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

A Haplotype GWAS in Syndromic Familial Colorectal Cancer

A previous genome-wide association study (GWAS) in colorectal cancer (CRC) patients with gastric and/or prostate cancer in their families suggested genetic loci with a shared risk for these three cancers. A second haplotype GWAS was undertaken in the same colorectal cancer patients and different controls with the aim of confirming the result and finding novel loci. The haplotype GWAS analysis involved 685 patients with colorectal cancer cases and 1642 healthy controls from Sweden. A logistic regression model was used with a sliding window haplotype approach. Whole-genome and exome sequencing datawere used to find candidate SNPs to be tested in a nested case-control study. In the analysis of 685 colorectal cancer cases and 1642 controls, all ten candidate loci from the previous study were confirmed. Fifty candidate loci were suggested with a p-value < 5 × 10-6 and odds ratios between 1.35-6.52. Two of the 50 loci, on 13q33.3 and 16q23.3, were the same as in the previous study. Whole-genome or exome data from 122 colorectal cancer patients was used to search for candidate variants in these 50 loci. A nested case-control study was performed to test genetic variants at 11 loci in a cohort of 827 familial colorectal cancer and a sub-cohort of 293 familial CRC cases with colorectal, gastric, and/or prostate cancer within their families and 1530 healthy controls. One SNP, rs115943733 on 10q11.21, reached statistical significance (OR = 3.26, p = 0.009). Seven SNPs in 4 loci had a higher OR in the smaller cohort compared to the larger study CRC cases. The results in this GWAS gave support for suggested loci with an increased shared risk of CRC, gastric, and/or prostate cancer. Further studies are needed to confirm the shared risk to be able to use this information in cancer prevention.

Integrated gut microbiota and serum metabolomics reveal the protective effect of oleanolic acid on liver and kidney-injured rats induced by Euphorbia pekinensis

Euphorbia pekinensis (EP) is a commonly used Chinese medicine treating edema with potential hepatorenal toxicity. However, its toxic mechanism and prevention are remained to be explored. Oleanolic acid (OA) is a triterpene acid with potential hepatorenal protective activities. We investigated the protective effect and potential mechanism of OA on EP-induced hepatorenal toxicity. In this study, rats were given total diterpenes from EP (TDEP, 16 mg/kg) combined with OA (10, 20, 40 mg/kg) by gavage for 4 weeks. The results showed that TDEP administration could lead to a 3-4-fold increasement in hepatorenal biochemical parameters with histopathological injuries, while OA treatment could ameliorate them in a dose-dependent manner. At microbial and metabolic levels, intestinal flora and host metabolism were perturbed after TDEP administration. The disturbance of bile acid metabolism was the most significant metabolic pathway, with secondary bile acids increasing while conjugated bile acids decreased. OA treatment can improve the disorder of intestinal flora and metabolic bile acid spectrum. Further correlation analysis screened out that Escherichia-Shigella, Phascolarctobacterium, Acetatifactor, and Akkermansia were closely related to the bile acid metabolic disorder. In conclusion, oleanolic acid could prevent hepatorenal toxicity induced by EP by regulating bile acids metabolic disorder via intestinal flora improvement.

Regulation of intestinal epithelial homeostasis by mesenchymal cells

The gastrointestinal tract harbors diverse microorganisms in the lumen. Epithelial cells segregate the luminal microorganisms from immune cells in the lamina propria by constructing chemical and physical barriers through the production of various factors to prevent excessive immune responses against microbes. Therefore, perturbations of epithelial integrity are linked to the development of gastrointestinal disorders. Several mesenchymal stromal cell populations, including fibroblasts, myofibroblasts, pericytes, and myocytes, contribute to the establishment and maintenance of epithelial homeostasis in the gut through regulation of the self-renewal, proliferation, and differentiation of intestinal stem cells. Recent studies have revealed alterations in the composition of intestinal mesenchymal stromal cells in patients with inflammatory bowel disease and colorectal cancer. A better understanding of the interplay between mesenchymal stromal cells and epithelial cells associated with intestinal health and diseases will facilitate identification of novel biomarkers and therapeutic targets for gastrointestinal disorders. This review summarizes the key findings obtained to date on the mechanisms by which functionally distinct mesenchymal stromal cells regulate epithelial integrity in intestinal health and diseases at different developmental stages.

