Retinoic acid receptors move in time with the clock in the hippocampus. Effect of a vitamin-A-deficient diet.
An endogenous time-keeping mechanism controls circadian biological rhythms in mammals. Previously, we showed that vitamin A deficiency modifies clock BMAL1 and PER1 as well as BDNF and neurogranin daily rhythmicity in the rat hippocampus when animals are maintained under 12-h-light:12-h-dark conditions. Retinoic acid nuclear receptors, retinoic acid receptors (RARs) and retinoid X receptors (RXRs), have been detected in the same brain area. Our objectives were (a) to analyze whether RARα, RARβ and RXRβ exhibit a circadian variation in the rat hippocampus and (b) to investigate the effect of a vitamin-A-deficient diet on the circadian expression of BMAL1, PER1 and retinoic acid receptors (RARs and RXRβ) genes. Holtzman male rats from control and vitamin-A-deficient groups were maintained under 12-h-light:12-h-dark or 12-h-dark:12-h-dark conditions during the last week of treatment. RARα, RARβ, RXRβ, BMAL1 and PER1 transcript and protein levels were determined in hippocampus samples isolated every 4 h in a 24-h period. Regulatory regions of RARs and RXRβ genes were scanned for clock-responsive sites, while BMAL1 and PER1 promoters were analyzed for retinoic acid responsive elements and retinoid X responsive elements. E-box and retinoid-related orphan receptor responsive element sites were found on regulatory regions of retinoid receptors genes, which display an endogenously controlled circadian expression in the rat hippocampus. Those temporal profiles were modified when animals were fed with a vitamin-A-deficient diet. Similarly, the nutritional vitamin A deficiency phase shifted BMAL1 and abolished PER1 circadian expression at both mRNA and protein levels. Our data suggest that vitamin A deficiency may affect the circadian expression in the hippocampus by modifying the rhythmic profiles of retinoic acid receptors.
Laboratory of Chronobiology, Multidisciplinary Institute of Biological Research San Luis (IMIBIO-SL), National Council of Science and Technology (CONICET), National University of San Luis (UNSL). Chacabuco y Pedernera, D5700HHW, San Luis, Argentina.
Lorena S
LS
Navigatore-Fonzo
Rebeca L
RL
Golini
Ivana T
IT
Ponce
Silvia M
SM
Delgado
Maria G
MG
Plateo-Pignatari
María S
MS
Gimenez
Ana C
AC
Anzulovich
D056930:ARNTL Transcription Factors / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D004032:Diet; D005786:Gene Expression Regulation; D006624:Hippocampus / Q000378:metabolism*; D008297:Male; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D000072482:Retinoic Acid Receptor alpha; D049230:Retinoid X Receptor beta / Q000235:genetics / Q000378:metabolism*; D014802:Vitamin A Deficiency / Q000378:metabolism*
D056930:ARNTL Transcription Factors; C539022:PER1 protein, human; D056950:Period Circadian Proteins; C000607071:RARA protein, human; D012333:RNA, Messenger; C000607073:Rara protein, rat; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D049230:Retinoid X Receptor beta; C082925:retinoic acid receptor beta