Nitric oxide mediates tumor necrosis factor-alpha cytotoxicity in endothelial cells

An Fc-free EGFR-specific 4-1BB-agonistic Trimerbody Displays Broad Antitumor Activity in Humanized Murine Cancer Models without Toxicity

PURPOSE

The induction of 4-1BB signaling by agonistic antibodies can drive the activation and proliferation of effector T cells and thereby enhance a T-cell-mediated antitumor response. Systemic administration of anti-4-1BB-agonistic IgGs, although effective preclinically, has not advanced in clinical development due to their severe hepatotoxicity.

EXPERIMENTAL DESIGN

Here, we generated a humanized EGFR-specific 4-1BB-agonistic trimerbody, which replaces the IgG Fc region with a human collagen homotrimerization domain. It was characterized by structural analysis and in vitro functional studies. We also assessed pharmacokinetics, antitumor efficacy, and toxicity in vivo.

RESULTS

In the presence of a T-cell receptor signal, the trimerbody provided potent T-cell costimulation that was strictly dependent on 4-1BB hyperclustering at the point of contact with a tumor antigen-displaying cell surface. It exhibits significant antitumor activity in vivo, without hepatotoxicity, in a wide range of human tumors including colorectal and breast cancer cell-derived xenografts, and non-small cell lung cancer patient-derived xenografts associated with increased tumor-infiltrating CD8⁺ T cells. The combination of the trimerbody with a PD-L1 blocker led to increased IFNγ secretion in vitro and resulted in tumor regression in humanized mice bearing aggressive triple-negative breast cancer.

CONCLUSIONS

These results demonstrate the nontoxic broad antitumor activity of humanized Fc-free tumor-specific 4-1BB-agonistic trimerbodies and their synergy with checkpoint blockers, which may provide a way to elicit responses in most patients with cancer while avoiding Fc-mediated adverse reactions.

Therapy and pharmacological properties of hydroxychloroquine and chloroquine in treatment of systemic lupus erythematosus, rheumatoid arthritis and related diseases

OBJECTIVES

This review examines the pharmacokinetics, modes of action and therapeutic properties of the anti-malarial drugs, hydroxychloroquine (HCQ) and chloroquine (CQ), in the treatment of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and related conditions, as well as osteoarthritis (OA).

KEY FINDINGS

Both HCQ and CQ have historically been employed successfully for the treatment of SLE and RA for over 70 years. HCQ has been used extensively for SLE where it has a good reputation for controlling the dermatological complications in SLE. It has also been reported to effectively control the symptoms of Sjøgren's syndrome, as well as preventing thrombosis in phospholipid antibody (aPL) syndrome. In RA and SLE, HCQ is preferred because of the lower incidence of gastrointestinal adverse reactions compared with CQ and it might have a lower risk of ocular adverse reactions. There is increasing evidence that HCQ may reduce atherosclerosis and risks of cardiovascular disease in rheumatic patients. Both HCQ and CQ have been shown to improve glycaemia and reduce the risks of type II diabetes mellitus. Although both HCQ and CQ are effective in low-moderate RA, HCQ is now preferred as part of combination therapy for more severe disease. The advantages of combination therapy are that the doses of the individual drugs may be lowered so reducing adverse reactions. Both HCQ and CQ are diastereoisomers, have basic properties and are given as the sulphate and phosphate salts. While being relatively well absorbed orally and with good bioavailability, they have long and variable plasma terminal elimination half-lives (approximately 40-60 days). This reflects their high volume of distribution, V D (HCQ 44,000L; CQ 65,000L) which extends into aqueous compartments, long mean residence time (HCQ 1300 h; CQ 900 h) and with about half the drugs (metabolites) undergoing renal clearance. The strong binding to melanin reflects the ocular injury and dermatological properties of these drugs. The consensus is that the occurrence of ocular adverse reactions can be minimised by close attention to the dose (which should be set on a body weight basis) with regular (e.g. quarterly) retinal examination. Although HCQ and CQ can pass through the placenta, the use of these drugs during pregnancy does not appear to risk harm to the baby and might be beneficial to the mother with SLE and her child by controlling the SLE disease activity, which is known to be an important factor affecting pregnancy outcome. The modes of action of HCQ and CQ in these arthritides represent somewhat of an enigma. Undoubtedly, these drugs have multiple actions related, in part, their ability to accumulate in lysosomes and autophagosomes of phagocytic cells as well as affecting MHC Class II expression and antigen presentation; actions of the production of pro-inflammatory cytokines [e.g. interleukin-1 (IL-1) tumour necrosis factor-α (TNFα)]; control of toll-like receptor-9 activation; and leucocyte generation of reactive oxygen species (ROS); i.e. antioxidant activity. The actions of these drugs on T and B cells are less clear but may depend on these leucocyte-mediated actions. Anti-malarials also protect against cytokine-mediated cartilage resorption. This and other actions may underlie the potential benefits in treating OA. The exact relationships of these various actions, mostly determined in vitro, have not been specifically defined in vivo or ex vivo in relation to clinical efficacy.

OUTCOMES

HCQ and CQ have a good reputation for being effective and relatively safe treatments in SLE, mild-moderate RA and Sjøgren's syndrome. There is need for (a) more information on their mode of action in relation to the control of these diseases, (b) scope for developing formulations that have improved pharmacokinetic and therapeutic properties and safety, and (c) further exploring their use in drug combinations not only with other disease modifying agents but also with biologics.

S-nitrosoglutathione accelerates recovery from 5-fluorouracil-induced oral mucositis

Introduction

Mucositis induced by anti-neoplastic drugs is an important, dose-limiting and costly side-effect of cancer therapy.

Aim

To evaluate the effect of the topical application of S-nitrosoglutathione (GSNO), a nitric oxide donor, on 5-fluorouracil (5-FU)-induced oral mucositis in hamsters.

Materials and Methods

Oral mucositis was induced in male hamsters by two intraperitoneal administrations of 5-FU on the first and second days of the experiment (60 and 40 mg/kg, respectively) followed by mechanical trauma on the fourth day. Animals received saline, HPMC or HPMC/GSNO (0.1, 0.5 or 2.0 mM) 1 h prior to the 5-FU injection and twice a day for 10 or 14 days. Samples of cheek pouches were harvested for: histopathological analysis, TNF-α and IL-1β levels, immunohistochemical staining for iNOS, TNF-α, IL-1β, Ki67 and TGF-β RII and a TUNEL assay. The presence and levels of 39 bacterial taxa were analyzed using the Checkerboard DNA-DNA hybridization method. The profiles of NO released from the HPMC/GSNO formulations were characterized using chemiluminescence.

Results

The HPMC/GSNO formulations were found to provide sustained release of NO for more than 4 h at concentration-dependent rates of 14 to 80 nmol/mL/h. Treatment with HPMC/GSNO (0.5 mM) significantly reduced mucosal damage, inflammatory alterations and cell death associated with 5-FU-induced oral mucositis on day 14 but not on day 10. HPMC/GSNO administration also reversed the inhibitory effect of 5-FU on cell proliferation on day 14. In addition, we observed that the chemotherapy significantly increased the levels and/or prevalence of several bacterial species.

Conclusion

Topical HPMC/GSNO accelerates mucosal recovery, reduces inflammatory parameters, speeds up re-epithelization and decreases levels of periodontopathic species in mucosal ulcers.

Development of next-generation macromolecular drugs based on the EPR effect: challenges and pitfalls

INTRODUCTION

A major problem with conventional antitumor therapeutics is nonselective delivery of cytotoxic drugs to normal vital organs and tissues but little delivery to tumor tissues.

AREAS COVERED

Here, the authors describe the tumor selective delivery of antitumor drugs by taking advantage of nano-sized drugs and the means to augment it further. Based on the enhanced permeability and retention (EPR) effect, the mechanism for more efficient universal tumor delivery using macromolecular drugs to cover wider tumor types than single molecular target is discussed. Unique properties of solid tumor vasculature in the tumor tissue are discussed, especially leakiness of the blood vessels and factors involved and impaired clearance of macromolecular drugs from the tumor interstitium via the lymphatic system. The criteria for such macromolecular drugs or nanomedicines for effective accumulation at tumor sites is commented on as well as the importance of long plasma retention time of such drugs and a need to release active principles from nanoparticles at target sites. Methods to augment the EPR effect and tumor delivery (2 - 3 times) and its application to photodynamic therapy are also discussed.

EXPERT OPINION

Tumor selective delivery of antitumor drugs based on the EPR effect can be accomplished and augmented by modulating the tumor environment. This methodology is favorable not only for tumor therapy but also for tumor imaging.

