G protein-coupled receptor 55 (GPR55) is a lipid-sensing receptor that plays a role as an immune mediator and is primarily upregulated during immune cell activation. There is a lack of knowledge about the role of GPR55 in allergic inflammatory diseases such as atopic dermatitis. The purpose of this study was to investigate the role of GPR55 through the use of its antagonist, CID16020046, in an atopic dermatitis mouse model. It was found that BALB/c mice develop lesions similar to those associated with atopic dermatitis following sensitization and repeated exposure to 1-chloro-2,4-dinitrobenzene (DNCB). It was found that CID16020046 (1 mg/kg, i. p.) alleviated the atopic dermatitis-like symptoms as well as immune dysregulation caused by DNCB. Based on histopathological analysis, CID16020046 reduced ear thickening and mast cell counts in the dermis. CID16020046 decreased DNCB-induced increases in serum IgE levels, as measured using enzyme-linked immunosorbent assays. A significant reduction in lymph node hypertrophy was also observed with CID16020046 as well as significant reductions in CD4+ T helper 1 (Th1), Th2, and Th17 cells in the lymph nodes. As a result of the administration of CID16020046, cytokines of Th1 (IFN-γ), Th2 (IL-4 and IL-13), and Th17 (IL-17 A) types were also reduced in the skin and lymph nodes. In conclusion, blocking GPR55 alleviates DNCB-induced atopic dermatitis-like symptoms, suggesting that GPR55 is a potential therapeutic target for allergic inflammatory diseases via immunoregulation.

p38 MAPK has been implicated in the pathogenesis of rheumatoid arthritis and psoriasis. To assess the therapeutic efficacy of the p38 MAPK inhibitor NJK14047 in the treatment of rheumatoid arthritis and psoriasis, we developed mouse models of collagen-induced rheumatoid arthritis (CIA) and imiquimod-induced psoriasis (IIP). NJK14047 was found to suppress arthritis development and psoriasis symptoms and also suppressed histopathological changes induced by CIA and IIP. Furthermore, we established that CIA and IIP evoked increases in the mRNA expression levels of Th1/Th17 inflammatory cytokines in the joints and skin, which was again suppressed by NJK14047. NJK14047 reversed the enlargement of spleens induced by CIA and IIP as well as increases in the levels of inflammatory cytokine in spleens following induction by CIA and IIP. In human SW982 synovial cells, NJK14047 was found to suppress lipopolysaccharide-induced increases in the mRNA expression of proinflammatory cytokines. NJK14047 inhibition of p38 MAPK suppressed the differentiation of naïve T cells to Th17 and Th1 cells. Our findings in this study provide convincing evidence indicating the therapeutic efficacy of the p38 MAPK inhibitor NJK14047 against CIA and IIP, which we speculate could be associated with the suppression on T-cell differentiation.

GPR55 is a receptor for lysophosphatidylinositols (LPIs) in digestive metabolites. Overnutrition leads to obesity, insulin resistance, and increased LPI levels in the plasma. The involvement of LPIs and GPR55 in adiposity, hepatic steatosis, and atherosclerosis has been previously elucidated. However, the therapeutic efficacy of GPR55 antagonists against obesity-induced airway inflammation has not been studied. The present study investigated whether CID16020046, a selective antagonist of GPR55, could modulate obesity-induced airway inflammation caused by a high-fat diet (HFD) in C57BL/6 mice. Administration of CID16020046 (1 mg/kg) inhibits HFD-induced adiposity and glucose intolerance. Analysis of immune cells in BALF showed that CID16020046 inhibited HFD-induced increase in immune cell infiltration. Histological analysis revealed the HFD induced hypersecretion of mucus and extensive fibrosis in the lungs. CID16020046 inhibited these HFD-induced pathological features. qRT-PCR revealed the HFD-induced increase in the expression of Ifn-γ, Tnf-α, Il-6, Il-13, Il-17A, Il-1β, Nlrp3, and Mpo mRNAs in the lungs. CID16020046 inhibited the HFD-induced increases in these genes. The expression levels of adipokines were regulated by the HFD and CID16020046. AdipoQ in the lungs and gonadal white adipose tissue was decreased by the HFD and reversed by CID16020046. In contrast, Lep was increased by the HFD and suppressed by CID16020046. The findings suggest the potential application of the GPR55 antagonist CID16020046 in obesity-induced airway inflammation.

