The Estrogen Receptor-Related Orphan Receptors Regulate Autophagy through TFEB.

Autophagy is an essential self-degradative and recycling mechanism that maintains cellular homeostasis. Estrogen receptor-related orphan receptors (ERRs) are fundamental in regulating cardiac metabolism and function. Previously, we showed that ERR agonists improve cardiac function in models of heart failure and induce autophagy. Here, we characterized a mechanism by which ERRs induce the autophagy pathway in cardiomyocytes. Transcription factor EB (TFEB) is a master regulator of the autophagy-lysosome pathway and has been shown to be crucial regulator of genes that control autophagy. We discovered that TFEB is a direct ERR target gene whose expression is induced by ERR agonists. Activation of ERR results in increased TFEB expression in both neonatal rat ventricular myocytes and C2C12 myoblasts. An ERR-dependent increase in TFEB expression results in increased expression of an array of TFEB target genes, which are critical for the stimulation of autophagy. Pharmacologically targeting ERR is a promising potential method for the treatment of many diseases where stimulation of autophagy may be therapeutic, including heart failure. SIGNIFICANCE STATEMENT: Estrogen receptor-related receptor agonists function as exercise mimetics and also display efficacy in animal models of metabolic disease, obesity, and heart failure.

A Synthetic ERR Agonist Alleviates Metabolic Syndrome.

Physical exercise induces physiologic adaptations and is effective at reducing the risk of premature death from all causes. Pharmacological exercise mimetics may be effective in the treatment of a range of diseases including obesity and metabolic syndrome. Previously, we described the development of SLU-PP-332, an agonist for the estrogen-related receptor (ERR)α, ß, and γ nuclear receptors that activates an acute aerobic exercise program. Here we examine the effects of this exercise mimetic in mouse models of obesity and metabolic syndrome. Diet-induced obese or ob/ob mice were administered SLU-PP-332, and the effects on a range of metabolic parameters were assessed. SLU-PP-332 administration mimics exercise-induced benefits on whole-body metabolism in mice including increased energy expenditure and fatty acid oxidation. These effects were accompanied by decreased fat mass accumulation. Additionally, the ERR agonist effectively reduced obesity and improved insulin sensitivity in models of metabolic syndrome. Pharmacological activation of ERR may be an effective method to treat metabolic syndrome and obesity. SIGNIFICANCE STATEMENT: An estrogen receptor-related orphan receptor agonist, SLU-PP-332, with exercise mimetic activity, holds promise as a therapeutic to treat metabolic diseases by decreasing fat mass in mouse models of obesity.

Novel Pan-ERR Agonists Ameliorate Heart Failure Through Enhancing Cardiac Fatty Acid Metabolism and Mitochondrial Function.

BACKGROUND: Cardiac metabolic dysfunction is a hallmark of heart failure (HF). Estrogen-related receptors ERRα and ERRγ are essential regulators of cardiac metabolism. Therefore, activation of ERR could be a potential therapeutic intervention for HF. However, in vivo studies demonstrating the potential usefulness of ERR agonist for HF treatment are lacking, because compounds with pharmacokinetics appropriate for in vivo use have not been available. METHODS: Using a structure-based design approach, we designed and synthesized 2 structurally distinct pan-ERR agonists, SLU-PP-332 and SLU-PP-915. We investigated the effect of ERR agonist on cardiac function in a pressure overload-induced HF model in vivo. We conducted comprehensive functional, multi-omics (RNA sequencing and metabolomics studies), and genetic dependency studies both in vivo and in vitro to dissect the molecular mechanism, ERR isoform dependency, and target specificity. RESULTS: Both SLU-PP-332 and SLU-PP-915 significantly improved ejection fraction, ameliorated fibrosis, and increased survival associated with pressure overload-induced HF without affecting cardiac hypertrophy. A broad spectrum of metabolic genes was transcriptionally activated by ERR agonists, particularly genes involved in fatty acid metabolism and mitochondrial function. Metabolomics analysis showed substantial normalization of metabolic profiles in fatty acid/lipid and tricarboxylic acid/oxidative phosphorylation metabolites in the mouse heart with 6-week pressure overload. ERR agonists increase mitochondria oxidative capacity and fatty acid use in vitro and in vivo. Using both in vitro and in vivo genetic dependency experiments, we show that ERRγ is the main mediator of ERR agonism-induced transcriptional regulation and cardioprotection and definitively demonstrated target specificity. ERR agonism also led to downregulation of cell cycle and development pathways, which was partially mediated by E2F1 in cardiomyocytes. CONCLUSIONS: ERR agonists maintain oxidative metabolism, which confers cardiac protection against pressure overload-induced HF in vivo. Our results provide direct pharmacologic evidence supporting the further development of ERR agonists as novel HF therapeutics.

