Pengyu Cao

Atorvastatin upregulates nitric oxide synthases with Rho-kinase inhibition and Akt activation in the kidney of spontaneously hypertensive rats

Objective 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, statins reduce blood pressure and have beneficial effects in cardiovascular and kidney diseases. The present study examined the effect of chronic treatment with atorvastatin (ATV) on the expression of nitric oxide synthase (NOS) and the activity of Rho-kinase and Akt in the kidney of spontaneously hypertensive rats (SHRs). Methods SHRs were treated with ATV for 8 weeks and the SBP was measured. The expressions of endothelial, neuronal and inducible NOS (eNOS, nNOS and iNOS, respectively) proteins in the kidney were examined by immunoblot analysis. The activity of eNOS, Rho-kinase and Akt in the kidney was examined by assessing the phosphorylation of eNOS, ezrin/radixin/moesin (ERM) and Akt, respectively. Results ATV reduced the SBP without changing the plasma cholesterol levels. ATV increased eNOS expression in the cortex and medulla and nNOS expression in the medulla, whereas it did not affect iNOS expression. Although it upregulated eNOS expression in the kidney, ATV decreased the levels of phosphorylated eNOS in the cortex and did not affect the ratio of phosphorylated eNOS to total eNOS in the medulla. ATV also inhibited Rho-kinase activity and enhanced Akt activity in the kidney of SHRs. Conclusion ATV upregulates eNOS and nNOS expressions with Rho-kinase inhibition and Akt activation in the kidney of SHRs. The renal nitric oxide system, Rho-kinase and Akt may contribute to the antihypertensive and renoprotective effects of statins.

Exercise training upregulates nitric oxide synthases in the kidney of rats with chronic heart failure.

There is an interaction between heart and kidney diseases, which is a condition termed cardiorenal syndrome. Exercise training has cardioprotective effects, involving upregulation of endothelial (e) nitric oxide synthase (NOS) in the cardiovascular system. However, the effects of exercise training on NOS in the kidney with heart disease are unknown. The aim of the present study was to investigate whether exercise training upregulates NOS in the kidney, left ventricle and aorta of rats with chronic heart failure (CHF). Male Sprague‐Dawley rats underwent left coronary artery ligation (LCAL) to induce CHF and were randomly assigned to sedentary or treadmill exercise groups 4 weeks after LCAL. Three days after exercising for 4 weeks, urine samples were collected for 24 h and blood samples were collected following decapitation. Nitric oxide synthase activity and protein expression were examined. Significant interactions between CHF and exercise training were observed on parameters of cardiac and renal function. Exercise training improved cardiac function, decreased plasma B‐type natriuretic peptide levels, decreased urinary albumin excretion and increased creatinine clearance in CHF rats. Nitric oxide synthase activity, eNOS expression and neuronal (n) NOS expression were significantly decreased in the left ventricle and kidney of CHF rats. Exercise training significantly increased NOS activity and eNOS and nNOS expression. Upregulation of NOS in the kidney and left ventricle may contribute, in part, to the renal and cardiac protective effects of exercise training in cardiorenal syndrome in CHF rats.

Chronic Running Exercise Alleviates Early Progression of Nephropathy with Upregulation of Nitric Oxide Synthases and Suppression of Glycation in Zucker Diabetic Rats

Exercise training is known to exert multiple beneficial effects including renal protection in type 2 diabetes mellitus and obesity. However, the mechanisms regulating these actions remain unclear. The present study evaluated the effects of chronic running exercise on the early stage of diabetic nephropathy, focusing on nitric oxide synthase (NOS), oxidative stress and glycation in the kidneys of Zucker diabetic fatty (ZDF) rats. Male ZDF rats (6 weeks old) underwent forced treadmill exercise for 8 weeks (Ex-ZDF). Sedentary ZDF (Sed-ZDF) and Zucker lean (Sed-ZL) rats served as controls. Exercise attenuated hyperglycemia (plasma glucose; 242 ± 43 mg/dL in Sed-ZDF and 115 ± 5 mg/dL in Ex-ZDF) with increased insulin secretion (plasma insulin; 2.3 ± 0.7 and 5.3 ± 0.9 ng/mL), reduced albumin excretion (urine albumin; 492 ± 70 and 176 ± 11 mg/g creatinine) and normalized creatinine clearance (9.7 ± 1.4 and 4.5 ± 0.8 mL/min per body weight) in ZDF rats. Endothelial (e) and neuronal (n) NOS expression in kidneys of Sed-ZDF rats were lower compared with Sed-ZL rats (p<0.01), while both eNOS and nNOS expression were upregulated by exercise (p<0.01). Furthermore, exercise decreased NADPH oxidase activity, p47phox expression (p<0.01) and α-oxoaldehydes (the precursors for advanced glycation end products) (p<0.01) in the kidneys of ZDF rats. Additionally, morphometric evidence indicated renal damage was reduced in response to exercise. These data suggest that upregulation of NOS expression, suppression of NADPH oxidase and α-oxoaldehydes in the kidneys may, at least in part, contribute to the renal protective effects of exercise in the early progression of diabetic nephropathy in ZDF rats. Moreover, this study supports the theory that chronic aerobic exercise could be recommended as an effective non-pharmacological therapy for renoprotection in the early stages of type 2 diabetes mellitus and obesity.

