A primary canine and an impacted permanent canine with infection potentially induced an intracranial abscess

Intracranial abscess is a rare but life-threatening disease. There have been no reports on intracranial abscess induced by the residual primary tooth and the impacted successive permanent tooth with infection. We report on an interesting case of a 29-year-old man suffering from an epidural abscess, potentially caused by an infection of the residual primary maxillary right canine and the impacted permanent maxillary right canine. The patient recovered completely after prolonged antibiotic treatment and extraction of both of the suspected teeth. Fusobacterium sp. was isolated from the culture of a peripheral blood sample. This case alerts us to realize that the lack of suitable and timely intervention in oral conditions might produce a harmful effect on general health.

Invasive Streptococcus mutans induces inflammatory cytokine production in human aortic endothelial cells via regulation of intracellular toll-like receptor 2 and nucleotide-binding oligomerization domain 2

Streptococcus mutans, the primary etiologic agent of dental caries, can gain access to the bloodstream and has been associated with cardiovascular disease. However, the roles of S. mutans in inflammation in cardiovascular disease remain unclear. The aim of this study was to examine cytokine production induced by S. mutans in human aortic endothelial cells (HAECs) and to evaluate the participation of toll-like receptors (TLRs) and cytoplasmic nucleotide-binding oligomerization domain (NOD) -like receptors in HAECs. Cytokine production by HAECs was determined using enzyme-linked immunosorbent assays, and the expression of TLRs and NOD-like receptors was evaluated by real-time polymerase chain reaction, flow cytometry and immunocytochemistry. The involvement of TLR2 and NOD2 in cytokine production by invaded HAECs was examined using RNA interference. The invasion efficiencies of S. mutans strains were evaluated by means of antibiotic protection assays. Five of six strains of S. mutans of various serotypes induced interleukin-6, interleukin-8 and monocyte chemoattractant protein-1 production by HAECs. All S. mutans strains upregulated TLR2 and NOD2 mRNA levels in HAECs. Streptococcus mutans Xc upregulated the intracellular TLR2 and NOD2 protein levels in HAECs. Silencing of the TLR2 and NOD2 genes in HAECs invaded by S. mutans Xc led to a reduction in interleukin-6, interleukin-8 and monocyte chemoattractant protein-1 production. Cytokine production induced by invasive S. mutans via intracellular TLR2 and NOD2 in HAECs may be associated with inflammation in cardiovascular disease.

Carbenoxolone alters the morphology of adipose tissues and downregulates genes involved in adipogenesis, glucose transport and lipid metabolism in high-fat diet-fed mice

Glucocorticoid (GC) excess promotes adipose tissue accumulation, and 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) plays an important role in the local amplification of GC. Therefore, in this study, we investigated the effects of carbenoxolone (CBX), an 11β-HSD1 inhibitor, on morphological changes in visceral fat, and the expression of genes involved in adipogenesis and lipid metabolism in high-fat (HF) diet-fed mice. Mice were fed a HF diet from 5 weeks of age. At 10 weeks of age, the mice received an intraperitoneal injection of CBX or vehicle every day for 2 weeks. CBX decreased body weight and visceral fat mass, and improved insulin sensitivity in HF-fed mice. This was accompanied by reduced adipocyte size and a decrease in large-sized adipocytes in visceral fat. The expression of adipogenesis (PPARγ and C/EBPα), glucose transport (GLUT4) and lipid metabolism (LPL, ATGL, and HSL)-related genes were suppressed in CBX mice. CBX treatment induced beneficial morphological changes in visceral fat and decreased the expression of adipogenesis, glucose transport and lipid metabolism-related genes. These findings reveal a potential mechanism underling the effects of CBX on reduced fat accumulation and improved insulin sensitivity.

Altered gene expressions of ghrelin, PYY, and CCK in the gastrointestinal tract of the hyperphagic intrauterine growth restriction rat offspring

Intrauterine growth restriction (IUGR) is associated with a substantially greater incidence of metabolic syndrome in adulthood. Animal studies have shown that IUGR offspring are hyperphagic during the early postnatal period and therefore exhibit obesity. The molecular mechanisms underlying food intake regulation in the gastrointestinal tract have not been clarified in IUGR. In the present study, we utilized a rat model of IUGR by restricting the food intake of the mother (50% of the normal intake, ad libitum; FR group) from day 7 of gestation until delivery. Pups from undernourished mothers were fostered by control mothers. We examined the food intake and assessed the gene expressions of ghrelin, peptide YY (PYY), and cholecystokinin (CCK) in the alimentary tract of male newborns (postnatal day1) and adult offspring (age, 7 months). Compared to the offspring whose mothers received the standard diet ad libitum (CON offspring), FR offspring were hyperphagic from the weaning time until the end of the experiment, and resulted in a heavier final weight. Both newborn and adult FR offspring had higher ghrelin gene expression in the stomach and higher ghrelin plasma levels than did the controls. Although the gastrointestinal gene expressions and plasma levels of the anorexic peptides, PYY and CCK, were elevated in the FR newborns, they decreased in the FR adults. Our findings suggest that the altered gene expressions of orexigenic and anorexigenic gut peptides in the gastrointestinal tract in the maternal undernutrition-induced IUGR offspring provide a potential mechanism to explain hyperphagia and obesity seen in these offspring.

Streptococcus anginosus l-cysteine desulfhydrase gene expression is associated with abscess formation in BALB/c mice

Streptococcus anginosus, an anginosus group bacterium, is frequently isolated from odontogenic abscesses, and is the oral bacterium that is primarily responsible for producing hydrogen sulfide from l-cysteine through the action of its l-cysteine desulfhydrase (βC-S lyase) enzyme. However, the relationship between its production of hydrogen sulfide and abscess formation has not been investigated. To elucidate the etiological role of hydrogen sulfide in abscess formation, we initially measured, using specific primers, expression of the lcd gene, which encodes βC-S lyase, in the pus of abscesses that formed in BALB/c mice following subcutaneous injection of S. anginosus into the dorsa. Expression of lcd was >15-fold higher when l-cysteine was present than when it was absent. A mouse virulence assay revealed that the mean diameter of abscesses caused by S. anginosus FW73 plus l-cysteine was greater than that of abscesses caused by S. anginosus FW73 in the absence of l-cysteine. These findings demonstrate that the lcd gene of S. anginosus is upregulated in mouse abscesses and that hydrogen sulfide, the product of a reaction catalyzed by βC-S lyase, plays an etiological role in odontogenic abscess formation.

