Background-C-reactive protein (CRP) has been suggested to actively amplify the inflammatory response underlying coronary heart diseases by directly activating endothelial cells. In this study, we investigated whether loss of the cyclic pentameric structure of CRP, resulting in formation of modified or monomeric CRP (mCRP), is a prerequisite for endothelial cell activation. Methods and Results-We examined the impact of native CRP and mCRP on the production of monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8), key regulators of leukocyte recruitment, and on the expression of intercellular adhesion molecule-1 (ICAM-1), E-selectin, and vascular adhesion molecule-1 (VCAM-1) in human cultured coronary artery endothelial cells (HCAECs). Incubation with mCRP for 4 hours increased MCP-1 and IL-8 secretion and mRNA levels and expression of ICAM-1, E-selectin, and VCAM-1 protein and mRNA. Significant induction occurred at 1 to 5 g/mL, reached a maximum at 30 g/mL, and did not require the presence of serum. Native CRP was without detectable effects at 4 hours, whereas it enhanced cytokine release after a 24-hour incubation. An anti-Fc␥RIII (CD16) but not an anti-Fc␥RII (CD32) antibody produced a 14% to 32% reduction of the mCRP effects (PϽ0.05). mCRP but not CRP evoked phosphorylation of p38 mitogen-activated protein kinase, and inhibition of this kinase with SB 203580 reversed the effects of mCRP. Furthermore, culture of HCAECs in the presence of SB203580 markedly decreased mCRP-stimulated E-selectin and ICAM-1-dependent adhesion of neutrophils to HCAECs (PϽ0.001). Conclusions-Loss of pentameric symmetry in CRP, resulting in formation of mCRP, promotes a proinflammatory HCAEC phenotype through a p38 MAPK-dependent mechanism.

Summary Dolichol is an obligate carrier of glycans for N-linked protein glycosylation, O-mannosylation, and GPI anchor biosynthesis. Cis-prenyltransferase (cis-PTase) is the first enzyme committed to the synthesis of dolichol. However, the proteins responsible for mammalian cis-PTase activity have not been delineated. Here we show that Nogo-B receptor (NgBR) is a subunit required for dolichol synthesis in yeast, mice and man. Moreover, we describe a family with a congenital disorder of glycosylation caused by a loss of function mutation in the conserved C terminus of NgBR-R290H and show that fibroblasts isolated from patients exhibit reduced dolichol profiles and enhanced accumulation of free cholesterol identically to fibroblasts from mice lacking NgBR. Mutation of NgBR-R290H in man and orthologs in yeast proves the importance of this evolutionarily conserved residue for mammalian cis-PTase activity and function. Thus, these data provides a genetic basis for the essential role of NgBR in dolichol synthesis and protein glycosylation.

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Rationale: Apoptosis is essential for removal of neutrophils from inflamed tissues and efficient resolution of inflammation. Myeloperoxidase (MPO), abundantly expressed in neutrophils, not only generates cytotoxic oxidants but also signals through the b 2 integrin Mac-1 to rescue neutrophils from constitutive apoptosis, thereby prolonging inflammation. Objectives: Because aspirin-triggered 15-epi-lipoxin A 4 (15-epi-LXA 4 ) modulates Mac-1 expression, we investigated the impact of 15-epi-LXA 4 on MPO suppression of neutrophil apoptosis and MPOmediated neutrophil-dependent acute lung injury. Methods: Human neutrophils were cultured with MPO with or without 15-epi-LXA 4 to investigate development of apoptosis. Acute lung injury was produced by intratracheal injection of carrageenan plus MPO or intraperitoneal injection of live Escherichia coli in mice, and the animals were treated with 15-epi-LXA 4 at the peak of inflammation. Measurements and Main Results: 15-Epi-LXA 4 through down-regulation of Mac-1 expression promoted apoptosis of human neutrophils by attenuating MPO-induced activation of extracellular signalregulated kinase and Akt-mediated phosphorylation of Bad and by reducing expression of the antiapoptotic protein Mcl-1, thereby aggravating mitochondrial dysfunction. The proapoptotic effect of 15-epi-LXA 4 was dominant over MPO-mediated effects even when it was added at 4 hours post MPO. In mice, treatment with 15-epi-LXA 4 accelerated the resolution of established carrageenan plus MPOevoked as well as E. coli-induced neutrophil-dependent pulmonary inflammation through redirecting neutrophils to caspase-mediated cell death and facilitating their removal by macrophages.Conclusions: These results demonstrate that aspirin-triggered 15-epi-LXA 4 enhances resolution of inflammation by overriding the powerful antiapoptosis signal from MPO, thereby demonstrating a hitherto unrecognized mechanism by which aspirin promotes resolution of inflammation.

