Induction of tumor necrosis factor alpha gene expression by lipoprotein lipase requires protein kinase C activation

Remote limb ischemic pre-conditioning prevents renal Ischemia/reperfusion injury in rats by modulating oxidative stress and TNF-α/NF-κB/TGF-/βapelin signaling pathway

BACKGROUND

Remote limb ischemic pre-conditioning (RIPreC) can invoke potent renal protection. The involvement of oxidative stress and inflammatory pathways in renal ischemia/reperfusion injury (I/RI) was also confirmed. This study was designed to investigate the RIPreC effects on IRI-induced kidney dysfunction in rats through NFĸB/TNF-α/TGF-ꞵ/apelin signaling pathway.

METHODS

Renal I/RI was induced by occluding the kidney arteries for 45 min, then reperfusion for 24 h. Four similar cycles of left femoral artery ischemia (2 min)/reperfusion (3 min) before the onset of kidney ischemia were performed to create RIPreC. Animals were randomly divided into three groups: sham, I/R, and RIPreC + I/R. Following the reperfusion phase, urine and blood samples were taken, and the kidney was removed for functional, molecular, and histological examination.

RESULTS

When compared to sham rats, renal IRI resulted in decreased creatinine clearance and increased sodium fractional excretion, lower antioxidant enzyme activities, higher malondialdehyde content and higher nuclear factor-kappa B (NF-κB), tumor necrosis factor-alpha (TNF-α), transforming growth factor-betta (TGF-β), and Apelin expression levels, and histologically damaged kidney tissue. All of the alterations, as mentioned earlier, were alleviated using the RIPreC treatment.

CONCLUSION

Thus, RIPreC can protect against renal dysfunction after renal I/RI via modulation of the TNF-α/NF-κB/TGF-ꞵ/Apelin signaling pathway and strengthening the antioxidant defense system.

Maternal choline supplementation during murine pregnancy modulates placental markers of inflammation, apoptosis and vascularization in a fetal sex-dependent manner

INTRODUCTION

Normal placental vascular development is influenced by inflammatory, angiogenic and apoptotic processes, which may be modulated by choline through its role in membrane biosynthesis, cellular signaling and gene expression regulation. The current study examined the effect of maternal choline supplementation (MCS) on placental inflammatory, angiogenic and apoptotic processes during murine pregnancy.

METHOD

Pregnant dams were randomized to receive 1, 2 or 4 times (X) the normal choline content of rodent diets, and tissues were harvested on embryonic day (E) 10.5, 12.5, 15.5 or 18.5 for gene expression, protein abundance and immunohistochemical analyses.

RESULTS

The choline-induced changes in the inflammatory and angiogenic markers were a function of fetal sex. Specifically, 4X (versus 1X) choline reduced the transcript (P ≤ 0.05) and protein (P ≤ 0.06) expression of TNF-a and IL-1β in the male placentas at E10.5 and E18.5, respectively. In the female placentas, 4X (versus 1X) choline modulated the transcript expression of Il1b in a biphasic pattern with reduced Il1b at E12.5 (P = 0.045) and E18.5 (P = 0.067) but increased Il1b at E15.5 (P = 0.031). MCS also induced an upregulation of Vegfa expression in the female placentas at E15.5 (P = 0.034; 4X versus 2X) and E18.5 (P = 0.026; 4X versus 1X). MCS decreased (P = 0.011; 4X versus 1X) placental apoptosis at E10.5. Additionally, the luminal area of the maternal spiral arteries was larger (P ≤ 0.05; 4X versus 1X) in response to extra choline throughout gestation.

DISCUSSION

MCS during murine pregnancy has fetal sex-specific effects on placental inflammation and angiogenesis, with possible consequences on placental vascular development.

