Acute Triclosan Exposure Alters Mitochondrial Form and Function inXenopus laevisTadpoles, Including the Developing Brain

Mitochondrial health is critical for normal brain development, and mitochondrial toxicants impair energy production and induce mitophagy, resulting in network fission. This can substantially impact cellular and molecular pathways essential for brain development. Recent studies have shown that triclosan, a once widely used antibacterial and antifungal agent, acts as a mitochondrial uncoupler. However, the impact of triclosan on mitochondrial function in the developing brain has yet to be thoroughly investigated. We performed a series of experiments designed to assess the effects of triclosan on mitochondrial form and function in the developing Xenopus laevis tadpole brain. We injected tadpole brains with TMRM, a fluorescent reporter of mitochondrial membrane potential. After two hours, we imaged the brain using high-resolution confocal microscopy to obtain a baseline level of TMRM fluorescence, then immediately treated tadpoles with either triclosan (10uM, 5uM, 1uM, 0.5uM 0.1uM), FCCP (0.5uM), or control, and then continued imaging the brain once every five min for 30 min. We found that 10uM triclosan significantly decreased TMRM fluorescence in mitochondria in the end feet of radial glial cells in ∼ 15-20 min; lower concentrations operated over a longer time course. We also observed that mitochondrial networking was disrupted as they underwent fission. We also measured metabolic function in vivo in whole tadpoles using an XF Seahorse Flux Analyzer, acutely exposing tadpoles to either triclosan (30uM, 10uM, 1uM) or control. Triclosan immediately increased oxygen consumption rates dose-dependently, suggesting mitochondrial uncoupling. These results show that triclosan has the capacity to impair mitochondrial form and function in developing neural tissue.