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Publications

Greifenhagen, U.; Frolov, A.; Blüher, M.; Hoffmann, R.; Site-specific analysis of advanced glycation end products in plasma proteins of type 2 diabetes mellitus patients Anal. Bioanal. Chem. 408, 5557-5566, (2016) DOI: 10.1007/s00216-016-9651-4

Advanced glycation end products (AGEs) are posttranslational modifications formed non-enzymatically from the reaction of carbohydrates and their degradation products with proteins. Accumulation of AGEs is associated with the progression of severe diabetic complications, for example, and elevated tissue levels of AGEs might even predict these pathologies. As AGE formation is often site-specific, mapping of these modification sites may reveal more sensitive and specific markers than the global tissue level. Here, 42 AGE modifications were identified in a bottom-up proteomic approach by tandem mass spectrometry, which corresponded to 36 sites in 22 high to medium abundant proteins in individual plasma samples obtained from type 2 diabetes mellitus (T2DM) patients with long disease duration (>10 years). Major modifications were glarg (11 modification sites) and carboxymethylation (5) of arginine and formylation (8), acetylation (7), and carboxymethylation (7) of lysine residues. Relative quantification of these sites in plasma samples obtained from normoglycemic individuals (n = 47) and patients with T2DM being newly diagnosed (n = 47) or of medium (2–5 years, n = 20) and long disease duration (>10 years, n = 20) did not reveal any significant differences.
Publications

Gladilovich, V.; Greifenhagen, U.; Sukhodolov, N.; Selyutin, A.; Singer, D.; Thieme, D.; Majovsky, P.; Shirkin, A.; Hoehenwarter, W.; Bonitenko, E.; Podolskaya, E.; Frolov, A.; Immobilized metal affinity chromatography on collapsed Langmuir-Blodgett iron(III) stearate films and iron(III) oxide nanoparticles for bottom-up phosphoproteomics J. Chromatogr. A 1443, 181-190, (2016) DOI: 10.1016/j.chroma.2016.03.044

Phosphorylation is the enzymatic reaction of site-specific phosphate transfer from energy-rich donors to the side chains of serine, threonine, tyrosine, and histidine residues in proteins. In living cells, reversible phosphorylation underlies a universal mechanism of intracellular signal transduction. In this context, analysis of the phosphoproteome is a prerequisite to better understand the cellular regulatory networks. Conventionally, due to the low contents of signaling proteins, selective enrichment of proteolytic phosphopeptides by immobilized metal affinity chromatography (IMAC) is performed prior to their LC–MS or -MS/MS analysis. Unfortunately, this technique still suffers from low selectivity and compromised analyte recoveries. To overcome these limitations, we propose IMAC systems comprising stationary phases based on collapsed Langmuir-Blodgett films of iron(III) stearate (FF) or iron(III) oxide nanoparticles (FO) and mobile phases relying on ammonia, piperidine and heptadecafluorooctanesulfonic acid (PFOS). Experiments with model phosphopeptides and phosphoprotein tryptic digests showed superior binding capacity, selectivity and recovery for both systems in comparison to the existing commercial analogs. As evidenced by LC–MS/MS analysis of the HeLa phosphoproteome, these features of the phases resulted in increased phosphoproteome coverage in comparison to the analogous commercially available phases, indicating that our IMAC protocol is a promising chromatographic tool for in-depth phosphoproteomic research.
Publications

Fröhlich, C.; Zschiebsch, K.; Gröger, V.; Paarmann, K.; Steffen, J.; Thurm, C.; Schropp, E.-M.; Brüning, T.; Gellerich, F.; Radloff, M.; Schwabe, R.; Lachmann, I.; Krohn, M.; Ibrahim, S.; Pahnke, J.; Activation of Mitochondrial Complex II-Dependent Respiration Is Beneficial for α-Synucleinopathies Mol. Neurobiol. 53, 4728-4744, (2016) DOI: 10.1007/s12035-015-9399-4

