Genicular Artery Embolisation in Patients with Osteoarthritis of the Knee (GENESIS 2): Protocol for a Double-Blind Randomised Sham-Controlled Trial.

Knee osteoarthritis is a leading cause of chronic disability and economic burden. In many patients who are not surgical candidates, existing treatment options are insufficient. Clinical evidence for a new treatment approach, genicular artery embolisation (GAE), is currently limited to single arm cohort, or small population randomised studies. This trial will investigate the use of a permanent embolic agent for embolisation of abnormal genicular arterial vasculature to reduce pain in patients with mild to moderate knee osteoarthritis. Up to 110 participants, 45 years or older, with knee pain for ≥ 3 months resistant to conservative treatment will be randomised (1:1) to GAE or a sham procedure. The treatment group will receive embolisation using 100-micron Embozene™ microspheres (Varian, a Siemens Healthineers Company) (investigational use for this indication in the UK), and the sham group will receive 0.9% saline in an otherwise identical procedure. Patients will be followed for 24 months. At 6 months, sham participants will be offered crossover to GAE. The primary endpoint is change of 4 Knee Injury and OA Outcome Score subscales (KOOS4) at 6 months post-randomisation. The study will also evaluate quality of life, health economics, imaging findings, and psychosocial pain outcomes. The primary manuscript will be submitted for publication after all participants complete 6 months of follow-up. The trial is expected to run for 3.5 years. Trial Registration: ClinicalTrials.gov, Identifier: NCT05423587.

The Influence of Acitretin on Brain Lipidomics in Adolescent Mice-Implications for Pediatric and Adolescent Dermatological Therapy.

Administration of systemic retinoids such as acitretin has not been approved yet for pediatric patients. An adverse event of retinoid-therapy that occurs with lower prevalence in children than in adults is hyperlipidemia. This might be based on the lack of comorbidities in young patients, but must not be neglected. Especially for the development of the human brain up to young adulthood, dysbalance of lipids might be deleterious. Here, we provide for the first time an in-depth analysis of the influence of subchronic acitretin-administration on lipid composition of brain parenchyma of young wild type mice. For comparison and to evaluate the systemic effect of the treatment, liver lipids were analogously investigated. As expected, triglycerides increased in liver as well as in brain and a non-significant increase in cholesterol was observed. However, specifically brain showed an increase in lyso-phosphatidylcholine and carnitine as well as in sphingomyelin. Group analysis of lipid classes revealed no statistical effects, while single species were tissue-dependently changed: effects in brain were in general more subtly as compared to those in liver regarding the mere number of changed lipid species. Thus, while the overall impact of acitretin seems comparably small regarding brain, the change in individual species and their role in brain development and maturation has to be considered.

COVID-19 vaccination in patients with immune thrombocytopenia.

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder that is characterized by low platelet count and increased bleeding risk. COVID-19 vaccination has been described as a risk factor for de novo ITP, but the effects of COVID-19 vaccination in patients with ITP are unknown. We aimed to investigate the effects of COVID-19 vaccination in patients with ITP on platelet count, bleeding complications, and ITP exacerbation (≥50% decline in platelet count, or nadir platelet count < 30 × 109/L with a >20% decrease from baseline, or use of rescue therapy). Platelet counts in patients with ITP and healthy controls were collected immediately before and 1 and 4 weeks after the first and second vaccinations. Linear mixed-effects modeling was applied to analyze platelet counts over time. We included 218 patients with ITP (50.9% female; mean age, 55 years; and median platelet count, 106 × 109/L) and 200 healthy controls (60.0% female; mean age, 58 years; median platelet count, 256 × 109/L). Platelet counts decreased by 6.3% after vaccination. We did not observe any difference in decrease between the groups. Thirty patients with ITP (13.8%; 95% confidence interval [CI], 9.5-19.1) had an exacerbation and 5 (2.2%; 95% CI, 0.7-5.3) suffered from a bleeding event. Risk factors for ITP exacerbation were platelet count < 50 × 109/L (odds ratio [OR], 5.3; 95% CI, 2.1-13.7), ITP treatment at time of vaccination (OR, 3.4; 95% CI, 1.5-8.0), and age (OR, 0.96 per year; 95% CI, 0.94-0.99). Our study highlights the safety of COVID-19 vaccination in patients with ITP and the importance of the close monitoring of platelet counts in a subgroup of patients with ITP. Patients with ITP with exacerbation responded well on therapy.

