The effect of heparin on antigen-induced mucus hypersecretion in the nasal epithelium of sensitized rats

BACKGROUND

Heparin is a potential anti-inflammatory drug for allergic airway inflammation. To elucidate the effects of heparin on allergic inflammation, we examined the in vivo effects of heparin on antigen-induced mucus hypersecretion and infiltration of eosinophils and neutrophils in the nasal epithelium of sensitized rats.

METHODS

We induced hypertrophic and metaplastic changes of goblet cells in the nasal epithelium of ovalbumin (OVA)-sensitized rats by intranasal challenge with OVA. The effects of intranasal instillation with low molecular weight heparin (LMWH; 1-1000IU/0.1ml) on mucus production and eosinophil/neutrophil infiltration were examined.

RESULTS

Intranasal instillation with low-dose LMWH (1-10IU/0.1ml) at 30 minutes before OVA instillation stimulated OVA-induced mucus production in the nasal epithelium of sensitized rats, whereas treatment with 100IU/0.1ml LMWH showed no effect. Intranasal instillation with high-dose LMWH (1000IU/0.1ml) significantly inhibited OVA-induced mucus production. Intranasal instillation with LMWH (1-1000IU/0.1ml) dose-dependently inhibited eosinophil and neutrophil infiltration into the rat nasal mucosa.

CONCLUSIONS

These results indicate that heparin inhibits mucus hypersecretion and infiltration of eosinophils and neutrophils in allergic inflammation, though the inhibitory effect against mucus production is obtained in high-dose heparin. Intranasal instillation with high-dose heparin may provide a new therapeutic strategy for the treatment of nasal allergic inflammation.

Elevated non-esterified fatty acids impair nitric oxide independent vasodilation, in humans: evidence for a role of inwardly rectifying potassium channels

To evaluate the role of elevation of non-esterified fatty acids on forearm nitric oxide (NO) dependent and independent relaxation, four studies were performed in the forearms of 14 normals: (1). endothelium-dependent and -independent vasodilations were assessed during acetylcholine (Ach) and sodium nitroprusside (SNP) infusions; (2). flow-mediated vasodilation (FMD) was assessed; (3) .bradykinin (BK) was infused during NO and prostaglandin inhibition (NO clamp); (4). blood flow (FBF) was measured during Ouabain, a Na(+)/K(+) ATPase, and BaCl(2), rectifying potassium channel (K(IR)) blockers, respectively. All studies were performed before and after 120 min. Intralipid+heparin (high-NEFA) infusion. Ach-mediated FBF increase was lower at high-NEFA (332+/-34 vs. 436+/-44% at 45 microg l forearm(-1) min(-1); % of ratio infused: control arm P<0.05), while SNP response was similar. FMD did not differ before and during high-NEFA, which induced a blunted response of FBF during BK with or without NO clamp. Ouabain and BaCl(2)-mediated FBF inhibition was lower (P<0.01) at high-NEFA. During ouabain alone FBF decreased slightly.

IN CONCLUSION

High-NEFA exerts a negative role on both NO-dependent and independent vasodilations. The decrease in FBF, mediated by K(IR) inhibition, is blunted by high-NEFA: these substrates interfere with hemodynamic/metabolism coupling, possibly through the inhibition of these channels.

Role of nitric oxide in heparin-induced attenuation of hypoxic pulmonary vascular remodeling

Heparin and nitric oxide (NO) attenuate changes to the pulmonary vasculature caused by prolonged hypoxia. Heparin may increase NO; therefore, we hypothesized that heparin may attenuate hypoxia-induced pulmonary vascular remodeling via a NO-mediated mechanism. In vivo, rats were exposed to normoxia (N) or hypoxia (H; 10% O(2)) with or without heparin (1,200 U x kg-1 x day-1) and/or the NO synthase (NOS) inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME; 20 mg x kg-1 x day-1) for 3 days or 3 wk. Heparin attenuated increases in pulmonary arterial pressure, the percentage of muscular pulmonary vessels, and their medial thickness induced by 3 wk of H. Importantly, although L-NAME alone had no effect, it prevented these effects of heparin on vascular remodeling. In H lungs, heparin increased NOS activity and cGMP levels at 3 days and 3 wk and endothelial NOS protein expression at 3 days but not at 3 wk. In vitro, heparin (10 and 100 U x kg-1 x ml-1) increased cGMP levels after 10 min and 24 h in N and anoxic (0% O2) endothelial cell-smooth muscle cell (SMC) coculture. SMC proliferation, assessed by 5-bromo-2'-deoxyuridine incorporation during a 3-h incubation period, was decreased by heparin under N, but not anoxic, conditions. The antiproliferative effects of heparin were not altered by L-NAME. In conclusion, the in vivo results suggest that attenuation of hypoxia-induced pulmonary vascular remodeling by heparin is NO mediated. Heparin increases cGMP in vitro; however, the heparin-induced decrease in SMC proliferation in the coculture model appears to be NO independent.

