Endogenous Cardiac Steroids in Bipolar Disorder: State of the Art

Evaluation of the activity of cardiac glycosides on RORγ and RORγT nuclear receptors

Cardiac glycosides, derived from plants and animals, have been recognized since ancient times. These substances hinder the function of the sodium-potassium pump within eukaryotic cells. Many reports have shown that these compounds influence the activity of nuclear receptors. Thus, we assessed the effects of various cardiac glycosides at nontoxic concentrations on RORγ and RORγT. RORγT is a crucial protein involved in the differentiation of Th17 lymphocytes. Sixteen analyzed cardiac glycosides exhibited varying toxicities in HepG2 cells, all of which demonstrated agonistic effects on RORγ, as confirmed in the RORγ-HepG2 reporter cell line. The overexpression of both the RORγ and RORγT isoforms intensified the effects of these compounds. Additionally, these glycosides induced the expression of G6PC, a gene regulated by RORγ, in HepG2 cells. Subsequently, the effects of two endogenous cardiac glycosides (marinobufagenin and ouabain) and the three most potent glycosides (bufalin, oleandrin, and telecinobufagenin) were evaluated in Th17 primary lymphocytes. All of these compounds increased the expression of the IL17A, IL17F, IFNG, and CXCL10 genes, but they exhibited varying effects on GZMB and CCL20 expression. Molecular docking analysis revealed the robust binding affinity of cardiac glycosides for the ligand binding domain of the RORγ/RORγT receptors. Thus, we demonstrated that at nontoxic concentrations, cardiac glycosides have agonistic effects on RORγ/RORγT nuclear receptors, augmenting their activity. This potential can be harnessed to modulate the phenotype of IL17-expressing cells (e.g., Th17 or Tc17 lymphocytes) in adoptive therapy for combating various types of cancer.

Concept article: Antidepressant-induced destabilization in bipolar illness mediated by serotonin 3 receptor (5HT3)

OBJECTIVES

Antidepressants used by patients with bipolar disorder have been associated with destabilization with an increase in mania, depression, and cycling. The most commonly proposed mechanism, that antidepressants 'overshoot' their antidepressant effect to create a manic or mixed state, is unlikely since antidepressants have actually been found to be ineffective in treating bipolar depression. Beginning with known bipolar-specific pathophysiologic abnormalities provides the greatest likelihood of insight.

METHODS

PubMed was queried with 'bipolar', 'sodium', 'intracellular sodium', 'serotonin 3', '5HT3', '5-hydroxytryptamine type 3 receptors', and 'antidepressant' either individually or in combination.

RESULTS

Pathologic mood states (both mania and depression) are associated with increased intracellular sodium (Na) concentrations that depolarize the resting membrane potential to increase cellular excitability (mania) or cause depolarization block (depression). Stimulation of the serotonin (5HT) receptors depolarizes the post-synaptic neuron. Stimulation of 5HT3 may be of particular importance since it is coupled to a cation channel that directly depolarizes the membrane. These effects directly impact the physiology of patients with bipolar disorder to alter neuronal excitability in a fashion that worsens both mania and depression.

PROPOSED CONCEPT

The most consistently observed biological abnormality in individuals going through mania or bipolar depression involves a decline in Na pump activity, with consequent elevation of intracellular Na levels. Antidepressant treatment potentiates this, particularly by activation of 5HT3. This hypothesis can be tested by coadministering a 5HT3 antagonist (e.g., vortioxetine or ondansetron) to achieve blockade of that receptor while treating bipolar depression with a serotoninergic antidepressant.

Onset of bipolar disorder by COVID-19: The roles of endogenous ouabain and the Na,K-ATPase

