Mediators involved in the febrile response induced by RANTES

Author(s)

Renes de Resende Machado

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC)
• Defense date: 2009-02-12

Examining board members

Gloria Emilia Petto de Souza; Marcia Eliana da Silva Ferreira; Cristoforo Scavone; Yara Maria Lucisano Valim; Dario Simões Zamboni

• Advisor: Gloria Emilia Petto de Souza

Abstract

We showed before that Met-RANTES, CCR1 and CCR5 receptor antagonist, intravenously injected (i.v.) reduced fever induced by lipopolysaccharide (LPS, E. coli), demonstrating the involvement of RANTES (Regulated on activation, normal T cells expressed and secreted) in this response. Also, intrahypothalamic (i.h.) injection of RANTES dose-dependently increased body temperature of rats, this increase was characterized as fever, because it was accompanied of a reduction in the tail skin temperature, a thermoregulatory response for heat retention. We also verified that RANTES increased the concentration of prostaglandin (PG)E2 in the cerebrospinal fluid (CSF), which was sensible to non-selective and selective blockers to cyclooxygenase (COX)-2 (Machado et al., 2007). In the present study, it was investigated which others mediators, including prostaglandins, are involved in the RANTES-induced fever. The effect of paracetamol and sodium diclofenac on fever induced by RANTES was also investigated. Paracetamol reduced, while sodium diclofenac abolished the RANTES-induced fever. The intrahypothalamic (i.h.) RANTES injection promoted a significant COX-2 mRNA expression in the hypothalamus, confirming the role of the COX-2 enzyme in the synthesis of prostaglandin involved in the pyrogenic effect of this chemokine. Through administration of dye in situ and histological analyses, we confirmed that the injection in the preoptic area of the anterior hypothalamus (AH/POA) was correct. Subsequently, we evaluated the effect of different doses of Met-RANTES (i.h.) in the fever induced by both LPS and RANTES. Centrally injected, Met-RANTES did not modify the fever induced by LPS or RANTES. On the other hand, Met-RANTES (i.v.) reduced TNF-alpha-induced fever, but did not modify the fever induced by interleukin (IL)-6, corticotrophin releasing factor (CRF) and bradykinin (BK). Additionally, the injection of LPS (i.v.) or TNF-alpha (i.h.) increased RANTES concentration in the hypothalamus. Antalarmin (a CRF receptor 1 antagonist) and alpha-helical CRF9-41 (CRF 1 and 2 receptor antagonist) that reduced CRF-induced fever did not modify the fever induced by RANTES (i.h.). DALBK (bradykinin B1 receptor antagonist) that reduced the second phase of BK-induced fever did not modify RANTES-induced fever. In the same way, Hoe-140 (bradykinin B2 receptor antagonist) that reduced the fever induced by BK during the whole period of observation, did not modify RANTES-induced fever. On the other hand, we verified that anti-rat IL-6 antibody (i.h.) reduced the fever induced by both IL-6 and RANTES. In addition, the administration of LPS (i.v.) or RANTES (i.h.) increased the CSF IL-6 concentration, but not of IL-1 and TNF-. RANTES promoted nuclear factor-kB (NF-kB) activation and increased IL-1beta, TNF-alpha and IL-6 mRNA expression in the hypothalamus. Pretreatment of the animals with Met-RANTES reduced the LPS-induced neutrophilia. In synthesis, our results suggest that in the fever induced by LPS, RANTES induces TNF- synthesis, which promotes the synthesis of RANTES that, activating CCR1/CCR5 receptors, promotes NF-kB transmigration of cytoplasm to the nucleus and subsequent synthesis of IL-6 and COX-2. The latter, in turn, is responsible by (PGE2) synthesis, one of the final mediators of the febrile response induced by LPS. Moreover, RANTES seem to be a mediator of the acute phase response since it promoted two important signs of this response, fever and neutrophilia. (AU)