PubMed Health⌕ Search

Biomedical subjects

J B Weinberg

Publications and source records attributed to J B Weinberg.

At least 19 recordsLinked to original sources
PubMed2006

NO synthase 2 (NOS2) deletion promotes multiple pathologies in a mouse model of Alzheimer's disease.

Alzheimer's disease is characterized by two primary pathological features: amyloid plaques and neurofibrillary tangles. The interconnection between amyloid and tau aggregates is of intense interest, but mouse models have yet to reveal a direct interrelationship. We now show that NO may be a key factor that connects amyloid and tau pathologies. Genetic removal of NO synthase 2 in mice expressing mutated amyloid precursor protein results in pathological hyperphosphorylation of mouse tau, its redistribution to the somatodendritic compartment in cortical and hippocampal neurons, and aggregate formation. Lack of NO synthase 2 in the amyloid precursor protein Swedish mutant mouse increased insoluble beta-amyloid peptide levels, neuronal degeneration, caspase-3 activation, and tau cleavage, suggesting that NO acts at a junction point between beta-amyloid peptides, caspase activation, and tau aggregation.

Alzheimer Disease↗
PubMed2003

IL-4 and interferon gamma regulate expression of inducible nitric oxide synthase in chronic lymphocytic leukemia cells.

Chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of long-lived non-dividing CD5(+) B cells. Nitric oxide (NO) is an important regulator of apoptosis, and the viability of cultured B-CLL cells may be dependent on the autocrine production of nitric oxide by inducible nitric oxide synthase (NOS2). We performed this study to determine whether cytokine factors that prevent spontaneous in vitroapoptosis of B-CLL cells induce B-CLL cell NOS2 enzyme activity. B-CLL cells expressed NOS enzyme activity and NOS2 protein and mRNA. IL-4 and IFN-gamma increased B-CLL cell NOS2 enzyme activity and protein expression during in vitro culture. IFN-gamma, but not IL-4, increased NOS2 mRNA expression in cultured B-CLL cells suggesting that IL-4-mediated changes of NOS2 protein expression occurred at the post-transcriptional level. We were unable to detect increased concentrations of nitrite or nitrate (NO(x)) as surrogate markers of NO production in B-CLL cell cultures treated with IL-4 or IFN-gamma. IL-4 and IFN-gamma diminished NOS inhibitor-induced B-CLL cell death. In summary, we found that B-CLL cells expressed NOS2 and that IL-4 and IFN-gamma increased B-CLL NOS2 expression. Cytokine-mediated expression of NOS2 by B-CLL cells may promote their survival, and therapeutic strategies that target NOS2 or quench NO may be beneficial in patients with B-CLL.

B-Lymphocytes↗
PubMed2002

A promoter polymorphism in the gene encoding interleukin-12 p40 (IL12B) is associated with mortality from cerebral malaria and with reduced nitric oxide production.

Interleukin-12 (IL-12) is an important regulatory cytokine in infection and immunity. Administration of IL-12 may reduce complications of severe malaria in rodents. Polymorphisms in IL12B, the gene encoding the IL-12 p40 subunit, influence the secretion of IL-12 and susceptibility to Type 1 diabetes. We therefore investigated whether IL12B polymorphisms may affect the outcome of severe malaria. Homozygosity for a polymorphism in the IL12B promoter was associated with increased mortality in Tanzanian children having cerebral malaria but not in Kenyan children with severe malaria. Furthermore, homozygotes for the IL12B promotor polymorphism had decreased production of nitric oxide, which is in part regulated by IL-12 activity. These studies suggest that IL12B polymorphisms, via regulation of IL-12 production, may influence the outcome of malaria infection in at least one African population.

Animals↗
PubMed2002

Induction of cyclooxygenase-2 by mechanical stress through a nitric oxide-regulated pathway.

