A PEPTIDE UNCOUPLING COLLAPSIN RESPONSE MEDIATOR PROTEIN-2 (CRMP-2) FROM THE VOLTAGE-GATED Ca2+ CHANNEL ATTENUATES MECHANICAL ALLODYNIA IN A RODENT MODEL OF DIABETIC NEUROPATHY
Wilson NM, Khanna R, & Wright DE
Rationale & Hypothesis: Ca2+ channel blockers have been demonstrated to be effective at alleviating pain in a number of neuropathic pain states, but the accompanying physiological side effects prevent their use. An alternative approach to channel blockade is channel modulation, and a short peptide modulator was developed with this in mind. Fusing the peptide, ST1-104, to transduction domain of HIV-1 transactivator of transcription (TAT) resulted in a cell permeable peptide that uncoupled the interaction between CRMP-2 and N-type voltage-gated Ca2+ channels (CaV2.2), thereby reducing Ca2+ currents and transmitter release. Since increased excitation and transmitter release peripheral nervous system in models of painful neuropathy, we hypothesized that the Ca2+ channel modulator, ST1-104, may reduce nociception in a model of diabetic neuropathy.
Objective: Test ability of systemic ST1-104 peptide to attenuate mechanical allodynia in STZ (Streptozotocin)-induced diabetic mice.
Methodology: 8 week old male A/J mice were injected with either STZ or citrate buffer. Weight, blood glucose, and mechanical behavior (von Frey filaments) were measured throughout the study duration. Following development of mechanical allodynia, mice were injections intraperitoneally with vehicle or ST1-104 (10 mg/kg) and mechanical behavior was assessed at 1 and 4 hours post-injection. Blood glucose was measured 4 hours after injection of vehicle or ST1-104.
Findings: ST1-104 and vehicle injections were administered 5 weeks post the induction of diabetes with STZ and mechanical behavior was assessed at 1 and 4 hours post injection. Diabetic vehicle treated mice had a significantly decreased mechanical threshold compared to non-diabetic vehicle controls at 1 and 4 hours (p<0.05). At 4 hours post injection, diabetic-ST1-104 mechanical threshold was significantly increased from diabetic-vehicle treated mice (2.67g±0.58 compared to 1.17g±0.32, p<0.05). Blood glucose was significantly increased in diabetic animals compared to non-diabetic but unaffected by ST1-104. These findings demonstrate the ability of ST1-104 to alleviate nociceptive behavior in a number of rodent pain models and suggest its broad therapeutic ability in neuropathic pain conditions. Mutagenesis, molecular dynamics simulations and chemical optimization strategies have yielded stable variants of ST1-104 with better cell penetrating abilities that will be tested in future work.