Nitric oxide and prostacyclin modulate the alterations in cardiac action potential duration mediated by platelets during ischaemia

OBJECTIVE

To investigate the effects of alterations of nitric oxide (NO) and prostacyclin (PGI2) availability on platelet-mediated electrophysiological effects during myocardial ischaemia.

METHODS

Transmembrane action potentials and electrograms were recorded from isolated, Langendorff-perfused guinea-pig hearts during normal perfusion, global myocardial ischaemia and reperfusion during infusion of washed human platelets. Experiments were performed in the presence of 100 microM NG-nitro-L-arginine methyl ester (L-NAME), 30 microM L-arginine, 10 microM haemoglobin, 100 microM sodium nitroprusside and 2.3 nM iloprost, or using hearts obtained from DL-lysine monoacetylsalicylate (Aspisol, 50 mg.kg-1 i.p.)-treated animals.

RESULTS

Perfusion with L-NAME and haemoglobin increased perfusion pressure by 33% (P = 0.0017) and 23% (P = 0.0026) while sodium nitroprusside and iloprost reduced it (17%, P = 0.0004, and 24%, P = 0.0006). In the absence of platelets, these compounds had no effect on arrhythmogenesis, but in the presence of platelets L-NAME reduced the onset time of ventricular tachycardia during ischaemia from 19.4 (s.e.m. 2.0) min to 12.9 (2.1) min, P = 0.04 and accentuated the ischaemia-induced reduction of action potential duration at 95% repolarization (APD95): 95(6) vs. 115(5) ms, P < 0.05 at 25 min. Sodium nitroprusside in the presence of platelets attenuated the ischaemia-induced reduction in APD95, while iloprost in the presence of platelets was antiarrhythmic (ventricular fibrillation 25 vs. 75%, P = 0.04) and attenuated the reduction in APD95 during ischaemia 115(4) vs. 94(4) ms, P < 0.05 at 20 min. Infusion of platelets into hearts obtained from DL-lysine-monoacetylsalicylate-treated guinea-pigs accentuated the ischaemia-induced reduction in APD95 (94(4) vs. 119(7) ms, P < 0.05 at 20 min) and this was reversed by sodium nitroprusside (117(7) ms, P < 0.05 at 20 min). L-NAME and haemoglobin had no effect on the aggregatory responses of the platelets to 5 microM ADP and 4 micrograms.ml-1 collagen, while sodium nitroprusside and iloprost ablated the responses to ADP and reduced the responses to collagen (maximum height of the aggregatory response reduced by 75 and 84%, respectively, both P = 0.03.)

CONCLUSIONS

Inhibition of NO and PGI2 synthesis exacerbates the reduction in cardiac action potential duration associated with platelet activation during ischaemia, while provision of exogenous NO and PGI2 attenuates the reduction in cardiac action potential duration. Provision of exogenous NO and PGI2 (as iloprost) was associated with inhibition of platelet reactivity.

Cicaprost inhibits collagen-induced platelet accumulation in rat lungs for some hours

A new method is introduced admitting of direct quantification of collagen-induced platelet trapping in the rat lung. The synthetic PG1(2)-mimetics, Iloprost and Cicaprost, are capable of inhibiting the trapping of platelets induced by collagen. The described method has proved to be suited for performing both pharmacodynamic and effectkinetic investigations with inhibitors of collagen-induced platelet trapping.

Inhibition of platelet recruitment to arterial lesions by predeposition of platelets containing encapsulated iloprost

Drugs can be encapsulated within blood platelets by reversible electroporation and can be haemostatically targeted to vessel wall injury sites. Initial studies with iloprost-loaded pig platelets and pig aorta tunica media in perfusion circuits are presented. After autologous reconstitution into blood, no significant difference was observed in the deposition of 111Indium labelled sham-loaded and untreated platelets onto the tunica media during perfusion under low and high shear conditions. In paired experiments (n = 10 pairs), the deposition of iloprost-loaded platelets was significantly lower (mean 61%) after 5 min perfusion than the deposition from blood containing sham-loaded (control) platelets. A similar significant reduction (mean 54%) was seen after 10 min perfusion. Pre-perfusion of iloprost-loaded platelets for 10 min under low shear conditions (212/s), followed by 5 min perfusion of 111Indium labelled normal platelets, significantly reduced the secondary platelet deposition (p < 0.01) when compared with the deposition seen when control untreated platelets were preperfused. Significant differences (p < 0.001) in secondary deposition were also observed when primary and secondary platelet perfusions were made under high shear (1690/s). Histology of the tunica media segments post perfusion, supported the inhibitory effect of predeposited iloprost-loaded platelets on secondary platelet recruitment. By exploiting their natural haemostatic propensity, drug-loaded platelets can be targeted to vessel wall injury sites. Appropriate drugs could be packaged that may passivate the carrier platelets at the lesion inhibiting thrombus formation or they may act as a depot for sustained drug release.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclooxygenase-2 inhibition prevents renal toxicity but not hypertension during sunitinib treatment

