Defective nitric oxide production by alveolar macrophages during Pneumocystis pneumonia.
The effect of nitric oxide (NO) on Pneumocystis (Pc) organisms, the role of NO in the defense against infection with Pc, and the production of NO by alveolar macrophages (AMs) during Pneumocystis pneumonia (PCP) were investigated. The results indicate that NO was toxic to Pc organisms and inhibited their proliferation in culture. When the production of NO was inhibited by intraperitoneal injection of rats with the nitric oxide synthase inhibitor L-N(5)-(1-iminoethyl) ornithine, progression of Pc infection in immunocompetent rats was enhanced. Concentrations of NO in bronchoalveolar lavage fluids from immunosuppressed, Pc-infected rats and mice were greatly reduced, compared with those from uninfected animals, and AMs from these animals were defective in NO production. However, inducible nitric oxide synthase (iNOS) mRNA and protein concentrations were high in AMs from Pc-infected rats and mice. Immunoblot analysis showed that iNOS in AMs from Pc-infected rats existed primarily as a monomer, but the homo-dimerization of iNOS monomers was required for the production of NO. When iNOS dimerization cofactors, including calmodulin, were added to macrophage lysates, iNOS dimerization increased, whereas incubation of the same lysates with all cofactors except calmodulin did not rescue iNOS dimer formation. These data suggest that NO is important in the defense against Pc infection, but that the production of NO in AMs during PCP is defective because of the reduced dimerization of iNOS.
Lasbury
Mark E
ME
Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN 46202-5113, USA.
Liao
Chung-Ping
CP
Hage
Chadi A
CA
Durant
Pamela J
PJ
Tschang
Dennis
D
Wang
Shao-Hung
SH
Zhang
Chen
C
Lee
Chao-Hung
CH
D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002457:Cell Extracts; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D003067:Coenzymes / Q000494:pharmacology; D003470:Culture Media / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000382:microbiology; D051379:Mice; D050296:Microbial Viability / Q000187:drug effects; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009952:Ornithine / Q000494:pharmacology; D011010:Pneumocystis / Q000166:cytology / Q000187:drug effects; D011020:Pneumonia, Pneumocystis / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D055503:Protein Multimerization / Q000187:drug effects; D051381:Rats; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects
D002457:Cell Extracts; D003067:Coenzymes; D003470:Culture Media; D009573:Nitrites; D009569:Nitric Oxide; D009952:Ornithine; D052247:Nitric Oxide Synthase Type II