Selective Activation of Cascade Assembly Amplification for DNA Methyltransferase Detection Using a Double-Loop Interlocked DNA Circuit.

Precise and reliable monitoring of DNA adenine methyltransferase (Dam) activity is essential for disease diagnosis and biological analysis. However, existing techniques for detecting Dam activity often rely on specific DNA recognition probes that are susceptible to DNA degradation and exhibit limited target sensitivity and specificity. In this study, we designed and engineered a stable and dynamic DNA nanodevice called the double-loop interlocked DNA circuit (DOOR) that enables the sensitive and selective monitoring of Dam activity in complex biological environments. The DOOR incorporates two interlocked specialized sequences: a palindromic sequence for Dam identification and an initiator sequence for signal amplification. In the presence of Dam, the DOOR is cleaved by double-stranded DNA phosphodiesterase I endonuclease, generating massive double-stranded DNA (dsDNA) units. These units can self-assemble into a long dsDNA scaffold, thereby enhancing the subsequent reaction kinetics. The dsDNA scaffold further triggers a hyperbranched hybrid chain reaction to produce a fluorescent 3D DNA nanonet, enabling more precise monitoring of the Dam activity. The DOOR device exhibits excellent sensitivity, specificity, and stability, rendering it a powerful tool for studying DNA methylation in various biological processes and diseases.

[Effect of Low-density Polyethylene Microplastics on Natural Attenuation of Oxygenated Polycyclic Aromatic Hydrocarbons in Soil].

The continuous accumulation of microplastics in agricultural soils may affect the natural attenuation of oxygen-containing polycyclic aromatic hydrocarbons (OPAHs). The effects of low-density polyethylene (LDPE) microplastics with the spiking proportion of 1 % and 0.01 % in soils on the natural attenuation of OPAHs were investigated via soil microcosm experiments. The relation between the response of bacterial communities and OPAHs dissipation was also explored. The initial content of OPAHs in the soil was 34.6 mg·kg-1. The dissipation of OPAHs in the soil on day 14 was inhibited by LDPE. The contents of OPAHs in LDPE groups were higher than that in the control by 0.9-1.6 mg·kg-1, and the inhibition degree increased with the proportion of LDPE. The contents of OPAHs were not significantly different among groups on day 28, indicating that the inhibitory effect of LDPE disappeared. LDPE did not change the composition of the dominant taxa in the OPAHs-contaminated soil community but influenced the relative abundances of some dominant taxa. LDPE increased the relative abundance of Proteobacteria and Actinobacteria at the phylum level and decreased that of Bacillus and increased those of Micromonospora, Sphingomonas, and Nitrospira (potential degrading bacteria of LDPE and endogenous substances) at the genus level, all four of which were the main genera dominating intergroup community differences. LDPE changed the α and ß diversity of bacterial communities, but the extents were not significant. LDPE affected the function of the bacterial community, reducing the total abundance of PAHs-degrading genes and some degrading enzymes, inhibiting the growth of PAHs-degrading bacteria and thus interfering with the natural decay of OPAHs.

Apelin-13 induces mitophagy in bone marrow mesenchymal stem cells to suppress intracellular oxidative stress and ameliorate osteoporosis by activation of AMPK signaling pathway.

Osteoporosis is characterized by impaired bone metabolism. Current estimates show that it affects millions of people worldwide and causes a serious socioeconomic burden. Mitophagy plays key roles in bone marrow mesenchymal stem cells (BMSCs) osteoblastic differentiation, mineralization, and survival. Apelin is an endogenous adipokine that participates in bone homeostasis. This study was performed to determine the role of Apelin in the osteoporosis process and whether it affects mitophagy, survival, and osteogenic capacity of BMSCs in in vitro and in vivo models of osteoporosis. Our results demonstrated that Apelin was down-regulated in ovariectomized-induced osteoporosis rats and Apelin-13 treatment activated mitophagy in BMSCs, ameliorating oxidative stress and thereby reviving osteogenic function via AMPK-α phosphorylation. Besides, Apelin-13 administration restored bone mass and microstructure as well as reinstated mitophagy, enhanced osteogenic function in OVX rats. Collectively, our findings reveal the intrinsic mechanisms underlying Apelin-13 regulation in BMSCs and its potential therapeutic values in the treatment of osteoporosis.

