A new mechanism of gastric epithelial injury induced by acid exposure: The role of Egr-1 and ERK signaling pathways

PGC-1α/SNAI1 axis regulates tumor growth and metastasis by targeting miR-128b in gastric cancer

Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is a transcriptional coactivator that has been characterized as master regulators of mitochondrial biogenesis. It has been reported that aberrant regulation of PGC-1α is involved in a variety of human cancers. However, whether PGC-1α is involved in the regulation of tumor growth and metastasis in gastric cancer (GC) remains unknown. In the present study, we found that the expression of PGC-1α was upregulated in GC tissues and GC cell lines. Inhibition of PGC-1α inhibited cell viability, migration, and invasion, and promoted cell apoptosis of GC cells. Furthermore, inhibition of PGC-1α downregulated the SNAI1 expression, whereas upregulated microRNA (miR)-128b expression. The expression of SNAI1 was upregulated and the expression of miR-128b was downregulated in GC tissues. We further found that there was a positive correlation between PGC-1α and SNAI1 expression, and a negative correlation between PGC-1α and miR-128b expression or between SNAI1 and miR-128b expression in GC tissues. Moreover, PGC-1α inhibition-induced increased miR-128b expression, and PGC-1α overexpression-induced decreased miR-128b expression were both markedly suppressed by SNAI1 overexpression. In addition, SNAI1 overexpression or miR-128b inhibition partly reversed the effects of PGC-1α inhibition in GC cells. Furthermore, inhibition of PGC-1α suppressed the tumor growth in a nude mouse model, which may be related with the dysregulation of SNAI1 and miR-128b. In conclusion, these data indicate that the PGC-1α/SNAI1/miR-128b axis plays a vital role in GC via regulating cell viability, migration, invasion, and apoptosis.

RETRACTED: The function of long non-coding RNA MT1JP in the development and progression of gastric cancer

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Executive Editor (Chairman) as panels from Figures 3A,B and 4D are similar to panels from Figures 4A,B and 5E of the article published by Mingjun Bi, Hongmei Yu, Bin Huang and Cuiyan Tang in Gene 626 (2017) 337–343 http://dx.doi.org/10.1016/j.gene.2017.05.049. Also, Figures 3C and 4A are similar to Figures 4C and 5A of the Gene article. One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. As such this article represents an abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

Long non-coding RNA CASC15 regulates gastric cancer cell proliferation, migration and epithelial mesenchymal transition by targeting CDKN1A and ZEB1

Long non‐coding RNA (lncRNA) is responsible for a diverse range of cellular functions, such as transcriptional and translational regulation and variance in gene expression. The lncRNA CASC15 (cancer susceptibility candidate 15) is a long intergenic non‐coding RNA (lincRNA) locus in chromosome 6p22.3. Previous research shows that lncRNA CASC15 is implicated in the biological behaviors of several cancers such as neuroblastoma and melanoma. Here, we aimed to explore in detail how CASC15 contributes to the growth of gastric cancer (GC). As predicted, the expression of CASC15 was enriched in GC tissues and cell lines as compared with healthy tissues and cells using qRT‐PCR. The Kaplan–Meier method was used to demonstrate that high expression of CASC15 is linked to a poor prognosis for patients suffering from GC. Additionally, functional experiments proved that the down‐ or up‐regulation of CASC15 inhibited or facilitated cell proliferation via the induction of cell cycle arrest and apoptosis, and also suppressed or accelerated cell migration and invasion by affecting the progression of the epithelial‐to‐mesenchymal transition (EMT). In vivo experiments showed that the knockdown of CASC15 lessened the tumor volume and weight and influenced the EMT process. This was confirmed by western blot assays and immunohistochemistry, indicating impaired metastatic ability in nude mice. CASC15 involvement in the tumorigenesis of GC occurs when CASC15 interacts with EZH2 and WDR5 to modulate CDKN1A in nucleus. Additionally, the knockdown of CASC15 triggered the silencing of ZEB1 in cytoplasm, which was shown to be associated with the competitive binding of CASC15 to miR‐33a‐5p.

