http://repub.eur.nl/res/aut/56622/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/37390/ 2013-01-01T00:00:00Z Hippocampal sclerosis, the main pathological sign of chronic temporal lobe epilepsy (TLE), is associated with oxidative injury, altered N-methyl d-aspartate receptor (NMDAR) stoichiometry, and loss of hippocampal neurons. However, the mechanisms that drive the chronic progression of TLE remain elusive. Our previous studies have shown that NADPH oxidase activation and ERK 1/2 phosphorylation are required for the up-regulation of the predominantly pre-synaptic NR2B subunit auto-receptor in both in vitro and in vivo pilocarpine (PILO) models of TLE. To provide further understanding of the cellular responses during the early-stages of hyper excitability, we investigated the role of oxidative damage and altered NR2B functions. In rat primary hippocampal cultures, we found that N-acetylcysteine (NAC) prevented PILO-mediated thiol oxidation, apoptosis, cell death and NR2B subunit over-expression. Interestingly, NAC did not block thiol oxidation when added to the neurons 6. h after the PILO exposure, suggesting that disulfide formation could rapidly become an irreversible phenomenon. Moreover, NAC pre-treatment did not prevent PILO-induced NR2A subunit over-expression, a critical event in hippocampal sclerosis. Pre-treatment with the highly specific NR2B subunit inhibitor, ifenprodil, partially decreased PILO-mediated thiol oxidation and was not effective in preventing apoptosis and cell death. However, if acutely administered 48. h after PILO exposure, ifenprodil blocked glutamate-induced aberrant calcium influx, suggesting the crucial role of NR2B over-expression in triggering neuronal hyper-excitability. Furthermore, ifenprodil treatment was able to prevent NR2A subunit over-expression by means of ERK1/2 phosphorylation. Our findings indicate oxidative stress and NR2B/NMDA signaling as promising therapeutic targets for co-treatments aimed to prevent chronic epilepsy following the seizure onset. http://repub.eur.nl/res/pub/35587/ 2007-02-01T00:00:00Z ABCC6 belongs to the adenosine triphosphate-binding cassette (ABC) gene subfamily C. This protein family is involved in a large variety of physiological processes, such as signal transduction, protein secretion, drug and antibiotic resistance, and antigen presentation [Kool et al. (1999) 59:175-182; Borst and Elferink (2002) 71:537-592]. ABCC6 is primarily and highly expressed in the liver and kidney [Kool et al. (1999) 59:175-182; Bergen et al. (2000) 25:228-2231]. The precise physiological function and natural substrate(s) transported by ABCC6 are unknown, but the protein may be involved in active transport of intracellular compounds to the extracellular environment [Kool et al. (1999) 59:175-182] [Scheffer et al. (2002) 82:515-518]. Recently, it was shown that loss of function mutations in ABCC6 cause pseudoxanthoma elasticum (PXE) [Bergen et al. (2000) 25:228-2231; Le Saux et al. (2000) 25:223-227]. PXE is an autosomal recessively inherited multi-organ disorder [Goodman et al. (1963) 42:297-334; Lebwohl et al. (1994) 30:103-107]. PXE is primarily associated with the accumulation of mineralized and fragmented elastic fibers of the connective tissue in the skin [Neldner (1988) 6:1-159], Bruch's membrane in the retina [Hu et al. (2003) 48:424-438], and vessel walls [Kornet et al. (2004) 30:1041-1048]. PXE patients usually have skin lesions and breaks in Bruch's membrane of the retina (angioid streaks). Also, a variety of cardiovascular complications has been observed [Hu et al. (2003) 48:424-438]. Recently, a mouse model for PXE was created by targeted disruption of Abcc6 [Gorgels et al. (2005) 14:1763-1773; Klement et al. (2005) 25:8299-8310], which may be useful to elucidate the precise function of Abcc6 and to develop experimental therapies.