Metabolic products of soluble epoxide hydrolase are essential for monocyte chemotaxis to MCP-1 in vitro and in vivo

Abstract

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

Soluble Epoxide Hydrolase Inhibitor Attenuates Inflammation and Airway Hyperresponsiveness in Mice

“…The mechanism is believed to be through stabilizing of the antiinflammatory EETs, which regulate NF-kB translocation (33), or through reducing production of proinflammatory diols, including DHOMEs (34) and dihydroxy eicosatrienoic acids (DHETs) (35). Here, our data show that the concentration of sEHI in the plasma significantly altered the circulating EET and DHET levels present in plasma, BALF, and lung homogenates ( Figures 3C and 3D).…”

“…At the same time, sEHI administration significantly reduced proinflammatory DHETs in BALF and lung homogenate ( Figures 3C and 3D). The DHETs were reported as essential for monocyte chemotaxis to MCP-1 (35). In particular, sEHI reduced the DHOMEs, metabolites of leukotoxin, and iso-leukotoxin.…”

Cytochrome P450 epoxygenase pathway of polyunsaturated fatty acid metabolism

“…14,15-DHET activates PPARα-mediated gene expression [79,80], 11,12-DHET regulates cAMP production in HEK293 cells [81], and PUFA diols including 12,13-DHOME are required for optimal progenitor cell proliferation and vascular repair [82]. Diol metabolites produced by sEH are essential for monocyte chemotaxis to monocyte chemoattractant protein-1 [83]. These findings indicate that some PUFA diols may have functional effects on physiological processes.…”

Soluble Epoxide Hydrolase Pharmacological Inhibition Ameliorates Experimental Acute Pancreatitis in Mice

“…1A, bottom). Previous reports demonstrate that a single dose of TPPU is efficient in reducing inflammation (Kundu et al, 2013;Liu et al, 2013). For cerulein-induced AP, mice were fasted overnight and then injected intraperitoneally with cerulein (50 mg/kg body weight) 12 consecutive times, at 1-hour intervals.…”