The role of novel chitin-like polysaccharides in Alzheimer disease

Structure Identification of Ganoderma lucidum Spore Polysaccharides and Their Antitumor Activity In Vivo

Ganoderma lucidum spore powder, valued for its nutritional and medicinal properties, contains polysaccharides crucial for its efficacy. However, the complex structural nature of these polysaccharides necessitates further investigation to fully realize their potential. This study aimed to investigate the effects of acid heat treatment on Ganoderma lucidum spore polysaccharides (GLSPs) to enhance their properties and application in antitumor activity. The GLSP was obtained via acid heat treatment, concentration, and centrifugal separation. This process led to a notable reduction in polysaccharide molecular weight, increasing water solubility and bioavailability. Analytical techniques including NMR spectroscopy and methylation analysis revealed a polysaccharide composition comprising four distinct monosaccharides, with molecular weights of 3291 Da (Mw) and 3216 Da (Mn). Six different linkage modes were identified, with a molar ratio of 1:5:2:3:4:3. In vivo experiments demonstrated the GLSP's significant inhibitory effect on the growth of four tumor models (sarcoma S180, Lewis lung cancer, liver cancer H22, and colon cancer C26) in mice, with no observed toxicity. These findings suggest the GLSP's potential as an antitumor therapeutic agent for clinical use.

Vaccines and Dementia: Part II. Efficacy of BCG and Other Vaccines Against Dementia

 There is growing awareness that infections may contribute to the development of senile dementia including Alzheimer's disease (AD), and that immunopotentiation is therefore a legitimate target in the management of diseases of the elderly including AD. In Part I of this work, we provided a historical and molecular background to how vaccines, adjuvants, and their component molecules can elicit broad-spectrum protective effects against diverse agents, culminating in the development of the tuberculosis vaccine strain Bacille Calmette-Guérin (BCG) as a treatment for some types of cancer as well as a prophylactic against infections of the elderly such as pneumonia. In Part II, we critically review studies that BCG and other vaccines may offer a measure of protection against dementia development. Five studies to date have determined that intravesicular BCG administration, the standard of care for bladder cancer, is followed by a mean ∼45% reduction in subsequent AD development in these patients. Although this could potentially be ascribed to confounding factors, the finding that other routine vaccines such as against shingles (herpes zoster virus) and influenza (influenza A virus), among others, also offer a degree of protection against AD (mean 29% over multiple studies) underlines the plausibility that the protective effects are real. We highlight clinical trials that are planned or underway and discuss whether BCG could be replaced by key components of the mycobacterial cell wall such as muramyl dipeptide. We conclude that BCG and similar agents merit far wider consideration as prophylactic agents against dementia.

Establishment of a consensus protocol to explore the brain pathobiome in patients with mild cognitive impairment and Alzheimer's disease: Research outline and call for collaboration

Microbial infections of the brain can lead to dementia, and for many decades microbial infections have been implicated in Alzheimer's disease (AD) pathology. However, a causal role for infection in AD remains contentious, and the lack of standardized detection methodologies has led to inconsistent detection/identification of microbes in AD brains. There is a need for a consensus methodology; the Alzheimer's Pathobiome Initiative aims to perform comparative molecular analyses of microbes in post mortem brains versus cerebrospinal fluid, blood, olfactory neuroepithelium, oral/nasopharyngeal tissue, bronchoalveolar, urinary, and gut/stool samples. Diverse extraction methodologies, polymerase chain reaction and sequencing techniques, and bioinformatic tools will be evaluated, in addition to direct microbial culture and metabolomic techniques. The goal is to provide a roadmap for detecting infectious agents in patients with mild cognitive impairment or AD. Positive findings would then prompt tailoring of antimicrobial treatments that might attenuate or remit mounting clinical deficits in a subset of patients.

