The Polysaccharide of Ligustrum Lucidum Ait. Protected from Renal Fibrosis by Interfering with Angiotensin II Signaling

Abstract

BackgroundA number of preclinical advances have indicated the cellular and molecular mechanisms underlying renal fibrosis, such as the signaling of angiotensin II (Ang II), which is a bioactive peptide in renin‐angiotensin system. As one of kidney‐tonifying herbs, Fructus Ligustri Lucidi (FLL), the fruit of Ligustrum lucidum Ait. (Oleaceae) recorded as a tonic and dietary supplement, is a commonly prescribed component in traditional kidney‐tonifying herbal formula. This study aimed to clarify the polysaccharide component in FLL and investigate its potential role in preservation against renal fibrosis.MethodsThe crude polysaccharide of FLL was prepared and deproteinized by Sevag reagent. After lyophilization, the DEAE‐cellulose DE52 column and the Sephacryl S‐200 HR column were used for further isolation and purification of homogenous polysaccharide. The mice with unilateral ureteral obstruction (UUO) underwent daily intraperitoneal injection with FLL polysaccharide starting 7 days before UUO surgery until day 7 after surgery. The murine mesangial SV40‐MES13 cells were treated with vehicle, Ang II (10‐7 M) either with the absence and presence of angiotensin type I receptor blocker (ARB) (10‐6M), or with low dose (50 μg/mL, Poly‐L) and high dose (200 μg/mL, Poly‐H) of FLL polysaccharide.ResultsThe purified homogenous polysaccharide (Poly) was explored from FLL and the carbohydrate content was 97.45%. A hypothetical structure for Poly was proposed considering the comprehensive data of methylation, monosaccharides, and NMR analyses. Treatment of UUO mice with Poly decreased kidney index and ameliorated glomerular sclerosis and interstitial fibrosis, as well as down‐regulated the expression of profibrogenic factor VEGF and matrix fibrotic protein fibronectin (FN). Furthermore, as the same effect to ARB, the pre‐incubation with Poly alleviated the Ang II‐induced up‐regulation of FN in mesangial cells by immunofluoresence staining. The protein expressions of FN and proinflammatory factors like MCP‐1 and Rantes were significantly lower in Poly‐treated cell group than those in Ang II treatment group.ConclusionThe polysaccharide of Ligustrum lucidum Ait. was accurately explored with structure clarification. This polysaccharide component repressed angiotensin II‐induced fibrotic phenotype of renal mesangial cells and exerted beneficial effects on kidney of UUO mice.