Responses of Sodium–Hydrogen Exchange to Nitric Oxide in Porcine Cultured Nonpigmented Ciliary Epithelium

Shahidullah, Mohammad; Mandal, Amritlal; Delamere, Nicholas A.

doi:10.1167/iovs.09-3453

Cited by 10 publications

(14 citation statements)

References 45 publications

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“…GC#22 cells displayed a slow, continuous drift of baseline pH i , which is due to dye leakage after photobleaching, a phenomenon that has been reported previously (22)(23)(24). Despite of the dye leakage-mediated baseline drift, we were able to detect significant intracellular acidification after addition of HOE-642.…”

Section: Nhe1 Activity Maintains Alkaline Ph I Of Glioma Cellssupporting

confidence: 74%

Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H⁺extrusion, cell migration and survival

Cong

Zhu

Shi

et al. 2014

CARCIN

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Sodium-hydrogen exchanger isoform 1 (NHE1) plays a role in survival and migration/invasion of several cancers and is an emerging new therapeutic target. However, the role of NHE1 in glioblastoma and the interaction of NHE1 expression and function in glioblastoma cells with cytotoxic temozolomide (TMZ) therapy remain unknown. In this study, we detected high levels of NHE1 protein only in primary human glioma cells (GC), glioma xenografts and glioblastoma, but not in human neural stem cells or astrocytes. GC exhibited an alkaline resting pH i (7.46 ± 0.04) maintained by robust NHE1-mediated H + extrusion. GC treatment with TMZ for 2-24 h triggered a transient decrease in pH i , which recovered by 48 h and correlated with concurrent upregulation of NHE1 protein expression. NHE1 protein was colocalized with ezrin at lamellipodia and probably involved in GC migration. The TMZ-treated GC exhibited increased migration and invasion, which was attenuated by addition of NHE1 inhibitor HOE-642. Most importantly, NHE1 inhibition prevented prosurvival extracellular signal-regulated kinase activation and accelerated TMZ-induced apoptosis. Taken together, our study provides the first evidence that GC upregulate NHE1 protein to maintain alkaline pH i . Combining TMZ therapy with NHE1 inhibition suppresses GC migration and invasion, and also augments TMZ-induced apoptosis. These findings strongly suggest that NHE1 is an important cytoprotective mechanism in GC and presents a new therapeutic strategy of combining NHE1 inhibition and TMZ chemotherapy.

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Section: Nhe1 Activity Maintains Alkaline Ph I Of Glioma Cellssupporting

confidence: 74%

Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H⁺extrusion, cell migration and survival

Cong

Zhu

Shi

et al. 2014

CARCIN

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“…Intracellular pH was measured in cells by epifluorescence microscopy using the pH-sensitive dye 2=-7=-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF; Invitrogen, Carlsbad, CA). Dye loading and calculation of the rate of recovery after acid load were performed as described previously (51). Cells were perfused with serum-free and phenol red-free RPMI at pH 7.4 to obtain a stable baseline intracellular pH (pHi).…”

Section: Methodsmentioning

confidence: 99%

Characterization of squamous esophageal cells resistant to bile acids at acidic pH: implication for Barrett's esophagus pathogenesis

Goldman

Chen²,

Roesly³

et al. 2011

American Journal of Physiology-Gastrointestinal and Liver Physi

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Barrett's esophagus (BE) is a premalignant condition, where normal squamous epithelium is replaced by intestinal epithelium. BE is associated with an increased risk of developing esophageal adenocarcinoma (EAC). However, the BE cell of origin is not clear. We hypothesize that BE tissue originates from esophageal squamous cells, which can differentiate to columnar cells as a result of repeated exposure to gastric acid and bile acids, two components of refluxate implicated in BE pathology. To test this hypothesis, we repeatedly exposed squamous esophageal HET1A cells to 0.2 mM bile acid (BA) cocktail at pH 5.5 and developed an HET1AR-resistant cell line. These cells are able to survive and proliferate after repeated 2-h treatments with BA at pH 5.5. HET1AR cells are resistant to acidification and express markers of columnar differentiation, villin, CDX2, and cytokeratin 8/18. HET1AR cells have increased amounts of reactive oxygen species, concomitant with a decreased level and activity of manganese superoxide dismutase compared with parental cells. Furthermore, HET1AR cells express proteins and activate signaling pathways associated with inflammation, cell survival, and tumorigenesis that are thought to contribute to BE and EAC development. These include STAT3, NF-κB, epidermal growth factor receptor (EGFR), cyclooxygenase-2, interleukin-6, phosphorylated mammalian target of rapamycin (p-mTOR), and Mcl-1. The expression of prosurvival and inflammatory proteins and resistance to cell death could be partially modified by inhibition of STAT3 signaling. In summary, our study shows that long-term exposure of squamous cells to BA at acidic pH causes the cells to display the same characteristics and markers as BE.

