Toll-like receptor signaling pathway involved in pathogenesis of thromboangiitis obliterans through activating of NF-κB.

OBJECTIVES: The pathogenic mechanisms of Thromboangiitis Obliterans (TAO) are not entirely known and autoimmune inflammation plays a vital role in the initiation and continuance of TAO activity. The authors investigated in this study the role of the TLR signaling pathway in the pathogenesis of TAO. METHODS: First, the authors detected the expressions of MyD88, TRIF and NF-κB in vascular walls of 46 patients with TAO and 32 patients with trauma and osteosarcoma by western blot assay. Second, the authors detected the cellular localization of MyD88, TRIF and NF-κB in vascular walls of patients with TAO by immunofluorescent assay. RESULTS: The protein expressions of MyD88, TRIF and NF-κB were much higher in vascular walls of TAO patients (p < 0.05). Higher expressions of MyD88 and NF-κB were detected both on vascular endothelial and vascular smooth muscle cells of TAO patients. However, higher expression of TRIF was just detected on vascular smooth muscle cells of TAO patients. CONCLUSIONS: These dates suggest that the TLR signaling pathway might play an important role in the pathogenesis of TAO, it might induce vasospasm, vasculitis and thrombogenesis to lead to the pathogenesis and progression of TAO.

MiR-223 alleviates thrombus and inflammation in thromboangiitis obliterans rats by regulating NLRP3.

OBJECTIVE: The aim of this study was to observe the regulatory effects of micro ribonucleic acid (miR)-223 on thromboangiitis obliterans (TAO) rats, and to explore the potential regulatory mechanism. MATERIALS AND METHODS: Online database TargetScan was used to predict the downstream regulatory targets of miR-223. A total of 45 Sprague Dawley (SD) rats were randomly divided into three groups, including sham operation group (Sham group), Model group, and miR-223 agonist group (miR-223 mimic group). TAO model was successfully established in rats through the injection of lauric acid via the femoral artery. The content of serum thromboxane B2 (TXB2) and endothelin (ET) was measured via enzyme-linked immunosorbent assay (ELISA). The pathological changes in the left hind limb were detected via hematoxylin-eosin (HE) staining. Moreover, the expressions of interleukin-6 (IL-6) and IL-1ß in the tissues of the rat left hind limb were determined via immunohistochemistry. In addition, the protein expression of Nod-like receptor protein 3 (NLRP3) in tissues was determined using Western blotting. RESULTS: TargetScan database predicted that NLRP3 was the downstream target gene of miR-223. Compared with the Sham group, Model group exerted significantly higher content of serum TXB2 and ET, severe lesions in the rat left hind limb, as well as significantly increased expressions of IL-6 and IL-1ß and protein expression of NLRP3 in tissues of the rat left hind limb (p<0.05). Besides, compared with the Model group, miR-223 mimic group showed remarkably lower content of serum TXB2 and ET, improved lesions in the rat left hind limb, as well as decreased expressions of IL-6 and IL-1ß and protein expression of NLRP3 in the tissues of the rat left hind limb (p<0.05). CONCLUSIONS: MiR-223 agonist can alleviate thrombus and inflammatory response in TAO rats. The possible underlying mechanism may be related to targeted regulation on NLRP3 inflammasome expression.

Effect of bradykinin on rats with thromboangiitis obliterans through PI3K/Akt signaling pathway.