OBJECTIVE: Biomechanical signals play important roles in regulating the homeostasis of articular cartilage, but under abnormal conditions may be a critical factor in the onset and progression of arthritis. Prostaglandin E(2) (PGE(2)) and nitric oxide (NO), derived from the enzymes cyclo-oxygenase 2 (COX2) and NO synthase 2 (NOS2), are inflammatory mediators that modulate numerous physiological and pathophysiological processes and are potentially important pharmacological targets in osteoarthritis. The goal of this study was to determine the effect of mechanical compression on PGE(2) production in the presence of selective NOS2 and COX2 inhibitors. METHODS: Articular cartilage explants harvested from 2-3-year-old pigs were subjected to intermittent compression at 0.5Hz over a range of stress magnitudes. PGE(2) and NO production into the media were determined in the presence and absence of the NOS2 inhibitor 1400W or the COX2 inhibitor NS398. COX2 protein levels were determined by immunoblot analysis. RESULTS: Mechanical compression significantly increased NO and PGE(2) synthesis in a manner that was dependent on the magnitude of stress. The selective COX2 inhibitor blocked compression-induced NO and PGE(2) production. Compression in the presence of 1400W further increased COX2 expression resulting in a 10-fold increase in PGE(2) production compared to uncompressed explants with 1400W and a 40-fold increase in PGE(2) compared to uncompressed explants without 1400W. CONCLUSION: Mechanical compression of articular cartilage increased COX2 and PGE(2) production through a NO-dependent pathway, and therefore pharmacological agents that target the NOS2 pathway in cartilage may have a significant influence on prostanoid production in the joint.

Animals↗
PubMed2001

Characterization of key residues in the subdomain encoded by exons 8 and 9 of human inducible nitric oxide synthase: a critical role for Asp-280 in substrate binding and subunit interactions.

Human inducible nitric oxide synthase (iNOS) is active as a dimer of two identical subunits. Each subunit has an amino-terminal oxygenase domain that binds the substrate l-Arg and the cofactors heme and tetrahydrobiopterin and a carboxyl-terminal reductase domain that binds FMN, FAD, and NADPH. We previously demonstrated that a subdomain in the oxygenase domain encoded by exons 8 and 9 is important for dimer formation and NO synthesis. Further, we identified Trp-260, Asn-261, Tyr-267, and Asp-280 as key residues in that subdomain. In this study, using an Escherichia coli expression system, we produced, purified, and characterized wild-type iNOS and iNOS-Ala mutants. Using H(2)O(2)-supported oxidation of N(omega)-hydroxy-l-Arg, we demonstrate that the iNOS mutants' inabilities to synthesize NO are due to selective defects in the oxygenase domain activity. Detailed characterization of the Asp-280-Ala mutant revealed that it retains a functional reductase domain, as measured by its ability to reduce cytochrome c. Gel permeation chromatography confirmed that the Asp-280-Ala mutant exists as a dimer, but, in contrast to wild-type iNOS, urea-generated monomers of the mutant fail to reassociate into dimers when incubated with l-Arg and tetrahydrobiopterin, suggesting inadequate subunit interaction. Spectral analysis reveals that the Asp-280-Ala mutant does not bind l-Arg. This indicates that, in addition to dimerization, proper subunit interaction is required for substrate binding. These data, by defining a critical role for Asp-280 in substrate binding and subunit interactions, give insights into the mechanisms of regulation of iNOS activity.

Aspartic Acid↗
PubMed2001

Mechanical stress and nitric oxide influence leukotriene production in cartilage.

Nitric oxide (NO) and leukotrienes regulate a variety of processes in joint tissues and are frequently elevated in arthritis. Mechanical stress can induce biochemical and functional changes in cartilage that may influence mediator production. To investigate the relationship between mechanical stress and the production of leukotriene B(4) (LTB(4)) and NO, explants of porcine articular cartilage were subjected to mechanical compression for 1 h followed by 23 h recovery in the presence or absence of the NOS2 inhibitor 1400W. Dynamic compression significantly increased LTB(4) and LOX protein production in the presence of 1400W. The induced LTB(4) was functional as evidenced by its ability to promote chemotaxis of RBL-2H3 cells expressing the LTB(4) receptor. Increased LOX protein but not LTB(4) occurred in response to compression alone. These findings provide a direct link between mechanical stress and inflammation in cartilage and may have implications in the pathogenesis and treatment of arthritis.

