Resveratrol reduction of infarct size in Long-Evans rats subjected to focal cerebral ischemia.

Resveratrol is found in a wide variety of plant species. It is present in the seeds and skin of grapes and constitutes one of the major components of red wine. This study was undertaken to evaluate whether resveratrol could effectively suppress infarct size from the damaging effects of focal cerebral ischemia. The middle cerebral artery was occluded for 1 hr and 24 hr reperfusion in anesthetized Long-Evans rats. In pretreatment or treatment groups, resveratrol, at dosages of 10(-6), 10(-7), 10(-8) and 10(-9) g/kg, was intravenous injected 15 minutes before middle cerebral artery (MCA) occlusion or when the common carotid arteries clips were removed respectively. Pretreatment or treatment of resveratrol (10(-6), 10(-7), 10(-8) and 10(-9) g/kg) did not produce any changes in pH, blood gases, heart rate or mean arterial blood pressure, but it significantly reduced the total volume of infarction at the doses 10(-6) and 10(-7) g/kg. Our study suggests resveratrol is a potent neuroprotective agent in focal cerebral ischemia. Its beneficial effects may be related to its anti-platelet aggregation activity, vasodilating effect, antioxidant property or by all mechanisms together.

Beneficial effects of astringinin, a resveratrol analogue, on the ischemia and reperfusion damage in rat heart.

Oxidative stress plays an important role in the pathogenesis of myocardial ischemia and infarction. Antioxidants might then be beneficial in the prevention of these diseases. Astringinin (3,3',4',5-tetrahydroxystilbene), a resveratrol (3,4',5-trihydroxystilbene) analogue with considerably higher antioxidative activity and free radical scavenging capacity, was introduced to examine its cardioprotective effects in ischemia or ischemia-reperfusion (I/R) rats. In the present study, the left main coronary artery was occluded by the following procedures: (i) 30 min occlusion, (ii) 5 min occlusion followed by 30 min reperfusion, and (iii) 4 h occlusion. Animals were infused with and without astringinin before coronary artery occlusion. Mortality, and the severity of ischemia- and I/R-induced arrhythmias were compared. Pretreatment of astringinin dramatically reduced the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) during either ischemia or I/R period. Astringinin at 2.5 x 10(-5) and 2.5 x 10(-4) g/kg completely prevented the mortality of animals during ischemia or I/R. During the same period, astringinin pretreatment also increased nitric oxide (NO) and decreased lactate dehydrogenase (LDH) levels in the carotid blood. In animals subjected to 4 h coronary occlusion, the cardiac infarct size (expressed as a percentage of occluded zone) was reduced from 44.4 + or - 4.1% to 19.1 + or - 2.4% by astringinin (2.5 x 10(-4) g/kg). We conclude that, astringinin is a potent antiarrhythmic agent with cardioprotective activity in ischemic and ischemic-reperfused rat heart. The beneficial effects of astringinin in the ischemic and ischemic-reperfused hearts may be correlated with its antioxidant activity and upregulation of NO production.

Cardioprotective effect of resveratrol, a natural antioxidant derived from grapes.

BACKGROUND: The major objective of the present study was to examine the cardioprotective effect of resveratrol, an antioxidant presents in red wines, in the rat after ischemia and ischemia-reperfusion (I-R). METHODS: The left main coronary artery was occluded for 30 or 5 min followed by a 30-min reperfusion in anesthetized rats. Animals were preinfused with and without resveratrol before occlusion and the severity of ischemia- and I-R-induced arrhythmias and mortality were compared. RESULTS: Resveratrol pretreatment had no effect on ischemia-induced arrhythmias nor on mortality. In contrast, a dramatic protective effects were observed against I-R-induced arrhythmias and mortality. Resveratrol pretreatment both reduced the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF). During the same period, resveratrol pretreatment also increased nitric oxide (NO) and decreased lactate dehydrogenase levels in the carotid blood. CONCLUSIONS: Resveratrol is a potent antiarrhythmic agent with cardioprotective properties in I-R rats. The cardioprotective effects of resveratrol in the I-R rats may be correlated with its antioxidant activity and upregulation of NO production.

Antiarrhythmic effect of magnolol and honokiol during acute phase of coronary occlusion in anesthetized rats: influence of L-NAME and aspirin.

