Application of the C3 inhibitor compstatin in a human whole blood model designed for complement research - 20 years of experience and future perspectives

The complex molecular and cellular biological systems that maintain host homeostasis undergo continuous crosstalk. Complement, a component of innate immunity, is one such system. Initially regarded as a system to protect the host from infection, complement has more recently been shown to have numerous other functions, including involvement in embryonic development, tissue modeling, and repair. Furthermore, the complement system plays a major role in the pathophysiology of many diseases. Through interactions with other plasma cascades, including hemostasis, complement activation leads to the broad host-protective response known as thromboinflammation. Most complement research has been limited to reductionistic models of purified components and cells and their interactions in vitro. However, to study the pathophysiology of complement-driven diseases, including the interaction between the complement system and other inflammatory systems, holistic models demonstrating only minimal interference with complement activity are needed. Here we describe two such models; whole blood anticoagulated with either the thrombin inhibitor lepirudin or the fibrin polymerization peptide blocker GPRP, both of which retain complement activity and preserve the ability of complement to be mutually reactive with other inflammatory systems. For instance, to examine the relative roles of C3 and C5 in complement activation, it is possible to compare the effects of the C3 inhibitor compstatin effects to those of inhibitors of C5 and C5aR1. We also discuss how complement is activated by both pathogen-associated molecular patterns, inducing infectious inflammation caused by organisms such as Gram-negative and Gram-positive bacteria, and by sterile damage-associated molecular patterns, including cholesterol crystals and artificial materials used in clinical medicine. When C3 is inhibited, it is important to determine the mechanism by which inflammation is attenuated, i.e., whether the attenuation derives directly from C3 activation products or via downstream activation of C5, since the mechanism involved may determine the appropriate choice of inhibitor under various conditions. With some exceptions, most inflammatory responses are dependent on C5 and C5aR1; one exception is venous air embolism, in which air bubbles enter the blood circulation and trigger a mainly C3-dependent thromboembolism, with the formation of an active C3 convertase, without a corresponding C5 activation. Under such conditions, an inhibitor of C3 is needed to attenuate the inflammation. Our holistic blood models will be useful for further studies of the inhibition of any complement target, not just C3 or C5. The focus here will be on targeting the critical complement component, activation product, or receptor that is important for the pathophysiology in a variety of disease conditions.

Staphylococcus aureus-induced complement activation promotes tissue factor-mediated coagulation

Essentials Complement, Toll-like receptors and coagulation cross-talk in the process of thromboinflammation. This is explored in a unique human whole-blood model of S. aureus bacteremia. Coagulation is here shown as a downstream event of C5a-induced tissue factor (TF) production. Combined inhibition of C5 and CD14 efficiently attenuated TF and coagulation.

SUMMARY

Background There is extensive cross-talk between the complement system, the Toll-like receptors (TLRs), and hemostasis. Consumptive coagulopathy is a hallmark of sepsis, and is often mediated through increased tissue factor (TF) expression. Objectives To study the relative roles of complement, TLRs and TF in Staphylococcus aureus-induced coagulation. Methods Lepirudin-anticoagulated human whole blood was incubated with the three S. aureus strains Cowan, Wood, and Newman. C3 was inhibited with compstatin, C5 with eculizumab, C5a receptor 1 (C5aR1) and activated factor XII with peptide inhibitors, CD14, TLR2 and TF with neutralizing antibodies, and TLR4 with eritoran. Complement activation was measured by ELISA. Coagulation was measured according to prothrombin fragment 1 + 2 (PTF1 + 2 ) determined with ELISA, and TF mRNA, monocyte surface expression and functional activity were measured with quantitative PCR, flow cytometry, and ELISA, respectively. Results All three strains generated substantial and statistically significant amounts of C5a, terminal complement complex, PTF1 + 2 , and TF mRNA, and showed substantial TF surface expression on monocytes and TF functional activity. Inhibition of C5 cleavage most efficiently and significantly inhibited all six markers in strains Cowan and Wood, and five markers in Newman. The effect of complement inhibition was shown to be completely dependent on C5aR1. The C5 blocking effect was equally potentiated when combined with blocking of CD14 or TLR2, but not TLR4. TF blocking significantly reduced PTF1 + 2 levels to baseline levels. Conclusions S. aureus-induced coagulation in human whole blood was mainly attributable to C5a-induced mRNA upregulation, monocyte TF expression, and plasma TF activity, thus underscoring complement as a key player in S. aureus-induced coagulation.

