Heparin protects cultured arterial endothelial cells from damage by toxic oxygen metabolites

The Role of Histones and Heparin in Sepsis: A Review

Septic shock with multiple organ failure is a devastating situation in clinical settings. Through the past decades, much progress has been made in the management of sepsis and its underlying pathogenesis, but a highly effective therapeutic has not been developed. Recently, macromolecules such as histones have been targeted in the treatment of sepsis. Histones primarily function as chromosomal organizers to pack DNA and regulate its transcription through epigenetic mechanisms. However, a growing body of research has shown that histone family members can also exert cellular toxicity once they relocate from the nucleus into the extracellular space. Heparin, a commonly used anti-coagulant, has been shown to possess life-saving capabilities for septic patients, but the potential interplay between heparin and extracellular histones has not been investigated. In this review, we summarize the pathogenic roles of extracellular histones and the therapeutic roles of heparin in the development and management of sepsis and septic shock.

The role of heparin in sepsis: much more than just an anticoagulant

Despite progress in antibiotic treatment, mechanical ventilation, fluid resuscitation and blood glucose maintenance, sepsis remains a cause of high mortality in the intensive care unit to date, there are no proven treatment strategies for the routine management of septic patients. The extensive interaction between inflammation and coagulation contributes to the basic pathophysiology of sepsis. Thus, the agents that attenuate the activation of both inflammation and coagulation may improve the outcome in sepsis. Apart from the well-known anticoagulant effects of heparin, it also possesses various immunomodulatory properties and protects glycocalyx from shedding. Hence, heparin seems to be such an agent. Immunothrombosis plays an important role in early host defence against bacterial dissemination, thus the proper timing for anticoagulant therapy should be determined. We review the available experimental and clinical data supporting the use of heparin in sepsis. At this time the use of heparin in the treatment of sepsis is conflicting. Future trials of heparin therapy for sepsis should concentrate on the very severely ill patients, in whom benefit is most likely to be demonstrated.

Glycosaminoglycans, hyperglycemia, and disease

SIGNIFICANCE

Diabetes is a widespread disease with many clinical pathologies. Despite numerous pharmaceutical strategies for treatment, the incidence of diabetes continues to increase. Hyperglycemia, observed in diabetes, causes endothelial injury resulting in microvascular and macrovascular complications such as nephropathy, retinopathy, neuropathy, and increased atherosclerosis.

RECENT ADVANCES

Proteoglycans are chemically diverse macromolecules consisting of a protein core with glycosaminoglycans (GAGs) attached. Heparan sulfate proteoglycans are important compounds found on the endothelial cell membrane and in the extracellular matrix, which play an important role in growth regulation and serve as a reservoir for cytokines and other bioactive molecules. Endothelial cells are altered in hyperglycemia by a reduction in heparan sulfate and upregulation and secretion of heparanase, an enzyme that degrades heparan sulfate GAGs on proteoglycans. Reactive oxygen species, increased in diabetes, also destroy GAGs.

CRITICAL ISSUES

Preservation of heparan sulfate proteoglycans on endothelial cells may be a strategy to prevent angiopathy associated with diabetes. The use of GAGs and GAG-like compounds may increase endothelial heparan sulfate and prevent an increase in the heparanase enzyme.

FUTURE DIRECTIONS

Elucidating the mechanisms of GAG depletion and its significance in endothelial health may help to further understand, prevent, and treat cardiovascular complications associated with diabetes. Further studies examining the role of GAGs and GAG-like compounds in maintaining endothelial health, including their effect on heparanase, will determine the feasibility of these compounds in diabetes treatment. Preservation of heparan sulfate by decreasing heparanase may have important implications not only in diabetes, but also in cardiovascular disease and tumor biology.

Efficacy of low molecular weight heparin in patients with acute exacerbation of chronic obstructive pulmonary disease receiving ventilatory support

INTRODUCTION

Severe and acute exacerbation of chronic obstructive pulmonary disease (COPD) is associated with a high mortality. Since COPD is an airway inflammatory disease, and heparin has shown anti-inflammatory effects in previous studies, we evaluated the clinical effect of low molecular weight heparin (LMWH; nadroparin) in COPD patients admitted into the hospital due to acute exacerbations.

METHODS

Sixty-six patients admitted to the intensive care unit (ICU) were randomly divided into control group (n = 33) and LMWH group (n = 33). The control group received conventional treatment, including oxygen therapy (non-invasive or conventional mechanical ventilation), anti-infection, atomization expectorant, spasmolysis, anti-asthmatics, and nutritional support. The LMWH group received the same treatment plus LMWH for 1 week. The levels of plasma C-reactive protein, interleukin-6, and fibrinogen were measured. The main outcomes were duration of mechanical ventilation, length of ICU stay, and hospital stay.

RESULTS

There were no significant differences between the groups with respect to demographics, severity of illness, and gas exchange variables. The levels of plasma C-reactive protein, interleukin-6, and fibrinogen were significantly decreased in the LMWH group. LMWH significantly reduced the mean duration of mechanical ventilation (6.6 days vs. 3.8 days; p < 0.01), the length of ICU stay (8.5 days vs. 5.6 days; p < 0.01) and hospital stay (14.3 days vs. 11.3 days; p < 0.01).

CONCLUSIONS

The addition of LMWH to standard therapy benefits COPD patients with acute exacerbation.

Inverse Association between Cardiac Troponin-I and Soluble Receptor for Advanced Glycation End Products in Patients with Non-ST-Segment Elevation Myocardial Infarction

Interaction of advanced glycation end products (AGEs) with the receptor for advanced AGEs (RAGE) results in activation of nuclear factor kappa-B, release of cytokines, expression of adhesion molecules, and induction of oxidative stress. Oxygen radicals are involved in plaque rupture contributing to thromboembolism, resulting in acute coronary syndrome (ACS). Thromboembolism and the direct effect of oxygen radicals on myocardial cells cause cardiac damage that results in the release of cardiac troponin-I (cTnI) and other biochemical markers. The soluble RAGE (sRAGE) compete with RAGE for binding with AGE, thus functioning as a decoy and exerting a cytoprotective effect. Low levels of serum sRAGE would allow unopposed serum AGE availability for binding with RAGE, resulting in the generation of oxygen radicals and proinflammatory molecules that have deleterious consequences and promote myocardial damage. sRAGE may stabilize atherosclerotic plaques. It is hypothesized that low levels of sRAGE are associated with high levels of serum cTnI in patients with ACS. The main objective of the study was to determine whether low levels of serum sRAGE are associated with high levels of serum cTnI in ACS patients. The serum levels of sRAGE and cTnI were measured in 36 patients with non-ST-segment elevation myocardial infarction (NSTEMI) and 30 control subjects. Serum levels of sRAGE were lower in NSTEMI patients (802.56 ± 39.32 pg/mL) as compared with control subjects (1311.43 ± 66.92 pg/mL). The levels of cTnI were higher in NSTEMI patients (2.18 ± 0.33 μg/mL) as compared with control subjects (0.012 ± 0.001 μg/mL). Serum sRAGE levels were negatively correlated with the levels of cTnI. In conclusion, the data suggest that low levels of serum sRAGE are associated with high serum levels of cTnI and that there is a negative correlation between sRAGE and cTnI.

Effects of pentoxyfilline and heparin on reperfusion injury island skin flaps in rats exposed to tobacco

BACKGROUND

Ischemia-reperfusion injury is believed to be a major cause of transferred skin flap failure. Cigarette smoking is known to be associated with endogenous antioxidant depletion, hypercoagulability, and cutaneous vasoconstriction. This investigation was carried out to study possible effects of pentoxyfilline or heparin on rat skin reperfusion injury under tobacco exposure.

