Dickkopf1 destabilizes atherosclerotic plaques and promotes plaque formation by inducing apoptosis of endothelial cells through activation of ER stress

High dose statin treatment reduces circulating Dickkopf-1 following acute myocardial infarction

BACKGROUND

Secreted glycoproteins of the Dickkopf (DKK) family modify Wnt signaling and may influence plaque destabilization but their modulation by statins in MI patients is not known.

METHODS

We measured plasma DKK-1 and DKK-3 in patients with acute ST-segment elevation MI (STEMI) before percutaneous coronary intervention (PCI) and after 2 and 7 days and 2 months in patients receiving short-term high-dose (40 mg rosuvastatin, given before PCI; n = 25) and moderate dose (20 mg simvastatin, given the day after PCI; n = 34). In vitro modulation of DKK-1 in human umbilical vein endothelial cells (HUVECs) by statins were assessed.

RESULTS

(i) Patients receiving high dose rosuvastatin had a marked decline in DKK-1 at day 2 which was maintained throughout the study period. However, a more prevalent use of β-blockers in the simvastatin group, that could have contributed to higher DKK-1 levels in these patients. (ii) There was a strong correlation between baseline DKK-1 levels and change in DKK-1 from baseline to day 2 in patients receiving high dose rosuvastatin treatment. (iii) DKK-3 increased at day 2 but returned to baseline levels at 2 months in both treatment groups. (iv) Statin treatment dose-dependently decreased DKK-1 mRNA and protein levels in HUVEC.

CONCLUSIONS

Our findings suggest that high dose statin treatment with 40 mg rosuvastatin could persistently down-regulate DKK-1 levels, even at 2 months after the initial event in STEMI patients.

Endothelial Dickkopf-1 Promotes Smooth Muscle Cell-derived Foam Cell Formation via USP53-mediated Deubiquitination of SR-A During Atherosclerosis

Background: Shear stress-induced Dickkopf-1 (DKK1) secretion by endothelial cells (ECs) promotes EC dysfunction and accelerates atherosclerosis (AS). However, the paracrine role of endothelial DKK1 in modulating adjacent smooth muscle cells (SMCs) in atherosclerosis remains unclear. This study investigated the role of EC-secreted DKK1 in SMC-derived foam cell formation under shear stress, in vitro and in vivo. Methods: Parallel-plate co-culture flow system was used to explore the cellular communication between ECs and SMCs under shear stress in vitro. Endothelium-specific knockout of DKK1 (DKK1ECKO/APOE-/-) and endothelium-specific overexpression of DKK1 (DKK1ECTg) mice were constructed to investigate the role of endothelial DKK1 in atherosclerosis and SMC-derived foam cell formation in vivo. RNA sequencing (RNA-seq) was used to identify the downstream targets of DKK1. Reverse transcription quantitative polymerase chain reaction (RT-qPCR), western blot, coimmunoprecipitation (Co-IP) assays and chromatin immunoprecipitation (ChIP) experiments were conducted to explore the underlying regulatory mechanisms. Results: DKK1 is transcriptionally upregulated in ECs under conditions of low shear stress, but not in co-cultured SMCs. However, DKK1 protein in co-cultured SMCs is increased via uptake of low shear stress-induced endothelial DKK1, thereby promoting lipid uptake and foam cell formation in co-cultured SMCs via the post-translational upregulation of scavenger receptor-A (SR-A) verified in parallel-plate co-culture flow system, DKK1ECKO and DKK1ECTg mice. RNA sequencing revealed that DKK1-induced SR-A upregulation in SMCs is dependent on Ubiquitin-specific Protease 53 (USP53), which bound to SR-A via its USP domain and cysteine at position 41, exerting deubiquitination to maintain the stability of the SR-A protein by removing the K48 ubiquitin chain and preventing proteasomal pathway degradation, thereby mediating the effect of DKK1 on lipid uptake in SMCs. Moreover, DKK1 regulates the transcription of USP53 by facilitating the binding of transcription factor CREB to the USP53 promoter. SMC-specific overexpression of USP53 via adeno-associated virus serotype 2 vectors in DKK1ECKO/APOE-/- mice reversed the alleviation of atherosclerotic plaque burden, SR-A expression and lipid accumulation in SMCs within plaques resulting from DKK1 deficiency. Conclusions: Our findings demonstrate that, endothelial DKK1, induced by pathological low shear stress, acts as an intercellular mediator, promoted the foam cell formation of SMCs. These results suggest that targeted intervention with endothelial DKK1 may confer beneficial effects on atherosclerosis.

The predictive value of serum Dickkopf-1, Dickkopf-3 level to coronary artery disease and acute coronary syndrome

BACKGROUND

Previous studies have already confirmed the association between Dickkopf (Dkk) protein and the occurrence and progression of atherosclerosis. However, there is limited clinical evidence regarding the serum levels of Dickkopf-1 (Dkk1) and Dickkopf-3 (Dkk3) in relation to atherosclerotic cardiovascular disease (ASCVD), particularly acute coronary syndrome (ACS).

MATERIALS AND METHODS

A total of 88 healthy volunteers and 280 patients with coronary artery disease (CAD) undergoing coronary angiography for angina between October 2021 and October 2022, including 96 cases of stable angina (SA), 96 of unstable angina (UA) and 88 of acute myocardial infarction (AMI) were included finally. The serum concentrations of Dkk1 and Dkk3 were measured using electrochemiluminescence of Meso Scale Discovery. The predictive value of single or combined application of serum Dkk1 and Dkk3 in CAD and ACS were evaluated.

RESULTS

The serum levels of Dkk1 were significantly higher in the SA group, UA group, and AMI group compared to the control group. Multivariable logistic regression analysis demonstrated that elevated serum Dkk1 levels were independent predictive factors for increased risk of CAD and ACS (OR = 1.027, 95%CI = 1.019-1.034, p < 0.001; OR = 1.045, 95%CI = 1.028-1.053, p < 0.001, respectively). Receiver operating characteristic curve (ROC) analysis showed that the optimal cutoff value of serum Dkk1 for predicting ACS was 205 ng/dl, with a sensitivity of 82.6% and specificity of 96.6%. The area under the curve (AUC) was 0.930 (95%CI: 0.899-0.961, p < 0.001). Regarding Dkk3, serum Dkk3 levels were elevated in CAD patients compared to the healthy control group, and significantly higher in ACS patients compared to SA patients. Serum Dkk3 was significantly associated with increased risk of CAD and ACS (OR = 1.131, 95%CI = 1.091-1.173, p < 0.001; OR = 1.201, 95%CI = 1.134-1.271, p < 0.001, respectively). ROC curve analysis showed that the optimal cutoff value of serum Dkk3 for predicting ACS was 50.82 ng/ml, with a sensitivity of 85.9% and specificity of 87.5%. The AUC was 0.925 (95%CI: 0.894-0.956, p < 0.001). When serum Dkk1 and Dkk3 are combined as predictive factors for ACS, the AUC was 0.975.

CONCLUSION

Serum levels of Dkk1 and Dkk3 are significantly associated with an increased risk of CAD and ACS, and they possess predictive value for CAD and ACS. The combination of serum Dkk1 and Dkk3 is a superior predictive factor for CAD and ACS.

Noncoding RNAs in atherosclerosis: regulation and therapeutic potential

Atherosclerosis, a chronic disease of arteries, results in high mortality worldwide as the leading cause of cardiovascular disease. The development of clinically relevant atherosclerosis involves the dysfunction of endothelial cells and vascular smooth muscle cells. A large amount of evidence indicates that noncoding RNAs, such as microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), are involved in various physiological and pathological processes. Recently, noncoding RNAs were identified as key regulators in the development of atherosclerosis, including the dysfunction of endothelial cells, and vascular smooth muscle cells and it is pertinent to understand the potential function of noncoding RNAs in atherosclerosis development. In this review, the latest available research relates to the regulatory role of noncoding RNAs in the progression of atherosclerosis and the therapeutic potential for atherosclerosis is summarized. This review aims to provide a comprehensive overview of the regulatory and interventional roles of ncRNAs in atherosclerosis and to inspire new insights for the prevention and treatment of this disease.

Endoplasmic reticulum stress-mediated cell death in cardiovascular disease

The endoplasmic reticulum (ER) plays a vital function in maintaining cellular homeostasis. Endoplasmic reticulum stress (ERS) can trigger various modes of cell death by activating the unfolded protein response (UPR) signaling pathway. Cell death plays a crucial role in the occurrence and development of diseases such as cancer, liver diseases, neurological diseases, and cardiovascular diseases. Several cardiovascular diseases including hypertension, atherosclerosis, and heart failure are associated with ER stress. ER stress-mediated cell death is of interest in cardiovascular disease. Moreover, an increasing body of evidence supports the potential of modulating ERS for treating cardiovascular disease. This paper provides a comprehensive review of the UPR signaling pathway, the mechanisms that induce cell death, and the modes of cell death in cardiovascular diseases. Additionally, we discuss the mechanisms of ERS and UPR in common cardiovascular diseases, along with potential therapeutic strategies.

