Serum amyloid P and related molecules associated with the acute-phase response in Alzheimer's disease

Inflammation as a potential mediator for the association between periodontal disease and Alzheimer's disease

Periodontal disease (PDD) is associated with increased risk of cardiovascular disease, cerebrovascular disease, and mortality in many studies, while other studies have begun to suggest an association of PDD with Alzheimer's disease (AD). This paper discusses how infectious pathogens and systemic infection may play a role in AD. The roles of infection and inflammation are addressed specifically with regard to known AD pathologic lesions including senile plaques, neuron death, neurofibrillary tangles, and cerebrovascular changes. A testable model of proposed pathways between periodontal infection and AD is presented including three possible mechanisms: a) direct effects of infectious pathogens, b) inflammatory response to pathogens, and c) the effects on vascular integrity. The role of gene polymorphisms is discussed, including apolipoprotein (APOE) varepsilon4 as a pro-inflammatory and pro-infection genotype.

Glycosaminoglycans inhibit neurodegenerative effects of serum amyloid P component in vitro

Serum amyloid P component, a member of pentraxin serum protein family, has been suggested to contribute to the progression of neurodegeneration including Alzheimer's disease by binding to beta-amyloid fibrils leading to an increased stability of the deposits against proteolytic degradation and by inducing neuronal apoptosis. Here, we show that glycosaminoglycans inhibit both the serum amyloid P component-beta-amyloid interaction and the neurotoxic effect of serum amyloid P component. These effects correlate with the structure of glycosaminoglycans and show different structure-activity relationship in the case of the two different effects. While the efficacy of the inhibition on the serum amyloid P component-induced cell death increases with the uronic acid content, the inhibitory activity on the serum amyloid P component-beta-amyloid interaction decreases with the increasing uronic acid content of the glycosaminoglycans. The inhibitory effect of glycosaminoglycans on the interaction between the first component of the complement cascade (C1q) and beta-amyloid shows a similar structure-activity relationship as on the serum amyloid P component-beta-amyloid interaction. This suggests that glycosaminoglycans interfere with the binding site on beta-amyloid for serum amyloid P component and C1q. The functional consequence of this binding has been demonstrated by heparin which promotes the proteolysis of beta-amyloid in vitro in the presence of serum amyloid P component. Our results suggest that glycosaminoglycans might have therapeutical potential on the neurodegeneration reducing its progress.

Serum amyloid P component induces neuronal apoptosis and beta-amyloid immunoreactivity

Previously we have reported serum amyloid P component (SAP) induced cell death in cerebro-cortical cultures of rat brain. In this paper we studied the types of target cells and the molecular mechanism of SAP-induced cell death. Immuno-electron and light microscopy revealed that SAP penetrates the plasma membrane and translocates selectively into the nuclei of neurons. Neuronal cells with SAP immunoreactivity exhibit the morphological hallmarks of apoptosis in vitro. The apoptotic mechanism of cell death is also supported by the increased Bax/Bcl-2 ratio. In addition to neurotoxic effects, we detected elevated beta-amyloid (Abeta) immunoreactivity following SAP treatment. This study supports the thesis that SAP plays an important role in the pathomechanism of neurodegenerative diseases, including Alzheimer's disease by inducing neuronal apoptosis.

The in vitro neuronal toxicity of pentraxins associated with Alzheimer's disease brain lesions

Serum amyloid P component (AP) and C-reactive protein (CRP) are normal serum components which belong to the pentraxin family of proteins. These proteins have been previously localized by immunohistochemical method to the brain lesions of Alzheimer's disease (AD). AP is a constant constituent of amyloid deposits including those found in AD. Both AP and CRP have been localized to AD neurofibrillary tangles. An indirect role for these proteins has been previously suggested in the etiology of AD. We studied the effects of serum AP and CRP on a human-derived neuronal cell line (hNT). In treated cell cultures, AP and CRP were detected immunohistochemically within hNT neurons, indicating cellular uptake of these proteins. Serum AP at the lowest serum physiological concentration (8 microgram/ml) showed a marked toxicity to hNT neurons. CRP also displayed toxicity to the hNT neurons but at a level compatible with inflammatory states (50 microgram/ml). These results suggest a more direct role for serum AP and CRP in the pathogenesis of AD.

