Porphyromonas gingivalis lipopolysaccharide upregulates insulin secretion from pancreatic β cell line MIN6

BACKGROUND

A close association between periodontitis and diabetes has been demonstrated in human cross-sectional studies, but an exact relationship between periodontitis and prediabetes has not been established. Previous studies using animal model systems consistently have shown that hyperinsulinemia occurs in animals with periodontitis compared to animals with healthy periodontium (while maintaining normoglycemia). Because bacterial lipopolysaccharide (LPS) plays an important role in the pathogenesis of periodontitis, we hypothesized that LPS may stimulate insulin secretion through a direct effect on β cell function. To test this hypothesis, pancreatic β cell line MIN6 cells were used to determine the effect of Porphyromonas gingivalis (Pg) LPS on insulin secretion. Furthermore, expression of genes altered by Pg LPS in innate immunity and insulin-signaling pathways was determined.

METHODS

MIN6 cells were grown in medium with glucose concentration of normoglycemia (5.5 mM). Pg LPS was added to each well at final concentrations of 50, 200, and 500 ng/mL. Insulin secretion was measured using enzyme-linked immunosorbent assay. Gene expression levels altered by Pg LPS were determined by polymerase chain reaction (PCR) array for mouse innate and adaptive immunity response and mouse insulin-signaling pathways, and results were confirmed for specific genes of interest by quantitative PCR.

RESULTS

Pg LPS stimulated insulin secretion in the normoglycemic condition by ≈1.5- to 3.0-fold depending on the concentration of LPS. Pg LPS treatment altered the expression of several genes involved in innate and adaptive immune response and insulin-signaling pathway. Pg LPS upregulated the expression of the immune response-related genes cluster of differentiation 8a (Cd8a), Cd14, and intercellular adhesion molecule-1 (Icam1) by about two-fold. LPS also increased the expression of two insulin signaling-related genes, glucose-6-phosphatase catalytic subunit (G6pc) and insulin-like 3 (Insl3), by three- to four-fold.

CONCLUSIONS

We have demonstrated for the first time that Pg LPS stimulates insulin secretion by pancreatic β cell line MIN cells. Pg LPS may have significant implications on the development of β cell compensation and insulin resistance in prediabetes in individuals with periodontitis.

Research on the epigenetic modification of pancreatic cancer vaccine

Pancreatic cancer is characterized as a type of gastrointestinal tumor with a poor prognosis and high degree of malignancy. CIITA gene was found highly methylated in pancreatic carcinoma cell line PANC-1 and responsible for the low expression of MHC-II that may lead to immune evasion. Here, we tried to prepare pancreatic cancer vaccine with PANC-1 cells via epigenetic modification to enhance the MHC-II expression. Then the vaccine was injected into C57BL/6J mice and the effect was examined. Our study found that the vaccine could promote the proliferation of antigen-specific T cells, enhance the killing activity of cytotoxic lymphocytes (CTL), promote Th1-type cells mediated secretion of cytokines IFN-gamma and IL-2 while inhibiting Th2-type cells mediated secretion of IL-4, and inhibit the secretion of TGF-beta. Generally, the epigenetically modified vaccine could enhance the body's anti-tumor immune response, providing feasibility research on cancer vaccine for therapy of pancreatic cancer.

Molecular changes of mesenchymal stromal cells in response to dexamethasone treatment

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent stromal cells that can differentiate into a variety of cell types. The MSCs can be activated and mobilized if needed.

AIM

This study aimed to investigate the response mechanism of MSCs under Dexamethasone (Dex) treatment by combining MSCs microarray and bioinformatics methods.

MATERIALS AND METHODS

We downloaded the gene expression profile of rat's MSCs challenge with or without Dex (GSE3339) from Gene Expression Omnibus database, including 2 Dex treated samples and 3 untreated samples. The differentially expressed genes (DEGs) were identified by packages in R language. Then, Gestalt (Genomic Sequence Total Analysis and Lookup Tool) and EASE (Expression Analysis Systematic Explorer) to were employed to obtain the molecular events of MSCs under Dex treatment.

RESULTS

A total of 17 genes were identified as DEGs between untreated and treated samples, and they were significant enriched in immune response and cell differentiation. The C3 gene was the common candidate gene selected from two different algorithms, and 24 conserved sites were identified in the 3'UTR of C3 gene.

CONCLUSIONS

Genes associated with immune response and cell differentiation were dysregulated in MSCs under Dex.

Phycocyanobilin promotes PC12 cell survival and modulates immune and inflammatory genes and oxidative stress markers in acute cerebral hypoperfusion in rats

Since the inflammatory response and oxidative stress are involved in the stroke cascade, we evaluated here the effects of Phycocyanobilin (PCB, the C-Phycocyanin linked tetrapyrrole) on PC12 cell survival, the gene expression and the oxidative status of hypoperfused rat brain. After the permanent bilateral common carotid arteries occlusion (BCCAo), the animals were treated with saline or PCB, taking samples 24h post-surgery. Global gene expression was analyzed with GeneChip Rat Gene ST 1.1 from Affymetrix; the expression of particular genes was assessed by the Fast SYBR Green RT-PCR Master Mix and Bioplex methods; and redox markers (MDA, PP, CAT, SOD) were evaluated spectrophotometrically. The PCB treatment prevented the H2O2 and glutamate induced PC12 cell injury assessed by the MTT assay, and modulated 190 genes (93 up- and 97 down-regulated) associated to several immunological and inflammatory processes in BCCAo rats. Furthermore, PCB positively modulated 19 genes mostly related to a detrimental pro-inflammatory environment and counteracted the oxidative imbalance in the treated BCCAo animals. Our results support the view of an effective influence of PCB on major inflammatory mediators in acute cerebral hypoperfusion. These results suggest that PCB has a potential to be a treatment for ischemic stroke for which further studies are needed.

Induction on differentiation and modulation of bone marrow progenitor of dendritic cell by methionine enkephalin (MENK)

Methionine enkephalin (MENK), the endogenous neuropeptide, is known to exert direct effects on the neuroendocrine and the immune systems and participates in regulation of various functions of cells related to both the innate and adaptive immune systems. Dendritic cells (DCs) play important role in initiating and regulating T cell responses. The aim of this work is to investigate the effects of MENK on differentiation, maturation, and function of DCs derived from murine bone marrow progenitors (BM-derived DCs). Our result showed that MENK could induce BM-derived DCs to polarize predominantly to mDC subtype, rather than pDC both in vivo and in vitro, and this was in favor of Th1 response. BM-derived DCs, after treatment with MENK, up-regulated the expressions of MHC class II and key costimulatory molecules. Result by RT-PCR showed MENK could increase expressions of delta and kappa receptors on BM-derived DCs. Also MENK promoted BM-derived DCs to secret higher levels of proinflammatory cytokines of IL-12p70, TNF-α. Furthermore, differentiated BM-derived DCs treated with MENK displayed higher activity to induce allogeneic T cell proliferation and MENK also inhibited tumor growth in vivo and induced apoptosis of tumor cells in vitro. Thus, it is concluded that MENK could be an effective inducer of BM-derived DCs and might be a new therapeutic agent for cancer, as well as other immune handicapped disease. Also we may consider MENK as a potential adjuvant in vaccine preparation.

Lead effects on development and function of bone marrow-derived dendritic cells promote Th2 immune responses

Although lead (Pb) has significant effects on the development and function of macrophages, B cells, and T cells and has been suggested to promote allergic asthma in mice and humans, Pb modulation of bone marrow (BM)-derived dendritic cells (DCs) and the resultant DC effects on Th1 and Th2 development have not been examined. Accordingly, we cultured BM cells with murine granulocyte macrophage-colony stimulating factor (mGM-CSF)+/-PbCl(2). At day 10, culture supernatant (SN) and non-adherent cells were harvested for analysis. Additionally, day 10 non-adherent BM-DCs were harvested and recultured with mGM-CSF+LPS+/-Pb for 2 days. The day 10 Pb exposure significantly inhibited BM-DC generation, based on CD11c expression. Although fewer DCs were generated with Pb, the existing Pb-exposed DCs had significantly greater MHC-II expression than did the non-Pb-exposed DCs. However, these differences diminished upon LPS stimulation. After LPS stimulation, CD80, CD86, CD40, CD54, and MHC-II were all up-regulated on both Pb-DCs and DCs, but Pb-DCs expressed significantly less CD80 than did DCs. The CD86:CD80 ratio suggests a Pb-DC potential for Th2 cell development. After LPS stimulation, IL-6, IL-10, IL-12 (p70), and TNF-alpha levels significantly increased with both Pb-DCs and DCs, but Pb-DCs produced significantly less cytokines than did DCs, except for IL-10, which further supports Pb-DC preferential skewing toward type-2 immunity. In vitro studies confirm that Pb-DCs have the ability to polarize antigen-specific T cells to Th2 cells. Pb-DCs also enhanced allogeneic and autologous T cell proliferation in vitro, and in vivo studies suggested that Pb-DCs inhibited Th1 effects on humoral and cell-mediated immunity. The Pb effect was mainly on DCs, rather than on T cells, and Pb's modification of DC function appears to be the main cause of Pb's promotion of type-2-related immunity, which may relate to Pb's enhanced activation of the Erk/MAP kinase pathway.

