Der Einfluss AICD abhängiger Lipidveränderungen auf die APP-Prozessierung und die mögliche Implikation der Methylxanthine bei der Alzheimer Erkrankung

Die Alzheimer Krankheit (AD) ist die häufigste Form der Demenz und eine der häufigsten Todesursachen in den Industrienationen. AD ist durch neuronale Degeneration gekennzeichnet und führt so zum Verlust kognitiver Funktion. Die Pathogenese von AD ist unter anderem durch die Akkumulation extrazellulärer amyloider Plaques, bestehend aus Amyloid-β (Aβ), dem Auftreten intrazellulärer Neurofibrillenbündel sowie erhöhtem oxidativen Stress, einer Veränderung der Elektrophysiologie und einer veränderten Lipidkomposition charakterisiert. Aβ entsteht infolge der amyloidogenen Prozessierung des Vorläuferproteins APP. Die amyloidogene APP-Prozessierung erfolgt durch die proteolytische Aktivität der β- und γ-Sekretase, während die nicht-amyloidogene Prozessierung durch die α- und γ-Sekretase vermittelt wird und die Entstehung von Aβ unterbindet. Es wird seit längerem eine genregulatorische Aktivität der intrazellulären Domäne von APP (AICD) diskutiert. Verschiedene Forschungsgruppen konnten zeigen, dass AICD durch die Aktivität der γ-Sekretase in das Zytosol freigesetzt wird und dort mit Adaptorproteinen interagieren kann, um schließlich in den Nukleus zu translozieren. Es wurde eine Vielzahl möglicher Zielgene postuliert. Sowohl APP als auch die APP-prozessierenden Sekretasen sind membranständige Proteine. Ein Einfluss der Lipidumgebung auf die APP-Prozessierung konnte in zahlreichen Studien bestätigt werden. Weiterhin konnten markante Veränderungen des Lipidprofils im Hirngewebe von AD-Patienten demonstrieren werden. Daher werden Veränderungen der Lipidkomposition sowohl in der Entstehung der AD als auch im Verlauf der Erkrankung diskutiert. Diese Arbeit untersucht den Einfluss von AICD auf die Lipidspezies der Phosphatidylcholine, Phosphatidylethanolamine, Ceramide und lysierten Phosphatidylcholine. Im ersten Teil der vorliegenden Arbeit wurden Lipidextrakte von AICD-defizienten Zellen und von Wildtyp-Zellen extrahiert, massenspektrometrisch analysiert und der Anteil der mehrfach ungesättigten Fettsäuren der einzelnen Lipidspezies untersucht. Die Lipidextrakte AICD-defizienter Zellen zeigten vor allem in der Lipidspezies der Phosphatidylethanolamine ein erhöhtes Verhältnis von mehrfach ungesättigten Fettsäuren im Vergleich zu gesättigten oder einfach ungesättigten Fettsäuren sowie eine erhöhte Konzentration von Docosahexaensäure. Außerdem wurde der bereits publizierte Einfluss von AICD auf die Ceramide und Plasmalogene bestätigt. Im zweiten Teil der Arbeit wurde der Einfluss der generierten Lipidextrakte auf die β- und auf die γ-Sekretase untersucht. Hierfür wurden humane Neuroblastom-Zellen und murine Fibroblasten mit Lipidextrakten behandelt. Die Lipidextrakte AICD-defizienter Zellen führten zu einer signifikanten Reduktion des Gesamt-Aβ, während die Lipidextrakte von Wildtyp- und von AICD-überexprimierenden Zellen zu einer Erhöhung führten. Als Mechanismus konnte eine direkte, modifizierende Wirkung der Lipidextrakte sowohl auf die β- als auch auf die γ-Sekretase identifiziert werden. Es besteht eine bidirektionale Wechselwirkung zwischen der APP-Prozessierung und der Lipidhomöostase. Das Verständnis dieser Interaktion soll in dieser Arbeit durch den Einfluss von AICD auf die mehrfach ungesättigten Fettsäuren ergänzt werden. Abschließend untersucht diese Arbeit die Methylxanthine Coffein und Propentofyllin. Beide Substanzen werden als therapeutische Optionen für die Behandlung der AD diskutiert. Im Rahmen dieser Arbeit konnte ein direkter Effekt der Methylxanthine auf die α- und β-Sekretase nachgewiesen werden.Alzheimer´s disease (AD) is the most common type of dementia and a leading cause of death in the first world. AD is defined by neuronal degeneration leading to a loss of cognitive function. The pathogenesis of AD is characterized by the accumulation of amyloid plaques, consisting of amyloid-β, the occurrence of intracellular neurofibrillary tangles, oxidative stress, alterations of the electrophysiology and a change in lipid composition. Aβ is produced as a result of the amyloidogenic processing of its precursor protein APP. The amyloidogenic proteolysis of APP is mediated by the β- and γ-secretase, while the non-amyloidogenic pathway mediated by α- and γ-secretase activity excludes the production of Aβ. The intracellular domain of APP is discussed to have gene-regulatory properties. Various research teams demonstrated that AICD is liberated into the cytosol by γ-secretase activity and able to interact with adaptor proteins, finally translocating in to the nucleus. A multitude of possible target genes were postulated in this context. Both APP and the APP-processing secretases are membrane bound proteins and an effect of the lipid environment on the processing of APP was demonstrated in multiple studies. Additionally, various research teams observed striking alterations of the lipid profile in the brain tissue of AD patients. As a result, changes of the lipid profile are discussed in the development and the course of AD. This thesis studies the impact of AICD on phosphatidylcholin, phosphatidylethanolamin, ceramides and lysed phosphatidylcholin. Lipid extractions of both AICD-deficient cells and wild type cells were generated and analyzed by mass spectrometry. The saturation level of each lipid was investigated. The lipid extractions of AICD-deficient cells showed an increase in poly unsaturated phosphatidylethanolamine as compared to single unsaturated or saturated fatty acids and an increase in docosahexaenoic acid. Additionally the already published effect of AICD on ceramid and plasmalogen levels was reproduced. The second part of the thesis studied the effect of the generated lipid extracts on the β- and γ-secretase. Humane neuroblastoma cells and murine fibroblasts were treated with 4 the lipid extracts and total Aβ was quantified using Western blotting. The incubation of lipid extracts from AICD-deficient cells resulted in a significant reduction of total Aβ levels, while the lipid extracts of AICD expressing cells lead to an increase. Mechanistically, this thesis demonstrates a direct modification of β- and γ-secretase activity by the lipid extractions. A bidirectional interaction between APP-processing and the lipid homeostasis has been described. The effect of AICD on poly unsaturated fatty acids additionally contributes to this interaction. Lastly, this thesis examines the xanthine compounds Caffeine and Propentofylline. Both substances have been discussed as therapeutic options in the treatment of AD. The methylxanthine derivates showed a direct effect on α- and β-secretase activity

