Explore the vast range of titles available.

Gut microbiota mediates the effects of diet, thereby modifying host metabolism and the incidence of metabolic disorders. Increased consumption of omega-6 polyunsaturated fatty acid (PUFA) that is abundant in Western diet contributes to obesity and related diseases. Although gut-microbiota-related metabolic pathways of dietary PUFAs were recently elucidated, the effects on host physiological function remain unclear. Here, we demonstrate that gut microbiota confers host resistance to high-fat diet (HFD)-induced obesity by modulating dietary PUFAs metabolism. Supplementation of 10-hydroxy- cis -12-octadecenoic acid (HYA), an initial linoleic acid-related gut-microbial metabolite, attenuates HFD-induced obesity in mice without eliciting arachidonic acid-mediated adipose inflammation and by improving metabolic condition via free fatty acid receptors. Moreover, Lactobacillus -colonized mice show similar effects with elevated HYA levels. Our findings illustrate the interplay between gut microbiota and host energy metabolism via the metabolites of dietary omega-6-FAs thereby shedding light on the prevention and treatment of metabolic disorders by targeting gut microbial metabolites. The gut microbiome is an important regulator of metabolic health. Here the authors show that intestinal bacteria metabolize dietary linoleic acid to 10-hydroxy- cis -12-octadecenoic acid (HYA) which confers host resistance to high fat diet-induced obesity in mice.

Direct cardiac reprogramming from fibroblasts can be a promising approach for disease modeling, drug screening, and cardiac regeneration in pediatric and adult patients. However, postnatal and adult fibroblasts are less efficient for reprogramming compared with embryonic fibroblasts, and barriers to cardiac reprogramming associated with aging remain undetermined. In this study, we screened 8400 chemical compounds and found that diclofenac sodium (diclofenac), a non-steroidal anti-inflammatory drug, greatly enhanced cardiac reprogramming in combination with Gata4 , Mef2c , and Tbx5 (GMT) or GMT plus Hand2 . Intriguingly, diclofenac promoted cardiac reprogramming in mouse postnatal and adult tail-tip fibroblasts (TTFs), but not in mouse embryonic fibroblasts (MEFs). Mechanistically, diclofenac enhanced cardiac reprogramming by inhibiting cyclooxygenase-2, prostaglandin E2/prostaglandin E receptor 4, cyclic AMP/protein kinase A, and interleukin 1β signaling and by silencing inflammatory and fibroblast programs, which were activated in postnatal and adult TTFs. Thus, anti-inflammation represents a new target for cardiac reprogramming associated with aging. Fibroblasts can be directly reprogrammed to cardiomyocytes, but reprogramming is less efficient for adult compared to embryonic fibroblasts. Here, the authors find that inhibition of inflammation and Cox-2-prostaglandin-cAMP-IL-1β signaling enhances reprogramming efficiency of adult, but not embryonic fibroblasts.

Prostaglandins play a key role in inflammation in a variety of settings. Now, Shuh Narumiya and colleagues show that prostaglandin E2 drives the production of inflammatory T helper cells, and that this can be blocked by inhibiting its EP4 receptor subtype. EP4 inhibitors were also effective at inhibiting disease pathogenesis in animal models of two inflammatory diseases. Two distinct helper T (T H ) subsets, T H 1 and T H 17, mediate tissue damage and inflammation in animal models of various immune diseases such as multiple sclerosis, rheumatoid arthritis, inflammatory bowel diseases and allergic skin disorders. These experimental findings, and the implication of these T H subsets in human diseases, suggest the need for pharmacological measures to manipulate these T H subsets. Here we show that prostaglandin E 2 (PGE 2 ) acting on its receptor EP4 on T cells and dendritic cells not only facilitates T H 1 cell differentiation but also amplifies interleukin-23–mediated T H 17 cell expansion in vitro . Administration of an EP4-selective antagonist in vivo decreases accumulation of both T H 1 and T H 17 cells in regional lymph nodes and suppresses the disease progression in mice subjected to experimental autoimmune encephalomyelitis or contact hypersensitivity. Thus, PGE 2 -EP4 signaling promotes immune inflammation through T H 1 differentiation and T H 17 expansion, and EP4 antagonism may be therapeutically useful for various immune diseases.

Prostaglandin E receptor EP4, a G-protein-coupled receptor, is involved in disorders such as cancer and autoimmune disease. Here, we report the crystal structure of human EP4 in complex with its antagonist ONO-AE3-208 and an inhibitory antibody at 3.2 Å resolution. The structure reveals that the extracellular surface is occluded by the extracellular loops and that the antagonist lies at the interface with the lipid bilayer, proximal to the highly conserved Arg316 residue in the seventh transmembrane domain. Functional and docking studies demonstrate that the natural agonist PGE 2 binds in a similar manner. This structural information also provides insight into the ligand entry pathway from the membrane bilayer to the EP4 binding pocket. Furthermore, the structure reveals that the antibody allosterically affects the ligand binding of EP4. These results should facilitate the design of new therapeutic drugs targeting both orthosteric and allosteric sites in this receptor family. The structure of human prostaglandin E receptor EP4 in complex with antagonist ONO-AE3-208 and a functional antibody reveals a ligand-binding site at the interface of the lipid bilayer that is unique among GPCRs.

