Long-term consequences of wildfire smoke exposure on the central nervous system of rats in experimental modeling

Abstract

Introduction. The annual increase in air temperature is one of the reasons for the occurrence of large-scale destructive fires throughout the world. The consequences of the negative impact of air pollution during forest fires on the respiratory and cardiovascular systems have been widely and well studied. At the same time, insufficient attention is paid to the influence of forest fire smoke on the functioning of the central nervous system. The study aims to study the morphofunctional state of the central nervous system of white male rats under prolonged exposure to forest fire smoke. Materials and methods. The study was conducted on 60 outbred white mature male rats weighing 200–220 grams. Animals in the experimental group (n=30) were exposed to daily smoke inhalation for 4 weeks, 4 hours a day, 5 days a week. Rats in the control group (n=30) were supplied with clean air into the chamber. The examination of animals exposed to smoke was carried out in two stages. At the first stage, the morphofunctional state of experimental animals was assessed 24 hours after the end of exposure. At the second stage — 60 days after exposure (long-term period). The examination included an analysis of indicators of the central nervous system: histology and morphometry of the brain. Results. Analysis of the results of the studied indicators indicates a decrease in motor and exploratory activity in animals exposed to smoke, as well as impairment of the ability to navigate and spatial memory. In the tissue structure of the sensorimotor cerebral cortex, multiple foci of neuronophagia, an increase in the number of degeneratively changed neurons, the formation of glial nodules and expansion of perivascular spaces were found. At the same time, the results of the examination in the long-term period indicated the absence of complete restoration of the identified violations. Conclusions. The results of experimental modeling revealed cause-and-effect relationships between exposure to forest fire smoke and disturbances in the morphofunctional state of the central nervous system. Limitations. The study is limited to studying the effects of prolonged 4 weeks, 5 days a week, 4 hours a day, exposure to wildfire smoke on outbred male white rats. Ethics. The study was conducted in compliance with the rules of humane treatment of animals in accordance with the Helsinki Association of the World Medical Association for the Humane Treatment of Animals (edition – October 2008) in accordance with the requirements of applicability to the protection of vertebrate animals or in another scientific research (ETS). No. 123), Directive 2010/63/EC of the European Parliament and of the Council of the European Union of September 22, 2010, on the protection of animals used for scientific purposes. Permission was obtained from the Local Ethics Committee of the Federal State Budgetary Scientific Institution VSIMEI to conduct experiments (protocol No. 32/19 dated May 10, 2019).