Integrando as hipóteses inflamatória e neurotrófica na fisiopatologia dos transtornos de humor : foco nas alterações periférico-centrais e perspectivas de novos alvos terapêuticos

Os transtornos de humor são doenças mentais graves, recorrentes e complexas, com alta prevalência na população mundial e caracterizados por alterações de humor. Entre os mais prevalentes estão o transtorno depressivo maior (TDM) e o transtorno bipolar (TB). Sem uma única causa definida, as alterações genéticas e de resposta ao estresse são fatores etiológicos relacionados ao aparecimento dos sintomas de humor, contribuindo significativamente para a suscetibilidade a outros fatores fisiopatológicos. Estudos mais recentes têm integrado as hipóteses inflamatória e neurotrófica à teoria monoaminérgica, a fim de propor uma nova abordagem para o entendimento da fisiopatologia e resposta ao tratamento nos TDM e TB. Portanto, a utilização e validação de modelos animais que mimetizem as manifestações clínicas são essenciais para o progresso da pesquisa acerca dos transtornos de humor. Este trabalho teve por objetivo utilizar diferentes modelos animais para avaliar a relação das alterações periféricas de parâmetros inflamatórios, neurotrófico e de estresse oxidativo com desfechos em nível central. Ainda, investigar o potencial efeito neuroprotetor da exendina-4 (EX-4), um agonista do receptor de peptídeo semelhante ao glucagon 1, comumente utilizado para o controle glicêmico. No modelo animal de administração de lipopolissacarídeo (LPS) seguida de exposição a estresse crônico moderado e imprevisível (CUMS), os animais CUMS+ apresentaram uma redução do ganho de peso corporal, dos níveis séricos do fator neurotrófico derivado do encéfalo (BNDF) e do consumo e preferência a sacarose, bem como um aumento no peso da glândula adrenal e da atividade exploratória no campo aberto – incluindo o tempo de permanência na periferia considerado um comportamento tipo-ansioso. Ainda, os animais dos grupos LPS apresentaram uma hipertrofia do baço. Porém, apenas no grupo do protocolo combinado (LPS/CUMS+) foi observado um aumento dos níveis séricos de interferon (IFN) γ que se correlacionou de forma moderada à redução do consumo de sacarose, um comportamento tipo-anedônico clássico. Esta é uma importante evidência que corrobora o papel da inflamação no surgimento dos sintomas depressivos como observado em indivíduos com transtornos de humor. No modelo de mania induzido por anfetamina (AMPH), buscou-se identificar uma possível alteração de permeabilidade da barreira hematoencefálica (BHE), mecanismo fisiopatológico proposto recentemente nos transtornos de humor, bem como o efeito do tratamento com lítio. Conforme esperado, os animais que receberam administração de AMPH apresentaram aumento da atividade exploratória no campo aberto. Por sua vez, níveis séricos aumentados de substâncias reativas ao ácido tiobarbitúrico (TBARS) foram observados nos animais tratados com lítio. Embora não tenha sido observada alteração dos níveis centrais de fator de necrose tumoral (TNF) α e da expressão de claudina-5, uma das proteínas importantes para manutenção da integridade da BHE, a investigação deste parâmetro deve ser introduzida na pesquisa pré-clínica. Por fim, em um modelo agudo de inflamação induzida por LPS, foi observado um significativo efeito anti-inflamatório do tratamento com a maior dose de EX-4 proposta (0,5 μg/kg). Porém, não foram observados efeitos no comportamento e nos níveis séricos e hipocampais de BDNF e TBARS. Assim, a utilização de modelos animais permite explorar a relação das alterações periféricas e centrais, o que muitas vezes não é possível na clínica. Além disso, é possível utilizá-los para avaliação do redirecionamento de fármacos, com potencial ação neuroprotetora, que possam ser capazes de auxiliar no tratamento dos transtornos de humor, melhorando a resposta terapêutica.Mood disorders are severe, recurrent and multifactorial mental illnesses, characterized by changes in the mood and high prevalence rates in the general population. The most prevalent are Major depressive disorder (MDD) and Bipolar disorder (BD). Without a specific etiology, genetic variations and stress response are known to be important triggers of the mood symptoms increasing the susceptibility to other pathophysiological factors. Recent evidence had been integrating inflammatory and neurotrophic hypothesis to the monoaminergic theory, proposing a new perspective to elucidate the physiopathology and treatment response in MDD and BD. Thus, the use and validation of animal models that mimic clinical symptoms are essential to develop research regarding mood disorders further. The aim of this work was to employ different animal models to evaluate the relationship between peripheral changes on inflammatory, neurotrophic and oxidative stress parameters and central outcomes. In addition, the neuroprotective potential of exendin-4 (EX-4) treatment, an agonist of the glucagon-like receptor 1 (GLP-1r), commonly used in glycemic control. In the model of lipopolysaccharide (LPS) injection associated with chronic unpredictable mild stress (CUMS) exposure, CUMS+ animals exhibited reduced gain of body weight, brain-derived neurotrophic factor (BDNF) serum levels and sucrose consumption and preference, as well as increased adrenal gland weight and exploratory activity in the open field – including time spent in the periphery indicating an anxiety-like behavior. Also, LPS animals presented with splenic hypertrophy. Interestingly, animals submitted to the combined protocol (LPS/CUMS+) displayed increased serum levels of interferon (IFN) γ which were further correlated with reduced sucrose consumption, a classical anhedonic-like behavior. This is a relevant finding that corroborates the implication of inflammation on the development of depressive symptoms commonly observed in patients. In the animal model of mania induced by amphetamine (AMPH), we aimed to evaluate its effect on blood-brain barrier (BBB) disruption, which has been proposed as a new mechanism in the pathophysiology of mood disorders, as well as the effect of lithium treatment. As expected, AMPH-injected animals exhibited an increase in the exploratory behavior in the open field. Also, increased serum levels of thiobarbituric acid reactive substances (TBARS) were observed in the animals treated with lithium. Although no changes were observed in the central levels of tumor necrosis factor (TNF) α and protein levels of claudin-5, a protein involved in the maintenance of the integrity of the blood-brain, the evaluation of similar parameters should be performed in preclinical research. Lastly, in the animal model of acute inflammation induced by LPS, we observed a significant anti-inflammatory effect of the higher dose of EX-4 evaluated (0.5 μg/kg). However, no other effects of EX-4 were observed in the behavior and in the serum and hipocampal levels of BDNF and TBARS. Thus, animal models facilitate the investigation of peripheral and central changes, which is not always possible in the clinical setting. Besides, it is possible to use them to evaluate drug repurposing of compounds with neuroprotective potential that can improve the treatment responsiveness in mood disorders

