A novel in vitro model of metastasis supporting passive shedding hypothesis from murine pancreatic cancer Panc-02

Cancer metastasis is believed to happen through active intravasation but there might be also another way to metastasize. According to passive shedding hypothesis, proposed by Munn et al., tumor cells detach from the tumor mass and passively shed to blood stream through leaky blood vessels. We propose a novel In Vitro Migrational Selection (IVMS) assay that enables the pre-selection of invasive pancreatic cancer Panc-02 cells and create a model of passive shedding. We established invasive sub-cell line of murine pancreatic cancer Panc-02 cells (refered to as Panc02-RS), which exhibited higher metastatic potential in vivo and at the same time decrease in vitro migratory skills, comparing to the initial Panc-02 cell line. In in vitro cell cultures Panc-02 spontaneously detached from the cell culture surface and later reattached and colonized new areas. We believe it can mimic the new way of metastasis, namely passive shedding. We concentrated on Panc-02 model but believe that IVMS might be used to create sub cell lines of many solid tumors to model passive shedding. Our results support the passive shedding hypothesis.

Comparative Analysis of Microbicidal and Anti-inflammatory Properties of Novel Taurine Bromamine Derivatives and Bromamine T

Taurine, the most abundant free amino acid in leukocyte cytosol traps hypohalous acids (HOCl and HOBr) to produce N-chlorotaurine (taurine chloramine, NCT and N-bromotaurine (taurine bromamine, Tau-NHBr,) respectively. Both haloamines show anti-inflammatory and antimicrobial properties. However, the therapeutic applicability of Tau-NHBr is limited due to its relatively poor stability. To overcome this disadvantage, we have synthesized the stable N-bromotaurine compounds N-monobromo-2,2-dimethyltaurine (Br-612) and N-dibromo-2,2-dimethyltaurine (Br-422). The aim of this study was to compare anti-inflammatory and microbicidal properties of Br-612 and Br-422 with that of Tau-NHBr and bromamine T (BAT). We have shown that all the tested compounds show similar anti-inflammatory properties. Importantly, the stable N-bromotaurine compounds exerted even stronger microbicidal activity than Tau-NHBr. Finally, for the purpose of topical application of these compounds we have developed a carbomer-based bioadhesive solid dosage form of BAT and Br-612, featuring sustained release of the active substance.

Angiotensin-(1-7) receptor Mas agonist ameliorates progress of atherosclerosis in apoE-knockout mice

Our interest focused on an open question whether AT-(1-7), nonpeptide receptor agonist: AVE 0991, is able to ameliorate atherosclerosis. We used an apolipoprotein E (apoE) - knockout mice model of atherosclerosis. Experimental groups received the same diet as control, mixed with: AVE 0991 at a dose of 0.58 μmol/kg b.w./day, perindopril at a dose of 0.4 mg/kg b.w./day or with tiorphan at a dose of 2.5 mg/kg b.w./day. A-779 [(D-alanine)-angiotensin (1-7)] was given at a dose of 3.3 mg/kg b.w., 3 times a week i.p. Measured by "en face" method, the percentage of occupied by Sudan IV-stained surfaces were as follows: 14.2±1.9 % in control group, whereas in AVE 0991-treated as well as in perindopril-treated groups percentages were statistically significantly lower. In tiorphan group there was no change comparing to control group, whereas in A-779 group percentage was statistically significantly higher. "Cross-section" of aortic roots revealed also the difference in atherosclerotic lesions. The mean surfaces, occupied by oil red O-stained changes were: 91.213±8.123 μm(2) in control group, while in AVE 0991-treated as well as in perindopril-treated groups lesions were statistically significantly lower. In tiorphan group there was no change; however, in A-779 group lesions were statistically significantly higher. Measured by real time RT-PCR relative p22phox (submit of NADPH oxidase) expression was significantly decreased in AVE 0991-treated mice. As revealed by flow cytometry, the expression of co-stimulatory molecules: CD86, CD80 and CD40 on both dendritic cells (CD11c+) and macrophages (F4/80+) was reduced in AVE 0991-treated group, which correlated with decreased expression of CD69 activation marker on CD4+T cells. In our report we showed the beneficial effect of AVE 0991 on atherogenesis in gene-targeted mice.

Pulsating electromagnetic field stimulation prevents cell death of puromycin treated U937 cell line

Aim of study was to verify whether pulsating electromagnetic field (PEMF) can affect cancer cells proliferation and death. U937 human lymphoid cell line at densities starting from 1 x 10(6) cells/ml to 0.0625 x 10(6) cells/ml, were exposed to a pulsating magnetic field 50 Hz, 45+/-5 mT three times for 3 h per each stimulation with 24 h intervals. Proliferation has been studied by counting number of cells stimulated and non-stimulated by PEMF during four days of cultivation. Viability of cells was analyzed by APC labeled Annexin V and 7-AAD (7-amino-actinomycin D) dye binding and flow cytometry. Growing densities of cells increase cell death in cultures of U937 cells. PEMF exposition decreased amount of cells only in higher densities. Measurement of Annexin V binding and 7-AAD dye incorporation has shown that density-induced cell death corresponds with decrease of proliferation activity. PEMF potentiated density-induced death both apoptosis and necrosis. The strongest influence of PEMF has been found for 1 x 10(6)cells/ml and 0.5 x 10(6) cells/ml density. To eliminate density effect on cell death, for further studies density 0.25 x 10(6) cells/ml was chosen. Puromycin, a telomerase inhibitor, was used as a cell death inducer at concentration 100 microg/ml. Combined interaction of three doses of puromycin and three fold PEMF interaction resulted in a reduced of apoptosis by 24,7% and necrosis by 13%. PEMF protects U937 cells against puromycin- induced cell death. PEMF effects on the human lymphoid cell line depends upon cell density. Increased density induced cells death and on the other hand prevented cells death induced by puromycin.

The immunological and metabolic responses to exercise of varying intensities in normoxic and hypoxic environments

The purpose of this study was to determine the effects of varying intensities of exercise in normoxic and hypoxic environments on selected immune regulation and metabolic responses. Using a within-subjects design, subjects performed maximal tests on a cycle ergometer in both normoxic (PiO2 = 20.94%) and hypoxic (PiO2 = 14.65%) environments to determine [latin capital V with dot above]O2max. On separate occasions, subjects then performed four randomly assigned, 1-hour exercise bouts on a cycle ergometer (two each in normoxic and hypoxic environments). The hypoxic environment was created by reducing the O2 concentration of inspired air using a commercially available hypoxic chamber. The intensities for the exercise bouts were predetermined as 40 and 60% of their normoxic [latin capital V with dot above]O2max for the normoxic exercise bouts and as 40 and 60% of their hypoxic [latin capital V with dot above]O2max for the hypoxic exercise bouts. Blood samples were collected preexercise, postexercise, 15 minutes postexercise, 2 hours postexercise, and 24 hours postexercise for the determination of interleukin-1 (IL-1), tumor necrosis factor-[alpha] (TNF-[alpha]), glucose, glycerol, free fatty acids, epinephrine, norepinephrine, and cortisol. There were no significant differences (p < 0.05) between condition or intensity for IL-1 or TNF-[alpha]. Significant differences (p < 0.05) between intensities were demonstrated for epinephrine, norepinephrine, and cortisol (p < 0.05). A significant difference was identified between normoxic and hypoxic environments with respect to nonesterifed fatty acids (0.45 +/- 0.37 vs. 0.58 +/- 0.31 mEq x L-1, respectively; p = 0.012). During prolonged exercise at 40 and 60% of their respective [latin capital V with dot above]O2max values, hypoxia did not seem to dramatically alter the response of the selected immune system or metabolic markers. Exercise training that uses acute hypoxic environments does not adversely affect immune regulation system status and may be beneficial for those individuals looking to increase endurance performance.

Regulation of prohepcidin processing and activity by the subtilisin-like proprotein convertases Furin, PC5, PACE4 and PC7

BACKGROUND AND AIMS

Hepcidin is an iron homoeostasis regulator peptide. Loss-of-function mutations cause juvenile haemochromatosis while its over-expression results in anaemia. However, the mechanism and function of preprohepcidin conversion to mature hepcidins (25, 22 and 20 amino acid C-terminal peptides) are not well known. After removal of the signal peptide, the first proteolytic cleavage occurs within the basic motif RRRRR(59)DT, suggesting the involvement of proprotein convertase (PC) family members in this process.

