T0901317 is a potent PXR ligand: Implications for the biology ascribed to LXR

AbstractThe liver X receptors (LXRα and β) are nuclear receptors that coordinate carbohydrate and lipid metabolism. Insight into the physiologic roles of the LXRs has been greatly facilitated by the discovery of potent synthetic agonists. Here we show that one of these compounds, T0901317, is also a high-affinity ligand for the xenobiotic receptor pregnane X receptor (PXR). T0901317 binds and activates PXR with the same nanomolar potency with which it stimulates LXR activity. T0901317 induces expression not only of LXR target genes, but also of PXR target genes in cells and animals, including the scavenger receptor CD36, a property not shared by more specific LXR ligands, such as GW3965. Activation of PXR targets may explain why T0901317 induces dramatic liver steatosis, while GW3965 has a milder effect. These results suggest that many of the biological activities heretofore associated with LXR activation may be mediated by PXR, not LXR. Since T0901317 has been widely used in animals to study LXR function, the in vivo effects of this compound ascribed to LXR activation should be re-examined

The negative effects of bile acids and tumor necrosis factor-alpha on the transcription of cholesterol 7alpha-hydroxylase gene (CYP7A1) converge to hepatic nuclear factor-4: a novel mechanism of feedback regulation of bile acid synthesis mediated by nuclear receptors.

Bile acids regulate the cholesterol 7alpha-hydroxylase gene (CYP7A1), which encodes the rate-limiting enzyme in the classical pathway of bile acid synthesis. Here we report a novel mechanism whereby bile acid feedback regulates CYP7A1 transcription through the nuclear receptor hepatocyte nuclear factor-4 (HNF-4), which binds to the bile acid response element (BARE) at nt -149/-118 relative to the transcription start site. Using transient transfection assays of HepG2 cells with Gal4-HNF-4 fusion proteins, we show that chenodeoxycholic acid (CDCA) dampened the transactivation potential of HNF-4. Overexpression of a constitutive active form of MEKK1, an upstream mitogen-activated protein kinase (MAPK) module triggered by stress signals, strongly repressed the promoter activity of CYP7A1 via the consensus sequence for HNF-4 embedded in the BARE. Similarly, MEKK1 inhibited the activity of HNF-4 in the Gal4-based assay. The involvement of the MEKK1-dependent pathway in the bile acid-mediated repression of CYP7A1 was confirmed by co-transfecting a dominant negative form of the stress-activated protein kinase kinase, SEK, which abolished the effect of CDCA upon CYP7A1 transcription. Treatment of transfected HepG2 cells with tumor necrosis factor alpha (TNF-alpha), an activator of the MEKK1 pathway, led to the repression of CYP7A1 via the HNF-4 site in the BARE. TNF-alpha also inhibited the transactivation potential of HNF-4. Collectively, our results demonstrate for the first time that HNF-4, in combination with a MAPK signaling pathway, acts as a bile acid sensor in the liver. Furthermore, the effects of CDCA and TNF-alpha converge to HNF-4, which binds to the BARE of CYP7A1, suggesting a link between the cascades elicited by bile acids and pro-inflammatory stimuli in the liver

Role of Neuroactive Steroids in the Peripheral Nervous System

Several reviews have so far pointed out on the relevant physiological and pharmacological role exerted by neuroactive steroids in the central nervous system. In the present review we summarize observations indicating that synthesis and metabolism of neuroactive steroids also occur in the peripheral nerves. Interestingly, peripheral nervous system is also a target of their action. Indeed, as here reported neuroactive steroids are physiological regulators of peripheral nerve functions and they may also represent interesting therapeutic tools for different types of peripheral neuropathy

Extracellular matrix mechanical cues regulate lipid metabolism through Lipin-1 and SREBP

Extracellular matrix (ECM) mechanical cues have powerful effects on cell proliferation, differentiation and death. Here, starting from an unbiased metabolomics approach, we identify synthesis of neutral lipids as a general response to mechanical signals delivered by cell\u2013matrix adhesions. Extracellular physical cues reverberate on the mechanical properties of the Golgi apparatus and regulate the Lipin-1 phosphatidate phosphatase. Conditions of reduced actomyosin contractility lead to inhibition of Lipin-1, accumulation of SCAP/SREBP to the Golgi apparatus and activation of SREBP transcription factors, in turn driving lipid synthesis and accumulation. This occurs independently of YAP/TAZ, mTOR and AMPK, and in parallel to feedback control by sterols. Regulation of SREBP can be observed in a stiffened diseased tissue, and contributes to the pro-survival activity of ROCK inhibitors in pluripotent stem cells. We thus identify a general mechanism centered on Lipin-1 and SREBP that links the physical cell microenvironment to a key metabolic pathway

