Interleukin-10 modulates [Ca2+]i response induced by repeated NMDA receptor activation with brief hypoxia through inhibition of InsP3-sensitive internal stores in hippocampal neurons

The goal of this study was to evaluate an effect of interleukin-10 (IL-10) on the Ca2+ response induced by repeated NMDA receptor activation with brief hypoxia in cultured hippocampal neurons. We focused on the importance of internal Ca2+ stores in the modulation of this Ca2+ response by IL-10. To test this, we compared roles of InsP3- and ryanodine-sensitive internal stores in the effects of IL-10. Measurements of intracellular cytosolic calcium concentration ([Ca2+]i) in cultured hippocampal neurons were made by imaging Fura-2AM loaded hippocampal cells. Repeated episodes of NMDA receptor activation with brief hypoxia induced the spontaneous (s) [Ca2+]i increases about 3 min after each hypoxic episode. The amplitude of the s[Ca2+]i increases was progressively enhanced from the first hypoxic episode to the third one. IL-10 (1 ng/ml) abolished these s[Ca2+]i increases. Exposure of cultured hippocampal neurons with thapsigargin (1 μM) or an inhibitor of phospholipase C (U73122, 1 μM) for 10 min also abolished the s[Ca2+]i increases. On the other hand, antagonist of ryanodine receptors (ryanodine, 1 μM) did not affect this Ca2+ response. These studies appear to provide the first evidence that Ca2+ release from internal stores is affected by anti-inflammatory cytokine IL-10 in brain neurons. It is suggested that these data increase our understanding of the neuroprotective mechanisms of IL-10 in the early phase of hypoxia.

► Repeated episodes of NMDA receptor activation with hypoxia induce the spontaneous Ca2+i increases. ► IL-10 abolishes this Ca2+i response. ► Ryanodine does not affect the spontaneous Ca2+i increases. ► U73122, an inhibitor of phospholipase C, and thapsigargin abolish the spontaneous Ca2+i increases. ► IL-10 abolishes this Ca2+i response through inhibition of InsP3-sensitive internal stores.