Endoplasmic reticulum stress-related apoptosis pathway is involved in unilateral ureteral obstruction-induced renal interstitial fibrosis in rats / 中华肾脏病杂志

ABSTRACT

Objective To investigate the effect of endoplasmic reticulum stress (ERS)-associated apoptosis on renal interstitial fibrosis induced by unilateral ureteral obstruction (UUO) in rats. Methods Eighteen healthy male Wistar rats undergoing UUO were sacrificed at 3,7,14 days after operation. Additional seven rats underwent sham operation. Histological changes were observed by HE and Masson staining. Immunohistochemistry was performed on renal tissue for α-smooth muscle actin (α-SMA). Chromatometry was used to detect the content of hydroxyproline. Apoptosis cells were determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and the electrophoresis analysis of genome DNA. The mRNA expression of glucose-regulated protein 78 (GRP78), which are important markers of ERS, were detected by RT-PCR. Western blotting was used to assess the protein level of GRP78 and cysteinyl aspartate specific proteinase-3 (caspase-3). Results Compared with sham operation group, the degree of renal interstitial and the level of hydroxyproline content of UUO group increased significantly (P<0.05). Immunohistochemistry staining indicated that a-SMA extensively expressed in renal tubular and interstitial cells. The apoptotic cells in the renal tubular and interstitium were continuously increased from day 3 to the end of experiment of UUO group. As early as 3 days after surgery, the mRNA level of GRP78 in UUO group increased compared with sham operation group (P<0.01), while the protein expression increased on day 7 after surgery (P<0.01). Prolonged ERS triggered apoptosis, the protein expression of caspase-3 increased significantly on day 3 after surgery (P< 0.05), and the expression sustained high level during the experiment afterwards. There was a positive correlation between GRP78 protein expression and hydroxyproline content (r =0.657, P< 0.01) as well as caspase-3 protein expression (r=0.714, P<0.01). Conclusions UUO induces a significant up-regulation in endoplasmic reticulum molecular chaperones at early stage, indicating that ERS response is activated in the rat kidney. Prolonged ERS can lead to renal tubular and interstitial cell apoptosis, and caspase-3-mediated ERS associated apoptosis may contribute to the fibrosis.