Nobel lecture, 8th December 1982. Adventures and excursions in bioassay: the stepping stones to prostacyclin

Thrombocytopathy and endotheliopathy: crucial contributors to COVID-19 thromboinflammation

The core pathology of coronavirus disease 2019 (COVID-19) is infection of airway cells by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that results in excessive inflammation and respiratory disease, with cytokine storm and acute respiratory distress syndrome implicated in the most severe cases. Thrombotic complications are a major cause of morbidity and mortality in patients with COVID-19. Patients with pre-existing cardiovascular disease and/or traditional cardiovascular risk factors, including obesity, diabetes mellitus, hypertension and advanced age, are at the highest risk of death from COVID-19. In this Review, we summarize new lines of evidence that point to both platelet and endothelial dysfunction as essential components of COVID-19 pathology and describe the mechanisms that might account for the contribution of cardiovascular risk factors to the most severe outcomes in COVID-19. We highlight the distinct contributions of coagulopathy, thrombocytopathy and endotheliopathy to the pathogenesis of COVID-19 and discuss potential therapeutic strategies in the management of patients with COVD-19. Harnessing the expertise of the biomedical and clinical communities is imperative to expand the available therapeutics beyond anticoagulants and to target both thrombocytopathy and endotheliopathy. Only with such collaborative efforts can we better prepare for further waves and for future coronavirus-related pandemics.

Aspirin as a COX inhibitor and anti-inflammatory drug in human skeletal muscle

Although aspirin is one of the most common anti-inflammatory drugs in the world, the effect of aspirin on human skeletal muscle inflammation is almost completely unknown. This study examined the potential effects and related time course of an orally consumed aspirin dose on the inflammatory prostaglandin E₂ (PGE₂)/cyclooxygenase (COX) pathway in human skeletal muscle. Skeletal muscle biopsies were taken from the vastus lateralis of 10 healthy adults (5 male and 5 female, 25 ± 2 yr old) before (Pre) and 2, 4, and 24 h after (Post) a standard dose (975mg) of aspirin and partitioned for analysis of 1) in vivo PGE₂ levels in resting skeletal muscle and 2) ex vivo skeletal muscle PGE₂ production when stimulated with the COX substrate arachidonic acid (5 μM). PGE₂ levels in vivo and PGE₂ production ex vivo were generally unchanged at each time point after aspirin consumption. However, most individuals clearly showed suppression of PGE₂, but at varying time points after aspirin consumption. When the maximum suppression after aspirin consumption was examined for each individual, independent of time, PGE₂ levels in vivo (184 ± 17 and 104 ± 23pg/g wet wt at Pre and Post, respectively) and PGE₂ production ex vivo (2.74 ± 0.17 and 2.09 ± 0.11pg·mg wet wt^-1·min^-1 at Pre and Post, respectively) were reduced ( P < 0.05) by 44% and 24%, respectively. These results provide evidence that orally consumed aspirin can inhibit the COX pathway and reduce the inflammatory mediator PGE₂ in human skeletal muscle. Findings from this study highlight the need to expand our knowledge regarding the potential role for aspirin regulation of the deleterious influence of inflammation on skeletal muscle health in aging and exercising individuals. NEW & NOTEWORTHY This study demonstrated that orally consumed aspirin can target the prostaglandin/cyclooxygenase pathway in human skeletal muscle. This pathway has been shown to regulate skeletal muscle metabolism and inflammation in aging and exercising individuals. Given the prevalence of aspirin consumption, these findings may have implications for skeletal muscle health in a large segment of the population.

Resolution of Inflammation: What Controls Its Onset?

