The low molecular weight fraction of commercial human serum albumin induces acetylation of α-tubulin and reduces transcytosis in retinal endothelial cells.

It has long been appreciated that the microtubule network plays a critical role in endothelial cell function. Chemical inhibition of tubulin polymerization has been shown to drastically increases endothelial permeability via interactions with the actin cytoskeleton. Conversely, stabilization of microtubules significantly decreases vascular permeability. The purpose of this investigation was to determine if the low molecular weight fraction of commercial 5% human serum albumin (LMWF5A) alters endothelial cell cytoskeletal dynamics and function. To investigate this, human retinal endothelial cells (HREC) were treated with LMWF5A and the acetylation of α-tubulin was determined by immunofluorescent staining and immunoblotting. In addition, permeability assays were performed to evaluate functional changes. We found that HREC treated with LMWF5A exhibit a rapid increase in the amount and distribution of acetylated α-tubulin. This was accompanied by a reduction in macromolecular permeability. Calcium depletion and inhibition of PI3-kinase reduced LMWF5A-induced acetylation while p38 MAPK inhibition potentiated this effect. These findings suggest that LMWF5A mediates changes in the microtubule network and reduces transcytosis in HREC.

The low molecular weight fraction of human serum albumin upregulates production of 15d-PGJ2 in Peripheral Blood Mononuclear Cells.

Activation of the innate immune system involves a series of events designed to counteract the initial insult followed by the clearance of debris and promotion of healing. Aberrant regulation can lead to systemic inflammatory response syndrome, multiple organ failure, and chronic inflammation. A better understanding of the innate immune response may help manage complications while allowing for proper immune progression. In this study, the ability of several classes of anti-inflammatory drugs to affect LPS-induced cytokine and prostaglandin release from peripheral blood mononuclear cells (PBMC) was evaluated. PBMC were cultured in the presence of dexamethasone (DEX), ibuprofen (IBU), and the low molecular weight fraction of 5% albumin (LMWF5A) followed by stimulation with LPS. After 24 h, TNFα, PGE2, and 15d-PGJ2 release was determined by ELISA. Distinct immunomodulation patterns emerged following LPS stimulation of PBMC in the presence of said compounds. DEX, a steroid with strong immunosuppressive properties, reduced TNFα, PGE2, and 15d-PGJ2 release. IBU caused significant reduction in prostaglandin release while TNFα release was unchanged. An emerging biologic with known anti-inflammatory properties, LMWF5A, significantly reduced TNFα release while enhancing PGE2 and 15d-PGJ2 release. Incubating LMWF5A together with IBU negated this observed increased prostaglandin release without affecting the suppression of TNFα release. Additionally, LMWF5A caused an increase in COX-2 transcription and translation. LMWF5A exhibited a unique immune modulation pattern in PBMC, disparate from steroid or NSAID administration. This enhancement of prostaglandin release (specifically 15d-PGJ2), in conjunction with a decrease in TNFα release, suggests a switch that favors resolution and decreased inflammation.

Anti-Inflammatory Activity in the Low Molecular Weight Fraction of Commercial Human Serum Albumin (LMWF5A).

The innate immune system is increasingly being recognized as a critical component in osteoarthritis (OA) pathophysiology. An ex vivo immunoassay utilizing human peripheral blood mononuclear cells (PBMC) was developed in order to assess the OA anti-inflammatory properties of the low molecular weight fraction (<5 kDa) of commercial human serum albumin (LMWF5A). PBMC from various donors were pre-incubated with LMWF5A before LPS stimulation. TNFα release was measured by ELISA in supernatants after an overnight incubation. A ≥ 30% decrease in TNFα release was observed. This anti-inflammatory effect is potentially useful in assessing potency of LMWF5A for the treatment of OA.

The low molecular weight fraction of human serum albumin upregulates COX2, prostaglandin E2, and prostaglandin D2 under inflammatory conditions in osteoarthritic knee synovial fibroblasts.

