Figure 3.

MAP kinase phosphatase (MKP)-3 expression is regulated by the p38 MAP kinase. (A) Blood monocytes were cultured in the presence or absence of SB203580 (SB) for 30 minutes before exposing to crocidolite asbestos for 3 hours. Total RNA was isolated and reverse transcribed to cDNA. Real-time PCR amplification was performed as described in Materials and Methods. Data are expressed as fold increase of MKP-3 mRNA expression from control. For statistical analysis, * denotes a comparison of crocidolite asbestos to control and to crocidolite + SB (P < 0.025). (B) Blood monocytes were exposed to crocidolite asbestos for the indicated amount of time. Whole cell lysates were separated by SDS-PAGE, and Western blot analysis was performed using the MKP-3 rabbit polyclonal and β-actin monoclonal antibodies to determine expression and equal loading of the proteins. (C) THP-1 cells were transfected with 100 nM of either a scrambled or a p38 siRNA. After 48 hours, the cells were exposed to crocidolite asbestos for 2 hours. Whole cell lysates were separated by SDS-PAGE, and Western blot analysis was performed for p38, MKP-3, or β-actin.