Benzo(a)pyrene inhibits growth and functional differentiation of mouse bone marrow-derived dendritic cellsDownregulation of RelB and eIF3 p170 by benzo(a)pyrene

In this study, we have investigated effects of benzo(a)pyrene (BP) on growth and functional differentiation of mouse bone marrow (BM)-derived dendritic cells (DC). 1 microM BP dramatically inhibited growth of BM cultured in the presence of granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-4 (IL-4). Although little alterations in surface expression of CD11c, major histocompatibility complex (MHC II), and CD86 molecules characteristic of mature DC were induced by BP, production of cytokines including IL-12, IL-10, and TNF-alpha, and allogeneic T cell stimulating ability were severely impaired. Some of the effects of BP were dependent on arylhydrocarbon receptor (AhR), because alpha-naphthoflavone, an AhR antagonist, suppressed the effects of BP on IL-12 production and T cell stimulating ability, but not on DC proliferation. Expression of RelB, a transcription factor necessary for DC differentiation and function, and eIF3 p170, a subunit of eukaryotic translation initiation factor (eIF)3, was reduced upon BP treatment.

Immunoregulatory effects of atorvastatin on experimental autoimmune myocarditis in Lewis rats

Experimental autoimmune myocarditis (EAM) in rats is a T-cell-mediated disorder and has been shown to involve immune imbalance. The aim of this study was to examine the immunomodulatory effects of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase inhibitor, atorvastatin, on the expression of MHC class II molecules in the myocardium of rats with EAM, and to examine its therapeutic potential for EAM. EAM was induced in Lewis rats by injection of porcine cardiac myosin. High-dosage (10 mg/kg per day) or low-dosage (1 mg/kg per day) atorvastatin or vehicle was given orally for 3 weeks. On day 21 after immunization, echocardiography was carried out and the severity of myocarditis was evaluated by histopathological investigations. Immunohistochemistry techniques were used to examine the expression of MHC class II molecules in the myocardium. Type I, III and IV class II transactivator (CIITA) promoter transcription was evaluated by reverse transcription-PCR. Cardiomyocytes were isolated and the expression of MHC class II molecules by them was detected using cytometry. Serum Th1/Th2 cytokines were examined on day 21 by ELISA. Cardiac function was improved in the two atorvastatin-treated groups compared with the untreated one. In atorvastatin groups, the histopathological severity of myocarditis was attenuated and the expression of MHC class II molecules on the 'nonprofessional' APC, the cardiomyocytes, was reduced. mRNA level of type IV CIITA promoter was downregulated in the statin-treated groups in a dosage-dependent manner, but levels of type I and III CIITA mRNA did not differ between the groups statistically. Levels of IFN-gamma and IL-2 increased, whereas levels of IL-4 and IL-10 decreased, in immunized rats from day three through day 21. Atorvastatin reversed these trends in the treated groups. Atorvastatin improves cardiac function and histopathology of the myocardium in EAM by inducing Th2-biased immune responses, and thus 3-hydroxy-3-methyl-glutaryl coenzyme A reductase blockade may be a promising new strategy for the treatment of cardiac autoimmune impairments. The underlying mechanisms may be related to downregulation of MHC class II Ag expression due to silencing of the CIITA mRNA transcription.

MHC Class II–Mediated Apoptosis by a Nonpolymorphic MHC Class II Peptide Proceeds by Activation of Protein Kinase C

It was demonstrated previously that a peptide derived from a conserved region of MHC class II, HLA-DQA1, inhibits proliferation of allogeneic T cells in vitro. Administration of HLA-DQA1 in conjunction with allogeneic cells at the time of priming or at the time of rechallenge prevented the development of the delayed type hypersensitivity response in vivo. The immunomodulatory effects of HLA-DQA1 were associated with the induction of apoptosis in B cells, macrophages, and dendritic cells via a caspase-independent pathway. This study investigated the binding site and mechanism that mediates cell death induced by HLA-DQA1. It was demonstrated that HLA-DQA1 binds to MHC class II on the cell surface, causing MHC class II signaling, initiation of protein kinase C signaling, and mitochondrial membrane depolarization with resultant apoptosis. The data indicate that HLA-DQA1 binds to MHC class II outside the groove, in a manner similar to superantigen. These results suggest that HLA-DQA1 is a novel immunotherapy that may provide an effective means of targeting professional antigen-presenting cells, in particular B cells.

Prostaglandin E(2) modulation of gene expression in an Atlantic salmon (Salmo salar) macrophage-like cell line (SHK-1)

Following lipopolysaccharide (LPS)-stimulation of Atlantic salmon (Salmo salar) macrophage-like SHK-1 cells, prostaglandin E(2) (PGE(2)) exhibited dose-dependent inhibition of the antigen presenting molecules major histocompatability class I and II and the pro-inflammatory cytokine interleukin-1 beta gene expression. Prostaglandin E(2) was found to be stimulatory towards cyclooxygenase-2 (COX-2) expression at higher concentrations (1 x 10(-6) and 1 x 10(-8)M) and inhibitory at lower concentrations (1 x 10(-10) and 1 x 10(-12)M) after 4h exposure. After 24h exposure, however, LPS-induced COX-2 expression decreased and was completely inhibited by all PGE(2) concentrations (1 x 10(-6)-1 x 10(-10)M). Incubation of SHK-1 cells with LPS alone had no effect on tumour necrosis factor alpha (TNFalpha)-like gene or transforming growth factor beta-like gene expression after 4h, however, LPS and PGE(2) showed a synergistic effect on TNFalpha-like gene expression after 24h. This study provides evidence for the existence of a PGE(2)-mediated negative feedback mechanism in the control of PGs through down-regulation of COX-2, as well as for inflammatory responses by the down-regulation of both COX-2 and IL-1 beta. The differential regulation of immune-related genes under these conditions further demonstrates the usefulness of the SHK-1 cell line for studying aspects of salmonid immunology.

Apoptotic and necrotic cells induced by different agents vary in their expression of MHC and costimulatory genes

We have recently reported, in a murine tumor model, that apoptotic cells induced by different agents may vary in their ability to elicit host immunity. The basis for this observation is unclear but may involve varying efficiencies of cross-presentation and/or direct activation of immunity by different apoptotic preparations. As a first step in addressing this issue, we compared expression patterns of selected immune genes (MHC class I, class II, CD40, B7-1, B7-2) on viable and apoptotic populations induced by four different agents. The histone deacetylase inhibitor trichostatin A (TSA) induced MHC class II expression on viable and apoptotic cell populations, while LPAM, H2O2 and gamma-irradiation did not activate class II. Each agent employed elicited a different expression pattern of costimulatory molecules (CD40, B7-1, B7-2) on both apoptotic and 7-AAD+ 'necrotic' populations. In striking contrast to the TSA induction of MHC class II, class I cell surface protein was diminished on the apoptotic populations. These effects were not a result of changes in the cell cycle produced by the various treatments. The data demonstrate that distinctive gene expression patterns on viable and apoptotic cells are elicited by different apoptosis inducing agents. We discuss how expression patterns on dead or dying tumor cells could potentially affect the tumor's ability to elicit immunity.

Effect of influenza virus vaccine on the expression of human immunodeficiency virus co-receptor CCR5

BACKGROUND

Administration of influenza vaccine to human immunodeficiency virus (HIV)-infected children can lead to increased viral load. CCR5 and CXCR4 are known to play an important role in HIV cell entry and viral replication.

OBJECTIVE

To determine the effects of influenza vaccine on chemokine receptors and on viral load in HIV-infected children.

METHODS

Eight HIV-infected children receiving stable therapy and 11 healthy adults were enrolled. Chemokine expression and immune activation were determined before and 48 hours after influenza vaccination. CCR5 and beta-chemokine gene expression were analyzed using real-time polymerase chain reaction. Viral load was measured at baseline, 48 hours, and 6 to 12 weeks.

