Metabolism Of Prostaglandin E2 Research Articles

Targeting Metabolomics in Primary Hypertrophic Osteoarthropathy: Uncovering Novel Insights into Disease Pathogenesis.

Primary hypertrophic osteoarthropathy (PHO) is a rare genetic disorder characterized by skeletal and skin abnormalities. Genetic defects in prostaglandin E2 (PGE2) metabolism are known to cause PHO. However, the global impact and clinical significance of eicosanoids and oxylipins beyond PGE2 remain to be elucidated. This study aimed to investigate oxylipin networks in PHO, including the 2 subtypes, PHOAR1 and PHOAR2, and examine their associations with clinical characteristics. We conducted a targeted metabolomic study involving 16 patients with PHO and 16 age- and sex-matched healthy controls. Serum samples were collected at the time of diagnosis. Metabolites were quantified using ultra-high-performance liquid chromatography-tandem mass spectrometry. Laboratory analyses confirmed elevated levels of PGE2 in patients with PHO, consistent with the established pathogenesis. About 60 oxidized lipid metabolites were identified, with 19 differentially expressed in PHO. Besides the COX/PGE2 pathway, the lipoxygenase-mediated pathway was also involved in PHO. The metabolites 5-OxoETE, 15-OxoETE, 8S,15S-DiHETE, PGE2, 11β-PGE2, PGB2, LTB4, and LTE4 were significantly altered. Correlation analyses revealed associations between oxylipin metabolites and clinical features, including bone microarchitecture. Notably, the study highlighted differences in the oxylipin metabolite profiles between patients with PHOAR1 and patients with PHOAR2, suggesting distinct metabolic signatures for each subtype. Our study indicated a significant perturbation in oxylipin metabolism among patients with PHO, with distinct metabolic signatures observed between PHOAR1 and PHOAR2. The disruption extended beyond the metabolism of PGE2. It encompassed a broader alteration across the polyunsaturated fatty acid metabolism spectrum, including various eicosanoids and oxylipins. Our work provided a comprehensive understanding of the pathogenesis of PHO, and underscored the potential for subtype-specific therapeutic interventions.

Tissue lipidomic profiling supports a mechanistic role of the prostaglandin E2 pathway for albuminuria development in glomerular hyperfiltration.

Background: Glomerular hyperfiltration (GH) is an important mechanism in the development of albuminuria in hypertension. The Munich Wistar Frömter (MWF) rat is a non-diabetic model of chronic kidney disease (CKD) with GH due to inherited low nephron number resulting in spontaneous albuminuria and podocyte injury. In MWF rats, we identified prostaglandin (PG) E2 (PGE2) signaling as a potential causative mechanism of albuminuria in GH. Method: For evaluation of the renal PGE2 metabolic pathway, time-course lipidomic analysis of PGE2 and its downstream metabolites 15-keto-PGE2 and 13-14-dihydro-15-keto-PGE2 was conducted in urine, plasma and kidney tissues of MWF rats and albuminuria-resistant spontaneously hypertensive rats (SHR) by liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Results: Lipidomic analysis revealed no dysregulation of plasma PGs over the time course of albuminuria development, while glomerular levels of PGE2 and 15-keto-PGE2 were significantly elevated in MWF compared to albuminuria-resistant SHR. Overall, averaged PGE2 levels in glomeruli were up to ×150 higher than the corresponding 15-keto-PGE2 levels. Glomerular metabolic ratios of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) were significantly lower, while metabolic ratios of prostaglandin reductases (PTGRs) were significantly higher in MWF rats with manifested albuminuria compared to SHR, respectively. Conclusion: Our data reveal glomerular dysregulation of the PGE2 metabolism in the development of albuminuria in GH, resulting at least partly from reduced PGE2 degradation. This study provides first insights into dynamic changes of the PGE2 pathway that support a role of glomerular PGE2 metabolism and signaling for early albuminuria manifestation in GH.

