Biomedical Sciences ETDs

Publication Date

7-1-2014

Abstract

Our laboratory has demonstrated an important role for acid-sensing ion channel 1 (ASIC1) in pulmonary hypertension through augmented Ca2+ influx in pulmonary arterial smooth muscle cells (PASMC) following chronic hypoxia (CH). However, this enhanced calcium (Ca2+) influx is not dependent on an increase in ASIC1 protein expression. This suggests other regulatory mechanisms influencing ASIC1 activity are altered following CH. ASIC1 is a redox sensitive ion channel and recent studies from our laboratory have shown that the oxidant hydrogen peroxide (H2O2) inhibits ASIC1-dependent Ca2+ influx in PASMC. Reactive oxygen species are known to be altered in pulmonary hypertension, however the direction of these changes remains largely controversial. We hypothesized that H2O2 levels are decreased following CH due to diminished production and enhanced degradation. To test this hypothesis we assessed H2O2 levels by Amplex Red fluorescence and found a decrease in H2O2 in pulmonary arteries from CH rats (4 wks @ 380 Torr) compared to control. To determine the effect of CH on H2O2 production, we examined the expression and activity of superoxide dismutase (SOD) 1, 2, and 3. The expression of SOD1 and SOD3 was decreased; and total and Cu/ZnSOD (SOD1 and SOD3) activities were reduced in pulmonary arteries from CH rats compared to those of controls. To determine the effect of CH on H2O2 decomposition, we examined the rate of catalysis of H2O2 and the expression and activity of the enzymes responsible for the catalysis of H2O2: catalase and glutathione peroxidase. We found the rate of H2O2 degradation was greater in pulmonary arteries from CH rats compared to control. While there was no difference in catalase expression or activity between groups, glutathione peroxidase expression and activity was augmented following CH. Together these data suggest the decrease in pulmonary arterial H2O2 levels in CH-induced pulmonary hypertension is a result of 1) decreased production due to diminished SOD1 and SOD3 expression and activity; and 2) increased catalysis via glutathione peroxidase. The decreased H2O2 levels correlate with enhanced ASIC1-dependent Ca2+ influx in PASMC following CH. Further studies are needed to determine the mechanism by which H2O2 regulates ASIC1 Ca2+ influx.

Keywords

ASIC1, Chronic Hypoxia, Superoxide Dismutase, Glutathione Peroxidase

Document Type

Thesis

Language

English

Degree Name

Biomedical Sciences

Level of Degree

Masters

Department Name

Biomedical Sciences Graduate Program

First Committee Member (Chair)

Resta, Thomas

Second Committee Member

Walker, Mary

Third Committee Member

Walker, Benjimen

Fourth Committee Member

Bizzozero, Oscar

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