Estrogen-Related Receptor Agonism Reverses Mitochondrial Dysfunction and Inflammation in the Aging Kidney.

A gradual decline in renal function occurs even in healthy aging individuals. In addition to aging, per se, concurrent metabolic syndrome and hypertension, which are common in the aging population, can induce mitochondrial dysfunction and inflammation, which collectively contribute to age-related kidney dysfunction and disease. This study examined the role of the nuclear hormone receptors, the estrogen-related receptors (ERRs), in regulation of age-related mitochondrial dysfunction and inflammation. The ERRs were decreased in both aging human and mouse kidneys and were preserved in aging mice with lifelong caloric restriction (CR). A pan-ERR agonist, SLU-PP-332, was used to treat 21-month-old mice for 8 weeks. In addition, 21-month-old mice were treated with a stimulator of interferon genes (STING) inhibitor, C-176, for 3 weeks. Remarkably, similar to CR, an 8-week treatment with a pan-ERR agonist reversed the age-related increases in albuminuria, podocyte loss, mitochondrial dysfunction, and inflammatory cytokines, via the cyclic GMP-AMP synthase-STING and STAT3 signaling pathways. A 3-week treatment of 21-month-old mice with a STING inhibitor reversed the increases in inflammatory cytokines and the senescence marker, p21/cyclin dependent kinase inhibitor 1A (Cdkn1a), but also unexpectedly reversed the age-related decreases in PPARG coactivator (PGC)-1α, ERRα, mitochondrial complexes, and medium chain acyl coenzyme A dehydrogenase (MCAD) expression. These studies identified ERRs as CR mimetics and as important modulators of age-related mitochondrial dysfunction and inflammation. These findings highlight novel druggable pathways that can be further evaluated to prevent progression of age-related kidney disease.

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023.

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

Development and pharmacological evaluation of a new chemical series of potent pan-ERR agonists, identification of SLU-PP-915.

Estrogen-related receptors (ERR) are an orphan nuclear receptor sub-family that play a critical role in regulating gene transcription for several physiological processes including mitochondrial function, cellular energy utilization and homeostasis. They have also been implicated to play a role in several pathological conditions. Herein, we report the identification, synthesis, structure-activity relationships and pharmacological evaluation of a new chemical series of potent pan-ERR agonists. This template was designed for ERRγ starting from the known acyl hydrazide template and compounds such as agonist GSK-4716 employing a structure-based drug design approach. This led to the preparation of a series of 2,5-disubstituted thiophenes from which several were found to be potent agonists of ERRγ in cell-based co-transfection assays. Additionally, direct binding to ERRγ was established through 1H NMR protein-ligand binding experiments. Compound optimization revealed that the phenolic or aniline groups could be replaced with a boronic acid moiety, which was able to maintain activity and demonstrated improved metabolic stability in microsomal in vitro assays. Further pharmacological evaluation of these compounds showed that they had roughly equivalent agonist activity on ERR isoforms α and ß representing an ERR pan-agonist profile. One potent agonist, SLU-PP-915 (10s), which contained a boronic acid moiety was profiled in gene expression assays and found to significantly upregulate the expression of ERR target genes such as peroxisome-proliferator activated receptor γ co-activators-1α, lactate dehydrogenase A, DNA damage inducible transcript 4 and pyruvate dehydrogenase kinase 4 both in vitro and in vivo.

Synthetic ERRα/ß/γ Agonist Induces an ERRα-Dependent Acute Aerobic Exercise Response and Enhances Exercise Capacity.