BACKGROUND

Anticancer angiogenesis inhibitors cause hypertension and renal injury. Previously we observed in rats that high-dose aspirin (capable of blocking cyclooxygenase (COX)-1 and-2) was superior to low-dose aspirin (blocking COX-1 only) to prevent these side-effects during treatment with the angiogenesis inhibitor sunitinib, suggesting a role for COX-2. High-dose aspirin additionally prevented the rise in COX-derived prostacyclin (PGI2). Therefore, we studied the preventive effects of selective COX-2 inhibition and the hypothesized contributing role of PGI2 during angiogenesis inhibition.

METHODS

Male WKY rats received vehicle, sunitinib ((SU), 14 mg/kg/day) alone or combined with COX-2 inhibition (celecoxib, 10 mg/kg/day) or a PGI2 analogue (iloprost, 100 μg/kg/day) for 8 days (n = 8-9 per group). Mean arterial pressure (MAP) was measured via radiotelemetry, biochemical measurements were performed via ELISA and vascular function was assessed via wire myography.

RESULTS

SU increased MAP (17±1mmHg versus 3±1mmHg after vehicle on day 4, P < 0.002), which could not be significantly blunted by celecoxib (+12±3mmHg on day 4, P = 0.247), but was temporarily attenuated by iloprost (treatment days 1 + 2 only). Urinary PGI2 (996 ± 112 versus 51 ± 11ng/24h after vehicle, P < 0.001), but not circulating PGI2 increased during SU, which remained unaffected by celecoxib and iloprost. Celecoxib reduced sunitinib-induced albuminuria (0.36 ± 0.05 versus 0.58 ± 0.05mg/24h after SU, P = 0.005). Wire myography demonstrated increased vasoconstriction to endothelin-1 after SU (Emax P = 0.005 versus vehicle), which remained unaffected by celecoxib or iloprost.

CONCLUSION

Selective COX-2 inhibition ameliorates albuminuria during angiogenesis inhibition with sunitinib, which most likely acts independently of PGI2. To combat angiogenesis inhibitor-induced hypertension, dual rather than selective COX-1/2 blockade seems preferential.

Permanent life support by kidneys perfused with a vitrifiable (7.5 molar) cryoprotectant solution

BACKGROUND

Vitrification (glass formation) is a potential method for indefinite term organ preservation that eliminates all of the conventional problems of freezing and thawing. A 7.5 M mixture of cryoprotectants known as VS4 is sufficiently concentrated, in combination with applied pressure, to preclude ice formation entirely during cooling to below the glass transition temperature (about -125 degrees C), at which point vitrification takes place, arresting further changes over time.

METHODS

Rabbit kidneys were perfused with VS4 according to three different protocols. The kidneys were evaluated using an autograft model with immediate contralateral nephrectomy.

RESULTS

All three methods permitted long-term survival, but the best results were obtained when the highest concentrations were perfused at about -3 degrees C. Using the latter protocol, the survival rate was 10/10, serum creatinine returned to a normal baseline after transient elevation, other clinical chemistry results normalized, and no histological damage was apparent 3 weeks after autografting.

CONCLUSIONS

The results described provide the strongest evidence to date that it may be possible to bank kidneys for unlimited periods in the absence of ice for later transplantation.

