NLRP3 regulates macrophage M2 polarization through up-regulation of IL-4 in asthma

Activation of nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome received substantial attention recently in inflammatory diseases. Macrophages contribute to allergic inflammation in asthma. The present study was aimed to investigate the effect of NLRP3 inflammasome on the polarization of macrophages. We utilized human primary monocytes and monocyte-derived macrophages to study the expression of NLRP3 inflammasome components (NLRP3, apoptosis-associated specklike protein, and caspase-1) and its downstream cytokine interleukin-1β (IL-1β). By gain- or loss-of-function assays, we next explored the effects of NLRP3 inflammasome on M1/M2 polarization and secretion of IL-4, interferon-γ, tumor necrosis factor-α, and IL-1β. The results showed increased numbers of M2 cells in asthma. And NLRP3 inflammasome was activated and involved in the inflammation of asthma. Furthermore, silence of NLRP3 down-regulated IL-4 secretion and up-regulated M1/M2. In contrast, overexpression of NLRP3 increased IL-4 and decreased M1/M2. As expected, IL-4 was involved in NLRP3-mediated down-regulation of Ml/M2 ratio. Moreover, NLRP3 interacted with IRF4 and was required for optimal IRF4-dependent IL-4 transcription. Subsequently, deficiency of NLRP3 in ovalbumin-induced allergic asthmatic mice impaired lung inflammation and up-regulated M1/M2, and diminished IL-4 in bronchoalveolar lavage fluid. Collectively, we demonstrated here that activation of NLRP3 was engaged in the promotion of asthma. NLRP3, but not the inflammasome adaptor ASC or caspase-1, promoted the polarization of M2 macrophages through up-regulating the expression of IL-4, thereby contributing to its regulation of asthma.

Rosuvastatin inhibits high glucose-stimulated upregulation of VCAM-1 via the MAPK-signalling pathway in endothelial cells

OBJECTIVE

The aim of this study is to investigate the molecular mechanisms and effect of rosuvastatin on adhesion molecule induction in human endothelial cells under high-glucose conditions (HG).

METHODS AND RESULTS

The effects of rosuvastatin on vascular cell adhesion molecule (VCAM)-1 production and pERK phosphorylation were measured in HG-induced human umbilical vein endothelial cells (HUVECs) with inhibitors targeting the mitogen-activated protein kinase (MAPK) signal pathway. HG increased levels of VCAM-1. Treatment with rosuvastatin inhibited VCAM-1 expression in a concentration- and time-dependent manner. In addition, we investigated the effects of rosuvastatin on the extracellular signal-regulated kinase (ERK) 1/2 signal pathway. Rosuvastatin completely inhibited HG-induced phosphorylation of ERK. ERK/MAPK inhibitors completely prevented the VCAM-1 inhibition effect of rosuvastatin under HG condition.

CONCLUSIONS

This study demonstrated that rosuvastatin suppresses HG-induced VCAM-1 production via the MAPK signalling pathway, playing a role in the suppression of atherosclerosis.

Vascular injury and repair: a potential target for cell therapies

ABSTRACT 

Whether due to atherosclerotic disease or mechanical intervention, vascular injury is a frequently encountered pathology in cardiovascular medicine. The past decade has seen growing interest in the role of circulating endothelial progenitor cells in vessel recovery postinjury. Despite this, the definition, origin and potential role of endothelial progenitor cells in vascular regeneration remains highly controversial. While animal work has shown early promise, evidence of a therapeutic role for endothelial progenitor cells in humans remains elusive. To date, clinical trials involving direct cell administration, growth factor therapy and endothelial cell capture stents have largely been disappointing, although this may in part reflect limitations in study design. This article will outline the pathophysiological mechanisms of vascular injury with an emphasis on endothelial progenitor cell biology and the potential therapeutic role of this exciting new field.

Endothelial progenitor cells in diabetic patients with myocardial infarction - can statins improve their function?