Features of the clinical course of pachydermoperiostosis with a verified mutation in the European type gene

Pachydermoperiostosis (primary hypertrophic osteoarthropathy) is an orphan disease, the main clinical manifestations of which include pin-shaped deformity of the fingers according to the type of «drumsticks», periostosis (non-inflammatory changes of the periosteum) of tubular bones, pachydermia of the face (hypertrophy and hyperplasia of all skin layers). Two genes associated with the development of pachydermoperiostosis are known — HPGD and SLCO2A1. Mutations in these genes lead to impaired prostaglandin E2 metabolism. This article describes a clinical case of a patient with pachydermoperiostosis, in which two mutations in the HPGD gene were detected during a molecular genetic study: in 1 exon (chr4-174522451-T-A, NM_000860.6:c.1A>T) and in 2 exon (chr4-174521985-AG-, NM_000860.6:c.175_176del) in compound-heterozygous state, while the c.1A>T mutation was previously described once, and the revealed biallelic combination of mutations in the HPGD gene was not previously found in the literature. This clinical case of pachydermoperiostosis is the second described in the Russian population, and the first with confirmed mutations in the HPGD gene. The article expands the knowledge about the correlation of genotype and phenotype in pachydermoperiostosis, which contributes to a faster and more correct interpretation of genetic information during genetic counseling.

Clinical and genetic characteristics of primary hypertrophic osteoarthropathy

Background. Primary hypertrophic osteoarthropathy is a rare genetically heterogeneous disease with three clinical variants. The classic one is a combination of hyperostosis, arthropathy and pachyderma and two variants with damage to only bone structures or pachyderma. Two genes responsible for the occurrence of primary hypertrophic osteoarthropathy have been identified: HPGD (debut age up to one year) and SLCO2A1 (debut in puberty and adolescence), whose products are involved in prostaglandin E2 metabolism. Two recurrent variants were identified in the HPGD gene: c.175_176delCT(p.Leu59fs) in patients from Europe and c.310_311delCT in patients from China. There were no clinical and genetic correlations in patients with different variants in the identified genes, which may be due to a small number of observations. The analysis of clinical manifestations in patients with newly identified variants or previously unidentified combinations of variants in a compound‑heterozygous state helps to understand the pathogenesis and prognosis of the course of the disease.Aim. To present the clinical and genetic characteristics of two Russian patients with primary hypertrophic osteoarthropathy caused by a newly identified combination of nucleotide variants in a compound‑heterozygous state in the HPGD and SLCO2A1 genes.Materials and methods. Clinical examination, radiography of the skeleton and chest, electrocardiography, echocardiography. Confirmation of the pathogenicity of the identified variants and clarification of the type of disease was carried out using automatic Sanger sequencing.Results. The clinical and genetic characteristics of two unrelated patients with primary hypertrophic osteoarthropathy caused by an undescribed combination of variants in the compound heterozygous state in the HPGD and SLCO2A1 genes were analyzed. In a patient with variants in the SLCO2A1 gene, the disease debuts at the age of 14 with deformities of the fingers, nails on the hands and feet, followed by the addition of burning pain in the distal parts of the arms and legs. At the age of 33, the examination revealed deformity of the fingers of the hands and feet by the type of drumsticks and nails by the type of watch glasses, enlargement of the knee joints, pronounced arthralgia. There were no signs of pachyderma. The new generation sequencing revealed two variants in the SLCO2A1 gene c.764G>A(p.Gly255Glu) in exon 6 and c.1333C>T(p.Arg445Cys) in exon 10. These variants were identified earlier in a compound‑heterozygous combination with other variants in patients with the classical phenotype of the disease, which were not present in the patient we observed. A feature of the case was pronounced hyperhidrosis and burning pain in the extremities, which may be due to stimulation of nociceptors in the musculoskeletal structures.Deformities of the fingers, nails of the hands and feet occurred in a patient with variants in the HPGD gene at 6 months. At the age of 9 years, a change in shape, stiffness and arthralgia of the knee and elbow joints without pachyderma were revealed. The identified variant with c.175_176delCT(p.Leu59fs) in this gene is often found in patients from European countries, and the other is c.1A>G(p.Met1?) discovered for the first time.Conclusion. The results allow us to conclude that when we found combinations of two variants in the HPGD and SLCO2A1 genes, there will be no pachyderma in the spectrum of clinical manifestations of primary hypertrophic osteoarthropathy. Sequencing of the new generation exome is the optimal diagnostic method.

Idiopathic hypertrophic osteoarthropathy misdiagnosed as juvenile idiopathic arthritis. Case study

Background. Pachydermoperiostosis (or primary hypertrophic osteoarthropathy) is a rare genetic disease that usually begins in childhood or adolescence, is characterized by certain clinical signs (pachydermia, periostosis, drum sticks) that gradually progress over many years until the disease stabilizes. Currently, there are 2 genes in which mutations are associated with the development of pachydermoperiostosis - HPGD and SLCO2A1. The functions of these genes are not fully understood, but their influence on the metabolism of prostaglandin E2 is known. Case presentation. We present a case of a 20-year-old patient mistakenly diagnosed as juvenile idiopathic arthritis. Symptoms on admission to the hospital: pain accompanied by swelling in the hands and feet, arthralgias in the talocrural joints, knees with slight swelling, paresthesia in the extremities, hyperhidrosis, fatigue. Clinical and paraclinical examinations confirmed the diagnosis of pachydermoperiostosis. Conclusions. Pachydermoperiostosis should be considered as a differential diagnosis when a patient presents with hypertrophic osteoarthropathy and acromegalic features.

