Vasoinhibin generation and effect on neuronal apoptosis in the hippocampus of late mouse embryos.

Morphological and behavioral evidence suggests that vasoinhibin is present in the central nervous system (CNS), triggering neuroendocrine and behavioral responses to stress. Moreover, vasoinhibin reduces neuronal survival and differentiation of primary sensory neurons of the peripheral nervous system. 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 embryonic day 16 (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 and increased immunoreactive activated caspase-3 and TUNEL-positive staining at 72, 16, and 24 h, respectively. Furthermore, vasoinhibin increased the expression of proapoptotic genes BAX, BAD, BIM, and PUMA and decreased that of the antiapoptotic gene BCL-2 at 24 h, as assessed by quantitative real-time reverse transcription-polymerase chain reaction. Vasoinhibin effects were blocked by coincubation 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.

Vasoinhibin Suppresses the Neurotrophic Effects of VEGF and NGF in Newborn Rat Primary Sensory Neurons.

BACKGROUND/AIMS: Studies on the biological actions of vasoinhibins have focused mainly on endothelial cells. However, there is incipient knowledge about how vasoinhibins affect the nervous system, even if the target cells and mechanisms of action involved in these effects are unknown. METHODS: In order to determine if neurons are direct targets of vasoinhibins, we examined cellular outcomes and the intracellular pathways involved in the neuronal actions of vasoinhibins using newborn rat dorsal root ganglion (DRG) neurons as a model system. RESULTS: Vascular endothelial growth factor (VEGF) or nerve growth factor (NGF) treatment for 48 h resulted in neurite outgrowth stimulation in both DRG cultured explants and isolated primary sensory neurons. Interestingly, a recombinant vasoinhibin containing the first 123 amino acids of human prolactin antagonized the VEGF- and NGF-induced stimulation of neurite outgrowth. Vasoinhibin significantly reduced the density of neurites in DRG explants and obliterated neuritogenesis in isolated DRG neurons in primary culture, supporting a direct neuronal effect of vasoinhibin. In cultures of isolated DRG cells, virtually all ß3-tubulin-labeled cells express TrkA, and the majority of these cells also express VEGFR2. Short-term VEGF or NGF treatment of DRG explants resulted in increased ERK1/2 and AKT phosphorylation, whereas incubation of DRG with the combination of either VEGF or NGF together with vasoinhibin resulted in blunted VEGF- or NGF-induced phosphorylation of both ERK1/2 and AKT. CONCLUSION: Our results show that primary sensory neurons are direct targets of vasoinhibin, and suggest that vasoinhibin inhibition of neurite outgrowth involves the disruption of ERK and AKT phosphorylation cascades.

Prolactin mitigates deficiencies of retinal function associated with aging.

Aging causes the progressive degeneration of retinal cells leading to the eventual loss of vision. The hormone prolactin (PRL) is a neurotrophic factor able to compensate for photoreceptor cell death and electroretinogram deficits induced by light retinal damage. Here, we used adult 4-month old and aged 20-month old pigmented mice, null or not for the PRL receptor to explore whether PRL provides trophic support against age-related retinal dysfunction. Retinal functionality, apoptosis, glia activation, and neurotrophin expression were assessed by electroretinogram, TUNEL, glial fibrillary acidic protein and ionized calcium binding adaptor molecule 1 immunohistochemistry, and real-time PCR, respectively. Lack of PRL signaling in aged mice, but not in adult mice, correlated with photosensitive retinal dysfunction, increased photoreceptor apoptosis, differential expression of proapoptotic mediators, and microglia activation. We conclude that PRL is required for maintaining retinal functionality in both female and male mice during aging and has potential therapeutic value against age-related retinal disorders.