Neuroprotective Effect of the n-Hexane Extracts of Laurus nobilis L. in Models of Parkinson's Disease

Abstract

Free radical scavenging and antioxidants have attracted attention as a way to prevent the progression of Parkinson's disease (PD). This study was carried out to investigate the effects of n-hexane fraction from Laurus nobilis L. (Lauraceae) leaves (HFL) on dopamine (DA)-induced intracellular reactive oxygen species (ROS) production and apoptosis in human neuroblastoma SH-SY5Y cells. Compared with apomorphine (APO, <TEX>$IC_{50}=18.1\;{\mu}M$</TEX>) as a positive control, the HFL <TEX>$IC_{50}$</TEX> value for DA-induced apoptosis was <TEX>$3.0\;{\mu}g/ml$</TEX>, and two major compounds from HFL, costunolide and dehydrocostus lactone, were <TEX>$7.3\;{\mu}M$</TEX> and <TEX>$3.6\;{\mu}M$</TEX>, respectively. HFL and these major compounds significantly inhibited ROS generation in DA-induced SH-SY5Y cells. A rodent 6-hydroxydopamine (6-OHDA) model of PD was employed to investigate the potential neuroprotective effects of HFL in vivo. 6-OHDA was injected into the substantia nigra of young adult rats and an immunohistochemical analysis was conducted to quantitate the tyrosine hydroxylase (TH)-positive neurons. HFL significantly inhibited 6-OHDA-induced TH-positive cell loss in the substantia nigra and also reduced DA induced <TEX>$\alpha$</TEX>-synuclein (SYN) formation in SH-SY5Y cells. These results indicate that HFL may have neuroprotective effects against DA-induced in vitro and in vivo models of PD.