The Association of Type 2 Diabetes Mellitus with Cerebral Gray Matter Volume Is Independent of Retinal Vascular Architecture and Retinopathy

It is uncertain whether small vessel disease underlies the relationship between Type 2 Diabetes Mellitus (T2DM) and brain atrophy. We aimed to study whether retinal vascular architecture, as a proxy for cerebral small vessel disease, may modify or mediate the associations of T2DM with brain volumes. In this cross-sectional study using Magnetic Resonance Imaging (MRI) scans and retinal photographs in 451 people with and without T2DM, we measured brain volumes, geometric measures of retinal vascular architecture, clinical retinopathy, and MRI cerebrovascular lesions. There were 270 people with (mean age 67.3 years) and 181 without T2DM (mean age 72.9 years). T2DM was associated with lower gray matter volume (p = 0.008). T2DM was associated with greater arteriolar diameter (p = 0.03) and optimality ratio (p = 0.04), but these associations were attenuated by adjustments for age and sex. Only optimality ratio was associated with lower gray matter volume (p = 0.03). The inclusion of retinal measures in regression models did not attenuate the association of T2DM with gray matter volume. The association of T2DM with lower gray matter volume was independent of retinal vascular architecture and clinical retinopathy. Retinal vascular measures or retinopathy may not be sufficiently sensitive to confirm a microvascular basis for T2DM-related brain atrophy.

Novel antiplatelet drugs in clinical development

The clinical value of antiplatelet compounds strongly depends on the benefit-risk balance between their anti-thrombotic effects and the bleeding risk they incur. This ratio is especially important in the treatment of cerebro-vascular disease. Several novel compounds in clinical development hold promise to improve this benefit-risk ratio.

The recombinant bifunctional protein αCD133-GPVI promotes repair of the infarcted myocardium in mice

BACKGROUND

Bone-marrow-derived progenitor cells are important in myocardial repair mechanisms following prolonged ischemia. Cell-based therapy of diseased myocardium is limited by a low level of tissue engraftment.

OBJECTIVES

The aim of this study was the development of the bifunctional protein αCD133-glycoprotein (GP)VI as an effective treatment for supporting vascular and myocardial repair mechanisms.

RESULTS

We have generated and characterized a bifunctional molecule (αCD133-GPVI) that binds both to the subendothelium of the injured microvasculature and to CD133(+) progenitor cells with high affinity. αCD133-GPVI enhances progenitor cell adhesion to extracellular matrix proteins and differentiation into mature endothelial cells. In vivo studies showed that αCD133-GPVI favors adhesion of circulating progenitor cells to the injured vessel wall (intravital microscopy). Also, treatment of mice undergoing experimental myocardial infarction with αCD133-GPVI-labeled progenitor cells reduces infarction size and preserves myocardial function.

CONCLUSIONS

The bifunctional trapping protein αCD133-GPVI represents a novel and promising therapeutic option for limiting heart failure of the ischemic myocardium.

Effect of dominant negative SNAP-23 expression on platelet function

BACKGROUND

The protein SNAP-23 is part of the secretory pathway in platelets. It is, however, not entirely clear to what extent this protein contributes to the secretory function of platelets. Therefore, we overexpressed a dominant negative mutant with a novel technology that allows the creation of intact transgene-expressing platetets.

RESULTS

Overexpression of a dominant negative SNAP-23 mutant that inhibited the binding of the native protein to the docking site within the secretory machinery resulted in significant suppression of the agonist-dependent surface recruitment of P-selectin and CD40L. Simultaneously, release from dense granules was clearly suppressed in the presence of this construct. Also agonist-dependent surface expression of fibrinogen receptor markers CD41 and CD61 was reduced, and agonist-triggered aggregation was inhibited.

CONCLUSION

The dominant negative inhibition of SNAP-23 resulted in clear effects on platelet functions. The novel method using recombinant culture-derived platelets allowed the rapid clarification of the functional importance of this protein in intact platelets.

Hydrogen peroxide is a true first messenger

Hydrogen peroxide has been shown to act as a second messenger mediating intracellular redox-sensitive signal transduction. Here we show that hydrogen peroxide is also able to transmit pro-inflammatory signals from one cell to the other and that this action can be inhibited by extracellularly added catalase. If these data can be further substantiated, hydrogen peroxide might become as important as nitric oxide as a small molecule intercellular (first) messenger.

Cell cycle related signaling in neuro2a cells proceeds via the receptor for advanced glycation end products

Re-expression of cell cycle related genes such as cyclin-dependent kinases (cdk), cyclins, or cdk inhibitors in differentiated neurons in Alzheimer's disease (AD) is rooted in aberrant mitogenic signaling. Since microglia and astroglia proliferate in the vicinity of amyloid plaques, it is likely that plaque components or factors secreted from plaque-activated glia induce mitogenic signaling in neurons. Mitogenic compounds might be S100B, overexpressed by activated astrocytes, or advanced glycation end products (AGEs), a component of plaques. Both S100B and AGEs may interact with the multiligand receptor for AGEs (RAGE) and trigger for the activation of the p42/44 mitogen-activated protein kinase (p42/44 MAPK), whether they also count for cell cycle related signaling in neurons remains unresolved. By immunohistochemical staining, we confirmed that cyclin D(1) positive neurons are surrounded by AGE deposits, demonstrating the potential relevance in vivo. For exploring the mitogenic signal cascade, we used Neuro2a cells overexpressing human full-length RAGE (FL-RAGE) or the cytosolic deletion mutant (Delta-RAGE). In both cell lines, S100B and AGEs induced the production of reactive oxygen species but not in a RAGE-dependent manner. By contrast, in FL-RAGE cells but not in Delta-RAGE cells S100B and AGEs activate p42/44 MAPK, augment cyclin D(1)/cdk4 protein and RNA levels and the transition into the S-phase. Moreover, in FL-RAGE cells, decreased protein levels of the cdk inhibitor p16 were observed, and the p42/44 MAPK inhibitor UO126 prevented AGE and S100B stimulated cyclin D(1) expression and hindered cells to enter the S-phase. Our results demonstrate that S100B and AGE may serve as mitogenic sources for the stimulation of neurons to progress through the cell cycle whereby signaling proceeds via RAGE --> p42/44 MAPK --> cyclin D(1)/cdk4.

