Interleukin (IL)-18 was identified as a molecule that induces IFN- production and enhances NK cel... more Interleukin (IL)-18 was identified as a molecule that induces IFN- production and enhances NK cell cytotoxicity. In this paper, we report upon the purification and characterization of human IL-18 receptor (hIL-18R). We selected the Hodgkin's disease cell line, L428, as the most ...
American Journal of Physiology-Gastrointestinal and Liver Physiology
Effects of short-term infusion and long-term injection of gastric inhibitory polypeptide (GIP) on... more Effects of short-term infusion and long-term injection of gastric inhibitory polypeptide (GIP) on changes in pancreatic lipase and colipase contents in rats were studied, and mRNAs encoding for lipase and colipase were determined by Northern blot hybridization with specific cDNA probes. GIP infused at a dose of 3 micrograms/h for 24 h significantly increased the pancreatic lipase content by 34% (P less than 0.05) but had no significant effect on colipase and amylase contents. No change in mRNAs encoding for these proteins was found after infusion of GIP for 24 h. Injection of GIP (5-60 micrograms/kg) three times a day for 5 days dose dependently increased the contents of lipase and colipase, with the increase in colipase being more prominent. Injection of GIP for 5 days at a dose of 30 micrograms.kg-1.day-1 increased colipase and lipase contents by 52 and 25%, and their corresponding mRNAs by 60 and 160%, respectively. The amylase mRNA was not changed by injection of GIP. It is conc...
Intestinal alkaline sphingomyelinase (alk-SMase) cleaves phosphocholine from sphingomyelin, plate... more Intestinal alkaline sphingomyelinase (alk-SMase) cleaves phosphocholine from sphingomyelin, platelet-activating factor (PAF), and lysophosphatidylcholine. We recently found that colitis-associated colon cancer was 4-5 fold enhanced in alk-SMase knockout mice. Here we further studied pathogenesis of colitis induced by dextran sulfate sodium (DSS) in wild type (WT) and the knockout mice. Comparing with WT mice, knockout mice demonstrated greater body weight loss, more severe bloody diarrhea, broader inflammatory cell infiltration, and more serious epithelial injury. Higher levels of PAF and lower levels of IL10 were identified in knockout mice 2 days after DSS treatment. A greater and progressive increase of lysophosphatidic acid (LPA) was identified. The change was associated with increased autotaxin expression in both small intestine and colon, which was identified by immunohistochemistry study, Western blot and sandwich ELISA. The upregulation of autotaxin coincided with early incr...
Alkaline sphingomyelinase cleaves phosphocholine from sphingomyelin, platelet-activating factor, ... more Alkaline sphingomyelinase cleaves phosphocholine from sphingomyelin, platelet-activating factor, lysophosphatidylcholine, and less effectively phosphatidylcholine. The enzyme shares no structure similarities with acid or neutral sphingomyelinase but belongs to ecto-nucleotide pyrophosphatase/phosphodiesterase (NPP) family and therefore is also called NPP7 nowadays. The enzyme is expressed in the intestinal mucosa in many species and additionally in human liver. The enzyme in the intestinal tract has been extensively studied but not that in human liver. Studies on intestinal alkaline sphingomyelinase show that it inhibits colonic tumorigenesis and inflammation, hydrolyses dietary sphingomyelin, and stimulates cholesterol absorption. The review aims to summarize the current knowledge on liver alkaline sphingomyelinase in human and strengthen the necessity for close study on this unique human enzyme in hepatobiliary diseases.
Sphingomyelin (SM) and cholesterol are two types of lipid closely related biophysically. Treating... more Sphingomyelin (SM) and cholesterol are two types of lipid closely related biophysically. Treating the cells with exogenous sphingomyelinase (SMase) induces trafficking of cholesterol from membrane to intracellular pools and inhibition of cholesterol synthesis. In the present work, we address a question whether increased cholesterol synthesis affects hydrolysis of SM by endogenous SMases. Both HepG2 and Caco-2 cells were incubated with mevalonate. The SMase activity was determined and its mRNA examined by qPCR. The cellular levels of cholesterol, SM, and phosphatidylcholine (PC) were determined and cell proliferation rate assayed. We found that mevalonate dose-dependently decreased acid but not neutral SMase activity in both HepG2 and Caco-2 cells with HepG2 cells being more sensitive to mevalonate. Kinetic examination in HepG2 cells revealed that acid SMase activity was increasing with cell proliferation, and such an increase was reversed by mevalonate treatment. Acid SMase mRNA was...
