IL-16- and other CD4 ligand-induced migration is dependent upon protein kinase C

Genetically Predicted Levels of Circulating Inflammatory Cytokines and the Risk and Age at Onset of Parkinson’s Disease: A Two-Sample Mendelian Randomization Study

Parkinson’s disease (PD) is widely considered to be a disabling neurodegenerative disorder, which has been ranked second worldwide just after Alzheimer’s disease. Until present, a wide range of studies has focused on the role of circulating inflammatory cytokines in the development of PD. However, the causal relationship between circulating inflammatory cytokines and the risk and age at the onset of PD has not been elucidated. Hence, to evaluate the effects of circulating inflammatory cytokines on the risk or age at the onset of PD more accurately, we conducted this two-sample Mendelian randomization (MR) study involving summary statistics from genome-wide association studies (GWASs). Totally, we included a GWAS for inflammatory cytokines (8,293 participants), a meta-analysis of GWASs for PD risk (482,730 participants), and a GWAS dataset for age at the onset of PD (17,996 patients with PD). A total of 149 and 131 polymorphisms for exploring relationships between 19 inflammatory cytokines and the risk and age at the onset of PD were obtained as instrumental variants. Then, we used a total of five MR methods, including inverse-variance weighted (IVW), Wald ratio, MR Egger regression, weighted median, and MR-pleiotropy residual sum and outlier (MR-PRESSO) methods. Finally, we found a causal association between circulating levels of macrophage inflammatory protein-1 beta (MIP1b) and PD risk in the IVW method (OR: 1.06; 95% CI: 1.02–1.10; P = 0.001). Meanwhile, other MR estimates by weighted median and MR-PRESSO methods yielded similar effect estimates. Besides, we identified a suggestive association of interleukin-16 (IL-16) levels with PD risk (OR: 1.08; 95% CI: 1.00–1.17; P = 0.037). For age at PD onset, there was no evidence supporting its correlation with inflammatory cytokines. Our findings implied that MIP1b and IL-16 may be novel biomarkers and promising therapeutic targets for PD development.

CCL3 contributes to secondary damage after spinal cord injury

Background

Secondary damage after spinal cord injury (SCI) is characterized by a cascade of events including hemorrhage, apoptosis, oxidative stress, and inflammation which increase the lesion size which can influence the functional impairment. Thus, identifying specific mechanisms attributed to secondary injury is critical in minimizing tissue damage and improving neurological outcome. In this work, we are investigating the role of CCL3 (macrophage inflammatory protein 1-α, MIP-1α), a chemokine involved in the recruitment of inflammatory cells, which plays an important role in inflammatory conditions of the central and peripheral nervous system.

Methods

A mouse model of lower thoracic (T11) spinal cord contusion injury was used. We assessed expression levels of CCL3 and its receptors on the mRNA and protein level and analyzed changes in locomotor recovery and the inflammatory response in the injured spinal cord of wild-type and CCL3^−/− mice.

Results

The expression of CCL3 and its receptors was increased after thoracic contusion SCI in mice. We then examined the role of CCL3 after SCI and its direct influence on the inflammatory response, locomotor recovery and lesion size using CCL3^−/− mice. CCL3^−/− mice showed mild but significant improvement of locomotor recovery, a smaller lesion size and reduced neuronal damage compared to wild-type controls. In addition, neutrophil numbers as well as the pro-inflammatory cytokines and chemokines, known to play a deleterious role after SCI, were markedly reduced in the absence of CCL3.

Conclusion

We have identified CCL3 as a potential target to modulate the inflammatory response and secondary damage after SCI. Collectively, this study shows that CCL3 contributes to progressive tissue damage and functional impairment during secondary injury after SCI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-020-02037-3.

Oral immunization of BALB/c mice with recombinant Helicobacter pylori antigens and double mutant heat-labile toxin (dmLT) induces prophylactic protective immunity against H. pylori infection

Helicobacter pylori infection and associated diseases remain a major public health problem worldwide. Much effort has been made over the last several decades in vaccine development, but there is no licensed vaccine on the market. We have previously reported that oral immunization with H. pylori lysates and double mutant heat-labile toxin (dmLT) affords prophylactic protection against H. pylori infection in mice. In the present study, we investigated the effects of oral immunization with recombinant H. pylori protein antigens (NAP/UreA/UreB) and dmLT on H. pylori challenge in BALB/c mice. We found that oral immunization with candidate antigens and dmLT significantly reduced the gastric colonization of H. pylori 6 weeks after challenge, as compared to unimmunized mice. Moreover, the subunit vaccine appeared to provide a better protection than the bacterial lysate vaccine. The immunized mice showed enhanced antigen-specific lymphocyte proliferation, and serum IgG and mucosal IgA responses. Furthermore, the immunization increased the proportion of CD4⁺ IL-17+ lymphocytes in spleen and mesenteric lymph nodes, and enhanced the production of IL-17, IL-16, IL-6 and TNF-α in lymphocyte culture supernatants. Taken together, our results suggest that oral vaccination with recombinant H. pylori antigens (NAP/UreA/UreB) and dmLT confers more effective prophylactic protection against H. pylori infection than whole bacterial lysates in BALB/c mice. The reduction of H. pylori colonization was associated with the induction of antigen-specific Th17 and local mucosal IgA immune responses.

IL-16/miR-125a axis controls neutrophil recruitment in pristane-induced lung inflammation

Severe lung inflammation and alveolar hemorrhage can be life-threatening in systemic lupus erythematosus (SLE) patients if not treated early and aggressively. Neutrophil influx is the driver key of this pathology, but little is known regarding the molecular events regulating this recruitment. Here, we uncover a role for IL-16/mir-125a in this pathology and show not only that IL-16 is a target for miR-125a but that reduced miR-125a expression in SLE patients associates with lung involvement. Furthermore, in the pristane model of acute "SLE-like" lung inflammation and alveolar hemorrhage, we observed reduced pulmonary miR-125a and enhanced IL-16 expression. Neutrophil infiltration was markedly reduced in the peritoneal lavage of pristane-treated IL-16-deficient mice and elevated following i.n. delivery of IL-16. Moreover, a miR-125a mimic reduced pristane-induced IL-16 expression and neutrophil recruitment and rescued lung pathology. Mechanistically, IL-16 acts directly on the pulmonary epithelium and markedly enhances neutrophil chemoattractant expression both in vitro and in vivo, while the miR-125a mimic can prevent this. Our results reveal a role for miR-125a/IL-16 in regulating lung inflammation and suggest this axis may be a therapeutic target for management of acute lung injury in SLE.