BACKGROUND: The ability to decrease inflammation and promote healing is important in the intervention and management of a variety of disease states, including osteoarthritis of the knee (OAK). Even though cyclooxygenase 2 (COX2) has an established pro-inflammatory role, evidence suggests it is also critical to the resolution that occurs after the initial activation phase of the immune response. In this study, we investigated the effects of the low molecular weight fraction of 5% human serum albumin (LMWF-5A), an agent that has proven to decrease pain and improve function in OAK patients after intra-articular injection, on the expression of COX2 and its downstream products, prostaglandins (PGs). METHODS: Fibroblast-like synoviocytes from the synovial membrane of OAK patients were treated with LMWF-5A or saline as a control with or without the addition of interleukin-1ß (IL-1ß) or tumor necrosis factor α (TNFα) to elicit an inflammatory response. Cells were harvested for RNA and protein at 2, 4, 8, 12, and 24 h, and media was collected at 24 h for analysis of secreted products. COX2 mRNA expression was determined by qPCR, and COX2 protein expression was determined by western blot analysis. Levels of prostaglandin E2 (PGE2) and prostaglandin D2 (PGD2) in the media were quantified by competitive ELISA. RESULTS: In the presence of either IL-1ß or TNFα, LMWF-5A increased the expression of both COX2 mRNA and protein, and this increase was significant compared to that observed with IL-1ß- or TNFα-stimulated, saline-treated cells. Downstream of COX2, the levels of PGE2 were increased only in TNFα-stimulated, LMWF-5A-treated cells; however, in both IL-1ß- and TNFα-stimulated cells, LMWF-5A increased the release of the anti-inflammatory prostaglandin PGD2. CONCLUSION: LMWF-5A appears to trigger increased anti-inflammatory PG signaling, and this may be a primary component of its therapeutic mode of action in the treatment of OAK.

Low Molecular Weight Fraction of Commercial Human Serum Albumin Induces Morphologic and Transcriptional Changes of Bone Marrow-Derived Mesenchymal Stem Cells.

Osteoarthritis (OA) is the most common chronic disease of the joint; however, the therapeutic options for severe OA are limited. The low molecular weight fraction of commercial 5% human serum albumin (LMWF5A) has been shown to have anti-inflammatory properties that are mediated, in part, by a diketopiperazine that is present in the albumin preparation and that was demonstrated to be safe and effective in reducing pain and improving function when administered intra-articularly in a phase III clinical trial. In the present study, bone marrow-derived mesenchymal stem cells (BMMSCs) exposed to LMWF5A exhibited an elongated phenotype with diffuse intracellular F-actin, pronounced migratory leading edges, and filopodia-like projections. In addition, LMWF5A promoted chondrogenic condensation in "micromass" culture, concurrent with the upregulation of collagen 2α1 mRNA. Furthermore, the transcription of the CXCR4-CXCL12 axis was significantly regulated in a manner conducive to migration and homing. Several transcription factors involved in stem cell differentiation were also found to bind oligonucleotide response element probes following exposure to LMWF5A. Finally, a rapid increase in PRAS40 phosphorylation was observed following treatment, potentially resulting in the activation mTORC1. Proteomic analysis of synovial fluid taken from a preliminary set of patients indicated that at 12 weeks following administration of LMWF5A, a microenvironment exists in the knee conducive to stem cell infiltration, self-renewal, and differentiation, in addition to indications of remodeling with a reduction in inflammation. Taken together, these findings imply that LMWF5A treatment may prime stem cells for both mobilization and chondrogenic differentiation, potentially explaining some of the beneficial effects achieved in clinical trials.

Inflammatory Pathways in Knee Osteoarthritis: Potential Targets for Treatment.

