Reelin Protects against Colon Pathology via p53 and May Be a Biomarker for Colon Cancer Progression.

Previous observations made in human and mouse colons suggest that reelin protects the colon from pathology. In this study, we evaluated reelin expression during the transition from either colitis or precancerous lesions to colon cancer and tried to elucidate reelin regulation under these transition processes. Samples of healthy and pathological colons from humans and mice treated with either azoxymethane/dextran sulfate sodium (DSS) or azoxymethane alone were used. The relative abundances of reelin, DNMT-1 and ApoER2 mRNAs were determined by PCR in the colon samples cited above and in the tissue adjacent to mouse colon polyps and adenocarcinomas. In both, humans and mice, reelin mRNA abundance increased significantly in ulcerative colitis and slightly in polyps and decreased in adenomas and adenocarcinomas. Reelin expression was higher in the tissue adjacent to the colon adenocarcinoma and lower in the lesion itself. The reelin expression changes may result, at least in part, from those in DNMT-1 and appear to be independent of ApoER2. Lack of reelin downregulated p-Akt and p53 in healthy colon and prevented their increases in the inflamed colon, whereas it increased GSK-3ß in DSS-untreated mice. In conclusion, reelin mRNA abundance depends on the severity of the colon pathology, and its upregulation in response to initial injuries might prevent the beginning of colon cancer, whereas reelin repression favors it. Increased p53 expression and activation may be involved in this protection. We also propose that changes in colon reelin abundance could be used to predict colon pathology progression.

Acute Colon Inflammation Triggers Primary Motor Cortex Glial Activation, Neuroinflammation, Neuronal Hyperexcitability, and Motor Coordination Deficits.

Neuroinflammation underlies neurodegenerative diseases. Herein, we test whether acute colon inflammation activates microglia and astrocytes, induces neuroinflammation, disturbs neuron intrinsic electrical properties in the primary motor cortex, and alters motor behaviors. We used a rat model of acute colon inflammation induced by dextran sulfate sodium. Inflammatory mediators and microglial activation were assessed in the primary motor cortex by PCR and immunofluorescence assays. Electrophysiological properties of the motor cortex neurons were determined by whole-cell patch-clamp recordings. Motor behaviors were examined using open-field and rotarod tests. We show that the primary motor cortex of rats with acute colon inflammation exhibited microglial and astrocyte activation and increased mRNA abundance of interleukin-6, tumor necrosis factor-alpha, and both inducible and neuronal nitric oxide synthases. These changes were accompanied by a reduction in resting membrane potential and rheobase and increased input resistance and action potential frequency, indicating motor neuron hyperexcitability. In addition, locomotion and motor coordination were impaired. In conclusion, acute colon inflammation induces motor cortex microglial and astrocyte activation and inflammation, which led to neurons' hyperexcitability and reduced motor coordination performance. The described disturbances resembled some of the early features found in amyotrophic lateral sclerosis patients and animal models, suggesting that colon inflammation might be a risk factor for developing this disease.

Fecal Volatile Organic Compounds and Microbiota Associated with the Progression of Cognitive Impairment in Alzheimer's Disease.

Metabolites produced by an altered gut microbiota might mediate the effects in the brain. Among metabolites, the fecal volatile organic compounds (VOCs) are considered to be potential biomarkers. In this study, we examined both the VOCs and bacterial taxa in the feces from healthy subjects and Alzheimer's disease (AD) patients at early and middle stages. Remarkably, 29 fecal VOCs and 13 bacterial genera were differentiated from the healthy subjects and the AD patients. In general, higher amounts of acids and esters were found in in the feces of the AD patients and terpenes, sulfur compounds and aldehydes in the healthy subjects. At the early stage of AD, the most relevant VOCs with a higher abundance were short-chain fatty acids and their producing bacteria, Faecalibacterium and Lachnoclostridium. Coinciding with the development of dementia in the AD patients, parallel rises of heptanoic acid and Peptococcus were observed. At a more advanced stage of AD, the microbiota and volatiles shifted towards a profile in the feces with increases in hexanoic acid, Ruminococcus and Blautia. The most remarkable VOCs that were associated with the healthy subjects were 4-ethyl-phenol and dodecanol, together with their possible producers Clostridium and Coprococcus. Our results revealed a VOCs and microbiota crosstalk in AD development and their profiles in the feces were specific depending on the stage of AD. Additionally, some of the most significant fecal VOCs identified in our study could be used as potential biomarkers for the initiation and progression of AD.