OBJECTIVE: To explore the effect of bradykinin on rats with thromboangiitis obliterans (TAO) through the phosphatidylinositol 3-hydroxy kinase/protein kinase B (PI3K/Akt) signaling pathway. MATERIALS AND METHODS: The female Wistar rats were injected with lauric acid via the femoral artery to establish the TAO model, and they were randomly divided into control group (healthy rats), model group (TAO rats) and bradykinin group (TAO rats injected with bradykinin B2 receptor-specific inhibitor). The control was set in each group before the operation. The level of serum bradykinin in each group was detected via enzyme-linked immunosorbent assay (ELISA), and the reactive oxygen species (ROS) level, Caspase-3 activity and PI3K/Akt protein concentration in vascular tissues were measured via ELISA, Western blotting, ROS assay, and Caspase-3 activity assay, respectively. Moreover, the specific therapeutic mechanism of bradykinin was analyzed. RESULTS: In control group, the intima of the lower extremity venous tissues was smooth, the extima had no evident changes, and there was no inflammatory cell invasion around the arteries and veins. In model group, there was massive inflammatory cell invasion into the lower extremity venous tissues. In bradykinin group, fibrosis and atrophy occurred in venous tissues, the extima was thickened without fibrosis, and there was phagocytosis of neutrophils and mononuclear macrophages around the arteries and veins, as well as massive inflammatory infiltration. The PI3K/Akt protein concentration in lower extremity venous tissues was the highest in control group and the lowest in bradykinin group, and there were statistically significant differences (p<0.01). At 24 h after administration of doxorubicin (DOX), the level of ROS in lower extremity venous tissues was higher in bradykinin group than that in model group (p<0.05), and it was also higher in model group than that in control group (p<0.05). Besides, the activity of Caspase-3 in lower extremity venous tissues was significantly increased in bradykinin group compared with that in model group and control group, while it was slightly higher in model group than that in control group (p<0.05). CONCLUSIONS: The low expression of bradykinin can promote TAO in rats by the mechanism that it inhibits the PI3K/Akt signaling pathway to raise the oxidative stress level, thereby aggravating TAO.

Levistilide A Ameliorates NLRP3 Expression Involving the Syk-p38/JNK Pathway and Peripheral Obliterans in Rats.

BACKGROUND: Inflammation is one of the most important pathogeneses of thromboangiitis obliterans (TAO). The NLRP3 inflammasome plays a vital role in the body's immune response and disease development. It can be activated by numerous types of pathogens or danger signals. As the core of the inflammatory response, the NLRP3 inflammasome may provide a new target for the treatment of various inflammatory diseases. Levistilide A (LA) is a phthalide dimer isolated from umbelliferous plants. Its pharmacological effect is largely unknown. This study revealed the effects of LA on endothelial cell activation, NLRP3, IL-1ß, TNF-α, IL-32, and CCL-2, VCAM-1, MCP-1, and the spleen tyrosine kinase (Syk)--p38/JNK signaling axis and its effect on vasculitis in rats. RESULTS: LA inhibited endothelial activation and the expression of IL-1ß, TNF-α, IL-32, CCL-2, VCAM-1, and MCP-1. LA directly obstructed Syk phosphorylation and activity in a dose-dependent manner, inhibited the activity of p38 and JNK, and reduced the expression of NLRP3 in human umbilical vein endothelial cells and vascular tissue of rats with vasculitis. CONCLUSION: LA suppressed NLRP3 gene expression by blocking the Syk--p38/JNK pathway and reduced damage to the rats' limbs in the thromboangiitis obliterans model.

The IL-6/STAT3 pathway regulates adhesion molecules and cytoskeleton of endothelial cells in thromboangiitis obliterans.

Thromboangiitis obliterans (TAO) (also known as Buerger's disease) is an inflammatory vascular disease that predominantly affects small- and medium-sized blood vessels of extremities. Endothelial cells play critical roles in the initiation and progression of this disease, but the underlying mechanisms remain unclear. In the present study, we demonstrate that patients with TAO had significantly higher levels of interleukin-6 (IL-6), soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) in their plasmas, and the involved arterial tissues expressed higher levels of phosphorylated signal transducer and activator of transcription 3 (p-STAT3), ICAM-1 and VCAM-1. In exploring the molecular mechanisms with human aortic endothelial cells (HAECs), we found that recombinant IL-6 activated the STAT3 pathway, leading to the upregulation and overproduction of ICAM-1 and VCAM-1. RhoA (Ras homolog family member A), eNOS (endothelial nitric oxide synthase) and MMP-9 (matrix metalloproteinase-9) participated in this cellular signaling, and their interaction regulated the expression of ICAM-1 and VCAM-1. The activated STAT3 pathway by IL-6 also modulated the cytoskeleton of HAECs by regulating phosphorylation of focal adhesion kinase (FAK) and acetylation of α-tubulin through interplaying with RhoA. In summary, the present results indicate that activation of the IL-6/STAT3 pathway contributes to the pathogenesis of TAO by regulating cellular adhesion molecules and cytoskeleton of vascular endothelial cells, suggesting that targeting this pathway may provide a potential approach for the management of TAO.