Zc3h10 regulates adipogenesis by controlling translation and F-actin/mitochondria interaction

The commitment of mesenchymal stem cells to preadipocytes is stimulated by hormonal induction. Preadipocytes induced to differentiate repress protein synthesis, remodel their cytoskeleton, and increase mitochondrial function to support anabolic pathways. These changes enable differentiation into mature adipocytes. Our understanding of the factors that coordinately regulate the early events of adipocyte differentiation remains incomplete. Here, by using multipronged approaches, we have identified zinc finger CCCH-type containing 10 (Zc3h10) as a critical regulator of the early stages of adipogenesis. Zc3h10 depletion in preadipocytes resulted in increased protein translation and impaired filamentous (F)-actin remodeling, with the latter detrimental effect leading to mitochondrial and metabolic dysfunction. These defects negatively affected differentiation to mature adipocytes. In contrast, Zc3h10 overexpression yielded mature adipocytes with remarkably increased lipid droplet size. Overall, our study establishes Zc3h10 as a fundamental proadipogenic transcription factor that represses protein synthesis and promotes F-actin/mitochondria dynamics to ensure proper energy metabolism and favor lipid accumulation

Frataxin deficiency shifts metabolism to promote reactive microglia via glucose catabolism

Immunometabolism investigates the intricate relationship between the immune system and cellular metabolism. This study delves into the consequences of mitochondrial frataxin (FXN) depletion, the primary cause of Friedreich's ataxia (FRDA), a debilitating neurodegenerative condition characterized by impaired coordination and muscle control. By using single-cell RNA sequencing, we have identified distinct cellular clusters within the cerebellum of an FRDA mouse model, emphasizing a significant loss in the homeostatic response of microglial cells lacking FXN. Remarkably, these microglia deficient in FXN display heightened reactive responses to inflammatory stimuli. Furthermore, our metabolomic analyses reveal a shift towards glycolysis and itaconate production in these cells. Remarkably, treatment with butyrate counteracts these immunometabolic changes, triggering an antioxidant response via the itaconate-Nrf2-GSH pathways and suppressing the expression of inflammatory genes. Furthermore, we identify Hcar2 (GPR109A) as a mediator involved in restoring the homeostasis of microglia without FXN. Motor function tests conducted on FRDA mice underscore the neuroprotective attributes of butyrate supplementation, enhancing neuromotor performance. In conclusion, our findings elucidate the role of disrupted homeostatic function in cerebellar microglia in the pathogenesis of FRDA. Moreover, they underscore the potential of butyrate to mitigate inflammatory gene expression, correct metabolic imbalances, and improve neuromotor capabilities in FRDA

Obesity-Induced Metabolic Stress Leads to Biased Effector Memory CD4+ T Cell Differentiation via PI3K p110δ-Akt-Mediated Signals.

Low-grade systemic inflammation associated to obesity leads to cardiovascular complications, caused partly by infiltration of adipose and vascular tissue by effector T cells. The signals leading to T cell differentiation and tissue infiltration during obesity are poorly understood. We tested whether saturated fatty acid-induced metabolic stress affects differentiation and trafficking patterns of CD4+ T cells. Memory CD4+ T cells primed in high-fat diet-fed donors preferentially migrated to non-lymphoid, inflammatory sites, independent of the metabolic status of the hosts. This was due to biased CD4+ T cell differentiation into CD44hi-CCR7lo-CD62Llo-CXCR3+-LFA1+ effector memory-like T cells upon priming in high-fat diet-fed animals. Similar phenotype was observed in obese subjects in a cohort of free-living people. This developmental bias was independent of any crosstalk between CD4+ T cells and dendritic cells and was mediated via direct exposure of CD4+ T cells to palmitate, leading to increased activation of a PI3K p110δ-Akt-dependent pathway upon priming

