2019 Volume 69 Issue 2 Pages 65-69
Eushearilide, a newly isolated macrolide antibiotic isolated from Eupenicillium shearii, has been examined for its toxic effects on mitochondrial respiration and structure to gain insight into the molecular mechanism for the antifungal activity, by using freshly isolated rat liver mitochondria. Eushearilide inhibited the respiration oxidizing both L-glutamate and succinate. The inhibition was not reversed by N,N,N',N'-tetramethyl-1,4-phenylenediamine dihydrochloride, which generates an electron transport shunt over the inhibition sites of rotenone and antimycin A, and was not restored by ascorbate, an artificial substrate for the cytochrome c oxidase. The all of cytochromes a, b and c were kept reduced in the presence of eushearilide in the reducedminus oxidized difference spectrum of cytochromes. Eushearilide induced a large amplitude swelling in the mitochondria suspended in an isotonic KCl solution. This amplitude swelling was prevented by cyclosporine A, indicating the generation of the permeability pore in the inner membrane. These results suggested that eushearilide could impair mitochondrial respiratory function by inhibiting the electron transport at the site of complex IV (cytochrome c oxidase) in the respiratory chain and by inducing swelling.