Tissue-infiltrating neutrophils constitute the major in vivo source of angiogenesis-inducing MMP-9 in the tumor microenvironment

According to established notion, one of the major angiogenesis-inducing factors, pro-matrix metalloproteinase-9 (proMMP-9), is supplied to the tumor microenvironment by tumor-associated macrophages (TAMs). Accumulated evidence, however, indicates that tumor-associated neutrophils (TANs) are also critically important for proMMP-9 delivery, especially at early stages of tumor development. To clarify how much angiogenic proMMP-9 is actually contributed by TAMs and TANs, we quantitatively evaluated TAMs and TANs from different tumor types, including human xenografts and syngeneic murine tumors grown in wild-type and Mmp9-knockout mice. Whereas host MMP-9 competence was required for full angiogenic potential of both normal and tumor-associated leukocytes, direct comparisons of neutrophils versus macrophages and TANs versus TAMs demonstrated that macrophages and TAMs secrete 40- to 50-fold less proMMP-9 than the same numbers of neutrophils or TANs. Correspondingly, the levels of MMP-9–mediated in vivo angiogenesis induced by neutrophils and TANs substantially exceeded those induced by macrophages and TAMs. MMP-9–delivering TANs were also required for development of metastasis-supporting intratumoral vasculature, characterized by ≥ 11-μm size lumens and partial coverage with stabilizing pericytes. Importantly, MMP-9–producing TAMs exhibit M2-skewed phenotype but do not express tissue inhibitor of metalloproteinases-1 (TIMP-1), a novel characteristic allowing them to secrete TIMP-1–free, neutrophil-like MMP-9 zymogen unencumbered by its natural inhibitor. Together, our findings support the notion whereby TANs, capable of immediate release of their pre-stored cargo, are the major contributors of highly angiogenic MMP-9, whereas tumor-influxing precursors of macrophages require time to differentiate, polarize into M2-skewed TAMs, shut down their TIMP-1 expression, and only then, initiate relatively low-level production of TIMP-free MMP-9 zymogen.

Cysteine proteases as therapeutic targets: does selectivity matter? A systematic review of calpain and cathepsin inhibitors

Cysteine proteases continue to provide validated targets for treatment of human diseases. In neurodegenerative disorders, multiple cysteine proteases provide targets for enzyme inhibitors, notably caspases, calpains, and cathepsins. The reactive, active-site cysteine provides specificity for many inhibitor designs over other families of proteases, such as aspartate and serine; however, a) inhibitor strategies often use covalent enzyme modification, and b) obtaining selectivity within families of cysteine proteases and their isozymes is problematic. This review provides a general update on strategies for cysteine protease inhibitor design and a focus on cathepsin B and calpain 1 as drug targets for neurodegenerative disorders; the latter focus providing an interesting query for the contemporary assumptions that irreversible, covalent protein modification and low selectivity are anathema to therapeutic safety and efficacy.

Miltirone induces cell death in hepatocellular carcinoma cell through GSDME-dependent pyroptosis

Pyroptosis is a form of programmed cell death, and recently described as a new molecular mechanism of chemotherapy drugs in the treatment of tumors. Miltirone, a derivative of phenanthrene-quinone isolated from the root of Salvia miltiorrhiza Bunge, has been shown to possess anti-cancer activities. Here, we found that miltirone inhibited the cell viability of either HepG2 or Hepa1-6 cells, and induced the proteolytic cleavage of gasdermin E (GSDME) in each hepatocellular carcinoma (HCC) cell line, with concomitant cleavage of caspase 3. Knocking out GSDME switched miltirone-induced cell death from pyroptosis to apoptosis. Additionally, the induction effects of miltirone on GSDME-dependent pyroptosis were attenuated by siRNA-mediated caspase three silencing and the specific caspase three inhibitor Z-DEVD-FMK, respectively. Miltirone effectively elicited intracellular accumulation of reactive oxygen species (ROS), and suppressed phosphorylation of mitogen-activated and extracellular signal-regulated kinase (MEK) and extracellular regulated protein kinases 1/2 (ERK1/2) for pyroptosis induction. Moreover, miltirone significantly inhibited tumor growth and induced pyroptosis in the Hepa1-6 mouse HCC syngeneic model. These results provide a new insight that miltirone is a potential therapeutic agent for the treatment of HCC via GSDME-dependent pyroptosis.

