Effect of synthetic retinoid, TAC-101, on experimental autoimmune disease

Vitamin A and Its Multi-Effects on Pancreas: Recent Advances and Prospects

Vitamin A (VA), which is stored in several forms in most tissues, is required to maintain metabolite homeostasis and other processes, including the visual cycle, energy balance, epithelial cell integrity, and infection resistance. In recent years, VA molecules, also known as retinoids, have been extensively explored and used in the treatment of skin disorders and immune-related tumors. To date, several observational and interventional studies have explored the relationship between VA status and the pathogenesis of diabetes. In particular, VA micronutrients have been shown to regulate pancreatic development, β-cell function, pancreatic innate immune responses, and pancreatic stellate cells phenotypes through multiple mechanisms. However, there are still many problems to be proven or resolved. In this review, we summarize and discuss recent and available evidence on VA biological metabolism in the pancreas. Analysis of the effects of VA on metabolism in the pancreas will contribute to our understanding of the supportive physiological roles of VA in pancreas protection.

Co-Stimulation-Impaired Bone Marrow-Derived Dendritic Cells Prevent Dextran Sodium Sulfate-Induced Colitis in Mice

Dendritic cells (DC) are important in the onset and severity of inflammatory bowel disease (IBD). Tolerogenic DC induce T-cells to become therapeutic Foxp3+ regulatory T-cells (Tregs). We therefore asked if experimental IBD could be prevented by administration of bone marrow-derived DC generated under conventional GM-CSF/IL-4 conditions but in the presence of a mixture of antisense DNA oligonucleotides targeting the primary transcripts of CD40, CD80, and CD86. These cell products (which we call AS-ODN BM-DC) have demonstrated tolerogenic activity in preventing type 1 diabetes and preserving beta cell mass in new-onset type 1 diabetes in the NOD mouse strain, in earlier studies. In addition to measuring efficacy in prevention of experimental IBD, we also sought to identify possible mechanism(s) of action. Weight, behavior, stool frequency, and character were observed daily for 7–10 days in experimental colitis in mice exposed to dextran sodium sulfate (DSS) following injection of the AS-ODN BM-DC. After euthanasia, the colons were processed for histology while spleen and mesenteric lymph nodes (MLNs) were made into single cells to measure Foxp3+ Treg as well as IL-10+ regulatory B-cell (Breg) population frequency by flow cytometry. AS-ODN BM-DC prevented DSS-induced colitis development. Recipients of these cells exhibited significant increases in Foxp3+ Treg and IL-10+ Breg in MLN and spleen. Histological examination of colon sections of colitis-free mice remained largely architecturally physiologic and mostly free of leukocyte infiltration when compared with DSS-treated animals. Although DSS colitis is mainly an innate immunity-driven condition, our study adds to the growing body of evidence showing that Foxp3+ Treg and IL-10 Bregs can suppress a mainly innate-driven inflammation. The already-established safety of human DC generated from monocytic progenitors in the presence of the mixture of antisense DNA targeting the primary transcripts of CD40, CD80, and CD86 in humans offers the potential to adapt them for clinical IBD therapy.

All-trans retinoic acid attenuates bleomycin-induced pulmonary fibrosis via downregulating EphA2-EphrinA1 signaling

The role of all-trans retinoic acid (ATRA) in pulmonary fibrosis is relatively unknown, although this metabolite modulates cell differentiation, proliferation, and development. We aimed to evaluate the role of ATRA in bleomycin-induced pulmonary fibrosis, and whether the mechanism involves EphA2-EphrinA1 and PI3K-Akt signaling. We evaluated three groups of mice: a control group (intraperitoneal DMSO injection 3 times weekly after PBS instillation), bleomycin group (intraperitoneal DMSO injection 3 times weekly after bleomycin instillation), and bleomycin + ATRA group (intraperitoneal ATRA injection 3 times weekly after bleomycin instillation). The cell counts and protein concentration in the bronchoalveolar lavage fluid (BALF), changes in histopathology, Ashcroft score, hydroxyproline assay, expression of several signal pathway proteins including EphA2-EphrinA1, and PI3K-Akt, and cytokine levels were compared among the groups. We found that bleomycin significantly increased the protein concentration in the BALF, Ashcroft score in lung tissue, and hydroxyproline contents in lung lysates. Furthermore, bleomycin upregulated EphA2, EphrinA1, PI3K 110γ, Akt, IL-6 and TNF-α. However, administration of ATRA attenuated the upregulation of EphA2-EphrinA1 and PI3K-Akt after bleomycin instillation, and decreased pulmonary fibrosis. In addition, ATRA suppressed IL-6 and TNF-α production induced by bleomycin-induced injury. Collectively, these data suggest that ATRA attenuates bleomycin-induced pulmonary fibrosis by regulating EphA2-EphrinA1 and PI3K-Akt signaling.

