Effects of Mycobacterium tuberculosis on the bioelectric properties of the alveolar epithelium

Abstract

To investigate the hypothesis that Mycobacterium tuberculosis penetrates the alveolar epithelium by down-regulating its barrier properties, we evaluated the interactions between M. tuberculosis and rat alveolar epithelial cell monolayers that are believed to share electrophysiologic properties of the human alveolar epithelium. Nonproteinaceous components of M. tuberculosis caused marked declines in electrical resistance and equivalent short-circuit current of the alveolar epithelial cell monolayers, indicating a reduction in the capacity to maintain tight intercellular junctions and to actively reabsorb sodium. M. tuberculosis elicited production of TNF-α mRNA and protein by alveolar epithelial cells, and the effects of recombinant TNF-α on the bioelectric properties of the alveolar epithelial paralleled those of M. tuberculosis. Furthermore, the effects of M. tuberculosis on alveolar epithelial resistance were abrogated by neutralizing anti-TNF-α antibodies. These results indicate that M. tuberculosis elicits production of TNF-α, which in turn reduces the bioelectric barrier properties of the alveolar epithelium. These findings provide insight into potential mechanisms by which M. tuberculosis establishes infection and disease in the lung.