Inducible deletion of the prostaglandin EP3 receptor in kidney tubules of male and female mice has no major effect on water homeostasis.

The prostaglandin E2 (PGE2) receptor EP3 has been detected in the thick ascending limb (TAL) and the collecting duct of the kidney, where its actions are proposed to inhibit water reabsorption. However, EP3 is also expressed in other cell types, including vascular endothelial cells. The aim here was to determine the contribution of EP3 in renal water handling in male and female adult mice by phenotyping a novel mouse model with doxycycline-dependent deletion of EP3 throughout the kidney tubule (EP3-/- mice). RNAscope demonstrated that EP3 was highly expressed in the cortical and medullary TAL of adult mice. Compared with controls EP3 mRNA expression was reduced by >80% in whole kidney (RT-qPCR) and nondetectable (RNAscope) in renal tubules of EP3-/- mice. Under basal conditions, there were no significant differences in control and EP3-/- mice of both sexes in food and water intake, body weight, urinary output, or clinical biochemistries. No differences were detectable between genotypes in handling of an acute water load or in their response to the vasopressin analog 1-deamino-8-d-arginine-vasopressin (dDAVP). No differences in water handling were observed when PGE2 production was enhanced using 1% NaCl load. Expression of proteins involved in kidney water handling was not different between genotypes. This study demonstrates that renal tubular EP3 is not essential for body fluid homeostasis in males or females, even when PGE2 levels are high. The mouse model is a novel tool for examining the role of EP3 in kidney function independently of potential developmental abnormalities or systemic effects.NEW & NOTEWORTHY The prostanoid EP3 receptor is proposed to play a key role in the kidney tubule and antagonize the effects of vasopressin on aquaporin-mediated water reabsorption. Here, we phenotyped a kidney tubule-specific inducible knockout mouse model of the EP3 receptor. Our major finding is that, even under physiological stress, tubular EP3 plays no detectable role in renal water or solute handling. This suggests that other EP receptors must be important for renal salt and water handling.

Posttranscriptional regulation of the prostaglandin E receptor spliced-isoform EP3-γ and its implication in pancreatic ß-cell failure.

In Type 2 diabetes (T2D), elevated lipid levels have been suggested to contribute to insulin resistance and ß-cell dysfunction. We previously reported that the expression of the PGE2 receptor EP3 is elevated in islets of T2D individuals and is preferentially stimulated by palmitate, leading to ß-cell failure. The mouse EP3 receptor generates three isoforms by alternative splicing which differ in their C-terminal domain and are referred to as mEP3α, mEP3ß, and mEP3γ. We bring evidence that the expression of the mEP3γ isoform is elevated in islets of diabetic db/db mice and is selectively upregulated by palmitate. Specific knockdown of the mEP3γ isoform restores the expression of ß-cell-specific genes and rescues MIN6 cells from palmitate-induced dysfunction and apoptosis. This study indicates that palmitate stimulates the expression of the mEP3γ by a posttranscriptional mechanism, compared to the other spliced isoforms, and that the de novo synthesized ceramide plays an important role in FFA-induced mEP3γ expression in ß-cells. Moreover, induced levels of mEP3γ mRNA by palmitate or ceramide depend on p38 MAPK activation. Our findings suggest that mEP3γ gene expression is regulated at the posttranscriptional level and defines the EP3 signaling axis as an important pathway mediating ß-cell-impaired function and demise.

Thermoregulatory pathway underlying the pyrogenic effects of prostaglandin E2 in the lateral parabrachial nucleus of male rats.

