Daphnetin Alleviates Bleomycin-Induced Pulmonary Fibrosis through Inhibition of Epithelial-to-Mesenchymal Transition and IL-17A

Idiopathic pulmonary fibrosis (IPF) is a chronic and refractory interstitial lung disease. Although there is no cure for IPF, the development of drugs with improved efficacy in the treatment of IPF is required. Daphnetin, a natural coumarin derivative, has immunosuppressive, anti-inflammatory, and antioxidant activities. However, its antifibrotic effects have not yet been elucidated. In this study, we investigated the antifibrotic effects of daphnetin on pulmonary fibrosis and the associated molecular mechanism. We examined the effects of daphnetin on splenocytes cultured in Th17 conditions, lung epithelial cells, and a mouse model of bleomycin (BLM)-induced pulmonary fibrosis. We identified that daphnetin inhibited IL-17A production in developing Th17 cells. We also found that daphnetin suppressed epithelial-to-mesenchymal transition (EMT) in TGF-β-treated BEAS2B cells through the regulation of AKT phosphorylation. In BLM-treated mice, the oral administration of daphnetin attenuated lung histopathology and improved lung mechanical functions. Our findings clearly demonstrated that daphnetin inhibited IL-17A and EMT both in vitro and in vivo, thereby protecting against BLM-induced pulmonary fibrosis. Taken together, these results suggest that daphnetin has potent therapeutic effects on lung fibrosis by modulating both Th17 differentiation and the TGF-β signaling pathway, and we thus expect daphnetin to be a drug candidate for the treatment of IPF.

Daphnetin alleviates neuropathic pain in chronic constrictive injury rats via regulating the NF-κB dependent CXCL1/CXCR2 signaling pathway

CONTEXT

Daphnetin is a natural product with anti-inflammatory, antioxidant, and neuroprotective properties. Reports have found that it has a strong analgesic effect; however, its analgesic mechanism is unknown.

OBJECTIVE

We explored the effect and mechanism of daphnetin on neuropathic pain (NP).

MATERIALS AND METHODS

The rat model of NP was established by ligation of the sciatic nerve. Male Sprague-Dawley rats were divided into six groups: Control, Model, Sham, morphine (0.375 mg/kg), and daphnetin (0.0625 and 0.025 mg/kg). Rats were intrathecally injected with drugs or normal saline once daily for three days. Hyperalgesia was evaluated by mechanical withdrawal threshold (MWT) and thermal withdrawal threshold (TWT). Protein levels were detected using ELISA, immunofluorescence, and western blotting.

RESULTS

Compared to the Model group, daphnetin improved TWT (46.70 °C vs. 42.20 °C) and MWT (45.60 g vs. 23.60 g), reduced the expression of interleukin-1β (0.99 ng/g vs. 1.42 ng/g), interleukin-6 (0.90 ng/g vs. 1.52 ng/g), and tumor necrosis factor-α (0.93 ng/g vs. 1.52 ng/g) in the sciatic nerve. Daphnetin decreased the expression of toll-like receptor 4 (TLR4) (0.47-fold), phosphorylated inhibitor of NF-κB (p-IKBα) (0.29-fold), nuclear factor kappaB (NF-κB) (0.48-fold), glial fibrillary acidic protein (GFAP) (0.42-fold), CXC chemokine ligand type 1 (CXCL1) (0.84-fold), CXC chemokine receptor type 2 (CXCR2) (0.78-fold) in the spinal cord.

DISCUSSION AND CONCLUSIONS

Daphnetin alleviates NP by inhibiting inflammation and astrocyte activation in the spinal cord, providing theoretical support for the extensive clinical treatment of NP.

Daphnetin attenuates intestinal inflammation, oxidative stress, and apoptosis in ulcerative colitis via inhibiting REG3A-dependent JAK2/STAT3 signaling pathway

Daphnetin is a natural coumarin compound with anti-inflammatory, anti-oxidant, and anti-apoptotic effects, which has been previously demonstrated to ameliorate DSS-induced ulcerative colitis (UC). However, the molecular mechanism involved in the daphnetin-mediated pathological process of UC remains unclarified. The current study used DSS-induced mice and LPS-challenged Caco-2 cells as UC models. Bodyweight, disease activity index (DAI) score, and colon length were used to evaluate the severity of colitis. The histological changes in colon tissues were observed using H&E and PAS staining. Protein levels were detected by western blot. The malondialdehyde (MDA) and superoxide dismutase (SOD) activities were used to assess oxidative stress. Inflammatory responses were evaluated by detecting the levels of inflammatory cytokines (IFN-r, IL-1β, IL-6, and TNF-α) using flow cytometry. CCK-8 and TUNEL assay were employed to determine cell growth and cell death, respectively. The results showed that daphnetin could ameliorate the severity of colitis and attenuate the damage to intestinal structure in DSS-induced mice. Compared with the DSS group, the expression of ZO-1, occludin, and anti-apoptotic protein (BCL-2) was increased while the level of pro-apoptotic proteins (Bax and cleaved caspase 3) was decreased in DSS + daphnetin group. The activity of MDA and SOD, as well as the levels of inflammatory cytokines were substantially suppressed by daphnetin. In consistency, in vitro assays indicated that daphnetin protected Caco-2 cells from LPS-stimulated viability impairment, apoptosis, oxidative stress, and inflammation. Furthermore, daphnetin suppressed the activity of JAK2/STAT signaling in LPS-induced Caco-2 cells in a REG3A-dependent manner. REG3A overexpression abated the ameliorative effects of daphnetin while JAK2/STAT signaling inhibition functioned synergically with daphnetin in LPS-stimulated Caco-2 cells. Collectively, this study deepened the understanding of the therapeutic effects of daphnetin on UC and uncovered for the first time that daphnetin functioned through REG3A-activated JAK2/STAT3 signaling in UC, which may provide novel insights for the treatment of UC.

