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Biomedical subjects

S Murthy

Publications and source records attributed to S Murthy.

At least 55 records · Page 3Linked to original sources
PubMed1999

Combination therapy of pentoxifylline and TNFalpha monoclonal antibody in dextran sulphate-induced mouse colitis.

BACKGROUND: Tumour necrosis factor-alpha (TNFalpha) has been suspected of playing an important role in the pathogenesis of inflammatory bowel diseases, and has become a target for the treatment of these diseases. Open-label, placebo controlled studies have shown that engineered CDP571 and chimeric anti-TNF antibody (cA2) provide a significant benefit in Crohn's disease. Since these antibodies have to be used repeatedly to maintain remission in inflammatory bowel disease, there is a concern that their use may compromise host defence and produce toxic side-effects. METHODS: We evaluated the combined use of mouse specific TNFalpha mab (25 microg/mouse, Endogen) and pentoxifylline (PF, 100 mg/kg/day, p.o., TNFalpha release inhibitor) in the DSS (3% dextran sulphate solution) model of mouse colitis. Colitis was induced by the feeding of 3% DSS for three cycles. The study groups were: Group I: single injection of rat anti-mouse IgG, Group II: single injection of TNFalpha mab, Group III: daily PF for three cycles, Group IV: single injection of TNFalpha mab + PF for three cycles, Group V: TNFalpha mab at the beginning of each cycle (three injections) and Group VI: TNFalpha mab (three injections) + daily PF for three cycles. Daily disease activity (DAI) was measured throughout the study. At the end of each cycle, colon tissue was processed for histology, myeloperoxidase (MPO) and plasma TNFalpha. RESULTS: Mice treated with a single injection of TNFalpha alone or TNFalpha mab + PF showed significantly lower DAI, inflammation scores and ulcer index compared with the IgG treated group. Mice treated with TNFalpha mab + PF had no ulcers. Multiple injections of TNFalpha mab or TNFalpha mab + PF showed greater inhibition in DAI and cytokines in the first two cycles. However, in the third cycle, multiple injections of TNFalpha mab showed adverse proinflammatory effects. CONCLUSION: The simultaneous administration of pentoxifylline and TNFalpha mab may enhance therapeutic outcomes in inflammatory bowel disease and reduce the side-effects associated with the repeated use of TNFalpha mab.

Animals↗
PubMed1999

Depletion of colonic detoxication enzyme activity in mice with dextran sulphate sodium-induced colitis.

BACKGROUND: The increased risk of colonic malignancies in individuals with ulcerative colitis has prompted a search for early biomarkers of disease progression. AIM: To characterize Phase II detoxication enzyme expression during acute and chronic colitis. The mouse model of dextran sulphate sodium (DSS)-induced colitis represents a relevant system with which to sequentially evaluate the spectrum of biochemical changes associated with colorectal cancer risk. METHODS: Acute and chronic colitis were induced in Swiss Webster mice by administering DSS in the drinking water (5%) for 1-4 cycles. Each cycle consisted of 7 days DSS and 14 days of water. The glutathione S-transferase (GST) activity, gamma-glutamylcysteine synthetase (gamma-GCS) activity and glutathione content of the colonic tissues were determined at various time points throughout the experiment. Alterations in GST isozyme expression were confirmed by Western and Northern blot. RESULTS: GST activity was reduced significantly in the colon by the end of Cycle 1 (84% of control values). Specific activities continued to decrease with subsequent cycles of DSS exposure. By the end of Cycle 4, glutathione levels and gamma-GCS activity had reached 29% and 56% of control, respectively. CONCLUSIONS: These data suggest that detoxication enzyme depletion is associated with both acute and chronic colitis and may be an important event in the progression of ulcerative colitis to colon cancer.

Animals↗
PubMed1999

Hemorrhage from recanalized umbilical vein in a patient with cirrhosis.

The formation of portosystemic collaterals occurs frequently in portal hypertension; however, the finding of a patent or recanalized umbilical vein has more often been incidental, with only six cases of recanalized umbilical veins or patent paraumbilical veins demonstrated with clinical significance This is only the second documented case of an umbilical vein with external hemorrhage significant enough to cause hemodynamic instability. It raises important questions with regard to prognostic indices for rebleeding at the umbilicus as well as at other, more common, portosystemic collateral sites.

