Oncogenic transformation and hypoxia synergistically act to modulate vascular endothelial growth factor expression

Hypoxia can select for cells that have lost their apoptotic potential, thereby making them resistant to adverse conditions. However, long-term survival of transformed cells which have diminished apoptotic sensitivity when exposed to low oxygen conditions would require the activation of their angiogenic program to compensate for an insufficient oxygen supply. In this report, we show that the activity (of oncogenic Ha-ras, either constitutively or transiently, enhances the induction of the angiogenic mitogen, vascular endothelial growth factor (VEGF), by hypoxia. Analysis of the 5' flanking region of the VEGF promoter indicates that a HIF-1-like sequence is to promote a 15-fold increase in reporter gene activity in Ha-ras-transformed cells when exposed to hypoxia, whereas mutations in the same site totally inhibited VEGF induction. Under low oxygen conditions, VEGF induction is inhibited in cells expressing a mutant inhibitory allele of Ha-ras (RasN17), indicating a direct role for Ras in modulating VEGF activity. We propose that the angiogenic switch in Ras-transformed cells may be physiologically promoted by the tumor microenvironment through VEGF induction.

Functional fetal nigral grafts in a patient with Parkinson's disease: chemoanatomic, ultrastructural, and metabolic studies

A patient with Parkinson's disease received bilateral fetal human nigral implants from six donors aged 6.5 to 9 weeks post-conception. Eighteen months following a post-operative clinical course characterized by marked improvement in clinical function, this patient died from events unrelated to the grafting procedure. Post-mortem histological analyses revealed the presence of viable grafts in all 12 implant sites, each containing a heterogeneous population of neurons and glia. Approximately 210,146 implanted tyrosine hydroxylase-immunoreactive (TH-ir) neurons were found. A greater number of TH-ir grafted neurons were observed in the right (128,162) than the left (81,905) putamen. Grafted TH-ir neurons were organized in an organotypic fashion. These cells provided extensive TH-ir and dopamine transporter-ir innervation to the host striatum which occurred in a patch-matrix fashion. Quantitative evaluations revealed that fetal nigral grafts reinnervated 53% and 28% of the post-commissural putamen on the right and left side, respectively. Grafts on the left side innervated a lesser area of the striatum, but optical density measurements were similar on both sides. There was no evidence that the implants induced sprouting of host TH-ir systems. Electron microscopic analyses revealed axo-dendritic and occasional axo-axonic synapses between graft and host. In contrast, axo-somatic synapses were not observed. In situ hybridization for TH mRNA revealed intensely hybridized grafted neurons which far exceeded TH mRNA expression within residual host nigral cells. In addition, gamma-amino butyric acid (GABA)-ergic neurons were observed within the graft that formed a dense local neuropil which was confined to the implant site. Serotonergic neurons were not observed within the graft. Cytochrome oxidase activity was increased bilaterally within the grafted post-commissural putamen, suggesting increased metabolic activity. In this regard, a doubling of cytochrome oxidase activity was observed within the grafted post-commissural putamen bilaterally relative to the non-grafted anterior putamen. The grafts were hypovascular relative to the surrounding striatum and host substantia nigra. Blood vessels within the graft stained intensely for GLUT-1, suggesting that this marker of blood--brain barrier function is present within human nigral allografts. Taken together, these data indicate that fetal nigral neurons can survive transplantation, functionally reinnervate the host putamen, establish synaptic contacts with host neurons, and sustain many of the morphological and functional characteristics of normal nigral neurons following grafting into a patient with PD.

