Participation of manganese-superoxide dismutase in the neuroprotection exerted by copper sulfate against 1-methyl 4-phenylpyridinium neurotoxicity

Copper sulfate pretreatment prevents mitochondrial electron transport chain damage and apoptosis against MPP+-induced neurotoxicity

Intrastriatal injection of 1-methyl-4-phenylpyridinium (MPP⁺) is considered a model to reproduce some biochemical alterations observed in Parkinson's disease (PD) patients. Among those alterations, inhibition of mitochondrial complex I activity, increased free radical production and reduced antioxidant responses have been reported. Copper (Cu) plays an important role in the metabolism and antioxidative responses through its participation as a cofactor in the cytochrome c oxidase enzyme (COX), Cu/Zn-superoxide dismutase (Cu/Zn-SOD), and metallothioneins. We tested the effect of copper sulfate (CuSO₄) pretreatment on the mitochondrial electron transport chain (METC) in the striatum after MPP⁺ toxicity in rats. The results showed that the MPP⁺ intrastriatal injection reduced mitochondrial complex I, II, IV and V activities; while 10 μmol of CuSO₄ pretreatment counteracted this damage. Activities of complexes I, II and IV, were coincident with ATP recovery. Moreover, Cu/Zn-SOD activity was reduced as a consequence of MPP⁺ damage; however, copper pre-treatment kept the striatal Cu/Zn-SOD activity unchanged in MPP⁺-damaged animals. We observed that MPP⁺ also reduced the metallothionein (MT) content and that CuSO₄ pretreatment maintained baseline values. CuSO₄ pretreatment also reduced the striatal caspase-3 and caspase-9 activities that were increased three days after MPP⁺-induced damage. The present study provided evidence that copper pretreatment reduced MPP⁺-induced apoptotic damage, probably through direct action on copper-dependent proteins or indirectly on proteins in the apoptotic pathway.

Toxicity of copper salts is dependent on solubility profile and cell type tested

Copper (Cu) is considered an essential metal for living organisms. However, disruption of Cu homeostasis is toxic and can lead to disorders such as Menkes and Wilson's diseases. The brain appears to be a vulnerable target organ. This study investigated the toxicity of Cu based on its solubility profile and cell type tested. Human A-172 (glioblastoma), SK-N-SH (neuroblastoma) and CCF-STTG1 (astrocytoma) cells were assessed after exposure to different concentrations (0.5-500μM) of copper sulfate (CuSO4) or copper (II) oxide (CuO). Since Cu is a redox active transition metal, we hypothesized that oxidative stress would be the main mechanism underlying cell toxicity. Therefore, cell viability was correlated with the extent of reactive oxygen species (ROS) formation. Cell viability decreased at the higher concentrations of the Cu salts and CuO was more toxic compared to CuSO4. The astrocytoma and glioblastoma cells were more vulnerable compared to the neuronal cells. Furthermore, it appears that oxidative stress only partially accounts for Cu-induced cell toxicity. Further studies are needed to better understand the unique susceptibility of glial cells and determine the physicochemical properties of insoluble Cu which accounts for its enhanced toxicity.

Medical management of Parkinson's disease: focus on neuroprotection

Neuroprotection refers to the protection of neurons from excitotoxicity, oxidative stress and apoptosis as principal mechanisms of cell loss in a variety of diseases of the central nervous system. Our interest in Parkinson’s disease (PD) treatment is focused on drugs with neuroprotective properties in preclinical experiments and evidence-based efficacy in human subjects. To this date, neuroprotection has never been solidly proven in clinical trials but recent adequate markers and/or strategies to study and promote this important goal are described. A myriad of compounds with protective properties in cell cultures and animal models yield to few treatments in clinical practice. At present, markers of neuronal vitality, disease modifying effects and long term clinical stability are the elements searched for in clinical trials. This review highlights new strategies to monitor patients with PD. Currently, neuroprotection in subjects has not been solidly achieved for selegiline and pramipexole; however, a recent rasagiline trial design is showing new indications of disease course modifying effects. In neurological practice, it is of utmost importance to take into account the potential neuroprotection exerted by a treatment in conjunction with its symptomatic efficacy.