METHODS AND RESULTS

Using cell transfection experiments, the processing of preprohepcidin in the human hepatocyte line Huh-7 was found to be inhibited by the Furin inhibitors serpin alpha1-antitrypsin (alpha1-PDX) and prosegment preproFurin (ppFurin). Site-directed mutagenesis analysis confirmed the RRRRR(59)DT preprohepcidin cleavage site. In parallel, the lack of preprohepcidin processing found in the PC activity-deficient cell line LoVo was restored by the expression of Furin, paired basic amino acid cleaving enzyme 4 (PACE4), PC5 or PC7. This finding is consistent with the in vitro digestions of a synthetic peptide mimicking the cleavage site of preprohepcidin. In addition, during mouse embryonic development the major expression of hepcidin found in the liver coincided with that of Furin. While hepcidin induces the degradation of the iron transporter ferroportin, its RRRRR(59) to SSSSS(59) mutant is not active.

CONCLUSIONS

These results demonstrate the key role of the convertases Furin, PACE4, PC5 and/or PC7 in the generation and secretion of active hepcidin and suggest that the control of hepcidin processing as a potential therapeutic/diagnostic strategy in hepcidin-related disorders such as haemochromatosis, inflammatory diseases, anaemia and cancer.

Differential inflammatory mediator response in vitro from murine macrophages to lactobacilli and pathogenic intestinal bacteria

Chronic active colitis (including inflammatory bowel disease - IBD) is maintained by a variety of pro-inflammatory mediators. Certain intestinal bacterial strains may induce colitis, whereas some strains (e.g. Lactobacillus spp.) show a protective effect in colitis owing to their anti-inflammatory activity. In this study, we have examined the production of selected inflammatory cytokines, reactive oxygen species (ROS), nitric oxide (NO) and the expression of haeme oxygenase-1 (HO-1) by murine peritoneal macrophages stimulated in vitro by the intestinal bacterial strains, isolated from mice with colitis. Lactobacillus strains (Lactobacillus reuteri, L. johnsonii, L. animalis/murinus) and two potentially pathogenic bacteria (Escherichia coli and Enterococcus faecalis) induced the production of substantial amounts of cytokines with a strain specific profile. Despite some interstrain differences, all lactobacilli induced production of anti-inflammatory cytokines (IL-10(high), IL-6(low), IL-12p70(low)). Conversely, E. faecalis and E. coli induced the production of proinflammatory cytokines (TNF-alpha, IL-12p70), the cytokines essential for chronic IBD. Macrophages released comparably substantial amounts of ROS in response to all Lactobacillus strains tested, while E. coli and E. faecalis ability to induce generation of ROS was negligible. In contrast to ROS, the production of NO/NO(2) (-) by macrophages activated with all bacterial strains tested was similar. Moreover, for the first time, it has been shown that intestinal bacteria differed in their ability to induce expression of HO-1, a stress-inducible enzyme with antioxidant and anti-inflammatory properties. The beneficial immunoregulatory properties of candidate probiotic bacteria for the treatment of IBD are discussed.

Taurine chloramine inhibits proliferation of rheumatoid arthritis synoviocytes by triggering a p53-dependent pathway

OBJECTIVE AND DESIGN

Taurine chloramine (Tau-Cl), originating from activated neutrophils, possesses antiinflammatory activities. Fibroblast-like synoviocytes (FLS) participate in the chronic synovitis and synovial membrane hyperplasia that are characteristic pathological features of rheumatoid arthritis (RA). The present study was conducted to investigate the mechanism of the Tau-Cl effect on the proliferation of these cells in culture.

MATERIALS AND METHODS

FLS were stimulated in vitro with platelet derived growth factor (PDGF) alone or together with Tau-Cl. Cell proliferation was evaluated by counting the total and dividing cell numbers and by measurement of (3)H-thymidine incorporation. Expression of the key cell-cycle regulators was evaluated at the protein (Western blotting) and/or mRNA (RT-PCR) levels.

RESULTS

Treatment of RA FLS with Tau-Cl (200-500 microM) resulted in an early nuclear accumulation of p53 tumor suppressor protein. Moreover, Tau-Cl inhibited PDGF-triggered cell proliferation (IC(50) value approximately 250-300 microM), accompanied by characteristic modulation of p53 transcriptional targets: down-regulation of proliferating cell nuclear antigen (PCNA) and survivin, and concomitant up-regulation of p21 mitotic inhibitor.

CONCLUSION

We propose that Tau-Cl inhibits proliferation of RA FLS by triggering a p53-dependent cell-cycle arrest and conclude that this compound suppresses pathways in FLS that are known to contribute to the pathology of RA.

Is Taurolidine a candidate for treatment of rheumatoid arthritis?

OBJECTIVE

To study the therapeutic potential of taurolidine (TRD), a derivative of taurine with known anti-inflammatory and anti-proliferative properties, in various experimental models of synovitis.

METHODS

In vitro: fibroblast-like synoviocytes (RA FLS) isolated from the synovial tissue of patients with rheumatoid arthritis (RA) were cultured in the presence of either TRD or polyvinylpyrrolidine (PVP), the pharmaceutical stabilizer of TRD, which was used as a control. Proliferation of RA FLS and cytokine (IL-6 and IL-8) release were measured. In vivo: (A). The effect of systemic TRD treatment on the development of collagen-induced arthritis (CIA) in female DBA1/J mice was investigated. Mice were treated either with intraperitoneal injections of 1 ml of 2% Taurolin Boehringer Ingelheim (TRD +PVP) or with PVP as placebo. The incidence of arthritis, myeloperoxidase (MPO) activity in periarticular tissue, as well as serum concentration of IgG specific to collagen II (IgG alphaCII) were determined. (B). The effect of intra-articular TRD treatment was studied in rabbits with antigen-induced monoarthritis (AIA). After the induction of AIA of right knees rabbits were treated either with intra-articular injections of 0.5 ml of 2% Taurolin or 0.5ml PVP ( placebo). The animals were examined for clinical signs of arthritis and diameter of joints was measured. After termination of the experiment, the arthritic knees were examined and histopathology of the joints was assessed. In addition, serum amyloid A (SAA) concentration was measured.

RESULTS

n vitro: TRD exerted cytotoxic effect on RA FLS when applied at concentrations >100 microM. TRD at non-cytotoxic concentrations, inhibited PDGF-triggered RA FLS proliferation, reduced IL-1beta - stimulated production of IL-6 and slightly decreased intracellular content of IL-8. In vivo: (A). Intraperitoneal treatment with Taurolin significantly reduced the incidence (30%) of CIA when compared to the control mice (79%). However, Taurolin failed to control the development of CIA in mice with high serum level of IgG alphaCII (>1000 U).(B). Intra-articular application of 2% Taurolin resulted in amelioration of AIA in all treated rabbits (reduced diameter of arthritic joints and smaller rise of SAA level as compared to the control animals). Histopathologic evaluation revealed pannus formation in both groups and extensive necrotic lesions of synovial tissue treated with TRD, suggesting synoviorthesis-like effect.

CONCLUSION

Results from AIA and from in vitro RA FLS studies suggest that intra-articular administration of TRD could be used as a "pharmacological scalpel" to remove the inflamed synovium. Our data confirmed anti-inflammatory and anti-proliferative properties of TRD in all experimental models encouraging further studies which should evaluate its therapeutic potential in RA.

Comparison of taurine chloramine and taurine bromamine effects on rheumatoid arthritis synoviocytes

Fibroblast-like synoviocytes (FLS) participate in rheumatoid arthritis (RA) chronic synovitis by producing pro-inflammatory cytokines (IL-6, IL-8), growth factors (VEGF) and other inflammatory mediators (PGE2, NO). We have previously reported that Tau-Cl, generated by neutrophils, inhibits in vitro some of these pathogenic RA FLS functions. Taurine bromamine (Tau-Br) originates from eosinophils and neutrophils, and its immunoregulatory activities are poorly known. Therefore, we investigated the effects of Tau-Br on RA FLS functions and compared it to Tau-Cl anti-inflammatory action. When applied at noncytotoxic concentrations: (i) Tau-Br inhibited IL-6 and PGE2 production with potency similar to Tau-Cl (IC50 approximately 250 microM), (ii) Tau-Br failed to affect VEGF and IL-8 synthesis, while Tau-Cl exerted inhibitory effect (IC50 approximately 400 microM), (iii) none of these compounds affected NO generation and iNOS expression. Thus, Tau-Cl is more effective than Tau-Br in normalization of pro-inflammatory RA FLS functions.

