Daily rhythms of CAT and GPx enzymes are endogenously driven in the hippocampus and are modified by a vitamin A-free diet.

NAVIGATORE FONZO LS; DELGADO SM; GIMÉNEZ MS; ANZULOVICH AC

Potrero de los Funes

Congreso; XXX Reunión Anual de la Soc. de Biología de Cuyo; 2012

Alterations in the enzymatic antioxidant defense system lead to altered hippocampal synaptic plasticity and to a deficit in cognitive functions. Objectives of this study were: to investigate endogenous rhythms of catalase (CAT) and glutathione peroxidase (GPx) expression and activity, as well as RXRγ and CREB1 mRNA, in the rat hippocampus and, to evaluate to which extent the nutritional vitamin A deficiency (VAD) could affect those temporal patterns. Holtzman rats from control and vitamin A-deficient groups received a diet containing 4000 IU of vitamin A/Kg diet, or the same diet devoided of vitamin A, respectively, during 3 months. Rats were maintained under constant darkness conditions, during 10 days before the experiment. Circadian rhythms of CAT, GPx, RXRγ and CREB1 mRNA levels were determined by RT-PCR, in hippocampus samples isolated every 4 h during a 24h period. CAT and GPx enzymatic activities were determined by kinetic assays. Regulatory regions of antioxidant enzymes genes were scanned for clock-, retinoic acid- and CREB1-responsive elements. E-box, RXRE and CRE sites were found in regulatory regions of GPx and CAT genes, which display a circadian expression in the rat hippocampus. VAD phase shifted CAT, GPx and RXRγ endogenous rhythms without affecting circadian expression of CREB1.