Cryo-EM elucidates the uroplakin complex structure within liquid-crystalline lipids in the porcine urothelial membrane

The urothelium, a distinct epithelial tissue lining the urinary tract, serves as an essential component in preserving urinary tract integrity and thwarting infections. The asymmetric unit membrane (AUM), primarily composed of the uroplakin complex, constitutes a critical permeability barrier in fulfilling this role. However, the molecular architectures of both the AUM and the uroplakin complex have remained enigmatic due to the paucity of high-resolution structural data. In this study, we utilized cryo-electron microscopy to elucidate the three-dimensional structure of the uroplakin complex within the porcine AUM. While the global resolution achieved was 3.5 Å, we acknowledge that due to orientation bias, the resolution in the vertical direction was determined to be 6.3 Å. Our findings unveiled that the uroplakin complexes are situated within hexagonally arranged crystalline lipid membrane domains, rich in hexosylceramides. Moreover, our research rectifies a misconception in a previous model by confirming the existence of a domain initially believed to be absent, and pinpointing the accurate location of a crucial Escherichia coli binding site implicated in urinary tract infections. These discoveries offer valuable insights into the molecular underpinnings governing the permeability barrier function of the urothelium and the orchestrated lipid phase formation within the plasma membrane.

Unveiling Liquid-Crystalline Lipids in the Urothelial Membrane through Cryo-EM

The urothelium, a distinct epithelial tissue lining the urinary tract, serves as an essential component in preserving urinary tract integrity and thwarting infections. The asymmetric unit membrane (AUM), primarily composed of the uroplakin complex, constitutes a critical permeability barrier in fulfilling this role. However, the molecular architectures of both the AUM and the uroplakin complex have remained enigmatic due to the paucity of high-resolution structural data. In this study, we utilized cryo-electron microscopy to elucidate the three-dimensional structure of the uroplakin complex within the porcine AUM. While the global resolution achieved was 3.5 Å, we acknowledge that due to orientation bias, the resolution in the vertical direction was determined to be 6.3 Å. Our findings unveiled that the uroplakin complexes are situated within hexagonally arranged crystalline lipid membrane domains, rich in hexosylceramides. Moreover, our research rectifies a misconception in a previous model by confirming the existence of a domain initially believed to be absent, and pinpointing the accurate location of a crucial Escherichia coli binding site implicated in urinary tract infections. These discoveries offer valuable insights into the molecular underpinnings governing the permeability barrier function of the urothelium and the orchestrated lipid phase formation within the plasma membrane.

Unveiling Liquid-Crystalline Lipids in the Urothelial Membrane through Cryo-EM

The urothelium, a distinct epithelial tissue lining the urinary tract, serves as an essential component in preserving urinary tract integrity and thwarting infections. The asymmetric unit membrane (AUM), primarily composed of the uroplakin complex, constitutes a critical permeability barrier in fulfilling this role. However, the molecular architectures of both the AUM and the uroplakin complex have remained enigmatic due to the paucity of high-resolution structural data. In this investigation, we employed cryo-electron microscopy to elucidate the three-dimensional structure of the uroplakin complex embedded within the porcine AUM at a resolution of 3.5 Å. Our findings unveiled that the uroplakin complexes are situated within hexagonally arranged crystalline lipid membrane domains, rich in hexosylceramides. Moreover, our research rectifies a misconception in a previous model by confirming the existence of a domain initially believed to be absent, and pinpointing the accurate location of a crucial Escherichia coli binding site implicated in urinary tract infections. These discoveries offer valuable insights into the molecular underpinnings governing the permeability barrier function of the urothelium and the orchestrated lipid phase formation within the plasma membrane.

Hepatic phosphatidylcholine catabolism driven by PNPLA7 and PNPLA8 supplies endogenous choline to replenish the methionine cycle with methyl groups

Choline supplies methyl groups for regeneration of methionine and the methyl donor S-adenosylmethionine in the liver. Here, we report that the catabolism of membrane phosphatidylcholine (PC) into water-soluble glycerophosphocholine (GPC) by the phospholipase/lysophospholipase PNPLA8-PNPLA7 axis enables endogenous choline stored in hepatic PC to be utilized in methyl metabolism. PNPLA7-deficient mice show marked decreases in hepatic GPC, choline, and several metabolites related to the methionine cycle, accompanied by various signs of methionine insufficiency, including growth retardation, hypoglycemia, hypolipidemia, increased energy consumption, reduced adiposity, increased fibroblast growth factor 21 (FGF21), and an altered histone/DNA methylation landscape. Moreover, PNPLA8-deficient mice recapitulate most of these phenotypes. In contrast to wild-type mice fed a methionine/choline-deficient diet, both knockout strains display decreased hepatic triglyceride, likely via reductions of lipogenesis and GPC-derived glycerol flux. Collectively, our findings highlight the biological importance of phospholipid catabolism driven by PNPLA8/PNPLA7 in methyl group flux and triglyceride synthesis in the liver.

Characteristics of shifting ability in children with mild intellectual disabilities: an experimental study with a task-switching paradigm

BACKGROUND

Shifting enables flexible switch between tasks or mental sets. It is a component of the executive function that plays critical roles in human behaviour control. However, shifting ability in individuals with intellectual disability (ID) has not been well clarified because of the use of intellectually demanding tasks in previous studies. The present study invented a novel shifting task with minimal intellectual demands and aimed to clarify the characteristics of shifting in adolescents with ID.

METHODS

Adolescents with ID (n = 21) and chronological-age-matched (n = 10) and mental-age-matched controls (n = 33) performed a novel shifting task with simple rule switching (i.e. change in direction). Analyses focused on the switch cost or the increase in the reaction time associated with rule switching.

RESULTS

Two subtypes of adolescents with ID were found with respect to the switch cost: one that lacks it and another with an increased switch cost. The lack of a switch cost was unique to the subgroup adolescents with ID and was not indicated in the control group.

CONCLUSIONS

The present study indicated that shifting in adolescents with ID does not depend solely on their intellectual function and is highly heterogeneous. This finding further implies that executive functions, including shifting, must be evaluated separately from their intellectual functions.

Lipid Profiles of Human Serum Fractions Enhanced with CD9 Antibody-Immobilized Magnetic Beads

Blood samples are minimally invasive and can be collected repeatedly, but they are far from the site of disease and the target molecules are diluted by the large amount of blood. Therefore, we performed lipidomics using immunoprecipitation as a method to enrich specific fractions of serum. In this study, a CD9 antibody was immobilized on magnetic beads to enrich CD9-containing components in the serum for lipidomics. The percentages of phospholipids recovered from serum by methanol and isopropanol extractions were not significantly different, but triglycerides were barely recovered from serum by methanol extraction, requiring the use of isopropanol. However, once the serum was enriched with CD9 magnetic beads, triglycerides, and phospholipids were recovered at similar levels in both methanol and isopropanol extractions. Therefore, it is possible that the triglyceride fraction of the whole serum and the triglyceride fraction were enriched in CD9 magnetic beads differ in localization and properties. In addition, the variation per disease was small in general serum lipidomics; however, the difference per disease appeared larger when CD9 magnetic bead enrichment was employed.