Is there a role of taurine bromamine in inflammation? Interactive effects with nitrite and hydrogen peroxide

OBJECTIVE AND DESIGN

The myeloperoxidase system of neutrophils generates chlorinating and brominating oxidants in vivo. The major haloamines of the system are taurine chloramine (TauCl) and taurine bromamine (TauBr). It has been demonstrated in vitro that TauCl exerts both antiinflammatory and anti-bacterial properties. Much less is known about TauBr. The present study was conducted to compare bactericidal and immunoregulatory capacity of TauBr with that of the major chlorinating oxidants: HOCl and TauCl. Moreover, the effect of nitrites and H(2)O(2) on TauBr activity was investigated.

MATERIALS

TauBr was prepared by reaction of HOBr with taurine. The reaction was monitored by UV absorption spectra.

METHODS

Bactericidal activity of TauBr, TauCl and HOCl was tested by incubation of E. coli with the compounds and determined by the pour-plate method. To test the anti-inflammatory activity the compounds were incubated with LPS and IFN-gamma stimulated murine peritoneal macrophages. The production of following mediators was measured: nitrites by Griess reaction; TNF-alpha, IL-6, IL-10, IL-12p40 using capture ELISA. In some experiments the compounds were incubated with either nitrites or H(2)O(2).

RESULTS

In our experimental set-up TauBr and HOCl exerted strong bactericidal effects on E. coli (MBC = 110 microM and 8 microM, respectively), while TauCl (< 1000 microM) did not kill test bacteria. However, both, TauBr and TauCl, at noncytotoxic concentrations (< 300 microM) inhibited the cytokine and nitric oxide production by macrophages. H(2)O(2) completely abolished the biological activities of TauBr but not those of TauCl. Nitrites did not affect any activity of TauBr or TauCl while they diminished the HOCl(-) mediated bacterial killing.

CONCLUSION

TauBr, despite very low concentration of Br(-) in body fluids, may support TauCl and HOCl in the regulation of inflammatory response and in killing of bacteria by neutrophils. However, TauBr activity in vivo will depend on the presence of H(2)O(2) and possible other mediators of inflammation which can compete with target molecules for TauBr.

The effect of taurine chloramine on pro-inflammatory cytokine production by peripheral blood mononuclear cells isolated from rheumatoid arthritis and osteoarthritis patients

OBJECTIVE

Pro-inflammatory cytokines play a critical role in the pathogenesis of RA. A natural oxidant, TauCl exerts anti-inflammatory activities. Here, the effects of Tau and TauCl on key pro-inflammatory cytokines--IL-1beta, IL-6 and TNF-alpha production by LPS-triggered peripheral blood mononuclear cells (PBMCs) isolated from RA and OA patients and healthy blood donors--were examined.

METHODS

PBMCs were stimulated with LPS (24 h) in the presence of Tau or TauCl (200-400 microM). Cytokine production was measured in culture supernatants (secreted) and cells lysates (cell-associated) using specific ELISAs.

RESULTS

Production of the secretedforms of IL-1beta and IL-6 was inhibited by TauCl with IC50 approximately equal to 250 microM and 300-400 microM respectively, in all investigated groups. In all cultures of PBMCs TauCl raised the TNF-alpha production at the low concentration (200 mM), while at the higher concentration (400 microM) either reduced it (55% of RA, 70% of OA patients and 55% of healthy donors) or exerted no effect (remainder of patients). Interestingly, Tau did not significantly affect any cytokine production.

CONCLUSION

TauCl at high concentrations down-regulates pro-inflammatory cytokine production. However, the impact of TauCl on TNF-alpha production by PBMCs from RA is more limited than in cells isolated from OA patients.

Taurine chloramine and taurine bromamine induce heme oxygenase-1 in resting and LPS-stimulated J774.2 macrophages

Taurine chloramine (TauCl) and taurine bromamine (TauBr) are products of activated neutrophils and eosinophils, respectively. It has been reported that TauCl, has strong anti-inflammatory properties. In a number of separate studies it has been shown that heme oxygenase-1 (HO-1), a stress inducible protein, exerts similar anti-inflammatory effects. In this study we investigated the influence of HO-1 on TauCl/TauBr mediated suppression of NO generation in J774.2 macrophages. Expression of HO-1 and inducible nitric oxide synthase (NOS-2) in LPS stimulated J774.2 cells provides an opportunity for determining these interactions. TauCl and TauBr, at non-cytotoxic concentrations, in a similar, dose-dependent manner, inhibited the expression of NOS-2, as evidenced by western blotting technique. Surprisingly, TauCl and TauBr induced expression of HO-1 in both non-activated and LPS-activated macrophages. Importantly, the fall in NOS-2 protein level was associated with a concomitant, dose-dependent induction of HO-1. In addition, an inhibitor of HO-1 activity, chromium III mesoporhyrin (CrMP), attenuated the inhibitory activity of TauBr but not that of TauCl, as measured by nitrite accumulation. These results suggest that at a site of inflammation, TauCl and TauBr may provide a link between taurine-dependent and HO-1-dependent cytoprotective mechanisms.

Taurine chloramine modulates cytokine production by human peripheral blood mononuclear cells

The effect of taurine (Tau) and taurine chloramine (Tau-Cl) on the production of TNF- alpha, IL-1 beta, and IL-6 by peripheral blood mononuclear cells of healthy volunteers was examined. Cells were stimulated with bacterial lipopolysaccharide (LPS) in the presence of either Tau or Tau-Cl. After 24 h culture the cytokine concentrations were measured in both culture supernatants (secreted) and cell lysates (cell-associated) using ELISA. In LPS-stimulated cells Tau-Cl inhibited both the secreted and cell-associated IL-1 beta and IL-6, while exerted dual effect on TNF- alpha production: raising it slightly at low and reducing at higher concentration. By contrast, Tau had no significant effect on the cytokine production. These results indicate that Tau-Cl modulates synthesis of pro-inflammatory cytokines, and therefore it may play a role in the initiation and propagation of immune response.

Effect of taurine chloramine, the product of activated neutrophils, on the development of collagen-induced arthritis in DBA 1/J mice

Taurine chloramine (TauCl), a product of neutrophil myeloperoxidase - halide system, formed by a reaction of taurine with HOCl, is known as an anti-microbial and anti-inflammatory long-lived oxidant. We previously reported that TauCl inhibits in vitro the production of proinflammatory cytokines (IL-6, IL-8) by RA synoviocytes. Therefore we performed this study to investigate the effect of TauCl treatment on the development of collagen-induced arthritis (CIA) in DBA1/J mice. Early administration of TauCl (after primary immunization) resulted in the delay of the onset of CIA, but had no effect on severity of arthritis. TauCl, given daily for 21 days after booster immunization, did not reduce the symptoms of arthritis in those mice, which already developed CIA, but significantly diminished incidence of the disease (55% vs. 90% of placebo mice). The mechanism of this effect is unknown. This is the first in vivo study suggesting that TauCl may be used for immune intervention in chronic inflammatory diseases.

Selective expression of the proprotein convertases furin, pc5, and pc7 in proliferating vascular smooth muscle cells of the rat aorta in vitro

The aim of this study was to investigate whether transformation of quiescent vascular smooth muscle cells (VSMCs) into proliferating secretory cells is accompanied by an expression of processing enzymes that activate de novo-synthesized growth factors. Three enzymes belonging to the family of the kexin/subtilisin-like mammalian proprotein convertases (PCs), furin, PC5, and PC7, were found to be upregulated after balloon denudation in vivo. To determine their importance in these cell processes, we investigated their gene regulation using a short-term organ culture system. After incubation of rat aorta for 4 and 24 hr in serum-free medium, we demonstrated a significant induction of VSMC proliferation. The affected subset of VSMCs, positive for alpha-smooth muscle actin, also expressed proliferating cell nuclear antigen (PCNA). Our results revealed a parallel upregulation of furin, PC5, and PC7 in PCNA-immunolabeled cells. As a substrate model for comparison with PCs we used nerve growth factor (NGF). NGF is known to be activated by PCs. As shown by Northern blotting analysis, NGF mRNA concentration was significantly increased in cultured explants. NGF was released into the culture medium. In conclusion, both PCs and NGF are coordinately modulated on induction of VSMC proliferation.