RESULTS

Forty-eight hours after influenza vaccination, mean CCR5 expression was significantly decreased on the CD3 (21.1% vs 11.3% in HIV-infected children; P = .02; and 18.3% vs 10.7% in controls; P = .008) and CD4 (13.0% vs 3.6% in the HIV group; P = .04; and 13.6% vs 6.5% in controls; P = .02) lymphocytes. This was observed in conjunction with an increase in HLA-DR expression on T lymphocytes in HIV-infected children (P = .046). No significant changes were observed in HIV viral load, CD3 and CD8 lymphocyte counts, expression of interleukin 2 receptor and CXCR4, or gene expression of CCR5 and beta-chemokines 48 hours after vaccination.

CONCLUSIONS

Influenza virus vaccine markedly decreased chemokine receptor CCR5 expression on CD4 T lymphocytes. However, this immunomodulatory effect does not seem to affect overall viral replication in HIV-infected children who received highly active antiretroviral therapy.

Macrophage production of inflammatory mediators is potently inhibited by a butyric acid derivative demonstrated to inactivate antigen-stimulated T cells

The butyric acid derivative, 2-(4-morpholynl) ethyl butyrate hydrochloride (MEB), has been reported to induce antigen-specific T cell unresponsiveness and to block T cell-mediated graft-versus-host disease. As a potential therapeutic agent, it was important to determine the effects of MEB on other cells that contribute to immunopathology. Accordingly, we tested the effects of MEB on macrophage functions. MEB did not affect macrophage viability, phagocytic activity, or the activation-induced up-regulation of molecules associated with antigen presentation: MHC-II, CD86, CD40, or ICAM-1. However, MEB potently inhibited activation-induced production of inflammatory mediators, including tumor necrosis factor-alpha (TNF-alpha), IL-6, chemokine CCL2 and nitric oxide (NO). MEB inhibited the induction of NO synthase (NOS2), which is necessary for inducible NO, and inhibited nuclear translocation of NFkappaB, suggesting that MEB interferes with the signaling pathway involved in NOS2 induction. Thus, while inducing specific T cell unresponsiveness, MEB also exerts anti-inflammatory activity by acting on macrophages to suppress production of cytokines and NO.

An epigenetically altered tumor cell vaccine

Functional inactivation of genes critical to immunity may occur by mutation and/or by repression, the latter being potentially reversible with agents that modify chromatin. This study was constructed to determine whether reversal of gene silencing, by altering the acetylation status of chromatin, might lead to an effective tumor vaccine. We show that the expression of selected genes important to tumor immunity, including MHC class II, CD40, and B7-1/2 are altered by treating tumor cells in vitro with a histone deacetylase inhibitor, trichostatin A (TSA). Tumor cells treated in vitro with TSA showed delayed onset and rate of tumor growth in 70% of the J558 plasmacytoma and 100% of the B16 melanoma injected animals. Long-term tumor specific immunity was elicited to rechallenge with wild-type cells in approximately 30% in both tumor models. Splenic T cells from immune mice lysed untreated tumor cells, and SCID mice did not manifest immunity, suggesting that T cells may be involved in immunity. We hypothesize that repression of immune genes is involved in the evasion of immunity by tumors and suggest that epigenetically altered cancer cells should be further explored as a strategy for the induction of tumor immunity.

Glycyrrhizin enhances interleukin-10 production by liver dendritic cells in mice with hepatitis

BACKGROUND

Glycyrrhizin (GL), an aqueous extract of licorice root, is known to have various immune-modulating and biological response-modifier activities. GL is used in patients with hepatitis to reduce the activity of liver inflammation; however, the mechanism underlying the anti-inflammatory activity of GL is poorly understood. As antigen-presenting dendritic cells (DC) in the tissue play a major role in the regulation of the inflammatory mucosal milieu during tissue inflammation, we studied whether the function of liver DC was altered by GL therapy in a murine model of concanavalin-A (con A)-induced hepatitis.

METHODS

Liver DC were propagated from control mice or mice with Con-A-induced hepatitis, and the effect of GL on liver DC was evaluated in vivo and in vitro.

RESULTS

The levels of interleukin (IL)-10 produced by liver DC were significantly lower in mice with Con-A-induced hepatitis compared with control mice. However, treatment with GL caused increased production of IL-10 in mice with Con A-induced hepatitis. The increased production of IL-10 by mice with Con A-induced hepatitis was also confirmed in vitro by culturing liver DC with GL.

CONCLUSIONS

This study indicates that increased production of IL-10 by liver DC due to GL administration may be involved in downregulation of the levels of liver inflammation in mice with Con A-induced hepatitis. Glycyrrhizin (GL), an aqueous extract of licorice root, is known to have various immune-modulating and biological response-modifier activities. GL is used in patients with hepatitis to reduce the activity of liver inflammation; however, the mechanism underlying the anti-inflammatory activity of GL is poorly understood. As antigen-presenting dendritic cells (DC) in the tissue play a major role in the regulation of the inflammatory mucosal milieu during tissue inflammation, we studied whether the function of liver DC was altered by GL therapy in a murine model of concanavalin-A (Con A)-induced hepatitis.

Effects of TGF-β2 on Immune Response–Related Gene Expression Profiles in the Human Corneal Endothelium

PURPOSE

To determine the effects of transforming growth factor (TGF)-beta2 on immune-response-related gene expression profiles in the stimulated human corneal endothelium (HCE).

METHODS

A human complementary DNA (cDNA) expression array analysis was used to investigate the effects of TGF-beta2 on cultured HCE incubated with interleukin (IL)-1alpha and tumor necrosis factor (TNF)-alpha. Gene-specific semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) were performed to examine the gene expression patterns revealed by the cDNA expression array analysis. Moreover, the expression of newly identified genes in HCE was confirmed by RT-PCR in human donor corneas.

RESULTS

cDNA expression array analysis and semiquantitative RT-PCR revealed that TGF-beta2 downregulated the expression of IL-6, growth-related (Gro)-alpha (CXCL1), monocyte chemotactic protein (MCP)-1 (CCL2), granulocyte-colony stimulating factor (G-CSF), and insulin-like growth factor binding protein (IGFBP)-5 and upregulated the expression of tissue inhibitor of metalloproteinase (TIMP)-1. ELISA confirmed TGF-beta2-mediated changes in the expression of IL-6, CXCL1, CCL2, G-CSF, IGFBP-5, and TIMP-1 at the protein level. CXCL1, G-CSF, and IGFBP-5 mRNAs were detected for the first time in the HCE of donor corneas.

CONCLUSIONS

TGF-beta2 downregulates IL-6, CXCL1, CCL2, G-CSF, and IGFBP-5, and upregulates TIMP-1 in cultured HCE stimulated with proinflammatory cytokines, suggesting the immunomodulatory role of TGF-beta2 in the aqueous humor and the pathophysiological significance of TGF-beta2 in the anterior chamber of the eye.

Regulation of gene expression associated with acute experimental autoimmune encephalomyelitis by Lovastatin

The attenuation of experimental autoimmune encephalomyelitis (EAE) by Lovastatin (LOV) has now been well established. The present study was designed to explore the global effect of LOV treatment on expression of immune-related genes in lumbar spinal cord (LSC) during acute EAE by using Affymetrix DNA microarrays. LOV treatment demonstrated the limited infiltration of inflammatory cells into the LSC, and microarray analysis further validated those interpretations by demonstrating relatively less alteration in expression of immune response genes in LOV-treated EAE rats on peak clinical day and recovery vs. untreated EAE counterparts. There was significant change in expression of about 158 immune-related genes (including 127 genes reported earlier) in LOV-treated vs. untreated EAE (>1.5 or <-1.5 fold change; P </=.05), of which 140 genes were suppressed and only 18 genes were up-regulated. These altered genes encode for leukocyte-specific markers and receptors, histocompatibility complex, cytokines/receptors, chemokines/receptors, adhesion molecules, components of the complement cascade, cellular activation, and transcription factors and signal transduction-related molecules. Interestingly, T(H)2 phenotype cytokines such as interleukin-4, interleukin-10, and transforming growth factor-beta1 and transcription factors such as peroxisome proliferator-activated receptor (PPAR)-gamma were up-regulated in LSC by LOV treatment as further revealed by real-time PCR and immunoblotting. These findings indicate that PPARs may be mediating the antiinflammatory and immunomodulatory effects of LOV. Together, these findings provide new insight into the molecular events associated with the protection provided by statins during treatment of demyelinating diseases such as multiple sclerosis.

