Inhibition of human monocyte adhesion to endothelial cells by the coumarin derivative, cloricromene

Anti-Inflammatory Activity of Ferula assafoetida Oleo-Gum-Resin (Asafoetida) against TNF-α-Stimulated Human Umbilical Vein Endothelial Cells (HUVECs)

Inflammation is the body’s biological reaction to endogenous and exogenous stimuli. Recent studies have demonstrated several anti-inflammatory properties of Ferula species. In this paper, we decided to study the anti-inflammatory effect of ethanolic extract of Ferula assafoetida oleo-gum-resin (asafoetida) against TNF-α-stimulated human umbilical vein endothelial cells (HUVECs). HUVECs were cultured in a flat-bottom plate and then treated with ethanolic extract of asafoetida (EEA, 0-500 μg/ml) and TNF-α (0-100 ng/ml) for 24 h. We used the MTT test to assess cell survival. In addition, the LC-MS analysis was performed to determine the active substances. HUVECs were pretreated with EEA and then induced by TNF-α. Intracellular reactive oxygen species (ROS) and adhesion of peripheral blood mononuclear cells (PBMCs) to HUVECs were evaluated with DCFH-DA and CFSE fluorescent probes, respectively. Gene expression of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin and surface expression of ICAM-1 protein were measured using real-time PCR and flow cytometry methods, respectively. While TNF-α significantly increased intracellular ROS formation and PBMC adhesion to TNF-α-induced HUVECs, the pretreatment of HUVECs with EEA (125 and 250 μg/ml) significantly reduced the parameters. In addition, EEA pretreatment decreased TNF-α-induced mRNA expression of VCAM-1 and surface protein expression of ICAM-1 in the target cells. Taken together, the results indicated that EEA prevented ROS generation, triggered by TNF-α, and inhibited the expression of VCAM-1 and ICAM-1, leading to reduced PBMC adhesion. These findings suggest that EEA can probably have anti-inflammatory properties.

Retinal and Systemic Pharmacokinetics of the Anti-Inflammatory Drug Cloricromene Following Oral Administration in the Rat and Rabbit

PURPOSE

The aim of this study was to evaluate the retina and plasma distribution of cloricromene, a coumarin derivative, and its active metabolite (MET) after an oral administration in rabbits and rats.

METHODS

A single dose of cloricromene was orally administered to rabbits (10 or 100 mg/kg) and to rats (100 mg/kg). Retina and plasma samples were collected at 15, 30, 60, and 90 min following administration. Drug concentrations in the retina and plasma were measured by high-performance liquid chromatography.

RESULTS

As anticipated, only the active metabolite was found in all samples. The retina and plasma showed the same T(max); peak levels of the drug were achieved at 15 min in rats and at 30 min in rabbits. In rabbits, MET exposure was approximately dose-proportional in both retina and plasma between the 10- and 100-mg/kg dose. Substantial retinal exposure was observed in both the rat and rabbit, at exposures approximately nine- to sixteenfold lower in the retina than in plasma.

CONCLUSIONS

The results showed that the active metabolite of cloricromene reached the retina after a single oral dose with exposures proportional to those in plasma. These data, along with the previously published potency data for cloricromene, suggest that cloricromene could be potentially useful in ischemic-retinal diseases where amelioration of blood flow and inflammation is desirable.

Cloricromene, a semi-synthetic coumarin derivative, inhibits tumor necrosis factor-alpha production at a pre-transcriptional level

Cloricromene decreases myocardial infarct size after ischemic-reperfusion injury in vivo, and it has been suggested that this is due to inhibition of tumor necrosis factor-alpha (TNF-alpha). The purpose of this work was to characterize the mechanism of cloricromene-induced inhibition of TNF-alpha in rat macrophages. Cloricromene inhibited lipopolysaccharide-induced TNF-alpha release in a dose-dependent manner (IC(50)=5.9 +/- 0.8 microM). This was not due to cytotoxicity, as cloricromene was well tolerated up to 500 microM. Cloricromene inhibited lipopolysaccharide-induced expression of TNF-alpha mRNA, which suggests a pre-transcriptional effect. We then investigated the early signal transduction pathway triggered by lipopolysaccharide. The binding of lipopolysaccharide to its receptor CD14 activates protein kinase C and nuclear factor-kappaB (NF-kappaB). Cloricromene inhibited NF-kappaB activation in a dose-dependent manner, but affected protein kinase C translocation only slightly. We then established that cloricromene inhibited lipopolysaccharide-induced cellular oxidative activity, which is important for NF-kappaB activation. Our results show that cloricromene interferes with the early signal transduction pathway triggered by lipopolysaccharide.

