IRAK-M alters the polarity of macrophages to facilitate the survival of Mycobacterium tuberculosis

Targeting Macrophage Polarization in Infectious Diseases: M1/M2 Functional Profiles, Immune Signaling and Microbial Virulence Factors

INTRODUCTION

An event of increasing interest during host-pathogen interactions is the polarization of patrolling/naive monocytes (MOs) into macrophage subsets (MФs). Therapeutic strategies aimed at modulating this event are under investigation.

METHODS

This review focuses on the mechanisms of induction/development and profile of MФs polarized toward classically proinflammatory (M1) or alternatively anti-inflammatory (M2) phenotypes in response to bacteria, fungi, parasites, and viruses.

RESULTS AND DISCUSSION

It highlights nuclear, cytoplasmic, and cell surface receptors (pattern recognition receptors/PPRs), microenvironmental mediators, and immune signaling. MФs polarize into phenotypes: M1 MФs, activated by IFN-γ, pathogen-associated molecular patterns (PAMPs, e.g. lipopolysaccharide) and membrane-bound PPRs ligands (TLRs/CLRs ligands); or M2 MФs, induced by interleukins (ILs-4, -10 and -13), antigen-antibody complexes, and helminth PAMPs. Polarization toward M1 and M2 profiles evolve in a pathogen-specific manner, with or without canonicity, and can vary widely. Ultimately, this can result in varying degrees of host protection or more severe disease outcome. On the one hand, the host is driving effective MФs polarization (M1 or M2); but on the other hand, microorganisms may skew the polarization through virulence factors to increase pathogenicity. Cellular/genomic reprogramming also ensures plasticity of M1/M2 phenotypes. Because modulation of polarization can occur at multiple points, new insights and emerging perspectives may have clinical implications during the inflammation-to-resolution transition; translated into practical applications as for therapeutic/vaccine design target to boost microbicidal response (M1, e.g. triggering oxidative burst) with specifics PAMPs/IFN-γ or promote tissue repair (M2, increasing arginase activity) via immunotherapy.

Ketogenic diet and β-Hydroxybutyrate alleviate ischemic brain injury in mice via an IRAKM-dependent pathway

Ketogenic diet (KD) is a classical nonpharmacological therapy that has recently been shown to benefit cerebral ischemia, but the mechanism remains unclear. This study investigated the neuroprotective effects of KD pretreatment and β-hydroxybutyrate (BHB, bioactive product of KD) post-treatment in a mouse model of temporary middle cerebral artery occlusion (tMCAO). Neurological function, infarct volume, as well as inflammatory reactions are evaluated 24 h after ischemia. Results showed that both KD pretreatment or BHB post-treatment improved the Bederson score and Grip test score, reduced infarct volume and the extravasation of IgG, suppressed the over-activation of microglia, and modulated the expression of cytokines. Mechanically, we found that both KD pretreatment or BHB post-treatment significantly stimulated the expression of interleukin-1 receptor-associated kinase M (IRAKM) and then inhibited the nuclear translocation of NF-κB. IRAKM deletion (Irakm-/-) exacerbated tMCAO-induced neurovascular injuries, and aggravated neuroinflammatory response. Moreover, KD pretreatment or BHB post-treatment lost their neuroprotection in the tMCAO-treated Irakm-/- mice. Our results support that KD pretreatment and BHB post-treatment alleviate ischemic brain injury in mice, possibly via an IRAKM-dependent way.

