Regulation of LPS stimulated ROS production in peritoneal macrophages from alloxan-induced diabetic rats: Involvement of high glucose and PPARγ Luiz Fernando de Souza ⁎ , Fabiano Barreto, Evandro Gomes da Silva, Michael Everton Andrades, Eduardo Linck Machado Guimarães, Guilherme Antonio Behr, José Cláudio Fonseca Moreira, Elena Aida Bernard Departamento de Bioquímica, UFRGS, Porto Alegre, RS, Brazil Received 10 January 2007; accepted 27 April 2007 Abstract An increased occurrence of long term bacterial infections is common in diabetic patients. Bacterial cell wall components are described as the main antigenic agents from these microorganisms and high blood glucose levels are suggested to be involved in altered immune response. Hyperglycemia is reported to alter macrophages response to lipopolysaccharide (LPS) and peroxisome proliferators activated receptor gamma (PPARγ) expression. Additionally, glucose is the main metabolic fuel for reduced nicotinamide adenine dinucleotide phosphate (NADPH) production by pentose phosphate shunt. In this work, lipopolysaccharide (LPS) stimulated reactive oxygen species (ROS) and nitrite production were evaluated in peritoneal macrophages from alloxan-induced diabetic rats. Cytosolic dehydrogenases and PPARγ expression were also investigated. LPS was ineffective to stimulate ROS and nitrite production in peritoneal macrophages from diabetic rats, which presented increased glucose-6-phosphate dehydrogenase and malate dehydrogenase activity. In RAW 264.7 macrophages, acute high glucose treatment abolished LPS stimulated ROS production, with no effect on nitrite and dehydrogenase activities. Peritoneal macrophages from alloxan-treated rats presented reduced PPARγ expression. Treating RAW 264.7 macrophages with a PPARγ antagonist resulted in defective ROS production in response to LPS, however, stimulated nitrite production was unaltered. In conclusion, in the present study we have reported reduced nitric oxide and reactive oxygen species production in LPS-treated peritoneal macrophages from alloxan-induced diabetic rats. The reduced production of reactive oxygen species seems to be dependent on elevated glucose levels and reduced PPARγ expression. © 2007 Elsevier Inc. All rights reserved. Keywords: Lipopolysaccharide; Macrophages; Alloxan; Hyperglycemia; PPAR; ROS; Nitric oxide Introduction Diabetes is a prevalent metabolic disorder with several sec- ondary complications. An increased occurrence of long-term bacterial infections is common in diabetic patients, being a major complication in these individuals (Smitherman and Peacock, 1995). It was suggested that high blood glucose levels are involved in reduced bactericidal activity (Nielson and Hindson, 1989) and it has further been demonstrated that high glucose reduces interleukin 1 release from murine macrophages (Hill et al., 1998). Bacterial cell wall components are described as the main antigenic agents from these microorganisms (Van Amersfoort et al., 2003) and their recognition by Toll-like receptors (TLR) initiates cellular responses to bacterial infections (Takeuchi and Akira, 2001). Lipopolyssacharide (LPS) is a major constituent of the outer membrane of gram negative bacteria and is recognized by animals as a molecular correlate to infection. It binds to TLR 4, triggering multiple signaling cascades (Van Amersfoort et al., 2003; Takeuchi and Akira, 2001). Macrophages are key me- diators of innate immunity and their phagocytic activity in re- sponse to microbial infections and antigens produces and releases reactive oxygen species (ROS), as well as reactive nitrogen species (RNS). Both ROS and RNS have antimicrobial activity; moreover, they also act as cellular signaling molecules (Forman and Torres, 2001; Ferret et al., 2002). Additionally, exacerbated Life Sciences 81 (2007) 153 – 159 www.elsevier.com/locate/lifescie ⁎ Corresponding author. Rua Ramiro Barcelos, 2600, ANEXO, Porto Alegre, CEP 90035-003, RS, Brazil. Tel.: +55 51 33165547; fax: +55 51 33165540. E-mail address: lzfsouza@yahoo.com.br (L.F. de Souza). 0024-3205/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.lfs.2007.04.035