8308-135X (2020)
    Disruptions in the bidirectional communications of the brain-gut axis are increasingly implicated in the onset and progression of a variety of gastrointestinal and neurological disorders, diseases, and injuries including traumatic brain injury (TBI). In addition to the effects in the brain, TBI can result in gastrointestinal dysfunction, potentially affecting TBI pathogenesis and outcomes. This preclinical study examined the effects of colonic inflammation induced during chronic (long-term) experimental TBI on TBI-associated neurobehavioral and neuropathological outcomes. Additionally, the potential involvement of the neural and immunological pathways of the brain-gut axis in colonic inflammation induced changes in neurobehavior and neuropathology was examined. Dextran sodium sulfate (DSS) was administered to adult male C576Bl/6 mice 28 days following craniotomy (Sham) or TBI for 7 days to induce colonic inflammation (DSS injury phase), followed by a return to normal drinking water for an additional 7 to 28 days for recovery (DSS recovery phase). Uninjured animals (Naïve) served as an additional control group. Colonic inflammation during chronic experimental TBI in mice persistently exacerbated deficits in fine motor coordination and anxiety-like behavior and induced deficits in social behavior in TBI-injured mice. These behavioral changes were associated with an induction, or exacerbation, of ipsilateral hippocampal neuronal cell loss and microglial activation in Sham and TBI mice subjected to acute DSS administration, respectively. Colonic inflammation resulted in a sustained systemic immune response with increases in myeloid cells in blood and spleen, as well as myeloid cells and lymphocytes in mesenteric lymph nodes (mLN) in all DSS experimental groups. A sustained increase in spleen and mLN weights in all DSS groups, and thymus weight in Sham and TBI mice administered DSS, was observed up to 28 days following DSS administration. Dysautonomia was also induced in Sham and TBI mice subjected to acute colonic inflammation, with increased sympathetic tone beginning during DSS injury phase and persisting through the end of the first DSS recovery week. These data show that acute colonic inflammation during chronic experimental TBI results in enhanced neurocognitive deficits, neurodegeneration, microglial-related neuroinflammation, and a sustained systemic immune response with altered autonomic balance.
  • The Role of Self-efficacy, Technology Acceptance, and Support, in E-Learning for Child Welfare Workers

    Gunn, Meredith W.; Bright, Charlotte Lyn; 0000-0002-4092-0026 (2020)
    Over the last 15 years, the use of online technology for training and workforce development has increased due to cost savings, convenience, ease of tracking, uniformity of training delivery and messaging, and accessibility. The Association for Talent Development indicated in its 2017 State of the Industry Report that 45% of all employee training was being delivered through technology. Despite its growth, much of the research on online workforce training is limited to training outcomes (e.g., passing the knowledge posttest in order to receive a certificate, certification, or Continuing Education Units) and trainee evaluations (e.g., trainee satisfaction surveys) with no higher level analysis regarding the role of the following: theory, learning or technology; enablers, like technological savvy or organizational support; and/or barriers, like technological difficulties or lack of organizational support in users’ success The specific aims of this study were: (1) to examine what user characteristics and/or factors associated with use of helpdesk support, video tutorials, and test reset, and (2) to identify what factors predicted online training completion. Data for this dissertation were obtained from the National Adoption Competency Training Initiative which was established in October 2014 through a 5-year, $9 million cooperative agreement with the Center for Adoption Support and Education, the U.S. Department of Health and Human Services, and the Administration for Children and Families, Children’s Bureau. The University of Maryland School of Social Work and The Institute for Innovation and Implementation were primary partners in the initiative. Regression analysis showed that older users were more likely to use the help desk, to have a test reset, and less likely than younger users to complete the training; mandated users were more likely to complete the training but were also more likely to require a test rest and to use the video tutorials; and race/ethnicity was significant across all research questions. Findings revealed factors that impact success with online learning, as well as areas for future research into the role of race/ethnicity, personal agency, and variation of training types (self-paced or timed) in online training success.
  • Investigating the pathophysiological significance of obscurin immunoglobulin domains Ig58/59 in the heart

