Effect of heparin and a low-molecular weight heparinoid on PAF-induced airway responses in neonatally immunized rabbits

Pharmacology of Heparin and Related Drugs

Heparin has been recognized as a valuable anticoagulant and antithrombotic for several decades and is still widely used in clinical practice for a variety of indications. The anticoagulant activity of heparin is mainly attributable to the action of a specific pentasaccharide sequence that acts in concert with antithrombin, a plasma coagulation factor inhibitor. This observation has led to the development of synthetic heparin mimetics for clinical use. However, it is increasingly recognized that heparin has many other pharmacological properties, including but not limited to antiviral, anti-inflammatory, and antimetastatic actions. Many of these activities are independent of its anticoagulant activity, although the mechanisms of these other activities are currently less well defined. Nonetheless, heparin is being exploited for clinical uses beyond anticoagulation and developed for a wide range of clinical disorders. This article provides a "state of the art" review of our current understanding of the pharmacology of heparin and related drugs and an overview of the status of development of such drugs.

Non-anticoagulant derivatives of heparin for the management of asthma: distant dream or close reality?

INTRODUCTION

Approximately 300 million people worldwide are currently affected by asthma. Improvements in the understanding of the mechanisms involved in such inflammatory airway disorders has led to the recognition of new therapeutic approaches. Heparin, a widely used anticoagulant, has been shown to be beneficial in the management of asthma. It belongs to the family of highly sulphated polysaccharides referred to as glycosaminoglycans, containing a heterogeneous mixture of both anticoagulant and non-anticoagulant polysaccharides. Experimental findings have suggested that heparin has potential anti-asthmatic properties owing to the ability of its non-anticoagulant oligosaccharides to bind and modulate the activity of a wide range of biological molecules involved in the inflammatory process.

AREAS COVERED

This review focuses on the potential mechanisms of action and clinical application of heparin as an anti-inflammatory agent for the management of asthma.

EXPERT OPINION

Heparin may play a significant role in the management of asthma. However, these properties are often hindered by the presence of anticoagulant oligosaccharides, which possess a significant risk of bleeding. Therefore, its therapeutic potential must be explored using well-designed clinical studies that focus on identifying and isolating the anti-inflammatory oligosaccharides of heparin and further elucidating the structure and mechanisms of actions of these non-anticoagulant oligosaccharides.

Heparin and related drugs: beyond anticoagulant activity

Heparin has been widely used as an anticoagulant for more than 80 years. However, there is now considerable evidence that heparin also possesses anti-inflammatory activity, both experimentally and clinically. Importantly in many instances, the anti-inflammatory actions of heparin are independent of anticoagulant activity raising the possibility of developing novel drugs based on heparin that retain the anti-inflammatory activity. Heparin exhibits anti-inflammatory activities via a variety of mechanisms including neutralization of cationic mediators, inhibition of adhesion molecules, and the inhibition of heparanase, all involved in leukocyte recruitment into tissues. It is anticipated that furthering our understanding of the anti-inflammatory actions of heparin will lead to the development of novel anti-inflammatory drugs for a variety of clinical indications.

Non-anticoagulant effects of heparin: an overview

Heparin has long been known to possess biological effects that are unrelated to its anticoagulant activity. In particular, much emphasis has been placed upon heparin, or novel agents based upon the heparin template, as potential anti-inflammatory agents. Moreover, heparin has been reported to possess clinical benefit in humans, including in chronic inflammatory diseases and cancer, that are over and above the expected effects on blood coagulation and which in many cases are entirely separable from this role. This chapter aims to provide an overview of the non-anticoagulant effects that have been ascribed to heparin, from those involving the binding and inhibition of specific mediators involved in the inflammatory process to effects in whole system models of disease, with reference to the effects of heparin that have been reported to date in human diseases.