Invasion of human aortic endothelial cells by oral viridans group streptococci and induction of inflammatory cytokine production

Oral viridans group streptococci are the major commensal bacteria of the supragingival oral biofilm and have been detected in human atheromatous plaque. Atherosclerosis involves an ongoing inflammatory response, reportedly involving chronic infection caused by multiple pathogens. The aim of this study was to examine the invasion of human aortic endothelial cells (HAECs) by oral viridans group streptococci and the subsequent cytokine production by viable invaded HAECs. The invasion of HAECs by bacteria was examined using antibiotic protection assays and was visualized by confocal scanning laser microscopy. The inhibitory effects of catalase and cytochalasin D on the invasion of HAECs were also examined. The production of cytokines by invaded or infected HAECs was determined using enzyme-linked immunosorbent assays, and a real-time polymerase chain reaction method was used to evaluate the expression of cytokine messenger RNA. The oral streptococci tested were capable of invading HAECs. The number of invasive bacteria increased with the length of the co-culture period. After a certain co-culture period, some organisms were cytotoxic to the HAECs. Catalase and cytochalasin D inhibited the invasion of HAECs by the organism. HAECs invaded by Streptococcus mutans Xc, Streptococcus gordonii DL1 (Challis), Streptococcus gordonii ATCC 10558 and Streptococcus salivarius ATCC 13419 produced more cytokine(s) (interleukin-6, interleukin-8, monocyte chemoattractant protein-1) than non-invaded HAECs. The HAECs invaded by S. mutans Xc produced the largest amounts of cytokines, and the messenger RNA expression of cytokines by invaded HAECs increased markedly compared with that by non-invaded HAECs. These results suggest that oral streptococci may participate in the pathogenesis of atherosclerosis.

Effects of maternal high-fat diet on serum lipid concentration and expression of peroxisomal proliferator-activated receptors in the early life of rat offspring

Peroxisomal proliferator-activated receptors (PPARs) play an important role in the regulation of lipid metabolism. The aim of this study was to investigate the effects of a maternal high-fat (HF) diet on serum lipid concentration and PPAR gene expression in liver and adipose tissue in the early life of the rat offspring. Female Sprague-Dawley rats were fed either an HF or control (CON) diet 6 weeks before mating and throughout gestation and lactation. Blood and tissue samplings of male offspring were carried out at birth or weaning. Birth weights were similar and serum triglyceride (TG) and nonesterified fatty acid (NEFA) levels showed no significant difference between HF and CON newborns, despite greatly increased hepatic PPARα mRNA expression in the HF newborns (p<0.05). Both HF newborns and weanlings revealed significantly decreased hepatic PPARγ expression compared with controls (p<0.0001). Hepatic PPARα expression in the HF weanlings was reduced markedly compared with CON weanlings (p<0.0001) and showed a negative correlation with serum TG levels (r=-0.743, p<0.05). However, epididymal expression of PPARγ in the HF weanlings was upregulated significantly compared with controls (p<0.05) and demonstrated a positive correlation with epididymal fat mass (r=0.733, p<0.05). These were accompanied by obesity as well as a rise in serum TG by 79% (p<0.05) and NEFA concentration by 36% (p<0.05) in these HF weanlings. Our findings suggest that maternal HF diet leads to alterations in PPAR gene expression in the weanling offspring, which is associated with the disturbed lipid homeostasis.

A novel compound heterozygous dysferlin mutation in Miyoshi myopathy siblings responding to dantrolene

Miyoshi myopathy (MM) is an autosomal recessive distal muscular dystrophy characterized by mutations of the dysferlin gene. Although several pairs of homozygous/heterozygous mutations have been reported, few effective treatments of MM are available. We had observed the decreased serum creatine kinase (CK) before and after administration of dantrolene in the elder brother and the increased serum CK before and after discontinuance of the drug on suspicion of drug-induced hepatopathy in the younger sister. We report a novel pair of heterozygous mutations in the 3'-splicing site of exon 26 and the translation site of exon 28 of the dysferlin gene in two siblings, and effective treatment of their MM with dantrolene.

Novel mutation of the Notch3 gene in a Japanese patient with CADASIL

We report a novel missense mutation of the Notch3 gene in a Japanese family with CADASIL. The Cys49Gly mutation in this family is located in exon 2 of the Notch3 gene. Most of the documented Notch3 gene mutations occur in exons 3 or 4. On the other hand, there are few reports around the world of mutations in exon 2 of the Notch3 gene, and this is the first report of a mutation in exon 2 of the gene in a Japanese family. In general, CADASIL mutations involve a cysteine residue. Such mutations may influence the tertiary structure of the Notch3 protein, resulting in protein dysfunction. Thus, the CADASIL in the present case may be a consequence of the mutation in exon 2 causing a structural change in the Notch3 protein.

Serotype-specific polysaccharide of Streptococcus mutans contributes to infectivity in endocarditis

Streptococcus mutans and other viridans streptococci have been implicated as major etiological agents of infective endocarditis. The serotype-specific rhamnose-glucose polysaccharide (RGP) of S. mutans has several biological functions that appear to be essential for the induction of infective endocarditis. The aim of this study was to examine the contribution of RGP to the infectivity of S. mutans in infective endocarditis using a rat model. The RGP-defective mutant of S. mutans showed reduced ability to induce infective endocarditis compared to the parental strain. The ability of S. mutans to induce infective endocarditis was not consistent with the binding capacity of the organism to extracellular matrix proteins. The results suggest that S. mutans containing whole RGP is more virulent than the RGP-defective mutant, and the RGP has an important role for the induction of infective endocarditis by S. mutans.

