Enhancement of osteoblast biocompatibility on titanium surface with Terrein treatment

Loading rutin on surfaces by the layer-by-layer assembly technique to improve the oxidation resistance and osteogenesis of titanium implants in osteoporotic rats

The purpose of this study was to construct a rutin-controlled release system on the surface of Ti substrates and investigate its effects on osteogenesis and osseointegration on the surface of implants. The base layer, polyethylenimine (PEI), was immobilised on a titanium substrate. Then, hyaluronic acid (HA)/chitosan (CS)-rutin (RT) multilayer films were assembled on the PEI using layer-by-layer (LBL) assembly technology. We used scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and contact angle measurements to examine all Ti samples. The drug release test of rutin was also carried out to detect the slow-release performance. The osteogenic abilities of the samples were evaluated by experiments on an osteoporosis rat model and MC3T3-E1 cells. The results (SEM, FTIR and contact angle measurements) all confirmed that the PEI substrate layer and HA/CS-RT multilayer film were effectively immobilised on titanium. The drug release test revealed that a rutin controlled release mechanism had been successfully established. Furthermore, thein vitrodata revealed that osteoblasts on the coated titanium matrix had greater adhesion, proliferation, and differentiation capacity than the osteoblasts on the pure titanium surface. When MC3T3-E1 cells were exposed to H2O2-induced oxidative stressin vitro, cell-based tests revealed great tolerance and increased osteogenic potential on HA/CS-RT substrates. We also found that the HA/CS-RT coating significantly increased the new bone mass around the implant. The LBL-deposited HA/CS-RT multilayer coating on the titanium base surface established an excellent rutin-controlled release system, which significantly improved osseointegration and promoted osteogenesis under oxidative stress conditions, suggesting a new implant therapy strategy for patients with osteoporosis.

Breaking Osteoclast-Acid Vicious Cycle to Rescue Osteoporosis via an Acid Responsive Organic Framework-Based Neutralizing and Gene Editing Platform

In the osteoporotic microenvironment, the acidic microenvironment generated by excessive osteoclasts not only causes irreversible bone mineral dissolution, but also promotes reactive oxygen species (ROS) production to induce osteoblast senescence and excessive receptor activator of nuclear factor kappa-B ligand (RANKL) production, which help to generate more osteoclasts. Hence, targeting the acidic microenvironment and RANKL production may break this vicious cycle to rescue osteoporosis. To achieve this, an acid-responsive and neutralizing system with high in vivo gene editing capacity is developed by loading sodium bicarbonate (NaHCO3) and RANKL-CRISPR/Cas9 (RC) plasmid in a metal-organic framework. This results showed ZIF8-NaHCO3@Cas9 (ZNC) effective neutralized acidic microenvironment and inhibited ROS production . Surprisingly, nanoparticles loaded with NaHCO3 and plasmids show higher transfection efficiency in the acidic environments as compared to the ones loaded with plasmid only. Finally, micro-CT proves complete reversal of bone volume in ovariectomized mice after ZNC injection into the bone remodeling site. Overall, the newly developed nanoparticles show strong effect in neutralizing the acidic microenvironment to achieve bone protection through promoting osteogenesis and inhibiting osteolysis in a bidirectional manner. This study provides new insights into the treatment of osteoporosis for biomedical and clinical therapies.

Oxidative stress: A common pathological state in a high-risk population for osteoporosis

Osteoporosis is becoming a major concern in the field of public health. The process of bone loss is insidious and does not directly induce obvious symptoms. Complications indicate an irreversible decrease in bone mass. The high-risk populations of osteoporosis, including postmenopausal women, elderly men, diabetic patients and obese individuals need regular bone mineral density testing and appropriate preventive treatment. However, the primary changes in these populations are different, increasing the difficulty of effective treatment of osteoporosis. Determining the core pathogenesis of osteoporosis helps improve the efficiency and efficacy of treatment among these populations. Oxidative stress is a common pathological state secondary to estrogen deficiency, aging, hyperglycemia and hyperlipemia. In this review, we divided oxidative stress into the direct effect of reactive oxygen species (ROS) and the reduction of antioxidant enzyme activity to discuss their roles in the development of osteoporosis. ROS initiated mitochondrial apoptotic signaling and suppressed osteogenic marker expression to weaken osteogenesis. MAPK and NF-κB signaling pathways mediated the positive effect of ROS on osteoclast differentiation. Antioxidant enzymes not only eliminate the negative effects of ROS, but also directly participate in the regulation of bone metabolism. Additionally, we also described the roles of proinflammatory factors and HIF-1α under the pathophysiological changes of inflammation and hypoxia, which provided a supplement of oxidative stress-induced osteoporosis. In conclusion, our review showed that oxidative stress was a common pathological state in a high-risk population for osteoporosis. Targeted oxidative stress treatment would greatly optimize the therapeutic schedule of various osteoporosis treatments.

