Ribosomal DNA transcription in prefrontal pyramidal neurons is decreased in suicide

The left-lateralisation of citrate synthase activity in the anterior cingulate cortex of male violent suicide victims

The anterior cingulate cortex (AC) as a part of prefrontal cortex plays a crucial role in behavioural regulation, which is profoundly disturbed in suicide. Citrate synthase (CS) is a key enzyme of tricarboxylic acid cycle fundamental for brain energetics and neurotransmitter synthesis, which are deteriorated in suicidal behaviour. However, CS activity has not been yet studied in brain structures of suicide victims. CS activity assay was performed bilaterally on frozen samples of the rostral part of the AC of 24 violent suicide completers (21 males and 3 females) with unknown psychiatric diagnosis and 24 non-suicidal controls (20 males and 4 females). Compared to controls, suicide victims revealed decreased CS activity in the right AC, however, insignificant. Further statistical analysis of laterality index revealed the left-lateralisation of CS activity in the AC in male suicides compared to male controls (U-test P = 0.0003, corrected for multiple comparisons). The results were not confounded by postmortem interval, blood alcohol concentration, age, and brain weight. Our findings suggest that disturbed CS activity in the AC plays a role in suicide pathogenesis and correspond with our previous morphological and molecular studies of prefrontal regions in suicide.

Ribosomal DNA transcription is increased in the left nucleus accumbens of heroin-dependent males

Opioid addiction is a worldwide problem accentuated in the USA and European countries by the COVID-19 pandemic. The nucleus accumbens (NAc) plays an outstanding neurobiological role in opioid addiction as a part of the striatum and key component of brain reward system. The striatal GABAergic medium spiny projection neurons (MSNs) are the main neuronal type in the NAc where addiction-specific synaptic plasticity occurs. The activity of ribosomal DNA (rDNA) transcription is crucial for neural plasticity and molecular studies suggest its increase in the NAc of heroin addicts. Silver-stained argyrophilic nucleolar organizer region (AgNOR) areas visualised in neuronal nuclei in paraffin-embedded brain sections are reliable morphological estimators of rDNA transcription and thus surrogate markers for the activity of brain regions. Our study revealed increased AgNOR areas in MSNs of the left NAc in 11 heroin addicts versus 11 healthy controls from the Magdeburg Brain Bank (U-test P = 0.007). No differences were observed in another investigated part of the striatum, namely the head of caudate nucleus, which is located closely to the NAc. The results were not confounded by significant differences in the age, brain volume and time of formalin fixation existing between compared groups. Our findings suggest an increased NAc activity in heroin addicts, which is consistent with human and animal experimental data.

Reduced ribosomal DNA transcription in the prefrontal cortex of suicide victims: consistence of new molecular RT-qPCR findings with previous morphometric data from AgNOR-stained pyramidal neurons

Prefrontal cortical regions play a key role in behavioural regulation, which is profoundly disturbed in suicide. The study was carried out on frozen cortical samples from the anterior cingulate cortex (dorsal and ventral parts, ACd and ACv), the orbitofrontal cortex (OFC), and the dorsolateral cortex (DLC) obtained from 20 suicide completers (predominantly violent) with unknown psychiatric diagnosis and 21 non-suicidal controls. The relative level of ribosomal RNA (rRNA) as a marker of the transcriptional activity of ribosomal DNA (rDNA) was evaluated bilaterally in prefrontal regions mentioned above (i.e. in eight regions of interest, ROIs) by reverse transcription and quantitative polymerase chain reaction (RT-qPCR). The overall statistical analysis revealed a decrease in rDNA activity in suicide victims versus controls, particularly in male subjects. Further ROI-specific post hoc analyses revealed a significant decrease in this activity in suicides compared to non-suicides in five ROIs. This effect was accentuated in the ACv, where it was observed bilaterally. Our findings suggest that decreased rDNA transcription in the prefrontal cortex plays an important role in suicide pathogenesis and corresponds with our previous morphometric analyses of AgNOR-stained neurons.