Search

Center for Alzheimer Research (CAR) is a hub for the research in Alzheimer's disease and other dementias conducted at Karolinska Institutet (Stockholm, Sweden). CAR started in 2014 with Professor Bengt Winblad to unite basic, clinical, and epidemiological dementia research from several divisions of the department of Neurobiology, Care Sciences and Society (NVS). Since then, the goal of CAR is to (i) promote the connection between the CAR's research and the clinics at adjacent Karolinska University Hospital, (ii) strengthen and promote the visibility of dementia research, and (iii) coordinate and increase the quality of the research and education on dementia. CAR has around 300 affiliates and is supported by administrative personnel of NVS. Director and steering group composed of one member from each of NVS's divisions run the center. This representation of basic, clinical, and epidemiological research provides the foundation for a unique model of translational science and education. CAR accelerates Alzheimer's and dementia research through extensive activities. Some examples are the role of CAR's researchers in leading world‐recognized projects such as FINGER, SNAC‐K, and SVEDEM, as well as participation in EU and NIH projects like MOPEAD, EPAD, and RADAR‐AD. CAR researchers contribute to developing biobanks like GEDOC, which includes brain tissue, cerebrospinal fluid and blood samples; and support clinical trials in collaboration with Karolinska University Hospital and pharma industry situated around hospital and institute. Education is central activity with many CAR affiliates involved in under‐ and post‐graduate teaching. CAR catapults the Alzheimer's research community by providing the structure for social interaction and gathering. Examples are research seminars every Wednesday, monthly theme‐specific seminars, opponent lectures connected to PhD dissertations, initiation of working groups, and organization of workshops, webinars and open‐house days for patients and relatives. All these are open and announced at ki.se/en/nvs/center‐for‐alzheimer‐research. In 2019 and 2022, CAR organized a national conference for Alzheimer's research. CAR increases social awareness about Alzheimer's disease and dementias through collaborations with main Swedish foundations like the Aging Center from Stockholm Region, Silviahemmet, and Alzheimer Funding. Recently, CAR coordinated with Alzheimer Funding a national popular science report about Alzheimer's disease, with participations from all across Sweden. [ABSTRACT FROM AUTHOR]

Mitochondrial dysfunction is implicated in most neurodegenerative diseases, including Alzheimer's disease (AD). We here combined experimental and computational approaches to investigate mitochondrial health and bioenergetic function in neurons from a double transgenic animal model of AD (PS2APP/B6.152H). Experiments in primary cortical neurons demonstrated that AD neurons had reduced mitochondrial respiratory capacity. Interestingly, the computational model predicted that this mitochondrial bioenergetic phenotype could not be explained by any defect in the mitochondrial respiratory chain (RC), but could be closely resembled by a simulated impairment in the mitochondrial NADH flux. Further computational analysis predicted that such an impairment would reduce levels of mitochondrial NADH, both in the resting state and following pharmacological manipulation of the RC. To validate these predictions, we utilized fluorescence lifetime imaging microscopy (FLIM) and autofluorescence imaging and confirmed that transgenic AD neurons had reduced mitochondrial NAD(P)H levels at rest, and impaired power of mitochondrial NAD(P)H production. Of note, FLIM measurements also highlighted reduced cytosolic NAD(P)H in these cells, and extracellular acidification experiments showed an impaired glycolytic flux. The impaired glycolytic flux was identified to be responsible for the observed mitochondrial hypometabolism, since bypassing glycolysis with pyruvate restored mitochondrial health. This study highlights the benefits of a systems biology approach when investigating complex, nonintuitive molecular processes such as mitochondrial bioenergetics, and indicates that primary cortical neurons from a transgenic AD model have reduced glycolytic flux, leading to reduced cytosolic and mitochondrial NAD(P)H and reduced mitochondrial respiratory capacity. [ABSTRACT FROM AUTHOR]

