Abstract: FR-PO360

Sonic Hedgehog Promotes Kidney Injury by Activating Renin-Angiotensin System via a Non-Canonical Pathway

Session Information

Category: Chronic Kidney Disease (Non-Dialysis)

  • 308 CKD: Mechanisms of Tubulointerstitial Fibrosis

Authors

  • Wu, Songzhao, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
  • Zhou, Lili, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
  • Wang, Chunhong, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
  • Liu, Youhua, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Background

Sonic hedgehog (Shh) is a lipid-modified glycoprotein that plays a crucial role in embryonic development. Earlier studies indicate that Shh is a tubule-derived growth factor that specifically targets interstitial fibroblasts via a paracrine mechanism after various kidney injuries. Using hedgehog-responding reporter mice, studies show that kidney tubular epithelial cells are not responsive to hedgehog ligands via Gli-dependent canonical pathway. Whether Shh can target tubular epithelium via other mechanisms, however, remains to be defined.

Results

In this study, we investigated this issue using both in vitro and in vivo approaches. We found that in cultured kidney proximal tubule cells (HKC-8), recombinant Shh protein induced multiple components of renin-angiotensin stystem (RAS), including renin, angiotensin-converting enzyme, and angiotensin II type 1 receptor (AT1). Shh also activated MAPK by inducing ERK, JNK and p38 phosphorylation, as well as its upstream PLC phosphorylation and activation. This cascade of events was dependent on Smo receptor, as either cyclopamine (CPN), a small molecule Smo inhibitor, or MAPK inhibitors abolished the Shh-mediated activation of MAPK and induction of RAS components, suggesting that Shh activates RAS via Gli-independent, MAPK-dependent non-canonical pathway. In vivo, overexpression of Shh aggravated the glomerular injury, interstitial matrix proteins expression and deposition, and renal fibrosis at 6 weeks after 5/6 nephrectomy. Shh also promoted the activation of PLC and MAPK and induction of multiple RAS proteins, and elevated blood pressure. However, CPN therapy attenuated glomerular lesions, reduced renal fibrosis. CPN also inhibited renal MAPK activation, repressed RAS protein expression and normalized blood pressure.

Conclusion

Collectively, these studies demonstrate that tubule-derived Shh can target tubular epithelium by inducing RAS protein expression via PLC/MAPK-dependent non-canonical pathway. Our results indicate that blockade of Shh signaling can repress multiple RAS genes, thereby leading to amelioration of kidney injury.

Funding

  • NIDDK Support