Statin Potentiates Human Platelet eNOS Activity without Enhancing eNOS mRNA and Protein Levels

Abstract

Background/Aims: Experimental studies suggest an enhanced endothelial and platelet nitric oxide (NO) generation after statin treatment, possibly due to increased endothelial NO synthase (eNOS) activity and protein levels. In parallel with experimental research, statins were shown to increase the forearm blood flow independently of serum cholesterol in humans. However, it was not possible to correlate blood flow changes with eNOS levels in these studies due to limitations in obtaining arterial samples. Hence, we investigated changes in eNOS activity, mRNA and protein levels after statin treatment in human platelets, which are readily accessible unlike arteries. Methods: In vitro bleeding times were measured in 22 patients by stimulating platelets with collagen-epinephrine or collagen-ADP. To assess platelet eNOS activity, the bleeding times were also determined after incubating platelets with L-arginine. The measurements were repeated following 14 days of pravastatin (40 mg/day) treatment. Platelet-rich plasma was collected before and after statin treatment to evaluate eNOS mRNA (semiquantitative RT-PCR) and protein levels (Western blotting). Results: The basal bleeding time was prolonged by 24 ± 3% (mean ± SE) when the samples were incubated with 500 µM of L-arginine. The NOS inhibitor L-N⁵-(I-iminoethyl)ornithine reversed this effect, suggesting that it was mediated by NO. After statin treatment, the NO-mediated prolongation of the bleeding time with 500 µM of L-arginine was significantly potentiated (to 44 ± 10%). Despite enhanced eNOS activity, there was no significant change in platelet eNOS mRNA and protein levels after statin treatment. Conclusion: These data demonstrate that platelet eNOS activity is potentiated after statin treatment in humans in parallel with experimental studies.

Brain Natriuretic Peptide Improves Long-Term Functional Recovery after Acute CNS Injury in Mice

“…Because cerebrovascular tone and blood flow are mediated in part by eNOS (Morikawa et al, 1994;Yamada et al, 2000), the beneficial effects of BNP agonists on post-traumatic cerebral perfusion could be due to upregulation of eNOS; however, there are several mechanisms by which BNP may enhance eNOS activity without affecting RNA levels (Yemisci et al, 2008). As an example, HMG-CoA reductase inhibitors (statins) have been demonstrated to enhance eNOS activity acutely through post-translational modification, increasing NO generation by enhancing phosphorylation of eNOS by the protein kinase Akt, but not affecting mRNA levels .…”

High-Dose Lovastatin for Acute Ischemic Stroke: Results of the Phase I Dose Escalation Neuroprotection with Statin Therapy for Acute Recovery Trial (NeuSTART)

“…There is, however, consistent evidence of a benefit of statins when administered to rodent models of acute ischemic stroke, and of a dose-response effect on neuroprotection [6,7,8,9,10,11,12, 14]. There is some evidence that higher doses may have less benefit than lower doses when administered at 24 h after stroke.…”

“…Experimental and clinical evidence suggest that by reducing downstream products of the mevalonate pathway other than cholesterol, statins can have beneficial effects on endothelial function, coronary and cerebral blood flow, inflammation, and hemostasis [4, 5]. More recently, experimental studies have demonstrated that several statins can reduce neuronal injury and infarct size in rodent models of acute ischemic stroke [6,7,8,9,10,11,12,13]. In these animal models, statins have been given both before the experimental stroke and as an acute treatment early (3 h) after the stroke.…”

Current Therapeutic Strategies to Mitigate the eNOS Dysfunction in Ischaemic Stroke

“…In this context, a comparative study between neonatal and adult models of rodent ischaemic stroke has shown that statin-mediated neuroprotection may somewhat be independent of eNOS modulation and be attributed to the pleiotropic effects of statins pertaining to inhibition of PKCa activity despite other recent studies revealing statinevoked significant simultaneous increases in endothelial cell Kruppel-like factor-2, a novel endothelial inflammation regulator and thrombomodulin expressions and platelet eNOS activity (Cimino et al 2005;Paumelle et al 2006;Yemisci et al 2008;Rossi et al 2010). …”