Osteoarthritis (OA) of the knee is a wide-spread, debilitating disease that is prominent in Western countries. It is associated with old age, obesity, and mechanical stress on the knee joint. By examining the recent literature on the effect of the anti-inflammatory prostaglandins 15d-PGJ2 and Δ12-PGJ2, we propose that new therapeutic agents for this disease could facilitate the transition from the COX-2-dependent pro-inflammatory synthesis of the prostaglandin PGE2 (catalyzed by mPGES-1), to the equally COX-2-dependent synthesis of the aforementioned anti-inflammatory prostaglandins. This transition could be instrumental in halting the breakdown of cartilage via matrix metalloproteinases (MMPs) and aggrecanases, as well as promoting the matrix regeneration and synthesis of cartilage by chondrocytes. Another desirable property of new OA therapeutics could involve the recruitment of mesenchymal stem cells to the damaged cartilage and bone, possibly resulting in the generation of chondrocytes, synoviocytes, and, in the case of bone, osteoblasts. Moreover, we propose that research promoting this transition from pro-inflammatory to anti-inflammatory prostaglandins could aid in the identification of new OA therapeutics.

Biphasic effect of danazol on human vascular endothelial cell permeability and f-actin cytoskeleton dynamics.

Breakdown of endothelial barrier function is a hallmark event across a variety of pathologies such as inflammation, cancer, and diabetes. It has also been appreciated that steroid hormones impart direct biological activity on endothelial cells at many levels. The purpose of this investigation was to explore the effect of the androgen-like steroid, danazol, on endothelial cell barrier function in vitro. Primary human endothelial cells exposed to 0.01-50 µM danazol were evaluated for changes in permeability. We found that danazol altered endothelial permeability in a biphasic manner in which nanomolar concentrations enhance barrier function while micromolar concentrations are detrimental. Monitoring of trans-endothelial electrical resistance demonstrated that these barrier enhancing effects were rapid (within 5 min) and lasted for over 24h. Analysis of intracellular f-actin organization showed that barrier enhancement also correlated with the formation of a submembranous cortical actin ring. Conversely, at higher danazol concentrations, contractile cell phenotypes were observed, represented by stress fiber formation. Competitive binding studies performed using steroid hormone receptor antagonists proved that this activity is the result of androgen and estrogen receptor ligation. These findings suggest that low dose danazol may provide a therapeutic window for diseases involving vascular leakage.

Potential dysregulation of the pyruvate dehydrogenase complex by bacterial toxins and insulin.

BACKGROUND: The pyruvate dehydrogenase complex (PDC) catalyzes the conversion of pyruvate to acetyl CoA, effectively controlling the entrance of glycolysis products into aerobic metabolism. Because hyperlactatemia is one of the hallmarks of sepsis, we hyphothesized that gram-positive and negative bacterial toxin treatment will interfere with mRNA levels of regulatory enzymes of the PDC and overall enzyme activity in hepatocytes. METHODS: HEP G2 hepatocarcinoma cells were incubated for 24 hours in the presence of lipopolysaccaride (LPS) or lipoteichoic acid. Total RNA was then isolated and message RNA levels for both pyruvate dehydrogense kinase 4 and phosphatase 2 were determined by RTPCR. Amplified DNA fragments were visualized by ethidium bromide in agarose gels and densitometry of the bands was performed. Data were then normalized to the housekeeping gene, GAPDH. Enzyme activity was then determined by capturing intact PDC on nitrocellulose membranes then determining PDC-dependent production of NADH. RESULTS: LPS treatment led to a time dependent increase in PDK4 message while decreasing PDP2 levels. Enzyme activity, in these cells, also significantly decreased 24 hours after exposure to LPS. Cells cultured in the presence of lipoteichoic acid and insulin exhibited differing message ratios and activity levels when evaluated at 4 hours, but at 24 hours shifted to mimic those observed in LPS treated cells. CONCLUSION: This data may indicate that exposure to bacterial cell wall components and insulin could create cellular environments that result in a build-up of lactate.

Mechanisms of delayed wound healing by commonly used antiseptics.