Lipidomic Analyses Reveal Specific Alterations of Phosphatidylcholine in Dystrophic Mdx Muscle

In Duchenne muscular dystrophy (DMD), lack of dystrophin increases the permeability of myofiber plasma membranes to ions and larger macromolecules, disrupting calcium signaling and leading to progressive muscle wasting. Although the biological origin and meaning are unclear, alterations of phosphatidylcholine (PC) are reported in affected skeletal muscles of patients with DMD that may include higher levels of fatty acid (FA) 18:1 chains and lower levels of FA 18:2 chains, possibly reflected in relatively high levels of PC 34:1 (with 16:0_18:1 chain sets) and low levels of PC 34:2 (with 16:0_18:2 chain sets). Similar PC alterations have been reported to occur in the mdx mouse model of DMD. However, altered ratios of PC 34:1 to PC 34:2 have been variably reported, and we also observed that PC 34:2 levels were nearly equally elevated as PC 34:1 in the affected mdx muscles. We hypothesized that experimental factors that often varied between studies; including muscle types sampled, mouse ages, and mouse diets; may strongly impact the PC alterations detected in dystrophic muscle of mdx mice, especially the PC 34:1 to PC 34:2 ratios. In order to test our hypothesis, we performed comprehensive lipidomic analyses of PC and phosphatidylethanolamine (PE) in several muscles (extensor digitorum longus, gastrocnemius, and soleus) and determined the mdx-specific alterations. The alterations in PC 34:1 and PC 34:2 were closely monitored from the neonate period to the adult, and also in mice raised on several diets that varied in their fats. PC 34:1 was naturally high in neonate’s muscle and decreased until age ∼3-weeks (disease onset age), and thereafter remained low in WT muscles but was higher in regenerated mdx muscles. Among the muscle types, soleus showed a distinctive phospholipid pattern with early and diminished mdx alterations. Diet was a major factor to impact PC 34:1/PC 34:2 ratios because mdx-specific alterations of PC 34:2 but not PC 34:1 were strictly dependent on diet. Our study identifies high PC 34:1 as a consistent biochemical feature of regenerated mdx-muscle and indicates nutritional approaches are also effective to modify the phospholipid compositions.

TRPV4 is activated by mechanical stimulation to induce prostaglandins release in trabecular meshwork, lowering intraocular pressure

Trabecular meshwork constitutes the conventional outflow pathway and controls intraocular pressure by regulating aqueous outflow. Mechanical stimulation has been studied as one of the triggers to regulate aqueous outflow in trabecular meshwork, but it is not well understood. We investigated that how transient receptor potential cation channel subfamily V member 4 (TRPV4) functions in human trabecular meshwork cells (HTMC) and affects intraocular pressure (IOP). HTMC were treated with TRPV4 siRNA, followed by incubation for 24 hours. We confirmed the suppression of TRPV4 mRNA expression and the reduction of Ca²⁺ influx by the TRPV4 agonist GSK1016790A in TRPV4 siRNA-treated HTMC. TRPV4 siRNA-treated HTMC exhibited a significant reduction in Ca²⁺ influx and production of arachidonic acid and prostaglandin (PG) E₂ induced by mechanical stretch, and direct activation of TRPV4 by GSK1016790A increased production of arachidonic acid, PGE₂, and PGD₂ and inhibited gel contraction. Furthermore, TRPV4-deficient mice had higher IOP than wild-type mice, and GSK1016790A administration lowered IOP. These results suggest that TRPV4 mediates the cellular response induced by trabecular meshwork stretch, leading to IOP reduction through the production of prostaglandins and inhibition of cell contraction. Targeting TRPV4 may have therapeutic benefits that lead to lowering IOP in glaucoma patients.

Mutagenesis and homology modeling reveal a predicted pocket of lysophosphatidylcholine acyltransferase 2 to catch Acyl-CoA

Platelet-activating factor (PAF) is a potent proinflammatory phospholipid mediator that elicits various cellular functions and promotes several pathological events, including anaphylaxis and neuropathic pain. PAF is biosynthesized by two types of lyso-PAF acetyltransferases: lysophosphatidylcholine acyltransferase 1 (LPCAT1) and LPCAT2, which are constitutive and inducible forms of lyso-PAF acetyltransferase, respectively. Because LPCAT2 mainly produces PAF under inflammatory stimuli, understanding the structure of LPCAT2 is important for developing specific drugs against PAF-related inflammatory diseases. Although the structure of LPCAT2 has not been determined, the crystal structure was reported for Thermotoga maritima PlsC, an enzyme in the same gene family as LPCAT2. Here, we identified residues in mouse LPCAT2 essential for its enzymatic activity and a potential acyl-coenzyme A (CoA)-binding pocket, based on homology modeling of mouse LPCAT2 with PlsC. We also found that Ala115 of mouse LPCAT2 was important for acyl-CoA selectivity. In conclusion, these results predict the three-dimensional (3D) structure of mouse LPCAT2. Our findings have implications for the future development of new drugs against PAF-related diseases.

LimeMap: a comprehensive map of lipid mediator metabolic pathways

Lipid mediators are major factors in multiple biological functions and are strongly associated with disease. Recent lipidomics approaches have made it possible to analyze multiple metabolites and the associations of individual lipid mediators. Such systematic approaches have enabled us to identify key changes of biological relevance. Against this background, a knowledge-based pathway map of lipid mediators would be useful to visualize and understand the overall interactions of these factors. Here, we have built a precise map of lipid mediator metabolic pathways (LimeMap) to visualize the comprehensive profiles of lipid mediators that change dynamically in various disorders. We constructed the map by focusing on ω-3 and ω-6 fatty acid metabolites and their respective metabolic pathways, with manual curation of referenced information from public databases and relevant studies. Ultimately, LimeMap comprises 282 factors (222 mediators, and 60 enzymes, receptors, and ion channels) and 279 reactions derived from 102 related studies. Users will be able to modify the map and visualize measured data specific to their purposes using CellDesigner and VANTED software. We expect that LimeMap will contribute to elucidating the comprehensive functional relationships and pathways of lipid mediators.