Repetitive physical exercise induces physiological adaptations in skeletal muscle that improves exercise performance and is effective for the prevention and treatment of several diseases. Genetic evidence indicates that the orphan nuclear receptors estrogen receptor-related receptors (ERRs) play an important role in skeletal muscle exercise capacity. Three ERR subtypes exist (ERRα, ß, and γ), and although ERRß/γ agonists have been designed, there have been significant difficulties in designing compounds with ERRα agonist activity. Additionally, there are limited synthetic agonists that can be used to target ERRs in vivo. Here, we report the identification of a synthetic ERR pan agonist, SLU-PP-332, that targets all three ERRs but has the highest potency for ERRα. Additionally, SLU-PP-332 has sufficient pharmacokinetic properties to be used as an in vivo chemical tool. SLU-PP-332 increases mitochondrial function and cellular respiration in a skeletal muscle cell line. When administered to mice, SLU-PP-332 increased the type IIa oxidative skeletal muscle fibers and enhanced exercise endurance. We also observed that SLU-PP-332 induced an ERRα-specific acute aerobic exercise genetic program, and the ERRα activation was critical for enhancing exercise endurance in mice. These data indicate the feasibility of targeting ERRα for the development of compounds that act as exercise mimetics that may be effective in the treatment of numerous metabolic disorders and to improve muscle function in the aging.

Emerging Role of Nuclear Receptors for the Treatment of NAFLD and NASH.

Non-alcoholic fatty liver (NAFLD) over the past years has become a metabolic pandemic linked to a collection of metabolic diseases. The nuclear receptors ERRs, REV-ERBs, RORs, FXR, PPARs, and LXR are master regulators of metabolism and liver physiology. The characterization of these nuclear receptors and their biology has promoted the development of synthetic ligands. The possibility of targeting these receptors to treat NAFLD is promising, as several compounds including Cilofexor, thiazolidinediones, and Saroglitazar are currently undergoing clinical trials. This review focuses on the latest development of the pharmacology of these metabolic nuclear receptors and how they may be utilized to treat NAFLD and subsequent comorbidities.

Structure-based design and synthesis of conformationally constrained derivatives of methyl-piperidinopyrazole (MPP) with estrogen receptor (ER) antagonist activity.

Nuclear Estrogen receptors (ER) are cytoplasmic proteins; translocated to the nucleus to induce transcriptional signals after getting bound to the estrogen hormone. ER activation implicated in cancer cell proliferation of female reproductive organs. Thus, the discovery of ER antagonists is a reliable strategy to combat estrogen-dependent breast cancer. Endometrial carcinoma is one of the complications encountered upon long-term therapy by selective estrogen receptor modulators (SERMs) like Tamoxifen (TMX) and methyl piperidinopyrazole (MPP). Thus, the ER-full antagonist is a solution to improve the safety of this class of therapeutics during the treatment of breast cancer. We selected MPP as a lead structure to design conformationally constrained analogs. Structural rigidification is a proven strategy to transform the SERMs into full antagonists. Accordingly, we synthesized 7-methoxy-3-(4-methoxyphenyl)-4,5-dihydro-2H-benzo[g]indazoles (4), (6a-c),(8-12) along with the biphenolic counterparts(13-19)that are the anticipated active metabolites. The 4-nitrophenyl derivative(4)is with the most balanced profile regardingthe in vivoanti-uterotrophic potential (EC50 = 4.160 µM); and the cytotoxicity assay of the corresponding active metabolite(13)against ER+ breast cancer cell lines (MCF-7 IC50 = 7.200 µM, T-47D IC50 = 11.710 µM). The inconsiderable uterotrophic activities of the elaborated ER-antagonists and weak antiproliferative activity of the compound(13)against ovarian cancer (SKOV-3 IC50 = 29.800 µM) highlighted it as a good start point to elaborate potential ER-full antagonists devoid of endometrial carcinoma. Extending the pendant chain that protrudes from the 2-(4-(substituted)-phenyl) ring of the new benzo-indazoles is recommended for enhancing the potency based on the binding mode of compound(13)in the ligand-binding domain (LBD) of ER.

A Selective ERRα/γ Inverse Agonist, SLU-PP-1072, Inhibits the Warburg Effect and Induces Apoptosis in Prostate Cancer Cells.

