Brain-derived Neurotrophic Factor (BDNF) Acts Primarily Via the JAK/STAT Pathway to Promote Neurite Growth in the Major Pelvic Ganglion of the Rat: Part I

Introduction: Identification of the molecular mechanism of cavernous nerve regeneration is essential for future development of neuroprotective and regenerative strategies.

Aim: To identify specific signal transduction pathway(s) associated with brain-derived neurotrophic factor (BDNF) enhanced cavernous nerve regeneration in an in vitro model.

Materials And Methods: Using 6-month-old male Fisher rats, inhibitors of four candidate signaling pathways were added to BDNF-treated explant cultures of major pelvic ganglia with attached cavernous nerve fragments. Study groups comprised of controls, BDNF alone at 50 ng/mL, or BDNF 50 ng/mL and inhibitors against MEK, PI3-K, PKA, and JAK/STAT pathways at increasing concentrations.

Main Outcome Measure: The maximal neurite length for each tissue culture was measured and the mean maximal length +/- standard deviation was determined for all groups at 24, 36, and 48 hours.

Results: The JAK/STAT specific inhibitor AG490 significantly reduced BDNF-enhanced neurite growth. Maximum neurite lengths at 24, 36, and 48 hours for BDNF 50 ng/mL treated groups were 182.3, 348.1, and 528.1 microm, compared with AG490 at 25 microM (86.4, 165.1, 278.3 microm), 50 microM (78.8, 151.7, 235.3 microm), and 100 microM (71.83, 107.0, 219.6 microm) (P < 0.05). Neurite measures for BDNF with 25 and 50 microM U0126 (MEK pathway) were reduced to 402.0 and 424.3 microm at 48 hours, respectively (P < 0.05), likely reflecting an accessory molecular pathway. A similar observation was made for 100 uM LY294002 (PI3-K). No difference was observed for PKA inhibition.

Conclusion: The JAK/STAT pathway is the major signal-transduction pathway of BDNF-enhanced cavernous nerve growth in an in vitro rat model.