Low levels of Nogo-B in human carotid atherosclerotic plaques are associated with an atheromatous phenotype, restenosis, and stenosis severity

Rewiring Endothelial Sphingolipid Metabolism to Favor S1P Over Ceramide Protects From Coronary Atherosclerosis

BACKGROUND

Growing evidence correlated changes in bioactive sphingolipids, particularly S1P (sphingosine-1-phosphate) and ceramides, with coronary artery diseases. Furthermore, specific plasma ceramide species can predict major cardiovascular events. Dysfunction of the endothelium lining lesion-prone areas plays a pivotal role in atherosclerosis. Yet, how sphingolipid metabolism and signaling change and contribute to endothelial dysfunction and atherosclerosis remain poorly understood.

METHODS

We used an established model of coronary atherosclerosis in mice, combined with sphingolipidomics, RNA-sequencing, flow cytometry, and immunostaining to investigate the contribution of sphingolipid metabolism and signaling to endothelial cell (EC) activation and dysfunction.

RESULTS

We demonstrated that hemodynamic stress induced an early metabolic rewiring towards endothelial sphingolipid de novo biosynthesis, favoring S1P signaling over ceramides as a protective response. This finding is a paradigm shift from the current belief that ceramide accrual contributes to endothelial dysfunction. The enzyme SPT (serine palmitoyltransferase) commences de novo biosynthesis of sphingolipids and is inhibited by NOGO-B (reticulon-4B), an ER membrane protein. Here, we showed that NOGO-B is upregulated by hemodynamic stress in myocardial EC of ApoE-/- mice and is expressed in the endothelium lining coronary lesions in mice and humans. We demonstrated that mice lacking NOGO-B specifically in EC (Nogo-A/BECKOApoE-/-) were resistant to coronary atherosclerosis development and progression, and mortality. Fibrous cap thickness was significantly increased in Nogo-A/BECKOApoE-/- mice and correlated with reduced necrotic core and macrophage infiltration. Mechanistically, the deletion of NOGO-B in EC sustained the rewiring of sphingolipid metabolism towards S1P, imparting an atheroprotective endothelial transcriptional signature.

CONCLUSIONS

These data demonstrated that hemodynamic stress induced a protective rewiring of sphingolipid metabolism, favoring S1P over ceramide. NOGO-B deletion sustained the rewiring of sphingolipid metabolism toward S1P protecting EC from activation under hemodynamic stress and refraining coronary atherosclerosis. These findings also set forth the foundation for sphingolipid-based therapeutics to limit atheroprogression.

Nogo-B mediates endothelial oxidative stress and inflammation to promote coronary atherosclerosis in pressure-overloaded mouse hearts

AIMS

Endothelial dysfunction plays a pivotal role in atherosclerosis, but the detailed mechanism remains incomplete understood. Nogo-B is an endoplasmic reticulum (ER)-localized protein mediating ER-mitochondrial morphology. We previously showed endothelial Nogo-B as a key regulator of endothelial function in the setting of hypertension. Here, we aim to further assess the role of Nogo-B in coronary atherosclerosis in ApoE-/- mice with pressure overload.

METHODS AND RESULTS

We generated double knockout (DKO) mouse models of systemically or endothelium-specifically excising Nogo-A/B gene on an ApoE-/- background. After 7 weeks of transverse aortic constriction (TAC) surgery, compared to ApoE-/- mice DKO mice were resistant to the development of coronary atherosclerotic lesions and plaque rapture. Sustained elevation of Nogo-B and adhesion molecules (VCAM-1/ICAM-1), early markers of atherosclerosis, was identified in heart tissues and endothelial cells (ECs) isolated from TAC ApoE-/- mice, changes that were significantly repressed by Nogo-B deficiency. In cultured human umbilical vein endothelial cells (HUVECs) exposure to inflammatory cytokines (TNF-α, IL-1β), Nogo-B was upregulated and activated reactive oxide species (ROS)-p38-p65 signaling axis. Mitofusin 2 (Mfn2) is a key protein tethering ER to mitochondria in ECs, and we showed that Nogo-B expression positively correlated with Mfn2 protein level. And Nogo-B deletion in ECs or in ApoE-/- mice reduced Mfn2 protein content and increased ER-mitochondria distance, reduced ER-mitochondrial Ca2+ transport and mitochondrial ROS generation, and prevented VCAM-1/ICAM-1 upregulation and EC dysfunction, eventually restrained atherosclerotic lesions development.

CONCLUSION

Our study revealed that Nogo-B is a critical modulator in promoting endothelial dysfunction and consequent pathogenesis of coronary atherosclerosis in pressure overloaded hearts of ApoE-/- mice. Nogo-B may hold the promise to be a common therapeutic target in the setting of hypertension.

Decreased soluble Nogo-B in serum as a promising biomarker for Parkinson's disease

Background

Recently, the neurite outgrowth inhibitor-B (Nogo-B) receptor has been reported as a novel candidate gene for Parkinson's disease (PD). Nogo-B receptors need to combine with soluble Nogo-B to exert their physiological function. However, little is known about the relationship between serum soluble Nogo-B and PD.

Methods

Serum levels of sNogo-B and α-Synuclein (α-Syn) were measured in a cohort of 53 patients with PD and 49 healthy controls with the ELISA kit method.

Results

Serum sNogo-B level is significantly lower in the PD group than that in healthy controls and is negatively correlated with UPDRS-III score (p = 0.049), H&Y stage (p = 0.0108) as well as serum α-Syn level (p = 0.0001). The area under the curve (AUC) of serum sNogo-B in differentiating patients with PD from controls was 0.801 while the AUC of serum α-Syn was 0.93. Combining serum sNogo-B and α-Syn in differentiating patients with PD from HC presented higher discriminatory potential (AUC = 0.9534).

