Potential role of the antimicrobial peptide Tachyplesin III in regulating nontypeable Haemophilus influenzae-induced inflammation in airway epithelial cells

The respiratory bacterium nontypeable (non-encapsulated) Haemophilus influenzae (NTHi) is a key pathogen driving exacerbations in chronic obstructive pulmonary disease (COPD), and is associated with an excessive airway inflammation. Increasing issues with tolerance and unwanted side effects of existing pharmaceuticals present an urgent need for new, effective and minimally toxic therapeutic options. This study aimed to investigate the potential role of Tachyplesin III, an antimicrobial peptide derived from the hemolysates of Southeast Asian horseshoe crabs, in regulating NTHi-induced airway inflammation. The results revealed that Tachyplesin III effectively inhibited the production of IL-1β in NTHi-stimulated human lung epithelial cells (A549), without causing cytotoxic effects. Additionally, Tachyplesin III significantly reduced TNF-α, PGE₂ and NO production in NTHi-stimulated A549 cells. Moreover, this peptide inhibited the nuclear translocation of the NF-κB p65 subunit in NTHi-stimulated lung epithelial cells. It also reduced transcriptional activation of NF-κB target genes, as shown by lower mRNA levels of IL-1β, TNF-α, COX-2 and iNOS, which correlated with corresponding decreases in their protein expression. Tachyplesin III peptide also inhibited pro-IL-1β and NLRP3 protein expression and prevented NTHi-induced caspase-1 cleavage and IL-1β maturation. Together, our findings demonstrate that Tachyplesin III effectively reduced NTHi-mediated inflammation via the NF-κB/NLRP3 inflammasome signaling pathway, highlighting its important anti-inflammatory activity. Complementing these findings, in silico analysis revealed key pharmacokinetic and toxicological attributes, establishing a foundational understanding of Tachyplesin III as a promising therapeutic agent for managing NTHi-associated inflammation.