Heart failure, a leading cause of death in humans, can emanate from myocarditis. Although most individuals with myocarditis recover spontaneously, some develop chronic dilated cardiomyopathy. Myocarditis may result from both infectious and noninfectious causes, including autoimmune responses to cardiac antigens. In support of this notion, intracellular cardiac antigens, like cardiac myosin heavy chain-a, cardiac troponin-I, and adenine nucleotide translocator 1 (ANT 1 ), have been identified as autoantigens in cardiac autoimmunity. Herein, we demonstrate that ANT 1 can induce autoimmune myocarditis in A/J mice by generating autoreactive T cells. We show that ANT 1 encompasses multiple immunodominant epitopes (namely, ANT 1 21-40, ANT 1 31-50, ANT 1 171-190, and ANT 1 181-200). Although all four peptides induce comparable T-cell responses, only ANT 1 21-40 was found to be a major myocarditogenic epitope in immunized animals. The myocarditis-inducing ability of ANT 1 21-40 was associated with the generation of T cells producing predominantly IL-17A, and the antigen-sensitized T cells could transfer the disease to naïve recipients. These data indicate that cardiac mitochondrial proteins can be target autoantigens in myocarditis, supporting the notion that the antigens released as a result of primary damage may contribute to the persistence of chronic inflammation through autoimmunity. Myocarditis can occur as a result of exposure to various infectious and noninfectious insults, but does not generally lead to a fatal outcome (ie, most affected individuals can recover spontaneously). However, a proportion of those affected can develop dilated cardiomyopathy (DCM). Estimates indicate that approximately half of DCM patients undergo heart transplantation because of a lack of alternative therapeutic options.1e3 Furthermore, several clinical studies suggest that DCM patients can have autoantibodies to several cardiac antigens, including adenine nucleotide translocator (ANT).4e6 Because DCM can arise as a sequel to myocarditis, it has been postulated that autoimmune response may be an underlying mechanism in its pathogenesis. 7ANT exists in multiple isoforms, all four of which are expressed in humans (ANT 1 , ANT 2 , ANT 3 , and ANT 4 ), but only three in mice (ANT 1 , ANT 2 , and ANT 4 ). ANT 1 is expressed in muscle tissues (heart and skeletal) and the brain, ANT 2 can be expressed in liver, kidney, and heart, and ANT 4 expression is restricted to the testes in mice.

Environmental exposure to inorganic arsenic compounds has been reported to have serious health effects on humans. Recent studies reported that arsenic targets endothelial cells lining blood vessels, and endothelial cell activation or dysfunction, may underlie the pathogenesis of arsenic-induced diseases and developmental toxicity. It has been reported that microRNAs (miRNAs) may act as an angiogenic switch by regulating related genes. The present study was designed to test the hypothesis that arsenite-regulated miRNAs play pivotal roles in arsenic-induced toxicity. Fertilized eggs were injected via the yolk sac with 100  nM sodium arsenite at Hamburger-Hamilton (HH) stages 6, 9, and 12, and harvested at HH stage 18. To identify the individual miRNAs and mRNAs that may regulate the genetic network, the expression profiles of chick embryos were analyzed by microarray analysis. Microarray analyses revealed that the expression of a set of miRNAs changed after arsenite administration, especially miRNA-9, 181b, 124, 10b, and 125b, which exhibited a massive decrease in expression. Integrative analyses of the microarray data revealed that several miRNAs, including miR-9 and miR-181b, might target several key genes involved in arsenic-induced developmental toxicity. A luciferase reporter assay confirmed neuropilin-1 (Nrp1) as a target of mir-9 and mir-181b. Data from the transwell migration assay and the tube-formation assay indicated that miR-9 and mir-181b inhibited the arsenic-induced EA.hy926 cell migration and tube formation by targeting NRP1. Our study demonstrates that the environmental toxin, sodium arsenite, induced angiogenesis by altering the expression of miRNAs and their cognate mRNA targets.

The potential of arsenic to induce neural tube defects (NTDs) remains a topic of controversy. In our previous study, oxidative stress and altered DNA methylation were observed in arsenic-exposed animal models. However, the correlation between these conditions was not fully understood. Therefore, our present aim was to determine whether arsenic exposure results in altered reactive oxygen species levels that affect DNA methylation and may contribute to NTDs in chick embryos. We demonstrated that arsenic-induced NTDs were associated with oxidative stress. Increased intracellular oxidative species and DNA methylation changes were observed following arsenic exposure. These changes were accompanied by a decrease in manganese superoxide dismutase activity. Furthermore, a significant decrease in DNA methyltransferase (DNMT) 1 and 3a expression was observed following arsenic exposure. The known antioxidant N-acetyl-l-cysteine, a known antioxidant, ameliorated global DNA hypomethylation and the decreased DNMT 1 and 3a expression observed during arsenic exposure. In addition, arsenic caused a significant decrease in S-adenosylmethionine (SAM) and significant increase in S-adenosylhomocysteine (SAH). This effect resulted in a significant reduction of the SAM/SAH ratio, which may also contribute to DNA hypomethylation. In conclusion, oxidative stress and reduction in SAM/SAH ratio during arsenic exposure in chick embryos seem to modulate DNA methylation and contribute to arsenic-induced NTDs via epigenetic mechanisms.