Daphnetin, a Coumarin with Anticancer Potential against Human Melanoma: In Vitro Study of Its Effective Combination with Selected Cytostatic Drugs

(1) The treatment of metastatic or drug-resistant melanoma is still a significant therapeutic problem. The aim of this study was to evaluate the anticancer potential of daphnetin (7,8-dihydroxycoumarin) and its combinations with five different cytostatic drugs (mitoxantrone, docetaxel, vemurafenib, epirubicin and cisplatin). (2) The viability, proliferation and cytotoxicity of daphnetin against four human malignant melanoma cell lines were evaluated. The interactions were assessed using isobolographic analysis for the combinations of daphnetin with each of the five cytostatic drugs. (3) Daphnetin showed anticancer activity against malignant melanoma, with IC₅₀ values ranging from 40.48 ± 10.90 µM to 183.97 ± 18.82 µM, depending on the cell line. The combination of daphnetin with either vemurafenib or epirubicin showed an antagonistic interaction. Moreover, additive interactions were observed for the combinations of daphnetin with cisplatin and docetaxel. The most desirable synergistic interactions for human melanoma metastatic cell lines were observed for the combination of daphnetin with mitoxantrone. (4) The obtained results suggest that daphnetin should not be combined with vemurafenib or epirubicin in the treatment of malignant melanoma due to the abolition of their anticancer effects. The combination of daphnetin with mitoxantrone is beneficial in the treatment of metastatic melanoma due to their synergistic interaction.

Antiplatelet Effect of Daphnetin Is Regulated by cPLA2-Mediated Thromboxane A2 Generation in Mice

Coumarin derivatives have been recognized for their antithrombotic, anti-inflammatory, and antioxidant properties, and daphnetin is one of the natural coumarin derivatives isolated from Daphne Koreana Nakai. Although the pharmacological value of daphnetin is well documented in diverse biological activities, its antithrombotic effect has not been studied to date. Here, we characterized the role and underlying mechanism of daphnetin in the regulation of platelet activation using murine platelets. In order to check the effect of daphnetin on platelet function, we first measured the effect of daphnetin on platelet aggregation and secretion. Collagen-induced platelet aggregation and dense granule secretion were partially inhibited by daphnetin. Interestingly, 2-MeSADP-induced secondary waves of aggregation and secretion were completely inhibited by daphnetin. It is known that 2-MeSADP-induced secretion and the resultant secondary wave of aggregation are mediated by the positive feedback effect of thromboxane A₂ (TxA₂) generation, suggesting the important role of daphnetin on TxA₂ generation in platelets. Consistently, daphnetin did not affect the 2-MeSADP-induced platelet aggregation in aspirinated platelets where the contribution of TxA₂ generation was blocked. Additionally, platelet aggregation and secretion induced by a low concentration of thrombin, which is affected by the positive feedback effect of TxA₂ generation, were partially inhibited in the presence of daphnetin. Importantly, 2-MeSADP- and thrombin-induced TxA₂ generation was significantly inhibited in the presence of daphnetin, confirming the role of daphnetin on TxA₂ generation. Finally, daphnetin significantly inhibited 2-MeSADP-induced cytosolic phospholipase A₂ (cPLA₂) and ERK phosphorylation in non-aspirinated platelets. Only cPLA₂ phosphorylation, not ERK phosphorylation, was significantly inhibited by daphnetin in aspirinated platelets. In conclusion, daphnetin plays a critical role in platelet function by inhibiting TxA₂ generation through the regulation of cPLA₂ phosphorylation.

Daphnetin Improves Neuropathic Pain by Inhibiting the Expression of Chemokines and Inflammatory Factors in the Spinal Cord and Interfering with Glial Cell Polarization

Neuropathic pain (NP) is a common pain disease that seriously affects the quality of life and physical and mental health of patients. Daphnetin is extracted from the Daphne giraldii Nitsche and has the structure of 7,8-dihydroxy coumarin. As a natural product, daphnetin displays a wide range of pharmacological activities, such as analgesia and anti-inflammatory activities, but whether it is able to improve NP through anti-inflammatory effects is unknown. Therefore, this paper intends to investigate the mechanism of daphnetin in improving NP rats affected by the intrathecal injection of tumor necrosis factor-α (TNF-α) from the perspective of anti-inflammation. Our results showed that daphnetin significantly improved hyperalgesia in NP rats. Daphnetin inhibited the activation and polarization of glial cells and neurons in the spinal cord of NP rats and reduced the expression of mRNA and protein of inflammatory factors and chemokine pairs in the spinal cord. Daphnetin inhibited the polarization of human microglia cell 3 (HMC3) cells and human glioma cells (U251) cells toward M1 microglia and A1 astrocytes, respectively, and induced the conversion of M1 microglia and A1 astrocytes to M2 microglia and A2 astrocytes, respectively. In conclusion, daphnetin ameliorates NP by inhibiting the expression of inflammatory factors and chemokines and the polarization of glial cells in the spinal cord of NP rats. This study provides a theoretical basis for the treatment of NP with daphnetin to expand the clinical application of daphnetin.

