Prostaglandin E2 induced polymerization of human alpha-1-antichymotrypsin and suppressed its protease inhibitory activity: implications for Alzheimer's disease

Prostaglandin E2 rescues cortical neurons from amyloid beta protein-induced apoptosis

Cerebrospinal fluid prostaglandin E(2) (PGE(2)) levels are elevated in patients with Alzheimer's disease (AD), suggesting an involvement of PGE(2) in the neurodegeneration. AD is characterized by deposits of amyloid beta protein (Abeta) in various regions of the brain, e.g. the cerebral cortex. In the present study, we investigated the effects of PGE(2) on neuronal survival in primary cultures of rat cortical neurons. PGE(2) had no effect on neuronal cell viability or its morphology. Therefore, we examined the synergistic effects of PGE(2) with Abeta, a neurotoxin. Abeta caused neuronal cell death via apoptosis. PGE(2) significantly suppressed Abeta neurotoxicity, but did not promote the neurotoxicity. Furthermore, PGE(2) ameliorated Abeta-induced apoptotic features such as the condensation of chromatin and the fragmentation of DNA. Abeta increased the influx of Ca(2+) into neurons before cell death. Nimodipine, an inhibitor of the L-type voltage-sensitive calcium channel (L-VSCC), significantly reduced Abeta-potentiated Ca(2+) uptake. On the other hand, there was no effect on the Abeta-induced Ca(2+) influx by an N-VSCC blocker or P/Q-VSCC blockers. Moreover, the inhibitor of L-VSCC suppressed Abeta-induced neuronal cell death, whereas neither an N-VSCC blocker nor P/Q-VSCC blockers affected the neurotoxicity of Abeta. PGE(2) also suppressed the Abeta-induced Ca(2+) influx in a concentration-dependent manner. This study demonstrated that PGE(2) rescues cortical neurons from Abeta-induced apoptosis by reducing Ca(2+) influx in the primary culture. Furthermore, the present study suggested that the inhibition of L-VSCC contributes to the neuroprotective effect of PGE(2).

Immunological aspects of alzheimer's disease: therapeutic implications

Alzheimer's disease (AD) is a chronic neurodegenerative disease causing progressive impairment of memory and cognitive function. The amyloid cascade hypothesis suggests that mismetabolism of the beta-amyloid (A beta) precursor protein (APP) followed by subsequent formation of non-fibrillar and fibrillar A beta deposits leads to glial activation and eventually to neurotoxicity, causing cognitive impairment. Several lines of evidence indicate that an inflammatory process contributes to the pathology of AD. First, inflammatory proteins have been identified as being associated with neuritic plaques and in glial cells surrounding these plaques. Second, certain polymorphisms of acute-phase proteins and cytokines associated with AD plaques increase the risk or predispose for earlier onset of developing AD. Third, epidemiological studies indicate that anti-inflammatory drugs can retard the development of AD. Several steps in the pathological cascade of AD have been identified as possible targets for actions of nonsteroidal anti-inflammatory drugs. For instance, microglia are considered a target because this cell type is closely involved in AD pathology through secretion of neurotoxic substances and by modulating a positive feedback loop of the inflammatory mechanism that may be involved in the pathological cascade in AD. On the basis of studies in APP transgenic mice, immunisation with A beta was recently suggested as a novel immunological approach for the treatment of AD. Immunisation elicits A beta-specific antibodies that could affect several early steps of the amyloid-driven cascade. Antibodies could prevent A beta from aggregating into fibrils and accelerate clearance of A beta by stimulating its removal by microglial cells. This review outlines the pathological and genetic evidence that an inflammatory mechanism is involved in AD and the therapeutic approaches based on inhibition or mediation of inflammation.

Does the insulin-like growth factor system interact with prostaglandins and proinflammatory cytokines during neurodegeneration?

Prostaglandins and proinflammatory cytokines are implicated in the etiology of neurodegenerative diseases, such as Alzheimer's disease. Signaling cascades initiated by these factors may result in reactive oxygen species generation and cell death. The insulin-like growth factors (IGF) are ubiquitous polypeptides involved in all aspects of growth and development. Additionally, the IGF are regarded as survival factors that display potent antiapoptotic activity. Interfering with IGF production, distribution, or signaling may result in greater susceptibility to apoptotic stimuli. In neurodegenerative conditions, the IGF appear to be antagonized by prostaglandins and proinflammatory cytokines. In this review, the relationship among specific prostaglandins, the proinflammatory factors, tumor necrosis factor, interleukin-1, and interleukin-6, and the IGF system will be investigated.

New anti-inflammatory treatment strategy in Alzheimer's disease

Numerous reports have indicated that patients suffering from inflammatory diseases (e.g., arthritis) who take anti-inflammatory medication have a reduced risk of developing Alzheimer's disease (AD). Thus, the first generation of anti-inflammatory cyclooxygenase (COX) inhibitors, such as aspirin and indomethacin, have been tested as potential therapeutics in AD. Because the inhibition of COX-1 is also known to cause tissue damage in the gastrointestinal system from the resultant reduced cytoprotection, selective COX-2 inhibitors are being investigated and tested clinically as potentially better therapeutics for AD patients. However, such drugs may also trigger unwanted effects; for example, the COX-2 inhibitors, which reduce the production of one type of eicosanoids, the prostaglandins, may increase the production of other eicosanoids; i.e., the leukotriene B4 (LTB4), which is one of the most potent endogenous chemotactic/inflammatory factors. LTB4 production is initiated by the enzyme 5-lipoxygenase (5-LOX). The expression of the 5-LOX gene is upregulated during neurodegeneration and with aging. In spite of the fact that 5-LOX and leukotrienes are major players in the inflammation cascade, their role in AD pathobiology/therapy has not been extensively investigated. We propose that the 5-LOX inflammatory cascade may take part in the process of aging-associated neurodegenerative diseases, and we point to the role of 5-LOX in neurodegeneration and discuss its relevance for anti-inflammatory therapy of AD.

A role for apoE in regulating the levels of alpha-1-antichymotrypsin in the aging mouse brain and in Alzheimer's disease

This study was designed to explore the possible functional relationships between apolipoprotein E (apoE) and the protease inhibitor alpha-1-antichymotrypsin in the aging mouse brain and in Alzheimer's disease. For this purpose, levels of EB22/5 (the mouse homologue to human alpha-1-antichymotrypsin) mRNA expression was studied in apoE-deficient mice. These mice showed an age-dependent increase of EB22/5 mRNA expression in the brain. Furthermore, overexpression of allele 3 of human APOE gene in transgenic mice (in an apoE-deficient background) resulted in normalization of levels of EB22/5 mRNA expression compatible with levels found in control mice. In contrast, overexpression of human APOE4 allele or down-regulation of the apoE receptor low density lipoprotein receptor-related protein by deletion of the receptor-associated protein was associated with elevated levels of EB22/5 similar to apoE-deficient mice. Consistent with the findings in murine models, human alpha-1-antichymotrypsin protein was increased in brain homogenates from patients with Alzheimer's disease, and levels of this serpin were the highest in patients with the APOE4 allele. In summary, the present study showed evidence supporting a role for apoE in regulating alpha-1-antichymotrypsin expression. This is relevant to Alzheimer's disease because these two molecules appear to be closely associated with the pathogenesis of this disorder.