Immune responses against Abeta1-42 in HLA class II transgenic mice: implications for Abeta1-42 immune-mediated therapies

We have investigated whether polymorphic differences in the major histocompatibility complex (MHC) class II molecules influence humoral and cellular immune responses against Abeta1-42. To analyze the effects of mouse MHC class II and tolerance effects of overexpression of human APP in mice, we immunized Tg2576 and non-transgenic littermates bred into two different MHC backgrounds with Abeta1-42 and compared both B and T cell responses. We found that in the presence of the mouse C57BL/6 background, both B and T cell responses against Abeta1-42 were significantly suppressed. To directly test the contribution of human MHC class II, we immunized various human HLA class II transgenic (TG) mice with Abeta1-42 and analyzed anti-Abeta immune responses. HLA-DR3 and HLA-DQ8 TG mice generated modest B and T cell responses against Abeta1-42. The presence of HLA-DR3/DQ8 in double TG mice enhanced the overall immune response against Abeta1-42. In contrast, HLA-DR4 TG mice mounted strong T cell responses but failed to generate high titer antibody responses against Abeta1-42, whereas, the HLA-DQ6 TG mice were not able to mount significant B or T cell responses against Abeta1-42. These studies in mice suggest that the presence of certain MHC class II molecules or combinations of class II molecules can potentially influence the overall immune response against Abeta1-42.

Aldosteronism and peripheral blood mononuclear cell activation: a neuroendocrine-immune interface

Aldosteronism eventuates in a proinflammatory/fibrogenic vascular phenotype of the heart and systemic organs. It remains uncertain whether peripheral blood mononuclear cells (PBMCs) are activated before tissue invasion by monocytes/macrophages and lymphocytes, as is the case for responsible pathogenic mechanisms. Uninephrectomized rats treated for 4 weeks with dietary 1% NaCl and aldosterone (ALDOST, 0.75 microg/h) with or without spironolactone (Spi, 100 mg/kg per daily gavage) were compared with unoperated/untreated and uninephrectomized/salt-treated controls. Before intramural coronary vascular lesions appeared at week 4 of ALDOST, we found (1) a reduction of PBMC cytosolic free [Mg2+]i, together with intracellular Mg2+ and Ca2+ loading, whereas plasma and cardiac tissue Mg2+ were no different from controls; (2) increased H2O2 production by monocytes and lymphocytes together with upregulated PBMC gene expression of oxidative stress-inducible tyrosine phosphatase and Mn2+-superoxide dismutase and the presence of 3-nitrotyrosine in CD4+ and ED-1-positive inflammatory cells that had invaded intramural coronary arteries; (3) B-cell activation, including transcription of immunoglobulins, intracellular adhesion molecule-1, and CC and CXC chemokines and their receptors; (4) expansion of B lymphocyte subset and myosin heavy chain class II-expressing lymphocytes; and (5) autoreactivity with gene expression for antibodies to acetylcholine receptors and a downregulation of RT-6.2, which is in keeping with cell activation and associated with autoimmunity. Spi cotreatment attenuated the rise in intracellular Ca2+, the appearance of oxidative/nitrosative stress in PBMCs and invading inflammatory cells, and alterations in PBMC transcriptome. Thus, aldosteronism is associated with an activation of circulating immune cells induced by iterations in PBMC divalent cations and transduced by oxidative/nitrosative stress. ALDO receptor antagonism modulates this neuroendocrine-immune interface. The full text of this article is available online at http://www.circresaha.org.

Oxazole- and imidazole-based Ser-Leu dipeptide mimetics in potent inhibitors of antigen presentation by MHC class II DR molecules

Imidazole and oxazole derivatives 1 to 4 were designed and prepared as dipeptide mimetics to replace the Ser-Leu dipeptide sequence of Ro-25-9980 (Ac-(Cha)-RAMA-S-L-NH2), a peptidic inhibitor of antigen binding to major histocompatibility complex (MHC) class II DR molecules linked to rheumatoid arthritis (RA). The most potent analog in binding assays (IC50 = 30 nM in DRB1*0401 binding; 1.6 times as potent as Ro 25-9980) was 16, Ac-(Cha)RAMA-(S)S-psi(oxazole)-L-NH2. The SAR of peptide hybrids 10 to 24, prepared by incorporating the dipeptide mimetics 1 to 4 is discussed. Of these hybrids, 23 and 24, analogs that incorporated the imidazole and oxazole mimetics as well as optimized variants at positions 3 to 5, were found to have 70 to 80 nM binding affinity comparable to the parent peptide in DRB 1*0401 binding and were also active in DRB1*0101 binding, while being resistant to proteolysis by cathepsin B. Both of these compounds showed inhibitory activity in an antigen-stimulated T-cell proliferation assay, indicating their potential to suppress autoimmune responses and as leads for therapeutic agents to treat RA.

Granulocyte-macrophage colony stimulating factor is an anti-apoptotic cytokine for thymic dendritic cells and a significant modulator of their accessory function

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a growth-promoting factor for myeloid-derived dendritic cells (DC) but not for lymphoid DC. The data about its effect on thymic DC (TDC), which are both of lymphoid and myeloid origin, are very scarce. Using an in vitro model, we demonstrated in this work that GM-CSF significantly increased the survival of rat TDC in culture by inhibiting their apoptosis and the effect correlated with up-regulation of Bcl-2 expression. GM-CSF also stimulated differentiation and maturation of TDC as judged by higher expression of MHC class I and II molecules, CD54, CD80 and CD86. These changes correlated with stronger stimulatory activity of GM-CSF-pulsed TDC in syngeneic thymocyte proliferation assay and MLR. The stimulatory potential of TDC was further increased when thymocytes were cultivated with an anti-alphabeta TCR (R73) monoclonal antibody (mAb). The influence of unstimulated TDC on proliferation of thymocytes was inhibited by anti-CD86 but not anti-CD80 mAb, whereas in cultures with GM-CSF-treated TDC both mAbs exerted an additive blocking effect. After separation of TDC on CD11b(+) and CD11b(-) we demonstrated that GM-CSF inhibited apoptosis and potentiated accessory activity of both TDC subsets independently of the myeloid marker expression. Cummulatively, our results suggest that GM-CSF is one of the regulatory cytokine involved in survival, maturation, differentiation and accessory function of TDC.

Toward a Role for Statins in Immunomodulation

The family of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) inhibitors, collectively known as statins, is used clinically to reduce cholesterol levels in patients. Recent reports suggest that not only would statin therapy be beneficial for at-risk (genetically predisposed) people without symptoms of hypercholesterolemia, but that statins may have beneficial, pleiotropic effects in the treatment of autoimmune diseases. Youssef et al. have described how an HMG-CoA inhibitor, atorvastatin, might ameliorate experimental autoimmune encephalomyelitis (EAE), the mouse model for human multiple sclerosis. The possible clinical use of statins as anti-inflammatory drugs has also been demonstrated in other published reports. These provocative results suggest a role for statins in relieving autoimmune diseases such as multiple sclerosis.

DNA alkylating agents alleviate silencing of class II transactivator gene expression in L1210 lymphoma cells

MHC class II (Ia) Ag expression is inversely correlated with tumorigenicity and directly correlated with immunogenicity in clones of the mouse L1210 lymphoma (1 ). Understanding the mechanisms by which class II Ag expression is regulated in L1210 lymphoma may facilitate the development of immunotherapeutic approaches for the treatment of some types of lymphoma and leukemia. This study demonstrates that the variation in MHC class II Ag expression among clones of L1210 lymphoma is due to differences in the expression of the class II transactivator (CIITA). Analysis of stable hybrids suggests that CIITA expression is repressed by a dominant mechanism in class II-negative L1210 clones. DNA-alkylating agents such as ethyl methanesulfonate and the chemotherapeutic drug melphalan activate CIITA and class II expression in class II negative L1210 cells, and this effect appears to be restricted to transformed cell lines derived from the early stages of B cell ontogeny. Transient transfection assays demonstrated that the CIITA type III promoter is active in class II(-) L1210 cells, despite the fact that the endogenous gene is not expressed, which suggests that these cells have all of the transacting factors necessary for CIITA transcription. An inverse correlation between methylation of the CIITA transcriptional regulatory region and CIITA expression was observed among L1210 clones. Furthermore, 5-azacytidine treatment activated CIITA expression in class II-negative L1210 cells. Collectively, our results suggest that 1) CIITA gene expression is repressed in class II(-) L1210 cells by methylation of the CIITA upstream regulatory region, and 2) treatment with DNA-alkylating agents overcomes methylation-based silencing of the CIITA gene in L1210 cells.