    Grogan, Alyssa; Kontrogianni-Konstantopoulos, Aikaterini; 0000-0002-1505-3311 (2020)
    Obscurin (720-870 kDa) is a giant cytoskeletal protein that surrounds the periphery of myofibrils at M-bands and Z-disks where it plays key structural and regulatory roles in striated muscles. Immunoglobulin domains 58/59 (Ig58/59) of obscurin mediate binding to several important modulators of muscle structure and function, including canonical titin, a smaller splice isoform of titin termed novex-3, and phospholamban (PLN). Importantly, missense mutations identified within obscurin Ig58/59 that affect binding to titins and/or PLN are linked to cardiac and skeletal myopathies in humans. To assess the pathophysiological role of Ig58/59 in vivo, we generated a constitutive deletion mouse model, Obscn-ΔIg58/59, that expresses obscurin lacking Ig58/59. Our studies revealed that young Obscn-ΔIg58/59 animals, which do not exhibit cardiac pathologies under sedentary conditions, experience tachycardia and severe arrhythmia following acute β-adrenergic stimulation and develop enlarged atria following prolonged exercise stress. Moreover, sedentary Obscn-ΔIg58/59 mice develop compensatory left ventricular hypertrophy that progresses to dilation, atrial enlargement, contractile dysfunction, and arrhythmia through aging in which males are more affected than females. Together, these findings demonstrate that deletion of obscurin Ig58/59 leads to both ventricular and atrial pathologies as a function of aging and in response to stress that manifest to different extents between sexes. We therefore aimed to decipher the cellular and molecular impact of the Ig58/59 deletion in Obscn-ΔIg58/59 ventricular and atrial myocardia, specifically focusing on males due to their enhanced disease severity. Our findings revealed that ventricular and atrial cardiomyocytes isolated from sedentary aging Obscn-ΔIg58/59 mice are enlarged and display tissue-specific alterations in Ca2+ cycling kinetics compared to controls, associated with distinct changes in the expression and phosphorylation status of major Ca2+ cycling proteins including PLN, the sarco-endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) and the ryanodine receptor 2 (RyR2). Lastly, proteomics and phospho-proteomics studies conducted on aged Obscn-ΔIg58/59 atria revealed significant changes in the levels of cytoskeletal proteins, Ca2+ regulators, and Z-disk associated complexes. Taken together, our studies demonstrate that obscurin Ig58/59 is a key regulatory module in the heart, and its deletion leads to age- and sex-dependent cardiac remodeling and arrhythmia associated with tissue-specific molecular alterations in the ventricles and atria.
  • The PAX-SIX-EYA-DACH Network regulates GATA factors and drives human erythropoiesis

    Creed, Timothy M.; Kingsbury, Tami (2020)
    Erythropoiesis is orchestrated by the coordinated action of multiple transcription factors. The master erythropoietic-regulator GATA1 is itself modulated via interactions with multiple co-regulatory factors. Though the PAX-SIX-EYA-DACH network (PSEDN) of conserved transcription factors has been well characterized in human organogenesis, a role for PSEDN members in hematopoietic systems has only recently been recognized (Liu et al., Nature 2019). Here we studied the PSEDN member SIX and discovered its ability to drive erythropoiesis of human hematopoietic cells. Overexpression of SIX1 or SIX2 in human TF1 erythroleukemia or primary CD34+ hematopoietic stem-progenitor cells (HSPCs) stimulated the generation of erythroid cells, as measured by flow cytometry, qPCR, and Western blot. Conversely, SIX1 knockout in TF1 cells or primary HSPCs reduced erythroid cell generation in response to erythropoietin. By gene set enrichment analysis of RNA-seq data, SIX1/SIX2 overexpression stimulated heme metabolism genes as well as genes known to be regulated by GATA1. SIX1/SIX2 overexpression reduced GATA2 and increased GATA1 expression, resembling GATA switching downstream of EPO signaling. To determine whether GATA1 was necessary for SIX1 to stimulate erythropoiesis, we generated GATA1-knockout cells using CRISPR/Cas9. In contrast to control cells, SIX1 OE in GATA1-knockout cells failed to stimulate erythropoiesis, indicating that SIX1 stimulation of erythropoiesis requires GATA1. To gain further insight into the mechanism by which SIX1/SIX2 stimulates erythropoiesis we generated a BirA*-SIX fusion protein to determine its interactome. Streptavidin-enrichment of biotinylated proteins in BirA*-SIX overexpression lysates revealed GATA1 and FOG1 as proximal interactors of BirA*-SIX. When co-expressed in HEK293T cells GATA1 and SIX1 were found to coimmunoprecipitate, suggesting the two proteins can physically interact in a complex. We demonstrated the functional consequence of the SIX1/SIX2 and GATA1 using a GATA1-dependent luciferase reporter construct. Cells in which SIX1/SIX2 and GATA1 were co-expressed exhibited significantly higher levels of luciferase expression compared to cells expressing only GATA1, suggesting SIX1 could stimulate GATA1-dependent transcription. Together our results suggest that SIX1 can stimulate erythropoiesis via multiple mechanisms. This thesis provides the first demonstration of a role for the PSEDN in erythropoiesis and reveal physical and functional interactions between two central developmental transcriptional networks (GATA/FOG and PSEDN).
  • Targeting Aberrant alpha-Helix Mediated Protein-Protein Interactions with Densely Functionalized Heterocycles