Inclusion body myositis and associated diseases: an argument for shared immune pathologies

Inclusion body myositis (IBM) is the most prevalent idiopathic inflammatory myopathy (IIM) affecting older adults. The pathogenic hallmark of IBM is chronic inflammation of skeletal muscle. At present, we do not classify IBM into different sub-entities, with the exception perhaps being the presence or absence of the anti-cN-1A-antibody. In contrast to other IIM, IBM is characterized by a chronic and progressive disease course. Here, we discuss the pathophysiological framework of IBM and highlight the seemingly prototypical situations where IBM occurs in the context of other diseases. In this context, understanding common immune pathways might provide insight into the pathogenesis of IBM. Indeed, IBM is associated with a distinct set of conditions, such as human immunodeficiency virus (HIV) or hepatitis C-two conditions associated with premature immune cell exhaustion. Further, the pathomorphology of IBM is reminiscent of other muscle diseases, notably HIV-associated myositis or granulomatous myositis. Distinct immune pathways are likely to drive these commonalities and senescence of the CD8(+) T cell compartment is discussed as a possible mechanism of pathogenesis. Future effort directed at understanding the co-occurrence of IBM and associated diseases could prove valuable to better understand the enigmatic IBM pathophysiology

Effect of Caffeine and Other Methylxanthines on Aβ-Homeostasis in SH-SY5Y Cells

Methylxanthines (MTX) are alkaloids derived from the purine-base xanthine. Whereas especially caffeine, the most prominent known MTX, has been formerly assessed to be detrimental, this point of view has changed substantially. MTXs are discussed to have beneficial properties in neurodegenerative diseases, however, the mechanisms of action are not completely understood. Here we investigate the effect of the naturally occurring caffeine, theobromine and theophylline and the synthetic propentofylline and pentoxifylline on processes involved in Alzheimer’s disease (AD). All MTXs decreased amyloid-β (Aβ) level by shifting the amyloid precursor protein (APP) processing from the Aβ-producing amyloidogenic to the non-amyloidogenic pathway. The α-secretase activity was elevated whereas β-secretase activity was decreased. Breaking down the molecular mechanism, caffeine increased protein stability of the major α-secretase ADAM10, downregulated BACE1 expression and directly decreased β-secretase activity. Additionally, APP expression was reduced. In line with literature, MTXs reduced oxidative stress, decreased cholesterol and a decreased in Aβ1-42 aggregation. In conclusion, all MTXs act via the pleiotropic mechanism resulting in decreased Aβ and show beneficial properties with respect to AD in neuroblastoma cells. However, the observed effect strength was moderate, suggesting that MTXs should be integrated in a healthy diet rather than be used exclusively to treat or prevent AD

