[Effect of gingipain extracts on anxiety-like behavior in mice].

Purpose: To observe the effect of gingipain extracts on anxiety-like behavior in mice.

Methods: Gingipain extracts were derived from Porphyromonas gingivalis(P. gingivalis) ATCC33277 by sonication and ultra-speed centrifugation and identified by Western blot and enzyme activity assay. Gingipains infection models were established by intraperitoneal injection of gingipain extracts with/without iodoacetamide (IAM). Enzyme activity assays were used to detect the activity of arginine-gingipain (Rgp) and lysine-gingipain (Kgp) in plasma of mice. Open field experiments and elevated zero maze experiments were used to detect anxiety-like behavior in mice. Immunofluorescence staining of brain tissue slices was used to observe changes in astrocytes of the brain. GraphPad Prism software was used for statistical analysis.

Results: The gingipain extracts were collected from P. gingivalis ATCC33277 and they showed Rgp and Kgp activity. The activity of Rgp and Kgp could be detected in mice plasma after intraperitoneal injection of gingipain extracts. Compared with the control group, there were no significant changes in the autonomous activity ability of the gingipain group mice. In the open field experiment, the central area staying time of the gingipain groups was significantly reduced(P＜0.05). In the elevated zero maze experiment, the open area frequency of the gingipain groups was obviously shortened(P＜0.05). Anxiety-like behavior was significantly enhanced. Immunofluorescence staining showed that gingipain extracts could significantly activate astrocytes in the hippocampus of mice. The above results could be significantly alleviated by gingipain inhibitor IAM.

Conclusions: Gingipain extracts could induce anxiety-like behavior in mice, which may be related to neuroinflammation due to activation of astrocytes.