Cerebrospinal Fluid from Alzheimer's Disease Patients Contains Fungal Proteins and DNA

The identification of biomarkers for Alzheimer's disease is important for patient management and to assess the effectiveness of clinical intervention. Cerebrospinal fluid (CSF) biomarkers constitute a powerful tool for diagnosis and monitoring disease progression. We have analyzed the presence of fungal proteins and DNA in CSF from AD patients. Our findings reveal that fungal proteins can be detected in CSF with different anti-fungal antibodies using a slot-blot assay. Additionally, amplification of fungal DNA by PCR followed by sequencing distinguished several fungal species. The possibility that these fungal macromolecules could represent AD biomarkers is discussed.

Evidence for fungal infection in cerebrospinal fluid and brain tissue from patients with amyotrophic lateral sclerosis

Among neurogenerative diseases, amyotrophic lateral sclerosis (ALS) is a fatal illness characterized by a progressive motor neuron dysfunction in the motor cortex, brainstem and spinal cord. ALS is the most common form of motor neuron disease; yet, to date, the exact etiology of ALS remains unknown. In the present work, we have explored the possibility of fungal infection in cerebrospinal fluid (CSF) and in brain tissue from ALS patients. Fungal antigens, as well as DNA from several fungi, were detected in CSF from ALS patients. Additionally, examination of brain sections from the frontal cortex of ALS patients revealed the existence of immunopositive fungal antigens comprising punctate bodies in the cytoplasm of some neurons. Fungal DNA was also detected in brain tissue using PCR analysis, uncovering the presence of several fungal species. Finally, proteomic analyses of brain tissue demonstrated the occurrence of several fungal peptides. Collectively, our observations provide compelling evidence of fungal infection in the ALS patients analyzed, suggesting that this infection may play a part in the etiology of the disease or may constitute a risk factor for these patients.

Argyrophilic grain pathology as a natural model of tau propagation

Argyrophilic grain disease (AGD) is a sporadic 4 R tauopathy that usually presents in combination with other sporadic tauopathies or with Alzheimer's disease (AD) pathology, and may contribute to dementia in older age patients. In previous studies, a detailed analysis of AGD pathology in the medial temporal lobe has been hampered by the common presence of concurrent AD changes. With the objective to assess the potentiality of AGD in research on tau propagation, here we present a study of a series of AGD postmortem cases (n = 53). The total series was divided in a subgroup of cases with Braak-stage ≤ II (n = 23) and a subgroup with Braak-stage>II or indeterminate (n = 30) in order to minimize interference with AD pathology. A detailed neuropathological evaluation of the medial temporal lobe was performed at three coronal levels with Gallyas stain, and immunostains with p62, AT8, and AT100 antibodies. Western blot analysis of the entorhinal and hippocampal cortex was performed in 8 cases with a panel of anti-tau antibodies. Cases were genotyped for APOE polymorphism and for H1/H2 alleles of the MAPT gene. All cases, and particularly lower Braak-stage cases, displayed a highly homogeneous pattern of involvement by argyrophilic grains and pretangles between connected regions (primarily basolateral nuclei of the amygdala, entorhinal/transentorhinal cortex, and hippocampal cortex). Staging of cases reveals progression of pathology along well-established neuroanatomical pathways. Western blot studies yielded a specific pattern of isoforms with a characteristic predominant band at 64 kDa. Genetic analysis showed a strong association with the H1 allele of the MAPT gene. AGD may thus be an optimal natural disease model for testing hypotheses related to tau propagation in human tissue.

On the diagnosis of CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a genetic arteriopathy related to Notch3 mutations, is difficult to diagnosis. The goal of this study was to determine the value of clinical, immunohistochemical, and molecular techniques for the diagnosis of CADASIL. Clinical features and the immunohistochemical and molecular findings in 200 subjects with suspected CADASIL in whom 93 biopsies and 190 molecular studies are reported. Eighteen pathogenic mutations of the Notch3 gene, six of them previously unreported, were detected in 67 patients. The clinical features did not permit differentiation between CADASIL and CADASIL-like syndromes. The sensitivity and specificity of the skin biopsies was 97.7% and 56.5%, respectively, but increased to 100% and 81.5%, respectively, in cases with proven family history. In conclusion, a clinical diagnosis of CADASIL is difficult to determine and confirmatory techniques should be used judiciously.

