Pseudomonas aeruginosa Impairs Mitochondrial Function During Infection of Corneal Epithelial Cells

Pseudomonas aeruginosa (PA) is a Gram-negative opportunistic bacterial pathogen that can infect the cornea as a result of trauma or contact lens wear. Mitochondria, originally derived from bacteria, play important roles in host defense. This study investigated the effect of PA on mitochondrial structure and function during the early stages of infection in corneal epithelial cells.

Telomerase-immortalized human corneal epithelial cells and primary cultured human corneal epithelial cells were infected with a standard invasive test strain of PA (strain PAO1). Changes in mitochondrial dynamics, mitophagy, and metabolic proteins were assessed by Western blot. Mitochondrial polarization was quantified using JC-1 labeling. Mitochondrial metabolism was measured in real time using Seahorse, and mass spectrometry was performed for metabolomic analysis. Mitochondrial morphology was assessed by transmission electron microscopy.

PA infection induced rapid mitochondrial fission, followed by PINK1-mediated mitophagy. PA infection also reduced NADH-linked respiration through a reduction in complex I and impaired dihydroorotate and glycerolipid metabolism. Other changes in the metabolite profile included an increase in arginine biosynthesis, purine metabolism, and the pentose phosphate pathway, all pathways that can be readily exploited by bacteria. Following treatment with gentamicin to kill all extracellular bacteria, metabolic flux analysis showed that corneal epithelial cells were able to restore mitochondrial function despite the continued presence of intracellular PA.

Taken together, these data demonstrate that extracellular PA triggers mitochondrial dysfunction and metabolic rewiring in corneal epithelial cells. This may represent a potential mechanism whereby PA disables host cell mitochondria to facilitate invasion.