Mechanisms of thrombosis, available treatments and management challenges presented by thromboangiitis obliterans.

Thromboangiitis obliterans (TAO) is a thrombotic-occlusive and an inflammatory peripheral arterial disease with unidentified aetiology. Thrombotic events can lead to limb loss in TAO patients, who are typically young male smokers of low socioeconomic status. It is still unknown whether the initial process is thrombosis or inflammation, so it is difficult to ascertain whether managing inflammation or thrombosis improves the outcome of the disease. In this review, the possible mechanisms of thrombosis in TAO are evaluated; the treatments, based on the discussed mechanisms of thrombosis in TAO, are then reviewed and the challenges and limitations associated with the management of TAO are discussed.

Integrated treatment for lower-limb stage II thromboangiitis obliterans by interventional therapy and oral administration of Chinese medicine: a randomized controlled clinical trial.

METHODS: Ninety lower-limb stage II or worse TAO patients were randomly divided into three groups: group A (30 cases) treated by intervention and oral administration of Chinese medicine; group B (30 cases) treated by intervention alone; and group C (30 cases) treated only with oral administration of Chinese medicine. Therapeutic effects were observed, including the cure rate; the recurrence rate after one month, three months, six months, nine months, and one year; the ankle brachial indexes; the incidence of complications; and the level of C-reactive protein and erythrocyte sedimentation rate. RESULTS: Group A had significantly better clinically curative effects, related indexes, and outcomes during the long-term follow-up survey, than that of groups B and C. CONCLUSION: Integrated treatment is more effective for treating lower-limb stage II or worse TAO. OBJECTIVE: To observe if integrated treatment is better than other therapies for lower-limb stage II thromboangiitis obliterans (TAO).

Possible involvement of Notch signaling in the pathogenesis of Buerger's disease.

PURPOSE: Under pathological conditions, the Notch signal pathway is involved in the inflammatory process in arteriosclerosis, atherosclerosis and angiogenesis under ischemic conditions. The purpose of this study was to observe whether or not Buerger's disease is associated with Notch signal activation. METHODS: All the patients were diagnosed between 1980 and 2009 at Nagoya University Hospital. Twenty-two specimens from 12 patients with Buerger's disease (TAO) and 13 specimens from nine patients with arteriosclerosis obliterans (ASO) were analyzed by immunohistochemistry for Notch1, Jagged-1 (a Notch ligand) and Hes-1 (a Notch 1 target transcription factor). RESULTS: Notch1 and Jagged-1 were highly expressed in the endothelium in the new vasa vasorum and in the smooth muscle cells in the media of specimens from both groups. These Notch-related proteins were also remarkably expressed in inflammatory cells in the intima of specimens from TAO patients. Fewer inflammatory cells expressed Notch-related proteins in atheromatous plaques (Notch1 (%): 8.4 ± 0.76 versus 1.3 ± 0.43, P < 0.001; Jagged-1(%): 9.3 ± 1.1 versus 5.2 ± 1.1, P = 0.03). Indeed, Hes-1, which is a transcription factor downstream of Notch1, was remarkably expressed in the endothelium of new capillary vessels and inflammatory cells in TAO patients. Notch1-positive mononuclear cells were also seen in the thrombus in samples from the TAO group. CONCLUSIONS: Our findings are the first demonstration that Notch signal activation in inflammatory cells may be involved in the pathophysiological mechanism underlying Buerger's disease.

Reduced circulating endothelial progenitor cells in thromboangiitis obliterans (Buerger's disease).