Collateral Circulation↗
PubMed1999

A novel therapy for colitis utilizing PPAR-gamma ligands to inhibit the epithelial inflammatory response.

Peroxisome proliferator-activated receptor gamma (PPAR-gamma), a member of the nuclear hormone receptor superfamily originally shown to play a critical role in adipocyte differentiation and glucose homeostasis, has recently been implicated as a regulator of cellular proliferation and inflammatory responses. Colonic epithelial cells, which express high levels of PPAR-gamma protein, have the ability to produce inflammatory cytokines that may play a role in inflammatory bowel disease (IBD). We report here that PPAR-gamma ligands dramatically attenuate cytokine gene expression in colon cancer cell lines by inhibiting the activation of nuclear factor-kappaB via an IkappaB-alpha-dependent mechanism. Moreover, thiazolidinedione ligands for PPAR-gamma markedly reduce colonic inflammation in a mouse model of IBD. These results suggest that colonic PPAR-gamma may be a therapeutic target in humans suffering from IBD.

Animals↗
PubMed1998

Human outer dense fiber gene, ODF2, localizes to chromosome 9q34.

We have isolated the human homolog of the rat Odf2 gene. In rat, Odf2, the 84-kDa major outer dense fiber protein, interacts strongly and specifically with Odf1, the 27-kDa major outer dense fiber protein. The interaction is mediated by leucine zippers during ODF assembly along the sperm axoneme. We compared homology and genomic structure to rat and mouse Odf2 genes. Using fluorescence in situ hybridization, we mapped the human Odf2 gene (ODF2) to chromosome 9q34.

Animals↗
PubMed1998

Transport of cholesterol from the endoplasmic reticulum to the plasma membrane is constitutive in CaCo-2 cells and differs from the transport of plasma membrane cholesterol to the endoplasmic reticulum.

The transport of newly synthesized cholesterol from its site of synthesis, the endoplasmic reticulum, to the plasma membrane was studied in CaCo-2 cells. The appearance of newly synthesized cholesterol on the cell surface was rapid. By 30 min, 50% of the total labeled cholesterol was observed in the plasma membrane. The arrival of cholesterol at the plasma membrane was independent of new protein synthesis, a functional Golgi apparatus, or microtubular function. Progesterone, verapamil, and trifluoperazine, inhibitors of p-glycoprotein which are known to inhibit cholesterol transport from the plasma membrane to the endoplasmic reticulum, reduced the amount of newly synthesized cholesterol reaching the plasma membrane. The p-glycoprotein inhibitors, however, caused the accumulation of sterol intermediates in the plasma membrane, suggesting that sterol trafficking to the plasma membrane remained intact, but that trafficking from the plasma membrane to the endoplasmic reticulum was disrupted. In contrast, nigericin, another potent inhibitor of cholesterol movement from the plasma membrane to the endoplasmic reticulum, did not alter the transport of newly synthesized cholesterol to the plasma membrane. Moreover, promoting cholesterol transport from the plasma membrane to the endoplasmic reticulum by sphingomyelin hydrolysis or by micellar cholesterol influx did not alter the percent of newly synthesized cholesterol transported to the plasma membrane. Likewise, preventing plasma membrane cholesterol from reaching the endoplasmic reticulum by incubating cells with lysophosphatidylcholine, filipin, or digitonin did not alter the arrival of newly synthesized cholesterol to the plasma membrane. The results suggest that the amount of cholesterol moving to the plasma membrane from the endoplasmic reticulum is constitutive and regulated at the level of cholesterol synthesis and not at the level of the transport process. The pathways of cholesterol transport to and from the plasma membrane are distinct.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

13-hydroxy octadecadienoic acid (13-HODE) inhibits triacylglycerol-rich lipoprotein secretion by CaCo-2 cells.

