Comparing the Effects of Chlorogenic Acid and Ilex paraguariensis Extracts on Different Markers of Brain Alterations in Rats Subjected to Chronic Restraint Stress.

Positive influence of yerba mate (Ilex paraguariensis) on human health issues has been attributed to its frequent consumption in South American countries and is assumed to be due to its high content of antioxidant compounds, including chlorogenic acid (CGA); however, hard evidence about its positive effects under chronic stress conditions is still required. In this study, the effects of yerba mate extracts (IpE), and its main compound chlorogenic acid (CGA), on behavioral and morphological endpoints of brain damage induced by chronic restraint stress (CRS) to rats were evaluated and compared. CRS sessions were performed during 21 days. IpE (200 mg/mL, p.o.) or CGA (2 mg/mL, p.o.) were administered daily 30 min before stress. Behavioral tests comprised motor skills and anxiety-like activity. Histological (H&E) and histochemical changes were explored in three brain regions: cortex (Cx), hippocampus (Hp), and striatum (S). Rats subjected to CRS exhibited hypoactive patterns of locomotor activity. Rats receiving IpE before CRS preserved the basal locomotor activity. Stressed animals also augmented the anxiety-like activity, whereas IpE normalized exploratory behavior. Stressed animals presented cell damage in all regions. Morphological damage was more effectively prevented by IpE than CGA. Stressed animals also augmented the expression/localization pattern of the tumor necrosis factor alpha in the striatum and the expression of the glial fibrillary acidic protein in the hippocampus (stratum moleculare) and cortex, whereas IpE and CGA reduced the expression of these molecules. In turn, CGA exhibited only moderate protective effects on all markers analyzed. Our findings support a protective role of IpE against CRS, which may be related to the antioxidant and anti-inflammatory properties of its compounds. Since CGA was unable to prevent all the alterations induced by CRS, it is concluded that the protective properties of the whole extract of Ilex paraguariensis are the result of the combined effects of all its natural antioxidant compounds, and not only of the properties of CGA.

Compounds from Ilex paraguariensis extracts have antioxidant effects in the brains of rats subjected to chronic immobilization stress.

Immobilization induces oxidative damage to the brain. Ilex paraguariensis extracts (Mate) and their major natural compound, chlorogenic acid (CGA), exert protective effects against reactive oxygen species formation. Here, the effects of Mate and CGA on oxidative damage induced by chronic immobilization stress (CIS) in the cortex, hippocampus, and striatum were investigated. For CIS, animals were immobilized for 6 h every day for 21 consecutive days. Rats received Mate or CGA by intragastric gavage 30 min before every restraint session. Endpoints of oxidative stress (levels of lipid peroxidation, protein carbonylation, and reduced (GSH) and oxidized (GSSG) forms of glutathione) were evaluated following CIS. While CIS increased oxidized lipid and carbonyl levels in all brain regions, CGA (and Mate to a lesser extent) attenuated lipid and protein oxidation as compared with control groups. GSH/GSSG balance showed a tendency to increase in all regions in response to stress and antioxidants. Taken together, our results support a protective role of dietary antioxidants against the neuronal consequences of stress.

S-allyl cysteine protects against MPTP-induced striatal and nigral oxidative neurotoxicity in mice: participation of Nrf2.

The neuroprotective properties of S-allyl cysteine (SAC) have been demonstrated in different neurotoxic paradigms, and it may be partially attributable to its antioxidant and anti-inflammatory profile. Recently, SAC has also been shown to induce neuroprotection in the rat striatum in a toxic model induced by 6-hydroxydopamine in rats through a concerted antioxidant response involving Nrf2 transcription factor nuclear transactivation and Phase 2 enzymes' upregulation. In this work, we investigated whether the SAC-induced in vivo striatal and nigral neuroprotection against 1-methyl-4-phenyl-1,2,3,6-tetrahydropiridinium (MPTP) toxicity recruits Nrf2 transactivation in C57BL/6J mice. SAC (120 mg/kg, i.p. × 5 days) partially ameliorated the MPTP (30 mg/kg, i.p. × 5 days)-induced striatal and nigral dopamine and tyrosine hydroxylase depletion, attenuated the loss of Mn-SOD and HO-1 activities, and preserved the protein content of these enzymes. While no significant changes were detected for the striatal Nrf2 nuclear protein levels, the nigral Nrf2 nuclear content was decreased by MPTP and stimulated by SAC. Our findings suggest that SAC can exert neuroprotection since the origin of the dopaminergic lesion-at the substantia nigra (SN)-not only by means of direct antioxidant actions, but also through Nrf2 nuclear transactivation and Phase 2 enzymes upregulation.

Selenium reduces the proapoptotic signaling associated to NF-kappaB pathway and stimulates glutathione peroxidase activity during excitotoxic damage produced by quinolinate in rat corpus striatum.

