Pharmacokinetics and tolerability of oral iloprost in thromboangiitis obliterans patients

Incorporation of iloprost in phospholipase-resistant phospholipid scaffold enhances its barrier protective effects on pulmonary endothelium

Correction of barrier dysfunction and inflammation in acute lung injury (ALI) represents an important problem. Previous studies demonstrate barrier-protective and anti-inflammatory effects of bioactive lipid prostacyclin and its stable analog iloprost (ILO). We generated a phospholipase resistant synthetic phospholipid with iloprost attached at the sn-2 position (ILO-PC) and investigated its biological effects. In comparison to free ILO, ILO-PC caused sustained endothelial cell (EC) barrier enhancement, linked to more prolonged activation of Rap1 and Rac1 GTPases and their cytoskeletal and cell junction effectors: cortactin, PAK1, p120-catenin and VE-cadherin. ILO and ILO-PC equally efficiently suppressed acute, Rho GTPase-dependent EC hyper-permeability caused by thrombin. However, ILO-PC exhibited more sustained barrier-protective and anti-inflammatory effects in the model of chronic EC dysfunction caused by bacterial wall lipopolysacharide (LPS). ILO-PC was also more potent inhibitor of NFκB signaling and lung vascular leak in the murine model of LPS-induced ALI. Treatment with ILO-PC showed more efficient ALI recovery over 3 days after LPS challenge than free ILO. In conclusion, this study describes a novel synthetic phospholipid with barrier-enhancing and anti-inflammatory properties superior to existing prostacyclin analogs, which may be used as a prototype for future development of more efficient treatment for ALI and other vascular leak syndromes.

Effects of prostaglandin lipid mediators on agonist-induced lung endothelial permeability and inflammation

Prostaglandins (PG), the products of cyclooxygenase-mediated conversion of arachidonic acid, become upregulated in many situations including allergic response, inflammation, and injury, and exhibit a variety of biological activities. Previous studies described barrier-enhancing and anti-inflammatory effects of PGE₂ and PGI₂ on vascular endothelial cells (EC). Yet, the effects of other PG members on EC barrier and inflammatory activation have not been systematically analyzed. This study compared effects of PGE₂, PGI₂, PGF_2α, PGA₂, PGJ₂, and PGD₂ on human pulmonary EC. EC permeability was assessed by measurements of transendothelial electrical resistance and cell monolayer permeability for FITC-labeled tracer. Anti-inflammatory effects of PGs were evaluated by analysis of expression of adhesion molecule ICAM1 and secretion of soluble ICAM1 and cytokines by EC. PGE₂, PGI₂, and PGA₂ exhibited the most potent barrier-enhancing effects and most efficient attenuation of thrombin-induced EC permeability and contractile response, whereas PGI₂ effectively suppressed thrombin-induced permeability but was less efficient in the attenuation of prolonged EC hyperpermeability caused by interleukin-6 or bacterial wall lipopolysaccharide, LPS. PGD₂ showed a modest protective effect on the EC inflammatory response, whereas PGF_2α and PGJ₂ were without effect on agonist-induced EC barrier dysfunction. In vivo, PGE₂, PGI₂, and PGA₂ attenuated LPS-induced lung inflammation, whereas PGF_2α and PGJ₂ were without effect. Interestingly, PGD₂ exhibited a protective effect in the in vivo model of LPS-induced lung injury. This study provides a comprehensive analysis of barrier-protective and anti-inflammatory effects of different prostaglandins on lung EC in vitro and in vivo and identifies PGE₂, PGI₂, and PGA₂ as prostaglandins with the most potent protective properties.

The effects of iloprost on colonic anastomotic healing in rats under obstructive ileus conditions

BACKGROUND

The aim of this study was to investigate the effects of iloprost, on colonic anastomotic healing in rats, under obstructive ileus conditions.

MATERIALS AND METHODS

Eighty male Albino rats were randomized into four groups of 20 animals each. They underwent colonic resection followed by an inverted anastomosis. The rats of group 1 (control) and group 2 (ileus) received 3 mL of saline 0.9% intraperitoneally and those of group 3 (iloprost), and group 4 (ileus + iloprost) iloprost (2 μg/kg of body weight), immediately postoperatively and daily until the day of sacrifice. Each group was further divided into two equal subgroups, depending on the day of sacrifice. The animals of subgroup "a" were sacrificed on the fourth postoperative day, whereas those of "b" on the eighth day. Macroscopic and histologic assessment was performed, whereas anastomotic bursting pressures and the tissue concentrations in hydroxyproline and collagenase I were evaluated.