Brain-derived neurotrophic factor superinduction parallels anti-epileptic--neuroprotective treatment in the pilocarpine epilepsy model

Antiepileptic drugs provide neuroprotection in several animal models of brain damage, including those induced by status epilepticus (SE). The mechanisms involved in this action are unknown, but neurotrophic factors such as brain-derived neurotrophic factor (BDNF) may play a role. In this study we investigated the changes in BDNF levels in rats in which SE had been induced by pilocarpine injection (400 mg/kg i.p.) and continued for several hours (unprotected group). In other animals (protected groups), SE was suppressed after 30 min by intraperitoneal injection of either diazepam (10 mg/kg) + pentobarbital (30 mg/kg) or paraldehyde (0.3 mg/kg). In diazepam + pentobarbital-treated rats the hippocampal damage caused by SE was significantly lower (p < 0.05) than in unprotected animals. In addition, 2 and 24 h after pilocarpine injection, the levels of BDNF mRNA were moderately increased in the unprotected group, but 'superinduced' in protected animals, especially in the neocortex and hippocampus. A time-dependent increase in BDNF immunoreactivity was also found by western blot analysis in rats treated with diazepam + pentobarbital. In contrast, a decrease of BDNF immunoreactivity occurred in the unprotected group. In conclusion, these results show that neuroprotection induced by anti-epileptic drugs in pilocarpine-treated rats is accompanied by strong potentiation of BDNF synthesis in brain regions involved in SE.

A defect in bone marrow derived dendritic cell maturation in the nonobesediabetic mouse

The pathogenesis of diabetes in the nonobese diabetic (NOD) mouse is characterized by a selective destruction of the insulin-producing beta-cells in the islets of Langerhans mediated by autoreactive T cells. The function of T cells is controlled by dendritic cells (DC), which are not only the most potent activators of naïve T cells, but also contribute significantly to the establishment of central and peripheral tolerance. In this study, we demonstrate that the NOD mouse (H2: K(d), Ag(7), E*, D(b)) shows selective phenotypic and functional abnormalities in DC derived from bone marrow progeny cells in response to GM-CSF (DC(NOD)). NOD DC, in contrast to CBA DC, have very low levels of intracellular I-A molecules and cell surface expression of MHC class II, CD80, CD86 and CD40 but normal beta 2-microglobulin expression. Incubation with the strong inflammatory stimulus of LPS and IFN-gamma does not increase class II MHC, CD80 or CD86, but upregulates the level of CD40. The genetic defect observed in the DC(NOD) does not map to the MHC, because the DC from the MHC congenic NOD.H2(h4) mouse (H2: K(k), A(k), E(k), D(k)) shares the cell surface phenotype of the DC(NOD). DC from these NOD.H2(h4) also fail to present HEL or the appropriate HEL-peptide to an antigen-specific T cell hybridoma. However all the DC irrespective of origin were able to produce TNF-alpha, IL-6, low levels of IL-12(p70) and NO in response to LPS plus IFN-gamma. A gene or genes specific to the NOD strain, but outside the MHC region, therefore must regulate the differentiation of DC in response to GM-CSF. This defect may contribute to the complex genetic aetiology of the multifactorial autoimmune phenotype of the NOD strain.

The mechanism of taurine chloramine inhibition of cytokine (interleukin-6, interleukin-8) production by rheumatoid arthritis fibroblast-like synoviocytes

OBJECTIVE

Taurine chloramine (Tau-Cl) has been shown to inhibit the production of proinflammatory cytokines (interleukin-6 [IL-6] and IL-8) by fibroblast-like synoviocytes (FLS) isolated from rheumatoid arthritis (RA) patients. The present study was conducted to elucidate the mechanism of inhibitory action exerted by Tau-Cl.

METHODS

The effects of Tau-Cl on 1) the transcription of genes coding for IL-6 and IL-8, and 2) the activity of nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1) transcription factors, which are crucial for the transcription of these cytokine genes, were investigated in FLS isolated from the synovial tissue of RA patients. FLS were cultured in vitro for 3-6 passages and stimulated with recombinant human IL-1beta (1 ng/ml) in the presence of either Tau or Tau-Cl, which were added simultaneously with the stimulus at concentrations of 250 microM or 500 microM. The relative expression of IL-6 and IL-8 messenger RNA (mRNA) was evaluated after 4 hours of stimulation, using competitive reverse transcriptase-polymerase chain reaction. The DNA binding activity of NF-kappaB and AP-1 was examined 30 minutes and 2 hours after cell stimulation, respectively, using electromobility gel shift assay.

RESULTS

IL-1beta triggered a significant rise in the activity of transcription factors NF-kappaB and AP-1, followed by an elevation of cytokine IL-6 and IL-8 mRNA expression. Tau-Cl, but not Tau, reduced IL-1beta-triggered cytokine mRNA expression, exerting stronger inhibitory activity on the levels of IL-6 than on those of IL-8. Importantly, Tau-Cl also diminished the activity of NF-kappaB and, to a lesser extent, that of AP-1 transcription factor. Neither IL-1beta nor Tau-Cl affected the activity of octamer transcription factor 1.

CONCLUSION

Tau-Cl inhibition of IL-6 and IL-8 synthesis in FLS from RA patients results from the ability of this compound to diminish the activity of the major transcriptional regulators (NF-kappaB and AP-1), which subsequently reduces the transcription of these cytokine genes.

Differential effects of pentoxifylline, a non-specific phosphodiesterase inhibitor, on the production of IL-10, IL-12 p40 and p35 subunits by murine peritoneal macrophages

Pentoxifylline (PTX), a methylxanthine derivative, has been reported to be an effective drug in inhibiting TNF-alpha responses during septic shock. The inhibition of TNF-alpha production seems to be correlated with increased intracellular cAMP levels. PTX also affects the production of other cytokines such as IL-1, IL-6, IL-10, IL-12, and IFN-gamma. However, inhibition, as well as enhancement of cytokine production, has been observed in vitro, depending on the PTX concentration and cell type used.IL-12 is a heterodimeric cytokine that plays an important role in the development of Th1-mediated inflammatory responses. IL-12 along with TNF-alpha and other proinflammatory cytokines has shown to be responsible for the pathological reaction, which may lead to septic shock. For biological activity, the expression of both subunits of IL-12, p35 and p40, is required. Moreover, the p40 chain of IL-12 specifically inhibits the effects of the IL-12 heterodimer. In this study, we investigated the effects of PTX on the production of both proinflammatory (TNF-alpha, IL-6, IL-12) and anti-inflammatory (IL-10) cytokines by murine macrophages (M&phi;). We have found that PTX, at concentrations below 100 microg/ml, selectively inhibited the production of TNF-alpha. Forskolin, a cAMP-elevating agent, similarly affected the production of the cytokines tested. However, at higher concentrations, PTX inhibited the production of TNF-alpha, IL-10, and IL-12 p35, but surprisingly, PTX enhanced the production of IL-12 p40. Concentrations of IL-10 were negatively correlated with the concentrations of IL-12 p40 subunit. These results further confirm the relevance of the use of PTX in clinical trials of immunological disorders characterised by inappropriate Th1 type immune responses.

The influence of gender and menstrual phase on thermosensitivity during cold water immersion

BACKGROUND

This investigation evaluated the influence of gender and phase of menstrual cycle [follicular (FOL: days 2-6) and luteal (LUT: days 19-24) phases] on thermosensitivity and metabolic heat production (HP) during cold water immersion (20 degrees C) in 10 females (22.4 +/- 2.8 yr) and 16 males (22.4 +/- 2.9 yr).

METHODS

Following a 20-min baseline period (BASE), subjects were immersed until esophageal temperature (Tes) reached 36.5 degrees C or for a maximum pre-occlusion (Pre-OCC) time of 40 min. An arm and thigh cuff were then inflated to 180 and 220 mmHg, respectively, for 10 min (OCC). Following release of the inflated cuffs (Post-OCC), the slope (beta) of the relationship between the decrease in Tes and the increase in HP was used to quantify thermosensitivity.

RESULTS

ANOVA revealed no significant difference in thermosensitivity between phases of the menstrual cycle or between men and women (FOL = -2.76, LUT = -3.05, Males = -3.24 W x kg(-1) x degrees C(-1)). A significant (p < 0.05) main effect for gender for HP, and a significant (p < 0.05) main effect for menstrual phase for mean skin temperature (Tsk) were observed.

CONCLUSIONS

These data suggest, despite gender differences in HP, that the thermosensitivity of HP during cold water immersion is similar between males and females and is not influenced by menstrual cycle phase. Therefore, these data indicate that when faced with a cold challenge, women respond similarly to men in both phases of their menstrual cycle.

Antimicrobial and cytotoxic activity of hypochlorous acid: interactions with taurine and nitrite

OBJECTIVE

HOCl, a major bactericidal product of neutrophil MPO-halide system reacts with taurine to form taurine chloramine (TauCl), a less toxic anti-inflammatory mediator. Recently, it has been reported that HOCl may also react with nitrite (NO2-), a major end-product of nitric oxide (NO) metabolism, to form very active oxidant, nitryl chloride (NO2Cl). The present study was conducted to elucidate the effect of nitrite on bactericidal and some immunoregulatory properties of HOCl and TauCl.

