Received: July 1, 2005, Accepted: July 1, 2005, Published online: February 24, 2006.

EFFECT OF TRANSFORMING GROWTH FACTOR BETA ON THE FUNCTIONAL ACTIVITY OF HUMAN MONOCYTES “IN VITRO” INFECTED WITH Paracoccidioides brasiliensis

THESIS: R. A. R. Martins submitted this thesis for her Doctorate in Tropical Diseases at Botucatu School of Medicine, São Paulo State University, UNESP, Botucatu, São Paulo, Brazil, 2005.

Advisor: Professor Maria Terezinha Serrão Peraçoli

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ABSTRACT: Transforming Growth Factor-beta (TGF-b1) is a cytokine produced by cells such as macrophages and T cells having both pro- and anti-inflammatory properties depending on their environment and concentration. The aim of this study was to analyze the effect of TGF-b1 on the hydrogen peroxide (H2O2) release, Tumor Necrosis Factor-alpha (TNF-a) production, and fungicidal activity of human monocytes challenged with high-virulent strain of Paracoccidioides brasiliensis (Pb18). Peripheral blood monocytes from healthy individuals were preincubated with or without different concentrations (7.8 pg/ml to 500 pg/ml) of TGF-b1 for 24 h at 37ºC, and then challenged with Pb18 in a ratio of 50:1 monocyte:fungus. The release of H2O2 by monocytes in response to Phorbol Myristate Acetate (PMA) was evaluated during and after 4h of monocyte infection with the fungus. TNF-a production by these cells was determined in supernatant cultures by enzyme immunoassay (ELISA), and fungicidal activity of monocytes against Pb18 was assessed by viable fungi recovery from 4h co-culture in Blood Heart Infusion-Agar (BHI-Agar) and counting of colony-forming units after 10 days. The results showed that monocyte incubation with TGF-b1 concentrations (31.2 pg/ml to 500 pg/ml) suppressed H2O2 release in a dose-dependent manner. The Pb18 infection of monocytes pretreated with TGF-b1 maintained the inhibitory effect on the H2O2 production by these cells stimulated with PMA, even in low doses of TGF-b1, suggesting that Pb18 may also interfere with H2O2 production by monocytes. These cells challenged with Pb18 produced significantly higher levels of TNF-a in comparison to monocytes not infected. However this production was inhibited when these cells were previously cultured with high concentrations of TGF-b1. On the other hand, pretreatment of monocytes with high doses of this cytokine enhanced their fungicidal activity against P. brasiliensis. Together the results suggest that exogenous TGF-b1 can exert a dual modulatory effect on monocytes infected with P.brasiliensis, when used in high concentrations. The effects are stimulatory on fungicidal activity and inhibitory on H2O2 release and TNF-a production.

KEY WORDS: cytokines, human monocytes, P. brasiliensis

CORRESPONDENCE TO:

R. A. R. MARTINS, Rua Rafael Sampaio, 768, Boa Vista, 18601-080, Botucatu, SP, Brasil. Phone: 55 14 3815 7277. Email: rarmartins@laser.com.br