Alpha-lipoic acid as a new treatment option for Alzheimer's disease--a 48 months follow-up analysis

Oxidative stress and neuronal energy depletion are characteristic biochemical hallmarks of Alzheimer's disease (AD). It is therefore conceivable that pro-energetic and antioxidant drugs such as alpha-lipoic acid might delay the onset or slow down the progression of the disease. In a previous study, 600mg alpha-lipoic acid was given daily to nine patients with AD (receiving a standard treatment with choline-esterase inhibitors) in an open-label study over an observation period of 12 months. The treatment led to a stabilization of cognitive functions in the study group, demonstrated by constant scores in two neuropsychological tests (the mini mental state exam, MMSE and the Alzheimer's disease assessment score cognitive subscale, ADAScog). In this report, we have extended the analysis to 43 patients over an observation period of up to 48 months. In patients with mild dementia (ADAScog < 15), the disease progressed extremely slowly (ADAScog: +1.2 points/year, MMSE: -0.6 points/year), in patients with moderate dementia at approximately twice the rate. However, the progression appears dramatically lower than data reported for untreated patients or patients on choline-esterase inhibitors in the second year of long-term studies. Despite the fact that this study was not double-blinded, placebo-controlled and randomized, our data suggest that treatment with alpha-lipoic acid might be a successful 'neuroprotective' therapy option for AD. However, a state-of-the-art phase II trial is needed urgently.

[Maillard reaction products in food as pro-inflammatory and pro-arteriosclerotic factors of degenerative diseases]

Heating of food induces the formation of Maillard reaction products (MRPs) caused by the reaction of reducing sugars with proteins or amino acids. Analogous reactions occur in the human body, eventually forming "Advanced Glycation Endproducts" (AGEs). AGEs accumulate in aging tissues accelerating degenerative-inflammatory and proliferative processes. MRPs present in food can also directly cause inflammatory processes in the intestines and, once absorbed, would support and reinforce any inflammatory and degenerative process occurring in the body. The contribution of AGEs (and additional MRPs) in the development of diabetic complications as well as nephropathy, neuropathy, micro- and macroangiopathies is now well established. Which of the MRPs or AGEs in particular induce these cellular processes is currently unknown. Thus the exact knowledge of the chemical structures of the MRPs could help to minimize the formation of "harmful MRPs" that occur due to heating in food processing. Because MRPs play a decisive role in the successful marketing of edibles due to their characteristics as flavor components, it is important to increase the amount of innocuous and palatable MRPs, and minimize signal active pro-inflammatory MRPs by the use of defined preparation methods. It is practicable to use low-priced immunological methods for the quantitative determination of specific MRPs or AGEs. In the medical area, the knowledge of the signal active MRP/AGE structures provides the opportunity to measure their concentrations in body fluids and tissues and thus determine their influence on inflammatory and age-related degenerative processes (e. g., late diabetic complications, arteriosclerosis, degeneration of neurons). From a clinical perspective, the application of RAGE antagonists after an appropriate chemical diagnosis could be effective in supporting the treatment of affected patient groups, especially older diabetic and dialysis patients.

Renal accumulation and clearance of advanced glycation end-products in type 2 diabetic nephropathy: effect of angiotensin-converting enzyme and vasopeptidase inhibition

AIMS/HYPOTHESIS

Renal accumulation of AGEs may contribute to the progression of diabetic nephropathy. We evaluated the effect of ramipril (a pure ACE inhibitor) and AVE7688 (a dual inhibitor of ACE and neutral endopeptidase) on renal accumulation of the advanced glycation end-product (AGE) 3-deoxyglucosone-imidazolone, carboxymethyllysine (CML) and pentosidine, and on clearance of CML in type 2 diabetes.

METHODS

Male Zucker diabetic fatty rats (ZDF, Gmi-fa/fa) rats were treated from age 10 to 37 weeks with ramipril (1 mg.kg(-1).day(-1)), AVE7688 (45 mg.kg(-1).day(-1)) or without drug. Ramipril and AVE7688 reduced albuminuria by 30 and 90%, respectively.

RESULTS

ZDF rats showed increased renal accumulation of the AGE subtypes 3-deoxyglucosone-imidazolone, pentosidine and CML by about 40, 55 and 55%, respectively compared with heterozygous, non-diabetic control animals at the age of 37 weeks. AVE7688 but not ramipril attenuated the renal accumulation of 3-deoxyglucosone-imidazolone, pentosidine and CML and improved CML clearance in ZDF rats. During glycation reactions in vitro, AVE7688 also demonstrated potent chelating activity and inhibited metal-catalysed formation of pentosidine and CML.

CONCLUSIONS/INTERPRETATION

Improved AGE clearance and direct inhibition of AGE formation by chelation may contribute to reduced accumulation of renal AGEs and to the nephroprotective effects of vasopeptidase inhibition in type 2 diabetes.

Alzheimer?s associated inflammation, potential drug targets and future therapies

Alzheimer's disease is the most common cause of dementia in the elderly population. The most widely used treatment for Alzheimer's disease at present is acetylcholinesterase inhibitors, which aim to prolong cognitive function through increased synaptic activity, without providing neuroprotection. This treatment is only symptomatic and provides modest outcomes for patients. The recent elucidation of the inflammatory pathways involved in Alzheimer's disease however, has opened doors for better treatment and prevention by identification of areas of therapeutic intervention that target the cause of the disease rather than the symptoms. This review describes the inflammatory pathways that are thought to be present in Alzheimer's disease and some of the new therapies that have shown promise, via alteration or inhibition of these pathways. Some of the therapies included in this review, which have already demonstrated beneficial effects in the treatment of Alzheimer's disease, or have the potential to do so, are nonsteroidal anti-inflammatory drugs, statins, RAGE antagonists and antioxidants.

Pentoxyphylline and propentophylline are inhibitors of TNF-? release in monocytes activated by advanced glycation endproducts

Non-enzymatic glycation of proteins with reducing sugars and subsequent transition metal-catalyzed oxidation leads to the formation of protein-bound "advanced glycation endproducts" (AGEs). They accumulate on long-lived protein deposits inducing senile plaques in Alzheimer's disease. AGE-modified proteins are able to activate microglia and astroglia and can cause chronic inflammation. The aim of the present study was to confirm the stimulatory effect of different AGEs on TNF-alpha release in human monocytes. Furthermore, the effects of four xanthine derivatives on AGE-induced TNF-alpha release were investigated. We show that chicken egg albumin-AGEs prepared with glucose and chicken egg albumin-AGEs prepared with methylglyoxal dose-dependently induce TNF-alpha release. The xanthine derivatives pentoxyphylline and propentophylline attenuate AGE-induced TNF-alpha release in a dose-dependent manner. Theophylline at low concentrations slightly stimulated TNF-alpha release whereas caffeine had no effect. The inhibition of the AGE-induced TNF-alpha release by pentoxyphylline and propentophylline provides interesting pharmacological strategies for diseases with local neuroinflammation such as Alzheimer's disease.