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“…Dye loading and calculation of the rate of recovery after acid load were performed as described previously 20. Cells were superfused with medium at pH 7.4 to obtain a stable baseline pH i .…”

Section: Methodsmentioning

confidence: 99%

A novel mechanism of acid and bile acid-induced DNA damage involving Na⁺/H⁺exchanger: implication for Barrett's oesophagus

Goldman

Shahidullah

Goldman

et al. 2010

Gut

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Objective-Barrett's oesophagus is a premalignant disease associated with oesophageal adenocarcinoma. The major goal of this study was to determine the mechanism responsible for bile acid-induced alteration in intracellular pH (pH i ) and its effect on DNA damage in cells derived from normal oesophagus (HET1A) or Barrett's oesophagus (CP-A).Design-Cells were exposed to bile acid cocktail (BA) and/or acid in the presence/absence of inhibitors of nitric oxide synthase (NOS) or sodium-hydrogen exchanger (NHE). Nitric oxide (NO), pH i and DNA damage were measured by fluorescent imaging and comet assay. Expression of NHE1 and NOS in cultured cells and biopsies from Barrett's oesophagus or normal squamous epithelium was determined by RT-PCR, immunoblotting or immunohistochemistry.Results-A dose dependent decrease in pH i was observed in CP-A cells exposed to BA. This effect of BA is the consequence of NOS activation and increased NO production, which leads to NHE inhibition. Exposure of oesophageal cells to acid in combination with BA synergistically decreased pH i . The decrease was more pronounced in CP-A cells and resulted in >2-fold increase in DNA damage compared to acid treatment alone. Examination of biopsies and cell lines revealed robust expression of NHE1 in Barrett's oesophagus but an absence of NHE1 in normal epithelium. Conclusions-The results of this study identify a new mechanism of bile acid-induced DNA damage. We found that bile acids present in the refluxate activate immediately all three isoforms of NOS, which leads to an increased NO production and NHE inhibition. This consequently results in increased intracellular acidification and DNA damage, which may lead to mutations and cancer progression. Therefore, we propose that in addition to gastric reflux, bile reflux should be controlled in patients with Barrett's oesophagus.

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Responses of Sodium–Hydrogen Exchange to Nitric Oxide in Porcine Cultured Nonpigmented Ciliary Epithelium

Cited by 10 publications

References 45 publications

Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H⁺extrusion, cell migration and survival

Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H⁺extrusion, cell migration and survival

Characterization of squamous esophageal cells resistant to bile acids at acidic pH: implication for Barrett's esophagus pathogenesis

A novel mechanism of acid and bile acid-induced DNA damage involving Na⁺/H⁺exchanger: implication for Barrett's oesophagus

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Responses of Sodium–Hydrogen Exchange to Nitric Oxide in Porcine Cultured Nonpigmented Ciliary Epithelium

Cited by 10 publications

References 45 publications

Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H+extrusion, cell migration and survival

Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H+extrusion, cell migration and survival

Characterization of squamous esophageal cells resistant to bile acids at acidic pH: implication for Barrett's esophagus pathogenesis

A novel mechanism of acid and bile acid-induced DNA damage involving Na+/H+exchanger: implication for Barrett's oesophagus

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Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H⁺extrusion, cell migration and survival

Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H⁺extrusion, cell migration and survival

A novel mechanism of acid and bile acid-induced DNA damage involving Na⁺/H⁺exchanger: implication for Barrett's oesophagus