IL-32: an emerging player in the immune response network against tuberculosis?

Interleukin 32 as a Potential Marker for Diagnosis of Tuberculous Pleural Effusion

Accurate differential diagnosis is the key to choosing the correct treatment for pleural effusion. The present study aimed to assess whether interleukin 32 (IL-32) could be a new biomarker of tuberculous pleural effusion (TPE) and to explore the biological role of IL-32 in TPE. IL-32 levels were evaluated in the pleural effusions of 131 patients with undetermined pleural effusion from Wuhan and Beijing cohorts using an enzyme-linked immunosorbent assay method. Macrophages from TPE patients were transfected with IL-32-specific small interfering RNA (siRNA), and adenosine deaminase (ADA) expression was determined by real-time PCR and colorimetric methods. With a cutoff value of 247.9 ng/mL, the area under the curve of the receiver operating characteristic (ROC) curve for IL-32 was 0.933 for TPE, and the sensitivity and specificity were 88.4% and 93.4%, respectively. A multivariate logistic regression model with relatively good diagnostic performance was established. IL-32-specific siRNA downregulated ADA expression in macrophages, and IL-32γ treatment significantly induced ADA expression. Our results indicate that IL-32 in pleural effusion may be a novel biomarker for identifying patients with TPE. In addition, our multivariate model is acceptable to rule in or rule out TPE across diverse prevalence settings. Furthermore, IL-32 may modulate ADA expression in the tuberculosis microenvironment. (This study has been registered at ChiCTR under registration number ChiCTR2100051112 [https://www.chictr.org.cn/index.aspx].) IMPORTANCE Tuberculous pleural effusion (TPE) is a common form of extrapulmonary tuberculosis, with manifestations ranging from benign effusion with spontaneous absorption to effusion with pleural thickening, empyema, and even fibrosis, which can lead to a lasting impairment of lung function. Therefore, it is of great significance to find a rapid method to establish early diagnosis and apply antituberculosis therapy in the early stage. This study indicates that interleukin 32 (IL-32) in pleural effusion is a new high-potency marker to distinguish TPE from pleural effusions with other etiologies. A multivariate model combining age, adenosine deaminase (ADA), lactic dehydrogenase, and IL-32 may reliably rule in TPE in intermediate- or high-prevalence areas. Additionally, we observed that IL-32 might regulate ADA expression in macrophages in the tuberculosis microenvironment. Therefore, this study provides new insights into the role of IL-32 in the tuberculosis microenvironment.

Role of IL-32 Gamma on Bone Metabolism in Autoimmune Arthritis

IL-32 acts as a pro-inflammatory cytokine by inducing the synthesis of inflammatory molecules as well as promoting the morphological changes involved in the transformation of monocytes into osteoclasts (OCs). Evaluation of the functions of IL-32 has mainly focused on its inflammatory properties, such as involvement in the pathogenesis of various autoimmune diseases. Recently, IL-32 was shown to be involved in bone metabolism, in which it promotes the differentiation and activation of OCs and plays a key role in bone resorption in inflammatory conditions. IL-32γ also regulates bone formation in conditions such as ankylosing spondylitis and osteoporosis. In this review, we summarize the results of recent studies on the role of IL-32γ in bone metabolism in inflammatory arthritis.

Potential effect of exercise in ameliorating insulin resistance at transcriptome level

BACKGROUND

Insulin resistance can lead to the pathogenesis of type 2 diabetes and exercise can increase insulin sensitivity. And different exercises may have different influences on the mitigation of insulin resistance. It is still unclear how exercise affects inherited insulin resistance at transcriptome level. The purpose of our study was to analyze the potential effects of exercise in ameliorating insulin resistance at transcriptome level.

METHODS

Herein, we analyzed two skeletal muscle transcriptome profiles, including gene profiles between inherited insulin resistant patients and matched healthy controls, and between trained and sedentary subjects (young and old subjects, respectively).