Anti-AGEing defences against Alzheimer's disease

Accumulation of insoluble protein deposits and their cross-linking by AGEs (advanced glycation end products) in the brain is a feature of aging and neurodegeneration, especially in AD (Alzheimer's disease). In AD, two types of fibrillar protein aggregates are present: extracellular deposits (plaques) consisting mainly of Aβ (β-amyloid peptide), and intracellular deposits (tangles) composed predominantly of microtubule-associated protein tau. Both plaques and tangles are modified by AGEs, which occurs particularly at lysine and arginine residues. Interaction of a synthetic amyloid plaque (fibrillar Aβ) with microglia leads to a strong pro-inflammatory response, indicating that priming of immune cells with β-amyloid potentiates their response to secondary stimuli such as AGE and cytokines such as interferon-γ. Formation of hyperphosphorylated and cross-linked microtubule-associated protein tau aggregates, especially tau dimers as the first step in tangle formation, can be induced in vitro by the combination of okadaic acid, a PP2A phosphatase inhibitor, and methylglyoxal. These results suggest that excess production of reactive carbonyl compound (‘carbonyl stress’) and subsequent AGE formation can contribute to cross-linking of protein fibrils and to pathological pro-inflammatory signalling, which all contribute to pathological changes and dementia progression in AD. However, the human brain has developed the glyoxalase system, a most effective defence system to scavenge small dicarbonyl compounds such as glyoxal and methylglyoxal. Very importantly, this system needs GSH as a rate-limiting cofactor. Since GSH is limited under conditions of oxidative stress and inflammation, supplementation with antioxidants such as lipoic acid, vitamin E or flavonoids could indirectly strengthen the anti-glycation defence system in AD. In addition, synthetic carbonyl scavengers and anti-inflammatory drugs could also be valuable drugs for the ‘anti-glycation’ treatment of AD.

Effect of advanced glycation endproducts on cell cycle and their relevance for Alzheimer's disease

In Alzheimer's disease, neurons in affected regions re-enter the cell cycle, leave the G0 state and appear to be arrested at both the G1/S and G2/M phase with resulting cell death, predominantly by apoptosis. Further hallmarks of AD are crosslinked protein deposits (amyloid plaques and neurofibrillary tangles), which time-dependently become modified by "advanced glycation endproducts (AGEs)". Since AGEs activate both mitogenic and redox-sensitive pathways, they might be involved both in cell cycle re-entry and arrest.

Differential effects of "Advanced glycation endproducts" and beta-amyloid peptide on glucose utilization and ATP levels in the neuronal cell line SH-SY5Y

Beta-amyloid peptide (Abeta) and "Advanced glycation endproducts" (AGEs) are components of the senile plaques in Alzheimer's disease patients. It has been proposed that both AGEs and Abeta exert many of their effects, which include the upregulation of pro-inflammatory cytokines, through RAGE ("receptor for advanced glycation endproducts"). To investigate whether Abeta and AGEs cause similar or identical effects on cell survival and energy metabolism, we have compared the effects of a model-AGE and Abeta on cell viability, ATP level, glucose consumption and lactate production in the neuroblastoma cell line SH-SY5Y. The results show that AGEs and Abeta increase glucose consumption and decrease ATP levels in a dose dependent manner. Furthermore, both compounds decrease mitochondrial activity measured by the MTT assay. However, only AGEs decrease the number of cells and significantly increase lactate production. These data indicate that both AGEs and Abeta can cause differential disturbances in neuronal metabolism, which may contribute to the pathophysiological findings in Alzheimer's disease. However, their signalling pathways are apparently quite distinct, a fact which should stimulate a more detailed investigation in this field, e.g. for the purpose of a rational design of potential "neuroprotective" RAGE antagonists.

Effects of two Gbetagamma-binding proteins--N-terminally truncated phosducin and beta-adrenergic receptor kinase C terminus (betaARKct)--in heart failure

Myocardial overexpression of the C-terminus of beta-adrenergic receptor kinase (betaARKct) has been shown to result in a positive inotropic effect or an improvement of survival in heart failure. However, it is not clear whether this beneficial effect is mainly because of dominant-negative inhibition of betaARK1, and a consecutive resensitization of beta-adrenergic receptors (betaAR), or rather due to inhibition of other Gbetagamma-mediated effects. In this study, we tested whether overexpression of N-terminally truncated phosducin (nt-del-phosducin), another Gbetagamma-binding protein that does not resensitize betaARs owing to simultaneous inhibition of GDP release from Galpha subunits, shows the same effects as betaARKct. Adenoviral gene transfer was used to express nt-del-phosducin and betaARKct in isolated ventricular cardiomyocytes and in myocardium of rabbits, which suffered from heart failure because of rapid ventricular pacing. BetaAR-stimulated cAMP formation was increased by betaARKct, but not by nt-del-phosducin, whereas both proteins inhibited Gbetagamma-mediated effects. Both transgenes also increased contractility of normal and failing isolated cardiomyocytes and improved contractility in rabbits with heart failure after gene transfer in vivo. In conclusion, overexpression of nt-del-phosducin enhances the contractility of cardiomyocytes to the same extent as betaARKct, suggesting that the effects of betaARKct might be owing to inhibition of Gbetagamma rather than to betaAR resensitization.

