TP53 status regulates ACSL5-induced expression of mitochondrial mortalin in enterocytes and colorectal adenocarcinomas.

Acyl-CoA synthetase 5 (ACSL5), a mitochondrially localized enzyme, catalyzes the synthesis of long-chain fatty acid thioesters and is physiologically involved in pro-apoptotic sensing of enterocytes. The aim of the present study is to identify an ACSL5-dependent regulation of mitochondrially expressed proteins and the characterization of related pathways in normal and diseased human intestinal mucosa. Proteomics of isolated mitochondria from ACSL5 transfectants and CaCo2 controls were performed. ACSL5-dependent protein synthesis was verified with quantitative reverse transcription plus the polymerase chain reaction, Western blotting, short-interfering-RNA-mediated gene silencing and additional cell culture experiments. Lipid changes were analyzed with tandem mass spectrometry. ACSL5-related pathways were characterized in normal mucosa and sporadic adenocarcinomas of the human intestine. In CaCo2 cells transfected with ACSL5, mortalin (HSPA9) was about two-fold increased in mitochondria, whereas cytoplasmic mortalin levels were unchanged. Disturbance of acyl-CoA/sphingolipid metabolism, induced by ACSL5 over-expression, was characterized as crucial. ACSL5-related over-expression of mitochondrial mortalin was found in HEK293 and Lovo (wild-type TP53 [tumor protein p53]) and CaCo2 (p53-negative; TP53 mutated) cells but not in Colo320DM cells (mutated TP53). In normal human intestinal mucosa, an increasing gradient of both ACSL5 and mortalin from bottom to top was observed, whereas p53 (wild-type TP53) decreased. In sporadic intestinal adenocarcinomas with strong p53 immunostaining (mutated TP53), ACSL5-related mortalin expression was heterogeneous. ACSL5-induced mitochondrial mortalin expression is assumed to be a stress response to ACSL5-related changes in lipid metabolism and is regulated by the TP53 status. Uncoupling of ACSL5 and mitochondrial mortalin by mutated TP53 could be important in colorectal carcinogenesis.

Increased levels of deleted in malignant brain tumours 1 (DMBT1) in active bacteria-related appendicitis.

AIMS: Deleted in malignant brain tumours 1 (DMBT1; gp340) is a secreted glycoprotein which is found in the surface lining epithelia of human small and large intestine. DMBT1 is suggested to play a role in enterocyte differentiation and surface protection from intestinal bacteria. The aim of this study was to elucidate DMBT1 expression in bacteria-related active intestinal inflammation such as appendicitis. METHODS AND RESULTS: mRNA and protein levels of DMBT1 were analysed in surgical resections of 50 appendices (active inflammation: n = 25). In non-actively inflamed appendices, inter-individual differences in basal DMBT1 levels of enterocytes and some non-epithelial cells were found. In active appendicitis, enterocytic DMBT1 mRNA expression was increased approximately fivefold, which was paralleled by a corresponding increase of cytoplasmic and secreted DMBT1 protein levels. Increased DMBT1 expression was predominant in enterocytes adjacent to erosive lesions or ulcers. CONCLUSIONS: Our data demonstrate that bacteria-related active inflammation results in a sharp increase of DMBT1 levels in enterocytes. These findings substantiate the view that DMBT1 is of functional relevance for host defence and modulation of the course of intestinal bacteria-related inflammatory responses.

Small intestinal mucosa expression of putative chaperone fls485.

BACKGROUND: Maturation of enterocytes along the small intestinal crypt-villus axis is associated with significant changes in gene expression profiles. fls485 coding a putative chaperone protein has been recently suggested as a gene involved in this process. The aim of the present study was to analyze fls485 expression in human small intestinal mucosa. METHODS: fls485 expression in purified normal or intestinal mucosa affected with celiac disease was investigated with a molecular approach including qRT-PCR, Western blotting, and expression strategies. Molecular data were corroborated with several in situ techniques and usage of newly synthesized mouse monoclonal antibodies. RESULTS: fls485 mRNA expression was preferentially found in enterocytes and chromaffine cells of human intestinal mucosa as well as in several cell lines including Rko, Lovo, and CaCo2 cells. Western blot analysis with our new anti-fls485 antibodies revealed at least two fls485 proteins. In a functional CaCo2 model, an increase in fls485 expression was paralleled by cellular maturation stage. Immunohistochemistry demonstrated fls485 as a cytosolic protein with a slightly increasing expression gradient along the crypt-villus axis which was impaired in celiac disease Marsh IIIa-c. CONCLUSIONS: Expression and synthesis of fls485 are found in surface lining epithelia of normal human intestinal mucosa and deriving epithelial cell lines. An interdependence of enterocyte differentiation along the crypt-villus axis and fls485 chaperone activity might be possible.

