Secreted gingipains from Porphyromonas gingivalis increase permeability in human cerebral microvascular endothelial cells through intracellular degradation of tight junction proteins.

Abstract

Despite a clear correlation between the infiltration of periodontal pathogens in the brain and cognitive decline in Alzheimer's disease (AD), the precise mechanism underlying bacteria crossing the blood-brain barrier (BBB) remains unclear. The periodontal pathogen Porphyromonas gingivalis produces a unique class of cysteine proteases termed gingipains. Gingipains appear to be key virulence factors that exacerbate sporadic AD. We herein report that gingipains are involved in increasing permeability of hCMEC/D3 cell monolayer, human cerebral microvascular endothelial cell lines, through degradation of tight junction proteins including Zonula occludens-1 (ZO-1) and occludin. There was a significant decrease in the mean protein levels of ZO-1 and occludin after infection of hCMEC/D3 cells with wild-type (WT) P. gingivalis. However, infection of these cells with a gingipain-deficient P. gingivalis strain showed significantly lower reduction of the mean protein levels of either ZO-1 and occludin, compared to the WT strain. Similar results were obtained after treatment with culture supernatant from WT and gingipain-deficient P. gingivalis strains. In vitro digestion of human recombinant ZO-1 and occludin by WT P. gingivalis culture supernatant in the absence or presence of gingipain inhibitors indicated that gingipains directly degraded these tight junction proteins. A close immunohistochemical examination using anti-gingipain antibody further revealed that gingipains localized in the cytosol and nuclei of hCMEC/D3 cells after infection with WT P. gingivalis and treatment with its culture supernatant. Furthermore, intracellular localization of outer membrane vesicles (OMVs) bound gingipains from WT P. gingivalis and OMV-induced degradation of ZO-1 and occludin were also observed in hCMEC/D3 cells. Thus, the delivery of gingipains into the cerebral microvascular endothelial cells, probably through OMV, may be responsible for the BBB damage through intracellular degradation of ZO-1 and occludin.

• Authors: Saori Nonaka, Tomoko Kadowaki, Hiroshi Nakanishi
• Journal: Neurochemistry international (Neurochem Int) Vol. 154 Pg. 105282 (03 2022) ISSN: 1872-9754 [Electronic] England
• PMID: 35032577 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.

Chemical References

• Adhesins, Bacterial
• Gingipain Cysteine Endopeptidases
• Tight Junction Proteins

Topics

• Adhesins, Bacterial (metabolism)
• Endothelial Cells (metabolism)
• Gingipain Cysteine Endopeptidases
• Humans
• Permeability
• Porphyromonas gingivalis (metabolism)
• Tight Junction Proteins