Metabolic reprogramming of inner ear cell line HEI-OC1 after dexamethasone application.

INTRODUCTION: One approach to dampen the inflammatory reactions resulting from implantation surgery of cochlear implant hearing aids is to embed dexamethasone into the matrix of the electrode carrier. Possible side effects for sensory cells in the inner ear on the metabolomics have not yet been evaluated. OBJECTIVE: We examined changes in the metabolome of the HEI-OC1 cell line after dexamethasone incubation as a cell model of sensory cells of the inner ear. RESULTS AND CONCLUSION: Untargeted GC-MS-profiling of metabolic alterations after dexamethasone treatment showed that dexamethasone had antithetical effects on the metabolic signature of the cells depending on growth conditions. The differentiated state of HEI-OC1 cells is better suited for elucidating metabolic changes induced by external factors. Dexamethasone treatment of differentiated cells led to an increase in intracellular amino acids and enhanced glucose uptake and ß-oxidation in the cells. Increased availability of precursors for glycolysis and ATP production by ß-oxidation stabilizes the energy supply in the cells, which could be assumed to be beneficial in coping with cellular stress. We found no negative effects of dexamethasone on the metabolic level, and changes may even prepare sensory cells to better overcome cellular stress following implantation surgery.

ATF3-Dependent Regulation of EGR1 in vitro and in vivo.

BACKGROUND/AIMS: Activating transcription factor 3 (ATF3) and early growth response protein 1 (EGR1) are reported to interact, but their use as prognostic factors in cancer is discussed controversially. METHODS: We measured ATF3 and EGR1 gene expression changes in human mini-organ cultures (MOCs) of healthy nasal epithelia, UM-SCC-22B, and FADUDD cells after acid reflux exposure. Next, ATF3 and EGR1 gene expression was analysed in tumour tissues and related to the median expression of autologous reference tissue samples. RESULTS: ATF3 and EGR1 mRNA expression was significantly reduced after consecutive exposure of MOCs at pH <7.0 to artificial gastric juice (refluxate). In contrast, ATF3 mRNA was upregulated significantly within the first hour of incubation. EGR1 mRNA exhibited no significant changes. The analysed cell lines exhibited a cell line-specific alteration. In FADUDD cells, the upregulation of EGR1 was significant after refluxate exposure, but in HN-SCC 22B, no significant changes were detected. The analysis of the HNSCC samples confirmed the heterogeneous data of the literature. CONCLUSION: The data maintain the hypothesis that ATF3 and EGR1 are involved in the beginning of inflammatory processes. Whether these two transcription factors act as tumour suppressors or promoters is context dependent and warrants analysis in further studies.

Reflux induces DNA strand breaks and expression changes of MMP1+9+14 in a human miniorgan culture model.

Gastroesophageal reflux disease has been implicated in the pathogenesis of adenocarcinoma of the oesophagus. The same applies to laryngopharyngeal reflux (LPR) and squamous cell cancer of the head and neck, but so far, this link has not been proven. The impact of low pH and bile acids has not been studied extensively in cells other than oesophageal cancer cell lines and tissue. The aims of this study were to investigate the pathogenic potential of reflux and its single components on the mucosa of the upper respiratory tract. We measured DNA stability in human miniorgan cultures (MOCs) and primary epithelial cell cultures (EpCs) in response to reflux by the alkaline comet assay. As matrix metalloproteinases (MMPs) are involved in extracellular matrix remodelling processes and may contribute to cancer progression, we studied the expression of MMP1, -9, and -14 in MOCs, EpC, UM-SCC-22B, and FADUDD. DNA strand breaks (DNA-SBs) increased significantly at low pH and after incubation with human or artificial gastric juice. Single incubation with glycochenodeoxycholic acid also showed a significant increase in DNA-SBs. In epithelial cell cultures, human gastric juice increased the number of DNA-SBs at pH 4.5 and 5.5. Artificial gastric juice significantly up regulated the gene expression of MMP9. Western blot analysis confirmed the results of gene expression analysis, but the up regulation of MMP1, -9, and -14 was donor-specific. Reflux has the ability to promote genomic instability and may contribute to micro environmental changes suitable for the initiation of malignancy. Further functional gene analysis may elucidate the role of laryngopharyngeal reflux in the development of head neck squamous cell carcinoma (HNSCC).