Epidemiological studies have demonstrated that air pollution is a significant risk factor for age-related
dementia, including
Alzheimer's disease (AD). It has been posited that traffic-related air pollution (TRAP) promotes AD neuropathology by exacerbating
neuroinflammation. To test this hypothesis, serum and hippocampal
cytokines were quantified in male and female TgF344-AD rats and wildtype (WT) Fischer 344 littermates exposed to TRAP or filtered air (FA) from 1 to 15 months of age. Luminex™ rat 23-cytokine panel assays were used to measure the levels of hippocampal and serum
cytokines in 3-, 6-, 10-, and 15-month-old rats (corresponding to 2, 5, 9, and 14 months of exposure, respectively). Age had a pronounced effect on both serum and hippocampal
cytokines; however, age-related changes in hippocampus were not mirrored in the serum and vice versa. Age-related changes in serum
cytokine levels were not influenced by sex, genotype, or TRAP exposure. However, in the hippocampus, in 3-month-old TgF344-AD and WT animals, TRAP increased IL-1ß in females while increasing TNF ɑin males. In 6-month-old animals, TRAP increased hippocampal levels of
M-CSF in TgF344-AD and WT females but had no significant effect in males.
At 10 and 15 months of age, there were minimal effects of TRAP, genotype or sex on hippocampal
cytokines. These observations demonstrate that TRAP triggers an early inflammatory response in the hippocampus that differs with sex and age and is not reflected in the serum
cytokine profile. The relationship of TRAP effects on
cytokines to
disease progression remains to be determined.