The key roles of complement and tissue factor in Escherichia coli-induced coagulation in human whole blood

The complement system and the Toll-like (TLR) co-receptor CD14 play important roles in innate immunity and sepsis. Tissue factor (TF) is a key initiating component in intravascular coagulation in sepsis, and long pentraxin 3 (PTX3) enhances the lipopolysaccharide (LPS)-induced transcription of TF. The aim of this study was to study the mechanism by which complement and CD14 affects LPS- and Escherichia coli (E. coli)-induced coagulation in human blood. Fresh whole blood was anti-coagulated with lepirudin, and incubated with ultra-purified LPS (100 ng/ml) or with E. coli (1 × 10(7) /ml). Inhibitors and controls included the C3 blocking peptide compstatin, an anti-CD14 F(ab')2 antibody and a control F(ab')2 . TF mRNA was measured using quantitative polymerase chain reaction (qPCR) and monocyte TF surface expression by flow cytometry. TF functional activity in plasma microparticles was measured using an amidolytic assay. Prothrombin fragment F 1+2 (PTF1.2) and PTX3 were measured by enzyme-linked immunosorbent assay (ELISA). The effect of TF was examined using an anti-TF blocking antibody. E. coli increased plasma PTF1.2 and PTX3 levels markedly. This increase was reduced by 84->99% with compstatin, 55-97% with anti-CD14 and > 99% with combined inhibition (P < 0·05 for all). The combined inhibition was significantly (P < 0·05) more efficient than compstatin and anti-CD14 alone. The LPS- and E. coli-induced TF mRNA levels, monocyte TF surface expression and TF functional activity were reduced by > 99% (P < 0·05) with combined C3 and CD14 inhibition. LPS- and E. coli-induced PTF1.2 was reduced by 76-81% (P < 0·05) with anti-TF antibody. LPS and E. coli activated the coagulation system by a complement- and CD14-dependent up-regulation of TF, leading subsequently to prothrombin activation.

The effects of selective complement and CD14 inhibition on the E. coli-induced tissue factor mRNA upregulation, monocyte tissue factor expression, and tissue factor functional activity in human whole blood

BACKGROUND

The complement pathway and CD14 play essential roles in inflammation, but little is known about the relative roles of complement and CD14 in E. coli-induced tissue factor (TF) mRNA upregulation, expression by monocytes, and functional activity in human whole blood.

METHODS

Whole E. coli bacteria were incubated for up to 4 h in human whole blood containing the anticoagulant lepirudin, which does not affect complement activation. TF mRNA levels were analyzed using reverse transcription, quantitative real-time PCR (RT-qPCR), and the expression of TF on the cell surface was analyzed using flow cytometry. Complement was selectively inhibited using the C3 convertase inhibitor compstatin or a C5a receptor antagonist (C5aRa), while CD14 was blocked by an anti-CD14 F(ab')2 monoclonal antibody.

RESULTS

The E. coli-induced TF mRNA upregulation was reduced to virtually background levels by compstatin, whereas anti-CD14 had no effect. Monocyte TF expression and TF activity in plasma microparticles were significantly reduced by C5aRa. Anti-CD14 alone only slightly reduced E. coli-induced monocyte TF expression but showed a modest additive effect when combined with the complement inhibitors. Inhibiting complement and CD14 efficiently reduced the expression of the E. coli-induced cytokines IL-1beta, IL-6, IL-8, and platelet-derived growth factor bb.