Obese asthma is recognized to have different asthma phenotypes. N-3 polyunsaturated fatty acids (PUFAs) have shown beneficial effects in obesity and metabolic syndrome. Free fatty acid receptor 4 (FFA4, also known as GPR120) is a receptor for n-3 PUFAs. In the present study, we investigated whether FFA4 activation ameliorates high-fat diet (HFD)-induced obese asthma. We investigated whether FFA4 activation ameliorates obese asthma using an FFA4 agonist, compound A (CpdA), in combination with FFA4 wild-type (WT) and knock-out (KO) mice. Administration of an FFA4 agonist, compound A (CpdA, 30 mg/kg), suppressed HFD-induced weight gain, adiposity, and airway hypersensitivity (AHR), and increased immune cell infiltration in an FFA4-dependent manner. Histological analysis revealed that CpdA treatment suppressed HFD-induced mucus hypersecretion, inflammation, and fibrosis in an FFA4-dependent manner. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) showed an HFD-induced increase in the mRNA levels of pro-inflammatory cytokines in the lungs and gonadal white adipose tissue, whereas CpdA inhibited this increase in an FFA4-dependent manner. In the fluorescence-activated cell sorting (FACS) analysis, HFD induced an increase in the lung innate lymphoid cells (ILC) ILC1, ILC2, and ILC3; however, CpdA reversed this increase. In addition, HFD induced an increase in the pro-inflammatory M1 macrophage population and a decrease in the anti-inflammatory M2 macrophage population in the lungs, whereas CpdA treatment reversed these changes. The present study suggests that FFA4 activation may have therapeutic potential in obese asthma.

The prevalence of obesity-induced asthma increases in women after menopause. We hypothesized that the increase in obese asthma in middle-aged women results from estrogen loss. In particular, we focused on the acute action of estrogen through the G protein-coupled estrogen receptor 1 (GPER), previously known as GPR30. We investigated whether GPER activation ameliorates obesity-induced asthma with a high-fat diet (HFD) using G-1, the GPER agonist, and G-36, the GPER antagonist. Administration of G-1 (0.5 mg/kg) suppressed HFD-induced airway hypersensitivity (AHR), and increased immune cell infiltration, whereas G-36 co-treatment blocked it. Histological analysis showed that G-1 treatment inhibited HFD-induced inflammation, fibrosis, and mucus hypersecretion in a GPER-dependent manner. G-1 inhibited the HFD-induced rise in the mRNA levels of pro-inflammatory cytokines in the gonadal white adipose tissue and lungs, whereas G-36 co-treatment reversed this effect. G-1 increased anti-inflammatory M2 macrophages and inhibited the HFD-induced rise in pro-inflammatory M1 macrophages in the lungs. In addition, G-1 treatment reversed the HFD-induced increase in leptin expression and decrease in adiponectin expression in the lungs and gonadal white adipose tissue. The results suggest that activation of GPER could be a therapeutic option for obesity-induced asthma.

Free fatty acid 3 receptor (FFA3; previously GPR41) is a G protein-coupled receptor that senses short-chain fatty acids and dietary metabolites produced by the gut microbiota. FFA3 deficiency reportedly exacerbates inflammatory events in asthma. Herein, we aimed to determine the therapeutic potential of FFA3 agonists in treating inflammatory diseases. We investigated the effects of N-(2,5-dichlorophenyl)-4-(furan-2-yl)-2-methyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxamide (AR420626), an FFA3 agonist, in in vivo models of chemically induced allergic asthma and eczema in BALB/c mice. Administration of AR420626 decreased the number of immune cells in the bronchoalveolar lavage fluid and skin. AR420626 suppressed inflammatory cytokine expression in the lung and skin tissues. Histological examination revealed that AR420626 suppressed inflammation in the lungs and skin. Treatment with AR420626 significantly suppressed the enhanced lymph node size and inflammatory cytokine levels. Overall, FFA3 agonist AR420626 could suppress allergic asthma and eczema, implying that activation of FFA3 might be a therapeutic target for allergic diseases.

As angiotensin II is associated with inflammation, type I angiotensin II receptor blockers (ARBs) exibit anti-inflammatory effects in patients with hypertension as well as inflammatory disease animal models including arthritis models. The present study aimed to investigate whether ARBs exert anti-inflammatory effects in vivo in skin disorders. We tested effects of ARBs on 1-chloro-2,4-dinitrobenzene(CDNB)-induced atopic dermatitis-like and imiquimod-induced psoriasis-like skin models. CDNB-induced atopic dermatitis-like skin lesions were suppressed by administration of candesartan or telmisartan. The suppressive effect of telmisartan was blocked by the presence of GW9662, a selective PPARγ inhibitor, but not that of candesartan. Both ARBs suppressed increases in pro-inflammatory cytokine (IL-4, IL-13, IFN-γ, and IL-17A) levels, and GW9662 inhibited telmisartan-induced suppression but not candesartan. Candesartan significantly inhibited in vitro differentiation of naïve T cells into Th17 cells to a greater extent than telmisartan. In the imiquimod-induced psoriasis model, whose primary etiology is activation of IL-23/IL-17 axis, candesartan significantly suppressed psoriasis-like skin lesions and Th17 cell populations in both lymph nodes and spleens to a greater extent than telmisartan. Overall, certain ARBs may have anti-inflammatory effects in skin diseases. Candesartan may have therapeutic implications in inflammatory skin disorders by suppressing Th17 differentiation, while telmisartan might have therapeutic potential by activating PPARγ.

