TFAM Deficiency‒Mediated Mitochondrial Disorder Affects Langerhans Cell Maintenance and Function

Mitochondrial-dependent oxidative phosphorylation is key for postnatal metabolic adaptation of alveolar macrophages in the lung

Alveolar macrophages (AMs) seed in lung during embryogenesis and become mature in perinatal period. Establishment of acclimatization to environmental challenges is important, whereas the detailed mechanisms that drive metabolic adaptation of AMs remains to be elucidated. Here, we showed that energy metabolism of AMs was transformed from glycolysis prenatally to oxidative phosphorylation (OXPHOS) postnatally accompanied by up-regulated expression of mitochondrial transcription factor A (TFAM). TFAM deficiency disturbed mitochondrial stability and decreased OXPHOS, which finally impaired AM maintenance and function, but not AM embryonic development. Mechanistically, Tfam-deletion resulted in impaired mitochondrial respiration and decreased ATP production, which triggered endoplasmic reticulum (ER) stress to cause B cell lymphoma 2 ovarian killer (BOK) accumulation and abnormal distribution of intracellular Ca2+, eventually led to induce AM apoptotic death. Thus, our data illustrated mitochondrial-dependent OXPHOS played a key role in orchestrating AM postnatal metabolic adaptation.

Investigation of Mitochondrial Homeostasis Changes in Lens Epithelium of High-Myopic Cataract

PURPOSE

High myopia is demonstrated as a pathogenic factor for nuclear cataract. The main mechanism of high-myopia cataracts (HMC) is oxidative damage, which causes mitochondrial homeostasis imbalance. This study aimed to explore the mitochondrial homeostasis alterations in lens epithelial cells (LECs) of HMC.

METHODS

The lens epithelium tissues of 20 patients with HMC and 20 control subjects with age-related cataracts (ARC) were collected. The real-time quantitative PCR and western blot assays were performed for gene expressions. Immunofluorescence (IF) assays were performed for mitochondrial marker TOM20, DNA damage marker 15A3, and autophagosome marker LC3. Transmission electron microscopy (TEM) was used to observe the changes in mitochondria morphology. Mitochondrial ROS, and mitochondrial membrane potential were detected by MitoSOX fluorescence, and JC-1 MitoMP staining, respectively. Rat lenses cultured in vitro were pretreated with CCCP and H2O2 (10 and 400 µM) for 24 h.

RESULTS

The copy number of mtDNA was decreased in HMC patients compared to the ARC patients. Increased mitochondrial-oriented oxidative stress response was detected in LECs of HMC compared to that of ARC. Altered expressions of mitochondrial homeostasis and mitophagy markers, including TFAM, PGC1α, MFN1, MFN2, Drp1, PINK1, Parkin and LC3, were found in HMC patients. Reciprocally, no significant differences in the expression of BNIP3 and FUNDC1 were found between HMC and ARC patients. Importantly, TEM revealed that the obvious mitochondrial fission and mitophagy phenomena occur in the LECs of HMC patients compared to the ARC patients. Moreover, CCCP aggreated the mitoROS production and depolarized mitochondrial membrane potential in the H2O2-treated human lens epithelial cells line (SRA01/04); Most important, rat lens organ culture experiments indicated a significant increase in H2O2-induced lens opacity following mitochondrial uncoupling CCCP treatment.

CONCLUSION

This study has identified for the first time the abnormal mitochondrial homeostasis in HMC, and provide a new perspective on the potential mechanisms of HMC, which occurs earlier and at a higher incidence rate than ARC.