Induction of Non-Apoptotic Cell Death by Adrenergic Agonists in Human Oral Squamous Cell Carcinoma Cell Lines.

Background/aim: Although adrenergic agonists have been used in dental treatments and oral surgery for general anesthesia, their cytotoxicity against human oral malignant and non-malignant cell has not been well- understood. The present study was undertaken to investigate the cytotoxicity of five adrenergic agonists against human oral squamous cell carcinoma (OSCC), glioblastoma, promyelocytic leukemia, and normal oral mesenchymal cells (gingival fibroblast, pulp cell, periodontal ligament fibroblast) and normal epidermal keratinocytes.

Materials And Methods: Tumor-specificity (TS) was calculated by the ratio between the mean 50% cytotoxic concentration against normal cells to that of tumor cells. Internucleosomal DNA fragmentation was detected using agarose gel electrophoresis. Caspase-3 activity was measured by substrate cleavage.

Results: Both cytotoxicity and tumor-specificity of adrenergic agonists against OSCC cell lines was in the order of isoprenaline>dexmedetomidine> adrenaline>clonidine and phenylephrine. Isoprenaline and dexmedetomidine did not induce apoptosis markers, such as internucleosomal DNA fragmentation and caspase-3 activation, but induced a smear pattern of DNA fragmentation in OSCC cell lines. Their cytotoxicity was not reduced by pretreatment with autophagy inhibitors, or by adrenoceptors antagonists. Addition of superoxide dismutase and catalase significantly reduced the cytotoxicity of isoprenaline, but not that of dexmedetomidine.

Conclusion: Isoprenaline and dexmedetomidine induce non-apoptotic cell death by different mechanisms.