Astrocytes modulate thapsigargin-induced changes in calcium concentration and neuronal survival.
When mature cerebellar granule neurons (CGN) grown in high K+ (25 mM K+, HK)-serum containing medium are subjected to the HK/serum deprivation, they are destined for neuronal death. In this study, we attempted to elucidate the roles of endoplasmic reticular (ER) Ca2+-store and co-cultured astrocytes in HK/serum deprivation induced neuronal death. Thapsigargin (TG), an inhibitor of ER Ca2+-ATPase was simultaneously applied with normal K+ (5 mM K+, NK) serum free medium, and its effects on neuronal death in either astrocyte-poor or astrocyterich culture were examined. By means of the fura-2 microfluorimetric technique, we monitored the changes of the intracellular Ca2+ concentration, [Ca2+]i, associated with neuronal death under various treatments. The results obtained showed that in astrocyte-poor cultures of mature CGN (10 days in vitro, DIV), the basal level of [Ca2+]i markedly decreased from 184 +/- 5 to 89.7 +/- 5 nM 24 h after HK/serum deprivation. Although treatment with TG slightly increased the [Ca2+]i to 117.6 +/- 4 nM, the survival rate of the neurons was even worse; it was reduced from 49 +/- 4% to 28 +/- 2%. In the astrocyte-rich cultures, HK/serum deprivation also caused a profound reduction of neuronal [Ca2+]i, from 166 +/- 3 to 90.2 +/- 6 nM, accompanied by even more serious neuronal death (95.5 +/- 1%). On the other hand, treatment with TG in astrocyterich cultures further lowered the [Ca2+]i to 65 +/- 2 nM but markedly improved the neuronal survival rate from 4.5 +/- 1% to 60 +/- 2% in a concentration-dependent manner. The strong implication of these findings is that ER Ca2+-store and astrocytes participate in modulating the responses of neurons to stress stimulation.
Yao
C J
CJ
Institutes of Toxicology, College of Medicine, National Taiwan University, Taipei, ROC.
Lin
C W
CW
Lin-Shiau
S Y
SY
D000818:Animals; D001253:Astrocytes / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D018920:Coculture Techniques; D016895:Culture Media, Serum-Free; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D019284:Thapsigargin / Q000494:pharmacology*
D016895:Culture Media, Serum-Free; D019284:Thapsigargin; D011188:Potassium; D002118:Calcium