Diabetes, a disease in which the body does not produce or use insulin properly, is a serious global health problem 1 , 2 , 3 . Gut polypeptides secreted in response to food intake, such as glucagon-like peptide-1 (GLP-1), are potent incretin hormones that enhance the glucose-dependent secretion of insulin from pancreatic beta cells 4 , 5 , 6 . Free fatty acids (FFAs) provide an important energy source and also act as signaling molecules in various cellular processes, including the secretion of gut incretin peptides 7 , 8 . Here we show that a G-protein-coupled receptor, GPR120, which is abundantly expressed in intestine, functions as a receptor for unsaturated long-chain FFAs. Furthermore, we show that the stimulation of GPR120 by FFAs promotes the secretion of GLP-1 in vitro and in vivo , and increases circulating insulin. Because GLP-1 is the most potent insulinotropic incretin 9 , 10 , our results indicate that GPR120-mediated GLP-1 secretion induced by dietary FFAs is important in the treatment of diabetes.

Lymphatic endothelial cells arise from the venous endothelial cells in embryonic lymphatic development. However, the molecular mechanisms remain to be elucidated. We here report that prostaglandin (PG) E 2 plays essential roles in the embryonic lymphatic development through the EP3 receptor, one of the PGE 2 receptors. Knockdown of the EP3 receptor or inhibition of cyclooxygenases (COX; rate-limiting enzymes for PG synthesis) impaired lymphatic development by perturbing lymphatic specification during zebrafish development. These impairments by COX inhibition were recovered by treatment with sulprostone (EP1/3 agonist). Knockdown of the EP3 receptor further demonstrated its requirement in the expression of sex determining region Y-box 18 (sox18) and nuclear receptor subfamily 2, group F, member 2 (nr2f2), essential factors of the lymphatic specification. The EP3 receptor was expressed in the posterior cardinal vein (region of embryonic lymphatic development) and the adjacent intermediate cell mass (ICM) during the lymphatic specification. COX1 was expressed in the region more upstream of the posterior cardinal vein relative to the EP3 receptor, and the COX1-selective inhibitor impaired the lymphatic specification. On the other hand, two COX2 subtypes did not show distinct sites of expression around the region of expression of the EP3 receptor. Finally, we generated EP3-deficient zebrafish, which also showed defect in lymphatic specification and development. Thus, we demonstrated that COX1-derived PGE 2 -EP3 pathway is required for embryonic lymphatic development by upregulating the expression of key factors for the lymphatic specification.

Leukotriene B4 (LTB4) receptor 1 (BLT1) is a chemotactic G protein-coupled receptor expressed by leukocytes, such as granulocytes, macrophages, and activated T cells. Although there is growing evidence that BLT1 plays crucial roles in immune responses, its role in dendritic cells remains largely unknown. Here, we identified novel DC subsets defined by the expression of BLT1, namely, BLT1hi and BLT1lo DCs. We also found that BLT1hi and BLT1lo DCs differentially migrated toward LTB4 and CCL21, a lymph node-homing chemoattractant, respectively. By generating LTB4-producing enzyme LTA4H knockout mice and CD11c promoter-driven Cre recombinase-expressing BLT1 conditional knockout (BLT1 cKO) mice, we showed that the migration of BLT1hi DCs exacerbated allergic contact dermatitis. Comprehensive transcriptome analysis revealed that BLT1hi DCs preferentially induced Th1 differentiation by upregulating IL-12p35 expression, whereas BLT1lo DCs accelerated T cell proliferation by producing IL-2. Collectively, the data reveal an unexpected role for BLT1 as a novel DC subset marker and provide novel insights into the role of the LTB4-BLT1 axis in the spatiotemporal regulation of distinct DC subsets.

