Interleukin-1 beta activates expression of cyclooxygenase-2 and inducible nitric oxide synthase in primary hippocampal neuronal culture: platelet-activating factor as a preferential mediator of cyclooxygenase-2 expression

Interleukin-1 beta (IL-1beta) is an inflammatory cytokine whose expression is elevated in brain during seizures, ischemia, and injury. Expression of IL-1beta and its receptor can also be observed in normal brain. Platelet-activating factor (PAF) is also a dual mediator that promotes neuronal plasticity responses as well as inflammation. We have determined the role of PAF in the regulation of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) genes by IL-1beta in rat primary hippocampal cultures. As assessed by reverse transcriptase/polymerase chain reaction (RT/PCR), recombinant mouse IL-1beta (1 nM) led to an induction of COX-2 mRNA which peaked at 2 hours, declined to baseline levels by 4 hours, began to rise again by 6 hours, and remained elevated at 24 hours post-treatment. iNOS mRNA was also induced, but unlike COX-2, its abundance peaked at 4 hours and decreased by 6 hours to a plateau lasting through 24 hours. Pretreatment with PAF antagonist BN50730 blocked induction of COX-2 mRNA by 2-hour IL-1beta treatment, and 2-hour treatment with the PAF analog mcPAF mimicked the effects of IL-1beta on COX-2 mRNA levels. Following injury, synaptic plasticity changes may be affected by IL-1beta-PAF-COX-2 neuronal signaling.

Platelet-activating factor inhibits ionotropic GABA receptor activity in cultured hippocampal neurons

Platelet-activating factor (PAF), one of the most potent bioactive lipids, has been implicated in modulating long-term potentiation (LTP) and neurotoxicity. In the CNS, glutamate and GABA are the major excitatory and inhibitory neurotransmitters, respectively. Previous work has focused on the effects of PAF on glutamatergic receptor responses. The purpose of the present study was to investigate the possible actions of PAF on ionotropic GABA receptor responses in primary cultured hippocampal neurons using the whole-cell and single channel patch clamp techniques. Extracellular application of PAF induced a reduction of the GABA gated Cl- current in a majority of cells (29 of 44 cells), while it caused an enhancement in 10 of 44 cells. A similar heterogeneous modulation of PAF on the GABA receptor activities was also observed in outside-out patch recordings. Moreover, the cell-attached single channel recordings showed that PAF decreased the GABA channel activity. Therefore, PAF may modulate synaptic activity by inhibiting GABA receptor channels. During seizures and neural injury, when enhanced synthesis of this lipid mediator takes place, the actions of PAF on inhibitory GABA receptors may contribute to synaptic dysfunction.

Secretory phospholipase A2 potentiates glutamate-induced rat striatal neuronal cell death in vivo

The secretory phospholipases A2 (sPLA2) OS2 (10, 20 and 50 pmol) or OS1, (50 pmol) purified from taipan snake Oxyuranus scutellatus scutellatus venom, and the excitatory amino acid glutamate (Glu) (2.5 and 5.0 micromol) were injected into the right striatum of male Wistar rats. Injection of 10 and 20 pmol OS2 caused no neurological abnormalities or tissue damage. OS2 (50 pmol) caused apathy and circling towards the injection side. Histology revealed an infarct at the injection site. Injection of 50 pmol OS1 showed very little or no signs of neurotoxicity. Injection of 2.5 micromol Glu caused no tissue damage or neurological abnormality. After injection of 5.0 micromol Glu, the animals initially circled towards the side of injection, and gradually developed generalized clonic convulsions. These animals showed a well demarcated striatal infarct. When non-toxic concentrations of 20 pmol OS2 and 2.5 micromol Glu were co-injected, a synergistic neurotoxicity was observed. Extensive histological damage occurred in the entire right hemisphere, and in several rats comprising part of the contralateral hemisphere. These animals were apathetic in the immediate hours following injection, with circling towards the side of injection in the following days. Thus, OS2 greatly potentiates glutamate excitoxicity in vivo.

