Losartan ameliorates renal injury, hypertension, and adipocytokine imbalance in 5/6 nephrectomized rats

Renoprotective effects of the novel prostaglandin EP4 receptor-selective antagonist ASP7657 in 5/6 nephrectomized chronic kidney disease rats

Prostaglandins (PGs) are important lipid mediators of numerous physiologic and pathophysiologic processes in the kidney. PGE₂, the most abundant renal PG, plays a major role in renal physiology, including renin release and glomerular hemodynamics. We investigated the renoprotective properties of the novel PGE₂ EP4 receptor-selective antagonist ASP7657 in 5/6 nephrectomized rats, a chronic kidney disease (CKD) model. Eight weeks of repeated administration of ASP7657 (0.001-0.1 mg/kg) dose-dependently and significantly reduced urinary protein excretion and attenuated the development of glomerulosclerosis and tubulointerstitial damage, including fibrosis and inflammatory cell infiltration, without affecting blood pressure. Additionally, ASP7657 tended to have beneficial effects on renal function, as indicated by the decrease in plasma creatinine and blood urea nitrogen levels and attenuation of the decline in creatinine clearance (Ccr). The angiotensin II receptor blocker losartan (10 mg/kg) also showed these renoprotective effects while significantly reducing blood pressure. ASP7657 dose-dependently and significantly reduced the EP4 receptor agonist-induced increase in plasma renin activity, as assessed by angiotensin I release in normal rats. Additionally, ASP7657 attenuated hyperfiltration assessed by Ccr without changing the renal blood flow or blood pressure in diabetic rats. These results suggest that ASP7657 suppresses the progression of chronic renal failure by modulating renin release and improving renal hemodynamics, and may therefore be a promising therapeutic option for inhibiting the progression of CKD.

Effect of Shenkang granules on the progression of chronic renal failure in 5/6 nephrectomized rats

Shenkang granules (SKGs) are a Chinese herbal medicinal formula, consisting of rhubarb (Rheum palmatum L.), Salvia miltiorrhiza, milkvetch root [Astragalus membranaceus (Fisch.) Bunge] and safflower (Carthamus tinctorius L.). The aim of the present study was to investigate the effect of SKG on chronic renal failure (CRF) in 5/6 nephrectomized (5/6 Nx) rats. The rats were randomly divided into seven groups (n=10 per group) as follows: (i) 5/6 Nx (model group; 2.25 ml/kg/day normal saline); (ii) SKGL (low dose; 5/6 Nx treated with 2 g crude drug/kg/day SKG); (iii) SKGM (moderate dose; 5/6 Nx treated with 4 g crude drug/kg/day SKG); (iv) SKGH (high dose; 5/6 Nx treated with 8 g crude drug/kg/day SKG); (v) benazepril treatment group (5/6 Nx treated with 5 mg/kg/day benazepril); (vi) Shenkang injection (SKI) group (5/6 Nx with 13.3 ml/kg/day SKI); and (vii) sham-operated group (2.25 ml/kg/day normal saline). After 30 days, the levels of microalbumin, total protein, serum creatinine, blood urea nitrogen and serum lipid were found to be significantly decreased in the SKGL and SKGM rats, showing histological improvement compared with the untreated 5/6 Nx rats, as determined by hematoxylin and eosin, and Masson's trichrome staining. In addition, SKG was found to significantly improve the levels of glutathione peroxidase and reduce the damage caused by free radicals to the kidney tissues. Furthermore, SKG prevented the accumulation of extracellular matrix by decreasing the expression of collagen I and III and inhibiting the expression of matrix metalloproteinases-2 and -9 in the renal tissue, as determined by western blot analysis. SKG was also shown to decrease the concentrations of serum transforming growth factor-β₁, as determined by ELISA, and kidney angiotensin II, as determined using a radioimmunoassay kit. In conclusion, SKG was demonstrated to ameliorate renal injury in a 5/6 Nx rat model of CRF. Thus, SKG may exert a good therapeutic effect on CRF.

Up-regulation of intrarenal renin-agiotensin system contributes to renal damage in high-salt induced hypertension rats

BACKGROUND/AIMS

To investigate the change of intrarenal renin-agiotensin system (RAS) and its role in high-salt induced hypertension.

METHODS

Wistar rats were divided into normal-salt (NS), high-salt diet (HS) and high-salt diet with Losartan group (HS+L), for 6 weeks. Systolic blood pressure (SBP) was monitored. Blood and urine samples were collected every 2 weeks. Angiotensinogen (AGT) was measured by ELISA. AGT mRNA and protein were measured by real-time PCR and immunohistochemistry. Renin activity and angiotensin II (Ang II) were measured by radioimmunoassay.

RESULTS

HS versus NS group, SBP increased from 2(nd) week (P<0.05), urinary protein increased at 6(th) week (P<0.05). Although plasma renin, AGT and Ang II had no significant changes (P>0.05), renal cortex renin, AGT, and Ang II increased significantly in HS (P<0.05). In HS+L, Losartan failed to reduce SBP (P>0.05) but abolished the increase of proteinuria (P<0.01), renal cortex renin, AGT, Ang II and urinary AGT reduced (P<0.05) while plasma renin, AGT and Ang II enhanced (P<0.05) when compared with HS. Urinary AGT was positively correlated with renal AGT (r=0.592, P <0.01) and Ang II (r=0.726, P <0.01).

CONCLUSION

Inappropriate response of the renal RAS to a high salt diet may contribute to hypertension and renal damage, and urinary AGT could reflect intrarenal RAS activity.

The role of adiponectin in renal physiology and development of albuminuria

Adiponectin is secreted by the adipose tissue and is downregulated in states of obesity and insulin resistance. There is a growing body of evidence indicating that adiponectin has renoprotective effects and protects against the development of albuminuria in rodent experiments. Adiponectin crossing the glomerular filtration barrier possibly inhibits inflammation, fibrosis and oxidative stress in kidneys through activation of AMP-activated protein kinase. Moreover, microalbuminuria is a well established early sign of progressive cardiovascular and renal disease, even in subjects with preserved glomerular filtration rate. Studies investigating the relationship between serum adiponectin levels and urinary albumin excretion rate (UAE) have yielded conflicting data and the mechanisms underlying the interplay between adiponectin and albuminuria remain to be elucidated. This article constitutes a critical review attempting to clarify any remaining confusion about this matter. Furthermore, this article examines the clinical significance of adiponectin-albuminuria interplay, suggesting that adiponectin is possibly involved in the development of albuminuria that is associated with obesity, diabetes and cardiovascular disease and may mediate, at least in part, the actions of medical treatments that influence UAE, such as angiotensin-converting-enzyme inhibitors, angiotensin II receptor blockers, thiazolidinediones, fenofibrate and diet. Further studies to investigate more thoroughly the renoprotective role of adiponectin in the human setting should be carefully planned, focusing on causality and the possible influence of adiponectin on the development of albuminuria in specific clinical settings.