Neutrophil-Hepatic Stellate Cell Interactions Promote Fibrosis in Experimental Steatohepatitis

BACKGROUND & AIMS

Hepatic infiltration of neutrophils is a hallmark of steatohepatitis; however, the role of neutrophils in the progression of steatohepatitis remains unknown.

METHODS

A clinically relevant mouse model of steatohepatitis induced by high-fat diet (HFD) plus binge ethanol feeding was used. Liver fibrosis was examined. In vitro cell culture was used to analyze the interaction of hepatic stellate cells (HSCs) and neutrophils.

RESULTS

HFD plus one binge ethanol (HFD+1B) feeding induced significant hepatic neutrophil infiltration, liver injury, and fibrosis. HFD plus multiple binges of ethanol (HFD+mB) caused more pronounced liver fibrosis. Microarray analyses showed that the most highly activated signaling pathway in this HFD+1B model was related to liver fibrosis and HSC activation. Blockade of chemokine (C-X-C motif) ligand 1 or intercellular adhesion molecule-1 expression reduced hepatic neutrophil infiltration and ameliorated liver injury and fibrosis. Disruption of the p47phox gene (also called neutrophil cytosolic factor 1), a critical component of reactive oxygen species producing nicotinamide adenine dinucleotide phosphate-oxidase in neutrophils, diminished HFD+1B-induced liver injury and fibrosis. Co-culture of HSCs with neutrophils, but not with neutrophil apoptotic bodies, induced HSC activation and prolonged neutrophil survival. Mechanistic studies showed that activated HSCs produce granulocyte-macrophage colony-stimulating factor and interleukin-15 to prolong the survival of neutrophils, which may serve as a positive forward loop to promote liver damage and fibrosis.

CONCLUSIONS

The current data from a mouse model of HFD plus binge ethanol feeding suggest that obesity and binge drinking synergize to promote liver fibrosis, which is partially mediated via the interaction of neutrophils and HSCs. Microarray data in this article have been uploaded to NCBI's Gene Expression Omnibus (GEO accession number: GSE98153).

New method to assess mitophagy flux by flow cytometry

Mitochondrial autophagy, also known as mitophagy, is an autophagosome-based mitochondrial degradation process that eliminates unwanted or damaged mitochondria after cell stress. Most studies dealing with mitophagy rely on the analysis by fluorescence microscopy of mitochondrial-autophagosome colocalization. However, given the fundamental role of mitophagy in the physiology and pathology of organisms, there is an urgent need for novel quantitative methods with which to study this process. Here, we describe a flow cytometry-based approach to determine mitophagy by using MitoTracker Deep Red, a widely used mitochondria-selective probe. Used in combination with selective inhibitors it may allow for the determination of mitophagy flux. Here, we test the validity of the use of this method in cell lines and in primary cell and tissue cultures.

Reciprocal regulation of cilia and autophagy via the MTOR and proteasome pathways

Primary cilium is an organelle that plays significant roles in a number of cellular functions ranging from cell mechanosensation, proliferation, and differentiation to apoptosis. Autophagy is an evolutionarily conserved cellular function in biology and indispensable for cellular homeostasis. Both cilia and autophagy have been linked to different types of genetic and acquired human diseases. Their interaction has been suggested very recently, but the underlying mechanisms are still not fully understood. We examined autophagy in cells with suppressed cilia and measured cilium length in autophagy-activated or -suppressed cells. It was found that autophagy was repressed in cells with short cilia. Further investigation showed that MTOR activation was enhanced in cilia-suppressed cells and the MTOR inhibitor rapamycin could largely reverse autophagy suppression. In human kidney proximal tubular cells (HK2), autophagy induction was associated with cilium elongation. Conversely, autophagy inhibition by 3-methyladenine (3-MA) and chloroquine (CQ) as well as bafilomycin A1 (Baf) led to short cilia. Cilia were also shorter in cultured atg5-knockout (KO) cells and in atg7-KO kidney proximal tubular cells in mice. MG132, an inhibitor of the proteasome, could significantly restore cilium length in atg5-KO cells, being concomitant with the proteasome activity. Together, the results suggest that cilia and autophagy regulate reciprocally through the MTOR signaling pathway and ubiquitin-proteasome system.