Oxidized lipids present in atherogenic lipoproteins are derived, in part, from the diet. To address the effects of an oxidized lipid on intestinal lipoprotein assembly and secretion, CaCo-2 cells were incubated with 13-HODE or its native fatty acid, linoleic acid, and triacylglycerol-rich lipoprotein synthesis and secretion were investigated. 13-HODE was readily taken up by cells and esterified to lipids. Although both fatty acids were largely esterified to neutral lipids, in comparison to neutral lipids containing linoleic acid, a greater proportion of cellular neutral lipids containing 13-HODE and/or its metabolites was secreted. Compared to linoleic acid, however, 13-HODE caused less triacylglycerol, derived from de novo synthesis, and less triacylglycerol mass to be secreted. Cells incubated with both linoleic acid and 13-HODE together secreted less triacylglycerol mass than did cells incubated with linoleic acid alone. Less newly synthesized apoB and apoB mass were secreted by cells incubated with 13-HODE without altering the abundance of apoB mRNA. The fraction of newly synthesized apoB translocated into the secretory pathway of cells exposed to 13-HODE was significantly less than that observed in cells incubated with linolenic acid, suggesting that 13-HODE interfered with the assembly and secretion of triacylglycerol-rich lipoprotein particles.

Apolipoproteins B↗
PubMed1998

Caveolin is present in intestinal cells: role in cholesterol trafficking?

It was postulated that specialized microdomains of the plasma membrane, consistent with caveolae, might play a role in cholesterol trafficking in intestinal cells. The existence, therefore, of caveolin and the role of detergent-resistant microdomains of the plasma membrane in cholesterol trafficking were investigated in human small intestine and CaCo-2 cells. Caveolin mRNA was detected by RT-PCR in small intestinal brushings and biopsies and in CaCo-2 cells. Northern hybridization of caveolin mRNA detected 3 kb and 0.8 kb transcripts in CaCo-2 cells. From brushings of distal duodenum and in CaCo-2 cells, Western analysis for detection of caveolin protein demonstrated a 21 kDa-sized protein and a 600 kDa homooligomer. In CaCo-2 cells, caveolin was demonstrated by immunofluorescence in apical membranes as well as within cells. Using sucrose-density gradients, caveolin was localized to detergent-resistant microdomains of the plasma membrane. As determined by cholesterol oxidase-accessible cholesterol, 3-5% of plasma membrane cholesterol in CaCo-2 cells was estimated to be in these detergent-resistant microdomains. After the absorption of cholesterol from bile-salt micelles, more plasma membrane cholesterol moved to these specialized microdomains within the plasma membrane and was esterified. In CaCo-2 cells, filipin, N-ethyl maleimide, and cholesterol depletion, treatments that disrupt caveolar function, interfered with the transport of plasma membrane cholesterol to the endoplasmic reticulum, whereas okadaic acid, sphingomyelinase, and cholesterol oxidase did not. Changes in cholesterol flux at the apical membrane of the cell did not alter mRNA levels or mass of caveolin. The results suggest that caveolin is present in intestinal and CaCo-2 cells and is associated with detergent-resistant microdomains of cellular membranes. With the influx of micellar cholesterol from the lumen, plasma membrane cholesterol moves or "clusters" to these microdomains and is transported to the endoplasmic reticulum for esterification and eventual transport. Caveolin/caveolae may play a role in cholesterol trafficking in intestinal cells.

Biological Transport↗
PubMed1997

The efficacy of BAY y 1015 in dextran sulfate model of mouse colitis.

OBJECTIVE AND DESIGN: There is crucial evidence that leukotrienes are significant mediators of inflammation in inflammatory bowel diseases (IBD). Thus, selective inhibition of leukotriene synthesis is believed to provide a novel approach to therapy of IBD. The aim of the study is to study the efficacy of a potent 5-lipoxygenase activating protein inhibitor (FLAP), BAY y 1015 in a dextran sulfate model of mouse colitis. MATERIAL: Outbred female mice weighing approximately 25 grams were used to produce acute or chronic colitis by feeding 5% dextran sulfate in drinking water. TREATMENT: Colitic mice were treated with placebo (3% starch suspension, 0.1 ml. p.o., bid) or BAY y 1015 at 8 or 24 mg/kg, p.o., bid or olsalazine, 150 mg/kg/day, p.o. METHODS: Efficacy was determined by measuring daily disease activity index (DAI), quantitative histological scores, qualitative histology and measurement of tissue myeloperoxidase (MPO) and leukotriene B4 (LTB4) levels. RESULTS: BAY y 1015 was significantly more effective in improving the qualitative histology, inhibiting the DAI, inflammation scores (37-79%), crypt scores (28-71%), MPO (49-57%) and LTB4 levels (56-63%) compared to placebo treatment at all levels of colitis. The two doses of BAY y 1015 were equipotent in decreasing TLB4 levels. BAY y 1015 was significantly better than olsalazine in two of the three protocols used in this study. In the advanced disease level both doses of BAY y 1015 were equipotent in inhibiting crypt and (28-32%) inflammation scores (34-36%), LTB4 (34-56%) and MPO 41-49%) compared to olsalazine. CONCLUSION: This study suggests the possibility of investigating the use of this compound for the treatment of human inflammatory bowel diseases.

