Papel da mitocôndria e das interações entre mitocôndria e reticulo endoplasmático na Doença de Huntington : estudo em um modelo animal

A doença de Huntington (DH) é uma doença neurodegenerativa herdada de forma dominante e causada por uma expansão de repetição de bases de nucleotídeos CAG no gene huntingtin, resultando na síntese de uma proteína huntingtina mutante (mHTT). A tríade sintomatológica da DH inclui disfunções motoras, cognitivas e psiquiátricas. A primeira região cerebral a apresentar anormalidades é o estriado, sendo relatada uma degeneração de neurônios GABAérgicos em estágio avançando da doença. Outros achados, como perda de função de células gliais, bem como uma ativação de astrócitos, contribuem para um fenótipo neurotóxico na DH. Além disso, vários eventos celulares e moleculares desempenham um papel importante na patologia da DH. Em destaque estão as possíveis alterações mitocondriais, uma vez que a mitocôndria é uma organela essencial para diversos processos celulares, como a produção de ATP, metabolismo do cálcio e homeostase redox. Neste contexto, já é bem estabelecido que doenças neurodegenerativas apresentam disfunção mitocondrial, podendo alterar os processos envolvidos na dinâmica mitocondrial e nas interações dessa organela com outros constituintes celulares, em particular o retículo endoplasmático (RE). Assim, no presente estudo um modelo experimental animal para a DH induzido pela administração intraperitoneal do ácido 3-nitropropiônico (3-NP, 20 mg/kg) durante 3 dias consecutivos, investigamos parâmetros chave relacionados à mitocôndria no período de 7, 14, 21 e 28 dias após indução. Nossos resultados mostraram alterações na homeostase redox em estriado, com aumento da peroxidação lipídica 28 dias após a administração de 3-NP, e diminuição de defesas antioxidantes enzimáticas e não-enzimáticas em diferentes tempos. Também observamos disfunção do metabolismo bioenergético, com redução do estado 3, estado 4 e não-acoplado em 7 dias após a administração de 3-NP, aumento dos estados 4 e não acoplado e capacidade de reserva em 28 dias, e diminuição da atividade dos complexos da cadeia respiratória em 7 e 28 dias. Observamos alterações na dinâmica mitocondrial através do aumento da expressão proteica da mitofusina 1 (MFN1) em 7, 14 e 28 dias, uma importante proteína para a fusão mitocondrial, sugerindo uma resposta compensatória ao insulto oxidativo. Além disso, nossos resultados sugerem que em 28 dias após a administração 3-NP ocorreram alterações na interação mitocôndria-RE, com o aumento do conteúdo proteico de canal aniônico voltagem dependente 1 (VDAC1) e da proteína reguladora de glicose 75 kDa (GRP75). Também houve um aumento inicial observado no conteúdo da proteína sinaptofisina, seguido de diminuição, sugerindo uma resposta transitória da atividade sináptica, buscando a manutenção da neurotransmissão normal. Nossos achados mostram que um prejuízo grave na função mitocondrial, com alteração na dinâmica mitocondrial, homeostase do cálcio e redox, bem como um dano na interação mitocôndria-RE os quais estão envolvidos na fisiopatologia do dano estriatal observado na DH.Huntington's disease (HD) is a dominantly inherited neurodegenerative condition caused by a CAG nucleotide base repeat expansion in the huntingtin gene, resulting in the production of a mutant huntingtin protein (mHTT). The symptomatologic triad of HD confers motor, cognitive and psychiatric dysfunctions. In the initial stage, patients present with abnormalities in the striatum caused by mHTT, whereas degeneration of GABAergic neurons is observed in an advanced stage of the disease. Other findings, such as glial cells dysfunctions, particularly reactive astrocytes, contribute to a neurotoxic phenotype in HD. On the other hand, several cellular and molecular events have been shown to play a role in HD pathology. In this scenario, mitochondrial dysfunction has a key role since mitochondria are essential organelles for various cellular processes, such as ATP production, calcium metabolism and redox homeostasis. Furthermore, it is suggested that disrupted mitochondrial dynamics and alterations in the interactions of mitochondria with other cellular constituents, in particular the endoplasmic reticulum (ER), are common findings in neurodegenerative diseases. Thus, in the present study an experimental animal model for HD induced by intraperitoneal administration of 3- nitropropionic acid (3-NP, 20 mg/kg) for 3 consecutive days, we investigated key parameters related to mitochondria in the period of 7, 14, 21 and 28 days after induction. Our results showed changes in redox homeostasis in striatum, with an increase in lipid peroxidation 28 days after 3-NP treatment, and a decrease in defenses enzymatic and non-enzymatic antioxidant at different periods after 3-NP exposure. We also observed bioenergetic dysfunction, with reduced state 3, state 4 and non-coupled at 7 days, augmented state 4 and non-coupled state and reserve capacity at 28 days, and decreased activity of the respiratory chain complexes at 7 and 28 days. We observed changes in mitochondrial dynamics through increased protein expression of mitofusin 1 (MFN1) at 7, 14, and 28 days, an important protein for mitochondrial fusion, suggesting a compensatory response to 3-NP induced oxidative insult. Furthermore, our results demonstrated that, at 28 days after 3-NP administration, alterations in mitochondria-ER interactions occurred, with increased protein content of voltage-dependent anion channel 1 (VDAC1) and 75 kDa glucose regulated protein (GRP75). Additionally, an initial increase of synaptophysin protein content followed by a reduction of this content was seen, indicating a transient response aiming the maintenance of a normal neurotransmission. Our findings show that impaired mitochondrial function, with changes in mitochondrial dynamics, calcuim and redox homeostasis, as well as disturbances in mitochondria-endoplasmic reticulum interactions are involved in the pathophysiology of striatal damage seen in DH

