title: Mitochondrial modulation of Ca2+ sparks and transient KCa currents in smooth muscle cells of rat cerebral arteries.
abstract: Mitochondria sequester and release calcium (Ca(2+)) and regulate intracellular Ca(2+) concentration ([Ca(2+)](i)) in eukaryotic cells. However, the regulation of different Ca(2+) signalling modalities by mitochondria in smooth muscle cells is poorly understood. Here, we investigated the regulation of Ca(2+) sparks, Ca(2+) waves and global [Ca(2+)](i) by mitochondria in cerebral artery smooth muscle cells. CCCP (a protonophore; 1 microm) and rotenone (an electron transport chain complex I inhibitor; 10 microm) depolarized mitochondria, reduced Ca(2+) spark and wave frequency, and elevated global [Ca(2+)](i) in smooth muscle cells of intact arteries. In voltage-clamped (-40 mV) cells, mitochondrial depolarization elevated global [Ca(2+)](i), reduced Ca(2+) spark amplitude, spatial spread and the effective coupling of sparks to large-conductance Ca(2+)-activated potassium (K(Ca)) channels, and decreased transient K(Ca) current frequency and amplitude. Inhibition of Ca(2+) sparks and transient K(Ca) currents by mitochondrial depolarization could not be explained by a decrease in intracellular ATP or a reduction in sarcoplasmic reticulum Ca(2+) load, and occurred in the presence of diltiazem, a voltage-dependent Ca(2+) channel blocker. Ru360 (10 microm), a mitochondrial Ca(2+) uptake blocker, and lonidamine (100 microm), a permeability transition pore (PTP) opener, inhibited transient K(Ca) currents similarly to mitochondrial depolarization. In contrast, CGP37157 (10 microm), a mitochondrial Na(+)-Ca(2+) exchange blocker, activated these events. The PTP blockers bongkrekic acid and cyclosporin A both reduced inhibition of transient K(Ca) currents by mitochondrial depolarization. These results indicate that mitochondrial depolarization leads to a voltage-independent elevation in global [Ca(2+)](i) and Ca(2+) spark and transient K(Ca) current inhibition. Data also suggest that mitochondrial depolarization inhibits Ca(2+) sparks and transient K(Ca) currents via PTP opening and a decrease in intramitochondrial [Ca(2+)].
authors.affiliation: Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
authors.forename: Serguei Y
authors.initials: SY
authors.lastname: Cheranov
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Jaggar
mesh_terms: D000818:Animals; D001865:Bongkrekic Acid / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002478:Cells, Cultured; D002536:Cerebral Arteries / Q000166:cytology / Q000502:physiology*; D002998:Clonazepam / Q000031:analogs & derivatives* / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D004110:Diltiazem / Q000494:pharmacology; D005260:Female; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007191:Indazoles / Q000494:pharmacology; D007473:Ion Channels / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D018613:Microscopy, Confocal; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000502:physiology*; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology*; D009840:Oligomycins / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D012235:Rhodamines / Q000737:chemistry; D012402:Rotenone / Q000494:pharmacology; D017975:Ruthenium Compounds / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000502:physiology; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors; D019284:Thapsigargin / Q000494:pharmacology; D013841:Thiazepines / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D007191:Indazoles; D007473:Ion Channels; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D009840:Oligomycins; D012235:Rhodamines; C112020:Ru 360; D017975:Ruthenium Compounds; D019831:Sodium-Calcium Exchanger; D013841:Thiazepines; C034703:mitochondrial calcium uniporter; C401833:tetramethylrhodamine methyl ester; D012402:Rotenone; D001865:Bongkrekic Acid; C048335:oligomycin B; D002110:Caffeine; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D002998:Clonazepam; D019284:Thapsigargin; C079032:CGP 37157; D016572:Cyclosporine; D006861:Hydrogen Peroxide; D000252:Calcium-Transporting ATPases; D004110:Diltiazem; C016371:lonidamine