The Bacterial Toxin CNF1 Protects Human Neuroblastoma SH-SY5Y Cells against 6-Hydroxydopamine-Induced Cell Damage: The Hypothesis of CNF1-Promoted Autophagy as an Antioxidant Strategy

Abstract

Several chronic neuroinflammatory diseases, including Parkinson’s disease (PD), have the so-called ‘redox imbalance’ in common, a dynamic system modulated by various factors. Among them, alteration of the mitochondrial functionality can cause overproduction of reactive oxygen species (ROS) with the consequent induction of oxidative DNA damage and apoptosis. Considering the failure of clinical trials with drugs that eliminate ROS directly, research currently focuses on approaches that counteract redox imbalance, thus restoring normal physiology in a neuroinflammatory condition. Herein, we used SH-SY5Y cells treated with 6-hydroxydopamine (6-OHDA), a neurotoxin broadly employed to generate experimental models of PD. Cells were pre-treated with the Rho-modulating Escherichia coli cytotoxic necrotizing factor 1 (CNF1), before the addition of 6-OHDA. Then, cell viability, mitochondrial morphology and dynamics, redox profile as well as autophagic markers expression were assessed. We found that CNF1 preserves cell viability and counteracts oxidative stress induced by 6-OHDA. These effects are accompanied by modulation of the mitochondrial network and an increase in macroautophagic markers. Our results confirm the Rho GTPases as suitable pharmacological targets to counteract neuroinflammatory diseases and evidence the potentiality of CNF1, whose beneficial effects on pathological animal models have been already proven to act against oxidative stress through an autophagic strategy.

Pharmacological Modulators of Small GTPases of Rho Family in Neurodegenerative Diseases

“…Structurally, CNF1 acts by deamidating Rho GTPases on a specific glutamine residue inside the GTP-binding domain, which then blocks the molecule in their activated GTP-bound state. This allows CNF1 to modulate the actin cytoskeleton (Travaglione et al, 2020 ). Furthermore, CNF1 has been proven to stimulate an increase of cell energy production in mouse models of PD, as well as AD, epilepsy, and Rett syndrome (Travaglione et al, 2020 ).…”

“…This allows CNF1 to modulate the actin cytoskeleton (Travaglione et al, 2020 ). Furthermore, CNF1 has been proven to stimulate an increase of cell energy production in mouse models of PD, as well as AD, epilepsy, and Rett syndrome (Travaglione et al, 2020 ).…”

Effects of the Escherichia coli Bacterial Toxin Cytotoxic Necrotizing Factor 1 on Different Human and Animal Cells: A Systematic Review

“…Indeed, in IEC-6 and SH-SY5Y cells a significant increase in the phospho-Drp1 protein was observed (IEC-6 [81]; SH-SY5Y [29]).…”

“…The effect of CNF1 on mitochondrial activity has been analyzed in seven cell lines (BL6-10 [64]; HEp-2 [47,51,58,96]; T24 [25]; SH-SYS5 [29]; IEC-6 [81]; human fibroblasts MERRF [84]). Overall, CNF1 seems to affect mitochondrial metabolism by stimulating an increase in ATP synthesis (IEC-6 [81]; human fibroblasts MERRF [84]) and counteracting the negative effects produced on these organelles under particular experimental or pathological conditions [29,64,84].…”

“…The effect of CNF1 on mitochondrial activity has been analyzed in seven cell lines (BL6-10 [64]; HEp-2 [47,51,58,96]; T24 [25]; SH-SYS5 [29]; IEC-6 [81]; human fibroblasts MERRF [84]). Overall, CNF1 seems to affect mitochondrial metabolism by stimulating an increase in ATP synthesis (IEC-6 [81]; human fibroblasts MERRF [84]) and counteracting the negative effects produced on these organelles under particular experimental or pathological conditions [29,64,84]. In four of the above-mentioned cell lines (SH-SY5Y, HEp-2, IEC-6, human fibroblasts MERRF), metabolic stimulation was accompanied by a prominent modification in the mitochondrial morphology, consisting of the formation of a complex network of elongated organelles (Figure 2B).…”