Recombinant guinea pig CCL5 (RANTES) differentially modulates cytokine production in alveolar and peritoneal macrophages

The CC chemokine ligand 5 (CCL5; regulated on activation, normal T expressed and secreted) is known to recruit and activate leukocytes; however, its role in altering the responses of host cells to a subsequent encounter with a microbial pathogen has rarely been studied. Recombinant guinea pig (rgp)CCL5 was prepared, and its influence on peritoneal and alveolar macrophage activation was examined by measuring cytokine and chemokine mRNA expression in cells stimulated with rgpCCL5 alone or exposed to rgpCCL5 prior to lipopolysaccharide (LPS) stimulation. Levels of mRNA for guinea pig tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1beta, CCL2 (monocyte chemoattractant protein-1), and CXC chemokine ligand 8 (IL-8) were analyzed by reverse transcription followed by real-time polymerase chain reaction analysis using SYBR Green. Bioactive TNF-alpha protein concentration was measured using the L929 bioassay. Both macrophage populations displayed significant enhancement of all the genes and TNF-alpha protein levels when stimulated with rgpCCL5, except for CCL2 in alveolar macrophages. When peritoneal or alveolar macrophages were pretreated with rgpCCL5 for 2 h and then exposed to low concentrations of LPS, diminished cytokine and chemokine mRNA levels were apparent at 6 h compared with LPS alone. At the protein level, there was a reduction in TNF-alpha protein at 6 h in the CCL5-pretreated cells compared with LPS alone. These results further support a role for CCL5 in macrophage activation in addition to chemotactic properties and suggest a role in regulating the inflammatory response to LPS in the guinea pig by modulating the production of proinflammatory cytokines by macrophages.