Macrophages restrict Pseudomonas aeruginosa growth, regulate polymorphonuclear neutrophil influx, and balance pro- and anti-inflammatory cytokines in BALB/c mice.
The role of macrophages in Pseudomonas aeruginosa corneal infection in susceptible (cornea perforates), C57BL/6 (B6) vs resistant (cornea heals), BALB/c mice was tested by depleting macrophages using subconjunctival injections of clodronate-containing liposomes before corneal infection. Both groups of inbred mice treated with clodronate-liposomes compared with PBS-liposomes (controls) exhibited more severe disease. In B6 mice, the cornea perforated and the eye became extremely shrunken, whereas in BALB/c mice, the cornea perforated rather than healed. The myeloperoxidase assay detected significantly more PMN in the cornea of both groups of mice treated with clodronate-liposomes vs PBS-liposomes. In independent experiments, ELISA analysis showed that protein levels for IL-1 beta, macrophage-inflammatory protein 2, and macrophage-inflammatory protein 1 alpha, all regulators of PMN chemotaxis, also were elevated in both groups of mice treated with clodronate-liposomes. Bacterial plate counts in B6 mice treated with clodronate-liposomes were unchanged at 3 days and were higher in control-treated mice at 5 days postinfection (p.i.), whereas in BALB/c mice, bacterial load was significantly elevated in the cornea of mice treated with clodronate-liposomes at both 3 and 5 days p.i. mRNA expression levels for pro (IFN-gamma and TNF-alpha)- and anti (IL-4 and IL-10)-inflammatory cytokines also were determined in BALB/c mice treated with clodronate-liposomes vs control-treated mice. Expression levels for IFN-gamma were significantly elevated in mice treated with clodronate-liposomes at 3 and 5 days p.i., while IL-10 levels (mRNA and protein) were reduced. These data provide evidence that macrophages control resistance to P. aeruginosa corneal infection through regulation of PMN number, bacterial killing and balancing pro- and anti-inflammatory cytokine levels.
McClellan
Sharon A
SA
Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI 48201,USA.
Huang
Xi
X
Barrett
Ronald P
RP
van Rooijen
Nico
N
Hazlett
Linda D
LD
D000818:Animals; D018925:Chemokines / Q000096:biosynthesis; D004002:Clodronic Acid / Q000008:administration & dosage; D015169:Colony Count, Microbial; D003228:Conjunctiva; D003315:Cornea / Q000187:drug effects / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D016207:Cytokines / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D015818:Eye Infections, Bacterial / Q000276:immunology / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D005260:Female; D007165:Immunosuppression Therapy; D018836:Inflammation Mediators / Q000378:metabolism*; D016753:Interleukin-10 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D007958:Leukocyte Count; D008264:Macrophages / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D020556:Neutrophil Infiltration / Q000187:drug effects / Q000276:immunology*; D011552:Pseudomonas Infections / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D011550:Pseudomonas aeruginosa / Q000254:growth & development / Q000276:immunology*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D018417:Th1 Cells / Q000276:immunology / Q000378:metabolism; D018418:Th2 Cells / Q000276:immunology / Q000378:metabolism
D018925:Chemokines; D016207:Cytokines; D018836:Inflammation Mediators; D012333:RNA, Messenger; D004002:Clodronic Acid; D016753:Interleukin-10