RESULTS

Means of bursting pressure, neoangiogenesis, fibroblast activity, and hydroxyproline concentration were significantly increased in group 4 compared with group 2. In addition, on the fourth postoperative day, the inflammatory cell infiltration and the collagenase I concentration were significantly decreased in group 4 compared with group 2. Moreover, on the eighth postoperative day, collagen deposition was significantly increased in group 4 compared with group 2.

CONCLUSIONS

Iloprost after intraperitoneal administration reverses the negative effect of obstructive ileus. It promotes not only the angiogenic activity but also collagen formation, resulting in increased bursting pressures on the fourth and eighth postoperative days.

Commentary on a recent article-"A prostacyclin analogue, Iloprost, protects from bleomycin-induced fibrosis in mice" Zhu Y et al. Respir Res. 2010 Mar 20;11(1):34

Data from our laboratory show that in vitro fibroblasts are exquisitely responsive to prostacyclin and the prostacyclin derivative Iloprost, which block their activation by TGFβ. A recent article by Zhu Y et al confirm these effects in vivo showing that Iloprost, given as a single intraperitoneal injection, blocks lung fibrosis in the bleomycin model of lung injury and fibrosis. These results are important because at present no effective clinical treatments are available to treat idiopathic lung fibrosis, which progresses and leads to respiratory failure. Limiting factors for the clinical use of prostacyclin derivatives as anti-fibrotics are failure to achieve therapeutic levels in the involved fibrotic tissues, and dose limiting side effects due to vasodilatation and binding to the IP receptor on vascular cells. Possible approaches include fibroblast directed gene therapies or amelioration of the vascular side effects.

Review of inhaled iloprost for the control of pulmonary artery hypertension in children

In the pediatric population, pulmonary hypertension may present as an acute event in the setting of lung or cardiac pathology or as a chronic disease, mainly as idiopathic pulmonary hypertension or associated with congenital heart disease. Recently, new pharmacologic approaches have demonstrated significant efficacy in the management of adults with pulmonary arterial hypertension; these include intravenous epoprostenol, prostacyclin analogs, endothelin receptor antagonists and phosphodiesterase type 5 inhibitors. The same treatment strategies are currently used in children. There are only few reports of the use of inhaled iloprost in pediatrics, only one of which reported the use of chronic inhaled iloprost in a significant number of children. This report showed that 1) the acute pulmonary vasodilator response to inhaled iloprost is equivalent to that of inhaled nitric oxide; 2) acute inhalation of iloprost can induce bronchoconstriction 3) the addition of inhaled iloprost can reduce the need for intravenous prostanoid therapy in some patients; 4) most children tolerated the combination of inhaled iloprost and endothelin receptor antagonist or phosphodiesterase inhibitors; 5) Several patients had clinical deterioration during chronic inhaled iloprost therapy and required rescue therapy with intravenous prostanoids. In this review we will discuss the role of inhaled iloprost in acute and chronic pulmonary hypertension in children.

Decrease in the Incidence of Buerger's Disease Recurrence in Northern Thailand

PURPOSE

Buerger's disease is a peripheral arterial occlusive disease (PAOD), which occurs mainly in young male smokers. It is common in Asia, the Middle East, and Eastern European countries, but rare in North America and Western European countries. We investigated the changes in the prevalence and recurrence of Buerger's disease at a referral hospital in northern Thailand.

METHODS

We conducted a retrospective study of patients with Buerger's disease admitted to Chiang Mai University Hospital between January 1988 and December 2002. Buerger's disease was diagnosed according to Shionoya's clinical criteria.

RESULTS

We evaluated 78 patients with Buerger's disease, with a collective total of 108 admissions. Forty-one patients were admitted for initial treatment, and 37 patients had a history of treatment and were admitted for worsening of Buerger's disease. Between 1988 and 1995, 23 patients were admitted with newly diagnosed Buerger's disease, 52 were admitted because of Buerger's disease exacerbation, and 372 were admitted for a PAOD; whereas between 1996 and 2002, the respective numbers were 18, 15, and 632 (2.9 +/- 1.9/year vs 2.6 +/- 1.3/year, P = 0.25; 6.5 +/- 1.1/year vs 2.1 +/- 1.1/year, P = 0.001; 54.1 +/- 6.7/year vs 81.6 +/- 5.2/year, P < 0.0001). Of the 78 patients with Buerger's disease, 76 were men and 2 were women, with a mean age at onset of 34.1 +/- 5 years. The predominant symptom on admission was burning pain in the feet and hands in 75%, digital gangrene in 74%, and a digital ulcer in 43.5%.

CONCLUSIONS

The incidence of recurrence of Buerger's disease seems to be decreasing in our institution, whereas the incidence of this disease and its recurrence both seem to be decreasing in Western countries and Japan.

