SMAD3 and renal fibrosis: The Klotho-derived peptide, KP1, mimicked the renal-protected function of full-length Klotho and ameliorated renal fibrosis of UUO and UIRI mice.363 SIS3 is a specific inhibitor abolishing Smad3 but not Smad2 phosphorylation and attenuates renal fibrosis in diabetic and obstructive nephropathy.364 GQ5 inhibited the phosphorylation of Smad3 by blocking the interaction of Smad3 with TGFBR1 and attenuated fibrotic lesions in obstructive nephropathy.365