Effects of partial suppression of parkin on huntingtin mutant R6/1 mice

Huntington's disease (HD) is a neurodegenerative disorder caused by an expansion of polyglutamines which makes huntingtin more resistant to degradation. Parkin is an ubiquitin ligase which promotes proteosomal degradation of abnormal proteins. We investigated whether partial suppression of parkin increases HD phenotype. We studied the behavior and brain histology and biochemistry of the mice produced by interbreeding of R6/1 (model of HD in mice) with Park-2(-/-) (parkin null mice): R6/1, WT (wild-type), PK(+/-) (hemizygotic deletion of Park-2) and R6/1/PK(+/-). R6/1 and R6/1/PK(+/-) mice had abnormal motor and exploratory behavior. R6/1/PK(+/-) mice were more akinetic. These two groups of mice had severe but similar loss of nigrostriatal dopamine neurons and monoamine levels in striatum. R6/1/PK(+/-) mice had fewer huntingtin inclusions and a greater number of TUNEL(+) cells than R6/1 in striatum but there were no differences in the hippocampus. DARPP-32 protein was equally reduced in striatum of R6/1 and R6/1/PK(+/-) mice. Striatal levels of GSH were increased, of HSP-70 reduced and of CHIP unchanged in both R6/1 and R6/1/PK(+/-) mice. LC-3 II/I ratios were significantly increased in striatum of R6/1/PK(+/-) mice. Partial suppression of parkin slightly aggravates the phenotype in R6/1 mice, confirming a pathogenic role of the UPS in the processing of mutant huntingtin. The absence of massive additional cellular lesions in R6/1/PK(+/-) mice suggests the existence of compensatory mechanisms, such as autophagy, for the processing of huntingtin.

NP7 protects from cell death induced by oxidative stress in neuronal and glial midbrain cultures from parkin null mice

Parkin mutations produce Parkinson's disease (PD) in humans and nigrostriatal dopamine lesions related to increased free radicals in mice. We examined the effects of NP7, a synthetic, marine derived, free radical scavenger which enters the brain, on H(2)O(2) toxicity in cultured neurons and glia from wild-type (WT) and parkin null mice (PK-KO). NP7, 5-10 microM, prevented the H(2)O(2) induced apoptosis and necrosis of midbrain neuronal and glial cultures from WT and PK-KO mice. NP7 suppressed microglial activation and the H(2)O(2) induced drop-out of dopamine neurons(.) Furthermore, NP7 prevented the increased phosphorylation of ERK and AKT induced by H(2)O(2). NP7 may be a promising neuroprotector against oxidative stress in PD.

Parkin deletion causes cerebral and systemic amyloidosis in human mutated tau over-expressing mice

Deposition of proteins leading to amyloid takes place in some neurodegenerative diseases such as Alzheimer's disease and Huntington's disease. Mutations of tau and parkin proteins produce neurofibrillary abnormalities without deposition of amyloid. Here we report that mature, parkin null, over-expressing human mutated tau (PK(-/-)/Tau(VLW)) mice have altered behaviour and dopamine neurotransmission, tau pathology in brain and amyloid deposition in brain and peripheral organs. PK(-/-)/Tau(VLW) mice have abnormal behaviour and severe drop out of dopamine neurons in the ventral midbrain, up to 70%, at 12 months and abundant phosphorylated tau positive neuritic plaques, neuro-fibrillary tangles, astrogliosis, microgliosis and plaques of murine beta-amyloid in the hippocampus. PK(-/-)/Tau(VLW) mice have organomegaly of the liver, spleen and kidneys. The electron microscopy of the liver confirmed the presence of a fibrillary protein deposits with amyloid characteristics. There is also accumulation of mouse tau in hepatocytes. These mice have lower levels of CHIP-HSP70, involved in the proteosomal degradation of tau, increased oxidative stress, measured as depletion of glutathione which, added to lack of parkin, could trigger tau accumulation and amyloidogenesis. This model is the first that demonstrates beta-amyloid deposits caused by over-expression of tau and without modification of the amyloid precursor protein, presenilins or secretases. PK(-/-)/Tau(VLW) mice provide a link between the two proteins more important for the pathogenesis of Alzheimer disease.

