Avaliação do sistema purinérgico e colinérgico em córtex de ratos após hipóxia-isquemia neonatal

Abstract

Hypoxia-ischemia (HI) neonatal is a major cause of morbidity and mortality during the perinatal period and it is an important risk factor for the development of a number of human neurological disorders, such as cerebral palsy, epilepsy, and motor and learning deficits. Cerebral HI results in hemodynamic, biochemical and neurophysiological alterations as a direct consequence of the lack of oxygen and glucose. The central nervous system presents a relatively high consumption of oxygen and glucose which relies almost exclusively on the oxidative phosphorylation process for the production of energy thus it is highly susceptible to hypoxic-ischemic insult. During the HI event, the rapid suppression in the process of oxidative phosphorylation initiates a series of poisonings that occur simultaneously and are directly related to the evolution of brain injury. Thus, knowing that the pathogenesis of neonatal HI is a highly complex and multifactorial event, this study aimed to investigate possible changes in the purinergic and cholinergic systems in the cerebral cortex of newborn rats subjected to HI, at different post-insult (immediately, 72 h and 8 days after neonatal HI),. Furthermore, analyzes were performed to assess the levels of lipid peroxidation and some peripheral markers of inflammation such as tumor necrosis factor alpha TNF-α; Interferon-gamma - IFN-γ; interleukins IL-1β and IL-6. Results demonstrated that immediately after HI, the activity of nucleotide triphosphate diphosphohydrolase (NTPDase) and 5 '-nucleotidase (5`-NT) cytosolic increased in the cerebral cortex. In synaptosomes, an increase in the activity of ecto-adenosine deaminase (ecto-ADA) was observed, while the activity of Na+/K+ ATPase was inhibited. There was no change in the expression of adenosine kinase (ADK). Interestingly, the Na+/K+ ATPase activity was correlated negatively with the cytosolic NTPDase activity and TBARS content. Our results showed an increase in lipid peroxidation levels immediately, 72 h and 8 days after HI. The activity of acetylcholinesterase (AChE) showed time-dependent changes in the cerebral cortex of these animals. The same was observed for AChE activity in erythrocytes and ADA. Regarding the levels of proinflammatory cytokines (TNF-α, IFN-γ, IL-1β and IL-6) investigated, all showed increased serum levels. Immediately after HI, the ADA activity showed a strong positive correlation with all cytokines analyzed. Eight days after HI there was an inflammatory process with increased activity of ADA, myeloperoxidase (MPO) and N-acetyl-glucosaminidase (NAG). In this same period, we observed that ADA1 isoenzyme was responsible for the increase in the ADA activity after HI insult. Interestingly, adenosine receptors A1 (A1Rs) and ADK protein expression showed a decrease 8 days after insult. Thus, the results described here suggest that neonatal HI alters the cholinergic and purinergic signaling in the cortex of newborn rats. However, the understanding of these events may help in the development of new therapies for hypoxic-ischemic brain injury.