Selective retinal pigment epithelial cell lipid metabolism and remodeling conserves photoreceptor docosahexaenoic acid following phagocytosis

Retinal pigment epithelial cells (RPE) actively retrieve and recycle docosahexaenoic acid (DHA, 22:6n-3) from phagosomal phospholipids back to photoreceptor cells. Here we studied the fate of DHA in primary culture rat RPE cells after feeding with a suspension of rod outer segments (ROS) for 4 hr. Phospholipids (PLs), triacylglycerols (TAG), and free fatty acids were isolated from cells and media by thin layer chromatography (TLC), and their acyl groups quantified by gas liquid chromatography (GLC). In RPE cells, DHA-PLs increased 3. 5-fold by 4 hr, decreasing thereafter to 1.6-fold above basal by 24 hr. In contrast, 18:1-PLs were decreased by 13%-18% below RPE basal values by 8-24 hr, respectively. DHA-TAG showed the highest increase (21-fold) by 8 hr. Free DHA displayed a small increase in the cells with a preferential release and accumulation into the media by 24 hr. These results show that in rat RPE cells, photoreceptor cell DHA is transiently incorporated into TAG prior to its release and uptake into 18:1-PLs. These metabolic pathways and remodeling may be critical in the conservation of this essential, photoreceptor cell fatty acid.

Neuroprotection by pigment epithelial-derived factor against glutamate toxicity in developing primary hippocampal neurons

Pigment epithelial-derived factor (PEDF) has been shown to be a survival factor for cerebellar granule neurons. Here we investigated the ability of PEDF to enhance the survival of hippocampal neurons in culture, and to protect these neurons against acute glutamate toxicity. Hippocampal neurons prepared from 1- to 3-day postnatal rat brain were cultured for either 7 or 14 days in vitro (DIV). At 14 DIV, neurons were only slightly protected (13% +/- 4%) against 50 microM glutamate toxicity when treated with 1 microg/ml of PEDF for 3 successive days before glutamate exposure as measured by lactate dehydrogenase (LDH) release. In comparison, basic fibroblast growth factor (bFGF) at 10 ng/ml for the same treatment period protected 58% +/- 8% of the neurons against glutamate. Using quantitative image analysis of digitized micrographs, we found that the average size of neurons in young, developing hippocampal cultures (7 DIV), was greatly decreased by treatment with 50 microM glutamate. Treatment for up to 5 successive days with 1 microg/ml of PEDF before glutamate addition dramatically increased the average hippocampal neuron soma size, compared to cells treated with glutamate alone. Thus, PEDF may promote the growth of hippocampal neurons, and, if added to developing hippocampal neurons, can also protect these cells from subsequent injury, such as the excitotoxicity of glutamate.

The interleukin-1 type 2 receptor gene displays immediate early gene responsiveness in glucocorticoid-stimulated human epidermal keratinocytes

Human epidermal keratinocytes (HEKs) in primary culture (P2-P4) were used to study glucocorticoid (GC)-mediated transcription of the genes encoding the constitutively expressed interleukin-1 type 1 receptor (IL-1R1) and the inducible interleukin-1 type 2 receptor (IL-1R2). Utilizing Northern dot blot analysis and a quantitative reverse transcription-polymerase chain reaction protocol for IL-1R1 and IL-1R2, dexamethasone and, in particular, the budesonide epimer R were shown to effectively and rapidly induce transcription from the IL-IR2 gene when compared with IL-1R1 or beta-actin RNA message levels in the same sample. Southern blot analysis of newly generated IL-1R2 reverse transcription-polymerase chain reaction products using end-labeled IL-1R2 intron probes suggested that GC enhancement of IL-1R2 expression was regulated primarily at the level of de novo transcription. GC-induced IL-1R2 gene transcription displayed features characteristic of a classical immediate early gene response, including a signal transduction function, a relatively low basal abundance, a rapid, transient induction, cycloheximide superinduction, actinomycin D suppression, and a rapid decay of IL-1R2 RNA message. Parallel time course kinetic analysis of IL-1R2 RNA message levels with Western immunoblotting revealed tight coupling of de novo IL-IR2 gene transcription with translation of the IL-1R2 RNA message; a newly synthesized ( approximately 46-kDa) IL-1R2 protein was detected in the HEK growth medium as early as 1 h after budesonide epimer R treatment. These data indicate that different GC compounds can variably up-regulate the IL-1R2 response in HEKs through transcription-mediated mechanisms and, for the first time, suggest that a gene encoding a soluble cytokine receptor can respond like an immediate early gene.

Glutamate receptor signaling interplay modulates stress-sensitive mitogen-activated protein kinases and neuronal cell death

Glutamate receptors modulate multiple signaling pathways, several of which involve mitogen-activated protein (MAP) kinases, with subsequent physiological or pathological consequences. Here we report that stimulation of the N-methyl-D-aspartate (NMDA) receptor, using platelet-activating factor (PAF) as a messenger, activates MAP kinases, including c-Jun NH2-terminal kinase, p38, and extracellular signal-regulated kinase, in primary cultures of hippocampal neurons. Activation of the metabotropic glutamate receptor (mGluR) blocks this NMDA-signaling through PAF and MAP kinases, and the resultant cell death. Recombinant PAF-acetylhydrolase degrades PAF generated by NMDA-receptor activation; the hetrazepine BN50730 (an intracellular PAF receptor antagonist) also inhibits both NMDA-stimulated MAP kinases and neuronal cell death. The finding that the NMDA receptor-PAF-MAP kinase signaling pathway is attenuated by mGluR activation highlights the exquisite interplay between glutamate receptors in the decision making process between neuronal survival and death.

