Role of prefrontal cortical calcium-independent phospholipase A2 in antinociceptive effect of the norepinephrine reuptake inhibitor antidepresssant maprotiline.

The prefrontal cortex is essential for executive functions such as decision-making and planning. There is also accumulating evidence that it is important for the modulation of pain. In this study, we investigated a possible role of prefrontal cortical calcium-independent phospholipase A2 (iPLA2) in antinociception induced by the norepinephrine reuptake inhibitor (NRI) and tetracyclic (tricyclic) antidepressant, maprotiline. Intraperitoneal injections of maprotiline increased iPLA2 mRNA and protein expression in the prefrontal cortex. This treatment also reduced grooming responses to von-Frey hair stimulation of the face after facial carrageenan injection, indicating decreased sensitivity to pain. The antinociceptive effect of maprotiline was abrogated by iPLA2 antisense oligonucleotide injection to the prefrontal cortex, indicating a role of this enzyme in antinociception. In contrast, injection of iPLA2 antisense oligonucleotide to the somatosensory cortex did not reduce the antinociceptive effect of maprotiline. Lipidomic analysis of the prefrontal cortex showed decrease in phosphatidylcholine species, but increase in lysophosphatidylcholine species, indicating increased PLA2 activity, and release of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) after maprotiline treatment. Differences in sphingomyelin/ceramide were also detected. These changes were not observed in maprotiline-treated mice that received iPLA2 antisense oligonucleotide to the prefrontal cortex. Metabolites of DHA and EPA may help to strengthen a known supraspinal antinociceptive pathway from the prefrontal cortex to the periaqueductal gray. Together, results indicate a role of prefrontal cortical iPLA2 and its enzymatic products in the antinociceptive effect of maprotiline.

An intraosseous sclerosing odontogenic tumor predominantly composed of epithelial cells: relation to (so-called) sclerosing odontogenic carcinoma and epithelial-rich central odontogenic fibroma.

We report a case of an asymptomatic sclerosing odontogenic tumor in a 31-year-old woman. Radiologically, the tumor was well circumscribed, was predominantly radiolucent, and had a peripheral sclerotic margin. Histopathologically, the tumor showed small clusters, strands, and cords of small to medium-sized epithelial tumor cells in a sclerotic collagenous stroma. Immunohistochemically, the tumor cells were positive for broad-spectrum cytokeratins (CKs) (CK7, CK5/6, CK19, and CAM 5.2) and p63. Membranous staining for E-cadherin was present. There was weak to moderate nuclear expression of p16 in 30% of cells. Rare tumor cells were positive for p53. Progesterone receptors were expressed in about 60% of the tumor cells. The proliferative activity (Ki-67) was approximately 2%. A molecular genetic (fluorescence in situ hybridization) study showed no EWSR1 (EWS RNA-binding protein 1) gene rearrangement. No recurrence or metastatic events have been documented at 1-year follow-up. This tumor represents a classification dilemma mainly between epithelial-rich central odontogenic fibroma and the so-called sclerosing odontogenic carcinoma.

Human embryonic stem cells derived keratinocyte as an in vitro research model for the study of immune response.

BACKGROUND: The innate immune response (IMR) is critical for the oral mucosa due to their continuous exposure to various oral pathogens. Keratinocytes play important role in IMR. Therefore, to date, keratinocytes from different sources have been used as in vitro research model for the study of IMR. However, current keratinocyte research models are hampered by the limited supply, patients' dependency and batch to batch variation. Therefore, in this study, we demonstrated the use of human embryonic stem cells (hESCs) derived keratinocytes (H9-Kert) as an alternative research model for the study of IMR. METHODS: The expression kinetics of toll-like receptor (TLR) 2, TLR 4, interleukin (IL) -6, IL-8, inducible nitric oxide synthase (iNOS) and tumour necrosis factor-alpha (TNF-α), in H9-Kert and immortalized human keratinocyte cell line (HaCaT) were analysed at mRNA levels by both reverse transcription polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR. The activation of the inflammatory transcription factor nuclear factor kappa-b (NFĸB) was assayed in these cells by transiently transfecting the cells with NFĸB reporter plasmid. Activation of NFĸB following treatment with heat-killed Porphyromonas gingivalis (P. gingivalis), an oral pathogen, was determined by assaying for the reporter, secreted alkaline phosphatase activity. RESULTS: The expression of TLRs, cytokines and activation of NFĸB following bacterial stimulation showed in both H9-Kert and the widely used HaCaT keratinocyte cell line was similar. CONCLUSION: Overall, our results support the potential application of hESCs as an alternative limitless cell source for primary keratinocytes which can be used as consistent and dependable research tool with minimum variations and no donor's dependency.