Development of Tandem Mass Tag Labeling Method for Lipid Molecules Containing Carboxy and Phosphate Groups, and Their Stability in Human Serum

In clinical lipidomics, it is a challenge to measure a large number of samples and to reproduce the quantitative results. We expanded the range of application of the tandem mass tag (TMT) method, which is widely used in proteomics, to lipidomic fields. There are various types of lipid molecule, for example, eicosanoids have a carboxyl group and phosphatidic acid has a phosphate group. We modified these functional groups simultaneously with TMT. This approach allows for a single analysis by mixing six samples and using one of the six samples as a bridging sample; the quantitative data can be easily normalized even if the number of measurements increases. To accommodate a large number of samples, we utilize a pooled serum sample of 300 individuals as a bridging sample. The stability of these lipid molecules in serum was examined as an analytical validation for the simultaneous TMT labeling. It was found that the stability of these lipid molecules in serum differs greatly depending on the lipid species. These findings reaffirmed the importance of proper sample preparation and storage to obtain reliable data. The TMT labeling method is expected to be a useful method for lipidomics with high-throughput and reliable reproducibility.

Limitations of deuterium-labeled internal standards for quantitative electrospray ionization mass spectrometry analysis of fatty acid metabolites

RATIONALE

The electrospray ionization mass spectrometry (ESI-MS) methodology often shows poor ionization reproducibility in the analysis of biological samples. Therefore, normalization of the measured peak intensities is essential. It is believed that quantitative data with high reproducibility can be obtained by adding a constant amount of an internal standard (IS) material labeled with stable isotopes to each sample, thus allowing the correction of the quantitative value of the target compound by that of the IS. We investigated whether the presence or absence of a labeled IS improves the accuracy of these quantitative values.

METHODS

Triple quadrupole MS coupled with liquid chromatography was used to analyze fatty acid metabolites in biological samples as target compounds. Two independent systems were used to provide a measure of reproducibility in two different laboratories.

RESULTS

Data having poor reproducibility in the raw peak areas were efficiently normalized using the IS, but, crucially, the IS method using stable isotopes was not always necessary. In some cases, the reproducibility was relatively good even without using the IS. In a contaminant matrix, the MS response behavior of the target compound and its stable isotope-labeled material was complicated. Since ion suppression by matrix contaminants was dependent on the concentration of the target compound, the added amounts of the ISs were also important, Furthermore, an equivalent normalization effect was obtained by using a pooled quality control sample as an external standard, thus obviating the need for labeled IS samples, which are often expensive and sometimes not commercially available.

CONCLUSIONS

Our results raise the question as to whether the quantitative method using stable-isotope-labeled ISs is always necessary and beneficial. However, the results obtained in this study cannot be generalized because only fatty acid metabolites were examined using ESI-MS and only a highly substituted deuterium-labeled IS was used.

Multiplex fatty acid imaging inside cells by Raman microscopy

Visualizing intracellular fatty acids (including free and esterified form) is very useful for understanding how and where such molecules are incorporated, stored, and metabolized within cells. However, techniques of imaging multiple intracellular fatty acids have been limited by their small size, making it difficult to label and track without changing their biological and biophysical characteristics. Here, we present a new method for simultaneously visualizing up to five atomically labeled intracellular fatty acid species. For this, we utilized the distinctive Raman spectra depending on the labeling patterns and created a new, extensible opensource software to perform by-pixel analysis of extracting original spectra from mixed ones. Our multiplex imaging method revealed that fatty acids with more double bonds tend to concentrate more efficiently at lipid droplets. This novel approach contributes to reveal not only the spatial dynamics of fatty acids, but also of any other metabolites inside cells.

Quantification of Fatty Acids in Mammalian Tissues by Gas Chromatography-Hydrogen Flame Ionization Detection

In mammalian organisms, fatty acids (FAs) exist mostly in esterified forms, as building blocks of phospholipids, triglycerides, and cholesteryl esters, while some exist as non-esterified free FAs. The absolute quantification of FA species in total lipids or in a specific lipid class is critical in lipid-metabolism studies. To quantify FAs in biological samples, gas chromatography-hydrogen flame ionization detection (GC-FID)-based methods have been used as highly robust and reliable techniques. Prior to GC-FID analysis, FAs need to be derivatized to volatile FA methyl esters (FAMEs). The derivatization of unsaturated FAs using classical derivatization methods that rely on high reaction temperature requires skill; consequently, the quantification results are often unreliable. The recently available FA-methylation procedure rapidly and reliably derivatizes a variety of FA species, including poly-unsaturated FAs (PUFAs). To analyze FAs in mammalian tissue samples, lipid extraction and fractionation are also critical for robust analysis. In this report, we describe a whole protocol for the GC-FID-based FA quantification of mammalian tissue samples, including lipid extraction, fractionation, derivatization, and quantification. The protocol is useful when various FAs, especially unsaturated FAs, need to be reliably quantified.

The COX-2/PGE2 pathway suppresses apical elimination of RasV12-transformed cells from epithelia

At the initial stage of carcinogenesis, when RasV12-transformed cells are surrounded by normal epithelial cells, RasV12 cells are apically extruded from epithelia through cell competition with the surrounding normal cells. In this study, we demonstrate that expression of cyclooxygenase (COX)-2 is upregulated in normal cells surrounding RasV12-transformed cells. Addition of COX inhibitor or COX-2-knockout promotes apical extrusion of RasV12 cells. Furthermore, production of Prostaglandin (PG) E2, a downstream prostanoid of COX-2, is elevated in normal cells surrounding RasV12 cells, and addition of PGE2 suppresses apical extrusion of RasV12 cells. In a cell competition mouse model, expression of COX-2 is elevated in pancreatic epithelia harbouring RasV12-exressing cells, and the COX inhibitor ibuprofen promotes apical extrusion of RasV12 cells. Moreover, caerulein-induced chronic inflammation substantially suppresses apical elimination of RasV12 cells. These results indicate that intrinsically or extrinsically mediated inflammation can promote tumour initiation by diminishing cell competition between normal and transformed cells.

Isobaric mass tagging and triple quadrupole mass spectrometry to determine lipid biomarker candidates for Alzheimer's disease

The isobaric tagging method widely used in proteomic and lipidomic fields, with the multiple reaction monitoring (MRM) approach using a triple quadrupole mass spectrometer, was applied to identify biomarker candidates from plasma samples for Alzheimer’s disease (AD). We focused on the following phospholipids that have amino groups as the functional group: phosphatidylethanolamine (PE), Lyso-PE, phosphatidylserine, and Lyso-phosphatidylserine. We also investigated fatty acids that have a carboxy group. A sixplex tandem mass tag (TMT) was used for the isobaric tagging method in this study. The TMT reaction had high reproducibility in human plasma. A total of 196 human plasma samples from three AD cohorts were used for the study, and compared to pooled plasma quality control (QC) samples. The described method required only 40 MRM measurements, including the pooled QC samples, for a full comparison of the data. We found that the content of free fatty acids increased in AD samples in all the three cohorts, alkenyl PEs (ePEs) decreased over a one-year interval in AD patients, and ePEs weakly correlated with amyloid peptide (a-beta) 1–42 in cerebrospinal fluid. In conclusion, total free fatty acids in plasma are a risk factor for AD, and ePEs monitor candidates for AD. Therefore, TMT-lipidomics is a powerful approach for the determination of plasma biomarkers because of the high sample throughput.