Real-world evidence on siponimod treatment in patients with secondary progressive multiple sclerosis

BACKGROUND: Therapeutic options targeting inflammation in multiple sclerosis (MS) have evolved rapidly for relapsing–remitting MS, whereas few therapies are available for progressive forms of MS, in particular secondary progressive MS (SPMS). The approval of siponimod for SPMS has allowed for optimism in the otherwise discouraging therapeutic landscape. METHODS: We conducted a retrospective, multicenter, non-interventional study analyzing the efficacy and safety of siponimod under real-world conditions in 227 SPMS patients. According to the retrospective study framework, data was acquired at prespecified time points. Clinical readouts were assessed every three months. Disease progression was determined as increase in expanded disability status scale (EDSS), radiological progression, or the occurrence of new relapses under treatment. For safety analyses, adverse events (AE) and reasons for discontinuation were documented. The collected data points were analyzed at baseline and after 6, 12 and 18 months. However, data were predominately collected at the 6- and 12-month time points as many patients were lost to follow-up. In a group consisting of 41 patients, a more detailed investigation regarding disease progression was conducted, including data from measurement of cognitive and motoric functions. RESULTS: Under siponimod therapy, 64.8% of patients experienced sustained clinical disease stability at 12 months. Out of the stable patients 21.4% of patients improved. Of the remaining patients, 31.5% experienced EDSS progression, 3.7% worsened without meeting the threshold for progression. Relapses occurred in 7.4%. Radiological disease activity was detected in 24.1% of patients after six months of treatment and in 29.6% of patients at 12 months follow-up. The in-depth cohort consisting of 41 patients demonstrated no substantial changes in cognitive abilities measured by Paced Auditory Serial Addition Test and Symbol Digit Modalities Test or motoric functions measured with Timed 25-Foot Walk, 100-m timed test, and 9-Hole Peg Test throughout the 12-month study period. Radiological assessment showed a stable volume of white and grey matter, as well as a stable lesion count at 12 months follow-up. AE were observed in nearly half of the included patients, with lymphopenia being the most common. Due to disease progression or AE, 31.2% of patients discontinued therapy. CONCLUSION: Treatment with siponimod had an overall stabilizing effect regarding clinical and radiological outcome measures. However, there is a need for more intensive treatment management and monitoring to identify disease progression and AE. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s42466-022-00219-3

Tocotrienol Affects Oxidative Stress, Cholesterol Homeostasis and the Amyloidogenic Pathway in Neuroblastoma Cells: Consequences for Alzheimer’s Disease

One of the characteristics of Alzheimer´s disease (AD) is an increased amyloid load and an enhanced level of reactive oxidative species (ROS). Vitamin E has known beneficial neuroprotective effects, and previously, some studies suggested that vitamin E is associated with a reduced risk of AD due to its antioxidative properties. However, epidemiological studies and nutritional approaches of vitamin E treatment are controversial. Here, we investigate the effect of α-tocotrienol, which belongs to the group of vitamin E, on AD-relevant processes in neuronal cell lines. In line with the literature, α-tocotrienol reduced the ROS level in SH-SY5Y cells. In the presence of tocotrienols, cholesterol and cholesterol esters, which have been shown to be risk factors in AD, were decreased. Besides the unambiguous positive effects of tocotrienol, amyloid-β (Aβ) levels were increased accompanied by an increase in the activity of enzymes responsible for Aβ production. Proteins and gene expression of the secretases and their components remained unchanged, whereas tocotrienol accelerates enzyme activity in cell-free assays. Besides enhanced Aβ production, tocotrienols inhibited Aβ degradation in neuro 2a (N2a)-cells. Our results might help to understand the controversial findings of vitamin E studies and demonstrate that besides the known positive neuroprotective properties, tocotrienols also have negative characteristics with respect to AD

Vitamin D and Its Analogues Decrease Amyloid-β (Aβ) Formation and Increase Aβ-Degradation