Familial Incomplete Hypertrophic Osteoarthropathy: A Rare Disorder

Dear Editor, Hypertrophic osteoarthropathy is a condition in which there is abnormal proliferation of skin and soft tissue, particularly around the periosteal tissues. It is a very rare condition which is mainly described as two types, in which the common form is secondary hypertrophic osteoarthropathy caused by underlying disease and the rare primary idiopathic form. Here, we present a case of incomplete familial form of hypertrophic osteoarthropathy where a young male presented with multiple joint pains and Grade 4 clubbing and large patella. A 24-year-old male presented with multiple joint pains predominantly involving both knees, elbows, and shoulders. There was no history of any joint swelling or morning stiffness. There was no other history suggestive of connective tissue disorder. On examination, Grade 4 clubbing was present [Figure 1]. Systemic examination was unremarkable. Musculoskeletal (MSK) examination revealed a significantly large patella on both sides [Figure 1]. There were no signs of inflammation. On further probing, the patient gave a history of similar clubbing and joint pains for his sister, brother, and grandfather. His father also has similar complaints but with less severity (pedigree charting below mentioned) [Figure 2]. On investigations, blood counts and liver and kidney function tests were normal. C-reactive protein was negative. Thyroid profile was normal. To rule out acromegaly, growth hormone levels and magnetic resonance imaging brain were done which were normal. X-ray hands and both knees were done suggestive of periostosis. MSK ultrasonography of the knees was done suggestive of zigzag appearance of the patella [Figure 3]. A diagnosis of incomplete familial hypertrophic osteoarthropathy was made as there was no skin thickening and no coarse facial features and no other systems such as hematological or endocrine are involved. He was prescribed etoricoxib, and on follow-up, he was symptomatically better. Genetic testing was not done in our patient as he is not willing for that.Figure 1: Digital clubbing with large patellaFigure 2: Pedigree chart showing affected individuals in three generationsFigure 3: X-ray showing periosteal reaction involving the terminal phalanges, both bones of forearm, and long bones of lower limbs. USG image showing Zigzag appearance of the patella. USG: UltrasonographyPrimary or idiopathic form of hypertrophic osteoarthropathy is very rare and constitutes only 2%–3% of cases. It is inherited as autosomal dominant or recessive disorder, and it was thought to be caused by impaired metabolism of prostaglandin E2.[1] Pachydermoperiostosis is an another name given to this disorder due to the presence of coarse facial features with underlying thickening and furrowing of skin.[2] If both skin involvement and periosteal components are present then it is called complete form. The other two forms are incomplete with prominent periosteal with less skin involvement (like our case) and fruste form with more skin features and less periosteal features. The diagnostic criteria for PDP (pachydermo-periostosis) include major criteria and minor criteria. Major consists of pachyderma, periostosis, and finger clubbing and minor criteria includes hyperhidrosis, arthralgia, gastric ulcer, cutis verticis gyrata, blepharoptosis, joint effusion, edema, seborrhea, acne, and flushing.[3] Endocrine disorders like acromegaly, hypothyroidism, acropathy and other conditions like multifocal periostitis to be ruled out before labeling this condition. The other mimic of this condition is psoriatic onycho-pachydermo-periostitis except for the presence of psoriatic lesions.[4] Nonsteroidal anti-inflammatory drugs are the main stay of treatment as they act by blocking prostaglandin synthesis. They can have a good prognosis and normal life span.[5] Other treatment modalities available are corticosteroids, colchicine, or bisphosphonates.[6] Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Prostaglandin E2 (PGE2) synthesis pathway is involved in coronary artery stenosis and restenosis.

