title: Expression of CYP 4A ω-hydroxylase and formation of 20-hydroxyeicosatetreanoic acid (20-HETE) in cultured rat brain astrocytes.
abstract: Astrocytes secrete vasodilator and vasoconstrictor factors via end feet processes, altering blood flow to meet neuronal metabolic demand. Compared to what is known about the ability of astrocytes to release factors that dilate local cerebral vasculature, very little is known regarding the source and identity of astrocyte derived constricting factors. The present study investigated if astrocytes express CYP 4A ω-hydroxylase and metabolize arachidonic acid (AA) to 20-hydroxyeicotetraenoic acid (20-HETE) that regulates KCa channel activity in astrocytes and cerebral arterial myocyte contractility. Here we report that cultured astrocytes express CYP 4A2/3 ω-hydroxylase mRNA and CYP 4A protein and produce 20-HETE and the CYP epoxygenase metabolites epoxyeicosatrienoic acids (EETs) when incubated with AA. The production of 20-HETE and EETs was enhanced following stimulation of metabotropic glutamate receptors (mGluR) on the astrocytes. Exogenous application of 20-HETE attenuated, whereas inhibition of 20-HETE production with HET-0016 increased the open state probabilities (NPo) of 71pS and 161pS KCa single-channel currents recorded from astrocytes. Exposure of isolated cerebral arterial myocytes to conditioned media from cultured astrocytes caused shortening of the length of freshly isolated cerebral arterial myocytes that was not evident following inhibition of astrocyte 20-HETE synthesis and action. These findings suggest that astrocytes not only release vasodilator EETs in response to mGluR stimulation but also synthetize and release the cerebral arterial myocyte constrictor 20-HETE that also functions as an endogenous inhibitor of the activity of two types of KCa channel currents found in astrocytes.
authors.affiliation: Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Debebe
authors.initials: D
authors.lastname: Gebremedhin
authors.affiliation: Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: David X
authors.initials: DX
authors.lastname: Zhang
authors.affiliation: Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Koryn A
authors.initials: KA
authors.lastname: Carver
authors.affiliation: Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Nicole
authors.initials: N
authors.lastname: Rau
authors.affiliation: Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Rarick
authors.affiliation: Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, MS 39216, United States.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Roman
authors.affiliation: Department of Physiology, Milwaukee, WI 53226, United States; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, United States; Clement Zablocki VA Medical Center, Milwaukee, WI 53226, United States. Electronic address: dharder@mcw.edu.
authors.forename: David R
authors.initials: DR
authors.lastname: Harder
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000008:administration & dosage / Q000378:metabolism; D001253:Astrocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D001921:Brain / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis* / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000235:genetics / Q000378:metabolism*
chemical_list: D006893:Hydroxyeicosatetraenoic Acids; D018094:Receptors, Metabotropic Glutamate; D016718:Arachidonic Acid; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D003577:Cytochrome P-450 Enzyme System; C409986:cytochrome P-450 omega-hydroxylase
keywords: 20-HETE; Arachidonic acid; Astrocyte; CYP 4A ω-hydroxylase; Cerebral circulation; Neurovascular unit