Lithium. Current status in psychiatric disorders

Parkinson's Disease: Potential Actions of Lithium by Targeting the WNT/β-Catenin Pathway, Oxidative Stress, Inflammation and Glutamatergic Pathway

Parkinson's disease (PD) is one of the major neurodegenerative diseases (ND) which presents a progressive neurodegeneration characterized by loss of dopamine in the substantia nigra pars compacta. It is well known that oxidative stress, inflammation and glutamatergic pathway play key roles in the development of PD. However, therapies remain uncertain and research for new treatment is mandatory. This review focuses on the potential effects of lithium, as a potential therapeutic strategy, on PD and some of the presumed mechanisms by which lithium provides its benefit properties. Lithium medication downregulates GSK-3beta, the main inhibitor of the WNT/β-catenin pathway. The stimulation of the WNT/β-catenin could be associated with the control of oxidative stress, inflammation, and glutamatergic pathway. Future prospective clinical trials could focus on lithium and its different and multiple interactions in PD.

Is There Justification to Treat Neurodegenerative Disorders by Repurposing Drugs? The Case of Alzheimer's Disease, Lithium, and Autophagy

Lithium is the prototype mood-stabilizer used for acute and long-term treatment of bipolar disorder. Cumulated translational research of lithium indicated the drug's neuroprotective characteristics and, thereby, has raised the option of repurposing it as a drug for neurodegenerative diseases. Lithium's neuroprotective properties rely on its modulation of homeostatic mechanisms such as inflammation, mitochondrial function, oxidative stress, autophagy, and apoptosis. This myriad of intracellular responses are, possibly, consequences of the drug's inhibition of the enzymes inositol-monophosphatase (IMPase) and glycogen-synthase-kinase (GSK)-3. Here we review lithium's neurobiological properties as evidenced by its neurotrophic and neuroprotective properties, as well as translational studies in cells in culture, in animal models of Alzheimer's disease (AD) and in patients, discussing the rationale for the drug's use in the treatment of AD.

Lithium therapy

Since the introduction of lithium therapy 30 years ago it has become a major weapon in psychiatrists' armamentarium. It is the drug of first choice for the prevention of recurrent mood disorders, and it is estimated that about one person in every thousand people in Britain receives lithium at any one time. It therefore behoves doctors to be familiar with its use. This article is not a comprehensive account of the pharmacology of lithium (for this the reader is referred to Johnson (1987) and Peet & Pratt (1993)) but concentrates on its clinical use in practice and some less well known, but important, phenomena.

Amiloride restores renal medullary osmolytes in lithium-induced nephrogenic diabetes insipidus

In lithium-induced nephrogenic diabetes insipidus (NDI), alterations in renal medullary osmolyte concentrations have been assumed but never investigated. Amiloride can modify lithium-induced NDI, but the impact of amiloride in lithium-induced NDI on renal medullary osmolytes, aquaporins, and urea transporters is unknown and is the basis of this study. Rats fed lithium (60 mmol/kg dry food) over 4 wk developed NDI. Urine osmolality fell to 287 ± 19 mosmol/kgH2O (controls 1,211 ± 90 mosmol/kgH2O). Organic osmolytes in the renal medulla showed significant decreases compared with controls [inositol 221 ± 35 to 85 ± 10 mmol/kg protein; sorbitol 35 ± 9 to 3 ± 1 mmol/kg protein; glycerophosphorylcholine (GPC) 352 ± 80 to 91 ± 20 mmol/kg protein; and glycine betaine 69 ± 11 to 38 ± 38 mmol/kg protein]. Medullary urea content fell from 2,868 ± 624 to 480 ± 117 mmol/kg protein. Concurrent administration of amiloride (0.2 mmol/l) in the drinking water restored urine osmolality (1,132 ± 154 mosmol/kgH2O), and reduced urine volume. Medullary osmolyte content were restored to control values (inositol, 232 ± 12; sorbitol 32 ± 6; GPC, 244 ± 26; glycine betaine, 84 ± 5 mmol/kg protein). Medullary urea rose to 2,122 ± 305 mmol/kg protein. Reduced AQP2, AQP3, and urea transporter (UT-A1) expression was significantly reversed following amiloride therapy. Data presented here provide further understanding of how amiloride may substantially restore the lithium-induced impaired renal concentrating mechanism.

