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The distal serpin subcluster contains genes encoding α1-antichymotrypsin (ACT), protein C inhibitor (PCI), kallistatin (KAL), and the KAL-like protein that are expressed in hepatocytes but only the act gene is expressed in astrocytes. We show here that the tissue-specific expression of these genes associates with astrocyte- and hepatocyte-specific chromatin structures. In hepatocytes, we identified twelve DNase I-hypersenitive sites (DHS) that were distributed throughout the entire subcluster, with the promoters of expressed genes accessible to restriction enzyme digestion. In astrocytes, only six DHSs were located exclusively in the 5′ flanking region of the act gene, with its promoter also accessible to restriction enzyme digestion. The acetylation of histone H3 and H4 has been found throughout the subcluster in both cell types but this acetylation did not correlate with the expression pattern of these serpin genes. Analysis of histone modifications at the promoters of the act and pci genes revealed that methylation of histone H3 on lysine 4 correlates with their expression pattern in both cells types. In addition, inhibition of methyltransferase activity resulted in suppression of ACT and PCI mRNA expression. We propose that lysine 4 methylation of histone H3 correlates with the tissue-specific expression pattern of these serpin genes.

H2O2 and free radical-mediated oxidative stresses have been implicated in mediating amyloid beta (1-40) [A beta (1-40)] neurotoxicity to cultured neurons. In this study, we confirm that addition of the H2O2-scavenging enzyme catalase protects neurons in culture against A beta-mediated toxicity; however, it does so by a mechanism that does not involve its ability to scavenge H2O2. A beta-mediated elevation in intracellular H2O2 production is suppressed by addition of a potent H2O2 scavenger without any significant neuroprotection. Three intracellular biochemical markers of H2O2-mediated oxidative stress were unchanged by A beta treatment: (a) glyceraldehyde-3-phosphate dehydrogenase activity, (b) hexose monophosphate shunt activity, and (c) glucose oxidation via the tricarboxylic acid cycle. lonspray mass spectra of A beta in the incubation medium indicated that A beta itself is an unlikely source of reactive oxygen species. In this study we demonstrate that intracellular ATP concentration is compromised during the first 24-h exposure of neurons to A beta. Our results challenge a pivotal role for H2O2 generation in mediating A beta toxicity, and we suggest that impairment of energy homeostasis may be a more significant early factor in the neurodegenerative process.

The beta-amyloid precursor protein (beta APP) is the source of the amyloid beta-peptide that accumulates in the brain in Alzheimer's disease. A major processing pathway for beta APP involves an enzymatic cleavage within the amyloid beta-peptide sequence that liberates secreted forms of beta APP (APPss) into the extracellular milieu. We now report that postischemic administration of these APPss intracerebroventricularly protects neurons in the CA1 region of rat hippocampus against ischemic injury. Treatment with APPs695 or APPs751 resulted in increased neuronal survival, and the surviving cells were functional as demonstrated by their ability to synthesize protein. These data provide direct evidence for a neuroprotective action of APPss in vivo.

Amylin forms large beta-pleated neurotoxic oligomers but shows only 38% sequence similarity to A beta. As patterns of gene expression during neuronal apoptosis appear stimulus and cell type specific, we compared the pattern of amylin-induced gene expression in rat cortical neurons with that shown previously to be induced by A beta in order to evaluate whether these two peptides with different primary but similar secondary structure induce apoptosis similarly. Morphologic and quantitative measures of cell death show widespread apoptotic death after amylin treatment. Amylin treatment results in time- and concentration-dependent inductions of oxidative stress genes, such as cox-2 and IkappaB-alpha. "Apoptotic" genes are also induced in a time- and concentration-dependent manner, including c-jun, junB, c-fos, and fosB, followed temporally by a gene known to be modulated by these transcription factors, i.e., transin. In situ hybridization analyses show that c-fos expression is restricted largely to neurons with condensed chromatin, a hallmark of apoptosis. As these genes are not induced in all models of apoptosis, that amylin-induced neuronal death is genetically similar to that of A beta suggests that these peptides may be neurotoxic through a common mechanism.

Glial cells that produce and respond to various cytokines mediate inflammatory processes in the brain. Here, we show that oncostatin M (OSM) and interleukin-1 (IL-1) regulate the expression of plasminogen activator inhibitor-1 (PAI-1) and urokinase-type plasminogen activator (uPA) in human astrocytes. Using the PAI-1 reporter constructs we show that the -58 to -51 proximal element mediates activation by both cytokines. This element is already bound by c-fos/c-jun heterodimers in unstimulated astrocytes, and treatment with cytokine strongly stimulates both expression of c-fos and binding of c-fos/c-jun heterodimers. In addition, IL-1 activates an inhibitory mechanism that down-regulates PAI-1 expression after longer exposure to this cytokine. Overexpression of dominant-negative signal transducer and activator of transcription-1 (STAT1), STAT3, STAT5 and inhibitor of nuclear factor-kappaB (IkappaB) suppressed OSM/IL-1-induced expression of the PAI-1 reporter construct. We conclude that OSM and IL-1 regulate the PAI-1 gene expression via up-regulating c-fos levels and subsequent binding of c-fos/c-jun heterodimers to the proximal element of the PAI-1 gene.