Platelet-derived growth factor subunit-B mediating the effect of dickkopf-1 on acute myocardial infarction risk: a two-step Mendelian randomization study

Previous studies have indicated a potential connection between plasma levels of Dickkopf-1 (DKK1) and platelet-derived growth factor subunit-B (PDGF-B) with the development of atherosclerosis. However, the causal relationship between DKK1, PDGF-B, and the risk of acute myocardial infarction (AMI) is yet to be established. To address this research gap, we conducted Mendelian randomization (MR) and mediation analyses to investigate the potential mediating role of PDGF-B in the association between DKK1 and AMI risk. Summary statistics for DKK1 (n = 3,301) and PDGF-B (n = 21,758) were obtained from the GWAS meta-analyses conducted by Sun et al. and Folkersen et al., respectively. Data on AMI cases (n = 3,927) and controls (n = 333,272) were retrieved from the UK Biobank study. Our findings revealed that genetic predisposition to DKK1 (odds ratio [OR]: 1.00208; 95% confidence interval [CI]: 1.00056-1.00361; P = 0.0072) and PDGF-B (OR: 1.00358; 95% CI: 1.00136-1.00581; P = 0.0015) was associated with an increased risk of AMI. Additionally, genetic predisposition to DKK1 (OR: 1.38389; 95% CI: 1.07066-1.78875; P = 0.0131) was linked to higher PDGF-B levels. Furthermore, our MR mediation analysis revealed that PDGF-B partially mediated the association between DKK1 and AMI risk, with 55.8% of the effect of genetically predicted DKK1 being mediated through genetically predicted PDGF-B. These findings suggest that genetic predisposition to DKK1 is positively correlated with the risk of AMI, and that PDGF-B partially mediates this association. Therefore, DKK1 and PDGF-B may serve as promising targets for the prevention and treatment of AMI.

Investigating the causal effect of Dickkopf-1 on coronary artery disease and ischemic stroke: a Mendelian randomization study

Epidemiological investigations have indicated a correlation between elevated plasma levels of Dickkopf-related protein 1 (DKK1) and the presence of atherosclerosis. However, the exact causal relationship of DKK1 with the development of coronary artery disease (CAD) and ischemic stroke (IS) remains unclear. To address this gap, our study aimed to explore their causal association using a two-sample Mendelian randomization (MR) approach. We obtained summary statistics from genome-wide association studies (GWAS) meta-analyses conducted by Folkersen et al. and Nikpay et al., which included data from 21,758 individuals for DKK1 and 42,096 cases of CAD. Additionally, we obtained data from the FinnGen biobank analysis round 5, which included 10,551 cases of IS. Eight MR methods were employed to estimate causal effects and detect directional pleiotropy. Our findings demonstrated that genetic liability to DKK1 was associated with increased risks of CAD (odds ratio [OR]: 1.087; 95% confidence interval [CI]: 1.024-1.154; P = 0.006) and IS (OR: 1.096; 95% CI: 1.004-1.195; P = 0.039). These results establish a causal link between genetic liability to DKK1 and elevated risks of CAD and IS. Consequently, DKK1 may represent a promising therapeutic target for the prevention and treatment of CAD and IS.

Endothelial Dysfunction in Cardiorenal Conditions: Implications of Endothelial Glucocorticoid Receptor-Wnt Signaling

The endothelium constitutes the innermost lining of the blood vessels and controls blood fluidity, vessel permeability, platelet aggregation, and vascular tone. Endothelial dysfunction plays a key role in initiating a vascular inflammatory cascade and is the pivotal cause of various devastating diseases in multiple organs including the heart, lung, kidney, and brain. Glucocorticoids have traditionally been used to combat vascular inflammation. Endothelial cells express glucocorticoid receptors (GRs), and recent studies have demonstrated that endothelial GR negatively regulates vascular inflammation in different pathological conditions such as sepsis, diabetes, and atherosclerosis. Mechanistically, the anti-inflammatory effects of GR are mediated, in part, through the suppression of Wnt signaling. Moreover, GR modulates the fatty acid oxidation (FAO) pathway in endothelial cells and hence can influence FAO-mediated fibrosis in several organs including the kidneys. This review summarizes the relationship between GR and Wnt signaling in endothelial cells and the effects of the Wnt pathway in different cardiac and renal diseases. Available data suggest that GR plays a significant role in restoring endothelial integrity, and research on endothelial GR-Wnt interactions could facilitate the development of novel therapies for many cardiorenal conditions.

Dickkopf-1 promotes vascular smooth muscle cell foam cell formation and atherosclerosis development through CYP4A11/SREBP2/ABCA1

Vascular smooth muscle cells (VSMCs) are considered to be a crucial source of foam cells in atherosclerosis due to their low expression level of cholesterol exporter ATP-binding cassette transporter A1 (ABCA1) intrinsically. While the definite regulatory mechanisms are complicated and have not yet been fully elucidated, we previously reported that Dickkopf-1 (DKK1) mediates endothelial cell (EC) dysfunction, thereby aggravating atherosclerosis. However, the role of smooth muscle cell (SMC) DKK1 in atherosclerosis and foam cell formation remains unknown. In this study, we established SMC-specific DKK1-knockout (DKK1SMKO ) mice by crossbreeding DKK1flox/flox mice with TAGLN-Cre mice. Then, DKK1SMKO mice were crossed with APOE-/- mice to generate DKK1SMKO /APOE-/- mice, which exhibited milder atherosclerotic burden and fewer SMC foam cells. In vitro loss- and gain-of-function studies of DKK1 in primary human aortic smooth muscle cells (HASMCs) have proven that DKK1 prevented oxidized lipid-induced ABCA1 upregulation and cholesterol efflux and promoted SMC foam cell formation. Mechanistically, RNA-sequencing (RNA-seq) analysis of HASMCs as well as chromatin immunoprecipitation (ChIP) experiments showed that DKK1 mediates the binding of transcription factor CCAAT/enhancer-binding protein delta (C/EBPδ) to the promoter of cytochrome P450 epoxygenase 4A11 (CYP4A11) to regulate its expression. In addition, CYP4A11 as well as its metabolite 20-HETE-promoted activation of transcription factor sterol regulatory element-binding protein 2 (SREBP2) mediated the DKK1 regulation of ABCA1 in SMC. Furthermore, HET0016, the antagonist of CYP4A11, has also shown an alleviating effect on atherosclerosis. In conclusion, our results demonstrate that DKK1 promotes SMC foam cell formation during atherosclerosis via a reduction in CYP4A11-20-HETE/SREBP2-mediated ABCA1 expression.

Hypoxia Affects Autophagy in Human Umbilical Vein Endothelial Cells via the IRE1 Unfolded Protein Response

OBJECTIVE

The purpose of this study was to investigate the role of the unfolded protein response, specifically the inositol-requiring enzyme 1 (IRE1) signaling pathway, in hypoxia-induced autophagy in human umbilical venous endothelial cells (HUVECs).

METHODS

The expression of IRE1 and autophagy relative protein in HUVECs with hypoxia was explored by Western blotting, qRT-PCR and confocal microscopy. Further, we evaluated the biological effects of HUVECs by tube formation assay and wound healing assay in vitro. Finally, we examined the function of IRE1 in local blood vessels through animal models.

RESULTS

Hypoxia activated the IRE1 signaling pathway and induced autophagy in a time-dependent manner in HUVECs and further influenced the biological effects of HUVECs. Intraperitoneal injection of IRE1 inhibitors inhibited local vascular autophagy levels and lipid accumulation in model animals.

CONCLUSION

Hypoxia can induce autophagy and activate the IRE1 signaling pathway in HUVECs and the IRE1 signaling pathway is involved in autophagy in hypoxic conditions.

USP14-mediated NLRC5 upregulation inhibits endothelial cell activation and inflammation in atherosclerosis

Atherosclerosis, a chronic inflammatory condition that leads to a variety of life-threatening cardiovascular diseases, is a worldwide public health concern. Endothelial cells (ECs), which line the inside of blood vessels, play an important role in atherogenic initiation. Endothelial activation and inflammation are indispensable for the early stage of atherosclerosis. Ubiquitin-specific protease 14 (USP14), a deubiquitinating enzyme that regulates the stability and activity of target proteins, has been identified as a potential therapeutic target for many inflammatory diseases. However, the role of USP14 on ECs is undefined. In this study, we found that USP14 is downregulated in either atherosclerosis patient specimens or oxidized low-density lipoprotein (ox-LDL)-stimulated ECs as compared to the control group. Overexpression of USP14 in ECs restrains ox-LDL-stimulated nuclear transcription factor kappa B (NF-κB) activation and subsequent adhesion molecule production. USP14 inhibits endothelium proinflammatory activation by suppressing the degradation of the negative regulator of NF-κB signaling, nod-like receptor family caspase recruitment domain family domain containing 5 (NLRC5). Finally, our in vivo experiments confirmed that USP14 adenovirus injection in apolipoprotein E deficient (ApoE^-/-) mice fed with a western diet reduced the atherosclerotic lesion size, inhibited macrophage accumulation in the intima, and restricted the progression of atherosclerosis. Our results reveal that USP14 may represent a new therapeutic target for atherosclerosis.

Correlation between serum Dickkopf-1 (DKK1) levels and coronary artery stenosis

BACKGROUND AND AIMS

To study the correlation between the level of serum Dickkopf-1 (DKK1) and the degree of coronary artery stenosis in patients with coronary atherosclerotic heart disease.

