Grape seed procyanidin B2 inhibits advanced glycation end product-induced endothelial cell apoptosis through regulating GSK3β phosphorylation

Procyanidin B2 alleviates oxidized low-density lipoprotein-induced cell injury, inflammation, monocyte chemotaxis, and oxidative stress by inhibiting the nuclear factor kappa-B pathway in human umbilical vein endothelial cells

BACKGROUND

Oxidized low-density lipoprotein (ox-LDL) can initiate and affect almost all atherosclerotic events including endothelial dysfunction. In this text, the role and underlying molecular basis of procyanidin B2 (PCB2) with potential anti-oxidant and anti-inflammatory activities in ox-LDL-induced HUVEC injury were examined.

METHODS

HUVECs were treated with ox-LDL in the presence or absence of PCB2. Cell viability and apoptotic rate were examined by CCK-8 assay and flow cytometry, respectively. The mRNA and protein levels of genes were tested by RT-qPCR and western blot assays, respectively. Potential downstream targets and pathways of apple procyanidin oligomers were examined by bioinformatics analysis for the GSE9647 dataset. The effect of PCB2 on THP-1 cell migration was examined by recruitment assay. The effect of PCB2 on oxidative stress was assessed by reactive oxygen species (ROS) level, malondialdehyde (MDA) content, and mitochondrial membrane potential (MMP).

RESULTS

ox-LDL reduced cell viability, induced cell apoptosis, and facilitated the expression of oxidized low-density lipoprotein receptor 1 (LOX-1), C-C motif chemokine ligand 2 (MCP-1), vascular cell adhesion protein 1 (VCAM-1) in HUVECs. PCB2 alleviated ox-LDL-induced cell injury in HUVECs. Apple procyanidin oligomers triggered the differential expression of 592 genes in HUVECs (|log2fold-change| > 0.58 and adjusted p-value < 0.05). These dysregulated genes might be implicated in apoptosis, endothelial cell proliferation, inflammation, and monocyte chemotaxis. PCB2 inhibited C-X-C motif chemokine ligand 1/8 (CXCL1/8) expression and THP-1 cell recruitment in ox-LDL-stimulated HUVECs. PCB2 inhibited ox-LDL-induced oxidative stress and nuclear factor kappa-B (NF-κB) activation in HUVECs.

CONCLUSION

PCB2 weakened ox-LDL-induced cell injury, inflammation, monocyte recruitment, and oxidative stress by inhibiting the NF-κB pathway in HUVECs.

Procyanidin B2: A promising multi-functional food-derived pigment for human diseases

Natural edible pigments play a paramount part in the food industry. Procyanidin B2 (PB2), one of the most representative naturally occurring edible pigments, is usually isolated from the seeds, fruits, and leaves of lots of common plants, such as grapes, Hawthorn, black soybean, as well as blueberry, and functions as a food additive in daily life. Notably, PB2 has numerous bioactivities and possesses the potential to treat/prevent a wide range of human diseases, such as diabetes mellitus, diabetic complications, atherosclerosis, and non-alcoholic fatty liver disease, and the underlying mechanisms were partially elucidated, including mediating signaling pathways like NF-κB, MAPK, PI3K/Akt, apoptotic axis, and Nrf-2/HO-1. This paper presents a review of the natural sources, bioactivities, and the therapeutic/preventive potential of PB2 and the possible mechanisms, with the aim of promoting the development of PB2 as a functional food and providing references for its clinical application in the treatment of diseases.

Milk Fat Globule Epidermal Growth Factor VIII Fragment Medin in Age-Associated Arterial Adverse Remodeling and Arterial Disease