Immunogenetic biomarkers in inflammatory bowel diseases: Role of the IBD3 region

Many studies have demonstrated the linkage between the IBD3 region (6p21.1-23), an area which encompasses the famous human leukocyte antigen (HLA) complex, and Crohn’s disease (CD) or ulcerative colitis (UC). IBD3 is the only region that meets genome-wide significance, and provides stronger evidence of the linkage than 16p13.1-16q12.2 (IBD1), the locus that contains the susceptibility gene CARD15. However, despite these findings, IBD3 susceptibility genes remain elusive and unclear due to the strong linkage disequilibrium, extensive polymorphism, and high gene density that characterize this area and also due to varying allele frequencies in populations around the world. This area presents an extremely high abundance of genes, including the classical and non-classical major histocompatibility complex (MHC) class I and II genes, and other genes, namely MHC class III genes tumor necrosis factor (TNF)-α and -β, and Hsp, whose proteins play key functions in immunological processes. To date, it is not clear which genes within the MHC family contribute to the IBD pathogenesis, although certain HLA alleles have been associated with IBD. Recent insights into the biological function of other genes encoded within the IBD3 region, such as the MHC class I chain-related (MIC) genes, have led investigators to a more comprehensive exploration of this region. MHC class I chain-related molecule A (MICA) is highly polymorphic and interacts with NKG2D, its receptor on the surface of NK, Tγδ and T CD8⁺ cells. Increased expression of MICA in intestinal epithelial cells and increased expression of NKG2D in CD4⁺ T cells (lamina propria) in patients with CD have also been reported. MICA alleles have also been associated with IBD, and a variation at amino acid position 129 of the α2-heavy chain domain seems to categorize MICA alleles into strong and weak binders of NKG2D receptor, thereby influencing the effector cells’ function. In this regard, a relevant role of MICA-129-Val/Met single nucleotide polymorphism has recently been implicated in the pathogenesis of IBD. TNF-α and -β also play an important role in inflammatory response. In fact, IBD is commonly treated with TNF-α inhibitors. Additionally, polymorphisms of TNF-α gene are known to affect the gene expression level and particular TNF-α genotypes may influence the response of IBD patients treated with TNF-α inhibitors.

Mutual modulation between norepinephrine and nitric oxide in haemocytes during the mollusc immune response

Nitric oxide (NO) is one of the most important immune molecules in innate immunity of invertebrates, and it can be regulated by norepinephrine in ascidian haemocytes. In the present study, the mutual modulation and underlying mechanism between norepinephrine and NO were explored in haemocytes of the scallop Chlamys farreri. After lipopolysaccharide stimulation, NO production increased to a significant level at 24 h, and norepinephrine concentration rose to remarkable levels at 3 h and 12~48 h. A significant decrease of NO production was observed in the haemocytes concomitantly stimulated with lipopolysaccharide and α-adrenoceptor agonist, while a dramatic increase of NO production was observed in the haemocytes incubated with lipopolysaccharide and β-adrenoceptor agonist. Meanwhile, the concentration of cyclic adenosine monophosphate (cAMP) decreased significantly in the haemocytes treated by lipopolysaccharide and α/β-adrenoceptor agonist, while the content of Ca(2+) was elevated in those triggered by lipopolysaccharide and β-adrenoceptor agonist. When the haemocytes was incubated with NO donor, norepinephrine concentration was significantly enhanced during 1~24 h. Collectively, these results suggested that norepinephrine exerted varied effects on NO production at different immune stages via a novel α/β-adrenoceptor-cAMP/Ca(2+) regulatory pattern, and NO might have a feedback effect on the synthesis of norepinephrine in the scallop haemocytes.

Endocrine and metabolic changes in human aging

Numerous alterations in hormonal secretion occur with aging. In general, these tend towards a disintegration of the normal cyclic secretory patterns resulting in lower total circulating levels. In addition, declines in receptors and postreceptor function further decreases the ability of the hormonal orchestra to maintain coordinated function throughout the organism. Clues to some of these age-related changes in humans may come from the study of simpler organisms where regulatory systems are known to modulate the aging process. In particular, the interactions among the environment, hormones, and insulin receptor genes have led to new insights into the genetic control of longevity and the development of syndrome X.

Genetic polymorphisms of tumour necrosis factor alpha (TNF-α) promoter gene and response to TNF-α inhibitors in Spanish patients with inflammatory bowel disease

Tumour necrosis factor alpha (TNF-α) has an important role in inflammatory response. Alterations in the regulation of TNF-α have been implicated in a variety of inflammatory disorders, including Inflammatory bowel disease (IBD). Indeed, a common treatment for IBD is the use of TNF-α inhibitors. Polymorphisms in the TNF-α promoter region are known to affect the level of gene expression. Our aim was to investigate the influence of these single nucleotide polymorphisms (SNPs) in TNF-α promoter gene play in the risk of IBD in a Spanish population and their individual response to anti-TNF-α treatment. DNA samples from patients with IBD and controls were screened for TNF-α -238G/A (rs361525) and -308G/A (rs1800629) SNPs by PCR-SSOP using a microbeads luminex assay and compared with response to TNF-α inhibitors. There were not statistical differences in -238G/A and -308G/A allele and genotype frequencies between patients. However, we found an increased frequency of -308A allele and -308GA genotype in these nonresponders patients to TNF-α inhibitors with respect to responders patients (Pc < 0.05). This -308GA genotype has been classified as high producer of this cytokine. This fact could actually be interesting to explain the different response of patients with IBD with respect to TNF-α inhibitors. TNF-α promoter gene polymorphism does not seem to play a role in IBD susceptibility, but particular TNF-α genotypes may be involved in the different responses to TNF-α inhibitor treatment in Spanish patients with IBD.

The effect of lysolecithin on prostanoid and platelet-activating factor formation by human gall-bladder mucosal cells

It has been demonstrated that lysolecithin (lysophosphatidyl choline, LPC) produces experimental cholecystitis in cats mediated by arachidonic acid metabolites. LPC is a cytolytic agent that has been postulated as a contributing factor in the development of cholecystitis in humans. The purpose of this research was to evaluate the effect of LPC on human gall-bladder mucosal cell phospholipase A₂ and cyclooxygenase activity. Gall-bladder mucosal cells were isolated from the gall-bladders of patients undergoing routine cholecystectomy. Fresh, isolated cells were maintained in tissue culture and stimulated with varying doses of LPC. Platelet-activating factor concentration was quantitated as an index of phospholipase A₂ activity and prostanoids were measured as an index of cyclooxygenase activity. Also, the effect of LPC on cyclooxygenase 1 and 2 expression in microsomal protein was evaluated. LPC caused dose related increases in 6-keto-PGF_1α and PAF produced by human gall-bladder mucosal cells. Exposure of human gall-bladder mucosal cells to LPC failed to elicit expression of constitutive cyclooxygenase-1, while the expression of inducible cyclooxygenase-2 was increased. The results of this study indicate that LPC induces the formation of prostanoids and PAF by human gall-bladder mucosal cells, suggesting that this substance may promote the development of gall-bladder inflammation.

Modulation of macrophage activation by prostaglandins

The effect of prostaglandtn E(2), iloprost and cAMP on both nitric oxide and tumour necrosis factor-alpha release in J774 macrophages has been studied. Both prostaglandin E(2) and iloprost inhibited, in a concentration-dependent fashion, the lipopolysaccharide-induced generation of nitric oxide and tumour necrosis factor-alpha. The inhibitory effect of these prostanoids seems to be mediated by an increase of the second messenger cAMP since it was mimicked by dibutyryl cAMP and potentiated by the selective type IV phosphodiesterase inhibitor RO-20-1724. Our results suggest that the inhibition of nitric oxide release by prostaglandin E(2) and iloprost in lipopolysaccharide-activated J774 macrophages may be secondary to the inhibition of tumour necrosis factor-alpha generation, which in turn is likely to be mediated by cAMP.

Role of inducible nitric oxide synthase pathway on methotrexate-induced intestinal mucositis in rodents

BACKGROUND

Methotrexate treatment has been associated to intestinal epithelial damage. Studies have suggested an important role of nitric oxide in such injury. The aim of this study was to investigate the role of nitric oxide (NO), specifically iNOS on the pathogenesis of methotrexate (MTX)-induced intestinal mucositis.

METHODS

Intestinal mucositis was carried out by three subcutaneous MTX injections (2.5 mg/kg) in Wistar rats and in inducible nitric oxide synthase knock-out (iNOS-/-) and wild-type (iNOS+/+) mice. Rats were treated intraperitoneally with the NOS inhibitors aminoguanidine (AG; 10 mg/Kg) or L-NAME (20 mg/Kg), one hour before MTX injection and daily until sacrifice, on the fifth day. The jejunum was harvested to investigate the expression of Ki67, iNOS and nitrotyrosine by immunohistochemistry and cell death by TUNEL. The neutrophil activity by myeloperoxidase (MPO) assay was performed in the three small intestine segments.

RESULTS

AG and L-NAME significantly reduced villus and crypt damages, inflammatory alterations, cell death, MPO activity, and nitrotyrosine immunostaining due to MTX challenge. The treatment with AG, but not L-NAME, prevented the inhibitory effect of MTX on cell proliferation. MTX induced increased expression of iNOS detected by immunohistochemistry. MTX did not cause significant inflammation in the iNOS-/- mice.

CONCLUSION

These results suggest an important role of NO, via activation of iNOS, in the pathogenesis of intestinal mucositis.

Recent advances in cytokines: therapeutic implications for inflammatory bowel diseases

Inflammatory bowel diseases (IBDs) are complex and chronic disabling conditions resulting from a dysregulated dialogue between intestinal microbiota and components of both the innate and adaptive immune systems. Cytokines are essential mediators between activated immune and non-immune cells, including epithelial and mesenchymal cells. They are immunomodulatory peptides released by numerous cells and these have significant effects on immune function leading to the differentiation and survival of T cells. The physiology of IBD is becoming a very attractive field of research for development of new therapeutic agents. These include cytokines involved in intestinal immune inflammation. This review will focus on mechanisms of action of cytokines involved in IBD and new therapeutic opportunities for these diseases.

Effect of atorvastatin on 5-fluorouracil-induced experimental oral mucositis

PURPOSE

Oral mucositis (OM) is a frequent side effect in patients with cancer. We investigate the effect of atorvastatin (ATV), a cholesterol-lowering drug, on OM induced by 5-fluorouracil (5-FU) in hamsters.