Lipoprotein lipase in chronic lymphocytic leukemia: function and prognostic implications

Chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease characterized by the accumulation of a clonal population of B cells in peripheral blood, bone marrow, and lymphoid organs. More than 10 years ago, lipoprotein lipase (LPL) mRNA was identified as being strongly expressed in patients experiencing a more aggressive phenotype, while CLL patients with an indolent disease course lack expression of this marker. Since then, several reports confirmed the capability of LPL to predict CLL disease evolution at the moment of diagnosis. In contrast, data on the functional implications of LPL in CLL are scarce. LPL exerts a central role in overall lipid metabolism and transport, but plays additional, non-catalytic roles as well. Which of those is more important in the pathogenesis of CLL remains largely unclear. Here, we review the current knowledge on the prognostic and biological relevance of LPL in CLL.

Investigating the Role of TNF-α and IFN-γ Activation on the Dynamics of iNOS Gene Expression in LPS Stimulated Macrophages

Macrophage produced inducible nitric oxide synthase (iNOS) is known to play a critical role in the proinflammatory response against intracellular pathogens by promoting the generation of bactericidal reactive nitrogen species. Robust and timely production of nitric oxide (NO) by iNOS and analogous production of reactive oxygen species are critical components of an effective immune response. In addition to pathogen associated lipopolysaccharides (LPS), iNOS gene expression is dependent on numerous proinflammatory cytokines in the cellular microenvironment of the macrophage, two of which include interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α). To understand the synergistic effect of IFN-γ and TNF-α activation, and LPS stimulation on iNOS expression dynamics and NO production, we developed a systems biology based mathematical model. Using our model, we investigated the impact of pre-infection cytokine exposure, or priming, on the system. We explored the essentiality of IFN-γ priming to the robustness of initial proinflammatory response with respect to the ability of macrophages to produce reactive species needed for pathogen clearance. Results from our theoretical studies indicated that IFN-γ and subsequent activation of IRF1 are essential in consequential production of iNOS upon LPS stimulation. We showed that IFN-γ priming at low concentrations greatly increases the effector response of macrophages against intracellular pathogens. Ultimately the model demonstrated that although TNF-α contributed towards a more rapid response time, measured as time to reach maximum iNOS production, IFN-γ stimulation was significantly more significant in terms of the maximum expression of iNOS and the concentration of NO produced.

Prostacyclin-induced peroxisome proliferator-activated receptor-alpha translocation attenuates NF-kappaB and TNF-alpha activation after renal ischemia-reperfusion injury

Prostacyclin and peroxisome proliferator-activated receptors (PPAR) protect against ischemia-reperfusion (I/R) injury by the induction of an anti-inflammatory pathway. In this study, we examined the prostacyclin-enhanced protective effect of PPARalpha in I/R-induced kidney injury. PPAR-alpha reduced the NF-kappaB-induced overexpression of TNF-alpha and apoptosis in cultured kidney cells. In a murine model, pretreating wild-type (WT) mice with a PPAR-alpha activator, docosahexaenoic acid (DHA), significantly reduced I/R-induced renal dysfunction (lowered serum creatinine and urea nitrogen levels), apoptotic responses (decreased apoptotic cell number and caspase-3, -8 activation), and NF-kappaB activation. By comparison, I/R-induced injury was exacerbated in PPAR-alpha knockout mice. This indicated that PPAR-alpha attenuated renal I/R injury via NF-kappaB-induced TNF-alpha overexpression. Overexpression of prostacyclin using an adenovirus could also induce PPAR-alpha translocation from the cytosol into the nucleus to inhibit caspase-3 activation. This prostacyclin/PPAR-alpha pathway attenuated TNF-alpha promoter activity by binding to NF-kappaB. Using a cAMP inhibitor (CAY10441) and a prostacyclin receptor antibody, we also found that there was another prostacyclin/IP receptor/cAMP pathway that could inhibit TNF-alpha production. Taken together, our results demonstrate for the first time that prostacyclin induces the translocation of PPAR-alpha from the cytosol into the nucleus and attenuates NF-kappaB-induced TNF-alpha activation following renal I/R injury. Treatments that can augment prostacyclin, PPAR-alpha, or the associated signaling pathways may ameliorate conditions associated with renal I/R injury.