Medin, a small 50-amino acid peptide, is an internal cleaved product from the second discoidin domain of milk fat globule epidermal growth factor VIII (MFG-E8) protein. Medin has been reported as the most common amylogenic protein in the upper part of the arterial system, including aortic, temporal, and cerebral arterial walls in the elderly. Medin has a high affinity to elastic fibers and is closely associated with arterial degenerative inflammation, elastic fiber fragmentation, calcification, and amyloidosis. In vitro, treating with the medin peptide promotes the inflammatory phenotypic shift of both endothelial cells and vascular smooth muscle cells. In vitro, ex vivo, and in vivo studies demonstrate that medin enhances the abundance of reactive oxygen species and reactive nitrogen species produced by both endothelial cells and vascular smooth muscle cells and promotes vascular endothelial dysfunction and arterial stiffening. Immunostaining and immunoblotting analyses of human samples indicate that the levels of medin are increased in the pathogenesis of aortic aneurysm/dissection, temporal arteritis, and cerebrovascular dementia. Thus, medin peptide could be targeted as a biomarker diagnostic tool or as a potential molecular approach to curbing the arterial degenerative inflammatory remodeling that accompanies aging and disease.

Increased MFG-E8 at neuromuscular junctions is an exacerbating factor for sarcopenia-associated denervation

Sarcopenia is an important health problem associated with adverse outcomes. Although the etiology of sarcopenia remains poorly understood, factors apart from muscle fibers, including humoral factors, might be involved. Here, we used cytokine antibody arrays to identify humoral factors involved in sarcopenia and found a significant increase in levels of milk fat globule epidermal growth factor 8 (MFG‐E8) in skeletal muscle of aged mice, compared with young mice. We found that the increase in MFG‐E8 protein at arterial walls and neuromuscular junctions (NMJs) in muscles of aged mice. High levels of MFG‐E8 at NMJs and an age‐related increase in arterial MFG‐E8 have also been identified in human skeletal muscle. In NMJs, MFG‐E8 is localized on the surface of terminal Schwann cells, which are important accessory cells for the maintenance of NMJs. We found that increased MFG‐E8 at NMJs precedes age‐related denervation and is more prominent in sarcopenia‐susceptible fast‐twitch than in sarcopenia‐resistant slow‐twitch muscle. Comparison between fast and slow muscles further revealed that arterial MFG‐E8 can be uncoupled from sarcopenic phenotype. A genetic deficiency in MFG‐E8 attenuated age‐related denervation of NMJs and muscle weakness, providing evidence of a pathogenic role of increased MFG‐E8. Thus, our study revealed a mechanism by which increased MFG‐E8 at NMJs leads to age‐related NMJ degeneration and suggests that targeting MFG‐E8 could be a promising therapeutic approach to prevent sarcopenia.

Effects and mechanisms of Danshen-Shanzha herb-pair for atherosclerosis treatment using network pharmacology and experimental pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

The danshen (the root of Salvia miltiorrhiza Bge.)-shanzha (the fruit of Crataegus pinnatifida Bge. var. major N.E.Br.) (DS) herb combination is a commonly used traditional Chinese medicine with cardiovascular disease (CVD) treatment potential.

MATERIALS AND METHODS

In this study, we investigated the anti-atherosclerotic effects and mechanisms of DS by the integration of network pharmacology and polypharmacology. Eight main components were selected for target fishing by PharmMapper.

RESULTS

The network pharmacological study indicated that DS may target 41 proteins and 16 pathways associated with inflammation, lipid metabolism and endothelial protection, which indicates that DS probably adjusts these processes as part of its anti-atherosclerotic activities. Furthermore, this hypothesis was verified by polypharmacology using an atherosclerotic model. Histopathological examination showed that DS inhibited pathological changes in the arteries of atherosclerotic rats and reduced the intima-media thickness (IMT). DS significantly reduced the levels of total cholesterol (TC), triglyceride (TG), and low-density lipoprotein-cholesterol (LDL-C) and increased the high-density lipoprotein-cholesterol (HDL-C) level in the blood. DS also decreased the concentrations of interleukin (IL)-1β and IL-18, indicating anti-inflammation activity. In addition, DS increased the serum levels of nitric oxide (NO) and 6-keto-prostaglandin F_1α (6-keto-PGF_1α) and decreased the serum levels of endothelin (ET) and thromboxane B₂ (TXB₂), indicating an endothelial protective effect.

CONCLUSIONS

In conclusion, DS has an anti-atherosclerotic ability to lower lipid concentrations and to protect endothelial function, and it also has anti-inflammatory activity.