Dual induction of TREM2 and tolerance-related transcript, Tmem176b, in amyloid transgenic mice: implications for vaccine-based therapies for Alzheimer's disease

Vaccine-based autoimmune (anti-amyloid) treatments are currently being examined for their therapeutic potential in Alzheimer's disease. In the present study we examined, in a transgenic model of amyloid pathology, the expression of two molecules previously implicated in decreasing the severity of autoimmune responses: TREM2 (triggering receptor expressed on myeloid cells 2) and the intracellular tolerance-associated transcript, Tmem176b (transmembrane domain protein 176b). In situ hybridization analysis revealed that both molecules were highly expressed in plaque-associated microglia, but their expression defined two different zones of plaque-associated activation. Tmem176b expression was highest in the inner zone of amyloid plaques, whereas TREM2 expression was highest in the outer zone. Induced expression of TREM2 occurred co-incident with detection of thioflavine-S-positive amyloid deposits. Transfection studies revealed that expression of TREM2 correlated negatively with motility, but correlated positively with the ability of microglia to stimulate CD4⁺ T-cell proliferation, TNF (tumour necrosis factor) and CCL2 (chemokine ligand 2) production, but not IFNγ (interferon γ) production. TREM2 expression also showed a positive correlation with amyloid phagocytosis in unactivated cells. However, activating cells with LPS (lipopolysaccharide), but not IFNγ, reduced the correlation between TREM2 expression and phagocytosis. Transfection of Tmem176b into both microglial and macrophage cell lines increased apoptosis. Taken together, these data suggest that, in vivo, Tmem176b⁺ cells in closest apposition to amyloid may be the least able to clear amyloid. Conversely, the phagocytic TREM2⁺ microglia on the plaque outer zones are positioned to capture and present self-antigens to CNS (central nervous system)-infiltrating lymphocytes without promoting pro-inflammatory lymphocyte responses. Instead, plaque-associated TREM2⁺ microglia have the potential to evoke neuroprotective immune responses that may serve to support CNS function during pro-inflammatory anti-amyloid immune therapies.

Critical role of CAV1/caveolin-1 in cell stress responses in human breast cancer cells via modulation of lysosomal function and autophagy

CAV1 (caveolin 1, caveolae protein, 22kDa) is well known as a principal scaffolding protein of caveolae, a specialized plasma membrane structure. Relatively, the caveolae-independent function of CAV1 is less studied. Autophagy is a process known to involve various membrane structures, including autophagosomes, lysosomes, and autolysosomes for degradation of intracellular proteins and organelles. Currently, the function of CAV1 in autophagy remains largely elusive. In this study, we demonstrate for the first time that CAV1 deficiency promotes both basal and inducible autophagy. Interestingly, the promoting effect was found mainly in the late stage of autophagy via enhancing lysosomal function and autophagosome-lysosome fusion. Notably, the regulatory function of CAV1 in lysosome and autophagy was found to be caveolae-independent, and acts through lipid rafts. Furthermore, the elevated autophagy level induced by CAV1 deficiency serves as a cell survival mechanism under starvation. Importantly, downregulation of CAV1 and enhanced autophagy level were observed in human breast cancer cells and tissues. Taken together, our data reveal a novel function of CAV1 and lipid rafts in breast cancer development via modulation of lysosomal function and autophagy.

The autophagy gene Wdr45/Wipi4 regulates learning and memory function and axonal homeostasis

WDR45/WIPI4, encoding a WD40 repeat-containing PtdIns(3)P binding protein, is essential for the basal autophagy pathway. Mutations in WDR45 cause the neurodegenerative disease β-propeller protein-associated neurodegeneration (BPAN), a subtype of NBIA. We generated CNS-specific Wdr45 knockout mice, which exhibit poor motor coordination, greatly impaired learning and memory, and extensive axon swelling with numerous axon spheroids. Autophagic flux is defective and SQSTM1 (sequestosome-1)/p62 and ubiquitin-positive protein aggregates accumulate in neurons and swollen axons. Nes-Wdr45(fl/Y) mice recapitulate some hallmarks of BPAN, including cognitive impairment and defective axonal homeostasis, providing a model for revealing the disease pathogenesis of BPAN and also for investigating the possible role of autophagy in axon maintenance.