Bipolar Disorder (BD) is a psychiatric disorder marked by mood swings between manic and depressive episodes. The reduction in the Na,K-ATPase (NKA) enzyme activity and the inability of individuals with BD to produce endogenous ouabain (EO) at sufficient levels to stimulate this enzyme during stressful events are factors proposed for BD etiology. According to these hypotheses, reduction in NKA activity would result in altered neuronal resting potential, leading to BD symptoms. Recently, damage to the adrenals (EO synthesis site) in coronavirus disease (COVID-19) patients has been reported, however studies pointing to the pathophysiological mechanisms shared by these two diseases are scarce. Through a literature review, this study aims to correlate COVID-19 and BD, focusing on the role of NKA and EO to identify possible mechanisms for the worsening of BD due to COVID-19. The search in the PubMed database for the descriptors ("bipolar disorder" AND "Na,K-ATPase"), ("bipolar disorder" AND "endogenous ouabain"), ("covid-19" AND "bipolar disorder") and ("covid-19" AND "adrenal gland") resulted in 390 articles. The studies identified the adrenals as a vulnerable organ to SARS-CoV-2 infection. Cases of adrenal damage in patients with COVID-19 showing lower levels of adrenal hormones were reported. Cases of COVID-19 patients with symptoms of mania were reported worldwide. Given these results, we propose that adrenal cortical cell damage could lead to EO deficiency following neuronal NKA activity impairment, with small reductions in activity leading to mania and greater reductions leading to depression.

Photobiomodulation of Na,K-ATPase in native membrane fraction and reconstituted in DPPC:DPPE-liposome

Studies focusing on how photobiomodulation (PBM) can affect the structure and function of proteins are scarce in the literature. Few previous studies have shown that the enzymatic activity of Na,K-ATPAse (NKA) can be photo-modulated. However, the variability of sample preparation and light irradiation wavelengths have not allowed for an unequivocal conclusion about the PBM of NKA. Here, we investigate minimal membrane models containing NKA, namely, native membrane fraction and DPPC:DPPE proteoliposome upon laser irradiation at wavelengths 532, 650, and 780 nm. Interestingly, we show that the PBM on the NKA enzymatic activity has a bell-shaped profile with a stimulation peak (~15% increase) at around 20 J.cm-2 and 6 J.cm-2 for the membrane-bound and the proteoliposome samples, respectively, and are practically wavelength independent. Further, by normalizing the enzymatic activity by the NKA enzyme concentration, we show that the PBM response is related to the protein amount with small influence due to protein's environment. The stimulation decays over time reaching the basal level around 6 h after the irradiation for the three lasers and both NKA samples. Our results demonstrate the potential of using low-level laser therapy to modulate NKA activity, which may have therapeutic implications and benefits.

Differentially Altered Metabolic Pathways in the Amygdala of Subjects with Schizophrenia, Bipolar Disorder and Major Depressive Disorder

Background and hypothesis

A growing number of studies implicate a key role for metabolic processes in psychiatric disorders. Recent studies suggest that ketogenic diet may be therapeutically effective for subgroups of people with schizophrenia (SCZ), bipolar disorder (BPD) and possibly major depressive disorder (MDD). Despite this promise, there is currently limited information regarding brain energy metabolism pathways across these disorders, limiting our understanding of how brain metabolic pathways are altered and who may benefit from ketogenic diets. We conducted gene expression profiling on the amygdala, a key region involved in in the regulation of mood and appetitive behaviors, to test the hypothesis that amygdala metabolic pathways are differentially altered between these disorders.

Study Design

We used a cohort of subjects diagnosed with SCZ, BPD or MDD, and non-psychiatrically ill control subjects (n=15/group), together with our bioinformatic 3-pod analysis consisting of full transcriptome pathway analysis, targeted pathway analysis, leading-edge gene analysis and iLINCS perturbagen analysis.

Study Results

We identified differential expression of metabolic pathways in each disorder. Subjects with SCZ displayed downregulation of mitochondrial respiration and nucleotide metabolism pathways. In comparison, we observed upregulation of mitochondrial respiration pathways in subjects with MDD, while subjects with BPD displayed enrichment of pathways involved in carbohydrate metabolism. Several pathways associated with brain metabolism including immune system processes and calcium ion transport were also differentially altered between diagnosis groups.

Conclusion

Our findings suggest metabolic pathways are differentially altered in the amygdala in these disorders, which may impact approaches for therapeutic strategies.

Sensational site: the sodium pump ouabain-binding site and its ligands

Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.