The inflammatory events related to prostaglandins may play an important role in the progression of vessel stenosis. The aim of this study was to investigate the monocyte PTGES and 15-PGDH gene expression levels and the serum 13,14-dihyro-15-keto-PGF2α value involved in PGE2 metabolism in patients with coronary artery stenosis and restenosis. Moreover, the effects of miR-520, miR-1297 and miR-34 were studied on the gene expression levels. A total of sixty subjects referred for coronary angiography including healthy controls (stenosis <5%), subjects with stent no restenosis) SNR, stenosis <5%) and subjects in stent restenosis (ISR, restenosis >70%) were participated in the study. The gene expression levels and the serum 13,14-dihyro-15-keto- PGF2α value were measured by RT-qPCR and ELISA techniques, respectively. Moreover, the effects of miRNAs on the gene expression levels were investigated by the monocyte transfection of miR/PEI complexes. The PTGES and 15-PGDH gene expression levels and serum 13,14-dihyro-15-keto- PGF2α value increased significantly (P <0.05). Based on the miR-520 and miR-34 expression levels, the miR/PEI transfection studies were confirmed significantly the gene expression changes. The monocyte PGE2 synthesis pathway is actively considered in the SNR and ISR patients and might be related to miR-34 and miR-520 functions.

Dietary Selenium in Immune Mechanisms During an Enteric Bacterial Infection (OR12-08-19)

ObjectivesEnteropathogenic Escherichia coli (EPEC) poses a great threat to developing countries, as EPEC can result in diarrhea and colitis in children. Interestingly, the effect of trace element nutritional deficiencies as well as their supplementation on disease pathogenesis is increasingly being recognized. We have previously reported that supplementation of mice with selenium (Se), a trace element that is incorporated into selenoproteins as the 21st amino acid, resulted in the amelioration of chemically induced colitis through the downregulation of pro-inflammatory mediators of the arachidonic acid pathway, including prostaglandin E2 (PGE2). Here we examined the effects of Se supplementation on immune responses during an enteric infection with Citrobacter rodentium, a natural murine enteropathogen. MethodsC57BL/6 mice placed on Se-deficient (0.01 ppm Se), Se-adequate (0.08 ppm Se), or Se-supplemented (0.4 ppm Se) diets for 8 weeks were infected with Citrobacter rodentium, the murine equivalent of EPEC with a shared core set of virulence factors. Mice were euthanized, and colons were collected for further analysis including western blots and flow cytometry. ResultsSe-deficient mice experienced increased bacterial burden, mortality, and decreased colon length following infection, compared to Se-adequate and Se-supplemented mice. Studies revealed that there was an increase type 3 innate-lymphoid cells (ILC3s) and IL-22 producing T helper 17 (Th17) cells, but a decrease in regulatory T- cells (Tregs) and 15-prostaglandin dehydrogenase (15-PGDH), the enzyme that preferentially oxidizes PGE2, in the colon of Se-deficient mice compared to Se-adequate and Se-supplemented mice. Treatment of Se-adequate mice with CAY10397, an inhibitor of 15-PGDH, increased the bacterial burden following infection. Infection of mice that lack expression of selenoproteins in macrophages (Trspfl/fl LysMCre) showed increased mortality despite being fed diets replete with Se. ConclusionsAdequate to supplemental levels of dietary Se is required to maximize the expression of selenoproteins to effectively mediate resolution of enteric infections. Selenoproteins act through diverse mechanisms, including modulation of immune responses and inflammation through the oxidative metabolism of PGE2. Funding SourcesNational Institute of Health.

Novel SLCO2A1 mutations cause gender differentiated pachydermoperiostosis.

Primary hypertrophic osteoarthropathy (PHO) is a rare familial disorder with reduced penetrance for females. The genetic mutations associated with PHO have been identified in HPGD and SLCO2A1, which involved in prostaglandin E2 metabolism. Here, we report 5 PHO patients from four non-consanguineous families. Two heterozygous mutations in solute carrier organic anion transporter family member 2A1 (SLCO2A1) were identified in two brothers by whole-exome sequencing. Three heterozygous mutations and one homozygous mutation were identified in other three PHO families by Sanger sequencing. However, there was no mutation in HPGD. These findings confirmed that homozygous or compound heterozygous mutations of SLCO2A1 were the pathogenic cause of PHO. A female individual shared the same mutations in SLCO2A1 with her PHO brother but did not have any typical PHO symptoms. The influence of sex hormones on the pathogenesis of PHO and its implication were discussed.

Effects of Combined Treatment with Vitamin D and COX2 Inhibitors on Breast Cancer Cell Lines.

