Effect of IL-1β on survival and energy metabolism of R28 and RGC-5 retinal neurons

PURPOSE. Interleukin-(IL)1β expression is increased in the retina during a variety of diseases involving the death of retinal neurons and contributes to neurodegenerative processes through an unknown mechanism. This study was conducted to examine the effects of IL-1β on the metabolism and viability of RGC-5 and R28 retinal neuronal cells. METHODS. Cellular reductive capacity was evaluated using WST-1 tetrazolium salt. Mitochondrial transmembrane potential was determined by JC-1 fluorescence. Cellular ATP levels were measured with a luciferase assay. Caspase-3/7 activation was detected with a DEVDase activity assay. Cell death and lysis was evaluated by measuring release of lactate dehydrogenase (LDH). Glycolysis was assessed by measuring glucose disappearance and lactate appearance in cell culture medium. Cellular respiration was followed polarographically. RESULTS. IL-1β treatment caused a pronounced decrease in cellular reductive potential. IL-1β caused depletion of intracellular ATP, loss of mitochondrial transmembrane potential, caspase-3/7 activation, and LDH release. IL-1β treatment increased rates of glucose utilization and lactate production. The cells were partially protected from IL-1β toxicity by ample ambient glucose. However, glucose did not block the ability of IL-1β to cause a decline in mitochondrial transmembrane potential or ATP depletion. IL-1β decreased oxygen consumption of the R28 cells by nearly half, but did not lower cytochrome c oxidase activity. CONCLUSIONS. The present results suggest that IL-1β inhibits mitochondrial energy metabolism of these retinal neuronlike cells.