Painful neuropathy is the major dose-limiting side effect of
paclitaxel chemotherapy.
Mitochondrial dysfunction and
adenosine triphosphate (
ATP) deficit have previously been shown in peripheral nerves of
paclitaxel-treated rats, but the effects of
paclitaxel in the dorsal root ganglia (DRGs) have not been explored. The aim of this study was to determine the bioenergetic status of DRG neurons following
paclitaxel exposure in vitro and in vivo. Utilising isolated DRG neurons, we measured respiratory function under basal conditions and at maximal capacity, glycolytic function, and
Adenosine diphosphate (
ADP)/
ATP levels at 3 key behavioural timepoints; prior to
pain onset (day 7), peak
pain severity and
pain resolution. At day 7, maximal respiration and spare reserve capacity were significantly decreased in DRG neurons from
paclitaxel-treated rats. This was accompanied by decreased basal
ATP levels and unaltered
ADP levels. At peak
pain severity, respiratory function was unaltered, yet glycolytic function was significantly increased. Reduced
ATP and unaltered
ADP levels were also observed at the peak
pain timepoint. All these effects in DRG neurons had dissipated by the
pain resolution timepoint. None of these
paclitaxel-evoked changes could be replicated from in vitro
paclitaxel exposure to naive DRG neurons, demonstrating the impact of in vivo exposure and the importance of in vivo models. These data demonstrate the nature of
mitochondrial dysfunction evoked by in vivo
paclitaxel in the DRG for the first time. Furthermore, we have identified
paclitaxel-evoked changes in the bioenergetics of DRG neurons, which result in a persistent energy deficit that is causal to the development and maintenance of
paclitaxel-induced
pain.