title: TNF-alpha dilates cerebral arteries via NAD(P)H oxidase-dependent Ca2+ spark activation.
abstract: Expression of TNF-alpha, a pleiotropic cytokine, is elevated during stroke and cerebral ischemia. TNF-alpha regulates arterial diameter, although mechanisms mediating this effect are unclear. In the present study, we tested the hypothesis that TNF-alpha regulates the diameter of resistance-sized ( approximately 150-microm diameter) cerebral arteries by modulating local and global intracellular Ca(2+) signals in smooth muscle cells. Laser-scanning confocal imaging revealed that TNF-alpha increased Ca(2+) spark and Ca(2+) wave frequency but reduced global intracellular Ca(2+) concentration ([Ca(2+)](i)) in smooth muscle cells of intact arteries. TNF-alpha elevated reactive oxygen species (ROS) in smooth muscle cells of intact arteries, and this increase was prevented by apocynin or diphenyleneiodonium (DPI), both of which are NAD(P)H oxidase blockers, but was unaffected by inhibitors of other ROS-generating enzymes. In voltage-clamped (-40 mV) cells, TNF-alpha increased the frequency and amplitude of Ca(2+) spark-induced, large-conductance, Ca(2+)-activated K(+) (K(Ca)) channel transients approximately 1.7- and approximately 1.4-fold, respectively. TNF-alpha-induced transient K(Ca) current activation was reversed by apocynin or by Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP), a membrane-permeant antioxidant, and was prevented by intracellular dialysis of catalase. TNF-alpha induced reversible and similar amplitude dilations in either endothelium-intact or endothelium-denuded pressurized (60 mmHg) cerebral arteries. MnTMPyP, thapsigargin, a sarcoplasmic reticulum Ca(2+)-ATPase blocker that inhibits Ca(2+) sparks, and iberiotoxin, a K(Ca) channel blocker, reduced TNF-alpha-induced vasodilations to between 15 and 33% of control. In summary, our data indicate that TNF-alpha activates NAD(P)H oxidase, resulting in an increase in intracellular H(2)O(2) that stimulates Ca(2+) sparks and transient K(Ca) currents, leading to a reduction in global [Ca(2+)](i), and vasodilation.
authors.affiliation: Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 426 Nash Research Bldg., Memphis, 38163, USA.
authors.forename: Sergey Y
authors.initials: SY
authors.lastname: Cheranov
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Jaggar
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002536:Cerebral Arteries / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014664:Vasodilation / Q000502:physiology*
chemical_list: D024681:Potassium Channels, Calcium-Activated; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D019255:NADPH Oxidases; D000252:Calcium-Transporting ATPases