Induction of IL-1 beta, IL-6, TNF-alpha, GM-CSF and G-CSF in human macrophages by smooth transparent and smooth opaque colonial variants of Mycobacterium avium

Sex, ancestry, senescence, and aging (SAnSA) are stark drivers of nontuberculous mycobacterial pulmonary disease

Nontuberculous mycobacterial (NTM) pulmonary disease (PD) disproportionately affects otherwise healthy, older, Caucasian females. The reasons behind this are likely multifactorial involving several conspiring factors. A variety of factors are thought to contribute to increased susceptibility to NTM in the older adult including exposure to various environmental conditions and contaminants across the lifespan, genetic risk factors, hormonal changes, and immunodeficiency. Independent of sex and ancestry, respiratory muscle atrophy intensifies with age and an aging immune system can show functional decline of macrophages, poor lung migration and homing of dendritic cells, promotion of aberrant pro-inflammatory responses, acceleration of inflammation related to aging, and increased immunosenescence. The purpose of this review is to synthesize the current body of knowledge regarding the roles of sex, ancestry, senescence, and aging (SAnSA) in NTM acquisition and the possible mechanisms involved in NTM PD, highlighting age-related respiratory and immune system changes. We also summarize molecular tools and biomarkers of these fields and contextualize these into the study of NTM PD. Finally, we discuss the relevance of biomarkers described for senescence and aging and senolytic therapies as potentially new adjunctive strategies to reduce the burden of NTM PD.

Identification and bioactivity of a granulocyte colony-stimulating factor a homologue from large yellow croaker (Larimichthys crocea)

Granulocyte colony-stimulating factor (GCSF) is a growth factor that drives the proliferation and differentiation of granulocytes and monocytes/macrophages. Currently, two copies of GCSF, named GCSFa and GCSFb, have been identified in teleost fish, but data on the functions and signal pathways of these fish GCSFs are still limited. In the present study, a GCSFa homologue (LcGCSFa) was identified from large yellow croaker (Larimichthys crocea). The open reading frame (ORF) of LcGCSFa is 636 bp long and encodes a protein of 211 amino acids (aa), with a 19-aa signal peptide and a typical IL-6 domain, conserved in fish GCSF sequences. The phylogenetic analysis showed that LcGCSFa clustered with other fish GCSFa homologues. LcGCSFa was constitutively expressed in all tissues tested and significantly up-regulated in head kidney and spleen by Vibrio alginolyticus or poly(I:C). LcGCSFa transcripts were also detected in primary head kidney leucocytes (PKL), primary head kidney macrophages (PKM), and primary head kidney granulocytes (PKG), and significantly up-regulated in PKL and PKG by LPS or poly(I:C). These data indicated that LcGCSFa may be involved in the immune responses induced by bacterium and virus. The recombinant LcGCSFa protein (rLcGCSFa) produced in Pichia pastoris promoted the proliferation of PKL both in vivo and in vitro. Furthermore, rLcGCSFa significantly increased both transcription and phosphorylation levels of the signal transducers and activators of transcription (STAT) proteins (LcSTAT3 and LcSTAT5) in PKL, which are required for the GCSF-dependent proliferation. These results showed that LcGCSFa may promote the proliferation of PKL via the activation of LcSTAT3 and LcSTAT5, suggesting a conserved role across vertebrate GCSFs.

Genetic Variation/Evolution and Differential Host Responses Resulting from In-Patient Adaptation of Mycobacterium avium

Members of the Mycobacterium avium complex (MAC) are characterized as nontuberculosis mycobacteria and are pathogenic mainly in immunocompromised individuals. MAC strains show a wide genetic variability, and there is growing evidence suggesting that genetic differences may contribute to a varied immune response that may impact the infection outcome.

Members of the Mycobacterium avium complex (MAC) are characterized as nontuberculosis mycobacteria and are pathogenic mainly in immunocompromised individuals. MAC strains show a wide genetic variability, and there is growing evidence suggesting that genetic differences may contribute to a varied immune response that may impact the infection outcome. The current study aimed to characterize the genomic changes within M.avium isolates collected from single patients over time and test the host immune responses to these clinical isolates. Pulsed-field gel electrophoresis and whole-genome sequencing were performed on 40 MAC isolates isolated from 15 patients at the Department of Medical Microbiology at St. Olavs Hospital in Trondheim, Norway. Isolates from patients (patients 4, 9, and 13) for whom more than two isolates were available were selected for further analysis. These isolates exhibited extensive sequence variation in the form of single-nucleotide polymorphisms (SNPs), suggesting that M. avium accumulates mutations at higher rates during persistent infections than other mycobacteria. Infection of murine macrophages and mice with sequential isolates from patients showed a tendency toward increased persistence and the downregulation of inflammatory cytokines by host-adapted M. avium strains. The study revealed the rapid genetic evolution of M. avium in chronically infected patients, accompanied by changes in the virulence properties of the sequential mycobacterial isolates.

