USP18 enhances dengue virus replication by regulating mitochondrial DNA release

Dengue virus (DENV) infection remains a challenging health threat worldwide. Ubiquitin-specific protease 18 (USP18), which preserves the anti-interferon (IFN) effect, is an ideal target through which DENV mediates its own immune evasion. However, much of the function and mechanism of USP18 in regulating DENV replication remains incompletely understood. In addition, whether USP18 regulates DENV replication merely by causing IFN hyporesponsiveness is not clear. In the present study, by using several different approaches to block IFN signaling, including IFN neutralizing antibodies (Abs), anti-IFN receptor Abs, Janus kinase inhibitors and IFN alpha and beta receptor subunit 1 (IFNAR1)knockout cells, we showed that USP18 may regulate DENV replication in IFN-associated and IFN-unassociated manners. Localized in mitochondria, USP18 regulated the release of mitochondrial DNA (mtDNA) to the cytosol to affect viral replication, and mechanisms such as mitochondrial reactive oxygen species (mtROS) production, changes in mitochondrial membrane potential, mobilization of calcium into mitochondria, 8-oxoguanine DNA glycosylase 1 (OGG1) expression, oxidation and fragmentation of mtDNA, and opening of the mitochondrial permeability transition pore (mPTP) were involved in USP18-regulated mtDNA release to the cytosol. We therefore identify mitochondrial machineries that are regulated by USP18 to affect DENV replication and its association with IFN effects.

Mitochondrial CMPK2 mediates immunomodulatory and antiviral activities through IFN-dependent and IFN-independent pathways

Mitochondria regulate the immune response after dengue virus (DENV) infection. Microarray analysis of genes identified the upregulation of mitochondrial cytidine/uridine monophosphate kinase 2 (CMPK2) by DENV infection. We used small interfering RNA-mediated knockdown (KD) and CRISPR-Cas9 knockout (KO) approaches, to investigate the role of CMPK2 in mouse and human cells. The results showed that CMPK2 was critical in DENV-induced antiviral cytokine release and mitochondrial oxidative stress and mitochondrial DNA release to the cytosol. The DENV-induced activation of Toll-like receptor (TLR)-9, inflammasome pathway, and cell migration was suppressed by CMPK2 depletion; however, viral production increased under CMPK2 deficiency. Examining mouse bone marrow-derived dendritic cells from interferon-alpha (IFN-α) receptor-KO mice and signal transducer and activator of transcription 1 (STAT1)-KO mice, we confirmed that CMPK2-mediated antiviral activity occurred in IFN-dependent and IFN-independent manners. In sum, CMPK2 is a critical factor in DENV-induced immune responses to determine innate immunity.

Mitochondrial protein CMPK2 regulates IFN alpha-enhanced foam cell formation, potentially contributing to premature atherosclerosis in SLE

Background

Premature atherosclerosis occurs in patients with SLE; however, the mechanisms remain unclear. Both mitochondrial machinery and proinflammatory cytokine interferon alpha (IFN-α) potentially contribute to atherogenic processes in SLE. Here, we explore the roles of the mitochondrial protein cytidine/uridine monophosphate kinase 2 (CMPK2) in IFN-α-mediated pro-atherogenic events.

Methods

Foam cell measurements were performed by oil red O staining, Dil-oxLDL uptake and the BODIPY approach. The mRNA and protein levels were measured by qPCR and Western blotting, respectively. Isolation of CD4+ T cells and monocytes was performed with monoclonal antibodies conjugated with microbeads. Manipulation of protein expression was conducted by either small interference RNA (siRNA) knockdown or CRISPR/Cas9 knockout. The expression of mitochondrial reactive oxygen species (mtROS) was determined by flow cytometry and confocal microscopy.

Results

IFN-α enhanced oxLDL-induced foam cell formation and Dil-oxLDL uptake by macrophages. In addition to IFN-α, several triggers of atherosclerosis, including thrombin and IFN-γ, can induce CMPK2 expression, which was elevated in CD4+ T cells and CD14+ monocytes isolated from SLE patients compared to those isolated from controls. The analysis of cellular subfractions revealed that CMPK2 was present in both mitochondrial and cytosolic fractions. IFN-α-induced CMPK2 expression was inhibited by Janus kinase (JAK)1/2 and tyrosine kinase 2 (Tyk2) inhibitors. Both the knockdown and knockout of CMPK2 attenuated IFN-α-mediated foam cell formation, which involved the reduction of scavenger receptor class A (SR-A) expression. CMPK2 also regulated IFN-α-enhanced mtROS production and inflammasome activation.

Conclusions

The study suggests that CMPK2 plays contributing roles in the pro-atherogenic effects of IFN-α.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02470-6.

Epigallocatechin-3-gallate exhibits immunomodulatory effects in human primary T cells

T cells secrete several inflammatory cytokines that play a critical role in the progression of atherosclerosis. Although green tea epigallocatechin-3-gallate (EGCG) exerts anti-inflammatory and anti-atherosclerotic effects in animals, few studies have identified the mechanism underlying these effects in human primary T cells. This study investigated the pathway involved in EGCG modulation of cytokine secretion in activated human primary T cells. We pre-treated human primary T cells with EGCG (0.1, 1, 5, 10, and 20 μM) for 4 h and incubated them with or without phorbol 12-myristate 13-acetate and ionomycin (P/I) for 20 h. The cytokine production, activator protein (AP)-1 binding activity, and level of mitogen-activated protein kinase (MAPK) were assessed using enzyme-linked immunosorbent assay, electrophoretic mobility shift assay, and Western blotting, respectively. At 10 and 20 μM, EGCG decreased interleukin (IL)-2 levels by 26.0% and 38.8%, IL-4 levels by 41.5% and 55.9%, INF-γ levels by 31.3% and 34.7%, and tumor-necrosis factor (TNF)-α levels by 23.0% and 37.6%, respectively. In addition, the level of phosphorylated c-Jun N-terminal (p-JNK) and extracellular signal-regulated kinase (p-ERK) was decreased, but not the level of p-p38 MAPK. EGCG did not alter any of the total protein amounts, suggesting a selective effect on specific types of MAPKs in stimulated human T cells. EGCG tended to inactivate AP-1 DNA-binding activity. The P/I-induced production of IL-2, IL-4, INF-γ, and TNF-α by human T cells was suppressed by AP-1 inhibitor in a concentration-dependent manner. In conclusion, EGCG suppressed cytokine secretion in activated human primary T cells, and this effect was likely mediated by AP-1 inactivation through the ERK and JNK, but not p38 MAPK, pathways. These results may be related to the mechanisms through which EGCG inhibits immune- or inflammation-related atherogenesis.

Compound K inhibits priming and mitochondria-associated activating signals of NLRP3 inflammasome in renal tubulointerstitial lesions

BACKGROUND

Renal tubulointerstitial lesions (TILs), a key pathological hallmark for chronic kidney disease to progress to end-stage renal disease, feature renal tubular atrophy, interstitial mononuclear leukocyte infiltration and fibrosis in the kidney. Our study tested the renoprotective and therapeutic effects of compound K (CK), as described in our US patent (US7932057B2), on renal TILs using a mouse unilateral ureteral obstruction (UUO) model.

METHODS

Renal pathology was performed and renal draining lymph nodes were subjected to flow cytometry analysis. Mechanism-based experiments included the analysis of mitochondrial dysfunction, a model of tubular epithelial cells (TECs) under mechanically induced constant pressure (MICP) and tandem mass tags (TMT)-based proteomics analysis.

RESULTS

Administration of CK ameliorated renal TILs by reducing urine levels of proinflammatory cytokines, and preventing mononuclear leukocyte infiltration and fibrosis in the kidney. The beneficial effects clearly correlated with its inhibition of: (i) NF-κB-associated priming and the mitochondria-associated activating signals of the NLRP3 inflammasome; (ii) STAT3 signalling, which in part prevents NLRP3 inflammasome activation; and (iii) the TGF-β-dependent Smad2/Smad3 fibrotic pathway, in renal tissues, renal TECs under MICP and/or activated macrophages, the latter as a major inflammatory player contributing to renal TILs. Meanwhile, TMT-based proteomics analysis revealed downregulated renal NLRP3 inflammasome activation-associated signalling pathways in CK-treated UUO mice.

CONCLUSIONS

The present study, for the first time, presents the potent renoprotective and therapeutic effects of CK on renal TILs by targeting the NLRP3 inflammasome and STAT3 signalling.

Useful message in choosing optimal biological agents for patients with autoimmune arthritis

The introduction of biological disease-modifying antirheumatic drug (bDMARD) treatments for various types of autoimmune arthritis, such as rheumatoid arthritis, psoriatic arthropathy and ankylosing spondylitis, represents a new era of treatment for patients with a refractory response to conventional synthetic DMARDs (csDMARDs). Many new bDMARDs with different modalities or that target different pro-inflammatory molecules, likely cytokines, are rapidly emerging. Hence, physicians in the field may be confused about choosing appropriate bDMARDs for their patients. Considering the high cost of bDMARDs and the rapid destructive process of autoimmune arthritis in patients, the choice of optimal bDMARDs for patients who fail to respond or show an inadequate therapeutic response to csDMARDs designed to control the disease is very critical. Here, we summarize the strengths and weaknesses of bDMARDs and specifically focus on their uses in patients with comorbid conditions or with specific medical conditions, such as pregnancy. This commentary provides a solid up-to-date review on commercially available bDMARDs and very useful information for physicians to facilitate the choice of more appropriate bDMARDs to treat patients with autoimmune arthritis and for basic researchers to understand the current strategies of bDMARD usage and hopefully to develop more powerful bDMARDs with fewer safety concerns.