CONCLUSION

Our results indicate that E. coli-induced TF mRNA upregulation is mainly dependent on complement activation, while CDI4 plays a modest role in monocyte TF expression and the plasma TF activity in human whole blood.

Differential effect of inhibiting MD-2 and CD14 on LPS- versus whole E. coli bacteria-induced cytokine responses in human blood

BACKGROUND

Sepsis is a major world-wide medical problem with high morbidity and mortality. Gram-negative bacteria are among the most important pathogens of sepsis and their LPS content is regarded to be important for the systemic inflammatory reaction. The CD14/myeloid differentiation factor 2 (MD-2)/TLR4 complex plays a major role in the immune response to LPS . The aim of this study was to compare the effects of inhibiting MD-2 and CD14 on ultra-pure LPS - versus whole E. coli bacteria-induced responses.

METHODS

Fresh human whole blood was incubated with upLPS or whole E. coli bacteria in the presence of MD-2 or CD14 neutralizing monoclonal antibodies, or their respective controls, and/or the specific complement-inhibitor compstatin. Cytokines were measured by a multiplex (n = 27) assay. NFκB activity was examined in cells transfected with CD14, MD-2 and/or Toll-like receptors.

RESULTS

LPS-induced cytokine response was efficiently and equally abolished by MD-2 and CD14 neutralization. In contrast, the response induced by whole E. coli bacteria was only modestly reduced by MD-2 neutralization, whereas CD14 neutralization was more efficient. Combination with compstatin enhanced the effect of MD-2 neutralization slightly. When compstatin was combined with CD14 neutralization, however, the response was virtually abolished for all cytokines, including IL-17, which was only inhibited by this combination. The MD-2-independent effect observed for CD14 could not be explained by TLR2 signaling.

CONCLUSION

Inhibition of CD14 is more efficient than inhibition of MD-2 on whole E. coli-induced cytokine response, suggesting CD14 to be a better target for intervention in Gram-negative sepsis, in particular when combined with complement inhibition.

Effect of supraphysiologic levels of C1-inhibitor on the classical, lectin and alternative pathways of complement

C1-inhibitor is increasingly used experimentally and clinically in inflammatory conditions like septicemia and ischemia-reperfusion injury. Several mechanisms may account for the anti-inflammatory effects of C1-inhibitor, including inhibition of complement. The aim of the present study was to investigate and compare the supraphysiologic effect of C1-inhibitor on the three complement pathways. Novel assays for specific evaluation of the classical, lectin and alternative pathways were employed using normal human serum supplemented with increasing concentrations of C1-inhibitor. Solid-phase classical- and lectin pathway activation was dose-dependently and significantly reduced up to 85% in the range of 2-28 times physiologic C1-inhibitor concentration. The lectin pathway was more potently inhibited than the classical at low doses. A functional lectin pathway assay demonstrated a significant reduction of C4 deposition up to 86% even at low concentration of C1-inhibitor and documented the effect to be at the level of MBL/MASPs. In contrast, C1-inhibitor had no effect on solid-phase alternative pathway activation, but significantly reduced cobra venom factor-induced fluid-phase activation up to 88%. The negative controls albumin and IgG had no effect on complement activation. The positive inhibitory controls compstatin (C3 inhibition), EDTA- or MBL-deficient sera reduced complement activation by 82-100%. We conclude that C1-inhibitor in high physiologic doses differentially inhibits all three-complement pathways. The inhibition pattern was strikingly different in the classical and lectin pathway, compared to the alternative. Previous studies interpreting the effects of C1-inhibitor as only due to classical pathway inhibition needs reconsideration. The data has implications for the therapeutic use of C1-inhibitor.