Mutations in the Vicinity of the IRAK3 Guanylate Cyclase Center Impact Its Subcellular Localization and Ability to Modulate Inflammatory Signaling in Immortalized Cell Lines

Interleukin-1 receptor-associated kinase 3 (IRAK3) modulates the magnitude of cellular responses to ligands perceived by interleukin-1 receptors (IL-1Rs) and Toll-like receptors (TLRs), leading to decreases in pro-inflammatory cytokines and suppressed inflammation. The molecular mechanism of IRAK3's action remains unknown. IRAK3 functions as a guanylate cyclase, and its cGMP product suppresses lipopolysaccharide (LPS)-induced nuclear factor kappa-light-chain-enhancer of activated B cell (NFκB) activity. To understand the implications of this phenomenon, we expanded the structure-function analyses of IRAK3 through site-directed mutagenesis of amino acids known or predicted to impact different activities of IRAK3. We verified the capacity of the mutated IRAK3 variants to generate cGMP in vitro and revealed residues in and in the vicinity of its GC catalytic center that impact the LPS-induced NFκB activity in immortalized cell lines in the absence or presence of an exogenous membrane-permeable cGMP analog. Mutant IRAK3 variants with reduced cGMP generating capacity and differential regulation of NFκB activity influence subcellular localization of IRAK3 in HEK293T cells and fail to rescue IRAK3 function in IRAK3 knock-out THP-1 monocytes stimulated with LPS unless the cGMP analog is present. Together, our results shed new light on the mechanism by which IRAK3 and its enzymatic product control the downstream signaling, affecting inflammatory responses in immortalized cell lines.

Macrophages in aseptic loosening: Characteristics, functions, and mechanisms

Aseptic loosening (AL) is the most common complication of total joint arthroplasty (TJA). Both local inflammatory response and subsequent osteolysis around the prosthesis are the fundamental causes of disease pathology. As the earliest change of cell behavior, polarizations of macrophages play an essential role in the pathogenesis of AL, including regulating inflammatory responses and related pathological bone remodeling. The direction of macrophage polarization is closely dependent on the microenvironment of the periprosthetic tissue. When the classically activated macrophages (M1) are characterized by the augmented ability to produce proinflammatory cytokines, the primary functions of alternatively activated macrophages (M2) are related to inflammatory relief and tissue repair. Yet, both M1 macrophages and M2 macrophages are involved in the occurrence and development of AL, and a comprehensive understanding of polarized behaviors and inducing factors would help in identifying specific therapies. In recent years, studies have witnessed novel discoveries regarding the role of macrophages in AL pathology, the shifts between polarized phenotype during disease progression, as well as local mediators and signaling pathways responsible for regulations in macrophages and subsequent osteoclasts (OCs). In this review, we summarize recent progress on macrophage polarization and related mechanisms during the development of AL and discuss new findings and concepts in the context of existing work.

MicroRNAs induced by Listeria monocytogenes and their role in cells

Listeria monocytogenes (Lm) causes abortions at high rates and threatens newborns' lives. Also, the elderly and immunocompromised individuals are particularly vulnerable neurologically. The bacterium exerts its pathogenesis intracellularly by manipulating cell organs. It manipulates nucleus elements, microRNAs (miRNAs), in order to increase survival and evade immunity. miRNAs are small non-coding RNAs that degrade gene expression post-transcriptionally. Any alteration to the expression of miRNAs affects various cascades in cells, especially immunity-related responses. Thus, utilizing miRNAs as a novel therapeutic agent not only restricts infection but enhances immunity reactions. This review provides an overview of miRNAs in listeriosis, their role in cells, and their prospects as therapy.

Human M1 macrophages express unique innate immune response genes after mycobacterial infection to defend against tuberculosis

