Inhibition of Human Dendritic Cell Maturation and Function by the Novel Immunosuppressant FK778

Impact of disease-modifying therapy on dendritic cells and exploring their immunotherapeutic potential in multiple sclerosis

Dendritic cells (DCs) are the most potent professional antigen-presenting cells (APCs), which play a pivotal role in inducing either inflammatory or tolerogenic response based on their subtypes and environmental signals. Emerging evidence indicates that DCs are critical for initiation and progression of autoimmune diseases, including multiple sclerosis (MS). Current disease-modifying therapies (DMT) for MS can significantly affect DCs' functions. However, the study on the impact of DMT on DCs is rare, unlike T and B lymphocytes that are the most commonly discussed targets of these therapies. Induction of tolerogenic DCs (tolDCs) with powerful therapeutic potential has been well-established to combat autoimmune responses in laboratory models and early clinical trials. In contrast to in vitro tolDC induction, in vivo elicitation by specifically targeting multiple cell-surface receptors has shown greater promise with more advantages. Here, we summarize the role of DCs in governing immune tolerance and in the process of initiating and perpetuating MS as well as the effects of current DMT drugs on DCs. We then highlight the most promising cell-surface receptors expressed on DCs currently being explored as the viable pharmacological targets through antigen delivery to generate tolDCs in vivo.

Suppression of Dendritic Cell Maturation by Kefir Peptides Alleviates Collagen-Induced Arthritis in Mice

Arthritis is a disorder that is characterized by joint inflammation and other symptoms. Rheumatoid arthritis (RA), an autoimmune disease, is one of the most common arthritis in worldwide. Inflammation of the synovium is the main factor that triggers bone erosion in the joints in RA, but the pathogenesis of RA is not clearly understood. Kefir grain-fermented products have been demonstrated to enhance immune function and exhibit immune-modulating bioactivities. This study aims to explore the role of kefir peptides (KPs) on the regulation of dendritic cell, which are found in RA synovial fluid, and the protection effects of KPs on mice with collagen-induced arthritis (CIA). Immature mouse bone marrow-derived dendritic cells (BMDCs) were treated with KPs (2.2 and 4.4 mg/ml) and then exposed to lipopolysaccharide (LPS) to study the immune regulation function of KPs in dendritic cells. Mice with CIA (n = 5 per group) were orally administrated KPs (3.75 and 7.5 mg/day/kg) for 21 days and therapeutic effect of KPs on mice with arthritis were assessed. In this study, we found that KPs could inhibit surface molecule expression, reduce inflammatory cytokine release, and repress NF-κB and MAPK signaling in LPS-stimulated mouse BMDCs. In addition, a high dose of KPs (7.5 mg/kg) significantly alleviated arthritis symptoms, decreased inflammatory cytokine expression, suppressed splenic DC maturation and decrease the percentage of Th1 and Th17 in the spleens on mice with CIA. Our findings demonstrated that KPs ameliorate CIA in mice through the mechanism of suppressing DC maturation and inflammatory cytokine releases.

Effects of Omega-3 Fatty Acids on Immune Cells

Alterations on the immune system caused by omega-3 fatty acids have been described for 30 years. This family of polyunsaturated fatty acids exerts major alterations on the activation of cells from both the innate and the adaptive immune system, although the mechanisms for such regulation are diverse. First, as a constitutive part of the cellular membrane, omega-3 fatty acids can regulate cellular membrane properties, such as membrane fluidity or complex assembly in lipid rafts. In recent years, however, a new role for omega-3 fatty acids and their derivatives as signaling molecules has emerged. In this review, we describe the latest findings describing the effects of omega-3 fatty acids on different cells from the immune system and their possible molecular mechanisms.

Atractylodin Suppresses Dendritic Cell Maturation and Ameliorates Collagen-Induced Arthritis in a Mouse Model

The aim of this study was to evaluate the immunomodulatory effects of atractylodin, a polyethylene alkyne, on the maturation of bone marrow-derived dendritic cells (BM-DC) as well as its antirheumatic effect on collagen-induced arthritis (CIA) in DBA/1 mice. Our results indicate that atractylodin effectively suppressed the secretion of pro-inflammatory cytokines, expression of costimulatory molecules, and p38 MAPK, ERK, and NF-κBp65 signaling pathways in LPS-incubated dendritic cells (DCs). Additionally, the proliferation and cytokine secretion (IFN-γ and IL-17A) of CD8⁺ and CD4⁺ T cells were reduced. In a murine CIA model, intraperitoneal injection of atractylodin significantly alleviated the severity of the disease progression, as indicated by reduced paw swelling, clinical arthritis scores, and pathological changes of joint tissues. In addition, the overall proliferation of T cells stimulated by type II collagen and the abundance of Th1 and Th17 in the spleens were also significantly decreased with atractylodin treatments. Furthermore, atractylodin significantly downregulated the expression levels of CD40, CD80, and CD86 of DCs in the spleens. In conclusion, this study shows for the first time that atractylodin has potential to manipulate the maturation of BM-DCs and should be further explored as a therapeutic agent in the treatment of rheumatoid arthritis (RA).

