Pharmacological Ischemic Conditioning with Roxadustat Does Not Affect Pain-Like Behaviors but Mitigates Sudomotor Impairment in a Murine Model of Deep Hind Paw Incision

Abstract

Fanglin Lu,1,2 Jungo Kato,2 Tomoko Toramaru,2 Mengting Zhang,1,2 Hiroshi Morisaki2 1Keio University Graduate School of Medicine Doctoral Programs, Tokyo, Japan; 2Department of Anesthesiology, Keio University School of Medicine, Tokyo, JapanCorrespondence: Jungo Kato, Department of Anesthesiology, Keio University School of Medicine, 35 Shinanoamchi, Shinjuku-ku, Tokyo, 160-8582, Japan, Tel [phone], Fax [phone], Email [email protected]: The involvement of hypoxic response mechanisms in local functional impairments in surgical wounds is unclear. In the present study, we characterized tissue hypoxia in surgical wounds and investigated the role of pharmacological ischemic conditioning (PIC) using roxadustat, an oral prolyl hydroxylase domain enzyme inhibitor, in postoperative local functional impairments in a murine model of deep hind paw incision.Methods: Male BALB/cAJcl mice aged 9– 13 weeks were used in all experiments. Plantar skins of mice that underwent surgical incision were subjected to immunohistochemistry to localise tissue hypoxia. Pain-like behaviours and sudomotor function were compared between mice treated with 6-week perioperative PIC and control mice. The effects of PIC were examined in vitro by immunocytochemistry using sympathetically differentiated PC12 cells and in vivo by immunohistochemistry using plantar skins collected on postoperative day 21.Results: Prominent tissue hypoxia was detected within axons in the nerve bundles underneath surgical wounds. Six-week perioperative PIC using roxadustat failed to ease spontaneous pain-like behaviors; however, it mitigated local sudomotor impairment postoperatively. Upregulation of sympathetic innervation to the eccrine glands was observed in the PIC-treated skins collected on postoperative day 21, in accordance with the in vitro study wherein roxadustat promoted neurite growth of sympathetically differentiated PC12 cells.Conclusion: This study suggests that tissue hypoxia is involved in the pathogenesis of local sudomotor dysfunction associated with surgical trauma. Targeting the hypoxic response mechanisms with PIC may be of therapeutic potential in postsurgical local sympathetic impairments that can be present in complex regional pain syndrome.Keywords: complex regional pain syndrome, hypoxic response mechanisms, postoperative pain, sudomotor dysfunction, sympathetic denervation

Keywords

• complex regional pain syndrome
• hypoxic response mechanisms
• postoperative pain
• sudomotor dysfunction
• sympathetic denervation.