1. Department of Nephrology, Shenzhen University General Hospital, Shenzhen University, Shenzhen, Guangdong, China.
2. Department of Medicine and Therapeutics, and Li Ka Shing Institute of Health Sciences, the Chinese University of Hong Kong, Hong Kong, China.
3. School of Chinese Medicine, Li Ka Shing Faculty of Medicine, the University of Hong Kong, Hong Kong, China.
4. Guangdong-Hong Kong Joint Laboratory for Immunological and Genetic Kidney Disease, Guangdong Academy of Medical Science, Guangdong Provincial People's Hospital, Guangzhou, China.
5. Dongguan Key Laboratory of Medical Bioactive Molecular Developmental and Translational Research, Guangdong Provincial Key Laboratory of Medical Molecular Diagnostics, Guangdong Medical University, Dongguan, Guangdong, China.
6. CUHK-Guangdong Provincial People's Hospital Joint Research Laboratory for Immunological and Genetic Kidney Disease, the Chinese University of Hong Kong, Hong Kong, China.
Introduction and Aims: Elevated plasma levels of C-reactive protein (CRP) are closely associated with progressive renal injury in patients with chronic kidney disease (CKD). Here, we tested a hypothesis that CRP may promote renal fibrosis and inflammation via a TGF-β/Smad3-dependent mechanism.
Methods: Role and mechanisms of TGF-β/Smad3 in CRP-induced renal fibrosis and inflammation were examined in a mouse model of unilateral ureteral obstruction (UUO) induced in CRP Tg/Smad3 KO mice and in a rat tubular epithelial cell line in which Smad3 gene is stably knocked down (S3KD-NRK52E).
Results: We found that mice overexpressing the human CRP gene were largely promoted renal inflammation and fibrosis as evidenced by increasing IL-1β, TNF-α, MCP-1 expression, F4/80+ macrophages infiltration, and marked accumulation of α-smooth muscle actin (α-SMA), collagen I and fibronectin in the UUO kidney, which were blunted when Smad3 gene was deleted in CRPtg-Smad3KO. Mechanistically, we found that the protection of renal inflammation and fibrosis in the UUO kidney of CRPtg-Smad3KO mice was associated with the inactivation of CD32-NF-κB and TGF-β/Smad3 signaling.
Conclusion: In conclusion, Smad3 deficiency protects against CRP-mediated renal inflammation and fibrosis in the UUO kidney by inactivating CD32-NF-κB and TGF-β/Smad3 signaling.
Keywords: C-reactive protein, renal fibrosis and inflammation, TGF-β/Smad3, NF-κB, UUO