Three Classes of Antioxidant Defense Systems and the Development of Postmenopausal Osteoporosis

Osteoporosis is a common bone imbalance disease that threatens the health of postmenopausal women. Estrogen deficiency accelerates the aging of women. Oxidative stress damage is regarded as the main pathogenesis of postmenopausal osteoporosis. The accumulation of reactive oxygen species in the bone microenvironment plays a role in osteoblast and osteoclast apoptosis. Improving the oxidative state is essential for the prevention and treatment of postmenopausal osteoporosis. There are three classes of antioxidant defense systems in the body to eliminate free radicals and peroxides including antioxidant substances, antioxidant enzymes, and repair enzymes. In our review, we demonstrated the mechanism of antioxidants and their effect on bone metabolism in detail. We concluded that glutathione/oxidized glutathione (GSH/GSSG) conversion involved the PI3K/Akt-Nrf2/HO-1 signaling pathway and that the antioxidant enzyme-mediated mitochondrial apoptosis pathway of osteoblasts was necessary for the development of postmenopausal osteoporosis. Since the current therapeutic effects of targeting bone cells are not significant, improving the systemic peroxidation state and then regulating bone homeostasis will be a new method for the treatment of postmenopausal osteoporosis.

Recent Advances in Isolation, Synthesis and Biological Evaluation of Terrein

Terrein is a small-molecule polyketide compound with a simple structure mainly isolated from fungi. Since its discovery in 1935, many scholars have conducted a series of research on its structure identification, isolation source, production increase, synthesis and biological activity. Studies have shown that terrein has a variety of biological activities, not only can inhibit melanin production and epidermal hyperplasia, but also has anti-cancer, anti-inflammatory, anti-angiopoietic secretion, antibacterial, insecticidal activities, and so on. It has potential application prospects in beauty, medicine, agriculture and other fields. This article reviews the process of structural identification of terrein since 1935, and summarizes the latest advances in its isolation, source, production increase, synthesis, and biological activity evaluation, with a view to providing a reference and helping for the in-depth research of terrein.

The fungal metabolite (+)-terrein abrogates osteoclast differentiation via suppression of the RANKL signaling pathway through NFATc1

Pathophysiological bone resorption is commonly associated with periodontal disease and involves the excessive resorption of bone matrix by activated osteoclasts. Receptor activator of nuclear factor (NF)-κB ligand (RANKL) signaling pathways have been proposed as targets for inhibiting osteoclast differentiation and bone resorption. The fungal secondary metabolite (+)-terrein is a natural compound derived from Aspergillus terreus that has previously shown anti-interleukin-6 properties related to inflammatory bone resorption. However, its effects and molecular mechanism of action on osteoclastogenesis and bone resorption remain unclear. In the present study, we showed that 10 µM synthetic (+)-terrein inhibited RANKL-induced osteoclast formation and bone resorption in a dose-dependent manner and without cytotoxicity. RANKL-induced messenger RNA expression of osteoclast-specific markers including nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), the master regulator of osteoclastogenesis, cathepsin K, tartrate-resistant acid phosphatase (Trap) was completely inhibited by synthetic (+)-terrein treatment. Furthermore, synthetic (+)-terrein decreased RANKL-induced NFATc1 protein expression. This study revealed that synthetic (+)-terrein attenuated osteoclast formation and bone resorption by mediating RANKL signaling pathways, especially NFATc1, and indicated the potential effect of (+)-terrein on inflammatory bone resorption including periodontal disease.