MATERIALS

TauCl was prepared from NaOCl and taurine. The reaction was carried out at pH 5.0 and pH 7.4, in the presence or absence of nitrite. All reactions were monitored by UV absorption spectra.

METHODS

Bactericidal activity of HOCl and TauCl in the presence of nitrite was tested by incubation of E. coli with the compounds and determined by the pour-plate method. To test the effect of the compounds on activity of inflammatory cells, murine peritoneal neutrophils (PMN) and macrophages were used. The cells were activated in vitro with either LPS, IFN-gamma or zymosan and the production of following mediators was measured: reactive oxygen species using luminol-dependent chemiluminescence; nitric oxide by Griess reaction; TNF-alpha using capture ELISA. In addition, we tested the effect of HOCl and TauCl on activity of myeloperoxidase (MPO).

RESULTS

At physiological pH nitrite reacts with HOCl but not with TauCl. This reaction was abolished in the presence of taurine. Nitrite prevented HOCl-mediated bacterial killing, inhibition of MPO activity, cellular cytotoxicity and inhibition of TNF-alpha production. Nitrite did not affect any activity of TauCl.

CONCLUSION

We have shown that nitrite may react in vitro with HOCl but not with TauCl, to form new biologically active product(s). We did not confirm the hypothesis that a product of HOCl reaction with nitrite is more toxic than HOCl. To the contrary, we found that nitrite diminished bactericidal and immunoregulatory properties of HOCl. In vivo, nitrite will also compete with taurine for reaction with PMN-released HOCl. Nevertheless, due to high concentration of taurine in PMN cytosol, formation of TauCl will be a major regulatory mechanism of MPO-halide-system.

The effects of gender and menstrual phase on carbohydrate utilization during acute cold exposure

OBJECTIVE

The purpose of this study was to evaluate the effects of gender and menstrual cycle on the percent of carbohydrate (CHO) utilized during cold water immersion (20 degrees C). Previous research has suggested that males and females utilize CHO differently during submaximal exercise. This study examined whether this differential response is replicated during a submaximal elevation in metabolism, as demonstrated during thermogenesis (i.e., shivering during acute cold exposure).

METHODS

Male and female subjects between the ages of 18 and 30 years were recruited for this study. Female subjects underwent the experimental trial once during the follicular phase and once during the luteal phase of their menstrual cycle. Subjects were immersed to the first thoracic vertebra until esophageal temperature reached 36.5 degrees C or for a maximum preocclusion period of 40 minutes. Peripheral temperature homeostasis via cuff occlusion (right arm and left leg) took place for 10 minutes, after which the pressure cuffs were released (postocclusion) and the subjects remained in the water for an additional 10 minutes. The following variables were measured: respiratory exchange ratio, percent of CHO utilization, and oxygen consumption (Vo2).

RESULTS

Analysis of variance demonstrated no significant difference between genders or phases of the menstrual cycle in respiratory exchange ratio, percent CHO utilization, or Vo2 during cold water immersion. A significant difference was observed between men and women for absolute Vo2.

CONCLUSIONS

These data suggest that although men and women differ with respect to absolute aerobic metabolism, this distinction does not cause a differential response with respect to substrate utilization during acute cold exposure.

Influence of gender and menstrual cycle on a cold air tolerance test and its relationship to thermosensitivity

This investigation evaluated the influence of gender and phase of menstrual cycle [follicular (FOL): Days 2-6) and luteal (LUT: Days 19-24)] on a cold air tolerance test (CATT: 90-min of exposure to 5 degrees C air) in 8 females (22.7 +/- 3.0 yr) and 15 males (22.3 +/- 2.9 yr). In addition, central thermosensitivity (beta; W x kg(-1) x degrees C(-1) [i.e., the slope of the relationship between the decrease in esophageal temperature (Tes) and the increase in heat production (HP)], gathered during a separate water trial in 20 degrees C water, was correlated to the change (delta) in Tes and HP across the 90 min of resting exposure during the CATT. Analysis of variance revealed no significant differences between phase of menstrual cycle or gender for HP, mean skin temperature (Tsk), and insulation; however, a main effect for time for these parameters was demonstrated. Despite these similarities, Tes differed (P < 0.05) between males and females. Additionally, no relationship was found between beta and deltaHP and deltaTes in the males and females. Also, there was no relationship between beta and thermoregulation during the CATT in these subjects. These data suggest that menstrual cycle phase did not cause a differential response in Tes, Tsk, and HP during a CATT. Furthermore, women maintained a higher Tes than men during the CATT despite similarities in HP and Tsk.

Taurine chloramine inhibition of cell proliferation and cytokine production by rheumatoid arthritis fibroblast-like synoviocytes

OBJECTIVE

To examine whether taurine (Tau) or its physiologic chlorinated derivative, taurine chloramine (Tau-CI), affects proliferation of, and proinflammatory cytokine (interleukin-6 [IL-6] and IL-8) production by, fibroblast-like synoviocytes (FLS) isolated from rheumatoid arthritis (RA) patients.

METHODS

FLS, isolated from the synovial tissue of 19 RA patients and cultured in vitro for 3-6 passages, were stimulated with the recombinant human cytokines IL-1beta (1 ng/ml), tumor necrosis factor alpha (TNFalpha; 10 ng/ml), or IL-17 (10 ng/ml) in the presence of either Tau or Tau-Cl, which were added at concentrations of 50-500 microM. Tau and Tau-Cl were added simultaneously with, 2 hours before, or 24 hours after the stimuli. The concentrations of IL-6 and IL-8 were determined in culture supernatants using specific enzyme-linked immunosorbent assays. Proliferation of FLS was estimated on the basis of 3H-thymidine incorporation into the cells, which were cultured for 72 hours in the presence of recombinant human basic fibroblast growth factor (bFGF) (1 ng/ml) and Tau or Tau-Cl, which were added simultaneously at the beginning of the culture.

RESULTS

Cultured in vitro, RA FLS spontaneously secreted low levels of IL-6 and IL-8, but when RA FLS were stimulated with IL-1beta, TNFalpha, or IL-17, significantly higher amounts of IL-6 and IL-8 were produced. Tau-Cl, but not Tau, inhibited cytokine-triggered synthesis of IL-6 (50% inhibitory concentration [IC50] approximately 225 microM) and IL-8 (IC50 approximately 450 microM) when added simultaneously with the stimuli. However, IL-17-induced production of IL-8 was not affected by Tau-Cl. In the cells prestimulated with IL-1beta for 24 hours, Tau-Cl still inhibited synthesis of IL-6, but did not affect IL-8 production. Moreover, Tau-Cl inhibited spontaneous and bFGF-triggered proliferation of FLS in a dose-dependent manner. Neither Tau nor Tau-Cl affected cell viability.

CONCLUSION

The results of these studies demonstrate that Tau-Cl inhibits production of proinflammatory cytokines by RA FLS, as well as proliferation of these cells. Thus, Tau-Cl may act as a physiologic modulator of FLS functions related to their pathogenic role in RA.

Regulation of murine dendritic cell functions in vitro by taurine chloramine, a major product of the neutrophil myeloperoxidase-halide system

Taurine chloramine (TauCl) is a major chloramine generated in activated neutrophils as a result of the reaction of highly toxic hypochlorous acid and taurine, the most abundant free amino acid in cytosol. In this study we have tested the influence of TauCl on the properties of murine dendritic cells (DC), the major cell population involved in the initiation of an adaptive immune response against pathogenic organisms. N418+, MHC II+, B7-2+ dendritic cells, generated from the mouse bone marrow cells cultured in the presence of granulocyte-macrophage colony-stimulating factor, were stimulated by interferon-gamma and lipopolysaccharide to produce nitric oxide, reactive oxygen species, interleukin-6 (IL-6), tumour necrosis factor-alpha, and IL-12, in the presence of different doses of TauCl. TauCl differently inhibited the generation of these inflammatory mediators in a dose-dependent manner. Furthermore, TauCl selectively modulated the ability of DC to induce the release IL-2 and IL-10 from T cells. These results suggest that neutrophil-derived mediators, such as TauCl, at a site of inflammation, may affect the functions of sentinel DC and macrophages, and play a role in maintaining the balance between the inflammatory response and the induction of an antigen-specific immune response.