To determine the role of endothelial progenitor cells (EPCs) in the pathogenesis of thromboangiitis obliterans (TAO), EPC numbers and colony-forming units, migratory function and tubular structure formation in vitro were compared between 13 young male TAO patients and two age-matched healthy control groups: 11 smokers and 12 non-smokers. TAO patients had significantly lower numbers of EPCs and EPC colonies compared to both non-smokers [190 (97.0-229) vs 528 (380-556), p < 0.001 for EPCs and 0.80 (0.53-1.00) vs 2.80 (2.08-4.00) per mm(2), p = 0.001 for EPC colonies] and smokers [190 (97.0-229) vs 272 (229-326), p = 0.012 for EPCs and 0.80 (0.53-1.00) vs 2.80 (1.80-3.93) per mm(2), p = 0.001 for EPC colonies]. However, there were no significant differences in migratory function or tube formation between the three groups. These results suggest that TAO patients have an intrinsic decrease in EPCs not entirely associated with smoking, which may be the cause of endothelial dysfunction seen in TAO patients leading to the development of this disease at early ages.

High-mobility-group box protein 1A box reduces development of sodium laurate-induced thromboangiitis obliterans in rats.

OBJECTIVE: High-mobility-group box protein 1 (HMGB1), as a late mediator of inflammation, plays a key role in inflammatory responses by inducing and extending the production of proinflammatory cytokines. The effect of HGMB1 in the inflammatory disease thromboangiitis obliterans (TAO) is unknown. We aimed to investigate the role of HMGB1 in sodium laurate-induced TAO in rats. METHODS: Male Wistar rats were randomly divided into five groups (n=8 each) for treatment: normal, sham-operated, TAO model, and low-dose (15 mg/kg) or high-dose (30 mg/kg) recombinant A box (rA box) infection (administered intraperitoneally once daily for 15 days). The TAO model was induced by sodium laurate and graded by gross appearance on day 15 after femoral artery injection. Histologic changes were measured by histopathology in rat femoral arteries. Plasma levels of HMGB1, thromboxane B2, 6-keto-prostaglandin F1-α, and blood cell counts and blood coagulation levels were measured. Expression of HMGB1, receptor for advanced glycation end-products (RAGE), interleukin-6, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 was assessed by immunohistochemistry and immunofluorescence, Western blot analysis, and quantitative reverse-transcription polymerase chain reaction. RESULTS: The typical signs and symptoms of TAO were observed on day 15 after sodium laurate injection. The expression of HMGB1, RAGE, interleukin-6, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 was markedly increased in rat femoral arteries. Plasma levels of HMGB1 and thromboxane B2 were elevated, but the level of 6-keto-prostaglandin F1-α was decreased. Blood was in a hypercoagulable state, and prothrombin, thrombin, and activated partial thromboplastin times were all significantly shortened, whereas fibrinogen level was increased in TAO rats compared with sham-operated rats. These effects were terminated by the HMGB1 antagonist rA box. CONCLUSIONS: HMGB1 is involved in the inflammatory state in a model of TAO induced by sodium laurate in rats, probably via its receptor RAGE. As the antagonist of HMGB1, rA box can attenuate the development of TAO, which may be a potential therapeutic target for the treatment of TAO.

Transfection of human HGF plasmid DNA improves limb salvage in Buerger's disease patients with critical limb ischemia.

AIM: Hepatocyte growth factor is a potent angiogenic agent. This study investigated the efficacy and safety of intramuscular injection of naked plasmid DNA encoding the human hepatocyte growth factor gene in Japanese patients with Buerger's disease and critical limb ischemia. METHODS: An open-label clinical study was performed at eight hospitals in Japan from May 2004 to April 2008. Ten patients were enrolled. They had Buerger's disease with ischemic ulcers, were not candidates for revascularization, and were unresponsive to conventional drug therapy. Treatment consisted of 8 injections (total dose: 4 mg) of hepatocyte growth factor plasmid, which were administered into the calf muscles and/or distal thigh muscles of the ischemic limbs under ultrasound guidance. Administration was done twice at an interval of 4 weeks. If there was no improvement after 2 doses, a 3rd dose could be administered. The response to treatment was evaluated from the reduction of ischemic ulcer size. RESULTS: The size of ischemic ulcers showed a decrease in 6/9 (66.7%) patients and the ulcers healed completely in 5/9 (55.6%) patients after gene therapy. Major amputation was not required. There were no deaths and no major safety concerns. CONCLUSION: Hepatocyte growth factor gene therapy is safe and effective for critical limb ischemia in patients with Buerger's disease.