Identification and characterization of a novel inositol hexakisphosphate kinase

The inositol pyrophosphate disphosphoinositol pentakisphosphate (PP-InsP(3)/InsP(7)) is formed in mammals by two recently cloned inositol hexakiphosphate kinases, InsP(6)K1 and InsP(6)K2 (Saiardi, A., Erdjument-Bromage, H., Snowman, A. M., Tempst, P., and Snyder, S. H. (1999) Curr. Biol. 9, 1323-1326). We now report the identification, cloning, and characterization of a third InsP(7) forming enzyme designated InsP(6)K3. InsP(6)K3 displays 50 and 45% sequence identity to InsP(6)K1 and InsP(6)K2, respectively, with a smaller mass (46 kDa) and a more basic character than the other two enzymes. InsP(6)K3 is most enriched in the brain where its localization resembles InsP(6)K1 and InsP(6)K2. Intracellular disposition discriminates the three enzymes with InsP(6)K2 being exclusively nuclear, InsP(6)K3 predominating in the cytoplasm, and InsP(6)K1 displaying comparable nuclear and cytosolic densities.

GRAB: a physiologic guanine nucleotide exchange factor for Rab3A, which interacts with inositol hexakisphosphate kinase

Diphosphoinositol-pentakisphosphate (InsP7) and bis-diphosphoinositol tetrakisphosphate (InsP8) possess pyrophosphate bonds. InsP7 is formed from inositol hexakisphosphate (InsP6) by recently identified InsP6 kinases designated InsP6K1 and InsP6K2. We now report the identification, cloning, and characterization of a novel protein, GRAB (guanine nucleotide exchange factor for Rab3A), which interacts with both InsP6K1 and Rab3A, a Ras-like GTPase that regulates synaptic vesicle exocytosis. GRAB is a physiologic GEF (guanine nucleotide exchange factor) for Rab3A. Consistent with a role of Rab3A in synaptic vesicle exocytosis, GRAB regulates depolarization-induced release of dopamine from PC12 cells and nicotinic agonist-induced hGH release from bovine adrenal chromaffin cells. The association of InsP6K1 with GRAB fits with a role for InsP7 in vesicle exocytosis.

Upregulation of toll-like receptor 2 gene expression in macrophage response to peptidoglycan and high concentration of lipopolysaccharide is involved in NF-kappa b activation

Toll-like receptors 2 and 4 (TLR2 and TLR4) have been found to transduce signals of peptidoglycan (PGN) and lipopolysaccharide (LPS), respectively, for NF-kappa B activation. However, little is known about the expression and regulation of the TLR2 gene in monocytes/macrophages in response to the two typical bacterial products. We show in the present study that both PGN and a high concentration of LPS increase TLR2 gene expression in macrophage-like cells, 1 alpha,25-dihydroxyvitamin D(3)-differentiated human HL60 and mouse RAW264.7 cells, and human monocytes in a dose- and time-dependent manner. Actinomycin D and pyrrolidine dithiocarbamate inhibition of gene transcription and NF-kappa B activation, respectively, blocks LPS- and PGN-elevated TLR2 mRNA in monocytic cells. The LPS-induced increase in TLR2 mRNA in monocytic cells is abolished by polymyxin B pretreatment and is observed in peripheral blood mononuclear cells from pigs subjected to endotoxic shock. Further, high concentrations of LPS and synthetic lipid A increase TLR2 mRNA expression in peritoneal macrophages from both TLR4-deficient C3H/HeJ mice and normal C3H/HeN mice, a process that constitutes induction of TLR4-independent TLR2 expression. These findings demonstrate that TLR2 gene expression is upregulated in macrophage responses to PGN and to high concentrations of LPS in vitro and in vivo and correlates with NF-kappa B activation.

The effects of olprinone (a phosphodiesterase III inhibitor) on hepatic vascular bed in a porcine model of endotoxemia

Decreased hepatic blood flow, and impaired hepatic oxygen delivery caused by endotoxin, result in hepatic metabolic deterioration followed by liver dysfunction and multiple organ failure. Among phosphodiesterase III inhibitors, only olprinone increases hepatosplanchnic blood flow. We evaluated the effects of olprinone on systemic hemodynamics, hepatic circulation, and hepatic oxygen delivery in a porcine model of endotoxemia. Fifteen pigs received a continuous infusion (1.7 microg. kg(-1). h(-1)) of endotoxin (lipopolysaccharide [LPS]) via the portal vein for 240 min. Seven of these pigs received olprinone infusion (0.3 microg. kg(-1). min(-1)) via a central vein from t = 150 min to t = 240 min, whereas the eight remaining pigs served as LPS controls. Continuous infusion of LPS caused significant reductions in hemodynamic variables and a significant increase in arterial lactate. After the administration of olprinone during the LPS infusion, portal venous flow and hepatic oxygen delivery were increased and were higher than in the LPS group. Furthermore, olprinone prevented any further increase in arterial lactate. We conclude that the administration of olprinone halted the disturbances in the hepatic circulation, especially in portal venous flow and hepatic oxygen delivery, in a porcine model of endotoxemia.

IMPLICATIONS

Endotoxin is a causative factor in peripheral vascular failure, resulting in a hemodynamic depression that includes a reduction in liver blood flow. The administration of olprinone (phosphodiesterase III inhibitor) improves the liver blood flow circulation in a porcine model of endotoxemia.

Mammalian inositol polyphosphate multikinase synthesizes inositol 1,4,5-trisphosphate and an inositol pyrophosphate

Using a consensus sequence in inositol phosphate kinase, we have identified and cloned a 44-kDa mammalian inositol phosphate kinase with broader catalytic capacities than any other member of the family and which we designate mammalian inositol phosphate multikinase (mIPMK). By phosphorylating inositol 4,5-bisphosphate, mIPMK provides an alternative biosynthesis for inositol 1,4,5-trisphosphate [Ins(1,4,5)P(3)]. mIPMK also can form the pyrophosphate disphosphoinositol tetrakisphosphate (PP-InsP(4)) from InsP(5). Additionally, mIPMK forms InsP(4) from Ins(1,4,5)P(3) and InsP(5) from Ins(1,3,4,5)P(4).