Protein kinase C in heart failure: a therapeutic target?

Heart failure (HF) afflicts about 5 million people and causes 300,000 deaths a year in the United States alone. An integral part of the pathogenesis of HF is cardiac remodelling, and the signalling events that regulate it are a subject of intense research. Cardiac remodelling is the sum of responses of the heart to causes of HF, such as ischaemia, myocardial infarction, volume and pressure overload, infection, inflammation, and mechanical injury. These responses, including cardiomyocyte hypertrophy, myocardial fibrosis, and inflammation, involve numerous cellular and structural changes and ultimately result in a progressive decline in cardiac performance. Pharmacological and genetic manipulation of cultured heart cells and animal models of HF and the analysis of cardiac samples from patients with HF are all used to identify the molecular and cellular mechanisms leading to the disease. Protein kinase C (PKC) isozymes, a family of serine-threonine protein kinase enzymes, were found to regulate a number of cardiac responses, including those associated with HF. In this review, we describe the PKC isozymes that play critical roles in specific aspects of cardiac remodelling and dysfunction in HF.

Monocyte gene-expression profile in men with familial combined hyperlipidemia and its modification by atorvastatin treatment

AIM

The genetic origin of familial combined hyperlipidemia (FCH) is not well understood. We used microarray profiling of peripheral blood monocytes to search novel genes and pathways involved in FCH.

METHODS

Fasting plasma for determination of lipid profiles, inflammatory molecules and adipokines was obtained and peripheral blood monocytes were isolated from male FCH patients basally and after 4 weeks of atorvastatin treatment. Sex-, age- and adiposity-matched controls were also studied. Gene-expression profiles were analyzed using Affymetrix Human Genome U133A 2.0 GeneChip arrays.

RESULTS

Analysis of gene expression by cDNA microarrays showed that 82 genes were differentially expressed in FCH monocytes compared with controls. Atorvastatin treatment modified the expression of 86 genes. Pathway analysis revealed the over-representation of the complement and coagulation cascades, the hematopoietic cell lineage and the arachidonic acid metabolism pathways. Changes in the expression of some genes, confirmed by real-time RT-PCR, (CD36, leucine-rich repeats and immunoglobulin-like domains-1, tissue factor pathway inhibitor 2, myeloid cell nuclear differentiation antigen, tumor necrosis factor receptor superfamily, member 25, CD96 and lipoprotein lipase), may be related to a proinflammatory environment in FCH monocytes, which is partially reversed by atorvastatin. Higher plasma levels of triglycerides and free fatty acids and lower levels of adiponectin in FCH patients could also trigger changes in gene expression that atorvastatin cannot modify.

CONCLUSION

Our results show clear differences in gene expression in FCH monocytes compared with those of matched healthy controls, some of which are influenced by atorvastatin treatment.

Lipoprotein lipase protects bovine endothelial cells from human NK cytotoxic activity

Human lipoprotein lipase (LPL), in a dose dependent fashion, significantly inhibited spontaneous human natural killer (NK) cells, but not lymphokine-activated killer (LAK) cytotoxic activity against bovine pulmonary endothelial cells. The effect was dependent on endothelial heparan sulfate (HS) sites, since heparitinase reverted it. When HS is added before LPL, NK and LAK cytotoxicity are markedly reduced. Endothelial and NK cell priming, with LPL and HS+LPL, significantly induced CD40 and CD154 expression, respectively. Furthermore, CD40 expression was inversely proportional to lytic units (R2 = 0.9, P < 0.001). Treating endothelial cells simultaneously with indomethacin, CD154 fusion protein, and Wortmanin prevented the CD40 effect increasing xenograft rejection. LPL and HS+LPL protect bovine endothelial cells from NK cytotoxicity by inducing CD40, CD154 expression, and secretion of soluble factors. The high, non-modulated expression of adhesion receptors and the low number of HS sites account for the minor effect of CD40 in LAK cytotoxic responses against bovine endothelial cells.