Secretory and cytosolic phospholipase A(2)regulate the long-term cytokine-induced eicosanoid production in human keratinocytes

The involvement of cytosolic phospholipase A(2)(cPLA(2)) and secretory non-pancreatic PLA(2)(npPLA(2)) in release of arachidonic acid (AA) preceding eicosanoid formation in the human keratinocyte cell line HaCaT was examined. Interleukin 1beta (IL-1beta) and tumour necrosis factor-alpha (TNF), phorbol myristate acetate (PMA) and calcium ionophore A(23187)increased the extracellular AA release, and stimulated eicosanoid synthesis as determined by HPLC analysis. The main metabolites after stimulation with IL-1beta, PMA or A(23187)were PGE(2), an unidentified PG and LTB(4), while TNF stimulated HETE-production. Both cPLA(2)and npPLA(2)message and enzyme activity were detected in unstimulated HaCaT cells. IL-1beta, PMA and TNF increased both cPLA(2)enzyme activity and expression, but did not lead to any increase in npPLA(2)expression or activity. The selective npPLA(2)inhibitors LY311727 and 12-epi-scalaradial, or the cPLA(2)inhibitor arachidonyl trifluoro methyl ketone (AACOCF(3)) reduced IL-1beta-induced eicosanoid production in a concentration dependent manner. The results presented strongly suggest that both cPLA(2)and npPLA(2)contribute to the long-term generation of AA preceding eicosanoid production in differentiated, human keratinocytes. Inhibitors against npPLA2 or cPLA2 enzymes should be useful in treating inflammatory skin diseases, such as psoriasis.

Specificity of endogenous fatty acid release during tumor necrosis factor-induced apoptosis in WEHI 164 fibrosarcoma cells

Recombinant tumor necrosis factor alpha (rTNF-alpha)-induced release of endogenous fatty acids was examined in WEHI 164 clone 13 fibrosarcoma cells using a highly sensitive HPLC method. The initial rTNF-alpha-induced extracellular release of endogenous fatty acids was dominated by 20:4n;-6, 22:4n;-6, 24:4n;-6, and 18:1n;-9 showing relative rates of 2.9, 0.9, 1.1, and 1.0, respectively. Release of endogenous AA and DNA fragmentation occurred simultaneously and preceded cell death by approx. 2 h. Methyl arachidonoyl fluorophosphonate and LY311727, specific inhibitors of Ca(2+)-dependent cytosolic PLA(2) (cPLA(2)) and secretory PLA(2) (sPLA(2)), respectively, neither blocked rTNF-alpha-induced cytotoxicity or endogenous AA release. However, both inhibitors reduced rTNF-alpha-induced release of other endogenous fatty acids. In comparison, the antioxidant butylated hydroxyanisole (BHA) completely inhibited the rTNF-alpha-induced cytotoxicity as well as AA release mediated through the TNF receptor p55, while the very similar antioxidant butylated hydroxytoluene had no effect. BHA did not inhibit recombinant cPLA(2) or sPLA(2) enzyme activity in vitro. Furthermore, stimulation of cells with rTNF-alpha for 4 h did not increase cPLA(2) enzyme activity. The data indicate that neither cPLA(2) or sPLA(2) mediate rTNF-alpha-induced apoptosis and extracellular AA release in WEHI cells. The results suggest that a BHA-sensitive signaling pathway coupled to AA release is a key event in TNF-induced cytotoxicity in these cells.

Selective inhibitors of cytosolic or secretory phospholipase A2 block TNF-induced activation of transcription factor nuclear factor-kappa B and expression of ICAM-1

