Evaluation of ASK-1 pro-apoptotic dependent signaling of respiratory nuclei in an animal model of Parkinson's Disease treated by apocynin

• Grant number: 21/04314-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2021
• End date: July 31, 2022
• Field of knowledge: Biological Sciences - Physiology - Physiology of Organs and Systems
• Principal Investigator: Bárbara Falquetto
• Grantee: Mayara Spadari da Costa Moura
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 19/00065-1 - Oxidative stress in respiratory control of Parkinson Disease animal model, AP.JP

Abstract

Parkinson's disease (PD) is a degenerative disease of dopaminergic neurons of the substantia nigra pars compacta (SNpc), characterized both by motor deficits, such as muscle stiffness, tremor at rest, and bradykinesia and by non-motor deficits, such as respiratory failure and dementia. The respiratory deficit is associated with pathogenesis and is mainly linked to impaired chest mobility due to muscle stiffness and bradykinesia, causing ventilatory disorders in patients, as well as neurodegeneration of the respiratory nuclei of the brainstem. In experimental models of bilateral 6-OHDA injections into the murine striatum, the lesion is quite consistent with idiopathic PD, as it manifests a progressive pattern in the cerebral hemispheres. Despite not being fully elucidated, it is possible to observe a vast cell death of dopaminergic neurons in cultures of the midbrain after injection of 6-OHDA, in addition to ROS concentrations derived from the superoxide anion (O2-) and, because of high expression of NADPH in neurons, it supports the apoptosis model due to ROS accumulation in pathogenesis. Apoptosis is an energy-dependent mechanism that unfolds a biochemical cascade with two distinct pathways that lead to a common, terminal pathway. The intrinsic pathway is a cell death mechanism regulated by loss of mitochondrial permeability, induced by positive or negative intracellular signals. Apoptosis type 1 signal-regulating kinase (ASK1) is a constitutively expressed MAPKKK that, in the presence of hydrogen peroxide (H2O2, that is, oxidative stress), activates two signaling pathways: JNK and p38. Although not completely elucidated, it is known that ASK1, by activating the two pathways, is capable of inducing apoptosis in the dopaminergic cell via the mitochondrial pathway. ASK1 is regulated by Thioredoxin (Trx), an enzyme sensitive to the redox state of the cell, so that when linked, the pathway is not activated, as Trxse binds to the non-catalytic N-terminal portion of ASK1 and prevents it from exercising its function. This dependence on the redox state of the cell was evaluated in cultured catecholaminergic cells, which, exposed to levodopa, one of the main drugs used in the treatment of PD, was also responsible for increasing the activation of the pro-apoptotic pathway ASK1 and phosphorylation of JNK and p38. Upon activating p38 MAPK, the protein phosphorylates other proteins responsible for the balance of pro-apoptotic signals, such as BimEL, in order to further stimulate apoptosis, and like p53 which, among its diverse functions in the cell, is able to induce apoptosis by serving as a transcription factor for Bax, which in turn increases the permeability of the mitochondrial cell membrane and release of cytochrome C, activating the apoptotic cascade through effector caspases. In models of diamide injections, causing the formation of thiol species, it has been proven that the ASK1-p38 MAPK pathway is activated by mechanisms dependent on the oxidation of Trx, which, when dissociated from ASK1, allows its oxidation and initiation of the pro-cascade apoptotic in the ventral midbrain, mainly. In light of the facts presented, it is possible to conclude that the oxidative imbalance of a cell is able, through ASK1, to induce neurodegeneration in neurons, suggesting that this pathway is linked to PD. The aim of this study is to evaluate this apoptotic signaling in the respiratory neurons in an animal model of PD with 6-OHDA injection in the striatum after treatment with apocynin, an inhibitor of NAPH oxidase.(AU)