Large-Scale Production of Bioactive Terrein by Aspergillus terreus Strain S020 Isolated from the Saudi Coast of the Red Sea

The diversity of symbiotic fungi derived from two marine sponges and sediment collected off Obhur, Jeddah (Saudi Arabia), was investigated in the current study. A total of 23 isolates were purified using a culture-dependent approach. Using the morphological properties combined with internal transcribed spacer-rDNA (ITS-rDNA) sequences, 23 fungal strains (in the majority Penicillium and Aspergillus) were identified from these samples. The biological screening (cytotoxic and antimicrobial activities) of small-scale cultures of these fungi yielded several target fungal strains which produced bioactive secondary metabolites. Amongst these isolates, the crude extract of Aspergillus terreus strain S020, which was cultured in fermentation static broth, 21 L, for 40 days at room temperature on potato dextrose broth, displayed strong antimicrobial activities against Pseudomonas aeruginosa and Staphylococcus aureus and significant antiproliferative effects on human carcinoma cells. Chromatographic separation of the crude extract by silica gel column chromatography indicated that the S020 isolate could produce a series of chemical compounds. Among these, pure crystalline terrein was separated with a high yield of 537.26 ± 23.42 g/kg extract, which represents the highest fermentation production of terrein to date. Its chemical structure was elucidated on the basis of high-resolution electrospray ionization mass spectrometry (HRESIMS) or high-resolution mass spectrometry (HRMS), 1D, and 2D NMR spectroscopic analyses and by comparison with reported data. The compound showed strong cytotoxic activity against colorectal carcinoma cells (HCT-116) and hepatocellular carcinoma cells (HepG2), with IC₅₀ values of 12.13 and 22.53 µM, respectively. Our study highlights the potential of A. terreus strain S020 for the industrial production of bioactive terrein on a large scale and the importance of future investigations of these strains to identify the bioactive leads in these fungal extracts.

Adverse Effects of Fine-Particle Exposure on Joints and Their Surrounding Cells and Microenvironment

Current understanding of the health risks and adverse effects upon exposure to fine particles is premised on the direct association of particles with target organs, particularly the lung; however, fine-particle exposure has also been found to have detrimental effects on sealed cavities distant to the portal-of-entry, such as joints. Moreover, the fundamental toxicological issues have been ascribed to the direct toxic mechanisms, in particular, oxidative stress and proinflammatory responses, without exploring the indirect mechanisms, such as compensated, adaptive, and secondary effects. In this Review, we recapitulate the current findings regarding the detrimental effects of fine-particle exposure on joints, the surrounding cells, and microenvironment, as well as their deteriorating impact on the progression of arthritis. We also elaborate the likely molecular mechanisms underlying the particle-induced detrimental influence on joints, not limited to direct toxicity, but also considering the other indirect mechanisms. Because of the similarities between fine air particles and engineered nanomaterials, we compare the toxicities of engineered nanomaterials to those of fine air particles. Arthritis and joint injuries are prevalent, particularly in the elderly population. Considering the severity of global exposure to fine particles and limited studies assessing the detrimental effects of fine-particle exposure on joints and arthritis, this Review aims to appeal to a broad interest and to promote more research efforts in this field.

Fungal metabolite (+)-terrein suppresses IL-6/sIL-6R-induced CSF1 secretion by inhibiting JAK1 phosphorylation in human gingival fibroblasts

Control of bacterial infection-induced inflammatory responses is one of the effective therapeutic approaches of periodontal diseases. Natural products such as lipid mediators and metabolites from microorganisms have been used for decreasing inflammation. We previously reported that (+)-terrein inhibited activation of STAT3 and ERK1/2 in interleukin-6 (IL-6) signaling cascade, leading to prevent vascular endothelial growth factor (VEGF) secretion in human gingival fibroblasts (HGFs). However, little is still known about the role of (+)-terrein on inflammatory responses. In this study, we provided the possibility of novel action that (+)-terrein inhibits activation of Janus-activated kinase 1 (JAK1), which has a central function in IL-6 signaling cascade, and alters expression of mRNAs and proteins induced by IL-6/soluble IL-6 receptor (sIL-6R) stimulation in HGFs. First, we performed PCR array to examine IL-6/sIL-6R-induced mRNA expression, and then expression of mRNA and protein of colony stimulating factor-1 (CSF1) and VEGF were clearly determined by quantitative RT-PCR and ELISA, respectively. Treatment with (+)-terrein suppressed expression of mRNA and protein of CSF1 and VEGF by IL-6/sIL-6R stimulation. Next, to test the effect of (+)-terrein on IL-6/sIL-6R signaling cascade, we demonstrated whether (+)-terrein affects phosphorylation of JAK1 and its downstream proteins, Akt and SHP-2. Western blotting revealed that (+)-terrein inhibited IL-6/sIL-6R-induced phosphorylation of JAK1, Akt, and SHP-2. Therefore, (+)-terrein suppresses IL-6/sIL-6R-induced expression of CSF1 and VEGF via inhibition of JAK1, Akt, and SHP-2. Based on our results, we suggest that (+)-terrein is a candidate compound for anti-inflammatory effect associated with IL-6 signaling.