Operation of mitochondrial machinery in viral infection-induced immune responses

Mitochondria have been recognized as ancient bacteria that contain evolutionary endosymbionts. Metabolic pathways and inflammatory signals interact within mitochondria in response to different stresses, such as viral infections. In this commentary, we address several interesting questions, including (1) how do mitochondrial machineries participate in immune responses; (2) how do mitochondria mediate antiviral immunity; (3) what mechanisms involved in mitochondrial machinery, including the downregulation of mitochondrial DNA (mtDNA), disturbances of mitochondrial dynamics, and the induction of mitophagy and regulation of apoptosis, have been adopted by viruses to evade antiviral immunity; (4) what mechanisms involve the regulation of mitochondrial machineries in antiviral therapeutics; and (5) what are the potential challenges and perspectives in developing mitochondria-targeting antiviral treatments? This commentary provides a comprehensive review of the roles and mechanisms of mitochondrial machineries in immunity, viral infections and related antiviral therapeutics.

Infection with the dengue RNA virus activates TLR9 signaling in human dendritic cells

Toll-like receptors (TLRs) are important sensors that recognize pathogen-associated molecular patterns. Generally, TLR9 is known to recognize bacterial or viral DNA but not viral RNA and initiate an immune response. Herein, we demonstrate that infection with dengue virus (DENV), an RNA virus, activates TLR9 in human dendritic cells (DCs). DENV infection induces release of mitochondrial DNA (mtDNA) into the cytosol and activates TLR9 signaling pathways, leading to production of interferons (IFNs). The DENV-induced mtDNA release involves reactive oxygen species generation and inflammasome activation. DENV infection disrupts the association between transcription factor A mitochondria (TFAM) and mtDNA and activates the mitochondrial permeability transition pores. The side-by-side comparison of TLR9 and cyclic GMP-AMP synthase (cGAS) knockdown reveals that both cGAS and TLR9 comparably contribute to DENV-induced immune activation. The significance of TLR9 in DENV-induced immune response is also confirmed in examination with the bone marrow-derived DCs prepared from Tlr9-knockout mice. Our study unravels a previously unrecognized phenomenon in which infection with an RNA virus, DENV, activates TLR9 signaling by inducing mtDNA release in human DCs.

JNK/AP-1 activation contributes to tetrandrine resistance in T-cell acute lymphoblastic leukaemia

T-cell acute lymphoblastic leukaemia (T-ALL) is a challenging malignancy with a high relapse rate attributed to drug resistance. Tetrandrine (TET), a bisbenzylisoquinoline alkaloid extracted from a Chinese herb, is a potential anti-cancer and anti-leukaemic drug. In this study we investigated the mechanisms of TET resistance in T-ALL cells in vitro. Among the four T-ALL cell lines tested, Jurkat and CEM cells exhibited the lowest and highest resistance to TET with IC₅₀ values at 24 h of 4.31±0.12 and 16.53±3.32 μmol/L, respectively. When treated with TET, the activity of transcription factor activator protein 1 (AP-1) was significantly decreased in Jurkat cells but nearly constant in CEM cells. To avoid cell-specific variation in drug resistance and transcription factor activities, we established a TET-R Jurkat subclone with the estimated IC₅₀ value of 10.90±.92 μmol/L by exposing the cells to increasing concentrations of TET. Interestingly, when treated with TET, TET-R Jurkat cells exhibited enhanced AP-1 and NF-κB activity, along with upregulation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) signaling pathways, whereas the expression of P-gp was not altered. Selective inhibition of JNK but not ERK suppressed AP-1 activity and TET resistance in TET-R Jurkat cells and in CEM cells. These results demonstrate that Jurkat cells acquire TET resistance through activation of the JNK/AP-1 pathway but not through P-gp expression. The JNK/AP-1 pathway may be a potential therapeutic target in relapsed T-ALL.

Epigallocatechin-3-gallate Reduces Scavenger Receptor A Expression and Foam Cell Formation in Human Macrophages

Foam cells are formed when macrophages imbibe low-density lipoprotein (LDL) through scavenger receptors. Here we examined how epigallocatechin-3-gallate (EGCG) influences foam cell formation. We found that EGCG dose-dependently reduced oxidized LDL (oxLDL) uptake in THP-1 (10 μM, 20.0 ± 0.50, p < 0.05) and primary macrophages (134.6 ± 15.6, p < 0.05) and reduced intracellular cholesterol content in these cells, respectively (10 μM, 32.6 ± 0.14, p < 0.05; 31.7 ± 1.26, p < 0.05). EGCG treatment decreased scavenger receptor A expression, but not the expression of CD36 or of reverse cholesterol transporters. Moreover, EGCG stimulated translocation of the p50 and p65 subunits of NF-κB and enhanced NF-κB DNA-binding activity, thus suppressing SR-A promoter activity. EGCG's suppression of SR-A expression was blocked by the NF-κB inhibitor Bay. The present findings suggest that EGCG regulates NF-κB activity and thus suppresses SR-A expression, oxLDL uptake, and foam cell formation.

Gentiana scabra Reduces SR-A Expression and Oxidized-LDL Uptake in Human Macrophages

BACKGROUND

Macrophages can imbibe low-density lipoprotein (LDL) through scavenger receptors to become foam cells, which is critical in the initiation and progression of atherosclerosis. Mounting evidence suggests that the anti-inflammatory nature of Chinese herbs have the capacity to halt the complex mechanisms underlying atherosclerosis. This study examined the effects of Chinese herbs on foam cell formation.

METHODS

Chinese herbs were obtained from the Sun Ten pharmaceutic company. Using oxidized LDL (OxLDL) uptake and a cell toxicity assay, we screened more than 30 types of Chinese herbs. Western blotting was used to determine expressions of scavenger receptors (SRs) and extracellular-signal-regulated kinase (ERK) activities.

RESULTS

We found that Gentiana scabra reduced oxidized LDL uptake effectively in THP-1 macrophages (p < 0.05 vs. OxLDL treated control). Moreover, treatment with Gentiana scabra in THP-1 macrophages resulted in decreased expression of scavenger receptor- A (SR-A) (p < 0.05 vs. control). Molecular investigation revealed that Gentiana scabra inhibited SR-A protein expression, possibly by regulating ERK signaling pathways (p < 0.05 vs. control).

CONCLUSIONS

By regulating SR-A expression, Gentiana scabra reduced oxidized LDL uptake in human macrophages. These results support the potential use of Gentiana scabra in treating atherosclerosis.

Dengue virus infection induces interferon-lambda1 to facilitate cell migration

A marked increase in the rate of dengue virus (DENV) infection has resulted in more than 212 deaths in Taiwan since the beginning of 2015, mostly from fatal outcomes such as dengue hemorrhagic fever and dengue shock syndrome. The pathogenic mechanisms of these fatal manifestations are poorly understood. Cytokines induce an overwhelming immune reaction and thus have crucial roles. Interferon-lambda (IFN-λ), a newly identified IFN subtype, has antiviral effects, but its immunologic effects in DENV infection have not been investigated. In the present study, we show that DENV infection preferentially induced production of IFN-λ1 in human dendritic cells (DCs) and human lung epithelial cells. Virus nonstructural 1 (NS1) glycoprotein was responsible for the effect. DENV-induced production of IFN-λ1 was dependent on signaling pathways involving toll-like receptor (TLR)-3, interferon regulation factor (IRF)-3, and nuclear factor-kappaB (NF-κB). Blocking interaction between IFN-λ1 and its receptor IFN-λR1 through siRNA interference reduced DENV-induced DC migration towards the chemoattractants CCL19 and CCL21, by inhibiting CCR7 expression. Furthermore, IFN-λ1 itself induced CCR7 expression and DC migration. Our study presents the first evidence of the mechanisms and effects of IFN-λ1 induction in DENV-infected DCs and highlights the role of this cytokine in the immunopathogenesis of DENV infection.

A New Application of Parallel Synthesis Strategy for Discovery of Amide-Linked Small Molecules as Potent Chondroprotective Agents in TNF-α-Stimulated Chondrocytes

As part of an effort to profile potential therapeutics for the treatment of inflammation-related diseases, a diversity of amide-linked small molecules was synthesized by using parallel synthesis strategy. Moreover, these new compounds were also evaluated for their inhibitory effects on nitric oxide (NO) by using tumor necrosis factor alpha (TNF-α)-induced inflammatory responses in chondrocytes. Among the tested compounds, N-(3-chloro-4-fluorophenyl)-2-hydroxybenzamide (HS-Ck) was the most potent inhibitor of NO production and inducible nitric oxide synthase (iNOS) expression in TNF-α-stimulated chondrocytes. In addition, our biological results indicated that HS-Ck might suppress the expression levels of iNOS and matrix metalloproteinases-13 (MMP-13) activities through downregulating the activation of nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT-3) transcriptional factors. Therefore, the parallel synthesis was successful used to develop a new class of potential anti-inflammatory agents as chondroprotective candidates for the treatment of osteoarthritis.

