Changes of KEAP1/NRF2 and IKB/NF‐κB Expression Levels Induced by Cell‐Free DNA in Different Cell Types

Abstract

Cell-free DNA (cfDNA) is a circulating DNA of nuclear and mitochondrial origin mainly derived from dying cells. Recent studies have shown that cfDNA is a stress signaling DAMP (damage-associated molecular pattern) molecule. We report here that the expression profiles of cfDNA-induced factors NRF2 and NF-κB are distinct depending on the target cell's type and the GC-content and oxidation rate of the cfDNA. Stem cells (MSC) have shown higher expression of NRF2 without inflammation in response to cfDNA. In contrast, inflammatory response launched by NF-κB was dominant in differentiated cells HUVEC, MCF7, and fibroblasts, with a possibility of transition to massive apoptosis. In each cell type examined, the response for oxidized cfDNA was more acute with higher peak intensity and faster resolution than that for nonoxidized cfDNA. GC-rich nonoxidized cfDNA evoked a weaker and prolonged response with proinflammatory component (NF-κB) as predominant. The exploration of apoptosis rates after adding cfDNA showed that cfDNA with moderately increased GC-content and lightly oxidized DNA promoted cell survival in a hormetic manner. Novel potential therapeutic approaches are proposed, which depend on the current cfDNA content: either preconditioning with low doses of cfDNA before a planned adverse impact or eliminating (binding, etc.) cfDNA when its content has already become high.

The Role of NADPH Oxidases and Oxidative Stress in Neurodegenerative Disorders

“…Once activated, they relay the stress signals to induce apoptosis, stress resistance, or senescence [55,56]. Activation of NF-κB via oxidation-induced degradation of the inhibitory subunit IκB results in the activation of several antioxidant defence-related genes such as Nrf2, HO-1 [57]. NF-κB also regulates the expression of genes regulating immune responses, such as IL-1β, IL-6, tumour necrosis factor-α (TNF-α), IL-8, and several adhesion molecules [50,58].…”

Oxidized cell-free DNA as a stress-signaling factor activating the chronic inflammatory process in patients with autism spectrum disorders

“…We showed earlier that model fragments of oxidized DNA has the property of penetrating cell's structures located close to the nuclear membrane, provoking activation of DNA sensors, and inducing a boost of gene expression of the NF-kB signaling pathway [41,42]. We proposed that ASD patient PBL response to oxidized DNA treatment is markedly differed from that of healthy controls.…”

“…Dying cells release damaged DNA, thus introducing oxidized DNA fragments in the cfDNA pool [38,39]. Oxidized cellular DNA can be a stress-signaling molecule, which activates the transcription factor NF-kB, resulting in the synthesis of pro-inflammatory cytokines and induction of inflammation [40][41][42]. Thus, cfDNA may be a link between the progression of oxidative stress and induction of the inflammatory process in ASD patients.…”

Oxidized Cell-Free DNA Role in the Antioxidant Defense Mechanisms under Stress

“…Сell-free DNA affects many body cells, increasing oxidative stress and activating proinflammatory cellular response [8, 13, 14]. Under oxidative stress, both nuclear and cfDNA undergo oxidative modification [7, 15–18].…”