Lipid imaging mass spectrometry: Towards a new molecular histology.

Lipid research is attracting greater attention, as these molecules are key components to understand cell metabolism and the connection between genotype and phenotype. The study of lipids has also been fueled by the development of new and powerful technologies, able to identify an increasing number of species in a single run and at decreasing concentrations. One of such key developments has been the image techniques that enable the visualization of lipid distribution over a tissue with cell resolution.

Lipid fingerprint-based histology accurately classifies nevus, primary melanoma, and metastatic melanoma samples.

Probably, the most important factor for the survival of a melanoma patient is early detection and precise diagnosis. Although in most cases these tasks are readily carried out by pathologists and dermatologists, there are still difficult cases in which no consensus among experts is achieved. To deal with such cases, new methodologies are required.

Nonionic Surfactants can Modify the Thermal Stability of Globular and Membrane Proteins Interfering with the Thermal Proteome Profiling Principles to Identify Protein Targets.

The membrane proteins are essential targets for understanding cellular function. The unbiased identification of membrane protein targets is still the bottleneck for a system-level understanding of cellular response to stimuli or perturbations. It has been suggested to enrich the soluble proteome with membrane proteins by introducing nonionic surfactants in the solubilization solution.

Using the Synergy between HPLC-MS and MALDI-MS Imaging to Explore the Lipidomics of Clear Cell Renal Cell Carcinoma.

Lipid imaging mass spectrometry (LIMS) has been tested in several pathological contexts, demonstrating its ability to segregate and isolate lipid signatures in complex tissues, thanks to the technique's spatial resolution. However, it cannot yet compete with the superior identification power of high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS), and therefore, very often, the latter is used to refine the assignment of the species detected by LIMS. Also, it is not clear if the differences in sensitivity and spatial resolution between the two techniques lead to a similar panel of biomarkers for a given disease.

Ferrostatin-1 modulates dysregulated kidney lipids in acute kidney injury.

Ferroptosis, a form of regulated necrosis characterized by peroxidation of lipids such as arachidonic acid-containing phosphatidylethanolamine (PE), contributes to the pathogenesis of acute kidney injury (AKI). We have characterized the kidney lipidome in an experimental nephrotoxic AKI induced in mice using folic acid and assessed the impact of the ferroptosis inhibitor Ferrostatin-1. Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) was used to assess kidney lipidomics and it discriminated between glomeruli, medulla, and cortex in control kidneys, AKI kidneys, and AKI + Ferrostatin-1 kidneys.

A UHPLC-Mass Spectrometry View of Human Melanocytic Cells Uncovers Potential Lipid Biomarkers of Melanoma.

Melanoma is the deadliest form of skin cancer due to its ability to colonize distant sites and initiate metastasis. Although these processes largely depend on the lipid-based cell membrane scaffold, our understanding of the melanoma lipid phenotype lags behind most other aspects of this tumor cell. Here, we examined a panel of normal human epidermal and nevus melanocytes and primary and metastatic melanoma cell lines to determine whether distinctive cell-intrinsic lipidomes can discern non-neoplastic from neoplastic melanocytes and define their metastatic potential.

High-Resolution Human Kidney Molecular Histology by Imaging Mass Spectrometry of Lipids.

For many years, traditional histology has been the gold standard for the diagnosis of many diseases. However, alternative and powerful techniques have appeared in recent years that complement the information extracted from a tissue section. One of the most promising techniques is imaging mass spectrometry applied to lipidomics.

Molecular and cellular insights into the role of SND1 in lipid metabolism.

Staphylococcal nuclease and Tudor domain containing 1 (SND1) is an evolutionarily conserved protein present in eukaryotic cells from protozoa to mammals. SND1 has gained importance because it is overexpressed in aggressive cancer cells and diverse primary tumors. Indeed, it is regarded as a marker of cancer malignity.

Application of Bioactive Thermal Proteome Profiling to Decipher the Mechanism of Action of the Lipid Lowering 13-Hydroxy-pheophytin Isolated from a Marine Cyanobacteria.

The acceleration of the process of understanding the pharmacological application of new marine bioactive compounds requires identifying the compound protein targets leading the molecular mechanisms in a living cell. The thermal proteome profiling (TPP) methodology does not fulfill the requirements for its application to any bioactive compound lacking chemical and functional characterization. Here, we present a modified method that we called bTPP for bioactive thermal proteome profiling that guarantees target specificity from a soluble subproteome.

