Human chimera-type galectin-3: defining the critical tail length for high-affinity glycoprotein/cell surface binding and functional competition with galectin-1 in neuroblastoma cell growth regulation

Many human proteins have a modular design with receptor and structural domains. Using adhesion/growth-regulatory galectin-3 as model, we describe an interdisciplinary strategy to define the functional significance of its tail established by nine non-triple helical collagen-like repeats (I-IX) and the N-terminal peptide. Genetic engineering with sophisticated mass spectrometric product analysis provided the tools for biotesting, i.e. eight protein variants with different degrees of tail truncation. Evidently,various aspects of galectin-3 activity (cis binding and cell bridging) are affected by tail shortening in a different manner. Thus, this combined approach reveals an unsuspected complexity of structure-function relationship, encouraging further application beyond this chimera-type galectin.

TP53 status regulates ACSL5-induced expression of mitochondrial mortalin in enterocytes and colorectal adenocarcinomas

Acyl-CoA synthetase 5 (ACSL5), a mitochondrially localized enzyme, catalyzes the synthesis of long-chain fatty acid thioesters and is physiologically involved in pro-apoptotic sensing of enterocytes. The aim of the present study is to identify an ACSL5-dependent regulation of mitochondrially expressed proteins and the characterization of related pathways in normal and diseased human intestinal mucosa. Proteomics of isolated mitochondria from ACSL5 transfectants and CaCo2 controls were performed. ACSL5-dependent protein synthesis was verified with quantitative reverse transcription plus the polymerase chain reaction, Western blotting, short-interfering-RNA-mediated gene silencing and additional cell culture experiments. Lipid changes were analyzed with tandem mass spectrometry. ACSL5-related pathways were characterized in normal mucosa and sporadic adenocarcinomas of the human intestine. In CaCo2 cells transfected with ACSL5, mortalin (HSPA9) was about two-fold increased in mitochondria, whereas cytoplasmic mortalin levels were unchanged. Disturbance of acyl-CoA/sphingolipid metabolism, induced by ACSL5 over-expression, was characterized as crucial. ACSL5-related over-expression of mitochondrial mortalin was found in HEK293 and Lovo (wild-type TP53 [tumor protein p53]) and CaCo2 (p53-negative; TP53 mutated) cells but not in Colo320DM cells (mutated TP53). In normal human intestinal mucosa, an increasing gradient of both ACSL5 and mortalin from bottom to top was observed, whereas p53 (wild-type TP53) decreased. In sporadic intestinal adenocarcinomas with strong p53 immunostaining (mutated TP53), ACSL5-related mortalin expression was heterogeneous. ACSL5-induced mitochondrial mortalin expression is assumed to be a stress response to ACSL5-related changes in lipid metabolism and is regulated by the TP53 status. Uncoupling of ACSL5 and mitochondrial mortalin by mutated TP53 could be important in colorectal carcinogenesis.

In contrast to its anti-inflammatory and anti-apoptotic peripheral effect, levosimendan failed to induce a long-term neuroprotective effect in a rat model of mild septic encephalopathy: a pilot study

Levosimendan shows protective myocardial characteristics and is administered to enhance cardiac contractility in patients. However, currently little is known about levosimendan's effect on brain. The aim of this pilot study was to investigate the long-term effect of levosimendan on brain and during mild rat sepsis in comparison to its peripheral mode of action. Adult rats (n=40) were divided into four groups with n=10 per group: (I) sham, (II) levosimendan (283 μg/kg body weight i.v.), (III) lipopolysaccharide (LPS, 8 mg/kg body weight i.p.), and (IV) LPS+levosimendan. Levosimendan was given 24h after injecting LPS. Psychometric investigations were conducted using a Morris water maze (MWM) and a holeboard test. In cerebral and splenic tissue, IL-1β, Il-6, TNFalpha levels, and apoptosis were determined; cerebral tissue corticosterone concentration was measured 6 days after injecting LPS. Blood cytokine concentrations were determined 1 day and 6 days after injecting LPS. Rats that received an LPS injection spent more time in the outer zone of the MWM according to increased cerebral corticosterone levels, and showed decreased cognitive abilities. LPS induced a reduction in body weight, increased splenic apoptosis and blood cytokine level. Levosimendan showed anti-inflammatory and anti-apoptotic properties in spleen but failed to show a long-term neuroprotective effect.

[Role of energy metabolism in retinal pigment epithelium]

The universal energy source adenosine triphosphate (ATP)is reduced by approximately 30 % in the retinal pigment epithelium (RPE) of elderly persons. Increased oxidative stress and decreased antioxidative capacity, such as glutathione in aging eyes cause impairment of energy-dependent RPE processes and lead to loss of visual function. We developed a cell culture model of aging RPE using atractyloside to inhibit mitochondrial ATP synthesis and tert-butyl hydroperoxide as oxidant. The ATP levels were reduced by 30 % and oxidative damaged proteins and DNA increased whereas antioxidative glutathione decreased. Autophagy as an internal cellular repair mechanism and phagocytosis of photoreceptors were impaired. Antioxidative and mitochondria-activating Ginkgo biloba extract EGb 761 increased the intracellular ATP level and antioxidative glutathione. This cell culture model seems to be suitable to investigate in vitro the effect of protective substances and their compounds on aging processes in RPE.

In-depth mass spectrometric mapping of the human vitreous proteome

Mapping of proteins involved in normal eye functions is a prerequisite to identify pathological changes during eye disease processes. We therefore analysed the proteome of human vitreous by applying in-depth proteomic screening technologies. For ethical reasons human vitreous samples were obtained by vitrectomy from “surrogate normal patients” with epiretinal gliosis that is considered to constitute only negligible pathological vitreoretinal changes. We applied different protein prefractionation strategies including liquid phase isoelectric focussing, 1D SDS gel electrophoresis and a combination of both and compared the number of identified proteins obtained by the respective method. Liquid phase isoelectric focussing followed by SDS gel electrophoresis increased the number of identified proteins by a factor of five compared to the analysis of crude unseparated human vitreous. Depending on the prefractionation method proteins were subjected to trypsin digestion either in-gel or in solution and the resulting peptides were analysed on a UPLC system coupled online to an LTQ Orbitrap XL mass spectrometer. The obtained mass spectra were searched against the SwissProt database using the Mascot search engine. Bioinformatics tools were used to annotate known biological functions to the detected proteins. Following this strategy we examined the vitreous proteomes of three individuals and identified 1111 unique proteins. Besides structural, transport and binding proteins, we detected 261 proteins with known enzymatic activity, 51 proteases, 35 protease inhibitors, 35 members of complement and coagulation cascades, 15 peptide hormones, 5 growth factors, 11 cytokines, 47 receptors, 30 proteins of visual perception, 91 proteins involved in apoptosis regulation and 265 proteins with signalling activity. This highly complex mixture strikingly differs from the human plasma proteome. Thus human vitreous fluid seems to be a unique body fluid. 262 unique proteins were detected which are present in all three patient samples indicating that these might represent the constitutive protein pattern of human vitreous. The presented catalogue of human vitreous proteins will enhance our understanding of physiological processes in the eye and provides the groundwork for future studies on pathological vitreous proteome changes.

