Nuclear pro-IL-16 regulation of T cell proliferation: p27(KIP1)-dependent G0/G1 arrest mediated by inhibition of Skp2 transcription

Proteome study of cutaneous lupus erythematosus (CLE) and dermatomyositis skin lesions reveals IL-16 is differentially upregulated in CLE

Background

The objective of the study was to explore the disease pathways activated in the inflammatory foci of skin lesions in cutaneous lupus erythematosus (CLE) and dermatomyositis (DM).

Methods

Skin biopsies acquired from active CLE and DM lesions, patient (PC), and also healthy controls (HC) were investigated. Biopsy sections were examined by a pathologist, inflammatory foci were laser micro-dissected and captured, and proteins within captured tissue were detected in an unbiased manner by mass spectrometry. Protein pathway analysis was performed by the string-db.org platform. Findings of interest were confirmed by immunohistochemistry (IHC).

Results

Proteome investigation identified abundant expression of interferon-regulated proteins (IRP) as a common feature of CLE and DM. Interleukin (IL)-16 was the only abundant cytokine differentially expressed in CLE compared to DM. Caspase-3, an enzyme that cleaves IL-16 into its active form, was detected in low levels. Significantly higher proportion of IL-16- and caspase-3-positive cells was identified in CLE lesions in comparison with DM, PC, and HC. Proteomic results indicate more abundant complement deposition in CLE skin lesions.

Conclusions

Using unbiased mass spectrometry investigation of CLE and DM inflammatory infiltrates, we confirmed that high IRP expression is a common feature of both CLE and DM, while IL-16 is the only differentially expressed cytokine in CLE. IHC confirmed high expression of IL-16 and caspase-3 in CLE. Our novel molecular findings indicate that IL-16 detection could be useful in differential diagnostics between the two conditions that can display similar histopathological appearance. IL-16 could be of interest as a future therapeutic target for CLE.

Cytokine Levels in Human Vitreous in Proliferative Diabetic Retinopathy

In this study, we compare the vitreous cytokine profile in patients with proliferative diabetic retinopathy (PDR) to that of patients without PDR. The identification of novel cytokines involved in the pathogenesis of PDR provides candidate therapeutic targets that may stand alone or work synergistically with current therapies in the management of diabetic retinopathy. Undiluted vitreous humor specimens were collected from 74 patients undergoing vitrectomy for various vitreoretinal disorders. Quantitative immunoassay was performed for a panel of 36 neuroinflammatory cytokines in each specimen and assessed to identify differences between PDR (n = 35) and non-PDR (n = 39) patients. Levels of interleukin-8 (IL-8), IL-15, IL-16, vascular endothelial growth factor (VEGF), VEGF-D, c-reactive protein (CRP), serum amyloid-A (SAA), and intracellular adhesion molecule-1 (ICAM1) were significantly increased in the vitreous of PDR patients compared to non-PDR patients (p < 0.05). We report novel increases in IL-15 and IL-16, in addition to the expected VEGF, in the human vitreous humor of patients with PDR. Additionally, we confirm the elevation of ICAM-1, VCAM-1, SAA, IL-8 and CRP in the vitreous of patients with PDR, which has previously been described.

Interleukin 16 contributes to gammaherpesvirus pathogenesis by inhibiting viral reactivation

Gammaherpesviruses have evolved various strategies to take advantage of host cellular factors or signaling pathways to establish a lifelong latent infection. Like the human gammaherpesvirus Epstein-Barr virus, murine gammaherpesvirus 68 (MHV68) establishes and maintains latency in the memory B cells during infection of laboratory mice. We have previously shown that MHV68 can immortalize fetal liver-derived B cells that induce lymphomas when injected into immunodeficient mice. Here we identify interleukin 16 (IL16) as a most abundantly expressed cytokine in MHV68-immortalized B cells and show that MHV68 infection elevates IL16 expression. IL16 is not important for MHV68 lytic infection but plays a critical role in MHV68 reactivation from latency. IL16 deficiency increases MHV68 lytic gene expression in MHV68-immortalized B cells and enhances reactivation from splenic latency. Correlatively, IL16 deficiency increases the frequency of MHV68-infected plasma cells that can be attributed to enhanced MHV68 reactivation. Furthermore, similar to TPA-mediated lytic replication of Kaposi's sarcoma-associated herpesvirus, IL16 deficiency markedly induces Tyr705 STAT3 de-phosphorylation and elevates p21 expression, which can be counteracted by the tyrosine phosphatase inhibitor orthovanadate. Importantly, orthovanadate strongly blocks MHV68 lytic gene expression mediated by IL16 deficiency. These data demonstrate that virus-induced IL16 does not directly participate in MHV68 lytic replication, but rather inhibits virus reactivation to facilitate latent infection, in part through the STAT3-p21 axis.

