LRP5/canonical Wnt signalling and healing of ischemic myocardium

Targeting Wnt Pathways with Small Molecules as New Approach in Cardiovascular Disease

The increasing incidences of morbidity and mortality associated with cardiovascular diseases represent significant difficulties for clinical treatment and have a major impact on patient health. Wnt signaling pathways are highly conserved and are well known for their regulatory roles in embryonic development, tissue regeneration, and adult tissue homeostasis. Wnt signaling is classified into two distinct pathways: canonical Wnt/β-catenin signaling and noncanonical pathways, including planar cell polarity and Wnt/Ca2+ pathways. A growing body of experimental evidence suggests the involvement of both canonical and non-canonical Wnt signaling pathways in the development of cardiovascular diseases, including myocardial hypertrophy, arrhythmias, diabetic cardiomyopathy, arrhythmogenic cardiomyopathy, and myocardial infarction. Thus, to enhance patient quality of life, diagnosing and treating cardiac illnesses may require a thorough understanding of the molecular functions played by the Wnt pathway in these disorders. Many small-molecule inhibitors specifically target various components within the Wnt signaling pathways, such as Frizzled, Disheveled, Porcupine, and Tankyrase. This study aims to present an overview of the latest findings regarding the functions of Wnt signaling in human cardiac disorders and possible inhibitors of Wnt, which could lead to novel approaches for treating cardiac ailments.

Unique Splicing of Lrp5 in the Brain: A New Player in Neurodevelopment and Brain Maturation

Low-density lipoprotein receptor-related protein 5 (LRP5) is a constitutively expressed receptor with observed roles in bone homeostasis, retinal development, and cardiac metabolism. However, the function of LRP5 in the brain remains unexplored. This study investigates LRP5's role in the central nervous system by conducting an extensive analysis using RNA-seq tools and in silico assessments. Two protein-coding Lrp5 transcripts are expressed in mice: full-length Lrp5-201 and a truncated form encoded by Lrp5-202. Wt mice express Lrp5-201 in the liver and brain and do not express the truncated form. Lrp5-/- mice express Lrp5-202 in the liver and brain and do not express Lrp5-201 in the liver. Interestingly, Lrp5-/- mouse brains show full-length Lrp5-201 expression, suggesting that LRP5 has a role in preserving brain function during development. Functional gene enrichment analysis on RNA-seq unveils dysregulated expression of genes associated with neuronal differentiation and synapse formation in the brains of Lrp5-/- mice compared to Wt mice. Furthermore, Gene Set Enrichment Analysis highlights downregulated expression of genes involved in retinol and linoleic acid metabolism in Lrp5-/- mouse brains. Tissue-specific alternative splicing of Lrp5 in Lrp5-/- mice supports that the expression of LRP5 in the brain is needed for the correct synthesis of vitamins and fatty acids, and it is indispensable for correct brain development.

Single-cell RNA-seq analysis reveals the Wnt/Ca2+ signaling pathway with inflammation, apoptosis in nucleus pulposus degeneration

BACKGROUND

Increasing studies have shown degeneration of nucleus pulposus cells (NPCs) as an critical part of the progression of intervertebral disc degeneration (IVDD). However, there are relatively few studies on single-cell transcriptome contrasts in human degenerated NPCs. Moreover, differences in Wnt/Ca2+ signaling in human degenerated nucleus pulposus cells have not been elucidated. The aim of this study is to investigate the differential expression of Wnt/Ca2+ signaling pathway between normal and degenerated nucleus pulposus cells in humans and try to investigate its mechanism.

METHODS

We performed bioinformatics analysis using our previously published findings to construct single cell expression profiles of normal and degenerated nucleus pulposus. Then, in-depth differential analysis was used to characterize the expression of Wnt/Ca2+ signaling pathway between normal and degenerated nucleus pulposus cells in humans.