Role of endothelin-1 in cerebral hematoma-induced modification of cerebral vascular reactivity in piglets

Endothelin-1 (ET-1) has been implicated in hematoma-induced cerebral vasoconstriction and modification of cerebral microvascular reactivity, particularly attenuation of vasodilation to cAMP-dependent dilators and enhanced vasoconstriction to ET-1. We examined effects of the ET-1 antagonist, BQ-123, on hematoma-induced modification of pial arteriolar responses to ET-1 and iloprost, a cAMP-dependent dilator, in vivo, plus the effects of such treatment on the cortical CSF cAMP. Closed cranial windows were implanted in alpha-chloralose anesthetized piglets 4 days following cortical subarachnoid injection of: (1) artificial cerebrospinal fluid (aCSF); (2) autologous blood; (3) BQ-123 alone; or (4) BQ-123 in combination with blood. ET-1 in CSF was significantly elevated from 3 in control to 45 fmol/ml 6 h following hematoma, dropping to 24 fmol/ml at 24 h but remaining above control 4 days later (14 fmol/ml). The mean diameters of pial arterioles were reduced 30% 4 days following blood injection. This reduction was prevented by pretreatment with BQ-123. In the control piglets, pial arterioles dose-dependently dilated to topical application of iloprost with increases in diameter of 10%, 16% and 21% at 10(-12) M, 10(-10) M and 10(-8) M, respectively. Iloprost-induced dilation was attenuated by hematoma to 4%, 9% and 14% at 10(-12) M, 10(-10) M and 10(-8) M, respectively. Treating piglets with BQ-123 along with hematoma on day 1 prevented the hematoma-induced attenuation of pial arteriolar dilation to iloprost on day 4 (14%, 21% and 29% at 10(-12) M, 10(-10) M and 10(-8) M, respectively). Conversely, dilation to sodium nitroprusside (SNP) was not different among the groups. Topical ET-1 dilated pial arterioles at 10(-12) M and produced dose-dependent constriction at higher doses in the control piglets. The dilation at 10(-12) M ET-1 was reversed to constriction 4 days following hematoma and constrictions to higher doses were enhanced. BQ-123 treatment along with hematoma prevented both the loss of low dose dilation and the enhanced vasoconstriction to ET-1. Treatment with BQ-123 alone on day 1 did not affect the dilation to iloprost or constriction to ET-1, 4 days later. The cortical CSF level of cAMP was significantly reduced from 1637 fmol/ml in controls to 294 fmol/ml in piglets with hematoma. Treatment with BQ-123 along with hematoma blocked the reduction in cAMP (3369 fmol/ml). Initial elevation of ET-1 and the subsequent activation of ETA, receptor may play an important role in hematoma-induced alterations of cerebral vascular reactivity and prolonged cerebral vasoconstriction that occur 4 days later. Thus, cerebral hematoma appears to attenuate iloprost-induced dilation and reduce basal cAMP level 4 days following hematoma via release that involves ET-1 of substance(s) on day 1 of hematoma. This substance(s) may act by inhibiting adenylyl cyclase. These results suggest that ET-1 plays an important role in the blood-induced prolonged cerebral vasoconstriction and altered vasoreactivity that follows cerebral hemorrhage via stimulation of ETA receptor.

Iloprost enhances portal flow velocity and volume in patients with systemic sclerosis

BACKGROUND

Iloprost, a prostacyclin analog, reduces hepatic microcirculatory damage after ischemia-reperfusion injury in animal liver models. The objective of this study was to evaluate whether the portal flow velocity changes after Iloprost infusion in patients with systemic sclerosis and Raynaud's phenomenon, who usually have increased risk of microvascular thrombosis and transient liver disturbances.

PATIENTS AND METHODS

Fifteen patients (3 males and 12 females, median age 58 years, range 47-66 years), with systemic sclerosis and Raynaud's phenomenon, were exclusively treated with an infusion of Iloprost (2 ng/kg/min, 6 h/day) for 5 days. In each subject, the portal flow velocity (PV, cm/sec) and portal flow volume (PFV, mL/min) were obtained by using portal color Doppler ultrasonography equipment.

RESULTS

Iloprost administration significantly (p<0.001) increased both the PV (23.6+/-3.4 cmlsec vs. 29.1+/-3.9 cm/sec) and PFV (1748.8+/-310. 7 mL/min vs. 2254.9+/-404.1 mL/min) values.

CONCLUSION

Hepatic perfusion significantly improved after Iloprost administration, suggesting that such treatment might be useful in preventing vascular complications in patients with systemic sclerosis. Iloprost improves the portal hemodynamics, favoring local microvascular patency, and its effectiveness may be safely monitored by using portal color Doppler ultrasonography.

Enhanced portal flow velocity and volume following Iloprost treatment

OBJECTIVE

We studied, with color Doppler sonography, portal flow velocity (PV) and volume (PFV) before and after Iloprost infusion.