Development and validation of a prognostic scoring model for Mycobacterium avium complex lung disease: an observational cohort study

Background

Patients with Mycobacterium avium complex (MAC) lung disease (LD) have a heterogeneous prognosis. This study aimed to develop and validate a prognostic scoring model for these patients using independent risk factors for survival.

Methods

We retrospectively analyzed the data of patients with MAC-LD from two hospitals (cohort 1, n = 368; cohort 2, n = 118). Cohort 1 was evaluated using a multivariate Cox proportional hazards model to identify independent risk factors for overall survival (OS). A prognostic scoring model composed of these factors was developed, and cohort 1 was stratified into three groups according to risk using the log-rank test. Finally, the prognostic scoring model was validated using the data of cohort 2.

Results

Seven independent risk factors for OS were selected from cohort 1, including the male sex, age ≥ 70 years, the presence of a malignancy, body mass index <18.5 kg/m², lymphocyte count <1000 cells/μL, serum albumin levels <3.5 g/dL, and fibrocavitary disease. The areas under the receiver operating characteristic curves for the prognostic scoring model were 0.84 [95% confidence interval (CI), 0.80 − 0.89] for cohort 1 and 0.84 (95% CI, 0.75 − 0.92) for cohort 2. The 5-year OS rates of patients stratified into low-risk, intermediate-risk, and high-risk groups were 97.6, 76.6, and 30.8%, respectively (P < 0.001), in cohort 1, and 97.2, 82.3, and 45.4%, respectively (P < 0.001), in cohort 2.

Conclusions

This study is the first to develop and validate a prognostic scoring model for patients with MAC-LD. This model may prove useful in clinical settings and practical in estimating the prognosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2544-0) contains supplementary material, which is available to authorized users.

The rLrp of Mycobacterium tuberculosis inhibits proinflammatory cytokine production and downregulates APC function in mouse macrophages via a TLR2-mediated PI3K/Akt pathway activation-dependent mechanism

We demonstrate that Mycobacterium tuberculosis recombinant leucine-responsive regulatory protein (rLrp) inhibits lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF-α), interleukin-6, and interleukin-12 production and blocks the nuclear translocation of subunits of the nuclear-receptor transcription factor NF-κB (Nuclear factor-kappa B). Moreover, rLrp attenuated LPS-induced DNA binding and NF-κB transcriptional activity, which was accompanied by the degradation of inhibitory IκBα and a consequent decrease in the nuclear translocation of the NF-κB p65 subunit. RLrp interfered with the LPS-induced clustering of TNF receptor-associated factor 6 and with interleukin-1 receptor-associated kinase 1 binding to TAK1. Furthermore, rLrp did not attenuate proinflammatory cytokines or the expression of CD86 and major histocompatibility complex class-II induced by interferon-gamma in the macrophages of Toll-like receptor 2 deletion (TLR2^-/-) mice and in protein kinase b (Akt)-depleted mouse cells, indicating that the inhibitory effects of rLrp were dependent on TLR2-mediated activation of the phosphatidylinositol 3-OH kinase (PI3K)/Akt pathway. RLrp could also activate the PI3K/Akt pathway by stimulating the rapid phosphorylation of PI3K, Akt, and glycogen synthase kinase 3 beta in macrophages. In addition, 19 amino acid residues in the N-terminus of rLrp were determined to be important and required for the inhibitory effects mediated by TLR2. The inhibitory function of these 19 amino acids of rLrp raises the possibility that mimetic inhibitory peptides could be used to restrict innate immune responses in situations in which prolonged TLR signaling has deleterious effects. Our study offers new insight into the inhibitory mechanisms by which the TLR2-mediated PI3K/Akt pathway ensures the transient expression of potent inflammatory mediators.

Association between pulmonary mycobacterium avium complex infection and lung cancer

INTRODUCTION

Patients with lung cancer are sometimes found to have respiratory cultures growing Mycobacterium avium complex (MAC). This study describes the clinical, pathologic, and radiographic -characteristics of individuals who harbor concomitant lung cancer and MAC.

METHODS

Retrospective analysis of patients with positive respiratory cultures for MAC (370 men, 475 women) and with newly diagnosed lung cancer (792 men, 840 women) from 1995 to 2010.

