Long-term cardiovascular reprogramming by short-term perinatal exposure to nicotine's main metabolite cotinine.

AIM: Gather 'proof-of-concept' evidence of the adverse developmental potential of cotinine (a seemingly benign biomarker of recent nicotine/tobacco smoke exposure).

METHODS: Pregnant C57 mice drank nicotine- or cotinine-laced water for 6 wks from conception (NPRE = 2% saccharin + 100 μg nicotine/mL; CPRE = 2% saccharin + 10 μg cotinine/mL) or 3 wks after birth (CPOST = 2% saccharin + 30 μg cotinine/mL). Controls drank 2% saccharin (CTRL). At 17 ± 1 weeks (male pups; CTRL n = 6; CPOST n = 6; CPRE n = 8; NPRE n = 9), we assessed (i) cardiovascular control during sleep; (ii) arterial reactivity ex vivo; and (iii) expression of genes involved in arterial constriction/dilation.

RESULTS: Blood cotinine levels recapitulated those of passive smoker mothers' infants. Pups exposed to cotinine exhibited (i) mild bradycardia - hypotension at rest (p < 0.001); (ii) attenuated (CPRE , p < 0.0001) or reverse (CPOST ; p < 0.0001) BP stress reactivity; (iii) adrenergic hypocontractility (p < 0.0003), low protein kinase C (p < 0.001) and elevated adrenergic receptor mRNA (p < 0.05; all drug-treated arteries); and (iv) endothelial dysfunction (NPRE only).

CONCLUSION: Cotinine has subtle, enduring developmental consequences. Some cardiovascular effects of nicotine can plausibly arise via conversion into cotinine. Low-level exposure to this metabolite may pose unrecognised perinatal risks. Adults must avoid inadvertently exposing a foetus or infant to cotinine as well as nicotine.