Amidines↗
PubMed2001

Nitric oxide synthase 2(Lambaréné) (G-954C), increased nitric oxide production, and protection against malaria.

A point mutation in the promoter of the nitric oxide synthase 2 gene (NOS2), termed NOS2(Lambaréné) (NOS2-G954C), protects heterozygous carriers against severe malaria as effectively as the sickle cell trait. In a prospective longitudinal study, 841 individual infections of initially 200 children (151 wild-type vs. 49 NOS2(Lambaréné) carriers) were monitored for 4 years, to assess the rates of malarial attacks in the 2 groups; carriers of the NOS2(Lambaréné) polymorphism were significantly less likely to experience malarial attacks than were others (P=.002). The distribution of the NOS2(Lambaréné) polymorphism was investigated in malaria-endemic areas. It was found to be present with the highest frequency in Africa and at a lower frequency in Asia. Ex vivo studies showed that cells isolated from people with this polymorphism have a 7-fold higher baseline NOS activity, compared with the levels detected in cells from subjects with the wild-type gene (P=.003).

Case-Control Studies↗
PubMed2001

Interleukin-1, tumor necrosis factor alpha, and interleukin-17 synergistically up-regulate nitric oxide and prostaglandin E2 production in explants of human osteoarthritic knee menisci.

OBJECTIVE: In osteoarthritis (OA), a combination of biochemical and biomechanical factors may damage both menisci and articular cartilage. Nitric oxide (NO) and prostaglandin E2 (PGE2) have been implicated as mediators of inflammation in OA. The goals of this study were to determine if menisci from patients with OA produce NO and PGE2, and if the proinflammatory cytokines interleukin-1beta (IL-1beta), tumor necrosis factor a (TNFalpha), and IL-17 augment NO and PGE2 production by these tissues. METHODS: Menisci were obtained from 17 patients (age 47-75 years) undergoing total knee replacement for OA. Tissue explants were cultured alone or with IL-1beta, IL-17, or TNFalpha, and the release of NO and PGE2 from the tissue as well as the presence of type 2 nitric oxide synthase (NOS2) and cyclooxygenase 2 (COX-2) antigens were measured. RESULTS: All menisci constitutively produced NO, and significant increases in NO production were observed in the presence of IL-1beta, TNFalpha, or IL-17 (P < 0.05). The combination of IL-17 and TNFalpha significantly increased NO production compared with either cytokine alone. Basal and cytokine-stimulated NO synthesis was inhibited by the NOS inhibitors NG-monomethyl-L-arginine or N-3-aminoethylbenzylacetamidine (1400W). IL-1beta significantly increased PGE2 production. The combination of IL-1beta and TNFalpha had an additive effect on PGE2 production, while addition of IL-17 to TNFalpha or IL-1beta synergistically enhanced PGE2 production. Inhibition of NO production by 1400W significantly increased IL-1beta-stimulated PGE2 production, and inhibition of PGE2 production by the COX-2 inhibitor N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide significantly increased IL-17-stimulated NO production. CONCLUSION: Menisci from humans with OA spontaneously produced NO and PGE2 in a manner that was synergistically or additively augmented by cytokines. NO and PGE2 exhibited reciprocal regulatory effects on one another, suggesting that pharmaceutical agents designed to inhibit NOS2 or COX-2 production may in fact be influencing both pathways.

Aged↗
PubMed2001

The effects of static and intermittent compression on nitric oxide production in articular cartilage explants.

Nitric oxide (NO) production and NO synthase (NOS) expression are increased in osteoarthritis and rheumatoid arthritis, suggesting that NO may play a role in the destruction of articular cartilage. To test the hypothesis that mechanical stress may increase NO production by chondrocytes, we measured the effects of physiological levels of static and intermittent compression on NOS activity, NO production, and NOS antigen expression by porcine articular cartilage explants. Static compression significantly increased NO production at 0.1 MPa stress for 24 h (P < 0.05). Intermittent compression at 0.5 Hz for 6 h followed by 18 h recovery also increased NO production and NOS activity at 1.0 MPa stress (P < 0.05). Intermittent compression at 0.5 Hz for 24 h at a magnitude of 0.1 or 0.5 MPa caused an increase in NO production and NOS activity (P < 0.05). Immunoblot analysis showed stress-induced upregulation of NOS2, but not NOS1 or NOS3. There was no loss in cell viability following any of the loading regimens. Addition of 2 mM 1400 W (a specific NOS2 inhibitor) reduced NO production by 51% with no loss of cell viability. These findings indicate that NO production by chondrocytes is influenced by mechanical compression in vitro and suggest that biomechanical factors may in part regulate NO production in vivo.