RESULTS

The obtained cell data were clustered into five different chondrocytes clusters, which chondrocyte 4 and chondrocyte 5 mainly accounted for a high proportion in degenerated nucleus pulposus tissues, but rarely in normal nucleus pulposus tissues. Genes associated within the Wnt/Ca2+ signaling pathway, such as Wnt5B, FZD1, PLC (PLCB1), CaN (PPP3CA) and NAFATC1 are mainly present in chondrocyte 3, chondrocyte 4 and chondrocyte 5 from degenerated nucleus pulposus tissues. In addition, as a receptor that activates Wnt signaling pathway, LRP5 is mainly highly expressed in chondrocyte 5 of degenerated nucleus pulposus cells. Six genes, ANGPTL4, PTGES, IGFBP3, GDF15, TRIB3 and TNFRSF10B, which are associated with apoptosis and inflammatory responses, and are widespread in chondrocyte 4 and chondrocyte 5, may be closely related to degenerative of nucleus pulposus cells.

CONCLUSIONS

Single-cell RNA sequencing revealed differential expression of Wnt/Ca2+ signaling in human normal and degenerated nucleus pulposus cells, and this differential expression may be closely related to the abundance of chondrocyte 4 and chondrocyte 5 in degenerated nucleus pulposus cells. In degenerated nucleus pulposus cells, LRP5 activate Wnt5B, which promotes nucleus pulposus cell apoptosis and inflammatory response by regulating the Wnt/Ca2+ signaling pathway, thereby promoting disc degeneration. ANGPTL4, IGFBP3, PTGES in chondrocyte 4 and TRIB3, GDF15, TNFRSF10B in chondrocyte 5 may play an important role in this process.

LDL receptor-related protein 5 selectively transports unesterified polyunsaturated fatty acids to intracellular compartments

Polyunsaturated fatty acids (PUFAs), which cannot be synthesized by animals and must be supplied from the diet, have been strongly associated with human health. However, the mechanisms for their accretion remain poorly understood. Here, we show that LDL receptor-related protein 5 (LRP5), but not its homolog LRP6, selectively transports unesterified PUFAs into a number of cell types. The LDLa ligand-binding repeats of LRP5 directly bind to PUFAs and are required and sufficient for PUFA transport. In contrast to the known PUFA transporters Mfsd2a, CD36 and FATP2, LRP5 transports unesterified PUFAs via internalization to intracellular compartments including lysosomes, and n-3 PUFAs depend on this transport mechanism to inhibit mTORC1. This LRP5-mediated PUFA transport mechanism suppresses extracellular trap formation in neutrophils and protects mice from myocardial injury during ischemia-reperfusion. Thus, this study reveals a biologically important mechanism for unesterified PUFA transport to intracellular compartments.

Canonical Wnt pathway and the LDL receptor superfamily in neuronal cholesterol homeostasis and function

AIMS

There is little information on the regulation of cholesterol homeostasis in the brain. Whether cholesterol crosses the blood-brain barrier is under investigation, but the present understanding is that cholesterol metabolism in the brain is independent from that in peripheral tissues. Lipoprotein receptors from the LDL receptor family (LRPs) have key roles in lipid particle accumulation in cells involved in vascular and cardiac pathophysiology; however, their function on neural cells is unknown.

METHODS AND RESULTS

The expression of LRP5 and the components and targets of its downstream signalling pathway, the canonical Wnt pathway, including β-catenin, LEF1, VEGF, OPN, MMP7, and ADAM10, is analysed in the brains of Wt and Lrp5-/- mice and in a neuroblastoma cell line. LRP5 expression is increased in a time- and dose-dependent manner after lipid loading in neuronal cells; however, it does not participate in cholesterol homeostasis as shown by intracellular lipid accumulation analyses. Neurons challenged with staurosporin and H2O2 display an anti-apoptotic protective role for LRP5.

CONCLUSIONS

For the first time, it has been shown that neurons can accumulate intracellular lipids and lipid uptake is performed mainly by the LDLR, while CD36, LRP1, and LRP5 do not play a major role. In addition, it has been shown that LRP5 triggers the canonical Wnt pathway in neuronal cells to generate pro-survival signals. Finally, Lrp5-/- mice have maintained expression of LRP5 only in the brain supporting the biological plausible concept of the need of brain LRP5 to elicit pro-survival processes and embryonic viability.

