Increased expression of lipocalin-type-prostaglandin D synthase in ulcerative colitis and exacerbating role in murine colitis

Fatty acids and lipid mediators in inflammatory bowel disease: from mechanism to treatment

Inflammatory Bowel Disease (IBD) is a chronic, relapsing inflammatory disorder of the gastrointestinal tract. Though the pathogenesis of IBD remains unclear, diet is increasingly recognized as a pivotal factor influencing its onset and progression. Fatty acids, essential components of dietary lipids, play diverse roles in IBD, ranging from anti-inflammatory and immune-regulatory functions to gut-microbiota modulation and barrier maintenance. Short-chain fatty acids (SCFAs), products of indigestible dietary fiber fermentation by gut microbiota, have strong anti-inflammatory properties and are seen as key protective factors against IBD. Among long-chain fatty acids, saturated fatty acids, trans fatty acids, and ω-6 polyunsaturated fatty acids exhibit pro-inflammatory effects, while oleic acid and ω-3 polyunsaturated fatty acids display anti-inflammatory actions. Lipid mediators derived from polyunsaturated fatty acids serve as bioactive molecules, influencing immune cell functions and offering both pro-inflammatory and anti-inflammatory benefits. Recent research has also highlighted the potential of medium- and very long-chain fatty acids in modulating inflammation, mucosal barriers, and gut microbiota in IBD. Given these insights, dietary intervention and supplementation with short-chain fatty acids are emerging as potential therapeutic strategies for IBD. This review elucidates the impact of various fatty acids and lipid mediators on IBD and delves into potential therapeutic avenues stemming from these compounds.

Crosstalk between omega-6 oxylipins and the enteric nervous system: Implications for gut disorders?

The enteric nervous system (ENS) continues to dazzle scientists with its ability to integrate signals, from the outside as well as from the host, to accurately regulate digestive functions. Composed of neurons and enteric glial cells, the ENS interplays with numerous neighboring cells through the reception and/or the production of several types of mediators. In particular, ENS can produce and release n-6 oxylipins. These lipid mediators, derived from arachidonic acid, play a major role in inflammatory and allergic processes, but can also regulate immune and nervous system functions. As such, the study of these n-6 oxylipins on the digestive functions, their cross talk with the ENS and their implication in pathophysiological processes is in full expansion and will be discussed in this review.

Maternal prebiotic supplementation impacts colitis development in offspring mice

Background and aims

Maternal diet plays a key role in preventing or contributing to the development of chronic diseases, such as obesity, allergy, and brain disorders. Supplementation of maternal diet with prebiotics has been shown to reduce the risk of food allergies and affect the intestinal permeability in offspring later in life. However, its role in modulating the development of other intestinal disorders, such as colitis, remains unknown. Therefore, we investigated the effects of prebiotic supplementation in pregnant mice on the occurrence of colitis in their offspring.

Materials and methods

Offspring from mothers, who were administered prebiotic galacto-oligosaccharides and inulin during gestation or fed a control diet, were subjected to three cycles of dextran sulphate sodium (DSS) treatment to induce chronic colitis, and their intestinal function and disease activity were evaluated. Colonic remodelling, gut microbiota composition, and lipidomic and transcriptomic profiles were also assessed.

Results

DSS-treated offspring from prebiotic-fed mothers presented a higher disease score, increased weight loss, and increased faecal humidity than those from standard diet-fed mothers. DSS-treated offspring from prebiotic-fed mothers also showed increased number of colonic mucosal lymphocytes and macrophages than the control group, associated with the increased colonic concentrations of resolvin D5, protectin DX, and 14-hydroxydocosahexaenoic acid, and modulation of colonic gene expression. In addition, maternal prebiotic supplementation induced an overabundance of eight bacterial families and a decrease in the butyrate caecal concentration in DSS-treated offspring.

Conclusion

Maternal prebiotic exposure modified the microbiota composition and function, lipid content, and transcriptome of the colon of the offspring. These modifications did not protect against colitis, but rather sensitised the mice to colitis development.

