Antinoceptive effect of triterpenoid alpha,beta-amyrin in rats on orofacial pain induced by formalin and capsaicin.

The effects of alpha,beta-amyrin, a pentacyclic triterpene isolated from Protium heptaphylum was investigated on rat model of orofacial pain induced by formalin or capsaicin. Rats were pretreated with alpha,beta-amyrin (10, 30, and 100mg/kg, i.p.), morphine (5mg/kg, s.c.) or vehicle (3% Tween 80), before formalin (20 microl, 1.5%) or capsaicin (20 microl, 1.5 microg) injection into the right vibrissa. In vehicle-treated controls, formalin induced a biphasic nociceptive face-rubbing behavioral response with an early first phase (0-5 min) and a late second phase (10-20 min) appearance, whereas capsaicin produced an immediate face-rubbing (grooming) behavior that was maximal at 10-20 min. Treatment with alpha,beta-amyrin or morphine significantly inhibited the face-rubbing response in both test models. While morphine produced significant antinociception in both phases of formalin test, alpha,beta-amyrin inhibited only the second phase response, more prominently at 30 mg/kg, in a naloxone-sensitive manner. In contrast, alpha,beta-amyrin produced much greater antinociceptive effect at 100mg/kg in the capsaicin test, which was also naloxone-sensitive. These results provide first time evidence to show that alpha,beta-amyrin attenuates orofacial pain at least, in part, through a peripheral opioid mechanism but warrants further detailed study for its utility in painful orofacial pathologies.

Anti-inflammatory effect of alpha, beta-Amyrin, a pentacyclic triterpene from Protium heptaphyllum in rat model of acute periodontitis.

This study was aimed to evaluate the anti-inflammatory potential of triterpene alpha, beta-amyrin in rats on acute phase periodontitis. Periodontitis was induced by ligature placement around the maxillary right second molar tooth. Rats (n = 8/group) were pretreated with alpha, beta-amyrin (5 and 10 mg/kg, p. o.), two hours before the induction of periodontal inflammation. Sham-operated and positive controls (lumiracoxib and dexamethasone) were included. Six hours later, plasma levels of TNF-alpha were analysed. Rats were sacrificed at 24 h, and the gingival tissue analysed for myeloperoxidase (MPO) and thiobarbituric acid-reactive substances (TBARS), as measures of neutrophil influx and lipid-peroxidation, respectively alpha, beta-Amyrin as well as dexamethasone significantly inhibited the periodontitis-associated increases of TNF-alpha, and the gingival MPO and TBARS. alpha, beta-Amyrin effect was more prominent at 5 mg/kg. Lumiracoxib manifested varied influence on the studied parameters. These results provide evidence to show that alpha, beta-Amyrin retards acute inflammation in rat model of periodontitis and warrant further study on its efficacy to prevent chronic periodontitis-associated bone loss.

Increased density and synapto-protective effect of adenosine A2A receptors upon sub-chronic restraint stress.

Stress initially causes adaptive changes in the brain and can lead to neurodegeneration if continuously present. Noxious brain conditions trigger the release of adenosine that can control brain function and neurodegeneration through inhibitory A(1) and facilitatory A(2A) receptors. We tested the effect of restraint stress on the density of adenosine receptors and their effect on the outcome of stress, focusing in a known affected region, the hippocampus. Sub-chronic restraint stress (6 h/day for 7 days) caused a parallel decrease of the density of A(1) receptors (15-20%) and an increase (near 250%) of A(2A) receptor density in rat hippocampal nerve terminals. This indicates that sub-chronic stress unbalances adenosine receptors, up-regulating A(2A) and down-regulating A(1) receptors. Sub-chronic stress did not cause hippocampal neurodegeneration but decreased the immunoreactivity (immunohistochemistry and Western blot) of a synaptic marker, synaptophysin. The blockade of A(2A) receptors with 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine (0.05 mg/kg, daily i.p. injection) attenuated the loss of synaptophysin immunoreactivity observed in the hippocampus of rats subjected to sub-chronic restraint stress. This ability of A(2A) receptor antagonists to prevent the earliest stress-induced synaptic modifications provides a neurochemical and morphological correlate for the interest of A(2A) receptor antagonists to attenuate the burden of chronic stress.

Quebrachitol (2-O-methyl-L-inositol) attenuates 6-hydroxydopamine-induced cytotoxicity in rat fetal mesencephalic cell cultures.