Mycobacterium tuberculosis (Mtb) is responsible for approximately 1.5 million deaths each year. Though 10% of patients develop tuberculosis (TB) after infection, 90% of these infections are latent. Further, mice are nearly uniformly susceptible to Mtb but their M1-polarized macrophages (M1-MΦs) can inhibit Mtb in vitro, suggesting that M1-MΦs may be able to regulate anti-TB immunity. We sought to determine whether human MΦ heterogeneity contributes to TB immunity. Here we show that IFN-γ-programmed M1-MΦs degrade Mtb through increased expression of innate immunity regulatory genes (Inregs). In contrast, IL-4-programmed M2-polarized MΦs (M2-MΦs) are permissive for Mtb proliferation and exhibit reduced Inregs expression. M1-MΦs and M2-MΦs express pro- and anti-inflammatory cytokine-chemokines, respectively, and M1-MΦs show nitric oxide and autophagy-dependent degradation of Mtb, leading to increased antigen presentation to T cells through an ATG-RAB7-cathepsin pathway. Despite Mtb infection, M1-MΦs show increased histone acetylation at the ATG5 promoter and pro-autophagy phenotypes, while increased histone deacetylases lead to decreased autophagy in M2-MΦs. Finally, Mtb-infected neonatal macaques express human Inregs in their lymph nodes and macrophages, suggesting that M1 and M2 phenotypes can mediate immunity to TB in both humans and macaques. We conclude that human MФ subsets show unique patterns of gene expression that enable differential control of TB after infection. These genes could serve as targets for diagnosis and immunotherapy of TB.

E3 Ligase FBXW7 Facilitates Mycobacterium Immune Evasion by Modulating TNF-α Expression

Tumor necrosis factor alpha (TNF-α) is a crucial factor in the control of Mycobacterium tuberculosis (Mtb) infection. Pathogenic mycobacteria can inhibit and/or regulate host cell TNF-α production in a variety of ways to evade antituberculosis (anti-TB) immunity as well as facilitate immune escape. However, the mechanisms by which TNF-α expression in host cells is modulated to the benefit of mycobacteria is still an interesting topic and needs further study. Here, we report that macrophages infected with Mycobacterium marinum (Mm)—a close relative of Mtb—upregulated the expression of E3 ubiquitin ligase FBXW7. Specific silencing FBXW7 with small interfering RNA (siRNA) significantly elevates TNF-α expression and eventually promotes the elimination of intracellular bacteria. In turn, overexpression of FBXW7 in Raw264.7 macrophages markedly decreased TNF-α production. Furthermore, partial inhibition of FBXW7 in an Mm-infected murine model significantly reduced TNF-α tissue content, alleviated tissue damage as well as reduced the bacterial load of mouse tails. Finally, FBXW7 could decrease TNF-α in a K63-linked ubiquitin signaling dependent manner. Taken together, our study uncovered a previously unknown role of FBXW7 in regulating TNF-α dynamics during mycobacterial infection, which provides new insights into understanding the role of FBXW7 in anti-tuberculosis immunity and its related clinical significance.

Host factors subverted by Mycobacterium tuberculosis: Potential targets for host directed therapy

INTRODUCTION

Despite new approaches in the diagnosis and treatment of tuberculosis (TB), it continues to be a major health burden. Several immunotherapies that potentiate the immune response have come up as adjuncts to drug therapies against drug resistant TB strains; however, there needs to be an urgent appraisal of host specific drug targets for improving their clinical management and to curtail disease progression. Presently, various host directed therapies (HDTs) exist (repurposed drugs, nutraceuticals, monoclonal antibodies and immunomodulatory agents), but these mostly address molecules that combat disease progression.

AREAS COVERED

The current review discusses major Mycobacterium tuberculosis (M. tuberculosis) survival paradigms inside the host and presents a plethora of host targets subverted by M. tuberculosis which can be further explored for future HDTs. The host factors unique to M. tuberculosis infection (in humans) have also been identified through an in-silico interaction mapping.

EXPERT OPINION

HDTs could become the next-generation adjunct therapies in order to counter antimicrobial resistance and virulence, as well as to reduce the duration of existing TB treatments. However, current scientific efforts are largely directed toward combatants rather than host molecules co-opted by M. tuberculosis for its survival. This might drive the immune system to a hyper-inflammatory condition; therefore, we emphasize that host factors subverted by M. tuberculosis, and their subsequent neutralization, must be considered for development of better HDTs.