TRK and p75 neurotrophin receptor systems in the developing human brain

The prenatal development of the neurons immunoreactive for high-affinity tropomycin-related kinase (trk) receptor (pan trk which recognizes trkA, trkB, and trkC) and low-affinity p75 neurotrophin receptor (p75NTR) was examined in the human brain from embryonic weeks 10 to 34 of gestation. In the embryonic week 10 specimen in which only brainstem regions were available for evaluation, trk immunoreactivity (trk-ir) was observed in the ventral cochlear, solitary, raphe, spinal trigeminal, and hypoglossal nuclei, as well as the vestibular complex and medullary reticular formation. At this time point of gestation, p75ntr-immunoreactive (p75NTR-ir) staining was observed within these same regions plus the inferior olivary and ambiguus nuclei. At embryonic week 14, trk-ir neurons were seen within the subplate zone of the entorhinal cortex, basal forebrain, caudate nucleus, putamen, external segment of the globus pallidus, specific thalamic nuclei, lateral mammillary nucleus, habenula nucleus, select brainstem nuclei, and the dentate nucleus of cerebellum. At this gestational time point, p75NTR-ir neurons were observed in each of these structures, with the exception of the caudate nucleus, specific thalamic nuclei, lateral mammillary nucleus, and habenula nucleus. Additionally, p75NTR-ir neurons were observed within the corpus callosum. The staining pattern for both trk and p75NTR remained unchanged at embryonic weeks 15 to 16 except for the addition of trk-ir and p75NTR-ir within the cortical subplate zone, hippocampus, and subthalamic nucleus. By embryonic week 18, trk-ir neurons were widely expressed within mostly all thalamic nuclei. In contrast, trk-ir was no longer seen within the hypoglossal, cuneate, and gracile nuclei at this time point. This staining pattern for trk and p75NTR remained virtually unchanged from embryonic weeks 19 to 20 and embryonic weeks 16 to 20, respectively. From embryonic weeks 22 to 34, the distribution of both trk-ir and p75NTR-ir neurons changed gradually. During this period, neurons in most thalamic and some brainstem nuclei became progressively immunonegative for trk, whereas neurons in the neocortical subplate zone, corpus callosum, and hilar region of dentate gyrus gradually lost immunoreactivity for p75NTR. These data demonstrate an important and complex role for both the high-(trk) and low- (p75) affinity neurotrophin receptors during the development of multiple neuronal systems in the human brain.

Neurological signs, age, and illness duration in schizophrenia

Although increased prevalence of neurological signs in schizophrenia may reflect the presence of subtle brain dysfunctions, it is not clear whether there is progressive deterioration in such neurological function as the illness advances. This study compared neurological signs in patients with different durations of illness, controlling for age and education level. No deterioration in neurological signs as a function of illness duration was observed. Although there was an increase in neurological signs with age, there was a parallel increase in a control group. In addition, no change in the profile of subgroups of neurological signs was detected. These data provide further evidence for the stability of neurological dysfunction in schizophrenia. The findings are discussed in the context of the developmental origin of neurological dysfunction in schizophrenia.

Long-range sequence analysis in Xq28: thirteen known and six candidate genes in 219.4 kb of high GC DNA between the RCP/GCP and G6PD loci

DNA comprising 219 447 bp was sequenced in nine cosmids and verified at > 99.9% precision. Of the standard repetitive elements, 187 Alus make up 20.6% of the sequence, but there were only 27 MERs (2.9%) and 17 L1 fragments (1.6%). This may be characteristic of such high GC (57%) regions. The sequence also includes an 11.3 kb tract duplicated with 99.2% identity at a distance of 38 kb. The region is 80-90% transcribed and 12.5% translated. Thirteen known genes and their exon-intron borders are all accurately predicted at least in part by GRAIL programs, as are six additional genes. From centromere to telomere, the orientation of transcription varies among the first eight genes, then runs centromeric to telomeric for the next five, and is in the opposite sense for the last six. Eighteen of the 19 genes are associated with CpG islands. Two islands are exact copies in the 11.3 kb repeat units, and could thus give rise to double dosage levels of an X-linked gene. Another island is associated with two genes transcribed in opposite directions. From the sequence data, three genes and their exon structure are inferred. One of them, previously associated with HEX2, is shown to be a different gene unrelated to hexokinases; a second gene, previously known by an EST, is plexin, from its 65.5% identity with the Xenopus analog; and a third is a subunit of a vacuolar H-ATPase, and is named VATPS1.