[Unclear pulmonary infiltrates with eosinophilia, a problem of differential diagnosis]

Unclear pulmonary infiltrates with eosinophilia, a problem of differential diagnosis. HISTORY AND ADMISSION FINDINGS: A 60-year-old woman was admitted for the diagnosis of pulmonary infiltrates. A year before she had been exposed to tuberculosis when working as a doctor in Manila, the Philippines. Ten days before admission she had spent 10 days in Sao Paulo, Brazil. On admission she complained of fatigue, dry cough and nocturnal sweating. Her body temperature was 37.8; C. At auscultation of the chest fine rales were heard with diminished percussion sounds over both lungs. INVESTIGATIONS: The chest radiogram showed bilateral apical infiltrates. Blood count indicated normal white and red cells, but platelets were raised to 606 x 10 9/l. The differential blood count revealed an eosinophilia of 30%, ESR was raised at 91 mm/h and C-reactive protein increased to 103 mg/l. Angiotensin-converting enzyme, IgG, IgA, IgM, IgE, C3 and C4, paraproteins, antinuclear antibodies and double-strand DNA antibodies were all within normal limits. There was no direct or indirect evidence of tuberculosis and no parasites were found in sputum, stool, urine and blood. DIAGNOSIS, TREATMENT AND COURSE: After bronchoscopy with bronchial biopsy had failed to establish a diagnosis, an open lung biopsy with partial lung resection was performed. This revealed histologically an eosinophilic pneumonia with intra-alveolar protein precipitation and multinucleated giant cells, as well as interstitial fibroblast proliferation without demonstrable mincroorganisms. Under cortisone administration there was striking improvement of symptoms within a few days, and C-reactive proteins fell to 3 mg/l, ESR to 25 mm/h and the eosino-philia to 2%. CONCLUSION: Eosinophilic pneumonia should be included in the differential diagnosis of unclear pulmonary infiltrations with eosinophilia, once parasitological and malignant diseases, tuberculosis and allergic pulmonary aspergillosis have been excluded.

Glycoxidative stress creates a vicious cycle of neurodegeneration in Alzheimer's disease--a target for neuroprotective treatment strategies?

Accumulation of Advanced Glycation Endproducts (AGEs) in the brain is a feature of ageing and degeneration, especially in Alzheimer's disease (AD). Increased AGE levels explain many of the neuropathological and biochemical features of AD such as extensive protein crosslinking (beta-amyloid and MAP-tau), glial activation, oxidative stress and neuronal cell death. Oxidative stress and AGEs initiate a positive feedback loop, where normal age-related changes develop into a pathophysiological cascade. Combined intervention using antioxidants, anti-inflammatory drugs and AGE-inhibitors may be a promising neuroprotective strategy.

Potential neurotoxic inflammatory responses to Abeta vaccination in humans

Studies in transgenic mouse models of Alzheimer's disease suggested the development of a vaccine that would induce the production of antibodies against amyloid-beta (Abeta) peptide, which in turn would stimulate microglia to phagocytose and remove senile plaques. However, some patients in the human clinical trials developed symptoms of brain inflammation, demonstrated by lymphocyte infiltration and elevated protein levels. These parameters are indicative of a breakdown of the blood-brain-barrier and entry of T-cells into the brain. Abeta-specific activated T-helper cells have the potential to amplify the existing pro-inflammatory conditions that are present in the brains of Alzheimer's disease patients. Cytotoxic T-cells might even attack the amyloid precursor protein which is present on the surface of many cells, including neurons. Before undertaking further vaccination trials there is a need to re-assess the risks associated with Abeta vaccination and with the therapeutic containment of a neuroinflammatory response. These risks may not be justified in the light of recent studies which have shown the efficacy of conventional, low-risk treatments in slowing the progress of AD.

Alzheimer's vaccine: a cure as dangerous as the disease?

Studies in transgenic mouse models of Alzheimer's disease suggested the potential for a vaccine development. However, some patients in the human clinical trials developed symptoms of brain inflammation, demonstrating the high risk of a deliberately induced auto-immune response.

AGES in brain ageing: AGE-inhibitors as neuroprotective and anti-dementia drugs?

In Alzheimer's disease, age-related cellular changes such as compromised energy production and increased radical formation are worsened by the presence of AGEs as additional, AD specific stress factors. Intracellular AGEs (most likely derived from methylglyoxal) crosslink cytoskeletal proteins and render them insoluble. These aggregates inhibit cellular functions including transport processes and contribute to neuronal dysfunction and death. Extracellular AGEs, which accumulate in ageing tissue (but most prominently on long-lived protein deposits like the senile plaques) exert chronic oxidative stress on neurons. In addition, they activate glial cells to produce free radicals (superoxide and NO) and neurotoxic cytokines such as TNF-alpha. Drugs, which inhibit the formation of AGEs by specific chemical mechanisms (AGE-inhibitors), including aminoguanidine, carnosine, tenilsetam, OPB-9195 and pyridoxamine, attenuate the development of (AGE-mediated) diabetic complications. Assuming that 'carbonyl stress' contributes significantly to the progression of Alzheimer's disease, AGE-inhibitors might also become interesting novel therapeutic drugs for treatment of AD.

Protein "AGEing"--cytotoxicity of a glycated protein increases with its degree of AGE-modification

Non-enzymatic glycation of proteins with reducing sugars and subsequent transition metal-catalyzed oxidations leads to the formation of protein-bound "advanced glycation endproducts" (AGEs). They accumulate on long-lived proteins including on and in the vicinity of the beta-amyloid plaques in Alzheimer's disease (AD). Since the AGE modification of a protein increases with time, and such a "long-term incubation" might also occur in the AD brain, we investigated whether an increase in the cytotoxic effects of an AGE-modified model protein occurs over time. Bovine serum albumin (BSA) was modified by glucose for defined time periods, and the viability of SH-SY5Y neuroblastoma cells, incubated with the differentially AGE-modified BSA samples, was measured with the MTT assay. Cytotoxicity of the AGE-modified BSAs increased in correlation to the incubation time with glucose. Among the AGE-specific markers, browning (OD 400) correlated best with cytotoxicity, followed by AGE-specific fluorescence and the defined AGE, carboxymethyllysine. Since AGEs accumulate in AD over time, they may be one of the "age-related" factors contributing to neuronal cell death in Alzheimer's disease.