Boswellic acids, a type of pentacyclic triterpenoids, have been shown to induce apoptosis in colo... more Boswellic acids, a type of pentacyclic triterpenoids, have been shown to induce apoptosis in colon cancer cells. The phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) pathway is crucial for cell proliferation and survival. Whether the apoptotic effects of boswellic acid could be affected by inhibition of PI3K/Akt pathway was examined. Colon cancer HT29 cells were treated with 3-acetyl-11-keto-beta boswellic acid AKBA in the absence and presence of LY294002 or Wortmanin, inhibitors of PI3K. Apoptosis was determined by flow cytometry and caspase assay. The activation of Akt was examined by Western blot. AKBA at 30 microM only slightly induced apoptosis. Preincubation of the cells with LY294002 or wortmannin significantly enhanced the AKBA-induced apoptosis up to 20-fold. Further study showed that at the doses used, AKBA induced phosphorylation of Akt at both Ser473 and Thr308 positions, indicating an activation of the PI3K/Akt pathway. AKBA may activate the PI3K/Akt pathway ...
The hydrolysis of sphingomyelin generates key molecules regulating cell growth and inducing apopt... more The hydrolysis of sphingomyelin generates key molecules regulating cell growth and inducing apoptosis. Data from animal cancer models support an inhibitory role for this pathway in the malignant transformation of the colonic mucosa. In the intestinal tract, a sphingomyelinase with an optimum alkaline pH has been identified. We recently found that the activity of alkaline sphingomyelinase is significantly decreased in colorectal adenocarcinomas, indicating a potential anticarcinogenic role of this enzyme. To further examine whether the reduction of sphingomyelinase is present already in the premalignant state of neoplastic transformation, we measured sphingomyelinase activities in patients with familial adenomatous polyposis (FAP) and in sporadic colorectal tubulovillous adenomas. Tissue samples were taken from adenomas and surrounding macroscopically normal mucosa from 11 FAP patients operated with ileorectal anastomosis, from three FAP patients with intact colon, from 13 patients w...
Alkaline sphingomyelinase (NPP7) is an ecto-enzyme expressed in intestinal mucosa, which hydrolys... more Alkaline sphingomyelinase (NPP7) is an ecto-enzyme expressed in intestinal mucosa, which hydrolyses sphingomyelin (SM) to ceramide and inactivates platelet activating factor. It is also expressed in human liver and released in the bile. The enzyme may have anti-tumour and anti-inflammatory effects in colon and its levels are decreased in patients with colon cancer and ulcerative colitis. Active NPP7 is translated from a transcript of 1.4 kb, whereas an inactive form from a 1.2 kb mRNA was found in colon and liver cancer cell lines. While the roles of NPP7 in colon cancer have been intensively studied, less is known about the function and implications of NPP7 in the bile. The present study examines the changes of NPP7 in bile of patients with various hepatobiliary diseases. Bile samples were obtained at endoscopic retrograde cholangiopancreatography (ERCP) in 59 patients with gallstone, other benign disease, tumour, and primary sclerosing cholangitis (PSC). The NPP7 activity was dete...
Alkaline sphingomyelinase (alk-SMase) is expressed in the intestine and human liver. It may inhib... more Alkaline sphingomyelinase (alk-SMase) is expressed in the intestine and human liver. It may inhibit colonic tumorigenesis, and loss of function mutations have been identified in human colon cancer. The present study investigates its expression in human liver cancer. In HepG2 liver cancer cells, RT-PCR identified three transcripts with 1.4, 1.2 and 0.4 kb, respectively. The 1.4 kb form is the wild-type cDNA with five translated exons, the 1.2 kb product lacks exon 4 and the 0.4 kb form is a combination of exons 1 and 5. Genomic sequence showed that these aberrant transcripts were products of alternative splicing. Transient expression of the 1.2 kb form showed no alk-SMase activity. In HepG2 cells, the alk-SMase activity is low in monolayer condition and increased with cell polarisation. Coexistence of 1.4 and 1.2 kb forms was also identified in one hepatoma biopsy. GenBank search identified a cDNA clone from human liver tumour, which codes a protein containing full length of alk-SMas...