TNF signaling mechanisms involved in activation of transcription factor NF-kappaB were studied in the human keratinocyte cell line HaCaT. We show that TNF-induced activation of NF-kappaB was inhibited by the well-known selective inhibitors of cytosolic phospholipase A2 (cPLA2): the trifluoromethyl ketone analogue of arachidonic acid (AACOCF3) and methyl arachidonyl fluorophosphate. The trifluoromethyl ketone analogue of eicosapentaenoic acid (EPACOCF3) also suppressed TNF-induced NF-kappaB activation and inhibited in vitro cPLA2 enzyme activity with a similar potency as AACOCF3. The arachidonyl methyl ketone analogue (AACOCH3) and the eicosapentanoyl analogue (EPACHOHCF3), which both failed to inhibit cPLA2 enzyme activity in vitro, had no effect on TNF-induced NF-kappaB activation. TNF-induced NF-kappaB activation was also strongly reduced in cells stimulated in the presence of the secretory PLA2 (sPLA2) inhibitors 12-epi-scalaradial and LY311727. Addition of excess arachidonic acid suppressed the inhibitory effect of 12-epi-scalaradial and LY311727. Moreover, both methyl arachidonyl fluorophosphate and 12-epi-scalaradial blocked TNF-mediated enhancement of expression of ICAM-1. Activation of NF-kappaB by IL-1beta was markedly less sensitive to both cPLA2 and sPLA2 inhibitors. The results indicate that both cPLA2 and sPLA2 may be involved in the TNF signal transduction pathway leading to nuclear translocation of NF-kappaB and to NF-kappaB-activated gene expression in HaCaT cells.

Reduced production of PGE2 and PGF2 alpha from decidual cell cultures supplemented with N-3 polyunsaturated fatty acids

A diet rich in n-3 polyunsaturated fatty acid (PUFA) may reduce the intrauterine production of prostaglandins and prolong pregnancy. We tested this hypothesis by assessing the influence of various PUFAs on the spontaneous production of PGE2 and PGF2 alpha from decidual cell cultures. In addition, we assessed prostaglandin and cytokine production stimulated by lipopolysaccharides (LPS) in order to mimic parturition where infection is involved. In both settings, we found that after supplementing with n-3 PUFA, PGE2 and PGF2 alpha were significantly reduced. After supplementing with n-6 PUFA, there was a significant increase in both prostaglandins. Both n-3 and n-6 PUFAs reduced the production of interleukin 1 (IL-1), while n-6 PUFAs reduced TNF production. PUFAs did not influence IL-6 production. Our findings support the hypothesis that dietary n-3 PUFA may prolong pregnancy by reducing intrauterine production of prostaglandins.

Tumor necrosis factor-induced release of endogenous fatty acids analyzed by a highly sensitive high-performance liquid chromatography method

A highly sensitive method to determine agonist-induced release of endogenous fatty acids from cells in culture was developed using high-performance liquid chromatography and fluorescence detection. Fatty acids were selectively derivatized with 1-pyrenyldiazomethane and separated on a LC18 reversed phase column using an acetonitrile-water gradient. The detection limit was approx. 20 fmol and the recovery of the complete method using oleic acid was 93-98%. Tumor necrosis factor alpha (TNF-alpha) increased the extracellular release of endogenous arachidonic acid (20:4n-6) from 21 to 153 pmol/well per 4 h using 2.7 x 10(6) WEHI fibrosarcoma cells. In cells preincubated with 50 microM 20:4n-6, the corresponding figures were 463 and 3379 pmol 20:4n-6/well. Simultaneously, nearly equimolar amounts of 22:4n-6 were released together with slightly lower amounts of 24:4n-6, 16:0, 16:1n-9, and 18:1n-9. Analysis of cell lipid fatty acids showed that phosphatidylcholine was the major source of the released fatty acids. TNF-alpha increased the intracellular concentration of unesterified 20:4n-6 and 22:4n-6 by 368% and 451%, respectively. This suggests that released 20:4n-6 is rapidly chain elongated to 22:4n-6. The results indicate that the present method facilitates studies on agonist-induced release of endogenous fatty acids, and that TNF-induced fatty acid release seems to be less selective for 20:4n-6 than previously reported.

