Immunostimulatory CpG-DNA activates murine microglia

Bacterial DNA containing motifs of unmethylated CpG dinucleotides (CpG-DNA) triggers innate immune cells through the pattern recognition receptor Toll-like receptor 9 (TLR-9). CpG-DNA possesses potent immunostimulatory effects on macrophages, dendritic cells, and B lymphocytes. Therefore, CpG-DNA contributes to inflammation during the course of bacterial infections. In contrast to other TLR-dependent microbial patterns, CpG-DNA is a strong inductor of IL-12. Thus, it acts as a Th1-polarizing agent that can be utilized as potent vaccine adjuvant. To assess the role of CpG-DNA in immune reactions in the CNS, we analyzed the effects of CpG-DNA on microglial cells in vitro and in vivo. Primary microglial cells as well as microglial cell lines express TLR-9 mRNA. Consequently, CpG-DNA activated microglial cells in vitro and induced TNF-alpha, IL-12p40, IL-12p70, and NO. Furthermore, MHC class II, B7-1, B7-2, and CD40 molecules were up-regulated. In addition, phagocytic activity of microglia was enhanced. After intracerebroventricular injection of CpG-DNA, microglial cells were activated and produced TNF-alpha and IL-12p40 transcripts, as shown by in situ hybridization. These results indicate that microglia is sensitive to CpG-DNA. Thus, bacterial DNA containing CpG motifs could not only play an important role during infections of the CNS, but also might trigger and sustain Th1-dominated immunopathogenic reactions.

Borna disease virus-induced accumulation of macrophage migration inhibitory factor in rat brain astrocytes is associated with inhibition of macrophage infiltration

To test the hypothesis that macrophage migration inhibitory factor (MIF) plays a role in macrophage invasion during virus-induced encephalitis, we analyzed the expression and cellular localization of MIF in the Borna disease virus (BDV)-infected rat brain, monitored monocyte/macrophage infiltration, and evaluated the influence of anti-inflammatory treatment with dexamethasone. MIF mRNA expression was restricted to neurons and remained unchanged after BDV infection or after dexamethasone treatment of either BDV-infected or uninfected control rats. In contrast, MIF protein immunoreactivity (ir) was not only seen in neurons but also in glia. After BDV-induced encephalitis and treatment of uninfected rats with dexamethasone, MIF ir was only slightly altered in neurons but moderately enhanced in tanycytes, ependyma, and choroid plexus epithelium and markedly increased or induced in astrocyte end-feet at the blood-brain barrier (BBB). The increase in MIF ir in astrocytes after BDV infection was blocked by dexamethasone. The induction or enhancement of MIF ir at the BBB significantly correlated with reduced numbers of infiltrating ED1-positive monocytes/macrophages after BDV infection. Increased macrophage invasion was observed in regions where no astrocytic MIF was detected. The BDV- or dexamethasone-induced accumulation of MIF protein in astrocytes in vivo in absence of detectable astrocytic MIF mRNA expression is most likely due to MIF translocation from neurons rather than to a constitutive or induced MIF mRNA expression in astrocytes. In conclusion, we provide evidence that translocation of MIF from neurons or other extracellular sources into astrocytes is likely to modulate the inflammatory process during the course of virus-induced encephalitis by limiting monocyte/macrophage migration through the BBB.

Pituitary adenylate cyclase-activating polypeptide is a sympathoadrenal neurotransmitter involved in catecholamine regulation and glucohomeostasis

The adrenal gland is important for homeostatic responses to metabolic stress: hypoglycemia stimulates the splanchnic nerve, epinephrine is released from adrenomedullary chromaffin cells, and compensatory glucogenesis ensues. Acetylcholine is the primary neurotransmitter mediating catecholamine secretion from the adrenal medulla. Accumulating evidence suggests that a secretin-related neuropeptide also may function as a transmitter at the adrenomedullary synapse. Costaining with highly specific antibodies against the secretin-related neuropeptide pituitary adenylate cyclase-activating peptide (PACAP) and the vesicular acetylcholine transporter (VAChT) revealed that PACAP is found in nerve terminals at all mouse adrenomedullary cholinergic synapses. Mice with a targeted deletion of the PACAP gene had otherwise normal cholinergic innervation and morphology of the adrenal medulla, normal adrenal catecholamine and blood glucose levels, and an intact initial catecholamine secretory response to insulin-induced hypoglycemia. However, insulin-induced hypoglycemia was more profound and longer-lasting in PACAP knock-outs, and was associated with a dose-related lethality absent in wild-type mice. Failure of PACAP-deficient mice to adequately counterregulate plasma glucose levels could be accounted for by impaired long-term secretion of epinephrine, secondary to a lack of induction of tyrosine hydroxylase, normally occurring after insulin hypoglycemia in wild-type mice, and a consequent depletion of adrenomedullary epinephrine stores. Thus, PACAP is needed to couple epinephrine biosynthesis to secretion during metabolic stress. PACAP appears to function as an "emergency response" cotransmitter in the sympathoadrenal axis, where the primary secretory response is controlled by a classical neurotransmitter but sustained under paraphysiological conditions by a neuropeptide.