It has been shown that prostaglandin (PG) E2 synthesized in the lateral parabrachial nucleus (LPBN) is involved in lipopolysaccharide-induced fever. But the neural mechanisms of how intra-LPBN PGE2 induces fever remain unclear. In this study, we investigated whether the LPBN-preoptic area (POA) pathway, the thermoafferent pathway for feed-forward thermoregulatory responses, mediates fever induced by intra-LPBN PGE2 in male rats. The core temperature (Tcore) was monitored using a temperature radiotelemetry transponder implanted in rat abdomen. We showed that microinjection of PGE2 (0.28 nmol) into the LPBN significantly enhanced the density of c-Fos-positive neurons in the median preoptic area (MnPO). The chemical lesioning of MnPO with ibotenate or selective genetic lesioning or inhibition of the LPBN-MnPO pathway significantly attenuated fever induced by intra-LPBN injection of PGE2. We demonstrated that EP3 receptor was a pivotal receptor for PGE2-induced fever, since microinjection of EP3 receptor agonist sulprostone (0.2 nmol) or EP3 receptor antagonist L-798106 (2 nmol) into the LPBN mimicked or weakened the pyrogenic action of LPBN PGE2, respectively, but this was not the case for EP4 and EP1 receptors. Whole-cell recording from acute LPBN slices revealed that the majority of MnPO-projecting neurons originating from the external lateral (el) and dorsal (d) LPBN were excited and inhibited, respectively, by PGE2 perfusion, initiating heat-gain and heat-loss mechanisms. The amplitude but not the frequency of spontaneous and miniature glutamatergic excitatory postsynaptic currents (sEPSCs and mEPSCs) in MnPO-projecting LPBel neurons increased after perfusion with PGE2; whereas the frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs) and the A-type potassium (IA) current density did not change. In MnPO-projecting LPBd neurons, neither sEPSCs nor sIPSCs responded to PGE2; however, the IA current density was significantly increased by PGE2 perfusion. These electrophysiological responses and the thermoeffector reactions to intra-LPBN PGE2 injection, including increased brown adipose tissue thermogenesis, shivering, and decreased heat dissipation, were all abolished by L-798106, and mimicked by sulprostone. These results suggest that the pyrogenic effects of intra-LPBN PGE2 are mediated by both the inhibition of the LPBd-POA pathway through the EP3 receptor-mediated activation of IA currents and the activation of the LPBel-POA pathway through the selective enhancement of glutamatergic synaptic transmission via EP3 receptors.

Deduction of CDC42EP3 suppress development and progression of osteosarcoma.

BACKGROUND: Osteosarcoma is a disease with high mortality of malignant tumors in children and adolescents. CDC42 effector protein 3 (CDC42EP3) has been reported to be associated with human cancer cell progression. This study aimed to investigate the biological function and preliminary molecular mechanism of CDC42EP3 in osteosarcoma. METHODS: CDC42EP3 expression in osteosarcoma was analyzed by immunohistochemical (IHC) staining. Secondly, the biological effects of CDC42EP3 in osteosarcoma cells was determined by loss/gain-of-function assays in vitro and in vivo. RESULTS: CDC42EP3 expression was higher in osteosarcoma tissue than in noncancerous tissue. The expression of CDC42EP3 was positively correlated with age, pathological stage and grade of patients with osteosarcoma. Furthermore, downregulation of CDC42EP3 suppressed tumor progression by inhibiting proliferation, migration and inducing apoptosis in vivo. Importantly, knockdown of CDC42EP3 reduced the expression of interstitial markers (N-cadherin, Vimentin and Snail) and increased the expression of epithelial markers (E-cadherin). In addition, CDC42EP3 knockdown downregulated PI3K and reduced the phosphorylation levels of AKT and mTOR. The mice xenograft model further confirmed that CDC42EP3 knockdown inhibited osteosarcoma growth in vitro. CONCLUSIONS: In summary, these findings highlighted the significance of CDC42EP3 in tumor progression, which implicated CDC42EP3 as a promising candidate molecular target for osteosarcoma therapy.

A Phytoprostane from Gracilaria longissima Increases Platelet Activation, Platelet Adhesion to Leukocytes and Endothelial Cell Migration by Potential Binding to EP3 Prostaglandin Receptor.

