Sodium Salicylate-Induced Apoptosis of Human Peripheral Blood Eosinophils Is Independent of the Activation of c-Jun N-Terminal Kinase and p38 Mitogen-Activated Protein Kinase

Abstract

Background: It has been shown that the inhibition of eosinophilic apoptosis is an important mechanism for the development of blood and tissue eosinophilia in allergic diseases. Considerable attention has recently been focused on the role played by different intracellular kinase cascades in the control of apoptosis. In the present study, we investigated the effect of sodium salicylate (NaSal), a nonsteroidal anti-inflammatory drug, on mitogen-activated protein kinases (MAPK) and apoptosis of human eosinophils. Methods: Human blood eosinophils were purified from buffy coat. NaSal-induced apoptosis of eosinophils was assessed by morphological changes and Annexin-V binding assay. Changes of MAPK activity upon treatment with NaSal were measured by kinase activity assay and Western blot. Results: NaSal could induce apoptosis of human blood eosinophils in a dose- and time-dependent manner. It could also activate c-Jun N-terminal kinase (JNK) and p38 MAPK but not extracellular signal-regulated protein kinase (ERK) activity within 1 h. Pretreatment of eosinophils with p38 MAPK and JNK anti-sense (AS) phosphorothioate oligodeoxynucleotides (ODN) or specific p38 MAPK inhibitor SB 203580 did not have any significant effect on NaSal-induced apoptosis. However, ERK AS ODNs could trigger the apoptosis of normal eosinophils. Conclusion: There is no direct relationship between the activation of JNK and p38 MAPK pathways and NaSal-induced apoptosis in human peripheral blood eosinophils.

Nuclear Factor-κB-Independent Anti-Inflammatory Action of Salicylate in Human Endothelial Cells: Induction of Heme Oxygenase-1 by the c-Jun N-Terminal Kinase/Activator Protein-1 Pathway

“…Experiments using a pharmacological JNK inhibitor (SP600125) (Bennett et al, 2001) and inhibiting DNA binding of AP-1 by decoy oligonucleotides (Jan et al, 2000) in fact indicate a crucial role for the JNK/AP-1 pathway in the signaling events responsible for the up-regulation of HO-1. In support of our findings, JNK activation by salicylate has also been observed in human eosinophils (Wong et al, 2000), HO-29 colon cancer (Schwenger et al, 1999), and COS-1 cells (Schwenger et al, 1999). Interestingly, salicylate inhibits an already activated JNK in fibroblasts and mouse epidermal cells Schwenger et al, 1997), suggesting that the effects of salicylate on JNK activity highly depend both on the cellular context and on the activity status of JNK in the current experimental setting.…”

“…However, all these opposing studies show inhibitory effects of salicylates only in settings where the cells have already been activated by diverse stimuli. Publications reporting basal stimulatory effects on the JNK/AP-1 pathway are rare (Schwenger et al, 1999;Wong et al, 2000;Vartiainen et al, 2003), and none are available for the human endothelium. Thus, to the best of our knowledge, this is the first report proving that activation of the JNK/AP-1 signaling pathway is crucial for the salicylate-induced HO-1 expression in the human endothelium.…”

Pharmacological Regulation of Human Eosinophil Apoptosis

“…Sodium salicylate has been reported to induce JNK and p38 MAP kinase activation in human eosinophils as well as to induce apoptosis, but the effects of sodium salicylate on apoptosis could not be reversed by inhibiting JNK and p38 with antisense oligodeoxynucleotides or with the specific p38 MAP kinase inhibitor SB203580 [85], thus suggesting that JNK and p38 MAP kinase are not mediating sodium salicylate-induced eosinophil apoptosis.…”

“…The role of MAP kinases in the survival prolonging-action of cytokines such as IL-5 or GM-CSF remains controversial [24,82,85]. Recently, the functional roles of MAP kinases in eosinophils have been characterized using pharmacological inhibitors for MEK1/2 (PD98059, U0126) and p38 (SB203580).…”

Sodium Salicylate Increases CYP2E1 Levels and Enhances Arachidonic Acid Toxicity in HepG2 Cells and Cultured Rat Hepatocytes

“…One major mechanism to explain salicylate action as an anti-inflammatory agent is the prevention of activation of nuclear factor-B by inhibition of phosphorylation and subsequent degradation of IB␣ or direct inhibition of IB kinase (Kopp and Ghosh, 1994;Schwenger et al, 1996;McDade et al, 1999;Alpert and Vilcek, 2000). Salicylate also interferes with mitogen-activated protein kinase and other kinase-dependent signaling pathways (Schwenger et al, 1996;1997;Chen et al, 1999;Wong et al, 2000), can inhibit transcription of certain genes [e.g., iNOS (Farivar and Brecher, 1996)], and affects mitochondrial function and calcium homeostasis (Biban et al, 1995;Trost and Lemasters, 1997). Our interest in salicylate was sparked by recent reports that CYP2E1 (and CYP3A4) can hydroxylate salicylate in the 5-position to produce 2,5-dihydroxybenzoic acid (Dupont et al, 1999) and that acetylsalicylic acid can induce hepatic CYP2E1 when administered in vivo to rats (Damme et al, 1996).…”