In Vitro and In Vivo Characterization of N-Acetyl-L-Cysteine Loaded Beta-Tricalcium Phosphate Scaffolds

Beta-tricalcium phosphate bioceramics are widely used as bone replacement scaffolds in bone tissue engineering. The purpose of this study is to develop beta-tricalcium phosphate scaffold with the optimum mechanical properties and porosity and to identify the effect of N-acetyl-L-cysteine loaded to beta-tricalcium phosphate scaffold on the enhancement of biocompatibility. The various interconnected porous scaffolds were fabricated using slurries containing various concentrations of beta-tricalcium phosphate and different coating times by replica method using polyurethane foam as a passing material. It was confirmed that the scaffold of 40 w/v% beta-tricalcium phosphate with three coating times had optimum microstructure and mechanical properties for bone tissue engineering application. The various concentration of N-acetyl-L-cysteine was loaded on 40 w/v% beta-tricalcium phosphate scaffold. Scaffold group loaded 5 mM N-acetyl-L-cysteine showed the best viability of MC3T3-E1 preosteoblastic cells in the water-soluble tetrazolium salt assay test.

Novel antioxidant capability of titanium induced by UV light treatment

The intracellular production of reactive oxygen species (ROS) is a representative form of cellular oxidative stress and plays an important role in triggering adverse cellular events, such as the inflammatory reaction and delayed or compromised differentiation. Osteoblastic reaction to titanium with particular focus on ROS production remains unknown. Ultraviolet (UV) light treatment improves the physicochemical properties of titanium, specifically the induction of super hydrophilicity and removal of hydrocarbon, and eventually enhances its osteoconductivity. We hypothesized that there is a favorable regulatory change of ROS production within osteoblasts in contact with UV-treated titanium. Osteoblasts were cultured on titanium disks with or without UV-pretreatment. The intracellular production of ROS was higher on acid-etch-created rough titanium surfaces than on machine-prepared smooth ones. The ROS production was reduced by 40-50% by UV pretreatment of titanium regardless of the surface roughness. Oxidative DNA damage, as detected by 8-OHdG expression, was alleviated by 50% on UV-treated titanium surfaces. The expression of inflammatory cytokines was consistently lower in osteoblasts cultured on UV-treated titanium. ROS scavenger, glutathione, remained more without being depleted in osteoblasts on UV-treated titanium. Bio-burden test further showed that culturing osteoblasts on UV-treated titanium can significantly reduce the ROS production even with the presence of hydrogen peroxide, an oxidative stress inducer. These data suggest that the intracellular production of ROS and relevant inflammatory reaction, which unavoidably occurs in osteoblasts in contact with titanium, can be significantly reduced by UV pretreatment of titanium, implying a novel antioxidant capability of the particular titanium.

Terrein reduces age-related inflammation induced by oxidative stress through Nrf2/ERK1/2/HO-1 signalling in aged HDF cells

