In primary murine and human aortic endothelial cells, the PKC-JNK mitogen-activated protein kinase pathway importantly contributes to oxLDL-mediated induction of MMP2 expression. apoE/mice fed ruboxistaurin chow (PKC inhibitor)vs.vehicle. In primary murine and human aortic endothelial cells, the PKC-JNK mitogen-activated protein kinase pathway importantly contributes to oxLDL-mediated induction of MMP2 expression. Blockade of PKC may be beneficial in mitigating endothelial perturbation and atherosclerosis.Harja, E., Chang, J. S., Lu, Y., Leitges, M., Zou, Y. S., Schmidt, A. M., Yan, S.-F. Mice deficient in PKC and apolipoprotein E display decreased atherosclerosis. Keywords:signal transduction, MMP-2, JNK, Egr-1 Atherosclerosis is usually a complexdisease that begins with endothelial activation, which CDN1163 causes macrophages and other inflammatory cells to adhere to the stimulated endothelium(1,2,3,4). Sustained dysfunction or activation of the endothelium elicited by low-density lipoproteins (LDLs), particularly their oxidatively altered species (oxLDL), is usually a key step in the initiation of atherosclerosis(2, 4, 5). However, the precise mechanisms by which oxLDL influences the development of atherosclerosis remain incompletely defined. Our earlier studies demonstrated that activated protein kinase C (PKC), especially the II isoform, is a critical upstream regulator of early growth response-1 (Egr-1) in the response to acute vascular stresses, such as hypoxia/hypoxemia and ischemia/reperfusion (I/R)(6,7,8). Egr-1, in turn, functions as a grasp switch controlling the regulation of a diverse array of genes linked to expression of cytokines, chemokines, procoagulant molecules, and cell adherence molecules(9). Evidence from our laboratory as well as others has accumulated linking activation of Egr-1 to chronic vascular stress, such as atherosclerosis. Pivotal studies in the discovery of the biological impact of Egr-1 in atherosclerosis came from experiments by the laboratories of McCaffreyet al.(10), who showed that transcripts for Egr-1 were up-regulated in human atherosclerotic lesions and in the lesions of mice deficient in the LDL receptor fed a high-fat diet. Moreover, increased Egr-1 expression in the human lesion was associated with an elevation in the expression of several known Egr-1 target genes, such as tumor necrosis factor, intercellular adhesion molecule (ICAM)-1, and macrophage colony-stimulating factor (M-CSF), suggesting that Egr-1 is usually transcriptionally active in human atheroma(10). We previously reported that Egr-1//apoE/mice display less atherosclerosis than apoE/control mice at 14 and 24 wk of age(11). In parallel, transcripts for proinflammatory and procoagulant mediators such as JE/MCP-1, interleukin (IL)-1, vascular cell adhesion molecule (VCAM)-1, ICAM-1, tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1) were significantly reduced in the aortas of Egr-1// apoE/micevs.apoE/mice(11). These observations led us to hypothesize that PKC might be a central upstream regulator of Egr-1 implicated in atherosclerotic lesion initiation and/or progression in hyperlipidemic stress. Here, we tested these concepts in homozygous PKC/mice(12)bred into the hypercholesterolemic apoE/background. Furthermore, based on the early and prominent up-regulation of Egr-1 antigen in the CDN1163 endothelium in the aortas of apoE/mice, we probed the role of this pathway in oxLDL-mediated stress in Bmp7 primary cultures of murine and human aortic endothelial cells (MAECs and HAECs). == MATERIALS AND METHODS == == Animal studies == Homozygous apoE/mice in the C57BL/6 background were purchased from Jackson Laboratories (Bar Harbor, ME, USA). Homozygous PKC/mice were backcrossed CDN1163 >10 generations into C57BL/6 in our laboratory, followed by intercrossing with apoE/mice. The progeny were used for breeding that generated PKC//apoE/and PKC-+/+/apoE/littermate offspring. All procedures were carried out with the approval of the Institutional Animal Care and Use Committee of Columbia University. All of the mice were fed normal chow. Genomic DNA was isolated from tail biopsies. Polymerase chain reaction (PCR) analysis was used to identify the deficiency of apoE according to the website of the Jackson Laboratories (www.jax.org). Southern blotting was used to identify the deficiency of PKC based on previously published methods(12). In other studies, apoE/mice were fed chow made up of the PKC inhibitor ruboxistaurin (LY-333531; 10 mg/kg daily) or vehicle chow without inhibitor from age 5 to 24 wk(8, 45, 46). Ruboxistaurin and vehicle chow were generously supplied by Dr..