RESULTS

Of the patients with respiratory cultures growing MAC, 8.6% of men and 6.3% of women had lung cancer. Twenty-five percent of patients with lung cancer and 3% with nonbronchiectatic benign lung disease grew MAC from their respiratory cultures. Significantly fewer women with both MAC and lung cancer were smokers than the control group of women with lung cancer and negative MAC cultures (68% versus 89%, p < 0.01). Squamous cell carcinoma occurred in 40% of women in the MAC/lung cancer group versus 28% of women in the lung cancer control group. Peripherally located squamous cell carcinomas were found in 71% of the MAC/lung cancer group versus 40% of the lung cancer control group (p = 0.01)

CONCLUSIONS

The percentage of smokers among women with both MAC and lung cancer was lower than among the lung cancer control group who did not grow MAC. The presence of MAC in respiratory cultures of lung cancer patients was particularly associated with squamous cell carcinomas located in the periphery of the lung. Because MAC typically affects distal airways, this possible association between MAC infection and lung cancer warrants further study.

The PPE18 protein of Mycobacterium tuberculosis inhibits NF-κB/rel-mediated proinflammatory cytokine production by upregulating and phosphorylating suppressor of cytokine signaling 3 protein

Mycobacterium tuberculosis bacteria are known to suppress proinflammatory cytokines like IL-12 and TNF-α for a biased Th2 response that favors a successful infection and its subsequent intracellular survival. However, the signaling pathways targeted by the bacilli to inhibit production of these cytokines are not fully understood. In this study, we demonstrate that the PPE18 protein of M. tuberculosis inhibits LPS-induced IL-12 and TNF-α production by blocking nuclear translocation of p50, p65 NF-κB, and c-rel transcription factors. We found that PPE18 upregulates the expression as well as tyrosine phosphorylation of suppressor of cytokine signaling 3 (SOCS3), and the phosphorylated SOCS3 physically interacts with IκBα-NF-κB/rel complex, inhibiting phosphorylation of IκBα at the serine 32/36 residues by IκB kinase-β, and thereby prevents nuclear translocation of the NF-κB/rel subunits in LPS-activated macrophages. Specific knockdown of SOCS3 by small interfering RNA enhanced IκBα phosphorylation, leading to increased nuclear levels of NF-κB/rel transcription factors vis-a-vis IL-12 p40 and TNF-α production in macrophages cotreated with PPE18 and LPS. The PPE18 protein did not affect the IκB kinase-β activity. Our study describes a novel mechanism by which phosphorylated SOCS3 inhibits NF-κB activation by masking the phosphorylation site of IκBα. Also, this study highlights the possible mechanisms by which the M. tuberculosis suppresses production of proinflammatory cytokines using PPE18.

The hydroxy-naphthoquinone lapachol arrests mycobacterial growth and immunomodulates host macrophages

The present study reports the anti-mycobacterial activity of 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone (lapachol) as well as its influence on macrophage functions. Lapachol (L) did not induce apoptosis/necrosis of THP-1 macrophages at ≤32 μg/mL. Mycobacterium avium liquid growth was arrested by ≥32 μg/mL and intra-macrophage proliferation by ≥16 μg/mL lapachol. The main immuno-modulatory effects of lapachol observed were an up-regulation of interferon-γ-receptor 1 (IFN-γR1) and major histocompatibility complex class II (MHCII) surface expression, and a marked inhibition of IL-10 secretion. Lapachol did not affect resting, IFN-γ- or toll-like receptor 2 (TLR2)-induced levels of oxygen and nitrogen metabolism key proteins nor the TLR2-mediated secretion of TNF-α, nor induced either oxidative or endoplasmic reticulum (ER) stress. Lapachol inhibited the surface expression of the co-stimulatory molecule CD86 but not that of CD80 and CD83. The results obtained indicate that the substituted naphthoquinone lapachol exhibits an anti-mycobacterial activity that is more efficient intra- than extra-cellularly, and exerts immuno-modulatory effects some of which may enhance the capacity of the host cell to control mycobacterial growth. The immune-modulatory action of lapachol could contribute to its more efficient intra-macrophage anti-mycobacterial activity.

Molecular cloning and expression of cDNAs for two distinct granulocyte colony stimulating factor genes from black rockfish Sebastes schlegelii

Granulocyte-colony stimulating factor (G-CSF) is a cytokine that stimulates the proliferation and differentiation of hematopoietic progenitor cells committed to the neutrophil/granulocyte lineage. Here, we report the two distinct granulocyte colony stimulating factor homologues from black rockfish Sebastes schlegelii. The G-CSF homologue cDNAs were isolated from the black rockfish LPS or Con A/PMA stimulated leukocyte cDNA libraries. The cDNA for the Black rockfish G-CSF-1 homologue predicts a peptide of 202 amino acids that is the closest to the Bastard halibut (Paralichthys olivaceus) G-CSF, whereas the cDNA of the Black rockfish G-CSF-2 homologue predicts a peptide of 212 amino acids that is the closest to the Fugu (Takifugu rubripes). In a healthy fish, the mRNAs of both G-CSF homologues were predominantly expressed in leukocytes, spleen, and gill. Expression of the black rockfish G-CSF-1 homologue was induced in peripheral blood leukocytes (PBLs) after stimulation with LPS, Con A/PMA, or Poly I:C, and G-CSF-2 homologue was strongly induced in PBLs after stimulation with Con A/PMA for 24 h only.

