Chronic lithium treatment decreases neuronal activity in the nucleus accumbens and cingulate cortex of the rat

Effect of neuropsychiatric medications on mitochondrial function: For better or for worse

Individuals with mitochondrial disease often present with psychopathological comorbidity, and mitochondrial dysfunction has been proposed as the underlying pathobiology in various psychiatric disorders. Several studies have suggested that medications used to treat neuropsychiatric disorders could directly influence mitochondrial function. This review provides a comprehensive overview of the effect of these medications on mitochondrial function. We collected preclinical information on six major groups of antidepressants and other neuropsychiatric medications and found that the majority of these medications either positively influenced mitochondrial function or showed mixed effects. Only amitriptyline, escitalopram, and haloperidol were identified as having exclusively adverse effects on mitochondrial function. In the absence of formal clinical trials, and until such trials are completed, the data from preclinical studies reported and discussed here could inform medication prescribing practices for individuals with psychopathology and impaired mitochondrial function in the underlying pathology.

Psychotropic and neurological medication effects on mitochondrial complex I and IV in rodent models

Mitochondrial complex I (NADH-dehydrogenase) and complex IV (cytochrome-c-oxidase) are reported to be affected by drugs used to treat psychiatric or neurodegenerative diseases, including antidepressants, antipsychotics, anxiolytics, mood stabilizers, stimulants, antidementia, and antiparkinsonian drugs. We conducted meta-analyses examining the effects of each drug category on complex I and IV. The electronic databases Pubmed, EMBASE, CENTRAL, and Google Scholar were searched for studies published between 1970 and 2018. Of 3105 screened studies, 68 articles covering 53 drugs were included in the meta-analyses. All studies assessed complex I and IV in rodent brain at the level of enzyme activity. Results revealed that selected antidepressants increase or decrease complex I and IV, antipsychotics and stimulants decrease complex I but increase complex IV, whereas anxiolytics, mood stabilizers, antidementia, and antiparkinsonian drugs preserve or even enhance both complex I and IV. Potential contributions to the drug effects were found to be related to the drugs' neurotransmitter receptor profiles with adrenergic (α1B), dopaminergic (D1/2), glutaminergic (NMDA1,3), histaminergic (H1), muscarinic (M1,3), opioid (OP1-3), serotonergic (5-HT_2A, 5-HT_2C, 5-HT_3A) and sigma (σ1) receptors having the greatest effects. The findings are discussed in relation to pharmacological mechanisms of action that might have relevance for clinical and research applications.

Mitochondrial dysfunction in bipolar disorder: Evidence, pathophysiology and translational implications

Bipolar disorder (BD) is a chronic psychiatric illness characterized by severe and biphasic changes in mood. Several pathophysiological mechanisms have been hypothesized to underpin the neurobiology of BD, including the presence of mitochondrial dysfunction. A confluence of evidence points to an underlying dysfunction of mitochondria, including decreases in mitochondrial respiration, high-energy phosphates and pH; changes in mitochondrial morphology; increases in mitochondrial DNA polymorphisms; and downregulation of nuclear mRNA molecules and proteins involved in mitochondrial respiration. Mitochondria play a pivotal role in neuronal cell survival or death as regulators of both energy metabolism and cell survival and death pathways. Thus, in this review, we discuss the genetic and physiological components of mitochondria and the evidence for mitochondrial abnormalities in BD. The final part of this review discusses mitochondria as a potential target of therapeutic interventions in BD.

Lithium-induced enhancement of mitochondrial oxidative phosphorylation in human brain tissue

OBJECTIVES

Extensive preclinical and clinical evidence suggests mitochondrial dysfunction in bipolar disorder. Studies of brain energy metabolism in bipolar disorder suggest an impairment of energy generation by mitochondrial oxidative phosphorylation. Lithium is an effective drug widely used in treating bipolar disorder, but its mechanism of action has remained uncertain. The aim of this study was to clarify the effect of lithium on mitochondrial oxidative phosphorylation.

