p38 MAP kinase is involved in PDE2A expression. HUVECs were incubated for 6 hours with TNF-α (10 ng/mL). p38 MAPK inhibitor SB202190 (10 μM) or ERK1/2 inhibitor U0126 (1 μM) were coincubated with TNF-α to identify involvement of the respective kinase pathway for TNF-α–mediated PDE2 expression (A). HUVEC protein lysates were denatured and subjected to electrophoresis on 7.5% (wt/vol) SDS–polyacrylamide gels. Proteins were transferred to nitrocellulose and probed simultaneously with anti-PDE2A and ERK2 antibody. The latter antibody detects nonphosphorylated ERK2 protein to control for equal loading. After exposure to the IRDye 800–labeled antigoat and Cy5.5-labeled secondary antirabbit antibody, proteins were visualized using an infrared imaging system. The gels are representative of 5 independent experiments. HUVECs were transfected with a dominant-negative p38 MAPK cDNA construct (ip38) prior to stimulation with TNF-α (10 ng/mL) (B). Constitutively active MKK6 cDNA construct (aMKK6) was transfected into HUVECs and incubated with p38 MAPK inhibitor SB202190 (10 μM). After 18 hours, PDE2 activity was measured and normalized to total cellular protein and expressed as pmol cAMP × minute^-1 × mg protein^-1 (B). Data presented are mean ± SEM of 4 independent experiments. ^**P < .01 versus untreated cells; #P < .05 versus TNF-α–stimulated cells; and §P < .05 versus MKK6-transfected cells.