Positive evidence for vitamin A role in prevention of type 1 diabetes

Type 1 diabetes mellitus (T1DM) as one of the most well-known autoimmune disease, results from the destruction of β-cells in pancreas by autoimmune process. T1DM is fatal without insulin treatment. The expansion of alternative treatment to insulin is a dream to be fulfilled. Currently autoimmunity is considered as main factor in development of T1DM. So manipulation of the immune system can be considered as alternative treatment to insulin. For the past decades, vitamin A has been implicated as an essential dietary micronutrient in regulator of immune function. Despite major advantage in the knowledge of vitamin A biology, patients who present T1DM are at risk for deficiency in vitamin A and carotenoids. Applying such evidences, vitamin A treatment may be the key approach in preventing T1DM.

Vitamin A deficient mice exhibit increased viral antigens and enhanced cytokine/chemokine production in nasal tissues following respiratory virus infection despite the presence of FoxP3+ T cells

The World Health Organization (WHO) estimates that 250 million children under the age of five suffer from vitamin A deficiencies (VAD). Individuals with VAD experience higher rates of mortality and increased morbidity during enteric and respiratory infections compared with those who are vitamin A sufficient. Previously, our laboratory has demonstrated that VAD mice have significantly impaired virus-specific IgA and CD8(+) T-cell responses in the airways. Here, we demonstrate that VAD mice experience enhanced cytokine/chemokine gene expression and release in the respiratory tract 10 days following virus infection compared with control vitamin A sufficient animals. Cytokines/chemokines that are reproducibly up-regulated at the gene expression and protein levels include IFNγ and IL-6. Despite previous indications that cytokine dysregulation in VAD animals might reflect low forkhead box P3 (FoxP3)-positive regulatory T-cell frequencies, we found no reduction in FoxP3(+) T cells in VAD respiratory tissues. As an alternative explanation for the high cytokine levels, we found that the extent of virus infection and the persistence of viral antigens were increased on day 10 post-infection in VAD animals compared with controls, and consequently that respiratory tract tissues had an increased potential to activate virus-specific T cells. Results encourage cautious management of viral infections in patients with VAD, as efforts to enhance FoxP3(+) T cell frequencies and quell immune effectors could potentially exacerbate disease if the virus has not been cleared.

Integrative analysis of mRNA and miRNA array data reveals the suppression of retinoic acid pathway in regulatory T cells of Graves' disease

CONTEXT

It is well known that regulatory T cells (Tregs) are abnormal in Graves' disease (GD) and play crucial roles in the breakdown of immune tolerance and GD development. However, there are controversies about whether the quantity and/or function of Tregs is aberrant in GD. The molecular mechanism of Tregs abnormality and its effects on GD development was still unclear, until now.

OBJECTIVE

MiRNAs play important roles in the function and development of the immune system including Tregs. To reveal the Tregs abnormality and its molecular mechanism in GD, we systematically studied the quantity and immunosuppressive function as well as the differential expression profiles of miRNA and mRNA of Tregs in newly diagnosed patients with GD using TaqMan miRNA array and mRNA microarray.

RESULTS

Our results showed that the quantity and immunosuppressive function of Tregs in initial patients with GD was significantly decreased. More importantly, the retinoic acid (RA) pathway was markedly suppressed and its agonist, all-trans retinoic acid, could notably improve the quantity and immunosuppressive function of Tregs from patients with GD in vitro. In addition, many other pathways including protein ubiquitination and circadian rhythm were also significantly regulated in Tregs of GD.

