Oxidative stress induced by HIV-1 F34IVpr in Schizosaccharomyces pombe is one of its multiple functions

Human immunodeficiency virus type 1 (HIV-1) viral protein R (Vpr) exerts multiple effects on viral and host cellular activities during infection, including induction of cell cycle G₂ arrest and cell death in both human and the fission yeast Schizosaccharomyces pombe cells. In this study, a mutant derivative of Vpr (F34IVpr), which causes transitent G₂ arrest with little or no effect of cell killing, was used to study the molecular impact of Vpr on cellular oxidative stress responses in S. pombe. We demonstrated here that F34IVpr triggers low level of complex and atypical oxidative stress responses in comparison with its parental strain SP223 in early (14-h) and late (35-h) log phase cultures. Specifically, F34IVpr production in S. pombe causes significantly elevated levels of reactive oxygen species such as superoxide and peroxides; meanwhile, it also induces decreased levels of glutathione, hydroxyl radical concentrations and specific enzyme activities such as those of antioxidant enzymes including superoxide dismutases, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and glutathione transferase. These observations may provide functional insights into the significance of Vpr-induced oxidative stress as part of the multifaceted functions of Vpr, and contribute to the development of future new strategies aimed to reduce the adverse Vpr-mediated effects in HIV-infected patients.     

Mitochondrial antiviral signaling protein defect links impaired antiviral response and liver injury in steatohepatitis in mice

Mitochondrial dysfunction is a pathogenic feature of nonalcoholic steatohepatitis (NASH). NASH complicates hepatotropic viral disease. The mitochondrial antiviral signaling protein (MAVS) is the adapter of helicase receptors involved in sensing double-stranded RNA (dsRNA). We hypothesized that impaired MAVS function may contribute to insufficient antiviral response and liver damage in steatohepatitis. We identified reduced MAVS protein levels and increased MAVS association with the proteasome subunit alpha type 7 (PSMA7) in livers from mice given a methionine-choline-deficient (MCD) diet. Decreased association of MAVS with mitochondria and increased cytosolic cytochrome c indicated mitochondrial damage in steatohepatitis. In vivo administration of the synthetic dsRNA polyinosinic:polycytidylic acid [poly(I:C)], but not lipopolysaccharide or cytidine-phosphate-guanosine-rich DNA, resulted in impaired induction of type I interferons (IFNs) and proinflammatory cytokines in steatohepatitis. Consistent with a defect in helicase receptor-induced signaling, there was loss of poly(I:C)-induced translocation of MAVS to the cytosol and decreased IFN regulatory factor 3 phosphorylation. Caspases 1 and 8, both of which cleave MAVS, were increased in MCD diet-fed mice. At baseline, steatohepatitis was associated with increased serum alanine aminotransferase (ALT), apoptosis and caspase 3 activation compared with controls. In contrast to apoptosis in controls, necrosis was induced by poly(I:C) stimulation in steatohepatitis. Hepatocyte necrosis was indicated by elevated serum high-mobility group box protein-1 and ALT and was correlated with increased expression of receptor-interacting protein 3 (RIP3), a master regulator of necrosis. Increased expression of MAVS, PSMA7, and RIP3 messenger RNA was also present in human NASH livers. CONCLUSION: Our novel findings suggest that mitochondrial damage in steatohepatitis extends to MAVS, an adapter of helicase receptors, resulting in inefficient type I IFN and inflammatory cytokine response but increased hepatocyte necrosis and RIP3 induction in response to a dsRNA viral challenge. These mechanisms may contribute to progressive liver damage and impaired viral clearance in NASH.     

