However, the spe cific mechanisms whereby losartans salutary effect is brought about was unknown until our Vorinostat CAS current finding that treatment of dopaminergic cells with losartan attenuates MPP induced ROS with kinetics suggestive of a temporally regulated, two wave response. In addi tion, a characteristic distinguishing between the waves was shown by the observation that protein synthesis is required for superoxide production in the context of the second wave, but not the first. Thus, we can now say that MPP treatment of dopaminergic Inhibitors,Modulators,Libraries neurons elicits protein synthesis as a requirement for generation of NADPH oxidase subunit, including the catalytic subunit Nox2. Experiments using another neurotoxin, 6 OHDA, support such occurrence of de novo synthesis of NADPH oxidase subunits as a part of ROS generation in rat striatal and ventral midbrain tissues.
Although Inhibitors,Modulators,Libraries it is clear that superoxide is a potent signal ing molecule that activates a multitude of signaling pathways, the mechanism by which oxidative stress and mitochondrial dysfunction leads to changes in gene expression is unknown. We show here for the first time that the stress induced initial wave of ROS production comes from mitochondrial respiration, leads to the acti vation of signaling pathways involved in a second wave of ROS production that depends on protein generation required for assembly and phosphorylation of NADPH oxidase subunits. Therefore, it seems logical that the generation and phosphorylation of a cytosolic subunit of NADPH oxidase is required for setting in motion events giving rise to the second wave.
One such example has been suggested to be important in protein kinase C mediated phosphorylation of p47phox, which is required for p47phox translocation from the cytosol to the plasma membrane Inhibitors,Modulators,Libraries for the activation of the Nox2 subunit of the NADPH oxidase and initiation of the second wave. Although the functional significance of the second wave remains to be characterized in full, the two waves in the neuron resulting from��mitochondrial complex I inhibition and extramitochondrial NADPH oxidase acti vation ��may play a role in preconditioning as an adap tive stress response in which brief exposure to a sub lethal stressor fortifies cellular defenses in an effort to protect cells from Inhibitors,Modulators,Libraries a Inhibitors,Modulators,Libraries subsequent exposure to severe stress.
Such hormetic effects could be explained, for example, by activation of AT1 recep torNox pathway by angiotensin II, which elevates activ ity of key antioxidant enzymes such as catalase, superoxide dismutase and glutathione peroxidase in rat hypothalamus. Furthermore, mitochondrially pro duced ROS and ATP sensitive potassium channels have been shown to play a role more in the preconditioning machinery. Whether neuronal ROS originating from the two waves act to balance such adaptive machinery awaits assessment.