Hydrogen peroxide

About: Hydrogen peroxide is a research topic. Over the lifetime, 42583 publications have been published within this topic receiving 1043732 citations. The topic is also known as: H2O2 & dioxidane.

Enhanced antioxidant enzymes are associated with reduced hydrogen peroxide in barley roots under saline stress.

Abstract: Antioxidant enzymes are related to the resistance to various abiotic stresses including salinity. Barley is relatively tolerant to saline stress among crop plants, but little information is available on barley antioxidant enzymes under salinity stress. We investigated temporal and spatial responses of activities and isoform profiles of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), non-specific peroxidase (POX), and glutathione reductase (GR) to saline stress in barley seedlings treated with 200 mM NaCl for 0, 1, 2, 5 days, respectively. In the control plant, hydrogen peroxide content was about 2-fold higher in the root than in the shoot. Under saline stress, hydrogen peroxide content was decreased drastically by 70% at 2 d after NaCl treatment (DAT) in the root. In the leaf, however, the content was remained unchanged by 2 DAT and increased about 14 % at 5 DAT. In general, the activities of antioxidant enzymes were increased in the root and shoot under saline stress. But the increase was more significant and consistent in the root. The activities of SOD, CAT, APX, POX, and GR were increased significantly in the root within 1 DAT, and various elevated levels were maintained by 5 DAT. Among the antioxidant enzymes, CAT activity was increased the most drastically. The significant increase in the activities of SOD, CAT, APX, POX, and GR in the NaCl-stressed barley root was highly correlated with the increased expression of the constitutive isoforms as well as the induced ones. The hydrogen peroxide content in the root.

The haber-weiss cycle

Abstract: — The Haber-Weiss cycle: was investigated at low pH by radiolysis of oxygen or nitrogen saturated solutions of hydrogen peroxide. It was found that reaction 2 has a low rate constant: k2= 3.0 ± 0.6 M-1 s-1 (pH 2.3, 22°C). The rate determining step of reaction 2 is most probably the transfer of an electron from a π8* orbital of HO2 to the empty su* orbital of H2O2. Overlap between these two orbitals is hindered by the filled π8* orbitals of H2O2. Fe(HI)EDTA catalyses reaction 2.

Microglia Proliferation Is Regulated by Hydrogen Peroxide from NADPH Oxidase

Abstract: Microglia are resident brain macrophages that become activated and proliferate following brain damage or stimulation by immune mediators, such as IL-1β or TNF-α. We investigated the mechanisms by which microglial proliferation is regulated in primary cultures of rat glia. We found that basal proliferation of microglia was stimulated by proinflammatory cytokines IL-1β or TNF-α, and this proliferation was completely inhibited by catalase, implicating hydrogen peroxide as a mediator of proliferation. In addition, inhibitors of NADPH oxidase (diphenylene iodonium or apocynin) also prevented microglia proliferation, suggesting that this may be the source of hydrogen peroxide. IL-1β and TNF-α rapidly stimulated the rate of hydrogen peroxide produced by isolated microglia, and this was inhibited by diphenylene iodonium, implying that the cytokines were acting directly on microglia to stimulate the NADPH oxidase. Low concentrations of PMA or arachidonic acid (known activators of NADPH oxidase) or xanthine/xanthine oxidase or glucose oxidase (generating hydrogen peroxide) also increased microglia proliferation and this was blocked by catalase, showing that NADPH oxidase activation or hydrogen peroxide was sufficient to stimulate microglia proliferation. In contrast to microglia, the proliferation of astrocytes was unaffected by the presence of catalase. In conclusion, these findings indicate that microglial proliferation in response to IL-1β or TNF-α is mediated by hydrogen peroxide from NADPH oxidase.