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IL-4Rα-dependent alternative activation of macrophages is not decisive for Mycobacterium tuberculosis pathology and bacterial burden in mice.

Guler R, Parihar SP, Savvi S, Logan E, Schwegmann A, Roy S, Nieuwenhuizen NE, Ozturk M, Schmeier S, Suzuki H, Brombacher F - PLoS ONE (2015)

Bottom Line: Interestingly, we observed no differences in the lung expression of inducible nitric oxide synthase (iNOS) and Arginase 1 (Arg1), well-established markers for M1/M2 macrophages among the Mtb-infected groups.Kinetic expression studies of IL-4/IL-13 activated bone marrow-derived macrophages (BMDM) infected with HN878, followed by gene set enrichment analysis, revealed that the MyD88 and IL-6, IL-10, G-CSF pathways are significantly enriched, but not the IL-4Rα driven pathway.Together, these results suggest that IL-4Rα-macrophages do not play a central role in TB disease progression.

View Article: PubMed Central - PubMed

Affiliation: International Centre for Genetic Engineering & Biotechnology (ICGEB), Cape Town component and Institute of Infectious Diseases and Molecular Medicine (IDM), Division of Immunology, University of Cape Town, Cape Town, South Africa.

ABSTRACT
Classical activation of macrophages (caMph or M1) is crucial for host protection against Mycobacterium tuberculosis (Mtb) infection. Evidence suggests that IL-4/IL-13 alternatively activated macrophages (aaMph or M2) are exploited by Mtb to divert microbicidal functions of caMph. To define the functions of M2 macrophages during tuberculosis (TB), we infected mice deficient for IL-4 receptor α on macrophages (LysMcreIL-4Rα-/lox) with Mtb. We show that absence of IL-4Rα on macrophages does not play a major role during infection with Mtb H37Rv, or the clinical Beijing strain HN878. This was demonstrated by similar mortality, bacterial burden, histopathology and T cell proliferation between infected wild-type (WT) and LysMcreIL-4Rα-/lox mice. Interestingly, we observed no differences in the lung expression of inducible nitric oxide synthase (iNOS) and Arginase 1 (Arg1), well-established markers for M1/M2 macrophages among the Mtb-infected groups. Kinetic expression studies of IL-4/IL-13 activated bone marrow-derived macrophages (BMDM) infected with HN878, followed by gene set enrichment analysis, revealed that the MyD88 and IL-6, IL-10, G-CSF pathways are significantly enriched, but not the IL-4Rα driven pathway. Together, these results suggest that IL-4Rα-macrophages do not play a central role in TB disease progression.

No MeSH data available.


Related in: MedlinePlus

Increased acute bacterial burden and chronic pulmonary pathology in absence of IL-4Rα responsive macrophages following low-dose Mtb H37Rv infection. Wild-type (BALB/c), IL-4Rα-/- and IL-4Rα macrophage cell-specific deficient mice (LysMcreIL-4Rα-/lox) were infected with Mtb H37Rv (100 CFU/mouse) by aerosol (n = 12–13 mice/group). (A) Percentages in body weight change are shown. (B) Mice were sacrificed at 4 and 18 weeks PI to determine bacterial loads in the lungs and spleen. (C) Lung weight indexes are shown. (D) At 0, 4 and 18 weeks PI, formalin-fixed lung sections were stained with H&E. Original magnification: 40X. (E) Lung sections of 5 mice per group were evaluated for pulmonary histopathology scores and quantification of total lesion sizes. N.D. = not detectable. (F) IL-4Rα expression was measured by flow cytometry on alveolar macrophages (SiglecF+CD11c+) at 0 and 18 weeks PI (*P < 0.05, **P < 0.01). Data shown are representative (A, D, E and F) and pooled (B, C) from two independent experiments.
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pone.0121070.g001: Increased acute bacterial burden and chronic pulmonary pathology in absence of IL-4Rα responsive macrophages following low-dose Mtb H37Rv infection. Wild-type (BALB/c), IL-4Rα-/- and IL-4Rα macrophage cell-specific deficient mice (LysMcreIL-4Rα-/lox) were infected with Mtb H37Rv (100 CFU/mouse) by aerosol (n = 12–13 mice/group). (A) Percentages in body weight change are shown. (B) Mice were sacrificed at 4 and 18 weeks PI to determine bacterial loads in the lungs and spleen. (C) Lung weight indexes are shown. (D) At 0, 4 and 18 weeks PI, formalin-fixed lung sections were stained with H&E. Original magnification: 40X. (E) Lung sections of 5 mice per group were evaluated for pulmonary histopathology scores and quantification of total lesion sizes. N.D. = not detectable. (F) IL-4Rα expression was measured by flow cytometry on alveolar macrophages (SiglecF+CD11c+) at 0 and 18 weeks PI (*P < 0.05, **P < 0.01). Data shown are representative (A, D, E and F) and pooled (B, C) from two independent experiments.