Activation of hypoxia-inducible factor 1 (Hif-1) enhanced bactericidal effects of macrophages to Mycobacterium tuberculosis

BACKGROUND

Tuberculosis is chronic infection caused by Mycobacterium tuberculosis (M.tb), which infects specifically macrophages. Hif-1, hypoxia-inducible factor-1, was reported to act as master regulator of killing functions in macrophages.

AIM

To investigate whether Hif-1 activation would enhance bactericidal effect of macrophages and anti-tuberculosis effect of chemical reagent.

METHODS

Hif-1 and LC3B were detected in tissues from pulmonary tuberculosis. U937, human monocytic leukemia cell line, was stimulated with PMA and differentiated into macrophages. Cells were pretreated with Hif-1 chemical inhibitor YC-1, stimulated with CoCl₂ (Hif-1 activator), to detect LC3B with Western blot and confocal microscopy. Cells were infected with M. tb H37Rv strain, stimulated with CoCl₂, following rifampine treatment. Expression of autophagy markers was detected using Western blot. IL-6 and TNF-α were detected in cell supernatant with ELISA. Acid-fast staining and CFU assay were performed to evaluate intracellular bacterial load.

RESULTS AND CONCLUSIONS

Hif-1 and LC3B increased in tissues of pulmonary tuberculosis. Hif-1 activation enhanced autophagy in M. tb infected U937 cells and production of IL-6 and TNF-α. Data from acid-fast staining and CFU indicated that Hif-1 activation enhanced anti-tuberculosis effect of rifampine in macrophages. Conclusively, to activate Hif-1 would strengthen bactericidal effect of macrophages, to further enhance anti-tuberculosis effect of chemical reagent.

HIV and the tuberculosis "set point": how HIV impairs alveolar macrophage responses to tuberculosis and sets the stage for progressive disease

As HIV has fueled a global resurgence of tuberculosis over the last several decades, there is a growing awareness that HIV-mediated impairments in both innate and adaptive immunity contribute to the heightened risk of tuberculosis in people with HIV. Since early immune responses to Mycobacterium tuberculosis (Mtb) set the stage for subsequent control or progression to active tuberculosis disease, early host-pathogen interactions following Mtb infection can be thought of as establishing a mycobacterial "set point," which we define as the mycobacterial burden at the point of adaptive immune activation. This early immune response is impaired in the context of HIV coinfection, allowing for a higher mycobacterial set point and greater likelihood of progression to active disease with greater bacterial burden. Alveolar macrophages, as the first cells to encounter Mtb in the lungs, play a critical role in containing Mtb growth and establishing the mycobacterial set point. However, a number of key macrophage functions, ranging from pathogen recognition and uptake to phagocytosis and microbial killing, are blunted in HIV coinfection. To date, research evaluating the effects of HIV on the alveolar macrophage response to Mtb has been relatively limited, particularly with regard to the critical early events that help to dictate the mycobacterial set point. A greater understanding of alveolar macrophage functions impacted by HIV coinfection will improve our understanding of protective immunity to Mtb and may reveal novel pathways amenable to intervention to improve both early immune control of Mtb and clinical outcomes for the millions of people worldwide infected with HIV.

Hacking the host: exploitation of macrophage polarization by intracellular bacterial pathogens

Macrophages play an integral role in host defenses against intracellular bacterial pathogens. A remarkable plasticity allows for adaptation to the needs of the host to orchestrate versatile innate immune responses to a variety of microbial threats. Several bacterial pathogens have adapted to macrophage plasticity and modulate the classical (M1) or alternative (M2) activation bias towards a polarization state that increases fitness for intracellular survival. Here, we summarize the current understanding of the host macrophage and intracellular bacterial interface; highlighting the roles of M1/M2 polarization in host defense and the mechanisms employed by several important intracellular pathogens to modulate macrophage polarization to favor persistence or proliferation. Understanding macrophage polarization in the context of disease caused by different bacterial pathogens is important for the identification of targets for therapeutic intervention.

