Endothelin receptors in the kidney of patients with proteinuric and non-proteinuric nephropathies

Endothelin Inhibitors in Chronic Kidney Disease: New Treatment Prospects

The endothelin system is reported to play a significant role in glomerular and tubulointerstitial kidney disease. In the kidney, endothelins are produced in mesangial cells and the glomerular basement membrane by the endothelium and podocytes. The endothelin system regulates glomerular function by inducing proliferation, increasing permeability and in effect proteinuria, and stimulating inflammation, tubular fibrosis, and glomerular scarring. Endothelin A receptor antagonists have been proven to delay the progression of chronic kidney disease and play a protective role in immunoglobulin A nephropathy, focal segmental glomerulosclerosis, and diabetic nephropathy. There are several ongoing research studies with ETAR antagonists in nondiabetic nephropathy, Alport disease, vasculitis and scleroderma nephropathy, which results are promising. Some reports suggest that the endothelin system might contribute to ischemia-reperfusion injury, acute graft rejection and deterioration of graft function. Endothelin inhibition in renal transplantation and its influence on graft survival is the future direction needing further research. The most frequent side effects associated with ETAR antagonists is fluid retention. Additionally, it should be considered if selective ETAR antagonists therapy needs to be co-administered with sodium-glucose co-transporter 2 inhibitors, renin-angiotensin-aldosterone inhibitors or diuretics and which patients should be recruited to such treatment to minimize the risk of adverse outcomes.

Evolving spectrum of diabetic nephropathy

Diabetes remains an important health issue as more patients with chronic and uncontrolled diabetes develop diabetic nephropathy (DN), which classically presents with proteinuria followed by a progressive decrease in renal function. However, an increasing proportion of DN patients have a decline in kidney function and vascular complications without proteinuria, known as non-proteinuric DN (NP-DN). Despite the increased incidence of NP-DN, few clinical or experimental studies have thoroughly investigated the pathophysiological mechanisms and targeted treatment for this form of DN. In this review, we will examine the differences between conventional DN and NP-DN and consider potential pathophysiological mechanisms, diagnostic markers, and treatment for both DN and NP-DN. The investigation of the pathophysiology of NP-DN should provide additional insight into the cardiovascular factors influencing renal function and disease and provide novel treatments for the vascular complications seen in diabetic patients.

Inhibition of heparanase protects against chronic kidney dysfunction following ischemia/reperfusion injury

Renal ischemia/reperfusion (I/R) injury occurs in patients undergoing renal transplantation and with acute kidney injury and is responsible for the development of chronic allograft dysfunction as characterized by parenchymal alteration and fibrosis. Heparanase (HPSE), an endoglycosidase that regulates EMT and macrophage polarization, is an active player in the biological response triggered by ischemia/reperfusion (I/R) injury. I/R was induced in vivo by clamping left renal artery for 30 min in wt C57BL/6J mice. Animals were daily treated and untreated with Roneparstat (an inhibitor of HPSE) and sacrificed after 8 weeks. HPSE, fibrosis, EMT-markers, inflammation and oxidative stress were evaluated by biomolecular and histological methodologies together with the evaluation of renal histology and measurement of renal function parameters. 8 weeks after I/R HPSE was upregulated both in renal parenchyma and plasma and tissue specimens showed clear evidence of renal injury and fibrosis. The inhibition of HPSE with Roneparstat-restored histology and fibrosis level comparable with that of control. I/R-injured mice showed a significant increase of EMT, inflammation and oxidative stress markers but they were significantly reduced by treatment with Roneparstat. Finally, the inhibition of HPSE in vivo almost restored renal function as measured by BUN, plasma creatinine and albuminuria. The present study points out that HPSE is actively involved in the mechanisms that regulate the development of renal fibrosis arising in the transplanted organ as a consequence of ischemia/reperfusion damage. HPSE inhibition would therefore constitute a new pharmacological strategy to reduce acute kidney injury and to prevent the chronic pro-fibrotic damage induced by I/R.