Cytocompatibility of a tissue conditioner containing vinyl ester as a plasticizer

In the current study, we examined the cytocompatibility of eight vinyl esters as candidate plasticizers for producing phthalate- and ethanol-free tissue conditioners. We measured the estrogenic activity and cytotoxicity of vinyl esters in human fibroblasts and keratinocytes using an E-screen assay and a mitochondrial dye conversion assay, respectively. We also assessed the cytotoxicity of three prototype materials and commercially available tissue conditioners on human fibroblasts grown in collagen gels. Finally, we measured the effects of these materials on the expression of cytokines in three-dimensional cultures by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assays. None of the tested vinyl esters had estrogenic activity. Vinyl octanoate and vinyl pivalate were the least cytotoxic of the eight tested vinyl esters. In the same vein, a prototype tissue conditioner containing vinyl octanoate had equivalent or weaker cytotoxicity and induction of cytokine expression than conventional materials.

Pathogenesis of Mycobacterium avium infection: typical responses to an atypical mycobacterium?

Studying infections with Mycobacterium avium in mouse models has allowed the dissection of the antimycobacterial pathways of the mammalian host. Whereas the paradigm of cell-mediated immunity to intracellular pathogens has been confirmed, namely with regard to the pivotal roles of CD4+ T cells, macrophages, and the IL12-IFNgamma cytokine axis, atypical features have been uncovered such as the resistance to NO, the involvement of minor players in the induction of type 1 protective immunity (such as TLR2, CD40, and CD30), and the development of immunopathology during the infection with highly virulent strains such as the development of caseous necrosis of granulomas or the progressive emergence of severe lymphopenia.

Pulmonary infection of Mycobacterium avium-intracellulare complex with simultaneous organizing pneumonia

A 67-year-old woman presented high-grade fever and dyspnea. Sputum culture confirmed Mycobacterium avium-intracellulare complex (MAC). Transbronchial lung biopsies revealed organizing pneumonia (OP) that was rapidly improved with corticosteroid. Five months after onset, a nodule emerged in the right lung. Although MAC was confirmed, the lesion was deemed too small to merit anti-mycobacterial chemotherapy. Four months later, diffuse infiltrates developed on chest X-ray. Bronchoalveolar lavage study identified MAC and exhibited OP patterns. We commenced antimycobacterial chemotherapy. The infiltrates almost completely improved within a month without corticosteroid.

Induction and regulation of endogenous granulocyte colony-stimulating factor formation

Granulocyte colony-stimulating factor (G-CSF) is one of the most prominent endogenous proteins in broad clinical use. While its biological and clinical effects are relatively well studied, little is known about its endogenous formation in health and disease. However, such knowledge is crucial to decide in which situations G-CSF should be applied efficiently in the clinic, ie. when endogenous production does not suffice. The dramatic changes induced by G-CSF in the differential blood cell count are directly immunomodulatory, strengthening the innate defence by multiplying neutrophilic granulocytes. A multitude of further immunomodulatory effects contribute to the regulation of the concerted host defence. In this review, following a short introduction into the biology of G-CSF, the available data on endogenous formation in a number of animal models and human diseases is compiled. The cellular sources and inducers of G-CSF formation are reviewed and the regulation of G-CSF expression on both the transcriptional and translational level are discussed. The emerging understanding of the role and regulation of endogenous G-CSF formation opens up possibilities to define therapeutic windows as well as targets for diagnostics or drug development. Lastly, the modulation of G-CSF formation by various pharmacological agents alerts to putative side effects of these drug treatments.

Difference in neutrophil cytokine production induced by pathogenic and non-pathogenic mycobacteria

This study shows differences between Mycobacterium tuberculosis and Mycobacterium avium (opportunistic) and Mycobacterium smegmatis (non-pathogenic), with respect to their abilities to induce cytokine/chemokine release from human neutrophils. Neutrophils incubated with live cells of M. tuberculosis, M. avium, or M. smegmatis produced and released TNF-alpha, IL-6, and IL-8. No or very small amounts of these cytokines/chemokines were found in resting neutrophils, suggesting that they were newly synthesised. The levels of TNF-alpha, IL-6, and IL-8 produced/released from neutrophils incubated with M. tuberculosis were markedly lower than those of the opportunistic or non-pathogenic bacterial species. The production of TNF-alpha reached a maximum level at a time (4 h) when the production of IL-8 had only just started, and this was true for all three mycobacteria tested. However, the time course for IL-6 production differed between the species, reaching a peak value after 8 h for M. tuberculosis not seen with the other bacteria. It is likely that the relatively high levels of cytokines induced by opportunistic/non-pathogenic mycobacteria are of importance for the induction of an innate immune response through which these organisms are eliminated, while the low levels of cytokines released by neutrophils interfering with M. tuberculosis might help the bacteria to persist.