Intrastriatal implants of polymer encapsulated cells genetically modified to secrete human nerve growth factor: trophic effects upon cholinergic and noncholinergic striatal neurons

Nerve growth factor selectively prevents the degeneration of cholinergic neurons following intrastriatal infusion but rescues both cholinergic and noncholinergic striatal neurons if the nerve growth factor is secreted from grafts of genetically modified fibroblasts. The present study evaluated whether grafted fibroblasts genetically modified to secrete human nerve growth factor could provide trophic influences upon intact cholinergic and noncholinergic striatal neurons. Unilateral striatal grafts of polymer-encapsulated cells genetically modified to secrete human nerve growth factor induced hypertrophy and significantly increased the optical density of choline acetyltransferase-immunoreactive striatal neurons one, two, and four weeks post-transplantation relative to rats receiving identical grafts missing only the human nerve growth factor construct. Nerve growth factor secreting grafts also induced a hypertrophy of noncholinergic neuropeptide Y-immunoreactive striatal neurons one, two, and four weeks post-transplantation. Glutamic acid decarboxylase-immunoreactive neurons were unaffected by the human nerve growth factors secreting grafts. The effects upon choline acetyltransferase-immunoreactive and neuropeptide Y-immunoreactive striatal neurons dissipated following retrieval of the implants. Immunocytochemistry for nerve growth factor revealed intense graft-derived immunoreactivity for up to 1000 microns from the capsule extending along the dorsoventral axis of the striatum. Nerve growth factor-immunoreactivity was also observed within a subpopulation of striatal neurons and may represent nerve growth factor consumer neurons which retrogradely transported graft-derived nerve growth factor. When explanted, grafts produced 2-4 ng human nerve growth factor/24 h over the time course of this study indicating that this level of continuous human nerve growth factor secretion was sufficient to mediate the effects presently observed.

Mutations in GPC3, a glypican gene, cause the Simpson-Golabi-Behmel overgrowth syndrome

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked condition characterized by pre- and postnatal overgrowth with visceral and skeletal anomalies. To identify the causative gene, breakpoints in two female patients with X;autosome translocations were identified. The breakpoints occur near the 5' and 3' ends of a gene, GPC3, that spans more than 500 kilobases in Xq26; in three families, different microdeletions encompassing exons cosegregate with SGBS. GPC3 encodes a putative extracellular proteoglycan, glypican 3, that is inferred to play an important role in growth control in embryonic mesodermal tissues in which it is selectively expressed. Initial western- and ligand-blotting experiments suggest that glypican 3 forms a complex with insulin-like growth factor 2 (IGF2), and might thereby modulate IGF2 action.

Prefrontal neuropsychological impairment and illness duration in schizophrenia: a study of 204 patients in Hong Kong

Previous studies investigating the progression of neuropsychological impairment in schizophrenia have yielded conflicting results. We compared prefrontal neuropsychological function and other cognitive performance in a larger sample of schizophrenic patients with different duration of illness. The inclusion of a normal control group also allowed the effect of age to be taken into account. Performance in the Wisconsin Card Sorting Test (WCST) and semantic fluency were both impaired at an early stage in the illness and did not significantly deteriorate as the illness duration increased. Against this background there was preliminary evidence for deterioration in verbal memory function. The data support a lack of progression in prefrontal dysfunction and in most other cognitive domains.

Analysis of a nuclear localization signal of simian virus 40 major capsid protein Vp1

The nuclear localization signal of the major structural protein, Vp1, of simian virus 40 was further defined by mutagenesis. The targeting activity was examined in cells microinjected with SV-Vp1 variant viral DNAs bearing either an initiation codon mutation of the agnoprotein or mutations in the Vp1 coding sequence or microinjected with pSG5-Vp1 and pSG5-Vp1 mutant DNAs in which Vp1 or mutant Vp1 is expressed from simian virus 40 early promoter. The Vp1 nuclear localization signal functioned autonomously without agno-protein once the Vp1 protein was synthesized in the cytoplasm. The targeting activity was localized to the amino-terminal 19 residues. While replacement of cysteine 10 with glycine, alanine, or serine did not affect the activity, replacement of arginine 6 with glycine caused the cytoplasmic phenotype. When multiple mutations were introduced among residue 5, 6, 7, 16, 17, or 19, the targeting activity was found to reside in two clusters of basic residues, a cluster of lysine 5, arginine 6, and lysine 7 and a cluster of lysine 16, lysine 17, and lysine 19. The clusters are independently important for nuclear localization activity.

Negative symptoms, neurological signs and neuropsychological impairments in 204 Hong Kong Chinese patients with schizophrenia

BACKGROUND

Studies of the relationship between negative symptoms, neuropsychological impairments and neurological signs in schizophrenia have yielded inconsistent results. In addition, little attention has been directed to address the extent of cultural modulation of negative symptoms.

