Cytokine Profile Produced from LPS-stimulated Mcrophage-Adipocyte Co-cultures

Objectives: Chronic low-grade inflammatory conditions such as periodontal disease have been suggested to associate with insulin resistance as well as vascular disorders such as atherosclerosis. Therefore, it is essential to understand as to why such local low-grade inflammation is intensified to the level of influencing systemic conditions. Recent studies suggested circulating macrophages are integrated in adipose tissues, interacting with adipocytes, thereby exacerbating inflammatory responses. We recently reported co-cultures of macrophages and adipocytes markedly enhanced IL-6 and MCP-1 production as compared with independent cultures when stimulated with low concentration of LPS (Yamashita et al., Obesity, 2007). Therefore, it is interesting to see the production of other cytokine and/or biologically active molecules from co-cultures stimulated with LPS. The aim of this study is to detect molecules whose production was markedly enhanced by co-cultures stimulated with LPS.

Methods: RAW264.7 mouse macrophage cell line and differentiated 3T3-L1 mouse preadipocytes were co-cultured by using Transwell^® Culture System as our previous publication. After incubation of the cells with or without E. coli LPS (1 ng/ml) for 24 h, cytokines produced in culture supernatants were screened by using a cytokine array (Ray Biotech, Inc), and quantified by ELISA.

Results: 1) Cytokine array analyses revealed that, besides IL-6 and MCP-1, co-culture of macrophage and adipocyte with low concentration of LPS markedly up-regulated RANTES and KC production. 2) The amounts of RANTES and KC production by co-cultures were over 6- and 4-fold higher than those of independent cultures.

Conclusion: Enhanced RANTES production is associated with the recruitment of T-cells into adipose tissues, while enhanced KC production with angiogenesis, both of which are typical features of mature adipose tissues. These results suggest that macrophages activated by low-grade infections such as periodontitis are involved in the patho-physiology of obesity-associated disorders such as metabolic syndrome.