Progression of periodontal destruction and the roles of advanced glycation end products in experimental diabetes.

BACKGROUND: Progression of diabetes-associated periodontal destruction and the roles of advanced glycation end products (AGEs) are investigated. METHODS: Diabetes was induced by streptozocotin injection, and periodontitis was induced via silk ligature placement with Porphyromonas gingivalis lipopolysaccharide injection in 64 Sprague-Dawley rats for 7 to 21 days. The quality of alveolar bone and attachment loss (AL) were measured by microcomputed tomography and histology. Destruction profiles were evaluated by histology, histochemistry, immunohistochemistry, and quantitative assessments of inflammatory cells, expression of receptors for AGEs (RAGE), tartrate-resistant acid phosphatase, and proliferating cell nuclear antigen. RESULTS: Without periodontitis induction, there was no obvious morphologic change in the periodontium, although slight elevations of AGEs and RAGE levels were noted in animals with diabetes. In the group with experimental periodontitis, significant periodontal bone loss was noted in animals both with and without diabetes from day 7, with more progressive bone loss in animals with diabetes during days 14 to 21. Histologically, the disruption of attachment and inflammation were observed from day 7, but subsequently subsided in animals without diabetes. A stronger and more prolonged response with significant AL was observed in animals with diabetes. Stronger inflammation, attenuated and persistent resorptive activity, and weaker proliferating potential were demonstrated by animals with diabetes. AGE deposition and RAGE expression were noted in animals without diabetes but with periodontitis, although levels were considerably elevated in the later stages in animals with diabetes. CONCLUSIONS: Diabetes augments periodontal destruction by reducing the proliferating capability and activating resorptive activities. Presence of the AGE-RAGE axis without diabetes implies that it is involved in the regulation of inflammation.

Comprehensive gene expression profiling in the prefrontal cortex links immune activation and neutrophil infiltration to antinociception.

Functional neuroimaging studies have implicated the prefrontal cortex (PFCTX) in descending modulation of pain and the placebo effect. This study was performed to elucidate comprehensive PFCTX gene expression in an animal model of persistent trigeminal pain. Adult male C57BL/6J mice received facial carrageenan injection and showed sustained increase in nociceptive responses. Microarray analyses of differentially expressed genes in the PFCTX at 3 d after injection showed "immune system process" as the dominant ontology term and increased mRNA expression of S100a8, S100a9, Lcn2, Il2rg, Fcgr1, Fcgr2b, C1qb, Ptprc, Ccl12, and Cd52 were verified by RT-PCR. Upregulation of S100A8, S100A9, and lipocalin 2 (LCN2) were confirmed by Western blots, and cells in the PFCTX were double immunolabeled with MPO, indicating they were neutrophils. Analyses of blood of facial carrageenan-injected mice also showed increased mRNA expression of these markers, suggesting transmigration of activated neutrophils into the brain. Other immune-related genes, Il2rg, Fcgr2b, C1qb, Ptprc, and Ccl12 were upregulated in the PFCTX but not blood. Approximately 70% of S100A9-positive cells in the PFCTX of carrageenan-injected mice were located in capillaries adherent to endothelial cells, whereas 30% were within the brain parenchyma. Carrageenan-injected mice showed significantly reduced nociceptive responses after injection of C terminus of murine S100A9 protein in the lateral ventricles and PFCTX but not somatosensory barrel cortex. Together, these findings demonstrate activation of immune-related genes in the PFCTX during inflammatory pain and highlight an exciting role of neutrophils in linking peripheral inflammation with immune activation of the PFCTX and antinociception.

MicroRNA changes in the mouse prefrontal cortex after inflammatory pain.