Nonlinear DNA methylation trajectories in aging male mice

Although DNA methylation data yields highly accurate age predictors, little is known about the dynamics of this quintessential epigenomic biomarker during lifespan. To narrow the gap, we investigate the methylation trajectories of male mouse colon at five different time points of aging. Our study indicates the existence of sudden hypermethylation events at specific stages of life. Precisely, we identify two epigenomic switches during early-to-midlife (3-9 months) and mid-to-late-life (15-24 months) transitions, separating the rodents' life into three stages. These nonlinear methylation dynamics predominantly affect genes associated with the nervous system and enrich in bivalently marked chromatin regions. Based on groups of nonlinearly modified loci, we construct a clock-like classifier STageR (STage of aging estimatoR) that accurately predicts murine epigenetic stage. We demonstrate the universality of our clock in an independent mouse cohort and with publicly available datasets.

Safety of Anti-Reelin Therapeutic Approaches for Chronic Inflammatory Diseases

Reelin, a large extracellular glycoprotein, plays critical roles in neuronal development and synaptic plasticity in the central nervous system (CNS). Recent studies have revealed non-neuronal functions of plasma Reelin in inflammation by promoting endothelial-leukocyte adhesion through its canonical pathway in endothelial cells (via ApoER2 acting on NF-κB), as well as in vascular tone regulation and thrombosis. In this study, we have investigated the safety and efficacy of selectively depleting plasma Reelin as a potential therapeutic strategy for chronic inflammatory diseases. We found that Reelin expression remains stable throughout adulthood and that peripheral anti-Reelin antibody treatment with CR-50 efficiently depletes plasma Reelin without affecting its levels or functionality within the CNS. Notably, this approach preserves essential neuronal functions and synaptic plasticity. Furthermore, in mice induced with experimental autoimmune encephalomyelitis (EAE), selective modulation of endothelial responses by anti-Reelin antibodies reduces pathological leukocyte infiltration without completely abolishing diapedesis. Finally, long-term Reelin depletion under metabolic stress induced by a Western diet did not negatively impact the heart, kidney, or liver, suggesting a favorable safety profile. These findings underscore the promising role of peripheral anti-Reelin therapeutic strategies for autoimmune diseases and conditions where endothelial function is compromised, offering a novel approach that may avoid the immunosuppressive side effects associated with conventional anti-inflammatory therapies.

Molecular Mechanisms of Reelin in the Enteric Nervous System and the Microbiota-Gut-Brain Axis: Implications for Depression and Antidepressant Therapy

Current pharmacological treatments for depression fail to produce adequate remission in a significant proportion of patients. Increasingly, other systems, such as the microbiome-gut-brain axis, are being looked at as putative novel avenues for depression treatment. Dysbiosis and dysregulation along this axis are highly comorbid with the severity of depression symptoms. The endogenous extracellular matrix protein reelin is present in all intestinal layers as well as in myenteric and submucosal ganglia, and its receptors are also present in the gut. Reelin secretion from subepithelial myofibroblasts regulates cellular migration along the crypt-villus axis in the small intestine and colon. Reelin brain expression is downregulated in mood and psychotic disorders, and reelin injections have fast antidepressant-like effects in animal models of depression. This review seeks to discuss the roles of reelin in the gastrointestinal system and propose a putative role for reelin actions in the microbiota-gut-brain axis in the pathogenesis and treatment of depression, primarily reflecting on alterations in gut epithelial cell renewal and in the clustering of serotonin transporters.

Cardiac and intestinal tissue conduct developmental and reparative processes in response to lymphangiocrine signaling

Lymphatic vessels conduct a diverse range of activities to sustain the integrity of surrounding tissue. Besides facilitating the movement of lymph and its associated factors, lymphatic vessels are capable of producing tissue-specific responses to changes within their microenvironment. Lymphatic endothelial cells (LECs) secrete paracrine signals that bind to neighboring cell-receptors, commencing an intracellular signaling cascade that preludes modifications to the organ tissue's structure and function. While the lymphangiocrine factors and the molecular and cellular mechanisms themselves are specific to the organ tissue, the crosstalk action between LECs and adjacent cells has been highlighted as a commonality in augmenting tissue regeneration within animal models of cardiac and intestinal disease. Lymphangiocrine secretions have been owed for subsequent improvements in organ function by optimizing the clearance of excess tissue fluid and immune cells and stimulating favorable tissue growth, whereas perturbations in lymphatic performance bring about the opposite. Newly published landmark studies have filled gaps in our understanding of cardiac and intestinal maintenance by revealing key players for lymphangiocrine processes. Here, we will expand upon those findings and review the nature of lymphangiocrine factors in the heart and intestine, emphasizing its involvement within an interconnected network that supports daily homeostasis and self-renewal following injury.

