Neurotrophic effects of tianeptine on hippocampal neurons: a proteomic approach

The antidepressant tianeptine reverts synaptic AMPA receptor defects caused by deficiency of CDKL5

Mutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5) gene cause a complex neurological disorder, characterized by infantile seizures, impairment of cognitive and motor skills and autistic features. Loss of Cdkl5 in mice affects dendritic spine maturation and dynamics but the underlying molecular mechanisms are still far from fully understood. Here we show that Cdkl5 deficiency in primary hippocampal neurons leads to deranged expression of the alpha-amino-3-hydroxy-5-methyl-4-iso-xazole propionic acid receptors (AMPA-R). In particular, a dramatic reduction of expression of the GluA2 subunit occurs concomitantly with its hyper-phosphorylation on Serine 880 and increased ubiquitination. Consequently, Cdkl5 silencing skews the composition of membrane-inserted AMPA-Rs towards the GluA2-lacking calcium-permeable form. Such derangement is likely to contribute, at least in part, to the altered synaptic functions and cognitive impairment linked to loss of Cdkl5. Importantly, we find that tianeptine, a cognitive enhancer and antidepressant drug, known to recruit and stabilise AMPA-Rs at the synaptic sites, can normalise the expression of membrane inserted AMPA-Rs as well as the number of PSD-95 clusters, suggesting its therapeutic potential for patients with mutations in CDKL5.

Novel Approaches for the Treatment of Alzheimer's and Parkinson's Disease

Neurodegenerative disorders affect around one billion people worldwide. They can arise from a combination of genomic, epigenomic, metabolic, and environmental factors. Aging is the leading risk factor for most chronic illnesses of old age, including Alzheimer’s and Parkinson’s diseases. A progressive neurodegenerative process and neuroinflammation occur, and no current therapies can prevent, slow, or halt disease progression. To date, no novel disease-modifying therapies have been shown to provide significant benefit for patients who suffer from these devastating disorders. Therefore, early diagnosis and the discovery of new targets and novel therapies are of upmost importance. Neurodegenerative diseases, like in other age-related disorders, the progression of pathology begins many years before the onset of symptoms. Many efforts in this field have led to the conclusion that exits some similar events among these diseases that can explain why the aging brain is so vulnerable to suffer neurodegenerative diseases. This article reviews the current knowledge about these diseases by summarizing the most common features of major neurodegenerative disorders, their causes and consequences, and the proposed novel therapeutic approaches.

Effects of tianeptine on symptoms of fibromyalgia via BDNF signaling in a fibromyalgia animal model

Previous reports have suggested that physical and psychological stresses may trigger fibromyalgia (FM). Stress is an important risk factor in the development of depression and memory impairments. Antidepressants have been used to prevent stress-induced abnormal pain sensation. Among various antidepressants, tianeptine has been reported to be able to prevent neurodegeneration due to chronic stress and reverse decreases in hippocampal volume. To assess the possible effect of tianeptine on FM symptoms, we constructed a FM animal model induced by restraint stress with intermittent cold stress. All mice underwent nociceptive assays using electronic von Frey anesthesiometer and Hargreaves equipment. To assess the relationship between tianeptine and expression levels of brain-derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB), and phosphorylated cAMP response element-binding protein (p-CREB), western blotting and immunohistochemistry analyses were performed. In behavioral analysis, nociception tests showed that pain threshold was significantly decreased in the FM group compared to that in the control group. Western blot and immunohistochemical analyses of medial prefrontal cortex (mPFC) and hippocampus showed downregulation of BDNF and p-CREB proteins in the FM group compared to the control group. However, tianeptine recovered these changes in behavioral tests and protein level. Therefore, this FM animal model might be useful for investigating mechanisms linking BDNF-CREB pathway and pain. Our results suggest that tianeptine might potentially have therapeutic efficacy for FM.

Collapsin Response Mediator Protein-2 (CRMP2) is a Plausible Etiological Factor and Potential Therapeutic Target in Alzheimer's Disease: Comparison and Contrast with Microtubule-Associated Protein Tau

Alzheimer’s disease (AD) has long been viewed as a pathology that must be caused either by aberrant amyloid-β protein precursor (AβPP) processing, dysfunctional tau protein processing, or a combination of these two factors. This is a reasonable assumption because amyloid-β peptide (Aβ) accumulation and tau hyperphosphorylation are the defining histological features in AD, and because AβPP and tau mutations can cause AD in humans or AD-like features in animal models. Nonetheless, other protein players are emerging that one can argue are significant etiological players in subsets of AD and potentially novel, druggable targets. In particular, the microtubule-associated protein CRMP2 (collapsin response mediator protein-2) bears striking analogies to tau and is similarly relevant to AD. Like tau, CRMP2 dynamically regulates microtubule stability; it is acted upon by the same kinases; collects similarly in neurofibrillary tangles (NFTs); and when sequestered in NFTs, complexes with critical synapse-stabilizing factors. Additionally, CRMP2 is becoming recognized as an important adaptor protein involved in vesicle trafficking, amyloidogenesis and autophagy, in ways that tau is not. This review systematically compares the biology of CRMP2 to that of tau in the context of AD and explores the hypothesis that CRMP2 is an etiologically significant protein in AD and participates in pathways that can be rationally engaged for therapeutic benefit.

