Growth hormone signalling and apoptosis in neonatal rat cardiomyocytes

Growth hormone (GH) has been reported to be useful to treat heart failure. To elucidate whether GH has direct beneficial effects on the heart, we examined effects of GH on oxidative stress-induced apoptosis in cardiac myocytes. TUNEL staining and DNA ladder analysis revealed that hydrogen peroxide (H2O2)-induced apoptosis of cardiomyocytes was significantly suppressed by the pretreatment with GH. GH strongly activated extracellular signal-regulated kinases (ERKs) in cardiac myocytes and the cardioprotective effect of GH was abolished by inhibition of ERKs. Overexpression of dominant negative mutant Ras suppressed GH-stimulated ERK activation. Overexpression of Csk that inactivates Src family tyrosine kinases also inhibited ERK activation evoked by GH. A broad-spectrum inhibitor of protein tyrosine kinases (PTKs), genistein, strongly suppressed GH-induced ERK activation and the cardioprotective effect of GH against apoptotic cell death. GH induced tyrosine phosphorylation of EGF receptor and JAK2 in cardiac myocytes, and an EGF receptor inhibitor tyrphostin AG1478 and a JAK2 inhibitor tyrphostin B42 completely inhibited GH-induced ERK activation. Tyrphostin B42 also suppressed the phosphorylation of EGF receptor stimulated by GH. These findings suggest that GH has a direct protective effect on cardiac myocytes against apoptosis and that the effect of GH is attributed at least in part to the activation of ERKs through Ras and PTKs including JAK2, Src, and EGF receptor tyrosine kinase.

Subcellular localization of insulin receptor substrate family proteins associated with phosphatidylinositol 3-kinase activity and alterations in lipolysis in primary mouse adipocytes from IRS-1 null mice

To clarify the roles of insulin receptor substrate (IRS) family proteins in phosphatidylinositol (PI) 3-kinase activation and insulin actions in adipocytes, we investigated the intracellular localization of IRS family proteins and PI 3-kinase activation in response to insulin by fractionation of mouse adipocytes from wild-type and IRS-1 null mice. In adipocytes from wild-type mice, tyrosine-phosphorylated IRS-1 and IRS-2, which were found to associate with PI 3-kinase in response to insulin, were detected in the plasma membrane (PM) and low-density microsome (LDM) fractions. By contrast, tyrosine-phosphorylated IRS-3 (pp60), which was found to associate with PI 3-kinase, was predominantly localized in the PM fraction. In adipocytes from IRS-1-null mice, insulin-stimulated PI 3-kinase activity in anti-phosphotyrosine (alphaPY) immunoprecipitates in the LDM fraction was almost exclusively mediated via IRS-2 and was reduced to 25%; however, insulin-stimulated PI 3-kinase activity in the PM fraction was primarily mediated via IRS-3 and was reduced to 60%. To determine the potential functional impact of the distinct subcellular localization of IRSs and associating PI 3-kinase activity on adipocyte-specific metabolic actions, we examined lipolysis in IRS-1 null mice. The level of isoproterenol-induced lipolysis was increased 5.1-fold in adipocytes from IRS-1 null mice as compared with wild-type mice. Moreover, hormone-sensitive lipase (HSL) protein was increased 4.3-fold in adipocytes from IRS-1-null mice compared with wild-type mice, and HSL mRNA expression was also increased. The antilipolytic effect of insulin in IRS-1 null adipocytes, however, was comparable to that in wild-type mice. Thus, discordance between these two insulin actions as well as the transcriptional and translational effect (HSL mRNA and protein regulation) and the PM effect (antilipolysis) of insulin may be explained by distinct roles of both PI 3-kinase activity associated with IRS-1/IRS-2 and PI 3-kinase activity associated with IRS-3 in insulin actions related to their subcellular localization.

