Immune responses are crucial to maintaining tissue homeostasis upon tissue injury. Upon various types of challenges, macrophages play a central role in regulating inflammation and tissue repair processes. While an immunomodulatory role of Wnt antagonist Dickkopf1 (DKK1) has been implicated, the role of Wnt antagonist DKK1 in regulating macrophage polarization in inflammation and the tissue repair process remains elusive. Here we found that DKK1 induces gene expression profiles to promote inflammation and tissue repair in macrophages. Importantly, DKK1 induced various genes, including inflammation and tissue repair, via JNK (c-jun N-terminal kinase) in macrophages. Furthermore, DKK1 potentiated IL-13-mediated macrophage polarization and activation. The co-inhibition of JNK and STAT6 markedly decreased gene expressions relevant to inflammation and fibrosis by DKK1 and IL-13. Interestingly, thrombocyte-specific deletion of DKK1 in mice reduced collagen deposition and decreased Arg1, CD206, HIF1α, and IL1β protein expressions in monocyte-derived alveolar macrophages in the acute sterile bleomycin (BLM)-induced lung injury model. These data suggested that thrombocytes communicate with macrophages via DKK1 to orchestrate inflammation and repair in this model. Taken together, our study demonstrates DKK1\'s role as an important regulatory ligand for macrophage polarization in the injury-induced inflammation and repair process in the lung.

Osteoblast Wnt/β-catenin signaling conditions skeletal development and health. Bone formation is stimulated when on the osteoblast surface a Wnt binds to low-density lipoprotein receptor-related protein 5 (LRP5) or 6 (LRP6), in turn coupled to a frizzled receptor. Sclerostin and dickkopf1 inhibit osteogenesis if either links selectively to the first β-propeller of LRP5 or LRP6, thereby disassociating these cognate co-receptors from the frizzled receptor. Sixteen heterozygous mutations identified since 2002 within LRP5 and three heterozygous mutations identified since 2019 within LRP6 prevent this binding of sclerostin or dickkopf1 and account for the exceptionally rare, but highly instructive, autosomal dominant disorders called LRP5 and LRP6 high bone mass (HBM). Herein, we characterize LRP6 HBM in the first large affected family. Their novel heterozygous LRP6 missense mutation (c.719C>T, p.Thr240Ile) was present in two middle-aged sisters and three of their sons. They considered themselves healthy. Their broad jaw and torus palatinus developed during childhood and, contrary to the two previous reports of LRP6 HBM, the appearance of their adult dentition was unremarkable. Skeletal modeling, defined radiographically, supported classification as an endosteal hyperostosis. Areal bone mineral density (g/cm2) of the lumbar spine and total hip featured accelerated increases reaching Z-scores of ~ +8 and +6, respectively, although biochemical markers of bone formation were normal. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Coronavirus disease 19 (COVID-19) trajectories show high interindividual variability, ranging from asymptomatic manifestations to fatal outcomes, the latter of which may be fueled by immunometabolic maladaptation of the host. Reliable identification of patients who are at risk of severe disease remains challenging. We hypothesized that serum concentrations of Dickkopf1 (DKK1) indicate disease outcomes in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected individuals.
We recruited hospitalized patients with PCR-confirmed SARS-CoV-2 infection and included 80 individuals for whom blood samples from 2 independent time points were available. DKK1 serum concentrations were measured by ELISA in paired samples. Clinical data were extracted from patient charts and correlated with DKK1 levels. Publicly available datasets were screened for changes in cellular DKK1 expression on SARS-CoV-2 infection. Plasma metabolites were profiled by nuclear magnetic resonance spectroscopy in an unbiased fashion and correlated with DKK1 data. Kaplan-Meier and Cox regression analysis were used to investigate the prognostic value of DKK1 levels in the context of COVID-19.
We report that serum levels of DKK1 predict disease outcomes in patients with COVID-19. Circulating DKK1 concentrations are characterized by high interindividual variability and change as a function of time during SARS-CoV-2 infection, which is linked to platelet counts. We further find that the metabolic signature associated with SARS-CoV-2 infection resembles fasting metabolism and is mirrored by circulating DKK1 abundance. Patients with low DKK1 levels are twice as likely to die from COVID-19 than those with high levels, and DKK1 predicts mortality independent of markers of inflammation, renal function, and platelet numbers.
Our study suggests a potential clinical use of circulating DKK1 as a predictor of disease outcomes in patients with COVID-19. These results require validation in additional cohorts.