EP4 prostanoid receptor-mediated vasodilatation of human middle cerebral arteries

1. Dilatation of the cerebral vasculature is recognised to be involved in the pathophysiology of migraine. Furthermore, elevated levels of prostaglandin E(2) (PGE(2)) occur in the blood, plasma and saliva of migraineurs during an attack, suggestive of a contributory role. In the present study, we have characterised the prostanoid receptors involved in the relaxation and contraction of human middle cerebral arteries in vitro. 2. In the presence of indomethacin (3 microm) and the TP receptor antagonist GR32191 (1 microM), PGE(2) was found to relax phenylephrine precontracted cerebral arterial rings in a concentration-dependent manner (mean pEC(50) 8.0+/-0.1, n=5). 3. Establishment of a rank order of potency using the EP(4)>EP(2) agonist 11-deoxy PGE(1), and the EP(2)>EP(4) agonist PGE(1)-OH (mean pEC(50) of 7.6+/-0.1 (n=6) and 6.4+/-0.1 (n=4), respectively), suggested the presence of functional EP(4) receptors. Furthermore, the selective EP(2) receptor agonist butaprost at concentrations <1 microM failed to relax the tissues. 4. Blockade of EP(4) receptors with the EP(4) receptor antagonists AH23848 and EP(4)A caused significant rightward displacements in PGE(2) concentration-response curves, exhibiting pA(2) and pK(B) values of 5.7+/-0.1, n=3, and 8.4, n=3, respectively. 5. The IP receptor agonists iloprost and cicaprost relaxed phenylephrine precontracted cerebral arterial rings (mean pEC(50) values 8.3+/-0.1 (n=4) and 8.1+/-0.1 (n=9), respectively). In contrast, the DP and FP receptor agonists PGD(2) and PGF(2 alpha) failed to cause appreciable relaxation or contraction at concentrations of up to 30 microm. In the absence of phenylephrine contraction and GR32191, the TP receptor agonist U46619 caused concentration-dependent contraction of cerebral artery (mean pEC(50) 7.4+/-0.3, n=3). 6. These data demonstrate the presence of prostanoid EP(4) receptors mediating PGE(2) vasodilatation of human middle cerebral artery. IP receptors mediating relaxation and TP receptors mediating contraction were also functionally demonstrated.

Inhibition of intracellular tumour necrosis factor (TNF)-alpha and interleukin (IL)-6 production in human monocytes by iloprost

BACKGROUND

To investigate the effects of iloprost as a stable prostacyclin analogue on intracellular expression of IL-6 and TNF-alpha of lipopolysaccharide (LPS)-stimulated human monocytes in a whole blood system assessed by flow cytometry.

MATERIAL AND METHODS

Whole blood of six healthy volunteers processed immediately after withdrawal and twice on different days (six measurements per experiment) was stimulated in two different settings with LPS (final concentrations 0.2 ng mL(-1) and 10 ng mL(-1)) and incubated with iloprost (final concentrations in each experiment were 0.01 nm, 0.1 nm, 0.3 nm, 1 nm, 3 nm, 10 nm, 30 nm and 100 nm) for 3 h at 37 degrees C and 5% CO2. Intracellular expression of IL-6 and TNF-alpha was assessed by flow cytometry.

RESULTS

Our investigations showed, for the first time, that iloprost (0.1 nm up to 100 nm) caused a dose-dependent inhibitory effect of IL-6 production in human monocytes stimulated with LPS (10 ng mL(-1)), which was even more obvious in monocytes stimulated with lower concentrated LPS (0.2 ng mL(-1)). Iloprost (0.1 nm up to 100 nm) was found to inhibit TNF-alpha production of LPS-stimulated monocytes in a dose-dependent fashion not influenced by LPS concentration.

CONCLUSIONS

Apart from the vasodilatory and antithrombotic effects, iloprost may also down-regulate the intracellular expression of IL-6 and TNF-alpha in human monocytes.

Inhaled iloprost in patients with chronic thromboembolic pulmonary hypertension: effects before and after pulmonary thromboendarterectomy

BACKGROUND

In primary pulmonary hypertension, aerosolized prostanoids selectively reduce pulmonary vascular resistance and improve right ventricular function. In this study, hemodynamic effects of inhaled iloprost, a stable prostacyclin analogue, were evaluated in patients with chronic thromboembolic pulmonary hypertension (CTEPH) before and early after pulmonary thromboendarterctomy (PTE).

METHODS

Ten patients (mean age 49 years old [32 to 70 years old], New York Heart Association functional class III and IV) received a dose of 33 micro g aerosolized iloprost immediately before surgery (T1), after intensive care unit admission (T2), and 12-hours postoperatively (T3). Effects on pulmonary and systemic hemodynamics and gas exchange were recorded and compared with preinhalation baseline values.