Amyloid myopathy: an underdiagnosed entity

Amyloidosis can involve multiple organs, including kidney, heart, peripheral nerve, skin, joints, and skeletal muscle, but rarely presents as a myopathy. We studied 13 adults with muscle weakness for between 3 months and 4 years in whom the diagnosis of systemic amyloidosis was unsuspected before or until just before the time of the muscle biopsy. All muscle specimens demonstrated congophilic deposits around blood vessels and muscle fibers, some necrotic and regenerating fibers, and signs of mild denervation. Immunostains in 10 patients revealed immunoglobulin amyloidosis in 7 and gelsolin amyloidosis in 1. Apolipoprotein E co-localized with the congophilic deposits in all 10, and a C-terminal epitope of the beta-amyloid precursor protein was detected in 6. The frequency of the diagnosis of amyloid myopathy increased 10-fold when we adopted the fluorescent Congo red stain as a routine procedure in assessing muscle biopsy specimens.

Effects of hormone replacement therapy on serum amyloid P component in postmenopausal women

The pentraxin serum amyloid P component (SAP) is a 9.5Sz1-glycoprotein and it has recently been found to be deposited in atherosclerotic lesions or neurofibrillary tangles, which are related to the aging process and Alzheimer's disease. The level of SAP was measured by micro single radial-immunodiffusion. Sample sera were obtained from 420 healthy humans, from newborn to 86 years old. The changes in SAP during the menstrual cycle were investigated in 6 women that were 20-21 years. Fifty of the postmenopausal women, suffering from climacteric symptoms, were administered either conjugated estrogen (E), or dehydroepiandrosterone (DHEA). The SAP levels increased with age, being 1.12 +/- 0.82 mg/dl (means +/- S.D.) in neonates, and 6.15 +/- 0.92 mg/dl in persons over 80 years. The SAP level in the females between 15 and 49 years (3.32 +/- 0.95 mg/dl) was significantly (P < 0.001) lower than that in the males in the same age group (5.19 +/- 1.25 mg/dl). The SAP level in the follicular phase was significantly (P < 0.01) lower than that in menstrual phase (menstrual: 4.36 +/- 0.90 mg/dl versus follicular: 2.61 +/- 0.99 mg/dl). In the post-menopausal women that were administered E (1.25 mg/day), the SAP decreased significantly (P < 0.001) from the prelevel of 5.64 +/- 1.40 mg/dl to 4.26 +/- 0.98 mg/dl on the 14th day. In the postmenopausal women that were administered DHEA (60 mg/day), the SAP increased rapidly from the prelevel of 4.97 +/- 0.76 mg/dl to 6.17 +/- 1.20 mg/dl on the 21st day. SAP seems to be a marker that can monitor the effect of hormone replacement therapy.

C-reactive protein-like immunoreactivity in the neurofibrillary tangles of Alzheimer's disease

C-reactive protein (CRP) is a plasma acute-phase protein, normally not found in the brain. Previous studies have demonstrated the presence of CRP in the senile plaques of Alzheimer's disease (AD). In this study, the presence of CRP-like immunoreactivity in AD neurofibrillary tangles (NFT) was demonstrated following pre-treatment of tissue sections with formic acid. CRP-like immunoreactivity was observed in both extracellular and intracellular NFT and was co-localized with the NFT marker PHF-1 and the amyloid P component (AP). The CRP-like immunoreactive NFT were less numerous and more limited in their distribution than PHF-1 or AP-immunoreactive NFT. The present results further support an involvement of inflammatory processes in the etiology of AD.

Increased regional brain concentrations of ceruloplasmin in neurodegenerative disorders

Ceruloplasmin (CP), the major plasma anti-oxidant and copper transport protein, is synthesized in several tissues, including the brain. We compared regional brain concentrations of CP and copper between subjects with Alzheimer's disease (AD, n = 12), Parkinson's disease (PD, n = 14), Huntington's disease (HD, n = 11), progressive supranuclear palsy (PSP, n = 11), young adult normal controls (YC, n = 6) and elderly normal controls (EC, n = 7). Mean CP concentrations were significantly increased vs. EC (P < 0.05) in AD hippocampus, entorhinal cortex, frontal cortex, and putamen. PD hippocampus, frontal, temporal, and parietal cortices, and HD hippocampus, parietal cortex, and substantia nigra. Immunocytochemical staining for CP in AD hippocampus revealed marked staining within neurons, astrocytes, and neuritic plaques. Increased CP concentrations in brain in these disorders may indicate a localized acute phase-type response and/or a compensatory increase to oxidative stress.