Oral exposure to DEHP may stimulate prostatic hyperplasia associated with upregulation of COX-2 and L-PGDS expressions in male adult rats

Di-(2-ethylhexyl) phthalate (DEHP), a typical environmental endocrine disruptor (EED), can disrupt estrogen and androgen secretion and metabolism process, thus inducing dysfunctional reproduction such as impaired gonadal development and spermatogenesis disorder. Prostaglandin synthases (PGS) catalyze various prostaglandins biosynthesis, involved in inflammatory cascade and tumorigenesis. Yet, little is known about how PGS may impact prostatic hyperplasia development and progression. This study concentrates predominantly on the potential prostatic toxicity of DEHP exposure and the mediating role of PGS. In vivo study, adult male rats were administered via oral gavage 30 μg/kg/d, 90 μg/kg/d, 270 μg/kg/d, 810 μg/kg/d DEHP or vehicle for four weeks. The results elucidated that low-dose DEHP may cause the proliferation of the prostate with an increased PCNA/TUNEL ratio. Given the importance of estrogens and androgens in prostatic hyperplasia, our first objective was to evaluate the levels of sex hormones. DEHP improved the ratio of estradiol (E₂)/testosterone (T) in a dose-dependent manner and upregulated estrogen receptor alpha (ERα) and androgen receptor (AR) expressions. Prostaglandin synthases, including cyclooxygenase-2 (COX-2) and lipocalin-type prostaglandin D synthase (L-PGDS), were significantly upregulated in the ventral prostate. COX-2 and L-PGDS might mediate the tendency of prostatic hyperplasia induced by low-dose DEHP through estradiol/androgen regulation and imbalance between proliferation and apoptosis in vivo. These findings provide the first evidence that prostaglandin synthases contribute to the tendency toward benign prostatic hyperplasia induced by DEHP. Further investigations will have to be performed to facilitate an improved understanding of the role of prostaglandin synthases in DEHP-induced prostatic lesions.

Facilitation of colonic T cell immune responses is associated with an exacerbation of dextran sodium sulfate-induced colitis in mice lacking microsomal prostaglandin E synthase-1

Background

Microsomal prostaglandin E synthase-1 (mPGES-1) is a key enzyme that acts downstream of cyclooxygenase and plays a major role in inflammation by converting prostaglandin (PG) H₂ to PGE₂. The present study investigated the effect of genetic deletion of mPGES-1 on the development of immunologic responses to experimental colitis induced by dextran sodium sulfate (DSS), a well-established model of inflammatory bowel disease (IBD).

Methods

Colitis was induced in mice lacking mPGES-1 (mPGES-1^−/− mice) and wild-type (WT) mice by administering DSS for 7 days. Colitis was assessed by body weight loss, diarrhea, fecal bleeding, and histological features. The colonic expression of mPGES-1 was determined by real-time PCR, western blotting, and immunohistochemistry. The impact of mPGES-1 deficiency on T cell immunity was determined by flow cytometry and T cell depletion in vivo.

Results

After administration of DSS, mPGES-1^−/− mice exhibited more severe weight loss, diarrhea, and fecal bleeding than WT mice. Histological analysis further showed significant exacerbation of colonic inflammation in mPGES-1^−/− mice. In WT mice, the colonic expression of mPGES-1 was highly induced on both mRNA and protein levels and colonic PGE₂ increased significantly after DSS administration. Additionally, mPGES-1 protein was localized in the colonic mucosal epithelium and infiltrated inflammatory cells in underlying connective tissues and the lamina propria. The abnormalities consistent with colitis in mPGES-1^−/− mice were associated with higher expression of colonic T-helper (Th)17 and Th1 cytokines, including interleukin 17A and interferon-γ. Furthermore, lack of mPGES-1 increased the numbers of Th17 and Th1 cells in the lamina propria mononuclear cells within the colon, even though the number of suppressive regulatory T cells also increased. CD4⁺ T cell depletion effectively reduced symptoms of colitis as well as colonic expression of Th17 and Th1 cytokines in mPGES-1^−/− mice, suggesting the requirement of CD4⁺ T cells in the exacerbation of DSS-induced colitis under mPGES-1 deficiency.

Conclusions

These results demonstrate that mPGES-1 is the main enzyme responsible for colonic PGE₂ production and deficiency of mPGES-1 facilitates the development of colitis by affecting the development of colonic T cell–mediated immunity. mPGES-1 might therefore impact both the intestinal inflammation and T cell–mediated immunity associated with IBD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41232-021-00188-1.

