Uptake and toxicity of polystyrene micro/nanoplastics in gastric cells: Effects of particle size and surface functionalization

Toxicity of micro or nanoplastics (MP/NP) in aquatic life is well-documented, however, information about the consequences of exposure to these particles in terrestrial species is scarce. This study was used to evaluate the uptake and/or toxicity of polystyrene MP/NP in human gastric cells, comparing doses, particle sizes (50, 100, 200, 500, 1000 or 5000 nm) and surface functionalization (aminated, carboxylated or non-functionalized). In general, the uptake of 50 nm particles was significantly higher than 1000 nm particles. Among the 50 nm particles, the aminated particles were more avidly taken up by the cells and were cytotoxic at a lower concentration (≥ 7.5 μg/mL) compared to same sized carboxylated or non-functionalized particles (≥ 50 μg/mL). High toxicity of 50 nm aminated particles corresponded well with significantly high rates of apoptosis-necrosis induced by these particles in 4 h (29.2% of total cells) compared to all other particles (≤ 16.8%). The trend of apoptosis-necrosis induction by aminated particles in 4 h was 50 > 5000 > 1000 > 500 > 200 > 100 nm. The 50 nm carboxylated or non-functionalized particles also induced higher levels of apoptosis-necrosis in the cells compared to 100, 1000 and 5000 nm particles with same surface functionalization but longer exposure (24 h) to 50 nm carboxylated or non-functionalized particles significantly (p<0.0001) increased apoptosis-necrosis in the cells. The study demonstrated that the toxicity of MP/NP to gastric cells was dependent on particle size, dose surface functionalization and exposure period.

Transcription factor-mediated intestinal metaplasia and the role of a shadow enhancer

Barrett's esophagus (BE) and gastric intestinal metaplasia are related premalignant conditions in which areas of human stomach epithelium express mixed gastric and intestinal features. Intestinal transcription factors (TFs) are expressed in both conditions, with unclear causal roles and cis-regulatory mechanisms. Ectopic CDX2 reprogrammed isogenic mouse stomach organoid lines to a hybrid stomach–intestinal state transcriptionally similar to clinical metaplasia; squamous esophageal organoids resisted this CDX2-mediated effect. Reprogramming was associated with induced activity at thousands of previously inaccessible intestine-restricted enhancers, where CDX2 occupied DNA directly. HNF4A, a TF recently implicated in BE pathogenesis, induced weaker intestinalization by binding a novel shadow Cdx2 enhancer and hence activating Cdx2 expression. CRISPR/Cas9-mediated germline deletion of that cis-element demonstrated its requirement in Cdx2 induction and in the resulting activation of intestinal genes in stomach cells. dCas9-conjugated KRAB repression mapped this activity to the shadow enhancer's HNF4A binding site. Altogether, we show extensive but selective recruitment of intestinal enhancers by CDX2 in gastric cells and that HNF4A-mediated ectopic CDX2 expression in the stomach occurs through a conserved shadow cis-element. These findings identify mechanisms for TF-driven intestinal metaplasia and a likely pathogenic TF hierarchy.

MS-Based Metabolomics Reveals Metabolic Dysregulation in Erastin-Induced Gastric Adenocarcinoma Cells

Gastric cancer (GC) is one of the most malignant tumors with high morbidity and mortality in the world, particularly in China. Erastin, a classical ferroptosis inducer, exerts cytotoxicity in several types of cancer cells including gastric cancer cells. However, the mechanism of erastin in regulating metabolic pathways in gastric cancer remains largely unclear. To investigate the gastric cellular response to erastin therapy, we adopted a cell pseudotargeted metabolomics method based on liquid chromatography-hybrid triple quadrupole linear ion trap mass spectrometry (LC-QTRAP MS). The developed method was used to investigate the differential metabolites between erastin-treated MGC-803 cells and the controls at different time points. We found that erastin induced tremendous impact on the metabolome of gastric cells by affecting key metabolic processes, such as cysteine and methionine metabolism, glutathione (GSH) biosynthesis, glycolysis and TCA cycle. Interestingly, S-adenosylmethionine (SAM), methionine, serine, glycine and cysteine were obviously increasing treads after erastin treatment, but S-adenosylhomocysteine (SAH) and GSH were always down-regulated up to 48 h. The results indicated that DNA methylation was activated and glutathione biosynthesis was blocked in erastin-treated MGC-803 gastric cells, highlighting the importance of erastin as a promising drug candidate for in vivo treatment of gastric tumor.

Bile acids increase intestinal marker expression via the FXR/SNAI2/miR-1 axis in the stomach

Purpose Intestinal metaplasia (IM) is a precancerous lesion that increases the risk of subsequent gastric cancer (GC) development. Previously, miR-1 has been shown to play an essential role in the initiation of bile acid (BA)-induced IM. The objective of the present study was to investigate the mechanism underlying miR-1 inhibition by BA in gastric cells. Methods Ingenuity pathway analysis (IPA) was used to identify molecules acting upstream of miR-1. The effects of deoxycholic acid (DCA), FXR and SNAI2 on the expression of intestinal markers were assessed using quantitative real-time PCR (qRT-PCR) and Western blotting. The expression level of major molecules was detected by immunohistochemistry (IHC) in tissue microarrays. The transcriptional regulation of miR-1 was verified using luciferase reporter and chromatin immunoprecipitation (ChIP) assays. Results We found that BA treatment caused aberrant expression of FXR and intestinal markers in gastric cells. Augmented FXR led to transcriptional activation of SNAI2, which in turn suppressed the miR-1 promoter. Moreover, we found that compared with normal tissues, the expression levels of both FXR and SNAI2 were increased and positively correlated with each other in IM tissues. Additionally, their expression showed an inverse correlation with that of miR-1 in IM tissues. Conclusions Our findings indicate that FXR may be responsible for a series of molecular changes in gastric cells after BA treatment, and that the FXR/SNAI2/miR-1 axis exhibits a crucial role in BA-induced progression of IM. Blocking the FXR-oriented axis may provide a promising approach for IM or even GC treatment.

