Regulation of cytokine-induced iNOS expression by a hairpin oligonucleotide in murine cerebral endothelial cells

Inhibition of cerebral vascular inflammation by brain endothelium-targeted oligodeoxynucleotide complex

The present study generated a novel DNA complex to specifically target endothelial NF-κB to inhibit cerebral vascular inflammation. This DNA complex (GS24-NFκB) contains a DNA decoy which inhibits NF-κB activity, and a DNA aptamer (GS-24), a ligand of transferrin receptor (TfR), which allows for targeted delivery of the DNA decoy into cells. The results indicate that GS24-NFκB was successfully delivered into a murine brain-derived endothelial cell line, bEND5, and inhibited inflammatory responses induced by tumor necrosis factor α (TNF-α) or oxygen-glucose deprivation/re-oxygenation (OGD/R) via down-regulation of the nuclear NF-κB subunit, p65, as well as its downstream inflammatory cytokines, inter-cellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule (VCAM-1). The inhibitory effect of the GS24-NFκB was demonstrated by a significant reduction in TNF-α or OGD/R induced monocyte adhesion to the bEND5 cells after GS24-NFκB treatment. Intravenous (i.v.) injection of GS24-'NFκB (15mg/kg) was able to inhibit the levels of phoseph-p65 and VCAM-1 in brain endothelial cells in a mouse lipopolysaccharide (LPS)-induced inflammatory model in vivo. In conclusion, our approach using DNA nanotechnology for DNA decoy delivery could potentially be utilized for inhibition of inflammation in ischemic stroke and other neuro-inflammatory diseases affecting cerebral vasculature.

Bcl-x pre-mRNA splicing regulates brain injury after neonatal hypoxia-ischemia

The bcl-x gene appears to play a critical role in regulating apoptosis in the developing and mature CNS and following CNS injury. Two isoforms of Bcl-x are produced as a result of alternative pre-mRNA splicing: Bcl-x(L) (the long form) is anti-apoptotic, while Bcl-x(S) (short form) is pro-apoptotic. Despite the antagonistic activities of these two isoforms, little is known about how regulation of alternative splicing of bcl-x may mediate neural cell apoptosis. Here, we report that apoptotic stimuli (staurosporine or C2-ceramide) reciprocally altered Bcl-x splicing in neural cells, decreasing Bcl-x(L) while increasing Bcl-x(S). Specific knockdown of Bcl-x(S) attenuated apoptosis. To further define regulatory elements that influenced Bcl-x splicing, a Bcl-x minigene was constructed. Deletional analysis revealed several consensus sequences within intron 2 that altered splicing. We found that the splicing factor, CUG-binding-protein-1 (CUGBP1), bound to a consensus sequence close to the Bcl-x(L) 5' splice site, altering the Bcl-x(L)/Bcl-x(S) ratio and influencing cell death. In vivo, neonatal hypoxia-ischemia reciprocally altered Bcl-x pre-mRNA splicing, similar to the in vitro studies. Manipulation of the splice isoforms using viral gene transfer of Bcl-x(S) shRNA into the hippocampus of rats before neonatal hypoxia-ischemia decreased vulnerability to injury. Moreover, alterations in nuclear CUGBP1 preceded Bcl-x splicing changes. These results suggest that alternative pre-mRNA splicing may be an important regulatory mechanism for cell death after acute neurological injury and may potentially provide novel targets for intervention.

Role of cerebral endothelial cells in the astrocyte swelling and brain edema associated with acute hepatic encephalopathy

Brain edema is an important complication of acute hepatic encephalopathy (AHE), and astrocyte swelling is largely responsible for its development. Elevated blood and brain ammonia levels have been considered as major etiological factors in this edema. In addition to ammonia, recent studies have suggested that systemic infection, inflammation (and associated cytokines (CKs)), as well as endotoxin (lipopolysaccharide (LPS)) are also involved in AHE-associated brain edema. As endothelial cells (ECs) are the first resident brain cells exposed to blood-borne "noxious agents" (i.e., ammonia, CKs, LPS) that are present in AHE, these cells may be in a critical position to react to these agents and trigger a process resulting in astrocyte swelling/brain edema. We therefore examined the effect of conditioned media (CM) from ammonia, LPS and cytokine-treated cultured brain ECs on cell swelling in cultured astrocytes. CM from ammonia-treated ECs when added to astrocytes caused significant cell swelling, and such swelling was potentiated when astrocytes were exposed to CM from ECs treated with a combination of ammonia, LPS and CKs. We also found an additive effect when astrocytes were exposed to ammonia along with CM from ammonia-treated ECs. Additionally, ECs treated with ammonia showed a significant increase in the production of oxy-radicals, nitric oxide (NO), as well as evidence of oxidative/nitrative stress and activation of the transcription factor nuclear factor kappa B (NF-κB). CM derived from ECs treated with ammonia, along with antioxidants (AOs) or the NF-κB inhibitor BAY 11-7082, when added to astrocytes resulted in a significant reduction in cell swelling, as compared to the effect of CM from ECs-treated only with ammonia. We also identified increased nuclear NF-κB expression in rat brain cortical ECs in the thioacetamide (TAA) model of AHE. These studies suggest that ECs significantly contribute to the astrocyte swelling/brain edema in AHE, likely as a consequence of oxidative/nitrative stress and activation of NF-κB.

A common 5'-UTR variant in MATE2-K is associated with poor response to metformin

Multidrug and toxin extrusion 2 (MATE2-K (SLC47A2)), a polyspecific organic cation exporter, facilitates the renal elimination of the antidiabetes drug metformin. In this study, we characterized genetic variants of MATE2-K, determined their association with metformin response, and elucidated their impact by means of a comparative protein structure model. Four nonsynonymous variants and four variants in the MATE2-K basal promoter region were identified from ethnically diverse populations. Two nonsynonymous variants-c.485C>T and c.1177G>A-were shown to be associated with significantly lower metformin uptake and reduction in protein expression levels. MATE2-K basal promoter haplotypes containing the most common variant, g.-130G>A (>26% allele frequency), were associated with a significant increase in luciferase activities and reduced binding to the transcriptional repressor myeloid zinc finger 1 (MZF-1). Patients with diabetes who were homozygous for g.-130A had a significantly poorer response to metformin treatment, assessed as relative change in glycated hemoglobin (HbA1c) (-0.027 (-0.076, 0.033)), as compared with carriers of the reference allele, g.-130G (-0.15 (-0.17, -0.13)) (P=0.002). Our study showed that MATE2-K plays a role in the antidiabetes response to metformin.

