A succinate/SUCNR1-brush cell defense program in the tracheal epithelium.

Host-derived succinate accumulates in the airways during bacterial infection. Here, we show that luminal succinate activates murine tracheal brush (tuft) cells through a signaling cascade involving the succinate receptor 1 (SUCNR1), phospholipase Cß2, and the cation channel transient receptor potential channel subfamily M member 5 (TRPM5). Stimulated brush cells then trigger a long-range Ca2+ wave spreading radially over the tracheal epithelium through a sequential signaling process. First, brush cells release acetylcholine, which excites nearby cells via muscarinic acetylcholine receptors. From there, the Ca2+ wave propagates through gap junction signaling, reaching also distant ciliated and secretory cells. These effector cells translate activation into enhanced ciliary activity and Cl- secretion, which are synergistic in boosting mucociliary clearance, the major innate defense mechanism of the airways. Our data establish tracheal brush cells as a central hub in triggering a global epithelial defense program in response to a danger-associated metabolite.

Targeting of Scavenger Receptors Stabilin-1 and Stabilin-2 Ameliorates Atherosclerosis by a Plasma Proteome Switch Mediating Monocyte/Macrophage Suppression.

BACKGROUND: Scavenger receptors Stabilin-1 (Stab1) and Stabilin-2 (Stab2) are preferentially expressed by liver sinusoidal endothelial cells. They mediate the clearance of circulating plasma molecules controlling distant organ homeostasis. Studies suggest that Stab1 and Stab2 may affect atherosclerosis. Although subsets of tissue macrophages also express Stab1, hematopoietic Stab1 deficiency does not modulate atherogenesis. Here, we comprehensively studied how targeting Stab1 and Stab2 affects atherosclerosis. METHODS: ApoE-KO mice were interbred with Stab1-KO and Stab2-KO mice and fed a Western diet. For antibody targeting, Ldlr-KO mice were also used. Unbiased plasma proteomics were performed and independently confirmed. Ligand binding studies comprised glutathione-S-transferase-pulldown and endocytosis assays. Plasma proteome effects on monocytes were studied by single-cell RNA sequencing in vivo, and by gene expression analyses of Stabilin ligand-stimulated and plasma-stimulated bone marrow-derived monocytes/macrophages in vitro. RESULTS: Spontaneous and Western diet-associated atherogenesis was significantly reduced in ApoE-Stab1-KO and ApoE-Stab2-KO mice. Similarly, inhibition of Stab1 or Stab2 by monoclonal antibodies significantly reduced Western diet-associated atherosclerosis in ApoE-KO and Ldlr-KO mice. Although neither plasma lipid levels nor circulating immune cell numbers were decisively altered, plasma proteomics revealed a switch in the plasma proteome, consisting of 231 dysregulated proteins comparing wildtype with Stab1/2-single and Stab1/2-double KO, and of 41 proteins comparing ApoE-, ApoE-Stab1-, and ApoE-Stab2-KO. Among this broad spectrum of common, but also disparate scavenger receptor ligand candidates, periostin, reelin, and TGFBi (transforming growth factor, ß-induced), known to modulate atherosclerosis, were independently confirmed as novel circulating ligands of Stab1/2. Single-cell RNA sequencing of circulating myeloid cells of ApoE-, ApoE-Stab1-, and ApoE-Stab2-KO mice showed transcriptomic alterations in patrolling (Ccr2-/Cx3cr1++/Ly6Clo) and inflammatory (Ccr2+/Cx3cr1+/Ly6Chi) monocytes, including downregulation of proatherogenic transcription factor Egr1. In wildtype bone marrow-derived monocytes/macrophages, ligand exposure alone did not alter Egr1 expression in vitro. However, exposure to plasma from ApoE-Stab1-KO and ApoE-Stab2-KO mice showed a reverted proatherogenic macrophage activation compared with ApoE-KO plasma, including downregulation of Egr1 in vitro. CONCLUSIONS: Inhibition of Stab1/Stab2 mediates an anti-inflammatory switch in the plasma proteome, including direct Stabilin ligands. The altered plasma proteome suppresses both patrolling and inflammatory monocytes and, thus, systemically protects against atherogenesis. Altogether, anti-Stab1- and anti-Stab2-targeted therapies provide a novel approach for the future treatment of atherosclerosis.

Adhesion receptor ADGRG2/GPR64 is in the GI-tract selectively expressed in mature intestinal tuft cells.

