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PHARMACOLOGICAL CHARACTERIZATION OF THE FUNCTIONAL ROLE OF CALCIUM-ACTIVATED POTASSIUM CHANNELS IN PLATELETS
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BifA, ICAA and flare could potentially help in the early identification of patients at high risk of developing carotid artery atherosclerosis.
336 PHARMACOLOGICAL CHARACTERIZATION OF THE FUNCTIONAL ROLE OF CALCIUMACTIVATED POTASSIUM CHANNELS IN PLATELETS V Back, F Plane, P Jurasz Edmonton, Alberta BACKGROUND:
In arteries, stimulation of endothelial cell small (SKCa) and intermediate (IKCa) conductance calcium-activated potassium channels provides a negative-feedback mechanism to limit agonist-induced vasoconstriction. Additionally, endothelial cell KCa channels in conjunction with nitric oxide (NO) mediate vasodilation in response to agonists and physical stimuli such as increases in blood flow. Platelets, like endothelial cells, possess KCa channels and have the capability to generate NO via endothelial nitric oxide synthase (eNOS). NO is known to limit platelet aggregation but the role of KCa channels in platelet function and NO-generation has not been explored. Our objective was to pharmacologically characterize SKCa and IKCa channel function in platelets, and to investigate their role in platelet NO production. Our hypothesis was that pharmacological activation of KCa channels would inhibit platelet aggregation and enhance platelet NO production. METHODS: Platelets were isolated from the blood of healthy volunteers and aggregometry performed in the presence of SKCa (CyPPA) and IKCa (SKA-31) channel activators. Dense granule secretion was measured by ATP chemiluminesence. DAF-FM flow cytometry was used to measure NO generation.
Canadian Journal of Cardiology Volume 32 2016 RESULTS:
CyPPA and SKA-31 inhibited collagen-induced aggregation in a concentration dependent manner (control: 75.337.21%, vs. CyPPA 10mM 29.6722.32% and 100mM 2.001.15%, N¼3, P<0.05) (control: 75.338.65% vs. SKA-31 10mM 31.3311.35% and 100mM 0.330.33%, N¼3, P<0.05). CyPPA and SKA-31 demonstrated similar inhibitory effects on platelet dense granule secretion (CyPPA 10 mM: 65.7411.04% reduction, N¼4; SKA-31 10mM: 55.306.74% reduction, N¼5). CyPPA and SKA-31 inhibited NO generation back to basal resting platelet levels. Calcium channel blocker nifedipine (10mM) potentiated the anti-aggregatory effects of 10mM CyPPA and SKA-31 (control 95.233.63% vs. CyPPA 79.122.87% vs. CyPPA and nifedipine 27.0614.17%, N¼4; control: 95.801.60% vs. SKA-31 67.1910.06% vs. 26.1713.31% SKA-31 and nifedipine, N¼4, P<0.05). IKCa selective channel blocker TRAM-34 reversed the antiaggregatory effects of 10mM SKA-31 but not CyPPA (control 95.801.60% vs. SKA-31 67.1910.06% vs. 73.697.76% SKA-31 and TRAM-34, N¼4, P<0.05) (control 95.233.63% vs. CyPPA 79.122.87% vs. 82.323.45% CyPPA and TRAM-34, N¼3). SKCa channel-selective blocker apamin did not reverse the effect of either CyPPA or SKA-31 (control 95.233.63% vs. CyPPA 79.122.87% vs. CyPPA and apamin 65.997.10% N¼3) (control 95.801.60% vs. SKA-31 67.1910.06% vs. 60.219.97% SKA-31 and apamin, N¼4). CONCLUSIONS: Activation of SKCa and IKCa channels inhibits both platelet aggregation and platelet NO generation. Furthermore, the use of selective blockers suggests that IKCa is the dominant KCachannel within platelets. These data indicate that KCa channels may provide novel targets for therapeutics to inhibit platelet aggregation.
337 SEX-RELATED HISTOLOGICAL DISCREPANCIES IN AORTIC STENOSIS: CONTRIBUTION OF VALVULAR FIBROSIS TO THE PATHOPHYSIOLOGY OF THE DISEASE L Simard, N Côté, P Pibarot, F Dagenais, P Mathieu, C Couture, S Trahan, Y Bossé, S Mohammadi, S Pagé, P Joubert, M Clavel Québec, Québec BACKGROUND:
We previously showed that, in aortic stenosis (AS), women present lower aortic valve calcium load than men for the same hemodynamic severity of AS. Since the two major mechanisms involved in AS are calcification and fibrosis of the valve, we hypothesized that women develop relatively more fibrosis and less calcification compared to men. METHODS: 12 men and 12 women were matched for AS severity, major clinical characteristics and comorbidities. 5 men and 5 women without AS who underwent a heart
BifA, ICAA and flare could potentially help in the early identification of patients at high risk of developing carotid artery atherosclerosis.