    Conlon, Ivie; Fletcher, Steven; 0000-0002-8269-299X (2020)
    Protein-protein interactions (PPIs) play crucial roles in cell proliferation, differentiation, and apoptosis. Apoptosis is a highly regulated process of cell death and its dysregulation can lead to a multitude of different pathophysiologies, such as cancer. In particular, the overexpression of pro-life Bcl-2 proteins, such as Bcl-2, Bfl-1, and Mcl-1, has been linked to cancer progression and tumorigenesis, as well as chemoresistance to a number of different chemotherapeutics. The binding counterparts of these proteins, pro-death Bcl-2 proteins such as Bim, and p53 transactivation domain (TAD), exert their effects through α-helix mediated PPIs with key residues i, i+ 3/4, and i+ 7 oriented on one side of the helix. In addition, HDM2, the E3 ubiquitin protein ligase responsible for the degradation of p53, is upregulated in numerous cancers, and given the similarities of the recognition profiles of Bim-BH3 and p53TAD, we have designed α-helix mimetic inhibitors that target Mcl-1 and HDM2. The first generation of compounds included various heterocyclic scaffolds, including isoxazoles, pyrazoles, and thiazoles, that project functional groups in a similar manner to the native α-helices. In addition, bicyclic scaffolds have been utilized in Mcl-1 selective inhibition. Therefore, we developed a second generation of compounds of isoxazoles, pyrazoles, and functionalized indoles to further explore the binding interface of Mcl-1. The recent resurgence of covalent inhibition and targeted protein degradation has led to the development of successful Bcl-2 family inhibitors. We have designed two tris-aryl α-helix mimetic scaffolds targeting the Bfl-1 pro-life protein. A unique surface-accessible cysteine within the BH3 domain allows for the development of reversible and irreversible small molecule covalent inhibitors. In addition, we have also designed a venetoclax-based PROTAC targeting Bcl-2.
  • In vitro and in vivo Models of Biofilm-Mediated Infections