Proanthocyanidins-Mediated Nrf2 Activation Ameliorates Glucocorticoid-Induced Oxidative Stress and Mitochondrial Dysfunction in Osteoblasts.

The widespread use of therapeutic glucocorticoids has increased the frequency of glucocorticoid-induced osteoporosis (GIOP). One of the potential pathological processes of GIOP is an increased level of oxidative stress and mitochondrial dysfunction, which eventually leads to osteoblast apoptosis. Proanthocyanidins (PAC) are plant-derived antioxidants that have therapeutic potential against GIOP. In our study, a low dose of PAC was nontoxic to healthy osteoblasts and restored osteogenic function in dexamethasone- (Dex-) treated osteoblasts by suppressing oxidative stress, mitochondrial dysfunction, and apoptosis. Mechanistically, PAC neutralized Dex-induced damage in the osteoblasts by activating the Nrf2 pathway, since silencing Nrf2 partly eliminated the protective effects of PAC. Furthermore, PAC injection restored bone mass and promoted the expression of Nrf2 in the distal femur of Dex-treated osteoporotic rats. In summary, PAC protect osteoblasts against Dex-induced oxidative stress and mitochondrial dysfunction via the Nrf2 pathway activation and may be a promising drug for treating GIOP.

Vitamin K2 Can Rescue the Dexamethasone-Induced Downregulation of Osteoblast Autophagy and Mitophagy Thereby Restoring Osteoblast Function In Vitro and In Vivo.

Chronic long-term glucocorticoids (GC) use is associated with glucocorticoid-induced osteoporosis (GIOP) by inhibiting the survival and impairing the functions of osteoblasts. Autophagy and mitophagy play key roles in osteoblast differentiation, mineralization and survival, and mounting evidence have implicated osteoblast autophagy and mitophagy as a novel mechanism in the pathogenesis of GIOP. Vitamin K2 (VK2) is an essential nutrient supplement that have been shown to exert protective effects against osteoporotic bone loss including GIOP. In this study, we showed that the glucocorticoid dexamethasone (Dex) deregulated osteoblast autophagy and mitophagy by downregulating the expression of autophagic and mitophagic markers LC3-II, PINK1, Parkin. This consequently led to inhibition of osteoblast differentiation and mineralization function in vitro. Interestingly, co-treatment with VK2 significantly attenuated the Dex-induced downregulation of LC3-II, PINK1, Parkin, thereby restoring autophagic and mitophagic processes and normal osteoblastic activity. In addition, using an established rat model of GIOP, we showed that VK2 administration can protect rats against the deleterious effects of Dex on bone by reinstating autophagic and mitophagic activities in bone tissues. Collectively, our results provide new insights into the role of osteoblast autophagy and mitophagy in GIOP. Additionally, the use of VK2 supplementation to augment osteoblast autophagy/mitophagy may significantly improve clinical outcomes of GIOP patients.

Combined treatment with vitamin K2 and PTH enhanced bone formation in ovariectomized rats and increased differentiation of osteoblast in vitro.