Host nucleotide polymorphism in hepatitis B virus-associated hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is etiologically linked with hepatitis B virus (HBV) and is the leading cause of death amongst 80% of HBV patients. Among HBV affected patients, genetic factors are also involved in modifying the risk factors of HCC. However, the genetic factors that regulate progression to HCC still remain to be determined. In this review, we discuss several single nucleotide polymorphisms (SNPs) which were reportedly associated with increased or reduced risk of HCC occurrence in patients with chronic HBV infection such as cyclooxygenase (COX)-2 expression specifically at COX-2 -1195G/A in Chinese, Turkish and Egyptian populations, tumor necrosis factor α and the three most commonly studied SNPs: PAT-/+, Lys939Gln (A33512C, rs2228001) and Ala499Val (C21151T, rs2228000). In genome-wide association studies, strong associations have also been found at loci 1p36.22, 11q22.3, 6p21 (rs1419881, rs3997872, rs7453920 and rs7768538), 8p12 (rs2275959 and rs37821974) and 22q11.21. The genes implicated in these studies include HLA-DQB2, HLA-DQA1, TCF19, HLA-C, UBE2L3, LTL, FDX1, MICA, UBE4B and PG. The SNPs found to be associated with the above-mentioned genes still require validation in association studies in order to be considered good prognostic candidates for HCC. Screening of these polymorphisms is very beneficial in clinical experiments to stratify the higher or lower risk for HCC and may help in designing effective and efficient HCC surveillance programs for chronic HBV-infected patients if further genetic vulnerabilities are detected.

p21WAF1 Is Required for Interleukin-16-Induced Migration and Invasion of Vascular Smooth Muscle Cells via the p38MAPK/Sp-1/MMP-9 Pathway

Interleukin-16 (IL-16) is a lymphocyte chemoattractant factor well known for its role in immune responses, but its role in vascular disease is unknown. Here, we explored the novel physiological function of IL-16 in vascular smooth muscle cells (VSMCs). The expression of IL-16 and its receptor CD4 was observed in VSMCs. Treatment with IL-16 enhanced the migration and invasion by VSMCs without altering the proliferative potential. IL-16 induced MMP-9 expression via the binding activity of transcription factors NF-κB, AP-1, and Sp-1 motifs in VSMCs. Among the relevant signaling pathways examined, only p38MAPK phosphorylation was significantly stimulated in IL-16-treated VSMCs. Treatment with p38MAPK inhibitor SB203580 prevented the IL-16-induced migration and invasion of VSMCs. SB203580 treatment inhibited the MMP-9 expression and activation of Sp-1 binding in IL-16-treated VSMCs, and siRNA knockdown of CD4 expression blocked the induction of migration, invasion, p38MAPK phosphorylation, MMP-9 expression, and Sp-1 binding activation stimulated by IL-16. The IL-16 induced cell-cycle-inhibitor p21WAF1 expression in VSMCs, but had no effect on the expression levels of other cell-cycle negative regulators. Finally, blockage of p21WAF1 function with specific siRNA abolished the IL-16-induced elevation of migration, invasion, p38MAPK phosphorylation, MMP-9 expression, and Sp-1 binding activation in VSMCs. Taken together, p21WAF1 was required for the induction of p38MAPK-mediated MMP-9 expression via activation of the Sp-1 binding motif, which led to migration and invasion of VSMCs interacting with IL-16/CD4. These results could provide that IL-16 is a new target in the treatment of vascular diseases such as atherosclerosis and re-stenosis.

CCR4+T cell recruitment to the skin in mycosis fungoides: potential contributions by thymic stromal lymphopoietin and interleukin-16

Mycosis fungoides (MF) is characterized by skin accumulation of CCR4+CCR7- effector memory T cells; however the mechanism for their recruitment is not clearly identified. Thymic Stromal Lymphopoietin (TSLP) is a keratinocyte-derived cytokine that triggers Th2 immunity and is associated with T cell recruitment to the skin in atopic dermatitis. Interleukin-16 (IL-16) is a chemoattractant and growth factor for CD4+T cells. We hypothesized that TSLP and IL-16 could contribute to recruitment of malignant T cells in MF. We found elevated TSLP and IL-16 in very early stage patients' plasma and skin biopsies, prior to elevation in CCL22. Both TSLP and IL-16 induced migratory responses of CCR4+TSLPR+CD4+CCR7-CD31+cells, characteristic of malignant T cells in the skin. Co-stimulation also resulted in significant proliferative responses. We conclude that TSLP and IL-16, expressed at early stages of disease, function to recruit malignant T cells to the skin and contribute to their enhanced proliferation.

Functional characterization of late outgrowth endothelial progenitor cells in patients with end-stage renal failure

Renal transplantation is potentially curative in renal failure, but long-term efficacy is limited by untreatable chronic rejection. Endothelial damage contributes to chronic rejection and is potentially repairable by circulating endothelial progenitor cells (EPC). The frequency and function of EPC are variably influenced by end-stage renal failure (ESRF). Here, we isolated and functionally characterized the late outgrowth EPC (LO-EPC) from ESRF patients to investigate their potential for endothelial repair. Patients with ESRF generated more LO-EPC colonies than healthy controls and had higher plasma levels of IL-1rα, IL-16, IL-6, MIF, VEGF, Prolactin, and PLGF. Patients' LO-EPC displayed normal endothelial cell morphology, increased secretion of PLGF, MCP-1, and IL-1β, and normal network formation in vitro and in vivo. They demonstrated decreased adhesion to extracellular matrix. Integrin gene profiles and protein expression were comparable in patients and healthy volunteers. In some patients, mesenchymal stem cells (MSC) were co-isolated and could be differentiated into adipocytes and osteocytes in vitro. This is the first study to characterize LO-EPC from patients with ESRF. Their behavior in vitro reflects the presence of elevated trophic factors; their ability to proliferate in vitro and angiogenic function makes them candidates for prevention of chronic rejection. Their impaired adhesion and the presence of MSC are areas for potential therapeutic intervention.

