Limitations of this study include the use of HL

Limitations of this study include the use of HL-1 cardiomyocytes, which show different characteristics than primary cardiomyocytes [56]. Furthermore, sustained TAC in Ampkα1-deficient mice did not favorably influence cardiac function [33]. It must be kept in mind that global Ampkα1-deficiency may affect further functions indirectly influencing circulation and cardiac function, such as exaggerated eryptosis, anemia and splenomegaly [57]. Also Ampkα1 may exert important functions in cardiomyocytes besides regulation of AP-1.
Disclosures
Acknowledgements The authors gratefully acknowledge Dr. W.C. Claycomb for providing the HL-1 cardiomyocyte cell line and Dr. B. Viollet for providing the Ampkα1−/− mouse. The authors are grateful for the outstanding technical assistance of E. Faber and K. Streil and the meticulous preparation of the manuscript by T. Loch and A. Soleimanpour. This work was supported by grants from the Deutsche Forschungsgemeinschaft (La315/4-5 and SFB-Transregio 19), the German Cardiac Society (DGK Stipendium 2012) and the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement: 603288.
Introduction Inflammation is a protective response of organisms caused by pathogens or tissue damage, though the accumulation of immune Naproxen Sodium receptor like macrophages and microglia for eliminating harmful stimuli (Cameron and Landreth, 2010, Wynn and Vannella, 2016). However, excessive or abnormal inflammation has been proven harmful and may provoke various diseases, such as atherosclerosis, arthritis, obesity, and neurodegenerative diseases (Baker et al., 2011, Woo et al., 2015). The pathogenesis of inflammation associated with the activation of immunocytes is a complicated process. Excessive activation of macrophages and microglia triggered by LPS, a prototypical endotoxin, generates many pro-inflammatory mediators, including NO, ROS, IL-6 and TNF-a, which further aggravate the inflammation progress (Khan et al., 2017). Herein, suppression of macrophages and microglia-mediated inflammation may be a promising treatment strategy for various inflammatory diseases. Several TLR4-dependent intracellular signaling pathways like NF-κB, AP-1, PI3K/AKT and MAPKs have been reported for the regulation of inflammatory response in LPS-induced inflammatory models. The specific blockage of NF-κB activation can suppress the production of inflammatory mediators upon LPS stimuli (Chantong et al., 2012). On the other hand, HO-1 which may be modulated by the activation of MAPK-mediated Nrf2 signaling, has been demonstrated the pivotal role in inhibiting of the overproduction of pro-inflammatory cytokines as well as ROS in inflammatory response (Khan et al., 2017). Moreover, many efforts have been seeking to develop new anti-inflammatory agents from natural compounds that suppress TLRs-mediated inflammation (Borges et al., 2017). Limonoids, a kind of highly oxygenated tetranortriterpenoids, have been receiving considerable interest due to the highly complex skeletons and broad range of bioactivities (Tan and Luo, 2011). A growing number of evidences indicate that limonoids possess significant anti-inflammatory properties, and some of which modulate the inflammatory mediators through TLR-mediated signaling pathways (Borges et al., 2017, Li et al., 2016, Li et al., 2015b, Zhang et al., 2013). Khaya senegalensis (Desr.) A. Juss., a timber tree from Meliaceae family, was traditionally used to treat fever, lumbago and rheumatism in Africa, and its crude extracts had the anti-inflammatory, and hypertensive activities (Ibrahim et al., 2006, Olayinka et al., 1992). Based on the references and our previous studies, K. senegalensis was rich in structurally diverse limonoids (Li et al., 2015a, Li et al., 2015b, Nakatani et al., 2001). Therefore, it is necessary to study whether the limonoids are responsible for the anti-inflammatory activity of K. senegalensis. Khayandirobilide A (KLA, Fig. 1A), a new andirobin-type limonoid with modified furan ring, was isolated and identified from the stem barks of K.senegalensis in our group. Furthermore, KLA exerted inhibitory effects on NO (IC50 5.04 ± 0.14 and 4.97 ± 0.5 µM) in LPS-induced RAW 264.7 and BV-2 cells, which suggested that it may possess potential anti-inflammatory properties. Herein, the effects on inflammatory mediators, including NO, TNF-α, IL-6 and ROS, were valuated to elucidate the anti-inflammatory activity of KLA in LPS-stimulated RAW 264.7 and BV-2 cells. Moreover, we further explored its underlying mechanisms including NF-κB, AP-1 and MAPKs/Nrf2/HO-1 signaling pathways.