    Brao, Kristen; Ernst, Robert K.; 0000-0003-0804-7105 (2020)
    Biofilms are microbial communities encased in a matrix of polysaccharides, extracellular DNA, and proteins. When growing in biofilms, bacteria display increased resistance to immune clearance and antibiotic tolerance. For these reasons, biofilms are responsible for many chronic infections. Treatment of biofilm-mediated infections is challenging, and often requires surgical debridement and/or lengthy courses of antibiotics. In order to develop more effective treatment strategies and therapeutics, it is important to develop and utilize model systems that incorporate the biofilm phenotype. In this dissertation, we describe the use of a rabbit model of internal fixation to evaluate the use of prophylactic antibiotic powders in surgery, characterize Scnn1b-Tg mice as models of Pseudomonas aeruginosa and Staphylococcus aureus infections in cystic fibrosis lungs, and use a continuous flow biofilm reactor to study the interactions of S. aureus and P. aeruginosa in chronic biofilms. We found that tobramycin powder is able to prevent surgical site infection with tobramycin-resistant Enterobacter cloacae, demonstrating the potential utility of antibiotic powders in preventing infections in orthopedic surgery. We also found that Scnn1b-Tg mice clear infections with P. aeruginosa and S. aureus more slowly than wildtype littermates. When Scnn1b-Tg mice were infected with a mucoid CF isolate, bacterial aggregates like those observed in cystic fibrosis patients’ sputum were found in the lungs, illustrating the potential of Scnn1b-Tg mice as models of cystic fibrosis lung infection. Finally, we found that P. aeruginosa modifies the structure of its lipid A by adding 4-amino-4-deoxy-L-arabinose (Ara4N) to the terminal phosphates when introduced to established S. aureus biofilms. The addition of Ara4N is associated with resistance to polymyxin antibiotics, such as colistin. This finding represents a potential mechanism by which interactions in polymicrobial biofilms can lead to changes in antibiotic resistance. These studies illustrate the importance of incorporating biofilm models when developing treatments for biofilm-mediated infections.
  • From Nanoparticles to Zinc Finger Proteins to Electronic Nicotine Delivery Systems: The Clinical and Biomolecular Evaluation of Potentially Toxic Heavy Metals

    Brandis, Joel; Michel, Sarah L. J.; 0000-0003-2163-5243 (2020)
    Physicochemical Properties of Sodium Ferric Gluconate There are concerns that differences in iron release between brand sodium ferric gluconate (SFG) (Ferrlecit) and generic SFG (generic SFG) intravenous (IV) iron nanoparticle drugs, which are used to treat chronic kidney disease can be caused by differences in the products’ physicochemical properties. However, a standardized, SFG product specific, physicochemical measurement regulatory guidance is not available. Iron core measurements including optical spectroscopy, ICP-MS, XRPD, 57Fe Mössbauer spectroscopy, and XAS, found both products’ cores to be similar ferric-iron-oxide structures. Measurements focused on the carbohydrate shell including forced acid degradation, concentration dependent DLS, AUC, and GPC found differences in particle size, acid stability/iron lability, and molecular weight distribution, that may impact iron release. Cadmium Targeting of Tristetraprolin Zinc finger (ZF) proteins regulate inflammation and are a potential target for cadmium. Zinc bound double Cys3His domain ZF protein tristetraprolin (TTP) regulates inflammation by binding to AU-rich cytokine mRNA. Using a TTP peptide (TTP-2D), Zn2-TTP-2D, cadmium was observed to displace Zn in a concentration dependent manner by spin-filter/ICP-MS coupled to native ESI-MS. Cadmium was also found to displace zinc from RNA bound Zn2-TTP-2D complex (Zn2-TTP-2D/RNA) by ESI in a concentration dependent manner, resulting in Cd1Zn1-TTP-2D/RNA and Cd2-TTP-2D/RNA complexes. Using fluorescence anisotropy cadmium displacement of zinc from Zn2-TTP-2D/RNA complex did not disrupt RNA binding. E-Cig E-liquid Matrix’s Effect on Metal Aerosolization Potentially toxic levels of metals, such as chromium, nickel, copper, and lead, have been reported in e-liquids (liquids composed primarily of a mixture of propylene glycol (PG), glycerol (G)) and nicotine, and generated aerosols of electronic nicotine delivery systems (ENDS). However, the variables that affect metal transfer from the e-liquid to the aerosols are unknown. Using a custom ENDS aerosolization device and aerosolization approach, following CORESTA 81 guidance, the aerosolization of metal spiked model e-liquids (PG and G) were measured. Using ICP-MS to measure aerosol metal content to determine the effect of e-liquid on chromium, nickel, copper, and lead, it was found that all four metals are more readily aerosolized in PG dominant e-liquids than G dominant e-liquids.
  • LRP1 as a Regulator of the Vasculature and Extracellular Matrix

