Effects Of Manganese Exposure On Iron Homeostasis And It’s Regulatory Pathway

OBJECTIVE:In this study,we aimed to evaluate the effect of drinking water manganese（Mn）exposure on iron（Fe）homeostasis,by measuring the concentration of Mn and Fe in the samples of the mice after Mn exposure,detecting the expression of Bone morphogenetic protein（BMP）-SMAD signaling pathway in vitro and in vivo.METHODS:Male C57BL/6 mice were randomly divided into 4 groups according to their body weight after adaptive feeding.Each group was given drinking water without added or containing 100 mg/L,200 mg/L or 400 mg/L Mn²⁺,respectively.After 32 weeks of exposure the mice were sacrificed by ether anesthesia,organs and blood samples were collected immediately.The concentration of Mn and Fe in the mice liver,spleen,duodenum,red blood cells and feces were detected by the inductively coupled plasma mass spectrometry（ICP-MS）.The expression of BMP/SMAD signaling pathway-related genes and proteins in the mice liver were detected by quality Real-Time Polymerase Chain Reaction（qRT-PCR）andWestern-Blot（WB）.Finally,weused3-（4,5-dimethyl-2-thiazolyl）-2,5-diphenyl-2-H-tetrazolium bromide（MTT）and WB to detect the survival rate of human liver cell line HL-7702 after 24 hours of Mn exposure for determining the dose.The expression of proteins related to BMP/SMAD signaling pathway in human hepatocyte cell line HL-7702 after exposing to Mn at the doses of 0,50,100,and 200μM for 24 hours were detected by WB.RESULTS:Under the exposure conditions of this study:1.Among each group,there was no difference in body weight form the study begin to the end;2.The concentration of Mn in the mice liver,red blood cells,and feces were increased significantly on the exposure groups（P<0.05）,while the spleen and duodenum remained the same.3.The concentration of Fe in the mice spleen,duodenum,and feces were decreased significantly on the exposure groups（P<0.05）,but the concentration of Fe in the liver,heart and red blood cells were not changed.4.The expression of proteins in the BMP/SMAD signaling pathway included BMP 6 and SMAD 4 which involved in the regulation of hepcidin in the mice liver decreased significantly on the exposure groups（P<0.05）,but the expression of hemojuvelin（HJV）was the same in each group.The expression of SMAD 4 and FPN massage RNA（mRNA）increased significantly（P<0.05）,but the expression of HAMP mRNA decreased significantly on the exposure groups（P<0.05）.5.The expression of proteins indicated SMAD 4 decreased significantly with the increase of Mn doses after 24 hours of exposure in human hepatic cell line HL-7702（P<0.05）,but the expression of HJV and BMP 6 did not changed.CONCLUSIONS:Under the exposure conditions of this study:1.The body weight of the mice was not affected by Mn exposure,but the imbalance of Fe homeostasis appeared.2.The distribution of iron in the body may be affected by manganese exposure through the BMP/SMAD signaling pathway.