Regulation of cellular processes by interleukin-16 in homeostasis and cancer

Interleukin-16 (IL-16) is generated as a precursor molecule that is cleaved by caspase-3 to produce a pro-IL-16 molecule that functions as a regulator of T cell growth, and a secreted peptide that functions as a CD4 and/or CD9 ligand for induction of cell motility and activation. IL-16 has been predominantly studied as a contributing factor in the orchestration of an immune response; however, more recently IL-16 bioactivity has been closely associated with the progression of a number of different cancers. While the association between IL-16 plasma levels and tumor progression has been reported for many types of cancer, the mechanism for IL-16 involvement has been partially elucidated for three of the cancer types, cutaneous T cell lymphoma (CTCL), multiple myeloma (MM), and breast cancer. The mechanism for promoting cell growth is different in each of these cancers and involves a sequence mutation in the pro-molecule facilitating decreased p27(KIP1) levels in CTCL; over expression of the secreted IL-16 molecule to induce proliferation in CTCL T cells, and plasma cells in MM; and increased secreted IL-16 acting to recruit CD4+ pro-tumor macrophages in breast cancer. This article will review the cellular process for generating IL-16, the biological activities for both the pro- and secreted forms of the protein, and then the mechanism by which these forms contribute to cancer progression. As a soluble cytokine the ability to reduce or eliminate IL-16 synthesis through siRNA approaches or bioactivity through the use of neutralizing antibody treatment may represent a novel therapeutic approach.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

The identification of unique serum proteins of HIV-1 latently infected long-term non-progressor patients

BACKGROUND

The search for disease biomarkers within human peripheral fluids has become a favorable approach to preventative therapeutics throughout the past few years. The comparison of normal versus disease states can identify an overexpression or a suppression of critical proteins where illness has directly altered a patient's cellular homeostasis. In particular, the analysis of HIV-1 infected serum is an attractive medium with which to identify altered protein expression due to the ease and non-invasive methods of collecting samples as well as the corresponding insight into the in vivo interaction of the virus with infected cells/tissue. The utilization of proteomic techniques to globally identify differentially expressed serum proteins in response to HIV-1 infection is a significant undertaking that is complicated due to the innate protein profile of human serum.

RESULTS

Here, the depletion of 12 of the most abundant serum proteins, followed by two-dimensional gel electrophoresis coupled with identification of these proteins using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, has allowed for the identification of differentially expressed, low abundant serum proteins. We have analyzed and compared serum samples from HIV-1 infected subjects who are being treated using highly active antiretroviral therapy (HAART) to those who are latently infected but have not progressed to AIDS despite the absence of treatment, i.e. long term non-progressors (LTNPs). Here we have identified unique serum proteins that are differentially expressed in LTNP HIV-1 patients and may contribute to the ability of these patients to combat HIV-1 infection in the absence of HAART. We focused on the cdk4/6 cell cycle inhibitor p16INK4A and found that the treatment of HIV-1 latently infected cell lines with p16INK4A decreases viral production despite it not being expressed endogenously in these cells.

CONCLUSIONS

Identification of these unique proteins may serve as an indication of altered viral states in response to infection as well as a natural phenotypic variability in response to HIV-1 infection in a given population.

Measurement of interleukin 16

Interleukin 16 (IL-16) is a chemoattractant immunomodulatory cytokine that initiates its cellular responses through interaction with membrane-expressed CD4. The protein may be detected by a number of methods; the choice of protocol will depend on the ultimate object of a particular experiment. The first method presented is the use of ELISA to measure IL-16 in cell culture supernatants or biological fluids. For some applications, such as identification of IL-16 in an unknown fluid or medium or direct assessment of its bioactivity, functional assays of IL-16-induced responses may be more appropriate. The chemotactic effects of IL-16 on CD4+ T cells and its specific inhibition may be measured using anti-IL-16 antibodies; the same approach may also be applied to monocytes or eosinophils. Another effect of IL-16 is the induction of CD25, which can be assayed using immunological staining. Finally, cell cycle progression in target cells can be measured by the incorporation of radiolabeled thymidine and confirmed by inhibition with neutralizing antibody.

IL-16 signaling specifically induces STAT6 activation through CD4

Biologic activities of IL-16 have been well described (e.g., chemotaxis of CD4+ cells, CD25 upregulation, secretion of IL-1b, IL-4 and TNF-a secretion) but very few signaling events have been described. To gain a better understanding of how the biologic activities of IL-16 are regulated following receptor engagement (CD4) we have analyzed the activation state of numerous STAT proteins in primary human peripheral blood mononuclear cells (PBMCs) and the human monocytic cell line THP-1 following IL-16 stimulation. Of the four STAT proteins tested, only STAT6 was activated (phosphorylated) in a dose-dependant manner by IL-16. The activation of STAT6 was completely abolished when IL-16 was pre-incubated with soluble CD4 (the IL-16 cell surface receptor), demonstrating the need for CD4 engagement in STAT6 activation. These results are the first to demonstrate a link between IL-16 and STAT6 activation.

