1. Lithium up-regulates the cytoprotective protein Bcl-2 in the CNS in vivo: a role for neurotrophic and neuroprotective effects in manic depressive illness
H K Manji, G J Moore, G Chen J Clin Psychiatry. 2000;61 Suppl 9:82-96.
Although mood disorders have traditionally been conceptualized as "neurochemical disorders," considerable literature from a variety of sources demonstrates significant reductions in regional central nervous system (CNS) volume and cell numbers (both neurons and glia) in persons with mood disorders. It is noteworthy that recent advances in cellular and molecular biology have resulted in the identification of 2 novel, hitherto completely unexpected targets of lithium's actions, discoveries that may have a major impact on the future use of this unique cation in biology and medicine. Chronic lithium treatment has been demonstrated to markedly increase the levels of the major neuroprotective protein bc1-2 in rat frontal cortex, hippocampus, and striatum. Similar lithium-induced increases in bc1-2 are also observed in cells of human neuronal origin and are observed in rat frontal cortex at lithium levels as low as approximately 0.3 mM. Bc1-2 is widely regarded as a major neuroprotective protein, and genetic strategies that increase bc1-2 levels have demonstrated not only robust protection of neurons against diverse insults, but have also demonstrated an increase in the regeneration of mammalian CNS axons. Lithium has also been demonstrated to inhibit glycogen synthase kinase 3beta (GSK-3beta), an enzyme known to regulate the levels of phosphorylated tau and beta-catenin (both of which may play a role in the neurodegeneration observed in certain forms of Alzheimer's disease). Consistent with the increases in bc1-2 levels and inhibition of GSK-3beta, lithium has been demonstrated to exert robust protective effects against diverse insults both in vitro and in vivo. These findings suggest that lithium may exert some of its long-term beneficial effects in the treatment of mood disorders via underappreciated neurotrophic and neuroprotective effects. To date, lithium remains the only medication demonstrated to markedly increase bc1-2 levels in several brain areas; in the absence of other adequate treatments, an investigation of the potential efficacy of lithium in the long-term treatment of several neurodegenerative disorders is warranted. Additionally, we suggest that a reconceptualization of the use of lithium in mood disorders may be warranted-namely, that the use of lithium as a neurotrophic/neuroprotective agent should be considered in the long-term treatment of mood disorders, irrespective of the "primary" treatment modality being used for the condition.
2. [Neurobiology of lithium]
G Chazot, I V Gogoleva, O A Gromova, N M Ullubiev, A A Nikonov Zh Nevrol Psikhiatr Im S S Korsakova. 2008;Suppl 22:49-55.
In addition to well-documented mood-stabilizing effects, lithium can be used in the treatment of acute brain injuries (ischemia) and chronic (neurodegenerative) diseases. Recent in vitro and in vivo studies reveal that the long-term treatment with lithium up-regulates cell survival molecules (Bcl-2, cAMP-responsive element binding protein, GRP 78, brain-derived neurotrophic factor, Hsp70) and down-regulates pro-apoptotic activities (e.g., excitotoxicity, p53, Bax, caspase, cytochrome C release, beta-amyloid peptide production and tau hyperphosphorylation) thus preventing or even reversing the neuronal cell death and neurogenesis retardation.
3. Neuroprotective and neurotrophic actions of the mood stabilizer lithium: can it be used to treat neurodegenerative diseases?
De-Maw Chuang Crit Rev Neurobiol. 2004;16(1-2):83-90. doi: 10.1615/critrevneurobiol.v16.i12.90.
The mood stabilizing drug lithium has emerged as a robust neuroprotective agent in preventing apoptosis of neurons. Long-term treatment with lithium effectively protects primary cultures of rat brain neurons from glutamate-induced, NMDA receptor-mediated excitotoxicity. This neuroprotection is accompanied by an inhibition of NMDA-receptor-mediated calcium influx, upregulation of anti-apoptotic Bcl-2, downregulation of pro-apoptotic p53 and Bax, and activation of cell survival factors. Lithium treatment antagonizes glutamate-induced activation of c-Jun-N-terminal kinase (JNK), p38 kinase, and AP-1 binding, which has a major role in cytotoxicity, and suppresses glutamate-induced loss of phosphorylated cAMP responsive element binding protein (CREB). Lithium also induces the expression of brain-derived neurotrophic factor (BDNF) and subsequent activation TrkB, the receptor for BDNF, in cortical neurons. The activation of BDNF/TrkB signaling is essential for the neuroprotective effects of this drug. In addition, lithium stimulates the proliferation of neuroblasts in primary cultures of CNS neurons. Lithium also shows neuroprotective effects in rodent models of diseases. In a rat model of stroke, post-insult treatment with lithium or valproate, another mood stabilizer, at therapeutic doses markedly reduces brain infarction and neurological deficits. This neuroprotection is associated with suppression of caspase-3 activation and induction of chaperone proteins such as heat shock protein 70. In a rat model of Huntington's disease (HD) in which an excitotoxin is unilaterally infused into the striatum, both long- and short-term pretreatment with lithium reduces DNA damage, caspase-3 activation, and loss of striatal neurons. This neuroprotection is associated with upregulation of Bcl-2. Lithium also induces cell proliferation near the injury site with a concomitant loss of proliferating cells in the subventricular zone. Some of these proliferating cells display neuronal or astroglial phenotypes. These results corroborate our findings obtained in primary neuronal cultures. The neuroprotective and neurotrophic actions of lithium have profound clinical implications. In addition to its present use in bipolar patients, lithium could be used to treat acute brain injuries such as stroke and chronic progressive neurodegenerative diseases.