Mechanisms of the Wnt Pathways as a Potential Target Pathway in Atherosclerosis

The proteins of the Wnt family are involved in a variety of physiological processes by means of several canonical and noncanonical signaling pathways. Wnt signaling has been recently identified as a major player in atherogenesis. In this review, we summarize the existing knowledge on the influence of various components of the Wnt signaling pathways on the initiation and progression of atherosclerosis and associated conditions. We used the PubMed database to search for recent papers on the involvement of the Wnt pathways in atherosclerosis. We used the combination of "Wnt" and "atherosclerosis" keywords to find the initial papers, and chose papers published after 2018. In the first section of the paper, we describe the general mechanisms of the Wnt signaling pathways and their components. The next section is dedicated to existing studies assessing the implication of Wnt signaling elements in different atherogenic processes, such as cholesterol retention, endothelial dysfunction, vascular inflammation, and atherosclerotic calcification of the vessels. Lastly, various therapeutic strategies based on interference with the Wnt signaling pathways are considered. We also compare the efficacy and availability of the proposed treatment methods. Wnt signaling can be considered a potential target in the treatment and prevention of atherosclerosis. Therefore, in this review, we reviewed evidences showing that wnt signaling is an important signal for developing appropriate treatment strategies for atherosclerosis.

Differential cholesterol uptake in liver cells: A role for PCSK9

The clearance of low-density lipoprotein (LDL) particles from the circulation is regulated by the LDL receptor (LDLR) and proprotein convertase subtilisin/kexin 9 (PCSK9) interaction. Its disruption reduces blood cholesterol levels and delays atherosclerosis progression. Whether other members of the LDLR superfamily are in vivo targets of PCSK9 has been poorly explored. The aim of this work was to study the interaction between PCSK9 and members of the LDLR superfamily in the regulation of liver cholesterol homeostasis in an in vivo low-density lipoprotein receptor related protein 5 (LRP5) deficient mice model challenged with high-fat diet. Our results show that Wt and Lrp5^-/- mice fed a hypercholesterolemic diet (HC) have increased cholesterol ester accumulation and decreased liver LDLR and LRP5 gene and protein expression. Very low-density lipoprotein receptor (VLDLR), LRP6, LRP2, and LRP1 expression levels were analyzed in liver samples and show that they do not participate in Lrp5^-/- liver cholesterol uptake. Immunoprecipitation experiments show that LRP5 forms a complex with PCSK9 in liver-specific fat-storing stellate cells but not in structural HepG2 cells. Hepatic stellate cells silenced for LRP5 and/or PCSK9 expression and challenged with lipids show reduced cholesterol ester accumulation, indicating that both proteins are involved in lipid processing in the liver. Our results indicate that cholesterol esters accumulate in livers of Wt mice in a LDLR-family-members dependent manner as VLDLR, LRP2, and LRP6 show increased expression in HC mice. However, this increase is lost in livers of Lrp5^-/- mice, where scavenger receptors are involved in cholesterol uptake. PCSK9 expression is strongly downregulated in mice livers after HC feeding. However PCSK9 and LRP5 bind in the cytoplasm of fat storing liver cells, indicating that this PCSK9-LRP5 interaction is cell-type specific and that both proteins contribute to lipid uptake.

LRP5 Promotes Gastric Cancer via Activating Canonical Wnt/β-Catenin and Glycolysis Pathways

The overactivation of canonical Wnt/β-catenin pathway is one of the main cascades for the initiation, progression, and recurrence of most human malignancies. As an indispensable coreceptor for the signaling transduction of the canonical Wnt/β-catenin pathway, LRP5 is up-regulated and exerts a carcinogenic role in most types of cancer. However, its expression level and role in gastric cancer (GC) has not been clearly elucidated. The current work showed that LRP5 was overexpressed in GC tissues and the expression of LRP5 was positively associated with the advanced clinical stages and poor prognosis. Ectopic expression of LRP5 enhanced the proliferation, invasiveness, and drug resistance of GC cells in vitro, and accelerated the tumor growth in nude mice, through activating the canonical Wnt/β-catenin signaling pathway and up-regulating aerobic glycolysis, thus increasing the energy supply for GC cells. Additionally, the expression of LRP5 and glycolysis-related genes showed an obviously positive correlation in GC tissues. By contrast, the exact opposite results were observed when the endogenous LRP5 was silenced in GC cells. Collectively, these results not only reveal the carcinogenic role of LRP5 during GC development through activating the canonical Wnt/β-catenin and glycolysis pathways, but also provide a valuable candidate for the diagnosis and treatment of human GC.