Activation of the prefrontal cortex occurs during acute and chronic pain and models of experimental hyperalgesia. The present study was carried out to determine possible miRNA changes in the prefrontal cortex, after inflammatory pain induced by facial carrageenan injection in mice. miRNA microarray analyses showed significantly increased levels of miR-155 and miR-223 in the prefrontal cortex of carrageenan-injected mice. The changes were verified by real-time RT-PCR, and shown to occur bilaterally. The potential targets of the two miRNAs were predicted, and changes in two of the miRNA targets, c/ebp Beta and granulocyte colony-stimulating factor (GCSF) verified by real-time RT-PCR. Significantly downregulated c/ebp Beta but upregulated GCSF, accompanied by increased immunolabeling with an antibody to myeloperoxidase were found in the prefrontal cortex of facial carrageenan treated mice. It is postulated that this could lead to increased inflammation and activation of the prefrontal cortex. Further studies are necessary to determine if specific miRNAs could be useful as therapeutic molecules for pain.

Role of calcium independent phospholipase A2 in maintaining mitochondrial membrane potential and preventing excessive exocytosis in PC12 cells.

This study was carried out to elucidate the effects of calcium independent phospholipase A(2) (iPLA(2)) on mitochondrial function and exocytosis in neuroendocrine cells. iPLA(2) mRNA and protein were detected in cell lysates and mitochondria from PC12 cells. Treatment of cells with the iPLA(2) inhibitor, bromoenol lactone (BEL), resulted in reduction in the mitochondrial membrane potential. Increase in membrane capacitance and number of spikes at amperometry, indicating exocytosis, were detected from PC12 cells after treatment with BEL. The induced exocytosis was abolished by pre-incubation of cells with the antioxidant, glutathione monoethyl ester, spin-trap/free radical scavenger, PBN, or inhibitors of the mitochondrial permeability transition pore, cyclosporine A and bongkrekic acid. These findings indicate that inhibition of iPLA(2) results in excessive exocytosis through increased oxidative damage (or failure to repair such damage) and defects in mitochondrial function. A similar process may occur in neurons with mutations in iPLA(2), leading to neuronal injury.

Expression profile of multiple secretory phospholipase A(2) isoforms in the rat CNS: enriched expression of sPLA(2)-IIA in brainstem and spinal cord.

Phospholipases A(2) (PLA(2)) are enzymes which cleave the sn-2 ester bond in membrane phospholipids to release free fatty acids and lysophospholipids. The present study aimed to elucidate the expression profile of multiple secretory phospholipase A(2) (sPLA(2)) isoforms in the normal rat CNS with focus on sPLA(2)-IIA in the brainstem and spinal cord. Quantitative RT-PCR analysis showed that sPLA(2)-IB expression was low throughout the CNS, sPLA(2)-IIA expression was high in the brainstem and spinal cord, sPLA(2)-IIC expression was high in the cerebral neocortex, hippocampus and thalamus/hypothalamus, sPLA(2)-V expression was high in the olfactory bulb and cerebellum, and sPLA(2)-X was expressed at very low levels in the normal CNS. Of the isoforms, sPLA(2)-IIA mRNA expression was highest in the brainstem and spinal cord suggesting that this could be the most relevant isoform in the ascending pain pathway. Western blot analysis showed high level of sPLA(2)-IIA expression in the brainstem and cervical, thoracic and lumbar spinal segments but low level of expression in other parts of the brain. sPLA(2)-IIA was localized by immunohistochemistry to the spinal trigeminal and facial motor nuclei and dorsal- and ventral-horns of the spinal cord. The enzyme was found on the endoplasmic reticulum of neuronal cell bodies and small diameter dendrites or dendritic spines at electron microscopy. The expression of sPLA(2)-IIA in the dorsal horn and spinal trigeminal nucleus is consistent with previous results which showed an important role of CNS sPLA(2) in nociceptive transmission.

Differential effects of lysophospholipids on exocytosis in rat PC12 cells.

