The Biological Function Of Deuterohemin-?-Ala-His-Thr-Val-Glu-Lys Peroxidase And Its Therapeutic Effect On Periodontitis

Periodontitis is a chronic infectious oral disease caused by plaque microorganisms.It can lead to inflammation of the gingival epithelium,resulting in the dissolution and destruction of the collagen fibers in the gingival and periodontal membrane,as well as the absorption of alveolar bone,leading to the loosening and falling out of teeth.Periodontitis has a high incidence of disease,great harm,complex etiology,repeated pathological process,and difficult to cure.It has a high prevalence rate worldwide and it is the primary cause of tooth loss in Chinese adults.At present,periodontal mechanical therapy and drug therapy are still the most effective treatment for periodontitis,but the prognosis is still unsatisfactory.Therefore,it is extremely urgent to understand the etiological factors,to find new treatment methods and means of treatment of periodontitis.Deuteroheme hexapeptide?Deuterohemin-Ala-His-Thr-Val-Glu-Lys,DhHP-6? is an oxidase-mimicase enzyme,which is developed from microperoxidase-11?MP-11?.Compared with natural peroxidase,DhHP-6 has advantages of easy synthesis,low cost and high stability.Previous studies have shown that DhHP-6 can easily enter cells and has a strong ability of scavenging free radicals.Therefore,this paper first explored the enzymatic properties of DhHP-6 molecule in the complex pH,temperature and solvent range,and then studied its therapeutic effect on periodontitis and its mechanism of action at the cellular and animal levels.The main research contents and results are as follows:1.Study on the activity of DhHP-6 peroxidaseThe activity and catalytic mechanism of DhHP-6 were studied by enzyme activity analysis and spectroscopy,and the influencing factors of phenol reaction catalyzed by DhHP-6 were investigated and analyzed.The results showed that DhHP-6 exhibited good catalytic performance over a wide range of p H and temperature,and showed good tolerance to a variety of organic solvents.In the model reaction with phenol as substrate,the activity of DhHP-6 Peroxidase was significantly higher than that of MP-11,and the optimal enzyme activity was 16 times higher than that of Horse Radish Peroxidase?HRP?.Raman spectrum and EPR spectrum revealed that under the action of methanol,imidazoll on DhHP-6 coordinated the central iron of iron porphyrin in an axial direction,making it change from a high spin state to a low spin state,which was conducive to catalyzing H₂O₂ to produce highly active oxygen free radicals,thus promoting the oxidation reaction of phenol.It is DhHP-6 that has good peroxidase activity under a wide range of conditions,which makes it possible to apply it in the treatment of diseases associated with oxidative stress,such as periodontitis,Alzheimer's disease and diabetes.2.Studies on antioxidant damage effect of DhHP-6 on Human gingival fibroblasts?HGFs?cellsA model of H₂O₂-induced oxidative stress injury in HGFs cells was established to detect the effects of DhHP-6 on the production of ROS,the activity of related apoptotic proteins and the expression of antioxidant factors in HGFs cells.It was found that DhHP-6 increased glutathione?GSH?,Catalase?CAT?and Superoxide dismutase?SOD?levels in HGFs cells.In addition,DhHP-6 can inhibit the production of intracellular ROS in HGFs and reduce the activities of intracellular apoptotic proteins caspase3,Caspase8 and Caspase9.DhHP-6 also reduces concentrations of Malondialdehyde?MDA?and expression of TNF-? and IL-1? in HGFs supernatant.The above results showed that DhHP-6 had a good effect on H₂O₂-induced HGFs cells in terms of anti-oxidative stress damage.3.Study on antioxidant damage and anti-inflammatory effects of DhHP-6 on experimental periodontitis in ratsThe experimental periodontitis model of rats was established to detect the therapeutic effect of DhHP-6 on periodontitis from the perspective of in vivo.Results showed that the DhHP-6 effectively improve the gum tissue and serum of rats in the anti-oxidation factor GSH,expression level of SOD and CAT,cut down the content of rat serum MDA oxidation products,at the same time reduce the serum TNF-a and IL-1?,reduce the inflammation in the rat periodontitis,and DhHP-6 to periodontitis alveolar bone absorption has a protective effect.Therefore,DhHP-6 has a good therapeutic effect on experimental periodontitis in rats by improving the expression level of antioxidant factors in the whole body and local tissues,and reducing the content of oxidative products and inflammatory cytokines in cells.