Human IL-32 expression protects mice against a hypervirulent strain of Mycobacterium tuberculosis.

Silencing of interleukin-32 (IL-32) in a differentiated human promonocytic cell line impairs killing of Mycobacterium tuberculosis (MTB) but the role of IL-32 in vivo against MTB remains unknown. To study the effects of IL-32 in vivo, a transgenic mouse was generated in which the human IL-32γ gene is expressed using the surfactant protein C promoter (SPC-IL-32γTg). Wild-type and SPC-IL-32γTg mice were infected with a low-dose aerosol of a hypervirulent strain of MTB (W-Beijing HN878). At 30 and 60 d after infection, the transgenic mice had 66% and 85% fewer MTB in the lungs and 49% and 68% fewer MTB in the spleens, respectively; the transgenic mice also exhibited greater survival. Increased numbers of host-protective innate and adaptive immune cells were present in SPC-IL-32γTg mice, including tumor necrosis factor-alpha (TNFα) positive lung macrophages and dendritic cells, and IFN-gamma (IFNγ) and TNFα positive CD4(+) and CD8(+) T cells in the lungs and mediastinal lymph nodes. Alveolar macrophages from transgenic mice infected with MTB ex vivo had reduced bacterial burden and increased colocalization of green fluorescent protein-labeled MTB with lysosomes. Furthermore, mouse macrophages made to express IL-32γ but not the splice variant IL-32ß were better able to limit MTB growth than macrophages capable of producing both. The lungs of patients with tuberculosis showed increased IL-32 expression, particularly in macrophages of granulomas and airway epithelial cells but also B cells and T cells. We conclude that IL-32γ enhances host immunity to MTB.

A successful model for longitudinal community-engaged health research: the 2040 Partners for Health Student Program.

Introduction: Community-based participatory research [CBPR] is an emerging approach to collaborative research aimed at creating locally effective and sustainable interventions. The 2040 Partners for Health student program was developed as a unique model of longitudinal CBPR. Analysis of this program and its components illuminates both the challenges and the opportunities inherent in community engagement. Methods: The program rests on a foundation of a community-based, non-profit organization and a supportive academic university centre. Inter-professional health students and community members of underserved populations work together on different health projects by employing an adapted CBPR methodology. Three successful examples of sustainable CBPR projects are briefly described. Results: The three projects are presented as primary outcomes resulting from this model. Benefits and challenges of the model as an approach to community-engaged research are discussed as well as secondary benefits of student participation. Conclusion: The 2040 Partners for Health student program represents a successful model of CBPR, illuminating common challenges and reiterating the profound value of community-engaged research.

Curcumin enhances human macrophage control of Mycobacterium tuberculosis infection.

BACKGROUND AND OBJECTIVE: With the worldwide emergence of highly drug-resistant tuberculosis (TB), novel agents that have direct antimycobacterial effects or that enhance host immunity are urgently needed. Curcumin is a polyphenol responsible for the bright yellow-orange colour of turmeric, a spice derived from the root of the perennial herb Curcuma longa. Curcumin is a potent inducer of apoptosis-an effector mechanism used by macrophages to kill intracellular Mycobacterium tuberculosis (MTB). METHODS: An in vitro human macrophage infection model was used to determine the effects of curcumin on MTB survival. RESULTS: We found that curcumin enhanced the clearance of MTB in differentiated THP-1 human monocytes and in primary human alveolar macrophages. We also found that curcumin was an inducer of caspase-3-dependent apoptosis and autophagy. Curcumin mediated these anti-MTB cellular functions, in part, via inhibition of nuclear factor-kappa B (NFκB) activation. CONCLUSION: Curcumin protects against MTB infection in human macrophages. The host-protective role of curcumin against MTB in macrophages needs confirmation in an animal model; if validated, the immunomodulatory anti-TB effects of curcumin would be less prone to drug resistance development.

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 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.

Patients with nontuberculous mycobacterial lung disease exhibit unique body and immune phenotypes.

