# Polyphenols Limit Cerebral Endothelial Cell Dysfunction Under Inflammatory Conditions Related to Oral and Gut Microbiota

## TL;DR

Polyphenols from a medicinal plant protect brain blood vessels from inflammation caused by harmful bacteria in the gut and mouth.

## Contribution

This study demonstrates that polyphenols and epicatechin reduce LPS-induced endothelial dysfunction in brain cells.

## Key findings

- LPSs from P. gingivalis and E. coli trigger inflammation and oxidative stress in cerebral endothelial cells.
- Polyphenols and epicatechin reduce inflammatory markers and restore cell integrity affected by LPSs.
- The protective effects of polyphenols suggest potential therapeutic use in microbiota-related brain disorders.

## Abstract

Background/Objectives: During oral and gut microbiota dysbiosis, lipopolysaccharides (LPSs) of major bacteria, such as Porphyromonas gingivalis and Escherichia coli, translocate into the bloodstream and lead to endotoxemia. Cerebral endothelial cells are targets of LPSs that may aggravate inflammation and cerebrovascular disorders. This study aimed to evaluate the protective role of the characterized polyphenol-rich extract of the Dodonaea viscosa medicinal plant and a predominant component, epicatechin, on murine bEnd.3 cerebral endothelial cells exposed to P. gingivalis or E. coli LPSs. Methods: The effects of LPSs and polyphenols were assessed on cell viability (MTT, trypan blue exclusion assays) and inflammatory, redox, vasoactive and permeability markers (RT-qPCR, Western blot, ELISA, FITC-Dextran test). Results: The data show that LPSs activated the TLR2-4/NFĸB signaling pathway and promoted IL-1β, IL-6, TNF-α, MCP-1, COX-2, iNOS, ICAM-1, VCAM-1 and E-selectin production without affecting cell viability. LPSs induced oxidative stress by elevating intracellular ROS levels and altering the expression of genes encoding NOX2-4, SOD, catalase, GPx, HO-1 and Nrf2. LPSs imbalanced NO vasodilator and ET-1 vasoconstrictor levels and reduced the production of occludin and ZO-1 tight junction proteins. Meanwhile, LPSs raised the permeability to FITC-Dextran, suggesting cell integrity loss. The extent of endothelial dysfunction caused by LPSs depended on their bacterial origin. Importantly, plant polyphenols and epicatechin exerted anti-inflammatory and antioxidant effects, and attenuated LPSs’ deleterious action on vasoactive and permeability markers. Conclusions: This study shows that polyphenols limit cerebral endothelial cell dysfunction under inflammatory conditions mediated by LPSs, highlighting their therapeutic potential in protecting brain homeostasis during oral and gut microbiota dysbiosis.