Size-fractionated heparins have differential effects on human neutrophil function in vitro

BACKGROUND AND PURPOSE

Heparin is known to possess a range of activities, other than effects on blood coagulation, many of which are anti-inflammatory. Effects with potential anti-inflammatory applications include the inhibition of elastase release from neutrophils, as well as the adhesion of these cells to vascular endothelium. In the present study we aimed to investigate whether fractionation of heparin may yield molecules with enhanced or specific effects on human neutrophil function.

EXPERIMENTAL APPROACH

Fractions of defined molecular size were obtained from heparin by different methods and assessed for their effects on elastase release induced by formyl Met-Leu-Phe (fMLP), from neutrophils, in some cases following the priming of these cells with tumour necrosis factor-alpha (TNF-alpha). Effects of the fractions on neutrophil adhesion to interleukin-1beta (IL-beta)-stimulated human umbilical vein endothelial cells (HUVECs) were also examined.

KEY RESULTS

Elastase release was inhibited by very low molecular weight fractions of heparin, with an apparent minimum chain length of 10 saccharides required for full effect. In contrast, neutrophil-endothelial adhesion was unaffected by these fractionated heparins, suggesting that certain non-anticoagulant actions of heparin may be lost by such an approach.

CONCLUSIONS AND IMPLICATIONS

These data suggest that an optimum chain length of heparin possibly exists for certain non-anticoagulant actions of heparin, which may prove to be useful in the design of novel drugs with specific anti-inflammatory actions.

Enoxaparin reduces H2O2-induced activation of human endothelial cells by a mechanism involving cell adhesion molecules and nuclear transcription factors

There are data that document the anti-inflammatory effect of enoxaparin (EP) and its possible antioxidant potential. This study was designed to search for the antioxidant mechanism(s) of EP directly on endothelial cells exposed to an oxidant stimulus. For this purpose cultured human endothelial cells were exposed to nontoxic concentrations of hydrogen peroxide in the presence or absence of EP, and the adhesion of monocytes, the expression of cell adhesion molecules and transcription factors possibly involved in the process were tested. Adhesion assays, ELISA and Western blot analysis revealed that EP reduced monocyte adhesion, ICAM-1 and P-selectin expression, decreased the nuclear levels of c-Jun and p65 proteins, and diminished the phosphorylation of c-Jun protein, MAPK p38 and JNK. Together, the data demonstrate the antioxidant effect of EP and the involvement of ICAM-1, P-selectin, MAPK p38, JNK and the transcription factors NF-kappaB and AP-1 in the mechanism of action of this drug.

Hypersensitivity of pulmonary chemoreflex induced by poly-l-lysine: Role of cationic charge

This study was carried out to investigate the role of cationic charge in the hypersensitivity of pulmonary C-fibers induced by airway exposure to synthetic cationic protein poly-L-lysine (PLL) in anesthetized rats. Inhalation of PLL aerosol induced a distinctly irregular breathing pattern, and significantly enhanced the pulmonary chemoreflex responses to capsaicin. However, after the cationic charges were completely removed from PLL by succinylation, the succinylated PLL no longer produced any change in either the baseline breathing pattern or the reflex responses to capsaicin. In addition, the effects of PLL were also abolished after premixing it with a polyanion, poly-L-glutamic or poly-L-aspartic acid, before delivery. In sharp contrast, when delivered within 5 min after the PLL aerosol, these two polyanions were completely ineffective in reversing the effects of PLL. Electrophysiological recording of the afferent activity of single pulmonary C-fibers further supported our conclusion that the cationic charge carried by this protein is primarily responsible for generating the stimulatory and sensitizing effects of PLL on these afferents.

