Hiroki Sugita

Inducible Nitric-oxide Synthase and NO Donor Induce Insulin Receptor Substrate-1 Degradation in Skeletal Muscle Cells

Chronic inflammation plays an important role in insulin resistance. Inducible nitric-oxide synthase (iNOS), a mediator of inflammation, has been implicated in many human diseases including insulin resistance. However, the molecular mechanisms by which iNOS mediates insulin resistance remain largely unknown. Here we demonstrate that exposure to NO donor or iNOS transfection reduced insulin receptor substrate (IRS)-1 protein expression without altering the mRNA level in cultured skeletal muscle cells. NO donor increased IRS-1 ubiquitination, and proteasome inhibitors blocked NO donor-induced reduction in IRS-1 expression in cultured skeletal muscle cells. The effect of NO donor on IRS-1 expression was cGMP-independent and accentuated by concomitant oxidative stress, suggesting an involvement of nitrosative stress. Inhibitors for phosphatidylinositol-3 kinase, mammalian target of rapamycin, and c-Jun amino-terminal kinase failed to block NO donor-induced IRS-1 reduction, whereas these inhibitors prevented insulin-stimulated IRS-1 decrease. Moreover iNOS expression was increased in skeletal muscle of diabetic (ob/ob) mice compared with lean wild-type mice. iNOS gene disruption or treatment with iNOS inhibitor ameliorated depressed IRS-1 expression in skeletal muscle of diabetic (ob/ob) mice. These findings indicate that iNOS reduces IRS-1 expression in skeletal muscle via proteasome-mediated degradation and thereby may contribute to obesity-related insulin resistance.

Applicability of disseminated intravascular coagulation parameters in the assessment of the severity of acute pancreatitis.

Objectives: To evaluate the clinical applicability of the determination of disseminated intravascular coagulation (DIC) parameters in acute pancreatitis. Methods: The subjects for this study were 139 consecutive patients with acute pancreatitis. DIC parameters were assessed at the initial observation of these patients. Results: The levels of the DIC parameters at admission were significantly associated with the severity and the prognosis of acute pancreatitis. Antithrombin III (AT-III), fibrin/fibrinogen degradation products-E, platelet count, D-dimer, and thrombin-AT-III complex at admission showed better area under the receiver operating characteristics curve values compared with C-reactive protein. An AT-III value of 69% at admission was the best cut-off value to predict fatal outcome (sensitivity, 81%; specificity, 86%). Conclusions: The aggravated coagulation parameters predict a fatal outcome in patients with acute pancreatitis. AT-III level (<69%) was the most accurate marker for poor outcome of acute pancreatitis at admission.

Pancreatoduodenectomy using a no-touch isolation technique.

BACKGROUND Pancreatoduodenectomy is the only effective treatment for cancers of the periampullary region. Because surgeons usually grasp tumors during pancreatoduodenectomy, this procedure may increase the risk of squeezing and shedding the cancer cells into the portal vein, retroperitoneum, and/or peritoneal cavity. In an effort to overcome these problems, we have developed a surgical technique for no-touch pancreatoduodenectomy. METHODS From March 2005 through May 2008, 42 patients have been operated on following this technique. Resected margins were microscopically analyzed. RESULTS We describe a technique for pancreatoduodenectomy using a no-touch isolation technique. We resect cancers with wrapping them within Gerotas fascia and transect the retroperitoneal margin along the right surface of the superior mesenteric artery and abdominal aorta without grasping tumors. CONCLUSIONS No-touch pancreatoduodenectomy has many potential advantages that merit further investigation in future randomized controlled trials.

Neutrophil elastase inhibitor (ONO-5046) prevents lung hemorrhage induced by lipopolysaccharide in rat model of cerulein pancreatitis

The protective effects of a neutrophil elastase inhibitor (ONO-5046) on cerulein-induced pancreatitis followed by a septic challenge with intraperitoneal lipopolysaccharide (LPS) were studied in a rat model. Pancreatitis was induced by four intramuscular injections of cerulein (50 μg/kg at 1-hr intervals). ONO-5046 was administered by continuous intravenous infusion via the right jugular vein (50 mg/kg/hr, 30 min prior to the first cerulein injection to 20 hr following the last cerulein injection). Significant differences in serum amylase and pancreatic wet weight ratio were not observed between the animals with pancreatitis treated with or without ONO-5046. There was no significant difference in thein vitro tumor necrosis factor-alpha (TNF-α) production by peritoneal macrophages from rats with pancreatitis treated with or without ONO-5046. In a second experiment, LPS (10 mg/kg) was administered intraperitoneally as the septic challenge 6 hr following the first cerulein injection. Lung hemorrhage was seen in the animals with pancreatitis untreated with ONO-5046 24 hr following the first cerulein injection. No significant lung hemorrhage was observed in the animals with pancreatitis treated with ONO-5046 administering 30 min prior to the first cerulein injection. These results suggest that lung hemorrhage in cerulein-induced pancreatitis that follows a septic challenge with LPS can be prevented by the intravenous administration of ONO-5046. Thus there is a significant role for neutrophil elastase in pancreatitisassociated lung injury.