Effects of blockade of voltage-sensitive Ca(2+)/Na(+) channels by a novel phenylpyrimidine derivative, NS-7, on CREB phosphorylation in focal cerebral ischemia in the rat

NS-7 is a novel blocker of voltage-sensitive Ca(2+) and Na(+) channels, and it significantly reduces infarct size after occlusion of the middle cerebral artery. Persistent activation of cyclic AMP response element binding protein (CREB), which can be induced by increase in intracellular Ca(2+) concentrations or other second messengers, has recently been found to be closely associated with neuronal survival in cerebral ischemia. The present study was therefore undertaken to evaluate the neuroprotective effects of NS-7 by analyzing changes in CREB phosphorylation in a focal cerebral ischemia model. CREB phosphorylation in the brain of rats was investigated immunohistochemically at 3.5-48-h recirculation after 1. 5-h occlusion of the middle cerebral artery. NS-7 (1 mg/kg; NS-7 group) or saline (saline group) was intravenously injected 5 min after the start of recirculation. The NS-7 group showed significantly milder activation of CREB phosphorylation in various cortical regions after 3.5 h of recirculation than the saline group. The inner border zone of ischemia in the NS-7 group subsequently exhibited a moderate, but persistent, increase in number of phosphorylated CREB-positive neurons with no apparent histological damage. By contrast, the saline group displayed a marked, but only transient, increase in number of immunopositive neurons in this border zone after 3.5 h of recirculation, and this was followed by clear suppression of CREB phosphorylation and subsequent loss of normal neurons. These findings suggest that: (1) the marked enhancement of CREB phosphorylation in the acute post-ischemic phase may be triggered largely by an influx of calcium ions as a result of activation of the voltage-sensitive Ca(2+) and Na(+) channels; and that (2) the neuroprotective effects of NS-7 may be accompanied by persistent activation of CREB phosphorylation in the inner border zone of ischemia.

p12(DOC-1), a growth suppressor, associates with DNA polymerase alpha/primase

p12(DOC-1) is a growth suppressor identified and isolated from normal keratinocytes. Ectopic expression of p12(DOC-1) in squamous carcinoma cells led to the reversion of in vitro transformation phenotypes including anchorage independence, doubling time, and morphology. Here we report that p12(DOC-1) associates with DNA polymerase alpha/primase (pol-alpha:primase) in vitro and in cells. The pol-alpha:primase binding domain in p12(DOC-1) is mapped to the amino-terminal six amino acid (MSYKPN). The biological effect of p12(DOC-1) on pol-alpha:primase was examined using in vitro DNA replication assays. Using the SV40 DNA replication assay, p12(DOC-1) suppresses DNA replication, leveling at approximately 50%. Similar results were obtained using the M13 single-stranded DNA synthesis assay. Analysis of the DNA replication products revealed that p12(DOC-1) affects the initiation step, not the elongation phase. The p12(DOC-1) suppression of DNA replication is likely to be mediated either by a direct inhibitory effect on pol-alpha:primase or by its effect on cyclin-dependent kinase 2 (CDK2), a recently identified p12(DOC-1)-associated protein known to stimulate DNA replication by phosphorylating pol-alpha:primase. p12(DOC-1) suppresses CDK2-mediated phosphorylation of pol-alpha:primase. These data support a role of p12(DOC-1) as a regulator of DNA replication by direct inhibition of pol-alpha:primase or by negatively regulating the CDK2-mediated phosphorylation of pol-alpha:primase.

Disruption of the epilepsy KCNQ2 gene results in neural hyperexcitability

Benign familial neonatal convulsion (BFNC) is a common idiopathic epilepsy with autosomal dominant inheritance. Recently, two novel voltage-dependent potassium channel genes, KCNQ2 and KCNQ3, were identified by positional cloning as being responsible for BFNC. Heterotetramers of the products of these genes form M-channels and regulate the threshold of electrical excitability of neurons. We disrupted the mouse KCNQ2 gene via gene targeting to study the relationship between KCNQ2 and epilepsy. Homozygous pups (KCNQ2 -/-) died within a few hours after birth owing to pulmonary atelectasis that was not due to the status of epileptic seizures, although their development was morphologically normal. Heterozygous mice had decreased expression of KCNQ2 and showed hypersensitivity to pentylenetetrazole, an inducer of seizure. These data indicate that the decreased expression of KCNQ2 might cause a hyperexcitability of the CNS, which accounts for the mechanism of BFNC.

Persistent CREB phosphorylation with protection of hippocampal CA1 pyramidal neurons following temporary occlusion of the middle cerebral artery in the rat

Phosphorylation of the DNA-binding transcription factor, cyclic AMP response element binding protein (CREB), was immunohistochemically examined in rat brain hippocampal CA1 in order to examine the ischemic vulnerability of this region from the viewpoint of CREB activation. The rat brain had been subjected to 90-min focal ischemia followed by various periods of recirculation. Focal ischemia was induced by occlusion of the middle cerebral artery using the intraluminal suture method. CA1 pyramidal neurons in the sham animals showed definite immunoreactivity with anti-CREB antibody, which binds to both unphosphorylated and phosphorylated CREB, while reactivity with anti-phosphorylated CREB antibody was barely detectable in these neurons. In contrast, at 3.5 h of recirculation, a significant increase in the number of phosphorylated CREB-positive neurons was noted in the CA1 on both sides, and the increase continued until 48 h of recirculation with a tendency for gradual decline. At each period, the ischemic side showed a more marked increase in the number of immunoreactive cells as compared to the nonischemic side. Cresyl violet staining revealed CA1 pyramidal neurons to be maintained intact until 14 day of recirculation, at which time CREB phosphorylation has returned to the control level. Transient global ischemia is known to induce only mild CREB phosphorylation in the CA1 followed by a frank neuronal loss in this region. These data suggest that CREB phosphorylation can be persistently activated in CA1 neurons after focal ischemia and that this phenomenon may be closely associated with protection of these neurons.

Uncoupling of cerebral blood flow and glucose utilization in the regenerating facial nucleus after axotomy

Axotomy is known to activate various metabolic processes including protein synthesis and glucose utilization in the motor nucleus. Although it is generally assumed that the local cerebral blood flow (CBF) fluctuates in response to the axonal reaction, there has been no direct evidence for changes in CBF in the motor nucleus following axotomy. In this study, the CBF in the facial nuclei was measured after axotomy of the facial nerve employing the [14C]iodoantipyrine method to evaluate the relation between the CBF and axonal reaction. Following unilateral facial nerve axotomy in neonates, which induced neuronal degeneration in the facial nucleus, the CBF and glucose uptake was significantly decreased on the operated nucleus, suggesting that CBF and glucose metabolism are coupled in the degenerating nucleus. In contrast, after axotomy in adults, which induced regeneration of neurons and glial reactions, glucose uptake was increased on the operated nucleus, while the CBF did not differ significantly between the operated and unoperated nucleus. These findings imply that glucose metabolism and CBF are uncoupled in the regenerating nucleus, suggesting that the relation between CBF and metabolism in the regenerating nucleus following axotomy may clearly contradict the classical concept of a tight coupling between CBF and metabolism.