RATIONALE: Among patients with nontuberculous mycobacterial lung disease is a subset of previously healthy women with a slender body morphotype, often with scoliosis and/or pectus excavatum. We hypothesize that unidentified factors predispose these individuals to pulmonary nontuberculous mycobacterial disease. OBJECTIVES: To compare body morphotype, serum adipokine levels, and whole-blood cytokine responses of patients with pulmonary nontuberculous mycobacteria (pNTM) with contemporary control subjects who are well matched demographically. METHODS: We enrolled 103 patients with pNTM and 101 uninfected control subjects of similar demographics. Body mass index and body fat were quantified. All patients with pNTM and a subset of control subjects were evaluated for scoliosis and pectus excavatum. Serum leptin and adiponectin were measured. Specific cytokines important to host-defense against mycobacteria were measured in whole blood before and after stimulation. MEASUREMENTS AND MAIN RESULTS: Patients with pNTM and control subjects were well matched for age, gender, and race. Patients with pNTM had significantly lower body mass index and body fat and were significantly taller than control subjects. Scoliosis and pectus excavatum were significantly more prevalent in patients with pNTM. The normal relationships between the adipokines and body fat were lost in the patients with pNTM, a novel finding. IFN-γ and IL-10 levels were significantly suppressed in stimulated whole blood of patients with pNTM. CONCLUSIONS: This is the first study to comprehensively compare body morphotype, adipokines, and cytokine responses between patients with NTM lung disease and demographically matched controls. Our findings suggest a novel, predisposing immunophenotype that should be mechanistically defined.

Cooccurrence of free-living amoebae and nontuberculous Mycobacteria in hospital water networks, and preferential growth of Mycobacterium avium in Acanthamoeba lenticulata.

The incidence of lung and other diseases due to nontuberculous mycobacteria (NTM) is increasing. NTM sources include potable water, especially in households where NTM populate pipes, taps, and showerheads. NTM share habitats with free-living amoebae (FLA) and can grow in FLA as parasites or as endosymbionts. FLA containing NTM may form cysts that protect mycobacteria from disinfectants and antibiotics. We first assessed the presence of FLA and NTM in water and biofilm samples collected from a hospital, confirming the high prevalence of NTM and FLA in potable water systems, particularly in biofilms. Acanthamoeba spp. (genotype T4) were mainly recovered (8/17), followed by Hartmannella vermiformis (7/17) as well as one isolate closely related to the genus Flamella and one isolate only distantly related to previously described species. Concerning mycobacteria, Mycobacterium gordonae was the most frequently found isolate (9/17), followed by Mycobacterium peregrinum (4/17), Mycobacterium chelonae (2/17), Mycobacterium mucogenicum (1/17), and Mycobacterium avium (1/17). The propensity of Mycobacterium avium hospital isolate H87 and M. avium collection strain 104 to survive and replicate within various FLA was also evaluated, demonstrating survival of both strains in all amoebal species tested but high replication rates only in Acanthamoeba lenticulata. As A. lenticulata was frequently recovered from environmental samples, including drinking water samples, these results could have important consequences for the ecology of M. avium in drinking water networks and the epidemiology of disease due to this species.

Patients with non-tuberculous mycobacterial lung disease have elevated transforming growth factor-beta following ex vivo stimulation of blood with live Mycobacterium intracellulare.

We previously found that a subset of patients with pulmonary non-tuberculous mycobacterial (pNTM) disease were taller, leaner, and had a higher prevalence of pectus excavatum and scoliosis than uninfected controls. Additionally, whole blood of pNTM patients stimulated ex vivo with live Mycobacterium intracellulare produced significantly less interferon-gamma (IFNγ) compared to that of uninfected controls. Since IFNγ production can be suppressed by transforming growth factor-beta (TGFß), an immunosuppressive cytokine, we measured basal and M. intracellulare-stimulated blood levels of TGFß in a group of 20 pNTM patients and 20 uninfected controls. In contrast to the IFNγ findings, we found that stimulated blood from pNTM patients produced significantly higher levels of TGFß compared to controls. Since pNTM patients frequently possess body features that overlap with Marfan syndrome (MFS), and increased TGFß expression is important in the pathogenesis of MFS, we posit that a yet-to-be-identified syndrome related to MFS predisposes certain individuals to develop pNTM disease.