METHODS AND RESULTS

In 2018, general data and biochemical indexes of 311 patients who underwent coronary angiography were recorded. Before procedure, arterial blood was drawn and the concentrations of DKK1, retinol binding protein 4 (RBP4), plasminogen activator inhibitor (PAI-1) were measured. Based on coronary angiography results, subjects were divided into a coronary heart disease (CHD) group; and a non-coronary heart disease (non-CHD)group. The CHD group was divided into three subgroups: the low Gensini score; the middle Gensini score; and the high Gensini score subgroups. Compared with those of the non-CHD group, DKK1, RBP4 and PAI-1 of the CHD group were significantly higher, while the OC was lower. DKK1,RBP4 and PAI-1 levels of the middle and high Gensini subgroups were significantly higher, compared with that of the low Gensini subgroup. Differences between osteocalcin (OC), beta-isomerized C-terminal telopeptidase (β-CTX), and 25(OH)₂D₃ of the three subgroups were not significant. Correlation between DKK1 and the inflammatory factors, RBP4 and PAI-1, was positive. Correlation between DKK1 and β - CTX, 25(OH)₂D₃ and OC was not significant. DKK1 was a risk factor for CHD. The degree of coronary artery stenosis was related to DKK1 concentration.

CONCLUSIONS

Serum DKK1 levels in coronary heart disease patients were significantly higher, and positively correlated with the degree of coronary artery stenosis. DKK1 level is an independent risk factor for coronary heart disease.

SMARCC2 mediates the regulation of DKK1 by the transcription factor EGR1 through chromatin remodeling to reduce the proliferative capacity of glioblastoma

Switch/sucrose-nonfermenting (SWI/SNF) complexes play a key role in chromatin remodeling. Recent studies have found that SMARCC2, as the core subunit of the fundamental module of the complex, plays a key role in its early assembly. In this study, we found a unique function of SMARCC2 in inhibiting the progression of glioblastoma by targeting the DKK1 signaling axis. Low expression of SMARCC2 is found in malignant glioblastoma (GBM) compared with low-grade gliomas. SMARCC2 knockout promoted the proliferation of glioblastoma cells, while its overexpression showed the opposite effect. Mechanistically, SMARCC2 negatively regulates transcription by dynamically regulating the chromatin structure and closing the promoter region of the target gene DKK1, which can be bound by the transcription factor EGR1. DKK1 knockdown significantly reduced the proliferation of glioblastoma cell lines by inhibiting the PI3K-AKT pathway. We also studied the functions of the SWIRM and SANT domains of SMARCC2 and found that the SWIRM domain plays a more important role in the complete chromatin remodeling function of SMARCC2. In addition, in vivo studies confirmed that overexpression of SMARCC2 could significantly inhibit the size of intracranial gliomas in situ in nude mice. Overall, this study shows that SMARCC2, as a tumor suppressor, inhibits the proliferation of glioblastoma by targeting the transcription of the oncogene DKK1 through chromatin remodeling, indicating that SMARCC2 is a potentially attractive therapeutic target in glioblastoma.

High mobility group box 1 and Dickkopf-related protein 1 as biomarkers of glucose toxicity, atherogenicity, and lower β cell function in patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is associated with increased atherogenicity and inflammatory responses, which may be related to high mobility group box 1 (HMGB1) and Dickkopf-related protein 1 (DKK1). The role of HMGB1 and DKK1 in T2DM is examined in association with lipid and insulin profiles. Serum HMGB1 and DKK1 were measured in T2DM with and without hypertension and compared with controls. The results showed that HMGB1 and DKK1 are higher in T2DM irrespective of hypertension. A large part of the variance in the β-cell index and glucose toxicity was explained by the combined effects of HMGB1 and DKK1. In conclusion, both HMGB1 and DKK1 may contribute to increased atherogenicity in T2DM. Moreover, both biomarkers may cause more deficits in β-cell function and increase glucose toxicity leading to the development of more inflammation and diabetic complications. HMGB1 and the Wnt pathways are other drug targets in treating T2DM.

A Synergistic Effect between Plasma Dickkopf-1 and Obstructive Coronary Artery Disease on the Prediction of Major Adverse Cardiac Events in Patients with Angina: An Observational Study

The canonical β-catenin-dependent wingless (Wnt) pathway is associated with endothelial function. We examined the effect of plasma dickkopf-1 (DKK-1), an inhibitor of the Wnt pathway, on the prediction of major adverse cardiac events (MACEs). We enrolled patients who had undergone selective coronary angiography for angina. DKK-1 levels were determined using plasma collected at the outpatient visit after fasting. MACEs served as the primary endpoint. All 470 enrolled patients were divided into four groups according to their median plasma DKK-1 levels and the presence of obstructive coronary artery disease (CAD). Forty-eight patients reached the primary endpoint during a median follow-up time of 4.8 years. Kaplan-Meier survival analysis indicated that the group with high DKK-1 and obstructive CAD had a significantly higher mortality rate than the other three groups (log-rank test p = 0.001). Compared with the low plasma DKK-1 without significant coronary obstruction group, the high DKK-1 with obstructive CAD group had a hazard ratio of 10.640 (95% confidence interval: 1.350-83.874) for MACEs, as determined by multivariable Cox proportional hazard regression analysis. In conclusion, we observed a synergistic effect between high plasma DKK-1 and obstructive CAD on the prediction of MACEs in patients with angina.

Understanding ER homeostasis and the UPR to enhance treatment efficacy of acute myeloid leukemia

Protein biogenesis, maturation and degradation are tightly regulated processes that are governed by a complex network of signaling pathways. The endoplasmic reticulum (ER) is responsible for biosynthesis and maturation of secretory proteins. Circumstances that alter cellular protein homeostasis, determine accumulation of misfolded and unfolded proteins in the ER, a condition defined as ER stress. In case of stress, the ER activates an adaptive response called unfolded protein response (UPR), a series of pathways of major relevance for cancer biology. The UPR plays a preeminent role in adaptation of tumor cells to the harsh conditions that they experience, due to high rates of proliferation, metabolic abnormalities and hostile environment scarce in oxygen and nutrients. Furthermore, the UPR is among the main adaptive cell stress responses contributing to the development of resistance to drugs and chemotherapy. Clinical management of Acute Myeloid Leukemia (AML) has improved significantly in the last decade, thanks to development of molecular targeted therapies. However, the emergence of treatment-resistant clones renders the rate of AML cure dismal. Moreover, different cell populations that constitute the bone marrow niche recently emerged as a main determinant leading to drug resistance. Herein we summarize the most relevant literature regarding the role played by the UPR in expansion of AML and ability to develop drug resistance and we discuss different possible modalities to overturn this adaptive response against leukemia. To this aim, we also describe the interconnection of the UPR with other cellular stress responses regulating protein homeostasis. Finally, we review the newest findings about the crosstalk between AML cells and cells of the bone marrow niche, under physiological conditions and in response to therapies, discussing in particular the importance of the niche in supporting survival of AML cells by favoring protein homeostasis.

Modulatory action of withaferin-A on oxidative damage through regulation of inflammatory mediators and apoptosis via PI3K/AKT signaling pathway in high cholesterol-induced atherosclerosis in experimental rats

Statins are widely used lipid-lowering drugs that cause many side effects. Withaferin-A (WA), popularly known as Ashwagandha, an ancient Indian medicinal herb, is extracted from Withania somnifera. Anti-atherosclerotic effect of WA has been reported. However, the mechanism remains unknown. Hence, we planned this study to investigate the WA mechanism in anti-atherosclerosis in a rat model. High cholesterol diet (HCD) was fed to induce atherosclerosis in Sprague-Dawley male rats. Five groups (N = 6 rats/group) were fed with normal diet, HCD, WA (10 mg/kg bw)+HCD, lovastatin (LS: 10 mg/kg bw)+HCD, WA (10 mg/kg bw) respectively for 90 days. Statistical analysis was done by GraphPad Prism (version 8.0.1) using one-way analysis of variance (ANOVA) followed by post hoc Duncan's test with a significance level (p < 0.05). The groups were compared for lipid profiles, oxidative stress, lipid peroxidation, inflammatory mediators, apoptotic markers, and histopathological changes in the liver and aorta. Treatment with HCD increased lipid profiles, inflammatory mediators, cytokines, and lipid peroxidation. WA as well as LS treatments significantly decreased these parameters restored the antioxidant status, and reduced lipid peroxidation (p < 0.05). Histopathological studies revealed that WA and LS reduced the hepatic fat and aortic plaque. WA reduced apoptosis via augmentation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway; increased B-cell lymphoma 2 and inhibited Bcl-2 associated X-protein proapoptotic proteins; TNF receptor superfamily member 6, Bim, caspase-3, and -9; demonstrated significant hypolipidemic and anti-inflammatory properties against HCD induced atherosclerosis in rats through regulation of inflammatory mediators and apoptosis via the PI3K/AKT signaling pathway.

