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Authors
Abstract(s)
Os ritmos circadianos sĂŁo controlados por um relĂłgio central, o nĂșcleo supraquiasmĂĄtico (SCN) do hipotĂĄlamo. A nĂvel molecular, o sistema circadiano Ă© composto por circuitos de feedback de transcrição e tradução que envolvem vĂĄrios genes da via do ritmo circadiano. Os ritmos circadianos sĂŁo observĂĄveis numa variedade de tecidos perifĂ©ricos em todo o corpo. Estudos em animais sugerem que o ciclo circadiano Ă© modulado pelas hormonas sexuais, sobretudo pelos esteroides ovĂĄricos em fĂȘmeas. Estes efeitos hormonais na ritmicidade circadiana sĂŁo conhecidos, no entanto, o que falta Ă© a compreensĂŁo clara de como o SCN integra essas influĂȘncias hormonais. Um estudo de microarrays de cDNA, realizado anteriormente pelo nosso grupo de investigação, mostrou que os genes do ritmo circadiano sĂŁo expressos no plexo coroideu (CP) de rato. Neste trabalho, confirmou-se a presença de alguns genes da via do ritmo circadiano, particularmente BMAL1, CLOCK, Cry 1, Cry 2, Per 1, Per 2 e Per 3 no CP de rato. A expressĂŁo dos genes do ritmo circadiano no CP de ratos fĂȘmeas e machos foi analisada por PCR em tempo real. No CP, a expressĂŁo rĂtmica do BMAL1 nos machos, Cry2 nas fĂȘmeas, CLOCK e Per1 nos machos e fĂȘmeas foi considerada nĂŁo significativa. Pelo contrĂĄrio, a expressĂŁo de mRNA de BMAL1 nas fĂȘmeas, Cry2 nos machos e do Per2 nos machos e nas fĂȘmeas apresentaram ritmicidade significativa. Concluiu-se que, o CP de rato expressa todos os genes do ritmo circadiano estudados, o que sugere que este tecido seja um oscilador extra-SCN. Como os esteroides sexuais atuam noutros osciladores extra-SCN por vias indiretas e diretas Ă© possĂvel que o CP possa contribuir para a interpretação dos estĂmulos hormonais, atuando como um local extra-SCN que participe numa via indireta da passagem desta informação para o oscilador central.
Circadian rhythms are controlled by the master clock, the suprachiasmatic nucleus (SCN) of the hypothalamus. At the molecular level, the clock system is composed of interlocked transcriptional and translational feedback loops which involve several genes of the circadian rhythm. Circadian rhythms also exist in a variety of peripheral tissues throughout the body. Studies in animals suggest that the circadian cycle is modulated by the sex hormones, especially by ovarian steroids in females. The effects of sex hormones on circadian rhythmicity are established; however, clear understanding of how the SCN integrates these hormonal influences is lacking. In previous work, using a cDNA microarray approach, we found that several genes of the brain clock machinery are expressed in the choroid plexus (CP) of rats. This work confirmed the presence of some genes of the circadian rhythm, particularly BMAL1, CLOCK, Cry 1, Cry 2, Per 1, Per 2 and Per 3 in the rat CP. In addition, the rhythmic expression of clock genes in female and male rat CP was investigated by real time PCR. In CP, the rhythmic expression of BMAL1 in male rats, Cry2, Per1 in female rats and CLOCK in male and female rats was not significant. In contrast, the mRNA expression of Bmal1 in females, Cry2 in males and Per2 in males and females showed significant rhythmicity in the CP. It was concluded that the CP expressed all genes the mouse circadian rhythm studied, thus suggesting that this tissue is extra-SCN oscillator. As sex hormones influence other extra SCN oscillators by direct and indirect routes it is possible that CP may contribute to the interpretation of hormonal stimuli, acting as an extra-SCN clock participating in an indirect route to veinculate this information to the master clock.
Circadian rhythms are controlled by the master clock, the suprachiasmatic nucleus (SCN) of the hypothalamus. At the molecular level, the clock system is composed of interlocked transcriptional and translational feedback loops which involve several genes of the circadian rhythm. Circadian rhythms also exist in a variety of peripheral tissues throughout the body. Studies in animals suggest that the circadian cycle is modulated by the sex hormones, especially by ovarian steroids in females. The effects of sex hormones on circadian rhythmicity are established; however, clear understanding of how the SCN integrates these hormonal influences is lacking. In previous work, using a cDNA microarray approach, we found that several genes of the brain clock machinery are expressed in the choroid plexus (CP) of rats. This work confirmed the presence of some genes of the circadian rhythm, particularly BMAL1, CLOCK, Cry 1, Cry 2, Per 1, Per 2 and Per 3 in the rat CP. In addition, the rhythmic expression of clock genes in female and male rat CP was investigated by real time PCR. In CP, the rhythmic expression of BMAL1 in male rats, Cry2, Per1 in female rats and CLOCK in male and female rats was not significant. In contrast, the mRNA expression of Bmal1 in females, Cry2 in males and Per2 in males and females showed significant rhythmicity in the CP. It was concluded that the CP expressed all genes the mouse circadian rhythm studied, thus suggesting that this tissue is extra-SCN oscillator. As sex hormones influence other extra SCN oscillators by direct and indirect routes it is possible that CP may contribute to the interpretation of hormonal stimuli, acting as an extra-SCN clock participating in an indirect route to veinculate this information to the master clock.
Description
Keywords
Ritmo circadiano Ritmo circadiano - NĂșcleo supraquiasmĂĄtico Ritmo circadiano - Plexo coroideu - Hormonas sexuais Genes clock