Plant phytoprostanes (PhytoPs) are lipid oxidative stress mediators that share structural similarities with mammal prostaglandins (PGs). They have been demonstrated to modulate inflammatory processes mediated by prostaglandins. The present study aims to test the effects of the most abundant oxylipin from Gracilaria longissima, ent-9-D1t-Phytoprostane (9-D1t-PhytoP), on platelet activation and vascular cells as well as clarify possible interactions with platelets and the endothelial EP3 receptor Platelet and monocyte activation was assessed by flow cytometry in the presence of purified 9-D1t-PhytoP. Cell migration was studied using the human Ea.hy926 cell line by performing a scratch wound healing assay. The RNA expression of inflammatory markers was evaluated by RT-PCR under inflammatory conditions. Blind docking consensus was applied to the study of the interactions of selected ligands against the EP3 receptor protein. The 9D1t-PhytoP exerts several pharmacological effects; these include prothrombotic and wound-healing properties. In endothelial cells, 9D1t-PhytP mimics the migration stimulus of PGE2. Computational analysis revealed that 9D1t-PhytP forms a stable complex with the hydrophobic pocket of the EP3 receptor by interaction with the same residues as misoprostol and prostaglandin E2 (PGE2), thus supporting its potential as an EP3 agonist. The potential to form procoagulant platelets and the higher endothelial migration rate of the 9-D1t-PhytoP, together with its capability to interact with PGE2 main target receptor in platelets suggest herein that this oxylipin could be a strong candidate for pharmaceutical research from a multitarget perspective.

Prostaglandin E2 receptor 3 promotes M1 macrophages polarization in unexplained recurrent pregnancy loss.

Unexplained recurrent pregnancy loss (uRPL) is associated with macrophage polarization, which can be modulated by prostaglandin E2 (PGE2). Our previous study demonstrated that PGE2 receptor 3 (EP3) signaling is induced in the first-trimester placentas of uRPL patients compared with its expression in healthy controls. However, whether EP3 plays a role in macrophage polarization at the maternal-fetal interface of uRPL women remains unknown. The positive expression of EP3 in decidual macrophages was confirmed by double immunofluorescence staining in the first-trimester placentas collected from uRPL patients and healthy controls. Antibodies CD68, iNOS, and CD163 were used as immunofluorescence marker for decidual macrophages, M1, and M2 macrophages. To clarify the effects of EP3 on macrophage polarization, THP-1 monocyte cells were applied as M0 macrophages after phorbol 12-myristate 13-acetate (PMA) treatment for in vitro study. The mRNA levels of representative M1 markers (interleukin-1ß and interleukin-6) and M2 markers (interleukin-10 and arginase-1) were quantified with qPCR in M0 macrophages being stimulated with sulprostone (an EP3 agonist) or L-798,106 (an EP3 antagonist). We found that EP3 expression was upregulated in the decidual macrophages of first-trimester placentas from uRPL patients compared with healthy controls. Furthermore, EP3 expression was increased in M1 macrophages compared with that in M2 macrophages in first-trimester placentas of uRPL patients. Sulprostone intensified the mRNA levels of IL-6 together with interferon-γ, whereas L-798,106 stimulated the mRNA expression of IL-10 and Arg-1 in a dose-dependent manner.

Endothelium-dependent contraction: The non-classical action of endothelial prostacyclin, its underlying mechanisms, and implications.

Although commonly thought to produce prostacyclin (prostaglandin I2 ; PGI2 ) that evokes vasodilatation and protects vessels from the development of diseases, the endothelial cyclooxygenase (COX)-mediated metabolism has also been found to release substance(s) called endothelium-derived contracting factor(s) (EDCF) that causes endothelium-dependent contraction and implicates in endothelial dysfunction of disease conditions. Various mechanisms have been proposed for the process; however, the major endothelial COX metabolite PGI2 , which has been classically considered to activate the I prostanoid receptor (IP) that mediates vasodilatation and opposes the effects of thromboxane (Tx) A2 produced by COX in platelets, emerges as a major EDCF in health and disease conditions. Our recent studies from genetically altered mice further suggest that vasomotor reactions to PGI2 are collectively modulated by IP, the vasoconstrictor Tx-prostanoid receptor (TP; the prototype receptor of TxA2 ) and E prostanoid receptor-3 (EP3; a vasoconstrictor receptor of PGE2 ) although with differences in potency and efficacy; a contraction to PGI2 reflects activities of TP and/or EP3 outweighing that of the concurrently activated IP. Here, we discuss the history of endothelium-dependent contraction, evidences that support the above hypothesis, proposed mechanisms for the varied reactions to endothelial PGI2 synthesis as well as the relation of its dilator activity to the effect of another NO-independent vasodilator mechanism, the endothelium-derived hyperpolarizing factor. Also, we address the possible pathological and therapeutic implications as well as questions remaining to be resolved or limitations of our above findings obtained from genetically altered mouse models.

