Dibromoacetic acid induced Cl.Ly1+2/-9 T-cell apoptosis and activation of MAPKs signaling cascades.

Dibromoacetic acid (DBA), a haloacetic acid by-product of disinfection of drinking water, can cause many adverse effects in test animals, including immunotoxicity. However, the underlying molecular mechanism for the immunomodulatory effects remains unclear. The present study was undertaken to help in defining some potential mechanisms for this type of toxicity. Here, Cl.Ly1+2/-9 T-cells were exposed to varying levels of DBA and then several parameters, including cell survival, apoptosis, changes in mitochondrial potentials, and effects on select kinases (i.e., p38, ERK1/2, JNK1/2) were examined. The data showed that DBA significantly decreased Cl.Ly1+2/-9 cell viability in a dose-related manner. DBA also induced apoptosis, a decrease in mitochondrial trans-membrane potential, and up-regulated the protein expression of cleaved caspase-3. Moreover, DBA increased the phosphorylation of all three mitogen-activated protein kinases (MAPKs) evaluated. Pre-treatment with specific p38, ERK1/2, and JNK1/2 inhibitors (SB203580, U0126, SP600125, respectively) attenuated the inducible phosphorylation events. DBA also induced up-regulation of mRNA levels of the MAPKs downstream transcription factors ATF-2 and Elk-1. When taken together, the results suggest that DBA could induce murine Cl.Ly1+2/-9 T-cells apoptosis through mitochondria-dependent way, and activate the MAPKs pathways and downstream transcription factors ATF-2 and Elk-1.

Resveratrol ameliorates benzo(a)pyrene-induced testicular dysfunction and apoptosis: involvement of p38 MAPK/ATF2/iNOS signaling.

Benzo(a)pyrene [B(a)P] is an environmental toxicant that alters the steroidogenic profile of testis and induces testicular dysfunction. In the present study, we have investigated the molecular signaling of B(a)P and the ameliorative potential of the natural aryl hydrocarbon receptor (AhR) antagonist and antioxidant, resveratrol, on B(a)P-induced male reproductive toxicity. Studies showed that B(a)P treatment resulted in p38 MAPK activation and increased inducible nitric oxide synthase (iNOS) production along with testicular apoptosis and steroidogenic dysfunction. Resveratrol cotreatment maintained testicular redox potential, increased serum testosterone level and enhanced expression of major testicular steroidogenic proteins (CYPIIA1, StAR, 3ßHSD, 17ßHSD) and prevented subsequent onset of apoptosis. Resveratrol cotreatment resulted inhibition of testicular cytochrome P4501A1 (CYP1A1) expression, which is the major B(a)P metabolizing agent for BPDE-DNA adduct formation. Resveratrol also significantly decreased the B(a)P-induced AhR protein level, its nuclear translocation and subsequent promoter activation, thereby decreased the expression of CYP1A1. Resveratrol also down-regulated B(a)P-induced testicular iNOS production through suppressing the activation of p38 MAPK and ATF2, thus improved the oxidative status of the testis and prevented apoptosis. Our findings cumulatively suggest that resveratrol inhibits conversion of B(a)P into BPDE by modulating the transcriptional regulation of CYP1A1 and acting as an antioxidant thus prevents B(a)P-induced oxidative stress and testicular apoptosis.

Clustering of Helicobacter pylori VacA in lipid rafts, mediated by its receptor, receptor-like protein tyrosine phosphatase beta, is required for intoxication in AZ-521 Cells.

Helicobacter pylori vacuolating cytotoxin, VacA, induces multiple effects on epithelial cells through different cellular events: one involves pore formation, leading to vacuolation, mitochondrial damage, and apoptosis, and the second involves cell signaling, resulting in stimulation of proinflammatory responses and cell detachment. Our recent data demonstrated that VacA uses receptor-like protein tyrosine phosphatase beta (RPTPbeta) as a receptor, of which five residues (QTTQP) at positions 747 to 751 are involved in binding. In AZ-521 cells, which mainly express RPTPbeta, VacA, after binding to RPTPbeta in non-lipid raft microdomains on the cell surface, is localized with RPTPbeta in lipid rafts in a temperature- and VacA concentration-dependent process. Methyl-beta-cyclodextrin (MCD) did not block binding to RPTPbeta but inhibited translocation of VacA with RPTPbeta to lipid rafts and all subsequent events. On the other hand, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), which disrupts anion channels, did not inhibit translocation of VacA to lipid rafts or VacA-induced activation of p38 mitogen-activated protein (MAP) kinase, but inhibited VacA internalization followed by vacuolation. Thus, p38 MAP kinase activation did not appear to be required for internalization. In contrast, phosphatidylinositol-specific phospholipase C (PI-PLC) inhibited translocation, as well as p38 MAP kinase/ATF-2 activation, internalization, and VacA-induced vacuolation. Neither NPPB nor PI-PLC affected VacA binding to cells and to its receptor, RPTPbeta. Thus, receptor-dependent translocation of VacA to lipid rafts is critical for signaling pathways leading to p38 MAP kinase/ATF-2 activation and vacuolation.