Chemokine Receptor CXCR3 Desensitization by IL-16/CD4 Signaling Is Dependent on CCR5 and Intact Membrane Cholesterol

Previous work has shown that IL-16/CD4 induces desensitization of both CCR5- and CXCR4-induced migration, with no apparent effect on CCR2b or CCR3. To investigate the functional relationship between CD4 and other chemokine receptors, we determined the effects of IL-16 interaction with CD4 on CXCR3-induced migration. In this study we demonstrate that IL-16/CD4 induced receptor desensitization of CXCR3 on primary human T cells. IL-16/CD4 stimulation does not result in surface modulation of CXCR3 or changes in CXCL10 binding affinity. This effect does require p56(lck) enzymatic activity and the presence of CCR5, because desensitization is not transmitted in the absence of CCR5. Treatment of human T cells with methyl-beta-cyclodextrin, a cholesterol chelator, prevented the desensitization of CXCR3 via IL-16/CD4, which was restored after reloading of cholesterol, indicating a requirement for intact cholesterol. These studies demonstrate an intimate functional relationship among CD4, CCR5, and CXCR3, in which CCR5 can act as an adaptor molecule for CD4 signaling. This process of regulating Th1 cell chemoattraction may represent a mechanism for orchestrating cell recruitment in Th1-mediated diseases.

The role of glycosphingolipids in HIV signaling, entry and pathogenesis

Although HIV uses CD4 and coreceptors (CCR5 and CXCR4) for productive infection of T cells, glycosphingolipids (GSL) may play ancillary roles in lymphoid and non-lymphoid cells. Interactions of the HIV Envelope Glycoprotein (Env) with GSL may help HIV in various steps of its pathogenesis. Physical-chemical aspects of the interactions between HIV Env and GSL leading to CD4-dependent entry into lymphocytes, the role of GSL in HIV transcytosis, and CD4-independent entry into non-lymphoid cells are reviewed. An overview of signaling properties of HIV receptors is provided with some speculation on how GSL may play a role in these events by virtue of being in membrane rafts. Finally, we summarize how interactions between HIV and coreceptors leading to signaling and/or fusion can be analyzed by the use of various tyrosine kinase and cytoskeletal inhibitors.

Human and mouse mast cells use the tetraspanin CD9 as an alternate interleukin-16 receptor

Interleukin-16 (IL-16) induces the chemotaxis and activation of mast cells (MCs) and other cell types. While it has been concluded that CD4 is the primary IL-16 receptor on T cells, at least one other IL-16 receptor exists. We now show that the IL-16-responsive human MC line HMC-1 lacks CD4, and that the IL-16-mediated chemotactic and Ca2+ mobilization responses of this cell can be blocked by anti-CD9 monoclonal antibodies (mAbs) but not by mAbs directed against CD4 or other tetraspanins. Anti-CD9 mAbs also inhibited the IL-16-mediated activation of nontransformed human cord blood-derived MCs and mouse bone marrow-derived MCs by 50% to 60%. The chemotactic response of HMC-1 cells to IL-16, as well as the binding of the cytokine to the cell's plasma membrane, was inhibited by CD9-specific antisense oligonucleotides. CD9 is therefore essential for the IL-16-mediated chemotaxis and activation of the HMC-1 cell line. In support of this conclusion, IL-16 bound to CD9-expressing CHO cell transfectants. The ability of wortmannin and xestopongin C to inhibit the IL-16-mediated chemotactic response of these cells suggests that the cytokine activates a phosphatidylinositol 3-kinase (PI3K)/inositol trisphosphate-dependent signaling pathway in MCs. This is the first report of a tetraspanin that plays a prominent role in a cytokine-mediated chemotactic response of human MCs.

Interleukin-16 and peptide derivatives as immunomodulatory therapy in allergic lung disease

The therapeutic potential of interleukin (IL)-16 and derived peptides in allergic asthma is considered, focusing on key interactions with CD4 and associated chemokine receptors. IL-16 is a pleiotropic cytokine that has multiple effector functions with putative roles in varied T cell-mediated inflammatory diseases, such as asthma, inflammatory bowel disease and atopic dermatitis. Both in vitro and in vivo, IL-16 downregulates antigen-driven T cell activation, T helper 2 cytokine production and allergic airway inflammation. Peptides derived from the C-terminal bioactive portion of IL-16 offer advantages related to their retained immunomodulatory properties and absence of signalling in and chemoattraction to T cells.

Cardiovascular diabetology in the core of a novel interleukins classification: the bad, the good and the aloof

Background

The impressive correlation between cardiovascular disease and glucose metabolism alterations has raised the likelihood that atherosclerosis and type 2 diabetes may share common antecedents. Inflammation is emerging as a conceivable etiologic mechanism for both. Interleukins are regulatory proteins with ability to accelerate or inhibit inflammatory processes.

Presentation of the hypothesis

A novel interleukins classification is described, based on their role in diabetes and atherosclerosis, hypothesizing that each interleukin (IL) acts on both diseases in the same direction – regardless if harmful, favorable or neutral.

Testing the hypothesis

The 29 known interleukins were clustered into three groups: noxious (the "bad", 8 members), comprising IL-1, IL-2, IL-6, IL-7, IL-8, IL-15, IL-17 and IL-18; protective (the "good", 5 members), comprising IL-4, IL-10, IL-11, IL-12 and IL-13; and "aloof", comprising IL-5, IL-9, IL-14, IL-16 and IL-19 through IL-29 (15 members). Each group presented converging effects on both diseases. IL-3 was reluctant to clustering.

Implications

These observations imply that 1) favorable effects of a given IL on either diabetes or atherosclerosis predicts similar effects on the other; 2) equally, harmful IL effects on one disease can be extrapolated to the other; and 3) absence of influence of a given IL on one of these diseases forecasts lack of effects on the other. These facts further support the unifying etiologic theory of both ailments, emphasizing the importance of a cardiovascular diabetologic approach to interleukins for future research. Pharmacologic targeting of these cytokines might provide an effective means to simultaneously control both atherosclerosis and diabetes.

