Apoptosis Signal–Regulating Kinase 1 Deficiency Accelerates Hyperlipidemia-Induced Atheromatous Plaques via Suppression of Macrophage Apoptosis

Major Vault Protein Prevents Atherosclerotic Plaque Destabilization by Suppressing Macrophage ASK1-JNK Signaling

BACKGROUND

Macrophages are implicated in atherosclerotic plaque instability by inflammation and degradation of extracellular matrix. However, the regulatory mechanisms driving these macrophage-associated processes are not well understood. Here, we aimed to identify the plaque destabilization-associated cytokines and signaling pathways in macrophages.

METHODS

The atherosclerotic models of myeloid-specific MVP (major vault protein) knockout mice and control mice were generated. Atherosclerotic instability, macrophage inflammatory signaling, and active cytokines released by macrophages were examined in vivo and in vitro by using cellular and molecular biological approaches.

RESULTS

MVP deficiency in myeloid cells exacerbated murine plaque instability by increasing production of both MMP (matrix metallopeptidase)-9 and proinflammatory cytokines in artery wall. Mechanistically, expression of MMP-9 was mediated via ASK1 (apoptosis signal-regulating kinase 1)-MKK-4 (mitogen-activated protein kinase kinase 4)-JNK (c-Jun N-terminal kinase) signaling in macrophages. MVP and its α-helical domain could bind with ASK1 and inhibit its dimerization and phosphorylation. A 62 amino acid peptide (MVP-[686-747]) in the α-helical domain of MVP showed a crucial role in preventing macrophage MMP-9 production and plaque instability.

CONCLUSIONS

MVP may act as an inhibitor for ASK1-JNK signaling-mediated MMP-9 production in macrophages and, thereby, attenuate unstable plaque formation. Our findings suggest that suppression of macrophage ASK1-JNK signaling may be a useful strategy antagonizing atherosclerotic diseases.

Guan Xin Dan Shen formulation protects db/db mice against diabetic cardiomyopathy via activation of Nrf2 signaling

Guan Xin Dan Shen formulation (GXDSF) is a widely used treatment for the management of coronary heart disease in China and is composed of three primary components: Dalbergiae odoriferae Lignum, Salviae miltiorrhizae Radix et Rhizoma and Panax notoginseng Radix et Rhizoma. However, the potential use of GXDSF for the management of diabetic cardiomyopathy (DCM) has not been previously assessed. The present study aimed to assess the effects of GXDSF on DCM, as well as the underlying mechanism. In the present study, db/db mice were used. Following treatment with GXDSF for 10 weeks, fasting blood glucose, insulin sensitivity, serum lipid levels and cardiac enzyme levels were detected. Cardiac pathological alterations and cardiac function were assessed by performing hematoxylin and eosin staining and echocardiograms, respectively. TUNEL assays were conducted to assess cardiomyocyte apoptosis. Additionally, reverse transcription‑quantitative PCR and western blotting were performed to evaluate the expression of apoptosis‑associated genes and proteins, respectively. In the model group, the db/db mice displayed obesity, hyperlipidemia and hyperglycemia, accompanied by noticeable myocardial hypertrophy and diastolic dysfunction. Following treatment with GXDSF for 10 weeks, serum triglyceride levels were lower and insulin sensitivity was enhanced in db/db mice compared with the model group, which indicated improvement in condition. Cardiac hypertrophy and dysfunction were also improved in db/db mice following treatment with GXDSF, resulting in significantly increased left ventricular ejection fraction and fractional shortening compared with the model group. Following treatment with metformin or GXDSF, model‑induced increases in levels of myocardial enzymes were decreased in the moderate and high dose groups. Moreover, the results indicated that, compared with the model group, GXDSF significantly inhibited cardiomyocyte apoptosis in diabetic heart tissues by increasing Bcl‑2 expression and decreasing the expression levels of Bax, cleaved caspase‑3 and cleaved caspase‑9. Mechanistically, GXDSF enhanced Akt phosphorylation, which upregulated antioxidant enzymes mediated by nuclear factor erythroid 2‑related factor 2 (Nrf2) signaling. Collectively, the results of the present study indicated that GXDSF attenuated cardiac dysfunction and inhibited cardiomyocyte apoptosis in diabetic mice via activation of Akt/Nrf2 signaling. Therefore, GXDSF may serve as a potential therapeutic agent for the management of DCM.

