Transcriptional regulation of adipogenin expression in liver steatosis by hepatic peroxisome proliferator-activated receptor gamma.

The nuclear receptors peroxisome proliferator-activated receptor gamma (PPARγ) and adipogenin (ADIG) play vital roles in lipid metabolism. However, the interaction between PPARγ and ADIG during liver steatosis remains unclear. In this study, we aimed to investigate the role of PPARγ in the transcriptional regulation of hepatic ADIG expression. Adig was found to be highly expressed in various fatty liver mouse models. Although hepatic Adig was expressed at high levels in the fatty liver of type 2 diabetic ob/ob mice and was upregulated by PPARγ agonist treatment, it was expressed at significantly low levels in liver-specific Pparg-knockout mice. Moreover, hepatic Adig expression was observed in other mouse models of liver steatosis, such as the leptin receptor mutant db/db and alcohol-fed mice. Adig was also highly expressed in the white and brown adipose tissues, skeletal muscles, and heart of ob/ob mice. Reporter and electromobility shift assays showed that PPARγ positively regulates Adig transcriptional activity by directly binding to a functional PPARγ-responsive element in the promoter region. Our results indicate that Adig is a novel target gene of hepatic PPARγ in liver steatosis.

Activation of HSP90/HSF1 Signaling as an Adaptive Response to an Electrophilic Metabolite of Morphine.

Morphinone (MO) is an electrophilic metabolite of morphine that covalently binds to protein thiols, resulting in toxicity in vitro and in vivo. We have previously identified a variety of redox signaling pathways that are activated during electrophilic stress. However, the role of MO in such activation remains unknown. In this study, we examined whether MO could activate heat shock protein (HSP) 90/heat shock factor (HSF) 1 signaling in HepG2 cells. MO exposure caused S-modification of HSP90 (determined using biotin-PEAC5-maleimide labeling) and nuclear translocation of transcription factor HSF1, thereby up-regulating its downstream genes encoding B-cell lymphoma 2-associated anthanogene 3 and heat shock 70 kDa protein 1. However, dihydromorphinone, a non-electrophilic metabolite of morphine, had little effect on HSF1 activation or upregulation of these genes, suggesting that covalent modification plays a role in this process and that the HSP90/HSF1 pathway is a redox-signaled adaptive response to morphine metabolism.

Activation of the Keap1/Nrf2 Pathway as an Adaptive Response to an Electrophilic Metabolite of Morphine.

Morphinone (MO) is an electrophilic metabolite of morphine that covalently binds to protein thiols via its α,ß-unsaturated carbonyl group, resulting in toxicity in vitro and in vivo. Our previous studies identified a variety of redox signaling pathways that are activated during electrophilic stress. Here, we examined in vitro activation of a signaling pathway involving Kelch-like ECH-associated protein 1 (Keap1) and nuclear factor erythroid 2-related factor 2 (Nrf2) in response to MO. Exposure of HepG2 cells to MO caused covalent modification of Keap1 thiols (evaluated using biotin-PEAC5-maleimide labeling) and nuclear translocation of Nrf2, thereby up-regulating downstream genes encoding ATP binding cassette subfamily C member 2, solute carrier family 7 member 11, glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, glutathione S-transferase alpha 1, and heme oxygenase 1. However, dihydromorphinone, a metabolite of morphine lacking the reactive C7-C8 double bond, had little effect on Nrf2 activation. These results suggest that covalent modification is crucial in the Keap1/Nrf2 pathway activation and that this pathway is a redox signaling-associated adaptive response to MO metabolism.

Oxysterol-binding protein-like 3 is a novel target gene of peroxisome proliferator-activated receptor γ in fatty liver disease.