Vitamin D is known for its anticancer potential. Prostaglandin E2 (PGE2) is a proliferative and inflammation-activating agent. The production of PGE2 is dependent on the activity of cyclooxygenase-2 (COX2). A link between vitamin D and PGE2 metabolism was shown recently. In MDA-MB-231 and MCF-7 breast cancer cell lines, we investigated the influence of calcitriol and the COX2 inhibitor celecoxib on cell growth via the MTT test, as well as on the protein and mRNA expression of COX2 using western blot and quantitative real-time polymerase chain reaction (qRT-PCR). The proliferation of MCF-7 and MDA-MB-231 was inhibited by both calcitriol and the COX2 inhibitor celecoxib and even more strongly by their combination. Moreover, calcitriol inhibited COX2 protein expression in MDA-MB-231 cells, as well as COX2 mRNA expression in both cell lines. The combination of calcitriol and celecoxib demonstrated a synergistic growth-inhibitory effect in breast cancer cell lines.

Pachydermoperiostosis: a case report

Pachydermoperiostosis (PHO) or primary hypertrophic osteoarthropathy is a rare genetic disease that typically begins during childhood or adolescence. It is characterized by digital clubbing, pachydermia and periosteal reaction and progresses gradually over the years prior to disease stabilization. Two genes are reported to be associated with PHO – HPGD and SLCO2A1. These genes are involved in prostaglandin E2 metabolism.&#x0D; We present a description of a 19-year-old patient with PHO. We found two mutations in the SLCO2A1 gene: p.Gly183Ar (chr3:133673888, NM_005630.2:c.547G&gt;A) and p.Cys444Gly (chr3:133664070, NM_005630.2:c.1330T&gt;G) through molecular genetic analysis. The mutation (p.Cys444Gly) has never been recorded in previous studies.&#x0D; This work expands our knowledge of the mutation spectrum of PHO, which will facilitate faster genetic diagnosis and interpretation of genetic information in prenatal diagnosis and genetic counseling.

Primary hypertrophic osteoarthropathy due to a novel SLCO2A1 mutation masquerading as acromegaly

SummaryA 20-year-old man with an 8-year history of progressive enlargement of his hands and feet, coarsening facial features, painful joints and thickened, oily skin was referred for investigation of acromegaly. On examination, the subject was of normal height and weight. He had markedly increased skin thickness around the forehead, eyelids and scalp with redundant skin folds. Bilateral painful knee swelling was accompanied by enlargement of the extremities, and his fingers were markedly clubbed. Routine hematological, biochemical and hormonal blood tests, including GH and IGF-1 were normal. The clinical picture suggested primary hypertrophic osteoarthropathy (PHOA) rather than acromegaly and radiological studies were supportive of this, demonstrating increased subperiosteal bone formation and increased bone density and cortical thickening. There was widespread joint disease, with narrowing of joint spaces, whereas the knees demonstrated effusions and calcification. A skull X-ray revealed calvarial hyperostosis and a normal sellar outline. Family history was negative. Genetic studies were performed on peripheral blood leukocyte DNA for mutations in the two genes associated with PHOA, 15-hydroxyprostaglandin dehydrogenase (HPGD; OMIM: 601688) and solute carrier organic anion transporter family member 2A1 (SLCO2A1; OMIM: 601460). The sequence of HPGD was normal, whereas the subject was homozygous for a novel pathological variant in SLCO2A1, c.830delT, that predicted a frameshift and early protein truncation (p.Phe277Serfs*8). PHOA, also known as pachydermoperiostosis, is a rare entity caused by abnormal prostaglandin E2 metabolism, and both HPGD and SLCO2A1 are necessary for normal prostaglandin E2 handling. High prostaglandin levels lead to bone formation and resorption and connective tissue inflammation causing arthropathy, in addition to soft tissue swelling.Learning points:The differential diagnosis of enlarged extremities, coarsened facial features, skin changes and increased sweating in suspected acromegaly is quite limited and primary hypertrophic osteoarthropathy (PHOA) is one of the few conditions that can mimic acromegaly at presentation.PHOA is not associated with abnormalities in GH and IGF-1 secretion and can be readily differentiated from acromegaly by hormonal testing.Clubbing in the setting of diffuse enlargement of joints and extremities in addition to skin changes should alert the physician to the possibility of PHOA, as clubbing is not a usual feature of acromegaly. Underlying causes of secondary hypertrophic osteoarthroapthy (e.g. bronchial neoplasia) should be considered.PHOA is a very rare condition caused by abnormalities in prostaglandin metabolism and has two known genetic causes (HPGD and SLCO2A1 mutations). SLCO2A1 gene mutations lead usually to autosomal recessive PHOA; fewer than 50 SLCO2A1 mutations have been described to date and the current case is only the second in a Hispanic patient.Treatment of primary hypertrophic osteoarthropathy is focused on the management of joint pain usually in the form of non-steroidal anti-inflammatory drug therapy.