Regulatory myeloid cells in transplantation

Regulatory myeloid cells (RMC) are emerging as novel targets for immunosuppressive (IS) agents and hold considerable promise as cellular therapeutic agents. Herein, we discuss the ability of regulatory macrophages, regulatory dendritic cells, and myeloid-derived suppressor cells to regulate alloimmunity, their potential as cellular therapeutic agents, and the IS agents that target their function. We consider protocols for the generation of RMC and the selection of donor- or recipient-derived cells for adoptive cell therapy. Additionally, the issues of cell trafficking and antigen (Ag) specificity after RMC transfer are discussed. Improved understanding of the immunobiology of these cells has increased the possibility of moving RMC into the clinic to reduce the burden of current IS agents and to promote Ag-specific tolerance. In the second half of this review, we discuss the influence of established and experimental IS agents on myeloid cell populations. IS agents believed historically to act primarily on T cell activation and proliferation are emerging as important regulators of RMC function. Better insights into the influence of IS agents on RMC will enhance our ability to develop cell therapy protocols to promote the function of these cells. Moreover, novel IS agents may be designed to target RMC in situ to promote Ag-specific immune regulation in transplantation and to usher in a new era of immune modulation exploiting cells of myeloid origin.

A decrease in the percentage of circulating mDC precursors in patients with coronary heart disease: a relation to the severity and extent of coronary artery lesions?

Inflammation plays a pivotal role in coronary heart disease. Dendritic cells (DCs) are principal players in inflammation and atherosclerosis. Although the percentage of circulating DC precursors in coronary heart disease have been investigated, circulating myeloid DC (mDC) and plasmacytoid DC (pDC) precursors have not been extensively studied, particularly in relation to the severity of coronary artery lesions in patients with coronary heart disease. In this study, we recruited controls (n = 29), patients with stable angina pectoris (SAP, n = 30), patients with unstable angina pectoris (UAP, n = 56), and patients with acute myocardial infarction (AMI, n = 50). The severity and extent of coronary artery lesions was evaluated by Gensini score, following coronary angiograms. The percentage of circulating mDC and pDC precursors was determined by fluorescence-activated cell sorting (FACS). Plasma levels of MCP-1 and MMP-9, which correlate with atherosclerosis and DC migration, were also measured. The percentage of circulating mDC precursors was reduced in patients with AMI and UAP compared with control and SAP patients, respectively (p < 0.01 for AMI vs. SAP and Control, p < 0.05 for UAP vs. SAP and Control). The percentage of circulating pDC precursors was not significant changed. The levels of plasma MMP-9 and MCP-1 and Genisi score were all increased in patients with AMI and UAP, compared to control and SAP patients, respectively (p < 0.01 for AMI vs. SAP and control, p < 0.05 for UAP vs. SAP and control). Overall, the percentage of circulating mDC precursors was negatively correlated with MCP-1 (p < 0.001), MMP-9 (p < 0.001) and Genisi scores (p < 0.001). Genisi scores were positively correlated with the levels of MCP-1 (p < 0.001) and MMP-9 (p < 0.001). Our study suggested that the percentage of circulating mDC precursors is negatively correlated with the severity and extent of coronary artery lesions in patients with coronary heart disease.