The estrogen related receptors (ERRs) are a subgroup of nuclear receptors that play a role in regulation of cellular metabolism. Prostate cancer (PCa) cells display altered metabolic signatures, such as the Warburg effect, and the ERRs have been implicated in driving this phenotype. Despite the lack of a known endogenous ligand, synthetic ligands that target the ERRs have been discovered. For example, the ERRα inverse agonist XCT790 modulates metabolic pathways in PCa cells, but it also functions as a mitochondrial uncoupler independent of targeting ERRα. Here, we describe a novel dual ERRα/γ inverse agonist, SLU-PP-1072, derived from the GSK4716 ERRγ agonist scaffold that is distinct from the XCT790 scaffold. SLU-PP-1072 alters PCa cell metabolism and gene expression, resulting in cell cycle dysregulation and increased apoptosis without acute mitochondrial uncoupling activity. Our data suggest that inhibition of ERRα/γ may be beneficial in treatment of PCa, and SLU-PP-1072 provides a unique chemical tool to evaluate the pharmacology of ERRα and ERRγ.

The Orphan Nuclear Receptor TLX Is a Receptor for Synthetic and Natural Retinoids.

TLX is an orphan nuclear receptor that plays a critical role in both embryonic and adult neurogenesis, as well in the pathogenesis of glioblastomas. TLX functions predominately as a transcriptional repressor, but no natural ligands or high-affinity synthetic ligands have been identified. Here, we describe the identification of natural and synthetic retinoids as functional ligands for TLX. We identified potent synthetic retinoids that directly bind to TLX and either activate or inhibit its transcriptional repressor activity. Furthermore, we identified all-trans and 11-cis retinaldehyde (retinal), retinoids that play an essential role in the visual cycle, as the preferential natural retinoids that bind to and modulate the function of TLX. Molecular dynamics simulations followed by mutational analysis provided insight into the molecular basis of retinoid binding to TLX. Our data support the validity of TLX as a target for development of therapeutics to treat cognitive disorders and/or glioblastomas.

Modulation of estrogen-related receptors subtype selectivity: Conversion of an ERRß/γ selective agonist to ERRα/ß/γ pan agonists.

Estrogen Related Receptors (ERRs) are key regulators of energy homeostasis and play important role in the etiology of metabolic disorders, skeletal muscle related disorders, and neurodegenerative diseases. Among the three ERR isoforms, ERRα emerged as a potential drug target for metabolic and neurodegenerative diseases. Although ERRß/γ selective agonist chemical tools have been identified, there are no chemical tools that effectively target ERRα agonism. We successfully engineered high affinity ERRα agonism into a chemical scaffold that displays selective ERRß/γ agonist activity (GSK4716), providing novel ERRα/ß/γ pan agonists that can be used as tools to probe the physiological roles of these nuclear receptors. We identified the structural requirements to enhance selectivity toward ERRα. Molecular modeling shows that our novel modulators have favorable binding modes in the LBP of ERRα and can induce conformational changes where Phe328 that originally occupies the pocket is dislocated to accommodate the ligands in a rather small cavity. The best agonists up-regulated the expression of target genes PGC-1α and PGC-1ß, which are necessary to achieve maximal mitochondrial biogenesis. Moreover, they increased the mRNA levels of PDK4, which play an important role in energy homeostasis.

Rev-erbα heterozygosity produces a dose-dependent phenotypic advantage in mice.

Numerous mutational studies have demonstrated that circadian clock proteins regulate behavior and metabolism. Nr1d1(Rev-erbα) is a key regulator of circadian gene expression and a pleiotropic regulator of skeletal muscle homeostasis and lipid metabolism. Loss of Rev-erbα expression induces muscular atrophy, high adiposity, and metabolic syndrome in mice. Here we show that, unlike knockout mice, Nr1d1 heterozygous mice are not susceptible to muscular atrophy and in fact paradoxically possess larger myofiber diameters and improved neuromuscular function, compared to wildtype mice. Heterozygous mice lacked dyslipidemia, a characteristic of Nr1d1 knockout mice and displayed increased whole-body fatty-acid oxidation during periods of inactivity (light cycle). Heterozygous mice also exhibited higher rates of glucose uptake when fasted, and had elevated basal rates of gluconeogenesis compared to wildtype and knockout littermates. Rev-erbα ablation suppressed glycolysis and fatty acid-oxidation in white-adipose tissue (WAT), whereas partial Rev-erbα loss, curiously stimulated these processes. Our investigations revealed that Rev-erbα dose-dependently regulates glucose metabolism and fatty acid oxidation in WAT and muscle.