Osteoporosis is accompanied by insufficient osteogenic capacity. Several lines of evidence suggested that solutions to enhance osteoblastogenesis were important strategies for osteoporotic bone defect repair. This study investigated the effect of combined treatment with vitamin K2 and PTH on bone formation in calvarial bone defect in osteoporotic rats and its influence on osteoblast in vitro. Bilateral ovariectomy was used in SPF Sprague Dawley rats to generate an osteoporosis model. Subsequently, a calvarial defect model was established and all osteoporotic rats were randomly assigned to the following groups: control, VK (vitamin K2, 30 mg/kg everyday), PTH (recombinant human PTH (1-34), 60 µg/kg, three times a week) or VK + PTH (vitamin K2, 30 mg/kg everyday plus PTH, 60 µg/kg three times a week) for 8 weeks. In vitro, bone marrow-derived stem cells (BMSCs) were cultured and treated with vitamin K2, PTH or vitamin K2+PTH. ALP staining and western blot were performed to observe the influence of combined treatment on BMSCs. Bone formation within calvarial defect were assessed by serum γ-carboxylated osteocalcin (Gla-OC), micro-CT, histological and immunofluorescent labeling. In this study, combined treatment of PTH and vitamin K2 showed positive effects on preventing bone loss in femurs in OVX rats. Combined treatment increased serum Gla-OC and promoted bone formation in osteoporotic calvarial bone defects. Immunohistochemistry showed that OCN and RUNX2 were more highly expressed in the VK + PTH group than in the control groups. In vitro studies results suggested that combined treatment with PTH and vitamin K2 increased expression of ALP, BMP2 and RUNX2 in BMSCs. Our data suggested that the combination of vitamin K2 and PTH increased differentiation of osteoblast and had a synergistic effect on bone formation in osteoporotic calvarial bone defect.

Effects of combined menaquinone-4 and PTH1-34 treatment on osetogenesis and angiogenesis in calvarial defect in osteopenic rats.

PURPOSE: The aim of this study was to evaluate the effect of combining human parathyroid hormone (1-34) (PTH1-34; PTH) and menaquinone-4 (MK-4) on calvarial bone defect repair in osteopenic rats. METHODS: Fourteen week olds were subject to craniotomy for the establishment of osteopenic animal models fed through a chronically low-protein diet. After that, critical calvarial defect model was established and all rats were randomly divided into four groups: sham, MK-4, PTH, and PTH + MK-4. The animals received MK-4 (30 mg/kg/day), PTH1-34 (60 µg/kg, three times a week), or PTH1-34 (60 µg/kg, three times a week) plus MK-4 (30 mg/kg/day) for 8 weeks, respectively. Serum γ-carboxylated osteocalcin (Gla-OC) levels, histological and immunofluorescent labeling were employed to evaluate the bone formation and mineralization in calvarial bone defect. In addition, Microfil perfusion, immunohistochemical, and micro-CT suggested enhanced angiogenesis and bone formation in calvarial bone healing. RESULTS: In this study, treatment with either PTH1-34 or MK-4 promoted bone formation and vascular formation in calvarial bone defects compared with the sham group. In addition, combined treatment of PTH1-34 plus MK-4 increased serum level of Gla-OC, improved vascular number and vascular density, and enhanced bone formation in calvarial bone defect in osteopenic conditions as compared with monotherapy. CONCLUSIONS: In summary, this study indicated that PTH1-34 plus MK-4 combination therapy accelerated bone formation and angiogenesis in calvarial bone defects in presence of osteopenia.

Combined treatment with Cinnamaldehyde and ß-TCP had an additive effect on bone formation and angiogenesis in critical size calvarial defect in ovariectomized rats.

Accumulating evidence suggests that improvements in osteogenesis and angiogenesis play an important role in repairing osteoporotic bone defects. Cinnamomum cassia (C. cassia), a traditional Chinese medicinal herb, is reported to show anabolic effects on osteoblasts. However, whether C. cassia could actually repair bone defects in osteoporotic conditions remains unknown. The purpose of this study was to evaluate the effect of combined treatment with Cinnamaldehyde (main oil isolated from the C. cassia) and ß-tricalcium phosphate (ß-TCP) on bone formation and angiogenesis in critical size calvarial defects in ovariectomized (OVX) rats. Using a previously established OVX model, 5 mm critical size calvarial defect was established in OVX rats. All OVX rats were then randomly divided into OVX group (OVX rats + empty defect), TCP group (OVX rats + ß-TCP), and CTCP group (Cinnamaldehyde 75 mg/kg/day for 12 weeks + ß-TCP). Twelve weeks after treatment, according to Micro-CT and HE staining, combination of Cinnamaldehyde and ß-TCP had an additive effect on bone regeneration compared with other groups (p < 0.05). Based on dynamic fluorochrome-labelling analysis, Cinnamaldehyde+ß-TCP continuously promoted new bone mineralization compared with other groups at each time point (p < 0.05). Microfil perfusion suggested that CTCP group showed more neovascularization compared with other groups (p < 0.05). Immunohistochemical assay supported the findings that Cinnamaldehyde+ß-TCP enhanced expression of OCN, VEGF and CD31. The present study demonstrated that combined treatment with Cinnamaldehyde and ß-TCP promoted bone formation and angiogenesis in osteoporotic bone defects, which provides a promising new strategy for repairing bone defects in osteoporotic conditions.