Programmed ageing: decline of stem cell renewal, immunosenescence, and Alzheimer's disease

The characteristic maximum lifespan varies enormously across animal species from a few hours to hundreds of years. This argues that maximum lifespan, and the ageing process that itself dictates lifespan, are to a large extent genetically determined. Although controversial, this is supported by firm evidence that semelparous species display evolutionarily programmed ageing in response to reproductive and environmental cues. Parabiosis experiments reveal that ageing is orchestrated systemically through the circulation, accompanied by programmed changes in hormone levels across a lifetime. This implies that, like the circadian and circannual clocks, there is a master 'clock of age' (circavital clock) located in the limbic brain of mammals that modulates systemic changes in growth factor and hormone secretion over the lifespan, as well as systemic alterations in gene expression as revealed by genomic methylation analysis. Studies on accelerated ageing in mice, as well as human longevity genes, converge on evolutionarily conserved fibroblast growth factors (FGFs) and their receptors, including KLOTHO, as well as insulin-like growth factors (IGFs) and steroid hormones, as key players mediating the systemic effects of ageing. Age-related changes in these and multiple other factors are inferred to cause a progressive decline in tissue maintenance through failure of stem cell replenishment. This most severely affects the immune system, which requires constant renewal from bone marrow stem cells. Age-related immune decline increases risk of infection whereas lifespan can be extended in germfree animals. This and other evidence suggests that infection is the major cause of death in higher organisms. Immune decline is also associated with age-related diseases. Taking the example of Alzheimer's disease (AD), we assess the evidence that AD is caused by immunosenescence and infection. The signature protein of AD brain, Aβ, is now known to be an antimicrobial peptide, and Aβ deposits in AD brain may be a response to infection rather than a cause of disease. Because some cognitively normal elderly individuals show extensive neuropathology, we argue that the location of the pathology is crucial - specifically, lesions to limbic brain are likely to accentuate immunosenescence, and could thus underlie a vicious cycle of accelerated immune decline and microbial proliferation that culminates in AD. This general model may extend to other age-related diseases, and we propose a general paradigm of organismal senescence in which declining stem cell proliferation leads to programmed immunosenescence and mortality.

Chitosan Nanoparticles-Based Cancer Drug Delivery: Application and Challenges

Chitin is the second most abundant biopolymer consisting of N-acetylglucosamine units and is primarily derived from the shells of marine crustaceans and the cell walls of organisms (such as bacteria, fungi, and algae). Being a biopolymer, its materialistic properties, such as biodegradability, and biocompatibility, make it a suitable choice for biomedical applications. Similarly, its deacetylated derivative, chitosan, exhibits similar biocompatibility and biodegradability properties, making it a suitable support material for biomedical applications. Furthermore, it has intrinsic material properties such as antioxidant, antibacterial, and antitumor. Population studies have projected nearly 12 million cancer patients across the globe, where most will be suffering from solid tumors. One of the shortcomings of potent anticancer drugs is finding a suitable cellular delivery material or system. Therefore, identifying new drug carriers to achieve effective anticancer therapy is becoming essential. This paper focuses on the strategies implemented using chitin and chitosan biopolymers in drug delivery for cancer treatment.

Chitinase Signature in the Plasticity of Neurodegenerative Diseases

Several reports have pointed out that Chitinases are expressed and secreted by various cell types of central nervous system (CNS), including activated microglia and astrocytes. These cells play a key role in neuroinflammation and in the pathogenesis of many neurodegenerative disorders. Increased levels of Chitinases, in particular Chitotriosidase (CHIT-1) and chitinase-3-like protein 1 (CHI3L1), have been found increased in several neurodegenerative disorders. Although having important biological roles in inflammation, to date, the molecular mechanisms of Chitinase involvement in the pathogenesis of neurodegenerative disorders is not well-elucidated. Several studies showed that some Chitinases could be assumed as markers for diagnosis, prognosis, activity, and severity of a disease and therefore can be helpful in the choice of treatment. However, some studies showed controversial results. This review will discuss the potential of Chitinases in the pathogenesis of some neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, and multiple sclerosis, to understand their role as distinctive biomarkers of neuronal cell activity during neuroinflammatory processes. Knowledge of the role of Chitinases in neuronal cell activation could allow for the development of new methodologies for downregulating neuroinflammation and consequently for diminishing negative neurological disease outcomes.

