[Effect of Echinococcus multilocularis infections on mitochondrial functions of macrophages]

To investigate the changes of mitochondrial metabolic functions of macrophages following Echinococcus multilocularis infections, so as to provide insights into the pathogenesis of alveolar echinococcosis.

Two groups were assigned according to different treatment methods. In the culture group, mouse leukemic monocyte macrophage RAW264.7 cells were cultured with 2 000 E. multilocularis at a ratio of 500∶1, while RAW264.7 cells in the control group were given no treatment. Then, both the culture and control groups were further divided into the 24 h and 72 h subgroups. Mitochondria were stained with MitoTracker^® Deep Red FM and the mean fluorescence intensity of macrophage mitochondria was measured with the Cytation 5 Cell Imaging Multi-Mode Reader. The mitochondrial DNA copy number was quantified using the quantitative real-time PCR (qPCR) assay, and the mitochondrial energy metabolism was monitored using the Seahorse XF assay. In addition, the mitochondrial reactive oxygen species and mitochondrial membrane potential were detected using flow cytometry.

The mean fluorescence intensities of macrophage mitochondria were significantly lower in the 24 h (15 341 ± 2 532 vs. 17 823 ± 3 429; t = 6.379, P < 0.01) and 72 h (18 102 ± 3 505 vs. 21 511 ± 5 144; t = 17.680, P < 0.01) culture subgroups than in the corresponding control subgroups, and lower mitochondrial DNA copy numbers were measured in the 72 h culture subgroup than in the 72 h control group [(3.23 × 10⁹ ± 1.78 × 10⁷) vs. (4.39 × 10⁹ ± 3.70 × 10⁷); t = 8.85, P < 0.001]. The oxygen consumption rates were significantly greater in the 24 h [(241.70 ± 73.13) pmol/min vs. (69.05 ± 52.30) pmol/min; t = 7.89, P < 0.01] and 48 h culture groups [(249.50 ± 42.06) pmol/min vs. (60.28 ± 40.66) pmol/min; t = 8.64, P < 0.01] than in the corresponding control groups, and a higher extracellular acidification rate was seen in the 48 h culture group than in the 48 h control group ([ 111.6 ± 17.49) mpH/min vs. (35.05 ± 7.57) mpH/min; t = 16.90, P < 0.01]. In addition, flow cytometry detected higher mean fluorescence intensity of mitochondrial reactive oxygen species (58 264 ± 10 087 vs. 4 307 ± 97; t = 12.930, P < 0.01) and lower mitochondrial membrane potential (9.833% ± 2.285% vs. 2.667% ± 0.208%; t = 6.645, P < 0.01) in the 72 h culture group than in the control group.

E. multilocularis infection may impair mitochondrial functions and inhibit oxidative phosphorylation of macrophages, resulting in increased macrophage glycolysis. It is speculated that the alteration of macrophage metabolic states may contribute to the mechanisms underlying the development and progression of alveolar echinococcosis.