Cardiomyocyte-specific deletion of β-catenin protects mouse hearts from ventricular arrhythmias after myocardial infarction

Wnt/β-catenin signaling is activated in the heart after myocardial infarction (MI). This study aims to investigate if β-catenin deletion affects post-MI ion channel gene alterations and ventricular tachycardias (VT). MI was induced by permanent ligation of left anterior descending artery in wild-type (WT) and cardiomyocyte-specific β-catenin knockout (KO) mice. KO mice showed reduced susceptibility to VT (18% vs. 77% in WT) at 8 weeks after MI, associated with reduced scar size and attenuated chamber dilation. qPCR analyses of both myocardial tissues and purified cardiomyocytes demonstrated upregulation of Wnt pathway genes in border and infarct regions after MI, including Wnt ligands (such as Wnt4) and receptors (such as Fzd1 and Fzd2). At 1 week after MI, cardiac sodium channel gene (Scn5a) transcript was reduced in WT but not in KO hearts, consistent with previous studies showing Scn5a inhibition by Wnt/β-catenin signaling. At 8 weeks after MI when Wnt genes have declined, Scn5a returned to near sham levels and K⁺ channel gene downregulations were not different between WT and KO mice. This study demonstrated that VT susceptibility in the chronic phase after MI is reduced in mice with cardiomyocyte-specific β-catenin deletion primarily through attenuated structural remodeling, but not ion channel gene alterations.

Microvesicles carrying LRP5 induce macrophage polarization to an anti-inflammatory phenotype

Microvesicles (MV) contribute to cell-to-cell communication through their transported proteins and nucleic acids. MV, released into the extracellular space, exert paracrine regulation by modulating cellular responses after interaction with near and far target cells. MV are released at high concentrations by activated inflammatory cells. Different subtypes of human macrophages have been characterized based on surface epitopes being CD16+ macrophages associated with anti-inflammatory phenotypes. We have previously shown that low-density lipoprotein receptor-related protein 5 (LRP5), a member of the LDLR family that participates in lipid homeostasis, is expressed in macrophage CD16+ with repair and survival functions. The goal of our study was to characterize the cargo and tentative function of macrophage-derived MV, whether LRP5 is delivered into MV and whether these MV are able to induce inflammatory cell differentiation to a specific CD16- or CD16+ phenotype. We show, for the first time, that lipid-loaded macrophages release MV containing LRP5. LDL loading induces increased expression of macrophage pro-inflammatory markers and increased release of MV containing pro-inflammatory markers. Conditioning of fresh macrophages with MV released by Lrp5-silenced macrophages induced the transcription of inflammatory genes and reduced the transcription of anti-inflammatory genes. Thus, MV containing LRP5 induce anti-inflammatory phenotypes in macrophages.

LRP5 Regulates HIF-1α Stability via Interaction with PHD2 in Ischemic Myocardium

Low-density lipoprotein receptor-related protein 5 (LRP5) has been studied as a co-receptor for Wnt/β-catenin signaling. However, its role in the ischemic myocardium is largely unknown. Here, we show that LRP5 may act as a negative regulator of ischemic heart injury via its interaction with prolyl hydroxylase 2 (PHD2), resulting in hypoxia-inducible factor-1α (HIF-1α) degradation. Overexpression of LRP5 in cardiomyocytes promoted hypoxia-induced apoptotic cell death, whereas LRP5-silenced cardiomyocytes were protected from hypoxic insult. Gene expression analysis (mRNA-seq) demonstrated that overexpression of LRP5 limited the expression of HIF-1α target genes. LRP5 promoted HIF-1α degradation, as evidenced by the increased hydroxylation and shorter stability of HIF-1α under hypoxic conditions through the interaction between LRP5 and PHD2. Moreover, the specific phosphorylation of LRP5 at T1492 and S1503 is responsible for enhancing the hydroxylation activity of PHD2, resulting in HIF-1α degradation, which is independent of Wnt/β-catenin signaling. Importantly, direct myocardial delivery of adenoviral constructs, silencing LRP5 in vivo, significantly improved cardiac function in infarcted rat hearts, suggesting the potential value of LRP5 as a new target for ischemic injury treatment.