LncRNA TRERNA1 Function as an Enhancer of SNAI1 Promotes Gastric Cancer Metastasis by Regulating Epithelial-Mesenchymal Transition

Long noncoding RNA (lncRNA) has been implicated in cancer, but little is known about the role of lncRNAs as regulators of tumor metastasis. In the present study, we demonstrate that lncRNA TRERNA1 acts like an enhancer of SNAI1 to promote cell invasion and migration and to contribute to metastasis of gastric cancer (GC). TRERNA1 is significantly unregulated in GCs and GC cell lines. Increased TRERNA1 is positively correlated with lymph node metastasis of GCs. RNA immunoprecipitation (RIP) and chromatin immunoprecipitation (ChIP) assays revealed that TRERNA1 functions as a scaffold to recruit EZH2 to epigenetically silence epithelial-mesenchymal transition marker CDH1 by H3K27me3 of its promoter region. TRERNA1 knockdown markedly reduced GC cell migration, invasion, tumorigenicity, and metastasis. Depletion of TRERNA1 reduced cell metastasis of GCs in vivo. Taken together, our findings indicated that TRERNA1 serves as a critical effector in GC progression by regulating CDH1 at the transcription level. It is implied that TRERNA1/CDH1 is a new potential target for GC therapy.

Post-natal heart adaptation in a knock-in mouse model of calsequestrin 2-linked recessive catecholaminergic polymorphic ventricular tachycardia

Cardiac calsequestrin (CASQ2) contributes to intracellular Ca(2+) homeostasis by virtue of its low-affinity/high-capacity Ca(2+) binding properties, maintains sarcoplasmic reticulum (SR) architecture and regulates excitation-contraction coupling, especially or exclusively upon β-adrenergic stimulation. Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease associated with cardiac arrest in children or young adults. Recessive CPVT variants are due to mutations in the CASQ2 gene. Molecular and ultra-structural properties were studied in hearts of CASQ2(R33Q/R33Q) and of CASQ2(-/-) mice from post-natal day 2 to week 8. The drastic reduction of CASQ2-R33Q is an early developmental event and is accompanied by down-regulation of triadin and junctin, and morphological changes of jSR and of SR-transverse-tubule junctions. Although endoplasmic reticulum stress is activated, no signs of either apoptosis or autophagy are detected. The other model of recessive CPVT, the CASQ2(-/-) mouse, does not display the same adaptive pattern. Expression of CASQ2-R33Q influences molecular and ultra-structural heart development; post-natal, adaptive changes appear capable of ensuring until adulthood a new pathophysiological equilibrium.

Extracellular acidosis stimulates NHE2 expression through activation of transcription factor Egr-1 in the intestinal epithelial cells

Na(+)/H(+) exchangers (NHEs) play important roles in regulating internal pH (pHi), cell volume and neutral Na(+) absorption in the human intestine. Earlier studies have shown that low extracellular pH (pHe) and metabolic acidosis increases the expression and function of NHE1-3 genes. However, transcriptional mechanisms involved remained unknown. Therefore, we investigated the molecular mechanisms underlying acid-induced NHE2 expression in C2BBe1 and SK-CO15 intestinal epithelial cells. Assessing total RNA and protein by RT-PCR and Western blot analysis, respectively, displayed significant increases in the NHE2 mRNA and protein levels in cells exposed to acidic media (pH 6.5 and 6.7) compared to normal medium. Acid treatment was also associated with a significant enhancement in NHE2 transport activity. Quantification of the heterogeneous nuclear RNA indicated that the rate of NHE2 transcription was increased in response to acid. Furthermore, acid caused a significant increase in NHE2 promoter activity confirming transcriptional upregulation. Through functional and mutational studies the acid-response element was mapped to a 15-nucleotide GC-rich sequence at bp -337 to -323 upstream from the transcription start site. We previously identified this element as an overlapping Egr-1/Sp1/Egr-1 motif that was essential for the NHE2 upregulation by mitogen-induced transcription factor Egr-1. Cells exposed to acid exhibited a temporal increase in Egr-1 mRNA and protein expression. These events were followed by Egr-1 nuclear accumulation, as detected by immunofluorescence microscopy, and potentiated its in vitro and in vivo interaction with the NHE2 promoter. Disruption of ESE motif and knockdown of Egr-1 expression by targeted small interfering RNA abrogated the acid-induced NHE2 transcriptional activity. These data indicate that the acid-dependent NHE2 stimulation is implemented by transcriptional upregulation of NHE2 via acid-induced Egr-1 in the intestinal epithelial cells.

