Non-steroidal anti-inflammatory drugs conjugated ultra-short Peptidomimetics as potent Antibacterials against methicillin resistant S. aureus with anti-inflammatory activity

Abstract

Towards design of novel therapeutics against multidrug-resistant (MDR) pathogens, we reported here a focused series of drug-conjugated ultrashort peptidomimetics. Recognizing the moderate antibacterial activity of non-steroidal anti-inflammatory drugs (NSAIDs), the aim of this study was to enhance their antibacterial potential by conjugating them with an amphiphilic tetrapeptide template (H-Orn-Orn-Trp-Trp-NH₂), while preserving their anti-inflammatory effects. These NSAID-peptide conjugates were synthesized via solid phase peptide synthesis and their antibacterial properties were assessed. Within the library, three peptidomimetics (USP-1, USP-2, USP-3) showed potent antibacterial activity, with minimum inhibitory concentrations (MICs) ranging from 1.9 to 62.5 μg/mL against both Gram-positive and Gram-negative bacteria, including MDR methicillin resistant S. aureus. Interestingly, these potent compounds demonstrated non-hemolytic and non-cytotoxic with up to >100-fold higher concentrations than their antibacterial MICs. The antibacterial mode of action studies revealed that these peptidomimetics primarily depolarized and disrupted the bacterial cell membranes at their MICs. Furthermore, resistance development was not observed in MRSA even after 18 passages with continue exposure of their respective sub-MIC concentrations. Importantly, the conjugated NSAIDs retained their anti-inflammatory activity, by selectively inhibiting COX-2 enzyme. Finally, in vivo efficacy studies in mice revealed that optimized conjugates significantly reduced bacterial load and inflammation at a single intra-peritoneal dose of 10 mg/kg. Overall, these conjugates exhibit dual antibacterial and anti-inflammatory properties, coupled with a low propensity for resistance and favourable safety profile, representing them as promising candidates for the treatment of drug-resistant infections.

Keywords: Antimicrobial peptides; Antimicrobial resistance; Depolarization assay; Drug resistance; MRSA; Non-steroidal anti-inflammatory drugs (NSAIDs); Peptidomimetics.