Identification of the differentiation-associated Na+/PI transporter as a novel vesicular glutamate transporter expressed in a distinct set of glutamatergic synapses

Glutamate transport into synaptic vesicles is a prerequisite for its regulated neurosecretion. Here we functionally identify a second isoform of the vesicular glutamate transporter (VGLUT2) that was previously identified as a plasma membrane Na+-dependent inorganic phosphate transporter (differentiation-associated Na+/P(I) transporter). Studies using intracellular vesicles from transiently transfected PC12 cells indicate that uptake by VGLUT2 is highly selective for glutamate, is H+ dependent, and requires Cl- ion. Both the vesicular membrane potential (Deltapsi) and the proton gradient (DeltapH) are important driving forces for vesicular glutamate accumulation under physiological Cl- concentrations. Using an antibody specific for VGLUT2, we also find that this protein is enriched on synaptic vesicles and selective for a distinct class of glutamatergic nerve terminals. The pathway-specific, complementary expression of two different vesicular glutamate transporters suggests functional diversity in the regulation of vesicular release at excitatory synapses. Together, the two isoforms may account for the uptake of glutamate by synaptic vesicles from all central glutamatergic neurons.

Effect of repeated treatment with high doses of selegiline on behaviour, striatal dopaminergic transmission and tyrosine hydroxylase mRNA levels

The anti-parkinsonian drug selegiline is a monoamine oxidase B (MAO-B) inhibitor and a potential neuroprotective agent which facilitates dopaminergic transmission. Its metabolites (-)-amphetamine and (-)-metamphetamine might contribute to the pharmacological effects as they are also able to increase dopaminergic transmission and in addition might lead to behavioural sensitization after repeated administration. We investigated the effects of acute and repeated treatment with a high dose of selegiline on dopamine overflow in the striatum as well as on behaviour and on tyrosine hydroxylase (TH) mRNA levels in midbrain. Two experiments were performed. In the first one, rats were implanted with microdialysis probes into the striatum and received daily injections of selegiline (10 mg/kg, i.p.) for 1 or 8 days or a single dose of saline. In vivo microdialysis was carried out on days 1, 8 or 17 (after withdrawal of 9 days) to measure dopamine overflow. Motility was measured at the same time. In the second experiment, rats were injected daily with selegiline (10 mg/kg, i.p.) or saline over a time period of 6 weeks or only once before the brains were processed for in situ hybridization with a (35)S-radiolabelled probe for TH. Repeated treatment led to higher levels in motility scores than acute administration after administration of the same dose, indicating behavioural sensitization, which was still manifest after an interruption of 9 days in the supply of selegiline. In contrast, acute administration of selegiline increased dopamine levels to a similar degree as the same dose after subchronic treatment, with or without interruption of 9 days. The dopamine metabolite DOPAC was reduced by more than 50% after acute administration of selegiline and even more so on day 8 by the same dose, after repeated administration. The basal concentrations of dopamine (before challenge with selegiline) were not altered by the repeated administration, whereas the basal concentrations of DOPAC were decreased by more than 80% by the repeated administration of selegiline, suggesting a decrease in dopamine turnover. Acute administration did not have any influence on TH mRNA levels, whereas chronic treatment significantly reduced TH mRNA levels in substantia nigra and ventral tegmental area. In conclusion, repeated administration of selegiline leads to behavioural sensitization independent of altered dopamine levels. In addition, it leads to a decrease, probably due to a down-regulation, of dopamine turnover and tyrosine hydroxylase.

