Developmental Endothelial Locus-1 Research Articles

Overexpression of DEL-1 Downregulates SH3BP2 Expression and Inhibits Porphyromonas gingivalis-induced Gingival Inflammation In Vivo and In Vitro.

The role of developmental endothelial locus-1 (DEL-1) in Porphyromonas gingivalis (P. gingivalis)-induced periodontitis and the related molecular mechanisms are unclear. This study aimed to investigate the effect of DEL-1 on SH3 Domain Binding Protein 2 (SH3BP2) expression, and to explore the regulatory role of DEL-1 in periodontal inflammation. We constructed a P. gingivalis-induced rat experimental periodontitis model, and cultured P. gingivalis-stimulated THP-1 cells in vitro. THP-1 cell viability and cell cycle were examined by CCK-8 and flow cytometry. Rat gingival tissues were collected for hematoxylin-eosin staining. The expression of SH3BP2 and nicotinamide phosphoribosyltransferase (NAMPT) was examined using Western blot. We found that the proliferation of P. gingivalis-infected THP-1 cells was increased by DEL-1. DEL-1 inhibited the expression of NAMPT and SH3BP2 in gingiva tissues of rats with periodontitis as well as in P. gingivalis-infected THP-1 cells. Overexpression of DEL-1 downregulated SH3BP2 expression and reduced gingival inflammation induced by P. gingivalis. DEL-1 presents some regulatory effects on gingival inflammation in a P. gingivalis-induced rat experimental periodontitis model, suggesting the therapeutic potential of DEL-1 in regulating periodontal inflammation.

Developmental endothelial locus-1 protects from hypertension-induced cardiovascular remodeling via immunomodulation.

The causative role of inflammation in hypertension-related cardiovascular diseases is evident and calls for development of specific immunomodulatory therapies. We tested the therapeutic efficacy and mechanisms of action of developmental endothelial locus-1 (DEL-1), an endogenous antiinflammatory factor, in angiotensin II– (ANGII–) and deoxycorticosterone acetate–salt–induced (DOCA-salt–induced) cardiovascular organ damage and hypertension. By using mice with endothelial overexpression of DEL-1 (EC-Del1 mice) and performing preventive and interventional studies by injecting recombinant DEL-1 in mice, we showed that DEL-1 improved endothelial function and abrogated aortic adventitial fibrosis, medial thickening, and loss of elastin. DEL-1 also protected the mice from cardiac concentric hypertrophy and interstitial and perivascular coronary fibrosis and improved left ventricular function and myocardial coronary perfusion. DEL-1 prevented aortic stiffness and abolished the progression of hypertension. Mechanistically, DEL-1 acted by inhibiting αvβ3 integrin–dependent activation of pro-MMP2 in mice and in human isolated aorta. Moreover, DEL-1 stabilized αvβ3 integrin–dependent CD25+FoxP3+ Treg numbers and IL-10 levels, which were associated with decreased recruitment of inflammatory cells and reduced production of proinflammatory cytokines in cardiovascular organs. The demonstrated effects and immune-modulating mechanisms of DEL-1 in abrogation of cardiovascular remodeling and progression of hypertension identify DEL-1 as a potential therapeutic factor.

Modulating the immune response to reduce hypertension-associated cardiovascular damage

Cardiovascular diseases are a leading cause of mortality and disability worldwide. Hypertension, a major risk factor for these diseases, remains difficult to treat despite numerous drugs being available. In this issue of the JCI, Failer et al. show that the endogenous antiinflammatory agent developmental endothelial locus-1 (DEL-1) decreased blood pressure and cardiac and aortic hypertrophy in mouse models of hypertension through reduction in αvβ3 integrin–dependent metalloproteinase activity and immune cell recruitment, leading to reduced production of proinflammatory cytokines in cardiovascular tissues. This study offers an alternative in the treatment of hypertension-mediated organ damage through the immunomodulatory effect of DEL-1.