[Alteration of cAMP-mediated signal transduction in cerebral ischemia--binding activity of PKA and phosphorylation of CREB]

Binding of cAMP to the regulatory subunit of cAMP-dependent protein kinase (PKA) is an essential step for cAMP-mediated signal transduction including phosphorylation of cAMP response element binding protein (CREB). In the present study, binding activity of PKA with cAMP and CREB phosphorylation were examined in rat focal brain ischemia induced by occlusion of the middle cerebral artery for 1.5 hours followed by various time of recirculation. Binding activity of PKA with cAMP was progressively inhibited during the acute phase of ischemia from the ischemic core to peri-ischemia area. Phosphorylated CREB-positive cells in the ischemic core revealed a significant, but transient increase in number at 3.5 hours of recirculation, followed by a rapid decrease below the control level during the subsequent period. On the other hand, in the peri-ischemia area, the number of phosphorylated CREB-positive cells showed a more marked increase as compared to that in the ischemic core, and the increase continued until 48 hours of recirculation with a tendency for gradual decline. Persistent enhancement of CREB phosphorylation may thus be closely related to the neuronal viability and neuroprotective mechanisms, whereas rapid disappearance of CREB phosphorylation following ischemic insult may clearly precede neuronal death.

Inhibition of cyclic AMP-dependent protein kinase in the acute phase of focal cerebral ischemia in the rat

Binding of cyclic AMP to the regulatory subunit of cyclic AMP-dependent protein kinase is an essential step in cyclic AMP-mediated intracellular signal transduction. In the present study, the binding capacity of cyclic AMP-dependent protein kinase for cyclic AMP was examined by autoradiography with local cerebral blood flow in focal cerebral ischemia in the rat, which was induced by occlusion of the middle cerebral artery using the intraluminal suture method. The binding capacity of cyclic AMP-dependent protein kinase and local cerebral blood flow were assessed by the in vitro [3H]cyclic AMP binding and the [14C]iodoantipyrine methods, respectively. At 3 h of occlusion, a significant reduction in the binding of cyclic AMP-dependent protein kinase to cyclic AMP was already noted in the lateral region of the caudate-putamen and the parietal cortex. Between three and five hours of occlusion, the area with reduced cyclic AMP binding was significantly expanded to the peri-ischemic regions including the frontal cortex and the medial region of the caudate-putamen. The threshold in local cerebral blood flow for reduced cyclic AMP binding was clearly noted at 5 h of ischemia, and was 45 ml/100 g per min in the cerebral cortices, and 38 ml/100 g per min in the caudate-putamen, respectively. No threshold was noted at 3 h of ischemia, since cyclic AMP binding showed a large variation ranging from reduced to normal values even when local cerebral blood flow was below 20 ml/100 g per min. Recirculation for 3.5 h following 1.5 h of ischemia restored the normal cyclic AMP binding in the cerebral cortices, but failed to normalize cyclic AMP binding in the caudate-putamen despite good recovery of local cerebral blood flow. Western blot analysis suggested that this reduction in cyclic AMP binding was not due to loss or degradation of the subunit protein of cyclic AMP-dependent protein kinase, and may therefore have resulted from conformational changes in the protein. A significant increase in cyclic AMP binding was noted after recirculation in the non-ischemic regions such as the frontal and the cingulate cortices on the occluded side and in the contralateral cortices. These data indicate that cyclic AMP-mediated signal transduction in the brain tissue may be very susceptible to ischemic stress, and the region of disrupted signal transduction may expand progressively from the ischemic core to peri-ischemic regions in the acute phase of ischemia. Such impairment of signal transduction may not be restored in the caudate-putamen even when cerebral circulation is fully recovered after short-term ischemia, suggesting that a regional vulnerability to ischemic stress may also exist in cyclic AMP-mediated signal transduction. A significant increase in cyclic AMP binding after recirculation in regions outside of ischemic area may be closely related with the protective mechanisms of brain tissue, since cyclic AMP has been reported to exert various neuroprotective actions.

Temporal profile and cellular localization of interleukin-6 protein after focal cerebral ischemia in rats

Although interleukin-6 (IL-6) has various neuroprotective effects against cerebral ischemia, the topographic distribution and cellular source of IL-6 after cerebral ischemia remain unclear. In the current study, the localization of IL-6 protein was immunohistochemically examined in rats after 3.5, 12, 24, and 48 hours of reperfusion after 1.5 hours of middle cerebral artery occlusion. Middle cerebral artery occlusion was induced by the intraluminal suture method. The specificity of the anti-IL-6 antibody used in the current study was confirmed by Western blot analysis and an immunoabsorption test. To identify the cellular source, lectin histochemical study and immunohistochemical study with microtubule-associated protein-2, ED1, and glial fibrillary acidic protein also were carried out. The sham group did not show any clear IL-6 immunoreactivity. After 3.5 hours of reperfusion, IL-6 immunoreactivity was first detected on the reperfused side, and it was upregulated, especially in the periinfarct region, after 24 hours of reperfusion. Also, IL-6 was expressed after 3.5 hours of reperfusion in the contralateral cerebral cortex and bilateral hippocampi. Double staining showed that the cells containing IL-6 were neurons and round-type microglia, not astrocytes. The current findings suggest that IL-6 expression in ischemically threatened neurons and reactive microglia is closely associated with brain tissue neuroprotective mechanisms against cerebral ischemia.

Facilitation of NMDAR-independent LTP and spatial learning in mutant mice lacking ryanodine receptor type 3

To evaluate the role in synaptic plasticity of ryanodine receptor type 3 (RyR3), which is normally enriched in hippocampal area CA1, we generated RyR3-deficient mice. Mutant mice exhibited facilitated CA1 long-term potentiation (LTP) induced by short tetanus (100 Hz, 100 ms) stimulation. Unlike LTP in wild-type mice, this LTP was not blocked bythe NMDA receptor antagonist D-AP5 but was partially dependent on L-type voltage-dependent Ca2+ channels (VDCCs) and metabotropic glutamate receptors (mGluRs). Long-term depression (LTD) was not induced in RyR3-deficient mice. RyR3-deficient mice also exhibited improved spatial learning on a Morris water maze task. These results suggest that in wild-type mice, in contrast to the excitatory role of Ca2+ influx, RyR3-mediated intracellular Ca2+ ([Ca2+]i) release from endoplasmic reticulum (ER) may inhibit hippocampal LTP and spatial learning.