Subcellular distribution of mitochondria in neurons is crucial for meeting the energetic demands, as well as the necessity to buffer Ca2+ within the axon, dendrites and synapses. Mitochondrial impairment is an important feature of Parkinson disease (PD), in which both familial parkinsonism genes DJ‐1 and PINK1 have a great impact on mitochondrial function. We used differentiated human dopaminergic neuroblastoma cell lines with stable PINK1 or DJ‐1 knockdown to study live motility of mitochondria in neurites. The frequency of anterograde and retrograde mitochondrial motility was decreased in PINK1 knockdown cells and the frequency of total mitochondrial motility events was reduced in both cell lines. However, neither the distribution nor the size of mitochondria in the neurites differed from the control cells even after downregulation of the mitochondrial fission protein, Drp1. Furthermore, mitochondria from PINK1 knockdown cells, in which motility was most impaired, had increased levels of GSK3βSer9 and higher release of mitochondrial Ca2+ when exposed to CCCP‐induced mitochondrial uncoupling. Further analysis of the ER‐mitochondria contacts involved in Ca2+ shuttling showed that PINK1 knockdown cells had reduced contacts between the two organelles. Our results give new insight on how PINK1 and DJ‐1 influence mitochondria, thus providing clues to novel PD therapies. [ABSTRACT FROM AUTHOR]

Mitochondria are physically and biochemically in contact with other organelles including the endoplasmic reticulum ( ER). Such contacts are formed between mitochondria-associated ER membranes ( MAM), specialized subregions of ER, and the outer mitochondrial membrane ( OMM). We have previously shown increased expression of MAM-associated proteins and enhanced ER to mitochondria Ca2+ transfer from ER to mitochondria in Alzheimer's disease ( AD) and amyloid β-peptide (Aβ)-related neuronal models. Here, we report that si RNA knockdown of mitofusin-2 (Mfn2), a protein that is involved in the tethering of ER and mitochondria, leads to increased contact between the two organelles. Cells depleted in Mfn2 showed increased Ca2+ transfer from ER to mitchondria and longer stretches of ER forming contacts with OMM. Interestingly, increased contact resulted in decreased concentrations of intra- and extracellular Aβ40 and Aβ42. Analysis of γ-secretase protein expression, maturation and activity revealed that the low Aβ concentrations were a result of impaired γ-secretase complex function. Amyloid-β precursor protein ( APP), β-site APP-cleaving enzyme 1 and neprilysin expression as well as neprilysin activity were not affected by Mfn2 si RNA treatment. In summary, our data shows that modulation of ER-mitochondria contact affects γ-secretase activity and Aβ generation. Increased ER-mitochondria contact results in lower γ-secretase activity suggesting a new mechanism by which Aβ generation can be controlled. [ABSTRACT FROM AUTHOR]

Markers for caspase activation and apoptosis have been shown in brains of Alzheimer's disease (AD) patients and AD-mouse models. In neurons, caspase activation is associated with elevated amyloid β-peptide (Aβ) production. Caspases cleave numerous substrates including presenilin-1 (PS1). The cleavage takes place in the large cytosolic loop of PS1-C-terminal fragment (PS1CTF), generating a truncated PS1CTF lacking half of the loop domain (caspCTF). The loop has been shown to possess important regulatory functions with regard to Aβ40 and Aβ42 production. Previously, we have demonstrated that γ-secretase complexes are active during apoptosis regardless of caspase cleavage in the PS1CTF-loop. Here, a PS1/PS2-knockout mouse blastocyst-derived cell line was used to establish stable or transient cell lines expressing either caspCTF or full-length CTF (wtCTF). We show that caspCTF restores γ-secretase activity and forms active γ-secretase complexes together with Nicastrin, Pen-2, Aph-1 and PS1-N-terminal fragment. Further, caspCTF containing γ-secretase complexes have a sustained capacity to cleave amyloid precursor protein (APP) and Notch, generating APP and Notch intracellular domain, respectively. However, when compared to wtCTF cells, caspCTF cells exhibit increased intracellular production of Aβ42 accompanied by increased intracellular Aβ42/Aβ40 ratio without changing the Aβ secretion pattern. Similarly, induction of apoptosis in wtCTF cells generate a similar shift in intracellular Aβ pattern with increased Aβ42/Aβ40 ratio. In summary, we show that caspase cleavage of PS1 generates a γ-secretase complex that increases the intracellular Aβ42/Aβ40 ratio. This can have implications for AD pathogenesis and suggests caspase inhibitors as potential therapeutic agents. [ABSTRACT FROM AUTHOR]