The Ability of Some Polysaccharides to Disaggregate Lysozyme Amyloid Fibrils and Renature the Protein

The deposition of proteins in the form of insoluble amyloid fibril aggregates is linked to a range of diseases. The supramolecular architecture of such deposits is governed by the propagation of β-strands in the direction of protofilament growth. In the present study, we analyze the structural changes of hen egg-white lysozyme fibrils upon their interactions with a range of polysaccharides, using AFM and FTIR spectroscopy. Linear anionic polysaccharides, such as κ-carrageenan and sodium alginate, are shown to be capable to disaggregate protofilaments with eventual protein renaturation. The results help to understand the mechanism of amyloid disaggregation and create a platform for both the development of new therapeutic agents for amyloidose treatment, and the design of novel functional protein-polysaccharide complex-based nanomaterials.

Pharmacotherapeutic Potential of Garlic in Age-Related Neurological Disorders

Age-related neurological disorders [ANDs] involve neurodegenerative diseases [NDDs] such as Alzheimer's disease [AD], the most frequent kind of dementia in elderly people, and Parkinson's disease [PD], and also other disorders like epilepsy and migraine. Although ANDs are multifactorial, Aging is a principal risk factor for them. The common and most main pathologic features among ANDs are inflammation, oxidative stress, and misfolded proteins accumulation. Since failing brains caused by ANDs impose a notable burden on public health and their incidence is increasing, a lot of works has been done to overcome them. Garlic, Allium sativum, has been used for different medical purposes globally and more than thousands of publications have reported its health benefits. Garlic and aged garlic extract are considered potent anti-inflammatory and antioxidants agents and can have remarkable neuroprotective effects. This review is aimed to summarize knowledge on the pharmacotherapeutic potential of garlic and its components in ANDs.

Increased chitotriosidase 1 concentration following nusinersen treatment in spinal muscular atrophy

Background

Studies regarding the impact of (neuro)inflammation and inflammatory response following repetitive, intrathecally administered antisense oligonucleotides (ASO) in 5q-associated spinal muscular atrophy (SMA) are sparse. Increased risk of hydrocephalus in untreated SMA patients and a marginal but significant increase of the serum/CSF albumin ratio (Qalb) with rare cases of communicating hydrocephalus during nusinersen treatment were reported, which confirms the unmet need of an inflammatory biomarker in SMA. The aim of this study was to investigate the (neuro)inflammatory marker chitotriosidase 1 (CHIT1) in SMA patients before and following the treatment with the ASO nusinersen.

Methods

In this prospective, multicenter observational study, we studied CSF CHIT1 concentrations in 58 adult and 21 pediatric patients with SMA type 1, 2 or 3 before treatment initiation in comparison to age- and sex-matched controls and investigated its dynamics during nusinersen treatment. Concurrently, motor performance and disease severity were assessed.

Results

CHIT1 concentrations were elevated in treatment-naïve SMA patients as compared to controls, but less pronounced than described for other neurodegenerative diseases such as amyotrophic lateral sclerosis. CHIT1 concentration did not correlate with disease severity and did not distinguish between clinical subtypes. CHIT1 concentration did show a significant increase during nusinersen treatment that was unrelated to the clinical response to nusinersen therapy.

Conclusions

CHIT1 elevation in treatment-naïve SMA patients indicates the involvement of (neuro)inflammation in SMA. The lacking correlation of CHIT1 concentration with disease severity argues against its use as a marker of disease progression. The observed CHIT1 increase during nusinersen treatment may indicate an immune response-like, off-target reaction. Since antisense oligonucleotides are an establishing approach in the treatment of neurodegenerative diseases, this observation needs to be further evaluated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01961-8.

Cerebrospinal Fluid Chitinases as Biomarkers for Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative neuromuscular disease that affects motor neurons controlling voluntary muscles. Survival is usually 2–5 years after onset, and death occurs due to respiratory failure. The identification of biomarkers would be very useful to help in disease diagnosis and for patient stratification based on, e.g., progression rate, with implications in therapeutic trials. Neurofilaments constitute already-promising markers for ALS and, recently, chitinases have emerged as novel marker targets for the disease. Here, we investigated cerebrospinal fluid (CSF) chitinases as potential markers for ALS. Chitotriosidase (CHIT1), chitinase-3-like protein 1 (CHI3L1), chitinase-3-like protein 2 (CHI3L2) and the benchmark marker phosphoneurofilament heavy chain (pNFH) were quantified by an enzyme-linked immunosorbent assay (ELISA) from the CSF of 34 ALS patients and 24 control patients with other neurological diseases. CSF was also analyzed by UHPLC-mass spectrometry. All three chitinases, as well as pNFH, were found to correlate with disease progression rate. Furthermore, CHIT1 was elevated in ALS patients with high diagnostic performance, as was pNFH. On the other hand, CHIT1 correlated with forced vital capacity (FVC). The three chitinases correlated with pNFH, indicating a relation between degeneration and neuroinflammation. In conclusion, our results supported the value of CHIT1 as a diagnostic and progression rate biomarker, and its potential as respiratory function marker. The results opened novel perspectives to explore chitinases as biomarkers and their functional relevance in ALS.