Biochemical and Structural Characteristics, Gene Regulation, Physiological, Pathological and Clinical Features of Lipocalin-Type Prostaglandin D2 Synthase as a Multifunctional Lipocalin

Lipocalin-type prostaglandin (PG) D₂ synthase (L-PGDS) catalyzes the isomerization of PGH₂, a common precursor of the two series of PGs, to produce PGD₂. PGD₂ stimulates three distinct types of G protein-coupled receptors: (1) D type of prostanoid (DP) receptors involved in the regulation of sleep, pain, food intake, and others; (2) chemoattractant receptor-homologous molecule expressed on T helper type 2 cells (CRTH2) receptors, in myelination of peripheral nervous system, adipocyte differentiation, inhibition of hair follicle neogenesis, and others; and (3) F type of prostanoid (FP) receptors, in dexamethasone-induced cardioprotection. L-PGDS is the same protein as β-trace, a major protein in human cerebrospinal fluid (CSF). L-PGDS exists in the central nervous system and male genital organs of various mammals, and human heart; and is secreted into the CSF, seminal plasma, and plasma, respectively. L-PGDS binds retinoic acids and retinal with high affinities (Kd < 100 nM) and diverse small lipophilic substances, such as thyroids, gangliosides, bilirubin and biliverdin, heme, NAD(P)H, and PGD₂, acting as an extracellular carrier of these substances. L-PGDS also binds amyloid β peptides, prevents their fibril formation, and disaggregates amyloid β fibrils, acting as a major amyloid β chaperone in human CSF. Here, I summarize the recent progress of the research on PGD₂ and L-PGDS, in terms of its “molecular properties,” “cell culture studies,” “animal experiments,” and “clinical studies,” all of which should help to understand the pathophysiological role of L-PGDS and inspire the future research of this multifunctional lipocalin.

PGI2 Inhibits Intestinal Epithelial Permeability and Apoptosis to Alleviate Colitis

BACKGROUND & AIMS

Inflammatory bowel diseases (IBDs) that encompass both ulcerative colitis and Crohn's disease are a major public health problem with an etiology that has not been fully elucidated. There is a need to improve disease outcomes and preventive measures by developing new effective and lasting treatments. Although polyunsaturated fatty acid metabolites play an important role in the pathogenesis of several disorders, their contribution to IBD is yet to be understood.

METHODS

Polyunsaturated fatty acids metabolite profiles were established from biopsy samples obtained from Crohn's disease, ulcerative colitis, or control patients. The impact of a prostaglandin I₂ (PGI₂) analog on intestinal epithelial permeability was tested in vitro using Caco-2 cells and ex vivo using human or mouse explants. In addition, mice were treated with PGI₂ to observe dextran sulfate sodium (DSS)-induced colitis. Tight junction protein expression, subcellular location, and apoptosis were measured in the different models by immunohistochemistry and Western blotting.

RESULTS

A significant reduction of PGI₂ in IBD patient biopsies was identified. PGI₂ treatment reduced colonic inflammation, increased occludin expression, decreased caspase-3 cleavage and intestinal permeability, and prevented colitis development in DSS-induced mice. Using colonic explants from mouse and human control subjects, the staurosporine-induced increase in paracellular permeability was prevented by PGI₂. PGI₂ also induced the membrane location of occludin and reduced the permeability observed in colonic biopsies from IBD patients.

CONCLUSIONS

The present study identified a PGI₂ defect in the intestinal mucosa of IBD patients and demonstrated its protective role during colitis.