Up-regulation of galectin-9 induces cell migration in human dendritic cells infected with dengue virus

Galectin-9 (Gal-9) exerts immunosuppressive effects by inducing apoptosis in T cells that produce interferon-γ and interleukin (IL)-17. However, Gal-9 can be pro-inflammatory in lipopolysaccharide-stimulated monocytes. Using microarray analysis, we observed that Gal-9 was up-regulated in human dendritic cells (DCs) after dengue virus (DV) infection. The investigation into the immunomodulatory effects and mechanisms of Gal-9 in DCs exposed to DV revealed that DV infection specifically increased mRNA and protein levels of Gal-9 but not those of Gal-1 or Gal-3. Blocking p38, but not c-Jun N-terminal kinase or extracellular signal-regulated kinase (ERK), inhibited DV-induced expression of Gal-9. Reduction in Gal-9 by small interference RNA treatment suppressed DV-stimulated migration of DCs towards the chemoattractants CCL19 and CCL21. In addition, DV-induced IL-12p40 production was reduced after knockdown of Gal-9 in DCs. Furthermore, Gal-9 deficiency suppressed DV-induced activation of nuclear factor-κB. Inhibition of DV-induced DC migration under conditions of Gal-9 deficiency was mediated through suppressing ERK activation but not by regulating the expression of CCR7, the receptor for CCL19 and CCL21. Both the reduction in IL-12 production and the suppression of ERK activity might account for the inhibition of DV-induced DC migration after knockdown of Gal-9. In summary, this study reveals the roles of Gal-9 in DV-induced migration of DCs. The findings indicate that Gal-9 might be a therapeutic target for preventing immunopathogenesis induced by DV infection.

Modulation of both activator protein-1 and nuclear factor-kappa B signal transduction of human T cells by amiodarone

Amiodarone, a common and effective antiarrhythmic drug, has been reported to have anti-inflammatory effects such as reducing the activation and movement of neutrophils. However, its effects on human T cells remain unclear. The aim of this study was to elucidate the effects and possible underlying mechanisms of amiodarone on human T cells. We isolated human primary T cells from the peripheral blood of healthy volunteers and performed enzyme-linked immunosorbent assay (ELISA), flow cytometry, electrophoretic mobility shift assay, luciferase assay, and Western blotting to evaluate the modulatory effects of amiodarone on human T cells. We found that amiodarone dose dependently inhibited the production of cytokines, including interleukin-2 (IL-2), IL-4, tumor necrosis factor-alpha, and interferon-gamma in activated human T cells. By flow cytometry, we demonstrated that amiodarone suppressed the expression of IL-2 receptor-alpha (CD25) and CD69, the cell surface markers of activated T cells. Moreover, molecular investigations revealed that amiodarone down-regulated activator protein-1 (AP-1) and nuclear factor kappa-B (NF-κB) DNA-binding activities in activated human T cells and also inhibited DNA binding and transcriptional activities of both AP-1 and NF-κB in Jurkat cells. Finally, by Western blotting, we showed that amiodarone reduced the activation of c-Jun NH(2)-terminal protein kinase and P38 mitogen-activated protein kinase, and suppressed stimuli-induced I-kappa B-alpha degradation in activated human T cells. Through regulation of AP-1 and NF-κB signaling, amiodarone inhibits cytokine production and T cell activation. These results show the pleiotropic effects of amiodarone on human T cells and suggest its therapeutic potential in inflammation-related cardiovascular disorders.

Induction of immunomodulatory monocytes by human mesenchymal stem cell-derived hepatocyte growth factor through ERK1/2

Monocytes are a population of leukocytes that terminally differentiate into macrophages and DCs. Whereas these differentiated progeny have inflammatory and resident--which are more immunomodulatory--phenotypes, less has been reported on the plasticity of monocytes themselves. We found that MSCs, a population of somatic stem cells, can rapidly induce human and murine monocytes through secretion of HGF to acquire an immunomodulatory phenotype to suppress T cell effector function. MSCs are multilineage postnatal progenitor cells with strong immunomodulatory effects toward T lymphocytes, NK lymphocytes, and DCs, but less is known regarding their interactions with monocytes. We found that CD14(+) human monocytes express c-Met, the receptor for HGF, and both depletion of HGF-treated CD14(+) monocytes and knockdown of HGF secretion in MSCs abrogate the suppression of anti-CD3/28-activated T cell proliferation. HGF-treated monocytes remain undifferentiated and can alter activated T cell cytokine expression from a Th1 toward Th2 profile. Moreover, monocytes cocultured with MSCs or treated with HGF alone can produce high levels of IL-10, a potent immunomodulatory cytokine. Injection of HGF to WT mice also results in an increase in IL-10(+)-expressing monocytes from the spleen, a known reservoir for circulating monocytes. Mechanistically, HGFs modulate IL-10 production in monocytes through the ERK1/2 pathway. Our data demonstrate further the pleomorphic nature of MSC immunomodulation, as well as highlight the important role of immunomodulatory monocytes in altering T cell effector function.

Useful biomarkers for assessment of hepatitis C virus infection-associated autoimmune disorders

During the course of chronic hepatitis C virus (HCV) infection, various extrahepatic manifestations of autoimmune disorders may occur, including arthralgia/arthritis, sicca complex, purpura, cutaneous ulcer, and thyroid dysfunction. In addition, the prevalence of circulating autoantibodies is high among patients with HCV infection. Commonly detected autoantibodies in HCV-infected patients include rheumatoid factor, antinuclear antibody, anti-SSA/anti-SSB antibody, cryoglobulin, antineutrophil cytoplasmic antibody, anti-smooth muscle antibody, anti-liver and anti-thyroid autoantibodies. These autoantibodies may be associated with underlying autoimmune disorders or liver inflammation in HCV infection. A possible reason for antibody production is overactivation and proliferation of B lymphocytes, via the interaction with the surface protein of HCV. Because immunotherapy can cause HCV flare-up or liver damage, overdiagnosis of HCV-related autoimmune symptoms as primary autoimmune disorders should be avoided. This review describes biomarkers that are useful in clinically evaluating autoimmune manifestations and disorders associated with HCV infection.

Ginkgo biloba extract individually inhibits JNK activation and induces c-Jun degradation in human chondrocytes: potential therapeutics for osteoarthritis

Osteoarthritis (OA) is a common joint disorder with varying degrees of inflammation. The ideal anti-OA drug should have immunomodulatory effects while at the same time having limited or no toxicity. We examined the anti-inflammatory effects of Ginkgo biloba extract (EGb) in interleukin-1 (IL-1)-stimulated human chondrocytes. Chondrocytes were prepared from cartilage specimens taken from patients with osteoarthritis who had received total hip or total knee replacement. The concentrations of chemokines and the degree of cell migration were determined by ELISA and chemotaxis assays, respectively. The activation of inducible nitric oxide synthase (iNOS), mitogen-activated protein kinases (MAPKs), activator protein-1 (AP-1), and nuclear factor-kappaB (NF-κB) was determined by immunoblotting, immunohistochemistry, and electrophoretic mobility shift assay. We found that EGb inhibited IL-1-induced production of chemokines, which in turn resulted in attenuation of THP-1 cell migration toward EGb-treated cell culture medium. EGb also suppressed IL-1-stimulated iNOS expression and release of nitric oxide (NO). The EGb-mediated suppression of the iNOS-NO pathway correlated with the attenuation of activator protein-1 (AP-1) but not nuclear factor-kappaB (NF-κB) DNA-binding activity. Of the mitogen-activated protein kinases (MAPKs), EGb inhibited only c-Jun N-terminal kinase (JNK). Unexpectedly, EGb selectively caused degradation of c-Jun protein. Further investigation revealed that EGb-mediated c-Jun degradation was preceded by ubiquitination of c-Jun and could be prevented by the proteosome inhibitor MG-132. The results imply that EGb protects against chondrocyte degeneration by inhibiting JNK activation and inducing ubiquitination-dependent c-Jun degradation. Although additional research is needed, our results suggest that EGb is a potential therapeutic agent for the treatment of OA.

Differential immunomodulatory effects by Tripterygium wilfordii Hook f-derived refined extract PG27 and its purified component PG490 (triptolide) in human peripheral blood T cells: potential therapeutics for arthritis and possible mechanisms explaining in part Chinese herbal theory "Junn-Chenn-Zuou-SS"

Background

For thousands of years, it remains unclear why Chinese prefer complex herbal remedy and seldom try to purify it. One of the reasons is that they believe Chinese herbs compared to Western drugs are relatively less toxic and better tolerated. The so called “Junn-Chenn-Zuou-SS” theory illustrates a concept of coordinated effects from a combination of different Chinese herbs. PG27, a refined extract from a well-known Chinese antirheumatic herb Tripterygium wilfordii Hook f (TwHf), is effective in attenuating transplantation rejection and extending survival of cardiac xenografts.