Conclusion

Decreased serum sNogo-B may be a potential biomarker for PD. Lower Nogo-B level reflects worse motor function and disease progression of PD. Serum sNogo-B is of added value to serum α-Syn panel in distinguishing PD from controls. Future studies are needed to confirm in larger samples and different populations.

Kidney disease in diabetes: From mechanisms to clinical presentation and treatment strategies

Metabolic and haemodynamic perturbations and their interaction drive the development of diabetic kidney disease (DKD) and its progression towards end stage renal disease (ESRD). Increased mitochondrial oxidative stress has been proposed as the central mechanism in the pathophysiology of DKD, but other mechanisms have been implicated. In parallel to increased oxidative stress, inflammation, cell apoptosis and tissue fibrosis drive the relentless progressive loss of kidney function affecting both the glomerular filtration barrier and the renal tubulointerstitium. Alteration of glomerular capillary autoregulation is at the basis of glomerular hypertension, an important pathogenetic mechanism for DKD. Clinical presentation of DKD can vary. Its classical presentation, often seen in patients with type 1 diabetes (T1DM), features hyperfiltration and albuminuria followed by progressive fall in renal function. Patients can often also present with atypical features characterised by progressive reduction in renal function without albuminuria, others in conjunction with non-diabetes related pathologies making the diagnosis, at times, challenging. Metabolic, lipid and blood pressure control with lifestyle interventions are crucial in reducing the progressive renal function decline seen in DKD. The prevention and management of DKD (and parallel cardiovascular disease) is a huge global challenge and therapies that target haemodynamic perturbations, such as inhibitors of the renin-angiotensin-aldosterone system (RAAS) and SGLT2 inhibitors, have been most successful.

The Regulatory Role of Reticulons in Neurodegeneration: Insights Underpinning Therapeutic Potential for Neurodegenerative Diseases

In the last few decades, cytoplasmic organellar dysfunction, such as that of the endoplasmic reticulum (ER), has created a new area of research interest towards the development of serious health maladies including neurodegenerative diseases. In this context, the extensively dispersed family of ER-localized proteins, i.e. reticulons (RTNs), is gaining interest because of its regulative control over neural regeneration. As most neurodegenerative diseases are pathologically manifested with the accretion of misfolded proteins with subsequent induction of ER stress, the regulatory role of RTNs in neural dysfunction cannot be ignored. With the limited information available in the literature, delineation of the functional connection between rising consequences of neurodegenerative diseases and RTNs need to be elucidated. In this review, we provide a broad overview on the recently revealed regulatory roles of reticulons in the pathophysiology of several health maladies, with special emphasis on neurodegeneration. Additionally, we have also recapitulated the decisive role of RTN4 in neurite regeneration and highlighted how neurodegeneration and proteinopathies are mechanistically linked with each other through specific RTN paralogues. With the recent findings advocating zebrafish Rtn4b (a mammalian Nogo-A homologue) downregulation following central nervous system (CNS) lesion, RTNs provides new insight into the CNS regeneration. However, there are controversies with respect to the role of Rtn4b in zebrafish CNS regeneration. Given these controversies, the connection between the unique regenerative capabilities of zebrafish CNS by distinct compensatory mechanisms and Rtn4b signalling pathway could shed light on the development of new therapeutic strategies against serious neurodegenerative diseases.

Nogo-B is a key mediator of hepatic ischemia and reperfusion injury

Nogo-B is an endoplasmic reticulum-residential protein with distinctive functions in different diseases. However, it remains unclear the role of Nogo-B in liver sterile inflammatory injury. This study aims to elucidate the functions and mechanisms in liver ischemia and reperfusion injury (IRI). The Nogo-B expression and liver function were analyzed in biopsy/serum specimens from 36 patients undergoing ischemia-related hepatectomy and in a mouse model of liver IRI. Human specimens were harvested prior to ischemia and post-reperfusion. The Nogo-B knockout (Nogo-B^KO) and myeloid-specific Nogo-B knockout (Nogo-B^MKO) mice were used to analyze the function and mechanism of Nogo-B in a mouse model of liver IRI. In human specimens, the Nogo-B expression was positively correlated with higher levels of serum transaminase (sALT) and severe histopathological injury at one day post-hepatectomy. Moreover, Nogo-B is mainly expressed on macrophages in normal and ischemic liver tissues from human and mice. Unlike in controls, the Nogo-B^KO or Nogo-B^MKO livers was protected against IRI, with reduced reactive oxygen species (ROS) production and liver inflammation in ischemic livers. In parallel in vitro studies, Nogo-B deficiency reduced M1 macrophage polarization and inhibited proinflammatory cytokines (TNF-α, IL-6, MCP-1 and iNOS) in response to LPS or HMGB-1 stimulation. Mechanistic studies showed that Nogo-B bound to MST1/2, increased MST1/2, LAST1, and YAP phosphorylation, leading to reduced YAP activity. Interestingly, disruption of macrophage YAP abolished Nogo-B deficiency-mediated cytoprotective effects in vitro and in vivo. Thus, YAP is crucial for the regulation of macrophage Nogo-B-triggered liver inflammation. Nogo-B promotes macrophage-related innate inflammation and contributes to IR-induced liver injury by activating the MST-mediated Hippo/YAP pathway, which provides a potential therapeutic target for clinical management in liver IRI.