Selective inhibition of inositol 1,4,5-triphosphate-induced Ca2+ release in the CA1 region of the hippocampus in the ischemic gerbil

We examined the effect of ischemia on inositol 1,4,5-trisphosphate receptor-induced Ca2+ release by functional and morphological approaches, using the gerbil model after 6-h unilateral occlusion of the common carotid artery. Autoradiographic study revealed that the basal uptake of 45Ca2+ into the endoplasmic reticulum and caffeine-induced 45Ca2+ release from the endoplasmic reticulum were normal in the presence of ATP in each ischemic brain region, whereas inositol 1,4,5-trisphosphate receptor-induced 45Ca2+ release from the endoplasmic reticulum was inhibited only in the CA1 region of the hippocampus on the ischemic side. In moderately ischemic gerbils, electron microscopic study demonstrated aggregation of swollen endoplasmic reticulum in the CA1 region of the hippocampus, so that abundant endoplasmic reticulum assembled in close contact to form endoplasmic reticulum cisternal stacks. In severely ischemic gerbils, immunohistochemical analysis of the hippocampus showed loss of type 1 inositol 1,4,5-trisphosphate receptor protein with preservation of immunoreactivity for type 2 and 3 inositol 1,4,5-trisphosphate receptor proteins, which was confirmed by western blot analysis. Such selective inhibition of inositol 1,4,5-trisphosphate receptor-induced Ca2+ release and the loss of type 1 inositol 1,4,5-trisphosphate receptor in the CA1 region of the hippocampus in cerebral ischemia may be associated with its region-specific vulnerability to ischemia.

Giant cell interstitial pneumonia in two hard metal workers: the role of bronchoalveolar lavage in diagnosis

Two cases of hard metal lung disease and pathological findings of giant cell interstitial pneumonia are reported. The cases worked in different factories manufacturing hard metal parts from tungsten carbide and cobalt. Pathological specimens were obtained by percutaneous thoracoscopy and transbronchial lung biopsy. X-ray microanalysis detected only tungsten carbide in the lung specimen of one case. Bronchoalveolar lavage showed diagnostic bizarre macrophages in the lavage fluid.

Temporal profile of CREB phosphorylation after focal ischemia in rat brain

The phosphorylation of cAMP response element binding protein (CREB) in the rat brain was examined immunohistochemically at 3.5 h, 12 h, 24 h and 48 h of recirculation after focal ischemia induced by occlusion of the middle cerebral artery for 1.5 h. Brain sections were stained with affinity purified anti-phosphorylated CREB antibody. The ischemic core revealed a significant, but transient increase in number of phosphorylated CREB-positive cells at 3.5 h of recirculation, followed by a rapid decrease during the subsequent period. In the peri-ischemia area, the number of phosphorylated CREB-positive cells showed a more marked increase as compared to that in the ischemic core at 3.5 h of recirculation, and the increase continued until 48 h of recirculation with a tendency for gradual decline. Persistent enhancement of CREB phosphorylation may thus be closely related to the neuronal viability and neuroprotective mechanisms, whereas rapid disappearance of CREB phosphorylation may clearly precede neuronal death.

Type 1 inositol 1,4,5-trisphosphate receptor knock-out mice: their phenotypes and their meaning in neuroscience and clinical practice

Cytoplasmic calcium, which acts as a second messenger, is derived not only from outside the cell but also from intracellular stores. A receptor for inositol 1,4,5-trisphosphate (IP3), an intracellular second messenger, is located on these internal calcium stores and functions as a calcium releasing channel. The "type 1" IP3 receptor (IP3R1) is concentrated predominantly in cerebellar Purkinje cells and is also widely present in other neural and peripheral tissues, but many of its physiological roles in these cells are still unclear. We have previously succeeded in obtaining mice with disruption of this IP3R1 gene, in which brain IP3-induced calcium release was almost completely abolished. They were rarely born alive, indicating that IP3R1 has some functions during embryonic development. Animals exhibited severe neurological symptoms, ataxia and epilepsy, and were shown to be deficient in the cerebellar long-term depression. They give us promising clues regarding the physiological roles of calcium release from internal stores and serve as a model for the relevant human disease states.

Cerebral neurons express interleukin-6 after transient forebrain ischemia in gerbils

Markedly increased interleukin-6 (IL-6) mRNA levels occur in experimental cerebral ischemia, although the protein production and cellular sources of IL-6 remain unclear. We examined the cellular localization of IL-6 protein in gerbil brain following transient forebrain ischemia employing immunohistochemistry and Western blot analysis. The ischemia/recirculation groups revealed distinct IL-6 immunoreactivity predominantly in cortical and hippocampal neurons after 3 hours to 3 days recirculation. At 12 h recirculation, the IL-6 expression declined specifically in the hippocampus CA1. Microglia, but not activated astrocytes, also expressed IL-6 immunoreactivity. The sham group showed no apparent immunoreactivity. IL-6 protein may thus be expressed mainly in neurons following transient forebrain ischemia. Its transient decline in the CA1 at 12 h recirculation could reflect the specific vulnerability of this region.

Immunohistochemical analysis of cyclic AMP response element binding protein phosphorylation in focal cerebral ischemia in rats

Phosphorylation of cyclic AMP response element binding protein (CREB) is one of the most important mechanisms controlling various gene transcriptions. In the present study, the phosphorylation of CREB was examined immunohistochemically at 24 h of recirculation following 1.5 h of middle cerebral artery occlusion (MCAO) in rats. MCAO was induced by the intraluminal suture method. The infarct core revealed a significant reduction in the number of immunoreactive cells with the anti-phosphorylated CREB and with the anti-CREB antibody, which binds to both unphosphorylated and phosphorylated CREB. In contrast, the peri-infarct area exhibited a marked increase in the number of immunopositive cells as well as in the intensity of nuclear staining with each antibody, so that almost all of the cells expressing CREB demonstrated phosphorylation of CREB. On the other hand, about half of the CREB immunopositive cells reacted weakly with the anti-phosphorylated CREB antibody in the sham group. These findings indicated that the expression as well as phosphorylation of CREB protein was significantly activated in the regions surrounding the infarct area. Since phosphorylation of CREB has recently been implicated in signal transductions that promote the survival and differentiation of neurons, the present data suggest that tissue repair mechanisms may be markedly activated in the peri-infarct area.