Beta-7 integrin controls enterocyte migration in the small intestine.

AIM: To hypothesize that beta-7 integrin affects cellular migration of both, lymphocytes and enterocytes. METHODS: The nucleoside analog BrdU was ip injected in beta-7-deficient mice (C57BL/6-Itgb(tmlcgn)/J) of male gender and age-matched male C57BL/J J mice (wild type) 4, 20, or 40 h before analysis. The total small intestine was isolated, dissected, and used for morphometrical studies. BrdU-positive epithelial cells were numbered in at least 15 hemi-crypts per duodenum, jejunum, and ileum of each animal. The outer most BrdU-positive cell (cell(max)) was determined per hemi-crypt, numerically documented, and statistically analysed. RESULTS: Integrins containing the beta-7-chain were exclusively expressed on leukocytes. In the small intestinal mucosa of beta-7 integrin-deficient mice the number of intraepithelial lymphocytes was drastically decreased. Moreover, the Peyer's patches of beta-7 integrin-deficient mice appeared hypoplastic. In beta-7 integrin-deficient mice the location of cell(max) was found in a higher position than it was the case for the controls. The difference was already detected at 4 h after BrdU application, but significantly increased with time (40 h after BrdU injection) in all small intestinal segments investigated, i.e., duodenum, jejunum, and ileum. Migration of small intestinal enterocytes was different between the experimental groups measured by cell(max) locations. CONCLUSION: The E-cadherin beta-7 integrin pathway probably controls migration of enterocytes within the small intestinal surface lining epithelial layer.

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 loxP 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 BrdU 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-BrdU-immunostained cells (cell(max)) 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 cell(max) 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 model to 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 BrdU-labeled Casp8(∆int) mice, cell(max) 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 cell(max) 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: Casp8-dependent migration of enterocytes is likely involved in intestinal physiology and inflammation-related pathophysiology.

Modulating effects of acyl-CoA synthetase 5-derived mitochondrial Wnt2B palmitoylation on intestinal Wnt activity.

AIM: To investigate the role of acyl-CoA synthetase 5 (ACSL5) activity in Wnt signaling in intestinal surface epithelia. METHODS: Several cell lines were used to investigate the ACSL5-dependent expression and synthesis of Wnt2B, a mitochondrially expressed protein of the Wnt signaling family. Wnt activity was functionally assessed with a luciferase reporter assay. ACSL5-related biochemical Wnt2B modifications were investigated with a modified acyl-exchange assay. The findings from the cell culture models were verified using an Apc(min/+) mouse model as well as normal and neoplastic diseased human intestinal tissues. RESULTS: In the presence of ACSL5, Wnt2B was unable to translocate into the nucleus and was enriched in mitochondria, which was paralleled by a significant decrease in Wnt activity. ACSL5-dependent S-palmitoylation of Wnt2B was identified as a molecular reason for mitochondrial Wnt2B accumulation. In cell culture systems, a strong relation of ACSL5 expression, Wnt2B palmitoylation, and degree of malignancy were found. Using normal mucosa, the association of ACSL5 and Wnt2B was seen, but in intestinal neoplasias the mechanism was only rudimentarily observed. CONCLUSION: ACSL5 mediates antiproliferative activities via Wnt2B palmitoylation with diminished Wnt activity. The molecular pathway is probably relevant for intestinal homeostasis, overwhelmed by other pathways in carcinogenesis.

Intestinal acyl-CoA synthetase 5: activation of long chain fatty acids and behind.

The intestinal mucosa is characterized by a high complexity in terms of structure and functions and allows for a controlled demarcation towards the gut lumen. On the one hand it is responsible for pulping and selective absorption of alimentary substances ensuring the immunological tolerance, on the other hand it prevents the penetration of micro-organisms as well as bacterial outgrowth. The continuous regeneration of surface epithelia along the crypt-villus-axis in the small intestine is crucial to assuring these various functions. The core phenomena of intestinal epithelia regeneration comprise cell proliferation, migration, differentiation, and apoptosis. These partly contrarily oriented processes are molecularly balanced through numerous interacting signaling pathways like Wnt/ß-catenin, Notch and Hedgehog, and regulated by various modifying factors. One of these modifiers is acyl-CoA synthetase 5 (ACSL5). It plays a key role in de novo lipid synthesis, fatty acid degradation and membrane modifications, and regulates several intestinal processes, primarily through different variants of protein lipidation, e.g., palmitoylation. ACSL5 was shown to interact with proapoptotic molecules, and besides seems to inhibit proliferation along the crypt-villus-axis. Because of its proapoptotic and antiproliferative characteristics it could be of significant relevance for intestinal homeostasis, cellular disorder and tumor development.

Molecular classification of colorectal carcinomas: the genotype-to-phenotype relation.

