Ca2+ metabolic disorder and abnormal expression of cardiac troponin involved in fluoride-induced cardiomyocyte damage

Our previous study indicated that excessive fluoride (F) induces ATP5J and ATP5H proactive expression by interfering cardiomyocyte mitochondrial dysfunction in mice. This study aimed to investigate underlying mechanisms of F¯ induced damage to cardiomyocytes. A total of 100 mg/L F¯ was added to distilled water to treat Kunming mice for 70 days. Pathological and morphological changes in myocardial tissues were observed under transmission electron microscope and light microscope. Content of ATP and ATP enzyme distributed in cardiomyocytes were determined by fluorescence and ATP enzyme staining. Expression levels of troponin (Tn) C, TnI, TnT and tropomyosin (TPM) were measured by immunofluorescence, western blot, and real-time polymerase chain reaction. Contents of Ca2+ in blood, myocardial cells and faeces were also detected by confocal microscopy and ethylenediaminetetraacetic acid. Using 100 mg/L F¯ resulted in nuclaer enrichment, the myocardial fibre breakage and mitochondrial lysis. Following mitochondrial structure damage, contents of ATP and ATP enzyme significantly decreased in the fluoride group. Expression levels of TnT and TnI were significantly down-regulated, whereas that of TPM was up-regulated. Content of Ca2+ in cardiomyocytes of fluoride group visibly increased. Interestingly, contents of Ca2+ in blood and faeces decreased. These findings reveal that excessive F ingestion induces Ca2+ metabolic disorder, and an abnormal expression of cardiac Tn are involved in F-induced cardiomyocyte damage.