Abstract-Polymorphonuclear neutrophil granulocytes have a central role in innate immunity and their programmed cell death and removal are critical for efficient resolution of acute inflammation. Myeloperoxidase (MPO), a heme protein abundantly expressed in neutrophils, is generally associated with killing of bacteria and oxidative tissue injury. Because MPO also binds to neutrophils, we investigated whether MPO could affect the lifespan of neutrophils. Here, we report that MPO independent of its catalytic activity through signaling via the adhesion molecule CD11b/CD18 rescued human neutrophils from constitutive apoptosis and prolonged their life span. MPO evoked a transient concurrent activation of extracellular signal-regulated kinase and Akt, leading to phosphorylation of Bad at both Ser112 and Ser136, prevention of mitochondrial dysfunction, and subsequent activation of caspase-3. Consistently, pharmacological inhibition of extracellular signal-regulated kinase, Akt, or caspase-3 reversed the antiapoptosis action of MPO. Acute increases in plasma MPO delayed murine neutrophil apoptosis assayed ex vivo. In a mouse model of self-resolving inflammation, MPO also prolonged the duration of carrageenan-induced acute lung injury, as evidenced by enhanced alveolar permeability and accumulation of neutrophils parallel with suppression of neutrophil apoptosis.

Human neutrophil granulocytes die rapidly, and their survival is contingent upon rescue from programmed cell death by signals from the environment. Here we report that a novel signal for delaying neutrophil apoptosis is the classic acute phase reactant, C-reactive protein (CRP). However, this anti-apoptotic activity is expressed only when the cyclic pentameric structure of CRP is lost, resulting in formation of modified or monomeric CRP (mCRP), which may be formed in inflamed tissues. By contrast, native pentameric CRP and CRP peptides 77-82, 174 -185, and 201-206 failed to affect neutrophil apoptosis. The apoptosis delaying action of mCRP was markedly attenuated by an antibody against the low affinity IgG immune complex receptor (CD16) but not by an anti-CD32 antibody. mCRP evoked a transient concurrent activation of the extracellular signalregulated kinase (ERK) and phosphatidylinositol 3-kinase/Akt signaling pathways, leading to inhibition of caspase-3 and consequently to delaying apoptosis. Consistently, pharmacological inhibition of either ERK or Akt reversed the anti-apoptotic action of mCRP; however, they did not produce additive inhibition. Thus, mCRP, but not pentameric CRP or peptides derived from CRP, promotes neutrophil survival and may therefore contribute to amplification of the inflammatory response.

Myeloperoxidase (MPO), a heme protein abundantly expressed in the azurophilic granules in neutrophils generates cytotoxic oxidants and signals through the adhesion molecule CD11b/CD18 (Mac‐1) to activate and rescue neutrophils from apoptosis. Since aspirin‐triggered 15‐epi‐lipoxin A4 (15‐epi‐LXA4) inhibits Mac‐1‐mediated neutrophil adhesion, we studied its impact on MPO suppression of neutrophil apoptosis. Pretreatment of neutrophils with 15‐epi‐LXA4 or its metabolically stable analog 15‐epi‐16‐p‐fluorophenoxy‐LXA4 through downregulation of surface expression of Mac‐1 and inhibition of MPO release overcame the powerful anti‐apoptosis signal from MPO. 15‐epi‐LXA4 promoted apoptosis by attenuating MPO‐induced concurrent activation of ERK and phosphatidylinositol 3‐kinase/Akt‐mediated phosphorylation of Bad and reducing the expression of the anti‐apoptotic protein Mcl‐1. These led to collapse of mitochondrial transmembrane potential, cytochrome c release, resulting in increased caspase‐3 activity. The pro‐apoptotic action of 15‐epi‐LXA4 was predominant over MPO‐mediated effects even when 15‐epi‐LXA4 was added at 4‐hour post‐MPO. 15‐epi‐LXA4 did not inhibit the catalytic activity of MPO. Our results indicate that through overriding the MPO survival signal, aspirin‐triggered lipoxins may prevent neutrophil‐mediated tissue injury. (Grant support: CIHR MOP‐64283).

Objective-Deletion of Akt1 leads to severe atherosclerosis and occlusive coronary artery disease. Vascular smooth muscle cells (VSMCs) are an important component of atherosclerotic plaques, responsible for promoting plaque stability in advanced lesions. Fibrous caps of unstable plaques contain less collagen and ECM components and fewer VSMCs than caps from stable lesions. Here, we investigated the role of Akt1 in VSMC proliferation, migration, and oxidative stress-induced apoptosis. In addition, we also characterized the atherosclerotic plaque morphology and cardiac function in an atherosclerosis-prone mouse model deficient in Akt1. Methods and Results-Absence of Akt1 reduces VSMC proliferation and migration. Mechanistically, the proliferation and migratory phenotype found in Akt1-null VSMCs was linked to reduced Rac-1 activity and MMP-2 secretion. Serum starvation and stress-induced apoptosis was enhanced in Akt1 null VSMCs as determined by flow cytometry using Annexin V/PI staining. Immunohistochemical analysis of atherosclerotic plaques from Akt1 Ϫ/ϪApoEϪ/Ϫ mice showed a dramatic increase in plaque vulnerability characteristics such as enlarged necrotic core and reduced fibrous cap and collagen content. Finally, we show evidence of myocardial infarcts and cardiac dysfunction in Akt1 Ϫ/ϪApoEϪ/Ϫ mice analyzed by immunohistochemistry and echocardiography, respectively. Conclusion-Akt1 is essential for VSMC proliferation, migration, and protection against oxidative stress-induced apoptosis. Absence of Akt1 induces features of plaque vulnerability and cardiac dysfunction in a mouse model of atherosclerosis.