The Vasorelaxant Effects Of Vascular Smooth Muscle By Novel Potassium Channel Opener QO-58

Hypertension is the most common chronic cardiovascular disease, whichcan damage heart, brain, kidney and other organs. To control high bloodpressure is the key to the prevention and treatment of cardiac and cerebralvessels disease. Therefore, it is necessary to research and develop efficient andsafe anti-hypertensive drugs.Potassium channels are widely distributed in vascular smooth muscles.The voltage dependent potassium channels (Kv7) encoded by KCNQ genescan control the tention of vascular smooth muscle effectively.QO-58is one ofpyrazolo[1,5-a]pyrimidin-7(4H)-one (PPO) compounds. It can open KCNQ/Mchannels. We aimed to study the effects of QO-58on isolated arteriole ringsand the underlying mechanisms; to study the effects of QO-58on bloodpressure and heart rate of SHRs; to further explore its posslble mechanism.Itwill provide theoretical and experimental basis for the treatment of high bloodpressure.Part1The effects of QO-58on isolated arteriole ringsObjective: To observe the vasorelaxant effects of QO-58on mesentericarteriole, renal arteriole, basilar artery and coronary artery and to explore itsposslble mechanism.Methods: The vasorelaxant effects of QO-58on mesenteric arteriole,renal arteriole, basilar artery and coronary artery induced by KCl orPhenylephrine (PHE) using Multi Myograph and compare with the group ofnifedipine. In addition, we also observe the response of Kv7channel blockerXE991to QO-58.The real-time PCR method was employed to measure thecontent of KCNQ4RNA of mesenteric arteriole, renal arteriole, basilar arteryand coronary artery.Results: 1Vasorelaxant effects of QO-58on isolated mesenteric arteriolesQO-58in the concentration of1μmol/L~300μmol/L produced aconcentration-dependent relaxation on mesenteric arterioles precontractedwith60mmol/L KCl with or without10μmol/L XE991, and EC50value:19.1±1.0μmol/L and18.4±3.1μmol/L. The two have no statistical difference (P>0.05). Vasorelaxant effects of QO-58induced by KCl and XE991in theconcentration of100μmol/L and300μmol/L is reduced significantlycompared with the group of induced by KCl(P <0.01，P <0.05).QO-58in the concentration of1μmol/L~300μmol/L produced aconcentration-dependent relaxation on mesenteric arterioles precontractedwith10μmol/L PHE with or without10μmol/L XE991, and EC50value:3.3±0.3μmol/L and5.77±0.25μmol/L. The two have significant difference (P<0.05). Vasorelaxant effects of QO-58induced by PHE and XE991in theconcentration of1μmol/L and3μmol/L is reduced significantly comparedwith the group of induced by PHE (P <0.01). And the dose effect curve movedto the right.QO-58in the concentration of1μmol/L~300μmol/L produced aconcentration-dependent relaxation on mesenteric arterioles precontractedwith120mmol/L KCl, EC50value:17.97±1.58μmol/L. It has no statisticaldifference compared with the group of induced by60mmol/L KCl,which EC50value is19.1±1.0μmol/L (P>0.05). But significantly reduced in theconcentration of30μmol/L,100μmol/L and300μmol/L(P <0.01，P <0.05).The dose effect curve of QO-58on isolated mesenteric arteriolesprecontracted with60mmol/L KCl is moved to the right compared with thegroup of induced by PHE (P <0.01).Nifedipine in the concentration of1×10-4μmol/L~10μmol/L produced aconcentration-dependent relaxation on mesenteric arterioles precontractedwith60mmol/L KCl. EC50value is3.5±0.4nmol/L. It significantly reducedcompared with the relaxation of QO-58(P <0.01).The potency of nifedipine isgreater than QO-58.2Vasorelaxant effects of QO-58on isolated renal arterioles QO-58in the concentration of1μmol/L~300μmol/L produced aconcentration-dependent relaxation on renal arterioles precontracted with60mmol/L KCl with or without10μmol/L XE991, and EC50value:55.0±21.7μmol/L