Nephro-protective effect of Daphnetin in hyperoxaluria-induced rat renal injury via alterations of the gut microbiota

It is well proved that hyperoxaluria induces the renal injury and finally causes the end stage kidney disease. Daphnetin (coumarin derivative) already confirmed renal protective effect in renal model, but hyperoxaluria protective effect still unexplore. The objective of this research was to scrutinize the renal protective effect of daphnetin against ethylene glycol (GC)-induced hyperoxaluria via altering the gut microbiota. GC (1% v/v) was used for the induction of hyperoxaluria in the rats and the rats were received the oral administration of daphnetin (5, 10 and 15 mg/kg). The body and renal weight were assessed. Urine, renal, inflammatory cytokines, antioxidant, inflammatory parameters, and gut microbiota were appraised. Daphnetin effectually improved the body weight and reduced the renal weight. Its also remarkably boosted the magnesium, calcium, citrate level and suppressed the level of uric acid and oxalate formation. Daphnetin significantly (p < .001) ameliorate the level of urinary kidney injury molecule 1 (KIM-1), blood urea nitrogen (BUN), urea, serum creatinine (Scr), neutrophil gelatinase-associated lipocalin (NGAL) and uric acid along with inflammatory cytokines and inflammatory mediators. Daphnetin considerably repressed the malonaldehyde (MDA) level, protein carbonyl and improved the level of glutathione reductase (GR), superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT). Daphnetin treatment considerably altered the microbial composition of different bacteria at phylum, genus and family level. Daphnetin significantly suppressed the Firmicutes relative abundance and boosted the Bacteroidetes relative abundance. Our result clearly indicated that daphnetin remarkably ameliorates the GC induced hyperoxaluria in rats via altering the oxidative stress, inflammatory reaction and gut microbiota. PRACTICAL APPLICATION: Nephrotoxicity is a serious health disease worldwide. We induce the renal toxicity in the experimental rats using the ethylene glycol and scrutinized the renal protective effect of daphnetin. Daphnetin considerably suppress the renal, urine parameters. For estimation the underlying mechanism, we estimated the gut microbiota in all group rats. Daphnetin remarkably altered the level of gut microbiota and suggesting the renal protective effect.

Daphnetin Alleviates Senile and Disuse Osteoporosis by Distinct Modulations of Bone Formation and Resorption

Senile and disuse osteoporosis have distinct bone turnover status and lack effective treatments. In this study, senescence-accelerated mouse prone 8 (SAMP8) and hindlimb unloading mouse models were used to explore the protective effects of daphnetin on these two types of osteoporosis, and primary osteoblasts and bone marrow monocyte-derived osteoclasts, as well as pre-osteoblast MC3T3-E1, and osteoclast precursor RAW264.7 cells were used to investigate the underlying mechanisms. The results showed that daphnetin administration effectively improved bone remodeling in both senile and disuse osteoporosis, but with different mechanisms. In senile osteoporosis with low bone turnover, daphnetin inhibited NOX2-mediated ROS production in osteoblasts, resulting in accelerated osteogenic differentiation and bone formation, while in disuse osteoporosis with high bone turnover, daphnetin restored SIRT3 expression, maintained mitochondrial homeostasis, and additionally upregulated SOD2 to eliminate ROS in osteoclasts, resulting in attenuation of osteoclast differentiation and bone resorption. These findings illuminated that daphnetin has promising potential for the prevention and treatment of senile and disuse osteoporosis. The different mechanisms may provide clues and basis for targeted prevention and treatment of osteoporosis according to distinct bone turnover status.

Daphnetin Mitigates Ovalbumin-Induced Allergic Rhinitis in Mice by Regulating Nrf2/HO-1 and TLR4/NF-kB Signaling

BACKGROUND

Allergic rhinitis (AR) is an inflammatory disorder of nasal mucosa resulting from allergen exposure. Daphnetin (DAP) is a coumarin derivative that has various bioactivities. Nevertheless, its specific function in AR is unclear.

OBJECTIVES

This study is aimed to explore the specific function of DAP in AR.

METHODS

An AR murine model was established by ovalbumin (OVA) induction. Murine sneezing and rubbing behaviors were observed. Hematoxylin-eosin was used for histopathological observation of nasal mucosa. ELISA was utilized for detection of cytokine production in murine serum. Oxidative stress-associated markers were assessed by commercial assay kits. Western blotting was utilized for evaluating protein levels of Toll-like receptor 4 (TLR4) and nuclear factor kappa B (NF-κB) in nasal mucosa.

RESULTS

DAP alleviated OVA-induced nasal symptoms, inflammatory response and oxidative stress in the AR murine model. DAP activated nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) signaling and inactivated TLR4/NF-κB signaling in murine nasal mucosa.

CONCLUSION

DAP mitigates OVA-induced AR in mice by activating Nrf2/HO-1 signaling and inactivating TLR4/NF-κB signaling.

Daphnetin inhibits α-MSH-induced melanogenesis via PKA and ERK signaling pathways in B16F10 melanoma cells

Daphnetin is a dehydroxylated derivative of coumarin isolated from Daphne species. However, the effect of daphnetin on melanogenesis has not been elucidated. This study aims to investigate the inhibitory effect of daphnetin on melanogenesis in α-melanocyte stimulating hormone (α-MSH)-treated B16F10 cells and its potential mechanism. Melanin content analysis and cellular tyrosinase activity assay showed that daphnetin inhibited melanin biosynthesis in α-MSH-treated B16F10 cells. Immunoblotting and qRT-PCR also indicated that daphnetin suppressed the expression of microphthalmia-associated transcription factor, a mastering transcription factor of melanogenesis and its downstream melanogenic enzymes including tyrosinase and tyrosinase-related proteins. Moreover, daphnetin downregulated the phosphorylation of PKA, ERK, MSK1, and CREB. Additionally, daphnetin inhibited melanin synthesis in UVB-irradiated HaCaT conditioned medium system suggesting that daphnetin has potential as an antipigmentation activity in a physiological skin condition. Our data propose that daphnetin inhibits melanogenesis via modulating both the PKA/CREB and the ERK/MSK1/CREB pathways.