Overexpression of cytochrome C by a recombinant rabies virus attenuates pathogenicity and enhances antiviral immunity

The pathogenicity of individual rabies virus strains appears to correlate inversely with the extent of apoptotic cell death they induce and with the expression of rabies virus glycoprotein, a major inducer of an antiviral immune response. To determine whether the induction of apoptosis by rabies virus contributes to a decreased pathogenicity by stimulating antiviral immunity, we have analyzed these parameters in tissue cultures and in mice infected with a recombinant rabies virus construct that expresses the proapoptotic protein cytochrome c. The extent of apoptosis was strongly increased in primary neuron cultures infected with the recombinant virus carrying the active cytochrome c gene [SPBN-Cyto c(+)], compared with cells infected with the recombinant virus containing the inactive cytochrome c gene [SPBN-Cyto c(-)]. Mortality in mice infected intranasally with SPBN-Cyto c(+) was substantially lower than in SPBN-Cyto c(-)-infected mice. Furthermore, virus-neutralizing antibody (VNA) titers were significantly higher in mice immunized with SPBN-Cyto c(+) at the same dose. The VNA titers induced by these recombinant viruses paralleled their protective activities against a lethal rabies virus challenge infection, with SPBN-Cyto c(+) revealing an effective dose 20 times lower than that of SPBN-Cyto c(-). The strong increase in immunogenicity, coupled with the marked reduction in pathogenicity, identifies the SPBN-Cyto c(+) construct as a candidate for a live rabies virus vaccine.

The central nervous system inflammatory response to neurotropic virus infection is peroxynitrite dependent

We have recently demonstrated that increased blood-CNS barrier permeability and CNS inflammation in a conventional mouse model of experimental allergic encephalomyelitis are dependent upon the production of peroxynitrite (ONOO(-)), a product of the free radicals NO* and superoxide (O2*(-)). To determine whether this is a reflection of the physiological contribution of ONOO(-) to an immune response against a neurotropic pathogen, we have assessed the effects on adult rats acutely infected with Borna disease virus (BDV) of administration of uric acid (UA), an inhibitor of select chemical reactions associated with ONOO(-). The pathogenesis of acute Borna disease in immunocompetent adult rats results from the immune response to the neurotropic BDV, rather than the direct effects of BDV infection of neurons. An important stage in the BDV-specific neuroimmune response is the invasion of inflammatory cells into the CNS. UA treatment inhibited the onset of clinical disease, and prevented the elevated blood-brain barrier permeability as well as CNS inflammation seen in control-treated BDV-infected rats. The replication and spread of BDV in the CNS were unchanged by the administration of UA, and only minimal effects on the immune response to BDV Ags were observed. These results indicate that the CNS inflammatory response to neurotropic virus infection is likely to be dependent upon the activity of ONOO(-) or its products on the blood-brain barrier.

Independent patterns of transcription for the products of the rat cholinergic gene locus

The cholinergic phenotype requires the expression of the vesicular acetylcholine transporter and choline acetyltransferase proteins. Both genes are encoded at one chromosomal location called the cholinergic gene locus. We have identified by in situ hybridization histochemistry distinct patterns of transcription from the cholinergic gene locus in the subdivisions of the rat cholinergic nervous system. The vesicular acetylcholine transporter and choline acetyltransferase are co-expressed in cholinergic neurons at all developmental stages in all major types of cholinergic neurons. The relative levels of vesicular acetylcholine transporter and choline acetyltransferase transcripts, however, change substantially during development in the CNS. They also differ dramatically in distinct subdivisions of the mature cholinergic nervous system, with vesicular acetylcholine transporter mRNA expressed at high levels relative to choline acetyltransferase mRNA in the peripheral nervous system, but at equivalent levels in the CNS. Expression of the R-exon, the presumptive first non-coding exon common to both the vesicular acetylcholine transporter and choline acetyltransferase, was not detectable at any developmental stage in any of the cholinergic neuronal subtypes in the rat nervous system. Thus, in contrast to less complex metazoan organisms, production of the vesicular acetylcholine transporter and choline acetyltransferase via a common differentially spliced transcript does not seem to occur to a significant extent in the rat. We suggest that separate transcriptional start sites within the cholinergic gene locus control vesicular acetylcholine transporter and choline acetyltransferase transcription, while additional elements are responsible for the specific transcriptional control of the entire locus in cholinergic versus non-cholinergic neurons. Independent transcription of the vesicular acetylcholine transporter and choline acetyltransferase genes provides a mechanism for regulating the relative expression of these two proteins to fine-tune acetylcholine quantal size in different types of cholinergic neurons, both centrally and peripherally.

