Action of dipyridamole and warfarin on growth of human endothelial cells cultured in serum-free media

Combination therapy with or without warfarin and dipyridamole for severe childhood IgA nephropathy: an RCT

BACKGROUND

Two previous randomized controlled trials showed that treatment of severe childhood immunoglobulin A (IgA) nephropathy using prednisolone with azathioprine, heparin-warfarin, or dipyridamole prevented the increase of sclerosed glomeruli. Prednisolone alone, however, did not prevent further increase. These studies indicated the importance of immunosuppressants in the treatment. An additional pilot study using mizoribine instead of azathioprine enabled us to complete 2 years of combined regimen. It showed non-numerical inferior effectiveness compared with the azathioprine regimen. Further examination of the additional efficacy of warfarin and dipyridamole was required.

METHODS

A randomized control trial of prednisolone and mizoribine with (group 1) or without (group 2) warfarin and dipyridamole was administered for treatment of 71 children with severe IgA nephropathy to evaluate the efficacy of additional warfarin and dipyridamole.

RESULTS

Thirty of 34 patients (88.2%) in group 1, and 27 of 36 patients (75.0%) showed the disappearance of proteinuria as defined by early morning urinary protein to creatinine ratio of < 0.2 during the 2-year treatment period. The cumulative disappearance rate of proteinuria determined by the Kaplan-Meier method showed that the disappearance rate of proteinuria was significantly higher in group 1 than in group 2 (log-rank P = 0.04). There was no significant difference in pathological findings, but there was a tendency of increase of global sclerosis in group1 which might be related to warfarin. Most of the adverse effects were related to prednisolone, but fortunately transient.

CONCLUSIONS

The balance between minimal benefits of warfarin/dipyridamole and potential adverse effects may be in favor of avoiding them in children with IgA nephropathy.

Intracellular adenosine regulates epigenetic programming in endothelial cells to promote angiogenesis

The nucleoside adenosine is a potent regulator of vascular homeostasis, but it remains unclear how expression or function of the adenosine‐metabolizing enzyme adenosine kinase (ADK) and the intracellular adenosine levels influence angiogenesis. We show here that hypoxia lowered the expression of ADK and increased the levels of intracellular adenosine in human endothelial cells. Knockdown (KD) of ADK elevated intracellular adenosine, promoted proliferation, migration, and angiogenic sprouting in human endothelial cells. Additionally, mice deficient in endothelial ADK displayed increased angiogenesis as evidenced by the rapid development of the retinal and hindbrain vasculature, increased healing of skin wounds, and prompt recovery of arterial blood flow in the ischemic hindlimb. Mechanistically, hypomethylation of the promoters of a series of pro‐angiogenic genes, especially for VEGFR2 in ADK KD cells, was demonstrated by the Infinium methylation assay. Methylation‐specific PCR, bisulfite sequencing, and methylated DNA immunoprecipitation further confirmed hypomethylation in the promoter region of VEGFR2 in ADK‐deficient endothelial cells. Accordingly, loss or inactivation of ADK increased VEGFR2 expression and signaling in endothelial cells. Based on these findings, we propose that ADK downregulation‐induced elevation of intracellular adenosine levels in endothelial cells in the setting of hypoxia is one of the crucial intrinsic mechanisms that promote angiogenesis.

Effects of anti-aggregant, anti-inflammatory and anti-coagulant drug consumption on the preparation and therapeutic potential of plasma rich in growth factors (PRGF)

The prevalence and incidence of trauma-related injuries, coronary heart disease and other chronic diseases increase dramatically with age. This population sector is therefore a regular consumer of different types of drugs that may affect platelet aggregation and the coagulation cascade. We have evaluated whether the consumption of acetylsalicylic acid, acenocoumarol, glucosamine sulfate and chondroitin sulfate, and therefore their presence in blood, could interfere with the preparation and biological outcomes of plasma rich in growth factors (PRGF). Clotting time, clot retraction and platelet activation of PRGF was evaluated. PRGF growth factor content and the release of different biomolecules by tendon fibroblasts were also quantified, as well as cell proliferation and cell migration. The preparation and biological potential of PRGF is not affected by the intake of the evaluated drugs, and solely its angiogenic potential and its capacity to induce HA and fibronectin synthesis, is reduced in patients taking anti-coagulants.