Outside-in signaling by femoral cuff injury induces a distinct vascular lesion in adipose triglyceride lipase knockout mice

Genetic deficiency of adipose triglyceride lipase (ATGL), a rate-limiting enzyme for intracellular triglyceride (TG) hydrolysis, causes TG-deposit cardiomyovasculopathy (TGCV), a recently identified rare cardiovascular disorder (ORPHA code: 565612) in humans. One of the major characteristics of TGCV is a novel type of diffuse and concentric coronary atherosclerosis with ATGL-deficient smooth muscle cells (SMCs). Patients with TGCV have intractable coronary artery disease. Therefore, it is crucial to investigate the mechanisms underlying vascular lesions in ATGL deficiency using animal models. Cuff injury is an experimental procedure to induce vascular remodeling with neointimal formation with SMCs after placing a cuff around the adventitial side of the artery without direct influence on endothelium. We report the effect of cuff injury on femoral arteries of ATGL-knockout (ATGL⁻/⁻) mice. Cuff-induced concentric neointimal formation with migrating SMCs was exacerbated in ATGL⁻/⁻ mice, mimicking atherosclerotic lesions in patients with TGCV. In the media, cell death of SMCs and loss of elastic fibers increased. Perivascular infiltrating cells expressing tumor necrosis factor-α (TNF-α) were more prominent in ATGL⁻/⁻ mice than in wild-type (WT) mice. In Boyden chamber experiments, a greater number of ATGL⁻/⁻ SMCs migrated in response to TNF-α compared to WT SMCs. These data, for the first time, demonstrated that outside-in signaling by cuff-induced neointimal formation where paracrine stimuli from adventitial infiltrating cells may lead to neointimal formation and mediolysis in ATGL-deficient conditions. Cuff injury might be a valuable model for understanding the mechanisms underlying the development of atherosclerotic lesions in patients with TGCV.

Targeted invalidation of SR-B1 in macrophages reduces macrophage apoptosis and accelerates atherosclerosis

AIMS

SR-B1 is a cholesterol transporter that exerts anti-atherogenic properties in liver and peripheral tissues in mice. Bone marrow (BM) transfer studies suggested an atheroprotective role in cells of haematopoietic origin. Here, we addressed the specific contribution of SR-B1 in the monocyte/macrophage.

METHODS AND RESULTS

We generated mice deficient for SR-B1 in monocytes/macrophages (Lysm-Cre × SR-B1f/f) and transplanted their BM into Ldlr-/- mice. Fed a cholesterol-rich diet, these mice displayed accelerated aortic atherosclerosis characterized by larger macrophage-rich areas and decreased macrophage apoptosis compared with SR-B1f/f transplanted controls. These findings were reproduced in BM transfer studies using another atherogenic mouse recipient (SR-B1 KOliver × Cholesteryl Ester Transfer Protein). Haematopoietic reconstitution with SR-B1-/- BM conducted in parallel generated similar results to those obtained with Lysm-Cre × SR-B1f/f BM; thus suggesting that among haematopoietic-derived cells, SR-B1 exerts its atheroprotective role primarily in monocytes/macrophages. Consistent with our in vivo data, free cholesterol (FC)-induced apoptosis of macrophages was diminished in the absence of SR-B1. This effect could not be attributed to differential cellular cholesterol loading. However, we observed that expression of apoptosis inhibitor of macrophage (AIM) was induced in SR-B1-deficient macrophages, and notably upon FC-loading. Furthermore, we demonstrated that macrophages were protected from FC-induced apoptosis by AIM. Finally, AIM protein was found more present within the macrophage-rich area of the atherosclerotic lesions of SR-B1-deficient macrophages than controls.

CONCLUSION

Our findings suggest that macrophage SR-B1 plays a role in plaque growth by controlling macrophage apoptosis in an AIM-dependent manner.

Induction of HLA-A2 restricted CD8 T cell responses against ApoB100 peptides does not affect atherosclerosis in a humanized mouse model

Cardiovascular diseases form the most common cause of death worldwide, with atherosclerosis as main etiology. Atherosclerosis is marked by cholesterol rich lipoprotein deposition in the artery wall, evoking a pathogenic immune response. Characteristic for the disease is the pathogenic accumulation of macrophages in the atherosclerotic lesion, which become foam cells after ingestion of large quantities of lipoproteins. We hypothesized that, by inducing a CD8 T cell response towards lipoprotein derived apolipoprotein-B100 (ApoB100), lesional macrophages, that are likely to cross-present lipoprotein constituents, can specifically be eliminated. Based on in silico models for protein processing and MHC-I binding, 6 putative CD8 T cell epitopes derived from ApoB100 were synthesized. HLA-A2 binding was confirmed for all peptides by T2 cell binding assays and recall responses after vaccination with the peptides proved that 5 of 6 peptides could induce CD8 T cell responses. Induction of ApoB100 specific CD8 T cells did not impact plaque size and cellular composition in HLA-A2 and human ApoB100 transgenic LDLr^−/− mice. No recall response could be detected in cultures of cells isolated from the aortic arch, which were observed in cell cultures of splenocytes and mesenteric lymph nodes, suggesting that the atherosclerotic environment impairs CD8 T cell activation.

Depletion of WNT10A Prevents Tumor Growth by Suppressing Microvessels and Collagen Expression

Background: We recently reported that WNT10A plays a pivotal role in wound healing by regulating collagen expression/synthesis, as the depletion of WNT10A dramatically delays skin ulcer formation. WNT signaling also has a close correlation with the cancer microenvironment and proliferation, since tumors are actually considered to be 'unhealing' or 'overhealing' wounds. To ascertain the in vivo regulatory functions of WNT10A in tumor growth, we examined the net effects of WNT10A depletion using Wnt10a-deficient mice (Wnt10a ^-/-). Methods and Results: We subjected C57BL/6J wild-type (WT) or Wnt10a ^-/- mice to murine melanoma B16-F10 cell transplantation. Wnt10a ^-/- mice showed a significantly smaller volume of transplanted melanoma as well as fewer microvessels and less collagen expression and more necrosis than WT mice. Conclusions: Taken together, our observations suggest that critical in vivo roles of Wnt10a-depleted anti-stromagenesis prevent tumor growth, in contrast with true wound healing/scarring.