Effects of antidepressant drugs on the behavioral and physiological responses to lipopolysaccharide (LPS) in rodents

Antidepressants produce various immunomodulatory effects, as well as an attenuation of the behavioral responses to immune challenges, such as lipopolysaccharide (LPS). To explore further the effects of antidepressants on neuroimmune interactions, rats were treated daily with either fluoxetine (Prozac) or saline for 5 weeks, and various behavioral, neuroendocrine, and immune functions were measured following administration of either LPS or saline. Chronic fluoxetine treatment significantly attenuated the anorexia and body weight loss, as well as the depletion of CRH-41 from the median eminence and the elevation in serum corticosterone levels induced by LPS. Chronic treatment with imipramine also attenuated LPS-induced adrenocortical activation. In rats and in mice, which normally display a biphasic body temperature response to LPS (initial hypothermia followed by hyperthermia), chronic treatment with fluoxetine completely abolished the hypothermic response and facilitated and strengthened the hyperthermic response. The effects of antidepressants on the responsiveness to LPS are probably not mediated by their effects on peripheral proinflammatory cytokine production, because LPS-induced expression of TNFalpha and IL-1beta mRNA in the spleen (assessed by semiquantitative in situ hybridization) was not altered following chronic treatment with either fluoxetine or imipramine. The effects of antidepressants on the acute phase response may have important clinical implications for the psychiatric and neuroendocrine disturbances that are commonly associated with various medical conditions.

Sensitization to the behavioural effects of cocaine: alterations in tyrosine hydroxylase or endogenous opioid mRNAs are not necessarily involved

After repeated administration of cocaine at intervals, sensitization phenomena can be observed, so that its behavioural effects are enhanced. Since this phenomenon is long-lasting, it was of interest to study which persistent alterations in the activity of dopaminergic neurones or of endogenous opioid systems downstream of dopaminergic synapses in the basal ganglia are involved in the sensitization. Cocaine (10 mg/kg i.p.) was administered to rats on days 1, 3, 5 and 7 and saline on days 2, 4 and 6 ("repeated cocaine"), or saline was injected on days 1-6 and cocaine on day 7 ("acute cocaine"), or saline was injected on days 1-7 ("saline group"). The "repeated cocaine" schedule led to a significant sensitization to the locomotor activation produced by cocaine on day 7 or on day 17, 10 days after the end of sensitization protocol. Microdialysis in the nucleus accumbens which was performed after administration of cocaine (10 mg/kg i.p.) on day 7, or after an administration of the same dose 10 days after the last administration of cocaine, respectively, revealed significant acute increases of extracellular dopamine to about 200% of basal values. These increases were similar in "acute cocaine" and in "repeated cocaine" animals both after 7 days and after 17 days. For in situ hybridization studies, rats were sacrificed on day 7, 4.5 h after the last cocaine or saline administration. The mRNA for tyrosine hydroxylase (TH) in substantia nigra + ventral tegmental area was significantly elevated to about 140% of saline controls both in the "repeated cocaine" and the "acute cocaine" group as compared with the "saline group". In contrast, there were no differences between the three groups in the mRNAs of preprodynorphin or preproenkephalin levels measured in the nucleus accumbens (core and shell). These results suggest that sensitization phenomena to cocaine are not necessarily connected with alterations in the dopaminergic activity in the mesolimbic system or in the transcription of precursors of endogenous opioid peptides which are located downstream of the dopaminergic synapses.

Adaptive plasticity in tachykinin and tachykinin receptor expression after focal cerebral ischemia is differentially linked to gabaergic and glutamatergic cerebrocortical circuits and cerebrovenular endothelium

To test the hypothesis of an involvement of tachykinins in destabilization and hyperexcitation of neuronal circuits, gliosis, and neuroinflammation during cerebral ischemia, we investigated cell-specific expressional changes of the genes encoding substance P (SP), neurokinin B (NKB), and the tachykinin/neurokinin receptors (NK1, NK2, and NK3) after middle cerebral artery occlusion (MCAO) in the rat. Our analysis by quantitative in situ hybridization, immunohistochemistry, and confocal microscopy was concentrated on cerebrocortical areas that survive primary infarction but undergo secondary damage. Here, SP-encoding preprotachykinin-A and NK1 mRNA levels and SP-like immunoreactivity were transiently increased in GABAergic interneurons at 2 d after MCAO. Coincidently, MCAO caused a marked expression of SP and NK1 in a subpopulation of glutamatergic pyramidal cells, and in some neurons SP and NK1 mRNAs were coinduced. Elevated levels of the NKB-encoding preprotachykinin-B mRNA and of NKB-like immunoreactivity at 2 and 7 d after MCAO were confined to GABAergic interneurons. In parallel, the expression of NK3 was markedly downregulated in pyramidal neurons. MCAO caused transient NK1 expression in activated cerebrovenular endothelium within and adjacent to the infarct. NK1 expression was absent from activated astroglia or microglia. The differential ischemia-induced plasticity of the tachykinin system in distinct inhibitory and excitatory cerebrocortical circuits suggests that it may be involved in the balance of endogenous neuroprotection and neurotoxicity by enhancing GABAergic inhibitory circuits or by facilitating glutamate-mediated hyperexcitability. The transient induction of NK1 in cerebrovenular endothelium may contribute to ischemia-induced edema and leukocyte diapedesis. Brain tachykinin receptors are proposed as potential drug targets in stroke.

