Calcium sensitization involved in dexmedetomidine-induced contraction of isolated rat aorta

Abstract

Dexmedetomidine, a full agonist of the α2B-adrenoceptor that is mainly involved in vascular smooth muscle contraction, is primarily used for analgesia and sedation in intensive care units. High-dose dexmedetomidine produces hypertension in children and adults. The goal of this in vitro study was to investigate the role of the calcium (Ca(2+)) sensitization mechanism involving Rho-kinase, protein kinase C (PKC), and phosphoinositide 3-kinase (PI3-K) in mediating contraction of isolated rat aortic smooth muscle in response to dexmedetomidine. The effect of dexmedetomidine on the intracellular Ca(2+) level ([Ca(2+)]i) and tension was measured simultaneously. Dexmedetomidine concentration-response curves were generated in the presence or absence of the following antagonists: rauwolscine, Y 27632, LY 294002, GF 109203X, and verapamil. Dexmedetomidine-induced phosphorylation of PKC and membrane translocation of Rho-kinase were detected with Western blotting. Rauwolscine, Y 27632, GF 109203X, LY 294002, and verapamil attenuated dexmedetomidine-induced contraction. The slope of the [Ca(2+)]i-tension curve for dexmedetomidine was higher than that for KCl. Dexmedetomidine induced phosphorylation of PKC and membrane translocation of Rho-kinase. These results suggest that dexmedetomidine-induced contraction involves a Ca(2+) sensitization mechanism mediated by Rho-kinase, PKC, and PI3-K that is secondary to α2-adrenoceptor stimulation in rat aortic smooth muscle.

Dexmedetomidine-Induced Contraction Involves CPI-17 Phosphorylation in Isolated Rat Aortas

“…In agreement with previous reports, rauwolscine attenuated dexmedetomidine-induced contraction, suggesting that dexmedetomidine-induced contraction involves activation of the α-2 adrenoceptor [15,21,22,23]. Similar to previous reports, chelerythrine and Y-27632 attenuated dexmedetomidine-induced contraction in a concentration-dependent manner, suggesting that dexmedetomidine-induced contraction is mediated by PKC and Rho-kinase [15,21,23,24].…”

“…Similar to previous reports, chelerythrine and Y-27632 attenuated dexmedetomidine-induced contraction in a concentration-dependent manner, suggesting that dexmedetomidine-induced contraction is mediated by PKC and Rho-kinase [15,21,23,24]. Consistent with a previous report, ML-7 hydrochloride attenuated dexmedetomidine-induced contraction, suggesting that dexmedetomidine-induced contraction involves activation of myosin light chain kinase [24].…”

“…A previous study demonstrated that the slope of the [Ca 2+ ] i -tension curve induced by dexmedetomidine is steeper than the slope of the [Ca 2+ ] i -tension curve induced by high KCl, suggesting that dexmedetomidine-induced α-2 adrenoceptor-mediated contraction would be mediated by calcium sensitization [15]. However, the downstream cellular signal pathways associated with specific protein kinases that contribute to calcium sensitization remain unknown.…”

“…The inhibition of MLCP in vascular smooth muscle is mediated by phosphorylation of either the phosphorylation-dependent inhibitory protein of myosin phosphatase (CPI-17) or the myosin phosphatase target subunit of MLCP via either Rho-kinase or protein kinase C (PKC), which leads to attenuated dephosphorylation of MLC 20 [13,14]. We previously reported that the slopes of [Ca 2+ ] i -tension curves induced by dexmedetomidine are higher than those induced by high KCl in isolated rat aortas, suggesting that dexmedetomidine-induced contraction produces a relatively greater increase in calcium sensitization [15]. However, the specific protein kinases and associated cellular pathways primarily responsible for increased calcium sensitization in response to dexmedetomidine remain unknown.…”

A polymorphism in the protein kinase C gene PRKCB is associated with α2-adrenoceptor-mediated vasoconstriction

“…Interactions of α 2 -ARs with PKC have been suggested to lead to Ca 2+ influx and vasoconstriction [14,17]. Kim et al recently reported that activation of α 2 -ARs by dexmedetomidine resulted in a constriction response involving a Ca 2+ sensitization mechanism mediated by Rho kinase, PKC, and phosphatidylinositol 3-kinase [26]. …”