Arg-gingipain is responsible for the degradation of cell adhesion molecules of human gingival fibroblasts and their death induced by Porphyromonas gingivalis

Arg-gingipain (Rgp) and Lys-gingipain (Kgp) are two major cysteine proteinases produced by the oral anaerobic bacterium Porphyromonas gingivalis, which has been shown to act as major pathogen in the development and progression of periodontal diseases. These enzymes are also important for this organism to proliferate and survive in periodontal pockets. Here we show that Rgp is responsible for the disruption of fibronectin-integrin interactions in human gingival fibroblasts by P. gingivalis. Fibroblasts incubated with the culture supernatant of P. gingivalis showed a time-dependent loss of the adhesion activity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting revealed that fibronectin and integrin subunits alpha2, beta1 and beta3 in the fibroblast culture largely disappeared with the treatment. The detached cells became committed to death by disruption of contacts between adhesion molecules. In contrast, the culture supernatants from the Rgp-deficient mutants produced no significant changes in either cell adhesion or viability. Prior treatment of the culture supernatant of P. gingivalis with an Rgp inhibitor, but not a Kgp inhibitor, strongly inhibited the detachment of fibroblasts followed by cell death. These results suggest that Rgp disrupts the integrin-fibronectin interactions in fibroblasts, thereby contributing to the damage of periodontal tissues in periodontal diseases caused by P. gingivalis.

The Pro12 -->Ala substitution in PPAR-gamma is associated with resistance to development of diabetes in the general population: possible involvement in impairment of insulin secretion in individuals with type 2 diabetes

The allele frequencies for a Pro12-->Ala substitution in peroxisome proliferator-activated receptor-gamma differ among ethnic groups, and its relationship with diabetes and associated diseases is controversial. The prevalence of this polymorphism and its effects on clinical characteristics have now been evaluated with a large number of Japanese individuals with type 2 diabetes (n = 2,201) and normal control subjects (n = 1,212) recruited by 10 institutions located in seven different cities in Japan. The allele frequency for the Ala12 variant was significantly lower in the type 2 diabetic group than in the control group (2.39 vs. 4.13%, P = 0.000054). However, compared with subjects without the Ala12 variant, the diabetic subjects with this variant exhibited a significantly higher serum concentration of total cholesterol (P = 0.001), manifested a reduced capacity for insulin secretion as evaluated by homeostasis model assessment (P = 0.007), and tended to possess a higher level of HbA1c. These data suggest that the Ala12 variant is associated with a reduced risk for the development of diabetes in the general population, but that it may be also a risk factor for insulin deficiency and disease severity in individuals with type 2 diabetes.

Essential role of insulin receptor substrate 1 (IRS-1) and IRS-2 in adipocyte differentiation

To investigate the role of insulin receptor substrate 1 (IRS-1) and IRS-2, the two ubiquitously expressed IRS proteins, in adipocyte differentiation, we established embryonic fibroblast cells with four different genotypes, i.e., wild-type, IRS-1 deficient (IRS-1(-/-)), IRS-2 deficient (IRS-2(-/-)), and IRS-1 IRS-2 double deficient (IRS-1(-/-) IRS-2(-/-)), from mouse embryos of the corresponding genotypes. The abilities of IRS-1(-/-) cells and IRS-2(-/-) cells to differentiate into adipocytes are approximately 60 and 15%, respectively, lower than that of wild-type cells, at day 8 after induction and, surprisingly, IRS-1(-/-) IRS-2(-/-) cells have no ability to differentiate into adipocytes. The expression of CCAAT/enhancer binding protein alpha (C/EBPalpha) and peroxisome proliferator-activated receptor gamma (PPARgamma) is severely decreased in IRS-1(-/-) IRS-2(-/-) cells at both the mRNA and the protein level, and the mRNAs of lipoprotein lipase and adipocyte fatty acid binding protein are severely decreased in IRS-1(-/-) IRS-2(-/-) cells. Phosphatidylinositol 3-kinase (PI 3-kinase) activity that increases during adipocyte differentiation is almost completely abolished in IRS-1(-/-) IRS-2(-/-) cells. Treatment of wild-type cells with a PI 3-kinase inhibitor, LY294002, markedly decreases the expression of C/EBPalpha and PPARgamma, a result which is associated with a complete block of adipocyte differentiation. Moreover, histologic analysis of IRS-1(-/-) IRS-2(-/-) double-knockout mice 8 h after birth reveals severe reduction in white adipose tissue mass. Our results suggest that IRS-1 and IRS-2 play a crucial role in the upregulation of the C/EBPalpha and PPARgamma expression and adipocyte differentiation.

Drosophila mitochondrial transcription factor A (d-TFAM) is dispensable for the transcription of mitochondrial DNA in Kc167 cells

We have cloned cDNA encoding Drosophila mitochondrial (mt) transcription factor A (d-TFAM). RNA interference (RNAi) of d-TFAM by lipofection of haemocyte-derived Kc167 cells with double-stranded RNA reduced d-TFAM to less than 5% of the normal level. Reflecting the ability of TFAM to stabilize mtDNA, RNAi of d-TFAM reduced mtDNA to 40%. Nonetheless, transcription of the ND2 and ND5 genes and their mRNAs remained unchanged for 8 days of the duration of RNAi. We thus show that d-TFAM is not essential for the transcription of Drosophila mtDNA.

Hexamminecobalt(III) chloride inhibits glucose-induced insulin secretion at the exocytotic process

Hexamminecobalt(III) (HAC) chloride was found to have a potent inhibitory effect on glucose-induced insulin secretion from pancreatic islets. HAC at 2 mm inhibited the secretion in response to 22.2 mm glucose by 90% in mouse islets. Perifusion experiments revealed that the first phase of insulin secretion was severely suppressed and that the second phase of secretion was completely abrogated. Removal of HAC from the perifusate immediately restored insulin secretion with a transient overshooting above the normal level. However, HAC failed to affect glucose-induced changes in d-[6-(14)C]glucose oxidation, levels of reduced forms of NAD and NADP, mitochondrial membrane potential, ATP content, cytosolic calcium concentration, or calcium influx into mitochondria. Furthermore, HAC inhibited 50 mm potassium-stimulated insulin secretion by 77% and 10 microm mastoparan-stimulated insulin secretion in the absence of extracellular Ca(2+) by 80%. The results of a co-immunoprecipitation study of lysates from insulin-secreting betaHC9 cells using anti-syntaxin and anti-vesicle-associated membrane protein antibodies for immunoprecipitation or Western blotting suggested that HAC inhibited disruption of the SNARE complex, which is normally observed upon glucose challenge. These results suggest that the inhibitory effect of HAC on glucose-induced insulin secretion is exerted at a site(s) distal to the elevation of cytosolic [Ca(2+)], possibly in the exocytotic machinery per se; and thus, HAC may serve as a useful tool for dissecting the molecular mechanism of insulin exocytotic processes.

Variants of neurogenin 3 gene are not associated with Type II diabetes in Japanese subjects

AIMS/HYPOTHESIS

Neurogenin 3 (ngn3) is a transcription factor expressed in the endocrine precursor cells of the pancreas. It has recently been reported that ngn3-deficient mice show absence of pancreatic endocrine cells and die of postnatal diabetes. The purpose of this investigation was to screen for polymorphisms of the ngn3 gene and to test whether these polymorphisms are associated with Type II (non-insulin-dependent) diabetes mellitus in the Japanese subjects.

METHODS

We screened ngn3 gene and upstream region by direct sequencing and estimated the prevalence of polymorphisms in 197 patients with Type II (non-insulin-dependent) diabetes mellitus and 216 control subjects.

