Function of K⁺-Cl⁻ cotransporters in the acid secretory mechanism of gastric parietal cells

AMPK/mTOR-driven autophagy & Nrf2/HO-1 cascade modulation by amentoflavone ameliorates indomethacin-induced gastric ulcer

Gastric ulcer (GU) is a worldwide gastrointestinal disorder associated with NSAID use. Recently, amentoflavone proved to be a potent autophagy modulator, antioxidant, anti-inflammatory, and anti-apoptotic agent. Eight-week-old male Wistar rats received amentoflavone orally for 14 days at 25, 50, or 100 mg/kg/day. On day 14 of treatment, GU was induced by a single oral instillation of 100 mg/kg indomethacin, one hour after the last treatment. Amentoflavone dose-dependently alleviated indomethacin-induced GU, as demonstrated by repression of gastric mucosa pathological manifestations (ulcer index, ulcer surface area, histopathological deviations, and score) and increased ulcer inhibition percentage. These protective effects were due to the enhancement of gastric mucosa autophagy, as demonstrated by increased levels of beclin-1, MAP1LC3B, and CTSD, and reduced expression of p62 (SQSTM1). In addition, amentoflavone modulated the AMPK/mTOR pathway by increasing p-AMPK and reducing mTORC1 levels. Moreover, it hindered the redox aberrations by reducing MDA level and enhancing SOD activity, GSH level, and Nrf2/HO-1 cascade. Furthermore, a decrease in caspase-3 levels, Bax/Bcl-2 ratio and an increase in Bcl-2 expression suggest inhibition of the apoptotic process. Additionally, amentoflavone suppressed gastric mucosal inflammation by decreasing IL-1β, TNF-α, IFN-γ levels, IL-4, IL-6 mRNA expressions and MPO activity, and increasing IL-10 mRNA expresion. Therefore, amentoflavone could consider a promising natural agent protecting against indomethacin-induced GU.

Indomethacin can induce cell death in rat gastric parietal cells through alteration of some apoptosis- and autophagy-associated molecules

In clinical medicine, indomethacin (IND, a non-steroidal anti-inflammatory drug) is used variously in the treatment of severe osteoarthritis, rheumatoid arthritis, gouty arthritis or ankylosing spondylitis. A common complication found alongside the therapeutic characteristics is gastric mucosal damage. This complication is mediated through apoptosis and autophagy of the gastrointestinal mucosal epithelium. Apoptosis and autophagy are critical homeostatic pathways catalysed by caspases downstream of the gastrointestinal mucosal epithelial injury. Both act through molecular signalling pathways characterized by the initiation, mediation, execution and regulation of the cell regulatory cycle. In this study we hypothesized that dysregulated apoptosis and autophagy are associated with IND-induced gastric damage. We examined the spectra of in vivo experimental gastric ulcers in male Sprague-Dawley rats through gastric gavage of IND. Following an 18-hour fast, IND was administered to experimental rats. They were sacrificed at 3-, 6- and 12-hour intervals. Parietal cells (H⁺ , K⁺ -ATPase β-subunit assay) and apoptosis (TUNEL assay) were determined. The expression of apoptosis-signalling caspase (caspases 3, 8, 9 and 12), DNA damage (anti-phospho-histone H2A.X) and autophagy (MAP-LC3, LAMP-1 and cathepsin B)-related molecules in gastric mucosal cells was examined. The administration of IND was associated with gastric mucosal erosions and ulcerations mainly involving the gastric parietal cells (PCs) of the isthmic and upper neck regions and a time-dependent gradual increase in the number of apoptotic PCs with the induction of both apoptotic (upregulation of caspases 3 and 8) cell death and autophagic (MAP-LC3-II, LAMP-1 and cathepsin B) cell death. Autophagy induced by fasting and IND 3 hours initially prompted the degradation of caspase 8. After 6 and 12 hours, damping down of autophagic activity occurred, resulting in the upregulation of active caspase 8 and its nuclear translocation. In conclusion we report that IND can induce time-dependent apoptotic and autophagic cell death of PCs. Our study provides the first indication of the interactions between these two homeostatic pathways in this context.

Ultra-structural study of the indomethacin-induced apoptosis and autophagy in rat gastric parietal cells

BACKGROUND AND AIM OF THE WORK

Indomethacin (IND), a non-steroidal anti-inflammatory drug, can induce gastric mucosal ulcerations. To date, the ultra-structural changes in the parietal cells (PCs) of the gastric mucosa following the intake of IND are mostly unknown. We carried out the current investigation to get insights into this issue.

