Impact of E-Cigarette Vapor and Cigarette Smoke on Brain Expression of ABCB1 and ABCG2 Efflux Transporters

ABCB1 and ABCG2 are major efflux transporters at the blood–brain barrier, regulating CNS exposure to xenobiotics and therapeutic agents. Chronic exposure to cigarette smoke and e-cigarette vapor contains toxicants capable of modulating their expression. Adult rats were exposed to cigarette smoke or e-cigarette vapor for two months. Abcb1 and Abcg2 mRNA expression in the amygdala and hippocampus was assessed using quantitative PCR (qPCR), and protein levels were quantified using ELISA. Statistical analysis was performed with one-way ANOVA. Both cigarette smoke and e-cigarette vapor significantly upregulated Abcb1 and Abcg2 mRNA and protein expression in the amygdala and hippocampus compared to controls. Long-term exposure to cigarette smoke and e-cigarette vapor causes a significant increase in transcriptional and translational upregulation of ABCB1 and ABCG2 in limbic brain regions. This change is probably mediated by oxidative stress and xenobiotic-sensing transcription factors. While this may enhance neuroprotection, it could also limit CNS drug penetration and disrupt neurochemical homeostasis, with potential implications for cognition, mood, and therapeutic efficacy.