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Insulin induces the release of vasodilator compounds from platelets by a nitric oxide-G kinase-VAMP-3-dependent pathway.

Randriamboavonjy V, Schrader J, Busse R, Fleming I - J. Exp. Med. (2004)

Bottom Line: Insulin failed to relax endothelium-intact rings of porcine coronary artery.Insulin induced the release of adenosine trisphosphate (ATP), adenosine, and serotonin from platelet-dense granules in a NO-dependent manner.The mechanism of dense granule secretion involves the G kinase-dependent association of syntaxin 2 with vesicle-associated membrane protein 3.

View Article: PubMed Central - PubMed

Affiliation: Institut für Kardiovaskuläre Physiologie, Klinikum der J.W.Goethe-Universität, D-60590 Frankfurt am Main, Germany.

ABSTRACT
Insulin-induced vasodilatation is sensitive to nitric oxide (NO) synthase (NOS) inhibitors. However, insulin is unable to relax isolated arteries or to activate endothelial NOS in endothelial cells. Since insulin can enhance platelet endothelial NOS activity, we determined whether insulin-induced vasodilatation can be attributed to a NO-dependent, platelet-mediated process. Insulin failed to relax endothelium-intact rings of porcine coronary artery. The supernatant from insulin-stimulated human platelets induced complete relaxation, which was prevented by preincubation of platelets with a NOS inhibitor, the soluble guanylyl cyclase inhibitor, NS 2028, or the G kinase inhibitor, KT 5823, and was abolished by an adenosine A2A receptor antagonist. Insulin induced the release of adenosine trisphosphate (ATP), adenosine, and serotonin from platelet-dense granules in a NO-dependent manner. This response was not detected using insulin-stimulated platelets from endothelial NOS-/- mice, although a NO donor elicited ATP release. Insulin-induced ATP release from human platelets correlated with the association of syntaxin 2 with the vesicle-associated membrane protein 3 but was not associated with the activation of alphaIIbbeta3 integrin. Thus, insulin elicits the release of vasoactive concentrations of ATP and adenosine from human platelets via a NO-G kinase-dependent signaling cascade. The mechanism of dense granule secretion involves the G kinase-dependent association of syntaxin 2 with vesicle-associated membrane protein 3.

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Relaxing factor derived from insulin-stimulated washed human platelets. (a) Original tracings and (b) statistical summary showing the effect of the direct application of human insulin (1 μmol/L), the supernatant from unstimulated platelets (Sol), the supernatant from insulin-stimulated (1 μmol/l, 10 min) platelets, and from platelets stimulated with insulin in the presence of L-NA (300 μmol/L) on the tone of endothelium-intact small porcine coronary arteries precontracted with the thromboxane analogue U46619. (c) Statistical summary showing the concentration-dependent effect of insulin (1 nmol/L–1 μmol/L) on the release of a relaxing factor from platelets. The results shown represent the mean ± SEM of data obtained in six independent experiments; *P < 0.05, **P < 0.01, and ***P < 0.001 versus the response obtained using the supernatant from unstimulated platelets (Sol).
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fig1: Relaxing factor derived from insulin-stimulated washed human platelets. (a) Original tracings and (b) statistical summary showing the effect of the direct application of human insulin (1 μmol/L), the supernatant from unstimulated platelets (Sol), the supernatant from insulin-stimulated (1 μmol/l, 10 min) platelets, and from platelets stimulated with insulin in the presence of L-NA (300 μmol/L) on the tone of endothelium-intact small porcine coronary arteries precontracted with the thromboxane analogue U46619. (c) Statistical summary showing the concentration-dependent effect of insulin (1 nmol/L–1 μmol/L) on the release of a relaxing factor from platelets. The results shown represent the mean ± SEM of data obtained in six independent experiments; *P < 0.05, **P < 0.01, and ***P < 0.001 versus the response obtained using the supernatant from unstimulated platelets (Sol).

Mentions: The direct application of insulin (1 μmol/L) to precontracted, endothelium-intact, small porcine coronary artery rings failed to elicit any change in tone (Fig. 1 a). However, the addition of washed human platelets to the organ chamber resulted in platelet aggregation, as a consequence of the activation by the thromboxane analogue used to precontract the coronary arteries (not depicted). However, the supernatant from insulin (1 mmol/L)-stimulated human platelets elicited the rapid relaxation of arterial rings; Rmax values were 11.4 ± 3.1 in response to the supernatant of unstimulated platelets versus 68.5 ± 8.3% in response to the supernatant from insulin-stimulated platelets. The supernatant from insulin-stimulated platelets, which were pretreated with the NOS inhibitor L-NA (300 μmol/L, 30 min), failed to relax coronary artery rings. The effect of insulin on the release of the platelet-derived relaxing factor was concentration dependent, and a small but significant relaxation was observed in response to the application of supernatant removed from platelets stimulated with 1 nmol/L insulin (Fig. 1 c).