Anti-inflammatory effects of limonene from yuzu (Citrus junos Tanaka) essential oil on eosinophils

Yuzu (Citrus junos Tanaka) has been used as a traditional medicine in Japan. We investigated in vitro anti-inflammatory effects of limonene from yuzu peel on human eosinophilic leukemia HL-60 clone 15 cells. To examine anti-inflammatory effects of limonene on the cells, we measured the level of reactive oxygen species (ROS), monocyte chemoattractant protein-1 (MCP-1), nuclear factor (NF) kappa B, and p38 mitogen-activated protein kinase (MAPK). We found that low concentration of limonene (7.34 mmol/L) inhibited the production of ROS for eotaxin-stimulated HL-60 clone 15 cells. 14.68 mmol/L concentration of limonene diminished MCP-1 production via NF-kappa B activation comparable to the addition of the proteasomal inhibitor MG132. In addition, it inhibited cell chemotaxis in a p38 MAPK dependent manner similar to the adding of SB203580. These results suggest that limonene may have potential anti-inflammatory efficacy for the treatment of bronchial asthma by inhibiting cytokines, ROS production, and inactivating eosinophil migration.

Identification and characterization of novel polymorphisms in the basal promoter of the human transporter, MATE1

OBJECTIVES

Human multidrug and toxin extrusion member 1, MATE1 (SLC47A1), plays an important role in the renal and biliary excretion of endogenous and exogenous organic cations including many therapeutic drugs. In this study, we characterized the transcriptional effects of five polymorphic variants and six common haplotypes in the basal promoter region of MATE1 that were identified in 272 DNA samples from ethnically diverse US populations.

METHODS

We measured luciferase activities of the six common promoter haplotypes of MATE1 using in-vitro and in-vivo reporter assays.

RESULTS

Haplotypes that contain the most common variant (mean allele frequency in four ethnic groups: 0.322), g.-66T>C, showed a significant decrease in reporter activities compared to the reference. Two transcription factors, activating protein-1 (AP-1) and activating protein-2 repressor (AP-2rep), were predicted to bind to the promoter in the region of g.-66T>C. Results from electrophoretic mobility shift assays showed that the g.-66T allele, exhibited greater binding to AP-1 than the g.-66C allele. AP-2rep inhibited the binding of AP-1 to the MATE1 basal promoter region, and the effect was considerably greater for the g.-66T>C. These data suggest that the reduced transcriptional activity of g.-66T>C results from a reduction in the binding potency of the transcriptional activator, AP-1, and an enhanced binding potency of the repressor, AP-2rep to the MATE1 basal promoter region. Consistent with the reporter assays, MATE1 mRNA expression levels were significantly lower in kidney samples from individuals who were homozygous or heterozygous for g.-66T>C in comparison with samples from individuals who were homozygous for the g.-66T allele.

CONCLUSION

Our study suggests that the rate of transcription of MATE1 is regulated by AP-1 and AP-2rep and that a common promoter variant, g.-66T>C may affect the expression level of MATE1 in human kidney, and ultimately result in variation in drug disposition and response.

DNA methylation and not allelic variation regulates STAT6 expression in human T cells

STAT6 transcription factor, which has been implicated in commitment to Th2, is known to be activated by IL-4 and IL-13. Accordingly, STAT6 is primarily responsible for the transcriptional effects of IL-4 and IL-13. STAT6-deficient mice are known to have defective IL-4-mediated functions, such as B cell proliferation, Th2 cell development and IgE secretion; therefore, they primarily contain the Th1 phenotype. However, the mechanism responsible for regulation of STAT6 expression transcriptionally and post-transcriptionally has yet to be elucidated. Here, we characterized the human STAT6 promoter gene and found that the transcriptional regulatory elements CCAAT and ATF were important for the STAT6 promoter activity. Direct sequencing analysis revealed that the 13 GT repeat allelic variation in noncoding exon 1 of the STAT6 gene appeared more frequently in 91 patients with asthma or rheumatoid arthritis than the 15 GT repeat variation, which is the dominant phenotype in healthy controls. However, it appears that this allelic variation did not affect the STAT6 transcriptional activity. Interestingly, treatment with a DNA methyltransferase inhibitor markedly increased the expression of STAT6 mRNA and protein in human primary T cells. In contrast, IFN-gamma treatment significantly repressed the STAT6 transcriptional activity. Therefore, the present study provides insight into the molecular basis of STAT6 expression, and in particular, demonstrates that STAT6 expression is associated with DNA hypermethylation rather than promoter polymorphisms or allelic variations.