Proteomic analysis of lithium-induced nephrogenic diabetes insipidus: mechanisms for aquaporin 2 down-regulation and cellular proliferation

Lithium is a commonly prescribed mood-stabilizing drug. However, chronic treatment with lithium induces numerous kidney-related side effects, such as dramatically reduced aquaporin 2 (AQP2) abundance, altered renal function, and structural changes. As a model system, inner medullary collecting ducts (IMCD) isolated from rats treated with lithium for either 1 or 2 weeks were subjected to differential 2D gel electrophoresis combined with mass spectrometry and bioinformatics analysis to identify (i) signaling pathways affected by lithium and (ii) unique candidate proteins for AQP2 regulation. After 1 or 2 weeks of lithium treatment, we identified 6 and 74 proteins with altered abundance compared with controls, respectively. We randomly selected 17 proteins with altered abundance caused by lithium treatment for validation by immunoblotting. Bioinformatics analysis of the data indicated that proteins involved in cell death, apoptosis, cell proliferation, and morphology are highly affected by lithium. We demonstrate that members of several signaling pathways are activated by lithium treatment, including the PKB/Akt-kinase and the mitogen-activated protein kinases (MAPK), such as extracellular regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK), and p38. Lithium treatment increased the intracellular accumulation of beta-catenin in association with increased levels of phosphorylated glycogen synthase kinase type 3beta (GSK3beta). This study provides a comprehensive analysis of the proteins affected by lithium treatment in the IMCD and, as such, provides clues to potential lithium targets in the brain.

Acquired nephrogenic diabetes insipidus

Nephrogenic diabetes insipidus (NDI) is defined as the inability of the kidney to concentrate urine owing to the insensitivity of the distal nephron to the antidiuretic hormone, arginine vasopressin. NDI can be either a congenital or an acquired disorder. Acquired NDI most commonly is secondary to drugs such as lithium or metabolic disturbances, such as hypokalemia and hypercalcemia. Disturbance of the aquaporin-2 shuttle is the underlying molecular basis of acquired NDI. NDI is diagnosed with the help of a water-deprivation test. Patients with the disorder will have a urinary osmolality of less than 300 mosm/kg H2O despite water deprivation. On administration of aqueous vasopressin, patients with NDI will show little or no increase in urine osmolality. Therapy consists of identifying and correcting the underlying disorder, or withdrawing the offending drug. Other treatment options that may be beneficial include diuretics, nonsteroidal anti-inflammatory drugs, decreased dietary solute intake, and desmopressin (DDAVP).

Management of Lithium Toxicity

Lithium salts have been used in the prophylaxis and treatment of depression and bipolar disorder for >50 years. Lithium has a narrow therapeutic range, and several well characterised adverse effects limit the potential usefulness of higher doses. Acute ingestion in lithium-naive patients is generally associated with only short-lived exposure to high concentrations, due to extensive distribution of lithium throughout the total body water compartment. Conversely, chronic toxicity and acute-on-therapeutic ingestion are associated with prolonged exposure to higher tissue concentrations and, therefore, greater toxicity. Lithium toxicity may be life threatening, or result in persistent cognitive and neurological impairment. Therefore, enhanced lithium clearance has been explored as a means of minimising exposure to high tissue concentrations. Although haemodialysis is highly effective in removing circulating lithium, serum concentrations often rebound so repeated or prolonged treatment may be required. Continuous arteriovenous haemodiafiltration and continuous venovenous haemodiafiltration increase lithium clearance, albeit to a lesser extent than haemodialysis, and are more widely accessible. Haemodiafiltration sustained for >16 hours allows effective removal of total body lithium, thereby avoiding rebound effects. Enhanced elimination should be considered in patients at greatest risk of severe poisoning: namely those with chronic or acute-on-therapeutic toxicity, those with clinically significant features, and those with chronic toxicity whose serum lithium concentration is >2.5 mmol/L. The choice between haemodialysis and continuous haemodiafiltration techniques will depend on local accessibility and urgency of enhancing lithium elimination. Further research is required to establish the potential benefits of assisted elimination on clinical outcome in patients with lithium poisoning.

Intoxicación aguda por comprimidos de liberación sostenida de carbonato de litio. A propósito de un caso clínico

OBJECTIVE

To describe the case of a patient who ingested 50 sustained release lithium carbonate 400 mg tablets, and reached a late peak concentration above 3 mEq/L.

CASE REPORT

A 32-year-old male with bipolar mood disorder ingested 50 sustained-release lithium carbonate tablets. Upon admission to the emergency room, a gastric wash was performed,from which several tablet remnants were obtained, as well as an intestinal lavage using activated carbon.