Animals↗
PubMed2001

Nitric oxide enhancement of fludarabine cytotoxicity for B-CLL lymphocytes.

Fludarabine is active but not curative in the treatment of chronic lymphocytic leukemia (B-CLL). Nitric oxide (NO) supplied from exogenous, NO-donating pro-drugs can also induce apoptosis and death of acute leukemia cells. This study investigated combinations of fludarabine with NO-donating pro-drugs for their cytotoxicity against freshly isolated B-CLL lymphocytes following a 72 h exposure in vitro. The median IC(50)for fludarabine was 2.2 microM (n = 85). The nitric oxide donors DETA-NO, PAPA-NO, and MAHMA-NO were also cytotoxic, and their effects were inversely related to rates of NO release. Neither DETA-NO depleted of NO nor DETA itself was effective, indicating that NO was required for cytotoxicity. Drug interactions were evaluated by a modified combination index method. Synergy was observed in combinations of fludarabine or nelarabine (506U78) with DETA-NO in 52% and 88% of samples, respectively. Interestingly, the combination of fludarabine and DETA-NO was more cytotoxic in B-CLL cells less sensitive to fludarabine. DETA-NO did not enhance the activity of other DNA anti-metabolites, topoisomerase I and II inhibitors, or alkylating agents. Finally, the anti-leukemic activity of fludarabine alone or in combination with DETA-NO was found to correlate with inhibition of cellular RNA synthesis. These results indicate that NO donors could enhance fludarabine therapy for B-CLL.

Adult↗
PubMed2001

The effect of dynamic mechanical compression on nitric oxide production in the meniscus.

OBJECTIVE: The menisci play an important role in the biomechanics of the knee, and loss of meniscal function has been associated with progressive degenerative changes of the joint in rheumatoid arthritis as well as in osteoarthritis. However, little is known about the underlying mechanisms that link meniscal injury or degeneration to arthritis. Meniscal fibrochondrocytes respond to environmental mediators such as growth factors and cytokines, but the influence of mechanical stress on their metabolic activity is not well understood. Nitric oxide (NO) is believed to play a role in mechanical signal transduction, and there is also significant evidence of its role in cartilage and meniscus degeneration. The goal of this study was to determine if meniscal fibrochondrocytes respond to mechanical stress by increasing NO production in vitro. DESIGN: Explants of lateral and medial porcine menisci were dynamically compressed in a precisely controlled manner, and NO production, nitric oxide synthase antigen expression and cell viability were measured. The relative responses of the meniscal surface and deep layers to dynamic compression were also investigated separately. RESULTS: Meniscal NO production was significantly (P< 0.01) increased by dynamic compression in both the medial and lateral menisci. Dynamically compressed menisci contained inducible nitric oxide synthase antigen, while uncompressed menisci did not. Significant (P< 0.05) zonal differences were observed in basal and compression-induced NO production. DISCUSSION: Our findings provide direct evidence that dynamic mechanical stress influences the biological activity of meniscal cells. These results suggest that NO production in vivo may be in part regulated by mechanical stress acting upon the menisci. Since NO affects matrix metabolism in various intraarticular tissues, alterations in the distribution and magnitude of stress in the menisci may have important metabolic as well as biomechanical consequences on joint physiology and function.

Animals↗
PubMed2001

Host response to infection: the role of CpG DNA in induction of cyclooxygenase 2 and nitric oxide synthase 2 in murine macrophages.