Circadian rhythm-dependent and circadian rhythm-independent impacts of the molecular clock on type 3 innate lymphoid cells.

Many gut functions are attuned to circadian rhythm. Intestinal group 3 innate lymphoid cells (ILC3s) include NKp46+ and NKp46- subsets, which are RORγt dependent and provide mucosal defense through secretion of interleukin-22 (IL-22) and IL-17. Because ILC3s highly express some key circadian clock genes, we investigated whether ILC3s are also attuned to circadian rhythm. We noted circadian oscillations in the expression of clock and cytokine genes, such as REV-ERBα, IL-22, and IL-17, whereas acute disruption of the circadian rhythm affected cytokine secretion by ILC3s. Because of prominent and rhythmic expression of REV-ERBα in ILC3s, we also investigated the impact of constitutive deletion of REV-ERBα, which has been previously shown to inhibit the expression of a RORγt repressor, NFIL3, while also directly antagonizing DNA binding of RORγt. Development of the NKp46+ ILC3 subset was markedly impaired, with reduced cell numbers, RORγt expression, and IL-22 production in REV-ERBα-deficient mice. The NKp46- ILC3 subsets developed normally, potentially due to compensatory expression of other clock genes, but IL-17 secretion paradoxically increased, probably because RORγt was not antagonized by REV-ERBα. We conclude that ILC3s are attuned to circadian rhythm, but clock regulator REV-ERBα also has circadian-independent impacts on ILC3 development and functions due to its roles in the regulation of RORγt.

Doubled lifespan and patient-like pathologies in progeria mice fed high-fat diet.

Hutchinson-Gilford Progeria Syndrome (HGPS) is a devastating premature aging disease. Mouse models have been instrumental for understanding HGPS mechanisms and for testing therapies, which to date have had only marginal benefits in mice and patients. Barriers to developing effective therapies include the unknown etiology of progeria mice early death, seemingly unrelated to the reported atherosclerosis contributing to HGPS patient mortality, and mice not recapitulating the severity of human disease. Here, we show that progeria mice die from starvation and cachexia. Switching progeria mice approaching death from regular diet to high-fat diet (HFD) rescues early lethality and ameliorates morbidity. Critically, feeding the mice only HFD delays aging and nearly doubles lifespan, which is the greatest lifespan extension recorded in progeria mice. The extended lifespan allows for progeria mice to develop degenerative aging pathologies of a severity that emulates the human disease. We propose that starvation and cachexia greatly influence progeria phenotypes and that nutritional/nutraceutical strategies might help modulate disease progression. Importantly, progeria mice on HFD provide a more clinically relevant animal model to study mechanisms of HGPS pathology and to test therapies.

RORγ regulates the NLRP3 inflammasome.

RAR-related orphan receptor γ (RORγ) is a nuclear receptor that plays an essential role in the development of T helper 17 (Th17) cells of the adaptive immune system. The NLRP3 inflammasome is a component of the innate immune system that processes interleukin (IL)-1ß into a mature cytokine. Elevated activity of the NLRP3 inflammasome contributes to the progression of an array of inflammatory diseases. Bone marrow-derived macrophages (BMDMs) isolated from RORγ-null mice displayed reduced capacity to secrete IL-1ß, and they also displayed a reduction in Nlrp3 and Il1b gene expression. Examination of the promoters of the Il1b and Nlrp3 genes revealed multiple putative ROR response elements (ROREs) that were occupied by RORγ. RORγ inverse agonists were effective inhibitors of the inflammasome. RORγ inverse agonists suppressed lipopolysaccharide (LPS)/ATP-stimulated IL-1ß secretion and expression of Il1b and Nlrp3 in BMDMs. Additionally, the ability of the RORγ inverse agonists to suppress IL-1ß secretion was lost in Nlrp3-null macrophages. The potential for targeting the NLRP3 inflammasome in vivo using RORγ inverse agonists was examined in two models: LPS-induced sepsis and fulminant hepatitis. Pharmacological inhibition of RORγ activity reduced plasma IL-1ß as well as IL-1ß production by peritoneal macrophages in a model of LPS-induced sepsis. Additionally, RORγ inverse agonists reduced mortality in an LPS/d-galactosamine-induced fulminant hepatitis mouse model. These results illustrate a major role for RORγ in regulation of innate immunity via modulation of NLRP3 inflammasome activity. Furthermore, these data suggest that inhibiting the NLRP3 inflammasome with RORγ inverse agonists may be an effective method to treat NLRP3-associated diseases.