Siah2 control of T-regulatory cells limits anti-tumor immunity

Understanding the mechanisms underlying anti-tumor immunity is pivotal for improving immune-based cancer therapies. Here, we report that growth of BRAF-mutant melanoma cells is inhibited, up to complete rejection, in Siah2^-/- mice. Growth-inhibited tumors exhibit increased numbers of intra-tumoral activated T cells and decreased expression of Ccl17, Ccl22, and Foxp3. Marked reduction in Treg proliferation and tumor infiltration coincide with G1 arrest in tumor infiltrated Siah2^-/- Tregs in vivo or following T cell stimulation in culture, attributed to elevated expression of the cyclin-dependent kinase inhibitor p27, a Siah2 substrate. Growth of anti-PD-1 therapy resistant melanoma is effectively inhibited in Siah2^-/- mice subjected to PD-1 blockade, indicating synergy between PD-1 blockade and Siah2 loss. Low SIAH2 and FOXP3 expression is identified in immune responsive human melanoma tumors. Overall, Siah2 regulation of Treg recruitment and cell cycle progression effectively controls melanoma development and Siah2 loss in the host sensitizes melanoma to anti-PD-1 therapy.

High-Dose Dexamethasone Alters the Increase in Interleukin-16 Level in Adult Immune Thrombocytopenia

Adult primary immune thrombocytopenia (ITP) is an autoimmune-mediated haemorrhagic disorder. Interleukin-16 (IL-16) can directly affect cellular or humoural immunity by mediating the cellular cross-talk among T cells, B cells and dendritic cells. Several studies have focused on IL-16 as an immunomodulatory cytokine that takes part in Th1 polarization in autoimmune diseases. In this study, we investigated IL-16 expression in the bone marrow supernatant and plasma of ITP patients and healthy controls. What's more, we detected IL-16 expression in ITP patients with the single-agent 4-day high-dose dexamethasone (HD-DXM) therapy. In patients with active ITP, bone marrow supernatant and plasma IL-16 levels increased (P < 0.05) compared with those of healthy controls. In the meantime, the mRNA expression in BMMCs (pro-IL-16, caspase-3) and PBMCs (pro-IL-16, caspase-3 and T-bet) of ITP patients was increased (P < 0.05) relative to those of healthy controls. In patients who responded to HD-DXM therapy, both plasma IL-16 levels and gene expression in PBMCs (pro-IL-16, caspase-3, and T-bet) were decreased (P < 0.05). In summary, the abnormal level of IL-16 plays important roles in the pathogenesis of ITP. Regulating Th1 polarization associated with IL-16 by HD-DXM therapy may provide a novel insight for immune modulation in ITP.

Oscillating expression of interleukin-16 in multiple myeloma is associated with proliferation, clonogenic growth, and PI3K/NFKB/MAPK activation

Multiple myeloma (MM) is an incurable hematologic malignancy emerging from a plasma cell clone located in the bone marrow and is characterized by a high rate of fatal relapses after initially effective treatment. We have previously identified Interleukin-16 (IL-16) as an important factor promoting the proliferation of MM cells. We demonstrate here an upregulated, periodic expression, and secretion of IL-16 by MM cells leading to high extracellular IL-16 levels. The level of IL-16 released from a given MM cell line correlated with its proliferative activity. Establishing an inducible knockdown system and performing gene expression arrays we observed an association between IL-16 expression and activation of PI3, NFκB and MAP kinase pathways and, specifically, genes involved in tumor cell proliferation. Functional assays showed that IL-16 knockdown reduced the proliferative activity with a significant delay in cell cycle progression to G2 phase of conventional MM cells and completely suppressed the growth of clonogenic MM cells, which are suspected to be responsible for the high relapse rates in MM. Overall, our results demonstrate that tumor-regenerating MM cells may be particularly susceptible to IL-16 neutralization, suggesting an important role of anti-IL-16 therapies in the treatment of MM, particularly in combination with existing strategies targeting the bulk of myeloma cells.