Sustained developmental endothelial locus-1 overexpression promotes spinal cord injury recovery in mice through the SIRT1/SERCA2 signaling pathway

Although the anti-inflammatory properties of developmental endothelial locus-1 (DEL-1) are well known, few studies have examined the role of DEL-1 in spinal cord injury (SCI). Here, the protective effect of DEL-1 on SCI was investigated using hypoxia/recovery (H/R) injury of astrocytes and a mouse SCI model. The effects of DEL-1 overexpression/silencing on primary astrocytes were assessed by flow cytometry, immunofluorescence, and western blotting. Female Sprague-Dawley rats were intrathecally injected with recombinant adeno-associated virus (AAV) at T10, and DEL-1 was permanently expressed. Protein levels in the spinal cord, functional testing, and electrophysiology, pathology, and immunofluorescence were all measured after treatment. DEL-1 overexpression significantly increased the expression of SIRT1/SERCA2At the same time, inflammation, endoplasmic reticulum stress, and apoptosis were all significantly inhibited, the motor function of SCI rats was noticeably restored, and the myelin sheath of the injured site was more complete. Furthermore, after DEL-1 silencing SIRT1/SERCA2 expression decreased, while inflammation, endoplasmic reticulum stress, and apoptotic responses increased significantly. DEL-1 treatment, however, did not increase SERCA2 expression after SIRT1 silencing. These findings demonstrate that DEL-1 protects against SCI via SIRT1/SERCA2 signaling, promoting spinal neural recovery.

The Effects of Developmental Endothelial Locus-1 in Osteoclast Differentiation and Activation

The Effects of Developmental Endothelial Locus-1 in Osteoclast Differentiation and Activation

Developmental endothelial locus-1 as a potential biomarker for the incidence of acute exacerbation in patients with chronic obstructive pulmonary disease

BackgroundDespite the high disease burden of chronic obstructive pulmonary disease (COPD) and risk of acute COPD exacerbation, few COPD biomarkers are available. As developmental endothelial locus-1 (DEL-1) has been proposed to possess beneficial effects, including anti-inflammatory effects, we hypothesized that DEL-1 could be a blood biomarker for COPD.ObjectiveTo elucidate the role of plasma DEL-1 as a biomarker of COPD in terms of pathogenesis and for predicting acute exacerbation.MethodsCigarette smoke extract (CSE) or saline was intratracheally administered to wild-type (WT) and DEL-1 knockout (KO) C57BL/6 mice. Subsequently, lung sections were obtained to quantify the degree of emphysema using the mean linear intercept (MLI). Additionally, plasma DEL-1 levels were compared between COPD and non-COPD participants recruited in ongoing prospective cohorts. Using negative binomial regression analysis, the association between the plasma DEL-1 level and subsequent acute exacerbation risk was evaluated in patients with COPD.ResultsIn the in vivo study, DEL-1 KO induced emphysema (KO saline vs. WT saline; P = 0.003) and augmented CSE-induced emphysema (KO CSE vs. WT CSE; P < 0.001) in 29 mice. Among 537 participants, patients with COPD presented plasma log (DEL-1) levels lower than non-COPD participants (P = 0.04), especially non-COPD never smokers (P = 0.019). During 1.2 ± 0.3 years, patients with COPD in the lowest quartile of Log(DEL-1) demonstrated an increased risk of subsequent acute exacerbation, compared with those in the highest quartile of Log(DEL-1) (adjusted incidence rate ratio, 3.64; 95% confidence interval, 1.03–12.9).ConclusionLow DEL-1 levels are associated with COPD development and increased risk of subsequent COPD acute exacerbation. DEL-1 can be a useful biomarker in patients with COPD.

