SuO029
PARKIN INHIBITS ACCELERATING SENESCENCE OF RENAL TUBULAR CELLS BY PROMOTING GATA4 DEGRADATION IN DIABETIC NEPHROPATHY

INTRODUCTION AND AIMS: Accelerating senescence of renal tubular epithelial cell (RTEC) plays a fundamental role in the pathogenesis of diabetic nephropathy (DN). Parkin, as an E3 ubiquitin ligase, can promote protein ubiquitination and degradation. Parkin gene mutation can accelerate neuron senescence in several neuropsychiatric disorders. GATA binding factor 4 (GATA4), as a substrate of E3 ubiquitin ligase, is a key regulatory factor for senescence phenotype. We investigated the role of Parkin in accelerating senescence of RTEC and its mechanism.

METHODS: 149 cases of patients with DN diagnosed by renal biopsy were recruited in our study. 32 normal kidney samples were obtained from renal carcinoma as control. Renal Parkin expression was detected by immunohistochemistry. The correlation between Parkin expression and renal pathological injury scores, renal function injury parameters were analyzed. In vivo, we generated Parkin overexpressed streptozotocin-induced DN mice using ultrasound- mediated adenovirus transfection. In vitro, knockdown and overexpression experiments were performed by parkin siRNA or Parkin overexpressed adenovirus in high glucose (HG) stimulated mouse primary RTEC. Moreover, we used co-immunoprecipitation and pull down experiments to evaluate the interaction of GATA4 with parkin.

RESULTS: Expression of parkin was gradually decreased with development of tubulointerstitial injury and negatively correlated with renal tissue injury scores (tubular atrophy and interstitial fibrosis, renal interstitial inflammation score), renal function injury parameter Scr. Parkin positive tubular epithelial cell did not express senescent marker P16. Compared to wild type DN mice, parkin overexpressed DN mice had lower renal tissue injury scores and better renal function. P16 and GATA4 expression of renal tubules were inhibited in parkin overexpressed DN mice. In vitro, parkin overexpression inhibited HG-induced GATA4 expression and RTEC senescence, whereas parkin knockdown enhanced GATA4 expression in RTECs under HG conditions. Furthermore, we found parkin co-immunoprecipitated with GATA4. Parkin overexpression increased GATA4 ubiquitination under HG conditions, whereas parkin knockdown decreased GATA4 ubiquitination.

CONCLUSIONS: Parkin may inhibit HG-induced RTEC senescence by promoting GATA4 ubiquitination and degradation. Parkin is a potential anti-senescence factor in the development of DN.