Regulation of human dendritic cells by a novel specific nuclear factor-kappaB inhibitor, dehydroxymethylepoxyquinomicin

Regulation of antigen-presenting cells (APC) is crucial in controlling allograft rejection. Dendritic cells (DC) are the most potent APC and must mature to present antigens to T-cell receptors. During DC maturation, nuclear factor-kappaB (NF-kappaB) is a key transcriptional factor. We synthesized dehydroxymethylepoxyquinomicin (DHMEQ), which specifically inhibits the final step of nuclear translocation of activated NF-kappaB proteins and examined its immunoregulatory effects on human monocyte-derived DC (Mo-DC). Regulatory Mo-DC were generated by pretreatment with DHMEQ before LPS stimulation, which were termed dl-DC. DHMEQ pretreatment (5 microg/ml) completely inhibited nuclear translocation of activated NF-kappaB. DHMEQ significantly inhibited DC production of proinflammatory cytokines (IL-6, TNF-alpha, and IL-12 p70) in a dose-dependent manner. IL-12 was most potently inhibited. However, IL-10 production by dl-DC was only moderately affected by DHMEQ. Although CD40 and the expression of HLA-DR (HLA-DR) expression on dl-DC was downregulated, CD80 and CD86 expression was moderately upregulated. Induction of T helper 1 cell responses was efficiently impaired by dl-DC. This confirmed that DHMEQ-treated Mo-DC exhibited immunoregulatory effects. These findings suggest that DHMEQ has potential as an immunosuppressive drug for human immune cells.

Characterization of pulmonary T cell response to helper-dependent adenoviral vectors following intranasal delivery

In spite of the extensive research in the field of gene therapy, host immune responses continue to be the major barrier in translating basic research to clinical practice. Helper-dependent adenoviral (HD-Ad) vectors show great potential for pulmonary gene therapy, but the knowledge of pulmonary immune responses toward these vectors is very limited. In this study, we show that HD-Ad vectors are potent stimulators of dendritic cell (DC) maturation, thus leading to stimulation of T cell proliferation with approximately 6% of naive CD4(+) T cells from pulmonary mediastinal lymph node responding to HD-Ad-treated DCs. In contrast to the belief that HD-Ad vectors are unable to prime adaptive immune response, we show for the first time, through in vivo pulmonary studies in mice, that HD-Ad vectors can prime CD4(+) and CD8(+) T cell responses in the lung at high and substantially low doses. This indicates cross-presentation of HD-Ad-derived epitopes by DCs to prime CD8(+) T cell responses. To assess the basis of pulmonary T cell response against HD-Ad vectors, we examined the response of conventional DCs (cDCs) and plasmacytoid DCs (pDCs) in the lung. In response to HD-Ad delivery, there is induction of maturation in both cDC and pDC subsets, but it is the cDCs, not pDCs, that migrate rapidly to draining lymph nodes within the first 2 days after vector delivery to prime adaptive immune response against these vectors. These findings have implications for development of strategies to prevent adaptive immune responses against gene therapy vectors.

Prolonged Survival With FK778 (Malononitrilamide) Monotherapy After Small Bowel Transplantation: A Large Animal Study

Malononitrilamide 715 (FK778) is a new class of immunosuppressant, derived from the active metabolite of leflunomide A77 1726. We investigated the efficacy of two different immunosuppressive induction protocols with tacrolimus plus FK778 followed by FK778 monotherapy. In a swine model of small bowel transplantation, we observed three groups, divided by different therapy regimens: group 1 (n = 5): no immunosuppressant (control group); group 2 (n = 10): oral tacrolimus (from postoperative day [POD] 0 to 30) and FK778 (from POD 0 to 60); group 3 (n = 8): oral tacrolimus, as group 2, and FK778 (from POD 7 to POD 60). Median survival was 11, 60, and 21 days in groups 1, 2, and 3, respectively. In group 1 all animals died of acute rejection; in group 2 the causes of death were technical complication (n = 1) and sepsis (n = 1); in group 3, one animal died from obstruction, two from pneumonia, one from peritonitis, one from sepsis. Group 2 accounted for 0.5 infection episode/animal versus 0.62 in group 3 (P < .05). Acute rejection was absent or mild in 66% and 75% of group 3 and 2 biopsies, respectively (P < .05). The D-xylose absorption curves from groups 2 and 3 were similar to those of the nontransplanted healthy animals. In conclusion, FK778 monotherapy after a consistent induction period with tacrolimus combined immunosuppression is able to extend survival and preserve optimal absorptive capacity of the small bowel allograft in our pig model. The association of tacrolimus and FK778 from day 1, compared to the delayed administration of FK778 from day 7, results in a significant reduction of infections and postoperative complications.

The new malononitrilamide immunosuppressant FK778 prolongs corneal allograft survival in the rat keratoplasty model

PURPOSE

Aim of this study was to prove the efficacy and safety of the new malononitrilamide immunosuppressive FK778 in prolonging clear graft survival following allogeneic orthotopic keratoplasty in rats.