Oxysterol-binding protein-like 3 (OSBPL3) plays a key role in the development of fatty liver disease. Herein, we found that OSBPL3 is highly expressed in the fatty liver of humans and mice. Although high expression of Osbpl3 was observed in the fatty liver of type 2 diabetic ob/ob mice, liver-specific Pparg knockout ameliorated this increase in these mice. Moreover, high hepatic Osbpl3 expression was observed in other mice models of fatty liver disease, such as leptin receptor-mutant db/db and alcohol-fed mice. Analysis of the human liver transcriptome data revealed that hepatic OSBPL3 expression is higher in patients with advanced non-alcoholic fatty liver disease (NAFLD) when compared to those with mild NAFLD. Reporter and electrophoretic mobility shift assays showed that PPARγ positively regulates Osbpl3 transcription by binding to the two functional PPARγ-responsive elements present in the 5' upstream region. Overall, our results indicate that Osbpl3 is a novel PPARγ target in the fatty liver.

Gene repression through epigenetic modulation by PPARA enhances hepatocellular proliferation.

Peroxisome proliferator-activated receptor α (PPARA) is a key mediator of lipid metabolism and inflammation. Activation of PPARA in rodents causes hepatocyte proliferation, but the underlying mechanism is poorly understood. This study focused on genes repressed by PPARA and analyzed the mechanism by which PPARA promotes hepatocyte proliferation in mice. Activation of PPARA by agonist treatment was autoregulated, and induced expression of the epigenetic regulator UHRF1 via activation of the newly described PPARA target gene E2f8, which, in turn, regulates Uhrf1. UHRF1 strongly repressed the expression of CDH1 via methylation of the Cdh1 promoter marked with H3K9me3. Repression of CDH1 by PPARA activation was reversed by PPARA deficiency or knockdown of E2F8 or UHRF1. Furthermore, a forced expression of CDH1 inhibited expression of the Wnt signaling target genes such as Myc after PPARA activation, and suppressed hepatocyte hyperproliferation. These results demonstrate that the PPARA-E2F8-UHRF1-CDH1 axis causes epigenetic regulation of hepatocyte proliferation.

Lipase family member N is a novel target gene for CCAAT/enhancer-binding protein α in type 2 diabetic model mouse liver.

CCAAT/enhancer-binding protein α (C/EBPα) is a transcription factor abundantly expressed in the liver and white adipose tissue (WAT). In this study, we investigated the mechanism by which C/EBPα regulates the lipase family member N (Lipn) gene in the mouse liver. Mouse Lipn consists of non-coding exon 1 and the translation start site located in exon 2. Lipn expression in the fatty liver of ob/ob mice was significantly higher than that in OB/OB mice and was significantly repressed by liver-specific C/EBPα deficiency. Lipn expression in ob/ob mice was detected in the liver, epididymal WAT (eWAT), subcutaneous WAT (sWAT), brown adipose tissue (BAT), and skeletal muscle, but not in the kidney, brain, and heart. Lipn expression in the liver, eWAT, and sWAT of wild-type mice was undetectable, although C/EBPα was highly expressed in these tissues. The database analysis revealed four putative C/EBP-responsive elements (CEBPREs), highly homologous with the typical CEBPRE consensus sequence at positions -2,686/-2,678, -1,364/-1,356, -106/-98, and -45/-37 from the transcription start site (+1) of Lipn. Reporter assays using reporter constructs with serial or internal deletions of the 5'-flanking regions of Lipn showed that two functional CEBPREs (-106/-98 and -45/-37) in the Lipn promoter region are essential for enhancing Lipn transcriptional activity by C/EBPα. Electrophoretic mobility shift assay showed that C/EBPα/ß binds to CEBPRE (-106/-98). These results suggest that C/EBPα and type 2 diabetic environment may be required for hepatic Lipn expression.

Fat-specific protein 27b is regulated by hepatic peroxisome proliferator-activated receptor γ in hepatic steatosis.