An effective resolution program may be able to prevent the progression from non-resolving acute inflammation to persistent chronic inflammation. It has now become evident that coordinated resolution programs initiate shortly after inflammatory responses begin. In this context, several mechanisms provide the fine-tuning of inflammation and create a favorable environment for the resolution phase to take place and for homeostasis to return. In this review, we focus on the events required for an effective transition from the proinflammatory phase to the onset and establishment of resolution. We suggest that several mediators that promote the inflammatory phase of inflammation can simultaneously initiate a program for active resolution. Indeed, several events enact a decrease in the local chemokine concentration, a reduction which is essential to inhibit further infiltration of neutrophils into the tissue. Interestingly, although neutrophils are cells that characteristically participate in the active phase of inflammation, they also contribute to the onset of resolution. Further understanding of the molecular mechanisms that initiate resolution may be instrumental to develop pro-resolution strategies to treat complex chronic inflammatory diseases, in humans. The efforts to develop strategies based on resolution of inflammation have shaped a new area of pharmacology referred to as "resolution pharmacology."

Resolution of Inflammation: What Controls Its Onset?

An effective resolution program may be able to prevent the progression from non-resolving acute inflammation to persistent chronic inflammation. It has now become evident that coordinated resolution programs initiate shortly after inflammatory responses begin. In this context, several mechanisms provide the fine-tuning of inflammation and create a favorable environment for the resolution phase to take place and for homeostasis to return. In this review, we focus on the events required for an effective transition from the proinflammatory phase to the onset and establishment of resolution. We suggest that several mediators that promote the inflammatory phase of inflammation can simultaneously initiate a program for active resolution. Indeed, several events enact a decrease in the local chemokine concentration, a reduction which is essential to inhibit further infiltration of neutrophils into the tissue. Interestingly, although neutrophils are cells that characteristically participate in the active phase of inflammation, they also contribute to the onset of resolution. Further understanding of the molecular mechanisms that initiate resolution may be instrumental to develop pro-resolution strategies to treat complex chronic inflammatory diseases, in humans. The efforts to develop strategies based on resolution of inflammation have shaped a new area of pharmacology referred to as “resolution pharmacology.”

Physiology of Kidney Renin

The protease renin is the key enzyme of the renin-angiotensin-aldosterone cascade, which is relevant under both physiological and pathophysiological settings. The kidney is the only organ capable of releasing enzymatically active renin. Although the characteristic juxtaglomerular position is the best known site of renin generation, renin-producing cells in the kidney can vary in number and localization. (Pro)renin gene transcription in these cells is controlled by a number of transcription factors, among which CREB is the best characterized. Pro-renin is stored in vesicles, activated to renin, and then released upon demand. The release of renin is under the control of the cAMP (stimulatory) and Ca2+(inhibitory) signaling pathways. Meanwhile, a great number of intrarenally generated or systemically acting factors have been identified that control the renin secretion directly at the level of renin-producing cells, by activating either of the signaling pathways mentioned above. The broad spectrum of biological actions of (pro)renin is mediated by receptors for (pro)renin, angiotensin II and angiotensin-( 1 – 7 ).

The human prostacyclin receptor from structure function to disease

Thirty years have passed since Vane and colleagues first described a substance, prostanoid X, from microsomal fractions (later called prostacyclin) that relaxed rather than contracted mesenteric arteries. The critical role of prostacyclin in many pathophysiological conditions, such as atherothrombosis, has only recently become appreciated (through receptor knockout mice studies, selective cyclooxygenase-2 inhibition clinical trials, and the discovery of dysfunctional prostacyclin receptor genetic variants). Additionally, important roles in such diverse areas as pain and inflammation, and parturition are being uncovered. Prostacyclin-based therapies, currently used for pulmonary hypertension, are accordingly emerging as possible treatments for such diseases, fueling interests in structure function studies for the receptor and signal transduction pathways in native cells. The coming decade is likely to yield many further exciting advances.

A critique of paradoxes in current advice on dietary lipids

Beliefs about credible hypotheses of dietary causes of disease still need well-defined mediators to test for logical proof or disproof. We know that food energy causes transient postprandial oxidative insults that may not be fully reversible. Also, eating vitamin-like 18-carbon polyunsaturated fatty acids (PUFA) in foods maintains the 20- and 22-carbon highly unsaturated fatty acids (HUFA) in tissues. Tissue HUFA form hormone-like mediators that each amplify transient postprandial insults into fatal inflammatory, thrombotic and arrhythmic events in cardiovascular disease, a major preventable cause of death. Similar diet-based amplified events may also occur in other inflammatory proliferative disorders including cancer, dementia, arthritis and asthma. Puzzling paradoxes come from fragmented views of this situation which convey incomplete knowledge in oversimplified messages. Tools now exist to demonstrate successful prevention of two fatal food imbalances with credible dietary preventive interventions, but organizers and financers to help gather the evidence remain unknown. The overall evidence accumulated about diet, disease and death may be nearing a paradigm shift in which prior observed facts remain while beliefs about their accepted interpretation change.