IL-16 in the airways of lung allograft recipients with acute rejection or obliterative bronchiolitis

Acute rejection (AR) is the principal risk factor for obliterative bronchiolitis (OB), the major complication of lung transplantation. It is known that activated CD4+ T lymphocytes are involved in the development of AR and that interleukin (IL)-16 can inhibit the activity of CD4+ T lymphocytes. In this study, we evaluated whether the concentration of IL-16 in the airways is altered in AR or OB and, if so, how this IL-16 concentration relates to the number or activity of airway lymphocytes. The concentration of IL-16 protein was measured in bronchoalveolar lavage (BAL) fluid at three time-points in lung allograft recipients with either AR or OB and in matched controls using ELISA. The concentration of soluble IL-2 receptor (R) protein was measured in BAL fluid using ELISA as well, as an indicator of lymphocyte activity. The percentage of airway lymphocytes was evaluated by performing BAL differential cell counts. Lung allograft recipients with AR displayed lower IL-16 concentrations compared with matched control patients and this IL-16 concentration correlated negatively with the sIL-2R concentration, but it did not correlate with the percentage of lymphocytes in BAL fluid. In contrast, in BAL fluid from lung allograft recipients with OB, the IL-16 concentration was not altered compared with matched control patients and it did not correlate with the percentage of lymphocytes or with the sIL-2R concentration. These data are compatible with an increase in IL-16 playing a protective role against AR but not against OB and, hypothetically, this type of protective effect could be exerted via a down-regulation of the activity of T lymphocytes.

CD4 dependence of gp120IIIB-CXCR4 interaction is cell-type specific

The HIV-1 envelope protein gp120IIIB is selective for the CXCR4 chemokine receptor and has been shown to induce apoptosis in neurons both in vivo and in vitro. We examined the ability of gp120IIIB to signal through the rat CXCR4 (rCXCR4) receptor and its dependence on the presence of the human CD4 (hCD4) protein in a number of cell systems. SDF-1alpha potently inhibited N-type Ca channels in cultured HEK293 cells expressing both the Ca channel subunits and rCXCR4 receptors. However, gp120IIIB was ineffective in producing either Ca channel inhibition or in blocking the effects of SDF-1alpha. However, when hCD4 was coexpressed with rCXCR4 and Ca channel subunits, gp120IIIB also produced Ca channel inhibition. Similarly, in PC12 cells transfected with the rCXCR4, SDF-1alpha produced mobilization of intracellular Ca, while gp120IIIB was only effective when hCD4 was coexpressed. SDF-1alpha induced endocytosis of Yellow Fluorescent Protein (YFP)-tagged rCXCR4 expressed in PC12 cells, as did gp120IIIB, an effect which was enhanced by hCD4 coexpression. When tagged rCXCR4 was expressed in F-11 cells or in rat DRG neurons, SDF-1alpha produced extensive receptor endocytosis. However, the ability of gp120IIIB to produce endocytosis was dependent on the coexpression of hCD4. Our results demonstrate that the degree of hCD4 dependence of the agonist effects of gp120IIIB at the rCXCR4 receptor is cell-type specific.

Effect of caprine arthritis-encephalitis virus infection on expression of interleukin-16 in goats

OBJECTIVE

To determine the effect of caprine arthritis-encephalitis virus (CAEV) infection on expression of interleukin-16 (IL-16).

ANIMALS

6 goats experimentally infected with CAEV and 6 age-matched healthy uninfected control goats.

PROCEDURE

Peripheral blood mononuclear cells (PBMCs) and synovial membrane cells from infected and control goats cultured with or without phytohemagglutinin were analyzed for IL-16 mRNA by use of a reverse transcriptase-polymerase chain reaction assay with goat-specific primers, after cloning and sequencing of a 384-bp fragment of the goat IL-16 gene. Synovial fluid, serum, and culture supernatants of PBMCs and synovial cells of control and CAEV-infected goats were analyzed for IL-16 by use of an ELISA.

RESULTS

The 384-bp product was 86% homologous to the corresponding human IL-16 nucleotide sequence. Higher expression of IL-16 mRNA in PBMCs (unstimulated or stimulated with phytohemagglutinin) was detected in samples from CAEV-infected goats, compared with control goats, but the difference was not significant. Synovial membrane cells infected in vitro had higher expression than uninfected control cells. Higher IL-16 concentration was detected in synovial fluid, serum, and culture supernatants of PBMCs of infected goats than in samples from control goats.

CONCLUSIONS AND CLINICAL RELEVANCE

infection with CAEV increases expression of IL-16, a proinflammatory and chemotactic cytokine. This cytokine appears to be constitutively expressed at low concentrations in normal uninfected PBMCs and synovial membrane cells. Increased production of IL-16 in CAEV infection may partly be responsible for increased lymphoid cell infiltrations observed in arthritic joints and other tissues of CAEV-infected goats.

Relationship between CD4(+)/CD8(+) T cell ratio and T cell activation in multiple myeloma: reference to IL-16

We found that the ratio of CD4(+) to CD8(+) T cells (CD4/CD8 ratio) was decreased in patients with multiple myeloma (MM) and that this decrease was significantly related to an increase of human leukocyte antigen (HLA)-DR expression by CD8(+) (but not CD4(+)) T cells (P<0.005). In addition, the serum level of interleukin (IL)-16 was significantly higher in stage III MM patients than in healthy controls (P<0.001). The decrease of CD4(+) T cells in MM may be mediated by activation of CD8(+) T cells derived cytokine IL-16. In addition, these T cell phenotypic changes and the IL-16 level appear to be useful indicators of disease activity.

Functional IL-2 receptor beta (CD122) and gamma (CD132) chains are expressed by fibroblast-like synoviocytes: activation by IL-2 stimulates monocyte chemoattractant protein-1 production

The expression of the IL-2R alpha-, beta-, and gamma-chains, CD25, CD122, and CD132, respectively, was investigated on fibroblast-like synoviocytes (FLS) and dermal fibroblasts (DF). Both protein and mRNA for CD122 and CD132 were observed but there was no evidence of CD25 expression. Quantification of the Ag binding sites for CD122 showed that FLS expressed 4 times more receptor molecules than DF. The functional capability of these receptors was confirmed by the production of monocyte chemoattractant protein-1 (MCP-1) in direct response to stimulation by IL-2, which could be inhibited by neutralizing anti-CD122 mAb. Both rheumatoid arthritis (RA) and osteoarthritis (OA) FLS and DF spontaneously produced MCP-1 in culture over a similar range of concentrations. However, RA and OA FLS produced significantly greater levels of MCP-1 following stimulation by IL-2 and IL-1 beta; RA FLS produced significantly more MCP-1 than OA FLS. Addition of exogenous IL-2 caused a slight, but significant, decrease in MCP-1 production by DF. The addition of neutralizing anti-CD122 mAb to FLS cultures partially, but significantly, reduced the IL-2-induced MCP-1 secretion, but did not effect either the spontaneous or IL-1 beta-induced secretion of MCP-1. Increased tyrosine phosphorylation was observed in FLS lysates following 30-min incubation with IL-2. In conclusion, in the inflamed synovium, as activated T cells migrate through the sublining and lining layer, T cell-derived IL-2 may activate FLS to secrete MCP-1, thus recruiting macrophages into the rheumatoid synovium and perpetuating inflammation.