Daphnetin ameliorates Aβ pathogenesis via STAT3/GFAP signaling in an APP/PS1 double-transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) has become a major public health problem that affects the elderly population. Therapeutic compounds with curative effects are not available due to the complex pathogenesis of AD. Daphnetin, a natural coumarin derivative and inhibitor of various kinases, has anti-inflammatory and antioxidant activities. In this study, we found that daphnetin improved spatial learning and memory in an amyloid precursor protein (APP)/presenilin 1 (PS1) double-transgenic mouse model of AD. Daphnetin markedly decreased the levels of amyloid-β peptide 1-40 (Aβ₄₀) and 1-42 (Aβ₄₂) in the cerebral cortex, downregulated the expressions of enzymes involved in APP processing, e.g., beta-site APP-cleaving enzyme (BACE), nicastrin and presenilin enhancer protein 2 (PEN2). We further found the reduced serum levels of inflammatory factors, including interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and chemokine (C-C motif) ligand 3 (CCL3), while daphnetin increased total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) levels in the serum. Interestingly, daphnetin markedly decreased the expression of glial fibrillary acidic protein (GFAP) and the upstream regulatory molecule- phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in APP/PS1 mice, and mainly inhibited the phosphorylation of STAT3 at Ser727 to decrease GFAP expression evidenced in a LPS-activated glial cell model. These results suggest that daphnetin ameliorates cognitive deficits and that Aβ deposition in APP/PS1 mice is mainly correlated with astrocyte activation and APP processing.

Characterization of Sodium Alginate-Locust Bean Gum Films Reinforced with Daphnetin Emulsions for the Development of Active Packaging

In this study, we characterized an active film made of sodium alginate (SA)—locust bean gum (LBG) containing daphnetin-based film. Physicochemical characteristics, as well as antioxidant and antibacterial properties, were investigated. The results showed that the addition of a low concentration of daphnetin increased the flexibility of SA–LBG cling film, leading to an improvement in elongation at break and tensile strength. As the daphnetin content increased, solubility, brightness and transparency of the cling film decreased, and the moisture permeability increased. The antioxidant capacity and antibacterial activity of films with daphnetin were improved compared to those of the basal film. In addition, the cling film formed by adsorption had higher bacterial (Shewanella putrefaciens and Pseudomonas fluorescens) inhibition and antioxidant activity rates than direct film formation. The results indicate that the combination of daphnetin in SA–LBG film provides an active film with antioxidant and antibacterial properties, with potential for the development of food-grade packaging material.

Shelf-Life Extension of Refrigerated Turbot (Scophthalmus maximus) by Using Weakly Acidic Electrolyzed Water and Active Coatings Containing Daphnetin Emulsions

This research was to investigate the effect of weakly acidic electrolytic water (WAEW) treatments combining with the locust bean gum (LBG) and sodium alginate (SA) active coatings, containing daphnetin emulsions on microbiological, physicochemical, and sensory changes of turbot (Scophthalmus maximus) during refrigerated storage at 4°C for 24 days. Results showed that WAEW, together with LBG-SA coatings containing daphnetin emulsions treatments, could significantly lower the total viable count (TVC), H₂S-producing bacteria, pseudomonas spp., and psychrotrophic bacteria counts, and inhibit the productions of off-flavor compounds, including the total volatile basic nitrogen (TVB-N), inosine (HxR), and hypoxanthine (Hx). Furthermore, the treatments also prevented textural deterioration, delayed water migration, and had higher organoleptic evaluation results. Therefore, WAEW, together with LBG-SA coatings, containing daphnetin emulsions treatments, had the potential to improve the quality of turbot during refrigerated storage.

Daphnetin exerts an anticancer effect by attenuating the pro-inflammatory cytokines

Leukemia is a malignant tissue-forming disease, which induces the overproduction of large numbers of immature blood cells entering the peripheral blood. It is well documented that inflammation plays a crucial role in the expansion of leukemia. Daphnetin has confirmed anti-inflammatory effects against various diseases. In this experimental study, we evaluated the anti-leukemia and anti-inflammatory effect of daphnetin against benzene-induced leukemia in rats and explored the underlying mechanism. Benzene was used for inducing leukemia in experimental rats. The rats were divided into different groups and the body weight, hematological parameters, bone marrow cells, cytokines, and inflammatory mediators were estimated. Reverse transcription polymerase chain reaction (RT-PCR) was used for estimating the messenger RNA (mRNA) expression of sphingosine-1-phosphate receptor-1. Daphnetin-treated rats showed upregulation of body weight compared to other groups. Moreover, Daphnetin reduced blasts in leukemic rats. It also altered hematological parameters such as red blood cells, white blood cells, lymphocytes, neutrophils, monocytes, eosinophils, monocytes, and basophils, respectively. Daphnetin-treated rats showed a reduction of pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β (IL-1β), IL-2, IL-6, and inflammatory mediators including nuclear factor-κB. RT-PCR showed upregulated mRNA expression of sphingosine-1-phosphate receptor-1 of daphnetin-treated group rats compared to other groups. The current study showed that the anti-inflammatory effect of daphnetin against the benzene-induced leukemia via alteration of cytokines.

Regulatory effect of daphnetin on the balance of Th17 and Treg cells in the peripheral blood mononuclear cells from patients with unexplained recurrent pregnancy loss

Introduction

There has a close relationship between the balance of T helper 17 (Th17) cells and Foxp3+ regulatory T cells (Treg) and unexplained recurrent pregnancy loss (URPL). The present study is to investigate the regulatory effect of daphnetin, which is extracted from Daphne odora Var, on the balance of Th17 and Treg cells in the peripheral blood mononuclear cells (PBMCs) from patients with URPL.

Material and methods

PBMCs were isolated from 35 pregnant women with URPL and 35 women with normal early pregnancies, respectively and treated with daphnetin for three days. Flow cytometry was performed to measure the proportions of Th17 and Treg cells. The level of expression of IL-6, TGF-β1 and IL-2 were detected using enzyme-linked immunosorbent assay (ELISA) and the level of expression of FoxP3, RORγt, signal transducers and activators of transcriotion 3 (STAT3) and STAT5 were detected by RT-PCR.

Results

The concentrations of Th17-type cytokines IL-2 were significantly decreased in the URPL group after treatment (p < 0.01). Treg-type cytokines such as TGF-β1 and IL-6 were significantly increased after treatment (p < 0.01). At the same time, daphnetin may induce a decrease in the ratio of RORγt to Foxp3 and a Treg cell bias, which would be beneficial for pregnancy maintenance. Futhermore the expression level of STAT3 were higher in the URPL patients whereas STAT5 were lower than those in the control subjects.

