Thrombin-mediated increases in cytosolic [Ca2+] involve different mechanisms in human pulmonary artery smooth muscle and endothelial cells.
Thrombin is a procoagulant inflammatory agonist that can disrupt the endothelium-lumen barrier in the lung by causing contraction of endothelial cells and promote pulmonary cell proliferation. Both contraction and proliferation require increases in cytosolic Ca(2+) concentration ([Ca(2+)](cyt)). In this study, we compared the effect of thrombin on Ca(2+) signaling in human pulmonary artery smooth muscle (PASMC) and endothelial (PAEC) cells. Thrombin increased the [Ca(2+)](cyt) in both cell types; however, the transient response was significantly higher and recovered quicker in the PASMC, suggesting different mechanisms may contribute to thrombin-mediated increases in [Ca(2+)](cyt) in these cell types. Depletion of intracellular stores with cyclopiazonic acid (CPA) in the absence of extracellular Ca(2+) induced calcium transients representative of those observed in response to thrombin in both cell types. Interestingly, CPA pretreatment significantly attenuated thrombin-induced Ca(2+) release in PASMC; this attenuation was not apparent in PAEC, indicating that a PAEC-specific mechanism was targeted by thrombin. Treatment with a combination of CPA, caffeine, and ryanodine also failed to abolish the thrombin-induced Ca(2+) transient in PAEC. Notably, thrombin-induced receptor-mediated calcium influx was still observed in PASMC after CPA pretreatment in the presence of extracellular Ca(2+). Ca(2+) oscillations were triggered by thrombin in PASMC resulting from a balance of extracellular Ca(2+) influx and Ca(2+) reuptake by the sarcoplasmic reticulum. The data show that thrombin induces increases in intracellular calcium in PASMC and PAEC with a distinct CPA-, caffeine-, and ryanodine-insensitive release existing only in PAEC. Furthermore, a dynamic balance between Ca(2+) influx, intracellular Ca(2+) release, and reuptake underlie the Ca(2+) transients evoked by thrombin in some PASMC. Understanding of such mechanisms will provide an important insight into thrombin-mediated vascular injury during hypertension.
Division of Pulmonary and Critical Care Medicine, Dept. of Medicine, Univ. of California, San Diego, 9500 Gilman Drive, MC 0725, La Jolla, CA 92093-0725,USA.
Richard S
RS
Sacks
Amy L
AL
Firth
Carmelle V
CV
Remillard
Negin
N
Agange
Jocelyn
J
Yau
Eun A
EA
Ko
Jason X-J
JX
Yuan
D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009928:Organ Specificity / Q000502:physiology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology*
D007211:Indoles; D010726:Phosphodiesterase Inhibitors; D012433:Ryanodine; D002110:Caffeine; D013917:Thrombin; D002118:Calcium; C000543:cyclopiazonic acid