Study Of BCG's Effect On Asthma And Its Mechanism, And The Effect Of A New PDE4 Inhibitor, Zl-n-91, On COPD Rats

cAMP and cGMP can mediate many biological responses(e.g.,regulation of important cell functions such as secretion,contraction,metabolism,and growth),they have regulatory effects on protein kinase A(PKA) and protein kinase G(PKG),the guanine-nucleotide exchange factors(GEFs),and the cyclic-nucleotide gated(CNG) sodium and calcium channel.Manipulation of cAMP and cGMP levels in the cell represents a powerful nechanism for controlling cellular physiology.To maintain their intracellular levels,cAMP and cGMP are synthesized by adenylyl cyclases(ACs) and guanylate cyclases(GCs) whereas their degradation(hydrolysis) is mediated by a variety of phosphodiesterases(PDEs) present in the cells.PDEs are a group of 11 families(PDE1-11) which is essential important in cells and hydrolyze the phosphodiester bond of cAMP and cGMP to provide the inactive products,e.g.,5'-AMP and 5'-GMR To inhibit PDEs can regulate a variety of cell functions and PDE inhibitors have potential value in therapy of lung diseases such as asthma and chronic obstructive pulmonary disease(COPD).Particular emphasis will be placed on PDE4 inhibitors which include roflumilast,cilomilast,piclomilast,tetomilst in development.Roflumilast and cilomilast had reached the stageⅢof clinical trials and may become available for treating asthma and COPD.Mycobacteria are among the most potent inducers of T helper 1(Th1) type response, Bacillus Calmette-Guérin(BCG) is attenuated live Mycobacterium bovis and used as a vaccine for tuberculosis.There had studies shown that BCG infection regulates Th1/Th2 balance,and could be used in asthma,but the mechanism of which is not entirely clarified.The first part of this thesis studied the effect of BCG and its compositions on asthma in rats,and detected Th1/Th2,PDEs activity and mRNA expressions,cAMP and its signal pathways in asthma rats using PDEs as a center to further clarify the possible mechanism of it.Objective:To study the effect of BCG on asthma in rats and find it possible mechanism. Methods:male Sprague-Dawley rats are sensitized and challenged with ovalbumin (OVA) and infected with BCG and its compositions,the inflammation in lungs and airway hyperresponsivness(AHR),Th1/Th2,the activity and mRNA expressions of PDEs,cAMP and PKA,Epac1 were detected.A549 cells were used to further study the effect of BCG on PDEs mRNA expressions and PKA,Epacl expressions with or without LPS injury.Results:BCG and its compositions inhibited inflammation in asthma rats and decreased AHR,inhibited PDEs activity and mRNA expressions, decreased cAMP and PKA.Different contents of BCG could also inhibit PDEs mRNA and PKA expression in A549 cells.Conclusion:BCG infection is of some benefit on asthma improvement and PDE inhibition may be one of the mechanism,and BCG and/or its composition may have potential multiple PDE inhibition effect.PDE4 inhibitors is a group of significant importance among new therapeutic agents that are under development in COPD treatment.The two selective PDE4 inhibitors that are at PhaseⅢclinical trial stage are cilomilast and roflumilast.The studies have demonstrated that anti-inflammatory effects of cilomilast and roflumilast positively contribute to the respiratory function,frequency of exacerbations and quality of life of COPD patients.Treatment options for COPD are quite limited and there is an urgent need for new treatment strategies.PDE4 inhibitors is a group of potent COPD drugs with great prospect because of their anti-inflammatory actions.The second part of this thesis studied the effect of a new selective PDE4 inhibitor,Z1-n-91 on COPD rat,and suggested its potent value in clinical application.Objective:To investigate the therapeutic effect of a new selective PDE4 inhibitor, Z1-n-91 on COPD rats,provide some basis for its futher clinical application.Methods: Male Sprague-Dawley rats are exposed to cigarette smoking and intracheal lipopolysaccharide(LPS) instillation to induce COPD.0.03,0.3 or 3mg/kg Z1-n-91 were administered.Cells in bronchoalveolar lavage fluid(BALF) were counted, cAMP-PDE and PDE4 activities were assayed,MPO activity and MMP-9 level were assayed using assay kits,and lung function of rats were measured.Results:Z1-n-91 at 0.03,0.3 and 3 mg/kg inhibited inflammatory cells infiltration in lungs and significantly decreased total number of cells and numbers of eosinophils and neutrophils in BALF, inhibited PDE4 activity and MPO activity,and decreased MMP-9 level in lungs, fininally Z1-n-91 markedly improved lung function.Conclusion:Z1-n-91 could inhibit inflammation and improve the symptoms in COPD rats,and it may be of therapeutic potential as an alternative medicine in COPD therapy.