The effect of statins on endothelial progenitor cells (EPCs) function derived from diabetic patients (DMpts) with acute myocardial infarction (AMI) is unknown. In this study we assess the response of early and late EPCs from diabetic versus non-diabetic patients (NDMpts) with AMI to statins. EPCs were obtained from 10 diabetic and 10 age-matched non-diabetic male patients with AMI. For each patient, cultures of early and late EPCs were performed under 4 different conditions: normal glucose concentration (control); high glucose concentration; normal glucose concentration with atorvastatin supplementation and normal glucose concentration with pravastatin supplementation. To compare the effect of these treatments on EPC function in DMpts versus NDMpts, we performed in vitro: EPC colony-forming units (CFU) assay; cell cycle analysis; viability assessment and expression of the surface markers CXCR4, CD133, CD34 and KDR. Under control conditions, CFU numbers were reduced in DMpts-derived EPCs when compared to those of NDMpts (1.4±0.8 vs 2.6±1.2 CFU/well, P=0.021). When early EPCs from DMpts were cultured in the presence of statins, CFU capacity was restored, surmounting that of NDMpts under control conditions. Statins significantly improved viability of early EPCs and delayed the onset of late EPCs senescence, even in cells from DMpts. In addition, statins induced approximately a 2-fold increase in the proportion of late EPCs in S-phase of the cell cycle (P<0.05). Statins have a beneficial effect on both early and late EPCs from DMpts with AMI. Despite the functional impairment of EPCs from DMpts, they exhibit similar responsiveness to statins as equivalent cells from NDMpts.

Vasculogenic conditioning of peripheral blood mononuclear cells promotes endothelial progenitor cell expansion and phenotype transition of anti-inflammatory macrophage and T lymphocyte to cells with regenerative potential

Background

Cell‐based therapies involving mononuclear cells (MNCs) have been developed for vascular regeneration to treat ischemic diseases; however, quality control of therapeutic MNCs has not been evaluated. We investigated the therapeutic potential of peripheral blood (PB) MNCs, operated by recently developed quality and quantity (QQ) culture of endothelial progenitor cells (EPCs).

Methods and Results

PBs were collected from healthy volunteers; peripheral blood mononuclear cells (PBMNCs) isolated from these PBs were subjected to QQ culture for 7 days with medium containing stem cell factor, thrombopoietin, Flt‐3 ligand, vascular endothelial growth factor, and interleukin‐6. The resulting cells (QQMNCs) in EPC colony‐forming assay generated significantly more definitive EPC colonies than PBMNCs. In flow cytometry, macrophages and helper T lymphocytes of QQMNCs became phenotypically polarized into angiogenic, anti‐inflammatory, and regenerative subsets: classical M1 to alternative M2; T helper (Th)1 to Th2; angiogenic or regulatory T‐cell expansion. Quantitative real‐time polymerase chain reaction (qRT‐PCR) assay revealed the predominant proangiogenic gene expressions in QQMNCs versus PBMNCs. Using murine ischemic hindlimb models, the efficacy of QQMNC intramuscular transplantation (Tx) was compared to that of PBMNCTx, cultured “early EPC” Tx (eEPCTx), and granulocyte colony‐stimulating factor mobilized CD34⁺ cell Tx (GmCD34Tx). Laser Doppler imaging revealed the blood perfusion recovery in ischemic hindlimbs after QQMNCTx superior to after PBMNCTx and eEPCTx, but also earlier than after GmCD34Tx. Histological evaluations and qRT‐PCR assays in ischemic hindlimbs demonstrated that QQMNCTx, similarly to GmCD34Tx, enhanced angiovasculogenesis and myogenesis, whereas it preponderantly inhibited inflammation and fibrosis versus PBMNCTx and eEPCTx.