Parkinson’s disease and dementia with Lewy bodies are major challenges in research and clinical medicine world-wide and contribute to the most common neurodegenerative disorders. Previously, specific mitochondrial polymorphisms have been found to enhance clearance of amyloid-β from the brain of APP-transgenic mice leading to beneficial clinical outcome. It has been discussed whether specific mitochondrial alterations contribute to disease progression or even prevent toxic peptide deposition, as seen in many neurodegenerative diseases. Here, we investigated α-synuclein-transgenic C57BL/6J mice with the A30P mutation, and a novel A30P C57BL/6J mouse model with three mitochondrial DNA polymorphisms in the ND3, COX3 and mtRNAArg genes, as found in the inbred NOD/LtJ mouse strain. We were able to detect that the new model has increased mitochondrial complex II-respiration which occurs in parallel to neuronal loss and improved motor performance, although it exhibits higher amounts of high molecular weight species of α-synuclein. High molecular weight aggregates of different peptides are controversially discussed in the light of neurodegeneration. A favourable hypothesis states that high molecular weight species are protective and of minor importance for the pathogenesis of neurodegenerative disorders as compared to the extreme neurotoxic monomers and oligomers. Summarising, our results point to a potentially protective and beneficial effect of specific mitochondrial polymorphisms which cause improved mitochondrial complex II-respiration in α-synucleinopathies, an effect that could be exploited further for pharmaceutical interventions.
Publications

Edeler, D.; Kaluđerović, M. R.; Dojčinović, B.; Schmidt, H.; Kaluđerović, G. N.; SBA-15 mesoporous silica particles loaded with cisplatin induce senescence in B16F10 cells RSC Adv. 6, 111031-111040, (2016) DOI: 10.1039/C6RA22596A

The anticancer drug cisplatin (CP) is loaded into SBA-15 mesoporous silica (SBA-15|CP) and its release from the nanomaterial is studied. The CP-loaded SBA-15 is tested against four tumor cell lines: mouse malignant melanoma B16F10, human adenocarcinoma HeLa, colon HT-29 and prostate PC3. Most importantly, the superiority of this novel material in comparison to CP arises from the fact that the CP-grafted nanomaterial SBA-15 (→SBA-15|CP) is enhancing cessation of proliferation along with induction of senescence in B16F10 in approximately 3.5 times lower concentration. The control material loaded with therapeutically inactive K2[PtCl4] (→SBA-15|TC) showed no antitumor activity. To a large extent, SBA-15|CP-induced senescence might present a safe approach in tumor treatment. Such cells can be cleared by immune cells resulting in efficient tumor regression. So far only apoptotic agents are being exploited in clinics, thus an understanding of the chemotherapeutic-induced senescence will allow oncologists to explore this essential tumor suppressor mechanism.
Publications

Bilova, T.; Lukasheva, E.; Brauch, D.; Greifenhagen, U.; Paudel, G.; Tarakhovskaya, E.; Frolova, N.; Mittasch, J.; Balcke, G. U.; Tissier, A.; Osmolovskaya, N.; Vogt, T.; Wessjohann, L. A.; Birkemeyer, C.; Milkowski, C.; Frolov, A.; A Snapshot of the Plant Glycated Proteome: STRUCTURAL, FUNCTIONAL, AND MECHANISTIC ASPECTS J. Biol. Chem. 291, 7621-7636, (2016) DOI: 10.1074/jbc.M115.678581

Glycation is the reaction of carbonyl compounds (reducing sugars and α-dicarbonyls) with amino acids, lipids, and proteins, yielding early and advanced glycation end products (AGEs). The AGEs can be formed via degradation of early glycation intermediates (glycoxidation) and by interaction with the products of monosaccharide autoxidation (autoxidative glycosylation). Although formation of these potentially deleterious compounds is well characterized in animal systems and thermally treated foods, only a little information about advanced glycation in plants is available. Thus, the knowledge of the plant AGE patterns and the underlying pathways of their formation are completely missing. To fill this gap, we describe the AGE-modified proteome of Brassica napus and characterize individual sites of advanced glycation by the methods of liquid chromatography-based bottom-up proteomics. The modification patterns were complex but reproducible: 789 AGE-modified peptides in 772 proteins were detected in two independent experiments. In contrast, only 168 polypeptides contained early glycated lysines, which did not resemble the sites of advanced glycation. Similar observations were made with Arabidopsis thaliana. The absence of the early glycated precursors of the AGE-modified protein residues indicated autoxidative glycosylation, but not glycoxidation, as the major pathway of AGE formation. To prove this assumption and to identify the potential modifying agents, we estimated the reactivity and glycative potential of plant-derived sugars using a model peptide approach and liquid chromatography-mass spectrometry-based techniques. Evaluation of these data sets together with the assessed tissue carbohydrate contents revealed dihydroxyacetone phosphate, glyceraldehyde 3-phosphate, ribulose, erythrose, and sucrose as potential precursors of plant AGEs.
Publications