PHYSICAL EXAMINATION

good general status, no fever, blood pressure 160/90 mm Hg, no edemas. Neurologic, pulmonary, and cardiac examinations were normal. CBC and the chemistry panel were normal. The patient's psychopathological examination suggested a stable status with no apparent manifestations arising from a decompensated mood disorder. Five hours after his massive lithium ingestion the drug's plasma levels were 0.75 mEq/L. At 22 hours post-ingestion a chemistry panel was obtained, which showed serum creatinin at 1.38 mg/dL and a lithium plasma concentration of 3.15 mEq/L. A hemodyalisis trial was attempted for 4 hours. At 73 hours post-ingestion, lithium plasma levels were 0.6 mEq/L, that is, within therapeutic range. The patient was hemodynamically stable and serial blood tests were normal; he was discharged.

COMMENT

Acute lithium intoxication with plasma levels above 3 mEq/l can be fatal or result in irreversible neurologicsequelae in almost one third of cases, with persistent cerebellar dysfunction in association with dementia of variable degree, andrenal, blood, and liver disturbances. Sustained-release tablets may prolong absorption and delay peak plasma concentrations. In such cases, therefore, it is recommended that drug plasma concentrations be monitored during 48-72 hours post-ingestion.

Clonazepam and lorazepam in acute mania: a Bayesian meta-analysis

BACKGROUND

Clonazepam and lorazepam are used in the treatment of acute mania but trial results are conflicting.

METHODS

Studies were identified by searching MEDLINE and EMBASE for lorazepam or clonazepam in acute mania between 1966 and 2000. Seven randomized controlled trials were found comparing clonazepam or lorazepam to placebo, haloperidol or lithium in acute mania. Data on 206 patients were analyzed.

RESULTS

The heterogeneity of trial designs and the use of different comparators necessitated a Bayesian hierarchical meta-analysis with three models: (a) random trial effect and fixed treatment effects, (b) random trial and treatment effects, (c) random trial and treatment effects with trial variance unknown. With all models, clonazepam decreased psychopathology scores statistically significantly with the following standardized responses: model (a): 1.26 (95% predictive interval (PI) 0.33 to 2.28), model (b): 1.21 (95% PI 0.08 to 2.53), model (c): 1.41 (95% PI 0.12 to 2.67). Lorazepam did not yield statistically significant standardized responses for any of the three models: model (a): 0.79 (95% PI -0.29 to 1.89), model (b): 0.77 (95% PI -0.57 to 2.24) and model (c): 0.74 (-0.82 to 2.20). Haloperidol yielded statistically significant standardized responses in the three models but lithium effect was statistically significant only in model (a). Safety data were in line with the usual safety profile of benzodiazepines.

LIMITATIONS

Trial designs were heterogenous and patient number was limited.

CONCLUSIONS

This meta-analysis suggests that clonazepam is efficient and safe in the treatment of acute mania, but the results remain inconclusive for lorazepam.

Reverse pharmacological effect of loop diuretics and altered rBSC1 expression in rats with lithium nephropathy

BACKGROUND

Renal urinary concentration is associated with enhanced expression of rBSC1, a rat sodium cotransporter, in the thick ascending limb of Henle. Increased expression of rBSC1 was reported recently in nephrogenic diabetes insipidus induced by lithium chloride (Li nephropathy). However, the pathophysiological implication of altered rBSC1 expression has not yet been investigated.

METHODS

Li nephropathy was induced in rats by an oral administration of 40 mmol lithium/kg dry food. In rats with reduced urinary osmolality to less than 300 mOsm/kg H2O, we examined the expression of rBSC1 mRNA and protein, plasma arginine vasopressin (AVP) and RNA expression of kidney-specific water channel, aquaporin-2 (AQP2), of collecting ducts. Rats with Li nephropathy were treated with furosemide (3 mg/kg body weight), which blocks the activity of rBSC1, and changes in urine concentration, plasma AVP, medullary accumulation of Li ions, and apical AQP2 expression were determined.

RESULTS

Rats with Li nephropathy showed increased rBSC1 RNA and protein expression and reduced AQP2 RNA. In these rats, furosemide, which induces dilution of urine and polyuria in normal rats, resulted in a progressive and significant rise in urine osmolality from 167 +/- 11 (mean +/- SD) at baseline to 450 +/- 45 mOsm/kg H2O at three hours after administration, and significant oliguria. In the same rats, plasma AVP decreased significantly from 5.7 to 3.0 pg/mL. In addition, recovery of apical AQP2 expression was noted in a proportion of epithelial cells of the collecting ducts. Although Li+ in the renal medulla was slightly lower in rats with Li nephropathy treated with furosemide, statistical significance was not achieved.

