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 1

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 mu m, compared with AG490 at 25 mu M (86.4, 165.1, 278.3 mu m), 50 mu M (78.8, 151.7, 235.3 mu m), and 100 mu M (71.83, 107.0, 219.6 mu m) (P < 0.05). Neurite measures for BDNF with 25 and 50 mu M U0126 (MEK pathway) were reduced to 402.0 and 424.3 mu m 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.