Expression Of BMAL1 Protein In Hypertrophic Myocardium Of Hypertensive Rats And Hypertrophic Cardiomyocytes

Background: Most physiological phenomena of mammals have endogenetic circadian rhythms, such as blood pressure, heart rate, breath, temperature, immunological and neuro-endocrine activities, cell division and the functions of DNA. This can be regarded as a character of adaptability through natural selection and long-term evolution. However, these rhythms alter with the change of outside environment (especially light). When the creature is exposed to the light, the biological clock is resetted. Light adjusts circadian phase via a monosynaptic retinofugal pathway (the retinohypothalamic tract, RHT), a direct pathway linking a small population of retinal ganglion cells (RGCs) to the SCN. So it is a general phenomenon that light is the most potent circadian entraining agent for mammals.Cardiac hypertrophy is an important complication of hypertension and is deemed as a sign of coronary heart disease and heart failure. Now many kinds of mechanisms have been proved to be related with the development of the hypertrophy of myocardium such as the frequent activities of renal angiotensin system (RAS) and abnormal expression of different kinds of genes, to name a few, c-fos, fas etc. Recent research on clock genes has also shed light on the possible mechanisms of theoccurrence of hypertrophy. The maintenance of circadian rhythm of mammals is dependent on the rhythmic expression of clock genes. The main oscillating mechanism includes a series of different clock genes (per, cry, bmall) and the feedback loop of clock output genes. Among these genes, bmall is the most important promoter. After BMALl and CLOCK protein form BMAL1/CLOCK heterodimers, per's transcription together with cry's transcription in nucleus can be enhanced when CLOCK/BMAL1 heterodimers bind to the E-box (CACGTG) of per and cry's promoters, which provides the basic drive to the timekeeping system. The main circadian clock is supposed to be located in the suprachiasmatic nuclei (SCN) in mammals, which can generate a free-running rhythm independent of environmental cues. Additionally, most peripheral tissues also harbor their own oscillators. The SCN coordinates peripheral clocks to synchronize with the real time. For example, the heart possesses its own circadian clock. Some types of cardiovascular event, such as myocardiac infarction, happen at the regular time of a day, that is to say, at dawn.Objective: we try to explore the expression of BMALl protein in the myocardiums from three kinds of rats (spontaneous hypertensive rat/SHR, renal hypertensive rat/RHR, NORMAL) respectively and elucidate the role which clock genes play in the process of cardiac hypertrophy. To exclude other impact factors, we also established themodel of hypertrophic cardiomycytes. We then detected the expression of BMAL1 protein in normal and hypertrophic cardiomycytes to try to explain the relationship between clock genes and cardiac hypertrophy.Method: (1) we established the two-kidney, one -clip model of RHR. After raising 8 weeks, we measured the blood pressure of all rats to determine whether the models are successfully established. If the blood pressure of a rat increased more than 6.7 kPa, it is considered as a successful model. (2) The rats were divided into 3 groups: RHR, SHR, and NORMAL. They were housed in a separate environment-controlled room for two weeks, in which a strict 12-hour light/12-hour dark cycle regimen was enforced (lights on at 9 am, zeitgeber time [ZT] 0). (3) We then detected the expression of BMAL1 protein of three groups respectively. (4) We cultured the cardiac cells of newborn rats and induced them with Angll for 3 days to establish the model of hypertrophic cardiac cells. (5) We then detected the expression of BMAL1 protein in hypertrophic and normal cardiac cells.Results: (1) The blood pressure, BW/HW and LVW/HW of SHR and RHR groups have significant difference compared with normal group, which suggests that the SHR and RHR have developed left ventricular hypertrophy and hypertrophic hearts. (2) According to the results of western blot, the expression of...