Abstract:

:Morphological and behavioral evidence suggests that vasoinhibin is present in the central nervous system, triggering neuroendocrine and behavioral responses to stress. Moreover, vasoinhibin reduces neuronal survival and differentiation of primary sensory neurons of the peripheral nervous system. In order to address the functional role played by vasoinhibin at the CNS, and to better understand the underlying mechanisms involved in its actions, we treated primary cultured hippocampal neurons obtained from E16 mice with a human recombinant vasoinhibin. We examined the resulting cellular changes focusing on neuronal cell death and explored the local generation of vasoinhibin within the hippocampus. Our results show that vasoinhibin significantly reduced neuronal cell density, increased immunoreactive activated caspase-3, and TUNEL-positive staining at 72, 16, and 24 h, respectively. Furthermore, vasoinhibin increased the expression of pro-apoptotic genes BAX, BAD, BIM and PUMA and decreased that of the anti-apoptotic gene BCL-2 at 24 h, as assessed by RT-qPCR. Vasoinhibin effects were blocked by co-incubation with a vasoinhibin antibody or with prolactin. Immunoreactive bands consistent with vasoinhibin were observed in hippocampal extracts by Western blot analysis, and a prolactin standard was cleaved to vasoinhibin by a hippocampal lysate in a heat- and cathepsin D inhibitor pepstatin A-dependent fashion. Taken together, these data support the notion that vasoinhibin is locally produced by cathepsin D within the embryonic mouse hippocampus, a brain region that plays a critical role in emotional regulation, resulting in decreased neuronal cell viability via the activation of the intrinsic apoptosis pathway.