Prostaglandin E1 attenuates AngII-induced cardiac hypertrophy via EP3 receptor activation and Netrin-1upregulation.

AIMS: Pathological cardiac hypertrophy induced by activation of the renin-angiotensin-aldosterone system (RAAS) is one of the leading causes of heart failure. However, in current clinical practice, the strategy for targeting the RAAS is not sufficient to reverse hypertrophy. Here, we investigated the effect of prostaglandin E1 (PGE1) on angiotensin II (AngII)-induced cardiac hypertrophy and potential molecular mechanisms underlying the effect. METHODS AND RESULTS: Adult male C57 mice were continuously infused with AngII or saline and treated daily with PGE1 or vehicle for two weeks. Neonatal rat cardiomyocytes were cultured to detect AngII-induced hypertrophic responses. We found that PGE1 ameliorated AngII-induced cardiac hypertrophy both in vivo and in vitro. The RNA sequencing (RNA-seq) and expression pattern analysis results suggest that Netrin-1 (Ntn1) is the specific target gene of PGE1. The protective effect of PGE1 was eliminated after knockdown of Ntn1. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the PGE1-mediated signaling pathway changes are associated with the mitogen-activated protein kinase (MAPK) pathway. PGE1 suppressed AngII-induced activation of the MAPK signaling pathway, and such an effect was attenuated by Ntn1 knockdown. Blockade of MAPK signaling rescued the phenotype of cardiomyocytes caused by Ntn1 knockdown, indicating that MAPK signaling may act as the downstream effector of Ntn1. Furthermore, inhibition of the E-prostanoid (EP) 3 receptor, as opposed to the EP1, EP2, or EP4 receptor, in cardiomyocytes reversed the effect of PGE1, and activation of EP3 by sulprostone, a specific agonist, mimicked the effect of PGE1. CONCLUSION: In conclusion, PGE1 ameliorates AngII-induced cardiac hypertrophy through activation of the EP3 receptor and upregulation of Ntn1, which inhibits the downstream MAPK signaling pathway. Thus, targeting EP3, as well as the Ntn1-MAPK axis, may represent a novel approach for treating pathological cardiac hypertrophy.

Breast adipose tissue macrophages (BATMs) have a stronger correlation with breast cancer survival than breast tumor stroma macrophages (BTSMs).

BACKGROUND: An abundance of tumor-associated macrophages has been shown to be an independent prognostic factor for a poor prognosis of human breast cancer (BC). Adipose tissue accounts for the largest proportion of the breast and has also been identified as an independent indicator of poor survival in BC. This study aims to elucidate if the influence of adipose tissue in BC might be mediated by macrophages. The roles of macrophages in the breast tumor-stroma (breast tumor stroma macrophages, BTSM) and macrophages in the surrounding adipose tissue (breast adipose tissue macrophages, BATM) were explored separately. METHODS: Two hundred ninety-eight BC tissue samples were analyzed immunohistochemically. The number of macrophages was detected by CD68+ staining. The quantity of BATMs and BTSMs was correlated to clinical and pathological parameters as well as to disease-free survival (DFS) and overall survival (OS). RESULTS: The amounts of BATMs and BTSMs strongly correlated with each other (r = 0.5, p = 2.98E-15). The quantity of BTSMs, but not of BATMs, was significantly associated with the BC molecular subtype (p = 0.000011), and all triple-negative BC tumors contained high amounts of BTSMs. BATMs were negatively associated with DFS (p = 0.0332). Both BATMs (p = 0.000401) and BTSMs (p = 0.021) were negatively associated with OS in the Kaplan-Meier analysis, but only BATMs remained an independent factor in the multivariate Cox-regression analysis (HR = 4.464, p = 0.004). Combining prostaglandin E2 receptor 3 (EP3)-expression and the quantity of BATMs, a subgroup with an extremely poor prognosis could be identified (median OS 2.31 years in the "high BATMs/low EP3" subgroup compared to 11.42 years in the most favorable "low BATMs/high EP3" subgroup, p = 0.000002). CONCLUSION: Our findings suggest that BTSMs and BATMs seem to be involved differently in BC. Breast adipose tissue might contribute to the aggressiveness of BC via BATMs, which were independently associated with BC survival. BATMs' role and occurrence might be functionally dependent on EP3, as a combination of both factors was strongly associated with survival. Targeting BATMs-eventually in combination with targeting the EP3-pathway-might be promising for future therapies.