Manganese induces oxidative stress, redox state unbalance and disrupts membrane bound ATPases on murine neuroblastoma cells in vitro: protective role of silymarin

Manganese (Mn) is an essential trace element required for ubiquitous enzymatic reactions. Chronic overexposure to this metal may promote potent neurotoxic effects. The mechanism of Mn toxicity is not well established, but several studies indicate that oxidative stress play major roles in the Mn-induced neurodegenerative processes. Silymarin (SIL) has antioxidant properties and stabilizes intracellular antioxidant defense systems. The aim of this study was to evaluate the toxic effects of MnCl₂ on the mouse neuroblastoma cell lines (Neuro-2A), to characterize the toxic mechanism associated with Mn exposure and to investigate whether SIL could efficiently protect against neurotoxicity induced by Mn. A significant increase in LDH release activity was observed in Neuro-2A cells associated with a significant decrease in cellular viability upon 24 h exposure to MnCl₂ at concentrations of 200 and 800 μM (P < 0.05) when compared with control unexposed cells. In addition, exposure cells to MnCl₂ (200 and 800 μM), increases oxidant biomarkers and alters enzymatic and non enzymatic antioxidant systems. SIL treatment significantly reduced the levels of LDH, nitric oxide, reactive oxygen species and the oxidants/antioxidants balance in Neuro-2A cells as compared to Mn-exposed cells. These results suggested that silymarin is a powerful antioxidant through a mechanism related to its antioxidant activity, able to interfere with radical-mediated cell death. SIL may be useful in diseases known to be aggravated by reactive oxygen species and in the development of novel treatments for neurodegenerative disorders such as Alzheimer or Parkinson diseases.

Silibinin prevents amyloid beta peptide-induced memory impairment and oxidative stress in mice

BACKGROUND AND PURPOSE

Accumulated evidence suggests that oxidative stress is involved in amyloid beta (Abeta)-induced cognitive dysfunction. Silibinin (silybin), a flavonoid derived from the herb milk thistle (Silybum marianum), has been shown to have antioxidative properties; however, it remains unclear whether silibinin improves Abeta-induced neurotoxicity. In the present study, we examined the effect of silibinin on the memory impairment and accumulation of oxidative stress induced by Abeta(25-35) in mice.

EXPERIMENTAL APPROACH

Aggregated Abeta(25-35) (3 nmol) was intracerebroventricularly administered to mice. Treatment with silibinin (2, 20 and 200 mg.kg(-1), once a day, p.o.) was started immediately after the injection of Abeta(25-35). Locomotor activity was evaluated 6 days after the Abeta(25-35) treatment, and cognitive function was evaluated in a Y-maze and novel object recognition tests 6-11 days after the Abeta(25-35) treatment. The levels of lipid peroxidation (malondialdehyde) and antioxidant (glutathione) in the hippocampus were measured 7 days after the Abeta(25-35) injection.

KEY RESULTS

Silibinin prevented the memory impairment induced by Abeta(25-35) in the Y-maze and novel object recognition tests. Repeated treatment with silibinin attenuated the Abeta(25-35)-induced accumulation of malondialdehyde and depletion of glutathione in the hippocampus.

CONCLUSIONS AND IMPLICATIONS

Silibinin prevents memory impairment and oxidative damage induced by Abeta(25-35) and may be a potential therapeutic agent for Alzheimer's disease.

The effect of supplementation with omega-3 polyunsaturated fatty acids on markers of oxidative stress in elderly exposed to PM(2.5)

BACKGROUND

The mechanisms of particulate matter (PM)-induced health effects are believed to involve inflammation and oxidative stress. Increased intake of omega-3 polyunsaturated fatty acids (n-3 PUFA) appears to have anti-inflammatory effects.

OBJECTIVE

As part of a trial to evaluate whether n-3 PUFA supplementation could protect against the cardiac alterations linked to PM exposure, we measured biomarkers of response to oxidative stimuli [copper/zinc (Cu/Zn) superoxide dismutase (SOD) activity, lipoperoxidation (LPO) products, and reduced glutathione (GSH)] and evaluated the impact of supplementation on plasma levels.

METHODS

We recruited residents from a nursing home in Mexico City chronically exposed to PM < or = 2.5 microm in aerodynamic diameter (PM(2.5)) and followed them from 26 September 2001 to 10 April 2002. We randomly assigned subjects in a double-blind fashion to receive either fish oil (n-3 PUFA) or soy oil. We measured PM(2.5) levels indoors at the nursing home, and measured Cu/Zn SOD activity, LPO products, and GSH at different times during presupplementation and supplementation phases.