Fibrotic Signaling in Cardiac Fibroblasts and Vascular Smooth Muscle Cells: The Dual Roles of Fibrosis in HFpEF and CAD

Patients with heart failure with preserved ejection fraction (HFpEF) and atherosclerosis-driven coronary artery disease (CAD) will have ongoing fibrotic remodeling both in the myocardium and in atherosclerotic plaques. However, the functional consequences of fibrosis differ for each location. Thus, cardiac fibrosis leads to myocardial stiffening, thereby compromising cardiac function, while fibrotic remodeling stabilizes the atherosclerotic plaque, thereby reducing the risk of plaque rupture. Although there are currently no drugs targeting cardiac fibrosis, it is a field under intense investigation, and future drugs must take these considerations into account. To explore similarities and differences of fibrotic remodeling at these two locations of the heart, we review the signaling pathways that are activated in the main extracellular matrix (ECM)-producing cells, namely human cardiac fibroblasts (CFs) and vascular smooth muscle cells (VSMCs). Although these signaling pathways are highly overlapping and context-dependent, effects on ECM remodeling mainly act through two core signaling cascades: TGF-β and Angiotensin II. We complete this by summarizing the knowledge gained from clinical trials targeting these two central fibrotic pathways.

Upregulation of Endothelial DKK1 (Dickkopf 1) Promotes the Development of Pulmonary Hypertension Through the Sp1 (Specificity Protein 1)/SHMT2 (Serine Hydroxymethyltransferase 2) Pathway

BACKGROUND

Pulmonary hypertension (PH) is a cancer-like proliferative disease, which has no curative treatment options. The dysfunction of pulmonary artery endothelial cells plays a key role in PH. DKK1 (Dickkopf 1) is a secretory glycoprotein that exerts proproliferative effects on tumor cells. In the present study, we aimed to identify the role and underlying mechanism of DKK1 in the development of PH, which still remain unclear.

METHODS AND RESULTS

We found endothelial DKK1 expression was upregulated in serum and lung tissues obtained from patients with PH, mice with hypoxia-induced PH, and human pulmonary artery endothelial cells cultured under hypoxic conditions. Endothelium-specific DKK1-knockout (DKK1ECKO) mice significantly ameliorated hypoxia+Sugen5416 and hypoxia-induced PH. More importantly, neutralizing anti-DKK1 antibody treatment significantly attenuated established hypoxia+Sugen5416 PH. Results of proteome analysis of control and DKK1-knockdown human pulmonary artery endothelial cells identified a significantly differentially expressed protein, SHMT2 (serine hydroxymethyltransferase 2), a key metabolic enzyme in one-carbon metabolism, as a novel DKK1 target. DKK1 knockdown in human pulmonary artery endothelial cells cultured under hypoxic conditions decreased the cellular NADPH/NADP+ ratio, increased reactive oxygen species levels and the extent of mitochondrial DNA damage, and inhibited mitochondrial membrane hyperpolarization. In the context of this altered redox defense and mitochondrial disorder, DKK1 induced a proproliferative and antiapoptotic phenotype in endothelial cells. Furthermore, we confirmed that DKK1 regulated SHMT2 transcription through the AKT-Sp1 (specificity protein 1) signaling axis.

CONCLUSIONS

Our data provide robust evidence and molecular explanations for the associations between DKK1, redox defense, mitochondrial disorders, and PH and reveal a novel target for PH treatment.

Inflammatory factors driving atherosclerotic plaque progression new insights

Coronary atherosclerosis is a chronic inflammatory disease that can lead to varying degrees of blood flow obstruction and a common pathophysiological basis of cardiovascular disease. Inflammatory factors run through the whole process of atherosclerotic lesions. Macrophages, T cells, and neutrophils play important roles in the process of atherosclerotic inflammation. Considering the evolutionary characteristics, atherosclerosis can be divided into different stages as early atherosclerotic plaque, plaque formation stage, and plaque rupture stage. In this paper, the changes in inflammatory cells at different stages of lesions and their related mechanisms are discussed, which can provide new insights from a clinical to bench perspective for atherosclerosis me chanism.

Inhibition of microRNA-494-3p activates Wnt signaling and reduces proinflammatory macrophage polarization in atherosclerosis

We have previously shown that treatment with third-generation antisense oligonucleotides against miR-494-3p (3GA-494) reduces atherosclerotic plaque progression and stabilizes lesions, both in early and established plaques, with reduced macrophage content in established plaques. Within the plaque, different subtypes of macrophages are present. Here, we aimed to investigate whether miR-494-3p directly influences macrophage polarization and activation. Human macrophages were polarized into either proinflammatory M1 or anti-inflammatory M2 macrophages and simultaneously treated with 3GA-494 or a control antisense (3GA-ctrl). We show that 3GA-494 treatment inhibited miR-494-3p in M1 macrophages and dampened M1 polarization, while in M2 macrophages miR-494-3p expression was induced and M2 polarization enhanced. The proinflammatory marker CCR2 was reduced in 3GA-494-treated atherosclerosis-prone mice. Pathway enrichment analysis predicted an overlap between miR-494-3p target genes in macrophage polarization and Wnt signaling. We demonstrate that miR-494-3p regulates expression levels of multiple Wnt signaling components, such as LRP6 and TBL1X. Wnt signaling appears activated upon treatment with 3GA-494, both in cultured M1 macrophages and in plaques of hypercholesterolemic mice. Taken together, 3GA-494 treatment dampened M1 polarization, at least in part via activated Wnt signaling, while M2 polarization was enhanced, which is both favorable in reducing atherosclerotic plaque formation and increasing plaque stability.

The pro-angiogenesis effect of miR33a-5p/Ets-1/DKK1 signaling in ox-LDL induced HUVECs

Objective: Angiogenesis is involved in multiple biological processes, including atherosclerosis (AS) and cancer. Dickkopf1 (DKK1) plays many roles in both tumors and AS and has emerged as a potential biomarker of cancer progression and prognosis. Targeting DKK1 is a good choice for oncological treatments. Many anticancer therapies are associated with specific cardiovascular toxicity. However, the effects of DKK1 neutralizing therapy on AS are unclear. We focused on how DKK1 affected angiogenesis in AS and ox-LDL-induced human umbilical vein endothelial cells (HUVECs).

Methods: ApoE-/- mice were fed a high-fat diet and then injected with DKK1i or DKK1 lentivirus to study the effects of DKK1. In vitro, promoter assays, protein analysis, database mining, dual-luciferase reporter assay (DLR), electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), and coimmunoprecipitation (co-IP) were used to study the mechanism of DKK1 biogenesis. Cell migration and angiogenesis assays were performed to investigate the function and regulatory mechanisms of DKK1.

Results: DKK1 participated in angiogenesis both in the plaques of ApoE-/- mice by knockdown or overexpression of DKK1 and ox-LDL-induced HUVECs. DKK1 induced angiogenesis (increasing migration and capillary formation, inducing expression of VEGFR-2/VEGF-A/MMP) via the CKAP4/PI3K pathway, independent of Wnt/β-catenin. ox-LDL increased the expression and nuclear transfer of Ets-1 and c-jun, and induced the transcriptional activity of DKK1 in HUVECs. Ets-1, along with c-jun and CBP, could bind to the promoter of DKK1 and enhance DKK1 transcription. MiR33a-5p was downregulated in ox-LDL induced HUVECs and aortic artery of high-fat diet ApoE-/- mice. Ets-1 was a direct target of miR33a-5p. MiR33a-5p/Ets-1/ DKK1 axis contributed to angiogenesis.

Conclusions: MiR33a-5p/Ets-1/DKK1 signaling participated in ox-LDL-induced angiogenesis of HUVECs via the CKAP4/PI3K pathway. These new findings provide a rationale and notable method for tumor therapy and cardiovascular protection.

Targeting non-coding RNAs in unstable atherosclerotic plaques: Mechanism, regulation, possibilities, and limitations

Cardiovascular diseases (CVDs) caused by arteriosclerosis are the leading cause of death and disability worldwide. In the late stages of atherosclerosis, the atherosclerotic plaque gradually expands in the blood vessels, resulting in vascular stenosis. When the unstable plaque ruptures and falls off, it blocks the vessel causing vascular thrombosis, leading to strokes, myocardial infarctions, and a series of other serious diseases that endanger people's lives. Therefore, regulating plaque stability is the main means used to address the high mortality associated with CVDs. The progression of the atherosclerotic plaque is a complex integration of vascular cell apoptosis, lipid metabolism disorders, inflammatory cell infiltration, vascular smooth muscle cell migration, and neovascular infiltration. More recently, emerging evidence has demonstrated that non-coding RNAs (ncRNAs) play a significant role in regulating the pathophysiological process of atherosclerotic plaque formation by affecting the biological functions of the vasculature and its associated cells. The purpose of this paper is to comprehensively review the regulatory mechanisms involved in the susceptibility of atherosclerotic plaque rupture, discuss the limitations of current approaches to treat plaque instability, and highlight the potential clinical value of ncRNAs as novel diagnostic biomarkers and potential therapeutic strategies to improve plaque stability and reduce the risk of major cardiovascular events.

Multiple functions of autophagy in vascular calcification

Background

Vascular calcification is a closely linked to cardiovascular diseases, such as atherosclerosis, chronic kidney disease, diabetes, hypertension and aging. The extent of vascular calcification is closely correlate with adverse clinical events and cardiovascular all-cause mortality. The role of autophagy in vascular calcification is complex with many mechanistic unknowns.

