Document Type

Dissertation - Open Access

Award Date

2019

Degree Name

Doctor of Philosophy (PhD)

Department / School

Pharmaceutical Sciences

First Advisor

Teresa Seefeldt

Abstract

The thioredoxin (Trx) system is an endogenous antioxidant system that affects cell function and survival through controlling cellular redox status. Trx and TrxR are the main enzymes in this system while thioredoxin interacting protein (TXNIP) is a negative regulator. This study’s goal was to better understand the Trx system’s involvement in the cardiovascular disease and modulate the pathway through drug treatment. Carvedilol is a non-selective β-blocker that also exhibits antioxidant properties, but the exact mechanism of the antioxidant effect is still unclear. H9c2 rat cardiomyocytes were used to examine the effect of carvedilol on the Trx system under normal conditions. Interestingly, carvedilol was able to decrease TXNIP not through its expression or proteasomal degradation but through increased TXNIP nuclear localization. Immunoprecipitation also showed an increase in TXNIP-PARP complexation in the nucleus and a decrease in Trx-TXNIP complexation in the cytosol. The results indicate that carvedilol may exhibit its antioxidant activity through altering TXNIP subcellular localization. TXNIP is known to be important in both physiologic and pathophysiologic conditions. Western blot data showed that TXNIP in the cytosol will increase with increasing glucose concentration. Oxidative stress inducers such as doxorubicin, hypoxiareoxygenation, and radiation were able to decrease cytosolic TXNIP. Doxorubicin is a commonly utilized anticancer drug that induces oxidative stress and therefore causes cardiac toxicity. A study was conducted to determine if carvedilol could protect against doxorubicin-induced cardiotoxicity through TXNIP modulation. Carvedilol and doxorubicin alone reduced cytosolic TXNIP. Doxorubicin increased mitochondrial translocation of TXNIP accompanied by the induction of apoptosis. However, carvedilol was not able to prevent TXNIP mitochondrial translocation, but it did protect against doxorubicin-induced apoptosis. The complex of Trx2 and the proapoptotic ASK1 in the mitochondria was increased with carvedilol pretreatment followed by doxorubicin exposure. The increase in the ASK1-Trx2 complex can reduce apoptosis through decreased ASK1 activation. This was confirmed through Western blot of cleaved PARP. The findings are consistent with reports of TXNIP’s response to mild oxidative stress conditions. In conclusion, this study shows for the first time that carvedilol impacts TXNIP localization and complexation and that the Trx pathway may be involved in carvedilol’s observed cardioprotective effect.

Library of Congress Subject Headings

Thioredoxin.
Adrenergic beta blockers.
Antioxidants.
Heart cells
Cardiovascular system -- Diseases -- Chemotherapy.

Format

application/pdf

Number of Pages

145

Publisher

South Dakota State University

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Rights Statement

In Copyright