Deposition of Alzheimer's vascular amyloid-beta is associated with decreased expression of brain L-3-hydroxyacyl-coenzyme A dehydrogenase (ERAB)

The total withanolides from the leaves of Datura stramonium L. Improves Alzheimer's disease pathology by restraining neuroinflammation through NLRP3/IL-1β/IL1R1/TOM 1 pathway

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the deposition of beta-amyloid (Aβ) peptides. Microglia-mediated neuroinflammation is one of the primary contributors to the pathogenesis of AD. Withanolides, the main constituents in the leaves of Datura stramonium L., exhibit anti-neuroinflammatory activity. It is unknown if total withanolide from Datura stramonium L. leaves (TWD) reduces nerve inflammation and potentially mitigates the pathogenic elements of AD. This study examined the potential effects of TWD on neuroinflammation in triple transgenic AD (3 × Tg-AD) mice and LPS-induced BV-2, as well as associated signaling pathways. HPLC-Q-TOF-MS/MS was used in this study to examine the main chemical components of the TWD extract. 3 × Tg-AD as in vivo AD models and LPS induce BV-2 cells in vitro AD models. The molecular process was investigated by ELISA, WB, IHC, and IF. In 3 × Tg-AD mice, TWD dramatically ameliorates cognitive impairment. Treatment with TWD can counteract the increased activation of microglia and Aβ deposits observed in 3 × Tg-AD mice. Further research indicates that TWD can enhance TOM 1 and mitigate inflammatory responses by reducing the levels of IL-1β, TNF-α, IL-6, IL1R1, and IL-18. Additionally, TWD may inhibit neuroinflammation through the pathways of IL1R1/MyD88/NF-κB and NLRP3/IL-1β/IL1R1. In summary, this study reveals for the first time that TWD effectively improves cognitive deficits in 3 × Tg-AD mice by modulating the IL1R1/MyD88/NF-κB and NLRP3/IL-1β/IL1R1 pathways. It also alleviates excessive activation of microglia and suppresses Aβ accumulation. Therefore, TWD has the potential as a therapeutic agent for AD.

Involvement of Type 10 17β-Hydroxysteroid Dehydrogenase in the Pathogenesis of Infantile Neurodegeneration and Alzheimer's Disease

Type 10 17β-hydroxysteroid dehydrogenase (17β-HSD10) is the HSD17B10 gene product playing an appreciable role in cognitive functions. It is the main hub of exercise-upregulated mitochondrial proteins and is involved in a variety of metabolic pathways including neurosteroid metabolism to regulate allopregnanolone homeostasis. Deacetylation of 17β-HSD10 by sirtuins helps regulate its catalytic activities. 17β-HSD10 may also play a critical role in the control of mitochondrial structure, morphology and dynamics by acting as a member of the Parkin/PINK1 pathway, and by binding to cyclophilin D to open mitochondrial permeability pore. 17β-HSD10 also serves as a component of RNase P necessary for mitochondrial tRNA maturation. This dehydrogenase can bind with the Aβ peptide thereby enhancing neurotoxicity to brain cells. Even in the absence of Aβ, its quantitative and qualitative variations can result in neurodegeneration. Since elevated levels of 17β-HSD10 were found in brain cells of Alzheimer's disease (AD) patients and mouse AD models, it is considered to be a key factor in AD pathogenesis. Since data underlying Aβ-binding-alcohol dehydrogenase (ABAD) were not secured from reported experiments, ABAD appears to be a fabricated alternative term for the HSD17B10 gene product. Results of this study would encourage researchers to solve the question why elevated levels of 17β-HSD10 are present in brains of AD patients and mouse AD models. Searching specific inhibitors of 17β-HSD10 may find candidates to reduce senile neurodegeneration and open new approaches for the treatment of AD.

Infantile Neurodegeneration Results from Mutants of 17β-Hydroxysteroid Dehydrogenase Type 10 Rather Than Aβ-Binding Alcohol Dehydrogenase

Type 10 17β-hydroxysteroid dehydrogenase (17β-HSD10), a homo-tetrameric multifunctional protein with 1044 residues encoded by the HSD17B10 gene, is necessary for brain cognitive function. Missense mutations result in infantile neurodegeneration, an inborn error in isoleucine metabolism. A 5-methylcytosine hotspot underlying a 388-T transition leads to the HSD10 (p.R130C) mutant to be responsible for approximately half of all cases suffering with this mitochondrial disease. Fewer females suffer with this disease due to X-inactivation. The binding capability of this dehydrogenase to Aβ-peptide may play a role in Alzheimer's disease, but it appears unrelated to infantile neurodegeneration. Research on this enzyme was complicated by reports of a purported Aβ-peptide-binding alcohol dehydrogenase (ABAD), formerly referred to as endoplasmic-reticulum-associated Aβ-binding protein (ERAB). Reports concerning both ABAD and ERAB in the literature reflect features inconsistent with the known functions of 17β-HSD10. It is clarified here that ERAB is reportedly a longer subunit of 17β-HSD10 (262 residues). 17β-HSD10 exhibits L-3-hydroxyacyl-CoA dehydrogenase activity and is thus also referred to in the literature as short-chain 3-hydorxyacyl-CoA dehydrogenase or type II 3-hydorxyacyl-CoA dehydrogenase. However, 17β-HSD10 is not involved in ketone body metabolism, as reported in the literature for ABAD. Reports in the literature referring to ABAD (i.e., 17β-HSD10) as a generalized alcohol dehydrogenase, relying on data underlying ABAD's activities, were found to be unreproducible. Furthermore, the rediscovery of ABAD/ERAB's mitochondrial localization did not cite any published research on 17β-HSD10. Clarification of the purported ABAD/ERAB function derived from these reports on ABAD/ERAB may invigorate this research field and encourage new approaches to the understanding and treatment of HSD17B10-gene-related disorders. We establish here that infantile neurodegeneration is caused by mutants of 17β-HSD10 but not ABAD, and so we conclude that ABAD represents a misnomer employed in high-impact journals.