MATERIALS AND METHODS

Thirty-six rats were randomized into two major groups: 18 were exposed to cigarette smoke during a 4 wk period prior to surgery; the remaining 18 underwent a sham smoking procedure. Each group was further divided into three equal subgroups: heparin, pentoxyfilline, and saline solution. One identical skin flap was raised in each animal. The vasculature of the flap was clamped for 3 h and reperfused for 5 min. A venous blood sample was obtained from the flap after reperfusion for serum malondialdehyde (MDA) and myeloperoxidase (MPO) analysis. Flap survival was assessed 7 d after the procedure.

RESULTS

The lipid peroxidation levels and flap necrosis were significantly higher in the cigarette-smoking group skin flaps. There was also a decrease of MPO activity in this group compared with the non-smoking group. Heparin-treated rats had significantly lower MDA levels and showed the most viable percent area among smoking rats.

CONCLUSIONS

These data suggest that heparin had a significant beneficial effect both on flap survival and on the lipid peroxidation reduction after smoke exposure in the rat axial-pattern skin flap subjected to ischemia and reperfusion injury. Pharmacologic therapy may represent an alternative way to counteract tobacco effects in flap surgery in emergency situations.

Heparin and low-molecular weight heparins in thrombosis and beyond

Heparin and its improved version, low-molecular weight heparin (LMWH), are known to exert polypharmacological effects at various levels. Early studies focused on the plasma anti-Xa and anti-IIa pharmacodynamics of different LMWHs. Other important pharmacodynamic parameters for heparin and LMWH, including effects on vascular tissue factor pathway inhibitor (TFPI) release, inhibition of inflammation through NFkappaB, inhibition of key matrix-degrading enzymes, selectin modulation, inhibition of platelet-cancer cell interactions, and inflammatory cell adhesion, help explain the diverse clinical impact of this class of agents in thrombosis and beyond.

Vitamin E Does Not Regress Hypercholesterolemic Atherosclerosis

Background: Suppression of hypercholesterolemic atherosclerosis with vitamin E is associated with reductions in oxidative stress without reductions in serum lipids. The objectives of this study were to determine if (1) vitamin E regresses hypercholesterolemic atherosclerosis; and (2) regression is associated with reductions in serum lipids and aortic oxidative stress. Methods and Results: The studies were conducted in 4 groups of rabbits: group I, control, regular diet (2 months); group II, 0.25% cholesterol diet (2 months); group III, 0.25% cholesterol diet (2 months) followed by regular diet (2 months); and group IV, 0.25% cholesterol diet (2 months) followed by regular diet with vitamin E (40 mg/kg body weight/day) (2 months). Blood samples were collected monthly for the measurement of serum lipids and oxidative stress (chemiluminescent activity of white blood cells [WBC-CL]). Aortas were removed at the end of the protocol for assessment of atherosclerotic lesions, and oxidative stress (malondialdehyde [MDA] and CL). Increases in serum lipids in group II were associated with an increase in oxidative stress and development of atherosclerosis. Serum lipids decreased to a similar extent in groups III and IV but the atherosclerotic lesions increased by 63% and 141% compared to group II. Acceleration of atherosclerosis in the rabbits on regular diet with or without vitamin E was associated with practically no change in the oxidative stress. Conclusion: These results suggest that (1) regular diet following a high-cholesterol diet decreased oxidative stress but did not induce regression of atherosclerosis; (2) vitamin E did not produce regression; and (3) regular diet with vitamin E following a high-cholesterol diet was not associated with an increase in oxidative stress but produced acceleration of atherosclerosis.

Chemically modified heparin inhibits mesangial cell proliferation induced by high glucose through interfering with the cell cycle

The aims of this study were to investigate whether chemically modified non-anticoagulation heparin derivate (Periodate-Oxidized/Borohydride-Reduced modified heparin (OR-heparin)) can inhibit high glucose-induced human mesangial cell proliferation and its influence on the cell cycle. OR-heparin with low anticoagulation activity inhibited high glucose-induced early proliferation in a dose-dependent manner. OR-heparin released high glucose-arrested mesangial cells at G(1) phase, and dose-dependently increased S phase. OR-heparin also inhibited high glucose-activated ERK1/2 phosphorylation, induced p27(Kip1) expression, and suppressed reactive oxygen species (ROS) accumulation in a dose-dependent manner. Our results suggest that OR-heparin releases high glucose-arrested cells on G(1) phase and inhibits high glucose-induced mesangial cell proliferation through blocking ERK1/2 phosphorylation and delaying S phase progression, which may be in correlation with OR-heparin suppressing ROS accumulation.

Influence of hypersulfated and low molecular weight heparins on ischemia/reperfusion: injury and allograft rejection in rat kidneys

The aim of the study was to evaluate the effect of the hypersulfated nonanticoagulant heparin derivative LU 51198 (LU) and of the low molecular weight heparin reviparin (REVI) on ischemia/reperfusion (I/R) injury, acute rejection (AR) and chronic allograft nephropathy (CAN) in rats. Organs were harvested 5 days after 60 min of renal I/R injury. For investigation of AR and CAN we used the allogeneic Fisher-Lewis model. Kidneys were harvested at one respectively 32 weeks after transplantation. Rats were treated with either vehicle, LU or REVI. After I/R injury, treatment with REVI or LU reduced infiltration with MHC II and R73-positive cells, whereas only REVI reduced ED1-positive cells and expression of monocyte chemoattractant protein-1. There was no effect of REVI and LU on acute allograft rejection. Treatment with LU or REVI reduced glomerular infiltration with ED1 and MHCII-positive cells and renal expression of transforming growth factor-beta 32 weeks after transplantation. Only REVI treatment reduced albuminuria, interstitial infiltration and histological signs of CAN. LU, and in a more potent manner REVI, reduce signs of CAN and renal inflammation after I/R injury. Chemically modified heparins without anticoagulatory effects may offer a new treatment option in preventing I/R injury and CAN in human kidney transplantation.

Endothelial cell injury by high glucose and heparanase is prevented by insulin, heparin and basic fibroblast growth factor

BACKGROUND

Uncontrolled hyperglycemia is the main risk factor in the development of diabetic vascular complications. The endothelial cells are the first cells targeted by hyperglycemia. The mechanism of endothelial injury by high glucose is still poorly understood. Heparanase production, induced by hyperglycemia, and subsequent degradation of heparan sulfate may contribute to endothelial injury. Little is known about endothelial injury by heparanase and possible means of preventing this injury.

OBJECTIVES

To determine if high glucose as well as heparanase cause endothelial cell injury and if insulin, heparin and bFGF protect cells from this injury.

METHODS

Cultured porcine aortic endothelial cells were treated with high glucose (30 mM) and/or insulin (1 U/ml) and/or heparin (0.5 microg/ml) and /or basic fibroblast growth factor (bFGF) (1 ng/ml) for seven days. Cells were also treated with heparinase I (0.3 U/ml, the in vitro surrogate heparanase), plus insulin, heparin and bFGF for two days in serum free medium. Endothelial cell injury was evaluated by determining the number of live cells per culture and lactate dehydrogenase (LDH) release into medium expressed as percentage of control.

RESULTS

A significant decrease in live cell number and increase in LDH release was found in endothelial cells treated with high glucose or heparinase I. Insulin and/or heparin and/or bFGF prevented these changes and thus protected cells from injury by high glucose or heparinase I. The protective ability of heparin and bFGF alone or in combination was more evident in cells damaged with heparinase I than high glucose.

CONCLUSION

Endothelial cells injured by high glucose or heparinase I are protected by a combination of insulin, heparin and bFGF, although protection by heparin and/or bFGF was variable.

New insights into the molecular biology of the glomerular filtration barrier and associated disease. Review Article

The glomerular filtration barrier of the kidney can no longer be considered as an inert and adynamic structure, viewed by electron microscopy. Molecular biology, medical genetics and protein chemistry have enabled us to further understand the complex structure and function of this highly specialized barrier of the kidney. Minor aberrations of physiology can lead to fatal disease. Recent advances in the understanding of the physiology of endothelial cells, glomerular epithelial cells and the glomerular basement membrane and its components, and how these relate to disease, will be considered systematically.

