Aliskiren directly improves endothelial progenitor cell function from Type II diabetic patients

Inhibition of CCL7 improves endothelial dysfunction and vasculopathy in mouse models of diabetes mellitus

Diabetic vascular disease is a major complication of diabetes mellitus (DM). Chemokine C-C motif ligand 7 (CCL7) attracts macrophages and monocytes, amplifying inflammatory processes in the vasculature. We hypothesized a causal role for CCL7 in diabetic vasculopathy. CCL7 concentrations were higher in the plasma of patients with type 2 DM, as well as in supernatants from their endothelial progenitor cells (EPCs). High-glucose stimulation increased the secretion of CCL7 from human dermal microvascular endothelial cells (HDMECs) through the c-Fos and c-Jun signaling pathways. CCL7 inhibition using knockdown or neutralization antibody treatment reversed the high glucose-induced impaired tube formation and migration abilities of EPCs, human aortic endothelial cells, human coronary artery endothelial cells, and HDMECs. Administration of recombinant human CCL7 protein impaired tube formation and migration abilities by down-regulating the AKT-endothelial nitric oxide synthase and AKT/nuclear factor erythroid 2-related factor 2/heme oxygenase-1/vascular endothelial growth factor/stromal cell-derived factor-1 pathways and by up-regulating ERK/phosphorylated p65/interleukin-1β/interleukin-6/tumor necrosis factor-α pathways through CC chemokine receptor 3 in endothelial cells. Ccl7 knockout in streptozotocin-treated mice showed improved neovasculogenesis in ischemic limbs and accelerated wound repair, with increased circulating EPCs and capillary density. CCL7 antibody treatment in db/db mice and high-fat diet-induced hyperglycemia mice showed improved neovasculogenesis in ischemic limbs and wound areas, accompanied by up-regulation of angiogenic proteins and down-regulation of inflammatory proteins. Endothelial cell-specific Ccl7-knockout mice showed ameliorated diabetic vasculopathy in streptozotocin-induced DM. This study highlights the potential of CCL7 as a therapeutic target for diabetic vasculopathy.

RAAS in diabetic retinopathy: mechanisms and therapies

Diabetic retinopathy (DR) is a complication of diabetes with a complex pathophysiology and multiple factors involved. Recently, it has been found that the upregulation of the renin-angiotensin-aldosterone system (RAAS) leads to overexpression of angiotensin II (Ang II), which induces oxidative stress, inflammation, and angiogenesis in the retina. Therefore, RAAS may be a promising therapeutic target in DR. Notably, RAAS inhibitors are often used in the treatment of hypertension. Still, the potential role and mechanism of DR must be further studied. In this review, we discuss and summarize the pathology and potential therapeutic goals of RAAS in DR.

Aliskiren Improved the Endothelial Repair Capacity of Endothelial Progenitor Cells from Patients with Hypertension via the Tie2/PI3k/Akt/eNOS Signalling Pathway

Background

Studies show that aliskiren exerts favourable effects not only on endothelial progenitor cells (EPCs) but also on endothelial function. However, the mechanism of the favourable effect of aliskiren on EPCs from patients with hypertension is unclear and remains to be further studied.

Methods

The object of this study was to investigate and assess the in vitro function of EPCs pretreated with aliskiren. After treated with aliskiren, the human EPCs were transplanted into a nude mouse model of carotid artery injury, and the in vivo reendothelialization of injured artery was estimated by staining denuded areas with Evans blue dye via tail vein injection.

Results

We found that aliskiren increased the in vitro migration, proliferation, and adhesion of EPCs from patients with hypertension in a dose-dependent manner and improved the reendothelialization capability of these EPCs. Furthermore, aliskiren increased the phosphorylation of Tie2, Akt, and eNOS. After the blockade of the Tie2 signalling pathway, the favourable effects of aliskiren on the in vitro function and in vivo reendothelialization capability of EPCs were suppressed.

Conclusions

This study demonstrates that aliskiren can improve the in vitro function and in vivo reendothelialization capability of EPCs from patients with hypertension via the activation of the Tie2/PI3k/Akt/eNOS signalling pathway. These findings further indicate that aliskiren is an effective pharmacological treatment for cell-based repair in hypertension-related vascular injury.