Methods

Experiments were conducted in human primary T lymphocytes isolated from buffy coat. The activities of the inhibitor of kappaB alpha kinase-inhibitor of kappaB alpha-nuclear factor kappaB (IKK-IκBα-NF-κB) and mitogen activated protein kinase-activator protein-1 (MAPK-AP-1) signaling pathways were determined via electrophoretic mobility shift assays, immunoprecipitation kinase assays, Western blots, and transfection assays.

Results

We showed that PG27 inhibited IKKα-IκBα-NF-κB and MAPK-AP-1 signaling pathways; however, IKKβ activity was less susceptible to inhibition by PG27. In contrast, the purified component of TwHf, PG490 (triptolide), reduced both MAPK-AP-1 and IKK-IκBα-NF-κB signaling pathways, including both IKKα and IKKβ, with similar potency. By means of high performance liquid chromatography analysis, it was estimated that PG490 constituted 1.27 ± 0.06% of the total PG27 content. Further analysis demonstrated that compared to PG490 alone, PG27 that contained an equal amount of PG490 was less toxic and less immunosuppressive, suggesting the presence of cytoprotective ingredient(s) in the non-PG490 components of PG27.

Conclusions

In addition to demonstrating the immunomodulatory capacity of PG27 as the potential therapeutics for arthritis and prevention of transplantation rejection, the differential regulatory effects and mechanisms by PG27 and PG490 further support in part a possibly-existing Chinese herbal theory “Junn-Chenn-Zuou-SS”.

Protective roles of interferon-induced protein with tetratricopeptide repeats 3 (IFIT3) in dengue virus infection of human lung epithelial cells

Interferons (IFNs) are critical cytokines that regulate immune response against virus infections. Dengue virus (DV) infections are a major public health concern worldwide, and especially in Asia. In the present study, we investigated the effects and mechanisms of action of IFN-induced protein with tetratricopeptide repeats 3 (IFIT3) in human lung epithelial cells. The results demonstrated that DV infection induced expression of several IFITs, including IFIT1, IFIT2, IFIT3, and IFIT5 in A549 cells. Induction of IFIT3 by DV infection was also observed in human dendritic cells. In a knockdown study, we showed that a signal transducer and activator of transcription 2 (STAT2), but not STAT1 or STAT3, regulated DV-induced IFIT3 production. By using several different methods to evaluate cell death, we demonstrated that knockdown of IFIT3 led to cellular apoptosis. Furthermore, knockdown of IFIT3 induced the expression of several apoptotic regulators such as caspase 3, caspase 8, caspase 9, and Bcl-2-associated X protein (BAX). Such apoptotic effects and mechanisms were synergistically enhanced after DV infection. Moreover, under conditions of IFIT3 deficiency, viral production increased, suggesting an anti-viral effect of IFIT3. Interestingly, DV could suppress IFN-α-induced but not IFN-γ-induced IFIT3 expression, a phenomenon similar to the regulation of STATs by DV. In conclusion, this study revealed some mechanisms of IFIT3 induction, and also demonstrated the protective roles of IFIT3 following IFN-α production in DV infection of human lung epithelial cells.

PKCδ signalling regulates SR-A and CD36 expression and foam cell formation

AIMS

The formation of foam cells is crucial in the initiation and progression of atherosclerosis. One of the critical steps in foam cell formation is the uptake of low-density lipoprotein (LDL) by macrophages via scavenger receptors (SRs). This study examined the role of protein kinase C (PKC) isoforms on foam cell formation.

METHODS AND RESULTS

The effects of short-hairpin RNA (shRNA) and small interfering RNA (siRNA) against classical PKC and novel PKC isoforms were investigated in THP-1-derived macrophages and primary macrophages. The knockdown of PKCδ inhibited oxidized LDL (OxLDL) uptake and intracellular cholesterol accumulation in both cell models. The reduction of PKCδ resulted in decreased expression of SR-A and CD36. Similar conclusions were obtained in examining the effects of a PKCδ inhibitor, rottlerin. Molecular investigation revealed that a decrease in PKCδ inhibited protein kinase B (PKB/Akt) expression and extracellular-signal-regulated kinase (ERK) phosphorylation. Surprisingly, PKCδ-knockdown selectively decreased protein but not the mRNA level of PKCβI and PKCβII. We showed that the inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt upstream of ERK decreased SR-A and CD36 expression; however, the inhibition of ERK or PKCβ downstream of ERK attenuated SR-A but not CD36 expression. We further demonstrated that PKCδ could be induced by pro-atherogenic mediators, OxLDL and interferon-γ. Notably, PKCδ, phosphorylated ERK, Akt, and SR-A were highly expressed in human atherosclerotic arteries and CD68-positive macrophages as visualized by immunohistochemical staining.

CONCLUSION

Through regulating PI3K/Akt and ERK activity, PKCδ affects SR-A and CD36 expression and foam cell formation. The results suggest PKCδ as a potential target for atherosclerosis therapeutics.

Magnesium lithospermate B mediates anti-inflammation targeting activator protein-1 and nuclear factor-kappa B signaling pathways in human peripheral T lymphocytes

The activation of T lymphocytes contributes to the inflammatory processes of atherosclerotic diseases. Danshen is a traditional Chinese medicine and has shown therapeutic effects in patients with cardiovascular and cerebrovascular diseases. We investigated the effects of aqueous extract of Danshen (magnesium lithospermate B (MLB)) on phorbol 12-myristate acetate+ionomycin and anti-CD3+anti-CD28 monoclonal antibody-activated T cells. We showed that MLB inhibited interleukin (IL)-2, IL-4, tumor necrosis factor-alpha and interferon-gamma production from activated T cells. The expressions of T cell activation markers CD 25 and CD 69 were effectively reduced. EMSA analysis indicated that MLB down-regulated activator protein-1 (AP-1), nuclear factor kappa B (NF-κB) and octamer binding transcription factor (Oct-1) DNA-binding activity. In addition, MLB inhibited c-jun N-terminal kinase (JNK) but not extracellular signal regulated protein kinase activity. MLB also inhibited IκBα degradation, nuclear translocation of p65 and p50 as well as decreased IκBα kinase (IKK) activity. Through suppressing JNK-AP-1, IKK-IκBα-NF-κB and Oct-1 signaling pathways by MLB in activated T cells, our results provide support for efficacy of MLB in inflammatory diseases and raise its therapeutic potential in activated T cell-mediated pathologies.

A benzamide-linked small molecule HS-Cf inhibits TNF-α-induced interferon regulatory factor-1 in porcine chondrocytes: a potential disease-modifying drug for osteoarthritis therapeutics

BACKGROUND

Using tumor necrosis factor-alpha (TNF-α)-activated porcine chondrocytes as a screening tool, we aim to synthesize and identify small-molecule inhibitors preserving immunomodulatory effects as therapeutics for osteoarthritis (OA).

METHODS

Chondrocytes were isolated from pig joints. A minilibrary of 300 benzamide-linked small molecules was established. The levels of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) were measured by Western blot and Griess reaction, respectively. Proteoglycan degradation in cartilage explants was determined by histochemistry analysis. The activation of transcription factors and protein kinases was determined by electrophoretic mobility shift assays or Western blots. Zymography and real-time reverse transcriptase-polymerase chain reaction were used to determine enzyme activity and expression of matrix metalloproteinases (MMPs) and aggrecanases, respectively.

RESULTS

Bioassay screening of benzamide-linked small molecules revealed that 2-hydroxy-N-[3-(trifluoromethyl)phenyl]benzamide (HS-Cf) was a potent inhibitor of NO production and iNOS expression in TNF-α-stimulated porcine chondrocytes. HS-Cf suppressed TNF-α-induced activity of MMP-13 and expressions of several aggrecanases and prevented TNF-α-mediated reduction of collagen II. Histochemistry analysis confirmed that HS-Cf could prevent TNF-α-induced degradation and release of proteoglycan/aggrecan in cartilage explants. Such effects by HS-Cf were likely through suppressing TNF-α-induced interferon regulatory factor-1 (IRF-1) but not nuclear factor-kappaB signaling. The significance of IRF-1 was further confirmed by short hairpin knockdown studies.

CONCLUSIONS

In a minilibrary containing 300 small molecules, we identified a benzamide-linked small molecule, HS-Cf, that through down-regulating TNF-α-induced IRF-1 activity suppressed chondrocyte activation and prevented cartilage destruction. HS-Cf might be a potential disease-modifying drug for OA therapeutics.

Immunosuppressive effects and mechanisms of leflunomide in dengue virus infection of human dendritic cells

BACKGROUND

Dengue virus (DENV) infection is a serious public health issue without specific treatment. We examined the potential immunomodulatory effects of leflunomide, a dihydroorotate dehydrogenase inhibitor commonly prescribed for arthritis, in DENV-stimulated monocyte-derived dendritic cells (mo-DCs).