Methylprednisolone protects oligodendrocytes but not neurons after spinal cord injury

Methylprednisolone (MP) is used to treat a variety of neurological disorders involving white matter injury, including multiple sclerosis, acute disseminated encephalomyelitis, and spinal cord injury (SCI). Although its mechanism of action has been attributed to anti-inflammatory or antioxidant properties, we examined the possibility that MP may have direct neuroprotective activities. Neurons and oligodendrocytes treated with AMPA or staurosporine died within 24 h after treatment. MP attenuated oligodendrocyte death in a dose-dependent manner; however, neurons were not rescued by the same doses of MP. This protective effect was reversed by the glucocorticoid receptor (GR) antagonist (11, 17)-11-[4-(dimethylamino)phenyl]-17-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one (RU486) and small interfering RNA directed against GR, suggesting a receptor-dependent mechanism. MP reversed AMPA-induced decreases in the expression of anti-apoptotic Bcl-x(L), caspase-3 activation, and DNA laddering, suggesting anti-apoptotic activity in oligodendrocytes. To examine whether MP demonstrated this selective protection in vivo, neuronal and oligodendrocyte survival was assessed in rats subjected to spinal cord injury (SCI); groups of rats were treated with or without MP in the presence or absence of RU486. Eight days after SCI, MP significantly increased oligodendrocytes (CC-1-immunoreactive cells) after SCI, but neuronal (neuronal-specific nuclear protein-immunoreactive cells) number remained unchanged; RU486 reversed this protective effect. MP also inhibited SCI-induced decreases in Bcl-x(L) and caspase-3 activation. Consistent with these findings, the volume of demyelination, assessed by Luxol fast blue staining, was attenuated by MP and reversed by RU486. These results suggest that MP selectively inhibits oligodendrocyte but not neuronal cell death via a receptor-mediated action and may be a mechanism for its limited protective effect after SCI.

In vitro toxicity evaluation of diesel exhaust particles on human eosinophilic cell

Diesel exhaust particles (DEPs), comprised mainly of particles less than 2.5 microm (PM 2.5) in aerodynamic diameter, have been assumed to enhance the response of asthma to allergen inhalation. Although eosinophilic infiltration is remarkable in the event of bronchial asthma induced by DEPs, the precise mechanisms leading to eosinophilia are unknown. To examine the effect of DEPs on eosinophils, we measured the cytokine products and activity of nuclear factor-kappa B (NF-kappa B) after addition of the proteasomal inhibitor MG132 in HL-60 clone 15 cells differentiated into eosinophils. We measured eotaxin-induced chemotaxis of cells and their activity of p38 mitogen-activated protein (MAP) kinase was analysed. Interleukin (IL)-8 and monocyte chemoattractant protein-1 (MCP-1) were increased markedly in DEPs-treated cells. The active form of NF-kappaB in cells treated with DEPs was increased, and this effect was significantly decreased by the administration of MG132. Cell migration in the presence of DEPs was significantly greater, and inhibited by adding N-acetyl l-cysteine. P38 MAP kinase activity was highly influenced by DEPs-treatment. DEPs induce MCP-1 and IL-8 production by up-regulating NF-kappa B activity, which is inhibited in the presence of an inhibitor of proteasomal degradation. DEP also promotes eotaxin-induced chemotaxis in a p38-dependent manner.

Localization of annexin II in the paranodal regions and Schmidt-Lanterman incisures in the peripheral nervous system

Annexin II (AX II) is a member of the family of calcium-dependent actin- and phospholipid-binding proteins implicated in numerous intracellular functions such as signal transduction, membrane trafficking, and mRNA transport, as well as in the regulation of membrane/cytoskeleton contacts and extracellular functions. AX II is expressed in the central nervous system (CNS) and is upregulated in some pathological conditions. However, expression and localization of this protein in the peripheral nervous system (PNS) is still uncertain. In the present study, we examined the expression and distribution of AX II in the PNS. By western blot analysis, we found that a higher level of AX II was present in sciatic nerve homogenates than in brain homogenates. RT-PCR of total RNA from rat sciatic nerves revealed that AX II was synthesized within the nerves. Immunohistological analysis showed the characteristic distribution of AX II in Schmidt-Lanterman incisures (SLI) as well as in the paranodal regions. Localization of AX II in the PNS was examined in two mutant mouse models, shiverer and cerebroside sulfotransferase knockout mice, both of which show increased numbers of SLI. The paranodal axo-glial junction is also disrupted in the latter. Interestingly, the staining intensities of AX II in these regions were increased markedly in both mutants, suggesting that not only the numbers but also AX II content in each incisure and paranodal loop were affected. From its characteristic distribution and molecular features, AX II may be important for myelin function in the PNS.

Heparin Inhibits NF-κB Activation and Increases Cell Death in Cerebral Endothelial Cells after Oxygen-Glucose Deprivation

Heparin is a classic anticoagulant that is commonly used in the treatment of acute ischemic stroke (AIS). Its use remains controversial, however, due to the risk of cerebral hemorrhagic transformation. In addition to anticoagulant effects, diverse effects on transcription factors can be caused by heparin. Among the transcription factors potentially affected is nuclear factor kappa B (NF-kappaB), a protein that is reportedly related to the survival of cerebral endothelial cells. We investigated the effect of heparin on NF-kappaB activation and cell death following oxygen-glucose deprivation (OGD), an experimental model of AIS. We subjected bEnd.3 cells from a murine cerebral microvascular endothelial cell line to OGD. We examined the effect of heparin on OGD-induced NF-kappaB activation and its mechanism of action, using electrophoretic mobility shift assays, reporter gene analysis, real-time RT-PCR, Western blot analysis, and confocal microscopy. We also measured the effect of heparin on OGD-induced cell death using an MTT assay. Heparin inhibited both tumor necrosis factor alpha- and OGD-induced NF-kappaB activation. Heparin was taken up by endocytosis and then entered the nucleus. Heparin did not affect the nuclear translocation of NF-kappaB, but instead inhibited the DNA binding of NF-kappaB in the nucleus. Cells were more susceptible to OGD-induced cell death after heparin treatment. Besides producing an anticoagulation effect, heparin also inhibits NF-kappaB activation, resulting in increased susceptibility to OGD-induced cell death. This effect may be responsible for hemorrhagic transformation in patients following heparin treatment for AIS.