The fat-specific protein 27 gene (Fsp27) belongs to the cell death-inducing DNA fragmentation factor 45-like effector family. Fsp27 is highly expressed in adipose tissue and fatty liver. In adipocytes, FSP27 localizes to the membrane of lipid droplets and promotes lipid droplet hypertrophy. Recently, FSP27 was shown to consist of two isoforms, FSP27α and FSP27ß. Previously, we demonstrated that Fsp27a is directly regulated by peroxisome proliferator-activated receptor γ (PPARγ) in fatty livers of genetically obese leptin deficient ob/ob mice and that Fsp27b may potentially be regulated by different factors transcriptionally as they both have a different promoter region. Thus, the aim of the present study was to elucidate whether Fsp27b is regulated by PPARγ in fatty liver. Fsp27a and Fsp27b were markedly induced in fatty liver of ob/ob mice compared with those in the normal liver. However, both Fsp27a/b were expressed at markedly lower levels in liver-specific PPARγ knockout mice with an ob/ob background. Further, the PPAR response element (PPRE) for the PPARγ-dependent promotion of Fsp27b promotor activity was revealed at position -1,163/-1,151 from the transcriptional start site (+1). Interestingly, the cis-element responsible for the PPARγ-dependent induction of Fsp27b was the same as that responsible for PPARγ-dependent induction of Fsp27a. These results suggest that PPARγ regulates not only Fsp27a but also Fsp27b in fatty liver of ob/ob mice through a common PPRE.

Insulin induces expression of the hepatic vaspin gene.

Visceral adipose tissue-derived serine protease inhibitor (vaspin), initially identified in the visceral adipose tissue, is an adipokine that improves endoplasmic reticulum stress in obesity or insulin sensitivity and glucose tolerance. However, the transcriptional regulation of the hepatic vaspin gene remains elusive. We have previously shown that CCAAT-enhancer-binding protein α, a transcription factor of the basic leucine zipper class, positively regulates the vaspin gene. The present study aimed to investigate the nutritional or hormonal regulators of vaspin expression in the liver. For the fasting and refeeding study, mice in the fasting group were subjected to fasting for 24 h and then sacrificed. Mice in the refeeding group were subjected to fasting for 24 h and then refed with a 50% (w/w) sucrose/MF diet for further 24 h and then sacrificed. For the streptozotocin (STZ) study, STZ (50 mg/kg) was intraperitoneally injected into C57BL/6JJc1 mice for 5 d. Hepatic vaspin was repressed due to fasting for 24 h and was induced upon refeeding with a high-sucrose diet. In studies on liver-specific C/EBPα-deficient mice, C/EBPα was not involved in the induction of hepatic vaspin upon refeeding. In addition, the depletion of insulin by streptozotocin treatment markedly decreased hepatic vaspin expression. Finally, fasting-repressed vaspin expression in the liver was significantly increased by direct injection of insulin into fasting mice. In conclusion, our results suggest that insulin is a positive regulator of hepatic vaspin expression.

Vaspin is a novel target gene of hepatic CCAAT-enhancer-binding protein.

Vaspin, initially identified in visceral adipose tissue, is an adipokine, and administration of recombinant vaspin leads to lowering of the endoplasmic reticulum stress which is elevated in obesity or enhancement of insulin sensitivity. CCAAT/enhancer binding protein (C/EBP), as a basic leucine zipper transcription factor, plays a critical role in adipocyte development and glucose and lipid metabolisms in liver. The present study aimed to investigate the effect of C/EBPα on vaspin gene expression. The expression of hepatic vaspin was markedly decreased in liver-specific C/EBPα knockout mice. A reporter assay indicated that two C/EBP-responsive elements (CEBPREs) are necessary for C/EBPα-dependent induction of vaspin promoter activities. Furthermore, electrophoretic mobility shift assay showed that C/EBPα in mouse liver is capable of directly binding the two CEBPREs. These results suggest that C/EBPα positively regulates hepatic vaspin expression through two functional CEBPREs. Thus, vaspin is a novel C/EBPα target gene in the liver.

