Biomedical subjects

Guochuan Ma

Publications and source records attributed to Guochuan Ma.

3 recordsLinked to original sources

PubMed2006

Protection against myocardial ischemia/reperfusion injury by short-term diabetes: enhancement of VEGF formation, capillary density, and activation of cell survival signaling.

The aims of this study were to determine effects of diabetes duration on myocardial ischemia/reperfusion (I/R) injury and test whether time-dependent differences in sensitivity of the streptozotocin diabetic rat heart to I/R are related to differences in vascular density, levels of vascular endothelial growth factor (VEGF) or endothelial nitric oxide synthase (eNOS) expression, NO formation, activation of Akt, and/or oxidative stress. After 2 or 6 weeks of streptozotocin-induced diabetes, I/R injury was induced by occlusion (30 min) and reperfusion of the left descending coronary artery. After 2 weeks of diabetes, infarct size and cleavage of caspase-3, a proapoptosis signal, were decreased as compared with normoglycemic controls or rats that had been diabetic for 6 weeks, whereas capillary density and levels of VEGF and eNOS protein and cardiac NO(x) levels were all increased. Phosphorylation of Akt, a prosurvival signal, was also significantly increased after 2 weeks of diabetes. Cardiac lipid peroxidation was comparable to controls after 2 weeks of diabetes, whereas levels of nitrotyrosine, a peroxynitrite biomarker, were reduced. After 6 weeks of diabetes, lipid peroxidation was increased and levels of VEGF and plasma NO were reduced as compared with controls or rats diabetic for 2 weeks. Our results indicate endogenous cardioprotective mechanisms become transiently activated in this early stage of diabetes and that this may protect the heart from I/R injury through enhancement of VEGF and eNOS expression, NO formation, activation of cell survival signals, and decreased oxidative stress.

Animals↗

PubMed2006

Simvastatin improves diabetes-induced coronary endothelial dysfunction.

3-Hydroxy-3-methylglutaryl CoA reductase inhibitors decrease cardiovascular morbidity in diabetic patients, but the mechanism is unclear. We studied the actions of simvastatin (SIM) in enhancing NO bioavailability and reducing oxidative stress in coronary vessels from diabetic rats and in rat coronary artery endothelial cells (RCAEC) exposed to high glucose. Coronary arteries isolated from diabetic rats showed decreases in acetylcholine (ACh)-mediated maximal relaxation from 81.0 +/- 4.5% in controls to 43.5 +/- 7.6% at 4 weeks and 22.3 +/- 0.6% at 10 weeks of diabetes. This effect was associated with oxidative stress in coronary vessels as shown by dichlorofluorescein (DCF) imaging and nitrotyrosine labeling. Diabetes also reduced trans-coronary uptake of [(3)H]l-arginine. Supplemental l-arginine (50 mg/kg/day p.o.) did not improve coronary vasorelaxation to ACh. However, SIM treatment (5 mg/kg/day subcutaneously) improved maximal ACh relaxation to 65.8 +/- 5.1% at 4 weeks and 47.1 +/- 3.9% at 10 weeks. Coronary arteries from rats treated with both SIM and l-arginine demonstrated the same maximal relaxation to ACh (66.1 +/- 3%) as SIM alone. Mevalonate and l-NAME (N(omega)-nitro-l-arginine methyl ester hydrochloride) inhibited the response to ACh in SIM-treated diabetic rats. Coronary arteries from all groups relaxed similarly to sodium nitroprusside. SIM increased endothelial NO synthase protein levels and blocked diabetes-induced increases in DCF and nitrotyrosine labeling in diabetic coronary vessels. SIM treatment restored normal NO levels in media from high-glucose-treated RCAEC and plasma of diabetic rat. Treatment with SIM or the NADPH oxidase inhibitor apocynin also blocked high-glucose-induced increases in reactive oxygen species and superoxide formation in RCAEC. Taken together, these data suggest that SIM improves diabetes-induced coronary dysfunction by reducing oxidative stress and increasing NO bioavailability.

Animals↗

PubMed2006

Effect of simvastatin on high glucose- and angiotensin II-induced activation of the JAK/STAT pathway in mesangial cells.

In the current study, we investigated the effect of simvastatin on the ability of high glucose (HG) and ANG II to activate the JAK2-STAT signaling cascade and induce glomerular mesangial cell (GMC) growth. We found that pretreatment with simvastatin significantly inhibited HG- and ANG II-induced collagen IV production, JAK2 activation, and phosphorylation of STAT1 and STAT3 in GMC. We also found that the activation of JAK2 by HG and ANG II was dependent on the Rho family of GTPases. Consistent with these in vitro results, both albumin protein excretion and phosphorylation of JAK2, STAT1, and STAT3 were attenuated in renal glomeruli by administration of simvastatin in a streptozotocin-induced rat model of HG diabetes. This study demonstrates that simvastatin blocks ANG II-induced activation of the JAK/STAT pathway in the diabetic environment, in vitro and in vivo, and, thereby, provides new insights into the molecular mechanisms underlying early diabetic nephropathy.

Angiotensin II↗