This study was to investigate the circadian rhythms and light responses of Clock gene and arylalkylamine N-acetyltransferase (NAT) gene expressions in the rat pineal gland under the 12 h-light : 12 h-dark cycle condition (LD) and constant darkness (DD). Sprague-Dawley rats housed under the light regime of LD (n=36) for 4 weeks and of DD (n=36) for 8 weeks were sampled for the pineal gland once a group (n=6) every 4 h in a circadian day. The total RNA was extracted from each sample and the semiquantitative reverse transcription polymerase chain reaction (RT-PCR) was used to determine the temporal changes in mRNA levels of Clock and NAT genes during different circadian times or zeitgeber times. The data were analysed by the cosine function software, Clock Lab software and the amplitude F test was used to reveal the circadian rhythm. The main results obtained are as follows. (1) In DD or LD condition, both of Clock and NAT genes mRNA levels in the pineal gland showed robust circadian oscillation (P< 0.05) with the peak at the subjective night or at night-time. (2) In comparison with DD regime, the amplitudes and the mRNA levels at peaks of Clock and NAT genes expressions in LD in the pineal gland were significantly reduced (P< 0.05). (3) In DD or LD condition, the circadian expressions of NAT gene were similar in pattern to those of Clock gene in the pineal gland (P> 0.05). These findings suggest that the expressions of Clock and NAT genes in the pineal gland not only show remarkably synchronous endogenous circadian rhythmic changes, but also response to the ambient light signal in a reduced manner.
Animals ; Arylalkylamine N-Acetyltransferase ; genetics ; metabolism ; CLOCK Proteins ; genetics ; metabolism ; Circadian Rhythm ; Light ; Male ; Pineal Gland ; enzymology ; metabolism ; RNA ; genetics ; metabolism ; Random Allocation ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo study the effect of Kaixin San on the rate-limiting enzyme in biosynthesis of melatonin (MT) and pineal body in rat depression model.

METHODThe unpredictable chronic mild stress was used to establish the rat depression model for 21 days. The rats were divided into the normal control group, the model group, Kaixin San low, medium and high dose groups (KXS 65, 130, 260 mg x kg x d(-1)) and the trazodone group. All groups were administered at 30 min after modeling each day. Rats were sacrificed and the pineal glands were isolated immediately after acquisition tail venous blood at 2:00a. m on the 22nd day. The plasma was analyzed for melatonin content by using a rat metabolic panel Milliplex kit. The pineal glands were analyzed for AANAT and HIOMT mRNA levels by Real-time quantitative PCR and for AANAT and HIOMT activity by a radiometric assay simultaneously.

RESULTThe plasma MT concentration, expression of AANT and HIOMT mRNA, activity of AANAT in rat pineal glands of the model group were significantly lower than the control group (P < 0.05), but the activity of HIOMT showed not change. Compared with the model group, all of Kaixin San groups showed increase in MT concentration in plasma (P <0. 05) , with the medium dose group revealing the highest level. Besides, the medium dose group displayed significant increase in AANAT, HIOMT mRNA level and AANAT activity (P < 0.05), but no increase in HIOMT activity.

CONCLUSIONKaixin San can regulate AANAT activity of pineal bodyand regulate MT biosynthesis in rat depression model.

Acetylserotonin O-Methyltransferase ; genetics ; Animals ; Arylalkylamine N-Acetyltransferase ; genetics ; Depression ; blood ; genetics ; metabolism ; Disease Models, Animal ; Drugs, Chinese Herbal ; pharmacology ; Gene Expression Regulation, Enzymologic ; drug effects ; Male ; Melatonin ; biosynthesis ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Wistar

Arylalkylamine N-acetyltransferase (AANAT) and Hydroxyindole O-methyltransferase(HIOMT) are the key regulation enzymes in the melatonin biosynthesis pathway in mammals. The AANAT and HIOMT genes were constructed into a binary plant expression vector YXu55. Using leaf strips as the recipiences, we efficiently transformed tobacco (Nicotiana tabacum) variety qinyan 95 by the Agrobacterium mediated method. After gradient selection with gentamycin, a number of transgenic plants were regenerated. Southern blot and RT-PCR analyses showed that the AANAT-HIOMT genes were integrated into the genome of the transgenic plants and the target genes could express at the level of RNA transcription. By RP-HPLC, we measured the melatonin contents in transgenic plants. The results showed that the melatonin level in YXu55 (containing the gentamycin-resistance gene, the AANAT gene and HIOMT gene) transgenic plants were much higher than those in pZP122 (control containing only the gentamycin-resistance gene) transgenic plants and nontransgenic plants. The content of melatonin in pZP122 transgenic plants was nearly the same as that in nontransgenic plants. Physiological determination of antioxidative characteristics demonstrated that 1) the capacity of total antioxidation, 2) the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) and 3) the content of glutathione (GSH) were increased in YXu55 transgenic plants containing the AANAT-HIOMT genes as compared to the control plants (pZP122 or nontransgenic plants). At the same time, malonaldehyde (MDA) content did not appear remarkably difference between transgenic plants and nontransgenic plants. The above mentioned facts indicate enhancement of melatonin levels in YXu55 transgenic plants might help to reduce damage by oxidative stress.
Acetylserotonin O-Methyltransferase ; genetics ; Agrobacterium tumefaciens ; genetics ; Arylalkylamine N-Acetyltransferase ; genetics ; Catalase ; metabolism ; Gene Expression Regulation, Enzymologic ; Gene Expression Regulation, Plant ; Melatonin ; biosynthesis ; Peroxidase ; metabolism ; Plants, Genetically Modified ; enzymology ; genetics ; Superoxide Dismutase ; metabolism ; Tobacco ; enzymology ; genetics ; Transduction, Genetic ; methods

Melatonin affects diverse physiological functions through its receptor and plays an important role in the central nervous system. In the present study, we compared immunoreactivity patterns of arylalkylamine N-acetyltransferase (AANAT), an enzyme essential for melatonin synthesis, and melatonin receptor type 1B (MT2) in the spinal cord of young adult (2~3 years) and aged (10~12 years) beagle dogs using immunohistochemistry and Western blotting. AANAT-specific immunoreactivity was observed in the nuclei of spinal neurons, and was significantly increased in aged dog spinal neurons compared to young adult spinal neurons. MT2-specific immunoreactivity was found in the cytoplasm of spinal neurons, and was predominantly increased in the margin of the neuron cytoplasm in aged spinal cord compared to that in the young adult dogs. These increased levels of AANAT and MT2 immunoreactivity in aged spinal cord might be a feature of normal aging and associated with a feedback mechanism that compensates for decreased production of melatonin during aging.
Age Factors ; Aging/physiology ; Animals ; Arylalkylamine N-Acetyltransferase/*analysis/immunology/physiology ; Blotting, Western ; Dogs ; Fluorescent Antibody Technique ; Male ; Receptor, Melatonin, MT2/*analysis/immunology/physiology ; Spinal Cord/*chemistry/immunology/physiology