Plantaginis Semen polysaccharides ameliorate renal damage through regulating NLRP3 inflammasome in gouty nephropathy rats

Abstract

Gouty nephropathy (GN) is considered to be a prevalent renal disease and is an inflammatory event mainly induced by MSU crystals. Plantaginis Semen is a traditional Chinese herb that has been used in the treatment of gout, gouty arthritis and GN, but the mechanism and ingredients have been unclear. In this study, we explored and evaluated the preliminary structural characterizations of Plantaginis Semen polysaccharides (PSPs) and the activity of protecting against renal damage in GN rats. Three polysaccharide fractions, PSP-D, PSP-H and PSP-S, were sequentially extracted by different processes from the seed of Plantago asiatica L. The Fourier transform infrared spectral (FTIR) results showed that there were significant differences between PSP-S and the other two polysaccharides (PSP-D and PSP-H). PSP-D and PSP-H have pyrene monomers and linkages of β-glycosides in their structures, and PSP-S has furanoside in the molecular structure. The scanning electron microscope (SEM) images of three polysaccharides showed that PSP-D has a smooth surface and a small curve, PSP-H is block-like and uneven in magnitude, whereas PSP-S is sea-tent-like and its surface is very distinct from the others. Main components and molar ratios are also different. Rats were randomly divided into six groups (n^1/6 8 per group): the control group, model group, positive group, and three treatment groups (PSP-D, PSP-H and PSP-S). For all groups except the control group, rats were intragastrically administered the adenine suspension (50 mg kg^-1 d^-1) and fed with a high-yeast diet (15 g kg^-1 d^-1) for 28 days. On the 9th day, the control group and the model group were administered normal saline at the same time. Treatment groups were individually given corresponding drugs for 20 days. We found that PSPs could prevent renal damage, including decreasing the inflammatory response and regulating the (NOD)-like receptor protein 3 (NLRP3) protein in renal tissue. The underlying mechanism was related to NLRP3 inflammasome signal pathways, and it could take effect through the down-regulation of the protein expression levels of NLRP3, ASC and caspase-1 and inhibit the release of downstream inflammatory factors. PSPs are promising polysaccharides that could protect against renal injury through ameliorating renal inflammation in GN rats. Plantaginis Semen polysaccharides are potential functional food ingredients or pharmacological agents for treating GN in clinical practice.