Animals↗
PubMed1997

Neurohormonal mechanisms of cigarette smoke-induced duodenal mucosal bicarbonate secretion in the rat.

The effect of cigarette smoke and nicotine on duodenal mucosal bicarbonate secretion (DMBS) was studied in rats. Cigarette smoke but not intravenous nicotine administered acutely to anesthetized rats via a tracheostomy tube stimulated DMBS by 47 +/- 6%. The increase was neurally mediated via atropine-sensitive postganglionic cholinergic neurons. Introduction of cigarette smoke after the infusion of vasoactive intestinal peptide and porcine histidine isoleucine (PHI) also caused a delayed increase in DMBS. However, the magnitude of this increase was similar to that seen in control non-peptide-infused rats. The increase in bicarbonate secretion predominantly involved Brunner's glands. Rats exposed to cigarette smoke for 4 and 8 days before direct instillation of smoke via tracheostomy tube did not show any increase in their DMBS. These studies indicate that in the rat, cigarette smoke increases DMBS, most likely secreted by the Brunner's glands. The increase is neurally mediated via atropine-sensitive postganglionic cholinergic neurons. Gastroenteric neuropeptides do not exert any influence on cigarette smoke-mediated DMBS secretion in the rat. Unlike acute exposure to cigarette smoke, chronic exposure (4 and 8 days) of rats to cigarette smoke abolishes increase in DMBS induced by subsequent exposure to cigarette smoke. This last observation may, in part, may explain the tendency of chronic smokers who have duodenal bulb ulcers to show greater propensity to higher rate of recurrence and protracted healing.

Animals↗
PubMed1997

Ischemia/reperfusion injury in the rat colon.

This study investigated metabolic and biochemical consequences of colonic ischemia/reperfusion (I/R) in the rat and evaluated whether antioxidants prevent I/R-induced functional damage in the rat colon. The surgical preparation involved a 10 cm segment of the colon and occlusion of the superior mesenteric artery (SMA) to induce I/R. Arterial blood from the aorta and venous blood from the superior mesenteric vein (SMV) was collected to measure blood gases, lactic acid (LA) and arachidonic acid (AA) metabolites. Tissue xanthine oxidase (XO) and thiobarbituric acid (TBA) derivatives were measured before and after reperfusion. In addition, vascular and mucosal permeability, and the effect of MDL 73404 (a water soluble vitamin E analog) and 5-aminosalicylic acid on LA, AA, XO and TBA was measured. After ischemia, the colon displayed a metabolic shift from aerobic to anaerobic course by increasing lactic acid production in the colon (183% increase in SMV lactate level compared 87% in the SMA; p < 0.03). After 10 minutes of reperfusion, circulating 6-keto-prostaglandin F1 alpha increased by 3.85 fold (p < 0.001) and thromboxane B2 increased by 2 to 3 fold. An Ischemia time longer than 60 minutes was required to cause changes in tissue XO levels. Tissue TBA levels showed a good dose response corresponding with I/R time. I/R (60 minutes) caused a three and 16 fold increase (p < 0.01) in vascular and mucosal permeability, respectively. MDL 73404 and 5-aminosalicylic acid significantly inhibited the vascular permeability and decreased LA, AA, XO and TBA. These observations provide the first direct experimental evidence for I/R-induced damage in the colon and some of its effects can be reversed by conventional and novel antioxidants.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Microsomal triglyceride transfer protein in CaCo-2 cells: characterization and regulation.

