The direct antioxidative and anti-inflammatory effects of peroxisome proliferator-activated receptors ligands are associated with the inhibition of angiotensin converting enzyme expression in streptozotocin-induced diabetic rat aorta.

Peroxisome proliferator-activated receptors (PPARs) are expressed on vascular tissue. To investigate the direct vasoprotective effects of PPARgamma and PPARalpha ligands, pioglitazone (3 mg/kg/day) and bezafibrate (10 mg/kg/day) were given by gavage to streptozotocin-induced diabetic rats for 4 weeks. Streptozotocin (65 mg/kg, i.p.) significantly increased NADPH oxidase, vascular call adhesion molecule-1 (VCAM-1), and osteopontin mRNA levels in the aorta, as determined by reverse transcription (RT)-polymerase chain reaction (PCR). Immunohistochemical analysis revealed that the expression of osteopontin protein was also enhanced in the streptozotocin-injected rat aorta. Pioglitazone or bezafibrate attenuated the streptozotocin-induced increase in the expression of NADPH oxidase and VCAM-1 mRNA. The enhanced expression of osteopontin gene and protein induced by streptozotocin was suppressed by pioglitazone, whereas treatment with bezafibrate had no effect on the expression of osteopontin. We also demonstrated that pioglitazone or bezafibrate prevented the streptozotocin-induced increase in angiotensin converting enzyme (ACE) gene and protein content, by the means of RT-PCR and Western blotting. On the other hand, the treatment of pioglitazone or bezafibrate in the present study did not affect glucose tolerance, serum insulin or lipid level in streptozotocin-induced diabetic rats. These results suggest that the direct anti-oxidant and anti-inflammatory effects of PPARs ligands in the aorta of streptozotocin-induced diabetic rats were not likely to have been mediated by the normalization of glucose or lipid metabolism, but instead these salutary effects appear to have been associated with the inhibition of the expression of ACE. In addition, pioglitazone appeared to be more effective on the suppression of osteopontin expression compared with bezafibrate.

Calcium [corrected] channel blockers reduce angiotensin II-induced superoxide generation and inhibit lectin-like oxidized low-density lipoprotein receptor-1 expression in endothelial cells.

Calcium channel blockers have been shown to limit the progression of atherosclerosis and decrease the incidence of cardiovascular events. To investigate vasoprotective effects beyond the blood pressure-lowering effects of these agents, amlodipine (10(-6) mol/) and manidipine (10(-6) mol/l) were used to pretreat angiotensin (Ang) II-stimulated rat cultured aortic endothelial cells. A 3-h period of Ang II treatment enhanced superoxide generation and the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase protein, as detected by dihydroethidium staining and Western blotting, respectively. Pretreatment with amlodipine or manidipine attenuated the increased production of superoxide and the overexpression of NADPH oxidase. The enhanced expression of heme oxygenase-1 (HO-1) mRNA induced by Ang II was further increased by amlodipine, whereas pretreatment with manidipine led to a reduction in the expression of HO-1. Furthermore, Ang II increased vascular cell adhesion molecule-1 (VCAM-1), intracellular adhesion molecule-1 (ICAM-1), and monocyte chemoattractant protein-1 (MCP-1) mRNA levels, as determined by reverse transcription (RT)-polymerase chain reaction (PCR). Pretreatment with either amlodipine or manidipine decreased the overexpression of VCAM-1, ICAM-1, and MCP-1. We also demonstrated that amlodipine or manidipine prevented the Ang II-induced increase in lectin-like oxidized low-density lipoprotein receptor1 (LOX-1) content, thereby restoring control levels. These observations showed that amlodipine and manidipine reduced superoxide generation by the inhibition of the overexpression of NADPH oxidase in Ang II-stimulated endothelial cells. Such antioxidant effects of these agents might in turn have led to a decrease in the expression of VCAM-1, ICAM-1 and MCP-1. The salutary effects of calcium channel blockers in atherogenesis include the inhibition of the expression of LOX-1.

Hyperinsulinaemia increases the gene expression of endothelial nitric oxide synthase and the phosphatidylinositol 3-kinase/Akt pathway in rat aorta.

1. Hyperinsulinaemia has been reported to be an independent risk factor for cardiovascular diseases. Insulin stimulates both the phosphatidylinositol 3-kinase (PI3-K)/Akt and mitogen-activated protein kinase (MAPK) pathways. To investigate the direct effects of insulin on vascular tissues, we examined the gene and protein expression of insulin signalling molecules, endothelial nitric oxide synthase (eNOS) and MAPK in aortas obtained from established hyperinsulinaemic rats under deep urethane anaesthesia (1.2 g/kg, i.p.). 2. High plasma insulin levels significantly enhanced the gene and protein expression of eNOS in aortas. This was accompanied not only by increased mRNA levels of insulin receptor substrate (IRS)-1, IRS-2, PI3-K and Akt, but also by a high protein content of Akt and phospho-Akt (Ser473). 3. In contrast, MAPK mRNA levels were decreased in hyperinsulinaemic rats compared with normoinsulinaemic rats. 4. Insulin receptor mRNA levels were also lower in insulin-treated rats rather than controls. The overexpression of mRNA for vascular endothelial growth factor (VEGF) and insulin-like growth factor (IGF)-I receptor was also observed in aortas from hyperinsulinaemic rats. 5. To our knowledge, these data provide the first direct measurements of the mRNA of insulin signalling molecules and the downstream eNOS and MAPK. We conclude that hyperinsulinaemia itself can lead to the upregulation of eNOS and the PI3-K/Akt pathway in the vasculature and may also induce the overexpression of VEGF and IGF-I receptor genes.

Calcium channel blockades exhibit anti-inflammatory and antioxidative effects by augmentation of endothelial nitric oxide synthase and the inhibition of angiotensin converting enzyme in the N(G)-nitro-L-arginine methyl ester-induced hypertensive rat aorta: vasoprotective effects beyond the blood pressure-lowering effects of amlodipine and manidipine.

Long-acting dihydropyridine calcium channel blockades have been shown to limit the progression of atherosclerosis and decrease the incidence of cardiovascular events in humans and animals. To investigate the vasoprotective effects beyond the blood pressure-lowering effects of these agents, amlodipine (20 mg/kg/ day) and manidipine (10 mg/kg/day) were administered by gavage to N(G)-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats for 2 weeks. L-NAME treatment (0.7 mg/ml in drinking water) significantly decreased the gene and protein expression of endothelial nitric oxide synthase (eNOS) and increased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, vascular cell adhesion molecule-1 (VCAM-1), and monocyte chemoattractant protein-1 (MCP-1) mRNA levels in the aorta, as determined by Western blotting and reverse transcription (RT)-polymerase chain reaction (PCR). Amlodipine and manidipine normalized the decreased expression of eNOS gene and protein, and attenuated the overexpression of NADPH oxidase, VCAM-1, and MCP-1 mRNA. Furthermore, amlodipine and manidipine prevented the L-NAME-induced increase in the angiotensin converting enzyme (ACE) mRNA content, thereby restoring control levels in the aorta. On the other hand, hydralazine treatment had no such effect in L-NAME treated rats. Furthermore, the increased expression of manganese superoxide dismutase (Mn-SOD) by L-NAME treatment was not affected by amlodipine, manidipine, or hydralazine. We concluded that the direct anti-inflammatory and antioxidative effects of calcium channel blockades in the aorta of rats with L-NAME-induced hypertension were not likely to have been mediated by the blood pressure-lowering action of these agents, but instead these beneficial effects appear to have been mediated by an augmentation of eNOS expression and by the inhibition of the expression of ACE.