Potential therapeutic efficacy via avB3-integrin dependent interaction of developmental endothelial locus-1 (Del-1) after established angiotensin-II dependent hypertension

Abstract Introduction Cardiovascular diseases (CVDs) contribute to about 31% of global death. Hypertension is a major risk factor and also increases the risk of CVDs. An important regulator of systemic blood pressure in the body, the Renin Angiotensin Aldosterone system becomes overactivated during hypertension releasing a critical product, angiotensin-II (ANG-II), a known vasoconstrictor, activating the immune system leading to inflammation and as such mediating the effects of hypertension and subsequent end-organ damage due to the critical role of the innate and adaptive cells in producing pro-inflammatory cytokines such interleukin-17. Del-1, an extracellular matrix protein expressed mostly by endothelial cells is a known potent inhibitor of leukocyte recruitment. Aim We tested the hypothesis that, Del-1 via αvβ3-integrin dependent interaction protects against ANG-II induced cardiovascular remodeling after established hypertension. Methods Wild type (WT) mice were infused with 2 mg/kg/day of ANG-II for 14 days. Soluble Del-1 (Del-1-Fc) and a point mutant unable to bind to αvβ3-integrin (Del-1-RGE-Fc) was injected (50 μg/per injection) daily after 6 days of ANG-II infusion. SBP was measured using tail-cuff. Endothelial function was assessed using Mulvany myograph and quantification of inflammatory cells and IL-17 by flow cytometry. Histological staining for fibrosis, myocardial/medial hypertrophy and elastin degradation was used to evaluate both aortic and cardiac remodeling. Results After 6 days, mice infused with ANG-II showed significantly higher SBP of 140 mmHg as compared to control mice (110 mmHg). However, further progression of SBP after 6 days was blunted in infused mice treated with soluble Del-1 (ANGII+Del-1-Fc) as compared to similar increase in SBP in both infused mice treated with the point mutant (ANGII+Del-1-RGE-Fc) and non-treated infused mice (ANGII+Fc) leading to a difference of ∼20 mmHg. This effect was due to, the well protected endothelium dependent relaxation and reduced wall tension of the aorta in ANGII+Del-1-Fc mice. Further infiltration of CD45+ leukocytes, CD45+/IL-17A+ and TCRβ+T cells was significantly reduced in the aorta and heart of ANGII+Del-1-Fc mice as compared to both ANGII+Del-1-RGE-Fc and ANGII+Fc mice. However, the aorta and heart of ANGII+Del-1-Fc mice showed increased levels of anti-inflammatory regulatory T-cells (CD25+FOXP3+Treg). Also, aortic medial thickness, adventitial collagen and elastin degradation was decreased significantly in ANGII+Del-1-Fc mice. Additionally, in comparison to both ANGII+Del-1-RGE-Fc and ANGII+Fc mice, the hearts of ANGII+Del-1-Fc mice had significantly less interstitial and pericoronary collagen, smaller cardiomyocyte area and subsequently higher lumen-to-wall ratio. Conclusion Our study reveals the cardiovascular protective effects of Del-1 mediated via its association with αvβ3-integrin after established hypertension which could serve as potential therapeutic target. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): German Research Foundation (DFG)National Institutes of Health (NIH)

Stromal cell-derived DEL-1 inhibits Tfh cell activation and inflammatory arthritis.

The secreted protein developmental endothelial locus 1 (DEL-1) regulates inflammatory cell recruitment and protects against inflammatory pathologies in animal models. Here, we investigated DEL-1 in inflammatory arthritis using collagen-induced arthritis (CIA) and collagen Ab-induced arthritis (CAIA) models. In both models, mice with endothelium-specific overexpression of DEL-1 were protected from arthritis relative to WT controls, whereas arthritis was exacerbated in DEL-1-deficient mice. Compared with WT controls, mice with collagen VI promoter-driven overexpression of DEL-1 in mesenchymal cells were protected against CIA but not CAIA, suggesting a role for DEL-1 in the induction of the arthritogenic Ab response. Indeed, DEL-1 was expressed in perivascular stromal cells of the lymph nodes and inhibited Tfh and germinal center B cell responses. Mechanistically, DEL-1 inhibited DC-dependent induction of Tfh cells by targeting the LFA-1 integrin on T cells. Overall, DEL-1 restrained arthritis through a dual mechanism, one acting locally in the joints and associated with the anti-recruitment function of endothelial cell-derived DEL-1; the other mechanism acting systemically in the lymph nodes and associated with the ability of stromal cell-derived DEL-1 to restrain Tfh responses. DEL-1 may therefore be a promising therapeutic for the treatment of inflammatory arthritis.