Effects of lithium on inflammatory and neurotrophic factors after an immune challenge in a lisdexamfetamine animal model of mania

Objective: To evaluate whether an animal model of mania induced by lisdexamfetamine dimesylate (LDX) has an inflammatory profile and whether immune activation by lipopolysaccharides (LPS) has a cumulative effect on subsequent stimuli in this model. We also evaluated the action of lithium (Li) on inflammatory and neurotrophic factors. Methods: Adult male Wistar rats were subjected to an animal model of mania. After the open-field test, they were given LPS to induce systemic immune activation. Subsequently, the animals’ blood was collected, and their serum levels of brain-derived neurotrophic factor and inflammatory markers (tumor necrosis factor [TNF]-a, interleukin [IL]-6, IL-1b, IL-10, and inducible nitric oxide synthase [iNOS]) were measured. Results: LDX induced hyperactivity in the animals, but no inflammatory marker levels increased except brain-derived neurotrophic factor (BDNF). Li had no effect on serum BDNF levels but prevented iNOS levels from increasing in animals subjected to immune activation. Conclusion: Although Li prevented an LPS-induced increase in serum iNOS levels, its potential antiinflammatory effects in this animal model of mania were conflicting

Attenuated inflammatory response of monocyte-derived macrophage from patients with BD : a preliminary report

Background: Innate immune system dysfunction has been recognized as an important element in the pathophysiology of bipolar disorder (BD). We aimed to investigate whether there are differences in the response of macrophages derived from patients in the early stages and late stages of BD and healthy subjects. Methods: Human monocytes purified from peripheral blood mononuclear cells (PBMCs) of patients with BD type I (n = 18)—further classified into early- and late stage BD patients according to their functioning- and from healthy individuals (n = 10) were differentiated into macrophages in vitro. Monocyte-derived macrophages (M) were exposed to IFNγ plus LPS-M(IFNγ + LPS)- or IL-4-M(IL-4)—to induce their polarization into the classical (also called M1) or alternative (also called M2) activation phenotypes, respectively; or either Mψ were not exposed to any stimuli characterizing the resting state (denominated M0). In vitro secretion of cytokines, such as IL-1β, IL-6, IL-10, and TNF-α, was used as an index of macrophage activity. Results: M(IFNγ + LPS) from late-stage BD patients produced less amount of IL-1β, IL-6, and IL-10 when compared to early-stage BD patients and healthy controls. Following alternative activation, M(IL-4) derived from late-stage patients secreted less IL-6 compared to the other groups. TNFα was less secreted by all macrophage phenotypes derived from late-stage patients when compared to healthy controls only (p < 0.005). Mψ from late-stage patients exhibited lower production of IL-1β and IL-10 compared to macrophages from healthy subjects and early-stage patients respectively. Interestingly, cytokines secretion from M(IFNγ + LPS), M(IL-4) and Mψ were similar between early-stage patients and healthy controls. Conclusion: Our results suggest a progressive dysfunction in the response of peripheral innate immune cells of BD patients in the late stages of the illness. This failure in the regulation of the immune system function may be implicated in the multisystemic progression of BD