Medium-Chain Length Fatty Acids Enhance Aß Degradation by Affecting Insulin-Degrading Enzyme.

The accumulation of amyloid ß-protein (Aß) is one of the major pathological hallmarks of Alzheimer's disease. Insulin-degrading enzyme (IDE), a zinc-metalloprotease, is a key enzyme involved in Aß degradation, which, in addition to Aß production, is critical for Aß homeostasis. Here, we demonstrate that saturated medium-chain fatty acids (MCFAs) increase total Aß degradation whereas longer saturated fatty acids result in an inhibition of its degradation, an effect which could not be detected in IDE knock-down cells. Further analysis of the underlying molecular mechanism revealed that MCFAs result in an increased exosomal IDE secretion, leading to an elevated extracellular and a decreased intracellular IDE level whereas gene expression of IDE was unaffected in dependence of the chain length. Additionally, MCFAs directly elevated the enzyme activity of recombinant IDE, while longer-chain length fatty acids resulted in an inhibited IDE activity. The effect of MCFAs on IDE activity could be confirmed in mice fed with a MCFA-enriched diet, revealing an increased IDE activity in serum. Our data underline that not only polyunsaturated fatty acids such as docosahexaenoic acid (DHA), but also short-chain fatty acids, highly enriched, for example in coconut oil, might be beneficial in preventing or treating Alzheimer's disease.

Effect of Prophylactic Subcutaneous Scopolamine Butylbromide on Death Rattle in Patients at the End of Life: The SILENCE Randomized Clinical Trial.

Importance: Death rattle, defined as noisy breathing caused by the presence of mucus in the respiratory tract, is relatively common among dying patients. Although clinical guidelines recommend anticholinergic drugs to reduce the death rattle after nonpharmacological measures fail, evidence regarding their efficacy is lacking. Given that anticholinergics only decrease mucus production, it is unknown whether prophylactic application may be more appropriate. Objective: To determine whether administration of prophylactic scopolamine butylbromide reduces the death rattle. Design, Setting, and Participants: A multicenter, randomized, double-blind, placebo-controlled trial was performed in 6 hospices in the Netherlands. Patients with a life expectancy of 3 or more days who were admitted to the participating hospices were asked to give advance informed consent from April 10, 2017, through December 31, 2019. When the dying phase was recognized, patients fulfilling the eligibility criteria were randomized. Of the 229 patients who provided advance informed consent, 162 were ultimately randomized. The date of final follow-up was January 31, 2020. Interventions: Administration of subcutaneous scopolamine butylbromide, 20 mg four times a day (n = 79), or placebo (n = 78). Main Outcomes and Measures: The primary outcome was the occurrence of a grade 2 or higher death rattle as defined by Back (range, 0-3; 0, no rattle; 3, rattle audible standing in the door opening) measured at 2 consecutive time points with a 4-hour interval. Secondary outcomes included the time between recognizing the dying phase and the onset of a death rattle and anticholinergic adverse events. Results: Among 162 patients who were randomized, 157 patients (97%; median age, 76 years [IQR, 66-84 years]; 56% women) were included in the primary analyses. A death rattle occurred in 10 patients (13%) in the scopolamine group compared with 21 patients (27%) in the placebo group (difference, 14%; 95% CI, 2%-27%, P = .02). Regarding secondary outcomes, an analysis of the time to death rattle yielded a subdistribution hazard ratio (HR) of 0.44 (95% CI, 0.20-0.92; P = .03; cumulative incidence at 48 hours: 8% in the scopolamine group vs 17% in the placebo group). In the scopolamine vs placebo groups, restlessness occurred in 22 of 79 patients (28%) vs 18 of 78 (23%), dry mouth in 8 of 79 (10%) vs 12 of 78 (15%), and urinary retention in 6 of 26 (23%) vs 3 of 18 (17%), respectively. Conclusions and Relevance: Among patients near the end of life, prophylactic subcutaneous scopolamine butylbromide, compared with placebo, significantly reduced the occurrence of the death rattle. Trial Registration: trialregister.nl Identifier: NTR6264.