Insulin induces the release of vasodilator compounds from platelets by a nitric oxide-G kinase-VAMP-3-dependent pathway.

Randriamboavonjy V, Schrader J, Busse R, Fleming I - J. Exp. Med. (2004)

Relaxing factor derived from insulin-stimulated washed human platelets. (a) Original tracings and (b) statistical summary showing the effect of the direct application of human insulin (1 μmol/L), the supernatant from unstimulated platelets (Sol), the supernatant from insulin-stimulated (1 μmol/l, 10 min) platelets, and from platelets stimulated with insulin in the presence of L-NA (300 μmol/L) on the tone of endothelium-intact small porcine coronary arteries precontracted with the thromboxane analogue U46619. (c) Statistical summary showing the concentration-dependent effect of insulin (1 nmol/L–1 μmol/L) on the release of a relaxing factor from platelets. The results shown represent the mean ± SEM of data obtained in six independent experiments; *P < 0.05, **P < 0.01, and ***P < 0.001 versus the response obtained using the supernatant from unstimulated platelets (Sol).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2211801&req=5

fig1: Relaxing factor derived from insulin-stimulated washed human platelets. (a) Original tracings and (b) statistical summary showing the effect of the direct application of human insulin (1 μmol/L), the supernatant from unstimulated platelets (Sol), the supernatant from insulin-stimulated (1 μmol/l, 10 min) platelets, and from platelets stimulated with insulin in the presence of L-NA (300 μmol/L) on the tone of endothelium-intact small porcine coronary arteries precontracted with the thromboxane analogue U46619. (c) Statistical summary showing the concentration-dependent effect of insulin (1 nmol/L–1 μmol/L) on the release of a relaxing factor from platelets. The results shown represent the mean ± SEM of data obtained in six independent experiments; *P < 0.05, **P < 0.01, and ***P < 0.001 versus the response obtained using the supernatant from unstimulated platelets (Sol).
Mentions: The direct application of insulin (1 μmol/L) to precontracted, endothelium-intact, small porcine coronary artery rings failed to elicit any change in tone (Fig. 1 a). However, the addition of washed human platelets to the organ chamber resulted in platelet aggregation, as a consequence of the activation by the thromboxane analogue used to precontract the coronary arteries (not depicted). However, the supernatant from insulin (1 mmol/L)-stimulated human platelets elicited the rapid relaxation of arterial rings; Rmax values were 11.4 ± 3.1 in response to the supernatant of unstimulated platelets versus 68.5 ± 8.3% in response to the supernatant from insulin-stimulated platelets. The supernatant from insulin-stimulated platelets, which were pretreated with the NOS inhibitor L-NA (300 μmol/L, 30 min), failed to relax coronary artery rings. The effect of insulin on the release of the platelet-derived relaxing factor was concentration dependent, and a small but significant relaxation was observed in response to the application of supernatant removed from platelets stimulated with 1 nmol/L insulin (Fig. 1 c).

Bottom Line: Insulin failed to relax endothelium-intact rings of porcine coronary artery.Insulin induced the release of adenosine trisphosphate (ATP), adenosine, and serotonin from platelet-dense granules in a NO-dependent manner.The mechanism of dense granule secretion involves the G kinase-dependent association of syntaxin 2 with vesicle-associated membrane protein 3.

View Article: PubMed Central - PubMed

Affiliation: Institut für Kardiovaskuläre Physiologie, Klinikum der J.W.Goethe-Universität, D-60590 Frankfurt am Main, Germany.

ABSTRACT
Insulin-induced vasodilatation is sensitive to nitric oxide (NO) synthase (NOS) inhibitors. However, insulin is unable to relax isolated arteries or to activate endothelial NOS in endothelial cells. Since insulin can enhance platelet endothelial NOS activity, we determined whether insulin-induced vasodilatation can be attributed to a NO-dependent, platelet-mediated process. Insulin failed to relax endothelium-intact rings of porcine coronary artery. The supernatant from insulin-stimulated human platelets induced complete relaxation, which was prevented by preincubation of platelets with a NOS inhibitor, the soluble guanylyl cyclase inhibitor, NS 2028, or the G kinase inhibitor, KT 5823, and was abolished by an adenosine A2A receptor antagonist. Insulin induced the release of adenosine trisphosphate (ATP), adenosine, and serotonin from platelet-dense granules in a NO-dependent manner. This response was not detected using insulin-stimulated platelets from endothelial NOS-/- mice, although a NO donor elicited ATP release. Insulin-induced ATP release from human platelets correlated with the association of syntaxin 2 with the vesicle-associated membrane protein 3 but was not associated with the activation of alphaIIbbeta3 integrin. Thus, insulin elicits the release of vasoactive concentrations of ATP and adenosine from human platelets via a NO-G kinase-dependent signaling cascade. The mechanism of dense granule secretion involves the G kinase-dependent association of syntaxin 2 with vesicle-associated membrane protein 3.

Show MeSH
Related in: MedlinePlus