BACKGROUND: The cytotoxic effects of antiseptics on pivotal cell types of the healing process have been well documented. The purpose of our investigation was to explore the ability of subcytotoxic levels of antiseptics to interfere with fibroblast function. METHODS: Cell proliferation assays were performed by culturing fibroblasts in the presence of commonly used antiseptics. Migration was evaluated using scratch assays in which monolayers were "wounded" and cellular movement was monitored by digital photography. Matrix metalloproteinase (MMP) release was analyzed by zymography. RESULTS: H2O2 and povidone-iodine reduced both migration and proliferation of fibroblasts in a dose-dependent fashion. Treatment with silver-containing antiseptics and chlorhexidine exhibited reductions in proliferation at high concentrations, but enhanced growth at lower doses. Silver-containing compounds and chlorhexidine also proved to be the least detrimental to migration in these assays. metalloproteinase release from the cells was differently affected depending on the dosage and class of antiseptic applied. CONCLUSIONS: When debridement of the wound bed is not sufficient to reduce bacterial loads, the application of broad-spectrum antiseptics maybe indicated. Our data would suggest that H2O2 and iodine are poor choices, potentially retarding the contribution of fibroblasts to the healing process. Silver sulfadiazine and chlorhexidine, at levels still proven to be bactericidal, had fewer detrimental effects on fibroblast activity in these assays. The silver-containing antiseptics may even increase the proliferative potential of these cells in culture.

Combined cupric- and cuprous-binding peptides are effective in preventing IL-8 release from endothelial cells and redox reactions.

Copper mobilization and subsequent redox reactions have been implicated in the pathogenesis of numerous inflammation-based diseases. Reduction of the cupric ion (Cu(2+)) to the cuprous ion (Cu(+)) is necessary for the production of copper-induced reactive oxygen species (ROS). Peptides, designed to bind both Cu(2+) and Cu(+) and have the ability to prevent copper redox reactions, were studied. The peptides DAHGMTCANC and DAHKGMTCANC were effective at preventing the formation of thiobarbituric acid-reactive species (TBARS) in a copper/ascorbate solution at a 1:1 peptide/Cu ratio. This was observed in the reducing potential of the copper/ascorbate solutions containing these peptides at a 1:1 ratio based on oxidation-reduction potential (ORP) measurements. The peptide DAHGMTCARC was effective at a 2:1 ratio, but not at a 1:1 ratio in which an increase in the oxidation potential was observed. This suggests that a positively charged amino acid such as arginine (R) in the Cu(+)-binding motif interferes with metal chelation. All peptides tested were effective at preventing IL-8 release from phorbol 12-myristate 13-acetate (PMA)/copper-stimulated human umbilical vein endothelial cells (HUVEC). The use of Cu(+)/Cu(2+)-binding peptides might be beneficial in the treatment of ROS-related diseases associated with copper.

Effects of danazol on endothelial cell function and angiogenesis.

OBJECTIVE: To determine the effects of the androgen-like synthetic steroid, danazol, on endothelial cell function and angiogenesis. DESIGN: In vitro cell culture models were designed to investigate three critical steps involved in angiogenesis: endothelial cell proliferation, invasion, and tube formation. SETTING: Research laboratory at a level one trauma center. PATIENT(S): Commercially available human umbilical vein endothelial cells (HUVEC) were purchased from a pooled patient source. INTERVENTION(S): The HUVEC cells were treated with danazol at concentrations ranging from 1 to 100 microM and evaluated using a series of angiogenesis assays. MAIN OUTCOME MEASURE(S): Absolute cells numbers were quantified using colorimetric methods and fluorescent dyes for cells exposed to danazol in both proliferation assays and invasion chambers. AngiQuant vl.33 software was used to evaluate the formation of capillary-like structures on extracellular matrix gels in the presence of danazol. RESULT(S): Endothelial cells scrutinized by our in vitro models exhibited decreased proliferation (up to 86%) and tube length (up to 115%) in the presence danazol. Cellular invasion through extracellular matrix, however, was not apparently affected by danazol under the conditions used. CONCLUSION(S): Danazol interfered with two of the three steps of angiogenesis studied in vitro. This data may help elucidate the mode of action for danazol in vivo.

