Effect of low molecular weight heparin on coronary endothelial function in acute cellular heart transplant rejection

Liberation of vessel adherent myeloperoxidase by enoxaparin improves endothelial function

BACKGROUND

Myeloperoxidase (MPO), a leukocyte-derived heme enzyme binds to the endothelium and depletes vascular nitric oxide (NO) bioavailability in animal models. Unfractionated heparins release vessel-bound MPO and increase endothelial NO bioavailability. Whether low molecular weight heparins also affect circulating MPO levels and NO dependent vasoreactivity however remains elusive.

METHODS AND RESULTS

In a randomized, double-blind, placebo-controlled trial patients with stable coronary artery disease received either 1 mg/kg enoxaparin or an equivalent volume of sodium chloride (NaCl) subcutaneously. Enoxaparin led to a significant improvement of FMD (5.51+/-0.53% vs. 6.55+/-0.58%, p=0.01) accompanied by a significant increase in plasma MPO levels (2.51 [IR: 2.04-3.62] ng/ml vs. 3.70 [IR: 2.80-5.50] ng/ml; p<0.001) whereas NaCl revealed neither a change in FMD (5.56+/-0.67% vs. 5.34+/-0.61%, p=ns) nor in plasma MPO levels (3.04 [IR: 2.22-4.67] ng/ml vs. 2.90 [IR: 1.95-4.32] ng/ml; p=ns). The extent of enoxaparin-induced MPO release and the improvement in endothelial function showed a good correlation (r=0.67, p<0.001).

DISCUSSION

This study confirms the concept that heparins improve endothelial function, an established read-out of vascular NO bioavailability, by mobilizing vessel bound MPO. These data not only support the notion of extracoagulant, anti-inflammatory properties of heparins but reinforce the concept of MPO-dependent NO oxidation as a central mechanism for regulation of vascular tone in inflammatory vascular disease. (Eudra-CT number: 2005-006113-40).

Low-molecular-weight heparin lowers the recurrence rate of preeclampsia and restores the physiological vascular changes in angiotensin-converting enzyme DD women

Data from literature report that angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism affects the recurrence of preeclampsia and that low-molecular-weight heparin (LMWH) prevents adverse outcomes in thrombophilic women. We investigated the effect of LMWH on the pregnancy outcome, on maternal blood pressure values, and on uteroplacental flow in ACE DD nonthrombophilic women with history of preeclampsia. Eighty nonthrombophilic ACE DD women were randomized in 2 groups: 41 treated with dalteparin 5000 IU/day and 39 untreated (control group). Women underwent 24-hour automated blood pressure monitoring in the preconceptional period and every 2 weeks from weeks 8 to 36 and transabdominal color flow/pulsed Doppler examination at weeks 16, 20, and 24. LMWH reduced the risk of clinical negative outcomes (74.1% reduction of preeclampsia and 77.5% reduction of fetal growth restriction) and the severity (88.3% reduction of early onset of preeclampsia and 86.4% reduction of early onset of fetal growth restriction). In treated women, the relative risk for preeclampsia was 0.26 (P=0.02), and the relative risk for fetal growth restriction was 0.14 (P<0.001). Systolic (P=0.002) and diastolic (P=0.002) blood pressures, as well as awake (P=0.04) and asleep (P=0.01) period values, and the resistance indexes of both uterine arteries (P=0.002) were lower in the treated group. LMWH reduces the recurrence of preeclampsia, of negative outcomes, and the resistance of uteroplacental flow, and also prevents maternal blood pressure increase in ACE DD homozygote women with a previous history of preeclampsia.

Enoxaparin--a low molecular weight heparin, restores the altered vascular reactivity of resistance arteries in aged and aged-diabetic hamsters

We questioned whether the low molecular weight heparin enoxaparin acts upon the altered vascular reactivity of the resistance arteries in normal biological aging and in aging associated with diabetes. Experiments were performed on isolated resistance arteries of young (4 months old), aged (16 months old), and aged-diabetic hamsters (16 months old and 5 months since streptozotocin injection), and the reactivity was assessed by the myograph technique. The results showed that enoxaparin (60 microg/ml) had favorable effects on the vascular reactivity in aged and aged-diabetic conditions, i.e., diminished the contractility of the arterial wall to 10(-8)-10(-6) M noradrenaline (NA) and to K(+), and potentiated the impeded endothelium-dependent relaxation to 10(-8)-10(-4) M acetylcholine (ACh). The effect was more pronounced compared to that produced by unfractionated heparin (UFH). These pharmacological effects supplement the anticoagulant properties of enoxaparin and may be of relevance for improving perfusion/circulation in the microvasculature of aged and of aged-diabetic persons.

Coronary artery vasculopathy in pediatric cardiac transplant patients: the therapeutic potential of immunomodulators

The single largest cause of late graft loss in pediatric cardiac transplantation is transplant coronary artery vasculopathy (CAV). The mechanism of CAV remains unknown; it appears to have both immune and non-immune causes. The final common pathway of these mechanisms is endothelial activation, a prothrombotic environment, and endothelial damage with subsequent diffuse intimal proliferation. The disease process has largely been thought to be progressive and unresponsive to treatment. Re-transplantation has been advocated as the only definitive treatment. The appropriate management is largely unknown; intervention or surgical management has had limited utility, while medical management appears to have the most promise. Improvement in outcome can be achieved by optimizing non-immune factors and aggressive management of the immune mechanisms. Long-term survival of transplant patients after diagnosis with CAV is now being reported.