RESULTS

Analysis of differentially expressed genes revealed that 12 genes (SGK1, LOC101929876, MYL5, COL6A3, MLF1, LUM, MSTN, COL1A2, COL3A1, IL32, IRS2, and ID1) associated with insulin resistance were reversed by exercise in young subjects, while six genes (MSTN, CFHR1, PFKFB3, IL32, RGCC, and NMRK2) were identified in old subjects, suggesting that those genes play potential roles in insulin resistance response to exercise. In addition, we observed that two insulin resistance-related genes, MSTN and IL32, were identified in muscle cells of both young and old subjects, indicating their important roles in the mechanisms behind the beneficial effects of exercise on humans with inherited insulin resistance. Several pathways were also identified, such as "collagen metabolic process," "focal adhesion," and "negative regulation of myoblast differentiation."

CONCLUSIONS

Taken together, our findings provide novel markers in insulin resistant patients and exercise, and some valuable information for future functional studies on how exercise ameliorating insulin resistance.

The expression of interleukin-32 is activated by human cytomegalovirus infection and down regulated by hcmv-miR-UL112-1

BACKGROUND

Interleukin-32 (IL-32) is an important factor in innate and adaptive immune responses, which activates the p38MAPK, NF-kappa B and AP-1 signaling pathways. Recent reports have highlighted that IL-32 is regulated during viral infection in humans.

METHODS

Enzyme-linked immunosorbent assays (ELISA) were carried out to detect IL-32 levels in serum samples. Detailed kinetics of the transcription of IL-32 mRNA and expression of IL-32 protein during human cytomegalovirus (HCMV) infection were determined by semi-quantitative RT-PCR and western blot, respectively. The expression levels of hcmv-miR-UL112-1 were detected using TaqMan® miRNA assays during a time course of 96 hours. The effects of hcmv-miR-UL112-1 on IL-32 expression were demonstrated by luciferase assay and western blot, respectively.

RESULTS

Serum levels of IL-32 in HCMV-IgM positive patients (indicating an active HCMV infection) were significantly higher than those in HCMV-IgM negative controls. HCMV infection activated cellular IL-32 transcription mainly in the immediately early (IE) phase and elevated IL-32 protein levels between 6 and 72 hours post infection (hpi) in the human embryonic lung fibroblast cell line, MRC-5. The expression of hcmv-miR-UL112-1 was detected at 24 hpi and increased gradually as the HCMV-infection process was prolonged. In addition, it was demonstrated that hcmv-miR-UL112-1 targets a sequence in the IL-32 3'-UTR. The protein level of IL-32 in HEK293 cells could be functionally down-regulated by transfected hcmv-miR-UL112-1.

CONCLUSIONS

IL-32 expression was induced by active HCMV infection and could be functionally down-regulated by ectopically expressed hcmv-miR-UL112-1. Our data may indicate a new strategy of immune evasion by HCMV through post-transcriptional regulation.

Characterizing antiviral mechanism of interleukin-32 and a circulating soluble isoform in viral infection

Interleukin-32 (IL-32) is an inflammatory cytokine, and its activity is associated with various auto-inflammatory disorders as well as infectious pathogens such as Mycobacterium tuberculosis, and viral infections. However, the precise antiviral mechanism of IL-32 remains unclear. We assessed the IL-32 level in the sera of H1N1 influenza A patients and IL-32 level was significantly elevated. Next we examined the antiviral activity of recombinant IL-32γ (rIL-32γ) with WISH cells infected by vesicular stomatitis virus (VSV) but no antiviral activity was observed. Therefore we investigated the supernatant of rIL-32-treated THP-1 cells since this cell line effectively responded to rIL-32γ. The supernatant of rIL-32-treated THP-1 cell possessed an antiviral effect and in addition, an agonistic monoclonal antibody further enhanced a specific antiviral activity of rIL-32γ. The fractionation and mass spectrometer analysis of the THP-1 cell supernatant revealed that the antiviral activity of rIL-32γ is via a THP-1 cell-produced factor, transferrin, rather than the direct effects of rIL-32γ on epithelial cells. We also characterized a secreted soluble IL-32γ protein in serum of IL-32γ transgenic mouse (TG), but not in that of IL-32α TG. The present results suggest that IL-32γ expression and its genetic variation in individual could be an important aspect of viral infections.

