The nuclear factor (NF)-kappaB/inhibitory (I)kappaBalpha pathway is one of the most important intracellular signal transduction pathways during inflammation which is induced by a variety of major early response cytokines. Recent studies suggest that volatile anesthetics interfere with inflammatory cytokine production through inhibition of intracellular signal transduction pathways. We, therefore, aimed to investigate the effects of the volatile anesthetics sevoflurane and isoflurane on NF-kappaB/IkappaBalpha-dependent intracellular signal transduction in human monocytic THP-1 cells induced by tumor necrosis factor-alpha (TNF-alpha) and production of interleukin-8 (IL-8) and downstream heme oxygenase-1 (HO-1). THP-1 cells, a human monocytic cell line, were used in an in vitro model which enables the exposure to volatile anesthetics. Using this model, THP-1 cells were subjected to sevoflurane or isoflurane exposure (1 MAC each) and were stimulated with TNF-alpha (50 or 100 ng/ml). Compared to untreated cells, expression of intracellular HO-1-protein and release of IL-8 into cell culture supernatants and corresponding mRNA expression were attenuated in THP-1 cells exposed to sevoflurane and isoflurane, respectively. Moreover, translocation of NF-kappaB and degradation of IkappaBalpha were markedly reduced by both anesthetics. Notably, under unstimulated conditions, exposure to sevoflurane induced a sustained upregulation of the IkappaBalpha content in THP-1 cells. We demonstrated inhibition of TNF-alpha-induced gene expression and release of IL-8 and HO-1 in human monocytic THP-1 cells exposed to both volatile anesthetics. This was associated with an upregulated intracellular IkappaBalpha content followed by decreased NF-kappaB translocation. This was more sustained during exposure to sevoflurane and may provide an additional intracellular mechanism for the anti-inflammatory effects associated with sevoflurane administration.