3-Hydroxyacyl-CoA and Alcohol Dehydrogenase Activities of Mitochondrial Type 10 17β-Hydroxysteroid Dehydrogenase in Neurodegeneration Study

BACKGROUND

Mitochondrial 17β-hydroxysteroid dehydrogenase type 10 (17β-HSD10) is necessary for brain cognitive function, but its studies were confounded by reports of Aβ-peptide binding alcohol dehydrogenase (ABAD), formerly endoplasmic reticulum-associated Aβ-peptide binding protein (ERAB), for two decades so long as ABAD serves as the alternative term of 17β-HSD10.

OBJECTIVE

To determine whether those ABAD reports are true or false, even if they were published in prestigious journals.

METHODS

6xHis-tagged 17β-HSD10 was prepared and characterized by well-established experimental procedures.

RESULTS

The N-terminal 6xHis tag did not significantly interfere with the dehydrogenase activities of 17β-HSD10, but the kinetic constants of its 3-hydroxyacyl-CoA dehydrogenase activity are drastically distinct from those of ABAD, and it was not involved in ketone body metabolism as previously reported for ABAD. Furthermore, it was impossible to measure its generalized alcohol dehydrogenase activities underlying the concept of ABAD because the experimental procedures described in ABAD reports violated basic chemical and/or biochemical principles. More incredibly, both authors and journals had not yet agreed to make any corrigenda of ABAD reports.

CONCLUSION

Brain 17β-HSD10 plays a key role in neurosteroid metabolism and further studies in this area may lead to potential treatments of neurodegeneration including AD.

Friend or enemy? Review of 17β-HSD10 and its role in human health or disease

17β-hydroxysteroid dehydrogenase (17β-HSD10) is a multifunctional human enzyme with important roles both as a structural component and also as a catalyst of many metabolic pathways. This mitochondrial enzyme has important functions in the metabolism, development and aging of the neural system, where it is involved in the homeostasis of neurosteroids, especially in regard to estradiol, changes in which make it an essential part of neurodegenerative pathology. These roles therefore, indicate that 17β-HSD10 may be a possible druggable target for neurodegenerative diseases including Alzheimer's disease (AD), and in hormone-dependent cancer. The objective of this review was to provide a summary about physiological functions and pathological roles of 17β-HSD10 and the modulators of its activity.

Comparative mitochondrial proteomic analysis of human large cell lung cancer cell lines with different metastasis potential

Background

Lung cancer is a highly aggressive cancer with a poor prognosis and is associated with distant metastasis; however, there are no clinically recognized biomarkers for the early diagnosis and prediction of lung cancer metastasis. We sought to identify the differential mitochondrial protein profiles and understand the molecular mechanisms governing lung cancer metastasis.

Methods

Mitochondrial proteomic analysis was performed to screen and identify the differential mitochondrial protein profiles between human large cell lung cancer cell lines with high (L‐9981) and low (NL‐9980) metastatic potential by two‐dimensional differential gel electrophoresis. Western blot was used to validate the differential mitochondrial proteins from the two cells. Bioinformatic proteome analysis was performed using the Mascot search engine and messenger RNA expression of the 37 genes of the differential mitochondrial proteins were detected by real‐time PCR.

Results

Two hundred and seventeen mitochondrial proteins were differentially expressed between L‐9981 and NL‐9980 cells (P < 0.05). Sixty‐four analyzed proteins were identified by matrix‐assisted laser desorption/ionization‐time of flight mass spectrometry coupled with database interrogation. Ontology analysis revealed that these proteins were mainly involved in the regulation of translation, amino acid metabolism, tricarboxylic acid cycle, cancer invasion and metastasis, oxidative phosphorylation, intracellular signaling pathway, cell cycle, and apoptosis.

Conclusion

Our results suggest that the incorporation of more samples and new datasets will permit the definition of a collection of proteins as potential biomarkers for the prediction and diagnosis of lung cancer metastasis.

GRK5 - A Functional Bridge Between Cardiovascular and Neurodegenerative Disorders

Complex aging-triggered disorders are multifactorial programs that comprise a myriad of alterations in interconnected protein networks over a broad range of tissues. It is evident that rather than being randomly organized events, pathophysiologies that possess a strong aging component such as cardiovascular diseases (hypertensions, atherosclerosis, and vascular stiffening) and neurodegenerative conditions (dementia, Alzheimer's disease, mild cognitive impairment, Parkinson's disease), in essence represent a subtly modified version of the intricate molecular programs already in place for normal aging. To control such multidimensional activities there are layers of trophic protein control across these networks mediated by so-called "keystone" proteins. We propose that these "keystones" coordinate and interconnect multiple signaling pathways to control whole somatic activities such as aging-related disease etiology. Given its ability to control multiple receptor sensitivities and its broad protein-protein interactomic nature, we propose that G protein coupled receptor kinase 5 (GRK5) represents one of these key network controllers. Considerable data has emerged, suggesting that GRK5 acts as a bridging factor, allowing signaling regulation in pathophysiological settings to control the connectivity between both the cardiovascular and neurophysiological complications of aging.