CONCLUSIONS

Our results suggest that dehydration or high plasma AVP results in an enhanced rBSC1 expression in Li nephropathy, and that rBSC1 expression is closely associated with the adverse effects of Li ions on collecting duct function.

Mood Disorders in Family Practice: Beyond Unipolarity to Bipolarity

Primary care physicians increasingly have treated depressive disorders over the last decade. Unrecognized bipolar disorder, sometimes misdiagnosed as unipolar depression, may lead to treatment resistance or nonresponse. We describe differences between unipolar and bipolar disorders, focusing on recognition, diagnosis, and treatment of bipolar spectrum disorders such as bipolar I, bipolar II, antidepressant-induced mania, and cyclothymia. Broadening the understanding of these different disorders and their presentation in primary care settings can enable earlier and more targeted treatment. Though 3 mood stabilizers are U.S. Food and Drug Administration-approved for treatment of acute mania, no medications are currently approved for treating bipolar depression.

Serum concentration of chlormethiazole and therapeutic effect in acute alcohol withdrawal syndrome: an open clinical trial

It was the aim of this study to find a relationship between the serum concentration of chlormethiazole and its therapeutic effect in acute alcohol withdrawal syndrome. As a secondary subject, the concentration of chlormethiazole was investigated in relation to variables of treatment and variables of physical status of patients. In an open clinical trial, the clinical status of patients was rated by the Mainz Alcohol Withdrawal Scale (MAWS) and the Delirium Rating Scale (DRS). Chlormethiazole concentration was measured by gas-liquid chromatography. Patients were dichotomized according to minimum values of MAWS and DRS after 2 days of treatment (good response and retarded or no response). Chlormethiazole concentration and dose per body weight and MAWS and DRS scores before treatment were compared by the Student t test and the Mann-Whitney test. The two groups were also analyzed by logistic regression with chlormethiazole concentration, MAWS and DRS score before treatment, age, gender, body weight, years of alcoholism, and dose per body weight as independent variables. Chlormethiazole concentration was analyzed by multiple regression with dose, age, gender, smoking, initial alcohol, body weight, and liver dysfunction as independent variables. Forty-three patients were included in the study. Twenty-four patients reached a minimum time of investigation of 2 days. The chlormethiazole concentration was in the range of 0.3 to 5.4 microg/mL at doses of 10 to 24 capsules/d (1 capsule = 192 mg chlormethiazole). As the main result, significantly increased chlormethiazole concentrations were found in patients with retarded or no response; however, in addition the DRS score before treatment and dose per body weight were increased. In addition, the final models of logistic regression contained only DRS score before treatment. As a secondary result, the final model of multiple regression revealed an increased chlormethiazole concentration with dose of chlormethiazole and concentration of alcohol in blood and a decreased chlormethiazole concentration with body weight. This was the first study to investigate the relationship between the chlormethiazole concentration and therapeutic effect in alcohol withdrawal. No robust relationship could be detected that could be separated from the control of treatment by clinical variables. Rather, a poor therapeutic outcome is mainly predicted by an increased initial severity of symptoms, and higher doses are applied in more severely ill patients. Thus, pharmacokinetic control of treatment is not recommended.

Activation of hypothalamic neuronal nitric oxide synthase in lithium-induced diabetes insipidus rats

The expression of the neuronal nitric oxide synthase (nNOS) gene in the paraventricular (PVN) and supraoptic nuclei (SON) in rats with lithium (Li)-induced polyuria was examined by using in situ hybridization histochemistry. The state of the thyroid axis in these rats was also examined by in situ hybridization histochemistry for thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH) mRNAs and radioimmunoassay for circulating thyroid hormones. Adult male Wistar rats consuming a diet that contained LiCl (60 mmol/kg) for 4 weeks developed remarkable polyuria. The urine in the Li-treated rats was hypotonic and had a large volume and low ionic concentration. The nNOS mRNA in the PVN and SON was significantly increased in the Li-treated rats in comparison with that in control. The increased levels of the nNOS mRNA in the PVN and SON were confirmed by NADPH-diaphorase histochemical staining. There were no differences of TRH mRNA in the PVN, TSH mRNA in the anterior pituitary and plasma concentrations of free T3 and free T4 between Li-treated rats and control rats. These results suggest that Li-induced diabetes insipidus may activate nNOS in the PVN and SON without change of the thyroid axis.

