Human intestinal acyl-CoA synthetase 5 is sensitive to the inhibitor triacsin C

AIM:To investigate whether human acyl-CoA synthetase 5(ACSL5) is sensitive to the ACSL inhibitor triacsin C.METHODS:The ACSL isoforms ACSL1 and ACSL5 from rat as well as human ACSL5 were cloned and recombinantly expressed as 6xHis-tagged enzymes.Ni 2+-affinity purified recombinant enzymes were assayed at pH 7.5 or pH 9.5 in the presence or absence of triacsin C.In addition,ACSL5 transfected CaCo2 cells and intestinal human mucosa were monitored.ACSL5 expression in cellular systems was verified using Western blot and immunofluorescence.The ACSL assay mix included TrisHCl(pH 7.4),ATP,CoA,EDTA,DTT,MgCl 2,[9,103 H] palmitic acid,and triton X-100.The 200 μL reaction was initiated with the addition of solubilized,purified recombinant proteins or cellular lysates.Reactions were terminated after 10,30 or 60 min of incubation with Doles medium.RESULTS:Expression of soluble recombinant ACSL proteins was found after incubation with isopropyl betaD-1-thiogalactopyranoside and after ultracentrifugation these were further purified to near homogeneity with Ni 2+-affinity chromatography.Triacsin C selectively and strongly inhibited recombinant human ACSL5 protein at pH 7.5 and pH 9.5,as well as recombinant rat ACSL1(sensitive control),but not recombinant rat ACSL5(insensitive control).The IC50 for human ACSL5 was about 10 μmol/L.The inhibitory triacsin C effect was similar for different incubation times(10,30 and 60 min) and was not modified by the N-or C-terminal location of the 6xHis-tag.In order to evaluate ACSL5 sensitivity to triacsin C in a cellular environment,stable human ACSL5 CaCo2 transfectants and mechanically dissected normal human intestinal mucosa with high physiological expression of ACSL5 were analyzed.In both models,ACSL5 peak activity was found at pH 7.5 and pH 9.5,corresponding to the properties of recombinant human ACSL5 protein.In the presence of triacsin C(25 μmol/L),total ACSL activity was dramatically diminished in human ACSL5 transfectants as well as in ACSL5-rich human intestinal mucosa.CONCLUSION:The data strongly indicate that human ACSL5 is sensitive to triacsin C and does not compensate for other triacsin C-sensitive ACSL isoforms.

Intestinal genetic inactivation of caspase-8 diminishes migration of enterocytes

AIM: To verify the hypothesis that caspase-8(Casp8), which regulates cellular apoptosis and necroptosis, is critically involved in enterocyte migration.METHODS: Casp8-silenced Caco2 cells were used in migration assays. In addition, enterocyte-specific Casp8 heterozygous(Casp8+/?int) or homozygous knockout mice(Casp8?int) were generated by crossing genetically modified mice carrying lox P recombination sites in intron 2 and 4 of the murine Casp8 gene with transgenic animals expressing a cre-transgene under control of the villin promoter in a pure C57/BL6 genetic background. The nucleoside analog Brd U was injected i.p. in male Casp8+/?int and Casp8?int animals 4 h, 20 h, or 40 h before performing morphometric studies. Locations of anti-Brd U-immunostained cells(cellmax) in at least 50 hemi-crypts of 6 histoanatomically distinct intestinal mucosal regions were numbered and extracted for statistical procedures. For the mice cohort(n = 28), the walking distance of enterocytes was evaluated from cellmax within crypt(n = 57), plateau(n = 19), and villus(n = 172) positions, resulting in a total of 6838 observations. Data analysis was performed by fitting a three-level mixed effects modelto the data.RESULTS: In cell culture experiments with Caco2 cells, Casp8 knockdown efficiency mediated by RNA interference on Casp8 transcripts was 80% controlled as determined by Western blotting. In the scratch assay, migration of Casp8-deleted Caco2 cells was significantly diminished when compared with controls(Casp8?scramble and Caco2). In Brd U-labeled Casp8?int mice, cellmax locations were found along the hemi-crypts in a lower position than it was for Casp8+/?int or control(cre-negative) animals. Statistical data analysis with a three-level mixed effects model revealed that in the six different intestinal locations(distinct segments of the small and large intestine), cell movement between the three mice groups differed widely. Especially in duodenal hemi-crypts, enterocyte movement was different between the groups. At 20 h, duodenal cellmax location was significantly lower in Casp8?int(25.67 ± 2.49) than in Casp8+/?int(35.67 ± 4.78; P < 0.05) or control littermates(44.33 ± 0.94; P < 0.01).CONCLUSION: C a s p 8- d e p e n d e n t m i g ra t i o n o f enterocytes is likely involved in intestinal physiology and inflammation-related pathophysiology.

Fatty acid binding receptors in intestinal physiology and pathophysiology

Free fatty acids are essential dietary components and recognized as important molecules in the maintenance of cellular homeostasis.In the last decade,the molecular pathways for free fatty acid sensing in the gastrointestinal tract have been further elucidated by molecular identification and functional characterization of fatty acid binding receptors.These sensing molecules belong to the family of G proteincoupled receptors.In the intestine,four important receptors have been described so far.They differ in molecular structure,ligand specificity,expression pattern,and functional properties.In this review,an overview of intestinal fatty acid binding receptors and their role in intestinal physiology and pathophysiology is given.