Adropin: An endocrine link between the biological clock and cholesterol homeostasis.

OBJECTIVE: Identify determinants of plasma adropin concentrations, a secreted peptide translated from the Energy Homeostasis Associated (ENHO) gene linked to metabolic control and vascular function. METHODS: Associations between plasma adropin concentrations, demographics (sex, age, BMI) and circulating biomarkers of lipid and glucose metabolism were assessed in plasma obtained after an overnight fast in humans. The regulation of adropin expression was then assessed in silico, in cultured human cells, and in animal models. RESULTS: In humans, plasma adropin concentrations are inversely related to atherogenic LDL-cholesterol (LDL-C) levels in men (n = 349), but not in women (n = 401). Analysis of hepatic Enho expression in male mice suggests control by the biological clock. Expression is rhythmic, peaking during maximal food consumption in the dark correlating with transcriptional activation by RORα/γ. The nadir in the light phase coincides with the rest phase and repression by Rev-erb. Plasma adropin concentrations in nonhuman primates (rhesus monkeys) also exhibit peaks coinciding with feeding times (07:00 h, 15:00 h). The ROR inverse agonists SR1001 and the 7-oxygenated sterols 7-ß-hydroxysterol and 7-ketocholesterol, or the Rev-erb agonist SR9009, suppress ENHO expression in cultured human HepG2 cells. Consumption of high-cholesterol diets suppress expression of the adropin transcript in mouse liver. However, adropin over expression does not prevent hypercholesterolemia resulting from a high cholesterol diet and/or LDL receptor mutations. CONCLUSIONS: In humans, associations between plasma adropin concentrations and LDL-C suggest a link with hepatic lipid metabolism. Mouse studies suggest that the relationship between adropin and cholesterol metabolism is unidirectional, and predominantly involves suppression of adropin expression by cholesterol and 7-oxygenated sterols. Sensing of fatty acids, cholesterol and oxysterols by the RORα/γ ligand-binding domain suggests a plausible functional link between adropin expression and cellular lipid metabolism. Furthermore, the nuclear receptors RORα/γ and Rev-erb may couple adropin synthesis with circadian rhythms in carbohydrate and lipid metabolism.

Nuclear Receptor Subfamily 1 Group D Member 1 Regulates Circadian Activity of NLRP3 Inflammasome to Reduce the Severity of Fulminant Hepatitis in Mice.