Shotgun lipidomics of liver and brain tissue of Alzheimer's disease model mice treated with acitretin.

Alzheimer's disease (AD) is a very frequent neurodegenerative disorder characterized by an accumulation of amyloid-ß (Aß). Acitretin, a retinoid-derivative and approved treatment for Psoriasis vulgaris, increases non-amyloidogenic Amyloid-Precursor-Protein-(APP)-processing, prevents Aß-production and elicits cognitive improvement in AD mouse models. As an unintended side effect, acitretin could result in hyperlipidemia. Here, we analyzed the impact of acitretin on the lipidome in brain and liver tissue in the 5xFAD mouse-model. In line with literature, triglycerides were increased in liver accompanied by increased PCaa, plasmalogens and acyl-carnitines, whereas SM-species were decreased. In brain, these effects were partially enhanced or similar but also inverted. While for SM and plasmalogens similar effects were found, PCaa, TAG and acyl-carnitines showed an inverse effect in both tissues. Our findings emphasize, that potential pharmaceuticals to treat AD should be carefully monitored with respect to lipid-homeostasis because APP-processing itself modulates lipid-metabolism and medication might result in further and unexpected changes. Moreover, deducing effects of brain lipid-homeostasis from results obtained for other tissues should be considered cautiously. With respect to acitretin, the increase in brain plasmalogens might display a further positive probability in AD-treatment, while other results, such as decreased SM, indicate the need of medical surveillance for treated patients.

Methylxanthines and Neurodegenerative Diseases: An Update.

Methylxanthines (MTX) are purine derived xanthine derivatives. Whereas naturally occurring methylxanthines like caffeine, theophylline or theobromine are widely consumed in food, several synthetic but also non-synthetic methylxanthines are used as pharmaceuticals, in particular in treating airway constrictions. Besides the well-established bronchoprotective effects, methylxanthines are also known to have anti-inflammatory and anti-oxidative properties, mediate changes in lipid homeostasis and have neuroprotective effects. Known molecular mechanisms include adenosine receptor antagonism, phosphodiesterase inhibition, effects on the cholinergic system, wnt signaling, histone deacetylase activation and gene regulation. By affecting several pathways associated with neurodegenerative diseases via different pleiotropic mechanisms and due to its moderate side effects, intake of methylxanthines have been suggested to be an interesting approach in dealing with neurodegeneration. Especially in the past years, the impact of methylxanthines in neurodegenerative diseases has been extensively studied and several new aspects have been elucidated. In this review we summarize the findings of methylxanthines linked to Alzheimer´s disease, Parkinson's disease and Multiple Sclerosis since 2017, focusing on epidemiological and clinical studies and addressing the underlying molecular mechanisms in cell culture experiments and animal studies in order to assess the neuroprotective potential of methylxanthines in these diseases.

Unique Role of Caffeine Compared to Other Methylxanthines (Theobromine, Theophylline, Pentoxifylline, Propentofylline) in Regulation of AD Relevant Genes in Neuroblastoma SH-SY5Y Wild Type Cells.

Methylxanthines are a group of substances derived from the purine base xanthine with a methyl group at the nitrogen on position 3 and different residues at the nitrogen on position 1 and 7. They are widely consumed in nutrition and used as pharmaceuticals. Here we investigate the transcriptional regulation of 83 genes linked to Alzheimer's disease in the presence of five methylxanthines, including the most prominent naturally occurring methylxanthines-caffeine, theophylline and theobromine-and the synthetic methylxanthines pentoxifylline and propentofylline. Methylxanthine-regulated genes were found in pathways involved in processes including oxidative stress, lipid homeostasis, signal transduction, transcriptional regulation, as well as pathways involved in neuronal function. Interestingly, multivariate analysis revealed different or inverse effects on gene regulation for caffeine compared to the other methylxanthines, which was further substantiated by multiple comparison analysis, pointing out a distinct role for caffeine in gene regulation. Our results not only underline the beneficial effects of methylxanthines in the regulation of genes in neuroblastoma wild-type cells linked to neurodegenerative diseases in general, but also demonstrate that individual methylxanthines like caffeine mediate unique or inverse expression patterns. This suggests that the replacement of single methylxanthines by others could result in unexpected effects, which could not be anticipated by the comparison to other substances in this substance class.

