Effect of transforming growth factor beta on the functional activity of human monocytes "in vitro" infected with Paracoccidioides brasiliensis

THESIS

Effect of transforming growth factor beta on the functional activity of human monocytes "in vitro" infected with Paracoccidioides brasiliensis

R. A. R. Martins

^{Correspondence to}

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

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

Publication Dates

• Publication in this collection
  22 Mar 2006
• Date of issue
  2006