Early nerve ending rescue from oxidative damage and energy failure by l-carnitine as post-treatment in two neurotoxic models in rat: recovery of antioxidant and reductive capacities

Cell rescue is a primary need during acute and chronic insults to the central nervous system. Functional preservation during the early stages of toxicity in a given degenerative event may represent a significant amelioration of detrimental processes linked to neuronal cell loss. Excitotoxicity and depleted cellular energy are toxic events leading to cell death in several neurodegenerative disorders. In this work, the effects of the well-known antioxidant and energy precursor, l-carnitine (l-CAR), were tested as a post-treatment in two neurotoxic models under in vitro and in vivo conditions. The experimental models tested included: (1) a typical excitotoxic and pro-oxidant inducer, quinolinic acid (QUIN); and (2) a mitochondrial energy inhibitor, 3-nitropropionic acid (3-NP). For in vitro studies, increasing concentrations of l-CAR (10-1,000 mu M) were added to the isolated brain synaptosomes at different times (1, 3 and 6 h) after the incubation with toxins (100 mu M QUIN and 1 mM 3-NP), and 30 min later, lipid peroxidation (LP) and mitochondrial dysfunction (MD) were evaluated. For in vivo purposes, l-CAR (100 mg/kg, i.p.) was given to rats either as a single administration 120 min after the intrastriatal infusion of QUIN (240 nmol/mu l) or 3-NP (500 nmol/mu l), or for 7 consecutive days (starting 120 min post-lesion). LP and MD were evaluated 4 h and 7 days post-lesions in isolated striatal synaptosomes. Our results show that, despite some variations depending on the toxic model tested, the time of exposure, or the biomarker evaluated, nerve ending protection can be mostly achieved by l-CAR within the first hours after the toxic insults started, suggesting that targeting the ongoing oxidative damage and/or energy depletion during the first stages of neurotoxic events is essential to rescue nerve endings.