SLC6A14 impacts cystic fibrosis lung disease severity via mTOR and epithelial repair modulation

Cystic fibrosis (CF), due to variants in CFTR gene, is associated with chronic infection/inflammation responsible for airway epithelium alteration and lung function decline. Modifier genes induce phenotype variability between people with CF (pwCF) carrying the same CFTR variants. Among these, the gene encoding for the amino acid transporter SLC6A14 has been associated with lung disease severity and age of primary airway infection by the bacteria Pseudomonas aeruginosa. In this study, we investigated whether the single nucleotide polymorphism (SNP) rs3788766, located within SLC6A14 promoter, is associated with lung disease severity in a large French cohort of pwCF. We also studied the consequences of this SNP on SLC6A14 promoter activity using a luciferase reporter and the role of SLC6A14 in mammalian target of rapamycin (mTOR) signaling pathway and airway epithelial repair. We confirm that SLC6A14 rs3788766 SNP is associated with lung disease severity in pwCF (p=0.020; n=3,257, pancreatic insufficient, aged 6 to 40 years old), with the minor allele G being deleterious. In bronchial epithelial cell lines deficient for CFTR, SLC6A14 promoter activity is reduced in the presence of the rs3788766 G allele. SLC6A14 inhibition with a specific pharmacological blocker reduced 3H-arginine transport, mTOR phosphorylation and bronchial epithelial repair rates in wound healing assays. To conclude, our study highlights that SLC6A14 genotype might affect lung disease severity of people with cystic fibrosis via mTOR and epithelial repair mechanisms modulation in the lung.

Cells and Mediators of Inflammation as Effectors of Epithelial Repair in the Inflamed Intestine

Mucosal and histological healing have become the gold standards for assessing the efficacy of therapy in patients living with inflammatory bowel diseases (IBD). Despite these being the accepted goals in therapy, the mechanisms that underlie the healing of the mucosa after an inflammatory insult are not well understood, and many patients fail to meet this therapeutic endpoint. Here we review the emerging evidence that mediators (e.g. prostaglandins, cytokines, proteases, reactive oxygen and nitrogen species) and innate immune cells (e.g. neutrophils and monocytes/macrophages), that are involved in the initiation of the inflammatory response, are also key players in the mechanisms underlying mucosal healing to resolve chronic inflammation in the colon. The dual function mediators comprise an inflammation/repair program that returns damaged tissue to homeostasis. Understanding details of the dual mechanisms of these mediators and cells may provide the basis for the development of drugs that can help to stimulate epithelial repair in patients affected by IBD.

Pathogenic Mechanisms Underlying Idiopathic Pulmonary Fibrosis

The pathogenesis of idiopathic pulmonary fibrosis (IPF) involves a complex interplay of cell types and signaling pathways. Recurrent alveolar epithelial cell (AEC) injury may occur in the context of predisposing factors (e.g., genetic, environmental, epigenetic, immunologic, and gerontologic), leading to metabolic dysfunction, senescence, aberrant epithelial cell activation, and dysregulated epithelial repair. The dysregulated epithelial cell interacts with mesenchymal, immune, and endothelial cells via multiple signaling mechanisms to trigger fibroblast and myofibroblast activation. Recent single-cell RNA sequencing studies of IPF lungs support the epithelial injury model. These studies have uncovered a novel type of AEC with characteristics of an aberrant basal cell, which may disrupt normal epithelial repair and propagate a profibrotic phenotype. Here, we review the pathogenesis of IPF in the context of novel bioinformatics tools as strategies to discover pathways of disease, cell-specific mechanisms, and cell-cell interactions that propagate the profibrotic niche. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Single-cell sequencing of rotavirus-infected intestinal epithelium reveals cell-type specific epithelial repair and tuft cell infection

Intestinal epithelial damage is associated with most digestive diseases and results in detrimental effects on nutrient absorption and production of hormones and antimicrobial defense molecules. Thus, understanding epithelial repair and regeneration following damage is essential in developing therapeutics that assist in rapid healing and restoration of normal intestinal function. Here we used a well-characterized enteric virus (rotavirus) that damages the epithelium at the villus tip but does not directly damage the intestinal stem cell, to explore the regenerative transcriptional response of the intestinal epithelium at the single-cell level. We found that there are specific Lgr5+ cell subsets that exhibit increased cycling frequency associated with significant expansion of the epithelial crypt. This was accompanied by an increase in the number of immature enterocytes. Unexpectedly, we found rotavirus infects tuft cells. Transcriptional profiling indicates tuft cells respond to viral infection through interferon-related pathways. Together these data provide insights as to how the intestinal epithelium responds to insults by providing evidence of stimulation of a repair program driven by stem cells with involvement of tuft cells that results in the production of immature enterocytes that repair the damaged epithelium.

The Promotive Effect of the Active Ingredients of Atractylodes macrocephala on Intestinal Epithelial Repair Through Activating Ca2+ Pathway

Atractylodes macrocephala ( AM) is a famous traditional Chinese medicine for intestinal epithelial restitution through activating Ca2+ channels. However, the roles of specific AM compositions in intestinal epithelial restitution are sparse. Therefore, this study aimed to compare the concrete effects of the 4 active ingredients (atractylon, β-eudesmol, atractylenolide II, atractylenolide III) of AM and their combination on intestinal epithelial repair and the Ca2+ pathway in intestinal epithelial cell (IEC-6) cells. First, the best combination of the 4 ingredients with an optimal mixing ratio of atractylon: β-eudesmol: atractylenolide II: atractylenolide III = 1:2:2:2 was demonstrated by a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide orthogonal experiment. Subsequently, enzyme-linked immunosorbent assay was used to measure anti-inflammatory cytokine levels, the migratory ability was evaluated by cell scratch experiments, cell cycle analysis and [Ca2+]cyt concentration in cells were detected by flow cytometry, and the expression of the Ca2+ pathway-related genes was detected by immunofluorescence staining, quantitative polymerase chain reaction and whole blood assays. Our result showed that atractylon, β-Eudesmol, atractylenolide II, and atractylenolide III showed different abilities to promote the IEC-6 cells proliferation, migration, and the expression of anti-inflammatory cytokines interleukin (IL)-2, IL-10, and ornithine decarboxylase, as well as the intracellular [Ca2+]cyt concentration through stromal interaction molecule 1 transposition to activate Ca2+ pathway. Thereinto, atractylenolide III was the main active ingredient of AM for pro-proliferation and anti-inflammation, and the combination of 4 AM ingredients performed better beneficial effects on IEC-6 cells. Therefore, our study suggested that atractylenolide III was the active ingredient of AM for intestinal epithelial repair through activating the Ca2+ pathway, and the 4 ingredients of AM have a synergy in intestinal epithelial repair.