Neuroprotection and intracellular Ca2+ modulation with fructose-1,6-bisphosphate during in vitro hypoxia-ischemia involves phospholipase C-dependent signaling.

Abstract

The neuroprotectant fructose-1,6-bisphosphate (FBP) preserves cellular [ATP] and prevents catastrophic increases in [Ca2+]i during hypoxia. Because FBP does not enter neurons or glia, the mechanism of protection is not clear. In this study, we show that FBP's capacity to protect neurons and stabilize [Ca2+]i during hypoxia derives from signaling by a phospholipase-C-intracellular Ca2+-protein kinases pathway, rather than Ca2+ chelation or glutamate receptor inhibition. FBP reduced [Ca2+]i changes in hypoxic hippocampal neurons, regardless of [Ca2+]e, and preserved cellular integrity as measured by trypan blue or propidium iodide exclusion and [ATP]. FBP also prevented hypoxia-induced increases in [Ca2+]i when glucose was absent and when [Ca2+]e was increased to negate Ca2+ chelation by FBP. These protective effects were observed equally in postnatal day 2 (P2) and P16 neurons. Inhibiting glycolysis with iodoacetate eliminated the protective effects of FBP in P16 neurons. FBP did not alter Ca2+ influx stimulated by brief applications of NMDA or glutamate during normoxia or hypoxia, but did reduce the increase in [Ca2+]i produced by 10 min of glutamate exposure during hypoxia. Because FBP increases basal [Ca2+]i and stimulates membrane lipid hydrolysis, we tested whether FBP's protective action was dependent on phospholipase C signaling. The phospholipase C inhibitor U73122 prevented FBP-induced increases in [Ca2+]i and eliminated FBP's ability to stabilize [Ca2+]i and increase survival during anoxia. Similarly, FBP's protection was eliminated in the presence of the mitogen/extracellular signal protein kinase (MEK) inhibitor U0126. We conclude that FBP may produce neuroprotection via activation of neuroprotective signaling pathways that modulate Ca2+ homeostasis.

• Authors: P H Donohoe, C S Fahlman, P E Bickler, Z S Vexler, G A Gregory
• Journal: Brain research (Brain Res) Vol. 917 Issue 2 Pg. 158-66 (Nov 02 2001) ISSN: 0006-8993 [Print] Netherlands
• PMID: 11640901 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Fructosediphosphates
• Neuroprotective Agents
• Receptors, Glutamate
• Adenosine Triphosphate
• Type C Phospholipases
• fructose-1,6-diphosphate
• Calcium

Topics

• Adenosine Triphosphate (metabolism)
• Animals
• Brain Ischemia (metabolism)
• Calcium (metabolism)
• Cell Survival (drug effects)
• Fructosediphosphates (pharmacology)
• Hypoxia (metabolism)
• In Vitro Techniques
• Intracellular Membranes (metabolism)
• Mice
• Neuroprotective Agents (pharmacology)
• Osmolar Concentration
• Rats
• Rats, Sprague-Dawley
• Receptors, Glutamate (physiology)
• Signal Transduction (physiology)
• Type C Phospholipases (physiology)