IL-32 expression in the airway epithelial cells of patients with Mycobacterium avium complex lung disease.

Lung disease due to Mycobacterium avium complex (MAC) organisms is increasing. A greater understanding of the host immune response to MAC organisms will provide a foundation to develop novel therapies for these recalcitrant infections. IL-32 is a newly described pro-inflammatory cytokine that enhances host immunity against various microbial pathogens. Cytokines that induce IL-32 such as interferon-gamma, IL-18, IL-12 and tumor necrosis factor-alpha are of considerable importance to mycobacterial immunity. We performed immunohistochemistry and morphometric analysis to quantify IL-32 expression in the lungs of 11 patients with MAC lung disease and 10 controls with normal lung tissues. After normalizing for basement membrane length, there was a profound increase in IL-32 expression in the airway epithelial cells of the MAC-infected lungs compared with controls. Following normalization for alveolar surface area, there was a trend toward increased IL-32 expression in type II alveolar cells and alveolar macrophages in the lungs of MAC patients. Human airway epithelial cells (BEAS-2B) infected with M. avium produced IL-32 by a nuclear factor-kappa B-dependent mechanism. In both BEAS-2B cells and human monocyte-derived macrophages, exogenous IL-32γ significantly reduced the growth of intracellular M. avium. This finding was corroborated by an increase in the number of intracellular M. avium recovered from THP-1 monocytes silenced for endogenous IL-32 expression. The anti-mycobacterial effect of IL-32 may be due, in part, to increased apoptosis of infected cells. These findings indicate that IL-32 facilitates host defense against MAC organisms but may also contribute to the airway inflammation associated with MAC pulmonary disease.

Cigarette smoke increases susceptibility to tuberculosis--evidence from in vivo and in vitro models.

BACKGROUND: Cigarette smoke (CS) exposure is an epidemiological risk factor for tuberculosis, although the biological basis has not been elucidated. METHODS: We exposed C57BL/6 mice to CS for 14 weeks and examined their ability to control an aerosol infection of Mycobacterium tuberculosis Erdman. RESULTS: CS-exposed mice had more M. tuberculosis isolated from the lungs and spleens after 14 and 30 d, compared with control mice. The CS-exposed mice had worse lung lesions and less lung and splenic macrophages and dendritic cells (DCs) producing interleukin12 and tumor necrosis factor α (TNF-α). There were significantly more interleukin 10-producing macrophages and DCs in the spleens of infected CS-exposed mice than in non-CS-exposed controls. CS-exposed mice also showed a diminished influx of interferon γ-producing and TNF-α-producing CD4(+) and CD8(+) effector and memory T cells into the lungs and spleens. There was a trend toward an increased number of viable intracellular M. tuberculosis in macrophages isolated from humans who smoke compared with nonsmokers. THP-1 human macrophages and primary human alveolar macrophages exposed to CS extract, nicotine, or acrolein showed an increased burden of intracellular M. tuberculosis. CONCLUSION: CS suppresses the protective immune response to M. tuberculosis in mice, human THP-1 cells, and primary human alveolar macrophages.

Pathogenic nontuberculous mycobacteria resist and inactivate cathelicidin: implication of a novel role for polar mycobacterial lipids.