Chemical neuroanatomy of the vesicular amine transporters

Acetylcholine, catecholamines, serotonin, and histamine are classical neurotransmitters. These small molecules also play important roles in the endocrine and immune/inflammatory systems. Serotonin secreted from enterochromaffin cells of the gut epithelium regulates gut motility; histamine secreted from basophils and mast cells is a major regulator of vascular permeability and skin inflammatory responses; epinephrine is a classical hormone released from the adrenal medulla. Each of these molecules is released from neural, endocrine, or immune/inflammatory cells only in response to specific physiological stimuli. Regulated secretion is possible because amines are stored in secretory vesicles and released via a stimulus-dependent exocytotic event. Amine storage-at concentrations orders of magnitude higher than in the cytoplasm-is accomplished in turn by specific secretory vesicle transporters that recognize the amines and move them from the cytosol into the vesicle. Immunohistochemical visualization of specific vesicular amine transporters (VATs) in neuronal, endocrine, and inflammatory cells provides important new information about how amine-handling cell phenotypes arise during development and how vesicular transport is regulated during homeostatic response events. Comparison of the chemical neuroanatomy of VATs and amine biosynthetic enzymes has also revealed cell groups that express vesicular transporters but not enzymes for monoamine synthesis, and vice versa: their function and regulation is a new topic of investigation in mammalian neurobiology. The chemical neuroanatomy of the vesicular amine transporters is reviewed here. These and similar data emerging from the study of the localization of the recently characterized vesicular inhibitory and excitatory amino acid transporters will contribute to understanding chemically coded synaptic circuitry in the brain, and amine-handling neuroendocrine and immune/inflammatory cell regulation.

Localization of xenin-immunoreactive cells in the duodenal mucosa of humans and various mammals

Xenin is a 25-amino-acid peptide extractable from mammalian tissue. This peptide is biologically active. It stimulates exocrine pancreatic secretion and intestinal motility and inhibits gastric secretion of acid and food intake. Xenin circulates in the human plasma after meals. In this study, the cellular origin of xenin in the gastro-entero-pancreatic system of humans, Rhesus monkeys, and dogs was investigated by immunohistochemistry and immunoelectron microscopy. Sequence-specific antibodies against xenin detected specific endocrine cells in the duodenal and jejunal mucosa of all three species. These xenin-immunoreactive cells were distinct from enterochromaffin, somatostatin, motilin, cholecystokinin, neurotensin, and secretin cells, and comprised 8.8% of the chromogranin A-positive cells in the dog duodenum and 4.6% of the chromogranin A-positive cells in human duodenum. In all three species, co-localization of xenin was found with a subpopulation of gastric inhibitory polypeptide (GIP)-immunoreactive cells. Immunoelectron microscopy in the canine duodenal mucosa demonstrated accumulation of gold particles in round, homogeneous, and osmiophilic secretory granules with a closely adhering membrane of 187 +/- 19 nm diameter (mean +/- SEM). This cell type was found to be identical to the previously described canine GIP cell. Immunocytochemical expression of the peptide xenin in a subpopulation of chromogranin A-positive cells as well as the localization of xenin immunoreactivity in ultrastructurally characterized secretory granules permitted the identification of a novel endocrine cell type as the cellular source of circulating xenin.

Somatomotor neuron-specific expression of the human cholinergic gene locus in transgenic mice

We examined the expression pattern of the vesicular acetylcholine transporter in the mouse nervous system, using rodent-specific riboprobes and antibodies, prior to comparing it with the distribution of vesicular acetylcholine transporter expressed from a human transgene in the mouse, using riboprobes and antibodies specific for human. Endogenous vesicular acetylcholine transporter expression was high in spinal and brainstem somatomotor neurons, vagal visceromotor neurons, and postganglionic parasympathetic neurons, moderate in basal forebrain and brainstem projection neurons and striatal interneurons, and low in intestinal intrinsic neurons. Vesicular acetylcholine transporter expression in intrinsic cortical neurons was restricted to the entorhinal cortex. The sequence of the mouse cholinergic gene locus to 5.1kb upstream of the start of transcription of the vesicular acetylcholine transporter gene was determined and compared with the corresponding region of the human gene. Cis-regulatory domains implicated previously in human or rat cholinergic gene regulation are highly conserved in mouse, indicating their probable relevance to the regulation of the mammalian cholinergic gene locus in vivo. Mouse lines were established containing a human transgene that included the vesicular acetylcholine transporter gene and sequences spanning 5kb upstream and 1.8kb downstream of the vesicular acetylcholine transporter open reading frame. In this transgene, the intact human vesicular acetylcholine transporter was able to act as its own reporter. This allowed elements within the vesicular acetylcholine transporter open reading frame itself, shown previously to affect transcription in vitro, to be assessed in vivo with antibodies and riboprobes that reliably distinguished between human and mouse vesicular acetylcholine transporters and their messenger RNAs. Expression of the human vesicular acetylcholine transporter was restricted to mouse cholinergic somatomotor neurons in the spinal cord and brainstem, but absent from other central and peripheral cholinergic neurons. The mouse appears to be an appropriate model for the study of the genetic regulation of the cholinergic gene locus, and the physiology and neurochemistry of the mammalian cholinergic nervous system, although differences exist in the distribution of cortical cholinergic neurons between the mouse and other mammals. The somatomotor neuron-specific expression pattern of the transgenic human vesicular acetylcholine transporter suggests a mosaic model for cholinergic gene locus regulation in separate subdivisions of the mammalian cholinergic nervous system.