Immunohistochemical properties in the patients with Buerger's disease--possible role of plasminogen activator inhibitor-1 for preservation of vessel wall architecture.

BACKGROUND: The architecture of the arterial wall affected with Buerger's disease has been known to be preserved in all three layers, while the one affected by arteriosclerosis obliterans (ASO) is degenerated and destroyed. We analyzed affected arteries with immunohistochemical methods to clarify the differences between Buerger's disease and ASO. MATERIALS AND METHODS: Crural arteries obtained from 13 patients with Buerger's disease and 6 patients with ASO at our institute were studied. In addition, we examined seven specimens from six patients who were thought to be normal (without Buerger's disease or ASO) as negative control. Immunohistochemical studies were performed on paraffin-embedded tissues. The primary antibodies were urokinase-type plasminogen activator (uPA) and matrix metalloproteinase-3 (MMP-3). Both are known to play an important role of extracellular proteolysis and to activate each other. Additionally, plasminogen activator inhibitor-1(PAI-1) was also examined. RESULTS: In Buerger's disease, PAI-1 was well expressed along the internal elastic lamina. Urokinase-type plasminogen activator and MMP-3 were slightly positive in intima and media. In ASO, a slight amount of PAI-1 was recognized on vessel walls, and both uPA and MMP-3 were strongly positive in media. In addition, in the control group, PAI-1, uPA, and MMP-3 were well expressed in media. CONCLUSION: In Buerger's disease, PAI-1 was strongly expressed around the internal elastic lamina, while both uPA and MMP-3 were slightly recognized on vessel walls. These findings could be one of the reasons the general architecture of vessel walls in Buerger's disease is preserved.

Urocortin promotes the development of vasculitis in a rat model of thromboangiitis obliterans via corticotrophin-releasing factor type 1 receptors.

BACKGROUND AND PURPOSE: Urocortin is a locally expressed pro-inflammatory peptide. Here we have examined the effects of urocortin on sodium laurate-induced peripheral arterial vasculitis in rats, modelling the mechanisms of thromboangiitis obliterans (TAO). EXPERIMENTAL APPROACH: Peripheral vasculitis in rats was induced by sodium laurate and graded by gross appearance on the 12th day after injection. Histological changes in rat femoral arteries were assessed by histopathology and transmission electron microscopy. Blood cell counts, blood rheology, blood coagulation and plasma urocortin, thromboxane B(2), prostaglandin E(2) and soluble intercellular adhesion molecule-1 levels were measured. Expression of urocortin, corticotrophin-releasing factor (CRF(1/2)) receptors, cyclooxygenase (COX)-2 and intercellular adhesion molecule-1 (ICAM-1) at both mRNA and protein levels were determined by RT-PCR and Western blot. KEY RESULTS: Rats showed grossly visible signs and symptoms of TAO on the 12th day after sodium laurate injection. In these rats, blood was in a hypercoagulable state; plasma urocortin, prostaglandin E(2) and soluble intercellular adhesion molecule-1 levels were elevated; and the expression of urocortin, CRF(1) and CRF(1alpha)-receptors, COX-2 and ICAM-1 in rat femoral arteries were markedly increased. Exogenous urocortin, given for 12 days after sodium laurate, exacerbated the hypercoagulable state and augmented expression of CRF(1alpha)-receptors, COX-2 and ICAM-1. These effects were abolished by a CRF(1)-receptor antagonist, NBI-27914, or a non-selective CRF-receptor antagonist, astressin, but not by the CRF(2)-receptor antagonist, antisauvagine-30, given with exogenous urocortin. CONCLUSION AND IMPLICATIONS: Urocortin exacerbated the hypercoagulable state and vasculitis in a model of TAO induced by sodium laurate in rats, via CRF(1)-receptors. COX-2 and ICAM-1 might also have contributed to this exacerbation.

