Abstract 1416: Chronic TNF-Alpha Infusion Induces Mitochondrial Damage in the Heart and Kidney of Rats by Depleting Mitochondrial Membrane Permeability Proteins
TNF-α is multifunctional cytokine and plays an important role in cardiovascular regulation. In this study, we demonstrate that chronic TNF-α induces mitochondrial oxidative stress, and depletes superoxide dismutase in heart and renal medulla of rats.
Methods: Rats were treated with TNF-α (40μg/kg, subcutaneously), TNF-α + Apocyanin (APO, 200 micromolar/kg, intraperitoneally), TNF-α + Tempol (TEMP, 300 micromolar, orally) or vehicle for 5 days. On day 5 left ventricular (LV) function was measured using echocardiography, followed by conscious renal sympathetic nerve activity (RSNA) measurement. Subsequently, rats were sacrificed the LV and renal medullary tissue was removed for gene expression studies and mitochondrial assay. The structural integrity of mitochondrial membrane was measured using swelling assay and Western blot, and the antioxidant status in the mitochondria and the tissues were measured using enzymatic assay.
Results: TNF-α treatment induced significant increase in RSNA, increased the expression of NADPH oxidase subunits, AT-1 receptor and induced mitochondrial damage to the LV and kidney medulla and decreased the membrane permeability transitional pore proteins ANT, and VDAC. The SOD2 mRNA and enzyme activity decreased, compared with vehicle treated animals. Treatment with TNF-α + TEMP prevented mitochondrial damage, and restored antioxidant enzymes and improved SOD2 activity and restored RSNA. It also decreased AT1 receptor expression and NADPH oxidase subunits. Treatment with TNF-α + APO, decreased NADPH oxidase subunits, AT-1 receptor and attenuated mitochondrial damage but did not restore antioxidant defense system in the mitochondria. These results suggest that TNF-α causes damage to both the cell membrane and mitochondrial membrane by increasing superoxide production both in the cytosol and in the mitochondria of the heart and kidneys. Apocyanin partially restores cell membrane damage by preventing induction of NADPH oxidase and does not restore mitochondrial membrane damage.
Conclusion: TNF-a induced mitochondrial damage in the heart and kidney could contribute to the pathophysiology of cardiovascular disease. Preventing excessive production of TNF-a might benefit patients with cardiovascular disease.