METHODS

OM was induced by the i.p. administration of 5-FU, with excoriations of the cheek pouch mucosa. The animals were pretreated with i.p. ATV 1, 5 or 10 mg/kg or vehicle (saline and 5% (vol/vol) ethanol) 30 min before 5-FU injection and daily for 5 or 10 days. Samples of cheek pouches and main organs were removed for histopathological analysis, determination of TNF-α, IL-1β, nitrite, non-protein sulfhydryl group (NP-SH) levels, myeloperoxidase (MPO) assay and immunohistochemistry for induced nitric oxide synthase (iNOS). Blood was collected for a leukogram analysis of biochemical parameters and analysis of bacteremia.

RESULTS

ATV at doses of 1 and 5 mg/kg reduced mucosal damage and inflammation, as well as the levels of cytokines, nitrite and myeloperoxidase activity on the 5th and 10th day of OM and immunostaining for iNOS on the 5th day of OM.ATV at 1 mg/kg increased cheek pouch NP-SH when compared to 5-FU groups on the 10th day of OM. The association between ATV 5 mg/kg and 5-FU decreased the survival rate, amplified the leukopenia of animals, increased transaminase serum levels and caused liver lesions. We also detected the presence of Gram-negative bacillus in the blood of 100% of the animals treated with ATV 5 mg/kg + 5-FU.

CONCLUSIONS

Atorvastatin prevented mucosal damage and inflammation associated with 5-FU-induced OM, but the association of a higher dose of ATV with 5-FU induced hepatotoxicity and amplified leukopenia.

Lymphocyte activation gene-3 fusion protein increases the potency of a granulocyte macrophage colony-stimulating factor-secreting tumor cell immunotherapy

PURPOSE

The purpose of the present study was to evaluate granulocyte macrophage colony-stimulating factor (GM-CSF)-secreting tumor cell immunotherapy, which is known to stimulate a potent and long-lasting antigen-specific immune response in combination with lymphocyte activation gene-3 fusion protein (LAG-3Ig), which has been shown to act as an adjuvant for priming T helper type 1 and cytotoxic T-cell responses.

EXPERIMENTAL DESIGN

Survival and immune monitoring studies were done in the B16 melanoma model. GM-CSF-secreting tumor cell immunotherapy was administered as a single s.c. injection and LAG-3Ig was administered s.c. at the immunotherapy site.

RESULTS

The studies reported here show that combining LAG-3Ig with GM-CSF-secreting tumor cell immunotherapy prolonged the survival of tumor-bearing animals compared with animals treated with either therapy alone. Prolonged survival correlated with increased numbers of systemic IFN gamma-secreting CD8+ T cells and a significantly increased infiltration of activated effector CD8+ T cells into the tumor. Moreover, an increase in antigen-specific IgG1 humoral responses was detected in serum of animals injected with the combination therapy compared with animals injected with either therapy alone.

CONCLUSION

LAG-3Ig combined with a GM-CSF-secreting tumor cell immunotherapy stimulated both cellular and humoral antitumor immune responses that correlated with prolonged survival in tumor-bearing animals.

Modulating TNF-alpha signaling with natural products

Natural products have been, and continue to be, a major source of pharmacologically active substances from which drugs can be developed. Currently, tumor necrosis factor-alpha (TNF-alpha) inhibitors from natural origins are being advanced for the treatment of inflammatory disorders. Elevated TNF-alpha synthesis has been associated with the development of diabetes, septic shock, tumorigenesis, rheumatoid arthritis, psoriatic arthritis and inflammatory bowel disease. Currently, only protein-based drugs are available for the clinical inhibition of TNF-alpha activity. Small-molecule drugs that can regulate TNF-alpha levels or activity might provide a cost-effective alternative to protein-based therapeutics. This review briefly highlights the physiological and pathological roles of TNF-alpha, and covers those natural compounds capable of interfering with TNF-alpha activity.

Role of nitric oxide on pathogenesis of 5-fluorouracil induced experimental oral mucositis in hamster

INTRODUCTION

Mucositis induced by antineoplastic drugs is an important, dose-limiting, and costly side effect of cancer therapy.

AIM

To investigate the role of nitric oxide (NO) on the pathogenesis of 5-fluorouracil (5-FU)-induced oral mucositis.

MATERIALS AND METHODS

Oral mucositis was induced by two intraperitoneal (i.p) administrations of 5-FU on the first and second days of the experiment (60 and 40 mg/kg, respectively) in male hamsters. Animals were treated subcutaneously with saline (0.4 ml), 1,400 W (1 mg/kg), aminoguanidine (5 or 10 mg/kg) or Nphi-Nitro-L-Arginine Methyl Ester (L-NAME) (5, 10, or 20 mg/kg) 1 h before the injections of 5-FU and daily until sacrifice, on the tenth day. Macroscopic and histopathological analyses were evaluated and graded. Tissues from the cheek pouches were harvested for measurement of myeloperoxidase (MPO) activity, nitrite level, and immunohistochemistry for induced nitric oxide synthase (iNOS).

RESULTS

Treatment with 1,400 W or aminoguanidine reduced macroscopic and histological parameters of oral mucositis, and reduced the inflammatory cell infiltration as detected by histopathology and by MPO activity. In contrast, the administration of L-NAME did not significantly reverse the inflammatory alterations induced by experimental mucositis. Increased NOS activity, nitrite level and immunostaining for iNOS were detected on the check pouch tissue of animals submitted to 5-FU-induced oral mucositis on the tenth day.

CONCLUSION

These results suggest an important role of NO produced by iNOS in the pathogenesis of oral mucositis induced by 5-FU.

Effects of the new ethacrynic acid derivative SA9000 on intraocular pressure in cats and monkeys

To evaluate the pharmacological characteristics of the new ethacrynic acid (ECA) derivative SA9000, we examined its ocular hypotensive effects in cats and cynomolgus monkeys, its corneal toxicity in rabbits, and its binding affinities for forty-three receptors, ion channels, and second messenger systems. A 20 microl injection into the anterior chamber of eye (intracameral injection) of 0.1 mM SA9000 significantly reduced intraocular pressure (IOP) 3.8 mmHg in cats. A 10 microl intracameral injection of 1 mM SA9000 significantly reduced IOP 7 mmHg in living monkeys without evidence of in vivo (or in vitro) toxicity. The ocular hypotensive effect of SA9000 in monkeys was greater than that of ECA. The morphology of corneal endothelial and epithelial cells in rabbit eyes after intracameral injection of SA9000 was observed using electron microphotography. SA9000 at 2 mM did not induce any abnormalities, indicating that it has no corneal toxicity at a concentration higher than the minimum needed for an ocular hypotensive effect (1 mM). SA9000 at 0.01 mM showed negligible binding affinity for, or inhibition of, forty-three different receptors, ion channel proteins, and second messenger systems. These findings indicate that SA9000 has the potential to be both effective and safe as an ocular hypotensive drug, although the mechanism of action remains unclear.

Crucial role for interferon gamma in the synergism between tumor vasculature-targeted tumor necrosis factor alpha (NGR-TNF) and doxorubicin

NGR-TNF is a derivative of TNF-alpha, consisting of TNF fused to CNGRCG, a tumor vasculature-targeting peptide. Previous studies showed that NGR-TNF can exert synergistic antitumor effects with doxorubicin and with other chemotherapeutic drugs in murine models. In this study, we have investigated the role of endogenous IFN-gamma on the antitumor activity of NGR-TNF in combination with doxorubicin. The study was carried out using murine B16F1 melanoma and TS/A mammary adenocarcinoma implanted subcutaneously in (a) immunocompetent mice, (b) athymic nude mice, and (c) IFN-gamma-knockout mice. Synergism between NGR-TNF and doxorubicin was observed in immunocompetent mice but not in nude or IFN-gamma-knockout mice. Preadministration of a neutralizing anti-IFN-gamma antibody to immunocompetent mice inhibited the NGR-TNF/doxorubicin synergism, whereas administration of IFN-gamma to nude and to IFN-gamma-knockout mice restored the synergistic activity. The synergism in nude mice was restored also by transfecting tumor cells with the IFN-gamma cDNA. Administration of NGR-TNF in combination with IFN-gamma to nude mice, but not of NGR-TNF alone, doubled the penetration of doxorubicin in TS/A tumors. These findings point to a crucial role for locally produced IFN-gamma in tumor vascular targeting with NGR-TNF and doxorubicin. Finally, addition of IFN-gamma to the treatment of immunocompetent mice with NGR-TNF/doxorubicin induced only modest improvement in response, suggesting that exogenous IFN-gamma can improve the therapeutic activity of these drugs only in case of suboptimal production of endogenous IFN-gamma.

Endothelial cells from bovine pulmonary microvasculature respond to Mycoplasma bovis preferentially with signals for mononuclear cell transmigration

Mycoplasma bovis can cause arthritis or mastitis following pneumonia and mycoplasmemia in cattle. Interactions with pulmonary vascular endothelium have been recorded as localized vasculitis, perivascular mononuclear cell infiltrations, and accumulation of inflammatory cells in lesions. We compared adhesion mediators and cytokine gene expression as well as cytotoxicity of cultured primary bovine aortic and bovine pulmonary microvascular endothelial cells (BPMEC) challenged with M. bovis. We also tested if abscess-forming ability of strains of M. bovis is associated with changes on endothelial cells. Increased VCAM-1 surface expression was found in both cell types, while only infected BPMEC increased MCP-1 transcription, both mediators specific for mononuclear cell transmigration. Given no induction of ICAM-1 mRNA in either cell type, induction of IL-8 mRNA by BPMEC suggested that neutrophil transmigration was signaled in microvascular areas. Infected BPMEC showed early induction of IL-1beta and IL-6 mRNA. Excepting VCAM-1, differential strain effects were limited to BPMEC and not correlated with their abscess-forming capability. In addition, only strain DSA16 had minor cytotoxic effect on both cell types. We thus show that BPMEC are more susceptible than aortic cells to M. bovis-induced activation. Activation preferentially yielded signals for mononuclear cell transmigration, correlating well with in vivo observations of infiltrating cells at pulmonary sites.