Curcumin has been shown to inhibit cell growth and induce apoptosis in colon cancer cells. The me... more Curcumin has been shown to inhibit cell growth and induce apoptosis in colon cancer cells. The metabolism of sphingomyelin has implications in the development of colon cancert. We examined whether curcumin affects the enzymes that hydrolyse sphingomyelin in Caco-2 cells. The cells were cultured in both monolayer and polarized conditions and stimulated with curcumin. The activities of sphingomyelinases were determined. Sphingomyelin and its hydrolytic products were analysed by thin layer chromatography. The changes of acid sphingomyelinase protein were examined by Western blotting. We found that curcumin reduced the hydrolytic capacity of the cells against choline-labelled sphingomyelin, associated with a mild increase of cellular sphingomyelin in the cells. Analysis of the hydrolytic products revealed that the activity was derived from acid sphingomyelinase not from phospholipase D. The curcumin-induced reduction of acid SMase required more than 8 h stimulation. Western blotting sho...
Sphingomyelin metabolism generates anticancer signals such as ceramide and sphingosine that may i... more Sphingomyelin metabolism generates anticancer signals such as ceramide and sphingosine that may inhibit cell proliferation, and induce differentiation and apoptosis. Changes of sphingomyelin metabolism are found to be associated with tumorigenesis in various tissues and a particular link between sphingomyelin metabolism and colon cancer has been indicated. The effects of several anticancer drugs on sphingomyelin metabolism have been examined recently and there is an increasing interest in discovering new drugs taking sphingomyelin as a target. The present review outlines the sphingomyelin metabolism pathway, introduces the evidence linking sphingomyelin to colon cancer, and summarizes the anticancer drugs and dietary factors that affect the metabolism of sphingomyelin and, thus, the production of the anticancer messengers in the colon.
Interleukin (IL)-18 was identified as a molecule that induces IFN- production and enhances NK cel... more Interleukin (IL)-18 was identified as a molecule that induces IFN- production and enhances NK cell cytotoxicity. In this paper, we report upon the purification and characterization of human IL-18 receptor (hIL-18R). We selected the Hodgkin's disease cell line, L428, as the most ...
American Journal of Physiology-Gastrointestinal and Liver Physiology
Effects of short-term infusion and long-term injection of gastric inhibitory polypeptide (GIP) on... more Effects of short-term infusion and long-term injection of gastric inhibitory polypeptide (GIP) on changes in pancreatic lipase and colipase contents in rats were studied, and mRNAs encoding for lipase and colipase were determined by Northern blot hybridization with specific cDNA probes. GIP infused at a dose of 3 micrograms/h for 24 h significantly increased the pancreatic lipase content by 34% (P less than 0.05) but had no significant effect on colipase and amylase contents. No change in mRNAs encoding for these proteins was found after infusion of GIP for 24 h. Injection of GIP (5-60 micrograms/kg) three times a day for 5 days dose dependently increased the contents of lipase and colipase, with the increase in colipase being more prominent. Injection of GIP for 5 days at a dose of 30 micrograms.kg-1.day-1 increased colipase and lipase contents by 52 and 25%, and their corresponding mRNAs by 60 and 160%, respectively. The amylase mRNA was not changed by injection of GIP. It is conc...
Intestinal alkaline sphingomyelinase (alk-SMase) cleaves phosphocholine from sphingomyelin, plate... more Intestinal alkaline sphingomyelinase (alk-SMase) cleaves phosphocholine from sphingomyelin, platelet-activating factor (PAF), and lysophosphatidylcholine. We recently found that colitis-associated colon cancer was 4-5 fold enhanced in alk-SMase knockout mice. Here we further studied pathogenesis of colitis induced by dextran sulfate sodium (DSS) in wild type (WT) and the knockout mice. Comparing with WT mice, knockout mice demonstrated greater body weight loss, more severe bloody diarrhea, broader inflammatory cell infiltration, and more serious epithelial injury. Higher levels of PAF and lower levels of IL10 were identified in knockout mice 2 days after DSS treatment. A greater and progressive increase of lysophosphatidic acid (LPA) was identified. The change was associated with increased autotaxin expression in both small intestine and colon, which was identified by immunohistochemistry study, Western blot and sandwich ELISA. The upregulation of autotaxin coincided with early incr...