Levels of 17β-hydroxysteroid dehydrogenase type 10 in CSF are not a valuable biomarker for multiple sclerosis

Aim: We aimed to characterize the role of mitochondrial 17β-hydroxysteroid dehydrogenase type 10 (17β-HSD10) overexpression in multiple sclerosis (MS) and to evaluate its use as a biomarker. Materials & methods: We estimated levels of 17β-HSD10, amyloid β 1–42, cyclophilin D, 17β-HSD10-cyclophilin D complexes or 17β-HSD10-parkin complexes in cerebrospinal fluid (CSF) samples. Results: The increase in 17β-HSD10 levels or in 17β-HSD10-parkin complexes and links to leukocytes were found only in relapsing–remitting MS. The sensitivity of the biomarker was 64%, the specificity equaled 60–63% compared with controls. Conclusion: Increased CSF levels of 17β-HSD10 in later stages of MS could be interpreted via its upregulation in demyelinated neuronal axons. CSF levels of 17β-HSD10 are not the valuable biomarker for the early diagnosis or for the progression of MS.

Proteomic differences in brain vessels of Alzheimer's disease mice: Normalization by PPARγ agonist pioglitazone

Cerebrovascular insufficiency appears years prior to clinical symptoms in Alzheimer's disease. The soluble, highly toxic amyloid-β species, generated from the amyloidogenic processing of amyloid precursor protein, are known instigators of the chronic cerebrovascular insufficiency observed in both Alzheimer's disease patients and transgenic mouse models. We have previously demonstrated that pioglitazone potently reverses cerebrovascular impairments in a mouse model of Alzheimer's disease overexpressing amyloid-β. In this study, we sought to characterize the effects of amyloid-β overproduction on the cerebrovascular proteome; determine how pioglitazone treatment affected the altered proteome; and analyze the relationship between normalized protein levels and recovery of cerebrovascular function. Three-month-old wildtype and amyloid precursor protein mice were treated with pioglitazone- (20 mg/kg/day, 14 weeks) or control-diet. Cerebral arteries were surgically isolated, and extracted proteins analyzed by gel-free and gel-based mass spectrometry. 193 cerebrovascular proteins were abnormally expressed in amyloid precursor protein mice. Pioglitazone treatment rescued a third of these proteins, mainly those associated with oxidative stress, promotion of cerebrovascular vasocontractile tone, and vascular compliance. Our results demonstrate that amyloid-β overproduction perturbs the cerebrovascular proteome. Recovery of cerebrovascular function with pioglitazone is associated with normalized levels of key proteins in brain vessel function, suggesting that pioglitazone-responsive cerebrovascular proteins could be early biomarkers of Alzheimer's disease.

Estrogen-mediated regulation of mitochondrial gene expression

Estrogens, in particular 17β-estradiol, are well-known regulators of essential cellular functions; however, discrepancies remain over the mechanisms by which they act on mitochondria. Here we propose a novel mechanism for the direct regulation of mitochondrial gene expression by estrogen under metabolic stress. We show that in serum-depleted medium, estrogen stimulates a rapid relocation of estrogen receptor-α to mitochondria, in which it elicits a cellular response, resulting in an increase in mitochondrial RNA abundance. Mitochondrial RNA levels are regulated through the association of estrogen receptor-α with 17β-hydroxysteroid dehydrogenase 10, a multifunctional protein involved in steroid metabolism that is also a core subunit of the mitochondrial ribonuclease P complex responsible for the cleavage of mitochondrial polycistronic transcripts. Processing of mitochondrial transcripts affects mitochondrial gene expression by controlling the levels of mature RNAs available for translation. This work provides the first mechanism linking RNA processing and estrogen activation in mitochondrial gene expression and underscores the coordinated response between the nucleus and mitochondria in response to stress.

PPAR alpha: a novel radiation target in locally exposed Mus musculus heart revealed by quantitative proteomics

Radiation exposure of the thorax is associated with a markedly increased risk of cardiac morbidity and mortality with a latency period of decades. Although many studies have confirmed the damaging effect of ionizing radiation on the myocardium and cardiac endothelial structure and function, the molecular mechanism behind this damage is not yet elucidated. Peroxisome proliferator-activated receptor alpha (PPAR alpha), a transcriptional regulator of lipid metabolism in heart tissue, has recently received great attention in the development of cardiovascular disease. The goal of this study was to investigate radiation-induced cardiac damage in general and the role of PPAR alpha in this process in particular. C57BL/6 mice received local heart irradiation with X-ray doses of 8 and 16 gray (Gy) at the age of 8 weeks. The mice were sacrificed 16 weeks later. Radiation-induced changes in the cardiac proteome were quantified using the Isotope Coded Protein Label (ICPL) method followed by mass spectrometry and software analysis. Significant alterations were observed in proteins involved in lipid metabolism and oxidative phosphorylation. Ionizing radiation markedly changed the phosphorylation and ubiquitination status of PPAR alpha. This was reflected as decreased expression of its target genes involved in energy metabolism and mitochondrial respiratory chain confirming the proteomics data. This study suggests that persistent alteration of cardiac metabolism due to impaired PPAR alpha activity contributes to the heart pathology after radiation.