Anthocyanins from black soybean inhibit Helicobacter pylori-induced inflammation in human gastric epithelial AGS cells

Infection with Helicobacter pylori leads to gastritis, peptic ulcers and gastric cancer. Moreover, when the gastric mucosa is exposed to H. pylori, gastric mucosal inflammatory cytokine interleukin-8 (Il-8) and reactive oxygen species increase. Anthocyanins have anti-oxidative, antibacterial and anti-inflammatory properties. However, the effect of anthocyanins in H. pylori-infected cells is not yet clear. In this study, therefore, the effect of anthocyanins on H. pylori-infected human gastric epithelial cells was examined. AGS cells were pretreated with anthocyanins for 24 hrs followed by H. pylori 26695 infection for up to 24 hrs. Cell viability and ROS production were examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and 2',7'-dichlorofluorescein diacetate assay, respectively. Western blot analyses and RT-PCR were performed to assess gene and protein expression, respectively. IL-8 secretion in AGS cells was measured by ELISA. It was found that anthocyanins decrease H. pylori-induced ROS enhancement. Anthocyanins also inhibited phosphorylation of mitogen-activated protein kinases, translocation of nuclear factor-kappa B and Iκβα degradation. Furthermore anthocyanins inhibited H. pylori-induced inducible nitric oxide synthases and cyclooxygenase-2 mRNA expression and inhibited IL-8 production by 45.8%. Based on the above findings, anthocyanins might have an anti-inflammatory effect in H. pylori-infected gastric epithelial cells.

PKCδ-dependent activation of ERK1/2 leads to upregulation of the human NHE2 transcriptional activity in intestinal epithelial cell line C2BBe1

The apical Na+/H+ exchanger (NHE) isoform NHE2 is involved in transepithelial Na+ absorption in the intestine. Our earlier studies have shown that mitogenic agent phorbol 12-myristate 13-acetate (PMA) induces the expression of NHE2 through activation of transcription factor early growth response-1 (Egr-1) and its interactions with the NHE2 promoter. However, the signaling pathways involved in transcriptional stimulation of NHE2 in response to PMA in the intestinal epithelial cells are not known. Chemical inhibitors and genetic approaches were used to investigate the signaling pathways responsible for the stimulation of NHE2 expression by PMA via Egr-1 induction. We show that, in response to PMA, PKCδ, a member of novel PKC isozymes, and MEK-ERK1/2 pathway of mitogen-activated protein kinases stimulate the NHE2 expression in C2BBe1 intestinal epithelial cells. PMA rapidly and transiently induced activation of PKCδ. Small inhibitory RNA-mediated knockdown of PKCδ blocked the stimulatory effect of PMA on the NHE2 promoter activity. In addition, blockade of PKCδ by rottlerin, a PKCδ-specific inhibitor, and ERK1/2 by U0126, a MEK-ERK inhibitor, abrogated PMA-induced Egr-1 expression. Immunofluorescence studies revealed that inhibition of ERK1/2 activation prevents translocation of PMA-induced Egr-1 into the nucleus. Consistent with these data, PMA-induced Egr-1 interaction with the NHE2 promoter region was prevented in nuclear extracts from U0126-pretreated cells. In conclusion, our data provide the first evidence that the stimulatory effect of PMA on NHE2 expression is mediated through the initial activation of PKCδ, subsequent PKCδ-dependent activation of MEK-ERK1/2 signaling pathway, and stimulation of Egr-1 expression. Furthermore, we show that transcription factor Egr-1 acts as an intermediate effector molecule that links the upstream signaling cues to the long-term stimulation of NHE2 expression by PMA in C2BBe1 cells.

Effect of aging on gastric mucosal defense mechanisms: ROS, apoptosis, angiogenesis, and sensory neurons

Aging changes in the stomach lead to a decreased capacity for tissue repair in response to gastric acid. The aim of this study was to determine the mechanism associated with the increased susceptibility to injury of aging mucosa including reactive oxygen species (5), apoptosis, angiogenesis, and sensory neuron activity. Fischer 344 rats at four different ages (6, 31, 74 wk, and 2 yr of age) were studied. The connective tissue indicators [salt-soluble collagen and sulfated glycosaminoglycan (sGAG)], lipid hydroperoxide (LPO), myeloperoxidase (MPO), and hexosamine were assessed. We also evaluated the expression of early growth response-1 (Egr-1), phosphatase and tension homologue deleted on chromosome 10 (PTEN), caspase-9 (index of apoptosis), VEGF (index of angiogenesis), calcitonin gene-related peptide (CGRP, index of sensory neurons), and neuronal nitric oxide synthase (nNOS). The histological connective tissue area in the lower part of rat gastric mucosa increased with aging, with increase of salt-soluble collagen and sGAG. LPO and MPO in old rats were significantly greater than in the young rats, whereas hexosamine was significantly reduced. The old gastric mucosa had increased expression of Egr-1, PTEN, and caspase-9, whereas the VEGF, CGRP, and nNOS expression were significantly reduced. These results indicate that the lower part of rat gastric mucosa was found to be replaced by connective tissue with accumulation of oxidative products with aging. In addition, impairment of apoptosis, angiogenesis, and sensory neuron activity via the activation of Egr-1 and PTEN might increase the susceptibility of gastric mucosa to injury during aging.