Inhibition of resveratrol glucosides (REs) on advanced glycation endproducts (AGEs) formation: inhibitory mechanism and structure-activity relationship.

The study on inhibitory effects of resveratrol glucosides (REs) on advanced glycation endproducts (AGEs) formation is still unmet. Herein, for the first time, the antiglycation activities of five REs in the fetal bovine serum proteins (FBS)/fructose system were evaluated, and its structure-activity relationship and antiglycation mechanism were further explored. These REs showed remarkable inhibition toward AGEs formation. Among them, Piceatannol-3'-O-glucoside (PG) exhibited highest antiglycation activity as reflected in approximately 80% inhibition of fluorescent AGEs at the concentration of 1.0 mM. The structure-activity relationship analysis indicated that glucoside attached to the B ring of resveratrol displays a superior antiglycation activity. Moreover, the results of antiglycation mechanism showed that the antiglycation activity of REs was proportional to their antioxidant capacity and methylglyoxal (MGO) trapping capacity. Therefore, the REs are promising candidates worthy of further exploration for preventing AGEs accumulation in vivo, thereby treating AGEs-associated diseases.

[Role of mitochondrial permeability transition pore in mediating the inhibitory effect of gastrodin on oxidative stress in cardiac myocytes in vitro].

OBJECTIVE: To explore the role of mitochondrial permeability transition pore (mPTP) in mediating the protective effect of gastrodin against oxidative stress damage in H9c2 cardiac myocytes. METHODS: H9c2 cardiac myocytes were treated with H2O2, gastrodin, gastrodin+H2O2, cyclosporin A (CsA), or CsA+gas+H2O2 group. MTT assay was used to detect the survival ratio of H9c2 cells, and flow cytometry with Annexin V-FITC/PI double staining was used to analyze the early apoptosis rate after the treatments. The concentration of ATP and level of reactive oxygen species (ROS) in the cells were detected using commercial kits. The mitochondrial membrane potential of the cells was detected with laser confocal microscopy. The expression of cytochrome C was detected with Western blotting, and the activity of caspase-3 was also assessed in the cells. RESULTS: Gastrodin pretreatment could prevent oxidative stress-induced reduction of mitochondrial membrane potential, and this effect was inhibited by the application of CsA. Gastrodin significantly lowered the levels of ROS and apoptosis-related factors in H2O2-exposed cells, and such effects were reversed by CsA. CsA significantly antagonized the protective effect of gastrodin against apoptosis in H2O2-exposed cells. CONCLUSIONS: Gastrodin prevents oxidative stress-induced injury in H9c2 cells by inhibiting mPTP opening to reduce the cell apoptosis.

Paeoniflorin Promotes Non-rapid Eye Movement Sleep via Adenosine A1 Receptors.

Paeoniflorin (PF, C23H28O11), one of the principal active ingredients of Paeonia Radix, exerts depressant effects on the central nervous system. We determined whether PF could modulate sleep behaviors and the mechanisms involved. Electroencephalogram and electromyogram recordings in mice showed that intraperitoneal PF administered at a dose of 25 or 50 mg/kg significantly shortened the sleep latency and increased the amount of non-rapid eye movement (NREM). Immunohistochemical study revealed that PF decreased c-fos expression in the histaminergic tuberomammillary nucleus (TMN). The sleep-promoting effects and changes in c-fos induced by PF were reversed by 8-cyclopentyl-1,3-dimethylxanthine (CPT), an adenosine A1 receptor antagonist, and PF-induced sleep was not observed in adenosine A1 receptor knockout mice. Whole-cell patch clamping in mouse brain slices showed that PF significantly decreased the firing frequency of histaminergic neurons in TMN, which could be completely blocked by CPT. These results indicate that PF increased NREM sleep by inhibiting the histaminergic system via A1 receptors.

Paeoniflorin exerts analgesic and hypnotic effects via adenosine A1 receptors in a mouse neuropathic pain model.

