Nrf2 Signaling in Sodium Azide-Treated Oligodendrocytes Restores Mitochondrial Functions

Abstract

Mitochondrial dysfunctions mark a critical step in many central nervous system (CNS) pathologies, including multiple sclerosis (MS). Such dysfunctions lead to depolarization of mitochondrial membranes and imbalanced redox homeostasis. In this context, reactive oxygen species (ROS) are potentially deleterious but can also act as an important signaling step for cellular maintenance. The transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2), the key regulator in the cellular oxidative stress-response, induces a battery of genes involved in repair and regeneration. Here, we investigated the relevance of Nrf2 signaling for the prevention of cellular damage caused by dysfunctional mitochondria. We employed sodium azide (SA) as mitochondrial inhibitor on oligodendroglial OliNeu cells in vitro, and the cuprizone model with wild type and GFAP-Cre::Keap1 mice to induce mitochondrial defects. The importance of Nrf2 for cellular functions and survival after SA treatment was elucidated by in vitro knockdown experiments with shRNA directed against Nrf2 and its inhibitor Keap1 as well as by methysticin treatment. Metabolic activity, cytotoxicity, and depolarization of the mitochondrial membrane were analyzed after SA treatment. The expression of Nrf2 target genes as well as endoplasmic reticulum stress response genes was additionally measured by real-time PCR (in vitro) and PCR gene arrays (in vivo). Treatment of OliNeu cells with SA resulted in significant depolarization of the mitochondrial membrane, decreased metabolic activity, and increased cytotoxicity. This was partly counteracted in Nrf2-hyperactivated cells and intensified in Nrf2-knockdown cells. Our studies demonstrate a key role of Nrf2 in maintaining cellular functions and survival in the context of mitochondrial dysfunction.

Oxidative stress and impaired oligodendrocyte precursor cell differentiation in neurological disorders

“…Complex IV inhibition by sublethal doses of sodium azide briefly prior to or throughout OPC differentiation substantially impaired the formation of complex oligodendrocyte processes [ 64 ]. The adverse effect of sodium azide on the mitochondria was intensified in Nrf2-knockdown cells and partly counteracted in Nrf2-hyperactivated (via Keap1 knockdown) cells, implying the importance of antioxidant defence [ 232 ]. In addition, homozygous deletion of succinate dehydrogenase subunit D, an important component of both the citric acid cycle and ETC complex II, hindered neuronal and oligodendrocyte (but not astrocyte) differentiation causing brain atrophy [ 233 ].…”

Lemon‐Derived Extracellular Vesicles Nanodrugs Enable to Efficiently Overcome Cancer Multidrug Resistance by Endocytosis‐Triggered Energy Dissipation and Energy Production Reduction

“…Sodium azide (NaN 3 ) is an inhibitor of cytochrome c oxidase related to the oxidative respiratory chain, and low temperature enables to lead to a decrease in enzyme activity, both of which can reduce the production of ATP. [31][32][33][34] Thus, we first examined the role of energy in the cellular uptake of EVs-based nanodrugs (EVs, HRE, ED, and HRED) in SKOV3/DOX cells by treating with 4 °C or mitochondrial inhibitor NaN 3 . As expected, the results indicated that when SKOV3/DOX cells were incubated at 4 °C or treated with mitochondrial inhibitor NaN 3 , the internalization capacity of PKH67-EVs, PKH67-HRE, ED, and HRED were dramatically reduced, suggesting that the intracellular uptakes of EVs-based nanodrugs (EVs, HRE, ED, and HRED) were energy dissipation process (Figure 5d).…”

Nrf2/ARE Signaling Directly Regulates SOX9 to Potentially Alter Age-Dependent Cartilage Degeneration

“…Further, a successful, direct pharmacological activation of Nrf2 target genes by methysticin has already been shown in vitro and in vivo in another context [ 24 , 25 ]. Interestingly, Cao et al [ 26 ] reported that cyanidin-induced Nrf2 overexpression reduced the relative mRNA expression of Sox9 and Col II in the murine embryonic mesenchymal progenitor cell line C3H10T1/2.…”