Ca2+ signaling in HCO3- secretion and protection of upper GI tract

Divergent roles of estrogen receptor subtypes in regulating estrogen-modulated colonic ion transports and epithelial repair

Although it was described previously for estrogen (E2) regulation of intestinal epithelial Cl- and HCO3- secretion in sex difference, almost nothing is known about the roles of estrogen receptor (ER) subtypes in regulating E2-modulated epithelial ion transports and epithelial restitution. Here, we aimed to investigate ERα and ERβ subtypes in the regulation of E2-modulated colonic epithelial HCO3- and Cl- secretion and epithelial restitution. Through physiological and biochemical studies, in combination of genetic knockdown, we showed that ERα attenuated female colonic Cl- secretion but promoted Ca2+-dependent HCO3- secretion via store-operated calcium entry (SOCE) mechanism in mice. However, ERβ attenuated HCO3- secretion by inhibiting Ca2+via the SOCE and inhibiting cAMP via protein kinases. Moreover, ERα but not ERβ promoted epithelial cell restitution via SOCE/Ca2+ signaling. ERα also enhanced cyclin D1, proliferating cell nuclear antigen, and β-catenin expression in normal human colonic epithelial cells. All ERα-mediated biological effects could be attenuated by its selective antagonist and genetic knockdown. Finally, both ERα and ERβ were expressed in human colonic epithelial cells and mouse colonic tissues. We therefore conclude that E2 modulates complex colonic epithelial HCO3- and Cl- secretion via ER subtype-dependent mechanisms and that ERα is specifically responsible for colonic epithelial regeneration. This study provides novel insights into the molecular mechanisms of how ERα and ERβ subtypes orchestrate functional homeostasis of normal colonic epithelial cells.

Particulate matter 10 exposure affects intestinal functionality in both inflamed 2D intestinal epithelial cell and 3D intestinal organoid models

Background

A growing body of evidence suggests that particulate matter (PM10) enters the gastrointestinal (GI) tract directly, causing the GI epithelial cells to function less efficiently, leading to inflammation and an imbalance in the gut microbiome. PM10 may, however, act as an exacerbation factor in patients with inflamed intestinal epithelium, which is associated with inflammatory bowel disease.

Objective

The purpose of this study was to dissect the pathology mechanism of PM10 exposure in inflamed intestines.

Methods

In this study, we established chronically inflamed intestinal epithelium models utilizing two-dimensional (2D) human intestinal epithelial cells (hIECs) and 3D human intestinal organoids (hIOs), which mimic in vivo cellular diversity and function, in order to examine the deleterious effects of PM10 in human intestine-like in vitro models.

Results

Inflamed 2D hIECs and 3D hIOs exhibited pathological features, such as inflammation, decreased intestinal markers, and defective epithelial barrier function. In addition, we found that PM10 exposure induced a more severe disturbance of peptide uptake in inflamed 2D hIECs and 3D hIOs than in control cells. This was due to the fact that it interferes with calcium signaling, protein digestion, and absorption pathways. The findings demonstrate that PM10-induced epithelial alterations contribute to the exacerbation of inflammatory disorders caused by the intestine.

Conclusions

According to our findings, 2D hIEC and 3D hIO models could be powerful in vitro platforms for the evaluation of the causal relationship between PM exposure and abnormal human intestinal functions.

Transcriptomic analysis and transgenerational effects of ZnO nanoparticles on Daphnia magna: Endocrine-disrupting potential and energy metabolism