Somatic treatment of psychotic depression: review and recommendations for practice

The diagnosis, classification, and course of psychotic major depression (PMD) is considered with regard to its status as a distinct syndrome. Several factors, especially biological markers, suggest, although as yet do not confirm, that PMD is distinct from nonpsychotic major depression (NPMD), particularly for the purposes of treatment. This article provides a critical review of somatic treatments for PMD, with attention to problems of inadequate treatment, as well as underused and more recently introduced treatments. The somatic treatment options reviewed include (1) combined antidepressant (AD) and antipsychotic (AP) therapy with tricyclic antidepressants (TCAs) and typical APs; (2) electroconvulsive therapy (ECT); (3) amoxapine; (4) selective serotonin reuptake inhibitors (SSRIs), alone and in combination; (5) several atypical APs, alone and in combination; (6) mood stabilizers and anticonvulsants; and (7) some experimental treatments and surgery. A comprehensive treatment algorithm (heuristic) is presented, which draws on some previous guidelines and the critical review. This heuristic is conservative in its aims, but forward-looking in its recommendations. The status of the TCA plus typical AP regime is challenged as the default first-line treatment, and preferable alternatives are discussed. ECT has been shown to be at least as effective in short-term treatment and should be considered more frequently, especially in severe presentations and as a maintenance treatment. Some single compounds should be considered as first-line monotherapies in less severe cases. For cases in which combined AD+AP regimes are instituted, SSRIs and atypical APs should be used before older classes of drugs are considered. These recommendations aim to minimize the number of treatments used and unwanted effects experienced.

Tol1, a fission yeast phosphomonoesterase, is an in vivo target of lithium, and its deletion leads to sulfite auxotrophy

Lithium is the drug of choice for the treatment of bipolar affective disorder. The identification of an in vivo target of lithium in fission yeast as a model organism may help in the understanding of lithium therapy. For this purpose, we have isolated genes whose overexpression improved cell growth under high LiCl concentrations. Overexpression of tol1(+), one of the isolated genes, increased the tolerance of wild-type yeast cells for LiCl but not for NaCl. tol1(+) encodes a member of the lithium-sensitive phosphomonoesterase protein family, and it exerts dual enzymatic activities, 3'(2'),5'-bisphosphate nucleotidase and inositol polyphosphate 1-phosphatase. tol1(+) gene-disrupted cells required high concentrations of sulfite in the medium for growth. Consistently, sulfite repressed the sulfate assimilation pathway in fission yeast. However, tol1(+) gene-disrupted cells could not fully recover from their growth defect and abnormal morphology even when the medium was supplemented with sulfite, suggesting the possible implication of inositol polyphosphate 1-phosphatase activity for cell growth and morphology. Given the remarkable functional conservation of the lithium-sensitive dual-specificity phosphomonoesterase between fission yeast and higher-eukaryotic cells during evolution, it may represent a likely in vivo target of lithium action across many species.

Endocrine effects of lithium carbonate in healthy premenopausal women: relationship with body weight regulation

The mechanisms involved in Li-induced weight gain remain unclear. The higher frequency of obesity in women than in men under Li treatment, suggests a role for reproductive hormones. The serum levels of the following hormones were evaluated in healthy young women at diverse stages of a control menstrual cycle, and during Li carbonate (900 mg/day) or placebo administration: prolactin, luteinizing hormone, follicle-stimulating hormone, 17-1 estradiol, progesterone, thyroxine, thyrotropin, cortisol, dehidroepiandrosterone sulfate, free testosterone, leptin and an oral glucose tolerance test, in order to measure the areas under the glucose and insulin curve. The body weight was assessed the day before and the last day of treatment. The Li serum levels 15 hours after the last dose were 0.31 +/- 0.1 mEq/L. No significant changes in body weight and in the normal fluctuations of the reproductive hormones along the menstrual cycle were observed during Li administration. An increase in the serum levels of thyrotropic hormone ( p = 0.0001) was the only significant effect of Li, which may predispose to excessive weight gain after prolonged administration of the cation. The remarkable lack of effects of Li on these hormones, question the pertinence of studies conducted in healthy volunteers for the comprehension of the obesity observed in psychiatric patients who may be particularly prone to gain weight under prolonged treatment with high dose of Li.