Critical in vivo roles of WNT10A in wound healing by regulating collagen expression/synthesis in WNT10A-deficient mice

Background

We have reported that WNT10A plays a critical role in the growth of fibroblasts/myofibroblasts and microvascular endothelial cells, i.e.; wound healing/scarring. To ascertain the in vivo regulatory, central functions of WNT10A, we examined the net effects of WNT10A depletion using WNT10A-deficient mice (WNT10A^–/–).

Methods and results

We generated WNT10A^–/–mice, displaying a range of unique phenotypes of morpho/organogenetic failure, such as growth retardation, alopecia, kyphosis and infertility, and then focused on the functions of WNT10A in wound healing. We subjected C57BL/6J wild-type (WT) or WNT10A^–/–mice to skin ulcer formation. The WNT10A^–/–mice had significantly larger injured areas and delayed wound healing, which were associated with (a) a smaller number of fibroblasts/myofibroblasts and microvessels; and (b) more reduced expression and synthesis of collagen, compared with WT mice with intact WNT10A expression, especially in those with activated myofibroblasts.

Conclusions

These observations indicate that WNT10A signaling can play a pivotal in vivo role in wound healing by regulating the expression and synthesis of collagen, as one of fibrogenic factors, at least in part, and critical in vivo roles of WNT10A-mediated effective wound healing are extremely closely associated with collagen expression.

ASK family in cardiovascular biology and medicine

Cardiovascular disease is a major cause of death worldwide. Mitogen-activated protein kinase (MAPK) signal cascades signaling pathways play crucial roles in cardiovascular pathophysiology. Apoptosis signal-regulating kinase (ASK) family members ASK1, ASK2 and ASK3 are the key molecules in MAPK signal cascades and are activated by various stresses. ASK1 is the most extensively studied MAPKKK and is involved in regulation of the cellular functions such as cell survival, proliferation, inflammation and apoptosis. The current review focuses on the relationship between ASK1 and cardiovascular disease, while exploring the novel therapeutic strategies for cardiovascular disease involved in the ASK1 signal pathway.

Association of Platelet to lymphocyte ratio with non-culprit atherosclerotic plaque vulnerability in patients with acute coronary syndrome: an optical coherence tomography study

Background

The platelet to lymphocyte ratio (PLR), an indirect inflammatory biomarker, has been recently demonstrated to be associated with severity of coronary artery disease. In the present study, we sought to investigate whether PLR is associated with vulnerable plaque characteristics of non-culprit lesions in patients with acute coronary syndrome (ACS).

Methods

The patients in our study were divided into two groups (high PLR group and low PLR group). A total of 119 non-culprit plaques from 71 patients with ACS were assessed by optical coherence tomography (OCT).

Results

The non-culprit plaques in high PLR group exhibited thinner fibrous cap thickness (FCT) (88.60 ± 44.70 vs. 119.28 ± 50.22 μm, P = 0.001), greater maximum lipid arc (271.73 ± 71.66 vs. 240.60 ± 76.69°, P = 0.027) and increased incidence of thin-cap fibroatheroma (TCFA) (34.0% vs. 15.9%, P = 0.022) compared with those in low PLR group. Meanwhile, PLR was negatively associated with FCT (r = −0.329, P < 0.001). Furthermore, multivariate regression analysis showed that PLR [OR: 1.023 (95% CI: 1.005–1.041), P = 0.012] and LDL-C [OR: 1.892 (95% CI: 1.106–3.239), P = 0.020] were significant predictors of TCFA.

Conclusions

High level of PLR may be associated with vulnerable plaque features of non-culprit lesions in patients with ACS. PLR, a cheap and easily available index, may surve as a useful inflammatory marker in reflecting plaque vulnerability.

FADD, Caspase-3, and Caspase-8 and Incidence of Coronary Events

Objective—

To investigate the relationship between 3 markers of apoptosis, that is, FADD (Fas-associated death domain–containing protein), caspase-3, and caspase-8, and incidence of coronary events (CEs) in a population-based cohort study.

Approach and Results—

In vitro experiments were performed to assess the response of the apoptotic biomarkers after Fas stimulation of peripheral blood mononuclear cells. The experiments showed significantly increased releases of FADD, caspase-3, and caspase-8 after Fas stimulation. The relationship between FADD, caspase-3, and caspase-8, respectively, and incidence of CEs was studied in 4284 subjects from the population-based Malmö Diet and Cancer Study. Cox’ proportional hazards regression was used to examine the association between the apoptotic biomarkers and incidence of CE over a mean follow-up of 19 years. A total of 381 individuals had CE during the follow-up. High FADD at baseline was significantly associated with incident CE. In the highest compared with the lowest quartile of FADD, the risk factor adjusted hazards ratio for CE was 1.82 (95% confidence interval, 1.35–2.46; P for trend <0.001). A significant association was also found between caspase-8 and CE; the hazards ratio (Q4 versus Q1) was 1.90 (95% confidence interval, 1.39–2.60; P for trend <0.001) after adjustment for risk factors. No association was found between caspase-3 and CEs.