Endogenous Secretory Receptor for Advanced Glycation End Products Protects Endothelial Cells from AGEs Induced Apoptosis

Endogenous secretory receptor for advanced glycation end products (esRAGE) binds extracellular RAGE ligands and blocks RAGE activation on the cell surface, protecting endothelial cell function. However, the underlying mechanism remains unclear. Endothelial cells overexpressing the esRAGE gene were generated using a lentiviral vector. Then, quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) were used to assess esRAGE mRNA and protein levels, respectively. Hoechst-PI double staining was used to assess apoptosis. Western blot and qRT-PCR were used to assess the expression levels of apoptosis-related factors and the proinflammatory cytokine NF-кB. Compared with the control group, AGEs significantly induced endothelial cell apoptosis, which was significantly reduced by esRAGE overexpression. Incubation with AGEs upregulated the proapoptotic factor Bax and downregulated the antiapoptotic factor Bcl-2. Overexpression of esRAGE reduced Bax expression induced by AGEs and increased Bcl-2 levels. Furthermore, AGEs increased the expression levels of proinflammatory cytokine NF-кB, which were reduced after esRAGE overexpression. esRAGE protects endothelial cells from AGEs associated apoptosis, by downregulating proapoptotic (Bax) and inflammatory (NF-кB) factors and upregulating the antiapoptotic factor Bcl-2.

TRB3 mediates advanced glycation end product-induced apoptosis of pancreatic β-cells through the protein kinase C β pathway

Advanced glycation end products (AGEs), which accumulate in the body during the development of diabetes, may be one of the factors leading to pancreatic β-cell failure and reduced β-cell mass. However, the mechanisms responsible for AGE‑induced apoptosis remain unclear. This study identified the role and mechanisms of action of tribbles homolog 3 (TRB3) in AGE-induced β-cell oxidative damage and apoptosis. Rat insulinoma cells (INS-1) were treated with 200 µg/ml AGEs for 48 h, and cell apoptosis was then detected by TUNEL staining and flow cytometry. The level of intracellular reactive oxygen species (ROS) was measured by a fluorescence assay. The expression levels of receptor of AGEs (RAGE), TRB3, protein kinase C β2 (PKCβ2) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) were evaluated by RT-qPCR and western blot analysis. siRNA was used to knockdown TRB3 expression through lipofection, followed by an analysis of the effects of TRB3 on PKCβ2 and NOX4. Furthermore, the PKCβ2-specific inhibitor, LY333531, was used to analyze the effects of PKCβ2 on ROS levels and apoptosis. We found that AGEs induced the apoptosis of INS-1 cells and upregulated RAGE and TRB3 expression. AGEs also increased ROS levels in β-cells. Following the knockdown of TRB3, the AGE-induced apoptosis and intracellular ROS levels were significantly decreased, suggesting that TRB3 mediated AGE-induced apoptosis. Further experiments demonstrated that the knockdown of TRB3 decreased the PKCβ2 and NOX4 expression levels. When TRB3 was knocked down, the cells expressed decreased levels of PKCβ2 and NOX4. The PKCβ2‑specific inhibitor, LY333531, also reduced AGE-induced apoptosis and intracellular ROS levels. Taken together, our data suggest that TRB3 mediates AGE-induced oxidative injury in β-cells through the PKCβ2 pathway.

Functional Role of Milk Fat Globule-Epidermal Growth Factor VIII in Macrophage-Mediated Inflammatory Responses and Inflammatory/Autoimmune Diseases

Inflammation involves a series of complex biological processes mediated by innate immunity for host defense against pathogen infection. Chronic inflammation is considered to be one of the major causes of serious diseases, including a number of autoimmune/inflammatory diseases, cancers, cardiovascular diseases, and neurological diseases. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a secreted protein found in vertebrates and was initially discovered as a critical component of the milk fat globule. Previously, a number of studies have reported that MFG-E8 contributes to various biological functions including the phagocytic removal of damaged and apoptotic cells from tissues, the induction of VEGF-mediated neovascularization, the maintenance of intestinal epithelial homeostasis, and the promotion of mucosal healing. Recently, emerging studies have reported that MFG-E8 plays a role in inflammatory responses and inflammatory/autoimmune diseases. This review describes the characteristics of MFG-E8-mediated signaling pathways, summarizes recent findings supporting the roles of MFG-E8 in inflammatory responses and inflammatory/autoimmune diseases, and discusses MFG-E8 targeting as a potential therapeutic strategy for the development of anti-inflammatory/autoimmune disease drugs.

