title: Heme Oxygenase-1 Deficiency Diminishes Methicillin-Resistant Staphylococcus aureus Clearance Due to Reduced TLR9 Expression in Pleural Mesothelial Cells.
abstract: Methicillin Resistant Staphylococcus aureus (MRSA) cause pneumonia and empyema thoraces. TLR9 activation provides protection against bacterial infections and Heme oxygenase-1 (HO-1) is known to enhance host innate immunity against bacterial infections. However, it is still unclear whether HO-1 regulates TLR-9 expression in the pleura and modulates the host innate defenses during MRSA empyema. In order to determine if HO-1 regulates host innate immune functions via modulating TLR expression, in MRSA empyema, HO-1+/+ and HO-1-/- mouse pleural mesothelial cells (PMCs) were infected with MRSA (1:10, MOI) in the presence or absence of Cobalt Protoporphyrin (CoPP) and Zinc Protoporphyrin (ZnPP) or CORM-2 (a Carbon monoxide donor) and the expression of mTLR9 and mBD14 was assessed by RT-PCR. In vivo, HO-1+/+ and HO-1-/- mice were inoculated with MRSA (5x106 CFU) intra-pleurally and host bacterial load was measured by CFU, and TLR9 expression in the pleura was determined by histochemical-immunostaining. We noticed MRSA inducing differential expression of TLR9 in HO-1+/+ and HO-1 -/- PMCs. In MRSA infected HO-1+/+ PMCs, TLR1, TLR4, and TLR9 expression was several fold higher than MRSA infected HO-1-/- PMCs. Particularly TLR9 expression was very low in MRSA infected HO-1-/- PMCs both in vivo and in vitro. Bacterial clearance was significantly higher in HO-1+/+ PMCs than compared to HO-1-/- PMCs in vitro, and blocking TLR9 activation diminished MRSA clearance significantly. In addition, HO-1-/- mice were unable to clear the MRSA bacterial load in vivo. MRSA induced TLR9 and mBD14 expression was significantly high in HO-1+/+ PMCs and it was dependent on HO-1 activity. Our findings suggest that HO-1 by modulating TLR9 expression in PMCs promotes pleural innate immunity in MRSA empyema.
authors.affiliation: North Florida/South Georgia Veterans Health System, Malcom Randall Veterans Affairs Medical Center, Gainesville, Florida, United States of America.|Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Satindra
authors.initials: S
authors.lastname: Gahlot
authors.affiliation: North Florida/South Georgia Veterans Health System, Malcom Randall Veterans Affairs Medical Center, Gainesville, Florida, United States of America.|Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Najmunnisa
authors.initials: N
authors.lastname: Nasreen
authors.affiliation: Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Judith A
authors.initials: JA
authors.lastname: Johnson
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Medical University of South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Sahn
authors.affiliation: North Florida/South Georgia Veterans Health System, Malcom Randall Veterans Affairs Medical Center, Gainesville, Florida, United States of America.|Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Kamal A
authors.initials: KA
authors.lastname: Mohammed
mesh_terms: D000743:Anemia, Hemolytic / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D004847:Epithelial Cells / Q000201:enzymology* / Q000378:metabolism*; D005260:Female; D006130:Growth Disorders / Q000235:genetics / Q000378:metabolism*; D051547:Heme Oxygenase-1 / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology; D019189:Iron Metabolism Disorders / Q000235:genetics / Q000378:metabolism*; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000472:pathogenicity*; D051379:Mice; D018345:Mice, Knockout; D010994:Pleura / Q000201:enzymology* / Q000378:metabolism / Q000382:microbiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism*
chemical_list: D051217:Toll-Like Receptor 9; D051547:Heme Oxygenase-1