Hyperalgesia and upregulation of cytokines and nerve growth factor by cutaneous leishmaniasis in mice Salim A. Kanaan a , Nayef E. Saade  b,c, * , Mark Karam a , Hala Khansa d , Suhayl J. Jabbur c , Abdo R. Jurjus b a Department of Biology, Faculty of Arts and Sciences, American University of Beirut, Beirut, Lebanon b Department of Human Morphology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon c Department of Physiology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon d Faculty of Health Sciences, Lebanese University, Beirut, Lebanon Received 27 July 1999; accepted 24 November 1999 Abstract Classical description of syndromes produced by cutaneous leishmaniasis (CL) does not include sensory manifestations such as pain and/or itching, despite the evident upregulation of proin¯ammatory cytokines. Using a murine model of CL we report on evident hyperalgesia, as assessed by acute pain tests, and sustained upregulation of interleukin (IL-1b ) and nerve growth factor (NGF). This upregulation, especially that of NGF, may explain the observed hyperalgesia, in the light of recent evidence on the role of cytokines in the sensitization of nerve afferents and the subsequent hyperalgesia. q 2000 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved. Keywords: Cutaneous leishmaniasis; Hyperalgesia; Nerve growth factor; Interleukin 1b ; Cytokines 1. Introduction Classical description of cutaneous leishmaniasis (CL) due to Leishmania major includes the following: (a) after an incubation period of 1 week to 3 months, a red papule appears and enlarges to a plaque or a nodule; (b) the lesion often develops into an ulcer; and (c) painless, rubbery and subcutaneous nodules or cords may develop around the ulcer (refer to review by Grevelink and Lerner, 1996). In contrast to lepromatous leprosy, nerve involvement in CL has been considered not to occur (Magill, 1995). No pain or itching are usually observed or reported by the patients, since peripheral neural involvement has been regarded as unique to leprosy (Kubba et al., 1987). It is also well known that this parasitic disease upregu- lates the levels of the cytokines including interleukins (IL)- 1b , 2, 3, and 10, interferon g and tumor necrosis factor alpha (TNF-a ), (for review, see Liew and O'Donnell, 1993; Bogdan and Ro Èllinghoff, 1998). In addition to their involvement in immunoregulations, some of these cytokines (especially IL-1b and TNF-a ) can produce hyperalgesia (Dray, 1994) and illness-related behavior (Watkins et al., 1994). Pain and hyperalgesia, however, are not included in the classical description of CL syndromes. In the present study, we report on evidence for nocicep- tive behavior and upregulation of IL-1b and nerve growth factor (NGF) in a model of CL induced by Leishmania major in BALB/c mice. 2. Methods All experiments were performed on female BALB/c mice (20±30 g), housed in groups of ®ve per cage under standard colony conditions (12/12-h dark/light cycle, temperature 22 ^ 28C) with free access to food and water. Pain tests and surgical procedures were carried out with strict adher- ence to the ethical guidelines for the study of experimental pain in conscious animals (Zimmerman, 1983). This study is based on the results obtained from 12 groups (n  5±6 each) of mice distributed as follows: eight groups, injected with Leishmania promastigotes, were used either for the behavioral pain tests (two groups) or the determina- tion of cytokine levels (six groups); four groups, injected with saline or liquid culture-medium (overlay) were used as Pain 85 (2000) 477±482 0304-3959/00/$20.00 q 2000 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved. PII: S0304-3959(99)00297-3 www.elsevier.nl/locate/pain * Corresponding author. Department of Human Morphology, Faculty of Medicine, American University of Beirut, P.O. Box 1-0236/41, Beirut, Lebanon. Tel.: 1961-1-350-000 ext. 4754; fax: 1961-1-744-464. E-mail address: nesaade@aub.edu.lb (N.E. Saade Â)