B cell autophagy mediates TLR7-dependent autoimmunity and inflammation

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease, defined by loss of B cell self-tolerance that results in production of antinuclear antibodies (ANA) and chronic inflammation. While the initiating events in lupus development are not well defined, overexpression of the RNA-recognizing toll-like receptor (TLR)7 has been linked to SLE in humans and mice. We postulated that autophagy plays an essential role in TLR7 activation of B cells for the induction of SLE by delivering RNA ligands to the endosomes, where this innate immune receptor resides. To test this hypothesis, we compared SLE development in Tlr7 transgenic (Tg) mice with or without B cell-specific ablation of autophagy (Cd19-Cre Atg5(f/f)). We observed that in the absence of B cell autophagy the 2 hallmarks of SLE, ANA and inflammation, were eliminated, thus curing these mice of lupus. This was also evident in the significantly extended survival of the autophagy-deficient mice compared to Tlr7.1 Tg mice. Furthermore, glomerulonephritis was ameliorated, and the serum levels of inflammatory cytokines in the knockout (KO) mice were indistinguishable from those of control mice. These data provide direct evidence that B cells require TLR7-dependent priming through an autophagy-dependent mechanism before autoimmunity is induced, thereafter involving many cell types. Surprisingly, hyper-IgM production persisted in Tlr7.1 Tg mice in the absence of autophagy, likely involving a different activation pathway than the production of autoantibodies. Furthermore, these mice still presented with anemia, but responded with a striking increase in extramedullary hematopoiesis (EMH), possibly due to the absence of pro-inflammatory cytokines.

Inactivation of SOCS3 in leptin receptor-expressing cells protects mice from diet-induced insulin resistance but does not prevent obesity

Therapies that improve leptin sensitivity have potential as an alternative treatment approach against obesity and related comorbidities. We investigated the effects of Socs3 gene ablation in different mouse models to understand the role of SOCS3 in the regulation of leptin sensitivity, diet-induced obesity (DIO) and glucose homeostasis. Neuronal deletion of SOCS3 partially prevented DIO and improved glucose homeostasis. Inactivation of SOCS3 only in LepR-expressing cells protected against leptin resistance induced by HFD, but did not prevent DIO. However, inactivation of SOCS3 in LepR-expressing cells protected mice from diet-induced insulin resistance by increasing hypothalamic expression of Katp channel subunits and c-Fos expression in POMC neurons. In summary, the regulation of leptin signaling by SOCS3 orchestrates diet-induced changes on glycemic control. These findings help to understand the molecular mechanisms linking obesity and type 2 diabetes, and highlight the potential of SOCS3 inhibitors as a promising therapeutic approach for the treatment of diabetes.

Opening of the mitochondrial permeability transition pore links mitochondrial dysfunction to insulin resistance in skeletal muscle

Insulin resistance is associated with mitochondrial dysfunction, but the mechanism by which mitochondria inhibit insulin-stimulated glucose uptake into the cytoplasm is unclear. The mitochondrial permeability transition pore (mPTP) is a protein complex that facilitates the exchange of molecules between the mitochondrial matrix and cytoplasm, and opening of the mPTP occurs in response to physiological stressors that are associated with insulin resistance. In this study, we investigated whether mPTP opening provides a link between mitochondrial dysfunction and insulin resistance by inhibiting the mPTP gatekeeper protein cyclophilin D (CypD) in vivo and in vitro. Mice lacking CypD were protected from high fat diet-induced glucose intolerance due to increased glucose uptake in skeletal muscle. The mitochondria in CypD knockout muscle were resistant to diet-induced swelling and had improved calcium retention capacity compared to controls; however, no changes were observed in muscle oxidative damage, insulin signaling, lipotoxic lipid accumulation or mitochondrial bioenergetics. In vitro, we tested 4 models of insulin resistance that are linked to mitochondrial dysfunction in cultured skeletal muscle cells including antimycin A, C2-ceramide, ferutinin, and palmitate. In all models, we observed that pharmacological inhibition of mPTP opening with the CypD inhibitor cyclosporin A was sufficient to prevent insulin resistance at the level of insulin-stimulated GLUT4 translocation to the plasma membrane. The protective effects of mPTP inhibition on insulin sensitivity were associated with improved mitochondrial calcium retention capacity but did not involve changes in insulin signaling both in vitro and in vivo. In sum, these data place the mPTP at a critical intersection between alterations in mitochondrial function and insulin resistance in skeletal muscle.