Effects of heparin and related molecules upon neutrophil aggregation and elastase release in vitro

1 Neutrophil-derived elastase is an enzyme implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Heparin inhibits the enzymatic activity of elastase and here we provide evidence for the first time that heparin can inhibit the release of elastase from human neutrophils. 2 Unfractionated and low molecular weight heparins (UH and LMWH, 0.01-1000 U ml(-1)) and corresponding concentrations (0.06-6000 micro g ml(-1)) of nonanticoagulant O-desulphated heparin (ODH), dextran sulphate (DS) and nonsulphated poly-L-glutamic acid (PGA) were compared for their effects on both elastase release from and aggregation of neutrophils. 3 UH, ODH and LMWH inhibited (P<0.05) the homotypic aggregation of neutrophils, in response to both N-formyl-methionyl-leucyl-phenylalanine (fMLP, 10(-6) M) and platelet-activating factor (PAF, 10(-6) M), as well as elastase release in response to these stimuli, in the absence and presence of the priming agent tumour necrosis factor-alpha (TNF-alpha, 100 U ml(-1)). 4 DS inhibited elastase release under all the conditions of cellular activation tested (P<0.05) but had no effect on aggregation. PGA lacked efficacy in either assay, suggesting general sulphation to be important in both effects of heparin on neutrophil function and specific patterns of sulphation to be required for inhibition of aggregation. 5 Further investigation of the structural requirements for inhibition of elastase release confirmed the nonsulphated GAG hyaluronic acid and neutral dextran, respectively, to be without effect, whereas the IP(3) receptor antagonist 2-aminoethoxydiphenylborate (2-APB) mimicked the effects of heparin, itself an established IP(3) receptor antagonist, suggesting this to be a possible mechanism of action.

Novel drug development opportunities for heparin

The glycosaminoglycan heparin has been used in the clinic as an anticoagulant for more than 50 years. A fully characterized sequence in native heparin is known to be responsible for this activity. However, heparin is a complex polysaccharide, which has an array of properties that are unrelated to its anticoagulant activity. Recent research has provided us with an increased understanding of the specific structural requirements for the various actions of heparin, indicating that it might be possible to create 'tailor-made' sequences based on the heparin template to isolate specific therapeutic activities. This research should provide the basis for novel drug treatments for a range of diseases, including cancer and various inflammatory diseases.

Modulation of airway responsiveness by anionic and cationic polyelectrolyte substances

To elucidate the effects of anionic and cationic polyelectrolyte substance on bronchoconstriction, we examined the serial changes in respiratory resistance (Rrs) in ovalbumin-sensitized guinea pigs after antigen exposure with or without pre-inhalation of low-molecular-weight heparin, poly-L-glutamic acid, poly-L-lysine and dextran, and with or without oral intake of dalteparin. Both immediate and late responses after antigen exposure were significantly decreased after pretreatment with inhaled low-molecular-weight heparin and poly-L-glutamic acid compared with saline alone. The late response was significantly decreased after pretreatment with oral dalteparin. Both low-molecular-weight heparin and poly-L-glutamic acid significantly decreased the airway response to methacholine in sensitized guinea pigs. In sensitized guinea pigs, the airway response to methacholine was significantly increased after pretreatment with inhaled poly-L-lysine. Pretreatment with inhaled low-molecular-weight heparin before poly-L-lysine exposure significantly suppressed the airway hyperresponsiveness after inhaled poly-L-lysine. These findings indicated that the "cationic-anionic interaction" plays an important role in airway responsiveness.

Heparin inhibits hyperventilation-induced late-phase hyperreactivity in dogs

Inhalation of heparin attenuates hyperventilation-induced bronchoconstriction in humans and dogs. The purpose of this study was to determine whether heparin inhibits the late-phase response to hyperventilation, which is characterized by increased peripheral airway resistance (RP), eicosanoid mediator production, neutrophilic/ eosinophilic inflammation, and airway hyperreactivity (AHR) at 5 h after dry air challenge (DAC). Fiberoptic bronchoscopy was used to record RP and airway reactivity (DeltaRP) to aerosol and intravenous histamine before and 5 h after DAC. Bronchoalveolar lavage fluid (BALF) cells and eicosanoid mediators were also measured approximately 5 h after DAC. DAC of vehicle-treated bronchi resulted in late-phase airway obstruction (approximately 120% increase over baseline RP), inflammation, increased BALF concentrations of leukotriene (LT) C(4), LTD(4), and LTE(4) and prostaglandin (PG)D(2), and AHR. Pretreatment with aerosolized heparin attenuated late-phase airway obstruction by approximately 50%, inhibited eosinophil infiltration, reduced BALF concentrations of LTC(4), LTD(4), and LTE(4) and PGD(2), and abolished AHR. We conclude that heparin inhibits hyperventilation-induced late-phase changes in peripheral airway function, and does so in part via the inhibition of eosinophil migration and eicosanoid mediator production and release.