Reelin protects from colon pathology by maintaining the intestinal barrier integrity and repressing tumorigenic genes.

We previously reported that reelin, an extracellular matrix protein first known for its key role in neuronal migration, reduces the susceptibility to dextran sulphate sodium (DSS)-colitis. The aim of the current study was to determine whether reelin protects from colorectal cancer and how reelin defends from colon pathology. In the colon of wild-type and of mice lacking reelin (reeler mice) we have analysed the: i) epithelium cell renewal processes, ii) morphology, iii) Sox9, Cdx2, Smad5, Cyclin D1, IL-6 and IFNγ mRNA abundance in DSS-treated and untreated mice, and iv) development of azoxymethane/DSS-induced colorectal cancer, using histological and real time-PCR methodologies. The reeler mutation increases colitis-associated tumorigenesis, with increased tumours number and size. It also impairs the intestinal barrier because it reduces cell proliferation, migration, differentiation and apoptosis; decreases the number and maturation of goblet cells, and expands the intercellular space of the desmosomes. The intestinal barrier impairment might explain the increased susceptibility to colon pathology exhibited by the reeler mice and is at least mediated by the down-regulation of Sox9 and Cdx2. In response to DSS-colitis, the reeler colon increases the mRNA abundance of IL-6, Smad5 and Cyclin D1 and decreases that of IFNγ, conditions that might result in the increased colitis-associated tumorigenesis found in the reeler mice. In conclusion, the results highlight a role for reelin in maintaining intestinal epithelial cell homeostasis and providing resistance against colon pathology.

Reelin expression is up-regulated in mice colon in response to acute colitis and provides resistance against colitis.

Reelin is an extracellular matrix protein first known for its key role in neuronal migration. Studies in rodent small intestine suggested that reelin protects the organism from intestinal pathology. Here we determined in mice colon, by real time-PCR and immunological assays, the expression of the reelin signalling system; its response to dextran sulphate sodium (DSS) and the response of wild-type and reeler mice to DSS-treatment. DNA methylation was determined by bisulfite modification and sequencing of genomic DNA. In the colon mucosa reelin expression is restricted to the myofibroblasts, whereas both epithelial cells and myofibroblasts express reelin receptors (ApoER2 and VLDLR) and its effector protein Dab1. The muscle layer also expresses reelin. DSS-treatment reduces reelin expression in the muscle but it is activated in the mucosa. Activation of mucosal reelin is greater in magnitude and is delayed until after the activation of the myofibroblasts marker, α-SMA. This indicates that the DSS-induced reelin up-regulation results from changes in the reelin gene expression rather than from myofibroblasts proliferation. DSS-treatment does not modify Sp1 or Tbr1 mRNA abundance, but increases that of TGF-ß1 and ApoER2, decreases that of CASK and DNMT1 and it also decreases the reelin promoter methylation. Finally, the reeler mice exhibit higher inflammatory scores than wild-type mice, indicating that the mutation increases the susceptibility to DSS-colitis. In summary, this data are the first to demonstrate that mouse distal colon increases reelin production in response to DSS-colitis via a DNMT1-dependent hypo-methylation of the gene promoter region and that reelin provides protection against colitis.

Na+-dependent and Na+-independent betaine transport across the apical membrane of rat renal epithelium.