Uranium induces TNFα secretion and MAPK activation in a rat alveolar macrophage cell line

Uranium is a toxic heavy metal found mainly in the nuclear industry, but it is also used in the manufacturing of military munitions. Inhalation studies using animal models have demonstrated that long-term exposure to uranium can lead to the development of neoplasia and fibrosis at the pulmonary level. Because it has been demonstrated that such effects are often associated with inflammation, the effect of uranium on TNFalpha, IL-1beta, and IL-10 synthesis by macrophages was assessed in vitro using the NR8383 cell line. Our results show that a significant TNFalpha secretion was induced by uranium but not by other metals such as gadolinium. However, IL-1beta and IL-10 secretions were unaffected by uranium treatment. TNFalpha secretion was detectable since 50 microM of uranium and was maximal after 24 h of exposure. Determination of the mechanisms of uranium-induced TNFalpha production was assessed through the evaluation of protein kinases activation. Our results showed that uranium treatment induced c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK) activation. The use of pharmacological inhibitors suggested that both p38 MAPK and protein kinase C (PKC) participate in the signal transduction of uranium-induced TNFalpha secretion. The regulation of TNFalpha secretion involves TNFalpha mRNA accumulation at least through the stabilization of TNFalpha mRNA, but p38 MAPK did not appear to be involved in this stabilization. However, this observation does not exclude regulation of TNFalpha synthesis at the transcriptional level, which remains to be demonstrated. Taking together, these results suggest that uranium can induce TNFalpha secretion by macrophages, thus contributing to a better understanding of the pathological effect of uranium on the lung.

Lipopolysaccharide induces overexpression of MUC2 and MUC5AC in cultured biliary epithelial cells: possible key phenomenon of hepatolithiasis

Bacterial infection, bile stasis, mucin hypersecretion, and an alteration of the mucin profile such as an aberrant expression of gel-forming apomucin (MUC2 and MUC5AC) in the intrahepatic biliary tree are thought to be important in the lithogenesis of hepatolithiasis. So far, there have been no detailed studies linking bacterial infection to altered mucus secretion of biliary epithelium. In this study, the influence of lipopolysaccharide (LPS), a bacterial component, on apomucin expression in cultured murine biliary epithelial cells was examined with emphasis on the participation of tumor necrosis factor (TNF)-alpha. It was found that LPS up-regulated the expression of MUC2 and MUC5AC in cultured murine biliary epithelial cells. LPS also induced the expression of TNF-alpha in biliary epithelial cells and its secretion into the culture medium. The up-regulation of these apomucins was inhibited by pretreatment with TNF-alpha antibody. TNF-alpha alone also induced the overexpression of MUC2 and MUC5AC in cultured biliary epithelial cells. This overexpression was inhibited by pretreatment with calphostin C, an inhibitor of protein kinase C. These findings suggest that LPS can induce overexpression of MUC2 and MUC5AC in biliary epithelial cells via synthesis of TNF-alpha and activation of protein kinase C. This mechanism might be involved in the lithogenesis of hepatolithiasis.

The role of linoleic acid in endothelial cell gene expression. Relationship to atherosclerosis

There is evidence that linoleic acid plays a critical role in gene expression and vascular function as it relates to the pathogenesis of atherosclerosis. The lipid environment, particularly linoleic acid and its derivatives, of the vascular endothelium may profoundly influence the inflammatory response mediated by cytokines. Modulations in the level of activity of a select set of endothelial transcription factors appear to provide a mechanism for linking lipid/cytokine-mediated vessel wall dysfunction, including endothelial cell activation, altered proteoglycan metabolism, and endothelial barrier dysfunction, with the onset of atherosclerotic lesion formation. The activity of endothelial transcription factors is in part regulated by the balance of cellular oxidative stress and antioxidant status. Our data suggest that linoleic acid can activate the vascular endothelium and may thus be an atherogenic fatty acid. Furthermore, nutrients/chemicals with antioxidant properties can protect endothelial cells against lipid-mediated cell injury, suggesting that oxidative stress is a critical component in linoleic acid-mediated gene expression. Our discoveries that linoleic acid can influence significantly the cytokine-mediated inflammatory response may open new fields in dietary intervention of atherosclerosis.