Epidemiological and clinical studies have suggested that intake of n-3 polyunsaturated fatty acids (PUFA) reduces the incidence of allergic airway diseases and improves pulmonary function in patients with allergic asthma. However, the pharmacological targets of PUFA have not been elucidated upon. We investigated whether free fatty acid receptor 4 (FFA4, also known as GPR120) is a molecular target for beneficial PUFA in asthma therapy. In an ovalbumin (OVA)-induced allergic asthma model, compound A (a selective agonist of FFA4) was administrated before OVA sensitization or OVA challenge in FFA4 wild-type (WT) and knock-out (KO) mice. Compound A treatment of RBL-2H3 cells suppressed mast cell degranulation in vitro in a concentration-dependent manner. Administration of compound A suppressed in vivo allergic characteristics in bronchoalveolar lavage fluid (BALF) and lungs, such as inflammatory cytokine levels and eosinophil accumulation in BALF, inflammation and mucin secretion in the lungs. Compound A-induced suppression was not only observed in mice treated with compound A before OVA challenge, but in mice treated before OVA sensitization as well, implying that compound A acts on mast cells as well as dendritic cells. Furthermore, this suppression by compound A was only observed in FFA4-WT mice and was absent in FFA4-KO mice, implying that compound A action is mediated through FFA4. Activation of FFA4 may be a therapeutic target of PUFA in allergic asthma by suppressing the activation of dendritic cells and mast cells, suggesting that highly potent specific agonists of FFA4 could be a novel therapy for allergic asthma.

Dietary supplementation with n-3 polyunsaturated fatty acids (n-3 PUFA) has been used as an adjunct therapy for psoriasis due to its anti-inflammatory properties. Free fatty acid receptor 4 (FFA4 or GPR120) is a receptor-sensing n-3 PUFA. In the present study, we examined whether FFA4 acted as a therapeutic target for n-3 PUFA in psoriasis therapy. Experimentally, psoriasis-like skin lesions were induced by treatment with imiquimod for 6 consecutive days. A selective FFA4 agonist, Compound A (30 mg/kg), was used in FFA4 WT and FFA4 KO mice. Imiquimod-induced psoriasis-like skin lesions, which present as erythematous papules and plaques with silver scaling, as well as markedly elevated IL-17/IL-23 cytokine levels in skin tissues, were significantly suppressed by Compound A in FFA4 WT mice, but not in FFA4 KO mice. Enlarged lymph nodes and spleens, as well as imiquimod-induced, elevated IL-17/IL-23 cytokine levels, were also strongly suppressed by Compound A in FFA4 WT mice, but not in FFA4 KO mice. Imiquimod-induced increases in the CD4+IL-17A+ T cell population in lymph nodes and spleens were suppressed by Compound A treatment in FFA4 WT mice; however, this was not seen in FFA4 KO mice. Furthermore, compound A suppressed the differentiation of CD4+ naïve T cells from splenocytes into TH17 cells in an FFA4-dependent manner. In conclusion, we demonstrated that the activation of FFA4 ameliorates imiquimod-induced psoriasis, and the suppression of the differentiation of TH17 cells may partly contribute to its efficacy. Therefore, we suggest that FFA4 could be a therapeutic target for psoriasis therapy.

Till the 21st century, fatty acids were considered as merely building blocks for triglycerides, phospholipids, or cholesteryl esters. However, the discovery of G protein-coupled receptors (GPCRs) for free fatty acids at the beginning of the 21st century challenged that idea and paved way for a new field of research, merged into the field of receptor pharmacology for intercellular lipid mediators. Among the GPCRs for free fatty acids, free fatty acid receptor 4 (FFA4, also known as GPR120) recognizes long-chain polyunsaturated fatty acids such as DHA and EPA. It is significant in drug discovery because it regulates obesity-induced metaflammation and GLP-1 secretion. Our study reviews information on newly developed FFA4 agonists and their application in pathophysiologic studies and drug discovery. It also offers a potency comparison of the FFA4 agonists in an AP-TGF-α shedding assay.