Non-neuronal cells in amyotrophic lateral sclerosis - from pathogenesis to biomarkers

The prevailing motor neuron-centric view of amyotrophic lateral sclerosis (ALS) pathogenesis could be an important factor in the failure to identify disease-modifying therapy for this neurodegenerative disorder. Non-neuronal cells have crucial homeostatic functions within the CNS and evidence of involvement of these cells in the pathophysiology of several neurodegenerative disorders, including ALS, is accumulating. Microglia and astrocytes, in crosstalk with peripheral immune cells, can exert both neuroprotective and adverse effects, resulting in a highly nuanced range of neuronal and non-neuronal cell interactions. This Review provides an overview of the diverse roles of non-neuronal cells in relation to the pathogenesis of ALS and the emerging potential of non-neuronal cell biomarkers to advance therapeutic development.

Chitin and Chitosan Derivatives as Biomaterial Resources for Biological and Biomedical Applications

Chitin is a long-chain polymer of N-acetyl-glucosamine, which is regularly found in the exoskeleton of arthropods including insects, shellfish and the cell wall of fungi. It has been known that chitin can be used for biological and biomedical applications, especially as a biomaterial for tissue repairing, encapsulating drug for drug delivery. However, chitin has been postulated as an inducer of proinflammatory cytokines and certain diseases including asthma. Likewise, chitosan, a long-chain polymer of N-acetyl-glucosamine and d-glucosamine derived from chitin deacetylation, and chitosan oligosaccharide, a short chain polymer, have been known for their potential therapeutic effects, including anti-inflammatory, antioxidant, antidiarrheal, and anti-Alzheimer effects. This review summarizes potential utilization and limitation of chitin, chitosan and chitosan oligosaccharide in a variety of diseases. Furthermore, future direction of research and development of chitin, chitosan, and chitosan oligosaccharide for biomedical applications is discussed.

Chitotriosidase, a biomarker of amyotrophic lateral sclerosis, accentuates neurodegeneration in spinal motor neurons through neuroinflammation

Background

Cerebrospinal fluid from amyotrophic lateral sclerosis patients (ALS-CSF) induces neurodegenerative changes in motor neurons and gliosis in sporadic ALS models. Search for identification of toxic factor(s) in CSF revealed an enhancement in the level and enzyme activity of chitotriosidase (CHIT-1). Here, we have investigated its upregulation in a large cohort of samples and more importantly its role in ALS pathogenesis in a rat model.

Methods

CHIT-1 level in CSF samples from ALS (n = 158), non-ALS (n = 12) and normal (n = 48) subjects were measured using ELISA. Enzyme activity was also assessed (ALS, n = 56; non-ALS, n = 10 and normal-CSF, n = 45). Recombinant CHIT-1 was intrathecally injected into Wistar rat neonates. Lumbar spinal cord sections were stained for Iba1, glial fibrillary acidic protein and choline acetyl transferase to identify microglia, astrocytes and motor neurons respectively after 48 h of injection. Levels of tumour necrosis factor-α and interleukin-6 were measured by ELISA.

Findings

CHIT-1 level in ALS-CSF samples was increased by 20-fold and it can distinguish ALS patients with a sensitivity of 87% and specificity of 83.3% at a cut off level of 1405.43 pg/ml. Enzyme activity of CHIT-1 was also 15-fold higher in ALS-CSF and has a sensitivity of 80.4% and specificity of 80% at cut off value of 0.1077989 μmol/μl/min. Combining CHIT-1 level and activity together gave a positive predictive value of 97.78% and negative predictive value of 100%. Administration of CHIT-1 increased microglial numbers and astrogliosis in the ventral horn with a concomitant increase in the levels of pro-inflammatory cytokines. Amoeboid-shaped microglial and astroglial cells were also present around the central canal. CHIT-1 administration also resulted in the reduction of motor neurons.