OBJECTIVE: GPR64/ADGRG2 is an orphan Adhesion G protein-coupled receptor (ADGR) known to be mainly expressed in the parathyroid gland and epididymis. This investigation aimed to delineate the cellular expression of GPR64 throughout the body with focus on the gastrointestinal (GI) tract. METHODS: Transgenic Gpr64mCherry reporter mice were histologically examined throughout the body and reporter protein expression in intestinal tuft cells was confirmed by specific cell ablation. The GPCR repertoire of intestinal Gpr64mCherry-positive tuft cells was analyzed by quantitative RT-PCR analysis and in situ hybridization. The Gpr64mCherry was crossed into the general tuft cell reporter Trpm5GFP to generate small intestinal organoids for time-lapse imaging. Intestinal tuft cells were isolated from small intestine, FACS-purified and transcriptionally compared using RNA-seq analysis. RESULTS: Expression of the Gpr64mCherry reporter was identified in multiple organs and specifically in olfactory microvillous cells, enteric nerves, and importantly in respiratory and GI tuft cells. In the small intestine, cell ablation targeting Gpr64-expressing epithelial cells eliminated tuft cells. Transcriptional analysis of small intestinal Gpr64mCherry -positive tuft cells confirmed expression of Gpr64 and the chemo-sensors Sucnr1, Gprc5c, Drd3, and Gpr41/Ffar3. Time-lapse studies of organoids from Trpm5GFP:Gpr64mCherry mice revealed sequential expression of initially Trpm5GFP and subsequently also Gpr64mCherry in maturing intestinal tuft cells. RNA-seq analysis of small intestinal tuft cells based on these two markers demonstrated a dynamic change in expression of transcription factors and GPCRs from young to mature tuft cells. CONCLUSIONS: GPR64 is expressed in chemosensory epithelial cells across a broad range of tissues; however, in the GI tract, GPR64 is remarkably selectively expressed in mature versus young immunoregulatory tuft cells.

Disturbed flow-induced Gs-mediated signaling protects against endothelial inflammation and atherosclerosis.

Atherosclerosis develops preferentially in areas of the arterial system, in which blood flow is disturbed. Exposure of endothelial cells to disturbed flow has been shown to induce inflammatory signaling, including NF-κB activation, which leads to the expression of leukocyte adhesion molecules and chemokines. Here, we show that disturbed flow promotes the release of adrenomedullin from endothelial cells, which in turn activates its Gs-coupled receptor calcitonin receptor-like receptor (CALCRL). This induces antiinflammatory signaling through cAMP and PKA, and it results in reduced endothelial inflammation in vitro and in vivo. Suppression of endothelial expression of Gαs, the α subunit of the G-protein Gs; CALCRL; or adrenomedullin leads to increased disturbed flow-induced inflammatory signaling in vitro and in vivo. Furthermore, mice with induced endothelial-specific deficiency of Gαs, CALCRL, or adrenomedullin show increased atherosclerotic lesions. Our data identify an antiinflammatory signaling pathway in endothelial cells stimulated by disturbed flow and suggest activation of the endothelial adrenomedullin/CALCRL/Gs system as a promising approach to inhibit progression of atherosclerosis.

Shear Stress-Induced miR-143-3p in Collateral Arteries Contributes to Outward Vessel Growth by Targeting Collagen V-α2.

OBJECTIVE: Arteriogenesis, describing the process of collateral artery growth, is activated by fluid shear stress (FSS). Since this vascular mechanotransduction may involve microRNAs (miRNAs), we investigated the FSS-induced expression of vascular cell miRNAs and their functional impact on collateral artery growth during arteriogenesis. Approach and Results: To this end, rats underwent femoral artery ligation and arteriovenous anastomosis to increase collateral blood flow to maximize FSS and trigger collateral vessel remodeling. Five days after surgery, a miRNA expression profile was obtained from collateral tissue, and upregulation of 4 miRNAs (miR-24-3p, miR-143-3p, miR-146a-5p, and miR-195-5p) was verified by quantitative polymerase chain reaction. Knockdown of miRNAs at the same time of the surgery in an in vivo mouse ligation and recovery model demonstrated that inhibition of miR-143-3p only severely impaired blood flow recovery due to decreased arteriogenesis. In situ hybridization revealed distinct localization of miR-143-3p in the vessel wall of growing collateral arteries predominantly in smooth muscle cells. To investigate the mechanotransduction of FSS leading to the increased miR-143-3p expression, cultured endothelial cells were exposed to FSS. This provoked the expression and release of TGF-ß (transforming growth factor-ß), which increased the expression of miR-143-3p in smooth muscle cells in the presence of SRF (serum response factor) and myocardin. COL5A2 (collagen type V-α2)-a target gene of miR-143-3p predicted by in silico analysis-was found to be downregulated in growing collaterals. CONCLUSIONS: These results indicate that the increased miR-143-3p expression in response to FSS might contribute to the reorganization of the extracellular matrix, which is important for vascular remodeling processes, by inhibiting collagen V-α2 biosynthesis.