Urinary 8-iso PGF2α and 2,3-dinor-8-iso PGF2α can be indexes of colitis-associated colorectal cancer in mice

Early diagnosis of colorectal cancer is needed to reduce the mortal consequence by cancer. Lipid mediators play critical role in progression of colitis and colitis-associated colon cancer (CAC) and some of their metabolites are excreted in urine. Here, we attempted to find novel biomarkers in urinary lipid metabolite of a murine model of CAC. Mice were received single administration of azoxymethane (AOM) and repeated administration of dextran sulfate sodium (DSS). Lipid metabolites in their urine was measured by liquid chromatography mass spectrometry and their colon was collected to perform morphological study. AOM and DSS caused inflammation and tumor formation in mouse colon. Liquid chromatography mass spectrometry-based comprehensive analysis of lipid metabolites showed that cyclooxygenase-mediated arachidonic acid (AA) metabolites, prostaglandins, and reactive oxygen species (ROS)-mediated AA metabolites, isoprostanes, were predominantly increased in the urine of tumor-bearing mice. Among that, urinary prostaglandin (PG)E2 metabolite tetranor-PGEM and PGD2 metabolite tetranor-PGDM were significantly increased in both of urine collected at the acute phase of colitis and the carcinogenesis phase. On the other hand, two F2 isoprostanes (F2-IsoPs), 8-iso PGF2α and 2,3-dinor-8-iso PGF2α, were significantly increased only in the carcinogenesis phase. Morphological study showed that infiltrated monocytes into tumor mass strongly expressed ROS generator NADPH (p22phox). These observations suggest that urinary 8-iso PGF2α and 2,3-dinor-8-iso PGF2α can be indexes of CAC.

Genetic Influences on the Development of Fibrosis in Crohn's Disease

Fibrostenotic strictures are an important complication in patients with Crohn’s disease (CD), very often necessitating surgery. This fibrotic process develops in a genetically susceptible individual and is influenced by an interplay with environmental, immunological, and disease-related factors. A deeper understanding of the genetic factors driving this fibrostenotic process might help to unravel the pathogenesis, and ultimately lead to development of new, anti-fibrotic therapy. Here, we review the genetic factors that have been associated with the development of fibrosis in patients with CD, as well as their potential pathophysiological mechanism(s). We also hypothesize on clinical implications, if any, and future research directions.

Microbiota-inducible Innate Immune, Siderophore Binding Protein Lipocalin 2 is Critical for Intestinal Homeostasis

BACKGROUND & AIMS

Lipocalin 2 (Lcn2) is a multifunctional innate immune protein whose expression closely correlates with extent of intestinal inflammation. However, whether Lcn2 plays a role in the pathogenesis of gut inflammation is unknown. Herein, we investigated the extent to which Lcn2 regulates inflammation and gut bacterial dysbiosis in mouse models of IBD.

METHODS

Lcn2 expression was monitored in murine colitis models and upon microbiota ablation/restoration. WT and Lcn2 knockout (Lcn2KO) mice were analyzed for gut bacterial load, composition by 16S rRNA gene pyrosequencing and, their colitogenic potential by co-housing with Il-10KO mice. Acute (dextran sodium sulfate) and chronic (IL-10R neutralization and T-cell adoptive transfer) colitis was induced in WT and Lcn2KO mice with or without antibiotics.

RESULTS

Lcn2 expression was dramatically induced upon inflammation and was dependent upon presence of a gut microbiota and MyD88 signaling. Use of bone-marrow chimeric mice revealed non-immune cells are the major contributors of circulating Lcn2. Lcn2KO mice exhibited elevated levels of entA-expressing gut bacteria burden and, moreover, a broadly distinct bacterial community relative to WT littermates. Lcn2KO mice developed highly colitogenic T-cells and exhibited exacerbated colitis upon exposure to DSS or neutralization of IL-10. Such exacerbated colitis could be prevented by antibiotic treatment. Moreover, exposure to the microbiota of Lcn2KO mice, via cohousing, resulted in severe colitis in Il-10KO mice.

CONCLUSION

Lcn2 is a bacterially-induced, MyD88-dependent, protein that play an important role in gut homeostasis and a pivotal role upon challenge. Hence, therapeutic manipulation of Lcn2 levels may provide a strategy to help manage diseases driven by alteration of the gut microbiota.

