Limei Ma

Haloemodin as novel antibacterial agent inhibiting DNA gyrase and bacterial topoisomerase I.

Drug-resistant bacterial infections and lack of available antibacterial agents in clinical practice are becoming serious risks to public health. We synthesized a new class of haloemodins by modifying a traditional Chinese medicine component, emodin. The novel haloemodin exerts strong inhibitory activity on bacterial topoisomerase I and DNA gyrase, and not on the topoisomerases of human origin. In principle, it shows remarkable antibacterial activities against laboratory and clinically isolated Gram-positive bacteria, including vancomycin-resistant Enterococcus faecium and methicillin-resistant Staphylococcus aureus. We further expanded its antibacterial spectrum into against Gram-negative bacteria with the assistance of polymyxin B nonapeptide, which helps haloemodin to penetrate through the bacterial outer membrane. Finally, the therapeutic effect of haloemodin in vivo was confirmed in curing S. aureus-induced keratitis on rabbit model. With distinctive structural difference from the antibiotics we used, the haloemodins are of value as promising antibacterial pharmacophore, especially for combat the infections caused by drug-resistant pathogens.

Metformin Uniquely Prevents Thrombosis by Inhibiting Platelet Activation and mtDNA Release

Thrombosis and its complications are the leading cause of death in patients with diabetes. Metformin, a first-line therapy for type 2 diabetes, is the only drug demonstrated to reduce cardiovascular complications in diabetic patients. However, whether metformin can effectively prevent thrombosis and its potential mechanism of action is unknown. Here we show, metformin prevents both venous and arterial thrombosis with no significant prolonged bleeding time by inhibiting platelet activation and extracellular mitochondrial DNA (mtDNA) release. Specifically, metformin inhibits mitochondrial complex I and thereby protects mitochondrial function, reduces activated platelet-induced mitochondrial hyperpolarization, reactive oxygen species overload and associated membrane damage. In mitochondrial function assays designed to detect amounts of extracellular mtDNA, we found that metformin prevents mtDNA release. This study also demonstrated that mtDNA induces platelet activation through a DC-SIGN dependent pathway. Metformin exemplifies a promising new class of antiplatelet agents that are highly effective at inhibiting platelet activation by decreasing the release of free mtDNA, which induces platelet activation in a DC-SIGN-dependent manner. This study has established a novel therapeutic strategy and molecular target for thrombotic diseases, especially for thrombotic complications of diabetes mellitus.

Xanthohumol isolated from Humulus lupulus prevents thrombosis without increased bleeding risk by inhibiting platelet activation and mtDNA release

Aim As the global population has reached 7 billion and the baby boom generation reaches old age, thrombosis has become the major contributor to the global disease burden. It has been reported that, in moderate doses, beer may protect against thrombosis. Xanthohumol (XN), an antioxidant, is found at high concentrations in hop cones (Humulus lupulus L.) and is a common ingredient of beer. Here, the aim of the present work was to investigate the effects of XN on antithrombotic and antiplatelet activities, and study its mechanism. Approach and Results Using ferric chloride‐induced carotid artery injury, inferior vena cava ligation model, and platelet function tests, we demonstrated that XN uniquely prevents both venous and arterial thrombosis by inhibiting platelet activation. Interestingly, in tail bleeding time studies, XN did not increase bleeding risk, which is recognized as a major limitation of current antithrombotic therapies. We also demonstrated that XN induces Sirt1 expression and thereby decreases reactive oxygen species (ROS) overload, prevents mitochondrial dysfunction, and reduces activated platelet‐induced mitochondrial hyperpolarization, respiratory disorders, and associated membrane damage at low concentrations. In mitochondrial function assays designed to detect amounts of extracellular mitochondrial DNA (mtDNA), we found that XN prevents mtDNA release, which induces platelet activation in a DC‐SIGN‐dependent manner. Conclusions XN exemplifies a promising new class of antiplatelet agents that are highly effective at inhibiting platelet activation by decreasing ROS accumulation and platelet mtDNA release without incurring a bleeding risk. This study has also provided novel insights into mechanisms of thrombotic diseases with possible therapeutic implications. Graphical abstract Figure. No Caption available. HighlightsXanthohumol prevents thrombosis by inhibiting platelet activation.Xanthohumol induces Sirt1 expression and thereby prevents mitochondrial dysfunction.mtDNA induces platelet activation in a DC‐SIGN‐dependent manner.

pH-Responsive nanoparticles based on ibuprofen prodrug as drug carriers for inhibition of primary tumor growth and metastasis