Portal hypertension in cirrhosis: Pathophysiological mechanisms and therapy

Portal hypertension, defined as increased pressure in the portal vein, develops as a consequence of increased intrahepatic vascular resistance due to the dysregulation of liver sinusoidal endothelial cells (LSECs) and hepatic stellate cells (HSCs), frequently arising from chronic liver diseases. Extrahepatic haemodynamic changes contribute to the aggravation of portal hypertension. The pathogenic complexity of portal hypertension and the unsuccessful translation of preclinical studies have impeded the development of effective therapeutics for patients with cirrhosis, while counteracting hepatic and extrahepatic mechanisms also pose a major obstacle to effective treatment. In this review article, we will discuss the following topics: i) cellular and molecular mechanisms of portal hypertension, focusing on dysregulation of LSECs, HSCs and hepatic microvascular thrombosis, as well as changes in the extrahepatic vasculature, since these are the major contributors to portal hypertension; ii) translational/clinical advances in our knowledge of portal hypertension; and iii) future directions.

Role of farnesoid X receptor and bile acids in alcoholic liver disease

Alcoholic liver disease (ALD) is one of the major causes of liver morbidity and mortality worldwide. Chronic alcohol consumption leads to development of liver pathogenesis encompassing steatosis, inflammation, fibrosis, cirrhosis, and in extreme cases, hepatocellular carcinoma. Moreover, ALD may also associate with cholestasis. Emerging evidence now suggests that farnesoid X receptor (FXR) and bile acids also play important roles in ALD. In this review, we discuss the effects of alcohol consumption on FXR, bile acids and gut microbiome as well as their impacts on ALD. Moreover, we summarize the findings on FXR, FoxO3a (forkhead box-containing protein class O3a) and PPARα (peroxisome proliferator-activated receptor alpha) in regulation of autophagy-related gene transcription program and liver injury in response to alcohol exposure.

N-cadherin-based adherens junction regulates the maintenance, proliferation, and differentiation of neural progenitor cells during development

This review addresses our current understanding of the regulatory mechanism by which N-cadherin, a classical cadherin, affects neural progenitor cells (NPCs) during development. N-cadherin is responsible for the integrity of adherens junctions (AJs), which develop in the sub-apical region of NPCs in the neural tube and brain cortex. The apical domain, which contains the sub-apical region, is involved in the switching from symmetric proliferative division to asymmetric neurogenic division of NPCs. In addition, N-cadherin-based AJ is deeply involved in the apico-basal polarity of NPCs and the regulation of Wnt-β-catenin, hedgehog (Hh), and Notch signaling. In this review, we discuss the roles of N-cadherin in the maintenance, proliferation, and differentiation of NPCs through components of AJ, β-catenin and αE-catenin.

Divergent roles of BECN1 in LC3 lipidation and autophagosomal function

BECN1/Beclin 1 is regarded as a critical component in the class III phosphatidylinositol 3-kinase (PtdIns3K) complex to trigger autophagy in mammalian cells. Despite its significant role in a number of cellular and physiological processes, the exact function of BECN1 in autophagy remains controversial. Here we created a BECN1 knockout human cell line using the TALEN technique. Surprisingly, the complete loss of BECN1 had little effect on LC3 (MAP1LC3B/LC3B) lipidation, and LC3B puncta resembling autophagosomes by fluorescence microscopy were still evident albeit significantly smaller than those in the wild-type cells. Electron microscopy (EM) analysis revealed that BECN1 deficiency led to malformed autophagosome-like structures containing multiple layers of membranes under amino acid starvation. We further confirmed that the PtdIns3K complex activity and autophagy flux were disrupted in BECN1^−/− cells. Our results demonstrate the essential role of BECN1 in the functional formation of autophagosomes, but not in LC3B lipidation.

The regulatory and modulatory roles of TRP family channels in malignant tumors and relevant therapeutic strategies

Transient receptor potential (TRP) channels are one primary type of calcium (Ca²⁺) permeable channels, and those relevant transmembrane and intracellular TRP channels were previously thought to be mainly associated with the regulation of cardiovascular and neuronal systems. Nowadays, however, accumulating evidence shows that those TRP channels are also responsible for tumorigenesis and progression, inducing tumor invasion and metastasis. However, the overall underlying mechanisms and possible signaling transduction pathways that TRP channels in malignant tumors might still remain elusive. Therefore, in this review, we focus on the linkage between TRP channels and the significant characteristics of tumors such as multi-drug resistance (MDR), metastasis, apoptosis, proliferation, immune surveillance evasion, and the alterations of relevant tumor micro-environment. Moreover, we also have discussed the expression of relevant TRP channels in various forms of cancer and the relevant inhibitors' efficacy. The chemo-sensitivity of the anti-cancer drugs of various acting mechanisms and the potential clinical applications are also presented. Furthermore, it would be enlightening to provide possible novel therapeutic approaches to counteract malignant tumors regarding the intervention of calcium channels of this type.

