Axolotl mucus peptides attack breast cancer cells and MRSA

4 3 minutes read

Among animals that can regrow their detached limbs, Mexico’s axolotls stand out. These endangered amphibians can also regrow organs, including parts of its brain and heart. Now, biologists are looking closer at the mucus on these masters of regrowth. The antimicrobial peptides (AMP) in the axolotls’ mucus membranes protect them from pathogens. Now, a new study believes that this internet-famous animal could hold some solutions to antibiotic resistance. Its antimicrobial peptides were effective against multi-resistant bacteria, including the dreaded methicillin-resistant Staphylococcus aureus (MRSA), and helped combat cancer cells. The results are described in a study recently published in the journal PLOS ONE.

Mucus massage

Antimicrobial peptides are among the most promising candidates for tackling further antibiotic resistance. They are found in almost all living organisms and are part of the innate immune system.

“Antimicrobial peptides could be an alternative to antibiotics in the future,” study co-author Dr. Peter M. Vogt, a surgeon and Clinic Director at the Kerstin Reimers Laboratory for Regenerative Biology at the Clinic for Plastic, Aesthetic, Hand and Reconstructive Surgery at Hannover Medical School in Germany, said in a statement. “They have a broad spectrum of activity and at the same time it is more difficult for pathogens to develop resistance.”

Axolotls in the wild are threatened with extinction largely due to habitat degradation, pollution, and non-native predators in their small geographic range in southern Mexico City’s lakes and canals. The Ambystoma Mexicanum Bioregeneration Center (ABMC) of the Kerstin Reimers Laboratory for Regenerative Biology, is currently home to the axolotl species Ambystoma mexicanum among other amphibian species that scientists can examine. All of the animals in this study come from captive breeding.

[ Related: A chemical in acne medicine can help regenerate limbs. ]

To obtain skin mucus for this new study, the axolotls were gently massaged with sterile gloves. The mucus produced by the amphibians was removed from the gloves with sterile scrapers. According to the team, this work was done in accordance with the guidelines of the German Animal Welfare Act.

Out of the thousands of antimicrobial peptides extracted from the mucus and synthesized, the team selected 22 likely effective peptide candidates. It was not an easy feat.

“This is time-consuming and expensive, but unfortunately AMPs [antimicrobial peptides] are not as easy to produce in microorganisms as some antibiotics,” explained Vogt.

The chemical structure and mechanism of action of the antimicrobial peptides are what make them so difficult to produce. They all contain amino acids with a positive charge and have water-repellent components, so that they can bind to the cell wall of bacteria. Once attached to the bacterial cell wall, they either create small holes in it to penetrate the cell or bind to molecules. Both processes damage the cell and lead to death. Antimicrobial peptides can also act against viruses and fungi.

a scientist puts her hands on an aquarium tank holding four salamander-like amphibians with feathered gills called an axolotol — *Little helper for science: Sarah Strauß has found effective antibiotic alternatives on the skin of the axolotl, which also fight tumour cells. CREDIT: Karin Kaiser/MHH.*

Tackling MRSA

According to study co-author and Hannover Medical School biologist Sarah Strauß, that special chemical structure could be what makes antimicrobial peptides effective against resistant bacterial strains–and might reduce the risk of further resistance. Harnessing the power of that chemical structure could yield a decisive advantage, since even reserve antibiotics are at risk of losing efficacy against bacteria. Reserve antibiotics are used for infections caused by bacteria when conventional antibiotics are no longer effective. This is the case in MRSA, which causes roughly 20,000 infections per year in the United States.

Four of the axolotl antimicrobial peptides showed efficacy against MRSA. In some cases, they were even more effective than the reserve antibiotic vancomycin.

“The results against MRSA are particularly significant because the spread of this multi-resistant bacterial strain will continue to increase with the overuse of antibiotics in both health care and agriculture,” said Vogt.

Tackling cancer

The team also detected an anti-carcinogenic effect in three of the four antimicrobial peptides. This group also was effective against MRSA. In a cell culture, these peptides triggered a programmed cell death in breast cancer cells. Programmed cell death is a controlled biological program in which the affected cell dies in a lab.

“We observed that the peptides specifically kill cancer cells without attacking healthy breast tissue cells,” Strauß said in a statement. “Overall, our results suggest that these identified AMPs could be promising candidates for combating antibiotic resistance and for anti-cancer strategies.”

While more studies are needed to verify these results, these results are a basis for additional research into what future therapeutics are lurking in axolotl mucus.