Apolipoprotein C1 and apolipoprotein E are differentially expressed in atheroma of the carotid and femoral artery.

BACKGROUND: A number of the genes and proteins as the causes of carotid atherosclerotic disease have been recently reported, but the major factors for atherosclerosis have still not been identified. METHODS: The atherosclerotic atheromas were obtained during endarterectomy for each of 10 cases of diseased carotid and femoral arteries. As the nonatherosclerotic arteries, the iliac arteries were obtained during organ harvest from five cases of brain-dead donors, and the leg arteries were obtained during leg amputation from five cases of Buerger's disease. The total RNAs and proteins were isolated from the atheromas and arteries. The annealing control primer method was used to screen the differentially expressed mRNAs. To identify if the mRNA expression of screened gene was associated with the protein expression, we performed an immunohistochemical analysis. RESULTS: We found that the apolipoprotein C1 (apo C1) gene was prominently expressed in the atheroma of the carotid and femoral arteries, as compared to the nonatherosclerotic arteries. Immunohistochemical analysis showed the high expression of apo C1 protein in the atheromas of the carotid and femoral arteries. Apo E protein was also highly expressed in atheromas compared with the nonatherosclerotic arteries, but there was no difference for apo C2 protein between those four groups of arteries. DISCUSSION: The expression of apo C1 and apo E are closely associated with the susceptibility to the pathogenesis of atherosclerosis. This study suggests that these factors might play important roles in the future to screen for preventing atherosclerosis and for diagnostic testing of patients.

[Indices of antioxidant system of blood in differential diagnosis of obliterating atherosclerosis and obliterating thromboangiitis of the lower limbs].

The work was aimed at elucidating the role of the indices of the antioxidant system (AOS) of the blood and nitrogen oxide content in differential diagnosis of atherosclerosis obiiterans (AO) and thromboangiitis obiiterans (TO) of the lower extremities. Presented herein are the findings of examining a total of one hundred and thirteen 30-to-45-year-old patients (of these, 60 had TO and 53 had AO) with various level of occlusion (from the femoropoplietal segment to the aortoiliac zone) and the stage of chronic arterial insufficiency (CAI IIA-IV). The control group was composed of 30 apparently healthy age-matched male subjects. Besides the clinical, laboratory and special instrumental methods of study, we determined the parameters of the AOS of blood and the content of nitrogen oxide degradation products. It was determined that the directedness and pronouncedness of deviations in the parameters of the AOS and nitrogen oxide from the physiological norm depended on not only the aetiology of the disease involved, but on the degree of tissue hypoxia predetermined by the stage of CAI of the lower limbs. For differential diagnosis between AO and TO, the most informative should be considered the coefficient: SOD activity/catalase activity, index of peroxide-luminol-dependent chemiluminescence and the content of nitrogen oxide degradation products.

[Correlation of expressions of ER and CD59 in Buerger disease].

OBJECTIVE: To inquire into the expression conditions of ER, CD59 and IgG in Buerger disease arteria vessels and probe their correlation. METHODS: Two groups of arteria vascular endothelial cells were investigated. The cells in Buerger group were derived from 30 male Buerger disease patients; the cells in the other group were derived from 30 normal men. The levels of ER, CD59 and IgG expression were detected by immunohistochemistry staining. RESULTS: The levels of ER and CD59 expression in Buerger disease group were higher than those of control group (P<0.05); the level of IgG expression on arteria intima in Buerger group was lower than that of control group (P<0.05); the level of IgG expression under arteria intima in Buerger group was higher than that of control group (P<0.05). Spearman rank correlation analysis of the Buerger group showed that ZD59 expression and IgG expression are significantly correlated and ER expression and IgG expression are significantly correlated, too. CONCLUSION: The expressions of CD59 and ER are up-regulated, which are probably

Expression of ICAM-1, VCAM-1, E-selectin and TNF-alpha on the endothelium of femoral and iliac arteries in thromboangiitis obliterans.