New insights of CYP1A in endogenous metabolism: a focus on single nucleotide polymorphisms and diseases

Cytochrome P450 1A (CYP1A), one of the major CYP subfamily in humans, not only metabolizes xenobiotics including clinical drugs and pollutants in the environment, but also mediates the biotransformation of important endogenous substances. In particular, some single nucleotide polymorphisms (SNPs) for CYP1A genes may affect the metabolic ability of endogenous substances, leading to some physiological or pathological changes in humans. This review first summarizes the metabolism of endogenous substances by CYP1A, and then introduces the research progress of CYP1A SNPs, especially the research related to human diseases. Finally, the relationship between SNPs and diseases is discussed. In addition, potential animal models for CYP1A gene editing are summarized. In conclusion, CYP1A plays an important role in maintaining the health in the body.

Inhibiting heat-shock protein 90 reverses sensory hypoalgesia in diabetic mice

Increasing the expression of Hsp70 (heat-shock protein 70) can inhibit sensory neuron degeneration after axotomy. Since the onset of DPN (diabetic peripheral neuropathy) is associated with the gradual decline of sensory neuron function, we evaluated whether increasing Hsp70 was sufficient to improve several indices of neuronal function. Hsp90 is the master regulator of the heat-shock response and its inhibition can up-regulate Hsp70. KU-32 (N-{7-[(2R,3R,4S,5R)-3,4-dihydroxy-5-methoxy-6,6-dimethyl-tetrahydro-2H-pyran-2-yloxy]-8-methyl-2-oxo-2H-chromen-3-yl}acetamide) was developed as a novel, novobiocin-based, C-terminal inhibitor of Hsp90 whose ability to increase Hsp70 expression is linked to the presence of an acetamide substitution of the prenylated benzamide moiety of novobiocin. KU-32 protected against glucose-induced death of embryonic DRG (dorsal root ganglia) neurons cultured for 3 days in vitro. Similarly, KU-32 significantly decreased neuregulin 1-induced degeneration of myelinated Schwann cell DRG neuron co-cultures prepared from WT (wild-type) mice. This protection was lost if the co-cultures were prepared from Hsp70.1 and Hsp70.3 KO (knockout) mice. KU-32 is readily bioavailable and was administered once a week for 6 weeks at a dose of 20 mg/kg to WT and Hsp70 KO mice that had been rendered diabetic with streptozotocin for 12 weeks. After 12 weeks of diabetes, both WT and Hsp70 KO mice developed deficits in NCV (nerve conduction velocity) and a sensory hypoalgesia. Although KU-32 did not improve glucose levels, HbA1c (glycated haemoglobin) or insulin levels, it reversed the NCV and sensory deficits in WT but not Hsp70 KO mice. These studies provide the first evidence that targeting molecular chaperones reverses the sensory hypoalgesia associated with DPN.

Notoginsenoside Ft1 acts as a TGR5 agonist but FXR antagonist to alleviate high fat diet-induced obesity and insulin resistance in mice

Obesity and its associated complications are highly related to a current public health crisis around the world. A growing body of evidence has indicated that G-protein coupled bile acid (BA) receptor TGR5 (also known as Gpbar-1) is a potential drug target to treat obesity and associated metabolic disorders. We have identified notoginsenoside Ft1 (Ft1) from Panax notoginseng as an agonist of TGR5 in vitro. However, the pharmacological effects of Ft1 on diet-induced obese (DIO) mice and the underlying mechanisms are still elusive. Here we show that Ft1 (100 mg/100 diet) increased adipose lipolysis, promoted fat browning in inguinal adipose tissue and induced glucagon-like peptide-1 (GLP-1) secretion in the ileum of wild type but not Tgr5 -/- obese mice. In addition, Ft1 elevated serum free and taurine-conjugated bile acids (BAs) by antagonizing Fxr transcriptional activities in the ileum to activate Tgr5 in the adipose tissues. The metabolic benefits of Ft1 were abolished in Cyp27a1 -/- mice which have much lower BA levels. These results identify Ft1 as a single compound with opposite activities on two key BA receptors to alleviate high fat diet-induced obesity and insulin resistance in mice.