Role of the ryanodine receptor in ischemic brain damage--localized reduction of ryanodine receptor binding during ischemia in hippocampus CA1

1. The ryanodine receptor has recently been shown to play a pivotal role in the regulation of intracellular Ca2+ concentration via Ca(2+)-induced Ca2+ release (CICR). Effects of ischemia on CICR in the brain tissue, however, remain largely unknown since only a few reports have been published on this subject. In this paper we report on work in this area by our group and review related progress in this field. 2. We examined alterations of ryanodine receptor binding and local cerebral blood flow (LCBF) at 15 min, 30 min, and 2 hr after occlusion of the right common carotid artery in the gerbil brain. A quantitative autoradiographic method permitted simultaneous measurement of these parameters in the same brain. The LCBF was significantly reduced in most of the cerebral regions on the occluded side during each time period of ischemia. In contrast, only in the hippocampus CA1 on the occluded side was a significant reduction in ryanodine binding found at 15 min, 30 min and 2 hr after the occlusion. 3. These findings suggest that suppression of ryanodine binding in the hippocampus CA1 may be attributable to a regionally specific perturbation of CICR and that this perturbation may be closely associated with the pathophysiological mechanism that leads to be selective ischemic vulnerability of this region. 4. Other recent studies have also reported an important role for ryanodine receptors in neuronal injury such as the delayed neuronal death in the hippocampus CA1. These data suggest that derangement of CICR is likely to be involved in acute neuronal necrosis as well as in delayed neuronal death in ischemia. 5. Further studies on clarifying the role of CICR in ischemic brain damage are needed in order to develop new therapeutic strategies for stroke patients.

Cloning, mapping, expression, function, and mutation analyses of the human ortholog of the hamster putative tumor suppressor gene Doc-1

doc-1 is a putative tumor suppressor gene isolated and identified from the hamster oral cancer model. Here, we report the molecular cloning and the functional characterization of the human ortholog of the hamster doc-1 gene. Human doc-1 cDNA is 1.6 kilobase pairs in length and encodes for a 115-amino acid polypeptide (12.4 kDa, pI 9. 53). Sequence analysis showed 98% identity between human and hamster doc-1 protein sequences. DOC-1 is expressed in all normal human tissues examined. In oral keratinocytes, expression of DOC-1 is restricted to normal oral keratinocytes. By immunostaining of normal human mucosa, DOC-1 is detected in both the cytoplasm and nuclei of basal oral keratinocytes; while in suprabasilar cells, it is primarily found in the nuclei. Human oral cancers in vivo did not exhibit immunostaining for DOC-1. Like murine DOC-1, human DOC-1 associates with DNA polymerase alpha/primase and mediates the phosphorylation of the large p180 catalytic subunit, suggesting it may be a potential regulator of DNA replication in the S phase of the cell cycle. Using a human doc-1 cosmid as a probe, human doc-1 is mapped to chromosome 12q24. We identified four exons in the entire human doc-1 gene and determined the intron-exon boundaries. By polymerase chain reaction and direct sequencing, we examined premalignant oral lesion and oral cancer cell lines and found no intragenic mutations.

Effects of washing procedure on platelets pretreated with serotonin uptake inhibitors in vitro: low Ki values predict long-lasting inhibition of serotonin uptake in vivo

The effect of a washing procedure on serotonin (5-HT) uptake in vitro was investigated using human platelets pretreated with nine 5-HT uptake inhibitors and various Ki values to confirm the assumption that a drug with high affinity for the 5-HT uptake site would be hardly removed and have a long-lasting effect in vivo. Among the drugs tested, those with low Ki values, such as clomipramine, duloxetine and paroxetine, inhibited 5-HT uptake even after removal from the medium, while those with high Ki values such as amitriptyline, desipramine, imipramine, mianserin, trazodone, and zimelidine were easily removed by washing. The results indicated that low Ki values might be proportionally related to the long-lasting binding of drugs to the 5-HT uptake site. The results also suggested that the threshold Ki value which could separate 5-HT uptake inhibitors with a probable long-lasting effect in vivo from those without the effect would be between 5 nM and 42 nM.

Partial inhibition of reverse tolerance by a high dose of ritanserin or low dose of haloperidol in methamphetamine-sensitized rat

To clarify the implication of antagonism of serotonin (5-HT)2 receptors in the treatment of schizophrenia, the effects of ritanserin (RIT) on the development of reverse tolerance in rats repeatedly administered methamphetamine (MAP) were investigated and compared with those of low doses of haloperidol (HPD). RIT administered at a dose of 2 mg/kg and low doses of HPD (0.05, 0.1 mg/kg) shared partial inhibition of the development of reverse tolerance in MAP-sensitized rats; the drugs inhibited sniffing but not head moving and had no effect on locomotion or rearing. A combination of low doses of HPD and RIT resulted in the inhibition of head moving. These results suggested that strong antagonism for 5-HT2 receptors would be useful to some extent to treat MAP-induced psychosis and schizophrenia as well as weak antagonism of dopamine D2 receptors, and that a combination of these two actions would produce better results in these psychoses than that obtained from D2 antagonism alone. In the presence of 0.05 mg/kg of HPD, RIT caused increased locomotion and rearing, whereas it decreased them in the presence of 0.1 mg/kg of HPD. This result suggested that the interactions between 5-HT and dopamine (DA) neurons are complex, and that 5-HT2 antagonism may inhibit or disinhibit DA neurons depending on the level of D2 blockade.