Secretory phospholipase A2 (sPLA2) activity is present in the CNS and the sPLA2-IIA isoform has been shown to induce exocytosis in cultured hippocampal neurons. However, little is known about possible contributions of various lysophospholipid species to exocytosis in neuroendocrine cells. This study was therefore carried out to examine the effects of several lysophospholipid species on exocytosis on rat pheochromocytoma-12 (PC12) cells. An increase in vesicle fusion, indicating exocytosis, was observed in PC12 cells after external infusion of lysophosphatidylinositol (LPI), but not lysophosphatidylcholine or lysophosphatidylserine by total internal reflection microscopy. Similarly, external infusion of LPI induced significant increases in capacitance, or number of spikes detected at amperometry, indicating exocytosis. Depletion of cholesterol by pre-incubation of cells with methyl beta cyclodextrin and depletion of Ca2+ by thapsigargin and incubation in zero external Ca2+ resulted in attenuation of LPI induced exocytosis, indicating that exocytosis was dependent on the integrity of lipid rafts and intracellular Ca2+. Moreover, LPI induced a rise in intracellular Ca2+ suggesting that this could be the trigger for exocytosis. It is postulated that LPI may be an active participant in sPLA2-mediated exocytosis in the CNS.

Anti-allodynic effect of intracerebroventricularly administered antioxidant and free radical scavenger in a mouse model of orofacial pain.

AIMS: To evaluate possible effects of the intracerebroventricular (icv) injection of either O-Tricyclo [5.2.1.0(2,6)] dec-9-yl dithiocarbonate potassium salt (D609), a potent antioxidant and inhibitor of phosphatidylcholine specific phospholipase C (PtdCho-PLC) and acid sphingomyelinase (ASMase), or the spin trap/free radical scavenger N-tert-Butyl-alpha-phenylnitrone (PBN), on mechanical allodynia induced by facial carrageenan injection in mice. METHODS: Balb/c mice received icy injection of D609/PBN plus facial carrageenan injection, and the number of face wash strokes to von Frey hair mechanical stimulation of the maxillary skin was quantified. PtdCho-PLC and ASMase activities were also assayed in the brainstem, thalamus, and somatosensory cortex. RESULTS: Mice that received the icy injection of 10 nmol D609 plus facial carrageenan injection showed significantly fewer face wash strokes evoked by von Frey hair stimulation (indicating reduced mechanical allodynia) at 1 and 3 days post-injection, compared to mice that received icy injection of isotonic saline plus facial carrageenan injection. Mice that received icy injection of 1.13 micromol PBN plus facial carrageenan injection likewise showed significantly fewer face wash strokes after facial carrageenan injection, compared to isotonic saline-injected plus carrageenan-injected controls. D609 injection also resulted in significantly reduced ASMase activity in the brainstem, thalamus, and somatosensory cortex 3 days after injection, compared to controls. CONCLUSION: The icv injections of D609 and PBN were effective in reducing mechanical allodynia after facial carrageenan injection-induced pain. Together, the results point to a possible role of central nervous system sphingolipids and/or free radicals in orofacial pain.

Histological evaluation of osteogenesis of 3D-printed poly-lactic-co-glycolic acid (PLGA) scaffolds in a rabbit model.

Utilizing a suitable combination of lactide and glycolide in a copolymer would optimize the degradation rate of a scaffold upon implantation in situ. Moreover, 3D printing technology enables customizing the shape of the scaffold to biometric data from CT and MRI scans. A previous in vitro study has shown that novel 3D-printed poly-lactic-co-glycolic acid (PLGA) scaffolds had good biocompatibility and mechanical properties comparable with human cancellous bone, while they could support proliferation and osteogenic differentiation of osteoblasts. Based on the previous study, this study evaluated PLGA scaffolds for bone regeneration within a rabbit model. The scaffolds were implanted at two sites on the same animal, within the periosteum and within bi-cortical bone defects on the iliac crest. Subsequently, the efficacy of bone regeneration within the implanted scaffolds was evaluated at 4, 12 and 24 weeks post-surgery through histological analysis. In both the intra-periosteum and iliac bone defect models, the implanted scaffolds facilitated new bone tissue formation and maturation over the time course of 24 weeks, even though there was initially observed to be little tissue ingrowth within the scaffolds at 4 weeks post-surgery. Hence, the 3D-printed porous PLGA scaffolds investigated in this study displayed good biocompatibility and are osteoconductive in both the intra-periosteum and iliac bone defect models.