Alarmins: Feel the Stress

Over the last decade, danger-associated molecular pattern molecules, or alarmins, have been recognized as signaling mediators of sterile inflammatory responses after trauma and injury. In contrast with the accepted passive release models suggested by the "danger hypothesis," it was recently shown that alarmins can also directly sense and report damage by signaling to the environment when released from live cells undergoing physiological stress, even without loss of subcellular compartmentalization. In this article, we review the involvement of alarmins such as IL-1α, IL-33, IL-16, and high-mobility group box 1 in cellular and physiological stress, and suggest a novel activity of these molecules as central initiators of sterile inflammation in response to nonlethal stress, a function we denote "stressorins." We highlight the role of posttranslational modifications of stressorins as key regulators of their activity and propose that targeted inhibition of stressorins or their modifiers could serve as attractive new anti-inflammatory treatments for a broad range of diseases.

Assessment of Interleukin 16 Serum Levels and Skin Expression in Psoriasis Patients in Correlation with Clinical Severity of the Disease

Interleukin 16 (IL-16) has been described as a significant cytokine involved in the recruitment of CD4+ cells during inflammation; however, its potential role in psoriasis has not been defined. Our aim was to investigate the IL-16 serum levels and IL-16 mRNA skin expression in psoriasis patients in correlation with disease severity and mRNA skin expression for CD4. Moreover, the IL-16 skin localization was assessed and the -295 T/C IL-16 polymorphism was analyzed. For this exploratory, observational, and cross-sectional study, 97 unrelated patients with chronic plaque type psoriasis and 104 healthy controls were enrolled. IL-16 serum levels were significantly increased in patients compared with controls (P = 0.000022) and positively correlated with Psoriasis Area and Severity Index (r = 0.34, P = 0.0007), Body Surface Area (r = 0.34, P = 0.01) and were significantly higher in individuals with moderate to severe psoriasis (P = 0.0029). There was no significant correlation between IL-16 serum levels and Dermatology Quality of Life Index and no differences in genotype and allele frequencies for -295 T/C IL-16 polymorphism. The expression of IL-16 (mRNA and protein) was elevated in the margin of psoriatic skin while statistically significant increase in IL-16 immunoreactivity, but not in mRNA level, was observed within plaques. Furthermore, the IL-16 mRNA levels within psoriatic lesions positively correlated with the levels of CD4 mRNA, but not with Psoriasis Area and Severity Index. In conclusion, our data revealed an association between circulating IL-16 and severity of psoriasis which indicates that this cytokine could serve as a potential marker of disease activity. However, further investigations are required.

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.

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.

Modulation of cell cycle regulators by HDACs

Histone deacetylases (HDACs) catalyze the deacetylation of lysine residues on histones and non-histone proteins. HDACs have been shown to control the functions of key cell cycle proteins. Consistent with this, the overexpression of HDACs has been observed in multiple cancers, resulting in deregulation of the cell cycle and uncontrolled proliferation. This review focuses on the impact that HDACs have on cell cycle control through the deacetylation of proteins.

Loss of nuclear pro-IL-16 facilitates cell cycle progression in human cutaneous T cell lymphoma

Cutaneous T cell lymphomas (CTCLs) represent a heterogeneous group of non-Hodgkin lymphomas that affect the skin. The pathogenesis of these conditions is poorly understood. For example, the signaling mechanisms contributing to the dysregulated growth of the neoplastic T cells are not well defined. Here, we demonstrate that loss of nuclear localization of pro-IL-16 facilitates CTCL cell proliferation by causing a decrease in expression of the cyclin dependent-kinase inhibitor p27Kip1. The decrease in p27Kip1 expression was directly attributable to an increase in expression of S-phase kinase-associated protein 2 (Skp2). Regulation of Skp2 is in part attributed to the nuclear presence of the scaffold protein pro-IL-16. T cells isolated from 11 patients with advanced CTCL, but not those from healthy controls or patients with T cell acute lymphocytic leukemia (T-ALL), demonstrated reduction in nuclear pro-IL-16 levels. Sequence analysis identified the presence of mutations in the 5' end of the PDZ1 region of pro-IL-16, a domain required for association of pro-IL-16 with the nuclear chaperone HSC70 (also known as HSPA8). HSC70 knockdown led to loss of nuclear translocation by pro-IL-16 and subsequent increases in Skp2 levels and decreases in p27Kip1 levels, which ultimately enhanced T cell proliferation. Thus, our data indicate that advanced CTCL cell growth is facilitated, at least in part, by mutations in the scaffold protein pro-IL-16, which directly regulates Skp2 synthesis.

