Photolysis of Caged Inositol Pyrophosphate InsP8 Directly Modulates Intracellular Ca2+ Oscillations and Controls C2AB Domain Localization.

Inositol pyrophosphates constitute a family of hyperphosphorylated signaling molecules involved in the regulation of glucose uptake and insulin sensitivity. While our understanding of the biological roles of inositol heptaphosphates (PP-InsP5) has greatly improved, the functions of the inositol octaphosphates ((PP)2-InsP4) have remained unclear. Here we present the synthesis of two enantiomeric cell-permeant and photocaged (PP)2-InsP4 derivatives and apply them to study the functions in living ß-cells. Photorelease of the naturally occurring isomer 1,5-(PP)2-InsP4 led to an immediate and concentration-dependent reduction of intracellular calcium oscillations, while other caged inositol pyrophosphates (3,5-(PP)2-InsP4, 5-PP-InsP5, 1-PP-InsP5, 3-PP-InsP5) showed no immediate effect. Furthermore, uncaging of 1,5-(PP)2-InsP4 but not 3,5-(PP)2-InsP4 induced translocation of the C2AB domain of granuphilin from the plasma membrane to the cytosol. Granuphilin is involved in membrane docking of secretory vesicles. This suggests that 1,5-(PP)2-InsP4 impacts ß-cell activity by regulating granule localization and/or priming and calcium signaling in concert.

Synthesis and Cellular Labeling of Caged Phosphatidylinositol Derivatives.

Phosphatidylinositol (PI) is the biosynthetic precursor for seven phosphoinositides, important signaling lipids in cells. A membrane-permeant caged PI derivative featuring a photo-removable coumarinyl group masking the negative charge of the phosphate, as well as two enzymatically removable butyrate esters for increased lipophilicity and for preventing phosphate migration, were synthesized. Rapid cell entry and cellular labeling in fixed cells was demonstrated by a photo-cross-linkable diazirine followed by attachment of a fluorophore through click chemistry. Using this technique, we found that the multifunctional caged PI derivative resided predominantly at internal membranes but rapidly changed to the plasma membrane after uncaging. Accordingly, a preliminary proteomic analysis of the lipid-protein conjugates revealed that the two major PI transport proteins PITPα and ß were prime targets of the photo-cross-linked PI derivative.

Trifunctional lipid probes for comprehensive studies of single lipid species in living cells.

Lipid-mediated signaling events regulate many cellular processes. Investigations of the complex underlying mechanisms are difficult because several different methods need to be used under varying conditions. Here we introduce multifunctional lipid derivatives to study lipid metabolism, lipid-protein interactions, and intracellular lipid localization with a single tool per target lipid. The probes are equipped with two photoreactive groups to allow photoliberation (uncaging) and photo-cross-linking in a sequential manner, as well as a click-handle for subsequent functionalization. We demonstrate the versatility of the design for the signaling lipids sphingosine and diacylglycerol; uncaging of the probe for these two species triggered calcium signaling and intracellular protein translocation events, respectively. We performed proteomic screens to map the lipid-interacting proteome for both lipids. Finally, we visualized a sphingosine transport deficiency in patient-derived Niemann-Pick disease type C fibroblasts by fluorescence as well as correlative light and electron microscopy, pointing toward the diagnostic potential of such tools. We envision that this type of probe will become important for analyzing and ultimately understanding lipid signaling events in a comprehensive manner.

Photorelease of 2-Arachidonoylglycerol in Live Cells.

2-Arachidonoylglycerol (2-AG) is acting as a full agonist of cannabinoid receptor 1 and 2. Direct manipulation of 2-AG levels is a challenging task. The amphiphilic properties and the instability of 2-AG in aqueous media complicate its use as a drug-like molecule. Additionally, inhibition of the protein machinery that regulates 2-AG levels may also affect other monoacylglycerols. Therefore, we developed a novel method to elevate 2-AG levels with a flash of light. The resulting tool is a photoactivatable "caged" 2-arachidonoylglycerol (cg2-AG) allowing for the rapid photorelease of the signaling lipid in live cells. We characterized the mechanism of uncaging and the effect of 2-AG on the regulation of the ß-cell signaling network. After uncaging of 2-AG, we monitored calcium levels, CB1-GIRK channel coupling, and CB1-mediated inhibition of adenylate cyclase and protein kinase A activity.

