Homotrimeric macrophage migration inhibitory factor (MIF) drives inflammatory responses in the corneal epithelium by promoting caveolin-rich platform assembly in response to infection.
Acute inflammation that arises during Pseudomonas aeruginosa-induced ocular infection can trigger tissue damage resulting in long term impairment of visual function, suggesting that the appropriate treatment strategy should include the use of anti-inflammatory agents in addition to antibiotics. We recently identified a potential target for modulation during ocular infection, macrophage migration inhibitory factor (MIF). MIF deficiency protected mice from inflammatory-mediated corneal damage resulting from acute bacterial keratitis. To gain a better understanding of the molecular mechanisms of MIF activity, we analyzed the oligomeric states and functional properties of MIF during infection. We found that in human primary corneal cells infected with P. aeruginosa, MIF is primarily in a homotrimeric state. Homotrimeric MIF levels correlated with the severity of infection in the corneas of infected mice, suggesting that the MIF homotrimers were the functionally active form of MIF. During infection, human primary corneal cells released more IL-8 when treated with recombinant, locked MIF trimers than when treated with lower MIF oligomers. MIF promoted P. aeruginosa-induced IL-8 responses via the formation of caveolin-1-rich "signaling hubs" in the corneal cells that led to elevated MAPK p42/p44 activation and sustained inflammatory signaling. These findings suggest that inhibiting homotrimerization of MIF or the functional activities of MIF homotrimers could have therapeutic benefits during ocular inflammation.
Division of Infectious Disease, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
Thomas
T
Reidy
Division of Infectious Disease, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
Alexander
A
Rittenberg
Division of Infectious Disease, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
Markryan
M
Dwyer
Division of Infectious Disease, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
Samantha
S
D'Ortona
Division of Infectious Disease, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
Gerald
G
Pier
Division of Infectious Disease, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115. Electronic address: mgadjeva@rics.bwh.harvard.edu.
Mihaela
M
Gadjeva
D000818:Animals; D022461:Caveolins / Q000378:metabolism*; D002478:Cells, Cultured; D003234:Conjunctivitis, Bacterial / Q000276:immunology / Q000378:metabolism*; D019573:Epithelium, Corneal / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism / Q000502:physiology; D016209:Interleukin-8 / Q000096:biosynthesis; D020935:MAP Kinase Signaling System; D008263:Macrophage Migration-Inhibitory Factors / Q000378:metabolism* / Q000502:physiology; D021962:Membrane Microdomains / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D061251:Primary Cell Culture; D020836:Protein Structure, Quaternary; D011552:Pseudomonas Infections / Q000276:immunology / Q000378:metabolism*; D011550:Pseudomonas aeruginosa
C508606:CXCL8 protein, human; D022461:Caveolins; D018836:Inflammation Mediators; D016209:Interleukin-8; D008263:Macrophage Migration-Inhibitory Factors