Colorectal carcinomas (CRCs) are frequently found in industrialized countries and lead to a high incidence of malignancy-related mortality. Defined by histomorphological features, CRCs and their pre-invasive lesions are quite heterogeneous. The underlying molecular mechanisms include genomic instability, genomic mutation of tumor suppressor genes or oncogenes, epigenetic changes, and the microRNA network. The molecular mechanisms are guided by repeated clonal selections. The genotype-to-phenotype relation is assumed to be the great challenge of cancer research and the development of effective targeted therapies. At present a strong genotype-to-phenotype relation is characterized only for a minority of CRCs. Consequently, the molecular characterization of CRCs is essential to interpret histological patterns and to identify prognostic groups as well as patients for targeted therapy.

Intestinal barrier: Molecular pathways and modifiers.

The gastrointestinal tract is frequently challenged by pathogens/antigens contained in food and water and the intestinal epithelium must be capable of rapid regeneration in the event of tissue damage. Disruption of the intestinal barrier leads to a number of immune-mediated diseases, including inflammatory bowel disease, food allergy, and celiac disease. The intestinal mucosa is composed of different types of epithelial cells in specific barrier functions. Epithelial cells control surface-associated bacterial populations without disrupting the intestinal microflora that is crucial for host health. They are also capable of modulating mucosal immune system, and are thus essential in maintaining homeostasis in the gut. Thus, the regulation of intestinal epithelial homeostasis is crucial for the maintenance of the structure of the mucosa and the defensive barrier functions. Recent studies have demonstrated that multiple molecular pathways are involved in the regulation of intestinal epithelial cell polarity. These include the Wnt, Notch, Hippo, transforming growth factor-ß (TGF-ß)/bone morphogenetic protein (BMP) and Hedgehog pathways, most of which were identified in lower organisms where they play important roles during embryogenesis. These pathways are also used in adult organisms to regulate multiple self-renewing organs. Understanding the interactions between these molecular mechanisms and intestinal barrier function will therefore provide important insight into the pathogenesis of intestinal-based immune-mediated diseases.

Levels of acyl-coenzyme A synthetase 5 in urothelial cells and corresponding neoplasias reflect cellular differentiation.

Metabolic components like fatty acids and acyl-Coenzyme A (acyl-CoA) thioesters have been implicated in the pathogenesis of various tumours. The activation of fatty acids to acyl-CoAs is catalysed by long chain acyl-CoA synthetases (ACSLs), and impairment of ACSL expression levels has been associated with tumourigenesis and progression. Since ACSLs have never been investigated in bladder tissues, the study aims to characterize ACSL expression and acyl-CoA synthesis in normal and neoplastic bladder tissues, as well as cell lines. ACSL isoforms 1, 3, 4 and 5 and synthesis of acyl-CoAs were analysed using qRT-PCR, western blot analysis, immunohistochemistry and lipid mass spectrometry. In normal urothelium, expression of ACSL1, 3, 4 and 5, with highest levels of ACSL isoform 5 was found. However, ACSL5 expression was reduced in corresponding neoplastic tissues and urothelial cell lines depending on the grade of cellular differentiation. Anti-ACSL5 immunostainings showed expression in normal urothelium and a gradual loss of ACSL5 protein via pre-invasive lesions to invasive carcinomas. High expression of ACSL5 correlated with increased α-galactosidase activity and positive Uroplakin III staining in tumours. In contrast, synthesis of acyl-CoAs was enhanced in neoplastic bladder tissues compared to normal urothelium, and reflected an increase with respect to cellular differentiation. These results confirm an expression of ACSLs, especially isoform 5, in human urothelium, prove enzymatic/lipidomic changes in bladder cancer tissues, and suggest an involvement of ACSL5 in cellular maturation and/or senescence with possible effects onto induction of tumour formation or progression. Further work may identify responsible pathway alterations, and attempting to re-balance the metabolic equilibrium of the urothelium may offer a further opportunity for tumour treatment and prevention.

Modifier-concept of colorectal carcinogenesis: lipidomics as a technical tool in pathway analysis.

In the modifier concept of intestinal carcinogenesis, lipids have been established as important variables and one focus is given to long-chain fatty acids. Increased consumption of long-chain fatty acids is in discussion to modify the development of colorectal carcinoma in humans. Saturated long-chain fatty acids, in particular, are assumed to promote carcinogenesis, whereas polyunsaturated forms are likely to act in the opposite way. At present, the molecular mechanisms behind these effects are not well understood. Recently, it has been demonstrated by lipidomics and associated molecular techniques, that activation and metabolic channeling of long-chain fatty acids are important mechanisms to modify colorectal carcinogenesis. In this Editorial, an overview about the present concept of long-chain fatty acids and its derivatives in colorectal carcinogenesis as well as technical algorithms in lipid analysis is given.

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 protein-coupled 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.