Increased calcium influx in a monocytic cell line on exposure to ultrafinecarbon black

Ultrafine particles have been shown to induce pro-inflammatory effects both in vivo and in vitro. Increased expression of pro-inflammatory genes proba bly requires the activation of specific transcription factors such as nucle ar factor kappa B (NF-kappa B) via a number of possible pathways including Ca2+ and reactive oxygen species. The fluorescent dye fura 2, was used to measure cytsolic Ca2+ in the human monocytic cell line, Monomac 6 on exposure to 66 mu g.mL(-1) of either ultr afine carbon black (ufCB; diameter 14 nm), carbon black (CB; diameter 260 n m), quartz (diameter 1.45 mu m), or medium alone. UfCB but not fine CB induced a 1.6-fold increase (p<0.01) in the resting cy tosolic Ca2+ concentration of Monomac 6 cells. In addition ufCB induced a 2 .6-fold increase (p<0.001) in the response to the endoplasmic reticulum Ca2 +- adenosine triphosphatase (ATPase) inhibitor, thapsigargin, suggesting th e Ca2+ release-activated Ca2+ current across the plasma membrane was enhanc ed. This response was inhibited by the removal of extracellular Ca2+ and by the Ca2+ channel blocker, verapamil, Tn addition, ufCB stimulated the entr y of extracellular Mn2+. Finally, the antioxidants mannitol and nacystelin both inhibited the effects of ufCB on the response to thapsigargin, These data suggest that ultrafine carbon black particles stimulated an incr ease in cytosolic Ca2+, possibly through the entry of extracellular Ca2+ vi a Ca2+ channels in the plasma membrane. The particles may in part activate the opening of Ca2+ channels via a mechanism involving reactive oxygen spec ies.