Human galectins as sensors for apoptosis/necrosis-associated surface changes of granulocytes and lymphocytes.

Changes in the glycomic profile can significantly affect the cells' communication with the environment. Plant lectins have so far been used to address the issue as to whether the courses of apoptosis or necrosis are associated with such alterations. We, here, initiate the study of members of the family of functionally pleiotropic human galectins in this respect. Established protocols for the induction of apoptosis/necrosis of blood cells and for flow cytometry using annexin V/propidium iodide were combined with cell surface staining using biotinylated galectins at a nontoxic concentration. The galectin panel covered members from all three subfamilies. Flow cytometry revealed specific binding of galectins to viable control cells and conspicuous staining differences when testing apoptotic or necrotic cells. Onset and especially progression of cell death led to pronounced reactivity with the proto-type galectins-1, -2, and -7 and tandem-repeat-type galectin-4. Extent of staining depended on the nature and stage of cell death, type of dying cell, and type of galectin. Galectins act as sensors for cell-death-associated surface changes. Staining of late-apoptotic polymorphonuclear cells was particularly strong. Examining the functional significance of this result may reveal a new aspect within the surveillance system to protect against autoinflammation.

Evaluation of Four Blood Glucose Monitoring Systems for Self-Testing with Built-in Insulin Dose Advisor Based on ISO 15197:2013: System Accuracy and Hematocrit Influence.

BACKGROUND: Self-monitoring of blood glucose (SMBG) is important in diabetes therapy; however, not all SMBG systems are sufficiently accurate. In addition, some SMBG systems are influenced by the user's hematocrit value. METHODS: System accuracy and hematocrit influence was evaluated for four SMBG systems with built-in insulin dose advisors (Accu-Chek® Aviva Expert [1], FreeStyle InsuLinx [2], FreeStyle Precision Neo [3], MyStar DoseCoach® [4]) based on International Organization for Standardization (ISO) 15197:2013 section 6.3 (system accuracy) and 6.4.3 (packed cell volume [hematocrit]) with three test strip lots for each system. Two different established comparison methods were used to investigate a possible impact of the comparison method on analytical performance data. RESULTS: Two systems (2, 4) fulfilled ISO 15197:2013 accuracy criteria when the manufacturer's comparison measurement method was applied and showed with all three tested lots 97% to 99.5% of results within ±15 mg/dL and ±15% of the comparison measurement results at blood glucose (BG) concentrations <100 and ≥100 mg/dL, respectively, and 100% of results within consensus error grid zones A and B. Regarding hematocrit influences, two systems (3, 4) showed with all three tested lots ≤10 mg/dL and ≤10% difference between the test sample and the respective control sample for BG concentrations <100 and ≥100 mg/dL, respectively, when using the manufacturer's comparison measurement method. CONCLUSIONS: When using the manufacturer's comparison measurement method, two out of four SMBG systems fulfilled the minimum system accuracy requirements of ISO 15197:2013. In addition, varying hematocrit levels can affect measurement results with some SMBG systems with built-in insulin dose advisors.

Sweet clearance: involvement of cell surface glycans in the recognition of apoptotic cells.

Glycans cover the surfaces of all mammalian cells. Their structural variety provides enormous potential for information storage and transfer. According to the concept of the sugar code, they act as biochemical signals decoded by a large number of lectins which are defined as sugar binding proteins. The importance of glycan-lectin interaction in diverse immune system functions becomes increasingly apparent. Here, we review apoptotic cell clearance and especially focus on modifications of glycans on apoptotic cells.

Lectins detect changes of the glycosylation status of plasma membrane constituents during late apoptosis.

BACKGROUND: Mechanisms governing the normal resolution processes of inflammation are poorly understood, yet their elucidation may lead to a greater understanding of the pathogenesis of chronic inflammation. The removal of apoptotic cell material and their potentially histotoxic contents is a prerequisite of resolution. Engulfment by macrophages is an important disposal route, and changes in the apoptotic cells that are associated with their recognition by macrophages are the subject of this report. METHODS: Apoptosis and necrosis in primary cells and cell lines were induced by various stimuli. The binding profile of 23 different lectins for vital, apoptotic, and necrotic cells were analyzed by flow cytometry. RESULTS: We observed that lectins were able to attach to the cell surfaces of vital and dying cells. Some lectins exhibited membrane destructive properties and, consecutively, changed the morphology of the cells as detected by flow cytometry. Other lectins did not show differences in their binding to viable and apoptotic cells. Those lectins were, therefore, not used for analyses of surface changes. The lectins Griffonia simplificolia II (GSL II), Narcissus pseudonarcissus (NPn), and Ulex europaeus I (UEA I) showed no cytotoxic activity and bound preferentially to dying cells. Primary and secondary necrotic cells displayed an equal staining intensity, which was substantially higher than for apoptotic cells. The binding of GSL II, NPn, and UEA to dying cells increased in a time-dependent manner and was delayed to AxV positivity and the decrease in the mitochondrial membrane potential of apoptotic cells. The kinetic of the lectin staining correlated with the increase in subG1-DNA. GSL II, NPn, and UEA are specific for N-acetylglucosamine, mannose, and fucose, respectively. CONCLUSION: According to their binding specificity, we conclude that N-acetylglucosamine-, mannose-, and fucose-containing epitopes are increasingly exposed on cells undergoing apoptosis.