METHODS

Sixty-seven penetrating keratoplasties were performed using Fisher and Lewis rats as donors and recipients, respectively: group 1 (n=11), allogeneic control without therapy; group 2 (n=12), syngeneic control; group 3 (n=11), mycophenolate mofetil (MMF) 40 mg/kg bodyweight; group 4 (n=12), FK778 5 mg/kg bodyweight; group 5 (n=12), FK778 10 mg/kg bodyweight; and group 6 (n=9), FK778 20 mg/kg bodyweight. Four animals in each group were killed for immunohistological evaluation on day 14. Therapy was administered orally for 18 days. The grafts were evaluated every three days by means of a scoring system including opacity, oedema, and vascularization. Time to rejection was analysed with the Kaplan-Meier survival analysis and compared with the log-rank test. The densities of infiltrating immune cells were compared statistically using the non-parametric Mann-Whitney test.

RESULTS

Mean rejection-free graft survival was 11.4 days in group 1 (allogeneic control), 100 days (total follow-up time) in group 2 (syngeneic control), 24.0 days in group 3 (MMF 40 mg/kg), 15.7 days in group 4 (FK778 5 mg/kg), 19.1 days in group 5 (FK778 10 mg/kg), and 25.4 days in group 6 (FK778 20 mg/kg) (P<0.005).

CONCLUSIONS

Systemic immunosuppression with FK778 prolongs graft survival in the rat keratoplasty model. FK778's efficacy is comparable with that of MMF in preventing immunologic graft rejection.

Is the Malononitrilamide FK778 Better for the Prevention of Acute or Chronic Rejection?

OBJECTIVE

The aim of this study was to assess the efficacy of FK778 to prevent acute and chronic allograft rejection compared with other immunosuppressive agents.

MATERIALS AND METHODS

Heterotopic Brown-Norway (BN)-to-Lewis rat cardiac transplantations and heterotopic BN-to-Lewis tracheal transplantations were performed to study acute heart rejection and the development of chronic obliterative airway disease (OAD), respectively. Recipients were treated with FK778, tacrolimus, MMF, or sirolimus for 10 days (acute rejection study) or 28 days (chronic OAD study) at varying doses.

RESULTS

In untreated recipients, cardiac allograft survival was 6.2 +/- 0.4 days. FK778 (20 mg/kg), tacrolimus (2 or 8 mg/kg), mycophenolate mofetil (MMF; 40 mg/kg), or sirolimus (0.5 or 2 mg/kg) significantly prolonged graft survival to 17.0 +/- 2.8, 18.5 +/- 2.7, 25.0 +/- 2.5, 20.7 +/- 3.8, 14.5 +/- 2.2, and 23.2 +/- 1.5 days, respectively (P < .05). Tracheal grafts in untreated recipients showed intense infiltration and complete luminal obliteration by day 28. FK778 (20 mg/kg), tacrolimus (1 or 4 mg/kg), MMF (10 or 40 mg/kg), or sirolimus (0.5 or 2 mg/kg) significantly inhibited tracheal luminal obliteration (19.5% +/- 16.4%, 44.2% +/- 33.6%, 12.3% +/- 3.3%, 61.7% +/- 18.6%, 18.3% +/- 11.3%, 55.0% +/- 30.9%, and 8.5% +/- 3.5% (P < .05). All 4 high-dose groups showed similar efficacy.

CONCLUSIONS

When used in therapeutic doses, tacrolimus and sirolimus were more effective than FK778 to prolong cardiac allograft survival. However, with its antiproliferative effects on smooth muscle cells, its good tolerability, and its blockade of cytomegalovirus replication, FK778 proved effective to prevent chronic OAD development. Thus, FK778 may acquire an important role in maintenance therapy for the prevention of long-term fibroproliferative complications.

Liver X receptors regulate dendritic cell phenotype and function through blocked induction of the actin-bundling protein fascin

Liver X receptors (LXRs) are nuclear receptors regulating lipid and cholesterol metabolism. Recent data revealed a cross talk between LXR and Toll-like receptor signaling in macrophages, indicating a role in immunity. Here, we show that LXRalpha is expressed in human myeloid dendritic cells (DCs) and induced during differentiation of monocyte-derived DCs, whereas LXRbeta is expressed constitutively at a very low level. LXR activation by 2 different LXR agonists strongly interfered with lipopolysaccharide (LPS)-induced but not with CD40L-induced DC maturation by altering DC morphology and suppressing interleukin-12-but enhancing interleukin-10-secretion. LXR activation in DCs largely blocked their T-cell stimulatory ability despite essentially unaltered expression of various antigen-presenting and costimulatory molecules. Immunologic synapse formation was significantly inhibited by LXR activation along with a complete block in LPS- but not CD40L-induced expression of the actin-bundling protein fascin. Notably, overexpression of fascin in LXR agonist-treated DCs restored immunologic synapse formation and restored their ability to activate T cells. In conclusion, our data reveal LXR as a potent modulator of DC maturation and function mediated in part by blocking the expression of fascin. Due to the central position of DCs in immunity, LXRalpha could be a potential novel target for immunomodulation.