Conclusions

In conclusion, daphnetin may have regulatory effect on the balance of Th17 and Treg cells in the peripheral blood mononuclear cells from patients with URPL.

Immunosuppressive activity of daphnetin on the humoral immune responses in ovalbumin-sensitized BALB/c mice

INTRODUCTION

Most of the immunosuppressive drugs are used for the treatment of autoimmune disease, allergic diseases, and transplant rejection, but toxicity is the major obstacle for the potent drugs in the wide use of these immunosuppressive drugs. Daphnetin, a Chinese herbal product, has been reported that daphnetin possesses antimicrobial, anticoagulation, antimalarial, anticancer, and antioxidant activity. In a previous study, we found that daphnetin exhibited a potential immunosuppressive effect on LPS-induced B lymphocyte cells in vitro, therefore, in this research, we investigated the immunosuppressive effects of daphnetin in BALB/c mice use OVA as a prototype antigen.

METHODS

Sixty BALB/c mice were divided into six groups. The emulsion (100 μL containing 100 μg OVA) was injected subcutaneously with OVA + CFA into the shaved backs of the BALB/c mice on day 1, and a boosting injection was administered in OVA + IFA 2 weeks later. Beginning on the day of immunization, the immunized mice were administered intraperitoneally with daphnetin at a dose of 5, 10, and 20 mg/kg in saline solution for 28 consecutive days. We measured the effect of daphnetin on OVA-specific antibody, cytokine production, and Splenocyte proliferation in vivo.

RESULTS

The results revealed that daphnetin significantly suppressed serum immunoglobulin G levels (IgG), and the OVA-specific IgG subclasses IgG1 and IgG2b, daphnetin was also significantly decreased the Th1 and Th2 cytokine productions, inhibited the splenocytes proliferation rate in vivo.

CONCLUSIONS

It proved that daphnetin could suppress humoral response activity on OVA-sensitized mice, suggesting a potential role on daphnetin as a new immunosuppressive drug.

Daphnetin suppresses experimental abdominal aortic aneurysms in mice via inhibition of aortic mural inflammation

Rupture of abdominal aortic aneurysm (AAA) is a devastating event that can be prevented by inhibiting the growth of small aneurysms. Therapeutic strategies targeting certain events that promote the development of AAA must be developed, in order to alter the course of AAA. Chronic inflammation of the aortic mural is a major characteristic of AAA and is related to AAA formation, development and rupture. Daphnetin (DAP) is a coumarin derivative with anti-inflammatory properties that is extracted from Daphne odora var. However, the effect of DAP on AAA development remains unclear. The present study investigated the effect of DAP on the formation and development of experimental AAAs and its potential underlying mechanisms. A mice AAA model was established by intra-aortic infusion of porcine pancreatic elastase (PPE), and mice were intraperitoneally injected with DAP immediately after PPE infusion. The maximum diameter of the abdominal aorta was measured by ultrasound system, and aortic mural changes were investigated by Elastica van Gieson (EVG) staining and immunohistochemical staining. The results demonstrated that DAP significantly suppressed PPE-induced AAA formation and attenuated the depletion of aortic medial elastin and smooth muscle cells in the media of the aorta. Furthermore, the density of mural macrophages, T cells and B cells were significantly attenuated in DAP-treated AAA mice. In addition, treatment with DAP resulted in a significant reduction in mural neovessels. These findings indicated that DAP may limit the formation and progression of experimental aneurysms by inhibiting mural inflammation and angiogenesis. These data confirmed the translational potential of DAP inclinical AAA inhibition strategies.

Daphnetin attenuates LPS-induced osteolysis and RANKL mediated osteoclastogenesis through suppression of ERK and NFATc1 pathways

Aseptic prosthetic loosening and periprosthetic infection resulting in inflammatory osteolysis is a leading complication of total joint arthroplasty (TJA). Excessive bone destruction around the bone and prosthesis interface plays a key role in the loosening prostheses leading to revision surgery. The bacterial endotoxins or implant-derived wear particles-induced inflammatory response is the major cause of the elevated osteoclast formation and activity. Thus, agents or compounds that can attenuate the inflammatory response and/or inhibit the elevated osteoclastogenesis and excessive bone resorption would provide a promising therapeutic avenue to prevent aseptic prosthetic loosening in TJA. Daphnetin (DAP), a natural coumarin derivative, is clinically used in Traditional Chinese Medicine for the treatment of rheumatoid arthritis due to its anti-inflammatory properties. In this study, we report for the first time that DAP could protect against lipopolysaccharide-induced inflammatory bone destruction in a murine calvarial osteolysis model in vivo. This protective effect of DAP can in part be attributed to its direct inhibitory effect on RANKL-induced osteoclast differentiation, fusion, and bone resorption in vitro. Biochemical analysis found that DAP inhibited the activation of the ERK and NFATc1 signaling cascades. Collectively, our findings suggest that DAP as a natural compound has potential for the treatment of inflammatory osteolysis.

[Effects of daphnetin combined with insulin-like growth factor 1 on chondrogenic differentiation of adipose-derived mesenchymal stem cells in rats]

OBJECTIVE

To investigate the effect of daphnetin (DAP) combined with insulin-like growth factor 1 (IGF-1) gene transfection on chondrogenic differentiation of adipose-derived mesenchymal stem cells (ADSCs) in rats.

METHODS

Rat ADSCs were isolated and amplified by enzymatic digestion. The third generation ADSCs were treated with IGF-1 gene transfection as experimental group and normal ADSCs as control group. The cells of the two groups were treated with different concentrations of DAP (0, 30, 60, 90 μg/mL), respectively. Cell proliferation was detected by cell counting kit 8 (CCK-8) after cultured for 72 hours. After 14 days, real-time fluorescence quantitative PCR and Western blot were used to detect the mRNA and protein expressions of chondrocyte markers (collagen type Ⅱ and Aggrecan) in each group; and toluidine blue staining and collagen type Ⅱ immunohistochemical staining were performed.