Effects of exercise training on nitric oxide synthase in the kidney of spontaneously hypertensive rats.

Exercise training is known to have antihypertensive effects in humans and animals with hypertension, as well as to exhibit renal protective effects in animal models of hypertension and chronic renal failure. However, the mechanisms regulating these effects of exercise training remain unclear. The present study examined the effects of exercise training on nitric oxide synthase (NOS) in the kidneys of spontaneously hypertensive rats (SHR) and normotensive Wistar‐Kyoto (WKY) rats. Male SHR and WKY rats were randomly divided into a sedentary group and a treadmill exercise group for 8 weeks. Systolic blood pressure (SBP) was measured every 2 weeks by the tail‐cuff method and urine and blood samples were collected after the exercise protocol. Nitric oxide synthase activity and protein expression and endothelial (e) NOS phosphorylation in the kidney were examined. Exercise training significantly lowered SBP, decreased urinary albumin excretion, thiobarbituric acid‐reactive substances levels and renal NADPH oxidase activity, and increased creatinine clearance in SHR. Exercise training significantly increased plasma and urinary nitrate/nitrite, NOS activity and eNOS and neuronal NOS expression, but decreased eNOS phosphorylation at Ser1177 and Thr495 in kidneys of SHR and WKY rats. Renal NOS may be involved in the antihypertensive and renal protective effects of exercise training in SHR.

Endogenous hydrogen peroxide up-regulates the expression of nitric oxide synthase in the kidney of SHR.

Background and method Both nitric oxide synthase (NOS) expression and oxidative stress are elevated in the tissues of spontaneously hypertensive rats (SHR) compared with Wistar–Kyoto rats (WKY). The purpose of the present study was to determine the relationship between the endothelial and neuronal NOS (eNOS and nNOS) expression and oxidative stress in the kidney of SHR and WKY. Results Plasma and urinary hydrogen peroxide (H2O2) and nitrate/nitrite (NOx), the renal NADPH oxidase activity and eNOS and nNOS expressions were all higher in SHR than in WKY. Although the treatment with either the NADPH oxidase inhibitor, apocynin or the superoxide dismutase mimetic, tempol for 8 weeks decreased the systolic blood pressure (SBP) and inhibited the renal NADPH oxidase activity in SHR, apocynin decreased but tempol increased the plasma and urinary H2O2 and NOx and the eNOS and nNOS expressions in the renal cortex and medulla of SHR. In contrast to SHR, neither apocynin nor tempol affected these parameters in WKY. H2O2 administered intravenously for 1 week in WKY increased plasma and urinary H2O2 and NOx and the eNOS and nNOS expressions in the renal cortex and medulla in a dose-dependent manner without changing the renal NADPH oxidase activity. Conclusion These results indicate that oxidative stress up-regulates the NOS expression in the kidney of SHR compared with WKY; and that endogenous H2O2 is a mediator of the up-regulation of the NOS expression in the kidney of SHR.