Conclusions—

High levels of FADD and caspase-8, but not caspase-3, were associated with increased incidence of CE in subjects from the general population. The in vitro experiments support the view that these biomarkers could reflect activation of the extrinsic apoptotic pathway.

Macrophage Apoptosis and Necrotic Core Development in Atherosclerosis: A Rapidly Advancing Field with Clinical Relevance to Imaging and Therapy

Cardiovascular diseases represent 1 of the main causes of death worldwide, and atherosclerosis is 1 of the major contributors leading to ischemic heart disease. Macrophages actively participate in all stages of atherosclerosis development, from plaque initiation to the transition to vulnerable plaques. Macrophage apoptosis, in particular, has been recognized as a critical step in the formation of the necrotic core, a key characteristic of unstable lesions. In this review, we discuss the role of macrophage apoptosis and clearance of apoptotic cells by efferocytosis in the development of atherosclerosis, with particular emphasis on their contribution to the development of the necrotic core and the clinical implications of this process for plaque stabilization. We consider the molecular triggers of macrophage apoptosis during atherogenesis, the role of endoplasmic reticulum (ER) stress, the roles of key cellular mediators of apoptosis and efferocytosis, and mechanisms of defective efferocytosis in the progression of atherosclerotic plaques. Finally, we discuss the important clinical implications of rapidly evolving macrophage science, such as novel approaches to imaging vulnerable atherosclerotic plaques with macrophage-sensitive positron emission tomography and magnetic resonance imaging, the role of macrophages in mediating beneficial pleiotropic actions of lipid-lowering therapies, and novel therapeutic modalities targeting ER stress, autophagy, and deficient efferocytosis. Advances in understanding the critical role of macrophages in the progression and destabilization of atherosclerosis have the potential to greatly improve the prevention and management of atherosclerotic diseases over the next decade.

Critical in vivo roles of histamine and histamine receptor signaling in animal models of metabolic syndrome

Histamine, a classic low-molecular-weight amine, is synthesized from L-histidine by histidine decarboxylase (HDC), and histamine-specific receptors (HRs) are essential for its actions. Our serial in vivo studies have uniquely reported that expression of histamine/HRs is variably identified in atherosclerotic lesions, and that HDC-gene knockout mice without histamine/HRs signaling show a marked reduction of atherosclerotic progression. These data have convinced us that histamine plays a pivotal role in the pathogenesis of atherosclerosis. Among four subclasses of HRs, the expression profile of the main receptors (H1/2R) has been shown to be switched from H2R to H1R during monocyte to macrophage differentiation, and H1R is also predominant in smooth muscle and endothelial cells of atheromatous plaque. Using various animal models of H1/2R-gene knockout mice, H1R and H2R were found to reciprocally but critically regulate not only hypercholesterolemia-induced atherosclerosis and injury-induced arteriosclerosis, but also hyperlipidemia-induced nonalcoholic fatty liver disease (NAFLD). Metabolic syndrome manifests obesity, dyslipidemia, insulin resistance, atherosclerosis, and/or NAFLD, i.e. the dysregulation of lipid/bile acid/glucose metabolism. Therefore, although its etiology is complicated and multifactorial, histamine/HRs signaling has a close relationship with the development of metabolic syndrome. We herein review diverse, key in vivo roles of histamine/HR signaling in the pathogenesis of metabolic syndrome.

Jnk1 Deficiency in Hematopoietic Cells Suppresses Macrophage Apoptosis and Increases Atherosclerosis in Low-Density Lipoprotein Receptor Null Mice

OBJECTIVE

The c-Jun NH2-terminal kinases (JNK) are regulated by a wide variety of cellular stresses and have been implicated in apoptotic signaling. Macrophages express 2 JNK isoforms, JNK1 and JNK2, which may have different effects on cell survival and atherosclerosis.

APPROACH AND RESULTS

To dissect the effect of macrophage JNK1 and JNK2 on early atherosclerosis, Ldlr(-/-) mice were reconstituted with wild-type, Jnk1(-/-), and Jnk2(-/-) hematopoietic cells and fed a high cholesterol diet. Jnk1(-/-)→Ldlr(-/-) mice have larger atherosclerotic lesions with more macrophages and fewer apoptotic cells than mice transplanted with wild-type or Jnk2(-/-) cells. Moreover, genetic ablation of JNK to a single allele (Jnk1(+/-)/Jnk2(-/-) or Jnk1(-/-)/Jnk2(+/-)) in marrow of Ldlr(-/-) recipients further increased atherosclerosis compared with Jnk1(-/-)→Ldlr(-/-) and wild-type→Ldlr(-/-) mice. In mouse macrophages, anisomycin-mediated JNK signaling antagonized Akt activity, and loss of Jnk1 gene obliterated this effect. Similarly, pharmacological inhibition of JNK1, but not JNK2, markedly reduced the antagonizing effect of JNK on Akt activity. Prolonged JNK signaling in the setting of endoplasmic reticulum stress gradually extinguished Akt and Bad activity in wild-type cells with markedly less effects in Jnk1(-/-) macrophages, which were also more resistant to apoptosis. Consequently, anisomycin increased and JNK1 inhibitors suppressed endoplasmic reticulum stress-mediated apoptosis in macrophages. We also found that genetic and pharmacological inhibition of phosphatase and tensin homolog abolished the JNK-mediated effects on Akt activity, indicating that phosphatase and tensin homolog mediates crosstalk between these pathways.