METHODS

mo-DCs were prepared from purified monocytes. Cytokine and chemokine concentrations were determined by enzyme-linked immunosorbent assay. Expression of cell surface markers or viral E protein was measured by flow cytometry. The activation of transcription factors and kinases was determined by electrophoretic mobility shift assays, Western blotting, or immunoprecipitation kinase assays. Chemotaxis assays were used to determine cell migration.

RESULTS

Leflunomide at therapeutic concentrations inhibited cytokine and chemokine production from DENV-infected mo-DCs. Leflunomide suppressed mo-DC maturation by downregulating the expression of both CD80 and CD86. In addition, leflunomide inhibited DENV-induced mo-DC migration and mo-DC response to chemoattractants CCL19 and CCL21. Inhibition of mo-DC migration was likely due to the suppression of CCR7 expression on mo-DCs. These events were associated with the suppression of nuclear factor kappa B and activator protein-1 signaling pathways by leflunomide.

CONCLUSIONS

Leflunomide preserves immunosuppressive effects, inhibiting activation of DENV-stimulated mo-DCs. Leflunomide may be helpful in the development of therapeutics for DENV infection.

Advanced glycation end products cause collagen II reduction by activating Janus kinase/signal transducer and activator of transcription 3 pathway in porcine chondrocytes

OBJECTIVES

The major risk factor for OA is ageing; however, the mechanisms remain largely unclear. We investigated the effects and mechanisms of advanced glycation end products (AGEs) that accumulate in aged joints in chondrocytes.

METHODS

Porcine chondrocytes or cartilage fragments were prepared. Gene expression of MMPs and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) was assessed by real-time RT-PCR. Gelatin zymography was used to determine MMP-13 enzyme activity. Histochemistry or immunoblotting analysis was applied to determine the expression of collagen II, proteoglycan and aggrecan. Electrophoretic mobility shift assay and immunoblotting were used to study the activation of signal transducer and activator of transcription 3 (STAT3). Genetic manipulations with short hairpin RNA (shRNA) or dominant negative constructs were applied.

RESULTS

AGE enhanced expression and enzyme activity of MMP and ADAMTS genes and resulted in reduction of collagen II. Both janus kinase 2 (JAK2) and JAK3 inhibitors suppressed AGE-induced MMP-13, ADAMTS-4 and ADAMTS-5 expression and enzyme activity. Inhibition of JAK2 or JAK3 prevented AGE-mediated decrease of collagen II in chondrocytes and proteoglycan (aggrecan) degradation in cartilage fragments. In addition, interference of STAT3 expression inhibited AGE-induced MMP-13 and ADAMTS enzyme activities and mRNA levels. Furthermore, expression of the dominant negative receptor of AGE (DN-RAGE) blocked AGE-induced STAT3 phosphorylation.

CONCLUSION

Blocking JAK/STAT3 signalling pathway inhibited AGE-induced activation of MMP-13 and ADAMTS and prevented AGE-mediated decrease of collagen II and proteoglycan (aggrecan). The results indicated that JAK/STAT3 pathway may be a potential target for designing disease-modifying drugs for the treatment of OA.

Advanced glycation end products induce T cell apoptosis: Involvement of oxidative stress, caspase and the mitochondrial pathway

Accumulation of advanced glycation end products (AGEs) is a hallmark in aged people. T cells play important roles in maintaining homeostasis of immune function. This study investigated the effects of AGEs-bovine serum albumin (AGEs) in human T cells. Incubation of Jurkat and several immortalized T cell lines with AGEs resulted in cell death dose-dependently. AGEs-induced cell death was partially but significantly blocked by neutralizing antibodies recognizing receptor of AGEs. In addition to detecting DNA nick, simultaneous stainings of annexin V with 7-amino-actinomycin D further confirmed the apoptotic nature of cell death. AGEs also caused apoptosis in purified T cells. Although AGEs-induced apoptosis could be blocked by the pan-caspase inhibitor, Ala-Asp-fluomethyl ketone (Z-VAD-fmk), there was no activation of caspase-3, -5, -8 and -9. AGEs caused mitochondrial outer membrane permeabilization and this process was prevented by an antioxidant or Z-VAD-fmk. Furthermore, AGEs treatment led to translocation of apoptosis inducing factor (AIF) from the mitochondria into the nucleus. Altogether, this report demonstrated that AGEs induced T cell apoptosis in an oxidative stress-associated and caspase-dependent manner with involvement of the mitochondrial pathway. It is likely that AGEs-induced T cell apoptosis may play a role in T cell homeostasis in ageing.

Chondroprotective effects and mechanisms of resveratrol in advanced glycation end products-stimulated chondrocytes

Introduction

Accumulation of advanced glycation end products (AGEs) in joints contributes to the pathogenesis of cartilage damage in osteoarthritis (OA). We aim to explore the potential chondroprotective effects of resveratrol on AGEs-stimulated porcine chondrocytes and cartilage explants.

Methods

Chondrocytes were isolated from pig joints. Activation of the IκB kinase (IKK)-IκBα-nuclear factor-kappaB (NF-κB) and c-Jun N-terminal kinase (JNK)/extracellular signal-regulated kinase (ERK)-activator protein-1 (AP-1) pathways was assessed by electrophoretic mobility shift assay (EMSA), Western blot and transfection assay. The levels of inducible nitric oxide synthase (iNOS)-NO and cyclooxygenase-2 (COX-2)-prostaglandin E₂ (PGE₂) were measured by Western blot, Griess reaction or ELISA. The expression and enzyme activity of matrix metalloproteinase-13 (MMP-13) were determined by real time RT/PCR and gelatin zymography, respectively.

Results

We show that AGEs-induced expression of iNOS and COX-2 and production of NO and PGE₂ were suppressed by resveratrol. Such effects of resveratrol were likely mediated through inhibiting IKK-IκBα-NF-κB and JNK/ERK-AP-1 signaling pathways induced by AGEs. By targeting these critical signaling pathways, resveratrol decreased AGEs-stimulated expression and activity of MMP-13 and prevented AGEs-mediated destruction of collagen II. Histochemistry analysis further confirms that resveratrol could prevent AGEs-induced degradation of proteoglycan and aggrecan in cartilage explants.

Conclusions

The present study reveals not only the effects and mechanisms regarding how resveratrol may protect cartilage from AGEs-mediated damage but also the potential therapeutic benefit of resveratrol in the treatment of OA.

Triggering of DC migration by dengue virus stimulation of COX-2-dependent signaling cascades in vitro highlights the significance of these cascades beyond inflammation

A term "bone-breaking fever" is used in Chinese medicine to describe the symptoms of patients infected with dengue virus (DV). We examined the significance of the COX-prostaglandin pathway in human DC infected by DV. We show that DV infection induced the expression of COX-2 and the production of prostaglandin E2 (PGE2) in DC, and stimulated the DNA binding of NF-kappaB and the kinase activity of both IkappaBalpha kinase (IKK) alpha and beta. DV infection also activated MAPK and AP-1 signaling. Both IkappaBalpha kinase-NF-kappaB and MAPK-AP-1 were upstream of COX-2 activation. Our investigation into the significance of COX-2-PGE2 pathway also revealed that DV infection enhances DC migration by inducing CC chemokine receptor 7 (CCR7) expression, and that blocking COX-2 or MAPK activity suppresses DV-induced DC migration. Our data also suggest that PGE2 can induce CCR7 expression on DC and that antagonists of the PGE2 receptors EP2 and EP4 suppress DV-induced DC migration. We further show that the increased CCR7 expression was observed in both DV-infected and bystander DC, suggesting the presence of secondary effects in inducing CCR7 expression. Collectively, this study reveals not only the pathways involved in COX-2 synthesis in DV-infected DC but also the autocrine action of PGE2 on the migration of DV-infected DC.

Infection of Human Dendritic Cells by Dengue Virus Activates and Primes T Cells Towards Th0‐Like Phenotype Producing Both Th1 and Th2 Cytokines

Dengue viruses (DV) infection is an important public health issue all over the world. Although the pathogenesis remains unclear, the overwhelmingly triggered immune responses have been consistently observed. Recently, we and other researchers demonstrated that the natural hosts for DV are dendritic cells (DC), the primary sentinels of immune system. In light of the significance of T cells in dengue virus pathogenesis, here, we examine the possible consequences of DC-T cell interaction that is supposed to be happening in lymphoid tissues after infection. We showed that DV-infected DC induced the interacting T cells to proliferate, to produce interleukin-2 as well as to express activation markers on cell surface. Compared to mock-infected DC, the infection of DC by DV also induced T cells to produce interleukin-4, interleukin-10 and interferon-gamma, a cytokine pattern suggesting Th0 phenotype. Such an effect was either totally abolished or greatly reduced when DV were pre-inactivated with heat or ultraviolet before infection. In addition, we demonstrated that such a Th0 phenotype shift of T cells was affected neither by different dosages of viruses that infected DC nor by different durations of DC-T cell interaction. Our results provide a basic support for clinical observations and may be of help in understanding the pathogenesis of DV infection.