Improvement of the Chemosensitivity of Gastric Carcinoma Cells by Celastrus orbiculatus Extracts

Gastric carcinoma is one of the most prevalent malignancies with high morbidity and mortality. While chemotherapy is the major means for the management gastric carcinoma, tumors gradually exhibit drug resistance. Therefore, there is a need for agents capable of enhancing the sensitivity of tumor cells to chemotherapy. Herein, we have examined the effect of Celastrus orbiculatus extracts on chemosensitivity of drug resistant gastric carcinoma cells. Human gastric carcinoma cells (MGC-803 and SGC-7901) were cultured in the presence of cisplatin for the selection of drug resistant gastric cells. Next, the effect of C. orbiculatus extracts on multiplication capacity of drug resistant MGC-803 and SGC-7901 cells was examined by a variety of measures. Following C. orbiculatus extract treatment, the multiplication and invasiveness of drug resistant MGC-803 and SGC-7901 cells declined remarkably, with increased apoptosis and decreased levels of β-catenin, c-Myc, and cyclin D1 proteins, protein markers critical to cell proliferation, differentiation, and apoptosis. In summary, C. orbiculatus extract can effectively improve the sensitivity of cisplatin resistant gastric carcinoma cells to cisplatin and promote the apoptosis of tumor cells through the inhibition of the expression of proteins associated with the Wnt/β-catenin axis.

On the goals of functional diagnostics in general and in relation to gastric cells in particular

If you take the point of view held by my unforgettable teacher, prof. Tarkhanov, that life is the explosive decomposition of the protoplasm of the organism in response to stimuli, and its decomposition is a kind of definite and suitable reflex to a corresponding and suitable stimulus, then it must be admitted that the stimulus must be specific, for it is not always a response to stimulation that a reaction is obtained.

Session 21 / III

Prof. S. S. Zimnitsky made a report entitled "Results of functional searches in the pathology of gastric cells" (see the article by prof. 3. on this topic in the March book of the "Journal" for the current year).

Gastric Serotonin Biosynthesis and Its Functional Role in L-Arginine-Induced Gastric Proton Secretion

Among mammals, serotonin is predominantly found in the gastrointestinal tract, where it has been shown to participate in pathway-regulating satiation. For the stomach, vascular serotonin release induced by gastric distension is thought to chiefly contribute to satiation after food intake. However, little information is available on the capability of gastric cells to synthesize, release and respond to serotonin by functional changes of mechanisms regulating gastric acid secretion. We investigated whether human gastric cells are capable of serotonin synthesis and release. First, HGT-1 cells, derived from a human adenocarcinoma of the stomach, and human stomach specimens were immunostained positive for serotonin. In HGT-1 cells, incubation with the tryptophan hydroxylase inhibitor p-chlorophenylalanine reduced the mean serotonin-induced fluorescence signal intensity by 27%. Serotonin release of 147 ± 18%, compared to control HGT-1 cells (set to 100%) was demonstrated after treatment with 30 mM of the satiating amino acid L-Arg. Granisetron, a 5-HT3 receptor antagonist, reduced this L-Arg-induced serotonin release, as well as L-Arg-induced proton secretion. Similarly to the in vitro experiment, human antrum samples released serotonin upon incubation with 10 mM L-Arg. Overall, our data suggest that human parietal cells in culture, as well as from the gastric antrum, synthesize serotonin and release it after treatment with L-Arg via an HTR3-related mechanism. Moreover, we suggest not only gastric distension but also gastric acid secretion to result in peripheral serotonin release.

In Vitro Framework to Assess the Anti-Helicobacter pylori Potential of Lactic Acid Bacteria Secretions as Alternatives to Antibiotics

Helicobacter pylori is a prevalent bacterium that can cause gastric ulcers and cancers. Lactic acid bacteria (LAB) ameliorate treatment outcomes against H. pylori, suggesting that they could be a source of bioactive molecules usable as alternatives to current antibiotics for which resistance is mounting. We developed an in vitro framework to compare the anti-H. pylori properties of 25 LAB and their secretions against H. pylori. All studies were done at acidic and neutralized pH, with or without urea to mimic various gastric compartments. Eighteen LAB strains secreted molecules that curtailed the growth of H. pylori and the activity was urea-resistant in five LAB. Several LAB supernatants also reduced the urease activity of H. pylori. Pre-treatment of H. pylori with acidic LAB supernatants abrogated its flagella-mediated motility and decreased its ability to elicit pro-inflammatory IL-8 cytokine from human gastric cells, without reverting the H. pylori-induced repression of other pro-inflammatory cytokines. This study identified the LAB that have the most anti-H. pylori effects, decreasing its viability, its production of virulence factors, its motility and/or its ability to elicit pro-inflammatory IL-8 from gastric cells. Once identified, these molecules can be used as alternatives or complements to current antibiotics to fight H. pylori infections.