Introduction of pro-interleukin-16 inhibits T-lymphoblastic leukemia growth in mice

PURPOSE

Pro-interleukin-16 (pro-IL-16) is the precursor to mature interleukin-16 (IL-16) protein. Previous studies have demonstrated that pro-IL-16 can function as a regulator of cell cycle. A number of human T-cell leukemia and lymphoma cell lines are pro-IL-16 deficient. Intracellular expression of pro-IL-16 causes these cell lines to become quiescent, implicating loss of pro-IL-16 as a contributory step in T-cell malignancy. Therefore, we tested whether or not reintroduction of pro-IL-16 into solid tumors in mice could halt tumor growth.

METHODS

MOLT-4 lymphoblastic leukemia cells were stably transfected with a dsRed-tomato virus and were injected subcutaneously into NOD/SCID/γ chain-knockout mice. Tumor growth was monitored with an in vivo imaging system. A pro-IL-16-GFP fusion virus or control GFP only virus was injected into the tumors, and mice were monitored for 1 week.

RESULTS

Injection of the pro-IL-16-containing lentivirus inhibited growth of established MOLT-4 tumors in mice. Tumor explants exhibited diminished proliferative capacity.

CONCLUSIONS

Our data support the concept that restoration of pro-IL-16 expression in malignant T cells may have therapeutic value.

Interleukin-16 as a marker of Sézary syndrome onset and stage

INTRODUCTION

Sézary syndrome is one of the most common forms of cutaneous T cell lymphoma (CTCL). It is characterized by skin infiltration of malignant T cells. We examined interleukin-16, a potent T cell chemoattractant and cell-cycle regulator, as a prospective marker of disease onset and stage.

METHODS

The correlation of total intracellular interleukin-16 and surface CD26 was studied by flow cytometry. Confocal microscopy was performed to determine localization of interleukin-16 at different stages of the disease. The levels of interleukin-16 in plasma and culture supernatants were examined by enzyme-linked immunoassay. Additionally, lymphocytes from stage IB patients were cultured in the presence of interleukin-16 alone and in combination with interleukin-15, and their ability to survive and proliferate was determined by cell counts and [3H]TdR incorporation.

RESULTS

The data indicate that loss of both nuclear and intracellular pro-interleukin-16 highly correspond to disease stage, with a concomitant increase in secreted mature interleukin-16 in both culture supernatants and patients' plasma that peaks at stage IB. Loss of intracellular interleukin-16 strongly corresponded to loss of surface CD26, which has been shown to occur with more advanced stage of CTCL. Nuclear translocation of pro-interleukin-16 was not observed in late stages of Sézary syndrome, indicating this loss is not reversible.

CONCLUSIONS

We propose that it is feasible to use plasma levels of IL-16 as a potential diagnostic marker of Sézary syndrome and to use loss of intracellular IL-16 as a prognostic indicator of disease severity and stage.

Tissue expression of IL16 in prostate cancer and its association with recurrence after radical prostatectomy

BACKGROUND

Genetic polymorphism located within the IL16 gene has been reported to be associated with aggressive prostate cancer (PCa). Our aim was to establish whether the tissue expression of IL16 is a prognostic factor of survival in PCa.

METHODS

The files of patients who underwent radical prostatectomy (RP) between 1995 and 2001 were reviewed. The cases were selected and classified according to the D'Amico classification for risk of recurrence (intermediate or high). The value of IL16 and its receptor CCR5 (chemokine (C-C motif) receptor 5) expression levels were determined as witness of aggressiveness patterns and markers of biological relapse in patients with PCa treated by RP. A tissue microarray of 304 cases was constructed. IL16 and CCR5 expression levels were characterized by immunohistochemistry.