Orphan G Protein-Coupled Receptor GPRC5B Controls Smooth Muscle Contractility and Differentiation by Inhibiting Prostacyclin Receptor Signaling.

BACKGROUND: G protein-coupled receptors are important regulators of contractility and differentiation in vascular smooth muscle cells (SMCs), but the specific function of SMC-expressed orphan G protein-coupled receptor class C group 5 member B (GPRC5B) is unclear. METHODS: We studied the role of GPRC5B in the regulation of contractility and dedifferentiation in human and murine SMCs in vitro and in iSM-Gprc5b-KO (tamoxifen-inducible, SMC-specific knockout) mice under conditions of arterial hypertension and atherosclerosis in vivo. RESULTS: Mesenteric arteries from SMC-specific Gprc5b-KOs showed ex vivo significantly enhanced prostacyclin receptor (IP)-dependent relaxation, whereas responses to other relaxant or contractile factors were normal. In vitro, knockdown of GPRC5B in human aortic SMCs resulted in increased IP-dependent cAMP production and consecutive facilitation of SMC relaxation. In line with this facilitation of IP-mediated relaxation, iSM-Gprc5b-KO mice were protected from arterial hypertension, and this protective effect was abrogated by IP antagonists. Mechanistically, we show that knockdown of GPRC5B increased the membrane localization of IP both in vitro and in vivo and that GPRC5B, but not other G protein-coupled receptors, physically interacts with IP. Last, we show that enhanced IP signaling in GPRC5B-deficient SMCs not only facilitates relaxation but also prevents dedifferentiation during atherosclerosis development, resulting in reduced plaque load and increased differentiation of SMCs in the fibrous cap. CONCLUSIONS: Taken together, our data show that GPRC5B regulates vascular SMC tone and differentiation by negatively regulating IP signaling.

Shear stress-induced endothelial adrenomedullin signaling regulates vascular tone and blood pressure.

Hypertension is a primary risk factor for cardiovascular diseases including myocardial infarction and stroke. Major determinants of blood pressure are vasodilatory factors such as nitric oxide (NO) released from the endothelium under the influence of fluid shear stress exerted by the flowing blood. Several endothelial signaling processes mediating fluid shear stress-induced formation and release of vasodilatory factors have been described. It is, however, still poorly understood how fluid shear stress induces these endothelial responses. Here we show that the endothelial mechanosensitive cation channel PIEZO1 mediated fluid shear stress-induced release of adrenomedullin, which in turn activated its Gs-coupled receptor. The subsequent increase in cAMP levels promoted the phosphorylation of endothelial NO synthase (eNOS) at serine 633 through protein kinase A (PKA), leading to the activation of the enzyme. This Gs/PKA-mediated pathway synergized with the AKT-mediated pathways leading to eNOS phosphorylation at serine 1177. Mice with endothelium-specific deficiency of adrenomedullin, the adrenomedullin receptor, or Gαs showed reduced flow-induced eNOS activation and vasodilation and developed hypertension. Our data identify fluid shear stress-induced PIEZO1 activation as a central regulator of endothelial adrenomedullin release and establish the adrenomedullin receptor and subsequent Gs-mediated formation of cAMP as a critical endothelial mechanosignaling pathway regulating basal endothelial NO formation, vascular tone, and blood pressure.

ß-Hydroxybutyrate protects from alcohol-induced liver injury via a Hcar2-cAMP dependent pathway.