Nogo-B fosters HCC progression by enhancing Yap/Taz-mediated tumor-associated macrophages M2 polarization

Tumor-associated macrophages (TAMs) and their M2-type extremely promote tumor angiogenesis, invasion and metastasis, including hepatocellular carcinoma (HCC). Nogo-B is expressed in most tissues and participates in macrophage polarization. However, whether Nogo-B is involved in the polarization and the effects of TAMs has been unclear. The expression of Nogo-B in TAMs of HCC patients is significantly increased, which correlated with the poor prognosis of the patients with HCC. Coincidentally, HCC conditioned medium (HCM) facilitated Nogo-B expression and the M2 phenotype of macrophages. Nogo-B knockdown Nogo-B significantly suppressed the M2-type polarization of macrophages and inhibited HCC cells proliferation both in vivo and in vitro. Furthermore, interference of Nogo-B facilitates macrophage-mediated apoptosis of tumor cells. Nogo-B meaningfully enhanced IL4-stimulated the alternative activation of macrophages as well as expression of the transcriptional regulators Yes-associated protein (Yap)/transcriptional coactivator with PDZ-binding motif (Taz). An inhibitor of Yap, Verteporfin, could block Nogo-B-Yap/Taz-mediated macrophages M2 polarization. Nogo-B expression in macrophages facilitates tumor-associated macrophages M2 polarization and protumoral effects of TAMs in HCC. Targeting Nogo-B/Yap/Taz in macrophages could provide a new therapeutic strategy in HCC therapy.

Overexpression of Circulating Soluble Nogo-B Improves Diabetic Kidney Disease by Protecting the Vasculature

Damage to the vasculature is the primary mechanism driving chronic diabetic microvascular complications such as diabetic nephropathy, which manifests as albuminuria. Therefore, treatments that protect the diabetic vasculature have significant therapeutic potential. Soluble neurite outgrowth inhibitor-B (sNogo-B) is a circulating N-terminus isoform of full-length Nogo-B, which plays a key role in vascular remodeling following injury. However, there is currently no information on the role of sNogo-B in the context of diabetic nephropathy. We demonstrate that overexpression of sNogo-B in the circulation ameliorates diabetic kidney disease by reducing albuminuria, hyperfiltration, and abnormal angiogenesis and protecting glomerular capillary structure. Systemic sNogo-B overexpression in diabetic mice also associates with dampening vascular endothelial growth factor-A signaling and reducing endothelial nitric oxide synthase, AKT, and GSK3β phosphorylation. Furthermore, sNogo-B prevented the impairment of tube formation, which occurred when human endothelial cells were exposed to sera from patients with diabetic kidney disease. Collectively, these studies provide the first evidence that sNogo-B protects the vasculature in diabetes and may represent a novel therapeutic target for diabetic vascular complications.

ER-residential Nogo-B accelerates NAFLD-associated HCC mediated by metabolic reprogramming of oxLDL lipophagy

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome that elevates the risk of hepatocellular carcinoma (HCC). Although alteration of lipid metabolism has been increasingly recognized as a hallmark of cancer cells, the deregulated metabolic modulation of HCC cells in the NAFLD progression remains obscure. Here, we discovers an endoplasmic reticulum-residential protein, Nogo-B, as a highly expressed metabolic modulator in both murine and human NAFLD-associated HCCs, which accelerates high-fat, high-carbohydrate diet-induced metabolic dysfunction and tumorigenicity. Mechanistically, CD36-mediated oxLDL uptake triggers CEBPβ expression to directly upregulate Nogo-B, which interacts with ATG5 to promote lipophagy leading to lysophosphatidic acid-enhanced YAP oncogenic activity. This CD36-Nogo-B-YAP pathway consequently reprograms oxLDL metabolism and induces carcinogenetic signaling for NAFLD-associated HCCs. Targeting the Nogo-B pathway may represent a therapeutic strategy for HCC arising from the metabolic syndrome.

The role of novel cytokines in inflammation: Defining peripheral artery disease among patients with coronary artery disease

Coronary artery disease (CAD) patients with concomitant peripheral artery disease (PAD) experience more extensive and calcified atherosclerosis, greater lesion progression and more common coronary events compared to patients with CAD only. To characterize the distinct features of this aggressive atherosclerotic disease, we studied novel cytokines that code different stages of atherogenesis. One hundred and eighty consecutive subjects (60 patients into each group of CAD+PAD, CAD and controls) were recruited among patients with stable angina pectoris scheduled for coronary angiography. An ankle-brachial index (ABI) ≤0.9 was determined as occlusive PAD. Fasting serum tumor necrosis factor (TNF)-like antigen 1A (TL1A) and its receptor death receptor 3 (DR3), NOGO-B (reticulon 4B) and its receptor NUS1, high-sensitivity C-reactive protein (hsCRP), A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) 1, 4, 5 and interleukin (IL) 6 levels were determined. Serum hsCRP and DR3/TL1A concentrations were similar and higher than controls in the CAD and CAD+PAD groups. Levels of NOGO-B and its receptor NUS1 were increased and ADAMTS-5 was decreased in patients with CAD+PAD. Independent predictors of ABI in multivariate analysis were smoking (B = -0.13, p = 0.04), NUS1 (B = -0.88, p < 0.001), ADAMTS-5 (B = 0.63, p < 0.001) and SYNTAX score (B = -0.26, p < 0.001). Similarly, smoking (OR = 5.5, p = 0.019), SYNTAX score (OR = 1.2, p < 0.001), NUS1 (OR = 14.4, p < 0.001), ADAMTS-5 (OR = 1.1, p < 0.001) and age (OR = 1.1, p = 0.042) independently predicted the involvement of peripheral vasculature in logistic regression. The diagnostic performance of these cytokines to discriminate CAD+PAD were AUC 0.79 ( p < 0.001) for NUS1 and 0.37 ( p = 0.013) for ADAMTS-5. We report herein that circulating cytokines can give clues to the ongoing atherosclerotic process and the extent of vascular involvement in which distinct features of ADAMTS-5 and NUS1 make them promising cytokines for future research.

