Abstract. In addition to the well-documented mood-stabilizing effects of lithium in manicdepressive illness patients, recent in vitro and in vivo studies in rodents and humans have increasingly implicated that lithium can be used in the treatment of acute brain injuries (e.g., ischemia) and chronic neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, tauopathies, and Huntington's disease). Consistent with this novel view, substantial evidences suggest that depressive illness is not a mere neurochemical disease, but is linked to gray matter atrophy due to the reduced number / size of neurons and glia in brain. Importantly, neurogenesis, that is, birth / maturation of functional new neurons, continues to occur throughout the lifetime in human adult brains (e.g., hippocampus); the neurogenesis is impaired by multiple not-fully defined factors (e.g., aging, chronic stress-induced increase of glucocorticoids, and excitotoxicity), accounting for brain atrophy in patients with depressive illness and neurodegenerative diseases. Chronic treatment of lithium, in agreement with the delayed-onset of mood-stabilizing effects of lithium, up-regulates cell survival molecules (e.g., Bcl-2, cyclic AMP-responsive element binding protein, brain-derived neurotrophic factor, Grp78, Hsp70, and β-catenin), while down-regulating pro-apoptotic activities (e.g., excitotoxicity, p53, Bax, caspase, cytochrome c release, β-amyloid peptide production, and tau hyperphosphorylation), thus preventing or even reversing neuronal cell death and neurogenesis retardation.

Abstract:In cultured bovine adrenal chromaffin cells, our [ 3 H]saxitoxin ([ 3 H]STX) binding, immunoblot, and northern blot analyses specified protein kinase C (PKC) isoform-specific posttranscriptional and posttranslational mechanisms that direct down-regulation of cell surface Na channels. Immunoblot analysis showed that among 11 PKC isoforms, adrenal chromaffin cells contained only conventional (c)PKC-␣, novel (n)PKC-⑀, and atypical (a)PKC-. Treatment of adrenal chromaffin cells with 100 nM 12-O-tetradecanoylphorbol 13-acetate (TPA) or 100 nM phorbol 12,13-dibutyrate (PDBu) caused a rapid (Ͻ15 min) and sustained (Ͼ15 h) translocation of PKC-␣ and -⑀ (but not -) from cytosol to membranes, whereas a biologically inactive 4␣-TPA had no effect. Thymeleatoxin (TMX), an activator of cPKC, produced similar membrane association of only PKC-␣ at 100 nM, with the potency of TMX being comparable with those of TPA and PDBu. Treatment with either 100 nM TPA or 100 nM TMX reduced cell surface [ 3 H]STX binding to a comparable extent at 3, 6, and 12 h, whereas TPA lowered the binding to a greater extent than TMX at 15, 18, and 24 h; at 15 h, Gö 6976, a specific inhibitor of cPKC, completely blocked TMX-induced decrease of [ 3 H]STX binding while preventing by merely 57% TPA-induced decrease of [ 3 H]STX binding. Treatment with 100 nM TPA lowered the Na channel ␣-subunit mRNA level between 3 and 12 h, with its maximum 52% fall at 6 h, and it was accompanied by a subsequent 61% rise of the ␤ 1 -subunit mRNA level at 24 h. Gö 6976 failed to prevent TPA-induced reduction of the ␣-subunit mRNA level; TMX did not change the ␣-and ␤ 1 -subunit mRNA levels throughout the 24-h treatment. Brefeldin A, an inhibitor of vesicular exit from the trans-Golgi network, augmented TPA-and TMX-induced decrease of [ 3 H]STX binding at 1 and 3 h. Our previous and present studies suggest that PKC down-regulates cell surface Na channels without altering the allosteric gating of Na channels via PKC isoform-specific mechanisms; cPKC-␣ promotes Na channel internalization, whereas nPKC-⑀ decreases the ␣-subunit mRNA level by shortening the half-life of ␣-subunit mRNA without changing its gene transcription.

Abstract. Long after the pioneering studies documenting the existence of insulin (year 1967) and insulin receptor (year 1978) in brain, the last decade has witnessed extraordinary progress in the understanding of brain region-specific multiple roles of insulin receptor signalings in health and disease. In the hypothalamus, insulin regulates food intake, body weight, peripheral fat deposition, hepatic gluconeogenesis, reproductive endocrine axis, and compensatory secretion of counter-regulatory hormones to hypoglycemia. In the hippocampus, insulin promotes learning and memory, independent of the glucoregulatory effect of insulin. Defective insulin receptor signalings are associated with the dementia in normal aging and patients with age-related neurodegenerative diseases (e.g., Alzheimer's disease); the cognitive impairment can be reversed with systemic administration of insulin in the euglycemic condition. Intranasal administration of insulin enhances memory and mood and decreases body weight in healthy humans, without causing hypoglycemia. In the hypothalamus, insulin-induced activation of the phosphoinositide 3-kinase pathway followed by opening of ATP-sensitive K + channel has been shown to be related to multiple effects of insulin. However, the precise molecular mechanisms of insulin's pleiotropic effects still remain obscure. More importantly, much remains unknown about the quality control mechanisms ensuring correct conformational maturation of the insulin receptor, and the cellular mechanisms regulating density of cell surface functional insulin receptors.

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Treatment of cultured bovine adrenal chromaffin cells with a therapeutic concentration (0.6 mM) of valproic acid (VPA) for >24 h caused a time-dependent (t 112 = 74 h) increase in [ 3H]saxitoxinbinding up to 1.4fold without altering the KD value; it was prevented by the simultaneous treatment with cycloheximide (an inhibitor of protein synthesis). VPA also raised Na~channel aand /3 1-subunit mRNA levels 1.4-and 1.7-fold at 24 h, and 1 .6-and 1.8-fold at 72 h, respectively. Chronic (but not acute) exposure to VPA enhanced