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Over past decades, targeted therapies and immunotherapy have improved survival and reduced the morbidity of patients with BRAF-mutated melanoma. However, drug resistance and relapse hinder overall success. Therefore, there is an urgent need for novel compounds with therapeutic efficacy against BRAF-melanoma. This prompted us to investigate the antiproliferative profile of a tachykinin-peptide from the Octopus kaurna, Octpep-1 in melanoma.We evaluated the cytotoxicity of Octpep-1 by MTT assay. Mechanistic insights on viability and cellular damage caused by Octpep-1 were gained via flow cytometry and bioenergetics. Structural and pharmacological characterization was conducted by molecular modelling, molecular biology, CRISPR/Cas9 technology, high-throughput mRNA and calcium flux analysis. In vivo efficacy was validated in two independent xerograph animal models (mice and zebrafish).Octpep-1 selectively reduced the proliferative capacity of human melanoma BRAFWe unravel the intrinsic anti-tumoural properties of a tachykinin peptide. This peptide mediates the selective cytotoxicity in BRAF-mutated melanoma in vitro and prevents tumour progression in vivo, providing a foundation for a therapy against melanoma.

Background and Aims Growth hormone (GH) is important for liver regeneration after partial hepatectomy (PHx). We investigated this process in C57BL/6 mice that express different forms of the GH receptor (GHR) with deletions in key signaling domains. Approach and Results PHx was performed on C57BL/6 mice lacking GHR (Ghr −/−), disabled for all GH‐dependent Janus kinase 2 signaling (Box1 −/−), or lacking only GH‐dependent signal transducer and activator of transcription 5 (STAT5) signaling (Ghr391 −/−), and wild‐type littermates. C57BL/6 Ghr −/−mice showed striking mortality within 48 hours after PHx, whereas Box1 −/− or Ghr391 −/− mice survived with normal liver regeneration. Ghr −/− mortality was associated with increased apoptosis and elevated natural killer/natural killer T cell and macrophage cell markers. We identified H2‐Bl, a key immunotolerance protein, which is up‐regulated by PHx through a GH‐mediated, Janus kinase 2–independent, SRC family kinase–dependent pathway. GH treatment was confirmed to up‐regulate expression of the human homolog of H2‐Bl (human leukocyte antigen G [HLA‐G]) in primary human hepatocytes and in the serum of GH‐deficient patients. We find that injury‐associated innate immune attack by natural killer/natural killer T cell and macrophage cells are instrumental in the failure of liver regeneration, and this can be overcome in Ghr −/− mice by adenoviral delivery of H2‐Bl or by infusion of HLA‐G protein. Further, H2‐Bl knockdown in wild‐type C57BL/6 mice showed elevated markers of inflammation after PHx, whereas Ghr −/− backcrossed on a strain with high endogenous H2‐Bl expression showed a high rate of survival following PHx. Conclusions GH induction of H2‐Bl expression is crucial for reducing innate immune‐mediated apoptosis and promoting survival after PHx in C57BL/6 mice. Treatment with HLA‐G may lead to improved clinical outcomes following liver surgery or transplantation.

Current diagnostic methods for the diagnosis of Cystic fibrosis (CF)-associated liver disease (CFLD) are non-specific and assessment of disease progression is difficult prior to the advent of advanced disease with portal hypertension. This study investigated the potential of Supersonic shear-wave elastography (SSWE) to non-invasively detect CFLD and assess hepatic fibrosis severity in children with CF.125 children were enrolled in this study including CFLD (n = 55), CF patients with no evidence of liver disease (CFnoLD = 41) and controls (n = 29). CFLD was diagnosed using clinical, biochemical and imaging best-practice guidelines. Advanced CFLD was established by the presence of portal hypertension and/or macronodular cirrhosis on ultrasound. Liver stiffness measurements (LSM) were acquired using SSWE and diagnostic performance for CFLD detection was evaluated alone or combined with aspartate aminotransferase-to-platelet ratio index (APRI).LSM was significantly higher in CFLD (8.1 kPa, IQR = 6.7-11.9) versus CFnoLD (6.2 kPa, IQR = 5.6-7.0; P 0.0001) and Controls (5.3 kPa, IQR = 4.9-5.8; P 0.0001). LSM was also increased in CFnoLD versus Controls (P = 0.0192). Receiver Operating Characteristic (ROC) curve analysis demonstrated good diagnostic accuracy for LSM in detecting CFLD using a cut-off = 6.85 kPa with an AUC = 0.79 (Sensitivity = 75%, Specificity = 71%, P 0.0001). APRI also discriminated CFLD (AUC = 0.74, P = 0.004). Classification and regression tree modelling combining LSM + APRI showed 14.8 times greater odds of accurately predicting CFLD (AUC = 0.84). The diagnostic accuracy of SSWE for discriminating advanced disease was excellent with a cut-off = 9.05 kPa (AUC = 0.95; P 0.0001).SSWE-determined LSM shows good diagnostic accuracy in detecting CFLD in children, which was improved when combined with APRI. SSWE alone discriminates advanced CFLD.