This study investigated whether multiple bioactivity of terrein such as anti-inflammatory and anti-oxidant inhibits age-related inflammation by promoting an antioxidant response in aged human diploid fibroblast (HDF) cells. HDF cells were cultured serially for in vitro replicative senescence. To create the ageing cell phenotype, intermediate stage (PD31) HDF cells were brought to stress-induced premature senescence (SIPS) using hydrogen peroxide (H2 O2). Terrein increased cell viability even with H2O2 stress and reduced inflammatory molecules such as intracellular adhesion molecule-1 (ICAM-1), cyclooxygenase-2 (COX-2), interleukin-1beta (IL-1β) and tumour necrosis factor-alpha (TNF-α). Terrein reduced also phospho-extracellular kinase receptor1/2 (p-EKR1/2) signalling in aged HDF cells. SIPS cells were attenuated for age-related biological markers including reactive oxygen species (ROS), senescence associated beta-galactosidase (SA β-gal.) and the aforementioned inflammatory molecules. Terrein induced the induction of anti-oxidant molecules, copper/zinc-superoxide defence (Cu/ZnSOD), manganese superoxide dismutase (MnSOD) and heme oxygenase-1 (HO-1) in SIPS cells. Terrein also alleviated reactive oxygen species formation through the Nrf2/HO-1/p-ERK1/2 pathway in aged cells. The results indicate that terrein has an alleviative function of age-related inflammation characterized as an anti-oxidant. Terrein might be a useful nutraceutical compound for anti-ageing.

Modification of artificial sea water for the mass production of (+)-terrein by Aspergillus terreus strain PF26 derived from marine sponge Phakellia fusca

(+)-Terrein shows multiple bioactivities, however, its mass production is a big challenge. Aspergillus terreus strain PF26 derived from South China Sea sponge Phakellia fusca has been cultured to produce (+)-terrein successfully, but artificial sea water (ASW) of high salinity used in the fermentation medium may cause the corrosion risk of metal bioreactor, which limits the fermentation on a large scale. In this study, we modified the components of ASW by removing NaCl and CaCl2 from the original formula, which reduced about 80% salinity of ASW. As a result, 7·56 g l(-1) (+)-terrein production was achieved in shake flask, which was 78·72% higher than using the original ASW, and the cultivation time was decreased from 24 to 15 days. Then, the modified ASW was used for the fermentation of A. terreus strain PF26 in a 500 l stirred bioreactor, consequently 2·5 g l(-1) of (+)-terrein production was achieved.

SIGNIFICANCE AND IMPACT OF THE STUDY

The fermentation of marine micro-organisms always needs to use sea water or artificial sea water (ASW), which limits the fermentation on a large scale, as the high-salinity medium may cause the corrosion risk of bioreactor. In this study, the ASW formula is simplified to reduce the sea water salinity and improve the yield of (+)-terrein, finally, the modified ASW was successfully used for the mass production of (+)-terrein by A. terreus strain PF26 in a 500 l bioreactor.

Insulin-like growth factor binding protein-3 affects osteogenic efficacy on dental implants in rat mandible

Insulin like growth factor binding protein-3 (IGFBP-3) in bone cells and its utilization in dental implants have not been well studied. The aim of this study was to determine the osteogenic efficacy of chitosan gold nanoparticles (Ch-GNPs) conjugated with IGFBP-3 coated titanium (Ti) implants. Ch-GNPs were conjugated with IGFBP-3 plasmid DNA through a coacervation process. Conjugation was cast over Ti surfaces, and cells were seeded on coated surfaces. For in vitro analysis the expression of different proteins was analyzed by immunoblotting. For in vivo analysis, Ch-GNP/IGFBP-3 coated implants were installed in rat mandibles. Four weeks post-implantation, mandibles were examined by microcomputed tomography (μCT), immunohistochemistry, hematoxylin & eosin and tartrate resistance acid phosphatase staining. In vitro overexpressed Ch-GNP/IGFBP-3 coated Ti surfaces was associated with activation of extracellular signal related kinase (ERK), inhibition of the stress activated protein c-Jun N-terminal kinase (JNK) and enhanced bone morphogenetic protein (BMP)-2 and 7 compared to control. Further, in vivo, Ch-GNP/IGFBP-3 coated implants were associated with inhibition of implant induced osteoclastogenesis molecules, receptor activator of nuclear factor kappa-B ligand (RANKL) and enhanced expression of osteogenic molecules including BMP2/7 and osteopontin (OPN). The μCT analysis demonstrated that IGFBP-3 increased the volume of newly formed bone surrounding the implants compared to control (n=5; p<0.05). These results support the view that IGFBP-3 overexpression diminishes osteoclastogenesis and enhances osteogenesis of Ti implants, and can serve as a potent molecule for the development of good implantation.

