Astrocytes protect neurons from hydrogen peroxide toxicity

TLDR

Neurons are highly vulnerable to hydrogen peroxide toxicity. This study examined whether astrocytes modulate the neurotoxic effects of H₂O₂. Neuronal survival was quantified using an MTT assay or an ELISA for microtubule‑associated protein‑2. H₂O₂ induced concentration‑dependent neuronal death, but co‑culture with astrocytes—especially at a 1:20 astrocyte‑to‑neuron ratio—strongly attenuated this effect, with catalase activity in astrocytes and glutathione peroxidase in neurons mediating protection, suggesting astrocytes can delay neuronal death in H₂O₂‑related pathology.

Abstract

Recent reports indicate that neurons are particularly sensitive to hydrogen peroxide (H2O2). The present study was undertaken to investigate the putative role of astrocytes in the modulation of the neurotoxic effect of H2O2. The exposure to H2O2 of cultured striatal neurons from mouse embryos induced a concentration-dependent (10-1000 microM) cell death as estimated 24 hr later. Two methods were used to estimate neuronal survival: the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay or an enzyme-linked immunosorbent assay with antibodies directed against an antigen located in neurons (microtubule-associated protein-2). The neurotoxic effect of H2O2 on neurons cocultured with astrocytes was strongly attenuated compared with that observed on a pure population of neurons seeded at the same density. Moreover, the protective effect of astrocytes depended on the astrocytes/neurons ratio, a significant neuroprotection being detectable for 1 astrocyte to 20 neurons. Catalase seems to be the main hydrogen peroxidase activity involved in the neuroprotective effect of astrocytes. Indeed, in the culture conditions used, this enzymatic activity was enriched in this cell type compared with neurons; its inhibition, and not that of glutathione peroxidase, reduced the disappearance rate of the oxidant. On the contrary, glutathione peroxidase appeared to be the main enzymatic activity involved in the neuronal defense against H2O2 toxicity. Therefore, astrocytes could delay neuronal death in pathological situations in which H2O2 has been, at least partially, demonstrated to be involved.