Lipid peroxidation activity mediated by NADPH-cytochrome C reductase purified from rabbit liver microsomes

Renin-angiotensin system acting on reactive oxygen species in paraventricular nucleus induces sympathetic activation via AT1R/PKCγ/Rac1 pathway in salt-induced hypertension

Brain renin-angiotensin system (RAS) could regulate oxidative stress in the paraventricular nucleus (PVN) in the development of hypertension. This study was designed to explore the precise mechanisms of RAS acting on reactive oxygen species (ROS) in salt-induced hypertension. Male Wistar rats were administered with a high-salt diet (HS, 8.0% NaCl) for 8 weeks to induced hypertension. Those rats were received PVN infusion of AT1R antagonist losartan (LOS, 10 μg/h) or microinjection of small interfering RNAs for protein kinase C γ (PKCγ siRNA) once a day for 2 weeks. High salt intake resulted in higher levels of AT1R, PKCγ, Rac1 activity, superoxide and malondialdehyde (MDA) activity, but lower levels of copper/zinc superoxide dismutase (Cu/Zn-SOD), superoxide dismutase (SOD) and glutathione (GSH) in PVN than control animals. PVN infusion of LOS not only attenuated the PVN levels of AT1R, PKCγ, Rac1 activity, superoxide and decreased the arterial pressure, but also increased the PVN antioxidant capacity in hypertension. PVN microinjection of PKCγ siRNA had the same effect on LOS above responses to hypertension but no effect on PVN level of AT1R. These results, for the first time, identified that the precise signaling pathway of RAS regulating ROS in PVN is via AT1R/PKCγ/Rac1 in salt-induced hypertension.

Metabolic activation of carbon tetrachloride: induction of cytochrome P-450 with phenobarbital or 3-methylcholanthrene and its effect on covalent binding

Anaerobic incubation of [14C]carbon tetrachloride with normal rat liver microsomes and microsomes from rats treated with the inducers phenobarbital (PB) and 3-methylcholanthrene (MC) reveals distinct differences in metabolic activation. While the increase in CO-binding pigment is comparable for both inducers, metabolism of CC14 is enhanced only by PB-induction; MC-induced microsomes are equivalent to microsomes from untreated animals. Sodium dodecyl sulphate (SDS)-electrophoresis of microsomal proteins confirms the expected increase at 52 000 daltons (cytochrome P-450 PB) on PB-induction, at 56 000 daltons (cytochrome P-450MC) on MC-induction; after anaerobic incubation with [14C]CC14 the electrophoretic pattern is largely unchange. The highly reactive radical intermediates of CC14-metabolism should attack the closest possible partner. Most of protein-bound radioactivity is located in the mass range between 47 000 and 54 000 daltons, indicating that cytochrome P-450PB is the isoenzyme mainly responsible for CC14-activation; cytochrome P-450MC plays virtually no role in metabolic activation. The direct participation of NADPH-cytochrome P-450 reductase appears unlikely, since the specific binding to proteins in the corresponding mass range is not elevated. A significant percentage of label is attached to proteins at 120 000 daltons and above, presumably oligomers of cytochrome P-450 apoprotein.

Effects of various compounds on lipid peroxidation mediated by detergent-solubilized rat liver NADPH-cytochrome C reductase

A reconstituted lipid peroxidation system containing NADPH-cytochrome c reductase isolated from detergent-solubilized rat liver microsomes was used to determine the effects of several compounds, including drugs, on the lipid peroxidation activity. EDTA and ferrous ion were essential requirements for reconstitution of the activity. The addition of 1,10-phenanthroline to the system containing both EDTA and ferrous ion further enhanced the activity. Pyrocatecol, thymol, p-aminophenol, imipramine, p-chloromercuribenzoate (PCMB) and alpha-tocopherol exhibited strong inhibition, aniline, N-monomethylaniline, aminopyrine, benzphetamine, SKF 525-A and NADP exhibited moderate inhibition, and phenol, benzoic acid, acetanilide and nicotinamide exhibited less or no inhibition at the concentrations lower than 1000 micron M. Metal ions such as Hg+, Hg2+, Co2+, Cu2+, Mn2+ and U6+ inhibited lipid peroxidation strongly. In addition, Cd2+, St2+ and Ca2+ exhibited less potent to moderate inhibition, and Ba2+ and Mg2+ were without effects on the activity. Among sulfhydryl compounds tested, dithiothreitol inhibited lipid peroxidation to a greater extent than did the other three compounds, glutathione, cysteine and mercaptoethanol.