Tissue fibroblasts are a critical source of prostacyclin and anti-thrombotic

Prostacyclin is an anti-thrombotic hormone long considered to be derived from the vascular endothelium. However, the role of non-vascular sources for prostacyclin synthesis has not been systematically evaluated due to a lack of tools. Here we used cell-specific knockout mice and human tissues to show that lung, and other tissues, are powerful producers of prostacyclin independent of their vascular components. Instead, in mice and humans, lung prostacyclin synthesis is associated with fibroblasts. The fibroblast-derived prostaglandins enter the circulation and provide systemic anti-thrombotic protection. These observations define a new paradigm in prostacyclin biology in which fibroblast/non-vascular-derived prostacyclin works in parallel with prostaglandins produced by the endothelium to control cardiovascular health. These results may explain how local diseases of the lung and elsewhere result in cardiovascular risk.

Effects of dipyridamole and its use in neurology

Dipyridamole has been on the pharmaceutical market since 1959 and, as a pyrimidyl-pyrimidine compound, has a variety of mechanisms of action. The very first action of dipyridamole was its antianginal effect. In subsequent years, attention was drawn to the antiplatelet properties of dipyridamole, which are related to inhibition of platelet phosphodiesterase as well as to blocking adenosine transport. Another important property of dipyridamole is its effect on the deformability of red blood cells, thereby improving microcirculation. Dipyridamole affects changes in the dynamics of platelet activity and vascular reactivity and causes improvement of cerebral perfusion. Due to its pronounced antiplatelet properties, the drug has been widely studied for the prevention of ischemic strokes and transient ischemic attacks, both as monotherapy and in combination with other drugs. Unlike other platelet antiaggregants, dipyridamole does not have a damaging effect on mucous membranes. Its antiplatelet effect is not accompanied with inhibition of cyclooxygenase activity and reduction of prostacyclin synthesis. In the treatment of cerebral circulation disorders, dipyridamole can be used to control the antithrombotic effect by selecting the optimal dose of the drug. Dipyridamole has antioxidant properties, enhances NO-mediated pathways, has indirect anti-inflammatory effects via adenosine and prostaglandin-2 as well as direct anti-inflammatory effects and several other effects. Dipyridamole is considered a safe drug based on decades of clinical experience. Its side effects are usually limited and transient. Given the diverse effects of dipyridamole, it can be used for a wide range of pathologies other than thrombosis prevention. Data on the efficacy and safety of dipyridamole in various diseases of the neurological spectrum are presented.

Comparative Effects of Metamizole (Dipyrone) and Naproxen on Renal Function and Prostacyclin Synthesis in Salt-Depleted Healthy Subjects - A Randomized Controlled Parallel Group Study

Aim: The objective was to investigate the effect of metamizole on renal function in healthy, salt-depleted volunteers. In addition, the pharmacokinetics of the four major metamizole metabolites were assessed and correlated with the pharmacodynamic effect using urinary excretion of the prostacyclin metabolite 6-keto-prostaglandin F1α.Methods: Fifteen healthy male volunteers were studied in an open-label randomized controlled parallel group study. Eight subjects received oral metamizole 1,000 mg three times daily and seven subjects naproxen 500 mg twice daily for 7 days. All subjects were on a low sodium diet (50 mmol sodium/day) starting 1 week prior to dosing until the end of the study. Glomerular filtration rate was measured using inulin clearance. Urinary excretion of sodium, potassium, creatinine, 6-keto-prostaglandin F1α, and pharmacokinetic parameters of naproxen and metamizole metabolites were assessed after the first and after repeated dosing.Results: In moderately sodium-depleted healthy subjects, single or multiple dose metamizole or naproxen did not significantly affect inulin and creatinine clearance or sodium excretion. Both drugs reduced renal 6-keto-prostaglandin F1α excretion after single and repeated dosing. The effect started 2 h after intake, persisted for the entire dosing period and correlated with the concentration-profile of naproxen and the active metamizole metabolite 4-methylaminoantipyrine (4-MAA). PKPD modelling indicated less potent COX-inhibition by 4-MAA (EC50 0.69 ± 0.27 µM) compared with naproxen (EC50 0.034 ± 0.033 µM).Conclusions: Short term treatment with metamizole or naproxen has no significant effect on renal function in moderately sodium depleted healthy subjects. At clinically relevant doses, 4-MAA and naproxen both inhibit COX-mediated renal prostacyclin synthesis.