Tissue plasminogen (plgn) activator (tPA) modulates neuronal death in models of stroke, excitotoxicity, and oxidative stress. Amyloid-beta (Abeta) appears central to Alzheimer's disease and is neurotoxic to neurons in vitro. Here, we evaluate tPA effects on Abeta toxicity. We report that tPA alone had no effect on Abeta toxicity. However, in combination with plgn, tPA reduced Abeta toxicity in a robust fashion. Moreover, the combined tPA and plgn treatment markedly inhibited Abeta accumulation. The addition of phenylmethylsulfonyl fluoride, a serine protease inhibitor, to a sample of tPA, plgn, and Abeta resulted in a marked reduction of Abeta degradation. We interpret the actions of tPA and plgn within the context of the ability of plasmin to degrade Abeta.

Expression of alpha1antichymotrypsin (ACT) is significantly activated by interleukin-1 (IL-1) in human astrocytes; however, it is barely affected by IL-1 in hepatocytes. This tissue-specific regulation depends upon an enhancer that contains both nuclear factor kappaB (NF-kappaB) and activating protein 1 (AP-1) elements, and is also observed for an NF-kappaB reporter but not for an AP-1 reporter. We found efficient activation of NF-kappaB binding in both cell types; however, this binding was persistent in glial cells and only transient in hepatocytes. IL-1-activated NF-kappaB complexes consisted of p65 and p50, with p65 transiently phosphorylated on serine 536 in glial cells whereas more persistently in hepatic cells. Overexpression of p65 or constitutively active IKKbeta (inhibitor of NF-kappaB kinase beta) resulted in an efficient activation of the ACT reporter in hepatic cells, indicating that a specific mechanism exists in these cells terminating IL-1 signaling. IL-1 effectively induced the degradation of inhibitor of NF-kappaBalpha (IkBalpha) and IkBepsilon in both cell types but IkBbeta was not affected. However, IkBalpha was resynthesized much more rapidly in hepatic cells in comparison to glial cells. In addition, the initial levels of IkBalpha were much lower in glial cells. We propose that the tissue-specific regulation of the ACT gene expression by IL-1 is determined by different efficiencies of IkBalpha resynthesis in glial and hepatic cells.

The role of gene expression in neuronal apoptosis may be cell- and apoptotic stimulus-specific. Previously, we and others showed that amyloid beta (Abeta)-induced neuronal apoptosis is accompanied by c-jun induction. Moreover, c-Jun contributes to neuronal death in several apoptosis paradigms involving survival factor withdrawal. To evaluate the role of c-Jun in Abeta toxicity, we compared Abeta-induced apoptosis in neurons from murine fetal littermates that were deficient or wild-type with respect to c-Jun. We report that neurons deficient for c-jun are relatively resistant to Abeta toxicity, suggesting that c-Jun contributes to apoptosis in this model. When changes in gene expression were quantified in neurons treated in parallel, we found that Abeta treatment surprisingly led to an apparent activation of the c-jun promoter in both the c-jun-deficient and wild-type neurons, suggesting that c-Jun is not necessary for activation of the c-jun promoter. Indeed, several genes induced by Abeta in wild-type neurons were also induced in c-jun-deficient neurons, including c-fos, fosB, ngfi-B, and ikappaB. In summary, these results indicate that c-Jun contributes to Abeta-induced neuronal death but that c-Jun is not necessary for c-jun induction.

Proteolytic cleavage of beta-amyloid precursor protein (beta APP) by alpha-secretase results in release of one secreted form (sAPP) of APP (sAPP alpha), whereas cleavage by beta-secretase releases a C-terminally truncated sAPP (sAPP beta) plus amyloid beta-peptide (A beta). beta APP mutations linked to some inherited forms of Alzheimer's disease may alter its processing such that levels of sAPP alpha are reduced and levels of sAPP beta increased. sAPP alpha s may play important roles in neuronal plasticity and survival, whereas A beta can be neurotoxic. sAPP alpha was approximately 100-fold more potent than sAPP beta in protecting hippocampal neurons against excitotoxicity, A beta toxicity, and glucose deprivation. Whole-cell patch clamp and calcium imaging analyses showed that sAPP beta was less effective than sAPP alpha in suppressing synaptic activity, activating K+ channels, and attenuating calcium responses to glutamate. Using various truncated sAPP alpha and sAPP beta APP695 products generated by eukaryotic and prokaryotic expression systems, and synthetic sAPP peptides, the activity of sAPP alpha was localized to amino acids 591-612 at the C-terminus. Heparinases greatly reduced the actions of sAPP alpha s, indicating a role for a heparin-binding domain at the C-terminus of sAPP alpha in receptor activation. These findings indicate that alternative processing of beta APP has profound effects on the bioactivity of the resultant sAPP products and suggest that reduced levels of sAPP alpha could contribute to neuronal degeneration in Alzheimer's disease.