John R. Vane, « pharmacologue de l’endothélium vasculaire », 1927–2004

The work of John Vane greatly contributed to the use of aspirin in cardiology. The impact of aspirin administration at low dose for the prevention of stroke or coronary attack results from its effect on enzymes regulating the production of prostaglandins. After understanding the mechanism of interaction between aspirin and the vascular endothelium, Vane proposed assigning a major physiological function to the vascular endothelium which then became a pharmacological target for new drugs. Using an ingenious "real time" biological assay of bloodstream hormones irrigating an isolated organ called the "blood-bathed organ cascade", John Vane developed a system for highly sensitive monitoring of several mediators like angiotensin, bradykinin and prostaglandins and discovered prostacyclin, a potent platelet aggregation inhibitor. Vane explained anti-inflammatory drugs effects (among which aspirin remains the leader) through their activity on cyclo-oxygenase and inhibition of prostacyclin and thromboxane production. Another cyclooxygenase isoform, so-called type 2, has been discovered in 1991. Thus, besides the constitutive COX-1, participating to stomach protection and renal artery vasodilatation, a COX-2 enzyme is existing, induced by inflammatory phenomenons and cytokines stimulation, allowing to design specific inhibitors "coxibs", playing an increasing but controversial role in the struggle against inflammation. He won Albert Lasker Prize in 1977 and Nobel Prize in medicine and physiology (shared with Sune Bergström and Bengt I. Samuelson) in 1982.

Clinical efficacy and tolerability of tenoxicam in African patients with osteoarthritis, rheumatoid arthritis, tendinitis and/or bursitis: an open study

An open clinical evaluation was carried out in 736 African out-patients suffering from rheumatic and inflammatory disorders to assess the efficacy and tolerability of tenoxicam in relieving the signs and symptoms of their condition. On entry, all previous treatment was discontinued and patients received a simple daily dose of 20 mg tenoxicam orally for 15 days in the case of those with rheumatoid arthritis or tendinitis, or for 30 days in those with osteoarthritis. Paracetamol was allowed as a rescue analgesic. Subjective verbal scale assessments were used to determine levels of pain at rest, on movement and at night, sleep disturbance and functional incapacity, on entry and during treatment. At the end of the study period, both physicians and patients gave an overall opinion of the clinical response to tenoxicam, and patients were asked how their current compared with their previous treatment. The results showed that approximately 90% of patients had an excellent or good response to tenoxicam with marked improvement in all the signs and symptoms evaluated. Moreover, tenoxicam proved to be well tolerated, only a small number of patients reporting adverse events, mainly gastro-intestinal.

Improved survival of transplanted cortical brain tissue grafts by iloprost in rats

The cytoprotective effect of iloprost on the viability and survival of embryonic cortical brain tissue grafts was examined ultrastructurally under light and electron microscopy before and 4 weeks after transplantation surgery. It was shown that neural grafts stored in iloprost solution (50 ng/mL) for 3 hours were more or less in a normal cytoarchitecture compared with saline-preserved grafts. Moreover, it was demonstrated that 4 weeks after transplantation, graft tissues stored in iloprost solution for 3 hours before implantation maintained a successful survival. Thus, a higher cellular population with new vascularization areas and preservation of myelin formation were accepted as a desirable integration of the graft tissue into the host brain tissue. The mechanism of action of iloprost is discussed.