Regulation of allergic airways inflammation by cytokines and glucocorticoids

Cytokines mediate the allergic inflammatory response of the airways, and glucocorticosteroids ameliorate allergy symptoms by regulating cytokine expression. Recent studies provide insight into the manner by which cytokines work together to mediate allergic airway disease. Real progress has also been gained in our understanding of subcellular mechanisms of allergic inflammation, particularly the role of transcription factors in regulating the expression of specific cytokine profiles and the differentiation of the TH2 subset. This article provides an update of recently reported findings in this field and highlights emerging concepts of allergic inflammation.

The changes of protein kinase C activity in peripheral blood lymphocytes in the patients with obstructive jaundice and the implication

The roles of protein kinase C (PKC) signal pathway in the pathogenesis of obstructive jaundice were studied. PKC from cytosolic and membrane fractions of peripheral blood lymphocytes (PBL) in 51 patients with obstructive jaundice and 16 cases of normal controls was isolated and purified. The activities of PKC were determined by radioactive isotope gamma-32P-ATP-catalyzing assay. The results showed that the total PKC activities in PBL in the patients with obstructive jaundice were significantly increased as compared with those in the normal controls (P < 0.01). Moreover, the membrane PKC activities and their percentages of the total PKC activities were higher in obstructive jaundice group than in those in the normal controls (P < 0.05). The total PKC activities in PBL in the patients with obstructive jaundice were significantly positively correlated with the levels of soluble IL-2 receptor (sIL-2R) (r = 0.58, P < 0.01) and the degree of jaundice (T-BIL) (r = 0.67, P < 0.01) in serum. It was concluded that the activities of PKC signal pathway was related with the degree of T-BIL. PKC signal pathway might took part in the activation of T-lymphocytes in the patients with obstructive jaundice and play an important role in the immune regulation and the assessment of pathosis in the patients with obstructive jaundice.

Antigen triggering selectively increases TCRBV gene transcription

When the TCR binds Ag it is phosphorylated, internalized, and degraded. We wished to examine whether this process was accompanied by a specific concomitant increase in TCR mRNA levels. To do this, PBMC and a T cell clone were cultured with a series of superantigens and an alloantigen. Only T cells specifically responding to an antigenic stimulus had increased levels of TCR beta-chain variable (TCRBV)-specific mRNA. This response was apparent after 48 h, peaked around 72 h, and was still elevated after 7 days. Increased gene transcription appeared to be driven solely by Ag as specific Ag depletion prevented culture supernatants transferring this effect. The level of TCRBV mRNA elevation was not influenced by the stimulating Ag, but appeared dependent on the gene encoding the stimulated TCR. Reporter gene assays, using cloned TCRBV gene promoters, confirmed both that TCR gene transcription rises after stimulation and that basal and stimulated levels of TCR transcription vary between different TCRBV genes. These data conclusively demonstrate that there is no direct relationship between TCRBV mRNA and T cell number, and that future repertoire studies must take both factors into account.

Inhibition of Tyrosine Kinase Activation Blocks the Down-Regulation of CXC Chemokine Receptor 4 by HIV-1 gp120 in CD4+ T Cells

Because the binding of HIV-1 envelope to CD4 initiates a configurational change in glycoprotein 120 (gp120), enabling it to interact with fusion coreceptors, we investigated how this process interferes with the expression and function of CXC chemokine receptor 4 (CXCR4) in CD4+ T lymphocytes. A recombinant gp120 (MN), after preincubation with CD4+ T lymphocytes, significantly inhibited the binding and chemotaxis of the cells in response to the CXCR4 ligand stromal cell-derived factor-1α (SDF-1α), accompanied by a markedly reduced surface expression of CXCR4. gp120, but not SDF-1α, induced rapid tyrosine phosphorylation of src-like kinase p56lck in CD4+ T cells, whereas both gp120 and SDF-1α caused phosphorylation of the CXCR4. The tyrosine kinase inhibitor herbimycin A abolished the phosphorylation of p56lck and CXCR4 induced by gp120 in association with maintenance of normal expression of cell surface CXCR4 and a migratory response to SDF-1α. Thus, a CD4-associated signaling molecule(s) including p56lck is activated by gp120 and is required for the down-regulation of CXCR4.

T20/DP178, an Ectodomain Peptide of Human Immunodeficiency Virus Type 1 gp41, Is an Activator of Human Phagocyte N-Formyl Peptide Receptor

Human immunodeficiency virus type 1 (HIV-1) envelope protein gp41 mediates viral fusion with human host cells. The peptide segment T20/DP178, located in the C-terminus of the ectodomain of gp41, interacts with the N-terminal leucine zipper-like domain on gp41 to establish the fusogenic conformation of the virus. Synthetic T20/DP178 peptide is highly efficacious in inhibiting HIV-1 infection in vitro by disrupting the transformation of fusogenic status of viral gp41; thus, it has been proposed for clinical trial. We report that synthetic T20/DP178 is a chemoattractant and activator of human peripheral blood phagocytes but not of T lymphocytes. We further demonstrate that T20/DP178 specifically activates a seven-transmembrane, G-protein–coupled phagocyte receptor for N-formylated chemotactic peptides, formyl peptide receptor (FPR). Moreover, synthetic T20/DP178 analogs lacking N-terminal amino acids acted as FPR antagonists. Our results suggest that gp41 peptides regulate phagocyte function via FPR and identify a novel mechanism by which HIV-1 may modulate innate immunity.

