Figure 5. JAK2 activation is required for LTB₄-induced STAT1 phosphorylation.

(A) WT, 5-LO^–/–, and BLT1^–/– macrophages were treated for 30 minutes with or without LTB₄, and pJAK2, pJAK1, pTyk2, total JAK2, and actin were determined by immunoblotting. Densitometric analysis of pJAK2 protein levels in 5-LO^–/– and BLT1^–/– macrophages is also shown, expressed relative to their respective strain-matched WT cells. (B) WT macrophages were pretreated for 30 minutes with JAK2 inhibitors AG490 (1 μM) and JAK2 inhibitor I (JAK2 i; 10 nM), followed by 30 minutes of treatment with or without LTB₄; pJAK2 (Tyr1007/1008) and pSTAT1 (Tyr701) were subsequently determined by immunoblotting. Densitometric analysis of pJAK2 and pSTAT1 protein levels in WT macrophages treated with LTB₄ in the absence or presence of JAK2 inhibitors is also shown. Immunoblots are representative of at least 3 independent experiments; densitometry values are mean ± SEM from 3 independent experiments. *P < 0.05 versus untreated WT; ^#P < 0.05 versus LTB₄ alone.