Pharmacologic response of endothelium to microvascular temporary clip application

To assess the effects of microvascular temporary clip application on vessel relaxing capability and endothelial substance release, the carotid rings of rats clipped for various durations were studied via bioassay. Noradrenaline and phenylephrine produced an immediate contraction and subsequent relaxation that failed to be suppressed by lysine acetylsalicylate or nicotine in the controls and in the arteries clipped for 0.5, 1, and 5 minutes; however, this relaxation was greatly reduced when the duration was 10 minutes. The results suggest the possible role of inadequate endothelium-derived relaxing factor release following prolonged application of the clips.

Involvement of prostanoids in the pulmonary pressor effect of histamine

The role of prostanoids in the pulmonary actions of histamine(HA) was investigated using various antagonists and assay organs in superfusion cascade. Intraarterial injection of HA to the perfused lung caused contractions of rabbit aorta, rat stomach strips, guinea pig trachea, but contraction followed by relaxation of bovine coronary artery, superfused with lung effluent. Lung effluent produced no significant changes in resting tensions of guinea pig ileum or rat colon. The thromboxane synthetase inhibitor, UK 38485, reduced and the thromboxane/prostaglandin receptor antagonist, SQ 29548 abolished HA-induced contractions of all superfused assay tissues. Both contractile and relaxant responses of bovine coronary artery were completely inhibited by indomethacin. The pulmonary pressor effect of HA was also significantly inhibited by all of these antagonists. Our results indicate that HA releases thromboxane A2, prostaglandin endoperoxides, and prostacyclin but not leukotriene and prostaglandin E2- like substances from the guinea pig lung.

Experimental cerebral vasospasm: resolution by iloprost

A new stable analogue of prostacyclin, iloprost, was tested on the basilar artery of anaesthetized rabbits constricted by electrical stimulation and intracisternal injection of autologous blood. The vasospasm induced by these stimuli was effectively relieved (about 100%) by topical application of iloprost, a stable analogue of prostacyclin (PGI2), and no constriction occurred on further stimulation within one hour. The mechanisms of the action of iloprost and its possible therapeutic value in subarachnoid haemorrhage are discussed.

Enzymes functional in the syntheses of leukotrienes and related compounds

1. Leukotrienes (LT) constitute a family of bioactive compounds mainly involved in inflammatory and immunological responses. 2. LTs are produced via an unstable intermediate, LTA4 which is synthesized by the action of arachidonate 5-lipoxygenase, a calcium-dependent enzyme. 3. LTA4 is converted to either LTB4 by cytosolic LTA4 hydrolase or to LTC4 by LTC4 synthase present in the microsomal fraction. 4. Three enzymes (5-lipoxygenase, LTA4 hydrolase and LTC4 synthase) were purified, and molecular and kinetic properties have been extensively investigated. 5. The cDNA of LTA4 hydrolase was recently isolated, and the primary structure was fully determined in our laboratory. 6. I report herein recent progress in studies on arachidonic acid metabolism, with the focus primarily on enzymes linked to the 5-lipoxygenase pathway.

Individual variations of prostanoid agonist responses in rabbit aorta: evidence for the independent regulation of prostanoid receptor subtypes