Single-site mutational engineering and following monoPEGylation of the human lectin galectin-2: effects on ligand binding, functional aspects, and clearance from serum

The emerging insights into the physiological significance of endogenous lectins prompted us to characterize the effect of monosubstitution with poly(ethylene glycol) (PEG; 5 kDa) on a human lectin. As role model, we used a member of the galectin family, that is, galectin-2, the Cys57Met (single-site) mutant and its monoPEGylated derivative. The activities of these three proteins were comparatively studied by biochemical, cell biological, and histochemical methods, using surface-immobilized glycoproteins, different types of cells presenting gangliosides or (glyco)proteins as counterreceptors in vitro and tissue sections. PEGylation led to decreases in affinity/signal intensity with context dependence. The introduction of the mutation, too, can influence reactivity. Assays on haemagglutination and inhibition of cell proliferation underscored that mutational engineering and substitution can (but must not necessarily) affect this protein's activity. Serum clearance in rats was markedly retarded by PEGylation. Overall, the bulky substitution, spatially comparable to N-glycans, can markedly reduce binding of the galectin to physiological binding sites.

Context-dependent multifunctionality of galectin-1: a challenge for defining the lectin as therapeutic target

INTRODUCTION

One route of translating the information encoded in the glycan chains of cellular glycoconjugates into physiological effects is via receptor (lectin) binding. A family of endogenous lectins, sharing folding, a distinct sequence signature and affinity for β-galactosides (thus termed galectins), does so effectively in a context-dependent manner.

AREAS COVERED

An overview is given on the multifunctional nature of galectins, with emphasis on galectin-1. The broad range of functions includes vital processes such as adhesion via glycan bridging, glycoconjugate transport or triggering signaling relevant, for example, for growth regulation. Besides distinct glycoconjugates, this lectin can also interact with certain proteins so that it can target counterreceptors at all sites of location, that is, in the cytoplasm and/or nucleus, at both sides of the membrane or extracellularly. Approaches to strategically exploit galectin activities with therapeutic intentions are outlined.

EXPERT OPINION

The wide versatility of sugar coding and the multifunctionality of galectin-1 explain why considering to turn the protein into a therapeutic target is an ambitious aim. Natural pathways shaped by physiologic master regulators (e.g., the tumor suppressor p16(INK4a)) are suggested to teach inspiring lessons as to how the lectin might be recruited to clinical service.

T cell responses against microsatellite instability-induced frameshift peptides and influence of regulatory T cells in colorectal cancer

High-level microsatellite-unstable (MSI-H) colorectal carcinomas (CRC) represent a distinct subtype of tumors commonly characterized by dense infiltration with cytotoxic T cells, most likely due to expression of MSI-H-related frameshift peptides (FSP). The contribution of FSP and classical antigens like MUC1 and CEA to the cellular immune response against MSI-H CRC had not been analyzed so far. We analyzed tumor-infiltrating and peripheral T cells from MSI-H (n = 4 and n = 14, respectively) and microsatellite-stable (MSS) tumor patients (n = 26 and n = 17) using interferon gamma ELISpot assays. Responses against 4 FSP antigens and peptides derived from MUC1 to CEA were compared with and without depletion of regulatory T cells, and the results were related to the presence of the respective antigens in tumor tissue. Preexisting FSP-specific T cell responses were detected in all (4 out of 4) tumor-infiltrating and in the majority (10 out of 14) of peripheral T cell samples from MSI-H CRC patients, but rarely observed in MSS CRC patients. Preexisting T cell responses in MSI-H CRC patients were significantly more frequently directed against FSP tested in the present study than against peptides derived from classical antigens MUC1 or CEA (p = 0.049). Depletion of regulatory T cells increased the frequency of effector T cell responses specific for MUC1/CEA-derived peptides and, to a lesser extent, T cell responses specific for FSP. Our data suggest that the analyzed FSP may represent an immunologically relevant pool of antigens capable of eliciting antitumoral effector T cell responses.

The influence of preoperative serum anticholinergic activity and other risk factors for the development of postoperative cognitive dysfunction after cardiac surgery

OBJECTIVE

Patients undergoing cardiac surgery are at risk for postoperative cognitive dysfunction (POCD). Evaluating preoperative risk factors represents 1 possible way to minimize the postoperative risk of cognitive dysfunction. We investigated marked deterioration in cholinergic neurotransmission as 1 such potential risk factor for transient and long-lasting POCD. Serum anticholinergic activity (SAA) has already been described as a risk factor for developing delirium in an elderly study population. However, the role of SAA for long-lasting POCD is unknown.

METHODS

Following local ethics board approval and written informed consent, we recruited a cohort of patients aged ≥ 55 years undergoing cardiac surgery. Before surgery, levels of SAA were measured and a battery of neuropsychologic tests (NPTs) was applied. S100 calcium binding protein ß concentration was measured intraoperatively. Pre-, intra-, and postoperative patient-specific characteristics were recorded. The NPTs were repeated 3 months after hospital discharge to evaluate 3-month POCD. A group of nonsurgical patients (n = 34) was recruited as control subjects to adjust NPT scores, using reliable methods for the change index. Logistic multivariate regression was used to evaluate independent predictors of POCD.

RESULTS

One hundred fifty-four patients were screened before surgery, and 117 completed the second NPT. POCD was identified in 25.6% of patients. In contrast to intraoperatively increased S100 calcium binding protein ß, preoperative SAA was not associated with POCD following adjustment for covariates.

CONCLUSIONS

Preoperatively increased SAA did not predict POCD 3 months after cardiac surgery.

Moderately reduced ATP levels promote oxidative stress and debilitate autophagic and phagocytic capacities in human RPE cells

PURPOSE

Aging of the RPE is associated with a decrease of intracellular ATP levels and increased oxidative stress. We investigated the effects of moderate energy deficit on intracellular glutathione levels, oxidative damage of cellular proteins and DNA, and autophagy rates using an RPE cell culture model. Additionally, phagocytosis of photoreceptor outer segments was assayed as an example of an ATP-dependent normal function of the RPE.

METHODS

ATP synthesis of primary human RPE cells was moderately inhibited by atractyloside. Oxidative stress was induced by tert-butyl hydroperoxide (tBH). ATP, reduced glutathione (rG), malondialdehyde (MDA) adduct formation and 8-hydroxydeoxyguanosine (8OHdG) levels were measured. Autophagy and phagocytosis of photoreceptor outer segments were assayed by radiometric methods.

