Role of the Fas pathway in Pseudomonas aeruginosa keratitis.
OBJECTIVE
The role of the Fas pathway was tested in Pseudomonas aeruginosa-infected mouse cornea by contrasting the responses of FasL(-/-) and wild-type (WT) mice.


METHODS
TUNEL staining, real-time RT-PCR, immunostaining, and ELISA assay were used.


RESULTS
Compared with WT (resistant) mice, BALB/c FasL(-/-) exhibited significantly elevated bacterial counts and polymorphonuclear leukocyte numbers at 1 and 3 days postinfection (p.i.) and worse outcomes from disease. Similar bacterial challenges in C57BL/6 FasL(-/-) compared with WT mice also led to worsened disease as evidenced by earlier corneal perforation in the susceptible mouse strain. Intense TUNEL staining of apoptotic cells was seen earlier (1 day vs. 3 days) p.i. in BALB/c WT than in knockout mice, This earlier apoptotic pattern correlated with increased expression of caspases 3, 8, and 9 and BAX and with decreased expression of the antiapoptotic molecule Bcl-2. Furthermore, expression levels of the proinflammatory molecule TNF-alpha and its receptor, MIP-2, inducible nitric oxide synthase (iNOS), and nitrite also were significantly elevated in the infected cornea of BALB/c FasL(-/-) compared with WT mice. In vitro, LPS-stimulated Mphi from BALB/c FasL(-/-) mice expressed significantly less caspase 3 and 9, BAX, and IL-10 and more TNF-alpha, MIP-2, and IL-1beta than did cells from WT mice.


CONCLUSIONS
Fas-FasL interaction in the cornea balances the host innate immune response to improve disease outcome by promoting earlier apoptosis and regulating proinflammatory cytokines/chemokines and nitric oxide (nitrite) production. Dysregulation of this interaction contributes to bystander tissue damage, enhancing nutrients for bacterial growth and worsened disease outcome after P. aeruginosa infection.
Zhou
Zimei
Z
Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Wu
Minhao
M
Barrett
Ronald P
RP
McClellan
Sharon A
SA
Zhang
Yunfan
Y
Hazlett
Linda D
LD
D000818:Animals; D017209:Apoptosis / Q000276:immunology; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D015169:Colony Count, Microbial; D003320:Corneal Ulcer / Q000276:immunology* / Q000382:microbiology; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D015818:Eye Infections, Bacterial / Q000276:immunology* / Q000382:microbiology; D053222:Fas Ligand Protein / Q000502:physiology*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D020287:In Situ Nick-End Labeling; D007958:Leukocyte Count; D008262:Macrophage Activation / Q000502:physiology; D017737:Macrophages, Peritoneal / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D009504:Neutrophils / Q000276:immunology; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D009573:Nitrites / Q000378:metabolism; D011552:Pseudomonas Infections / Q000276:immunology* / Q000382:microbiology; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019014:fas Receptor / Q000502:physiology*
D051017:Apoptosis Regulatory Proteins; D016207:Cytokines; D053222:Fas Ligand Protein; C491899:Fas protein, mouse; C505658:Fasl protein, mouse; D009573:Nitrites; D012333:RNA, Messenger; D019014:fas Receptor; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse