Synergistic interaction of p185c-neu and the EGF receptor leads to transformation of rodent fibroblasts

The protein product of the rodent neu oncogene, p185neu, is a tyrosine kinase with structural similarity to the epidermal growth factor receptor (EGFR). Transfection and subsequent overexpression of the human p185c-erbB-2 protein transforms NIH 3T3 cells in vitro. However, NIH 3T3 cells are not transformed by overexpressed rodent p185c-neu. NIH 3T3 transfectants overexpressing EGF receptors are not transformed unless incompletely transformed. Several groups have recently demonstrated EGF-induced, EGFR-mediated phosphorylation of p185c-neu. During efforts to characterize the interaction of p185c-neu with EGFR further, we created cell lines that simultaneously overexpress both p185c-neu and EGFR and observed that these cells become transformed. These observations demonstrate that two distinct, overexpressed tyrosine kinases can act synergistically to transform NIH 3T3 cells, thus identifying a novel mechanism that can lead to transformation.     

The development of porcine zona pellucida using monoclonal antibodies: I. Immunochemistry and light microscopy

We established three monoclonal antibodies (Mabs) against the zonae pellucidae (ZP) of porcine oocytes, named STA-1, STA-2, and STA-3, and eventually we determined that they all reacted with the isolated ZP. Based on Western blotting without 2-mercaptoethanol (2-ME), STA-1 reacted with the 80,000-110,000 Mr component, STA-2 with the 42,000-63,000 Mr component, and STA-3 with the 40,000-80,000 Mr component of ZP. We immunohistochemically specified the components of porcine ZP reactive with the three Mabs during the course of follicular development. Each Mab reacted with both the ZP and the interfollicular cell space (IFCS). One ZP component, reactive with STA-2 and STA-3, was first produced in the primordial follicle and was not found at the cumulus follicle stage, which corresponds to the stage of large antral follicles more than 5 mm in diameter. Another ZP component, reactive with STA-1, was not produced until the secondary follicle stage, and was never found at the antral follicle stage. These results suggest that each ZP component is produced and secreted at a specific stage or stages of folliculogenesis.     

Effect of diabetes mellitus induced by streptozotocin on renal Superoxide dismutases in the rat

Two forms of superoxide dismutase, CuZn-SOD and MnSOD, have been investigated in the kidneys of streptozotocin-induced diabetic rats using both radio-immunoassay and immunoenzyme staining. The rats were killed 2, 8 and 12 weeks after the induction of diabetes mellitus and the kidneys excised. Two weeks after the induction of diabetes, the kidneys were hypertrophied because of the proliferation of renal tubular epithelium. However, the total CuZnSOD content of the kidneys did not increase and, because of the epithelial proliferation, the CuZnSOD concentration in each proximal tubular cell was decreased. Armanni-Ebstein lesions were found in the distal tubules 8 and 12 weeks after the induction of diabetes. The cells in these lesions were intensely stained for CuZnSOD, suggesting an adaptive response to the enhanced oxidative stress. The MnSOD staining in the thick ascending limbs of Henle's loops was enhanced in the diabetic kidneys, while that in the cortical tubules was unaltered. MnSOD was assumed to increase in response to hypermetabolism associated with the proliferation of renal tubules. This was most marked in the cells which were rich in mitochondria, again suggesting an adaptive response to enhanced oxidative stress induced by diabetes mellitus. The glomeruli of both the diabetic and control groups were not stained for SODs, and no significant microscopic change was found even 12 weeks after the induction of diabetes mellitus.     

Purification and physicochemical characterization of murine T cell replacing factor (TRF)

Murine T cell replacing factor (TRF) was purified from a cellfree supernatant of a T cell hybridoma (B151K12) that constitutively produces TRF. Two assay systems for TRF activity were employed: 1) induction of anti-DNP IgG PFC responses in cultures of splenic B cells from DNP-KLH-primed BALB/c mice, and 2) induction of IgM PFC in chronic B cell leukemic cells (BCL1). The purification scheme consisted of ammonium sulfate precipitation, DEAE-cellulose chromatography, Blue-Sepharose chromatography, hydroxylapatite chromatography, gel permeation with fast protein liquid chromatography (FPLC), and disc polyacrylamide gel electrophoresis. Overall, TRF was purified approximately 34,000-fold with a maximum 3.8% recovery of activity, and the specific activity of the purified TRF was approximately 9.6 X 10(4) U/mg. The TRF that is active in these systems is distinct from the other lymphokines such as IL 1, IL 2, BCGFI (now known as BSFp1), and gamma-interferon. The TRF is extremely hydrophobic, with an apparent m.w. of 50,000 to 60,000 on gel permeation chromatography and 18,000 on SDS-PAGE under reducing conditions. Highly purified B151-TRF abrogated the activity by treatment with trypsin but not with RNase. Moreover, it bound to lima bean agglutinin-Sepharose specific for N-acetylgalactosamine residues, indicating that B151-TRF is a glycosylated glycoprotein containing N-acetylgalactosamine residues. The role of N-acetylgalactosamine residues on TRF activity was additionally substantiated by the fact that the addition of appropriate amounts of N-acetylgalactosamine in the assay systems for TRF preferentially induced a profound suppression for TRF-mediated PFC responses.     