RESULTS

Atractyloside-treatment reduced cellular ATP levels by 30%, mimicking the energy status of aged RPE. tBH decreased rG in RPE cells with lowered ATP levels whereas cells with normal ATP content were not affected. tBH-induced oxidative stress resulted in substantial accumulation of MDA protein adducts in cells with lowered ATP while cells with regular ATP levels were only modestly affected. tBH induced more oxidative DNA damage (8OHdG formation) in cells with lowered ATP levels than in cells with regular ATP. In atractyloside-treated cells, autophagy rates decreased 3-fold as compared with controls. Phagocytic capacity for uptake and degradation of photoreceptor segments was reduced in RPE with low ATP.

CONCLUSIONS

Moderately decreased ATP levels such as seen in aged individuals might contribute to the vulnerability of RPE to oxidative stress damage and to dysfunction.

Notch1 signaling promotes survival of glioblastoma cells via EGFR-mediated induction of anti-apoptotic Mcl-1

The Notch1-mediated signaling pathway has a central role in the maintenance of neural stem cells and contributes to growth and progression of glioblastomas, the most frequent malignant brain tumors in adults. Here, we demonstrate that the Notch1 receptor promotes survival of glioblastoma cells by regulation of the anti-apoptotic Mcl-1 protein. Notch1-dependent regulation of Mcl-1 occurs cell type dependent at a transcriptional or post-translational level and is mediated by the induction of epidermal growth factor receptor (EGFR). Inhibition of the Notch1 pathway overcomes apoptosis resistance and sensitizes glioblastoma cells to apoptosis induced by ionizing radiation, the death ligand TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) or the Bcl-2/Bcl-XL inhibitor ABT-737. In conclusion, targeting Notch1 might represent a promising novel strategy in the treatment of glioblastomas.

Lysosomal stress and lipid peroxidation products induce VEGF-121 and VEGF-165 expression in ARPE-19 cells

BACKGROUND

Pathologically increased VEGF-A expression is considered a major pathogenic factor in exudative AMD. Since VEGF-A can exist in isoforms with different individual functions, for a detailed understanding of the role of VEGF-A in normal and disease associated processes, in particular in wet AMD, the expression pattern of VEGF-A isoforms has to be taken into account. Therefore in the present study, adressing the effects of lysosomal dysfunction on VEGF expression and secretion by RPE cells induced by lipid peroxidation products and an inhibitor of lysosomal acidification, we applied quantitative methods discriminating the major VEGF-A isoforms.

METHODS

ARPE-19 cells were treated with the primary lipid peroxidation products 4-hydroxynonenal (HNE), malondialdehyde (MDA) or the lysosomal inhibitor bafilomycin A. VEGF-A isoforms were determined by splice-variant-specific RT-PCR. For detection of protein levels, a protein prefractionation strategy based on the strikingly different isoelectric points of VEGF isoforms was used prior to quantification of VEGF-A 121, -165, -189 and -206 expression by ELISA.

RESULTS

On mRNA level, VEGF-A 165 represents the major isoform (60%), VEGF-A 121 accounts for about one-third, and VEGF-A 189 for about 10% of total mRNA detected in untreated cells. No VEGF-A 206 mRNA was detected. Treatment with bafilomycin A increased VEGF-A 121 and VEGF-A 165 mRNA levels. VEGF-A 189 expression remained unaffected, and no induction of VEGF-A 206 mRNA was detectable. Similar effects were observed when cells were stressed with HNE or MDA. On protein level, bafilomycin A as well as the lipid peroxidation products caused an increase of total VEGF-A protein secretion into the culture medium. In analysis of VEGF-A for different splice variants, only VEGF-A 121 and VEGF-A 165 were detected, the latter representing the major secreted isoform, with the ratio of both isoforms being slightly changed in favour of VEGF-A 165 secretion.

CONCLUSION

Lysosomal dysfunction and lipid peroxidation damage might be an inducer of VEGF-A 121 and VEGF-A 165 expression in the retina. Furthermore, the novel technique used to analyze the protein expression pattern of VEGF- A isoforms in biological samples may represent a valuable tool in future analyses of specific VEGF-A isoforms in normal and pathogenic functions.

Increased cortisol levels and anticholinergic activity in cognitively unimpaired patients

Increased patients' serum anticholinergic activity (SAA) is described as a marker of cognitive dysfunction and can be influenced by different exogenous and endogenous factors. The role of cortisol in relation to SAA and cognition in perioperative conditions has not been investigated so far. In 30 men scheduled for urological surgery, the authors determined SAA and cortisol levels in blood and CSF and conducted neuropsychological testing in two subgroups with comparable pre- and intraoperative characteristics, one group with low SAA (mean=2.4 [SD=0.9], n=23) and the other with high SAA (mean=5.1 [SD=2.4], n=7) values. Increased SAA was associated with two times the number of anticholinergic medications but not with patients' age, medical history or impaired cognition. A significant linear correlation was detected between anticholinergic activities and cortisol levels. Thus, endogenous factors such as patients' stress levels should be taken into account for interpretation of the role of SAA.

[Juvenile neuronal ceroid lipofuscinosis. Ophthalmologic findings and differential diagnosis]

Neuronal ceroid lipofuscinoses (NCL) are a heterogeneous group of neurodegenerative diseases with mostly autosomal recessive inheritance whose common feature is the intralysosomal accumulation of ceroid lipofuscin. With varying manifestation ages the diseases result in cognitive and motor deterioration, epilepsy, diffuse retinal degeneration, and eventually death. Juvenile ceroid lipofuscinosis (JNCL, CLN3, Batten disease) has the distinctive feature that the ophthalmologic symptoms precede the neurologic symptoms by several years, and thus the ophthalmologist plays a central role in early diagnosis. Important clinical signs of JNCL include bull's eye maculopathy, severely reduced Ganzfeld ERG already at initial presentation, and unusually rapid progression of the functional decline. If JNCL is clinically suspected the diagnosis can be made by means of a standard blood smear and confirmed by genetic detection of the mutation. Although causal therapeutic options are currently only in the developmental stage, early diagnosis by the ophthalmologist is of utmost importance to allow for medical and educational support of the affected child and for adequate counseling of the parents.

How adhesion/growth-regulatory galectins-1 and -3 attain cell specificity: case study defining their target on neuroblastoma cells (SK-N-MC) and marked affinity regulation by affecting microdomain organization of the membrane

Galectins are potent effectors with conspicuous cell-type-specific activity profile. Its occurrence poses the question on the nature of the underlying biochemical determinants, in human SK-N-MC neuroblastoma cells involved in negative growth regulation. Since increase of surface presentation of ganglioside GM1 and homodimeric galectin-1 precedes growth inhibition, a direct interaction is suggested. We thus examined cell binding depending on glucosylceramide synthesis. It was drastically reduced by N-butyldeoxynojirimycin and threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol, adding decisive evidence for the assumed galectin/ganglioside binding. Glycoproteins do not compensate ganglioside depletion which was verified by measuring lipid-bound sialic acid. Binding affinity is significantly lowered by disrupting microdomain integrity, also effective for the competitive inhibitor galectin-3. This was caused by cell treatment with either 2-hydroxypropyl-beta-cyclodextrin or filipin III. In this cell system, target specificity and topology of ligand presentation act together to enable high-affinity binding.

Danger signaling protein HMGB1 induces a distinct form of cell death accompanied by formation of giant mitochondria

Cells dying by necrosis release the high-mobility group box 1 (HMGB1) protein, which has immunostimulatory effects. However, little is known about the direct actions of extracellular HMGB1 protein on cancer cells. Here, we show that recombinant human HMGB1 (rhHMGB1) exerts strong cytotoxic effects on malignant tumor cells. The rhHMGB1-induced cytotoxicity depends on the presence of mitochondria and leads to fast depletion of mitochondrial DNA, severe damage of the mitochondrial proteome by toxic malondialdehyde adducts, and formation of giant mitochondria. The formation of giant mitochondria is independent of direct nuclear signaling events, because giant mitochondria are also observed in cytoplasts lacking nuclei. Further, the reactive oxygen species scavenger N-acetylcysteine as well as c-Jun NH(2)-terminal kinase blockade inhibited the cytotoxic effect of rhHMGB1. Importantly, glioblastoma cells, but not normal astrocytes, were highly susceptible to rhHMGB1-induced cell death. Systemic treatment with rhHMGB1 results in significant growth inhibition of xenografted tumors in vivo. In summary, rhHMGB1 induces a distinct form of cell death in cancer cells, which differs from the known forms of apoptosis, autophagy, and senescence, possibly representing an important novel mechanism of specialized necrosis. Further, our findings suggest that rhHMGB1 may offer therapeutic applications in treatment of patients with malignant brain tumors.

Early postoperative delirium after open-heart cardiac surgery is associated with decreased bispectral EEG and increased cortisol and interleukin-6

PURPOSE

It is difficult to substantiate the clinical diagnosis of postoperative delirium with objective parameters in intensive care units (ICU). The purpose of this study was to analyze (1) whether the bilateral bispectral (BIS) index, (2) cortisol as a stress marker, and (3) interleukin-6 as a marker of inflammation were different in delirious patients as compared to nondelirious ones after cardiac surgery.

METHODS

On the first postoperative day, delirium was analyzed in 114 patients by using the confusion assessment method for ICU (CAM-ICU). Bilateral BIS data were determined; immediately thereafter plasma samples were drawn to analyze patients' blood characteristics. The current ICU medication, hemodynamic characteristics, SOFA and APACHE II scores, and artificial ventilation were noted.

RESULTS

Delirium was detected at 19.1 ± 4.8 h after the end of surgery in 32 of 114 patients (28%). Delirious patients were significantly older than nondelirious ones and were artificially ventilated 4.7-fold more often during the testing. In delirious patients, plasma cortisol and interleukin-6 levels were higher (p = 0.01). The mean BIS index was significantly lower in delirious patients (72.6 (69.6-89.1); median [interquartile range (IQR), 25th-75th percentiles] than in nondelirious patients, 84.8 (76.8-89.9). BIS EEG raw data analysis detected significant lower relative alpha and higher theta power. A significant correlation was found between plasma cortisol levels and BIS index.

CONCLUSIONS

Early postoperative delirium after cardiac surgery was characterized by increased stress levels and inflammatory reaction. BIS index measurements showed lower cortical activity in delirious patients with a low sensitivity (27%) and high specificity (96%).

N-domain of human adhesion/growth-regulatory galectin-9: preference for distinct conformers and non-sialylated N-glycans and detection of ligand-induced structural changes in crystal and solution

Human tandem-repeat-type galectin-9 is a potent adhesion/growth-regulatory effector via lectin capacity of its N- and C-terminal domains. This bioactivity prompted further crystallographic study of the N-domain, combined with analysis in solution. Binding of lactose markedly increased the N-domain's resistance to thermal denaturation. Crystallography revealed its intimate contact profile, besides detecting an extension of the beta-sandwich fold by an antiparallel beta-strand F0 aligned to the C-terminal F1 strand. Ligand accommodation in its low-energy conformation leads to a movement of Arg87's side chain. As consequence, the ligand's glucose moiety and Arg87 become hydrogen bonded. The resulting predictions for spatial parameters in solution were verified by determining (a) the pattern of magnetization transfer from the protein to protons of lactose and Forssman disaccharide by NMR spectroscopy and (b) the ellipticity changes at wavelengths characteristic for Trp/Tyr residues in near-UV CD spectroscopy. Whereas solid-phase assays confirmed a previously noted tendency for homo- and heterotypic aggregation, gel filtration and ultracentrifugation disclosed monomeric status in solution, in line with crystallographic data. Using cell mutants with defects in glycosylation, this lectin domain was shown to preferentially bind N-glycans without alpha2,3-sialylation. Since proximal promoter sequences were delineated to diverge markedly among galectin genes and resulting differences in expression profiles were exemplarily documented immunohistochemically, the intrafamily diversification appears to have assigned this protein to a characteristic expression and activity profile among galectins. Our data thus take the crystallographic information to the level of the lectin in solution and in tissues by a strategic combination of spectroscopic and cell/histochemical assays.

Small intestinal mucosa expression of putative chaperone fls485

Background

Maturation of enterocytes along the small intestinal crypt-villus axis is associated with significant changes in gene expression profiles. fls485 coding a putative chaperone protein has been recently suggested as a gene involved in this process. The aim of the present study was to analyze fls485 expression in human small intestinal mucosa.

Methods

fls485 expression in purified normal or intestinal mucosa affected with celiac disease was investigated with a molecular approach including qRT-PCR, Western blotting, and expression strategies. Molecular data were corroborated with several in situ techniques and usage of newly synthesized mouse monoclonal antibodies.

Results

fls485 mRNA expression was preferentially found in enterocytes and chromaffine cells of human intestinal mucosa as well as in several cell lines including Rko, Lovo, and CaCo2 cells. Western blot analysis with our new anti-fls485 antibodies revealed at least two fls485 proteins. In a functional CaCo2 model, an increase in fls485 expression was paralleled by cellular maturation stage. Immunohistochemistry demonstrated fls485 as a cytosolic protein with a slightly increasing expression gradient along the crypt-villus axis which was impaired in celiac disease Marsh IIIa-c.

Conclusions

Expression and synthesis of fls485 are found in surface lining epithelia of normal human intestinal mucosa and deriving epithelial cell lines. An interdependence of enterocyte differentiation along the crypt-villus axis and fls485 chaperone activity might be possible.

Crosstalk between Hsp70 molecular chaperone, lysosomes and proteasomes in autophagy-mediated proteolysis in human retinal pigment epithelial cells

The pathogenesis of age-related macular degeneration involves chronic oxidative stress, impaired degradation of membranous discs shed from photoreceptor outer segments and accumulation of lysosomal lipofuscin in retinal pigment epithelial (RPE) cells. It has been estimated that a major part of cellular proteolysis occurs in proteasomes, but the importance of proteasomes and the other proteolytic pathways including autophagy in RPE cells is poorly understood. Prior to proteolysis, heat shock proteins (Hsps), agents that function as molecular chaperones, attempt to refold misfolded proteins and thus prevent the accumulation of cytoplasmic protein aggregates. In the present study, the roles of the Hsp70 molecular chaperone and proteasomal and lysosomal proteolytic pathways were evaluated in human RPE cells (ARPE-19). The Hsp70 and ubiquitin protein levels and localization were analysed by Western blotting and immunofluorescense. Confocal and transmission electron microscopy were used to detect cellular organelles and to evaluate the morphological changes. Hsp70 levels were modulated using RNA interference and overexpression techniques. Cell viability was measured by colorimetric assay. The proteasome inhibitor MG-132 evoked the accumulation of perinuclear aggregates positive for Hsp70, ubiquitin-protein conjugates and the lysosomal membrane protein LAMP-2. Interestingly, the hsp70 mRNA depletion significantly increased cell death in conjunction with proteasome inhibition. We found that the accumulation of lysosomes was reversible: a cessation of proteasome inhibition led to clearance of the deposits via a mechanism believed to include autophagy. The molecular chaperone Hsp70, proteasomes and autophagy have an important regulatory role in the protein turnover of human RPE cells and may thus open new avenues for understanding degenerative processes in retinal cells.

Apical-to-basolateral transcytosis of photoreceptor outer segments induced by lipid peroxidation products in human retinal pigment epithelial cells

PURPOSE

Progressive accumulation of extracellular material at the basolateral side of the retinal pigment epithelium (RPE) is a key event in the pathogenesis of age-related macular degeneration (AMD). The authors previously demonstrated that modifications with lipid peroxidation products, such as 4-hydroxynonenal (HNE) and malondialdehyde (MDA), stabilize photoreceptor outer segment (POS) proteins against lysosomal degradation. Herein, they tested RPE cells for the basolateral release of undegraded modified POS proteins.

METHODS

Polarized cultures of the human RPE cell line ARPE-19 on permeable membranes were incubated with iodine-125-labeled POS on the apical side. After 24 hours, radioactivity was quantified in apical medium, cell lysates, and basolateral medium after separation of undegraded proteins by precipitation. Protein composition of basolaterally released POS material was analyzed by two-dimensional gel electrophoresis. C3a- and SC5b-9-specific enzyme-linked immunosorbent assays were used to assess complement activation by modified POS.

RESULTS

The amount of phagocytic uptake was similar for native and modified POS. Unmodified POS proteins were almost completely (98.1%) degraded, whereas degradation of HNE- and MDA-modified POS proteins was significantly reduced (47.2%; 56.5%). Undegraded POS proteins accumulated intracellularly (14.2%; 12.1%) and were trafficked through the cells to be released into the basolateral medium (38.5%; 31.5%). Protein composition of basolaterally released material matched the original POS preparations. Protein modifications did not confer increased complement-activating capacity to POS material.

CONCLUSIONS

Inhibition of lysosomal degradation by lipid peroxidation-related protein modifications induces apical-to-basolateral transcytosis of undegraded POS proteins by human RPE cells in vitro. This mechanism may contribute to sub-RPE deposit formation and drusen biogenesis in AMD.

Compensation of loss of protein function in microsatellite-unstable colon cancer cells (HCT116): a gene-dependent effect on the cell surface glycan profile

Tumors that display a high level of microsatellite instability (MSI-H) accumulate somatic frameshift mutations in several genes. The compensation of this loss of function by transfection represents a suitable approach to tie respective gene deficiency to alterations in cellular characteristics. In view of the emerging significance of cell surface glycans as biochemical signals for presentation/activity of various receptors/integrins and for susceptibility to adhesion/growth-regulatory tissue lectins, we examined the glycophenotype in the MSI-H colon cancer cell line HCT116 for activin type 2 receptor (ACVR2), absent in melanoma 2 (AIM2), and transforming growth factor beta-type 2 receptor (TGFBR2) known to be associated with MSI colorectal carcinogenesis. A panel of probes specific for functional carbohydrate epitopes including human lectins was used to trace changes in cell surface levels, thereby initiating glycan analysis related to MSI. In particular, the presence of core substitutions and branching in N-glycans, the sialylation status of N- and O-glycans, and the presence of Le(a/x)-epitopes were profiled. Transient transfection affected the glycophenotype, depending on the nature of the gene and the probe. The TGFBR2 presence reduced binding of probes specific for a core substitution and increased branch length in N-glycosylation, even reaching a P-value of 0.0016. ACVR2/AIM2 influenced core 1 mucin-type O-glycosylation differentially, upregulation by ACVR2, and downregulation by AIM2. These alterations of cell surface glycosylation by gene products that are not directly associated with the machinery for glycan generation direct attention to pursue analysis of glycosylation in MSI tumor cells on the level of target glycoproteins and open the way for functional studies.

Characterization of humoral immune responses against p16, p53, HPV16 E6 and HPV16 E7 in patients with HPV-associated cancers

The cellular tumor suppressor p16 is strongly overexpressed in cervical cancers and precancers. We have previously demonstrated that infiltrating T lymphocytes reactive against p16 can be found in cervical cancer patients. Here, we analyzed whether p16 induces humoral immune responses. Sera of patients with cervical cancer, oropharyngeal cancer, colorectal cancer and autoimmune disease were included. A total of 919 sera were analyzed, including 486 matched sera from a cervical cancer case control study. p16 antibodies were analyzed in Western blot and a newly developed peptide ELISA covering the complete p16 protein. In addition, a Luminex-based multiplex assay was used for simultaneous detection of antibodies directed against p16, p53, HPV16 E6 and HPV16 E7. In all entities, only low p16 antibody reactivity was observed. Epitope mapping revealed 2 predominant epitope regions of the p16 protein. No significant difference in p16 antibody frequency (OR = 0.9; 95% CI = 0.6-1.3) and p53 antibody frequency (OR = 0.6; 95% CI = 0.3-1.2) was found between patients and healthy controls in the cervical cancer case control study. Antibodies against the HPV16 oncoproteins E6 and E7 were detected more frequently in cervical cancer patients when compared with healthy controls (E6 OR = 27.8; 95% CI = 11.1-69.7, E7 OR = 5.7; 95% CI = 2.9-11.1). In conclusion, despite the strong expression of p16 and the observed induction of cellular immune responses, antibody reactivity against p16 was observed only at very low levels independent of the disease background.