Conclusions

CHIT-1, an early diagnostic biomarker of sporadic ALS, activates glia priming them to attain a toxic phenotype resulting in neuroinflammation leading to motor neuronal death.

CA-30, an oligosaccharide fraction derived from Liuwei Dihuang decoction, ameliorates cognitive deterioration via the intestinal microbiome in the senescence-accelerated mouse prone 8 strain

Mounting evidence points to alterations in the gut microbiota-neuroendocrine immunomodulation (NIM) network that might drive Alzheimer’s Disease (AD) pathology. In previous studies, we found that Liuwei Dihuang decoction (LW) had beneficial effects on the cognitive impairments and gastrointestinal microbiota dysbiosis in an AD mouse model. In particular, CA-30 is an oligosaccharide fraction derived from LW. We sought to determine the effects of CA-30 on the composition and function of the intestinal microbiome in the senescence-accelerated mouse prone 8 (SAMP8) mouse strain, an AD mouse model. Treatment with CA-30 delayed aging processes, ameliorated cognition in SAMP8 mice. Moreover, CA-30 ameliorated abnormal NIM network in SAMP8 mice. In addition, we found that CA-30 mainly altered the abundance of four genera and 10 newborn genera. Advantageous changes in carbohydrate-active enzymes of SAMP8 mice following CA-30 treatment, especially GH85, were also noted. We further found that seven genera were significantly correlated with the NIM network and cognitive performance. CA-30 influenced the relative abundance of these intestinal microbiomes in SAMP8 mice and restored them to SAMR1 mouse levels. CA-30 ameliorated the intestinal microbiome, rebalanced the NIM network, improved the AD-like cognitive impairments in SAMP8 mice, and can thus be a potential therapeutic agent for AD.

Possible Role of Chitin-Like Proteins in the Etiology of Alzheimer's Disease

Chitin is a β-linked straight chain carbohydrate matrix monopolymer prominent in invertebrates, from fungi to arthropods. Surprisingly, chitin is now documented in vertebrates, including humans, a component of vertebrate physiology that has been neglected until now. Chitin levels are elevated in Alzheimer's disease (AD) patients, not only in the central nervous system but also in the cerebrospinal fluid and plasma. Elevated levels of chitin lectin have been reported in patients with AD. Chitinase activity varies widely in the human population. Chitin levels can increase in individuals with intrinsically low chitinase activity. Elevated amounts of chitin can reflect accumulation of the small chitin fragments that remain wherever rapid hyaluronan synthesis occurs. Another source of chitin may be from remote fungal infections. Chitin can be toxic for neurons, and its accumulation may lead to the development of AD. We present new suggestions for animal models and treatment modalities that could prove useful in future research endeavors. An unexpected connection with Gaucher's disease patients and their heterozygote relatives is also identified. These chitin-related mechanisms are novel approaches to AD whose etiology until now has defied explication.

Chitin, chitinases, and chitin lectins: Emerging roles in human pathophysiology

Chitin is a simple β-linked repeating sugar polymer prominent in the building block structures of a wide variety of organisms, from the yeast cell wall to the exoskeleton and shells of arthropods and other forms of invertebrate life. It had previously been assumed that vertebrates did not contain chitins. However, chitin and chitinases are now documented to occur in vertebrate tissues. Chitin, chitinases and particularly chitinase-like proteins are involved in important human pathologies, though the mechanisms by which these function is unknown. These chitinase-like proteins bind to chitin and function as chitin lectins in that they bind to chitin but have lost the ability to degrade it. Emphasis is placed on one of the chitinase-like proteins, CHI3L1, that has acquired wide clinical importance. The purpose of this review is to place an array of bewildering observations associated with various human disorders into a framework, particularly the pathologies of the human gastro-intestinal tract. A reasonably cohesive story may eventually emerge.

Chitotriosidase (CHIT1) is increased in microglia and macrophages in spinal cord of amyotrophic lateral sclerosis and cerebrospinal fluid levels correlate with disease severity and progression

OBJECTIVES

Neurochemical markers of amyotrophic lateral sclerosis (ALS) that reflect underlying disease mechanisms might help in diagnosis, staging and prediction of outcome. We aimed at determining the origin and differential diagnostic and prognostic potential of the putative marker of microglial activation chitotriosidase (CHIT1).