Specificity of hydroperoxy fatty acid inhibition of cell growth and the lack of effect on tumour necrosis factor-induced cytotoxicity in WEHI clone 13 cells

We have examined whether different omega6-hydroperoxy fatty acids affect tumour cell growth or modulate TNF-induced toxicity in a fatty acid specific way in WEHI clone 13 fibrosarcoma cells. The omega6-hydroperoxides were synthesized from 8 different n - 6 and n - 3 PUFAs by soybean lipoxygenase. The omega6-hydroperoxy fatty acids inhibited cell growth in a concentration-dependent way by a mechanism that is related to the hydroperoxy moiety. Intracellular GSH seemed to protect since the GSH synthase inhibitor L-buthionine-S,R-sulfoximine (BSO) increased cell growth inhibition further. The antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene and alpha-tocopherol did not affect the toxicity. The extent of growth inhibition varied between the hydroperoxides, but the difference was relatively small. The most toxic was hydroperoxy-alpha-linolenic acid which reduced cell survival by 56% after 44 h incubation at 35 microM, while the least toxic, hydroperoxy-gamma-linolenic acid, reduced cell survival by only 10%. The data also show that there is no correlation between toxicity and degree of unsaturation of the hydroperoxy fatty acids. None of the 8 different hydroperoxy fatty acids potentiated TNF-induced toxicity. This, together with the differential effects of BHA and BSO on TNF- and hydroperoxy fatty acid toxicity, indicate that neither the hydroperoxides nor their metabolites are involved in mediating or modulating the TNF-effect.

Soluble tumour necrosis factor receptors, tumour necrosis factor and interleukin-6 in serum in granulocytopenic patients with fever

Serum levels of TNF, IL-6 and soluble TNF receptors p55 and p75 (sTNFR-p55 and sTNFR-p75) were examined in 14 patients with acute myeloid leukaemia during 43 courses of chemotherapy. The patients experienced 30 episodes of fever which occurred during granulocytopenia (defined as granulocyte counts < 0.2 x 10(9)/l) and six fever episodes when granulocyte counts were > 1.0 x 10(9)/l. Febrile episodes were classified as microbiologically defined infection, clinically defined infection, and unexplained fever. Levels of bioactive IL-6 and immunoreactive TNF increased in response to fever during granulocytopenia, whereas bioactive TNF was not detected in any sample in this study. During granulocytopenia, both sTNFR rose significantly in microbiologically defined infection (P < 0.01 for sTNFR-p55 and P < 0.05 for sTNFR-p75), but not in the other two categories. The ratio of sTNFR-p55 to sTNFR-p75 was higher during febrile periods in granulocytopenia than in a non-granulocytopenic situation with granulocyte counts > 1.0 x 10(9)/l (P < 0.01). We conclude that granulocytopenia affects release of the two sTNFR differently during febrile periods, and that release of sTNFR-p75 in response to fever is reduced during granulocytopenia, suggesting a role for the granulocytes in systemic release of sTNFR-p75.

TNF and IL-6 are potent growth factors for OH-2, a novel human myeloma cell line

A novel human myeloma cell line, OH-2, was established from pleural fluid of a myeloma patient in end stage of the disease. Effects of cytokines on proliferation were analyzed by measuring uptake of 3H-thymidine. Cell surface antigens were detected by flow cytometry. The cell line is dependent on IL-6 for growth and proliferates in response to TNF. There is synergy between the stimulatory response of TNF and IL-6. The cells express both the p55 and p75 TNF receptors. Neutralizing anti-IL-6 did not inhibit TNF-mediated proliferation, showing that TNF acts through a pathway that is independent of IL-6. TNF was more potent than IL-6 in stimulating the growth of primary myeloma cultures (> 99% pure) from the same patient (OH-2-PC), indicating that TNF in selected myeloma patients has a growth-promoting effect equal to IL-6. OH-2 cells produce and secrete monoclonal IgG-kappa.