RESULTS

We identified four novel polymorphisms, Ser199Phe (596C/T), -43insCA, -983C/T and -1822G/A. In an association study the allelic frequencies of the major allele of these four polymorphisms were 0.721, 0.914, 0.912 and 0.530 in diabetic patients, respectively, and 0.694, 0.905, 0.917 and 0.537 in control subjects, respectively.

CONCLUSION/INTERPRETATION

Mutations and polymorphisms of ngn3 gene are not significantly associated with Type II (non-insulin-dependent) diabetes mellitus in the Japanese subjects.

Endogenous PPAR gamma mediates anti-inflammatory activity in murine ischemia-reperfusion injury

BACKGROUND & AIMS

Peroxisome proliferator-activated receptor gamma (PPAR gamma) is a nuclear receptor whose activation has been linked to several physiologic pathways including those related to the regulation of intestinal inflammation. We sought to determine whether PPAR gamma could function as an endogenous anti-inflammatory pathway in a murine model of intestinal ischemia-reperfusion (I/R) injury.

METHODS

PPAR gamma-deficient and wild-type mice were examined for their response to I/R procedure. Treatment with a PPAR gamma-specific ligand was also performed.

RESULTS

In a murine model of intestinal I/R injury, we observed more severe injury in PPAR gamma-deficient mice and protection against local and remote tissue injury in mice treated with a PPAR gamma-activating ligand, BRL-49653. Activation of PPAR gamma resulted in down-regulation of intercellular adhesion molecule 1 expression by intestinal endothelium and tissue tumor necrosis factor alpha messenger RNA levels most likely by inhibition of the NF-kappa B pathway.

CONCLUSIONS

These data strongly suggest that an endogenous PPAR gamma pathway exists in tissues that may be amenable to therapeutic manipulation in I/R-related injuries.

Fatty-acyl-CoA thioesters inhibit recruitment of steroid receptor co-activator 1 to alpha and gamma isoforms of peroxisome-proliferator-activated receptors by competing with agonists

Peroxisome-proliferator-activated receptors (PPARs) alpha and gamma are ligand-dependent transcription factors that are key regulators of lipid and carbohydrate homoeostasis. Fatty acids bind to the ligand-binding domains (LBDs) of PPARalpha and PPARgamma and activate these receptors. To clarify whether fatty-acyl-CoAs interact directly with the LBDs of PPARalpha and PPARgamma, we performed a competition binding assay with radiolabelled KRP-297, a known dual agonist for these receptors. We show here that fatty-acyl-CoAs bind directly to PPARalpha and PPARgamma. Interestingly, fatty-acyl-CoAs, unlike fatty acids, failed to recruit steroid receptor co-activator 1 (SRC-1), on the basis of conformational changes in the LBDs of PPARalpha and PPARgamma. Moreover, fatty-acyl-CoAs also markedly inhibited agonist-induced recruitment of SRC-1. These findings demonstrate that fatty-acyl-CoAs have a novel function in the signalling pathways of PPARalpha and PPARgamma.

A Japanese case of congenital hyperinsulinism with hyperammonemia due to a mutation in glutamate dehydrogenase (GLUD1) gene

We describe a Japanese case of neonatal hyperinsulinism due to a de novo mutation (Gly446Asp) in glutamate dehydrogenase gene (GLUD1). A boy suffered from hypoglycemic coma with relative hyperinsulinemia on day 1 after birth, and received subtotal pancreatectomy. Examination of the resected pancreas revealed a diffuse increase in endocrine cells, consistent with 'nesidioblastosis'. He is now 15 years old and has exhibited mild but persistent hyperammonemia, which is a very unique feature of the disorder caused by GLUD1 activating mutations. He has also been suffering from seizures and mental retardation. Thus, GLUD1 mutations can be a cause of congenital hyperinsulinism in Japanese.