Identification of a novel non-invasive biological marker to overcome the shortcomings of PSA in diagnosis and risk stratification for prostate cancer: Initial prospective study of developmental endothelial locus-1 protein

This prospective study sought to clarify the developmental endothelial locus-1 (Del-1) protein as values of diagnosis and risk stratification of prostate cancer (PCa). From February 2017 to December 2019, a total 458 patients who underwent transrectal ultrasound guided prostate biopsy or surgery of benign prostatic hyperplasia agreed to research of Del-1 protein. We prospectively compared and analyzed the Del-1 protein and prostate specific antigen (PSA) in relation to the patients' demographic and clinicopathological characteristics. Mean age was 68.86±8.55 years. Mean PSA and Del-1 protein was 21.72±89.37, 0.099±0.145, respectively. Two hundred seventy-six (60.3%) patients were diagnosed as PCa. Among them, 181 patients underwent radical prostatectomy (RP). There were significant differences in Del-1 protein between benign and PCa group (0.066±0.131 vs 0.121±0.149, respectively, p<0.001). When we set the cut-off value of del-1 protein as 0.120, in patients with 3≤PSA≤8, positive predictive value and specificity of Del-1 protein (≥0.120) for predicting PCa were 88.9% (56/63) and 93.5% (101/108), respectively. Among 181 patients who underwent RP, there were significant differences in Del-1 protein according to stage (pT2 vs pT3a vs ≥pT3b) (0.113±0.078, 0.171±0.121, 0.227±0.161, respectively, p<0.001) and to Gleason score (6 (3+3) or 7 (3+4) vs 7 (4+3) or 8 (4+4) vs 9 or 10) (0.134±0.103, 0.150±0.109, 0.212±0.178, respectively, P = 0.044). Multivariate analysis showed that PSA, Del-1 protein and high Gleason score (≥9) were the independent prognostic factors for predicting higher pT stage (≥3b). Furthermore, age, PSA and Del-1 protein were independent prognostic factors for predicting significant PCa. Patients with PCa showed higher expression of Del-1 protein than benign patients. Del-1 protein increased with the stage and Gleason score of PCa. Collaboration with PSA, Del-1 protein can be a non-invasive useful marker for diagnosis and risk stratification of PCa.

Exosomal Del-1 as a Potent Diagnostic Marker for Breast Cancer: Prospective Cohort Study

BackgroundThe differential diagnostic role of plasma developmental endothelial locus-1 (Del-1) was proposed in our previous study. Therefore the current study aimed to confirm the diagnostic role and explore the prognostic role of exosomal Del-1 in a prospective cohort of female patients with breast cancer. Patients and MethodsTo determine the optimal sampling time for the postoperative Del-1 measurements, blood was serially collected on days 1, 3, 5, and 7 after surgery in 22 patients (cohort 1). Thereafter, 111 female patients with breast cancer were prospectively enrolled (cohort 2) to compare exosomal Del-1 levels before and after surgery. ResultsAmong the subsequent prospective cohort, 107 patients (96.4%) showed a high exosomal Del-1 level (optical density [OD] value > 0.5) at the time of diagnosis. Of these patients, 101 (94.6%) in this high-level group showed normalized Del-1 levels postoperatively, representing a significant difference (mean OD value, 1.232 vs. 0.196; P < .00001). High postoperative Del-1 level was significantly associated with a worse disease-free survival adjusted to the clinicopathological characteristics (hazard ratio, 24.0; P = .0011). ConclusionThis study confirmed the normalization of exosomal Del-1 after surgery, indicating exosomal Del-1 as a potent diagnostic biomarker for breast cancer. In addition, because a high Del-1 level after surgery was associated with early relapse, this suggests exosomal Del-1 as a potential prognostic marker by identifying the existence of residual cancer.