Channeling of newly synthesized fatty acids to cholesterol esterification limits triglyceride synthesis in SND1-overexpressing hepatoma cells.

SND1 is a putative oncoprotein whose molecular function remains unclear. Its overexpression in hepatocellular carcinoma impairs cholesterol homeostasis due to the altered activation of the sterol regulatory element-binding protein (SREBP) 2, which results in the accumulation of cellular cholesteryl esters (CE). In this work, we explored whether high cholesterol synthesis and esterification originates changes in glycerolipid metabolism that might affect cell growth, given that acetyl-coenzyme A is required for cholesterogenesis and fatty acids (FA) are the substrates of acyl-coenzyme A:cholesterol acyltransferase (ACAT).

Atorvastatin provides a new lipidome improving early regeneration after partial hepatectomy in osteopontin deficient mice.

Osteopontin (OPN), a multifunctional cytokine that controls liver glycerolipid metabolism, is involved in activation and proliferation of several liver cell types during regeneration, a condition of high metabolic demands. Here we investigated the role of OPN in modulating the liver lipidome during regeneration after partial-hepatectomy (PH) and the impact that atorvastatin treatment has over regeneration in OPN knockout (KO) mice. The results showed that OPN deficiency leads to remodeling of phosphatidylcholine and triacylglycerol (TG) species primarily during the first 24 h after PH, with minimal effects on regeneration.

High-fat diet overfeeding promotes nondetrimental liver steatosis in female mice.

High-fat diet (HFD) feeding or leptin-deficient mice are extensively used as models resembling features of human nonalcoholic fatty liver disease (NAFLD). The concurrence of experimental factors as fat content and source or total caloric intake leads to prominent differences in the development of the hepatic steatosis and related disturbances. In this work, we characterized the hepatic lipid accumulation induced by HFD in wild-type (WT) and ob/ ob mice with the purpose of differentiating adaptations to HFD from those specific of increased overfeeding due to leptin deficiency-associated hyperphagia.

Adenosine: Direct and Indirect Actions on Gastric Acid Secretion.

Composed by a molecule of adenine and a molecule of ribose, adenosine is a paradigm of recyclable nucleoside with a multiplicity of functions that occupies a privileged position in the metabolic and regulatory contexts. Adenosine is formed continuously in intracellular and extracellular locations of all tissues. Extracellular adenosine is a signaling molecule, able to modulate a vast range of physiologic responses in many cells and organs, including digestive organs.

Expression of Adenosine A Receptor and Adenosine Deaminase in Rabbit Gastric Mucosa ECL Cells.

Adenosine is readily available to the glandular epithelium of the stomach. Formed continuously in intracellular and extracellular locations, it is notably produced from ATP released in enteric cotransmission. Adenosine analogs modulate chloride secretion in gastric glands and activate acid secretion in isolated parietal cells through A adenosine receptor (A2BR) binding.

SND1 overexpression deregulates cholesterol homeostasis in hepatocellular carcinoma.

SND1 is a multifunctional protein participating, among others, in gene transcription and mRNA metabolism. SND1 is overexpressed in cancer cells and promotes viability and tumourigenicity of hepatocellular carcinoma cells. This study shows that cholesterol synthesis is increased in SND1-overexpressing hepatoma cells.

Stimulation of gastric acid secretion by rabbit parietal cell A(2B) adenosine receptor activation.

Adenosine modulates different functional activities in many cells of the gastrointestinal tract; some of them are believed to be mediated by interaction with its four G protein-coupled receptors. The renewed interest in the adenosine A2B receptor (A2BR) subtype can be traced by studies in which the introduction of new genetic and chemical tools has widened the pharmacological and structural knowledge of this receptor as well as its potential therapeutic use in cancer and inflammation- or hypoxia-related pathologies. In the acid-secreting parietal cells of the gastric mucosa, the use of various radioligands for adenosine receptors suggested the presence of the A2 adenosine receptor subtype(s) on the cell surface.

Cholesterol mobilization from hepatic lipid droplets during endotoxemia is altered in obese ob/ob mice.