METHODS

We spectrophotometrically determined the activities of the respiratory chain complexes I + III [antimycin A-sensitive nicotinamide adenine dinucleotide (NADH) cytochrome c oxidorductase], complexes II + III (succinate cytochrome c oxidoreductase), succinate dehydrogenase, and complex IV [cytochrome c oxidase (COX)], and of the mitochondrial matrix enzyme citrate synthase in postmortem human brain cortex homogenates following exposure to lithium (up to 10 mM).

RESULTS

Activities of complexes I + III and of complexes II + III were dose-dependently increased by lithium with maximum values at 1 mM (165%, p = 0.03, and 146%, p = 0.00002, of controls). Activity of succinate dehydrogenase remained unchanged up to 2 mM, but was raised at higher drug concentrations (maximum 220%, p = 0.01, of controls). In contrast, activity of COX was not significantly affected by the drug (decrease of 12% at 1 mM, p = 0.4).

CONCLUSIONS

Our study suggests that lithium stimulates mitochondrial respiratory chain enzyme activities at clinically relevant concentrations. Lithium's effect on the mitochondrial respiratory chain presents further evidence of the pathophysiological significance of mitochondrial dysfunction in bipolar disorder. The effect may be relevant to the therapeutic efficacy of the drug by potentially reversing a disease-related alteration.

Medication-induced mitochondrial damage and disease

Since the first mitochondrial dysfunction was described in the 1960s, the medicine has advanced in its understanding the role mitochondria play in health and disease. Damage to mitochondria is now understood to play a role in the pathogenesis of a wide range of seemingly unrelated disorders such as schizophrenia, bipolar disease, dementia, Alzheimer's disease, epilepsy, migraine headaches, strokes, neuropathic pain, Parkinson's disease, ataxia, transient ischemic attack, cardiomyopathy, coronary artery disease, chronic fatigue syndrome, fibromyalgia, retinitis pigmentosa, diabetes, hepatitis C, and primary biliary cirrhosis. Medications have now emerged as a major cause of mitochondrial damage, which may explain many adverse effects. All classes of psychotropic drugs have been documented to damage mitochondria, as have stain medications, analgesics such as acetaminophen, and many others. While targeted nutrient therapies using antioxidants or their precursors (e. g., N-acetylcysteine) hold promise for improving mitochondrial function, there are large gaps in our knowledge. The most rational approach is to understand the mechanisms underlying mitochondrial damage for specific medications and attempt to counteract their deleterious effects with nutritional therapies. This article reviews our basic understanding of how mitochondria function and how medications damage mitochondria to create their occasionally fatal adverse effects.

Effect of lithium on norepinephrine metabolic pathways

We investigated lithium-induced changes in norepinephrine (NE) catabolism. NE and its major metabolites 3-methoxy-4-hydroxyphenylglycol (MHPG) and 3,4-dihydroxyphenyl glycol (DHPG), ions such as lithium (Li(+)), magnesium (Mg(2+)), and potassium (K(+)) were measured in rat plasma and cerebral cortex using an HPLC method with electrochemical detection for amines. The results obtained with a group of rats treated by lithium chloride (2 mmol/kg/IP) were compared with a control group receiving sodium chloride (2 mmol/kg/IP). Animals were killed at different times over a period of six hours in the morning following salt administration to minimize possible chronobiological effects. There are two pathways leading to MHPG formation: way A, without DHPG, and way B, with DHPG. In plasma and cerebral cortex of lithium treated rats, way A catabolism seems to be preferential. Lithium increases Mg(2+) and K(+) plasma levels. These results suggest that lithium may increase inactivation of NE and decrease NE available for adrenergic receptors.

Thyroid hormones in the rat amygdala as common targets for antidepressant drugs, mood stabilizers, and sleep deprivation

BACKGROUND

There have been repeated reports of antidepressant effects of thyroid hormones. In this study, we investigated whether antidepressant treatments enhance the concentrations of thyroid hormones in rat brain.