An Epidermal Growth Factor Motif of Developmental Endothelial Locus 1 Protein Inhibits Efficient Angiogenesis in Explanted Squamous Cell Carcinoma In Vivo.

Cancer gene therapy using a nonviral vector is expected to be repeatable, safe, and inexpensive, and to have longterm effectiveness. Gene therapy using the E3 and C1 (E3C1) domain of developmental endothelial locus-1 (Del1) has been shown to improve prognosis in a mouse transplanted tumor model. In this study, we examined how this treatment affects angiogenesis in mouse transplanted tumors. Mouse transplanted tumors (SCCKN human squamous carcinoma cell line) were injected locally with a nonviral plasmid vector encoding E3C1 weekly. Histochemical analysis of the transplanted tumors was then performed to assess the effects of E3C1 on prognosis. All mice in the control group had died or reached an endpoint within 39 days. In contrast, one of ten mice in the E3C1 group had died by day 39, and eight of ten had died or reached an endpoint by day 120 (p < 0.01). Enhanced apoptosis in tumor stroma was seen on histochemical analyses, as was inhibited tumor angiogenesis in E3C1-treated mice. In addition, western blot analysis showed decreases in active Notch and HEY1 proteins. These findings indicate that cancer gene therapy using a nonviral vector encoding E3C1 significantly improved life-span by inhibiting tumor angiogenesis.

Combination Cancer Therapy of a Del1 Fragment and Cisplatin Enhanced Therapeutic Efficiency In Vivo.

Combination cancer therapy is currently under investigation. This study examined the effect of cancer combination therapy using the E3 and C1 (E3C1) domains of developmental endothelial locus-1 (Del1) and cisplatin (CDDP) in murine transplanted tumors. Mice with transplanted tumors (A431, SCCKN or SCC-4 cells) were injected intraperitoneally with CDDP and injected locally with nonviral plasmid vectors encoding E3C1. Histochemical analysis of the transplanted tumors was then performed to assess the effects on prognosis. The CDDP+E3C1 injected group had reduced tumor growth and longer survival compared to the CDDP injected group. In addition, cell death was observed in the tumor of the CDDP+E3C1 group.. Furthermore, angiogenesis and increased blood vessels were observed together with stromal development. The CDDP+E3C1 treatment resulted in improved survival and poor tumor stromal development in mice with transplanted tumors.

Endogenous DEL-1 restrains melanoma lung metastasis by limiting myeloid cell-associated lung inflammation.

Distant metastasis represents the primary cause of cancer-associated death. Pulmonary metastasis is most frequently seen in many cancers, largely driven by lung inflammation. Components from primary tumor or recruited leukocytes are known to facilitate metastasis formation. However, contribution of target site-specific host factor to metastasis is poorly understood. Here, we show that developmental endothelial locus-1 (DEL-1), an anti-inflammatory factor abundant in the lung and down-regulated by inflammatory insults, protects from melanoma lung metastasis independently of primary tumor development and systemic immunosurveillance. DEL-1 deficiency is associated with gene profiles that favor metastatic progression with inflammation and defective immunosurveillance. Mechanistically, DEL-1 deficiency primarily influences Ly6G+ neutrophil accumulation in lung metastatic niche, leading to IL-17A up-regulation from γδ T cells and reduced antimetastatic NK cells. In support, neutrophil depletion or recombinant DEL-1 treatment profoundly reverses these effects. Thus, our results identify DEL-1 as a previously unrecognized link between tumor-induced inflammation and pulmonary metastasis.

