Green Tea Attenuates the Particulate Matter (PM)_2.5-Exposed Gut-Brain Axis Dysfunction through Regulation of Intestinal Microenvironment and Hormonal Changes

Chronic exposure to particulate matter (PM)_2.5 causes brain damage through intestinal imbalance. This study was estimated to confirm the regulatory activity of green tea against chronic PM_2.5 exposure-induced abnormal gut-brain axis (GBA) in BALB/c mice. The green tea, as an aqueous extract of matcha (EM), ameliorated the colon length, short chain fatty acid contents, antioxidant biomarkers, myeloperoxidase (MPO) activity, and serum inflammatory cytokines. EM regulated the gut microbiota related to tryptophan intake and hormone metabolism. EM showed regulatory effect of intestinal tight junction (TJ) protein, inflammatory response, and apoptotic biomarkers. In addition, EM improved PM_2.5-induced tryptophan-related hormonal metabolic dysfunction in intestinal tissue and serum. Through the ameliorating effect on GBA function, the consumption of EM presented the protective effect against inflammatory effect, apoptosis, synaptic damage, and hormonal activity in cerebral tissue, and suppressed abnormal change of brain lipid metabolites. In particular, EM intake showed relatively excellent improvement effects on indicators including <i>Bacteroides</i>, <i>Ruminococcus</i>, <i>Murinobaculaceae</i>, <i>Allopreyotella</i>, cyclooxygenase-2 (COX-2), acetylcholinesterase (AChE), 11,12-dihydroxyeicosatrienoic acid (DHET), and intestinal acetate from the PM group. These findings indicate that the dietary intake of EM might provide a regulatory effect against PM_2.5-exposed GBA dysfunction via the intestinal microbiota and hormonal changes.