title: Role of TRPV1 and intracellular Ca2+ in excitation of cardiac sensory neurons by bradykinin.
abstract: Bradykinin is an important mediator produced during myocardial ischemia and infarction that can activate and/or sensitize cardiac spinal (sympathetic) sensory neurons to trigger chest pain. Because a long-onset latency is associated with the bradykinin effect on cardiac spinal afferents, a cascade of intracellular signaling events is likely involved in the action of bradykinin on cardiac nociceptors. In this study, we determined the signal transduction mechanisms involved in bradykinin stimulation of cardiac nociceptors. Cardiac dorsal root ganglion (DRG) neurons in rats were labeled by intracardiac injection of a fluorescent tracer, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine percholate (DiI). Whole cell current-clamp recordings were performed in acutely isolated DRG neurons. In DiI-labeled DRG neurons, 1 microM bradykinin significantly increased the firing frequency and lowered the membrane potential. Iodoresiniferatoxin, a highly specific transient receptor potential vanilloid type 1 (TRPV1) antagonist, significantly reduced the excitatory effect of bradykinin. Furthermore, the stimulating effect of bradykinin on DiI-labeled DRG neurons was significantly attenuated by baicalein (a selective inhibitor of 12-lipoxygenase) or 2-aminoethyl diphenylborinate [an inositol 1,4,5-trisphosphate (IP(3)) antagonist]. In addition, the effect of bradykinin on cardiac DRG neurons was abolished after the neurons were treated with BAPTA-AM or thapsigargin (to deplete intracellular Ca(2+) stores) but not in the Ca(2+)-free extracellular solution. Collectively, these findings provide new evidence that 12-lipoxygenase products, IP(3), and TRPV1 channels contribute importantly to excitation of cardiac nociceptors by bradykinin. Activation of TRPV1 and the increase in the intracellular Ca(2+) are critically involved in activation/sensitization of cardiac nociceptors by bradykinin.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Unit 110, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030-4009, USA.
authors.forename: Zi-Zhen
authors.initials: ZZ
authors.lastname: Wu
authors.forename: Hui-Lin
authors.initials: HL
authors.lastname: Pan
mesh_terms: D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000502:physiology; D044950:Flavanones / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology; D006321:Heart / Q000294:innervation*; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology; D042541:Intracellular Space / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D009619:Nociceptors / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D050916:TRPV Cation Channels / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D002614:Chelating Agents; D004791:Enzyme Inhibitors; D044950:Flavanones; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; C006680:baicalein; D004533:Egtazic Acid; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D001092:Arachidonate 12-Lipoxygenase; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D001920:Bradykinin; D002118:Calcium