Phthalate plasticizer di(2-ethyl-hexyl) phthalate induces cyclooxygenase-2 expression in gastric adenocarcinoma cells.

The phthalate plasticizer, di(2-ethyl-hexyl) phthalate (DEHP), and its derived metabolites are common anthropogenic environmental toxins, which are known to act as endocrine disruptors. Numerous studies have associated DEHP with disruption of sex hormones, abnormal development of reproductive organs, allergies, and inflammation. Its role in promoting inflammation has been reported by both human epidemiological and animal studies. In stomach tissue, chronic inflammation is known to accompany mucosal damage, and pave the way to gastritis, stomach ulcers, and ultimately gastric cancer. Eastern Asian populations possess the highest gastric cancer incidences in the world. Coincidentally, East Asia is one of the world's major sites for plastics manufacture and export. Thus, possible correlations between DEHP, a common plasticizer, and gastric cancer are of great interest. Our study revealed several critical findings. First, even at very low dosage, mimicking the residual plasticizer exposure, detrimental effects of DEHP on gastric cells can be detected. Second, gastric cells treated with DEHP increased cyclooxygenase-2 (COX-2) in a time-dependent manner. Third, promoter deletion studies revealed a critical role of nuclear factor-kappa B (NF-κB) for COX-2 gene responses. Finally, our results indicated that a low concentration of DEHP is able to trigger COX-2 activation via the extracellular signal-regulated kinase (ERK1/2) and NF-κB signaling pathway. Taken together, we demonstrate that very low doses of DEHP enhance the expression of the prototypical inflammatory gene, COX-2, in gastric cancer cells via ERK1/2 and NF-κB activation. This study provides important insights into the inflammatory process and damages associated with phthalate plasticizers exposure.

Store-operated Ca2+ Entry Facilitates the Lipopolysaccharide-induced Cyclooxygenase-2 Expression in Gastric Cancer Cells.

Helicobacter pylori has been identified as one of the major causes of chronic gastritis, gastric and duodenal ulcers, and gastric cancer. Lipopolysaccharide (LPS) is a major component of the outer membrane of gram-negative bacteria, and H. pylori LPS might play an exclusively important role in activating inflammatory pathways in monocytes and macrophages. To study the role of LPS in the underlying mechanism of inflammatory responses, we established an in vitro model using the human AGS gastric cancer cell line. We found that LPS mediates inflammation through setting off a cascade of events: activation of the store-operated calcium (SOC) channel, initiation of downstream NF-κB signaling, and phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). Phosphorylated ERK1/2 promotes the nuclear translocation of NF-κB, and eventually elevates the expression level of COX-2, a major inflammatory gene.

Involvement of L-type Ca²âº channel and toll-like receptor-4 in nickel-induced interleukin-8 gene expression.

The metal nickel (Ni(2+)) is found everywhere in our daily lives, including coins, costume jewelry, and even nuts and chocolates. Nickel poisoning can cause inflammatory reactions, respiratory diseases, and allergic contact dermatitis. To clarify the mechanism by which nickel induces mediators of inflammation, we used the human acute monocytic leukemia THP-1 cell line as a model. Interleukin (IL)-8 promoter activity as well as gene expression were tested by luciferase assay and real-time polymerase chain reaction. The underlying mechanisms of nickel-induced IL-8 were investigated. We found that nickel induced IL-8 gene expression via the L-type Ca(2+) channel, Toll-like receptor-4 (TRL-4) and nuclear factor NF-κB signal transduction pathways. Nickel activated NF-κB expression through extracellular signal-regulated kinase 1/2 phosphorylation and then increased IL-8 expression. Thus, the L-type Ca(2+) channel and TRL-4 play important roles in nickel-induced inflammatory gene expressions.

Translocation of NF-κB and expression of cyclooxygenase-2 are enhanced by ketamine-induced ulcerative cystitis in rat bladder.