Activating α7nAChRs enhances endothelial progenitor cell function partially through the JAK2/STAT3 signaling pathway

Microvascular injury is a common pathological process in ischemia-reperfusion injury. Endothelial progenitor cells (EPCs) are vital cells for angiogenesis and endothelial repair. These cells can home to injury sites and secrete angiogenic growth factors. α7nAChRs are pivotal in cholinergic angiogenesis, which is associated with endothelial cells and EPCs. Our study was designed to determine whether activating α7nAChRs enhances the function of EPCs and to explore the underlying mechanism. EPCs were derived from the bone marrow of male Sprague-Dawley rats and treated with an α7nAChR agonist (PNU282987), an α7nAChR antagonist (MLA) and a JAK2 antagonist (AG490). We then assayed the angiogenic abilities of the EPCs, including proliferation ability, adhesion ability, migration ability and in vitro tube formation ability. The levels of total JAK2 (t-JAK2), phosphorylated JAK2 (p-JAK2), total STAT3 (t-STAT3) and phosphorylated STAT3 (p-STAT3) were estimated by western blot analysis. PNU282987 treatment facilitated the angiogenic abilities of EPCs compared with the control regimen. The western blot data suggested that PNU282987 increased the levels of p-JAK2 and p-STAT3. However, the differences in t-JAK2 levels and t-STAT3 levels between the agonist-treated group and the control group were not significant. Moreover, treating EPCs with AG490 reduced STAT3 phosphorylation and attenuated the PNU282987-induced enhancement of EPCs. We demonstrated that activating α7nAChRs can enhance EPC functions partially through the JAK2/STAT3 signaling pathway. This study reveals that α7nAChRs are potential therapeutic targets for angiogenesis and that the JAK2/STAT3 pathway plays a vital role in the associated therapeutic mechanism.

MiR-92a regulates endothelial progenitor cells (EPCs) by targeting GDF11 via activate SMAD2/3/FAK/Akt/eNOS pathway

Background

The effects of miR-92a on EPCs are still poorly elucidated. This study aimed to investigate the effects of miR-92a on EPCs (Endothelial progenitor cells) in a model of hypoxia (HO) or high glucose (HG)-induced EPCs injury by targeting GDF11 (Differentiation growth factor 11).

Methods

The effects of miR-92a on EPCs subjected to HO or HG were investigated firstly. Subsequently, the action mechanism of miR-92a on EPCs by targeting GDF11 was elucidated. Proliferation, apoptosis, migration, angiogenesis was measured with MTT, flow cytometry, transwell, tube formation respectively. After 24 h, levels of reactive oxygen species (ROS) were measured by fluorescence intensity. LDH and NO (nitric oxide) levels were determined by ELISA. The expression of FLK-1 (fetal liver kinase 1) and vWF (von Willebrand factor) was detected by immunofluorescence. mRNA and protein expression levels were examined using PCR and western blotting respectively. The interaction between miR-92a and GDF11 was evaluated by dual-luciferase reporter assay.

Results

Our results showed that HO or HG increased apoptosis, production of LDH and generation of ROS, but decreased the ability of migration and tube formation and generation of NO in EPCs; inhibiting of miR-92a decreased HO or HG-induced injury of EPCs, whereas miR-92a over-expression had the opposite effect; the protective effects induced by inhibiting of miR-92a on EPCs could be reversed by GDF11 siRNA and the harmful effects induced by over-expression of miR-92a could be rescued by over-expression of GDF11, which showed that the harmful effects of miR-92a be related to its inhibition of GDF11 and subsequent inactivation of the SMAD2/3/FAK/Akt/eNOS signaling pathway.

Conclusions

Inhibiting miR-92a can protect EPCs from HO or HG-induced injury. The effect of miR-92a on EPCs are mediated by regulating of GDF11 and downstream SMAD2/3/FAK/Akt/eNOS signaling pathway.

Inhibition of macrophage inflammatory protein-1β improves endothelial progenitor cell function and ischemia-induced angiogenesis in diabetes

Systemic inflammation might contribute to the impairment of neovasculogenesis and endothelial progenitor cell (EPC) function in clinical diabetes mellitus (DM). Macrophage inflammatory protein-1β (MIP-1β) is an inflammatory chemokine that may be up-regulated in clinical DM. Its role in diabetic vasculopathy was not clarified. This study aimed to investigate the role of MIP-1β in human EPCs and in neovasculogenesis in different diabetic animal models with hindlimb ischemia. EPCs chamber assay and in vitro tube formation assay were used to estimate the degree of EPC migration and tube formation abilities. Lepr^db/JNarl mice, C57BL/6 mice fed a high-fat diet, and streptozotocin-induced diabetic mice were used as different diabetic animal models. Laser Doppler imaging and flow cytometry were used to evaluate the degree of neovasculogenesis and the circulating levels of EPCs, respectively. MIP-1β impaired human EPC function for angiogenesis in vitro. Plasma MIP-1β levels were up-regulated in type 2 DM patients. MIP-1β inhibition enhanced the function and the C-X-C chemokine receptor type 4 expression of EPCs from type 2 diabetic patients, and improved EPC homing for ischemia-induced neovasculogenesis in different types of diabetic animals. MIP-1β directly impaired human EPC function. Inhibition of MIP-1β improved in vitro EPC function, and enhanced in vivo EPC homing and ischemia-induced neovasculogenesis, suggesting the critical role of MIP-1β for vasculopathy in the presence of DM.

