Nicotine Prevents Experimental Parkinsonism in Rodents and Induces Striatal Increase of Neurotrophic Factors

TLDR

Epidemiological studies consistently show that cigarette smoking reduces Parkinson’s disease risk, and nicotine—the principal alkaloid in tobacco—exerts CNS stimulatory effects through nicotinic acetylcholine receptors. The study aimed to determine whether (−)-nicotine protects against parkinsonism in animal models. To assess this, the authors tested nicotine’s effects in diethyldithiocarbamate‑enhanced MPTP toxicity in mice and methamphetamine‑induced neurotoxicity in rats and mice. (−)-Nicotine produced neuroprotection comparable to the NMDA antagonist (+)-MK‑801, upregulated striatal FGF‑2 and BDNF, an effect blocked by the nAChR antagonist mecamylamine, and these trophic factor increases likely mediate its protective action.

Abstract

Abstract: The repeated finding of an apparent protective effect of cigarette smoking on the risk of Parkinson's disease is one of the few consistent results in the epidemiology of this disorder. Among the numerous substances that originate from tobacco smoke, nicotine is by far the most widely studied. Nicotine is a natural alkaloid that has considerable stimulatory effects on the CNS. Its effects on the CNS are mediated by the activation of neuronal heteromeric acetylcholine‐gated ion channel receptors (nAChRs, also termed nicotinic acetylcholine receptors). In the present study, we describe the neuroprotective effects of (−)‐nicotine in two animal models of parkinsonism: diethyldithiocarbamate‐induced enhancement of 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine toxicity in mice and methamphetamine‐induced neurotoxicity in rats and mice. The neuroprotective effect of (−)‐nicotine was very similar to that of the noncompetitive NMDA receptor antagonist (+)‐MK‐801. In parallel experiments, we found that (−)‐nicotine induces the basic fibroblast growth factor‐2 (FGF‐2) and the brain‐derived neurotrophic factor in rat striatum. The effect of (−)‐nicotine on the induction of FGF‐2 was prevented by the nAChR antagonist mecamylamine. We also found that (+)‐MK‐801 was able to induce FGF‐2 in the striatum. As trophic factors have been reported to be neuroprotective for dopaminergic cells, our data suggest that the increase in neurotrophic factors is a possible mechanism by which (−)‐nicotine protects from experimental parkinsonisms.