RESULTS

Preoperatively, inhaled iloprost did not significantly change mean pulmonary artery pressure (mPAP), cardiac index (CI), or pulmonary vascular resistance (PVR). Postoperatively, inhaled iloprost induced a significant reduction of mPAP and PVR and a significant increase of CI at T2 and T3. Preinhalation versus postinhalation PVR was as follows: at T1, 847 versus 729 dynes. s. cm(-5), p = 0.45; at T2, 502 versus 316 dynes. s. cm(-5), p = 0.008; and at T3, 299 versus 227 dynes. s. cm(-5), p = 0.004.

CONCLUSIONS

In patients with CTEPH, inhalation of iloprost elicits no significant pulmonary vasodilation before surgery, and may have detrimental effects on systemic hemodynamics. Postoperatively, it significantly reduces mPAP and PVR, and enhances CI. Following PTE, inhalation of iloprost is useful to improve early postoperative hemodynamics.

Enhanced platelet force development despite drug-induced inhibition of platelet aggregation in patients with thromboangiitis obliterans--two case reports

Thromboangiitis obliterans (TAO) is a nonatherosclerotic, nonnecrotizing, nonspecific, segmental inflammatory obliterative vasculitis, characterized by decreased flow to the distal extremities and increased risk of amputation. While smoking cessation is viewed as critical to successful treatment, various therapeutic options have been employed. While many treatment regimens seek to diminish platelet function, there are relatively few studies of platelet function in this disease entity and even fewer that have offered evidence of increased platelet activity. The authors report here 2 cases of TAO in which evaluations for hypercoagulable states and of platelet function were performed. Platelet contractile force (PCF) was found to be 82% higher than a normal control in 1 TAO patient and 340% higher than normal in the second patient. This was true despite the fact that platelet aggregations confirmed suppression of aggregation by antiplatelet medications. Elevated PCF has been seen in a variety of conditions, such as coronary artery disease and diabetes mellitus, in which endothelial function is abnormal. Whether high PCF values play a role in the pathogenesis of these diseases or simply serve as markers of enhanced platelet function and/or endothelial dysfunction awaits additional evaluations.

Novel mode of action of iloprost: in vitro down-regulation of endothelial cell adhesion molecules

Iloprost is a stable prostacyclin analog commonly employed in the treatment of peripheral vascular disease and also indicated in the treatment of patients affected by systemic sclerosis (SSc) in the presence of severe Raynaud's phenomenon (RP). Several mechanisms of action of the drug other than vasodilation and antiplatelet effect have been demonstrated that may be involved in the exertion of its clinical efficacy. Aim of the present study was to investigate whether iloprost down-regulated lymphocyte adhesion to endothelium through a modulation of adhesion molecule expression on the surface of endothelial cells. In the presence of iloprost, both lymphocyte adhesion and IL-1 stimulated expression of ICAM-1 and ELAM-1 exhibited a significant reduction, while unstimulated adhesion molecule expression was not significantly affected. Our results confirm that iloprost is able to down-regulate lymphocyte adhesion to endothelial cells and indicate that endothelium itself could be target of iloprost administration. Attenuation of the inflammatory response through modulation of cellular interactions could be suggested as a potential mechanism of action of iloprost, when used in the treatment of pathological conditions characterized by endothelial activation.

Oral iloprost in the treatment of thromboangiitis obliterans (Buerger's disease): a double-blind, randomised, placebo-controlled trial. The European TAO Study Group

OBJECTIVES

To assess efficacy and tolerability of two dosages of the oral prostacyclin analogue iloprost versus placebo in thromboangiitis obliterans (TAO).

DESIGN

Placebo-controlled, double-blind, study; TAO patients randomised to iloprost 100, 200 micrograms, or placebo bid for 8 weeks, with 6 months' follow-up.

METHODS

Three-hundred and nineteen TAO patients with rest pain, trophic lesions (or both) from 23 clinics in six European countries. Primary endpoint: total healing of most important lesion. Secondary endpoint: relief of rest pain without need of analgesics. Combined endpoint: alive without major amputation, no lesions, no rest pain, no use of analgesics.

RESULTS

Total healing of lesions was not significantly different between treatment groups at any time point. For relief of rest pain without need of analgesics, low dose (LD) iloprost was significantly more effective than placebo at end of follow-up (placebo 49%; LD iloprost 63%; p = 0.020). This also applied to the combined endpoint (placebo 35%; LD iloprost 50%; p = 0.016). High dose iloprost (HD) failed to show significant treatment effects over placebo.

CONCLUSIONS

Iloprost LD was significantly more effective than placebo for relief of rest pain without need of analgesics and for a combined endpoint at 6 months of follow-up, whilst both iloprost doses showed no significant effects vs. placebo on total healing of lesions.