The effects of heparin and related molecules on vascular permeability and neutrophil accumulation in rabbit skin

Unfractionated heparin (UH) has been shown to possess a wide range of properties which are potentially anti-inflammatory. Many of these studies, including effects of heparin on adhesion of inflammatory cells to endothelium, have been carried out in vitro. In the present study, we have used radioisotopic techniques to study the effect of UH, and related molecules, on in vivo inflammatory responses (plasma exudation (PE) and PMN accumulation) in rabbit skin induced by cationic proteins, mediators and antigen. Intradermal (i.d.) pretreatment with UH dose-dependently inhibited poly-L-lysine (PLL)-induced responses. The same treatment had no effect on antigen (extract of Alternaria tenuis, AT)-, formyl-methionyl-leucyl-phenylalanine (fMLP)- or leukotriene (LT) B(4)-induced responses, although i.d. dextran sulphate (DS) significantly inhibited responses to all of these mediators. High dose (10,000 u kg(-1)) intravenous UH significantly decreased cutaneous responses to fMLP and LTB(4). By comparison, the selectin inhibitor, fucoidin, and DS, were very effective inhibitors of these responses, and of responses to AT and PLL. In contrast to the weak effect in the in vivo studies, UH significantly inhibited in vitro homotypic aggregation of rabbit PMNs, showing that it can modify PMN function. Our data with i.d. UH confirm the important ability of this molecule to interact with and neutralize polycationic peptides in vivo, suggesting that this is a prime role of endogenous heparin. The lack of effect of exogenous heparin on acute inflammatory responses induced by allergen, suggests that cationic proteins are unlikely to be primary mediators of the allergen-induced PE or PMN accumulation.

The effects of heparin on the adhesion of human peripheral blood mononuclear cells to human stimulated umbilical vein endothelial cells

1. The effects of unfractionated heparin (UH) and a selectively O-desulphated derivative of heparin (ODSH), lacking anticoagulant activity, on the adhesion of human peripheral blood mononuclear cells (HPBMNC) to human stimulated umbilical vein endothelial cells (HUVECs), were investigated. 2. For comparison, the effects of poly-L-glutamic acid (PGA), a large polyanionic molecule without sulphate groups and two different molecular weight sulphated dextrans (DS 5 k and DS 10 k) were studied. 3. UH (50 - 1000 u ml(-1)) significantly (P<0.05) inhibited the adhesion of HPBMNC to HUVECs, stimulated with IL-1beta (100 u ml(-1)), TNF-alpha (1000 u ml(-1)) or LPS (100 microg ml(-1)), when the drugs were added together with stimuli to HUVECs and coincubated for 6 h. Such effects on adhesion occurred with limited influence on expression of relevant endothelial adhesion molecules (ICAM-1 and VCAM-1). 4. UH (100 - 1000 u ml(-1)), when added to prestimulated HUVECs, significantly (P<0.05) increased adhesion of mononuclear cells to endothelium at the higher concentrations tested, without any effect on adhesion molecule expression. In contrast, the opposite effect was observed when human polymorphonuclear leucocyte adhesion was examined, under the same experimental conditions, suggesting that the observed potentiation of HPBMNC adhesion is cell specific. 5. The effects of UH on HPBMNC adhesion were shared by the non-anticoagulant ODSH (600 - 6000 microg ml(-1)) but not by sulphated dextrans or PGA (300 - 6000 microg ml(-1)). 6. Heparin affects the adhesion of HPBMNC to stimulated endothelium, in both an inhibitory and potentiating manner, effects which are unrelated to its anticoagulant activity and not solely dependent on molecular charge characteristics.