Induction of endothelial nitric oxide synthase expression by melanoma sensitizes endothelial cells to tumor necrosis factor-driven cytotoxicity

PURPOSE

The cascade of molecular events leading to tumor necrosis factor (TNF)-mediated tumor regression is still incompletely elucidated. We investigated the role of endothelial nitric oxide synthase in determining the tumor-selective activity of TNF.

EXPERIMENTAL DESIGN

Using quantitative real-time PCR, endothelial nitric oxide synthase gene levels were measured in melanoma metastases of the skin and normal skin biopsies obtained from 12 patients before undergoing TNF-based therapy. In vitro, the ability of melanoma cells supernatant to affect endothelial nitric oxide synthase transcription by endothelial cells and the influence of nitric oxide synthase inhibition on TNF cytotoxicity toward endothelial cells was evaluated.

RESULTS

Endothelial nitric oxide synthase transcript abundance resulted significantly greater in tumor samples rather than in normal skin samples and in patients showing complete response to TNF-based treatment rather than in those showing partial/minimal response. In vitro, melanoma cells' supernatant induced endothelial nitric oxide synthase gene expression by endothelial cells. Nitric oxide synthase inhibition slowed endothelial cells proliferation and, if induced before TNF administration, decreased the cytokine-mediated cytotoxicity on endothelial cells.

CONCLUSIONS

Taken together, these findings support the hypothesis that high expression of endothelial nitric oxide synthase in the tumor microenvironment might increase or be a marker for endothelial cells sensitivity to TNF. These observations may have important prognostic and/or therapeutic implications in the clinical setting.

Argininosuccinate synthase expression is required to maintain nitric oxide production and cell viability in aortic endothelial cells

Although cellular levels of arginine greatly exceed the apparent K(m) for endothelial nitric-oxide synthase, current evidence suggests that the bulk of this arginine may not be available for nitric oxide (NO) production. We propose that arginine regeneration, that is the recycling of citrulline back to arginine, defines the essential source of arginine for NO production. To support this proposal, RNA interference analysis was used to selectively reduce the expression of argininosuccinate synthase (AS), because the only known metabolic role for AS in endothelial cells is in the regeneration of l-arginine from l-citrulline. Western blot analysis demonstrated a significant and dose-dependent reduction of AS protein as a result of AS small interfering RNA treatment with a corresponding diminished capacity to produce basal or stimulated levels of NO, despite saturating levels of arginine in the medium. Unanticipated, however, was the finding that the viability of AS small interfering RNA-treated endothelial cells was significantly decreased when compared with control cells. Trypan blue exclusion analysis suggested that the loss of viability was not because of necrosis. Two indicators, reduced expression of Bcl-2 and an increase in caspase activity, which correlated directly with reduced expression of AS, suggested that the loss of viability was because of apoptosis. The exposure of cells to an NO donor prevented apoptosis associated with reduced AS expression. Overall, these results demonstrate the essential role of AS for endothelial NO production and cell viability.

Increased TIA-1 gene expression in the tumor microenvironment after locoregional administration of tumor necrosis factor-alpha to patients with soft tissue limb sarcoma

Although it is known that TNF-alpha is effective in the treatment of advanced solid tumors such as melanoma and soft tissue sarcoma, the molecular mechanism underlying its anticancer activity remains unclear. Nineteen patients with locally advanced soft tissue sarcoma underwent isolated limb perfusion with doxorubicin alone (n = 9) or combined with TNF-alpha (n = 10). mRNA from posttreatment tumor biopsies was linearly amplified to create an RNA bank. The transcriptional levels of 22 genes were analyzed by qrt-PCR. On the basis of in vivo findings, we investigated the in vitro gene expression of different cell types representing the tumor microenvironment cell population. TIA-1, which encodes an RNA-binding protein with translation-regulatory functions, was the only gene differentially expressed between the 2 study groups, its transcriptional levels in tumor biopsies from patients receiving TNF-alpha being higher than in those from patients not given the cytokine. In vitro, TIA-1 was expressed by endothelial cells, fibroblasts, CTLs and NK cells. TNF-alpha significantly upregulated TIA-1 gene expression only in endothelial and NK cells. Furthermore, TIA-1 transcriptional levels significantly increased during NK activity, which was enhanced by TNF-alpha. These findings support the hypothesis that TNF-alpha-induced TIA-1 overexpression might sensitize endothelial cells to proapoptotic stimuli present in the tumor microenvironment and enhance NK cell cytotoxic activity against cancer cells.

Identification of a protein fragment of interleukin 2 responsible for vasopermeability

BACKGROUND

The cytokine interleukin 2 (IL-2) is involved in the activation of T cells and has been shown to play a central role in cancer immunotherapy. The full therapeutic potential of IL-2, however, has not been realized because of its dose-limiting systemic toxicity. We sought to identify a region of IL-2 that is responsible for the induction of vasopermeability (leaky tumor endothelium), a property associated with the toxicity of the molecule.

METHODS

Intact IL-2 or overlapping synthetic peptides of IL-2 that were chemically conjugated to tumor-targeting monoclonal antibodies (TNT-1 or Lym-1) were injected into groups of mice (n = 4) that had previously been xenotransplanted with human tumor cells (ME-180 cervical carcinoma and Raji lymphoma). Two hours later, mice received intravenous injections of radiolabeled tracer antibody, and 3 days later they were subjected to biodistribution analysis to measure the ability of each immunoconjugate to enhance tumor uptake of the tracer antibody (i.e., vasopermeability activity). The cytokine activity of the immunoconjugates was determined by assaying their ability to promote the proliferation of a mouse IL-2-dependent cell line.

RESULTS

Pretreatment of mice with an antibody/IL-2 immunoconjugate resulted in an approximately fourfold increase in radiolabeled tracer antibody uptake in the xenograft tumor as compared with uptake in mice injected with antibody alone. One synthetic fragment consisting of amino acids 22-58 contained 100% of the vasopermeability activity of IL-2 and was designated permeability-enhancing peptide (PEP). PEP had vasopermeability activity only when conjugated to a tumor-targeting antibody, had maximal activity as a dimer, and was devoid of cytokine activity.

CONCLUSIONS

The identification of PEP should aid in the discovery of ways to decrease the toxicity of IL-2. Moreover, PEP is a promising candidate for the generation of agents that can enhance the delivery of antibodies and drugs to tumors.

Protective role of nitric oxide in mice with Shiga toxin-induced hemolytic uremic syndrome

BACKGROUND

Nitric oxide (NO) is an endogenous vasodilator and platelet inhibitor. An enhanced NO production has been detected in patients with hemolytic uremic syndrome (HUS), although its implication in HUS pathogenesis has not been clarified.

METHODS

A mouse model of Shiga toxin 2 (Stx2)-induced HUS was used to study the role of NO in the development of the disease. Modulation of l-arginine-NO pathway was achieved by oral administration of NO synthase (NOS) substrate or inhibitors, and renal damage, mortality and platelet activity were evaluated. The involvement of platelets was studied by means of a specific anti-platelet antibody.

RESULTS

Inhibition of NO generation by the NOS inhibitor L-NAME enhanced Stx2-mediated renal damage and lethality; this effect was prevented by the addition of l-arginine. The worsening effect of L-NAME involved enhanced Stx2-mediated platelet activation, and it was completely prevented by platelet depletion.

CONCLUSIONS

NO exerts a protective role in the early pathogenesis of HUS, and its inhibition potentiates renal damage and mortality through a mechanism involving enhanced platelet activation.

Increased rectal nitric oxide in children with active inflammatory bowel disease

BACKGROUND

Luminal nitric oxide increases in ulcerative colitis and Crohn disease. The authors have previously used a minimally invasive method to demonstrate increased luminal nitric oxide in ulcerative colitis and Crohn disease of the colon. The aim of the current study was to determine whether this method could be applied to identify inflammatory activity in ulcerative colitis and Crohn disease in children.

METHODS

Thirty-six children (18 of whom had active disease) with inflammatory bowel disease localized to the colon were studied. The control group comprised 12 healthy children. To measure nitric oxide, a silicon catheter with an inflatable balloon was inserted into the rectum and inflated with 10 mL of nitric oxide-free air. After a 10-minute incubation time, the air was withdrawn and nitric oxide concentrations were immediately analyzed using a chemiluminescence technique.

RESULTS

Children with active ulcerative colitis and Crohn disease of the colon had greatly increased luminal nitric oxide concentrations in the rectum (8,840 +/- 5,120 and 15,170 +/- 4,757 parts per billion [ppb], respectively) compared with controls (77 +/- 17 ppb) (P < 0.001). Children with nonactive ulcerative colitis or Crohn disease displayed low concentrations of rectal nitric oxide (356 +/- 110 and 188 +/- 55 ppb, respectively), which was not different from that of healthy controls.

CONCLUSION

Rectal nitric oxide measurement is a feasible and useful method for monitoring disease activity in inflammatory bowel disease, especially in children.

