RESUMO
Oxidative stress is believed to play a central role in the pathogenesis of amyotrophic lateral sclerosis (ALS). We investigated the protective effects of overexpression of catalase in primary cultures of rat spinal motoneurons against the oxidative stress of hydrogen peroxide. Using microinjection, catalase-encoding cDNA was transferred into the motoneurons. In another approach, motoneurons were injected with a catalase solution. Both procedures elevated the intracellular antioxidant status of the cultured motoneurons as evidenced by a significant protection against H2O2 toxicity. We conclude that modulating the expression of enzymes involved in cellular defense against oxidative stress can render cells more resistant to oxidant toxicity.
Assuntos
Catalase/genética , Morte Celular/efeitos dos fármacos , DNA Complementar/genética , Peróxido de Hidrogênio/antagonistas & inibidores , Neurônios Motores/efeitos dos fármacos , Neurotoxinas/antagonistas & inibidores , Animais , Astrócitos/efeitos dos fármacos , Células Cultivadas , Técnicas de Cocultura , Microinjeções , Neuroglia/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos WistarRESUMO
Evidence is growing that reactive oxygen species (ROS), by-products of (normal) cellular aerobic metabolism, are involved in the pathogenesis of neurodegenerative diseases. One of these diseases is amyotrophic lateral sclerosis (ALS), in which motoneurons die, leading to paralysis and death. It remains uncertain whether ROS are the cause of (apoptotic) motoneuron death in ALS. To further understand the role of ROS in motoneuron death, we investigated the effects of ROS on isolated spinal rat motoneurons in culture. ROS were generated with a combination of iron(III) and ascorbate, or with hydrogen peroxide. Both toxic treatments resulted in a dose-dependent motoneuron death. Iron(III)/ascorbate toxicity was completely prevented with the hydrogen peroxide detoxifying enzyme catalase and partially prevented with the antioxidant vitamin E. SOD1, the enzyme that removes superoxide, did not protect against iron(III)/ascorbate toxicity. ROS treatment caused apoptotic motoneuron death: low doses of iron(III)/ ascorbate or hydrogen peroxide resulted in complete apoptosis ending in nuclear fragmentation, while high doses of ROS resulted in incomplete apoptosis (nuclear condensation). Thus, depending on the dose of ROS, the motoneurons complete the apoptotic pathway (low dose) or are stopped somewhere during this route (high dose).