Genome-wide analysis of DNA methylation and gene expression defines molecular characteristics of Crohn's disease-associated fibrosis

BACKGROUND

Fibrosis of the intestine is a common and poorly understood complication of Crohn's disease (CD) characterized by excessive deposition of extracellular matrix and accompanied by narrowing and obstruction of the gut lumen. Defining the molecular characteristics of this fibrotic disorder is a vital step in the development of specific prediction, prevention, and treatment strategies. Previous epigenetic studies indicate that alterations in DNA methylation could explain the mechanism by which mesenchymal cells adopt the requisite pro-fibrotic phenotype that promotes fibrosis progression. However, to date, genome-wide analysis of the DNA methylome of any type of human fibrosis is lacking. We employed an unbiased approach using deep sequencing to define the DNA methylome and transcriptome of purified fibrotic human intestinal fibroblasts (HIF) from the colons of patients with fibrostenotic CD.

RESULTS

When compared with normal fibroblasts, we found that the majority of differential DNA methylation was within introns and intergenic regions and not associated with CpG islands. Only a low percentage occurred in the promoters and exons of genes. Integration of the DNA methylome and transcriptome identified regions in three genes that inversely correlated with gene expression: wingless-type mouse mammary tumor virus integration site family, member 2B (WNT2B) and two eicosanoid synthesis pathway enzymes (prostacyclin synthase and prostaglandin D2 synthase). These findings were independently validated by RT-PCR and bisulfite sequencing. Network analysis of the data also identified candidate molecular interactions relevant to fibrosis pathology.

CONCLUSIONS

Our definition of a genome-wide fibrosis-specific DNA methylome provides new gene networks and epigenetic states by which to understand mechanisms of pathological gene expression that lead to fibrosis. Our data also provide a basis for development of new fibrosis-specific therapies, as genes dysregulated in fibrotic Crohn's disease, following functional validation, can serve as new therapeutic targets.

Professional phagocytic granulocyte-derived PGD2 regulates the resolution of inflammation in fish

Prostaglandins (PGs) play a key role in the development on the immune response through the regulation of both pro- and anti-inflammatory processes. PGD(2) can be either pro- or anti-inflammatory depending on the inflammatory milieu. Prostaglandin D synthase (PGDS) is the enzyme responsible for the conversion of PGH(2) to PGD(2). In mammals, two types of PGDS synthase have been described, the hematopoietic (H-PGDS) and the lipocalin (L-PGDS). In the present study we describe the existence of two orthologs of the mammalian L-PGDS (PGDS1 and PGDS2) in the gilthead seabream and characterize their gene expression profiles and biological activity. The results showed a dramatic induction of the gene coding for PGDS1 in acidophilic granulocytes (AGs), which are functionally equivalent to mammalian neutrophils, after a prolonged in vitro activation with different pathogen associated molecular patterns (PAMPs). In contrast PGDS2 was not expressed in these cells. The functional relevance of the induction of PGDS1 in AGs was confirmed by the ability of these cells to release PGD(2) upon PAMP stimulation. To gain further insight into the role of PGD(2) in the resolution of inflammation in fish, we examined the ability of PGD(2) or its cyclopentenone derivates (cyPGs) to modulate the main functional activities of AGs. It was found that both PGD(2) and cyPGs inhibited the production of reactive oxygen species and downregulated the transcript levels of the gene encoding interleukin-1β. Taken together, these results demonstrate that the use of PGD(2) and its metabolites in the resolution of inflammation was established before the divergence of fish from tetrapods more than 450 million years ago and support a critical role for granulocytes in the resolution of inflammation in vertebrates.

The GPR55 antagonist CID16020046 protects against intestinal inflammation

BACKGROUND

G protein-coupled receptor 55 (GPR55) is a lysophospholipid receptor responsive to certain cannabinoids. The role of GPR55 in inflammatory processes of the gut is largely unknown. Using the recently characterized GPR55 inhibitor CID16020046, we determined the role of GPR55 in experimental intestinal inflammation and explored possible mechanisms of action.

METHODS

Colitis was induced by either 2.5% dextran sulfate sodium (DSS) supplemented in the drinking water of C57BL/6 mice or by a single intrarectal application of trinitrobenzene sulfonic acid (TNBS).