Nitric oxide-induced apoptosis in tumor cells

Nitric oxide (NO), an important molecule involved in neurotransmission, vascular homeostasis, immune regulation, and host defense, is generated from a guanido nitrogen of L-arginine by the family of NO synthase enzymes. Large amounts of NO produced for relatively long periods of time (days to weeks) by inducible NO synthase in macrophages and vascular endothelial cells after challenge with lipopolysaccharide or cytokines (such as interferons, tumor necrosis factor-alpha, and interleukin-1), are cytotoxic for various pathogens and tumor cells. This cytotoxic effect against tumor cells was found to be associated with apoptosis (programmed cell death). The mechanism of NO-mediated apoptosis involves accumulation of the tumor suppressor protein p53, damage of different mitochondrial functions, alterations in the expression of members of the Bcl-2 family, activation of the caspase cascade, and DNA fragmentation. Depending on the amount, duration, and the site of NO production, this molecule may not only mediate apoptosis in target cells but also protect cells from apoptosis induced by other apoptotic stimuli. In this review, we will concentrate on the current knowledge about the role of NO as an effector of apoptosis in tumor cells and discuss the mechanisms of NO-mediated apoptosis.

Roles of tumor necrosis factor p55 and p75 receptors in TNF-alpha-induced vascular permeability

We have investigated the role of p55 and p75 tumor necrosis factor receptors 1 and 2 (TNFR1 and TNFR2, respectively) in TNF-induced alteration of endothelial permeability in vitro and in vivo. Stimulation of TNFR1 with an agonist antibody or a receptor-selective TNF mutein increased the flux of (125)I-albumin through endothelial cell monolayers. An antagonist anti-TNFR1 antibody, but not antagonist anti-TNFR2 antibodies, blocked the activity of TNF in vitro. Stimulation of TNFR1, but not TNFR2, induced cytoskeletal reorganization associated with increased permeability. SB-203580, a p38 mitogen-activated protein kinase inhibitor, blocked TNFR1-induced cytoskeletal reorganization and permeability. A selective mouse TNFR1 agonist and human TNF, which binds to murine TNFR1, increased the leakage of trypan blue-albumin from liver vessels in mice. These results indicate that stimulation of TNFR1 is necessary and sufficient to increase endothelial permeability in vitro and in vivo. However, an antagonist anti-murine TNFR2 antibody partially inhibited the effect of murine TNF on liver vessels, suggesting that TNFR2 also plays a role in the regulation of TNF-induced vascular permeability in vivo.

Interleukin 12 gene therapy of cancer by peritumoral injection of transduced autologous fibroblasts: outcome of a phase I study

A phase I dose-escalation clinical trial of peritumoral injections of interleukin 12 (IL-12)-transduced autologous fibroblasts was performed in patients with disseminated cancer for whom effective treatment does not exist. The goals of this study were to assess the safety and toxicities as well as the efficacy, and ancillarily the immunomodulatory effects, of peritumoral IL-12 gene transfer. Primary dermal fibroblasts cultured from the patients were transduced with retroviral vector carrying human IL-12 genes (p35 and p40) as well as the neomycin phosphotransferase gene (TFG-hIL-12-Neo). Patients received four injections at intervals of 7 days. Nine patients were enrolled in this dose-escalation study, with secreted IL-12 doses ranging from 300 ng/24 hr for the first three patients to 1000, 3000, and 5000 ng/24 hr for two patients in each subsequent dosage level. Although a definite statement cannot be made, there appears to be perturbation of systemic immunity. Also, the locoregional effects mediated by tumor necrosis factor alpha (TNF-alpha) and CD8+ T cells were observed with tumor regression. Treatment-related adverse events were limited to mild to moderate pain at the injection site; clinically significant toxicities were not encountered. Transient but clear reductions of tumor sizes were observed at the injected sites in four of nine cases, and at noninjected distant sites in one melanoma patient. Hemorrhagic necrosis of tumors was observed in two melanoma patients. These data indicate that gene therapy by peritumoral injection of IL-12-producing autologous fibroblasts is feasible, and promising in patients with advanced cancer.

Effect of LPS on the permeability of the blood-brain barrier to insulin

Insulin has emerged as an important neuropeptide. Central actions of insulin appear to oppose those in the periphery. Insulin is transported across the blood-brain barrier (BBB) by a saturable transport system. The permeability of the BBB to insulin is altered by various events, but no studies exist that have examined the permeability of the BBB to insulin during infection or inflammation, states which can induce peripheral insulin resistance. We looked at the effects of lipopolysaccharide (LPS), a bacterial endotoxin and a powerful cytokine releaser, on the permeability of the BBB to human insulin in CD-1 mice. Intraperitoneal injections of LPS significantly increased the uptake by the brain of 131I-insulin and disrupted the BBB to 125I-albumin. After subtraction of the brain/serum ratio for 125I-albumin, brain/serum ratios for insulin were increased: 10.38 +/- 0.70 microl/g (LPS) vs. 3.62 +/- 0.27 microl/g (no LPS), P<0.0001, showing that LPS increased the uptake of insulin independent of BBB disruption. This increase in insulin uptake was due to enhanced saturable transport. Pretreatment with indomethacin 10 min before LPS injections enhanced BBB disruption, but not insulin transport. Pretreatment with the nitric oxide (NO) synthase inhibitor aminoguanidine had no effect on insulin or albumin uptake, but pretreatment with NG-nitro-L-arginine methyl ester (L-NAME) enhanced insulin transport, but not BBB disruption. We conclude that LPS increases the saturable transport of insulin across the BBB independent of disruption and prostaglandins with potentiation by NO inhibition. Such increased transport could potentiate the central effects of insulin and so contribute to the peripheral insulin resistance seen with infection and inflammation.

beta-adrenergic stimulation of rat cardiac fibroblasts enhances induction of nitric-oxide synthase by interleukin-1beta via message stabilization

We have investigated factors modulating expression of inducible NO synthase (iNOS) in isolated adult rat cardiac fibroblasts. Treatment of cardiac fibroblasts with interleukin-1beta (IL-1beta) promotes induction of iNOS mRNA and protein and production of NO. Simultaneous incubation of cells with isoproterenol enhances the response to IL-1beta, even though isoproterenol alone is without effect. N(G)-nitro-L-arginine methyl ester inhibits the effect of isoproterenol + IL-1beta on NO production. beta(2)-Adrenergic receptors appear to mediate this effect of isoproterenol. Reverse transcriptase-polymerase chain reaction analyses show that beta(2)-receptor mRNA is the predominant beta-receptor message; in pharmacologic studies, ICI-118,551 significantly antagonizes isoproterenol-stimulated cyclic AMP production whereas CGP20712A does not. Dibutyryl-cyclic AMP and forskolin mimic the synergistic effect of isoproterenol on IL-1beta-induced NO production; H-89, a cyclic AMP-dependent protein kinase (PKA) inhibitor, antagonizes the enhancing effect of isoproterenol. Nuclear run-off experiments indicate that enhancement of iNOS by isoproterenol does not occur at the level of transcription. Message stability studies demonstrate that isoproterenol increases the half-life of iNOS mRNA from 1.0 to 1.9 h; this change is sufficient to account for the observed augmentation of iNOS mRNA and protein. Thus, cardiac fibroblasts produce significant amounts of NO in response to IL-1beta via induction of iNOS; beta-adrenergic stimulation enhances the IL-1beta effect by stabilizing the iNOS message. These data suggest that cardiac fibroblasts could participate in a paracrine mechanism whereby the direct positive inotropic effect of beta(1)-adrenergic stimulation of myocytes is opposed by beta(2)-adrenergic enhancement of NO production, a negative inotropic event, in neighboring fibroblasts.

Recombinant human interleukin-11 decreases severity of acute necrotizing pancreatitis in mice

Interleukin (IL)-11 has anti-inflammatory activity in animal models of gut inflammation, endotoxemia, and radiation-induced thoracic injury. The aim of the present study was to investigate the protective role of IL-11 in a model of acute necrotizing pancreatitis in mice. Acute pancreatitis was induced by administration of seven intraperitoneal injections of cerulein (50 microg/kg) at hourly intervals. Lipopolysaccharide (LPS) was injected 5 hours after the first cerulein injection. Treatment with recombinant human IL-11 (rhIL-11) was started 30 minutes before the first cerulein injection and repeated 4 hours later. Serum levels of amylase, lipase, and tumor necrosis factor (TNF)-alpha were measured at the end of the experiments. The severity of pancreatitis was evaluated by histological scoring using a semiquantitative analysis of hematoxylin and eosin-stained sections of the pancreas. Competitive reverse transcription-polymerase chain reaction (RT-PCR) was performed to quantify the intrapancreatic TNF-alpha mRNA levels. Serum amylase and lipase levels progressively increased with a maximum reached between 8 and 11 hours. Treatment with rhIL-11 significantly decreased amylase and lipase levels at 6 and 8 hours. Serum TNF-alpha peaked at 6 hours and rapidly decreased thereafter. The elevation of serum TNF-alpha was markedly inhibited by treatment with rhIL-11. Histologically, treatment of rhIL-11 reduced the severity of pancreatic injury including edema, inflammatory cell infiltration, and hemorrhage at 6 hours. Intrapancreatic TNF-alpha mRNA levels were reduced by >50% in the rhIL-11-treated group at 6 hours. In conclusion, rhIL-11 decreased the severity of experimental pancreatitis early on but not later and inhibited the intrapancreatic TNF mRNA expression in vivo, suggesting that the protective effect of IL-11 during the early stage of acute pancreatitis may be mediated, at least in part, through modulation of TNF production.

