The effects of growth hormone on opioid-induced toxicity in vitro

Sammanfattning: There is an ongoing opioid crisis in the United States that is portrayed by a large number of opioid-related deaths. Many of these cases involve commonly used prescription opioids, such as morphine, oxycodone, fentanyl, and methadone. This is concerning and highlights the problems associated with long-term opioid treatment. In addition to opioid-related deaths, long-term opioid use may impact higher brain functions, such as cognitive function. The cause of cognitive decline following opioid treatment may be associated with increased neuronal cell death, inhibited neurogenesis, and altered volumes of specific brain regions important for cognition. Growth hormone (GH), a pituitary hormone regulated by the hypothalamic somatotropic axis, may counteract several of these effects. The hormone, alongside with its mediator insulin-like growth factor-1 (IGF-1), is associated with pro-cognitive effects and display promising neuroprotective actions in the CNS. The main aim for this thesis was to examine the impact of opioids on cell viability and the potentially protective, restorative, and effects linked to pro-cognitive properties of GH in mixed neuronal cell cultures and cell lines. The results clearly display that specific opioids, such as methadone, decrease cell viability, possibly via negative effects on mitochondrial morphology. GH treatment alleviated the negative effects of methadone in cortical cell cultures as well as successfully restored mitochondrial and membrane integrity past injury. Moreover, GH treatment to primary hippocampal cell cultures increased the number of dendritic spines, which are linked to higher cognitive functions, indicating that the hormone act as a cognitive enhancer in the CNS. In conclusion, this thesis provides further evidence that opioids negatively impact cell viability, an effect that may underlie reduced cognitive function as seen in several patients consuming opioids-long term. GH was able to counteract these effects and also able to restore damaged cellular functions. This thesis further confirms the essential role of GH in acting as a cognitive enhancer in the CNS, highlighting the potential role of GH as a treatment for cognitive dysfunctions.