KEY RESULTS

Daily application of CID16020046 (20 mg/kg) significantly reduced inflammation scores and myeloperoxidase (MPO) activity. In the DSS colitis model, levels of tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β), and the expression of cyclooxygenase (Cox)-2 and signal transducer and activator of transcription 3 (STAT-3) were reduced in colon tissues while in TNBS-induced colitis, levels of Cox-2, IL-1β and IL-6 were significantly lowered. Evaluation of leukocyte recruitment by flow cytometry indicated reduced presence of lymphocytes and macrophages in the colon following GPR55 inhibition in DSS-induced colitis. In J774A.1 mouse macrophages, inhibition of GPR55 revealed reduced migration of macrophages and decreased CD11b expression, suggesting that direct effects of CID16020046 on macrophages may have contributed to the improvement of colitis. GPR55(-/-) knockout mice showed reduced inflammation scores as compared to wild type mice in the DSS model suggesting a pro-inflammatory role in intestinal inflammation.

CONCLUSIONS & INFERENCES

Pharmacological blockade of GPR55 reduces experimental intestinal inflammation by reducing leukocyte migration and activation, in particular that of macrophages. Therefore, CID16020046 represents a possible drug for the treatment of bowel inflammation.

Activation of the prostaglandin D2 metabolic pathway in Crohn's disease: involvement of the enteric nervous system

Background

Recent works provide evidence of the importance of the prostaglandin D2 (PGD2) metabolic pathway in inflammatory bowel diseases. We investigated the expression of PGD2 metabolic pathway actors in Crohn’s disease (CD) and the ability of the enteric nervous system (ENS) to produce PGD2 in inflammatory conditions.

Methods

Expression of key actors involved in the PGD2 metabolic pathway and its receptors was analyzed using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) in colonic mucosal biopsies of patients from three groups: controls, quiescent and active CD patients. To determine the ability of the ENS to secrete PGD2 in proinflammatory conditions, Lipocalin-type prostaglandin D synthase (L-PGDS) expression by neurons and glial cells was analyzed by immunostaining. PGD2 levels were determined in a medium of primary culture of ENS and neuro-glial coculture model treated by lipopolysaccharide (LPS).

Results

In patients with active CD, inflamed colonic mucosa showed significantly higher COX2 and L-PGDS mRNA expression, and significantly higher PGD2 levels than healthy colonic mucosa. On the contrary, peroxysome proliferator-activated receptor Gamma (PPARG) expression was reduced in inflamed colonic mucosa of CD patients with active disease. Immunostaining showed that L-PGDS was expressed in the neurons of human myenteric and submucosal plexi. A rat ENS primary culture model confirmed this expression. PGD2 levels were significantly increased on primary culture of ENS treated with LPS. This production was abolished by AT-56, a specific competitive L-PGDS inhibitor. The neuro-glial coculture model revealed that each component of the ENS, ECG and neurons, could contribute to PGD2 production.

Conclusions

Our results highlight the activation of the PGD2 metabolic pathway in Crohn’s disease. This study supports the hypothesis that in Crohn’s disease, enteric neurons and glial cells form a functional unit reacting to inflammation by producing PGD2.

[Dual role for prostaglandin D2 in intestinal epithelial homeostasis]

Prostaglandin D2 (PGD2) and derivatives are lipid mediators involved in the control of the intestinal epithelial barrier homeostasis. Their involvement in the pathophysiology of chronic inflammatory bowel disease (IBD) is still debated. Several results highlight the duality of PGD2 as an anti- or pro-inflammatory mediator. This duality seems to be related to a differential expression of its receptors by intestinal epithelial cells and the surrounding immunocompetent cells. The enteric glial cells from the enteric nervous system (ENS) express the lipocalin-type-prostaglandin D synthase and secrete PGD2 and 15d-PGJ2. The protective role of the ENS in the homeostatic control of the epithelial intestinal barrier and its involvement in the pathogenesis of IBD have already been demonstrated. Thus, these lipid mediators seem to be new actors of the neuro-glio-epithelial unit and could play a crucial role maintaining gut barrier integrity.

