peoniflorin and 1-3-dipropyl-8-cyclopentylxanthine

Paeoniflorin (PF), the most abundant active ingredient of traditional Chinese herbal medicine Paeoniae Radix, has been recognized as a potential neuroprotectant due to its remarkable efficacy on mitigating cerebral infarction and preventing the neurodegenerative diseases. However, the precise mechanisms of PF remain incompletely understood. In this study, we first provided evidence for the protective effect of PF on hydrogen peroxide-induced injury on mouse brain microvascular endothelial bEnd.3 cells, and for transactivation of the epidermal growth factor receptor (EGFR) signal induced by PF, suggesting that EGFR transactivation might be involved in the beneficial role of PF. Next, by detecting the phosphorylation of a disintegrin and metalloprotease 17 (ADAM17) at Thr 735 and performing loss-of-function experiments with the ADAM17 inhibitor and ADAM 17-siRNA, we showed that PF-induced transactivation of EGFR and downstream ERKs and AKT signaling pathways were dependent on ADAM17. Furthermore, PF-induced phosphorylation of ADAM17 and the EGFR transactivation were inhibited by the inhibitors of adenosine A1 receptor (A1R) or Src kinase that were applied to cells prior to PF treatment, implying the involvement of A1R, and Src in the activation of ADAM17. Finally, PF reduced the cell surface level of TNF-receptor 1 (TNFR1) and increased the content of soluble TNFR1 (sTNFR1) in the culture media, indicating that PF might enhance the shedding of sTNFR1. Taken together, we conclude that A1R and Src-dependent activation of ADAM17 participates in PF-induced EGFR transactivation and TNFR1 shedding on mouse brain microvascular endothelial cells, which may contributes to the neuroprotective effects of PF.

Topics: ADAM17 Protein; Animals; Brain; Cell Line; Cell Membrane; Cell Survival; Endothelial Cells; ErbB Receptors; Glucosides; Hydrogen Peroxide; Mice; Microvessels; Models, Biological; Monoterpenes; Neuroprotective Agents; Phosphorylation; Receptor, Adenosine A1; Receptors, Tumor Necrosis Factor, Type I; Signal Transduction; Solubility; src-Family Kinases; Transcriptional Activation; Xanthines

The effects of paeoniflorin (PF), a compound isolated from Paeony radix, on neurological impairment and histologically measured infarction volume following transient and permanent focal ischemia were examined in Sprague-Dawley rats. In transient ischemia model, rats were subjected to a 1.5-h occlusion of the middle cerebral artery (MCA). The administration of PF (2.5 and 5 mg kg(-1), s.c.) produced a dose-dependent decrease in both neurological impairment and the histologically measured infarction volume. Similar results were also obtained when PF (2.5, 5, and 10 mg kg(-1), s.c.) was given in permanent ischemia model. The neuroprotective effect of PF (10 mg kg(-1), s.c.) was abolished by pretreatment of DPCPX (0.25 mg kg(-1), s.c.), a selective adenosine A1 receptor (A1R) antagonist. PF (10, 40, and 160 mg kg(-1), i.v.) had no effect on mean arterial pressure (MAP) and heart rates (HR) in the conscious rat. Additionally, PF (10(-3) mol l(-1)) had no effect on noradrenaline- (NA-) or high K+ concentration-induced contractions of isolated rabbit primary artery. In competitive binding experiments, PF did not compete with the binding of [3H]DPCPX, but displaced the binding of [3H]NECA to the membrane preparation of rat cerebral cortex. This binding manner was distinguished from the classical A1R agonists. The results demonstrated that activation of A1R might be involved in PF-induced neuroprotection in cerebral ischemia in rat. However, PF had no 'well-known' cardiovascular side effects of classical A1R agonists. The results suggest that PF might have the potential therapeutic value as an anti-stroke drug.

Topics: Adenosine-5'-(N-ethylcarboxamide); Animals; Benzoates; Binding, Competitive; Bridged-Ring Compounds; Cerebral Cortex; Disease Models, Animal; Dose-Response Relationship, Drug; Glucosides; Infarction, Middle Cerebral Artery; Inhibitory Concentration 50; Ischemic Attack, Transient; Male; Monoterpenes; Neuroprotective Agents; Paeonia; Plant Roots; Rats; Rats, Sprague-Dawley; Receptor, Adenosine A1; Time Factors; Xanthines

