| Mycoplasma gallisepticum(MG)is a pathogen that causes chronic respiratory disease(CRD)in chickens.It is widely prevalent worldwide,and is often mixed with other pathogenic microorganisms or secondary infections,causing huge economic losses to the poultry industry.At present,one of the main measures to treat CRD in production is to use antibiotics,but antibiotics can easily lead to the generation of drug-resistant strains and cause drug residues in poultry products,which seriously threatens public health.Chinese herbal medicine has the characteristics of significant bactericidal,anti-inflammatory,and immune-boosting properties,and long-term use is not easy to develop drug resistance.It is an ideal drug to replace antibiotics in the treatment of MG infection.This topic explored the effect and molecular mechanism of andrographolide in preventing and controlling MG infection at the animal and cellular levels,and provided a scientific basis for the application of andrographolide in the prevention and control of CRD in poultry production.The main findings are as follows:1.The results of the double dilution method showed that the minimum inhibitory concentration of andrographolide on MG was 3.75μg/m L,and the concentration of andrographolide was less than 200μg/m L on primary alveolar type II epithelial cells(AECII)activity had no effect,and andrographolide significantly inhibited the expression of MG adhesion protein p MGA1.2 in lung tissue and AEC-II.2.In the model group of broilers,the incidence of MG-induced CRD was 90%,but in the andrographolide prevention group,the incidence of MG was below 50%.The cure rate of andrographolide for CRD was over 90%,and all broilers in the high-dose andrographolide control group were cured.The mortality rates of broilers in the model group,tiamulin treatment group and low-dose andrographolide treatment group were16.67%,10.00%,and 6.67%,respectively,and there was no death in the high-dose andrographolide treatment group and the combined control group.Compared with the model group,the average body weight gain,relative weight gain rate and feed efficiency of broilers treated with andrographolide were significantly restored,and andrographolide treatment alone could significantly increase the average body weight gain of healthy broilers(P≤0.05).It shows that andrographolide can effectively restore the production performance of MG broilers and can promote the growth of broilers.3.Compared with the model group,andrographolide treatment significantly reduced the average air sac injury score and thymus,spleen,and bursa index of broilers(P≤0.05).Histopathological examination showed that andrographolide could significantly alleviate the thymus,spleen,bursa,liver,trachea and lung tissue damage caused by MG infection.And andrographolide treatment alone did not cause these organ damage in normal broilers.The results of serum biochemical analysis showed that compared with the model group,serum total protein,albumin,globulin,alanine aminotransferase,aspartate aminotransferase,bilirubin,urea,creatinine,Uric acid and total cholesterol were significantly decreased,albumin/globulin ratio,alkaline phosphatase,apolipoprotein B and apolipoprotein A-I were significantly increased(P≤0.05),but MG infection had no effect on the serum glucose concentration of broilers(P>0.05),and both MG infection and andrographolide treatment could significantly reduce the serum total cholesterol concentration of broilers(P≤0.05).In addition,andrographolide treatment alone significantly decreased the serum creatinine concentration and increased the alkaline phosphatase concentration in normal broiler chickens(P≤0.05).The results showed that andrographolide could effectively alleviate the organ damage of broiler chickens caused by MG.4.RT-q PCR and ELISA results showed that compared with the model group,andrographolide treatment significantly reduced the m RNA and level of IL-1β,TNF-α,IL-6 in lung tissue,serum and AEC-II caused by MG infection.protein expression.The results of terminal deoxynucleotidyl transferase labeling(TUNEL)and western blotting(WB)showed that compared with the model group,andrographolide treatment significantly reduced the apoptosis of lung tissue and AEC-II,and decreased the levels of Bax,Caspase9,and AEC-II.The protein expression of Caspase 3,p-JAK,PI3 K and p-AKT increased the protein expression of Bcl-2 and Bcl-x L.In AEC-II,inhibition of JAK/PI3/Akt signaling pathway significantly reduced the expression of IL-1β,TNF-α,IL-6,Bax,Caspase 9,and Caspase3 induced by MG infection,and increased Bcl-2 and Bcl-x L expression level.This indicates that andrographolide may alleviate MG-induced lung inflammation and apoptosis by inhibiting the JAK/PI3K/AKT signaling pathway.The results of this study show that andrographolide can significantly inhibit the proliferation of MG and the expression of adhesion proteins,and restore the production performance of broilers caused by MG infection.It inhibits the inflammatory response and tissue organ damage caused by MG infection by inhibiting the JAK/PI3K/AKT signaling pathway. |
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