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Liver injury in NASH and ASH is associated with increased hepatocyte apoptosis mediated by death receptors. Further, apoptosis correlates with active NF-kappaB expression, and disease severity. This potential mechanistic link might provide multiple interesting targets for therapeutic intervention.

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The vasculotropic E22Q mutant of the amyloid-β (Aβ) peptide is associated with hereditary cerebral hemorrhage with amyloidosis Dutch type. The cellular mechanism(s) of toxicity and nature of the AβE22Q toxic assemblies are not completely understood. Comparative assessment of structural parameters and cell death mechanisms elicited in primary human cerebral endothelial cells by AβE22Q and wild-type Aβ revealed that only AβE22Q triggered the Bax mitochondrial pathway of apoptosis. AβE22Q neither matched the fast oligomerization kinetics of Aβ42 nor reached its predominant β-sheet structure, achieving a modest degree of oligomerization with a secondary structure that remained a mixture of β and random conformations. The endogenous molecule tauroursodeoxycholic acid (TUDCA) was a strong modulator of AβE22Q-triggered apoptosis but did not significantly change the secondary structures and fibrillogenic propensities of Aβ peptides. These data dissociate the pro-apoptotic properties of Aβ peptides from their distinct mechanisms of aggregation/fibrillization in vitro, providing new perspectives for modulation of amyloid toxicity.

Neurotoxicity associated with increased glutamate release results in cell death through both necrotic and apoptotic processes. In addition, tauroursodeoxycholic acid (TUDCA), an endogenous bile acid, is a strong modulator of apoptosis in several cell types. The aims of this study were to test the hypothesis that TUDCA reduces the apoptotic threshold induced by glutamate in rat cortical neurons and examine potential transduction pathways involved in both apoptotic signaling and neuroprotection by TUDCA. The results demonstrated that exposure of cortical neurons to glutamate induced cytochrome c release and caspase activation, as well as morphologic changes of apoptosis. These events were associated with down-regulation of antiapoptotic members of the Bcl-2 family,

Amyloid b-peptide (Ab)-induced cell death may involve activation of the E2F-1 transcription factor and other cell cyclerelated proteins. In previous studies, we have shown that tauroursodeoxycholic acid (TUDCA), an endogenous bile acid, modulates Ab-induced apoptosis by interfering with crucial events of the mitochondrial pathway. In this study, we examined the role of E2F and p53 activation in the induction of apoptosis by Ab, and investigated novel molecular targets for TUDCA. The results showed that despite Bcl-2 up-regulation, PC12 neuronal cells underwent significant apoptosis after incubation with the active fragment Ab (25-35), as assessed by DNA fragmentation, nuclear morphology and caspase-3-like activation. In addition, transcription through the E2F-1 promoter was significantly induced and associated with loss of the retinoblastoma protein. In contrast, levels of E2F-1, p53 and Bax proteins were markedly increased. Overexpression of E2F-1 in PC12 cells was sufficient to induce p53 and Bax proteins, as well as nuclear fragmentation. Notably, TUDCA modulated Ab-induced apoptosis, E2F-1 induction, p53 stabilization and Bax expression. Further, TUDCA protected PC12 cells against p53-and Bax-dependent apoptosis induced by E2F-1 and p53 overexpression, respectively. In conclusion, the results demonstrate that Ab-induced apoptosis of PC12 cells proceeds through an E2F-1/p53/Bax pathway, which, in turn, can be specifically inhibited by TUDCA, thus underscoring its potential therapeutic use. Keywords: Bcl-2 proteins, bile acids, caspases, neuroprotection, retinoblastoma protein. Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive memory loss and deficit of cognitive skills. The pathological hallmarks of AD include selective damage to synapses and neurons, neurofibrillary tangles, activated glia and presence of senile plaques (Selkoe 2001). Amyloid b-peptide (Ab) is the major constituent of senile or amyloid plaques found in the brains of AD patients. Ab is derived from the processing of the amyloid precursor protein (Haass and Selkoe 1993), and is thought to play a critical role in the onset or progression of AD. Previous studies have shown that Abinduced cytotoxicity involves oxidative stress, inflammation and perturbation of calcium homeostasis (Selkoe 2001). In fact, both necrosis and apoptosis are thought to occur in primary neurons and neuronal cell lines after exposure to Ab, as well as in brains of AD patients (Yankner et al. 1990;Loo et al. 1993;Behl et al. 1994;Su et al. 1994;Mark et al. 1995).Cell cycle-related molecules are up-regulated in postmitotic neurons within affected brain regions during AD (McShea et al. 1997;Vincent et al. 1997;Busser et al. 1998). However, it is unclear whether deregulation of cell cycle events contributes to neurodegeneration in AD. E2F-1 Received February 11, 2004; revised manuscript received March 18, 2004; accepted March 19, 2004. Address correspondence and reprint requests to C. M. P. Rodrigues, Centro de Patogénese Molecul...

The results show that liver injury in NASH and ASH is associated with apoptosis and NF-kappaB activation. Anti-apoptotic Bcl-2 is strongly expressed, probably reflecting an adaptive response to obesity or alcohol-related stress.

Ursodeoxycholic acid (UDCA) inhibits classical mitochondrial pathways of apoptosis by either directly stabilizing mitochondrial membranes or modulating specific upstream targets. Furthermore, UDCA regulates apoptosis-related genes from transforming growth factor ␤1 (TGF-␤1)-induced hepatocyte apoptosis by a nuclear steroid receptor (NSR)-dependent mechanism. In this study, we further investigated the potential role of the glucocorticoid receptor (GR) in the antiapoptotic function of UDCA. Our results with short interference RNA (siRNA) technology confirmed that UDCA significantly reduces TGF-␤1-induced apoptosis of primary rat hepatocytes through a GR-dependent effect. Immunoprecipitation assays and confocal microscopy showed that UDCA enhanced free GR levels with subsequent GR nuclear translocation. Interestingly, when a carboxy-terminus deleted form of GR was used, UDCA no longer increased free GR and/or GR translocation, nor did it protect against TGF-␤1-induced apoptosis. In co-transfection experiments with GR response element reporter and overexpression constructs, UDCA did not enhance the transactivation of GR with TGF-␤1. Finally, using a flourescently labeled UDCA molecule, the bile acid appeared diffuse in the cytosol but was aggregated in the nucleus of hepatocytes. Both siRNA assays and transfection experiments with either wild-type or mutant forms of GR showed that nuclear trafficking occurs through a GR-dependent mechanism. In conclusion, these results further clarify the antiapoptotic mechanism(s) of UDCA and suggest that GR is crucial for the nuclear translocation of this bile acid for reducing apoptosis. (HEPATOLOGY 2005;42:925-934.)