title: Heme oxygenase-1 promotes granuloma development and protects against dissemination of mycobacteria.
abstract: Non-tuberculous mycobacterial (NTM) infections occur in both immunocompromised and immunocompetent hosts and are an increasingly recognized cause of morbidity and mortality. The hallmark of pulmonary mycobacterial infections is the formation of granuloma in the lung. Our study focuses on the role of heme oxygenase-1 (HO-1), a cytoprotective enzyme, in the regulation of granuloma development and maturation following infection with Mycobacterium avium. We examined the role of HO-1 in regulating monocyte chemoattractant protein-1 (MCP-1) and chemokine receptor 2 (CCR2), two molecules involved in monocyte-macrophage cell trafficking after infection. We showed that RAW 264.7 mouse monocytes exposed to M. avium expressed HO-1 and MCP-1. Inhibition of HO by zinc protoporphyrin-IX led to inhibition of MCP-1 and increased expression of CCR2, its cognate receptor. HO-1⁻/⁻ mice did not develop organized granuloma in their lungs, had higher lung colony forming unit of M. avium when infected with intratracheal M. avium, and had loose collections of inflammatory cells in the lung parenchyma. Mycobacteria were found only inside defined granulomas but not outside granuloma in the lungs of HO-1⁺/⁺ mice. In HO-1⁻/⁻ mice, mycobacteria were also found in the liver and spleen and showed increased mortality. Peripheral blood monocytes isolated from GFP⁺ mice and given intravenously to HO-1⁺/⁺ mice localized into tight granulomas, while in HO-1⁻/⁻ mice they remained diffusely scattered in areas of parenchymal inflammation. Higher MCP-1 levels were found in bronchoalveolar lavage fluid of M. avium infected HO-1(-/-) mice and CCR2 expression was higher in HO-1⁻/⁻ alveolar macrophages when compared with HO-1⁺/⁺ mice. CCR2 expression localized to granuloma in HO-1⁺/⁺ mice but not in the HO-1⁻/⁻ mice. These findings strongly suggest that HO-1 plays a protective role in the control of M. avium infection.
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine, College of Medicine, University of Florida, Gainesville, FL, USA.
authors.forename: Doron
authors.initials: D
authors.lastname: Regev
authors.forename: Ranu
authors.initials: R
authors.lastname: Surolia
authors.forename: Suman
authors.initials: S
authors.lastname: Karki
authors.forename: Jason
authors.initials: J
authors.lastname: Zolak
authors.forename: Ana
authors.initials: A
authors.lastname: Montes-Worboys
authors.forename: Ocatvio
authors.initials: O
authors.lastname: Oliva
authors.forename: Purushotum
authors.initials: P
authors.lastname: Guroji
authors.forename: Vikram
authors.initials: V
authors.lastname: Saini
authors.forename: Adrie Jc
authors.initials: AJ
authors.lastname: Steyn
authors.forename: Anupam
authors.initials: A
authors.lastname: Agarwal
authors.forename: Veena B
authors.initials: VB
authors.lastname: Antony
mesh_terms: D000818:Animals; D002460:Cell Line; D018932:Chemokine CCL2 / Q000378:metabolism*; D015169:Colony Count, Microbial; D006099:Granuloma / Q000201:enzymology* / Q000382:microbiology; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D008168:Lung / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009162:Mycobacterium avium; D011524:Protoporphyrins; D012333:RNA, Messenger / Q000378:metabolism; D054390:Receptors, CCR2 / Q000378:metabolism*; D014397:Tuberculosis, Pulmonary / Q000201:enzymology* / Q000382:microbiology / Q000473:pathology
chemical_list: C491768:Ccl2 protein, mouse; C515335:Ccr2 protein, mouse; D018932:Chemokine CCL2; D008565:Membrane Proteins; D011524:Protoporphyrins; D012333:RNA, Messenger; D054390:Receptors, CCR2; C017803:zinc protoporphyrin; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse