Abstract 13367: Glyceraldehyde-3'-Phosphate Dehydrogenase Reduces Cell Apoptosis, Prevents DNA Damage and Suppresses Atherogenesis.

We have demonstrated previously that glyceraldehyde-3'-phosphate dehydrogenase (GAPDH) protected smooth muscle cells (SMC) against oxidant-induced apoptosis via upregulation of Ape1 endonuclease, the major DNA repair enzyme. To obtain in vivo data, we immunostained murine aortic valve atherosclerotic plaques for GAPDH, N-tyrosine (marker of oxidative stress), alpha-SM actin (SMC marker) and stained with TUNEL (apoptotic assay). We found that GAPDH was reduced in SMC in atherosclerotic plaque's cap compared to SMC in adjacent plaque-free vascular media and cells with downregulated GAPDH had high level of N-tyrosine and they were apoptotic. We hypothesized that SMC-specific GAPDH overexpression will reduce atherosclerosis. To test this hypothesis we generated Apoe-null mice with SMC-specific SM22a promoter-driven GAPDH overexpression (SM-GAPDH mice). Aortas isolated from SM-GAPDH mice had >2-fold increase in GAPDH levels, increased Ape1 endonuclease levels (31±5% increase), decreased levels of pH2AX(DNA damage marker) and reduced cleaved PARP expression (apoptotic marker, 74±12% decrease) (all are P<0.05) compared to Apoe-null controls. These data suggests that increase in SMC' GAPDH upregulates Ape1 expression, reduces DNA damage and cell apoptosis. SM-GAPDH mice were fed with a high-fat diet for 4 and for 12 weeks. SM-GAPDH mice had reduced atherosclerotic burden after 4 weeks on diet (22±3% decrease, P<0.05) and after 12 weeks (28±3% decrease vs. control, P<0.05). Plaques in SM-GAPDH mice (4 weeks on diet) have elevated SMC levels (IHC with alpha-SM actin, 3.22-fold increase, P<0.01; IHC with calponin, 3.4-fold increase, P<0.05) and increased collagen (Trichrome, 3.1-fold increase, P<0.05). Plaque SMC apoptosis was markedly suppressed in SM-GAPDH mice (12 weeks on diet, TUNEL/co-staining for calponin, 5.2-fold decrease, P<0.05). In summary, we have found that SMC-specific GAPDH upregulates Ape1 endonuclease, reduces DNA damage, suppresses SMC apoptosis and decreases atherogenesis. These in vivo data taken together with our in vitro findings indicates that stimulation of GAPDH-Ape1 axis is potential therapy to protect DNA and suppress atherogenesis. [ABSTRACT FROM AUTHOR]