Blood M2a monocyte polarization and increased formyl peptide receptor 1 expression are associated with progression from latent tuberculosis infection to active pulmonary tuberculosis disease

OBJECTIVES

This study aims to explore the role of M2a polarization and formyl peptide receptor (FPR) regulation in the reactivation of Mycobacterium tuberculosis (Mtb) infection.

METHODS

M1/M2a monocyte percentage and FPR1/2/3 protein expression of blood immune cells were measured in 38 patients with sputum culture (+) active pulmonary TB disease, 18 subjects with latent TB infection (LTBI), and 28 noninfected healthy subjects (NIHS) using flow cytometry method.

RESULTS

M1 percentage was decreased in active TB versus either NIHS or LTBI group, while M2a percentage and M2a/M1 percentage ratio were increased. FPR1 expression on M1/M2a, FPR2 expression on M1, and FPR3 expression of M1 were all decreased in active TB versus LTBI group, while FPR1 over FPR2 expression ratio on NK T cell was increased in active TB versus either NIHS or LTBI group. In 11 patients with active TB disease, M1 percentage became normal again after anti-TB treatment. In vitro Mtb-specific antigen stimulation of monocytic THP-1 cells resulted in M2a polarization in association with increased FPR2 expression on M2a.

CONCLUSIONS

Increased M2a and decreased M1 phenotypes of blood monocyte may serve as a marker for active TB disease, while decreased FPR1 on blood monocyte may indicate LTBI status.

Arginase 1 is involved in lacrimal hyposecretion in male NOD mice, a model of Sjögren's syndrome, regardless of dacryoadenitis status

Key points

Few reports have explored the possibility of involvement of non‐inflammatory factors in lacrimal hyposecretion in Sjögren's syndrome (SS).

RNA‐sequencing analysis revealed that only four genes, including arginase 1, were downregulated in the lacrimal gland of SS model male mice (NOD mice) after onset of lacrimal hyposecretion and dacryoadenitis.

Even in non‐dacryoadenitis‐type NOD mice, tear secretion and arginase 1 expression remained low.

An arginase 1 inhibitor reduced tear secretion and partially reduced saliva secretion in BALB/c mice.

The results indicate that a non‐inflammatory factor, arginase 1, is involved in lacrimal hyposecretion in male NOD mice, regardless of dacryoadenitis status.

Abstract

Lacrimal fluid (tears) is important for preservation of the ocular surface, and thus lacrimal hyposecretion in Sjögren's syndrome (SS) leads to reduced quality of life. However, the cause(s) of lacrimal hyposecretion remains unknown, even though many studies have been conducted from the perspective of inflammation. Here, we hypothesized that a non‐inflammatory factor induces lacrimal hyposecretion in SS pathology, and to elucidate such a factor, we conducted transcriptome analysis of the lacrimal glands in male non‐obese diabetic (NOD) mice as an SS model. The NOD mice showed inflammatory cell infiltration and decreased pilocarpine‐induced tear secretion at and after 6 weeks of age compared to age‐matched BALB/c mice. RNA‐sequencing analysis revealed that only four genes, including arginase 1, were downregulated, whereas many genes relating to inflammation were upregulated, in the lacrimal glands of male NOD mice after onset of lacrimal hyposecretion and dacryoadenitis (lacrimal gland inflammation). Changes in the level of arginase 1 expression were confirmed by real‐time RT‐PCR and western blot analysis. Furthermore, non‐dacryoadenitis‐type NOD mice were used to investigate the relationships among arginase 1 expression, lacrimal hyposecretion and dacryoadenitis. Interestingly, these NOD mice retained the phenotype of dacryoadenitis with regard to tear secretion and arginase 1 expression level. An arginase 1 inhibitor reduced tear secretion and partially reduced saliva secretion in BALB/c mice. In conclusion, a non‐inflammatory factor, arginase 1, is involved in lacrimal hyposecretion in male NOD mice, regardless of dacryoadenitis status. These results shed light on the pathophysiological role of arginase 1 in SS (dry eye).