    Arai, Allison Lindsay; Strickland, Dudley K.; Muratoglu, Selen C.; 0000-0002-0431-1856 (2020)
    The arterial wall and extracellular matrix (ECM) constantly remodel in response to physiological and pathophysiological signals including aging, atherosclerosis, and aneurysm formation. Low-density lipoprotein receptor-related protein 1 (LRP1) is an endocytic and signaling receptor capable of binding and internalizing over 100 structurally unrelated ligands. LRP1 has an important role in vascular maintenance and homeostasis. Global knock-out of LRP1 in mice results in embryonic lethality due to failure to recruit mural cells to developing vessels. Smooth muscle cell (SMC)-specific knock-out of LRP1 (smLRP1-/-) causes fully penetrant aortic aneurysm formation in mice. Collaborators at University of Texas Health Science Center and Johns Hopkins University have identified multiple rare human LRP1 variants associated with aortic disease. We hypothesize that genetic variants of LRP1 associated with aneurysm formation will impact ligand binding, trafficking, or signaling of LRP1. We used biochemical, cell-based, and mouse studies to determine the functional impact of rare LRP1 variants. We used surface plasmon resonance to investigate the binding relationship between LRP1 and matrix metalloprotease-1 (MMP-1), an ECM protease associated with aneurysm formation. We found that MMP-1 was a novel LRP1 ligand and the endogenous inhibitory MMP-1 complex was the preferred MMP-1 form for LRP1 binding. Complex formation of MMP-1 with tissue inhibitor of metalloproteases 1 (TIMP-1) resulted in a 30- to 40-fold increase in the binding affinity for LRP1 compared to other forms of MMP-1. Next, we introduced rare LRP1 variants by site-directed mutagenesis into truncated forms of LRP1 called mini-receptors to examine LRP1 trafficking. Specific LRP1 mutations impacted LRP1 turnover and/or maturation. We also found that LRP1 mini-receptors have a trafficking impairment that results in targeted, proteasomal degradation and limited LRP1 cell surface delivery. We suggest future caution when using mini-receptors in assays dependent on LRP1 trafficking. Finally, our mouse-based studies examined the impact of loss of LRP1 in SMCs (smLRP1-/-) on the cerebrovasculature and found that the vascular branching pattern and geometry was unaffected. In summary, our results demonstrate that LRP1 rare variants associated with aneurysm formation have functional deficits in LRP1 and that LRP1 is an important regulator of the vasculature and ECM.
  • Quest for New Drugs Against HIV-1 Multi-Drug Resistant Proteases

    Vernon, Kasey; Zhao, Richard Y.; 0000-0002-6294-503X (2020)
    HIV-1 protease inhibitors (PIs) are the most potent class of drugs in combinational antiretroviral therapies (cART). However, the current therapies are still not adequate due to the emergence of drug resistance. There is still a need for development of more potent PIs. The objective of this study was to search for multi-drug resistant inhibitors to combat HIV-1 and viral resistant proteases. Our lab developed a fission yeast (Schizosaccharomyces pombe) cell-based system that allows large-scale or high-throughput drug screening. We first used a cell growth-based assay to test a drug candidate. We then used a HIV-1 enzymatic assay to confirm it. We explored four batches of potential anti-HIV compounds as well as nine FDA approved PIs. All FDA-approved PIs potentially inhibited HIV-1 PR with 3 small molecule compounds showed minimal inhibitory effects. Results of this study demonstrated the use of fission yeast cell-based system as a means to discover new PIs.
  • Estradiol Action at the Median Preoptic Nucleus Modulates Adenosinergic Homeostatic Sleep Pressure