Shared genetic architecture between irritable bowel syndrome and psychiatric disorders reveals molecular pathways of the gut-brain axis

BACKGROUND

Irritable bowel syndrome (IBS) often co-occurs with psychiatric and gastrointestinal disorders. A recent genome-wide association study (GWAS) identified several genetic risk variants for IBS. However, most of the heritability remains unidentified, and the genetic overlap with psychiatric and somatic disorders is not quantified beyond genome-wide genetic correlations. Here, we characterize the genetic architecture of IBS, further, investigate its genetic overlap with psychiatric and gastrointestinal phenotypes, and identify novel genomic risk loci.

METHODS

Using GWAS summary statistics of IBS (53,400 cases and 433,201 controls), and psychiatric and gastrointestinal phenotypes, we performed bivariate casual mixture model analysis to characterize the genetic architecture and genetic overlap between these phenotypes. We leveraged identified genetic overlap to boost the discovery of genomic loci associated with IBS, and to identify specific shared loci associated with both IBS and psychiatric and gastrointestinal phenotypes, using the conditional/conjunctional false discovery rate (condFDR/conjFDR) framework. We used functional mapping and gene annotation (FUMA) for functional analyses.

RESULTS

IBS was highly polygenic with 12k trait-influencing variants. We found extensive polygenic overlap between IBS and psychiatric disorders and to a lesser extent with gastrointestinal diseases. We identified 132 independent IBS-associated loci (condFDR < 0.05) by conditioning on psychiatric disorders (n = 127) and gastrointestinal diseases (n = 24). Using conjFDR, 70 unique loci were shared between IBS and psychiatric disorders. Functional analyses of shared loci revealed enrichment for biological pathways of the nervous and immune systems. Genetic correlations and shared loci between psychiatric disorders and IBS subtypes were different.

CONCLUSIONS

We found extensive polygenic overlap of IBS and psychiatric and gastrointestinal phenotypes beyond what was revealed with genetic correlations. Leveraging the overlap, we discovered genetic loci associated with IBS which implicate a wide range of biological pathways beyond the gut-brain axis. Genetic differences may underlie the clinical subtype of IBS. These results increase our understanding of the pathophysiology of IBS which may form the basis for the development of individualized interventions.

Reelin through the years: From brain development to inflammation

Reelin was originally identified as a regulator of neuronal migration and synaptic function, but its non-neuronal functions have received far less attention. Reelin participates in organ development and physiological functions in various tissues, but it is also dysregulated in some diseases. In the cardiovascular system, Reelin is abundant in the blood, where it contributes to platelet adhesion and coagulation, as well as vascular adhesion and permeability of leukocytes. It is a pro-inflammatory and pro-thrombotic factor with important implications for autoinflammatory and autoimmune diseases such as multiple sclerosis, Alzheimer's disease, arthritis, atherosclerosis, or cancer. Mechanistically, Reelin is a large secreted glycoprotein that binds to several membrane receptors, including ApoER2, VLDLR, integrins, and ephrins. Reelin signaling depends on the cell type but mostly involves phosphorylation of NF-κB, PI3K, AKT, or JAK/STAT. This review focuses on non-neuronal functions and the therapeutic potential of Reelin, while highlighting secretion, signaling, and functional similarities between cell types.

Neurotransmitter signaling: a new frontier in colorectal cancer biology and treatment

The brain-gut axis, a bidirectional network between the central and enteric nervous system, plays a critical role in modulating the gastrointestinal tract function and homeostasis. Recently, increasing evidence suggests that neuronal signaling molecules can promote gastrointestinal cancers, however, the mechanisms remain unclear. Aberrant expression of neurotransmitter signaling genes in colorectal cancer supports the role of neurotransmitters to stimulate tumor growth and metastatic spread by promoting cell proliferation, migration, invasion, and angiogenesis. In addition, neurotransmitters can interact with immune and endothelial cells in the tumor microenvironment to promote inflammation and tumor progression. As such, pharmacological targeting of neurotransmitter signaling represent a promising novel anticancer approach. Here, we present an overview of the current evidence supporting the role of neurotransmitters in colorectal cancer biology and treatment.