The neuromessenger platelet-activating factor in plasticity and neurodegeneration

Synaptic activation leads to the formation of arachidonic acid, platelet-activating factor (PAF, 1-O-alkyl-2-acyl-sn-3-phosphocholine) and other lipid messengers. PAF is a potent bioactive phospholipid in synaptic plasticity. PAF enhances presynaptic glutamate release, is a retrograde messenger in long-term potentiation and enhances memory formation. PAF also couples synaptic events with gene expression by stimulating a FOS/JUN/AP-1 transcriptional signaling system, as well as transcription of COX-2 (inducible prostaglandin synthase). Since the COX-2 gene is also involved in synaptic plasticity, the PAF-COX-2 pathway may have physiological significance. Seizures, ischemia and other forms of brain injury promote phospholipase A2 (PLA2) overactivation, resulting in the accumulation of bioactive lipids at the synapse. PAF, under these pathological conditions, behaves as a neuronal injury messenger by at least two mechanisms: (a) enhancing glutamate release; and, (b) by sustained augmentation of COX-2 transcription. These events link PAF with neurodegeneration. The upstream intracellular pathways of signal transduction involved in neuronal or photoreceptor cell apoptosis are not well understood and involve stress sensitive kinases. PAF is a transcriptional activator of the COX-2 gene. BN 50730, a potent intracellular PAF antagonist, blocks COX-2 induction. COX-2 transcription and protein expression are upregulated in the hippocampus in kainic acid induced epileptogenesis. There is a selectively elevated induction of COX-2 (72-fold) by kainic acid preceding neuronal cell death. BN 50730 administered by i.c.v. injection blocks seizure-induced COX-2 induction. Overall, PAF is a dual modulator of neural function and becomes an endogenous neurotoxin when over produced.

Selective changes in protein kinase C (PKC) isoform expression in rabbit corneal epithelium during wound healing. Inhibition of corneal epithelial repair by PKCalpha antisense

Protein kinase C (PKC) isoforms display different sensitivities to modulators, tissue specificities and subcellular localizations. PKCalpha increases during rabbit corneal epithelial wound healing. Here we report differential expression of PKC isoforms in the cornea of rabbits at 1, 2, 4 and 8 days during re-epithelization. Cytosolic, membrane and detergent-insoluble fractions from epithelium were analysed by Western blot using monoclonal antibodies against the different PKC isoforms. We have identified PKCalpha, gamma, epsilon, mu and iota. PKCalpha and gamma were expressed only in the cytosolic fraction, with the expression of PKCalpha markedly increasing 4 days after injury. Corneas cultured in the presence of rabbit-specific PKCalpha antisense showed a greater than 50% inhibition of wound closure, compared to controls. The PKCepsilon and mu were expressed in the soluble, as well as in the membrane fraction. Additionally, 12% of PKCmu was found attached to the detergent insoluble fraction. The expression of the membrane-bound PKCepsilon and mu isoforms decreased between 1 and 2 days following injury. Only 10% of the PKCiota expressed in corneal epithelium was membrane bound, but between 4 and 8 days after de-epithelization, the expression in this fraction increased three-fold. Our results suggest that changes in the expression and distribution within the various fractions of selective isoforms of PKC after injury could be involved in events leading to wound healing and that PKCalpha is a key modulator in rabbit corneal wound repair.

Effects of posttraining intrahippocampal injections of platelet-activating factor and PAF antagonists on memory