Long-term regulation of aquaporins in the kidney

The discovery of the aquaporin family of water channels has greatly improved our understanding of how water crosses epithelial cells, particularly in the kidney. The study of the mechanisms involved in the regulation of collecting duct water permeability, in particular, has advanced very rapidly since the identification and characterization of aquaporin-2 (AQP2) in 1993. One of the more surprising findings has been the dramatic long-term changes that are seen in the abundance of this protein, as well as the recognition that these changes represent a way of modulating the acute antidiuretic effects of vasopressin. Furthermore, such changes seem to be of etiological and pathological significance in a number of clinical disorders of water balance. This review focuses on the various conditions in which AQP2 expression is altered (either increased or decreased) and on what this can tell us about the signals and mechanisms controlling these changes. Ultimately, this may be of great value in the clinical management of water balance disorders. Evidence is also now beginning to emerge that there are similar changes in the expression of other renal aquaporins, which had previously been thought to provide an essentially constitutive water permeability pathway, suggesting that they too should be considered as regulatory factors in the control of body water balance.

Action potential broadening induced by lithium may cause a presynaptic enhancement of excitatory synaptic transmission in neonatal rat hippocampus

Lithium enhances excitatory synaptic transmission in CA1 pyramidal cells, but the mechanisms remain unclear. The present study demonstrates that lithium enhances the N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-isoxazole propionic acid (AMPA) receptor-mediated components of the excitatory postsynaptic current (EPSC). Lithium decreased the magnitude of paired-pulse facilitation and presented an inverse correlation between the lithium-induced enhancement of synaptic transmission and initial paired-pulse facilitation, which is consistent with a presynaptic mode of action. The enhancement of synaptic strength is likely to act, at least in part, by increasing the amplitude of the presynaptic Ca2+ transient. One mechanism which could account for this change of the presynaptic Ca2+ transient is an increase in the duration of the action potential. We investigated action potential in hippocampal pyramidal neurons and found that lithium (0.5-6 mM) increased the half-amplitude duration and reduced the rate of repolarization, whereas the rate of depolarization remained similar. To find out whether the lithium synaptic effects might be explained by spike broadening, we investigated the field recording of the excitatory postsynaptic potential (EPSP) in hippocampal slices and found three lines of evidence. First, the prolongation of the presynaptic action potential with 4-aminopyridine and tetraethylammonium blocked or reduced the synaptic effects of lithium. Second, the lithium-induced synaptic enhancement was modulated when presynaptic Ca2+ influx was varied by changing the external Ca2+ concentration. Finally, both effects, the synaptic transmission increment and the action potential broadening, were independent of inositol depletion. These results suggest that lithium enhances synaptic transmission in the hippocampus via a presynaptic site of action: the mechanism underlying the potentiating effect may be attributable to an increased Ca2+ influx consequent to the broadening effect of lithium on the action potential.

Efferent-mediated protection of the cochlear base from acoustic overexposure by low doses of lithium

Many studies on anaesthetized animals and a few on awake animals have suggested that the cholinergic olivocochlear efferent feedback to outer hair cells can participate in the protection of the cochlea from acoustic overexposure. Lithium is known to stimulate acetylcholine synthesis and release in the brain and it is likely to act similarly at the level of the cochlear efferent synapses. We demonstrate here that, in the awake guinea-pig with a chronically implanted electrode on the round window of the cochlea, the temporary threshold shift induced by 1 minute exposure to different pure tones at around 90 dB sound pressure level (SPL) was reduced by as much as 40 dB, when exposure occurred after lithium treatment. The protection effect was not observed in anaesthetized animals. The effect was seen across the test frequency range of 6.4-12.5 kHz, suggesting that both 'fast' and 'slow' efferent effects are likely to be mediated by acetylcholine. Together our results provide new evidence that the olivocochlear efferents can provide a more efficient protection from acoustic overexposure when animals are awake.

Monoaryl- and bisaryldihydroxytropolones as potent inhibitors of inositol monophosphatase

The first successful preparation of mono- and disubstituted 3,7-dihydroxytropolone involves a four-step synthetic scheme. Thus, bromination of 3,7-dihydroxytropolone (8) followed by permethylation of the resultant products furnished gram quantities of intermediates 13-18. Single or double Suzuki coupling reactions between these permethylated monobromo- and dibromodihydroxytropolone derivatives and a variety of boronic acids delivered the expected products whose deprotection yielded the desired compounds 1a-u and 26a-n, usually in fair to good yields. Tropolones 1 and 26 were found to be potent inhibitors of inositol monophosphatase with IC50 values in the low-micromolar range. The results are discussed in the context of the recently described novel mode of inhibition of the enzyme by 3,7-dihydroxytropolones.

