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IL-17A Promotes Intracellular Growth of Mycobacterium by Inhibiting Apoptosis of Infected Macrophages.

Cruz A, Ludovico P, Torrado E, Gama JB, Sousa J, Gaifem J, Appelberg R, Rodrigues F, Cooper AM, Pedrosa J, Saraiva M, Castro AG - Front Immunol (2015)

Bottom Line: Mechanistically, we show that IL-17 inhibits p53, and impacts on the intrinsic apoptotic pathway, by increasing the Bcl2 and decreasing Bax expression, decreasing cytochrome c release from the mitochondria, and inhibiting caspase-3 activation.The same effect of IL-17 was observed in infected macrophages upon blockade of p53 nuclear translocation.These results reveal a previously unappreciated role for the IL-17/p53 axis in the regulation of mycobacteria-induced apoptosis and can have important implications in a broad spectrum of diseases where apoptosis of the infected cell is an important host defense mechanism.

View Article: PubMed Central - PubMed

Affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho , Braga , Portugal ; ICVS/3B's - PT Government Associate Laboratory, University of Minho , Braga , Portugal.

ABSTRACT
The fate of infected macrophages is a critical aspect of immunity to mycobacteria. By depriving the pathogen of its intracellular niche, apoptotic death of the infected macrophage has been shown to be an important mechanism to control bacterial growth. Here, we show that IL-17 inhibits apoptosis of Mycobacterium bovis BCG- or Mycobacterium tuberculosis-infected macrophages thus hampering their ability to control bacterial growth. Mechanistically, we show that IL-17 inhibits p53, and impacts on the intrinsic apoptotic pathway, by increasing the Bcl2 and decreasing Bax expression, decreasing cytochrome c release from the mitochondria, and inhibiting caspase-3 activation. The same effect of IL-17 was observed in infected macrophages upon blockade of p53 nuclear translocation. These results reveal a previously unappreciated role for the IL-17/p53 axis in the regulation of mycobacteria-induced apoptosis and can have important implications in a broad spectrum of diseases where apoptosis of the infected cell is an important host defense mechanism.

No MeSH data available.


Related in: MedlinePlus

Blockade of p53 impairs apoptosis of infected macrophages and bacterial growth control. BMDM were infected with M. bovis BCG in the presence (+) or absence (−) of the p53 inhibitor PFTα. Four days post-infection (A) caspase-3 activation was assessed by immunofluorescence and (B) the bacterial load was assessed as indicated before. Representative images used for the calculations are in Figure S3 in Supplementary Material. (C) At 24 or 48 h post-M. bovis BCG infection, the Bcl2 and Bax mRNA was determined by real-time PCR. The fold increase of Bcl2 or Bax mRNA over the NI control was calculated for each independent experiment. (D) BMDM were left uninfected or infected with M. bovis BCG in the presence or absence of IL-17 or of PFTα as indicated. Four days post-infection the bacterial load was assessed as indicated before. Represented are the mean ± SE of three independent experiments. Significance determined by Student’s t test (***p < 0.001).
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Figure 4: Blockade of p53 impairs apoptosis of infected macrophages and bacterial growth control. BMDM were infected with M. bovis BCG in the presence (+) or absence (−) of the p53 inhibitor PFTα. Four days post-infection (A) caspase-3 activation was assessed by immunofluorescence and (B) the bacterial load was assessed as indicated before. Representative images used for the calculations are in Figure S3 in Supplementary Material. (C) At 24 or 48 h post-M. bovis BCG infection, the Bcl2 and Bax mRNA was determined by real-time PCR. The fold increase of Bcl2 or Bax mRNA over the NI control was calculated for each independent experiment. (D) BMDM were left uninfected or infected with M. bovis BCG in the presence or absence of IL-17 or of PFTα as indicated. Four days post-infection the bacterial load was assessed as indicated before. Represented are the mean ± SE of three independent experiments. Significance determined by Student’s t test (***p < 0.001).

Mentions: As IL-17 decreases the capacity of macrophages to limit bacterial growth (Figure 1), reduces availability of p53, and limits apoptosis in mycobacterially infected macrophages, we hypothesized that IL-17 impacts mycobacterial growth via modulation of p53 activity. To test this hypothesis, we chemically inhibited the nuclear translocation of p53 during infection of macrophages with M. bovis BCG. Blocking the nuclear activity of p53 led to a significant decrease on the percentage of caspase 3-positive cells (Figure 4A and Figure S3A in Supplementary Material) accompanied by a significant increase in the number of bacteria (Figure 4B). Also, we observed that PFT-α addition to M. bovis BCG-infected macrophages increased the expression of the Bcl2, whereas that of Bax was not significantly altered (Figure 4C). The effect of PFT-α in increasing the number of bacteria was not further potentiated by IL-17 (Figure 4D), suggesting that p53 is a downstream mediator of IL-17 in this experimental setting. All our data show that IL-17, by modulating cell survival, impacts mycobacterial control by macrophages.


