Apolipoprotein A-I mimetic peptide D-4F promotes human endothelial progenitor cell proliferation, migration, adhesion though eNOS/NO pathway

D4F alleviates the C/EBP homologous protein-mediated apoptosis in glycated high-density lipoprotein-treated macrophages by facilitating autophagy

The present study aimed to investigate the role of D4F, an apolipoprotein A-I mimetic peptide, in macrophage apoptosis induced by the glycated high-density lipoprotein (gly-HDL)-induced endoplasmic reticulum (ER) stress C/EBP homologous protein (CHOP) pathway, and unravel the regulatory role of autophagy in this process. Our results revealed that except for suppressing the accumulation of lipids within RAW264.7 macrophages caused by gly-HDL, D4F inhibited gly-HDL-induced decrease in the cell viability and increase in lactate dehydrogenase leakage and cell apoptosis, which were similar to 4-phenylbutyric acid (PBA, an ER stress inhibitor). Besides, similar to PBA, D4F inhibited gly-HDL-induced ER stress response activation evaluated through the decreased PERK and eIF2α phosphorylation, together with reduced ATF6 nuclear translocation as well as the downregulation of GRP78 and CHOP. Interestingly, D4F facilitated gly-HDL-triggered activation of autophagy, measured as elevated levels of beclin-1, LC3-II, and ATG5 expressions in macrophages. Furthermore, the inhibition effect of D4F on gly-HDL-induced ER stress-CHOP-induced apoptosis of macrophages was restrained after beclin-1 siRNA and 3-methyladenine (3-MA, an inhibitor of autophagy) treatments, while this effect was further reinforced after rapamycin (Rapa, an inducer of autophagy) treatment. Furthermore, administering D4F or Rapa to T2DM mice upregulated LC3-II and attenuated CHOP expression, cell apoptosis, and atherosclerotic lesions. However, the opposite results were obtained when 3-MA was administered to these mice. These results support that D4F effectively protects macrophages against gly-HDL-induced ER stress-CHOP-mediated apoptosis by promoting autophagy.

NMR-Based Metabolomic Analysis on the Protective Effects of Apolipoprotein A-I Mimetic Peptide against Contrast Media-Induced Endothelial Dysfunction

Endothelial dysfunction plays key roles in the pathological process of contrast media (CM)-induced acute kidney injury (CI-AKI) in patients undergoing vascular angiography or intervention treatment. Previously, we have demonstrated that an apolipoprotein A-I (apoA-I) mimetic peptide, D-4F, inhibits oxidative stress and improves endothelial dysfunction caused by CM through the AMPK/PKC pathway. However, it is unclear whether CM induce metabolic impairments in endothelial cells and whether D-4F ameliorates these metabolic impairments. In this work, we evaluated vitalities of human umbilical vein endothelial cells (HUVECs) treated with iodixanol and D-4F and performed nuclear magnetic resonance (NMR)-based metabolomic analysis to assess iodixanol-induced metabolic impairments in HUVECs, and to address the metabolic mechanisms underlying the protective effects of D-4F for ameliorating these metabolic impairments. Our results showed that iodixanol treatment distinctly impaired the vitality of HUVECs, and greatly disordered the metabolic pathways related to energy production and oxidative stress. Iodixanol activated glucose metabolism and the TCA cycle but inhibited choline metabolism and glutathione metabolism. Significantly, D-4F pretreatment could improve the iodixanol-impaired vitality of HUVECs and ameliorate the iodixanol-induced impairments in several metabolic pathways including glycolysis, TCA cycle and choline metabolism in HUVECs. Moreover, D-4F upregulated the glutathione level and hence enhanced antioxidative capacity and increased the levels of tyrosine and nicotinamide adenine dinucleotide in HUVECs. These results provided the mechanistic understanding of CM-induced endothelial impairments and the protective effects of D-4F for improving endothelial cell dysfunction. This work is beneficial to further exploring D-4F as a potential pharmacological agent for preventing CM-induced endothelial impairment and acute kidney injury.

Inhibition of Col6a5 Improve Lipid Metabolism Disorder in Dihydrotestosterone-Induced Hyperandrogenic Mice

Hyperandrogenism is a key pathological feature of polycystic ovarian syndrome (PCOS). Excess androgen can lead to PCOS-like cell hypertrophy in the ovaries and adipose tissue of rodents. Here, we established a dihydrotestosterone (DHT)-induced hyperandrogenic mouse model to analyze the differences in gene expression and signaling pathways of the ovaries and gonad fat pads of mice treated with or without DHT by RNA microarray analysis. From the results, we focused on the overlapping differentially expressed gene—Col6a5—and the major differentially enriched signaling pathway—lipid metabolism. We employed DHT-induced mouse ovarian stromal cell, adipogenic 3T3-L1 cell and hepatic cell line NCTC1469 models to investigate whether androgens directly mediate lipid accumulation and hypertrophy. We found that DHT increased lipid droplet accumulation in ovarian stromal cells and adipogenic 3T3-L1 cells but not NCTC1469 cells. DHT significantly altered stromal cell cholesterol metabolism and steroidogenesis, as indicated by changes in cholesterol levels and the expression of related genes, but these effects were not observed in 3T3-L1 cells. Moreover, Col6a5 expression was significantly increased in ovaries and gonadal fat pads of DHT-treated mice, and Col6a5 inhibition alleviated DHT-induced excess lipid accumulation and hypertrophy of ovarian stromal cells and adipogenic 3T3-L1 cells, even improved lipid metabolism in overnourished NCTC1469 cells. Our results indicate that Col6a5 plays important roles in the pathogenesis of DHT-induced lipid metabolism disorder and the hypertrophy of ovarian stromal cells and adipocytes.