Promoter region methylation and reduced expression of thrombospondin-1 after oxygen-glucose deprivation in murine cerebral endothelial cells

Angiogenesis is induced in response to ischemia. Thrombospondin-1 (TSP-1) is a potent angiostatic factor. Silencing of TSP-1 expression may contribute to the postischemic angiogenesis. Upregulation of TSP-1, in contrast, may terminate the postischemic angiogenesis. A possible mechanism that silences TSP-1 expression is the DNA methylation of its promoter region. DNA methylation has been reported following cerebral ischemia. The present study aimed to explore whether methylation of the promoter region of TSP-1 regulates its expression after oxygen-glucose deprivation (OGD) in murine cerebral endothelial cells (CECs) in vitro. Sublethal OGD increased the extent of methylation of the promoter region of TSP-1 with a concurrent decrease in TSP-1 mRNA and protein expression in CECs. After reoxygenation, demethylation of the TSP-1 promoter region led to the restoration of TSP-1 mRNA and protein expression. The extent of methylation of the promoter region of TSP-1 was inversely correlated with the extent of TSP-1 gene expression at mRNA and protein levels after OGD. Oxygen-glucose deprivation-induced reduction in the TSP-1 mRNA level was not accompanied by a change in mRNA stability. These findings raise the possibility that OGD downregulation of TSP-1 expression is at least in part due to methylation of its promoter region.

Evidence that N-acetylcysteine inhibits TNF-alpha-induced cerebrovascular endothelin-1 upregulation via inhibition of mitogen- and stress-activated protein kinase

N-acetylcysteine (NAC) is neuroprotective in animal models of acute brain injury such as caused by bacterial meningitis. However, the mechanism(s) by which NAC exerts neuroprotection is unclear. Gene expression of endothelin-1 (ET-1), which contributes to cerebral blood flow decline in acute brain injury, is partially regulated by reactive oxygen species, and thus a potential target of NAC. We therefore examined the effect of NAC on tumor necrosis factor (TNF)-alpha-induced ET-1 production in cerebrovascular endothelial cells. NAC dose dependently inhibited TNF-alpha-induced preproET-1 mRNA upregulation and ET-1 protein secretion, while upregulation of inducible nitric oxide synthase (iNOS) was unaffected. Intriguingly, NAC had no effect on the initial activation (i.e., IkappaB degradation, nuclear p65 translocation, and Ser536 phosphorylation) of NF-kappaB by TNF-alpha. However, transient inhibition of NF-kappaB DNA binding suggested that NAC may inhibit ET-1 upregulation by inhibiting (a) parallel pathway(s) necessary for full transcriptional activation of NF-kappaB-mediated ET-1 gene expression. Similar to NAC, the MEK1/2 inhibitor U0126, the p38 inhibitor SB203580, and the protein kinase inhibitor H-89 selectively inhibited ET-1 upregulation without affecting nuclear p65 translocation, suggesting that NAC inhibits ET-1 upregulation via inhibition of mitogen- and stress-activated protein kinase (MSK). Supporting this notion, cotreatment with NAC inhibited the TNF-alpha-induced rise in MSK1 and MSK2 kinase activity, while siRNA knock-down experiments showed that MSK2 is the predominant isoform involved in TNF-alpha-induced ET-1 upregulation.

Antisense RNA to inducible nitric oxide synthase reduces cytokine-mediated brain endothelial cell death

We test whether inhibition of inducible nitric oxide synthase (iNOS) can exert a cytoprotective effect on cerebral endothelial cells upon stimulation by pro-inflammatory cytokines. Mouse brain endothelial cells were stably transfected to express an antisense RNA against iNOS driven by an endothelium-specific von Willebrand factor (vWF) promoter. Upon stimulation with tumor necrosis factor-alpha (TNF-alpha) plus interferon-gamma (IFN-gamma), antisense transfectants showed less iNOS enzymatic activity with less nitric oxide (NO) when compared to the sense control cells. Correspondingly, the antisense cells showed a reduced LDH release and less cytosolic content of oligonucleosomes. These findings establish a cell-specific antisense strategy and confirm the cytotoxic role of iNOS expression in cultured cerebral endothelial cells.

Characterization of cis-regulatory elements of the vascular endothelial growth inhibitor gene promoter

VEGI (vascular endothelial growth inhibitor), a member of the tumour necrosis factor superfamily, has been reported to inhibit endothelial cell proliferation, angiogenesis and tumour growth. We identified and cloned approx. 2.2 kb of the VEGI promoter from mouse cerebral endothelial cells. The promoter contained an atypical TATA-box-binding protein sequence TAAAAAA residing at -32/-26 relative to the transcription initiation site (+1), 83 bp upstream from the ATG start codon. To investigate critical sequences in the VEGI promoter, a series of deleted and truncated segments were constructed from a 2300 bp promoter construct (-2201/+96) linked to a luciferase reporter gene. Transient transfection of cerebral microvascular cells (bEND.3) and rat C6 glioma cells demonstrated that a 1700 bp deletion from the -2201 to -501 did not significantly affect promoter activity; however, a truncated construct (-501/+96) lacking the region between -312 and -57 resulted in nearly 90% loss of promoter activity. A consensus NF-kappaB (nuclear factor kappaB) and several SP1 (specificity protein-1)-binding sequences were identified within the deleted segment. Supershift analysis revealed that NF-kappaB subunits, p50 and p65, interacted with the VEGI promoter. Exposure of cerebral endothermic cells to the pro-inflammatory cytokine, tumour necrosis factor-alpha, increased VEGI mRNA levels and DNA-binding activities, whereas an NF-kappaB inhibitor attenuated this increase. In addition, p65 overexpression enhanced, whereas p50 overexpression decreased, the luciferase activity. Furthermore, mutation of the NF-kappaB DNA binding site blocked this p65- and tumour necrosis factor-alpha-induced luciferase activity. These findings suggest that the transcription factor NF-kappaB plays an important role in the regulation of VEGI expression.

