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Heme oxygenase-1 promotes granuloma development and protects against dissemination of mycobacteria.

Regev D, Surolia R, Karki S, Zolak J, Montes-Worboys A, Oliva O, Guroji P, Saini V, Steyn AJ, Agarwal A, Antony VB - Lab. Invest. (2012)

Bottom Line: Inhibition of HO by zinc protoporphyrin-IX led to inhibition of MCP-1 and increased expression of CCR2, its cognate receptor.Mycobacteria were found only inside defined granulomas but not outside granuloma in the lungs of HO-1⁺/⁺ mice.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Pulmonary, Critical Care and Sleep Medicine, College of Medicine, University of Florida, Gainesville, FL, USA.

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.

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M. avium CFU counts are higher in lung tissue of infected HO-1 -/- mice as compared to lung tissue form infected HO-1+/+ miceMouse lung tissue was homogenized in 2ml of 7H9 broth medium. Then, 100 μl of 10-fold serial dilutions were plated on 7H10 agar plates and incubated for 10-21 days in 37°C after which colony forming units were counted. CFU counts were significantly higher (* P<0.05) in lung tissue of infected HO-1-/- mice as compared to HO-1+/+ mouse tissue. Values represent the average CFU counts from four mice in either non-infected or M. avium infected groups.
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Figure 6: M. avium CFU counts are higher in lung tissue of infected HO-1 -/- mice as compared to lung tissue form infected HO-1+/+ miceMouse lung tissue was homogenized in 2ml of 7H9 broth medium. Then, 100 μl of 10-fold serial dilutions were plated on 7H10 agar plates and incubated for 10-21 days in 37°C after which colony forming units were counted. CFU counts were significantly higher (* P<0.05) in lung tissue of infected HO-1-/- mice as compared to HO-1+/+ mouse tissue. Values represent the average CFU counts from four mice in either non-infected or M. avium infected groups.

Mentions: To test whether the failure of HO-1-/- mice to form mature granulomas had any effect on their ability to control and contain the infection, we harvested lung tissue from infected HO-1+/+ and HO-1-/- mice and counted CFU in the tissue. M. avium were recovered from liver and spleen culture (Table-1). In HO-1+/+ mice there was no dissemination of infection. There was no mortality (n=8) in this group even at 16 weeks following intratracheal infection of M. avium. In contrast, HO-1-/- mice infected with M. avium had persistent infection in the liver and spleen at all-time points (Table 1). Notably, HO-1-/- mice which failed to form organized, mature granulomas, also had significantly higher average M. avium CFU counts in their lung tissue as compared with HO-1+/+ mice (Figure 6). It is possible that the increased mortality seen in the HO-1-/- is secondary to the dissemination of the organisms to other vital organs.


Heme oxygenase-1 promotes granuloma development and protects against dissemination of mycobacteria.

Regev D, Surolia R, Karki S, Zolak J, Montes-Worboys A, Oliva O, Guroji P, Saini V, Steyn AJ, Agarwal A, Antony VB - Lab. Invest. (2012)

M. avium CFU counts are higher in lung tissue of infected HO-1 -/- mice as compared to lung tissue form infected HO-1+/+ miceMouse lung tissue was homogenized in 2ml of 7H9 broth medium. Then, 100 μl of 10-fold serial dilutions were plated on 7H10 agar plates and incubated for 10-21 days in 37°C after which colony forming units were counted. CFU counts were significantly higher (* P<0.05) in lung tissue of infected HO-1-/- mice as compared to HO-1+/+ mouse tissue. Values represent the average CFU counts from four mice in either non-infected or M. avium infected groups.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4017357&req=5

Figure 6: M. avium CFU counts are higher in lung tissue of infected HO-1 -/- mice as compared to lung tissue form infected HO-1+/+ miceMouse lung tissue was homogenized in 2ml of 7H9 broth medium. Then, 100 μl of 10-fold serial dilutions were plated on 7H10 agar plates and incubated for 10-21 days in 37°C after which colony forming units were counted. CFU counts were significantly higher (* P<0.05) in lung tissue of infected HO-1-/- mice as compared to HO-1+/+ mouse tissue. Values represent the average CFU counts from four mice in either non-infected or M. avium infected groups.
Mentions: To test whether the failure of HO-1-/- mice to form mature granulomas had any effect on their ability to control and contain the infection, we harvested lung tissue from infected HO-1+/+ and HO-1-/- mice and counted CFU in the tissue. M. avium were recovered from liver and spleen culture (Table-1). In HO-1+/+ mice there was no dissemination of infection. There was no mortality (n=8) in this group even at 16 weeks following intratracheal infection of M. avium. In contrast, HO-1-/- mice infected with M. avium had persistent infection in the liver and spleen at all-time points (Table 1). Notably, HO-1-/- mice which failed to form organized, mature granulomas, also had significantly higher average M. avium CFU counts in their lung tissue as compared with HO-1+/+ mice (Figure 6). It is possible that the increased mortality seen in the HO-1-/- is secondary to the dissemination of the organisms to other vital organs.

Bottom Line: Inhibition of HO by zinc protoporphyrin-IX led to inhibition of MCP-1 and increased expression of CCR2, its cognate receptor.Mycobacteria were found only inside defined granulomas but not outside granuloma in the lungs of HO-1⁺/⁺ mice.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Pulmonary, Critical Care and Sleep Medicine, College of Medicine, University of Florida, Gainesville, FL, USA.

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.

Show MeSH
Related in: MedlinePlus