Nontuberculous mycobacteria (NTM) are a large group of environmental organisms with worldwide distribution, but only a relatively few are known to be pathogenic. Chronic, debilitating lung disease is the most common manifestation of NTM infection, which is often refractory to treatment. The incidence and prevalence of NTM lung disease are increasing in the United States and in many parts of the world. Hence, a more complete understanding of NTM pathogenesis will provide the foundation to develop innovative approaches to treat this recalcitrant disease. Herein, we demonstrate that several species of NTM show broad resistance to the antimicrobial peptide, cathelicidin (LL-37). Resistance to LL-37 was not significantly different between M. avium that contain serovar-specific glycopeptidolipid (GPL, M. aviumssGPL) and M. avium that do not (M. aviumΔssGPL). Similarly, M. abscessus containing non-specific GPL (M. abscessusnsGPL(+)) or lacking nsGPL (M. abscessusnsGPL(-)) remained equally resistant to LL-37. These findings would support the notion that GPL are not the components responsible for NTM resistance to LL-37. Unexpectedly, the growth of M. abscessusnsGPL(-) increased with LL-37 or scrambled LL-37 peptide in a dose-dependent fashion. We also discovered that LL-37 exposed to NTM had reduced antimicrobial activity, and initial work indicates that this is likely due to inactivation of LL-37 by lipid component(s) of the NTM cell envelope. We conclude that pathogenic NTM resist and inactivate LL-37. The mechanism by which NTM circumvent the antimicrobial activity of LL-37 remains to be determined.

A surface with a biomimetic micropattern reduces colonization of Mycobacterium abscessus.

Nontuberculous mycobacteria (NTM) are ubiquitous organisms found in soil, water, and biofilms. Engineered surface topography has been proposed as a method to reduce microbial biofilm formation. The Sharklet(®) micropattern silicone surface has been shown to reduce biofilm formation of pyogenic bacteria. We hypothesized that this micropattern surface will also reduce colonization by Mycobacterium abscessus, a human pathogen. Smooth and micropattern silicone samples were incubated with 1 × 10(6) M. abscessus mL(-1) for 2 and 4 days. After processing to optimize recovery of adhered mycobacteria, there was a 75% and 50% reduction in the number of viable M. abscessus recovered from the micropattern surfaces compared to the smooth surfaces at 2 and 4 days after inoculation, respectively. Ziehl-Neelsen staining after measures to remove the adherent microorganisms revealed fewer residual M. abscessus on the micropattern samples as compared to smooth samples, validating the quantitative culture results. Microscopic observation of 2, 4, and 8 day M. abscessus cultures on micropattern samples showed that the organisms preferentially colonized within the channels between the rectangular features. In summary, a micropattern surface reduces the colonization of a pathogenic NTM. It remains to be seen whether this micropattern can reduce infections in humans.

Inhibition of nuclear factor-kappa B activation decreases survival of Mycobacterium tuberculosis in human macrophages.

Nuclear factor-kappa B (NFκB) is a ubiquitous transcription factor that mediates pro-inflammatory responses required for host control of many microbial pathogens; on the other hand, NFκB has been implicated in the pathogenesis of other inflammatory and infectious diseases. Mice with genetic disruption of the p50 subunit of NFκB are more likely to succumb to Mycobacterium tuberculosis (MTB). However, the role of NFκB in host defense in humans is not fully understood. We sought to examine the role of NFκB activation in the immune response of human macrophages to MTB. Targeted pharmacologic inhibition of NFκB activation using BAY 11-7082 (BAY, an inhibitor of IκBα kinase) or an adenovirus construct with a dominant-negative IκBα significantly decreased the number of viable intracellular mycobacteria recovered from THP-1 macrophages four and eight days after infection. The results with BAY were confirmed in primary human monocyte-derived macrophages and alveolar macrophages. NFκB inhibition was associated with increased macrophage apoptosis and autophagy, which are well-established killing mechanisms of intracellular MTB. Inhibition of the executioner protease caspase-3 or of the autophagic pathway significantly abrogated the effects of BAY. We conclude that NFκB inhibition decreases viability of intracellular MTB in human macrophages via induction of apoptosis and autophagy.

