Potentiation of Protein Kinase C ζ Activity by 15-Deoxy-Δ(12,14)-Prostaglandin J(2) Induces an Imbalance between Mitogen-Activated Protein Kinases and NF-κB That Promotes Apoptosis in Macrophages

Activation of the macrophage cell line RAW 264.7 with lipopolysaccharide (LPS) transiently activates protein kinase C ζ (PKCζ) and Jun N-terminal kinase (JNK) through a phosphoinositide-3-kinase (PI3-kinase)-dependent pathway. Incubation of LPS-treated cells with the cyclopentenone 15-deoxy-Δ(12,14)-prostaglandin J(2) (15dPGJ(2)) promoted a sustained activation of PKCζ and JNK and inhibited IκB kinase (IKK) and NF-κB activity. Accordingly, 15dPGJ(2) induced an imbalance between JNK and IKK activities by increasing the former signaling pathway and inhibiting the latter signaling pathway. Under these conditions, apoptosis was significantly enhanced; this response was very dependent on PKCζ and JNK activation. The effect of 15dPGJ(2) on PKCζ activity observed in LPS-activated macrophages was not dependent on a direct action of this prostaglandin on the enzyme but was due to the activation of a step upstream of PI3-kinase. Moreover, LPS promoted the redistribution of activated PKCζ from the cytosol to the nucleus, a process that was enhanced by treatment of the cells with 15dPGJ(2) that favored a persistent and broader distribution of PKCζ in the nucleus. These results indicate that 15dPGJ(2) and other cyclopentenone prostaglandins, through the sustained activation of PKCζ, might contribute significantly to the process of resolution of inflammation by promoting apoptosis of activated macrophages.