Summary Excessive consumption of high-fructose diets is associated with insulin resistance, obesity, and non-alcoholic fatty liver disease (NAFLD). However, fructose differentially affects hepatic regulation of lipogenesis in males and females. Hence, additional studies are necessary in order to find strategies taking gender disparities in fructose-induced liver damage into consideration. Although the eighth member of facilitated glucose transporters (GLUT8) has been linked to fructose-induced macrosteatosis in female mice, its contribution to the inflammatory state of NAFLD remains to be elucidated. Combining pharmacological, biochemical, and proteomic approaches, we evaluated the preventive effect of targeted liver GLUT8 silencing on liver injury in a mice female fructose-induced non-alcoholic steatohepatitis female mouse model. Liver GLUT8-knockdown attenuated fructose-induced ER stress, recovered liver inflammation, and dramatically reduced fatty acid content, in part, via the omega oxidation. Therefore, this study links GLUT8 with liver inflammatory response and suggests GLUT8 as a potential target for the prevention of NAFLD., Graphical abstract, Highlights • Liver injury induced by high-fat or fructose diet occurs through different mechanisms • Fructose increases inflammatory responses and activates pathological ER stress • Liver-specific GLUT8 knockdown ameliorates fructose-induced injury • GLUT8 knockdown increased lipid mobilization partially driven by omega oxidation, Biological sciences; physiology; endocrinology

Melanoma is the main cause of skin cancer deaths, with special emphasis in those cases carrying BRAF mutations that trigger the mitogen-activated protein kinases (MAPK) signaling and unrestrained cell proliferation in the absence of mitogens. Current therapies targeting MAPK are hindered by drug resistance and relapse that rely on metabolic rewiring and Akt activation. To identify new drug candidates against melanoma, we investigated the molecular mechanism of action of the Octopus Kaurna-derived peptide, Octpep-1, in human BRAF(V600E) melanoma cells using proteomics and RNAseq coupled with metabolic analysis. Fluorescence microscopy verified that Octpep-1 tagged with fluorescein enters MM96L and NFF cells and distributes preferentially in the perinuclear area of MM96L cells. Proteomics and RNAseq revealed that Octpep-1 targets PI3K/AKT/mTOR signaling in MM96L cells. In addition, Octpep-1 combined with rapamycin (mTORC1 inhibitor) or LY3214996 (ERK1/2 inhibitor) augmented the cytotoxicity against BRAF(V600E) melanoma cells in comparison with the inhibitors or Octpep-1 alone. Octpep-1-treated MM96L cells displayed reduced glycolysis and mitochondrial respiration when combined with LY3214996. Altogether these data support Octpep-1 as an optimal candidate in combination therapies for melanoma BRAF(V600E) mutations.

Snakes of the genera Pseudocerastes and Eristicophis (Viperidae: Viperinae) are known as the desert vipers due to their association with the arid environments of the Middle East. These species have received limited research attention and little is known about their venom or ecology. In this study, a comprehensive analysis of desert viper venoms was conducted by visualising the venom proteomes via gel electrophoresis and assessing the crude venoms for their cytotoxic, haemotoxic, and neurotoxic properties. Plasmas sourced from human, toad, and chicken were used as models to assess possible prey-linked venom activity. The venoms demonstrated substantial divergence in composition and bioactivity across all experiments. Pseudocerastes urarachnoides venom activated human coagulation factors X and prothrombin and demonstrated potent procoagulant activity in human, toad, and chicken plasmas, in stark contrast to the potent neurotoxic venom of P. fieldi. The venom of E. macmahonii also induced coagulation, though this did not appear to be via the activation of factor X or prothrombin. The coagulant properties of P. fieldi and P. persicus venoms varied among plasmas, demonstrating strong anticoagulant activity in the amphibian and human plasmas but no significant effect in that of bird. This is conjectured to reflect prey-specific toxin activity, though further ecological studies are required to confirm any dietary associations. This study reinforces the notion that phylogenetic relatedness of snakes cannot readily predict venom protein composition or function. The significant venom variation between these species raises serious concerns regarding antivenom paraspecificity. Future assessment of antivenom is crucial.

We would like to provide information that address the Letter to Editors submitted on 17 July 2020 by Lin and Yan regarding our publication.(1) We have provided a response to each point raised by the authors below.

Understanding the mechanisms of liver injury, hepatic fibrosis, and cirrhosis that underlie chronic liver diseases (i.e., viral hepatitis, non-alcoholic fatty liver disease, metabolic liver disease, and liver cancer) requires experimental manipulation of animal models and in vitro cell cultures. Both techniques have limitations, such as the requirement of large numbers of animals for in vivo manipulation. However, in vitro cell cultures do not reproduce the structure and function of the multicellular hepatic environment. The use of precision-cut liver slices is a technique in which uniform slices of viable mouse liver are maintained in laboratory tissue culture for experimental manipulation. This technique occupies an experimental niche that exists between animal studies and in vitro cell culture methods. The presented protocol describes a straightforward and reliable method to isolate and culture precision-cut liver slices from mice. As an application of this technique, ex vivo liver slices are treated with bile acids to simulate cholestatic liver injury and ultimately assess the mechanisms of hepatic fibrogenesis.

