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Nonalcoholic fatty liver disease (NAFLD) has been shown to be associated with extrahepatic comorbidities including neuronal inflammation and Alzheimer's-like pathology. Environmental and genetic factors also act as a second hit to modulate severity and are expected to enhance the NAFLD-linked neuropathology. We hypothezied that environmental microcystin-LR (MC-LR), a toxin produced by harmful algal blooms of cyanobacteria, exacerbates the neuroinflammation and degeneration of neurons associated with NAFLD. Using a mouse model of NAFLD, exposed to MC-LR subsequent to the onset of fatty liver, we show that the cyanotoxin could significantly increase proinflammatory cytokine expression in the frontal cortex and cause increased expression of Lcn2 and HMGB1. The above effects were NLRP3 inflammasome activation-dependent since the use of NLRP3 knockout mice abrogated the increase in inflammation. NLRP3 was also responsible for decreased expression of the blood-brain barrier (BBB) tight junction proteins Occludin and Claudin 5 suggesting BBB dysfunction was parallel to neuroinflammation following microcystin exposure. An increased circulatory S100B release, a hallmark of astrocyte activation in MC-LR exposed NAFLD mice also confirmed BBB integrity loss, but the astrocyte activation observed in vivo was NLRP3 independent suggesting an important role of a secondary S100B mediated crosstalk. Mechanistically, conditioned medium from reactive astrocytes and parallel S100B incubation in neuronal cells caused increased inducible NOS, COX-2, and higher BAX/ Bcl2 protein expression suggesting oxidative stress-mediated neuronal cell apoptosis crucial for neurodegeneration. Taken together, MC-LR exacerbated neuronal NAFLD-linked comorbidities leading to cortical inflammation, BBB dysfunction, and neuronal apoptosis., (Published by Elsevier B.V.)

Diethylstilbestrol (DES) is an endocrine disruptor that was used to prevent adverse effects of pregnancy in women in late 1940s until early 1970s. Its use was banned following significant toxicity and negative effects not only in the mothers but also transgenerationally. Previous studies from our laboratory showed that DES induces thymic atrophy and immunosuppression in mice. In this study, we investigated the molecular mechanisms through which DES triggers thymic atrophy, specifically autophagy. To that end, we treated C57BL/6 mice with DES, and determined expression of two autophagy-related proteins, microtubule-associated protein-1 light chain 3 (LC3) and Beclin-1 (Becn1). We observed that DES-induced thymic atrophy was associated with increased autophagy in thymocytes and significant upregulation in the expression of both Becn1 and LC3. DES also caused downregulation in the expression of miR-30a in thymocytes, and transfection studies revealed that miR-30a targeted Becn1. Upon examination of methylation status of Becn1, we noted hypomethylation of Becn1 in thymocytes of mice exposed to DES. Together, these data demonstrate for the first time that DES induces autophagy in thymocytes potentially through epigenetic changes involving hypomethylation of Becn1 and down-regulation of miR-30a expression., (Copyright © 2018. Published by Elsevier B.V.)

In the current study, we used pathway-specific cDNA arrays to detect the transcriptional signature induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in vivo by studying simultaneously the expression profiles of 83 genes involved in apoptosis, cytokine production and angiogenesis. To this end, C57BL/6 mice were injected i.p. with 50 microg/kg body weight of TCDD and 1 or 3 days later, the thymus was analyzed for gene expression profiles. In the thymus, 23 out of 37 apoptotic genes screened were up-regulated by TCDD by a factor of two or more when compared to the vehicle-treated controls. In contrast, in the spleen, 20 out of 22 and in the liver, 16 out of 37 apoptotic genes were up-regulated. In the thymus, several genes encoding caspases, and members of the TNF family, including Fas ligand, were induced. Also, in the thymus, eight out of 23, and in the spleen, six out of 23 cytokine genes were up-regulated. In the liver and to a lesser extent in the thymus, certain angiogenesis genes were induced while others were repressed. When mice were injected with 0.1, 1, 10 or 50 microg/kg body weight of TCDD and the thymus was analyzed for apoptotic genes 1 day later, a dose-dependent response was not seen with most apoptotic genes. However, certain apoptotic genes were induced in the thymus even at low doses of 0.1 microg/kg body weight of TCDD. These data demonstrate that TCDD alters the expression of a large array of genes involved in apoptosis, cytokine production and angiogenesis. Thus, pathway-specific cDNA arrays may help in the identification of specific gene expression profiles induced by xenobiotics and to delineate the molecular mechanisms of toxicity.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is well known for its immunotoxic effects particularly on the thymus as well as on T and B lymphocyte functions. Previous studies have suggested that TCDD may induce apoptosis in thymocytes although its demonstration in vivo has met with limited success. TCDD has also been shown to alter the major histocompatability complex- (MHC) encoded molecules, however, its role in immunotoxicity is not clear. In the current study, we investigated the role of Fas (CD95), an important molecule involved in the induction of apoptosis, on TCDD-mediated immunotoxicity using mice bearing homozygous lpr mutation which leads to failure of expression of Fas. When TCDD was administered orally at 0, 0.1, 1.0, or 5.0 micrograms/kg body weight for 11 days, it was found to be less toxic to the thymocytes from C57BL/6 lpr/lpr mice (Ah-responsive, Fas-) when compared to C57BL/6 +/+ mice (Ah-responsive, Fas+). Similar results were obtained when peripheral T cell responsiveness to antigenic challenge with conalbumin was studied in these mice. When mice that differed only at the MHC were compared for immunotoxic effects of TCDD, it was noted that B10.D2 (Ah-responsive, H-2d) were more sensitive to TCDD-mediated thymic atrophy and peripheral T cell dysfunction when compared to B10 mice (Ah-responsive, H-2b). In all TCDD-sensitive strains tested, the thymic atrophy was accompanied by a uniform depletion of all four subset of T cells (CD4+, CD4+CD8+, CD4-CD8-, and CD8+) and the percentage of these subsets was not altered. Furthermore, in these strains, TCDD suppressed the antigen-specific peripheral T cell responsiveness but not the responsiveness of naive resting T cells to polyclonal mitogens. Lastly, using cell-mixing experiments, it was demonstrated that TCDD directly affected the T cells responding to conalbumin but not the antigen presenting cells (APCs). Together, our studies demonstrate that although Ah locus plays the primary role, determining the toxicity of TCDD on the T cells, there are secondary factors such as expression of Fas or the MHC-phenotype which may play an important role in TCDD-mediated immunotoxicity. The role of Fas further suggests that TCDD may induce toxicity in T cells by triggering apoptosis.