Methods

In this review, we analyze the current known mechanisms of autophagy in vascular calcification and discuss the theoretical advantages of targeting autophagy as an intervention against vascular calcification.

Results

Here we summarize the functional link between vascular calcification and autophagy in both animal models of and human cardiovascular disease. Firstly, autophagy can reduce calcification by inhibiting the osteogenic differentiation of VSMCs related to ANCR, ERα, β-catenin, HIF-1a/PDK4, p62, miR-30b, BECN1, mTOR, SOX9, GHSR/ERK, and AMPK signaling. Conversely, autophagy can induce osteoblast differentiation and calcification as mediated by CREB, degradation of elastin, and lncRNA H19 and DUSP5 mediated ERK signaling. Secondly, autophagy also links apoptosis and vascular calcification through AMPK/mTOR/ULK1, Wnt/β-catenin and GAS6/AXL synthesis, as apoptotic cells become the nidus for calcium-phosphate crystal deposition. The failure of mitophagy can activate Drp1, BNIP3, and NR4A1/DNA‑PKcs/p53 mediated intrinsic apoptotic pathways, which have been closely linked to the formation of vascular calcification. Additionally, autophagy also plays a role in osteogenesis by regulating vascular calcification, which in turn regulates expression of proteins related to bone development, such as osteocalcin, osteonectin, etc. and regulated by mTOR, EphrinB2 and RhoA. Furthermore, autophagy also promotes vitamin K2-induced MC3T3 E1 osteoblast differentiation and FGFR4/FGF18- and JNK/complex VPS34–beclin-1-related bone mineralization via vascular calcification.

Conclusion

The interaction between autophagy and vascular calcification are complicated, with their interaction affected by the disease process, anatomical location, and the surrounding microenvironment. Autophagy activation in existent cellular damage is considered protective, while defective autophagy in normal cells result in apoptotic activation. Identifying and maintaining cells at the delicate line between these two states may hold the key to reducing vascular calcification, in which autophagy associated clinical strategy could be developed.

Effect of androgen deprivation therapy on serum levels of sclerostin, Dickkopf-1, and osteoprotegerin: a cross-sectional and longitudinal analysis

Androgen deprivation therapy (ADT) for men with prostate cancer (PCa) results in accelerated bone loss and increased risk of bone fracture. The aim of the present study was to evaluate serum bone markers—sclerostin, Dickkopf-1 (DKK-1) and osteoprotegerin (OPG), in a cohort of 88 PCa patients without known bone metastases, managed with and without ADT, and to analyse their relationship with bone mineral density (BMD) and sex steroids. The cross-sectional analysis between acute-, chronic- and former-ADT groups and PCa controls showed that sclerostin and OPG levels significantly differed between them (p = 0.029 and p = 0.032). Groups contributing to these significant changes were recorded. There were no significant differences in serum DKK-1 levels across the four groups (p = 0.683). In the longitudinal analysis, significant % decreases within groups were seen for DKK-1 [chronic-ADT (− 10.06%, p = 0.0057), former-ADT (− 12.77%, p = 0.0239), and in PCa controls group (− 16.73, p = 0.0022); and OPG levels in chronic ADT (− 8.28%, p = 0.003) and PCa controls group (− 12.82%, p = 0.017)]. However, % changes in sclerostin, DKK-1, and OPG did not differ significantly over 6-months across the evaluated groups. Sclerostin levels showed significant positive correlations with BMD at baseline in the ADT group, while in PCa controls this correlation existed at both baseline and 6-month time points. Sclerostin correlated negatively with testosterone in former ADT users and in PCa controls. Possible prognostic features denoted by parallel increases in sclerostin and BMD are discussed.

Assessment of Cardiovascular Safety of Anti-Osteoporosis Drugs

The incidence of osteoporosis and cardiovascular disease increases with age, and there are potentially shared mechanistic associations between the two conditions. It is therefore highly relevant to understand the cardiovascular implications of osteoporosis medications. These are presented in this narrative review. Calcium supplementation could theoretically cause atheroma formation via calcium deposition, and in one study was found to be associated with myocardial infarction, but this has not been replicated. Vitamin D supplementation has been extensively investigated for cardiac benefit, but no consistent effect has been found. Despite findings in the early 21st century that menopausal hormone therapy was associated with coronary artery disease and venous thromboembolism (VTE), this therapy is now thought to be potentially safe (from a cardiac perspective) if started within the first 10 years of the menopause. Selective estrogen receptor modulators (SERMs) are associated with increased risk of VTE and may be related to fatal strokes (a subset of total strokes). Bisphosphonates could theoretically provide protection against atheroma. However, data from randomised trials and observational studies have neither robustly supported this nor consistently demonstrated the potential association with atrial fibrillation. Denosumab does not appear to be associated with cardiovascular disease and, although parathyroid hormone analogues are associated with palpitations and dizziness, no association with a defined cardiovascular pathology has been demonstrated. Finally, romosozumab has been shown to have a possible cardiovascular signal, and therefore post-market surveillance of this therapy will be vital.

Dickkopf-2 knockdown protects against classic macrophage polarization and lipid loading by activation of Wnt/β-catenin signaling

OBJECTIVES

Wnt/β-catenin signaling pathway plays an important role in regulation of macrophage activation implicated in the development of atherosclerosis. However, as a negative regulator of Wnt/β-catenin, the potential role of Dickkopf-2 (Dkk2) on macrophage activation remains unexplored.

MATERIALS AND METHODS

Bone marrow-derived macrophages (BMDMs) and mouse peritoneal macrophages (MPMs) collected from ApoE knockout mice upon oxidation low lipoprotein (Ox-LDL) administration were performed to test the expression of Dkk2. The loss-of-function strategy using siRNA-Dkk2 was further utilized for the function of Dkk2. Inhibition of β-catenin with XAV939 (a β-catenin specific inhibitor) was further used for testing its effect on macrophage activation mediated by Dkk2 knockdown.

RESULTS AND CONCLUSION

In the current study, real time-polymerase chain reaction analysis demonstrated that an up-regulated Dkk2 expression was observed in BMDMs and MPMs of ApoE knockout mice upon Ox-LDL administration, which was confirmed by western blot. The double immunofluorescence staining further exhibited that Dkk2 showed a strong immunoreactivity in BMDMs and primarily located in cytoplasm of macrophages. Dkk2 knockdown significantly decreased the genes related to classic M1 polarized macrophage but increased alternative M2 polarized macrophage markers. Moreover, Dkk2 silencing dramatically attenuated foam cell formation which was contributed by promoted markers' expression associated with cholesterol efflux but attenuated markers to cholesterol influx. Mechanistically, we observed that Dkk2 knockdown activated Wnt/β-catenin signaling by promoting β-catenin to translocate into the nuclei of macrophages, and XAV939 reversed the ameliorated effect of Dkk2 silencing macrophage activation. Taken together, these results suggested that downregulated Dkk2 expression in macrophages was responsible for the inactivation of macrophage through targeting Wnt/β-catenin pathway.

Dickkopf-1 promotes Vascular Smooth Muscle Cell proliferation and migration through upregulating UHRF1 during Cyclic Stretch application

Dickkopf-1 (DKK1) was recently shown to play an important role in cardiovascular disease. The aim of this work was to assess the role of DKK1 in the regulation of smooth muscle cell function by mechanical stretch and the mechanisms underlying this process.

Methods: Wild-type C57BL/6J mice were subjected to sham or abdominal aortic constriction (AAC) surgery. The expression level of DKK1 was examined by immunohistochemical staining and Western blotting. Analyses of DKK1 function in vascular smooth muscle cell (VSMC) proliferation and migration were performed. Transcriptome sequencing analysis was performed to identify the differentially expressed genes and pathways regulated by DKK1. Smooth muscle-specific Dkk1 knockout mice were used to confirm the function of DKK1 in vivo. Chromatin immunoprecipitation (ChIP) was used to confirm DNA-protein interactions. Promoter luciferase analysis was used to detect transcription factor activity.

Results: We found that AAC significantly increased DKK1 protein levels in the thoracic aorta and coronary artery in vivo. In vitro, high-level stretch (18%) induced the expression of DKK1 in VSMCs. Knocking down DKK1 inhibited VSMC proliferation and migration under high-level stretch (18%). We identified ubiquitin-like containing PHD and RING finger domains 1 (UHRF1) as a target gene of DKK1. Knockdown of UHRF1 with small interfering RNAs partially reversed the regulatory effect of recombinant DKK1 on VSMCs. Specific deletion of DKK1 in VSMCs was sufficient to attenuate the AAC-induced upregulation of UHRF1, thickening of arterial media and increase in VSMC proliferation. Furthermore, we found that DKK1 regulated UHRF1 expression through the YAP-TEAD pathway. TEAD1 and TEAD4 bound directly to the promoter of UHRF1, and blocking the YAP-TEAD interaction inhibited UHRF1 upregulation due to DKK1.

Conclusions: This study reveals that DKK1 mediates the mechanical stretch regulation of smooth muscle cell function by modulating UHRF1 expression through the YAP-TEAD pathway.