The serine-protease OMI/HTRA2, required for several cellular processes, including mitochondrial function, autophagy, chaperone activity, and apoptosis, has been implicated in the pathogenesis of both Alzheimer's disease (AD) and Parkinson's disease (PD). Western blot quantification of OMI/HTRA2 in frontal cortex of patients with AD (n10) and control subjects (n10) in two separate materials indicated reduced processed (active, 35 kDa) OMI/HTRA2 levels, whereas unprocessed (50 kDa) enzyme levels were not significantly different between the groups. Interestingly, the specific protease activity of OMI/HTRA2 was found to be significantly increased in patients with AD (n10) compared to matched control subjects (n10) in frontal cortex in two separate materials. Comparison of OMI/HTRA2 mRNA levels in frontal cortex and hippocampus, two brain areas particularly affected by AD, indicated similar levels in patients with AD (n10) and matched control subjects (n10). In addition, we analyzed the occurrence of the OMI/HTRA2 variants A141S and G399S in Swedish case-control materials for AD and PD and found a weak association of A141S with AD, but not with PD. In conclusion, our genetic, histological, and biochemical findings give further support to an involvement of OMI/HTRA2 in the pathology of AD; however, further studies are needed to clarify the role of this gene in neurodegeneration. [ABSTRACT FROM AUTHOR]

Intracellular amyloid-13 peptide (AI3) has been implicated in the pathogenesis of Alzheimer's disease (AD). Mitochondria were found to be the target both for amyloid precursor protein (APP) that accumulates in the mitochondrial import channels and for Aß that interacts with several proteins inside mitochondria and leads to mitochondrial dysfunction. Here, we have studied the role of mitochondrial γ-secretase in processing different substrates. We found that a significant proportion of APP is associated with mitochondria in cultured cells and that γ-secretase cleaves the shedded C-terminal part of APP identified as C83 associated with the outer membrane of mitochondria (OMM). Moreover, we have established the topology of the C83 in the OMM and found the APP intracellular domain (AICD) to be located inside mitochondria. Our data show for the first time that APP is a substrate for the mitochondrial γ-secretase and that AICD is produced inside mitochondria. Thus, we provide a mechanistic view of the mitochondria-associated APP metabolism where AICD, P3 peptide and potentially Aß are produced locally and may contribute to mitochondrial dysfunction in AD.-- Pavlov, P. F., Wiehager, B., Sakai, J., Frykman, S., Behbahani, H., Winblad, B., Ankarcrona, M. Mitochondrial γ-secretase participates in the metabolism of mitochondria-associated amyloid precursor protein. [ABSTRACT FROM AUTHOR]

• Introduction • Age and AD related mitochondrial changes in brain and peripheral tissues • Effect of APP accumulation on mitochondrial function • Mitochondria as a target and mediator of Aβ toxicity • Conclusions Accumulating evidence suggest that alterations in energy metabolism are among the earliest events that occur in the Alzheimer disease (AD) affected brain. Energy consumption is drastically decreased in the AD-affected regions of cerebral cortex and hippocampus pointing towards compromised mitochondrial function of neurons within specific brain regions. This is accompanied by an elevated production of reactive oxygen species contributing to increased rates of neuronal loss in the AD-affected brain regions. In this review, we will discuss the role of mitochondrial function and dysfunction in AD. We will focus on the consequences of amyloid precursor protein and amyloid-β peptide accumulation in mitochondria and their involvement in AD pathogenesis. [ABSTRACT FROM AUTHOR]