The DEL-1/β3 integrin axis promotes regulatory T cell responses during inflammation resolution.

FOXP3+CD4+ regulatory T cells (Tregs) are critical for immune homeostasis and respond to local tissue cues, which control their stability and function. We explored here whether developmental endothelial locus-1 (DEL-1), which, like Tregs, increases during resolution of inflammation, promotes Treg responses. DEL-1 enhanced Treg numbers and function at barrier sites (oral and lung mucosa). The underlying mechanism was dissected using mice lacking DEL-1 or expressing a point mutant thereof, or mice with T cell-specific deletion of the transcription factor RUNX1, identified by RNA sequencing analysis of the DEL-1-induced Treg transcriptome. Specifically, through interaction with αvβ3 integrin, DEL-1 promoted induction of RUNX1-dependent FOXP3 expression and conferred stability of FOXP3 expression upon Treg restimulation in the absence of exogenous TGF-β1. Consistently, DEL-1 enhanced the demethylation of the Treg-specific demethylated region (TSDR) in the mouse Foxp3 gene and the suppressive function of sorted induced Tregs. Similarly, DEL-1 increased RUNX1 and FOXP3 expression in human conventional T cells, promoting their conversion into induced Tregs with increased TSDR demethylation, enhanced stability, and suppressive activity. We thus uncovered a DEL-1/αvβ3/RUNX1 axis that promotes Treg responses at barrier sites and offers therapeutic options for modulating inflammatory/autoimmune disorders.

Association of chronic periodontitis and type 2 diabetes mellitus with salivary Del-1 and IL-17 levels

PurposeChronic periodontitis (CP) and Type 2 diabetes mellitus (T2DM) are chronic diseases affecting the humans and have interrelationship in their pathogenesis. Monitoring the progress with biomarker in these disease is important from treatment outcome point of view. We investigated the association of salivary developmental endothelial locus-1 (Del-1) and interleukin-17 (IL-17) levels in CP and T2DM. MethodsSaliva was collected from 17 healthy and 68 patients (divided into 4 groups based on presence or absence of CP and T2DM). Periodontal parameters were recorded at the time of visit. Del-1 and IL-17 levels in unstimulated salivary samples were determined using enzyme-linked immunosorbent assay. ResultsStudy found the lower levels of salivary Del-1 and higher levels of IL-17 in CP (2.23 ± 2.10 ng/mL, 56.54 ± 19.79 ng/mL), CCDM ((1.97 ± 1.36 ng/mL, 74.74 ± 17.79 ng/mL) and CUDM (1.02 ± 0.52 ng/mL, 63.84 ± 24.72 ng/mL) as compared to healthy individuals (6.54 ± 2.07; 24.47 ± 8.23 ng/mL) (p < 0.001). Del-1 and IL-17 levels were correlating with inflammatory state in CP and presence of T2DM aggravate the severity of disease in CP. An inverse correlation between salivary Del-1 & IL-17 levels was also seen. Furthermore, we also observed that the combination of T2DM and CP (CCDM and CUDM) increases the salivary IL-17 levels and decreases Del-1 levels. ConclusionsThere is an upregulation of salivary IL-17 and downregulation of salivary Del-1 with increase in severity of periodontal disease as well as T2DM. Furthermore, the presence of T2DM in chronic periodontitis patients can aggravate the inflammation related periodontal destruction.

Erythromycin inhibits neutrophilic inflammation and mucosal disease by upregulating DEL-1.