CONCLUSIONS

Loss of Jnk1, but not Jnk2, in macrophages protects them from apoptosis, increasing cell survival, and this accelerates early atherosclerosis.

Clopidogrel reduces apoptosis and promotes proliferation of human vascular endothelial cells induced by palmitic acid via suppression of the long non-coding RNA HIF1A-AS1 in vitro

Cardiovascular disease (CVD) is recognized as a major and increasing health problem affected older subjects in China, and clopidogrel has been widely used for treatment of CVD patients such as atherosclerosis, myocardial infarction, and myocardial ischaemia-reperfusion damage. However, the molecular mechanisms of clopidogrel for treatment of CVD are only partially understood. This study investigated the effects of clopidogrel on palmitic acid-induced damage of human vascular endothelial cells (HUVECs), and the molecular mechanisms of LncRNA HIF1A-AS1 in regulating the proliferation and apoptosis of HUVECs in vitro. We firstly established a damage model of HUVECs through palmitic acid (PA) treatment. And the effect of clopidogrel reducing PA-induced apoptosis of HUVECs was observed by the flow cytometric measurement. To further understand the molecular mechanism of clopidogrel rescues PA-induced apoptosis, we used human LncRNA PCR array to compare the LncRNA expression profile difference between clopidogrel-treated cells and control cells. The expression of LncRNA HIF 1 alpha-antisense RNA 1 (HIF1A-AS1) was significantly altered in clopidogrel-treated cells. We further proved that suppression of HIF1A-AS1 by siRNA reduce PA-induced apoptosis and promote proliferation of HUVECs. Furthermore, we also demonstrated inhibition apoptosis effect by HIF1A-AS1 is related to mitochondrial apoptosis pathway. Hence, our results suggest that clopidogrel rescues apoptosis and promotes proliferation of PA-induced damage model of HUVECs through inhibiting the mediator LncRNA HIF1A-AS1. These findings indicate that LncRNA HIF1A-AS1 may play an important role in the pathogenesis of CVD, and provide a novel molecular mechanism of clopidogrel for treatment of CVD.

CCL22/Macrophage-derived Chemokine Expression in Apolipoprotein E-deficient Mice and Effects of Histamine in the Setting of Atherosclerosis

AIM

Macrophage-derived chemokine (CCL22) is a member of the CC-family of chemokines synthesized by monocyte-derived macrophages. Previous studies have reported a relationship between CCL22 and atherosclerosis and the role of histamine in this pathway. Histamine ncreases the CCL22 expression in human monocytes via the H2 receptor. In this study, we investigated the effects of CCL22 and the role of histamine in mouse monocytes with respect to atherosclerosis.

METHODS AND RESULTS

The expression of CCL22 was investigated in apolipoprotein E (apoE)-deficient mice. The mice had high serum concentrations of CCL22 and their atherosclerotic lesions contained abundant levels of CCL22. In addition, when the mouse monocyte cell line (J774A.1 cells) differentiated into macrophage-like cells, the cells showed a similar expression of CCL22 and reduced expression of H2 receptors. Histamine is synthesized from l-histidine by histidine decarboxylase (HDC) in a single enzymatic step. HDC knockout mice were compared with apoE/HDC double knockout mice. The findings indicated that the expression of CCL22 in atherosclerosis models is under the influence of histamine. In addition, in vitro studies using J774A.1 cells and an in vivo study using histamine receptor knockout mice showed that histamine stimulates the CCL22 expression via the histamine H2 receptor.

CONCLUSIONS

The current results support our previous CCL22 studies in the setting of human atherosclerosis and suggest that this molecule is involved in the atherogenic processes in a mouse model of atherosclerosis.

Marine hydroquinone zonarol prevents inflammation and apoptosis in dextran sulfate sodium-induced mice ulcerative colitis

BACKGROUND AND AIM

We previously identified an anti-inflammatory compound, zonarol, a hydroquinone isolated from the brown algae Dictyopteris undulata as a marine natural product. To ascertain the in vivo functions of zonarol, we examined the pharmacological effects of zonarol administration on dextran sulfate sodium (DSS)-induced inflammation in a mouse model of ulcerative colitis (UC). Our goal is to establish a safe and effective cure for inflammatory bowel disease (IBD) using zonarol.