Heparin improves organ microcirculatory disturbances in caerulein-induced acute pancreatitis in rats

AIM: Microcirculatory disturbances are important early pathophysiological events in various organs during acute pancreatitis. The aim of the study was to evaluate changes in microperfusion of the pancreas, liver, kidney, stomach, colon, skeletal muscle, and to investigate the influence of heparin on the organ microcirculation in caerulein-induced experimental acute pancreatitis.

METHODS: Acute pancreatitis was induced by 4 intraperitoneal injections of caerulein (Cn) (15 μg/kg). The organ microcirculation was measured by laser Doppler flowmetry. Serum interleukin 6 and hematocrit levels were analysed.

RESULTS: Acute pancreatitis resulted in a significant drop of microperfusion in all examined organs. Heparin administration (2 ± 2.5 mg/kg) improved the microcirculation in pancreas (36.9% ± 4% vs 75.9% ± 10%), liver (56.6% ± 6% vs 75.2% ± 16%), kidney (45.1% ± 6% vs 79.3% ± 5%), stomach (65.2% ± 8% vs 78.1% ± 19%), colon (69.8% ± 6% vs 102.5% ± 19%), and skeletal muscle (59.2% ± 6% vs 77.9% ± 13%). Heparin treatment lowered IL-6 (359.0 ± 66 U/mL vs 288.558 U/mL) and hematocrit level (53% ± 4% vs 46% ± 3%).

CONCLUSION: Heparin administration has a positive influence on organ microcirculatory disturbances accompanying experimental Cn-induced acute pancreatitis.

Complications of endoscopic sphincterotomy: can heparin prevent acute pancreatitis after ERCP?

BACKGROUND

An exploratory analysis of a prospective study of risk factors for acute pancreatitis after ERCP combined with endoscopic sphincterotomy showed that the frequency of acute pancreatitis was lower in patients who received heparin compared with patients not treated with heparin. The study was continued to further analyze the effect of heparin on the frequency of acute pancreatitis.

METHODS

Potential risk factors for acute pancreatitis and outcomes were evaluated prospectively for all ERCP procedures with endoscopic sphincterotomy performed between September 1994 and December 1998. The results were analyzed by univariate and multivariate methods to determine risk factors for complications. Heparin was administered to 32.9% of the patients (heparin group [HEP group], n = 268) for various clinical reasons (low-molecular-weight heparin, n = 208, unfractionated heparin n = 60). A group of 547 patients who did not receive heparin served as control patients (CON group).

RESULTS

Eight hundred fifteen patients underwent ERCP with endoscopic sphincterotomy; acute pancreatitis occurred in 6.4% (n = 52). The frequency of acute pancreatitis was significantly lower in the HEP group versus the CON group in the final multivariate model, which included significant risk factors for acute pancreatitis (HEP group: 3.4%, 9/268 vs. CON group: 7.9%, 43/547; p = 0.005). HEP did not increase the risk of hemorrhage (HEP group: 1.1%, 3/268, 2 severe, none fatal vs. CON group: 2.0%, 11/547, 3 severe, 2 fatal). HEP (p = 0.005; OR 0.3: 95% CI [0.16, 0.73]) and the number of risk factors present (p = 0.0001; OR 2.5: 95% CI [1.80, 3.50]) influenced the frequency of acute pancreatitis independently.

CONCLUSIONS

Heparin was significantly associated with an extremely low frequency of post-ERCP pancreatitis without increasing the risk of hemorrhage after endoscopic sphincterotomy. Because this effect could not be attributed to other known or suspected confounders, our conclusion was that heparin administration before ERCP reduces the risk of pancreatitis.

New developments in the treatment of inflammatory bowel disease

Therapy of inflammatory bowel disease (IBD) is rapidly changing with the advent of new discoveries in disease pathogenesis. The need for targeted therapies against the uncontrolled immuno-inflammatory reaction in IBD together with a prerequisite for minimal side effects is driving improvement in old medicines and is leading to the development of new drugs. This review introduces emerging changes in IBD treatment, such as improvements in conventional IBD medications or their use. Balsalazide, budesonide and changes in the use of 5-aminosalicylate (5-ASA) products and purine analogues, such as azathioprine, are discussed. Additionally, studies examining the role of drugs newly introduced into IBD therapy, such as mycophenolate mofetil (MMF), thalidomide and heparin, are stated. Emerging biological therapies, such as therapies against TNF, therapies to enhance anti-inflammatory cytokines, therapeutic manoeuvres to disrupt immune cell trafficking, anti-oxidant therapies, as well as non-conventional treatments, such as diet therapies, prebiotics and probiotics, and helminth therapies are discussed.

Heparin and the nonanticoagulant N-acetyl heparin attenuate capillary no-reflow after normothermic ischemia of the lung

BACKGROUND

Ischemia-reperfusion injury of the lung frequently occurs after cardiopulmonary bypass, after pulmonary thromboendarterectomy, and especially after lung transplantation. Heparin is known to be protective in ischemia-reperfusion injury, but the risk for bleeding disorders may restrict its use in a variety of diseased conditions. Therefore, we tested the efficiency of nonanticoagulant N-acetyl (NA) heparin to protect from postischemic reperfusion injury of the lung.

METHODS

Pentobarbital-anesthetized, mechanically ventilated Lewis rats were heparinized (100 IU/kg) before insertion of catheters. Additionally, animals received either heparin (200 IU/kg; n = 7), NA heparin (1.1 mg/kg; n = 7), or saline (control, n = 7) before ischemia. After normothermic ischemia for 50 minutes, the left lung was reperfused for 120 minutes, or until the death of the animal. The nonischemic right lung was excluded after 10 minutes of reperfusion.

RESULTS

Survival rate at 120 minutes of reperfusion was 7 of 7 and 6 of 7 in the heparin and the NA-heparin group, but 0 in 7 in the control group (p < 0.01). At 30 minutes of reperfusion, PaO2, blood flow through the ascending aorta and mean systemic blood pressure were also significantly higher in the heparin and the NA-heparin group when compared with the control group (p < 0.05). Pulmonary vascular resistance was significantly lower in the heparin and the NA-heparin groups, and histologic examination of the lungs from these groups confirmed reperfusion of nutritive alveolar capillaries by the presence of red blood cells. Lack of red blood cells in the alveolar capillaries of lung specimens from the control group indicated failure of capillary reperfusion.

CONCLUSIONS

Heparin and NA heparin exert similar protection against capillary no-reflow after normothermic ischemia of the lung. This implies that the protective effect of heparin is mediated by properties different from its anticoagulant activity. Thus the nonanticoagulant N-acetyl heparin may pose a safe new therapeutic approach in lung ischemia-reperfusion injury without increasing the risk of hemorrhagic complications.

Treatment of chronic renal allograft rejection in rats with a low-molecular-weight heparin (reviparin)

BACKGROUND

Low-molecular-weight heparin (LMWH) has been shown to prolong survival of rat cardiac allografts independently from immunosuppressive treatment. Furthermore, long-term treatment reduces the development of chronic graft vascular disease after experimental heart transplantation. The aim of the present study was to determine whether treatment with the LMWH reviparin has a beneficial effect on chronic rejection in a rat renal allograft model.

METHODS

Kidneys of Fisher (F344) rats were transplanted into unilaterally nephrectomized Lewis (LEW) recipients. LEW-->LEW isografts served as controls. Animals were treated with cyclosporine (5 mg/kg/d) for the first 10 days. Nephrectomy of the remaining kidney was performed after 10 days. Allografted animals were treated either with reviparin (2 mg/kg/d subcutaneously) for 24 weeks (Allo-24), from week 12 to 24 (Allo-12), or with vehicle for 24 weeks. Proteinuria was determined at regular intervals. Kidneys were harvested after 24 weeks for histomorphological and immunohistochemical evaluation.