BACKGROUND

Iloprost is a prostacyclin analogue with arterial vasodilator and platelet aggregation inhibitor properties. Recently, hemodynamic effects after treatment with Iloprost have been demonstrated in subjects with arteriopathy of lower limbs.

METHODS

We treated 10 subjects (2 males and 8 females; mean age 64 +/- 8.2 years) affected by arteriopathy of lower limbs with intravenous infusion of Iloprost, at a dosage of 2 ng/Kg/min (16 hours/day) for 3 days. In all patients portal vein flow velocity (PV) (cm/s) and volume (PFV) (ml/min) were assessed. PV was directly determined by the Doppler system, whereas PFV was calculated using the formula "CSA x PV", after measuring the portal vein cross sectional area (CSA) (mm2).

RESULTS

The patients showed markedly increased PV and PFV after Iloprost infusion (pre-Iloprost vs post-Iloprost treatment mean portal flow velocity and volume values: 23.12 +/- 3.89 cm/s vs 28.49 +/- 3.90 cm/s, p < 0.01 and 1743.9 +/- 241.7 ml/min vs 2271.7 +/- 333.5 ml/min, p < 0.001, respectively).

CONCLUSIONS

This study confirms our previous results about increased PV and PFV values after Iloprost treatment. In the light of these results we suggest some possible therapeutic implications in patients undergoing liver transplantation. However, further studies are necessary to confirm this hypothesis.

Effect of a prostacyclin analogue on the vasopressin and oxytocin secretion in vitro

Iloprost (ZK 36374; a stable prostacyclin analogue) increases basal as well as potassium-evoked vasopressin and oxytocin secretion from rat neurointermediate lobes in vitro. This finding suggests a possible regulatory role of endogenous prostacyclin in the release of neurohypophysial hormones.

Factors that contribute to spontaneous platelet aggregation and streptokinase-induced aggregation in whole blood

When whole blood is stirred there is a "spontaneous" platelet aggregation (SPA) which is presumed to be caused by proaggregatory factors released from platelets and other blood cells. Adding streptokinase (SK) to stirred whole blood frequently increases the rate and extent of the platelet aggregation that occurs; this is likely to be via immune complex formation between SK and natural anti-SK antibodies leading to increased release of pro-aggregatory factors. In this investigation we have examined the effects of several inhibitors and antagonists in an attempt to identify the proaggregatory factors that contribute to both SPA and SK-induced aggregation (SKA) and to evaluate different means of inhibiting both processes. The effects of the inhibitors/antagonists were determined in vitro after adding them to citrated whole blood obtained from healthy volunteers. Platelet aggregation was measured using a platelet counting technique. Inhibition of both SPA and SKA by apyrase and by FPL 66096 (a P2T receptor antagonist) demonstrated the involvement of ADP in both processes. Inhibition by chlorpromazine indicated that the most likely source of the ADP is red cells. The effects of sulotroban (a TXA2 antagonist) indicated involvement of TXA2 in SKA but not in SPA. The lack of effect of specific antagonists at S2, alpha 2 and PAF receptors suggested lack of involvement of serotonin, catecholamines and platelet-activating factor in either SPA or SKA. Both SPA and SKA were potently inhibited by low concentrations of iloprost (a PGI2 analogue), but a high concentration of SIN-1 (a NO donor) was much less effective.(ABSTRACT TRUNCATED AT 250 WORDS)

Attenuation of anti-Thy1 glomerulonephritis in the rat by anti-inflammatory platelet-inhibiting agents

Although both ecto-ADPase and prostacyclin (PGI2) inhibit platelets and neutrophils, their action in acute glomerulonephritis is unknown. We tested the PGI2 analog Iloprost and 2chloroadenosine (2Cl-ADO), an analog of adenosine, the end product of nucleotidase activities, during anti-Thy1 nephritis. Rats received anti-Thy1 immunoglobulin G (5 mg/kg body weight, intravenously) and subsequently one subcutaneous injection of either 2Cl-ADO (10 mg/kg body weight; (n = 6) or Iloprost (1 mg/kg body weight; n = 6). Control rats received anti-Thy1 immunoglobulin G with saline (n = 6) or saline alone (n = 6). After 24 hours, kidneys were processed for light-microscopical evaluation. Proteinuria was studied in additional rats. Results showed that both drugs inhibited intraglomerular platelet activation (P < 0.005). 2Cl-ADO also reduced intraglomerular O2- production of neutrophils (P < 0.05), in contrast to Iloprost. Intraglomerular immunoglobulin G deposition, complement activation, neutrophil influx, and myeloperoxidase release were not affected by 2Cl-ADO or Iloprost. However, proteinuria was completely prevented by both drugs. It is concluded that PGI2 and nucleotidases are potentially able to attenuate this form of nephritis by inhibiting platelet activity, whereas nucleotidases also inhibit neutrophil activity in vivo.