BACKGROUND & AIMS: Sterile inflammation resulting in alcoholic hepatitis (AH) occurs unpredictably after many years of excess alcohol intake. The factors responsible for the development of AH are not known but mitochondrial damage with loss of mitochondrial function are common features. Hcar2 is a G-protein coupled receptor which is activated by ß-hydroxybutyrate (BHB). We aimed to determine the relevance of the BHB-Hcar2 pathway in alcoholic liver disease. METHODS: We tested if loss of BHB production can result in increased liver inflammation. We further tested if BHB supplementation is protective in AH through interaction with Hcar2, and analyzed the immune and cellular basis for protection. RESULTS: Humans with AH have reduced hepatic BHB, and inhibition of BHB production in mice aggravated ethanol-induced AH, with higher plasma alanine aminotransferase levels, increased steatosis and greater neutrophil influx. Conversely supplementation of BHB had the opposite effects with reduced alanine aminotransferase levels, reduced steatosis and neutrophil influx. This therapeutic effect of BHB is dependent on the receptor Hcar2. BHB treatment increased liver Il10 transcripts, and promoted the M2 phenotype of intrahepatic macrophages. BHB also increased the transcriptional level of M2 related genes in vitro bone marrow derived macrophages. This skewing towards M2 related genes is dependent on lower mitochondrial membrane potential (Δψ) induced by BHB. CONCLUSIONS: Collectively, our data shows that BHB production during excess alcohol consumption has an anti-inflammatory and hepatoprotective role through an Hcar2 dependent pathway. This introduces the concept of metabolite-based therapy for AH. LAY SUMMARY: Alcoholic hepatitis is a life-threatening condition with no approved therapy that occurs unexpectedly in people who consume excess alcohol. The liver makes many metabolites, and we demonstrate that loss of one such metabolite ß-hydroxybutyrate occurs in patients with alcoholic hepatitis. This loss can increase alcohol-induced liver injury, and ß-hydroxybutyrate can protect from alcohol-induced liver injury via a receptor on liver macrophages. This opens the possibility of metabolite-based therapy for alcoholic hepatitis.

P2Y2 and Gq/G11 control blood pressure by mediating endothelial mechanotransduction.

Elevated blood pressure is a key risk factor for developing cardiovascular diseases. Blood pressure is largely determined by vasodilatory mediators, such as nitric oxide (NO), that are released from the endothelium in response to fluid shear stress exerted by the flowing blood. Previous work has identified several mechanotransduction signaling processes that are involved in fluid shear stress-induced endothelial effects, but how fluid shear stress initiates the response is poorly understood. Here, we evaluated human and bovine endothelial cells and found that the purinergic receptor P2Y2 and the G proteins Gq/G11 mediate fluid shear stress-induced endothelial responses, including [Ca2+]i transients, activation of the endothelial NO synthase (eNOS), phosphorylation of PECAM-1 and VEGFR-2, as well as activation of SRC and AKT. In response to fluid shear stress, endothelial cells released ATP, which activates the purinergic P2Y2 receptor. Mice with induced endothelium-specific P2Y2 or Gq/G11 deficiency lacked flow-induced vasodilation and developed hypertension that was accompanied by reduced eNOS activation. Together, our data identify P2Y2 and Gq/G11 as a critical endothelial mechanosignaling pathway that is upstream of previously described mechanotransduction processes and demonstrate that P2Y2 and Gq/G11 are required for basal endothelial NO formation, vascular tone, and blood pressure.

Endogenous metabolites as ligands for G protein-coupled receptors modulating risk factors for metabolic and cardiovascular disease.

During the last decade, several G protein-coupled receptors activated by endogenous metabolites have been described. These receptors respond to fatty acids, mono- and disaccharides, amino acids, or various intermediates and products of metabolism, including ketone bodies, lactate, succinate, or bile acids. Receptors of endogenous metabolites are expressed in taste cells, the gastrointestinal tract, adipose tissue, endocrine glands, immune cells, or the kidney and are therefore in a position to sense food intake in the gastrointestinal tract or to link metabolite levels to the appropriate responses of metabolic organs. Some of the receptors appear to provide a link between metabolic and neuronal or immune functions. Given that many of these metabolic processes are dysregulated under pathological conditions, including diabetes, dyslipidemia, and obesity, receptors of endogenous metabolites have also been recognized as potential drug targets to prevent and/or treat metabolic and cardiovascular diseases. This review describes G protein-coupled receptors activated by endogenous metabolites and summarizes their physiological, pathophysiological, and potential pharmacological roles.

