title: NOX4 is an early initiator of neuropathic pain.
abstract: Treatment of neuropathic pain remains challenging as the etiology is heterogeneous and pathomechanisms are incompletely understood. One possible mechanism is oxidative stress due to unphysiological reactive oxygen species (ROS) formation. The only know dedicated enzymatic source of ROS are NADPH oxidases of which the type 4 isoform (NOX4) has been suggested to be involved in the subacute and chronic phase of neuropathic pain. Here, we aim to translate this finding into a treatment strategy by examining the efficacy of the NOX1/4-specific inhibitor GKT136901 using the chronic constriction injury (CCI) mouse model of neuropathic pain. Unexpectedly, post-nerve lesion treatment using GKT136901 was ineffective to reduce pain-related behavior after CCI. We therefore re-investigated the role of NOX4 using an independent KO mouse model. Early after CCI we found an increase in pro-inflammatory cytokines, ROS formation and the oxidative stress marker nitrotyrosine in the lesioned nerve together with an upregulated Nox4 gene expression. In NOX4 KO mice, mechanical allodynia was markedly reduced from day 4 after nerve injury as were all ROS related and acute biomarkers. In addition, we observed a reduction in the CCI-induced upregulation of pro-inflammatory cytokines in the sciatic nerve and dorsal root ganglia along with NOX4-deficiency. Thus, we conclude that NOX4 is involved in the development of neuropathic pain states by producing oxidative stress and subsequent cytokine dysregulation at the lesion site. This appears at very early stages immediately after nerve injury explaining ineffectiveness of post-acute pharmacological NOX inhibition. We suggest that future target validation of NOX4 should now focus on defining the possible therapeutic window in human neuropathic pain.
authors.affiliation: Hans-Berger Department of Neurology and Center of Sepsis Control and Care, Jena University Hospital, Erlanger Allee 101, 07747 Jena, Germany; Department of Neurology, University Hospital Würzburg, Josef-Schneider Straße 11, 97080 Würzburg, Germany. Electronic address: christian.geis@med.uni-jena.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Geis
authors.affiliation: Department of Neurology, University Hospital Würzburg, Josef-Schneider Straße 11, 97080 Würzburg, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Geuss
authors.affiliation: Hans-Berger Department of Neurology and Center of Sepsis Control and Care, Jena University Hospital, Erlanger Allee 101, 07747 Jena, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Sommer
authors.affiliation: Department for Pharmacology, Cardiovascular Research Institute, Maastricht University, (CARIM), PO Box 616, Maastricht, 6200 MD, The Netherlands.
authors.forename: Harald H H W
authors.initials: HH
authors.lastname: Schmidt
authors.affiliation: Department of Neurology, University Hospital Würzburg, Josef-Schneider Straße 11, 97080 Würzburg, Germany; Department of Neurology, University Hospital Essen, Hufelandstraße 55, 45147 Essen, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Kleinschnitz
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000235:genetics; D006930:Hyperalgesia / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D009437:Neuralgia / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology*; D010147:Pain Measurement; D011720:Pyrazoles / Q000627:therapeutic use; D011728:Pyridones / Q000627:therapeutic use; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012584:Sciatic Nerve / Q000473:pathology
chemical_list: C554850:2-(2-chlorophenyl)-4-methyl-5-(pyridin-2-ylmethyl)-1H-pyrazolo(4,3-c)pyridine-3,6(2H,5H)-dione; D016207:Cytokines; D011720:Pyrazoles; D011728:Pyridones; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C422943:Nox4 protein, mouse
keywords: Chronic constriction injury; GKT136901; NOX4; Neuropathic pain