Therapeutic effectiveness of intratumorally delivered dendritic cells engineered to express the pro-inflammatory cytokine, interleukin (IL)-32

Interleukin-32 (IL-32) is a pro-inflammatory cytokine conditionally produced by T cells, natural killer (NK) cells, monocytes, epithelial cells and keratinocytes, which has an important role in host resistance against infectious disease. Interestingly, elevated levels of IL-32 transcripts in fine needle aspirates of tumor tissue have also been correlated with objective clinical responses in cancer patients receiving immunotherapy. To evaluate the antitumor impact of IL-32 gene therapy, we treated BALB/c mice bearing established subcutaneous CMS4 sarcomas with intratumoral (i.t.) injections of syngenic dendritic cells (DCs) engineered to express human IL-32β complementary DNA (that is, DC.IL32). Although ectopic expression of IL-32β by DC resulted in only modest phenotypic changes in these antigen-presenting cells, DC.IL32 produced higher levels of IL-12p70 than control DC. DC.IL32 were more potent activators of type-1 T-cell responses in vitro and in vivo, with i.t. administration of DC.IL32 leading to the CD8(+) T-cell-dependent (but CD4(+) T-cell- and NK cell-independent) suppression of tumor growth. Effective DC.IL32-based therapy promoted infiltration of tumors by type-1 (that is, CXCR3(+)VLA-4(+)GrB(+)) CD8(+) T cells and CD11b(+)CD11c(+) host myeloid DC, but led to reductions in the prevalence of CD11b(+)Gr1(+) myeloid-derived suppressor cells and CD31(+) blood vessels.

Nontypeable Haemophilus influenzae in chronic obstructive pulmonary disease and lung cancer

Chronic obstructive pulmonary disease (COPD) is predicted to become the third leading cause of death in the world by 2020. It is characterized by airflow limitation that is not fully reversible. The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lungs to noxious particles and gases, most commonly cigarette smoke. Among smokers with COPD, even following withdrawal of cigarette smoke, inflammation persists and lung function continues to deteriorate. One possible explanation is that bacterial colonization of smoke-damaged airways, most commonly with nontypeable Haemophilus influenzae (NTHi), perpetuates airway injury and inflammation. Furthermore, COPD has also been identified as an independent risk factor for lung cancer irrespective of concomitant cigarette smoke exposure. In this article, we review the role of NTHi in airway inflammation that may lead to COPD progression and lung cancer promotion.

Activation of the interleukin-32 pro-inflammatory pathway in response to human papillomavirus infection and over-expression of interleukin-32 controls the expression of the human papillomavirus oncogene

High-risk variants of human papillomavirus (HPV) induce cervical cancer by persistent infection, and are regarded as the principal aetiological factor in this malignancy. The pro-inflammatory cytokine interleukin-32 (IL-32) is present at substantial levels in cervical cancer tissues and in HPV-positive cervical cancer cells. In this study, we identified the mechanism by which the high-risk HPV-16 E7 oncogene induces IL-32 expression in cervical cancer cells. We used antisense transfection, over-expression, or knock-down of IL-32 to assess the effects of the HPV-16 E7 oncogene on IL-32 expression in cervical cancer cells. Cyclo-oxygenase 2 (COX-2) inhibitor treatment was conducted, and the expression levels, as well as the promoter activities, of IL-32 and COX-2 were evaluated in human HPV-positive cervical cancer cell lines. E7 antisense treatment reduced the expression levels and promoter activities of COX-2, which is constitutively expressed in HPV-infected cells. Constitutively expressed IL-32 was also inhibited by E7 antisense treatment. Moreover, IL-32 expression was blocked by the application of the selective COX-2 inhibitor, NS398, whereas COX-2 over-expression resulted in increased IL-32 levels. These results show that the high-risk variant of HPV induces IL-32 expression via E7-mediated COX-2 stimulation. However, E7 and COX-2 were down-regulated in the IL-32γ over-expressing cells and recovered by IL-32 small interfering RNA, indicating that E7 and COX-2 were feedback-inhibited by IL-32γ in cervical cancer cells.