Macrolide antibiotics exert antiinflammatory effects; however, little is known regarding their immunomodulatory mechanisms. In this study, using 2 distinct mouse models of mucosal inflammatory disease (LPS-induced acute lung injury and ligature-induced periodontitis), we demonstrated that the antiinflammatory action of erythromycin (ERM) is mediated through upregulation of the secreted homeostatic protein developmental endothelial locus-1 (DEL-1). Consistent with the anti-neutrophil recruitment action of endothelial cell-derived DEL-1, ERM inhibited neutrophil infiltration in the lungs and the periodontium in a DEL-1-dependent manner. Whereas ERM (but not other antibiotics, such as josamycin and penicillin) protected against lethal pulmonary inflammation and inflammatory periodontal bone loss, these protective effects of ERM were abolished in Del1-deficient mice. By interacting with the growth hormone secretagogue receptor and activating JAK2 in human lung microvascular endothelial cells, ERM induced DEL-1 transcription that was mediated by MAPK p38 and was CCAAT/enhancer binding protein-β dependent. Moreover, ERM reversed IL-17-induced inhibition of DEL-1 transcription, in a manner that was dependent not only on JAK2 but also on PI3K/AKT signaling. Because DEL-1 levels are severely reduced in inflammatory conditions and with aging, the ability of ERM to upregulate DEL-1 may lead to a novel approach for the treatment of inflammatory and aging-related diseases.

The secreted protein DEL-1 activates a β3 integrin–FAK–ERK1/2–RUNX2 pathway and promotes osteogenic differentiation and bone regeneration

The integrin-binding secreted protein developmental endothelial locus-1 (DEL-1) is involved in the regulation of both the initiation and resolution of inflammation in different diseases, including periodontitis, an oral disorder characterized by inflammatory bone loss. Here, using a mouse model of bone regeneration and in vitro cell-based mechanistic studies, we investigated whether and how DEL-1 can promote alveolar bone regeneration during resolution of experimental periodontitis. Compared with WT mice, mice lacking DEL-1 or expressing a DEL-1 variant with an Asp-to-Glu substitution in the RGD motif ("RGE point mutant"), which does not interact with RGD-dependent integrins, exhibited defective bone regeneration. Local administration of DEL-1 or of its N-terminal segment containing the integrin-binding RGD motif, but not of the RGE point mutant, reversed the defective bone regeneration in the DEL-1-deficient mice. Moreover, DEL-1 (but not the RGE point mutant) promoted osteogenic differentiation of MC3T3-E1 osteoprogenitor cells or of primary calvarial osteoblastic cells in a β3 integrin-dependent manner. The ability of DEL-1 to promote in vitro osteogenesis, indicated by induction of osteogenic genes such as the master transcription factor Runt-related transcription factor-2 (Runx2) and by mineralized nodule formation, depended on its capacity to induce the phosphorylation of focal adhesion kinase (FAK) and of extracellular signal-regulated kinase 1/2 (ERK1/2). We conclude that DEL-1 can activate a β3 integrin-FAK-ERK1/2-RUNX2 pathway in osteoprogenitors and promote new bone formation in mice. These findings suggest that DEL-1 may be therapeutically exploited to restore bone lost due to periodontitis and perhaps other osteolytic conditions.

Salivary Del-1, IL-17, and LFA-1 levels in periodontal health and disease.