Terapia celular no tratamento do transtorno bipolar: estudo piloto em um modelo animal de mania

Introduction: The rationale of mesenchymal stem cells (MSCs) as a novel therapeutic approach in certain neurodegenerative diseases is based on their ability to promote neurogenesis. Hippocampal atrophy has been related to bipolar disorder (BD) in preclinical, imaging and postmortem studies. Therefore, the development of new strategies to stimulate the neurogenesis process in BD is crucial. Objectives: To investigate the behavioral and neurochemical changes induced by transplantation of MSCs in a model of manialike behavior induced by lisdexamfetamine dimesylate (LDX). Methods: Wistar rats (n=65) received one oral daily dose of LDX (10 mg/kg) or saline for 14 days. On the 8th day of treatment, the animals additionally received intrahippocampal saline or MSC (1 μL containing 25,000 cells) or lithium (47.5 mg/kg) as an internal experimental control. Two hours after the last administration, behavioral and neurochemical analyses were performed. Results: LDX-treated rats had increased locomotor activity compared to saline-saline rats (p=0.004), and lithium reversed LDX-related hyperactive behavior (p0.05) in the hippocampus of rats. Conclusion: Even though these results suggest that a single intrahippocampal injection of MSCs was not helpful to treat hyperactivity induced by LDX and neither influenced BDNF secretion, we cannot rule out the possible therapeutic effects of MSCs. Further research is required to determine direct effects of LDX on brain structures as well as in other pathophysiological targets related to BD.Introdução: Células-tronco mesenquimais (CTMs) têm emergido como um promissor tratamento em diversas doenças neurodegenerativas devido a sua plasticidade e capacidade de regenerar tecidos. Estudos pré-clínicos, clínicos e de neuroimagem têm demonstrado a presença de atrofia hipocampal no transtorno bipolar (TB). Portanto, o desenvolvimento de tratamentos capazes de regenerar tecido lesado e estimular a neurogênese poderia ser útil. Objetivos: Investigar mudanças comportamentais e neuroquímicas induzidas pelo transplante de CTMs no hipocampo de ratos em um modelo animal de mania induzido por dimesilato de lisdexanfetamina (LDX). Métodos: Ratos Wistar (n=65) receberam LDX (10 mg/kg) ou solução salina por via oral durante 14 dias. No oitavo dia, os animais foram transplantados com injeção de CTMs ou solução salina (1 μL contendo 25.000 células) ou lítio (47,5 mg/kg) como controle interno do experimento. Duas horas após a última dose, foram realizadas análises comportamentais e neuroquímicas. Resultados: Animais que receberam LDX tiveram um aumento da atividade locomotora comparados ao grupo que recebeu solução salina (p=0,004); já o lítio reverteu a hiperatividade locomotora desses animais (p0.05). Conclusão: Não foi possível demonstrar efeitos neuroprotetores das CTMs, administradas em dose única, em um modelo animal de mania induzido por LDX. No entanto, não se pode descartar os possíveis efeitos terapêuticos das CTMs. Mais estudos são necessários para determinar os efeitos das CTMs em estruturas cerebrais e outros alvos fisiopatológicos relacionados ao TB. Descritores: Células mesenquimais, terapia celular, transtorno bipolar, mania, neurogênese, hipocampo

The effect of taurine and enriched environment on behaviour, memory and hippocampus of diabetic rats

Diabetes mellitus (DM) has been studied recently as a major cause of cognitive deficits, memory and neurodegenerative damage. Taurine and enriched environment have stood out for presenting neuroprotective and stimulating effects that deserve further study. In this paper, we examined the effects of taurine and enriched environment in the context of diabetes, evaluating effects on behaviour, memory, death and cellular activity. Eighty-eight Wistar rats were divided into 2 groups (E = enriched environment; C = standard housing). Some animals (24/group) underwent induction of diabetes, and within each group, some animals (half of diabetics (D) and half of non-diabetics (ND)/group) were treated for 30 days with taurine (T). Untreated animals received saline (S). In total, there were eight subgroups: DTC, DSC, NDTC, NDSC, DTE, DSE, NDTE and NDSE. During the experiment, short-term memory was evaluated. After 30th day of experiment, the animals were euthanized and was made removal of brains used to immunohistochemistry procedures for GFAP and cleaved caspase-3. As a result, we observed that animals treated with taurine showed better performance in behavioural and memory tasks, and the enriched environment had positive effects, especially in non-diabetic animals. Furthermore, taurine and enriched environment seemed to be able to interfere with neuronal apoptosis and loss of glial cells, and in some instances, these two factors seemed to have synergistic effects. From these data, taurine and enriched environment may have important neurostimulant and neuroprotective effects