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Inositol-related gene knockouts mimic lithium's effect on mitochondrial function.

ABSTRACT: The inositol-depletion hypothesis proposes that lithium attenuates phosphatidylinositol signaling. Knockout (KO) mice of two genes (IMPA1 or Slc5a3), each encoding for a protein related to inositol metabolism, were studied in comparison with lithium-treated mice. Since we previously demonstrated that these KO mice exhibit a lithium-like neurochemical and behavioral phenotype, here we searched for pathways that may mediate lithium's/the KO effects. We performed a DNA-microarray study searching for pathways affected both by chronic lithium treatment and by the KO of each of the genes. The data were analyzed using three different bioinformatics approaches. We found upregulation of mitochondria-related genes in frontal cortex of lithium-treated, IMPA1 and Slc5a3 KO mice. Three out of seven genes differentially expressed in all three models, Cox5a, Ndufs7, and Ndufab, all members of the mitochondrial electron transfer chain, have previously been associated with bipolar disorder and/or lithium treatment. Upregulation of the expression of these genes was verified by real-time PCR. To further support the link between mitochondrial function and lithium's effect on behavior, we determined the capacity of chronic low-dose rotenone, a mitochondrial respiratory chain complex I inhibitor, to alter lithium-induced behavior as measured by the forced-swim and the amphetamine-induced hyperlocomotion paradigms. Rontenone treatment counteracted lithium's effect on behavior, supporting the proposition suggested by the bioinformatics analysis for a mitochondrial function involvement in behavioral effects of lithium mediated by inositol metabolism alterations.The results provide support for the notion that mitochondrial dysfunction is linked to bipolar disorder and can be ameliorated by lithium. The phenotypic similarities between lithium-treated wild-type mice and the two KO models suggest that lithium may affect behavior by altering inositol metabolism.

SUBMITTER: Toker L

PROVIDER: S-EPMC3870788 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Lithium is the prototype mood stabilizer but its mechanism is still unresolved. Two hypotheses dominate-the consequences of lithium's inhibition of inositol monophosphatase at therapeutically relevant concentrations (the 'inositol depletion' hypothesis), and of glycogen-synthase kinase-3. To further elaborate the inositol depletion hypothesis that did not decisively determine whether inositol depletion per se, or phosphoinositols accumulation induces the beneficial effects, we utilized knockout mice of either of two inositol metabolism-related genes-IMPA1 or SMIT1, both mimic several lithium's behavioral and biochemical effects. We assessed in vivo, under non-agonist-stimulated conditions, 3H-inositol incorporation into brain phosphoinositols and phosphoinositides in wild-type, lithium-treated, IMPA1 and SMIT1 knockout mice. Lithium treatment increased frontal cortex and hippocampal phosphoinositols labeling by several fold, but decreased phosphoinositides labeling in the frontal cortex of the wild-type mice of the IMPA1 colony strain by ~50%. Inositol metabolites were differently affected by IMPA1 and SMIT1 knockout. Inositoltrisphosphate administered intracerebroventricularly affected bipolar-related behaviors and autophagy markers in a lithium-like manner. Namely, IP3 but not IP1 reduced the immobility time of wild-type mice in the forced swim test model of antidepressant action by 30%, an effect that was reversed by an antagonist of all three IP3 receptors; amphetamine-induced hyperlocomotion of wild-type mice (distance traveled) was 35% reduced by IP3 administration; IP3 administration increased hippocampal messenger RNA levels of Beclin-1 (required for autophagy execution) and hippocampal and frontal cortex protein levels ratio of Beclin-1/p62 by about threefold (p62 is degraded by autophagy). To conclude, lithium affects the phosphatidylinositol signaling system in two ways: depleting inositol, consequently decreasing phosphoinositides; elevating inositol monophosphate levels followed by phosphoinositols accumulation. Each or both may mediate lithium-induced behavior.

Project description:BackgroundLithium is considered the gold standard treatment for bipolar disorder (BD). Current clinical guidelines and scientific evidence support its use as a first-line treatment in BD. However, over the last two decades, there has been a downward tendency in lithium's use in several developed countries. Based on a nationwide survey, this study's objective is to analyze in a large sample of psychiatrists relevant issues of the use of lithium salts in BD.MethodsData were collected through an anonymous survey sent by email among 500 psychiatrists who belong to a National Society of Psychiatry (Spanish Society of Biological Psychiatry). The survey is a self-administered questionnaire consisting of 21 items on the most key aspects of lithium's use (indication, dosage, monitoring, and information for patients).Results212 psychiatrists completed the survey. 70% of psychiatrists prescribe lithium to more than 50% of patients diagnosed with BD. Adverse effects are the main reason not to use lithium salts. Over 75% of the participants consider lithium salts the treatment of choice for the maintenance phase of BD, both in women and men. Most of the participants (> 50%) start lithium after the first affective episode, use conservative plasma concentrations (0.6-0.8 mmol/L), and generally prescribe it twice a day. 57% of psychiatrists who treat patients under 18 do not use lithium in this population. About 70% of the survey respondents use official protocols to inform and monitor patients on lithium treatment.ConclusionsFrom the results of the present study, it can be concluded that the use of lithium in Spain is in line with the recommendations of the main international clinical guidelines and current scientific literature. The first reason not to prescribe lithium in our country is the perception of its adverse effects and not the aspects related to its practical use or its effectiveness. Considering that BD is a chronic disease with a typical onset in adolescence, the low rate of prescription of lithium salts in patients under 18 must be thoroughly studied.

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Inositol-related gene knockouts mimic lithium's effect on mitochondrial function.

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