Tetracycline-inducible protein expression in pancreatic cancer cells: effects of CapG overexpression.

AIM: To establish stable tetracycline-inducible pancreatic cancer cell lines. METHODS: Suit-2, MiaPaca-2, and Panc-1 cells were transfected with a second generation reverse tetracycline-controlled transactivator protein (rtTA2S-M2), under the control of either a cytomegalovirus (CMV) or a chicken ß-actin promoter, and the resulting clones were characterised. RESULTS: Use of the chicken (ß-actin) promoter proved superior for both the production and maintenance of doxycycline-inducible cell lines. The system proved versatile, enabling transient inducible expression of a variety of genes, including GST-P, CYP2E1, S100A6, and the actin capping protein, CapG. To determine the physiological utility of this system in pancreatic cancer cells, stable inducible CapG expressors were established. Overexpressed CapG was localised to the cytoplasm and the nuclear membrane, but was not observed in the nucleus. High CapG levels were associated with enhanced motility, but not with changes to the cell cycle, or cellular proliferation. In CapG-overexpressing cells, the levels and phosphorylation status of other actin-moduating proteins (Cofilin and Ezrin/Radixin) were not altered. However, preliminary analyses suggest that the levels of other cellular proteins, such as ornithine aminotransferase and enolase, are altered upon CapG induction. CONCLUSION: We have generated pancreatic-cancer derived cell lines in which gene expression is fully controllable.

Analysis of serum proteins by LC-MS/MS.

Serum contains a vast array of proteins, some of which are specific to blood whilst others are secreted into blood from tissues and organs. The so-called tissue leakage factors reveal information about the tissue from which they originate and are therefore of great potential importance as disease biomarkers. There are already a number of blood-borne biomarkers in routine clinical use that aid in the diagnosis or management of cancer. However, there is a pressing need for additional markers, and new methods to find them are under development. Here we provide a protocol for serum protein profiling using liquid chromatography tandem mass spectrometry (LC-MS/MS). Included in this procedure, we detail the pre-processing steps of lipid and high-abundance protein removal. These procedures can also be employed up-stream of quantification methods such as isobaric tags for relative and absolute quantification (iTRAQ). Chapter 12 is devoted to the iTRAQ approach for quantifying proteins, and it is therefore not described in this chapter.

Smad4 loss is associated with fewer S100A8-positive monocytes in colorectal tumors and attenuated response to S100A8 in colorectal and pancreatic cancer cells.

S100A8 and its dimerization partner S100A9 are emerging as important chemokines in cancer. We previously reported that Smad4-negative pancreatic tumors contain fewer stromal S100A8-positive monocytes than their Smad4-positive counterparts. Here, we studied S100A8/A9-expressing cells in colorectal tumors relating their presence to clinicopathological parameters and Smad4 status. Two-dimensional gel electrophoresis (n = 12) revealed variation in the levels of S100A8 protein in colorectal cancer tumors, whereas immunohistochemical analysis (n = 313) showed variation in the numbers of stromal S100A8-positive and S100A9-positive cells. Loss of Smad4 expression was observed in 42/304 (14%) colorectal tumors and was associated with reduced numbers of S100A8-positive (P = 0.03) but not S100A9-positive stromal cells (P = 0.26). High S100A9 cell counts were associated with large tumor sizes (P = 0.0006) and poor differentiation grade (P = 0.036). However, neither S100A8 nor S100A9 cell counts predicted poor survival, except for patients with Smad4-negative tumors (P = 0.02). To address the impact of environmental S100A8/A9 chemokines on tumor cells, we examined the effects of exogenously added S100A8 and S100A9 proteins on cellular migration and proliferation of colorectal and pancreatic cancer cells. S100A8 and S100A9 enhanced migration and proliferation in Smad4-positive and Smad4-negative cancer cells. However, transient depletion of Smad4 resulted in loss of responsiveness to exogenous S100A8, but not S100A9. S100A8 and S100A9 activated Smad4 signaling as evidenced by phosphorylation of Smad2/3; blockade of the receptor for the advanced glycation end products inhibited this response. In conclusion, Smad4 loss alters the tumor's interaction with stromal myeloid cells and the tumor cells' response to the stromal chemokine, S100A8.

Dual-color proteomic profiling of complex samples with a microarray of 810 cancer-related antibodies.

