Natural Products in the Modulation of Farnesoid X Receptor Against Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a global health concern with a high prevalence and increasing economic burden, but official medicine remains unavailable. Farnesoid X receptor (FXR), a nuclear receptor member, is one of the most promising drug targets for NAFLD therapy that plays a crucial role in modulating bile acid, glucose, and lipid homeostasis, as well as inhibits hepatic inflammation and fibrosis. However, the rejection of the FXR agonist, obecholic acid, by the Food and Drug Administration for treating hepatic fibrosis raises a question about the functions of FXR in NAFLD progression and the therapeutic strategy to be used. Natural products, such as FXR modulators, have become the focus of attention for NAFLD therapy with fewer adverse reactions. The anti-NAFLD mechanisms seem to act as FXR agonists and antagonists or are involved in the FXR signaling pathway activation, indicating a promising target of FXR therapeutic prospects using natural products. This review discusses the effective mechanisms of FXR in NAFLD alleviation, and summarizes currently available natural products such as silymarin, glycyrrhizin, cycloastragenol, berberine, and gypenosides, for targeting FXR, which can facilitate development of naturally targeted drug by medicinal specialists for effective treatment of NAFLD.

Farnesoid X receptor in chronic liver diseases: an immunohistochemical study

Chronic hepatitis C virus (HCV) related liver diseases are still an ongoing cause of hepatic failure despite the effective role of direct-acting anti-viral agents. Farnesoid X receptor (FXR) agonists have a potential therapeutic effect on the management of chronic liver diseases (CLD). However, data regarding FXR protein expression in human CLDs are limited and conflicting. We aimed to assess the immunohistochemical expression of FXR in HCV-related chronic hepatitis and cirrhosis in comparison with metabolic-associated fatty liver disease (MAFLD) and normal liver tissue. The expression of FXR was low both in hepatocytes and bile ducts of HCV-related chronic hepatitis and cirrhosis (p = .001, respectively). In addition, a significantly low expression of FXR was observed in HCV-related hepatitis and cirrhosis groups compared to MAFLD in hepatocytes (p < .001, for both) and bile ducts (p = .004 and p = .018). FXR expression in HCV-related cirrhosis was significantly associated with compensated liver function (p = .032) and low inflammatory activity (p = .022). FXR expression decreases in HCV-related CLDs. There was some evidence that FXR expression could protect against post-hepatitis cirrhosis.

ELK4 Promotes Cell Cycle Progression and Stem Cell-like Characteristics in HPV-associated Cervical Cancer by Regulating the FBXO22/PTEN Axis

Background

Cervical cancer (CC) is a prevalent gynecological carcinoma, and patients infected with human papillomavirus (HPV) have a higher morbidity rate.

Aims

To explore the effects of ETS-like transcription factor 4 (ELK4) in patients with HPV+ CC.

Study design

In vitro cell lines and human-sample study.

Methods

The ELK4 levels in human tissue (65 HPV+ CC tissue and 25 HPV− normal cervical tissue) and cell lines (human cervical epithelial immortalized cell line H8 and CC cell lines HeLa [HPV18], CaSki [HPV16], and SiHa [HPV−]) were quantified using qRT-PCR and western blot assay. ELK4 knockdown transfection was effective and confirmed by western blotting. The MTT and EDU assays were used to evaluate cell viability and proliferation, respectively. Flow cytometry was used to detect the CC cell cycle stage. Stem cell markers, such as cluster of differentiation 133 (CD133), CD44, and aldehyde dehydrogenase 1, and the cervicospheres formed were measured. ChIP-qPCR and luciferase activity experiments were used to assess the bond between ELK4 and F-box protein 22 (FBXO22).

Results

ELK4 was highly expressed in the HPV+ CC tissue. CC cells with ELK4 knockdown had lower viability and proliferation than the control cells. ELK4 knockdown blocked the progression of the cell cycle from G1 to S phase. ELK4 knockdown suppressed the stem cell-like characteristics of the HPV+ CC cells. ELK4 bonded with the FBXO22 promoter, inhibiting the levels of phosphatase and tensin homolog (PTEN).

Conclusion

ELK4 facilitated cell cycle progression and stem cell-like characteristics by regulating the FBXO22/PTEN axis. Thus, ELK4 could be a potential therapeutic target to arrest the progress of HPV-associated CC.