RESULTS

Supplementation with either fish or soy oil was related to an increase of Cu/Zn SOD activity and an increase in GSH plasma levels, whereas exposure to indoor PM(2.5) levels was related to a decrease in Cu/Zn SOD activity and GSH plasma levels.

CONCLUSION

Supplementation with n-3 PUFA appeared to modulate the adverse effects of PM(2.5) on these biomarkers, particularly in the fish oil group. Supplementation with n-3 PUFA could modulate oxidative response to PM(2.5) exposure.

Possible Mechanisms of Neurodegeneration in Schizophrenia

Brain morphological alterations in schizophrenic patients have led to the neurodevelopmental hypothesis of schizophrenia. On the other hand, a progressive neurodegenerative process has also been suggested and some follow-up studies have shown progressive morphological changes in schizophrenic patients. Several neurotransmitter systems have been suggested to be involved in this disorder and some of them could lead to neuronal death under certain conditions. This review discusses some of the biochemical pathways that could lead to neurodegeneration in schizophrenia showing that neuronal death may have a role in the etiology or natural course of this disorder.

Silymarin protects dopaminergic neurons against lipopolysaccharide-induced neurotoxicity by inhibiting microglia activation

An inflammatory response in the central nervous system mediated by activation of microglia is a key event in the early stages of the development of neurodegenerative diseases. Silymarin is a polyphenolic flavanoid derived from milk thistle that has anti-inflammatory, cytoprotective and anticarcinogenic effects. In this study, we first investigated the neuroprotective effect of silymarin against lipopolysaccharide (LPS)-induced neurotoxicity in mesencephalic mixed neuron-glia cultures. The results showed that silymarin significantly inhibited the LPS-induced activation of microglia and the production of inflammatory mediators, such as tumour necrosis factor-alpha and nitric oxide (NO), and reduced the damage to dopaminergic neurons. Therefore, the inhibitory mechanisms of silymarin on microglia activation were studied further. The production of inducible nitric oxide synthase (iNOS) was studied in LPS-stimulated BV-2 cells as a model of microglia activation. Silymarin significantly reduced the LPS-induced nitrite, iNOS mRNA and protein levels in a dose-dependent manner. Moreover, LPS could induce the activation of p38 mitogen-activated protein kinase (MAPK) and c-jun N-terminal kinase but not extracellular signal-regulated kinase. The LPS-induced production of NO was inhibited by the selective p38 MAPK inhibitor SB203580. These results indicated that the p38 MAPK signalling pathway was involved in the LPS-induced NO production. However, the activation of p38 MAPK was not inhibited by silymarin. Nevertheless, silymarin could effectively reduce LPS-induced superoxide generation and nuclear factor kappaB (NF-kappaB) activation. It suggests that the inhibitory effect of silymarin on microglia activation is mediated through the inhibition of NF-kappaB activation.

MPTP: insights into parkinsonian neurodegeneration

MPTP burst upon the medical landscape two decades ago, first as a mysterious parkinsonian epidemic, triggering an unparalleled quest for the toxin's identity, and closely followed by an intense pursuit of its cellular mechanisms of action. MPTP treatment created an animal model of many features of Parkinson's disease (PD), used primarily in primates and later in mice. The critical role of oxidative stress damage to vulnerable dopamine neurons, as well as for neurodegenerative diseases in general, emerged from MPTP neurotoxicity. A remarkable cross-fertilization of basic and clinical findings, including genetic and epidemiologic studies, has greatly advanced our understanding of PD and revealed multiple factors contributing to the parkinsonian phenotypes. Brain imaging localizes sites of action and provides potential presymptomatic diagnostic testing. Epidemiologic reports linking PD with pesticide exposure were complimented by supportive evidence from biochemical studies of MPTP and structurally related compounds, especially after low-level, long-term exposure. Genetic studies on the role of risk genes, such as alpha-synuclein or parkin, have been validated by biochemical, anatomical and neurochemical investigations showing factors interacting to produce pathophysiology in the animal model. Focusing on the pivotal role of mitochondria, subcellular pathways participating in cell death have been clarified by unraveling similar sites of action of MPTP. Along the way, compounds antagonizing or potentiating MPTP effects indicated new PD therapies, some of the former achieving clinical trials. The future is encouraging for combating PD and will continue to benefit from the MPTP neurotoxicity model.