Repurposing the tyrosine kinase inhibitor nilotinib for use against intracellular multidrug-resistant Salmonella Typhimurium.

BACKGROUND/PURPOSE: The increasing incidence of infections caused by multidrug-resistant Salmonella enterica has become a serious threat to global public health. Here, we found that the tyrosine kinase inhibitor nilotinib exhibits antibacterial activity against intracellular S. enterica serovar Typhimurium in RAW264.7 macrophages. Thus, we aimed to pharmacologically exploit the anti-intracellular Salmonella activity of nilotinib and to elucidate its mechanism of action.

METHODS

The antibacterial activity of the compounds was assessed by high-content analysis (HCA) and intracellular CFU, minimum inhibitory concentration (MIC), and bacterial growth assays. The cytotoxicity of the compounds was evaluated by HCA and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) cell viability assays. The levels of cellular AMPK, phospho-AMPK, Atg7 and β-actin were determined by immunoblotting.

RESULTS

The screen identified two small molecule compounds (SCT1101 and SCT1104) with potent activity against intracellular S. Typhimurium. Moreover, SCT1101 and SCT1104 enhanced the efficacy of ciprofloxacin and cefixime against intracellular S. Typhimurium. However, only SCT1101 exhibited activity against intracellular MDR and fluoroquinolone-resistant S. Typhimurium isolates. Subsequent mechanistic studies showed that neither of these nilotinib derivatives increased the phospho-AMPK level in RAW264.7 cells. Neither the AMPK inhibitor compound C nor SBI-0206965 reversed the inhibitory effects of SCT1101 and SCT1104 on intracellular Salmonella. Furthermore, neither blockade of autophagy by 3-MA nor shRNA-mediated knockdown of Atg7 protein expression in RAW264.7 cells affected the antibacterial activity of SCT1101 and SCT1104.

CONCLUSION

The structure of nilotinib could be used to develop novel therapeutics for controlling MDR S. Typhimurium infections.