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Carboxyamidotriazole (CAI) has not only direct anti-cancer activities, but also anti-inflammation effects in a variety of inflammatory animal models. In the present study, we investigated whether macrophages, which are important both in cancer and inflammation, could be regulated by CAI. The results showed that CAI could inhibit tumour necrosis factor-α (TNF-α) production in macrophages in various environments, including those isolated from peritoneal cavity of adjuvant-induced arthritis (AA) rats, from Lewis lung carcinoma (LLC) transplanted tumours and those induced by LLC cells in vitro. Dexamethasone (DEX), one of the pro-inflammatory cytokines inhibitors, could enhance CAI's inhibition of LLC cells proliferation and invasion in macrophages and LLC cells co-culture systems, as well as the tumour growth in vivo. However, DEX failed to enhance CAI's inhibition of LLC cells proliferation when LLC cells were cultured alone, suggesting that the combination of CAI and DEX exerted great anti-tumour effects probably by acting on macrophages in the tumour environment. Over all, we found CAI could act on macrophages and regulate the production of TNF-α not only in inflammatory diseases but also in tumour microenvironment, which might be another anti-tumour mechanism of CAI., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Carboxyamidotriazole (CAI), originally developed as a non-cytotoxic anti-cancer drug, was shown to have anti-inflammatory activity according to recent studies in a number of animal models of inflammation. However, its mechanism of action has not been characterized. Therefore, the present study was performed to identify the anti-inflammatory action of CAI in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages and to identify the signal transduction pathways involved. The in vitro results revealed that CAI had no direct effect on the activity of cyclooxygenase (COX), suggesting a different anti-inflammatory mechanism compared with that of COX-inhibiting non-steroidal anti-inflammatory drugs. Further investigation in RAW264.7 macrophages revealed that CAI decreased the production of nitric oxide via decreasing the LPS-stimulated expression of inducible nitric oxide synthase, and downregulated both mRNA and protein expression levels of the cytokines tumor necrosis factor-α, interleukin (IL)-1β, and IL-6. CAI also significantly reduced the increased DNA-binding activity of nuclear factor (NF)-κB induced by LPS stimulation. With respect to the mechanisms involved on NF-κB activity, CAI exhibited suppression of the phosphorylation and degradation of the inhibitor of nuclear factor-κBα (IκB), and decreased the phosphorylation levels of the p65 subunit and its subsequent nuclear translocation. In addition, CAI significantly decreased the phosphorylated forms of p38, JNK and ERK, which were increased following LPS stimulation, while the total expression levels of p38, JNK and ERK remained unaltered. The results in the present study indicate that CAI alleviates the inflammatory responses of RAW 264.7 macrophages in response to LPS stimulation via attenuating the activation of NF-κB and MAPK signaling pathways and decreasing the levels of pro-inflammatory mediators. This offers a novel perspective for understanding the anti-inflammatory mechanism of CAI and suggests its potential use as a therapeutic treatment in inflammatory diseases with excessive macrophage activation. [ABSTRACT FROM AUTHOR]