Neurologic and motor dysfunctions in APP transgenic mice

The discovery of gene mutations underlying autosomal dominant Alzheimer's disease has enabled researchers to reproduce several hallmarks of this disorder in transgenic mice, notably the formation of Aβ plaques in brain and cognitive deficits. APP transgenic mutants have also been investigated with respect to survival rates, neurologic functions, and motor coordination, which are all susceptible to alteration in Alzheimer dementia. Several transgenic lines expressing human mutated or wild-type APP had higher mortality rates than non-transgenic controls with or without the presence of Aβ plaques. Mortality rates were also elevated in APP transgenic mice with vascular amyloid accumulation, thereby implicating cerebrovascular factors in the precocious death observed in all APP transgenic models. In addition, myoclonic jumping has been described in APP mutants, together with seizure activity, abnormal limb-flexion and paw-clasping reflexes, and motor coordination deficits. The neurologic signs resemble the myoclonic movements, epileptic seizures, pathological reflexes, and gait problems observed in late-stage Alzheimer's disease.

APP transgenic mice for modelling behavioural and psychological symptoms of dementia (BPSD)

The discovery of gene mutations responsible for autosomal dominant Alzheimer's disease has enabled researchers to reproduce in transgenic mice several hallmarks of this disorder, notably Aβ accumulation, though in most cases without neurofibrillary tangles. Mice expressing mutated and wild-type APP as well as C-terminal fragments of APP exhibit variations in exploratory activity reminiscent of behavioural and psychological symptoms of Alzheimer dementia (BPSD). In particular, open-field, spontaneous alternation, and elevated plus-maze tasks as well as aggression are modified in several APP transgenic mice relative to non-transgenic controls. However, depending on the precise murine models, changes in open-field and elevated plus-maze exploration occur in either direction, either increased or decreased relative to controls. It remains to be determined which neurotransmitter changes are responsible for this variability, in particular with respect to GABA, 5HT, and dopamine.

HSD10 disease: clinical consequences of mutations in the HSD17B10 gene

The HSD17B10 gene is located on chromosome Xp11.2 and codes for a multifunctional protein called 17β-hydroxysteroid dehydrogenase type 10 (HSD10). This protein catalyzes the 2-methyl-3-hydroxybutyryl-CoA dehydrogenation (MHBD) reaction in isoleucine metabolism and is an essential component of mitochondrial RNase P required for the processing of mtDNA transcripts. HSD10 is required for normal mitochondrial maintenance, and complete loss of HSD10 is incompatible with life. Mutations in the HSD17B10 gene have been reported in 19 families. The classical infantile form of what is best named HSD10 disease is characterized by a period of more or less normal development in the first 6-18 months of life. Some patients showed transient metabolic derangement in the neonatal period, with good clinical recovery but often persistent lactate elevation. Usually from age 6-18 months affected boys show a progressive neurodegenerative disease course in conjunction with retinopathy and cardiomyopathy leading to death at age 2-4 years or later. A more severe presentation in the neonatal period with little neurological development, severe progressive cardiomyopathy, and early death, is denoted neonatal form. Juvenile and atypical/asymptomatic forms of HSD10 disease have been recognized. Heterozygous females often show non-progressive developmental delay and intellectual disability but may also be clinically normal. The pathogenesis is poorly understood but is unrelated to MHBD function. Diagnosis is based on typical abnormalities in urinary organic acid analysis and molecular studies. The same de novo mutation p.R130C was found in over half of patient families; it is associated with the infantile disease form. There is no effective treatment.

The reconstruction and analysis of tissue specific human metabolic networks

Human tissues have distinct biological functions. Many proteins/enzymes are known to be expressed only in specific tissues and therefore the metabolic networks in various tissues are different. Though high quality global human metabolic networks and metabolic networks for certain tissues such as liver have already been studied, a systematic study of tissue specific metabolic networks for all main tissues is still missing. In this work, we reconstruct the tissue specific metabolic networks for 15 main tissues in human based on the previously reconstructed Edinburgh Human Metabolic Network (EHMN). The tissue information is firstly obtained for enzymes from Human Protein Reference Database (HPRD) and UniprotKB databases and transfers to reactions through the enzyme-reaction relationships in EHMN. As our knowledge of tissue distribution of proteins is still very limited, we replenish the tissue information of the metabolic network based on network connectivity analysis and thorough examination of the literature. Finally, about 80% of proteins and reactions in EHMN are determined to be in at least one of the 15 tissues. To validate the quality of the tissue specific network, the brain specific metabolic network is taken as an example for functional module analysis and the results reveal that the function of the brain metabolic network is closely related with its function as the centre of the human nervous system. The tissue specific human metabolic networks are available at .

(-)-CHANA, a fluorogenic probe for detecting amyloid binding alcohol dehydrogenase HSD10 activity in living cells

The association of 17β-hydroxysteroid dehydrogenase 10 (HSD10) with β-amyloid in the brain is known to contribute to the progression of Alzheimer's disease. Further, it has been shown that the interaction between the purified HSD10 and β-amyloid inhibits its enzymatic activity. However, to date no system has been developed to enable the study of HSD10 activity in intact living cells. To address this significant shortcoming, we have developed a novel fluorogenic probe, (-)-cyclohexenyl amino naphthalene alcohol [(-)-CHANA], to observe and measure the activity of HSD10 in living cells. The oxidation of (-)-CHANA by HSD10 results in the production and accumulation of a fluorescent product, which can be measured using real-time fluorescence microscopy. This compound permits the measurement of mitochondrial HSD10 activity and its inhibition by both a small molecule HSD10 inhibitor and by β-amyloid, in living cells. Herein, we define the parameters under which this probe can be used. This compound is likely to prove useful in future investigations aimed at developing therapeutic compounds targeting the HSD10-β-amyloid association.