METHOD

We carried out cross-cultural validation of the High Royds Evaluation of Negativity Scale (HEN) in 50 Hong Kong Chinese patients with schizophrenia. We then investigated the relationship between negative symptoms, neurological signs and neuropsychological impairment in 204 patients.

RESULTS

Good interrater reliability, internal reliability, convergent and discriminant validity were found with the HEN. The HEN contained four factors corresponding to 'behaviour', 'functioning', 'thought' and 'appearance'. Negative symptoms were correlated with semantic fluency but not with Wisconsin Card Sorting Test performance or sustained attention. Negative symptoms were also correlated with tardive dyskinesia and catatonia but not with soft neurological signs.

CONCLUSIONS

Cross-cultural robustness of the negative symptoms construct is supported. Association of negative symptoms with a specific profile of neurocognitive impairment suggests diversity within deficit domains in schizophrenia.

Insight and general public attitude on psychotic experiences in Hong Kong

Psychosis has been viewed with vastly different attitudes in different contexts. Medical professionals frequently assume that patients should have adequate insight into their abnormal experience. "Lack" of insight has been regarded as a characteristic feature of schizophrenic psychosis. However, these experiences have frequently been construed from a non-medically related perspective by the general public. We employed a case-vignette approach to study the opinion of a general public sample concerning attribution, intervention needs and concordance with medical professionals towards psychotic experience. Ninety eight healthy Chinese volunteers were recruited. Results showed that public opinion only agreed partly with the conventional medical model. Although most subjects agreed that the experience described in the case-vignette was psychological, they did not relate this to psychiatric treatment. Subjects having past contact with psychiatric patients showed a higher degree of agreement with the medical perspective than subjects without past contact. Potential implications of our results on management and health education are discussed.

CpG islands in human ZFX and ZFY and mouse Zfx genes: sequence similarities and methylation differences

The human ZFX, human ZFY, and mouse Zfx genes have CpG islands near their 5; ends. These islands are typical in that they span about 1.5 kb, contain transcription initiation sites, and encompass some 5' untranslated exons and introns. However, comparitive nucleotide sequencing of these human and mouse islands provided evidence of evolutionary conservation to a degree unprecedented among mammalian 5' CpG islands. In one stretch of 165 nucleotides containing 19 CpGs, mouse Zfx and human ZFX are identical to each other and differ from human ZFY at only 9 nucleotides. In contrast, we found no evidence of homologous CpG islands in the mouse Zfy genes, whose transcription is more circumscribed than that of human ZFX, human ZFY, and mouse Zfx. Using the isoschizomers HpaII and MspI to examine a highly conserved segment of the ZFX CpG island, we detected methylation on inactive mouse X chromosomes but not on inactive human X chromosomes. These observations parallel the previous findings that mouse Zfx undergoes X inactivation while human ZFX escapes it.

Peptides which bind to E-selectin and block neutrophil adhesion

E-selectin is an inducible cell adhesion molecule which mediates rolling of neutrophils on the endothelium, an early event in the development of an inflammatory response. Inhibition of selectin-mediated rolling is a possible means for controlling inflammation-induced diseases, and several classes of compounds have been tested for this use. We describe here the use of recombinant peptide library screening for identification and optimization of novel ligands which bind to E-selectin. Several of these peptides bind with Kd values in the low nanomolar range and block E-selectin-mediated adhesion of neutrophils in static and flow-cell assays. Administration of the peptide to mice undergoing an acute inflammatory response reduced the extent of neutrophil transmigration to the site of inflammation, demonstrating the utility of this compound as a potential therapeutic. The identification of a peptide ligand for E-selectin suggests that the complete natural ligand for this adhesion molecule may include protein as well as carbohydrate moieties.

The Cambridge Neurological Inventory: a clinical instrument for assessment of soft neurological signs in psychiatric patients

A schedule (the Cambridge Neurological Inventory) has been constructed for standardized neurological assessment of psychiatric patients. Normative data and data resulting from its application to a group of patients with schizophrenia are reported. The instrument is comprehensive, reliable, and easy to administer. In conjunction with other forms of clinical assessment, it may be useful for identifying soft neurological signs and other patterns of neurological impairment relevant to neurobiological localization and prognosis in schizophrenia and other psychiatric disorders.