The innate immune response to pathogens during the acute phase response includes lipid metabolism adaptations. Hepatic triacylglycerol (TG) and cholesteryl ester (CE) storage in and mobilization from lipid droplets (LDs) respond to metabolic changes under the control of liver X receptor (LXR) transactivation and cytokine transduction. To evaluate whether alterations of these mechanisms have an impact in the adaptive response to endotoxemia, we analysed liver metabolism changes in lipopolysaccharide (LPS)-treated ob/ob mice, which show altered metabolic and innate responses and a higher sensitivity to sepsis.

S-Adenosylmethionine increases circulating very-low density lipoprotein clearance in non-alcoholic fatty liver disease.

Background & Aims: Very-low-density lipoproteins (VLDLs) export lipids from the liver to peripheral tissues and are the precursors of low-density-lipoproteins. Low levels of hepatic S-adenosylmethionine (SAMe) decrease triglyceride (TG) secretion in VLDLs, contributing to hepatosteatosis in methionine adenosyltransferase 1A knockout mice but nothing is known about the effect of SAMe on the circulating VLDL metabolism. We wanted to investigate whether excess SAMe could disrupt VLDL plasma metabolism and unravel the mechanisms involved.

The E2F2 transcription factor sustains hepatic glycerophospholipid homeostasis in mice.

Increasing evidence links metabolic signals to cell proliferation, but the molecular wiring that connects the two core machineries remains largely unknown. E2Fs are master regulators of cellular proliferation. We have recently shown that E2F2 activity facilitates the completion of liver regeneration after partial hepatectomy (PH) by regulating the expression of genes required for S-phase entry.

Involvement of lipid droplets in hepatic responses to lipopolysaccharide treatment in mice.

Infection and inflammation induce important changes in lipid metabolism, which result in increased free fatty acids and triacylglycerol in plasma and altered high density lipoprotein (HDL) metabolism. Our aim was to elucidate whether hepatic lipid droplets (LDs) are involved in the adaptations of lipid metabolism to endotoxemia. We characterized the lipid content and several enzymatic activities in subcellular fractions and subpopulations of LDs from livers of mice 24h after lipopolysaccharide (LPS) treatment and analyzed the expression of key genes involved in lipid management.

Infection of primary hepatocytes with adenoviral vectors alters biliary lipid metabolism.

In the context of a study of the involvement of SND1 (also known as coactivator p100) in biliary lipid secretion by primary rat hepatocytes, first-generation adenoviral vectors were used to promote the overexpression and underexpression of the protein SND1. Although differential expression of SND1 did not result in significant changes in the processes studied, some effects of the adenoviral infection itself were observed. In particular, infected hepatocytes showed a higher intracellular taurocholate accumulation capacity.

A role for transcription factor E2F2 in hepatocyte proliferation and timely liver regeneration.

E2F transcription factors are key regulators of the cell cycle although the relative contribution of each E2F member in regulating cellular proliferation is still poorly defined. Present evidence suggests that E2F2 may act both as a suppressor and promoter of proliferation, depending on the cellular context. We used a loss-of-function mutant mouse model to investigate the function of E2F2 in liver regeneration after partial hepatectomy, a paradigm of cell-cycle progression.

Anatomical distribution of lipids in human brain cortex by imaging mass spectrometry.

Molecular mass images of tissues will be biased if differences in the physicochemical properties of the microenvironment affect the intensity of the spectra. To address this issue, we have performed-by means of MALDI-TOF mass spectrometry-imaging on slices and lipidomic analysis in extracts of frontal cortex, both from the same postmortem tissue samples of human brain. An external calibration was used to achieve a mass accuracy of 10 ppm (1σ) in the spectra of the extracts, although the final assignment was based on a comparison with previously reported species.

Lipid analysis reveals quiescent and regenerating liver-specific populations of lipid droplets.

The mammalian liver, a key organ in lipid homeostasis, can accumulate increased amounts of lipids in certain physiological conditions including liver regeneration. Lipid droplets (LD), the lipid storage organelles in the cytoplasm, are composed of a core of neutral lipids (mainly triacylglycerols and cholesteryl esters) surrounded by a monolayer of phospholipids and cholesterol with associated proteins. It is recognized that LD lipid composition is cell- and environment-specific and enables LD to carry out specific functions, but few descriptive studies aiming to interpret such differences have been published.