Soluble LILRA3 promotes neurite outgrowth and synapses formation through high affinity interaction with Nogo 66

Inhibitory proteins, particularly Nogo 66, a highly conserved 66 amino acid loop of Nogo A, play key roles in limiting the intrinsic capacity of the central nervous system to regenerate after injury. Ligation of surface Nogo receptors (NgRs) and/or leukocyte immunoglobulin like receptor B2 (LILRB2) and its mouse orthologue the paired-immunoglobulin-like receptor B (PIRB) by Nogo 66 transduces inhibitory signals that potently inhibit neurite outgrowth. Here we show that soluble leukocyte immunoglobulin-like receptor A3 (LILRA3) is a high affinity receptor for Nogo 66, suggesting that LILRA3 might be a competitive antagonist to these cell surface inhibitory receptors. Consistent with this, LILRA3 significantly reversed Nogo 66-mediated inhibition of neurite outgrowth and promoted synapse formation in primary cortical neurons via regulation of the MEK/ERK pathway. LILRA3 represents a new antagonist to Nogo 66-mediated inhibition of neurite outgrowth in the CNS, a function distinct from its immune-regulatory role in leukocytes. This report is also the first to demonstrate that a member of LILR family normally not expressed in rodents exerts functions on mouse neurons through the highly homologous Nogo 66 ligand.

Nogo-B protects mice against lipopolysaccharide-induced acute lung injury

Nogo-B, a member of the reticulon 4 protein family, plays a critical role in tissue repair and acute inflammation. Its role in acute lung injury (ALI) remains unclear. Here, we assessed the function of Nogo-B during tissue injury in a lipopolysaccharide (LPS)-induced ALI mouse model. We found that pulmonary Nogo-B was significantly repressed after LPS instillation in C57BL/6 mice. Over-expression of pulmonary Nogo-B using an adenovirus vector carrying the Nogo-B-RFP-3flag gene (Ad-Nogo-B) significantly prolonged the survival of mice challenged with a lethal dose of LPS. The Ad-Nogo-B-treated mice also had less severe lung injury, less alveolar protein exudation, and a higher number of macrophages but less neutrophil infiltration compared with Ad-RFP-treated mice. Interestingly, microarray analysis showed that the Ad-Nogo-B-treated mice had different gene expression profiles compared with the controls and the prominent expression of genes related to wound healing and the humoral immune response after LPS induction. Of the 49 differently expressed genes, we found that the expression of PTX3 was significantly up-regulated following Nogo-B over-expression as observed in lung tissues and RAW264.7 cells. In conclusion, Nogo-B plays a protective role against LPS-induced ALI, and this effect might be exerted through the modulation of alveolar macrophage recruitment and PTX3 production.

A new role for reticulon-4B/NOGO-B in the intestinal epithelial barrier function and inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by an impaired intestinal barrier function. We aimed to investigate the role of reticulon-4B (RTN-4B/NOGO-B), a structural protein of the endoplasmic reticulum, in intestinal barrier function and IBD. We used immunohistochemistry, confocal microscopy, real-time PCR, and Western blotting to study tissue distribution and expression levels of RTN-4B/NOGO-B in control and IBD samples from mouse and humans. We also targeted RTN-4B/NOGO-B using siRNAs in cultured human intestinal epithelial cell (IECs). Epithelial barrier permeability was assessed by transepithelial electrical resistance (TEER) measurement. RTN-4B/NOGO-B is expressed in the intestine mainly by IECs. Confocal microscopy revealed a colocalization of RTN-4B, E-cadherin, and polymerized actin fibers in tissue and cultured IECs. RTN-4B mRNA and protein expression were lower in the colon of IL-10(-/-) compared with wild-type mice. Colocalization of RTN-4B/E-cadherin/actin was reduced in the colon of IL-10(-/-) mice. Analysis of endoscopic biopsies from IBD patients showed a significant reduction of RTN-4B/NOGO-B expression in inflamed mucosa compared with control. Treatment of IECs with H2O2 reduced TEER values and triggered phosphorylation of RTN-4B in serine 107 residues as well as downregulation of RTN-4B expression. Acute RTN-4B/NOGO-B knockdown by siRNAs resulted in a decreased TEER values and reduction of E-cadherin and α-catenin expression and in the amount of F-actin-rich filaments in IECs. Epithelial RTN-4B/NOGO-B was downregulated in human and experimental IBD. RTN-4B participates in the intestinal epithelial barrier function, most likely via its involvement in E-cadherin, α-catenin expression, and actin cytoskeleton organization at sites of cell-to-cell contacts.

RTN4 and FBXL17 Genes are Associated with Coronary Heart Disease in Genome-Wide Association Analysis of Lithuanian Families

Coronary heart disease (CHD) is a complex and heterogeneous cardiovascular disease. There are many genome-wide association studies (GWAS) performed worldwide to extract the causative genetic factors. Moreover, each population may have some exceptional genetic characteristic. Thus, the background of our study is from the previous Lithuanian studies (the LiVicordia Project), which demonstrated the differences of the atherosclerosis process between Lithuanian and Swedish male individuals.