RESULTS

IL16 expression was correlated with high Gleason score (i.e., >7) (P < 0.01). It was not significant for CCR5. IL16 and CCR5 were not associated with prostate-specific antigen (PSA) or capsular extension of the disease. The accurate prediction of disease outcome, using stratification of cases, according to negative margins and D'Amico classification was significantly enhanced by status of IL16 expression (P ≤ 0.01). In univariate analyses, Gleason score, PSA level, stage and loss of IL16 expression were related to better biological-free survival (P < 0.05) but not CCR5. In a multivariate analysis, IL16 expression, Gleason score, and tumor stage were independent factors for biochemical-free survival (P = 0.001).

CONCLUSIONS

IL16 appears to be a useful prognostic factor in PCa. Its expression in PCa tissue was correlated to tumor aggressiveness and biochemical relapse of the disease.

FOXO1, T-cell trafficking and immune responses

Efficient T-cell adaptive immune response require a faultless coordination between migration of naive T-cells into secondary lymphoid organs and critical biological outcomes driven by antigen such as cell division and cell differentiation into effector and memory cells. Recent works have shown that the phosphoinositide 3-kinase (PI3K) pathway could govern several of these processes. In this control, transcriptional factors of the Forkhead box O (FoxO) family, in particular FOXO1, a downstream effector of PI3K, appears to play a major role by coordinating both cellular proliferation of T-cells after antigen recognition and expression of homing molecules essential for their trafficking in the body.

Dual functionality of interleukin-1 family cytokines: implications for anti-interleukin-1 therapy

Dysregulated inflammation contributes to disease pathogenesis in both the periphery and the brain. Cytokines are coordinators of inflammation and were originally defined as secreted mediators, released from expressing cells to activate plasma membrane receptors on responsive cells. However, a group of cytokines is now recognized as having dual functionality. In addition to their extracellular effects, these cytokines act inside the nuclei of cytokine-expressing or cytokine-responsive cells. Interleukin-1 (IL-1) family cytokines are key pro-inflammatory mediators, and blockade of the IL-1 system in inflammatory diseases is an attractive therapeutic goal. All current therapies target IL-1 extracellular actions. Here we review evidence that suggests IL-1 family members have dual functionality. Several IL-1 family members have been detected inside the nuclei of IL-1-expressing or IL-1-responsive cells, and intranuclear IL-1 is reported to regulate gene transcription and mRNA splicing. However, further work is required to determine the impact of IL-1 intranuclear actions on disease pathogenesis. The intranuclear actions of IL-1 family members represent a new and potentially important area of IL-1 biology and may have implications for the future development of anti-IL-1 therapies.

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.

Adenovirus expressing p27kip1 suppresses growth of established esophageal carcinoma xenografts

AIM: To investigate the growth suppression of ade-novirus expressing p27^kip1 on established esophageal tumors in nude mice.

METHODS: Esophageal carcinoma xenografts in nude mice were established by tumor tissue mass transplantation. The successfully constructed reco-mbinant adenoviral vectors carrying p27^kip1 gene (Ad-p27^kip1) were directly injected into the esophageal tumors in nude mice. Compared to control group, the growth curve of tumor was drawn and the growth inhibition rate of tumor was calculated. The histology of tumors was examined by hematoxylin and eosin (H&E) staining. The expression of p27^kip1 and survivin was detected in tumors by immunohistochemical technique.

RESULTS: The growth of tumors in gene therapy group with Ad-p27^kip1 was obviously suppressed compared to control group (0.42±0.08 g vs 1.17±0.30 g, t=6.39, P<0.01), the inhibition rate of tumor growth reached 64.1%. Pathological detection showed that the tumors in nude mice were poorly differentiated esophageal squamous carcinoma. In addition, the expression of p27^kip1 was increased, while the expression of survivin was decreased in tumors after being transfected with Ad-p27^kip1.

CONCLUSION: p27^kip1 gene therapy mediated by adenovirus vector has a significant inhibitory effect on esophageal carcinoma in vivo. Up-regulated p27^kip1 expression and down-regulated survivin expression may be its important mechanisms.