Amyloid-β peptide enhances tumor necrosis factor-α-induced iNOS through neutral sphingomyelinase/ceramide pathway in oligodendrocytes

Although accumulating evidence demonstrates that white matter degeneration contributes to pathology in Alzheimer's disease (AD), the underlying mechanisms are unknown. In order to study the roles of the amyloid-beta peptide in inducing oxidative stress damage in white matter of AD, we investigated the effects of amyloid-beta peptide 25-35 (Abeta) on proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha)-induced inducible nitric oxide synthase (iNOS) in cultured oligodendrocytes (OLGs). Although Abeta 25-35 by itself had little effect on iNOS mRNA, protein, and nitrite production, it enhanced TNF-alpha-induced iNOS expression and nitrite generation in OLGs. Abeta, TNF-alpha, or the combination of both, increased neutral sphingomyelinase (nSMase) activity, but not acidic sphingomyelinase (aSMase) activity, leading to ceramide accumulation. Cell permeable C2-ceramide enhanced TNF-alpha-induced iNOS expression and nitrite generation. Moreover, the specific nSMase inhibitor, 3-O-methyl-sphingomyelin (3-OMS), inhibited iNOS expression and nitrite production induced by TNF-alpha or by the combination of TNF-alpha and Abeta. Overexpression of a truncated mutant of nSMase with a dominant negative function inhibited iNOS mRNA production. 3-OMS also inhibited nuclear factor kappaB (NF-kappaB) binding activity induced by TNF-alpha or by the combination of TNF-alpha and Abeta. These results suggest that neutral sphingomyelinase/ceramide pathway is required but may not be sufficient for iNOS expression induced by TNF-alpha and the combination of TNF-alpha and Abeta.

Upregulation of annexins I, II, and V after traumatic spinal cord injury in adult rats

The posttraumatic inflammatory reaction contributes to progressive tissue damage after spinal cord injury (SCI). Annexins, a family of structurally related calcium- and phospholipid-binding proteins, have potent anti-inflammatory effects by inhibiting the activity of phospholipase A(2) (PLA(2)), a key enzyme responsible for inflammation and cytotoxicity. We investigated spatiotemporal expression of annexins I, II, and V after a contusive SCI using the New York University impact device (a 10-g rod, height 12.5 mm) in adult rats. Western blot analysis revealed that annexin I expression increased at 3 days after injury, peaked at 7 days (1.75-fold above the baseline level; P < 0.01), started to decline at 14 days, and returned to the baseline level at and beyond 28 days post-injury. The expression of annexin II started to increase at 3 days, reached its maximal level at 14 days (2.73-fold; P < 0.01), remained at a high level up to 28 days, and then declined to the basal level by 56 days after injury. Annexin V expression started at 3 days, reached its maximal level at 7 days (1.61-fold; P < 0.05) and remained at this level until 56 days after injury. RT-PCR results confirmed expression of all three annexins at the mRNA level after SCI. Immunohistochemistry and immunofluorescence double-labeling analyses revealed that increased annexins I, II, and V were localized in neurons and glial cells. The present study thus revealed increased expression of the three annexin isoforms after moderate contusive SCI. The precise role of annexins in posttraumatic inflammation and neuroprotection after SCI remains to be determined.

Interactions Between p38 Mitogen-Activated Protein Kinase and Caspase-3 in Cerebral Endothelial Cell Death After Hypoxia-Reoxygenation

Background and Purpose— The emerging concept of the neurovascular unit in stroke reemphasizes the need to focus on endothelial responses in brain. In this study we examined the role of mitogen-activated protein (MAP) kinase signaling in the regulation of hypoxic cell death in cerebral endothelial cells.

Methods— Human cerebral microvascular endothelial cells were exposed to 4 to 12 hours of hypoxia followed by 12 to 24 hours of reoxygenation. Cytotoxicity was measured by quantifying lactate dehydrogenase release. DNA laddering and caspase-3 activity were assessed to document a role for caspase-dependent cell death. zVAD-fmk and zDEVD-fmk were used to inhibit caspases. Activation of extracellular signal–regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK) was assessed with Western blotting and kinase activity assays. U0126, SB203580, and SP600125 were used to interrupt the ERK, p38, and JNK pathways, respectively.

Results— Endothelial cell death occurred primarily during reoxygenation. DNA laddering and caspase activation were observed, and cytotoxicity was ameliorated by caspase inhibitors (20 μmol/L of zVAD-fmk or zDEVD-fmk). Among the 3 major MAP kinases, only p38 was transiently activated during reoxygenation, and inhibition with 10 μmol/L of SB203580 significantly reduced cytotoxicity. No effects were observed with other MAP kinase inhibitors. Cytoprotection with SB203580 was not accompanied by caspase downregulation. In contrast, cytoprotection with zVAD-fmk was associated with a decrease in p38 activation. Furthermore, cleavage of MEKK1 (an upstream kinase of p38) was significantly reduced by zVAD-fmk.

Conclusions— Cerebral endothelial cell death after hypoxia-reoxygenation is mediated by interactions between caspases and p38 MAP kinase. Surprisingly, p38 pathways lie downstream of caspase mechanisms in this model system.

Zinc-induced NF-kappaB inhibition can be modulated by changes in the intracellular metallothionein level

Metallothionein (MT), a small metal-binding protein, is involved in the regulation of cellular metal homeostasis. Sequestration and the release of metals to and from MT plays an important role in the attenuation or amplification of signal transduction. Zinc has been suggested to be an important regulator of nuclear factor kappaB (NF-kappaB). In this study, the effect of MT expression on the zinc-induced inhibition of NF-kappaB activity was examined. In HeLa cells, pyrrolidine dithiocarbamate (PDTC), a zinc ionophore, and zinc itself inhibited NF-kappaB activity. When the cells were pretreated with MT-inducers, cadmium, or dexamethasone, PDTC did not inhibit NF-kappaB activity. We transfected HeLa cells with a DNA construct in which expression of MT-IIA is controlled by tet operator protein. Treatment of HeLa cells with doxycycline, a tetracycline analogue, induced the expression of MT-IIA, which attenuated the effect of PDTC on NF-kappaB activity. These results implicate MT in the zinc regulation of NF-kappaB and identify MT as one of the potential intracellular modulators of NF-kappaB activation.

