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