Cystic fibrosis (CF)-associated liver disease (CFLD) is a hepatobiliary complication of CF. Current diagnostic modalities rely on non-specific assessments, while liver biopsy is the gold standard to assess severity of fibrosis. MicroRNAs (miRNAs) regulate liver disease pathogenesis and are proposed as diagnostic biomarkers. We investigated the combined use of serum miRNAs and aspartate aminotransferase to platelet ratio (APRI) to diagnose and assess CFLD severity. This was a cross-sectional cohort study of the circulatory miRNA signature of 124 children grouped by clinical, biochemical and imaging assessments as follows: CFLD (n=44), CF patients with no evidence of liver disease (CFnoLD, n=40) and healthy controls (n=40). Serum miRNAs were analysed using miRNA-sequencing. Selected differentially expressed serum miRNA candidates were further validated by qRT-PCR and statistical analysis performed to evaluate utility to predict CFLD and fibrosis severity validated by liver biopsy, alone or in combination with APRI. Serum miR-122-5p, miR-365a-3p and miR-34a-5p levels were elevated in CFLD compared to CFnoLD, while miR-142-3p and let-7g-5p were downregulated in CFLD compared to CFnoLD. Logistic regression analysis combining miR-365a-3p, miR-142-3p and let-7g-5p with APRI showed 21 times greater odds of accurately predicting liver disease in CF with an AUROC=0.91 (sensitivity=83%, specificity=92%; P We identified a distinct circulatory miRNA profile in pediatric CFLD with potential to accurately discriminate liver disease and fibrosis severity in children with CF. This article is protected by copyright. All rights reserved.

Consistent with their diverse pharmacology, peptides derived from venomous animals have been developed as drugs to treat disorders as diverse as hypertension, diabetes and chronic pain. Melanoma has a poor prognosis due in part to its metastatic capacity, warranting further development of novel targeted therapies. This prompted us to examine the anti-melanoma activity of the spider peptides gomesin (AgGom) and a gomesin-like homolog (HiGom). AgGom and HiGom dose-dependently reduced the viability and proliferation of melanoma cells whereas it had no deleterious effects on non-transformed neonatal foreskin fibroblasts. Concordantly, gomesin-treated melanoma cells showed a reduced G0/G1 cell population. AgGom and HiGom compromised proliferation of melanoma cells via activation of the p53/p21 cell cycle check-point axis and the Hippo signaling cascade, together with attenuation of the MAP kinase pathway. We show that both gomesin peptides exhibit antitumoral activity in melanoma AVATAR-zebrafish xenograft tumors and that HiGom also reduces tumour progression in a melanoma xenograft mouse model. Taken together, our data highlight the potential of gomesin for development as a novel melanoma-targeted therapy This work was supported by Perpetual IMPACT Grant IDIPAP2015/1585 (to J.J.M.), Discovery Grants DP1095728 (to J.J.M.) and DP130103813 (to G.F.K.) from the Australian Research Council, and by QIMR Berghofer Medical Research Institute crowd funding and salary support (to M.P.I.). M.P.I. is a “Marie Curie” AMAROUT Fellow. M.A.F.R. is a fellow supported by the Talent Program from the Madrid Government of Spain (Grant No. T1-BIO-1854 to M.A.F.R.). J.J.M. is supported by a NHMRC Career Development Fellowship (APP1131732) and G.F.K. by a NHMRC Principal Research Fellowship (APP1136889) SI

Devil facial tumor disease (DFTD) and its lack of available therapies are propelling the Tasmanian devil population toward extinction. This study demonstrates that cholesterol homeostasis and carbohydrate energy metabolism sustain the proliferation of DFTD cells in a cell-type-dependent manner. In addition, we show that the liver-X nuclear receptor-β (LXRβ), a major cholesterol cellular sensor, and its natural ligand 24S-hydroxycholesterol promote the proliferation of DFTD cells via a metabolic switch toward aerobic glycolysis. As a proof of concept of the role of cholesterol homeostasis on DFTD proliferation, we show that atorvastatin, an FDA-approved statin-drug subtype used against human cardiovascular diseases that inhibits cholesterol synthesis, shuts down DFTD energy metabolism and prevents tumor growth in an in vivo DFTD-xenograft model. In conclusion, we show that intervention against cholesterol homeostasis and carbohydrate-dependent energy metabolism by atorvastatin constitutes a feasible biochemical treatment against DFTD, which may assist in the conservation of the Tasmanian devil.

