QiShenYiQi pill inhibits atherosclerosis by promoting TTC39B-LXR mediated reverse cholesterol transport in liver.

BACKGROUND: Tetranucleotide repeat domain protein 39B (TTC39B) was found to combine with ubiquitin ligase E3, and promote the ubiquitination modification of liver X receptor (LXR), which led to the inhibition of reverse cholesterol transport and development of atherosclerosis. QiShenYiQi pill (QSYQ) is a modern Chinese patent drug for treating ischemic cardiovascular diseases, the underlying mechanism is found to promote the expression of LXR-α/ ATP-binding cassette transporter G5 (ABCG5) in the liver of atherosclerotic mice. PURPOSE: The aim of this study is to investigate the effect of QSYQ on TTC39B-LXR mediated reverse cholesterol transport in atherosclerotic mice. STUDY DESIGN AND METHODS: Male apolipoprotein E gene knockout mice (7 weeks old) were fed with high-fat diet and treated with low dose of QSYQ (QSYQ-l, 0.3 g/kg·d), high dose of QSYQ (QSYQ-H, 1.2 g/kg·d) and LXR-α agonist (LXR-A, GW3965 10 mg/kg·d) for 8 weeks. C57BL/6 J mice were fed with normal diet and used as negative control. Oil red O staining, HE staining, ELISA, RNA sequencing, western blot, immunohistochemistry, RT-PCR, cell culture and RNA interference were performed to analyze the effect of QSYQ on atherosclerosis. RESULTS: HE staining showed that QSYQ reduced the atherosclerotic lesion significantly when compared to the control group. ELISA measurement showed that QSYQ decreased serum VLDL and increased serum ApoA1. Oil Red O staining showed that QSYQ reduced the lipid content of liver and protect liver function. Comparative transcriptome RNA-sequence of liver showed that DEGs after QSYQ treatment enriched in high-density lipoprotein particle, ubiquitin ligase complex, bile secretion, etc. Immunohistochemical staining and western blot proved that QSYQ increased the protein expression of hepatic SR-B1, LXR-α, LXR-ß, CYP7A1 and ABCG5. Targeted inhibiting Ttc39b gene in vitro further established that QSYQ inhibited the gene expression of Ttc39b, increased the protein expression of SR-B1, LXR-α/ß, CYP7A1 and ABCG5 in rat hepatocyte. CONCLUSION: Our results demonstrated the new anti-atherosclerotic mechanism of QSYQ by targeting TTC39B-LXR mediated reverse cholesterol transport in liver. QSYQ not only promoted reverse cholesterol transport, but also improved fatty liver and protected liver function.

Liver X receptors: From pharmacology to nanoparticle-based drug delivery.

Liver X receptors (LXRs) are master regulators of various biological processes, including metabolism, inflammation, development, and reproduction. As well-known nuclear oxysterol receptors of the nuclear receptor (NR) family, LXRs have two homologous subtypes, LXRα (NR1H3) and LXRß (NR1H2). Since the mid-1990s, numerous LXR-targeted drugs have been designed to treat diseases such as atherosclerosis, systemic lupus erythematosus, and cancer. These modulators include agonists and antagonists, and the selectivity of them have been development from diverse aspects, including subtype-specific, cell-specific, tissue-specific types. Meanwhile, advanced delivery systems are also exploreed to facilitate the application of LXR drugs in clinical setting. One of the most promising delivery systems involves the use of nanoparticles and is expected to increase the clinical potential of LXR modulators. This review discusses our current understanding of LXR biology and pharmacology, focusing on the development of modulators for LXRα and/or LXRß, and the nanoparticle-based delivery systems for promising LXR modulators with potential for use as drugs.

Fragment-based discovery of orphan nuclear receptor Nur77/NGFI-B ligands.

