Study On The Mechanism Of Selenium Alleviating Spleen Damage Caused By Mercuric Chloride In Chickens

Mercury?Hg?is a toxic heavy metal which difficult to be degraded,and is easy to be migrated and concentrated.There are three main types of mercury in nature including elemental mercury,organic mercury,and inorganic mercury.Mercuric chloride?HgCl₂?is widely used in chemical,electrical,and military fields and has threats to human health by biological enrichment.It has been found that HgCl₂ can cause a variety of organ damage,and the spleen is one of the target organs for its toxic damage.Selenium?Se?is an essential trace element of the body and an important part of glutathione peroxidase.It has the functions of anti-oxidation and previous studies have shown that Se can antagonize tissue and organ damage caused by heavy metals in chickens,however whether Se can antagonize spleen tissue damage caused by HgCl₂ and its specific mechanism has not been elucidated.Therefore,the objective of this study was to explore the protective effect of Se on the spleen injury induced by HgCl₂ and its mechanism.In this study,90 one-day-old male Hyland brown layer chickens were randomly divided into three groups with 30 in each group after one week of adaptation.The Cont group was fed with standard commercial diets and drinking water.The HgCl₂ group was fed a standard commercial diet and HgCl₂ supplemented drinking water?HgCl₂ content was 250 mg/L?.The HgCl₂+Se group was fed a standard commercial diet supplemented with sodium selenite?Na₂SeO₃ content was 10 mg/kg?and added HgCl₂ drinking water?HgCl₂ content of 250 mg/L?.After seven weeks of the experiment,the test animals were sacrificed to collect spleen tissue.Firstly,the effects of Se on spleen injury caused by HgCl₂ were studied by the changes in spleen index and histopathology.The results showed that HgCl₂ induced a significant reduction in spleen index and pathological damage of spleen tissue.Se effectively relieved this change in the spleen,and the results confirmed that Se antagonized the spleen injury caused by HgCl₂.Secondly,oxidative stress-related indicators were tested such as total antioxidant capacity?T-AOC?,glutathione peroxidase?GPx?,glutathione?GSH?,and malonaldehyde?MDA?in the spleen tissue.The results showed that Se effectively alleviated the increase of MDA level and the decrease of GSH,GPx and T-AOC levels in chicken spleen caused by HgCl_2.The results showed that Se could antagonize the spleen oxidative stress induced by HgCl₂.Thirdly,the mRNA levels of IL-1?,IL-4,IL-6,IL-8,IL-10,IL-12?,IL-13,IL-17,IL-18,TNF-?,NF-?B,COX-2,iNOS and the protein levels of NF-?B,COX-2,iNOS were detected.The results showed that Se can effectively relieve the increase of IL-1?,IL-4,IL-6,IL-8,IL-12?,IL-17,IL-18,TNF-?,NF-?B,COX-2 and iNOS mRNA levels,and NF-?B,COX-2 and iNOS protein levels,and the decrease mRNA levels of IL-10 and IL-13 caused by HgCl₂.The results showed that Se can effectively antagonize the inflammatory damage caused by HgCl₂.Fourthly,the mRNA levels of Bak1 and Bcl-2 and the protein levels of them were measured.The results confirmed that Se can effectively antagonize the increase of Bak1mRNA level and protein expression and the decrease of Bcl-2 mRNA level and protein expression induced by HgCl₂.It was suggested that Se effectively alleviated the apoptosis of spleen cells induced by HgCl₂.Finally,the mRNA and protein expression levels of heat shock proteins HSP60,HSP70 and HSP90 were detected.The results showed that Se can effectively alleviate the up-regulation of HSP60,HSP70 and HSP90 mRNA levels and protein levels caused by HgCl_2.The results confirmed that Se antagonized the activation of heat shock protein induced by HgCl₂ in chicken spleen.In summary,Se can relieve spleen damage caused by HgCl₂ by antagonizing oxidative stress,inflammatory damage,apoptosis and the activation of heat shock protein.