Interferon regulatory factor 3 and type I interferons are protective in alcoholic liver injury in mice by way of crosstalk of parenchymal and myeloid cells

Alcoholic liver disease (ALD) features increased hepatic exposure to bacterial lipopolysaccharide (LPS). Toll-like receptor-4 (TLR4) recognizes LPS and activates signaling pathways depending on MyD88 or TRIF adaptors. We previously showed that MyD88 is dispensable in ALD. TLR4 induces Type I interferons (IFNs) in an MyD88-independent manner that involves interferon regulatory factor-3 (IRF3). We fed alcohol or control diets to wild-type (WT) and IRF3 knock-out (KO) mice, and to mice with selective IRF3 deficiency in liver parenchymal and bone marrow-derived cells. Whole-body IRF3-KO mice were protected from alcohol-induced liver injury, steatosis, and inflammation. In contrast to WT or bone marrow-specific IRF3-KO mice, deficiency of IRF3 only in parenchymal cells aggravated alcohol-induced liver injury, associated with increased proinflammatory cytokines, lower antiinflammatory cytokine interleukin 10 (IL-10), and lower Type I IFNs compared to WT mice. Coculture of WT primary murine hepatocytes with liver mononuclear cells (LMNC) resulted in higher LPS-induced IL-10 and IFN-β, and lower tumor necrosis factor alpha (TNF-α) levels compared to LMNC alone. Type I IFN was important because cocultures of hepatocytes with LMNC from Type I IFN receptor KO mice showed attenuated IL-10 levels compared to control cocultures from WT mice. We further identified that Type I IFNs potentiated LPS-induced IL-10 and inhibited inflammatory cytokine production in both murine macrophages and human leukocytes, indicating preserved cross-species effects. These findings suggest that liver parenchymal cells are the dominant source of Type I IFN in a TLR4/IRF3-dependent manner. Further, parenchymal cell-derived Type I IFNs increase antiinflammatory and suppress proinflammatory cytokines production by LMNC in paracrine manner. CONCLUSION: Our results indicate that IRF3 activation in parenchymal cells and resulting type I IFNs have protective effects in ALD by way of modulation of inflammatory functions in macrophages. These results suggest potential therapeutic targets in ALD.     

The TRPA1 Activator Allyl Isothiocyanate (AITC) Contracts Human Jejunal Muscle: Pharmacological Analysis

The contractile effect of AITC (300 μM) on human jejunal longitudinal strips was inhibited by the TRPA1 antagonist HC 030031 and atropine or scopolamine, but was insensitive to tetrodotoxin, purinoceptor antagonists or capsaicin desensitization. It is concluded that TRPA1 activation stimulates a cholinergic mechanism in a tetrodotoxin‐resistant manner.     

Disease-promoting and -protective genomic loci on mouse chromosomes 3 and 19 control the incidence and severity of autoimmune arthritis

Proteoglycan (PG)-induced arthritis (PGIA) is a murine model of rheumatoid arthritis. Arthritis-prone BALB/c mice are 100% susceptible, whereas the major histocompatibility complex-matched DBA/2 strain is completely resistant to PGIA. To reduce the size of the disease-suppressive loci for sequencing and to find causative genes of arthritis, we created a set of BALB/c.DBA/2-congenic/subcongenic strains carrying DBA/2 genomic intervals overlapping the entire Pgia26 locus on chromosome 3 (chr3) and Pgia23/Pgia12 loci on chr19 in the arthritis-susceptible BALB/c background. Upon immunization of these subcongenic strains and their wild-type (BALB/c) littermates, we identified a major Pgia26a sublocus on chr3 that suppressed disease onset, incidence and severity via controlling the complex trait of T-cell responses. The region was reduced to 3?Mbp (11.8?Mbp with flanking regions) in size and contained gene(s) influencing the production of a number of proinflammatory cytokines. Additionally, two independent loci (Pgia26b and Pgia26c) suppressed the clinical scores of arthritis. The Pgia23 locus (～3?Mbp in size) on chr19 reduced arthritis susceptibility and onset, and the Pgia12 locus (6?Mbp) associated with low arthritis severity. Thus, we have reached the critical sizes of arthritis-associated genomic loci on mouse chr3 and chr19, which are ready for high-throughput sequencing of genomic DNA.