Evaluation of human pineal gland acetylserotonin O-methyltransferase immunoreactivity in suicide: A preliminary study

Abstract

Disorders of the serotonergic system are especially known to be present in the neurobiology of suicidal behavior. Studies investigating melatonin levels show that changes in pineal gland functions may also play a role in the pathogenesis of suicide. However, to our knowledge, there are no studies evaluating the activity of pinealocytes responsible for melatonin synthesis in suicide. This preliminary study aimed to investigate the relationship among pinealocyte, acetylserotonin O-methyltransferase (ASMT) immunoreactivity, and suicide. Samples of pineal gland, cerebrospinal fluid, blood, and urine were obtained from 21 suicide and 21 non-suicide cases on which medicolegal autopsies were performed. Expression of ASMT in human pineal gland was evaluated by immunohistochemical methods. A scoring system was used to define the anti-ASMT-positive staining in the sections. Enzyme-linked immunosorbent assays were employed to assess serum and cerebrospinal fluid melatonin levels and blood and urine noradrenaline levels. The ASMT-immunopositive pinealocyte count was observed to be lower in suicide cases compared to the non-suicide cases. With the exception of two cases (with moderate staining), all graded scores were 3 (strong staining) in non-suicide group, whereas scores were 1 (mild staining) or 2 (moderate staining) in the suicide group. Melatonin levels in the blood were lower among the suicide victims. These results support decreased pineal gland activity in suicide. However, further studies are needed to assess whether these changes are related to a psychiatric disorder.

The role of seasonality and photoperiod on the lethality of suicide attempts: A case-control study

“…the recurrence and frequency of episodes which have a predictive value for suicide attempts (Pawlak et al, 2017). Moreover, lower melatonin levels have been significantly associated with completed suicides in post-mortem studies (Kurtulus Dereli et al, 2018) and this may further support our findings of more lethal suicide attempts and lower levels of melatonin in spring -summer, when there are less hours of darkness during which melatonin is produced in pinealocytes. Interestingly, melatonin results from the n-acetylatylation of 5-HT via the catalyzation of enzymes aralkylamine n-acetyltransferase (AANAT) and acetylserotonin O-methyltransferase (ASMT) that are regulated by clock-genes.…”

The morphological and functional characteristics of the pineal gland

“…The secretory activity of melatonin was quantified and proved to be low in patients that have committed suicide. This is not enough to imply a direct and routine examination of the pineal gland during routine forensic autopsies, but it can provide a complementary argument for the neurobiological risk factors of suicide [86].…”

The investigation of relationship between serum melatonin levels with Beck Depression Inventory and Beck Scale for Suicidal Ideation in suicide patients

“…According to the reports, a decline in melatonin levels is observed in individuals with sleep difficulties, depression 12 , 13 , and suicide 13 - 15 . Arioz et al 16 have demonstrated that the administration of melatonin is associated with a reduction in depression-like behaviors.…”