Complement C1q is dramatically up-regulated in brain microglia in response to transient global cerebral ischemia

Recent evidence suggests that the pathophysiology of neurodegenerative and inflammatory neurological diseases has a neuroimmunological component involving complement, an innate humoral immune defense system. The present study demonstrates the effects of experimentally induced global ischemia on the biosynthesis of C1q, the recognition subcomponent of the classical complement activation pathway, in the CNS. Using semiquantitative in situ hybridization, immunohistochemistry, and confocal laser scanning microscopy, a dramatic and widespread increase of C1q biosynthesis in rat brain microglia (but not in astrocytes or neurons) within 24 h after the ischemic insult was observed. A marked increase of C1q functional activity in cerebrospinal fluid taken 1, 24, and 72 h after the ischemic insult was determined by C1q-dependent hemolytic assay. In the light of the well-established role of complement and complement activation products in the initiation and maintenance of inflammation, the ischemia-induced increase of cerebral C1q biosynthesis and of C1q functional activity in the cerebrospinal fluid implies that the proinflammatory activities of locally produced complement are likely to contribute to the pathophysiology of cerebral ischemia. Pharmacological modulation of complement activation in the brain may be a therapeutic target in the treatment of stroke.

Expression of vesicular monoamine transporters in endocrine hyperplasia and endocrine tumors of the oxyntic stomach

BACKGROUND

Gastric enterochromaffin-like (ECL) cells selectively express the vesicular monoamine transporter (VMAT) VMAT2, and enterochromaffin (EC) cells the VMAT1 isoform.

AIMS

We investigated whether VMAT isoform selection indicates the origin of endocrine hyperplasia and neoplasia from oxyntic ECL or EC cells and may be of prognostic significance in different types of gastric carcinoids.

METHODS

Tissue from patients with chronic atrophic gastritis (CAG), Zollinger-Ellison-syndrome (ZES), gastric carcinoids and neuroendocrine carcinoma (NEC) was investigated by immunohistology and in situ hybridization.

RESULTS

Endocrine cells forming diffuse, linear, and micronodular hyperplasia in CAG and ZES, as well as oxyntic microcarcinoids expressed both VMAT2 and chromogranin A (CgA) but neither VMAT1 nor serotonin. In five of six sporadic carcinoids VMAT2 and CgA but not VMAT1 were detected. One carcinoid was copositive for VMAT1 and serotonin but negative for VMAT2. Electron microscopy confirmed the VMAT2-positive tumors as ECLoma and the VMAT1-immunoreactive carcinoid as EComa.

CONCLUSIONS

VMAT2 and VMAT1 are reliable markers for differentiation of gastric endocrine hyperplasia and neoplasia from ECL and EC cells, respectively. The significance of VMAT2 and VMAT1 as prognostic markers lies in the relatively poor prognosis for EComa compared to ECLoma, characterized by VMAT2 positivity. The absence of both VMAT2 and VMAT1 in NEC may indicate poor prognosis.