Comparative proteomic analyses of the parietal lobe from rhesus monkeys fed a high-fat/sugar diet with and without resveratrol supplementation, relative to a healthy diet: Insights into the roles of unhealthy diets and resveratrol on function

A diet consisting of a high intake of saturated fat and refined sugars is characteristic of a Western-diet and has been shown to have a substantial negative effect on human health. Expression proteomics were used to investigate changes to the parietal lobe proteome of rhesus monkeys consuming either a high fat and sugar (HFS) diet, a HFS diet supplemented with resveratrol (HFS+RSV), or a healthy control diet for 2 years. Here we discuss the modifications in the levels of 12 specific proteins involved in various cellular systems including metabolism, neurotransmission, structural integrity, and general cellular signaling following a nutritional intervention. Our results contribute to a better understanding of the mechanisms by which resveratrol functions through the up- or down-regulation of proteins in different cellular sub-systems to affect the overall health of the brain.

The impact of mitochondrial aldehyde dehydrogenase (ALDH2) activation by Alda-1 on the behavioral and biochemical disturbances in animal model of depression

The etiology of depression remains still unclear. Recently, it has been proposed, that mitochondrial dysfunction may be associated with development of mood disorders, such as depression, bipolar disorder and anxiety disorders. Mitochondrial aldehyde dehydrogenase (ALDH2), an enzyme responsible for the detoxification of reactive aldehydes, is considered to exert protective function in mitochondria. We investigated the influence of Alda-1, a small-molecule activator of ALDH2, on depressive- and anxiety-like behaviors in an animal model of depression - the prenatally stressed rats - using behavioral, molecular and proteomic methods. Prolonged Alda-1 administration significantly increased the climbing time, tended to reduce the immobility time and increased the swimming time of the prenatally stressed rats in the forced swim test. Moreover, treatment of prenatally stressed rats with Alda-1 significantly increased number of entries into the open arms of the maze and the time spent therein, as assessed by elevated plus-maze test. Such actions were associated with reduction of plasma 4-HNE-protein content, decrease of TNF-α mRNA and increase of PGC-1α (regulator of mitochondrial biogenesis) mRNA level in the frontal cortex and hippocampus of the prenatally stressed rats as well as with normalization of peripheral immune parameters and significant changes in expression of 6 and 4 proteins related to mitochondrial functions in the frontal cortex and hippocampus, respectively. Collectively, ALDH2 activation by Alda-1 led to a significant attenuation of depressive- and anxiety-like behaviors in the prenatally stressed rats. The pattern of changes suggested mitoprotective effect of Alda-1, however the exact functional consequences of the revealed alterations require further investigation.

The contribution of proteomic studies in humans, animal models, and after antidepressant treatments to investigate the molecular neurobiology of major depression

The neurobiological basis of major depressive disorder (MDD) is only partially understood. The proposed hypotheses postulate dysregulations of monoaminergic and other neurotransmitter pathways, impaired stress responses, insufficient neurogenetic and neurotrophic processes generating maladaptive neuroplasticity, inappropriate inflammatory and metabolic responses. Proteomic approaches can provide useful contributions to the investigation of the molecular neurobiology of MDD due to their open-ended nature. Studies performed in brain regions of MDD patients which had received antidepressant (AD) treatment showed that affected proteins mainly belonged to energy pathways, transport of molecules, signaling, and synaptic transmission. Studies performed in animal models offer the advantage of more controlled experimental conditions at the expense of potential loss in relevance. The design of proteomic investigations included experiments carried out in MDD models, in naive animals treated with ADs, and in animal models subjected to AD treatments. A comparison of results suggested an overlap of several modulated pathways between MDD patients and animal models. Examples include the regulation of energy metabolism, especially oxidative phosphorylation and glycolysis, signal transduction pathways, including calcium-calmodulin kinase II, synaptic proteins, and cytoskeletal proteins. Nevertheless, the paucity of studies performed in human brains requires additional studies to confirm the correspondence.