Naturally occurring plant substances have the potential to prevent oxidative damage in various pathophysiological conditions including neurodegenerative disorders. Recent findings indicate that impaired energy metabolism plays a prominent role in neurodegeneration. The present study investigated whether quebrachitol (2-O-methyl-L-inositol) (QCT), a sugar like natural compound that was suggested to have both antioxidant and membrane stabilization activity prevents the cytotoxic effect of 6-hydroxydopamine (6-OHDA, 200 microM) on cultured rat fetal mesencephalic cells. While QCT (0.1-100 microg/ml) produced no effect per se on cell viability as measured in the 3[4,5-dimethylthiazole-2il]-2,5-diphenyltetrazolium bromide (MTT) test, it offered concentration-related protection against cell death induced by 6-OHDA. In addition, QCT demonstrated an antioxidant activity against 6-OHDA-induced oxidative stress as evidenced by reduced formation of nitrite-nitrate and thiobarbituric acid-related substances. Fluorescence microscopy using acridine orange/ethidium bromide double staining further affirmed the absence of 6-OHDA (200 microM)-induced morphological changes characteristic of apoptosis/necrosis in cultures pretreated with QCT (100 microg/ml). Also, results of tyrosine hydroxylase immunoreactivity indicated that 6-OHDA induces cell death in mesencephalic cultures affecting both TH+ positive and TH- negative (TH+ and TH-, respectively) and QCT pretreatment protects them from cell death, in a non-specific manner. Our data indicate that QCT has a cytoprotective role due, at least in part, to an antioxidant and free radical scavenging mechanism. Furthermore, the study suggests that inositol compounds might serve as leads in developing drugs for the treatment of various neurodegenerative disorders.

Amburoside A, a glucoside from Amburanacearensis, protects mesencephalic cells against 6-hydroxydopamine-induced neurotoxicity.

This study evaluates the potential neuroprotective properties of amburoside A, a glucoside isolated from Amburana cearensis, on rat mesencephalic cell cultures exposure to the neurotoxin 6-hydroxydopamine (6-OHDA). The parameters determined were cell viability by the 3[4,5-dimethylthiazole-2-il]-2,5-diphenyltetrazolium bromide (MTT) method, nitric oxide (NO) and free radical formation by the measurement of nitrite concentration and thiobarbituric acid reacting substance (TBARS) formation as an indication of cellular lipid peroxidation. The results showed that AMB was less effective as a curative agent in the MTT assay, since its addition after 6-OHDA did not reverse the neurotoxin's effect, except at the highest concentration (AMB, 100 microg/ml). Similarly, the higher nitrite levels observed after exposure of the cells to 6-OHDA were only partially reversed by AMB, at this highest concentration. However, when AMB (0.5, 1, 10 and 100 microg/ml) was added before the toxin, it appeared to protect neuronal cells against 6-OHDA toxicity in a concentration-dependent manner, as shown by MTT assay. AMB also prevented free radical formation indicated by the increased nitrite concentration induced by 6-OHDA. Cells exposed to 6-OHDA showed a 3.4 times increase in TBARS concentration as compared to controls, and this effect was inhibited from 24% up to 64% by AMB (0.1-100 microg/ml), indicative of a neuroprotective effect. In conclusion, we show that AMB, acting as an antioxidant compound, presents a significant neuroprotective effect, suggesting that this compound could provide benefits as a therapeutic agent in neurodegenerative disease such as Parkinson's.

l-Deprenyl prevents lipid peroxidation and memory deficits produced by cerebral ischemia in rats.

1. The present work shows the results on behavior and on biochemical parameters of l-deprenyl (0.1, 5, and 10 mg/kg, p.o.) administered daily for 5 days to rats submitted to global cerebral ischemia. 2. The transient global ischemia was carried out by clamping the animals bilateral common carotid arteries for 20 min. The parameters studied were memory acquisition and memory retention, locomotor activity and thiobarbituric acid reactive substances, as an index of lipid peroxidation. 3. l-Deprenyl treatment significantly improved memory deficits as compared to the ischemic group as measured by the elevated T maze test. A similar result was observed on the passive avoidance test where l-deprenyl improved late but not early memory as compared to the ischemic group. Except for an increased locomotor activity observed in the group treated with 5 mg/kg, no other alteration was detected in this behavioral test. Rats submitted to transient global ischemia (and without l-deprenyl) showed an increase in MDA levels in the hippocampus and the treatment with l-deprenyl (5 or 10 mg/kg) significantly reversed this effect bringing values close to those of the sham-operated controls. A similar profile was observed with nitrite levels. 4. In conclusion, the work showed a significant protective effect of l-deprenyl on memory deficits and lipid hyperperoxidation observed after cerebral ischemia. Possibly, the drug is acting at least in part through its antioxidant activity.

Catechin attenuates 6-hydroxydopamine (6-OHDA)-induced cell death in primary cultures of mesencephalic cells.