Critical Role of FoxO1 in Granulosa Cell Apoptosis Caused by Oxidative Stress and Protective Effects of Grape Seed Procyanidin B2

Reactive oxygen species (ROS) are closely related to the follicular granulosa cell apoptosis. Grape seed procyanidin B2 (GSPB2) has been reported to possess potent antioxidant activity. However, the GSPB2-mediated protective effects and the underlying molecular mechanisms in granulosa cell apoptosis process remain unknown. In this study, we showed for the first time that GSPB2 treatment decreased FoxO1 protein level, improved granulosa cell viability, upregulated LC3-II protein level, and reduced granulosa cell apoptosis rate. Under a condition of oxidative stress, GSPB2 reversed FoxO1 nuclear localization and increased its level in cytoplasm. In addition, FoxO1 knockdown inhibited the protective effects of GSPB2 induced. Our findings suggest that FoxO1 plays a pivotal role in regulating autophagy in granulosa cells, GSPB2 exerts a potent and beneficial role in reducing granulosa cell apoptosis and inducing autophagy process, and targeting FoxO1 could be significant in fighting against oxidative stress-reduced female reproductive system diseases.

Quantitative proteomics study of protective effects of grape seed procyanidin B2 on diabetic cardiomyopathy in db/db mice

Diabetic cardiomyopathy is one of the major complications of diabetes mellitus. Oxidative stress appears to play a substantial role in cardiomyopathy. Grape seed procyanidin B2 (GSPB2) has been known as an anti-oxidant in treating diabetes mellitus; however, little is known about its effects and underlying mechanisms on diabetic cardiomyopathy. The present study is to explore the molecular targets of GSPB2 responsible for the anti-oxidative effects in db/db mice by quantitative proteomics. GSPB2 (30 mg/kg body weight/day) were intragastric administrated to db/db mice for 10 weeks. Proteomics of the heart tissue extracts by isobaric tags for relative and absolute quantification analysis was obtained from db/db mice. Our study provides important evidence that GSPB2 protect against cardiomyopathy in diabetes mellitus, which are believed to result from regulating the expression of key proteins involving cardiac fibrosis and proliferation. GSPB2 could be expected to become novel clinical application in fighting against diabetic cardiomyopathy.

Milk fat globule epidermal growth factor VIII signaling in arterial wall remodeling

Arterial inflammation and remodeling, important sequellae of advancing age, are linked to the pathogenesis of age-associated arterial diseases e.g. hypertension, atherosclerosis, and metabolic disorders. Recently, high-throughput proteomic screening has identified milk fat globule epidermal growth factor VIII (MFG-E8) as a novel local biomarker for aging arterial walls. Additional studies have shown that MFG-E8 is also an element of the arterial inflammatory signaling network. The transcription, translation, and signaling levels of MFG-E8 are increased in aged, atherosclerotic, hypertensive, and diabetic arterial walls in vivo as well as activated vascular smooth muscle cells (VSMC) and a subset of macrophages in vitro. In VSMC, MFG-E8 increases proliferation and invasion as well as the secretion of inflammatory molecules. In endothelial cells (EC), MFG-E8 facilitates apoptosis. In addition, MFG-E8 has been found to be an essential component of the endothelial-derived microparticles that relay biosignals and modulate arterial wall phenotypes. This review mainly focuses upon the landscape of MFG-E8 expression and signaling in adverse arterial remodeling. Recent discoveries have suggested that MFG-E8 associated interventions are novel approaches for the retardation of the enhanced rates of VSMC proliferation and EC apoptosis that accompany arterial wall inflammation and remodeling during aging and age-associated arterial disease.