Conclusions

QQ culture potentiates the ability of PBMNCs to promote regeneration of injured tissue; considering the feasible cell preparation, QQ culture‐treated PBMNCs may provide a promising therapeutic option for ischemic diseases.

Clinical Trial Registration

URL: irb.med.u-tokai.ac.jp/d/2/monthly/2010.html; IRB No.: 10R‐020.

URL: irb.med.u-tokai.ac.jp/d/2/monthly/201312.html; IRB No.: 13R228.

A reappraisal of the role of circulating (progenitor) cells in the pathobiology of diabetic complications

Traditionally, the development of diabetic complications has been attributed to the biochemical pathways driving hyperglycaemic cell damage, while reparatory mechanisms have been long overlooked. A more comprehensive view of the balance between damage and repair suggests that an impaired regenerative capacity of bone marrow (BM)-derived cells strongly contributes to defective re-endothelisation and neoangiogenesis in diabetes. Although recent technological advances have redefined the biology and function of endothelial progenitor cells (EPCs), interest in BM-derived vasculotropic cells in the setting of diabetes and its complications remains high. Several circulating cell types of haematopoietic and non-haematopoietic origin are affected by diabetes and are potentially involved in the pathobiology of chronic complications. In addition to classical EPCs, these include circulating (pro-)angiogenic cells, polarised monocytes/macrophages (M1 and M2), myeloid calcifying cells and smooth muscle progenitor cells, having disparate roles in vascular biology. In parallel with the study of elusive progenitor cell phenotypes, it has been recognised that diabetes induces a profound remodelling of the BM stem cell niche. The alteration of circulating (progenitor) cells in the BM is now believed to be the link among distant end-organ complications. The field is rapidly evolving and interest is shifting from specific cell populations to the complex network of interactions that orchestrate trafficking of circulating vasculotropic cells.

Monocyte-macrophage polarization balance in pre-diabetic individuals

Pre-diabetes is characterized by increased cardiovascular risk and chronic inflammation. The activation of monocyte-macrophages plays major roles in vascular biology. Herein, we aimed to analyze monocyte-macrophage polarization status in subjects with IFG and/or IGT compared with normal glucose tolerant (NGT) individuals. We enrolled 87 middle-aged individuals with low prevalence of cardiovascular disease. Based on OGTT, they were divided into 49 NGT and 38 pre-diabetic (IFG and/or IGT). Using flow cytometry analysis of peripheral blood cells, we quantified traditional monocyte subsets based on CD14 and CD16 expression as well as novel monocyte-macrophage pro-inflammatory CD68(+)CCR2(+) M1 and anti-inflammatory CX3CR1(+)CD163(+)/CD206(+) M2 phenotypes. The M1/M2 ratio was taken to represent the polarization balance. There were no differences in traditional classical (CD14(++)CD16(-)), intermediate (CD14(++)CD16(+)) and nonclassical (CD14(+)CD16(+)) monocytes between groups. Rather, compared to NGT, pre-diabetic subjects showed a significant increase in pro-inflammatory M1 cells and percent expression of the oxLDL scavenger receptor CD68, without changes in anti-inflammatory M2 cells. M1 levels and CD68 expression were directly correlated with HbA1c. We show for the first time that otherwise healthy pre-diabetic subjects have excess M1 inflammatory cells in peripheral blood, which may contribute to cardiovascular risk.

Possible involvement of PPARγ-associated eNOS signaling activation in rosuvastatin-mediated prevention of nicotine-induced experimental vascular endothelial abnormalities