Paradoxical effects of constitutive human IL-32{gamma} in transgenic mice during experimental colitis

Inflammatory cytokines mediate inflammatory bowel diseases (IBDs) and cytokine blocking therapies often ameliorate the disease severity. IL-32 affects inflammation by increasing the production of IL-1, TNFα, and several chemokines. Here, we investigated the role of IL-32 in intestinal inflammation by generating a transgenic (TG) mouse expressing human IL-32γ (IL-32γ TG). Although IL-32γ TG mice are healthy, constitutive serum and colonic tissue levels of TNFα are elevated. Compared with wild-type (WT) mice, IL-32γ TG mice exhibited a modestly exacerbated acute inflammation early following the initiation of dextran sodium sulfate (DSS)-induced colitis. However, after 6 d, there was less colonic inflammation, reduced tissue loss, and improved survival rate compared with WT mice. Associated with attenuated tissue damage, colonic levels of TNFα and IL-6 were significantly reduced in the IL-32γ TG mice whereas IL-10 was elevated. Cultured colon explants from IL-32γ TG mice secreted higher levels of IL-10 compared with WT mice and lower levels of TNFα and IL-6. Constitutive levels of IL-32γ itself in colonic tissues were significantly lower following DSS colitis. Although the highest level of serum IL-32γ occurred on day 3 of colitis, IL-32 was below constitutive levels on day 9. The ability of IL-32γ to increase constitutive IL-10 likely reduces TNFα, IL-6, and IL-32 itself accounting for less inflammation. In humans with ulcerative colitis (UC), serum IL-32 is elevated and colonic biopsies contain IL-32 in inflamed tissues but not in uninvolved tissues. Thus IL-32γ emerges as an example of how innate inflammation worsens as well as protects intestinal integrity.

IL-32: a host proinflammatory factor against influenza viral replication is upregulated by aberrant epigenetic modifications during influenza A virus infection

Our previous studies with clinical data analysis have shown that the proinflammatory factor IL-32 is activated in response to influenza virus infection. However, little is known about how influenza virus induces IL-32 production, and the role of IL-32 in the host immune responses during viral infection remains unclear. In this study, we show that IL-32 production is stimulated by influenza A virus or dsRNA in human PBMCs from healthy volunteers. We demonstrate that the NF-κB and CREB pathways play key roles in the activation of IL-32 production in response to influenza virus infection in A549 human lung epithelial cells. We then show that aberrant epigenetic modifications in the IL32 promoter are important in the transcriptional regulation of IL-32 expression. Interestingly, one CpG demethylation within the CREB binding site increases the binding of CREB to the promoter, which is followed by IL32 transcriptional activation in influenza A virus-infected cells. Overexpression assays combined with RNA interference show that DNA methyltransferases DNMT1 and DNMT3b are critical for IL32 promoter methylation and gene silencing before viral infection. We have demonstrated the anti-influenza virus function of IL-32. Assays for each of the six IL-32 isoforms (α, β, γ, δ, ε, and ζ) during influenza virus infection indicated that all the isoforms have antiviral activity, with different inhibitory rates, and that the effect of IL-32γ is strongest. Our results indicate that the elevated IL-32 levels triggered by influenza virus infection in turn hamper viral replication.