Down-regulation of renal endothelial nitric oxide synthase expression in experimental glomerular thrombotic microangiopathy

Infection with certain strains of Escherichia coli and endotoxemia results in renal glomerular thrombotic microangiopathy (TMA) characterized by endothelial swelling and prominent glomerular microthrombus formation. Nitric oxide (NO) is an endogenous biologic modulator with diverse physiologic functions including vasodilation and inhibition of platelet adhesion and aggregation. NO is synthesized from conversion of L-arginine to L-citrulline by a family of NO synthases (NOS), which include constitutive and inducible isoforms. Indirect evidence supports the hypothesis that TMA is associated with depressed intrarenal NO production. However, the effect of TMA on renal tissue NOS expression has not been fully elucidated. We studied rats with TMA induced by iv bolus injection of high dose (20 mg/kg) E. coli endotoxin. Subgroups of six animals each were sacrificed before or at 30, 90, 180, 360, and 720 minutes after the administration of endotoxin. Renal histology and tissue expression of endothelial and inducible nitric oxide synthases (eNOS and iNOS) were examined. Additionally, we examined the effect of endotoxin on glomerular NO production, and eNOS and iNOS protein expression in vitro. Glomerular capillary thrombosis developed by 180 minutes after endotoxin administration in approximately half of the animals. The glomeruli without thrombotic lesions apparent by light microscopy disclosed early signs of TMA characterized by endothelial swelling, platelet accumulation/adhesion, and patchy fibrinogen deposition. These morphologic changes were associated with a marked reduction of renal tissue eNOS expression beyond 180 minutes after the endotoxin administration. The fall in eNOS expression was coupled with a significant rise in iNOS protein abundance, which was expressed largely by glomerular circulating neutrophils and endothelial cells, peritubular vascular endothelium, and collecting ducts of cortex and medulla. In vitro incubation of isolated glomeruli with endotoxin also resulted in a marked reduction in eNOS expression and a significant rise in iNOS content. Administration of E. coli endotoxin leads to a sustained fall in renal eNOS expression both in vivo and in vitro. The associated decline in intrarenal endothelial NO production/availability may result in renal vasoconstriction and a hypercoagulative state, which may contribute to the pathogenesis of endotoxin-induced TMA.

Lymphocyte migration through monolayers of endothelial cell lines involves VCAM-1 signaling via endothelial cell NADPH oxidase

Lymphocytes migrate from the blood across endothelial cells to reach foreign substances sequestered in peripheral lymphoid organs and inflammatory sites. To study intracellular signaling in endothelial cells during lymphocyte migration, we used murine endothelial cell lines that promote lymphocyte migration and constitutively express VCAM-1. The maximum rate of resting splenic lymphocyte migration across monolayers of the endothelial cells occurred at 0-24 h. This migration was inhibited by anti-VCAM-1 or anti-alpha4 integrin, suggesting that VCAM-1 adhesion was required for migration. To determine whether signals within the endothelial cells were required for migration, irreversible inhibitors of signal transduction molecules were used to pretreat the endothelial cell lines. Inhibitors of NADPH oxidase activity (diphenyleneiodonium and apocynin) blocked migration >65% without affecting adhesion. Because NADPH oxidase catalyzes the production of reactive oxygen species (ROS), we examined whether ROS were required for migration. Scavengers of ROS inhibited migration without affecting adhesion. Furthermore, VCAM-1 ligand binding stimulated NADPH oxidase-dependent production of ROS by the endothelial cells lines and primary endothelial cell cultures. Finally, VCAM-1 ligand binding induced an apocynin-inhibitable actin restructuring in the endothelial cell lines at the location of the lymphocyte or anti-VCAM-1-coated bead, suggesting that an NADPH oxidase-dependent endothelial cell shape change was required for lymphocyte migration. In summary, VCAM-1 signaled the activation of endothelial cell NADPH oxidase, which was required for lymphocyte migration. This suggests that endothelial cells are not only a scaffold for lymphocyte adhesion, but play an active role in promoting lymphocyte migration.

Pulmonary arterial smooth muscle cells modulate cytokine- and LPS-induced cytotoxicity in endothelial cells

Cytokines and lipopolysaccharide (LPS) are known to be injurious to vascular endothelial cells (ECs), but the influence of adjacent vascular smooth muscle cells (SMCs) on this injury is unknown. Exposure of cultured rat (RPMECs) or human (HPMECs) pulmonary microvascular ECs on tissue culture plastic to a mixture of cytokines (interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma) and LPS (cytomix) resulted in a significant increase in (51)Cr release to 35-40%. When unstimulated RPMECs were cocultured with cytomix-pretreated rat pulmonary microvascular SMCs (RPMSMCs) there was an increase in (51)Cr release to 8.4%, which was nitric oxide dependent. However, when RPMECs or HPMECs were stimulated in direct contact with their respective SMCs, rather than a further increase in cytomix-induced injury (e.g., >35-40%), (51)Cr release decreased to <10%. This cytoprotection was fully reproduced with fixed RPMSMCs, and partially reproduced by plating HPMECs on gelatin. These data show that the direct toxicity of a cytokine and endotoxin mixture on cultured ECs can be reduced by contact with vascular smooth muscle.

Modulation of collagen synthesis by tumor necrosis factor alpha in cultured vascular smooth muscle cells

Collagen synthesis in vascular smooth muscle cells (SMCs) after exposure to tumor necrosis factor alpha (TNF-alpha) was investigated using a culture system. The synthesis of collagenase-digestible proteins (CDP) and noncollagenous proteins (NCP) was evaluated by the [3H]proline incorporation. It was shown that TNF-alpha markedly suppresses the incorporation of [3H]proline into both CDP and NCP in confluent cultures of SMCs but not in sparse cultures of the cells. Such a marked suppression by TNF-alpha was not observed in confluent bovine aortic endothelial cells and human fibroblastic IMR-90 cells. In confluent SMCs, the synthesis of CDP was more strongly inhibited by TNF-alpha than that of NCP. When the CDP synthesis was stimulated by transforming growth factor beta, TNF-alpha suppressed the stimulation in both confluent and sparse SMCs. Human SMCs synthesized types I, III, IV and V collagens; TNF-alpha markedly decreased the relative proportion of types IV and V. It was therefore suggested that TNF-alpha modulates the collagen synthesis by SMCs depending on their cell density and modifies the formation of atherosclerotic lesions.

Cerebral Endothelial Cells Release TNF-α After Stimulation with Cell Walls of Streptococcus pneumoniae and Regulate Inducible Nitric Oxide Synthase and ICAM-1 Expression Via Autocrine Loops

TNF-α, inducible NO synthase (iNOS), and ICAM-1 are considered to be key proteins in the inflammatory response of most tissues. We tested the hypothesis that cell walls of Streptococcus pneumoniae (PCW), the most common cause of adult bacterial meningitis, induce TNF-α, iNOS, and ICAM-1 expression in rat primary brain microvascular endothelial cell cultures. We detected TNF-α mRNA by RT-PCR already 1 h after stimulation with PCW, while TNF-α protein peaked at 4 h (9.4 ± 3.6 vs 0.1 ± 0.1 pg/μg protein). PCW induced iNOS mRNA 2 h after stimulation, followed by an increase of the NO degradation product nitrite (18.1 ± 4 vs 5.8 ± 1.8 at 12 h; 18.1 ± 4 vs 5.8 ± 1.8 pmol/μg protein at 72 h). The addition of TNF-α Ab significantly reduced nitrite production to 62.2 ± 14.4% compared with PCW-stimulated brain microvascular endothelial cells (100%). PCW induced the expression of ICAM-1 (measured by FACS), which was completely blocked by TNF-α Ab (142 ± 18.6 vs 97.5 ± 12.4%; 100% unstimulated brain microvascular endothelial cells). Cerebral endothelial cells express TNF-α mRNA as well as iNOS mRNA and release the bioactive proteins in response to PCW. PCW-induced NO production is mediated in part by an autocrine pathway involving TNF-α, whereas ICAM-1 expression is completely mediated by this autocrine loop. By these mechanisms, cerebral endothelial cells may regulate critical steps in inflammatory blood-brain-barrier disruption of bacterial meningitis.

Tumor necrosis factor-alpha and phorbol 12-myristate 13-acetate differentially modulate cytotoxic effect of nitric oxide generated by serum deprivation in neuronal PC12 cells

Nitric oxide (NO) is a signaling molecule that mediates several physiological processes in a range of cell and tissue types. Here we investigated the effect of serum deprivation in the absence or presence of phorbol 12-myristate 1 3-acetate (PMA) or tumor necrosis factor-alpha (TNFalpha) on cell viability, NO formation, inducible NO synthase (iNOS) induction, and activation of mitogen-activated protein kinase in neuronal PC12 cells. Within 24 h of serum deprivation, apoptosis occurred in up to 65-70% of the cells, and significant levels of NO were generated. When PMA was added in serum-free medium, NO formation and cell death were decreased. In contrast, addition of TNFalpha in serum-free medium increased the levels of NO formation and apoptosis compared with those in serum-deprived cells. We have demonstrated that differential generation of NO levels by PMA or TNFalpha under conditions of serum deprivation is mediated by the same pattern of iNOS induction. NO formation via iNOS induction resulted in the activation of c-Jun N-terminal kinase (JNK) but not extracellular signal-regulated kinase. From this study it is suggested that the differential formation of cytotoxic NO by serum deprivation plus PMA or TNFalpha is primarily mediated by the induction of iNOS enzymes in neuronal PC12 cells and that its action is mediated by the activation of JNK.