METHODS AND RESULTS

We subjected Slc:ICR mice to the administration of 2% DSS in drinking water for 14 days. At the same time, 5-aminosalicylic acid (5-ASA) at a dose of 50 mg/kg (positive control) and zonarol at doses of 10 and 20 mg/kg, were given orally once a day. DSS-treated animals developed symptoms similar to those of human UC, such as severe bloody diarrhea, which were evaluated by the disease activity index (DAI). Treatment with 20 mg/kg of zonarol, as well as 5-ASA, significantly suppressed the DAI score, and also led to a reduced colonic ulcer length and/or mucosal inflammatory infiltration by various immune cells, especially macrophages. Zonarol treatment significantly reduced the expression of pro-inflammatory signaling molecules, and prevented the apoptosis of intestinal epithelial cells. Finally, zonarol protected against in vitro lipopolysaccharide (LPS)-induced activation in the RAW264.7 mouse macrophage cell line.

CONCLUSIONS

This is the first report that a marine bioproduct protects against experimental UC via the inhibition of both inflammation and apoptosis, very similar to the standard-of-care sulfasalazine, a well-known prodrug that releases 5-ASA. We believe that the oral administration of zonarol might offer a better treatment for human IBDs than 5-ASA, or may be useful as an alternative/additive therapeutic strategy against UC, without any evidence of side effects.

Subcellular localization of DAXX influence ox-LDL induced apoptosis in macrophages

Here we aimed to evaluate the effects of DAXX subcellular localization on ox-LDL induced macrophages apoptosis. Cytoplasmic localization vector DAXX-W621A and nuclear localization vector DAXX-S667A were constructed by point mutation in DAXX. Blank vector, full length DAXX, DAXX-W621A, DAXX-S667A was transfect into RAW264.7 cells, respectively. Then the cells were incubated with 100 mg/ml ox-LDL for 48 h. Immunofluorescent assay was used to assay the localization of DAXX. MTT and Flow cytometry was used to determine cellular viability and apoptosis. RT-PCR and Western blot were used to analyze the expression levels. A significantly increased expression of DAXX was found in transfected cells of DAXX. The content of DAXX in nucleus was significantly increased in DAXX(S667A), and DAXX was significantly increased in cytoplasm of DAXX(W621A). Besides, we found DAXX was mainly expressed in nucleus with a low-level expression in cytoplasm through immunofluorescence. However in DAXX(W621A) group, the DAXX began to transferred to cytoplasm, which exhibited significant florescence. After treated with ox-LDL, the cytoactive of DAXX-W621A exhibited significantly decreased level when compared DAXX group. However, after added inhibitor LMB, the inhibition was relieved. The cell viability was also significantly increased in DAXX-S667A group. The results of apoptosis rates were similar in each group. Furthermore, we found the expression of ASK1 and JNK was also consistent with the apoptosis rates. Cytoplasmic localization of DAXX can increase injury sensitivity of ox-LDL on cells, and nuclear localization can antagonise the effect of ox-LDL. Besides, it is certified ox-LDL induced apoptosis is mainly through ASK1-JNK pathway.

Histamine receptors expressed in circulating progenitor cells have reciprocal actions in ligation-induced arteriosclerosis

Histamine is synthesized as a low-molecular-weight amine from L-histidine by histidine decarboxylase (HDC). Recently, we demonstrated that carotid artery-ligated HDC gene-deficient mice (HDC(-/-)) showed less neointimal formation than wild-type (WT) mice, indicating that histamine participates in the process of arteriosclerosis. However, little is known about the roles of histamine-specific receptors (HHRs) in arteriosclerosis. To define the roles of HHRs in arteriosclerosis, we investigated intimal remodeling in ligated carotid arteries of HHR-deficient mice (H1R(-/-) or H2R(-/-)). Quantitative analysis showed that H1R(-/-) mice had significantly less arteriosclerogenesis, whereas H2R(-/-) mice had more, as compared with WT mice. Bone marrow transplantation from H1R(-/-) or H2R(-/-) to WT mice confirmed the above observation. Furthermore, the increased expression of monocyte chemoattractant protein (MCP-1), platelet-derived growth factor (PDGF), adhesion molecules and liver X receptor (LXR)-related inflammatory signaling factors, including Toll-like receptor (TLR3), interleukin-1 receptor (IL-1R) and tumor necrosis factor receptor (TNF-R), was consistent with the arteriosclerotic phenotype of H2R(-/-) mice. Peripheral progenitor cells in H2R(-/-) mice accelerate ligation-induced arteriosclerosis through their regulation of MCP-1, PDGF, adhesion molecules and LXR-related inflammatory signaling factors. In contrast, peripheral progenitor cells act to suppress arteriosclerosis in H1R(-/-) mice, indicating that HHRs reciprocally regulate inflammation in the ligation-induced arteriosclerosis.