Depending on sequence, bacterial and synthetic DNAs can activate the host immune system and influence the host response to infection. The purpose of this study was to determine the abilities of various phosphorothioate oligonucleotides with cytosine-guanosine-containing motifs (CpG DNA) to activate macrophages to produce nitric oxide (NO) and prostaglandin E(2) (PGE(2)) and to induce expression of NO synthase 2 (NOS2) and cyclooxygenase 2 (COX2). As little as 0.3 microg of CpG DNA/ml increased NO and PGE(2) production in a dose- and time-dependent fashion in cells of the mouse macrophage cell line J774. NO and PGE(2) production was noted by 4 to 8 h after initiation of cultures with the CpG DNA, with the kinetics of NO production induced by CpG DNA being comparable to that induced by a combination of lipopolysaccharide and gamma interferon. CpG DNA-treated J774 cells showed enhanced expression of NOS2 and COX2 proteins as determined by immunoblotting, with the relative potencies of the CpG DNAs generally corresponding to those noted for the induction of NO and PGE(2) production as well as to those noted for the induction of interleukin-6 (IL-6), IL-12, and tumor necrosis factor. Extracts from CpG DNA-treated cells converted L-arginine to L-citrulline, but the NOS inhibitor N(G)-monomethyl-L-arginine (NMMA) inhibited this reaction. The COX2-specific inhibitor NS398 inhibited CpG DNA-induced PGE(2) production and inhibited NO production to various degrees. The NOS inhibitors NMMA, 1400W, and N-iminoethyl-L-lysine effectively blocked NO production and increased the production of PGE(2) in a dose-dependent fashion. Thus, analogues of microbial DNA (i.e., CpG DNA) activate mouse macrophage lineage cells for the expression of NOS2 and COX2, with the production of NO and that of PGE(2) occurring in an interdependent manner.

Adjuvants, Immunologic↗
PubMed2000

Inverse relationship of plasma prostaglandin E2 and blood mononuclear cell cyclooxygenase-2 with disease severity in children with Plasmodium falciparum malaria.

Prostaglandins (PGs) derived from inducible cyclooxygenase (COX)-2 are important proinflammatory mediators of the host-immune response to infection. Since the role of host-derived PG in human malaria is unknown, plasma bicyclo-PGE2 (a stable catabolite of PGE2), peripheral blood mononuclear cell COX-2 protein, and mRNA were measured in Gabonese children with and without malaria (n=129). Relative to healthy children, bicyclo-PGE2 and COX-2 protein were lower in children with mild (P=.007 and P=.026, respectively) and severe malaria (P=.002 and P=.010, respectively). COX-2 mRNA was also reduced in children with malaria. Investigation of COX-2 regulatory cytokines revealed an inverse correlation (P<.001) between plasma levels of bicyclo-PGE2 and interleukin (IL)-10, a cytokine that suppresses COX-2 expression. On the basis of these results, elevated PGE2 in healthy malaria-exposed children may protect against malaria, whereas IL-10-induced decreases in PGE2 during acute malaria may increase susceptibility to severe disease.

Child↗
PubMed2000

Reduced interleukin-12 and transforming growth factor-beta1 in severe childhood malaria: relationship of cytokine balance with disease severity.

Interleukin (IL)-12 and transforming growth factor (TGF)-beta1 regulate the balance between pro- and anti-inflammatory cytokines in animal models of malaria. Since the cytokine balance may be an important determinant of whether a protective or a pathogenic immune response develops, plasma cytokine ratios were examined in Gabonese children with various degrees of malarial severity. Severe disease was characterized by high-density parasitemia and severe anemia. IL-12 and TGF-beta1 were significantly lower, whereas tumor necrosis factor (TNF)-alpha and IL-10 were significantly higher in children with severe malaria. The ratios of TGF-beta1/IL-12 and IL-10/IL-12 were significantly higher in the severe, compared with the mild, malaria group. In contrast, ratios of TGF-beta1/TNF-alpha and IL-10/TNF-alpha were significantly lower in the severe malaria group. These results suggest that the inflammatory cascade in severe malaria is characterized by suppression of the protective effects of TGF-beta1 and IL-12, and that overproduction of TNF-alpha may promote deleterious effects, such as severe anemia.