Few reports have explored the possibility of involvement of non‐inflammatory factors in lacrimal hyposecretion in Sjögren's syndrome (SS).

RNA‐sequencing analysis revealed that only four genes, including arginase 1, were downregulated in the lacrimal gland of SS model male mice (NOD mice) after onset of lacrimal hyposecretion and dacryoadenitis.

Even in non‐dacryoadenitis‐type NOD mice, tear secretion and arginase 1 expression remained low.

An arginase 1 inhibitor reduced tear secretion and partially reduced saliva secretion in BALB/c mice.

The results indicate that a non‐inflammatory factor, arginase 1, is involved in lacrimal hyposecretion in male NOD mice, regardless of dacryoadenitis status.

In vitro and in vivo immunomodulatory properties of octyl-β-D-galactofuranoside during Leishmania donovani infection

BACKGROUND

The chemotherapeutic arsenal available to treat visceral leishmaniasis is currently limited, in view of many drawbacks such as high cost, toxicity or emerging resistance. New therapeutic strategies are particularly needed to improve the management and the outcome in immunosuppressed patients. The combination of an immunomodulatory drug to a conventional anti-Leishmania treatment is an emerging concept to reverse the immune bias from Th2 to Th1 response to boost healing and prevent relapses.

METHODS

Here, immunostimulating and leishmanicidal properties of octyl-β-D-galactofuranose (Galf) were assessed in human monocyte-derived macrophages (HM) and in a murine model, after challenge with Leishmania donovani promastigotes. We recorded parasite loads and expression of various cytokines and immune effectors in HM and mouse organs (liver, spleen, bone marrow), following treatment with free (Galf) and liposomal (L-Galf) formulations.

RESULTS

Both treatments significantly reduced parasite proliferation in HM, as well as liver parasite burden in vivo (Galf, P < 0.05). Consistent with in vitro results, we showed that Galf- and L-Galf-treated mice displayed an enhanced Th1 immune response, particularly in the spleen where pro-inflammatory cytokines TNF-α, IL-1β and IL-12 were significantly overexpressed compared to control group. The hepatic recruitment of myeloid cells was also favored by L-Galf treatment as evidenced by the five-fold increase of myeloperoxidase (MPO) induction, which was associated with a higher number of MPO-positive cells within granulomas. By contrast, the systemic level of various cytokines such as IL-1β, IL-6, IL-17A or IL-27 was drastically reduced at the end of treatment.

CONCLUSIONS

Overall, these results suggest that Galf could be tested as an adjuvant in combination with current anti-parasitic drugs, to restore an efficient immune response against infection in a model of immunosuppressed mice.

Mycobacterial Trehalose 6,6'-Dimycolate-Induced M1-Type Inflammation

Murine models of Mycobacterium tuberculosis (Mtb) infection demonstrate progression of M1-like (proinflammatory) and M2-like (anti-inflammatory) macrophage morphology following primary granuloma formation. The Mtb cell wall cording factor, trehalose 6,6'-dimycolate (TDM), is a physiologically relevant and useful molecule for modeling early macrophage-mediated events during establishment of the tuberculosis-induced granuloma pathogenesis. Here, it is shown that TDM is a major driver of the early M1-like macrophage response as seen during initiation of the granulomas of primary pathology. Proinflammatory cytokines tumor necrosis factor-α, IL-1β, IL-6, and IL-12p40 are produced in lung tissue after administration of TDM to mice. Furthermore, CD11b⁺CD45⁺ macrophages with a high surface expression of the M1-like markers CD38 and CD86 were found present in regions of pathology in lungs of mice at 7 days post-TDM introduction. Conversely, only low phenotypic marker expression of M2-like markers CD206 and EGR-2 were present on macrophages. These findings suggest that TDM plays a role in establishment of the M1-like shift in the microenvironment during primary tuberculosis.

