Processing of Reelin by embryonic neurons is important for function in tissue but not in dissociated cultured neurons.

Reelin, the protein defective in reeler mutant mice, plays a key role during brain development. Reelin is processed proteolytically at two sites, and the central fragment mimics function in vitro. Here, we show that processing is functionally important in vivo, a question that could not be addressed in our previous study. New monoclonal antibodies directed against central Reelin block its binding to lipoprotein receptors and perturb cortical development in vitro, confirming the importance of the central fragment that is detected in tissue and body fluids. Processing occurs when Reelin is incubated with embryonic neurons in culture or with their supernatant, but inhibition of processing by a metalloproteinase blocker does not prevent Reelin signaling in neurons. Furthermore, neurons internalize similarly full-length or central Reelin. In contrast, inhibition of processing prevents signaling and perturbs cortical development in cultured embryonic brain slices. Moreover, in vivo, the concentration of central Reelin is dramatically and selectively increased in receptor-deficient tissue, suggesting its specific downregulation after binding to receptors and internalization. We propose that processing by end-migration neurons is required in tissue (where Reelin is likely anchored to the extracellular matrix) to release the central fragment that diffuses locally and signals to target cells, whereas, in vitro, all Reelin forms have indiscriminate access to cells, so that cleavage is not necessary for signaling.

[Pituitary adenylate cyclase activating polypeptide protects neuro-2a cells from beta amyloid protein cytotoxicity by modulating intracellular calcium].

MTT analysis and intracellular calcium measurement by using confocal laser scanning microscopy were used to study the possible mechanism of protective effect of pituitary adenylate cyclase activating polypeptide 27 (PACAP27) from beta amyloid protein (Abeta)-induced neurotoxicity. The results showed that treatment with PACAP (less than 0.1 micromol/L) increased the survival and reproductive ability of neuro-2a cells and protected the neuro-2a cells from being injured by Abeta. The protective effect of PACAP27 was reversed by the competitive PACAP receptor antagonist PACAP6-27. An increase in intracellular calcium was observed when the cells were challenged with Abeta and PACAP. But the calcium increase induced by Abeta kept stable for a long time while PACAP caused a transient rise in intracellular calcium. The intracellular calcium increase induced by Abeta was blocked by pretreatment with PACAP for 10 min. It is suggested that the neuroprotective effect of PACAP against neuronal damage induced by Abeta may result from its role in inhibiting the sustained rise in intracellular calcium.

[Relationship between amyloid beta-protein and oxidative stress and the protective role of pituitary adenylate cyclase activating polypeptide against oxidative stress induced damage on neuro-2a cells].

AIM: To observe the relationship between amyloid beta-protein (Abeta) and oxidative stress and the protective role of pituitary adenylate cyclase activating polypeptide (PACAP, PACAP-27) against damage induced by oxidative stress (H2O2) in neurem-2a cells. METHODS: With cultured neuro-2a cells the cell survival and apoptosis were measured by MTT assay, Hoechest33258 staining, DNA ladder and the percentage of small DNA fragment. RESULTS: Concentration-dependent toxicity was induced with H2O2 treatment for 24 h. The neurotoxicity of H2O2 was increased by about 10 times with cotreatment neurons with amyloid beta-protein fragment 25-35 (Abeta(25-35)). While decrease the percentage of small DNA fragmentation the cell survival was increased with co-treatment with PACAP-27(which were added to the culture everyday). The effect of PACAP was not reversed with antagonist of PACAP receptor, PACAP(6-27). CONCLUSION: Abeta and H2O2 can promote each other's neurotoxicity. Cultured neurons were protected by PACAP27 from the neurotoxicity of H2O2 but not through the activation of PACAP-27 receptor.

[Activation of PACAP receptor could protect cultured hippocampal neurons against beta amyloid peptide induced neurotoxicity].

AIM: To observe the protective role of pituitary adenylate cyclase activating polypeptide (PACAP) on hippocampal neuronal apoptosis induced by beta amyloid peptide in the culture. METHODS: Hippocampal neurons were isolated from 1d old SD rat and neuronal survival and apoptosis were measured by MTT assay and DNA ladder. RESULTS: 25 micromol/L Abeta could induce neuron apoptosis while co-treatment with PACAP could increase the survival of hippocampal neurons. The antagonist of PACAP receptor, P6-27, could reverse the effect of PACAP. CONCLUSION: PACAP could protects cultured neurons from the neurotoxicity of Abeta through the activation of PACAP receptor and may have a bright use in treatment of neurodegenerative disease.