METHODS

Altogether 316 patients were included, comprising patients with sporadic ALS, ALS mimics (disease controls (DCo)), frontotemporal lobar degeneration (FTLD), Creutzfeldt-Jakob disease (CJD), Alzheimer's disease (AD), Parkinson's disease (PD) and healthy controls (Con). CHIT1 and neurofilament levels were determined in cerebrospinal fluid (CSF) and blood and analysed with regard to diagnostic sensitivity and specificity and prognostic performance. Additionally, postmortem tissue was analysed for CHIT1 expression.

RESULTS

In ALS, CHIT1 CSF levels were higher compared with Con (p<0.0001), DCo (p<0.05) and neurodegenerative diseases (AD p<0.05, PD p<0.01, FTLD p<0.0001) except CJD. CHIT1 concentrations were correlated with ALS disease progression and severity but not with the survival time, as did neurofilaments. Serum CHIT1 levels were not different in ALS compared with any other study group. In the spinal cord of patients with ALS, but not Con, AD or CJD cases, CHIT1 was expressed in the corticospinal tract and CHIT1 staining colocalised with markers of microglia (IBA1) and macrophages (CD68).

CONCLUSIONS

CHIT1 concentrations in the CSF of patients with ALS may reflect the extent of microglia/macrophage activation in the white matter of the spinal cord. CHIT1 could be a potentially useful marker for differential diagnosis and prediction of disease progression in ALS and, therefore, seems suitable as a supplemental marker for patient stratification in therapeutic trials.

Chitinase1 contributed to a potential protection via microglia polarization and Aβ oligomer reduction in D-galactose and aluminum-induced rat model with cognitive impairments

Chitinase activity is increased in Alzheimer's disease (AD). However, the role of chitinase1 in AD is unknown. We investigated the effects of chitinase1 on Alzheimer's pathology and microglia function. Artificial chitinase1 and chitinase inhibitor (chitinase-IN-2) were used to determine the effects of chitinase1 on inflammatory factors and β-amyloid (Aβ) oligomers deposition in D-galactose/AlCl₃-induced rat model with cognitive impairments. Aβ-treated N9 microglia cells were analyzed to further verify whether the changes in inflammatory factors following chitinase1 treatment were associated with microglia alternative activation. Our data displayed that the activity of chitinase1 was both improved in D-galactose/AlCl₃-injected rats and Aβ-pretreated microglia. Moreover, there was an improvement in cognitive function in chitinase1-treated AD rats. Furthermore, anti-inflammation factors (Arginase 1, Arg-1, mannose receptor type C 1, MRC1/CD206) were increased and pro-inflammation factors (tumor necrosis factor alpha, TNFα, interleukin 1 beta, IL-1β) were decreased in D-galactose/AlCl₃-induced AD rats with chitinase1 treatment. A higher level of M2 markers (Arg-1, MRC1/CD206) and a lower level of classic M1 markers (TNFa, IL-1β) were obtained in Aβ-pretreated N9 cells with chitinase1, suggesting that chitinase1 polarized the microglia into an anti-AD M2 phenotype. We also detected that chitnase1 could weaken the deposition of Aβ oligomers in the brain of D-galactose/ AlCl_3-induced AD rats. In conclusion, Chitinase1 might exert protective effects against AD by polarizing microglia to an M2 phenotype and resisting Aβ oligomer deposition.

Fungal Enolase, β-Tubulin, and Chitin Are Detected in Brain Tissue from Alzheimer's Disease Patients

Recent findings provide evidence that fungal structures can be detected in brain tissue from Alzheimer’s disease (AD) patients using rabbit polyclonal antibodies raised against whole fungal cells. In the present work, we have developed and tested specific antibodies that recognize the fungal proteins, enolase and β-tubulin, and an antibody that recognizes the fungal polysaccharide chitin. Consistent with our previous studies, a number of rounded yeast-like and hyphal structures were detected using these antibodies in brain sections from AD patients. Some of these structures were intracellular and, strikingly, some were found to be located inside nuclei from neurons, whereas other fungal structures were detected extracellularly. Corporya amylacea from AD patients also contained enolase and β-tubulin as revealed by these selective antibodies, but were devoid of fungal chitin. Importantly, brain sections from control subjects were usually negative for staining with the three antibodies. However, a few fungal structures can be observed in some control individuals. Collectively, these findings indicate the presence of two fungal proteins, enolase and β-tubulin, and the polysaccharide chitin, in CNS tissue from AD patients. These findings are consistent with our hypothesis that AD is caused by disseminated fungal infection.

