Nicotinamide N-Methyltransferase (NNMT) is Involved in Gastric Adenocarcinoma Immune Infiltration by Driving Amino Acid Metabolism.

Objectives: This study investigates the role of Nicotinamide N-methyltransferase (NNMT) in immune infiltration modulation through amino acid metabolism in gastric adenocarcinoma (STAD). Methods: Utilizing data from The Cancer Genome Atlas (TCGA) and validated with clinical samples, we analyzed NNMT expression and its prognostic implications in STAD. Differential amino acid profiles between cancerous and adjacent normal tissues were assessed, along with their associations with NNMT. Results: NNMT exhibits heightened expression in STAD cancer tissues, positively correlating with tumor immune infiltration. Additionally, twenty-eight amino acids display differential expression in gastric tissue, with their metabolic enzymes showing connections to NNMT. Conclusions: Elevated NNMT expression in STAD tissues potentially influences amino acid metabolism, thereby affecting immune infiltration dynamics and tumorigenesis in gastric adenocarcinoma.

Synergistic suppression of BDNF via epigenetic mechanism deteriorating learning and memory impairment caused by Mn and Pb co-exposure.

Microglia, the resident immune cells of the central nervous system (CNS), play a dual role in neurotoxicity by releasing the NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome and brain-derived neurotrophic factor (BDNF) in response to environmental stress. Suppression of BDNF is implicated in learning and memory impairment induced by exposure to manganese (Mn) or lead (Pb) individually. Methyl CpG Binding Protein 2 (MeCp2) and its phosphorylation status are related to BDNF suppression. Protein phosphatase2A (PP2A), a member of the serine/threonine phosphatases family, dephosphorylates substrates based on the methylation state of its catalytic C subunit (PP2Ac). However, the specific impairment patterns and molecular mechanisms resulting from co-exposure to Mn and Pb remain unclear. Therefore, the purpose of this study was to explore the effects of Mn and Pb exposure, alone and in combination, on inducing neurotoxicity in the hippocampus of mice and BV2 cells, and to determine whether simultaneous exposure to both metals exacerbate their toxicity. Our findings reveal that co-exposure to Mn and Pb leads to severe learning and memory impairment in mice, which correlates with the accumulation of metals in the hippocampus and synergistic suppression of BDNF. This suppression is accompanied by up-regulation of the epigenetic repressor MeCp2 and its phosphorylation status, as well as demethylation of PP2Ac. Furthermore, inhibition of PP2Ac demethylation using ABL127, an inhibitor for its protein phosphatase methylesterase1 (PME1), or knockdown of MeCp2 via siRNA transfection in vitro effectively increases BDNF expression and mitigates BV2 cell damage induced by Mn and Pb co-exposure. We also observe abnormal activation of microglia characterized by enhanced release of the NLRP3 inflammasome, Casepase-1 and pro-inflammatory cytokines IL-1ß, in the hippocampus of mice and BV2 cells. In summary, our experiments demonstrate that simultaneous exposure to Mn and Pb results in more severe hippocampus-dependent learning and memory impairment, which is attributed to epigenetic suppression of BDNF mediated by PP2A regulation.