Challenges in a population-based registry of cardiovascular disease in Shiga, Japan

Background

Stroke and cardiovascular disease are one of the leading causes of death and disability in Japan. In order to investigate current burden, we conduct a population-based registry of cardiovascular disease in Shiga Prefecture, Japan since 2012. We will demonstrate challenges in conduct of the registry study.

Methods

In 2012, we established the Shiga Stroke Registry (SSR), a multicenter population-based registry study designed to build a complete information system for the management of stroke in Shiga Prefecture, Japan. The registry uses local monitoring, combined with remote data collection and quality control systems, to create an integrated surveillance system among a network of all acute care hospitals with neurology/neurosurgery facilities and smaller hospitals with rehabilitation facilities in the region. In 2019, study name has changed to Shiga Stroke and Heart Attack Registry (SSHR) and additional registration of coronary heart disease and aortic disease have started. Each case is reviewed and adjudicated by 2 or more specialists.

Results

In the financial year of 2018 (from April to March), a total of 4809 stroke cases were identified. From December 2018 to April 2019, a total of 515 coronary heart and aortic diseases were identified. A total 10 nurses work full-time for the registry and it takes average of 1 hour to collect information for each patient. Challenges in conduct of the cardiovascular registry involve regulatory and ethical approval, funding, associations with local hospitals, non-standardized hospital diagnosis, staff training for comprehensive data collection including pathophysiology, examination and treatment, and quality control of data collection.

Conclusions

SSHR is a population-based registry of wide range of stroke and cardiovascular disease in Shiga Prefecture, Japan. In order to keep quality of the data, we put a lot of efforts on staff training and quality control.

Key messages

Population-based registry of wide range of stroke and cardiovascular disease in Shiga, Japan. In order to keep quality of the data, we put a lot of efforts on staff training and quality control.

Inter-Laboratory Comparison of Metabolite Measurements for Metabolomics Data Integration

BACKGROUND

One of the current problems in the field of metabolomics is the difficulty in integrating data collected using different equipment at different facilities, because many metabolomic methods have been developed independently and are unique to each laboratory.

METHODS

In this study, we examined whether different analytical methods among 12 different laboratories provided comparable relative quantification data for certain metabolites. Identical samples extracted from two cell lines (HT-29 and AsPc-1) were distributed to each facility, and hydrophilic and hydrophobic metabolite analyses were performed using the daily routine protocols of each laboratory.

RESULTS

The results indicate that there was no difference in the relative quantitative data (HT-29/AsPc-1) for about half of the measured metabolites among the laboratories and assay methods. Data review also revealed that errors in relative quantification were derived from issues such as erroneous peak identification, insufficient peak separation, a difference in detection sensitivity, derivatization reactions, and extraction solvent interference.

CONCLUSION

The results indicated that relative quantification data obtained at different facilities and at different times would be integrated and compared by using a reference materials shared for data normalization.

Characterization of supported liquid extraction as a sample pretreatment method for eicosanoids and related metabolites in biological fluids

Sample pretreatment is an important process in liquid chromatography-mass spectrometry-based quantitative lipidomics. Reversed-phase solid phase extraction (RP-SPE) has been widely used for analyzing various types of samples, including aqueous samples such as cell culture media, plasma, serum, urine, and other biological fluids. Because lipid mediators are often protein-bound, prior deproteinization is necessary for their effective recovery. Deproteinization is typically performed by the addition of organic solvents, which requires time-consuming evaporation-reconstitution, or dilution with aqueous solvents before RP-SPE; however, both of these approaches compromise the analytical performance. As a potential alternative, we attempted to utilize supported liquid extraction (SLE), an automation-compatible variant of liquid-liquid extraction, for the determination of eicosanoids and related metabolites in aqueous samples. We screened 81 different sample diluent-eluent conditions and found that the use of 0.1% formic acid-water as the diluent and 0.1% formic acid-methyl acetate as the eluent enabled the optimum recovery of a variety of eicosanoids, except for peptide leukotrienes. The optimized SLE method efficiently removed protein from human plasma, while phospholipids and neutral lipids were modestly recovered. Moreover, the proposed method exhibited a quantitative performance comparable to that of typical ordinary RP-SPE method in the analysis of human platelets stimulated with thrombin receptor-activating peptide 6. Thus, we propose SLE as an attractive option for rapid lipid mediator extraction from aqueous samples.

Novel roles of lipid mediators in psoriatic skin inflammation

Psoriasis is a common chronic inflammatory cutaneous disease thought to arise as a result of infiltration of inflammatory cells and activation of keratinocytes. Psoriasis has been considered as a classical Th1 disease; however, Th17 cells are attracting much interest. Previous knowledge on the pathology of psoriasis has been obtained mostly through the study of human data and samples. In addition, recently developed animal models for psoriatic skin inflammation recapitulates the hallmarks of human psoriasis and provide us new insights on psoriasis. Lipid mediators and their receptors regulate a variety of physiological processes and involved in multiple pathologies including immune-related diseases. Here, we explored novel lipid mediators involved in psoriatic skin inflammation using clinical samples and imiquimod-induced psoriasis model. In particular, mass spectrometry analysis for multiplex quantitation of eicosanoids using imiquimod-treated murine skin samples revealed unique kinetics of various lipid mediators in the time-series from early induction phase to chronic resolution phase. These data motivated us to focus on some lipid mediators such as leukotriene B4 (LTB4) and prostaglandin E2 (PGE2). As an example, BLT1 (known as LTB4 receptor) and CXCR2 have been revealed to coordinately promote neutrophil infiltration into the skin during the early phase of imiquimod-induced inflammation. Further analysis on PGE2 is in progress and some data indicates the novel functions of PGE2 and mPGES-1, an upstream enzyme for PGE2 production, in the pathogenesis in psoriasis. These insights may aid in the rational design of novel treatments for broad spectrum of inflammatory and immune disorders beyond psoriasis.