Interleukin-1 receptor associated kinase (IRAK)-M -mediated type 2 microglia polarization ameliorates the severity of experimental autoimmune encephalomyelitis (EAE)

Toll-like receptor 4 (TLR4) play a key role in activating the innate immune system during pathogen recognition. In the pathogenesis of multiple sclerosis (MS), activated TLR4 together with myeloid differentiation primary response gene 88 (MyD88) produce an inflammatory microenvironment that promotes the differentiation of microglia into the M1 phenotype, who plays a key role in the pathogenesis of MS. Interleukin-1 receptor-associated kinase (IRAK)-M is specifically expressed in microglia in central nervous system (CNS) and act as a negative regulator of TLR4-MyD88 signaling pathway. Moreover, previous studies have shown that IRAK-M promotes the differentiation of type 2 microglia; however, its role in MS has not been explored. In the present study, we demonstrated that IRAK-M expression is elevated during EAE, and IRAK-M^-/- mice significantly accelerated course and increased severity of disease, accompanied by a visible increase of the M1 microglia infiltrated. In conclusion, these data indicates that IRAK-M significantly improves EAE onset through down-regulation of the TLR4-MyD88 signaling pathway, which finally leads to differentiation of M2 phenotype in the microglia. Our study suggests that IRAK-M may be a potential therapeutic target for the treatment of MS.

Macrophage heterogeneity and plasticity in tuberculosis

Macrophages are the primary host cells for Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), during its intracellular survival in humans. The pathogen has a remarkable capacity to survive within the hostile environment of macrophages. However, primary infection does not result in active TB disease in most individuals. The majority of individuals remain latently infected, wherein the bacteria are held in check by the host immune response. Nevertheless, such individuals can develop active TB later upon the decline in their immune status. In contrast, in a small fraction of infected individuals, the host immune response fails to control the growth of M. tuberculosis bacilli, and granulomatous TB develops progressively. Elucidating the molecular and phenotypic events that govern the outcome of the infection within macrophages is fundamental to understanding the key features of these cells that could be equally critical in infection control. The molecular details of the M. tuberculosis-macrophage interaction continue to be discerned, and emerging evidence suggests that macrophage population that participate in infection is heterogeneous. While the local environment and developmental origin could influence the phenotypic heterogeneity and functional plasticity of macrophages, M. tuberculosis has also been demonstrated to modulate the polarization of macrophages. In this review, we draw on work investigating specialized macrophage populations and their interactions with M. tuberculosis with respect to pathogenesis and specific immune responses. Understanding the mechanisms that control the repertoire of macrophage phenotypes and behaviors during infection may provide prospects for novel TB control strategies through modulation of immunobiological functions of macrophages.

Long non-coding RNA deep sequencing reveals the role of macrophage in liver disorders

Liver disorders such as hepatitis, cirrhosis and hepatocellular carcinoma are a series of the most life threatening diseases along with extensive inflammatory cellular infiltrations. Macrophage has been proved to be key regulators and initiators of inflammation, and long non-coding RNAs (lncRNAs) are recommended to play critical roles in the occurrence and development of a variety of diseases. To uncover the role of macrophage in liver disorders via lncRNA sequencing method, we first applied a lncRNA classification pipeline to identify 1247 lncRNAs represented on the Affymetrix Mouse Genome 430/430A 2.0 array. We then analyzed the lncRNA expression patterns in a set of previously published gene expression profiles of silica particle exposed macrophages and liver respectively, and identified and validated sets of differentially expressed lncRNAs shared by macrophages and liver. The functional enrichment analysis of these lncRNAs was processed on the basis of their expression signatures, three aspects including cis, trans and co-acting proteins were proposed. This is the first time to correlate macrophage with liver disorders via co-expressed lncRNAs. Our findings indicated that roles of macrophage in liver disorders were double-edged, the differentially expressed lncRNAs and their corresponding regulatory genes or proteins may serve as potential diagnostic biomarkers and therapeutic targets.