There are several findings on the action of magnesium ions supporting their possible therapeutic potential in affective disorders. Examinations of the sleep-electroencephalogram (EEG) and of endocrine systems point to the involvement of the limbic-hypothalamus-pituitary-adrenocortical axis as magnesium affects all elements of this system. Magnesium has the property to suppress hippocampal kindling, to reduce the release of adrenocorticotrophic hormone (ACTH) and to affect adrenocortical sensitivity to ACTH. The role of magnesium in the central nervous system could be mediated via the N-methyl-D-aspartate-antagonistic, gamma-aminobutyric acidA-agonistic or a angiotensin II-antagonistic property of this ion. A direct impact of magnesium on the function of the transport protein p-glycoprotein at the level of the blood-brain barrier has also been demonstrated, possibly influencing the access of corticosteroids to the brain. Furthermore, magnesium dampens the calciumion-proteinkinase C related neurotransmission and stimulates the Na-K-ATPase. All these systems have been reported to be involved in the pathophysiology of depression. Despite the antagonism of lithium to magnesium in some cell-based experimental systems, similarities exist on the functional level, i.e. with respect to kindling, sleep-EEG and endocrine effects. Controlled clinical trials examining the effect of Mg in affective disorder are warranted.

The role of the ACE2 enzyme in the COVID-19 infection is 2-fold, with opposing implications for the disease development. 1. The membrane bound angiotensin converting enzyme 2 (ACE2) serves as the entry point of COVID-19 2. Conversely, it supports an anti-inflammatory pathway. This led to the controversy of the impact of medications, which influence its expression. ACE2 is part of the wider renin-angiotensin-aldosterone system (RAAS) and is upregulated via compounds, which inhibits the classical ACE, thereby plasma aldosterone and aldosterone receptor (MR) activation. MR activation may therefore protect organs from binding the COVID-19 by reducing ACE2 expression. Glycyrrhizin (GL) is a frequent component in traditional Chinese medicines, which have been used to control COVID-19 infections. Its systemically active metabolite glycyrrhetinic acid (GA) inhibits 11beta hydroxysteroid dehydrogenase(11betaHSD2) and activates MR in organs, which express this enzyme, including the lungs. Does this affect the protective effect of ACE2? Importantly, GL has anti-inflammatory properties by itself via toll like receptor 4 (TLR4) antagonism and therefore compensates for the reduced protection of the downregulated ACE2. Finally, a direct effect of GL or GA to reduce virus transmission exists, which may involve reduced expression of type 2 transmembrane serine protease (TMPRSS2), which is required for virus uptake. Glycyrrhizin may reduce the severity of an infection with COVID-19 at the two stages of the COVID-19 induced disease process, 1. To block the number of entry points and 2. provide an ACE2 independent anti-inflammatory mechanism.

Changes in the activity of the renin-angiontensin-aldosterone system (RAAS) in depression have recently been reported. Renin and aldosterone secretion are coupled to sleep in healthy subjects. As total sleep deprivation (TSD) leads to a rapid mood improvement in patients with depression, it is of interest to investigate its effect on the response of the RAAS in the recovery night in this population as a possible probe for the neurobiological effects of TSD and potentially other rapid acting antidepressive interventions. Additionally we explored the HPA-system and the sleep-EEG-changes. We compared the sleep related activity of the RAAS before and after TSD in seven depressed patients. After an accommodation night, a polysomnographic examination was performed between 23.00 h and 7.00 h. This was followed by 40 h of TSD and a second polysomnography. During the examination blood samples were taken in the night every 20 min for analysis of renin, aldosterone, ACTH and cortisol. During recovery-sleep renin was significantly increased (p < 0.05). Aldosterone showed no change. ACTH and cortisol were decreased by trend in the first half of the night. REM-density and intermittent wakefulness was significantly decreased (p < 0.05), whereas slow wave sleep increased by trend in the first half of the night. TSD in patients with depression leads to an increase in renin secretion and a concomitant trend for a decrease in HPA axis activity in the recovery night. These changes could be a "fingerprint" of a rapidly antidepressive treatment.