Marine natural products as breast cancer resistance protein inhibitors

Breast cancer resistance protein (BCRP) is a protein belonging to the ATP-binding cassette (ABC) transporter superfamily that has clinical relevance due to its multi-drug resistance properties in cancer. BCRP can be associated with clinical cancer drug resistance, in particular acute myelogenous or acute lymphocytic leukemias. The overexpression of BCRP contributes to the resistance of several chemotherapeutic drugs, such as topotecan, methotrexate, mitoxantrone, doxorubicin and daunorubicin. The Food and Drugs Administration has already recognized that BCRP is clinically one of the most important drug transporters, mainly because it leads to a reduction of clinical efficacy of various anticancer drugs through its ATP-dependent drug efflux pump function as well as its apparent participation in drug resistance. This review article aims to summarize the different research findings on marine natural products with BCRP inhibiting activity. In this sense, the potential modulation of physiological targets of BCRP by natural or synthetic compounds offers a great possibility for the discovery of new drugs and valuable research tools to recognize the function of the complex ABC-transporters.

Insulin improves osteogenesis of titanium implants under diabetic conditions by inhibiting reactive oxygen species overproduction via the PI3K-Akt pathway

Clinical evidence indicates that insulin therapy improves implant survival rates in diabetic patients; however, the mechanisms responsible for this effect are unknown. Here, we test if insulin exerts anti-oxidative effects, thereby improving diabetes-associated impaired osteoblast behavior on titanium implants. To test this hypothesis, we cultured primary rabbit osteoblasts in the presence of titanium implants and studied the impact of treatment with normal serum (NS), diabetic serum (DS), DS + insulin, DS + tempol (a superoxide dismutase mimetic), DS + insulin + tempol, and DS + insulin + wortmannin. We analyzed cell function, apoptosis, and reactive oxygen species (ROS) production in osteoblasts following the various treatments. Treatment with DS induced osteoblast dysfunction, evidenced by impaired cell attachment and morphology, decreased cell proliferation and ALP activity, and decreased expression of osteogenesis-related genes. We also observed a significant increase in apoptosis. Importantly, treatment with DS resulted in increased production of ROS in osteoblasts. In contrast, treatment with insulin inhibited ROS production, alleviated cell dysfunction, and decreased apoptosis of osteoblasts on the implants. Scavenging ROS with tempol also attenuated cell dysfunction. Compared to insulin treatment alone, the combination of insulin and tempol failed to further improve osteoblast functional recovery. Moreover, the anti-oxidative and pro-osteogenic effects afforded by insulin were almost completely abolished by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin. These results demonstrate, for the first time, that insulin treatment alleviates the impaired osteogenesis of titanium implants under diabetic conditions by inhibiting ROS overproduction via a PI3K/Akt-dependent mechanism. Both the anti-oxidative and metabolic properties of insulin should make it a viable therapeutic option to combat diabetic implant failure.

The marine-derived fungal metabolite, terrein, inhibits cell proliferation and induces cell cycle arrest in human ovarian cancer cells

The difficulties faced in the effective treatment of ovarian cancer are multifactorial, but are mainly associated with relapse and drug resistance. Cancer stem-like cells have been reported to be an important contributor to these hindering factors. In this study, we aimed to investigate the anticancer activities of a bioactive fungal metabolite, namely terrein, against the human epithelial ovarian cancer cell line, SKOV3, primary human ovarian cancer cells and ovarian cancer stem-like cells. Terrein was separated and purified from the fermentation metabolites of the marine sponge-derived fungus, Aspergillus terreus strain PF26. Its anticancer activities against ovarian cancer cells were investigated by cell proliferation assay, cell migration assay, cell apoptosis and cell cycle assays. The ovarian cancer stem-like cells were enriched and cultured in a serum-free in vitro suspension system. Terrein inhibited the proliferation of the ovarian cancer cells by inducing G2/M phase cell cycle arrest. The underlying mechanisms involved the suppression of the expression of LIN28, an important marker gene of stemness in ovarian cancer stem cells. Of note, our study also demonstrated the ability of terrein to inhibit the proliferation of ovarian cancer stem-like cells, in which the expression of LIN28 was also downregulated. Our findings reveal that terrein (produced by fermention) may prove to be a promising drug candidate for the treatment of ovarian cancer by inhibiting the proliferation of cancer stem-like cells.