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

BackgroundThe pathogenesis of idiopathic nephrotic syndrome (INS) remains unclear, although recent studies suggest endothelin 1 (ET-1) and CD80 of podocytes are involved. We investigated the potential of antagonist to ET-1 receptor type A (ETRA) as therapeutic agent through the suppression of CD80 in a rat model of INS.MethodsPuromycin aminonucleoside (PAN) was injected to Wister rats to induce proteinuria: some were treated with ETRA antagonist and others were treated with 0.5% methylcellulose. Blood and tissue samples were collected. Quantitative PCR was used to determine the expression of Toll-like receptor-3 (TLR-3), nuclear factor-κB (NF-κB), CD80, talin, ETRA, and ET-1 in the kidney. To confirm the level of CD80 protein expression, immunofluorescence staining and western blot analysis of the renal tissue were performed.ResultsAmount of proteinuria in the treatment group was significantly lower than the other groups. The same-day body weight, serum creatinine values, and blood pressure were not significantly different. ETRA antagonist restores podocyte foot process effacement as well as the aberrant expression of TLR-3, nuclear factor-κB (NF-κB), and CD80 in PAN-injured kidneys.ConclusionsThe ETRA antagonist may be promising drug for INS as it showed an antiproteinuric effect. Its action was considered to be through suppression of CD80 expression on podocytes.

Endothelin-1 and endothelin a receptor immunoreactivity is increased in patients with diabetic nephropathy

BACKGROUND

Endothelin-1 (ET-1) is associated with progression of renal disease, acting as a vasoconstrictor and growth factor for mesangial cells. ET-1 and endothelin A receptor (ET-RA) might have a role in the development of diabetic nephropathy (DN). The aims of this study were to determine ET-1 and ET-RA expressions in patients with DN and to correlate these expressions with renal function and proteinuria.

MATERIALS AND METHODS

This is a cross-sectional study comprising 13 patients with type 2 diabetes mellitus and DN, 10 patients with proteinuric IgA nephropathy, and 13 samples of normal kidney from tumor nephrectomies. Demographic and selected data were collected from medical charts. The distribution and intensity of ET-1 and ET-RA immunostaining in renal biopsies were determined by immunohistochemistry and these correlated with the estimated glomerular filtration rate (eGFR) and proteinuria.

RESULTS

Patients with DN and IgA nephropathy on biopsy had markedly increased staining for ET-1 in endothelial cells of glomerular and peritubular capillaries when compared with controls (p < 0.001). ET-RA staining was also more intense and more diffuse in DN and IgA nephropathy than in controls (p = 0.019) and was restricted to tubular epithelial cells. A positive correlation was observed between ET-1 expression and proteinuria (r = 0.634, p = 0.027), but both ET-1 and ET-RA expressions did not correlate with eGFR.

CONCLUSION

In this preliminary report, the higher expressions of ET-1 and ET-RA found in both DN and IgA nephropathy suggest a potential role for the endothelin system in DN as well as in other nondiabetic glomerular diseases.

Endothelin-1 levels and albuminuria in patients with type 2 diabetes mellitus

AIM

To evaluate the relationship of plasma endothelin-1 (ET-1) levels, a marker of endothelial dysfunction, and urinary albumin excretion in patients with type 2 diabetes mellitus (DM).

METHODS

Cross-sectional study was conducted in 279 patients (132 males, mean age: 58.7+/-11.0 years, mean DM duration: 11.3+/-8.1 years). Urinary albumin excretion, ET-1, and insulin were measured. Insulin sensitivity was estimated by homeostasis model assessment (HOMA-ir) index.

RESULTS

ET-1 was associated with urinary albumin excretion after controlling for age, gender, body mass index, blood pressure, HbA1c test, and total cholesterol (R=0.436; adjusted R(2)=0.190, P<0.01). Furthermore, there was a progressive increase in plasma ET-1 levels from patients with normoalbuminuria (n=187, 0.92+/-0.50pg/ml), microalbuminuria (n=68, 1.13+/-0.52pg/ml) to macroalbuminuria (n=24, 1.93+/-1.10pg/ml, P<0.01).

CONCLUSION

There is an independent association of plasma ET-1 levels with urinary albumin excretion. In addition, plasma ET-1 levels started to increase in the normal values of urinary albumin excretion suggesting that in patients with type 2 DM endothelial dysfunction is already present, in urinary albumin excretion values considered normal.