CDC42EP3 promotes colorectal cancer through regulating cell proliferation, cell apoptosis and cell migration.

BACKGROUND: Nowadays, colorectal cancer (CRC) is one of the most commonly diagnosed malignant tumors worldwide, the incidence rate of which is still increasing year by year. Herein, the objective of this study is to investigate whether CDC42EP3 has regulatory effects in CRC. METHODS: First, CDC42EP3 knockdown cell model based on HCT116 and RKO cell lines was successfully constructed, which was further used for constructing mouse xenotransplantation models. Importantly, effects of CDC42EP3 knockdown on proliferation, colony formation, apoptosis, and migration of CRC were accessed by MTT assay, EdU staining assay, colony formation assay, Flow cytometry, and Transwell assay. RESULTS: As the results, we showed that CDC42EP3 was significantly upregulated in CRC, and its high expression was associated with tumor progression. Furthermore, knockdown of CDC42EP3 could inhibit proliferation, colony formation and migration, and promote apoptosis of CRC cells in vitro. In vivo results further confirmed knockdown of CDC42EP3 attenuated tumor growth in CRC. Interestingly, the regulation of CRC by CDC42EP3 involved not only the change of a variety of apoptosis-related proteins, but also the regulation of downstream signaling pathway. CONCLUSION: In conclusion, the role of CDC42EP3 in CRC was clarified and showed its potential as a target of innovative therapeutic approaches for CRC.

Differential properties of E prostanoid receptor-3 and thromboxane prostanoid receptor in activation by prostacyclin to evoke vasoconstrictor response in the mouse renal vasculature.

Vasomotor reactions of prostacyclin (prostaglandin I2 ; PGI2 ) can be collectively modulated by thromboxane prostanoid receptor (TP), E-prostanoid receptor-3 (EP3), and the vasodilator I prostanoid receptor (IP). This study aimed to determine the direct effect of PGI2 on renal arteries and/or the whole renal vasculature and how each of these receptors is involved. Experiments were performed on vessels or perfused kidneys of wild-type mice and/or mice with deficiency in TP (TP-/- ) and/or EP3. Here we show that PGI2 did not evoke relaxation, but instead resulted in contraction of main renal arteries (from ~0.001-0.01 µM) or reduction of flow in perfused kidneys (from ~1 µM); either of them was reversed into a dilator response in TP-/- /EP3-/- counterparts. Also, we found that in renal arteries although it has a lesser effect than TP-/- on the maximal contraction to PGI2 (10 µM), EP3-/- but not TP-/- resulted in relaxation to the prostanoid at 0.01-1 µM. Meanwhile, TP-/- only significantly reduced the contractile activity evoked by PGI2 at ≥0.1 µM. These results demonstrate that PGI2 may evoke an overall vasoconstrictor response in the mouse renal vasculature, reflecting activities of TP and EP3 outweighing that of the vasodilator IP. Also, our results suggest that EP3, on which PGI2 can have a potency similar to that on IP, plays a major role in the vasoconstrictor effect of the prostanoid of low concentrations (≤1 µM), while TP, on which PGI2 has a lower potency but higher efficacy, accounts for a larger part of its maximal contractile activity.

Prostaglandin E2 sequentially activates E-prostanoid receptor-3 and thromboxane prostanoid receptor to evoke contraction and increase in resistance of the mouse renal vasculature.