Alzheimer’s disease (AD) is characterized by extracellular plaques in the brain, mainly consisting of amyloid-β (Aβ), as derived from sequential cleavage of the amyloid precursor protein. Epidemiological studies suggest a tight link between hypovitaminosis of the secosteroid vitamin D and AD. Besides decreased vitamin D level in AD patients, an effect of vitamin D on Aβ-homeostasis is discussed. However, the exact underlying mechanisms remain to be elucidated and nothing is known about the potential effect of vitamin D analogues. Here we systematically investigate the effect of vitamin D and therapeutically used analogues (maxacalcitol, calcipotriol, alfacalcidol, paricalcitol, doxercalciferol) on AD-relevant mechanisms. D2 and D3 analogues decreased Aβ-production and increased Aβ-degradation in neuroblastoma cells or vitamin D deficient mouse brains. Effects were mediated by affecting the Aβ-producing enzymes BACE1 and γ-secretase. A reduced secretase activity was accompanied by a decreased BACE1 protein level and nicastrin expression, an essential component of the γ-secretase. Vitamin D and analogues decreased β-secretase activity, not only in mouse brains with mild vitamin D hypovitaminosis, but also in non-deficient mouse brains. Our results further strengthen the link between AD and vitamin D, suggesting that supplementation of vitamin D or vitamin D analogues might have beneficial effects in AD prevention

Myositis in Germany: epidemiological insights over 15 years from 2005 to 2019

Abstract Background The medical care of patients with myositis is a great challenge in clinical practice. This is due to the rarity of these disease, the complexity of diagnosis and management as well as the lack of systematic analyses. Objectives Therefore, the aim of this project was to obtain an overview of the current care of myositis patients in Germany and to evaluate epidemiological trends in recent years. Methods In collaboration with BARMER Insurance, retrospective analysis of outpatient and inpatient data from an average of approximately 8.7 million insured patients between January 2005 and December 2019 was performed using ICD-10 codes for myositis for identification of relevant data. In addition, a comparative analysis was performed between myositis patients and an age-matched comparison group from other populations insured by BARMER. Results 45,800 BARMER-insured individuals received a diagnosis of myositis during the observation period, with a relatively stable prevalence throughout. With regard to comorbidities, a significantly higher rate of cardiovascular disease as well as neoplasm was observed compared to the control group within the BARMER-insured population. In addition, myositis patients suffer more frequently from psychiatric disorders, such as depression and somatoform disorders. However, the ICD-10 catalogue only includes the specific coding of “dermatomyositis” and “polymyositis” and thus does not allow for a sufficient analysis of all idiopathic inflammatory myopathies subtypes. Conclusion The current data provide a comprehensive epidemiological analysis of myositis in Germany, highlighting the multimorbidity of myositis patients. This underlines the need for multidisciplinary management. However, the ICD-10 codes currently still in use do not allow for specific analysis of the subtypes of myositis. The upcoming ICD-11 coding may improve future analyses in this regard

Effect of Caffeine and Other Methylxanthines on Aβ-Homeostasis in SH-SY5Y Cells

Methylxanthines (MTX) are alkaloids derived from the purine-base xanthine. Whereas especially caffeine, the most prominent known MTX, has been formerly assessed to be detrimental, this point of view has changed substantially. MTXs are discussed to have beneficial properties in neurodegenerative diseases, however, the mechanisms of action are not completely understood. Here we investigate the effect of the naturally occurring caffeine, theobromine and theophylline and the synthetic propentofylline and pentoxifylline on processes involved in Alzheimer’s disease (AD). All MTXs decreased amyloid-β (Aβ) level by shifting the amyloid precursor protein (APP) processing from the Aβ-producing amyloidogenic to the non-amyloidogenic pathway. The α-secretase activity was elevated whereas β-secretase activity was decreased. Breaking down the molecular mechanism, caffeine increased protein stability of the major α-secretase ADAM10, downregulated BACE1 expression and directly decreased β-secretase activity. Additionally, APP expression was reduced. In line with literature, MTXs reduced oxidative stress, decreased cholesterol and a decreased in Aβ1-42 aggregation. In conclusion, all MTXs act via the pleiotropic mechanism resulting in decreased Aβ and show beneficial properties with respect to AD in neuroblastoma cells. However, the observed effect strength was moderate, suggesting that MTXs should be integrated in a healthy diet rather than be used exclusively to treat or prevent AD

An enigmatic case of cortical anopsia: Antemortem diagnosis of a 14-3-3 negative Heidenhain-variant MM1-sCJD

Sporadic Creutzfeldt-Jakob disease is the predominant type of human prion disease. While routine diagnostic in phenotypic cases has advanced considerably, the clinical heterogeneity and rarity of subtypes continue to constitute a major clinical and diagnostic challenge. Here, we report a peculiar case of the Heidenhain-variant of MM1 sporadic Creutzfeldt-Jakob disease presenting as a stroke mimic in an 81-year-old patient with a rapid and clinically distinct course of disease as compared to previously reported cases. While 14-3-3 protein was negative, clinical findings substantiated by 18F-FDG-PET imaging and RT-QuIC-Assay were able to establish the diagnosis. We conclude that in cases presenting with rapid progressive dementia secondary to sudden cortical anopsia the Heidenhain-variant of CJD should be considered