The present experiments examined the effects of posttraining intrahippocampal injections of the degradative enzyme-resistant methylcarbamyl analog of the bioactive phospholipid platelet-activating factor (mc-PAF) and the platelet-activating factor (PAF) receptor antagonists BN52021 and BN 50730 on memory in male Long-Evans rats trained in a hidden platform version of the Morris water maze. Following an eight-trial training session, rats received a unilateral intrahippocampal injection of mc-PAF (0.5, 1.0, or 2.0 microgram/0.5 microliter), lyso-PAF (1.0 microgram/0.5 microliter), the cell surface PAF receptor antagonist BN 52021 (0.25, 0.5, or 1.0 micrigram/0.5 microliter/, the intracellular PAF receptor antagonist BN 50730 (2.0, 5.0, or 10.0 microgram/0.5 microliter), or vehicle (50% DMSO in 0.9% saline; 0.5 microliter). On a retention test conducted 24 h after training, the escape latencies of rats administered mc-PAF (1.0 or 2.0 microgram) were significantly lower than those of the vehicle-injected controls, demonstrating a memory-enhancing effect of mc-PAF. Injections of lyso-PAF, a structurally similar metabolite of PAF, had no influence on memory, indicating that the memory-enhancing effect of mc-PAF is not caused by membrane perturbation by the phospholipid. The retention test escape latencies of rats administered BN 52021 (0.5 microgram) and BN 50730 (5.0 or 10 microgram) were significantly higher than those of the controls, indicating a memory impairing effect of both PAF antagonists. When mc-PAF, BN 52021, or BN 50730 was administered 2 h posttraining, no effect on retention was observed, indicating a time-dependent effect of the neuroactive substances on memory storage. The findings suggest a role for endogenous PAF in hippocampal-dependent memory processes.

Strong nuclear factor-kappaB-DNA binding parallels cyclooxygenase-2 gene transcription in aging and in sporadic Alzheimer's disease superior temporal lobe neocortex

Cyclooxygenase-2 (COX-2; EC 1.14.99.1) RNA message abundance in 25 control and Consortium to Establish a Registry for Alzheimer's Disease (CERAD)-confirmed sporadic Alzheimer's disease (AD) brains is remarkably heterogeneous when compared with 55 other AD brain RNA message levels that were previously characterized (Lukiw and Bazan: J Neurosci Res 50:937-945, 1997). Examination of nuclear protein extracts (NPXTs) that were derived from control and AD-affected brain neocortical nuclei (n = 20; age range, 60-82 years; postmortem interval, 0.5-6.5 hours) by using gel shift, gel supershift, and cold oligonucleotide competition assay revealed a highly significant relationship between the extent of inflammatory transcription factor, nuclear factor (NF)-kappaB: DNA binding and the abundance of the COX-2 RNA signal (P < 0.0001; analysis of variance). No strong correlation with AP-1-DNA binding was noted (P > 0.045). These data are the first linking inflammation-related transcription factor NF-KB-DNA binding to up-regulation of transcription from a key inflammatory gene, COX-2, in both normally aging brain and in AD-affected neocortex. Systematic deletion of NF-KB-DNA binding sites in human COX-2 promoter constructs attenuates COX-2 transcriptional induction by mediators of inflammation. Strong NF-kappaB-DNA binding has been reported previously to temporally precede COX-2 gene transcription in human epithelial (A549), hamster B-cell (HIT-T15), human endothelial (HUVEC), human lymphoblast (IM9), human fibroblast (IMR90), rat glioma/mouse neuroblastoma (NG108-15), human keratinocyte (NHEK), mouse fibroblast (NIH 3T3), rat neuroblastoma (SH-SY5Y) cell lines and in mouse and rat brain hippocampus, indicating a highly conserved inflammatory signaling pathway that is common to diverse species and cell types. The mouse, rat, and human COX-2 immediate promoters, despite 7.5 x 10(7) years of DNA sequence divergence, each retain multiple recognition sites specific for NF-kappaB-DNA binding. These data suggest that basic gene induction mechanisms, which have been conserved over long periods of evolution, that increase NF-kappaB-DNA binds ing may be fundamental in driving transcription from inflammation-related genes, such as COX-2, that operate in stressed tissues, in normally aging cell lines, and in neurodegenerative disorders that include AD brain.

Strong nuclear factor-kappaB-DNA binding parallels cyclooxygenase-2 gene transcription in aging and in sporadic Alzheimer's disease superior temporal lobe neocortex