T20/DP178, an Ectodomain Peptide of Human Immunodeficiency Virus Type 1 gp41, Is an Activator of Human Phagocyte N-Formyl Peptide Receptor

Human immunodeficiency virus type 1 (HIV-1) envelope protein gp41 mediates viral fusion with human host cells. The peptide segment T20/DP178, located in the C-terminus of the ectodomain of gp41, interacts with the N-terminal leucine zipper-like domain on gp41 to establish the fusogenic conformation of the virus. Synthetic T20/DP178 peptide is highly efficacious in inhibiting HIV-1 infection in vitro by disrupting the transformation of fusogenic status of viral gp41; thus, it has been proposed for clinical trial. We report that synthetic T20/DP178 is a chemoattractant and activator of human peripheral blood phagocytes but not of T lymphocytes. We further demonstrate that T20/DP178 specifically activates a seven-transmembrane, G-protein–coupled phagocyte receptor for N-formylated chemotactic peptides, formyl peptide receptor (FPR). Moreover, synthetic T20/DP178 analogs lacking N-terminal amino acids acted as FPR antagonists. Our results suggest that gp41 peptides regulate phagocyte function via FPR and identify a novel mechanism by which HIV-1 may modulate innate immunity.

HIV-1 Envelope gp120 Inhibits the Monocyte Response to Chemokines Through CD4 Signal-Dependent Chemokine Receptor Down-Regulation

Since HIV-1 infection results in severe immunosuppression, and the envelope protein gp120 has been reported to interact with some of the chemokine receptors on human T lymphocytes, we postulated that gp120 may also affect monocyte activation by a variety of chemokines. This study shows that human peripheral blood monocytes when preincubated with gp120 either purified from laboratory-adapted strains or as recombinant proteins exhibited markedly reduced binding, calcium mobilization, and chemotactic response to chemokines. The gp-120-pretreated monocytes also showed a decreased response to FMLP. This broad inhibition of monocyte activation by chemoattractants required interaction of gp120 with CD4, since the effect of gp120 was only observed in CD4+ monocytes and in HEK 293 cells only if cotransfected with both chemokine receptors and an intact CD4, but not a CD4 lacking its cytoplasmic domain. Anti-CD4 mAbs mimicked the effect of gp120, and both anti-CD4 Ab and gp120 caused internalization of CXCR4 in HEK 293 cells provided they also expressed CD4. Staurosporine blocked the inhibitory effect of gp120 on monocytes, suggesting that cellular signaling was required for gp120 to inhibit the response of CD4+ cells to chemoattractants. Our study demonstrates a broad suppressive effect of gp120 on monocyte activation by chemoattractants through the down-regulation of cell surface receptors. Thus, gp120 may be used by HIV-1 to disarm the monocyte response to inflammatory stimulation.

Molecular cloning and expression of rhesus macaque and sooty mangabey interleukin 16: biologic activity and effect on simian immunodeficiency virus infection and/or replication

Interleukin 16 (IL-16) has been shown to diminish HIV and SIV replication through inhibition of HIV and SIV mRNA transcription. To evaluate its role further, we compared IL-16 cloned from disease-susceptible rhesus macaques and disease-resistant sooty mangabeys. Recombinant rhesus macaque (rr) IL-16 was compared with recombinant sooty mangabey (rm), human, and other nonhuman primate IL-16 sequences and evaluated for its ability to induce chemotaxis and inhibit the mixed lymphocyte response (MLR). Also, rrIL-16 and rmIL-16 were evaluated for suppression of SIVmac251, which replicates efficiently in T cells and monocyte/macrophages (dual tropic), and cloned SIVmac239, which replicates efficiently in T cells (T tropic). Sequence comparison of rrIL-16 and rmIL-16 with human IL-16 showed >97% amino acid identity. Biocharacterization of rrIL-16 revealed potent induction of chemotaxis (p < 0.05) and marked inhibition of MLR (73 +/- 0.6%,p < 0.05) in rhesus and human cell systems. Using rrIL-16 and rmIL-16, p27 antigen production from PBMCs infected with SIVmac251 was decreased up to 70% (p < 0.05 and p < 0.01, respectively). In similar cultures infected with SIVmac239, rrIL-16 and rmIL-16 reduced p27 levels by 96 and 100%, respectively. These data demonstrate the biologic and antiviral functionality of rrIL-16 and rmIL-16.

Interleukin-16, produced by synovial fibroblasts, mediates chemoattraction for CD4+ T lymphocytes in rheumatoid arthritis

The massive infiltration of synovium with CD4+ T cells during the course of rheumatoid arthritis (RA) implies the expression of chemoattractant factors by resident synovial cells. Therefore, we analyzed the expression of IL-16, a potent chemoattractant for CD4+ T cells, to account for the accumulation of CD4+ T cells in RA. Indeed, IL-16 was found to be significantly elevated in synovial fluid (SF) from patients with RA as compared to non-RA arthritis (p < 0.001), osteoarthritis (p < 0.001) and controls (p < 0.001). Chemotaxis studies showed IL-16 to contribute to the strong chemotactic activities of RA-SF. In situ hybridization (ISH) revealed IL-16 mRNA-expressing cells located within the lining layer of rheumatoid synovial tissue. In the sublining area, only scattered IL-16 transcript-positive cells could be detected, mainly adjacent to blood vessels. By a double-labeling technique, combining ISH for IL-16 mRNA and immunohistochemistry for CD68, synovial fibroblast-like, CD68-negative cells were identified as a major source of IL-16 mRNA within RA synovium. This study demonstrates that synovial fibroblasts produce IL-16 in RA and thus mediate chemoattraction of CD4+ cells into synovial tissue.

