Athelia Rolfsii Exopolysaccharides Protection Against Liver And Kidney Injury In Lead-Exposed Mice Via Nrf2 Pathway

Athelia rolfsii exopolysaccharides(AEPS)is an expolysaccharide secreted by Athelia rolfsii,presents a highly ordered and rigid triple-helical structure when dissolved in water.AEPS is a pseudoplastic fluid,and shows the wide tolerance of temperature and pH.In our previous experiments,AEPS decreased lead accumulation in the organs and relieved brain,liver,kidney and testis injury induced by lead.Some researches showed that nuclear factor erythroid-2-related factor 2(Nrf2)signaling pathway is a defense mechanism against lead injury,therefore,Nrf2 can be regarded as an important research target for alleviating liver and kidney injury induced by lead.This study aimed to explore protective mechanism of AEPS on the liver and kidney injury of lead-exposed mice with a focus on the role of Nrf2 signaling pathway.1.Mice were randomly assigned into 5 groups: normal control group(NG),induction control group(IG),positive control group(PG),AEPS groups included three subgroups [AEPS low dose group(ELD),AEPS middle dose group(EMD)and AEPS high dose group(EHD)],inhibitor group included three subgroups [(ATRA group(AG),ATRA + lead group(AL),ATRA + lead + AEPS high dose(ALE)].The clinical status,body weight change rate,visceral index and feed intake of each group mice were collected,and Nrf2 protein levels in the liver and kidney tissues were determined by Western Blot.The results showed that AEPS made lead-exposed mice mental state better,promoted the growth of mice and decreased liver index.AEPS also activated Nrf2 signaling pathway by enhancing Nrf2 total protein expression levels and promoting Nrf2 nuclear translocation in the liver and kidney of lead-exposed mice.However,mice received intraperitoneal administration of 10 mg/kg bw all-transretinoic acid(ATRA),prevented Nrf2 nuclear translocation,and thereby abolished the activation effects of AEPS on Nrf2 signaling pathway in the mice liver and kidney.2.The antioxidant activity,apoptosis level,functional indexes and pathological changes of the liver and kidney tissueslead-exposed mice were analyzed.The results showed that AEPS protected mice liver and kidney injury induced by lead in a Nrf2-dependent manner.AEPS increased antioxidant activity by increasing superoxide dismutase(SOD),catalase(CAT)activities,decreasing malondialdehyde(MDA)levels(P<0.05).It restored liver function by decreasing the activity of aspartate aminotransferase(AST),alanine aminotransferase(ALT)and lactate dehydrogenase(LDH)in the serum(P<0.05),as well as restored kidney function by reducing the level of blood urea nitrogen(BUN)and creatinine(CRE)in the serum(P<0.01).And as observed in histopathological analysis,AEPS alleviated lead-induced liver and kidney injury.Moreover,AEPS suppressed apoptosis by down-regulating cysteine aspartic acid specific protease 3(Caspase-3),Bcl-2-associated X protein(Bax)protein expression levels and up-regulating B lymphocyte tumor-2(Bcl-2)protein expression levels(P<0.05).However,ATRA reversed the protective effect of AEPS on the liver and kidney of lead-exposed mice.3.Graphite furnace atomic absorption spectrometry was used for measuring lead levels in the liver,kidney and whole blood.Glutathione(GSH)level and glutathione-s-transferase(GST)activity were measured.The protein expression level of multidrug resistance-associated protein1(MRP1)and multidrug resistance-associated protein 2(MRP2)were determined by Western Blot.The results showed that AEPS reduced lead accumulation in the liver,kidney and whole blood(P<0.01),high dose of AEPS had the best reduction effect,which showed 59.76%,61.17% and 46.50% reduction in the liver,kidney and whole blood,respectively.MRP1 and MRP2,together with GSH and GST,were involved in the transport of heavy metals in cell.The results showed that AEPS enhanced the ability of MRP1 and MRP2 to transport lead ions in the liver and kidney tissues,while ATRA inhibited the ability,as well as the effect of AEPS on inhabitation lead accumulation in the liver and kidney were inhabited by ATRA.It suggested that AEPS reduced lead accumulation in the mice liver and kidney tissues in a Nrf2-dependent manner.In conclusion,AEPS reduced lead accumulation in the liver and kidney in a Nrf2-dependent manner,and showed liver and kidney protective effect.