Role of NFκB in an Animal Model of Complex Regional Pain Syndrome–type I (CRPS-I)

Abstract 

NFκB is involved in several pathogenic mechanisms that are believed to underlie the complex regional pain syndrome (CRPS), including ischemia, inflammation and sensitization. Chronic postischemia pain (CPIP) has been developed as an animal model that mimics the symptoms of CRPS-I. The possible involvement of NFκB in CRPS-I was studied using CPIP rats. Under sodium pentobarbital anesthesia, a tourniquet was placed around the rat left ankle joint, producing 3 hours of ischemia, followed by rapid reperfusion (IR injury). NFκB was measured in nuclear extracts of muscle and spinal cord tissue using ELISA. Moreover, the anti-allodynic (mechanical and cold) effect was tested for systemic, intrathecal, or intraplantar treatment with the NFκB inhibitor pyrrolidine dithiocarbamate (PDTC). At 2 and 48 hours after IR injury, NFκB was elevated in muscle and spinal cord of CPIP rats compared to shams. At 7 days, NFκB levels were normalized in muscle, but still elevated in spinal cord tissue. Systemic PDTC treatment relieved mechanical and cold allodynia in a dose-dependent manner, lasting for at least 3 hours. Intrathecal—but not intraplantar—administration also relieved mechanical allodynia. The results suggest that muscle and spinal NFκB plays a role in the pathogenesis of CPIP and potentially of human CRPS.

Perspective

Using the CPIP model, we demonstrate that NFκB is involved in the development of allodynia after a physical injury (ischemia and reperfusion) without direct nerve trauma. Since CPIP animals exhibit many features of human CRPS-I, this observation indicates a potential role for NFκB in human CRPS.

Key words: Chronic postischemia pain, CPIP, pyrrolidine dithiocarbamate, PDTC, ischemia, reperfusion, inflammation, neuropathic pain