Effect And Mechanism Of PLC-Γon The Nerve Growth Factor Mediated Experimental Asthma

PrefaceBronchial asthma is a kind of immunogenic inflammatory airway disease, and ischaracterized by airway smooth mucle spasm and increased airwayhyperresponsiveness. But the pathogenesis of the asthma is unclear. Recently,neurogenic inflammation is increasingly recognized .However it is known little aboutthe interaction between the nervouse system and inflammation process. Recently wefound that NGF is a kind of important mediator.The level of NGF in the serum ofasthmatic patient increase,the study about the bronchial asthma model shows that NGFregulates the airway hyperresponsiveness, exogenous NGF can increase the airwayhyperresponsiveness of the guinea pig caused by the histamine, antibody of NGF candecrease the airway hyperresponsiveness. In recent years,our previous resultsconfirmed that the expression of NGF is increased remarkably in the lower respiratorytract and viscerosensory afferent sites of the asthmatic guinea pigs. NGF upregulatesthe expression of TrkA, The intracellular signal transduction system mediated by TrkAmight be one of the main routes for the involvement of NGF in the pathogenesis ofasthma.Phospholipase C is a kind of enzyme that hydrolyzes glycerol phosphatide.Glycerol phosphatide is the main component of membrane. Recently we found thatglycerol phosphatide is a kind of store of second messenger.Since 20 century 50 era PLC is founded,we have identified 12 types phospholipase isoenzyme in the mammal.According to different molecular weight and amino acid sequence, phospholipaseisoenzyme is classified into five types including PLC-β,PLC-γ,PLC-δ,PLC-εandPLC-ζfounded lately, PLC-γis divided into PLC-γ1 and PLC-γ2 subtype。ExceptPLC-ζ,other phospholipase isoenzymes divide widely in the all kinds of organs in thebody. PH in the phospholipase isoenzymes is separated by two SH2 and one SH3.A lot of ecto informational molecules, such as cytokine and growth factor receptor,may ineract with the protein including SH2 domain, which result in the target proteinphosphorylated. TrkA is the high affinictor of NGF. TrkA may binds with PLC.Phosphorylated PLC can hydrolyze PIP2 and produce two main second messengerDAG and IP3.IP3 acts on sarcoplasmic reticulum then release Ca²⁺ from the cell, DAGthen activated PKC.PKC can regulate cell activity.PKC play an important role in thepathogenesis of asthma and cause the release of inflammation transmitter The researchshow that the activitiy of PKC of low density eosinophilic cell significantly increase inthe blood and bronchoalveolar lavage fluid,the activity of PKC increases markedly.This study evaluated the PLC is expressed in the lower respiratory tract andviscerosensory afferent sites of the asthmatic mice.(The bodies of sensory neurons oflower respiratory tract are located at nodose ganglion and C₇～T₅ spinal ganglion andthe central axons terminate at spinal dorsal horn and solitary nucleus), the expression ofPLC whether PLC is involved in TrkA signal mediated asthma? What effects of NGFon the expression of PLC? No reference was reported about these. Answer for thesequestions will make the machnism of asthma clear and provide evidence for noveltreatment.Methods1. Prepare the asthma model, Asthma was induced in BALB/c mice byintraperitoneal injection chicken egg ovalbumin(OVA) and challenged by exposure to OVA.2. By AniRes2005 lung fnnction meter to investigate the airway resistence ofBABL/C mice.3. By means of immunohistochemistry and Western blot to investigate the changesof PLC immunoreactivity and the regulatory effect of NGF and TrkA in the lowerrespiratory tract and viscerosensory afferent sites of the asthmatic mice model.Results1. Airway resistance measurement showed:Increased airway resistance toMethacholine(Mch) was observed in the asthmatic group compared with the normalcontrol group, but decreased in anti-NGF group and anti-TrkA compared with theasthmatic group(p＜0.01).2. Immunohistochemistry,Western blot showed: The expression of PLC wasincreased significantly in lower respiratory tract and visceral sensory afferentsites(C₇-T₅ spinal ganglia and the corresponding posterior horn of the spinal cord) ofthe asthmatic mice model compared with the normal control group(p＜0.01), but wasdecreased in the corresponding portion in anti-NGF group and anti-TrkA groupcompared with the asthmatic mice model (p＜0.01).Conclusions1.NGF mediated TrkA pathway might be involved in the asthmatic airwayhyperreactivity.2. There is overexpression of PLC in the lungs, C₇～T₅ spinal ganglia andcorresponding spinal dorsal horn.This finding suggests that PLC plays an importantrole in asthma and is involved in the regulation of the visceral sensory afferent system.3. NGF and TrkA upregulates the expression of PLC in the lungs, C₇～T₅ spinalganglia and corresponding spinal dorsal horn. This finding suggests that PLC mighttake part in the mechnism of NGF mediated asthma.