RATIONAL: Neuropathic pain is frequently comorbid with sleep disturbances. Paeoniflorin, a main active compound of total glucosides of paeony, has been well documented to exhibit neuroprotective bioactivity. OBJECTIVE: The present study evaluated effects of paeoniflorin on neuropathic pain and associated insomnia and the mechanisms involved. METHODS: The analgesic and hypnotic effects of paeoniflorin were measured by mechanical threshold and thermal latency, electroencephalogram (EEG) and electromyogram, and c-Fos expression in a neuropathic pain insomnia model. RESULTS: The data revealed that paeoniflorin (50 or 100 mg/kg, i.p.) significantly increased the mechanical threshold and prolonged the thermal latency in partial sciatic nerve ligation (PSNL) mice. Meanwhile, paeoniflorin increased non-rapid eye movement (NREM) sleep amount and concomitantly decreased wakefulness time. However, pretreatment with l,3-dimethy-8-cyclopenthylxanthine, an adenosine A1 receptor (R, A1R) antagonist, abolished the analgesic and hypnotic effects of paeoniflorin. Moreover, paeoniflorin at 100 mg/kg failed to change mechanical threshold and thermal latency and NREM sleep in A1R knockout PSNL mice. Immunohistochemical study showed that paeoniflorin inhibited c-Fos overexpression induced by PSNL in the anterior cingulate cortex and ventrolateral periaqueductal gray. CONCLUSIONS: The present findings indicated that paeoniflorin exerted analgesic and hypnotic effects via adenosine A1Rs and might be of potential use in the treatment of neuropathic pain and associated insomnia.

Empagliflozin for the treatment of type 2 diabetes.

INTRODUCTION: Despite the availability of numerous anti-diabetes drugs and treatment guidelines, many patients with type 2 diabetes mellitus (T2DM) do not reach recommended targets for glycemic control. There remains an unmet need for effective and well-tolerated anti-diabetes agents that can be used as monotherapy or in combination with other therapies to improve glycemic control in patients with T2DM. Sodium glucose cotransporter 2 (SGLT2) inhibitors are a new class of treatment for T2DM that reduce hyperglycemia by reducing renal glucose reabsorption and thereby increasing urinary glucose excretion. AREAS COVERED: This paper reviews the pharmacokinetic and pharmacodynamic properties of the SGLT2 inhibitor empagliflozin , the results of clinical trials investigating the efficacy of empagliflozin given as monotherapy or as add-on therapy on glycemic control, body weight, and blood pressure in patients with T2DM, and the safety and tolerability profile of empagliflozin. EXPERT OPINION: Empagliflozin offers good glycemic efficacy, weight loss, blood pressure reduction, and a low risk of hypoglycemia. These attributes, coupled with the ability to be used in virtually any combination with other anti-diabetes agents and at any stage in the disease process, provide a welcome new agent to our armamentarium of drugs to help manage T2DM.

[Salidroside via ERK1/2 and PI3K/AKT/mTOR signal pathway induces mouse bone marrow mesenchymal stem cells differentiation into neural cells].

To investigate the role of the extracellular signal-regulated kinase (ERK1/2) and PI3K/AKT/ mTOR signal pathway inducing bone marrow mesenchymal stem cells (BMSCs) differentiation into neural cells, mouse bone marrow-derived mesenchymal stem cell lines D1 cells were used as research object. And they were divided into control groups and salidroside (SD) groups. Different concentrations (5, 25, 50, 100 and 200 microg x mL(-1) of SD were used and SD (100 microg x mL(-1)) was used to induce at different time (0.5, 1, 3, 6, 9, 12, 24, 48 and 72 h). The immunofluorescence staining chemical technology, real-time PCR and Western blotting were used to detect the positive rates of NSE, MAP2, beta-Tubulin III, NES, GFAP and the expression levels of beta-Tubulin III, NSE, ERK1/2, AKT. The expression of ERK1/2 and NSE was detected when the ERK1/2 and PI3K/AKT/ mTOR signal pathway was blocked by PD98059 and LY294002. It indicated that the positive rates of NSE, MAP2, beta-Tubulin III, NES and GFAP were gradually enhanced with time increased. The expression level of NSE and beta-Tubulin III protein were significantly higher than those in control groups (P < 0.01). The expression of ERK1/2, AKT mRNA and protein were higher with concentration and time increased. When the ERK1/2 and PI3K/AKT/mTOR signal pathway were blocked, the expression levels of NSE, NES and beta-Tubulin III mRNA and NSE protein were inhibited significantly. It points out that SD can stimulate the ERK1/2 and PI3K/AKT/mTOR signal pathway to promote BMSCs differentiation into neural cells.