Analogs of cyclic nucleotides in rat liver preservation

BACKGROUND

Cyclic nucleotides mediate intracellular signal transduction of several vasodilators. In addition to its vascular relaxant effects, cAMP is known to protect endothelial cells and to suppress Kupffer cell activation. On the other hand, cGMP potently ameliorates adhesion of leukocytes and platelets. We tested the effects of two analogs of cyclic nucleotides (8bromo cyclic adenosine monophosphate [8br-cAMP] and 8bromo cyclic guanosine monophosphate [8br-cGMP]) in rat liver preservation.

METHODS

In experiment 1, either analog (0.1-1.0 mM) alone was added to University of Wisconsin (UW) solution in a survival study. In experiment 2, donors and recipients were also treated with 8br-cAMP or 8br-cGMP, with the following three groups tested: group 1=control; group 2=administration of 8br-cAMP to donors, UW solution, and recipients; group 3=administration of 8br-cGMP to donors, UW solution, and recipients. Experiment 3 tested combined treatments: group 4=administration of 8br-cGMP to donors and UW solution, and cAMP to recipients; group 5=administration of 8br-cAMP to donors and UW solution, and 8br-cGMP to recipients. To elucidate the roles of each nucleotide, two further groups were tested: group 6=administration of 8br-cAMP to donors and UW solution; group 7=administration of 8br-cGMP to recipients. In experiment 4, rats in groups 1, 5, 6, and 7 were killed at several time points after reperfusion, and percent graft blood flow (%BF), number of accumulated neutrophils, plasma levels of tumor necrosis factor-alpha and interleukin-1, and serum alanine aminotransferase levels were examined.

RESULTS

In experiments 1 and 2, no significant effect was observed on animal survival. In experiment 3, a significant increase in animal survival was observed only in group 5 (100%, 7/7, P=0.0004 vs. group 1: 16.7%, 2/12). In group 5, no improvement of %BF was observed during the early phase of reperfusion (15 and 30 min) compared with that in group 1. On the other hand, the %BF of group 5 was significantly higher in the later phase (6 hr), consistent with the decrease in accumulation of neutrophils observed then. Production of tumor necrosis factor-alpha and serum alanine aminotransferase levels were also reduced with this treatment. Histologically, the bleeding and segmental necrosis, observed in group 1, were completely prevented in group 5.

CONCLUSIONS

We conclude that restoration of grafts with cAMP and administration of cGMP to recipients led to successful transplantation, and that the two analogs acted synergistically in opposing preservation and reperfusion injury without improvement of graft blood flow during the early phase of reperfusion. The effect was due to their regulation of neutrophil activation and sequestration.

Interleukin 10 inhibits alveolar macrophage production of inflammatory mediators involved in adult respiratory distress syndrome

BACKGROUND

Adult respiratory distress syndrome (ARDS) causes severe morbidity and mortality in trauma patients. One potential method to attenuate the lung injury is to inhibit alveolar macrophage production of proinflammatory mediators. The purpose of this study was to investigate the cellular mechanism of interleukin 10 (IL-10) inhibition on LPS-stimulated macrophage (Mphi). We hypothesized that IL-10 inhibited phospholipase C signal pathways in Mphi. IL-10 inhibition would be restored by calcium ionophores and protein kinase C (PKC) activation.