The low renal excretion of betaine indicates that the kidney efficiently reabsorbs the betaine filtered by the glomeruli but the mechanisms involved in such a process have been scarcely investigated. We have detected concentrative and non-concentrative betaine transport activity in brush-border membrane vesicles (BBMV) from rat renal cortex and medulla. The concentrative system is the Sodium/Imino-acid Transporter 1 (SIT1) because it is Na+- and Cl--dependent, electrogenic and is inhibited by an anti-SIT1 antibody. Its apparent affinity constant for betaine, Kt, is 1.1±0.5 mM and its maximal transport velocity, Vmax, 0.5±0.1 nmol betaine/mg protein/s. Inhibitors of the Na+/Cl-/betaine uptake are L-proline (75%) and cold betaine, L-carnitine and choline (40-60%). Neither creatine, TEA, taurine, ß-alanine, GABA nor glycine significantly inhibited Na+/Cl-/betaine uptake. The non-concentrative betaine transport system is Na+- and H+-independent, electroneutral, with a Kt for betaine of 47±7 µM and a Vmax of 7.8±1 pmol betaine/mg protein/s. Its transport activity is nearly abolished by betaine, followed by L-carnitine (70-80%) and proline (40-50%), but a difference from the Na+/Cl-/betaine transport is that it is inhibited by TEA (approx. 50%) and unaffected by choline. The underlying carrier functions as an antiporter linking betaine entry into the BBMV with the efflux of either L-carnitine or betaine, an exchange unaffected by the anti-SIT1 antibody. As far as we know this is the first work reporting that betaine crosses the apical membrane of rat renal epithelium by SIT1 and by a Na+- and H+-independent transport system.

Dab2, megalin, cubilin and amnionless receptor complex might mediate intestinal endocytosis in the suckling rat.

We previously proposed that Dab2 participates in the endocytosis of milk macromolecules in rat small intestine. Here we investigate the receptors that may mediate this endocytosis by studying the effects of age and diet on megalin, VLDLR, and ApoER2 expression, and that of age on the expression of cubilin and amnionless. Of megalin, VLDLR and ApoER2, only the megalin expression pattern resembles that of Dab2 previously reported. Thus the mRNA and protein levels of megalin and Dab2 are high in the intestine of the suckling rat, down-regulated by age and up-regulated by milk diet, mainly in the ileum. Neither age nor diet affect ApoER2 mRNA levels. The effect of age on VLDLR mRNA levels depends on the epithelial cell tested but they are down-regulated by milk diet. In the suckling rat, the intestinal expressions of both cubilin and amnionless are similar to that of megalin and megalin, cubilin, amnionless and Dab2 co-localize at the microvilli and in the apical endocytic apparatus. Co-localization of Dab2 with ApoER2 and VLDLR at the microvilli and in the apical endocytic apparatus is also observed. This is the first report showing intestinal co-localization of: megalin/cubilin/amnionless/Dab2, VLDLR/Dab2 and ApoER2/Dab2. We conclude that the megalin/cubilin/amnionless/Dab2 complex/es participate in intestinal processes, mainly during the lactation period and that Dab2 may act as an adaptor in intestinal processes mediated by ApoER2 and VLDLR.

Dab1 and reelin participate in a common signal pathway that controls intestinal crypt/villus unit dynamics.

BACKGROUND INFORMATION: The myofibroblasts placed underneath the epithelium of the rodent small intestine express reelin, and the reelin absence modifies both the morphology and the cell renewal processes of the crypt-villus unit. In the developing central nervous system, the reelin effects are mediated by the disabled-1 (Dab1) protein. The present work explores whether Dab1 mediates the reelin control of the crypt-villus unit dynamics by examining in the mouse small intestine the consequences of the absence of (i) Dab1 (scrambler mutation) on crypt-villus unit cell renewal processes and morphology and (ii) reelin (reeler mutation) on the intestinal expression of Dab1. RESULTS: The effects of the scrambler mutation on the crypt-villus unit renewal processes are remarkably similar to those caused by the lack of reelin. Thus, both mutations significantly reduce epithelial cell proliferation, migration and apoptosis, and the number of Paneth cells; affect the morphology of the villus, and expand the intercellular space of the adherens junctions and desmosomes. The Western blot assays reveal that the Dab1 isoform present in the enterocytes has a molecular weight of ∼63 kDa and that in the brain of ∼82 kDa. They also reveal that the absence of reelin increases Dab1 abundance in both brain and enterocytes. CONCLUSIONS: All together, the current findings link reelin with Dab1 and suggest that Dab1 functions downstream of reelin action on the homeostasis of the crypt-villus unit.

Regulation of Dab2 expression in intestinal and renal epithelia by development.