Protein-specific localization of a rhodamine-based calcium-sensor in living cells.

A small synthetic calcium sensor that can be site-specifically coupled to proteins in living cells by utilizing the bio-orthogonal HaloTag labeling strategy is presented. We synthesized an iodo-derivatized BAPTA chelator with a tetramethyl rhodamine fluorophore that allows further modification by Sonogashira cross-coupling. The presented calcium sensitive dye shows a 200-fold increase in fluorescence upon calcium binding. The derivatization with an aliphatic linker bearing a terminal haloalkane-function by Sonogashira cross-coupling allows the localization of the calcium sensor to Halo fusion proteins which we successfully demonstrate in in vitro and in vivo experiments. The herein reported highly sensitive tetramethyl rhodamine based calcium indicator, which can be selectively localized to proteins, is a powerful tool to determine changes in calcium levels inside living cells with spatiotemporal resolution.

Two-step protein labeling utilizing lipoic acid ligase and Sonogashira cross-coupling.

Labeling proteins in their natural settings with fluorescent proteins or protein tags often leads to problems. Despite the high specificity, these methods influence the natural functions due to the rather large size of the proteins used. Here we present a two-step labeling procedure for the attachment of various fluorescent probes to a small peptide sequence (13 amino acids) using enzyme-mediated peptide labeling in combination with palladium-catalyzed Sonogashira cross-coupling. We identified p-iodophenyl derivatives from a small library that can be covalently attached to a lysine residue within a specific 13-amino-acid peptide sequence by Escherichia coli lipoic acid ligase A (LplA). The derivatization with p-iodophenyl subsequently served as a reactive handle for bioorthogonal transition metal-catalyzed Sonogashira cross-coupling with alkyne-functionalized fluorophores on both the peptide as well as on the protein level. Our two-step labeling strategy combines high selectivity of enzyme-mediated labeling with the chemoselectivity of palladium-catalyzed Sonogashira cross-coupling.

Single-balloon enteroscopy-assisted endoscopic retrograde cholangiopancreaticography in patients with surgically altered anatomy: higher failure rate in malignant biliary obstruction - a prospective single center cohort analysis.

INTRODUCTION: The performance of endoscopic retrograde cholangiopancreaticography (ERCP) in patients with post-surgically altered anatomy is technically ambitious. Our study aimed at comparing a cohort of patients having successfully undergone single-balloon enteroscopy (SBE)-assisted ERCP to those in whom SBE-ERCP failed. METHODS: This trial is a prospective single center cohort study. Participants included 30 patients (median age 69.5 years, range 20-86 years) with previous pancreaticobiliary surgery. First, a conventional ERCP approach was attempted in all patients. Additionally, those patients in whom prior conventional ERCP had failed underwent SBE-ERCP (n = 26). Patients' baseline characteristics were retrieved and patient cohorts with and without successful SBE-ERCPs were compared and analyzed. Statistical analysis was applied. Univariate analysis was performed to detect possible risk factors of SBE-ERCP failure. RESULTS: The overall success rate of SBE-ERCP, including two patients with percutaneous transhepatic cholangiography- assisted rendezvous technique was 65.4% (17/26). Patients with malignant obstructive cholestasis had a significantly higher failure rate compared to those with benign strictures (84.2% vs. 14.2%, p < 0.001). DISCUSSION: SBE-ERCP is a promising tool for diagnostic and therapeutic procedures in the pancreaticobiliary system of selected, previously operated patients with failure of conventional ERCP. However, higher failure rates in malignant biliary obstruction should be taken into account.

Valorization of Wheat Bran by Co-Cultivation of Fungi with Integrated Hydrolysis to Provide Sugars and Animal Feed.