Mentions: Wild-type (BALB/c), IL-4Rα-/- and IL-4Rα macrophage cell-specific deficient mice (LysMcreIL-4Rα-/lox) were infected via pulmonary aerosol route with 100 CFU/mouse of Mtb, H37Rv. All mice gradually increased in weight (Fig. 1A). The bacillary burden at 4 weeks after infection was significantly increased in macrophage cell-specific IL-4Rα deficient mice when compared to wild-type mice (Fig. 1B). However, in terms of biological significance this CFU increase was only marginal with a ½ log increase. In contrast, no significant difference was observed in bacillary burden in the lungs and spleens between all the groups at 18 weeks PI. The lung weight index, a surrogate indicator of inflammation, did not reveal any differences between the groups during the infection (Fig. 1C). At 4 and 18 weeks PI all mouse groups displayed similar well-defined granuloma formation (Fig. 1D). However, the histopathology score, as described in the Materials and Methods, at 18 weeks PI revealed significantly increased inflammation in macrophage cell-specific IL-4Rα deficient mice, when compared to wild-type BALB/c mice (Fig. 1E). Pulmonary histopathology, bacterial burden, iNOS and Arg1 expression were similar between wild-type BALB/c and IL-4Rα-/- mice (S1 Fig.). These results suggest that IL-4Rα responsive macrophages contribute to containing bacterial growth during the acute phase and down-modulate inflammation during the chronic phase of Mtb infection.


IL-4Rα-dependent alternative activation of macrophages is not decisive for Mycobacterium tuberculosis pathology and bacterial burden in mice.

Guler R, Parihar SP, Savvi S, Logan E, Schwegmann A, Roy S, Nieuwenhuizen NE, Ozturk M, Schmeier S, Suzuki H, Brombacher F - PLoS ONE (2015)

Increased acute bacterial burden and chronic pulmonary pathology in absence of IL-4Rα responsive macrophages following low-dose Mtb H37Rv infection. Wild-type (BALB/c), IL-4Rα-/- and IL-4Rα macrophage cell-specific deficient mice (LysMcreIL-4Rα-/lox) were infected with Mtb H37Rv (100 CFU/mouse) by aerosol (n = 12–13 mice/group). (A) Percentages in body weight change are shown. (B) Mice were sacrificed at 4 and 18 weeks PI to determine bacterial loads in the lungs and spleen. (C) Lung weight indexes are shown. (D) At 0, 4 and 18 weeks PI, formalin-fixed lung sections were stained with H&E. Original magnification: 40X. (E) Lung sections of 5 mice per group were evaluated for pulmonary histopathology scores and quantification of total lesion sizes. N.D. = not detectable. (F) IL-4Rα expression was measured by flow cytometry on alveolar macrophages (SiglecF+CD11c+) at 0 and 18 weeks PI (*P < 0.05, **P < 0.01). Data shown are representative (A, D, E and F) and pooled (B, C) from two independent experiments.
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Related In: Results  -  Collection

