Lin, R.-X. | Search bioRxiv

bioRxiv2021

CHRONIC INFLAMMATION IN ULCERATIVE COLITIS CAUSES LONG TERM CHANGES IN GOBLETCELL FUNCTION

ObjectiveOne of the features of ulcerative colitis (UC) is a defect in the protective mucus layer. This has been attributed to a reduced number of goblet cells (GC). However, it is not known whether abnormal GC mucus secretion also contributes to the reduced mucus layer. Our aims were to test the hypothesis that GC secretion was abnormal in UC with the changes persistent in colonoids even in the absence of immune cells. DesignColonoids were established from intestinal stem cells of healthy subjects (HS) and from patients with UC (inactive and active sites). Colonoids were maintained as undifferentiated (UD) or induced to differentiate (DF) and studied as 3D or monolayers on Transwell filters. Total RNA was extracted for quantitative real-time PCR analysis. Carbachol and PGE2 mediated stimulation followed by examination of mucus layer by MUC2 IF/confocal microscopy and TEM were performed. ResultsColonoids derived from patients with UC can be propagated over many passages; however, they exhibit a reduced rate of growth and TEER compared with colonoids from HS. Differentiated UC colonoid monolayers form a thin and non-continuous mucus layer. UC colonoids have increased expression of secretory lineage markers: ATOH1 and SPDEF, including MUC2 positive GCs and ChgA positive enteroendocrine cells but failed to secrete mucin when exposed to the cholinergic agonist carbachol and PGE2, which caused increased secretion in HS. Exposure to TNF- (5days), reduced the number of GC with a greater percentage decrease in UC colonoids compared to HS. ConclusionsAbnormal mucus layer in UC is due to long term changes in epithelial cells that lead to abnormal mucus secretion as well as effects of the inflammatory environment to reduce the number of GC. This continued defect in GC mucus secretion may be involved in UC recurrence.

physiology↗

bioRxiv2020

Chronic exposure of ErbB TKIs inhibits DRA expression and activity through an ERK/Elk-1/CREB/AP-1 dependent pathway

Diarrhea is the major side effect of first- and second-generation ErbB tyrosine kinase inhibitors (TKI), the mechanism of which remains incompletely understood. The current studies were carried out over the time frame that ErbB TKIs usually initiate diarrhea. We report in Caco-2/bbe cells that exposure of ErbB TKIs, but not non-ErbB TKIs for six days at clinically-relevant concentrations significantly reduced the expression of DRA and inhibited apical Cl-/HCO3-exchange activity. The ErbB TKIs decreased DRA expression through an ERK/Elk-1/CREB/AP-1 dependent pathway. The blockade of ERK phosphorylation by ErbB TKIs decreased the phosphorylation of Elk-1 and the amount of total and p-CREB, and reduced the expression of C-Fos, which is part of the AP-1 complex that maintain DRA expression. Altogether, our studies demonstrate that ErbB TKIs decrease expression and activity of DRA, which occurs over the time frame that these drugs clinically cause diarrhea, and since DRA is part of the intestinal neutral NaCl absorptive process, the reduced absorption is likely to represent a major contributor to the ErbB TKI-associated diarrhea.

pharmacology and toxicology↗