The transcription factor nerve growth factor-induced clone B (NGFI-B, Nur77, NR4A1) is an orphan nuclear receptor playing a role in cell survival and apoptosis regulation. Pharmacological Nur77 modulation holds promise for cancer and (neuro-)inflammatory disease treatment. The available Nur77 ligand scaffolds based on highly lipophilic natural products cytosporone B, celastrol and isoalantolactone are inadequate for the development of potent Nur77 modulators with favorable properties as chemical tools and future drugs. By fragment library screening and subsequent modeling for fragment extension, we have obtained a set of new Nur77 ligands offering alternative chemotypes for the development of Nur77 agonists and inverse agonists. Computer-aided fragment extension in a second stage screening yielded a Nur77 agonist with significant activation efficacy and preference over the related NR4A receptors.

The nuclear receptor TLX (NR2E1) inhibits growth and progression of triple- negative breast cancer.

Development of targeted therapies will be a critical step towards reducing the mortality associated with triple-negative breast cancer (TNBC). To achieve this, we searched for targets that met three criteria: (1) pharmacologically targetable, (2) expressed in TNBC, and (3) expression is prognostic in TNBC patients. Since nuclear receptors have a well-defined ligand-binding domain and are thus highly amenable to small-molecule intervention, we focused on this class of protein. Our analysis identified TLX (NR2E1) as a candidate. Specifically, elevated tumoral TLX expression was associated with prolonged recurrence-free survival and overall survival for breast cancer patients with either estrogen receptor alpha (ERα)-negative or basal-like tumors. Using two TNBC cell lines, we found that stable overexpression of TLX impairs in vitro proliferation. RNA-Seq analysis revealed that TLX reduced the expression of genes implicated in epithelial-mesenchymal transition (EMT), a cellular program known to drive metastatic progression. Indeed, TLX overexpression significantly decreased cell migration and invasion, and robustly decreased the metastatic capacity of TNBC cells in murine models. We identify SERPINB2 as a likely mediator of these effects. Taken together, our work indicates that TLX impedes the progression of TNBC. Several ligands have been shown to regulate the transcriptional activity of TLX, providing a framework for the future development of this receptor for therapeutic intervention.

Orphan nuclear receptor 4A1 (NR4A1) and novel ligands.

The nuclear receptor (NR) superfamily of transcription factors encodes expression of 48 human genes that are important for maintaining cellular homeostasis and in pathophysiology, and this has been observed for all sub-families including orphan receptors for which endogenous ligands have not yet been identified. The orphan NR4A1 (Nur77 and TR3) and other members of this sub-family (NR4A2 and NR4A3) are immediate early genes induced by diverse stressors, and these receptors play an important role in the immune function and are up-regulated in some inflammatory diseases including solid tumors. Although endogenous ligands for NR4A have not been identified, several different classes of compounds have been characterized as NR4A1 ligands that bind the receptor. These compounds include cytosporone B and structurally related analogs, bis-indole derived (CDIM) compounds, the triterpenoid celastrol and a number of other chemicals including polyunsaturated fatty acids. NR4A1 ligands bind different regions/surfaces of NR4A1 and exhibit selective NR4A1 modulator (SNR4AM) activities that are dependent on ligand structure and cell/tissue context. NR4A1 ligands exhibit pharmacologic activities in studies on cancer, endometriosis metabolic and inflammatory diseases and are promising agents with clinical potential for treating multiple diseases.

Orphan nuclear receptors as regulators of intratumoral androgen biosynthesis in castration-resistant prostate cancer.

Castration-resistant prostate cancer (CRPC) almost invariably occurs after androgen-deprivation therapy (ADT) for the advanced metastatic disease. It is generally believed that among multiple mechanisms and signaling pathways, CRPC is significantly driven by the reactivation of androgen receptor (AR) signaling in ADT-treated patients with castrate levels of androgen, partially at least mediated by the androgen biosynthesis within the tumor, also known as intratumoral or intraprostatic androgen biosynthesis. Steroidogenic enzymes, such as CYP11A1, CYP17A1, HSD3B1, AKR1C3 and SRD5A, are essential to catalyze the conversion of the initial substrate cholesterol into potent androgens that confers the CRPC progression. Accumulating evidences indicate that many steroidogenic enzymes are upregulated in the progression setting; however, little is known about the dysregulation of these enzymes in CRPC. Orphan nuclear receptors (ONRs) are members of the nuclear receptor superfamily, of which endogenous physiological ligands are unknown and which are constitutively active independent of any physiological ligands. Studies have validated that besides AR, ONRs could be the potential therapeutic targets for prostate cancer, particularly the lethal CRPC progression. Early studies reveal that ONRs play crucial roles in the transcriptional regulation of steroidogenic enzyme genes. Notably, we and others show that three distinct ONRs, including liver receptor homolog-1 (LRH-1, NR5A2), steroidogenic factor 1 (SF-1, AD4BP, NR5A1) and estrogen-related receptor α (ERRα, NR3B1), can contribute to the CRPC progression by promotion of the intratumoral androgen synthesis via their direct transcriptional regulation on multiple steroidogenic enzymes. This review presents an overview of the current understanding on the intratumoral androgen biosynthesis in CRPC, with a special focus on the emerging roles of ONRs in this process.