Glycosaminoglycans, airways inflammation and bronchial hyperresponsiveness

Glycosaminoglycans (GAGs) are large, polyanionic molecules expressed throughout the body. The GAG heparin, co-released with histamine, is synthesised by and stored exclusively in mast cells, whereas the closely related molecule heparan sulphate is expressed, as part of a proteoglycan, on cell surfaces and throughout tissue matrices. These molecules are increasingly thought to play a role in regulation of the inflammatory response and heparin, for many years, has been considered to hold potential in the treatment of diseases such as asthma. Heparin and related molecules have been found to exert antiinflammatory effects in a wide range of in vitro assays, animal models and, indeed, human patients. Moreover, the results of studies carried out to date indicate that the antiinflammatory activities of heparin are dissociable from its well-established anticoagulant nature, suggesting that the separation of these characteristics could yield novel antiinflammatory drugs which may be useful in the future treatment of diseases such as asthma

Heparin inhibits allergen-induced eosinophil infiltration into guinea-pig lung via a mechanism unrelated to its anticoagulant activity

There is considerable interest in the discovery of novel molecules for the treatment of allergic diseases and several recent studies have demonstrated that heparin can inhibit airway responses in subjects with asthma. However, heparin is also an anticoagulant which is potentially an unwanted effect in a molecule for treating asthma and allergic diseases. Recently, though, there have been a number of molecules described that are heparin-like but devoid of anticoagulant activity. The aim of this study was to evaluate whether the ability of heparin to inhibit allergen-induced eosinophil infiltration could be mimicked by analogues of heparin, some of which lack anticoagulant activity. We evaluated the effects of heparin and a number of modified heparins for their ability to inhibit allergen induced eosinophil infiltration into airways of suitably sensitised guinea-pigs assessed by bronchoalveolar lavage. Heparin and various modified heparins inhibited allergen-induced eosinophil infiltration into guinea-pig lung, including modified heparin preparations lacking anticoagulant activity. Our results suggest that heparin can inhibit eosinophil infiltration into lung tissue via a mechanism unrelated to its ability to act as an anticoagulant. Our results suggest that it may be possible to develop novel antiinflammatory agents for the treatment of asthma and allergic diseases related to the structure of heparin.

Advances in immunopharmacology of asthma

Asthma is a chronic inflammatory disease characterized by airway hyperresponsiveness and recurrent reversible airway obstruction. As there appears to be a preponderance of T-helper 2 (Th2) cells over Th1 cells in asthma, more attention has been focused on the role of Th2-derived cytokines such as interleukin (IL)-4 and IL-5 and their corresponding signaling pathways in the pathophysiology of the disease. These complex pathways may involve the activation of signal transducers and activators of transcription (STATs) and nuclear factor-kappaB (NF-kappaB). On the other hand, immunoglobulin (Ig) E-mediated mechanisms and the protein tyrosine kinase signaling cascade are important in triggering the release of mediators from inflammatory cells. In spite of all of these, host regulatory mechanisms exist to limit the inflammation. An increase in the 3', 5'-cyclic adenosine monophosphate (cAMP) level generally suppresses the activities of immune and inflammatory cells, and the level of cAMP is closely regulated by a family of phosphodiesterases (PDEs). Heparin, a glycosaminoglycan released exclusively from mast cells, also is believed to possess anti-inflammatory actions. Many new therapeutic agents have been developed either to attenuate the pro-inflammatory processes in asthma or to augment the host anti-inflammatory mechanisms. In this article, we discuss the immunopharmacology of several of these agents, which include heparin and inhibitors of PDEs, tyrosine kinases, and NF-kappaB, as well as antibodies and soluble receptors directed against IgE, IL-4, and IL-5.

