Luteolin Alleviates Immune Damage Caused By Mycoplasma Gallinum Infection In Broilers Through IL-17/NF-kB Pathway

Mycoplasma gallisepticum(MG)infection causes chronic respiratory disease(CRD)in chickens.After MG infection,there are symptoms,for instance,cough,rale,sneezing and poor mental state.It is usually latent and easy to develop when immunity is low.It is often mixed with bacteria such as Escherichia coli,which has a long course of disease and is difficult to cure.And it occurs repeatedly and is highly infectious,bring great economic loss to poultry industry.At present,antibiotics such as tylosin and tylosin are mainly used for the prevention and treatment of MG.Due to the increasingly serious problem of antibiotic resistance,it is urgent to find new drugs to replace antibiotics.Chinese herbal medicine has the unique advantages of wide source,natural green,antibacterial and anti-inflammatory,improving immunity and low drug resistance.It has made good research progress in the treatment of chronic respiratory disease(CRD).Luteolin(Lut)is extracted from honeysuckle and wild chrysanthemum.Previous studies have shown that Lut has antibacterial,antiviral,anti-inflammatory,anticancer and antitumor effects,and is easy to absorb,which has achieved good research results.In this experiment,the experimental group was divided into 10 groups:blank control group,Lut alone treatment group(100mg/kg),Taimiao treatment group,MG infection group,Lut prevention and treatment high/medium/low dose(200/100/50mg/kg),with 3 repetitions in each group,6green legged broilers in each repetition,and a total of 180 green legged broilers.The effect of Lut on MG infection and its mechanism have been explored through in vitro bacteriostatic tests,breeding tests and cell tests,enriching the theoretical effect of traditional Chinese medicine in the prevention and treatment of CRD.The main results are as follows:1.The minimum inhibitory concentration(MIC)of MG bacterial solution with Lut inhibitory concentration of 10~4CCU/ml is 12.5ug/ml,which has strong antibacterial activity.2.In the production test,there is no difference in production data between Lut alone treatment group and blank control group(P>0.05),indicating that Lut has no adverse side effects.After 7 days of Lut prevention and 5 days of poison injection,there is significant difference between MG group and blank control group and prevention group(P<0.05),indicating that MG infection model is successfully constructed,MG causes significant reduction in production performance,and Lut prevention is helpful to resist MG infection.After 7 days of treatment,there are significant differences in feed conversion ratio and weight gain between tamoxifen treatment group,Lut prevention group and Lut high/medium dose group and mg group(P<0.05).After 14 days of stop to observe,the feed conversion ratio and weight gain of each group are the same as those in the treatment period.Among them,the cure rate of high-dose treatment group and high/medium dose prevention group is more than 93.3%,and the effect is equivalent to tamoxifen,indicating that Lut has a good effect in the prevention and treatment of MG.3.Determining the airbag damage through gross airbag score,Lut can effectively reduce the airbag damage.The pathological damage is observed by thymus sections and spleen sections and HE staining.Lut can effectively alleviate the tissue damage caused by MG infection.4.The immune factors IgA,inflammatory factors IL-17 and IL-1 in serum are measured by statistical immune organ index and ELISAβ、TNF-α、to evaluate the effect of Lut and MG on immune function.Lut can improve immune organ index,enhance humoral immunity and alleviate the inflammatory injury caused by MG infection.5.Through network pharmacology to screen and enrich the pathway of Lut target and MG target,which including of IL-17,NF-KB and other signal pathways.6.The m RNA expressions of IL-17/NF-KB pathway related genes IL-17A,IL-17F,TRAF6,NFKBIA,CXCL1,CXCL2,IL-1β,TNF-α,MMP2,MMP9 andβ-defension in thymus were detected by RT-QPCR.Lut can significantly inhibit the expression of il-17/NF-KB pathway related genes after MG infection(P<0.05),and improve the immune response of the body to resist MG infection.7.After transfection of siil-17,RT-q PCR and ELISA are used to detect the expression of inflammatory factors IL-17、IL-1β、TNF-α、IL-6 related to IL-17/NF KB pathway in macrophages.Lut treatment and prevention could down regulate the expression of inflammatory factors after MG infection(P<0.05).After the addition of siil-17,the expression of inflammatory factors is further down regulated,indicating that Lut may inhibit the expression of inflammatory factors through IL-17/NF KB pathway,accordingly to inhibit MG.Comprehensive research results show that Lut prevention and treatment can effectively alleviate the decline of production performance caused by MG infection,reduce mortality,reduce airbag injury and pathological changes of immune organs,improve immune organ index and immunoglobulin content in serum,and improve body immunity.In thymus and macrophages,Lut can alleviate MG induced immune inflammation and resist MG infection by inhibiting IL-17/NF KB signaling pathway.