[Pathomechanisms for aging of retinal pigment epithelium (RPE) and prophylactic therapy options in regard to AMD]

An intact retinal pigment epithelium (RPE) represents an essential condition for the visual process. This post-mitotic RPE monolayer combines different functions such as degradation of photoreceptor outer segments, vitamin A cycle, support of retinal metabolism and maintenance of the outer blood-retina barrier. As a consequence of excessive metabolism, high oxygen levels, exposition to light of short wave length and ensuing radical formation, the RPE is highly dependent on protective systems. In spite of differentiated defence mechanisms, aging processes cause cumulative RPE damage, representing a major component of age-related macular degeneration (AMD), the leading cause of irreversible severe vision loss in people over 50 years old. A better understanding of the underlying pathophysiology will help to develop new prophylactic options which is becoming more and more important with increasing life expectancy.

Phosphorylated human galectin-3: facile large-scale preparation of active lectin and detection of structural changes by CD spectroscopy

Galectin-3 has a unique modular design. Its short N-terminal stretch can be phosphorylated, relevant for nuclear export and anti-anoikis/apoptosis activity. Enzymatic modification by casein kinase 1 at constant ATP concentration yielded mg quantities of mono- and diphosphorylated derivatives at Ser5/Ser11 in a 2:1 ratio. Their carbohydrate-inhibitable binding to asialofetuin, cell surfaces of three tumor lines, rabbit erythrocytes leading to haemagglutination and cytoplasmic sites in fixed tissue sections was not markedly altered relative to phosphate-free galectin-3. Spectroscopically, phosphorylation induced alterations in the far UV CD, indicative of an increase in ordered structure. This is accompanied by changes in the environment of aromatic amino acids signified by shifts in the near UV CD.

Prototype chicken galectins revisited: characterization of a third protein with distinctive hydrodynamic behaviour and expression pattern in organs of adult animals

Prototype galectins are versatile modulators of cell adhesion and growth via their reactivity to certain carbohydrate and protein ligands. These functions and the galectins' marked developmental regulation explain their attractiveness as models to dissect divergent evolution after gene duplication. Only two members have so far been assumed to constitute this group in chicken, namely the embryonic muscle/liver form {C-16 or CLL-I [16 kDa; chicken lactose lectin, later named CG-16 (chicken galectin-16)]} and the embryonic skin/intestine form (CLL-II or C-14; later named CG-14). In the present study, we report on the cloning and expression of a third prototype CG. It has deceptively similar electrophoretic mobility compared with recombinant C-14, the protein first isolated from embryonic skin, and turned out to be identical with the intestinal protein. Hydrodynamic properties unusual for a homodimeric galectin and characteristic traits in the proximal promoter region set it apart from the two already known CGs. Their structural vicinity to galectin-1 prompts their classification as CG-1A (CG-16)/CG-1B (CG-14), whereas sequence similarity to mammalian galectin-2 gives reason to refer to the intestinal protein as CG-2. The expression profiling by immunohistochemistry with specific antibodies discerned non-overlapping expression patterns for the three CGs in several organs of adult animals. Overall, the results reveal a network of three prototype galectins in chicken.

EEG changes and serum anticholinergic activity measured in patients with delirium in the intensive care unit

The aim of this study was to examine whether serum anticholinergic activity (SAA) is a reliable indicator of delirium in the ICU, and whether there is a significant correlation between SAA and quantitative electroencephalographic (EEG) data in delirious patients. In a prospective cohort study, we assessed ICU patients diagnosed with delirium (n = 37). EEG measurements and blood analysis including SAA were performed 48 h following ICU admission. The presence of delirium was evaluated using the Confusion Assessment Method for critically ill patients in ICU (CAM-ICU). The SAA level was measured using a competitive radioreceptor binding assay for muscarinergic receptors and quantitative EEG was measured using the CATEEM system. We found that, under comparable conditions, patients in the delirium group showed a higher relative EEG theta power and a reduced alpha power (n = 17) than did the non-delirious patients (n = 20). No difference in measured SAA levels were seen; therefore, there was no correlation between SAA and EEG measurements in delirious patients. We conclude that, in contrast to the EEG, the SAA level cannot be proposed as a tool for diagnosing delirium in ICU patients.

Regulation of enterocyte apoptosis by acyl-CoA synthetase 5 splicing

BACKGROUND AND AIMS

The constant renewal of enterocytes along the crypt-villus axis (CVA) of human small intestine is due to cell-inherent changes resulting in the apoptotic cell death of senescent enterocytes. The aim of the present study was to examine underlying molecular mechanisms of the cell death at the villus tip.

METHODS

Characterization of human acyl-coenzyme A (CoA) synthetase 5 (ACSL5) was performed by cloning, recombinant protein expression, biochemical approaches, and several functional and in situ analyses.

RESULTS

Our data show that different amounts of acyl-CoA synthetase 5-full length (ACSL5-fl) and a so far unknown splice variant lacking exon 20 (ACSL5-Delta 20) are found in human enterocytes. In contrast with the splice variant ACSL5-Delta 20, recombinant and purified ACSL5-fl protein is active at a highly alkaline pH. Over expression of ACSL5-fl protein is associated with a decrease of the anti-apoptotic FLIP protein in a ceramide-dependent manner and an increased cell-surface expression of the death receptor TRAIL-R1. Expression analyses revealed that the ACSL5-fl/ACSL5-Delta 20 ratio increases along the CVA, thereby sensitizing ACSL5-fl-dominated cells at the villus tip to the death ligand TRAIL, which is corroborated by functional studies with human small intestinal mucosal samples and an immortalized human small intestinal cell line.

CONCLUSIONS

Our results suggest an ACSL5-dependent regulatory mechanism that contributes to the cellular renewal along the CVA in human small intestine. Deregulation of the ACSL5-fl/ACSL5-Delta 20 homeostasis in the maturation and shedding of cells along the CVA might also be of relevance for the development of intestinal neoplasia.

