Persistent peripheral presence of Staphylococcus aureus promotes histone H3 hypoacetylation and decreases tyrosine hydroxylase protein level in rat brain tissues.

Objective: Growing evidences suggest systemic pathogen-induced neuroimmune interaction is a major risk factor for several neurological disorders. Our goal was to investigate whether asymptomatic peripheral carriage of Staphylococcus aureus, a widespread opportunistic pathogen, could modulate selective molecular features in brain tissues.

Methods: To address this, a peripheral infection model was developed by challenging Wistar rats repeatedly with a clinical strain of S. aureus. Animals infected with S. aureus (10 CFU for three times in 10 days) showed significant changes in acetylation profile of selective lysine (K) residues K9 (H3K9), K14 (H3K14) and K27 (H3K27) of histone H3 in the hippocampus and prefrontal cortex (PFC).

Results: Although S. aureus was restricted peripherally, the infection induced hypoacetylation of H3K9, H3K14 and H3K27 in the hippocampus and H3K27 in the PFC. Histone H3 hypoacetylation in the hippocampus and PFC was also detected when rats were challenged with an engineered invasive strain of E. coli K12, SK3842. This confirmed that modulation of epigenetic landscape in distal brain tissues may not be specific to S. aureus. Moreover, the tyrosine hydroxylase protein, the rate limiting enzyme in dopamine synthesis pathway whose gene-expression is regulated by H3 acetylation at the promoter, was remarkably reduced in the brain tissues of the infected hosts.

Conclusion: The results indicate that commensals like S. aureus, in spite of being largely restricted to the peripheral tissues, could modulate the homeostasis of molecular features in brain tissues whose maintenance is critical for preserving normal neurological functions.