Mechanism of amelioration of insulin resistance by beta3-adrenoceptor agonist AJ-9677 in the KK-Ay/Ta diabetic obese mouse model

The mechanism by which the specific beta3-adrenoceptor agonist AJ-9677 relieves insulin resistance in vivo was investigated by studying its effects in the white and brown adipose tissues of the KK-Ay/Ta diabetic obese mouse model. AJ-9677 reduced the total weight of white adipose tissues by reducing the size of the adipocytes, an effect associated with the normalization of tumor necrosis factor-alpha (TNF-alpha) and leptin expression levels. The levels of uncoupling protein (UCP)-1 mRNA in brown adipose tissue were increased threefold. AJ-9677 caused a marked increase (20- to 80-fold) in the expression of UCP-1 in white adipose tissues. The levels of UCP-2 mRNA were increased in both the white and brown adipose tissues of diabetic obese mice, and AJ-9677 further upregulated UCP-2 mRNA levels in brown adipose tissue, but reduced its levels in white adipose tissue. UCP-3 mRNA levels were not essentially changed by AJ-9677. However, AJ-9677 significantly (two- to four-fold) upregulated the GLUT4 mRNA and protein levels in white and brown adipose tissues and the gastrocnemius. The generation of small adipocytes, presumably mediated by increased expression of UCP-1 in addition to increased lipolysis in response to AJ-9677, was associated with decreased TNF-alpha and free fatty acid production and may be the mechanism of amelioration of insulin resistance in KK-Ay/Ta diabetic obese mice.

A novel low-density lipoprotein receptor-related protein mediating cellular uptake of apolipoprotein E-enriched beta-VLDL in vitro

We report here the identification of a novel member of the low-density lipoprotein receptor (the LDL receptor) family through signal sequence trap screening of a mouse lymphocyte cDNA library. The protein was termed LDL receptor-related protein 9 (LRP9). LRP9 is a type I membrane protein predicted to contain 696 amino acids with a calculated molecular mass of 74 764 Da. The NH(2)-terminal half of LRP9 contains two CUB domains separated by a single ligand-binding repeat. The second CUB domain is followed by a cluster of three additional ligand-binding repeats and a transmembrane domain. The COOH-terminal intracellular region contains a proline-rich region. LRP9 mRNA was expressed in the liver, kidney, lung, and heart at high levels, and in the spleen and brain at low levels. In situ hybridization analysis of mouse liver, kidney, and brain detected LRP9 transcripts in hepatocytes, sinusoidal lining cells, peritubular capillaries, choroid plexus, ependyma of the third ventricle, pia matter, and hippocampus. In particular, high levels of expression were observed in the vascular walls. Apolipoprotein E (apoE)-enriched beta-VLDL stimulated cellular cholesteryl ester formation in ldl-A7/LRP9. These results raise the possibility that this newly identified receptor, which is expressed in the liver, may play a physiological role in the uptake of apoE-containing lipoproteins.

The role of PPARgamma as a thrifty gene both in mice and humans

The biological role of peroxisome proliferator-activated receptor gamma (PPARgamma) was investigated by gene targeting and case-control study of the Pro12Ala PPARgamma2 polymorphism. Homozygous PPARgamma-deficient embryos died at 10.5-11.5 days post conception (dpc) due to placental dysfunction. Heterozygous PPARgamma-deficient mice were protected from the development of insulin resistance due to adipocyte hypertrophy under a high-fat diet, whose phenotypes were abrogated by PPARgamma agonist treatment. Heterozygous PPARgamma-deficient mice showed overexpression and hypersecretion of leptin despite the smaller size of adipocytes and decreased fat mass, which may explain these phenotypes at least in part. This study reveals a hitherto unpredicted role for PPARgamma in high-fat diet-induced obesity due to adipocyte hypertrophy and insulin resistance, which requires both alleles of PPARgamma. A Pro12Ala polymorphism has been detected in the human PPARgamma2 gene. Since this amino acid substitution may cause a reduction in the transcriptional activity of PPARgamma, this polymorphism may be associated with decreased insulin resistance and decreased risk of type 2 diabetes. To investigate this hypothesis, we performed a case-control study of the Pro12Ala PPARgamma2 polymorphism. In an obese group, subjects with Ala12 were more insulin sensitive than those without. The frequency of Ala12 was significantly lower in the diabetic group, suggesting that this polymorphism protects against type 2 diabetes. These results revealed that in both mice and humans, PPARgamma is a thrifty gene mediating type 2 diabetes.

