RORs in autoimmune disease

Targeting transcription factors for therapeutic benefit in rheumatoid arthritis

Rheumatoid arthritis (RA) is a destructive inflammatory autoimmune disease that causes pain and disability. Many of the currently available drugs for treating RA patients are aimed at halting the progression of the disease and alleviating inflammation. Further, some of these treatment options have drawbacks, including disease recurrence and adverse effects due to long-term use. These inefficiencies have created a need for a different approach to treating RA. Recently, the focus has shifted to direct targeting of transcription factors (TFs), as they play a vital role in the pathogenesis of RA, activating key cytokines, chemokines, adhesion molecules, and enzymes. In light of this, synthetic drugs and natural compounds are being explored to target key TFs or their signaling pathways in RA. This review discusses the role of four key TFs in inflammation, namely NF-κB, STATs, AP-1 and IRFs, and their potential for being targeted to treat RA.

Deregulation of Cholesterol Homeostasis by a Nuclear Hormone Receptor Crosstalk in Advanced Prostate Cancer

Metastatic castration-resistant prostate cancer (mCRPC) features high intratumoral cholesterol levels, due to aberrant regulation of cholesterol homeostasis. However, the underlying mechanisms are still poorly understood. The retinoid acid receptor-related orphan receptor gamma (RORγ), an attractive therapeutic target for cancer and autoimmune diseases, is strongly implicated in prostate cancer progression. We demonstrate in this study that in mCRPC cells and tumors, RORγ plays a crucial role in deregulation of cholesterol homeostasis. First, we found that RORγ activates the expression of key cholesterol biosynthesis proteins, including HMGCS1, HMGCR, and SQLE. Interestingly, we also found that RORγ inhibition induces cholesterol efflux gene program including ABCA1, ABCG1 and ApoA1. Our further studies revealed that liver X receptors (LXRα and LXRβ), the master regulators of cholesterol efflux pathway, mediate the function of RORγ in repression of cholesterol efflux. Finally, we demonstrated that RORγ antagonist in combination with statins has synergistic effect in killing mCRPC cells through blocking statin-induced feedback induction of cholesterol biosynthesis program and that the combination treatment also elicits stronger anti-tumor effects than either alone. Altogether, our work revealed that in mCRPC, RORγ contributes to aberrant cholesterol homeostasis by induction of cholesterol biosynthesis program and suppression of cholesterol efflux genes. Our findings support a therapeutic strategy of targeting RORγ alone or in combination with statin for effective treatment of mCRPC.

Evaluation of correlation between transcription factors and IL-17 in oral and cutaneous lichen planus lesions and Leukocytes

BACKGROUND

Lichen planus (LP) is a chronic autoimmune disease with different clinical subtypes including cutaneous LP (CLP) and oral LP (OLP). We aimed to compare mRNA expression of RORγt and IL-17 in paraffin-embedded blocks of OLP and CLP lesions with normal oral mucosa (NOM), and also its correlation with hematologic parameters.

MATERIALS & METHODS

This study included 89 paraffin-embedded blocks contain OLP (44 cases), CLP (45 cases) and NOM from the archive of Mashhad University of Medical Sciences, Mashhad, Iran. The expression of RORγt and IL-17 was evaluated by Real-time RT-PCR method. The result was compared to Leukocyte counts and the other hematological parameters of studied patients.

RESULTS

The results of our study showed IL-17 and RORγt expression in OLP lesions were significantly higher than CLP and NOM groups (P = 0.001). Although we found high expression of RORγt and IL-17 in erosive OLP in compared to classic OLP lesion, but this increment was not significant for IL-17 (P = 0.26) and RORγt (P = 0.14). Further, Leukocyte and monocyte counts were substantially high in OLP group in compared to the CLP and NOM groups (P < 0.05).

CONCLUSIONS

We concluded that increased expression of RORγt and IL-17 in LP lesions could play role in the pathogenesis of LP. As well, higher expression of RORγt and IL-17 in oral LP more than cutaneous LP might be associated with difference in clinical behavior of the two types of disease and role of these factors in premalignant behavior of OLP lesions.