Upregulation of the expression of vasopressin gene in the paraventricular and supraoptic nuclei of the lithium-induced diabetes insipidus rat

The expression of arginine vasopressin (AVP) gene in the paraventricular (PVN) and supraoptic nuclei (SON) was investigated in rats with lithium (Li)-induced polyuria, using in situ hybridization histochemistry and radioimmunoassay. The male Wistar rats consuming a diet that contained LiCl (60 mmol/kg) for 4 weeks developed marked polyuria. The Li-treated rats produced a large volume of hypotonic urine with low ionic concentrations. Plasma sodium concentrations were found to be slightly increased in the Li-treated rats compared with those in controls. Plasma concentration of AVP and transcripts of AVP gene in the PVN and SON were significantly increased in the Li-treated rats compared with controls. These results suggest that dehydration and/or the activation of visceral afferent inputs may contribute to the elevation of plasma AVP and the upregulation of AVP gene expression in the PVN and the SON of the Li-induced diabetes insipidus rat.

Reversible hearing impairment induced by lithium in the guinea pig

Lithium salts remain one of the most widely used treatments for depressive illness. The mechanisms involved probably include reduction in free inositol. Visual perceptive disturbances can be a side effect of the treatment. We report here for the first time that chronic lithium treatment in the guinea pig induces a predominantly low frequency hearing loss and, in the longer term, loss of sensitivity is observed across the whole audiogram. The changes are reversed when treatment is arrested. The observations could be accounted for, at least partially, by a lithium-induced perturbation of the phosphoinositide cascade within the inner ear.

Inositol monophosphatase inhibitors--lithium mimetics?

Given the putative role of inositol monophosphatase (IMPase) as the molecular target for the therapeutic effects of lithium, inhibitors of this enzyme have been proposed to be lithium-mimetics. Although cation and natural product inhibitors of IMPase have been described, these have not proved suitable for cell culture studies due to a lack of specificity. On the other hand, substrate (inositol 1-phosphate)-based inhibitors have proved useful for showing that this class of compounds mimic lithium with respect to effects on the phosphatidylinositol (PI) cell-signaling pathway. However, since these compounds are highly charged, their polarity means they are not suitable for in vivo use. Finally, the recent elucidation of the structure and mechanism of IMPase may provide the opportunity to develop compounds which specifically interact with key structural and mechanistic features of the enzyme and would represent novel structure- or mechanism-based inhibitors.

Chorea caused by lithium intoxication: a case report and literature review

We report a patient who developed an acute, reversible, generalized choreiform disorder from lithium (Li) intoxication. This medication was prescribed for manic-depressive disorder, and serum levels became elevated after the addition of a diuretic for the treatment of hypertension. There were no other apparent causes for the movement disorder, and it was associated with other known features of Li intoxication, including ataxia and encephalopathy. There was a delay between the initial symptoms of Li intoxication and the onset of chorea. The chorea improved as serum Li levels diminished, with some lag time. This represents the eleventh case report of Li-induced chorea, but only the sixth in a patient without concomitant neuroleptic therapy, and the first presented with videotape confirmation. A review of these other cases is included, and possible mechanisms are discussed.

Lithium and neuroleptics in combination: is there enhancement of neurotoxicity leading to permanent sequelae?

Neurotoxicity in relation to concomitant administration of lithium and neuroleptic drugs, particularly haloperidol, has been an ongoing issue. This study examined whether use of lithium with neuroleptic drugs enhances neurotoxicity leading to permanent sequelae. The Spontaneous Reporting System database of the United States Food and Drug Administration and extant literature were reviewed for spectrum cases of lithium/neuroleptic neurotoxicity. Groups taking lithium alone (Li), lithium/haloperidol (LiHal) and lithium/ nonhaloperidol neuroleptics (LiNeuro), each paired for recovery and sequelae, were established for 237 cases. Statistical analyses included pairwise comparisons of lithium levels using the Wilcoxon Rank Sum procedure and logistic regression to analyze the relationship between independent variables and development of sequelae. The Li and Li-Neuro groups showed significant statistical differences in median lithium levels between recovery and sequelae pairs, whereas the LiHal pair did not differ significantly. Lithium level was associated with sequelae development overall and within the Li and LiNeuro groups; no such association was evident in the LiHal group. On multivariable logistic regression analysis, lithium level and taking lithium/haloperidol were significant factors in the development of sequelae, with multiple possibly confounding factors (e.g., age, sex) not statistically significant. Multivariable logistic regression analyses with neuroleptic dose as five discrete dose ranges or actual dose did not show an association between development of sequelae and dose. Database limitations notwithstanding, the lack of apparent impact of serum lithium level on the development of sequelae in patients treated with haloperidol contrasts notably with results in the Li and LiNeuro groups. These findings may suggest a possible effect of pharmacodynamic factors in lithium/neuroleptic combination therapy.