Involvement of the Na+, K+-ATPase α1 Isoform and Endogenous Cardiac Steroids in Depression- and Manic-like Behaviors

Bipolar disorder (BD) is a severe and common chronic mental illness characterized by recurrent mood swings between depression and mania. The biological basis of the disease is poorly understood, and its treatment is unsatisfactory. Na+, K+-ATPase is a major plasma membrane transporter and signal transducer. The catalytic α subunit of this enzyme is the binding site for cardiac steroids. Three α isoforms of the Na+, K+-ATPase are present in the brain. Previous studies have supported the involvement of the Na+, K+-ATPase and endogenous cardiac steroids (ECS) in the etiology of BD. Decreased brain ECS has been found to elicit anti-manic and anti-depressive-like behaviors in mice and rats. However, the identity of the specific α isoform involved in these behavioral effects is unknown. Here, we demonstrated that decreasing ECS through intracerebroventricular (i.c.v.) administration of anti-ouabain antibodies (anti-Ou-Ab) decreased the activity of α1+/- mice in forced swimming tests but did not change the activity in wild type (wt) mice. This treatment also affected exploratory and anxiety behaviors in α1+/- but not wt mice, as measured in open field tests. The i.c.v. administration of anti-Ou-Ab decreased brain ECS and increased brain Na+, K+-ATPase activity in wt and α1+/- mice. The serum ECS was lower in α1+/- than wt mice. In addition, a study in human participants demonstrated that serum ECS significantly decreased after treatment. These results suggest that the Na+, K+-ATPase α1 isoform is involved in depressive- and manic-like behaviors and support that the Na+, K+-ATPase/ECS system participates in the etiology of BD.

Non-enzymatic antioxidants, macro-minerals and monocyte/high-density lipoprotein cholesterol ratio among patients with bipolar disorder

OBJECTIVE

Recent studies show that oxidative stress is related to the pathogenesis of BD. Non-enzymatic antioxidants, macro-minerals and MHR (monocyte divided by high-density lipoprotein cholesterol) participated oxidative stress and can be obtained quickly in hematological examination. This study used large-scale clinical data to investigate them between BD and healthy controls (HCs), as well as between psychotic and non-psychotic BD to explore their roles in disease progression.

METHODS

A total of 3442 BD-manic (BD-M) and 1405 BD-depression (BD-D) in acute stage and 5000 HCs were enrolled, including 1592 BD-M with psychotic symptoms (P-BD-M), 1850 BD-M without psychotic symptoms (NP-BD-M), 655 P-BD-D, 750 NP-BD-D. The differences in these biological parameter levels among different groups were compared, and the contributing factors for the occurrence of BD-M or BD-D and psychotic symptoms of BD were analyzed.

RESULTS

We found higher levels of Na and MHR, and lower levels of K, Ca and ALB in BD-M or BD-D compared with the HCs respectively; levels of K, Na, Ca, ALB and MHR have differences among P-BD-M, NP-BD-M and HC; levels of K, Na, Ca and ALB have differences among P-BD-D, NP-BD-D and HC. In multiple logistic regression, higher levels of MHR and Na were associated with BD-M; MHR was shown to be independently associated with P-BD-M; K, Na, ALB were shown to be independently associated with P-BD-D.

CONCLUSIONS

Our study highlights the role of oxidative stress in the pathophysiology of BD. There is heterogeneity between BD-M and BD-D, and different oxidative stress mechanisms of psychotic symptoms exist in BD-M and BD-D.

Vanadium in Bipolar Disorders-Reviving an Old Hypothesis

Bipolar disorder (BD) is a severe and common chronic mental illness. The biological basis of the disease is poorly understood and its treatment is unsatisfactory. Our previous studies supported the notion that alterations in Na⁺, K⁺-ATPase activity were involved in the etiology of BD. As various chemical elements inhibit Na⁺, K⁺-ATPase, we determined the concentration of 26 elements in the serum of BD patients before and after treatment and in postmortem brain samples from BD patients, and compared them with matched controls. The only element that was reduced significantly in the serum following treatment was vanadium (V). Furthermore, the concentration of V was significantly lower in the pre-frontal cortex of BD patients compared with that of the controls. Intracerebroventricular administration of V in mice elicited anxiolytic and depressive activities, concomitantly inhibited brain Na⁺, K⁺-ATPase activity, and increased extracellular signal-regulated kinase phosphorylation. A hypothesis associating V with BD was set forth decades ago but eventually faded out. Our results are in accord with the hypothesis and advocate for a thorough examination of the possible involvement of chemical elements, V in particular, in BD.