Clinical relevance of circadian melatonin release in relapsing-remitting multiple sclerosis

A growing body of evidence indicates the role of melatonin (MT) in the pathogenesis of multiple sclerosis (MS): It modulates immune function, alleviates oxidative stress and it is linked to seasonality of MS relapse. This report addresses the potential clinical relevance of circadian MT rhythms in relapsing-remitting MS (RRMS) patients. The study sample comprised of fifty-five RRMS patients and fifty age- and sex-matched healthy control (HC) subjects. Circadian salivary MT was measured non-invasively at 12 time points over day in participants' home environment. 6-Hydroxy-melatoninsulfate (MT sulfate) concentration in night-time urine was assessed as an estimate for nocturnal MT. Ratings for neurological disability, health-related quality of life (HrQoL), fatigue, depressive symptoms and sleep patterns were additionally obtained. There was no evidence for an overall disturbed MT rhythm in RRMS patients. However, lower MT levels within the first hour after awakening were associated with longer disease duration. MT levels only correlated moderately with neurological disability. Sleep disruptions were more common in patients than in controls and were associated with lower nocturnal MT sulfate levels. MT also correlated moderately with fatigue and HrQoL. We did not find evidence for a generally disturbed circadian MT rhythm in RRMS patients but longer disease duration was associated with significantly lower MT levels. Moreover, MT correlated with a series of clinical features. The exact nature of this relationship remains unclear and future studies are needed in order to determine whether MT could serve as a potential therapeutic target in MS. KEY MESSAGES: Melatonin acts as a free radical scavenger and modulates immune function. In multiple sclerosis, low melatonin levels were associated with acute exacerbations. Melatonin levels are not generally disturbed in multiple sclerosis patients. But lower levels are associated with disease duration and clinical aspects. Salivary melatonin after awakening might serve as a good measure of melatonin.

Regulation of RORγt in Inflammatory Lymphoid Cell Differentiation

T-helper 17 (Th17) cells differentiate from naïve CD4(+) T cells in response to signals from commensal microbiota and produce cytokines critical for the integrity of mucosal barriers. These cells also disseminate throughout the body, and are key participants in numerous inflammatory processes. A key challenge is to elucidate the mechanisms that govern Th17 cell beneficial versus pathogenic functions, characterized by different cytokine profiles. Mucosal Th17 cells require the nuclear hormone receptor RORγt for their differentiation in draining lymph nodes. Cytokine expression is enabled in select tissues, to which these cells migrate, by external cues, such as the serum amyloid A proteins produced in response to commensal bacteria by epithelial cells in the small intestine. Additional cell-intrinsic cues contributing to production of Th17 cytokines during both homeostasis and inflammation include the RORγt-associated DEAD-box RNA helicase DDX5 and long noncoding RNA (lncRNA) Rmrp. The helicase activity of DDX5 is required for Rmrp-mediated assembly of the complex and colocalization with RORγt throughout the genome to regulate key Th17 genes. How these are regulated in diverse microenvironments may provide insights for therapeutic intervention in autoimmune disease.

ROR nuclear receptors: structures, related diseases, and drug discovery

Nuclear receptors (NRs) are ligand-regulated transcription factors that regulate metabolism, development and immunity. The NR superfamily is one of the major classes of drug targets for human diseases. Retinoic acid receptor-related orphan receptor (ROR) α, β and γ belong to the NR superfamily, and these receptors are still considered as 'orphan' receptors because the identification of their endogenous ligands has been controversial. Recent studies have demonstrated that these receptors are regulated by synthetic ligands, thus emerge as important drug targets for the treatment of multiple sclerosis, rheumatoid arthritis, psoriasis, etc. Studying the structural basis and ligand development of RORs will pave the way for a better understanding of the roles of these receptors in human diseases. Here, we review the structural basis, disease relevance, strategies for ligand identification, and current status of development of therapeutic ligands for RORs.