The consequences of mitochondrial amyloid beta-peptide in Alzheimer's disease

The Abeta (amyloid-beta peptide) has long been associated with Alzheimer's disease, originally in the form of extracellular plaques. However, in the present paper we review the growing evidence for the role of soluble intracellular Abeta in the disease progression, with particular reference to Abeta found within the mitochondria. Once inside the cell, Abeta is able to interact with a number of targets, including the mitochondrial proteins ABAD (amyloid-binding alcohol dehydrogenase) and CypD (cyclophilin D), which is a component of the mitochondrial permeability transition pore. Interference with the normal functions of these proteins results in disruption of cell homoeostasis and ultimately cell death. The present review explores the possible mechanisms by which cell death occurs, considering the evidence presented on a molecular, cellular and in vivo level.

Molecular characterization of the response to chemotherapy in conventional osteosarcomas: predictive value of HSD17B10 and IFITM2

The therapy regimen of high-grade osteosarcoma includes chemotherapy followed by surgical resection and postoperative chemotherapy. The degree of necrosis following definitive surgery remains the only reliable prognostic factor and is used to guide the choice of postoperative chemotherapy. The aim of this study was to find molecular markers able to classify patients with an osteosarcoma as good or poor responders to chemotherapy before beginning treatment. Gene expression screening of 20 nonmetastatic high-grade osteosarcoma patients was performed using cDNA microarray. Expression of selected relevant genes was validated using QRT-PCR. Immunohistochemistry on tissue microarrays sections of 73 biopsies was performed to investigate protein expression. Fluorescent in situ hybridization was performed for RPL8 gene. We have found that HSD17B10 gene expression was up-regulated in poor responders and that immunohistochemistry expression of HSD17B10 on biopsy before treatment was correlated to response to chemotherapy. Other results include correlation of IFITM2, IFITM3, and RPL8 gene expression to chemotherapy response. A statistical correlation was found between polysomy 8 or gain of RPL8 and good response to chemotherapy. These data suggest that HSD17B10, RPL8, IFITM2, and IFITM3 genes are involved in the response to the chemotherapy and that HSD17B10 may be a therapeutic target. RPL8 and IFITM2 may be useful in the assessment at diagnosis and for stratifying patients taking part in randomized trials.

The role of overexpressed DYRK1A protein in the early onset of neurofibrillary degeneration in Down syndrome

The gene encoding the minibrain kinase/dual-specificity tyrosine phosphorylated and regulated kinase 1A (DYRK1A) is located in the Down syndrome (DS) critical region of chromosome 21. The third copy of DYRK1A is believed to contribute to abnormal brain development in patients with DS. In vitro studies showing that DYRK1A phosphorylates tau protein suggest that this kinase is also involved in tau protein phosphorylation in the human brain and contributes to neurofibrillary degeneration, and that this contribution might be enhanced in patients with DS. To explore this hypothesis, the brain tissue from 57 subjects including 16 control subjects, 21 patients with DS, and 20 patients with sporadic Alzheimer's disease (AD) was examined with two antibodies to the amino-terminus of DYRK1A (7F3 and G-19), as well as two polyclonal antibodies to its carboxy-terminus (X1079 and 324446). Western blots demonstrated higher levels of full-length DYRK1A in the brains of patients with DS when compared to control brains. Immunocytochemistry revealed that DYRK1A accumulates in neurofibrillary tangles (NFTs) in subjects with sporadic AD and in subjects with DS/AD. Overexpression of DYRK1A in patients with DS was associated with an increase in DYRK1A-positive NFTs in a gene dosage-dependent manner. Results support the hypothesis that overexpressed DYRK1A contributes to neurofibrillary degeneration in DS more significantly than in subjects with two copies of the DYRK1A gene and sporadic AD. Immunoreactivity with antibodies against DYRK1A not only in NFTs but also in granules in granulovacuolar degeneration and in corpora amylacea suggests that DYRK1A is involved in all three forms of degeneration and that overexpression of this kinase may contribute to the early onset of these pathologies in DS.

Physiological role of the cellular prion protein (PrPc): protein profiling study in two cell culture systems

The physiological role of the cellular prion protein (PrP (c)) is still not fully understood. Current evidence strongly suggests that PrP (c) overexpression in different cell lines sensitizes cells to apoptotic stimuli through a p53 dependent pathway. On the other hand, an expression of PrP (c) in PrP (c)-deficient cells undergoing apoptosis exhibited repeatedly antiapoptotic effects. Therefore, the presence/absence and/or the level of PrP (c) expression seem to be critical for the fluctuation between PrP (c)'s pro- and antiapoptotic properties. The present study examined whether an overexpression of PrP (c) itself, without addition of any apoptotic agent, can lead to proteome changes that might account for the higher responsiveness to apoptotic stimuli. Beyond this, we examined whether the sole introduction of PrP (c) into PrP (c)-deficient cells could be sufficient to up-regulate antiapoptotic proteins capable of mitigating apoptosis. For this purpose, we used two cell lines, one expressing [human embryonic kidney (HEK) 293 cells] and the other lacking (mouse neuronal PrP (c)-deficient cells) endogenous PrP (c). Protein profiling following transient PrP (c) overexpression in HEK 293 cells revealed a major PrP (c) involvement in regulation of proteins participating in energy metabolism and cellular homeostasis, whereas transient introduction of PrP (c) into mouse neuronal PrP (c)-deficient cells resulted mainly in the regulation of proteins involved in protection against oxidative stress and apoptosis. In addition, we report for the first time that PrP (c) overexpression influenced the regulation of several proteins known to have contributory roles in the pathogenesis of Alzheimer disease (AD). Revealing the correlation between presence/absence and/or different levels of PrP (c) expression with the regulation of certain cellular proteins might further contribute to our understanding of the complex role of PrP (c) in cell physiology.

