Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Dopaminergic system contribution to the antidepressant-like effect of 3-phenyl-4-(phenylseleno) isoquinoline in mice

Depression is a serious disorder characterized by imbalance of mood and emotions, which is accompanied by the reduction in the monoaminergic signaling. The monoamine oxidase inhibition could lead to an increase in monoaminergic neurotransmitter levels in the brain. According to our previous study, 3-phenyl-4-(phenylseleno) isoquinoline (PSI) is a selective and reversible MAO-B inhibitor in vitro. The present study investigated the putative ex vivo inhibitory effect of a single PSI dose on the cerebral MAO activity and its antidepressant-like action in the mouse forced swimming test (FST). Additionally, the dopaminergic system contribution to the antidepressant-like effect of PSI was also evaluated. For this, PSI was dissolved in canola oil to determine time-course (0.5-24 h) and dose-response (25-100 mg/kg, 10 ml/kg, intragastrically) curves of MAO activity inhibition using adult C57Bl/6 male mice. A single PSI dose of 100 mg/kg inhibited the MAO-B activity in the whole brain 8 h after administration to mice, while it did not alter the MAO-A activity. The FST was carried out 0.5, 8, and 24 h after the PSI administration (100 mg/kg) or vehicle, but its antidepressant-like effect was demonstrated only at 0.5 and 8 h after treatment. Lastly, the contribution of dopaminergic system in the PSI antidepressant-like effect was demonstrated by using dopamine receptors antagonists, SCH23390, haloperidol and sulpiride. Thus, a single PSI dose of 100 mg/kg had an antidepressant-like effect in mice subjected to the FST 0.5 and 8 h after its administration. Moreover, the inhibition of cerebral MAO-B activity and modulation of dopamine receptors contributed to the antidepressant-like effect of PSI in mice.