Identification of an alkaline sphingomyelinase activity in human bile

Nyberg, Lena; Duan, Rui‐Dong; Axelson, Jan; Nilsson, Åke

doi:10.1016/0005-2760(95)00245-6

Cited by 73 publications

(48 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Alk-SMase is expressed also in human liver [17], and high alkSMase activity was found in human bile [47,48]. Based on the findings in the present study, a protective effect of alk-SMase through hydrolysis and inactivating PAF in the liver and bile can be predicted.…”

Section: Discussionsupporting

confidence: 65%

Intestinal alkaline sphingomyelinase hydrolyses and inactivates platelet-activating factor by a phospholipase C activity

Nilsson

Jönsson

et al. 2006

Biochemical Journal

Self Cite

View full text Add to dashboard Cite

Alkaline sphingomyelinase (alk-SMase) is a new member of the NPP (nucleotide pyrophosphatase/phosphodiesterase) family that hydrolyses SM (sphingomyelin) to generate ceramide in the intestinal tract. The enzyme may protect the intestinal mucosa from inflammation and tumorigenesis. PAF (platelet-activating factor) is a pro-inflammatory phospholipid involved in pathogenesis of inflammatory bowel diseases. We examined whether alk-SMase can hydrolyse and inactivate PAF. [ 3 H]Octadecyl-labelled PAF was incubated with purified rat intestinal alk-SMase or recombinant human alk-SMase expressed in COS-7 cells. The hydrolytic products were assayed with TLC and MS. We found that alkSMase cleaved the phosphocholine head group from PAF and generated 1-O-alkyl-2-acetyl-sn-glycerol. Differing from the activity against SM, the activity against PAF was optimal at pH 7.5, inhibited by EDTA and stimulated by 0.1-0.25 mM Zn 2+ . The activity was abolished by site mutation of the predicted metalbinding sites that are conserved in all NPP members. Similar to the activity against SM, the activity against PAF was dependent on bile salt, particularly taurocholate and taurochenodeoxycholate. The V max for PAF hydrolysis was 374 µmol · h −1 · (mg of protein) −1 . The hydrolysis of PAF and SM could be inhibited by the presence of SM and PAF respectively, the inhibition of PAF hydrolysis by SM being stronger. The PAF-induced MAPK (mitogen-activated protein kinase) activation and IL-8 (interleukin 8) release in HT-29 cells, and chemotaxis in leucocytes were abolished by alk-SMase treatment. In conclusion, alk-SMase hydrolyses and inactivates PAF by a phospholipase C activity. The finding reveals a novel function, by which alk-SMase may counteract the development of intestinal inflammation and colon cancer.

show abstract

Section: Discussionsupporting

confidence: 65%

Intestinal alkaline sphingomyelinase hydrolyses and inactivates platelet-activating factor by a phospholipase C activity

Nilsson

Jönsson

et al. 2006

Biochemical Journal

Self Cite

View full text Add to dashboard Cite

show abstract

“…The effect is more potent on differentiated enterocytes than on proliferating cells. Another interesting feature of Alk-SMase is its biliary secretion in humans but not in other species, as convinced by activity assay, Western blot and Northern blot in our previous studies [3,4,18,19]. Bile salt dependent hydrolysis of SM in the gut lumen or in the brush border membrane may indirectly influence cholesterol absorption [20], which is highly dependent on bile salts.…”

Section: Introductionmentioning

confidence: 87%

Effects of bile diversion in rats on intestinal sphingomyelinases and ceramidase

Duan

Verkade

Cheng

et al. 2007

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biolog

View full text Add to dashboard Cite

1 Summary:Alkaline sphingomyelinase (Alk-SMase) and neutral ceramidase (N-CDase) in the intestinal microvillar membrane are responsible for dietary sphingomyelin digestion. The activities of the enzymes require the presence of bile salt, and the enzymes can be released into the gut lumen in active forms by bile salts and trypsin. It is unclear to what extent that the intestinal presence of bile salts is critical for the intraluminal activity of these enzymes. We compared the activities of Alk-SMase, N-CDase, and other types of SMases in control and permanently bile diverted rats. In the intestinal tract of control rats, the activity of Alk-SMase was profoundly higher than those of acid and neutral SMases. Bile diversion reduced Alk-SMase activity by 85% in the small intestinal content, and by 68% in the faeces, but did not significantly change the activity in the intestinal mucosa. Western blot showed a marked reduction of the enzyme in the intestinal lumen but not mucosa. N-CDase activities both in the intestinal mucosa and content were reduced by bile diversion. Bile diversion also decreased aminopeptidase N activity in the content and increased that in the mucosa, but had no effects on that of alkaline phosphatase. In conclusion, the presence of bile salts is important for maintaining high intraluminal levels of Alk-SMase and N-CDase, two key enzymes for hydrolysis of sphingomyelin in the gut. We speculate that the sphingomyelin hydrolysis in cholestatic conditions is impaired not only by reduced hydrolytic activity but also by deficient dissociation of the enzymes from the membrane.

