Analysis of gene expression with cDNA microarrays in rat brain after 7 and 42 days of oral lithium administration
Introduction
Bipolar disorder (BD) is a common psychiatric condition characterized by cycling periods of mania and severe depression. The established efficacy of lithium in the treatment and prophylaxis of BD is well known 7, 13. Many cellular effects of lithium have been described, although the basis of its therapeutic action is not agreed upon [24]. Several signal transduction pathways have been suggested to contribute to lithium’s action, in particular, guanine-nucleotide-binding proteins [28], adenylyl cyclase [10], protein kinase C isoenzymes [39], phosphoinositide cycle 1, 15, and the balance of neurotransmitter signaling [23]. Studies also suggest that lithium is neuroprotective, as it increases Bcl-2 and decreases p53 and Bax expression 9, 30. Additionally, we reported that therapeutically relevant brain concentrations of lithium (about 0.7 mM) [20] reduced, by 80%, the turnover of arachidonic acid within brain phospholipids of awake rats [8]. The mRNA and protein levels of an AA-selective cytosolic PLA2 (cPLA2, type IV) also were reduced, consistent with reduced AA turnover 22, 33.
Lithium’s action as a mood stabilizer generally requires weeks to develop 20, 29, suggesting alterations at the genomic level 17, 31. However, changes occurring over such a long time frame could also result from translational and post-translational modifications, or as a consequence of protein/RNA half-life modification.
Gene expression monitoring with cDNA arrays 11, 14 provides a simple way to explore the biochemical effects of lithium and therefore elucidate its potential therapeutic and negative side effects. We used this approach to determine the effect of feeding lithium chloride (LiCl) [8] to rats for periods of 7 days (subacute) and 42 days (chronic) on brain expression of 4132 genes. We report that the changes induced by subacute lithium do not overlap with the more chronic alterations in gene expression. The latter are more likely related to lithium’s mood-stabilizing effect, considering the latency in onset of therapeutic action, which is not immediately reversed upon discontinuation 17, 18. These findings have significant implications for understanding mechanisms of BD and identifying targets for treating it.
Section snippets
Lithium administration
The protocol conformed to the Guideline for the Care and Use of Laboratory Animals (NIH Publication No. 80-23). Adult male Fischer-344 rats (200–250 g; Charles River Laboratories, Wilmington, MA, USA) were acclimatized for 2 weeks, and then fed ad lib Purina chow (containing 1.70 g LiCl per kg chow for 7 days or 1.70 g LiCl per kg chow for 4 weeks followed by a diet containing 2.55 g LiCl per kg chow for 2 weeks, or LiCl-free chow [controls]) [8]. To prevent hyponatremia, water and NaCl
Results
Using atomic absorption spectrometry, lithium was not detected in plasma or brain of control rats fed a LiCl-free diet, whereas the lithium concentration (mean ± SEM, n = 4) was 0.39 ± 0.01 mM in brain and 0.56 ± 0.02 mM in plasma of rats fed LiCl for 7 days, and 0.79 ± 0.07 mM in brain and 0.74 ± 0.03 mM in plasma of rats fed LiCl for 42 days. The latter concentrations are therapeutically relevant [3]. As shown in Fig. 1, the brain lithium concentration became equivalent to the plasma
Discussion
In this study we used a high-density filter-based cDNA microarray, representing over 4000 known human genes, to determine the effects of subacute (7 days) and chronic (42 days) oral lithium administration on rat brain gene expression, compared with control brain. We identified many genes that were downregulated by a factor of at least 2 by chronic but not by subacute lithium, whereas no gene was upregulated by this factor at either time point. The expression of 11 genes was downregulated after
Acknowledgements
We thank Dr. Barry Horwitz for statistical help.
References (40)
- et al.
Increased anterior cingulate and caudate activity in bipolar mania
Biol. Psychiatry
(2000) - et al.
Lithium decreases turnover of arachidonate in several phospholipids
Neurosci. Lett.
(1996) - et al.
Long term lithium treatment suppresses p53 and Bax expression but increases Bcl-2 expression. A prominent role in neuroprotection against excitotoxicity
J. Biol. Chem.
(1999) - et al.
Clinical uses of lithium salts
Brain Res. Bull.
(1983) Powerful tools for genetic analysis come of age
Trends Biotechnol.
(1999)- et al.
The effects of lithium ion and other agents on the activity of myo-inositol-1-phosphatase from bovine brain
J. Biol. Chem.
(1980) - et al.
Differential gene expression of livers from ApoE deficient mice
Life Sci.
(2000) - et al.
AP-1 and NF-κB stimulated by carbachol in human neuroblastoma SH-SY5Y cells are differently sensitive to inhibition by lithium
Mol. Brain Res.
(1997) - et al.
Lithium and brain signal transduction systems
Biochem. Pharmacol.
(1994) - et al.
11C-glucose metabolism in manic and depressed patients
Psychiatry Res.
(1987)
Lithium decreases Gs, Gi−1 and Gi−2 alpha-subunit mRNA levels in rat cortex
Eur. J. Pharmacol.
A novel mammalian lithium-sensitive enzyme with a dual enzymatic activity, 3′-phosphoadenosine 5′-phosphate phosphatase and inositol-polyphosphate 1-phosphatase
J. Biol. Chem.
Gene expression profiling in human peripheral blood mononuclear cells using high-density filter-based cDNA microarrays
J. Immunol. Methods
Reduced brain inositol in lithium-treated rats
Nat. New Biol.
Comparative genome organization of vertebrates. The First International Workshop on Comparative Genome Organization
Mamm. Genome
Pharmacological treatment of bipolar disorder throughout the life cycle
Cerebral metabolic rates for glucose in mood disorders. Studies with positron emission tomography and fluorodeoxyglucose F 18
Arch. Gen. Psychiatry
Inositol trisphosphate and diacylglycerol as second messengers
Biochem. J.
Lithium salts in the treatment of psychotic excitement
Med. J. Aust.
Chronic lithium regulates the expression of adenylate cyclase and Gi-protein alpha subunit in rat cerebral cortex
Proc. Natl. Acad. Sci. USA
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Current address: NeuroLogic, Inc., Functional Genomics, 15010 Broschart Road, Rockville, MD 20850, USA.