RESULTS

No major bleeding complications were observed in reviparin-treated animals. Proteinuria was significantly reduced in allografted animals both by early as well as by late-onset treatment with reviparin. Transplant glomerulopathy was diminished in Allo-24 and in Allo-12 groups compared to vehicle-treated animals, whereas tubulointerstitial inflammation was influenced only in animals immediately treated with reviparin. Immunohistochemical studies demonstrated a marked reduction of renal monocyte and T-cell infiltration as well as expression of MHC II by treatment with reviparin.

CONCLUSIONS

Treatment with the LMWH reviparin significantly improved chronic renal allograft rejection in the F344-to-LEW rat model, both after early and late start of therapy. Although the exact mechanisms of this beneficial effect remain unclear, our data offer a potential new therapeutical approach for prevention of chronic allograft nephropathy.

Heparin in the treatment of burns: a review

Burns are difficult to treat, wounds with complex local and systemic pathology and high mortality, that often heal slowly with scars and contractures. Glycosaminoglycans (GAGs) have been used in parenteral and topical application studies. These studies have uncovered anticoagulative, antiinflammatory and neoangiogenic properties, which may stimulate tissue repair and reepithelializing effects. The endogenous GAGs utilized in treating burns are heparin, dermatan sulfate, heparan sulfate, keratin sulfate, chondroitin-4- and chondroitin-6-sulfate, and hyaluronic acid. Heparin, the most sulfated and acidic GAG, has been used parenterally, topically, by inhalation, in pellet, and in bioengineered membranes. Heparin relieved pain, inhibited clotting and inflammation, restored blood flow, and enhanced healing. Heparin effects that improved and reduced burn care were time, dose, pH, site, source and duration related in studies. Potential adverse effects with heparin use are bleeding, thrombocytopenia and allergy. Heparin preserved lung and improved function. Heparin preserved intestinal integrity and reduced bacterial translocation. Collagen restoration was enhanced. The healed skin was smooth. Heparin reduced needs for pain medicine, topical antibiotics, resuscitation fluids, blood, water baths, debridement, surgery and grafts. Cost of treatments were reduced. Although not as yet fully substantiated, topical heparin therapy of burns may be a useful addition to the range of available treatments for burn wounds.

Protective effect of defibrotide on perfusion induced endothelial damage

In the present study, in vitro effects of Defibrotide (D) on perfusion-induced changes in the morphology of endothelium were investigated by scanning (SEM) and transmission (TEM) electron microscope. Human umbilical cord veins were incubated or perfused with platelet-rich plasma alone (PRP) or platelet-rich plasma with Defibrotide (PRP+D) at 3ml/min or 14ml/min and the changes observed were compared. SEM examination of luminal surfaces demonstrated that perfusion with high flow rates may damage endothelial cells and lead to morphological changes which may be prevented by the presence of Defibrotide in the perfusate. Also, the marked reduction in the number of adhered platelets on luminal surface of veins incubated or perfused with Defibrotide compared to veins treated with platelet-rich plasma only revealed that Defibrotide has anti-thrombotic effects. TEM examination of ruthenium red (RR) stained thin sections of veins demonstrated that perfusion disrupts the glycosaminoglcan (GAG) coat on endothelial cells. But the presence of D in the perfusate preserves the integrity of GAG, indicating further cytoprotective effects of the drug on endothelium.

Brief ex vivo perfusion with heparinized and/or citrated whole blood enhances tolerance of free muscle flaps to prolonged ischemia

This study investigated the use of heparinized and/or citrated whole blood as a perfusate for enhancing muscle tolerance to warm ischemia. Unilateral cutaneous trunci muscle flaps were harvested from Sprague-Dawley rats and stored for 10 hr at 22-24 degrees C prior to transplantation to the groin. One group served as a non-perfused control. In three experimental groups, the flaps were hand-perfused ex vivo with 1.0 ml of heparinized, citrated, or heparinized and citrated autogenous whole blood at physiological pressures. Perfusion was administered over a 10-min period 5 hr into the ischemic period. Flaps were revascularized on the femoral vessels and then harvested 48 hr following revascularization. Tissue injury was assessed by calculation of flap weight change (indicator of tissue edema), histochemical evaluation of muscle dehydrogenase activity (nitroblue tetrazolium assay), and light microscopy. All perfused groups had significantly higher muscle dehydrogenase activity compared with non-perfused controls (P < 0.005). Perfusion with combined heparin-citrated blood was significantly more protective than perfusion with either anticoagulant alone (P < 0.025). The only statistically significant reduction in percent flap edema was seen in the combined heparin-citrate perfusion of flaps compared with nonperfused controls (P < 0.05). Histologic evaluation confirmed a reduction in tissue edema in the perfused flaps. We conclude that mid-ischemic perfusion with heparinized and/or citrated blood limits the deleterious effects of extended warm ischemia.

Glomerular heparan sulfate alterations: mechanisms and relevance for proteinuria

Heparan sulfate (HS) is the anionic polysaccharide side chain of HS proteoglycans (HSPGs) present in basement membranes, in extracellular matrix, and on cell surfaces. Recently, agrin was identified as a major HSPG present in the glomerular basement membrane (GBM). An increased permeability of the GBM for proteins after digestion of HS by heparitinase or after antibody binding to HS demonstrated the importance of HS for the permselective properties of the GBM. With recently developed antibodies directed against the GBM HSPG (agrin) core protein and the HS side chain, we demonstrated a decrease in HS staining in the GBM in different human proteinuric glomerulopathies, such as systemic lupus erythematosus (SLE), minimal change disease, membranous glomerulonephritis, and diabetic nephropathy, whereas the staining of the agrin core protein remained unaltered. This suggested changes in the HS side chains of HSPG in proteinuric glomerular diseases. To gain more insight into the mechanisms responsible for this observation, we studied GBM HS(PG) expression in experimental models of proteinuria. Similar HS changes were found in murine lupus nephritis, adriamycin nephropathy, and active Heymann nephritis. In these models, an inverse correlation was found between HS staining in the GBM and proteinuria. From these investigations, four new and different mechanisms have emerged. First, in lupus nephritis, HS was found to be masked by nucleosomes complexed to antinuclear autoantibodies. This masking was due to the binding of cationic moieties on the N-terminal parts of the core histones to anionic determinants in HS. Second, in adriamycin nephropathy, glomerular HS was depolymerized by reactive oxygen species (ROS), mainly hydroxyl radicals, which could be prevented by scavengers both in vitro (exposure of HS to ROS) and in vivo. Third, in vivo renal perfusion of purified elastase led to a decrease of HS in the GBM caused by proteolytic cleavage of the agrin core protein near the attachment sites of HS by the HS-bound enzyme. Fourth, in streptozotocin-induced diabetic nephropathy and during culture of glomerular cells under high glucose conditions, evidence was obtained that hyperglycemia led to a down-regulation of HS synthesis, accompanied by a reduction in the degree of HS sulfation.

Inhibition of glomerular cell apoptosis by heparin

BACKGROUND

Heparin, the multifunctional glycosaminoglycan, has been considered a therapeutic agent for glomerular diseases. Although a number of biological properties are postulated to explain its therapeutic utility, it is unknown whether heparin affects cell survival in the glomerulus. In this report, we investigated the effect of heparin on apoptosis of glomerular cells.

METHODS

Cultured rat mesangial cells were pretreated with heparin or heparan sulfate proteoglycan (HSPG) and were exposed to proapoptotic stimuli. To examine an effect of heparin on spontaneous apoptosis that occurs in explanted glomeruli, isolated rat glomeruli were incubated in the presence or absence of heparin. Apoptosis was evaluated by Hoechst 33258 staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, and agarose gel electrophoresis to detect DNA fragmentation. The effect of heparin on activator protein 1 (AP-1), a crucial mediator for oxidant-induced apoptosis, was examined by Northern blot analysis and a reporter assay.