Regulatory feedback cycle of the insulin-degrading enzyme and the amyloid precursor protein intracellular domain: Implications for Alzheimer's disease.

One of the major pathological hallmarks of Alzheimer´s disease (AD) is an accumulation of amyloid-ß (Aß) in brain tissue leading to formation of toxic oligomers and senile plaques. Under physiological conditions, a tightly balanced equilibrium between Aß-production and -degradation is necessary to prevent pathological Aß-accumulation. Here, we investigate the molecular mechanism how insulin-degrading enzyme (IDE), one of the major Aß-degrading enzymes, is regulated and how amyloid precursor protein (APP) processing and Aß-degradation is linked in a regulatory cycle to achieve this balance. In absence of Aß-production caused by APP or Presenilin deficiency, IDE-mediated Aß-degradation was decreased, accompanied by a decreased IDE activity, protein level, and expression. Similar results were obtained in cells only expressing a truncated APP, lacking the APP intracellular domain (AICD) suggesting that AICD promotes IDE expression. In return, APP overexpression mediated an increased IDE expression, comparable results were obtained with cells overexpressing C50, a truncated APP representing AICD. Beside these genetic approaches, also AICD peptide incubation and pharmacological inhibition of the γ-secretase preventing AICD production regulated IDE expression and promoter activity. By utilizing CRISPR/Cas9 APP and Presenilin knockout SH-SY5Y cells results were confirmed in a second cell line in addition to mouse embryonic fibroblasts. In vivo, IDE expression was decreased in mouse brains devoid of APP or AICD, which was in line with a significant correlation of APP expression level and IDE expression in human postmortem AD brains. Our results show a tight link between Aß-production and Aß-degradation forming a regulatory cycle in which AICD promotes Aß-degradation via IDE and IDE itself limits its own production by degrading AICD.

The impact of capsaicinoids on APP processing in Alzheimer's disease in SH-SY5Y cells.

The vanilloid capsaicin is a widely consumed spice, known for its burning and "hot" sensation through activation of TRPV1 ion-channels, but also known to decrease oxidative stress, inflammation and influence tau-pathology. Beside these positive effects, little is known about its effects on amyloid-precursor-protein (APP) processing leading to amyloid-ß (Aß), the major component of senile plaques. Treatment of neuroblastoma cells with capsaicinoids (24 hours, 10 µM) resulted in enhanced Aß-production and reduced Aß-degradation, leading to increased Aß-levels. In detailed analysis of the amyloidogenic-pathway, both BACE1 gene-expression as well as protein-levels were found to be elevated, leading to increased ß-secretase-activity. Additionally, γ-secretase gene-expression as well as activity was enhanced, accompanied by a shift of presenilin from non-raft to raft membrane-domains where amyloidogenic processing takes place. Furthermore, impaired Aß-degradation in presence of capsaicinoids is dependent on the insulin-degrading-enzyme, one of the major Aß-degrading-enzymes. Regarding Aß-homeostasis, no differences were found between the major capsaicinoids, capsaicin and dihydrocapsaicin, and a mixture of naturally derived capsaicinoids; effects on Ca2+-homeostasis were ruled out. Our results show that in respect to Alzheimer's disease, besides the known positive effects of capsaicinoids, pro-amyloidogenic properties also exist, enhancing Aß-levels, likely restricting the potential use of capsaicinoids as therapeutic substances in Alzheimer's disease.

Profiling of Alzheimer's disease related genes in mild to moderate vitamin D hypovitaminosis.