and56.3±5.0μmol/L. Vasorelaxant effects of QO-58induced by KCland XE991in the concentration of10μmol/L,30μmol/L and300μmol/L isreduced significantly compared with the group of induced by KCl(P <0.05).And the dose effect curve is moved to the right.QO-58in the concentration of1μmol/L~100μmol/L produced aconcentration-dependent relaxation on renal arterioles precontracted with1μmol/L PHE with or without10μmol/L XE991, and EC50value:6.25±1.04μmol/L and23.4±1.19μmol/L. Vasorelaxant effects of QO-58induced byPHE and XE991in the concentration of1μmol/L and3μmol/L is reducedsignificantly compared with the group of induced by PHE (P <0.01). And thedose effect curve moved to the right.These results indicatet that XE991canweaken the vasorelaxant effects of QO-58on isolated renal arterioles.The dose effect curve of QO-58on isolated renal arterioles precontractedwith60mmol/L KCl is moved to the right compared with the group ofinduced by PHE (P <0.01).QO-58in the concentration of1μmol/L~100μmol/L produced aconcentration-dependentrelaxation on renal arterioles from SHR precontractedwith1μmol/L PHE. And EC50value is5.28±0.78μmol/L,it reducedsignificantly compared with SD rat (P <0.05). This indicates that SHR is moresensitive to QO58than SD rat.Nifedipine in the concentration of1×10-4μmol/L~10μmol/L produced aconcentration-dependent relaxation on renal arterioles precontracted with1μmol/L PHE. EC50value is38.0±2.6nmol/L. It significantly reducedcompared with the relaxation of QO-58(P <0.01).The potency of nifedipine torelax renal arterioles is greater than QO-58.3Vasorelaxant effects of QO-58on isolated basilar arteryQO-58in the concentration of1μmol/L~300μmol/L produced aconcentration-dependent relaxation on basilar artery precontracted with60 mmol/L KCl with or without10μmol/L XE991, and EC50value:26.4±3.4μmol/L and26.4±0.6μmol/L. Vasorelaxant effects of QO-58induced by KCland XE991in the concentration of3μmol/L and10μmol/L is reducedsignificantly compared with the group of induced by KCl(P <0.05). Theseresults indicatet that XE991can weaken the vasorelaxant effects of QO-58onisolated basilar artery.Nifedipine in the concentration of1×10-4μmol/L~10μmol/L produced aconcentration-dependent relaxation on basilar artery precontracted with60mmol/L KCl. EC50value is12.6±3.6nmol/L. It significantly reducedcompared with the relaxation of QO-58(P <0.01).This indicates that thepotency of nifedipine to relax basilar artery is greater than QO-58.4Vasorelaxant effects of QO-58on isolated coronary arteryQO-58in the concentration of10μmol/L~1mmol/L produced aconcentration-dependent relaxation on coronary artery precontracted with60mmol/L KCl with or without10μmol/L XE991, and EC50value:105.8±0.7μmol/L and107.0±5.2μmol/L. Vasorelaxant effects of QO-58induced byKCl and XE991in the concentration of300μmol/L and1mmol/L is reducedsignificantly compared with the group of induced by KCl (P<0.05). Theseresults indicatet that XE991can weaken the vasorelaxant effects of QO-58onisolated coronary artery.Nifedipine in the concentration of1×10-4μmol/L~10μmol/L produceda concentration-dependent relaxation on coronary artery precontracted with60mmol/L KCl. EC50value is6.39±0.34nmol/L. It significantly reducedcompared with the relaxation of QO-58(P<0.01).This indicates that thepotency of nifedipine to relax coronary artery is greater than QO-58.5Compare the content of KCNQ4RNA of mesenteric arteriole, renalarteriole, basilar artery and coronary artery of SD rat.Compared with the coronary artery (Ct:11.21±0.27), the content ofKCNQ4RNA of mesenteric arteriole (Ct:9.29±0.29) increased significantly(P<0.01); the content of KCNQ4RNA of renal arteriole (Ct:9.48±0.72)increased significantly (P<0.05); the content of KCNQ4RNA of basilar artery (Ct:10.42±0.40) increased significantly (P<0.05); the content of KCNQ4RNA: mesenteric