In this study we performed GWAS of 32 families of Lithuanian origin in search of significant candidate genetic markers [single nucleotide polymorphisms (SNPs)] of CHD in this population. After careful clinical and biochemical phenotype evaluation, the ∼770K SNPs genotyping (Illumina HumanOmniExpress-12 v1.0 array) and familial GWAS analyses were performed.

Twelve SNPs were found to be significantly associated with the CHD phenotype (p value <0.0001; the power >0.65). The odds ratio (OR) values were calculated. Two SNPs (rs17046570 in the RTN4 gene and rs11743737 in the FBXL17 gene) stood out and may prove to be important genetic factors for CHD risk. Our results correspond with the findings in other studies, and these two SNPs may be the susceptibility loci for CHD.

Nogo-B expression, in arterial intima, is impeded in the early stages of atherosclerosis in humans

Nogo-B (Reticulon 4B) is considered to be a novel vascular marker, which may have a protective role in injury-induced neointima formation and atherosclerosis. Nogo A/B is found to be crucial for monocyte/macrophage recruitment in acute inflammation and it is expressed in CD68 + macrophages. We hypothesize that macrophage infiltration in atherosclerosis is not dependent on Nogo-B expression in arterial wall. We have assessed Nogo-B expression and macrophage accumulation in the iliac arteries of healthy organ donors and organ donors with cardiovascular risk factors. Paraffin sections of 66 iliac arteries, from 44 deceased organ donors (17 women and 27 men), were studied. The healthy and cardiovascular risk (CVR) subgroups were created. With regard to staging of the atherosclerotic process, the thickness of arterial intima was measured in digitalized images of H+E stained tissue sections. Immunohistochemical reactions (Nogo-B and CD68) were carried out in all arteries (66 samples). Western blotting (WB-19 samples) and real-time PCR (27 samples) were performed on selected arteries. Significantly higher Nogo-B expression was demonstrated in the intima of the healthy subjects' subgroup, using immunohistochemistry. WB and real-time PCR revealed a trend toward lower Nogo-B expression in the adventitia of the CVR subgroup. Furthermore, the thickness of the intima was found to negatively correlate with the expression of Nogo-B in the intima and media (r = -0.32; p < 0.05; r = -0.32; p < 0.05). Macrophage infiltrates were more prominent in intima of CVR subjects (0.65 vs 3.52 a.u.; p < 0.01). Macrophage density in intima increased with atherosclerosis progression (r = 0.37; p < 0.01). CD68 macrophages density in adventitia was lower in CVR arteries than in healthy arteries. The expression of Nogo-B, in arterial intima, is impeded in the early stages of atherosclerosis. Accumulation of arterial intimal CD68 macrophages has been shown to progress; however, the overall macrophage density in the adventitia is reduced in arteries shown to have intimal thickening. Macrophage infiltration is not accompanied by Nogo-B expression in atherosclerotic arteries.

10-years experience with the Athero-Express study

From cross-sectional studies we have learned that composition of atherosclerotic plaques differs, and that thrombosis on top of an inflammatory lipid rich plaque is a frequently observed pathological substrate of a cerebral or coronary event. Atherosclerosis develops over decades which hampers human studies on the natural history of the diseases. Therefore, the predictive value of atherosclerotic plaque composition for development of an adverse cardiovascular event is not clear. The elucidation of markers for atherosclerotic disease progression is essential to identify patients at high risk for vascular events, to refine treatment allocation and to serve as surrogate endpoints in pharmaceutical studies. The Athero-Express study is a large scale vascular biobank that collects vascular specimens including a clinical follow-up. This study design allows the prospective study of the local atherosclerotic plaque in relation to future local and systemic vascular outcome. The readout of the study can be assessed in terms of histology as well as RNA or protein level. This paper aims to give an overview of the results of the Athero-Express biobank since its initiation in 2002. We will also discuss the clinical implications and future directions in biobanking research.

Integrase-deficient lentiviral vectors mediate efficient gene transfer to human vascular smooth muscle cells with minimal genotoxic risk

We have previously shown that injury-induced neointima formation was rescued by adenoviral-Nogo-B gene delivery. Integrase-competent lentiviral vectors (ICLV) are efficient at gene delivery to vascular cells but present a risk of insertional mutagenesis. Conversely, integrase-deficient lentiviral vectors (IDLV) offer additional benefits through reduced mutagenesis risk, but this has not been evaluated in the context of vascular gene transfer. Here, we have investigated the performance and genetic safety of both counterparts in primary human vascular smooth muscle cells (VSMC) and compared gene transfer efficiency and assessed the genotoxic potential of ICLVs and IDLVs based on their integration frequency and insertional profile in the human genome. Expression of enhanced green fluorescent protein (eGFP) mediated by IDLVs (IDLV-eGFP) demonstrated efficient transgene expression in VSMCs. IDLV gene transfer of Nogo-B mediated efficient overexpression of Nogo-B in VSMCs, leading to phenotypic effects on VSMC migration and proliferation, similar to its ICLV version and unlike its eGFP control and uninfected VSMCs. Large-scale integration site analyses in VSMCs indicated that IDLV-mediated gene transfer gave rise to a very low frequency of genomic integration compared to ICLVs, revealing a close-to-random genomic distribution in VSMCs. This study demonstrates for the first time the potential of IDLVs for safe and efficient vascular gene transfer.