    Smith, Philip C.; Mong, Jessica Aurora; 0000-0001-6726-2781 (2020)
    To further our understanding of how gonadal steroids impact sleep biology, we sought to address the mechanism by which proestrus levels of cycling ovarian steroids, particularly estradiol (E2), suppress sleep in female rats. We showed that steroid replacement of proestrus levels of E2 to ovariectomized female rats, suppressed sleep to similar levels as those reported by endogenous ovarian hormones. We further showed that this suppression is due to the high levels of E2 alone, and that progesterone did not have a significant impact on sleep behavior. We found that E2 action within the Median Preoptic Nucleus (MnPN), which contains estrogen receptors (ERs), is necessary for this effect; antagonism of ERs in the MnPN attenuated the E2-mediated suppression of both non-Rapid Eye Movement (NREM) and Rapid Eye Movement (REM) sleep. Finally, we found E2 action at the MnPN is also sufficient for sleep suppression, as direct infusion of E2 into the MnPN suppressed sleep. Based on our findings, we predict proestrus levels of E2 alone, acting at the MnPN, mediate sex-hormone driven suppression of sleep in female rats. Furthermore, our findings have demonstrated that E2 has different effects on sleep time and slow wave activity (NREM-SWA), a measure of the homeostatic efficiency of sleep, under conditions of normal sleep and sleep deprivation. E2 serves to decrease NREM-SWA, but not sleep time, in the light phase under normal sleep, while in recovery, E2 decreases sleep time but not NREM-SWA following deprivation. We further found that E2 increased levels of extracellular adenosine, a measure of homeostatic sleep need, under both normal and deprivation sleep conditions. To resolve the discrepancy between the decrease in behavioral markers associated with homeostatic sleep need and increase in levels of adenosine, we employed an agonist of the A2A receptor to stimulate the adenosinergic sleep pressure system. These studies show that E2 blunts the ability of the A2A agonist to drive sleep behavior, showing an interposition of E2 into the adenosinergic sleep pressure system. Overall, these experiments show an interaction between E2 and adenosinergic homeostatic sleep pressure at the level of the MnPN.
  • FOXO1 Nucleo-Cytoplasmic Distribution and Regulation

    Russell, Sarah; Schneider, Martin F. (2020)
    Skeletal muscle atrophy is regulated at the cellular level by several signaling pathways that modulate the balance between protein degradation and protein synthesis. A primary pathway regulating skeletal muscle atrophy is the IGF1 or Insulin/PI3K/Akt/Foxo1 pathway. IGF1/insulin lead to activation of a cascade of kinases, ultimately activating Akt which phosphorylates specific sites on Foxo1 and causes Foxo1 to translocate out of myofiber nuclei. When present in myofiber nuclei, Foxo1 functions as a transcription factor that activates transcription of several pro-atrophic genes, such as MurF1 and MAFbx/atrogin1. Here we use fluorescence time lapse imaging of the nuclear cytoplasmic distribution of Foxo1-GFP in adult isolated skeletal muscle fibers a to investigate (a) variability of FOXO1 nucleo-cytoplasmic distribution in mature muscle fibers as well as FOXO1 nuclear influx and efflux, and (b) the effects of IGF1 and insulin on Foxo1-GFP translocation in the presence of pharmacological inhibitors that target specific sections of the canonical IGF1 or insulin/PI3K/Akt/Foxo1 pathway. For our first aim, our results demonstrate that FOXO1 N/C and apparent rate coefficient (kI’) of FOXO1 nuclear influx are nearly identical for nuclei within the same fiber, they are highly varied for nuclei belonging to different fibers. These results indicate that variability in cellular factors, but not extracellular factors, determine FOXO1 distribution from fiber to fiber. Additionally, we show that application of IGF1 is able to reduce variation in kI’ and N/C in all fibers while AKT-inhibitor application does not, indicating other pathways are involved. For our second aim, our results demonstrate Akt is absolutely necessary for the dramatic IGF1 or insulin-induced rapid and near complete nuclear efflux of Foxo1, PI3K is not. Insulin induced movement of the PIP3 biosensor PH ARNO-GFP to transverse tubules is prevented by PI3K inhibitor BKM120, demonstrating that PI3K inhibition was effective. We have also found that two additional protein kinases, Ack1 and ATM, contribute to IGF1-induced Akt activation and Foxo1-GFP nuclear efflux. These results indicate the presence of PI3K-dependent -independent parallel pathways from IGF1 to Akt activation in adult muscle that are not well understood in Foxo1 regulation.
  • The impact of the non-immune chemiome on T cell activation

