Nrf2 Induction Re-establishes a Proper Neuronal Differentiation Program in Friedreich’s Ataxia Neural Stem Cells

Abstract

Frataxin deficiency is the pathogenic cause of Friedreich’s Ataxia, an autosomal recessive disease characterized by the increase of oxidative stress and production of free radicals in the cell. Although the onset of the pathology occurs in the second decade of life, cognitive differences and defects in brain structure and functional activation are observed in patients, suggesting developmental defects to take place during fetal neurogenesis. Here, we describe impairments in proliferation, stemness potential and differentiation in neural stem cells (NSCs) isolated from the embryonic cortex of the Frataxin Knockin/Knockout mouse, a disease animal model whose slow-evolving phenotype makes it suitable to study pre-symptomatic defects that may manifest before the clinical onset. We demonstrate that enhancing the expression and activity of the antioxidant response master regulator Nrf2 ameliorates the phenotypic defects observed in NSCs, re-establishing a proper differentiation program.

Frataxin deficiency induces lipid accumulation and affects thermogenesis in brown adipose tissue

“…Along this line, we found a decrease of NRF2 and GPX4, altered expression of genes controlling iron metabolism and increased susceptibility to ferroptosis in brown adipocyte precursors, as well as in mature adipocytes isolated from KIKO mice. These results are in accordance with the findings pointing to oxidative stress, iron overload, and ferroptosis among the main pathogenic factors in FRDA 6,27,[53][54][55] . Interestingly, NRF2, besides being an up-stream modulator of the expression of antioxidant genes and protection against oxidative stress/ferroptosis 56,57 , positively regulates enzymes involved in mitochondrial oxidation of FAs 29 and adipogenesis 58,59 .…”

NRF2 as a Therapeutic Target in Neurodegenerative Diseases

“…A conditional frataxin knockout mouse line showed decreased NRF2 expression and increased KEAP1 expression (Anzovino et al, 2017) and in the mouse motor neuron cell line NSC-34, frataxin shRNA likewise reduced NRF2 expression and activity (Paupe et al, 2009). In contrast, inducing NRF2 with sulforaphane or the NRF2activating compound EPI-7443 in neural stem cells isolated from a Friedrich's ataxia mouse model was shown to reestablish proper differentiation which was previously impaired in those cells (La Rosa et al, 2019). In cultured motor neurons, sulforaphane also increased frataxin levels as well as neurite number and extension (Petrillo et al, 2017).…”

The NRF2 Signaling Network Defines Clinical Biomarkers and Therapeutic Opportunity in Friedreich’s Ataxia

“…The mechanism proposed in those studies highlighted an abnormal distribution of actin fibers causing a defective binding of the NRF2-KEAP1 complex and the failure of NRF2 nuclear translocation [58]. Beside this, defects in redox homeostasis and in the NRF2-dependent antioxidant response are reported in many other models of the disease, such as in the hearts of the muscle creatine kinase (MCK) conditional frataxin knockout mice [56], in dorsal root ganglia (DRG) neurons dissected from the YG8R mice [59] and in neural stem cells (NSCs) isolated from the knock-in knock-out (KIKO) FA mouse model [10]. These numerous reports strongly address therapeutic approaches aimed at re-establishing a functional NRF2 signaling in FA.…”

“…In line with this principle, as has been observed in other neurodegenerative diseases where oxidative stress is increased [76], in FA the frataxin deficiency-induced oxidative stress should stabilize NRF2 and induce an up-regulation of ARE-dependent gene transcription. Nevertheless, NRF2 signaling is impaired in several FA cells and animal models [10,36,[56][57][58][59]77]. The mechanisms underlying NRF2 deficiency in FA are still poorly understood, although, starting from the first decade of the 2000s some studies reported a reduced antioxidant defense as a consequence of frataxin depletion [78], while the over-expression of frataxinwas able to potentiate the antioxidant responses [79].…”

“…However, when this homeostasis cannot be maintained and oxidative stress (i.e., the pathologic condition caused by the imbalance between ROS production and antioxidant response) occurs, the cell reacts by upregulating the synthesis of specific antioxidants and enzymes, through the modulation of different transcriptional factors, whose master regulator is represented by NF-E2 p45-related factor 2 (NRF2) [5,6]. Beside its role in redox maintenance of homeostasis, NRF2 functions span multiple cellular processes, including survival, metabolic and protein homeostasis, inflammation, and regulation of cell proliferation/differentiation [7][8][9][10][11]. Thus, it is not surprising that the deregulation of NRF2 expression or activity has been found in many diseases in which oxidative stress represents a typical pathologic feature, including cancer [12], multiple sclerosis (MS) [9], Alzheimer's disease (AD) [13], Parkinson's disease (PD) [13], and amyotrophic lateral sclerosis (ASL) [14].…”