A vast majority of the elderly population shows a mild to moderate vitamin D deficiency. Besides the well-known function of vitamin D, vitamin D receptor is also expressed in brain and is discussed to regulate several genes. However very little is known whether genes are regulated, associated with Alzheimer's disease (AD). Here we investigate 117 genes, known to be affected in AD, in mouse brain samples with a mild vitamin D hypovitaminosis comparable to the vitamin D status of the elderly population (20%-30% deficiency). The 117 genes include two positive controls, Nep and Park7, already known to be affected by both AD and vitamin D hypovitaminosis. The 25 most promising candidates were verified in a second independent mouse cohort, resulting in eleven genes further evaluated against three additional housekeeping genes. Three of the remaining eight significantly altered genes are involved in APP homeostasis (Snca, Nep, Psmb5), and each one gene in oxidative stress (Park7), inflammation (Casp4), lipid metabolism (Abca1), signal transduction (Gnb5) and neurogenesis (Plat). Our results tighten the link of vitamin D and AD and underline that vitamin D influences several genes also in brain, highlighting that a strong link not only to AD but also to other neurodegenerative diseases might exist.

Volatile biomarkers of symptomatic and asymptomatic malaria infection in humans.

Malaria remains among the world's deadliest diseases, and control efforts depend critically on the availability of effective diagnostic tools, particularly for the identification of asymptomatic infections, which play a key role in disease persistence and may account for most instances of transmission but often evade detection by current screening methods. Research on humans and in animal models has shown that infection by malaria parasites elicits changes in host odors that influence vector attraction, suggesting that such changes might yield robust biomarkers of infection status. Here we present findings based on extensive collections of skin volatiles from human populations with high rates of malaria infection in Kenya. We report broad and consistent effects of malaria infection on human volatile profiles, as well as significant divergence in the effects of symptomatic and asymptomatic infections. Furthermore, predictive models based on machine learning algorithms reliably determined infection status based on volatile biomarkers. Critically, our models identified asymptomatic infections with 100% sensitivity, even in the case of low-level infections not detectable by microscopy, far exceeding the performance of currently available rapid diagnostic tests in this regard. We also identified a set of individual compounds that emerged as consistently important predictors of infection status. These findings suggest that volatile biomarkers may have significant potential for the development of a robust, noninvasive screening method for detecting malaria infections under field conditions.

Vitamin D and Its Analogues Decrease Amyloid-ß (Aß) Formation and Increase Aß-Degradation.

Alzheimer's disease (AD) is characterized by extracellular plaques in the brain, mainly consisting of amyloid-ß (Aß), 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 Aß-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 Aß-production and increased Aß-degradation in neuroblastoma cells or vitamin D deficient mouse brains. Effects were mediated by affecting the Aß-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 ß-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.

APP Function and Lipids: A Bidirectional Link.

Extracellular neuritic plaques, composed of aggregated amyloid-ß (Aß) peptides, are one of the major histopathological hallmarks of Alzheimer's disease (AD), a progressive, irreversible neurodegenerative disorder and the most common cause of dementia in the elderly. One of the most prominent risk factor for sporadic AD, carrying one or two aberrant copies of the apolipoprotein E (ApoE) ε4 alleles, closely links AD to lipids. Further, several lipid classes and fatty acids have been reported to be changed in the brain of AD-affected individuals. Interestingly, the observed lipid changes in the brain seem not only to be a consequence of the disease but also modulate Aß generation. In line with these observations, protective lipids being able to decrease Aß generation and also potential negative lipids in respect to AD were identified. Mechanistically, Aß peptides are generated by sequential proteolytic processing of the amyloid precursor protein (APP) by ß- and γ-secretase. The α-secretase appears to compete with ß-secretase for the initial cleavage of APP, preventing Aß production. All APP-cleaving secretases as well as APP are transmembrane proteins, further illustrating the impact of lipids on Aß generation. Beside the pathological impact of Aß, accumulating evidence suggests that Aß and the APP intracellular domain (AICD) play an important role in regulating lipid homeostasis, either by direct effects or by affecting gene expression or protein stability of enzymes involved in the de novo synthesis of different lipid classes. This review summarizes the current literature addressing the complex bidirectional link between lipids and AD and APP processing including lipid alterations found in AD post mortem brains, lipids that alter APP processing and the physiological functions of Aß and AICD in the regulation of several lipid metabolism pathways.