Butylated hydroxyanisole inhibits tumor necrosis factor-induced cytotoxicity and arachidonic acid release

The mechanisms by which the antioxidant butylated hydroxyanisole (BHA) inhibits recombinant tumor necrosis factor alpha (rTNF-alpha)-induced cytotoxicity have been studied in WEHI 164 clone 13 (WEHI) and L929 fibrosarcoma cells. When BHA was added simultaneously with rTNF-alpha, it completely inhibited rTNF-alpha cytotoxicity in the WEHI and L929 cells. BHA also inhibited the toxicity when added 2 h after rTNF-alpha in WEHI cells, suggesting that BHA inhibits some late intracellular event(s) in rTNF-alpha cytotoxicity. Pretreating WEHI cells with BHA for 4 h did not decrease the binding of rTNF-alpha to its receptors as measured using flow cytometry. BHA inhibited rTNF-alpha toxicity in the presence of actinomycin D and cycloheximide, indicating that neither mRNA nor protein synthesis is necessary for the BHA effect. The antioxidant butylated hydroxytoluene (BHT) and indomethacin did not inhibit the rTNF-alpha-induced cytotoxicity nor the rTNF-alpha-induced release of [3H]arachidonic acid. By comparison, BHA completely inhibited the rTNF-alpha-induced release of arachidonic acid, suggesting that BHA somehow inhibits rTNF-alpha-induced activation of phospholipase(s). In WEHI cells, rTNF-alpha increased the level of protein-associated thiobarbituric acid reactive substances (TBARS) dose-dependently. BHA, but not BHT, blocked rTNF-alpha-induced cytotoxicity and rTNF-alpha-induced accumulation of protein-associated TBARS, suggesting that rTNF-alpha cytotoxicity is correlated with protein-associated TBARS. In conclusion, the results suggest that BHA blocks some post receptor event in rTNF-alpha-induced cytotoxicity, and that activation of phospholipase(s) coupled with the enzymatic formation of specific oxidized lipids could be a pivotal event in rTNF-alpha-induced cytotoxicity.

Infusion of EPA and DHA lipid emulsions: effects on heart lipids and tolerance to ischaemia-reperfusion in the isolated rat heart

The aim of the present study was to examine the effect of acute infusion of lipid emulsions enriched with either docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) on heart lipids, tolerance to infusion and to ischaemia-reperfusion. Isolated rat hearts were subjected to a 10 min lipid infusion period prior to 25 min of total global ischaemia and 30 min of reperfusion. Effects on physiology and metabolism were recorded during infusion and reperfusion. A more than doubled increase of DHA and a 12-fold increase of EPA in terms of relative concentration was demonstrated in the free fatty acid fraction after infusion with the respective triglyceride emulsions, without any profound change in physiology. High levels of DHA were associated with a reduced recovery of left ventricular developed pressure (LVDP) and increased release of lactate dehydrogenase (LDH) during reperfusion, while the hearts infused with the EPA-emulsion showed a recovery comparable to the control group. Heart lipid peroxidation, evaluated by release of thiobarbituric acid reactive substances (TBARS) in effluate, was about 4-fold higher in the DHA-group compared to the EPA-group during start of reperfusion and may in part explain the reduced recovery observed in these hearts. The present study demonstrates enrichment of DHA and EPA in the free fatty acid fraction after a short period of infusion. Protective effects of the emulsions were not found, instead the data indicate harmful effects of DHA during ischaemia-reperfusion. However, the presence of TBARS in this emulsion could have influenced the results.

Butylated hydroxyanisole specifically inhibits tumor necrosis factor-induced cytotoxicity and growth enhancement