beta-cell glucokinase deficiency and hyperglycemia are associated with reduced islet amyloid deposition in a mouse model of type 2 diabetes

Type 2 diabetes is characterized by impaired beta-cell function, hyperglycemia, and islet amyloid deposition. The primary constituent of islet amyloid is the 37-amino acid beta-cell product called islet amyloid polypeptide (IAPP) or amylin. To study mechanisms of islet amyloid formation, we developed a transgenic mouse model that produces and secretes the amyloidogenic human IAPP (hIAPP) molecule and have shown that 81% of male transgenic mice develop islet amyloid after 14 months on a high-fat diet. To test whether impaired beta-cell function and hyperglycemia could enhance islet amyloid formation, we cross-bred our hIAPP transgenic mice with beta-cell glucokinase-knockout mice (GKKO) that have impaired glucose-mediated insulin secretion and fasting hyperglycemia. The resulting new (hIAPPxGKKO) line of mice had higher basal plasma glucose concentrations than the hIAPP transgenic mice at 3, 6, and 12 months of age (P < 0.05), as did GKKO mice compared with hIAPP transgenic mice at 6 and 12 months of age (P < 0.05). Basal plasma immunoreactive insulin (IRI) levels were lower in hIAPP x GKKO mice than in hIAPP transgenic mice at 6 months of age (P < 0.05). The area under the glucose curve in response to an intraperitoneal glucose challenge (1 g/kg body weight) was larger in hIAPPxGKKO mice than in hIAPP transgenic mice at 3, 6, and 12 months of age (P < 0.005) and in GKKO mice compared with hIAPP transgenic mice at 6 and 12 months of age (P < 0.005). The area under the IRI curve was lower in hIAPPxGKKO mice at 6 and 12 months of age (P < 0.05) than in hIAPP transgenic mice and in GKKO mice compared with hIAPP transgenic mice at 12 months of age (P < 0.05). Despite the presence of hyperglycemia, hIAPPxGKKO mice had a lower incidence (4 of 17 vs. 12 of 19, P < 0.05) and amount (0.40 +/- 0.24 vs. 1.2 +/- 0.3 arbitrary units, P < 0.05) of islet amyloid than hIAPP transgenic mice had. As expected, no islet amyloid was observed in GKKO mice lacking the hIAPP transgene (0 of 13). There was no difference in pancreatic content of IRI and hIAPP among the three groups of mice. Thus, despite the presence of impaired islet function and hyperglycemia, hIAPPxGKKO mice had a decreased incidence and quantity of islet amyloid. Therefore, our data suggest that impaired beta-cell glucose metabolism or hyperglycemia are not likely to contribute to islet amyloid formation in diabetes. Furthermore, this finding may explain the lack of progression of glycemia in patients with maturity-onset diabetes of the young.

Disruption of insulin receptor substrate 2 causes type 2 diabetes because of liver insulin resistance and lack of compensatory beta-cell hyperplasia

To investigate the role of insulin receptor substrate (IRS)-2 in vivo, we generated IRS-2-deficient mice by gene targeting. Although homozygous IRS-2-deficient mice (IRS-2-/- mice) had a body weight similar to wild-type mice, they progressively developed type 2 diabetes at 10 weeks. IRS-2-/- mice showed insulin resistance and a defect in the insulin-stimulated signaling pathway in liver but not in skeletal muscle. Despite insulin resistance, the amount of beta-cells was reduced to 83% of that in wild-type mice, which was in marked contrast to the 85% increase in the amount of beta-cells in IRS-1-deficient mice (IRS-1-/- mice) to compensate for insulin resistance. Thus, IRS-2 plays a crucial role in the regulation of beta-cell mass. On the other hand, insulin secretion by the same number of cells in response to glucose measured ex vivo was significantly increased in IRS-2-/- mice compared with wild-type mice but was decreased in IRS-1-/- mice. These results suggest that IRS-1 and IRS-2 may play different roles in the regulation of beta-cell mass and the function of individual beta-cells.