The enzymatic hydrolysis of agricultural residues like wheat bran enables the valorization of otherwise unused carbon sources for biotechnological processes. The co-culture of Aspergillus niger and Trichoderma reesei with wheat bran particles as substrate produces an enzyme set consisting of xylanases, amylases, and cellulases that is suitable to degrade lignocellulosic biomass to sugar monomers (D-glucose, D-xylose, and L-arabinose). An integrated one-pot process for enzyme production followed by hydrolysis in stirred tank bioreactors resulted in hydrolysates with overall sugar concentrations of 32.3 g L-1 and 24.4 g L-1 at a 25 L and a 1000 L scale, respectively, within 86 h. Furthermore, the residual solid biomass consisting of fermented wheat bran with protein-rich fungal mycelium displays improved nutritional properties for usage as animal feed due to its increased content of sugars, protein, and fat.

Miniprobe endoscopic ultrasound accurately stages esophageal cancer and guides therapeutic decisions in the era of neoadjuvant therapy: results of a multicenter cohort analysis.

BACKGROUND: Despite recent advances in imaging techniques, adequate classification of esophageal lesions is still challenging. Accurate staging of tumors of the esophagus is a precondition for targeted therapy. In this retrospective, multicenter study, we report the role of high-frequency endoscopic ultrasound (EUS) catheter probes in pretherapeutic staging of esophageal neoplasms and thus guiding treatment decisions. METHODS: A total of 143 patients (mean age of 63.8 ± 10.7 years) with esophageal carcinoma were recruited from five German centers (Münster, Oldenburg, Hannover, Wiesbaden, and Lüneburg). Tumor type was adenocarcinoma in 112 (78 %) cases and squamous cell carcinoma in 31 (22 %). Tumor localization was as follows: proximal 3, mid esophagus 7, and distal third 133. Histological correlation either through EMR or surgery was available. In all patients, pretherapeutic uT and uN classifications were compared to pT/pN classification obtained from surgically (esophagectomy, n = 93) or endoscopically (EMR, n = 50) resected tissue. RESULTS: Overall, accuracy of uT classification was 60 % and of uN classification was 74 %. Sensitivity, specificity, and accuracy rates for local tumor extension were as follows (%): T1: 68/97/83; T2: 39/84/75; T3: 72/81/79; T4: 13/97/93; T1/2: 73/81/75; T3/4: 78/82/81. Relating to positive lymph node detection, sensitivity and specificity were 76 and 71 %, respectively. CONCLUSIONS: Miniprobe EUS is an established method for the staging of esophageal tumors. Our large multicenter cohort shows a solid accuracy of miniprobe EUS with respect to differentiating locally advanced from limited cancer and assisting to determine the treatment regimen in the era of neoadjuvant therapy; consequently, 78 % of patients would have been assigned to the adequate therapeutic regimen, whereas 11 % of patients would have been overtreated and 11 % undertreated.

Endoscopic transpapillary biopsies are of limited value in the diagnostics of bile duct strictures of unknown etiology-results of a histopathologically controlled study in 312 patients.

BACKGROUND/AIMS: Our investigation aimed to evaluate the impact of endoscopic transpapillary forceps biopsies (ETP) in bile duct strictures of unknown etiology based on the largest European patient cohort at a tertiary referral center. To date only studies with limited patient numbers exist. METHODOLOGY: Three-hundred-and-twelve patients (162 males, 150 females, mean age 62±12.7 years) with bile duct strictures of unknown etiology were examined with ETP. Sensitivity, specificity and accuracy of ETP were compared to the definite diagnosis proved by histopathology of surgical resection specimens or long-term follow-up of those patients not undergoing surgery. RESULTS: Using ETP a correct pe-interventional diagnosis was achieved in 211 out of 312 patients resulting in an accuracy rate of 67.6%. Eighty-six out of 187 malignant stenoses were correctly diagnosed by ETP, giving rise to sensitivity and specificity rates of 46 and 100%, respectively. Sensitivity of ETP in cholangiocellular carcinoma was significantly superior to that in pancreatic carcinoma (52.5% vs. 35.6%, p = 0.026). Sensitivity and accuracy rates of ETP did not depend on the localization of the stenosis in the common bile duct. CONCLUSIONS: ETP alone is not reliable enough in diagnosing bile duct malignancies as shown by low sensitivity and accuracy rates (false-negative rate of 32%).

Artificial microbial consortia for bioproduction processes.