Carbohydrate chain of ganglioside GM1 as a ligand: identification of the binding strategies of three 15 mer peptides and their divergence from the binding modes of growth-regulatory galectin-1 and cholera toxin

The branched pentasaccharide chain of ganglioside GM1 is a prominent cell surface ligand, for example, for cholera toxin or tumor growth-regulatory homodimeric galectins. This activity profile via protein recognition prompted us to examine the binding properties of peptides with this specificity. Our study provides insights into the mechanism of molecular interaction of this thus far unexplored size limit of the protein part. We used three pentadecapeptides in a combined approach of mass spectrometry, NMR spectroscopy and molecular modelling to analyze the ligand binding in solution. Availability of charged and hydrophobic functionalities affected the intramolecular flexibility of the peptides differently. Backfolding led to restrictions in two cases; the flexibility was not reduced significantly by association of the ligand in its energetically privileged conformations. Major contributions to the interaction energy arise from the sialic acid moiety contacting Arg/Lys residues and the N-terminal charge. Considerable involvement of stacking between the monovalent ligand and aromatic rings could not be detected. This carbohydrate binding strategy is similar to how an adenoviral fiber knob targets sialylated glycans. Rational manipulation for an affinity enhancement can now be directed to reduce the flexibility, exploit the potential for stacking and acquire the cross-linking capacity of the natural lectins by peptide attachment to a suitable scaffold.

High clozapine concentrations in leukocytes in a patient who developed leukocytopenia

Up to now direct toxic effects or immunological processes have been said to explain clozapine-induced agranulocytosis. However, more recent studies may suggest that not yet metabolized clozapine is taken up by leukocytes and transformed by oxidative processes to apoptosis-inducing metabolites. To verify this hypothesis the concentrations of clozapine were measured in the plasma and the leukocytes of a patient receiving clozapine who developed clozapine-induced leukocytopenia and in 10 patients receiving clozapine who did not show any serious adverse side effects. The patient who developed leukocytopenia showed clozapine concentrations in the leukocytes that were about 8 times higher than the mean clozapine concentrations in the leukocytes in the group of 10 patients receiving clozapine with no changes in the leukocyte count in the history. However, no major difference was found in the clozapine plasma concentrations. The results may suggest that patients at risk of developing clozapine-induced leukocytopenia show increased clozapine concentrations in the leukocytes although the clozapine plasma concentration is in the therapeutic range. It is assumed that changes or abnormalities of clozapine uptake at the cell membrane might play a role in the development of clozapine-induced leukocytopenia and/or agranulocytosis.

Tumor suppressor p16INK4a--modulator of glycomic profile and galectin-1 expression to increase susceptibility to carbohydrate-dependent induction of anoikis in pancreatic carcinoma cells

Expression of the tumor suppressor p16(INK4a) after stable transfection can restore the susceptibility of epithelial tumor cells to anoikis. This property is linked to increases in the expression and cell-surface presence of the fibronectin receptor. Considering its glycan chains as pivotal signals, we assumed an effect of p16(INK4a) on glycosylation. To test this hypothesis for human Capan-1 pancreatic carcinoma cells, we combined microarray for selected glycosyltransferase genes with 2D chromatographic glycan profiling and plant lectin binding. Major differences between p16-positive and control cells were detected. They concerned expression of beta1,4-galactosyltransferases (down-regulation of beta1,4-galactosyltransferases-I/V and up-regulation of beta1,4-galactosyltransferase-IV) as well as decreased alpha2,3-sialylation of O-glycans and alpha2,6-sialylation of N-glycans. The changes are compatible with increased beta(1)-integrin maturation, subunit assembly and binding activity of the alpha(5)beta(1)-integrin. Of further functional relevance in line with our hypothesis, we revealed differential reactivity towards endogenous lectins, especially galectin-1. As a result of reduced sialylation, the cells' capacity to bind galectin-1 was enhanced. In parallel, the level of transcription of the galectin-1 gene increased conspicuously in p16(INK4a)-positive cells, and even figured prominently in a microarray on 1996 tumor-associated genes and in proteomic analysis. The cells therefore gain optimal responsiveness. The correlation between genetically modulated galectin-1 levels and anoikis rates in engineered transfectants inferred functional significance. To connect these findings to the fibronectin receptor, galectin-1 was shown to be co-immunoprecipitated. We conclude that p16(INK4a) orchestrates distinct aspects of glycosylation that are relevant for integrin maturation and reactivity to an endogenous effector as well as the effector's expression. This mechanism establishes a new aspect of p16(INK4a) functionality.

Tyrosinase biosynthesis and trafficking in adult human retinal pigment epithelial cells

BACKGROUND

Tyrosinase (EC 1.14.18.1) is the key enzyme of melanin pigment formation and it is unclear whether it is synthesized in human postnatal retinal pigment epithelium (RPE). In this study, we investigated if phagocytosis of rod outer segments (ROS) can increase tyrosinase expression in vitro.

METHODS

Primary cultures of human RPE cells were fed with isolated ROS from cattle and with latex particles. After phagocytosis, RPE cells were tested for tyrosinase presence and activity with several independent methods: (1) immunocytochemistry with anti-tyrosinase antibodies and (2) ultrastructural as well as light microscopic DOPA histochemistry; (3) mRNA was isolated from human RPE before incubation with ROS and 5, 20 and 40 h after feeding with ROS. The amount of tyrosinase mRNA was determined quantitatively by real-time reverse transcription polymerase chain reaction (RT-PCR), and the tyrosinase activity was investigated by measuring tyrosine hydroxylase activity using [(3)H]tyrosine.

RESULTS

Tyrosinase was found in fed RPE cells using these methods, but was absent without feeding. Furthermore, we showed co-localization of rhodopsin and tyrosinase in the fed RPE cells. Contrary to tyrosinase activity, the mRNA for tyrosinase was clearly present in the cultured RPE cells which had not been exposed to ROS, decreased significantly from 5 h after exposure to ROS and returned to its original non-fed level 40 h after ROS feeding.

CONCLUSION

Our study does not present new evidence that de novo melanogenesis takes place in the adult differentiated RPE. However, in contrast to the classic hypothesis, which states that tyrosinase is only detected in embryos, we provide evidence with several independent methods that the expression of tyrosinase and its enzymatic activity are induced in cultured human adult RPE by phagocytosis of ROS.

Tyrosinase biosynthesis in adult mammalian retinal pigment epithelial cells

Tyrosinase (EC 1.14.18.1) is the rate limiting enzyme of melanogenesis and it is unclear whether it is synthesized in postnatal retinal pigment epithelium (RPE). Cultured RPE cells from cattle were fed with isolated rod outer segments (ROS). After phagocytosis, RPE cells were tested for tyrosinase presence and activity with three independent methods: (1) ultrastructural DOPA (l-3,4-dihydroxyphenylalanine) histochemistry (2) immunocytochemistry with anti-tyrosinase antibodies (3) measuring tyrosine hydroxylase activity using [(3)H]tyrosine. With all three methods tyrosinase was found in RPE cells after ROS-feeding but was absent without feeding. In contrast to the classical hypothesis, we demonstrated with three independent methods that the expression of tyrosinase and its enzymatic activity are induced in cultured adult RPE by phagocytosis of rod outer segments (ROS) in vitro.

Coeliac disease is associated with impaired expression of acyl-CoA-synthetase 5

BACKGROUND AND AIMS

Coeliac disease and other disorders of the small intestine are associated with disturbances in mucosal architecture. The most severe injury to tissue architecture is villus atrophy. In coeliac disease, molecules reflecting the state of the villus architecture are not well characterized at present.

