Arachidonic acid activates Jun N-terminal kinase in vascular smooth muscle cells

Abstract

We have previously demonstrated that arachidonic acid activates extracellular signal-regulated protein kinases (ERKs) group of mitogen-activated protein kinases (MAPKs) in vascular smooth muscle cells (VSMC). To understand the role of arachidonic acid in cellular signaling events, we have now studied its eect on jun N-terminal kinases (JNKs) group of MAPKs in VSMC. Arachidonic acid activated JNK1 in a time-and concentration-dependent manner with maximum eects at 10 min and 50 mM. Induced activation of JNK1 by arachidonic acid is speci®c as other fatty acids such as linoleic and stearic acids had no such eect. Indomethacin and nordihydroguaiaretic acid (NDGA), potent inhibitors of the cyclooxygenase (COX) and the lipoxygenase (LOX)/monooxygenase (MOX) pathways, respectively, had no eect on arachidonic acid activation of JNK1 suggesting that the observed phenomenon is independent of its metabolism through either pathway. However, 12-hydroperoxyeicosatetraenoic acid (12-HpETE), the LOX metabolite of arachidonic acid signi®cantly induced JNK1 activity. Protein kinase C (PKC) depletion by prolonged treatment of VSMC with phorbol 12-myristate 13-acetate (PMA) resulted in partial decrease in the responsiveness of JNK1 to arachidonic acid suggesting a role for both PKCdependent and -independent mechanisms in the activation of JNK1 by this important fatty acid. On the other hand, the responsiveness of JNK1 to 12-HpETE was completely abolished in PKC-depleted cells, suggesting a major role for PKC in 12-HpETE-induced JNK1 activation. IL-1b and TNF-a activated JNK1 in a time-dependent manner with maximum eect at 10 min. Desensitization of JNK1 by arachidonic acid signi®-cantly reduced its responsiveness to both the cytokines. In addition, 4-bromophenacyl bromide (4-BPB), a potent and selective inhibitor of phospholipase A 2 (PLA 2 ), signi®cantly attenuated the cytokine-induced activation of JNK1. Together, these results show that (1) arachidonic acid and its LOX metabolite, 12-HpETE, activate JNK1 in VSMC, (2) PKC-dependent and -independent mechanisms play a role in the activation of JNK1 by arachidonic acid and 12-HpETE, and (3) arachidonic acid mediates, at least partially, the cytokine-induced activation of JNK1.

Convergence of Redox-Sensitive and Mitogen-Activated Protein Kinase Signaling Pathways in Tumor Necrosis Factor-α–Mediated Monocyte Chemoattractant Protein-1 Induction in Vascular Smooth Muscle Cells

“…As noted above, TNF-␣ activates JNK in some cell types, 38 and JNK has been shown to be redox sensitive. 42 However, to date, no role for JNK in MCP-1 mRNA upregulation has been demonstrated.…”

“…In VSMCs, TNF-␣ stimulates ERK1/2 and p38MAPK ( Figure 4 and References 13, 36, and 37), as well as JNK. 38 Furthermore, we have previously shown that p38MAPK but not ERK1/2 is downstream from agonist-induced ROS production in these cells. 17,31 The role of MAPK in TNF-␣-mediated MCP-1 induction, however, has not been examined.…”

Modulation of Cell-Substrate Adhesion by Arachidonic Acid: Lipoxygenase Regulates Cell Spreading and ERK1/2-inducible Cyclooxygenase Regulates Cell Migration in NIH-3T3 Fibroblasts

“…Epoxygenase metabolites are not known to be involved in cell adhesion although there are reports suggesting that they act in other signaling pathways (Madamanchi et al, 1998;Chen et al, 1999). Conversely, the LOX and COX pathways are widely involved in signaling a variety of cellular functions.…”

“…The 85-kDa cytosolic PLA2 (cPLA2) is a major source of intracellular AA release in signal transduction, because it exhibits specificity for phospholipids with AA in the sn2 position, whereas calcium-independent PLA2 (iPLA2) and the secretory PLA2 (sPLA2) do not show the same preference (reviewed in Murakami et al, 1997;Balsinde et al, 1999). AA participates in multiple signaling pathways by providing substrate to three types of oxidative enzymes, LOXs, COXs, and epoxygenase (EOX), all of which participate in diverse signal transduction pathways (reviewed in Piomelli, 1993;Seeds and Bass, 1999).Epoxygenase metabolites are not known to be involved in cell adhesion although there are reports suggesting that they act in other signaling pathways (Madamanchi et al, 1998;Chen et al, 1999). Conversely, the LOX and COX pathways are widely involved in signaling a variety of cellular functions.…”

Mechanisms of nordihydroguaiaretic acid-induced growth inhibition and apoptosis in human cancer cells

“…NDGA similarly activated JNK1/2 and p38 mapk but had no effect on ERK1/2 activation in SW 850 and C4-I cells. Again, this effect of NDGA is likely to be cell type specific: No effect of NDGA on JNK activation could be demonstrated in vascular smooth muscle cells (Madamanchi et al, 1998), HeLa cells and HL 60 cells (Hii et al, 1998). There is some controversy regarding the possible role of stress activated protein kinases as mediators of apoptosis.…”