As microsomal triglyceride transfer protein (MTP) is required for the assembly and secretion of apoB-containing lipoproteins by intestinal epithelial cells, the characterization and regulation of MTP in human intestinal cells, CaCo-2, was studied. CaCo-2 cells express MTP mRNA of 4.2 kb and a 97 kDa subunit of MTP protein. Similar to the expression of apoB mRNA, MTP mRNA expression was dependent upon cell differentiation and was directly related to the ability of the cells to assemble and secrete apoB-containing lipoproteins. MTP mRNA expression was highest in fully differentiated cells, with small but detectable amounts found in undifferentiated cells. Under conditions of increased apoB secretion by oleic acid, phosphatidylcholine, or lysophosphatidylcholine, MTP mass, MTP activity, and MTP gene expressions were not altered. In cells treated with calcium ionophore or phorbol 12-myristate 13-acetate, no relationship could be established between apoB secretion and MTP mRNA or activity. Similarly, in cells treated with sphingomyelinase, trifluoperazine, verapamil, okadaic acid, vanadate, or monensin, agents that decrease apoB secretion, no corresponding decrease in MTP activity or mass was observed. The results suggest that the various mediators of apoB secretion alter steps in lipoprotein assembly and secretion that are not dependent on MTP activity. CaCo-2 cells have an abundant supply of MTP for the assembly of lipoproteins when apoB secretion is stimulated by dietary lipids.

Apolipoproteins B↗
PubMed1997

Inhibition of apolipoprotein B secretion by IL-6 is mediated by EGF or an EGF-like molecule in CaCo-2 cells.

Small intestinal mucosal inflammation observed in celiac disease is associated with the local release of growth factors and various cytokines. In a previous study, we investigated the effect of various cytokines on triacylglycerol and apoB secretion by CaCo-2 cells and observed that TNF-alpha, IL-1 beta, and particularly IL-6, decreased apolipoprotein (apo) B and triacylglycerol secretion. In this study, we explored possible mechanisms to explain the inhibitory effect of IL-6 on apoB secretion. IL-6, 10 ng/mL, added to the basolateral medium of CaCo-2 cells grown on semi-permeable filters, decreased apoB secretion by 42%. Adding a blocking monoclonal antibody (mAb 528) to the EGF receptor completely prevented this effect. IL-6 decreased the amount of EGF receptor protein and the binding of iodinated EGF to its receptor by 50% and 30%, respectively. Incubation of cells with various ligands to the EGF receptor, such as EGF, TGF-alpha, HB-EGF, and amphiregulin, also decreased apoB secretion. Inhibition of apoB secretion by EGF was prevented by the mAb 528 or an EGF neutralizing antibody. In a dose-dependent manner, the neutralizing antibody to EGF prevented the decrease in secretion of apoB, triacylglycerol mass, and cell-surface binding of labeled EGF caused by IL-6. Similar to the effects of IL-6, EGF decreased the secretion of triacylglycerol mass and the synthesis and secretion on newly synthesized apoB. The results suggest that, in CaCo-2 cells, IL-6 causes the release of EGF or an EGF-like molecule. By binding to cell surface EGF receptors, the molecule then causes a decrease in triacylglycerol and apoB secretion.

Antibodies, Monoclonal↗
PubMed1996

Phosphatidylcholine increases the secretion of triacylglycerol-rich lipoproteins by CaCo-2 cells.

The regulation of lipid synthesis and secretion by phosphatidylcholine was investigated in CaCo-2 cells grown on semi-permeable filters. In cells incubated with 1 mM taurocholate and 100-500 microM phosphatidylcholine, cholesteryl ester synthesis was decreased, triacylglycerol synthesis was increased modestly, whereas phospholipid synthesis was unaffected. Acyl-CoA-cholesterol acyltransferase activity was decreased secondary to a decrease in the substrate (cholesterol) supply. The basolateral secretion of newly synthesized triacyglycerol and triacyglycerol mass was significantly increased by phosphatidylcholine, whereas cellular triacylglycerol mass decreased. This effect was no specific for phosphatidylcholine as phosphatidylethanolamine and phosphatidylserine also increased the secretion of newly synthesized triacylglycerols. Dioleoylphosphatidylcholine was as effective as egg phosphatidylcholine in increasing triacylglycerol transport. Dipalmitoylphosphatidylcholine, in contrast, was without effect. Phosphatidylcholine also increased the basolateral secretion of apolipoprotein B (apoB) mass without altering apoB mRNA levels. Disruption of the Golgi apparatus by monensin or brefeldin A prevented the increase in apoB secretion by phosphatidylcholine. Compared with microsomes prepared from control cells, those from cells incubated with phosphatidylcholine contained more newly synthesized apoB. The percentage of new synthesized apoB isolated from teh lumen of microsomes (as an estimate of apoB destined for secretion), however, was similar in the two preparations. Thus in CaCo-2 cells incubated with phosphatidylcholine, the transport of apoB and triacylglycerols is increased whereas cholesteryl ester synthesis and secretion are decreased. A normally functioning secretory pathway is required for phosphatidylcholine to increase triacylglycerol-rich lipoprotein secretion.

