Mangiferin, 2-b b-D-glucopyranosyl-1,3,6,7-tetrahydroxy-9H-xanthen-9-one, obtained directly from methanolic extracts of Bombax ceiba leaves in substantial amounts demonstrated strong antioxidant activity (EC 50 5.8؎0.96 m mg/ml or 13.74 m mM) using DPPH assay comparable to rutin, commonly used as antioxidant for medical purposes. The acetyl and cinnamoyl derivatives were found to be less active than mangiferin whereas, methyl and 3,6,7-trimethylether tetraacetate derivatives were inactive implying that for antioxidant activity, free hydroxyl groups and catechol moiety are essential. Moreover, mangiferin showed hepatoprotective activity against carbon tetrachloride induced liver injury further supporting the free radical scavenging property in the in vivo system. Additionally, plant extracts and mangiferin failed to exhibit acute anti-inflammatory activity whereas, it displayed significant analgesic effect in acetic acid-induced writhing and hot plate tests in mice. Using naloxone, it was revealed that plant extracts induced analgesia was independent of opioid receptor, whereas, mangiferin demonstrated significant interaction with it at peripheral site with a slight contribution at the neuronal level.

Zymosan, a mimic of fungal pathogens, and its opsonized form (ZOP) are potent stimulators of monocyte NADPH oxidase, resulting in the production of O(2)(.-), which is critical for host defense against fungal and bacterial pathogens and efficient immune responses; however, uncontrolled O(2)(.-) production may contribute to chronic inflammation and tissue injury. Our laboratory has focused on characterizing the signal transduction pathways that regulate NADPH oxidase activity in primary human monocytes. In this study, we examined the involvement of various pattern recognition receptors and found that Dectin-1 is the primary receptor for zymosan stimulation of O(2)(.-) via NADPH oxidase in human monocytes, whereas Dectin-1 and CR3 mediate the activation by ZOP. Further studies identified Syk and Src as important signaling components downstream of Dectin-1 and additionally identified PKCδ as a novel downstream signaling component for zymosan-induced O(2)(.-) as well as phagocytosis. Our results show that Syk and Src association with Dectin-1 is dependent on PKCδ activity and expression and demonstrate direct binding between Dectin-1 and PKCδ. Finally, our data show that PKCδ and Syk but not Src are required for Dectin-1-mediated phagocytosis. Taken together, our data identify Dectin-1 as the major PRR for zymosan in primary human monocytes and identify PKCδ as a novel downstream signaling kinase for Dectin-1-mediated regulation of monocyte NADPH oxidase and zymosan phagocytosis.

Monocyte migration from peripheral blood into infl ammatory sites is a complex phenomenon that occurs during acute and chronic infl ammatory diseases such as peritonitis, atherosclerosis, rheumatoid arthritis, and infl ammatory bowel disease. Monocyte chemoattractant protein-1 (MCP-1/CCL2) is one of the key chemokines that regulate migration and infi ltration of monocytes in response to infl ammatory conditions by attracting monocytes toward MCP-1 in a gradient-dependent manner ( 1, 2 ). MCP-1 expression has been demonstrated to be elevated in a number of different diseases, including atherosclerosis ( 3 ). In vivo studies with MCP-1-or MCP-1 receptor-defi cient mice have shown the reduction of atherosclerotic plaque size, supporting the relevance of MCP-1 in atherogenesis ( 4, 5 ).The cellular effect of MCP-1 is mediated through interaction with its receptor, CCR2 ( 6 ). Our laboratory has identifi ed several critical signaling pathways that are activated downstream of this receptor and regulate monocyte chemotaxis to MCP-1 both in vitro and in vivo ( 2,7,8 ).Abstract Monocyte chemoattractant protein-1 (MCP-1)-induced monocyte chemotaxis is a major event in infl ammatory disease. Our prior studies have demonstrated that MCP-1-dependent chemotaxis requires release of arachidonic acid (AA) by activated cytosolic phospholipase A 2 (cPLA 2 ). Here we investigated the involvement of AA metabolites in chemotaxis. Neither cyclooxygenase nor lipoxygenase pathways were required, whereas pharmacologic inhibitors of both the cytochrome-P450 (CYP) and the soluble epoxide hydrolase (sEH) pathways blocked monocyte chemotaxis to MCP-1. To verify specifi city, we demonstrated that the CYP and sEH products epoxyeiscosatrienoic acids (EETs) and dihydroxyeicosatrienoic acids (DHETs), respectively, restored chemotaxis in the presence of the inhibitors, indicating that sEH-derived products are essential for MCP-1-driven chemotaxis. Importantly, DHETs also rescued chemotaxis in cPLA 2 -defi cient monocytes and monocytes with blocked Erk1/2 activity, because Erk controls cPLA 2 activation. The in vitro fi ndings regarding the involvement of CYP/sEH pathways were further validated in vivo using two complementary approaches measuring MCP-1-dependent chemotaxis in mice. These observations reveal the importance of sEH in MCP-1-regulated monocyte chemotaxis and may explain the observed therapeutic value of sEH inhibitors in treatment of infl ammatory diseases, cardiovascular diseases, pain, and even carcinogenesis. Their effectiveness, often attributed to increasing EET levels, is probably infl uenced by the impairment of DHET formation and inhibition of chemotaxis. -Kundu, S

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