Different Brain Regions are Infected with Fungi in Alzheimer's Disease

The possibility that Alzheimer's disease (AD) has a microbial aetiology has been proposed by several researchers. Here, we provide evidence that tissue from the central nervous system (CNS) of AD patients contain fungal cells and hyphae. Fungal material can be detected both intra- and extracellularly using specific antibodies against several fungi. Different brain regions including external frontal cortex, cerebellar hemisphere, entorhinal cortex/hippocampus and choroid plexus contain fungal material, which is absent in brain tissue from control individuals. Analysis of brain sections from ten additional AD patients reveals that all are infected with fungi. Fungal infection is also observed in blood vessels, which may explain the vascular pathology frequently detected in AD patients. Sequencing of fungal DNA extracted from frozen CNS samples identifies several fungal species. Collectively, our findings provide compelling evidence for the existence of fungal infection in the CNS from AD patients, but not in control individuals.

Can oral infection be a risk factor for Alzheimer's disease?

Alzheimer's disease (AD) is a scourge of longevity that will drain enormous resources from public health budgets in the future. Currently, there is no diagnostic biomarker and/or treatment for this most common form of dementia in humans. AD can be of early familial-onset or sporadic with a late-onset. Apart from the two main hallmarks, amyloid-beta and neurofibrillary tangles, inflammation is a characteristic feature of AD neuropathology. Inflammation may be caused by a local central nervous system insult and/or by peripheral infections. Numerous microorganisms are suspected in AD brains ranging from bacteria (mainly oral and non-oral Treponema species), viruses (herpes simplex type I), and yeasts (Candida species). A causal relationship between periodontal pathogens and non-oral Treponema species of bacteria has been proposed via the amyloid-beta and inflammatory links. Periodontitis constitutes a peripheral oral infection that can provide the brain with intact bacteria and virulence factors and inflammatory mediators due to daily, transient bacteremias. If and when genetic risk factors meet environmental risk factors in the brain, disease is expressed, in which neurocognition may be impacted, leading to the development of dementia. To achieve the goal of finding a diagnostic biomarker and possible prophylactic treatment for AD, there is an initial need to solve the etiological puzzle contributing to its pathogenesis. This review therefore addresses oral infection as the plausible etiology of late-onset AD (LOAD).

Neurotoxicity and synaptic plasticity impairment of N-acetylglucosamine polymers: implications for Alzheimer's disease

We assessed whether polymers of N-acetylglucosamine (GlcNAc) have any pathogenetic role in Alzheimer's disease (AD). First, by using specific dyes, we found deposits of polymers of GlcNAc in sporadic but not in familial AD. We found that neurons and microglia exposed to GlcNAc and uridine diphosphate (UDP)-GlcNAc are able to form GlcNAc polymers, which display a significant neurotoxicity in vitro. Moreover, the exposure of organotypic hippocampal cultures to the same compounds led to synaptic impairment with decreased levels of syntaxin and synaptophysin. In addition, acute hippocampal slices treated with GlcNAc/UDP-GlcNAc showed a clear reduction of long-term potentiation of excitatory synapses. Finally, we demonstrated that microglial cells are able to phagocytose chitin particles and, when exposed to GlcNAc/UDP-GlcNAc, show cellular activation and intracellular deposition of GlcNAc polymers that are eventually released in the extracellular space. Taken together, our results indicate that both microglia and neurons produce GlcNAc polymers, which trigger neurotoxicity both directly and through microglia activation. GlcNAc polymer-driven neurotoxicity offers novel pathogenic insights in sporadic AD and new therapeutic options.

