There is increasing evidence that smokers have a lower incidence of some inflammatory and neurodegenerative diseases. Nicotine is immunosuppressive, which inhibits both the innate and adaptive immune responses.
Nicotine is not yet considered to be a carcinogen and may, in fact, have therapeutic potential as a neuroprotective and anti-inflammatory agent. A multitude of studies suggest that nicotine, a psychoactive component of tobacco products, acts in a similar fashion as the naturally occurring neurotransmitter, acetylcholine, on nicotinic acetylcholine receptors (nAChRs) found in many organ systems and has profound immunological effects.
Epidemiological studies have shown an association of smoking with a lower occurrence of PD. Nicotine activates the striatal or mesolimbic dopaminergic system and protects against glutamate-induced neurotoxicity in striatal, cortical and mesencephalic neurons, as well as nigrostriatal degeneration in MPTP-treated animals. Nicotine could suppress the formation of toxin by directly influencing enzyme activities, such as monoamine oxidases (MAO). Nicotine might also modulate the members of the cytochrome P450 (CYP) family [detox pathway]. Furthermore, nicotine could act by modulating mitochondrial complex Ι activity to preserve mitochondrial function and consequently reduce neuronal damage.
Numerous signaling pathways are altered in response to nACh receptor activation, including presynaptic pathways involved in control of neurotransmitter release (dopamine, ACh, GABA, and glutamate) and postsynaptic pathways involved in apoptosis (phospholipase C, arachidonic acid, reactive oxygen species, neuronal nitric oxide synthase, and cGMP) and necrosis (phospholipase C, protein kinase C, MAPK, ERK, and Bcl2), immune modulation (IL-1, IL-6, and TNFα) and neurotrophic factor production (brain derived neurotrophic factor, fibroblast growth factor 2). Activation of these pathways might subsequently lead to neuroprotection through inhibition of toxin-induced apoptosis, and increased expression of neurotrophic factors, which are crucial for neuronal maintenance, survival and regeneration.
You can read the entire study here: ncbi.nlm.nih.gov/labs/pmc/a...
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