Cyclooxygenase-2 (COX-2; EC 1.14.99.1) RNA message abundance in 25 control and Consortium to Establish a Registry for Alzheimer's Disease (CERAD)-confirmed sporadic Alzheimer's disease (AD) brains is remarkably heterogeneous when compared with 55 other AD brain RNA message levels that were previously characterized (Lukiw and Bazan: J Neurosci Res 50:937-945, 1997). Examination of nuclear protein extracts (NPXTs) that were derived from control and AD-affected brain neocortical nuclei (n = 20; age range, 60-82 years; postmortem interval, 0.5-6.5 hours) by using gel shift, gel supershift, and cold oligonucleotide competition assay revealed a highly significant relationship between the extent of inflammatory transcription factor, nuclear factor (NF)-kappaB: DNA binding and the abundance of the COX-2 RNA signal (P < 0.0001; analysis of variance). No strong correlation with AP-1-DNA binding was noted (P > 0.045). These data are the first linking inflammation-related transcription factor NF-KB-DNA binding to up-regulation of transcription from a key inflammatory gene, COX-2, in both normally aging brain and in AD-affected neocortex. Systematic deletion of NF-KB-DNA binding sites in human COX-2 promoter constructs attenuates COX-2 transcriptional induction by mediators of inflammation. Strong NF-kappaB-DNA binding has been reported previously to temporally precede COX-2 gene transcription in human epithelial (A549), hamster B-cell (HIT-T15), human endothelial (HUVEC), human lymphoblast (IM9), human fibroblast (IMR90), rat glioma/mouse neuroblastoma (NG108-15), human keratinocyte (NHEK), mouse fibroblast (NIH 3T3), rat neuroblastoma (SH-SY5Y) cell lines and in mouse and rat brain hippocampus, indicating a highly conserved inflammatory signaling pathway that is common to diverse species and cell types. The mouse, rat, and human COX-2 immediate promoters, despite 7.5 x 10(7) years of DNA sequence divergence, each retain multiple recognition sites specific for NF-kappaB-DNA binding. These data suggest that basic gene induction mechanisms, which have been conserved over long periods of evolution, that increase NF-kappaB-DNA binds ing may be fundamental in driving transcription from inflammation-related genes, such as COX-2, that operate in stressed tissues, in normally aging cell lines, and in neurodegenerative disorders that include AD brain.

Recombinant plasma-type platelet-activating factor acetylhydrolase attenuates NMDA-induced hippocampal neuronal apoptosis

The bioactive lipid platelet-activating factor (PAF) accumulates in brain during injury, seizures and ischemia and may, in addition, be significant in AIDS dementia and in other neurodegenerative diseases. We have used plasma-type recombinant PAF acetylhydrolase (rPAF-AH) to test the hypothesis that PAF accumulation is involved in early events leading to neuronal apoptosis during excitotoxic neuronal injury. Neuronal cultures were labeled with FITC-12-dUTP (TUNEL technique) and propidium iodide, digitized using fluorescence microscopy and a chilled 3CCD color camera, and analyzed with 2D graphics analysis software. N-methyl-D-aspartate (NMDA) (50 microM, 2 hr) induced a 2.5-fold increase in apoptosis of hippocampal neurons compared with controls when analyzed 24 hr after NMDA treatment. Hippocampal neurons receiving rPAF-AH (20 microg/ml) before, during, and after NMDA treatment demonstrated a concentration-dependent neuroprotective effect which resulted in 47% and 30% neuroprotection against 50 and 100 microM NMDA, respectively. The noncompetitive NMDA receptor antagonist MK-801(300 nM) completely inhibited apoptosis caused by NMDA. The neuroprotective effect of rPAF-AH against NMDA-induced apoptosis was confirmed using as additional criteria, histone release, electron microscopy, and DNA laddering. Neuroprotection elicited by rPAF-AH demonstrates that PAF is an injury mediator in NMDA-induced neuronal apoptosis and that the recombinant protein is potentially useful as a therapeutic approach.

Simultaneous analysis of multiple gene expression patterns as a function of development, injury or senescence

Concurrent changes in expression of eight genes were examined following cryogenic rat brain injury. Cortical RNA levels were catalogued at time 0, and at 1 h and 1 week following injury. The genes include thymidine kinase (TK), c-fos, renin, myelin basic protein (MBP), proteolipid protein (PLP), glial fibrillary acidic protein (GFAP), insulin-like growth factor-1 (IGF-1), and somatostatin. All demonstrate increased expression following injury. Renin and c-fos exhibit detectable changes as early as 1 h post-injury.

Strong nuclear factor-kappaB-DNA binding parallels cyclooxygenase-2 gene transcription in aging and in sporadic Alzheimer's disease superior temporal lobe neocortex

