A new NF-κB inhibitor attenuates a TH 1 type immune response in a murine model

IL-22 is rapidly induced by Pathogen Recognition Receptors Stimulation in Bone-Marrow-derived Dendritic Cells in the Absence of IL-23

In vertebrates, microorganisms are recognized by pathogen recognition receptors (PRRs). Exposure of immune cells to the ligands of these receptors activates intracellular signaling cascades that rapidly induce the expression of a variety of genes. Within these genes, the cytokines family plays a crucial function because of its role in adaptive immunity induction and in tissue-specific functional regulation, such as tissue repair and tissue homeostasis during steady state conditions. Within the myeloid compartment, dendritic cells (DCs) release a variety of inflammatory cytokines in response to microbes. In this study, we show that BMDCs release IL-22 directly upon PRRs activation without the need of IL-23 signaling as reported for other IL22-producing cells. Moreover, we demonstrate that cytokine IL-22 is rapidly released in a cell-specific manner as macrophages are not able to produce IL-22 through the same PRRs system. In addition, we characterize the intracellular signaling cascade required for IL-22 release in BMDCs. Myd88, MEK1/2, NFkb and AhR, but not p38, NFAT, and RORgt, were found to be involved in IL-22 regulation in DCs. Our study suggests that BMDCs possess a unique intracellular molecular plasticity which, once activated, directs different BMDCs functions in a cell-specific manner.

NF-κB Pathways in the Pathogenesis of Multiple Sclerosis and the Therapeutic Implications

Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathways are involved in cell immune responses, apoptosis and infections. In multiple sclerosis (MS), NF-κB pathways are changed, leading to increased levels of NF-κB activation in cells. This may indicate a key role for NF-κB in MS pathogenesis. NF-κB signaling is complex, with many elements involved in its activation and regulation. Interestingly, current MS treatments are found to be directly or indirectly linked to NF-κB pathways and act to adjust the innate and adaptive immune system in patients. In this review, we will first focus on the intricacies of NF-κB signaling, including the activating pathways and regulatory elements. Next, we will theorize about the role of NF-κB in MS pathogenesis, based on current research findings, and discuss some of the associated therapeutic implications. Lastly, we will review four new MS treatments which interrupt NF-κB pathways—fingolimod, teriflunomide, dimethyl fumarate (DMF) and laquinimod (LAQ)—and explain their mechanisms, and the possible strategy for MS treatments in the future.

Practical strategies for suppressing hypoxia-inducible factor activity in cancer therapy

The utility of anti-angiogenic strategies for cancer control is strongly compromised by hypoxia-driven phenotypic changes in cancer cells, which make cancer cells more invasive and more prone to give rise to metastases. A key mediator of this phenotypic shift is the transcription factor hypoxia-inducible factor-1 (HIF-1), which acts directly and indirectly to promote the epidermal-mesenchymal transition, boost cancer invasiveness, increase production of angiogenic factors, and induce chemoresistance. In some cancers, HIF-1 activity is constitutively elevated even in aerobic environments, making the cancer harder to treat and control. Practical strategies for suppressing HIF-1 activation may include the following: inhibiting NF-kappaB activation with salicylic acid and/or silibinin, which should decrease transcription of the HIF-1alpha gene; suppressing translation of HIF-1alpha mRNA with drugs that inhibit mTOR or topoisomerase I; supporting the effective activity of prolyl hydroxylases - which promote proteasomal degradation of HIF-1alpha under aerobic conditions - with antioxidant measures, alpha-ketoglutarate, and possibly dichloroacetate; promoting the O(2)-independent proteasomal degradation of HIF-1alpha with agents that inhibit the chaperone protein Hsp90; and blocking HIF-1 binding to its DNA response elements with anthracyclines. The utility of various combinations of these strategies should be tested in cancer cell cultures and rodent xenograft models; initial efforts in this regard have yielded encouraging results. Comprehensive strategies for suppressing HIF-1 activity can be expected to complement the efficacy of cancer chemotherapy and of effective anti-angiogenic regimens.