Synthetic (+)-terrein suppresses interleukin-6/soluble interleukin-6 receptor induced-secretion of vascular endothelial growth factor in human gingival fibroblasts

Interleukin (IL)-6 is a proinflammatory cytokine that performs a wide variety of biological functions, including important roles in the progression of chronic inflammatory diseases such as periodontal disease. (+)-Terrein, a secondary bioactive fungal metabolite isolated from Aspergillus terreus, has various biological activities; however, its anti-inflammatory effects are still unknown. The purpose of this study was to examine the effect of synthetic (+)-terrein on IL-6 signaling and related protein production in human gingival fibroblasts. To our knowledge, this study is the first to report that synthetic (+)-terrein is not cytotoxic at concentrations less than 20 μM and suppresses IL-6/soluble IL-6 receptor (sIL-6R)-induced phosphorylation of signal transducer and activator of transcription-3, extracellular signal-regulated kinase 1/2, and c-jun N-terminal kinase 1/2-signaling proteins that are downstream of IL-6 signaling. In addition, synthetic (+)-terrein suppresses IL-6/sIL-6R-induced vascular endothelial growth factor (VEGF) secretion in a concentration-dependent manner (p<0.01). These data suggest that synthetic (+)-terrein has potential anti-IL-6 signaling activity and suppresses VEGF-associated inflammatory disease progression.

Terrein biosynthesis in Aspergillus terreus and its impact on phytotoxicity

Terrein is a fungal metabolite with ecological, antimicrobial, antiproliferative, and antioxidative activities. Although it is produced by Aspergillus terreus as one of its major secondary metabolites, not much is known about its biosynthetic pathway. Here, we describe an unexpected discovery of the terrein biosynthesis gene locus made while we were looking for a PKS gene involved in production of conidia coloration pigments common for Aspergilli. The gene, ATEG_00145, here named terA, is essential for terrein biosynthesis and heterologous production of TerA in Aspergillus niger revealed an unusual plasticity in the products formed, yielding a mixture of 4-hydroxy-6-methylpyranone, orsellinic acid, and 6,7-dihydroxymellein. Biochemical and molecular genetic analyses indicate a low extension cycle specificity of TerA. Furthermore, 6-hydroxymellein was identified as a key intermediate in terrein biosynthesis. We find that terrein production is highly induced on plant-derived media, that terrein has phytotoxic activity on plant growth, and induces lesions on fruit surfaces.

Terrein induces apoptosis in HeLa human cervical carcinoma cells through p53 and ERK regulation

Terrein, a fungal metabolite derived from Aspergillus terreus, has been shown to have a variety of biological activities in human cells including inhibition of melanogenesis, as well as anti-inflammatory, antioxidant and anticancer properties. In the present study, terrein was shown to have marked anticancer activity on HeLa human cervical carcinoma cells. Terrein exhibited inhibition of proliferation within the same ranges for other cancer cell types with an IC50 at 0.29 mM. The growth inhibition that induced cell death was via apoptosis mechanisms. Chromatin condensation was observed using the Hoechst 33342 stain, a DNA-specific dye. The increase of DNA fragmentation or the sub-G0 peak was also detected by flow cytometry. The signaling used by terrein to induce apoptosis was via the death-receptor and mitochondrial pathways; the cleavage of specific fluorogenic substrates by caspase-3, -8 and -9 activities are clearly demonstrated. The mitochondria were damaged as demonstrated by the decrease of the red/green ratio of the JC-1 staining and the increase of the Bax/Bcl-2 expression ratio. Further analysis of the upstream signaling by the quantitative real-time polymerase chain reaction showed that p53, p21 and ERK were upregulated which indicates the importance of their roles on terrein signaling. This study is the first to show that terrein has an effect on the anticancer properties in cervical cancer cells by inducing apoptosis through p53 and ERK regulation. Our data may help expand the function of the terrein compound and may also aid in the discovery of new anticancer agents.

PPARγ delivered by Ch-GNPs onto titanium surfaces inhibits implant-induced inflammation and induces bone mineralization of MC-3T3E1 osteoblast-like cells

OBJECTIVES

To deliver the efficacy and safety of Ch-GNPs (Chitosan gold nanoparticles) conjugated anti-inflammatory molecules peroxisome proliferator activated receptor gamma (PPARγ) on implant surface titanium (Ti) to reduce implant-induced inflammation.