Although recognized to have an in vivo vasodepressor effect blunted by the vasoconstrictor effect of E-prostanoid receptor-3 (EP3), prostaglandin E2 (PGE2 ) evokes contractions of many vascular beds that are sensitive to antagonizing the thromboxane prostanoid receptor (TP). This study aimed to determine the direct effect of PGE2 on renal arteries and/or the whole renal vasculature and how each of these two receptors is involved in the responses. Experiments were performed on isolated vessels and perfused kidneys of wild-type mice and/or mice with deficiency in TP (TP-/- ), EP3 (EP3-/- ), or both TP and EP3 (TP-/- /EP3-/- ). Here we show that PGE2 (0.001-30 µM) evoked not only contraction of main renal arteries, but also a decrease of flow in perfused kidneys. EP3-/- diminished the response to 0.001-0.3 µM PGE2 , while TP-/- reduced that to the prostanoid of higher concentrations. In TP-/- /EP3-/- vessels and perfused kidneys, PGE2 did not evoke contraction but instead resulted in vasodilator responses. These results demonstrate that PGE2 functions as an overall direct vasoconstrictor of the mouse renal vasculature with an effect reflecting the vasoconstrictor activities outweighing that of dilation. Also, our results suggest that EP3 dominates the vasoconstrictor effect of PGE2 of low concentrations (≤0.001-0.3 µM), but its effect is further added by that of TP, which has a higher efficacy, although activated by higher concentrations (from 0.01 µM) of the same prostanoid PGE2 .

Optimization of physicochemical properties of pyridone-based EP3 receptor antagonists.

A novel series of pyridone-based EP3 receptor antagonists was optimized for good physical properties and oral bioavailability in rodents. The lead compounds 3h, 3l and 4d displayed good in vitro profiles, moderate to good metabolic stability and good rodent PK profiles with low clearance, high oral exposure and acceptable half-life.

Overactivated Cdc42 acts through Cdc42EP3/Borg2 and NCK to trigger DNA damage response signaling and sensitize cells to DNA-damaging agents.

The small GTPase Cdc42, a member of the Rho family, regulates essential biological processes such as cytoskeleton remodeling, migration, vesicular trafficking and cell cycle. It was demonstrated that Cdc42 overactivation through different molecular strategies increases cell sensitivity to genotoxic stress and affects the phosphorylation status of DNA damage response proteins by unknown mechanisms. By using a combination of approaches including affinity purification/mass spectrometry (AP/MS) and colocalization microscopy analysis we were able to identify Cdc42EP3/Borg2 as a putative molecular effector of these molecular and cellular events that seem to be independent of cell line or DNA damage stimuli. We then investigated the influence of Cdc42EP3/Borg2 and other potential protein partners, such as the NCK and Septin2 proteins, which could mediate cellular responses to genotoxic stress under different backgrounds of Cdc42 activity. Clonogenic assays showed a reduced cell survival when ectopically expressing the Cdc42EP3/Borg2, NCK2 or Septin2 in an overactivated Cdc42-dependent background. Moreover, endogenous NCK appears to relocate into the nucleus upon Cdc42 overactivation, especially under genotoxic stress, and promotes the suppression of Chk1 phosphorylation. In sum, our findings reinforce Cdc42 as an important player involved in the DNA damage response acting through Cdc42EP3/Borg2 and NCK proteins following genomic instability conditions.

The deleterious role of the prostaglandin E2 EP3 receptor in angiotensin II hypertension.

Angiotensin II (ANG II) plays a key role in regulating blood pressure and inflammation. Prostaglandin E2 (PGE2) signals through four different G protein-coupled receptors, eliciting a variety of effects. We reported that activation of the EP3 receptor reduces cardiac contractility. More recently, we have shown that overexpression of the EP4 receptor is protective in a mouse myocardial infarction model. We hypothesize in this study that the relative abundance of EP3 and EP4 receptors is a major determinant of end-organ damage in the diseased heart. Thus EP3 is detrimental to cardiac function and promotes inflammation, whereas antagonism of the EP3 receptor is protective in an ANG II hypertension (HTN) model. To test our hypothesis, male 10- to 12-wk-old C57BL/6 mice were anesthetized with isoflurane and osmotic minipumps containing ANG II were implanted subcutaneously for 2 wk. We found that antagonism of the EP3 receptor using L798,106 significantly attenuated the increase in blood pressure with ANG II infusion. Moreover, antagonism of the EP3 receptor prevented a decline in cardiac function after ANG II treatment. We also found that 10- to 12-wk-old EP3-transgenic mice, which overexpress EP3 in the cardiomyocytes, have worsened cardiac function. In conclusion, activation or overexpression of EP3 exacerbates end-organ damage in ANG II HTN. In contrast, antagonism of the EP3 receptor is beneficial and reduces cardiac dysfunction, inflammation, and HTN.NEW & NOTEWORTHY This study is the first to show that systemic treatment with an EP3 receptor antagonist (L798,106) attenuates the angiotensin II-induced increase in blood pressure in mice. The results from this project could complement existing hypertension therapies by combining blockade of the EP3 receptor with antihypertensive drugs.