Cyclooxygenase (COX)‐2 is known to correlate with poor cancer prognosis and to contribute to tumor metastasis. However, the precise mechanism of this phenomenon remains unknown. We have previously reported that host stromal prostaglandin E2 (PGE2)–prostaglandin E2 receptor (EP)3 signaling appears critical for tumor‐associated angiogenesis and tumor growth. Here we tested whether the EP3 receptor has a critical role in tumor metastasis. Lewis lung carcinoma (LLC) cells were intravenously injected into WT mice and mice treated with the COX‐2 inhibitor NS‐398. The nonselective COX inhibitor aspirin reduced lung metastasis, but the COX‐1 inhibitor SC560 did not. The expression of matrix metalloproteinases (MMP)‐9 and vascular endothelial growth factor (VEGF)‐A was suppressed in NS‐398‐treated mice compared with PBS‐treated mice. Lungs containing LLC colonies were markedly reduced in EP3 receptor knockout (EP3−/−) mice compared with WT mice. The expression of MMP‐9 and VEGF‐A was downregulated in metastatic lungs of EP3−/− mice. An immunohistochemical study revealed that MMP‐9‐expressing endothelial cells were markedly reduced in EP3−/− mice compared with WT mice. When HUVEC were treated with agonists for EP1, EP2, EP3, or EP4, only the EP3 agonist enhanced MMP‐9 expression. These results suggested that EP3 receptor signaling on endothelial cells is essential for the MMP‐9 upregulation that enhances tumor metastasis and angiogenesis. An EP3 receptor antagonist may be useful to protect against tumor metastasis. (Cancer Sci 2009; 100: 2318–2324)

Inflammatory responses in the kidney lead to tubulointerstitial fibrosis, a common feature of chronic kidney diseases. Here we examined the role of prostaglandin E2 (PGE2) in the development of tubulointerstitial fibrosis. In the kidneys of wild-type mice, unilateral ureteral obstruction leads to progressive tubulointerstitial fibrosis with macrophage infiltration and myofibroblast proliferation. This was accompanied by an upregulation of COX-2 and PGE2 receptor subtype EP4 mRNAs. In the kidneys of EP4 gene knockout mice, however, obstruction-induced histological alterations were significantly augmented. In contrast, an EP4-specific agonist significantly attenuated these alterations in the kidneys of wild-type mice. The mRNAs for macrophage chemokines and profibrotic growth factors were upregulated in the kidneys of wild-type mice after ureteral obstruction. This was significantly augmented in the kidneys of EP4-knockout mice and suppressed by the EP4 agonist but only in the kidneys of wild-type mice. Notably, COX-2 and MCP-1 proteins, as well as EP4 mRNA, were localized in renal tubular epithelial cells after ureteral obstruction. In cultured renal fibroblasts, another EP4-specific agonist significantly inhibited PDGF-induced proliferation and profibrotic connective tissue growth factor production. Hence, an endogenous PGE2–EP4 system in the tubular epithelium limits the development of tubulointerstitial fibrosis by suppressing inflammatory responses.

Aortic aneurysm is a common but life-threatening disease among the elderly, for which no effective medical therapy is currently available. Activation of prostaglandin E(2) (PGE(2)) is known to increase the expression of matrix metalloproteinase (MMP) and the release of inflammatory cytokines, and may thus exacerbate abdominal aortic aneurysm (AAA) formation. We hypothesized that selective blocking of PGE(2), in particular, EP4 prostanoid receptor signaling, would attenuate the development of AAA. Immunohistochemical analysis of human AAA tissues demonstrated that EP4 expression was greater in AAA areas than that in non-diseased areas. Interestingly, EP4 expression was proportional to the degree of elastic fiber degradation. In cultured human aortic smooth muscle cells (ASMCs), PGE(2) stimulation increased EP4 protein expression (1.4 ± 0.08-fold), and EP4 stimulation with ONO-AE1-329 increased MMP-2 activity and interleukin-6 (IL-6) production (1.4 ± 0.03- and 1.7 ± 0.14-fold, respectively, P<0.05). Accordingly, we examined the effect of EP4 inhibition in an ApoE(-/-) mouse model of AAA infused with angiotensin II. Oral administration of ONO-AE3-208 (0.01-0.5 mg/kg/day), an EP4 antagonist, for 4 weeks significantly decreased the formation of AAA (45-87% reduction, P<0.05). Similarly, EP4(+/-)/ApoE(-/-) mice exhibited significantly less AAA formation than EP4(+/+)/ApoE(-/-) mice (76% reduction, P<0.01). AAA formation induced by periaortic CaCl(2) application was also reduced in EP4(+/-) mice compared with wild-type mice (73% reduction, P<0.001). Furthermore, in human AAA tissue organ cultures containing SMCs and macrophages, doses of the EP4 antagonist at 10-100 nM decreased MMP-2 activation and IL-6 production (0.6 ± 0.06- and 0.7 ± 0.06-fold, respectively, P<0.05) without increasing MMP-9 activity or MCP-1 secretion. Thus, either pharmacological or genetic EP4 inhibition attenuated AAA formation in multiple mouse and human models by lowering MMP activity and cytokine release. An EP4 antagonist that prevents the activation of MMP and thereby inhibits the degradation of aortic elastic fiber may serve as a new strategy for medical treatment of AAA.