Past studies have shown the protective effects of tea catechins on oxidative cell damage induced by 6-OHDA in PC12 cells. In this study we verified whether or not catechin prevents 6-OHDA-induced oxidative cell damage in primary cultures of rat mesencephalic cells. On exposure to 6-OHDA (200 microM), the cultures showed a marked decrease in cell viability, disturbances in lipid peroxidation, and an increased generation of NO, as assayed by MTT, TBARS and nitrite assays, respectively. Introduction of catechin significantly attenuated the cell death caused by 6-OHDA at concentrations of 3.4, 34 and 340 microM in a dose-related manner. Catechin produced no marked changes on 6-OHDA-induced increases in NO, but caused a significant inhibition of lipid peroxidation. These results suggest that catechins offer similar cytoprotection against 6-OHDA-induced oxidative cell damage in mesencephalic cell cultures, as previously described in PC12 cells. The cytoprotective function of catechin results from its antioxidant property and is not due to the inhibition of nitric oxide synthase. These findings further support and substantiate traditional consumption of catechin rich green/black tea as protection against neurodegenerative diseases like Parkinsonism.

Toxicity to sea urchin egg development of the quinone fraction obtained from Auxemma oncocalyx.

Auxemma oncocalyx Taub. belongs to the Boraginaceae family and is native to the Brazilian northeast where it is known as "pau-branco". We investigated the ability of the water soluble fraction isolated from the heartwood of A. oncocalyx to inhibit sea urchin egg development. This fraction contains about 80% oncocalyxone A (quinone fraction), a compound known to possess strong cytotoxic and antitumor activities. In fact, the quinone fraction inhibited cleavage in a dose-dependent manner [IC50 of 18.4 (12.4-27.2) microg/ml, N = 6], and destroyed the embryos in the blastula stage [IC50 of 16.2 (13.7-19.2) microg/ml, N = 6]. We suggest that this activity is due to the presence of oncocalyxone A. In fact, these quinones present in A. oncocalyx extract have strong toxicity related to their antimitotic activity.

The cytotoxic and embryotoxic effects of kaurenoic acid, a diterpene isolated from Copaifera langsdorffii oleo-resin.

In this work, we studied the effects of kaurenoic acid, a diterpene isolated from the oleo-resin of Copaifera langsdorffii in developing sea urchin (Lytechinus variegatus) embryos, on tumor cell growth in microculture tetrazolium (MTT) test and on mouse and human erythrocytes in hemolysis assay. Continuous exposure of embryos to kaurenoic acid starting immediately after fertilization inhibited the first cleavage (IC(50): 84.2 microM) and progressively induced embryo destruction (IC(50): 44.7 microM and < 10 microM for blastulae and larvae stages, respectively). In MTT assay, kaurenoic acid at a concentration of 78 microM produced growth inhibition of CEM leukemic cells by 95%, MCF-7 breast and HCT-8 colon cancer cells by 45% each. Further, kaurenoic acid induced a dose-dependent hemolysis of mouse and human erythrocytes with an EC(50) of 74.0 and 56.4 microM, respectively. The destruction of sea urchin embryos, the inhibition of tumor cell growth and the hemolysis of mouse and human erythrocytes indicate the potential cytotoxicity of kaurenoic acid.

Toxicity to sea urchin egg development of the quinone fraction obtained from Auxemma oncocalyx

Auxemma oncocalyx Taub. belongs to the Boraginaceae family and is native to the Brazilian northeast where it is known as "pau-branco". We investigated the ability of the water soluble fraction isolated from the heartwood of A. oncocalyx to inhibit sea urchin egg development. This fraction contains about 80 percent oncocalyxone A (quinone fraction), a compound known to possess strong cytotoxic and antitumor activities. In fact, the quinone fraction inhibited cleavage in a dose-dependent manner [IC50 of 18.4 (12.4-27.2) æg/ml, N = 6], and destroyed the embryos in the blastula stage [IC50 of 16.2 (13.7-19.2) æg/ml, N = 6]. We suggest that this activity is due to the presence of oncocalyxone A. In fact, these quinones present in A. oncocalyx extract have strong toxicity related to their antimitotic activity

Evidence for the involvement of the muscarinic cholinergic system in the central actions of pentoxifylline.

This study shows that pentoxifylline (ptx), a xanthine derivative, significantly attenuates scopolamine-induced memory impairment in rats, as demonstrated in a passive avoidance task (50 mg/kg intraperitoneally [i.p.]) and in an elevated T-maze (10 and 50 mg/kg i.p.). Ptx (25, 50 and 100 mg/kg i.p.) also potentiates oxotremorine-induced tremors in mice, in a dose-dependent manner, and this effect was completely prevented by atropine. In addition, ptx (50 and 100 mg/kg i.p.) increased the number of animals developing pilocarpine-induced seizures, and potentiated the latency to the first pilocarpine-induced convulsion. Hippocampus homogenates from rats treated with ptx (100 mg/kg) for 1 week and sacrificed 15 min after the last injection showed a significant decrease in the muscarinic receptor numbers, indicative of a downregulation phenomenon. Similar effects were observed when assays were performed 24 h after the last ptx injection (10 and 50 mg/kg i.p.), but not after 72 h. Additionally, in vitro assays showed that ptx inhibits acetylcholinesterase activity in a dose-dependent manner when incubated with homogenates from rat hippocampus. Our data suggest that the muscarinic agonist effect of ptx could possibly depend on factors such as endogenous cholinergic activity.