Fat-specific protein 27 is a novel target gene of liver X receptor α.

Fat-specific protein 27 (FSP27) is highly expressed in the fatty liver of genetically obese ob/ob mice and promotes hepatic triglyceride (TG) accumulation. The nuclear hormone receptor liver X receptor α (LXRα) also plays a critical role in the control of TG levels in the liver. The present study demonstrated transcriptional regulation of Fsp27a and Fsp27b genes by LXRα. Treatment with the LXR ligand T0901317 markedly increased Fsp27a and Fsp27b mRNAs in wild-type C57BL/6J and ob/ob mouse livers. A reporter assay indicated that two LXR-responsive elements (LXREs) are necessary for LXRα-dependent induction of Fsp27a and Fsp27b promoter activities. Furthermore, the LXRα/retinoid X receptor α complex is capable of directly binding to the two LXREs both in vitro and in vivo. These results suggest that LXRα positively regulates Fsp27a and Fsp27b expression through two functional LXREs. Fsp27a/b are novel LXR target genes in the ob/ob fatty liver.

Insulin Represses Fasting-Induced Expression of Hepatic Fat-Specific Protein 27.

The fat-specific protein 27 (Fsp27) gene belongs to the cell death-inducing DNA fragmentation factor 45-like effector family. Fsp27 is highly expressed in adipose tissue as well as the fatty liver of ob/ob mice. Fsp27 is directly regulated by the peroxisome proliferator-activated receptor γ (PPARγ) in livers of genetically obese leptin deficient ob/ob mice. In the present study, Fsp27 was markedly induced by 24 h fasting in genetically normal mouse livers and repressed by refeeding a high sucrose diet. In contrast with the liver, Fsp27 expression was decreased in adipose tissue by fasting and increased by refeeding. Interestingly, fasting-induced Fsp27 liver expression was independent of PPARγ. Moreover, Fsp27 expression was induced in the insulin-depleted livers of streptozotocin-treated mice. Finally, Fsp27 expression was repressed by direct injection of glucose or insulin in fasting mice. These results suggest that insulin represses Fsp27 expression in the fasting liver.

Crizotinib, a MET inhibitor, prevents peritoneal dissemination in pancreatic cancer.

Peritoneal dissemination is a frequent occurrence in pancreatic cancer, which is associated with a poor prognosis. MET is associated with the progression of pancreatic cancer; therefore, we evaluated the effect of a MET inhibitor, crizotinib, on peritoneal dissemination of pancreatic cancer. Crizotinib inhibited the growth of 8 pancreatic cancer cell lines with the IC50 ranging from 1.4 to 4.3 µM. Invasion of the pancreatic cancer cell line Suit-2, was suppressed in vitro at a concentration of 1.0 µM, which is sufficient for the inhibition of MET phosphorylation. This effect on cell invasion was also recapitulated by the reduction of MET expression in Suit-2 with siRNA. Crizotinib also inhibited RhoA activation in addition to MET phosphorylation. We further evaluated the effect of crizotinib on peritoneal dissemination of pancreatic cancer in vivo. Crizotinib reduced tumor burden and ascites accumulation due to development of peritoneal dissemination after inoculation of Suit-2. Taken together, crizotinib may be a potent drug for treating peritoneal dissemination of pancreatic cancer by inhibiting cancer cell proliferation and invasion, at least in part through the suppression of HGF/MET signaling and RhoA activation.

Fat-Specific Protein 27/CIDEC Promotes Development of Alcoholic Steatohepatitis in Mice and Humans.