CONCLUSIONS

This integrative study first revealed the expression profiles of mRNA/miRNA in Tregs of initial GD and RA pathway might play important roles in GD development. Our results implied that all-trans RA, which had been used for a long time in the clinical setting, had potential value in the treatment of GD and was worthy of additional study.

All-trans retinoic acid attenuates experimental colitis through inhibition of NF-κB signaling

Inflammatory bowel disease (IBD) is characterized by excessive innate immune cell activation, which is responsible for tissue damage and induction of adaptive immune responses. All-trans retinoic acid (ATRA), the ligand of retinoic acid receptors (RAR), has been previously shown to regulate adaptive immune responses and restore Th17/Treg balance, while its role in regulation of innate immune cell function such as macrophages remains to be elucidated. The study was performed to explore the effect of ATRA on regulation of innate immune responses during dextran sulfate sodium (DSS) induced murine colitis. The mice with DSS colitis were administered with vehicle, ATRA, or LE135. Colitis was evaluated by clinical symptoms, tissue myeloperoxidase (MPO) activity, and the expressions of CD68 and nuclear factor (NF) κB p65, and tumor necrosis factor (TNF) level in inflamed colon. RAW 264.7 cells were pretreated with vehicle, ATRA, or LE135, followed by LPS challenge in vitro. ATRA administration ameliorates DSS-induced colitis evidenced with decreased TNF level and CD68 expression, while LE135 leads to exacerbation of colitis. ATRA treatment in vitro dampens LPS induced NF-κB activation and TNF production of RAW 264.7 cells. Together, our data show a crucial role of ATRA in the progress of acute colitis through inhibiting NF-κB activation, and suggest that ATRA represents a novel therapeutic approach for the management of IBD.

All-trans-retinoic acid ameliorates the inflammation by inducing transforming growth factor beta 1 and interleukin 10 in mouse epididymitis

PROBLEM

Epididymitis, one of the most common urological diseases, can lead to the destruction of the epididymal duct and cause transient or permanent sterility. The aim of this study was to investigate the functions and related mechanisms of all trans retinoic acid (atRA) in alleviating the acute inflammation of epididymitis.

METHOD OF STUDY

The mouse model of the epididymitis was induced by injecting Escherichia coli into the cauda epididymis. atRA was administrated for five consecutive days through intraperitoneal injection. The expression levels of inflammatory cytokines were measured by real-time PCR and Western blot. In addition, cultured primary mouse epididymal epithelial cells were treated with different concentrations of atRA and RAR antagonists to identify whether the effect of atRA was mediated through RAR.

RESULTS

Our results demonstrate that atRA ameliorates the inflammation in mouse epididymitis by decreasing the expression of the pro-inflammatory cytokines and increasing the expression of anti-inflammatory factors including TGF-β1 and IL-10. Our results show that the upregulating effect of atRA on TGF-β1 was mediated by RARα, and the enhancing effect of atRA on IL-10 expression was mediated via RARβ.

CONCLUSION

These new results suggest that atRA is involved in regulating the inflammatory response of epididymis.

Differential role of all-trans retinoic acid in promoting the development of CD4+ and CD8+ regulatory T cells

It is known that ATRA promotes the development of TGF-β-induced CD4(+)Foxp3(+) iTregs, which play a vital role in the prevention of autoimmune diseases; however, the role of ATRA in facilitating the differentiation and function of CD8(+)Foxp3(+) iTregs remains elusive. Using a head-to-head comparison, we found that ATRA promoted expression of Foxp3 and development of CD4(+) iTregs, but it did not promote Foxp3 expression on CD8(+) cells. Using a standard in vitro assay, we demonstrated that CD8(+) iTregs induced by TGF-β and ATRA were not superior to CD8(+) iTregs induced by TGF-β alone. In cGVHD, in a typical lupus syndrome model where DBA2 spleen cells were transferred to DBA2xC57BL/6 F1 mice, we observed that both CD8(+) iTregs induced by TGF-β and ATRA and those induced by TGF-β alone had similar therapeutic effects. ATRA did not boost but, conversely, impaired the differentiation and function of human CD8(+) iTregs. CD8(+) cells expressed the ATRA receptor RAR and responded to ATRA, similar to CD4(+) cells. We have identified the differential role of ATRA in promoting Foxp3(+) Tregs in CD4(+) and CD8(+) cell populations. These results will help to determine a protocol for developing different Treg cell populations and may provide novel insights into clinical cell therapy for patients with autoimmune diseases and those needing organ transplantation.