COX2/mPGES1/PGE2 pathway regulates PD-L1 expression in tumor-associated macrophages and myeloid-derived suppressor cells

In recent years, it has been established that programmed cell death protein ligand 1 (PD-L1)-mediated inhibition of activated PD-1+ T lymphocytes plays a major role in tumor escape from immune system during cancer progression. Lately, the anti-PD-L1 and -PD-1 immune therapies have become an important tool for treatment of advanced human cancers, including bladder cancer. However, the underlying mechanisms of PD-L1 expression in cancer are not fully understood. We found that coculture of murine bone marrow cells with bladder tumor cells promoted strong expression of PD-L1 in bone marrow-derived myeloid cells. Tumor-induced expression of PD-L1 was limited to F4/80+ macrophages and Ly-6C+ myeloid-derived suppressor cells. These PD-L1-expressing cells were immunosuppressive and were capable of eliminating CD8 T cells in vitro. Tumor-infiltrating PD-L1+ cells isolated from tumor-bearing mice also exerted morphology of tumor-associated macrophages and expressed high levels of prostaglandin E2 (PGE2)-forming enzymes microsomal PGE2 synthase 1 (mPGES1) and COX2. Inhibition of PGE2 formation, using pharmacologic mPGES1 and COX2 inhibitors or genetic overexpression of PGE2-degrading enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH), resulted in reduced PD-L1 expression. Together, our study demonstrates that the COX2/mPGES1/PGE2 pathway involved in the regulation of PD-L1 expression in tumor-infiltrating myeloid cells and, therefore, reprogramming of PGE2 metabolism in tumor microenvironment provides an opportunity to reduce immune suppression in tumor host.

Multiple drug resistance-associated protein (MRP4) exports prostaglandin E2 (PGE2) and contributes to metastasis in basal/triple negative breast cancer

Cyclooxygenase-2 (COX-2) and its primary enzymatic product, prostaglandin E2 (PGE2), are associated with a poor prognosis in breast cancer. In order to elucidate the factors contributing to intratumoral PGE2 levels, we evaluated the expression of COX-2/PGE2 pathway members MRP4, the prostaglandin transporter PGT, 15-PGDH (PGE2 metabolism), the prostaglandin E receptor EP4, COX-1, and COX-2 in normal, luminal, and basal breast cancer cell lines. The pattern of protein expression varied by cell line reflecting breast cancer heterogeneity. Overall, basal cell lines expressed higher COX-2, higher MRP4, lower PGT, and lower 15-PGDH than luminal cell lines resulting in higher PGE2 in the extracellular environment. Genetic or pharmacologic suppression of MRP4 expression or activity in basal cell lines led to less extracellular PGE2. The key finding is that xenografts derived from a basal breast cancer cell line with stably suppressed MRP4 expression showed a marked decrease in spontaneous metastasis compared to cells with unaltered MRP4 expression. Growth properties of primary tumors were not altered by MRP4 manipulation. In addition to the well-established role of high COX-2 in promoting metastasis, these data identify an additional mechanism to achieve high PGE2 in the tumor microenvironment; high MRP4, low PGT, and low 15-PGDH. MRP4 should be examined further as a potential therapeutic target in basal breast cancer.

Abstract 4132: Multiple drug resistance-associated protein 4 (MRP4): Role in triple negative breast cancer

