Specific oxidative stress profile associated with partial striatal dopaminergic depletion by 6-hydroxydopamine as assessed by a novel multifunctional marker molecule

Abstract

Real time oxidative stress in the extracellular compartment of rat striatum was characterized by microdialysis with synthetic non-dialyzable marker molecules composed of linoleic acid, tyrosine and guanosine (N-linoleoyl tyrosine (LT) and N-linoleoyl tyrosine 2'-deoxyguanosyl ester (LTG)). Partial dopaminergic deafferentation was induced by injection of 6-hydroxydopamine (250 microg) to the left lateral ventricle, which depleted ipsilateral striatal dopamine by 46% and dopaminergic cells in left substantia nigra by 44%, 5 weeks after administration. Resting microdialysate dopamine levels in dopamine-depleted striatum were not different from sham-operated rats, although the ratio of oxidized metabolites of dopamine to free dopamine was significantly increased. Hydroperoxide and epoxy products of the linoleoyl portion of LT and LTG were detected in the striatal microdialysate by LC/MS/MS following initial separation by HPLC and were significantly increased in dopamine-depleted compared with control striatum without an increase in guanosine or tyrosine oxidation or nitration. Systemic administration of N-acetyl cysteine (350 mg/kg i.p.) decreased the increment in hydroperoxide and epoxy metabolites to levels not significantly different from control. Oxidation activity towards polyunsaturated fatty acids is present in the extracellular space of partially dopamine-denervated striatum, whereas oxidized glutathione and oxysterol levels in striatal tissue are decreased, possibly indicative of a compensatory response.

Selective inhibition of monoamine oxidase A or B reduces striatal oxidative stress in rats with partial depletion of the nigro-striatal dopaminergic pathway

“…In keeping with our previous study using the same dose of 6-OHDA (Aluf et al, 2010), tissue DA levels were reduced by 46% in lesioned striata (Fig. 2a, p < 0.001), indicating a similar degree of depletion of dopaminergic neuronal cell bodies in substantia nigra pars compacta as found previously (i.e.…”

“…2a, p < 0.001) but rasagiline treatment caused no change. Basal levels of [DA ec ] were not different between 6-OHDA and SHAM animals, as reported previously (Aluf et al, 2010). Clorgyline treatment resulted in a 72 AE 8% and 66 AE 6% increase in [DA ec ] in SHAM and 6-OHDA rats, respectively (Fig.…”

“…2b, p < 0.01). Due to increased DA turnover seen in partially 6-OHDA-lesioned rats (Aluf et al, 2010), the amount of the oxidized metabolites of DA (DOPAC and HVA) were higher in the 6-OHDA animals by 82 AE 20% (Fig. 2c, p < 0.001).…”

“…The mechanism behind this compensation is still under debate, and can be either at the post-synaptic level through dopamine D1 and D2 receptors sensitization (Scherfler et al, 2006), or at the pre-synaptic level. Activation of compensatory mechanisms increases synthesis and turnover of DA, with generation of increased amounts of the oxidized DA metabolites, DOPAC and HVA, indicative of increased DA metabolism by monoamine oxidase (MAO) (Aluf et al, 2011(Aluf et al, , 2010Brotchie and Fitzer-Attas, 2009;Zigmond et al, 1984Zigmond et al, , 1990. The deamination of DA by MAO generates hydrogen peroxide and the cytotoxic aldehyde 3,4-dihydroxyphenylacetaldehyde (DOPAL) (Marchitti et al, 2007).…”

“…In a recent study (Aluf et al, 2010) we described the use of novel synthetic marker molecules, i.e. N-linoleoyl tyrosine (LT) and Nlinoleoyl tyrosine 2 0 -deoxyguanosyl ester (LTG), to estimate OS level.…”