Cyclooxygenase-2 (COX-2; EC 1.14.99.1) RNA message abundance in 25 control and Consortium to Establish a Registry for Alzheimer's Disease (CERAD)-confirmed sporadic Alzheimer's disease (AD) brains is remarkably heterogeneous when compared with 55 other AD brain RNA message levels that were previously characterized (Lukiw and Bazan: J Neurosci Res 50:937-945, 1997). Examination of nuclear protein extracts (NPXTs) that were derived from control and AD-affected brain neocortical nuclei (n = 20; age range, 60-82 years; postmortem interval, 0.5-6.5 hours) by using gel shift, gel supershift, and cold oligonucleotide competition assay revealed a highly significant relationship between the extent of inflammatory transcription factor, nuclear factor (NF)-kappaB: DNA binding and the abundance of the COX-2 RNA signal (P < 0.0001; analysis of variance). No strong correlation with AP-1-DNA binding was noted (P > 0.045). These data are the first linking inflammation-related transcription factor NF-KB-DNA binding to up-regulation of transcription from a key inflammatory gene, COX-2, in both normally aging brain and in AD-affected neocortex. Systematic deletion of NF-KB-DNA binding sites in human COX-2 promoter constructs attenuates COX-2 transcriptional induction by mediators of inflammation. Strong NF-kappaB-DNA binding has been reported previously to temporally precede COX-2 gene transcription in human epithelial (A549), hamster B-cell (HIT-T15), human endothelial (HUVEC), human lymphoblast (IM9), human fibroblast (IMR90), rat glioma/mouse neuroblastoma (NG108-15), human keratinocyte (NHEK), mouse fibroblast (NIH 3T3), rat neuroblastoma (SH-SY5Y) cell lines and in mouse and rat brain hippocampus, indicating a highly conserved inflammatory signaling pathway that is common to diverse species and cell types. The mouse, rat, and human COX-2 immediate promoters, despite 7.5 x 10(7) years of DNA sequence divergence, each retain multiple recognition sites specific for NF-kappaB-DNA binding. These data suggest that basic gene induction mechanisms, which have been conserved over long periods of evolution, that increase NF-kappaB-DNA binds ing may be fundamental in driving transcription from inflammation-related genes, such as COX-2, that operate in stressed tissues, in normally aging cell lines, and in neurodegenerative disorders that include AD brain.

Dominant expression of rat prostanoid DP receptor mRNA in leptomeninges, inner segments of photoreceptor cells, iris epithelium, and ciliary processes

Prostaglandin (PG) D2 is one of the major prostanoids in the mammalian brain and eye tissues. Its function is mediated by the prostanoid DP receptor, which is specific for PGD2 among the various prostanoids. In this study, we cloned the full-length cDNA for the rat DP receptor and used it for detection of DP receptor mRNA in various rat tissues. Northern blotting and RT-PCR analyses revealed that this DP receptor was expressed most intensely in the eye tissues, moderately in the leptomeninges and oviduct, and weakly in the epididymis. The tissue distribution profile of the mRNA for the rat DP receptor is overlapped with those of hematopoietic and lipocalin-type PGD synthases. Among rat eye tissues, the expression was the highest in the iris. In situ hybridization and in situ RT-PCR revealed DP receptor mRNA to be localized in the epithelium of the iris and ciliary body and in photoreceptor cells of the retina, suggesting the involvement of the receptor in the physiological regulation of intraocular pressure and the vision process. In the brain, DP receptor mRNA was dominantly expressed in the leptomeninges and was not detected in the brain parenchyma including the ventral rostral forebrain, the surface area of which is reportedly involved in sleep induction by PGD2.

Platelet-activating factor is a downstream messenger of kainate-induced activation of mitogen-activated protein kinases in primary hippocampal neurons

Excitatory amino acids transduce physiological and pathological signals to neurons. Similarly, the neuroactive lipid platelet-activating factor (PAF) has been implicated in modulating long-term potentiation and neuronal survival. Excitatory amino acids and PAF have been shown to increase mitogen-activated protein (MAP) kinases in different cell types. Here, we have investigated the similarities and differences between PAF and kainate in activating MAP kinases in primary hippocampal neurons in vitro. Extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 kinases were activated by kainate or PAF in hippocampal neurons. This activation was blocked by the receptor antagonists CNQX and BN 50730 for kainate and PAF, respectively. The PAF receptor antagonist BN 50730 also blocked kainate activation. CNQX had no effect on PAF activation of the kinases, indicating that PAF is downstream of kainate activation. Coapplication of submaximal concentrations of PAF and kainate resulted in a less than additive activation, suggesting similar routes of activation by the two agonists. Both CNQX and BN 50730 blocked kainate-induced neurotoxicity. These results indicate that PAF and kainate activate similar kinase pathways. Therefore, PAF acts downstream of the kainate subtype of glutamate receptors, and when excessive receptor activation takes place, this bioactive lipid may contribute to neuronal cell death.