    Rosenberg, Kenneth; Singh, Nevil; 0000-0002-1231-7836 (2020)
    T cells are critical organizers of the immune response and rigid control over their activation is necessary for balancing host defense and immunopathology. It takes 3 signals provided by dendritic cells (DC) to fully activate a T cell response – T cell receptor (TCR) engagement of antigen on MHC (Signal 1), co-stimulatory signals (Signal 2) and cytokines (Signal 3). Yet, even before activation T cells are typically exposed to a universe of chemicals (a “chemiome”) including drugs, metabolites, hormones etc. which are not typically ascribed an immunological role. In this thesis, we hypothesized that members of this non-immune chemiome acting on T cells, prior to antigen encounter, flavor specific signaling pathways to differentially influence subsequent T cell activation and fate. Unraveling these signals, which we termed “Signal 0”, could help us understand and manipulate tissue and time specific flavoring of immunity. In this thesis we first developed a pharmacological model for signal 0, by treating T cells with drugs that activate only subsets of the TCR-signaling network prior to full antigen exposure. We found that pharmacological pre-activation of the PKCƟ/ERK pathways modulates long time survival of T cells without changing proliferation or cytokine production. Next, we examined receptors for the non-immune chemiome that resting T cells express and identified neurotransmitter receptors (NR) as a major family. All T cells expressed a core NR signature, but very few NR were also modulated in a T cell lineage-specific fashion. Of these, we focused on VPAC1, the receptor for vasoactive intestinal peptide (VIP). We found that VIP signaling attenuates ERK phosphorylation, but paradoxically drives increased differentiation towards IL-17 and IL-22 secretion. In addition ERK signaling induced by drugs (phorbol esters) versus the TCR followed differential kinetics and recruited non-overlapping negative feedback mechanisms, suggesting that even the same branch of TCR signaling is subject to different localization and temporal controls. Taken together, our data suggest that the branches of the TCR-signaling network integrate pre-existing signals (Signal 0) into the activation program of T cells, allowing localized cues, including neurotransmitter levels, to modify the long-term trajectory of the immune response.
  • Regulation of intrinsic activation thresholds of T cells

    Matson, Courtney; Singh, Nevil; 0000-0002-9817-4986 (2020)
    T cells are activated when their T cell receptor (TCR) senses peptide-MHC (pMHC) molecules from pathogens and tumors. A network of signaling molecules downstream of the TCR drives the extent and nature of subsequent cellular responses. The activation threshold (AT) of these signaling pathways is a critical checkpoint for T cell responses. Here, we examined mechanisms by which the AT of a T cell is first determined and how it changes during the course of responding to antigen. The initial AT of a T cell is set during development by calibrating to how strongly it senses pMHC in the thymus. This calibration affects the surface levels of a receptor CD5, whose subsequent role is poorly defined. We found that CD5, independent of the TCR, sets basal levels of IκBα in T cells. Since IκBα critically modulates the transcription factor NFκB, which regulates multiple T cell functions including cell-survival, we hypothesized that variations in basal AT of T cells stem from varying NFκB depots maintained by CD5. Indeed, blocking NFκB abolished differences in cell-survival of thymocytes with different CD5 levels. The initial heterogeneities are further modified when peripheral T cells encounter antigen. Resulting memory T cells acquired higher CD5 levels and continuously required CD5 expression to maintain higher IκBα expression. If the stimulating antigen was not cleared efficiently, peripheral T cells further ‘tuned’ their AT in the opposite direction and resulted in loss of sensitivity to antigen (as seen in exhausted T cells). Importantly, this AT tuning involved additional regulation of TCR-proximal kinases such as Zap70 and was reversible in vivo, but not in vitro. We also found that rather than just the duration of antigen exposure, AT-tuning was potentially influenced by the rate at which antigen changes in vivo. This can help us understand how different persistent pathogens or tumors affect T cell responses, potentially based on the rates at which they replicate in the host. Finally, we characterized compounds that can target a T cell’s AT, identified in a high-throughput pharmacological screen, to potentially isolate drugs for altering T cell function during these physiological contexts.

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