Neurotoxicity of β-HgS differs from environmental mercury pollutants (MeHgCl and HgCl2) in Neuro-2a cell

Heterocyclic aromatic amines induce Neuro-2a cells cytotoxicity through oxidative stress-mediated mitochondria-dependent apoptotic signals

Heterocyclic aromatic amines (HAAs) are a class of hazardous compounds produced in food thermal processing. These compounds raise concerns because they have mutagenic and carcinogenic properties. However, the neurotoxicity of these compounds has received limited attention. Here, the toxic effects of three HAAs, i.e. 9H-pyrido[3,4-b]indole (Norharman), 1-methyl-9H-pyrido[3,4-b]indole (Harman), and 2-amino-3-methylimidazole[4,5-f]quinoline (IQ) were investigated in Neuro-2a cells model. The results showed that the survival rate of cells decreased in a dose-dependent manner and apoptosis occurred after exposure to the three HAAs for 24 h and 48 h. Their neurotoxicity was ranked as Harman > Norharman > IQ. Further, treatment of Harman, Norharman, or IQ at 50 and 100 μM for 48 h led to intracellular REDOX imbalance, which was manifested as increased ROS and malondialdehyde (MDA) levels, decreased GSH/GSSG ratio, and reduced SOD and CAT activities. Moreover, Norharman and Harman up-regulated the expression level of nuclear factor erythroid 2-related factor 2 (Nrf2), as well as the mRNA levels of Heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoredutase1 (NQO1), while IQ had no significant effect on the levels of Nrf2, HO-1, and NQO1. Additionally, Harman, Norharman, or IQ exposure significantly reduced mitochondrial membrane potential and intracellular ATP levels and up-regulated the levels of apoptosis-related genes and proteins. Collectively, our finding suggested that HAAs were neurotoxic, with mechanisms related to induction of oxidative stress and mitochondrial dysfunction.

In vitro and in silico Studies Reveal Bacillus cereus AA-18 as a Potential Candidate for Bioremediation of Mercury-Contaminated Wastewater

Mercury (Hg) pollution is a worldwide problem and increasing day by day due to natural and anthropogenic sources. In this study, mercury-resistant (HgR) bacterial isolates were isolated from industrial wastewater of Ittehad Chemicals Ltd., Kala Shah Kaku, Lahore, Pakistan. Out of 65 bacterial isolates, five isolates were screened out based on showing resistance at 30–40 μg/ml against HgCl2. Selected Hg-resistant bacterial isolates were characterized as Bacillus subtilis AA-16 (OK562835), Bacillus cereus AA-18 (OK562834), Bacillus sp. AA-20 (OK562833), Bacillus paramycoides AA-30 (OK562836), and Bacillus thuringiensis AA-35 (OK562837). B. cereus AA-18 showed promising results in the resistance of HgCl2 (40 μg/ml) due to the presence of merA gene. Scanning electron microscopy (SEM) analysis of immobilized B. cereus AA-18 showed the accumulation Hg on the cell surface. The inoculation of immobilized B. cereus AA-18 remediated 86% Hg of industrial wastewater up to 72 h at large scale (p < 0.05). In silico analysis showed structural determination of MerA protein encoded by merA gene of B. cereus AA-18 (OK562598) using ProtParam, Pfam, ConSurf Server, InterPro, STRING, Jpred4, PSIPRED, I-TASSER, COACH server, TrRosetta, ERRAT, VERIFY3D, Ramachandran plot, and AutoDock Vina (PyRx 8.0). These bioinformatics tools predicted the structural-based functional homology of MerA protein (mercuric reductase) associated with mer operon harboring bacteria involved in Hg-bioremediation system.