Mycobacterium tuberculosis increases IP-10 and MIG protein despite inhibition of IP-10 and MIG transcription.

Mycobacterium tuberculosis (MTB) has evolved methods to evade interferon-gamma (IFNγ) mediated protection. We sought to determine the effect of MTB infection on expression of IFNγ-inducible Protein 10 (IP-10) and Monokine Induced by IFNγ (MIG), two chemokines involved in host defense. MTB infection of THP-1 cells inhibited the transcription of IP-10 and MIG. A key mechanism for the inhibition is the disruption of binding of Signal Transduction and Activation of Transcription 1-alpha (STAT1α) to its cis-regulatory element, present in the 5'-flanking region of both IP-10 and MIG promoters. Use of inhibitors specific to the nuclear factor-kappa B (NFκB) and p38 mitogen-activated protein kinase (p38(mapk)) implicate these two signaling pathways in mediating the effect of MTB on the inhibition of IFNγ-induced IP-10 and MIG mRNA expression. Interestingly, despite transcriptional inhibition, there was an unexpected increase in IP-10 and MIG protein production after combined IFNγ and MTB stimulation. MTB also inhibited IFNγ induction of MIG mRNA but augmented MIG protein in primary human monocyte-derived macrophages. The synergy between MTB and IFNγ in the induction of IP-10 and MIG protein appears to involve novel post-transcriptional events that incorporates non-canonical functions of NFκB and p38(mapk).

An oxidative environment promotes growth of Mycobacterium abscessus.

Mycobacterium abscessus infections, particularly those causing chronic lung diseases, are becoming more prevalent worldwide. M. abscessus infections are difficult to treat because of antibiotic resistance. Thus, new treatment options are urgently needed. M. abscessus is an intracellular pathogen that primarily infects macrophages and fibroblasts. Because this bacterium has only recently been identified as a separate species, very little is known about M. abscessus-host interactions and how M. abscessus growth is regulated. Oxidative stress has long been shown to inhibit the growth of bacterial organisms. However, some intracellular bacteria, such as Mycobacterium tuberculosis, grow well in oxidizing environments. In this study, we show that M. abscessus infection causes the host cell environment to become more oxidizing. Furthermore, we show that a more oxidizing environment leads to enhanced growth of M. abscessus inside macrophages. In the presence of antioxidants, MnTE-2-PyP (chemical name: manganese(II) meso-tetrakis-(N-methylpyridinium-2-yl) porphyrin) or N-acetyl-l-cysteine, M. abscessus growth is inhibited. These results lead us to postulate that antioxidants may aid in the treatment of M. abscessus infections.

Chronic hyperoxia alters the early and late phases of the hypoxic ventilatory response in neonatal rats.

Chronic hyperoxia during the first 1-4 postnatal weeks attenuates the hypoxic ventilatory response (HVR) subsequently measured in adult rats. Rather than focusing on this long-lasting plasticity, the present study considered the influence of hyperoxia on respiratory control during the neonatal period. Sprague-Dawley rats were born and raised in 60% O2 until studied at postnatal ages (P) of 4, 6-7, or 13-14 days. Ventilation and metabolism were measured in normoxia (21% O2) and acute hypoxia (12% O2) using head-body plethysmography and respirometry, respectively. Compared with age-matched rats raised in room air, the major findings were 1) diminished pulmonary ventilation and metabolic O2 consumption in normoxia at P4 and P6-7; 2) decreased breathing stability during normoxia; 3) attenuation of the early phase of the HVR at P6-7 and P13-14; and 4) a sustained increase in ventilation during hypoxia (vs. the normal biphasic HVR) at all ages studied. Attenuation of the early HVR likely reflects progressive impairment of peripheral arterial chemoreceptors while expression of a sustained HVR in neonates before P7 suggests that hyperoxia also induces plasticity within the central nervous system. Together, these results suggest a complex interaction between inhibitory and excitatory effects of hyperoxia on the developing respiratory control system.