The subtilisin/kexin family of precursor convertases. Emphasis on PC1, PC2/7B2, POMC and the novel enzyme SKI-1

Proopiomelanocortin (POMC) is a precursor to various, bioactive peptides including ACTH, beta LPH, alpha MSH, and beta endorphin (beta END). Processing of POMC at dibasic residues is tissue-specific and is performed by either PC1 alone (resulting in ACTH and beta LPH, anterior pituitary corticotrophes) or by a combination of PC1 and PC2 (yielding alpha MSH and beta END, pituitary neurointermediate lobe and hypothalamus). The PC2-specific binding protein 7B2 is intimately involved in the zymogen activation of proPC2 into PC2. Structure-function studies of these enzymes demonstrated the presence of N- and C-terminal domains, as well as specific amino acids within the catalytic segment that influence the degree of activity of each enzyme and the interaction of PC2 with 7B2. The tissue distribution, plasticity of expression, and the multiple precursors that are differentially cleaved by PC1 and/or PC2, predict a wide array of combinatorial activities of these convertases within the endocrine and neuroendocrine system. The phenotypic consequences of the absence of genetic expression of either PC1 or PC2 are now explored using knockout mice and in human patients suffering from obesity and diabetes.

Mammalian subtilisin/kexin isozyme SKI-1: A widely expressed proprotein convertase with a unique cleavage specificity and cellular localization

Using reverse transcriptase-PCR and degenerate oligonucleotides derived from the active-site residues of subtilisin/kexin-like serine proteinases, we have identified a highly conserved and phylogenetically ancestral human, rat, and mouse type I membrane-bound proteinase called subtilisin/kexin-isozyme-1 (SKI-1). Computer databank searches reveal that human SKI-1 was cloned previously but with no identified function. In situ hybridization demonstrates that SKI-1 mRNA is present in most tissues and cells. Cleavage specificity studies show that SKI-1 generates a 28-kDa product from the 32-kDa brain-derived neurotrophic factor precursor, cleaving at an RGLT downward arrowSL bond. In the endoplasmic reticulum of either LoVo or HK293 cells, proSKI-1 is processed into two membrane-bound forms of SKI-1 (120 and 106 kDa) differing by the nature of their N-glycosylation. Late along the secretory pathway some of the membrane-bound enzyme is shed into the medium as a 98-kDa form. Immunocytochemical analysis of stably transfected HK293 cells shows that SKI-1 is present in the Golgi apparatus and within small punctate structures reminiscent of endosomes. In vitro studies suggest that SKI-1 is a Ca2+-dependent serine proteinase exhibiting a wide pH optimum for cleavage of pro-brain-derived neurotrophic factor.

Nerve growth factor and proprotein convertases furin and PC7 in transected sciatic nerves and in nerve segments cultured in conditioned media: their presence in Schwann cells, macrophages, and smooth muscle cells

Synthesis of proteins such as nerve growth factor (NGF) is induced after nerve lesion. The NGF precursor (pro-NGF) requires a posttranslational processing by proprotein convertases to become active. In this report, we re-examine the localization of NGF protein and mRNA in injured nerve and show that the candidate pro-NGF convertases furin and PC 7 colocalize with NGF in non-neuronal cells in nerve. By Northern blot analysis, 1.5-kb and 1.3-kb NGF mRNAs were shown to be increased in distal and immediately proximal nerve segments on days 1, 4, and 14 after lesion; by Western blot analysis, NGF proteins of high molecular weight were detected after injury. In vivo, two phases of NGF immunopositivity were observed, in macrophages and perivascular cells shortly after lesion and in endoneurial cells on day 1 and 4. To identify the cells containing NGF, nerve segments were incubated in serum-containing medium with or without conditioning by white blood cells isolated from the circulation. Both hybridization and immunoreactivity signals for NGF were elevated after incubation of nerve segments for 4 hours in conditioned media, so that cells with NGF immunoreactivity could be identified by antibodies to specific cell markers. In these nerve fragments, Schwann cells, perivascular smooth muscle cells, and macrophages contained NGF immunoreactivity. The concentration of furin and PC7 mRNA also increased in lesioned nerves. By immunocytochemical investigation of nerve explants, furin and PC7 were detected in endoneurial cells, macrophages and perivascular cells and were colocalized with NGF. These in vitro and in vivo findings suggest that both furin and PC7 are associated with NGF in several cell types of the sciatic nerve and, hence, may be implicated in intracellular processing of pro-NGF.

The pro-protein convertase PC1 is induced in the transected sciatic nerve and is present in cultured Schwann cells: comparison with PC5, furin and PC7, implication in pro-BDNF processing

Injury of peripheral nerves induces expression of several pro-protein convertases (PCs) involved in processing of precursor proteins into their diverse active end-products. In this study, the focus was on convertase PC1 which, although undetectable in control nerves, is strongly induced in injured nerves. High concentrations of PC1 mRNA of 9.0, 5.5, 3.0, 2.5 and 1.6 kb were observed on day 4 post-lesion in proximal and distal segments. By in situ hybridization PC1 mRNA was detected in most of endoneurial cells, which were further identified by immunocytochemistry as myelin 2', 3'-cyclic nucleotide 3'-phosphodiesterase containing Schwann cells. PC1 mRNA and protein were also present in cultured Schwann cells also containing convertases PC5, furin and PC7 as well as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Mostly unprocessed pro-NGF of 35 kDa and pro-BDNF of 35 kDa were found on Western blotting of Schwann cells. Expression of exogenous neurotrophins by infection with vaccinia virus vector showed that mouse pro-NGF and rat pro-BDNF are cleaved intracellularly on smaller forms of 13.5 kDa NGF and 14 kDa BDNF. Infection experiments demonstrated that Schwann cells contain active processing enzymes. In conclusion, this work provides in vivo evidence of the presence of several PCs in the injured rat sciatic nerve and ex vivo in cultured Schwann cells.

Taurine chloramine down-regulates the generation of murine neutrophil inflammatory mediators

We previously reported that taurine chloramine (TauCl), a product of activated neutrophils, inhibits the generation of macrophage inflammatory mediators such as nitric oxide (NO), TNF-alpha, and PGE2. Taurine, the most abundant free amino acid in the cytosol of neutrophils, is chlorinated to form TauCl by the halide-dependent myeloperoxidase (MPO) system. Under physiological conditions, TauCl reduces HOCl toxicity. In this study, we investigated the influence of TauCl on generation of oxygen free radicals, cytokines and eicosanoids by activated murine peritoneal neutrophils. We found that TauCl, but not taurine alone, inhibited the production of NO, prostaglandin E2, interleukin-6 and tumor necrosis factor-alpha, in a dose-dependent manner. In contrast, the products of the respiratory burst, as measured by luminol-dependent chemiluminescence (LCL), were reduced by both taurine and TauCl. However, taurine affected LCL at higher concentrations and to a lesser extent than TauCl. The results of these studies suggest that TauCl decreases production of tissue-damaging inflammatory mediators and may regulate the balance between protective, microbicidal and toxic effect of neutrophils.

Modulation of antigen-specific T-cell activation in vitro by taurine chloramine

Taurine chloramine (TauCl) is produced during inflammation by reaction of hypochlorous acid (HOCl) with taurine, the most abundant free amino acid in neutrophils. We previously reported that TauCl inhibits the generation of macrophage inflammatory mediators such as nitric oxide, prostaglandin E2 (PGE2), tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). In this study, the activity of TauCl in modulating T-cell activation was investigated. Treatment of T cells with TauCl (0.1-0.3 mM), prior to activation, was found to inhibit interleukin-2 (IL-2) release in response to both mitogen and antigen stimulation. Similarly, pretreatment of A-20 antigen presenting cells (APCs), at low cell numbers, was found to inhibit their ability to process and present ovalbumin (OVA) to a specific T-cell hybridoma. In contrast, pretreatment of higher numbers of A-20 cells with TauCl in the presence of OVA enhanced subsequent presentation of OVA. Finally, OVA modified with TauCl was processed and presented more efficiently than native OVA. Thus, TauCl is able to modulate induction of a specific adaptive immune response at several independent points of the overall antigen-presenting pathway.

Regulation of cytokine production by eicosanoids and nitric oxide

Cytokines are widely regarded as regulatory molecules of inflammatory and immune reactions. Nevertheless, the details of functioning of the complex cytokine network are not yet fully understood. Recent data indicate that eicosanoids, primarily the products of the inducible form of cyclooxygenase (COX-2), are involved in the regulation of cytokine production. We have shown that prostaglandins of E series are no longer only suppressor molecules but they selectively up- or down-regulate the cytokine production. Similarly, nitric oxide (NO) generated in activated immune cells by inducible isoform of nitric oxide synthase (iNOS), is considered to be an immunoregulatory molecule. In this article we present a new concept of interactions between cytokines, eicosanoids (prostaglandins and leukotrienes) and NO. Finally, the impact of these molecules on the regulation of the immune system is discussed.