Alkaline sphingomyelinase cleaves phosphocholine from sphingomyelin, platelet-activating factor, ... more Alkaline sphingomyelinase cleaves phosphocholine from sphingomyelin, platelet-activating factor, lysophosphatidylcholine, and less effectively phosphatidylcholine. The enzyme shares no structure similarities with acid or neutral sphingomyelinase but belongs to ecto-nucleotide pyrophosphatase/phosphodiesterase (NPP) family and therefore is also called NPP7 nowadays. The enzyme is expressed in the intestinal mucosa in many species and additionally in human liver. The enzyme in the intestinal tract has been extensively studied but not that in human liver. Studies on intestinal alkaline sphingomyelinase show that it inhibits colonic tumorigenesis and inflammation, hydrolyses dietary sphingomyelin, and stimulates cholesterol absorption. The review aims to summarize the current knowledge on liver alkaline sphingomyelinase in human and strengthen the necessity for close study on this unique human enzyme in hepatobiliary diseases.
Sphingomyelin (SM) and cholesterol are two types of lipid closely related biophysically. Treating... more Sphingomyelin (SM) and cholesterol are two types of lipid closely related biophysically. Treating the cells with exogenous sphingomyelinase (SMase) induces trafficking of cholesterol from membrane to intracellular pools and inhibition of cholesterol synthesis. In the present work, we address a question whether increased cholesterol synthesis affects hydrolysis of SM by endogenous SMases. Both HepG2 and Caco-2 cells were incubated with mevalonate. The SMase activity was determined and its mRNA examined by qPCR. The cellular levels of cholesterol, SM, and phosphatidylcholine (PC) were determined and cell proliferation rate assayed. We found that mevalonate dose-dependently decreased acid but not neutral SMase activity in both HepG2 and Caco-2 cells with HepG2 cells being more sensitive to mevalonate. Kinetic examination in HepG2 cells revealed that acid SMase activity was increasing with cell proliferation, and such an increase was reversed by mevalonate treatment. Acid SMase mRNA was...
Boswellic acids, a type of pentacyclic triterpenoids, have been shown to induce apoptosis in colo... more Boswellic acids, a type of pentacyclic triterpenoids, have been shown to induce apoptosis in colon cancer cells. The phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) pathway is crucial for cell proliferation and survival. Whether the apoptotic effects of boswellic acid could be affected by inhibition of PI3K/Akt pathway was examined. Colon cancer HT29 cells were treated with 3-acetyl-11-keto-beta boswellic acid AKBA in the absence and presence of LY294002 or Wortmanin, inhibitors of PI3K. Apoptosis was determined by flow cytometry and caspase assay. The activation of Akt was examined by Western blot. AKBA at 30 microM only slightly induced apoptosis. Preincubation of the cells with LY294002 or wortmannin significantly enhanced the AKBA-induced apoptosis up to 20-fold. Further study showed that at the doses used, AKBA induced phosphorylation of Akt at both Ser473 and Thr308 positions, indicating an activation of the PI3K/Akt pathway. AKBA may activate the PI3K/Akt pathway ...
The hydrolysis of sphingomyelin generates key molecules regulating cell growth and inducing apopt... more The hydrolysis of sphingomyelin generates key molecules regulating cell growth and inducing apoptosis. Data from animal cancer models support an inhibitory role for this pathway in the malignant transformation of the colonic mucosa. In the intestinal tract, a sphingomyelinase with an optimum alkaline pH has been identified. We recently found that the activity of alkaline sphingomyelinase is significantly decreased in colorectal adenocarcinomas, indicating a potential anticarcinogenic role of this enzyme. To further examine whether the reduction of sphingomyelinase is present already in the premalignant state of neoplastic transformation, we measured sphingomyelinase activities in patients with familial adenomatous polyposis (FAP) and in sporadic colorectal tubulovillous adenomas. Tissue samples were taken from adenomas and surrounding macroscopically normal mucosa from 11 FAP patients operated with ileorectal anastomosis, from three FAP patients with intact colon, from 13 patients w...