Run-on gene transcription in human neocortical nuclei. Inhibition by nanomolar aluminum and implications for neurodegenerative disease

The incorporation of [alpha-32P]-uridine triphosphate into DNA transcription products was examined in short post-mortem interval (PMI) human brain neocortical nuclei (n, 22; PMI, 0.5-24 h) using run-on-gene transcription. Reverse Northern dot-blot hybridization of newly synthesized RNA against either total cDNA or Alu repetitive DNA indicated that human brain neocortical nuclei of up to 4-h PMI were efficient in incorporating radiolabel into new transcription products, after which there was a graded decline in de novo RNA biosynthetic capacity. To test the effects of 0-3000 nM concentrations of ambient aluminum on RNA polymerase I (RNAP I) and RNA polymerase II (RNAP II) transcription, dot blots containing 0.5, 1.0, 2.0, and 5.0 micrograms of DNA for (1) the human-specific Alu repetitive element (2) the neurofilament light (NFL) chain, and (3) glial fibrillary acidic protein (GFAP) were Northern hybridized against newly synthesized radiolabeled total RNA. These DNAs represent heterogeneous nuclear RNA (hnRNA), neuronal-, and glial-specific markers, respectively. We report here a dose-dependent repression in the biosynthetic capabilities of brain RNAP II in the range of 50-100 nM aluminum, deficits similar to those previously described using a rabbit neocortical nuclei transcription system and at concentrations that have been reported in Alzheimer's disease (AD) euchromatin. Transcription from RNAP II and the neuron-specific NFL gene in the presence of aluminum was found to be particularly affected. These findings support the hypothesis that brain gene transcription in the presence of trace amounts of ambient aluminum impairs mammalian brain DNA to adequately read out genetic information.

KID-1, a protein kinase induced by depolarization in brain

Membrane depolarization leads to changes in gene expression that modulate neuronal plasticity. Using representational difference analysis, we have identified a previously undiscovered cDNA, KID-1 (kinase induced by depolarization), that is induced by membrane depolarization or forskolin, but not by neurotrophins or growth factors, in PC12 pheochromocytoma cells. KID-1 is an immediate early gene that shares a high degree of sequence similarity with the family of PIM-1 serine/threonine protein kinases. Recombinant KID-1 fusion protein is able to catalyze both histone phosphorylation and autophosphorylation. KID-1 mRNA is present in a number of unstimulated tissues, including brain. In response to kainic acid and electroconvulsive shock-induced seizures, KID-1 is induced in specific regions of the hippocampus and cortex.

Budesonide epimer R or dexamethasone selectively inhibit platelet-activating factor-induced or interleukin 1beta-induced DNA binding activity of cis-acting transcription factors and cyclooxygenase-2 gene expression in human epidermal keratinocytes

To further understand the molecular mechanism of glucocorticoid action on gene expression, DNA-binding activities of the cis-acting transcription factors activator protein 1 (AP1), AP2, Egr1 (zif268), NF-kappaB, the signal transducers and activators of transcription proteins gamma interferon activation site (GAS), Sis-inducible element, and the TATA binding protein transcription factor II D (TFIID) were examined in human epidermal keratinocytes. The cytokine interleukin 1beta (IL-1beta) and platelet-activating factor (PAF), both potent mediators of inflammation, were used as triggers for gene expression. Budesonide epimer R (BUDeR) and dexamethasone (DEX) were studied as potential antagonists. BUDeR or DEX before IL-1beta- or PAF-mediated gene induction elicited strong inhibition of AP1-, GAS-, and in particular NF-kappaB-DNA binding (P < 0.001, ANOVA). Only small effects were noted on AP2, Egr1 (zif268), and Sis-inducible element-DNA binding (P > 0.05). No significant effect was noted on the basal transcription factor TFIID recognition of TATA-containing core promoter sequences (P > 0.68). To test the hypothesis that changing cis-acting transcription factor binding activity may be involved in inflammatory-response related gene transcription, RNA message abundance for human cyclooxygenase (COX)-1 and -2 (E.C.1.14.99.1) was assessed in parallel by using reverse transcription-PCR. Although the COX-1 gene was found to be expressed at constitutively low levels, the TATA-containing COX-2 gene, which contains AP1-like, GAS, and NF-kappaB DNA-binding sites in its immediate promoter, was found to be strongly induced by IL-1beta or PAF (P < 0.001). BUDeR and DEX both suppressed COX-2 RNA message generation; however, no correlation was associated with TFIID-DNA binding. These results suggest that on stimulation by mediators of inflammation, although the basal transcription machinery remains intact, modulation of cis-activating transcription factor AP1, GAS, and NF-kappaB-DNA binding by the glucocorticoids BUDeR and DEX play important regulatory roles in the extent of specific promoter activation and hence the expression of key genes involved in the inflammatory response.