Antibody microarrays have the potential to enable comprehensive proteomic analysis of small amounts of sample material. Here, protocols are presented for the production, quality assessment, and reproducible application of antibody microarrays in a two-color mode with an array of 1,800 features, representing 810 antibodies that were directed at 741 cancer-related proteins. In addition to measures of array quality, we implemented indicators for the accuracy and significance of dual-color detection. Dual-color measurements outperform a single-color approach concerning assay reproducibility and discriminative power. In the analysis of serum samples, depletion of high-abundance proteins did not improve technical assay quality. On the contrary, depletion introduced a strong bias in protein representation. In an initial study, we demonstrated the applicability of the protocols to proteins derived from urine samples. We identified differences between urine samples from pancreatic cancer patients and healthy subjects and between sexes. This study demonstrates that biomedically relevant data can be produced. As demonstrated by the thorough quality analysis, the dual-color antibody array approach proved to be competitive with other proteomic techniques and comparable in performance to transcriptional microarray analyses.

A technically detailed and pragmatic protocol for quantitative serum proteomics using iTRAQ.

Blood is recognised as a highly important source of disease-related biomarkers, and proteomic approaches for identifying novel blood-borne biomarkers are in demand. The complexity and dynamic protein concentration range of plasma/serum however complicates the analysis process. A number of strategies for simplification of blood prior to proteomic analysis have been developed. In addition, methods for quantifying the levels of proteins in samples, such as isobaric tags for relative and absolute quantification (iTRAQ) are emerging. However, the successful application of these procedures is not always straightforward and technical hurdles must be overcome. Here we provide a technically detailed working protocol for iTRAQ-based quantification of serum proteins following immunodepletion of high abundance proteins. To improve the number of proteins identified and quantified we have introduced several modifications to the standard iTRAQ protocol. We report identifications of 217 proteins (5773 peptides) with a false discovery rate of 1% or 254 proteins with 95% confidence, respectively. Relative quantification data were obtained for 234 (95% confidence) serum proteins, including species present in the concentration range of tissue leakage factors. The samples described here relate to pancreatic cancer; however the protocol can be applied to serum from other control or disease types.

Pancreatic cancer: proteomic approaches to a challenging disease.

PURPOSE OF REVIEW: To describe progress in the application of proteomic approaches to advance our understanding of the biology of pancreatic cancer as well as contribute potential protein biomarkers for this disease. RECENT FINDINGS: Here we review proteomic studies relating to pancreatic cancer that have been published in the past 12 months. We describe novel techniques for the simplification of complex protein samples, focusing particularly on emerging methods for reducing the complexity of blood. We provide examples, where possible, of the application of these novel technologies to pancreatic cancer research. SUMMARY: Both the range of proteomic-based approaches and their sensitivities for the detection of low-abundance proteins has increased. This provides promise that further research will yield insight into pancreatic cancer, including valuable information on proteins that may ultimately serve as biomarkers for pancreatic cancer.

Expression of glucose transporter isoforms and the insulin receptor during hamster preimplantation embryo development.

During preimplantation development, embryos of many species are known to express up to five isoforms of the facilitative glucose transporter proteins (GLUT). Development of hamster blastocysts is inhibited by glucose. We therefore investigated GLUT isoform and insulin receptor (IR) expression in hamster preimplantation embryos cultured in glucose-free medium from the 8-cell stage onwards. We show that GLUT1, 3 and 8 mRNA are constitutively expressed from the 8-cell to the blastocyst stage. The IR is expressed from the morula stage onwards. Messenger RNA of the insulin-responsive GLUT4 was not detected at any stage. GLUT1 and 3 were localised by immunocytochemistry. GLUT1 was expressed in both embryoblast and trophoblast, in the latter, mainly in basal and lateral membranes directed towards the blastocoel and embryoblast. GLUT3 was exclusively localised in the apical membrane of trophoblast cells. We show that hamster preimplantation embryos express several GLUT isoforms thus closely resembling embryos of other mammalian species. Despite endogenous IR expression, the insulin-sensitive isoform GLUT4 was not expressed, indicating that the insulin-mediated glucose uptake known from classical insulin target cells may not be relevant for hamster blastocysts.

Confounding effect of obstructive jaundice in the interpretation of proteomic plasma profiling data for pancreatic cancer.

