PLAIDD,a type II death domain protein that interacts with p75 neurotrophin receptor

We describe the cloning and characterization of a rat single transmembrane protein that is homologous to the common neurotrophin receptor p75^NTR in its death domain and the transmembrane region but dissimilar outside these regions. We have dubbed this protein PLAIDD, for p75-like apoptosis-inducing death domain protein. PLAIDD messenger RNA, which is ubiquitously distributed, is highly expressed in the embryo, but downregulated in adult tissues. Alternative splicing within the extracellular region of PLAIDD generates four RNA species, but only two of them are translated, PLAIDD_L and PLAIDD_S (long and short isoforms, respectively). While the amino acid sequence of the intracellular region of PLAIDD displays 41% identity with the intracellular region of p75^NTR, the extracellular region of PLAIDD does not reveal any homology with p75^NTR. Overexpression of each isoform of PLAIDD led to cytotoxicity in superior cervical ganglion neurons and in human embryonic kidney 293T cells. Both isoforms of PLAIDD could be co-immunoprecipitated with p75^NTR, suggesting an interaction between these molecules.     

Ethanol exposure enhances cell death in the developing cerebral cortex: role of brain-derived neurotrophic factor and its signaling pathways

Exposure to ethanol during fetal development induces brain damage, causing cell loss in several brain areas and affecting synaptic connections. Because neurotrophin signaling plays an important role in neuronal survival and differentiation, we have investigated the effect of ethanol exposure on cell death in the developing cerebral cortex and whether this effect correlates with alterations in brain-derived neurotrophic factor (BDNF) levels, expression of its receptors, TrkB, and its signaling. We report that chronic ethanol intake during gestation and lactation enhances natural cell death and induces cell necrosis, decreases BDNF levels, and increases the ratio of the truncated to full-length TrkB mRNA receptors during postnatal developing cerebral cortex. Furthermore, we provide evidence that during brain development BDNF activates the extracellular signal-regulated kinases (ERK1 and ERK2) and the phosphoinoside-3-kinase (PI-3-K/Akt) pathways. However, BDNF-induced cell signaling throughout the above-mentioned survival pathways is significantly reduced by ethanol exposure. These findings suggest that ethanol-induced alterations in BDNF availability and in its receptor function might impair intracellular signaling pathways involved in cell survival, growth, and differentiation, leading to enhanced natural cell death during cerebral cortex development.     

Apoptotic death following Fas activation in human oligodendrocyte hybrid cultures

The purpose of this study was to determine how oligodendrocytes die following Fas receptor activation. An immortalized human oligodendrocyte hybrid line (MO3.13) was challenged with Fas ligand (FasL), and cell death was assessed by flow cytometry and DNA gel electrophoresis. Caspase activation was determined by either Western immunoblotting on cell extracts or by whole-cell flow cytometry. FasL challenge clearly induced substantial apoptotic cell death in the oligodendrocyte hybrid cell line, as judged by flow cytometry and by the presence of prominent low molecular weight DNA banding patterns after gel electrophoresis. Western immunoblots showed marked increases in cleaved caspase-1, 8, and 3, indicating that the extrinsic Fas death receptor-induced pathway was activated. The intrinsic mitochondrial pathway was also activated, but only at a minimal level. These findings demonstrate that there are several independent molecular sites within the extrinsic caspase cascade in oligodendrocytes where inhibitory compounds may be capable of blocking cell death in vivo.     

Mechanisms of apoptosis induced by purine nucleosides in astrocytes

Astrocytes release adenine-based and guanine-based purines under physiological and, particularly, pathological conditions. Thus, the aim of this study was to determine if adenosine induced apoptosis in cultured rat astrocytes. Further, if guanosine, which increases the extracellular concentration of adenosine, also induced apoptosis determined using the TUNEL and Annexin V assays. Adenosine induced apoptosis in a concentration-dependent manner up to 100 microM. Inosine, hypoxanthine, guanine, and guanosine did not. Guanosine or adenosine (100 microM) added to the culture medium was metabolized, with 35% or 15%, respectively, remaining after 2-3 h. Guanosine evoked the extracellular accumulation of adenosine, and particularly of adenine-based nucleotides. Cotreatment with EHNA and guanosine increased the extracellular accumulation of adenosine and induced apoptosis. Inhibition of the nucleoside transporters using NBTI (100 microM) or propentophylline (100 microM) significantly decreased but did not abolish the apoptosis induced by guanosine + EHNA or adenosine + EHNA, respectively. Apoptosis produced by either guanosine + EHNA or adenosine + EHNA was unaffected by A(1) or A(2) adenosine receptor antagonists, but was significantly reduced by MRS 1523, a selective A(3) adenosine receptor antagonist. Adenosine + EHNA, not guanosine + EHNA, significantly increased the intracellular concentration of S-adenosyl-L-homocysteine (SAH) and greatly reduced the ratio of S-adenosyl-L-methioine to SAH, which is associated with apoptosis. These data demonstrate that adenosine mediates apoptosis of astrocytes both, via activation of A(3) adenosine receptors and by modulating SAH hydrolase activity. Guanosine induces apoptosis by accumulating extracellular adenosine, which then acts solely via A(3) adenosine receptors.     