Prevalence of atopic dermatitis (AD), a chronic, pruritic, and relapsing inflammatory skin disorder, is growing. Because available therapeutics is limited, immune regulators from natural resources could be helpful for treating AD symptoms. The root of Salvia miltiorrhiza Bunge (Lamiaceae) has been studied for the treatment of inflammatory diseases, including dermatologic disorders in Korea. This study examined the effect of salvianolic acid A on AD-like symptoms. Sensitization on the dorsal skin and repeated application on the ears with 2,4-dinitrochlorobenzene (DNCB) were performed in BALB/c mice to induce AD-like skin lesions. After induction of atopic dermatitis, salvianolic acid A (5 and 10 mg/kg) or dexamethasone (10 mg/kg) were administrated via intraperitoneal injection for 3 weeks. Salvianolic acid A suppressed DNCB-induced AD-like symptoms like ear skin hypertrophy and decreased mast cell infiltration into skin lesions. Salvianolic acid A not only reduced DNCB-induced increase of serum IgE but also lowered levels of the Th2 cytokines (IL-4 and IL-13), Th1 cytokine (interferon-γ), and Th17 cytokine (IL-17A). Furthermore, salvianolic acid A blocked DNCB-induced lymph node enlargement. In summary, these results suggest that salvianolic acid A might have a therapeutic potential for the treatment of AD.

Background Several studies have reported on the expression of the type I angiotensin II receptor in human lung tissues. In severe acute attacks of asthma, the renin‐angiotensin system is activated by elevated plasma concentrations of renin and angiotensin II. Furthermore, angiotensin II potentiates methacholine‐induced bronchoconstriction in patients with mild asthma. However, the in vivo anti‐allergic effect of type I angiotensin II receptor antagonists has been poorly evaluated. We aimed to investigate effect of TCV116, an antagonist of the type I angiotensin II receptor on allergic asthma. METHODS To elucidate whether TCV116 lactone has beneficial effects on allergic asthma, anti‐asthma effects were studied using female Balb/c mice and rat RBL‐2H3 mast cells. Antigeninduced degranulation was measured in vitro by measuring b‐hexosaminidase activity. A murine ovalbumin‐induced allergic asthma model was used to test the in vivo efficacy of TCV116. RESULTS It was observed that while TCV116 inhibited the antigen‐induced degranulation in rat RBL‐2H3 mast cells. Administration of TCV116 and irbesartan decreased the number of immune cells in the bronchoalveolar lavage fluid and reduced the expression of Th2 (IL‐4, IL‐5, and IL‐13) and Th1 cytokines (IL‐2 and IFN‐g) in the lung tissues of mice with ovalbumin‐induced allergic asthma. Histological studies revealed that TCV116 and irbesartan reduced inflammation and mucin production in the lungs. CONCLUSION The present findings provide evidence that TCV116 and irbesartan could have potential applications as anti‐allergic agents. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

BackgroundSphingosine 1‐phosphate (S1P), a bioactive lysolipid, acts as a ligand for five G protein‐coupled receptors, S1P1–5. Up‐regulation or activation of sphingosine kinase 1 and subsequent increased generation of S1P have been observed in many cell types, including macrophages and microglia, in response to inflammatory stimuli. Functional roles of S1P1 and S1P2 have been reported in macrophage recruitment during inflammation and atherosclerosis. However, pro‐inflammatory function of S1P has not been fully elucidated at the receptor molecular level.METHODSIn order to assess the functional roles of S1P and S1P3, murine peritoneal macrophages were stimulated with lipopolysaccharide to evoke inflammatory response.RESULTSS1P3 receptor and sphingosine kinase 1 were induced by stimulation of lipopolysaccharide. Lipopolysaccharide treatment induced inflammatory genes, such cyclooxygenase‐2, interleukin‐1b, interleukin‐6, inducible nitric oxide synthase, and tumor necrosis factor‐a. Presence of TY52156, an antagonist of S1P3 suppressed the inductions of inducible nitric oxide synthase and interleukin‐1b in a concentration dependent manner. Suppression of inducible nitric oxide synthase induction was further confirmed by Western blotting and nitric oxide measurement. Suppression of interleukin‐1b induction was also confirmed by western blotting and enzyme‐linked immunosorbent assay. Caspase 1, which is responsible for interleukin‐1b production, was similarly induced by lipopolysaccharide and suppressed by TY52156.CONCLUSIONThe present findings suggest that S1P3 functions as a pro‐inflammatory receptor in primary mouse macrophages.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.