Nicotine exposure via cigarette smoking and tobacco chewing is associated with vascular complications. The present study investigated the effect of rosuvastatin in nicotine (2 mg/kg/day, i.p., 4 weeks)-induced vascular endothelial dysfunction (VED) in rats. The development of VED was assessed by employing isolated aortic ring preparation and estimating aortic and serum nitrite/nitrate concentration. Further, scanning electron microscopy and hematoxylin-eosin staining of thoracic aorta were performed to assess the vascular endothelial integrity. Moreover, oxidative stress was assessed by estimating aortic superoxide anion generation and serum thiobarbituric acid-reactive substances. The nicotine administration produced VED by markedly reducing acetylcholine-induced endothelium-dependent relaxation, impairing the integrity of vascular endothelium, decreasing aortic and serum nitrite/nitrate concentration, increasing oxidative stress, and inducing lipid alteration. However, treatment with rosuvastatin (10 mg/kg/day, i.p., 4 weeks) markedly attenuated nicotine-induced vascular endothelial abnormalities, oxidative stress, and lipid alteration. Interestingly, the co-administration of peroxisome proliferator-activated receptor γ (PPARγ) antagonist, GW9662 (1 mg/kg/day, i.p., 2 weeks) submaximally, significantly prevented rosuvastatin-induced improvement in vascular endothelial integrity, endothelium-dependent relaxation, and nitrite/nitrate concentration in rats administered nicotine. However, GW9662 co-administration did not affect rosuvastatin-associated vascular anti-oxidant and lipid-lowering effects. The incubation of aortic ring, isolated from rosuvastatin-treated nicotine-administered rats, with L-NAME (100 μM), an inhibitor of nitric oxide synthase (NOS), significantly attenuated rosuvastatin-induced improvement in acetylcholine-induced endothelium-dependent relaxation. Rosuvastatin prevents nicotine-induced vascular endothelial abnormalities by activating PPARγ and endothelial NOS signaling pathways. Moreover, the PPARγ-independent anti-oxidant and lipid-lowering effects of rosuvastatin might additionally play a role in the improvement of vascular endothelial function.

Restoring stem cell mobilization to promote vascular repair in diabetes

Diabetes triggers endothelial dysfunction, which is linked to increased risk of cardiovascular diseases. Stem and progenitor cells from the bone marrow are involved in the maintenance of vascular integrity. Diabetic patients show a dysfunction of these cells, which might represent a novel pathophysiological mechanism of vascular disease. Specifically, stem and progenitor cells fail to egress from the bone marrow (BM) due to BM pathological alterations and unresponsiveness to mobilizing stimuli. In this review, we describe impaired stem cell mobilization in diabetes as a mechanism of failed vascular repair and we provide evidence that pharmacological strategies can restore mobilization. We discuss recent advances in the knowledge of aberrant organization of the diabetic BM and its implications for impaired mobilization. Finally, we describe in detail the pharmacological exploitation of the G-CSF/DPP-4(CD26)/SDF-1α axis as a novel strategy to improve mobilization and attain vascular repair in diabetes.

Liver X receptor modulates diabetic retinopathy outcome in a mouse model of streptozotocin-induced diabetes

Endothelial progenitor cells (EPCs), critical for mediating vascular repair, are dysfunctional in a hyperglycemic and/or hypercholesterolemic environment. Their dysfunction contributes to the progression of diabetic macro- and microvascular complications. Activation of "cholesterol-sensing" nuclear receptors, the liver X receptors (LXRα/LXRβ), protects against atherosclerosis by transcriptional regulation of genes important in promoting cholesterol efflux and inhibiting inflammation. We hypothesized that LXR activation with a synthetic ligand would correct diabetes-induced EPC dysfunction and improve diabetic retinopathy. Studies were performed in streptozotocin (STZ)-injected DBA/2J mice fed a high-fat Western diet (DBA/STZ/WD) and treated with the LXR agonist GW3965 and in LXRα(-/-), LXRβ(-/-), and LXRα/β(-/-) mice. Retinas were evaluated for number of acellular capillaries and glial fibrillary acidic protein (GFAP) immunoreactivity. Bone marrow EPCs were analyzed for migratory function and gene expression. Compared with vehicle-treated DBA/STZ/WD mice, GW3965 treated mice showed fewer acellular capillaries and reduced GFAP expression. These mice also exhibited enhanced EPC migration and restoration of inflammatory and oxidative stress genes toward nondiabetic levels. LXRα(-/-), LXRβ(-/-), and LXRα/β(-/-) mice developed acellular capillaries and EPC dysfunction similar to the DBA/STZ/WD mice. These studies support a key role for LXR in retinal and bone marrow progenitor dysfunction associated with type 1 diabetes. LXR agonists may represent promising pharmacologic targets for correcting retinopathy and EPC dysfunction.