BACKGROUND & AIMS: Alcoholic steatohepatitis (ASH) is the progressive form of alcoholic liver disease and may lead to cirrhosis and hepatocellular carcinoma. We studied mouse models and human tissues to identify molecules associated with ASH progression and focused on the mouse fat-specific protein 27 (FSP-27)/human cell death-inducing DFF45-like effector C (CIDEC) protein, which is expressed in white adipose tissues and promotes formation of fat droplets. METHODS: C57BL/6N mice or mice with hepatocyte-specific disruption of Fsp27 (Fsp27(Hep-/-) mice) were fed the Lieber-Decarli ethanol liquid diet (5% ethanol) for 10 days to 12 weeks, followed by 1 or multiple binges of ethanol (5 or 6 g/kg) during the chronic feeding. Some mice were given an inhibitor (GW9662) of peroxisome proliferator-activated receptor γ (PPARG). Adenoviral vectors were used to express transgenes or small hairpin (sh) RNAs in cultured hepatocytes and in mice. Liver tissue samples were collected from ethanol-fed mice or from 31 patients with alcoholic hepatitis (AH) with biopsy-proved ASH and analyzed histologically and immunohistochemically and by transcriptome, immunoblotting, and real-time PCR analyses. RESULTS: Chronic-plus-binge ethanol feeding of mice, which mimics the drinking pattern of patients with AH, produced severe ASH and mild fibrosis. Microarray analyses revealed similar alterations in expression of many hepatic genes in ethanol-fed mice and humans with ASH, including up-regulation of mouse Fsp27 (also called Cidec) and human CIDEC. Fsp27(Hep-/-) mice and mice given injections of adenovirus-Fsp27shRNA had markedly reduced ASH following chronic-plus-binge ethanol feeding. Inhibition of PPARG and cyclic AMP-responsive element binding protein H (CREBH) prevented the increases in Fsp27α and FSP27ß mRNAs, respectively, and reduced liver injury in this chronic-plus-binge ethanol feeding model. Overexpression of FSP27 and ethanol exposure had synergistic effects in inducing production of mitochondrial reactive oxygen species and damage to hepatocytes in mice. Hepatic CIDEC mRNA expression was increased in patients with AH and correlated with the degree of hepatic steatosis and disease severity including mortality. CONCLUSIONS: In mice, chronic-plus-binge ethanol feeding induces ASH that mimics some histological and molecular features observed in patients with AH. Hepatic expression of FSP27/CIDEC is highly up-regulated in mice following chronic-plus-binge ethanol feeding and in patients with AH; this up-regulation contributes to alcohol-induced liver damage.

Hepatic PPARγ and LXRα independently regulate lipid accumulation in the livers of genetically obese mice.

The nuclear hormone receptors liver X receptor α (LXRα) and peroxisome proliferator-activated receptor γ (PPARγ) play key roles in the development of fatty liver. To determine the link between hepatic PPARγ and LXRα signaling and the development of fatty liver, a LXRα-specific ligand, T0901317, was administered to normal OB/OB and genetically obese (ob/ob) mice lacking hepatic PPARγ (Pparγ(ΔH)). In ob/ob-Pparγ(ΔH) and OB/OB-Pparγ(ΔH) mice, as well as ob/ob-Pparγ(WT) and OB/OB-Pparγ(WT) mice, the liver weights and hepatic triglyceride levels were markedly increased in response to T0901317 treatment. These results suggest that hepatic PPARγ and LXRα signals independently contribute to the development of fatty liver.

Involvement of CXCL14 in osteolytic bone metastasis from lung cancer.

