Filippo Caraci

β-Amyloid Monomers Are Neuroprotective

The 42-aa-long β-amyloid protein—Aβ1-42—is thought to play a central role in the pathogenesis of Alzheimers disease (AD) (Walsh and Selkoe, 2007). Data from AD brain (Shankar et al., 2008), transgenic APP (amyloid precursor protein)-overexpressing mice (Lesné et al., 2006), and neuronal cultures treated with synthetic Aβ peptides (Lambert et al., 1998) indicate that self-association of Aβ1-42 monomers into soluble oligomers is required for neurotoxicity. The function of monomeric Aβ1-42 is unknown. The evidence that Aβ1-42 is present in the brain and CSF of normal individuals suggests that the peptide is physiologically active (Shoji, 2002). Here we show that synthetic Aβ1-42 monomers support the survival of developing neurons under conditions of trophic deprivation and protect mature neurons against excitotoxic death, a process that contributes to the overall neurodegeneration associated with AD. The neuroprotective action of Aβ1-42 monomers was mediated by the activation of the PI-3-K (phosphatidylinositol-3-kinase) pathway, and involved the stimulation of IGF-1 (insulin-like growth factor-1) receptors and/or other receptors of the insulin superfamily. Interestingly, monomers of Aβ1-42 carrying the Arctic mutation (E22G) associated with familiar AD (Nilsberth et al., 2001) were not neuroprotective. We suggest that pathological aggregation of Aβ1-42 may also cause neurodegeneration by depriving neurons of the protective activity of Aβ1-42 monomers. This “loss-of-function” hypothesis of neuronal death should be taken into consideration when designing therapies aimed at reducing Aβ burden.

Role of Omega-3 Fatty Acids in the Treatment of Depressive Disorders: A Comprehensive Meta-Analysis of Randomized Clinical Trials

Background Despite omega-3 polyunsaturated fatty acids (PUFA) supplementation in depressed patients have been suggested to improve depressive symptomatology, previous findings are not univocal. Objectives To conduct an updated meta-analysis of randomized controlled trials (RCTs) of omega-3 PUFA treatment of depressive disorders, taking into account the clinical differences among patients included in the studies. Methods A search on MEDLINE, EMBASE, PsycInfo, and the Cochrane Database of RCTs using omega-3 PUFA on patients with depressive symptoms published up to August 2013 was performed. Standardized mean difference in clinical measure of depression severity was primary outcome. Type of omega-3 used (particularly eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) and omega-3 as mono- or adjuvant therapy was also examined. Meta-regression analyses assessed the effects of study size, baseline depression severity, trial duration, dose of omega-3, and age of patients. Results Meta-analysis of 11 and 8 trials conducted respectively on patients with a DSM-defined diagnosis of major depressive disorder (MDD) and patients with depressive symptomatology but no diagnosis of MDD demonstrated significant clinical benefit of omega-3 PUFA treatment compared to placebo (standardized difference in random-effects model 0.56 SD [95% CI: 0.20, 0.92] and 0.22 SD [95% CI: 0.01, 0.43], respectively; pooled analysis was 0.38 SD [95% CI: 0.18, 0.59]). Use of mainly EPA within the preparation, rather than DHA, influenced final clinical efficacy. Significant clinical efficacy had the use of omega-3 PUFA as adjuvant rather than mono-therapy. No relation between efficacy and study size, baseline depression severity, trial duration, age of patients, and study quality was found. Omega-3 PUFA resulted effective in RCTs on patients with bipolar disorder, whereas no evidence was found for those exploring their efficacy on depressive symptoms in young populations, perinatal depression, primary disease other than depression and healthy subjects. Conclusions The use of omega-3 PUFA is effective in patients with diagnosis of MDD and on depressive patients without diagnosis of MDD.

Depression and Alzheimer's disease: Neurobiological links and common pharmacological targets

Depression is one of the most prevalent and life-threatening forms of mental illnesses, whereas Alzheimers disease is a neurodegenerative disorder that affects more than 37 million people worldwide. Recent evidence suggests a strong relationship between depression and Alzheimers disease. A lifetime history of major depression has been considered as a risk factor for later development of Alzheimers disease. The presence of depressive symptoms can affect the conversion of mild cognitive impairment into Alzheimers disease. Neuritic plaques and neurofibrillary tangles, the two major hallmarks of Alzheimers disease brain, are more pronounced in the brains of Alzheimers disease patients with comorbid depression as compared with Alzheimers disease patients without depression. On the other hand, neurodegenerative phenomena have been observed in different brain regions of patients with a history of depression. Recent evidence suggests that molecular mechanisms and cascades that underlie the pathogenesis of major depression, such as chronic inflammation and hyperactivation of hypothalamic-pituitary-adrenal (HPA) axis, are also involved in the pathogenesis of Alzheimers disease. In particular, a specific impairment in the signaling of some neurotrophins such as transforming-growth-factor beta1 (TGF-beta1) and brain-derived neurotrophic factor (BDNF) has been observed both in depression and Alzheimers disease. In the present review we will examine the evidence on the common molecular pathways between depression and Alzheimers disease and we will discuss these pathways as new pharmacological targets for the treatment of both major depression and Alzheimers disease.