The present study investigated the role of adenosine in the stimulatory action of paeoniflorin on in vitro glucose transport. Paeoniflorin increased the uptake of a radiolabeled, non-metabolizable glucose derivative into isolated white adipocytes of Wistar rat in a concentration-dependent manner and this action was abolished by the antagonist, 8-cyclopentyltheophylline, at concentrations sufficient to block the adenosine A 1 receptor. However, paeoniflorin failed to displace the binding of [3H]-8-cyclopentyl-1,3-dipropylxanthine in the isolated cerebrocortex of Wistar rat. Direct activation of the adenosine A 1 receptor does not seem to be responsible for the action of paeoniflorin. The stimulatory effect of paeoniflorin on radioactive glucose uptake was abolished in isolated rat white adipocytes pre-incubated with the adenosine deaminase at concentrations sufficient to metabolize endogenous adenosine. Mediation of endogenous adenosine in the action of paeoniflorin was further supported by the assay of adenosine released into the medium from rat white adipocytes incubated with paeoniflorin. These findings suggest that paeoniflorin could induce the release of adenosine from isolated rat white adipocytes and the released adenosine may activate the adenosine A 1 receptor to enhance glucose uptake.

Topics: Adenosine; Adipocytes; Animals; Benzoates; Bridged-Ring Compounds; Carbon Radioisotopes; Deoxyglucose; Dose-Response Relationship, Drug; Glucose; Glucosides; Male; Monoterpenes; Paeonia; Phytotherapy; Plant Extracts; Rats; Rats, Wistar; Xanthines

We examined the effects of paeoniflorin on adenosine A1 receptor-mediated memory disturbance in the mouse passive avoidance test and inhibition of long-term potentiation (LTP) in the rat hippocampal CA1 region. The pretraining administration of the selective adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) significantly impaired the retention performance determined 24 h after the training test. The intraperitoneal injections of paeoniflorin and the adenosine A1 receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) significantly attenuated the deficit in retention performance caused by CPA. The in vitro studies revealed that adenosine (1 and 10 microM) dose dependently reduced both the population spike (PS) amplitudes and the tetanic stimulation-induced LTP in the hippocampus. DPCPX, at the concentration (0.1 microM) that had no effect on PS amplitudes or LTP induction, significantly reversed the suppressive effects of adenosine on both indices. Paeoniflorin also dose dependently reversed 10 microM adenosine-induced suppression of LTP but had no effect on PS reduced by adenosine. These results suggest that paeoniflorin ameliorates memory disruption mediated by adenosine A1 receptor and that modulation of adenosine-mediated inhibition of LTP in the hippocampus is implicated in its beneficial effect on learning and memory impairment in rodents.

Topics: Adenosine; Animals; Avoidance Learning; Benzoates; Bridged-Ring Compounds; Glucosides; Hippocampus; Long-Term Potentiation; Male; Mice; Monoterpenes; Rats; Rats, Wistar; Receptors, Purinergic P1; Xanthines

1. Intravenous injection of paeoniflorin, a glycoside purified from the root of Paeonia lactiflora, reversed guanethidine-induced hypotension in Wistar rats. 2. Pretreatment with the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine inhibited this effect of paeoniflorin in a dose-dependent manner. 3. The action of paeoniflorin was not modified by 8-(p-sulfophenyl)theophylline, the polar antagonist of the adenosine A1 receptor, which is not able to enter the central nervous system. 4. We conclude that paeoniflorin can reverse guanethidine-induced hypotension via activation of adenosine A1 receptors in the brain of Wistar rats.

Topics: Adrenergic Agents; Animals; Anti-Inflammatory Agents, Non-Steroidal; Benzoates; Blood Pressure; Bridged-Ring Compounds; Dose-Response Relationship, Drug; Glucosides; Guanethidine; Hypotension; Male; Monoterpenes; Plants, Medicinal; Purinergic P1 Receptor Antagonists; Rats; Rats, Wistar; Receptors, Purinergic P1; Xanthines

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.

Topics: Adipocytes; Alkaloids; Animals; Anti-Inflammatory Agents, Non-Steroidal; Benzoates; Benzophenanthridines; Bridged-Ring Compounds; Cell Membrane; Cytosol; Drug Interactions; Enzyme Inhibitors; Glucose Transporter Type 4; Glucosides; Isoenzymes; Monosaccharide Transport Proteins; Monoterpenes; Muscle Proteins; Phenanthridines; Phosphorylation; Protein Kinase C; Protein Kinase C beta; Purinergic P1 Receptor Agonists; Rats; Rats, Wistar; Signal Transduction; Stimulation, Chemical; Xanthines