Temporal expression patterns of the melatoninergic system in the human thymus of children

Abstract

ObjectivesTo obtain greater knowledge of the extra-pineal sources of melatonin during development, the amount of indolamine and the expression levels of the last two enzymes involved in its biosynthesis, Arylalkylamine N-acetyltransferase (AANAT) and acetylserotonin O-methyltransferase (ASMT), were analyzed in the human thymus from children from three different age groups (from days to years). The melatonin membrane and nuclear receptor expression levels also were studied.MethodsQuantitative reverse transcriptase PCR and western blot were performed to investigate the receptor and enzyme expression levels. The results were examined and correlated with the ages of the thymuses.ResultsWe found high levels of indolamine in the thymuses of newborns (younger than 1 month), which decreased during development; thymuses from the months (from 2 to 11 months) and years (from 1 to 12 years) groups showed lower levels. A similar decline was also observed in the mRNA of the AANAT enzyme and the expression levels of melatonin receptors. However, ASMT expression was exactly the opposite, with low levels in the newborn group and higher levels in the years group. Our results show that the thymic synthesis of melatonin occurs very early in childhood. Additionally, this is the first report that is focused on melatonin receptors expression in the human thymus.ConclusionConsidering the limited melatonin synthesis performed by the newborn pineal gland, we suggest that the high levels of melatonin found in human thymus in this experimental group arise from synthesis in the tissue itself, which could be contributing to the immune efficiency at the thymic level.

Melatonin attenuates diabetic cardiomyopathy and reduces myocardial vulnerability to ischemia‐reperfusion injury by improving mitochondrial quality control: Role of SIRT6

“…Interestingly, disturbed melatonin signaling has been indicated to participate in the development of diabetes [16][17][18] and cardiovascular complications. 6,19 In addition, reduced extrapineal melatonin content affected the architecture of thymus 20 and played a role in aging. 21,22 However, the alteration of heart melatonin and its potential role during the pathogenesis of DCM have not been observed.…”

Thymus-Pineal Gland Axis: Revisiting Its Role in Human Life and Ageing

“…Sci. 2020, 21, x FOR PEER REVIEW 20 of 39 increased especially above 1 year [247]. Thymic MT decreased especially from newborns to children of several months and was thereafter maintained.…”

“…In addition to the MT synthesizing enzymes, the MT receptors MT 1 and MT 2 have been demonstrated in the TG of various species [ 234 , 244 , 245 , 246 , 247 , 248 ]. MT receptor expression was also studied in dependence of age.…”

“…MT receptor expression was also studied in dependence of age. In human children, Cruz-Chamorro et al showed decreases in both receptors, at mRNA as well as protein levels [ 247 ]. In rats of older age, MT receptors decreased in many peripheral target tissues, but interestingly not in the TG, in which increases of both receptors were observed at mRNA level, and maintenance of expression at the protein level [ 246 ].…”

“…In addition to the changes in receptor expression, decreases in AA-NAT levels were observed from newborns to children of several months (less than 1 year) and older, whereas ASMT expression increased especially above 1 year [ 247 ]. Thymic MT decreased especially from newborns to children of several months and was thereafter maintained.…”