Pyrrolidine dithiocarbamate-induced neuronal cell death is mediated by Akt, casein kinase 2, c-Jun N-terminal kinase, and IkappaB kinase in embryonic hippocampal progenitor cells

Pyrrolidine dithiocarbamate (PDTC) is known to induce cell death by the stimulation of intracellular zinc transport and subsequent modulation of nuclear factor-kappaB (NF-kappaB) activity. Zinc is a signaling messenger that is released by neuronal activity at many central excitatory synapses. Excessive synaptic release of zinc followed by entry into vulnerable neurons contributes to severe neuronal cell death. In the present study, we explored how PDTC modulates intracellular signal transduction pathways, leading to neuronal cell death. The exposure of immortalized embryonic hippocampal cells (H19-7) to PDTC within the range of 1-100 microM caused cell death in a dose-dependent manner. During the cell death, NF-kappaB activity increased in response to PDTC, and this activity corresponded well with the increase of intracellular free zinc levels, implying that the activation of NF-kappaB transmits the cell death signals of PDTC. Furthermore, PDTC caused the activation of IkappaB kinase (IKK), casein kinase 2 (CK2), phosphatidylinositol 3-kinase (PI-3K), and Akt, as well as mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), but not p38 kinase. The blockade of PI-3K, JNK, and CK2 pathways resulted in a remarkable suppression of PDTC-induced cell death and also the activation of IKK, which subsequently led to a decrease of IkappaB phosphorylation. Although the overexpression of dominant-negative SEK in a transient manner did not inhibit the activation of Akt by PDTC, the transfection of kinase-inactive Akt mutants did cause a remarkable blockade of JNK activation, implying that Akt is present upstream of JNK in the PDTC-signaling pathways. Moreover, whereas selective CK2 inhibitors suppressed PDTC-induced JNK activation, the inhibition of JNK did not affect CK2 activity, suggesting that CK2 is directly related to the regulation of cell viability by PDTC and that the CK2-JNK pathway could be a downstream target of PDTC. Taken together, our results suggest that PDTC-mediated accumulation of intracellular zinc ions may affect cell viability by modulating several intracellular signaling pathways in neuronal hippocampal progenitor cells.

Role of high glucose-induced nuclear factor-kappaB activation in monocyte chemoattractant protein-1 expression by mesangial cells

Although high glucose (HG) has been shown to induce nuclear factor-kappaB (NF-kappaB) activation in vascular cells, the upstream regulation and the biologic significance of NF-kappaB activation in diabetic renal injury are not clear. It was, therefore, examined if HG-induced generation of reactive oxygen species (ROS) and protein kinase C (PKC) activation are involved in NF-kappaB activation in mesangial cells (MC), and the role of NF-kappaB activation in HG-induced monocyte chemoattractant protein-1 (MCP-1) expression by MC was further investigated. Recent observations suggest that MCP-1 may play a role in the development and progression of diabetic nephropathy. HG rapidly induced NF-kappaB activation in MC as estimated by electrophoretic mobility shift assay. Supershift assay suggests that most of the binding activity arose from p50/p50 and p50/p65 dimers. Antioxidants, pyrrolidine dithiocarbamate, N-acetyl-L-cystein, and trolox effectively inhibited HG-induced NF-kappaB activation in MC. HG rapidly generated dichlorofluorescin-sensitive intracellular ROS in MC as measured by laser-scanning confocal microscopy. HG also activated PKC rapidly in MC. Inhibition of PKC effectively blocked HG-induced intracellular ROS generation and NF-kappaB activation in MC. HG increased MCP-1 mRNA expression by 1.9-fold and protein secretion by 1.6-fold that of control glucose in MC transfected with control vector but not in MC transfected with dominant negative mutant inhibitor of NF-kappaB (IkappaBalphaM). Inhibition of either PKC or ROS effectively blocked HG-induced, but not basal, MCP-1 protein secretion by MC transfected with control vector. Thus this study demonstrates that HG rapidly activates NF-kappaB in MC through PKC and ROS and suggests that HG-induced NF-kappaB activation in MC may play a role in diabetic renal injury through upregulation of MCP-1 mRNA and protein expression.

iNOS and nitrotyrosine expression after spinal cord injury

Secondary tissue damage after spinal cord injury (SCI) may be due to inflammatory mediators. After SCI, the nuclear factor-kappaB (NF-kappaB) transcription factor can activate many pro-inflammatory genes, one of which is inducible nitric oxide synthase (iNOS). iNOS catalyzes the synthesis of nitric oxide (NO), a key inflammatory mediator, which in turn reacts with superoxide to generate peroxynitrite. Peroxynitrite is a strong oxidant that can damage cellular enzymes, membranes, and subcellular organelles through the nitration of tyrosine residues on proteins. The presence of nitrotyrosine (NT) is an indirect chemical indicator of toxic NO and peroxynitrite-induced cellular damage. Using a New York University (NYU) impactor to induce SCI in adult rats, we examined the temporal and cellular expression of iNOS and NT. We observed a progressive increase in iNOS expression in the injured cord starting at day 1 with maximal expression occurring at day 7, as determined by Western blot analysis. iNOS expression corresponded temporally to an increase in iNOS enzyme activity after SCI. In parallel with the progressive increase in iNOS activity, NT expression also increased with time after SCI. The iNOS and NT immunoreactivity was localized in neurons, astrocytes, endothelial cells and ependymal cells at the epicenter and adjacent to the region of spinal cord impact and injury. Results from the present study suggest that increased iNOS and peroxynitrite anion, as reflected by the progressive accumulation of NT in the injured impacted spinal cord, may contribute to the secondary injury process after SCI.