MATERIALS AND METHODS

The Ch-GNPs were conjugated with the PPARγ cDNA through a coacervation process. Conjugation was cast over Ti surfaces by dipping, and cells were seeded on different sizes (6 × 6 × 0.1 cm and 1 × 1 × 0.1 cm; n = 3) of Ti surfaces. The size of Ch-GNPs and surface characterization of Ti was performed using UV-vis spectroscopy, TEM (Transmission electron microscopy) and EDX (energy-dispersive X-ray). The DNA conjugation and transfection capacity of Ch-GNPs were simultaneously confirmed by agarose gel electrophoresis, β-galactosidase staining, and immunoblotting.

RESULTS

The Ch-GNPs were well dispersed and spherical in shape, with average size around 10-20 nm. Ti surfaces coated with Ch-GNPs/LacZ, as transfection efficacy molecule, showed strong β-galactosidase staining in MC-3T3 E1 cells. Cells cultured on Ch-GNPs/PPARγ-coated Ti surfaces were able to inhibit implant-induced inflammation by simultaneously suppressing the expression of tumor necrosis factor- alpha (TNF-α), interleukin-1 beta (IL-1β), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and matrix metalloproteinase-2 (MMP-2). The inhibition mechanism of Ch-GNPs/PPARγ was due to inhibition of both reactive oxygen species (ROS) and nitric oxide (NO) secretion (n = 3; P < 0.05). In addition, Ch-GNPs/PPARγ was able to increase expression of bone morphogenetic protein (BMP-7) and runt-related transcription factor-2 (RUNX-2). Furthermore, alkaline phosphatase activity (ALP) was also increased than that in control (n = 3; P < 0.01). Whereas, expression of receptor activator of NF-κB ligand (RANKL) was decreased.

CONCLUSIONS

The novel gene delivery materials, like Ch-GNPs, can carry the PPARγ cDNA into the required areas of the implant surfaces, thus aiding to inhibit inflammation and promote osteoblast function. Thus, the PPARγ on implant surfaces may promote its clinical application on peri-implantitis or periodontitis like diseases.

PPARγ inhibits inflammation and RANKL expression in epoxy resin-based sealer-induced osteoblast precursor cells E1 cells

OBJECTIVES

The AH26 of epoxy resin-based sealer is used widely owing to its excellent physical characteristics but it induces oxidative stress and cytotoxicity at the periapical tissues. AH26 exhibited cytotoxicity towards MC-3T3-E1 cells, which resulted in mitochondria-mediated apoptosis. Peroxisome proliferator-activated receptor (PPARγ) has an anti-inflammatory effect in several tissue and cells, but its action of AH26-related inflammation is not completely understood. The aim of this study is to investigate the anti-inflammatory and anti-osteoclastic mechanisms of PPARγ in AH26-induced MC-3T3 E1 cells.

METHODS

AH26 was prepared according to the manufacturer's instructions. The 1-day extraction sample, which was diluted by 30%, was tested in this experiment. Recombinant deficiency adenoviral PPARγ (Ad/PPARγ) was used to examine PPARγ over-expression in MC-3T3 E1 cells. AH26-induced reactive oxygen species (ROS) formation was analysed using 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) with fluorescence-activated cell sorting (FACS), and the expression of receptor activator of nuclear factor-κB ligand (RANKL) and inflammatory molecules was determined by immunoblotting. The anti-inflammatory and anti-osteoclastic mechanisms of the PPARγ-involved signal pathway was examined by immunoblotting.

RESULTS

The AH26 elutes induced inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), RANKL expression and ROS formation. In addition, the AH26 elutes suppressed the expression of PPARγ. However, the recovery of PPARγ expression with Ad/PPARγ resulted in the inhibition of iNOS, COX-2, RANKL and ROS formation despite the AH26 treatment in MC-3T3 E1 cells. The mechanism of PPARγ was confirmed by the blocking of nuclear factor kappa B (NF-κB) translocation to the nucleus after the suppression of ERK1/2, SAPK/JNK and AP-1 in AH26-induced MC-3T3 E1 cells.

CONCLUSION

From this result, PPARγ acts to inhibit bone destruction in AH26-induced bone cells. Therefore, the anti-inflammatory and anti-osteoclastic character of PPARγ might be applicable for healing periapical lesions more rapidly or reducing the induction of cellular inflammation caused by some endodontic sealers.