[Effects of Biochar Application Rates on Greenhouse Gas Emissions in the Purple Paddy Soil].

In order to explore the effects of different amounts of biochar applied in purple paddy soil on greenhouse gas (GHG) emissions, potted experiments using a static opaque chamber and gas chromatography method were used to study the regulations and influences of biochar on soil greenhouse gas emission using five treatments:no fertilizer (CK), conventional fertilization (NPK), 10 t ·hm-2 biochar+NPK (LBC), 20 t ·hm-2 biochar+NPK (MBC), and 40 t ·hm-2 biochar+NPK (HBC). ① Soil CH4 emission flux reduced significantly with all biochar application treatments; the emission flux followed the order, from large to small, of NPK > CK > LBC > MBC > HBC. The CH4 emission flux of each treatment showed a single peak curve, and the peak value was mainly concentrated in the late growth stage of the paddy cropland. During the entire observation period, the emission flux of CH4 was between -0.05 mg ·(m2 ·h)-1 and 47.34 mg ·(m2 ·h)-1. The CO2 emission flux of each treatment was complicated and ranged from 32.95 mg ·(m2 ·h)-1 to 1350.88 mg ·(m2 ·h)-1. The CO2 emission flux of the LBC and MBC treatments showed bimodal curves, and the CO2 emission flux of other treatments showed single peak curves. In addition, all biochar treatments delayed the peak time of the CO2 emission flux. The N2O emission flux of each treatment ranged from -309.39 to 895.48 µg ·(m2 ·h)-1, and the N2O emission flux of the LBC treatment showed a bimodal curve, while other treatments showed single peak curves. ② Compared with the CK treatment, biochar treatment can significantly reduce the cumulative emissions of CH4 and promote the cumulative emissions of CO2 and N2O. The average amount of CH4 cumulative emissions followed the order CK > LBC > MBC > HBC, while the average amount of CO2 cumulative emissions followed LBC > MBC > HBC > CK, and the average amount of N2O cumulative emissions followed HBC > MBC≈LBC > CK. Compared with conventional fertilization treatment, different application rates of biochar addition significantly reduced CH4 and CO2 emissions. As more biochar was added, CH4 and CO2 cumulative emissions were lower. Although the regulation of N2O cumulative emissions on biochar addition was not obvious, the application of nitrogen fertilizer could promote the emission flux of N2O to some extent. ③ Over the time scale of 100 years, the integrated global warming potentials (GWP) of CH4 and N2O emission under different biochar treatment were decreased significantly, indicating that biochar combined with chemical fertilizer is an effective GHG emission reduction measure.

Chitosan oligosaccharide promotes osteoclast formation by stimulating the activation of MAPK and AKT signaling pathways.

Chitosan Oligosaccharide (COS) has been widely used for the systemic treatment of clinical diseases such as bone tissue engineering. However, its influence on osteoclast formation, which plays a critical role in bone homeostasis, has never been investigated. The aim of this study was to investigate the effect of chitosan oligosaccharide on differentiation of osteoclast. Using cell counting kit-8, tartrate-resistant acid phosphatase staining, reverse transcription­quantitative polymerase chain reaction assay and western blot analysis, we demonstrated that chitosan oligosaccharide cannot inhibit RANKL-induced osteoclast precursor proliferation but does promote osteoclast differentiation by stimulating the activation of p38/mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK)/MAPK, extracellular signal-regulated kinase (ERK)/MAPK and protein kinase B (AKT) without affecting nuclear factor kappaB (NF-kB) signaling pathways. Based on the promoting effect of chitosan oligosaccharide on osteoclast differentiation, we suggest that this property of chitosan oligosaccharide may have potential detrimental effect on bone homeostasis.