Introduction: There has been demonstrated that pharmaceutical effect of epigallocatechin-3-gallate (EGCG), a polyphenol, which is found in green tea (Camellia sinensis), is implemented through the activation of Nrf2 (Nuclear Factor Erythroid 2-Related Factor 2).The importance of Keap1 / Nrf2 / antioxidant response element (ARE) system is determined by the fact that the state of NF-κB- and АР-1-associated pathways depends on its activity. Recent studies have demonstrated the property of quercetin to suppress ubiquitin-dependent proteolysis of complex of NF-κB and its inhibitory protein IκB. All this provides preconditions to eliminate the potentiality of NF-κB-dependent expression of the number of genes of pro-oxidant and pro-inflammatory proteins. However, co-effect produced by quercetin and EGCG on the oxidative nitrosative stress markers in the periodontal tissues is still unclear.
The aim: To investigate the co-effect produced by quercetin and an inducer of the Keap1 / Nrf2 / ARE epigallocatechin-3-gallate on markers of oxidative-nitrosative stress in rats’ periodontium under the systemic and local administration of Salmonella typhi lipopolysaccharide (LPS).
Material and methods: The studies were conducted on 30 white rats of the Wistar line, divided into 5 groups: the 1st included intact animals, the 2nd was made up of animals after their exposure to combined systemic and local LPS administration, the 3rd and 4th groups included animals, which were given injections with water-soluble form of quercetin (corvitin) and EGCG respectively, and the 5th group involved rats, which were injected with co-administered corvitin and EGCG. The formation of superoxide anion radical (.О-2 ) was evaluated by a test with nitro blue tetrazolium using spectrophotometry of the periodontal soft tissue homogenate. The total activity of NO-synthase and concentration of peroxynitrite in the homogenate of the soft components of periodontium were evaluated spectrophotometrically.
Results: Co-effect produced by corvitin and EGCG under systemic and local LPS administration is accompanied with reduced О-2 production by NADPH-dependent electron transport chains (microsomal and NOS) by 20.0 % (p <0.05) compared with values for the animals received separate corvitin during the experiment. .О-2 generation by the mitochondrial respiratory chain yielded to comparable data of the 3rd and 4th groups by 27.6 % (p <0.01) and 23.8 % (p <0.05) respectively. No differences were found between the groups exposed to combined or separate action of the above mentioned agents in the experiment when assessing О-2 generation by leukocyte NADPH-oxidase. Combined effect of corvitin and EGCG during systemic and local LSP administration showed the decrease in NOS activity and peroxynitrite concentration in periodontal tissues by 53.3 % (p <0.001) and 27.0 % (p <0.02) compared with the findings in the 3rd group, and by 42.0 % (p <0.01) and 22.3 % (p <0.01) in the 4th group.
Conclusions: The co-administration of water-soluble form of quercetin and epigallocatechin-3-gallate under systemic and local introducing of lipopolysaccharide Salmonella typhi has been proven to be more effective means for preventing and correcting oxidative-nitrosative stress in the periodontal tissues than this occurs at separate administration of each of the polyphenols.
Keywords: signal pathway Keap1 / Nrf2 / ARE; epigallocatechin-3-gallate; quercetin; lipopolysaccharide-induced systemic inflammatory response; oxidative-nitrosative stress; periodontium.