Inhibition of major histocompatibility complex class II gene transcription by nitric oxide and antioxidants

Interferon (IFN)-gamma facilitates cellular immune response, in part, by inducing the expression of major histocompatibility complex class II (MHC-II) molecules. We demonstrate that IFN-gamma induces the expression of HLA-DRA in vascular endothelial cells via mechanisms involving reactive oxygen species. IFN-gamma-induced HLA-DRA expression was inhibited by nitric oxide (NO) and antioxidants such as superoxide dismutase, catalase, pyrrolidine dithiocarbamate, and N-acetylcysteine. Nuclear run-on assays demonstrated that NO and antioxidants inhibited IFN-gamma-induced HLA-DRA gene transcription. Transient transfection studies using a fully functional HLA-DRA promoter construct ([-300]DR alpha.CAT) showed that inhibition of endogenous NO synthase activity by N(omega)-monomethyl-l-arginine or addition of exogenous hydrogen peroxide (H(2)O(2)) augmented basal and IFN-gamma-stimulated [-300]DR alpha.CAT activity. However, H(2)O(2) and N(omega)-monomethyl-l-arginine could induce HLA-DRA expression suggesting that H(2)O(2) is a necessary but not a sufficient mediator of IFN-gamma-induced HLA-DRA expression. Electrophoretic mobility shift assay and Western blotting demonstrated that NO and antioxidants had little or no effect on IFN-gamma-induced IRF-1 activation or MHC-II transactivator (CIITA) expression but did inhibit IFN-gamma-induced activation of STAT1 alpha (p91) and Y box transcription factors, NF-Y(A) and NF-Y(B). These results indicate that NO and antioxidants may attenuate vascular inflammation by antagonizing the effects of intracellular reactive oxygen species generation by IFN-gamma, which is necessary for MHC-II gene transcription.

Mutational switch of an IL-6 response to an interferon-gamma-like response

Signaling through Janus kinases (JAKs) and signal transducers and activators of transcription (STATs) is central to the responses to the majority of cytokines and some growth factors, including the interferons (IFNs) and the IL-6 family of cytokines. The biological responses to stimulation through the widely distributed IL-6 and IFN-gamma receptors are, however, completely different. Remarkably, it is shown here that, in mouse embryo fibroblasts lacking STAT3, IL-6 mediates an IFN-gamma-like response including prolonged activation of STAT1, the induction of multiple IFN-gamma-inducible genes, the expression of class II MHC antigens, and an antiviral state. Normal cells exposed to IL-6 thus require a STAT3-dependent function(s) to down-regulate STAT1 activity and prevent an IFN-gamma-like response. The data encourage the view that the very disparate IFN-gamma and IL-6 JAK/receptor complexes mediate a common set of generic or "core" signals which are subject to STAT3-dependent modulation to provide IL-6 specificity. The switching of one cytokine response to one closely mimicking another as a result of the loss of a single signaling component has profound implications, for example, for the interpretation of the phenotypes of knockout mice and for the clinical use of inhibitors of signaling.

Inhibitors of ATP-binding cassette transporters suppress interleukin-12 p40 production and major histocompatibility complex II up-regulation in macrophages

ATP-binding cassette (ABC) transporters are a large family of proteins whose role is to translocate various substances across biological membranes. They include the Tangier disease protein ABC1, sulfonylurea receptors (SUR), multidrug resistance protein (MDR), and cystic fibrosis transmembrane regulator (CFTR). In the current study, we investigated the involvement of ABC transporters in the regulation of lipopolysaccharide (LPS) and/or interferon (IFN)-gamma-induced interleukin (IL)-12 p40 and tumor necrosis factor (TNF)-alpha production, nitric oxide formation, as well as major histocompatibility complex II up-regulation in macrophages. The general ABC transporter inhibitor glibenclamide suppressed both IL-12 p40 and nitric oxide production. However, glibenclamide failed to affect the production of TNF-alpha. The selective ABC1 inhibitors 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and sulfobromophthalein mimicked the suppressive effect of glibenclamide on IL-12 p40 production. On the other hand, both the MDR inhibitor verapamil and CFTR blocker 2,2'-iminodibenzoic acid failed to suppress the production of IL-12 p40. Furthermore, selective inhibitors and activators of SURs were without effect. In agreement with the pharmacological data, macrophages expressed mRNA for ABC1, but not SURs or CFTR. Intracellular levels of IL-12 p40 were decreased by glibenclamide, suggesting that glibenclamide does not affect IL-12 p40 secretion. The effect of glibenclamide did not involve an interference with the activation of the p38 and p42/44 mitogen-activated protein kinases or c-Jun kinase. Glibenclamide also suppressed IFN-gamma-induced up-regulation of major histocompatibility complex II. Taken together, our results indicate that ABC proteins regulate LPS and/or IFN-gamma-induced macrophage activation.

IFN gamma/TNF alpha synergism in MHC class II induction: effect of nicotinamide on MHC class II expression but not on islet-cell apoptosis

AIMS/HYPOTHESIS

Interferon-gamma (IFN gamma) and TNFalpha synergistically induce pancreatic beta-cell apoptosis. Apart from their direct effect, we studied the possible indirect immunological role of IFNgamma/TNFalpha synergism on pancreatic beta-cell death by investigating MHC class II induction by cytokines. The effect of nicotinamide on the cytokine-induced MHC class II expression and pancreatic beta-cell death was also studied.

METHODS

Immunocytochemistry, flow cytometry and RNase protection assay were used to study MHC class II expression. Immunoblotting was done to study downstream signals of IFN gamma. The effects of nicotinamide on islet-cell apoptosis and diabetes mellitus were examined using MTT assay and adoptive transfer model.

RESULTS

IFN gamma alone induced MHC class II expression on a small number of insulinoma cells. TNFalpha alone did not induce MHC class II expression, but enhanced IFN gamma-induced MHC class II expression. MHC class II expression by cytokine(s) was due to the induction of class II transactivator (CIITA). Nicotinamide reduced MHC class II expression by cytokine(s) but did not protect insulinoma-cell apoptosis by IFN gamma and TNFalpha in combination or protect against the development of diabetes mellitus after adoptive transfer of diabetogenic lymphocytes.

CONCLUSION/INTERPRETATION

IFN gamma and TNFalpha synergistically induced MHC class II expression on insulinoma cells through the induction of CIITA; nicotinamide reduced the expression of cytokine-induced MHC class II expression on insulinoma cells through its effect on CIITA expression; and the preventive effect of nicotimamide on Type I (insulin-dependent) diabetes mellitus is probably due to its effect of MHC class II expression rather than that on islet cell apoptosis.

Contact sensitizers specifically increase MHC class II expression on murine immature dendritic cells

Contact sensitivity is a T-cell-mediated immune disease that can occur when low-molecular-weight chemicals penetrate the skin. In vivo topical application of chemical sensitizers results in morphological modification of Langerhans cells (LC). Moreover, within 18 h, LC increase their major histocompatibility complex (MHC) class II antigens expression and migrate to lymph nodes where they present the sensitizer to T lymphocytes. We wanted to determine if such an effect could also be observed in vitro. However, because of the high genetic diversity encountered in humans, assays were performed with dendritic cells (DC) obtained from a Balb/c mouse strain. The capacity of a strong sensitizer, DNBS (2,4-dinitrobenzene sulfonic acid), to modulate the phenotype of bone marrow-derived DC in vitro, was investigated. A specific and marked increase of MHC class II molecules expression was observed within 18 h. To eliminate the use of animals in sensitization studies, the XS52 DC line was tested at an immature stage. A 30-min contact with the strong sensitizers DNBS and oxazolone, or the moderate mercaptobenzothiazole, resulted in upregulation of MHC class II molecules expression, analyzed after 18-h incubation. This effect was not observed with irritants (dimethyl sulfoxide and sodium lauryl sulfate) nor with a neutral molecule (sodium chloride). These data suggested the possibility of developing an in vitro model for the identification of the sensitizing potential of chemicals, using a constant and non animal-consuming material.

Induction of class II molecules by cytomegalovirus in rat heart endothelial cells is inhibited by ganciclovir

Cytomegalovirus (CMV) has been demonstrated to induce class II antigen expression in endothelial cells. To study whether ganciclovir (DHPG) has an effect on CMV-induced class II expression, cultured rat heart endothelial cells were infected with rat CMV (RCMV) and treated with different DHPG concentrations. Class II antigens in endothelial cells were detected by a monoclonal antibody and immunoperoxidase technique. Control cells did not express class II antigen, but during RCMV infection 92% of cells were class II-positive. DHPG treatment (1, 10, 100 and 1000 microg/ml) decreased RCMV-induced class II expression from 73% to 59%, 6% and 0%, respectively. As DHPG inhibits CMV DNA polymerase, our present results suggest that DHPG affects RCMV-induced class II expression via the inhibition of RCMV DNA replication.