METHODS

Rabbit alveolar Mphi were obtained by bronchoalveolar lavage. Mphi were treated with Escherichia coli LPS (10 ng/ml) in the presence of various concentrations of human IL-10. Cell lysates and supernatant were analyzed for proagulants (PCA) and tumor necrosis factor (TNF), respectively. TNF mRNA expression of alveolar Mphi was also measured by Northern Blot assay. Macrophage PGE2 production was measured by ELISA.

RESULTS

IL-10 inhibited the production of both TNF and PCA by LPS-stimulated Mphi. In addition, IL-10 also reduced TNF mRNA expression. Similarly, PGE2 production by LPS-stimulated Mphi was also attenuated by IL-10. An increase in the intracellular [Ca2+] induced by A23187 failed to reverse this IL-10-mediated inhibition. In comparison, phorbol myristate acetate, a protein kinase C (PKC) activator, restored TNF and PCA production despite the presence of IL-10.

CONCLUSIONS

IL-10 inhibits Mphi production of inflammatory mediators. This inhibition is, at least in part, mediated by modulating the PKC activity.

Modulation of interferon-gamma-induced macrophage activation by phosphotyrosine phosphatases inhibition. Effect on murine Leishmaniasis progression

Phagocyte functions are markedly inhibited after infection with the intracellular protozoan parasite Leishmania. This situation strongly favors the installation and propagation of this pathogen within its mammalian host. Previous findings by us and others have established that alteration of several signaling pathways (protein kinase C-, Ca2+- and protein-tyrosine kinases-dependent signaling events) were directly responsible for Leishmania-induced macrophage (MO) dysfunctions. Here we report that modulation of phosphotyrosine-dependent events with a protein tyrosine phosphatases (PTP) inhibitor, the peroxovanadium (pV) compound bpV(phen) (potassium bisperoxo(1,10-phenanthroline)oxovanadate(Vi)), can control host-pathogen interactions by different mechanisms. We observed that the inhibition of parasite PTP resulted in an arrest of proliferation and death of the latter in coincidence with cyclin-dependent kinase (CDK1) tyrosine 15 phosphorylation. Moreover the treatment of MO with bpV(phen) resulted in an increased sensitivity to interferon-gamma stimulation, which was reflected by enhanced nitric oxide (NO) production. This enhanced IFN-gamma-induced NO generation was accompanied by a marked increase of inducible nitric oxide synthase (iNOS) mRNA gene and protein expression. Finally we have verified the in vivo potency of bpV(phen) over a 6-week period of daily administration of a sub-toxic dose. The results revealed its effectiveness in controlling the progression of visceral and cutaneous leishmaniasis. Therefore PTP inhibition of Leishmania and MO by the pV compound bpV(phen) can differentially affect these eukaryotic cells. This strongly suggests that PTP plays an important role in the progression of Leishmania infection and pathogenesis. The apparent potency of pV compounds along with their relatively simple and versatile structure render them attractive pharmacological agents for the management of parasitic infections.

Decoy administration of NF-kappaB into the subarachnoid space for cerebral angiopathy

Subarachnoid hemorrhage (SAH), encephalitis, meningitis, and autoimmune diseases sometimes lead to cerebral angiopathy, characterized specifically by narrowing of vessels, morphological changes in the structure of vessel walls, and a concomitant decrease in cerebral blood flow. Many patients also develop delayed ischemic neurological deficits. Thus, preventing vascular reactions is of paramount importance in treating SAH. Although cerebral vasospasm has some relationship with the inflammatory reaction of major cerebral vessels against the autologous blood, and many trials have attempted to prevent angiopathy after SAH, an effective treatment has not yet been established. The purpose of this article is to evaluate the preventive effect of nuclear factor KB (NF-kappaB) decoy oligo-DNA after SAH; since NF-kappaB is closely related to inflammation. In the rabbit angiopathy model after SAH, we evaluated the effectiveness of the decoy oligo-DNA using the angiographic (digital subtraction angiography) and histological (hematoxylin-eosin and Masson's trichrome staining) methods. Moreover, a gel-shift assay for NF-kappaB was also performed in order to evaluate the activity of NF-kappaB. We describe a new concept for treating cerebral angiopathy after SAH and for successfully inhibiting cerebral vasospasm and morphological changes in vessel walls in a rabbit model. In this treatment, we used synthetic double-strand oligo-DNA with a high affinity for transcription factor NF-kappaB, and cationic liposome complex administered through the cerebrospinal fluid.