Inhibition of Nuclear Receptor Related Orphan Receptor γ Ameliorates Mechanical Hypersensitivity Through the Suppression of Spinal Microglial Activation

Microglia are crucial in induction of central sensitization under a chronic pain state. Therefore, control of microglial activity is important to ameliorate nociceptive hypersensitivity. The nuclear receptor retinoic acid related orphan receptor γ (RORγ) contributes to the regulation of inflammation-related gene transcription in some immune cells, including T cells and macrophages. Their role and function in regulation of microglial activity and nociceptive transduction have yet to be elaborated. Treatment of cultured microglia with specific RORγ inverse agonists, SR2211 or GSK2981278, significantly suppressed lipopolysaccharide (LPS)-induced mRNA expression of pronociceptive molecules interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor (TNF). Intrathecal treatment of naïve male mice with LPS markedly induced mechanical hypersensitivity and upregulation of ionized calcium-biding adaptor molecule (Iba1) in the spinal dorsal horn, indicating microglial activation. In addition, intrathecal treatment with LPS significantly induced mRNA upregulation of IL-1β and IL-6 in the spinal dorsal horn. These responses were prevented by intrathecal pretreatment with SR2211. In addition, intrathecal administration of SR2211 significantly ameliorated established mechanical hypersensitivity and upregulation of Iba1 immunoreactivity in the spinal dorsal horn of male mice following peripheral sciatic nerve injury. The current findings demonstrate that blockade of RORγ in spinal microglia exerts anti-inflammatory effects, and that RORγ may be an appropriate target for the treatment of chronic pain.

Baohuoside I inhibits FXR signaling pathway to interfere with bile acid homeostasis via targeting ER α degradation

Epimedii folium (EF) is an effective herbal medicine in osteoporosis treatment, but the clinical utilization of EF has been limited due to potential hepatotoxicity. The previous studies identified that baohuoside I (BI), the main active component of EF, was relevant to EF-induced liver injury. However, the mechanisms of BI causing direct injury to hepatocytes remain unclear. Here, we reveal that BI inhibits FXR-mediated signaling pathway via targeting estrogen receptor α (ER α), leading to the accumulation of bile acids (BAs). Targeted bile acid analyses show BI alters the BA composition and distribution, resulting in impaired BA homeostasis. Mechanistically, BI induces FXR-dependent hepatotoxicity at transcriptional level. Additionally, ER α is predicted to bind to the FXR promoter region based on transcription factor binding sites databases and we further demonstrate that ER α positively regulates FXR promoter activity and affects the expression of target genes involved in BA metabolism. Importantly, we discover that ER α and its mediated FXR transcription regulation might be involved in BI-induced liver injury via ligand-dependent ER α degradation. Collectively, our findings indicate that FXR is a newly discovered target gene of ER α mediated BI-induced liver injury, and suggest BI may be responsible for EF-induced liver injury.

Nuclear receptor 5A2 regulation of Agrp underlies olanzapine-induced hyperphagia

Antipsychotic (AP) drugs are efficacious treatments for various psychiatric disorders, but excessive weight gain and subsequent development of metabolic disease remain serious side effects of their use. Increased food intake leads to AP-induced weight gain, but the underlying molecular mechanisms remain unknown. In previous studies, we identified the neuropeptide Agrp and the transcription factor nuclear receptor subfamily 5 group A member 2 (Nr5a2) as significantly upregulated genes in the hypothalamus following AP-induced hyperphagia. While Agrp is expressed specifically in the arcuate nucleus of the hypothalamus and plays a critical role in appetite stimulation, Nr5a2 is expressed in both the CNS and periphery, but its role in food intake behaviors remains unknown. In this study, we investigated the role of hypothalamic Nr5a2 in AP-induced hyperphagia and weight gain. In hypothalamic cell lines, olanzapine treatment resulted in a dose-dependent increase in gene expression of Nr5a2 and Agrp. In mice, the pharmacological inhibition of NR5A2 decreased olanzapine-induced hyperphagia and weight gain, while the knockdown of Nr5a2 in the arcuate nucleus partially reversed olanzapine-induced hyperphagia. Chromatin-immunoprecipitation studies showed for the first time that NR5A2 directly binds to the Agrp promoter region. Lastly, the analysis of single-cell RNA seq data confirms that Nr5a2 and Agrp are co-expressed in a subset of neurons in the arcuate nucleus. In summary, we identify Nr5a2 as a key mechanistic driver of AP-induced food intake. These findings can inform future clinical development of APs that do not activate hyperphagia and weight gain.