Reverse-D-4F improves endothelial progenitor cell function and attenuates LPS-induced acute lung injury

Background

Patients with acute lung injury (ALI) have increased levels of pro-inflammatory mediators, which impair endothelial progenitor cell (EPC) function. Increasing the number of EPC and alleviating EPC dysfunction induced by pro-inflammatory mediators play important roles in suppressing ALI development. Because the high density lipoprotein reverse-D-4F (Rev-D4F) improves EPC function, we hypothesized that it might repair lipopolysaccharide (LPS)-induced lung damage by improving EPC numbers and function in an LPS-induced ALI mouse model.

Methods

LPS was used to induce ALI in mice, and then the mice received intraperitoneal injections of Rev-D4F. Immunohistochemical staining, flow cytometry, MTT, transwell, and western blotting were used to assess the effect of Rev-D4F on repairment of lung impairment, and improvement of EPC numbers and function, as well as the signaling pathways involved.

Results

Rev-D4F inhibits LPS-induced pulmonary edema and decreases plasma levels of the pro-inflammatory mediators TNF-α and ET-1 in ALI mice. Rev-D4F inhibited infiltration of red and white blood cells into the interstitial space, reduced lung injury-induced inflammation, and restored injured pulmonary capillary endothelial cells. In addition, Rev-D4F increased numbers of circulating EPC, stimulated EPC differentiation, and improved EPC function impaired by LPS. Rev-D4F also acted via a PI3-kinase-dependent mechanism to restore levels of phospho-AKT, eNOS, and phospho-eNOS suppressed by LPS.

Conclusions

These findings indicate that Rev-D4F has an important vasculoprotective role in ALI by improving the EPC numbers and functions, and Rev-D4F reverses LPS-induced EPC dysfuncion partially through PI3K/AKT/eNOS signaling pathway.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1099-6) contains supplementary material, which is available to authorized users.

D4F alleviates macrophage-derived foam cell apoptosis by inhibiting the NF-κB-dependent Fas/FasL pathway

This study was designed to explore the protective effect of D4F, an apolipoprotein A-I mimetic peptide, on nuclear factor-κB (NF-κB)-dependent Fas/Fas ligand (FasL) pathway-mediated apoptosis in macrophages induced by oxidized low-density lipoprotein (ox-LDL). Our results showed that ox-LDL induced apoptosis, NF-κB P65 nuclear translocation and the upregulation of Fas/FasL pathway-related proteins, including Fas, FasL, Fas-associated death domain proteins (FADD), caspase-8 and caspase-3 in RAW264.7 macrophages, whereas silencing of Fas blocked ox-LDL-induced macrophage apoptosis. Furthermore, silencing of P65 attenuated macrophage apoptosis and the upregulation of Fas caused by ox-LDL, whereas P65 expression was not significantly affected by treatment with Fas siRNA. D4F attenuated the reduction of cell viability and the increase in lactate dehydrogenase leakage and apoptosis. Additionally, D4F inhibited ox-LDL-induced P65 nuclear translocation and upregulation of Fas/FasL pathway-related proteins in RAW264.7 cells and in atherosclerotic lesions of apoE^-/- mice. However, Jo2, a Fas-activating monoclonal antibody, reversed the inhibitory effect of D4F on ox-LDL-induced cell apoptosis and upregulation of Fas, FasL and FADD. These data indicate that NF-κB mediates Fas/FasL pathway activation and apoptosis in macrophages induced by ox-LDL and that D4F protects macrophages from ox-LDL-induced apoptosis by suppressing the activation of NF-κB and the Fas/FasL pathway.