Cftr Modulates Wnt/β-Catenin Signaling and Stem Cell Proliferation in Murine Intestine

BACKGROUND & AIMS

Cystic fibrosis (CF) patients and CF mouse models have increased risk for gastrointestinal tumors. CF mice show augmented intestinal proliferation of unknown etiology and an altered intestinal environment. We examined the role of the cystic fibrosis transmembrane conductance regulator (Cftr) in Wnt/β-catenin signaling, stem cell proliferation, and its functional expression in the active intestinal stem cell (ISC) population. Dysregulation of intracellular pH (pH_i) in CF ISCs was investigated for facilitation of Wnt/β-catenin signaling.

METHODS

Crypt epithelia from wild-type (WT) and CF mice were compared ex vivo and in intestinal organoids (enteroids) for proliferation and Wnt/β-catenin signaling by standard assays. Cftr in ISCs was assessed by immunoblot of sorted Sox9 ^{enhanced green fluorescent protein(EGFP)} intestinal epithelia and pH_i regulation by confocal microfluorimetry of leucine-rich G-protein-coupled receptor 5 ISCs. Plasma membrane association of the Wnt transducer Dishevelled 2 (Dvl2) was assessed by fluorescence imaging of live enteroids from WT and CF mice crossed with Dvl2-EGFP/ACTB-tdTomato,-EGFP)Luo/J (Rosa^mT/mG) mice.

RESULTS

Relative to WT, CF intestinal crypts showed an ∼30% increase in epithelial and Lgr5+ ISC proliferation and increased Wnt/β-catenin signaling. Cftr was expressed in Sox9^EGFPLo ISCs and loss of Cftr induced an alkaline pH_i in ISCs. CF crypt-base columnar cells showed a generalized increase in plasma membrane Dvl2-EGFP association as compared with WT. Dvl2-EGFP membrane association was charge- and pH-dependent and increased in WT crypt-base columnar cells by Cftr inhibition.

CONCLUSIONS

CF intestine shows increased ISC proliferation and Wnt/β-catenin signaling. Loss of Cftr increases pH_i in ISCs, which stabilizes the plasma membrane association of the Wnt transducer Dvl, likely facilitating Wnt/β-catenin signaling. Absence of Cftr-dependent suppression of ISC proliferation in the CF intestine may contribute to increased risk for intestinal tumors.

Novel Adult-Onset Systolic Cardiomyopathy Due to MYH7 E848G Mutation in Patient-Derived Induced Pluripotent Stem Cells

A novel myosin heavy chain 7 mutation (E848G) identified in a familial cardiomyopathy was studied in patient-specific induced pluripotent stem cell-derived cardiomyocytes. The cardiomyopathic human induced pluripotent stem cell-derived cardiomyocytes exhibited reduced contractile function as single cells and engineered heart tissues, and genome-edited isogenic cells confirmed the pathogenic nature of the E848G mutation. Reduced contractility may result from impaired interaction between myosin heavy chain 7 and cardiac myosin binding protein C.

Guo G. Farnesoid X receptor, the bile acid sensing nuclear receptor, in liver regeneration

The liver is unique in regenerative potential, which could recover the lost mass and function after injury from ischemia and resection. The underlying molecular mechanisms of liver regeneration have been extensively studied in the past using the partial hepatectomy (PH) model in rodents, where 2/3 PH is carried out by removing two lobes. The whole process of liver regeneration is complicated, orchestrated event involving a network of connected interactions, which still remain fully elusive. Bile acids (BAs) are ligands of farnesoid X receptor (FXR), a nuclear receptor of ligand-activated transcription factor. FXR has been shown to be highly involved in liver regeneration. BAs and FXR not only interact with each other but also regulate various downstream targets independently during liver regeneration. Moreover, recent findings suggest that tissue-specific FXR also contributes to liver regeneration significantly. These novel findings suggest that FXR has much broader role than regulating BA, cholesterol, lipid and glucose metabolism. Therefore, these researches highlight FXR as an important pharmaceutical target for potential use of FXR ligands to regulate liver regeneration in clinic. This review focuses on the roles of BAs and FXR in liver regeneration and the current underlying molecular mechanisms which contribute to liver regeneration.

