Propolis increases flies' tolerance to ethanol

Fruit flies Drosophila melanogaster fed a diet supplemented with propolis resisted ethanol stress better. The effect appeared without an increase in the expression of classic genes linked to alcohol metabolism or antioxidant defense. The result points to a direct role of innate immunity in the adaptation of insects to chemical stressors, according to Korean researchers.

The study evaluated adult females raised throughout their life cycle on an artificial diet with one gram of propolis. The control group received the same diet without supplementation. Then, the insects were exposed to ethanol vapor at concentrations ranging from zero to 20%. Survival was monitored hourly for eight hours.

At a concentration of 12,5% ​​ethanol, used in gene expression analyses, survival after eight hours reached 63,33% in the group with propolis. In the control group, the rate was 40,0%. The difference showed statistical significance, with p equal to 0,036.

Scientists did not observe increased activation of the Adh and Aldh genes, which are linked to ethanol metabolism. The expression of these genes remained lower in flies fed propolis. There was also no widespread induction of antioxidant genes, such as SOD1, SOD2, CAT, Trxr1, GstD2, and GstD5.

The main alteration occurred in genes for antimicrobial peptides dependent on the IMD pathway. A diet with propolis increased the expression of DptA, DptB, AttC, and Mtk before exposure to ethanol. Expression remained higher in the first hours of exposure.

According to the researchers, the data indicate a state of immune preparedness induced by the diet. This prior activation may increase ethanol tolerance in Drosophila melanogaster. The work also expands the role of antimicrobial peptides beyond defense against pathogens.

Further information at doi.org/10.3390/insects17060542