TGF-β1 targets the GSK-3β/β-catenin pathway via ERK activation in the transition of human lung fibroblasts into myofibroblasts

Transforming growth factor-beta1 (TGF-beta1) is known to induce the transition of human lung fibroblasts to myofibroblasts, a primary event in the pathogenesis of idiopathic pulmonary fibrosis. The molecular pathways involved in myofibroblast transformation are only partially identified. We found that a 24-h treatment with TGF-beta1 (10 ng/ml) induced alpha-smooth actin (SMA) expression and collagen production in human lung fibroblasts. These effects were abrogated by PD98059, a specific inhibitor of the mitogen-activated protein kinase (MAPK) pathway. TGF-beta1 treatment activated the MAPK pathway, as shown by an increased phosphorylation of extracellular-regulated kinases (ERK)1/2 after 30 min of exposure. TGF-beta1 also increased the expression of the Ser-9-phosphorylated inactive form of glycogen synthase kinase-3beta (GSK-3beta), an effect that was largely attenuated by PD98059. A nuclear translocation of beta-catenin in human lung fibroblasts was observed 2h after TGF-beta1 addition both by confocal microscopy and nuclear protein analysis. At this time, TGF-beta1 also increased the total levels of beta-catenin, an effect that was prevented by PD98059. Similarly to TGF-beta1, the GSK-3beta inhibitor lithium chloride (10mM), increased the total levels of beta-catenin and promoted alpha-SMA expression and collagen production. This study demonstrates that TGF-beta1 induces alpha-SMA expression and collagen production in human lung fibroblasts via ERK1/2 activation, GSK-3beta inhibition and nuclear beta-catenin translocation. The evidence that the silencing of beta-catenin by siRNAs was able to prevent the induction of alpha-SMA expression in TGF-beta1-treated fibroblasts further supports the hypothesis of a contribution of the GSK-3beta/beta-catenin pathway in the pathogenesis of idiopathic pulmonary fibrosis.

The Wnt pathway, cell-cycle activation and β-amyloid: novel therapeutic strategies in Alzheimer's disease?

Beta-amyloid protein (betaAP) is thought to cause neuronal loss in Alzheimers disease (AD). Applied to neurons in culture, betaAP induces neuronal death and hyperphosphorylation of tau protein, which forms neurofibrillary tangles (NFTs) in AD brains. Neurons also undergo rapid apoptotic death following reactivation of a mitotic cycle. However, the molecular events that determine the fate of neurons challenged with betaAP (apoptotic death, formation of NFTs and survival) are unclear. We discuss a scenario for the pathogenesis of AD. This links betaAP-induced changes to the Wnt signaling pathway that promotes proliferation of progenitor cells and directs cells into a neuronal phenotype during brain development. We propose that betaAP-mediated facilitation of mitogenic Wnt signaling activates unscheduled mitosis in differentiated neurons. Furthermore, late downregulation of Wnt signaling by betaAP might lead to NFT formation. We propose that drugs that both inhibit the cell cycle and rescue Wnt activity could provide novel AD therapeutics.

Methionine synthase (MTR) 2756 (A --> G) polymorphism, double heterozygosity methionine synthase 2756 AG/methionine synthase reductase (MTRR) 66 AG, and elevated homocysteinemia are three risk factors for having a child with Down syndrome.

Contradictory findings have been recently published on the evaluation of genetic polymorphisms of methylenetetrahydrofolate reductase (MTHFR 677 C→T) and methionine synthase reductase (MTRR 66 A→G) as risk factors for having a child with Down syndrome (DS); however, the influence of polymorphisms of methionine synthase (MTR 2756 A→G) and of MTHFR 1298 A→C has never been evaluated. In this study, the risk of being a DS case or having a DS child (case mother) was studied by multiple logistic regression analysis of the independent and combined genotypes and of plasma homocysteine, folates, and vitamin B12 in 92 DS cases and 140 control subjects as well as in 63 case mothers and 72 age‐matched control mothers from Sicily. (The MTHFR 677 T allele frequency was not different in DS cases and case mothers, compared to the respective control groups). After adjustment for age, total homocysteine (t‐Hcys) and MTR 2756 AG/GG genotype were significant risk factors for having a DS child, with odds ratio (OR) of 6.7 (95% CI: 1.4–32.0, P = 0.016) and of 3.5 (95% CI: 1.2–10.9, P = 0.028), respectively. By comparison, MTR 2756 AG/GG genotype increased significantly the risk of being a DS case, with an OR of 3.8 (95% CI: 1.4–10.5, P = 0.009). The double heterozygosity MTR 2756 AG/MTRR 66 AG was the single combined genotype that was a significant risk factor for having a DS child, with an OR estimated at 5.0 (95% CI: 1.1–24.1), after adjustment for t‐Hcys. In conclusion, our results provide evidences that homocysteine and MTR genetic polymorphism are two potent risk factors for mothers to have a DS child in Sicily.