IL-17A Promotes Intracellular Growth of Mycobacterium by Inhibiting Apoptosis of Infected Macrophages.

Cruz A, Ludovico P, Torrado E, Gama JB, Sousa J, Gaifem J, Appelberg R, Rodrigues F, Cooper AM, Pedrosa J, Saraiva M, Castro AG - Front Immunol (2015)

Blockade of p53 impairs apoptosis of infected macrophages and bacterial growth control. BMDM were infected with M. bovis BCG in the presence (+) or absence (−) of the p53 inhibitor PFTα. Four days post-infection (A) caspase-3 activation was assessed by immunofluorescence and (B) the bacterial load was assessed as indicated before. Representative images used for the calculations are in Figure S3 in Supplementary Material. (C) At 24 or 48 h post-M. bovis BCG infection, the Bcl2 and Bax mRNA was determined by real-time PCR. The fold increase of Bcl2 or Bax mRNA over the NI control was calculated for each independent experiment. (D) BMDM were left uninfected or infected with M. bovis BCG in the presence or absence of IL-17 or of PFTα as indicated. Four days post-infection the bacterial load was assessed as indicated before. Represented are the mean ± SE of three independent experiments. Significance determined by Student’s t test (***p < 0.001).
© Copyright Policy
Related In: Results  -  Collection

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Figure 4: Blockade of p53 impairs apoptosis of infected macrophages and bacterial growth control. BMDM were infected with M. bovis BCG in the presence (+) or absence (−) of the p53 inhibitor PFTα. Four days post-infection (A) caspase-3 activation was assessed by immunofluorescence and (B) the bacterial load was assessed as indicated before. Representative images used for the calculations are in Figure S3 in Supplementary Material. (C) At 24 or 48 h post-M. bovis BCG infection, the Bcl2 and Bax mRNA was determined by real-time PCR. The fold increase of Bcl2 or Bax mRNA over the NI control was calculated for each independent experiment. (D) BMDM were left uninfected or infected with M. bovis BCG in the presence or absence of IL-17 or of PFTα as indicated. Four days post-infection the bacterial load was assessed as indicated before. Represented are the mean ± SE of three independent experiments. Significance determined by Student’s t test (***p < 0.001).
Mentions: As IL-17 decreases the capacity of macrophages to limit bacterial growth (Figure 1), reduces availability of p53, and limits apoptosis in mycobacterially infected macrophages, we hypothesized that IL-17 impacts mycobacterial growth via modulation of p53 activity. To test this hypothesis, we chemically inhibited the nuclear translocation of p53 during infection of macrophages with M. bovis BCG. Blocking the nuclear activity of p53 led to a significant decrease on the percentage of caspase 3-positive cells (Figure 4A and Figure S3A in Supplementary Material) accompanied by a significant increase in the number of bacteria (Figure 4B). Also, we observed that PFT-α addition to M. bovis BCG-infected macrophages increased the expression of the Bcl2, whereas that of Bax was not significantly altered (Figure 4C). The effect of PFT-α in increasing the number of bacteria was not further potentiated by IL-17 (Figure 4D), suggesting that p53 is a downstream mediator of IL-17 in this experimental setting. All our data show that IL-17, by modulating cell survival, impacts mycobacterial control by macrophages.

Bottom Line: Mechanistically, we show that IL-17 inhibits p53, and impacts on the intrinsic apoptotic pathway, by increasing the Bcl2 and decreasing Bax expression, decreasing cytochrome c release from the mitochondria, and inhibiting caspase-3 activation.The same effect of IL-17 was observed in infected macrophages upon blockade of p53 nuclear translocation.These results reveal a previously unappreciated role for the IL-17/p53 axis in the regulation of mycobacteria-induced apoptosis and can have important implications in a broad spectrum of diseases where apoptosis of the infected cell is an important host defense mechanism.

View Article: PubMed Central - PubMed

Affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho , Braga , Portugal ; ICVS/3B's - PT Government Associate Laboratory, University of Minho , Braga , Portugal.

ABSTRACT
The fate of infected macrophages is a critical aspect of immunity to mycobacteria. By depriving the pathogen of its intracellular niche, apoptotic death of the infected macrophage has been shown to be an important mechanism to control bacterial growth. Here, we show that IL-17 inhibits apoptosis of Mycobacterium bovis BCG- or Mycobacterium tuberculosis-infected macrophages thus hampering their ability to control bacterial growth. Mechanistically, we show that IL-17 inhibits p53, and impacts on the intrinsic apoptotic pathway, by increasing the Bcl2 and decreasing Bax expression, decreasing cytochrome c release from the mitochondria, and inhibiting caspase-3 activation. The same effect of IL-17 was observed in infected macrophages upon blockade of p53 nuclear translocation. These results reveal a previously unappreciated role for the IL-17/p53 axis in the regulation of mycobacteria-induced apoptosis and can have important implications in a broad spectrum of diseases where apoptosis of the infected cell is an important host defense mechanism.

No MeSH data available.


Related in: MedlinePlus