Design and synthesis of sensitive fluorogenic substrates specific for Lys-gingipain

Lys-gingipain (Kgp) is a major cysteine proteinase produced by the oral anaerobic bacterium Porphyromonas gingivalis, and has been implicated as a major pathogen in the development and progression of advanced adult periodontitis. This enzyme is believed to act as a major virulence factor of the disease, yet there exist no convenient and sensitive substrates for analyzing its biological activity. For a better understanding of the importance of this enzyme in the organism, there is an urgent need for specific substrates. Here we designed and synthesized two peptide 4-methyl-coumaryl-7-amides (MCA), carbobenzoxy (Z)-His-Glu-Lys-MCA, and Z-Glu-Lys-MCA, and tested their possible use as sensitive substrates for Kgp with limited specificity. Both substrates exhibited greater k(cat)/K(m) values than the best known Kgp substrates described so far. Both substrates were resistant to Arg-gingipain, another pathogenic cysteine proteinase from P. gingivalis, as well as trypsin and cathepsins B, L, and H. The levels of Kgp in various microorganisms and human cells were determined with Z-His-Glu-Lys-MCA. Little or no Kgp-like activity was detected in either other microorganisms or human cells tested. These results indicate that the present substrates are a valuable and fast tool for routine assays and for mechanistic studies on Kgp.

Constitutive tyrosine phosphorylation of ErbB-2 via Jak2 by autocrine secretion of prolactin in human breast cancer

Overexpression of the oncogene for ErbB-2 is an unfavorable prognostic marker in human breast cancer. Its oncogenic potential appears to depend on the state of tyrosine phosphorylation. However, the mechanisms by which ErbB-2 is constitutively tyrosine-phosphorylated in human breast cancer are poorly understood. We now show that human breast carcinoma samples with ErbB-2 overexpression have higher proliferative and metastatic activity in the presence of autocrine secretion of prolactin (PRL). By using a neutralizing antibody or dominant negative (DN) strategies or specific inhibitors, we also show that activation of Janus kinase Jak2 by autocrine secretion of PRL is one of the significant components of constitutive tyrosine phosphorylation of ErbB-2, its association with Grb2 and activation of mitogen-activated protein (MAP) kinase in human breast cancer cell lines that overexpress ErbB-2. Furthermore, the neutralizing anti-PRL antibody or erbB-2 antisense oligonucleotide or DN Jak2 or Jak2 inhibitor or DNRas or MAP kinase kinase inhibitor inhibits the proliferation of both untreated and PRL-treated cells. Our results indicate that autocrine secretion of PRL stimulates tyrosine phosphorylation of ErbB-2 by Jak2, provides docking sites for Grb2 and stimulates Ras-MAP kinase cascade, thereby causing unrestricted cellular proliferation. The identification of this novel cross-talk between ErbB-2 and the autocrine growth stimulatory loop for PRL may provide new targets for therapeutic and preventive intervention of human breast cancer.