Differential regulation of the mitogen-activated protein kinases by pathogenic and nonpathogenic mycobacteria

Mycobacteria are the etiologic agents of numerous diseases which account for significant morbidity and mortality in humans and other animal species. Many mycobacteria are intramacrophage pathogens and therefore the macrophage response to infection, which includes synthesis of cytokines such as tumor necrosis factor alpha (TNF-alpha) and production of nitric oxide, has important consequences for host immunity. However, very little is known about the macrophage cell signaling pathways initiated upon infection or how pathogenic mycobacteria may modulate the macrophage responses. Using primary murine bone marrow macrophages, we established that p38 and extracellular signal-regulated kinases 1 and 2 of the mitogen-activated protein kinase (MAPK) pathways are activated upon infection with different species of mycobacteria. However, we observed decreased MAPK activity over time in macrophages infected with pathogenic Mycobacterium avium strains relative to infections with nonpathogenic mycobacteria. Furthermore, macrophages infected with M. avium produced lower levels of TNF-alpha, interleukin 1beta, and inducible nitric oxide synthase 2 than macrophages infected with nonpathogenic species. Inhibitor studies indicate that the MAPKs are required for the Mycobacterium-mediated induction of these effector proteins. Our data indicate that MAPKs are activated in macrophages upon invasion by mycobacteria and that this activation is diminished in macrophages infected with pathogenic strains of M. avium, resulting in decreased production of important immune effector proteins. The decreased MAPK activation associated with M. avium infections suggests a novel point of immune intervention by this mycobacterial species.

Apoptosis modulation by mycolic acid, tuberculostearic acid and trehalose 6,6'-dimycolate

The object of our study is to demonstrate that some components of M. tuberculosis, such as cord factor or mycolic acid or whole bacteria can prolong cell survival compared to controls. The cells treated with cord factor or mycolic acid at a concentration of 5 microg/ml were 65+/-8% viable reaching 70+/-8% at a concentration of 10 microg/ml. The cells treated with heat killed mycobacteria were 70+/-8% viable; while control cells exhibited a viability 50+/-7%. Conversely, tuberculostearic acid induced early cell death. The results also demonstrated a dose-dependent effect on the viability or induction of macrophage apoptosis. We also showed that prolonged viability of the treated cells with mycolic acid or cord factor (+20+/-4% and +25+/-5%, respectively) was correlated with a significant increase in Bcl-2 expression. The treated cells with whole bacteria presented a Bcl-2 expression of 40+/-6%, while Fas expression was not changed compared to controls. This study confirm that at the site of mycobacterial infection, necrosis, apoptosis or prolonged survival of the cells depend on the quantity and quality of the molecules expressed by the mycobacteria; whether necrosis or apoptosis or prolonged survival is more or less favorable to the host likely depends on several factors regarding the inflammatory and immune response, both markedly stimulated by mycobacteria.

Activation of the mitogen-activated protein kinase signaling pathway is instrumental in determining the ability of Mycobacterium avium to grow in murine macrophages

Of the two common morphotypes of Mycobacterium avium, designated smooth transparent (SmT) or smooth opaque (SmO), the SmO morphotype is avirulent, whereas the SmT morphotype is virulent. The role of the host macrophage in determining these different virulence phenotypes was analyzed using an in vitro model of macrophage infection. Initial studies confirmed previous reports of the increased ability of the SmT bacteria to grow in macrophages; this increased virulence correlated with reduced induction of inflammatory cytokines. Examination of the response of the mitogen-activated protein kinase (MAPK) pathway following infection with either morphotype revealed that all three members of the MAPK pathway were activated. Pharmacologic inhibition of either the extracellular signal-regulated kinase (ERK) or p38(MAPK) pathways resulted in distinct consequences for the growth of the two morphotypes. In particular, inhibition of the p38(MAPK) resulted in attenuated growth of the SmT morphotype, which correlated with reduced PGE(2) production. Inhibition of cyclooxygenase 2 by indomethacin also inhibited growth of SmT, substantiating the role for PGE(2) in promoting the growth of SmT. In contrast, SmO induction of the ERK pathway was increased compared with the SmT morphotype, and inhibition of ERK resulted in decreased TNF-alpha synthesis and enhanced SmO growth. Pharmacologic inhibitors of the MAPK pathway were present for only the first 4 h of infection and yet had consequences for bacterial growth at 7 days. Therefore, the data suggest that induction of the MAPK pathway during uptake of bacteria is instrumental in determining the eventual fate of the bacteria.