Anti-inflammatory antioxidants attenuate the expression of inducible nitric oxide synthase mediated by advanced glycation endproducts in murine microglia

Advanced glycation endproducts (AGEs) accumulate on long-lived protein deposits including beta-amyloid plaques in Alzheimer's disease (AD). AGE-modified amyloid deposits contain oxidized and nitrated proteins as markers of a chronic neuroinflammatory condition and are surrounded by activated microglial and astroglial cells. We show in this study that AGEs increase nitric oxide production by induction of the inducible nitric oxide synthase (iNOS) on the mRNA and protein level in the murine microglial cell line N-11. Membrane permeable antioxidants including oestrogen derivatives (e.g. 17beta-oestradiol) thiol antioxidants (e.g. (R+)-alpha-lipoic acid) and Gingko biloba extract EGb 761, but not phosphodiesterase inhibitors such as propentophylline, prevent the up-regulation of AGE-induced iNOS expression and NO production. These results indicate that oxygen free radicals serve as second messengers in AGE-induced pro-inflammatory signal transduction pathways. As this pharmacological mechanism is not only relevant for Alzheimer's disease, but also for many chronic inflammatory conditions, such membrane-permeable antioxidants could be regarded not only as antioxidant, but also as potent therapeutic anti-inflammatory drugs.

Advanced glycation endproducts co-localize with inducible nitric oxide synthase in Alzheimer's disease

Advanced glycation endproducts (AGEs), protein-bound oxidation products of sugars, have been shown to be involved in the pathophysiological processes of Alzheimer's disease (AD). AGEs induce the expression of various pro-inflammatory cytokines and the inducible nitric oxide synthase (iNOS) leading to a state of oxidative stress. AGE modification and resulting crosslinking of protein deposits such as amyloid plaques may contribute to the oxidative stress occurring in AD. The aim of this study was to immunohistochemically compare the localization of AGEs and beta-amyloid (Abeta) with iNOS in the temporal cortex (Area 22) of normal and AD brains. In aged normal individuals as well as early stage AD brains (i.e. no pathological findings in isocortical areas), a few astrocytes showed co-localization of AGE and iNOS in the upper neuronal layers, compared with no astrocytes detected in young controls. In late AD brains, there was a much denser accumulation of astrocytes co-localized with AGE and iNOS in the deeper and particularly upper neuronal layers. Also, numerous neurons with diffuse AGE but not iNOS reactivity and some AGE and iNOS-positive microglia were demonstrated, compared with only a few AGE-reactive neurons and no microglia in controls. Finally, astrocytes co-localized with AGE and iNOS as well as AGE and were found surrounding mature but not diffuse amyloid plaques in the AD brain. Our results show that AGE-positive astrocytes and microglia in the AD brain express iNOS and support the evidence of an AGE-induced oxidative stress occurring in the vicinity of the characteristic lesions of AD. Hence activation of microglia and astrocytes by AGEs with subsequent oxidative stress and cytokine release may be an important progression factor in AD.

Advanced glycation endproducts change glutathione redox status in SH-SY5Y human neuroblastoma cells by a hydrogen peroxide dependent mechanism

The reaction of proteins with reducing sugars leads to the formation of 'advanced glycation endproducts' (AGEs). They accumulate in Alzheimer's disease brain in the vicinity of beta-amyloid plaques. AGEs are cytotoxic by a mechanism involving reactive oxygen species, which implies that they could compromise glutathione redox status. In this study, we show that AGEs (BSA-AGE and beta-amyloid-AGE) persistently increase the ratio of oxidized to reduced glutathione in a dose- and time-dependent manner in SH-SY5Y neuroblastoma cells. The level of oxidized glutathione accounted to 10-14% and persisted for up to 24 h in the presence of added AGEs. In contrast, the unmodified beta-amyloid peptides A beta (1-40) and A beta (25-35) had no significant effect on glutathione redox status. The AGE-induced increase in oxidized glutathione could be prevented by the radical scavengers N-acetylcysteine, alpha-lipoic acid and 17beta-estradiol or by application of catalase, indicating that superoxide and hydrogen peroxide production precedes the AGE-mediated depletion of reduced glutathione.

Advanced glycation end products (AGEs)-induced expression of TGF-beta 1 is suppressed by a protease in the tubule cell line LLC-PK1

BACKGROUND

Advanced glycation end products (AGEs) are assumed to play a key role in diabetic nephropathy (DN). Since little is known about their action in tubule cells, we investigated in LLC-PK1 cells: (i) whether AGE-bovine serum albumin (AGE-BSA) affects cell proliferation and expression of transforming growth factor-beta (TGF-beta 1); and (ii) whether the AGE-induced effects can be modulated by trypsin due to interference with its binding proteins at the cell surface.

METHODS

Arrested cells were exposed to vehicle (control), AGE-BSA (19--76 microM) and BSA (38 microM) in the presence or absence of trypsin (0.625--5.0 microg/ml) (2.5 microg/ml) for 24 h. We evaluated cell proliferation by cell count and by [(3)H]thymidine incorporation, TGF-beta 1 expression by reverse transcription-polymerase chain reaction (RT-PCR), and TGF-beta 1 protein by ELISA. In addition, cell accumulation of AGEs was studied by immunohistochemical staining of the AGE imidazolone.

RESULTS

AGE-BSA inhibited [(3)H]thymidine incorporation, lowered cell number and increased cell protein content as well as TGF-beta 1 mRNA and protein as compared with control and BSA. Immunohistochemical staining revealed a marked intracellular accumulation of the AGE imidazolone. Co-incubation of AGE-BSA with trypsin ameliorated the impaired thymidine incorporation, the decreased cell count and the enhanced cell protein content. TGF-beta 1 overexpression was normalized, while TGF-beta 1 protein declined insignificantly. Intracellular imidazolone accumulation was strikingly suppressed.

CONCLUSIONS

In the tubule cell line LLC-PK1, AGE-BSA exerts an antiproliferative effect, most probably due to TGF-beta 1 overproduction. The co-administration of trypsin abrogated this alteration, very likely as a result of an interaction with AGE-binding protein(s), which is supported by the decreased intracellular AGE accumulation. These findings may be the starting point for the development of specific proteolytic enzymes to interfere with the interaction between AGEs and their receptors/binding proteins.

Increased expression of isoform 1 of the sarcoplasmic reticulum Ca(2+)-release channel in failing human heart

BACKGROUND

The sarcoplasmic reticulum (SR) Ca(2+)-release channel plays a key role in the excitation-contraction coupling of cardiac myocytes. Because respective alterations have been reported in human heart failure, we investigated isoform expression of the SR Ca(2+)-release channel in human hearts from patients with terminal heart failure (dilated cardiomyopathy [DCM], n=8) and nonfailing organ donors (NF, n=8).

METHODS AND RESULTS

Expression of mRNA of SR Ca(2+)-release channel isoforms in isolated human cardiomyocytes and myocardial tissue was analyzed by reverse-transcription polymerase chain reaction. Protein expression was quantified in myocardial tissue with [(3)H]-ryanodine binding and with Western blots, expressed as densitometric units per microgram of protein (DU), and cellular localization was visualized with immunohistochemistry. We found mRNA expression of isoforms 1, 2, and 3 in cardiomyocytes and myocardial tissue both in NF and DCM. Total SR Ca(2+)-release channel protein expression in NF (B(max) 2.16+/-0.43 pmol/mg protein) and in DCM (B(max) 2.33+/-0.22 pmol/mg protein) myocardium was unchanged. Expression of isoform 1 of the SR Ca(2+)-release channel was significantly (P=0.0037) increased in DCM myocardium (NF 1.97+/-0.25 versus DCM 3.37+/-0.31 DU), whereas protein expression of isoform 2 (NF 14.62+/-0.87 versus DCM 13.52+/-0.43 DU) and isoform 3 (NF 1.39+/-0.13 versus DCM 1.35+/-0.19 DU) was unchanged. All 3 isoforms of the protein could be localized in human ventricular myocytes with fluorescence immunohistochemistry.

CONCLUSIONS

All 3 isoforms of the SR Ca(2+)-release channel were determined in human ventricular cardiomyocytes. Increased expression of isoform 1 of the SR Ca(2+)-release channel could contribute to impaired excitation-contraction coupling in human heart failure.

Alpha-lipoic acid as a new treatment option for Alzheimer [corrected] type dementia

Oxidative stress and energy depletion are characteristic biochemical hallmarks of Alzheimer's disease (AD), thus antioxidants with positive effects on glucose metabolism such as thioctic (alpha-lipoic) acid should exert positive effects in these patients. Therefore, 600 mg alpha-lipoic acid was given daily to nine patients with AD and related dementias (receiving a standard treatment with acetylcholinesterase inhibitors) in an open study over an observation period of, on avarage, 337+/-80 days. The treatment led to a stabilization of cognitive functions in the study group, demonstrated by constant scores in two neuropsychological tests (mini-mental state examination: MMSE and AD assessment scale, cognitive subscale: ADAScog). Despite the fact that this study was small and not randomized, this is the first indication that treatment with alpha-lipoic acid might be a successful 'neuroprotective' therapy option for AD and related dementias.

Isoform expression of the sarcoplasmic reticulum Ca2+ release channel (ryanodine channel) in human myocardium

The Ca2+ release channel of the sarcoplasmic reticulum (SR) is essential for the release of Ca2+ from intracellular stores and is expressed widely in various excitable cells. It plays a key role particularly in excitation contraction coupling in myocytes in skeletal and cardiac muscle. Three isoforms of the SR Ca2+ release channel have been cloned. Recently coexpression of different isoforms was reported in different animal species and various tissues. In human cardiac tissue, however, isoform expression is not yet established. Therefore the aim of this study was to characterize isoform expression of the SR Ca2+ release channel in the human heart. We examined specific isoform expression of mRNA and proteins of the SR Ca2+ release channel in the four different chambers of the heart and the interventricular septum from explanted human hearts from nonfailing organ donors (n=8). Reverse transcriptase PCR from total cardiac RNA with isoform specific primers and western blots from myocardial homogenates with isoform specific antibodies were performed. Quantification of protein expression was achieved by densitometric scanning and computer analysis and is expressed as densitometric units per microgram of protein. A single band DNA signal was detected by reverse transcriptase PCR for the skeletal isoform 1 and the cardiac isoform 2 and isoform 3 in all regions of the human heart investigated. Specific protein expression was detected in all five myocardial regions of the human heart in western blots for the skeletal isoform I and cardiac isoform 2, and a weaker specific band was also detectable for isoform 3 of the SR Ca2+ release channel. Quantification of protein expression showed significant (P=0.008) lower expression of isoform 1 in the right ventricle (42+/-4 densitometric units/g tissue) and similar expression in all other regions (right atrium 58+/-3; septum 51+/-5, left atrium 54+/-5; left ventricle 51+/-6). Isoform 2 of the SR Ca2+ release channel was also significantly lower (P=0.001) in the right ventricle (33+/-4 densitometric/g tissue) and similar in the other heart chambers (right atrium 42+/-5: septum 41+/-3, left atrium 52+/-6, left ventricle 42+/-3). Differences in isoform 3 of the SR Ca2+ release channel for the various myocardial regions did not reach significant levels (right atrium 45+/-6, right ventricle 38+/-5, septum 49+/-8, left atrium 46+/-7, and in left ventricle 45+/-3 densitometric units/g tissue). In conclusion, all three isoforms of the SR Ca2+ release channel were determined in the human heart at both mRNA and protein levels with different quantitative expression in the different heart chambers. Coexpression of the three different isoforms with different functional properties might increase the complexity of regulation of excitation contraction coupling in the human heart in a chamber specific mode.

Crosslinking of alpha-synuclein by advanced glycation endproducts--an early pathophysiological step in Lewy body formation?

An excess of reactive carbonyl compounds (carbonyl stress) and their reaction products, advanced glycation endproducts (AGEs), are thought to play a decisive role in the pathogenesis of neurodegenerative disorders and Parkinson's disease (PD) in particular. Accumulation of AGEs in various intracellular pathological hallmarks of PD, such as Lewy bodies, densely crosslinked intracellular protein deposits formed from neurofilament components and alpha-synuclein, have already been described in patients in advanced stages of the disease. There is, however, no indication of the involvement of AGE-induced crosslinking of alpha-synuclein in very early stages of the disease. In this study, we observed that AGEs and alpha-synuclein are similarly distributed in very early Lewy bodies in the human brain in cases with incidental Lewy body disease. These cases might be viewed as pre-Parkinson patients, i.e. patients who came for autopsy before the possible development of clinical signs of PD. AGEs are both markers of transition metal induced oxidative stress as well as, inducers of protein crosslinking and free radical formation by chemical and cellular processes. Thus, it is likely that AGE promoted formation of Lewy bodies reflects very early causative changes rather than late epiphenomenons of PD.

Low-molecular but not high-molecular advanced glycation end products (AGEs) are removed by high-flux dialysis

BACKGROUND

Patients with end-stage renal disease (ESRD) display very high levels of advanced glycation end products (AGEs). These compounds are suspected to play a pathophysiological role in diabetic nephropathy and late diabetic cardiovascular complications. We investigated to what extent AGE levels can be reduced by high-flux dialysis.

PATIENTS AND METHODS

Ten ESRD patients were treated three times each with DIAPES and HF60, two different synthetic, high-flux hemodialysis membranes. The kinetics of AGE removal was studied by fluorescence spectroscopy (excitation 370 nm/ emission 440 nm) and by ELISA of serum samples and the removal of beta2-m was studied by immunonephelometry of plasma samples. Samples were taken during dialysis sessions at t = 0, 30 and 180 min. In addition, molecular weight distribution of AGE products in serum of three patients was analyzed by gel filtration and fluorescence detection.

RESULTS

A significant difference could be found when AGE levels in serum of controls (n = 10) were compared with serum AGE levels of ESRD patients (p < 0.01/fluorescence; p < 0.0001/ ELISA). After 3 h of dialysis AGE-related fluorescence in serum decreased by 25.5 +/- 6.8% for HF60 (p < 0.0001) and 24.3 +/- 6.9% tor DIAPES (p < 0.0001). The corresponding decline measured by ELISA was 23.3 +/- 8.9% for HF60 (p < 0.0001) and 26.1 +/- 7.0% for DIAPES (p < 0.0001). Both methods showed no significant differences for both types of dialysis membranes. Gel filtration revealed that the decrease of fluorescence can be attributed to the removal of AGE peptides with a molecular mass < 12 kDa, only. In the high molecular range (> 12 kDa) no removal but hemoconcentration was observed independent of the dialyzer type used. The reduction of beta2-m during 3 hours of dialysis was 61.8 +/- 6.9% for HF60 (p < 0.0001) and 161.7 +/- 7.0% for DIAPES (p < 0.0001).

CONCLUSION

Both high-flux dialyzers were equally effective to remove low-molecular AGE products, while AGE-modified proteins of higher molecular weight were only marginally affected. On the basis of our data we suggest the study of molecular mass-dependent uremic toxicity of AGEs and the examination of the influence of other treatment modalities on the level of high-molecular AGEs.

Transition metal-mediated glycoxidation accelerates cross-linking of beta-amyloid peptide

beta-Amyloid deposits, hallmarks of Alzheimer's disease, contain both sugar-derived 'advanced glycation end products' (AGEs) and copper and iron ions. Our in vitro experiments using synthetic beta-amyloid peptide and glucose or fructose show that formation of covalently cross-linked high-molecular-mass beta-amyloid peptide oligomers is accelerated by micromolar amounts of copper (Cu+, Cu2+) and iron (Fe2+, Fe3+) ions. Formation of these covalent AGE cross-links can be inhibited by capping agents of amino groups, redox-inactive metal chelators and antioxidants, suggesting that these drugs may be able to slow down the formation of insoluble beta-amyloid deposits in vivo and possibly the progression of Alzheimer's disease.

SERCA2a activity correlates with the force-frequency relationship in human myocardium

The present investigation addresses whether protein expression and function of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2a) and phospholamban (PLB) correlate in failing and nonfailing human myocardium. SERCA2a activity and protein expression, PLB phosphorylation, and the force-frequency relationship (FFR) have been determined in right atrium (RA) and left ventricle (LV) from nonfailing (NF, n = 12) and terminally failing [dilated cardiomyopathy (DCM), n = 12] human hearts. Only in LV of DCM hearts was SERCA2a activity significantly decreased [maximal turnover rate (V(max)) = 196 +/- 11 and 396 +/- 30 nmol. mg(-1). min(-1) in LV and RA, respectively], whereas protein expression of SERCA2a in the different chambers was unchanged in NF (3.9 +/- 0.3 and 3.2 +/- 0.4 densitometric units in LV and RA, respectively) and DCM hearts (4.8 +/- 0.8 and 3.4 +/- 0.1 densitometric units in LV and RA, respectively). Phosphorylation of PLB was higher in LV than in RA in NF (Ser(16): 180.5 +/- 19.0 vs. 56.8 +/- 6.0 densitometric units; Thr(17): 174.6 +/- 11.2 vs. 37.4 +/- 8.9 densitometric units) and DCM hearts (Ser(16): 132.0 +/- 5.4 vs. 22.4 +/- 3.5 densitometric units; Thr(17): 131.2 +/- 10.9 vs. 9.2 +/- 2.4 densitometric units). SERCA2a function, but not protein expression, correlated well with the functional parameters of the FFR in DCM and NF human hearts. Regulation of SERCA2a function depends on the phosphorylation of PLB at Ser(16) and Thr(17). However, direct SERCA2a regulation might also be affected by an unknown mechanism.

Investigations on oxidative stress and therapeutical implications in dementia

Alzheimer's disease (AD) is a progressive dementia affecting a large proportion of the aging population. The histopathological changes in AD include neuronal cell death and formation of amyloid plaques and neurofibrillary tangles (NFTs) NFTs are composed of hyperphosphorylated tau protein, and senile plaques contain aggregates of the beta-peptide. There is also evidence that brain tissue in patients with AD is exposed to oxidative stress during the course of the disease. Advanced glycation endproducts (AGEs), which are formed by a non-enzymatic reaction of glucose with long-lived protein deposits, are potentially toxic to the cell, are present in brain plaques in AD, and its extracellular accumulation in AD may be caused by an accelerated oxidation of glycated proteins. The microtubuli-associated protein tau is also subject to intracellular AGE formation. AGEs participate in neuronal death causing direct (chemical) radical production: Glycated proteins produce nearly 50-fold more radicals than non-glycated proteins, and indirect (cellular) radical production: Interaction of AGEs with cells increases oxidative stress. During aging cellular defence mechanisms weaken and the damages to cell constituents accumulate leading to loss of function and finally cell death. The development of drugs for the treatment of AD remains at a very unsatisfying state. However, pharmacological approaches which break the vicious cycles of oxidative stress and neurodegeneration offer new opportunities for the treatment of AD. Theses approaches include AGE-inhibitors, antioxidants, and anti-inflammatory substances, which prevent radical production. AGE inhibitors might be able to stop formation of AGE-modified beta-amyloid deposits, antioxidants are likely to scavenge intracellular and extracellular superoxide radicals and hydrogen peroxide before these radicals damage cell constituents or activate microglia, and anti-inflammatory drugs attenuating microglial radical and cytokine production.