arteriole>renal arteriole> basilar artery>coronary artery.This result is consistent with the potency of QO-58to relax blood vessels, alsoproved that QO58relax blood vessels associated with the open of Kv7.4potassium channels.Conclusion: QO-58can produce a concentration-dependent relaxation onprecontracted mesenteric arteriole, renal arteriole, basilar artery and coronaryartery of SD rat.And the effect to relax blood vessels is related to the open ofKv7potassium channelsPart2The effects of QO-58on heart rate and blood pressure of SHRsObjective: We aimed to study the influence of QO-58to the heart rateand blood pressure of spontaneous hypertensive rat (SHR).Methods: The group of solvent was used as the negative control.Theexperiment is divided into10groups:the SHRs is divided into9group:QO-581.25mg/kg, QO-582.5mg/kg, QO-585mg/kg, QO-5810mg/kg,QO-581.25mg/Kg+nifedipine1mg/kg, QO-582.5mg/kg+nifedipine1mg/kg,nifedipine1mg/kg, retigabine5mg/kg, only solvent (control);. SD rat: QO-585mg/kg. SHRs were injected with diffrrent drugs by tail vein and the heartrate and blood pressure were measured.Results:1The effects of QO-58on heart rateCompared with before dosing,the group of QO-582.5mg/kg,5mg/kg,10mg/kg, retigabine5mg/kg can reduce heart rate of SHRsconcentration-dependently,the group of nifedipine1mg/kg can increase heartrate of SHRs.The group of control has no statistical difference before and afterdosing. SD rats injected with QO-585mg/kg have no significant effect onheart rate (0.3±2.0)(P>0.05).The group of QO-585mg/kg and the group of retigabine5mg/kg cansignificantly slow down the heart rate compared with the control (p<0.05).The group of QO-581.25mg/kg (-17.7±9.2), QO-582.5mg/kg (-21.5±8.7),QO-5810mg/kg (-31.1±8.1) have a tendency to slow down heart rate, but no statistical difference (P>0.05). The group of nifedipine1mg/kg can increaseheart rate, but no statistical difference compared with the control (P>0.05).2The effects of QO-58on systolic pressureCompared with before dosing, QO-58can reduce systolic pressure ofSHRs concentration-dependently; the group of retigabine5mg/kg, nifedipine1mg/kg, QO-581.25mg/kg+nifedipine1mg/kg, QO-582.5mg/kg+nifedipine1mg/kg, all of them can reduce the systolic pressure significantly (P<0.01); The group of control has no statistical difference before and afterdosing. SD rats injected with QO-585mg/kg have no significant effect onheart rate (P>0.05).The group of QO-582.5mg/kg and the group of QO-5810mg/kg cansignificantly reduce the systolic pressure of SHR compared with the control (P<0.01). The group of QO-581.25mg/kg and the group of QO-585mg/kg canreduce the systolic pressure, but no statistical difference compared with thecontrol (P>0.05). The group of QO-581.25mg/kg+nifedipine1mg/kg,QO-582.5mg/kg+nifedipine1mg/kg, nifedipine1mg/kg and retigabine5mg/kg,all of them can reduce the systolic pressure significantly (P <0.01).3The effects of QO-58on diastolic pressureCompared with before dosing, the group of QO-585mg/kg, QO-5810mg/kg, retigabine5mg/kg, nifedipine1mg/kg, QO-582.5mg/kg+nifedipine1mg/kg, QO-581.25mg/kg+nifedipine1mg/kg,all of them can reducediastolic pressure of SHRs concentration-dependently（P <0.05，P <0.01）; SDrats injected with QO-585mg/kg have no significant effect on heart rate (P>0.05).The group of QO-5810mg/kg, the group of retigabine5mg/kg and thegroup of nifedipine1mg/kg can significantly reduce the diastolic pressure ofSHRs compared with the control (P<0.01). Other groups have no differencecompared with the control.Conclusion: SD rats injected with QO-58have no significant effect onheart rate, systolic pressure and diastolic pressure. But QO-58cansignificantly reduce the heart rate, systolic pressure and diastolic pressure of SHRs.This indicates that QO-58might therapy hypertension and protect theheart.