HIV-1 envelope gp41 is a potent inhibitor of chemoattractant receptor expression and function in monocytes

HIV-1 uses CD4 and chemokine receptors as cofactors for cellular entry. The viral envelope transmembrane protein gp41 is thought to participate in viral fusion with CD4(+) cells. We investigated whether gp41 interacts with chemokine receptors on human monocytes by testing its effect on the capacity of cells to respond to chemokine stimulation. Monocytes preincubated with gp41 of the MN strain showed markedly reduced binding, calcium mobilization, and chemotaxis in response to a variety of chemokines as well as to the bacterial peptide fMLP. This generalized inhibition of monocyte activation by chemoattractants required the presence of CD4, since the effect of gp41 was only observed in CD4(+) monocytes and in HEK293 cells cotransfected with chemokine receptors and an intact CD4, but not a CD4 lacking its cytoplasmic domain. Confocal microscopy showed that gp41 caused internalization of CXCR4 in HEK293 cells provided they were also cotransfected with intact CD4. In addition, pretreatment of monocytes with protein kinase C inhibitors partially reversed the inhibitory effect of gp41. Thus, gp41, which had not previously been implicated as interacting with HIV-1 fusion cofactors, downregulates chemoattractant receptors on monocytes by a CD4-dependent pathway.

Signaling and functional properties of interleukin-16

Interleukin-16 is secreted from a variety of immune cells as a peptide of 17 kDa which aggregates into tetrameric form essential for IL-16s direct interaction with and cross linking of its receptor, the CD4 antigen. IL-16 stimulation of CD4+ cells results in the induction of cell motility, and in addition can function as a competence growth factor for CD4+ lymphocytes. These activities suggest that IL-16 could play a role in the accumulation and activation of CD4+ cells recruited to sites of inflammation. Along those lines, IL-16 has been identified at sites of inflammation associated with several different disease states. Its function as a competence growth factor specifically for CD4+ T cells may be useful for immune reconstitution in immunodeficiency diseases such as AIDS.

IL-16 Activates the SAPK Signaling Pathway in CD4+ Macrophages

IL-16 has been reported as a modulator of T cell activation and was shown to function as chemoattractant factor. The chemotactic activity of IL-16 depends on the expression of CD4 on the surface of target cells, but the intracellular signaling pathways are only now being deciphered. This report describes IL-16 as an additional activator of the stress-activated protein kinase (SAPK) pathway in CD4+ macrophages. Treatment of these cells with recombinant expressed IL-16 leads to the phosphorylation of SEK-1, resulting in activation of the SAPKs p46 and p54. IL-16 stimulation also leads to the phosphorylation of c-Jun and p38 MAPK (mitogen-activated protein kinase), without inducing MAPK-family members ERK-1 and ERK-2. Interestingly, the IL-16-mediated activation of SAPKs and p38 MAPK in macrophages alone induces no detectable apoptotic cell death. These observations suggest specific regulatory functions of IL-16 distinct from the proinflammatory cytokines TNF-α and IL-1β.

CD4 regulates susceptibility to Fas ligand- and tumor necrosis factor-mediated apoptosis

The current knowledge of CD4 function is limited to its role as a necessary coreceptor in TCR-initiated signaling. We have investigated whether CD4 regulates additional T cell functions. Using human primary resting CD4+ T cells, we demonstrate that CD4 activation is sufficient to induce lymphocyte death. Immediately after CD4 cross-linking, CD4+ T cells are rendered susceptible to apoptosis mediated by TNF or FasL. This, together with the concomitant induction of FasL within the same population, results in significant CD4+ T cell death in vitro. The CD4-dependent induction of susceptibility to apoptosis that is mediated by TNF or FasL is protein synthesis independent but phosphorylation dependent. After CD4 activation, PKC regulates susceptibility to apoptosis mediated by FasL but not the induction of susceptibility to TNF-dependent apoptosis. Moreover, significant differences between CD3 and CD4 activation were observed with regards to the kinetics of induction of CD4+ T cell susceptibility to FasL- and TNF-mediated apoptosis. Altogether, these results provide a model with which to study the molecular mechanisms regulating lymphocyte survival after CD4 activation, and highlight the potential role of CD4 in controlling lymphocyte apoptosis under physiological conditions or in disease states such as HIV infection.

Synergistic Activation of CD4+ T Cells by IL-16 and IL-2

IL-16, in a CD4-dependent manner, induces high affinity IL-2R (CD25) selectively on CD4+ T cells. Based on this observation, we determined the relative effects of IL-16 on IL-2Rα, β, and γ expression on CD4+ T cells and of IL-16/IL-2 cotreatment of resting human PBMC obtained from normal individuals on CD4+ T cell proliferation and cytokine production, in vitro. IL-16 increased CD4+ T cell IL-2Rα and β expression, but had no effect on expression of IL-2Rγ. There was marked synergy of thymidine uptake and expansion of CD4+ T cell numbers in the presence of IL-16 and IL-2 or IL-16 and IL-15 compared with the responses to any of the cytokines alone. By 4 wk, IL-16/IL-2-cotreated PBMC cultures were predominantly CD4+, CD25+ CD45RO T cells. Of the cytokines measured, IL-16 treatment alone was sufficient to induce synthesis of granulocyte-macrophage CSF by 2 wk. IL-16/IL-2 cotreatment did not appear to induce selective proliferation of any Th subset, as cytokines of both Th1 (e.g., IFN-γ) and Th2 (e.g., IL-5) types were synthesized by the expanded cell populations at 2 and 4 wk. These results suggest that IL-16 can prime CD4+ T cells for IL-2 responsiveness, and therefore may be a useful adjunct to IL-2 therapy for immune reconstitution in disease or therapeutic conditions resulting in CD4+ T cell depletion.

A primer on cytokines: sources, receptors, effects, and inducers

Protection against pathogens is a prerequisite for survival of most organisms. To cope with this continuous challenge, complex defense mechanisms have evolved. The construction, adaptation, and maintenance of these mechanisms are under control of an extensive network of regulatory proteins called cytokines. A great number of cytokines have been described over the last 2 decades. This review consists of an overview of cytokines that are involved in immune responses and describes some historical and general aspects as well as prospective clinical applications. Major biological effects together with information on cytokine receptors, producers, inducers, and biochemical and molecular characteristics are listed in tables. In addition, some basic information is given on cytokine receptor signal transduction. Finally, the recent discoveries of cytokine receptors functioning as coreceptors in the pathogenesis of human immunodeficiency virus are summarized.