Developmental endothelial locus-1 (Del-1), lymphocyte function-associated antigen-1 (LFA-1), and interleukin 17 (IL-17) play critical roles in transendothelial migration of neutrophils in periodontal diseases. The aim of this study was to evaluate salivary Del-1, IL-17, and LFA-1 protein levels in patients with gingivitis (G), chronic periodontitis (CP), and generalized aggressive periodontitis (GAP). A total of 180 systemically healthy, non-smoking patients (45 periodontally healthy (H) and 45 G, 50 CP, and 40 GAP) individuals (between March 2014 and February 2016) were included in this study according to Armitage's (1999) classification. Clinical periodontal parameters, including clinical attachment level, probing depth, plaque index, and gingival index, were recorded. Del-1, IL-17, and LFA-1 protein expression levels were measured in unstimulated saliva samples collected from patients by using enzyme-linked immunosorbent assays. Kruskal-Wallis and Mann-Whitney U tests were used for multiple comparisons and post hoc statistical analyses, respectively. ROC curve analysis was used to evaluate the sensitivity and specificity of Del-1, IL-17, and LFA-1 in distinguishing periodontal disease from health and gingivitis. It was found a high level of IL-17 and a low level of Del-1 in the CP and GAP, as compared to the G and H groups (P<.001). Nevertheless, we found LFA-1 levels were higher in the GAP than in the CP or G groups (P=.00). Consistently, LFA-1 levels were lower in the H and G groups than in the CP and GAP groups (P=.00). The combination of three biomarkers was found as the best predictor yielded exhibited the highest AUC [0.893, 0.845-0.94 (%95 CI) P<.001] in discriminating periodontal disease from health and gingivitis. Salivary Del-1, LFA-1, and IL-17 levels might be useful markers for determining the clinical health and disease status of patients with periodontitis. However, further studies that evaluate the level of salivary Del-1, LFA-1, and IL-17 before and after periodontal therapy are required to understand the exact roles of these cytokines during the periodontal healing period.

DHEA Inhibits Leukocyte Recruitment through Regulation of the Integrin Antagonist DEL-1.

Leukocytes are rapidly recruited to sites of inflammation via interactions with the vascular endothelium. The steroid hormone dehydroepiandrosterone (DHEA) exerts anti-inflammatory properties; however, the underlying mechanisms are poorly understood. In this study, we show that an anti-inflammatory mechanism of DHEA involves the regulation of developmental endothelial locus 1 (DEL-1) expression. DEL-1 is a secreted homeostatic factor that inhibits β2-integrin-dependent leukocyte adhesion, and the subsequent leukocyte recruitment and its expression is downregulated upon inflammation. Similarly, DHEA inhibited leukocyte adhesion to the endothelium in venules of the inflamed mouse cremaster muscle. Importantly, in a model of lung inflammation, DHEA limited neutrophil recruitment in a DEL-1-dependent manner. Mechanistically, DHEA counteracted the inhibitory effect of inflammation on DEL-1 expression. Indeed, whereas TNF reduced DEL-1 expression and secretion in endothelial cells by diminishing C/EBPβ binding to the DEL-1 gene promoter, DHEA counteracted the inhibitory effect of TNF via activation of tropomyosin receptor kinase A (TRKA) and downstream PI3K/AKT signaling that restored C/EBPβ binding to the DEL-1 promoter. In conclusion, DHEA restrains neutrophil recruitment by reversing inflammation-induced downregulation of DEL-1 expression. Therefore, the anti-inflammatory DHEA/DEL-1 axis could be harnessed therapeutically in the context of inflammatory diseases.

Del-1, an Endogenous Inhibitor of TGF-β Activation, Attenuates Fibrosis.

Uncontrolled activation of transforming growth factor (TGF)-β results in a wide range of pathologic conditions. Therapeutic interventions to regulate TGF-β signaling during fibrosis have been developed but the effectiveness is still limited. Here, we show that developmental endothelial locus-1 (Del-1) ameliorates fibrosis in mice by inhibiting αv integrin-mediated activation of TGF-β. Del-1 bound to αvβ6 integrin, an important activator of TGF-β, and inhibited the binding of αvβ6 integrin to the latency-associated peptide (LAP), thereby suppressing αv integrin-mediated activation of TGF-β. Lack of Del-1 increased colocalization of αv integrin and LAP in the lungs, which was reversed by Del-1 supplementation. The crucial role of Del-1 in regulating TGF-β activity was recapitulated in a mouse model of fibrosis using an adenovirus expressing inactive TGF-β1. Del-1 supplementation improved the pathological characteristics of the mice and reduced mortality. Thus, we propose that Del-1 is a negative regulator of TGF-β activation and a potential anti-fibrotic factor.