To investigate the molecular mechanisms of lung cancer-induced bone metastasis, we established a bone-seeking subclone (HARA-B4) from a human squamous lung cancer cell line (HARA) using an in vivo selection method. We compared comprehensive gene expression profiles between HARA and HARA-B4, and identified the critical factors for the formation of bone metastasis using in vitro and in vivo assays. The number of bone metastatic colonies in the hind legs was significantly higher in HARA-B4-inoculated mice than in HARA-inoculated mice at 4 weeks after inoculation. In addition, visceral (adrenal) metastases were not found in HARA-B4-inoculated mice at autopsy, suggesting an increase in cancer cell tropism to bone in HARA-B4. Based on a comprehensive gene expression analysis, the expression level of CXC chemokine ligand 14 (CXCL14) was 5-fold greater in HARA-B4 than in HARA. Results of a soft agar colony formation assay showed that anchorage-independent growth ability was 4.5-fold higher with HARA-B4 than with HARA. The murine pre-osteoblast cell line MC3T3-E1 and the pre-osteoclast/macrophage cell line RAW264.7 migrated faster toward cultured HARA-B4 cells than toward HARA cells in a transwell cell migration assay. Interestingly, CXCL14 was shown to be involved in all events (enhancement of cancer cell tropism to the bone, anchorage-independent growth and/or recruitment of bone marrow cells) based on siRNA experiments in HARA-B4 cells. Furthermore, in clinical specimens of lung cancer-induced bone metastasis, expression of CXCL14 was observed in the tumor cells infiltrated in bone marrow in all specimens examined. CXCL14 was able to promote bone metastasis through enhancement of cancer cell tropism to the bone and/or recruitment of bone marrow cells around metastatic cancer cells.

Expression of hepatic fat-specific protein 27 depends on the specific etiology of fatty liver.

Fat-specific protein 27 gene (FSP27), isolated by screening for genes specifically expressed in fully differentiated mouse adipocytes, belongs to the cell death-inducing DNA fragmentation factor, alpha subunit-like effector family. FSP27 is induced in not only adipose tissue but also the liver of ob/ob mice, and it promotes the development of fatty liver. The FSP27 gene is expressed in a fatty liver-specific manner and is not detected in the normal mouse liver. FSP27 expression is directly regulated by the induction of the hepatic peroxisome proliferator-activated receptor γ (PPARγ) in ob/ob fatty liver. In the present study, expression of hepatic FSP27 mRNA was determined in non-genetic fatty liver models. The FSP27 gene was markedly induced in the high-fat- or methionine- and choline-deficient (MCD) diet-induced fatty liver, but it was not elevated in alcohol-induced fatty liver. Interestingly, the induction of FSP27 mRNA due to the MCD diet was independent of PPARγ levels and completely absent in the liver from PPARγ-null mice. These results suggest that FSP27 mRNA expression in the liver depends on the etiology of fatty liver.

[Novel mechanism for hepatic lipid accumulation: a physiological role for hepatic PPARγ-fsp27 signal].

Fat-specific protein 27 (fsp27) was originally isolated by screening for genes specifically expressed in fully differentiated mouse adipocytes. Fsp27 and cell death-inducing DFF45-like effector (CIDE) C, the human homologue of fsp27, belong to the CIDE family. Fsp27, which is highly expressed in mouse white and brown adipose tissues, was recently reported to be a lipid droplet (LD)-binding protein that promotes lipid accumulation in adipocytes. In contrast, we showed that fsp27 was also expressed in the fatty liver of the ob/ob type II diabetes model mouse. The expression of fsp27 was markedly decreased in livers lacking the nuclear receptor peroxisome proliferator-activated receptor γ(PPARγ). A functional PPAR response element site was identified in the fsp27 promoter region. Forced expression of fsp27 in hepatocytes in vitro or in vivo led to increased LD through increased triglyceride levels. The current status of the physiological roles of the PPARγ-fsp27 signal in fatty liver are discussed along with its significance as a factor involved in the development of metabolic disorders.

The bisphosphonate incadronate inhibits intraperitoneal dissemination in an in vivo pancreatic cancer model.