β-Trace protein: a marker of GFR and other biological pathways

β-Trace protein (BTP), also known as lipocalin prostaglandin D2 synthase (L-PGDS; encoded by the PTGDS gene), is a low-molecular-weight glycoprotein and an emerging novel marker of glomerular filtration rate. BTP is an important constituent of cerebral spinal fluid and is found in much lower concentrations in blood. Its serum origin and renal handling remain poorly understood. Unlike serum creatinine, BTP is not physiologically inert. It possesses both ligand-binding and enzymatic properties. BTP catalyzes the conversion of prostaglandin H2 (PGH2) to PGD2. PGD2 is an eicosanoid involved in a variety of important physiologic processes, including platelet aggregation, vasodilation, inflammation, adipogenesis, and bone remodeling. Several studies now have documented BTP's strong association with glomerular filtration rate, end-stage renal disease, cardiovascular disease, and death in a variety of different patient populations. This review provides an overview of the biochemistry, physiology and metabolism, biological functions, and measurement of BTP; summarizes the evidence for BTP as a marker of both kidney function and cardiovascular disease; and then considers the interplay between its biological properties, serum concentration, and patient outcomes.

Opposing roles of prostaglandin D2 receptors in ulcerative colitis

Proresolution functions were reported for PGD2 in colitis, but the role of its two receptors, D-type prostanoid (DP) and, in particular, chemoattractant receptor homologous molecule expressed on Th2 cells (CRTH2), is less well defined. We investigated DP and CRTH2 expression and function during human and murine ulcerative colitis (UC). Expression of receptors was measured by flow cytometry on peripheral blood leukocytes and by immunohistochemistry and immunoblotting in colon biopsies of patients with active UC and healthy individuals. Receptor involvement in UC was evaluated in a mouse model of dextran sulfate sodium colitis. DP and CRTH2 expression changed in leukocytes of patients with active UC in a differential manner. In UC patients, DP showed higher expression in neutrophils but lower in monocytes as compared with control subjects. In contrast, CRTH2 was decreased in eosinophils, NK, and CD3(+) T cells but not in monocytes and CD3(+)/CD4(+) T cells. The decrease of CRTH2 on blood eosinophils clearly correlated with disease activity. DP correlated positively with disease activity in eosinophils but inversely in neutrophils. CRTH2 internalized upon treatment with PGD2 and 11-dehydro TXB2 in eosinophils of controls. Biopsies of UC patients revealed an increase of CRTH2-positive cells in the colonic mucosa and high CRTH2 protein content. The CRTH2 antagonist CAY10595 improved, whereas the DP antagonist MK0524 worsened inflammation in murine colitis. DP and CRTH2 play differential roles in UC. Although expression of CRTH2 on blood leukocytes is downregulated in UC, CRTH2 is present in colon tissue, where it may contribute to inflammation, whereas DP most likely promotes anti-inflammatory actions.

The universe of arachidonic acid metabolites in inflammatory bowel disease: can we tell the good from the bad?

PURPOSE OF REVIEW

This review summarizes recent developments in the role of soluble mediators of inflammation, particularly arachidonic acid metabolites, in inflammatory bowel disease (IBD).

RECENT FINDINGS

The role of prostaglandin E2 in immune regulation has been better defined. Prostaglandin E2 promotes not only immune tolerance and epithelial homeostasis but also the proinflammatory Th17 pathway. Prostaglandin D2 has been established as promoting the resolution of inflammation in the gastrointestinal mucosa. The 12-lipoxygenase product hepoxilin A3 mediates the migration of neutrophils from the mucosa into the lumen.

SUMMARY

Recent studies of soluble mediators, especially arachidonic acid metabolites, have defined their proinflammatory and anti-inflammatory roles in IBD.

Comparative protective effect of hawthorn berry hydroalcoholic extract, atorvastatin, and mesalamine on experimentally induced colitis in rats

The protective effect of hydroalcoholic extract of hawthorn berries (HBE) on acetic acid (AA)-induced colitis in rats was investigated. Forty-two Wistar rats were divided into seven groups, including control and test groups (n=6). The control animals received saline, and the test animals were treated with saline (sham group), mesalamine (50 mg/kg; M group), atorvastatin (20 mg/kg; A group), HBE (100 mg/kg; H group), mesalamine and HBE (HM group), or atorvastatin plus HBE (HA group), 3 days before and a week after colitis induction. Colitis was induced by administration of 1 mL AA (4%) via a polyethylene catheter intrarectally. High-performance liquid chromatography analyses showed that HBE contained 0.13% and 0.5% oleanolic acid and ursolic acid, respectively. Elevated myeloperoxidase activity and lipid peroxidation were attenuated in the HA group. The H and HM groups showed marked reductions in colitis-induced decreases in total thiol molecules and body weight. The histopathological studies revealed that HBE decreased colitis-induced edema and infiltration of neutrophils. Our data suggest the anti-inflammatory and antioxidant effects of HBE and atorvastatin protect against AA-induced colitis. The anti-inflammatory effect of HBE may be attributable to its ability to decrease myeloperoxidase activity as a biomarker of neutrophil infiltration.