The widespread application of zinc oxide nanoparticles (ZnO NPs) has raised concerns over the adverse effects on aquatic species. In this study, transcriptomic analysis was applied to evaluate the chronic toxicity of ZnO NPs on the freshwater invertebrate Daphnia magna and the intergenerational effects were then further investigated. Parent daphnia (F0) were exposed to ZnO NPs at 3, 60, and 300 μg L^-1 for 21 days. ZnO NPs significantly inhibited the reproduction (first pregnancy and spawning time, total number of offspring) and growth (molting frequency and body length) of F0. Here, differentially expressed genes (DEGs) involved in lysosomal and phagosome, energy metabolism and endocrine disruption pathways were significantly downregulated. Furthermore, disruption on the transport and catabolic processes probably resulted in the particle accumulation. The inhibited pathways related to energy metabolism may partially account for the body length, molting and reproductive restriction. The suppression of growth and reproduction may attribute to the down-regulation of insulin secretion and ovarian steroidogenesis pathways, respectively. Partial recovery of growth and reproductive inhibition in F1 - F3 descended from the F0 generation exposure did not support constant transgenerational effects. This study unravels the molecular mechanisms and transgenerational consequences of the toxicity of nanoparticles on Daphnia.

Advances in Ca2+ modulation of gastrointestinal anion secretion and its dysregulation in digestive disorders (Review)

Intracellular calcium (Ca²⁺) is a critical cell signaling component in gastrointestinal (GI) physiology. Cytosolic calcium ([Ca²⁺]_cyt), as a secondary messenger, controls GI epithelial fluid and ion transport, mucus and neuropeptide secretion, as well as synaptic transmission and motility. The key roles of Ca²⁺ signaling in other types of secretory cell (including those in the airways and salivary glands) are well known. However, its action in GI epithelial secretion and the underlying molecular mechanisms have remained to be fully elucidated. The present review focused on the role of [Ca²⁺]_cyt in GI epithelial anion secretion. Ca²⁺ signaling regulates the activities of ion channels and transporters involved in GI epithelial ion and fluid transport, including Cl^- channels, Ca²⁺-activated K⁺ channels, cystic fibrosis (CF) transmembrane conductance regulator and anion/HCO₃^- exchangers. Previous studies by the current researchers have focused on this field over several years, providing solid evidence that Ca²⁺ signaling has an important role in the regulation of GI epithelial anion secretion and uncovering underlying molecular mechanisms. The present review is largely based on previous studies by the current researchers and provides an overview of the currently known molecular mechanisms of GI epithelial anion secretion with an emphasis on Ca²⁺-mediated ion secretion and its dysregulation in GI disorders. In addition, previous studies by the current researchers demonstrated that different regulatory mechanisms are in place for GI epithelial HCO₃^- and Cl^- secretion. An increased understanding of the roles of Ca²⁺ signaling and its targets in GI anion secretion may lead to the development of novel strategies to inhibit GI diseases, including the enhancement of fluid secretion in CF and protection of the GI mucosa in ulcer diseases.

Characterization of intracellular buffering power in human induced pluripotent stem cells and the loss of pluripotency is delayed by acidic stimulation and increase of NHE1 activity

The homeostasis of intracellular pH (pH_i ) affects many cellular functions. Our previous study has established a functional and molecular model of the active pH_i regulators in human induced pluripotent stem cells (hiPSCs). The aims of the present study were to further quantify passive pH_i buffering power (β) and to investigate the effects of extracellular pH and Na⁺ -H⁺ exchanger 1 (NHE1) activity on pluripotency in hiPSCs. pH_i was detected by microspectrofluorimetry with pH-sensitive dye-BCECF. Western blot, immunofluorescence staining, and flow cytometry were used to detect protein expression and pluripotency. Our study in hiPSCs showed that (a) the value of total (β_tot ), intrinsic (β_i ), and CO₂ -dependent ( β C O 2 ) buffering power all increased while pH_i increased; (b) during the spontaneous differentiation for 4 days, the β values of β_tot and β C O 2 changed in a tendency of decrease, despite the absence of statistical significance; (c) an acidic cultured environment retained pluripotency and further upregulated expression and activity of NHE1 during spontaneous differentiation; (d) inhibition on NHE1 activity promoted the loss of pluripotency. In conclusion, we, for the first time, established a quantitative model of passive β during differentiation and demonstrated that maintenance of NHE1 at a higher level was of critical importance for pluripotency retention in hiPSCs.