A neural network model of cortical information processing in schizophrenia. II--Role of hippocampal-cortical interaction: a review and a model

This paper considers the relevance of hippocampal dysfunction to symptom production in schizophrenia with the help of an integrative computational model of cortical processing. First, evidence for involvement of the hippocampus was systematically reviewed. Then, a neural network model of hippocampal-cortical interaction was proposed. The effects of a dysfunction in hippocampal-cortical interaction were explored through simulation experiments. Neural network simulation demonstrated that when the hippocampal function of classification and reduction of overlap in input is sub-optimal, increasing correlation among input patterns compromised storage capacity of the cortical network. Hippocampal dysfunction predisposes to the emergence of spurious retrieval states in cortical information processing. This provides a model for psychotic symptom formation in schizophrenia.

Sequence and gene content in 52 kb including and centromeric to the G6PD gene in Xq28

A cosmid containing 36.4 kb of high GC human DNA centromeric to the G6PD gene has been analyzed. The sequence was 99.9% precise, based on the comparison of 4.3 kb that overlaps an earlier analysis of 20.1 kb containing G6PD. Properties of the entire 52 kb region that may be characteristic of high GC portions of the genome include a very high density of sixty-two half or full Alu sequences, or 1.2/kb, and an absence of L1 sequences. Other highly repetitive sequences include 11 MER sequences, one of them interrupted at two positions by groups of 3 Alu elements. In segments of unique sequence, computer-aided analysis predicted three possible genes, one of which has thus far been confirmed by the recovery of a corresponding cDNA, both by a direct hybridization method and by a PCR-based method based on a primer pair inferred from the genomic sequence. The cDNA has been sequenced, and is completely concordant with counterpart genomic sequence; it has no resemblance to any previously described gene.

trk-immunoreactivity in the monkey central nervous system: forebrain

Neurotrophins such as nerve growth factor (NGF) mediate their effects through interactions with high-affinity tropomycin-related kinase (trk) receptors. The present study employed a polyclonal antibody to characterize the distribution of trk-immunoreactive neurons within the nonhuman primate brain. Both young adult and aged cebus and rhesus monkeys displayed trk-immunoreactive neurons within all subdivisions of the basal forebrain. Colocalization studies revealed that between 66% and 76% of trk-immunoreactive basal forebrain neurons also expressed immunoreactivity for the low-affinity p75 NGF receptor, an excellent marker for cholinergic basal forebrain cells. In this experiment, most single-labeled basal forebrain neurons contained only trk immunoreactivity, whereas 4% of basal forebrain neurons expressed only the low-affinity p75 NGF receptor. Scattered trk-immunoreactive neurons also were observed within the caudate nucleus and putamen. Although dual-localization studies with choline acetyltransferase (ChAT) were not performed, striatal neurons codistributed with ChAT-immunoreactive cells, and both types of cells were similar in size and morphology. This suggests that trk immunoreactivity is expressed within cholinergic interneurons within the primate striatum. Finally, lightly stained trk-immunoreactive neurons were observed within the stratum oriens of the hippocampal formation and within the hypothalamus. These data indicate that both cholinergic and, possibly, noncholinergic forebrain neurons express the protein for the high-affinity trk receptor, which transduces the signal mediating the trophic effects of neurotrophins. In addition, the pattern of trk immunoreactivity was preserved in two aged (26 and 29 years old) rhesus monkeys, suggesting that the expression of trk, for the most part, is sustained throughout the lifetime of the organism.

Hypoxic activation of nuclear factor-kappa B is mediated by a Ras and Raf signaling pathway and does not involve MAP kinase (ERK1 or ERK2)

