The Effects Of Orally Administered Porphyromonas Gingivalis On Gut Microbiota And Intestinal And Splenic Inflammation In Mice

Objectives:Periodontal disease,a chronic inflammatory disease mediated by disorders of the oral flora,has become an element of risk for many systemic diseases,including coronary heart disease,Alzheimer's disease,spondyloarthritis and inflammatory bowel disease.Some specific periodontal pathogens,such as Porphyromonas gingivalis(P.gingivalis),and their components may play an important role in the development of these systemic diseases.Previous studies have shown that oral administration of P.gingivalis can induce dysbiosis of gut microbiota and impair function of gut barrier leading to dissemination of enterobacteria to the liver.However,it is not clear to know how oral administration of P.gingivalis could induce intestinal and systemic inflammation.This study observed the inflammation in intestinal and spleen tissues by oral administration of P.gingivalis,aiming to preliminarily investigate the possible mechanism of P.gingivalis affecting the digestive system and provide new insights into the intrinsic link between periodontal disease and digestive diseases.Methods:P.gingivalis(strain W83)were cultured and enriched in Brain heart infusion broth(BHI).Ten C57BL/6 mice were randomly divided into two groups.Mice in the W83 group were fed with 0.2 mL P.gingivalis(1?10~9 CFU);those in the control group were fed with the same amount of PBS.Each mouse was orally administered P.gingivalis or PBS daily.After 6 weeks,the mice were sacrificed and their cecal contents,colons and spleens were collected.After extracting the bacterial DNA of the cecal contents,the changes of microbial communities in the gut were analyzed by pyrosequencing the 16S ribosomal RNA genes.The histological changes of colon were observed by hematoxylin and eosin(H&E)staining.The mRNA levels of CD3 antigen(CD3),protein tyrosine phosphatase receptor type C(B220),adhesion G protein-coupled receptor E1(F4/80),interferon-?(IFN-?)and interferon regulatory factor-1(IRF-1)were assessed by Quantitative Real-time PCR(qRT-PCR)in colons of mice.qRT-PCR was used to detect the mRNA level of interleukin 12a(IL-12a),interleukin 18(IL-18),interleukin 21(IL-21),IFN-?and IRF-1 in the spleens.The protein levels of IFN-?and IRF-1 was detected by Western blotting in the spleens.Moreover,the phosphorylation level of signal transducers and activators of transcription1(STAT1)and signal transducers and activators of transcription3(STAT3)in spleens was also detected by Western blotting.Results:1.Oral administration of P.gingivalis significantly altered gut microbiota,with an increased proportion of phylum Bacteroidetes and a decreased proportion of phylum Firmicutes(P<0.05).2.H&E staining showed an increase of lymphoid follicles in the colonic submucosal connective tissue of mice in the W83 group.The mRNA expression of B220,a surface marker of B cell,was significantly increased in the colon of mice in the W83 group(P<0.05).3.Mice in the W83 group showed swollen spleens,and their spleen indexs were significantly rised(P<0.05).4.The mRNA and protein expression levels of IFN-?and IRF-1 and the phosphorylation level of STAT1 in the spleen of the W83 group were significantly increased(P<0.05).Conclusions:P.gingivalis may induce or worsen the intestinal and splenic inflammation by regulating gut microbiota leading to the impairment of biological barriers,which may cause the imbalance of immunity and then increase the susceptibility of patients with periodontal disease to the digestive system and other systemic diseases;Activation of the IFN-?/STAT1 pathway by P.gingivalis may play a regulatory role in this process.