Role of Csk in intestinal epithelial barrier function and protection against colitis

Ginseng exosomes modulate M1/M2 polarisation by activating autophagy and target IKK/IкB/NF-кB to alleviate inflammatory bowel disease

BACKGROUND

Exosomes are involved in intercellular communication and regulation of the inflammatory microenvironment. In a previous study, we demonstrated that fresh ginseng exosomes (GEs) alleviated inflammatory bowel disease. However, the precise mechanism by which GEs activate the immune system and subsequently inhibit the formation of intestinal inflammatory microenvironment remains unknown.

METHODS

Herein, we investigated the effects of GEs on autophagy, macrophage polarisation, intestinal inflammation, and the epithelial barrier by means of transcriptome sequencing, network pharmacology, transmission electron microscopy, immunoblotting, flow cytometry and small molecule inhibitors.

RESULTS

GEs significantly activated autophagy and M2-like macrophage polarisation, which could be blocked by the autophagy inhibitor 3-methyladenine. In the co-culture system of macrophages and intestinal epithelial cells, macrophages treated with GEs secreted more interleukin-10 (IL-10) and significantly reduced Nitric oxide (NO) levels in intestinal epithelial cells in vitro. Furthermore, GEs acted directly on intestinal epithelial cells through the IKK/IкB/NF-кB signalling pathway to reduce inflammation and restore the intestinal barrier. Orally administered GEs could restore disrupted colonic barriers, alleviate inflammatory bowel responses, and regulate the polarisation of intestinal macrophages in vivo.

CONCLUSION

In summary, GEs may be a potential treatment for inflammatory bowel disease, and targeting autophagy and macrophage polarisation may help alleviate intestinal inflammation.

Regulation, targets and functions of CSK

The Src family kinases (SFK) plays an important role in multiple signal transduction pathways. Aberrant activation of SFKs leads to diseases such as cancer, blood disorders, and bone pathologies. By phosphorylating and inactivating SFKs, the C-terminal Src kinase (CSK) serves as the key negative regulator of SFKs. Similar to Src, CSK is composed of SH3, SH2, and a catalytic kinase domain. However, while the Src kinase domain is intrinsically active, the CSK kinase domain is intrinsically inactive. Multiple lines of evidence indicate that CSK is involved in various physiological processes including DNA repair, permeability of intestinal epithelial cells (IECs), synaptic activity, astrocyte-to-neuron communication, erythropoiesis, platelet homeostasis, mast cell activation, immune and inflammation responses. As a result, dysregulation of CSK may lead to many diseases with different underlying molecular mechanisms. Furthermore, recent findings suggest that in addition to the well-established CSK-SFK axis, novel CSK-related targets and modes of CSK regulation also exist. This review focuses on the recent progress in this field for an up-to-date understanding of CSK.

Long Noncoding RNA FBXL19-AS1-Mediated Ulcerative Colitis-Associated Intestinal Epithelial Barrier Defect

BACKGROUND

This study commenced to uncover the role of long non-coding RNA FBXL19 antisense RNA 1 (FBXL19-AS1) in the development of ulcerative colitis (UC) and its possible mechanism.

METHODS

FBXL19-AS1 expression in the colonic sigmoid mucosa of UC patients was detected. A colitis model was induced in mice using 5% dextran sodium sulfate. Hematoxylin-eosin staining was performed for histopathological examination. Apoptosis was detected by Tunel staining and tissue fibrosis was detected by immunohistochemistry. Also, intestinal permeability was examined. The concentrations of inflammatory factors IL-1β and IL-18 were detected by enzyme-linked immunosorbent assay. The relationship between FBXL19-AS1, miR-339-3p and RHOB was verified by RNA immunoprecipitation assay and dual luciferase reporter assay.

RESULTS

The expression of FBXL19-AS1 was increased in dextran sodium sulfate (DSS)-induced colitis mouse model. FBXL19-AS1 interference or miR-339-3p overexpression inhibited DSS-induced colonic epithelial cell apoptosis and inflammatory response, and improved intestinal epithelial barrier defects, thereby ameliorating DSS-induced colitis injury in mice. FBXL19-AS1 sponged miR-339-3p while miR-339-3p targeted RHOB. Overexpression of RHOB reversed the protective effect of inhibition of FBXL19-AS1 on DSS-induced colitis in mice.

CONCLUSION

FBXL19-AS1 reduces miR-339-3p-mediated targeting of RHOB and aggravates intestinal epithelial barrier defect in DSS-induced colitis in mice.