RESULTS

Heparin and HSPG inhibited apoptosis of mesangial cells triggered by hydrogen peroxide. It was associated with blunted expression of c-fos/c-jun mRNAs and suppression of AP-1 activation. The cytoprotective effect of heparin was also observed in other cell types and in apoptosis triggered by different stimuli. That is, (a) heparin inhibited mesangial cell apoptosis induced by staurosporine, pyrrolidine dithiocarbamate, and ultraviolet light, and (b) heparin suppressed oxidant-induced apoptosis of NRK49F fibroblasts and Madin-Darby canine kidney epithelial cells. Furthermore, heparin attenuated spontaneous apoptosis of podocytes in explanted glomeruli.

CONCLUSIONS

These results indicate the novel potential of heparin as an inhibitor of apoptosis in several cell types, including glomerular cells.

Oxidative modification of apolipoprotein E in human very-low-density lipoprotein and its inhibition by glycosaminoglycans

The mechanism of metal ion-catalyzed oxidative modification of apolipoprotein E (apoE) in human very-low-density lipoprotein (VLDL) and its inhibition by glycosaminoglycan (GAG) was investigated in vitro. The VLDL oxidation catalyzed by Cu2+ led to the lipid peroxidation, the formation of aggregates, and covalent modification of apoE. The modified apoE lost heparin-binding activity. These results suggest that the lipid peroxidation of VLDL and modification of apoE cause impairment of lipid uptake by cells and deposit the oxidized lipids in the tissues. The lipid peroxidation and oxidative modification of apoE in VLDL mediated by Cu2+ and an aqueous radical generator were suppressed by GAG, heparan sulfate, heparin, and chondroitin sulfate A, even though GAGs demonstrated no ability to scavenge alpha,alpha-diphenyl-beta-picrylhydrazyl radical. There were no relationships between inhibitory activity of GAGs in the VLDL oxidation and their number of sulfate groups which possess chelating activity of metal ion. Therefore, it can be considered that the inhibition of VLDL oxidation by GAGs is possibly due to the interaction between GAG and VLDL which bring about the steric hindrance, interference with the reaction between VLDL particle and the reactive oxygen species. These studies suggest that GAGs preserve the biological functions of apoE from oxidative stress.

The concept of glomerular self-defense

The balance between local offense factors and defense machinery determines the fate of tissue injury: progression or resolution. In glomerular research, the most interest has been on the offensive side, for example, the roles of leukocytes, platelets, complement, cytokines, eicosanoids, and oxygen radical intermediates. There has been little focus on the defensive side, which is responsible for the attenuation and resolution of disease. The aim of this review is to address possible mechanisms of local defense that may be exerted during glomerular injury. Cytokine inhibitors, proteinase inhibitors, complement regulatory proteins, anti-inflammatory cytokines, anti-inflammatory eicosanoids, antithrombotic molecules, and extracellular matrix proteins can participate in the extracellular and/or cell surface defense. Heat shock proteins, antioxidants, protein phosphatases, and cyclin kinase inhibitors may contribute to the intracellular defense. This article outlines how the glomerulus, when faced with injurious cells or exposed to pathogenic mediators, defends itself via the intrinsic machinery that is brought into play in resident glomerular cells.

Binding of xanthine oxidase to vascular endothelium. Kinetic characterization and oxidative impairment of nitric oxide-dependent signaling

Concentrations of up to 1.5 milliunits/ml xanthine oxidase (XO) (1.1 micrograms/ml) are found circulating in plasma during diverse inflammatory events. The saturable, high affinity binding of extracellular XO to vascular endothelium and the effects of cell binding on both XO catalytic activity and differentiated vascular cell function are reported herein. Xanthine oxidase purified from bovine cream bound specifically and with high affinity (Kd = 6 nM) at 4 degreesC to bovine aortic endothelial cells, increasing cell XO specific activity up to 10-fold. Xanthine oxidase-cell binding was not inhibited by serum or albumin and was partially inhibited by the addition of heparin. Pretreatment of endothelial cells with chondroitinase, but not heparinase or heparitinase, diminished endothelial binding by approximately 50%, suggesting association with chondroitin sulfate proteoglycans. Analysis of rates of superoxide production by soluble and cell-bound XO revealed that endothelial binding did not alter the percentage of univalent reduction of oxygen to superoxide. Comparison of the extent of CuZn-SOD inhibition of native and succinoylated cytochrome c reduction by cell-bound XO indicated that XO-dependent superoxide production was occurring in a cell compartment inaccessible to CuZn-SOD. This was further supported by the observation of a shift of exogenously added XO from extracellular binding sites to intracellular compartments, as indicated by both protease-reversible cell binding and immunocytochemical localization studies. Endothelium-bound XO also inhibited nitric oxide-dependent cGMP production by smooth muscle cell co-cultures in an SOD-resistant manner. This data supports the concept that circulating XO can bind to vascular cells, impairing cell function via oxidative mechanisms, and explains how vascular XO activity diminishes vasodilatory responses to acetylcholine in hypercholesterolemic rabbits and atherosclerotic humans. The ubiquity of cell-XO binding and endocytosis as a fundamental mechanism of oxidative tissue injury is also affirmed by the significant extent of XO binding to human vascular endothelial cells, rat lung type 2 alveolar epthelial cells, and fibroblasts.

Hydroxyl radicals depolymerize glomerular heparan sulfate in vitro and in experimental nephrotic syndrome

Heparan sulfate, the polysaccharide side chain of heparan sulfate proteoglycan, is important for the permselective properties of the glomerular basement membrane. In this report, we show a role for hydroxyl radicals in heparan sulfate degradation and an enhanced glomerular basement membrane permeability. First, in enzyme-linked immunosorbent assay, exposure of coated heparan sulfate (proteoglycan) to reactive oxygen species resulted in a +/-50% decrease of binding of a monoclonal antibody against heparan sulfate, whereas binding of an antibody against the core protein remained unaltered. Second, on polyacrylamide gel electrophoresis, the molecular weight of heparan sulfate exposed to radicals was reduced which indicates depolymerization. Both in enzyme-linked immunosorbent assay and gel electrophoresis, hydroxyl radicals are instrumental for heparan sulfate degradation as shown by the addition of various radical scavengers. Third, in an experimental model for human nephrotic syndrome (Adriamycin nephropathy in rats), glomerular basement membrane staining of two recently described anti-heparan sulfate antibodies (JM403 and KJ865) was reduced by 24 and 43%. Treatment of Adriamycin-exposed rats with the hydroxyl radical scavenger dimethylthiourea both reduced albuminuria by 37% (p < 0.01) and partly prevented loss of heparan sulfate staining by 53% (JM403) and 39% (KJ865) (p < 0.03). In contrast to the heparan sulfate side chains, the core protein expression and the extent of glycanation did not change in Adriamycin nephropathy. We conclude that glomerular basement membrane heparan sulfate is susceptible to depolymerization by hydroxyl radicals leading to loss of glomerular basement membrane integrity and albuminuria.

Hemostatic-endothelial interactions: a potential anticoagulant role of the endothelium in the pulmonary circulation during cardiac surgery

The use of extracorporeal circulation during cardiopulmonary bypass (CPB) procedures is associated with significant morbidity and mortality. Exposure of blood to the foreign surface of the extracorporeal circuit results in activation of complement, kinin, fibrinolytic and coagulation systems as well as cellular mediators of inflammation. Without the use of anticoagulants, the extracorporeal circuit would clot; high-dose heparin prevents coagulation, but activation of the coagulation system and consequent thrombin generation still occur. During CPB, the lungs are effectively removed from the circulation, and, hence, heparinized blood remains static within the pulmonary vasculature for this period. It was postulated that under these conditions, the hemostatic system may become activated and could contribute to pulmonary dysfunction in some patients after CPB. However, it appears that during CPB interactions among heparin, the hemostatic system, and the endothelium may exert a protective effect, at least against activation of the tissue factor coagulation pathway. In this article, the effect of CPB on the coagulation system, with particular reference to changes in coagulation proteins occurring in the pulmonary vasculature, are reviewed.