Upregulation of heme oxygenase-1 by acteoside through ERK and PI3 K/Akt pathway confer neuroprotection against beta-amyloid-induced neurotoxicity.

Our previous study has shown that acteoside, an antioxidative phenylethanoid glycoside, protect against beta-amyloid (Aß)-induced cytotoxicity in vitro. However, the precise protective mechanisms remains unclear. Heme oxygenase-1 (HO-1) is a crucial factor in the response to oxidative injury, protecting neurons against Aß-induced injury. In the present study we examined to determine whether acteoside upregulates HO-1 expression, and thereby protects PC12 cells against Aß-induced cell death. It was revealed that acteoside is an activator of Nrf2 and inducer of HO-1 expression. We showed that acteoside increased HO-1 expression in vitro and in vivo. Acteoside treatment resulted in nuclear translocation of the transcription factor NF-E2-related factor 2 (Nrf2). Acteoside activated both ERK and PI3 K/Akt, and treatments with the specific ERK inhibitor PD98059, the PI3 K inhibitor LY294002, and the specific Nrf2 siRNA suppressed the acteoside-induced HO-1 expression. The HO-1 inhibitor ZnPP, PD98059, and LY294002 markedly abolished the neuroprotective effect of acteoside against Aß-induced neurotoxicity. Taken together, these results demonstrate that acteoside is an activator of Nrf2 and inducer of HO-1 expression. We also showed that acteoside increased HO-1 expression through activation of ERK and PI3 K/Akt signal pathways in vitro. Upregulation of HO-1 by acteoside may involve in the neuroprotection against Aß-induced neurotoxicity.

Protective effect of a molecular chaperone inducer, paeoniflorin, on the HCl- and ethanol-triggered gastric mucosal injury.

AIMS: We previously found that paeoniflorin, a major constituent of Paeonia lactiflora Pall, could induce heat shock proteins (HSPs) in cultured mammalian cells without apparent toxicity (Yan et al. 2004). We here investigated the induction of HSPs by paeoniflorin in mouse stomach and the effect of paeoniflorin on the HCl- and ethanol-triggered gastric mucosal injury in mouse. MAIN METHODS: Paeoniflorin and quercetin were intraperitoneally administered in mouse and Hsp70 and other proteins in mouse tissues were detected by western blotting. KEY FINDINGS: The intraperitoneal administration of paeoniflorin clearly induced Hsp70 in mouse stomach, and paeoniflorin had a protective effect on the HCl- and ethanol-triggered gastric mucosal injury. When quercetin was injected before paeoniflorin administration, the induction of Hsp70 was suppressed and the protective effect of paeoniflorin was also diminished. Thus, the expression level of Hsp70 was well correlated with the extent of protection against irritant-induced gastric mucosal injury. Oral injection of HCl activated nuclear factor kappa B (NF-κB) and elicited the expression of cyclooxygenase-2 (COX-2) in gastric mucosa. Prior administration of paeoniflorin, however, suppressed these effects. No apparent systemic side effect of paeoniflorin has been observed so far. Hsp70 was also induced in the liver, heart, and brain by paeoniflorin. SIGNIFICANCE: From these results, it is suggested that paeoniflorin and paeoniflorin-containing herbal medicines might be used clinically as HSP inducers for the prevention and treatment of diseases associated with protein conformation and of various other pathological states, such as stress ulcers and irritant- or ischemia-induced injuries.

The effects of daidzin and its aglycon, daidzein, on the scopolamine-induced memory impairment in male mice.