Modulation of human T cells signaling transduction by lovastatin

Statins are applied clinically to treat hypercholesterolemia and proposed to have some kinds of anti-inflammatory properties for reducing the incidence of atherosclerosis-related cardiovascular events. However, it was rarely known about statins on the signal transduction on human primary T cells. To gain insight into the mechanism of statins on human T cells, we investigated the effects of both lovastatin and atorvastatin on activated human primary T cells. The human primary T cells from the blood of normal human beings were isolated. We found that lovastatin, but not atorvastatin, can dose-dependently inhibit cytokine production such as interleukin-2, interleukin-4, and interferon-gamma from activated human T cells. Neither lovastatin nor atorvastatin can regulate the TNF-alpha production on both activated human T cells and monocytes. Molecular investigation was performed that lovastatin, but not atorvastatin, could down-regulate both activator protein-1 and NF-kappaB DNA binding activities, assessed by electrophoretic mobility shift assay. Our observations may extend potential and differential therapeutic mechanisms of lovastatin with cell-mediated capacity to prevent or treat some of inflammation related diseases.

Suppression of tissue necrosis factor-alpha or hydrogen peroxide-activated primary human T lymphocytes by Ginkgo biloba extract through down-regulation of activator protein-1 signal transduction

PURPOSE

It was unknown whether Ginkgo biloba extract has regulatory effects on human T lymphocytes activated by tissue necrosis factor-alpha (TNF-alpha), which has an important role on the progression of inflammatory atherosclerotic plaques. We evaluated the effects of G. biloba extract on activated human peripheral T lymphocytes, which were isolated from human whole blood.

METHODS

The human T lymphocytes were treated with 25-100 microg G. biloba extract for 2h first. Then they were activated by TNF-alpha and H(2)O(2) to investigate the modulatory effects of G. biloba extract on human T lymphocytes. Electrophoretic mobility shift assay, Western blot (Immunoblot) analysis and immunoprecipitation kinase assays were used.

RESULTS

The inhibition of activated human T lymphocyte specifically correlated with the down-regulation of AP-1 DNA-binding activities. G. biloba extract was unique in its ability to inhibit the activation of c-Jun NH2-terminal protein kinase.

CONCLUSIONS

G. biloba extract might have its novel therapeutic effects on inflammation-based atherosclerotic diseases.

Dengue virus type 2 antagonizes IFN-alpha but not IFN-gamma antiviral effect via down-regulating Tyk2-STAT signaling in the human dendritic cell

The immunopathogenesis mechanism of dengue virus (DV) infection remains elusive. We previously showed that the target of DV in humans is dendritic cells (DCs), the primary sentinels of immune system. We also observed that despite the significant amount of IFN-alpha induced; DV particles remain massively produced from infected DCs. It suggests that DV may antagonize the antiviral effect of IFN-alpha. Recent work in animal studies demonstrated the differential critical roles of antiviral cytokines, namely IFN-alpha/IFN-beta and IFN-gamma, in blocking early viral production and in preventing viral-mediated disease, respectively. In this study, we examined the effects of IFN-alpha and IFN-gamma in DV infection of monocyte-derived DCs. We showed that the preinfection treatment with either IFN-alpha or IFN-gamma effectively armed DCs and limited viral production in infected cells. However, after infection, DV developed mechanisms to counteract the protection from lately added IFN-alpha, but not IFN-gamma. Such a selective antagonism on antiviral effect of IFN-alpha, but not IFN-gamma, correlated with down-regulated tyrosine-phosphorylation and DNA-binding activities of STAT1 and STAT3 transcription factors by DV. Furthermore, subsequent studies into the underlying mechanisms revealed that DV attenuated IFN-alpha-induced tyrosine-phosphorylation of Tyk2, an upstream molecule of STAT activation, but had no effect on expression of both IFN-alpha receptor 1 and IFN-alpha receptor 2. Moreover, DV infection by itself could activate STAT1 and STAT3 through IFN-alpha-dependent and both IFN-alpha-dependent and IFN-alpha-independent mechanisms, respectively. These observations provide very useful messages with physiological significance in investigation of the pathogenesis, the defense mechanisms of human hosts and the therapeutic considerations in DV infection.

Retinoic acid blocks pro-inflammatory cytokine-induced matrix metalloproteinase production by down-regulating JNK-AP-1 signaling in human chondrocytes

The development of osteoarthritis (OA) has recently been implicated as a result of immune-mediated damage of chondrocytes and their supporting matrixes. Pro-inflammatory cytokines like interleukin (IL)-1 and tumor necrosis factor alpha (TNF-alpha) play pivotal roles in immunopathogenesis of OA. Because vitamins preserving anti-oxidative effects are suggested to provide protection in OA patients from joint damage, in the present study, we examined the effects and mechanisms of all-trans retinoic acid (t-RA) in suppressing pro-inflammatory cytokine-induced matrix metalloproteinases (MMPs) production in human chondrocytes. Chondrocytes were prepared from cartilage specimens of OA patients receiving total hip or total knee replacement. The protein concentration was measured by ELISA, the mRNA expression by reverse transcriptase-polymerase chain reaction, the protein expression by Western blotting, the transcription factor DNA-binding activity by electrophoretic mobility shift assay and the protein kinase activity by kinase assay. We showed that both MMP-1 and MMP-13 mRNA expression, protein production and enzyme activity induced by either IL-1 or TNF-alpha were suppressed by t-RA or different retinoid derivatives. The molecular investigation revealed that the t-RA-mediated suppression was likely through blocking p38 kinase and c-Jun N-terminal kinase-activator protein-1 signaling pathways. In contrast, t-RA had no effect on extracellular signal-regulated kinase activity, nuclear factor (kappa)B (NF-(kappa)B) DNA-binding activity and I(kappa)B(alpha) degradation. Furthermore, we showed that t-RA could reduce IL-1-induced TNF-alpha production in chondrocytes. Our results suggest that vitamin A may protect OA patients from pro-inflammatory cytokine-mediated damage of chondrocytes and their supporting matrixes.

Plant alkaloid tetrandrine downregulates IkappaBalpha kinases-IkappaBalpha-NF-kappaB signaling pathway in human peripheral blood T cell

Plant alkaloid tetrandrine (Tet), purified from Chinese herb Han-Fang Chi, is a potent immunomodulator used to treat rheumatic disorders, silicosis and hypertension in mainland China. We previously demonstrated that Tet effectively suppresses cytokine production and proliferation of CD28-costimulated T cells. In the present study, we investigated the possible involvement of nuclear factor kappa B (NF-kappaB) transcription factors, critical in CD28 costimulation, in Tet-mediated immunosuppression in human peripheral blood T cells. We showed that Tet inhibited NF-kappaB DNA-binding activities induced by various stimuli, including CD28 costimulation. At equal molar concentrations, Tet was as strong as methotrexate in suppressing CD28-costimulated NF-kappaB activities. Since Tet itself did not affect NF-kappaB binding to its corresponding DNA sequence, the results suggested that Tet might regulate NF-kappaB upstream signaling molecules. Further studies demonstrated that Tet could prevent the degradation of IkappaBalpha and inhibit nuclear translocation of p65 by blocking IkappaBalpha kinases alpha and beta activities. In addition, the activation of mitogen-activated protein kinases such as c-jun N-terminal kinase, p38 and extracellular signal-regulated kinase and activator protein-1 DNA-binding activity were all downregulated by Tet. Transfection assays performed in purified human peripheral blood T cells also confirmed the inhibition of NF-kappaB transcriptional activity by Tet. When four Tet analogues were readily compared, dauricine appeared to preserve the most potent inhibition on CD28-costimulated but not on H(2)O(2)-induced NF-kappaB DNA-binding activities. Our results provide the molecular basis of immunomodulation of Tet for being a potential disease-modifying antirheumatic drug in the therapy of autoimmune disorders like rheumatoid arthritis.

Irbesartan inhibits human T-lymphocyte activation through downregulation of activator protein-1

1 Irbesartan is a promising antihypertensive drug with beneficial effects on atherosclerotic processes. In the progression of atherosclerosis, human T-lymphocytes play an important role, but it is not yet known how irbesartan modulates human T-lymphocytes activation. To gain insight into the mechanisms by which irbesartan acts, we investigated its effects on human T-lymphocytes. 2 Primary human T-lymphocytes were isolated from whole blood. Cytokines were determined by ELISA. Activator protein-1 (AP-1) and related protein activities were determined by electrophoretic mobility shift assays, kinase assays, Western blotting and transfection assays. 3 Irbesartan inhibited the production of both tumor necrosis factor-alpha and interferon-gamma by activated T-cells, especially at therapeutic concentrations. Further investigation at the molecular level indicated that the inhibition of activated human T-lymphocytes specifically correlated with the downregulation of AP-1 DNA-binding activity. In the Jurkat T-cell line, irbesartan also inhibited AP-1 transcriptional activity. Finally, we revealed that irbesartan is unique in its ability to inhibit the activation of both c-Jun NH2-terminal protein kinase and p38 MAPK. 4 Our studies show that irbesartan may modulate inflammation-based atherosclerotic diseases through a cell-mediated mechanism involving suppression of human T-lymphocytes activation via downregulation of AP-1 activity.

