Differential Cerebrovascular Toxicity of Various Tobacco Products: A Regulatory Perspective

Blood-Brain Barrier (BBB) is a dynamic anatomical interface that separates brain parenchyma from blood circulation and is principally constituted by the cerebral microcapillary endothelial cells [1,2]. BBB is composed of distinct structural and functional organization through the presence of inter-endothelial tight junction complexes, abundant expression of nutrient and efflux transporters including metabolically active sites. While the TJ complexes tightly seal the paracellular gaps and contribute to high resistance of BBB [3], the presence of specific nutrient transporters and receptor systems selectively regulate the delivery of metabolic substrates, nutrients and macromolecules to the brain. In addition, efflux transporters belonging to the ABC superfamily prevent the brain permeation of bloodborne neurotoxic chemicals including xenobiotics and eliminates the accumulation of toxic metabolites within the brain parenchyma [1]. Taken together, the BBB serves as a physiological, transport and metabolic barrier that critically regulates ion, molecular and cellular flux into the brain, thus maintaining the CNS microenvironment for optimal neuronal function [2]. Importantly, impairment of BBB integrity by various exogenous or endogenous pathological stimuli involving increased load of oxidative/inflammatory stress in the neurovascular unit, is a potential mechanism underlying the pathogenesis of a host of neurologic and degenerative disorders [3,4].