The apolipoprotein A-I mimetic peptide, D-4F, alleviates ox-LDL-induced oxidative stress and promotes endothelial repair through the eNOS/HO-1 pathway

Apolipoprotein A-I (apoA-I) mimetic peptide exerts many anti-atherogenic properties. However, the underlying mechanisms related to the endothelial protective effects remain elusive. In this study, the apoA-I mimetic peptide, D-4F, was used. Proliferation assay, wound healing, and transwell migration experiments showed that D-4F improved the impaired endothelial proliferation and migration resulting from ox-LDL. Endothelial adhesion molecules expression and monocyte adhesion assay demonstrated that D-4F inhibited endothelial inflammation. Caspase-3 activation and TUNEL stain indicated that D-4F reduced endothelial cell apoptosis. A pivotal anti-oxidant enzyme, heme oxygenase-1 (HO-1) was upregulated by D-4F. The Akt/AMPK/eNOS pathways were involved in the expression of HO-1 induced by D-4F. Moreover, the anti-oxidation, pro-proliferation, and pro-migration capacities of D-4F were diminished by the inhibitors of both eNOS (L-NAME) and HO-1 (Znpp). Additionally, downregulation of ATP-binding cassette transporter A1 (ABCA1) by siRNA abolished the activation of Akt, AMPK and eNOS, and reduced the upregulation of HO-1 triggered by D-4F. Furthermore, D-4F promoted the reendothelialization of injured intima in carotid artery injury model of C57BL/6J mice in vivo. In summary, these findings suggested that D-4F might be a powerful candidate in the protection of endothelial cells and the prevention of cardiovascular disease (CVD).

High-density lipoprotein mimetics: promises and challenges

The concept of lipoprotein mimetics was developed and extensively tested in the last three decades. Most lipoprotein mimetics were designed to recreate one or several functions of high-density lipoprotein (HDL) in the context of cardiovascular disease; however, the application of this approach is much broader. Lipoprotein mimetics should not just be seen as a set of compounds aimed at replenishing a deficiency or dysfunctionality of individual elements of lipoprotein metabolism but rather as a designer concept with remarkable flexibility and numerous applications in medicine and biology. In the present review, we discuss the fundamental design principles used to create lipoprotein mimetics, mechanisms of their action, medical indications and efficacy in animal models and human studies.

D4F alleviates macrophage-derived foam cell apoptosis by inhibiting CD36 expression and ER stress-CHOP pathway

This study was designed to explore the protective effect of D4F, an apoA-I mimetic peptide, on oxidized LDL (ox-LDL)-induced endoplasmic reticulum (ER) stress-CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) pathway-mediated apoptosis in macrophages. Our results showed that treating apoE knockout mice with D4F decreased the serum ox-LDL level and apoptosis in atherosclerotic lesions with concomitant downregulation of cluster of differentiation 36 (CD36) and inhibition of ER stress. In vitro, D4F inhibited macrophage-derived foam cell formation. Furthermore, like ER stress inhibitor 4-phenylbutyric acid (PBA), D4F inhibited ox-LDL- or tunicamycin (TM, an ER stress inducer)-induced reduction in cell viability and increase in lactate dehydrogenase leakage, caspase-3 activation, and apoptosis. Additionally, like PBA, D4F inhibited ox-LDL- or TM-induced activation of ER stress response as assessed by the reduced nuclear translocation of activating transcription factor 6 and the decreased phosphorylation of protein kinase-like ER kinase and eukaryotic translation initiation factor 2α, as well as the downregulation of glucose-regulated protein 78 and CHOP. Moreover, D4F mitigated ox-LDL uptake by macrophages and CD36 upregulation induced by ox-LDL or TM. These data indicate that D4F can alleviate the formation and apoptosis of macrophage-derived foam cells by suppressing CD36-mediated ox-LDL uptake and subsequent activation of the ER stress-CHOP pathway.

D-4F, an apolipoprotein A-I mimetic peptide, protects human umbilical vein endothelial cells from oxidized low-density lipoprotein-induced injury by preventing the downregulation of pigment epithelium-derived factor expression

AIM

To investigate the protective effects of D-4F, an apolipoprotein A-I mimetic peptide, on oxidized low-density lipoprotein (ox-LDL)-induced injury of vascular endothelial cells and the potential role of pigment epithelium-derived factor (PEDF).

METHODS

Cytotoxicity was assessed by the apoptotic rate, 3-(4,5-dimethylthiazol-2-y-l)-2,5-diphenyl-2H-tetrazolium bromide assay, and lactate dehydrogenase release. PEDF levels were analyzed with Western blot and quantitative real-time polymerase chain reaction. Redox status was measured by the levels of the reactive oxygen species, malondialdehyde, superoxide dismutase, and nitric oxide.

RESULTS

Ox-LDL reduced cell viability and induced apoptosis and LDH release from human umbilical vein endothelial cells, but the cytotoxic effects of ox-LDL were significantly inhibited by pretreatment with D-4F. Additionally, D-4F could scavenge intracellular reactive oxygen species, suppress the production of lipid peroxides, and improve endogenous antioxidant activity. Ox-LDL decreased PEDF expression in human umbilical vein endothelial cells in a concentration-dependent manner, and this decrease was markedly attenuated by D-4F. However, silencing PEDF by short interfering RNA blocked the inhibitory effects of D-4F on ox-LDL-induced oxidative stress and cellular injury.

CONCLUSIONS

D-4F effectively protects vascular endothelial cells against ox-LDL-induced injury by preventing the downregulation of PEDF expression.