The predominant protective effect of tianeptine over other antidepressants in models of neuronal apoptosis: the effect blocked by inhibitors of MAPK/ERK1/2 and PI3-K/Akt pathways

Tianeptine (Tian) possesses neuroprotective potential, however, little is known about the effect of this drug in models of neuronal apoptosis. In the present study, we aimed (1) to compare the neuroprotective capacities of some antidepressants (ADs) in the models of staurosporine (St)- and doxorubicin (Dox)-evoked cell death, activating the intracellular and the extracellular apoptotic pathway, respectively; (2) to identify the Tian-modulated steps underlying its neuroprotective action; (3) to test the effect of various ADs against Dox-evoked cell damage in glia cells. Primary neuronal and glia cell cultures and retinoic acid-differentiated human neuroblastoma SH-SY5Y (RA-SH-SY5Y) cells were co-treated with imipramine, fluoxetine, citalopram, reboxetine, mirtazapine or Tian and St or Dox. The data showed the predominant neuroprotective effect of Tian over other tested ADs against St- and Dox-induced cell damage in primary neurons and in RA-SH-SY5Y cells. This effect was shown to be caspase-3-independent but connected with attenuation of DNA fragmentation. Moreover, neuroprotection elicited by Tian was blocked by pharmacological inhibitors of MAPK/ERK1/2 and PI3-K/Akt signaling pathways as well by inhibitor of necroptosis, necrostatin-1. Interestingly, the protective effects of all tested ADs were demonstrated in primary glia cells against the Dox-evoked cell damage. The obtained data suggests the glial cells as a common target for protective action of various ADs whereas in relation to neuronal cells only Tian possesses such properties, at least against St- and Dox-induced cell damage. Moreover, this neuroprotective effect of Tian is caspase-3-independent and engages the regulation of survival pathways (MAPK/ERK1/2 and PI3-K/Akt).

Opening Pandora's jar: a primer on the putative roles of CRMP2 in a panoply of neurodegenerative, sensory and motor neuron, and central disorders

CRMP2, also known as DPYSL2/DRP2, Unc-33, Ulip or TUC2, is a cytosolic phosphoprotein that mediates axon/dendrite specification and axonal growth. Mapping the CRMP2 interactome has revealed previously unappreciated functions subserved by this protein. Together with its canonical roles in neurite growth and retraction and kinesin-dependent axonal transport, it is now known that CRMP2 interacts with numerous binding partners to affect microtubule dynamics; protein endocytosis and vesicular cycling, synaptic assembly, calcium channel regulation and neurotransmitter release. CRMP2 signaling is regulated by post-translational modifications, including glycosylation, oxidation, proteolysis and phosphorylation; the latter being a fulcrum of CRMP2 functions. Here, the putative roles of CRMP2 in a panoply of neurodegenerative, sensory and motor neuron, and central disorders are discussed and evidence is presented for therapeutic strategies targeting CRMP2 functions.

Collapsin response mediator protein-2: an emerging pathologic feature and therapeutic target for neurodisease indications

Collapsin response mediator protein-2 (DPYSL2 or CRMP2) is a multifunctional adaptor protein within the central nervous system. In the developing brain or cell cultures, CRMP2 performs structural and regulatory functions related to cytoskeletal dynamics, vesicle trafficking and synaptic physiology whereas CRMP2 functions in adult brain are still being elucidated. CRMP2 has been associated with several neuropathologic or psychiatric conditions including Alzheimer's disease (AD) and schizophrenia, either at the level of genetic polymorphisms; protein expression; post-translational modifications; or protein/protein interactions. In AD, CRMP2 is phosphorylated by glycogen synthase kinase-3β (GSK3β) and cyclin dependent protein kinase-5 (CDK5), the same kinases that act on tau protein in generating neurofibrillary tangles (NFTs). Phosphorylated CRMP2 collects in NFTs in association with the synaptic structure-regulating SRA1/WAVE1 (specifically Rac1-associated protein-1/WASP family verprolin-homologous protein-1) complex. This phenomenon could plausibly contribute to deficits in neural and synaptic structure that have been well documented in AD. This review discusses the essential biology of CRMP2 in the context of nascent data implicating CRMP2 perturbations as either a correlate of, or plausible contributor to, diverse neuropathologies. A discussion is made of recent findings that the atypical antidepressant tianeptine increases CRMP2 expression, whereas other, neuroactive small molecules including the epilepsy drug lacosamide and the natural brain metabolite lanthionine ketimine appear to bind CRMP2 directly with concomitant affects on neural structure. These findings constitute proofs-of-concept that pharmacological manipulation of CRMP2 is possible and hence, may offer new opportunities for therapy development against certain neurological diseases.