The number of ketamine abusers has increased significantly recently. Ketamine abusers exhibit urinary frequency, urgency, and at times urinary incontinence. Our aim was to investigate the role of transcription factor NF-κB and cyclooxygenase (COX)-2 in ketamine-induced cystitis. Sprague-Dawley rats were distributed into three groups, which received saline or treatment with ketamine or ketamine combined with a Cox-2 inhibitor (parecoxib). In addition, the toxic effect of ketamine and its metabolites were examined by primary urothelial cell culture. The ketamine-treated group displayed bladder hyperactivity and decreased bladder capacity. Treatment with ketamine + COX-2 inhibitor prevented these bladder dysfunctions. These bladder dysfunctions were accompanied by increases in the expression of NF-κB and COX-2 at the protein and mRNA levels. Ketamine treatment also enhanced bladder interstitial fibrosis, whereas ketamine + Cox-2 inhibitor decreased the intensity of fibrosis. Treatment of primary urothelial cells in vitro with ketamine or urine obtained from ketamine-treated rats stimulated the expression of NF-κB p65 and COX-2. Ketamine also initiated NF-κB translocation from cell cytoplasm to nucleus. Treatment with NF-κB inhibitor suppressed Cox-2 mRNA expression. Promoter-deletion analysis revealed that NF-κB was a necessary transcription factor for COX-2 gene (Ptgs2) activation. These results demonstrate that the regulation of COX-2 via the NF-κB pathway is involved in the inflammatory signaling of ketamine-induced cystitis in rat urinary bladder.

Involvement of intracellular calcium mobilization in IL-8 activation in human retinal pigment epithelial cells.

PURPOSE: Calcium signaling is an important intracellular pathway. Increased intracellular calcium is associated with cytokine regulation and inflammatory signals secretion. The purpose of this study is to understand the molecular mechanisms by which calcium signaling controls IL-8 activation in human RPE cells. METHODS: Fluorescence-based calcium imaging and different mutants of IL-8 plasmids were used in this study. The IL-8 promoter activation, gene expression, and secretion were detected by using luciferase reporter assay, quantitative real-time PCR (Q-PCR), and ELISA, respectively. In addition, pharmacological inhibitors and small interfering RNA (siRNA) were applied to clarify the mechanisms of IL-8 activation. RESULTS: Our study reported that intracellular calcium mobilization activated IL-8 gene expression and secretion. Application of pharmacological inhibitor BAY 11-7082, siRNA, and plasmids of the nuclear factor κ light chain enhancer of activated B cells (NF-κB) binding site, we identified that NF-κB is the main transcription factor involved in intracellular calcium mobilization-mediated IL-8 activation in human RPE cells. CONCLUSIONS: Collectively, our findings highlight the important role of intracellular calcium mobilization in the activation of IL-8. These findings may be helpful for the clinical applications in the age-related macular degeneration (AMD) prevention and treatment.

Pb²âº induced IL-8 gene expression by extracellular signal-regulated kinases and the transcription factor, activator protein 1, in human gastric carcinoma cells.

Divalent lead (Pb(2+) ) is a common industrial pollutant epidemiologically associated with gastric cancers. Pb(2+) was found to promote tumorigenesis, which may include interleukin (IL)-8, a pro-inflammatory chemokine that promotes angiogenesis and tumor metastasis. Given that the gastrointestinal tract is a major route of Pb(2+) exposure, we investigated the ability of Pb(2+) to induce IL-8 expression in gastric carcinoma cells and its underlying mechanism. At a concentration of 0.1 µM, Pb(2+) induced IL-8 gene activation in gastric carcinoma AGS cells. Using a IL-8 promoter-deletion analysis, transcription factor activator protein 1 (AP-1) was identified as a necessary component of Pb(2+) -induced IL-8 gene activation. Upregulation of the IL-8 gene was abrogated by the MEK inhibitor, PD98059, and partially suppressed by the epidermal growth factor receptor inhibitors, AG1478 and PD153035. Furthermore, c-Jun protein expression was induced in cells treated with Pb(2+) , and overexpression of c-Jun enhanced Pb(2+) -induced IL-8 activation. Collectively, our findings highlight the pivotal roles of AP-1 and extracellular signal-regulated kinase in signal transduction of Pb(2+) -induced IL-8 gene activation. These molecules may be potential therapeutic targets for Pb(2+) -related inflammation leading to stomach carcinogenesis. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 315-322, 2015.