Calcitonin gene-related peptide gene expression in collagen-induced arthritis is differentially regulated in primary afferents and motoneurons: influence of glucocorticoids

Calcitonin gene-related peptide is involved in peripheral and spinal mechanisms of inflammatory pain. In this paper, we used collagen II-induced arthritis in the rat as a model to investigate the influence of chronic arthritic pain on calcitonin gene-related peptide gene expression in sensory and motor pathways. Additionally, we examined the effect of the glucocorticoid drug budesonide on arthritis-induced changes of calcitonin gene-related peptide expression and constitutive calcitonin gene-related peptide expression. Thirteen days after the immunization with native rat collagen type II rats developed a progressive and chronic polyarthritis which was scored with respect to the degree of swelling and/or redness of the paw and ankle joints. Budesonide significantly attenuated the extent of arthritis. Changes in calcitonin gene-related peptide expression were evaluated by semiquantitative in situ hybridization and immunocytochemistry on day 21 post-immunization. In sensory neurons of dorsal root ganglia of arthritic rats, a significant increase in calcitonin gene-related peptide messenger RNA and protein levels was seen. These increases were completely blocked by budesonide. Also in dorsal root ganglia of non-arthritic rats, budesonide had an effect, with reduced calcitonin gene-related peptide messenger RNA levels below constitutive concentrations. Image analysis of calcitonin gene-related peptide immunoreactivity revealed that changes in calcitonin gene-related peptide expression were due to alterations in calcitonin gene-related peptide expression levels rather than to de novo synthesis or changes in the numbers of calcitonin gene-related peptide expressing neurons. In spinal motoneurons of arthritic rats, marked decreases in calcitonin gene-related peptide messenger RNA and protein levels were measured. These reductions were attenuated by budesonide. The changes in calcitonin gene-related peptide expression in motoneurons correlated with the severity of arthritis in the ipsilateral hind paw. Budesonide had no effects on calcitonin gene-related peptide messenger RNA levels in motoneurons of non-arthritic rats. The opposite regulation of calcitonin gene-related peptide gene expression in primary sensory and spinal somatomotor pathways in collagen-induced arthritis suggests that calcitonin gene-related peptide plays a specific role in both chronic inflammatory pain and arthritis-induced motor dysfunction. The sensitivity of constitutive and inflammation-induced sensory calcitonin gene-related peptide expression to budesonide treatment may indicate that the beneficial effects of steroid treatment in inflammation is partly mediated by down-regulation of calcitonin gene-related peptide in sensory neurons involved in neurogenic inflammation.

Clenbuterol induces growth factor mRNA, activates astrocytes, and protects rat brain tissue against ischemic damage

The induction of growth factor synthesis in brain tissue by beta2-adrenoceptor agonists, such as clenbuterol, is a promising approach to protect brain tissue from ischemic damage. Clenbuterol (0.01-0.5 mg/kg) reduced the cortical infarct volume in Long-Evans rats as measured 7 days after permanent occlusion of the middle cerebral artery. Dosages of clenbuterol higher than 1 mg/kg showed no cerebroprotective effect due to a decrease in blood pressure and an increase in plasma glucose level. The increase in the mRNA level of nerve growth factor (NGF), basic fibroblast growth factor (basic FGF), and transforming growth factor-beta1 (TGF-beta1) mRNA in cortical and hippocampal tissue occurred earlier after middle cerebral artery occlusion and was more pronounced in animals treated with clenbuterol than in controls. In addition, glial fibrillary acidic protein (GFAP) mRNA expression was enhanced in astrocytes 6 h after ischemia in clenbuterol-treated animals. The results suggest that growth factor synthesis is enhanced in activated astrocytes and that this could be the mechanism of clenbuterol-induced cerebroprotection after ischemia.

Neuroimmune appendicitis

BACKGROUND

15-25% of appendices removed from patients with suspected appendicitis appear normal on histological examination. The cause of pain in such patients is unknown. Since the content of neuropeptides seems to be altered in chronic inflammation, we investigated possible changes in peptidergic innervation for substance P (SP), vasoactive intestinal peptide (VIP), and growth-associated protein-43 (GAP-43).

METHODS

Appendices classified as showing acute appendicitis, non-acute appendicitis (clinical signs of acute appendicitis, but histologically not inflamed), or normal were processed for SP, VIP, and GAP-43 immunocytochemistry. The density of SP immunostaining was assessed by digitised morphometry.

FINDINGS

31 appendix specimens were studied (16 acute, 15 non-acute). 16 specimens were used as controls. Expression of GAP-43 was increased in the non-acute appendices. We observed larger amounts of SP-immunoreactive and VIP-immunoreactive nerves in the mucosal layer of the appendix in patients with non-acute appendicitis than in controls and patients with acute appendicitis (mean % area SP-immunoreactive 0.0496 [SD 0.0113] non-acute, 0.0221 [0.0049] acute, 0.0229 [0.0068] controls). In addition, a close spatial relation between SP-immunoreactive and VIP-immunoreactive nerve fibres and lymphoid cells was detected in the outer zone of lymph follicles.