Disorder of fatty acid metabolism in the kidney of PAN-induced nephrotic rats

Proteinuria is considered to play an essential role in the progression of tubulointerstitial damage, which causes end-stage renal disease. Fatty acid-binding albumins are filtered through glomeruli and reabsorbed into proximal tubular epithelial cells (PTECs). However, the role of fatty acid metabolism associated with albuminuria in the development of tubulointerstitial damage remains unclear. Thus, the present study was designed to determine the changes of fatty acid metabolism in the nephrotic kidney. To induce nephrotic syndrome, Sprague-Dawley rats (SDRs) and Nagase analbuminemic rats (NARs) with inherited hypoalbuminemia were treated with a single injection of puromycin aminonucleoside (PAN). In SDRs, PAN treatment induced massive proteinuria and albuminuria and caused tubular damage, apoptosis, and lipid accumulation in PTECs. Among the enzymes of fatty acid metabolism, expressions of medium-chain acyl-CoA dehydrogenase (MCAD) and cytochrome P-450 (CYP)4A significantly decreased in PTECs of PAN-treated SDRs. Expressions of peroxisome proliferator-activated receptor (PPAR)-γ coactivator (PGC)-1α and estrogen-related receptor (ERR)α also significantly decreased, without changes in the expression of PPAR-α. In NARs, PAN treatment induced proteinuria but not albuminuria and did not cause tubular damage, apoptosis, or lipid accumulation. Expressions of MCAD, PGC-1α, or ERRα did not change in the kidney cortex of PAN-treated NARs, but the expression of CYP4A significantly decreased. These results indicate that massive albuminuria causes tubular damage and lipid accumulation with the reduction of MCAD, CYP4A, PGC-1α, and ERRα in PTECs.

167 EFFECTS OF EXERCISE TRAINING ON NITRIC OXIDE SYNTHASES EXPRESSION AND PHOSPHORYLATION IN THE KIDNEY OF SPONTANEOUSLY HYPERTENSIVE RATS

Objective: Exercise training (Ex) shows antihypertensive effects in many epidemiological studies and also has renal protective effects in animal models with hypertension and chronic renal failure. However, the mechanisms of these effects of Ex are not fully elucidated. The present study examined the effects of Ex on the nitric oxide production in the kidneys of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Methods: Male SHR and WKY were divided randomly each into two groups, a sedentary group and an Ex group. Ex with treadmill was performed by the Ex group for 8 weeks. The expression and phosphorylation of nitric oxide synthase (NOS) proteins in the kidney were examined using Western blot analysis. Results: Ex lowered the systolic blood pressure with decreasing plasma creatinine and increasing creatinine clearance in SHR but not in WKY. Ex increased the plasma and urine nitrate/nitrite in both SHR and WKY. Ex increased the expression of endothelial and neuronal NOS (eNOS and nNOS) proteins and decreased the phosphorylation of eNOS at Ser-1177 and Thr-495 in the renal cortex, the outer medulla and inner medulla of both SHR and WKY. Conclusions: Ex increases the nitric oxide production and renal NOS expression. The increases of the nitric oxide production and NOS expression may be involved in the antihypertensive and renal protective effects of the Ex.

258 SOD MIMETIC TEMPOL ENHANCES EXERCISE TRAINING-INDUCED NITRIC OXIDE SYNTHASES IN THE KIDNEY OF SPONTANEOUSLY HYPERTENSIVE RATS

Background: The exercise training (Ex) and superoxide dismutase (SOD) mimetic tempol have antihypertensive effects in spontaneously hypertensive rats (SHR). To clarify the mechanism of antihypertensive and renal-protective effect of the Ex, the present study tested the effects of the Ex and tempol on the NOS expression in the kidney of SHR. Methods: 5-week-old, male SHRs were randomly divided into four groups; a control group, an Ex group, a tempol-treated (Tmp) group and an Ex+Tmp group. The treadmill running (20 m/min, 60 min/day, 6 times/week) was performed to the Ex and the Ex+Tmp groups, and tempol in drinking water (1 mmol/l) was given to the Tmp and the Ex+Tmp groups. H2O2 and NO2/NO3 (NOx) in plasma and urine were measured by Amplex Red and Griess reagents. The expression of endothelial and neuronal NOS (eNOS and nNOS) proteins in aorta and kidney sections was analyzed using Western blots. Results: Ex and tempol attenuated the development of hypertension while deceasing the renal NADPH oxidase activity in SHR. Ex and tempol also upregulated the eNOS and nNOS expressions in the kidneys of SHR with the increased plasma and urinary H2O2 and NOx. Furthermore, the effects of the combination therapy with Ex and tempol on these factors were cumulate in SHR. Conclusions: These results indicate that tempol enhances the Ex-induced antihypertensive and renal-protective effects through the upregulation of NOS expression and NO production in SHR. H2O2 may mediate these effects of the Ex and tempol in SHR.