Enhancement of innate immunity against Mycobacterium avium infection by immunostimulatory DNA is mediated by indoleamine 2,3-dioxygenase

Bacterial DNA and its synthetic immunostimulatory oligodeoxynucleotide analogs (ISS-ODN) activate innate immunity and promote Th1 and cytotoxic T-lymphocyte immune responses. Based on these activities, we investigated whether ISS-ODN could modify the course of Mycobacterium avium infection. M. avium growth in vitro was significantly inhibited by ISS-ODN treatment of human and mouse macrophages, and M. avium growth in vivo was similarly inhibited in C57BL/6 mice treated with ISS-ODN. This protective effect of ISS-ODN was largely independent of tumor necrosis factor alpha (TNF-alpha), interleukin 12 (IL-12), nitric oxide, NADPH oxidase, alpha/beta interferon (IFN-alpha/beta), and IFN-gamma. In contrast, we found that the induction of indoleamine 2,3-dioxygenase (IDO) was required for the antimycobacterial effect of ISS-ODN. To evaluate the potential for synergism between ISS-ODN and other antimycobacterial agents, treatment with a combination of ISS-ODN and clarithromycin (CLA) was tested in vitro and in vivo. ISS-ODN significantly enhanced the therapeutic effect of CLA in both human and mouse macrophages and in C57BL/6 mice. This study newly identifies IDO as being involved in the antimicrobial activity of ISS-ODN and suggests the usefulness of ISS-ODN when used in combination with conventional chemotherapy for microbial infections.

Production of matrix metalloproteinases in response to mycobacterial infection

Matrix metalloproteinases (MMPs) constitute a large family of enzymes with specificity for the various proteins of the extracellular matrix which are implicated in tissue remodeling processes and chronic inflammatory conditions. To investigate the role of MMPs in immunity to mycobacterial infections, we incubated murine peritoneal macrophages with viable Mycobacterium bovis BCG or Mycobacterium tuberculosis H37Rv and assayed MMP activity in the supernatants by zymography. Resting macrophages secreted only small amounts of MMP-9 (gelatinase B), but secretion increased dramatically in a dose-dependent manner in response to either BCG or M. tuberculosis in vitro. Incubation with mycobacteria also induced increased MMP-2 (gelatinase A) activity. Neutralization of tumor necrosis alpha (TNF-alpha), and to a lesser extent interleukin 18 (IL-18), substantially reduced MMP production in response to mycobacteria. Exogenous addition of TNF-alpha or IL-18 induced macrophages to express MMPs, even in the absence of bacteria. The immunoregulatory cytokines gamma interferon (IFN-gamma), IL-4, and IL-10 all suppressed BCG-induced MMP production, but through different mechanisms. IFN-gamma treatment increased macrophage secretion of TNF-alpha but still reduced their MMP activity. Conversely, IL-4 and IL-10 seemed to act by reducing the amount of TNF-alpha available to the macrophages. Finally, infection of BALB/c or severe combined immunodeficiency (SCID) mice with either BCG or M. tuberculosis induced substantial increases in MMP-9 activity in infected tissues. In conclusion, we show that mycobacterial infection induces MMP-9 activity both in vitro and in vivo and that this is regulated by TNF-alpha, IL-18, and IFN-gamma. These findings indicate a possible contribution of MMPs to tissue remodeling processes that occur in mycobacterial infections.

Release of monocyte chemoattractant protein (MCP)-1 by a human alveolar epithelial cell line in response to mycobacterium avium

Clinical strains of Mycobacterium avium isolated from patients with acquired immunodeficiency syndrome, but not a non-clinical laboratory strain (ATCC 25291), were found to stimulate the human alveolar epithelial cell line A549, to produce monocyte chemoattractant protein (MCP)-1. A549 cells were also found to produce elevated levels of MCP-1 in response to sonicates of the clinical strains of M. avium, and surprisingly, the non-clinical strain as well. However, sonic extracts of the clinical strains were found to induce significantly higher levels of MCP-1 production compared to extracts of the non-clinical strain (P < 0.001). These data suggest the existence of strain-related differences in antigen expression by M. avium. The clinical and non-clinical strains of M. avium were found to attach and invade, but not replicate in A549 cells indicating that MCP-1 production by A549 cells does require the presence of viable, replicating organisms. Activation of alveolar epithelial cells by exposure to M. avium resulting in the production of chemokines which recruit inflammatory cells to the site of infection may be an important regulatory pathway for the activation of pulmonary host defense.