Genetic mutations in exons 3 and 4 of the pancreatic secretory trypsin inhibitor in patients with pancreatitis.

Purpose. We hypothesized that mutations in the pancreatic secretory trypsin inhibitor (PSTI) gene could promote autodigestion, leading to acute or chronic pancreatitis. Our investigation involved mutation analysis of the PSTI gene in patients with acute or chronic pancreatitis. Methods. Mutation analysis for the PSTI gene was performed in patients with acute or chronic pancreatitis. Unrelated healthy volunteers and family members of a chronic pancreatitis patient with point mutations in the PSTI gene were also analyzed. Results. Two types of single-point mutation in the PSTI gene were observed in one patient with chronic pancreatitis: 34Asn (AAT)-to-Ser (AGT) (101 A > G N34S: N34S) in exon 3, and 67Arg (CGC)-to-Cys (TGC) (199 C > T R67C: R67C) in exon 4. No mutations with amino-acid substitution were found in other patients or in the volunteer group. In the patient with the PSTI gene mutations, no additional mutations were observed in the cationic trypsinogen gene. The family study revealed that the mother and a maternal uncle were homozygotes for the N34S mutation, while the father and brother were compound heterozygotes for the N34S and R67C mutations. The uncle (N34S/N34S) showed clinical manifestations of pancreatitis, but the other family members did not. Conclusions. The N34S mutation may cause a predisposition to pancreatitis, with incomplete penetrance. However, with the limited information available, it is not known whether the R67C mutation promotes pancreatitis.

Proinflammatory role of trypsin and protease-activated receptor-2 in a rat model of acute pancreatitis.

Objectives: The pathophysiology of acute pancreatitis is strongly associated with autoactivation of trypsin. The biologic activity of trypsin on cells is attributed to the activation of protease-activated receptor-2 (PAR-2). We hypothesize that trypsin may activate acinar cells or inflammatory cells through PAR-2 signals in acute pancreatitis. Methods: We immunochemically analyzed the expression of PAR-2 in the rat acinar cell line, ARIP, and the rat pancreas, using anti-rat PAR-2 cleavage site (PCS) and anti-rat PAR-2 N-terminal fragment (PNF) antibodies. Plasma levels of PNF were determined. Furthermore, the effects of the anti-rat PCS antibody and nafamostat mesylate, a potent trypsin inhibitor, on PAR-2 activation during acute pancreatitis were also analyzed. Results: ARIP cells expressed PAR-2, which was activated by exogenous trypsin activity. We also showed that PAR-2 is strongly expressed in pancreatic acinar and duct cells and that it is activated in rat cerulein-induced acute pancreatitis. The anti-rat PCS antibody and nafamostat mesylate reduced interleukin-6 and interferon γ production and alleviated distant organ injury. Conclusions: These results suggest that trypsin and its specific receptor, PAR-2, play an important role in cytokine production and the resultant development of distant organ injury during rat acute pancreatitis.

Enhanced expression of cytokine-induced neutrophil chemoattractant (CINC) by bronchoalveolar macrophages in cerulein-induced pancreatitis rats.

The role of bronchoalveolar macrophages (BAMs)in the aggravation of cerulein-induced pancreatitis wasstudied by measuring expression of cytokine-inducedneutrophil chemoattractant (CINC) in vitro. Pancreatitis was induced by four intramuscular injections ofcerulein (50 μg/kg at 1-hr intervals). Pancreatitisrats were injected intraperitoneally with 30 mg/kglipopolysaccharide (LPS) 6 hr following the first cerulein injection as a septic challenge. Ratswere divided into four groups: group I, nonpancreatitiswithout LPS; group II, pancreatitis without LPS; groupIII, nonpancreatitis with LPS; and group IV, pancreatitis with LPS. Hyperactivity of BAMs inresponse to LPS was assessed as a function of in vitroCINC production. CINC concentrations of the serum andbronchoalveolar lavage fluid in group IV were significantly higher than those in groups I,II, and III. BAMs in group II harvested 6 hr followingthe first cerulein injection had significantly greaterCINC production than those in group I. Northern blot analysis revealed abundant CINC mRNAtranscripts in BAMs from groups III and IV.Additionally, myeloperoxidase activity in the lung ofgroup IV rats 8 and 12 hr following the first ceruleininjection was significantly higher than that in group I,II, and III rats. Significant differences in static lungcompliance in group IV were found compared with groupsI, II, and III. These results indicate that BAMs from rats with cerulein-inducedpancreatitis were primed and had enhanced release ofCINC following LPS exposure. Enhanced expression of CINCmay modulate the pathogenesis of pancreatitis-associated lung injury complicated with sepsis.