Interleukin-32 expression in the pancreas

Interleukin (IL)-32 is a recently described proinflammatory cytokine characterized by the induction of nuclear factor (NF)-kappaB activation. We studied IL-32 expression in human pancreatic tissue and pancreatic cancer cell lines. Tissue samples were obtained surgically. IL-32 expression was evaluated by standard immunohistochemical procedures. IL-32 mRNA expression was analyzed by Northern blotting and real time PCR analyses. IL-32 was weakly immunoexpressed by pancreatic duct cells. In the inflamed lesions of chronic pancreas, the ductal expression of IL-32 was markedly increased. A strong expression of IL-32alpha was detected in the pancreatic cancer cells. In pancreatic cancer cell lines (PANC-1, MIA PaCa-2, and BxPC-3 cells), the expression of IL-32 mRNA and protein was enhanced by IL-1beta, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha. An inhibitor of phosphatidylinositol 3-kinase (LY294002) significantly suppressed the IL-1beta-, IFN-gamma- and TNF-alpha-induced IL-32 mRNA expression. The blockade of NF-kappaB and activated protein-1 activation markedly suppressed the IL-1beta-, IFN-gamma-, and/or TNF-alpha-induced IL-32 mRNA expression. Furthermore, IL-32-specific small interfering RNA significantly decreased the uptake of [3H]thymidine and increased the annexin V-positive population (apoptotic cells) in PANC-1 cells. IL-32 knockdown also suppressed the mRNA expression of antiapoptotic proteins (Bcl-2, Bcl-xL, and Mcl-1). Pancreatic duct cells are the local source of IL-32, and IL-32 may play an important role in inflammatory responses and pancreatic cancer growth.

Mucosal cytokine network in inflammatory bowel disease

Inflammatory bowel disease (IBD), ulcerative colitis (UC) and Crohn’s disease (CD) are characterized by ongoing mucosal inflammation in which dysfunction of the host immunologic response against dietary factors and commensal bacteria is involved. The chronic inflammatory process leads to disruption of the epithelial barrier, and the formation of epithelial ulceration. This permits easy access for the luminal microbiota and dietary antigens to cells resident in the lamina propria, and stimulates further pathological immune cell responses. Cytokines are essential mediators of the interactions between activated immune cells and non-immune cells, including epithelial and mesenchymal cells. The clinical efficacy of targeting TNF-α clearly indicates that cytokines are the therapeutic targets in IBD patients. In this manuscript, we focus on the biological activities of recently-reported cytokines [Interleukin (IL)-17 cytokine family, IL-31 and IL-32], which might play a role through interaction with TNF-α in the pathophysiology of IBD.

Activation of interleukin-32 pro-inflammatory pathway in response to influenza A virus infection

Background

Interleukin (IL)-32 is a recently described pro-inflammatory cytokine that has been reported to be induced by bacteria treatment in culture cells. Little is known about IL-32 production by exogenous pathogens infection in human individuals.

Methods and Findings

In this study, we found that IL-32 level was increased by 58.2% in the serum samples from a cohort of 108 patients infected by influenza A virus comparing to that of 115 healthy individuals. Another pro-inflammatory factor cyclooxygenase (COX)-2-associated prostaglandin E2 was also upregulated by 2.7-fold. Expression of IL-32 in influenza A virus infected A549 human lung epithelial cells was blocked by either selective COX-2 inhibitor NS398 or Aspirin, a known anti-inflammatory drug, indicating IL-32 was induced through COX-2 in the inflammatory cascade. Interestingly, we found that COX-2-associate PGE₂ production activated by influenza virus infection was significantly suppressed by over-expression of IL-32 but increased by IL-32-specific siRNA, suggesting there was a feedback mechanism between IL-32 and COX-2.

Conclusions

IL-32 is induced by influenza A virus infection via COX-2 in the inflammatory cascade. Our results provide that IL-32 is a potential target for anti-inflammatory medicine screening.

Phosphatidylinositol 3-kinase/Akt signaling mediates interleukin-32alpha induction in human pancreatic periacinar myofibroblasts