MATERIALS AND METHODS

Expression of acyl-CoA-synthetase 5 (ACS5) was studied in unaffected human small/large intestinal tissue and in coeliac disease using several methods including molecular techniques, as well as an in situ approach using a novel established monoclonal antibody directed against human ACS5.

RESULTS

Strong expression, synthesis, and enzymatic activity of ACS5 were found in normal small intestinal mucosa compared with unaffected colon mucosa. In normal small intestine, ACS5 preferentially located to the epithelium covering villi. In coeliac disease, expression of ACS5 was regularly associated with differentiation of villi. Thus, ACS5 was found in the villus epithelium of the small intestine with coeliac disease of Marsh grades I, II, IIIa, or IIIb respectively. In Marsh grade IIIc coeliac disease lesions, strong expression of ACS5 was detectable neither in the surface epithelium nor in the epithelium lining hyperplastic crypts.

CONCLUSION

These data suggest that ACS5 is a very suitable marker molecule for the detection of villus atrophy in the small intestine.

Impaired expression of acyl-CoA synthetase 5 in sporadic colorectal adenocarcinomas

Several pathways of fatty acid metabolism have been shown to be associated with the pathogenesis of colorectal cancer. Fatty acid acyl-CoA thioesters are formed from free fatty acids and coenzyme A by the activity of acyl-CoA synthetases (ACSs). Whilst an increase in ACS4 expression has been associated with colorectal carcinogenesis, little is known about possible pathogenetic functions of other ACS isoforms, such as ACS5, in tumourigenesis. In the present study, gene expression, protein synthesis, and enzymatic activity of ACS5 in sporadic colorectal adenocarcinomas, adenomas, and established cell lines were analysed using RT-PCR, western blot analysis, immunofluorescence, and an enzymatic assay. Enhanced expression of ACS5 mRNA and protein as well as enzymatic activity was found in adenomas and in 11 (73%; group 1) of 15 colorectal adenocarcinomas investigated, while a decrease of ACS5 was seen in four tumours (27%; group 2). However, basal ACS5 enzymatic activity was increased as a percentage of the total activity of ACSs in both groups, arguing for an absolute (group 1) or relative (group 2) increase in ACS5 enzymatic activity in all adenocarcinomas investigated. These findings are reflected by in vitro analysis of three established colorectal adenocarcinoma cell lines, in which activity of ACS5 occurred. The results suggest the involvement of ACS5 in the early genesis of colorectal cancer, most likely by modification of the transport and pool formation of long-chain acyl-CoA thioesters, as recently demonstrated for other isoforms of the ACS family.

Temperature dependent fluorescence of A2-E, the main fluorescent lipofuscin component in the RPE

PURPOSE

A2-E is the dominant fluorophore of lipofuscin in the retinal pigment epithelium. In an in-vitro setup, we determined the temperature-dependent changes of the A2-E fluorescence with the aim of also assessing the potential value of such measurements for determining retinal temperature by autofluorescence measurements during laser treatment.

METHODS

A2-E was biosynthesized and diluted in Dimethyl Sulfoxide (DMSO) to 1 microM. Fluorescence measurements were performed with a photospectrometer under various temperatures ranging from 20 degrees C to 75 degrees C. Autofluorescence was excited at 467 nm, and emission was detected around 632 nm.

RESULTS

A2-E fluorescence intensity showed a linear decrease concomitant with temperature increment. At 75 degrees C, the fluorescence intensity decreased by 43% compared to at 20 degrees C. Fluorescence intensity was completely reversible dependent on the temperature, which cannot be explained by thermal A2-E alteration.

CONCLUSIONS

If the A2-E temperature-dependent fluorescence in-vitro is transferable to human fundus auto-fluorescence, then it may be possible to apply an autofluorescence-based online detection device for noninvasive determination of fundus temperature during in vivo laser treatment. This is of clinical relevance, especially for the application of photodynamic therapy (PDT) and transpupillary thermotherpy (TTT).

Intrauterine onset of acute neuropathic type 2 Gaucher disease: identification of a novel insertion sequence

A subset of patients with type 2 Gaucher disease is characterized by intrauterine onset of rapidly progressive neuropathic disease, arthrogryposis, hydrops fetalis and in some cases restrictive dermopathy. beta-Glucocerebrosidase (beta-glucosidase) activity is usually low or undetectable. In most cases death ensues either in-utero or within hours or days after birth. We report on an infant born to non-consanguineous parents of Caucasian origin presenting at birth with hydrops, arthrogryposis, severe respiratory distress, hepatosplenomegaly, and liver failure. Death occurred within several hours after delivery and autopsy revealed typical Gaucher cells in multiple organs in combination with severe apoptotic neurodegeneration throughout the brain. beta-Glucocerebrosidase activity was 1% of the norm in fibroblasts and a novel heterozygous insertion c.1515_1516insAGTGAGGGCAAT was identified by genomic sequencing and an insertion-specific seminested PCR. In addition, molecular studies revealed a previously described in type 1 Gaucher disease missense mutation c.476G --> A which results in a heterozygous substitution of R120Q. Our observations confirm considerable genotypic heterogeneity in patients with type 2 Gaucher disease. The transheterozygous combination of a mutation, previously described in type 1 Gaucher disease, together with a newly identified insertion may result in this severe phenotype.

Hippocampal neurons and recombinant galectins as tools for systematic carbohydrate structure-function studies in neuronal differentiation

Membrane glycoconjugates play a central role in neuronal interactions and regulation. To define the precise links between membrane polysaccharides and neuronal functions, two main requirements must be fulfilled: (1) the availability of molecular tools able to finely discriminate among carbohydrate structures and (2) the use of an experimental system suitable for systematic and quantitative studies of particular neuronal processes. In this work, we used two chicken proto-type galectins, i.e., monomeric CG-14 and dimeric CG-16, with very similar carbohydrate affinities, and rat hippocampal neurons in culture to quantitatively measure the involvement of carbohydrate-protein interaction in axonal growth and directionality, neurite sprouting and axon regenerative capacity after section. CG-16 potently stimulated axonal growth and guidance. Neurite sprouting was enhanced by immobilized CG-16 and, notably, reduced by lectin in solution. Overall, cross-linking CG-16 invariably excelled CG-14 in these functional assays, although none of them were able to improve axon regenerative capacity when compared to mammalian galectin-1. Our results demonstrate the potential of the experimental set-up to perform a systematic study of galectin functionality in neuronal differentiation. In view of the concept of the sugar code, the presented results indicate that biological effects triggered by glycan binding engaging an endogenous lectin can be modulated by carbohydrate affinity and/or by other factors like differential cross-linking capacity.