Myelin disruption, neuroinflammation, and oxidative stress induced by sulfite in the striatum of rats are mitigated by the pan-PPAR agonist bezafibrate

Sulfite predominantly accumulates in the brain of patients with isolated sulfite oxidase (ISOD) and molybdenum cofactor (MoCD) deficiencies. Patients present with severe neurological symptoms and basal ganglia alterations, the pathophysiology of which is not fully established. Therapies are ineffective. To elucidate the pathomechanisms of ISOD and MoCD, we investigated the effects of intrastriatal administration of sulfite on myelin structure, neuroinflammation, and oxidative stress in rat striatum. Sulfite administration decreased FluoromyelinTM and myelin basic protein staining, suggesting myelin abnormalities. Sulfite also increased the staining of NG2, a protein marker of oligodendrocyte progenitor cells. In line with this, sulfite also reduced the viability of MO3.13 cells, which express oligodendroglial markers. Furthermore, sulfite altered the expression of interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1), indicating neuroinflammation and redox homeostasis disturbances. Iba1 staining, another marker of neuroinflammation, was also increased by sulfite. These data suggest that myelin changes and neuroinflammation induced by sulfite contribute to the pathophysiology of ISOD and MoCD. Notably, post-treatment with bezafibrate (BEZ), a pan-PPAR agonist, mitigated alterations in myelin markers and Iba1 staining, and IL-1β, IL-6, iNOS and HO-1 expression in the striatum. MO3.13 cell viability decrease was further prevented. Moreover, pretreatment with BEZ also attenuated some effects. These findings show the modulation of PPAR as a potential opportunity for therapeutic intervention in these disorders

Nanocapsules With Naringin And Naringenin Affect Hepatic and Renal Energy Metabolism Without Altering Serum Markers of Toxicity in Rats