In-vivo binding of lithium using the cation exchange resin sodium polystyrene sulfonate

The purpose of this study was to determine if the exchange resin sodium polystyrene sulfonate increases the clearance of lithium in a healthy volunteer. A single healthy volunteer received 900 mg lithium for each of three study phases. A sodium polystyrene sulfonate dose of either 0, 20, or 40 grams was administered one half hour after each lithium dose to assess the effect on lithium clearance. Multiple blood samples were obtained for serum lithium concentrations over a 36- to 48-hour time period. Pharmacokinetic parameter estimates were calculated and compared. Sodium polystyrene sulfonate was found to increase the clearance of lithium in a single volunteer. Sodium polystyrene sulfonate may be useful in the treatment of lithium intoxication by increasing the clearance of lithium.

Inositol monophosphatase--a putative target for Li+ in the treatment of bipolar disorder

Attenuation of the phosphatidylinositol (PI) signal transduction pathway as a consequence of inhibition of inositol monophosphatase (IMPase) has been proposed as the mechanism for the efficacy of Li+ in the treatment of bipolar disorder. Nevertheless, Li+ also affects other aspects of PI signal transduction, and it is therefore not clear whether modulation of PI responses by Li+ can be attributed solely to inhibition of IMPase. However, inhibitors of IMPase mimic the effects of Li+ on some aspects of PI cell signalling, thus highlighting the potential of IMPase as a target for the treatment of bipolar disorder. The recent description of the three-dimensional structure of IMPase in conjunction with site-directed mutagenesis and kinetic studies has led to the elucidation of the enzyme mechanism. These structural and mechanistic data should prove useful in the development of novel inhibitors of IMPase that might ultimately prove useful clinically.

In vitro binding of lithium using the cation exchange resin sodium polystyrene sulfonate

Sodium polystyrene sulfonate, a cation exchange resin, should be useful in the treatment of lithium overdosage. This in vitro study was conducted to assess the ability of sodium polystyrene sulfonate to bind lithium, effects of pH on binding, binding efficacy in comparison to charcoal, and affinity for lithium versus potassium. Stock solutions of lithium were added to fixed amounts of sodium polystyrene sulfonate and charcoal. Lithium and potassium concentrations in supernatant were measured by flame photometry. Increasing concentrations of sodium polystyrene sulfonate bound more lithium. Changes in pH had little effect on lithium binding. Lithium is bound to sodium polystyrene sulfonate more readily than to charcoal. Potassium is preferentially bound to sodium polystyrene sulfonate over lithium. Sodium polystyrene sulfonate may provide a useful therapeutic modality in the treatment of lithium overdosage.

Lithium-induced downregulation of aquaporin-2 water channel expression in rat kidney medulla

Lithium, a widely used treatment for bipolar affective disorders, often causes nephrogenic diabetes insipidus. The effect of chronic lithium therapy on the expression of the vasopressin-regulated water channel Aquaporin-2 (AQP2) in rat kidney was examined. Membranes were prepared from inner medulla of one kidney from each rat, while the contralateral one was fixed for immunofluorescence and immunoelectronmicroscopy. Immunoblotting revealed that lithium treatment reduced AQP2 expression dramatically, to 31 +/- 8% after 10 d and to 4 +/- 1% after 25 d, coincident with development of severe polyuria. Immunofluorescence and immunogold quantitation confirmed the lithium-induced decrease in AQP2 expression (from 11.2 +/- 1.0 to 1.1 +/- 0.2 particles/microns 2). The downregulation was only partly reversed by return to lithium-free diet for 1 wk (40 +/- 8% of control). Furthermore, immunoblotting and immunogold quantitation revealed that 2 d of thirsting or 7 d of dDAVP treatment, in the continued presence of lithium, increased AQP2 expression by six- and threefold, respectively, coincident with increased urinary osmolality. Thirsting increased AQP2 immunolabeling mainly of vesicles, whereas dDAVP caused accumulation of AQP2 predominantly in the subapical region and plasma membrane. Thus, lithium causes marked downregulation of AQP2 expression, only partially reversed by cessation of therapy, thirsting or dDAVP treatment, consistent with clinical observations of slow recovery from lithium-induced urinary concentrating defects.