MATERIALS AND METHODS

We established an animal model consisting of 35 adult male Sprague Dawley rats. The animals were divided into three groups, including; control (normal feeding), fasting, and indomethacin-treated groups. After treatment of 18-h fasting rats with IND, they were sacrificed at 3, 6, and 12-h intervals. The morphological features, including the apoptotic, and autophagic changes in the gastric mucosa PCs were examined using transmission electron microscopy.

RESULTS

In normal feeding animals (control group), the gastric PCs were present in various stages of activity. Fasting was associated with the predominance of the inactive parietal cells with features of up-regulated autophagy. In the IND -treated animals (at 3-h interval), PCs showed prominent autophagic changes, and subtle apoptotic cell death. In the IND -treated animals (at 6-12-h interval), PCs showed prominent apoptotic changes, and subtle autophagic features.

CONCLUSIONS

Our study indicates that IND treatment could induce gastropathy through time-dependent alterations in the autophagic and apoptotic machinery of PCs. Further studies are needed to examine the underlying molecular mechanisms.

Inhibition of Gastric H+,K+-ATPase Activity in Vitro by Dissolution Media of Original Brand-Name and Generic Tablets of Lansoprazole, a Proton Pump Inhibitor

To investigate the inhibitory effect of a commercial proton pump inhibitor (lansoprazole) on the gastric proton pump H⁺,K⁺-ATPase in vitro, we used orally disintegrating (OD) tablets including original brand-name and generic tablets. In the course of the development of generic products, dissolution and clinical tests are necessary to ensure their bioequivalence to the original brand-name products; by contrast, there is almost no opportunity to demonstrate their activity in vitro. This study initially compared the similarity of the dissolution of test generic tablets with that of the original brand-name tablets. The dissolution tests for 15 and 30-mg lansoprazole tablets found their dissolution properties were similar. Subsequently, the dissolution media were sampled and then their effects on the H⁺,K⁺-ATPase activity were measured using tubulovesicles prepared from the gastric mucosa of hogs. We confirmed that the inhibitory effects of the generic tablets on H⁺,K⁺-ATPase activity were consistent with those of the original brand-name tablets. Furthermore, lansoprazole contents in each tablet estimated from their inhibitory effects were in good agreement with their active pharmaceutical ingredient content. To our knowledge, this is the first technical report to compare the in vitro biochemical activity of lansoprazole OD tablets between the original brand-name and generic commercial products.

SLC12A7 alters adrenocortical carcinoma cell adhesion properties to promote an aggressive invasive behavior

BACKGROUND

Altered expression of Solute Carrier Family 12 Member 7 (SLC12A7) is implicated to promote malignant behavior in multiple cancer types through an incompletely understood mechanism. Recent studies have shown recurrent gene amplifications and overexpression of SLC12A7 in adrenocortical carcinoma (ACC). The potential mechanistic effect(s) of SLC12A7 amplifications in portending an aggressive behavior in ACC has not been previously studied and is investigated here using two established ACC cell lines, SW-13 and NCI-H295R.

METHODS

SW-13 cells, which express negligible amounts of SLC12A7, were enforced to express SLC12A7 constitutively, while RNAi gene silencing was performed in NCI-H295R cells, which have robust endogenous expression of SLC12A7. In vitro studies tested the outcomes of experimental alterations in SLC12A7 expression on malignant characteristics, including cell viability, growth, colony formation potential, motility, invasive capacity, adhesion and detachment kinetics, and cell membrane organization. Further, potential alterations in transcription regulation downstream to induced SLC12A7 overexpression was explored using targeted transcription factor expression arrays.

RESULTS

Enforced SLC12A7 overexpression in SW-13 cells robustly promoted motility and invasive characteristics (p < 0.05) without significantly altering cell viability, growth, or colony formation potential. SLC12A7 overexpression also significantly increased rates of cellular attachment and detachment turnover (p < 0.05), potentially propelled by increased filopodia formation and/or Ezrin interaction. In contrast, RNAi gene silencing of SLC12A7 stymied cell attachment strength as well as migration and invasion capacity in NCI-H295R cells. Transcription factor expression analysis identified multiple signally pathways potentially affected by SLC12A7 overexpression, including osmotic stress, bone morphogenetic protein, and Hippo signaling pathways.

CONCLUSIONS

Amplification of SLC12A7 observed in ACCs is shown here, in vitro, to exacerbate the malignant behavior of ACC cells by promoting invasive capacities, possibly mediated by alterations in multiple signaling pathways, including the osmotic stress pathway.

The Gastric and Intestinal Microbiome: Role of Proton Pump Inhibitors

PURPOSE OF REVIEW

The discovery of Helicobacter pylori and other organisms colonizing the stomach and the intestines has shed some light on the importance of microbiome in maintaining overall health and developing pathological conditions when alterations in biodiversity are present. The gastric acidity plays a crucial role in filtering out bacteria and preventing development of enteric infections. In this article, we discuss the physiology of gastric acid secretion and bacterial contribution to the composition of gastric and intestinal barriers and review the current literature on the role of proton pump inhibitors (PPIs) in the microbial biodiversity of the gastrointestinal tract.

