Background-Mice

Chronic granulomatous disease (CGD) is characterized by overexuberant inflammation and autoimmunity that are attributed to deficient anti-inflammatory signaling. Although regulation of these processes is complex, phosphatidylserine (PS)-dependent recognition and removal of apoptotic cells (efferocytosis) by phagocytes are potently anti-inflammatory. Since macrophage phenotype also plays a beneficial role in resolution of inflammation, we hypothesized that impaired efferocytosis in CGD due to macrophage skewing contributes to enhanced inflammation. Here we demonstrate that efferocytosis by macrophages from CGD (gp91 phox؊/؊ ) mice was suppressed ex vivo and in vivo. Alternative activation with interleukin 4 (IL-4) normalized CGD macrophage efferocytosis, whereas classical activation by lipopolysaccharide (LPS) plus interferon ␥ (IFN␥) had no effect. Importantly, neutralization of IL-4 in wildtype macrophages reduced macrophage efferocytosis, demonstrating a central role for IL-4. This effect was shown to involve 12/15 lipoxygenase and activation of peroxisome-proliferator activated receptor ␥ (PPAR␥). Finally, injection of PS (whose exposure is lacking on CGD apoptotic neutrophils) in vivo restored IL-4-dependent macrophage reprogramming and efferocytosis via a similar mechanism. Taken together, these findings support the hypothesis that impaired PS exposure on dying cells results in defective macrophage programming, with consequent efferocytic impairment and has important implications in understanding the underlying cause of enhanced inflammation in

Mitochondria are inherited maternally in most animals, but the mechanisms of selective paternal mitochondrial elimination (PME) are unknown. While examining fertilization in C. elegans, we observe that paternal mitochondria rapidly lose their inner membrane integrity. CPS-6, a mitochondrial endonuclease G, serves as a paternal mitochondrial factor that is critical for PME. The CPS-6 endonuclease relocates from the intermembrane space of paternal mitochondria to the matrix following fertilization to degrade mitochondrial DNA. It acts with maternal autophagy and proteasome machineries to promote PME. Loss of cps-6 delays breakdown of mitochondrial inner membranes, autophagosome enclosure of paternal mitochondria, and PME. Delayed removal of paternal mitochondria causes increased embryonic lethality, demonstrating that PME is important for normal animal development. Thus, CPS-6 functions as a paternal mitochondrial degradation factor during animal development.

Objective Platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31) has recently been shown to form an essential element of a mechanosensory complex that mediates endothelial responses to fluid shear stress. The aim of this study was to determine the in vivo role of PECAM-1 in atherosclerosis. Methods and Results We crossed C57BL/6 Pecam1−/− mice with apolipoprotein E–deficient (Apoe−/−) mice. On a Western diet, Pecam1−/−Apoe−/− mice showed reduced atherosclerotic lesion size compared to Apoe−/− mice. Striking differences were observed in the lesser curvature of the aortic arch, an area of disturbed flow, but not in the descending thoracic or abdominal aorta. Vascular cell adhesion molecule-1 (VCAM-1) expression, macrophage infiltration, and endothelial nuclear NF-κB were all reduced in Pecam1−/−Apoe−/− mice. Bone marrow transplantation suggested that endothelial PECAM-1 is the main determinant of atherosclerosis in the aortic arch, but that hematopoietic PECAM-1 promotes lesions in the abdominal aorta. In vitro data show that siRNA-based knockdown of PECAM-1 attenuates endothelial NF-κB activity and VCAM-1 expression under conditions of atheroprone flow. Conclusion These results indicate that endothelial PECAM-1 contributes to atherosclerotic lesion formation in regions of disturbed flow by regulating NF-κB–mediated gene expression.