The application of artificial microbial consortia for biotechnological production processes is an emerging field in research as it offers great potential for the improvement of established as well as the development of novel processes. In this review, we summarize recent highlights in the usage of various microbial consortia for the production of, for example, platform chemicals, biofuels, or pharmaceutical compounds. It aims to demonstrate the great potential of co-cultures by employing different organisms and interaction mechanisms and exploiting their respective advantages. Bacteria and yeasts often offer a broad spectrum of possible products, fungi enable the utilization of complex lignocellulosic substrates via enzyme secretion and hydrolysis, and microalgae can feature their abilities to fixate CO2 through photosynthesis for other organisms as well as to form lipids as potential fuelstocks. However, the complexity of interactions between microbes require methods for observing population dynamics within the process and modern approaches such as modeling or automation for process development. After shortly discussing these interaction mechanisms, we aim to present a broad variety of successfully established co-culture processes to display the potential of artificial microbial consortia for the production of biotechnological products.

ATP is an essential autocrine factor for pancreatic ß-cell signaling and insulin secretion.

ATP has been previously identified as an autocrine signaling factor that is co-released with insulin to modulate and propagate ß-cell activity within islets of Langerhans. Here, we show that ß-cell activity and insulin secretion essentially rely on the presence of extracellular ATP. For this, we monitored changes of the intracellular Ca2+ concentration ([Ca2+ ]i oscillations) as an immediate read-out for insulin secretion in live cell experiments. Extensive washing of cells or depletion of extracellular ATP levels by recombinant apyrase reduced [Ca2+ ]i oscillations and insulin secretion in pancreatic cell lines and primary ß-cells. Following ATP depletion, [Ca2+ ]i oscillations were stimulated by the replenishment of ATP in a concentration-dependent manner. Inhibition of endogenous ecto-ATP nucleotidases increased extracellular ATP levels, along with [Ca2+ ]i oscillations and insulin secretion, indicating that there is a constant supply of ATP to the extracellular space. Our combined results demonstrate that extracellular ATP is essential for ß-cell activity. The presented work suggests extracellular ATPases as potential drug targets for the modulation of insulin release. We further found that exogenous fatty acids compensated for depleted extracellular ATP levels by the recovery of [Ca2+ ]i oscillations, indicating that autocrine factors mutually compensate for the loss of others. Thereby, our results contribute to a more detailed and complete understanding of the general role of autocrine signaling factors as a fundamental regulatory mechanism of ß-cell activity and insulin secretion.

Single-step versus multi-step transmural drainage of pancreatic pseudocysts: the use of cystostome is effective and timesaving.

BACKGROUND AND AIMS: Pancreatic pseudocysts are a major complication of chronic and acute pancreatitis and often require endoscopic intervention. Endoscopic single-step and multi-step transmural drainage techniques have been reported in the literature. The aim of this study was to evaluate and compare technical results and clinical outcome rates of the single-step versus multi-step endoscopic ultrasonography (EUS)-guided endoscopic transmural drainage in patients with symptomatic pancreatic pseudocysts of >4 cm size. DESIGN: Retrospective study at an academic tertiary referral center. PATIENTS AND METHODS: A total of 38 consecutive patients comprising 42 interventions were studied: 16 patients with pancreatic pseudocysts (18 interventions) had undergone single-step EUS-guided transmural cystostome drainage between 2007 and 2010. Results were compared with a cohort of 22 patients who had submitted to multi-step EUS-guided transmural drainage of pancreatic pseudocysts in 24 cases between 2005 and 2007. RESULTS: The technical success rate for using the single-step procedure was 94% compared with multi-step procedure with 83% (n.s.). Primary clinical success rate was 88% for single-step drainage and 90% for the multi-step approach (n.s.). The mean procedure time was 36 ± 9 min in the single-step group compared with 62 ± 12 min for the multi-step access (p < 0.001). CONCLUSIONS: The use of single-step cystostome appears useful in managing selected patients with symptomatic pancreatic pseudocysts as it is effective and timesaving.

Outcome of supraselective transarterial chemoembolization in patients with hepatocellular carcinoma.

