title: Increased pain and neurogenic inflammation in mice deficient of neutral endopeptidase.
abstract: The complex regional pain syndrome (CRPS) is characterized by enhanced neurogenic inflammation, mediated by neuropeptides. Neutral endopeptidase (NEP) is a key enzyme in neuropeptide catabolism. We used NEP knock out (ko) mice to investigate whether NEP deficiency leads to increased pain behavior and signs of neurogenic inflammation after soft tissue trauma with and without nerve injury. After chronic constriction injury (CCI) of the right sciatic nerve, NEP ko mice were more sensitive to heat, to mechanical stimuli, and to cold than wild type mice. Tissue injury without nerve injury produced no differences between genotypes. After CCI, NEP ko mice showed increased hind paw edema but lower skin temperatures than wild type mice. Substance P (SP) and endothelin 1 (ET 1) determined by enzyme immuno assay (EIA) were increased in sciatic nerves from NEP ko mice after CCI. Tissue CGRP content did not differ between the genotypes. The results provide evidence that pain behavior and neurogenic inflammation are enhanced in NEP ko mice after nerve injury. These findings resemble human 'cold' CRPS and suggest that ET 1 plays an important role in the pathogenesis of CRPS with nerve injury.
authors.affiliation: Department of Neurology, Johannes Gutenberg University Mainz, Langenbeckstr. 1, Mainz 55101, Germany. hekr@neuro.gu.se
authors.forename: Heidrun H
authors.initials: HH
authors.lastname: Krämer
authors.forename: Lan
authors.initials: L
authors.lastname: He
authors.forename: Bao
authors.initials: B
authors.lastname: Lu
authors.forename: Frank
authors.initials: F
authors.lastname: Birklein
authors.forename: Claudia
authors.initials: C
authors.lastname: Sommer
mesh_terms: D000818:Animals; D003080:Cold Temperature; D004487:Edema; D019332:Endothelin-1 / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006614:Hindlimb / Q000473:pathology; D006358:Hot Temperature; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000378:metabolism; D015260:Neprilysin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020078:Neurogenic Inflammation / Q000378:metabolism*; D010146:Pain / Q000378:metabolism*; D010147:Pain Measurement; D010812:Physical Stimulation; D012584:Sciatic Nerve / Q000293:injuries / Q000378:metabolism; D012867:Skin / Q000378:metabolism; D012881:Skin Temperature / Q000502:physiology; D013373:Substance P / Q000378:metabolism
chemical_list: D019332:Endothelin-1; D013373:Substance P; D015260:Neprilysin