Global gene expression analysis in the mouse brainstem after hyperalgesia induced by facial carrageenan injection--evidence for a form of neurovascular coupling?

The present study was carried out to examine global gene expression in the brainstem, in a mouse facial carrageenan injection model of orofacial pain. Mice that received facial carrageenan injection showed increased mechanical allodynia, demonstrated by increased responses to von Frey hair stimulation of the face. The brainstem was harvested at 3 days post-injection, corresponding to the time of peak responses, and analyzed by Affymetrix Mouse Genome 430 2.0 microarrays. We sought to identify common genes that are changed in the respective sides of the brainstem after either right- or left-sided facial carrageenan injection. The result is a relatively small list of genes (22 genes), which were then classified using DAVID software. Many of them fell into the categories of "response to stress", "defence response", "response to biotic stimulus", "cell adhesion" and "leukocyte adhesion". Of these, increased expression of P-selectin, ICAM-1 and CCL12 after carrageenan injection could be verified by real-time RT-PCR on both the right and left sides, and increased in P-selectin and ICAM-1 further verified by Western blot analysis. P-selectin and ICAM-1 were immunolocalized to endothelial cells, and were double labelled with von Willebrand factor. Intraperitoneal injection of the P-selectin inhibitor KF38789 significantly reduced mechanical allodynia in the facial carrageenan-injected mice. P-selectin mediates the capturing of leukocytes from the bloodstream and rolling of leukocytes along the endothelial surface. We hypothesize that increased nociceptive input to the brainstem could attract circulating macrophages into the brain, resulting in neuroinflammation and pain.

An autologous cell lysate extract from human embryonic stem cell (hESC) derived osteoblasts can enhance osteogenesis of hESC.

It was recently demonstrated that osteogenesis of hESC was more efficient without the initial embryoid body formation step. This study sought to further improve this direct differentiation culture system, by developing an autologous osteogenic-inducing culture supplement extracted from hESC-derived osteogenic cells themselves. A whole cell lysate was prepared from hESC-derived osteogenic cells, simply by exposure to deionized water followed by free-thawing and subsequent filtration. The product was used to coat the surface of cell culture dishes together with gelatin, prior to culture of hESC under osteogenic-inducing conditions. The results showed that the autologous cell lysate extract promoted the aggregation and clustering of cells to form nodule-like structures. Immunohistochemical staining on day 9 demonstrated that these cellular aggregates strongly expressed STRO-1, while on day 14 the nodule-like structures stained positively for both osteocalcin and osteonectin (SPARC). By contrast, the negative control (gelatin coating alone) showed much less prominent cellular aggregation and clustering, and was stained much less intensely for these markers. Additionally, Von Kossa staining on day 14 was also more intense in the presence of the autologous cell lysate extract. Hence, this product can be used to further enhance the osteogenesis of hESC. This would save costs from the use of highly-expensive cytokines, growth factors and matrix components, as well as avoid pathogenic transmission from animal and human products.

Antinociceptive effect of CNS peroxynitrite scavenger in a mouse model of orofacial pain.

Peroxynitrite (ONOO(-)) and species derived from it can oxidize and nitrate lipids, proteins and DNA leading to changes in signaling molecules. The present study was carried out to elucidate possible effects of CNS peroxynitrite in a mouse model of orofacial pain. Mice that received facial carrageenan injection + intracerebroventricular (i.c.v.) injection of the peroxynitrite scavenger [5,10,15,20-Tetrakis (4-sulfonatophenyl) porphyrinato iron (III), chloride] (FeTPPS) showed significantly fewer face wash strokes upon probing the inflamed area of the face with a von Frey hair at 6 h after injection, compared to mice that received facial carrageenan alone, or facial carrageenan injection + i.c.v. injection of saline. Mice that received i.c.v. injection of FeTPPS without facial carrageenan injection showed no significant difference in response to von Frey hair stimulation, compared to mice that received i.c.v. injection of saline without facial carrageenan injection. These results indicate an anti-nociceptive effect of the peroxynitrite scavenger FeTPPS in carrageenan induced facial pain but no effect on normal tactile sensation and point to an important role of CNS peroxynitrite in nociception.