The role of Nogo and the mitochondria-endoplasmic reticulum unit in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is caused by excessive proliferation of vascular cells, which occlude the lumen of pulmonary arteries (PAs) and lead to right ventricular failure. The cause of the vascular remodeling in PAH remains unknown, and the prognosis of PAH remains poor. Abnormal mitochondria in PAH PA smooth muscle cells (SMCs) suppress mitochondria-dependent apoptosis and contribute to the vascular remodeling. We hypothesized that early endoplasmic reticulum (ER) stress, which is associated with clinical triggers of PAH including hypoxia, bone morphogenetic protein receptor II mutations, and HIV/herpes simplex virus infections, explains the mitochondrial abnormalities and has a causal role in PAH. We showed in SMCs from mice that Nogo-B, a regulator of ER structure, was induced by hypoxia in SMCs of the PAs but not the systemic vasculature through activation of the ER stress-sensitive transcription factor ATF6. Nogo-B induction increased the distance between the ER and mitochondria and decreased ER-to-mitochondria phospholipid transfer and intramitochondrial calcium. In addition, we noted inhibition of calcium-sensitive mitochondrial enzymes, increased mitochondrial membrane potential, decreased mitochondrial reactive oxygen species, and decreased mitochondria-dependent apoptosis. Lack of Nogo-B in PASMCs from Nogo-A/B-/- mice prevented these hypoxia-induced changes in vitro and in vivo, resulting in complete resistance to PAH. Nogo-B in the serum and PAs of PAH patients was also increased. Therefore, triggers of PAH may induce Nogo-B, which disrupts the ER-mitochondria unit and suppresses apoptosis. This could rescue PASMCs from death during ER stress but enable the development of PAH through overproliferation. The disruption of the ER-mitochondria unit may be relevant to other diseases in which Nogo is implicated, such as cancer or neurodegeneration.

The potential role of RTN3 in monocyte recruitment and atherosclerosis

The recruitment of monocytes to arterial wall and their transformation into macrophages are generally accepted as important early events in the pathogenesis of atherosclerosis (AS). Our research group found Reticulon3 (RTN3), a member of the reticulon family, may be a candidate pathogenic element in the progress of AS. But it is virtually unknown in which process RTN3 may participate in and regulate the pathogenesis of AS. Here, we hypothesis that RTN3 may participate in the continuous process of circulating monocyte recruitment in AS including: (1) monocyte spreading and adhesion to luminal endothelium; (2) transendothelial migration and may also contribute to the conversion of monocyte to macrophage in subendothelium.

Reticulon 4B (Nogo-B) is a novel regulator of hepatic fibrosis

Nogo-B, also known as Reticulon 4B, plays important roles in vascular injuries. Its function in the liver is not understood. The aim of this study was to characterize Nogo-B in liver fibrosis and cirrhosis. Nogo-B distribution was assessed in normal and cirrhotic human liver sections. We also determined the levels of liver fibrosis in wild-type (WT) and Nogo-A/B knockout (NGB KO) mice after sham operation or bile duct ligation (BDL). To investigate the mechanisms of Nogo-B's involvement in fibrosis, hepatic stellate cells were isolated from WT and NGB KO mice and transformed into myofibroblasts. Portal pressure was measured to test whether Nogo-B gene deletion could ameliorate portal hypertension. In normal livers, Nogo-B expression was found in nonparenchymal cells, whereas its expression in hepatocytes was minimal. Nogo-B staining was significantly elevated in cirrhotic livers. Fibrosis was significantly increased in WT mice 4 weeks after BDL compared with NGB KO mice. The absence of Nogo-B significantly reduced phosphorylation of Smad2 levels upon transforming growth factor β (TGF-β) stimulation. Reconstitution of the Nogo-B gene into NGB KO fibroblasts restored Smad2 phosphorylation. Four weeks after BDL, portal pressure was significantly increased in WT mice by 47%, compared with sham-operated controls (P = 0.03), whereas such an increase in portal pressure was not observed in NGB KO mice (P = NS).

CONCLUSION

Nogo-B regulates liver fibrosis, at least in part, by facilitating the TGFβ/Smad2 signaling pathway in myofibroblasts. Because absence of Nogo-B ameliorates liver fibrosis and portal hypertension, Nogo-B blockade may be a potential therapeutic target in fibrosis/cirrhosis.

Nogo-B regulates migration and contraction of airway smooth muscle cells by decreasing ARPC 2/3 and increasing MYL-9 expression

BACKGROUND

Abnormal proliferation, apoptosis, migration and contraction of airway smooth muscle (ASM) cells in airway remodeling in asthma are basically excessive repair responses to a network of inflammatory mediators such as PDGF, but the mechanisms of such responses remain unclear. Nogo-B, a member of the reticulum family 4(RTN4), is known to play a key role in arteriogenesis and tissue repair. Further studies are needed to elucidate the role of Nogo-B in airway smooth muscle abnormalities.

METHODS

A mouse model of chronic asthma was established by repeated OVA inhalation and subjected to Nogo-B expression analysis using immunohistochemistry and Western Blotting. Then, primary human bronchial smooth muscle cells (HBSMCs) were cultured in vitro and a siRNA interference was performed to knockdown the expression of Nogo-B in the cells. The effects of Nogo-B inhibition on PDGF-induced HBSMCs proliferation, migration and contraction were evaluated. Finally, a proteomic analysis was conducted to unveil the underlying mechanisms responsible for the function of Nogo-B.

RESULTS

Total Nogo-B expression was approximately 3.08-fold lower in chronic asthmatic mice compared to naïve mice, which was obvious in the smooth muscle layer of the airways. Interference of Nogo-B expression by siRNA resulted nearly 96% reduction in mRNA in cultured HBSMCs. In addition, knockdown of Nogo-B using specific siRNA significantly decreased PDGF-induced migration of HBSMCs by 2.3-fold, and increased the cellular contraction by 16% compared to negative controls, but had limited effects on PDGF-induced proliferation. Furthermore, using proteomic analysis, we demonstrate that the expression of actin related protein 2/3 complex subunit 5 (ARPC 2/3) decreased and, myosin regulatory light chain 9 isoform a (MYL-9) increased after Nogo-B knockdown.