Intracellular calcium mobilization induces immediate early gene pip92 via Src and mitogen-activated protein kinase in immortalized hippocampal cells

Regulation of intracellular calcium levels plays a central role in cell survival, proliferation, and differentiation. A cell-permeable, tumor-promoting thapsigargin elevates the intracellular calcium levels by inhibiting endoplasmic reticulum Ca(2+)-ATPase. The Src-tyrosine kinase family is involved in a broad range of cellular responses ranging from cell growth and cytoskeletal rearrangement to differentiation. The immediate early gene pip92 is induced in neuronal cell death as well as cell growth and differentiation. To resolve the molecular mechanism of cell growth by intracellular calcium mobilization, we have examined the effect of thapsigargin and subsequent intracellular calcium influx on pip92 expression in immortalized rat hippocampal H19-7 cells. An increase of intracellular calcium ion levels induced by thapsigargin stimulated the expression of pip92 in H19-7 cells. Transient transfection of the cells with kinase-inactive mitogen-activated protein kinase kinase (MEK) and Src kinase or pretreatment with the chemical MEK inhibitor PD98059 significantly inhibited pip92 expression induced by thapsigargin. When constitutively active v-Src or MEK was overexpressed, the transcriptional activity of the pip92 gene was markedly increased. Dominant inhibitory Raf-1 blocked the transcriptional activity of pip92 induced by thapsigargin. The transcription factor Elk1 is activated during thapsigargin-induced pip92 expression. Taken together, these results suggest that an increase of intracellular calcium ion levels by thapsigargin stimulates the pip92 expression via Raf-MEK-extracellular signal-regulated protein kinase- as well as Src kinase-dependent signaling pathways.

Inducible nitric oxide synthase expression is increased in the brain in fatal cerebral malaria

AIMS

Nitric oxide (NO) has been hypothesized to play a major role in the pathogenesis of cerebral malaria caused by P. falciparum infection. NO may act as a local neuroactive mediator contributing to the coma of cerebral malaria (CM). We hypothesized that increased expression of inducible nitric oxide synthase (iNOS) may cause increased release of NO, and examined the expression and distribution of iNOS in the brain during CM.

MATERIAL AND RESULTS

Brain tissues from fatal cases of cerebral malaria in Thai adults were examined using immunohistochemical staining to detect iNOS. The distribution and strength of staining was compared between 14 patients with CM, three of whom were recovering from coma, and controls. iNOS expression was found in endothelial cells, neurones, astrocytes and microglial cells in CM cases. There was also strong staining in macrophages surrounding ring haemorrhages. iNOS staining was decreased in recovering malaria cases compared to acute CM, and was low in controls. Quantification showed a significant association between the intensity and number of iNOS positive vessels with the severity of malaria related histopathological changes, although the total number of cells staining was not increased compared to recovering CM cases.

CONCLUSIONS

This study indicates that an acute induction of iNOS expression occurs in the brain during CM. This occurs in a number of different cells types, and is increased in the acute phase of CM compared to cases recovering from coma. As NO may activate a number of secondary neuropathological mechanisms in the brain, including modulators of synaptic function, induction of iNOS expression in cerebral malaria may contribute to coma, seizures and death.

Oxygen-glucose deprivation induces inducible nitric oxide synthase and nitrotyrosine expression in cerebral endothelial cells

BACKGROUND AND PURPOSE

The cerebral endothelial cells (ECs) are a primary target of hypoxic or ischemic brain insults. EC damage may contribute to postischemic secondary injury. Massive production of NO after inducible NO synthase (iNOS) expression has been implicated in cell death. This study aimed to characterize bovine cerebral EC death in relation to iNOS expression after oxygen-glucose deprivation (OGD) in vitro.

METHODS

OGD in bovine cerebral ECs in culture was induced by deleting glucose in the medium and by incubating the cells in a temperature-controlled anaerobic chamber. The extent of cell death was assessed by trypan blue exclusion, MTT assay, and LDH release. ELISA, gel electrophoresis, and staining by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling were used to examine DNA fragmentation. The expression of iNOS mRNA and protein was detected by reverse transcription-polymerase chain reaction and Western blotting, respectively. Nitrotyrosine expression was confirmed with Western blot analysis and immunostaining.

RESULTS

Bovine cerebral EC death was dependent on the duration of OGD and showed selected biochemical, morphological, and pharmacological features suggestive of apoptosis. OGD also induced the expression of iNOS mRNA and protein in bovine cerebral ECs. Increased expression of nitrotyrosine, the product formed by peroxynitrite reaction with proteins, was also detected after OGD. The involvement of iNOS in EC death was suggested by partial reduction of cell death by NO synthase inhibitors, including L-N(G)-(1-iminoethyl)ornithine and nitro-L-arginine, and an NO scavenger, the Fe(2+)-N-methyl-D-glucamine dithiocarbamate complex.

CONCLUSIONS

OGD-induced bovine cerebral EC death involves an apoptotic process. Induction of iNOS with subsequent peroxynitrite formation may contribute to bovine cerebral EC death caused by OGD.

Hypertonic mannitol loading of NF-kappaB transcription factor decoys in human brain microvascular endothelial cells blocks upregulation of ICAM-1

BACKGROUND AND PURPOSE

An acute inflammatory response exacerbates tissue injury during acute ischemic stroke. The transcription factor nuclear factor (NF)-kappaB plays a key role in endothelial cell activation and the inflammatory response. Targeted genetic disruption of NF-kappaB activation in cerebral endothelial cells may be protective in stroke. We determined whether a NF-kappaB transcription factor decoy (TFD) could block intercellular adhesion molecule (ICAM)-1 upregulation, an indicator of endothelial cell activation.

METHODS

We modeled ischemia-reperfusion in vitro by exposing cultured human brain microvascular endothelial cells (HBMEC) to tumor necrosis factor (TNF)-alpha and conditions of hypoxia-reoxygenation (H/R). Mannitol was used to load phosphothiorated oligonucleotides containing 3 copies of the kappaB binding sequences (TFDs) into cultured HBMEC. An NF-kappaB TFD, a mutated NF-kappaB TFD, and a scrambled TFD were studied for their effect on ICAM-1 mRNA levels and surface ICAM-1 by ELISA.

RESULTS

Hyperosmolar loading with mannitol permitted rapid transfection of TFD into endothelial cell nuclei. The NF-kappaB TFD but not the mutated or scrambled TFD competed with a kappaB sequence for binding to nuclear extracts from HBMEC exposed to TNF-alpha. The NF-kappaB TFD blocked the TNF-alpha-induced and H/R-induced increase in ICAM-1 mRNA levels and the upregulation of surface ICAM-1.