Amyloid-beta-induced mitochondrial dysfunction

As an important molecule in the pathogenesis of Alzheimer's disease (AD), amyloid-beta (Abeta) interferes with multiple aspects of mitochondrial function, including energy metabolism failure, production of reactive oxygen species (ROS) and permeability transition pore formation. Recent studies have demonstrated that Abeta progressively accumulates within mitochondrial matrix, providing a direct link to mitochondrial toxicity. Abeta-binding alcohol dehydrogenase (ABAD) is localized to the mitochondrial matrix and binds to mitochondrial Abeta. Interaction of ABAD with Abeta exaggerates Abeta-mediated mitochondrial and neuronal perturbation, leading to impaired synaptic function, and dysfunctional spatial learning/memory. Thus, blockade of ABAD/Abeta interaction may be a potential therapeutic strategy for AD.

Induction of the permeability transition and cytochrome c release by 15-deoxy-Delta12,14-prostaglandin J2 in mitochondria

The electrophilic lipid 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) is known to allow adaptation to oxidative stress in cells at low concentrations and apoptosis at high levels. The mechanisms leading to adaptation involve the covalent modification of regulatory proteins, such as Keap1, and augmentation of antioxidant defences in the cell. The targets leading to apoptosis are less well defined, but mitochondria have been indirectly implicated in the mechanisms of cell death mediated by electrophilic lipids. To determine the potential of electrophilic cyclopentenones to induce pro-apoptotic effects in the mitochondrion, we used isolated liver mitochondria and demonstrated that 15d-PGJ2 promotes Ca2+-induced mitochondrial swelling and cytochrome c release. The mechanisms involved are consistent with direct modification of protein thiols in the mitochondrion, rather than secondary formation of reactive oxygen species or lipid peroxidation. Using proteomic analysis in combination with biotinylated 15d-PGJ2, we were able to identify 17 potential targets of the electrophile-responsive proteome in isolated liver mitochondria. Taken together, these results suggest that electrophilic lipid oxidation products can target a sub-proteome in mitochondria, and this in turn results in the transduction of the electrophilic stimulus to the cell through cytochrome c release.

3-Hydroxyacyl-CoA dehydrogenase and short chain 3-hydroxyacyl-CoA dehydrogenase in human health and disease

3-Hydroxyacyl-CoA dehydrogenase (HAD) functions in mitochondrial fatty acid beta-oxidation by catalyzing the oxidation of straight chain 3-hydroxyacyl-CoAs. HAD has a preference for medium chain substrates, whereas short chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD) acts on a wide spectrum of substrates, including steroids, cholic acids, and fatty acids, with a preference for short chain methyl-branched acyl-CoAs. Therefore, HAD should not be referred to as SCHAD. SCHAD is not a member of the HAD family, but instead, belongs to the short chain dehydrogenase/reductase superfamily. Previously reported cases of SCHAD deficiency are due to an inherited HAD deficiency. SCHAD, also known as 17beta-hydroxysteroid dehydrogenase type 10, is important in brain development and aging. Abnormal levels of SCHAD in certain brain regions may contribute to the pathogenesis of some neural disorders. The human SCHAD gene and its protein product, SCHAD, are potential targets for intervention in conditions, such as Alzheimer's disease, Parkinson's disease, and an X-linked mental retardation, that may arise from the impaired degradation of branched chain fatty acid and isoleucine.

Intracellular oxidation of allopregnanolone by human brain type 10 17beta-hydroxysteroid dehydrogenase

Allopregnanolone is a positive allosteric modulator of GABAA receptors, generated by the reduction of 5alpha-dihydroprogesterone (5alpha-DHP) in astrocytes. This neuroactive steroid can be inactivated by its 3alpha-oxidation to yield 5alpha-DHP. It was found that 5alpha-DHP levels in HEK293 cells expressing type 10 17beta-hydroxysteroid dehydrogenase (17beta-HSD10), but not its catalytic inactive mutant, increased significantly as allopregnanolone was added to culture media. The results demonstrate that mitochondrial 17beta-HSD10 effectively catalyzes the intracellular oxidation of allopregnanolone. Moreover, brain astrocytes contain a moderate level of 17beta-HSD10, which is elevated in activated astrocytes of brains with Alzheimer type pathology, including sporadic Alzheimer's disease (AD) and Down's syndrome with AD. The distribution of 17beta-HSD10 was found not to parallel that of 3alpha-HSD3. Cerebral cortex has the lowest level of 17beta-HSD10; whereas the hippocampus, hypothalamus, and amygdala possess relatively higher levels of this enzyme. The catalysis of 17beta-HSD10 appears to be essential for maintaining normal functions of GABAergic neurons. The elevated level of 17beta-HSD10 in activated astrocytes is a new feature found in brains of people with AD, and it may have important impact on AD pathogenesis.