CONCLUSIONS

These data define a novel role for Nogo-B in airway remodeling in chronic asthma. Endogenous Nogo-B, which may exert its effects through ARPC 2/3 and MYL-9, is necessary for the migration and contraction of airway smooth muscle cells.

Epithelial reticulon 4B (Nogo-B) is an endogenous regulator of Th2-driven lung inflammation

The reticulon protein Nogo-B is highly expressed in the lungs, and its loss augments lung inflammation in part as a result of decreased expression of the antiinflammatory protein PLUNC.

Nogo-B is a member of the reticulon family of proteins (RTN-4B) that is highly expressed in lung tissue; however, its function remains unknown. We show that mice with Th2-driven lung inflammation results in a loss of Nogo expression in airway epithelium and smooth muscle compared with nonallergic mice, a finding which is replicated in severe human asthma. Mice lacking Nogo-A/B (Nogo-KO) display an exaggerated asthma-like phenotype, and epithelial reconstitution of Nogo-B in transgenic mice blunts Th2-mediated lung inflammation. Microarray analysis of lungs from Nogo-KO mice reveals a marked reduction in palate lung and nasal clone (PLUNC) gene expression, and the levels of PLUNC are enhanced in epithelial Nogo-B transgenic mice. Finally, transgenic expression of PLUNC into Nogo-KO mice rescues the enhanced asthmatic-like responsiveness in these KO mice. These data identify Nogo-B as a novel protective gene expressed in lung epithelia, and its expression regulates the levels of the antibacterial antiinflammatory protein PLUNC.

Identification and regulation of reticulon 4B (Nogo-B) in renal tubular epithelial cells

Nogo-B is a member of the reticulon family of proteins that has been implicated in diverse forms of vascular injury. Although Nogo-B is expressed in renal tissues, its localization and function in the kidney have not been examined. Here, we report that Nogo-B is expressed specifically in the epithelial cells of the distal nephron segments in the murine kidney. After unilateral ureteral obstruction (UUO) and ischemia/reperfusion, Nogo-B gene and protein levels increased dramatically in the kidney. This increase was driven in part by injury-induced de novo expression in proximal tubules. Examination of Nogo-B immunostaining in human biopsy specimens from patients with acute tubular necrosis showed similar increases in Nogo-B in cortical tubules. Mice genetically deficient in Nogo-A/B were indistinguishable from wild-type (WT) mice based on histological appearance and serum analyses. After UUO, there was a significant delay in recruitment of macrophages to the kidney in the Nogo-A/B-deficient mice. However, measurements of fibrosis, inflammatory gene expression, and histological damage were not significantly different from WT mice. Thus, Nogo-B is highly expressed in murine kidneys in response to experimental injuries and may serve as a marker of diverse forms of renal injury in tissues from mice and humans. Furthermore, Nogo-B may regulate macrophage recruitment after UUO, although it does not greatly affect the degree of tissue injury or fibrosis in this model.

Nogo-B receptor is essential for angiogenesis in zebrafish via Akt pathway

Our previous work has shown that axon guidance gene family Nogo-B and its receptor (NgBR) are essential for chemotaxis and morphogenesis of endothelial cells in vitro. To investigate NogoB-NgBR function in vivo, we cloned the zebrafish ortholog of both genes and studied loss of function in vivo using morpholino antisense technology. Zebrafish ortholog of Nogo-B is expressed in somite while expression of zebrafish NgBR is localized in intersomitic vessel (ISV) and axial dorsal aorta during embryonic development. NgBR or Nogo-B knockdown embryos show defects in ISV sprouting in the zebrafish trunk. Mechanistically, we found that NgBR knockdown not only abolished its ligand Nogo-B-stimulated endothelial cell migration but also reduced the vascular endothelial growth factor (VEGF)-stimulated phosphorylation of Akt and vascular endothelial growth factor-induced chemotaxis and morphogenesis of human umbilical vein endothelial cells. Further, constitutively activated Akt (myristoylated [myr]Akt) or human NgBR can rescue the NgBR knockdown umbilical vein endothelial cell migration defects in vitro or NgBR morpholino-caused ISV defects in vivo. These data place Akt at the downstream of NgBR in both Nogo-B- and VEGF-coordinated sprouting of ISVs. In summary, this study identifies the in vivo functional role for Nogo-B and its receptor (NgBR) in angiogenesis in zebrafish.

Serum Nogo-A levels are not elevated in amyotrophic lateral sclerosis patients

Improved biomarkers would facilitate the diagnosis and treatment of amyotrophic lateral sclerosis (ALS). Muscle content of the neuritic outgrowth inhibitor Nogo-A is increased in patients with ALS and other denervating conditions. Seeking a less invasive diagnostic method, we sought to determine whether or not Nogo increases in the serum of ALS patients. We developed a dissociation-enhanced lanthanide fluorescent immunoassay (DELFIA) protocol to screen serum samples from 172 ALS patients and 172 healthy controls for Nogo-A immunoreactivity. Unexpectedly, there was a trend toward decreased levels of serum Nogo-A in ALS. Mean serum Nogo-A level in ALS patients was 0.71 nM (95% confidence interval (CI) 0.42-1.00), as opposed to 1.15 nM (95% CI 0.72-1.59) in healthy controls. A significantly larger percentage of healthy control sera (11.0% vs 4.7%) displayed markedly elevated levels of Nogo-A. Additional study is required to determine the factors that lead to elevated Nogo-A levels in a subset of both ALS patients and healthy controls.