Transcriptomic Profile Reveals Deregulation of Hearing-Loss Related Genes in Vestibular Schwannoma Cells Following Electromagnetic Field Exposure

From MDPI via Jisc Publications RouterHistory: accepted 2021-07-18, pub-electronic 2021-07-20Publication status: PublishedFunder: Capita Foundation; Grant(s): grant 2019 to V.M.Funder: Università degli Studi di Milano; Grant(s): grant PSR_VMAGN_2019 to V.MFunder: MIUR Italian Ministry of Research; Grant(s): Progetto di EccellenzaHearing loss (HL) is the most common sensory disorder in the world population. One common cause of HL is the presence of vestibular schwannoma (VS), a benign tumor of the VIII cranial nerve, arising from Schwann cell (SC) transformation. In the last decade, the increasing incidence of VS has been correlated to electromagnetic field (EMF) exposure, which might be considered a pathogenic cause of VS development and HL. Here, we explore the molecular mechanisms underlying the biologic changes of human SCs and/or their oncogenic transformation following EMF exposure. Through NGS technology and RNA-Seq transcriptomic analysis, we investigated the genomic profile and the differential display of HL-related genes after chronic EMF. We found that chronic EMF exposure modified the cell proliferation, in parallel with intracellular signaling and metabolic pathways changes, mostly related to translation and mitochondrial activities. Importantly, the expression of HL-related genes such as NEFL, TPRN, OTOGL, GJB2, and REST appeared to be deregulated in chronic EMF exposure. In conclusion, we suggest that, at a preclinical stage, EMF exposure might promote the transformation of VS cells and contribute to HL

Intermittent fasting applied in combination with rotenone treatment exacerbates dopamine neurons degeneration in mice

Intermittent fasting (IF) was suggested to be a powerful nutritional strategy to prevent the onset of age-related neurodegenerative diseases associated with compromised brain bioenergetics. Whether the application of IF in combination with a mitochondrial insult could buffer the neurodegenerative process has never been explored yet. Herein, we defined the effects of IF in C57BL/6J mice treated once per 24 h with rotenone (Rot) for 28 days. Rot is a neurotoxin that inhibits the mitochondrial complex I and causes dopamine neurons degeneration, thus reproducing the neurodegenerative process observed in Parkinson\u2019s disease (PD). IF (24 h alternate-day fasting) was applied alone or in concomitance with Rot treatment (Rot/IF). IF and Rot/IF groups showed the same degree of weight loss when compared to control and Rot groups. An accelerating rotarod test revealed that only Rot/IF mice have a decreased ability to sustain the test at the higher speeds. Rot/IF group showed a more marked decrease of dopaminergic neurons and increase in alpha-synuclein (a-syn) accumulation with respect to Rot group in the substantia nigra (SN). Through lipidomics and metabolomics analyses, we found that in the SN of Rot/IF mice a significant elevation of excitatory amino acids, inflammatory lysophospholipids and sphingolipids occurred. Collectively, our data suggest that, when applied in combination with neurotoxin exposure, IF does not exert neuroprotective effects but rather exacerbate neuronal death by increasing the levels of excitatory amino acids and inflammatory lipids in association with altered brain membrane composition

Author Correction: Mutant p53 sustains serine-glycine synthesis and essential amino acids intake promoting breast cancer growth

Reprogramming of amino acid metabolism, sustained by oncogenic signaling, is crucial for cancer cell survival under nutrient limitation. Here we discovered that missense mutant p53 oncoproteins stimulate de novo serine/glycine synthesis and essential amino acids intake, promoting breast cancer growth. Mechanistically, mutant p53, unlike the wild-type counterpart, induces the expression of serine-synthesis-pathway enzymes and L-type amino acid transporter 1 (LAT1)/CD98 heavy chain heterodimer. This effect is exacerbated by amino acid shortage, representing a mutant p53-dependent metabolic adaptive response. When cells suffer amino acids scarcity, mutant p53 protein is stabilized and induces metabolic alterations and an amino acid transcriptional program that sustain cancer cell proliferation. In patient-derived tumor organoids, pharmacological targeting of either serine-synthesis-pathway and LAT1-mediated transport synergizes with amino acid shortage in blunting mutant p53-dependent growth. These findings reveal vulnerabilities potentially exploitable for tackling breast tumors bearing missense TP53 mutation