Immunohistochemical localization and quantitative analysis of cellular glutathione peroxidase in foetal and neonatal rat tissues: Fluorescence microscopy image analysis

Summary To quantitate the developmental changes in selenium-dependent cellular glutathione peroxidase during the perinatal period, tissue sections from foetal (day 12 to day 22) and neonatal (day 6) rats were stained immunohistochemically using specific polyclonal antiserum. The intensity of the staining was quantified by fluorescence microscopy image analysis. There was a general trend of enriched glutathione peroxidase in the epithelial linings and metabolically active sites. Significant fluorescence was detected in cardiomyocytes, hepatocytes, renal tubular epithelium, bronchiolar epithelium and intestinal epithelium at day 15. The intensity increased in a stepwise manner therafter. The overall increase in the intensity of staining in the heart, liver, kidneys, lungs and intestine was 1.5-, 2.3-, 1.6-, 1.7- and 3.0-fold, respectively. The phase of most rapid increase occurred during the foetal period in the liver, intestine and heart. In the kidneys and lungs, glutathione peroxidase increased significantly during foetal life, and to a similar extent postnatally. These results suggest that the intracellular H₂O₂-scavenging system develops during the foetal period as an essential mechanism for living under atmospheric oxygen conditions. The late development observed in the kidneys and lungs is consistent with the relative biological immaturity of these organs in full-term neonates.     

Chemical change involved in the oxidative reductive depolymerization of hyaluronic acid

The oxidative reductive depolymerization (ORD) of hyaluronate has been investigated. A solution of hyaluronate (Mr 4.07 x 10(5] in phosphate buffer (pH 7.2) was incubated in the presence of Fe2+ for 24 h at 37 degrees C under an oxygen atmosphere to yield depolymerized hyaluronate (ORD fragments; an average Mr of 2,600). The ORD fragments contain 21 and 24% less hexosamine and uronic acid, respectively, but no olefinic linkage. They were exhaustively digested with chondroitinase AC-II. The resulting oligosaccharides and monosaccharides were separated by gel filtration and ion-exchange chromatography, and their structures were determined by proton and carbon-13 NMR, fast atom bombardment mass spectrometry, and chromatographic techniques combined with chemical modifications. The following structures derived from the reducing ends of the ORD fragments were identified: 4,5-unsaturated GlcA(beta 1----3)-N-acetyl-D-glucosaminic acid (where GlcA- represents glucuronosyl-) (21%), 4,5-unsaturated GlcA(beta 1----3)GlcNAc(beta 1----3)-D-arabo-pentauronic acid (24%), and N-acetyl-D-glucosamine (51%). The following structures derived from the nonreducing ends were identified: L-threo-tetro-dialdosyl-(1----3)GlcNAc (a tentative structure, 8%), N-acetylhyalobiuronic acid (20%), and N-acetyl-D-glucosamine (45%). The results indicate that the ORD reaction of hyaluronate proceeds essentially by random destruction of unit monosaccharides due to oxygen-derived free radicals, followed by secondary hydrolytic cleavage of the resulting unstable glycosidic substituents.     

Effect of obesity and troglitazone on expression of two glutathione peroxidases: cellular and extracellular types in serum, kidney and adipose tissue

To determine the effect of obesity on expression of cellular- (C-) and extracellular (EC-) glutathione peroxidase (GPX) in serum, kidney and adipose tissue, we measured GPX in serum, kidneys and adipose tissue of the obese Otsuka-Long-Evans-Tokushima Fatty (OLETF) rat and its lean counterpart (LETO). We also investigated the effect of troglitazone. Five each of OLETF and LETO rats were fed diet with or without 0.2% troglitazone for 10 days. Final body weight, kidney weight, blood glucose and serum tumor necrosis factor-alpha (TNF-alpha) level were higher in OLETF rats than in LETO rats. Serum and kidney GPX activities were higher, but adipose tissue GPX activity was lower, in OLETF rats than in LETO rats. Troglitazone treatment decreased adipose tissue GPX activity and abolished overproduction of TNF-alpha in OLETF rats. Immunoblot analysis, for the first time, revealed that both obesity and troglitazone suppressed the protein signals for C-GPX and EC-GPX in adipose tissue. Serum protein carbonyl groups were increased in OLETF rats and troglitazone completely blocked this increase. Increased serum GPX activity in obese rat was due to the increased secretion of EC-GPX from the kidney. Troglitazone protected against the enhanced oxidative stress induced by obesity independently of the serum GPX concentration.     