RESULTS

CCK-8 assay showed that with the increase of DAP concentration, the cell absorbance ( A) value of the control group and the experimental group increased gradually ( P<0.05). At the same DAP concentration, the cell A value of the experimental group was significantly higher than that of the control group ( P<0.05). Real-time fluorescence quantitative PCR and Western blot showed that with the increase of DAP concentration, the relative mRNA and protein expressions of collagen type Ⅱ and Aggrecan in the control group did not change significantly, and there was no significant difference among the different concentration groups ( P>0.05). But the mRNA and protein expressions of collagen type Ⅱ and Aggrecan in the experimental group increased gradually, and the 60 and 90 μg/mL DAP concentration groups were significantly higher than 0 μg/mL DAP concentration group ( P<0.05). At the same DAP concentration, the relative mRNA and protein expressions of collagen type Ⅱ and Aggrecan were significantly higher in the experimental group than in the control group ( P<0.05). Toluidine blue staining showed that with the increase of DAP concentration, there was no significant difference in cell staining between the control group and the experimental group. At the same DAP concentration, the cells in the experimental group were slightly darker than those in the control group. Immunohistochemical staining of collagen type Ⅱ showed that with the increase of DAP concentration, there was no significant difference in the cytoplasmic brown-yellow coloring of the cells in the control group. The cytoplasmic brown-yellow coloring of the cells in the experimental group gradually deepened, with 60 and 90 μg/mL DAP concentration groups significantly deeper than 0 μg/mL DAP concentration group. At the same DAP concentration, the color of the cells in the experimental group was significantly deeper than that in the control group.

CONCLUSION

DAP can promote the proliferation of ADSCs in rats. The differentiation of ADSCs into chondrocytes induced by DAP alone was slightly, but DAP combined with IGF-1 gene transfection has obvious synergistic effect to promote chondrogenic differentiation of ADSCs.

Daphnetin: A Novel Anti-Helicobacter pylori Agent

Background: Antibiotic-resistant H. pylori was increasingly found in infected individuals, which resulted in treatment failure and required alternative therapeutic strategies. Daphnetin, a coumarin-derivative compound, has multiple pharmacological activities. Methods: The mechanism of daphnetin on H. pylori was investigated focusing on its effect on cell morphologies, transcription of genes related to virulence, adhesion, and cytotoxicity to human gastric epithelial (GES-1) cell line. Results: Daphnetin showed good activities against multidrug resistant (MDR) H. pylori clinical isolates, with minimal inhibitory concentration (MIC) values ranging from 25 to 100 μg/mL. In addition, daphnetin exposure resulted in H. pylori morphological changes. Moreover, daphnetin caused increased translocation of phosphatidylserine (PS), DNA damage, and recA expression, and RecA protein production vs. control group. Of great importance, daphnetin significantly decreased H. pylori adhesion to GES-1 cell line vs. control group, which may be related to the reduced expression of colonization related genes (e.g., babA and ureI). Conclusions: These results suggested that daphnetin has good activity against MDR H. pylori. The mechanism(s) of daphnetin against H. pylori were related to change of membrane structure, increase of DNA damage and PS translocation, and decrease of H. pylori attachment to GES-1 cells.

Daphnetin inhibits RANKL-induced osteoclastogenesis in vitro

Osteoporosis is a common orthopedic disease which is associated with hyper-activated osteoclastogenesis. Daphnetin is a natural coumarin derivative isolated from Genus Daphne, which possesses antiarthritis effect. However, the role of daphnetin in osteoclastogenesis has not been illustrated. This study aimed to investigate the effects of daphnetin on receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis in vitro. Our results showed that the osteoclast formation was significantly suppressed by daphnetin treatment in bone marrow-derived macrophages (BMMs), which was illustrated by reduced number of tartrate-resistant acid phosphatase positive multinucleated osteoclasts and decreased expression levels of tumor necrosis factor receptor-associated factors (TRAF6), c-Fos, nuclear factor of activated T cells c1, and cathepsin K. RANKL caused significant induction effects in reactive oxygen species (ROS) generation and nicotinamide adenine dinucleotide phosphate oxidase activity, whereas the induction was dramatically reduced after pretreatment with daphnetin. In addition, daphnetin prevented the RANKL-induced activation of NF-κB and Akt/GSK-3β pathways in BMMs. These findings indicated that daphnetin exhibited an inhibitory effect on RANKL-induced osteoclastogenesis in vitro. The effect of daphnetin might be mediated by inhibiting ROS signal transduction, as well as preventing the activation of NF-κB and Akt/GSK-3β signaling pathways. These findings indicated that daphnetin might be considered as a new therapeutic approach for the osteoporosis treatment.

Synthesis and Structure-Activity Relationship of Daphnetin Derivatives as Potent Antioxidant Agents

In this study, daphnetin 1 was chosen as the lead compound, and C-3 or C-4-substituted daphnetins were designed and synthesized to explore the potential relationship between the antioxidant activities and the chemical structures of daphnetin derivatives. The antioxidant activities of the generated compounds were evaluated utilizing the free radical scavenging effect on 2,2'-diphenyl-1-picrylhydrazyl, 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) cation, and the ferric reducing power assays, and were then compared with those of the standard antioxidant Trolox. The results showed that the catechol group was the key pharmacophore for the antioxidant activity of the daphnetins. The introduction of an electron-withdrawing hydrophilic group at the C-4 position of daphnetin enhanced the antioxidative capacity, but this trend was not observed for C-3 substitution. In addition, introduction of a a hydrophobic phenyl group exerted negative effects on the antioxidant activity in both the C-3 and C-4 substitutions. Among all of the derivatives tested, the most powerful antioxidant was 4-carboxymethyl daphnetin (compound 9), for which the strongest antioxidant activity was observed in all of the assays. In addition, compound 9 also displayed strong pharmaceutical properties in the form of metabolic stability. To summarize, compound 9 holds great potential to be developed as an antioxidant agent with excellent antioxidant activity and proper pharmacokinetic behavior.