Evaluation of sympathetic nerve terminals with [(11)C]epinephrine and [(11)C]hydroxyephedrine and positron emission tomography

BACKGROUND

The goal of the present study was to directly compare the new radiopharmaceutical agent [(11)C]epinephrine (EPI) with [(11)C]hydroxyephedrine (HED) through the use of PET.

METHODS AND RESULTS

Seven healthy volunteers and 10 patients were investigated after heart transplantation. PET images of both tracers were of excellent quality in the volunteers. Values for radiolabeled metabolites (measured in percent of blood activity) at 5, 20, and 60 minutes after injection were approximately 35%, approximately 82%, and approximately 86% for EPI and approximately 13%, approximately 47%, and approximately 78% for HED, respectively. At 35 minutes, metabolite-corrected mean myocardial retention fraction of EPI (0. 235+/-0.022 min(-1)) was significantly greater (P<0.01) than that of HED (0.142+/-0.012 min(-1)). Corrected tracer retention fractions of both EPI and HED were significantly reduced in transplant recipients (0.055+/-0.004 min(-1), P<0.0001; and 0.050+/-0.006 min(-1), P<0. 0001, respectively) compared with volunteers. Normalization of retention fractions of patients with transplantation within 1 year to volunteers resulted in a value (ratio expressed in percent) of 20. 6+/-1.8% for EPI, significantly (P<0.03) smaller than 27.8+/-0.8% for HED. In patients with transplantation later than 1 year, the values were 26.0+/-2.9% for EPI compared with 44.2+/-5.6% for HED (P<0.014).

CONCLUSIONS

Both tracers showed high selectivity for neuronal uptake in the heart, with a significant reduction in tracer retention in transplant recipients compared with volunteers. Compared with HED, EPI showed greater retention in volunteers and a lower retention ratio in transplant recipients, suggesting that EPI may be the superior tracer with higher sensitivity to neuronal abnormalities. Because EPI reflects neuronal uptake, metabolism, and storage, it may be more suitable for the study of neuronal integrity than HED, which primarily traces uptake-1 capacity.

N(2)-(1-Carboxyethyl)deoxyguanosine, a nonenzymatic glycation adduct of DNA, induces single-strand breaks and increases mutation frequencies

N(2)-(1-Carboxyethyl)deoxyguanosine (CEdG) is a major nonenzymatic glycation product of DNA. The effect of CEdG modification, which was specifically prepared by incubation with dihydroxyacetone, on plasmid DNA topology was evaluated by gel electrophoresis. A time-dependent decrease of supercoiled plasmid-DNA was observed in parallel to the increase of CEdG adducts; the half-life time of the supercoiled plasmid-DNA was estimated to be approximately 16-18 h. CEdG-modified plasmid DNA showed a 25-fold reduced transformation efficiency. When modified DNA was used to transform Escherichia coli cells, a 6-fold increase in mutation frequency was determined by measuring loss of alpha-complementation. For the mutator strain BMH71-18mutS, an 8-fold increase in mutation frequency was observed. Although the exact mechanism of DNA damage is unclear, the occurrence of spontaneous depurination is likely. These findings suggest that a defined DNA glycation reaction can lead to DNA damage in vivo.

Amino acid specificity of glycation and protein-AGE crosslinking reactivities determined with a dipeptide SPOT library

Advanced glycation end products (AGEs) contribute to changes in protein conformation, loss of function, and irreversible crosslinking. Using a library of dipeptides on cellulose membranes (SPOT library), we have developed an approach to systematically assay the relative reactivities of amino acid side chains and the N-terminal amino group to sugars and protein-AGEs. The sugars react preferentially with cysteine or tryptophan when both the alpha-amino group and the side chains are free. In peptides with blocked N-terminus and free side chains, cysteine, lysine, and histidine were preferred. Crosslinking of protein-AGEs to dipeptides with free side chains and blocked N termini occurred preferentially to arginine and tryptophan. Dipeptide SPOT libraries are excellent tools for comparing individual reactivities of amino acids for nonenzymatic modifications, and could be extended to other chemically reactive molecules.

Experimental induction of AGEs in fetal L132 lung cells changes the level of intracellular cathepsin D

The effect of the carbonyl compound glyoxal on the induction of advanced glycation end products (AGEs) in the fetal epithelial lung cells L132 was investigated using immunohistochemical, immunoelectron microscopic, and biochemical methods. It was found that glyoxal treatment resulted in morphological changes of the cells and in the membranous and cytosolic localization of AGEs such as methyl-glyoxal-derived compounds, N-(carboxymethyllysine) (CML) and imidazolone. The formation of AGEs was accompanied with a change in the intracellular expression of cathepsin D and a loss of enzymatic activity.

Advanced glycation end-product levels in subtotally nephrectomized rats: beneficial effects of angiotensin II receptor 1 antagonist losartan

The angiotensin II receptor 1 antagonist losartan (L) inhibited the advanced glycated end-products (AGEs) induced expression of transforming growth factor beta(1) in in vitro experiments performed on renal tubuloepithelial cells. To test the pathophysiological importance of these findings, the possible link between serum AGEs levels and angiotensin system was investigated in the model of normotensive subtotally nephrectomized rats(4/6-NX). Concentration of AGEs in serum of placebo administered 4/6-NX rats (n = 7, 1.09+/-0.09 U/l) increased slightly in comparison with sham-operated healthy controls (CTRL, n = 8, 0.94+/-0.10 U/l, p<0.02) as measured by competitive ELISA. Treatment of 4/6-NX rats with L over 12 weeks ameliorated the rise in serum AGEs concentration (1.00+/-0.12 U/l, n = 15 <0.005) almost to the level observed for CTRL. This effect was further corroborated by the observation, that the impaired renal excretion of AGEs in 4/6-NX-placebo rats (0.07+/-0.02 U/micromol creatinine) was significantly restored by L (0.09+/-0.02 U/micromol creatinine, <0.009) and resembled that of the CTRL (0.10+/-0.03 U/micromol creatinine). Administration of L to 4/6-NX rats significantly improved renal function as evaluated by a smaller rise in serum creatinine and urea concentration. In spite of the improvement in renal function, there were no differences in concentrations of transforming growth factor beta(1) in serum and in urine among the two groups. These effects were independent of blood pressure. Our data give first evidence, that long-term treatment with angiotensin II receptor 1 antagonist may exert salutary effects on AGEs levels in the rat remnant kidney model, probably due to improved renal function.