Browsing School, Graduate by Subject "ROS"
Now showing items 1-4 of 4
Acute ROS in Cardiac Calcium SignalingModulation of cardiac function usually involves changes in cellular Ca2+ signaling. Reactive oxygen species (ROS) have been implicated in effecting changes in cardiac Ca2+ signaling. It has been unclear, however, exactly what these changes are and if they are ultimately detrimental or beneficial. The work reported here investigates the effect of acute application of H2O2 in low concentrations on Ca2+ signaling in the heart cell. The driving hypothesis is that ROS in short bursts is a non - detrimental physiological signal that fine tunes Ca2+ signaling. To this end the effect of ROS is investigated in 3 modules. i. the effect of rapid application of 100 μM H2O2 on Ca2+ signaling in heart cells, ii. the effect of H2O2 on Ca2+ signaling during β-adrenergic activation in heart cells and finally to examine endogenously generated ROS, iii. Ca2+ signaling in a murine model of NOX2 overexpression (NOX2 is a ROS generating enzyme). Using a combination of confocal imaging of fluorescent Ca2+ dyes and electrophysiological techniques such as whole cell voltage clamp and current clamp; Ca2+ sparks, Ca2+ transients, ICa, Sarcoplasmic Reticulum (SR) Ca2+ load and Sarcoplasmic/Endoplasmic Reticulum Ca2+ ATPase (SERCA) function were measured in all three paradigms listed above. The work shows that low concentrations of H2O2 for a brief period deplete SR load without affecting other parameters of Ca2+ signaling, and this depletion of SR load is prevented by β-adrenergic activation. The results further our understanding of ROS modulation of Ca2+ signaling and lays some groundwork for further exploration into the pathways by which ROS may interact with other modifiers of the Ca2+ signaling machinery of the cardiac cell.
Farnesol-Induced Apoptosis in Oral Squamous Carcinoma Cells is Mediated by MRP1 Extrusion and Depletion of Intracellular GlutathioneFarnesol is a key intermediate in the sterol biosynthesis pathway in eukaryotic cells that has exhibited significant anti-cancer and antimicrobial activity. We have shown that farnesol triggers apoptosis in oral squamous carcinoma cells (OSCCs) and in the fungal pathogen Candida albicans via a classical apoptotic process. However, the exact mechanism of farnesol cytotoxicity in eukaryotic cells has not been fully elucidated. In the cell, hydrophobic xenobiotics conjugate with glutathione, an antioxidant crucial for cellular detoxification against damaging compounds. This process results in the formation of glutathione S-conjugates which act as substrates for export by ATP-binding cassette transporters (ABC transporter) and are extruded from the cell. This study was undertaken to validate the hypothesis that farnesol conjugation with intracellular glutathione coupled with multidrug resistance-associated protein 1 (MRP1) - mediated extrusion of glutathione-farnesol conjugates and oxidized glutathione results in total glutathione depletion, oxidative stress and ultimately cell death. The combined findings demonstrated that farnesol exposure resulted in significant decrease in intracellular glutathione levels concomitant with intracellular Reactive oxygen species (ROS) accumulation and decrease in cell viability. However, addition of exogenous glutathione maintained intracellular levels and enhanced cell viability. Furthermore, gene and protein expression studies demonstrated significant up-regulation of MRP1 in cells treated with farnesol. However, MRP1 blocking and monoclonal antibody specific inhibition of MRP1 enhanced cell tolerance to farnesol. This is the first study describing the involvement of MRP1-mediated glutathione efflux as a mechanism for farnesol-induced apoptosis in OSCCs. Understanding of the mechanisms underlying farnesol-cytotoxicity in eukaryotic cells may lead to the development of this redox-cycling agent as an alternative chemotherapeutic target.
Neuroprotective role of nicotinamide adenine dinucleotide precursor in modulation of mitochondrial fragmentation and brain energy metabolismNicotinamide adenine dinucleotide (NAD+) is a central signaling molecule and enzyme cofactor that is involved in a variety of fundamental biological processes. NAD+ levels decline with age, neurodegenerative conditions, acute brain injury, and in obesity or diabetes. Loss of NAD+ results in impaired mitochondrial and cellular functions. Administration of NAD+ precursor, nicotinamide mononucleotide (NMN), has shown to improve mitochondrial bioenergetics, reverse age associated physiological decline, and inhibit post-ischemic NAD+ degradation and cellular death. In this work we identified a novel link between NAD+ metabolism and mitochondrial dynamics. A single dose (62.5mg/kg) of NMN, administered in naïve animals and after animals are subjected to transient forebrain ischemia, increases hippocampal mitochondria NAD+ pools and drives a sirtuin 3 (SIRT3) mediated global decrease in mitochondrial protein acetylation. This results in a reduction of hippocampal reactive oxygen species (ROS) levels via SIRT3 driven deacetylation of mitochondrial manganese superoxide dismutase. Consequently, mitochondria in neurons become less fragmented due to lower interaction of phosphorylated fission protein, dynamin-related protein 1 (pDrp1 (S616)), with mitochondria. In conclusion, manipulation of mitochondrial NAD+ levels by NMN results in metabolic changes that protect mitochondria against ROS and excessive fragmentation, offering therapeutic approaches for pathophysiologic stress conditions.
Oxidative Stress Markers in Periodontitis: A Systematic ReviewPurpose: The aim of the present systematic review was to analyze the role of oxidative stress markers in patients with periodontal disease. Materials and Methods: A comprehensive search based on predetermined inclusion criteria was performed to identify studies evaluating oxidative stress markers in humans with and without periodontitis. The search included all studies up to February 2016 in the following databases: Ovid MEDLINE, Scopus, and Cochrane Library. Results: The initial search identified 2,523 entries. The final selection consisted of 16 articles. The characteristics of the studies and the outcomes measures were described. Conclusions: A clear relationship is suggested for oxidative stress and periodontitis. Besides the outcome patterns demonstrated, the findings of the present systematic review underline the necessity of methodological standardization. Future research focusing on disease susceptibility, predictive, prognostic and therapeutics aims need to be explored.