Retinofugal projections following early lesions of the visual cortex in the ferret

Extensive lesions of the occipital cortex comprising the developing occipital visual areas and beyond in young ferrets (postnatal day 5) are followed by massive, but incomplete, degeneration of the lateral geniculate (LGN) and lateralis posterior (LP) nuclei of the thalamus, and minor volumetric reduction of the superior colliculus. Retinal projections (revealed by intraocular tracer injections), while reduced, remain confined to their territories of normal termination, both in the adult and throughout development. Comparisons with other mammalian species point to several common features in the developmental plasticity of retinofugal pathway.     

Estimation of the incidence of pleural mesothelioma according to death certificates in France

BACKGROUND: The number of cases of pleural mesothelioma in France has varied substantially according to methods of assessment. MATERIALS AND METHODS: We collected information from certifying physicians about 316 subjects who died between 1 July 1992 and 30 June 1993 in three regions of France with a cause of death coded as ICD-9 category 163. The ICD codes selected as the cause of death for 178 deaths between 1 January 1987 and 31 December 1992 histologically confirmed and diagnosed as pleural mesothelioma by an expert committee were examined. Finally, we used this information to estimate the number of deaths from pleural mesothelioma in France in 1992. RESULTS: In Part I, 45% (men: 54%; women: 28%) of the cases coded as ICD-9 section 163 were definitely or probably mesothelioma; 18% (men: 16%; women: 21%) possibly mesothelioma; and 37% (men: 30%; women: 51%) other tumors, primarily adenocarcinoma metastases. In Part II, 74% of the confirmed pleural mesotheliomas were coded in category 163 (men: 75%; women: 70%). Extrapolation nationwide indicated that 902 deaths were coded as ICD-9 163 in 1992: 521 cases involved definite or probable mesothelioma and 724 definite, probable, and possible cases. CONCLUSIONS: The analysis of this sample suggests that estimating the number of mesothelioma cases from the cause-of-death statistics may overestimate their incidence, but that death certificates appeared to report the diagnosis of histologically confirmed mesothelioma accurately.     

Mechanisms of bFGF and NT-4 potentiation of necrotic neuronal death

The effects of neurotrophic factors on necrotic neuronal death are controversial. In this study we found that both neurotrophin-4 (NT-4) and basic fibroblast growth factor (bFGF) potentiated necrotic neuronal death caused by exposure to oxygen-glucose deprivation or iron-citrate (Fe) in cortical cultures. However, there were significant differences in the actions of the two neurotrophic factors. Neurotrophin-4 protected against apoptotic neuronal death, while bFGF had no effect on apoptotic death in these cultures. Furthermore, potentiation of oxygen-glucose deprivation induced necrotic death by NT-4 required pretreatment (24 h), while pretreatment with bFGF had no effect. However, acute treatment with bFGF during oxygen-glucose deprivation did potentiate neuronal death. Both neurotrophic factors potentiated free radical mediated necrotic neuronal death induced by exposure to Fe. However, the RNA synthesis inhibitor, actinomycin-D, blocked the injury potentiation by NT-4, but not that caused by bFGF. Also, NT-4, but not bFGF, potentiated Fe induced necrotic death in pure neuronal cultures. Expression of mRNA for FGF receptors FGFR1 and FGFR2 was observed at high levels in astrocytes. The results indicate that the injury enhancing effects of bFGF are acute, while those of NT-4 require prolonged exposure and new protein synthesis. Furthermore, the effects of bFGF appear to be mediated through actions on astrocytes, while NT-4 appears to act directly on neurons. The fact that neurotrophic factors from two distinct families can potentiate neuronal death by two different mechanisms suggests that such injury potentiation may be a common concern regarding the use of neurotrophic factors.