Pancreatic cancer is characterized by intraperitoneal dissemination and often by large volumes of ascites. Aminobisphosphonates exhibit potent antitumor effects and are currently being tested against human solid tumors. Several aminobisphosphonates inhibit cancer cell migration by preventing the activation of Rho through inhibition of the mevalonate pathway. We evaluated the ability of an aminobisphosphonate, incadronate, to inhibit the growth of disseminated pancreatic cancer in vivo. We established an in vivo pancreatic cancer model with i.p. carcinomatosis in nude mice. Incadronate administration started from the day of tumor inoculation, and reduced tumor burden and ascites accumulation. Further, we evaluated the effect of incadronate on the inhibition of pancreatic cancer cell proliferation, migration and invasion in vitro. Incadronate induced growth inhibition and apoptotic death of pancreatic cancer cells. It also inhibited migration presumably by preventing the activation of Rho by lysophosphatidic acid. Thus, the in vivo antitumor effect may result from the inhibition of cancer cell proliferation and migration. The potent effects of incadronate in reducing tumor burden and ascites suggest that it will be of value in regimens for the treatment of pancreatic cancer.

Hepatic peroxisome proliferator-activated receptor-γ-fat-specific protein 27 pathway contributes to obesity-related hypertension via afferent vagal signals.

AIMS: Obesity is commonly associated with hypertension. Increased sympathetic tonus in obese subjects contributes to the underlying mechanism. However, the precise mechanisms whereby obesity induces this sympathetic activation remain unclear. Hepatic peroxisome proliferator-activated receptor (PPAR)-γ2 expression, which is reportedly upregulated during obesity development, affects sympathetic activation via hepatic vagal afferents. Herein, we report involvement of this neuronal relay in obesity-related hypertension. METHODS AND RESULTS: Peroxisome proliferator-activated receptor-γ and a direct PPARγ target, fat-specific protein 27 (Fsp27), were adenovirally overexpressed or knocked down in the liver, in combination with surgical dissection or pharmacological deafferentation of the hepatic vagus. Adenoviral PPARγ2 expression in the liver raised blood pressure (BP) in wild-type but not in ß1/ß2/ß3 adrenergic receptor-deficient mice. In addition, knockdown of endogenous PPARγ in the liver lowered BP in murine obesity models. Either surgical dissection or pharmacological deafferentation of the hepatic vagus markedly blunted BP elevation in mice with diet-induced and genetically-induced obesity. In contrast, BP was not elevated in other models of hepatic steatosis, DGAT1 and DGAT2 overexpressions, in which PPARγ is not upregulated in the liver. Thus, hepatic PPARγ upregulation associated with obesity is involved in BP elevation during obesity development. Furthermore, hepatic expression of Fsp27 raised BP and the effect was blocked by hepatic vagotomy. Hepatic Fsp27 is actually upregulated in murine obesity models and its knockdown reversed BP elevation. CONCLUSION: The hepatic PPARγ-Fsp27 pathway plays important roles in the development of obesity-related hypertension via afferent vagal signals from the liver.

RhoA, a possible target for treatment of airway hyperresponsiveness in bronchial asthma.

Airway hyperresponsiveness to nonspecific stimuli is one of the characteristic features of allergic bronchial asthma. An elevated contractility of bronchial smooth muscle has been considered as one of the causes of the airway hyperresponsiveness. The contraction of smooth muscles including airway smooth muscles is mediated by both Ca²+-dependent and Ca²+-independent pathways. The latter Ca²+-independent pathway, termed Ca²+ sensitization, is mainly regulated by a monomeric GTP-binding protein, RhoA, and its downstream target Rho-kinase. In animal models of allergic bronchial asthma, an augmented agonist-induced, RhoA-mediated contraction of bronchial smooth muscle has been suggested. The RhoA/Rho-kinase signaling is now proposed as a novel target for the treatment of airway hyperresponsiveness in asthma. Herein, we will discuss the mechanism of development of bronchial smooth muscle hyperresponsiveness, one of the causes of the airway hyperresponsiveness, based on the recent studies using animal models of allergic bronchial asthma and/or cultured airway smooth muscle cells. The possibility of RhoA as a therapeutic target in asthma, especially airway hyperresponsiveness, will also be described.