Child↗
PubMed2000

Low interleukin-12 activity in severe Plasmodium falciparum malaria.

We compared interleukin-12 (IL-12) and other cytokine activities during and after an acute clinical episode in a matched-pair case-control study of young African children who presented with either mild or severe Plasmodium falciparum malaria. The acute-phase, pretreatment plasma IL-12 and alpha interferon (IFN-alpha) levels, as well as the acute-phase mitogen-stimulated whole-blood production capacity of IL-12, were significantly lower in children with severe rather than mild malaria. IL-12 levels, in addition, showed strong inverse correlations both with parasitemia and with the numbers of circulating malaria pigment-containing neutrophils. Acute-phase plasma tumor necrosis factor (TNF) and IL-10 levels were significantly higher in those with severe malaria, and the concentrations of both of these cytokines were positively correlated both with parasitemia and with the numbers of pigment-containing phagocytes in the blood. Children with severe anemia had the highest levels of TNF in plasma. In all the children, the levels in plasma and production capacities of all cytokines normalized when they were healthy and parasite free. The results indicate that severe but not mild P. falciparum malaria in young, nonimmune African children is characterized by down-regulated IL-12 activity, contrasting markedly with the up-regulation of both TNF and IL-10 in the same children. A combination of disturbed phagocyte functions resulting from hemozoin consumption, along with reduced IFN-gamma responses, may contribute to these differential effects.

Acute Disease↗
PubMed2000

Nitric oxide synthase 2 and cyclooxygenase 2 interactions in inflammation.

Nitric oxide (NO) and prostaglandin (PG) E2 produced by NO synthase type 2 (NOS2) and cyclooxygenase type 2 (COX2), respectively, are important mediators in inflammation. There is much information regarding their roles in models of inflammation in mice and in humans with diseases such as rheumatoid arthritis (RA). A variety of stimuli including cytokines, microbial components, immune complexes, and mechanical stress can induce both NOS2 and COX2 mRNA transcription and protein synthesis and enhance inflammation. This has been demonstrated in both mice and humans. NOS2-specific inhibitors reduce inflammation in mice, and COX2-specific inhibitors reduce inflammation in mice and in humans. There is significant cross-talk between PGE2/NO and COX2/NOS2. Treatments that inhibit both NOS2 and COX2 should provide the most potent antiinflammatory effects.

Animals↗
PubMed2000

Peroxynitrite formation and decreased catalase activity in autoimmune MRL-lpr/lpr mice.

BACKGROUND: (MRL)-lpr/lpr mice spontaneously develop autoimmune disease characterized by arthritis and glomerulonephritis. Nitric oxide is postulated to play a role in the disease pathogenesis, as mice treated with the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (NMMA) show markedly reduced manifestations of the disease. The purpose of this study was to examine the role of peroxynitrite in disease development in MRL-lpr/lpr mice. MATERIALS AND METHODS: We examined kidney extracts from control and MRL-lpr/lpr mice for nitrotyrosine by immunoblot with a rabbit polyclonal anti-nitrotyrosine antibody. Catalase activity was determined spectrophotometrically or by activity staining of native polyacrylamide gels. In some experiments, we studied the ability of peroxynitrite and other agents to modify purified catalase in vitro. RESULTS: Kidney extracts from diseased mice had elevated levels of nitrotyrosine, and decreased levels of catalase activity and protein, relative to control mice. MRL-lpr/lpr mice treated with NMMA in vivo had decreased levels of nitrotyrosine, and demonstrated a partial restoration of both catalase activity and protein levels. Treatment of catalase in vitro with peroxynitrite or tetranitromethane at pH 8.0 resulted in protein nitration and a decrease in catalase activity. 1,3-morpholinosydnonimine (SIN-1), a peroxynitrite generator, also decreased the activity of catalase. CONCLUSIONS: These observations suggest that peroxynitrite formation, with an associated decrease in catalase activity and general decrease in antioxidant enzyme activity, may result in increased levels of hydrogen peroxide and other oxidants that can contribute to the pathogenesis of disease in MRL-lpr/lpr mice.

Animals↗