γ-Secretase is a key enzyme involved in the processing of the β-amyloid precursor protein into amyloid β-peptides (Aβ). Aβ accumulates and forms plaques in Alzheimer's disease (AD) brains. A progressive neurodegeneration and cognitive decline occurs during the course of the disease, and Aβ is believed to be central for the molecular pathogenesis of AD. Apoptosis has been implicated as one of the mechanisms behind the neuronal cell loss seen in AD. We have studied preservation and activity of the γ-secretase complex during apoptosis in neuroblastoma cells (SH-SY5Y) exposed to staurosporine (STS). We report that the known components (presenilin, Nicastrin, Aph-1 and Pen-2) interact and form active γ-secretase complexes in apoptotic cells. In addition, the fragments corresponding to the PS1 N-terminal fragment and the caspase-cleaved PS1 C-terminal fragment (PS1-caspCTF) were found to form active γ-secretase complexes when co-expressed in presenilin (PS) knockout cells. Interestingly, PS1-caspCTF replaced the normal PS1 C-terminal fragment and was co-immunoprecipitated with the γ-secretase complex in SH-SY5Y cells exposed to STS. In addition, Aβ was detected in medium from apoptotic HEK APPswe cells. Together, the data show that γ-secretase complexes containing PS1-caspCTF are active, and suggest that this proteolytic activity is also important in dying cells and may affect the progression of AD. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) affects millions of people worldwide and the number of AD cases will increase with increased life expectancy. Today there is no cure for this devastating and always lethal disease and therefore it is of great interest for patients, relatives and societies to find new drugs that can hinder the disease process. During the progression of AD a substantial amount of neurons degenerate in the brain. The mechanisms of cell death involved in AD have not been fully elucidated. However, there are several reports showing that neurons die partly by apoptosis in the AD brain. Drugs blocking apoptosis could therefore be potentially useful for early prevention of neuronal cell death. Biomarkers for apoptosis should be important tools in the evaluation of drug effects and in the diagnostics of AD. Here we review the current knowledge in the field and discuss potential biomarkers for apoptosis in AD. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Markers for caspase activation and apoptosis have been shown in brains of Alzheimer's disease (AD) patients and AD-mouse models. In neurons, caspase activation is associated with elevated amyloid β-peptide (Aβ) production. Caspases cleave numerous substrates including presenilin-1 (PS1). The cleavage takes place in the large cytosolic loop of PS1-C-terminal fragment (PS1CTF), generating a truncated PS1CTF lacking half of the loop domain (caspCTF). The loop has been shown to possess important regulatory functions with regard to Aβ(40) and Aβ(42) production. Previously, we have demonstrated that γ-secretase complexes are active during apoptosis regardless of caspase cleavage in the PS1CTF-loop. Here, a PS1/PS2-knockout mouse blastocyst-derived cell line was used to establish stable or transient cell lines expressing either caspCTF or full-length CTF (wtCTF). We show that caspCTF restores γ-secretase activity and forms active γ-secretase complexes together with Nicastrin, Pen-2, Aph-1 and PS1-N-terminal fragment. Further, caspCTF containing γ-secretase complexes have a sustained capacity to cleave amyloid precursor protein (APP) and Notch, generating APP and Notch intracellular domain, respectively. However, when compared to wtCTF cells, caspCTF cells exhibit increased intracellular production of Aβ(42) accompanied by increased intracellular Aβ(42) /Aβ(40) ratio without changing the Aβ secretion pattern. Similarly, induction of apoptosis in wtCTF cells generate a similar shift in intracellular Aβ pattern with increased Aβ(42) /Aβ(40) ratio. In summary, we show that caspase cleavage of PS1 generates a γ-secretase complex that increases the intracellular Aβ(42) /Aβ(40) ratio. This can have implications for AD pathogenesis and suggests caspase inhibitors as potential therapeutic agents., (© 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.)