This study was designed to evaluate the in vivo effect of magnolol and honokiol on the acute phase of coronary ligation in the presence of nitric oxide inhibitor (L-NAME) or cyclooxygenase inhibitor (aspirin). After Sprague-Dawley rats were anesthetized with urethane, the changes of ventricular arrhythmia induced by coronary ligation for 30 min were determined with or without pretreatment with study medications. The incidence and duration of ventricular arrhythmia were significantly reduced after intravenous pretreatment (15 min before coronary ligation) with 10(-7) g/kg magnolol or 10(-7) g/kg honokiol. However, the antiarrhythmic effect of magnolol or honokiol could be abolished with the pretreatment of 1 mg/kg L-NAME, but not with pretreatment of 100 mg/kg aspirin. The abolishment of the myocardial beneficial effect of magnolol and honokiol by L-NAME, instead of aspirin, suggests an involvement of an increased nitric oxide synthesis in the protection offered by magnolol and honokiol against arrhythmia during myocardial ischemia.

cGMP-elevating agents suppress proliferation of vascular smooth muscle cells by inhibiting the activation of epidermal growth factor signaling pathway.

BACKGROUND: Abnormal proliferation of vascular smooth muscle cells (VSMC) is a key event in the pathogenesis of atherosclerosis and many vascular diseases. It is known that nitric oxide released from the endothelium participates in the regulation of VSMC proliferation via a cyclic 3',5'-guanosine monophosphate (cGMP)-mediated mechanism. In a series of experiments, sodium nitroprusside (SNP) and A02131-1 were evaluated for their antiproliferative effect and the mechanism of their cGMP-elevating action. METHODS AND RESULTS: The effect of SNP and A02131-1 on epidermal growth factor (EGF)-stimulated proliferation of rat aortic smooth muscle cells (VSMC) was examined. Cell proliferation was measured in terms of [3H]thymidine incorporation, flow cytometry, and the cell number. Further, their effect on the EGF-activated signal transduction pathway was assessed by measuring mitogen-activated protein kinases (MAPK), MAPK kinase (MEK). Raf-1 activity, and the formation of active form of Ras. SNP and A02131-1 inhibited EGF-induced DNA synthesis and subsequent proliferation of VSMC. These two increased cGMP but only a little cAMP in VSMC. A similar antiproliferative effect was observed with 8-bromo-cGMP. The antiproliferative effect of the two was reversed by KT5823 but not by dideoxyadenosine nor Rp-cAMPS. SNP and A02131-1 blocked the EGF-inducible cell cycle progression at the G1/S phase. Further experiments indicated that the two cGMP-elevating agents primarily blocked the activation of Raf-1 by EGF-activated Ras. CONCLUSIONS: These results demonstrate that cGMP-elevating agents inhibit [3H]thymidine incorporation and thus the growth of VSMC, and this inhibition appears to attenuate EGF-activated signal transduction pathway by preventing Ras-dependent activation of Raf-1.

TGF-beta1 selectively suppresses PDGF receptor signaling pathways in MG-63 human osteosarcoma cell.

We previously found that TGF-beta1 inhibits PDGF mitogenicity in MG-63 cells and the inhibition is correlated with a suppression of the PDGF-induced receptor autophosphorylation. In this study, we analyze if all the PDGF receptor signaling pathways are similarly affected by the TGF-beta1 pretreatment. We show that TGF-beta1 suppresses PDGF-stimulated tyrosine phosphorylation of PLC-gamma1, and the phosphorylation of Erk. In contrast, the tyrosine phosphorylation of PI3-kinase is not affected. Thus, TGF-beta1 selectively suppresses two out of three PDGF receptor signaling pathways despite of its prominent inhibition of the PDGF-induced receptor autophosphorylation. The results also indicate that activation of the PI3-kinase pathway alone by PDGF is not sufficient in supporting the optimum growth of MG-63 cells under the culture conditions employed.

Perturbation of the platelet-derived growth factor receptor signaling by dibutyryl-cAMP in human astrocytoma cells.