The HMG-CoA reductase inhibitor simvastatin inhibits IFN-gamma induced MHC class II expression in human vascular endothelial cells

HMG-CoA reductase inhibitors, or statins, are lipid-lowering agents that have been shown to effectively decrease severe rejection periods and development of transplant coronary artery disease after heart transplantation. Precise regulation of major histocompatibility complex class II (MHC class II) gene expression plays a pivotal role in control of the immune response after transplantation. The aim of this study was to evaluate the potential role of HMG-CoA reductase inhibitors in regulating the immune response. We have examined the effects of simvastatin on MHC class II expression in primary human endothelial cells. Using RNAse protection assay and flow cytometry, we observed that simvastatin dose-dependently reduced interferon-gamma (IFN-gamma) induced MHC class II expression (mRNA and protein). In contrast, simvastatin did not affect the expression of MHC class I, pointing to specific actions in the MHC class II signalling cascade. The transcriptional coactivator CIITA is the general regulator of both constitutive and inducible MHC class II expression. After stimulation with IFN-gamma, the CIITA gene is selectively activated via one (promotor IV) of its four promoters. Interestingly, mRNA levels of CIITA were decreased after treatment with simvastatin. In addition, using transient transfections of promoter-reporter constructs we observed that the activity of CIITA promoter IV was decreased by simvastatin. In conclusion, simvastatin selectively decreases IFN-gamma-induced MHC class II expression in human primary endothelial cells through actions on the CIITA promoter IV. Thus, the beneficial effects of statins reported after heart transplantation may result from this immunosuppressive action, suggesting possible therapeutic use for other immunological disorders as well.

Activation of MHC class I, II, and CD40 gene expression by histone deacetylase inhibitors

Epigenetic mechanisms are involved in regulating chromatin structure and gene expression through repression. In this study, we show that histone deacetylase inhibitors (DAIs) that alter the acetylation of histones in chromatin enhance the expression of several genes on tumor cells including: MHC class I, II, and the costimulatory molecule CD40. Enhanced transcription results in a significant increase in protein expression on the tumor cell surface, and expression can be elicited on some tumors that are unresponsive to IFN-gamma. The magnitude of induction of these genes cannot be explained by the effect of DAIs on the cell cycle or enhanced apoptosis. Induction of class II genes by DAIs was accompanied by activation of a repressed class II transactivator gene in a plasma cell tumor but, in several other tumor cell lines, class II was induced in the apparent absence of class II transactivator transcripts. These findings also suggest that the abnormalities observed in some tumors in the expression of genes critical to tumor immunity may result from epigenetic alterations in chromatin and gene regulation in addition to well-established mutational mechanisms.

The expression of MHC class II genes in macrophages is cell cycle dependent

Using different drugs, we stopped the cell cycle of bone marrow-derived macrophages at different points. After IFN-gamma stimulation, macrophages arrested at the G(1) phase of the cell cycle did not increase cell surface expression of the MHC class II IA. This inhibition is specific, because, under the same conditions, IFN-gamma induces the expression of Fcgamma receptors and the inducible NO synthase mRNA. Treatments that inhibit macrophage proliferation by blocking the cell cycle at the G(1) phase, such as adenosine, forskolin, or LPS, blocked the IFN-gamma induction of IA. Under IFN-gamma treatment, the steady-state levels of IAalpha and IAss mRNA did not increase in cells arrested at the G(1) phase and the half-life of the MHC mRNA was not modified. These data suggest that the cell cycle modulation of IFN-gamma-induced MHC II gene expression occurs at the transcriptional level. The expression of the class II transactivator mRNA induced by IFN-gamma was also blocked when macrophages were arrested at the G(1) phase of the cell cycle, suggesting that the lack of IFN-gamma response occurs at the early steps of MHC class II expression. Finally, macrophages arrested at the G(1) phase showed increased basal levels of cell surface IA due to an increase of the translational efficiency. These data show that the expression of MHC class II genes is regulated by the cell cycle.

Phagocytosis of neuronal or glial debris by microglial cells: upregulation of MHC class II expression and multinuclear giant cell formation in vitro

Most CNS pathologies are accompanied by the occurrence of activated, phagocytic microglial cells. We intended to investigate whether (1) isolated microglial cells removed from the CNS cytokine network sustain their capacity to acquire an activated phenotype when challenged with cellular or noncellular debris; and (2) different substrates lead to different patterns of microglial activation. It was observed that although removed from their usual surroundings microglial cells preserve their ability to transform to an amoeboid morphology, form multinucleated giant cells, and enhance their expression of MHC class II when exposed to membranes of neuronal or glial origin. Furthermore, cellular substrates derived from primary hippocampal neuronal cultures, neuroblastic cells (B50), or glial cells were all able to induce similar morphological changes and enhanced expression of MHC class II. In contrast, phagocytosis of Latex beads induced an amoeboid morphology but no increase in the expression of immunologically relevant molecules. Interferon-beta (IFN-beta), a substance clinically used in the treatment of the relapsing-remitting form of multiple sclerosis, was shown to inhibit the phagocytosis-induced upregulation of MHC-class II. In summary, phagocytic microglial cells are independent from the CNS cytokine network in their transition from a resting to an activated phenotype; and different cellular substrates, regardless whether they are of neuronal, glial, or even malignant origin, result in similar morphological and functional changes.

Central administration of methotrexate reduces mechanical allodynia in an animal model of radiculopathy/sciatica

We have recently reported that injury to a lumbar root in a rat model of radiculopathy produces spinal glial activation associated with elevated proinflammatory cytokines. Based on our hypothesis that central neuroinflammatory processes may manifest clinically as radicular pain, we undertook pharmacological intervention using the immunosuppressive agent methotrexate (MTX). The L5 lumbar spinal root (central to the dorsal root ganglia) was exposed unilaterally and loosely constricted with chromic gut. In the prevention (phase I) study, MTX was administered intrathecally (1 mg/kg) and around the spinal root (1 mg/kg) at surgery and at days 2 and 4 postsurgery (group A). Saline injection was employed for the control group (group B). Sham operated animals were administered MTX to determine the potential for behavioral/neural side effects (group C). In the existing pain paradigm (phase II) study, the experiment was extended to day 14 with three additional groups. The same dose and method of delivery of MTX or saline was administered as in phase I in the first week on days 0, 2, and 4 and in the second week on days 7, 9, and 11 postsurgery. To measure the effects of MTX on existing behaviors saline was administered in the first week and MTX during the second (group D; Saline:MTX). The control group received saline during both weeks (group E; Saline:Saline). To examine the possible recurrence of radicular pain after MTX termination, MTX was given in the first week and saline in the second (group F; MTX:Saline). Gait disturbance and mechanical allodynia (using von Frey filaments) were assessed up to day 7 in the prevention study (Phase I) and day 14 in the existing pain paradigm (Phase II). The L5 spinal cord segments were harvested for assessment of immunohistochemical glial activation using the antibodies OX-42 (microglial marker) and glial fibrillary acidic protein (GFAP: astrocytic marker) and for the presence of Major Histocompatibility Complex (MHC) Class II expression. Group C (Sham+MTX) did not demonstrate any evidence of gait disturbance or mechanical allodynia after MTX administration. The rats in group B (Surgery+Saline) demonstrated mechanical allodynia from one day postsurgery to the time of euthanization. When allodynia was assessed using the 12 g von Frey filament, the MTX treated rats in group A showed significantly decreased mechanical allodynia as compared to the saline treated rats (group B) (repeated measured ANOVA, P<0.0001). In the phase II study, the rats in group D (Saline:MTX) and E (Saline:Saline) showed robust allodynia in the first week after the surgery. In the second week, mechanical allodynia significantly decreased in group D, while mechanical allodynia continued in the saline treated group (repeated measured ANOVA, P=0.0121). Allodynia was significantly attenuated in group F (MTX: Saline) as compared to the response in groups D and E at day 7 (one-way ANOVA, P<0.0001) and remained significantly lower as compared to group E up to day 11 postsurgery (one-way ANOVA, P9=0. 0013: P11=0.0048). OX-42 and GFAP expression were elevated in the gray matter of the L5 spinal section in all groups that underwent the root ligature with chromic gut (Groups A, B, D-F). There were no significant differences in glial activation between the groups. However, spinal expression of MHC II was markedly reduced in the MTX treated group as compared with the saline treated group. The exact mechanism of action of MTX in attenuating mechanical allodynia has not yet been elucidated. The present results indicate that MTX administration may offer a new treatment modality for radicular pain with or without disc herniation as well as directing new research into the development of novel immunomodulators for the treatment of chronic neuropathic and radicular pain.