Differential inhibition of polymorphonuclear leucocyte functions by cloricromene

Leucocytes play an essential role in the pathogenesis of ischaemia and reperfusion injury and inhibition of their adhesion and of mediator release can reduce vascular and tissue damage. Previous studies have shown that cloricromene modifies several granulocyte as well as monocyte/macrophage functions and it has been shown that cloricromene administration exerts a clear protective action in several experimental models of ischaemia. The present work describes new data on polymorphonuclear leukocyte (PMN) inhibition exerted by cloricromene and compares these observations with earlier ones. Human washed PMN and human whole blood (HWB) were studied in vitro upon stimulation with f-MLP in the presence of cytochalasin B, with opsonized zymosan and with a phorbol ester (PMA). Amongst free radicals, superoxide anions were chosen as index of oxidative burst. Phagocytosis and beta-glucuronidase, as lysosomal release indicators, were measured to characterize PMN function: cloricromene inhibited concentration-dependently all the parameters upon stimulation by each activator tested. Experiments performed in rabbit whole blood (RWB) showed that cloricromene inhibited free radical generation with IC50 values similar to those obtained in human whole blood. Comparing the action of cloricromene on human cells in different tests, we found that some parameters were more sensitive than others, even when the same stimulus was used. In particular, free radical generation was inhibited by cloricromene with IC50 values below 36 microM, while other functions, like lysosomal release and phagocytosis were inhibited with IC50 values over 100 microM. These data confirm that cloricromene exerts a notable inhibitory effect on PMN and may explain the activity of the compound, observed in vivo in several experimental models of ischaemia-reperfusion and shock.

Inhibition of PAF synthesis by stimulated human polymorphonuclear leucocytes with cloricromene, an inhibitor of phospholipase A2 activation

1. A phospholipase A2 (PLA2) represents the key enzyme in the remodelling pathway of platelet-activating factor (PAF) synthesis in human polymorphonuclear (PMN) leucocytes. 2. PLA2 activation is also the rate-limiting step for the release of the arachidonic acid utilized for the synthesis of leukotrienes in stimulated leucocytes; however, it is unknown whether the PLA2s involved in the two biosynthetic pathways are identical. 3. Cloricromene (8-monochloro-3-beta-diethylaminoethyl-4-methyl-7-ethoxy- carbonylmethoxy coumarin) is an antithrombotic coumarin derivative which inhibits platelet and leucocyte function and suppresses arachidonic acid liberation by interfering with PLA2 activation. 4. The aim of the present study was to assess whether chloricromene inhibits PAF synthesis by stimulated human polymorphonuclear leucocytes (PMNs). 5. Cloricromene (50-500 microM) inhibited in a concentration-dependent manner the release of PAF, as measured by h.p.l.c. bioassay, from A23187-stimulated PMNs. Significant inhibition (45%) of PAF-release was obtained with 50 microM cloricromene and the IC50 was 85 microM. Mepacrine (500 microM), a non-specific PLA2 inhibitor, strikingly reduced PAF release. 6. The incorporation of [3H]-acetate into [3H]-PAF induced by serum-treated zymosan in human PMNs was also inhibited concentration-dependently by cloricromene, with an IC50 of 105 microM. Mepacrine also suppressed [3H]-acetate incorporation into [3H]-PAF. 7. Cloricromene did not affect the activities of the enzymes involved in PAF-synthesis acetyltransferase or phosphocholine transferase. 8. Our data demonstrate that cloricromene, an inhibitor of PLA2-activation in human leucocytes, reduces the synthesis of PAF by stimulated PMNs. This finding has a twofold implication: the PLA2s (or the mechanisms that regulate their activation) involved in PAF synthesis and arachidonate release in human leucocytes are either identical or else indistinguishable by their sensitivity to cloricromene; the inhibition of PAF release by activated leucocytes may contribute to the antithrombotic and anti-ischaemic activities exerted by cloricromene.

Endothelium as a therapeutical target in peripheral occlusive arterial diseases: consideration for pharmacological interventions

The aim of this review is to consider the role of endothelium in the establishment of injury induced by ischaemia and reperfusion with particular emphasis on the vascular beds of the legs. We review the main abnormalities found in the macro- and microcirculation in these conditions and discuss the various theories put forward to explain the mechanism by which endothelial injury is induced. Endothelial cells play a key role in maintaining patent and functional capillaries. When blood vessels are damaged they become unresponsive to vasodilatory stimuli and intraluminal thrombosis may occur. The relative contribution of platelets and leukocytes in the formation of final ischaemic damage is widely discussed. Furthermore, the role of reperfusion in causing damage to post-ischaemic vascular beds is considered as well. The degree to which post-ischaemic injury is reversible might define the opportunity for therapeutic interventions.