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For the past decade, there has been an increased concern about the health risks from arsenic (As) exposure, because of its neurotoxic effects on the developing brain. The exact mechanism underlying As-induced neurotoxicity during sensitive periods of brain development remains unclear, especially the role of blood-brain barrier's (BBB) tight junction (TJ) proteins during As-induced neurotoxicity. Here, we highlight the involvement of TJ proteins in As-induced autophagy in cerebral cortex and hippocampus during developmental periods [postnatal day (PND) 21, 28, 35 and 42]. Here, the administration of arsenic trioxide (AsO) at doses of 0.15 mg or 1.5 mg or 15 mg AsO/L in drinking water from gestational to lactational and continued to the pups till PND42 resulted in a significant decrease in the mRNA expression levels of TJ proteins (Occludin, Claudin, ZO-1 and ZO-2) and Occludin protein expression level. In addition, As exposure significantly decreased PI3K, Akt, mTOR, and p62 with a concomitant increase in Beclin1, LC3I, LC3II, Atg5 and Atg12. Moreover, As exposure also significantly downregulated the protein expression levels of mTOR with a concomitant upregulation of Beclin 1, LC3 and Atg12 in all the developmental age points. However, no significant alterations were observed in low and medium dose-exposed groups of PND42. Histopathological analysis in As-exposed mice revealed decreased number of pyramidal neurons in hippocampus; and neurons with degenerating axons, shrinkage of cells, remarkable vacuolar degeneration in cytoplasm, karyolysis and pyknosis in cerebral cortex. Ultrastructural analysis by transmission electron microscopy revealed the occurrence of autophagosomes and vacuolated axons in the cerebral cortex and hippocampus of the mice exposed to high dose As at PND21 and 42. The severities of changes were found to more persist in the cerebral cortex than in the hippocampus of As-exposed mice. Finally, we conclude that the leaky BBB in cerebral cortex and hippocampus may facilitate the transfer of As and induces autophagy by inhibiting PI3K/Akt/mTOR signaling pathway in an age-dependent manner, i.e., among the four different developmental age points, PND21 animals were found to be more vulnerable to the As-induced neurotoxicity than the other three age points.

Previous studies have reported that excessive fluoride exposure induced liver damage. However, the underlying mechanism of fluoride-induced hepatic toxicity is still unclear. Hence, this study was aimed to evaluate the fluoride-induced apoptosis, autophagy, and IL-17 signaling pathway-related genes to explore the possible mechanisms of NaF-induced liver injury in mice. For this, 48 male mice were allotted randomly to four groups, treated with deionized water, 25, 50, 100 mg/L NaF for 150 days continuously. Our results suggested that treatment with NaF decreased the PAS staining-positive area, with a concomitant increase in liver score, and serum ALT and AST levels which indicated that NaF induced the liver injury. In addition, the qRT-PCR, immunohistochemistry, and western blotting results indicated that NaF exposure activated IL-17 signaling, apoptosis, and autophagy pathways. In summary, these results suggested that NaF induced apoptosis and autophagy in liver by activating the IL-17 signaling pathway, eventually leading to impaired liver function.

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