TGFβ1 Suppressed Matrix Mineralization of Osteoblasts Differentiation by Regulating SMURF1-C/EBPβ-DKK1 Axis

Transforming growth factor β1 (TGFβ1) is a major mediator in the modulation of osteoblast differentiation. However, the underlying molecular mechanism is still not fully understood. Here, we show that TGFβ1 has a dual stage-dependent role in osteoblast differentiation; TGFβ1 induced matrix maturation but inhibited matrix mineralization. We discovered the underlying mechanism of the TGFβ1 inhibitory role in mineralization using human osteoprogenitors. In particular, the matrix mineralization-related genes of osteoblasts such as osteocalcin (OCN), Dickkopf 1 (DKK1), and CCAAT/enhancer-binding protein beta (C/EBPβ) were dramatically suppressed by TGFβ1 treatment. The suppressive effects of TGFβ1 were reversed with anti-TGFβ1 treatment. Mechanically, TGFβ1 decreased protein levels of C/EBPβ without changing mRNA levels and reduced both mRNA and protein levels of DKK1. The degradation of the C/EBPβ protein by TGFβ1 was dependent on the ubiquitin–proteasome pathway. TGFβ1 degraded the C/EBPβ protein by inducing the expression of the E3 ubiquitin ligase Smad ubiquitin regulatory factor 1 (SMURF1) at the transcript level, thereby reducing the C/EBPβ-DKK1 regulatory mechanism. Collectively, our findings suggest that TGFβ1 suppressed the matrix mineralization of osteoblast differentiation by regulating the SMURF1-C/EBPβ-DKK1 axis.

The Interplay of WNT and PPARγ Signaling in Vascular Calcification

Vascular calcification (VC), the ectopic deposition of calcium phosphate crystals in the vessel wall, is one of the primary contributors to cardiovascular death. The pathology of VC is determined by vascular topography, pre-existing diseases, and our genetic heritage. VC evolves from inflammation, mediated by macrophages, and from the osteochondrogenic transition of vascular smooth muscle cells (VSMC) in the atherosclerotic plaque. This pathologic transition partly resembles endochondral ossification, involving the chronologically ordered activation of the β-catenin-independent and -dependent Wingless and Int-1 (WNT) pathways and the termination of peroxisome proliferator-activated receptor γ (PPARγ) signal transduction. Several atherosclerotic plaque studies confirmed the differential activity of PPARγ and the WNT signaling pathways in VC. Notably, the actively regulated β-catenin-dependent and -independent WNT signals increase the osteochondrogenic transformation of VSMC through the up-regulation of the osteochondrogenic transcription factors SRY-box transcription factor 9 (SOX9) and runt-related transcription factor 2 (RUNX2). In addition, we have reported studies showing that WNT signaling pathways may be antagonized by PPARγ activation via the expression of different families of WNT inhibitors and through its direct interaction with β-catenin. In this review, we summarize the existing knowledge on WNT and PPARγ signaling and their interplay during the osteochondrogenic differentiation of VSMC in VC. Finally, we discuss knowledge gaps on this interplay and its possible clinical impact.

A neutralizing antibody against DKK1 does not reduce plaque formation in classical murine models of atherosclerosis: Is the therapeutic potential lost in translation?

BACKGROUND AND AIMS

Clinical interventions targeting nonlipid risk factors are needed given the high residual risk of atherothrombotic events despite effective control of dyslipidemia. Dickkopf-1 (DKK1) plays a lipid-independent role in vascular pathophysiology but its involvement in atherosclerosis development and its therapeutic attractiveness remain to be established.

METHODS

Patient data, in vitro studies and pharmacological intervention in murine models of atherosclerosis were utilized.

RESULTS

In patients' material (n = 127 late stage plaque specimens and n = 10 control vessels), DKK1 mRNA was found to be higher in atherosclerotic plaques versus control arteries. DKK1 protein was detected in the luminal intimal area and in the necrotic core of plaques. DKK1 was released from isolated primary human platelets (~12 - 21-fold) and endothelial cells (~1.4-2.5-fold) upon stimulation with different pathophysiological stimuli. In ApoE^-/- and Ldlr^-/- mice, plasma DKK1 concentrations were similar to those observed in humans, whereas DKK1 expression in different atheroprone arterial segments was very low/absent. Chronic treatment with a neutralizing DKK1 antibody effectively reduced plasma concentrations, however, plaque lesion area was not reduced in ApoE^-/- and Ldlr^-/- mice fed a western diet for 14 and 16 weeks. Anti-DKK1 treatment increased bone volume and bone mineral content.

CONCLUSIONS

Functional inhibition of DKK1 with an antibody does not alter atherosclerosis progression in classical murine models. This may reflect the absence of DKK1 expression in plaques and more advanced animal disease models could be needed to evaluate the role and therapeutic attractiveness of DKK1 in late stage complications such as plaque destabilization, calcification, rupture and thrombosis.

The role of Wnt signalling in development of coronary artery disease and its risk factors

The Wnt signalling pathways are composed of a highly conserved cascade of events that govern cell differentiation, apoptosis and cell orientation. Three major and distinct Wnt signalling pathways have been characterized: the canonical Wnt pathway (or Wnt/β-catenin pathway), the non-canonical planar cell polarity pathway and the non-canonical Wnt/Ca2+ pathway. Altered Wnt signalling pathway has been associated with diverse diseases such as disorders of bone density, different malignancies, cardiac malformations and heart failure. Coronary artery disease is the most common type of heart disease in the United States. Atherosclerosis is a multi-step pathological process, which starts with lipid deposition and endothelial cell dysfunction, triggering inflammatory reactions, followed by recruitment and aggregation of monocytes. Subsequently, monocytes differentiate into tissue-resident macrophages and transform into foam cells by the uptake of modified low-density lipoprotein. Meanwhile, further accumulations of lipids, infiltration and proliferation of vascular smooth muscle cells, and deposition of the extracellular matrix occur under the intima. An atheromatous plaque or hyperplasia of the intima and media is eventually formed, resulting in luminal narrowing and reduced blood flow to the myocardium, leading to chest pain, angina and even myocardial infarction. The Wnt pathway participates in all different stages of this process, from endothelial dysfunction to lipid deposit, and from initial inflammation to plaque formation. Here, we focus on the role of Wnt cascade in pathophysiological mechanisms that take part in coronary artery disease from both clinical and experimental perspectives.

Anti-DKK1 Enhances the Early Osteogenic Differentiation of Human Adipose-Derived Stem/Stromal Cells

Adipose-derived stem/stromal cells (ASCs) have been previously used for bone repair. However, significant cell heterogeneity exists within the ASC population, which has the potential to result in unreliable bone tissue formation and/or low efficacy. Although the use of cell sorting to lower cell heterogeneity is one method to improve bone formation, this is a technically sophisticated and costly process. In this study, we tried to find a simpler and more deployable solution-blocking antiosteogenic molecule Dickkopf-1 (DKK1) to improve osteogenic differentiation. Human adipose-derived stem cells were derived from = 5 samples of human lipoaspirate. In vitro, anti-DKK1 treatment, but not anti-sclerostin (SOST), promoted ASC osteogenic differentiation, assessed by alizarin red staining and real-time polymerase chain reaction (qPCR). Increased canonical Wnt signaling was confirmed after anti-DKK1 treatment. Expression levels of DKK1 peaked during early osteogenic differentiation (day 3). Concordantly, anti-DKK1 supplemented early (day 3 or before), but not later (day 7) during osteogenic differentiation positively regulated osteoblast formation. Finally, anti-DKK1 led to increased transcript abundance of the Wnt inhibitor SOST, potentially representing a compensatory cellular mechanism. In sum, DKK1 represents a targetable "molecular brake" on the osteogenic differentiation of human ASC. Moreover, release of this brake by neutralizing anti-DKK1 antibody treatment at least partially rescues the poor bone-forming efficacy of ASC.

Polygonum multiflorum extract support hair growth by elongating anagen phase and abrogating the effect of androgen in cultured human dermal papilla cells

Background

Dermal papilla cells (DPCs) play a key role in hair growth among the various cell types in hair follicles. Especially, DPCs determine the fate of hair follicle such as anagen to telogen transition and play a pivotal role in androgenic alopecia (AGA). This study was performed to elucidate the hair growth promoting effects of Polygonum multiflorum extract (PM extract) in cultured human DPCs and its underlying mechanisms.

Methods

The effects of PM extract on cultured DPCs were investigated. Cell viability and mitochondrial activity were measured by CCK-8 and JC-1 analysis, respectively. Western blotting, dot blotting, ELISA analysis, immunocytochemistry and real-time PCR analysis were also performed to elucidate the changes in protein and mRNA levels induced by PM extract. 3D cultured DPC spheroids were constructed for mimicking the in vivo DPs. The hair growth stimulatory effect of PM extract was evaluated using human hair follicle organ culture model.

Results

PM extract increased the viability and mitochondrial activity in cultured human DPCs in a dose dependent manner. The expression of Bcl2, an anti-apoptotic protein expressed dominantly in anagen was significantly increased and that of BAD, a pro-apoptotic protein expressed in early catagen was decreased by PM extract in cultured DPCs and/or 3D DPC spheroid culture. PM extract also decreased the expression of catagen inducing protein, Dkk-1. Growth factors including IGFBP2, PDGF and VEGF were increased by PM extract, revealed by dot blot protein analysis. We also have found that PM extract could reverse the androgenic effects of dihydrotestosterone (DHT), the most potent androgen. Finally, PM extract prolonged the anagen of human hair follicles by inhibiting catagen entry in human hair follicle organ culture model.