Engineering ‘Enzymelink’ for screening lead compounds to inhibit mPGES-1 while maintaining prostacyclin synthase activity

Aim: This study investigated our Enzymelinks, COX-2-10aa-mPGES-1 and COX-2-10aa-PGIS, as cellular cross-screening targets for quick identification of lead compounds to inhibit inflammatory PGE2 biosynthesis while maintaining prostacyclin synthesis. Methods: We integrated virtual and wet cross-screening using Enzymelinks to rapidly identify lead compounds from a large compound library. Results: From 380,000 compounds virtually cross-screened with the Enzymelinks, 1576 compounds were identified and used for wet cross-screening using HEK293 cells that overexpressed individual Enzymelinks as targets. The top 15 lead compounds that inhibited mPGES-1 activity were identified. The top compound that specifically inhibited inflammatory PGE2 biosynthesis alone without affecting COX-2 coupled to PGI2 synthase (PGIS) for PGI2 biosynthesis was obtained. Conclusion: Enzymelink technology could advance cyclooxygenase pathway-targeted drug discovery to a significant degree.

Effects of Paracetamol on NOS, COX, and CYP Activity and on Oxidative Stress in Healthy Male Subjects, Rat Hepatocytes, and Recombinant NOS

Paracetamol (acetaminophen) is a widely used analgesic drug. It interacts with various enzyme families including cytochrome P450 (CYP), cyclooxygenase (COX), and nitric oxide synthase (NOS), and this interplay may produce reactive oxygen species (ROS). We investigated the effects of paracetamol on prostacyclin, thromboxane, nitric oxide (NO), and oxidative stress in four male subjects who received a single 3 g oral dose of paracetamol. Thromboxane and prostacyclin synthesis was assessed by measuring their major urinary metabolites 2,3-dinor-thromboxane B2and 2,3-dinor-6-ketoprostaglandin F1α, respectively. Endothelial NO synthesis was assessed by measuring nitrite in plasma. Urinary 15(S)-8-iso-prostaglanding F2αwas measured to assess oxidative stress. Plasma oleic acid oxide (cis-EpOA) was measured as a marker of cytochrome P450 activity. Upon paracetamol administration, prostacyclin synthesis was strongly inhibited, while NO synthesis increased and thromboxane synthesis remained almost unchanged. Paracetamol may shift the COX-dependent vasodilatation/vasoconstriction balance at the cost of vasodilatation. This effect may be antagonized by increasing endothelial NO synthesis. High-dosed paracetamol did not increase oxidative stress. At pharmacologically relevant concentrations, paracetamol did not affect NO synthesis/bioavailability by recombinant human endothelial NOS or inducible NOS in rat hepatocytes. We conclude that paracetamol does not increase oxidative stress in humans.

Enhanced Prostacyclin Synthesis by Adenoviral Gene Transfer Reduced Glial Activation and Ameliorated Dopaminergic Dysfunction in Hemiparkinsonian Rats

Prostacyclin (PGI2), a potent vasodilator and platelet antiaggregatory eicosanoid, is cytoprotective in cerebral circulation. It is synthesized from arachidonic acid (AA) by the sequential action of cyclooxygenase- (COX-) 1 or 2 and prostacyclin synthase (PGIS). Because prostacyclin is unstablein vivo, PGI2analogs have been developed and demonstrated to protect against brain ischemia. This work attempts to selectively augment PGI2synthesis in mixed glial culture or in a model of Parkinson’s disease (PD) by direct adenoviral gene transfer of prostacyclin biosynthetic enzymes and examines whether it confers protection in cultures orin vivo. Confluent mixed glial cultures actively metabolized exogenous AA into PGE2and PGD2. These PGs were largely NS398 sensitive and considered as COX-2 products. Gene transfer of AdPGIS to the cultures effectively shunted the AA catabolism to prostacyclin synthesis and concurrently reduced cell proliferation. Furthermore, PGIS overexpression significantly reduced LPS stimulation in cultures.In vivo, adenoviral gene transfer of bicistronic COX-1/PGIS to substantia nigra protected 6-OHDA- induced dopamine depletion and ameliorated behavioral deficits. Taken together, this study shows that enhanced prostacyclin synthesis reduced glial activation and ameliorated motor dysfunction in hemiparkinsonian rats. Prostacyclin may have a neuroprotective role in modulating the inflammatory response in degenerating nigra-striatal pathway.