Secretion of cytokines by human macrophages upon infection by pathogenic and non-pathogenic mycobacteria

The interaction of various pathogenic (Mycobacterium tuberculosis, M. avium, M. kansasii, M. xenopi), and non-pathogenic mycobacteria (M. smegmatis, M. phlei) with human macrophages at the level of macrophage cytokine expression (TNFalpha, IL1, IL6 and GM-CSF) was investigated. Both for TNFalpha and GM-CSF, the lowest levels were obtained with pathogenic mycobacterial species, whereas about 2-8 times higher levels were observed for non-pathogenic species. Contrary to the above, the differences for IL6 and IL1 were not marked, although IL6 appeared to be more elevated for non-pathogenic species. Heat-killed bacteria induced a lower level of the cytokines for all the three cytokines assayed (TNFalpha, IL6 and IL1), except for M. tuberculosis for whom a significantly higher proportion of TNFalpha was induced by killed bacilli. The RT-PCR experiments performed on M. avium (as a low inducer of the cytokines) and M. smegmatis (as a high inducer of the cytokines) showed that the differences observed among pathogenic vs non-pathogenic strains were also reflected at the transcriptional level for TNFalpha and to a lesser extent for IL6, but not for IL1. This investigation underlined important differences existing between the pathogenic and non-pathogenic species, particularly as regards TNFalpha and GM-CSF.

Role of CD40 ligand in Mycobacterium avium infection

Mycobacterium avium is a common opportunistic pathogen in immunocompromised patients such as those infected with human immunodeficiency virus. Although M. avium is an intracellular organism replicating predominantly in macrophages, disseminated M. avium infection is seen in AIDS patients with CD4(+) cell counts of <50 cells/microliters, suggesting a possible involvement of a T cell-macrophage interaction for the elimination of M. avium. To determine whether CD40-CD40 ligand (CD40L) interactions play a role in M. avium infection, we studied the ability of CD40L to restrict M. avium replication in human monocyte-derived macrophages (MDM) in vitro. MDM were infected with M. avium and cocultured with CD40L-transfected 293 cells for 7 days. Intracellular growth of M. avium in these MDM was assessed by colony counting. CD40L-expressing cells inhibited growth of M. avium in MDM by 86.5% +/- 4.2% compared to MDM cultured with control cells. These findings were verified by assays using purified, soluble recombinant human CD40L (CD40LT). CD40LT (5 micrograms/ml) inhibited intracellular growth of M. avium by 76.9% +/- 18.0% compared to cells treated with medium alone. Inhibition by CD40LT was reduced by monoclonal antibodies (MAbs) against CD40 and CD40L. The inhibitory effect of CD40LT was not accompanied by enhancement of interleukin-12 (IL-12) production by M. avium-infected MDM, while CD40L-expressing cells stimulated IL-12 production by these cells. Treatment of M. avium-infected mice with MAb against murine CD40L resulted in recovery of larger numbers of organisms (0.8 to 1.0 log) from the spleens, livers, and lungs of these animals compared to infected mice which received normal immunoglobulin G. These results indicate that CD40-CD40L signaling may be an important step in host immune response against M. avium infection.

Apoptosis of human monocytes and macrophages by Mycobacterium avium sonicate

Mycobacterium avium is an intracellular organism which multiplies predominantly within human macrophages. This organism has previously been shown to induce apoptosis in human macrophages. With a view to identifying M. avium components that induce cell death in infected host cells, sonicated extracts of M. avium as well as individual components isolated from the M. avium sonicate were tested in various assays with a human monocytic cell line (THP-1). THP-1 cells incubated with M. avium sonicate showed significantly reduced viability after a 2-day exposure compared to control cells incubated with media alone. This effect was dose dependent, with only 6.6% +/- 5.2% and 48.8% +/- 10.3% of the cells being viable by trypan blue exclusion at 600 and 300 microg/ml, respectively. Control cells, on the other hand, exhibited a viability of 98.8% +/- 1.0%. In addition, an 80% ammonium sulfate fraction of the M. avium sonicate and the previously characterized 68-kDa protein were found to have similar effects on THP-1 cells. In both cases, the reduction in viability was due to apoptosis characterized by chromatin condensation, DNA fragmentation by agarose gel electrophoresis, or terminal deoxynucleotidyl transferase-mediated d-UTP nick end labeling (TUNEL) and release of nuclear matrix protein (NMP) into the culture medium. M. avium sonicate-induced apoptosis of THP-1 cells was completely inhibited by the commonly used antioxidants pyrrolidinedithiocarbamate (PDTC) and butylated hydroxyanisole (BHA), indicating that the generation of free oxygen radicals may be responsible for inducing cell death. M. avium sonicate was found to induce apoptosis of monocyte-derived macrophages (MDMs) as well. This effect was not reversed in the presence of PDTC and was not accompanied with DNA fragmentation when determined by agarose gel electrophoresis, as seen in the case of THP-1 cells. However, these MDMs were found to contain fragmented DNA by TUNEL. These findings suggest that the mechanism of cell death in MDMs may be different from that observed with THP-1 cells. Furthermore, these results provide new insight into the effect of M. avium components on host cell responses during M. avium infection.