Binding capacity of FK506 binding protein after 2-hour hemispheric ischemia in gerbil brain

The binding capacity of FK506 binding protein (FKBP) was examined after 2-h hemispheric ischemia in the gerbil brain in order to clarify the precise mechanism of the neuroprotective effects of FK506. Firstly, the FK506 binding was evaluated in vitro in the normal gerbil brain using 1 nM [3H]dihydro-FK506 as a specific ligand. FK506 binding sites were distributed in a rather homogeneous manner, although the greatest binding was noted in the hippocampus CA1. Secondly, Scatchard analysis demonstrated that the binding sites of FK506 could be composed of two components in each brain region. Thirdly, 18 Mongolian gerbils were divided into two groups: an ischemia group (n = 12) and a sham group (n = 6). The right common carotid artery was ligated to induce hemispheric ischemia for 2 h in the ischemia group. The local cerebral blood flow was measured at the end of the experiment by the [14C]iodoantipyrine method. The ligated animals with levels of local cerebral blood flow in the lateral nuclei of the thalamus of less than 50 ml/100 g/min were utilized as the ischemia group (n=6) for further data analysis. No significant differences in FK506 binding between the ischemia and sham groups were observed in any regions. The above data indicate that the binding capacity of FKBP tends to remain normal during 2-h ischemia, suggesting that FK506 may exert its neuroprotective effects through its binding to FKBP in the brain during the early phase of cerebral ischemia.

A novel neurological mutant mouse, yotari, which exhibits reeler-like phenotype but expresses CR-50 antigen/reelin

We present yotari, a novel neurological mutant mouse whose mutation is transmitted in an autosomal recessive manner. The phenotype of yotari is very similar to that of reeler. yotari mutants are recognizable by their unstable gait and tremor and by their early deaths at around the time of weaning. The cerebella of homozygous yotari are hypoplastic and have no foliation. A molecular and a granular cell layer can be identified, but Purkinje cells are scattered throughout both the granular layer and white matter. The laminar structure of the cerebral cortex and the hippocampal formation are also distorted. To test whether the mutated gene in yotari is the reeler gene, reelin, yotari heterozygotes were mated with reeler homozygotes or heterozygotes. The absence of abnormal offspring indicated that the yotari gene is distinct from reelin. Furthermore, expression of mRNA and protein of reelin was verified by Northern blotting and immunohistochemistry using a CR-50 monoclonal antibody (mAb) which is specific to Reelin, the reelin gene product. Although the mutation of several genes, including cyclin-dependent kinase 5 (Cdk 5), p35 and LIS1, 45 kDa subunits of platelet-activating factor acetylhydrolase (PAF-AH) Ib, in Miller-Dieker lissencephaly syndrome (MDS) has been reported to cause abnormal laminar structure in the brain, no abnormality was found in yotari by Western blotting with antibodies (Ab's) against these molecules. The close similarity of the phenotypes of yotari and reeler and the expression of reelin in yotari may suggest that the gene mutated in yotari encodes a molecule that is on the same signaling pathway as Reelin, the product of reelin. yotari will provide valuable clues to explore the molecular mechanism of neuronal migration and orderly laminar structure formation of the brain.

Immunohistochemical detection of nitrotyrosine in postischemic cerebral cortex in gerbil

We examined whether or not nitration of tyrosine residues takes place in the ischemic and postischemic reperfused brain. The nitration of tyrosine residues to produce nitrotyrosine is a sensitive marker elicited by peroxynitrite, a powerful oxidant formed by the reaction of nitric oxide (NO) with superoxide. Mongolian gerbils were subjected to 60 min ischemia induced by occlusion of the right common carotid artery (ischemia group), to 30 min recirculation following 60 min ischemia (reperfusion group) or to sham surgery (sham group). Immunohistochemical staining with polyclonal anti-nitrotyrosine antibody revealed the widespread and distinct occurrence of nitrotyrosine in cortical neurons on the reperfused side of the brain in the reperfusion group, while only partial or weak immunoreactivity was noted on the contralateral side. On the other hand, nitrotyrosine was not detected in the brain of the ischemia and sham groups. These findings suggest that nitration of tyrosine residues in various proteins may be closely associated with reperfusion injury of the brain.

Acute ischemic vulnerability of PKA in the dendritic subfields of the hippocampus CA1

Alterations of [3H]cyclic AMP (cAMP) binding, an indicator of the binding activity of particulate cyclic AMP-dependent protein kinase (PKA), were examined after 15 and 30 min of ischemia in the gerbil brain. Severe hemispheric cerebral ischemia was induced by occluding the right common carotid artery. Significant reductions in cAMP binding were noted only in the dendritic subfields of the hippocampus CA1 such as the strata oriens, radiatum and lacunosum-moleculare, on the ischemic side after 15 min of ischemia. After 30 min ischemia cAMP binding was significantly decreased not only in each dendritic subfield of the hippocampus CA1, but also in the layer of pyramidal cell bodies (stratum pyramidale) on the occluded side; other brain regions such as the hippocampus CA3, dentate gyrus and cerebral cortices revealed no significant changes in cAMP binding. These findings suggest that derangement of PKA may begin in the dendritic subfields of the hippocampus CA1 after as little as 15 min of severe ischemia, and proceed centrally to the neuronal cell bodies of the hippocampus CA1.

Rapid reduction in ryanodine binding of hippocampus CA1 in cerebral ischemia

Ryanodine receptors located on the sarcoplasmic or endoplasmic reticulum, play an important role in the regulation of the intracellular Ca2+ level via the mechanism of Ca(2+)-induced Ca2+ release (CICR). Perturbation of intracellular Ca2+ regulation has been considered to be one of the most important mechanisms underlying acute ischemic neuronal damage. The ryanodine binding, an indicator of intracellular channels of CICR, and local cerebral blood flow (LCBF) were therefore examined at 15 min post-ischemia in the gerbil brain. The autoradiographic method developed in our laboratory enabled us to determine both parameters within the same brain. Severe hemispheric cerebral ischemia was induced by occluding the right common carotid artery. LCBF was measured at the end of the experiment using [14C]iodoantipyrine method. The ryanodine binding was evaluated autoradiographically in vitro using [3H] ryanodine. A group of gerbils who underwent a sham procedure served as controls. LCBF was found to be significantly decreased in most cerebral regions on the occluded side. In contrast, a significant reduction in ryanodine binding was noted only in the hippocampus CA1 on the occluded side. Taken together, these findings indicate that the CICR in the hippocampus CA1 may be especially susceptible to acute ischemic stress, and be closely associated with the pathophysiological mechanisms of the selective vulnerability of this region.