Daphnetin protects hippocampal neurons from oxygen-glucose deprivation-induced injury

Daphnetin, a coumarin derivative extracted from Daphne odora var., was reported to possess a neuroprotective effect. Recently, it has been demonstrated that daphnetin attenuates ischemia/reperfusion (I/R) injury. However, the role of daphnetin in cerebral I/R injury and the potential mechanism have not been fully understood. The present study aimed to explore the regulatory roles of daphnetin on oxygen-glucose deprivation/reoxygenation (OGD/R)-induced cell injury in a model of hippocampal neurons. Our results demonstrated that daphnetin improved cell viability and reduced the lactate dehydrogenase leakage in OGD/R-stimulated hippocampal neurons. In addition, daphnetin inhibited oxidative stress and cell apoptosis in hippocampal neurons after OGD/R stimulation. Furthermore, daphnetin significantly enhanced the nuclear translocation of the nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expression in hippocampal neurons exposed to OGD/R. Knockdown of Nrf2 blocked the protective effect of daphnetin on OGD/R-induced hippocampal neurons. In conclusion, these findings demonstrated that daphnetin attenuated oxidative stress and neuronal apoptosis after OGD/R injury through the activation of the Nrf2/HO-1 signaling pathway in hippocampal neurons. Thus, daphnetin may be a novel therapeutic agent for cerebral I/R injury.

Daphnetin inhibits TNF-α and VEGF-induced angiogenesis through inhibition of the IKKs/IκBα/NF-κB, Src/FAK/ERK1/2 and Akt signalling pathways

Coumarins, identified as plant secondary metabolites possess diverse biological activities including anti-angiogenic properties. Daphnetin (DAP), a plant derived dihydroxylated derivative of coumarin has shown significant pharmacological properties such as anticancer, anti-arthritic and anti-inflammatory. The present study was performed to investigate the anti-angiogenic potential of DAP, focusing on the mechanism of action. The in vivo anti-angiogenic potential of DAP was evaluated by vascular endothelial growth factor (VEGF)-induced rat aortic ring (RAR) assay and chick chorioallantoic membrane (CAM) assay. For in vitro evaluation, wounding migration, transwell invasion, tube formation and apoptosis assays were performed on VEGF (8 ng/mL)-induced human umbilical vein endothelial cells (HUVECs). The cellular mechanism of DAP was examined on TNFα (10 ng/mL) and VEGF-induced HUVECs by extracting the mRNA and protein levels using RT-qPCR and western blotting. Our data demonstrated that DAP inhibited the in vivo angiogenesis in the RAR and CAM assay. DAP also inhibited the different steps of angiogenesis, such as migration, invasion, and tube formation in HUVECs. DAP inhibited nuclear factor-κB signalling together including TNF-α induced IκBα degradation; phosphorylation of IκB kinase (IKKα/β) and translocation of the NF-κB-p65 protein. Furthermore, western blotting revealed that DAP significantly down-regulated the VEGF-induced signalling such as c-Src, FAK, ERK1/2 and the related phosphorylation of protein kinase B (Akt) and VEGFR2 expressions. DAP reduced the elevated mRNA expression of iNOS, MMP2 and also, induced apoptosis in VEGF-stimulated HUVECs by the caspase-3 dependent pathway. Taken together, this study reveals that DAP may have novel prospective as a new multi-targeted medication for the anti-angiogenesis and cancer therapy.

Daphnetin inhibits inflammation in the NZB/W F1 systemic lupus erythematosus murine model via inhibition of NF-κB activity

Daphnetin is a compound extracted from Chinese medicinal herbs, which exerts analgesic and anti-inflammatory effects. The present study aimed to investigate the potential therapeutic effect of daphnetin on inflammation in the NZB/W F1 systemic lupus erythematosus (SLE) murine model. Female NZB/WF1 mice (age, 16–18 weeks) were intraperitoneally injected with daphnetin once a day for 12 weeks. It was revealed that daphnetin treatment significantly increased animal survival rates, reduced renal damage and blood urea nitrogen levels, and suppressed serum autoantibody production in the SLE-prone NZB/W F1 mice. In addition, daphnetin treatment significantly decreased the serum levels of tumor necrosis factor-α and interleukin-6, inhibited nuclear factor (NF)-κB activity, suppressed the protein expression of nuclear factor of activated T-cells and promoted A20 protein expression in SLE-prone NZB/W F1 mice. In conclusion, daphnetin inhibited inflammation in the NZB/W F1 murine SLE model via inhibition of NF-κB mediated by upregulation of A20.

Daphnetin protects oxidative stress-induced neuronal apoptosis via regulation of MAPK signaling and HSP70 expression

