Effects of ERK and p38MAPK inhibition on Mcl-1 expression in various oxygen conditions. Neutrophils were incubated for 6 hrs at normoxia (Nox), sustained hypoxia (SH), or 6 cycles of intermittent hypoxia (IH) without or with 10 μM U0126 (a specific inhibitor of MEK1/2, which blocks ERK1/2 activation), and 30 μM SB202190 (a competitive inhibitor of the p38 kinase). Mcl-1 expression was assessed by confocal laser scanning microscopy. (A-I) Representative photomicrographs of Mcl-1 expression (green) from 1 out of 4 experiments performed. (A) Neutrophils incubated in Nox, (B) IH and (C) SH. (D) Neutrophils incubated in Nox with MEK1/2 inhibitor, (E) in IH with MEK1/2 inhibitor, and (F) in SH with MEK1/2 inhibitor. (G) Neutrophils incubated in Nox with p38MAPK inhibitor (H) in IH with p38MAPK inhibitor, and (I) in SH with p38MAPK inhibitor. (J) The average values of Mcl-1 expression for ERK1/2 inhibitor and (K) for p38MAPK inhibitor by relative percent. The intensity of Mcl-1 expression at normoxia without inhibitors was considered as 100%, and the changes induced by the IH and SH with or without the inhibitors were plotted as a relative percentage of this value. P values represent significance of untreated vs. inhibitor treated neutrophils in each oxygen condition.