Triglyceride-induced cardiac lipotoxicity is mitigated by Silybum marianum

BACKGROUND AND AIMS

Silybum marianum (SM) is an herbal product with cytoprotective and antioxidant properties. We have previously demonstrated that SM ameliorates ventricular remodeling and improves cardiac performance. Here, we evaluated whether SM could exert beneficial effects against cardiac lipotoxicity in a pig model of closed-chest myocardial infarction (MI).

METHODS

Study 1 investigated the effect of SM administration on lipid profile and any potential SM-related adverse effects. Animals received SM or placebo during 10 days and were afterward sacrificed. Study 2 evaluated the effectiveness of SM daily administration in reducing cardiac lipotoxicity in animals subjected to a 1.5h myocardial infarction (MI), who were subsequently reperfused for 2.5h and euthanized or kept under study for three weeks and then sacrificed.

RESULTS

Animals administered a 10-day SM regime presented a sharp decline in plasma triglyceride levels vs. controls, with no other modifications in lipid profile. The decrease in triglyceride concentration was accompanied by a marked reduction in triglyceride intestinal absorption and glycoprotein-P expression. Three weeks post-MI the triglyceride content in the ischemic myocardium of the SM-treated animals was significantly lower than in the ischemic myocardium of placebo-controls. This effect was associated with an enhanced cardiac expression of PPARγ and triglyceride clearance receptors. This long-term SM-administration induced a lower expression of lipid receptors in subcutaneous adipose tissue. No SM-related side-effects were registered.

CONCLUSION

SM administration reduces plasma triglyceride levels through attenuation of triglyceride intestinal absorption and modulates cardiac lipotoxicity in the ischemic myocardium, likely contributing to improve ventricular remodeling.

Effect of Interventions in WNT Signaling on Healing of Cardiac Injury: A Systematic Review

The wound healing that follows myocardial infarction is a complex process involving multiple mechanisms, such as inflammation, angiogenesis and fibrosis. In the last two decades, the involvement of WNT signaling has been extensively studied and effects on virtually all aspects of this wound healing have been reported. However, as often is the case in a newly emerging field, inconsistent and sometimes even contradictory findings have been reported. The aim of this systematic review is to provide a comprehensive overview of studies in which the effect of interventions in WNT signaling were investigated in in vivo models of cardiac injury. To this end, we used different search engines to perform a systematic search of the literature using the key words "WNT and myocardial and infarction". We categorized the interventions according to their place in the WNT signaling pathway (ligand, receptor, destruction complex or nuclear level). The most consistent improvements of the wound healing response were observed in studies in which the acylation of WNT proteins was inhibited by administering porcupine inhibitors, by inhibiting of the downstream glycogen synthase kinase-3β (GSK3β) and by intervening in the β-catenin-mediated gene transcription. Interestingly, in several of these studies, evidence was presented for activation of cardiomyocyte proliferation around the infarct area. These findings indicate that inhibition of WNT signaling can play a valuable role in the repair of cardiac injury, thereby improving cardiac function and preventing the development of heart failure.

Sfrp1 protects against acute myocardial ischemia (AMI) injury in aged mice by inhibiting the Wnt/β-catenin signaling pathway

BACKGROUND

Aged patients suffering from acute myocardial ischemia (AMI) exhibit an increased mortality rate and worse prognosis, and a more effective treatment is currently in need. In the present study, we investigated potent targets related to Wnt/β-catenin pathway deregulation for AMI injury treatment.

METHODS

In the present study, AAV-Sfrp1 was transduced into the myocardium of aged mice, and an AMI model was established in these aged mice to study the effect and molecular mechanism of Sfrp1 overexpression on AMI-induced injury.

RESULTS

The results showed that Sfrp1 was successfully overexpressed in the myocardium of aged mice and remarkably reduced Wnt/β-catenin pathway activity in aged mice after AMI, effectively reducing the degree of myocardial fibrosis, inhibiting cardiomyocyte apoptosis, and improving cardiac function. We revealed that the exogenous introduction of Sfrp1 could be considered a promising strategy for improving post-AMI injury in aged mice by inhibiting Wnt/β-catenin pathway activity.