High glucose-induced endothelial progenitor cell dysfunction

Vascular complications contribute significantly to morbidity and mortality of diabetes mellitus. The primary cause of vascular complications in diabetes mellitus is hyperglycaemia, associated with endothelial dysfunction and impaired neovascularization. Circulating endothelial progenitor cells was shown to play important roles in vascular repair and promoting neovascularization. In this review, we will demonstrate the individual effect of high glucose on endothelial progenitor cells. Endothelial progenitor cells isolated from healthy subjects exposed to high glucose conditions or endothelial progenitor cells isolated from diabetic patients exhibit reduced number of endothelial cell colony forming units, impaired abilities of differentiation, proliferation, adhesion and migration, tubulization, secretion, mobilization and homing, whereas enhanced senescence. Increased production of reactive oxygen species by the mitochondria seems to play a crucial role in high glucose-induced endothelial progenitor cells deficit. Later, we will review the agents that might be used to alleviate dysfunction of endothelial progenitor cells induced by high glucose. The conclusions are that the relationship between hyperglycaemia and endothelial progenitor cells dysfunction is only beginning to be recognized, and future studies should pay more attention to the haemodynamic environment of endothelial progenitor cells and ageing factors to discover novel treatment agents.

Acarbose Accelerates Wound Healing via Akt/eNOS Signaling in db/db Mice

Refractory wound is a dreaded complication of diabetes and is highly correlated with EPC dysfunction caused by hyperglycemia. Acarbose is a widely used oral glucose-lowering drug exclusively for T2DM. Previous studies have suggested the beneficial effect of acarbose on improving endothelial dysfunction in patients with T2DM. However, no data have been reported on the beneficial efficacy of acarbose in wound healing impairment caused by diabetes. We herein investigated whether acarbose could improve wound healing in T2DM db/db mice and the possible mechanisms involved. Acarbose hastened wound healing and enhanced angiogenesis, accompanied by increased circulating EPC number in db/db mice. In vitro, a reversed BM-EPC dysfunction was observed after the administration of acarbose in db/db mice, as reflected by tube formation assay. In addition, a significantly increased NO production was also witnessed in BM-EPCs from acarbose treated db/db mice, with decreased O₂ levels. Akt inhibitor could abolish the beneficial effect of acarbose on high glucose induced EPC dysfunction in vitro, accompanied by reduced eNOS activation. Acarbose displayed potential effect in promoting wound healing and improving angiogenesis in T2DM mice, which was possibly related to the Akt/eNOS signaling pathway.

Hydroxysafflor yellow A promotes neovascularization and cardiac function recovery through HO-1/VEGF-A/SDF-1α cascade

AIM

The present study was to investigate the proangiogenic and cardioprotective effects of hydroxysafflor yellow A (HSYA) against myocardial infarction (MI) injury and the underlying mechanisms.

METHODS

MI model was induced by ligation of the left coronary artery in normal and heme oxygenase-1 (HO-1) knockout mice and the ones receiving vascular endothelial growth factor-A (VEGF-A) or stromal cell-derived factor-1α (SDF-1α) antagonists. They were treated with three doses or single dose of HSYA for 28days. The cardiac function, endothelial progenitor cells (EPCs) mobilization, angiogenesis, the expression of HO-1, VEGF-A, SDF-1α and apoptosis or fibrosis related proteins in the peri-infarct area were evaluated at respective times. We further examined the effect of HSYA on EPCs CXC chemokiner receptor 4 (CXCR4) expression and the role of SDF-1α on EPCs function in vitro.

RESULTS

HSYA could dose dependently reduce left ventricular function impairment, myocardial apoptosis and fibrosis, and promote EPCs mobilization and myocardial neovascularization. Further, HO-1 knockout abolished HSYA-induced up-regulation of HO-1, VEGF-A and SDF-1α. VEGF antagonist significantly reduced HSYA-increased VEGF-A and SDF-1α levels and SDF-1 antagonist abolished HSYA-simulated up-regulation of SDF-1α. Meanwhile, HO-1 knockout, administration of VEGF and SDF-1 antibodies abrogated HSYA-promoted expression of the marker proteins of newborn microvessels and cardiac functional recovery. In vitro, HSYA dose dependently promoted (CXCR4) expression on EPCs. SDF-1α significantly accelerated EPCs function which was reversed by CXCR4 antagonist.

CONCLUSION

HSYA could promote EPCs function through the HO-1/VEGF-A/SDF-1α signaling cascade, which contributed largely to myocardial neovascularization and further improved cardiac function in MI mice.