Halophilic archaeon Halorhabdus rudnickae enhances epithelial barrier integrity in Calu-3 cells

Halophilic archaea are a distinct domain of life, separate from Bacteria and Eukarya, that thrive in highly saline environments, including salt mines. Their impact on the human immune system is poorly known. The respiratory epithelium is the first line of defence against inhaled environmental agents, including pollutants, allergens and microorganisms. Disruption of epithelial barrier integrity is linked to the pathogenesis of allergic and inflammatory airway diseases. In this study we examined the interaction of Halorhabdus rudnickae WSM-64 T , isolated from the Barycz area of the Wieliczka Salt-Mine in Poland with the human bronchial epithelial cell line Calu-3. We found that this halophilic archaeal strain did not cause cytotoxic or genotoxic effects on Calu-3 cells and significantly enhanced the healing process of physically damaged monolayers of cells compared to unstimulated cells. Moreover, halophilic archaeal stimulation of Calu-3 was associated with significantly increased fluorescence intensity of ZO-1, scaffolding protein responsible for organizing the junctional proteins and stabilising cell barriers. Exposure to Hrd. rudnickae significantly decreased the secretion of TGF-beta by Calu-3 cells, suggesting a potential ability to counteract the pathological changes driven by TGF-beta. In the air-liquid interface model we observed significant reduction in FITC-dextran permeability, indicating improved barrier integrity after stimulation of Calu-3 with halophilic archaea. Our findings thus show that halophilic archaeon Hrd. rudnickae isolated from a Polish salt mine can induce the enhancement of epithelial barrier integrity in the Calu-3 cells, providing a conceptual framework for future immunomodulatory strategies in patients with pulmonary allergic disorders.