Bernstein, H.-G.; Hildebrandt, J.; Dobrowolny, H.; Steiner, J.; Bogerts, B.; Pahnke, J.; Morphometric analysis of the cerebral expression of ATP-binding cassette transporter protein ABCB1 in chronic schizophrenia: Circumscribed deficits in the habenula Schizophr. Res. 177, 52-58, (2016) DOI: 10.1016/j.schres.2016.02.036

There is increasing evidence that microvascular abnormalities and malfunction of the blood–brain barrier (BBB) significantly contribute to schizophrenia pathophysiology. The ATP-binding cassette transporter ABCB1 is an important molecular component of the intact BBB, which has been implicated in a number of neurodegenerative and psychiatric disorders, including schizophrenia. However, the regional and cellular expression of ABCB1 in schizophrenia is yet unexplored. Therefore, we studied ABCB1 protein expression immunohistochemically in twelve human post-mortem brain regions known to play a role in schizophrenia, in 13 patients with schizophrenia and nine controls. In ten out of twelve brain regions under study, no significant differences were found with regard to the numerical density of ABCB1-expressing capillaries between all patients with schizophrenia and control cases. The left and right habenular complex, however, showed significantly reduced capillary densities in schizophrenia patients. In addition, we found a significantly reduced density of ABCB1-expressing neurons in the left habenula. Reduced ABCB1 expression in habenular capillaries might contribute to increased brain levels of proinflammatory cytokines in patients with schizophrenia, while decreased expression of this protein in a subpopulation of medial habenular neurons (which are probably purinergic) might be related to abnormalities of purines and their receptors found in this disease.
Publications

Bensing, C.; Mojić, M.; Gómez-Ruiz, S.; Carralero, S.; Dojčinović, B.; Maksimović-Ivanić, D.; Mijatović, S.; Kaluđerović, G. N.; Evaluation of functionalized mesoporous silica SBA-15 as a carrier system for Ph3Sn(CH2)3OH against the A2780 ovarian carcinoma cell line Dalton Trans. 45, 18984-18993, (2016) DOI: 10.1039/C6DT03519A

SBA-15|Sn3, a mesoporous silica-based material (derivative of SBA-15) loaded with an organotin compound Ph3Sn(CH2)3OH (Sn3), possesses improved antitumor potential against the A2780 high-grade serous ovarian carcinoma cell line in comparison to Sn3. It is demonstrated that both the compound and the nanostructured material are internalized by the A2780 cells. A similar mode of action of Sn3 and SBA-15|Sn3 against the A2780 cell line was found. Explicitly, induction of apoptosis, caspase 2, 3, 8 and 9 activation, accumulation of cells in the hypodiploid phase as well as accumulation of ROS were observed. Interestingly, Sn3 loaded in the mesoporous silica-based material needed to reach a concentration 3.5 times lower than the IC50 value of the Sn3 compound, pointing out a higher effect of the SBA-15|Sn3 than Sn3 alone. Clonogenic potential, growth in 3D culture as well as mobility of cells were disturbed in the presence of SBA-15|Sn3. Such behavior could be associated with the suppression of p-38 MAPK. Less profound effect of Sn3 compared to SBA-15|Sn3 could be attributed to a different regulation of p-38 and STAT-3, which are mainly responsible for an appropriate cellular response to diverse stimuli or metastatic properties.
Publications

Alresly, Z.; Lindequist, U.; Lalk, M.; Porzel, A.; Arnold, N.; Wessjohann, L. A.; Bioactive Triterpenes from the Fungus Piptoporus betulinus Rec. Nat. Prod. 10, 103-108, (2016)

Phytochemical investigation of the ethyl acetate extract of the fruiting bodies from the basidiomycete Piptoporus betulinus led to the isolation of a new bioactive lanostane triterpene identified as 3 b -acetoxy-16-hydroxy-24-oxo-5α-lanosta-8- ene-21-oic acid (1). In addition, ten known triterpenes, polyporenic acid A (5), polyporenic acid C (4), three derivatives of polyporenic acid A (8, 10, 11), betulinic acid (3), betulin (2), ergosterol peroxide (6), 9,11-dehydroergosterol peroxide (7), and fomefficinic acid (9), were also isolated from the fungus. All isolated compounds were tested for antimicrobial activity against some Gram-positive and Gram-negative bacteria as well as against a fungal strain. The new triterpene and some of the other compounds showed antimicrobial activity against Gram-positive bacteria.
Publications