Galectin-3 Deletion Reduces LPS and Acute Colitis-Induced Pro-Inflammatory Microglial Activation in the Ventral Mesencephalon

Parkinson’s disease is a highly prevalent neurological disorder for which there is currently no cure. Therefore, the knowledge of risk factors as well as the development of new putative molecular targets is mandatory. In this sense, peripheral inflammation, especially the originated in the colon, is emerging as a predisposing factor for suffering this disease. We have largely studied the pleiotropic roles of galectin-3 in driving microglia-associated immune responses. However, studies aimed at elucidating the role of galectin-3 in peripheral inflammation in terms of microglia polarization are lacking. To achieve this, we have evaluated the effect of galectin-3 deletion in two different models of acute peripheral inflammation: intraperitoneal injection of lipopolysaccharide or gut inflammation induced by oral administration of dextran sodium sulfate. We found that under peripheral inflammation the number of microglial cells and the expression levels of pro-inflammatory mediators take place specifically in the dopaminergic system, thus supporting causative links between Parkinson’s disease and peripheral inflammation. Absence of galectin-3 highly reduced neuroinflammation in both models, suggesting an important central regulatory role of galectin-3 in driving microglial activation provoked by the peripheral inflammation. Thus, modulation of galectin-3 function emerges as a promising strategy to minimize undesired microglia polarization states.

Downregulation of reelin predicts poor prognosis for glioma

Aim: In the present study, we studied the relationship between RELN and prognosis in glioma. Materials & methods: Expression profiles and methylation data of RELN were obtained from bioinformatic datasets. Correlations between RELN and clinicopathological features and overall survival were respectively assessed using chi-square test and Kaplan-Meier analysis. Results: RELN was downregulated in glioma, and its downregulation correlated well with glioma malignancy and overall survival. Meanwhile, hypermethylation of RELN was significantly correlated with low RELN expression. Additionally, gene set enrichment analysis demonstrated that low expression of RELN correlated with many key cancer pathways, possibly highlighting the importance of RELN in carcinogenesis of brain. Conclusion: RELN may serve as a potential prognostic marker and promising target molecule for new therapy of glioma.

Dendrobium officinale polysaccharides alleviate colon tumorigenesis via restoring intestinal barrier function and enhancing anti-tumor immune response

Intact epithelial barrier and mucosal immune system are crucial for maintaining intestinal homeostasis. Previous study indicated that Dendrobium officinale polysaccharides (DOPS) can regulate immune responses and inflammation to alleviate experimental colitis. However, it remains largely unknown whether DOPS can suppress AOM/DSS-induced colorectal cancer (CRC) model through its direct impact on intestinal barrier function and intestinal mucosal immunity. Here, we demonstrated the therapeutic action of DOPS for CRC model and further illustrated its underlying mechanisms. Treatment with 5-aminosalicylic acid (5-ASA) and DOPS significantly improved the clinical signs and symptoms of chronic colitis, relieve colon damage, suppress the formation and growth of colon tumor in CRC mice. Moreover, administration of DOPS effectively preserved the intestinal barrier function via reducing the loss of zonula occludens-1 (ZO-1) and occludin in adjacent tissues and carcinomatous tissues. Further studies demonstrated that DOPS improved the metabolic ability of tumor infiltrated CD8⁺ cytotoxic T lymphocytes (CTLs) and reduced the expression of PD-1 on CTLs to enhance the anti-tumor immune response in the tumor microenvironments (TME). Together, the conclusions indicated that DOPS restore intestinal barrier function and enhance intestinal anti-tumor immune response to suppress CRC, which may be a novel strategy for the prevention and treatment of CRC.

Identification of differentially expressed genes regulated by methylation in colon cancer based on bioinformatics analysis

BACKGROUND

DNA methylation, acknowledged as a key modification in the field of epigenetics, regulates gene expression at the transcriptional level. Aberrant methylation in DNA regulatory regions could upregulate oncogenes and downregulate tumor suppressor genes without changing the sequences. However, studies of methylation in the control of gene expression are still inadequate. In the present research, we performed bioinformatics analysis to clarify the function of methylation and supply candidate methylation-related biomarkers and drivers for colon cancer.

AIM

To identify and analyze methylation-regulated differentially expressed genes (MeDEGs) in colon cancer by bioinformatics analysis.

METHODS

We downloaded RNA expression profiles, Illumina Human Methylation 450K BeadChip data, and clinical data of colon cancer from The Cancer Genome Atlas project. MeDEGs were identified by analyzing the gene expression and methylation levels using the edgeR and limma package in R software. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed in the DAVID database and KEGG Orthology-Based Annotation System 3.0, respectively. We then conducted Kaplan–Meier survival analysis to explore the relationship between methylation and expression and prognosis. Gene set enrichment analysis (GSEA) and investigation of protein-protein interactions (PPI) were performed to clarify the function of prognosis-related genes.