Chitotriosidase - a putative biomarker for sporadic amyotrophic lateral sclerosis

Background

Potential biomarkers to aid diagnosis and therapy need to be identified for Amyotrophic Lateral Sclerosis, a progressive motor neuronal degenerative disorder. The present study was designed to identify the factor(s) which are differentially expressed in the cerebrospinal fluid (CSF) of patients with sporadic amyotrophic lateral sclerosis (SALS; ALS-CSF), and could be associated with the pathogenesis of this disease.

Results

Quantitative mass spectrometry of ALS-CSF and control-CSF (from orthopaedic surgical patients undergoing spinal anaesthesia) samples showed upregulation of 31 proteins in the ALS-CSF, amongst which a ten-fold increase in the levels of chitotriosidase-1 (CHIT-1) was seen compared to the controls. A seventeen-fold increase in the CHIT-1 levels was detected by ELISA, while a ten-fold elevated enzyme activity was also observed. Both these results confirmed the finding of LC-MS/MS. CHIT-1 was found to be expressed by the Iba-1 immunopositive microglia.

Conclusion

Elevated CHIT-1 levels in the ALS-CSF suggest a definitive role for the enzyme in the disease pathogenesis. Its synthesis and release from microglia into the CSF may be an aligned event of neurodegeneration. Thus, high levels of CHIT-1 signify enhanced microglial activity which may exacerbate the process of neurodegeneration. In view of the multifold increase observed in ALS-CSF, it can serve as a potential CSF biomarker for the diagnosis of SALS.

Polarization optical-histochemical characterization and supramolecular structure of carbohydrate fibrils

Topo-optical staining reactions were used to investigate the structures of bacterial cellulose, insect chitosan and alginic acid from brown algae. Polysaccharide complexes, glycosaminoglycans and sulfate groups were presented and demonstrated selectively. Chitosan and alginic acid are structurally similar to glycosaminoglycans (GAGs), which are constituents of human amyloid fibrils. The staining sequences shown can be used as reliable methods for histochemistry with light and polarization microscopy. They will help to clarify the complex protein-polysaccharide structure of amyloid fibrils.

Chitin or chitin-like glycans as targets for late-term cancer chemoprevention

A consistent observation in studies of carcinogenesis is that some glycans are expressed differently in cancer cells than in normal cells. A well-known example is the aberrant β1-6 N-acetyl-d-glucosamine branching associated with metastasis and poor prognosis in many cancers. This commentary proposes that, although not found in normal mammalian cells, a chitin (β-1,4-linked N-acetyl-d-glucosamine) or a chitin-like polysaccharide (e.g., hyaluronan) may exist as a cancer-associated glycan, which can be targeted by the novel pyrimidine nucleotide derivative SP-1015 (designed as a chitin synthase inhibitor). Preliminary chemoprevention data of our group showed SP-1015 in the diet can inhibit benzo(a)pyrene-induced neoplasia in the forestomach of female A/J mice, and, of importance, this activity occurred at late stages in carcinogenesis. While no effect was seen in the murine lung, this may be due to the low bioavailability of the compound. A different route of administration (e.g. inhalation of an aerosol) may have potential to inhibit pulmonary carcinogenesis. We hypothesize that inhibitors of chitin or chitin-like glycan formation may be effective chemopreventive agents and suggest that further work is needed to study these novel targets for cancer prevention.

Different content of chitin-like polysaccharides in multiple sclerosis and Alzheimer's disease brains

Chitin is an insoluble N-acetyl-glucosamine polymer coating fungi cell wall and several human parasites. It is hydrolysed by chitotriosidase (Chit); however, as chitin is absent in humans, the significance of human Chit activity is unknown. The level of plasma Chit activity positively correlates with Alzheimer's disease (AD) and multiple sclerosis (MS). A recent study revealed the presence of potentially detrimental chitin-like substances in AD brain by Calcofluor histochemistry, whilst its search in MS brains has never been described to date. Through a comparative immunohistochemical analysis we confirm the presence of abundant chitin-like deposition in AD brains but fail to demonstrate it in MS brains. Interestingly, co-localization of beta-amyloid, Calcofluor and the nuclear marker DAPI was observed. Therefore, Chit production in MS patients is induced by mechanisms other than those operating in AD. Microglia-derived Chit activity in MS may counterbalance the naturally occurring glucosamine aggregation, protecting the brain from the chitin-like substance deposition.