Snakes of the genera Pseudocerastes and Eristicophis (Viperidae: Viperinae) are known as the desert vipers due to their association with the arid environments of the Middle East. These species have received limited research attention and little is known about their venom or ecology. In this study, a comprehensive analysis of desert viper venoms was conducted by visualising the venom proteomes via gel electrophoresis and assessing the crude venoms for their cytotoxic, haemotoxic, and neurotoxic properties. Plasmas sourced from human, toad, and chicken were used as models to assess possible prey-linked venom activity. The venoms demonstrated substantial divergence in composition and bioactivity across all experiments. Pseudocerastes urarachnoides venom activated human coagulation factors X and prothrombin and demonstrated potent procoagulant activity in human, toad, and chicken plasmas, in stark contrast to the potent neurotoxic venom of P. fieldi. The venom of E. macmahonii also induced coagulation, though this did not appear to be via the activation of factor X or prothrombin. The coagulant properties of P. fieldi and P. persicus venoms varied among plasmas, demonstrating strong anticoagulant activity in the amphibian and human plasmas but no significant effect in that of bird. This is conjectured to reflect prey-specific toxin activity, though further ecological studies are required to confirm any dietary associations. This study reinforces the notion that phylogenetic relatedness of snakes cannot readily predict venom protein composition or function. The significant venom variation between these species raises serious concerns regarding antivenom paraspecificity. Future assessment of antivenom is crucial.

Since its discovery twenty-five years ago, the fat-derived hormone leptin has provided a revolutionary framework for studying the physiological role of adipose tissue as an endocrine organ. Leptin exerts pleiotropic effects on many metabolic pathways and is tightly connected with the liver, the major player in systemic metabolism. As a consequence, understanding the metabolic and hormonal interplay between the liver and adipose tissue could provide us with new therapeutic targets for some chronic liver diseases, an increasing problem worldwide. In this review, we assess relevant literature regarding the main metabolic effects of leptin on the liver, by direct regulation or through the central nervous system (CNS). We draw special attention to the contribution of leptin to the non-alcoholic fatty liver disease (NAFLD) pathogenesis and its progression to more advanced stages of the disease as non-alcoholic steatohepatitis (NASH). Likewise, we describe the contribution of leptin to the liver regeneration process after partial hepatectomy, the mainstay of treatment for certain hepatic malignant tumors M.G.N. is recipient of “Juan de la Cierva-Incorporación” fellowship (IJCI-2017-32606) from Ministerio de Ciencia, Innovación y Universidades, Spain. This work was supported by grants from FEDER/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación (CD: BFU2017-87721) and the TALENTO Program from the Madrid Government (MAFR 2016/T1- BIO-1854). Financial support from the Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2019-2022- ED431G 2019/02) and the European Union (European Regional Development Fund—ERDF), is gratefully acknowledged. Centro de Investigación Biomédica en Red (CIBER) de Fisiopatología de la Obesidad y Nutrición (CIBERobn) is an initiative of the Instituto de Salud Carlos III (ISCIII) of Spain, which is supported by FEDER funds (EU) SI

The Tasmanian devil faces extinction due to devil facial tumour disease (DFTD), a highly transmittable clonal form of cancer without available treatment. In this study, we report the cell-autonomous antiproliferative and cytotoxic activities exhibited by the spider peptide gomesin (AgGom) and gomesin-like homologue (HiGom) in DFTD cells. Mechanistically, both peptides caused a significant reduction at G0/G1 phase, in correlation with an augmented expression of the cell cycle inhibitory proteins p53, p27, p21, necrosis, exacerbated generation of reactive oxygen species and diminished mitochondrial membrane potential, all hallmarks of cellular stress. The screening of a novel panel of AgGom-analogues revealed that, unlike changes in the hydrophobicity and electrostatic surface, the cytotoxic potential of the gomesin analogues in DFTD cells lies on specific arginine substitutions in the eight and nine positions and alanine replacement in three, five and 12 positions. In conclusion, the evidence supports gomesin as a potential antiproliferative compound against DFTD disease.

Background and Purpose Monocyte-derived macrophages are critical in the development of atherosclerosis and can adopt a wide range of functional phenotypes depending on their surrounding milieu. High-density lipoproteins (HDLs) have many cardio-protective properties including potent anti-inflammatory effects. We investigated the effects of HDL on human macrophage phenotype and the mechanisms by which these occur. Experimental Approach Human blood monocytes were differentiated into macrophages in the presence or absence of HDL and were then induced to either an inflammatory macrophage (M1) or anti-inflammatory macrophage (M2) phenotype using LPS and IFN-γ or IL-4, respectively. Key Results HDL inhibited the induction of macrophages to an M1-phenotype, as evidenced by a decrease in the expression of M1-specific cell surface markers CD192 and CD64, as well as M1-associated inflammatory genes TNF-α, IL-6 and MCP-1 (CCL2). HDL also inhibited M1 function by reducing the production of ROS. In contrast, HDL had no effect on macrophage induction to the M2-phenotype. Similarly, methyl-β-cyclodextrin, a non-specific cholesterol acceptor also suppressed the induction of M1 suggesting that cholesterol efflux is important in this process. Furthermore, HDL decreased membrane caveolin-1 in M1 macrophages. We confirmed that caveolin-1 is required for HDL to inhibit M1 induction as bone marrow-derived macrophages from caveolin-1 knockout mice continued to polarize into M1-phenotype despite the presence of HDL. Moreover, HDL decreased ERK1/2 and STAT3 phosphorylation in M1 macrophages. Conclusions and Implications We concluded that HDL reduces the induction of macrophages to the inflammatory M1-phenotype via redistribution of caveolin-1, preventing the activation of ERK1/2 and STAT3. Linked Articles This article is part of a themed section on Inflammation: maladies, models, mechanisms and molecules. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2016.173.issue-4