Impairment of T cell interactions with antigen-presenting cells by immunosuppressive drugs reveals involvement of calcineurin and NF-κB in immunological synapse formation

A stable supramolecular cluster in T cells at the contact site of APCs, the immunological synapse (IS), is essential for full T cell activation. Failure of IS maturation, as determined by defective relocalization of the TCR/CD3 complex at the T cell/APC contact site, is linked with T cell hyporesponsiveness. The effects of clinically used immunosuppressants on these critical events, however, are undefined. Here, we show that treatment of T cells with cyclosporin A, FK506, and dexamethasone, which are known to inhibit calcineurin and NF-kappaB, respectively, but not rapamycin, the inhibitor of mammalian target of rapamycin, selectively prevented TCR/CD3 relocalization into the IS, while relocalization of adhesion and cytoskeletal proteins as well as T cell/APC conjugate formation remained unaltered. The involvement of calcineurin and NF-kappaB in IS maturation was confirmed by using specific inhibitors of these molecules (FR901725, gossypol, SN50). FK778, as an inhibitor of DNA replication and also TCR/CD3-activated tyrosine kinases, globally abrogated cytoskeletal, adhesion, and signaling molecule relocalization, thereby preventing formation of an IS at an earlier, immature stage along with impaired, antigen-specific T cell/APC conjugate formation. Collectively, blocking IS formation at distinct stages may mediate effects on T cell activation of currently used immunosuppressants, apart from their capacity to block gene transcription, cytokine signaling, and DNA replication. Furthermore, these data imply novel functions of calcineurin and NF-kappaB for successful IS maturation.

Regulatory dendritic cell therapy in organ transplantation

Dendritic cells (DCs) are uniquely well equipped antigen (Ag)-presenting cells. Their classic function was thought to be that of potent initiators of innate and adaptive immunity to infectious organisms and other Ags (including transplanted organs). Evidence has emerged, however, that DCs have a central and crucial role in determining the fate of immune responses toward either immunity or tolerance. This dichotomous function of DCs, coupled with their remarkable plasticity, renders them attractive therapeutic targets for immune modulation. In transplantation, much recent work has focused on the ability of DCs to silence immune reactivity in an Ag-specific manner in the hope of preventing rejection and diminishing reliance on potentially harmful immunosuppressive agents. Experimental strategies have included in vivo targeting of DCs, as well as ex vivo generation of regulatory (or tolerogenic) DCs with subsequent reinfusion (i.e. cell therapy). Different approaches to 'program' DC toward tolerogenic properties include genetic (transgene insertion), biologic (differential culture conditions, anti-inflammatory cytokine exposure) and pharmacologic manipulation. Recent data suggest a promising role for pharmacologic treatment as a means of generating potent regulatory DCs and have further stimulated speculation regarding their potential clinical application. Herein, we discuss evidence that the potential of regulatory DC therapy is considerable and that there are compelling reasons to evaluate it in the setting of organ transplantation in the near future.

Immune dysfunction in uremia

Kidney dysfunction leads to disturbed renal metabolic activities and to impaired glomerular filtration, resulting in the retention of toxic solutes affecting all organs of the body. Cardiovascular disease (CVD) and infections are the main causes for the increased occurrence of morbidity and mortality among patients with chronic kidney disease (CKD). Both complications are directly or indirectly linked to a compromised immune defense. The specific coordinated roles of polymorphonuclear leukocytes (PMNLs), monocytes/macrophages, lymphocytes and antigen-presenting cells (APCs) in maintaining an efficient immune response are affected. Their normal response can be impaired, giving rise to infectious diseases or pre-activated/primed, leading to inflammation and consequently to CVD. Whereas the coordinated removal via apoptosis of activated immune cells is crucial for the resolution of inflammation, inappropriately high apoptotic rates lead to a diminished immune response. In uremia, the balance between pro- and anti-inflammatory and between pro- and anti-apoptotic factors is disturbed. This review summarizes the interrelated parameters interfering with the immune response in uremia, with a special focus on the non-specific immune response and the role of uremic toxins.