Quinolinate (QUIN) neurotoxicity has been attributed to degenerative events in nerve tissue produced by sustained activation of N-methyl-D-aspartate receptor (NMDAr) and oxidative stress. We have recently described the protective effects that selenium (Se), an antioxidant, produces on different markers of QUIN-induced neurotoxicity (Santamaría et al., 2003, J Neurochem 86:479-488.). However, the mechanisms by which Se exerts its protective actions remain unclear. Since some of these events are thought to be related with inhibition of deadly molecular cascades through the activation of antioxidant selenoproteins, in this study we investigated the effects of Se on QUIN-induced cell damage elicited by the nuclear factor kappaB (NF-kappaB) pathway, as well as the time-course response of striatal glutathione peroxidase (GPx) activity. Se (sodium selenite, 0.625 mg/kg/day, i.p.) was administered to rats for 5 days, and 120 min after the last administration, animals received a single striatal injection of QUIN (240 nmol/mul). Twenty-four hours later, their striata were tested for the expression of IkappaB-alpha (the NF-kappaB cytosolic binding protein), the immunohistochemical expression of NF-kappaB (evidenced as nuclear expression of P65), caspase-3-like activation, and DNA fragmentation. Additional groups were killed at 2, 6, and 24 h for measurement of GPx activity. Se reduced the QUIN-induced decrease in IkappaB-alpha expression, evidencing a reduction in its cytosolic degradation. Se also prevented the QUIN-induced increase in P65-immunoreactive cells, suggesting a reduction of NF-kappaB nuclear translocation. Caspase-3-like activation and DNA fragmentation produced by QUIN were also inhibited by Se. Striatal GPx activity was stimulated by Se at 2 and 6 h, but not at 24 h postlesion. Altogether, these data suggest that the protective effects exerted by Se on QUIN-induced neurotoxicity are partially mediated by the inhibition of proapoptotic events underlying IkappaB-alpha degradation, NF-kappaB nuclear translocation, and caspase-3-like activation in the rat striatum, probably involving the early activation of GPx.

S-Allylcysteine, a garlic-derived antioxidant, ameliorates quinolinic acid-induced neurotoxicity and oxidative damage in rats.

Excitotoxicity elicited by overactivation of N-methyl-D-aspartate receptors is a well-known characteristic of quinolinic acid-induced neurotoxicity. However, since many experimental evidences suggest that the actions of quinolinic acid also involve reactive oxygen species formation and oxidative stress as major features of its pattern of toxicity, the use of antioxidants as experimental tools against the deleterious effects evoked by this neurotoxin becomes more relevant. In this work, we investigated the effect of a garlic-derived compound and well-characterized free radical scavenger, S-allylcysteine, on quinolinic acid-induced striatal neurotoxicity and oxidative damage. For this purpose, rats were administered S-allylcysteine (150, 300 or 450 mg/kg, i.p.) 30 min before a single striatal infusion of 1 microl of quinolinic acid (240 nmol). The lower dose (150 mg/kg) of S-allylcysteine resulted effective to prevent only the quinolinate-induced lipid peroxidation (P < 0.05), whereas the systemic administration of 300 mg/kg of this compound to rats decreased effectively the quinolinic acid-induced oxidative injury measured as striatal reactive oxygen species formation (P < 0.01) and lipid peroxidation (P < 0.05). S-Allylcysteine (300 mg/kg) also prevented the striatal decrease of copper/zinc-superoxide dismutase activity (P < 0.05) produced by quinolinate. In addition, S-allylcysteine, at the same dose tested, was able to reduce the quinolinic acid-induced neurotoxicity evaluated as circling behavior (P < 0.01) and striatal morphologic alterations. In summary, S-allylcysteine ameliorates the in vivo quinolinate striatal toxicity by a mechanism related to its ability to: (a) scavenge free radicals; (b) decrease oxidative stress; and (c) preserve the striatal activity of Cu,Zn-superoxide dismutase (Cu,Zn-SOD). This antioxidant effect seems to be responsible for the preservation of the morphological and functional integrity of the striatum.

Protective effects of the antioxidant selenium on quinolinic acid-induced neurotoxicity in rats: in vitro and in vivo studies.

Quinolinic acid (QUIN), a well known excitotoxin that produces a pharmacological model of Huntington's disease in rats and primates, has been shown to evoke degenerative events in nerve tissue via NMDA receptor (NMDAr) overactivation and oxidative stress. In this study, the antioxidant selenium (as sodium selenite) was tested against different markers of QUIN-induced neurotoxicity under both in vitro and in vivo conditions. In the in vitro experiments, a concentration-dependent effect of selenium was evaluated on the regional peroxidative action of QUIN as an index of oxidative toxicity in rat brain synaptosomes. In the in vivo experiments, selenium (0.625 mg per kg per day, i.p.) was administered to rats for 5 days, and 2 h later animals received a single unilateral striatal injection of QUIN (240 nmol/ micro L). Rats were killed 2 h after the induction of lesions with QUIN to measure lipid peroxidation and glutathione peroxidase (GPx) activity in striatal tissue. In other groups, the rotation behavior, GABA content, morphologic alterations, and the corresponding ratio of neuronal damage were all evaluated as additional markers of QUIN-induced striatal toxicity 7 days after the intrastriatal injection of QUIN. Selenium decreased the peroxidative action of QUIN in synaptosomes both from whole rat brain and from the striatum and hippocampus, but not in the cortex. A protective concentration-dependent effect of selenium was observed in QUIN-exposed synaptosomes from whole brain and hippocampus. Selenium pre-treatment decreased the in vivo lipid peroxidation and increased the GPx activity in QUIN-treated rats. Selenium also significantly attenuated the QUIN-induced circling behavior, the striatal GABA depletion, the ratio of neuronal damage, and partially prevented the morphologic alterations in rats. These data suggest that major features of QUIN-induced neurotoxicity are partially mediated by free radical formation and oxidative stress, and that selenium partially protects against QUIN toxicity.