Urinary proteome analysis of irritable bowel syndrome (IBS) symptom subgroups

Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder characterized by chronic abdominal pain associated with alterations in bowel function. Given the heterogeneity of the symptoms, multiple pathophysiologic factors are suspected to play a role. We classified women with IBS into four subgroups based on distinct symptom profiles. In-depth shotgun proteomic analysis was carried out to profile the urinary proteomes to identify possible proteins associated with these subgroups. First void urine samples with urine creatinine level≥100 mg/dL were used after excluding samples that tested positive for blood. Urine from 10 subjects representing each symptom subgroup was pooled for proteomic analysis. The urine proteome was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a data-independent method known as Precursor Acquisition Independent From Ion Count (PAcIFIC) that allowed extended detectable dynamic range. Differences in protein quantities were determined by peptide spectral counting followed by validation of select proteins with ELISA or a targeted single reaction monitoring (LC-SRM/MS) approach. Four IBS symptom subgroups were selected: (1) Constipation, (2) Diarrhea+Low Pain, (3) Diarrhea+High Pain, and (4) High Pain+High Psychological Distress. A fifth group consisted of Healthy Control subjects. From comparisons of quantitative spectral counting data among the symptom subgroups and controls, a total of 18 proteins that showed quantitative differences in relative abundance and possible physiological relevance to IBS were selected for further investigation. Three of the 18 proteins were chosen for validation by either ELISA or SRM. An elevated expression of gelsolin (GSN) was associated with the high pain groups. Trefoil Factor 3 (TFF3) levels were higher in IBS groups compared to controls. In this study, the IBS patients subclassified by predominant symptoms showed differences in urine proteome levels. Proteins showing distinctive changes are involved in homeostasis of intestinal function and inflammatory response. These findings warrant future studies with larger, independent cohorts to enable more extensive assessment and validation of urinary protein markers as a diagnostic tool in adults with IBS.

PGD synthase and PGD2 in immune resposne

PGD₂ is formed from arachidonic acid by successive enzyme reactions: oxygenation of arachidonic acid to PGH₂, a common precursor of various prostanoids, catalyzed by cyclooxygenase, and isomerization of PGH₂ to PGD₂ by PGD synthases (PGDSs). PGD₂ can be either pro- or anti-inflammatory depending on disease process and etiology. The anti-inflammatory and immunomodulatory attributes of PGDS/PGD₂ provide opportunities for development of novel therapeutic approaches for resistant infections and refractory inflammatory diseases. This paper highlights the role of PGD synthases and PGD2 in immune inflammatory response.

L1 penalized continuation ratio models for ordinal response prediction using high-dimensional datasets

Health status and outcomes are frequently measured on an ordinal scale. For high-throughput genomic datasets, the common approach to analyzing ordinal response data has been to break the problem into one or more dichotomous response analyses. This dichotomous response approach does not make use of all available data and therefore leads to loss of power and increases the number of type I errors. Herein we describe an innovative frequentist approach that combines two statistical techniques, L(1) penalization and continuation ratio models, for modeling an ordinal response using gene expression microarray data. We conducted a simulation study to assess the performance of two computational approaches and two model selection criteria for fitting frequentist L(1) penalized continuation ratio models. Moreover, we empirically compared the approaches using three application datasets, each of which seeks to classify an ordinal class using microarray gene expression data as the predictor variables. We conclude that the L(1) penalized constrained continuation ratio model is a useful approach for modeling an ordinal response for datasets where the number of covariates (p) exceeds the sample size (n) and the decision of whether to use Akaike Information Criterion (AIC) or Bayesian Information Criterion (BIC) for selecting the final model should depend upon the similarities between the pathologies underlying the disease states to be classified.