Mitochondrial Features of Mouse Myoblasts Are Finely Tuned by Low Doses of Ozone: The Evidence In Vitro

Abstract

The mild oxidative stress induced by low doses of gaseous ozone (O3) activates the antioxidant cell response through the nuclear factor erythroid 2-related factor 2 (Nrf2), thus inducing beneficial effects without cell damage. Mitochondria are sensitive to mild oxidative stress and represent a susceptible O3 target. In this in vitro study, we investigated the mitochondrial response to low O3 doses in the immortalized, non-tumoral muscle C2C12 cells; a multimodal approach including fluorescence microscopy, transmission electron microscopy and biochemistry was used. Results demonstrated that mitochondrial features are finely tuned by low O3 doses. The O3 concentration of 10 μg maintained normal levels of mitochondria-associated Nrf2, promoted the mitochondrial increase of size and cristae extension, reduced cellular reactive oxygen species (ROS) and prevented cell death. Conversely, in 20 μg O3-treated cells, where the association of Nrf2 with the mitochondria drastically dropped, mitochondria underwent more significant swelling, and ROS and cell death increased. This study, therefore, adds original evidence for the involvement of Nrf2 in the dose-dependent response to low O3 concentrations not only as an Antioxidant Response Elements (ARE) gene activator but also as a regulatory/protective factor of mitochondrial function.

Harmonizing Magnetic Mitohormetic Regenerative Strategies: Developmental Implications of a Calcium–Mitochondrial Axis Invoked by Magnetic Field Exposure

“…Survival-based mitohormetic adaptations improve resistance to oxidative stress, mitochondrial efficiency, and cell survival in association with the activation of the redox-sensitive transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2), and are particularly well described in muscle adaptations to exercise [32,92,[118][119][120][121]. Notably, the administration of ozone (O 3 ) to C2C12 mouse myoblasts produced both beneficial (increased Nrf2 and improved cell survival) and detrimental (reduced Nrf2 and diminished cell survival) mitohormetic responses, depending on dose [122]. This effect showed key genetic and developmental parallels to that produced by graded ELF-EMF exposure (Efficacy Window) in the same myoblast cell line [10], providing further evidence of the fundamental contribution that oxidative stress plays in the cellular adaptations to magnetic field exposure.…”

The Molecular Key to Understanding the Medical Ozone Action

“…Experimental models linked to the activation of the Nrf2 metabolic pathway are more frequently established in the literature [11][12][13], mainly linked to oxidative stress. Indeed, like other agents acting through pharmacological modulation [14], moderate oxidative stimulus comparable to the physiological "eustress" is also able to dissociate the Nrf2-Keap1 bond, thus activating a cascade of events responsible for several actions induced by the upregulation of thousands of genes [12,15].…”

“…Experimental models linked to the activation of the Nrf2 metabolic pathway are more frequently established in the literature [ 11 , 12 , 13 ], mainly linked to oxidative stress.…”