Severe systemic immune response syndrome, low plasma paraoxonase activity, and a new albumin species in a traumatized patient with Gaucher's disease.

INTRODUCTION: Gaucher's disease (GD) is an inborn error, autosomal recessive lysosomal lipid storage disorder characterized by the lack of the enzyme glucocerebrosidase. We observed some abnormalities in the plasma of a traumatized patient with GD. CASE REPORT: We report of a traumatized patient with GD that developed a severe systemic immune response during the course of an extended hospital stay. Plasma paraoxonase (PON) activity was assayed and found to be extremely low possibly due to the existence of GD in this particular patient. Also, a potentially novel post-translational modification (PTM) of albumin was noticed in the patient's plasma that coincided with enzyme replacement therapy (ERT) with Cerezyme. CONCLUSIONS: The decreased plasma PON activity measured might be a contributive factor in the development of an accentuated systemic immune response in a traumatized patient with GD. A modified albumin species could serve as a biomarker for ERT in Gaucher patients.

Commercial human albumin preparations for clinical use are immunosuppressive in vitro.

OBJECTIVE: We previously reported significant variations in oxidation status and molecular length among sources and lots of human serum albumin (HSA) commercial preparations intended for clinical use. In this report, we investigated what effect the presence of HSA products have on the immune response in vitro. DESIGN: Laboratory study. SETTING: Trauma research basic science laboratory. SUBJECTS: Activated human peripheral blood mononuclear cells. INTERVENTIONS: Six commercial HSA preparations were tested for their effect on cytokine release from activated human peripheral blood mononuclear cells (PBMCs) and T-lymphocytes. Mass spectrometry analysis of aspartyl-alanyl diketopiperazine (DA-DKP) content of HSA and percentage of HSA having lost its amino terminal dipeptide aspartyl alanyl (HSA-DA) were correlated. MEASUREMENTS AND MAIN RESULTS: Human PBMCs were cultured in the presence of six commercial HSA preparations and activated via the T-cell receptor complex. A cloned T-lymphocyte cell line, activated with specific antigen, was also cultured with both synthetic DA-DKP and small molecular weight extracts from the commercial HSA tested. Supernatants were quantified by enzyme-linked immunosorbent assay for interferon-gamma and tumor necrosis factor-alpha content. DA-DKP was extracted from HSA by centrifugal filters and quantified by anion exchange liquid chromatography coupled to negative electrospray ionization mass spectrometry. HSA species were determined by reverse phase liquid chromatography coupled to positive electrospray ionization, time of flight mass spectrometry. All HSA preparations significantly inhibited the in vitro production of interferon-gamma and tumor necrosis factor-alpha by activated PBMCs. DA-DKP was detected in all HSA sources at concentrations ranging between 42.0 and 79.6 microM. A synthetic form of DA-DKP possessed similar immunosuppressive qualities in a dose-dependent manner on T lymphocytes. CONCLUSIONS: DA-DKP was present in significant concentrations in all HSA sources tested and was partially responsible for the immunosuppressive effects of HSA on activated PBMCs and T-lymphocytes in vitro. In view of these findings, administering HSA to immunocompromised critically ill patients might be reevaluated.

Diagnostic potential of phosphorylated cardiac troponin I as a sensitive, cardiac-specific marker for early acute coronary syndrome: preliminary report.