High-dose heparin decreases nitric oxide production by cultured bovine endothelial cells

BACKGROUND

Abrupt cessation of heparin therapy can lead to a recrudescence of thrombosis and acute ischemia. Endothelial NO is an important endogenous inhibitor of platelet-mediated thrombosis, yet biochemical studies examining the effect of heparin on NO production by the endothelium have heretofore been lacking.

METHODS AND RESULTS

In an attempt to address the effect of heparin on endothelial cell production of NO, confluent bovine aortic endothelial cells (BAECs) on microcarrier beads were incubated in the presence or absence of heparin. Results indicate that BAECs incubated with heparin were less able to inhibit platelet aggregation than control cells (P<.005 by ANOVA) and that this effect correlated with a decrease in NO production (36% decrease for heparin compared with control, P<.05). Dextran sulfate evoked the same response (67% decrease, P<.0001 compared with control), suggesting that the decrease in NO after heparin treatment is secondary to its negative charge rather than to a specific polysaccharide sequence. The decrease in NO production by heparin was accompanied by a 72% decrease in steady-state Nos 3 mRNA as well as a 49% decrease in immunodetectable endothelial NO synthase (eNOS) protein.

CONCLUSIONS

These data show that high-dose heparin at concentrations achieved in some acute cardiovascular settings increases in vitro platelet aggregation in media conditioned by endothelial cells by decreasing endothelial NO production through a mechanism that involves a decrease in steady-state Nos 3 mRNA and eNOS protein. These observations suggest a possible mechanism by which to explain in part the prothrombotic effects of heparin.

Xanthine oxidase binding to glycosaminoglycans: kinetics and superoxide dismutase interactions of immobilized xanthine oxidase-heparin complexes

Xanthine oxidoreductase (XDH + XO, EC 1.2.3.2) is released into the circulation from organs rich in XO activity. Herein we report the specific high affinity binding of XO to glycosaminoglycans (GAGs) and the preferential association of XO with heparin, compared with heparan sulfate, chondroitin sulfate, and dematan sulfate. The binding of XO to Sepharose 6B-conjugated heparin (HS6B) occurs at physiological ionic strength and increased with pH, with Scatchard analysis revealing a nonlinear binding pattern at pH 7.4. The dissociation constant (Kd) for XO binding was 0.4 to 1.8 x 10(-7) M, similar to the heparin-reversible binding of lipoprotein lipase to vascular endothelium. The binding energy of 9-13 kcal/mol was concordant with noncovalent electrostatic interactions. Xanthine oxidase immobilization to HS6B rendered a catalytically active enzyme from that had kinetic characteristics distinct from XO in free solution. While the Km and Ki for xanthine in phosphate buffer at pH 7.4 were 3 microM and 1.6 mM, respectively, for free XO, they were 15 microM and 2.8 mM for immobilized XO. Inhibition constants for guanine and uric acid were also increased upon XO binding to HS6B. Changes in kinetic parameters were related to a real and not apparent decrease in binding affinity for substrate and inhibitors and were not due to diffusion-controlled processes within the gel matrix. Changes in Km and Ki for xanthine also had a significant influence on the relative quantities of O2.- and H2O2 generated by a given substrate concentration. Superoxide formed by HS6B-bound XO was partially consumed within the gel microenvironment which electrostatically excluded CuZn SOD. Immobilization of XO increased the half-life of enzyme activity in buffer and in the absence of substrate from 67 to 120 h at 4 degrees C. These data indicate that binding to cell surfaces will strongly influence the catalytic properties, oxidant producing capacity, and stability of XO.

Unfractionated heparin and low molecular weight heparin do not inhibit the growth of proliferating human arterial smooth muscle cells in culture

OBJECTIVES

To clarify the effects of unfractionated heparin (UH) and low molecular weight heparin (LMWH) on proliferating human smooth muscle cells (SMC) compared to growth arrested SMC.

DESIGN

A cell culture study where proliferating SMC were exposed to different concentrations of UH and LMWH and the effect on proliferation and collagen secretion was studied. Growth arrested SMC were stimulated with serum and the effect of UH on proliferation was measured.

SETTING

Sections of Medical Angiology and Vascular Surgery, Malmö General Hospital, Sweden.

MATERIALS

Human SMC were established from arterial tissue obtained at vascular surgery or at organ donation.

CHIEF OUTCOME MEASURES

Effects of UH and LMWH on total cellular DNA, 3H-thymidine incorporation and collagen secretion using proliferating and growth arrested human SMC in culture.

MAIN RESULTS

In proliferating SMC that had not been growth arrested, 1 and 10 IU/ml UH and LMWH significantly increased total cellular DNA compared to controls while DNA synthesis was not influenced. The higher cellular DNA was probably not a consequence of increased proliferation as DNA synthesis was not affected by UH or LMWH. The increased total cellular DNA could instead be due to reduced cell death. Higher concentrations (10 IU/ml) of UH and LMWH also increased collagen secretion. In control experiments with UH DNA, synthesis was decreased in stimulated human SMC that had been growth arrested previously to heparin exposure.

CONCLUSIONS

The effects of UH and LMWH on SMC proliferation will depend on the proliferative state of the SMC. The results might be of relevance for the understanding of the atherosclerotic process and for pharmacologic interventions to prevent restenosis after angioplasty or surgery.

The effect of anticoagulant choice on apparent total antioxidant capacity using three different methods

We assessed total antioxidant capacity using three different methods, in plasma samples treated with either EDTA or heparin as anticoagulant, from 26 healthy subjects. Total antioxidant capacity was determined using an oxygen electrode (as the total peroxyl radical-trapping antioxidant parameter), by enhanced chemiluminescence, and by measurement of the antioxidant-mediated quenching of the absorbance of a radical cation. The choice of anticoagulant had a profound effect on antioxidant capacity with heparinized plasma giving consistently higher values than plasma anticoagulated with EDTA. Using the oxygen electrode the mean value was 786.5 +/- 171.5 mumol/L (heparin) compared to 681.4 +/- 160.4 mumol/L (EDTA, P < 0.01). The chemiluminescence technique gave a mean antioxidant capacity of 915.6 +/- 214.1 mumol/L in heparin samples and 714.4 +/- 195.4 mumol/L in EDTA samples (P < 0.0001). The absorbance quenching technique gave a mean value of 867.0 +/- 199.2 mumol/L (heparin) and 675.5 +/- 245.4 mumol/L (EDTA, P < 0.001). All methods tested showed comparable results for EDTA plasma, but the chemiluminescence technique gave higher apparent antioxidant capacity than either of the two techniques when heparin plasma was used. We suggest that either heparin is interacting to enhance antioxidant protection perhaps through release of superoxide dismutase, or the chelation of metal ions by EDTA is limiting the activity of antioxidant metalloenzymes. Consistency in the choice of anticoagulant is clearly extremely important.

Intravascular heparin protects muscle flaps from ischemia/reperfusion injury

Heparin has been found to decrease ischemia/reperfusion injury in skeletal muscle and other tissue/organ systems. The timing of heparin administration to the muscle vasculature has not been explored. We investigated the use of heparinized blood as a washout solution during ischemia to reduce ischemia/reperfusion injury. A rat cutaneous maximus muscle free flap was subjected to a 10-hr period of room temperature ischemia, then was heterotopically transplanted to the groin via microsurgical revascularization to the femoral vessels. In three experimental groups, flaps were subjected to brief ex vivo perfusion with autologous heparinized blood, at 2, 5, or 8 hr into the 10-hr ischemic interval. In the two other groups, the flaps were not perfused, and the animals were systemically heparinized either before ischemia or before transplantation, respectively. A control group underwent no flap perfusion or systemic heparinization. After transplantation, flaps were given a 48-hr period of in vivo reperfusion, then were harvested for evaluation. Flaps undergoing ex vivo perfusion or preischemic heparinization had no significant differences in weight gain (edema) compared with flaps receiving posttransplant heparinization or no heparinization (controls). The dehydrogenase staining of muscle biopsies was significantly faster (indicative of viable tissue) for perfused flaps and the flaps for which the animals received preischemic heparinization, when compared with flaps for which the animals received posttransplant heparinization or no heparinization. From these results, we conclude that heparin offers protection from ischemia/reperfusion injury when it can be introduced into the vascular network either prior to or during the ischemia period. These findings suggest the possibility of using heparinized washout solutions to enhance survival in amputated extremities.