METHODS

Each of the groups of rats was treated for 14 days with one of the following: an antidepressant drug (desipramine, paroxetine, venlafaxine, or tianeptine); a mood stabilizer (lithium or carbamazepine); or 8 hours' partial sleep deprivation. Thyroid hormone concentrations were quantified in homogenates, nuclei, mitochondria, synaptosomes, myelin, and microsomes in 11 rat brain areas.

RESULTS

No drug effects were seen on nuclear triiodothyronine (T(3)) concentrations in any brain area. In the amygdala, all antidepressant drugs enhanced the levels of T(3) in the myelin fraction. Triiodothyronine molecules were identified in the myelin by immunogold labeling. Quantification of the major lipid components showed a selective decrease in cholesterol in the myelin of the amygdala after desipramine treatment. Desipramine induced an increase in protein concentrations, 3,5-diiodothyronine levels, and the activity of the mitochondrial enzyme succinate dehydrogenase in the mitochondria of the amygdala. Lithium, carbamazepine, and partial sleep deprivation raised the levels of T(3) in synaptosomes of the amygdala.

CONCLUSIONS

These results demonstrate that thyroid hormones in the amygdala are a common target of different antidepressant and mood-stabilizing therapies.

The effects of chronic treatment with the mood stabilizers valproic acid and lithium on corticotropin-releasing factor neuronal systems

Corticotropin-releasing factor (CRF) plays a preeminent role in coordinating the endocrine, autonomic, and behavioral responses to stress. Dysregulation of both hypothalamic and extrahypothalamic CRF systems have been reported in patients with major depression and post-traumatic stress disorder. Moreover, effective treatment of these conditions leads to normalization of these CRF systems. Although there is virtually no data concerning alterations of CRF systems in bipolar disorder (manic depressive illness), previous work indicates that valproic acid, an anticonvulsant also effective in the treatment of acute mania, alters central CRF neuronal systems. In the current studies, we chronically administered valproic acid and lithium, two clinically effective mood stabilizers, in nonstressed rats to extend our previous findings. Chronic valproic acid administration decreased CRF mRNA expression in the paraventricular nucleus of the hypothalamus; lithium administration increased CRF mRNA expression in the central nucleus of the amygdala. Although valproic acid increased CRF(1) receptor mRNA expression in the cortex, CRF(1) receptor binding was decreased in both the basolateral amygdala and cortex, suggesting that chronic valproate treatment may in fact dampen the overall tone in this central stress pathway. Valproate treatment decreased CRF(2A) mRNA expression in both the lateral septum and hypothalamus, although CRF(2A) receptor binding was unchanged. Lithium administration decreased CRF(1) mRNA expression in both the amygdala and frontal cortex, but CRF(1) receptor binding also remained unchanged. These results suggest that the therapeutic actions of these mood stabilizers may, in part, result from their actions on central CRF neuronal systems. The distinct actions of each drug on CRF systems may underlie their synergistic clinical effects.

Acquisition of an appetitive behavior reverses the effects of long-term treatment with lithium in rats

Rats exposed to a long-term treatment with lithium chloride develop a deficit of avoidance accompanied by a reduction in the basal levels of extraneuronal dopamine and in dopamine accumulation in the nucleus accumbens shell after acute uptake inhibition. Such a condition is similar to that of an experimental model of depression induced by exposing rats to a chronic stress procedure. Rats exposed to chronic stress are also unable to acquire an appetitive behavior sustained by a highly palatable food. Thus, it was studied whether rats fed a diet containing lithium would develop an appetitive behavior induced by a pure hedonic stimulus. Rats on the lithium diet developed a clear-cut escape deficit condition accompanied by a decreased dopamine output in the nucleus accumbens shell; nevertheless, they learned the appetitive behavior within a similar period to controls. The development of the appetitive behavior coincided with the recovery of the capacity to avoid a noxious stimulus and with the return of the dopaminergic transmission in the nucleus accumbens shell to values similar to those of control rats. It may be concluded that the mechanism of action underlying the behavioral and neurochemical sequelae of a chronic stress is distinct from that of the analogous effects produced by lithium.