Monoacylglycerol lipase deficiency affects diet-induced obesity, fat absorption, and feeding behavior in CB1 cannabinoid receptor-deficient mice

Excess energy intake causes obesity, which leads to insulin resistance and various other complications of metabolic syndrome, including diabetes, atherosclerosis, dyslipidemia, and nonalcoholic fatty liver disease. Although recent studies have depicted altered lipid metabolism as an underlying feature, the detailed mechanisms are still unclear. Here we describe a possible role in high-fat diet (HFD)-induced obesity for monoacylglycerol lipase (MGL), an enzyme that is also known to hydrolyze the endocannabinoid 2-arachidonoylglycerol in brain. MGL-deficient [MGL-knockout (KO)] mice fed a HFD gained less body weight than wild-type mice and were protected from insulin resistance and hepatic steatosis. Food intake and energy expenditure were not altered in MGL-KO mice, but blood triglyceride levels after oral olive oil gavage were suppressed, indicating a role for MGL in intestinal fat absorption. Experiments with cannabinoid receptor type 1 (CB₁)/MGL double-KO mice revealed that these phenotypes may include mechanisms that are independent of CB₁-receptor-mediated endocannabinoid functions. We also noted that MGL-KO mice had less preference for HFD over normal chow diet. Oral but not intraperitoneal lipid administration strongly suppressed the appetites of MGL-KO and CB₁/MGL double-KO mice, but not of wild-type and CB₁-KO mice. Appetite suppression was reversed by vagotomy, suggesting involvement of MGL in the gut-brain axis regulation of appetite. Our results provide mechanistic insights of MGL's role in diet-induced obesity, lipid metabolic disorder, and regulation of appetite.-Yoshida, K., Kita, Y., Tokuoka, S. M., Hamano, F., Yamazaki, M., Sakimura, K., Kano, M., Shimizu, T. Monoacylglycerol lipase deficiency affects diet-induced obesity, fat absorption, and feeding behavior in CB₁ cannabinoid receptor-deficient mice.

Sex-specific relevance of diabetes to occlusive vascular and other mortality: a collaborative meta-analysis of individual data from 980 793 adults from 68 prospective studies

BACKGROUND

Several studies have shown that diabetes confers a higher relative risk of vascular mortality among women than among men, but whether this increased relative risk in women exists across age groups and within defined levels of other risk factors is uncertain. We aimed to determine whether differences in established risk factors, such as blood pressure, BMI, smoking, and cholesterol, explain the higher relative risks of vascular mortality among women than among men.

METHODS

In our meta-analysis, we obtained individual participant-level data from studies included in the Prospective Studies Collaboration and the Asia Pacific Cohort Studies Collaboration that had obtained baseline information on age, sex, diabetes, total cholesterol, blood pressure, tobacco use, height, and weight. Data on causes of death were obtained from medical death certificates. We used Cox regression models to assess the relevance of diabetes (any type) to occlusive vascular mortality (ischaemic heart disease, ischaemic stroke, or other atherosclerotic deaths) by age, sex, and other major vascular risk factors, and to assess whether the associations of blood pressure, total cholesterol, and body-mass index (BMI) to occlusive vascular mortality are modified by diabetes.

RESULTS

Individual participant-level data were analysed from 980 793 adults. During 9·8 million person-years of follow-up, among participants aged between 35 and 89 years, 19 686 (25·6%) of 76 965 deaths were attributed to occlusive vascular disease. After controlling for major vascular risk factors, diabetes roughly doubled occlusive vascular mortality risk among men (death rate ratio [RR] 2·10, 95% CI 1·97-2·24) and tripled risk among women (3·00, 2·71-3·33; χ2 test for heterogeneity p<0·0001). For both sexes combined, the occlusive vascular death RRs were higher in younger individuals (aged 35-59 years: 2·60, 2·30-2·94) than in older individuals (aged 70-89 years: 2·01, 1·85-2·19; p=0·0001 for trend across age groups), and, across age groups, the death RRs were higher among women than among men. Therefore, women aged 35-59 years had the highest death RR across all age and sex groups (5·55, 4·15-7·44). However, since underlying confounder-adjusted occlusive vascular mortality rates at any age were higher in men than in women, the adjusted absolute excess occlusive vascular mortality associated with diabetes was similar for men and women. At ages 35-59 years, the excess absolute risk was 0·05% (95% CI 0·03-0·07) per year in women compared with 0·08% (0·05-0·10) per year in men; the corresponding excess at ages 70-89 years was 1·08% (0·84-1·32) per year in women and 0·91% (0·77-1·05) per year in men. Total cholesterol, blood pressure, and BMI each showed continuous log-linear associations with occlusive vascular mortality that were similar among individuals with and without diabetes across both sexes.

INTERPRETATION

Independent of other major vascular risk factors, diabetes substantially increased vascular risk in both men and women. Lifestyle changes to reduce smoking and obesity and use of cost-effective drugs that target major vascular risks (eg, statins and antihypertensive drugs) are important in both men and women with diabetes, but might not reduce the relative excess risk of occlusive vascular disease in women with diabetes, which remains unexplained.

FUNDING

UK Medical Research Council, British Heart Foundation, Cancer Research UK, European Union BIOMED programme, and National Institute on Aging (US National Institutes of Health).

The impact of night-shift work on platelet function in healthy medical staff

Objectives:

Rotating shift work has been reported to increase the risk of cardiovascular diseases. Vascular endothelial dysfunction and platelet activation are among the leading causes of thrombus formation in patients with myocardial infarction or stroke. Endothelial function has been shown to be impaired immediately after night-shift work; however, it is not known whether platelets are also activated. The aim of this study was to investigate the acute impact of night-shift work on platelet function.

Methods:

This observational study included 11 healthy medical staff members (seven women, median age 32 years). We examined each subject's platelet aggregation rates and the serum concentrations of eicosanoid mediators after night-shift work and on day-shift work without preceding night-shift work (baseline).

Results:

Platelet aggregation did not differ from baseline levels after night-shift work. However, serum cyclooxygenase (COX)-metabolized eicosanoid mediators, particularly thromboxane (Tx) B₂ (a stable metabolite of TxA₂ and the most important marker of platelet activation), were significantly higher after the night-shift than at baseline (median 65.3 vs 180.4 ng/ml).

Conclusions:

Although platelet aggregation did not increase, there was an increase in serum COX-metabolized eicosanoid mediators such as TxB₂ in healthy medical staff after night-shift work. This platelet hypersensitivity may be one of the mechanisms underlying the significant association between night-shift work and adverse cardiovascular outcomes.

LPAAT3 incorporates docosahexaenoic acid into skeletal muscle cell membranes and is upregulated by PPARδ activation

Adaption of skeletal muscle to endurance exercise includes PPARδ- and AMP-activated protein kinase (AMPK)/PPARγ coactivator 1α-mediated transcriptional responses that result in increased oxidative capacity and conversion of glycolytic to more oxidative fiber types. These changes are associated with whole-body metabolic alterations including improved glucose handling and resistance to obesity. Increased DHA (22:6n-3) content in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) is also reported in endurance exercise-trained glycolytic muscle; however, the DHA-metabolizing enzymes involved and the biological significance of the enhanced DHA content are unknown. In the present study, we identified lysophosphatidic acid acyltransferase (LPAAT)3 as an enzyme that was upregulated in myoblasts during in vitro differentiation and selectively incorporated DHA into PC and PE. LPAAT3 expression was increased by pharmacological activators of PPARδ or AMPK, and combination treatment led to further increased LPAAT3 expression and enhanced incorporation of DHA into PC and PE. Our results indicate that LPAAT3 was upregulated by exercise-induced signaling pathways and suggest that LPAAT3 may also contribute to the enhanced phospholipid-DHA content of endurance-trained muscles. Identification of DHA-metabolizing enzymes in the skeletal muscle will help to elucidate broad metabolic effects of DHA.