INTERPRETATION

Neuroproliferation in the appendix, in association with an increase in neurotransmitters SP and VIP, may be involved in the pathophysiology of acute right abdominal pain in the absence of an acute inflammation of the appendix. Our data, together with increasing knowledge about the way in which the nervous system and immune cells interact, suggest that neuroimmune appendicitis is a distinct pathological entity.

Increased expression of nitric oxide synthase and dendritic injury in simian immunodeficiency virus encephalitis

OBJECTIVES

Widespread dendritic injury may be one mechanism involved in the neurologic impairment that occurs in HIV-1 infection. The objectives of this study were to quantitate the extent of dendritic injury in a primate model of central nervous system (CNS) infection, investigate the role of nitric oxide (NO) as a mediator of neuropathologic changes, and evaluate the relation of these changes to cognitive and motor function.

STUDY DESIGN/METHODS

Cognitive and motor function was assessed in rhesus macaque monkeys infected with simian immunodeficiency virus (SIV). In situ hybridization, immunohistochemistry, and quantitative image analysis were employed to assess the relations among productive infection, NO synthase (iNOS), and dendritic injury.

RESULTS

Productive infection of cells of the macrophage lineage in CNS is associated with inflammation, increased expression of iNOS, and dendritic injury. The tests of cognitive and motor function employed were abnormal in both animals that had evidence of productive infection and those that did not.

CONCLUSIONS

Increased NO accompanying productive infection and encephalitis may be one cause of neuronal injury in lentivirus infections of the CNS. Extension of tests of cognitive and motor function to late-stage AIDS in rhesus monkeys is needed to assess the potential role of NO-induced dendritic damage in lentiviral encephalopathy/AIDS dementia complex.

Upregulation of COX-2 and CGRP expression in resident cells of the Borna disease virus-infected brain is dependent upon inflammation

Infection of immunocompetent adult rats with Borna disease virus (BDV) causes severe encephalitis and neural dysfunction. The expression of COX-2 and CGRP, genes previously shown to be implicated in CNS disease and peripheral inflammation, was dramatically upregulated in the cortical neurons of acutely BDV-infected rats. Neuronal COX-2 and CGRP upregulation was predominantly seen in brain areas where ED1-positive macrophages/microglia accumulated. In addition, COX-2 expression was strongly induced in brain endothelial cells and the number of COX-2 immunoreactive microglial cells was increased. In contrast, despite increased expression of viral antigens, neither COX-2 nor CGRP expression was altered in the CNS of BDV-infected rats treated with dexamethasone, or tolerant to BDV. Thus, increased CGRP and COX-2 expression in the BDV-infected brain is the result of the inflammatory response and likely to be involved in the pathogenesis of virus-induced encephalitis.

Innervation of the fibro-elastic type of the penis: an immunohistochemical study in the male pig

The occurrence and colocalization of several biologically active neuropeptides, catecholamine-, acetylcholine- or nitric oxide-synthesizing enzymes-tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (D beta H), choline acetyl-transferase (ChAT) and nitric oxide synthase (NOS I), respectively, as well as the vesicular acetylcholine transporter (VAChT) were investigated in the penile glans (GP), corpus and crura (CP), as well as in the retractor penis muscle (RPM) of juvenile and adult boars. Immunohistochemistry revealed that nerves immunoreactive (IR) to TH, D beta H, vasoactive intestinal polypeptide (VIP) and somatostatin (SOM) were the most numerous, followed (in decreasing order of density) by nerves IR to NOS, neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP), galanin (GAL), Leu5-enkephalin (LENK) and ChAT/VAChT. The CP contained the largest number of nerve fibres followed by the RPM, GP and corpus. Enzyme/peptide-containing nerves were associated with both the vascular and non-vascular penile structures. However, differences existed for their density and intrapenile distribution. Nerve terminals IR for different combinations of VIP, GAL or SOM were more frequent than those IR for NOS or CGRP in the non-vascular penile structures while the vasculature and the RPM received a prominent TH/D beta H-, VIP-, SOM- or NOS-IR nerve input. The present data indicate that the porcine penis receives nerve fibres that exhibit diverse chemical codes and that differences in the chemical coding of the nerve fibres may depend on their penile target-structure.

Neuronal expression of fractalkine in the presence and absence of inflammation

Fractalkine is the only as yet known member of a novel class of chemokines. Besides its novel Cys-X-X-X-Cys motif, fractalkine exhibits features which have not been described for any other member of the chemokine family, including its unusual size (397 amino acids human, 395 mouse) and the possession of a transmembrane anchor, from which a soluble form may be released by extracellular cleavage. This report demonstrates the abundant mRNA and fractalkine protein expression in neuronal cells. The neuronal expression of fractalkine mRNA is unaffected by experimentally induced inflammation of central nervous tissue.