Combining selinexor with alisertib to target the p53 pathway in neuroblastoma

Neuroblastoma accounts for 15% of cancer-related deaths in children, highlighting an unmet need for novel therapies. Selinexor is a small molecule inhibitor of XPO1. XPO1 shuffles cargo proteins with a nuclear export sequence from the nucleus to the cytosol, many of which are essential for cancer growth and cell maintenance. We systematically tested the effect of selinexor against neuroblastoma cells in vitro and in vivo and used an advanced proteomic and phosphoproteomic screening approach to interrogate unknown mechanisms of action. We found that selinexor induced its cytotoxic effects in neuroblastoma through the predominantly nuclear accumulation of p53 and global activation of apoptosis pathways. Selinexor also induced p53 phosphorylation at site S315, which is one initiating step for p53 degradation. Since this phosphorylation step is undertaken mostly by aurora kinase A (AURKA), we used the clinically available AURKA inhibitor, alisertib, and found p53-mediated lethality could be further augmented in three orthotopic xenograft mouse models. These findings suggest a potential therapeutic benefit using selinexor and alisertib to synergistically increase p53-mediated cytotoxicity of high-risk neuroblastoma.

Farnesoid X Receptor as a Promising Therapeutic Target for Nonalcoholic Fatty Liver Disease (NAFLD) and the Current Development of Its Agonists

Nonalcoholic fatty liver disease (NAFLD) comprises a group of clinical syndromes characterized by excessive fat deposition in liver cells. Owing to its increasing incidence, NAFLD has becomea pertinent global health problem as well as an important contributor to the fatality rate of liver and metabolic diseases. Farnesoid X receptor (FXR) has emerged as a new target in the treatment of NAFLD, and related drugs are being reported. This review provides an overview of the structure and function of FXR, along with its important regulatory roles in bile acid metabolism and lipid metabolism. The review also highlights the clinical application of FXR and the progress on basic research related to FXR modulators in NAFLD treatment. Identifying potent FXR modulators, structure-based virtual screening strategy, and the development of new drugs to regulate the allosteric pathway of FXR activity have become effective approaches for the study of novel ligand, which can expand the therapeutic applications of novel FXR agonists. Identification of potential FXR modulators may help elucidate the physiological effects of FXR and provide new opportunities for targeting FXR for metabolic diseases.

Exportin 1 Inhibition Induces Nerve Growth Factor Receptor Expression to Inhibit the NF-κB Pathway in Preclinical Models of Pediatric High-Grade Glioma

High-grade glioma (HGG) is the leading cause of cancer-related death among children. Selinexor, an orally bioavailable, reversible inhibitor of the nuclear export protein, exportin 1, is in clinical trials for a range of cancers, including HGG. It inhibits the NF-κB pathway and strongly induces the expression of nerve growth factor receptor (NGFR) in preclinical cancer models. We hypothesized that selinexor inhibits NF-κB via upregulation of NGFR. In HGG cells, sensitivity to selinexor correlated with increased induction of cell surface NGFR expression. Knocking down NGFR in HGG cells increased proliferation, anchorage-independent growth, stemness markers, and levels of transcriptionally available nuclear NF-κB not bound to IκB-α, while decreasing apoptosis and sensitivity to selinexor. Increasing IκB-α levels in NGFR knockdown cells restored sensitivity to selinexor. Overexpression of NGFR using cDNA reduced levels of free nuclear NF-κB, decreased stemness markers, and increased markers of cellular differentiation. In all HGG lines tested, selinexor decreased phosphorylation of NF-κB at serine 536 (a site associated with increased transcription of proliferative and inflammatory genes). Because resistance to selinexor monotherapy occurred in our in vivo model, we screened selinexor with a panel of FDA-approved anticancer agents. Bortezomib, a proteasome inhibitor that inhibits the NF-κB pathway through a different mechanism than selinexor, showed synergy with selinexor against HGG in vitro Our results help elucidate selinexor's mechanism of action and identify NGFR as a potential biomarker of its effect in HGG and in addition suggest a combination therapy strategy for these challenging tumors.