The caveolar membrane microdomain plays an integral role in stabilizing the muscle fiber surface in mice and zebrafish., Dysfunction of caveolae is involved in human muscle disease, although the underlying molecular mechanisms remain unclear. In this paper, we have functionally characterized mouse and zebrafish models of caveolae-associated muscle disease. Using electron tomography, we quantitatively defined the unique three-dimensional membrane architecture of the mature muscle surface. Caveolae occupied around 50% of the sarcolemmal area predominantly assembled into multilobed rosettes. These rosettes were preferentially disassembled in response to increased membrane tension. Caveola-deficient cavin-1−/− muscle fibers showed a striking loss of sarcolemmal organization, aberrant T-tubule structures, and increased sensitivity to membrane tension, which was rescued by muscle-specific Cavin-1 reexpression. In vivo imaging of live zebrafish embryos revealed that loss of muscle-specific Cavin-1 or expression of a dystrophy-associated Caveolin-3 mutant both led to sarcolemmal damage but only in response to vigorous muscle activity. Our findings define a conserved and critical role in mechanoprotection for the unique membrane architecture generated by the caveolin–cavin system.

Cystic fibrosis liver disease (CFLD) in children causes progressive fibrosis leading to biliary cirrhosis; however, its cause(s) and early pathogenesis are unclear. We hypothesized that a bile acid-induced ductular reaction (DR) drives fibrogenesis. The DR was evaluated by cytokeratin-7 immunohistochemistry in liver biopsies, staged for fibrosis, from 60 children with CFLD, and it demonstrated that the DR was significantly correlated with hepatic fibrosis stage and biliary taurocholate levels. To examine the mechanisms involved in DR induction, liver progenitor cells (LPCs) were treated with taurocholate, and key events in DR evolution were assessed: LPC proliferation, LPC biliary differentiation, and hepatic stellate cell (HSC) chemotaxis. Taurocholate induced a time-dependent increase in LPC proliferation and expression of genes associated with cholangiocyte differentiation (cytokeratin 19, connexin 43, integrin β4, and γ-glutamyltranspeptidase), whereas the hepatocyte specification marker HNF4α was suppressed. Functional cholangiocyte differentiation was demonstrated via increased acetylated α-tubulin and SOX9 proteins, the number of primary cilia

Herbivorous turtle, Chelonia mydas, inhabiting the south China Sea and breeding in Peninsular Malaysia, and Natator depressus, a carnivorous turtle inhabiting the Great Barrier Reef and breeding at Curtis Island in Queensland, Australia, differ both in diet and life history. Analysis of plasma metabolites levels and six sex steroid hormones during the peak of their nesting season in both species showed hormonal and metabolite variations. When compared with results from other studies progesterone levels were the highest whereas dihydrotestosterone was the plasma steroid hormone present at the lowest concentration in both C. mydas and N. depressus plasma. Interestingly, oestrone was observed at relatively high concentrations in comparison to oestradiol levels recorded in previous studies suggesting that it plays a significant role in nesting turtles. Also, hormonal correlations between the studied species indicate unique physiological interactions during nesting. Pearson correlation analysis showed that in N. depressus the time of oviposition was associated with elevations in both plasma corticosterone and oestrone levels. Therefore, we conclude that corticosterone and oestrone may influence nesting behaviour and physiology in N. depressus. To summarise, these two nesting turtle species can be distinguished based on the hormonal profile of oestrone, progesterone, and testosterone using discriminant analysis.

Caveolae transduce mechanical stress into plasma membrane lipid alterations that disrupt Ras organization in an isoform-specific manner and modulate downstream signal transduction., The molecular mechanisms whereby caveolae exert control over cellular signaling have to date remained elusive. We have therefore explored the role caveolae play in modulating Ras signaling. Lipidomic and gene array analyses revealed that caveolin-1 (CAV1) deficiency results in altered cellular lipid composition, and plasma membrane (PM) phosphatidylserine distribution. These changes correlated with increased K-Ras expression and extensive isoform-specific perturbation of Ras spatial organization: in CAV1-deficient cells K-RasG12V nanoclustering and MAPK activation were enhanced, whereas GTP-dependent lateral segregation of H-Ras was abolished resulting in compromised signal output from H-RasG12V nanoclusters. These changes in Ras nanoclustering were phenocopied by the down-regulation of Cavin1, another crucial caveolar structural component, and by acute loss of caveolae in response to increased osmotic pressure. Thus, we postulate that caveolae remotely regulate Ras nanoclustering and signal transduction by controlling PM organization. Similarly, caveolae transduce mechanical stress into PM lipid alterations that, in turn, modulate Ras PM organization.