Conclusion

Our data strongly suggest that PM extract could promote hair growth by elongating the anagen and/or delaying the catagen induction of hair follicles through activation of DPCs.

atherosclerosis: gone with the Wnt?

Atherosclerosis, a pathology affecting large and medium-sized arteries, is the major cause of cardiovascular morbidity/mortality in industrialized countries. During atherosclerosis, cells accumulate large amounts of cholesterol through the uptake of modified low-density lipoprotein particles to form foam cells. This accumulation forms the basis for the development of the disease and for a large spectrum of other diseases in various organs. Massive research efforts have yielded valuable information about the underlying molecular mechanisms of atherosclerosis. In particular, newer discoveries on the early stage of lesion formation, cholesterol accumulation, reverse cholesterol transport, and local inflammation in the vascular wall have opened unanticipated horizons of understanding and raised novel questions and therapeutic opportunities. In this review, we focus on Wnt signaling, which has received little attention so far, yet affects lysosomal function and signalling pathways that limit cholesterol accumulation. This occurs in different tissues and cell types, including smooth muscle cells, endothelial cells and macrophages in the arterial wall, and thus profoundly impacts on atherosclerotic disease development and progression.

Associations of Serum Dickkopf-1 and Sclerostin With Cardiovascular Events: Results From the Prospective Bruneck Study

Background Dickkopf-1 and sclerostin have been implicated in atherosclerosis and vascular calcification. We aimed to quantify the association of their serum levels with incident cardiovascular disease (CVD) in the general population. Methods and Results Among 706 participants of the prospective, population-based Bruneck Study, mean±SD of serum levels were 44.5±14.7 pmol/L for dickkopf-1 and 47.1±17.5 pmol/L for sclerostin. The primary outcome was a composite CVD end point composed of ischemic or hemorrhagic stroke, transient ischemic attack, myocardial infarction, angina pectoris, peripheral vascular disease, and revascularization procedures. Over a median follow-up duration of 15.6 years, 179 CVD events occurred. For the primary CVD outcome, multivariable-adjusted hazard ratios (HRs) per SD higher level were 1.20 for dickkopf-1 (95% CI, 1.02-1.42; P=0.028) and 0.92 for sclerostin (95% CI, 0.78-1.08; P=0.286). Secondary outcome analyses revealed that the association of dickkopf-1 was primarily driven by ischemic and hemorrhagic stroke (67 events; HR, 1.37; 95% CI, 1.06-1.78; P=0.017), whereas no increase in risk was observed for transient ischemic attack (22 events; HR, 0.87; 95% CI, 0.53-1.44; P=0.593), myocardial infarction (45 events; HR, 1.10; 95% CI, 0.78-1.54; P=0.598), or for other CVD (45 events; HR, 1.25; 95% CI, 0.88-1.76; P=0.209). Conclusions In this prospective, population-based study, elevated baseline levels of dickkopf-1, but not sclerostin, were independently associated with incident cardiovascular events, which was mainly driven by stroke. Our findings support the hypothesis of a role of dickkopf-1 in the pathogenesis of CVD.

Cardioprotection of cortistatin against isoproterenol-induced myocardial injury in rats

Background

The present study was designed to examine whether cortistatin (CORT) could protect rats from myocardial injury induced by subcutaneously injecting isoproterenol (ISO) and to clarify the possible mechanisms.

Methods

Male Sprague-Dawley (SD) rats were placed at random into four groups: the control group, the ISO group, the ISO + CORT 25 µg/(kg·d) group, and the ISO + CORT 50 µg/(kg·d) group. Rat models of myocardial injury were established with the subcutaneous (s.c.) injections of 85 mg/kg ISO for 2 days. In the ISO+ CORT 25 µg/(kg·d) group and ISO+ CORT 50 µg/(kg·d) group, rats were given s.c. injections of CORT 25 µg/(kg·d) and CORT 50 µg/(kg·d) on the day before ISO, 3 days, respectively. Serum malondialdehyde (MDA) content, lactate dehydrogenase (LDH) activity, and creatine kinase isoenzyme (CK-MB) activity were measured by corresponding test kits. Western blot was applied to evaluate the expression of endoplasmic reticulum stress-related protein glucose regulatory protein 78 (GRP78), enhancer-binding protein homologous protein (CHOP), cysteinyl aspartate specific proteinase-12 (caspase-12), LC3-II, Beclin-1, and p62 in the rat myocardium.

Results

CORT alleviated the increased enzyme activities of serum LDH and CK-MB, and content of MDA (a typical marker of lipid peroxidation) in rats induced by ISO. CORT also prevented pathological myocardial injury in rats induced by ISO. Moreover, CORT attenuated the increased protein levels of GRP78, CHOP, and caspase-12, and reduced the increase of LC3-II, LC3-II/I, Beclin-1, and p62 in rats induced by ISO.

Conclusions

These data demonstrate that CORT can attenuate ISO-induced acute myocardial injury in rats likely by reducing lipid peroxidation, and inhibiting endoplasmic reticulum stress and autophagy. This supports CORT as a potentially being a new target for preventing and treating myocardial injury and its related disease.

Plasma biomarkers and plaque strain predict long-term cardiovascular events in patients with acute coronary syndrome

To test whether circulating and intracoronary biomarkers and coronary plaque strain have additive values to Global Registry of Acute Coronary Events (GRACE) score for predicting long-term cardiovascular events in ACS patients. One hundred ACS patients were enrolled and the GRACE score and plasma levels and intracoronary gradients of a number of biomarkers were measured. Coronary plaque burden and morphology in non-critical stenotic plaques were determined by intravascular ultrasound (IVUS) technique, and the maximal shear strain (SS_max) and maximal area strain (AS_max) were determined by intravascular ultrasound elastography (IVUSE) technique. Patients were followed for cardiovascular events and the predictive values of clinical characteristics, plasma biomarkers and plaque parameters were compared with GRACE score, and the incremental values of these measurements to the GRACE score were assessed. GRACE score, plasma biomarkers and plaque strain were independent predictors of cardiovascular events. Combination of GRACE score, plasma biomarkers and plaque strains significantly improved the predictive value of the GRACE score alone with the receiver-operating characteristic area increased from 0.457 to 0.667 (P=0.014). The combination of circulating and intracoronary biomarkers, plaque strain and GRACE score provides a better predictive tool than GRACE score alone in patients with ACS.

Dkk (Dickkopf) Proteins

Clinical and preclinical studies over the past 3 decades have uncovered a multitude of signaling pathways involved in the initiation and progression of atherosclerosis. From these studies, signaling by proteins of the Wnt family has recently emerged as an important player in the development of atherosclerosis. Wnt signaling is characterized by a large number of ligands, receptors, and coreceptors and can be regulated at many different levels. Among Wnt modulators, the evolutionary conserved Dkk (Dickkopf) proteins, and especially Dkk-1, the founding member of the family, are the best characterized. The role of Dkks in the pathophysiology of the arterial wall is only partially understood, but their involvement in atherosclerosis is becoming increasingly evident. This review introduces recent key findings on Dkk proteins and their functions in atherosclerosis and discusses the potential importance of modulating Dkk signaling as part of a novel, improved strategy for preventing and treating atherosclerosis-related diseases.

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Dkk1 exacerbates doxorubicin-induced cardiotoxicity by inhibiting the Wnt/β-catenin signaling pathway

The cancer clinical therapy of doxorubicin (Dox) treatment is limited by its life-threatening cardiotoxic effects. Dickkopf-1 (Dkk1), the founding and best-studied member of the Dkk family, functions as an antagonist of canonical Wnt/β-catenin. Dkk1 is considered to play a broad role in a variety of biological processes, but its effects on Dox-induced cardiomyopathy are poorly understood. Here, we found that the level of Dkk1 was significantly increased in Dox-treated groups, and this increase exacerbated Dox-induced cardiomyocyte apoptosis and mitochondrial dysfunction. Overexpressing Dkk1 aggravated Dox-induced cardiotoxicity in H₉C₂ cells. Similar results were detected when adding active Dkk1 protein extracellularly. Conversely, adding specific antibody blocking extracellular Dkk1 attenuated the cardiotoxic response to Dox. Adenovirus encoding Dkk1 was transduced through intramyocardial injection and exacerbated Dox-induced cardiomyocyte apoptosis, mitochondrial damage and heart injury in vivo Furthermore, Wnt/β-catenin signaling was inhibited during Dox-induced cardiotoxicity, and the re-activation of β-catenin prevented the effect of overexpressed Dkk1 and Dox-induced cardiotoxicity. In conclusion, these results reveal the crucial role of the Dkk1-Wnt/β-catenin signaling axis in the process of Dox-induced cardiotoxicity and provide novel insights into the potential mechanism of cardiomyopathy caused by clinical application of Dox.