We have previously shown that hypoxia causes the activation of nuclear factor-kappa B (NF-kappa B), and the phosphorylation of its inhibitory subunit, I kappa B alpha, on tyrosine residues. With the use of dominant negative mutants of Ha-Ras and Raf-1, we investigated some of the early signaling events leading to the activation of NF-kappa B by hypoxia. Both dominant negative alleles of Ha-Ras and Raf-1 inhibited NF-kappa B induction by hypoxia, suggesting that the hypoxia-induced pathway of NF-kappa B induction is dependent on Ras and Raf-1 kinase activity. Furthermore, although conditions of low oxygen can also activate mitogen-activated protein kinases (ERK1 and ERK2), these kinases do not appear to be involved in regulating NF-kappa B by low oxygen conditions, as dominant negative mutants of mitogen-activated protein kinase do not inhibit NF-kappa B activation by hypoxia. Since Ras and Raf-1 have been previously shown to work downstream from membrane-associated tyrosine kinases such as Src, we determined if the Src membrane-associated kinase was also activated by low oxygen conditions. We detected an increase in Src proto-oncogene activity within 15-30 min of cellular exposure to hypoxia. We postulate that Src activation by hypoxia may be one of the earliest events that precedes Ras activation in the signaling cascade which ultimately leads to the phosphorylation and dissociation of the inhibitory subunit of NF-kappa B, I kappa B alpha.

A neural network model of cortical information processing in schizophrenia. I: Interaction between biological and social factors in symptom formation

Exploiting the biological and psychological plausibility of parallel distributed processing, a neural network model of cortical processing is proposed in order to provide a framework for understanding pathological processes in schizophrenia. Major psychosocial and neurobiological factors are assigned to appropriate parameters in the model. Behaviour of the network is explored through simulation, in particular interaction between the temperature and memory loading parameters is studied. The emergent network behaviour provides a model for complex interaction between dopaminergic activity, cortical and hippocampal pathology, and psychosocial factors in the production of psychotic symptoms. This integrative model provides an account of a wide range of observations in schizophrenia. It also produces testable predictions concerning cognitive performance and the course of schizophrenia.

Nucleotide sequence of the SAC2 gene of Saccharomyces cerevisiae

A temperature-sensitive mutation (act1-1) in the essential actin gene of Saccharomyces cerevisiae can be suppressed by mutations in the SAC2 gene. A cloned genomic DNA fragment that complements the cold-sensitive growth phenotype associated with such a suppressor mutation (sac2-1) was sequenced. The fragment contained an open reading frame that encodes a 641 amino acid predicted hydrophilic protein with a molecular weight of 74,445. No sequences with significant similarity to SAC2 were found in the GenBank and EMBL databases. A SAC2 disruption mutation was constructed which had phenotypes similar to the sac2-1 point mutation. A haploid SAC2 disruption strain failed to grow at low temperature and the disruption allele suppressed the temperature-sensitive act1-1 growth defect. The suppression phenotype was dependent on the strain background.

Simultaneous expression of RBTN-2 and BCR-ABL oncogenes in a T-ALL with a t(11;14)(p13;q11) and a late-appearing Philadelphia chromosome

Cytogenetic analysis of a pediatric patient with T-cell acute lymphoblastic leukemia (T-ALL) revealed a mosaic karyotype, 47,XX,+17,t(11;14)(p13;q11)/47,XX,+17,t(9;22)(q34;q11),t(11;14) (p13;q11). DNA blot analysis was used to examine the break-point within the BCR gene on chromosome 22 and showed that the breakpoint occurred within the 20-kb minor breakpoint cluster region (m-bcr) located within the first intron of the BCR gene. Immunoprecipitation analysis demonstrated that the leukemic cells expressed the P185 BCR-ABL protein tyrosine kinase. P185 BCR-ABL has previously been shown to be expressed in most cases of Ph+ acute leukemia of myeloid and B-progenitor origin. Here, we demonstrate for the first time that P185 can also be expressed in the T-cell lineage. DNA blot hybridization was also used to characterize the t(11;14) translocation. This showed rearrangement on chromosome 11 within the T-ALLbcr region, upstream of the RBTN-2 gene. Polymerase chain reaction revealed the presence of RBTN-2 transcripts in the leukemic cells. Finally, comparison of the T-ALLbcr, BCR-ABL, IGH, TCR beta and gamma gene rearrangements in leukemic cells obtained at the time of diagnosis and at first relapse showed that relapse occurred in a leukemic clone indistinguishable from the major Ph+ clone involved at diagnosis. Together, these data support a multistep pathogenesis in which the Philadelphia (Ph) chromosome translocation appeared subsequent to the +17 and t(11;14) and imparted a growth advantage over the Ph-negative cells that carried these abnormalities.