Salsalate may have broad utility in the prevention and treatment of vascular disorders and the metabolic syndrome

In the high proportion of vascular disorders associated with excessive oxidative stress and production of pro-inflammatory cytokines, activation of NF-kappaB plays a key pathogenic role. Thus, there is considerable evidence that NF-kappaB is a mediator of atherogenesis, plaque destabilization, ischemia-reperfusion damage, cardiac remodeling, atrial fibrillation, and aneurysm formation and rupture; some studies suggest that it may also play a role in the microvascular complications of diabetes. I kappaB kinase-beta (IKK beta) is the upstream kinase that appears to be primarily responsible for NF-kappaB activation in these disorders; moreover, chronic IKK beta activation plays a prominent role in induction of insulin resistance in the metabolic syndrome. Salicylate inhibits IKK beta in concentrations that are achievable with dose schedules traditionally used in treating rheumatoid arthritis (3-4.5 g daily); indeed, this is likely to be the mechanism responsible for salicylate's utility in this disorder. Salicylate, unlike aspirin, is only a very weak, reversible inhibitor of cyclooxygenase in clinical doses, and thus is not associated with the potentially dangerous side effects seen with NSAIDs; fully reversible ototoxicity, the dose-limiting side effect in salicylate therapy, can be avoided in most patients by dosage adjustment. Hence, it is proposed that salicylate may have practical utility in the prevention or management of a wide range of vascular disorders as well as of metabolic syndrome and diabetes; its efficacy in these regards would likely be complemented by effective antioxidant measures, which would lessen the stimulus to NF-kappaB activation while providing benefits independent of NF-kappaB activity. Salsalate, consisting of two salicylate molecules united by an ester bond, is a venerable drug that may be the best tolerated delivery vehicle for salicylate. Appropriate rodent studies should pave the way for clinical trials with salsalate in patients at vascular risk.

Inhibition of ERK MAPK suppresses IL-23- and IL-1-driven IL-17 production and attenuates autoimmune disease

IL-17-producing CD4(+) T (Th17) cells are pathogenic in many autoimmune diseases. The induction and expansion of Th17 cells is directed by cytokines, including IL-23 and IL-1beta, produced by innate immune cells through activation of pathogen recognition receptors. The NF-kappaB and IFN regulatory factor families of transcriptional factors mediate IL-12 production; however, distinct signaling pathways appear to be required for IL-23 production. In this study, we show that inhibition of ERK MAPK suppressed IL-23 and IL-1beta production by dendritic cells stimulated with TLR or dectin-1 agonists but did not affect IL-12p70 production. Furthermore, an ERK inhibitor suppressed the ability of Ag-pulsed TLR-activated dendritic cells to induce Ag-specific Th17 cells in vivo, but interestingly also inhibited the induction of Th1 cells. Treatment with an ERK inhibitor attenuated experimental autoimmune encephalomyelitis (EAE), when administered either at the induction phase of acute EAE or during remission in the relapsing-remitting EAE model. This was associated with significant suppression of autoantigen-specific Th17 and Th1 responses. The suppressive effect of the ERK inhibitor on attenuation of EAE was reversed by administration of IL-1beta and IL-23. Our findings suggest that ERK MAPK plays a critical and hitherto undescribed role in activating innate production of IL-23 and IL-1beta, which promote pathogenic T cell responses, and therefore represents an important target for therapeutic intervention against autoimmune diseases.

Attenuating regulatory T cell induction by TLR agonists through inhibition of p38 MAPK signaling in dendritic cells enhances their efficacy as vaccine adjuvants and cancer immunotherapeutics

TLR ligands are potent adjuvants and promote Th1 responses to coadministered Ags by inducing innate IL-12 production. We found that TLR ligands also promote the induction of IL-10-secreting regulatory T (Treg) cells through p38 MAPK-induced IL-10 production by dendritic cells (DC). Inhibition of p38 suppressed TLR-induced IL-10 and PGE(2) and enhanced IL-12 production in DC. Incubation of Ag-pulsed CpG-stimulated DC with a p38 inhibitor suppressed their ability to generate Treg cells, while enhancing induction of Th1 cells. In addition, inhibition of p38 enhanced the antitumor therapeutic efficacy of DC pulsed with Ag and CpG and this was associated with an enhanced frequency of IFN-gamma-secreting T cells and a reduction of Foxp3(+) Treg cells infiltrating the tumors. Furthermore, addition of a p38 inhibitor to a pertussis vaccine formulated with CpG enhanced its protective efficacy in a murine respiratory challenge model. These data demonstrate that the adjuvant activity of TLR agonists is compromised by coinduction of Treg cells, but this can be overcome by inhibiting p38 signaling in DC. Our findings suggest that p38 is an important therapeutic target and provides a mechanism to enhance the efficacy of TLR agonists as vaccine adjuvants and cancer immunotherapeutics.

