Cigarette Smoking Accelerated Brain Aging and Induced Pre-Alzheimer-Like Neuropathology in Rats

Abstract

Cigarette smoking has been proposed as a major risk factor for aging-related pathological changes and Alzheimer's disease (AD). To date, little is known for how smoking can predispose our brains to dementia or cognitive impairment. This study aimed to investigate the cigarette smoke-induced pathological changes in brains. Male Sprague-Dawley (SD) rats were exposed to either sham air or 4% cigarette smoke 1 hour per day for 8 weeks in a ventilated smoking chamber to mimic the situation of chronic passive smoking. We found that the levels of oxidative stress were significantly increased in the hippocampus of the smoking group. Smoking also affected the synapse through reducing the expression of pre-synaptic proteins including synaptophysin and synapsin-1, while there were no changes in the expression of postsynaptic protein PSD95. Decreased levels of acetylated-tubulin and increased levels of phosphorylated-tau at 231, 205 and 404 epitopes were also observed in the hippocampus of the smoking rats. These results suggested that axonal transport machinery might be impaired, and the stability of cytoskeleton might be affected by smoking. Moreover, smoking affected amyloid precursor protein (APP) processing by increasing the production of sAPPβ and accumulation of β–amyloid peptide in the CA3 and dentate gyrus region. In summary, our data suggested that chronic cigarette smoking could induce synaptic changes and other neuropathological alterations. These changes might serve as evidence of early phases of neurodegeneration and may explain why smoking can predispose brains to AD and dementia.

The Effect of Waterpipe Tobacco Smoke Exposure on Learning and Memory Functions in the Rat Model

“…For example, Ho et al (2012) found that chronic smoking predisposed the brain to Alzheimer’s disease by increasing amyloid precursor protein processing, leading to greater production and accumulation of beta amyloid protein in the hippocampus (Ho et al, 2012). Amos-Kroohs et al (2013) showed that mice exposed to cigarette smoke throughout gestation and lactation had longer latencies and impaired learning on the Morris water maze task (Amos-Kroohs et al, 2013).…”

Cognitive outcomes after acute coronary syndrome: a population based comparison with transient ischaemic attack and minor stroke

“…While cardiac dysfunction may have an impact on the brain, differences in risk factor profile may also be important: more smoking and less hypertension and AF were seen in ACS patients compared to TIA and stroke patients. Smoking is a risk factor for memory impairment and Alzheimer's disease more than vascular cognitive impairment,28 29 whereas hypertension and AF are associated with stroke, small vessel disease, and vascular dementia.…”

Smoking and increased Alzheimer's disease risk: A review of potential mechanisms

“…Rueff-Barroso et al, 174 reported that mice exposed to daily cigarette smoke for 15 weeks demonstrated significant OxS in homogenized whole brain tissue as indicated by elevated malondialdehyde level, a marker of lipid peroxidation. Ho et al, 175 found that rats exposed to daily cigarette smoke for approximately 8 weeks showed significantly increased levels of 8-hydroxyguanine, a marker of oxidative damage to RNA and DNA nucleosides, in the dentate and CA3 subfields of the hippocampus. 175 Khanna et al, 147 reported rats exposed to cigarette smoke 5 days/week for 6 weeks exhibited significantly increased brain IFN-γ and TNF-α proinflammatory cytokine levels, as well as upregulation of the expression of multiple cytokine genes (e.g., TNF-α, IL1-α, IL1-β, Th17).…”