Identifition Of The Allergenicity Of Myosin Light Chain From Periplaneta Americana In The Allergic Asthma Rat Model

Objective: In this study, we aimed to develope a SD rat model ofallergic asthma caused by crude extract of P. americana, to identify the myosin lightchain of P. americana as the potential allergen.Methods: A total of40female SD rats were divided randomly into four group: thenegative control group (group A, n=10); the positive control group (group B, n=10);the myosin light chain group (group C, n=10), the crude extract of P. americana(PAE) group (group D, n=10). Group B were sensitized by subcutaneous injection ofovalbumin(OVA) on0d,7d,14d and21d, and then were activated by intranasaladministration of OVA from22d to27d (intranasal for30min per day). During theperiod of sensitization, behavioral changes of rats were observed for10minutes aftereach administration. Group A were sensitized by subcutaneous injection of PBS,group C were sensitized by subcutaneous injection of P er a8recombinant proteins,and group D were sensitized by subcutaneous injection of PAE. All rats weresacrificed24h after the nebulization. The serum samples, broncho-alveolar lavagefluids (BALF), and lung tissues were collected. Histopathology of the rats lungs andthe levels of T-IgE, IL-4were observed by ELISA. The levels of IL-5, IFN-γ in lungtissues were observed by Western-bloting. The number of eosinophils were counted,the Bcl-2proteins were stained using immunoctochemistry. The SPSS18.0packageprogram was used in the statistical analysis. Data were presented as mean±S.D.Thecomparisions between all groups were conducted by using the single-factor analysisof variance (one-Way ANOVA) method. When the P value (P<0.05) was consideredsignificant. The analysis were performed using GraphPad Prism Software V.5.0forwindows. Western-bloting data were analyzed by using Quantity-One program,immunohistochemistry was used Image-Pro Plus Software V.6.0for analysis. Restults: A SD rat model of allergic asthma was successfully developed. Comparedwith group A,the T-IgE and IL-4levels of the group B, group C, group D weresignificantly elevated in the serum (P <0.01). Histopathology of the rats lungs,thegroup A rats did not show any findings of pathological significance, the group B,C,Drats lungs demonstrated a marked perivascular and peribronchiolar cuffing consistingof mixed inflammatory cells. There was also an inflammatory infiltrate into thealveolar bed and alveolar airsparces. There was also demonstrated a markedaccumulation of eosinophilic within the epithelial reaction includung increasednumber of mucus producing goblet cells. The upregulation of Bcl-2protein weresignificantly higher in group B, group D and group C than in goup A (p<0.01). Theupgregulation of IL-5expression in group B, group C and group D (p<0.05). Thedownregulation of IFN-γ were significantly lower in group B, group C and group Dthan in group A (p<0.05).Conclusions: A allergic asthma SD rat model of f PAE was successfully developed.American cockroach MLC may be a potential novel allergen. The immunemechanisms of allergic asthma SD rat model may be an imbalance of Th1/Th2cells.