BACKGROUND: Cardiac troponin I (cTnI) has low sensitivity in the early hours of acute coronary syndrome (ACS). For patients with early ACS symptoms, we determined the diagnostic potential of an immunoassay for phosphorylated cTnI (PO(4)-cTnI). METHODS: In a prospective study of 61 emergency department patients with suspected ACS, we compared a novel plasma immunoassay for PO(4)-cTnI to cTnI overall and in a subgroup with symptoms < or =4 h duration (n = 31). Admission PO(4)-cTnI and cTnI assays (thresholds determined by ROC curve) were analyzed in a blinded fashion against the clinical, ECG and coronary angiographic diagnosis of ACS. RESULTS: Overall, PO(4)-cTnI sensitivity was significantly higher than cTnI (82% vs. 50%, respectively, P < 0.05) and PO(4)-cTnI specificity was 81% (n = 61). Addition of PO(4)-cTnI to cTnI improved sensitivity to 91% vs. 50% for cTnI alone (P < 0.001). In the < or =4 h subgroup (n = 31), PO(4)-cTnI sensitivity was significantly higher than cTnI (79% vs. 26%, respectively, P < 0.01) and PO(4)-cTnI specificity was 75%. In the same < or =4 h subgroup, addition of PO(4)-cTnI to cTnI improved sensitivity to 84% vs. 26% for cTnI alone (P = 0.001). CONCLUSIONS: The results suggest that PO(4)-cTnI, alone or in combination with cTnI, warrants further investigation as a sensitive, cardiac-specific diagnostic tool for early ACS.

Inhibitory effect of copper on cystathionine beta-synthase activity: protective effect of an analog of the human albumin N-terminus.

Copper was added to truncated, recombinant cystathionine beta-synthase (CBS), and the enzyme activity was assessed by measuring the production of cystathionine. 10 microM copper significantly decreased CBS activity by 50% while 25 microM copper decreased CBS activity by 70%. This inhibition was negated when an analog of the N-terminus of human albumin, Asp-Ala-His-Lys (DAHK), a strong transition metal binding peptide, was added. The use of copper chelators could significantly reduce in vivo homocysteine levels.

Lipid peroxidation and the thiobarbituric acid assay: standardization of the assay when using saturated and unsaturated fatty acids.

Saturated fatty acids are less vulnerable to lipid peroxidation than their unsaturated counterparts. In this investigation, individual fatty acids of the C(16), C(18) and (20) families were subjected to the thiobarbituric (TBA) assay. These fatty acids were chosen based on their degree of saturation and configuration of double bonds. Interestingly, an assay threshold was reached where increasing the fatty acid concentration resulted in no additional decrease in the TBARS concentrations. Therefore, the linear range of TBARS inhibition was determined for fatty acids in the C(16) and C(20) families. The rate of TBARS inhibition was greater for the saturated than for unsaturated fatty acids, as measured from the slope of the linear range. These findings demonstrate the need to standardize the TBARS assay using multiple fatty acid concentrations when using this assay for measuring in vitro lipid peroxidation.

Plasma albumin cysteinylation is regulated by cystathionine beta-synthase.

High homocysteine (Hcy) levels are a well-known independent risk factor for endothelial damage in atherosclerosis. We examined whether a rat intestinal model of ischemia-reperfusion was associated with high Hcy and with the modification of plasma albumin into cysteinylated species (CysAlb). The three treatment groups were as follows: midline abdominal incision (group A, n=10), followed by ligation of the superior mesenteric artery for a period of 2h (group B, n=3), and followed by reperfusion for 1h (group C, n=10). Hcy levels were 2.5-fold higher in group C than group A (p<0.05). 100% and 73.44+/-0.04% of Alb were modified into Cys species in groups C and B, respectively, compared to 51.2% in group A. A cystathionine beta-synthase (CBS) deficient mouse model, known to have high plasma Hcy levels, was also used to determine the extent of CysAlb. Hcy levels, %CysAlb, and %HcyAlb were 180.1+/-45.7 microM, 0%, and 23.4+/-4.4% in CBS deficient mice, while in control mice, those values were 5.7+/-1.8 microM, 24.2+/-4.1%, and 0%, respectively (p<0.05). High CysAlb and Hcy levels were observed in a rat model of bowel ischemia/reperfusion while high HcyAlb and Hcy levels with no CysAlb were observed in the CBS deficient mice. CysAlb may serve as a biomarker for the severity of gut ischemia, and high Hcy may explain endothelial damage associated with this model. Additionally, active CBS is essential for the formation of CysAlb.

An anti-inflammatory role for N-acetyl aspartate in stimulated human astroglial cells.