CONCLUSIONS

In conclusion, the Wnt/β-catenin pathway potentially represents a key target in AMI in aged mice. Sfrp1 might be used as a small molecule gene therapy drug to improve heart function, reduce the degree of myocardial fibrosis, inhibit cardiomyocyte apoptosis and reduce AMI injury in aged mice by inhibiting the Wnt/β-catenin pathway, thereby effectively protecting aged hearts from AMI injury.

The effect of nutraceuticals on multiple signaling pathways in cardiac fibrosis injury and repair

Cardiac fibrosis is one of the most common pathological conditions caused by different heart diseases, including myocardial infarction and diabetic cardiomyopathy. Cardiovascular disease is one of the major causes of mortality worldwide. Cardiac fibrosis is caused by different processes, including inflammatory reactions and oxidative stress. The process of fibrosis begins by changing the balance between production and destruction of extracellular matrix components and stimulating the proliferation and differentiation of cardiac fibroblasts. Many studies have focused on finding drugs with less adverse effects for the treatment of cardiovascular disease. Some studies show that nutraceuticals are effective in preventing and treating diseases, including cardiovascular disease, and that they can reduce the risk. However, big clinical studies to prove the therapeutic properties of all these substances and their adverse effects are lacking so far. Therefore, in this review, we tried to summarize the knowledge on pathways and mechanisms of several nutraceuticals which have shown their usefulness in the prevention of cardiac fibrosis.

Interventions in WNT Signaling to Induce Cardiomyocyte Proliferation: Crosstalk with Other Pathways

Myocardial infarction is a frequent cardiovascular event and a major cause for cardiomyocyte loss. In adult mammals, cardiomyocytes are traditionally considered to be terminally differentiated cells, unable to proliferate. Therefore, the wound-healing response in the infarct area typically yields scar tissue rather than newly formed cardiomyocytes. In the last decade, several lines of evidence have challenged the lack of proliferative capacity of the differentiated cardiomyocyte: studies in zebrafish and neonatal mammals have convincingly demonstrated the regenerative capacity of cardiomyocytes. Moreover, multiple signaling pathways have been identified in these models that-when activated in adult mammalian cardiomyocytes-can reactivate the cell cycle in these cells. However, cardiomyocytes frequently exit the cell cycle before symmetric division into daughter cells, leading to polyploidy and multinucleation. Now that there is more insight into the reactivation of the cell cycle machinery, other prerequisites for successful symmetric division of cardiomyocytes, such as the control of sarcomere disassembly to allow cytokinesis, require more investigation. This review aims to discuss the signaling pathways involved in cardiomyocyte proliferation, with a specific focus on wingless/int-1 protein signaling. Comparing the conflicting results from in vitro and in vivo studies on this pathway illustrates that the interaction with other cells and structures around the infarct is likely to be essential to determine the outcome of these interventions. The extensive crosstalk with other pathways implicated in cardiomyocyte proliferation calls for the identification of nodal points in the cell signaling before cardiomyocyte proliferation can be moved forward toward clinical application as a cure of cardiac disease. SIGNIFICANCE STATEMENT: Evidence is mounting that proliferation of pre-existing cardiomyocytes can be stimulated to repair injury of the heart. In this review article, an overview is provided of the different signaling pathways implicated in cardiomyocyte proliferation with emphasis on wingless/int-1 protein signaling, crosstalk between the pathways, and controversial results obtained in vitro and in vivo.

Study of the aqueous extract of Aloe vera and its two active components on the Wnt/β-catenin and Notch signaling pathways in colorectal cancer cells

ETHNOPHARMACOLOGICAL RELEVANCE

Aloe vera (L.) Burm. f. (Aloe vera) is a common Traditional Chinese Medicine (TCM) recorded in Pharmacopoeia of the People's Republic of China (version 2015). It has been traditionally used for treatment of constipation. Aloe vera requires much attention for its safety evaluation because several studies have reported the association between oral consumption of Aloe vera and the development of colorectal cancer (CRC). However the material basis and molecular mechanism are.still less well elucidated. Although Wnt/β-catenin and Notch signaling pathway have been known to be closely related to the initiation and development of CRC, the impacts of Aloe vera on these cancerous pathways have not been completely determined yet.

AIM OF THIS STUDY

Hence, this study aimed to study the impacts of Aloe vera on the Wnt/β-catenin and Notch signaling pathway, as well as proliferation of CRC cells.