CONCLUSIONS

Mannitol delivers phosphothiorated oligonucleotides into cultured HBMEC. An NF-kappaB decoy blocks both TNF-alpha-induced and H/R-induced ICAM-1 upregulation in HBMEC. Targeted genetic disruption of endothelial NF-kappaB activation may be of benefit in acute ischemic stroke.

Biphasic effects of dithiocarbamates on the activity of nuclear factor-kappaB

Dithiocarbamates are well-known antioxidants and nuclear factor-kappaB (NF-kappaB) inhibitors. Recently, they have been characterized as zinc ionophores. Concentration-dependent biphasic effects of dithiocarbamates on NF-kappaB activity have been widely reported. We studied the mechanism of this phenomenon in relation to Zn(2+) influx. Two dithiocarbamates, pyrrolidine dithiocarbamate and diethyldithiocarbamate, showed concentration-dependent biphasic effects in inhibiting NF-kappaB activation in cerebral endothelial cells. These unique effects of dithiocarbamates on NF-kappaB were tightly linked to their ability to elevate intracellular Zn(2+)500 microM), dithiocarbamates started to lose their ability to promote Zn(2+) influx and to inhibit NF-kappaB activation. These results might provide insight into the appropriate use of dithiocarbamates in various disorders.

Pyrithione, a zinc ionophore, inhibits NF-kappaB activation

Pyrrolidine dithiocarbamate (PDTC) suppresses NF-kappaB activity and exhibits cytotoxic effects in bovine cerebral endothelial cells (BCECs), and we have previously reported that these PDTC effects were accompanied by an increase in intracellular zinc levels. To further explore the role of zinc in the modulation of NF-kappaB activation, we studied the effect of pyrithione, a zinc ionophore, on NF-kappaB activation in BCECs. Pyrithione inhibited NF-kappaB activity in a time- and dose-dependent manner. Ca-EDTA, but not Zn-EDTA, prevented pyrithione inhibition of NF-kappaB activity. Pyrithione increased the intracellular zinc level within 15 min. This effect was also abolished by Ca-EDTA, but not by Zn-EDTA. The potency of pyrithione on NF-kappaB inhibition and zinc influx was approximately one order of magnitude more potent than PDTC. These findings establish the regulatory role of intracellular zinc levels on NF-kappaB activity in BCECs.

Zinc is required in pyrrolidine dithiocarbamate inhibition of NF-kappaB activation

Pyrrolidine dithiocarbamate (PDTC) is a potent inhibitor of nuclear factor kappa B (NF-kappaB) activation. PDTC inhibited basal NF-kappaB activity of endothelial cells. PDTC, however, failed to inhibit basal NF-kappaB activity after withdrawal of serum in the media, and the inhibitory effect of PDTC could be restored by addition of zinc. When various preparations of metal ion-EDTA were tested with PDTC in serum-containing media, only Zn-EDTA failed to block the inhibitory effect of PDTC. The dependence on zinc was also noted in PDTC inhibition of NF-kappaB stimulated by TNF alpha. These facts suggest that zinc is required for PDTC inhibition of NF-kappaB activation.

Methylprednisolone inhibition of TNF-alpha expression and NF-kB activation after spinal cord injury in rats

Post-traumatic inflammatory reaction has been implicated in the secondary injury after SCI. TNF-alpha is a key inflammatory mediator, which plays a pathogenetic role in cell death in inflammatory disorders and traumatic brain injury. TNF-alpha exerts its effector actions, at least partially, through the activation of a pro-inflammatory transcription factor, NF-kB, which in turn upregulates such genes as iNOS, cytokines, adhesive molecules, and others. Consistent with a post-traumatic inflammatory reaction after SCI, we noted an increase in TNF-alpha expression by Western blotting (4.5-fold increase at 1 day after SCI, P<0.01) and immunohistochemistry in a rat SCI model. Post-traumatic TNF-alpha expression was accompanied by an increase in NF-kB binding activity in nuclear proteins isolated from the injured cord (3.9-fold increase, P<0.01). MP is the only drug proven effective in improving neurological function in patients with acute SCI. The mechanism of action of MP is not fully understood, but is thought to be related to its antioxidant effects. MP is also a potent anti-inflammatory agent, which has been recently shown to inhibit NF-kB binding activity. MP (30 mg/kg, i.v.) given immediately after SCI reduced TNF-alpha expression by 55% (P<0.01) and NF-kB binding activity. These findings suggest that post-traumatic inflammatory activity that is mediated by the TNF-alpha-NF-kB cascade can be suppressed by MP.

Cytokine-induced nitric oxide formation in normal but not in neoplastic murine lung epithelial cell lines

Cytomix, a mixture of interferon-gamma, tumor necrosis factor-alpha, and interleukin-1beta, induces nitric oxide (NO) production in lung epithelial cell lines. It is not known whether neoplastic transformation alters a cell's ability to form NO in response to cytokines. The present study investigated NO formation in two murine lines of immortalized "normal" (nontumorigenic) lung epithelial cells of alveolar type II origin, E10 and C10, and their sibling spontaneous transformants, E9 and A5. Nontumorigenic cells elaborated much more NO after cytomix exposure than did their tumorigenic counterparts. NO production was prevented by inhibiting protein synthesis and NO synthase and attenuated by dexamethasone. Northern and Western blot analyses of inducible NO synthase (iNOS) demonstrated cytomix-induced induction of iNOS only in nontumorigenic cells. The deficiency in NO production in tumorigenic cells was not associated with reduced iNOS mRNA stability or with differences in cytomix-induced nuclear factor-kappaB activation. Although cytomix caused a greater production of NO in E10 cells than in E9 cells, the same treatment induced equivalent proliferation in both cell lines. These results indicate a specific deficiency in cytokine-induced NO synthesis in transformed murine lung epithelial cells relative to their normal progenitor cells and provide a model for investigating iNOS regulation.