Haemophilus influenzae triggers autophagy in HEp-2 cells

Area of Science:

• Cell Biology
• Microbiology
• Immunology

Background:

• The Microtubule-associated protein 1A/1B-light chain 3 (MAP1LC3) system regulates autophagy, a cellular degradation process.
• LC3 protein is a widely used marker for identifying autophagosomes, key structures in autophagy.

Purpose of the Study:

• To investigate the potential of Haemophilus influenzae strains and their secreted components to induce autophagy in the HEp-2 human larynx carcinoma cell line.
• To determine if bacterial components, specifically proteins in the supernatant, play a role in triggering this cellular response.

Main Methods:

• HEp-2 cells were exposed to Haemophilus influenzae strains and their cell-free supernatants.
• LC3B-II protein expression levels were quantified using Western blotting.
• Ultrastructural analysis using electron microscopy was performed to identify autophagic vacuoles.

Main Results:

• Exposure to Haemophilus influenzae, particularly nontypeable H. influenzae (NTHi) 49766, significantly increased LC3B-II protein expression in HEp-2 cells.
• Supernatants containing proteins under 50 kDa from both tested strains also induced higher LC3B-II expression.
• Ultrastructural examination revealed the formation of double-membraned vacuoles with internal material, characteristic of autophagosomes.

Conclusions:

• Haemophilus influenzae strains and their secreted factors can effectively trigger an autophagic response in human larynx carcinoma cells.
• The findings suggest a role for bacterial components in modulating host cell autophagy, potentially impacting infection dynamics.