Role of Ras in regulation of intestinal epithelial cell homeostasis and crosstalk with Wnt signaling

Cross talk between different signaling pathways is thought to be important for regulation of homeostasis of, as well as oncogenesis of, the intestinal epithelium. Expression of an active form of K-Ras specifically in intestinal epithelial cells (IECs) of mice (IEC-RasDA mice) resulted in the development of hyperplasia in the small intestine and colon of mice. IEC-RasDA mice also manifested the increased proliferation of IECs. In addition, the number of goblet cells markedly increased, while that of Paneth cells decreased in IEC-RasDA mice. Development of intestinal organoids was markedly enhanced for IEC-RasDA mice compared with control mice. Whereas, the expression of Wnt target genes was significantly reduced in the in intestinal crypts from IEC-RasDA mice compared with that apparent for the control. Our results thus suggest that K-Ras promotes the proliferation of IECs as well as generation of goblet cells. By contrast, Ras counter-regulates the Wnt signaling and thereby contribute to the proper regulation of intestinal epithelial cell homeostasis.

Regulation of colonic epithelial cell homeostasis by mTORC1

Cell signaling important for homeostatic regulation of colonic epithelial cells (CECs) remains poorly understood. Mammalian target of rapamycin complex 1 (mTORC1), a protein complex that contains the serine-threonine kinase mTOR, mediates signaling that underlies the control of cellular functions such as proliferation and autophagy by various external stimuli. We here show that ablation of tuberous sclerosis complex 2 (Tsc2), a negative regulator of mTORC1, specifically in intestinal epithelial cells of mice resulted in increased activity of mTORC1 of, as well as increased proliferative activity of, CECs. Such Tsc2 ablation also reduced the population of Lgr5-positive colonic stem cells and the expression of Wnt target genes in CECs. The stimulatory phosphorylation of the kinase Akt and inhibitory phosphorylation of glycogen synthase kinase 3β were both markedly decreased in the colon of the Tsc2 conditional knockout (CKO) mice. Development of colonic organoids with cryptlike structures was enhanced for Tsc2 CKO mice compared with control mice. Finally, Tsc2 CKO mice manifested increased susceptibility to dextran sulfate sodium-induced colitis. Our results thus suggest that mTORC1 activity promotes the proliferation of, as well as the expression of Wnt target genes in, CECs and thereby contributes to colonic organogenesis and homeostasis.

Src Family Tyrosine Kinases in Intestinal Homeostasis, Regeneration and Tumorigenesis

Src, originally identified as an oncogene, is a membrane-anchored tyrosine kinase and the Src family kinase (SFK) prototype. SFKs regulate the signalling induced by a wide range of cell surface receptors leading to epithelial cell growth and adhesion. In the intestine, the SFK members Src, Fyn and Yes regulate epithelial cell proliferation and migration during tissue regeneration and transformation, thus implicating conserved and specific functions. In patients with colon cancer, SFK activity is a marker of poor clinical prognosis and a potent driver of metastasis formation. These tumorigenic activities are linked to SFK capacity to promote the dissemination and tumour-initiating capacities of epithelial tumour cells. However, it is unclear how SFKs promote colon tumour formation and metastatic progression because SFK-encoding genes are unfrequently mutated in human cancer. Here, we review recent findings on SFK signalling during intestinal homeostasis, regeneration and tumorigenesis. We also describe the key nongenetic mechanisms underlying SFK tumour activities in colorectal cancer, and discuss how these mechanisms could be exploited in therapeutic strategies to target SFK signalling in metastatic colon cancer.

Refining critical regions in 15q24 microdeletion syndrome pertaining to autism

Chromosome 15q24 microdeletion syndrome is characterized by developmental delay, facial dysmorphism, hearing loss, hypotonia, recurrent infection, and other congenital malformations including microcephaly, scoliosis, joint laxity, digital anomalies, as well as sometimes having autism spectrum disorder (ASD) and attention deficit hyperactivity disorder. Here, we report a boy with a 2.58-Mb de novo deletion at chromosome 15q24. He is diagnosed with ASD and having multiple phenotypes similar to those reported in cases having 15q24 microdeletion syndrome. To delineate the critical genes and region that might be responsible for these phenotypes, we reviewed all previously published cases. We observe a potential minimum critical region of 650 kb (LCR15q24A-B) affecting NEO1 among other genes that might pertinent to individuals with ASD carrying this deletion. In contrast, a previously defined minimum critical region downstream of the 650-kb interval (LCR15q24B-D) is more likely associated with the developmental delay, facial dysmorphism, recurrent infection, and other congenital malformations. As a result, the ASD phenotype in this individual is potentially attributed by genes particularly NEO1 within the newly proposed critical region.