The physiological behaviour of IMR-32 neuroblastoma cells is affected by a 12-h hypoxia/24-h reoxygenation period.

Nervous system cells are highly dependent on adequate tissue oxygenation and are very susceptible to hypoxia, which causes mitochondrial dysfunctions involved in apoptosis and necrosis. In this paper, we examine the effect of a 12-h incubation of differentiated IMR-32 neuroblastoma cells in a hypoxic environment (73% N(2): 2% O(2): 5% CO(2), v:v) by evaluating cell viability, modifications of NO, intracellular Ca(2+) concentration [Ca(2+)](i) and membrane potential, the production of phosphorylated ERK, desferoxamine-chelatable free iron and esterified F2-isoprostane levels. The same parameters were evaluated after a subsequent 24-h re-oxygenation period. The NO concentration increased significantly immediately after hypoxia and returned to values similar to those of controls after the reoxygenation period. At the same time, we observed a significant increase of [Ca(2+)](i) immediately after hypoxia. Phosphorylated ERK proteins increased significantly during the first 2 h of hypoxia, then decreased, and remained practically unmodified after 12 h hypoxia and the following reoxygenation period. Moreover, IMR-32 cell mitochondria were significantly depolarized after hypoxia, while membrane potential returned to normal after the reoxygenation period. Finally, desferoxamine-chelatable free iron and F2-isoprostane levels also increased significantly after hypoxia. Our results indicate that 2% O(2) hypoxia induces variations of NO and [Ca(2+)](i) with subsequent mitochondrial depolarization, and it is responsible for oxidative stress, represented by increased free iron and F2-isoprostane, protein carbonyls and 4 hydroxynonenal protein adducts levels.

The effects of hypoxia/reoxygenation on the physiological behaviour of U373-MG astrocytes.

Nerve cells are very susceptible to hypoxia responsive for mitochondrial dysfunctions involved in the subsequent oxidative stress, apoptosis and necrosis. In this paper, we examined the effect of 12 h incubation of U-373 MG astrocytes in hypoxic environment (73% N(2): 2% O(2): 5% CO(2), v:v) by evaluating cell proliferation, modifications of NO and ATP production, intracellular Ca(2+) concentration [Ca(2+)](i), membrane potential, desferoxamine-chelatable free iron, esterified F2-isoprostanes levels and the production of phosphorylated ERK. The same parameters were evaluated also after a following re-oxygenation period of 24 h. Immediately after hypoxia the NO concentration increased significantly and returned to values similar to those of controls after the re-oxygenation period. At the same time, ATP levels remained similar to controls and the cell proliferation significantly decreased. This involved a significant increase of [Ca(2+)](i) immediately after hypoxia and the value remained significantly elevated after the following re-oxygenation period. Moreover, after hypoxia, astrocytes were slightly although not significantly depolarized. Indeed iron and F2-isoprostanes levels increased significantly after hypoxia. Finally ERK proteins increased slowly and not significantly after hypoxia and the same trend was observed after the re-oxygenation period. On the whole, our results indicate that 2% O(2) hypoxia induces a moderate oxidative stress, well tolerated by U-373 MG cells, remaining the ATP production, mitochondrial membrane potential and activated ERK proteins, similar to the values of controls.