Intragastric administration of heparin enhances gastric ulcer healing through a nitric oxide-dependent mechanism in rats

Our preliminary finding indicated that intravenous (i.v.) injection of heparin increased gastric ulcer healing in rats. However, the anticoagulant action of i.v. heparin could produce complications in ulcer patients if the drug was used as an anti-ulcer agent. The present study aimed to investigate whether intragastric (i.g.) administration of heparin, known to have no anticoagulant activity, would have the similar ulcer healing effect and the relationship of this effect, if any, with nitric oxide (NO), a substance suggested to be important for ulcer healing. Heparin (100, 500, 1000 U/kg, i.g. ) administered once daily for 4 days accelerated the healing of gastric ulcer induced by acetic acid in Sprague-Dawley rats, which was accompanied by an increase in mucosal proliferation and regeneration at the ulcer margin, microvessel number both at the ulcer margin and base, and the thickness of mucus layer. Both activity and content, but not the mRNA of constitutive nitric oxide synthase (cNOS) in the gastric mucosa were enhanced. L-N(G)-nitroarginine methyl ester (L-NAME), an inhibitor of NOS activity blocked the cNOS activity activated by heparin and reversed the beneficial effects of heparin on ulcer healing. The bleeding time was not altered by i.g. heparin. These findings demonstrate that i.g. heparin promotes the healing processes of gastric ulcer. Such effect is suggested to act through the stimulation of mucosal cNOS activity. In addition, i.g. heparin is better than i.v. heparin without the potential anticoagulation effect.

Heparin-induced vasodilation in human hand veins

OBJECTIVE

To investigate whether heparin produces vasodilation in human veins and to explore the underlying mechanisms.

METHODS

Eleven healthy volunteers were studied with the dorsal hand vein compliance technique. Dose-response curves to heparin and enoxaparin were generated. Dose-response curves to heparin were also constructed before and after heparin was infused with the nitric oxide synthase inhibitor N(G)-monomethyl-l-arginine (L-NMMA) or combined histamine H1- and H2-receptor blockade.

RESULTS

Heparin but not enoxaparin caused significant dose-dependent relaxation with an average apparent maximal response (at an infusion rate of 20 IU/min) of 47% +/- 23%. L-NMMA attenuated heparin-induced relaxation (P < .001). The combination of H1-and H2-receptor antagonists attenuated heparin-induced relaxation to a lesser extent (P < .05). Heparin-induced relaxation decreased by 52%, 73%, and 35% in the presence of L-NMMA, indomethacin (INN, indometacin) plus L-NMMA, and combined H1- and H2-receptor blockade, respectively.

CONCLUSION

Heparin is an endothelium-dependent venodilator in humans. The mechanism of heparin-induced relaxation involves an increased availability of nitric oxide, possibly partially related to local release of histamine.

High-dose heparin impairs nitric oxide pathway and vasomotion in rats

BACKGROUND

Platelet-activating effects have been reported with high-dose heparin in acute thrombotic disorders. Recent studies have shown that increased platelet aggregation is due to reduced nitric oxide (NO) production in endothelial cells cultured in the presence of high-dose heparin. The aim of this study was to determine whether heparin can affect the NO pathway and the regulation of the vascular tone in vivo.

METHODS AND RESULTS

Anesthetized and mechanically ventilated Sprague-Dawley rats were treated with high-dose heparin. After 4 hours, the endothelial constitutive NO synthase (ecNOS) protein content in the aorta decreased (36% reduction, P<0.05), as detected by immunoblotting, and NO-dependent vascular reactivity was impaired. In fact, the increase in mean arterial blood pressure after inhibition of ecNOS with NG-nitro-L-arginine methyl ester (30 mg/kg) was smaller in heparin-treated animals than in controls (+26. 9+/-4.8 versus +48.3+/-9.1 mm Hg, P<0.05), and further infusion of the biological ecNOS substrate L-arginine (0.5 g/kg) was ineffective in reversing systemic vasoconstriction (-1% versus 28% vasodilatation, P<0.001).

CONCLUSIONS

High-dose heparin can significantly affect vascular reactivity in vivo by downregulation of ecNOS protein expression.

Nonanticoagulant heparin prevents coronary endothelial dysfunction after brief ischemia-reperfusion injury in the dog

BACKGROUND

Coronary endothelial dysfunction after brief ischemia-reperfusion (IR) remains a clinical problem. We investigated the role of heparin and N-acetylheparin, a nonanticoagulant heparin derivative, in modulating coronary endothelial function after IR injury, with an emphasis on defining the role of the nitric oxide (NO)-cGMP pathway in the heparin-mediated effect.

METHODS AND RESULTS

Male mongrel dogs were surgically instrumented, and the effects of both bovine heparin and N-acetylheparin on coronary endothelial vasomotor function, expressed as percent change from baseline flow after acetylcholine challenge, were studied after 15 minutes of regional ischemia of the left anterior descending artery (LAD) followed by 120 minutes of reperfusion. In dogs treated with placebo (saline), coronary vasomotor function was significantly (P</=0.03) decreased after 15 and 30 minutes of reperfusion (65+/-12% and 73+/-12%) compared with preischemia (103+/-6%). In contrast, the vasodilatory response to the endothelium-independent vasodilator sodium nitroprusside was maintained during reperfusion. Preischemic administration of both bovine heparin and N-acetylheparin (6.0 mg/kg IV) preserved coronary endothelial function throughout reperfusion. In a parallel group of dogs, nitrate/nitrite (NOx) and cGMP levels in the LAD were measured after treatment and during 15-minute reperfusion. Preischemic administration of N-acetylheparin caused a significant increase in basal NOx and cGMP levels compared with saline controls. Pretreatment with N-acetylheparin also caused a significant increase in NOx and cGMP levels in the LAD after 15 minutes of reperfusion compared with IR alone.

CONCLUSIONS

These results suggest that heparin preserves coronary endothelial function after brief IR injury by a mechanism independent of its anticoagulant activity and that the effect of heparin may be mediated in part by activation of the NO-cGMP pathway.