Difference between tablet methods and paper questionnaire methods of conducting a survey with community-dwelling elderly

[Purpose] This study aimed to develop a tablet app that emulates paper questionnaires used in clinical care, and to verify the difference between the utility of tablet survey methods and paper questionnaire methods with elderly people. [Subjects and Methods] A tablet app was developed in the Java language. A questionnaire was provided to 30 community-dwelling elderly people. The subjects were randomly allocated to the group responding on the tablet (tablet group) or that responding to a paper-based questionnaire (questionnaire group). Assessed items included response time to questions, whether or not they had queries regarding the survey, and data input time. For the tablet group, a questionnaire was conducted regarding the operability of the tablet. [Results] There was no difference in response time between the two groups. Significantly more people in the tablet group had queries regarding the survey. Data input time was 426 seconds for the tablet group and 1268 seconds for the questionnaire group. In the survey regarding tablet operability, there were no negative opinions about the visibility of the screen. [Conclusion] Tablets can be used with elderly people to shorten the data input time. The present findings suggested that tablet surveys could be effective for a large-scale investigation.

Multiplex quantitative analysis of eicosanoid mediators in human plasma and serum: Possible introduction into clinical testing

Eicosanoid mediators play important roles in maintaining the physiological and pathophysiological homeostasis in the body. Their measurements, however, are rarely performed in clinical practice. In the present study, we analyzed 30 varieties of eicosanoid mediators that were detectable in human plasma and serum collected from healthy donors, using liquid chromatography-tandem mass spectrometry from the viewpoint of the clinical application of the multiplex quantitation of eicosanoid mediators. Wider variety of eicosanoid mediators were detected in serum (27 out of 30) than in plasma (14 out of 30), since the serum was thought to contain lipid mediators released from activated platelets. Larger inter-individual variations were observed in the plasma and serum eicosanoid levels. On the other hand, the concentrations of eicosanoids were not affected by the platelet count but were affected by the concentration of arachidonic acid (AA) within the reference interval (17.4-40.5×10¹⁰/L). When serum samples from patients with hematological disorders were analyzed, the concentrations of AA were positively correlated with the platelet count. When the patients underwent ASA therapy, a marked decrease in the concentrations of thromboxane B₂ (TXB₂) and 12-hydroxyl-heptadecatrienoic acid (12-HHT) was observed. Considering the availability of serum samples in clinical settings, the serum analysis of eicosanoids may be clinically useful.

Autophagy supports generation of cells with high CD44 expression via modulation of oxidative stress and Parkin-mediated mitochondrial clearance

High CD44 expression is associated with enhanced malignant potential in esophageal squamous cell carcinoma (ESCC), amongst the deadliest of all human carcinomas. Although alterations in autophagy and CD44 expression are associated with poor patient outcomes in various cancer types, the relationship between autophagy and cells with high CD44 expression remains incompletely understood. In transformed esophageal keratinocytes, CD44^Low-CD24^High (CD44L) cells give rise to CD44^High-CD24^−/Low (CD44H) cells via epithelial-mesenchymal transition (EMT) in response to transforming growth factor (TGF)-β. We couple patient samples and xenotransplantation studies with this tractable in vitro system of CD44L to CD44H cell conversion to investigate the functional role of autophagy in generation of cells with high CD44 expression. We report that high expression of the autophagy marker cleaved LC3 expression correlates with poor clinical outcome in ESCC. In ESCC xenograft tumors, pharmacological autophagy inhibition with chloroquine derivatives depletes cells with high CD44 expression while promoting oxidative stress. Autophagic flux impairment during EMT-mediated CD44L to CD44H cell conversion in vitro induces mitochondrial dysfunction, oxidative stress and cell death. During CD44H cell generation, transformed keratinocytes display evidence of mitophagy, including mitochondrial fragmentation, decreased mitochondrial content and mitochondrial translocation of Parkin, essential in mitophagy. RNA interference-mediated Parkin depletion attenuates CD44H cell generation. These data suggest that autophagy facilitates EMT-mediated CD44H generation via modulation of redox homeostasis and Parkin-dependent mitochondrial clearance. This is the first report to implicate mitophagy in regulation of tumor cells with high CD44 expression, representing a potential novel therapeutic avenue in cancers where EMT and CD44H cells have been implicated, including ESCC.

Relief from neuropathic pain by blocking of the platelet-activating factor-pain loop

Neuropathic pain resulting from peripheral neuronal damage is largely resistant to treatment with currently available analgesic drugs. Recently, ATP, lysophosphatidic acid, and platelet-activating factor (PAF) have been reported to play important inductive roles in neuropathic pain. In the present study, we found that pain-like behaviors resulting from partial sciatic nerve ligation (PSL) were largely attenuated by deficiency of lysophosphatidylcholine acyltransferase (LPCAT)2, which is one of the PAF biosynthetic enzymes. By contrast, deficiency of the other PAF biosynthetic enzyme, LPCAT1, did not ameliorate neuropathic pain. With regard to the mechanism of the observed effects, LPCAT2 was detected in wild-type spinal cord microglia, and the absence of LPCAT2 expression precluded spinal PAF expression in LPCAT2-knockout mice. Furthermore, ATP-stimulated PAF biosynthesis in macrophages was decreased by pretreatment with the PAF receptor antagonist ABT-491, indicating the existence of a positive feedback loop of PAF biosynthesis, which we designated the PAF-pain loop. In conclusion, LPCAT2 is a novel therapeutic target for newly categorized analgesic drugs; in addition, our data call for the re-evaluation of the clinical utility of PAF receptor antagonists.-Shindou, H., Shiraishi, S., Tokuoka, S. M., Takahashi Y., Harayama, T., Abe, T., Bando, K., Miyano, K., Kita, Y., Uezono, Y., Shimizu, T. Relief from neuropathic pain by blocking of the platelet-activating factor-pain loop.

Improving Public Awareness of Organ Transplantation in Japan

The goals of the Japanese chapter of the Transplant Recipients International Organization are to act as a mediator in the provision of mutual aid to transplant recipients, candidates, and their families and to provide education in both the public and professional arenas to promote organ transplantation in Japan. Since 1991, members of the Japanese chapter of the Transplant Recipients International Organization have acted as volunteer facilitators for more than 150 transplant candidates and recipients. The organization's activities have included fund-raising to cover the costs of transplantation, preparing an original donor card for distribution, and petitioning members of the Diet (the Japanese legislative body) 14 times, including speaking at public hearings twice and submitting a petition requesting early passage of the organ transplant bill. The Japanese Diet finally passed an organ transplant bill in June 1997. The activities of the Japanese chapter of the Transplant Recipients International Organization have contributed to the promotion of organ transplantation in Japan and to understanding and support for transplantation within the Japanese community as a whole.

