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Dexmedetomidine-induced contraction involves phosphorylation of caldesmon by JNK in endothelium-denuded rat aortas.

Baik J, Ok SH, Cho H, Yu J, Kim W, Nam IK, Choi MJ, Lee HK, Sohn JT - Int. J. Biol. Sci. (2014)

Bottom Line: The effects of GF109203X (a PKC inhibitor) on DMT- or PDBu-induced JNK phosphorylation in VSMCs were assessed.Chelerythrine resulted in the vasodilation of aortas pre-contracted with DMT.DMT induced PKC phosphorylation in rat aortic VSMCs.

View Article: PubMed Central - PubMed

Affiliation: 1. Department of Anesthesiology and Pain Medicine, Pusan National University Hospital, Biomed Research Institute, Pusan National University School of Medicine, Busan, Republic of Korea.

ABSTRACT
Caldesmon, an inhibitory actin binding protein, binds to actin and inhibits actin-myosin interactions, whereas caldesmon phosphorylation reverses the inhibitory effect of caldesmon on actin-myosin interactions, potentially leading to enhanced contraction. The goal of this study was to investigate the cellular signaling pathway responsible for caldesmon phosphorylation, which is involved in the regulation of the contraction induced by dexmedetomidine (DMT), an alpha-2 adrenoceptor agonist, in endothelium-denuded rat aortas. SP600125 (a c-Jun NH2-terminal kinase [JNK] inhibitor) dose-response curves were generated in aortas that were pre-contracted with DMT or phorbol 12,13-dibutyrate (PDBu), a protein kinase C (PKC) activator. Dose-response curves to the PKC inhibitor chelerythrine were generated in rat aortas pre-contracted with DMT. The effects of SP600125 and rauwolscine (an alpha-2 adrenoceptor inhibitor) on DMT-induced caldesmon phosphorylation in rat aortic vascular smooth muscle cells (VSMCs) were investigated by western blot analysis. PDBu-induced caldesmon and DMT-induced PKC phosphorylation in rat aortic VSMCs was investigated by western blot analysis. The effects of GF109203X (a PKC inhibitor) on DMT- or PDBu-induced JNK phosphorylation in VSMCs were assessed. SP600125 resulted in the relaxation of aortas that were pre-contracted with DMT or PDBu, whereas rauwolscine attenuated DMT-induced contraction. Chelerythrine resulted in the vasodilation of aortas pre-contracted with DMT. SP600125 and rauwolscine inhibited DMT-induced caldesmon phosphorylation. Additionally, PDBu induced caldesmon phosphorylation, and GF109203X attenuated the JNK phosphorylation induced by DMT or PDBu. DMT induced PKC phosphorylation in rat aortic VSMCs. These results suggest that alpha-2 adrenoceptor-mediated, DMT-induced contraction involves caldesmon phosphorylation that is mediated by JNK phosphorylation by PKC.

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The putative cellular signal transduction pathway responsible for the caldesmon phosphorylation involved in dexmedetomidine (DMT)-induced contraction of rat aortic smooth muscle cells. PKC: protein kinase C; JNK: c-Jun NH2-terminal kinase.
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Figure 6: The putative cellular signal transduction pathway responsible for the caldesmon phosphorylation involved in dexmedetomidine (DMT)-induced contraction of rat aortic smooth muscle cells. PKC: protein kinase C; JNK: c-Jun NH2-terminal kinase.

Mentions: Caldesmon binds to actin and inhibits the interaction between actin and myosin, thereby regulating smooth muscle contraction 14. The inhibitory effect of the heavy isoform of caldesmon on actin-myosin interactions is reversed by either Ca2+/calmodulin or caldesmon phosphorylation [21.22]. In addition, caldesmon phosphorylation induced by the PKC stimulant phorbol ester, which results in smooth muscle contraction, is mediated by an extracellular signal-regulated kinase 23. Similar to a previous report, SP600125 attenuated DMT-induced caldesmon phosphorylation (Fig. 3), and PDBu also induced caldesmon phosphorylation 23. Rauwolscine attenuated the caldesmon phosphorylation induced by DMT (Fig. 4A). Together, DMT-induced caldesmon phosphorylation, which increases actin availability for interaction with myosin, appears to be mediated by a pathway involving the alpha-2 adrenoceptor and JNK in rat aortic smooth muscle. GF109203X attenuated JNK phosphorylation (Fig. 4C and 5A) induced by DMT or PDBu, and these results suggest that PKC is an upstream effector of JNK that mediates DMT-induced caldesmon phosphorylation. Thus, together with results from isometric tension measurements, SP600125- and chelerythrine-induced inhibition of DMT-mediated contraction appears to be partially associated with the decreased availability of unbound actin. Consistent with a previous study and the results of current tension study, DMT induced PKC phosphorylation, suggesting the involvement of PKC in DMT-induced contraction 11. Further research regarding the involvement of PKC in DMT-induced caldesmon phosphorylation is needed to confirm the involvement of a PKC-JNK axis in this phosphorylation event. Combined with the results of previous studies, the putative cellular mechanism responsible for DMT-induced caldesmon phosphorylation is as follows: alpha-2 adrenoceptor-mediated, DMT-induced contraction involves caldesmon phosphorylation through the activation of JNK, which is mediated by PKC (Fig. 6) 10,11. Further studies regarding the effects of other signaling pathways (e.g., calcium/calmodulin or p21-activated protein kinase) on the caldesmon-mediated inhibition of actin availability during DMT-induced contraction and detailed information on the pathway downstream of caldesmon phosphorylation are warranted.