Heparin inhibits eicosanoid metabolism and hyperventilation-induced bronchoconstriction in dogs

Inhalation of heparin, an anticoagulant, attenuates exercise- induced asthma (EIA) in human subjects. The purpose of this study was to determine if heparin inhibits hyperventilation-induced bronchoconstriction (HIB) in a canine model of EIA, and if its mode of action involves the inhibition of eicosanoid mediator production and release. We used a wedged bronchoscope technique to measure baseline peripheral airway resistance (Rp). We then performed either a 2-min or 5-min dry air challenge (DAC) by temporarily increasing from 200 to 2,000 ml/min the flow of 5% CO(2) in air used to ventilate a wedged sublobar segment. We compared HIB before and 60 min after aerosol treatment with either bacteriostatic water (BW) or heparin. We found that (1) heparin had no effect on baseline Rp, (2) BW did not alter the response to DAC, and (3) heparin reduced HIB by approximately 50-60%. On the basis of bronchoalveolar lavage fluid (BALF) cell analysis, heparin and BW caused acute infiltration of macrophages and eosinophils, and heparin increased the number of erythrocytes recovered immediately after DAC. Despite these acute inflammatory effects initiated prior to DAC, BALF mediator analyses revealed that pretreatment with heparin either attenuated or abolished hyperventilation-induced leukotriene, prostaglandin, and thromboxane release. Thus, our data provide direct evidence that inhaled heparin inhibits eicosanoid mediator production and release caused by hyperventilation with dry air, and significantly attenuates HIB.

Effect of heparin on antigen-induced airway responses and pulmonary leukocyte accumulation in neonatally immunized rabbits

The effect of single administrations of aerosolized heparin, low molecular weight heparin (LMWH) and the linear polyanionic molecule, polyglutamic acid (PGA) were examined on antigen-induced airway hyperresponsiveness and leukocyte accumulation in neonatally immunized rabbits. Adult litter-matched NZW rabbits immunized within 24 h of birth with Alternaria tenuis antigen were treated with heparin, LMWH or PGA prior to or following antigen challenge (Alternaria tenuis). For each drug-treated group, a parallel group of rabbits were treated with the appropriate vehicle. In all groups, airway responsiveness to inhaled histamine and bronchoalveolar lavage (BAL) was performed 24 h prior to and following antigen challenge. Basal lung function in terms of resistance (R(L)) and dynamic compliance (C(dyn)) and acute bronchoconstriction was unaltered by pre-treatment with heparin, LMWH or PGA compared to their respective vehicles 24 h prior to or following antigen challenge. In vehicle-treated animals, airway hyperresponsiveness to inhaled histamine was indicated by an increase in the maximal responses of the cumulative concentration-effect curves to histamine and reductions in R(L)PC(50) and C(dyn)PC(35) values 24 h following antigen challenge. Heparin and LMWH given prior to antigen challenge significantly inhibited the development of airway hyperresponsiveness, whereas PGA did not. When given following antigen challenge, all three drugs failed to inhibit the development of airway hyperresponsiveness. Eosinophil and neutrophil cell numbers in BAL fluid increased significantly 24 h following antigen challenge. Heparin, LMWH and PGA failed to inhibit the increase in cell numbers following antigen challenge whether given prior to or following antigen challenge.

The effects of heparin and related molecules upon the adhesion of human polymorphonuclear leucocytes to vascular endothelium in vitro