Fat-soluble vitamins as disease modulators in multiple sclerosis

BACKGROUND

Fat-soluble vitamins (A, D, E and K) have properties that could be relevant as modulators of disease activity in multiple sclerosis (MS).

METHODS

We performed a systematic search on PubMed and Medline up to May 2012, using the search strings 'vitamin A', 'retinol', 'retinal', 'carotenoids', 'vitamin D', 'vitamin E', 'alpha-tocopherol', 'vitamin K' in conjunction with 'multiple sclerosis', 'animal model' and 'experimental autoimmune encephalitis (EAE)'. In addition, the reference lists of the publications identified were examined for further citations of relevance.

RESULTS

There is comprehensive evidence from epidemiological, observational, and experimental studies that vitamin D may be beneficial in MS. Results from small-scale clinical studies are inconclusive, and large-scale, adequately powered, randomized, controlled trials are still lacking. For vitamin D, Oxford Centre for Evidence-Based Medicine level 2c evidence exists for a positive therapeutic effect. Evidence from animal models indicates that all the examined fat-soluble vitamins could have potential as modulators of disease activity in MS. For vitamin A and E, level 4 and 5 evidence exists for a modulatory effect in MS; for vitamin K, too few studies have been conducted to indicate an effect in humans.

CONCLUSION

Vitamin D is a promising candidate as modulator of disease activity in MS, and controlled studies are currently being conducted. All the fat-soluble vitamins have, however, been demonstrated to be effective in different animal models for the disease, and vitamin A and E have biological properties that could be relevant for MS pathogenesis. Thus, vitamin A and E seem to be promising candidates for future case-control and cohort studies.

The influence of vitamin A supplementation on Foxp3 and TGF-β gene expression in atherosclerotic patients

The aim of this study was to investigate the role of vitamin A in Foxp3 and TGF-β gene expression in atherosclerotic patients. Patients and healthy controls in the vitamin A group received 25,000 IU retinyl palmitate per day, while patients in the placebo group took one capsule of placebo per day for 4 months. Gene expressions of regulatory T cells were studied by real-time PCR. The levels of Foxp3 expression in phytohemagglutinin-activated cells were much higher in the patients who received vitamin A than in placebo-treated patients and healthy controls, while Foxp3 gene expression in oxidized low-density lipoprotein-activated cells showed no significant differences between all groups (p=0.357). A significant difference in the expression level of TGF-β gene in fresh cells was observed between patients and healthy controls (p=0.009). TGF-β gene expression in oxidized low-density lipoprotein-activated cells increased in all groups; however, these changes were not statistically significant (p=0.65); the changes obtained were 2.8-, 2.2- and 3.9-fold in the vitamin A, placebo, and control groups, respectively. Based on suppressing actions of regulatory T cells on effector T cells and findings that show that vitamin A has the effect of increasing expression of regulatory T cells, it can be concluded that supplementation with vitamin A in atherosclerotic patients may be effective in slowing disease progression.

Environmental influences on T regulatory cells in inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by chronic, idiopathic inflammation of the intestine. The disease is thought to result from a combination of genetic and environmental factors which ultimately leads to a mucosal immune system that overreacts to normal constituents of the mucosal microbiota. The inflammation in IBD is primarily mediated by inappropriate production of proinflammatory cytokines by CD4(+) T effector cells, effects that are suppressed by CD4(+) T regulatory cells. Defects in both the function of T regulatory cells, and the ability of T effector cells to be suppressed, have been implicated in IBD. In this review we will discuss environmental factors, including cytokines, vitamins A and D, and commensal bacteria, which influence the phenotype and function of regulatory T cells and thereby alter the course of IBD. We will also discuss how these environmental signals can be manipulated therapeutically in order to improve the function of regulatory T cells and ultimately restore mucosal homeostasis in patients with IBD.