[Immunoregulatory mechanisms of action of intravenous gammaglobulin in Kawasaki syndrome]

Kawasaki Syndrome (KS) is an acute vasculitis in young children associated with the development of coronary artery abnormalities. KS has been reported to occur in over 40 countries including Poland. The etiology of this disease remains controversial. However, recent studies suggest a potential role of bacterial toxins (superantigens) in the immunopathogenesis of KS. Immunomodulatory benefit and potential toxin neutralisation by intravenous immune globulin (IVIG) support the hypothesis of superantigen-related activation of the immune system in KS. The prevalence of cardiovascular abnormalities can be significantly reduced by treating patients during the first 10 days of illness with high-dose of intravenous gammaglobulin. The following predominant and non-exclusive mechanisms of action have been proposed to account for the immunomodulatory effects of IVIG in Kawasaki and other immune-mediated diseases: (i) functional blockade of Fc receptor on monocytes/macrophages; (ii) modulation of the production of cytokines and cytokine antagonists; (iii) inhibition of complement mediated damage; (iv) neutralisation of bacterial toxins by specific antibodies; (v) neutralisation of circulating autoantibodies by complementary (e.g. anti-idiotypic) antibodies in IVIG. These observations provide an important information that early recognition and prompt treatment of this illness is critical for a successful outcome.

Neutrophil chloramines: missing links between innate and acquired immunity

Neutrophils are the major cellular component of the acute inflammatory response. By contrast, macrophages are the major cellular component in most chronic immunological responses, and act as key regulators of the specific acquired response. Here, Janusz Marcinkiewicz examines recent data indicating that chloramines, the neutrophil-specific products of the myeloperoxidase--hydrogen-peroxide--halide system, may provide a bridge between the afferent branches of the innate and acquired immune response.

Nitric oxide and antimicrobial activity of reactive oxygen intermediates

It is well documented that nitric oxide contributes to the bactericidal activities of phagocytes. Murine activated neutrophils and macrophages produce both reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI). However, only neutrophils in the presence of myeloperoxidase, produce an antimicrobial agent, hypochlorous acid (HOCl). Complex interactions of RNI (nitric oxide) with other antimicrobial agents of phagocytes are likely to exist, but these have not been clearly demonstrated. In this study, we treated bacteria (Escherichia coli) with the NO donor, S-nitrosoglutathione (GSNO) and hydrogen peroxide (H2O2) or HOCl. We found that exposure to H2O2 of the bacteria tested resulted in minimal toxicity. However the killing activities of H2O2 were potentiated by GSNO. On the contrary, the NO-donor completely abolished the bactericidal activity of HOCl. Our results indicate that NO-donating drugs in non toxic concentrations used for experimental purposes may strongly affect the cytotoxic activity of neutrophils and macrophages. We suggest that the similar interactions may exist at sites of inflammation.

Enhancement of CD4+ T-cell-dependent interleukin-2 production in vitro by murine alveolar macrophages: the role of leukotriene B4

Local tissue macrophages are known to play a key role in regulation of adaptive immune responses, often by inhibition of T-cell activation and proliferation. In this study, we compare the influence of alveolar and peritoneal macrophages on T-cell-dependent interleukin-2 (IL-2) release. Alveolar macrophages, in contrast to peritoneal macrophages, enhance IL-2 release. Assay of a panel of potential macrophage-derived mediators indicated that activated alveolar macrophages stimulated greater release of IL-1 beta, tumour necrosis factor-alpha and, especially, leukotriene B4 (> 100 times) than activated peritoneal macrophages. Inhibition of prostaglandin synthesis by alveolar macrophages further enhanced the production of IL-2, while inhibition of leukotriene synthesis abolished the enhancement. The addition of exogenous prostaglandin E2 inhibited IL-2 release, while exogenous leukotriene B4 enhanced IL-2 release. When added simultaneously, the two compounds antagonized each other's activity. In conclusion, this study confirms that alveolar macrophages enhance IL-2 secretion, and suggests that this enhancement may be due at least in part to the very high rates of production of leukotriene B4. The overall influence of macrophage populations on T cells in vivo will reflect the complex balance between the multiple mediators produced within the local tissue microenvironment.

Oxidative modification of ovalbumin

Stimulated neutrophils (PMNL) are a source of the active oxygen species: O2, H2O2 and HOCl/OCl- which in turn can act on proteins yielding a variety of mixed oxidation products. A system is proposed in which a model protein-ovalbumin (OVA) first undergoes chlorination by HOCl/OCl- and next is oxidised by H2O2. The modification of functional groups (-NH2, -SH, -S-S-, > C = O, Tyr and Trp) in OVA was monitored as well as their accessibility to promote aggregation. Chlorination resulted in additional inter- or intra -S-S- bond formation followed by a decrease in the total sulfhydryl group content. Amino groups were oxidised to carbonyl moieties with a concomitant acidic shift of pI. Formation of chlorotyrosine at the chlorination step was confirmed and its further H2O2-mediated transformation to bityrosine was demonstrated. It has also been confirmed that tryptophan, and not tyrosine, is the first target for chlorination. SDS/PAGE and HPLC profiles revealed that HOCl/OCl- chlorination promotes formation of aggregates stabilised by non covalent bonds. In conclusion, we suggest that a dramatic change in the OVA molecule structure begins when the molar excess of HOCl/OCl- is about 2 per one reactive group in OVA.

Is there a role for nitric oxide in regulation of T cell secretion of IL-2?

Nitric oxide (NO) can have both effector (cytotoxic) and regulatory roles in immune function. In this study, we have re-examined the potential role of nitric oxide in mediating the macrophage-dependent suppression of IL-2 synthesis. In our model, TNP-specific CD4+ T cells are cocultured with Ag and either peritoneal or alveolar macrophages. Both populations of macrophages after in vitro stimulation with IFN-gamma can inhibit IL-2 release. In vitro stimulation also induces substantial levels of NO release by these macrophages, as well as high levels of prostaglandin E2 (PGE2). However, there was no correlation between NO levels and inhibitory activity. Furthermore, NG-monomethyl-L-arginine monoacetate, a specific inhibitor of NO release had no effect on IL-2 release, while indomethacin, which blocked prostaglandin synthesis, largely abrogated the suppressor activity of both macrophage populations. Although the addition of exogenous NO donors at high concentrations could inhibit IL-2 release by T cells, our data does not support the hypothesis that NO is a major macrophage mediator of suppression in this model.

Is there a role for nitric oxide in regulation of T cell secretion of IL-2?

Nitric oxide (NO) can have both effector (cytotoxic) and regulatory roles in immune function. In this study, we have re-examined the potential role of nitric oxide in mediating the macrophage-dependent suppression of IL-2 synthesis. In our model, TNP-specific CD4+ T cells are cocultured with Ag and either peritoneal or alveolar macrophages. Both populations of macrophages after in vitro stimulation with IFN-gamma can inhibit IL-2 release. In vitro stimulation also induces substantial levels of NO release by these macrophages, as well as high levels of prostaglandin E2 (PGE2). However, there was no correlation between NO levels and inhibitory activity. Furthermore, NG-monomethyl-L-arginine monoacetate, a specific inhibitor of NO release had no effect on IL-2 release, while indomethacin, which blocked prostaglandin synthesis, largely abrogated the suppressor activity of both macrophage populations. Although the addition of exogenous NO donors at high concentrations could inhibit IL-2 release by T cells, our data does not support the hypothesis that NO is a major macrophage mediator of suppression in this model.

Oxidative modification of ovalbumin

Stimulated neutrophils (PMNL) are a source of the active oxygen species: O2, H2O2 and HOCl/OCl- which in turn can act on proteins yielding a variety of mixed oxidation products. A system is proposed in which a model protein-ovalbumin (OVA) first undergoes chlorination by HOCl/OCl- and next is oxidised by H2O2. The modification of functional groups (-NH2, -SH, -S-S-, > C = O, Tyr and Trp) in OVA was monitored as well as their accessibility to promote aggregation. Chlorination resulted in additional inter- or intra -S-S- bond formation followed by a decrease in the total sulfhydryl group content. Amino groups were oxidised to carbonyl moieties with a concomitant acidic shift of pI. Formation of chlorotyrosine at the chlorination step was confirmed and its further H2O2-mediated transformation to bityrosine was demonstrated. It has also been confirmed that tryptophan, and not tyrosine, is the first target for chlorination. SDS/PAGE and HPLC profiles revealed that HOCl/OCl- chlorination promotes formation of aggregates stabilised by non covalent bonds. In conclusion, we suggest that a dramatic change in the OVA molecule structure begins when the molar excess of HOCl/OCl- is about 2 per one reactive group in OVA.