In this study, the effect of daidzin or daidzein isolated from Pueraria lobata on the memory impairments induced by scopolamine was assessed in male mice using the passive avoidance and the Morris water maze tasks. Administration of daidzin (5 mg/kg) or daidzein (5 mg/kg) significantly reversed the scopolamine (1 mg/kg)-induced cognitive impairments in male mice as evidenced by the passive avoidance test (p < 0.05) and on the Morris water maze test (p < 0.05). Moreover, the ameliorating effects of daidzin or daidzein were antagonized by tamoxifen (1 mg/kg), the nonspecific estrogen receptor antagonist. These results indicate that daidzin or daidzein may be useful in cognitive impairment induced by cholinergic dysfunction, and this beneficial effect is mediated, in part, via estrogen receptor.

Tetrahydroxystilbene glucoside ameliorates diabetic nephropathy in rats: involvement of SIRT1 and TGF-ß1 pathway.

Oxidative stress caused by hyperglycaemia is believed to be a major molecular mechanism underlying diabetic nephropathy. 2,3,5,4'-tetrahydroxystilbene-2-O-ß-d-glucoside (TSG), an active component extract from Polygonum multiflorum Thunb, exhibits antioxidative and anti-inflammatory effects. Possible protective mechanisms of TSG on diabetic nephropathy were investigated in rats and cultured rat mesangial cells. Total cholesterol and triglyceride levels of diabetic rats were clearly increased and these increases were diminished by treatment with TSG. Treatment of diabetic rats with TSG also significantly reduced blood urea nitrogen, creatinine, 24 h urinary protein levels, and kidney weight/body weight. The activities of superoxide dismutase and glutathione peroxidase in renal homogenate were increased markedly, whereas malonaldehyde levels were decreased significantly in TSG-treated diabetic rats. TSG dramatically inhibited diabetes-induced overexpression of TGF-ß1 and COX-2, and restored the decrease of SIRT1 expression in diabetic rats. High glucose-induced overexpression of TGF-ß1 in cultured mesangial cells was significantly inhibited, whereas the decease of SIRT1 expression was restored by pretreatment of TSG. Nicotinamide, the inhibitor of SIRT1, partially relieved the inhibitory effect of TSG on TGF-ß1 expression under high glucose condition. These findings indicate that the protective mechanisms of TSG on diabetic nephropathy are involved in the alleviation of oxidative stress injury and overexpression of COX-2 and TGF-ß1, partially via activation of SIRT1.

The action of bromoconduritol on ER glucosidase II.

Bromoconduritol (6-bromo-3,4,5-trihydroxycyclohex-1-ene; BCD) has been known as an inhibitor of glucosidase II (G-II), which plays pivotal roles in glycoprotein processing and folding in the ER. Previous works suggested that BCD specifically inhibits the cleavage of the innermost glucose (Glc) among two alpha1-3 linked Glc residues (cleavage-2). This study addressed the mode of BCD's inhibition toward G-II by using fluorescently labeled substrates. Our analysis clarified that BCD inhibits both cleavage-1 and cleavage-2 activities of G-II. However, the inhibitory activity toward cleavage-2 was 6-fold higher than that toward cleavage-1. Inhibition against both of these activities was retained after dialysis, supporting that BCD exhibits inhibition through irreversible binding to G-II.

[Resistant effect of water decoction of root of Crataegus cuneata on male infertility induced by GTW in rats].

