A curcumina previne os efeitos da exposição à fumaça do cigarro sistema purinérgico, sistema colinérgico e memória

Abstract

Cigarette smoke exposure is a major risk factor to the development of cardiovascular diseases, neurocognitive and neurobiological deficits. Nowadays, phytotherapy is widely employed in the treatment of many illnesses. Curcumin, a polyphenol obtained from the rhizomes of Curcuma longa and commonly used in the oriental culinary and traditional medicine, has several pharmacological properties such as antioxidant, antiaggregant and neuroprotective. Despite its wide-ranging spectrum of pharmacological properties, curcumin possess potential to prevent the noxious effects caused by cigarette smoke exposure. In this context, the purpose of this study was to evaluate the effect of curcumin on memory and parameters involved in the homeostasis of central nervous system (CNS) in rats passively exposed to cigarette smoke. The experiments were performed in two different stages, being the first divided in two sets. In the first set, animals were randomly assigned into four groups: vehicle; curcumin 12.5 mg/kg; curcumin 25 mg/kg; and curcumin 50 mg/kg. In the second set, animals were randomly assigned into five groups: vehicle, cigarette smoke; curcumin 12.5 mg/kg along with cigarette smoke; curcumin 25 mg/kg along with cigarette smoke; and curcumin 50 mg/kg along with cigarette smoke. In the second experimental stage, animals were randomly divided into ten groups: vehicle; curcumin 12.5 mg/kg; curcumin 25 mg/kg; curcumin 50 mg/kg; nanoencapsulated curcumin 4 mg/kg; cigarette smoke; curcumin 12.5 mg/kg along with cigarette smoke; curcumin 25 mg/kg along with cigarette smoke; curcumin 50 mg/kg along with cigarette smoke; and nanoencapsulated curcumin 4 mg/kg along with cigarette smoke. The treatment with curcumin and cigarette smoke was carried out once a day, 5 days each week, during 30 days. Curcumin was administered orally and, approximately 10 minutes later, the smoking groups were exposed to the sidestream smoke of four commercial cigarettes (nicotine 0.9 mg, tar 10 mg each) inside a whole-body smoke exposure chamber. After thirty days, the animals were euthanized, the blood collected and the brain dissected in cerebral cortex, hippocampus, hypothalamus, striatum and cerebellum. The group of rats exposed to cigarette smoke showed an increase in the activity of the enzymes E-NTPDase (ATP as substrate) and E-5 -NT, and a reduction in the activity of the enzyme E-NTPDase (ADP as substrate) in platelets; an increase in the activities of the enzymes E-NTPDase, E-5 -NT and AChE in synaptosomes from the cerebral cortex; an increase in the activity of AChE in cerebellum, cerebral cortex, hippocampus, striatum, hypothalamus and peripheral blood; a decrease in the activities of the enzymes Na+,K+-ATPase and Ca2+-ATPase and a redox imbalance. Furthermore, in the same group of animals, it was observed a cognitive impairment evaluated through the inhibitory avoidance test and the object recognition test. We conclude that the use of both formulations of curcumin, free and nanostructured, prevents the effects observed in the purinergic and cholinergic system, in the enzymes involved in the ion homeostasis and in the oxidative stress parameters. Finally, the results obtained in this study indicate that curcumin administration as lipid-core nanocapsules may be an alternative to increase its efficacy, probably by the increase of its bioavailability when administered orally.