SummaryCaveolae and caveolin-1 (CAV1) have been linked to several cellular functions. However, a model explaining their roles in mammalian tissues in vivo is lacking. Unbiased expression profiling in several tissues and cell types identified lipid metabolism as the main target affected by CAV1 deficiency. CAV1−/− mice exhibited impaired hepatic peroxisome proliferator-activated receptor α (PPARα)-dependent oxidative fatty acid metabolism and ketogenesis. Similar results were recapitulated in CAV1-deficient AML12 hepatocytes, suggesting at least a partial cell-autonomous role of hepatocyte CAV1 in metabolic adaptation to fasting. Finally, our experiments suggest that the hepatic phenotypes observed in CAV1−/− mice involve impaired PPARα ligand signaling and attenuated bile acid and FXRα signaling. These results demonstrate the significance of CAV1 in (1) hepatic lipid homeostasis and (2) nuclear hormone receptor (PPARα, FXRα, and SHP) and bile acid signaling.

Caveolin-1 (CAV1), the structural protein of caveolae in the plasma membrane, has emerged as a regulator of liver function. CAV1 modulates several molecular pathways leading to the regulation of hepatic lipid accumulation, lipid and glucose metabolism, mitochondrial biology, and hepatocyte proliferation. CAV1 thus plays a crucial role in maintaining hepatic physiology during metabolic adaptation to fasting, liver steatosis, and hepatocyte proliferation associated with liver regeneration. With failure of such processes, CAV1 has been implicated in the modulation of cholestasis, hepatitis, cirrhosis, and hepatocarcinogenesis. This review discusses the latest research in CAV1 biology and related proteins, aiming to guide future endeavors that explore their role in liver physiology and disease.

Caveolin-1 (CAV1) has emerged as a promoter of proliferation, metastasis, and chemoresistance in hepatoma cells, as well as a marker of poor prognosis in liver cancer. We discuss here current knowledge and future approaches to elucidating the molecular mechanisms underlying CAV1 action during hepatocarcinogenesis and evaluate its potential use in clinical therapies.

Hormone-sensitive lipase (HSL) is a key enzyme regulating the acute activation of lipolysis. HSL functionality is controlled by multiple phosphorylation events, which regulate its association with the surface of lipid droplets (LDs). We determined the progression and stability of HSL phosphorylation on individual serine residues both spatially and temporally in adipocytes using phospho-specific antibodies. Within seconds of beta-adrenergic receptor activation, HSL was phosphorylated on Ser-660, the phosphorylated form appearing in the peripheral cytosol prior to rapid translocation to, and stable association with, LDs. In contrast, phosphorylation of HSL on Ser-563 was delayed, the phosphorylated protein was predominantly detected on LDs, and mutation of the Ser-659/Ser-660 site to Ala significantly reduced subsequent phosphorylation on Ser-563. Phosphorylation of HSL on Ser-565 was observed in control cells; the phosphorylated protein was translocated to LDs with similar kinetics to total HSL, and the degree of phosphorylation was inversely related to phospho-HSL(Ser-563). These results describe the remarkably rapid, sequential phosphorylation of specific serine residues in HSL at spatially distinct intracellular locales, providing new insight into the complex regulation of lipolysis.

Polymerase I and transcript release factor (PTRF)/Cavin is a cytoplasmic protein whose expression is obligatory for caveola formation. Using biochemistry and fluorescence resonance energy transfer–based approaches, we now show that a family of related proteins, PTRF/Cavin-1, serum deprivation response (SDR)/Cavin-2, SDR-related gene product that binds to C kinase (SRBC)/Cavin-3, and muscle-restricted coiled-coil protein (MURC)/Cavin-4, forms a multiprotein complex that associates with caveolae. This complex can constitutively assemble in the cytosol and associate with caveolin at plasma membrane caveolae. Cavin-1, but not other cavins, can induce caveola formation in a heterologous system and is required for the recruitment of the cavin complex to caveolae. The tissue-restricted expression of cavins suggests that caveolae may perform tissue-specific functions regulated by the composition of the cavin complex. Cavin-4 is expressed predominantly in muscle, and its distribution is perturbed in human muscle disease associated with Caveolin-3 dysfunction, identifying Cavin-4 as a novel muscle disease candidate caveolar protein.

Caveolae are an abundant feature of mammalian cells. Integral membrane proteins called caveolins drive the formation of caveolae but the precise mechanisms underlying caveola formation, and the origin of caveolae and caveolins during evolution, are unknown. Systematic evolutionary analysis shows conservation of genes encoding caveolins in metazoans. We provide evidence for extensive and ancient, local and genomic gene duplication, and classify distinct caveolin gene families. Vertebrate caveolin-1 and caveolin-3 isoforms, as well as an invertebrate (Apis mellifera, honeybee) caveolin, all form morphologically identical caveolae in caveolin-1-null mouse cells, demonstrating that caveola formation is a conserved feature of evolutionarily distant caveolins. However, coexpression of flotillin-1 and flotillin-2 did not cause caveola biogenesis in this system. In contrast to the other tested caveolins, C. elegans caveolin is efficiently transported to the plasma membrane but does not generate caveolae, providing evidence of diversity of function in the caveolin gene family. Using C. elegans caveolin as a template to generate hybrid caveolin constructs we now define domains of caveolin required for caveolae biogenesis. These studies lead to a model for caveola formation and novel insights into the evolution of caveolin function.

