Renal caveolin-1 expression in children with unilateral ureteropelvic junction obstruction.

Caveolae are plasma membrane invaginations that contain a variety of signal transduction molecules and receptors for growth factors and cytokines. This study was performed to examine the in vivo expression and localization of caveolin-1 in kidneys from 19 children who underwent surgery release of ureteropelvic junction obstruction (UPJO) in relation to renal function and degree of tubulointerstitial fibrosis. Renal biopsies were carried out at the time of surgery for obstruction release. Kidney tissue from children of similar age removed because of carcinoma was used as control. Expression of caveolin-1 at the protein level in renal tissue and urine was demonstrated in patients with technetium 99 m labeled diethylene triamine pentaacetate ((99)Tc DTPA) renal scan 28.8+/-2% and increased tubular interstitial fibrosis in seven patients at the time of obstruction release. Colocalization staining of AT(1) angiotensin II receptor with caveolin-1 in basolateral membrane of epithelial tubule cells, enhanced AT(1) messenger ribonucleic acid (mRNA) and decreased endothelial nitric oxide synthase (eNOS), were shown in these patients. In contrast, absence of association of caveolin-1 with AT(1) receptor expression in proximal and collecting tubule membranes with AT(1) receptor mRNA and eNOS mRNA expression near control were demonstrated in 12 patients, with (99)Tc DTPA renal scan 39.7+2.1% and no evidence of tubulointerstitial fibrosis. From our results, the role of caveolin-1 as a factor contributing to the severity of the tubulointerstitial process resulting from obstructive nephropathy could be suggested.

Heat shock protein 70 expression is associated with inhibition of renal tubule epithelial cell apoptosis during recovery from low-protein feeding.

The cellular stress response can mediate cellular protection through expression of heat shock protein (Hsp70), which can interfere with the process of apoptotic cell death. Factors regulating renal epithelial cell apoptosis include angiotensin II. In the present study, we have examined the relationship between the Hsp70 expression and the apoptotic pathway in the kidneys from low-protein-fed rats (8% protein). The possible cytoprotective role of Hsp70 has been evaluated during low-protein feeding and after reincorporation of 24% protein in the diet. The effect of angiotensin II AT1 receptor inhibition has also been studied. Rats were fed with a low-protein (LP) diet (8% protein) for 14 days, and then the animals were recovered by means of a normal protein diet (24% protein) (RP) for 14, 21, and 30 days, and control rats received 24% protein (NP) in the diet. LP and NP rats treated with Losartan (10 mg/kg) were also evaluated. The following methods were performed on the kidneys: terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling assay for apoptosis, reverse transcriptase-polymerase chain reaction assay for AT1, Bax, and Bcl-2 messenger ribonucleic acid (mRNA) expression, and immunohistochemical and Western blot for Hsp70 and caspase 3 protein expression and activity. In the LP group, the cells of the medullary ducts (MDs) showed increased apoptosis associated with weak immunoreaction for Hsp70 and decreased Hsp70 protein levels. In these animals, enhanced proapoptotic ratio Bax/Bcl-2 linked to decreased procaspase 3 protein levels with increased caspase 3 activation were demonstrated. A cytoprotection attributed to Hsp70 could be noted in the RP rats after 21 days of reincorporation of the normal diet, and in the LP-fed group treated with Losartan. In these cases, the MD cells displayed decreased apoptosis and increased Hsp70 expression in colocalization staining, and high Hsp70 levels in cytosolic fraction. A decreased proapoptotic ratio Bax/Bcl-2, associated with increased Bcl-2 mRNA, was also observed. Our results provide evidence for an antiapoptotic, cytoprotective effect of Hsp70 in kidney MD cells of rats with LP intake, when the animals were recovered with 24% protein in diet and after angiotensin II AT1 receptor inhibition. Angiotensin II seems to play a role in the pathogenesis of tubule epithelial cell apoptosis during LP feeding.