Mechanisms Of Transient Receptor Potential Channels Mediating Cadmium Poisoning

Cadmium is the primary heavy metal pollutant in some places of China in soil,water and air.Cadmium pollution from various sources directly and indirectly affects the safety of agricultural products and harms human health through the food chain.Cadmium exposure poses a huge threat to national health.The International Agency for Research on Cancer,IARC,has identified cadmium and its compounds as human Class I carcinogens.They cause damages in liver,kidney,lung and other important organs.Cadmium atom is structurally similar to calcium atom and can enter cells through calcium channels.Because calcium channels is frequently found in the small intestine,so they plays a main tunnel for cadmium absortion in intestine.In this project,we applied a mouse model of cadmium poisoning to analyze the role of one type of important calcium channels,transient receptor potential channels（TRP）,in cadmium absorption and cadmium poisoning.We further explored TRP-targeting diacylglycerol in reducing cadmium poisoning.We first identified the subtypes of TRP channels that related with intestinal cadmium poisoning.The expression of transient receptor potential channel C1（TRPC1）and transient receptor potential channel V4（TRPV4）in intestinal epithelial cells was determined by immunohistochemical staining.Then,we constructed the TRPC1 knockout(TRPC1^-/-)and TRPV4 knockout(TRPV4^-/-)mouse models of cadmium poisoning to observe the survival of the mice,injury of kidney and duodenum.We found that TRPC1^-/-mice effectively reduced the damage of cadmium compared with TRPV4^-/-mice.The detection of free cadmium ions by calcium imaging further proved that TRPC1^-/-mice can reduce the absorption of cadmium.Therefore,TRPC1 is a target for reducing cadmium absorption.The effect of the TRPC1-targeting diacylglycerol in cadmium absorption at the cellular level was subsequently explored.We used calcium imaging to detect intracellular free calcium ion concentration.Diacylglycerol analog 1-oleoyl-2-acetyl-sn-glycerol（OAG）activated TRPC1 at low concentration and inhibited TRPC1 channel at high concentration.Then we used the principle of calcium imaging to detect intracellular free cadmium ion concentration,which proved OAG activates the TRPC1 channel at low concentrations and promotes the uptake of cadmium by epithelial cells.Furthermore,the data suggest OAG inhibits the TRPC1channel at high concentrations and significantly inhibits the uptake of cadmium by epithelial cells.Finally,based on the regulation of diacylglycerol on TRPC1 at the cellular level,we further explored the effect and dose of diacylglycerol to inhibit acute and chronic cadmium poisoning at the animal level.We constructed mice with acute and chronic cadmium poisoning and fed different doses of diacylglycerol to mice at the same time.We evaluated the effect of diacylglycerol on cadmium poisoning mice by observing the survival rate of mice,intracellular free cadmium ions,and liver and kidney damage.The results showed that high dose of diacylglycerol could effectively reduce cadmium uptake by epithelial cells and reduce cadmium damage to kidney and liver of mice,which was consistent with the effect of OAG on regulating cadmium uptake by TRPC1 at cellular level.The dose of diacylglycerol effectively reduced cadmium poisoning in mice was 10 mL·kg^-1.To conclusion,TRPC1 is an effective target for reducing cadmium uptake in vitro and in vivo.Targeting TRPC1 by diacylglycerol can reduce cadmium uptake with an effective dose at 10 mL·kg^-1.This study provides scientific basis for the establishment of strategies to reduce cadmium poisoning.