It has been shown that cAMP may perturb the polypeptide growth factor-induced nuclear events. However, the possible interactions of the cAMP-protein kinase A (cAMP-PKA) and receptor tyrosine kinase pathways in the cytosol have not been fully elucidated. In this study, we use human astrocytoma cells as a model to investigate this issue. The results show that platelet-derived growth factor (PDGF)-induced receptor autophosphorylation in human astrocytoma cells is suppressed by dibutyryl-cAMP pretreatment and such suppression is not due to changes in the ligand-receptor binding properties. Further studies show that PDGF-induced tyrosine phosphorylation of phospholipase C-gamma 1 (PLC-gamma 1) and phosphatidylinositol 3-kinase (PI 3-kinase) are also suppressed in dibutyryl-cAMP-pretreated cells. The suppression of PLC-gamma 1 tyrosine phosphorylation was accompanied by a decreased production of water soluble inositol phosphates. In contrast, similar treatment with normal human astrocytes potentiates the tyrosine phosphorylation of PLC-gamma 1 and PI 3-kinase. The results indicate that cAMP can either negatively or positively modulate the PDGF receptor tyrosine kinase activity depending on the cell types examined.

Increased intracellular cyclic AMP levels suppress the mitogenic responses of human astrocytoma cells to growth factors.

It has been shown that the intracellular cAMP levels were decreased in human malignant astrocytomas. On the other hand, various growth factors and their receptors were found to be overexpressed in these tumors. It is therefore intriguing as to whether there is interplay between the two phenomena in the modulation of the astrocytoma cell growth. In a basal medium consisting of 75% DMEM, 25% Ham's F-12 supplemented with 2% FBS, we show that the mitogenic effects of platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF) on human astrocytoma cells were suppressed by dibutyryl-cAMP. Dibutyryl-cAMP alone neither potentiated nor inhibited the tumor cell growth. Further studies show that PDGF-induced receptor autophosphorylation in human astrocytoma cells is suppressed by increased intracellular cAMP levels as measured by immunoprecipitation with anti-PDGF receptor and antiphosphotyrosine antibodies. Our results indicate that there is antagonistic interplay between the receptor tyrosine kinase pathway and cAMP-dependent protein kinase pathway in the control of the malignantly transformed glial cells. A reduced cAMP level seen in many human astrocytoma cells may favor their response to growth factor mitogenesis.

Nucleotide sequence of the coat protein coding region of the potyvirus tobacco vein-banding mosaic virus.

The sequence of the 3' 1184 nucleotides of tobacco vein-banding mosaic virus (TVBMV) genome has been determined. It contains a single open reading frame which encompasses the whole of the coat protein of TVBMV. The sequence of the first 20 amino acids at the N-terminal region of the coat protein has also been determined chemically to be GDDQTVDAGKNVQSNQKQRN. The sequence matches the translation product of the open reading frame starting with amino acid-271; a glycine residue. Thus the coat protein of TVBMV has a calculated M(r) of 30,210. The 3' non-coding region of TVBMV is 185 nucleotides in length. Sequence alignment of the coat proteins or the 3' non-coding regions from TVBMV and other reported potyviruses indicated that TVBMV is a separate species of the potyvirus genus.

Circadian Rhythm in Amino Acid Uptake by Synechococcus RF-1.

In the prokaryote Synechococcus RF-1, circadian changes in the uptake of l-leucine and 2-amino isobutyric acid were observed. Uptake rates in the light period were higher than in the dark period for cultures entrained by 12/12 hour light/dark cycles. The periodic changes in l-leucine uptake persisted for at least 72 hours into continuous light (L/L). The rhythm had a free-running period of about 24 hours in L/L at 29 degrees C. A single dark treatment of 12 hours could initiate rhythmic leucine uptake in an L/L culture. The phase of rhythm could be shifted by a pulse of low temperature (0 degrees C). The free-running periodicity was "temperature-compensated" from 21 to 37 degrees C. A 24 hour depletion of extracellular Ca(2+) before the free-running L/L condition reduced the variation in uptake rate but had little effect on the periodicity of the rhythm. The periodicity was also not affected by the introduction of 25 mm NaNO(3). The uptake rates for 20 natural amino acids were studied at 12 hour intervals in cultures exposed to 12/12 hour light/dark cycles. For eight of these amino acids (l-Val, l-Leu, l-Ile, l-Pro, l-Phe, l-Trp, l-Met, and l-Tyr), the light/dark uptake rate ratios had values greater than 3 and the rhythm persisted in L/L.