336 PHARMACOLOGICAL CHARACTERIZATION OF THE FUNCTIONAL ROLE OF CALCIUMACTIVATED POTASSIUM CHANNELS IN PLATELETS V Back, F Plane, P Jurasz Edmonton, Alberta BACKGROUND:
In arteries, stimulation of endothelial cell small (SKCa) and intermediate (IKCa) conductance calcium-activated potassium channels provides a negative-feedback mechanism to limit agonist-induced vasoconstriction. Additionally, endothelial cell KCa channels in conjunction with nitric oxide (NO) mediate vasodilation in response to agonists and physical stimuli such as increases in blood flow. Platelets, like endothelial cells, possess KCa channels and have the capability to generate NO via endothelial nitric oxide synthase (eNOS). NO is known to limit platelet aggregation but the role of KCa channels in platelet function and NO-generation has not been explored. Our objective was to pharmacologically characterize SKCa and IKCa channel function in platelets, and to investigate their role in platelet NO production. Our hypothesis was that pharmacological activation of KCa channels would inhibit platelet aggregation and enhance platelet NO production. METHODS: Platelets were isolated from the blood of healthy volunteers and aggregometry performed in the presence of SKCa (CyPPA) and IKCa (SKA-31) channel activators. Dense granule secretion was measured by ATP chemiluminesence. DAF-FM flow cytometry was used to measure NO generation.
Canadian Journal of Cardiology Volume 32 2016 RESULTS:
CyPPA and SKA-31 inhibited collagen-induced aggregation in a concentration dependent manner (control: 75.337.21%, vs. CyPPA 10mM 29.6722.32% and 100mM 2.001.15%, N¼3, P<0.05) (control: 75.338.65% vs. SKA-31 10mM 31.3311.35% and 100mM 0.330.33%, N¼3, P<0.05). CyPPA and SKA-31 demonstrated similar inhibitory effects on platelet dense granule secretion (CyPPA 10 mM: 65.7411.04% reduction, N¼4; SKA-31 10mM: 55.306.74% reduction, N¼5). CyPPA and SKA-31 inhibited NO generation back to basal resting platelet levels. Calcium channel blocker nifedipine (10mM) potentiated the anti-aggregatory effects of 10mM CyPPA and SKA-31 (control 95.233.63% vs. CyPPA 79.122.87% vs. CyPPA and nifedipine 27.0614.17%, N¼4; control: 95.801.60% vs. SKA-31 67.1910.06% vs. 26.1713.31% SKA-31 and nifedipine, N¼4, P<0.05). IKCa selective channel blocker TRAM-34 reversed the antiaggregatory effects of 10mM SKA-31 but not CyPPA (control 95.801.60% vs. SKA-31 67.1910.06% vs. 73.697.76% SKA-31 and TRAM-34, N¼4, P<0.05) (control 95.233.63% vs. CyPPA 79.122.87% vs. 82.323.45% CyPPA and TRAM-34, N¼3). SKCa channel-selective blocker apamin did not reverse the effect of either CyPPA or SKA-31 (control 95.233.63% vs. CyPPA 79.122.87% vs. CyPPA and apamin 65.997.10% N¼3) (control 95.801.60% vs. SKA-31 67.1910.06% vs. 60.219.97% SKA-31 and apamin, N¼4). CONCLUSIONS: Activation of SKCa and IKCa channels inhibits both platelet aggregation and platelet NO generation. Furthermore, the use of selective blockers suggests that IKCa is the dominant KCachannel within platelets. These data indicate that KCa channels may provide novel targets for therapeutics to inhibit platelet aggregation.
337 SEX-RELATED HISTOLOGICAL DISCREPANCIES IN AORTIC STENOSIS: CONTRIBUTION OF VALVULAR FIBROSIS TO THE PATHOPHYSIOLOGY OF THE DISEASE L Simard, N Côté, P Pibarot, F Dagenais, P Mathieu, C Couture, S Trahan, Y Bossé, S Mohammadi, S Pagé, P Joubert, M Clavel Québec, Québec BACKGROUND:
We previously showed that, in aortic stenosis (AS), women present lower aortic valve calcium load than men for the same hemodynamic severity of AS. Since the two major mechanisms involved in AS are calcification and fibrosis of the valve, we hypothesized that women develop relatively more fibrosis and less calcification compared to men. METHODS: 12 men and 12 women were matched for AS severity, major clinical characteristics and comorbidities. 5 men and 5 women without AS who underwent a heart