Investigação da participação da via PI3KΓ/AKT/NO/GMPC/CANAIS para Potássio Sensíveis ao ATP no controle endógeno da dor neuropática induzida por dieta hiperlipídica em camundongos obesos
| Ano de defesa: | 2021 |
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| Autor(a) principal: | |
| Orientador(a): | |
| Banca de defesa: | |
| Tipo de documento: | Tese |
| Tipo de acesso: | Acesso aberto |
| Idioma: | por |
| Instituição de defesa: |
Universidade Federal de Minas Gerais
Brasil ICB - DEPARTAMENTO DE FARMACOLOGIA Programa de Pós-Graduação em Ciências Biológicas - Fisiologia e Farmacologia UFMG |
| Programa de Pós-Graduação: |
Não Informado pela instituição
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| Departamento: |
Não Informado pela instituição
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| País: |
Não Informado pela instituição
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| Palavras-chave em Português: | |
| Link de acesso: | http://hdl.handle.net/1843/38540 |
Resumo: | Diabetes mellitus (DM) is one of the most documented chronic diseases in the world and affects more than 100 million people on the planet. Its main characteristic is chronic hyperglycemia, resulting from the absence of insulin production or its resistance, type 2 diabetes mellitus is the most prevalent type, representing about 85-90% of cases. Inadequate diabetes control compromises muscle and nerve tissues, the metabolism of which depends fundamentally on the supply of glucose and increases the likelihood of the appearance of microvascular complications, such as: diabetic retinopathy, diabetic nephropathy, autonomic neuropathy and peripheral diabetic neuropathy. Diabetic neuropathies are characterized by the presence of symptoms and / or signs of somatic and / or autonomic nervous system nerve dysfunction in individuals diagnosed with DM. Currently, there is a reduced number of treatments available for diabetic neuropathic pain, and basically tricyclic antidepressants and anticonvulsants are used, however, these drugs are not very effective in controlling pain, with only 30% of patients showing some type of relief. In this context, the purpose of this study was to evaluate whether the PI3Kγ / AKT / NO / cGMP / channels for potassium sensitive to ATP, participates in endogenous control in diabetic neuropathic pain. The discovery of pathways that participate in modulatory mechanisms of pain can bring important answers to the choice of more effective drugs or the creation of specific drugs that guarantee satisfactory relief of this type of pain, with a consequent improvement in the quality of life of patients. Diabetic neuropathic pain was induced by a high-fat diet (HFD 40%), the animals were fed for 12 weeks until the onset of hyperalgesia, this phenomenon was then accompanied by the diagnosis of obesity, insulin resistance and glucose intolerance, thus representing a model similar to type 2 diabetes in humans. Hyperalgesia was tested using the mechanical paw compression method and to confirm that the pain at the mechanical stimulus has neuropathic and not just inflammatory characteristics, the histopathology of the paw and the sciatic nerve of the animals in the control group and fed with diabetogenic diet. The results found were satisfactory to prove that the pain evoked by the diet has typical neuropathic characteristics, records of disorganization of the connective tissue of the epineurium / perineurium, axons retracted and positioned eccentrically, an increase in the space corresponding to myelin and axonal loss were observed, guaranteeing thus the effectiveness of the model in the induction of diabetic neuropathic pain. For pharmacological tests, statistical analyzes used two-way ANOVA, followed by the Bonferroni post-test, for the quantification of morphological changes by histopathological and immunohistochemical analysis, a paired T test was used. All drugs were administered via the intraplantar route. To assess the participation of the PI3k pathway, AS-605240 was used, a selective inhibitor of PI3Kγ in the dosages of 90 and 180 µg / paw, it was observed that PI3Kγ when inhibited did not modulate the nociception induced by the hyperlipidic diet. For the determination of the expression of p-AKT / total AKT proteins, the Western blot technique was used and for this purpose plantar cushions were collected from the animals of the control group and fed with the diabetogenic diet. There was a statistically significant difference in the expression of the p-AKT protein, which represents the active form of this protein, the same, it is expressed in a smaller amount in animals affected by diabetic neuropathic pain (DNP), which reinforces the non-participation of this via endogenous modulation in the investigated pain. To evaluate the participation of the nitric oxide signaling pathway, the drugs L-NOarg, a non-selective inhibitor of the enzymes nitric oxide synthase, were used at doses of 24 and 48 µg / paw and ODQ, a selective inhibitor of the enzyme soluble guanylate cyclase, in doses of 100 and 200 µg / paw, endogenous modulation was not observed in diabetic neuropathic pain when used, L-NOarg or ODQ, meaning that the nitric oxide pathway does not participate in the endogenous modulation of the investigated pain. We proceeded to the analysis of the selective participation of these channels, thus, we used glibenclamide, a selective blocker of potassium channels sensitive to ATP, at doses 80 and 160 µg / paw, where a reduction in the nociceptive threshold was observed in animals with neuropathic pain diabetic, which means that these channels participate endogenously in the attempt to control diabetic neuropathic pain. After these findings, he investigated the expression of ATP-sensitive potassium channels, with the aim of observing whether, in a scenario of DNP induced exclusively by a high-fat diet, they showed their altered expression, for this, immunohistochemistry of the cushions was performed. plants, these were marked with Kir 6.2, a marker of potassium channels sensitive to ATP and the results found, showed an increase in the expression of these channels, which is believed to be a strategy of functional alteration of the endogenous system, in an attempt to control the ache. To determine the activity of voltage-sensitive potassium channels (KV), Tetraethylammonium, a selective blocker of channels for KV, was used at a dose of 30 µg, where modulation of the nociceptive threshold of animals affected by diabetic neuropathic pain was observed. Based on these findings, the participation of low- and high-conductivity calcium channels for potassium was also investigated. For such analyzes, Dequalíneo (selective blocker of potassium channels sensitive to calcium of low conductance) was used, respectively, in the dose of 50 µg / paw and Paxilína (selective blocker of channels for potassium sensitive to calcium of high conductance), in the dose 20 µg / paw. The nociceptive threshold of animals with diabetic neuropathic pain did not change when any of the aforementioned drugs were administered, thus ruling out the participation of calcium-sensitive potassium channels in the endogenous modulation of diabetic neuropathic pain. The results provide evidence that the pain evoked by the induction model exclusively by high-fat diet has a neuropathic characteristic. In addition, it was observed that the PI3Kγ / AKT / NO / cGMP pathway does not participate endogenously in the control of diabetic neuropathic pain, however, the ATP-sensitive potassium channels and voltage, endogenously modulate the pain, blocking these channels reduced the nociceptive threshold of animals affected by pain, in addition, the expression of KATP is increased. Our hypothesis is that the increased expression of these channels is a functional physiological adaptation of the peripheral endogenous system, an attempt to control diabetic neuropathic pain and that drugs that enhance the opening of these channels can contribute to the control of diabetic neuropathic pain. FINANCIAL SUPPORT: CAPES. CEUA PROTOCOL: 57/2017. |