1 The frequency and selectivity of individual variations of prostanoid agonist responses in aortic strips from a population of male rabbits was studied. Three levels of responsiveness to the thromboxane mimetic U46619 occurred: responders (R), intermediate responders (IR), and non-responders (NR). R could be subdivided into R1 and R2 based on an enhanced potency of prostaglandin F2 alpha (PGF2 alpha) in R2. In the total population (n = 92), the phenotype frequency was: R, 69%; IR, 11%; and NR, 20%. In a subgroup of this population in which R1 and R2 phenotypes were determined (n = 63), the phenotype frequency was: R1, 54%; R2, 19%; IR, 6%; and NR, 21%. 2 The four rabbit aorta phenotypes, R1, R2, IR, and NR, were characterized with respect to the rank orders of prostanoid agonist potency, agonist intrinsic activities, and the effects of the thromboxane receptor antagonist SQ29548. The rank order of prostanoid agonist potency was U46619 greater than PGF2 alpha greater than PGE2 in R1 and R2, and PGF2 alpha greater than or equal to PGE2 greater than U46619 in IR and NR. For each prostanoid agonist, the intrinsic activity was highest in R (R1 congruent to R2), intermediate in IR, and lowest in NR. In R1, SQ29548 inhibited all prostanoid agonist responses equally. The contractile effects of PGF2 alpha and PGE2 were partially resistant to inhibition by SQ29548 in R2. Prostanoid agonist responses were not inhibited by SQ29548 in IR. 3 The potency of histamine was equivalent in R1, R2, IR, and NR. 4 It is concluded that there are individual variations in the functional expression of thromboxane receptor sensitivity, i.e., prostanoid agonist responses inhibited by SQ29548. Also, there are individual variations in the functional expression of the sensitivity of a non-thromboxane receptor or receptors, i.e., prostanoid agonist responses not inhibited by SQ29548. It has been proposed by others that prostanoid receptors be termed P-receptors and that the prostanoid agonist to which they are most sensitive be indicated by a preceding letter, e.g., TP- for thromboxane receptor and FP- for PGF2 alpha-selective receptor. Accordingly, we proposed a working hypothesis that suggests the four phenotypes could result from the independent regulation of the functional expression of TP- and FP-receptor subtypes with (a) R2 containing both the TP- and FP-receptor subtypes in a fully functional state; (b) R1 containing only the functional TP-receptor; (c) IR containing only the functional FP-receptor; and (d) NR containing only a low efficacy FP-receptor system. 5 The mechanisms underlying the observed individual variations are unknown but could include changes in receptor number or affinity, changes in receptor-effector coupling, changes in a second messenger system, or changes in tissue degradative or uptake processes. Further study is needed to differentiate between these possibilities.

Modulation by endothelium of the vascular effects of angiotensin II

Modulation by vascular endothelium of the effects of AII was studied in the isolated rabbit aortic and superior mesenteric artery strips. The contractile effect of AII was enhanced in rubbed aortic strips. Similar enhancement was obtained in hydroquinone pretreated unrubbed strips. The relaxing effect of acetylcholine in AII--induced precontracted aortic strips was abolished after rubbing and hydroquinone pretreatment. However, no significant changes were observed in the contractile response to AII on aspirin and nicotine pretreated strips. In the isolated mesenteric artery strips AII produced a biphasic responses. The contractile effect of AII was enhanced in rubbed strips. Similar potentiation was also obtained in hydroquinone, aspirin and nicotine pretreated unrubbed strips. The relaxation phase of AII response was completely abolished in rubbed strips but partially inhibited in hydroquinone, aspirin and nicotine pretreated unrubbed strips. From these results it was concluded that EDRF is the main endothelial humoral factor which modulates the effect of AII in the rabbit aorta while both EDRF and PGI2 are involved for the modulation of the effects of octapeptide in the mesenteric artery.

Iloprost (ZK 36374) modulates the responses to beta-adrenoceptor agonists in guinea-pig airways and pulmonary vasculature

The effect of iloprost on airway smooth muscles and its influence on the actions of beta-agonists and histamine were studied in the isolated perfused lung and isolated tracheal strips from guinea-pigs. Bolus injection of iloprost into the pulmonary artery elicited a concentration-dependent decrease in pulmonary perfusion pressure and an increase in airway resistance. These effects are not mediated through cholinergic, serotoninergic and histaminergic receptors. A rapid tachyphylaxis affected the effect of iloprost in airway resistance but not in pulmonary perfusion pressure. Iloprost did not induce a response in the isolated tracheal strips and did not alter the effect of histamine in both tracheal strips and airway resistance. This compound, however, caused an inhibition in the airway resistance-reducing effect of adrenaline and isoprenaline in the isolated perfused lung and a potentiation in the perfusion pressure-increasing effect of adrenaline. Iloprost also inhibited the relaxing effect of adrenaline and isoprenaline in the isolated tracheal strips precontracted with histamine and potentiated the inhibitory effect of propranolol against adrenaline and isoprenaline. From these results it was concluded that: Iloprost, a stable analogue of prostacyclin, modulates the beta-adrenoceptor blocking effect of propranolol in both airway smooth muscles and pulmonary vasculature.