All-trans retinoic acid ameliorates trinitrobenzene sulfonic acid-induced colitis by shifting Th1 to Th2 profile

Inflammatory bowel disease is characterized with uncontrolled immune response in inflamed mucosa, with dominance of Th1 cells. Recently, all-trans retinoic acid has been shown that can lead T-cell response by suppressing Th17 development via retinoic acid receptor (RAR), but it is still unknown whether all-trans retinoic acid can modulate Th1 response of inflammatory bowel disease. In the experiment, we investigated the effect of all-trans retinoic acid on trinitrobenzene sulfonic acid (TNBS)-induced murine colitis, and the possible mechanism. Mice were intraperitoneally treated daily with all-trans retinoic acid (the agonist of RAR-alpha) or LE135 (the antagonist of RAR-alpha) or medium, and sacrificed 6 days later. Colon was collected for histological analysis and myeloperoxidase (MPO) activity measurement. Lamina propria mononuclear cells (LPMCs) were isolated, cultured, and assayed for the expressions of T-bet and GATA-3 by the use of Western blot and for cytokine levels by the use of ELISA. All-trans retinoic acid treatment inhibited inflammatory responses as shown by lower histological inflammatory scores and MPO activity, compared with LE135 and medium groups. Furthermore, in LPMCs culture supernatants, the levels of Th1 cytokines (INF-gamma, IL-12, and TNF-alpha) were decreased while those of Th2 cytokines (IL-4 and IL-10) were increased significantly in all-trans retinoic acid-treated mice. In addition, T-bet expression in LPMCs was inhibited and GATA-3 expression was up-regulated in all-trans retinoic acidtreated mice. On the contrary, LE135 showed the reverse effects in colon inflammation and cytokine profile. By shifting Th1 to Th2 profile in inflamed mucosa, all-trans retinoic acid down-regulates inflammatory response and ameliorates acute TNBS-induced colitis, which suggests the ligand of RAR-alpha-based pharmaceutical strategies for managing inflammatory bowel disease.

Towards retinoid therapy for Alzheimer's disease

Alzheimer's disease(AD) is associated with a variety of pathophysiological features, including amyloid plaques, inflammation, immunological changes, cell death and regeneration processes, altered neurotransmission, and age-related changes. Retinoic acid receptors (RARs) and retinoids are relevant to all of these. Here we review the pathology, pharmacology, and biochemistry of AD in relation to RARs and retinoids, and we suggest that retinoids are candidate drugs for treatment of AD.

All-trans retinoic acid down-regulates inflammatory responses by shifting the Treg/Th17 profile in human ulcerative and murine colitis

IBD is characterized by uncontrolled immune responses in inflamed mucosa, with dominance of IL-17-producing cells and deficiency of Treg cells. The aim of this study was to explore the effect and mechanisms of RA, the ligand of RARalpha, on immune responses in human and murine colitis. Colonic biopsies from patients with UC were cultured and treated with RA as the agonist of RARalpha or LE135 as the antagonist of RARalpha. Expressions of IL-17 and FOXP3 were detected by immunohistochemistry. Murine colitis was induced by intrarectal administration with TNBS at Day 1. Mice were then i.p.-treated with RA or LE135 daily for 7 days. Cytokine levels in the cultures of mouse LPMCs were measured. Expressions of FOXP3 and IL-17 in colon tissues or MLN were detected by immunohistological analysis. Body weight and colon inflammation were evaluated. RA treatment up-regulated FOXP3 expression and down-regulated IL-17 expression in colon biopsies of patients and in colon tissues and MLN of mice with colitis compared with controls. LPMCs from RA-treated mice produced lower levels of proinflammatory cytokines (TNF-alpha, IL-1beta, IL-17) but more regulatory cytokines (IL-10, TGF-beta) compared with that of untreated mice. LE135 showed the opposite effect of RA. Furthermore, RA ameliorated TNBS-induced colitis in a dose-dependent manner, as seen by improved body weight and colon inflammation. RA down-regulates colon inflammatory responses in patients with IBD in vitro and in murine colitis in vivo, representing a potential therapeutic approach in IBD treatment.