Multiple functions of type 10 17beta-hydroxysteroid dehydrogenase

Human 17beta-hydroxysteroid dehydrogenase type 10 (17beta-HSD10) is a mitochondrial enzyme encoded by the SCHAD gene, which escapes chromosome X inactivation. 17Beta-HSD10/SCHAD mutations cause a spectrum of clinical conditions, from mild mental retardation to progressive infantile neurodegeneration. 17Beta-HSD10/SCHAD is essential for the metabolism of isoleucine and branched-chain fatty acids. It can inactivate 17beta-estradiol and steroid modulators of GABA(A) receptors, and convert 5alpha-androstanediol into 5alpha-dihydrotestosterone (DHT). Certain malignant prostatic epithelial cells contain high levels of 17beta-HSD10, generating 5alpha-DHT in the absence of testosterone. 17Beta-HSD10 has an affinity for amyloid-beta peptide, and might be linked to the mitochondrial dysfunction seen in Alzheimer's disease. This versatile enzyme might provide a new drug target for neuronal excitability control and for intervention in Alzheimer's disease and certain cancers.

Type 10 17beta-hydroxysteroid dehydrogenase catalyzing the oxidation of steroid modulators of gamma-aminobutyric acid type A receptors

The steroids allopregnanolone and allotetrahydrodeoxycorticosterone (3alpha,5alpha-THDOC) are positive allosteric modulators of GABA(A) receptors, generated by the reduction of 5alpha-dihydroprogesterone (5alpha-DHP) and 5alpha-DHDOC, respectively, under the catalysis of human type 3 3alpha-hydroxysteroid dehydrogenase (HSD). However, brain enzymes catalyzing the conversion of such tetrahydrosteroids back to the corresponding 5alpha-dihydrosteroids remain to be identified. Characterization of human type 10 17beta-HSD provides a new insight into its importance for the oxidation of steroid modulators of GABA(A) receptors. The apparent catalytic efficiency (k(cat)/K(m)) of this enzyme for the oxidation of allopregnanolone and 3alpha,5alpha-THDOC are 432 and 1381 min(-1) mM(-1), respectively. This enzyme has negligible 3-ketosteroid reductase activity for 5alpha-DHP and 5alpha-DHDOC even in an acidic environment. Immunoreactivity against 17beta-HSD10 was found in a number of neuronal populations. Taken together, evidence suggests that 17beta-HSD10 is the brain enzyme capable of catalyzing the oxidation of steroid modulators of GABA(A) receptors.

Lysosomal deposition of Abeta in cultures of brain vascular smooth muscle cells is enhanced by iron

Recently, we found that brain vascular smooth muscle cells from Tg2576 mice over-expressed the APP transgene in culture, secreted amyloid-beta peptide (Abeta) and accumulated Abeta intracellularly. Now we detected this intracellular Abeta inside lysosomes, which were also rich in C-terminal domain of APP, but not in endoplasmic reticulum, Golgi apparatus, or trans-Golgi network. Treatment of cultures with ferrous ions (50-150 microM) increased the proportion of muscle cells with Abeta immunoreactive granules and the amounts of intracellular Abeta1-40 and Abeta1-42 in a dose-dependent manner. This increase of intracellular Abeta1-40 by iron was inhibited by alpha-tocopherol, but not by a water-soluble antioxidant melatonin. The increase of intracellular Abeta1-42 by iron was not inhibited by alpha-tocopherol or melatonin. Cell treatment with iron did not alter the lysosomal localization of Abeta immunoreactivity. Cell treatment with iron (II and III), copper (II), zinc (II) and aluminum (III) increased cellular levels of carbonyls. However, the effect of zinc on Abeta accumulation in cultures was weak, and there were no effects of copper and aluminum. The data suggest that iron may be the factor that triggers vascular amyloidosis. Lysosomal accumulation of APP and Abeta initiates deposition of amyloid in blood vessels in Tg2576 mice.

Cell type- and brain structure-specific patterns of distribution of minibrain kinase in human brain

The minibrain kinase (Mnb/Dyrk1A) gene is localized in the Down syndrome (DS) critical region of chromosome 21. This gene encodes a proline-directed serine/threonine protein kinase (minibrain kinase-Mnb/Dyrk1A), which is required for the proliferation of distinct neuronal cell types during postembryonic neurogenesis. To study the distribution of Mnb/Dyrk1A during human brain development and aging, we raised Mnb/Dyrk1A-specific antibody (mAb 7F3) and examined 22 brains of normal subjects from 8 months to 90 years of age. We found that neurons were the only cells showing the presence of 7F3-positive product in both cell nucleus and cytoplasm. Nuclear localization supports the concept that Mnb/Dyrk1A may be involved in control of gene expression. Synaptic localization of Mnb/Dyrk1A also supports our previous studies suggesting that Mnb/Dyrk1A is a regulator of assembly of endocytic apparatus and appears to be involved in synaptic vesicle recycling and synaptic signal transmission. Accumulation of numerous 7F3-positive corpora amylacea in the memory and motor system subdivisions in subjects older than 33 years of age indicates that Mnb/Dyrk1A is colocalized with markers of astrocyte and neuron degeneration. Differences in the topography and the amount of Mnb/Dyrk1A in neurons, astrocytes, and ependymal and endothelial cells appear to reflect cell type- and brain structure-specific patterns in trafficking and utilization of Mnb/Dyrk1A.