Macrophages play a critical role in the development and progression of atherosclerosis. Depending on their surrounding milieu, macrophages can adopt a wide range of functional phenotypes; pro-inflammatory (M1) and pro-resolving (M2). HDL has many cardio-protective properties including potent anti-inflammatory effects, largely through the removal of cholesterol from cells. It is currently not known if this extends to influencing human macrophage phenotypes. Thus, we aimed to investigate the effect of HDL on human macrophage polarisation. Human blood monocyte-derived macrophages were induced to either an M1-phenotype by incubation with LPS and IFN-γ or to an M2-phenotype with IL-4. Macrophages were differentiated in the presence or absence of human HDL and their phenotypes were characterised using cell surface markers, reactive oxygen species (ROS) production by flow cytometry, and mRNA expression by real-time PCR. Downstream signalling pathways were also explored. We discovered that HDL inhibited the induction to M1 as evidenced by a decrease in cell surface marker expression; CD192 and CD64. This was accompanied by a decreased expression of M1-associated inflammatory genes TNF-α, IL-6 and MCP-1. However, HDL had no effect on induction to the M2 phenotype. Similarly, methyl-beta-cyclodextrin (MβCD), a non-specific cholesterol acceptor was also able to suppress M1 induction suggesting cholesterol efflux is important in this process. Further we found that HDL decreased membrane caveolin-1 in M1 macrophages and redistributed it intracellularly. The requirement of caveolin-1 was revealed as bone marrow-derived macrophages from Cav-1-/- mice continued to differentiate into M1 despite the addition of HDL. Moreover, we demonstrated a decrease in STAT3 and ERK1/2 phosphorylation in M1 macrophages treated with HDL, suggesting cholesterol efflux inhibits the STAT3s and MAPKs during induction to the M1 phenotype. Finally, we found that HDL also inhibited M1 function; with reduced reactive oxygen species (ROS) production. We provide evidence that HDL reduces macrophage induction to the inflammatory M1 phenotype, but not M2, via cellular redistribution of caveolin-1 and inactivation of STAT3 and ERK1/2 signalling pathway.

Objective— Monocyte to macrophage differentiation is an essential step in atherogenesis. The structure protein of caveolae, caveolin-1, is increased in primary monocytes after its adhesion to endothelium. We explore the hypothesis that caveolin-1 plays a role in monocyte differentiation to macrophages. Methods and Results— Both phorbol myristate acetate–induced THP-1 and colony-stimulating factor–induced primary monocyte differentiation was associated with an increase in cellular caveolin-1 expression. Overexpression of caveolin-1 by transfection increased macrophage surface markers and inflammatory genes, whereas caveolin-1 knockdown by small interfering RNA or knockout reduced these. Also, caveolin-1 knockdown inhibited the differentiation–induced nuclear translocation of early growth response 1 (EGR-1) through extracellular signal-regulated kinase phosphorylation, further decreased the binding of EGR-1 to CD115 promoter, thus decreasing EGR-1 transcriptional activity. In functional assays, caveolin-1 inhibited transmigration but promoted phagocytosis in the monocyte–macrophage lineage. Decreasing caveolin-1 inhibited the uptake of modified low-density lipoprotein and reduced cellular lipid content. Finally, we showed that caveolin-1 knockout mice displayed less monocyte differentiation than wild-type mice and that EGR-1 transcription activity was also decreased in these mice because of the inhibition of extracellular signal-regulated kinase phosphorylation. Conclusion— Caveolin-1 promotes monocyte to macrophage differentiation through the regulation of EGR-1 transcriptional activity, suggesting that phagocytic caveolin-1 may be critical for atherogenesis.

Caveolin-1 (CAV1) is an important regulator of adipose tissue homeostasis. In the present study we examined the impact of CAV1 deficiency on the properties of mouse adipose tissue both in vivo and in explant cultures during conditions of metabolic stress. In CAV1(-/-) mice fasting caused loss of adipose tissue mass despite a lack of hormone-sensitive lipase (HSL) phosphorylation. In addition, fasting resulted in increased macrophage infiltration, enhanced deposition of collagen, and a reduction in the level of the lipid droplet protein perilipin A (PLIN1a). Explant cultures of CAV1(-/-) adipose tissue also showed a loss of PLIN1a during culture, enhanced secretion of IL-6, increased release of lactate dehydrogenase, and demonstrated increased susceptibility to cell death upon collagenase treatment. Attenuated PKA-mediated signaling to HSL, loss of PLIN1a and increased secretion of IL-6 were also observed in adipose tissue explants of CAV1(+/+) mice with diet-induced obesity. Together these results suggest that while alterations in adipocyte lipid droplet biology support adipose tissue metabolism in the absence of PKA-mediated pro-lipolytic signaling in CAV1(-/-) mice, the tissue is intrinsically unstable resulting in increased susceptibility to cell death, which we suggest underlies the development of fibrosis and inflammation during periods of metabolic stress.

