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Caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of Mycobacterium tuberculosis infection in THP-1 cells

BACKGROUND: Macrophages are the primary effector cells responsible for killing Mycobacterium tuberculosis (MTB) through various mechanisms, including apoptosis. However, MTB can evade host immunity to create a favorable environment for intracellular replication. MTB-infected human macrophages produc...

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Autores principales: Bai, Xiyuan, Kinney, William H, Su, Wen-Lin, Bai, An, Ovrutsky, Alida R, Honda, Jennifer R, Netea, Mihai G, Henao-Tamayo, Marcela, Ordway, Diane J, Dinarello, Charles A, Chan, Edward D
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4349755/
https://www.ncbi.nlm.nih.gov/pubmed/25887904
http://dx.doi.org/10.1186/s12866-015-0366-z
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author Bai, Xiyuan
Kinney, William H
Su, Wen-Lin
Bai, An
Ovrutsky, Alida R
Honda, Jennifer R
Netea, Mihai G
Henao-Tamayo, Marcela
Ordway, Diane J
Dinarello, Charles A
Chan, Edward D
author_facet Bai, Xiyuan
Kinney, William H
Su, Wen-Lin
Bai, An
Ovrutsky, Alida R
Honda, Jennifer R
Netea, Mihai G
Henao-Tamayo, Marcela
Ordway, Diane J
Dinarello, Charles A
Chan, Edward D
author_sort Bai, Xiyuan
collection PubMed
description BACKGROUND: Macrophages are the primary effector cells responsible for killing Mycobacterium tuberculosis (MTB) through various mechanisms, including apoptosis. However, MTB can evade host immunity to create a favorable environment for intracellular replication. MTB-infected human macrophages produce interleukin-32 (IL-32). IL-32 is a pro-inflammatory cytokine and has several isoforms. We previously found that IL-32γ reduced the burden of MTB in human macrophages, in part, through the induction of caspase-3-dependent apoptosis. However, based on our previous studies, we hypothesized that caspase-3-independent death pathways may also mediate IL-32 control of MTB infection. Herein, we assessed the potential roles of cathepsin-mediated apoptosis, caspase-1-mediated pyroptosis, and apoptosis-inducing factor (AIF) in mediating IL-32γ control of MTB infection in THP-1 cells. RESULTS: Differentiated human THP-1 macrophages were infected with MTB H37Rv alone or in the presence of specific inhibitors to caspase-1, cathepsin B/D, or cathepsin L for up to four days, after which TUNEL-positive cells were quantified; in addition, MTB was quantified by culture as well as by the percentage of THP-1 cells that were infected with green fluorescent protein (GFP)-labeled MTB as determined by microscopy. AIF expression was inhibited using siRNA technology. Inhibition of cathepsin B/D, cathepsin L, or caspase-1 activity significantly abrogated the IL-32γ-mediated reduction in the number of intracellular MTB and of the percentage of GFP-MTB-infected macrophages. Furthermore, inhibition of caspase-1, cathepsin B/D, or cathepsin L in the absence of exogenous IL-32γ resulted in a trend toward an increased proportion of MTB-infected THP-1 cells. Inhibition of AIF activity in the absence of exogenous IL-32γ also increased intracellular burden of MTB. However, since IL-32γ did not induce AIF and because the relative increases in MTB with inhibition of AIF were similar in the presence or absence of IL-32γ, our results indicate that AIF does not mediate the host-protective effect of IL-32γ against MTB. CONCLUSIONS: The anti-MTB effects of IL-32γ are mediated through classical caspase-3-dependent apoptosis as well as caspase-3-independent apoptosis.
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spelling pubmed-43497552015-03-06 Caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of Mycobacterium tuberculosis infection in THP-1 cells Bai, Xiyuan Kinney, William H Su, Wen-Lin Bai, An Ovrutsky, Alida R Honda, Jennifer R Netea, Mihai G Henao-Tamayo, Marcela Ordway, Diane J Dinarello, Charles A Chan, Edward D BMC Microbiol Research Article BACKGROUND: Macrophages are the primary effector cells responsible for killing Mycobacterium tuberculosis (MTB) through various mechanisms, including apoptosis. However, MTB can evade host immunity to create a favorable environment for intracellular replication. MTB-infected human macrophages produce interleukin-32 (IL-32). IL-32 is a pro-inflammatory cytokine and has several isoforms. We previously found that IL-32γ reduced the burden of MTB in human macrophages, in part, through the induction of caspase-3-dependent apoptosis. However, based on our previous studies, we hypothesized that caspase-3-independent death pathways may also mediate IL-32 control of MTB infection. Herein, we assessed the potential roles of cathepsin-mediated apoptosis, caspase-1-mediated pyroptosis, and apoptosis-inducing factor (AIF) in mediating IL-32γ control of MTB infection in THP-1 cells. RESULTS: Differentiated human THP-1 macrophages were infected with MTB H37Rv alone or in the presence of specific inhibitors to caspase-1, cathepsin B/D, or cathepsin L for up to four days, after which TUNEL-positive cells were quantified; in addition, MTB was quantified by culture as well as by the percentage of THP-1 cells that were infected with green fluorescent protein (GFP)-labeled MTB as determined by microscopy. AIF expression was inhibited using siRNA technology. Inhibition of cathepsin B/D, cathepsin L, or caspase-1 activity significantly abrogated the IL-32γ-mediated reduction in the number of intracellular MTB and of the percentage of GFP-MTB-infected macrophages. Furthermore, inhibition of caspase-1, cathepsin B/D, or cathepsin L in the absence of exogenous IL-32γ resulted in a trend toward an increased proportion of MTB-infected THP-1 cells. Inhibition of AIF activity in the absence of exogenous IL-32γ also increased intracellular burden of MTB. However, since IL-32γ did not induce AIF and because the relative increases in MTB with inhibition of AIF were similar in the presence or absence of IL-32γ, our results indicate that AIF does not mediate the host-protective effect of IL-32γ against MTB. CONCLUSIONS: The anti-MTB effects of IL-32γ are mediated through classical caspase-3-dependent apoptosis as well as caspase-3-independent apoptosis. BioMed Central 2015-02-21 /pmc/articles/PMC4349755/ /pubmed/25887904 http://dx.doi.org/10.1186/s12866-015-0366-z Text en © Bai et al.; licensee BioMed Central. 2015 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research Article
Bai, Xiyuan
Kinney, William H
Su, Wen-Lin
Bai, An
Ovrutsky, Alida R
Honda, Jennifer R
Netea, Mihai G
Henao-Tamayo, Marcela
Ordway, Diane J
Dinarello, Charles A
Chan, Edward D
Caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of Mycobacterium tuberculosis infection in THP-1 cells
title Caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of Mycobacterium tuberculosis infection in THP-1 cells
title_full Caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of Mycobacterium tuberculosis infection in THP-1 cells
title_fullStr Caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of Mycobacterium tuberculosis infection in THP-1 cells
title_full_unstemmed Caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of Mycobacterium tuberculosis infection in THP-1 cells
title_short Caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of Mycobacterium tuberculosis infection in THP-1 cells
title_sort caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of mycobacterium tuberculosis infection in thp-1 cells
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4349755/
https://www.ncbi.nlm.nih.gov/pubmed/25887904
http://dx.doi.org/10.1186/s12866-015-0366-z
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