Naringin and naringenin are flavonoids found in citrus fruits and have several health benefits, however these compounds are susceptible to degradation, limiting their therapeutic application. To solve this problem, an alternative is to incorporate them into nanocapsules. The aim of this work was to evaluate the toxicity of these nanocapsules against renal and hepatic serum markers and also on the activities of pyruvate kinase, Mg2+-ATPase, and creatine kinase. Nanocapsules containing naringin and naringenin, nanocapsules without the active compounds and the compounds in their free form were administered orally, once a day, for 28 days. After treatment, the serum levels of hepatic and renal markers were not altered, nor the activities of pyruvate kinase tissue, however, the treatment of nanocapsules with flavonoids increased the activities of mitochondrial creatine kinase in the kidney and hepatic Mg2+-ATPase. Thus, renal and hepatic serum markers, which are normally used as indicators of toxicity, did not change after the period of administration of the nanoparticles. However, the activities of important enzymes of the energy metabolism in these organs were affected. Our findings reinforce that nanomaterial testing for toxicity needs to go beyond traditional methods to ensure the safe use of nanoparticles for therapeutic purposes

Myelin Disruption, Neuroinflammation, and Oxidative Stress Induced by Sulfite in the Striatum of Rats Are Mitigated by the pan-PPAR agonist Bezafibrate

Sulfite predominantly accumulates in the brain of patients with isolated sulfite oxidase (ISOD) and molybdenum cofactor (MoCD) deficiencies. Patients present with severe neurological symptoms and basal ganglia alterations, the pathophysiology of which is not fully established. Therapies are ineffective. To elucidate the pathomechanisms of ISOD and MoCD, we investigated the effects of intrastriatal administration of sulfite on myelin structure, neuroinflammation, and oxidative stress in rat striatum. Sulfite administration decreased FluoromyelinTM and myelin basic protein staining, suggesting myelin abnormalities. Sulfite also increased the staining of NG2, a protein marker of oligodendrocyte progenitor cells. In line with this, sulfite also reduced the viability of MO3.13 cells, which express oligodendroglial markers. Furthermore, sulfite altered the expression of interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1), indicating neuroinflammation and redox homeostasis disturbances. Iba1 staining, another marker of neuroinflammation, was also increased by sulfite. These data suggest that myelin changes and neuroinflammation induced by sulfite contribute to the pathophysiology of ISOD and MoCD. Notably, post-treatment with bezafibrate (BEZ), a pan-PPAR agonist, mitigated alterations in myelin markers and Iba1 staining, and IL-1β, IL-6, iNOS and HO-1 expression in the striatum. MO3.13 cell viability decrease was further prevented. Moreover, pre-treatment with BEZ also attenuated some effects. These findings show the modulation of PPAR as a potential opportunity for therapeutic intervention in these disorders

Antioxidant system disturbances and mitochondrial dysfunction induced by 3-methyglutaric acid in rat heart are prevented by bezafibrate

Barth syndrome (BTHS) and dilated cardiomyopathy with ataxia syndrome (DCMA) are biochemically characterized by high levels of 3-methylglutaric acid (MGA) in the urine and plasma of affected patients. Although cardiolipin abnormalities have been observed in these disorders, their pathophysiology is not fully established. We evaluated the effects of MGA administration on redox homeostasis and mitochondrial function in heart, as well as on vascular reactivity in aorta of Wistar rats without cardiolipin genetic deficiency. Potential cardioprotective effects of a pretreatment with bezafibrate (BEZ), a pan-PPAR agonist that induces mitochondrial biogenesis, were also determined. Our findings showed that MGA induced lipid peroxidation, altered enzymatic and non-enzymatic antioxidant defenses and reduced respiratory chain function in rat heart. MGA also increased Drp1 and reduced MFN1 levels, suggesting mitochondrial fission induction. Moreover, MGA altered MAPK and Akt signaling pathways, and had a strong tendency to reduce Sirt1 and PGC-1α, indicative of mitochondrial biogenesis impairment. Aorta vascular reactivity was further altered by MGA. Additionally, BEZ mitigated most alterations on antioxidant defenses and mitochondrial quality control proteins provoked by MGA. However, vascular reactivity disturbances were not prevented. It may be presumed that oxidative stress, mitochondrial bioenergetics and control quality disturbances, and vascular reactivity impairment caused by MGA may be involved in the cardiac failure observed in BTHS and DCMA, and that BEZ should be considered as a pharmacological candidate for the treatment of these disorders