title: Voltage-independent calcium channels mediate lipopolysaccharide-induced hyporeactivity to endothelin-1 in the rat aorta.
abstract: The roles of intracellular calcium concentration ([Ca(2+)](i)) and Ca(2+) sensitization in lipopolysaccharide (LPS)-induced vascular smooth muscle (VSM) hyporesponsiveness are incompletely understood. To investigate these roles, contraction responses to endothelin-1 (ET-1) and 80 mM KCl; relaxation responses to nifedipine; the expression levels of mRNAs of ET-1 and its receptors (ET(A) or ET(B)); the expression levels of protein kinase C (PKC) and phosphorylation of Rho kinase (ROKalpha), CPI-17, and myosin phosphatase target subunit-1 (MYPT1); and changes in aortic VSM cell [Ca(2+)](i) were measured in LPS-treated aortic rings from male Wistar rats (250-300 g). LPS (10 mug/ml, 20 h) decreased contraction induced by ET-1 (0.3-100 nM) or 80 mM KCl. LPS-induced hypocontractility was not observed in the absence of external Ca(2+), but LPS-treated aorta remained hypocontractile on subsequent stepwise restoration of extracellular Ca(2+) (0.01-10 mM). Vascular relaxation to nifedipine; mRNA expression levels of ET-1, ET(A), or ET(B); protein expression levels of PKC; and phosphorylation levels of ROKalpha, CPI-17, and MYPT1 were not affected by LPS. In isolated aortic VSM cells, ET-1 caused a transient initial increase in [Ca(2+)](i), followed by a maintained tonic increase in [Ca(2+)](i), which was decreased by LPS pretreatment and was dependent on external Ca(2+). Subsequent restoration of extracellular Ca(2+) increased [Ca(2+)](i), but this increase was lower in the LPS-treated group. This difference in response to extracellular Ca(2+) addition was not affected by diltiazem, but was abolished by SKF-96365. Therefore, LPS induces hyporeactivity to ET-1 in rat aorta that depends on external Ca(2+) influx through non-voltage-operated Ca(2+) channels, but not on ET-1 receptor expression or Ca(2+) sensitization.
authors.affiliation: Dept. of Pharmacy and Pharmacology, Univ. of Bath, Bath BA2 7AY, UK.
authors.forename: Mohammed S H
authors.initials: MS
authors.lastname: El-Awady
authors.forename: Sergey V
authors.initials: SV
authors.lastname: Smirnov
authors.forename: Malcolm L
authors.initials: ML
authors.lastname: Watson
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D004110:Diltiazem / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D009924:Organ Culture Techniques; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D054645:Protein Phosphatase 1 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A / Q000378:metabolism; D044023:Receptor, Endothelin B / Q000378:metabolism; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D000634:Aminoquinolines; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D019332:Endothelin-1; D008070:Lipopolysaccharides; D009124:Muscle Proteins; D010750:Phosphoproteins; C491519:Ppp1r14a protein, rat; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D014665:Vasodilator Agents; C482199:lipopolysaccharide, E coli O55-B5; C069657:1-(2-methylphenyl)-4-methylamino-6-methyl-2,3-dihydropyrrolo(3,2-c)quinoline; D054460:rho-Associated Kinases; D011493:Protein Kinase C; C499850:Ppp1r12a protein, rat; D054645:Protein Phosphatase 1; D004110:Diltiazem; D009543:Nifedipine