Activation of Myofibroblast TRPA1 by Steroids and Pirfenidone Ameliorates Fibrosis in Experimental Crohn's Disease

BACKGROUND & AIMS

The transient receptor potential ankyrin 1 (TRPA1) channel is highly expressed in the intestinal lamina propria, but its contribution to gut physiology/pathophysiology is unclear. Here, we evaluated the function of myofibroblast TRPA1 channels in intestinal remodeling.

METHODS

An intestinal myofibroblast cell line (InMyoFibs) was stimulated by transforming growth factor-β1 to induce in vitro fibrosis. Trpa1 knockout mice were generated using the Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9) system. A murine chronic colitis model was established by weekly intrarectal trinitrobenzene sulfonic acid (TNBS) administration. Samples from the intestines of Crohn's disease (CD) patients were used for pathologic staining and quantitative analyses.

RESULTS

In InMyoFibs, TRPA1 showed the highest expression among TRP family members. In TNBS chronic colitis model mice, the extents of inflammation and fibrotic changes were more prominent in TRPA1^-/- knockout than in wild-type mice. One-week enema administration of prednisolone suppressed fibrotic lesions in wild-type mice, but not in TRPA1 knockout mice. Steroids and pirfenidone induced Ca²⁺ influx in InMyoFibs, which was antagonized by the selective TRPA1 channel blocker HC-030031. Steroids and pirfenidone counteracted transforming growth factor-β1-induced expression of heat shock protein 47, type 1 collagen, and α-smooth muscle actin, and reduced Smad-2 phosphorylation and myocardin expression in InMyoFibs. In stenotic intestinal regions of CD patients, TRPA1 expression was increased significantly. TRPA1/heat shock protein 47 double-positive cells accumulated in the stenotic intestinal regions of both CD patients and TNBS-treated mice.

CONCLUSIONS

TRPA1, in addition to its anti-inflammatory actions, may protect against intestinal fibrosis, thus being a novel therapeutic target for highly incurable inflammatory/fibrotic disorders.

Inhibition of citrate cotransporter Slc13a5/mINDY by RNAi improves hepatic insulin sensitivity and prevents diet-induced non-alcoholic fatty liver disease in mice

Objective

Non-alcoholic fatty liver disease is a world-wide health concern and risk factor for cardio-metabolic diseases. Citrate uptake modifies intracellular hepatic energy metabolism and is controlled by the conserved sodium-dicarboxylate cotransporter solute carrier family 13 member 5 (SLC13A5, mammalian homolog of INDY: mINDY). In Drosophila melanogaster and Caenorhabditis elegans INDY reduction decreased whole-body lipid accumulation. Genetic deletion of Slc13a5 in mice protected from diet-induced adiposity and insulin resistance. We hypothesized that inducible hepatic mINDY inhibition should prevent the development of fatty liver and hepatic insulin resistance.

Methods

Adult C57BL/6J mice were fed a Western diet (60% kcal from fat, 21% kcal from carbohydrate) ad libitum. Knockdown of mINDY was induced by weekly injection of a chemically modified, liver-selective siRNA for 8 weeks. Mice were metabolically characterized and the effect of mINDY suppression on glucose tolerance as well as insulin sensitivity was assessed with an ipGTT and a hyperinsulinemic-euglycemic clamp. Hepatic lipid accumulation was determined by biochemical measurements and histochemistry.

Results

Within the 8 week intervention, hepatic mINDY expression was suppressed by a liver-selective siRNA by over 60%. mINDY knockdown improved hepatic insulin sensitivity (i.e. insulin-induced suppression of endogenous glucose production) of C57BL/6J mice in the hyperinsulinemic-euglycemic clamp. Moreover, the siRNA-mediated mINDY inhibition prevented neutral lipid storage and triglyceride accumulation in the liver, while we found no effect on body weight.

Conclusions

We show that inducible mINDY inhibition improved hepatic insulin sensitivity and prevented diet-induced non-alcoholic fatty liver disease in adult C57BL6/J mice. These effects did not depend on changes of body weight or body composition.

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mINDY/Slc13a5 knockdown was induced by liver-selective siRNA in mice.

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Liver-selective knockdown of mINDY improved hepatic insulin sensitivity.

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Liver-selective knockdown of mINDY prevented steatosis hepatis.