The effect of commonly used food antioxidants on recombinant tumor necrosis factor alpha (rTNF-alpha)-induced cytotoxicity, growth enhancement and adhesion has been evaluated. Butylated hydroxyanisole (BHA) and 4-hydroxymethyl-2,6-di-t-butylphenol (HBP) were the only two of nine antioxidants that completely inhibited rTNF-alpha-induced cytotoxicity in L929 and WEHI 164 fibrosarcoma cells. Ethoxyquin, propyl gallate and butylated hydroquinone only partially inhibited rTNF-alpha-induced cytotoxicity, while the antioxidants butylated hydroxytoluene (BHT), alpha-tocopherol, ascorbic acid and thiodipropionic acid had minimal effects. The only difference between the molecular structure of the efficient HBP and the non-efficient BHT, is a hydroxymethyl group instead of a hydroxyl group on the phenolic ring. Neither BHA nor BHT inhibited the activation of NF kappa B after 10 or 60 min challenge with rTNF-alpha in L929 cells. BHA also inhibited rTNF-alpha-induced, but not rIL-1 beta-induced growth enhancement in FS-4 fibroblasts. Further, BHA blocked both rTNF-alpha-induced and rIL-1 beta-induced prostaglandin E2 synthesis in FS-4 fibroblasts. BHA inhibited the rTNF-alpha-induced release of arachidonic acid in both FS-4 and L929 cells, suggesting that BHA inhibits cellular phospholipase(s). Neither alpha-tocopherol nor BHA inhibited rTNF-alpha-induced adhesiveness of human endothelial cells. The results indicate that BHA is a specific and potent inhibitor of rTNF-alpha- and rTNF-beta-induced cytotoxicity, as well as of rTNF-alpha-induced growth enhancement.

Effects of n-3 and n-6 fatty acids on tumor necrosis factor cytotoxicity in WEHI fibrosarcoma cells

Modulation by fatty acids of the cytotoxic effect of recombinant tumor necrosis factor alpha (TNF) toward WEHI 164 mouse fibrosarcoma cells has been examined. Preincubating the highly TNF-sensitive WEHI clone 13 cells for 44 hr with 50 mumol/L of 20:5n-3, 22:6n-3, 18:3n-6, 20:3n-6 or 20:4n-6 reduced cell survival 22 hr after challenge with TNF (40 ng/L) by 65%, 72%, 60%, 98% and 85%, respectively. In comparison, 18:3n-3, 18:2n-6 and 18:1n-9 had only negligible effects on TNF-induced toxicity. Different extent of fatty acid incorporation into cell total phospholipids or triglycerides could not explain the observed effects on TNF cytotoxicity, and the enhanced cytotoxicity could therefore not be explained merely by an increased unsaturation of the cell membranes. In addition to the fatty acid supplied, preincubation with 18:2n-6, 18:3n-6 or 18:3n-3 also enriched the cells with 20:2n-6, 20:3n-6 and 20:3n-3, respectively, most likely due to chain elongation. The results suggest that the WEHI cells have a low delta 6 desaturase activity, and that n-6 and n-3 acids must have at least 3 or 4 double bonds, respectively, to enhance TNF cytotoxicity in WEHI cells. Dexamethasone partly inhibited TNF-induced cytotoxicity, while cyclooxygenase, thromboxane synthetase or lipoxygenase inhibitors had no or negligible effects. The antioxidant butylated hydroxyanisole (BHA) completely inhibited TNF-induced cytotoxicity, while the structurally and functionally similar antioxidant butylated hydroxytoluene had no such effect, indicating that BHA does not block TNF cytotoxicity through its antioxidant effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Griseofulvin-induced protoporphyria revisited

In nude mice grieofulvin given by intraperitoneal injections produces a severe porphyric state within 1 week. Compared with peroral administration of griseofulvin to produce experimental porphyria, this model is much more efficient and can be more easily controlled.

Aflatoxin in corn: ammonia inactivation and bioassay with rainbow trout

Four samples of corn were compared with respect to their hepatocarcinogenicity in rainbow trout. One corn sample was found by chemical analysis to contain no detectable aflatoxin. A second sample was contaminated with aflatoxins at a level of 180 microgram/kg. Each of the above-mentioned samples was divided, and one-half of each was ammoniated. These four samples were added to a semipurified basal diet and fed to a sensitive strain of rainbow trout. It was found that ammoniation inactivated the aflatoxins and reduced the carcinogenicity of the contaminated corn to a level that was not significantly different from that with the basal control diet. It was also found that the ammoniation process did not reduce the nutritive value of the corn.