Mechanism of neuroprotective function of taurine.

Taurine has potent protective function against glutamate-induced neuronal injury presumably through its function in regulation of intracellular free calcium level, [Ca2+]i. In this communication, we report that taurine exerts its protective function through one or more of the following mechanisms: 1. Inhibition of glutamate-induced calcium influx through L-, N- and P/Q-type voltage-gated calcium channels and NMDA receptor calcium channel; 2. Attenuation of glutamate-induced membrane depolarization; 3. Prevention of glutamate-induced apoptosis via preventing glutamate-mediated down-regulation of Bcl-2; 4. Prevention of cleavage of Bcl-2 by calpain. This action of taurine is due to its inhibition on glutamate induced calpain activation. Based on these observations, we propose that taurine protects neurons against glutamate-induced neurotoxicity in part, by preventing glutamate-induced membrane depolarization, elevation of [Ca2+]i, activation of calpain, reduction of Bcl-2 and apoptosis.

Effects of three purgative decoctions on inflammatory mediators.

In traditional Chinese medicine (TCM), there are three Cheng-Chi-Tang decoctions (CCTDs) including: Ta-Cheng-Chi-Tang (TCCT), Xiao-Chen-Chi-Tang (XCCT) and Tiao-Wei-Chen-Chi-Tang (TWCCT), which are the frequently used purgative remedies to treat "internal heat"-induced symptoms like a bloated and painful abdomen, hard stools and fever, etc. Constituents in each formulation are Rheum palmatum L. (Polygonaceae), Magnolia officinalis Rehd. et Wils. (Magnoliaceae), Citrus aurantium L. (Rutaceae), Mirabilitum (mirabilite, crystals of sodium sulfate, Na2SO4) for TCCT; Rheum palmatum, Magnolia officinalis, Citrus aurantium for XCCT; and Rheum palmatum, Mirabilitum, Glycyrrhiza uralensis Fisch. (Leguminosae) for TWCCT. However, the underlying mechanisms for purging internal pathological heat are far from fully clarified, and few scientific investigations have been carried out to delineate the relationships between the anti-inflammatory effects and laxative potencies of these formulations. In this study, the anti-inflammatory effects of the three CCTDs on lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E (PGE2) production in RAW 264.7 cells, carrageenan-induced paw edema in mice and the laxative effect in mice were explored. The results showed that TCCT inhibited LPS-induced NO and PGE2 production and inducible nitric oxide synthase (iNOS) expression in RAW 264.7 cells more effectively than did XCCT or TWCCT. Moreover, paw edema of carrageenan-treated mice was significantly attenuated in mice pretreated with 1 g/kg TCCT. TCCT also showed the strongest purgative activity among the three formulations. These findings indicate that TCCT has anti-inflammatory effects in addition to its traditionally known purgative activities. It may have potential to treat inflammatory disease conditions.

Differential effects of natural polyphenols on neuronal survival in primary cultured central neurons against glutamate- and glucose deprivation-induced neuronal death.

Neuronal injury in the central nervous system following ischemic insult is believed to result from glutamate toxicity and glucose deprivation. In this study, polyphenols isolated from Scutellaria baicalensis Georgi, including baicalin, baicalein, and wogonin, were investigated for their neuroprotective effects against glutamate/NMDA (Glu/NMDA) stimulation and glucose deprivation in primary cultured rat brain neurons. Cell death was accessed by lactate dehydrogenase (LDH) release assay for necrosis, and mitochondrial activity was accessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction activity assay. It was found that both baicalin and baicalein decreased LDH release of the cultured neurons after 24 h treatment, whereas wogonin profoundly increased LDH release after 2 h treatment and resulted in neuronal death after 24 h. Glu/NMDA treatment profoundly increased LDH release and moderately decreased MTT reduction activity in an NMDA receptor-dependent manner. Both baicalin and baicalein significantly reduced Glu/NMDA-increased LDH release, in which baicalein is much more potent than baicalin. Glu/NMDA-increased intracellular calcium was also significantly attenuated by baicalin and baicalein. Baicalin and baicalein did not affect glutamate receptor binding activity, but baicalein did moderately decrease Glu/NMDA-induced nitric oxide (NO) production. In the glucose deprivation (GD) study, baicalein but not baicalin showed significant protective effects on the GD-increased LDH release, without affecting the GD-induced NO production, in cultured rat brain neurons. These results suggest that baicalein is the most effective compound among three polyphenols tested in preventing neurotoxicity induced by both glutamate and GD, whereas baicalin was only effective in preventing glutamate toxicity. Wogonin might have a neurotoxic effect on the brain.

Neuroprotection and free radical scavenging effects of Osmanthus fragrans.

The ethanol extract of dried flowers Osmanthus fragrans (OFE) was assessed for free radical scavenging effects measured by the bleaching of the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical, scavenging of the hydroxyl anion, investigation of the ferric reducing/antioxidant power (FRAP) and lipid-peroxidation inhibition in rat tissues. OFE contained a high amount of total flavonoid and polyphenol. OFE presented the effects in the metal reducing power, FRAP assay with IC(50) values of 0.23 microg/ml, and 7.74 microg/ml, respectively. OFE presented similar activities toward the DPPH and hydroxyl anion scavenging ability with IC(50) values of 10 microg/ml. OFE with IC(50 )values between 46 and 97 microg/ml inhibited lipid peroxidation initiated by ferrous chloride in rat brain, liver, heart and kidney mitochodrias. Moreover, the neuroprotective activity of OFE was investigated under different insults (glutamate, arachidonic acid, and 6-hydroxydopamine) in Wistar rat primary cortical neurons. OFE with EC(50 )values between 66 and 165 microg/ml attenuated the neurotoxicity on MTT and LDH assays. In addition, the AKT protein expression of excitotoxicity and oxidative stress was displayed by western blotting analysis. OFE could up-regulate the glutamate and 6-OHDA decreased AKT expression. This is the first demonstration of the neuroprotective, free radical scavenging and anti-oxidative effects of O. fragrans.