Limits...
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

IL-17 inhibits the upregulation of p53 observed during infection of BMDM with M. bovis BCG. BMDM were infected with M. bovis BCG and treated (+) or not (−) with IL-17. (A) At the indicated time points, the expression of p53 was assessed by quantitative real-time PCR and normalized against HPRT. The fold increase of p53 mRNA expression over non-infected (NI) control was calculated. (B) Two days post-infection p53 levels were assessed by immunofluorescence and the fold increase of p53 mean intensity of cells over NI control calculated using ROI Manager application of the ImageJ program. The CFU controls for the represented experiments are plotted in Figure 1A. Representative images used for the calculations are in Figure S1 in Supplementary Material. Represented are the mean ± SE of three independent experiments each of them performed for triplicate conditions. Significance determined by Student’s t test (***p < 0.001).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4588696&req=5

Figure 2: IL-17 inhibits the upregulation of p53 observed during infection of BMDM with M. bovis BCG. BMDM were infected with M. bovis BCG and treated (+) or not (−) with IL-17. (A) At the indicated time points, the expression of p53 was assessed by quantitative real-time PCR and normalized against HPRT. The fold increase of p53 mRNA expression over non-infected (NI) control was calculated. (B) Two days post-infection p53 levels were assessed by immunofluorescence and the fold increase of p53 mean intensity of cells over NI control calculated using ROI Manager application of the ImageJ program. The CFU controls for the represented experiments are plotted in Figure 1A. Representative images used for the calculations are in Figure S1 in Supplementary Material. Represented are the mean ± SE of three independent experiments each of them performed for triplicate conditions. Significance determined by Student’s t test (***p < 0.001).

Mentions: Activation of the apoptotic pathway is thought to be a host defensive mechanism against mycobacterial pathogens (26). IL-17 has been shown to modulate apoptosis in viral infection (13) and in cancer (17, 18), but its role in the context of mycobacterial infection inducing apoptosis has not been addressed yet. Since IL-17 has been shown to down-regulate the activity of the apoptosis master regulator p53 (27, 28), we investigated whether IL-17 is able to modulate p53 in mycobacterially infected macrophages. While an upregulation of p53 transcription upon infection with M. bovis BCG was observed 48 h post-infection, this was not affected by the presence of IL-17 (Figure 2A). In contrast, the increase in p53 protein levels as measured by immunofluorescence, observed as early as 2 days post-M. bovis BCG infection, was abrogated by IL-17 (Figure 2B; Figure S1 in Supplementary Material). These data show that IL-17 down-regulates p53 at the protein level, suggesting that it may interfere with apoptosis of infected cells. Further, this interference may be the pathway by which IL-17 impacts the bacterial growth control.


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)

IL-17 inhibits the upregulation of p53 observed during infection of BMDM with M. bovis BCG. BMDM were infected with M. bovis BCG and treated (+) or not (−) with IL-17. (A) At the indicated time points, the expression of p53 was assessed by quantitative real-time PCR and normalized against HPRT. The fold increase of p53 mRNA expression over non-infected (NI) control was calculated. (B) Two days post-infection p53 levels were assessed by immunofluorescence and the fold increase of p53 mean intensity of cells over NI control calculated using ROI Manager application of the ImageJ program. The CFU controls for the represented experiments are plotted in Figure 1A. Representative images used for the calculations are in Figure S1 in Supplementary Material. Represented are the mean ± SE of three independent experiments each of them performed for triplicate conditions. Significance determined by Student’s t test (***p < 0.001).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588696&req=5

Figure 2: IL-17 inhibits the upregulation of p53 observed during infection of BMDM with M. bovis BCG. BMDM were infected with M. bovis BCG and treated (+) or not (−) with IL-17. (A) At the indicated time points, the expression of p53 was assessed by quantitative real-time PCR and normalized against HPRT. The fold increase of p53 mRNA expression over non-infected (NI) control was calculated. (B) Two days post-infection p53 levels were assessed by immunofluorescence and the fold increase of p53 mean intensity of cells over NI control calculated using ROI Manager application of the ImageJ program. The CFU controls for the represented experiments are plotted in Figure 1A. Representative images used for the calculations are in Figure S1 in Supplementary Material. Represented are the mean ± SE of three independent experiments each of them performed for triplicate conditions. Significance determined by Student’s t test (***p < 0.001).
Mentions: Activation of the apoptotic pathway is thought to be a host defensive mechanism against mycobacterial pathogens (26). IL-17 has been shown to modulate apoptosis in viral infection (13) and in cancer (17, 18), but its role in the context of mycobacterial infection inducing apoptosis has not been addressed yet. Since IL-17 has been shown to down-regulate the activity of the apoptosis master regulator p53 (27, 28), we investigated whether IL-17 is able to modulate p53 in mycobacterially infected macrophages. While an upregulation of p53 transcription upon infection with M. bovis BCG was observed 48 h post-infection, this was not affected by the presence of IL-17 (Figure 2A). In contrast, the increase in p53 protein levels as measured by immunofluorescence, observed as early as 2 days post-M. bovis BCG infection, was abrogated by IL-17 (Figure 2B; Figure S1 in Supplementary Material). These data show that IL-17 down-regulates p53 at the protein level, suggesting that it may interfere with apoptosis of infected cells. Further, this interference may be the pathway by which IL-17 impacts the bacterial growth control.

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