OBJECTIVE: To observe the effects of water decoction of the root of Crataegus cuneata on infertility induced by multi-glucoside of Tripterygium wilfordii (GTW) in rats. METHOD: Male adult rats were randomly divided into five groups, which were treated via gastric gavage of distilled water (1 mL x kg(-1)) , solution of GTW (10 mg x kg(-1)) and three doses of water decoction of root of C. cuneata (1.8, 5.4, 18 g x kg(-1)) + GTW (10 mg x kg(-1)), respectively. 8 weeks later, GTW was stopped and the decoction and water continued for another 4 weeks. And then, all the male rats were copulated with adult female rats. The rates of pregnancy, average numbers of embryos and luteum of female rats, relative weights of reproductive organs, sperm counts, sperm motility and viability were compared among all the groups. The histology and ultrastructure of testis and epididymis were observed, while the concentrations of follicle stimulating hormone (FSH), luteinizing hormone (LH) and testostorone (T) in serum and T in testicular homogenate were detected by radioimmunoassay. RESULT: Compared with those in GTW model group, the embryo numbers, the relative weight of testis and epididymis and sperm counts and motility in C. cuneata groups were increased obviously (P < 0.05). After treatment, the morphological damages of seminiferous tubules and sperms were recovered, while concentrations of T in testicular homogenate were also significantly increased (P < 0.01). CONCLUSION: C. cuneata could relieve the reproductive lesions induced by GTW, and hence improve the uberty of the male infertile model rats.

Restorative effect of repetitive administration of Shaoyao-Gancao-tang on bioavailability of paeoniflorin reduced by antibacterial synthetic drugs treatment in rats.

Paeoniflorin (PF) is an active glucoside in Shaoyao (peony root), and is transformed into an antispasmodic metabolite, paeonimetabolin-I (PM-I), by intestinal bacteria in the gut after oral administration of Shaoyao or Shaoyao-Gancao-tang (SGT, Shakuyaku-Kanzo-To in Japanese). SGT is a pain-relieving traditional Chinese formulation (Kampo-medicine in Japanese) and is often used together with antibacterial synthetic drugs, such as amoxicillin and metronidazole (AMPC-MET), in peptic ulcer therapy. Since the bioavailability of PF in SGT has been reported to be significantly reduced by co-administered antibacterial drugs, we investigated how to minimize this reducing effect of antibacterial treatment in the present study. We found that repetitive administration of SGT starting 24 h after AMPC-MET treatment rapidly restored the plasma PM-I concentration from SGT reduced by AMPC-MET, due to its restorative effect on the decreased PF-metabolizing activity of intestinal bacteria in rat feces. The present findings suggest that it may be clinically useful to administer SGT repetitively, starting 1 or 2 d after treatment with a mixture of AMPC-MET during their combination therapy, to accelerate the recovery of the reduced bioavailability of PF in SGT. Similar administration regimens may also be useful in other combination therapies involving traditional Chinese formulations and antibacterial synthetic drugs to ensure the efficacy of the bioactive glycosides in the formulations.

The beta-D-glucoside and sodium-dependent glucose transporter 1 (SGLT1)-inhibitor phloridzin is transported by both SGLT1 and multidrug resistance-associated proteins 1/2.

Phloridzin, a glucoside of the flavonoid-like polyphenol phloretin, has long been known to be a specific nontransportable inhibitor of the sodium-dependent glucose transporter SGLT1. The objective of this study was to determine whether efflux by multidrug resistance-associated protein (MRP) transporters might have masked the absorption by SGLT1 in previous studies. Various cells used as transport models were incubated with phloridzin (50 microM) in the absence and presence of 50 microM 3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid (MK-571), a highly selective MRP1/MRP2 inhibitor, and the cellular uptake of phloridzin was measured by high performance liquid chromatography. The uptake of phloridzin by SGLT1-transfected Chinese hamster ovary (CHO) (G6D3) cells was 1.7-fold higher than that by parent CHO cells (p < 0.01). In the presence of MK-571, the uptake of phloridzin by CHO cells increased 3.7-fold (p < 0.001). MK-571 caused an 8.0-fold increase in the uptake of phloridzin by G6D3 cells (p < 0.0001). Thus, in the absence of MRP1 efflux, transport of phloridzin by SGLT1 was clearly demonstrated. Similar results were obtained for the glycosides of the flavonoids quercetin, genistein, and diosmetin. A significantly lower accumulation of phloridzin in MRP2-transfected Madin-Darby canine kidney (MDCK) cells compared with parent MDCK cells demonstrated that phloridzin was a substrate also for MRP2 (p < 0.05). This conclusion was further strengthened when MK-571 increased the uptake by MRP2-MDCK cells as much as 3.6-fold (p < 0.01). These results demonstrate that phloridzin, in contrast to previous notions, is transported by SGLT1. In addition, they demonstrate that this and other flavonoid glycosides unexpectedly are efficiently effluxed by both MRP1 and MRP2.