Background-T lymphocytes are thought to be important in atherosclerosis, but very little is known about the mechanisms of lymphocyte recruitment into atherosclerosis-prone aortas. In this study we tested the hypothesis that CXCR6, a chemokine receptor that is expressed on a subset of CD4 ϩ T helper 1 cells and natural killer T cells, is involved in lymphocyte homing into the aortic wall and modulates the development and progression of atherosclerosis. Methods and Results-To investigate the role of CXCR6 in the development and progression of atherosclerosis, we bred CXCR6-deficient (CXCR6 GFP/GFP ) mice with apolipoprotein E-deficient (ApoE Ϫ/Ϫ ) mice. We found that CXCR6 Key Words: atherosclerosis Ⅲ immune system Ⅲ leukocytes Ⅲ lymphocytes Ⅲ vessels A therosclerotic lesions are characterized by lipid accumulation, cell death, fibrosis, and chronic vascular inflammation. 1 The body of evidence is growing that T and B lymphocytes, dendritic cells, and macrophages reside within the noninflamed aortic wall, and a significant influx of macrophages and T cells correlates with the development and progression of atherosclerosis. [2][3][4] The molecular mechanisms, kinetics of trafficking, and retention of different types of immune cells within the noninflamed and atherosclerosisprone aortic wall are not well defined. Most of the focus to date has been on the ability of monocytes to migrate to the atherosclerotic wall. 5 P-selectin, vascular cell adhesion molecule-1 (VCAM-1), P-selectin glycoprotein ligand-1 (PSGL-1), and ␣ 4 ␤ 1 integrin (VLA-4) are all involved in monocyte recruitment into atherosclerotic plaques, 6 and the chemokines CCL5 (regulated on activation, normal T cell expressed and secreted [RANTES]) and CXCL1 (keratinocyte-derived chemokine [KC]) are responsible for triggering monocyte adhesion on the atherosclerotic endothelium. [7][8][9] Lymphocyte trafficking into normal and atherosclerotic aortas is partially L-selectin dependent, 2 but little is known about other potential molecular mechanisms of lymphocyte recruitment. Clinical Perspective p 1811CXCR6 is a chemokine receptor expressed on some T helper 1 (Th1) and natural killer T (NKT) cells found in rheumatoid joints and inflamed livers. 10 CXCR6, also known as Bonzo/STRL33/TYMSTR, 11 is expressed on subpopulations of CD4 ϩ effector memory T cells, 10 on V␣ 24 ϩ NKT cells, 12,13 a Forkhead Box P3 The disintegrin and metalloproteinase ADAM10 is involved in CXCL16 cleavage from the cell membrane, 21 leading to the release of a soluble protein that functions as a chemoattractant for responsive leukocytes.In addition to its properties as a chemokine, CXCL16 acts also as a scavenger receptor for apoptotic cells, phosphatidylserine, and oxidized low-density lipoprotein. 16,19 Expression of CXCL16 has been reported in atherosclerosis-prone vessels from apolipoprotein-E-deficient (ApoE Ϫ/Ϫ ) mice 23 and human atherosclerotic plaques. 24 Absence of CXCL16 has been shown to accelerate atherosclerosis, enhance macrophage recruitment, and elevate mRNA levels for...

Infection with the hepatitis B virus (HBV) promotes the development of hepatitis, cirrhosis, and hepatocellular carcinoma (HCC) and is a leading cause of morbidity and mortality worldwide. HBV X protein (HBx) is an important effector for HBV pathogenesis, but its cellular targets and acting mechanisms remain elusive. We show here that HBx interacts with the anti-apoptotic proteins Bcl-2 and Bcl-xL through a Bcl-2 homology 3 (BH3)-like motif in mammalian cells. Importantly, mutations in the BH3-like motif that prevent HBx binding to Bcl-2 and Bcl-xL abrogate cytosolic calcium elevation and cell death induced by HBx expression in hepatocytes and severely impair HBV viral replication, which can be substantially rescued by restoring cytosolic calcium. These results suggest that HBx binding to Bcl-2 family members and subsequent elevation of cytosolic calcium are important for HBV viral replication. Consistently, RNAi knockdown of Bcl-2 or Bcl-xL results in reduced calcium elevation by HBx and decreased viral replication in hepatocytes. Our results suggest that HBx targets Bcl-2 proteins through its BH3-like motif to promote cytosolic calcium elevation, cell death, and viral replication during HBV pathogenesis, which presents an excellent therapeutic intervention point in treating patients with chronic HBV.calcium signaling | apoptosis | necrosis

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HBx is a multifunctional hepatitis B virus (HBV) protein that is crucial for HBV infection and pathogenesis and a contributing cause of hepatocyte carcinogenesis. However, the host targets and mechanisms of action of HBx are poorly characterized. We show here that expression of HBx in Caenorhabditis elegans induces both necrotic and apoptotic cell death, mimicking an early event of liver infection by HBV. Genetic and biochemical analyses indicate that HBx interacts directly with the B-cell lymphoma 2 (Bcl-2) homolog CED-9 (cell death abnormal) through a Bcl-2 homology 3 (BH3)-like motif to trigger both cytosolic Ca 2+ increase and cell death. Importantly, Bcl-2 can substitute for CED-9 in mediating HBx-induced cell killing in C. elegans, suggesting that CED-9 and Bcl-2 are conserved cellular targets of HBx. A genetic suppressor screen of HBx-induced cell death has produced many mutations, including mutations in key regulators from both apoptosis and necrosis pathways, indicating that this screen can identify new apoptosis and necrosis genes. Our results suggest that C. elegans could serve as an animal model for identifying crucial host factors and signaling pathways of HBx and aid in development of strategies to treat HBV-induced liver disorders.