phenanthrenes and Cerebrovascular-Disorders

Microsomal epoxide hydrolase (mEH) is a detoxifying enzyme for xenobiotic compounds. Enzymatic activity of mEH can be greatly increased by a point mutation, leading to an E404D amino acid exchange in its catalytic triad. Surprisingly, this variant is not found in any vertebrate species, despite the obvious advantage of accelerated detoxification. We hypothesized that this evolutionary avoidance is due to the fact that the mEH plays a dualistic role in detoxification and control of endogenous vascular signaling molecules. To test this, we generated mEH E404D mice and assessed them for detoxification capacity and vascular dynamics. In liver microsomes from these mice, turnover of the xenobiotic compound phenanthrene-9,10-oxide was four times faster compared to WT liver microsomes, confirming accelerated detoxification. mEH E404D animals also showed faster metabolization of a specific class of endogenous eicosanoids, arachidonic acid-derived epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acids (DHETs). Significantly higher DHETs/EETs ratios were found in mEH E404D liver, urine, plasma, brain and cerebral endothelial cells compared to WT controls, suggesting a broad impact of the mEH mutant on endogenous EETs metabolism. Because EETs are strong vasodilators in cerebral vasculature, hemodynamics were assessed in mEH E404D and WT cerebral cortex and hippocampus using cerebral blood volume (CBV)-based functional magnetic resonance imaging (fMRI). Basal CBV

Topics: Amino Acid Substitution; Animals; Catalytic Domain; Cerebral Cortex; Cerebrovascular Circulation; Cerebrovascular Disorders; Eicosanoids; Epoxide Hydrolases; Hippocampus; Inactivation, Metabolic; Mice; Mice, Mutant Strains; Microsomes, Liver; Neurons; Phenanthrenes; Point Mutation; Vascular Resistance; Vasodilation; Vasodilator Agents; Xenobiotics

Ischemic heart disease still remains the most common cause of cardiac death. During ischemia-reperfusion (I/R), reactive oxygen species (ROS) are produced in excess in cardiac tissue, where they induce cell death. Our previous study showed that 9-phenanthrol (9-Phe), a specific inhibitor of the TRPM4 channel, preserves cardiac contractile function and protects the heart from I/R injury-related infarction in the excised rat heart. Accordingly, we hypothesized that TRPM4 channels are involved in the 9-Phe-mediated cardioprotection against ROS-induced injury. In rats, intravenous 9-Phe mitigated the development of myocardial infarction caused by the occlusion of the left anterior descending artery. Immunohistochemical analysis indicated that TRPM4 proteins are expressed in ventricular myocytes susceptible to I/R injury. Hydrogen peroxide (H2O2) is among the main ROS overproduced during I/R. In the cardiomyocyte cell line H9c2, pretreatment with 9-Phe prevented cell death induced by conditions mimicking I/R, namely 200 μM H2O2 and hypoxia-reoxygenation. Gene silencing of TRPM4 preserved the viability of H9c2 cardiomyocytes exposed to 200 μM H2O2. These results suggest that the cardioprotective effects of 9-Phe are mediated through the inhibition of the TRPM4 channels.

Topics: Animals; Cardiotonic Agents; Cell Line; Cerebrovascular Disorders; Gene Expression; Hydrogen Peroxide; Ion Transport; Ischemic Preconditioning, Myocardial; Male; Myocardial Contraction; Myocardial Reperfusion Injury; Myocytes, Cardiac; Organ Culture Techniques; Phenanthrenes; Rats; Rats, Sprague-Dawley; RNA, Small Interfering; TRPM Cation Channels

Our goal was to identify the role of poly(ADP-ribose) polymerase (PARP) in cerebrovascular dysfunction in Type 1 diabetes mellitus (T1D). In a first series of studies, rats were assigned to nondiabetic and diabetic (streptozotocin; 50 mg/kg IP) groups. Two to three months after injection of streptozotocin, we examine in vivo responses of pial arterioles to nitric oxide synthase (NOS)-dependent (adenosine diphosphate (ADP), acetylcholine and histamine) and -independent (nitroglycerin) agonists. After the initial examination of reactivity to the agonists, we treated pial arterioles acutely with an inhibitor of PARP (PJ-34; 1 microM), and then we again examined responses to the agonists. In a second series of studies, we examine superoxide production (lucigenin chemiluminescence) by parietal cortex tissue in nondiabetic and diabetic rats. We found that dilation of pial arterioles in response to ADP, acetylcholine and histamine, but not to nitroglycerin, was impaired in diabetic compared to nondiabetic rats. In addition, although PJ-34 did not alter responses in nondiabetic rats, PJ-34 alleviated T1D-induced impairment of NOS-dependent vasodilation. We also found that basal production of superoxide was increased in diabetic compared to nondiabetic rats and that PJ-34 decreased this basal production of superoxide. Our findings suggest that T1D impairs NOS-dependent reactivity of cerebral arterioles by a mechanism that appears to be related to the formation of superoxide via activation of PARP.

Topics: Acetylcholine; Adenosine Diphosphate; Animals; Arterioles; Blood Glucose; Blood Pressure; Body Weight; Cerebrovascular Circulation; Cerebrovascular Disorders; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Enzyme Inhibitors; Histamine; Male; Models, Biological; Nitroglycerin; Parietal Lobe; Phenanthrenes; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Rats; Rats, Sprague-Dawley; Superoxides; Vasodilation

Topics: Adrenal Glands; Animals; Anthracenes; Benz(a)Anthracenes; Breast Neoplasms; Carcinogens; Cerebrovascular Disorders; DNA; Humans; Hydrocarbons; Mammary Neoplasms, Animal; Mammary Neoplasms, Experimental; Pharmacology; Phenanthrenes; Physiology; Proteins; Rats; Research