MATERIALS AND METHODS

Firstly, the effects of Aloe vera aqueous extract and its two active components (aloin and aloesin) on the Wnt/β-catenin and Notch signaling pathway were studied by luciferase reporter, RT-qPCR, western blotting and immunofluorescence assays, respectively. Furthermore, RNA sequencing analysis (RNA-seq) was then performed to verify their regulatory activities on the Wnt-related and Notch-related genes expression. Finally, their impacts on RKO cell proliferation and cell cycle phase were also evaluated via MTT assay and cell cycle analysis.

RESULTS

Our results indicate that the aqueous extract of Aloe vera and its active component aloin activated the Wnt/β-catenin pathway and inhibited the Notch signaling pathway only in the presence of Wnt3a. While aloesin was characterized to directly activate the Wnt/β-catenin pathway and inhibit the Notch pathway independent of Wnt3a. Within 24h, the Aloe vera extract and its two components were failed to affect the proliferation or cell cycle phase of RKO cells. Nevertheless, in the presence of Wnt3a, the aqueous extract of Aloe vera with the concentration of 33.3 μg/ml start to promote the cell proliferation of RKO cells after 48h incubation.

CONCLUSION

In conclusion, this study showed that Aloe vera extract and its active component aloin activated the Wnt/β-catenin pathway and inhibited the Notch pathway in the presence of Wnt3a. While another active component, aloesin, activated the Wnt/β-catenin pathway and inhibited the Notch signaling pathway independent of Wnt3a. Given that Wnt/β-catenin and Notch pathway are closely associated with the progression of CRC, these findings would be helpful to better understand the colonic carcinogenicity of Aloe vera.

GSK3β inhibition and canonical Wnt signaling in mice hearts after myocardial ischemic damage

Aims

Myocardial infarction induces myocardial injury and tissue damage. During myocardial infarction strong cellular response is initiated to salvage the damaged tissues. This response is associated with the induction of different signaling pathways. Of these, the canonical Wnt signaling is increasingly important for its prosurvival cellular role, making it a good candidate for the search of new molecular targets to develop therapies to prevent heart failure in infarcted patients.

Methods

Herein we report that GSK3β regulates the canonical Wnt signaling in C57Bl6 mice hearts. GSK3β is a canonical Wnt pathway inhibitor. Using GSK3β inhibitors and inducing myocardial injury (MI) in Lrp5^-/- mice model we show that GSK3β phosphorylation levels regulate downstream canonical Wnt pathway genes in the ischemic heart. In the setting of MI, myocardial damage assessment usually correlates with functional and clinical outcomes. Therefore, we measured myocardial injury size in Wt and Lrp5^-/- mice in the presence and absence of two different GSK3 inhibitors prior to MI. Myocardial injury was independent of GSK3 inhibitor treatments and GSK3β expression levels.

Results

These studies support a central role for GSK3β in the activation of the canonical Wnt pathway in the Wt heart. Although LRP5 is protective against myocardial injury, GSK3β expression levels do not regulate heart damage.

The role of Wnt signaling in the healing myocardium: a focus on cell specificity

Various cell types are involved in the healing process after myocardial infarction (MI). Besides cardiac resident cells (such as cardiomyocytes, fibroblasts and endothelial cells) already present at the lesion site, a massive influx of leukocytes (mainly monocytes and neutrophils) is observed within hours after the ischemic event. So far, little is known about modes of interaction of these cells. Wnt signaling is an evolutionary conserved signaling cassette known to play an important role in cell-cell communication. While the overall reactivation of Wnt signaling upon ischemic injury is well described, the precise expression pattern of Wnt proteins, however, is far from understood. We here describe known Wnt components that partake in MI healing and differentiate cell-specific aspects. The secretion of Wnt proteins and their antagonists in the context of cardiac inflammation after MI appear to be tightly regulated in a spatial-temporal manner. Overall, we aim to stress the importance of elucidating not only Wnt component-specific aspects, but also their sometimes contradicting effects in different target cells. A better understanding of Wnt signaling in MI healing may eventually lead to the development of successful therapeutic approaches in an often considered "un-druggable" pathway.