All-trans retinoic acid inhibits type 1 diabetes by T regulatory (Treg)-dependent suppression of interferon-gamma-producing T-cells without affecting Th17 cells

OBJECTIVE

All-trans retinoic acid (ATRA), a potent derivative of vitamin A, can regulate immune responses. However, its role in inducing immune tolerance associated with the prevention of islet inflammation and inhibition of type 1 diabetes remains unclear.

RESEARCH DESIGN AND METHODS

We investigated the mechanisms underlying the potential immunoregulatory effect of ATRA on type 1 diabetes using an adoptive transfer animal model of the disease.

RESULTS

Our data demonstrated that ATRA treatment inhibited diabetes in NOD mice with established insulitis. In addition, it suppressed interferon (IFN)-gamma-producing CD4(+) and CD8(+) T effector (Teff) cells and expanded T regulatory (Treg) cells in recipient mice transferred with diabetic NOD splenocytes, without affecting either interleukin (IL)-17--or IL-4-producing cells. Consistent with these results, ATRA reduced T-bet and STAT4 expression in T-cells and decreased islet-infiltrating CD8(+) T-cells, suppressing their activation and IFN-gamma/granzyme B expression. Depletion of CD4(+)CD25(+) Treg cells impaired the inhibitory effect of ATRA on islet-infiltrating T-cells and blocked its protective effect on diabetes. Therefore, ATRA treatment induced Treg cell-dependent immune tolerance by suppressing both CD4(+) and CD8(+) Teff cells while promoting Treg cell expansion.

CONCLUSIONS

These results demonstrate that ATRA treatment promoted in vivo expansion of Treg cells and induced Treg cell-dependent immune tolerance by suppressing IFN-gamma-producing T-cells, without affecting Th17 cells. Our study also provides novel insights into how ATRA induces immune tolerance in vivo via its effects on Teff and Treg cells.

A phase I/II trial of TAC-101, an oral synthetic retinoid, in patients with advanced hepatocellular carcinoma

PURPOSE

Preclinical models showed TAC-101 (4-[3,5-bis(trimethylsilyl) benzamide] benzoic acid), an oral synthetic retinoid, has anti-tumor activity in hepatocellular carcinoma (HCC). A phase I/II study was performed in advanced HCC patients (pts).

PATIENTS AND METHODS

Thirty-three patients were enrolled. During Phase I, pts received 40 mg daily for 14 days q3 weeks; 2 of 5 patients developed DLT so dose was reduced to 20 mg/day. Twenty-eight patients received 20 mg/day.

RESULTS

No pt had a CR or PR, but 12 of 21 (57%) had SD. Two pts (9.5%) had late PR after discontinuing TAC-101. Median survival (MS) for all 28 pts treated with 20 mg/day was 12.7 months (95% CI 8.8-22.7); MS for 21 evaluable pts was 19.2 months (95% CI 10.4-27.6).

CONCLUSIONS

20 mg of TAC- was well tolerated. Significant disease stabilization (12/21 pts, 57%), 2 late PRs, and prolonged MS (19.2 months) suggest that TAC-101 provides meaningful patient benefit.

Activation of retinoic acid receptor-alpha favours regulatory T cell induction at the expense of IL-17-secreting T helper cell differentiation

Autoimmunity is thought to reflect an imbalance between regulatory T helper lymphocytes (Treg) and pathogenic, IL-17-secreting T helper (Th17) cells. Induction of both adaptive Treg and Th17 cells requires signalling from TGF-beta. We now show that, in the context of TGF-beta signalling, all-trans retinoic acid (ATRA) leads to increased induction of CD4(+) T cells expressing the Treg specification factor forkhead box protein P3 (FoxP3) and decreased frequency of cells expressing IL-17, even in the presence of IL-6. Using a specific agonist and antagonist, as well as retroviral over-expression, we also provide evidence that the effects of ATRA are likely to be at least partially mediated by the nuclear retinoic acid receptor-alpha (RARalpha). These findings indicate that signalling through a specific nuclear retinoic acid receptor can favour the decision to adopt the Treg fate at the expense of Th17 fate. Specific agonists of RARalpha could, therefore, be considered candidates for the treatment of autoimmunity.