Neuroprotective effects of sigma-1 receptor agonists against beta-amyloid-induced toxicity.

Prolonged exposure of cultured cortical neurons to the residue 25–35 fragment of &bgr;-amyloid protein, in the presence of dizocilpine, an antagonist of the N-methyl-D-aspartate receptor, and of 6,7-dinitroquinoxaline-2,3-dione, an antagonist of &agr;-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors, resulted in the expression of the proapoptotic protein Bax and neuronal death. Beta-amyloid protein(25–35)-induced neuronal death was substantially attenuated by the σ1 receptor agonist 2-(4-morpholinethyl)1-phenylcyclohexanecarboxylate. The neuroprotective action of 2-(4-morpholinethyl)1-phenylcyclohexanecarboxylate was mimicked by the σ1 ligand methyl (1S,2R)-2-[1-adamantyl(methyl)amino]methyl-1-phenylcyclopropanecarboxylate and was antagonized by the σ1 receptor antagonist N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)-phenyl]-ethylamine monohydrochloride. These results suggest that σ1 receptor agonists might function as neuroprotectant agents in Alzheimers disease.

Efficacy and tolerability of Hypericum extract for the treatment of mild to moderate depression.

Depression is a common condition in the community with a significant impact on affected individuals, their relatives and society. Many patients with depression do not seek treatment and are often concerned about the possible adverse effects of antidepressant drugs. Extract of Hypericum perforatum (St. Johns wort) has long been recognized as a treatment for depression. Several published trials and meta-analyses have demonstrated the efficacy and tolerability of Hypericum extract for mild to moderate depression. Recent comparative trials of Hypericum extract and other antidepressants, including selective serotonin reuptake inhibitors (SSRIs), provide support for Hypericum extract efficacy. However, since the constituents of Hypericum extract differ between the individual manufacturers, the efficacy cannot be extrapolated from one extract to another. In this review, WS 5572, LI 160, WS 5570 and ZE 117 Hypericum extracts have been shown to be significantly more effective than placebo with at least similar efficacy and better tolerability compared to standard antidepressant drugs.

Clinically Significant Drug Interactions with Newer Antidepressants

After the introduction of selective serotonin reuptake inhibitors (SSRIs), other newer antidepressants with different mechanisms of action have been introduced in clinical practice. Because antidepressants are commonly prescribed in combination with other medications used to treat co-morbid psychiatric or somatic disorders, they are likely to be involved in clinically significant drug interactions. This review examines the drug interaction profiles of the following newer antidepressants: escitalopram, venlafaxine, desvenlafaxine, duloxetine, milnacipran, mirtazapine, reboxetine, bupropion, agomelatine and vilazodone.In general, by virtue of a more selective mechanism of action and receptor profile, newer antidepressants carry a relatively low risk for pharmacodynamic drug interactions, at least as compared with first-generation antidepressants, i.e. monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants (TCAs). On the other hand, they are susceptible to pharmacokinetic drug interactions. All new antidepressants are extensively metabolized in the liver by cytochrome P450 (CYP) isoenzymes, and therefore may be the target of metabolically based drug interactions. Concomitant administration of inhibitors or inducers of the CYP isoenzymes involved in the biotransformation of specific antidepressants may cause changes in their plasma concentrations. However, due to their relatively wide margin of safety, the consequences of such kinetic modifications are usually not clinically relevant. Conversely, some newer antidepressants may cause pharmacokinetic interactions through their ability to inhibit specific CYPs. With regard to this, duloxetine and bupropion are moderate inhibitors of CYP2D6. Therefore, potentially harmful drug interactions may occur when they are coadministered with substrates of these isoforms, especially compounds with a narrow therapeutic index. The other new antidepressants are only weak inhibitors or are not inhibitors of CYP isoforms at usual therapeutic concentrations and are not expected to affect the disposition of concomitantly administered medications.Although drug interactions with newer antidepressants are potentially, but rarely, clinically significant, the use of antidepressants with a more favourable drug interaction profile is advisable. Knowledge of the interaction potential of individual antidepressants is essential for safe prescribing and may help clinicians to predict and eventually avoid certain drug combinations.

Homocysteine and methylenetetrahydrofolate reductase polymorphism in Alzheimer's disease.

Homocysteine metabolism is influenced by genetic polymorphisms of the methylenetetrahydrofolate reductase (MTHFR 677 C→T and 1298 A→C) and transcobalamin genes (TCN1 776 C→G ). We evaluated the association of homocysteine with Alzheimers disease (AD) and the influence of related polymorphisms and APOE, in 180 cases and 181 controls from southern Italy. Homocysteine (upper tercile) was associated with AD risk, with an odds ratio of 2.8 (95% confidence interval (CI) 1.54–5.22, p=0.0008), which was increased 2.2- and 2.0-fold by MTHFR 677 T (odds ratio 6.28, 95% CI 2.88–16.20, p < 0.0001) and APOE &egr;4 (odds ratio: 5.60, 95% CI 1.12–28.05, p=0.0361), respectively. In conclusion, association of homocysteine with AD was aggravated by MTHFR 677 T and APOE &egr;4 alleles.