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Transl Psychiatry. 2016 Dec 6;6(12):e968. doi: 10.1038/tp.2016.217.

IP3 accumulation and/or inositol depletion: two downstream lithium's effects that may mediate its behavioral and cellular changes.

Sade Y1,2,3,4, Toker L5, Kara NZ1,2,3,6, Einat H6, Rapoport S7, Moechars D8, Berry GT9, Bersudsky Y2,3,4, Agam G1,2,3,4.

Author information

1
Department of Clinical Biochemistry and Pharmacology, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
2
Psychiatry Research Unit, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
3
Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
4
Mental Health Center, Beer-Sheva, Israel.
5
Department of Psychiatry and Centre for High-Throughput Biology, University of British Columbia Vancouver, BC, Canada.
6
School of Behavioral Sciences, Tel Aviv-Yaffo Academic College, Tel Aviv, Israel.
7
Brain Physiology and Metabolism Section, Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA.
8
Johnson & Johnson Pharmaceutical Research and Development, Beerse, Belgium.
9
Metabolism Program Division of Genetics, Children's Hospital Boston, Harvard Medical School, Boston, MA, USA.

Abstract

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.

PMID:
27922641
PMCID:
PMC5315558
DOI:
10.1038/tp.2016.217
[Indexed for MEDLINE]
Free PMC Article

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