Activators of protein kinase C selectively mediate cellular cytotoxicity to hypoxic cells and not aerobic cells

PURPOSE

By understanding the signal transduction pathways through which a cell responds to changes in environmental oxygen levels, we may be able to therapeutically exploit this response by manipulating these pathways.

MATERIALS AND METHODS

The human adenocarcinoma cell line A549 was exposed to varying durations of hypoxia alone and then plated for survival, or treated with PKC activating agents for 1 h before plating for survival. Western blots were used to determine the kinetics of PKC epsilon and phospholipase C induction.

RESULTS

The level of hypoxic killing was directly related to the time of exposure and inversely related to the level of oxygen in the environment. Exposure of the cells to protein kinase C (PKC) activators for 1 h after chronic hypoxic exposure increased cell killing by at least an additional three logs beyond that found for hypoxia alone. Treatment of cells with an inactive phorbol ester 4 alpha-phorbol-12,13-didecanoate (PDA) resulted in no increase in hypoxic cell killing, even at the highest concentrations of PDA which produced no detectable toxicity under normal aerobic conditions. Using inhibitors of phospholipases A2 and C, we were able to completely inhibit the additional hypoxic cell killing induced by TPA, but not the uninduced hypoxic cell killing.

CONCLUSION

These studies suggest that accumulation of phospholipid breakdown products may be responsible for TPA induced cell killing, and that hypoxic cells differ from aerobic cells in their ability to tolerate these products.

The regulation of GRP78 and messenger RNA levels by hypoxia is modulated by protein kinase C activators and inhibitors

In this study, we have shown that steady-state levels of glucose-regulated 78 kDa (GRP78) protein and messenger RNA increase during a 5-h exposure to 0.02% oxygen. This increase in GRP78 protein and mRNA induced by hypoxia can be abolished by a 1-h pretreatment of cells before hypoxia with the protein kinase C (PKC) inhibitors staurosporine and H7 at concentrations at which the drugs themselves do not cause cytotoxicity. Although all studies using protein kinase inhibitors must be interpreted with caution, staurosporine and H7 have been shown to be potent inhibitors of PKC activity, suggesting a role for PKC in mediating the transcriptional regulation of GRP78 by hypoxia. Further support for PKC in regulating GRP78 gene expression by hypoxia stems from gel-mobility shift studies in mixtures of nuclear extracts from aerobic or hypoxic cells with a 36 bp region of the GRP78 promoter (-170 to -135). Binding of this factor could be inhibited by pretreating cells with the PKC inhibitor staurosporine before hypoxia or activated by treating cells with the PKC-activating phorbol ester TPA. These data suggest that activation of this hypoxia-responsive factor is sensitive to oxygen levels and seems to be mediated through a PKC signal transduction pathway.

Hypoxia causes the activation of nuclear factor kappa B through the phosphorylation of I kappa B alpha on tyrosine residues

The response of mammalian cells to stress is controlled by transcriptional regulatory proteins such as nuclear factor kappa B (NF-kappa B) to induce a wide variety of early response genes. In this report, we show that exposure of cells to hypoxia (0.02% O2) results in I kappa B alpha degradation, increased NF-kappa B DNA binding activity, and transactivation of a reporter gene construct containing two NF-kappa B DNA binding sites. Pretreatment of cells with protein tyrosine kinase inhibitors and the dominant negative allele of c-Raf-1 (Raf 301) inhibited I kappa B alpha degradation, NF-kappa B binding, and transactivation of kappa B reporter constructs by hypoxia. To demonstrate a direct link between changes in the phosphorylation pattern of I kappa B alpha with NF-kappa B activation, we immunoprecipitated I kappa B alpha after varying times of hypoxic exposure and found that its tyrosine phosphorylation status increased during hypoxic exposure. Inhibition of the transfer of tyrosine phosphoryl groups onto I kappa B alpha prevented I kappa B alpha degradation and NF-kappa B binding. In comparison to other activators of NF-kappa B such as phorbol myristate acetate or tumor necrosis factor, we did not detect changes in the tyrosine phosphorylation status of I kappa B alpha following treatment with either of these agents. These results suggest that tyrosine phosphorylation of I kappa B alpha during hypoxia is an important proximal step which precedes its dissociation and degradation from NF-kappa B.