Temporal changes in gene expression following cryogenic rat brain injury

Expression of 18 genes was examined at 8 different time points between 1 h and 28 days following cryogenic rat brain injury. The genes include thymidine kinase (TK), p53 tumor suppressor, c-fos, renin, myelin basic protein (MBP), proteolipid protein (PLP), transferrin, transferrin receptor, platelet-derived growth factor A (PDGF A), platelet-derived growth factor B (PDGF B), platelet-derived growth factor receptor alpha (PDGF alpha receptor), platelet-derived growth factor receptor beta (PDGF beta receptor), glial fibrillary acidic protein (GFAP), transforming growth factor-beta 1 (TGF-beta 1), basic fibroblast growth factor (bFGF), fibroblast growth factor receptor-1 (FGF-R1), insulin-like growth factor-1 (IGF-1), and somatostatin. Time courses of gene expression were determined for RNAs derived from hippocampus and cortex. Genes were divided into categories based upon those in which statistically significant changes in expression were first observed at or before 24 h (early genes) and those in which changes were first observed at or after 72 h (late genes). In the present model, many genes demonstrate elevated RNA levels in the cortex prior to hippocampus, following injury. RNAs transcribed from late genes tend to be elevated concurrently in cortex and hippocampus.

Localization of lipocalin-type prostaglandin D synthase (beta-trace) in iris, ciliary body, and eye fluids

PURPOSE

Prostaglandin (PG) D synthase is present in neural tissues and cerebrospinal fluid (beta-trace). This enzyme belongs to the lipocalin family which consists of transporter proteins for lipophilic substances in the extracellular space. PGD synthase is found in retinal pigment epithelium, from where it is secreted into the interphotoreceptor matrix. The authors have undertaken the localization of this unique enzyme within the tissues and spaces of the anterior segment of the eye.

METHODS

Iris, ciliary body, lens, and aqueous and vitreous humors were collected from adult rats and mice. PGD synthase activity was determined, and the protein was quantified by Western blot analysis and localized immunohistochemically. Finally, in situ hybridization was performed to localize PGD synthase mRNA.

RESULTS

PGD synthase was most abundant in the aqueous and vitreous humors. It was less abundant in tissue cytosolic fractions; these fractions had almost 10-fold as much as their corresponding membrane-bound fractions. Lens tissue had the lowest amount observed. PGD synthase was localized to the epithelial cells of the iris and the ciliary body and to the adjacent extracellular chambers, but PGD synthase mRNA was found only within the epithelial cells. Several glycosylated forms of PGD synthase were also detected.

CONCLUSIONS

PGD synthase was synthesized within the epithelial cells of the iris and the ciliary body and was then secreted into the aqueous and vitreous humors, where it accumulated as an active enzyme.

Cyclooxygenase 2 RNA message abundance, stability, and hypervariability in sporadic Alzheimer neocortex

Long-term treatment by nonsteroidal anti-inflammatory drugs has been shown to decrease the incidence of Alzheimer's disease (AD). Both platelet-activating factor and interleukin-1beta, potent mediators of the inflammatory and immune response, strongly induce transcription of the cyclooxygenase-2 (COX-2) gene in brain cells. Using Northern and RT-PCR analysis, we have determined in 15 control and 10 sporadic AD human neocortical samples (age range, 60-82 yr; postmortem interval [PMI] range, 0.7-16.0 hr) the levels of COX-2 RNA in relation to the constitutively expressed COX-1 and beta-actin RNA message levels. Our results indicate that in short PMI brain, COX-1 and COX-2 transcripts are relatively low abundance RNA messages, ranging from a mean of 6.8% of the beta-actin signal in controls to 8.5% of the beta-actin signal in AD-affected brain. A large variation in the signal intensity for COX-2 RNA was noted in both control and AD; although there was a trend for higher COX-2 RNA message abundance in AD neocortex to +11.5% of that of controls, it did not reach statistical significance (ANOVA = 0.45). Several human tissues, including heart, skeletal muscle, lung, kidney, and spinal cord, displayed 4.6- and 2.8-kb COX-2 RNA message isoforms; however, the 4.6-kb COX-2 RNA predominated in the hippocampus and association neocortex. COX-2 RNA message was found to be degraded at similar rates in both control and AD tissues, and a strong positive correlation between the PMI and the intensity of the COX-2 RNA signal was noted (ANOVA = 0.006). Linear regression analysis indicated that the 4.6-kb COX-2 RNA is an unstable short-lived RNA species with a half-life of not more than 3.5 hr, a feature characteristic of immediate early gene transcripts. Individual hypervariability in COX-2 RNA message abundance may reflect various degrees of expression of AD-related inflammatory processes.