Human Carbonic Anhydrase-8 AAV8 Gene Therapy Inhibits Nerve Growth Factor Signaling Producing Prolonged Analgesia and Anti-Hyperalgesia in Mice

Carbonic anhydrase-8 (Car8; murine gene symbol) is an allosteric inhibitor of inositol trisphosphate receptor-1 (ITPR1), which regulates neuronal intracellular calcium release. We previously reported that wildtype Car8 overexpression corrects the baseline allodynia and hyperalgesia associated with calcium dysregulation in the waddle (wdl) mouse due to a 19 bp deletion in exon 8 of the Car8 gene. In this report, we provide preliminary evidence that overexpression of the human wildtype ortholog of Car8 (CA8(WT)), but not the reported CA8 S100P loss-of-function mutation (CA8(MT)); inhibits nerve growth factor (NGF)-induced phosphorylation of ITPR1, TrkA (NGF high affinity receptor); and ITPR1-mediated cytoplasmic free calcium release in vitro. Additionally, we show that gene-transfer using AAV8-V5-CA8(WT) viral particles via sciatic nerve injection demonstrates retrograde transport to dorsal root ganglia (DRG) producing prolonged V5-CA8(WT) expression, pITPR1 and pTrkA inhibition, and profound analgesia and anti-hyperalgesia in male C57BL/6J mice. AAV8-V5-CA8(WT) mediated overexpression prevented and treated allodynia and hyperalgesia associated with chronic neuropathic pain produced by the spinal nerve ligation (SNL) model. These AAV8-V5-CA8 data provide a proof-of-concept for precision medicine through targeted gene therapy of NGF-responsive somatosensory neurons as a long-acting local analgesic able to prevent and treat chronic neuropathic pain through regulating TrkA signaling, ITPR1 activation, and intracellular free calcium release by ITPR1.