Reticulon 4B (Nogo-B) is necessary for macrophage infiltration and tissue repair

Blood vessel formation during ischemia and wound healing requires coordination of the inflammatory response with genes that regulate blood vessel assembly. Here we show that the reticulon family member 4B, aka Nogo-B, is upregulated in response to ischemia and is necessary for blood flow recovery secondary to ischemia and wound healing. Mice lacking Nogo-B exhibit reduced arteriogenesis and angiogenesis that are linked to a decrease in macrophage infiltration and inflammatory gene expression in vivo. Bone marrow-derived macrophages isolated from Nogo knock-out mice have reduced spreading and chemotaxis due to impaired Rac activation. Bone marrow reconstitution experiments show that Nogo in myeloid cells is necessary to promote macrophage homing and functional recovery after limb ischemia. Thus, endogenous Nogo coordinates macrophage-mediated inflammation with arteriogenesis, wound healing, and blood flow control.

Atherosclerotic progression attenuates the expression of Nogo-B in autopsied coronary artery: pathology and virtual histology intravascular ultrasound analysis

The relation of Nogo-B to atherosclerotic plaque progression is not well understood. Thus, the purpose of this study was to assess the expression of Nogo-B in fibroatheromas (FA) of different stages, classified using virtual histology intravascular ultrasound (VH-IVUS) analysis in 19 autopsied cases of non-sudden cardiac death. VH-IVUS imaging analysis was performed 30 mm from the ostium of each coronary artery. VH-IVUS revealed 11 early FAs (34.5+/-8.3 yr), 12 late FAs (42.6+/-16.6 yr), 8 thick-cap FAs (TkCFAs) (46.4+/-11.1 yr), and 6 thin-cap FAs (TCFAs) (51.8+/-6.8 yr). TkCFAs and TCFAs were defined as advanced FA. FA progression advanced with age (P=0.04). VH-IVUS analysis of small, early FAs showed smaller necrotic cores and relatively less calcium compared to more advanced FAs with large necrotic cores (P<0.001). Histopathology and immunohistochemical stains demonstrated that early or late FAs had smaller necrotic cores, less empty space of decalcification, and greater Nogo-B expression compared to advanced FAs (vs. early FA, P=0.013; vs. late FA, P=0.008, respectively). These findings suggest that FA progression is inversely associated with Nogo-B expression. Local reduction of Nogo-B may contribute to plaque formation and/or instability.

In vivo modulation of Nogo-B attenuates neointima formation

Nogo-B was recently identified as a novel vascular marker; the normally high vascular expression of Nogo-B is rapidly lost following vascular injury. Here we assess the potential therapeutic effects of Ad-Nogo-B delivery to injured vessels in vivo. Nogo-B overexpression following Ad-Ng-B infection of vascular smooth muscle cells (VSMCs) was shown to block proliferation and migration in a dose-dependent manner in vitro. We next assessed the effects of Ad-Ng-B treatment on neointima formation in two in vivo models of acute vascular injury. Adventitial delivery of Ad-Ng-B to wire-injured murine femoral arteries led to a significant decrease in the intimal area [0.014 mm(2) versus 0.030 mm(2) (P = 0.049)] and the intima:media ratio [0.78 versus 1.67 (P = 0.038)] as compared to the effects of Ad-beta-Gal control virus at 21 days after injury. Similarly, lumenal delivery of Ad-Ng-B to porcine saphenous veins prior to carotid artery grafting significantly reduced the intimal area [2.87 mm(2) versus 7.44 mm(2) (P = 0.0007)] and the intima:media ratio [0.32 versus 0.55 (P = 0.0044)] as compared to the effects following the delivery of Ad- beta-Gal, at 28 days after grafting. Intimal VSMC proliferation was significantly reduced in both the murine and porcine disease models. Gene delivery of Nogo-B exerts a positive effect on vascular injury-induced remodeling and reduces neointimal development in two arterial and venous models of vascular injury.

Identification of Nogo as a novel indicator of heart failure

Numerous genetically engineered animal models of heart failure (HF) exhibit multiple characteristics of human HF, including aberrant beta-adrenergic signaling. Several of these HF models can be rescued by cardiac-targeted expression of the Gbetagamma inhibitory carboxy-terminus of the beta-adrenergic receptor kinase (betaARKct). We recently reported microarray analysis of gene expression in multiple animal models of HF and their betaARKct rescue, where we identified gene expression patterns distinct and predictive of HF and rescue. We have further investigated the muscle LIM protein knockout model of HF (MLP-/-), which closely parallels human dilated cardiomyopathy disease progression and aberrant beta-adrenergic signaling, and their betaARKct rescue. A group of known and novel genes was identified and validated by quantitative real-time PCR whose expression levels predicted phenotype in both the larger HF group and in the MLP-/- subset. One of these novel genes is herein identified as Nogo, a protein widely studied in the nervous system, where it plays a role in regeneration. Nogo expression is altered in HF and normalized with rescue, in an isoform-specific manner, using left ventricular tissue harvested from both animal and human subjects. To investigate cell type-specific expression of Nogo in the heart, immunofluorescence and confocal microscopy were utilized. Nogo expression appears to be most clearly associated with cardiac fibroblasts. To our knowledge, this is the first report to demonstrate the relationship between Nogo expression and HF, including cell-type specificity, in both mouse and human HF and phenotypic rescue.