Knockdown of Periostin Attenuates 5/6 Nephrectomy-induced Intrarenal Renin-angiotensin System Activation, Fibrosis, and Inflammation in Rats

To simulate clinical features in human chronic kidney disease (CKD), SD rats were subjected to 5/6 nephrectomy in this study. We found that periostin gene was upregulated in the remnant kidneys using Agilent gene microarrays, and further explored its role via in vivo and in vitro experiments. Intrarenal renin-angiotensin system (RAS) was activated in 5/6 nephrectomized rats and partly deactivated by injection of adenoviruses encoding short hairpin RNA against periostin (sh-periostin). Renal fibrosis in nephrectomized rats and profibrotic transforming growth factor-β-induced epithelial-mesenchymal transition (EMT) and ERK1/2 activation in NRK-52E cells were suppressed by sh-periostin. Moreover, knockdown of periostin decreased the generation of Interleukin 6 (IL6) and tumor necrosis factor-α (TNF-α) and accelerated p62 degradation in the remnant kidneys. Both HK-2 cells treated with recombinant periostin and NRK-52E cells infected with adenoviruses expressing periostin produced more IL6 and TNF-α than control cells and displayed impaired autophagy as evidenced by inhibition of LC3II to LC3I conversion, Beclin 1 expression, and p62 degradation. By treating cells with rapamycin, an inhibitor of mamalian target of rapamycin known to activate autophagy, we noted that periostin-induced inflammation was inhibited. Additionally, HK-2 cells transfected with periostin overexpression plasmid generated more CCL2 and CXCL10, two important chemotactic factors, than untransfected cells. Conditioned medium from HK-2 cells overexpressing periostin augmented chemotaxis of THP-1 macrophages. Collectively, our work demonstrates that knockdown of periostin attenuates 5/6 nephrectomy-induced intrarenal RAS activation, fibrosis, and inflammation in rats. These findings advance our understanding of periostin's role in CKD induced by nephron loss.