Andrographolide interferes quorum sensing to reduce cell damage caused by avian pathogenic Escherichia coli

- Andrographolide reduced cell damage of chicken type II pneumocytes induced by APEC.
- Andrographolide inhibited F-actin cytoskeleton polymerization induced by APEC.
- Andrographolide reduced the quantity of APEC adhering to chicken type II pneumocytes.
- Andrographolide inhibited the expression of virulence factors of APEC.
- Andrographolide restrained the quorum sensing of APEC by inhibiting AI-2 activity.

Avian pathogenic Escherichia coli (APEC) induce septicemia in chickens by invading type II pneumocytes to breach the blood-air barrier. The virulence of APEC can be regulated by quorum sensing (QS). Andrographolide is a QS inhibitor of Pseudomonas aeruginosa (P. aeruginosa). Therefore, we investigate whether andrographolide inhibits the injury of chicken type II pneumocytes by avian pathogenic E. coli O78 (APEC-O78) by disrupting the bacterial QS system. The results showed that sub-MIC of andrographolide significantly reduced the release of lactate dehydrogenase (LDH), F-actin cytoskeleton polymerization, and the degree of the adherence to chicken type II pneumocytes induced by APEC-O78. Further, we found that andrographolide significantly decreased the autoinducer-2 (AI-2) activity and the expression of virulence factors of APEC-O78. These results suggest that andrographolide reduce the pathogenicity of APEC-O78 in chicken type II pneumocytes by interfering QS and decreasing virulence. These results provide new evidence for colibacillosis prevention methods in chickens.

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