Investigation of the neuroprotective effects of humanin in A 6-hydroxydopamine (6-OHDA) induced in vitro parkinson's disease model

Humanin (HN), a 24 amino acid peptide, has been studied in several neurodegenerative diseases including Alzheimer's disease following its discovery. HN is a very bioactive peptide. Thus, it affects many intracellular and extracellular signaling mechanisms. HN, PI3k / Akt, JAK / STAT, MAPK / ERK pathways and IGFBP regulate cell growth, proliferation and survival through Bax proteins. The aim of this study was to investigate whether HN has a neuroprotective effect in an in vitro Parkinson's disease model induced by 6-hydroxydopamine (6-OHDA). In this study 6-OHDA induced human neuroblastoma cell line (SH-SY5Y) was used to experimentally mimic Parkinson's disease. The neuroprotective effect of HN against 6-OHDA neurotoxicity was evaluated by mitochondrial dysfunction, apoptosis and cytotoxicity parameters. MTT test for determination of mitochondrial dysfunction, caspase-3 test for apoptosis and LDH test for cytotoxicity were used. GraphPad Prism 8 program was used for statistical analysis and the differences between the groups were evaluated with one-way ANOVA. IC50 dose was 233.7 μM. In MTT test, HN did not have a proliferative effect when administered alone (p>0.05). However, 24 h pre-treatment cells containing 10 μM and 20 μM HN were shown to protect against 6-OHDA neurotoxicity (p<0.01). In the LDH assay, no lactate dehydrogenase release was detected in any HN dose group. In caspase-3 test, pretreatment with 20 μM HN decreased caspase-3 against 6-OHDA neurotoxicity, but did not make any statistical difference (p>0,05). Keywords: apoptosis, cytotoxicity, humanin, mitochondrial dysfunction, neuroprotective effect, Parkinson's disease