Effects of heparin and N-acetyl heparin on ischemia/reperfusion-induced alterations in myocardial function in the rabbit isolated heart

Evidence is presented that heparin pretreatment produces protective effects on myocardial tissue distinct from its anticoagulant activity. The present study examines the ability of heparin sulfate and N-acetyl heparin (a derivative of heparin devoid of anticoagulant effects) to protect the heart from injury associated with global ischemia and reperfusion. Male New Zealand White rabbits were administered either heparin sulfate (n = 7, 300 U/kg i.v.), N-acetyl heparin (n = 6, 1.73 mg/kg i.v.), or vehicle (n = 6). Two hours after treatment, the hearts were removed, perfused on a Langendorff apparatus, and subjected to 30 minutes of global ischemia, followed by 45 minutes of reperfusion. During reperfusion, creatine kinase concentrations in the coronary sinus effluent were greater in hearts from vehicle-treated rabbits compared with hearts from N-acetyl heparin-treated and heparin-treated rabbits. Left ventricular end-diastolic pressure after 45 minutes of reperfusion in the vehicle-treated group was 64 +/- 15 mm Hg compared with 17 +/- 4 and 10 +/- 3 mm Hg in the heparin-pretreated and N-acetyl heparin-pretreated groups, respectively. Heparin, but not N-acetyl heparin, increased the activated partial thromboplastin time, consistent with its known anticoagulant action. Heparin and N-acetyl heparin inhibited complement-mediated erythrocyte lysis in a concentration-dependent manner. The glycosaminoglycans, in contrast to r-hirudin, reduced complement activation-induced injury in the rabbit isolated heart. The results demonstrate that heparin or N-acetyl heparin, administered to the intact rabbit, protects the isolated heart from subsequent myocardial dysfunction secondary to ischemia/reperfusion. The cardioprotective effects of heparin and N-acetyl heparin are independent of an antithrombin mechanism.

Dextran sulphates protect porcine arterial endothelial cells from free radical injury

1. The ability of dextran sulphate to protect cultured porcine arterial endothelial cells injured by addition of xanthine and xanthine oxidase (X/XO) or hydrogen peroxide to cell medium was examined using a variety of drug preparations. Cell damage was assessed by determining cell viability (by trypan blue exclusion) and release of lactate dehydrogenase into the medium. 2. Dextran sulphates of average molecular weight (M(r)) 5000, 8000 (hydrogenated or unhydrogenated) at 0.05, 0.5, 5 and 50 micrograms ml-1 medium, added 24 h prior to X/XO, protected cells, whereas dextran sulphate M(r) 500,000 was protective only at 0.5 microgram ml-1. 3. None of the dextran sulphates used showed any toxic effect on cells in concentrations up to 500 micrograms ml-1 medium. 4. When the duration of pretreatment with dextran sulphate M(r) 8000 was varied, 6 h was required for a protective effect on cells damaged by X/XO, which was enhanced with durations of 16 and 24 h. 5. Dextran sulphates had a similar protective effect on cells damaged by hydrogen peroxide. 6. This study suggest that dextran sulphates may prevent conditions resulting from free radical injury.

Xanthine oxidase activity in the circulation of rats following hemorrhagic shock

Reactive oxygen metabolites generated from xanthine oxidase play an important role in the pathogenesis of ischemia-induced tissue injury. In a hemorrhagic shock model of ischemia-reperfusion, the intracellular enzyme xanthine oxidase was released into the vasculature. This intravascular source of superoxide (O2.-) and hydrogen peroxide (H2O2) interacted reversibly with glycosaminoglycans of vascular endothelium and markedly concentrated xanthine oxidase at cell surfaces, enhancing its ability to produce extensive damage to remote tissues. Rats were made hypotensive by hemorrhage, maintained for 2h, and reinfused with shed blood. Blood samples were obtained prior to hemorrhage and 15, 30, 60, and 90 min after reperfusion for determination of xanthine oxidase (XO), lactate dehydrogenase (LDH), and alanine transaminase (AST). These enzymes were not significantly elevated in control animals. Reperfusion after hemorrhage-induced ischemia resulted in significantly elevated AST and LDH in both low heparin (100 U/h) and high heparin (1000 U/h) groups. Xanthine oxidase was detected in the circulation only after 90 min reperfusion in the low heparin group and was elevated during the entire reperfusion period in the high heparin group. Studies with cultured vascular endothelium showed significant heparin-reversible binding of XO to cellular glycosaminoglycans. These results suggest that XO can gain access to the circulation following ischemia, where it then binds to the vascular endothelial cells to produce site-specific oxidant injury to organs remote from the site of XO release.

Elevated breath pentane in heart failure reduced by free radical scavenger

Pentane, a product of lipid peroxidation, has been detected in situations involving ischemic injury. Such injury may be limited if lipid peroxidation can be controlled by antioxidants. The role of lipid peroxidation in chronic heart failure (CHF) was assessed by measuring breath pentane in patients with CHF vs. age matched controls. The effect of a free radical scavenger on pentane released during CHF was also measured. Pentane levels were correlated with the daily dose of captopril, a sulfhydril-containing drug used to treat CHF, which is an angiotensin converting enzyme inhibitor. To separate the scavenging effects of captopril from the pharmacologic effects of converting enzyme inhibitors, a crossover study using a nonsulfhydril inhibitor was used. Patients with CHF excreted (p < 0.005) high concentrations of pentane (5.7 +/- 2.1 vs. control 3.6 +/- 1.2 nmol/l). Patients treated with captopril also had significantly higher (p < 0.05) excretion of pentane than the control patients (4.7 +/- 1.3 vs. 3.6 +/- 1.2 nmol/l). The dose of captopril was inversely proportional to the concentration of pentane excreted (r = 0.55, p < 0.05). Pentane excretion during captopril therapy was significantly lower before (p < 0.01) and after (p < 0.02) nonsulfhydril inhibitor therapy.

CONCLUSION

breath pentane is elevated in CHF and it can be reduced by a free radical scavenger. This reduction of pentane excretion is not a converting enzyme inhibitor class effect.

Heparin prevents postischemic endothelial cell dysfunction by a mechanism independent of its anticoagulant activity

PURPOSE

Heparin may have protective effects on postischemic vascular endothelial cell function that are distinct from its anticoagulant, antiplatelet, or anticomplement activity. We tested this hypothesis in isolated rat hindlimbs.

METHODS

Isolated rat hindlimbs underwent 60 minutes of normothermic ischemia and 10 minutes of reperfusion. Potential heparin interaction with plasma-based proteins or cells was eliminated by perfusion of the hindlimbs with a nonrecirculated albumin-enriched crystalloid buffer. Endothelial function was assessed by measurement of endothelium-derived relaxing factor (EDRF) activity. Limbs perfused at constant pressure were subjected to increasing log dose infusions of acetylcholine and nitroprusside to measure endothelial-dependent (EDRF-mediated) and endothelial-independent vasoreactivity, respectively. Fifty limbs were divided into seven groups: two nonischemic groups (one with heparin) and five ischemia/reperfusion groups treated with increasing doses of heparin (0 to 1.0 U/ml perfusate).

