['The body produces chromogranin A (ChgA) in response to stress as an adaptive reaction. While ChgA is used as an index of autonomic nervous system activity, it is also involved in the immunomodulation system, and an increase in its production in patients with periodontal disease and cigarette smokers has been reported. However, its production in periodontal tissue cells subjected to stress and its immunomodulatory action have not been clarified. To investigate the influence of nicotine on periodontal tissue, we measured ChgA production in nicotine-treated periodontal ligament fibroblasts.', 'Using normal human periodontal ligament-derived fibroblasts (HPdLF) as a periodontal tissue model, untreated cells (control) and cells treated with 10 and 100nM nicotine sulfate corresponding to passive and active cigarette smoking, respectively, were cultured for a specific time. The ChgA level in the culture fluid was measured as ChgA production in HPdLF employing ELISA. ChgA gene expression was quantified employing qPCR. In addition, intracellular localisation was confirmed by immunohistochemical staining.', 'In the control HPdLF group, a low level of ChgA was produced, and immunohistochemical ChgA-positive reactions were observed in the nucleus and cytoplasm. In the nicotine-treated HPdLF group, the ChgA mRNA expression level, protein production, and immunostaining-positive rate increased, and the levels were higher in the cells treated with 10nM nicotine corresponding to passive smoking than in the cells treated with 100nM nicotine corresponding to active smoking.'] Does nicotine in cigarettes promote chromogranin A production by human periodontal ligament fibroblasts?