Methylation of class II trans-activator promoter IV: a novel mechanism of MHC class II gene control

Inhibition of class II trans-activator (CIITA) expression prevents embryonic trophoblast cells from up-regulating MHC class II genes in response to IFN-gamma. This is thought to be one mechanism of maternal tolerance to the fetal allograft. The CIITA gene is regulated by four distinct promoters; promoter III directs constitutive (B cell) expression, and promoter IV regulates IFN-gamma-inducible expression. Using in vivo genomic footprinting, promoter-reporter analysis, Southern blot analysis, and RT-PCR, we have examined the cause of CIITA silencing in a trophoblast-derived cell line. We report here that methylation of promoter IV DNA at CpG sites in Jar cells prevents promoter occupancy and IFN-gamma-inducible transcription. The inhibition of CpG methylation in Jar cells by treatment with 5-aza-2'-deoxycytidine restores IFN-gamma inducibility to CIITA. This is the first description of an epigenetic mechanism involved in regulation of CIITA and MHC class II gene expression.

Coordinate suppression of superantigen-induced cytokine production and T-cell proliferation by a small nonpeptidic inhibitor of class II major histocompatibility complex and CD4 interaction

Proinflammatory cytokines mediate the toxic effect of superantigenic staphylococcal exotoxins (SE). TJU103, a small nonpeptidic molecule that blocks the interaction between major histocompatibility complex class II and CD4 molecules inhibited SE-stimulated T-cell proliferation (by 92%) and production of tumor necrosis factor, interleukin 1beta, interleukin 6, and gamma interferon (by 66, 56, 76, and 72%, respectively) by human peripheral blood mononuclear cells. These data suggest that TJU103 may be useful for mitigating the pathogenic effects of SE.

TGF-beta1 down-regulates induced expression of both class II MHC and B7-1 on primary murine renal tubular epithelial cells

BACKGROUND

We examined the immunomodulatory effects of transforming growth factor-beta1 (TGF-beta1) on the regulation of class II MHC and costimulatory molecule expression in a primary renal tubular epithelial cell line, called F1K.

METHODS

Class II major histocompatibility complex (MHC), class II transactivator, B7-1, intercellular adhesion molecule-1 (ICAM-1) and interferon-gamma (IFN-gamma) receptor beta chain were evaluated in untreated and cytokine-treated F1K by Northern hybridization analysis and flow cytometry. T cell activation studies were performed to assess TGF-beta1-mediated effects on antigen presenting cell function of F1K.

RESULTS

Pretreatment of F1K with TGF-beta1 markedly inhibited IFN-gamma-induced class II MHC expression, by both FACS and Northern analysis. Total class II transactivator mRNA levels were also diminished by TGF-beta1, indicating that class II MHC modulation in F1K results from inhibition of this intermediate protein. As previous studies demonstrated that cotreatment of F1K cells with IFN-gamma + lipopolysaccharide (LPS) induces B7-1, we evaluated the potential regulatory effects of TGF-beta1 exposure on B7-1 expression. Our studies revealed that B7-1 mRNA and cell-surface expression in IFN-gamma + LPS-treated F1K were decreased by TGF-beta1 pretreatment. Functional studies evaluating TGF-beta1-mediated effects were performed with IFN-gamma + LPS-treated F1K and MR1.3, a nephritogenic CD4+ Th2 clone derived from kidneys of animals with autoimmune glomerulonephritis. Interleukin (IL)-4 production assays demonstrated activation of MR1. 3 by IFN-gamma + LPS-treated cells, but not by IFN-gamma + LPS-treated cells previously exposed to TGF-beta1, indicating that TGF-beta1-mediated inhibition of class II MHC and B7-1 expression alters the antigen presenting cell function of F1K.

CONCLUSIONS

These studies describe the proscriptive influence of TGF-beta1 on class II MHC and B7-1 expression in renal tubular epithelial cells. Such findings indicate that TGF-beta1 alters the antigen presenting cell function of renal tubular epithelial cells in vitro, and suggest a potential mechanism for immunosuppression of T cell-mediated renal immune responses in vivo.

Cutting edge: phorbol ester induction of IFN-gamma receptors leads to enhanced DR alpha gene expression

We observed that IFN-gamma-inducible expression of the DR alpha gene was enhanced when THP-1 cells are differentiated into macrophage-like cells by phorbol ester treatment. Here, we observed that class II MHC trans-activator and STAT1 alpha mRNA, mediators of the signaling cascade from the IFN-gamma receptor to the DR alpha induction, were markedly increased by IFN-gamma stimulation in phorbol ester-activated THP-1 cells; however, both mRNAs were not increased by phorbol ester treatment alone. Then, we demonstrated that the mRNA and proteins of the IFN-gamma receptor alpha- and beta-chains were amplified by phorbol ester treatment in THP-1 cells. Consequently, these results indicate that the enhancement of DR alpha gene expression by IFN-gamma treatment in phorbol ester-activated THP-1 cells is due to the phorbol ester-induced up-regulation of IFN-gamma receptor alpha- and beta-chains. As a result, the amplification of STAT1 alpha and the increment of class II MHC trans-activator results in enhancement of DR alpha expression.

Antiproteinuric therapy while preventing the abnormal protein traffic in proximal tubule abrogates protein- and complement-dependent interstitial inflammation in experimental renal disease

In proteinuric glomerulopathies, the excess traffic of proteins into the renal tubule is a candidate trigger of interstitial inflammatory and immune events leading to progressive injury, and a key target for the renoprotective action of antiproteinuric drugs. Among proteins trafficked to the proximal tubule, the third component of complement (C3) can be activated locally and contribute to inflammation at sites of protein reabsorption. Experiments were performed in rats with renal mass reduction (RMR, 5/6 nephrectomy) with the following aims: (1) to study Ig (IgG) and complement deposition in proximal tubules, and interstitial macrophage infiltration and MHC class II expression at intervals after surgery by double immunofluorescence analysis; (2) to assess whether lisinopril (angiotensin-converting enzyme inhibitor [ACEi], 25 mg/L in the drinking water, from either day 1 or day 7) limited IgG and C3 accumulation and interstitial inflammation at day 30. In 7-d remnant kidneys, intracellular staining for both IgG and C3 was detectable in proximal tubules in focal areas; C3 was restricted to IgG-positive tubular cells, and there were no interstitial ED-1 macrophage and MHC II-positive cellular infiltrates. In 14-d and 30-d remnant kidneys, proximal tubular IgG and C3 staining was associated with the appearance of interstitial infiltrates that preferentially localized to areas of tubules positive for both proteins. RMR rats given ACEi had no or limited increases in levels of urinary protein excretion, tubular IgG, and C3 reactivity, and interstitial cellular infiltrates in kidneys at 30 d, even when ACEi was started from day 7 after surgery. These findings document that (1) in RMR, IgG and C3 accumulation in proximal tubular cells is followed by leukocyte infiltration and MHC II overexpression in the adjacent interstitium; (2) ACEi while preventing proteinuria limits both tubular accumulation of IgG and C3 and interstitial inflammation. The data suggest that ACE inhibition can be renoprotective by limiting the early abnormal protein traffic in proximal tubule and consequent deleterious effects of excess protein reabsorption, including the accumulation and local activation of complement as well as the induction of chemokines and endothelin genes known to promote interstitial inflammation and fibrosis.

A binding protein to the DNase I hypersensitive site II in HLA-DR alpha gene was identified as NF90

We previously observed that IFN gamma-inducible expression of the human MHC class II, HLA-DR alpha, gene was enhanced by treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) only in human monocytic leukemia THP-1 cells, but not in HeLa cells. In the HLA-DR alpha gene, three DNase I hypersensitive sites (DHS) are known to be present in the promoter region (DHS-I) and first intron (DHS-II and -III) and are assumed to be involved in HLA-DR alpha gene regulation. In this study, we found a binding factor which recognized a unique palindrome sequence (DHS-22) in the region of the DHS II site of the HLA-DR alpha gene in THP-1 cells and HeLa cells. The binding activity of this factor was decreased by TPA treatment in THP-1 cells, but not in HeLa cells. This binding activity was also detectable in nuclear extracts of bovine brains. Thus, we isolated the DHS-22 binding factor from bovine brain nuclear extracts and finally identified it as NF90 on the basis of molecular mass analysis of Lys-C-digested fragments and amino acid sequences of the two peptides of the trypsin-digested binding protein. The DHS-22 binding protein(s) in THP-1 cells is (are) further confirmed by reactivity to an antibody against NF90, and we have demonstrated that the GST fusion protein of NF90 interacts with DHS-22 by electrophoretic gel mobility shift assay (EMSA). The mRNA of NF90 was decreased by TPA treatment in THP-1 cells but not in HeLa cells. These results suggest that the binding of NF90 to the DNase I hypersensitive site II of HLA-DR alpha gene seems to negatively regulate HLA-DR alpha gene expression.