RESULTS

The nontreated ischemia/reperfusion group (n = 12) had a 46.2% reduction in endothelial-dependent vasodilation of the rat hindlimb when compared with the nonischemic control (n = 7, p < 0.05). Treatment with heparin 0.5 U/ml (n = 6) nearly abolished this attenuation of endothelial-dependent vasodilation (4.3% reduction, p = not significant vs nonischemic control). The endothelial protective effect of heparin was dose-dependent: groups treated with 0.25 U/ml (n = 6) and 0.1 U/ml heparin (n = 7) showed progressive impairment in postischemic EDRF-mediated vasodilation. Endothelial-independent vasodilation induced by nitroprusside was unchanged by ischemia/reperfusion or heparin treatment, which confirmed that the postischemic damage and its protection by heparin were specific to the endothelium.

CONCLUSIONS

Heparin prevented postischemic endothelial cell dysfunction by a mechanism independent of its interactions with plasma-based proteins or cells. This nonanticoagulant protective effect may contribute to the salutary effects of heparinization during acute ischemic events.

ESR-measurement of oxygen radicals in vivo after renal ischaemia in the rabbit. Effects of pre-treatment with superoxide dismutase and heparin

The effects of intracellular and extracellular superoxide dismutase and heparin administration on oxygen radical formation after ischaemia in the rabbit kidney were studied. Radicals were measured with ESR and spin trapping. At reperfusion after 60 min of renal ischaemia there was a significant increase in the production of free radicals in the venous effluent from the kidney. Administration of either intracellular superoxide dismutase or extracellular superoxide dismutase before ischaemia and before reperfusion prevented approximately 85% of the radical formation seen in the untreated control group. Administration of heparin 5 min before recirculation resulted in a 65% decrease in radical production compared to the control group.

Evaluation of colestipol/niacin therapy with computer-derived coronary end point measures. A comparison of different measures of treatment effect

BACKGROUND

The Cholesterol Lowering Atherosclerosis Study has demonstrated beneficial effect of colestipol/niacin on coronary atherosclerosis using a panel-determined global coronary change score. We now report treatment group comparisons using quantitative coronary angiographic (QCA) measures from all processable segments in 85 of 162 randomly selected baseline/2-year film pairs.

METHODS AND RESULTS

Treatment benefit was established for percent stenosis for either continuous or categorical analyses with regression established regardless of the per-patient scoring procedure. In addition, treatment benefit favoring regression was established in some cases for roughness and for percent involvement, a longitudinal estimate of the percent of coronary surface involved by raised lesions. Benefit on minimum diameter was directly related to whether the segment was proximal to a graft insertion and hemodynamically related to the bypass graft. QCA correlates of panel-determined progression were increases in percent stenosis and numbers of occluded lesions in native arteries and the number of progressing lesions in bypass grafts.

CONCLUSIONS

These results demonstrate that a variety of computer measures can be used as end points in coronary angiographic therapy trials, but change in percent stenosis correlates best with visual panel assessments and best reflects the treatment benefit; when treatment effect sizes are moderate to large, the required sample size of coronary angiographic trials can be reduced when QCA is used.

Inhibition by heparin of Fe(II)-catalysed free-radical peroxidation of linolenic acid

Heparin, in a concentration-dependent manner, inhibited the generation of conjugated dienes and thiobarbituric acid-positive substances when incubated with Fe2+ and gamma-linolenic acid. In the conjugated diene assay, other glycosaminoglycans, on a molar basis calculated with respect to their respective hydrated disaccharide repeat units, were less effective than heparin. Heparin which had been re-N-sulphonated after removal of both N-sulphonates and O-sulphates, and heparin in which iduronate residues had been reduced to idose residues, were largely unaffected in their activity. Removal of both N-sulphonates and O-sulphates greatly reduced the effectiveness of the heparin. Analysis of the effects of heparin fragments generated by heparinase I treatment of heparin showed that depolymerization decreased the effectiveness of the heparin. It is possible that heparins and related strongly acidic polysaccharides may function as endogenous antioxidants, and that sequestration by them, or harmless oxidation by them, of ions such as Fe2+, contributes to their effectiveness.

Altering the course of proliferative nephritides: the challenge of the 1990s

There is considerable evidence based on experimental pathology that heparin/heparinoids will benefit the course of the various forms of human proliferative nephritis. An alternative to heparin may be pentosan polysulphate. Another possibility is the infusion of prostaglandin E1 because of its anti-inflammatory and potentially antiproliferative actions. Both these approaches mimic natural pathophysiological control mechanisms.

Heparin: does it act as an antioxidant in vivo?

Previous studies have shown that heparin antagonizes oxygen radical-mediated injury to endothelial cells, suggesting an antioxidant role of the drug. In the present investigation, the hypothesis that heparin exerts direct antioxidant effects was tested in several experimental models. We have found that 1, 3, 5, 10, 20, 40 and 80 U/mL of heparin do not scavenge superoxide anion, hydrogen peroxide, hydroxyl radical or the stable free radical 1,1-diphenyl-2-pycrylhydrazyl. Moreover, the drug is ineffective towards iron-driven linolenic acid peroxidation, autooxidation of brain homogenate and linolenic acid peroxidation mediated by human internal mammary artery homogenate. Specific studies on the potential iron-binding-inactivating capacity of heparin prove the drug to be totally ineffective. Finally, the loss of protein sulphydryls from human plasma induced by hypoxanthine-xanthine oxidase-generated oxygen radicals is not prevented by heparin. In conclusion, heparin, even at concentrations far higher than those usually used therapeutically, has no direct antioxidant properties. Thus, other mechanisms not strictly antioxidant-type must be involved in heparin-mediated cell protection against toxic oxygen metabolites.

Protective role of heparin on in vitro functional aortic response in Watanabe heritable hyperlipidemic rabbits

The effects of prolonged in vivo heparin treatment upon vasomotor responses and content of cholesterol and energy related compounds were studied in isolated thoracic and abdominal aortas from Watanabe heritable hyperlipidemic (WHHL) rabbits. Unfractionated heparin was administered subcutaneously (2 mg/kg twice a day) to 3-month-old WHHL rabbits for a period of 6 months. A group of WHHL rabbits was treated with saline solution and considered as control. Aortic cholesterol infiltration and serum cholesterol were not significantly decreased by the prolonged heparin treatment. In heparin-treated WHHL rabbits, the in vitro aortic endothelium-dependent relaxation produced by acetylcholine or calcimycin (A 23187) was greater than in saline-treated WHHL group. ATP-induced aorta relaxation (endothelium-dependent and endothelium-independent) did not vary significantly in the two groups of WHHL rabbits, even after mechanical removal of endothelium. Also the noradrenaline-induced aorta contraction did not vary between the two groups of WHHL rabbits. No significant variation in energy-related compounds (except for ADP) was found in the aortic arch. These results suggest that heparin produces a protective effect on aortic tissue by acting mainly at endothelial level.

Heparin protects human endothelial cells infected by Rickettsia rickettsii

Routine culture of endothelial cells currently includes the use of heparin, which significantly reduces cell doubling time and increases cell population size. Heparin protects cultured arterial endothelial cells from damage by toxic oxygen metabolites produced by the action of xanthine and xanthine oxidase. Because of our hypothesis implicating free radicals in cell injury caused by Rickettsia rickettsii, we have carried out a series of experiments to examine the effects of heparin on injury to endothelial cells infected by this microorganism. These studies showed that heparin does not inhibit replication of R. rickettsii in the cytoplasm of endothelial cells. Furthermore, heparin appears to exhibit a protective effect on the infected host cell as measured by (i) reduced plaque size, (ii) increased longevity of the cell monolayer, (iii) reduction in the amount of lactic dehydrogenase released from infected cells, and (iv) reduction in the levels of intracellular peroxides formed in infected cells. Electron microscopic studies also show a significant reduction in dilatation of the rough-surfaced endoplasmic reticulum of the infected cells in the presence of heparin. These observations appear to lend additional support to involvement of an oxidative mechanism in human endothelial cell injury caused by R. rickettsii.