Enhancement Of Antihypertensive Effect And Reduction Of Cough By Combining Luteolin With Low-dose Captopril

Background and objectives:Antihypertensive and protecting target organ functions of angiotensin converting enzyme inhibitors(ACEI)have been recognized worldwide,but the incidence of excitant dry cough caused by ACEI is very high.It is of great clinical application significance in an effort to reduce the incidence of ACEI drugs cough.In view of the fact that luteolin has not only hypotensive effect,but also strong anti-inflammatory action,as well as reduction of airway hyperresponsiveness,the present study was attempted to determine whether luteolin could enhance the antihypertensive effect and reduce the cough incidence with low-dose captopril,and to explore the mechanism of action.Methods:1)A rat model of renovascular hypertension was established by clipping the left renal artery(two-kidney one-clip).The blood pressure was measured by tail arterial pressure measuring instrument.2)The effects of drugs on cough in mice were studied by the method of sulfur dioxide(SO2)induction.3)Ovalbumin solution was atomized and inhaled to establish airway hyperresponsiveness in mice,and the animals were grouped and administered.The levels of IL-4,IL-5 and IFN-gamma in bronchoalveolar lavage fluid(BALF)were assessed by ELISA.4)MTT was used to detect the effect of luteolin and captopril on the metabolic activity of mouse macrophage in mice induced by LPS.5)Effects of luteolin and captopril on the production of IL-1 beta,IL-10,TNF-alpha and nitric oxide(NO)were measured by ELISA and NO kit.6)Confocal laser scanning microscope was used to detect the fluorescence intensity of Ca2+ concentration and pH in mouse peritoneal macrophages induced by LPS.Results:1)The hypertensive rats were divided into groups and the blood pressure was measured.The results showed that the blood pressure began to decrease significantly on the seventh day after the drug administration.On the fourteenth day,there was no significant difference in terms of antihypertensive efficacy between the combined administration(low-dose captopril and luteolin)and the normal-dose captopril groups.2)The mouse cough incidence increased with the dose increment of captopril,while luteolin significantly inhibited the mice cough.A combination of captopril and lueolin could inhibit the incidence of cough.3)Luteolin decreased significantly the levels of IL-4 and IL-5,and increased IFN-gamma in the bronchoalveolar lavage fluid(BALF)of high airway reactivity mice model,while there had no obvious inhibition effect observed for captopril.The combination of captopril with lueolin could significantly inhibit the secretion of IL-4,and IL-5,and increase the level of IFN-gamma.4)Luteolin inhibited macrophage metabolic activity,and reduced the secretion of TNF-alpha,IL-1 beta,IL-10 and NO,while captopril only in high concentration had obviously inhibitory effect on those examined parameters except for NO.The combination of these two medicines could obviously inhibit the secretion of TNF-alpha,IL-1 beta,IL-10 and NO,and it had no synergistic effect,but had certain additive effect.5)Luteolin and captopril significantly reduced intracellular Ca2+ concentration and increased pH.When luteolin was combined with captopril,there was no obvious synergistic effect observed on the intracellular Ca2+ concentration and pH.Conclusion:1)The combination of low doses of captopril with luteolin can achieve the same antihypertensive effect caused by normal-dose captopril alone.2)Combination of low-dose captopril with luteolin can reduce the incidence of cough in mice,and its mechanism may include the reduction of the dosage of captopril and the inhibition of the secretion of IL-4 and IL-5,and increase in the level of IFN-gamma to regulate the ratio of TH1/TH2 cells as exerted by luteolin.3)Captopril combined with luteolin has no obvious synergistic anti-inflammatory effect in vitro,but the anti-inflammatory effect of luteolin may be beneficial in the reduction of cough,and its mechanism may be through reducing the concentration of intracellular Ca2+ and increasing pH in macrophages,which mediate the secretion of inflammatory factors from macrophages.