Mortality, oxidative stress and tau accumulation during ageing in parkin null mice

Young parkin null (pk-/-) mice have subtle abnormalities of behaviour, dopamine (DA) neurotransmission and free radical production, but no massive loss of DA neurons. We investigated whether these findings are maintained while ageing. Pk-/- mice have reduced life span and age-related reduced exploratory behaviour, abnormal walking and posture, and behaviours similar to those of early Parkinson's disease (PD), reduced number of nigrostriatal DA neurons and proapoptotic shifts in the survival/death proteins in midbrain and striatum. Contrary to young pk-/- animals 24-month-old pk-/- mice do not have compensatory elevation of GSH in striatum, glutathione reductase (GR) and glutathione peroxidase (GPx) activities are increased and catalase unchanged. Aged pk-/- mice accumulate high levels of tau and fail to up-regulate CHIP and HSP70. Our results suggest that aged pk-/- mice lack of the compensatory mechanisms that maintain a relatively normal DA function in early adulthood. This study could help to explain the effects of ageing in patients with genetic risks for Parkinson's disease.

Megalin mediates the transport of leptin across the blood-CSF barrier

Leptin, a peptide hormone secreted by adipose tissue, exhibits a large range of central and peripheral actions. It has been proposed that the participation of leptin in diseases such as obesity is due to, at least in part, its impaired transport across the blood-brain barrier (BBB). Since, the mechanisms by which brain takes up leptin remain unclear, we set out to study how leptin may cross the BBB. We have used different immunoassays and lentiviral vectors to analyze the role of megalin in the transport of leptin in rodents and humans. We demonstrate that circulating leptin is transported into the brain by binding to megalin at the choroid plexus epithelium. Indeed, the downregulation of megalin expression in physiological and pathological situations such as aging and Alzheimer's disease was correlated with poor entry of leptin into the brain. Moreover, amyloid beta (Abeta) deposits of choroid plexus could be disturbing megalin function. The present data indicate that leptin represents a novel megalin ligand of importance in the levels and therapeutic actions of leptin into the brain.

Suppression of Parkin enhances nigrostriatal and motor neuron lesion in mice over-expressing human-mutated tau protein

Abnormal deposition of protein tau takes place in the brain of patients with several neurodegenerative diseases. Few of these patients present frontotemporal dementia with parkinsonism and amyotrophy (FTDPA-17), an autosomal dominant tauopathy related to mutations of the gene that codes for protein tau, localized in chromosome 17. The great majority of patients with tauopathies such as Alzheimer's disease, sporadic frontotemporal dementia or progressive supranuclear palsy do not show a Mendelian pattern of inheritance. We have occasionally seen tauopathies in patients with parkin mutations and, therefore, hypothesized that the protein tau interacts with parkin. We have tested that hypothesis in mice with combined genetic modifications of tau (over-expression of human tau with three mutations known to produce FTDPA-17) and parkin (deleted) proteins. Homozygote parkin null or over-expressing mutated-human tau mice have subtle behavioral and molecular abnormalities but do not express a clinical phenotype of neurodegenerative disease. Mice with combined homozygous mutations of these two genes show progressively abnormal walking already noticeable at 3 months of age, loss of dopamine and dopamine markers in striatum, nuclear tau immunoreactive deposits in motor neurons of the spinal cord, abnormal expression of glial markers and enhanced levels of pro-apoptotic proteins; findings that were absent or less pronounced in homozygote animals with deletions of parkin or over-expression of tau. The double transgenic mice do not express normal mechanisms of adaptation to stress such as increased levels of GSH and Hsp-70. In addition, they have reduced levels of CHIP-Hsc70, a complex known to attenuate aggregation of tau and to enhance ubiquitination of phosphorylated tau. We have found high levels of phosphorylated tau in parkin-/-+tau(VLW) mice and a relative decrease of the inactivated pSer9 to total GSK-3 levels. Our data reveal that there are interactions between tau and parkin that could be relevant for the pathogenesis and treatment of tauopathies. Similarly, we hope that the double transgenic parkin-/-+tau(VLW) mice could be useful for testing of compounds with putative therapeutic value in human tauopathies.