Antiproteinuric effect of an endothelin-1 receptor antagonist in puromycin aminonucleoside-induced nephrosis in rat

RhoA/ROCK inhibition attenuates endothelin-1-induced elevated glomerular permeability to albumin, inflammation, and fibrosis

Endothelin-1 (ET-1) contributes to the development of kidney diseases. However, the underlying molecular mechanism is largely undefined. Here we sought to investigate the potential role of ET-1 receptors, ET_A and ET_B in the regulation of increased glomerular permeability and underlying signaling pathways post-ET-1 infusion. Male Sprague-Dawley rats were infused with ET-1 (2 pmol/kg per minute, i.v.) for four weeks, and the effect on glomerular permeability to albumin (P_alb) and albuminuria was measured. The selective ROCK-1/2 inhibitor, Y-27632, was administered to a separate group of rats to determine its effect on ET-1-induced P_alb and albuminuria. The role of ET_A and ET_B receptors in regulating RhoA/ROCK activity was determined by incubating isolated glomeruli from normal rats with ET-1 and with selective ET_A and ET_B receptor antagonists. ET-1 infusion for four weeks significantly elevated P_alb and albuminuria. Y-27632 significantly reduced the elevation of P_alb and albuminuria. The activities of both RhoA and ROCK-1/2 were increased by ET-1 infusion. Selective ET_B receptor antagonism had no effect on the elevated activity of both RhoA and ROCK-1/2 enzymes. Selective ET_A receptor and combined ET_A/ET_B receptors blockade restored the activity of RhoA and ROCK-1/2 to normal levels. In addition, chronic ET-1 infusion increased the levels of glomerular inflammatory and fibrotic markers. These effects were all attenuated in rats following ROCK-1/2 inhibition. These observations suggest that ET-1 contributes to increased albuminuria, inflammation, and fibrosis by modulating the activity of the ET_A-RhoA/ROCK-1/2 pathway. Selective ET_A receptor blockade may represent a potential therapeutic strategy to limit glomerular injury and albuminuria in kidney disease.

Combination CTLA-4 immunoglobulin treatment and ultrasound microbubble-mediated exposure improve renal function in a rat model of diabetic nephropathy

OBJECTIVE

This study explored the therapeutic impact of combined cytotoxic T lymphocyte-associated antigen 4 immunoglobulin (CTLA-4-Ig) treatment and microbubble-mediated exposure in a rat model of diabetic nephropathy (DN).

METHOD

We treated rats using CTLA-4-Ig and/or microbubble exposure. At 8 weeks post-intervention, key parameters were evaluated including blood biochemistry, damage to renal tissue, renal parenchymal elasticity, ultrastructural changes in podocytes, and renal parenchymal expression of CD31, CD34, IL-6, Fn, Collagen I, Talin, Paxillin, α3β1, podocin, nephrin, and B7-1.

RESULT

We found that renal function in the rat model of DN can be significantly improved by CTLA-4-Ig and CTLA-4-Ig + ultrasound microbubble treatment. Treatment efficacy was associated with reductions in renal parenchymal hardness, decreases in podocyte reduction, decreased IL-6, Fn and Collagen I expression, increased Talin, Paxillin and α3β1 expression, elevated podocin and nephrin expression, and decreased B7-1 expression. In contrast, these treatments did not impact CD31 or CD34 expression within the renal parenchyma.

CONCLUSION

These findings clearly emphasize that CTLA-4-Ig can effectively prevent podocyte damage, inhibiting inflammation and fibrosis, and thereby treating and preventing DN. In addition, ultrasound microbubble exposure can improve the ability of CTLA-4-Ig to pass through the glomerular basement membrane in order to access podocytes such that combination CTLA-4-Ig + microbubble exposure treatment is superior to treatment with CTLA-4-Ig only.