BACKGROUND & AIMS: The innate immune system responds not only to bacterial signals, but also to non-infectious danger-associated molecular patterns that activate the NLRP3 inflammasome complex after tissue injury. Immune functions vary over the course of the day, but it is not clear whether these changes affect the activity of the NLRP3 inflammasome. We investigated whether the core clock component nuclear receptor subfamily 1 group D member 1 (NR1D1, also called Rev-erbα) regulates expression, activity of the NLRP3 inflammasome, and its signaling pathway. METHODS: We collected naïve peritoneal macrophages and plasma, at multiple times of day, from Nr1d1-/- mice and their Nr1d1+/+ littermates (controls) and analyzed expression NLRP3, interleukin 1ß (IL1B, in plasma), and IL18 (in plasma). We also collected bone marrow-derived primary macrophages from these mice. Levels of NR1D1 were knocked down with small hairpin RNAs in human primary macrophages. Bone marrow-derived primary macrophages from mice and human primary macrophages were incubated with lipopolysaccharide (LPS) to induce expression of NLRP3, IL1B, and IL18; cells were incubated with LPS and adenosine triphosphate to activate the NLRP3 complex. We analyzed caspase 1 activity and cytokine secretion. NR1D1 was activated in primary mouse and human macrophages by incubation with SR9009; some of the cells were also incubated with an NLRP3 inhibitor or inhibitors of caspase 1. Nr1d1-/- mice and control mice were given intraperitoneal injections of LPS to induce peritoneal inflammation; plasma samples were isolated and levels of cytokines were measured. Nr1d1-/- mice, control mice, and control mice given injections of SR9009 were given LPS and D-galactosamine to induce fulminant hepatitis and MCC950 to specifically inhibit NLRP3; plasma was collected to measure cytokines and a marker of liver failure (alanine aminotransferase); liver tissues were collected and analyzed by quantitative polymerase chain reaction, immunohistochemistry, and flow cytometry. RESULTS: In peritoneal macrophages, expression of NLRP3 and activation of its complex varied with time of day (circadian rhythm)-this regulation required NR1D1. Primary macrophages from Nr1d1-/- mice and human macrophages with knockdown of NR1D1 had altered expression patterns of NLRP3, compared to macrophages that expressed NR1D1, and altered patterns of IL1B and 1L18 production. Mice with disruption of Nr1d1 developed more-severe acute peritoneal inflammation and fulminant hepatitis than control mice. Incubation of macrophage with the NR1D1 activator SR9009 reduced expression of NLRP3 and secretion of cytokines. Mice given SR9009 developed less-severe liver failure and had longer survival times than mice given saline (control). CONCLUSIONS: In studies of Nr1d1-/- mice and human macrophages with pharmacologic activation of NR1D1, we found NR1D1 to regulate the timing of NLRP3 expression and production of inflammatory cytokines by macrophages. Activation of NR1D1 reduced the severity of peritoneal inflammation and fulminant hepatitis in mice.

Pharmacological inhibition of REV-ERB stimulates differentiation, inhibits turnover and reduces fibrosis in dystrophic muscle.

Duchenne muscular dystrophy (DMD) is a debilitating X-linked disorder that is fatal. DMD patients lack the expression of the structural protein dystrophin caused by mutations within the DMD gene. The absence of functional dystrophin protein results in excessive damage from normal muscle use due to the compromised structural integrity of the dystrophin associated glycoprotein complex. As a result, DMD patients exhibit ongoing cycles of muscle destruction and regeneration that promote inflammation, fibrosis, mitochondrial dysfunction, satellite cell (SC) exhaustion and loss of skeletal and cardiac muscle function. The nuclear receptor REV-ERB suppresses myoblast differentiation and recently we have demonstrated that the REV-ERB antagonist, SR8278, stimulates muscle regeneration after acute injury. Therefore, we decided to explore whether the REV-ERB antagonist SR8278 could slow the progression of muscular dystrophy. In mdx mice SR8278 increased lean mass and muscle function, and decreased muscle fibrosis and muscle protein degradation. Interestingly, we also found that SR8278 increased the SC pool through stimulation of Notch and Wnt signaling. These results suggest that REV-ERB is a potent target for the treatment of DMD.

Metabolic Characterization of a Novel RORα Knockout Mouse Model without Ataxia.

The retinoic acid receptor-related receptor α (RORα) is a nuclear receptor that plays an important role in regulation of metabolism and the immune system. Genetic deletion of the receptor yields mice with significant cerebellar developmental issues associated with severe ataxia. Although many metabolic studies have been performed in these models, the impaired locomotor activity of these mice is known to affect their normal mobility and feeding behaviors. This creates some difficulty in interpretation of the role of RORα in models of metabolic disease where feeding and muscle function is a critical component of the pathophysiology. We generated a mouse with a floxed Rora allele that we crossed with a mouse line expressing Cre recombinase under the control of the EIIa promoter to obtain a full body deletion of Rora. This cross led to a partial deletion of the Rora locus likely due to mosaic expression of the EIIa-Cre transgene. These mice lack any signs of ataxia but display an improved metabolic profile relative to normal WT mice. The mice were resistant to diet- and age-induced metabolic syndrome and exhibited improved glucose tolerance and increased insulin sensitivity. Decreased RORα expression in the mice was also associated with reduced inflammation in models of metabolic syndrome. These data indicate that suppression of RORα activity improves metabolic function and reduces inflammation.