Preliminary Study On The Mechanism Of Peritesticular Adipocytes Apoptosis In Rats With Experimental Periodontitis

BackgroundPeriodontitis is a chronic inflammatory disease occurring in the oral cavity,which not only destroys the local soft and hard tissues of the oral cavity,but also has adverse effects on the general health^[1].Research shows that persistent infection of periodontitis can aggravate the course of systemic diseases such as obesity and diabetes^[2].The occurrence and prognosis of these diseases are closely related to the functional changes of visceral adipose tissue.Visceral adipose tissue plays an important role in achieving homeostasis and homeostasis.It is not only the energy reservoir of the body,but also the key organ of human endocrine and immune system,especially playing an important role in the progress of metabolic diseases^[3,4].Our previous study found that lipopolysaccharide from Porphyromonas gingivalis（P.gingivalis-LPS）,a characteristic pathogen of periodontitis,can promote insulin resistance of visceral adipocytes,and this regulatory effect is related to Endoplasmic Reticulum Stress（ERS）^[5].ERS is a protective stress response activated when the endoplasmic reticulum environment is disturbed and a large number of unmodified or even abnormally modified proteins are accumulated^[6].ERS exerts its effect through three classical downstream signal pathways,which are respectively mediated by the transmembrane protein inositol dependent enzyme 1 on the endoplasmic reticulumα（inositol-requiring enzyme 1α,IRE1α）,Protein kinase R-like ER kinase（PERK）and activating transcription factor 6（ATF6）^[7].Among them,PERK can cause apoptosis of various tissues and cells by regulating the C/EBP homologous protein（CHOP）in downstream molecules^[8],thus affecting the metabolism of the body.However,it has not been reported whether chronic periodontitis can mediate the apoptosis of visceral adipocytes through PERK-CHOP signal pathway.The purpose of this experiment is to build a rat model of experimental periodontitis,take the perididymal adipose tissue as the representative of visceral adipose tissue,and explore whether chronic periodontitis can mediate the apoptosis of perididymal adipocytes through PERK-CHOP signal pathway,so as to provide a basis for further mechanism research.ObjectiveTo investigate the effect of chronic periodontitis on the apoptosis of peritesticular adipocytes in rats through PERK-CHOP signal pathway.Material and MethodsTwenty male SD rats were randomly divided into experimental group and control group.Experimental group:The rat model of chronic periodontitis was established,and the bilateral maxillary second molars were ligated with silk thread and injected with P.gingivalis-LPS,control group:equivalent PBS was injected into gingival sulcus.The rats were killed 3 months after modeling,and periodontal soft and hard tissue inflammation was evaluated by measuring gingival bleeding index（GBI）and probing pocket depth（PPD）.Ultramicro computed tomography（Micro-CT）was used to analyze the alveolar bone resorption of the second molar in rats.Periodontal tissue sections were made and hematoxylin and eosin stain（HE）was used to evaluate the pathological changes of periodontal tissue.Peritesticular adipose tissue was used to represent visceral adipose tissue for sampling,and Quantitative Real-time polymerase chain reaction（q RT-PCR）was used to detect glucose regulated protein 78（GRP78）,PERK,IRE1αand ATF6 gene expression level in peritesticular adipocytes.Western blot（WB）was used to detect GRP78,PERK,p-PERK,IRE1α,p-IRE1α,ATF6,CHOP,Caspase-12 and Cleaved-Caspase-3 in peritesticular adipocytes.HE staining was used to evaluate the morphological changes of peritesticular adipocytes.Apoptosis of peritesticular adipocytes was observed by TUNEL staining.ResultsSilk suture ligation with gingival sulcus injection P.gingivalis-LPS successfully established the chronic periodontitis model of rats in 3 months.Compared with the control group,the experimental group showed obvious gingival soft tissue inflammation and alveolar bone destruction and absorption.In the experimental group,GRP78 and PERK gene expression levels in perididymal adipocytes were up-regulated（P<0.05）,and the average expression levels of GRP78,p-PERK,CHOP,Caspase-12,and Cleaved-Caspase-3 proteins were significantly increased（P<0.05）.Apoptosis rate of adipocytes around testes in experimental group was significantly increased（P<0.05）.ConclusionChronic periodontitis mediates the apoptosis of peritesticular adipocytes in rats through PERK-CHOP signaling pathway.