Immunohistochemical light and electron microscopical analysis of surgical biopsies obtained from femoral and iliac arteries of patients with thromboangiitis obliterans (TAO) were performed to investigate the presence of tumour necrosis factor-alpha (TNF-alpha) and expression of the endothelial cell adhesion molecules intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin. Expression of ICAM-1, VCAM-1 and E-selectin was increased on endothelium and some inflammatory cells in the thickened intima in all TAO patients. Ultrastructural immunohistochemistry revealed contacts between mononuclear blood cells and ICAM-1-, and E-selectin-positive endothelial cells. These endothelial cells showed morphological signs of activation. The present data indicate that endothelial cells are activated in TAO and that vascular lesions are associated with TNF-alpha secretion by tissue-infiltrating inflammatory cells, ICAM-1-, VCAM-1- and E-selectin expression on endothelial cells and leukocyte adhesion via their ligands. The preferential expression of inducible adhesion molecules in microvessels and mononuclear inflammatory cells suggests that angiogenesis contributes to the persistence of the inflammatory process in TAO.

Pharmacokinetics and tolerability of oral iloprost in thromboangiitis obliterans patients.

OBJECTIVE: Iloprost is a potent PGI2 mimetic, which has been shown to be therapeutically effective in several vascular disorders. Due to its rapid clearance from the central compartment, iloprost is administered mainly by i.v. infusion, which limits its use to hospitalized patients. In order to improve pharmacotherapeutic use of this PGI2 mimetic, an oral extended-release (ER) dosage form has been developed, which should mimic plasma level profiles as observed after i.v. infusion and serve as a therapeutic equivalent. METHODS: This trial was performed to investigate the tolerability and pharmacokinetics of iloprost administered perorally, compared with i.v. infusion, in 12 patients suffering from thromboangiitis obliterans (TAO). A dose titration was carried out for 1 week with i.v. iloprost, followed by a p.o. titration and treatment phase of 3 weeks' duration. Pharmacokinetics was investigated at the individually tolerated dose levels; i.e., on days 5-7 (i.v. infusion at 2, 2.5 and 3 ng.kg-1.min-1), and twice during p.o. treatment after b.i.d. administration of 50, 100, 150, 200 or 300 micrograms. RESULTS: Individual tolerability of iloprost varied: 7 patients out of 12 tolerated the maximum i.v. dose of 3 ng.kg-1.min-1; six tolerated the maximum oral dose of 600 micrograms. No patients withdrew from the study due to adverse events. Flush and headache were the most common adverse events and seemed to be related to the study drug. After i.v. infusion of iloprost, dose-normalized (3 ng.kg-1.min-1), steady-state plasma levels were 260 pg.ml-1. Terminal half-life was 0.57 h. Total clearance ranged from 8 to 17 ml.min-1.kg-1. Peroral administration of the ER formulation resulted in dose-dependent Cmax and AUC values. AUC values of the first and second daily dose interval, i.e., 0-5 h and 5-11 h after first dosing, were almost identical. Absolute bioavailability was 24%, with the exception of two patients who tolerated only 50 micrograms b.i.d. and exhibited a bioavailability of approx. 60%. The AUC values observed in weeks 2 and 4 were identical, demonstrating low day-to-day variability of iloprost plasma level profiles in TAO patients. CONCLUSION: Based upon pharmacokinetic data, the ER formulation provides an equivalent to the i.v. infusion of iloprost and broadens the range of therapy to nonhospitalized patients. The availability of capsules with 50 and 100 micrograms iloprost enables individual dose titration and pharmacotherapy. Beneficial effects, as observed with i.v. iloprost in TAO patients, should therefore be achievable by peroral pharmacotherapy using the new ER formulation.