The tunicamycin derivative TunR2 exhibits potent antibiotic properties with low toxicity in an in vivo Mycobacterium marinum - zebrafish TB infection model

Authors: NONARATH, HANNAH - Medical College Of Wisconsin; Jackson, Michael - Mike; PENOSKE, RENEE - Medical College Of Wisconsin; ZAHRT, THOMAS - Medical College Of Wisconsin; Price, Neil; LINK, BRIAN - Medical College Of Wisconsin

Submitted to: Journal of Antibiotics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2023
Publication Date: 1/18/2024
Citation: Nonarath, H.J.T., Jackson, M.A., Penoske, R.M., Zahrt, T.C., Price, N.P.J., Link, B.A. 2024. The tunicamycin derivative TunR2 exhibits potent antibiotic properties with low toxicity in an in vivo Mycobacterium marinum - zebrafish TB infection model. Journal of Antibiotics. https://doi.org/10.1038/s41429-023-00694-z.
DOI: https://doi.org/10.1038/s41429-023-00694-z

Interpretive Summary: Mycobacteria are antibiotic resistant microorganisms that cause numerous debilitating infections, such as tuberculosis (TB) in both humans and animals. Tunicamycin (TUN) is a natural product with excellent antibiotic activity against mycobacteria, but with unwanted side effects in mammals. We developed modified TUNs, called TunR1 and TunR2, which have significantly less mammalian toxicity, while retaining the potent antibacterial activity against mycobacteria. The present research describes the effectiveness of TunR1 and TunR2 for the treatment of Mycobacterium marinum infection of zebrafish, an established model of human tuberculosis. We also report on the pharmacological testing of TunR1 and TunR2 in zebrafish to look for cellular abnormalities that result from the treatment. We conclude that TunR1 and TunR2 have low toxicity in this well-defined animal disease model and potential for treatment of numerous mycobacterial diseases in animals. This research will benefit numerous animal producers by providing improved methods for treatment of antibiotic resistant strains.

Technical Abstract: Tunicamycins (TUN) are potent antibiotics that target cell wall synthesis in bacteria. However, the known eukaryotic toxicity associated with these compounds has limited their clinical use, thus far. Recently, two TUN compounds (TunR1 and TunR2), were developed that exhibit reduced eukaryotic toxicity when assayed in in vitro cell culture systems. Here, these two compounds were further investigated for their toxicity and antibacterial activity in zebrafish using a well-established Mycobacterium marinum (M. marinum) infection system, a model for studying human Mycobacterium tuberculosis infections. Specifically, we found that both TUN derivatives were less toxic when assayed in vivo, with TunR2 showing the most significant reduction in toxicity. TunR2 also showed the greatest reduction in its ability to activate the unfolded protein response (UPR), the known mechanism of action for the eukaryotic toxicity observed with TUN treatment. Importantly, TunR1 and TunR2 retained their antimicrobial properties, as evidenced by a reduction in M. marinum bacterial burden, compared to DMSO-treated zebrafish. In summary, findings from this study highlight the characteristics of recently developed TUN derivatives, mainly TunR2, and its potential to be used as an anti-bacterial agent, including in bacterial infections involving drug-resistant isolates.