Möhle, L.; Israel, N.; Paarmann, K.; Krohn, M.; Pietkiewicz, S.; Müller, A.; Lavrik, I. N.; Buguliskis, J. S.; Schott, B. H.; Schlüter, D.; Gundelfinger, E. D.; Montag, D.; Seifert, U.; Pahnke, J.; Dunay, I. R.; Chronic Toxoplasma gondii infection enhances β-amyloid phagocytosis and clearance by recruited monocytes Acta Neuropathol. Commun. 4, 25, (2016) DOI: 10.1186/s40478-016-0293-8

IntroductionAlzheimer’s disease (AD) is associated with the accumulation of β-amyloid (Aβ) as senile plaques in the brain, thus leading to neurodegeneration and cognitive impairment. Plaque formation depends not merely on the amount of generated Aβ peptides, but more importantly on their effective removal. Chronic infections with neurotropic pathogens, most prominently the parasite Toxoplasma (T.) gondii, are frequent in the elderly, and it has been suggested that the resulting neuroinflammation may influence the course of AD. In the present study, we investigated how chronic T. gondii infection and resulting neuroinflammation affect plaque deposition and removal in a mouse model of AD.ResultsChronic infection with T. gondii was associated with reduced Aβ and plaque load in 5xFAD mice. Upon infection, myeloid-derived CCR2hi Ly6Chi monocytes, CCR2+ Ly6Cint, and CCR2+ Ly6Clow mononuclear cells were recruited to the brain of mice. Compared to microglia, these recruited mononuclear cells showed highly increased phagocytic capacity of Aβ ex vivo. The F4/80+ Ly6Clow macrophages expressed high levels of Triggering Receptor Expressed on Myeloid cells 2 (TREM2), CD36, and Scavenger Receptor A1 (SCARA1), indicating phagocytic activity. Importantly, selective ablation of CCR2+ Ly6Chi monocytes resulted in an increased amount of Aβ in infected mice. Elevated insulin-degrading enzyme (IDE), matrix metalloproteinase 9 (MMP9), as well as immunoproteasome subunits β1i/LMP2, β2i/MECL-1, and β5i/LMP7 mRNA levels in the infected brains indicated increased proteolytic Aβ degradation. Particularly, LMP7 was highly expressed by the recruited mononuclear cells in the brain, suggesting a novel mechanism of Aβ clearance.ConclusionsOur results indicate that chronic Toxoplasma infection ameliorates β-amyloidosis in a murine model of AD by activation of the immune system, specifically by recruitment of Ly6Chi monocytes and by enhancement of phagocytosis and degradation of soluble Aβ. Our findings provide evidence for a modulatory role of inflammation-induced Aβ phagocytosis and degradation by newly recruited peripheral immune cells in the pathophysiology of AD.
Publications

Ludwig, G.; Mojić, M.; Bulatović, M.; Mijatović, S.; Maksimović-Ivanić, D.; Steinborn, D.; Kaluđerović, G. N.; Biological Potential of Halfsandwich Ruthenium(II) and Iridium (III) Complexes Anti-Cancer Agents Med. Chem. 16, 1455-1460, (2016) DOI: 10.2174/1871520615666151029100749

In vitro studies with the ruthenium(II) and analogous iridium(III) complexes [Ru(η6- p-cymene)Cl2{Ph2PCH2CH2CH2S(O)xPh-κP}], [Ru(η6-p-cymene)Cl{Ph2PCH2CH2CH2S(O)xPh- κP,κS}][PF6] (1–4), [Ir(η5-C5Me5)Cl2{Ph2PCH2CH2CH2S(O)xPh-κP}] and [Ir(η5-C5Me5)Cl{Ph2 PCH2CH2CH2S(O)xPh-κP,κS}][PF6] (5–8; x = 0, 1) revealed the high selectivity toward the 8505C, A253, MCF-7, SW480 and 518A2 cancer cell lines. Thus, the cationic ruthenium complex 4 proved to be the most selective one. In case of the neutral and cationic ruthenium complexes 1–4 the caspase-dependent apoptotic cell death was proven as the main cause of the drug’s tumoricidal action on 8505C cell line.

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