Effects of endogenous and exogenous nitric oxide on endothelin-1 production in cultured vascular endothelial cells

The effects of various spontaneous nitric oxide (NO) donors and NO synthase inhibitors on endothelin- production were examined using porcine cultured aortic endothelial cells. NO donors such as (+/-)-(E)-4-methyl-2-[(E)-hydroxyimino]-5-nitro-3-hexanamide (NOR 2), (+/-)-(E)-4-ethyl-2-[( E)-hydroxyimino]-5-nitro-3-hexanamide (NOR 3) and (+/-)-N-[(E)-4-ethyl-2-[(Z)-hydroxyimino]-5-nitro-3-hexen-1- yl]-3-pyridine carboxamide (NOR 4) suppressed effectively the release of endothelin-1 from the cells. Endothelin-1 mRNA expression was also attenuated by these compounds. Other NO donors such as 3-[2-hydroxy-1-(1-methylethyl)-2-nitrosohydrazino]-1-propanamin e (NOC 5), 2,2'-(hydroxynitrosohydrazino)bis-ethanamine (NOC 18), s-nitroso-n-acetyl-DL-penicillamine, N-morpholino sydnonimine (SIN-1) had no effects on endothelin-1 production. Endothelial intracellular cyclic guanosine monophosphate (cGMP) levels were significantly increased by all NO donors. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a selective soluble guanylyl cyclase inhibitor, had no effect on the NOR 3-induced decrease in endothelin-1 secretion, although cGMP production was abolished by ODQ. NOR 3 also inhibited endothelin-1 secretion even in the presence of 2-(4-carboxyphenyl)-4,4,5,5-tetrametylimidazole-1-oxyl 3-oxide (carboxy-PTIO), a NO scavenger. NOR 3-induced inhibitory effects on endothelin-1 secretion were abolished by preincubation of the compound in phosphate-buffered saline (37 degrees C, 4 h), a procedure by which about 98% of the parent compound's ability to release NO was lost. NO synthase inhibitors such as N(G)-nitro-L-arginine, N(G)-monomethyl-L-arginine and N(G)-nitro-L-arginine methyl ester (L-NAME) enhanced prepro endothelin-1 mRNA expression and significantly increased endothelin-1 release from endothelial cells. Endothelin-1 secretion was also increased effectively by carboxy-PTIO or ODQ. When the cells were exposed to L-NAME with carboxy-PTIO or ODQ, no significant further increase in endothelin-1 release was observed. These results suggest that endogenous NO inhibits endothelin-1 production through guanylyl cyclase/cGMP-dependent mechanisms. In contrast, it seems unlikely that exogenous NO has an inhibitory effect on endothelin-1 production in endothelial cells. NOR compounds inhibit endothelin-1 production perhaps through NO/cGMP-independent mechanisms, i.e., through an unknown effect of the parent compound itself.

Growth regulation of cultured endothelial cells by inflammatory cytokines: mitogenic, anti-proliferative and cytotoxic effects

The inflammatory cytokines tumor necrosis factor-alpha (TNF alpha) and interleukin-1 alpha (IL-1 alpha) have angiogenic properties but generally inhibit cultured endothelial cell (EC) proliferation. Investigations into the growth-regulatory effects of these two agents on a variety of cultured EC types showed that they exert mitogenic, anti-proliferative or cytotoxic effects depending upon cell type and cytokine combinations. The anti-proliferative effect was distinct from cytotoxicity. Nitric oxide (NO) release from EC, examined as a potential mechanism underlying some of these effects, did not appear to mediate the anti-proliferative effects of these cytokines. However, NO also seemed to have a bimodal effect on EC proliferation depending upon whether the NO was endogenous or exogenous. These data underscore the diversity in cytokine and NO effects on cultured EC which, if reproducible in vivo, may be partly responsible for the variable and sometimes contradictory results obtained with regards to the role of inflammatory cytokines and NO on angiogenesis.

Erratic behavior of nitric oxide within the immune system: illustrative review of conflicting data and their immunopharmacological aspects

The literature data assembled in this article document the variation of immunobiological effects of nitric oxide (NO). A number of factors are obviously responsible for the diversity, ranging from inactivity, alleviation, but not rarely to exacerbation of certain pathogenetic processes. A better understanding of NO interactions with the immune system can only be reached if more complex experimental designs to study the effects of reactive nitrogen species are adopted in the future. They should integrate major participating variables and take into account pharmacodynamic/kinetic aspects of NO production in triggering the ultimate effects. If manipulation of NO in the organism by means of recently developed NO inhibitors and NO donors is to become a rational tool of immunopharmacological strategies, detailed knowledge of their pharmacologies and toxicologies is urgently needed in order to differentiate between the effects of NO and other side effects. Hopefully, this approach could improve the predictability of the clinical outcomes of NO manipulation.

Nitric oxide decreases surfactant protein A gene expression in H441 cells

OBJECTIVE

To study the effects of nitric oxide (NO) on surfactant protein A (SP-A) gene expression.

DESIGN

In vitro study.

SUBJECTS

A human lung tumor cell line (H441) representative of distal respiratory epithelium.

INTERVENTIONS

Cells were treated with the NO donor S-nitroso-N-acetyl penicillamine (SNAP) at concentrations ranging from 0.3 to 3.0 mM for 24 hrs.

MEASUREMENTS AND MAIN RESULTS

Northern blot analyses using a radiolabeled cDNA probe for human SP-A demonstrated that SNAP modestly (approximately 30%) decreased SP-A mRNA expression in a dose-dependent manner. Western blot analyses using a polyclonal anti-human SP-A antibody demonstrated that SNAP also decreased SP-A peptide expression. mRNA stability assays demonstrated that SNAP did not affect the half-life of SP-A mRNA. Cell viability assays demonstrated that SNAP slightly decreased cell viability compared with control cells. There were no significant differences in cell viability among cells treated with the different concentrations of SNAP.

CONCLUSIONS

NO decreases in vitro SP-A gene expression by approximately 30% in a human lung tumor cell line representative of distal respiratory epithelium. This effect does not occur at the posttranscriptional level and cannot be entirely accounted for by changes in cell viability. The inhibitory effect of NO demonstrated in this study is of relatively small magnitude and it is therefore difficult to make strong conclusions regarding biological relevance. However, these data, coupled with previous data demonstrating that NO negatively affects surfactant function, suggest that NO has the potential to negatively impact surfactant homeostasis.

Response of the septic vasculature to prolonged vasopressor therapy with N(omega)-monomethyl-L-arginine and epinephrine in canines

OBJECTIVE

To investigate the effect of blocking nitric oxide production on cardiovascular function and survival in canine septic shock treated with or without a conventional vasopressor.

DESIGN

Randomized, controlled trial.

SETTING

An animal research laboratory at the National Institutes of Health.

SUBJECTS

Sixty purpose-bred beagles.

INTERVENTIONS

Fibrin clots containing Escherichia coli were surgically placed into the peritoneal cavity. N(omega)-monomethyl-L-arginine (L-NMMA) 10 mg/kg followed by 0.5, 1.0, or 4.0 mg/kg/hr), epinephrine (1 microg/kg/min), both, or neither were infused for 24 hrs beginning 6 hrs after the onset of infection. All animals received fluid and antibiotic therapy.

MEASUREMENTS AND MAIN RESULTS

Serum nitric oxide metabolites, nitrite and nitrate, increased with infection (p = .024) and decreased with L-NMMA (p = .004, all doses combined). Myocardial nitric oxide synthase activity was ranked as follows: nonsurvivors > survivors > noninfected controls (p < .01). Other tissues examined showed the same pattern. L-NMMA produced sustained increases in systemic vascular resistance index and mean arterial pressure 9 and 24 hrs after the onset of infection (p < or = .04). Left ventricular ejection fraction was depressed by septic shock (p = .01) and further decreased by L-NMMA (p = .02). However, control and L-NMMA cardiac index values were similar (p > .4), perhaps because L-NMMA increased pulmonary artery occlusion pressure (p = .02). From 9 to 24 hrs, epinephrine, in the absence or presence of L-NMMA, blunted recovery of cardiac index (p < .02) and had a diminishing vasopressor effect (p = .05). Neither L-NMMA nor epinephrine, individually or combined, significantly altered survival rates at the doses investigated (p > or = .69).

CONCLUSIONS

The tested doses showed that nitric oxide production was inhibited by L-NMMA in canine septic shock, but mortality and myocardial depression were unaffected. These results suggest that if L-NMMA has a beneficial effect on survival rates in septic shock, it is small.

