Increased mutant frequencies in the HPRT gene locus of leukemia HL-60 cells treated with succinylacetone.

Succinyl acetone (SA) was initially identified in the urine of patients with tyrosinemia type I, an autosomally recessive inherited disease. SA has been used to downregulate the activity of myeloperoxidase (MPO) through its specific inhibition of heme biosynthesis and to investigate the biological properties of MPO in the human myeloid leukemic (HL-60) cell line. The goal of this study is to evaluate the mutagenic potential of SA by determining the frequencies of somatic mutations in the hypoxanthine-guanine phosphoribosyl transferase (HPRT) reporter gene in HL-60 cells following treatment with the chemical. Treatments of HL-60 cells with 500 micromol/L SA for 72 h, a condition generally used to inhibit the MPO activity, resulted in a significantly increased HPRT mutant frequency (HPRT-Mf), compared with the control of untreated cells (47.25 x 10(-6) versus 7.5 x 10(-6), respectively, p <0.01). Treatment of the cells with lower doses of SA also led to an increase in HPRT-Mf but this was significant only with 200 micromol/L (28.67 x 10(-6), p<0.05) and not with doses lower than 100 micromol/L (p0.05), compared with the control of untreated cells (7.5 x 10(-6)). These data show a dose-response increase in HPRT-Mf in HL-60 cells treated with SA, suggesting that this chemical causes mutations in the HPRT locus in these cells either directly or indirectly through its inhibition of the MPO activity.

Elevated interleukin-4 and interleukin-6 in rats sensitized with toluene diisocyanate.

In order to investigate the cytokine profile in toluene diisocyanate (TDI)-induced occupational asthma, we conducted a quantification of cytokine production in a murine model of respiratory hyperreactivity to TDI. Wistar rats were sensitized with intranasal application of 10% TDI and provoked with 5% TDI to induce airway hypersensitivity. The blood leucocytes were counted, and bronchoalveolar lavage (BAL) was performed and the cellular responses in BAL fluid were analysed. Lung histological examination was performed to investigate the inflammatory status in the airway. The production of IL-2, IL-4, IL-6 and IFN-gamma in serum, BAL fluid and spleen cell were determined with ELISA kits. The cellular results demonstrated that neutrophils and eosinophils in blood were significantly increased and the total cells and each different cell, in particular eosinophils in BAL fluid were markedly increased in TDI sensitized rats. Histological analysis showed that a respiratory inflammation represented by prominent infiltration of eosinophils in central and peripheral airways was present in TDI-sensitized rats. The cytokine assays revealed that in TDI-sensitized rats, IL-4 was predominately secreted in serum, and IL-4 and IL-6 rather than IL-2 and IFN-gamma were predominately secreted in BAL fluid and in spleen cell. These findings suggested that IL-4 and IL-6 are preferentially produced and may have an important role in occupational asthma induced by TDI.