Abstract Introduction: MRP4 is responsible for the active export of prostaglandin E2 (PGE2) from cells. PGE2, derived from cyclooxygenase-2-mediated synthesis, contributes to tumor growth and metastasis of many epithelial tumors; however, the role of MRP4 in breast cancer has not been investigated. Methods: We employed publicly available breast cancer gene expression datasets and a panel of breast cancer cell lines to examine the expression and function of MRP4 as well as other members of the PGE2 pathway. In contrast to the export function of MRP4, the prostaglandin transporter PGT/SLCO2A1 imports PGE2 into the cell where 15-prostaglandin dehydrogenase (5-PGDH/HPGD) metabolizes PGE2 to terminate ligand-mediated activation of the prostaglandin E (EP) receptors. Results: We found that ABCC4, which encodes the MRP4 protein, is widely expressed in breast cancer but breast cancer subtypes have different expression profiles of PGE2 pathway members. ABCC4/MRP4 is elevated more frequently in basal breast tumors than in apocrine or luminal tumors. This is the first report that elevated expression of MRP4 is found in breast cancer subtypes (basal, HER2-enriched) with the worst prognoses. ABCC4 expression was also higher in breast cancer-associated stroma compared to healthy mammary tissue. Basal-type tumors also expressed the highest levels of PTGS2/COX-2 while the genes responsible for PGE2 metabolism (HPGD and SLCO2A1) are negatively correlated with TNBC. The same pattern was observed in breast cancer cell lines, where basal-type and HER2-enriched cell lines highly express MRP4 but luminal breast cancers do not. HPGD was decreased in most cancer cell lines compared to MCF10A immortalized cells, consistent with the known tumor suppressor role of HPGD/15PGDH. MRP4 exports PGE2 which was reduced in the presence of MRP4 small m.w. inhibitors or by MRP4 gene silencing. Lastly, expression of shMRP4 in highly metastatic, basal-type MDA-MB-231 human breast cancer cells reduced the ability of these cells to spontaneously metastasize to the lungs of NOD/SCID mice but did not affect the tumor growth properties of tumor cells implanted proximal to the mammary gland. Conclusions: Elevated MRP4 is a characteristic of aggressive breast cancer subtypes and is partially responsible for the high levels of PGE2 in the tumor microenvironment. Silencing of MRP4 reduces spontaneous metastasis in a xenograft model of TNBC. Further investigation of MRP4 as a potential therapeutic target is warranted. Citation Format: Tyler Kochel, Xinrong Ma, Namita Kundu, Jocelyn Reader, Olga Goloubeva, Amy M. Fulton. Multiple drug resistance-associated protein 4 (MRP4): Role in triple negative breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4132.

Increased Expression of 15-Hydroxyprostaglandin Dehydrogenase in Spinal Astrocytes During Disease Progression in a Model of Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is an adult-onset, progressive, and fatal neurodegenerative disease caused by selective loss of motor neurons. Both ALS model mice and patients with sporadic ALS have increased levels of prostaglandin E2 (PGE2). Furthermore, the protein levels of microsomal PGE synthase-1 and cyclooxygenase-2, which catalyze PGE2 biosynthesis, are significantly increased in the spinal cord of ALS model mice. However, it is unclear whether PGE2 metabolism in the spinal cord is altered. In the present study, we investigated the protein level of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), a key enzyme in prostaglandin metabolism, in ALS model mice at three different disease stages. Western blotting revealed that the 15-PGDH level was significantly increased in the lumbar spinal cord at the symptomatic stage and end stage. Immunohistochemical staining demonstrated that 15-PGDH immunoreactivity was localized in glial fibrillary acidic protein (GFAP)-positive astrocytes at the end stage. In contrast, 15-PGDH immunoreactivity was not identified in NeuN-positive large cells showing the typical morphology of motor neurons in the anterior horn. Unlike 15-PGDH, the level of PGE2 in the spinal cord was increased only at the end stage. These results suggest that the significant increase of PGE2 at the end stage of ALS in this mouse model is attributable to an imbalance of the synthetic pathway and 15-PGDH-dependent scavenging system for PGE2, and that this drives the pathogenetic mechanism responsible for transition from the symptomatic stage.

NO2 inhalation promotes Alzheimer's disease-like progression: cyclooxygenase-2-derived prostaglandin E2 modulation and monoacylglycerol lipase inhibition-targeted medication.

Air pollution has been reported to be associated with increased risks of cognitive impairment and neurodegenerative diseases. Because NO2 is a typical primary air pollutant and an important contributor to secondary aerosols, NO2-induced neuronal functional abnormalities have attracted greater attention, but the available experimental evidence, modulating mechanisms, and targeting medications remain ambiguous. In this study, we exposed C57BL/6J and APP/PS1 mice to dynamic NO2 inhalation and found for the first time that NO2 inhalation caused deterioration of spatial learning and memory, aggravated amyloid β42 (Aβ42) accumulation, and promoted pathological abnormalities and cognitive defects related to Alzheimer’s disease (AD). The microarray and bioinformation data showed that the cyclooxygenase-2 (COX-2)-mediated arachidonic acid (AA) metabolism of prostaglandin E2 (PGE2) played a key role in modulating this aggravation. Furthermore, increasing endocannabinoid 2-arachidonoylglycerol (2-AG) by inhibiting monoacylglycerol lipase (MAGL) prevented PGE2 production, neuroinflammation-associated Aβ42 accumulation, and neurodegeneration, indicating a therapeutic target for relieving cognitive impairment caused by NO2 exposure.

Tryptophan-2,3-dioxygenase is regulated by prostaglandin E2 in malignant glioma via a positive signaling loop involving prostaglandin E receptor-4.