Oxidative 3alpha-hydroxysteroid dehydrogenase activity of human type 10 17beta-hydroxysteroid dehydrogenase

In vitro enzyme assays have demonstrated that human type 10 17beta-hydroxysteroid dehydrogenase (17beta-HSD10) catalyzes the oxidation of 5alpha-androstane-3alpha,17beta-diol (adiol), an almost inactive androgen, to dihydrotestosterone (DHT) rather than androsterone or androstanedione. To further investigate the role of this steroid-metabolizing enzyme in intact cells, we produced stable transfectants expressing 17beta-HSD10 or its catalytically inactive Y168F mutant in human embryonic kidney (HEK) 293 cells. It was found that DHT levels in HEK 293 cells expressing 17beta-HSD10, but not its catalytically inactive mutant, will dramatically increase if adiol is added to culture media. Moreover, certain malignant prostatic epithelial cells have more 17beta-HSD10 than normal controls, and can generate DHT, the most potent androgen, from adiol. This event might promote prostate cancer growth. Analysis of the 17beta-HSD10 sequence shows that this enzyme does not have any ER retention signal or transmembrane segments and has not originated by divergence from a retinol dehydrogenase. The data suggest that the unique mitochondrial location of this HSD [Eur. J. Biochem. 268 (2001) 4899] does not prevent it from oxidizing the 3alpha-hydroxyl group of a C19 sterol in living cells. The experimental results lead to the conclusion that mitochondrial 17beta-HSD10 plays a significant part in a non-classical androgen synthesis pathway along with microsomal retinol dehydrogenases.

Secretion and accumulation of Abeta by brain vascular smooth muscle cells from AbetaPP-Swedish transgenic mice

Alzheimer amyloid-beta is deposited in the neuropil and in brain blood vessels in transgenic Tg2576 mice that overexpress human amyloid-beta precursor protein (AbetaPP) containing the Swedish mutation (AbetaPP-Swe). Because the AbetaPP transgene in Tg2576 mice is placed behind the PrP promoter, all amyloid-beta, including vascular amyloid, is considered to be of neuronal origin. We studied the expression of the transgenic AbetaPP in smooth muscle cells cultured from brain blood vessels from Tg2576 mice. We found that brain vascular smooth muscle cells overexpressed human AbetaPP-Swe approximately 4 times the physiological levels of mouse AbetaPP. The cultured cells secreted abundant Abeta1-40 and Abeta1-42 and formed intracellular Abeta-immunoreactive granules. The percentage of cells containing intracellular Abeta and the amount of intracellular Abeta were significantly higher in cultures obtained from 14-month-old than from 4-month-old mice, as tested on first or second passages. During cell senescence in culture, intracellular accumulation of Abeta and C-terminal fragments of AbetaPP increased in cells derived from both 4- and 14-month-old mice. Vascular muscle cells from Tg2576 mice appear to be a valuable model of the intracellular accumulation of Abeta. We suggest that vascular muscle cells may be involved in the production of cerebrovascular amyloid in Tg2576 mice.

2-Methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency is caused by mutations in the HADH2 gene

2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) deficiency is a novel inborn error of isoleucine degradation. In this article, we report the elucidation of the molecular basis of MHBD deficiency. To this end, we purified the enzyme from bovine liver. MALDI-TOF mass spectrometry analysis revealed that the purified protein was identical to bovine 3-hydroxyacyl-CoA dehydrogenase type II. The human homolog of this bovine enzyme is a short-chain 3-hydroxyacyl-CoA dehydrogenase, also known as the "endoplasmic reticulum-associated amyloid-beta binding protein" (ERAB). This led to the identification of the X-chromosomal gene involved, which previously had been denoted "HADH2." Sequence analysis of the HADH2 gene from patients with MHBD deficiency revealed the presence of two missense mutations (R130C and L122V). Heterologous expression of the mutant cDNAs in Escherichia coli showed that both mutations almost completely abolish enzyme activity. This confirms that MHBD deficiency is caused by mutations in the HADH2 gene.

Presence of hydroxysteroid dehydrogenase type 10 in amyloid plaques (APs) of Hsiao's APP-Sw transgenic mouse brains, but absence in APs of Alzheimer's disease brains

This immunocytochemical study using two anti-amyloid beta-protein (Abeta) monoclonal antibodies, 4G8 and 6E10, revealed the presence of Abeta in both amyloid plaques (APs) and blood vessels of brains of Hsiao's APP-Sw transgenic mice (also known as Tg2576) and human Alzheimer's disease (AD) brains. Further study using both monoclonal (5F3) and polyclonal (R-228) antibodies to hydroxysteroid dehydrogenase type 10 (HSD-10) [formerly called SCHAD (short-chain L-3-hydroxyacyl-CoA dehydrogenase); also called ERAB (endoplasmic-reticulum-associated amyloid beta-peptide-binding protein)] indicated that HSD-10 was present in the APs of Tg2576 mice but was absent or immunocytochemically undetectable in the APs of AD brains. Our observations also revealed that HSD-10 was present in the blood vessels of both Tg2576 mice and AD brains. Immunogold electron microscopy also indicated that HSD-10 was present in the amyloid fibers (AFs), mitochondria, nuclear heterochromatin, and nucleolus of Tg2576 mouse brains but was absent in APs of AD brains. These results suggest that the human APP gene transferred to mice may induce overexpression of HSD-10 in mouse APs and in various other cellular components of mouse brains. It is also possible that the human APP gene responsible for HSD-10 deposition in APs of these Tg2576 mice brains is different from that of AD brains. Alternatively, the HSD-10 gene and APP gene may function independently in AD brains. Despite these differences, the Tg2576 mouse, as shown in this study, is a proper animal model for the study of AD and also for the investigation of HSD-10.