Dual role for nitric oxide in the regulation of plasma volume and albumin escape during endotoxin shock in conscious rats

To assess the role of nitric oxide (NO) produced by the constitutive (cNOS) and inducible NO synthase (iNOS) in the regulation of vascular functions, we compared the effects of aminoguanidine, a relatively selective inhibitor of iNOS, and NG-nitro-L-arginine methyl ester (L-NAME), a nonselective NOS inhibitor on blood pressure, plasma volume, and albumin escape during the early and delayed phases of endotoxin shock in conscious, chronically catheterized rats. Red blood cell volume and plasma volume were determined by using chromium-51-tagged erythrocytes and iodine-125-labeled albumin, respectively. Injection of lipopolysaccharide (LPS) 10 mg/kg i.v. resulted in a fall in blood pressure, hemoconcentration, and increased total-body albumin escape, which is reflected by a 25% reduction in plasma volume. When LPS was injected into animals pretreated with L-NAME (7.4 mumol/kg i.v. 15 minutes before LPS), losses in plasma volume and albumin escape were significantly greater than in rats that received LPS alone, despite that L-NAME attenuated the hypotensive action of LPS. Aminoguanidine pretreatment (162 mumol/kg) had no effect on the early responses to LPS, whereas it was as potent as L-NAME in reversing hypotension when injected 70 minutes after LPS. Aminoguanidine treatment also prevented further losses in plasma volume and markedly attenuated total-body and organ albumin escape rates elicited by LPS. L-NAME produced only a slight attenuation of LPS-induced losses in plasma volume and albumin escape in most organs studied, whereas it potentiated albumin extravasation in the lung. These results demonstrate that inhibition of cNOS potentiates, whereas inhibition of iNOS markedly attenuates, losses in plasma volume and albumin escape elicited by LPS, and suggest that selective inhibitors of iNOS may be more effective than nonselective inhibitors of all forms of NOS in the therapy of septic shock.

The role of nitric oxide in cardiac surgery

The release of nitric oxide (NO) from coronary endothelial cells is impaired following reperfusion; however, several experimental studies have found that it exerts a cardioprotective effect during myocardial ischemia-reperfusion. Thus, attempts have been made to supplement NO production exogenously during reperfusion when endogenous NO release may be diminished. Conversely, other studies suggest that NO exacerbates reperfusion injury by inducing the production of peroxynitrite. NO has also been reported to provide beneficial effects as a selective pulmonary vasodilator to relieve pulmonary hypertension. A loss of NO-mediated relaxation caused by the dysfunction of endothelial cells is characteristic of intimal hyperplasia, and nitrosovasodilators have proven efficient against atherosclerotic coronary heart disease, which may be attributable to their antiplatelet effects as well as to vasodilation. Furthermore, protamine sulfate, which is rich in L-arginine, is thought to augment NO production by supplying exogenous L-arginine, or to act on endothelial cell receptors to stimulate the production of NO. This review summarizes the current role of NO in cardiac surgery.

Role of nitric oxide and tumor necrosis factor on lung injury caused by ischemia/reperfusion of the lower extremities

PURPOSE

Acute aortic occlusion with subsequent ischemia/reperfusion (I/R) of the lower extremities is known to predispose to lung injury. The pathophysiologic mechanisms of this injury are not clear. In the present study, we studied the role of tumor necrosis factor (TNF) and nitric oxide (NO) in lung injury caused by lower extremity I/R.

METHODS

A rat model in which the infrarenal aorta was cross-clamped for 3 hours followed by 1 hour of reperfusion was used. The rats were randomized into five groups: group 1, aorta exposed but not clamped; group 2, aorta clamped for 3 hours, followed by 1 hour of reperfusion; group 3, 1 mg/kg dexamethasone administered before the aorta was clamped; group 4, 25 mg aminoguanidine, a specific inducible NO synthase (iNOS) inhibitor, administered before the aorta was clamped; and group 5, 2 mg/kg TNFbp, a PEG-ylated dimeric form of the high-affinity p55 TNF receptor I (RI), administered before the aorta was clamped. NO concentration in the exhaled gas (ENO) was measured, as an index of NO production by the lung, in 30 minute intervals during I/R. Serial arterial blood samples for TNF assay were obtained during the course of the experiment. At the end of the experiment, the lungs were removed and histologically examined for evidence of injury.

RESULTS

ENO in group 2 increased from 0.7 +/- 0.3 ppb at baseline to 54.3 +/- 7.5 ppb at the end of ischemia and remained stable during reperfusion (54.6 +/- 8.5 ppb at the end of reperfusion). ENO production was blocked by aminoguanidine, by dexamethasone, and by TNFbp given before aortic occlusion. Serum TNF in groups 2, 3 and 4 increased rapidly during early ischemia, reaching its peak value 60 minutes after occlusion of the aorta, then gradually declined to baseline levels at the end of ischemia, and remained low during reperfusion. TNFbp decreased serum TNF concentration significantly when it was given before aortic occlusion. Histologic examination of the lungs at the end of the experiment revealed that aminoguanidine, dexamethasone, and TNFbp had a protective effect on the lungs.

CONCLUSIONS

Serum TNF increases rapidly during lower extremity ischemia and causes increased production of NO from the lung by upregulating iNOS. Increased NO is associated with more severe lung injury, and iNOS blockade has beneficial effects on the lung. TNF blockade before ischemia decreases NO production by the lung and attenuates lung injury. ENO can be used as an early marker of lung injury caused by lower extremity I/R.

Nitric oxide mediates down regulation of lipoprotein lipase activity induced by tumor necrosis factor-alpha in brown adipocytes

We previously reported that tumor necrosis factor-alpha (TNF-alpha)/cachectin suppresses lipoprotein lipase activity and its gene expression in brown adipocytes differentiated in culture. Recent evidence suggests that the effect of TNF-alpha over various cells is related to the enhanced production of nitric oxide (NO). The present study examined whether the suppressive effect of TNF-alpha on lipoprotein lipase activity is mediated by production of NO in the brown adipocytes. A reverse transcription-polymerase chain reaction (RT-PCR) assay revealed that TNF-alpha caused a concentration- and time-dependent expression of inducible NO synthase in brown adipocytes. Increasing concentrations of TNF-alpha (0.5-50 ng/ml) for 24 h resulted in a concentration-dependent decrease in lipoprotein lipase activity with reciprocal increase in nitrite production in the medium. The suppressive effect of TNF-alpha on lipoprotein lipase activity was significantly prevented by NO synthase inhibitors, NG-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine, but not by D-NAME, an inactive isomer. Furthermore, 8-bromoguanosine 3',5'-cyclic monophosphate, cell permeant cGMP, suppressed lipoprotein lipase activity and 1 H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one, a selective inhibitor for soluble guanylate cyclase, restored the TNF-alpha-suppressed lipoprotein lipase activity. These results suggest that TNF-alpha stimulates brown adipocytes to express inducible NO synthase, followed by production of NO, which in turn mediates the suppressive effect of TNF-alpha on lipoprotein lipase activity. The effect of NO is mediated, at least partly, through production of cGMP.

Inhaled nitric oxide: clinical applications, indications, and toxicology

PURPOSE

Although the analogy of nitric oxide (NO) to Endothelium-derived Relaxing Factor remains controversial, medical use of exogenous NO gas by inhalation has grown exponentially. This review presents the mechanisms of action of inhaled NO in pulmonary hypertension, hypoxaemia, inflammation and oedema, as well as its therapeutic and diagnostic indications with emphasis on acute respiratory distress syndrome (ARDS) and toxicology.

SOURCE

Two medical databases (Current Contents, Medline) were searched for citations containing the above-mentioned key words to December 1996. Moreover, many presentations in congresses such as 4th International Meeting of Biology of Nitric Oxide, 52nd and 53rd Annual Meeting of Canadian Anaesthetists' Society or 10th Annual Meeting of European Association of Cardiothoracic Anaesthesiologists were used.

PRINCIPAL FINDINGS

Inhaled NO is now recognized as an invaluable tool in neonatal and paediatric critical care, and for heart/lung surgery. Other clinical applications in adults, such as chronic obstructive pulmonary disease and ARDS, require a cautious approach. The inhaled NO therapy is fairly inexpensive, but it would seem that it is not indicated for everybody with regards to the paradigm of its efficiency and potential toxicity. The recent discovery of its anti-inflammatory and extrapulmonary effects open new horizons for future applications.

CONCLUSION

Clinical use of inhaled NO was mostly reported in case series, properly designed clinical trials must now be performed to establish its real therapeutic role. These trials would permit adequate selection of the cardiopulmonary disorders, and subsequently the patients that would maximally benefit from inhaled NO therapy.

Interleukin-10 prevents early cytokine release in severe intraabdominal infection and sepsis

Early release of macrophage-derived proinflammatory cytokines, such as tumor necrosis factor (TNF), interleukin (IL)-1, and IL-6, are important in the pathogenesis of septic shock and multisystem organ failure in various models of sepsis. IL-10 is a mediator that inhibits cytokine release from activated macrophages. The aim of this study was to determine if IL-10 would decrease serum cytokine elevation in a murine model of cecal ligation and puncture (CLP). CLP in animals is a model that closely mimics the physiologic changes seen in human sepsis. Four groups of 14 female Swiss-Webster mice were used. Group 1 underwent laparotomy alone, groups 2, 3, and 4 underwent laparotomy and CLP. Groups 1 and 2 received intraperitoneal (IP) saline injections to serve as control vehicle. Group 3 (prophylactic) received 10,000 U IP IL-10 1 hr prior to CLP and every 3 hr thereafter. Group 4 (therapeutic) received 10,000 U IP IL-10 1 hr following CLP and every 3 hr thereafter. Animals were sacrificed at 3 and 9 hr following CLP. Serum TNF-alpha, IL-1 beta, and IL-6 were determined by enzyme-linked immunosorbent assay (ELISA), CLP produced a significant rise in serum TNF,IL-6, and IL-1 in untreated controls. Prophylactic or therapeutic administration of IL-10 significantly attenuated this early rise in serum cytokines. These results support the hypothesis that (1) CLP produces an early systemic rise in macrophage-derived cytokines and (2) IL-10 given either before or after the onset of CLP-induced intraabdominal infection and sepsis is able to inhibit this early release of macrophage-derived systemic mediators. IL-10 has potential clinical benefits in the therapeutic management of intraabdominal infection and sepsis.