Molecular aspects of inflammatory and immune responses in Alzheimer's disease

Recent advances indicate numerous molecular and cellular elements of the immune system are involved in the pathogenesis of Alzheimer's disease. Amyloid beta protein deposition induces many molecules associated with a predominantly local inflammatory response within the brain parenchyma. These responses also provoke the release of immune system mediators including cytokines, which all seem largely to be produced by reactive cells such as astrocytes and microglia. Classical acute phase proteins of the pentraxin and serine protease inhibitor (serpin) families as well as a host of complement proteins and some coagulation factor seem the most intrinsically involved. These secreted molecules display variable binding with the amyloidotic lesions. Although our understanding of the molecular specificity and significance of the interaction of these proteins within the lesions is not replete, the development of unique inhibitors of the inflammatory reactions could provide therapeutic strategies to impede the pathogenetic process. Currently, this appears a more viable option than to inhibit amyloid beta production or modify amyloid beta precursor protein processing, an approach which seems more complex.

Genetic and aging epidemiology. The merging of two disciplines

For future research in aging epidemiology to be meaningful, it will have to integrate knowledge and skills from multiple areas, including the application of genetic and molecular epidemiologic techniques to the study of the elderly. This article begins with an overview of genetic and molecular epidemiology, followed by a discussion of several unique methodologic issues that need to be considered in the interpretation of genetic and molecular findings of epidemiologic studies of the elderly.

Demonstration of CRP immunoreactivity in brains of Alzheimer's disease: immunohistochemical study using formic acid pretreatment of tissue sections

C-reactive protein (CRP) is a well-known serum protein which increases during inflammation and deposits in damaged tissues. To establish whether CRP appears in brain of Alzheimer's disease (AD), we immunohistochemically investigated tissue sections which were pretreated with formic acid. Positive immunostaining by anti-CRP antibodies was clearly recognized in senile plaques (SP) in the pretreated tissue sections, with very weak immunostaining in non-treated sections. These findings may suggest that the formation process of SP includes an acute-phase inflammatory state.

Binding of human serum amyloid P component (hSAP) to human neutrophils

Human serum amyloid P component (hSAP) and human C-reactive protein (hCRP) are normal serum constituents related to the pentraxin family of plasma proteins. hSAP has morphological and immunochemical identity and extensive sequence similarity to the amyloid P (AP) component found in normal tissues and particularly in amyloid deposits. hCRP and its proteolytic products have been previously shown to bind and to interact with various types of human leukocytes. Binding-displacement experiments with 125I-labeled hSAP and hCRP show that both proteins have specific high-affinity binding sites on normal human polymorphonuclear leukocytes (PMN) and each can compete efficiently with the binding of the other. Scatchard analysis of hSAP-displacement curves reveals a heterogeneous population of hSAP-binding sites existing on the PMN cells, among them about 300,000 low-affinity binding sites with Kd < or = 5 x 10(-6) M and about 30,000 high-affinity binding sites with Kd < or = 5 x 10(-8) M. hAP was found to be degraded by enzymes from human neutrophils to yield a mixture of low-molecular-mass peptides, similarly to the case of CRP reported previously. The binding of hSAP can be efficiently inhibited by this peptide mixture. The results suggest that both hCRP and hSAP, together with related peptides, may participate in vivo in an unknown mechanism of regulation of human neutrophils.

Amyloid P component and other acute-phase proteins associated with cerebellar A beta-deposits in Alzheimer's disease

It is established that amyloid P (AP) component and complement proteins are associated with amyloid beta (A beta)-protein deposits in the cerebral cortex of Alzheimer's disease (AD) subjects. Here, we used immunocytochemical methods to examine the association of these acute-phase proteins with the characteristic diffuse plaques of cerebellum in AD. We observed AP and complement C3d, C1q, C5 and C4bp immunoreactivities in most A beta-protein-reactive plaques of the cerebellum. Further, a1-antichymotrypsin immunoreactivity was apparent in at least 60% of all the cerebellar diffuse plaques examined. Cerebellar tissue bearing the A beta-protein deposits also often exhibited marked angiopathy in the pial vessels. We suggest that diffuse plaques of the cerebellum also acquire components of the chronic inflammatory response evident in neocortical plaques.

The immunopathology of Alzheimer's disease and some related disorders

Current evidence clearly indicates that elements of the immune system are involved in the pathogenesis of the principal lesions characterizing Alzheimer's disease (AD). Findings are in accord with features associated with both the innate and adaptive immune mechanisms involved in a predominantly local inflammatory response within the parenchyma. Many of the features are unique to AD, presumably related to the unusual properties of beta amyloid protein. Remarkably, the brain holds the capacity to produce almost all the immune system mediators which largely seem to be generated by glia comprising both astrocytes and microglia. While a variety of humoral mediators including classical acute phase proteins (and serpins) are increased and released, the complement seems most intrinsically involved. The cellular response is elaborated by microglia which seem the main immunocompetent cells partaking in the response. These appear to function as pluripotent macrophages expressing both classes of MHC antigens. Further characterization of this interesting response to cerebral amyloidosis will be challenging.