Phosphatidylinositol 3-kinase and NF-kappa B/Rel are at the divergence of CD40-mediated proliferation and survival pathways

CD40 receptor ligation evokes several crucial outcomes for the fate of an activated B cell, including proliferation and survival. Although multiple signaling molecules in the CD40 pathways have been identified, their specific roles in regulating proliferation and maintaining cell viability are still obscure. In this report, we demonstrate that the activation of both phosphatidylinositol 3-kinase (PI-3K) and NF-kappaB/Rel transcription factors is crucial for CD40-mediated proliferation. Furthermore, our data indicate that PI-3K is indispensable for CD40-mediated NF-kappaB/Rel activation. This is achieved via activation of AKT and the degradation of IkappaBalpha. Furthermore, we show that PI-3K activity is necessary for the degradation of cyclin-dependent kinase inhibitor p27kip. Therefore, both of these events comprise the mechanism by which PI-3K controls cell proliferation. In contrast to the absolute requirement of PI-3K and NF-kappaB/Rel for proliferation, these signaling molecules are only partially responsible for CD40-mediated survival, as blocking of PI-3K activity did not lead to apoptosis of anti-CD40-treated cells. However, the PI-3K/NF-kappaB pathway is still required for CD40-induced Bcl-X gene expression. Taken together, our data indicate that multiple survival pathways are triggered via this receptor, whereas NF-kappaB/Rel and PI-3K are crucial for CD40-induced proliferation.

Effectiveness of smoking-cessation intervention in all of the smokers at a worksite in Japan

In Japan, the prevalence of smoking among males and females was 56.1% and 14.2%, respectively, in 1997. Male smoking prevalence was exceedingly high as compared to those in other industrialized countries. We conducted a randomized controlled intervention study on smoking cessation for all smokers in a worksite regardless of their willingness to quit smoking. All of the male smokers in a radiator manufacturing factory (n=263) were randomly allocated to an intervention group (n=132) or a control group (n=131). Subjects in the intervention group received individual counseling by a doctor, and those who signed a Smoking Cessation Declaration underwent a five-month intervention. Subjects in the control group received equivalent delayed intervention for four months. The cessation rate after the original intervention was 12.9% (17/132) and 3.1% (4/131) in the intervention and control groups, respectively (p=0.003). Among those who once succeeded in quitting, 48.6% (18/37) maintained cessation at the long-term survey. Overall, the cessation rate was 8.4% (22/263) and the prevalence of smoking among males significantly decreased from 62.9 to 56.7% (p=0.038). As a conclusion, intervention in all smokers at a worksite regardless of their willingness to quit is effective and impacts the overall smoking rate.

Overexpression of the glycogen targeting (G(M)) subunit of protein phosphatase-1

The G(M) glycogen-targeting subunit of protein phosphatase-1 (PP1) is believed to be involved in dephosphorylation of the enzymes of glycogen metabolism. To assess the roles of G(M) on glycogen metabolism, we created site-directed G(M) mutants and overexpressed them in Chinese hamster ovary (CHO) cells expressing human insulin receptor. Overexpressed G(M) recruited glycogen synthase as well as PP1 to the glycogen pellet, and upregulated basal glycogen synthase activity. Overexpressed G(M)-67A (Ser-67 replaced with alanine) exhibited decreased sensitivity to suppression of glycogen synthase activity by forskolin, while overexpression of G(M)-48A (Ser-48 replaced with alanine) preserved glycogen synthase activation in response to insulin. These observations indicate that in CHO cells overexpressing G(M); (1) G(M) translocates glycogen synthase to the glycogen pellet and affected basal glycogen synthase, (2) Ser-67 might be involved in the suppression of glycogen synthase activity by glycogenolytic agents, and (3) Ser-48 might not commit to activation of glycogen synthase by insulin.

Congenital ureteral diverticulum coexistent with hydronephrosis caused by vascular compression involving the uterine artery and umbilical ligament: report of a case

Coexistence of congenital ureteral diverticulum and hydronephrosis caused by vascular compression is a rare entity. The authors experienced a case of congenital ureteral diverticulum coexistent with hydronephrosis caused by aberrant vascular compression by uterine and umbilical arteries in a 14-year-old girl. The authors could not diagnose accurately this abnormality preoperatively by 3-dimensional computed tomography. After partial ureterectomy, including resection of the saccular lesion and ureteroneocystostomy, the frequency of urinary tract infection decreased.