Farnesyltransferase Inhibitor, Manumycin A, Prevents Atherosclerosis Development and Reduces Oxidative Stress in Apolipoprotein E-Deficient Mice

Objective—Statins are presumed to exert their antiatherogenic effects in part via lipid-lowering–independent mechanisms. Inhibition of protein farnesylation and/or geranylgeranylation by statins has been postulated to contribute to the lipid-lowering–independent effects. However, a role for protein farnesylation in atherogenesis has not yet been studied. Therefore, we examined the effects of farnesyltransferase inhibitor, manumycin A, on the development of atherosclerosis in apolipoprotein E (apoE)-deficient mice fed a high-fat diet. Methods and Results—Manumycin A treatment for 22 weeks decreased Ras activity, and reduced fatty streak lesion size at the aortic sinus to 43% of that in vehicle-treated apoE-deficient mice (P<0.05), while plasma total cholesterol was unaltered. Moreover, manumycin A reduced &agr;-smooth muscle actin-positive area to 29% of that in vehicle-treated apoE-deficient mice (P<0.01). The prevention of atherogenesis by manumycin A was accompanied by amelioration of oxidative stress, as judged by reduced ex vivo superoxide production and nitrotyrosine immunoreactivity. Conclusions—These results indicate that the inhibition of farnesyltransferase prevents the development of mature atherosclerosis with concomitant alleviation of oxidative stress in apoE-deficient mice. The present data highlight farnesyltransferase as a potential molecular target for preventive and/or therapeutic intervention against atherosclerosis.

Statins inhibit tumor progression via an enhancer of zeste homolog 2-mediated epigenetic alteration in colorectal cancer

While statin intake has been proven to reduce the risk of colorectal cancer (CRC), the mechanism of antitumor effects and clinical significance in survival benefits remain unclear. Statin‐induced antiproliferative effects and its underlying mechanism were examined using six CRC cell lines. Statins except pravastatin showed antiproliferative effects (simvastatin ≥ fluvastatin > atorvastatin) even though both of simvastatin and pravastatin could activate mevalonate pathways, suggesting the statin‐mediated antiproliferative effects depended on non‐mevalonate pathway. Indeed, statin induced p27KIP1 expression by downregulation of histone methyltransferase enhancer of zeste homolog 2 (EZH2), which acts as an epigenetic gene silencer. Additionally, the use of simvastatin plus classII histone deacetylase (HDAC) inhibitor (MC1568) induced further overexpression of p27KIP1 by inhibiting HDAC5 induction originated from downregulated EZH2 in CRC cells and synergistically led to considerable antiproliferative effects. In the clinical setting, Statin intake (except pravastatin) displayed the downregulated EZH2 expression and inversely upregulated p27KIP1 expression in the resected CRC by immunohistochemical staining and resulted in the significantly better prognoses both in overall survival (p = 0.02) and disease free survival (p < 0.01) compared to patients without statin intake. Statins may inhibit tumor progression via an EZH2‐mediated epigenetic alteration, which results in survival benefits after resected CRC. Furthermore, statin plus classII HDAC inhibitor could be a novel anticancer therapy by their synergistic effects in CRC.

Increased Insulin Receptor Substrate 1 Serine Phosphorylation and Stress-Activated Protein Kinase/c-Jun N-Terminal Kinase Activation Associated With Vascular Insulin Resistance in Spontaneously Hypertensive Rats

Insulin resistance is associated with cardiovascular disease. Impaired insulin receptor substrate (IRS)–mediated signal transduction is a major contributor to insulin resistance. Recently, IRS-1 phosphorylation at serine 307 by stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) has been highlighted as a molecular event that causes insulin resistance. We investigated IRS-1–mediated insulin signaling, IRS-1 phosphorylation at serine 307, and SAPK/JNK activation status in the aorta of spontaneously hypertensive rats (SHR) by immunoprecipitation and immunoblotting. Insulin-stimulated tyrosine phosphorylation of insulin receptor and IRS-1 in SHR was decreased to 55% (P<0.01) and 40% (P<0.01) of the levels in Wistar-Kyoto rats (WKY), respectively. Insulin-stimulated IRS-1–associated phosphatidylinositol 3-kinase activation in SHR was reduced to 28% of the level in WKY (P<0.0001). Immunoblot analysis revealed that phosphorylated IRS-1 at serine 307 in SHR was increased to 261% (P<0.001) of the level in WKY. Phosphorylated (activated) SAPK/JNK in SHR was increased to 223% of the level in WKY (P<0.01). Serine-phosphorylated IRS-1 that was immunoprecipitated from the aorta of SHR was capable of inhibiting in vitro tyrosine phosphorylation by recombinant insulin receptor compared with WKY-derived IRS-1. These findings demonstrate that insulin resistance in the aorta of SHR was associated with elevated IRS-1 phosphorylation at serine 307 and increased SAPK/JNK activation. The present study suggests that increased SAPK/JNK activation may play an important role in the pathogenesis of vascular insulin resistance via inhibitory serine phosphorylation of IRS-1.