Effect of aspirin and iloprost on adhesion of platelets to intact endothelium in vivo

Aspirin has been used for the prevention of platelet thrombi, both prophylactically and therapeutically, in a wide variety of conditions. Although the dosage used has also varied, it is now suggested that lower doses are as efficacious and probably safer than higher doses. Part of the problem in determining the amount to be used is that aspirin not only inhibits the formation of the proaggregatory thromboxane A2 in the platelet, at any dose, but also that it interferes with the production of prostacyclin (antiaggregatory) by the endothelial cells in a dose-dependent manner. Previously, utilizing a hamster cheek pouch preparation, we demonstrated that platelets would adhere to intact endothelium, in vivo, after an otherwise ineffectual dose of thrombin if the glycosaminoglycans of endothelial cells that produce antithrombin activity were first neutralized by protamine. Reported here is the effect of aspirin on the platelet thrombi produced by thrombin in this manner. Aspirin was found to inhibit platelet thrombosis by thrombin in low doses (optimum dose 2.5 mg/kg body weight), but at higher doses the aspirin was less effective. Actually, the higher doses of aspirin promoted platelet thrombus formation by thrombin even in the absence of protamine. Infusion of iloprost, an analog of prostacyclin, also prevented platelet thrombus formation by protamine and thrombin with or without the administration of aspirin, and this infusion overcame the thrombogenicity of the higher doses of aspirin. The results of these experiments in the hamster suggest that the optimum dosage of aspirin in the clinical treatment of prophylaxis of thrombosis in human patients would be 160 mg.(ABSTRACT TRUNCATED AT 250 WORDS)

Down-regulation in the production of matrix metalloproteinase 1 by human aortic intimal smooth muscle cells

Effects of dexamethasone, retinoic acid, prostaglandin E2 (PGE2), and Iloprost as a agonist of prostacyclin (A-PGI2) on DNA synthesis and production of a precursor of matrix metalloproteinase 1 (tissue procollagenase/proMMP-1) by human aortic smooth muscle cells were investigated. When after treatment with platelet-derived growth factor (PDGF), these agents were added to the cultures, DNA synthesis and production of proMMP-1 were inhibited in a dose-dependent manner. These results suggest that these agents are negative regulators of PDGF. Since these agents are present in the blood or produced in the blood wall, in addition, since PDGF plays the most important role in the process of atherosclerosis, we propose that these agents function in vivo as a systems of protection against atherosclerosis.

Effects of prostacyclin analogs on the synthesis of tissue factor, tumor necrosis factor-alpha and interleukin-1 beta in human monocytic THP-1 cells

Previous studies have shown that prostacyclin analogs can inhibit the expression of tissue factor (TF) procoagulant activity by human monocytes. The present studies have investigated this phenomenon further, by using a plasma coagulation assay to measure cellular TF activity, an immunoassay to measure TF antigen and reverse transcription/polymerase chain reaction with appropriate oligomer primers to measure TF mRNA. Iloprost and cicaprost inhibited lipopolysaccharide-induced increases in TF activity, antigen and mRNA (50% inhibition, 2-8 nM), with no apparent effect on TF mRNA stability. These agents therefore act at or before the level of transcription of the TF gene. The analogs were more potent inhibitors of tumor necrosis factor-alpha synthesis (50% inhibition at 334 +/- 40 pM cicaprost or 846 +/- 182 pM iloprost) and extraordinarily potent when combined with a phosphodiesterase inhibitor (50% inhibition at 101 +/- 31 pM iloprost in the presence of 20 microM isobutylmethylxanthine). Iloprost and cicaprost were less potent in inhibiting the synthesis of interleukin-1 beta (50% inhibition, 50-100 nM). Cicaprost inhibited lipopolysaccharide-induced increases in mRNA levels for TF, tumor necrosis factor-alpha and interleukin-1 beta; differential potency was again observed. We conclude that these three important monocyte functions can be down-regulated by prostacyclin analogs, and with differential sensitivity. Furthermore, the extreme sensitivity of tumor necrosis factor-alpha synthesis to inhibition suggests that such inhibition may be a major physiological function of prostacyclin itself.