RESULTS

A total of 5 up-regulated and 81 down-regulated genes were identified as MeDEGs. GO and KEGG pathway analyses indicated that MeDEGs were enriched in multiple cancer-related terms. Furthermore, Kaplan–Meier survival analysis showed that the prognosis was negatively associated with the methylation status of glial cell-derived neurotrophic factor (GDNF) and reelin (RELN). In PPI networks, GDNF and RELN interact with neural cell adhesion molecule 1. Besides, GDNF can interact with GDNF family receptor alpha (GFRA1), GFRA2, GFRA3, and RET. RELN can interact with RAFAH1B1, disabled homolog 1, very low-density lipoprotein receptor, lipoprotein receptor-related protein 8, and NMDA 2B. Based on GSEA, hypermethylation of GDNF and RELN were both significantly associated with pathways including “RNA degradation,” “ribosome,” “mismatch repair,” “cell cycle” and “base excision repair.”

CONCLUSION

Aberrant DNA methylation plays an important role in colon cancer progression. MeDEGs that are associated with the overall survival of patients may be potential targets in tumor diagnosis and treatment.

Oral delivery of a Lactococcus lactis strain secreting bovine lactoferricin-lactoferrampin alleviates the development of acute colitis in mice

Ulcerative colitis (UC) is a chronic relapsing disease. Treatment of UC would benefit from specific targeting of therapeutics to the intestine. Previous studies have demonstrated that bovine lactoferricin and lactoferrampin have bactericidal, anti-inflammatory, and immunomodulatory effects. Here, we investigated whether oral administration of a bovine lactoferricin-lactoferrampin (LFCA)-encoding Lactococcus lactis (LL-LFCA) strain could alleviate experimental colitis. LFCA derived from LL-LFCA inhibited the growth of Escherichia coli and Staphylococcus aureus in vitro. In mice, administration of LL-LFCA decreased the disease activity index and attenuated dextran sulfate sodium (DSS)-induced body weight loss and colon shortening. LL-LFCA treatment also ameliorated DSS-induced colon damage, inhibited inflammatory cell infiltration, significantly decreased myeloperoxidase activity, and ameliorated DSS-induced disruption of intestinal permeability and tight junctions. In addition, 16S rDNA sequencing showed that LL-LFCA reversed DSS-induced gut dysbiosis. The production of proinflammatory mediators in serum and the colon was also reduced by administration of LL-LFCA. In vitro, LFCA derived from LL-LFCA decreased the messenger RNA expression of proinflammatory factors. The underlying mechanisms may involve inhibition of the nuclear factor kappa B (NF-κB) pathway. The results demonstrate that LL-LFCA ameliorates DSS-induced intestinal injury in mice, suggesting that LL-LFCA might be an effective drug for the treatment of inflammatory bowel diseases.

Small and large intestine express a truncated Dab1 isoform that assembles in cell-cell junctions and co-localizes with proteins involved in endocytosis

Disabled-1 (Dab1) is an essential intracellular adaptor protein in the reelin pathway. Our previous studies in mice intestine showed that Dab1 transmits the reelin signal to cytosolic signalling pathways. Here, we determine the Dab1 isoform expressed in rodent small and large intestine, its subcellular location and co-localization with clathrin, caveolin-1 and N-Wasp. PCR and sequencing analysis reveal that rodent small and large intestine express a Dab1 isoform that misses three (Y¹⁹⁸, Y²⁰⁰ and Y²²⁰) of the five tyrosine phosphorylation sites present in brain Dab1 isoform (canonical) and contains nuclear localization and export signals. Western blot assays show that both, crypts, which shelter progenitor cells, and enterocytes express the same Dab1 isoform, suggesting that epithelial cell differentiation does not regulate intestinal generation of alternatively spliced Dab1 variants. They also reveal that the canonical and the intestinal Dab1 isoforms differ in their total degree of phosphorylation. Immunostaining assays show that in enterocytes Dab1 localizes at the apical and lateral membranes, apical vesicles, close to adherens junctions and desmosomes, as well as in the nucleus; co-localizes with clathrin and with N-Wasp but not with caveolin-1, and in Caco-2 cells Dab1 localizes at cell-to-cell junctions by a Ca²⁺-dependent process. In conclusion, the results indicate that in rodent intestine a truncated Dab1 variant transmits the reelin signal and may play a role in clathrin-mediated apical endocytosis and in the control of cell-to-cell junction assembly. A function of intestinal Dab1 variant as a nucleocytoplasmic shuttling protein is also inferred from its sequence and nuclear location.