1. The effects of an unfractionated heparin preparation (Multiparin), a low molecular weight heparin preparation (Fragmin) and a selectively O-desulphated derivative of heparin lacking anticoagulant activity, have been investigated for their effects on the adhesion of human polymorphonuclear leucocytes (PMNs) to cultured human umbilical vein endothelial cells (HUVECs) in vitro. The effect of poly-L-glutamic acid, a large, polyanionic molecule was also studied. 2. Unfractionated heparin (50-1000 U ml-1), the O-desulphated derivative (0.3-6 mg ml-1) and the low molecular weight heparin (50 U-1000 U ml-1) all inhibited significantly the adhesion of 51Cr labelled PMNs to HUVECs stimulated with interleukin-1 beta (IL-1 beta; 10 U ml-1), bacterial lipopolysaccharide (LPS; 2.5 micrograms ml-1) or tumour necrosis factor-alpha (TNF-alpha; 125 U ml-1) for 6 h, whereas poly-L-glutamic acid had no effect. In addition, the three heparin preparations in the same concentration range inhibited significantly the adhesion of f-met-leu-phe-stimulated PMNs to resting HUVECs. 3. The effects of unfractionated heparin upon the expression of adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and E-selection were also investigated, as were the effects of unfractionated heparin upon adhesion of human PMNs to previously stimulated HUVECs. Heparin had little effect upon levels of expression of these adhesion molecules on stimulated HUVECs. However, a profound effect upon PMN adhesion to previously stimulated HUVECs was demonstrated using the same preparation, suggesting that inhibition of adhesion molecule expression is not a major component of the described inhibitory effects of heparin. 4. Pre-incubation of PMNs with heparin followed by washing inhibited their adhesion to HUVECs, under different conditions of cellular activation, implying that heparin can bind to these cells and exert its anti-adhesive effects even when not directly present in the system. 5. These observations would suggest that both heparin and a low molecular weight heparin are capable of inhibiting adhesion of human PMNs to endothelial cells, an effect not dependent solely upon the polyanionic nature of these molecules, nor dependent upon their ability to act as anticoagulants.

Effect of heparin and related glycosaminoglycan on PDGF-induced lung fibroblast proliferation, chemotactic response and matrix metalloproteinases activity

Fibroblast migration, proliferation, extracellular matrix protein synthesis and degradation are the key events in various biological and pathological processes in pulmonary fibrosis. In addition, biopsy specimens from the lungs of patients with pulmonary fibrosis show increased numbers of mast cells which have metachromatic granules containing heparin, histamine and proteases. Little is known about how these products influence pulmonary fibrosis. In the present study, we investigated the effect of heparin and related glycosaminoglycans on PDGF-induced lung fibroblast proliferation and chemotactic response in vitro. In addition, we examined the effect of heparin on both the induction of matrix metalloproteinases (MMPs) and MMPs activity in lung fibroblasts in vitro. Heparin, de-N-sulphated heparin but not heparan sulphate inhibited PDGF-induced lung fibroblast proliferation. In contrast, only heparin inhibited PDGF-stimulated human lung fibroblast chemotaxis. Negatively charged poly-L-glutamic acid had no effect on either fibroblast proliferation or chemotaxis. Thus the negative charge alone cannot account for the ant-proliferative and anti-chemotactic effects of heparin. Furthermore, heparin and heparan sulphate also had no inhibitory effect on induction of MMPS, including MMP-1 (interstitial collagenase), MMP-2 (gelatinase A) and MMP-9 (gelatinase B). Only heparin inhibited both MMP-1 and MMP-2/MMP-9 activity. Additionally, tissue inhibitor of metalloproteinase type 1 (TIMP-1) and type 2 (TIMP-2) inhibited PDGF-stimulated human lung fibroblast chemotaxis. The ability of heparin to inhibit fibroblast chemotaxis may account for the inhibitory effect of heparin on MMP activity. The above results suggested that heparin and related glycosaminoglycans differentially regulate PDGF-induced lung fibroblast proliferation, chemotaxis and MMPs activity and further that these effects may have a key role in extracellular matrix remodeling in inflammatory lung disease.

Heparin in inflammation: potential therapeutic applications beyond anticoagulation

In this chapter we have described anti-inflammatory functions of heparin distinct from its traditional anticoagulant activity. We have presented in vivo data showing heparin's beneficial effects in various preclinical models of inflammatory disease as well as discussed some clinical studies showing that the anti-inflammatory activities of heparin may translate into therapeutic uses. In vivo models that use low-anticoagulant heparins indicate that the anticoagulant activity can be distinguished from heparin's anti-inflammatory properties. In certain cases such as hypovolemic shock, the efficacy of a low-anticoagulant heparin derivative (GM1892) exceeds heparin. Data also suggest that nonconventional delivery of heparin, specifically via inhalation, has therapeutic potential in improving drug pharmacokinetics (as determined by measuring blood coagulation parameters) and in reducing the persistent concerns of systemic hemorrhagic complications. Results from larger clinical trials with heparin and LMW heparins are eagerly anticipated and will allow us to assess our predictions on the effectiveness of this drug class to treat a variety of human inflammatory diseases.

