DNA damage mediates changes in neuronal sensitivity induced by the inflammatory mediators, MCP-1 and LPS, and can be reversed by enhancing the DNA repair function of APE1

Abstract

Although inflammation-induced peripheral sensitization oftentimes resolves as an injury heals, this sensitization can be pathologically maintained and contribute to chronic inflammatory pain. Numerous inflammatory mediators increase the production of reactive oxygen (ROS) and nitrogen species (RNS) during inflammation and in animal models of chronic neuropathic pain. Our previous studies demonstrate that ROS/RNS and subsequent DNA damage mediate changes in neuronal sensitivity induced by anticancer drugs and by ionizing radiation in sensory neurons, thus we investigated whether inflammation and inflammatory mediators also could cause DNA damage in sensory neurons and whether that DNA damage alters neuronal sensitivity. DNA damage was assessed by pH2A.X expression and the release of the neuropeptide, calcitonin gene-related peptide (CGRP), was measured as an index of neuronal sensitivity. Peripheral inflammation or exposure of cultured sensory neurons to the inflammatory mediators, LPS and MCP-1, elicited DNA damage. Moreover, exposure of sensory neuronal cultures to LPS or MCP-1 resulted in changes in the stimulated release of CGRP, without altering resting release or CGRP content. Genetically enhancing the expression of the DNA repair enzyme, apurinic/apyrimidinic endonuclease (APE1) or treatment with a small-molecule modulator of APE1 DNA repair activity, both which enhance DNA repair, attenuated DNA damage and the changes in neuronal sensitivity elicited by LPS or MCP-1. In conclusion, our studies demonstrate that inflammation or exposure to inflammatory mediators elicits DNA damage in sensory neurons. By enhancing DNA repair, we demonstrate that this DNA damage mediates the alteration of neuronal function induced by inflammatory mediators in peptidergic sensory neurons.

Inhibition of APE1/Ref-1 Redox Signaling Alleviates Intestinal Dysfunction and Damage to Myenteric Neurons in a Mouse Model of Spontaneous Chronic Colitis

“…APX3330 has the unique ability to suppress inflammation and chemotherapy-induced enhanced redox signalling activity of APE1/Ref-1 while providing neuroprotection in dorsal root ganglion neurons through an increase in oxidative DNA damage repair (Fehrenbacher et al 2017;Kelley et al 2016;Kim and Chang 2014;Kim et al 2015).…”

“…APX3330 treatment alleviated loss of myenteric neurons, improved nerve fibre and GFAP immunoreactivity in the myenteric ganglia when compared to Winnie shamtreated mice. APX3330 has been proven to be neuroprotective in sensory neurons after insults caused by ionizing radiation, cheotherapeutic agents and inflammatory stimuli all producing oxidative DNA damage acted upon by APE1/Ref-1 (Fehrenbacher et al 2017;Jiang et al 2009;Kelley et al 2014;Kim et al 2015;Vasko et al 2011).…”

“…Thus, APE1/Ref-1 is involved in the pathophysiology of GI inflammation. Furthermore, APE1/Ref-1 endonuclease activity protects dorsal root ganglion (DRG) neurons from inflammation and chemotherapy induced oxidative stress and DNA damage (Fehrenbacher et al 2017;Kelley and Fehrenbacher 2017).…”

APE1/Ref-1 as a Novel Target for Retinal Diseases

“…This could offer an unexpected further benefit in DR and AMD if confirmed in retinal neurons, which are damaged in these diseases. Neuronal protection by APX3330 has been observed in dorsal root ganglion (DRG) and myenteric neurons [30][31][32][33]. While APX3330 is a targeted inhibitor of Ref-1's redox function, additional data indicate that in the setting of neurons it can also enhance the DNA repair (Apurinic/ Apyrimidinic [AP] endonuclease) activity of Ref-1, a major step in DNA base excision repair (BER).…”

APE1 Upregulates MMP-14 via Redox-Sensitive ARF6-Mediated Recycling to Promote Cell Invasion of Esophageal Adenocarcinoma

“…E3330 (APE1 redox-specific inhibitor) was purchased from Novus Biologicals, and APE1-i3 (APE1 DNA repair-specific inhibitor) was purchased from Milli-poreSigma. The usage of inhibitors were following pharmacologic studies with recommended doses for the E3330 (25)(26)(27) and APE1-i3 (28). Transfection reagents (Polyjet and Lipojet) were obtained from SignaGen Laboratories.…”