Vascular calcification (VC) is a significant risk factor for cardiovascular mortality and morbidity in patients with atherosclerosis (AS), chronic kidney disease, and diabetes. Dickkopf1 (Dkk1) is a multifunctional secreted glycoprotein that has been explored as a novel potential antitumor target. Recently, Dkk1 was shown to be closely associated with AS development. However, the role of Dkk1 in VC remains elusive. In this study, we explored the role and molecular mechanisms of Dkk1 in VC based on a smooth muscle-specific Dkk1-knockout (Dkk1SMKO) mouse model. Our data indicated that Dkk1 expression was decreased under calcifying conditions and that Dkk1 overexpression alleviated high phosphate-induced vascular calcification. In vivo, smooth muscle Dkk1-specific knockout aggravated vascular calcification in mice. However, phospholipase D1 (PLD1) overexpression partially weakened the protective effect of Dkk1 against vascular calcification. Mechanistically, Dkk1 slowed vascular calcification by promoting the degradation of PLD1 via the regulating autophagosome formation and maturation. In conclusion, we found that Dkk1 could alleviate vascular calcification by regulating the degradation of PLD1.

Penile squamous cell cancer (PSCC) is the most frequent penile malignant disease. Infections with human papillomaviruses (HPV) are a major etiologic driver of PSCC. However, the molecular details of the underlying carcinogenesis are understudied because of rare clinical specimens and missing cell lines. Here, we investigated if the expression of high-risk HPV16 oncogenes causes an augmentation of the Wnt pathway using unique HPV-positive penile cancer (PeCa) cell lines in monolayer and organotypic 3D raft cultures as well as tissue micro arrays containing clinical tissue specimens. The HPV oncoproteins enhanced the expression of Leucine-rich repeat-containing G-protein coupled receptor 6 (LGR6) and the HPV-positive PeCa cells expressed a signature of Wnt target and stemness-associated genes. However, the notable lack of nuclear β-catenin in vitro and in situ raised the question if the enhanced expression of Wnt pathway factors is tantamount to an active Wnt signaling. Subsequent TOP-flash reporter assays revealed Wnt signaling as absent and not inducible by respective Wnt ligands in PeCa cell lines. The HPV-positive PeCa cells and especially HPV-positive PeCa specimens of the tumor core expressed the Wnt antagonist and negative feedback-regulator Dickkopf1 (DKK1). Subsequent neutralization experiments using PeCa cell line-conditioned media demonstrated that DKK1 is capable to impair ligand-induced Wnt signaling. While gene expression analyses suggested an augmented and active canonical Wnt pathway, the respective signaling was inhibited due to the endogenous expression of the antagonist DKK1. Subsequent TMA stainings indicated Dkk1 as linked with HPV-positivity and metastatic disease progression in PeCa suggesting potential as a prognostic marker.

Among all malignancies, lung cancer is the leading cause of cancer-related deaths in China. Bone metastasis is one of the most common complications and one of the most important factors affecting the prognosis of lung cancer patients, which resulting in very poor therapeutic effects. Previously, we have demonstrated that the expression levels of Dickkopf1 (DKK1), a protein involved in cell regulation and proliferation, was dramatically higher in cells that have a tendency to metastasize and invade the bone tissue (SBC-5 cells) compared with cells that do not (SBC-3 cells). Downregulation of DKK1 in SBC-5 cells inhibited cell malignancy in vitro, and the formation of bone metastasis in vivo. However, whether upregulating DKK1 would be sufficient to induce aggressive tumor behavior (proliferation, migration, invasion and metastasis) in SBC-3 cells remained to be investigated. The present study aimed to examine the role of DKK1 in SBC-3 cells, as well as to investigate the SBC-3 ability to metastasize and invade the bone tissue. The results demonstrated that upregulation of DKK1 in SBC-3 cells enhanced cell proliferation, colony formation, cell migration and invasion in vitro, as well as bone metastasis in vivo. These results indicate that DKK1 may be an important regulator in the development of small cell lung cancer (SCLC), and targeting DKK1 may be an effective method for preventing and/or treating skeletal metastases in SCLC cases.