Alkaline sphingomyelinase (NPP7) is an ecto-enzyme expressed in intestinal mucosa, which hydrolys... more Alkaline sphingomyelinase (NPP7) is an ecto-enzyme expressed in intestinal mucosa, which hydrolyses sphingomyelin (SM) to ceramide and inactivates platelet activating factor. It is also expressed in human liver and released in the bile. The enzyme may have anti-tumour and anti-inflammatory effects in colon and its levels are decreased in patients with colon cancer and ulcerative colitis. Active NPP7 is translated from a transcript of 1.4 kb, whereas an inactive form from a 1.2 kb mRNA was found in colon and liver cancer cell lines. While the roles of NPP7 in colon cancer have been intensively studied, less is known about the function and implications of NPP7 in the bile. The present study examines the changes of NPP7 in bile of patients with various hepatobiliary diseases. Bile samples were obtained at endoscopic retrograde cholangiopancreatography (ERCP) in 59 patients with gallstone, other benign disease, tumour, and primary sclerosing cholangitis (PSC). The NPP7 activity was dete...
Alkaline sphingomyelinase (alk-SMase) is expressed in the intestine and human liver. It may inhib... more Alkaline sphingomyelinase (alk-SMase) is expressed in the intestine and human liver. It may inhibit colonic tumorigenesis, and loss of function mutations have been identified in human colon cancer. The present study investigates its expression in human liver cancer. In HepG2 liver cancer cells, RT-PCR identified three transcripts with 1.4, 1.2 and 0.4 kb, respectively. The 1.4 kb form is the wild-type cDNA with five translated exons, the 1.2 kb product lacks exon 4 and the 0.4 kb form is a combination of exons 1 and 5. Genomic sequence showed that these aberrant transcripts were products of alternative splicing. Transient expression of the 1.2 kb form showed no alk-SMase activity. In HepG2 cells, the alk-SMase activity is low in monolayer condition and increased with cell polarisation. Coexistence of 1.4 and 1.2 kb forms was also identified in one hepatoma biopsy. GenBank search identified a cDNA clone from human liver tumour, which codes a protein containing full length of alk-SMas...
Curcumin has been shown to inhibit cell growth and induce apoptosis in colon cancer cells. The me... more Curcumin has been shown to inhibit cell growth and induce apoptosis in colon cancer cells. The metabolism of sphingomyelin has implications in the development of colon cancert. We examined whether curcumin affects the enzymes that hydrolyse sphingomyelin in Caco-2 cells. The cells were cultured in both monolayer and polarized conditions and stimulated with curcumin. The activities of sphingomyelinases were determined. Sphingomyelin and its hydrolytic products were analysed by thin layer chromatography. The changes of acid sphingomyelinase protein were examined by Western blotting. We found that curcumin reduced the hydrolytic capacity of the cells against choline-labelled sphingomyelin, associated with a mild increase of cellular sphingomyelin in the cells. Analysis of the hydrolytic products revealed that the activity was derived from acid sphingomyelinase not from phospholipase D. The curcumin-induced reduction of acid SMase required more than 8 h stimulation. Western blotting sho...
Sphingomyelin metabolism generates anticancer signals such as ceramide and sphingosine that may i... more Sphingomyelin metabolism generates anticancer signals such as ceramide and sphingosine that may inhibit cell proliferation, and induce differentiation and apoptosis. Changes of sphingomyelin metabolism are found to be associated with tumorigenesis in various tissues and a particular link between sphingomyelin metabolism and colon cancer has been indicated. The effects of several anticancer drugs on sphingomyelin metabolism have been examined recently and there is an increasing interest in discovering new drugs taking sphingomyelin as a target. The present review outlines the sphingomyelin metabolism pathway, introduces the evidence linking sphingomyelin to colon cancer, and summarizes the anticancer drugs and dietary factors that affect the metabolism of sphingomyelin and, thus, the production of the anticancer messengers in the colon.
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Papers by Rui-Dong Duan