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pone.0121070.g001: Increased acute bacterial burden and chronic pulmonary pathology in absence of IL-4Rα responsive macrophages following low-dose Mtb H37Rv infection. Wild-type (BALB/c), IL-4Rα-/- and IL-4Rα macrophage cell-specific deficient mice (LysMcreIL-4Rα-/lox) were infected with Mtb H37Rv (100 CFU/mouse) by aerosol (n = 12–13 mice/group). (A) Percentages in body weight change are shown. (B) Mice were sacrificed at 4 and 18 weeks PI to determine bacterial loads in the lungs and spleen. (C) Lung weight indexes are shown. (D) At 0, 4 and 18 weeks PI, formalin-fixed lung sections were stained with H&E. Original magnification: 40X. (E) Lung sections of 5 mice per group were evaluated for pulmonary histopathology scores and quantification of total lesion sizes. N.D. = not detectable. (F) IL-4Rα expression was measured by flow cytometry on alveolar macrophages (SiglecF+CD11c+) at 0 and 18 weeks PI (*P < 0.05, **P < 0.01). Data shown are representative (A, D, E and F) and pooled (B, C) from two independent experiments.
Mentions: Wild-type (BALB/c), IL-4Rα-/- and IL-4Rα macrophage cell-specific deficient mice (LysMcreIL-4Rα-/lox) were infected via pulmonary aerosol route with 100 CFU/mouse of Mtb, H37Rv. All mice gradually increased in weight (Fig. 1A). The bacillary burden at 4 weeks after infection was significantly increased in macrophage cell-specific IL-4Rα deficient mice when compared to wild-type mice (Fig. 1B). However, in terms of biological significance this CFU increase was only marginal with a ½ log increase. In contrast, no significant difference was observed in bacillary burden in the lungs and spleens between all the groups at 18 weeks PI. The lung weight index, a surrogate indicator of inflammation, did not reveal any differences between the groups during the infection (Fig. 1C). At 4 and 18 weeks PI all mouse groups displayed similar well-defined granuloma formation (Fig. 1D). However, the histopathology score, as described in the Materials and Methods, at 18 weeks PI revealed significantly increased inflammation in macrophage cell-specific IL-4Rα deficient mice, when compared to wild-type BALB/c mice (Fig. 1E). Pulmonary histopathology, bacterial burden, iNOS and Arg1 expression were similar between wild-type BALB/c and IL-4Rα-/- mice (S1 Fig.). These results suggest that IL-4Rα responsive macrophages contribute to containing bacterial growth during the acute phase and down-modulate inflammation during the chronic phase of Mtb infection.

Bottom Line: Interestingly, we observed no differences in the lung expression of inducible nitric oxide synthase (iNOS) and Arginase 1 (Arg1), well-established markers for M1/M2 macrophages among the Mtb-infected groups.Kinetic expression studies of IL-4/IL-13 activated bone marrow-derived macrophages (BMDM) infected with HN878, followed by gene set enrichment analysis, revealed that the MyD88 and IL-6, IL-10, G-CSF pathways are significantly enriched, but not the IL-4Rα driven pathway.Together, these results suggest that IL-4Rα-macrophages do not play a central role in TB disease progression.

View Article: PubMed Central - PubMed

Affiliation: International Centre for Genetic Engineering & Biotechnology (ICGEB), Cape Town component and Institute of Infectious Diseases and Molecular Medicine (IDM), Division of Immunology, University of Cape Town, Cape Town, South Africa.

ABSTRACT
Classical activation of macrophages (caMph or M1) is crucial for host protection against Mycobacterium tuberculosis (Mtb) infection. Evidence suggests that IL-4/IL-13 alternatively activated macrophages (aaMph or M2) are exploited by Mtb to divert microbicidal functions of caMph. To define the functions of M2 macrophages during tuberculosis (TB), we infected mice deficient for IL-4 receptor α on macrophages (LysMcreIL-4Rα-/lox) with Mtb. We show that absence of IL-4Rα on macrophages does not play a major role during infection with Mtb H37Rv, or the clinical Beijing strain HN878. This was demonstrated by similar mortality, bacterial burden, histopathology and T cell proliferation between infected wild-type (WT) and LysMcreIL-4Rα-/lox mice. Interestingly, we observed no differences in the lung expression of inducible nitric oxide synthase (iNOS) and Arginase 1 (Arg1), well-established markers for M1/M2 macrophages among the Mtb-infected groups. Kinetic expression studies of IL-4/IL-13 activated bone marrow-derived macrophages (BMDM) infected with HN878, followed by gene set enrichment analysis, revealed that the MyD88 and IL-6, IL-10, G-CSF pathways are significantly enriched, but not the IL-4Rα driven pathway. Together, these results suggest that IL-4Rα-macrophages do not play a central role in TB disease progression.

No MeSH data available.


Related in: MedlinePlus