Neurodegenerative disorders are characterized by progressive degeneration and loss of neurons in the brain. Oxidative stress is implicated in the pathogenesis of neurological disorders, although the pathological mechanism remains unelucidated. Daphnetin, an active ingredient extracted from Changbai daphne (Daphne Korean Nakai), exhibits various pharmacological effects, including anti-inflammatory, anti-oxidative and anti-tumor effects. However, the neuroprotective effects, as well as the specific mechanisms of daphnetin, remain unclear. Neuronal-like rat pheochromocytoma PC12 cells were pretreated with daphnetin for 2 h, then treated with or without H₂O₂ for various times. Cell morphology was detected using an inverted microscope, the apoptotic ratio was determined by Annexin V fluorescein isothiocyanate/propidium iodide assay, nuclear morphology was observed and photographed using a fluorescence microscope following 4',6-diamidino-2-phenylindole staining. The levels of pro-caspase 3, cleavage of poly ADP-ribose polymerase and caspase 3 were detected by western blotting. In addition, the activation of mitogen-activated protein kinase (MAPK) signal pathway and the expression of HSP70 were detected by western blotting. The present study demonstrated that daphnetin attenuated hydrogen peroxide (H₂O₂)-induced apoptosis in a concentration-dependent manner, reduced the cleavage of poly ADP ribose polymerase and caspase 3, and inhibited the phosphorylation of p38 MAPK and c-Jun N-terminal kinases (JNK) in H₂O₂-induced PC12 cells. In addition, daphnetin induced the expression of HSP70 in a dose- and time-dependent manner, and daphnetin-induced HSP70 expression was reduced by extracellular signal-regulated kinase (ERK) 1/2 inhibitor U0126 in PC12 cells. Therefore, the present results indicate that daphnetin protects PC12 cells against oxidative stress injury by regulating p38 MAPK and JNK signaling and increasing the expression of HSP70 via ERK signaling. This suggests that daphnetin may have the potential to treat certain neurodegenerative diseases. The present results not only provide insight into the potential use of daphnetin in H₂O₂-induced PC12 cell apoptosis, but also highlight the potential role of HSP70 in neuroprotection.

New Insights into the Antibacterial Activity of Hydroxycoumarins against Ralstonia solanacearum

Coumarins are important plant-derived natural products with wide-ranging bioactivities and extensive applications. In this study, we evaluated for the first time the antibacterial activity and mechanisms of action of coumarins against the phytopathogen Ralstonia solanacearum, and investigated the effect of functional group substitution. We first tested the antibacterial activity of 18 plant-derived coumarins with different substitution patterns, and found that daphnetin, esculetin, xanthotol, and umbelliferone significantly inhibited the growth of R. solanacearum. Daphnetin showed the strongest antibacterial activity, followed by esculetin and umbelliferone, with MICs of 64, 192, and 256 mg/L, respectively, better than the archetypal coumarin with 384 mg/L. We further demonstrated that the hydroxylation of coumarins at the C-6, C-7 or C-8 position significantly enhanced the antibacterial activity against R. solanacearum. Transmission electron microscope (TEM) and fluorescence microscopy images showed that hydroxycoumarins may interact with the pathogen by mechanically destroying the cell membrane and inhibiting biofilm formation. The antibiofilm effect of hydroxycoumarins may relate to the repression of flagellar genes fliA and flhC. These physiological changes in R. solanacearum caused by hydroxycoumarins can provide information for integral pathogen control. The present findings demonstrated that hydroxycoumarins have superior antibacterial activity against the phytopathogen R. solanacearum, and thus have the potential to be applied for controlling plant bacterial wilt.

Daphnetin inhibits invasion and migration of LM8 murine osteosarcoma cells by decreasing RhoA and Cdc42 expression

Daphnetin, 7,8-dihydroxycoumarin, present in main constituents of Daphne odora var. marginatai, has multiple pharmacological activities including anti-proliferative effects in cancer cells. In this study, using a Transwell system, we showed that daphnetin inhibited invasion and migration of highly metastatic murine osteosarcoma LM8 cells in a dose-dependent manner. Following treatment by daphnetin, cells that penetrated the Transwell membrane were rounder than non-treated cells. Immunofluorescence analysis revealed that daphnetin decreased the numbers of intracellular stress fibers and filopodia. Moreover, daphnetin treatment dramatically decreased the expression levels of RhoA and Cdc42. In summary, the dihydroxycoumarin derivative daphnetin inhibits the invasion and migration of LM8 cells, and therefore represents a promising agent for use against metastatic cancer.

Methylation, Glucuronidation, and Sulfonation of Daphnetin in Human Hepatic Preparations In Vitro: Metabolic Profiling, Pathway Comparison, and Bioactivity Analysis

Our previous study demonstrated that daphnetin is subject to glucuronidation in vitro. However, daphnetin metabolism is still poorly documented. This study aimed to investigate daphnetin metabolism and its consequent effect on the bioactivity. Metabolic profiles obtained by human liver S9 fractions and human hepatocytes showed that daphnetin was metabolized by glucuronidation, sulfonation, and methylation to form 6 conjugates which were synthesized and identified as 7-O-glucuronide, 8-O-glucuronide, 7-O-sulfate and 8-O-sulfate, 8-O-methylate, and 7-O-suflo-8-O-methylate. Regioselective 8-O-methylation of daphnetin was investigated using in silico docking calculations, and the results suggested that a close proximity (2.03 Å) of 8-OH to the critical residue Lysine 144 might be the responsible mechanism. Compared with glucuronidation and sulfonation pathways, the methylation of daphnetin had a high clearance rate (470 μL/min/mg) in human liver S9 fractions and contributed to a large amount (37.3%) of the methyl-derived metabolites in human hepatocyte. Reaction phenotyping studies showed the major role of SULT1A1, -1A2, and -1A3 in daphnetin sulfonation, and soluble COMT in daphnetin 8-O-methylation. Of the metabolites, only 8-O-methyldaphnetin exhibited an inhibitory activity on lymphocyte proliferation comparable to that of daphnetin. In conclusion, methylation is a crucial pathway for daphnetin clearance and might be involved in pharmacologic actions of daphnetin in humans.

Daphnetin prevents chronic unpredictable stress-induced cognitive deficits

Chronic exposure to stress hormones might impair cognitive functions such as learning and memory, which were associated with many mood disorders and neurodegenerative diseases. In this study, we aimed to screen for effective compounds to prevent cognitive deficits induced by chronic stress. Daphnetin was found to protect the cortical neurons against dexamethasone-induced reduction of cell viability in a dose-dependent manner in vitro. We further evaluated its effects on chronic unpredictable stress (CUS) mice in vivo. Two and 8 mg/kg administration of daphnetin could improve the performance of stress mice in Morris water maze tests and forced swimming tests. The results suggested that daphnetin might be a potent compound to treat cognitive deficits induced by CUS.