Перспективные методы лечения депрессий

Long-term stress harms cells in the brain and body. Stressful experiences are believed to be closely associated with the development of psychological alterations and, thus, neuropsychiatric disorders.
In conditions of chronic stress exposure, nerve cells in the hippocampus begin to atrophy. (The hippocampus is a part of the brain involved with emotions, learning, and memory formation.)
The new depression theories “should not be viewed as separate entities because they are highly interconnected,” researchers write.
“Integrating them provides for a more expansive understanding of the pathophysiology of depression and biomarkers that are involved.”
Such biomarkers are molecules in the body that can be indicators of depression. The authors identify more than a dozen potential biomarkers depression, including monoamine regulators; proinflammatory cytokines and other inflammatory mediators; mediators of glutaminergic activity and GABAergic activity; and regulators of neurogenesis.
A bevy of new depression treatments are currently offered or on the horizon include corticotropin-releasing hormone antagonists; dexamethasone; partial adrenalectomy; long-term cognitive behavioral therapy; ketamine and other NMDA antagonists. Other treatments include benzodiazepines; anesthetics; deep brain stimulation; transcranial magnetic stimulation; exogenous brain-derived neurotrophic factor; selective serotonin reuptake inhibitors; tricyclic antidepressants; atypical antidepressants; reduction in inflammation; and anti-inflammatory drugs.

 Beyond Antidepressants: Taking Stock of New Treatments

Возможные механизмы антидепрессивного действия антипсихотиков второго поколения

Although the exact mechanism of SGAs for MDD has not yet been clearly elucidated, several plausible underlying mechanisms are listed as follows: modulation of crucial neurotransmitter receptors and transporters such as dopamine, serotonin and noreinephrine resulting in net effect of enhancement of such neurotransmitters' transmission, effects on sleep, alteration of various hormones (ACTH, sex hormones, etc.), modification of immune functions including modulation of inflammation process (cytokines, etc.), antioxidation process and modulation of neurotrophic factors (BDNF, etc).[13]

Specifically, the main pharmacological rationale of SGAs as an antidepressant augmentation would be based on their effects on monoamine transporters or receptors of crucial neurotransmitters such as serotonin, norepinephrine and dopamine, which are also the main target of contemporary antidepressants. The partial agonism at D2 and/or D3 receptors may increase dopamine neurotransmission at the prefrontal cortex. The increase in the dopamine concentration in the prefrontal cortex may be also indirectly related to the antidepressive effect of 5-HT1A receptor agonist.[14,15] The antidepressant effect may also be mediated by 5-HT1A partial agonism and/or antagonism at 5-HT2A receptors.[16–18] Although, still controversial, the antidepressant effect of 5-HT1A receptor agonists may be predominantly mediated by postsynaptic 5-HT1A receptors, while the anxiolytic effect would be mainly associated with presynptic 5-HT1A receptors.[19] The antagonism of the 5-HT2C receptors has been also found to be involved in increased dopamine and norepinephrine transmission.[20] It is also well known that high affinity at the α2-adrenergic receptor may enhance the release of norepinephrine.[21] Unlike any other SGAs, ziprasidone was reported to block synaptic serotonin, norepinephrine and dopamine reuptake in vitro.[22,23] Evidence indicates that both 5-HT6 agonists and antagonists may evoke identical responses in animal models of MDD, although the possible mechanisms of these effects seem to be diverse and are not clearly understood. The augmented effects were notable by combining antidepressants with a selective 5-HT6 receptor antagonist.[24] There is also a considerable amount of evidence supporting a role for the 5-HT7 receptor in MDD. The blockade of the 5-HT7 receptor led to antidepressant-like effects in animal models of MDD. It should be also worthy to mention that augmentation of 5-HT7 receptor antagonists with antidepressants was remarkable in animal models of MDD.[25]

Another mechanism involving in the action of SGAs should be the alteration of the glutamate receptor activity, and thus restoring normal glutamatergic neurotransmission and reducing the chances of excitotoxicity.[26] Some SGA treatment may also cause a decrease in plasma adrenocorticotropic hormone concentration and a normalization of HPA-axis dynamics.[27] An impaired neuroprotection has also been implicated in the pathophysiology of MDD.[28,29] Interestingly, activation of the 5-HT1A receptors was shown to be neuroprotective against various brain insults such as N-methyl-daspartic acid.[30] Some SGAs have also demonstrated such neuroprotective effects indicating a potential role in the protection against excitotoxicity in vivo.[30]

Overall 5-HT2A antagonism should be a commonly shared biological relevance for most of the SGAs as a potential mechanism of their antidepressant effect. Interactive effects with the dopaminergic system may be more distinct with the action mechanism of amisulpride and aripiprazole, while norepinephrine- and/or serotonin-reuptake inhibition should be the unique case with quetiapine or ziprasidone.[31] Each antipsychotic has a distinct profile of affinities towards different neurotransmitter receptors, which should be associated mainly with mediation of antidepressant-like effects.