Caco-2 Cells↗
PubMed1996

Clinical effects of amifostine (Ethyol) in patients treated with carboplatin.

Amifostine is a compound that has been developed as a radio- and chemoprotectant. It is a prodrug, giving rise to the active thiol, WR-1065. Amifostine has been demonstrated to reduce the toxicity of ionising radiation, alkylating agents and platinum compounds. Preclinical studies have shown that amifostine can reduce the myelosuppression of carboplatin in a murine model tumour system without reducing the efficacy of therapy. In fact, in this model system, the antitumour effects of carboplatin against the OVCAR-3 cell line were actually greater with than without amifostine. Based on these preclinical studies, clinical trials of the combination of carboplatin and amifostine have been undertaken. A phase I trial of carboplatin and amifostine in pretreated patients demonstrated that two doses of amifostine 740 mg/m2/dose may be safely administered with carboplatin. The maximum tolerated dose (MTD) of carboplatin that could be administered with amifostine was 500 mg/m2, suggesting the hypothesis that amifostine increases the MTD of carboplatin from 400 to 500 mg/m2. To test this hypothesis, a randomised trial of carboplatin 500 mg/m2 versus carboplatin 500 mg/m2 plus two doses of amifostine 910 mg/m2/dose has been performed. Analysis of this trial is not complete, but initial results suggest a reduction of first-cycle thrombocytopenia, from a median platelet nadir value of 85 x 10(9) cells/l for carboplatin alone to 144 x 10(9) cells/l for the combination of carboplatin plus amifostine. Similarly, the median first-cycle granulocyte nadir was 1.6 x 10(9) cells/l without amifostine but 2.4 x 10(9) cells/l with the cytoprotectant. Neither of these first-cycle differences was statistically significant, but these effects are being maintained with repeated dosing, so that an increase in delivered cumulative carboplatin dose seems possible with the use of amifostine. These promising data indicate that continued studies of amifostine with carboplatin are justified and that the effects of amifostine on the thrombocytopenia produced by carboplatin-containing combination chemotherapy regimens should be investigated.

Amifostine↗
PubMed1996

Cytokines regulate apolipoprotein B secretion by Caco-2 cells: differential effects of IL-6 and TGF-beta 1.

A variety of cytokines are found in the intestinal mucosa of individuals with inflammatory diseases. The potential role of cytokines in mediating lipoprotein assembly and secretion in the human intestinal cell line, Caco-2, was investigated. Interleukin-1 beta, interleukin-6 (IL-6), and tumor necrosis factor-alpha all decreased the basolateral secretion of apolipoprotein B (apo B), with IL-6 being the most potent. IL-6 was also found to inhibit triacylglycerol secretion. In contrast, transforming growth factor-beta 1 (TGF-beta 1) increased the secretion of apo B and triacylglycerol. In pulse-chase experiments, IL-6 decreased the rate of synthesis and secretion of apo B-100 and apo B-48 without altering the rate of apo B degradation, whereas TGF-beta 1 increased the rate of synthesis and secretion of apo B-100 and apo B-48. Degradation of apo B was also not affected by TGF-beta 1. The abundance of apo B mRNA in cells incubated with IL-6 was decreased, whereas cells incubated with TGF-beta 1 had higher levels of apo B mRNA. In conditions of small intestinal inflammation, cytokines could contribute to the observed malabsorption of fat and other nutrients by the small intestine.

Animals↗