It is well established that variation in sampling, processing and storage protocols can alter the levels of potential biomarkers in serum and plasma. Here, using pancreatic cancer as an example, we demonstrate that consideration of clinical parameters related to the patient's illness is equally important when seeking cancer-specific biomarkers. Bile duct-obstruction is a feature of pancreatic disease that can cause jaundice. Comparing patients with pancreatic cancer, chronic pancreatitis or biliary duct obstruction, we observed that the plasma levels of apolipoprotein A1, transthyretin, and apolipoprotein E, when examined in isolation, were each associated with pancreatic cancer. However, when the effect of bile duct obstruction was considered, only transthyretin levels were independently associated with cancer likelihood. Our results demonstrate the importance of accounting for disease-related confounding factors when analyzing data for the detection of cancer biomarkers.

Significance of prolyl hydroxylase 2 in the interference of aryl hydrocarbon receptor and hypoxia-inducible factor-1 alpha signaling.

Hypoxia-inducible factor-1 alpha (HIF-1 alpha) and the aryl hydrocarbon receptor (AhR) work as environmental sensors in human tissues. These proteins are members of the helix-loop-helix/Per-ARNT-SIM transcription factor family and form heterodimers with the aryl hydrocarbon receptor nuclear translocator. HIF-1 alpha can be activated by low oxygen concentrations and hypoxia-inducing agents. The AhR is activated by xenobiotica such as dioxins. Here, we analyze the interference between the AhR signaling, activated by 10 nM 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD), and the HIF-1 alpha pathway, induced by hypoxia (5% O2), in two human cell lines, the breast carcinoma cell line MCF-7 and the hepatocyte cell line HepG2. In both cell lines, treatment with TCDD and hypoxia clearly reduced the stabilization of HIF-1 alpha and HRE-mediated promoter activity when compared to the induction under hypoxia alone. Because these effects were not observed after alpha-naphthoflavone treatment and HIF-1 alpha mRNA was not down-regulated, HIF-1 alpha stabilization was revealed to be the target by TCDD in an AhR-depended mechanism. Under exposure to TCDD or hypoxia, the main regulator of HIF-1 alpha stability, the prolyl hydroxylase domain containing protein 2 (PHD2) showed an increase in promoter activity, transcript numbers, and protein amount. Therefore, PHD2 expression is regulated in an AhR-dependent manner under normoxia. The AhR-dependent regulation of PHD2 under normoxia, however, is overwritten by the TCDD-mediated destabilization of HIF-1 alpha. The destabilization of HIF-1 alpha is the dominant effect causing the reduced PHD2 expression after simultaneous exposure to TCDD and hypoxia. We conclude that PHD2 does not mediate the TCDD-mediated HIF-1 alpha destabilization and does not control the interference of AhR and HIF-1 alpha pathways.

Cell lineage-specific signaling of insulin and insulin-like growth factor I in rabbit blastocysts.

The insulin/IGF system plays a critical role in embryo growth and development. We have investigated the expression of insulin receptor (IR) and IGF-I receptor (IGF-IR) and the activation of their downstream pathways in rabbit 6-d-old blastocysts. IR was expressed in embryoblast (Em, inner cell mass) and trophoblast (Tr) cells, whereas IGF-IR was localized mainly in Em. Isoform A (IR-A) represents the main insulin isoform in blastocysts and was found in Em and Tr cells. IR-B was detectable only in Tr. IR/IGF-IR signaling pathways were analyzed after stimulation with insulin (17 nm) or IGF-I (1.3 nm) in cultured blastocysts. Insulin stimulated Erk1/2 in Em and Tr and Akt in Tr but not in Em. IGF-I activated both kinases exclusively in Em. The target genes c-fos (for MAPK kinase-1/Erk signaling) and phosphoenolpyruvate carboxykinase (PEPCK, for PI3K/Akt signaling) were also specifically regulated. Insulin down-regulated PEPCK RNA amounts in Tr by activation of the phosphatidylinositol 3-kinase/Akt pathway. Expression of c-fos by insulin and IGF-I was different with respect to time and fortitude of expression, mirroring again the specific IR and IGF-IR expression patterns in Em and Tr. Taken together, we show that IGF-I acts primarily mitogenic, an effect that is cell lineage-specifically restricted to the Em. By contrast, insulin is the growth factor of the Tr stimulating mitogenesis and down-regulating metabolic responses. As soon as blastocyst differentiation in Em and Tr has been accomplished, insulin and IGF-I signaling is different in both cell lineages, implying a different developmental impact of both growth factors.