OBJECTIVE: Hepatocellular carcinoma (HCC) is the most common tumor in cirrhotic patients with a median survival of only 8-10 months if untreated. Supraselective transarterial chemoembolization (STACE) is supposed to be a well-established method for treating HCC patients. In the present study, we evaluated the effect of STACE on post-transplant survival in patients with HCC. MATERIAL AND METHODS: The charts of 53 HCC patients were retrospectively analyzed. Twenty-seven patients had STACE as a bridging therapy while 26 patients were scheduled for liver transplantation (LTX) without prior STACE therapy. A total of 53% of the patients who underwent LTX preoperatively fulfilled the Milan criteria, while 70.6% fulfilled the expanded University of California, San Francisco (UCSF) transplant criteria. Primary endpoint was the post-transplant survival. Statistical analysis included Kaplan-Meier-method, log rank, and chi square tests. RESULTS: Between the LTX groups (STACE vs. non-STACE), there was no significant difference in terms of age, Child classification, Okuda stage, co-morbidities, underlying disease, and post-transplant survival (p > 0.05). Independent of prior STACE, however, disease-free survival after LTX was highly significantly prolonged if LTX was performed within 3 months after initial diagnosis of HCC (p < 0.01) or if patients met the expanded transplant UCSF criteria (p = 0.02). Post-transplant survival did not depend on tumor size. CONCLUSIONS: We conclude that STACE performed prior to LTX does not secure any post-transplant survival benefit, while early LTX, i.e. within 3 months after HCC diagnosis, does improve survival regardless of whether STACE was performed or not. Additionally, fulfillment of the expanded transplant UCSF criteria leads to a prolonged post-transplant survival.

Regulation of Calcium Oscillations in ß-Cells by Co-activated Cannabinoid Receptors.

Pharmacological treatment of pancreatic ß cells targeting cannabinoid receptors 1 and 2 (CB1 and CB2) has been shown to result in significant effects on insulin release, possibly by modulating intracellular calcium levels ([Ca2+]i). It is unclear how the interplay of CB1 and CB2 affects insulin secretion. Here, we demonstrate by the use of highly specific receptor antagonists and the recently developed photo-releasable endocannabinoid 2-arachidonoylglycerol that both receptors have counteracting effects on cytosolic calcium oscillations. We further show that both receptors are juxtaposed in a way that increases [Ca2+]i oscillations in silent ß cells but dampens them in active ones. This study highlights a functional role of CB1 and CB2 acting in concert as a compensator/attenuator switch for regulating ß cell excitability.

Monitoring the cellular metabolism of a membrane-permeant photo-caged phosphatidylinositol 3,4,5-trisphosphate derivative.

To deliver charged lipid derivatives to the cell interior, bioactivatable and photo-activatable protecting groups are frequently used. The intracellular metabolism of the protecting groups, as well as the lipid itself, are key factors that determine biological activity. Here we followed the cellular metabolism of cell-permeant photo-activatable ("caged") and non-caged membrane-permeant analogs of dioctanoyl phosphatidylinositol 3,4,5-trisphosphate (diC8PIP3) carrying biodegradable protecting groups by mass spectrometry. After successful cell entry, the photo-activatable group can be removed on demand by a light pulse. Hence, UV irradiation acts as a switch to expose the cellular metabolism to a bolus of active compound. To investigate lipid metabolites and to capture a more complete metabolome, we adapted standard extraction methods and employed multi-reaction monitoring mass spectrometry (MRM-MS). This required a previously developed permethylation method that stabilized metabolites and enhanced volatility of the phosphoinositide metabolites. The mass spectrometric analysis allowed for the monitoring of the intracellular removal of photo-activatable caging as well as biodegradable protecting groups from the membrane-permeant phosphoinositides along with cellular turnover, namely by dephosphorylation. We found that phosphate masking groups, namely acetoxymethyl esters, were rapidly removed by endogenous enzymes while butyrates masking hydroxy groups showed a longer lifetime, giving rise to trapped intermediates. We further identified key intermediate metabolites and demonstrated the beneficial effect of caging groups and their removal on the formation of favorable metabolites. Surprisingly, caging and protecting groups were found to influence each other's stability.

Standard versus Endocuff versus cap-assisted colonoscopy for adenoma detection: A randomised controlled clinical trial.

