Modulation of Human Airway Barrier Functions during Burkholderia thailandensis and Francisella tularensis Infection

Abstract

The bronchial epithelium provides protection against pathogens from the inhaled environment through the formation of a highly-regulated barrier. In order to understand the pulmonary diseases melioidosis and tularemia caused by Burkholderia thailandensis and Fransicella tularensis, respectively, the barrier function of the human bronchial epithelium were analysed. Polarised 16HBE14o- or differentiated primary human bronchial epithelial cells (BECs) were exposed to increasing multiplicities of infection (MOI) of B. thailandensis or F. tularensis Live Vaccine Strain and barrier responses monitored over 24–72 h. Challenge of polarized BECs with either bacterial species caused an MOI- and time-dependent increase in ionic permeability, disruption of tight junctions, and bacterial passage from the apical to the basolateral compartment. B. thailandensis was found to be more invasive than F. tularensis. Both bacterial species induced an MOI-dependent increase in TNF-α release. An increase in ionic permeability and TNF-α release was induced by B. thailandensis in differentiated BECs. Pretreatment of polarised BECs with the corticosteroid fluticasone propionate reduced bacterial-dependent increases in ionic permeability, bacterial passage, and TNF-α release. TNF blocking antibody Enbrel® reduced bacterial passage only. BEC barrier properties are disrupted during respiratory bacterial infections and targeting with corticosteroids or anti-TNF compounds may represent a therapeutic option.

Integrating an aerosolized drug delivery device with conventional static cultures and a dynamic airway barrier microphysiological system

“…Through activation of TLR3, poly I:C induces an inflammatory response and disassembly of tight junctional complexes in epithelial cells. 46 Fluticasone is used to treat airway inflammation in asthmatic patients and exerts its effect on the epithelium by reducing inflammatory cytokine release (e.g., IL-8 and TNF-α) 47 , 48 and enhancing airway function 48 , 49 while also counteracting the poly I:C-induced disruption of barrier integrity. 47 …”

Real-time monitoring of epithelial barrier function by impedance spectroscopy in a microfluidic platform

“…Dissolution of the cell membrane by addition of Triton-X-100 led to the immediate disruption of barrier integrity while the addition of dsRNA (Poly I:C 25 μg mL −1 ) caused a time-dependent decrease in barrier integrity as a result of tight junction disassembly, where the response was modulated by a corticosteroid (fluticasone (100 nM)), consistent with previous findings. [54][55][56] The development of a barrier on a chip platform with a tuneable microfluidic flow providing individual perfusion along with the ability to measure barrier integrity in real-time through integrated impedance electrodes provides a distinct advantage over other platforms. This platform is scalable and easy to use with a simple chip to manifold interface.…”

“…Dissolution of the cell membrane by addition of Triton-X-100 led to the immediate disruption of barrier integrity while the addition of dsRNA (Poly I:C 25 μg mL −1 ) caused a time-dependent decrease in barrier integrity as a result of tight junction disassembly, where the response was modulated by a corticosteroid (fluticasone (100 nM)), consistent with previous findings. 54–56…”

Manning the Barricades: Lung Fibroblasts and CD4+ T Cells as the Last Line of Defense against Bacterial Invasion?

“…Further work is required to investigate if fibroblast-T cell interactions are also relevant to other lung PPMs, particularly invasive lung pathogens that are known to disrupt epithelial tight junctions, such as F. tularensis or Burkholderia pseudomallei (the causative agent of melioidosis). 97 The interaction between T cells and bacterially-activated fibroblasts may also be relevant to the formation of TLOs in COPD and CF, both of which are associated with chronic bacterial infection. 89 Furthermore, there is increasing evidence of both a role for bacterial infection and CD4+ T cells in idiopathic pulmonary fibrosis pathology.…”