Cancer metastases represent a major determinant of mortality in patients with cancer. Cyclooxygenase-2 (COX-2) and its metabolites play important roles in tumor growth and metastasis. Overexpression of COX-2 have been found in various types of cancers including melanoma. Nonsteroidal anti-inflammatory drugs (NSAIDs) have been widely used to inhibit COX-2 and can be a promising additive for the management of aggressive cancers. A novel pH-sensitive drug delivery carrier based on PEG-derivatized ibuprofen, MPEG-PHEI, was synthesized for dual delivery of anticancer agents and NSAIDs. This amphiphilic and biodegradable copolymer could self-assemble into core-shell nanoparticles (NPs) and the hydrophobic doxorubicin (DOX) could be loaded into the core of the nanoparticles. DOX-loaded MPEG-PHEI nanoparticles (DOX/NPs) could release DOX in endosome microclimate via micelle collapse and ibuprofen via ester bond hydrolysis. In vitro DOX/NPs showed comparable cytotoxicity to DOX·HCl and comparable inhibition of COX-2 to ibuprofen. More importantly, DOX/NPs revealed a significant in vivo therapeutic efficacy in both experimental subcutaneous tumors and lung metastasis model while decreasing the toxicity of DOX. This study demonstrated the advantages of combining NSAIDs with chemotherapy agents and provided a novel nanoparticle system for both primary and metastatic tumor treatment.

d-galactose induces premature senescence of lens epithelial cells by disturbing autophagy flux and mitochondrial functions

Cataract is the leading cause of blindness with an estimated 16 million people affected worldwide. d-galactose (d-gal) is a reducing sugar that widely distributed in foodstuffs, and studies show that d-gal could promote cataract formation by damaging nature lens epithelial cells (LECs). However, the underlying mechanism is unclear. In our present study, d-gal resulted in premature senescence of LECs, which was confirmed by determining the β-galactosidase activity, cell proliferative potential and cell cycle distribution, though apoptosis of LECs was not observed. We also verified that d-gal induced the impairment of autophagy flux by measuring the expression of LC3II and P62. Meanwhile, we found that d-gal induced mitochondrial dysfunctions of LECs through increasing reactive oxygen species (ROS), reducing ATP synthesis and mitochondrial potential (MMP), enhancing the concentration of cytoplasm Ca2+ and permeability transition pore (mPTP) opening. Metformin, as a potential anti-aging agent, suppressed the senescence of LECs by restoring autophagy flux and mitochondria functions. Nevertheless, the antioxidant N-acetylcysteine (NAC) scavenged ROS significantly but was not efficient in preventing LECs from premature senescence. Our data suggests that restoring autophagy activity and improving mitochondrial functions may be a potential strategy for the prevention of LECs senescence-related cataract.

Synthesis, characterization, and biological studies of diosgenyl analogs

Abstract A series of diosgenyl analogs were prepared from diosgenin to evaluate their anticancer activity and antithrombotic property. Analog 4, which had a spiroketal structure with a 6-aminohexanoic acid residue, exhibited the highest potency against all five tumor cell lines. It significantly blocked tumor growth, induced cell apoptosis and autophagy, and regulated cellular calcium concentration, mitochondrial membrane potential, adenosine triphosphate, and cell cycle. In addition, fluorescence-tagged compounds indicated that the analogs could rapidly accumulate in the cytoplasm, but no specific localization in the nucleus of cancer cells was observed. Furthermore, preliminary structure–activity relationship studies demonstrated that spiroketal analogs exhibit better antithrombotic activity than furostanic analogs, which exhibit the opposite effect by promoting thrombosis. Our study indicates that compound 4 may be a promising anticancer drug candidate for cancer patients with thromboembolism.

The diosgenin prodrug nanoparticles with pH-responsive as a drug delivery system uniquely prevents thrombosis without increased bleeding risk

Thrombosis is the leading cause of death in patients with cardiovascular disease in the world. Current antithrombotic agent aspirin has serious side effects such as higher bleeding risk and serious gastrointestinal ulcers. Diosgenin reported in clinical research could prevent thrombosis without side effects. However, poor bioavailability and low knowledge on its molecular targets limit its clinical application. A novel prodrug with antithrombotic effect was prepared based on conjugating diosgenin derivatives to PEG with Schiff-base bond. The prodrug with long blood circulation time and satisfying safety could self-assemble into micelles in water. The prodrug micelles with pH-responsibility could targetedly release diosgenin in position of thrombus in vivo. The results indicate that the prodrug micelles without bleeding risk and histological damages prevent thrombosis by inhibiting platelet activation and apoptosis. Our studies demonstrate that the prodrug micelles could obviously enhance the efficacy in the prevention of arterial thrombus and venous thrombus than aspirin.