Studies on scavenger receptor inhibitors. Part 1: synthesis and structure-activity relationships of novel derivatives of sulfatides

Scavenger receptors have been proven to be implicated in the formation of atherosclerotic lesions. A series of novel derivatives of sulfatides were synthesized, and their inhibitory activities against incorporation of DiI-acetyl-LDL into macrophages were evaluated in order to clarify the structure-activity relationships of sulfatides as a scavenger receptor inhibitor and find out novel inhibitors with synthetic easiness. The chemical modification of the substructures of sulfatides led to the establishment of the following structure-activity relationships; (1) the ceramide moiety can be replaced with another structure bearing two long chains, (2) the galactose moiety can be replaced with another structure or be deleted without a large decrease in the inhibitory activity, (3) the sulfate moiety was crucial, and it was the most preferable functional group for a potent inhibitory activity. The inhibitory activity of (S)-2-octadecanoylamino-2-tetradecylcarbamoyl)ethyl sulfate sodium salt (3a) against incorporation of DiI-acetyl-LDL into macrophages was proven to be based on the inhibition against the binding of acetyl-LDL to the surface of macrophages. We discovered novel scavenger receptor inhibitors with synthetic easiness, such as (S)-2-octadecanoylamino-2-(tetradecylcarbamoyl)ethyl sulfate sodium salt (3a) and 2-octadecanoylamino-1-(octadecanoylaminomethyl)ethyl sulfate sodium salt (13q).     

Tyrosine phosphorylation of a novel 100-kDa protein coupled to CD28 in resting human T cells is enhanced by a signal through TCR/CD3 complex

For T cell activation, two signals are required, i.e., a T cell receptor (TCR)/CD3-mediated main signal and a CD28-mediated costimulatory signal. CD28 binds to its ligand (CD80 or CD86) and transduces the most important costimulatory signal. The cytoplasmic domain of the CD28 molecule, composed of 41 amino acids, does not contain any intrinsic enzyme activity. The cytoplasmic domain of CD28 is remarkably conserved among species and is associated with a number of signaling molecules that affect the main signal. We report here that a tyrosine phosphorylated 100-kDa protein (ppl00) was coupled to the CD28 cytoplasmic domain in Jurkat and human peripheral T cells. The pp100 was distinguished from other CD28 associated molecules such as Vav, STAT5, PI 3-kinase, Valosin-containing protein (VCP), Nucleolin, Gab2 (Grb2-associated binding protein 2), and STAT6. The tyrosine phosphorylation of pp100 coprecipitated with CD28 was enhanced by CD3 stimulation by the specific antibody, tyrosine phosphatase inhibitor and PKC activator. Tyrosine phosphorylation of pp100 was attenuated by the prior addition of PKC inhibitor. These findings indicate that pp100 is a novel tyrosine phosphorylated protein coupled to CD28 under continuous control of tyrosine phosphatases and might play a role in T cell activation augmented by a TCR/CD3-mediated main signal.     

Troglitazone inhibits the expression of inducible nitric oxide synthase in adipocytes in vitro and in vivo study in 3T3-L1 cells and Otsuka Long-Evans Tokushima Fatty rats

The aim of this study was to determine the mechanism of troglitazone action on nitric oxide (NO) production via inducible NO synthase (iNOS) in adipocytes in vitro and in vivo. The treatment of 3T3-L1 adipocytes with the combination of lipopolysaccharide (LPS), tumor necrosis factor-alpha and interferon-gamma synergistically induced de novo iNOS expression leading to enhanced NO production. The NO production was inhibited by co-treatment with aminoguanidine or N-nitro-L-arginine methylester hydrochloride. Troglitazone inhibited the NO production in a dose dependent manner by the suppression of iNOS expression. In the 24 week-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats, the mean weight and the blood glucose were 21% and 30%, respectively, higher than in their lean counterparts. The serum nitrite concentration was increased after injection of LPS (4 mg/kg, i.p.), more markedly in OLETF rats than in the lean rats. The epididymal fats from LPS-injected groups, but not the ones from the non-injected groups, expressed mRNA and protein of iNOS. Troglitazone pre-treatment blocked the LPS-induced expression of iNOS in adipose tissue and the increase in serum nitrite concentration. These results suggest that troglitazone inhibits the cytokine-induced NO production in adipocytes by blocking iNOS expression both in vitro and in vivo.