Disabled-2 (Dab2) is an intracellular adaptor protein proposed to function in endocytosis. Here, we investigate the intestinal and renal Dab2 expression versus maturation. Dab2 mRNA levels measured by RT-PCR are greater in the small than in the large intestine. Immunological studies localize Dab2 to the terminal web domain of the enterocytes and reveal the presence of a 96-kDa Dab2 isoform in the apical membrane of the jejunum, ileum, and renal cortex of the suckling and adult rat. A 69-kDa Dab2 isoform is only observed in the apical membranes of the suckling ileum. During the suckling period, the Dab2 mRNA levels measured in the enterocytes and crypts and those of the 96-kDa Dab2 isoform are greater in the ileum than in the jejunum. No segmental differences are observed in the adult intestine. In the intestine, the levels of Dab2 mRNA and those of the 96-kDa Dab2 isoform decrease to adult values at weaning, whereas in the kidney they increase with development. Weaning the pups on a commercial milk diet slows the periweaning decline in the levels of Dab2 mRNA in the crypts and of those of the 96-kDa isoform. This is the first report showing that the 96-kDa Dab2 isoform is expressed at the apical domain of rat small intestine, that ontogeny regulates Dab2 gene expression in intestine and kidney and that retarding weaning affects intestinal Dab2 gene expression.

Ontogeny of Na(+)/L-carnitine transporter and of gamma-trimethylaminobutyraldehyde dehydrogenase and gamma-butyrobetaine hydroxylase genes expression in rat kidney.

The kidney synthesizes L-carnitine and reabsorbs it via the Na(+)/L-carnitine cotransporter OCTN2. This study investigates the ontogeny of OCTN2, gamma-trimethylaminobutyraldehyde dehydrogenase (TMABA-DH) and gamma-butyrobetaine hydroxylase (BBH) in rat kidneys. Foetuses, newborn, suckling, weaning and adult rats were used. The apical membranes of foetal and newborn rat kidneys express OCTN2 transport activity, which is up-regulated by age. Maturation significantly increased the V(max) of this transport system without changing the apparent K(t), which excludes a maturation-related expression of different transporter isoforms. Northern analysis showed a 3.7kb transcript for OCTN2 in all the ages tested. Northern and RT-PCR assays revealed that maturation increased renal expression of OCTN2 mRNA. Foetuses express TMABA-DH mRNA and this expression increased during postnatal life. BBH mRNA, however, was detected during the suckling period onwards and its abundance was not changed significantly by maturation. This study reports for the first time that, in rat kidneys: (i) an apical OCTN2 transporter is active in rat foetuses, (ii) ontogeny up-regulates OCTN2 activity by increasing the density and/or turnover of the transporters, (iii) the maturation-related changes in OCTN2 are in part mediated by transcriptional mechanism(s) and (iv) the expression of both, TMABA-DH and BBH mRNA is ontogenically regulated. Some of these results were published as an abstract (García-Delgado et al., 2003).

Creatine transport in brush-border membrane vesicles isolated from rat kidney cortex.

The kidney efficiently salvages creatine from the urine; however, the mechanism(s) that mediates renal creatine reabsorption has not been investigated. This study characterizes the creatine transport mechanism in brush-border membrane vesicles isolated from the rat renal cortex. An osmolality plot revealed that creatine is transported into an osmotically active space and that it is also bound to the membranes. An inwardly directed NaCl gradient stimulated creatine uptake and the time course of uptake exhibited an overshoot phenomenon, which indicates the presence of an active process for creatine in these membranes. The uptake of creatine showed an absolute requirement for both Na(+) and Cl(-). The NaCl gradient-dependent creatine uptake was stimulated by a valinomycin-induced, inside-negative, K(+)-diffusion potential, which suggests that the uptake process is electrogenic. Stoichiometric analyses indicated a probable couple ratio of 2 Na(+):1 Cl(-):1 creatine molecule. The kinetic study showed that creatine is transported by a high-affinity system (K(m) of 15 microM). Creatine uptake was inhibited by a 100-fold excess of various compounds with the following potency order: cold creatine = guanidinopropionic acid > nipecotic acid > gamma-aminobutyric acid (GABA) = beta-alanine = betaine, whereas carnitine, glycine, taurine, and choline were without effect. This pattern of inhibition differs from that observed for GABA uptake (unlabeled GABA = GPA > beta-alanine > nipecotic acid >> creatine). The conclusion drawn was that the apical membrane of the renal cortical tubules contains an active, high-affinity, electrogenic, 2 Na(+)/1 Cl(-)/creatine cotransporter.