Macrophage release of tumor necrosis factor-alpha by Mycobacterium avium antigens

Mycobacterium avium complex (MAC) infection is the most common disseminated opportunistic infection encountered in patients with AIDS. We have studied the ability of specific Mycobacterium avium (MA) antigen to stimulate human monocyte-derived macrophages (MDM) to produce tumor necrosis factor-alpha (TNF-alpha). MDM stimulated with MA sonicate, MA 68 kDa and MA 48-52 kDa antigens were found to produce TNF-alpha in a dose-dependent manner. Reverse transcriptase-polymerase chain reaction analysis of mRNA extracts from antigen-stimulated MDM indicated that TNF-alpha mRNA expression was of brief duration and the time point of peak TNF-alpha mRNA levels was found to be antigen-specific. A significant difference in TNF-alpha production in response to MA 48-52 kDa antigen and M. bovis 65 kDa antigen was observed between MDM from normal and HIV positive individuals.

Extracellular and surface-exposed polysaccharides of non-tuberculous mycobacteria

We studied the outermost constituents of the cell envelopes, which are involved in the interaction between the bacilli and the host cells, of five pathogenic and non-pathogenic mycobacterial species for comparison with those we have previously characterized from M. tuberculosis. The extracellular materials (ECMs) were isolated by ethanol precipitation and compared to the surface-exposed materials (SXMs) extracted by mechanical means. The materials from both sources were composed almost exclusively of polysaccharides and proteins. Two groups of mycobacteria were clearly distinguishable. The first group comprised the pathogenic species M. kansasii which produced large amounts of ECM, the glycosyl composition of which was similar to that of the SXM. The second group comprised M. avium and the non-pathogenic strains of M. gastri, M. phlei and M. smegmatis which produced small amounts of ECK This latter group could be subdivided into those which produced carbohydrate-rich ECM (M. avium and M. gastri) and those forming protein-rich ECM (M. phlei and M. smegmatis), a classification that correlated with the difference in the growth rate of the two subgroups. The glycosyl composition of the ECM of a given species was qualitatively similar to that of the SXM, except for M. avium and M. phlei whose SXM were devoid of arabinose. In addition to glucose, mannose and arabinose, xylose was detected in the hydrolysis products of the ECM and SXM of M. smegmatis, the SXM of M. phlei and the ECM of some batches of M. avium. The polysaccharide constituents of the ECM and SXM of the different mycobacteria were purified by anion-exchange and gel-filtration chromatography; all were found to be neutral compounds devoid of acyl substituents. The extracellular polysaccharides consisted of high-molecular-mass glycogen-like glucans, arabinomannans and mannans, structurally similar to the corresponding substances previously characterized from the capsule of M. tuberculosis. The same types of polysaccharides were characterized from the SXM of all the strains, except M. avium and M. phlei which were devoid of arabinomannans. This study questions the unique and universal representation of the mycobacterial cell envelope and the existence of the so-called acidic polysaccharide-rich outer layer.

Relationship between virulence of Mycobacterium avium strains and induction of tumor necrosis factor alpha production in infected mice and in in vitro-cultured mouse macrophages

We studied the ability of two Mycobacterium avium strains with different virulences to induce tumor necrosis factor alpha (TNF) synthesis by mouse resident peritoneal macrophages (RPM phi) in vitro in an experiment to look for a possible correlation between virulence and this TNF-inducing capacity. The low-virulence strain, 1983, induced significantly higher production of TNF by RPM phi than did the high-virulence strain, ATCC 25291. TNF neutralization during culture of infected RPM phi resulted in enhancement of growth of strain 1983 and had no effect on growth of strain ATCC 25291; TNF treatment of strain ATCC 25291-infected macrophages had no effect on mycobacterial growth. The extent of M. avium growth and the amount of TNF synthesis were independent of the presence of contaminating T cells or NK cells in the macrophage monolayers. Intraperitoneal administration of anti-TNF monoclonal antibodies to BALB/c mice infected intravenously with M. avium 1983 abrogated the elimination of the bacteria in the liver and caused a slight increase in bacterial growth in the spleen. Neutralization of TNF led to a minor increase in the proliferation of M. avium ATCC 25291 in the liver and spleen of BALB/c mice late in infection. Anti-TNF treatment did not affect the growth of the two M. avium strains in BALB/c.Bcgr (C.D2) mice, suggesting that restriction of M. avium strains to induce TNF production by macrophages may limit their ability to proliferate both in vitro and in vivo.