Regulation of nuclear Prointerleukin-16 and p27Kip1 in primary human T lymphocytes

Prointerleukin-16 (Pro-IL-16) is an abundant, PDZ domain-containing protein expressed in the nucleus and cytoplasm of resting human T lymphocytes. We have previously shown that ectopic expression of Pro-IL-16 in Pro-IL-16-negative human Jurkat cells represses transcription of the F-box protein, Skp2, resulting in accumulation of the cyclin-dependent kinase inhibitor, p27(Kip1), and G0/G1 cell cycle arrest. The current studies demonstrate the kinetics of Pro-IL-16 and p27(Kip1) expression in activated normal human T lymphocytes. We correlate nuclear Pro-IL-16 loss with decreased p27(Kip1) expression, increased cell cycle progression, and proliferation. Conversely, we show that constitutive expression of Pro-IL-16 by retroviral infection of activated human T lymphocytes induces G0/G1 cell cycle arrest, inhibits proliferation, and is associated with increased levels of p27(Kip1). These findings implicate nuclear Pro-IL-16 as a cell cycle regulatory protein for human T lymphocytes.

Pro-IL-16 Regulation in Activated Murine CD4+ Lymphocytes

Prior DNA microarray studies suggested that IL-16 mRNA levels decrease following T cell activation, a property unique among cytokines. We examined pro-IL-16 mRNA and protein expression in resting and anti-CD3 mAb-activated primary murine CD4(+) T cells. Consistent with the microarray reports, pro-IL-16 mRNA levels fell within 4 h of activation, and this response is inhibited by cyclosporin A. Total cellular pro-IL-16 protein also fell, reaching a nadir at 48 h. Pro-IL-16 comprises a C-terminal cytokine domain and an N-terminal prodomain that are cleaved by caspase-3. Pro-IL-16 expressed in transfected tumor cells was previously shown to translocate to the nucleus and to promote G(0)/G(1) arrest by stabilizing the cyclin-dependent kinase inhibitor p27(Kip1). In the present study, we observed increased S-phase kinase-associated protein 2 mRNA expression in IL-16 null mice, but basal expression and activation-dependent regulation of p27(Kip1) were no different from wild-type mice. Stimulation with anti-CD3 mAb induced transiently greater thymidine incorporation in IL-16-deficient CD4(+) T cells than wild-type controls, but there was no difference in cell survival or in the CFSE dilution profiles. Analysis of CD4(+) T cell proliferation in vivo using BrdU labeling similarly failed to identify a hyperproliferative phenotype in T cells lacking IL-16. These data demonstrate that pro-IL-16 mRNA and protein expression are dynamically regulated during CD4(+) T cell activation by a calcineurin-dependent mechanism, and that pro-IL-16 might influence T cell cycle regulation, although not in a dominant manner.

Inhibitory effect of ubiquitin-proteasome pathway on proliferation of esophageal carcinoma cells

AIM: To investigate the inhibitory effect of ubiquitin-proteasome pathway (UPP) on proliferation of esophageal carcinoma cells.

METHODS: Esophageal carcinoma cell strain EC9706 was treated with MG-132 to inhibit its UPP specificity. Cell growth suppression was evaluated with 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. DNA synthesis was evaluated by ³H-thymidine (³H-TdR) incorporation. Morphologic changes of cells were observed under microscope. Activity of telomerase was examined by telomeric repeat amplification protocol (TRAP) of PCR-ELISA. Cell cycle and apoptosis were detected by flow cytometry (FCM). DNA fragment analysis was used to confirm the presence of apoptosis. Expression of p27^kip1 was detected by immunocytochemical technique.

RESULTS: After exposed to MG-132, the growth and value of ³H-TdR incorporation of EC9706 cells were obviously inhibited. Cells became round, small and exfoliative under microscope. TRAP PCR-ELISA showed that light absorption of cells gradually decreased after exposed to 5 μmol/L of MG-132 for 24, 48, 72 and 96 h (P < 0.01). The percentage of cells at G₀/G₁ phase was increased and that at S and G₂/M was decreased (P < 0.01). The rate of apoptotic cells treated with 5 μmol/L of MG-132 for 48 and 96 h was 31.7% and 66.4%, respectively. Agarose electrophoresis showed marked ladders. In addition, the positive signals of p27^kip1 were located in cytoplasm and nuclei in MG-132 group in contrast to cytoplasm staining in control group.

CONCLUSION: MG-132 can obviously inhibit proliferation of EC9706 cells and induce apoptosis. The mechanisms include upregulation of p27^kip1 expression, G₁ arrest and depression of telomerase activity. The results indicate that inhibiting UPP is a novel strategy for esophageal carcinoma therapy.

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.