Endothelial cell dysfunction secondary to the adhesion of diabetic erythrocytes. Modulation by iloprost

We previously showed the correlation between the extent of vascular complications and erythrocyte adherence to endothelium in diabetes mellitus. The accumulation of advanced glycation end products (AGEs) on the erythrocyte surface in diabetes mediates their interaction with endothelial cells through a specific endothelial receptor for AGEs (RAGE). Binding of diabetic erythrocytes to endothelial cells resulted in evidence of oxidant stress responsible for a range of cellular perturbations. In the present study, we have investigated the effect of iloprost, a prostacyclin analog, on several activities modified by diabetic erythrocyte-endothelium interaction: 1) generation of oxidant stress based on production of thiobarbituric acid reactive substances (TBARS: control: 2.37 +/- 0.32 versus iloprost: 1.39 +/- 0.005 mumol/10(11) cells), 2) alteration of the endothelial barrier function as measured by an increase permeability to 125I-albumin (control: 13.31 +/- 0.85 versus iloprost: 9.45 +/- 0.7 10(-7) cm/s) of the endothelial cell monolayer, 3) modification of the endothelial cell function showed by an increase in interleukin-6 release (control: 21.66 +/- 3.11 versus iloprost 15.45 +/- 0.76 ng/10(6) cells). The increase in permeability to albumin as well ass TBARS production and interleukin-6 release were inhibited by iloprost (10(-8)-10(-6) mol/l) treatment in a dose-dependent fashion. These results indicate that erythrocyte associated AGEs might alter endothelial cell function. The perturbations can be limited in vitro by iloprost.

Expression of prostacyclin receptor in human megakaryocytes

Prostacyclin (prostaglandin I2, PGI2) is a potent vasodilator and inhibitor of platelet aggregation. Although it is well known that the specific receptor for prostacyclin (PGI2-R) is abundantly expressed on platelets, PGI2-R expression in megakaryocytes is poorly understood. In this study, we examined its expression in leukemic or normal megakaryocytes. PGI2-R mRNA was expressed in human leukemic cell lines of megakaryocytic nature as evaluated by Northern blot analysis. Phorbol 12-myristate 13-acetate (PMA), interleukin-1 (IL-1), IL-3, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), thrombopoietin (TPO), and tumor necrosis factor-alpha (TNF-alpha) enhanced PGI2-R mRNA expression. The enhancement of PGI2-R expression by PMA and TPO was associated with the upregulation of platelet factor 4 or glycoprotein IIb mRNA expression. Iloprost, an agonist of prostacyclin, induced significant cyclic (c)AMP synthesis in these leukemic cells indicating that interaction of PGI2-R and its ligand can induce postreceptor signal transduction. Furthermore, iloprost-induced cAMP synthesis was enhanced by the pretreatment with PMA or the cytokines that promoted PGI2-R expression. PMA and TPO also increased the specific binding of [3H]iloprost to these cells. Pooled normal megakaryocytic colonies from TPO-containing semisolid culture of purified human CD34+ cells expressed PGI2-R, which were increased as the megakaryocytes matured with the peak expression before proplatelet formation, as evaluated by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). These results indicate that PGI2-R is expressed in human megakaryocytes and is upregulated by cytokines involved in thrombopoiesis or inflammation. Also, it was indicated that megakaryocytic maturation accompanies enhancement of PGI2-R expression.

Evaluation of a prostacyclin analog in prevention of pulmonary oxygen toxicity

Prolonged exposure to high concentrations of oxygen can result in significant lung injury, although newborn animals are tolerant relative to adults. We previously reported that relative O2 tolerance in the rabbit is lost by 10 days of age, and is coincident with a decline in lung prostacyclin. In the current study we administered iloprost, a stable prostacyclin analog, by continuous infusion to maturing rabbits exposed to greater than 95% oxygen. Compared to vehicle-treated controls, iloprost-treated rabbits had significantly lower protein in bronchoalveolar lavage fluid at 84 h, a smaller percentage of neutrophils at 65 and 84 h, and lower mortality at 96 h. The partial protection against pulmonary oxygen toxicity afforded by iloprost is likely due to its membrane stabilizing effect, and its inhibitory actions on neutrophil migration, activation, production of oxygen radicals and proteolytic enzymes.