Caveolin-1 (CAV1) is a structural protein of caveolae involved in lipid homeostasis and endocytosis. Using newly generated pure Balb/C CAV1 null (Balb/CCAV1−/−) mice, CAV1−/− mice from Jackson Laboratories (JAXCAV1−/−), and CAV1−/− mice developed in the Kurzchalia Laboratory (KCAV1−/−), we show that under physiological conditions CAV1 expression in mouse tissues is necessary to guarantee an efficient progression of liver regeneration and mouse survival after partial hepatectomy. Absence of CAV1 in mouse tissues is compensated by the development of a carbohydrate-dependent anabolic adaptation. These results were supported by extracellular flux analysis of cellular glycolytic metabolism in CAV1-knockdown AML12 hepatocytes, suggesting cell autonomous effects of CAV1 loss in hepatic glycolysis. Unlike in KCAV1−/− livers, in JAXCAV1−/− livers CAV1 deficiency is compensated by activation of anabolic metabolism (pentose phosphate pathway and lipogenesis) allowing liver regeneration. Administration of 2-deoxy-glucose in JAXCAV1−/− mice indicated that liver regeneration in JAXCAV1−/− mice is strictly dependent on hepatic carbohydrate metabolism. Moreover, with the exception of regenerating JAXCAV1−/− livers, expression of CAV1 in mice is required for efficient hepatic lipid storage during fasting, liver regeneration, and diet-induced steatosis in the three CAV1−/− mouse strains. Furthermore, under these conditions CAV1 accumulates in the lipid droplet fraction in wildtype mouse hepatocytes. Conclusion: Our data demonstrate that lack of CAV1 alters hepatocyte energy metabolism homeostasis under physiological and pathological conditions. (HEPATOLOGY 2011)

M-CSF/CSF-1 supports the proliferation and differentiation of monocytes and macrophages. In mice, CSF-1 also promotes proinflammatory responses in vivo by regulating mature macrophage functions, but little is known about the acute effects of this growth factor on mature human macrophages. Here, we show that in contrast to its effects on mouse bone marrow-derived macrophages, CSF-1 did not induce expression of urokinase plasminogen activator mRNA, repress expression of apolipoprotein E mRNA, or prime LPS-induced TNF and IL-6 secretion in human monocyte-derived macrophages (HMDM) from several independent donors. Instead, we show by expression profiling that CSF-1 modulates the HMDM transcriptome to favor a proatherogenic environment. CSF-1 induced expression of the proatherogenic chemokines CXCL10/IFN-inducible protein 10, CCL2, and CCL7 but repressed expression of the antiatherogenic chemokine receptor CXCR4. CSF-1 also up-regulated genes encoding enzymes of the cholesterol biosynthetic pathway (HMGCR, MVD, IDI1, FDPS, SQLE, CYP51A1, EBP, NSDHL, DHCR7, and DHCR24), and expression of ABCG1, encoding a cholesterol efflux transporter, was repressed. Consistent with these effects, CSF-1 increased levels of free cholesterol in HMDM, and the selective CSF-1R kinase inhibitor GW2580 ablated this response. These data demonstrate that CSF-1 represents a further link between inflammation and cardiovascular disease and suggest two distinct mechanisms by which CSF-1, which is known to be present in atherosclerotic lesions, may contribute to plaque progression.

Lipid droplets (LDs) are dynamic organelles that collect, store, and supply lipids [1]. LDs have a central role in the exchange of lipids occurring between the cell and the environment and provide cells with substrates for energy metabolism, membrane synthesis, and production of lipid-derived molecules such as lipoproteins or hormones. However, lipid-derived metabolites also cause progressive lipotoxicity [2], accumulation of reactive oxygen species (ROS), endoplasmic reticulum stress, mitochondrial malfunctioning, and cell death [2]. Intracellular accumulation of LDs is a hallmark of prevalent human diseases, including obesity, steatosis, diabetes, myopathies, and arteriosclerosis [3]. Indeed, nonalcoholic fatty liver disease is the most common cause of abnormal hepatic function among adults [4, 5]. Lipotoxicity gradually promotes cellular ballooning and disarray, megamitochondria, accumulation of Mallory's hyaline in hepatocytes, and inflammation, fibrosis, and cirrhosis in the liver. Here, using confocal microscopy, serial-block-face scanning electron microscopy, and flow cytometry, we show that LD accumulation is heterogeneous within a cell population and follows a positive skewed distribution. Lipid availability and fluctuations in biochemical networks controlling lipolysis, fatty acid oxidation, and protein synthesis contribute to cell-to-cell heterogeneity. Critically, this reversible variability generates a subpopulation of cells that effectively collect and store lipids. This high-lipid subpopulation accumulates more LDs and more ROS and reduces the risk of lipotoxicity to the population without impairing overall lipid homeostasis, since high-lipid cells can supply stored lipids to the other cells. In conclusion, we demonstrate fat storage compartmentalization within a cell population and propose that this is a protective social organization to reduce lipotoxicity. © 2013 Elsevier Ltd., A.P. is supported by grants BFU2011-23745 and CSD2009-00016 from MICINN and Marató de TV3; S.P.G. by grant GM64624/NIH; F.T. by grant BFU2009-13526; C.E. by grants BFU2009-10335, CSD2009-00016, and Marató de TV3; and M.G. by grant CSD2009-00016. R.G.P. is supported by grants from the National Health and Medical Research Council of Australia.