The Tat protein of HIV-1 induces tumor necrosis factor-alpha production. Implications for HIV-1-associated neurological diseases

Human immunodeficiency virus (HIV) infection may cause a dementing illness. HIV-mediated dementia is clinically and pathologically correlated with the infiltration of activated macrophages and elevated levels of tumor necrosis factor (TNF)-alpha, both of which occur in an environment of small numbers of infected cells. We examined the possibility that HIV protein Tat, which is released extracellularly from infected cells, may induce the production of TNF-alpha. Tat induced TNF-alpha mRNA and protein production dose-dependently, primarily in macrophages but also in astrocytic cells. The TNF-alpha induction was NF-kappaB-dependent and could be eliminated by inhibiting protein kinase A or protein tyrosine kinase activity. In addition, Tat-induced TNF-alpha release was also linked to phospholipase C activation. However, Tat effects were independent of protein kinase C. These observations suggest that Tat may provide an important link between HIV and macrophage/glial cell activation and suggest new therapeutic approaches for HIV dementia.

Antiatherogenic properties of zinc: implications in endothelial cell metabolism

Zinc is an essential component of biomembranes and is necessary for maintenance of membrane structure and function. There is evidence that zinc can provide antiatherogenic properties by preventing metabolic physiologic derangements of the vascular endothelium. Because of its antioxidant and membrane-stabilizing properties, zinc appears to be crucial for the protection against cell-destabilizing agents such as polyunsaturated lipids and inflammatory cytokines. Zinc also may be antiatherogenic by interfering with signaling pathways involved in apoptosis. Most importantly, we have evidence that zinc can protect against inflammatory cytokine-mediated activation of oxidative stress-responsive transcription factors, such as nuclear factor kappa B and AP-1. It is very likely that certain lipids and zinc deficiency may potentiate the cytokine-mediated inflammatory response and endothelial cell dysfunction in atherosclerosis. Thus, the antiatherogenic role of zinc appears to be in its ability to inhibit oxidative stress-responsive factors involved in disruption of endothelial integrity and atherosclerosis. We discuss antiatherogenic properties of zinc with a focus on endothelial cell metabolism.

Lipoprotein lipase synergizes with interferon gamma to induce macrophage nitric oxide synthetase mRNA expression and nitric oxide production

Lipoprotein lipase (LPL) induces macrophage tumor necrosis factor-alpha (TNF-alpha) gene expression and protein secretion. Since TNF-alpha can increase interferon gamma (IFN-gamma)-dependent nitric oxide (NO) production, we studied whether LPL may synergize with IFN-gamma for the induction of macrophage NO production. Although ineffective by itself, LPL in combination with IFN-gamma increased L-arginine-dependent NO production in a dose-dependent manner. Preincubation of LPL with an anti-LPL neutralizing antibody totally suppressed this effect. Increased NO synthetase (NOS) mRNA expression was also observed after macrophage treatment with IFN-gamma and LPL. Protein synthesis was required for the induction of NOS mRNA, and a TNF-alpha-mediated effect of LPL on NOS gene expression and NO production was observed. The ability of LPL to augment IFN-gamma-dependent NOS mRNA expression was associated with an increase in the NOS gene transcriptional activity but not in the NOS mRNA stability. Finally, binding of nuclear proteins to the nuclear factor-kappa B- and TNF-alpha-responsive sequences of the macrophage NOS promotor was decreased by treatment of the cells by IFN-gamma alone or in combination with LPL. These data provide evidence for a link between LPL and arginine metabolism in macrophages and further stress the role of LPL in the regulation of macrophage activation.