The Regulation Mechanism Of Protein Arginine Methltransfrase1in Antigen Induced Pulmonary Inflammation In E3Rats

Objective and Significance:Asthma is characterized by chronic inflammation of the airways in which there is anoverabundance of eosinophils, mast cells, and activated T helper lymphocytes. It is asyndrome characterized by intermittent attacks, often nocturnal breathlessness, wheezing,and cough. Etiology of asthma remains unclear although several complicated gene-environmental hypotheses have been proposed in the past decades.Antigen induced pulmonary inflammation (AIPI) in rats, a classic animal model for asthma,has greatly contributed to the understanding of the disease pathogenesis, especially for theinflammation process. E3rats are recently used to induce AIPI model for its susceptibility topulmonary inflammation, but the features of AIPI with different antigen challenge terms onE3rats require to be elucidated systemically. The first aim of this study was to compare AIPIdisease patterns in E3rats with different challenge terms.The “epigenetics” was introduced to describe all meiotically and mitotically heritablechanges in phenotype or in gene expression states that are not coded in the DNA sequenceitself. All epigenetic mechanisms closely intertwine with each other and regulate the geneexpression program of a cell to ensure its proper cellular function, and the enzymes inepigenetic regulation is absolutely important for regular cellular process. Protein argininemethyltransferases (PRMTs), catalyzing methylation of both histones and other cellularproteins, have emerged as key regulators of various cellular processes. This study aimed toidentify key PRMTs involved in antigen induced pulmonary inflammation (AIPI), a ratmodel for asthma, and to explore the role of PRMT1in IL-4induced eosinophil infiltrationprocess.Methods and Results:1. E3rats were immunized and challenged with ovalbumin for1,4and8weeks. Histologicalmethods were used to determine morphological changes in lungs and cell types in BALF.NO concentration was assayed by Griess method. IL-4and TGF-β expression was detectedby real-time PCR. ELISA was used for the determination of serum IgE and OVA specificIgG1. The results showed that all the sensitized E3rats had a strong influx of eosinophils into theairway. In1-week challenge group, the rats showed stronger inflammation, such as elevatedlevels of NO, DTH, IL-4expression and inflammatory cell infiltration; while in8-weekchallenge group, rats manifested significant tissue destruction, accumulation of collagen andmucus production and higher levels of antibody production and TGF-β expression.2. E3rats were intraperitoneally sensitized with ovalbumin (OVA)/alum and intranasallychallenged with OVA to induce AIPI. The expressions of PRMT1-6, eotaxin-1and CCR3inlungs were screened by real-time quantitative polymerase chain reaction. AMI-1(apan-PRMT inhibitor) and siRNA-PRMT1were utilized to interrupt the function of PRMT1in A549cells. Construction and transfection of recombined pcDNA3.1-PRMT1in A549cellwere performed to upregulate PRMT1expression. In addition, AMI-1was administratedintranasally to AIPI rats to observe the effects on inflammatory parameters.The results showed that PRMT1expression was mainly expressed in bronchus and alveolusepithelium and significantly upregulated in lungs from AIPI rats. The inhibition of PRMTsby AMI-1and the knockdown of PRMT1expression were able to downregulate theexpressions of eotaxin-1and CCR3with the IL-4stimulation in the epithelial cells. Theupregulation of PRMT1resulted in high expression of eotaxin-1and CCR3in epithelial cells.Furthermore, AMI-1administration to AIPI rats can also ameliorate pulmonary inflammation,reduce IL-4production and humoral immune response, and abrogate eosinophil infiltrationinto the lungs. In summary, PRMT1expression is upregulated in AIPI rat lungs and can bestimulated by IL-4. Intervention of PRMT1activity can abrogate IL4-dependent eotaxin-1production to influence the pulmonary inflammation with eosinophil infiltration.Main conclusions:1. The detail characterizations of AIPI model challenged for different terms demonstratedthat E3rats challenged with antigen for1week are suitable for studying acute pulmonaryinflammation，meanwhile the model established in the rats challenged for8weeks isappropriate for understanding pathogenesis of lung remodeling in chronic inflammation.2. PRMT1plays a crucial role in AIPI through its regulation on eotaxin-1, and these findingsmay provide an important clue for further research in asthma pathogenesis and suggest a newremedy for asthma treatment.