Nitric oxide production in fluoro-edenite treated mouse monocyte-macrophage cultures

In the present study, we investigated the involvement of NO in the cytotoxic and genotoxic effects caused by fluoro-edenite in mouse monocyte-macrophage cell line J774. Fluoro-edenite is a new asbestos-like amphibole present in the benmoreitic lavas recently extracted from stone quarries in Biancavilla, a village located in the Etnean Volcanic Complex (Catania, Italy) of eastern Sicily, in which an epidemiological survey evidenced a cluster of cases of the mortality due to pleural mesothelioma. Fluoro-edenite appears as a probable carcinogenic agent. Nitrite and nitrate concentration (NO) in the supernatant was quantified by colorimetric assay based on the Griess reaction and iNOS (inducible nitric oxide synthetase) expression was determined by immunostaining in mouse monocyte-macrophage cell line J774 treated with different concentrations of fluoro-edenite (5, 50 and 100 µg/ml) for 24, 48, 72 and 96 h. Parallel experiments were performed treating the cultures also with lipopolysaccharides (LPS), used as inflammation-inducing molecule. In our experimental conditions, fluoro-edenite did not modify the level of NO and the expression of iNOS at the experimental used concentrations for 24, 48 and 72 h. These parameters were significantly modified at the higher doses (50 and 100 µg/ml) of fluoro-edenite for 96 h and were further more increased, in concentration- and time-dependent manner, when cell cultures were treated with fluoro-edenite and LPS. These findings provide convincing evidence that NO is involved in the fluoro-edenite-induced cytotoxicity and geno-toxicity in mouse monocyte-macrophage cell line J774 when the fiber remain for longer times and particularly in cultures treated with LPS, demonstrating that inflammatory disorders appear to increase the risk for lung cancer induced by fluoro-edenite probably by the involvement of NO.