Oxidative stress mediated by lipid metabolism contributes to high glucose-induced senescence in retinal pigment epithelium

ABSTRACT Retinal pigment epithelium (RPE) dysfunction is thought to increase the risk of the development and progression of diabetic retinopathy (DR), the leading cause of blindness. However, the molecular mechanism behind high glucose‐induced RPE cell damage is still blurred. We reported that ARPE‐19 exposed to 25 mM glucose for 48 h did not induce apoptosis, but senescence validated by SA‐&bgr;‐Gal staining, p21 expression and cell cycle distribution. High glucose also increased oxidant species that exerted a pivotal role in senescence, which could be relieved by the treatment with antioxidant N‐acetylcysteine (NAC). The accumulation of lipid droplets and the increase of lipid oxidation were also observed in ARPE‐19 treated with high glucose. And the supplementation of free fatty acids (FFAs) indicated that lipid metabolism was associated with the generation of hydrogen peroxide (H2O2) and subsequent senescence in ARPE‐19. PI3K/Akt/mTOR signaling pathway was shown to be responsible for the accumulation of intracellular lipids by regulating fatty acid synthesis, which in turn controlled senescence. Furthermore, high glucose induced autophagy in ARPE‐19 with the treatment of glucose for 48 h, and autophagy inhibitor hydroxychloroquine (HCQ) or bafilomycin further aggravated the senescence, accompanying by an increase in oxidant species. Whereas, prolonged high glucose exposure inhibited autophagy and increased apoptotic cells. Experiments above provide evidence that lipid metabolism plays an important role in oxidative stressed senescence of RPE. Graphical abstract Figure. No Caption available. HighlightsEarly high glucose exposure induces RPE cell senescence rather than apoptosis.Fatty acid synthesis induced by high glucose through PI3K/AKT/mTOR pathway leads to lipid accumulation.Lipid oxidation contributes to high glucose‐induced RPE senescence by accumulating oxidant species.Early high glucose treatment induces protective autophagy, while prolonged high glucose exposure inhibits autophagy.

Deoxyarbutin displays antitumour activity against melanoma in vitro and in vivo through a p38-mediated mitochondria associated apoptotic pathway

Deoxyarbutin (DeoxyArbutin, dA), a natural compound widely used in skin lighting, displayed selectively cytotoxicity in vitro. In the study, we found that dA significantly inhibited viability/proliferation of B16F10 melanoma cells, induced tumour cell arrest and apoptosis. Furthermore, dA triggered its pro-apoptosis through damaging the mitochondrial function (membrane potential loss, ATP depletion and ROS overload generation etc.) and activating caspase-9, PARP, caspase-3 and the phosphorylation of p38. Treatment with p38 agonist confirmed the involvement of p38 pathway triggered by dA in B16F10 cells. The in vivo finding also revealed that administration of dA significantly decreased the tumour volume and tumour metastasis in B16F10 xenograft model by inhibiting tumour proliferation and inducing tumour apoptosis. Importantly, the results indicated that dA was specific against tumour cell lines and had no observed systemic toxicity in vivo. Taken together, our study demonstrated that dA could combate tumour in vitro and in vivo by inhibiting the proliferation and metastasis of tumour via a p38-mediated mitochondria associated apoptotic pathway.

Eriodictyol 7‑O‑β‑D glucopyranoside from Coreopsis tinctoria Nutt. ameliorates lipid disorders via protecting mitochondrial function and suppressing lipogenesis

Coreopsis tinctoria (snow chrysanthemum) has been reported to exert antihyperlipidemic effects. The present study aimed to identify the active compounds of Coreopsis tinctoria and to investigate the molecular mechanisms underlying its effects on lipid dysregulation by measuring lipid levels, reactive oxygen species, lipid peroxidation and fatty acid synthesis. The present results demonstrated that snow chrysanthemum aqueous extracts significantly reduced serum lipid levels and oxidative stress in vivo. The main compounds that were isolated were identified as flavanomarein (compound 1) and eriodictyol 7-O-β-D glucopyranoside (compound 2). Compounds 1 and 2 demonstrated potent antioxidative properties, including free radical scavenging activity, inhibition of lipid peroxidation, as well as lipid-lowering effects in human HepG2 hepatocellular carcinoma cells treated with free fatty acids (FFAs). Compound 2 was revealed to suppress the elevation of triglyceride levels and inhibit lipid peroxidation following FFA treatment. In addition, it was demonstrated to significantly reduce intracellular levels of reactive oxygen species and improve the mitochondrial membrane potential and adenosine triphosphate levels, thus protecting mitochondrial function in FFA-treated HepG2 cells. Furthermore, compound 2 markedly suppressed the protein expression levels of disulfide-isomerase A3 precursor and fatty acid synthase, thus suppressing FFA-induced lipogenesis in HepG2 cells. In conclusion, the present study identified compound 2 as one of the main active compounds in Coreopsis tinctoria responsible for its lipid-lowering effects. Compound 2 was revealed to possess antihyperlipidemic properties, exerted via reducing oxidative stress, protecting mitochondrial function and suppressing lipogenesis.