Malignant gliomas and other types of tumors generate a local immunosuppressive microenvironment, which prohibits an effective anti-tumor immune response and promotes tumor growth. Along with others, we have recently demonstrated that catabolism of the essential amino acid tryptophan via tryptophan-2,3-dioxygenase (TDO) is an important mechanism mediating tumor-associated immunosuppression particularly in gliomas. The pathways regulating TDO in tumors, however, are poorly understood. Here, we show that prostaglandins enhance TDO expression and enzymatic activity in malignant gliomas via activation of prostaglandin E receptor-4 (EP4). Stimulation with prostaglandin E2 (PGE2 ) up-regulated TDO-mediated kynurenine release in human glioma cell lines, whereas knockdown of the PGE2 receptor EP4 inhibited TDO expression and activity. In human malignant glioma tissue expression of the PGE2 -producing enzyme cyclooxygenase-2 (COX2) and its receptor EP4 were associated with TDO expression both on transcript and protein level. High expression of EP4 correlated with poor survival in malignant glioma patients WHO III-IV. Importantly, treatment of glioma cells with an EP4 inhibitor decreased TDO expression and activity. Moreover, TDO-over-expressing murine gliomas showed increased COX2 and EP4 expression suggesting a positive feedback mechanism invivo. In summary, targeting EP4 may inhibit - in addition to immunosuppressive COX2 signaling - tryptophan degradation as another important immunosuppressive pathway and thus, could provide a dual clinically relevant immunotherapeutic avenue for the treatment of malignant gliomas. We proposed that in malignant gliomas prostaglandin E2 (PGE2 ) produced by cyclooxygenases (COX) up-regulates tryptophan-2,3-dioxygenase (TDO) expression and enzyme activity through binding to its Gs-coupled receptor EP4 and therefore may mediate tumor immune escape in part through aryl hydrocarbon receptor (AHR) activation. Moreover, TDO activity itself seems to induce intratumoral PGE2 metabolism suggesting an immunosuppressive loop involving COX/EP4/TDO.

Novel contraceptive targets to inhibit ovulation: the prostaglandin E2 pathway.

Prostaglandin E2 (PGE2) is an essential intrafollicular regulator of ovulation. In contrast with the one-gene, one-protein concept for synthesis of peptide signaling molecules, production and metabolism of bioactive PGE2 requires controlled expression of many proteins, correct subcellular localization of enzymes, coordinated PGE2 synthesis and metabolism, and prostaglandin transport in and out of cells to facilitate PGE2 action and degradation. Elevated intrafollicular PGE2 is required for successful ovulation, so disruption of PGE2 synthesis, metabolism or transport may yield effective contraceptive strategies. This review summarizes case reports and studies on ovulation inhibition in women and macaques treated with cyclooxygenase inhibitors published from 1987 to 2014. These findings are discussed in the context of studies describing levels of mRNA, protein, and activity of prostaglandin synthesis and metabolic enzymes as well as prostaglandin transporters in ovarian cells. The ovulatory surge of LH regulates the expression of each component of the PGE2 synthesis-metabolism-transport pathway within the ovulatory follicle. Data from primary ovarian cells and cancer cell lines suggest that enzymes and transporters can cooperate to optimize bioactive PGE2 levels. Elevated intrafollicular PGE2 mediates key ovulatory events including cumulus expansion, follicle rupture and oocyte release. Inhibitors of the prostaglandin-endoperoxide synthase 2 (PTGS2) enzyme (also known as cyclooxygenase-2 or COX2) reduce ovulation rates in women. Studies in macaques show that PTGS2 inhibitors can reduce the rates of cumulus expansion, oocyte release, follicle rupture, oocyte nuclear maturation and fertilization. A PTGS2 inhibitor reduced pregnancy rates in breeding macaques when administered to simulate emergency contraception. However, PTGS2 inhibition did not prevent pregnancy in monkeys when administered to simulate monthly contraceptive use. PTGS2 inhibitors alone may be suitable for use as emergency contraceptives. However, drugs of this class are unlikely to be effective as monthly contraceptives. Inhibitors of additional PGE2 synthesis enzymes or modulation of PGE2 metabolism or transport also hold potential for reducing follicular PGE2 and preventing ovulation. Approaches which target multiple components of the PGE2 synthesis-metabolism-transport pathway may be required to effectively block ovulation and lead to the development of novel contraceptive options for women. Therapies which target PGE2 may also impact disorders of the uterus and could also have benefits for women's health in addition to contraception.

Altered metabolism of prostaglandin E2 in asthma patients with aspirin hypersensitivity

Altered metabolism of prostaglandin E2 in asthma patients with aspirin hypersensitivity