Ability of the exopolymer excreted by Pseudoalteromonas antarctica NF3, to coat liposomes and to protect these structures against octyl glucoside.

The ability of an exopolymer of glycoproteic character (GP) excreted by a new gram-negative specie Pseudoalteromonas antarctica NF3, to coat phosphatidylcholine (PC) liposomes and to protect these bilayers against the action of the nonionic surfactant octyl glucoside (OG) has been investigated. TEM micrographs of freeze-fractured liposome/GP aggregates reveal that the addition of GP to liposomes led to the formation of a covering structure (polymer adsorbed onto the bilayers) that tightly coated PC bilayers. The complete coating was already achieved when the proportion of GP assembled with liposomes was approximately 10% (wt% vs total PC). Higher GP amounts resulted in a growth of this coating structure which exhibited at the highest GP proportion in the system (31% of assembled GP) a multilayered structure. An increasing resistance of PC liposomes to be affected by OG both at sublytic and lytic levels occurred as the proportion of GP in the system rose; this protective effect being more effective when the proportion of assembled GP was 10-20% in weight. Thus, although a direct dependence was found between the growth of the enveloping structure and the resistance of the coated liposomes to be affected by OG, the best protection occurred when the proportion of assembled GP was about 10 wt%.

Stimulatory effect of paeoniflorin on adenosine A-1 receptors to increase the translocation of protein kinase C (PKC) and glucose transporter (GLUT 4) in isolated rat white adipocytes.

In an attempt to understand the subcellular signals after activation of adenosine A-1 receptors, paeoniflorin was employed to incubate with rat white adipocytes in vitro. Translocation of protein kinase C (PKC) beta-subtype from cytosol to membrane was enhanced by an incubation with paeoniflorin in a concentration-dependent manner similar to that of porcine insulin. Also, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) inhibited this action of paeoniflorin in a concentration-related fashion and it markedly attenuated the action of paeoniflorin at a concentrations sufficient to block the action of adenosine. Moreover, chelerythrine inhibited the paeoniflorin-stimulated translocation of PKC in a way similar to that stimulated by porcine insulin. Subcellular inhibition is considered because stimulation of porcine insulin was not modified by DPCPX at concentrations sufficient to block adenosine A-1 receptors. Similar results were also observed in adipocytes regarding the translocation of glucose transporter (GLUT4) from cytosol to membrane. Thus, we found that paeoniflorin can activate adenosine A-1 receptors to increase the translocations of PKC and GLUT4, two major signals for glucose uptake, from cytosol to membrane of the white adipocytes in rats.

Time course and inhibition of stavaroside K, veratramine and cevine-induced hemolysis by other pregnane glycosides and Veratrum alkaloids.

Stavaroside K, veratramine and cevine induce hemolysis, whereas 7 other pregnane stavarosides and 8 Veratrum alkaloids are not hemolytic. On the other hand, erythrocytes pretreated or incubated with low concentrations of stavarosides D-F or with the 8 other Veratrum alkaloids were resistant to hemolysis induced by authentic saponin, stavaroside K, cevine or veratramine. Veratridine, zygadenine and angeloylzygadenine (the known Na-Channel-Gate toxins) revealed the most potent reduction of hemolytic activity.

Chemical constituents of Gentianaceae XIX: CNS-depressant effects of swertiamarin.

CNS activity of swertiamarin, a secoiridoid glucoside from Swertia chirata, was evaluated. An apparent anomaly, associated with the unanticipated finding that the alcoholic extracts (excluding mangiferin) of S. chirata significantly reversed the mangiferin-induced CNS-stimulating effects in albino mice and rats, was resolved. The results indicate that swertiamarin and mangiferin antagonize each other in vivo and thereby reverse their CNS effects.