Japanese Organ Transplant Law: A Historical Perspective

Although organ transplantation following brain death has progressed in the West, it has lagged far behind in Japan, following the first such case in 1968. As effective immunosuppressants made transplantation a better option, Japanese patients increasingly sought treatment overseas. Japanese physician groups studied issues related to transplantation but did not succeed in making brain-dead donor transplants available to patients, and the matter was referred to the government. However, transplant medicine was still marked by controversy, and as political pressure was applied the controversy deepened, splintering public opinion. At the same time, transplant groups continued working to establish structures to allow transplantation to proceed. Public awareness and knowledge of brain death grew, and acceptance widened. Eventually, legislation was passed in June 1997 that allowed organ donations from some brain-dead donors. The law is restrictive, and such organ transplants in Japan are still limited.

Imaging of intracellular fatty acids by scanning X-ray fluorescence microscopy

Fatty acids are taken up by cells and incorporated into complex lipids such as neutral lipids and glycerophospholipids. Glycerophospholipids are major constituents of cellular membranes. More than 1000 molecular species of glycerophospholipids differ in their polar head groups and fatty acid compositions. They are related to cellular functions and diseases and have been well analyzed by mass spectrometry. However, intracellular imaging of fatty acids and glycerophospholipids has not been successful due to insufficient resolution using conventional methods. Here, we developed a method for labeling fatty acids with bromine (Br) and applied scanning X-ray fluorescence microscopy (SXFM) to obtain intracellular Br mapping data with submicrometer resolution. Mass spectrometry showed that cells took up Br-labeled fatty acids and metabolized them mainly into glycerophospholipids in CHO cells. Most Br signals observed by SXFM were in the perinuclear region. Higher resolution revealed a spot-like distribution of Br in the cytoplasm. The current method enabled successful visualization of intracellular Br-labeled fatty acids. Single-element labeling combined with SXFM technology facilitates the intracellular imaging of fatty acids, which provides a new tool to determine dynamic changes in fatty acids and their derivatives at the single-cell level.—Shimura, M., Shindou, H., Szyrwiel, L., Tokuoka, S. M., Hamano, F., Matsuyama, S., Okamoto, M., Matsunaga, A., Kita, Y., Ishizaka, Y., Yamauchi, K., Kohmura, Y., Lobinski, R., Shimizu, I., Shimizu, T. Imaging of intracellular fatty acids by scanning X-ray fluorescence microscopy.

Fever Is Mediated by Conversion of Endocannabinoid 2-Arachidonoylglycerol to Prostaglandin E2

Fever is a common response to inflammation and infection. The mechanism involves prostaglandin E2 (PGE2)-EP3 receptor signaling in the hypothalamus, which raises the set point of hypothalamic thermostat for body temperature, but the lipid metabolic pathway for pyretic PGE2 production remains unknown. To reveal the molecular basis of fever initiation, we examined lipopolysaccharides (LPS)-induced fever model in monoacylglycerol lipase (MGL)-deficient (Mgll-/-) mice, CB1 receptor-MGL compound-deficient (Cnr1-/-Mgll-/-) mice, cytosolic phospholipase A2α (cPLA2α)-deficient (Pla2g4a-/-) mice, and diacylglycerol lipase α (DGLα)-deficient (Dagla-/-) mice. Febrile reactions were abolished in Mgll-/- and Cnr1-/-Mgll-/- mice, whereas Cnr1-/-Mgll+/+, Pla2g4a-/- and Dagla-/- mice responded normally, demonstrating that MGL is a critical enzyme for fever, which functions independently of endocannabinoid signals. Intracerebroventricular administration of PGE2 caused fever similarly in Mgll-/- and wild-type control mice, suggesting a lack of pyretic PGE2 production in Mgll-/- hypothalamus, which was confirmed by lipidomics analysis. Normal blood cytokine responses after LPS administration suggested that MGL-deficiency does not affect pyretic cytokine productions. Diurnal body temperature profiles were normal in Mgll-/- mice, demonstrating that MGL is unrelated to physiological thermoregulation. In conclusion, MGL-dependent hydrolysis of endocannabinoid 2-arachidonoylglycerol is necessary for pyretic PGE2 production in the hypothalamus.

Establishment of LC-MS methods for the analysis of palmitoylated surfactant proteins

The surfactant proteins (SPs), SP-B and SP-C, are important components of pulmonary surfactant involved in the reduction of alveolar surface tension. Quantification of SP-B and SP-C in surfactant drugs is informative for their quality control and the evaluation of their biological activity. Western blot analysis enabled the quantification of SP-B, but not SP-C, in surfactant drugs. Here, we report a new procedure involving chemical treatments and LC-MS to analyze SP-C peptides. The procedure enabled qualitative analysis of SP-C from different species with discrimination of the palmitoylation status and the artificial modifications that occur during handling and/or storage. In addition, the method can be used to estimate the total amount of SP-C in pulmonary surfactant drugs. The strategy described here might serve as a prototype to establish analytical methods for peptides that are extremely hydrophobic and behave like lipids. The new method provides an easy measurement of SP-C from various biological samples, which will help the characterization of various experimental animal models and the quality control of surfactant drugs, as well as diagnostics of human samples.

Fatty acid remodeling by LPCAT3 enriches arachidonate in phospholipid membranes and regulates triglyceride transport

Polyunsaturated fatty acids (PUFAs) in phospholipids affect the physical properties of membranes, but it is unclear which biological processes are influenced by their regulation. For example, the functions of membrane arachidonate that are independent of a precursor role for eicosanoid synthesis remain largely unknown. Here, we show that the lack of lysophosphatidylcholine acyltransferase 3 (LPCAT3) leads to drastic reductions in membrane arachidonate levels, and that LPCAT3-deficient mice are neonatally lethal due to an extensive triacylglycerol (TG) accumulation and dysfunction in enterocytes. We found that high levels of PUFAs in membranes enable TGs to locally cluster in high density, and that this clustering promotes efficient TG transfer. We propose a model of local arachidonate enrichment by LPCAT3 to generate a distinct pool of TG in membranes, which is required for normal directionality of TG transfer and lipoprotein assembly in the liver and enterocytes.

DOI:http://dx.doi.org/10.7554/eLife.06328.001

Membranes made of molecules called lipids surround every living cell and also form compartments inside the cell. There are hundreds of different lipid molecules that can be found in membranes. The amount of each type within the membrane can vary, which affects the flexibility and other physical properties of the membrane.