PIMT prevents the apoptosis of endothelial cells in response to glycated low density lipoproteins and protective effects of grape seed procyanidin B2

Background

The development of diabetic angiopathy is associated with profound vascular endothelial cells (VEC) dysfunction and apoptosis. Glycated low density lipoproteins (gly-LDL) continuously produced in the setting of diabetic patients play an important role in causing VEC dysfunction and apoptosis. However, the underlying molecular mechanism remains largely elusive. Protein L-isoaspartyl methyltransferase (PIMT) is a widely expressed protein repair enzyme by multiple cell types of arterial wall including VEC. Our previous proteomic studies showed that the expression of PIMT was significantly decreased in the aorta of diabetic rats as compared with control rats and treatment with grape seed procyanidin extracts significantly increased the PIMT expression in diabetic rats. We hypothesized that PIMT plays a critical role in gly-LDL induced VEC apoptosis; grape seed procyanidin B2 (GSPB2) protect against gly-LDL induced VEC apoptosis through PIMT regulation.

Methods and Results

HUVEC transfected negative control and PIMT siRNA were treated with or without GSPB2 (10 µmol/L) for 48 h. Moreover, HUVEC of PIMT overexpression were stimulated by gly-LDL (50 µg/ml) in the presence or absence of GSPB2 (10 µmol/L) for 48 h. Our results showed that gly-LDL downregulated PIMT expression and PIMT overexpression or GSPB2 significantly attenuated gly-LDL induced VEC apoptosis. PIMT siRNA increased VEC apoptosis with up-regulation of p53, cytochrome c release, caspase-9 and caspase-3 activation. Mechanistically, overexpression of PIMT or GSPB2 increased the phosphorylation of ERK1/2 and GSK3β in the gly-LDL induced VEC.

Conclusion

In summary, our study identified PIMT as a key player responsible for gly-LDL induced VEC apoptosis and GSPB2 protect against gly-LDL induced VEC apoptosis by PIMT up-regulation. Targeting PIMT including use of GSPB2 could be turned into clinical application in the fighting against diabetic vascular complications.

Proteomic analysis of aorta and protective effects of grape seed procyanidin B2 in db/db mice reveal a critical role of milk fat globule epidermal growth factor-8 in diabetic arterial damage

Background

Atherosclerosis is one of the major complications of type 2 diabetic patients (T2DM), leading to morbidity and mortality. Grape seed procyanidin B2 (GSPB2) has demonstrated protective effect against atherosclerosis, which is believed to be, at least in part, a result of its antioxidative effects. The aim of this study is to identify the target protein of GSPB2 responsible for the protective effect against atherosclerosis in patients with DM.

Methods and Results

GSPB2 (30 mg/kg body weight/day) were administrated to db/db mice for 10 weeks. Proteomics of the aorta extracts by iTRAQ analysis was obtained from db/db mice. The results showed that expression of 557 proteins were either up- or down-regulated in the aorta of diabetic mice. Among those proteins, 139 proteins were normalized by GSPB2 to the levels comparable to those in control mice. Among the proteins regulated by GSPB2, the milk fat globule epidermal growth factor-8 (MFG-E8) was found to be increased in serum level in T2DM patients; the serum level of MFG-E8 was positively correlated with carotid-femoral pulse wave velocity (CF-PWV). Inhibition of MFG-E8 by RNA interference significantly suppressed whereas exogenous recombinant MFG-E8 administration exacerbated atherogenesis the db/db mice. To gain more insights into the mechanism of action of MFG-E8, we investigated the effects of MFG-E8 on the signal pathway involving the extracellular signal-regulated kinase (ERK) and monocyte chemoattractant protein-1 (MCP-1). Treatment with recombinant MFG-E8 led to increased whereas inhibition of MFG-E8 to decreased expression of MCP-1 and phosphorylation of ERK1/2.

Conclusion

Our data suggests that MFG-E8 plays an important role in atherogenesis in diabetes through both ERK and MCP-1 signaling pathways. GSPB2, a well-studied antioxidant, significantly inhibited the arterial wall changes favoring atherogenesis in db/db mice by down-regulating MFG-E8 expression in aorta and its serum level. Measuring MFG-E8 serum level could be a useful clinical surrogate prognosticating atherogenesis in DM patients.