Although N-acetyl-L-aspartate (NAA) has been shown to be important to myelin synthesis and osmotic regulation, the biological rationale for the high levels of NAA found in the brain remains unknown. Here, a human astroglial cell line (STTG) was treated with NAA and stimulated with ionomycin, ionomycin/PMA, or IL-1beta. PGE(2) levels in ionomycin-stimulated STTG cells decreased by 76% and > 95% at NAA concentrations of 10 and 20mM, respectively. NAA also decreased the levels of COX-2 protein and activated NF-kappaB in IL-1beta-stimulated STTG cells but had little effect on unstimulated cells. Also, NAA significantly decreased intracellular calcium levels in ionomycin/PMA-stimulated cells. NAA had no effect on total COX-2 activity or COX-2 mRNA. Acetylation of IkappaBalpha kinase, an acetylation target of aspirin, was not observed when NAA was present. These results demonstrate that NAA appears to be important in the modulation of inflammation in the human STTG astroglial cell line. The results of these findings are discussed in relation to neuronal pathologies that exhibit abnormal NAA levels within the brain.

Copper stimulates the synthesis and release of interleukin-8 in human endothelial cells: a possible early role in systemic inflammatory responses.

Endogenous copper can play an important role in postischemic reperfusion injury, a condition associated with endothelial cell activation and increased interleukin 8 (IL-8) production. Excessive endothelial IL-8 secreted during trauma, major surgery, and sepsis may contribute to the development of systemic inflammatory response syndrome (SIRS), adult respiratory distress syndrome (ARDS), and multiple organ failure (MOF). No previous reports have indicated that copper has a direct role in stimulating human endothelial IL-8 secretion. Increased IL-8 in the culture medium of human umbilical vein (HUVEC), lung microvascular, and iliac artery endothelial cells was observed 24 h after the addition of 10 to 50 microM CuCl2 (cupric ions). HUVEC IL-8 induction by copper was higher than by 50 pg/mL tumor necrosis factor-alpha, whereas 50 pg/mL IL-1beta and 1 ng/mL platelet-activating factor did not stimulate IL-8 production or release. HUVEC IL-8 mRNA increased 3 h after CuCl2 stimulation and remained elevated after 24 h, implying sustained transcriptional activation. Copper did not stimulate HUVECs to secrete other cytokines. Cu(II) appeared to be the primary copper ion responsible for the observed increase in IL-8 because a specific high-affinity Cu(II)-binding peptide, d-Asp-d-Ala-d-His-d-Lys (d-DAHK), completely abolished this effect in a dose-dependent manner. These results suggest that Cu(II) may induce endothelial IL-8 by a mechanism independent of known Cu(I) generation of reactive oxygen species. Furthermore, in vivo studies are warranted to determine if copper is involved in the pathogenesis of systemic inflammation and if Cu(II) chelation can reduce this IL-8-induced endothelial inflammatory response.

Copper inhibits activated protein C: protective effect of human albumin and an analogue of its high-affinity copper-binding site, d-DAHK.

Activated protein C (APC) is useful in the treatment of sepsis. Ischemia and acidosis, which often accompany sepsis, cause the release of copper from loosely bound sites. We investigated (i) whether physiological concentrations of copper inhibit APC anticoagulant activity and (ii) if any copper-induced APC inhibition is reversible by human serum albumin (HSA) or a high-affinity copper-binding analogue of the human albumin N-terminus, d-Asp-d-Ala-d-His-d-Lys (d-DAHK). APC activity after 30 min of incubation with CuCl2 (10 microM) was decreased 26% below baseline. HSA, both alone and when combined with various ratios of CuCl2, increased APC activity significantly above baseline. d-DAHK alone and 2:1 and 4:1 ratios of d-DAHK:CuCl2 also increased APC activity. APC contained 1.4 microM copper, which helps explain the increased APC activity with HSA and d-DAHK alone. These in vitro results indicate that copper inhibits APC activity and that albumin and d-DAHK reverse the copper-induced APC deactivation.