Synergistic platelet inhibitory effect of the phosphodiesterase inhibitor piroximone and iloprost

Platelet activity is regulated through synthesis and degradation of the intracellular second messengers cAMP or cGMP. The antiplatelet effect of the phosphodiesterase (PDE) III inhibitor Piroximone (PIR) was studied in vitro in platelet rich plasma. ADP induced aggregation was inhibited by PIR with an IC50 of 67 +/- 43 microM. The inhibitory effect was time and dose dependent. The antiaggregatory effects in vivo were studied in anaesthetised rats. Reduction of platelet count following injection of 100 micrograms/kg bw collagen was measured after bolus injection of PIR and vehicle. Piroximone bolus 2 mg/kg bw resulted in a 50% inhibition of platelet aggregation in rats. Cyclic AMP levels in washed platelets rose time and dose dependently after PIR. Coincubation of PDE III inhibitor PIR and adenylate cyclase activator Iloprost (ILO) resulted in a significant synergistic enhancement of the antiaggregatory effect. The PDE III inhibitor PIR exerted an effective inhibition of platelet aggregation in vivo and in vitro. The inhibitory effects in vitro were synergistically augmented by the prostacyclin analog Iloprost. These platelet inhibitory effects might be of clinical importance.

Precision Cut Lung Slices as a Preclinical Model for Non-Small Cell Lung Cancer Chemoprevention

Lung cancer chemoprevention is critical to addressing cancer burden in high-risk populations. Chemoprevention clinical trials rely on data from preclinical models; however, in vivo studies have high financial, technical, and staffing requirements. Precision cut lung slices (PCLS) provide an ex vivo model that maintains the structure and function of native tissues. This model can be used for mechanistic investigations and drug screenings and reduces the number of animals and time required to test hypotheses compared with in vivo studies. We tested the use of PCLS for chemoprevention studies, demonstrating recapitulation of in vivo models. Treatment of PCLS with the PPARγ agonizing chemoprevention agent iloprost produced similar effects on gene expression and downstream signaling as in vivo models. This occurred in both wild-type tissue and Frizzled 9 knockout tissue, a transmembrane receptor required for iloprost's preventive activity. We explored new areas of iloprost mechanisms by measuring immune and inflammation markers in PCLS tissue and media, and immune cell presence with immunofluorescence. To demonstrate the potential for drug screening, we treated PCLS with additional lung cancer chemoprevention agents and confirmed activity markers in culture. PCLS offers an intermediate step for chemoprevention research between in vitro and in vivo models that can facilitate drug screening prior to in vivo studies and support mechanistic studies with more relevant tissue environments and functions than in vitro models.

PREVENTION RELEVANCE

PCLS could be a new model for premalignancy and chemoprevention research, and this work evaluates the model with tissue from prevention-relevant genetic and carcinogen exposed in vivo mouse models, in addition to evaluating chemoprevention agents.

Iloprost administration in acrodermatitis of Hallopeau complicated by acquired toes syndactyly: a case report and review of the literature

OBJECTIVE

Acrodermatitis Continua of Hallopeau (ACH) is a variant of pustular psoriasis often very difficult to treat. Secondary syndactyly, also called "pseudosyndactyly", is rare and can be a complication of burns, dystrophic epidermolysis bullosa or trauma. If left untreated, joint complications and definitive functional impairments may occur.

CASE REPORT

We report a case of a 74-year-old man with acrodermatitis continua of Hallopeau involving the toes and complicated by syndactyly. ACH regression following Iloprost administration was also observed.

DISCUSSION

Published studies are mainly limited to case reports only, due to the rarity of the disease. Therefore, there are no clear-cut therapeutic management guidelines available for this chronic and sometimes debilitating disease. ACH is often recalcitrant to the available therapies. Topical and systemic treatments have been described in literature with no long-lasting results.

CONCLUSIONS

To our knowledge, this is the first report of foot syndactyly associated to ACH. In our patient, ACH symptoms regressed with Iloprost administration: this finding has never been previously described in literature. If confirmed by other clinical experiences, Iloprost could be a further therapeutic option in ACH.