Depletion of apoptosis signal-regulating kinase 1 prevents bile duct ligation-induced necroinflammation and subsequent peribiliary fibrosis

Apoptosis signal-regulating kinase 1 (ASK1), also known as mitogen-activated protein kinase kinase kinase (MAP3K), is ubiquitously expressed and situated in an important upstream position of many signal transduction pathways. ASK1 plays a pivotal role in stressor-induced cell survival and inflammatory reactions. To ascertain the regulatory functions of ASK1 in bile duct ligation (BDL)-induced liver injury, we examined the net effects of ASK1 depletion on hepatic necroinflammation and/or fibrosis. We subjected C57BL/6 wild-type (WT) or ASK1-deficient (ASK1(-/-)) mice to sham or BDL surgery for 14 days. In day 3 BDL animals, ASK1(-/-) mice had significantly fewer bile infarcts along with more reduced interlobular or portal inflammatory infiltrate of various immune cells, including neutrophils, compared with WT mice in which ASK1 expression was markedly activated. Morphologically apoptotic hepatocytes or cholangiocytes were negligible in both the sham and BDL animals. In contrast, ASK1(-/-) mice had significantly less proliferating activity of not only hepatocytes but also large cholangiocytes than WT mice. Day 14 BDL ASK1(-/-) mice manifested potential antifibrogenic aspects of ASK1 deficiency, characterized by significantly fewer activated peribiliary fibrogenic cells and peribiliary fibrosis. These observations indicate that ASK1-mediated hepatic necroinflammation and proliferation, but not apoptosis, are closely linked to liver fibrosis and fibrogenesis. A specific ASK1 pathway blocker or inhibitor might offer a therapeutic strategy against human cholestatic diseases.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

Expanded granulocyte/monocyte compartment in myeloid-specific triple FoxO knockout increases oxidative stress and accelerates atherosclerosis in mice

RATIONALE

Increased neutrophil and monocyte counts are often associated with an increased risk of atherosclerosis, but their relationship to insulin sensitivity is unknown.

OBJECTIVE

To investigate the contribution of forkhead transcription factors (FoxO) in myeloid cells to neutrophil and monocyte counts, atherosclerosis, and systemic insulin sensitivity.

METHODS AND RESULTS

Genetic ablation of the 3 genes encoding FoxO isoforms 1, 3a, and 4, in myeloid cells resulted in an expansion of the granulocyte/monocyte progenitor compartment and was associated with increased atherosclerotic lesion formation in low-density lipoprotein receptor knockout mice. In vivo and ex vivo studies indicate that FoxO ablation in myeloid cells increased generation of reactive oxygen species. Accordingly, treatment with the antioxidant N-acetyl-l-cysteine reversed the phenotype, normalizing atherosclerosis.

CONCLUSIONS

Our data indicate that myeloid cell proliferation and oxidative stress can be modulated via the FoxO branch of insulin receptor signaling, highlighting a heretofore-unknown link between insulin sensitivity and leukocytosis that can affect the predisposition to atherosclerosis.

Apoptosis signal-regulating kinase 1 deficiency attenuates vascular injury-induced neointimal hyperplasia by suppressing apoptosis in smooth muscle cells

Apoptosis signal-regulating kinase 1 (ASK1) is a mitogen-activated protein kinase kinase kinase that plays a crucial role in stress-induced apoptosis. Recently, we have reported that suppressed macrophage apoptosis in ASK1 and apolipoprotein E double-knockout mice accelerates atheromatous plaques in the hyperlipidemia-induced atherosclerotic model. However, the pathogenic role of smooth muscle cell (SMC) apoptosis in atherosclerosis still remains unclear. We investigated neointimal remodeling in ligated carotid arteries of ASK1-deficient mice (ASK1(-/-)) for 3 weeks. ASK1(-/-) mice had significantly more suppressed intimal formation, inversely manifesting as potential anti-atherogenic aspects of ASK1 deficiency, characterized by fewer SMCs and less collagen synthesis; and fewer apoptotic SMCs, infiltrating T lymphocytes, and microvessels, associated with decreased apoptosis of luminal endothelial cells, compared with those of wild-type mice. Injured arteries of ASK1(-/-) mice also showed significantly down-regulated expression of pro-apoptotic markers, adhesion molecules, and pro-inflammatory signaling factors. Moreover, tumor necrosis factor-α-induced apoptosis was markedly suppressed in cultured aortic SMCs from ASK1(-/-) mice. These findings suggest that ASK1 accelerates mechanical injury-induced vascular remodeling with activated SMC migration via increased neovascularization and/or enhanced SMC and endothelial cell apoptosis. ASK1 expression, especially in the SMCs, might be crucial, and reciprocally responsible for various pro-atherogenic functions, and SMC apoptosis seems to be detrimental in this model.

Overexpression of peroxiredoxin 4 attenuates atherosclerosis in apolipoprotein E knockout mice

AIM

A growing body of evidence has shown that increased formation of oxidized molecules and reactive oxygen species within the vasculature (i.e., the extracellular space) plays a crucial role in the initiation and progression of atherosclerosis and in the formation of unstable plaques. Peroxiredoxin 4 (PRDX4) is the only known secretory member of the antioxidant PRDX family. However, the relationship between PRDX4 and susceptibility to atherosclerosis has remained unclear.