MHC class I and class II determinants and some adhesion molecules are engaged in the regulation of nitric oxide production in vitro by human monocytes stimulated with colon carcinoma cells

Surface molecules that are involved in tumor-monocyte interactions were studied. The in vitro system in which human blood monocytes are stimulated with human colon carcinoma cells for nitric oxide (NO) production was used. Monoclonal antibodies (mAbs) against various adhesion molecules (LFA-1, ICAM-1, VNR) were unable to block NO production in coculture of monocytes with carcinoma cells. However, anti-CD44, -LFA-3, and -VLA beta 1 chain mAbs effectively blocked NO production. Also mAbs against MHC class I and HLA-DR molecules inhibited, in a dose-dependent manner, No release. It was concluded that some adhesion molecules and MHC class I and/or class II determinants of monocytes may be involved in tumor-monocyte interactions leading to signal transduction for NO production.

Taurine chloramine, a product of activated neutrophils, inhibits in vitro the generation of nitric oxide and other macrophage inflammatory mediators

Taurine (Tau) is an exceptionally abundant free amino acid in the cytosol of inflammatory cells and especially in neutrophils. Taurine protects cells from self-destruction during processes that generate oxidants. The major function of Tau in leukocytes is to trap chlorinated oxidants (HOCl). Taurine reacts with HOCl to produce the long-lived compound taurine chloramine (TauCl). Previously, we have shown that other products of the neutrophil chlorinating system are able to modify functions of macrophages. In this study, we investigated in vitro the influence of TauCl on the generation of inflammatory mediators by activated macrophages. We have found that TauCl inhibited the generation of nitric oxide, prostaglandin E2, tumor necrosis factor alpha, and interleukin-6, but TauCl slightly enhanced the release of IL-1 alpha. The formation of nitrites by interferon-gamma-activated macrophages was inhibited by TauCl in a dose-dependent manner. Taurine chloramine also reduced the level of inducible nitric oxide synthase (iNOS) mRNA in macrophages, in a similar concentration-dependent manner. Although our experiments do not exclude a direct effect of TauCl on enzymatic activity of iNOS, the inhibition of iNOS expression seems to be the major mechanism responsible for suppression of NO formation. Finally, we discuss the biological role of TauCl in vivo. We suggest that at the site of inflammation TauCl works as a specific signaling molecule of activated neutrophils that coordinates the generation of inflammatory mediators in macrophages.

The modulation of IL-2 dependent proliferation of CTLL-2 cells by 2-methyl-thiazolidine-2,4-dicarboxylic acid

It is known that cysteine and other thiol compounds are able to modulate the immune response. The extracellular concentration of cysteine was shown to determine the intracellular level of glutathione (GSH). Thus cysteine, by enhancing GSH production, is able to affect some T-cell functions like IL-2 dependent cell proliferation and the generation of cytotoxic T cells. However, physiologically blood plasma cysteine is maintained at a very low concentration. The use of cysteine as a therapeutic compound in vivo is strongly limited due to its cytotoxicity. Recent studies demonstrate that N-acetyl-cysteine (NAC) as well as a variety of thiazolidine derivatives (TDs), which are the products of the reaction of L-cysteine with carbonyl compounds, could serve as a 'delivery' system for cysteine into the cell. In the present study, we have shown that 2-methyl-thiazolidine-2,4,-dicarboxylic acid (CP), the product of condensation of L-cysteine and pyruvate, strongly increases the proliferation of one particular cell line, IL-2 dependent CTLL-2 cells. We have also shown that this compound significantly increases the intracellular level of non-protein sulfhydryls (NPSH), but we did not find any correlation between NPSH levels and cell viability and proliferation. In contrast to CP, free cysteine showed its toxic properties by affecting cell viability of different cell lines and also by cancelling the influence of CP on the proliferation of CTLL cells.

Nitric oxide up-regulates the release of inflammatory mediators by mouse macrophages

Nitric oxide (NO) plays a key role in mediating macrophage cytotoxicity towards different targets, including tumoral cells and intracellular pathogens. However, its role in macrophage immunoregulation is less well defined. In this study, we have investigated the effect of altering NO levels on the production by mouse macrophages of cytokines, and reactive oxygen intermediates as measured by luminol-dependent chemiluminescence. Our results demonstrate that NO can enhance the release of both tumor necrosis factor-alpha and interleukin-1 alpha, and chemiluminescence. Thus, in addition to acting as a powerful effector molecule in mediating cytotoxic activities of mouse macrophages, NO can play a role in enhancing the production of a variety of other inflammatory mediators, and thus can contribute both directly and indirectly to the immunopathology of macrophage-dependent inflammation.

Effect of pentoxifylline on nitric oxide released by murine macrophages

The growing knowledge on the pathological role of tumor necrosis factor alpha (TNF-alpha) and nitric oxide in septic shock stimulated efforts to control their generation pharmacologically in clinical situations. Pentoxifylline (PTXF) is well known as an inhibitor of TNF synthesis, whereas information about its role in suppression of NO generation is much less available. In our study, we have shown that PTXF suppresses the synthesis of both mediators, TNF and NO, released by macrophages activated with different stimuli. However, in contrast to N-monomethyl-L-arginine (an inhibitor of NO synthase), PTXF influenced NO generation only during the induction phase. In conclusion, we suggest that a possible new therapeutic approach in septic shock may result from the inhibition of these two major mediators by simultaneous application of PTXF and a specific inhibitor of NO generation. Further experimental investigations and clinical trials are necessary to evaluate the safety and effectiveness of application of these inhibitors.

Differential effects of chlorination of bacteria on their capacity to generate NO, TNF-alpha and IL-6 in macrophages

Activated rodent macrophages produce high amounts of nitric oxide (NO). NO as a tumoricidal and defence molecule against intracellular parasites is commonly accepted. However, its role as an obligatory killing factor for extracellular bacteria is controversial. In the present study we stimulated murine peritoneal macrophages by heat-killed bacteria (Staphylococcus aureus, S. epidermidis and Escherichia coli). In some groups bacteria were pretreated with HOCl, to replace the chlorinating system in activated neutrophils that operates as a bactericidal system in vivo. High levels of NO, tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were detected after stimulation by all non-chlorinated bacteria strains tested. However, after chlorination Gram-positive bacteria lost their ability to induce NO and TNF-alpha, whereas phagocytosis and IL-6 production were not affected by chlorination.

Cyclophosphamide uncovers two separate macrophage subpopulations with opposite immunogenic potential and different patterns of monokine production

As shown previously, thioglycollate-induced peritoneal macrophages consist of two subpopulations which differ morphologically and functionally. When tagged with trinitrophenyl hapten (TNP), one macrophage subpopulation induced in vivo effector cells (Th1) of contact sensitivity (CS) reaction, while the other induced suppressor T cells (Ts) which inhibit CS and are highly sensitive to the in vivo action of cyclophosphamide (CY). Our present experiments show that CY-resistant (Th inducers) and CY-sensitive macrophages (Ts inducers) differ also in the spectrum of biologically relevant molecules which they secrete when stimulated by LPS. Thus macrophages which preferentially induce Th1 cells have a cytokine pattern IL-1LOW, IL-6HIGH, TNF-alpha LOW, while macrophages which recruit Ts cells are IL-1HIGH, IL-6LOW, TNF-alpha HIGH. TH1 inducers produced also somewhat better PGE2 then Ts inducers. Production of reactive nitrogen intermediates (NO/NO2-) was similar in both groups of macrophages. The reasons for the differential effect of CY on these two populations is not clear at present, although it is known that CY metabolites can bind to sulfhydryl groups on antigen presenting cells (APC) and thereby up- or downregulate the antigen presenting capacities of separate subpopulations of APC.

Human monocytes are stimulated for nitric oxide release in vitro by some tumor cells but not by cytokines and lipopolysaccharide

Nitric oxide (NO) has been recently identified as a potent mediator of tumoricidal activity of activated macrophages. Macrophages can be activated for tumor cell killing by microbial products, including lipopolysaccharide (LPS) and various cytokines. Here we report that in contrast to mouse macrophages, human peripheral blood monocytes stimulated with cytokines or LPS failed to release NO. Also priming of monocytes with interferon-gamma followed by activation with cytokines or LPS did not cause NO secretion. However, monocytes responded with NO production to stimulation with some human cancer cells but not with untransformed cells. NO production by monocytes was inhibited by NG-monomethyl-L-arginine, specific inhibitor of NO synthase and emetine, an irreversible blocker of protein synthesis. This may imply that human monocytes are unique in their restricted capacity to produce NO following interaction with some tumor cells, but not with other stimulators, and in this respect they may be able to distinguish between malignant and normal cells.