Scutellarin exerts protective effects against atherosclerosis in rats by regulating the Hippo-FOXO3A and PI3K/AKT signaling pathways

Atherosclerosis (AS), a progressive disorder, is one of the tough challenges in the clinic. Scutellarin, an extract from Herba Erigerontis, is found to have oxygen-free radicals scavenging effects and antioxidant effects. In this study, we aimed to investigate the anti-AS effects of scutellarin is related to controlling the Hippo-FOXO3A and PI3K/AKT signal pathway. To establish an AS model, the rats in the scutellarin and model groups were intraperitoneally injected with vitamin D ₃ and then fed a high-fat diet for 12 weeks. In addition, in vitro angiotensin II-induced apoptosis of human aortic endothelial cells (HAECs) were used to establish models. Scutellarin significantly reduced blood lipid levels and increased antioxidase levels in both models. Additionally, scutellarin inhibited reactive oxygen species generation and apoptosis in HAECs. The impaired vascular barrier function was restored by using scutellarin in AS rats and in HAECs cells characterized by inhibiting mammalian sterile-20-like kinases 1 (Mst1) phosphorylation, Yes-associated protein (YAP) phosphorylation, forkhead box O3A (FOXO3A) phosphorylation at serine 207, nuclear translocation of FOXO3A, and upregulating protein expression of AKT and FOXO3A phosphorylation at serine 253. Scutellarin significantly reduced Bcl-2 interacting mediator of cell death (Bim), caspase-3, APO-1, CD95 (Fas), and Bax: Bcl-2-associated X (Bax) levels and activated Bcl-2: B-cell lymphoma-2 (Bcl-2). Scutellarin also significantly inhibited the expression of Mst1, YAP, FOXO3A at the messenger RNA level. When Mst1 was overexpressed or phosphoinositide 3-kinases suppressed, the effects of scutellarin were significantly blocked. In conclusion, the results of the present study suggest that scutellarin exerts protective effects against AS by inhibiting endothelial cell injury and apoptosis by regulating the Hippo-FOXO3A and PI3K/AKT signal pathways.

Identification of DKK-1 as a novel mediator of statin effects in human endothelial cells

This study shows that DKK-1, a member of the Dickkopf family and a regulator of the Wnt pathways, represents a novel target of statins which, through the inhibition of HMG-CoA reductase and of non-steroidal isoprenoid intermediates, exert extra-beneficial effect in preventing atherosclerosis beyond their effect on the lipid profile. We found that atorvastatin downregulates DKK-1 protein (−88.3 ± 4.1%) and mRNA expression (−90 ± 4.2%) through the inhibition of Cdc42, Rho and Rac geranylgeranylated proteins. Further, a combined approach based on the integration of label-free quantitative mass spectrometry based-proteomics and gene silencing allowed us to demonstrate that DKK-1 itself mediates, at least in part, statin effects on human endothelial cells. Indeed, DKK-1 is responsible for the regulation of the 21% of the statin-modulated proteins, which include, among others, clusterin/apoJ, plasminogen activator inhibitor type 1 (PAI-1), myristoylated alanine-rich C-kinase substrate (MARCKS), and pentraxin 3 (PTX3). The Gene Ontology enrichment annotation revealed that DKK-1 is also a potential mediator of the extracellular matrix organization, platelet activation and response to wounding processes induced by statin. Finally, we found that plasma level of DKK-1 from cholesterol-fed rabbits treated with atorvastatin (2.5 mg/kg/day for 8 weeks) was lower (−42 ± 23%) than that of control animals. Thus, DKK-1 is not only a target of statin but it directly regulates the expression of molecules involved in a plethora of biological functions, thus expanding its role, which has been so far restricted mainly to cancer.

Cell-Specific Protective Signaling Induced by the Novel AT2R-Agonist NP-6A4 on Human Endothelial and Smooth Muscle Cells

Cardiovascular disease incidence continues to rise and new treatment paradigms are warranted. We reported previously that activation of Angiotensin II receptor (encoded by the X-linked Agtr2 gene) by a new peptide agonist, NP-6A4, was more effective in protecting mouse cardiomyocyte HL-1 cells and human coronary artery vascular smooth muscle cells (hCAVSMCs) from acute nutrient deficiency than other drugs tested. To elucidate further the protective effects of NP-6A4 in human cells, we studied the effects of NP-6A4 treatment on functions of human coronary artery endothelial cells (hCAECs), and hCAVSMCs. In hCAVSMCs, NP-6A4 (1 μM) increased Agtr2 mRNA (sixfold, p < 0.05) after 12-h exposure, whereas in hCAECs, significant increase in Agtr2 mRNA (hCAECs: eightfold) was observed after prolonged exposure. Interestingly, NP-6A4 treatment (1 μM, 12 h) increased AT2R protein levels in all human cells tested. Pre-treatment with AT2R-antagonist PD123319 (20 μM) and anti-AT2R siRNA (1 μM) suppressed this effect. Thus, NP-6A4 activates a positive feedback loop for AT2R expression and signaling in hCAVSMCs and hCAECs. NP-6A4 (1–20 μM) increased cell index (CI) of hCAVSMCs as determined by real time cell analyzer (RTCA), indicating that high concentrations of NP-6A4 were not cytotoxic for hCAVSMCs, rather promoting better cell attachment and growth. Seahorse Extracellular Flux Assay revealed that NP-6A4 (1 μM) treatment for 7 days increased whole cell-based mitochondrial parameters of hCAVSMCs, specifically maximal respiration (p < 0.05), spare respiratory capacity (p < 0.05) and ATP production (p < 0.05). NP-6A4 (1 μM; 7 days) also suppressed Reactive Oxygen Species (ROS) in hCAVSMCs. Exposure to Doxorubicin (DOXO) (1 μM) increased ROS in hCAVSMCs and this effect was suppressed by NP-6A4 (1 μM). In hCAECs grown in complete medium, NP-6A4 (1 μM) and Ang II (1 μM) exerted similar changes in CI. Additionally, NP-6A4 (5 μM: 12 h) increased expression of eNOS (sixfold, p < 0.05) and generation of nitric oxide (1.3-fold, p < 0.05) in hCAECs and pre-treatment with PD123319 (20 μM) suppressed this effect partially (65%). Finally, NP-6A4 decreased phosphorylation of Jun-N-terminal kinase, implicated in apoptosis of ECs in atherosclerotic sites. Taken together, NP-6A4, through its ability to increase AT2R expression and signaling, exerts different cell-specific protective effects in human VSMCs and ECs.

Endoplasmic Reticulum Stress in Metabolic Disorders

Metabolic disorders have become among the most serious threats to human health, leading to severe chronic diseases such as obesity, type 2 diabetes, and non-alcoholic fatty liver disease, as well as cardiovascular diseases. Interestingly, despite the fact that each of these diseases has different physiological and clinical symptoms, they appear to share certain pathological traits such as intracellular stress and inflammation induced by metabolic disturbance stemmed from over nutrition frequently aggravated by a modern, sedentary life style. These modern ways of living inundate cells and organs with saturating levels of sugar and fat, leading to glycotoxicity and lipotoxicity that induce intracellular stress signaling ranging from oxidative to ER stress response to cope with the metabolic insults (Mukherjee, et al., 2015). In this review, we discuss the roles played by cellular stress and its responses in shaping metabolic disorders. We have summarized here current mechanistic insights explaining the pathogenesis of these disorders. These are followed by a discussion of the latest therapies targeting the stress response pathways.

Blocking mitochondrial cyclophilin D ameliorates TSH-impaired defensive barrier of artery

AIMS

Endothelial cells (ECs) constitute the defensive barrier of vasculature, which maintains the vascular homeostasis. Mitochondrial oxidative stress (mitoOS) in ECs significantly affects the initiation and progression of vascular diseases. The higher serum thyroid stimulating hormone (TSH) level is being recognized as a nonconventional risk factor responsible for the increased risk of cardiovascular diseases in subclinical hypothyroidism (SCH). However, effects and underlying mechanisms of elevated TSH on ECs are still ambiguous. We sought to investigate whether cyclophilin D (CypD), emerging as a crucial mediator in mitoOS, regulates effects of TSH on ECs.

METHODS AND RESULTS

SCH patients with TSH > = 10mIU/L showed a positive correlation between serum TSH and endothelin-1 levels. When TSH levels declined to normal in these subjects after levothyroxine therapy, serum endothelin-1 levels were significantly reduced. Supplemented with exogenous thyroxine to keep normal thyroid hormones, thyroid-specific TSH receptor (TSHR)-knockout mice with injection of exogenous TSH exhibited elevated serum TSH levels, significant endothelial oxidative injuries and disturbed endothelium-dependent vasodilation. However, Tshr-/- mice resisted to TSH-impaired vasotonia. We further confirmed that elevated TSH triggered excessive mitochondrial permeability transition pore (mPTP) opening and mitochondrial oxidative damages in mouse aorta, as well as in cultured ECs. Genetic or pharmacological inhibition of CypD (the key regulator for mPTP opening) attenuated TSH-induced mitochondrial oxidative damages and further rescued endothelial functions. Finally, we confirmed that elevated TSH could activate CypD by enhancing CypD acetylation via inhibiting adenosine monophosphate-activated protein kinase/sirtuin-3 signaling pathway in ECs.

CONCLUSIONS

These findings reveal that elevated TSH triggers mitochondrial perturbations in ECs and provide insights that blocking mitochondrial CypD enhances the defensive ability of ECs under TSH exposure.