Hai Niu

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.

Robinetinidol-(4β→8)-epigallocatechin 3-O-gallate, a galloyl dimer prorobinetinidin from Acacia mearnsii De Wild, effectively protects human neuroblastoma SH-SY5Y cells against acrolein-induced oxidative damage.

Acrolein is a highly electrophilic alpha, beta-unsaturated aldehyde to which humans are exposed in many situations and has been implicated in neurodegenerative diseases such as Alzheimers disease. A galloyl dimer prorobinetinidin from Acacia mearnsii De Wild, robinetinidol-(4beta-->8)-epigallocatechin 3-O-gallate (REO), has antioxidant properties and could protect brain against acrolein-induced oxidative damage. In this study, the molecular basis of acrolein-induced cytotoxicity in human neuroblastoma SH-SY5Y cells and the modulating effects of REO were examined. Our results indicate that REO protects SH-SY5Y cells from acrolein-induced damage by the attenuation of reactive oxygen species, the remediation of NADPH oxidase activity, the enhancement of the glutathione system, and the prevention of protein oxidation/nitration and lipid peroxidation. In order to determine the effects of REO on mitochondrial events, mitochondrial membrane potentials (Delta Psim) and caspase cascades downstream of mitochondria were assessed. REO inhibited the collapse of Delta Psi m, suggesting that REO reduces the mitochondrial dysfunction associated with acrolein treatment. REO also inhibited caspase-3 activation, which can be triggered by mitochondrial malfunctions. Furthermore, REO induced a significant reduction in the level of phospho-JNK, which is known as an apoptotic mediator in acrolein-induced neuronal cell death. Our results indicate that REO protects neurons from the deleterious effects of acrolein via the attenuation of oxidative stress, NADPH oxidase activity, GSH depletion, protein oxidation/nitration, lipid peroxidation, mitochondrial dysfunction, JNK activation, and caspase activity. These findings suggest that REO could be potentially useful as a protective agent for people exposed to acrolein.

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.

One compound of saponins from Disocorea zingiberensis protected against experimental acute pancreatitis by preventing mitochondria-mediated necrosis

Acute pancreatitis (AP) is a painful inflammatory disorder of the exocrine pancreas, ranking as the most common gastrointestinal reasons for hospitalization with no specific therapy currently. Diosgenyl saponins extracted from natural products and diosgenin or its derivatives have been shown to exert anti-inflammatory effects in various diseases. However, the therapeutic effects of diosgenyl saponins from Dioscorea zingiberensis C. H. Wright in AP have not yet been determined. Five compounds were extracted and screened for taurocholate-induced necrosis in mouse pancreatic acinar cells. Particularly, 26-O-β-d-glucopyranosyl-3β, 22α, 26-trihydroxy-25(R)-furosta-5-en-3-O-[α-L-rhamnopyranosyl-(1 → 4)]-β-d-glucopyranoside (compound 1) exhibited the best protective effects with no toxicity observed. Next, we showed compound 1 concentration-dependently inhibited necrotic cell death pathway activation and 2.5 mM compound 1 also prevented the loss of mitochondrial membrane potential, adenosine triphosphate production, and reactive oxygen species generation in mouse pancreatic acinar cells. Finally, we showed compound 1 protected against three clinically representative murine models of AP and significantly improved pancreatitis-associated acute lung injury. These data provide in vitro and in vivo evidence that one compound of diosgenyl saponins can be potential treatment for AP. This study suggests natural saponins may serve as fruitful sources for exploring/identifying potential therapies for inflammatory diseases.

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.

Dihydrodiosgenin protects against experimental acute pancreatitis and associated lung injury through mitochondrial protection and PI3Kγ/Akt inhibition

Acute pancreatitis (AP) is a painful and distressing disorder of the exocrine pancreas with no specific treatment. Diosgenyl saponins extracted from from Dioscorea zingiberensis C. H. Wright have been reported to protect against experimental models of AP. Diosgenin, or its derivatives are anti‐inflammatory in various conditions. However, the effects of diosgenin and its spiroacetal ring opened analogue, dihydrodiosgenin (Dydio), on AP have not been determined.