Oxidized galectin-1 reduces lipopolysaccharide-induced increase of proinflammatory cytokine mRNA in cultured macrophages
Yukie Kogawa1, Kou Nakajima1, Kenichi Sasaguri1, Nobushiro Hamada2, Haruhisa Kawasaki3, Sadao Sato1, Toshihiko Kadoya4, Hidenori Horie5
1Department of Orthodontics, 2Department of Oral Microbiology, Kanagawa Dental College, Yokosuka; 3Keio University, Kanagawa; 4Maebashi Institute of Technology, Maebashi; 5Research Center of Brain and Oral Science, Kanagawa Dental College, Yokosuka, Japan
Background: Periodontitis is prevalent in older humans. Limiting the inflammation associated with periodontitis may provide a therapy for this condition, because Gram-negative bacteria expressing lipopolysaccharide (LPS) have a key role in initiation of inflammation by activating macrophage functions. Because oxidized galectin-1 regulates macrophage functions in other systems, we sought to establish whether this galectin-1 mRNA is expressed in the oral cavity, and whether it could dampen LPS-induced macrophage activation in vitro.
Methods: Using the reverse transcriptase polymerase chain reaction (RT-PCR), we measured galectin-1 mRNA expression to clarify its localization to rat gingival tissues and studied the effect of Porphyromonas gingivalis challenge on galectin-1 expression. Next, we tested the effects of adding oxidized galectin-1 to cultured LPS-activated peritoneal macrophages on mRNA expression of proinflammatory factors by RT-PCR and real-time RT-PCR.
Results: We established that galectin-1 mRNA is expressed in gingival tissues and also showed that galectin-1 mRNA was significantly increased by challenge with P. gingivalis, indicating that galectin-1 may regulate oral inflammation. On the other hand, LPS 100 ng/mL in serum-containing medium induced macrophages to upregulate mRNA associated with a proinflammatory response, ie, interleukins 1β and 6, and inducible nitric oxide synthase. We showed that application of 0.1–10 ng/mL of oxidized galectin-1 to LPS-treated macrophages reduced the intense LPS-induced increase by serum in proinflammatory mRNA expression in a concentration-dependent manner. Furthermore, application of oxidized galectin-1 10 ng/mL to LPS-treated macrophages in serum-free medium also showed a similar effect on LPS activity.
Conclusion: Oxidized galectin-1 restricts the proinflammatory actions of LPS, and this protein could limit the negative effects of inflammation.
Keywords: periodontitis, inflammation, macrophage, lipopolysaccharide, galectin-1, proinflammatory factors