RECENT FINDINGS

Culture-independent techniques, such as 16S rRNA sequencing, have revolutionized our understanding of the microbial biodiversity in the gastrointestinal tract. Luminal and mucosa-associated microbial populations are not identical. Streptococcus is overrepresented in the biopsies of patients with antral gastritis and may also be responsible for the development of peptic ulcer disease. The use of PPIs favors relative streptococcal abundance irrespective of H. pylori status and may explain the persistence of dyspeptic symptoms in patients on PPI therapy. Increased risk of enteric infections has also been seen in patients taking PPIs. The overuse of PPIs leads to significant shift of the gastrointestinal microbiome towards a less healthy state. With the advent of PPIs, many studies have demonstrated the significant changes in the microbial composition of both gastric and intestinal microbiota. Although they are considered relatively safe over-the-counter medications, PPIs in many cases are over- and even inappropriately used. Future studies assessing the safety of PPIs and their role in the development of microbiome changes should be encouraged.

Molecular evidence for a role for K(+)-Cl(-) cotransporters in the kidney

K(+)-Cl(-) cotransporter (KCC) isoforms 3 (KCC3) and 4 (KCC4) are expressed at the basolateral membrane of proximal convoluted tubule cells, and KCC4 is present in the basolateral membrane of the thick ascending loop of Henle's limb and α-intercalated cells of the collecting duct. Little is known, however, about the physiological roles of these transporters in the kidney. We evaluated KCC3 and KCC4 mRNA and protein expression levels and intrarenal distribution in male Wistar rats or C57 mice under five experimental conditions: hyperglycemia after a single dose of streptozotocin, a low-salt diet, metabolic acidosis induced by ammonium chloride in drinking water, and low- or high-K(+) diets. Both KCC3 mRNA and protein expression were increased during hyperglycemia in the renal cortex and at the basolateral membrane of proximal tubule cells but not with a low-salt diet or acidosis. In contrast, KCC4 protein expression was increased by a low-sodium diet in the whole kidney and by metabolic acidosis in the renal outer medulla, specifically at the basolateral membrane of α-intercalated cells. The increased protein expression of KCC4 by a low-salt diet was also observed in WNK4 knockout mice, suggesting that upregulation of KCC4 in these circumstances is not WNK4 dependent. No change in KCC3 or KCC4 protein expression was observed under low- or high-K(+) diets. Our data are consistent with a role for KCC3 in the proximal tubule glucose reabsorption mechanism and for KCC4 in salt reabsorption of the thick ascending loop of Henle's loop and acid secretion of the collecting duct.

The SLC12 family of electroneutral cation-coupled chloride cotransporters

The SLC12 family encodes electroneutral cation-coupled chloride cotransporters that are critical for several physiological processes including cell volume regulation, modulation of intraneuronal chloride concentration, transepithelial ion movement, and blood pressure regulation. Members of this family are the targets of the most commonly used diuretic drugs, have been shown to be the causative genes for inherited disease such as Gitelman, Bartter and Andermann syndromes, and potentially play a role in polygenic complex diseases like arterial hypertension, epilepsy, osteoporosis, and cancer.

Gastric secretion

PURPOSE OF REVIEW

This review summarizes the past year's literature regarding the regulation of gastric exocrine and endocrine secretion, both basic science and clinical.

RECENT FINDINGS

Gastric acid secretion facilitates the digestion of protein as well as the absorption of iron, calcium, vitamin B12, and certain medications as well as prevents bacterial overgrowth, enteric infection, and possibly community-acquired pneumonia, spontaneous bacterial peritonitis, and IgE-mediated food allergy. It is regulated by neural (e.g., pituitary adenylate cyclase-activating peptide), hormonal (e.g., gastrin, ghrelin, and apelin), and paracrine (e.g., histamine) pathways as well as by chemical (e.g., amino acids) and bacterial stimuli (e.g., Helicobacter pylori). Novel peptides, which may possess physiologic function, have been identified in gastric mucosal neuroendocrine cells including parathyroid hormone-like hormone in histamine-secreting enterochromaffin-like cells and hepcidin in acid-secreting parietal cells. The secretion of hydrochloric acid by parietal cells involves translocation of the proton pump, HK-ATPase, to the apical membrane along with activation of apical chloride and potassium channels. Serum markers include chromogranin A for neuroendocrine tumors, pepsinogen I for gastric atrophy, and pepsinogen II for H. pylori infection.

SUMMARY

We continue to make progress in our understanding of the regulation of gastric acid secretion in health and disease.