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-ß (Aß) levels were increased accompanied by an increase in the activity of enzymes responsible for Aß production. Proteins and gene expression of the secretases and their components remained unchanged, whereas tocotrienol accelerates enzyme activity in cell-free assays. Besides enhanced Aß production, tocotrienols inhibited Aß 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.

Eicosapentaenoic acid and docosahexaenoic acid increase the degradation of amyloid-ß by affecting insulin-degrading enzyme.

Omega-3 polyunsaturated fatty acids (PUFAs) have been proposed to be highly beneficial in Alzheimer's disease (AD). AD pathology is closely linked to an overproduction and accumulation of amyloid-ß (Aß) peptides as extracellular senile plaques in the brain. Total Aß levels are not only dependent on its production by proteolytic processing of the amyloid precursor protein (APP), but also on Aß-clearance mechanisms, including Aß-degrading enzymes. Here we show that the omega-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increase Aß-degradation by affecting insulin-degrading enzyme (IDE), the major Aß-degrading enzyme secreted into the extracellular space of neuronal and microglial cells. The identification of the molecular mechanisms revealed that EPA directly increases IDE enzyme activity and elevates gene expression of IDE. DHA also directly stimulates IDE enzyme activity and affects IDE sorting by increasing exosome release of IDE, resulting in enhanced Aß-degradation in the extracellular milieu. Apart from the known positive effect of DHA in reducing Aß production, EPA and DHA might ameliorate AD pathology by increasing Aß turnover.

Oxidized Docosahexaenoic Acid Species and Lipid Peroxidation Products Increase Amyloidogenic Amyloid Precursor Protein Processing.

One of the main characteristics of Alzheimer's disease (AD) is the ß-amyloid peptide (Aß) generated by ß- and γ-secretase processing of the amyloid precursor protein (APP). Previously it has been demonstrated that polyunsaturated fatty acids (PUFAs), especially docosahexaenoic acid (DHA), are associated with a reduced risk of AD caused by decreased Aß production. However, in epidemiological studies and nutritional approaches, the outcomes of DHA-dependent treatment were partially controversial. PUFAs are very susceptible to reactive oxygen species and lipid peroxidation, which are increased during disease pathology. In line with published results, lipid peroxidation was elevated in human postmortem AD brains; especially 4-hydroxy-nonenal (HNE) was increased. To investigate whether lipid peroxidation is only a consequence or might also influence the processes leading to AD, we analyzed 7 different oxidized lipid species including 5 oxidized DHA derivatives and the lipid peroxidation products of ω-3 and ω-6 PUFAs, HNE and 4-hydroxy-hexenal, in human neuroblastoma cells and mouse mixed cortical neurons. In the presence of oxidized lipids Aß and soluble ß-secreted APP levels were elevated, whereas soluble α-secreted APP was decreased, suggesting a shift from the nonamyloidogenic to the amyloidogenic pathway of APP processing. Furthermore, ß- and γ-secretase activity was increased by oxidized lipids via increased gene expression and additionally by a direct effect on ß-secretase activity. Importantly, only 1% oxidized DHA was sufficient to revert the protective effect of DHA and to significantly increase Aß production. Therefore, our results emphasize the need to prevent DHA from oxidation in nutritional approaches and might help explain the divergent results of clinical DHA studies.

APP intracellular domain derived from amyloidogenic ß- and γ-secretase cleavage regulates neprilysin expression.