show abstract

“…This hypothesis, which implies a redistribution of the enzyme from the lysosomal compartment to or near the plasma membrane, requires further verification (20,21). Despite the existence of the neutral and acidic SMases, an alkaline form of the enzyme has been described recently, although its role in signaling remains to be defined (22).…”

Section: From the Instituto Investigaciones Biomédicas Consejo Supermentioning

confidence: 99%

“…Therefore, we hypothesized that ceramide may directly affect mitochondria leading to production of hydrogen peroxide. To test this hypothesis, and to demonstrate a direct effect of ceramide on mitochondria, we isolated mitochondria from rat liver and examined the effect that incubation with C 2 exerts when monitoring the generation of hydrogen peroxide by flow cytometry using DCFDA as fluorescent probe to follow its conversion to DCF (22,24). Mitochondria were incubated with succinate to drive electron flow directly at succinic dehydrogenase complex.…”

Section: Ceramide Leads To Generation Of Reactive Oxygen Species In Imentioning

confidence: 99%

Direct Effect of Ceramide on the Mitochondrial Electron Transport Chain Leads to Generation of Reactive Oxygen Species

Garcı́a-Ruiz¹,

Colell²,

Marı́³

et al. 1997

Journal of Biological Chemistry

764

555

View full text Add to dashboard Cite

Ceramide is a sphingolipid that is generated in the signaling of inflammatory cytokines such as tumor necrosis factor (TNF), which exerts many functional roles depending on the cell type where it is produced. Since TNF cytotoxicity is mediated by overproduction of reactive oxygen species from mitochondria, we have examined the role of ceramide in generation of oxidative stress in isolated rat liver mitochondria. The present studies demonstrate that addition of N-acetylsphingosine (C 2 -ceramide) to mitochondria led to an increase of fluorescence of dihydrorhodamine 123 or dichlorofluorescein-stained mitochondria, indicating formation of hydrogen peroxide. Such effect was significant at 0.25 M and maximal at 1-5 M C 2 , decreasing at greater concentrations. This inductive effect of ceramide was mimicked by N-hexanoylsphingosine at the same concentration range, whereas the immediate precursor of C 2 , C 2 -dihydroceramide increased hydrogen peroxide at 1-5 M. Sphingosine generated hydrogen peroxide at concentrations 10 M, whereas diacylglycerol failed to increase hydrogen peroxide. The increase in hydrogen peroxide induced by C 2 was not triggered by mitochondrial permeability transition as C 2 did not induce mitochondrial swelling. Blocking electron transport chain at complex I and II prevented the increase in hydrogen peroxide induced by C 2 ; however, interruption of electron flow at complex III by antimycin A potentiated the inductive effect of C 2 . Depletion of matrix GSH prior to exposure to ceramide resulted in a potentiated increase (2-fold) of hydrogen peroxide generation, leading to lipid peroxidation and loss of activity of respiratory chain complex IV compared with GSH-repleted mitochondria. Mitochondria isolated from TNF-treated cells showed an increase (2-3-fold) in the amount of ceramide compared with mitochondria from untreated cells. These results suggest that mitochondria are a target of ceramide produced in the signaling of TNF whose effect on mitochondrial electron transport chain leads to overproduction of hydrogen peroxide and consequently this phenomena may account for the generation of reactive oxygen species during TNF cytotoxicity.

show abstract

Identification of an alkaline sphingomyelinase activity in human bile

Cited by 73 publications

References 26 publications

Intestinal alkaline sphingomyelinase hydrolyses and inactivates platelet-activating factor by a phospholipase C activity

Intestinal alkaline sphingomyelinase hydrolyses and inactivates platelet-activating factor by a phospholipase C activity

Effects of bile diversion in rats on intestinal sphingomyelinases and ceramidase

Direct Effect of Ceramide on the Mitochondrial Electron Transport Chain Leads to Generation of Reactive Oxygen Species

Contact Info

Product

Resources

About