Role of NGF in spared DRG following partial dorsal rhizotomy in cats

Endogenous TGFβ1 Plays a Crucial Role in Functional Recovery After Traumatic Brain Injury Associated with Smad3 Signal in Rats

Transforming growth factor-β 1 (TGFβ1) has a diverse role in astrogliosis and neuronal survival, but the underlying mechanism remains to be elucidated, especially in traumatic brain injury (TBI). Here, we show that the expression of TGFβ1 was increased in the pericontusional region, accompanied with astrogliosis and neuronal loss in TBI rats. Moreover, TGFβ1 knockdown not only reduced the number of neurons and inhibited astrogliosis but also resulted in a significant neurological dysfunction in rats with TBI. Subsequently, Smad3, a key downstream signal of TGFβ1, was involved in pericontusional region after TBI. These findings therefore indicate that TGFβ1 is involved in neuroprotection and astrogliosis, via activation of down stream Smad3 signal in the brain after injury.

Protective effects and anti-apoptotic role of nerve growth factor on spinal cord neurons in sciatic nerve-injured rats

OBJECTIVES

The purpose of this study is to demonstrate a dependence of spinal cord motoneurons on the communication with their targets, sciatic nerves, and investigate whether the effects of nerve growth factor (NGF) on the spinal cord neuron apoptosis and surviving through the regulation of nuclear factor-kappa B (NF-kappaB) in Schwann cells (SCs) in sciatic nerve injured rats.

METHODS

Ninety healthy adult Sprague-Dawley rats were divided randomly into normal control group, crushing group, and NGF-intervened group. When sciatic nerve crushed 1, 3, 7, 14, and 21 days, the expression of NF-kappaB in SCs and the apoptosis regulator Bcl-2 and Caspase-3 in spinal cord were examined by immunohistochemistry staining, Western blot analysis, and immunofluorescence double-labeling method, the motor neuron apoptosis were investigated by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), and the surviving neurons were tested by toluidine blue (Nissl) staining, respectively. All the data were further analyzed with SPSS10·0 application software.

RESULTS

The level of the expression of NF-kappaB in crushing group enhanced at 1 day after crushing, reached peak at 3 days, and reduced at least until 21 days, which was markedly higher than that in the normal control group. The expression of NF-kappaB in NGF-intervened group showed the same changes, reached peak at 7 days, and reduced until 21 days. However, when compared with crushing group, the expression of NF-kappaB in NGF-intervened group was down-regulated significantly until 3 days after injury, and up-regulated obviously with time going on. The same trend was observed in the time course on motor neuron apoptosis in crushing group and NGF-intervened group after sciatic nerves injury, while the reversing change was found in the surviving neurons. Moreover, the kinetics of Bcl-2 expression in spinal cord was consistent with that of NF-kappaB, while reversing with that of Caspase-3.

CONCLUSION

The findings revealed that NGF may play a pivotal role of anti-apoptosis in spinal cord neurons through retrograde transport of NF-kappaB in SCs following sciatic nerve injury in rats.

Gunjigake K, Kataoka S, N. Kuroishi K, Ono K, Toyono T, Kobayashi S, Yamaguchi K. Nerve Growth Factor Involves Mutual Interaction between Neurons and Satellite Glial Cells in the Rat Trigeminal Ganglion

Nerve growth factor (NGF) plays a critical role in the trigeminal ganglion (TG) following peripheral nerve damage in the oral region. Although neurons in the TG are surrounded by satellite glial cells (SGCs) that passively support neural function, little is known regarding NGF expression and its interactions with TG neurons and SGCs. This study was performed to examine the expression of NGF in TG neurons and SGCs with nerve damage by experimental tooth movement. An elastic band was inserted between the first and second upper molars of rats. The TG was removed at 0–7 days after tooth movement. Using in situ hybridization, NGF mRNA was expressed in both neurons and SGCs. Immunostaining for NGF demonstrated that during tooth movement the number of NGF-immunoreactive SGCs increased significantly as compared with baseline and reached maximum levels at day 3. Furthermore, the administration of the gap junction inhibitor carbenoxolone at the TG during tooth movement significantly decreased the number of NGF-immunoreactive SGCs. These results suggested that peripheral nerve damage may induce signal transduction from neurons to SGCs via gap junctions, inducing NGF expression in SGCs around neurons, and released NGF may be involved in the restoration of damaged neurons.

Functional roles of intrinsic neurotrophin-3 in spinal neuroplasticity of cats following partial ganglionectomy

This study detected the effects of endogenous neurotrophin-3 (NT-3) on the collateral sprouting derived from the L6 dorsal root ganglion (DRG) after unilateral removal of adjacent DRGs (L1–L5 and L7) in cats. Cholera toxin B tracing revealed significant neurite growth from the spared L6 DRG and axonal sprouting in the dorsal column. There was a significant increase in the number of NT-3 and trkC immunopositive neurons as well as in NT-3 protein level in the spared DRG by immunohistochemistry and enzyme-linked immunoadsorbent assay. NT-3 and its mRNA and trkC were located mainly in large- and medium-sized DRG neurons. NT-3 antibody neutralization in vivo and in vitro results in marked reduction in sprouted fibers. These findings point to an important role of NT-3 in neural plasticity at dorsal column axons.