title: Staphylococcus aureus-derived peptidoglycan induces Cx43 expression and functional gap junction intercellular communication in microglia.
abstract: Gap junctions serve as intercellular conduits that allow the exchange of small molecular weight molecules (up to 1 kDa) including ions, metabolic precursors and second messengers. Microglia are capable of recognizing peptidoglycan (PGN) derived from the outer cell wall of Staphylococcus aureus, a prevalent CNS pathogen, and respond with the robust elaboration of numerous pro-inflammatory mediators. Based on recent reports demonstrating the ability of tumor necrosis factor-alpha and interferon-gamma to induce gap junction coupling in macrophages and microglia, it is possible that pro-inflammatory mediators released from PGN-activated microglia are capable of inducing microglial gap junction communication. In this study, we examined the effects of S. aureus-derived PGN on Cx43, the major connexin in microglial gap junction channels, and functional gap junction communication using single-cell microinjections of Lucifer yellow (LY). Exposure of primary mouse microglia to PGN led to a significant increase in Cx43 mRNA and protein expression. LY microinjection studies revealed that PGN-treated microglia were functionally coupled via gap junctions, the specificity of which was confirmed by the reversal of activation-induced dye coupling by the gap junction blocker 18-alpha-glycyrrhetinic acid. In contrast to PGN-activated microglia, unstimulated cells consistently failed to exhibit LY dye coupling. These results indicate that PGN stimulation can induce the formation of a functional microglial syncytium, suggesting that these cells may be capable of influencing neuro-inflammatory responses in the context of CNS bacterial infections through gap junction intercellular communication.
authors.affiliation: Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
authors.forename: Sarita
authors.initials: S
authors.lastname: Garg
authors.forename: Mohsin
authors.initials: M
authors.lastname: Md Syed
authors.forename: Tammy
authors.initials: T
authors.lastname: Kielian
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D018031:Connexin 43 / Q000096:biosynthesis* / Q000502:physiology; D017630:Connexins / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology*; D006034:Glycyrrhetinic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007546:Isoquinolines; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D010457:Peptidoglycan / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013211:Staphylococcus aureus / Q000737:chemistry*
chemical_list: D018031:Connexin 43; D017630:Connexins; D007546:Isoquinolines; D010457:Peptidoglycan; D012333:RNA, Messenger; C119129:18alpha-glycyrrhetinic acid; C017475:lucifer yellow; D006034:Glycyrrhetinic Acid