Interleukin (IL)-32 is a recently described proinflammatory cytokine, characterized by the induction of nuclear factor (NF)-kappaB activation. We studied IL-32alpha expression in human pancreatic periacinar myofibroblasts, which play important roles in the regulation of extracellular matrix metabolism and inflammatory responses in the pancreas. IL-32alpha protein expression was evaluated by Western blot analyses, and IL-32alpha mRNA expression was analyzed by Northern blot and real-time PCR analyses. IL-32alpha mRNA was weakly expressed without a stimulus, and its expression was markedly enhanced by IL-1beta, IFN-gamma, and TNF-alpha. IL-1beta, IFN-gamma, and TNF-alpha enhanced intracellular accumulation of IL-32alpha protein, but IL-32alpha was not detected in supernatants. Each cytokine dose and time dependently induced IL-32alpha mRNA expression. An inhibitor of phosphatidylinositol 3-kinase (LY294002) significantly suppressed IL-1beta-, IFN-gamma-, and TNF-alpha-induced IL-32alpha mRNA expression, although MAPK inhibitors had no effect. Akt activation in response to these cytokines was confirmed by Western blot. Furthermore, LY294002 suppressed both IL-1beta- and TNF-alpha-induced NF-kappaB activation and IL-1beta-, TNF-alpha-, and IFN-gamma-induced activated protein-1 (AP-1) activation. Blockade of NF-kappaB and AP-1 activation by an adenovirus expressing a stable mutant form of IkappaBalpha and a dominant negative mutant of c-Jun markedly suppressed IL-1beta-, IFN-gamma-, and/or TNF-alpha-induced IL-32alpha mRNA expression. Human pancreatic periacinar myofibroblasts expressed IL-32alpha in response to IL-1beta, TNF-alpha, and IFN-gamma. IL-32alpha mRNA expression is dependent on interactions between the phosphatidylinositol 3-kinase/Akt-pathway and the NF-kappaB/AP-1 system.

Increased level of IL-32 during human immunodeficiency virus infection suppresses HIV replication

Interleukin-32 was recently identified as a pro-inflammatory cytokine produced by T-lymphocytes, natural killer cells, epithelial cells, and blood monocytes. IL-32 is induced by IFN-gamma in a time-dependent manner suggesting a role for IL-32 in innate and adaptive immune responses. In this study we present evidence that Human immunodeficiency virus promotes interleukin-32 production at both mRNA and protein levels. Our results showed that there is a 74% increase in the serum levels of IL-32 among HIV patients as compared to healthy individuals. There was a three-fold increase in the promoter activity of the IL-32 in the present infections HIV clone. This increase in IL-32 promoter activity was substantiated by increased IL-32 mRNA and protein levels. We have also demonstrated that IL-32 suppresses HIV replication. Our results show that HIV LTR activity was increased by more than six-folds when endogenous IL-32 was knocked down by IL-32-specific siRNA whereas it decreased by one-fold when IL-32 was over expressed in the cells. Similarly a more than two-fold increase and a 50% decrease in HIV p24 values were noted when IL-32 was knocked down and when IL-32 was over expressed in the cells, respectively. Our present work shows that raised IL-32 levels in HIV infection may in turn hamper HIV replication; one of the protective mechanisms of nature.

Epithelial overexpression of interleukin-32alpha in inflammatory bowel disease

Interleukin (IL)-32 is a recently described proinflammatory cytokine, characterized by induction of nuclear factor (NF)-kappaB activation. We studied IL-32alpha expression in the inflamed mucosa of inflammatory bowel disease (IBD). We also investigated mechanisms regulating IL-32alpha expression. Tissue samples were obtained endoscopically or surgically from patients with ulcerative colitis (UC) (n = 10), Crohn's disease (CD) (n = 10), ischaemic colitis (n = 4) and normal colorectal tissues (n = 10). IL-32alpha expression was evaluated by standard immunohistochemical procedure. IL-32 mRNA expression was analysed by Northern blot. IL-32alpha was expressed weakly by colonic epithelial cells from normal individuals and subjects with ischaemic colitis. In the inflamed mucosa of IBD patients, epithelial IL-32alpha expression was increased markedly. In UC and CD patients, IL-32alpha expression was enhanced in affected mucosa compared to non-affected mucosa. In intestinal epithelial cell lines, expression of IL-32alpha mRNA and protein was enhanced by IL-1beta, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha. A combination of TNF-alpha plus IFN-gamma exerted synergistic effects. IL-32alpha induction by IL-1beta and/or TNF-alpha was mediated by NF-kappaB activation. Epithelial IL-32alpha expression was increased in IBD patients, and in CD patients in particular. IL-32alpha might be involved in the pathophysiology of IBD as a proinflammatory cytokine and a mediator of innate immune response.