Adenylate cycalse toxin of Bordetella pertussis inhibits TLR-induced IRF-1 and IRF-8 activation and IL-12 production and enhances IL-10 through MAPK activation in dendritic cells

Adenylate cyclase toxin (CyaA) of Bordetella pertussis binds to CD11b/CD18 on macrophages and dendritic cells (DC) and confers virulence to the bacteria by subverting innate immune responses of the host. We have previously demonstrated that CyaA promotes the induction of IL-10-secreting regulatory T cells in vivo by modulating DC activation. Here, we examine the mechanism of immune subversion, specifically, the modulation of TLR signaling pathways in DC. We found that CyaA synergized with LPS to induce IL-10 mRNA and protein expression in DC but significantly inhibited IL-12p70 production. CyaA enhanced LPS-induced phosphorylation of p38 MAPK and ERK in DC, and inhibitors of p38 MAPK, MEK, or NF-kappaB suppressed IL-10 production in response to LPS and CyaA. However, inhibition of p38 MAPK, MEK, and NF-kappaB did not reverse the inhibitory effect of CyaA on TLR agonist-induced IL-12 production. Furthermore, CyaA suppression of IL-12 was independent of IL-10. In contrast, CyaA suppressed LPS- and IFN-gamma-induced IFN-regulatory factor-1 (IRF-1) and IRF-8 expression in DC. The modulatory effects of CyaA were dependent on adenylate cyclase activity and induction of intracellular cAMP, as an enzyme-inactive mutant of CyaA failed to modulate TLR-induced signaling in DC, whereas the effects of the wild-type toxin were mimicked by stimulation of the DC with PGE2. Our findings demonstrate that CyaA modulates TLR agonist-induced IL-10 and IL-12p70 production in DC by, respectively, enhancing MAPK phosphorylation and inhibiting IRF-1 and IRF-8 expression and that this is mediated by elevation of intercellular cAMP concentrations.

Effect of sinomenine on collagen-induced arthritis in mice

The present study was designed to investigate the effect of sinomenine (SIN), an alkaloid extracted from sinomenium acutum on collagen-induced arthritis (CIA) in mice. For this investigation, mice were s.c. immunized with type II collagen (CII) emulsified with complete Freund's adjuvant (day 0). Varying doses of SIN were orally administered daily commencing on day 0 daily over a period of 55 days. The severity of arthritis was evaluated according to clinical score, the effect of SIN on immune responses were determined by measurement of proliferative responses of spleen cells, antibody levels in serum and cytokine assays. Anti-CII IgG2a and IFN-gamma were measured as indicators of Th1 immune responses and anti-CII IgG1, IgE and IL-5 as those of Th2 responses. IL-10 and TGF-beta were measured as indicators of T cell regulator responses. The results showed that treatment with SIN was followed by decreases in the incidence and severity of CIA, anti-CII IgG and the antigen-specific splenocyte proliferation. Production of all isotypes of antibodies including anti-CII IgG2a, IgG1 and IgE as well as secretion of cytokines such as IFN-gamma and IL-5 were suppressed by SIN. In addition, SIN enhanced the secretion of TGF-beta while it had no obvious effect on production of IL-10. These results suggest that the anti-arthritic effect of SIN may be related to the suppression of both Th1 and Th2 immune responses. TGF-beta may at least in part contribute to the suppression of Th1 as well as Th2 immune responses.

Conjugated linoleic acid suppresses NF-kappa B activation and IL-12 production in dendritic cells through ERK-mediated IL-10 induction

Polyunsaturated fatty acids (PUFA) have been shown to modulate immune responses and have therapeutic effects in inflammatory disorders. However, the influence of PUFA on dendritic cells (DC), key cells of the innate immune system in shaping adaptive immune responses, has not yet been defined. In this study, we examine the effects of the cis-9, trans-11 isomer of conjugated linoleic acid (c9, t11-CLA), a dietary PUFA found in meat and dairy products, on murine DC activation. Treatment of DC with c9, t11-CLA suppressed LPS-induced IL-12, enhanced IL-10R expression, and enhanced IL-10 production at the transcriptional and protein level. The suppression of IL-12 by c9, t11-CLA was found to be IL-10 dependent. We investigated the involvement of the MAPK, ERK, and the transcription factor, NF-kappaB, in this IL-10-mediated effect. c9, t11-CLA enhanced ERK activation after LPS stimulation, and inhibition of ERK resulted in abrogation of IL-10 and recovery of IL-12 production. c9, t11-CLA decreased NF-kappaB:DNA binding after LPS stimulation, which was concomitant with delayed translocation of NF-kappaBp65 into the nucleus and an increase in IkappaBalpha. These effects were reversed by addition of a neutralizing anti-IL-10 Ab. Our findings demonstrate that c9, t11-CLA suppresses IL-12 production by LPS-stimulated DC by ERK mediated IL-10-induction. Furthermore, these IL-10-mediated effects are dependent on inhibition of NF-kappaB activation. This is the first study to demonstrate that c9, t11-CLA can enhance transcription and production of the anti-inflammatory cytokine IL-10, while inhibiting the Th1-promoting cytokine IL-12, and may explain certain of its immunosuppressive properties.