Electrospun biodegradable elastic polyurethane scaffolds with dipyridamole release for small diameter vascular grafts

Acellular biodegradable small diameter vascular grafts (SDVGs) require antithrombosis, intimal hyperplasia inhibition and rapid endothelialization to improve the graft patency. However, current antithrombosis and antiproliferation approaches often conflict with endothelial cell layer formation on SDVGs. To address this limitation, biodegradable elastic polyurethane urea (BPU) and the drug dipyridamole (DPA) were mixed and then electrospun into a biodegradable fibrous scaffold. The BPU would provide the appropriate mechanical support, while the DPA in the scaffold would offer biofunctions as required above. We found that the resulting scaffolds had tensile strengths and strains comparable with human coronary artery. The DPA in the scaffolds was continuously released up to 91 days in phosphate buffer solution at 37 °C, with a low burst release within the first 3 days. Compared to BPU alone, improved non-thrombogenicity of the DPA-loaded BPU scaffolds was evidenced with extended human blood clotting time, lower TAT complex concentration, lower hemolysis and reduced human platelet deposition. The scaffolds with a higher DPA content (5 and 10%) inhibited proliferation of human aortic smooth muscle cell significantly. Furthermore, the DPA-loaded scaffolds had no adverse effect on human aortic endothelial cell growth, yet it improved their proliferation. The attractive mechanical properties and biofunctions of the DPA-loaded BPU scaffold indicate its potential as an acellular biodegradable SDVG for vascular replacement.

Pre admission antithrombotics are associated with improved outcomes following ischaemic stroke: a cohort from the Registry of the Canadian Stroke Network

BACKGROUND

Several studies have attempted to identify predictors of outcome following ischaemic stroke. Reduced stroke severity has been reported with pre admission ASA use, and improved outcomes have been reported with pre admission statin treatment. The interaction between pre treatment medications and clinical response to tPA is less clear. The objective of our study was to assess clinical outcomes in patients with acute ischaemic stroke with respect to pre treatment medications.

METHODS

The Registry of the Canadian Stroke Network collected pre morbid and prospective outcome data on 5568 patients with ischaemic stroke. We applied multivariate analyses to correlate pre admission medications with stroke severity on presentation, in-hospital mortality, and modified Rankin at discharge. Analyses were adjusted for age, gender, medical history, tPA administration, blood pressure, and glucose on presentation.

RESULTS

Pre admission treatment with ASA and clopidogrel was associated with less severe stroke upon presentation. A similar trend was seen with dipyridamole and ticlopidine, but did not reach statistical significance. Pre treatment with ASA and warfarin was associated with improved Rankin scores at discharge. There was no interaction between tPA treatment and pre admission antiplatelets with respect to in-hospital mortality or disability at discharge, although tPA treatment was independently associated with improved Rankin at discharge. Pre treatment antiplatelet use did not result in increased intracerebral haemorrhage following tPA administration.

CONCLUSIONS

Patients with acute ischaemic stroke taking antithrombotic medications at hospital admission have improved functional outcomes. No interaction is noted between use of these medications and outcome following thrombolysis. This large prospective cohort study is consistent with previous published reports, and supports the notion that pre admission antithrombotics may mitigate brain injury during acute stroke.

Progress in clinical neurosciences: The 'antiplatelet' agents and the role of the endothelium

The antiplatelet drugs, commonly used in the prevention and treatment of cerebrovascular disease, possess a number of effects that are independent of direct antiplatelet actions. Beneficial and detrimental effects both occur. The endothelium is an important mediator of these non-antiplatelet effects. We performed a literature search to locate articles related to acetylsalicylic acid (aspirin), clopidogrel, ticlopidine, and dipyridamole and the interactions of these medications with the endothelium. The role of each of the above medications is explored in relation to vasodilation, inflammation, oxidation, platelet-leukocyte interactions, and thrombogenic tendency via platelet-vessel wall interactions.