DNA damage caused by etoposide and gamma-irradiation induces gene conversion of the MHC in a mouse non-germline testis cell line

We have explored the effects of gamma-irradiation and etoposide on the gene conversion frequency between the endogenous major histocompatibility complex class II genes Abk and Ebd in a mouse testis cell line of non-germline origin with a polymerase chain reaction assay. Both gamma-rays and etoposide were shown to increase the gene conversion frequency with up to 15-fold compared to untreated cells. Etoposide, which is an agent that stabilise a cleavable complex between DNA and DNA topoisomerase II, shows an increased induction of gene conversion events with increased dose of etoposide. Cells treated with gamma-rays, which induce strand breaks, had an increased gene conversion frequency when they were subjected to low doses of irradiation, but increasing doses of irradiation did not lead to an increase of gene conversion events, which might reflect differences in the repair process depending on the extent and nature of the DNA damage. These results where DNA damage was shown to be able to induce gene conversion of endogenous genes in mouse testis cells suggests that the DNA repair system could be involved in the molecular genetic mechanism that results in gene conversion in higher eukaryotes like mammals.

IL-1 beta inhibits IFN-gamma-induced class II MHC expression by suppressing transcription of the class II transactivator gene

Class II MHC Ags are critical for the initiation of immune responses by presenting Ag to T lymphocytes, leading to their activation and differentiation. The transcriptional activation of class II MHC genes requires the induction of the class II transactivator (CIITA) protein, a master regulator that is essential for both constitutive and IFN-gamma-inducible class II MHC expression. The cytokine IL-1beta has been shown to inhibit IFN-gamma-induced class II MHC expression in various cell types. We investigated the underlying mechanism of this inhibitory effect of IL-1beta using human astroglioma cell lines. Our findings demonstrate that IL-1beta prevents the expression of class II MHC mRNA and protein upon treatment with IFN-gamma. Furthermore, we demonstrate that IFN-gamma induction of CIITA mRNA expression is inhibited by treatment of cells with IL-1beta. IL-1beta suppressed IFN-gamma activation of the type IV CIITA promoter in astroglioma cells, indicating that the inhibitory influence of IL-1beta is mediated by inhibition of CIITA transcription. IL-1beta did not interfere with IFN-gamma receptor signal transduction, since tyrosine phosphorylation, nuclear translocation, and DNA binding of STAT-1alpha to an IFN-gamma activation sequence of the type IV CIITA promoter were not affected by IL-1beta. As well, IL-1beta treatment did not affect the ability of IFN-gamma-induced interferon-regulatory factor-1 (IRF-1) to bind the IRF-1 element within the type IV CIITA promoter. This study suggests that IL-1beta may play a role in regulating immunoreactivity by inhibiting transcription of the CIITA gene, thereby reducing subsequent class II MHC expression.

Translational control of MHC class II I-A molecules by IFN-gamma

MHC class II molecules are expressed in a limited number of cell types, including B lymphocytes and macrophages (M phi). IFN-gamma increases the surface expression of class II molecules in a murine B cell line without inducing detectable changes in either I-A or I-A mRNA levels. In bone marrow-derived M phi, IFN-gamma causes an increase in class II expression at both the mRNA and surface levels. In addition to the increase in transcription rates described for M phi, IFN-gamma increases the rate of synthesis of IA alpha and IA beta proteins and the ribosome loading for both mRNA molecules in both cell types. Interestingly, there is a significant peak of free I-A mRNA in noninduced cells. Therefore, IFN-gamma regulates the expression of MHC class II molecules at the translational level in both B cells and M phi and, as already reported, at the transcriptional level only in M phi. The actual mechanism of regulation causes changes in the translation initiation rates in both cell types, as demonstrated by an increase in ribosome loading in polysome gradients.

Suppression of major histocompatibility complex class I and class II gene expression in Listeria monocytogenes-infected murine macrophages

Macrophage cells play a central role during infection with Listeria monocytogenes by both providing a major habitat for bacterial multiplication and presenting bacterial antigens to the immune system. In this study, we investigated the influence of L. monocytogenes infection on the expression of MHC class I and class II genes in two murine macrophage cell lines. Steady-state levels of I-Abeta chain mRNA were decreased in both resting J774A.1 and P388D1 macrophages infected with L. monocytogenes whereas reduction of H-2K mRNA was only observed in P388D1 cells. In addition, L. monocytogenes suppressed induction of MHC class I and class II mRNAs in response to gamma-interferon as well as the maintenance of the induced state in activated P388D1 macrophages. Exposure to the non-pathogenic species L. innocua or a deletion mutant of L. monocytogenes, which lacks the lecithinase operon, did not cause a reduction in H-2K and I-Abeta mRNA levels nor suppress expression of Ia antigens. Inhibition of MHC gene expression may represent an important part of the cross-talk between L. monocytogenes and the macrophage that probably influences the efficiency of a T cell-mediated immune response and thus the outcome of a listerial infection.

Quantitative control of MHC class II expression by the transactivator CIITA

Activation of T lymphocytes is quantitatively controlled by the level of expression of MHC class II molecules. Both constitutive and inducible expression of MHC class II genes is regulated by the transactivator CIITA, which is itself tightly regulated. Since the level of MHC class II molecules expressed is a functionally essential parameter, it was of interest to explore whether MHC class II expression is quantitatively controlled by the level of the transactivator. This report shows that in a variety of experimental conditions one does indeed observe, in both mouse and man, a quantitative control of MHC class II expression by the level of CIITA. This relationship between the regulator gene, which behaves as a rate-limiting factor, and its target genes clarifies our understanding of the quantitative modulation of MHC class II expression, and thus of T lymphocyte activation.

HLA-DR7 in association with chlorpromazine-induced lupus anticoagulant (LA)

The presence of anti-phospholipid antibodies (aPL) has been associated with the major histocompatibility complex (MHC) genes. These autoantibodies occur in individuals with infections such as that produced by the human immunodeficiency virus 1 (HIV-1) or with syphilis, but they can also occur in drug-induced lupus-like syndromes. In the present study, we analysed the presence of aPL (detected as lupus anti-coagulant) and its relationship with the MHC markers in 93 Caucasian psychiatric patients chronically treated with chlorpromazine. Forty-one out of 93 patients were positive for LA, and the HLA-DR7 antigen was significantly increased in LA-positive patients as compared to normal controls or LA-negative patients (PC = 0.024, RR = 2.12 and P = 0.05, RR = 1.57, respectively). Likewise, we noted a significantly increased frequency of HLA-B44 in LA-positive patients as compared to normal controls (PC = 0.024, RR = 2.12), but not when compared to aPL-negative patients. No significant differences were found among any other class I, II or III MHC antigens. Haplotype analysis showed that DR7 was mostly part of the HLA-B44-DR7-FC31 and B7-DR7-SC31 haplotypes. These results suggest that the HLA-DR7 antigen might be playing a role in the production of aPL in chlorpromazine-treated patients.

TGF-beta suppresses IFN-gamma induction of class II MHC gene expression by inhibiting class II transactivator messenger RNA expression

Recently, a non-DNA binding protein, class II transactivator (CIITA), has been shown to be required for constitutive and IFN-gamma-inducible class II MHC transcription. The cytokine TGF-beta inhibits IFN-gamma-induced class II MHC expression at the transcriptional level. In this study, we provide evidence that TGF-beta blocks IFN-gamma-induced CIITA mRNA accumulation. TGF-beta down-regulates class II MHC and CIITA mRNA accumulation in human astroglioma and fibrosarcoma cell lines, but TGF-beta does not destabilize the CIITA message, suggesting an effect at the transcriptional level. In cells that stably overexpressed CIITA, leading to a constitutive class II MHC-positive phenotype, the inhibitory effect of TGF-beta on class II MHC was abrogated, but the cells remained responsive for expression of TGF-beta-inducible genes. Cell lines that possessed defects in TGF-beta signaling also became refractory to inhibition of IFN-gamma-induced CIITA and class II MHC expression. Our data indicate that TGF-beta suppresses IFN-gamma-induced class II MHC expression by inhibiting accumulation of CIITA mRNA.