The Protein Tyrosine Kinase Inhibitor Tyrphostin 23 Strongly Accelerates Glycolytic Lactate Production in Cultured Primary Astrocytes

Abstract

Tyrphostin 23 (T23) is a well-known inhibitor of protein tyrosine kinases. To investigate potential acute effects of T23 on the viability and the glucose metabolism of brain cells, we exposed cultured primary rat astrocytes to T23 for up to 4 h. While the viability and the morphology of the cultured astrocytes were not acutely affected by the presence of T23 in concentrations of up to 300 µM, this compound caused a rapid, time- and concentration-dependent increase in glucose consumption and lactate release. Maximal effects on glycolytic flux were found for incubations with 100 µM T23 for 2 h which doubled both glucose consumption and lactate production. The stimulation of glycolytic flux by T23 was reversible, completely abolished upon removal of the compound and not found in presence of other known inhibitors of endocytosis. Structurally related compounds such as tyrphostin 25 and catechol or modulators of AMP kinase activity did neither affect the basal nor the T23-stimulated lactate production by astrocytes. In contrast, the presence of the phosphatase inhibitor vanadate completely abolished the stimulation by T23 of astrocytic lactate production in a concentration-dependent manner. These data suggest that T23-sensitive phosphorylation/dephosphorylation events are involved in the regulation of astrocytic glycolysis.

β-lapachone-mediated WST1 Reduction as Indicator for the Cytosolic Redox Metabolism of Cultured Primary Astrocytes

“…This WST1 reduction in glucose-free incubation buffer was lowered by a 30 min preincubation of the cells in glucose-free medium, suggesting that the cells generated substantial amounts of the NAD(P)H used for NQO1-dependent WST1 reduction by the metabolism of substrates and metabolic intermediates that had been present in the cells at the onset of the glucose-free incubation, as also reported for incubations of astrocytes with menadione as redox cycler [ 6 ]. These substrates are likely to include free glucose in the cells that is derived from the initial high glucose concentration present in the culture medium [ 38 ] and cellular glycogen that is rapidly mobilised after glucose deprivation in astrocytes [ 39 ].…”