One type of lipid found in membranes is called arachidonic acid. It is involved in cell communication and other processes, and is required for young animals to grow and develop properly. An enzyme called LPCAT3 is thought to incorporate arachidonic acid into membranes, but this has not yet been proven to occur in living animals.

Here, Hashidate-Yoshida, Harayama et al. studied the role of LPCAT3 in newborn mice. The experiments show that this enzyme is found at high levels in the intestine and liver. Mice that lacked LPCAT3 had much lower levels of arachidonic acid compared with normal mice. These mice also showed signs of severe intestinal damage due to the build up of lipids from their mother's milk, and died within a few days of being born.

The mice that lacked LPCAT3 had different amounts of another type of lipid—called triacylglycerols—in their intestine and liver. Normally, these lipids would be assembled into larger molecules called lipoproteins that are released into the blood stream and used in the muscles and other parts of the body. However, Hashidate-Yoshida, Harayama et al. found that in the mice missing LPCAT3, the triacylglycerols did not get assembled into lipoproteins and so they accumulated inside the intestine and liver cells.

The experiments also show that high levels of arachidonic acid and other similar lipids in the membrane enable triacylglycerol molecules to cluster together, which increases the production of lipoproteins. Hashidate-Yoshida, Harayama et al.'s findings suggest that LPCAT3 incorporates arachidonic acid into the membrane of intestine and liver cells, which enables triacylglycerols to be assembled into lipoproteins. The next challenge will be to find out if LPCAT3 is also important for the production of lipoproteins in humans. If it is, then developing new therapies that alter the activity of this enzyme might be beneficial for patients with abnormal levels of lipids in the blood (known as dyslipidemia).

DOI:http://dx.doi.org/10.7554/eLife.06328.002

Interplay between CXCR2 and BLT1 facilitates neutrophil infiltration and resultant keratinocyte activation in a murine model of imiquimod-induced psoriasis

Psoriasis is an inflammatory skin disease with accelerated epidermal cell turnover. Neutrophil accumulation in the skin is one of the histological characteristics of psoriasis. However, the precise mechanism and role of neutrophil infiltration remain largely unknown. In this article, we show that orchestrated action of CXCR2 and leukotriene B4 receptor BLT1 plays a key role in neutrophil recruitment during the development of imiquimod (IMQ)-induced psoriatic skin lesions in mice. Depletion of neutrophils with anti-Ly-6G Ab ameliorated the disease severity, along with reduced expression of proinflammatory cytokine IL-1β in the skin. Furthermore, CXCR2 and BLT1 coordinately promote neutrophil infiltration into the skin during the early phase of IMQ-induced inflammation. In vitro, CXCR2 ligands augment leukotriene B4 production by murine neutrophils, which, in turn, amplifies chemokine-mediated neutrophil chemotaxis via BLT1 in autocrine and/or paracrine manners. In agreement with the increased IL-19 expression in IMQ-treated mouse skin, IL-1β markedly upregulated expression of acanthosis-inducing cytokine IL-19 in human keratinocytes. We propose that coordination of chemokines, lipids, and cytokines with multiple positive feedback loops might drive the pathogenesis of psoriasis and, possibly, other inflammatory diseases as well. Interference to this positive feedback or its downstream effectors could be targets of novel anti-inflammatory treatment.

Selective ablation of mast cells or basophils reduces peanut-induced anaphylaxis in mice

BACKGROUND

Studies with c-kit mutant mast cell (MC)-deficient mice and antibody-mediated depletion of basophils suggest that both MCs and basophils can contribute to peanut-induced anaphylaxis (PIA). However, interpretation of data obtained by using such approaches is complicated because c-kit mutant mice have several phenotypic abnormalities in addition to MC deficiency and because basophil-depleting antibodies can also react with MCs.

OBJECTIVE

We analyzed (1) the changes in the features of PIA in mice after the selective and inducible ablation of MCs or basophils and (2) the possible importance of effector cells other than MCs and basophils in the PIA response.

METHODS

Wild-type and various mutant mice were orally sensitized with peanut extract and cholera toxin weekly for 4 weeks and challenged intraperitoneally with peanut extract 2 weeks later.

RESULTS

Peanut-challenged, MC-deficient Kit(W-sh/W-sh) mice had reduced immediate hypothermia, as well as a late-phase decrease in body temperature that was abrogated by antibody-mediated depletion of neutrophils. Diphtheria toxin-mediated selective depletion of MCs or basophils in Mcpt5-Cre;iDTR and Mcpt8(DTR) mice, respectively, and treatment of wild-type mice with the basophil-depleting antibody Ba103 significantly reduced peanut-induced hypothermia. Non-c-kit mutant MC- and basophil-deficient Cpa3-Cre;Mcl-1(fl/fl) mice had reduced but still significant responses to peanut.

CONCLUSION

Inducible and selective ablation of MCs or basophils in non-c-kit mutant mice can significantly reduce PIA, but partial responses to peanut can still be observed in the virtual absence of both cell types. The neutrophilia in Kit(W-sh/W-sh) mice might influence the responses of these mice in this PIA model.

Acute inhibition of diacylglycerol lipase blocks endocannabinoid-mediated retrograde signalling: evidence for on-demand biosynthesis of 2-arachidonoylglycerol

The endocannabinoid (eCB) 2-arachidonoylglycerol (2-AG) produced by diacylglycerol lipase α (DGLα) is one of the best-characterized retrograde messengers at central synapses. It has been thought that 2-AG is produced 'on demand' upon activation of postsynaptic neurons. However, recent studies propose that 2-AG is pre-synthesized by DGLα and stored in neurons, and that 2-AG is released from such 'pre-formed pools' without the participation of DGLα. To address whether the 2-AG source for retrograde signalling is the on-demand biosynthesis by DGLα or the mobilization from pre-formed pools, we examined the effects of acute pharmacological inhibition of DGL by a novel potent DGL inhibitor, OMDM-188, on retrograde eCB signalling triggered by Ca(2+) elevation, Gq/11 protein-coupled receptor activation or synergy of these two stimuli in postsynaptic neurons. We found that pretreatment for 1 h with OMDM-188 effectively blocked depolarization-induced suppression of inhibition (DSI), a purely Ca(2+)-dependent form of eCB signalling, in slices from the hippocampus, striatum and cerebellum. We also found that at parallel fibre-Purkinje cell synapses in the cerebellum OMDM-188 abolished synaptically induced retrograde eCB signalling, which is known to be caused by the synergy of postsynaptic Ca(2+) elevation and group I metabotropic glutamate receptor (I-mGluR) activation. Moreover, brief OMDM-188 treatments for several minutes were sufficient to suppress both DSI and the I-mGluR-induced retrograde eCB signalling in cultured hippocampal neurons. These results are consistent with the hypothesis that 2-AG for synaptic retrograde signalling is supplied as a result of on-demand biosynthesis by DGLα rather than mobilization from presumptive pre-formed pools.