WNT Signaling in Cardiac and Vascular Disease

WNT signaling is an elaborate and complex collection of signal transduction pathways mediated by multiple signaling molecules. WNT signaling is critically important for developmental processes, including cell proliferation, differentiation and tissue patterning. Little WNT signaling activity is present in the cardiovascular system of healthy adults, but reactivation of the pathway is observed in many pathologies of heart and blood vessels. The high prevalence of these pathologies and their significant contribution to human disease burden has raised interest in WNT signaling as a potential target for therapeutic intervention. In this review, we first will focus on the constituents of the pathway and their regulation and the different signaling routes. Subsequently, the role of WNT signaling in cardiovascular development is addressed, followed by a detailed discussion of its involvement in vascular and cardiac disease. After highlighting the crosstalk between WNT, transforming growth factor-β and angiotensin II signaling, and the emerging role of WNT signaling in the regulation of stem cells, we provide an overview of drugs targeting the pathway at different levels. From the combined studies we conclude that, despite the sometimes conflicting experimental data, a general picture is emerging that excessive stimulation of WNT signaling adversely affects cardiovascular pathology. The rapidly increasing collection of drugs interfering at different levels of WNT signaling will allow the evaluation of therapeutic interventions in the pathway in relevant animal models of cardiovascular diseases and eventually in patients in the near future, translating the outcomes of the many preclinical studies into a clinically relevant context.

Therapeutic effect of a novel Wnt pathway inhibitor on cardiac regeneration after myocardial infarction

After myocardial infarction (MI), the heart is difficult to repair because of great loss of cardiomyoctyes and lack of cardiac regeneration. Novel drug candidates that aim at reducing pathological remodeling and stimulating cardiac regeneration are highly desirable. In the present study, we identified if and how a novel porcupine inhibitor CGX1321 influenced MI and cardiac regeneration. Permanent ligation of left anterior descending (LAD) coronary artery was performed in mice to induce MI injury. Cardiac function was measured by echocardiography, infarct size was examined by TTC staining. Fibrosis was evaluated with Masson's trichrome staining and vimentin staining. As a result, CGX1321 administration blocked the secretion of Wnt proteins, and inhibited both canonical and non-canonical Wnt signaling pathways. CGX1321 improved cardiac function, reduced myocardial infarct size, and fibrosis of post-MI hearts. CGX1321 significantly increased newly formed cardiomyocytes in infarct border zone of post-MI hearts, evidenced by the increased EdU⁺ cardiomyocytes. Meanwhile, CGX1321 increased Ki67⁺ and phosphohistone H3 (PH3⁺) cardiomyocytes in culture, indicating enhanced cardiomyocyte proliferation. The mRNA microarray showed that CGX1321 up-regulated cell cycle regulating genes such as Ccnb1 and Ccne1 CGX1321 did not alter YAP protein phosphorylation and nuclear translocation in cardiomyocytes. In conclusion, porcupine inhibitor CGX1321 reduces MI injury by limiting fibrosis and promoting regeneration. It promotes cardiomyocyte proliferation by stimulating cell cycle regulating genes with a Hippo/YAP-independent pathway.

Physiological and therapeutic regulation of PCSK9 activity in cardiovascular disease

Ischemic heart disease is the main cause of death worldwide and is accelerated by increased levels of low-density lipoprotein cholesterol (LDL-C). Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a potent circulating regulator of LDL-C through its ability to induce degradation of the LDL receptor (LDLR) in the lysosome of hepatocytes. Only in the last few years, a number of breakthroughs in the understanding of PCSK9 biology have been reported illustrating how PCSK9 activity is tightly regulated at several levels by factors influencing its transcription, secretion, or by extracellular inactivation and clearance. Two humanized antibodies directed against the LDLR-binding site in PCSK9 received approval by the European and US authorities and additional PCSK9 directed therapeutics are climbing up the phases of clinical trials. The first outcome data of the PCSK9 inhibitor evolocumab reported a significant reduction in the composite endpoint (cardiovascular death, myocardial infarction, or stroke) and further outcome data are awaited. Meanwhile, it became evident that PCSK9 has (patho)physiological roles in several cardiovascular cells. In this review, we summarize and discuss the recent biological and clinical data on PCSK9, the regulation of PCSK9, its extra-hepatic activities focusing on cardiovascular cells, molecular concepts to target PCSK9, and finally briefly summarize the data of recent clinical studies.