Intestine farnesoid X receptor agonist and the gut microbiota activate G-protein bile acid receptor-1 signaling to improve metabolism

Bile acids activate farnesoid X receptor (FXR) and G protein-coupled bile acid receptor-1 (aka Takeda G protein-coupled receptor-5 [TGR5]) to regulate bile acid metabolism and glucose and insulin sensitivity. FXR and TGR5 are coexpressed in the enteroendocrine L cells, but their roles in integrated regulation of metabolism are not completely understood. We reported recently that activation of FXR induces TGR5 to stimulate glucagon-like peptide-1 (GLP-1) secretion to improve insulin sensitivity and hepatic metabolism. In this study, we used the intestine-restricted FXR agonist fexaramine (FEX) to study the effect of activation of intestinal FXR on the gut microbiome, bile acid metabolism, and FXR and TGR5 signaling. The current study revealed that FEX markedly increased taurolithocholic acid, increased secretion of fibroblast growth factors 15 and 21 and GLP-1, improved insulin and glucose tolerance, and promoted white adipose tissue browning in mice. Analysis of 16S ribosomal RNA sequences of the gut microbiome identified the FEX-induced and lithocholic acid-producing bacteria Acetatifactor and Bacteroides. Antibiotic treatment completely reversed the FEX-induced metabolic phenotypes and inhibited taurolithocholic acid synthesis, adipose tissue browning, and liver bile acid synthesis gene expression but further increased intestinal FXR target gene expression. FEX treatment effectively improved lipid profiles, increased GLP-1 secretion, improved glucose and insulin tolerance, and promoted adipose tissue browning, while antibiotic treatment reversed the beneficial metabolic effects of FEX in obese and diabetic mice.

CONCLUSION

This study uncovered a mechanism in which activation of intestinal FXR shaped the gut microbiota to activate TGR5/GLP-1 signaling to improve hepatic glucose and insulin sensitivity and increase adipose tissue browning; the gut microbiota plays a critical role in bile acid metabolism and signaling to regulate metabolic homeostasis in health and disease. (Hepatology 2018).

The nitric oxide pathway participates in lordosis behavior induced by central administration of leptin

Intracerebroventricular (icv) administration of leptin facilitates lordosis behavior in ad libitum-fed, estrogen-primed rats. The cellular mechanism involved in this response is unknown. The present study tested the hypothesis that the nitric oxide-guanylyl cyclase, cGMP-dependent protein kinase (PKG) pathway is involved in the facilitation of lordosis behavior induced by the central administration of leptin. We tested the importance of the nitric oxide/cGMP pathway for lordosis stimulation by either icv infusion of a nitric oxide synthase inhibitor (L-NAME) or a nitric oxide-dependent, soluble guanylyl cyclase inhibitor (ODQ) 30 min before leptin administration (1 μg). This dose of leptin reliably induced lordosis behavior in ovariectomized estradiol benzoate treated rats. The lordosis induced by leptin at 1 and 2h after infusion was significantly reduced by the previous injection of either L-NAME or by ODQ. Intracerebroventricular infusion of the PKG inhibitor (KT5823) 30 min before leptin infusion, also significantly inhibited the lordosis behavior induced by leptin at 1 and 2h after hormone administration. These data support the hypothesis that the nitric oxide/cGMP/PKG pathway is involved in the facilitation of lordosis by leptin in estrogen-primed female rats.

Riociguat, an oral soluble guanylate cyclase stimulator for the treatment of pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a severe, progressive and often fatal disease for which only a limited number of drugs have proven to be of clinical benefit. One of the therapeutic approaches for this disease is the induction of pulmonary vasodilation via stimulation of the nitric oxide (NO)-mediated pathway. Abnormalities in the NO/soluble guanylate cyclase (sGC) axis and enhanced PDE5 activity render currently available drugs ineffective in many patients with PAH. Bayer AG is developing riociguat, an oral sGC stimulator, for the potential treatment of patients with PAH. Treatment with riociguat abrogated the severity of pulmonary hypertension in rodent models of the disease. Published data from phase I and II clinical trials demonstrated that riociguat was well tolerated, with single doses significantly decreasing pulmonary arterial pressure and increasing cardiac output and physical-exercise tolerance in patients with PAH. A decrease in systemic arterial diastolic pressure was the only significant side effect reported. Ongoing phase II and III trials for riociguat have been designed to address the long-term safety and clinical effectiveness of the drug in different types of pulmonary hypertension. Should the results of these trials demonstrate that riociguat is superior to current therapies, such as cyclic AMP-dependent drugs and endothelin receptor antagonists, the drug could become the preferred pharmacological treatment for patients with PAH.