RESULTS

To define the role of PRDX4 in hyperlipidemia-induced atherosclerosis, we generated hPRDX4 transgenic (Tg) and apolipoprotein E (apoE) knockout mice (hPRDX4(+/+)/apoE(-/-)). After feeding the mice a high-cholesterol diet, they showed fewer atheromatous plaques, less T-lymphocyte infiltration, lower levels of oxidative stress markers, less necrosis, a larger number of smooth muscle cells, and a larger amount of collagen, resulting in thickened fibrous cap formation and possible stable plaque phenotype as compared with apoE(-/-) mice. We also detected greater suppression of apoptosis and decreased Bax expression in hPRDX4(+/+)/apoE(-/-) mice than in apoE(-/-) mice. Bone marrow transplantation from hPRDX4(+/+) donors to apoE(-/-) mice confirmed the antiatherogenic aspects of PRDX4, revealing significantly suppressed atherosclerotic progression.

INNOVATION

In this study, we demonstrated for the first time that PRDX4 suppressed the development of atherosclerosis in apoE(-/-) mice fed a high-cholesterol diet.

CONCLUSION

These data indicate that PRDX4 is an antiatherogenic factor and, by suppressing oxidative damage and apoptosis, that it may protect against the formation of vulnerable (unstable) plaques.

Update on the Pathophysiological Role of Intracellular Signaling Pathways in Atherosclerotic Plaques and Ischemic Myocardium

Acute atherosclerotic complications, such as myocardial infarction, are often provoked by the rupture of an atherosclerotic plaque and the subsequent thrombotic occlusion of the arterial lumen, which interrupts the blood flow and renders ischemic the downstream peripheral tissue. Several inflammatory mediators (including cytokines, chemokines and matrix metalloproteases) have been shown to orchestrate common pathophysiological mechanisms regulating both plaque vulnerability and myocardial injury. In particular, the selective activation of certain protective intracellular signaling pathways might represent a promising target to reduce the dramatic consequences of an ischemic cardiac event. In the present review we will update evidence on the active role of intracellular kinase cascades (such as mitogen-activated protein kinases [MAPKs], Akt, Janus kinase [JAK]-signal transducer and activator of transcription [STAT]) to reduce the global patient vulnerability for acute myocardial infarction.

Apoptotic Cell Death and Efferocytosis in Atherosclerosis

Apoptotic cell death is an important feature of atherosclerotic plaques, and it seems to exert both beneficial and detrimental effects depending on the cell type and plaque stage. Because late apoptotic cells can launch proatherogenic inflammatory responses, adequate engulfment of apoptotic cells (efferocytosis) by macrophages is important to withstand atherosclerosis progression. Several efferocytosis systems, composed of different phagocytic receptors, apoptotic ligands, and bridging molecules, can be distinguished. Because phagocytes in atherosclerotic plaques are very much solicited, a fully operative efferocytosis system seems to be an absolute requisite. Indeed, recent studies demonstrate that deletion of just 1 of the efferocytosis pathways aggravates atherosclerosis. This review discusses the role of apoptosis in atherosclerosis and general mechanisms of efferocytosis, to end with indirect and direct indications of the significance of effective efferocytosis in atherosclerosis.

Genetic basis of atherosclerosis: insights from mice and humans

Atherosclerosis is a complex and heritable disease involving multiple cell types and the interactions of many different molecular pathways. The genetic and molecular mechanisms of atherosclerosis have, in part, been elucidated by mouse models; at least 100 different genes have been shown to influence atherosclerosis in mice. Importantly, unbiased genome-wide association studies have recently identified a number of novel loci robustly associated with atherosclerotic coronary artery disease. Here, we review the genetic data elucidated from mouse models of atherosclerosis, as well as significant associations for human coronary artery disease. Furthermore, we discuss in greater detail some of these novel human coronary artery disease loci. The combination of mouse and human genetics has the potential to identify and validate novel genes that influence atherosclerosis, some of which may be candidates for new therapeutic approaches.

Improving atherosclerosis risk assessment: looking beyond plaque accumulation to imaging of embolization and healing

Cerebrovascular and cardiovascular diseases constitute the most substantial disease burden worldwide and are only increasing in importance. Understanding how individuals with atherosclerosis may be better assessed for risk of stroke and myocardial infarction will have immense importance in deciding on therapeutic options. Carotid atherosclerosis is frequently portrayed as an orderly progression from asymptomatic plaque formation that enlarges with aging and culminates in either stable, calcified plaque or vulnerable, ruptured and inflamed plaque. New evidence suggests that atherosclerosis is better described as an equilibrium between synthetic and degradative processes. Putatively, plaques heal and decrease in size through processes such as efferocytosis in individuals unlikely to experience symptoms, whereas individuals who experience symptoms lack reparative mechanisms. Present clinically employed imaging strategies overlook plaque healing mechanisms. Other approaches that examine the downstream effects of plaque, rather than static plaque measurement, such as ultrasound emboli signal detection may address the gap between plaque that is vulnerable in appearance and that which is actually likely to cause symptoms. To ascertain the clinical risk of atherosclerosis optimally, both sides of the equation must be examined instead of relying on a unidirectional accumulative approach to atherosclerosis.