Carvedilol Differentially Regulates Cytokine Production from Activated Human Peripheral Blood Mononuclear Cells

Chronic inflammation is one of the important mechanisms involved in atherosclerosis formation. The activated monocytes and their secreted cytokines contribute significantly to this inflammatory process. Here we examined the effects of carvedilol, a recently introduced cardio-protective alpha-1- and beta-receptor blocker, on cytokine production from various stimuli-activated human immune effector cells. By ELISA analysis, we showed that carvedilol inhibited interferon-gamma (IFN-gamma), but enhanced interleukin (IL)-12 production in phytohemagglutinin (PHA)- and concanavalin A (ConA)-stimulated human peripheral blood mononuclear cells (PBMCs). The production of tumor necrosis factor-alpha (TNF-alpha) was marginally affected. When purified monocytes were examined, we observed the consistent up-regulation of IL-12 production while both IL-10 and TNF-alpha were unaffected or marginally down-regulated, respectively, by carvedilol. In agreement with the observation in monocytes, the production of IL-12 from activated macrophages was also up-regulated by carvedilol. We concluded that carvedilol might mediate its therapeutic effects through differentially regulating cytokine production from activated mononuclear cells, including at least monocytes and macrophages.

Chinese Herbs as Immunomodulators and Potential Disease-Modifying Antirheumatic Drugs in Autoimmune Disorders

Autoimmune diseases are a group of illnesses with multiple organ involvement. The prototype of this group of disorders is rheumatoid arthritis (RA) that aside from systemic organ involvement mainly presents with progressive destruction of many joints. Both activation and defective apoptosis of immune effector cells like T and B lymphocytes and macrophages play critical roles in the pathogenesis of autoimmune disorders. Current therapy for autoimmune diseases recommends a combination of several disease-modifying antirheumatic drugs (DMARDs) that preserve different immunomodulatory mechanisms. Because of limited success in prevention of RA joint destruction for currently available DMARDs, the development of more effective and less toxic DMARDs has been one of the major goals for pharmaceutical companies. The introduction of leflunomide and anti-tumor necrosis factor alpha therapies to the market recently serves as examples. In this context, the experience from ancient Chinese medicine gives an alternative consideration looking for potential DMARDs. Two commonly prescribed Chinese antirheumatic herbs are Tripterygium wilfordii hook f (TWHf) and tetrandrine (Tet) that preserve both anti-inflammatory and immunosuppressive effects. Importantly, the TWHf- or Tet-mediated immunomodulatory mechanisms are evidently different from the known DMARDs. The synergistic effects have also been demonstrated between these two Chinese antirheumatic herbs and DMARDs like FK506, cyclosporin and possibly chloroquine. Another potential Chinese herb for this consideration is Ginkgo biloba. This review summarizes evidence-based in vivo and in vitro studies on Chinese herbs as immunomodulators and potential DMARDs.

Carvedilol, a new antioxidative β-blocker, blocks in vitro human peripheral blood T cell activation by downregulating NF-κB activity

OBJECTIVE

The activation of T lymphocytes contributes to the inflammatory process of atherosclerosis. Here we examined the effects of carvedilol, a new beta-blocker containing an antioxidative property, on the activation of T cells.

METHODS

Human peripheral blood T cells were negatively selected from whole blood. Cytokines were measured by ELISA. The NF-kappaB and related protein activity was determined by electrophoretic mobility shift assays, Western blotting, kinase assays and transfection assays.

RESULTS

Carvedilol was nontoxic at concentrations </=10 microM, however, higher dosages (>/=20 microM) induced T cell apoptosis. We demonstrated that carvedilol inhibited cytokine production from various stimuli-activated T cells. Carvedilol also suppressed the expression of T cell activation markers, including CD25, CD69 and CD71. Molecular investigation indicated that carvedilol specifically downregulated NF-kappaB but not activator protein 1 DNA-binding activity in activated T cells. The inhibitory effect was likely due to its antioxidative property. Meanwhile, carvedilol prevented stimuli-induced IkappaBalpha degradation. Such an effect was mediated through the inhibition of IkappaBalpha kinase activity. The inhibitory specificity on NF-kappaB by carvedilol was also demonstrated in transfection assays.

CONCLUSIONS

Our results demonstrated a novel therapeutic mechanism of carvedilol in atherosclerosis, namely the inhibition of T cell activation via downregulating NF-kappaB activity.

Down-regulation of c-jun N-terminal kinase-activator protein-1 signaling pathway by Ginkgo biloba extract in human peripheral blood T cells

The activation of T lymphocytes contributes to inflammatory process of cardiovascular and cerebrovascular diseases. We investigated the effects of the extract of Ginkgo biloba (EGb), an ancient plant preserving antioxidant property, on phorbol 12-myristate 13-acetate+ionomycin or anti-CD3+anti-CD28 monoclonal antibodies-activated T cells. Human peripheral blood T cells were negatively selected from whole blood. Cytokines were measured by ELISA, cell surface markers by flow cytometry and the activities of transcription factors and kinases were determined by electrophoresis mobility shift assays, kinase assays and transfection assays. We showed that EGb inhibited several cytokines, including tumor necrosis factor-alpha, interleukin (IL)-2, IL-4 and interferon-gamma production from activated T cells. Electrophoresis mobility shift assay analysis indicated that EGb down-regulated activator protein-1 (AP-1) but not nuclear factor kappa B DNA-binding activity. In addition, EGb inhibited c-jun N-terminal kinase but not extracellular signal regulated protein kinase activity. The inhibitory specificity on AP-1 by EGb was also demonstrated in transfection assays. The inhibition of AP-1 signaling pathway in T cells by EGb provides a support for its efficacy in cardiovascular and cerebrovascular diseases and raises a therapeutic potential for this drug in activated T cell-mediated pathologies.

Carvedilol modulates in-vitro granulocyte-macrophage colony-stimulating factor-induced interleukin-10 production in U937 cells and human monocytes

Both granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-10 (IL-10) are important mediators regulating inflammatory responses. Inflammatory processes have an important role in atherogenesis. In this paper, the effects of carvedilol on GM-CSF-induced IL-10 production were examined on human monocytic cell line, U937, and purified human monocytes. First, we showed that one-time carvedilol pretreatment at concentrations 0.3-10 microM dose-dependently inhibited GM-CSF-induced IL-10 production in U937 cells. In addition, we found carvedilol to be non-cytotoxic at concentrations equal to or less than 10 microM. However, at concentrations higher than 10 microM, carvedilol induced programmed cell death in U937 cells. The inhibition of GM-CSF-induced IL-10 production by carvedilol was also observed at the expression of mRNA. Furthermore, the inhibition of IL-10 production was demonstrated in GM-CSF-activated purified human peripheral blood monocytes. Finally, long-term carvedilol pretreatment of U937 cells up to 2 months at concentrations of 1.0 microM mildly enhanced the IL-10 production. Our observations that carvedilol modulated GM-CSF-induced IL-10 production may have some implication in understanding the broad-spectrum effects of carvedilol in regulating inflammatory reactions.

Aspirin differentially regulates endotoxin-induced IL-12 and TNF-alpha production in human dendritic cells

OBJECTIVE

In the development of autoimmune diseases, dendritic cells (DC) play critical roles. Here, we examined the effect of aspirin on lipopolysaccharide (LPS)-induced DC activation.

METHODS

The monocyte-derived DC were established. The cytokine production was measured by ELISA, reverse transcriptase/polymerase chain reaction, or intracellular staining analyzed by flow cytometry. The expression of cell surface molecules was determined by flow cytometry.

RESULTS

Aspirin inhibited LPS-induced DC maturation and costimulatory molecules expression. Aspirin, at therapeutic concentrations, also decreased LPS-induced IL-12 and IL-10 production. In contrast, the LPS-induced TNF-alpha production was enhanced by aspirin. The differential effects of aspirin on IL-12 and TNF-alpha production may not be due to down-regulation of cyclooxygenase activities.

CONCLUSION

The various effects of aspirin on LPS-stimulated DC may influence the understanding of the diverse immunomodulatory mechanisms of this anti-inflammatory drug.