A1CF (apobec-1 complementation factor) acts as a component of the apolipoprotein-B messenger RNA editing complex. Previous researches mainly focused on its post-transcriptional cytidine to uridine RNA editing. However, few study reported its role in progression of breast carcinoma cells. Wound healing assay and flow cytometry were applied to detect the migration and apoptosis; western blot, real-time polymerase chain reaction, and dual-luciferase assays were applied to investigate the potential regulation mechanism of A1CF-mediated cell migration and apoptosis. Knockdown of A1CF decreased cell migration and enhanced cell apoptosis in MCF7 cells in vitro. Western blot analysis showed that knockdown of A1CF decreased Dickkopf1 but increased c-Myc and β-catenin expression, and overexpression of A1CF can get opposite results. Knockdown of Dickkopf1 in A1CF-overexpressed cells decreased cell migration and enhanced cell apoptosis compared with A1CF-overexpressed cells. Luciferase-fused 3\' untranslated region of human Dickkopf1 activity was highly upregulated in A1CF-overexpressed MCF7 cells, but this upregulation can be inhibited by mutating conserved binding motifs of Dickkopf1 3\' untranslated region. A1CF played a crucial role in cell migration and survival through affecting 3\' untranslated region of Dickkopf1 to upregulate its expression in MCF7 cells.

EZH2, a histone H3 lysine-27-specific methyltransferase, is involved in diverse physiological and pathological processes including cell proliferation and differentiation. However, the role of EZH2 in liver fibrosis is largely unknown. In this study, it was identified that EZH2 promoted Wnt pathway-stimulated fibroblasts in vitro and in vivo by repressing Dkk-1, which is a Wnt pathway antagonist. The expression of EZH2 was increased in CCl4 -induced rat liver and primary HSCs as well as TGF-β1-treated HSC-T6, whereas the expression of Dkk1 was reduced. Silencing of EZH2 prevented TGF-β1-induced proliferation of HSC-T6 cells and the expression of α-SMA. In addition, knockdown of Dkk1 promoted TGF-β1-induced activation of HSCs. Moreover, silencing of EZH2 could restore the repression of Dkk-1 through trimethylation of H3K27me3 in TGF-β1-treated HSC-T6 cells. Interestingly, inhibition of EZH2 had almost no effect on the activation of HSC when Dkk1 was silenced. Collectively, EZH2-mediated repression of Dkk1 promotes the activation of Wnt/β-catenin pathway, which is an essential event for HSC activation.

Melanocyte stem cells (McSCs) undergo cyclical activation and quiescence together with hair follicle stem cells (HFSCs). This process is strictly controlled by the autonomous and extrinsic signaling environment. However, the modulation of factors important for the activation of McSCs for hair pigmentation remains unclear. 12-O-tetradecanoylphorbol-13-acetate (TPA) mimics vital signaling pathways involved in melanocyte growth and melanogenesis in vitro. To investigate whether TPA regulates quiescent McSCs for hair pigmentation, we topically smeared TPA on 7-week-old mouse dorsal skin and found that TPA stimulated hair growth and hair matrix pigmentation. These changes were associated with a significant increase in the number of hair bulb melanocytes. Moreover, in the TPA-treated group, hair bulge McSCs and hair bulb melanoblasts actively proliferated. At the molecular level, nuclear β-catenin, a key factor of Wnt/β-catenin signaling, was highly synthesized in melanocytes and keratinocytes in TPA-induced hair bulbs. Inhibition of Wnt/β-catenin signaling by injecting Dickkopf1 plasmids into TPA-treated skin decreased hair matrix pigmentation and inhibited the proliferation and differentiation of McSCs. Our findings suggest that the topical application of TPA stimulates the proliferation and differentiation of McSCs and their progeny for hair matrix pigmentation by activating Wnt/β-catenin signaling. This might provide a useful experimental model for the study of signals controlling the activation of McSCs.

Dickkopf1 (DKK1), a canonical Wnt/β-catenin pathway antagonist, is closely associated with cardiovascular disease and adipogenesis. We performed an in vitro study to determine whether oxidized low-density lipoprotein (ox-LDL) increased the expression of DKK1 in macrophages and whether β-catenin and liver X receptor α (LXRα) were involved in this regulation. Induction of DKK1 expression by ox-LDL decreased the level of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) via a Wnt/β-catenin pathway and increased ATP-binding cassette transporter A/G1 (ABCA/G1) levels via a signal transducer and activator of transcription 3 (STAT3) pathway. Lower LOX-1 and higher ABCA/G1 levels inhibited cholesterol loading in macrophages. In conclusion, ox-LDL may induce DKK1 expression in macrophages to inhibit the accumulation of lipids through a mechanism that involves downregulation of LOX-1-mediated lipid uptake and upregulation of ABCA/G1-dependent cholesterol efflux.