Second-generation Antipsychotics in the Treatment of Major Depressive Disorder

Не связанные с дофамином механизмы действия антипсихотиков

APs suppress induction of pro-inflammatory cytokines. It is well established that psychotic episodes of schizophrenia are associated with neuroinflammation and elevations of cytokines such as interleukin 1 (IL-1), IL-6, tumor necrosis factor (TNF-α), and interferon gamma (IFN-γ). These inflammatory biomarkers are released by microglia, which are rapidly activated by psychosis and mediate brain tissue damage during psychosis. APs’ rapid inhibitory action on pro-inflammatory cytokines obviously is neuroprotective.
APs suppress immune-inflammatory pathways. This occurs with atypical agents but not haloperidol and results in decreased IL-1β and IL-6 and transforming growth factor-β.
APs significantly decrease levels of neurotoxic tryptophan catabolites (TRYCATS) such as 3-OHK and QUIN, which mediate the immune-inflammatory effects on neuronal activity. APs also increase levels of neuroprotective TRYCATS such as kynurenic acid.
APs activate cholesterol-transport proteins such as apolipoprotein E (APOE).6 This implies that APs may improve low levels of APOE observed during psychosis and decrease myelination abnormalities and mitigate impairment of synaptic plasticity.
APs increase neurotrophic growth factors that plummet during psychosis, such as brain-derived neurotrophic factor (BDNF) and nerve growth factor. This beneficial effect is seen with SGAs but not first-generation APs (FGAs) and is attributed to strong serotonin 5HT-2A receptor antagonism by SGAs.
SGAs but not FGAs significantly increase the number of newly divided cells in the subventricular zone by 200% to 300%. This enhancement of neurogenesis and increased production of progenitor cells that differentiate into neurons and glia may help regenerate brain tissue lost during psychotic episodes.
Various SGAs have neuroprotective effects:
Clozapine has neuroprotective effects against liposaccharide-induced neurodegeneration and reduces microglial activation by limiting production of reactive oxygen species (free radicals).
Aripiprazole inhibits glutamate-induced neurotoxicity and, in contrast to haloperidol, increases BDNF, glycogen synthase kinase (GSK)-β, and the anti-apoptotic protein Bcl-2.
Olanzapine increases BDNF, GSK-3β, and β-catenin, increases mitosis in neuronal cell culture, and protects against neuronal death in cell cultures that lack nutrients (which fluphenazine or risperidone do not).
Paliperidone demonstrates a higher antioxidant effect than any other SGA and clearly is better than haloperidol, olanzapine, or risperidone in preventing neuronal death when exposed to hydrogen peroxide.
Quetiapine, ziprasidone, and lurasidone have inhibitory effects on nitric oxide release. Quetiapine, but not ziprasidone, inhibits TNF-α.
Ziprasidone inhibits apoptosis and microglial activation and synthesis of nitric oxide and other free radicals.
Lurasidone increases BDNF expression in the prefrontal cortex of rodents.

 Beyond dopamine: The ‘other’ effects of antipsychotics

Потенциальные механизмы лечения депрессии

EMERGING THERAPEUTIC TARGETS


Consider the following novel mechanisms that may become the basis for creating entirely new antidepressants in the foreseeable future, by design, not by serendipity:

• corticotropin-releasing factor (CRF) and glucocorticoids

         – CRF antagonists
           – vasopressin receptor antagonists
           – glucocorticoids as agonists or antagonists

• neurokinin system
• brain derived neurotropic factor (BDNF) and other neurotropins, such as fibroblast growth factor (FGF) or vascular endothelial growth factor (VEGF)
• phosphodiesterase inhibitors
• glutamate pathway modulators

        – ketamine (IV infusion with immediate efficacy)
          – α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA) receptor modulators
          – glycine

• hypothalamic feeding peptides
• circadian gene products
• other evolving antidepressants

        – K-opioid receptor antagonists
          – CB1 cannabinoid receptor agonists/antagonists
          – cytokines
          – melatonin receptor agonists
          – galanin
          – neuropeptide Y
          – histone deacetylase inhibitors
          – tissue plasminogen activator

 The hazards of serendipity

Средиземноморская диета снижает риск возникновения депрессии

Dr. Martinez-Gonzalez said the risk for depression was substantially lower in participants with higher adherence to the MDP and that depression rates were about 30% lower in those with the highest consumption of fruit, nuts, legumes, and monounsaturated vs saturated fats.

"The important thing regarding fish is that a very low consumption of fish (lowest quintile) was in fact a risk factor when it was compared with the 3 upper categories of fish consumption (merged together)," he added.

The researchers were trying to determine why the lifetime prevalence of mental disorders is lower in Mediterranean than Northern European countries. One possible factor is diet, as previous research has suggested that the monounsaturated fatty acids in olive oil — used abundantly in the Mediterranean diet — may be associated with a lower risk for severe depressive symptoms.

The study included 10,094 healthy Spanish participants who reported their dietary intake on a food frequency questionnaire. After a median follow-up of 4.4 years, there were 480 new cases of depression. Individuals who followed the Mediterranean diet most closely had a greater than 30% reduction in the risk for depression than whose who had the lowest Mediterranean diet scores. The association did not change when the results were adjusted for other markers of a healthy lifestyle.

The strength of the inverse association between the [MDP] and depression surprised the investigators. "The new question for us is that if these results will be reproduced in a primary prevention trial," Dr. Martinez-Gonzalez said. "Another new question is whether the MDP is longitudinally associated with increased serum levels of BDNF," or brain-derived neurotrophic factor — a peptide critical for axonal growth, neuronal survival, and synaptic plasticity.

According to the authors, "An emerging concept in neuroscience is that perturbations in the health of cerebral endothelium (such as some loss of the neuroprotection afforded by BDNF) may mediate progressive neuronal dysfunction." Depression is associated with low BDNF in some patients.

Mediterranean Diet Cut Depression Risk by 30%

Ketamine Leaves BDNF Unchanged

Suicidal Ideation Abates After Ketamine Infusion