Differential effects of ceramide species on exocytosis in rat PC12 cells.

Increases in several ceramide species have been shown by non-targeted lipid profiling (lipidomics) of the rat hippocampus after kainate lesions (Guan et al. FASEB J 20:1152-1161, 2006). This study was carried out to examine possible effects of ceramide species on exocytosis. Significant increase in membrane capacitance in voltage-clamped rat pheochromocytoma (PC12) cells, an indication of exocytosis, was detected immediately after external application of C2, C6, and C18 ceramide. In contrast, no increase in capacitance was found after addition of C16 and C20 ceramide, or DMSO vehicle. The effect of ceramide on exocytosis was dependent on the integrity of lipid rafts. Treatment of cells with the cholesterol binding agent/disruptor of lipid rafts, methyl beta cyclodextrin, prior to addition of C18 ceramide suppressed the increase in capacitance induced by this lipid species. The ability of C2, C6 and C18 ceramide to trigger exocytosis was confirmed using total internal reflection fluorescence microscopy (TIRFM) experiments. External application of these species caused an exponential decrease in the number of subplasmalemmal neuropeptide Y (NPY)-enhanced green fluorescence protein (EGFP) labeled vesicles, indicating exocytosis. Interestingly, C18 is also the ceramide species that showed the greatest increase in the rat hippocampus after kainate excitotoxicity. It is postulated that C18 ceramide might facilitate exocytosis of glutamate from damaged neurons, thus propagating neuronal injury.

Clinicopathological study of dentigerous cysts in Singapore and Malaysia.

This was a retrospective study of dentigerous cysts in people from the Singapore-Malaysian region. The purpose of this study was to present the clinicopathologic features of dentigerous cysts in the Oriental population and to compare these data with those from other reported studies. Biopsy records from 1981 to 1993 of 119 cases of dentigerous cysts from patients in Malaysia and Singapore showed that 36.1% of patients were female and 63.9% patients were male. Among patients with cysts, 70.5% were Chinese, 23.2% were Malays, 2.7% were Indian and 3.6% were other ethnic groups. The mean age of these patients was 30.2 +/- 17.3 years with a peak incidence occurring in the second and third decades. The location of the lesions was almost equal to the maxilla (50.9%) and the mandible (49.1%). There was a marked predilection for the posterior mandible (42.7%) followed by the anterior maxilla (38.2%). Histologically, 90.8% of the cysts were lined by a non-keratinised stratified squamous epithelium. The cyst linings were mainly thin (90.0%) with 38.7% of cases having a mixed thick and thin lining. Mucous metaplasia was observed in 9 (7.6%) cases. Rushton bodies were seen in 3.4% of cases. Cholesterol clefts in the epithelial lining and lumen were found in 16.8% cases while 12.6% of cases exhibited cholesterol clefts in the cyst wall. Other cellular structures within the cyst wall were lymphocytes (66.4%), plasma cells (52.1%), Russell bodies (16.0%) and histiocytes (4.2%). Odontogenic keratocysts were observed in 5.0% of cases. One case of adenomatoid odontogenic tumour was also observed. Epithelial atypia was seen in 9.2% of cases, islands of stratified squamous epithelial cells in 8.4% of cases while one case showed a combination of these two features. In conclusion, some clinical features seen in this study are similar to that for the Caucasian population such as prevalence in male, peak incidence in the second and third decades and the predilection for the posterior mandible and anterior maxilla. Histopathologically, odontogenic keratocyst and adenomatoid odontogenic tumour were observed in dentigerous cysts.

Effects of intracerebroventricular injections of free fatty acids, lysophospholipids, or platelet activating factor in a mouse model of orofacial pain.

The present study was carried out to determine the effects of central nervous free fatty acids, lysophospholipids, or platelet activating factor (PAF), in a mouse facial carrageenan injection model of orofacial pain. Mice that received intracerebroventricular (I.C.V.) injection of arachidonic acid or oleic acid showed significantly reduced allodynia and behavioral responses to von Frey hair stimulation of a carrageenan-injected area of the face, at 8 h post-injection, compared to controls that received I.C.V. injection of vehicle. In contrast to free fatty acids, increased responses were observed in mice at 72 h after I.C.V. lysophosphatidic acid or lysophosphatidylcholine injection, and at 8 and 24 h after PAF injection, compared vehicle injected controls. Information regarding pro-nociceptive effect of specific brain lipids may be a useful basis for further studies to explore mechanism.