Dexmedetomidine-induced contraction involves phosphorylation of caldesmon by JNK in endothelium-denuded rat aortas.

Baik J, Ok SH, Cho H, Yu J, Kim W, Nam IK, Choi MJ, Lee HK, Sohn JT - Int. J. Biol. Sci. (2014)

The putative cellular signal transduction pathway responsible for the caldesmon phosphorylation involved in dexmedetomidine (DMT)-induced contraction of rat aortic smooth muscle cells. PKC: protein kinase C; JNK: c-Jun NH2-terminal kinase.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4202027&req=5

Figure 6: The putative cellular signal transduction pathway responsible for the caldesmon phosphorylation involved in dexmedetomidine (DMT)-induced contraction of rat aortic smooth muscle cells. PKC: protein kinase C; JNK: c-Jun NH2-terminal kinase.
Mentions: Caldesmon binds to actin and inhibits the interaction between actin and myosin, thereby regulating smooth muscle contraction 14. The inhibitory effect of the heavy isoform of caldesmon on actin-myosin interactions is reversed by either Ca2+/calmodulin or caldesmon phosphorylation [21.22]. In addition, caldesmon phosphorylation induced by the PKC stimulant phorbol ester, which results in smooth muscle contraction, is mediated by an extracellular signal-regulated kinase 23. Similar to a previous report, SP600125 attenuated DMT-induced caldesmon phosphorylation (Fig. 3), and PDBu also induced caldesmon phosphorylation 23. Rauwolscine attenuated the caldesmon phosphorylation induced by DMT (Fig. 4A). Together, DMT-induced caldesmon phosphorylation, which increases actin availability for interaction with myosin, appears to be mediated by a pathway involving the alpha-2 adrenoceptor and JNK in rat aortic smooth muscle. GF109203X attenuated JNK phosphorylation (Fig. 4C and 5A) induced by DMT or PDBu, and these results suggest that PKC is an upstream effector of JNK that mediates DMT-induced caldesmon phosphorylation. Thus, together with results from isometric tension measurements, SP600125- and chelerythrine-induced inhibition of DMT-mediated contraction appears to be partially associated with the decreased availability of unbound actin. Consistent with a previous study and the results of current tension study, DMT induced PKC phosphorylation, suggesting the involvement of PKC in DMT-induced contraction 11. Further research regarding the involvement of PKC in DMT-induced caldesmon phosphorylation is needed to confirm the involvement of a PKC-JNK axis in this phosphorylation event. Combined with the results of previous studies, the putative cellular mechanism responsible for DMT-induced caldesmon phosphorylation is as follows: alpha-2 adrenoceptor-mediated, DMT-induced contraction involves caldesmon phosphorylation through the activation of JNK, which is mediated by PKC (Fig. 6) 10,11. Further studies regarding the effects of other signaling pathways (e.g., calcium/calmodulin or p21-activated protein kinase) on the caldesmon-mediated inhibition of actin availability during DMT-induced contraction and detailed information on the pathway downstream of caldesmon phosphorylation are warranted.

Bottom Line: The effects of GF109203X (a PKC inhibitor) on DMT- or PDBu-induced JNK phosphorylation in VSMCs were assessed.Chelerythrine resulted in the vasodilation of aortas pre-contracted with DMT.DMT induced PKC phosphorylation in rat aortic VSMCs.

View Article: PubMed Central - PubMed

Affiliation: 1. Department of Anesthesiology and Pain Medicine, Pusan National University Hospital, Biomed Research Institute, Pusan National University School of Medicine, Busan, Republic of Korea.

ABSTRACT
Caldesmon, an inhibitory actin binding protein, binds to actin and inhibits actin-myosin interactions, whereas caldesmon phosphorylation reverses the inhibitory effect of caldesmon on actin-myosin interactions, potentially leading to enhanced contraction. The goal of this study was to investigate the cellular signaling pathway responsible for caldesmon phosphorylation, which is involved in the regulation of the contraction induced by dexmedetomidine (DMT), an alpha-2 adrenoceptor agonist, in endothelium-denuded rat aortas. SP600125 (a c-Jun NH2-terminal kinase [JNK] inhibitor) dose-response curves were generated in aortas that were pre-contracted with DMT or phorbol 12,13-dibutyrate (PDBu), a protein kinase C (PKC) activator. Dose-response curves to the PKC inhibitor chelerythrine were generated in rat aortas pre-contracted with DMT. The effects of SP600125 and rauwolscine (an alpha-2 adrenoceptor inhibitor) on DMT-induced caldesmon phosphorylation in rat aortic vascular smooth muscle cells (VSMCs) were investigated by western blot analysis. PDBu-induced caldesmon and DMT-induced PKC phosphorylation in rat aortic VSMCs was investigated by western blot analysis. The effects of GF109203X (a PKC inhibitor) on DMT- or PDBu-induced JNK phosphorylation in VSMCs were assessed. SP600125 resulted in the relaxation of aortas that were pre-contracted with DMT or PDBu, whereas rauwolscine attenuated DMT-induced contraction. Chelerythrine resulted in the vasodilation of aortas pre-contracted with DMT. SP600125 and rauwolscine inhibited DMT-induced caldesmon phosphorylation. Additionally, PDBu induced caldesmon phosphorylation, and GF109203X attenuated the JNK phosphorylation induced by DMT or PDBu. DMT induced PKC phosphorylation in rat aortic VSMCs. These results suggest that alpha-2 adrenoceptor-mediated, DMT-induced contraction involves caldesmon phosphorylation that is mediated by JNK phosphorylation by PKC.

Show MeSH
Related in: MedlinePlus