Heparin ameliorates pulmonary hypertension induced by platelet-activating factor in pigs

The purpose of this study was to investigate the effects of heparin on the haemodynamic changes which were induced by platelet-activating factor in the pulmonary and systemic circulation in pigs. Mean arterial pressure and mean pulmonary arterial pressure were measured continuously in five anaesthetised juvenile pigs. Bolus doses of platelet-activating factor (0.2-2 microg) were given intravenously to establish a dose response curve. Heparin (300 units/kg) was given intravenously. Thirty minutes later, the same doses of platelet-activating factor were repeated to establish a second dose response curve. Platelet-activating factor caused a dose dependent pulmonary artery hypertension, associated with an initial systemic hypotension followed by systemic hypertension. Heparin effectively reduced the low dose (0.2 microg) platelet-activating factor-induced pulmonary arterial hypertension (p<0.01) but not the higher doses. It had no effect on the platelet-activating factor-induced systemic hypotension or hypertension. The pulmonary and systemic circulation responded differently to platelet-activating factor after giving heparin. While heparin ameliorated the platelet-activating factor-induced pulmonary hypertension, it did not affect the changes in the systemic circulation.

In vivo neutralization of eosinophil-derived major basic protein inhibits antigen-induced bronchial hyperreactivity in sensitized guinea pigs

This study examines the effect of purified rabbit antiguinea pig eosinophil-derived major basic protein (MBP) Ig on antigen-induced bronchial hyperreactivity to inhaled acetylcholine in aerosol-sensitized guinea pigs. Ovalbumin inhalation by sensitized guinea pigs induced a rise in the numbers of eosinophils and in the levels of MBP in the bronchoalveolar lavage fluid, which peaked at 24 h and resolved at 72 h. Antigen-challenged animals exhibited bronchial hyperreactivity to inhale acetylcholine at 72 h, but not at 6 or 24 h. The intranasal administration of 200 microliter of purified rabbit anti-guinea pig MBP Ig, at 2.5 mg/ml, but not of the control preimmune rabbit Ig, 1 h before and 5 h after ovalbumin inhalation suppressed bronchial hyperreactivity to acetylcholine at 72 h without affecting the number of eosinophils accumulating in the bronchoalveolar lavage fluid. These findings indicate that antigen challenge in sensitized guinea pigs is followed by early eosinophil infiltration and activation within the airways and by late bronchial hyperreactivity. Neutralization of endogenously secreted MBP by a specific antiserum prevented antigen-induced bronchial hyperreactivity, suggesting that eosinophil degranulation plays an important role in the alterations of bronchopulmonary function in the guinea pig.

Heparin: pharmacological potentials from atherosclerosis to asthma

1. Heparin belongs to a family of polysaccharide species, whose best known property is, undoubtedly, anticoagulant activity. However, heparin has many other pharmacological effects, particularly on the cardiovascular system. 2. The therapeutic use of chronically inhaled heparin has been suggested as prophylaxis in atherosclerosis. 3. Heparin, physiologically stored in mast cells of the respiratory system, has also been recently studied in the prevention of immunological and non-immunological asthmatic attacks. 4. Experimental findings and new hypotheses of heparin action in asthma and atherosclerosis are discussed.

Therapeutic uses of heparin beyond its traditional role as an anticoagulant

A number of physiological effects have been ascribed to heparin since its discovery almost 80 years ago, many of which are independent from its first-described and best- characterized activity as an anticoagulant. Heparin and heparan sulphate are believed to possess many biological activities that include the ability to modulate embryonic development, neurite outgrowth, tissue homeostasis, wound healing, metastasis, cell differentation, cell proliferation and inflammation. In this review, David Tyrell, Stephen Kilfeather and Clive Page examine some of the activities of heparin (and heparin derivatives) beyond its effects as an anticoagulant, and discuss the therapeutic potential of this old, but certainly not antiquated, drug.