Differential effects of polyunsaturated fatty acids on membrane capacitance and exocytosis in rat pheochromocytoma-12 cells.

The fusion of synaptic vesicles with the plasma membrane during exocytosis can be recorded by membrane capacitance measurements under voltage-clamp conditions. These measurements enable high time-resolution quantitation of exocytosis. The present study was carried out using the above technique to elucidate the effects of various polyunsaturated fatty acids on exocytosis in a neuroendocrine cell, the rat pheochromocytoma-12 (PC12) cell. External application of eicosapentaenoic acid and arachidonic acid resulted in an increase in capacitance of PC12 cells, indicating fusion of secretory vesicles with cell membranes and exocytosis. In contrast, docosahexaenoic acid, linoleic acid, oleic acid, and vehicle control had no significant effect on capacitance. The above findings show differential effects of polyunsaturated fatty acids on exocytosis in PC12 cells. It is postulated that besides arachidonic acid, eicosapentaenoic acid could also play an important role in exocytosis and neurotransmitter release, in neurons and hormone-secreting cells.

Injury and recovery of pyramidal neurons in the rat hippocampus after a single episode of oxidative stress induced by intracerebroventricular injection of ferrous ammonium citrate.

The present study was carried out to elucidate the effect of a single episode of oxidative stress on pyramidal neurons of the rat hippocampus. A significant increase in the number of neurons that were immunolabeled for the toxic lipid peroxidation product, 4-hydroxynonenal (HNE) was observed in field CA3 of the hippocampus, at 1 day, 7 days and 14 days after intracerebroventricular injection of 1 microL of 5 mM ferrous ammonium citrate, compared to ammonium citrate injected controls at these time points. The number of HNE positive cells was fewer at 14 days, compared to 1 day, after ferrous ammonium citrate injection. The changes in HNE immunoreactivity were paralleled by changes in cytoplasmic phospholipase A2 (cPLA2) labeling in the pyramidal neurons in adjacent sections, suggesting that some of the HNE could have arisen as a result of peroxidation of arachidonic acid that was released by cPLA2. Interestingly, despite the HNE and cPLA2 labeling, no loss of neurons was observed in adjacent Nissl and Fluoro-Jade stained sections. Electron microscopy also showed that the HNE or cPLA2 labeled cells had features of injured neurons, rather than necrotic neurons. The reduction of HNE immunoreactivity in neurons at 14 days after oxidative injury, and the absence of cell loss at any of the time intervals, shows that hippocampal pyramidal neurons have remarkable ability to recover from a single episode of oxidative stress, if repeated injury such as seizures / excitotoxicity could be avoided.

Distribution of calcium-independent phospholipase A2 (iPLA 2) in monkey brain.

The present study was carried out to elucidate the distribution of calcium-independent phospholipase A(2) (iPLA(2)) in the normal monkey brain. iPLA(2) immunoreactivity was observed in structures derived from the telencephalon, including the cerebral neocortex, amygdala, hippocampus, caudate nucleus, putamen, and nucleus accumbens, whereas structures derived from the diencephalon, including the thalamus, hypothalamus and globus pallidus were lightly labeled. The midbrain, vestibular, trigeminal and inferior olivary nuclei, and the cerebellar cortex were densely labeled. Immunoreactivity was observed on the nuclear envelope of neurons, and dendrites and axon terminals at electron microscopy. Western blot analysis showed higher levels of iPLA(2) protein in the cytosolic, than the nuclear fraction, but little or no protein in the membrane fraction. Similarly, subcellular fractionation studies of iPLA(2) activity in rat brain cortical cell cultures showed greater enzymatic activity in the cytosolic, than the nuclear fraction, and the least activity in non-nuclear membranes. The association of iPLA(2) with the nuclear envelope suggests a role of the enzyme in nuclear signaling, such as during neuronal proliferation and differentiation or death. In addition, the localization of iPLA(2) in dendrites and axon terminals suggests a role of the enzyme in neuronal signaling.