Alzheimer's disease (AD) is characterized by an accumulation of Amyloid-ß (Aß), released by sequential proteolytic processing of the amyloid precursor protein (APP) by ß - and γ-secretase. Aß peptides can aggregate, leading to toxic Aß oligomers and amyloid plaque formation. Aß accumulation is not only dependent on de novo synthesis but also on Aß degradation. Neprilysin (NEP) is one of the major enzymes involved in Aß degradation. Here we investigate the molecular mechanism of NEP regulation, which is up to now controversially discussed to be affected by APP processing itself. We found that NEP expression is highly dependent on the APP intracellular domain (AICD), released by APP processing. Mouse embryonic fibroblasts devoid of APP processing, either by the lack of the catalytically active subunit of the γ-secretase complex [presenilin (PS) 1/2] or by the lack of APP and the APP-like protein 2 (APLP2), showed a decreased NEP expression, activity and protein level. Similar results were obtained by utilizing cells lacking a functional AICD domain (APPΔCT15) or expressing mutations in the genes encoding for PS1. AICD supplementation or retransfection with an AICD encoding plasmid could rescue the down-regulation of NEP further strengthening the link between AICD and transcriptional NEP regulation, in which Fe65 acts as an important adaptor protein. Especially AICD generated by the amyloidogenic pathway seems to be more involved in the regulation of NEP expression. In line, analysis of NEP gene expression in vivo in six transgenic AD mouse models (APP and APLP2 single knock-outs, APP/APLP2 double knock-out, APP-swedish, APP-swedish/PS1Δexon9, and APPΔCT15) confirmed the results obtained in cell culture. In summary, in the present study we clearly demonstrate an AICD-dependent regulation of the Aß-degrading enzyme NEP in vitro and in vivo and elucidate the underlying mechanisms that might be beneficial to develop new therapeutic strategies for the treatment of AD.

PS dependent APP cleavage regulates glucosylceramide synthase and is affected in Alzheimer's disease.

BACKGROUND: Gangliosides were found to be associated with Alzheimer's disease (AD). Here we addressed a potential function of γ-secretase (presenilin) dependent cleavage of the amyloid-precursor-protein (APP) in the regulation of ganglioside de novo synthesis. METHODS: To identify a potential role of γ-secretase and APP in ganglioside de novo synthesis we used presenilin (PS) deficient and APP deficient cells and mouse brains, mutated PS as well as transgenic mice and AD post mortem brains. Changes in glucosylceramide synthase (GCS) activity were identified by incorporation of radiolabeled UDP-glucose in glucosylceramide, changes in gene expression via real-time PCR and Western blot analysis. Alterations in ganglioside levels were determined by thin layer chromatography and mass spectrometry. RESULTS: We found that PS and APP deficiency, in vitro and in vivo, resulted in increased GCS gene expression, elevated enzyme activity and thus increased glucosylceramide and total ganglioside level. Using a specific γ-secretase inhibitor revealed that PS proteolytic activity alters ganglioside homeostasis. By the use of mutated PS causing early onset AD in cell culture and transgenic mice we found that GCS is increased in AD, further substantiated by the use of AD post mortem brains, suffering from sporadic AD. CONCLUSION: APP processing regulates ganglioside de novo synthesis and is affected in AD.

Malaria-induced changes in host odors enhance mosquito attraction.

Vector-borne pathogens may alter traits of their primary hosts in ways that influence the frequency and nature of interactions between hosts and vectors. Previous work has reported enhanced mosquito attraction to host organisms infected with malaria parasites but did not address the mechanisms underlying such effects. Here we document malaria-induced changes in the odor profiles of infected mice (relative to healthy individuals) over the course of infection, as well as effects on the attractiveness of infected hosts to mosquito vectors. We observed enhanced mosquito attraction to infected mice during a key period after the subsidence of acute malaria symptoms, but during which mice remained highly infectious. This attraction corresponded to an overall elevation in the volatile emissions of infected mice observed during this period. Furthermore, data analyses--using discriminant analysis of principal components and random forest approaches--revealed clear differences in the composition of the volatile blends of infected and healthy individuals. Experimental manipulation of individual compounds that exhibited altered emission levels during the period when differential vector attraction was observed also elicited enhanced mosquito attraction, indicating that compounds being influenced by malaria infection status also mediate vector host-seeking behavior. These findings provide important insights into the cues that mediate vector attraction to hosts infected with transmissible stages of malaria parasites, as well as documenting characteristic changes in the odors of infected individuals that may have potential value as diagnostic biomarkers of infection.