Immunohistochemical distribution of phosphatidylglucoside using anti-phosphatidylglucoside monoclonal antibody (DIM21)

Guidelines on antibody use in physiology research

Antibodies are one of the most used reagents in scientific laboratories and are critical components for a multitude of experiments in physiology research. Over the past decade, concerns about many biological methods, including those that use antibodies, have arisen as several laboratories were unable to reproduce the scientific data obtained in other laboratories. The lack of reproducibility could be largely attributed to inadequate reporting of detailed methods, no or limited verification by authors, and the production and use of unvalidated antibodies. The goal of this guideline article is to review best practices concerning commonly used techniques involving antibodies, including immunoblotting, immunohistochemistry, and flow cytometry. Awareness and integration of best practices will increase the rigor and reproducibility of these techniques and elevate the quality of physiology research.

Lysophosphatidylglucoside/GPR55 signaling promotes foam cell formation in human M2c macrophages

Atherosclerosis is a major cause of cerebral and cardiovascular diseases. Intravascular plaques, a well-known pathological finding of atherosclerosis, have a necrotic core composed of macrophages and dead cells. Intraplaque macrophages, which are classified into various subtypes, play key roles in maintenance of normal cellular microenvironment. Excessive uptake of oxidized low-density lipoprotein causes conversion of macrophages to foam cells, and consequent progression/exacerbation of atherosclerosis. G-protein-coupled receptor 55 (GPR55) signaling has been reported to associate with atherosclerosis progression. We demonstrated recently that lysophosphatidylglucoside (lysoPtdGlc) is a specific ligand of GPR55, although in general physiological ligands of GPR55 are poorly understood. Phosphatidylglucoside is expressed on human monocytes and can be converted to lysoPtdGlc. In the present study, we examined possible involvement of lysoPtdGlc/GPR55 signaling in foam cell formation. In monocyte-derived M2c macrophages, lysoPtdGlc/GPR55 signaling inhibited translocation of ATP binding cassette subfamily A member 1 to plasma membrane, and cholesterol efflux. Such inhibitory effect was reversed by GPR55 antagonist ML193. LysoPtdGlc/GPR55 signaling in M2c macrophages was involved in excessive lipid accumulation, thereby promoting foam cell formation. Our findings suggest that lysoPtdGlc/GPR55 signaling is a potential therapeutic target for inhibition of atherosclerosis progression.

Distribution of Glycolipids in the Plasma Membrane Monitored by Specific Probes in Combination with Sodium Dodecyl Sulfate-Digested Freeze-Fracture Replica Labeling (SDS-FRL)

Glycolipids are mainly distributed in the outer leaflet of the plasma membrane and are involved in cellular signaling by modulating the activity of cell surface receptor proteins. Glycolipids themselves also work as cell surface receptors of bacterial toxins. Anti-glycolipid antibodies are associated with various pathological conditions. The cellular distribution of glycolipids has been studied using specific toxins or antibodies. However, these proteins are multivalent and thus potentially induce the artificial aggregation of glycolipids. Since chemical fixative such as paraformaldehyde does not fix glycolipids, an alternative methodology is required to localize glycolipids with multivalent probes. Sodium dodecyl sulfate-digested freeze-fracture replica labeling (SDS-FRL) physically fixes glycolipids on the cast after quick freezing. Thus, SDS-FRL provides the opportunity to observe the natural distribution of glycolipids using multivalent probes. Here, we describe the application of SDS-FRL on the cell surface distribution of phosphatidylglucoside.

Fat of the Gut: Epithelial Phospholipids in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) comprise a distinct set of clinical symptoms resulting from chronic inflammation within the gastrointestinal (GI) tract. Despite the significant progress in understanding the etiology and development of treatment strategies, IBD remain incurable for thousands of patients. Metabolic deregulation is indicative of IBD, including substantial shifts in lipid metabolism. Recent data showed that changes in some phospholipids are very common in IBD patients. For instance, phosphatidylcholine (PC)/phosphatidylethanolamine (PE) and lysophosphatidylcholine (LPC)/PC ratios are associated with the severity of the inflammatory process. Composition of phospholipids also changes upon IBD towards an increase in arachidonic acid and a decrease in linoleic and a-linolenic acid levels. Moreover, an increase in certain phospholipid metabolites, such as lysophosphatidylcholine, sphingosine-1-phosphate and ceramide, can result in enhanced intestinal inflammation, malignancy, apoptosis or necroptosis. Because some phospholipids are associated with pathogenesis of IBD, they may provide a basis for new strategies to treat IBD. Current attempts are aimed at controlling phospholipid and fatty acid levels through the diet or via pharmacological manipulation of lipid metabolism.

The immunophenotype of antigen presenting cells of the mononuclear phagocyte system in normal human liver--a systematic review

The mononuclear phagocytic system (MPS), comprised of monocytes, macrophages, and dendritic cells, is essential in tissue homeostasis and in determining the balance of the immune response through its role in antigen presentation. It has been identified as a therapeutic target in infectious disease, cancer, autoimmune disease and transplant rejection. Here, we review the current understanding of the immunophenotype and function of the MPS in normal human liver. Using well-defined selection criteria, a search of MEDLINE and EMBASE databases identified 76 appropriate studies. The majority (n=67) described Kupffer cells (KCs), although the definition of KC differs between sources, and little data were available regarding their function. Only 10 papers looked at liver dendritic cells (DCs), and largely confirmed the presence of the major dendritic cell subsets identified in human blood. Monocytes were thoroughly characterized in four studies that utilized flow cytometry and fluorescent microscopy and highlighted their prominent role in liver homeostasis and displayed subtle differences from circulating monocytes. There was some limited evidence that liver DCs are tolerogenic but neither liver dendritic cell subsets nor macrophages have been thoroughly characterized, using either multi-colour flow cytometry or multi-parameter fluorescence microscopy. The lobular distribution of different subsets of liver MPS cells was also poorly described, and the ability to distinguish between passenger leukocytes and tissue resident cells remains limited. It was apparent that further research, using modern immunological techniques, is now required to accurately characterize the cells of the MPS in human liver.