BACKGROUND AND AIMS: Adenoma detection rate (ADR) in colon cancer screening is most important for cancer prophylaxis. This work is the first three-armed randomised controlled clinical trial aimed at comparing a head-to-head setting standard colonoscopy (SC) with Endocuff-assisted colonoscopy (EC) and cap-assisted colonoscopy (CAC) for improvement of ADR. METHODS: Patients from Poland and Germany with independent indication for colonoscopy were randomised into three arms of this trial: EC, CAC and SC. Exclusion criteria were age <18 years, active Crohn's disease or ulcerative colitis, known stenosis and post-colonic resection status. RESULTS: A total of 585 patients (195 SC, 189 EC and 186 CAC) were enrolled in this study. Indications were not different between the groups (colorectal cancer screening 51%, diagnostic colonoscopy in 31% and post-polypectomy follow-up in 18%; p = 0.94). Withdrawal time was a mean of 7 min in all groups (p = 0.658), and bowel preparation did not differ between the groups. The time to reach the caecum was significantly reduced when using the cap (a mean of 6 min for CAC vs. 7 min for SC; p = 0.0001). There was no significant difference in the primary outcome of the ADR between the groups (EC 32%, CAC 30%, SC 30%; p = 0.815). EC proved to be superior (EC vs. SC) in the sigmoid colon and transverse colon for polyp detection. CONCLUSION: The use of EC increased the total number of polyps seen during colonoscopy. In contrast to recent studies, no significant improvement of the ADR was detected.

Photo-releasable derivatives of inositol pyrophosphates.

The specific non-invasive control of intracellular signaling events requires advanced tools that enter cells by diffusion and are controllable by light. Here, we detail the synthesis and application of membrane-permeant caged inositol pyrophosphates with respect to cell entry and cell distribution. We recently published the synthesis of these tools as well as their effect on PH-domain localization in HeLa cells and oscillations of the intracellular calcium concentration in ß-cells, which are known to drive insulin secretion. In this chapter, we discuss the possibilities and limitations when using cell-penetrating inositol pyrophosphates. We provide a detailed protocol for the application in live mouse ß-cells and we discuss the image analysis needed for following effects on calcium signaling.

Reversible spatial and temporal control of lipid signaling.

Herein, we introduce versatile molecular tools that enable specific delivery and visualization of photoswitchable lipids at cellular membranes, namely at the plasma membrane and internal membranes. These molecules were prepared by tethering ortho-nitrobenzyl-based fluorescent cages with a signaling lipid bearing an azobenzene photoswitch. They permit two sequential photocontrolled reactions, which are uncaging of a lipid analogue and then its repeated activation and deactivation. We used these molecules to activate GPR40 receptor transiently expressed in HeLa cells and demonstrated downstream modulation of intracellular Ca2+ levels.

Endogenous Fatty Acids Are Essential Signaling Factors of Pancreatic ß-Cells and Insulin Secretion.

The secretion of insulin from ß-cells depends on extracellular factors, in particular glucose and other small molecules, some of which act on G-protein-coupled receptors. Fatty acids (FAs) have been discussed as exogenous secretagogues of insulin for decades, especially after the FA receptor GPR40 (G-protein-coupled receptor 40) was discovered. However, the role of FAs as endogenous signaling factors has not been investigated until now. In the present work, we demonstrate that lowering endogenous FA levels in ß-cell medium by stringent washing or by the application of FA-free (FAF) BSA immediately reduced glucose-induced oscillations of cytosolic Ca2+ ([Ca2+]i oscillations) in MIN6 cells and mouse primary ß-cells, as well as insulin secretion. Mass spectrometry confirmed BSA-mediated removal of FAs, with palmitic, stearic, oleic, and elaidic acid being the most abundant species. [Ca2+]i oscillations in MIN6 cells recovered when BSA was replaced by buffer or as FA levels in the supernatant were restored. This was achieved by recombinant lipase-mediated FA liberation from membrane lipids, by the addition of FA-preloaded FAF-BSA, or by the photolysis of cell-impermeant caged FAs. Our combined data support the hypothesis of FAs as essential endogenous signaling factors for ß-cell activity and insulin secretion.