Acyl Ghrelin Improves Synapse Recovery in an In Vitro Model of Postanoxic Encephalopathy

Abstract

Comatose patients after cardiac arrest have a poor prognosis. Approximately half never awakes as a result of severe diffuse postanoxic encephalopathy. Several neuroprotective agents have been tested, however without significant effect. In the present study, we used cultured neuronal networks as a model system to study the general synaptic damage caused by temporary severe hypoxia and the possibility to restrict it by ghrelin treatment. Briefly, we applied hypoxia (pO2 lowered from 150 to 20 mmHg) during 6 h in 55 cultures. Three hours after restoration of normoxia, half of the cultures were treated with ghrelin for 24 h, while the other, non-supplemented, were used as a control. All cultures were processed immunocytochemically for detection of the synaptic marker synaptophysin. We observed that hypoxia led to drastic decline of the number of synapses, followed by some recovery after return to normoxia, but still below the prehypoxic level. Additionally, synaptic vulnerability was selective: large- and small-sized neurons were more susceptible to synaptic damage than the medium-sized ones. Ghrelin treatment significantly increased the synapse density, as compared with the non-treated controls or with the prehypoxic period. The effect was detected in all neuronal subtypes. In conclusion, exogenous ghrelin has a robust impact on the recovery of cortical synapses after hypoxia. It raises the possibility that ghrelin or its analogs may have a therapeutic potential for treatment of postanoxic encephalopathy.

Ghrelin Regulates Expression of the Transcription Factor Pax6 in Hypoxic Brain Progenitor Cells and Neurons

“…Ghrelin has been shown to exert neuroprotection via attenuation of oxidative stress [ 41 ], blockade of apoptosis [ 18 ], and stimulation of synaptic plasticity [ 46 ]. Suda et al [ 47 ] have suggested that defective GHSR1 activity of dopaminergic neurons causes marked motor impairment.…”

Hypoxia and connectivity in the developing vertebrate nervous system

“…The expression of both pre- and post-synaptic genes is altered by hypoxia (Curristin et al, 2002; Milash et al, 2016). Cell culture experiments using mouse hippocampal neurons show that hypoxia causes a reduction in dendritic spine numbers and impairs synaptic activity (Segura et al, 2016), as well as a persistent decline in synapse numbers (Stoyanova et al, 2016; le Feber et al, 2018). However, these studies were performed on neurons from mature animals, so whether the findings can be extrapolated to synaptic changes during embryonal development is unknown.…”

MK-0677, a Ghrelin Agonist, Alleviates Amyloid Beta-Related Pathology in 5XFAD Mice, an Animal Model of Alzheimer’s Disease

“…Moreover, studies have revealed an association between ghrelin and neural function. Previous in vitro studies have demonstrated that ghrelin treatment enhances the synaptic density of dissociated cortical neurons with decreased synapses induced by hypoxia [ 28 ], attenuates oxygen/glucose deprivation-induced apoptosis in hypothalamic neurons [ 29 ], increases the proliferation of hippocampal neural stem cells via multiple signaling pathways [ 30 ], prevents apoptosis signal-regulating kinase 1-mediated apoptosis of rat pheochromocytoma (PC12) cells by increasing heat-shock protein 70 levels [ 31 ], and inhibits the increment of inflammatory cytokines induced by fibrillar Aβ in mice microglial cells [ 32 ]. Consistent with the in vitro studies, ghrelin has protective effects on the CNS in vivo.…”