Validation of an air/liquid interface device for TiO2 nanoparticle toxicity assessment on NR8383 cells: preliminary results.

nvestigations on adverse biological effects of nanoparticles (NP) are performed usually either in vivo on rodents or in vitro under submerged conditions where NP are in suspension into cell culture media. However, sedimentation of NP in vitro is a continuous process and to assess the exact deposited cellular dose remains difficult, as the cellular internal dose is a function of time. Moreover, the cellular responses to NP under submerged culture conditions or by exposing rodents by nose-only to NP aerosols might differ from those observed at physiological settings at the air-liquid interface (ALI). Rat alveolar NR8383 macrophages were exposed to aerosols at the air-liquid interface. We studied TiO2 NM105, a mixture of anatase and rutile. NR8383 cells were exposed to a single dose of 3.0 cm2/cm2 of TiO2 aerosol. Following RNA extraction, transcriptome allowing full coverage of the rat genome was performed, and differentially expressed genes were retrieved. Their products were analyzed for functions and interaction with String DB. Only 126 genes were differentially expressed and 98 were recognized by String DB and give us the gene expression signature of exposed rat alveolar NR8383 macrophages. Among them, 13 display relationships at a high confidence level and the ten most differentially expressed compared to unexposed cells were: Chac1, Ccl4, Zfp668, Fam129b, Nab2, Txnip, Id1, Cdc42ep3, Dusp6 and Myc, ranked from the most overexpressed to the most under-expressed. Some of them were previously described as over or under-expressed in NP exposed cell systems. We validated in our laboratory an easy-to-use device and a physiological relevant paradigm for studying the effects of cell exposure to TiO2. Ccl4 gene expression seems to be a positive marker of exposure evidenced as well as in vivo or in both in vitro conditions.

EP3 Is an Independent Prognostic Marker Only for Unifocal Breast Cancer Cases.

The aim of this study was to evaluate the prognostic impact of prostaglandin E2 receptor 3 (EP3) receptor expression might have on the two different breast cancer entities: multifocal/multicentric versus unifocal. As the prognosis determining aspects, we investigated the overall- and disease-free survival by uni-and multivariate analysis. To underline the study's conclusion, we additionally considered the histopathological grading and the tumor node metastasis (TNM) staging system. A retrospective statistical analysis was performed on survival related events in a series of 289 sporadic breast cancer (BC) patients treated at the Department of Obstetrics and Gynecology at the Ludwig-Maximillian's University in Munich between 2000 and 2002. The EP3 receptor expression was analyzed by immunohistochemistry and showed to have a significantly positive association with breast cancer prognosis for both entities, although with major differences. Patients with unifocal BC with EP3 receptor expression showed a significant improved overall survival, in contrast to the patient cohort with multifocal/multicentric BC. In this group, EP3 expression revealed its positive impact merely five years after initial diagnosis. Underlining the positive influence of EP3 as a positive prognosticator notably for unifocal breast cancer, only this patient cohort showed favorable outcomes in staging and grading. Especially EP3 expression in unifocal breast cancer was identified as an independent prognostic marker for the overall survival, when adjusted for age, grading, and staging. Altogether, our results strengthen the need to further investigate the behavior of EP3 in breast cancer and understand why markers linked to inflammation show different effects on prognosis and clinicopathological parameters on each focality type.

Correlative Study on Impaired Prostaglandin E2 Regulation in Epicardial Adipose Tissue and its Role in Maladaptive Cardiac Remodeling via EPAC2 and ST2 Signaling in Overweight Cardiovascular Disease Subjects.