Correction of NR2E3 Associated Enhanced S-cone Syndrome Patient-specific iPSCs using CRISPR-Cas9.

Enhanced S-cone syndrome (ESCS) is caused by recessive mutations in the photoreceptor cell transcription factor NR2E3. Loss of NR2E3 is characterized by repression of rod photoreceptor cell gene expression, over-expansion of the S-cone photoreceptor cell population, and varying degrees of M- and L-cone photoreceptor cell development. In this study, we developed a CRISPR-based homology-directed repair strategy and corrected two different disease-causing NR2E3 mutations in patient-derived induced pluripotent stem cells (iPSCs) generated from two affected individuals. In addition, one patient's iPSCs were differentiated into retinal cells and NR2E3 transcription was evaluated in CRISPR corrected and uncorrected clones. The patient's c.119-2A>C mutation caused the inclusion of a portion of intron 1, the creation of a frame shift, and generation of a premature stop codon. In summary, we used a single set of CRISPR reagents to correct different mutations in iPSCs generated from two individuals with ESCS. In doing so we demonstrate the advantage of using retinal cells derived from affected patients over artificial in vitro model systems when attempting to demonstrate pathophysiologic mechanisms of specific mutations.

Liver X receptors orchestrate osteoblast/osteoclast crosstalk and counteract pathologic bone loss.

Osteoporosis is characterized by enhanced differentiation of bone-resorbing osteoclasts, resulting in a rapid loss of functional trabecular bone. Bone-forming osteoblasts and osteoblast-derived osteocytes perform a key role in the regulation of osteoclast development by providing both the pro-osteoclastogenic cytokine receptor activator of NF-κB ligand (RANKL) and its natural decoy receptor osteoprotegerin (OPG). By regulating the RANKL/OPG ratio, osteoblasts hence determine the rate of both osteoclast differentiation and bone turnover. Here, we describe a novel role for liver X receptors (LXRs) during the crosstalk of bone-forming osteoblasts and bone-resorbing osteoclasts. By using a system of osteoblast/osteoclast cocultures, we identify LXRs as regulator of RANKL expression and the RANKL/OPG ratio in osteoblasts. Activation of LXRs drastically reduced the RANKL/OPG ratio and interfered with osteoblast-mediated osteoclast differentiation in vitro. During an ovariectomy (OVX)-induced model of postmenopausal osteoporosis, the application of an LXR agonist shifted the RANKL/OPG ratio in vivo, ameliorated the enhanced osteoclast differentiation, and provided complete protection from OVX-induced bone loss. These results reveal an unexpected involvement of LXRs in the regulation of bone turnover and highlight a potential role for LXRs as novel targets in the treatment of osteoporosis and related diseases.

Emerging therapeutic strategies to enhance HDL function.

Epidemiologic studies indicate a strong inverse correlation between plasma levels of high-density lipoproteins (HDL) and cardiovascular disease (CVD). The most relevant cardioprotective mechanism mediated by HDL is thought to be reverse cholesterol transport (RCT). New insights in HDL biology and RCT have allowed the development of promising agents aimed to increase HDL function and promote atherosclerosis regression. In this regard, apo-AI analogs and CETP inhibitors dalcetrapib and anacetrapib have aroused a great interest and opened new expectations in the treatment of CVD.