Western and Chinese antirheumatic drug-induced T cell apoptotic DNA damage uses different caspase cascades and is independent of Fas/Fas ligand interaction

Spontaneous or therapeutic induction of T cell apoptosis plays a critical role in establishing transplantation tolerance and maintaining remission of autoimmune diseases. We investigated the mechanisms of apoptosis induced by Chinese and Western antirheumatic drugs (ARDs) in human T cells. We found that hydroxychloroquine, Tripterygium wilfordii hook F, and tetrandrine (Tet), but not methotrexate, at therapeutic concentrations can cause T cell death. In addition, Tet selectively killed T cells, especially activated T cells. Although ARD-induced cytotoxicity was mediated through apoptotic mechanisms, Fas/Fas ligand interaction was not required. We further demonstrated that the processes of phosphatidylserine externalization and DNA damage along the ARD-induced T cell apoptotic pathway could operate independently, and that selective inhibition of DNA damage by caspase inhibitors did not prevent T cells from undergoing cell death. Moreover, we found that Tet- and Tripterygium wilfordii hook F-induced T cell DNA damage required caspase-3 activity, and hydroxychloroquine-induced T cell DNA damage was mediated through a caspase-3- and caspase-8-independent, but Z-Asp-Glu-Val-Asp-fluomethyl ketone-sensitive, signaling pathway. Finally, the observation that ARD-induced activation of caspase-3 in both Fas-sensitive and Fas-resistant Jurkat T cells indicates that Fas/Fas ligand interaction plays no role in ARD-induced T cell apoptosis. Our observations provide new information about the complex apoptotic mechanisms of ARDs, and have implications for combining Western and Chinese ARDs that have different immunomodulatory mechanisms in the therapy of autoimmune diseases and transplantation rejection.

Infection of human dendritic cells by dengue virus causes cell maturation and cytokine production

Dengue virus (DV) infection is a major problem in public health. It can cause fatal diseases such as Dengue hemorrhagic fever and Dengue shock syndrome. Dendritic cells (DC) are professional APCs required for establishing a primary immune response. Here, we investigated the role of human PBMC-derived DC in DV infection. Using different techniques, including plaque assay, flow cytometry analysis, nested RT-PCR, and confocal microscope and electron microscope examinations, we show that DV can enter cultured human DC and produce virus particles. After entrance, DV could be visualized in cystic vesicles, vacuoles, and the endoplasmic reticulum. The DV-infected DC also showed proliferation and hypertrophy of the endoplasmic reticulum as well as the swollen mitochondria. In addition, the DV-stimulated DC could express maturation markers such as B7-1, B7-2, HLA-DR, CD11b, and CD83. Furthermore, the infection of DC by DV induced production of TNF-alpha and IFN-alpha, but not IL-6 and IL-12. Although DC underwent spontaneous apoptosis in the absence of feeding cytokines, this process appeared to be delayed after DV infection. Our observations provide important information in understanding the pathogenesis of DV infection.

Plant alkaloid tetrandrine and its analog block CD28-costimulated activities of human peripheral blood T cells: potential immunosuppressants in transplantation immunology

BACKGROUND

T lymphocyte activation mediated by CD28 costimulation plays a critical role in graft rejection. Plant alkaloid tetrandrine, purified from a Chinese antirheumatic herb, is a potent immunosuppressant. Here, we examined its effects on several CD28-costimulated T-cell activities. In addition, such effects were readily compared with the effects of three tetrandrine analogs.

METHODS

T lymphocytes were purified from whole blood by negative selection. The stimuli that mimic CD28 costimulation included both anti-CD3 + anti-CD28 monoclonal antibody and PMA+anti-CD28 monoclonal antibody. The determination of CD28-costimulated cell proliferation was performed by tritium uptake, cytokine production by ELISA, cell surface interleukin 2Ra and CD69 expression by flow cytometry, and mixed leukocyte reaction by tritium uptake. Drug cytotoxicity was determined by trypan blue exclusion, propidium iodide staining, and MTT colorimetric assays.

RESULTS

Tetrandrine inhibited CD28-costimulated T-cell proliferation and cytokine production through a mechanism different from that of cyclosporine. In addition, tetrandrine down-regulated both T helper 1 and T helper 2 cytokine production in CD4+ and CD8+ T-cell subpopulations. By examining cytokine production and T-cell activation marker expression, we further demonstrated that, among tetrandrine and its analogs tested, dauricine was the most potent suppressor of CD28-costimulated T-cell activities. Furthermore, the different immunosuppressive activities of these compounds were not associated with their cytotoxic capacities. Finally, the unparalleled inhibitory potency of dauricine on both mixed leukocyte reaction and CD28-costimulated T-cell proliferation suggests that dauricine preferentially targeted CD28-costimulated T-cell activities.

CONCLUSIONS

This is the first report to show that tetrandrine and its analogs potently inhibited both PMA+CD28-costimulated and CD3 + CD28-costimulated activation of human peripheral blood T cells. Based upon their structural similarity and different immunosuppressive potency, these in vitro data also provide very useful information for further identification and development of more potent and less toxic immunosuppressants to achieve transplantation success.

Plant alkaloid tetrandrine downregulates protein kinase C-dependent signaling pathway in T cells

Tetrandrine, a purified traditional Chinese medicinal herb that acts as an immunosuppressant and a Ca2+ channel blocker, has been clinically used to treat patients with arthritis, silicosis and hypertension. Since T cells play a critical role as autoreactive and pathogenic population in autoimmune diseases, in this study, we examined the immunosuppressive effect of tetrandrine on human peripheral blood T cells. We showed that tetrandrine inhibited phorbol 12-myristate 13-acetate (PMA) + ionomycin-induced T cell proliferation, interleukin-2 secretion and the expression of the T cell activation antigen, CD71. Further investigation of the molecular mechanism demonstrated that tetrandrine inhibited the expression of the protein kinase C-dependent interleukin-2 receptor alpha chain and CD69 but not the expression of the Ca2+-dependent CD40 ligand and CD69. Interestingly, when tetrandrine and cyclosporin A were added together, significant synergism in the suppression of T cell activation was observed. Moreover, of the several tetrandrine analogues studied, hernandezine was the most potent inhibitor of protein kinase C signaling events. These results also suggest that the protein kinase C-inhibitory capacity of tetrandrine and its analogues may not be associated with their function as Ca2+ channel blockers. Lastly, we showed that, within therapeutic concentrations, tetrandrine and its analogues could induce cellular apoptosis, which is defective in autoimmune diseases. In conclusion, our findings provide novel information about the molecular mechanism of the immunosuppressive effect of tetrandrine and its analogues in human peripheral blood T cells.

Mechanism of immunosuppression of the antirheumatic herb TWHf in human T cells

OBJECTIVE

To investigate the immunosuppressive mechanism of Tripterygium wilfordii Hook-F (TWHf) in human T cells. TWHf, a traditional Chinese medicinal herb for rheumatoid arthritis, has been shown to inhibit the function of immune effector cells such as neutrophils, macrophages, and B lymphocytes.

METHODS

T cell survival was evaluated with trypan blue exclusion assay, morphologic changes with Wright's stain, the induction of endonuclease activity with DNA fragmentation assay, and the subdiploid DNA content with flow cytometry. T cell activation was measured with interleukin 2 (IL-2) ELISA and the expression of several surface molecules with flow cytometry.

RESULTS

At high dosages, TWHf caused inhibition of T cell proliferation and this mechanism was mediated through the induction of apoptosis. TWHf, in noncytotoxic dosages, was as potent as cyclosporin A and more potent than prednisolone and cyclophosphamide in inhibiting IL-2 production from activated T cells. TWHf also inhibited both phorbol 12-myristate 13-acetate induced IL-2Ralpha expression and ionomycin induced CD40 ligand expression. TWHf did not reverse downregulated expression of CD3 and CD4 by phorbol ester stimulation.

CONCLUSION

This is the first evidence that the immunosuppressive mechanism of TWHf in T cells was mediated through both downregulation of T cell receptor signaling pathway and induction of cellular apoptosis, which is defective in autoimmune diseases.

Development of prostate-specific antigen promoter-based gene therapy for androgen-independent human prostate cancer

PURPOSE

The goal of this study is to develop a tissue-specific toxic gene therapy utilizing the prostate specific antigen (PSA) promoter for both androgen-dependent (AD) and androgen-independent (AI) PSA-secreting prostate cancer cells. Ideally this gene therapy would be effective without the necessity of exposing the target cells to circulating androgens.

MATERIALS AND METHODS

An AI subline of LNCaP, an AD PSA-secreting human prostate cancer cell line, C4-2, was used in this study. Castrated mice bearing C4-2 tumors secrete PSA. A transient expression experiment was used to analyze the activity of two PSA promoters, a 5837 bp long PSA promoter and a 642 bp short PSA promoter, in C4-2 cells. A recombinant adenovirus (Ad-PSA-TK) carrying thymidine kinase under control of the long PSA promoter was generated. The tissue-specific activity of Ad-PSA-TK was tested in vitro and in vivo.

RESULTS

The long PSA promoter had superior activity over short PSA promoter, and higher activity in C4-2 cells than in LNCaP cells. High activity of Ad-PSA-TK was observed in C4-2 cells in an androgen deprived condition. In vitro, Ad-PSA-TK was further demonstrated to induce marked C4-2 cell-kill by acyclovir in medium containing 5% FBS. No cell-kill was observed in control WH cells (a human bladder cancer cell line). In vivo, Ad-PSA-P-TK with acyclovir significantly inhibited subcutaneous C4-2 tumor growth and PSA production in castrated animals.

CONCLUSION

The 5837 bp long PSA promoter was active in the androgen free environment and could be used to target both androgen-dependent and independent PSA-producing prostate cancer cells in vitro, and prostate tumors in castrated hosts.