There is recent evidence that the dysfunctional responses of a peculiar visceral fat deposit known as epicardial adipose tissue (EAT) can directly promote cardiac enlargement in the case of obesity. Here, we observed a newer molecular pattern associated with LV dysfunction mediated by prostaglandin E2 (PGE2) deregulation in EAT in a cardiovascular disease (CVD) population. A series of 33 overweight CVD males were enrolled and their EAT thickness, LV mass, and volumes were measured by echocardiography. Blood, plasma, EAT, and SAT biopsies were collected for molecular and proteomic assays. Our data show that PGE2 biosynthetic enzyme (PTGES-2) correlates with echocardiographic parameters of LV enlargement: LV diameters, LV end diastolic volume, and LV masses. Moreover, PTGES-2 is directly associated with EPAC2 gene (r = 0.70, p < 0.0001), known as a molecular inducer of ST2/IL-33 mediators involved in maladaptive heart remodelling. Furthermore, PGE2 receptor 3 (PTEGER3) results are downregulated and its expression is inversely associated with ST2/IL-33 expression. Contrarily, PGE2 receptor 4 (PTGER4) is upregulated in EAT and directly correlates with ST2 molecular expression. Our data suggest that excessive body fatness can shift the EAT transcriptome to a pro-tissue remodelling profile, may be driven by PGE2 deregulation, with consequent promotion of EPAC2 and ST2 signalling.

Receptor-specific crosstalk between prostanoid E receptor 3 and bombesin receptor subtype 3.

Bombesin receptor subtype 3 (BRS-3) is a GPCR that is expressed in the CNS, peripheral tissues, and tumors. Our understanding of BRS-3's role in physiology and pathophysiology is limited because its natural ligand is unknown. In an attempt to identify this ligand, we screened toad skin ( Bufo bufo gargarizans Cantor) extracts and identified prostaglandins as putative ligands. In BRS-3-transfected human embryonic kidney (HEK) cells, we found that prostaglandins, with prostaglandin E2 (PGE2) being the most potent, fulfill the pharmacologic criteria of affinity, selectivity, and specificity to be considered as agonists to the BRS-3 receptor. However, PGE2 is unable to activate BRS-3 in different cellular environments. We speculated that EP receptors might be the cause of this cellular selectivity, and we found that EP3 is the receptor primarily responsible for the differential PGE2 effect. Consequently, we reconstituted the HEK environment in Chinese hamster ovary (CHO) cells and found that BRS-3 and EP3 interact to potentiate PGE2 signaling. This potentiating effect is receptor specific, and it occurs only when BRS-3 is paired to EP3. Our study represents an example of functional crosstalk between two distantly related GPCRs and may be of clinical importance for BRS-3-targeted therapies.-Zhang, Y., Liu, Y., Wu, L., Fan, C., Wang, Z., Zhang, X., Alachkar, A., Liang, X., Civelli, O. Receptor-specific crosstalk between prostanoid E receptor 3 and bombesin receptor subtype 3.

Co-Stimulation of Purinergic P2X4 and Prostanoid EP3 Receptors Triggers Synergistic Degranulation in Murine Mast Cells.

Mast cells (MCs) recognize antigens (Ag) via IgE-bound high affinity IgE receptors (FcεRI) and trigger type I allergic reactions. FcεRI-mediated MC activation is regulated by various G protein-coupled receptor (GPCR) agonists. We recently reported that ionotropic P2X4 receptor (P2X4R) stimulation enhanced FcεRI-mediated degranulation. Since MCs are involved in Ag-independent hypersensitivity, we investigated whether co-stimulation with ATP and GPCR agonists in the absence of Ag affects MC degranulation. Prostaglandin E2 (PGE2) induced synergistic degranulation when bone marrow-derived MCs (BMMCs) were co-stimulated with ATP, while pharmacological analyses revealed that the effects of PGE2 and ATP were mediated by EP3 and P2X4R, respectively. Consistently, this response was absent in BMMCs prepared from P2X4R-deficient mice. The effects of ATP and PGE2 were reduced by PI3 kinase inhibitors but were insensitive to tyrosine kinase inhibitors which suppressed the enhanced degranulation induced by Ag and ATP. MC-dependent PGE2-triggered vascular hyperpermeability was abrogated in a P2X4R-deficient mouse ear edema model. Collectively, our results suggest that P2X4R signaling enhances EP3R-mediated MC activation via a different mechanism to that involved in enhancing Ag-induced responses. Moreover, the cooperative effects of the common inflammatory mediators ATP and PGE2 on MCs may be involved in Ag-independent hypersensitivity in vivo.