Imbalance of circulating endothelial cells and progenitors in idiopathic pulmonary fibrosis

BACKGROUND

Fibrogenesis during idiopathic pulmonary fibrosis (IPF) is strongly associated with abnormal vascular remodeling. Respective abundance of circulating endothelial cells (CEC) and endothelial progenitor cells (EPC) might reflect the balance between vascular injury and repair and potentially serve as biomarkers of the disease.

OBJECTIVES AND METHODS

We postulated that CEC and EPC subtypes might be differently modulated in IPF. Sixty-four consecutive patients with newly diagnosed IPF were prospectively enrolled and compared to thirteen healthy volunteers. CEC were counted with immunomagnetic CD146-coated beads; progenitors CD34+45(dim)/CD34+133+/CD34+KDR+were assessed through flow cytometry and EPC (colony-forming-units-Endothelial Cells, CFU-EC, and endothelial colonies forming cells, ECFC) were quantified by cell culture assays.

RESULTS

IPF patients were characterized by a marked increase in CEC associated to an EPC defect: both CD34(+)KDR(+) cells and CFU-EC were decreased versus controls. Moreover, in IPF subjects with a low diffusing capacity of the lung for carbon monoxide (DL(CO)) < 40 %, CFU-EC and ECFC were higher compared to those with DL(CO) > 40 %. Finally, ECFC were negatively correlated with DL(CO). During an 18 month follow up, CEC levels increased in patients with exacerbation, including those who died during follow up. Finally, ECFC from patients with exacerbation proliferative potential was strongly increased.

CONCLUSION

IPF is basically associated with both a vascular injury and a repair defect. This study highlights an adaptative process of EPC mobilization in the most severe forms of IPF, that could reflect enhanced homing to the pulmonary vasculature, which clinical consequences remain to be determined.

Effects of rosuvastatin and allopurinol on circulating endothelial progenitor cells in patients with congestive heart failure: the impact of inflammatory process and oxidative stress

OBJECTIVE

Endothelial progenitor cells (EPCs) contribute to the maintenance of endothelial integrity and function. We investigated the effects of rosuvastatin and allopurinol on the number of EPCs in patients with heart failure and aimed to provide insight into the molecular inflammatory and oxidative mechanisms that could be responsible for the alterations in EPC levels after treatment.

METHODS

Sixty patients with systolic heart failure were randomized to receive rosuvastatin 10mg/d, allopurinol 300mg/d or placebo and followed up for 1 month. The number of CD34(+)/KDR(+) and CD34(+)/CD133(+)/KDR(+) EPCs in blood was evaluated by flow cytometry. Endothelial function was assessed by brachial artery flow-mediated dilation. Levels of markers of inflammation and oxidative stress were also determined.

RESULTS

Circulating EPCs were significantly increased after rosuvastatin treatment (from 230 (170-380) and 10 (8-24) to 390 (230-520) and 19 (8-33) cells/10(6) lymphomonocytes, respectively, p=0.004 and p=0.008), whereas they remained unchanged in the other groups. The increase in EPC levels was not associated with the changes in the levels of the measured inflammatory and oxidative markers.

CONCLUSION

Short-term treatment with rosuvastatin, but not allopurinol, significantly increases the number of circulating EPCs in patients with heart failure providing further insights into its role in these individuals. The impact of rosuvastatin on EPCs is not mediated by changes in inflammatory and oxidative status.