Transcellular signalling pathways and TNF-α release involved in formation of reactive oxygen species in rat alveolar macrophages exposed to tert-butylcyclohexane

In the present work, the effects of aliphatic (n-nonane and n-decane), alicyclic (1,2,4-trimethylcyclohexane and tert-butylcyclohexane, t-BCH) and aromatic (trimethylbenzene and tert-butylbenzene) hydrocarbon solvents on formation of reactive oxygen species (ROS) and the proinflammatory cytokine TNF-alpha in rat alveolar macrophages (AM) have been investigated. Formation of ROS was assessed by monitoring oxidation of 2',7'-dichlorofluorescin to 2',7'-dichlorofluorescein (DCF), and the proinflammatory cytokine tumour necrosis factor alpha (TNF-alpha) was detected using an enzyme-linked immunosorbent assay. DCF fluorescence was elevated in a concentration-dependent manner by the alicyclic hydrocarbons. The involvement of transcellular signalling pathways in the production of ROS by t-BCH, the most active compound, was elucidated by use of specific inhibitors. Preincubation of the AM with the mitogen-activated protein kinase (ERK 1/2) inhibitor U0126, the protein kinase C inhibitor bisindolylmaleimide, the superoxide dismutase inhibitor diethyldithiocarbamate, and the iron ion chelating agent deferoxamine reduced the DCF fluorescence significantly. t-BCH gave an increase in TNF-alpha release. Further, nitric oxide production measured by a modified Griess method, and intracellular calcium concentration measured by fura-2, were increased in the rat AM after exposure to t-BCH.