3rd College of Physicians’ Lecture – Translational Research: From Bench to Bedside and From Bedside to Bench; Incorporating a Clinical Research Journey in IgA Nephritis (1976 to 2006)

Translational research (TR) can be defined as research where a discovery made in the laboratory (bench) can be applied in the diagnosis, treatment or prevention of a disease. Examples of medical discoveries contributing to translational medicine (TM) include the isolation of insulin by Banting (Nobel Laureate, 1923), the discovery of penicillin by Alexander Fleming (Nobel Laureate, 1945) and recently the discovery of the role of bacterium Helicobacter pylori in the causation of gastritis and peptic ulcer by Marshall and Warren (Nobel Laureates, 2005). Clinical research (CR) would be a more appropriate term for the bulk of research work undertaken by doctors. CR embraces both clinical based and laboratory-based research. The terminology “bedside to bench” applies more to CR as opposed to “bench to bedside” in the case of TR. But regardless of who does it, as long as the discovery can be translated to the bedside and results in improvement in patient care it can be considered a contribution to TM. Our work spans a 30-year period, involving laboratory-based research, clinical trials and genomics of IgA nephritis (Nx). This is a series of work to elucidate the pathogensis and therapy of IgANx. Plasma beta-thromboglobulin (BTG) an in-vivo index of platelet aggregation and anti-thrombin III increase due to a constant thrombogenecity resulting from platelet degranulation formed the basis for anti-platelet and low-dose warfarin therapy. A study of the natural history of IgANx revealed 2 courses, a slowly progressive course with end-stage renal failure (ESRF) at 7.7 years and a more rapid course at 3.3 years. Triple therapy (cyclophosphamide, persantin and low-dose warfarin) delayed progression to ESRF by about 8 years and for some patients up to 20 years. Documentation of abnormal suppressor T cell function provided the basis for immune therapy. Four patterns of proteinuria were present in IgANx and it is the quality and not so much the quantity of proteinuria which determined the prognosis. Low molecular weight proteinuria was a bad prognostic marker. A controlled therapeutic trial using ACEI/ATRA showed that therapy decreases proteinuria, improves renal function and converts non-selective to selective proteinuria. Subsequent work confirmed that it was the ATRA, not the ACEI which contributed to improved renal function. Individual anti proteinuria response to ATRA varies depending on ACE gene polymorphism. We found that the II genotype of the ACE gene was renoprotective and patients with this genotype had significantly reduced incidence of ESRF compared to those with the DD genotype. Patients responsive to ATRA therapy can retard progression to ESRF by up to 32 years. Mild renal failure can be reversed with possible regression of glomerulosclerosis because of glomerular remodelling by ATRA. Key words: Genomics, Glomerulonephritis, History, Therapy, Translational medicine

Porous graphitic carbon shows promise for the rapid screening partial DPD deficiency in lymphocyte dihydropyrimidine dehydrogenase in Chinese, Indian and Malay in Singapore by using semi-automated HPLC-radioassay

OBJECTIVE

Dihydropyrimidine dehydrogenase (DPD) catalyzes the degradation of thymine, uracil, and the chemotherapeutic drug 5-Fluorouracil. In general reverse-phase high pressure liquid chromatography is the standard method for separating 5-[2-(14)C]Fluorouracil and 5-[2-(14)C]Fluoro-5,6-dihydrouracil. However, the use of 100% aqueous solution (as HPLC mobile phase) may collapse the C-18 bonded phase and result in a retention time shift. The aim of this study is to develop a rapid, reproducible, sensitive method for screening partial DPD deficiency in healthy volunteers.

DESIGN AND METHODS

The activity of DPD was measured using 5-[2- (14)C]Fluorouracil (5-[2-(14)C]FUra) followed by separation of substrate and product 5-[2-(14)C]FUraH(2) with a 15 x 4.6 mm I.D., 5 microm particle size (d(p)) porous graphitic carbon (PGC) column (Hypercarb(R)) and HPLC with online detection of the radioactivity. This was standardized using the protein concentration of the cytosol (NanoOrange(R) Protein Quantitation).

RESULTS

Complete baseline separation of 5-[2-(14)C]Fluorouracil (5-[2-(14)C]FUra) and 5-[2-(14)C]Fluoro-5,6-dihydrouracil (5-[2-(14)C]FUraH(2)) was achieved using a porous graphitic carbon (PGC) column. The detection limit for 5-[2-(14)C]FUraH(2) was 0.4 pmol.

CONCLUSIONS

By using linear gradient separation (0.1% Trifluoroacetic acid [TFA] in water to 100% Methanol) protocols in concert with PGC columns (Hypercarb(R)), we have demonstrated that a PGC column has a distinct advantage over C-18 reverse phase columns in terms of column stability (pH 1-14). This method provides an improvement on the specific assay for DPD enzyme activity. It is rapid, reproducible and sensitive and can be used for routine screening for healthy and cancer patients for partial and profound DPD deficiency before treatment with 5- FUra.