New insights on glucosylated lipids: metabolism and functions

Ceramide, cholesterol, and phosphatidic acid are major basic structures for cell membrane lipids. These lipids are modified with glucose to generate glucosylceramide (GlcCer), cholesterylglucoside (ChlGlc), and phosphatidylglucoside (PtdGlc), respectively. Glucosylation dramatically changes the functional properties of lipids. For instance, ceramide acts as a strong tumor suppressor that causes apoptosis and cell cycle arrest, while GlcCer has an opposite effect, downregulating ceramide activities. All glucosylated lipids are enriched in lipid rafts or microdomains and play fundamental roles in a variety of cellular processes. In this review, we discuss the biological functions and metabolism of these three glucosylated lipids.

A world of sphingolipids and glycolipids in the brain--novel functions of simple lipids modified with glucose

Glycosphingolipids (GSLs) are present on cell surface membranes and are particularly abundant in the brain. Since over 300-400 GSLs are synthesized from glucosylceramide (GlcCer), GlcCer is believed to only serve as the source of most GSLs, including sialic acid-containing GSLs or gangliosides, in the brain. Recent studies, however, suggest that GlcCer itself plays a role in the heat stress response, as it functions as a glucose donor for the synthesis of cholesterylglucoside, a lipid mediator in heat stress responses in animals. GlcCer in adipose tissues is also thought to be involved in mechanisms that regulate energy (sugar and lipid) metabolism. Our extensive structural study revealed an additional novel glucosylated membrane lipid, called phosphatidylglucoside, in developing rodent brains and human neutrophils. These lipids, all modified with glucose, are enriched in lipid rafts and play important roles in basic cellular processes. Here, I summarize the recent progress regarding these glucosylated lipids and their biosynthesis and regulation in the central nervous system (CNS).

Long-term repopulation effects of donor BMDCs on intestinal epithelium

BACKGROUND

Bone marrow-derived cells (BMDCs) have the ability to differentiate into intestinal epithelial cells after transplantation and participate in the regeneration process of damaged epithelium.

AIMS

To investigate whether BMDCs could differentiate into intestinal epithelium long term in chimeric mice after transplantation and without special treatment.

METHODS

Forty irradiated C57BL/6 mice were used. Thirty of them (group A) received transplantation of BMDCs from GFP transgenic mice, and ten (group B) received PBS. The chimeric percentage at the 14th month was examined by flow cytometry. Engraftment of BMDCs was detected by immunohistochemistry in intestinal epithelium. Immunofluorescence observation was used to detect coexpression of PCK, CD45 and Chromogranin A with GFP. BMDCs in the epithelium were observed by an immune electron microscope. The percent of GFP(+) epithelial cells was also determined by flow cytometry.

RESULTS

Mice in group A had a survival rate of 93.3% 1 week after transplantation. BMDCs could engraft into recipients' intestinal epithelium. These cells expressed epithelial cell marker PCK, but could not express CD45. Some of them differentiated into enteroendocrine cells expressing Chromogranin A. GFP(+) villous epithelial cells ranged from 9.41 to 16.07% in different subgroups of group A. BMDCs in epithelium developed the characteristics of enterocytes and goblet cells. GFP(+)/PCK(+) epithelial cells at the 6th month made up a proportion of 16.11% among all the isolated epithelial cells.

CONCLUSIONS

Long term, BMDCs could repopulate recipient's intestinal epithelium even without any special treatment, which suggests a novel insight into the maintenance of the intestinal epithelial constitution.

Bone marrow derivation of interstitial cells of cajal in small intestine following intestinal injury

Interstitial cells of Cajal (ICCs) in gastrointestinal tract are specialized cells serving as pacemaker cells. The origin of ICCs is currently not fully characterized. In this work, we aimed to study whether bone marrow-derived cells (BMDCs) could contribute to the origin of ICCs in the muscular plexus of small intestine using GFP-C57BL/6 chimeric mice.Engraftment of BMDCs in the intestine was investigated for GFP expression. GFP positive bone marrow mononuclear cells reached a proportion of 95.65% ± 3.72% at different times in chimerism. Donor-derived cells distributed widely in all the layers of the gastrointestinal tract. There were GFP positive BMDCs in the myenteric plexus, which resembled characteristics of ICCs, including myenteric location, c-Kit positive staining, and ramified morphology. Donor-derived ICCs in the myenteric plexus contributed to a percentage ranging 9.25% ± 4.9% of all the ICCs in the myenteric plexus. In conclusion, here we described that donor-derived BMDCs might differentiate into gastrointestinal ICCs after radiation injury, which provided an alternative source for the origin of the ICCs in the muscular plexus of adult intestine. These results further identified the plasticity of BMDCs and indicated therapeutic implications of BMDCs for the gastrointestinal dysmotility caused by ICCs disorders.