Lovastatin Enhances Ecto-5′-Nucleotidase Activity and Cell Surface Expression in Endothelial Cells

Abstract

Abstract-Extracellular adenosine production by the GPI-anchored Ecto-5Ј-Nucleotidase (Ecto-5Ј-Nu) plays an important role in the cardiovascular system, notably in defense against hypoxia. It has been previously suggested that HMG-CoA reductase inhibitors (HRIs) could potentiate the hypoxic stimulation of Ecto-5ЈNu in myocardial ischemia. In order to elucidate the mechanism of Ecto-5Ј-Nu stimulation by HRIs, Ecto-5Ј-Nu activity and expression were determined in an aortic endothelial cell line (SVAREC) incubated with lovastatin. Lovastatin enhanced Ecto-5Ј-Nu activity in a dose-dependent manner. This increase was not supported by de novo synthesis of the enzyme because neither the mRNA content nor the total amount of the protein were modified by lovastatin. By contrast, lovastatin enhanced cell surface expression of Ecto-5Ј-Nu and decreased endocytosis of Ecto-5Ј-Nu, as evidenced by immunostaining. This effect appeared unrelated to modifications of cholesterol content or Ecto-5Ј-Nu association with detergent-resistant membranes. The effect of lovastatin was reversed by mevalonate, the substrate of HMG-CoA reductase, by its isoprenoid derivative, geranyl-geranyl pyrophosphate, and by cytotoxic necrotizing factor, an activator of Rho-GTPases. Stimulation of Ecto-5Ј-Nu by lovastatin enhanced the inhibition of platelet aggregation induced by endothelial cells. In conclusion, lovastatin enhances Ecto-5Ј-Nu activity and membrane expression in endothelial cells. This effect seems independent of lowering cholesterol content but could be supported by an inhibition of Ecto-5Ј-Nu endocytosis through a decrease of Rho-GTPases isoprenylation. This benefit is already apparent at the early step of endothelial dysfunction, which precedes the development of atherosclerosis. 4,5 Some of the effects of these cholesterol-lowering drugs, particularly those observed in short-term exposure, could be supported by mechanisms independent of lowering of plasma LDL concentration. 1,6 Induction of adenosine production in the extracellular space by the GPI-anchored Ecto-5Ј-Nu could be one of these mechanisms. Indeed, the production of adenosine by Ecto-5Ј-Nu is implicated in the regulation of endothelial functions 7-9 and in defense against hypoxia. 9 -12 Ecto-5Ј-Nu activity is increased by tissular hypoxia, notably in cardiomyocytes and endothelial cells. 13,14 The enzyme has been implicated in myocardial preconditioning, 13,15 and it was recently shown that HRIs potentiate the stimulation of Ecto-5Ј-Nu activity induced by ischemia in cardiomyocytes. 16 However, it is not known whether HRIs also enhance Ecto-5Ј-Nu activity in endothelium, a main site of adenosine production, 17 and the mechanisms whereby HRIs enhance Ecto-5Ј-Nu have not been studied. Some hypotheses can be put forward. First, it has been shown that HRIs can modulate the activity of enzymes, such as endothelial nitric oxide synthase, at the transcriptional level. 6 On the other hand, HRIs can induce posttranslational events, which influence cell surface expression of proteins....

IFN‐β regulates CD73 and adenosine expression at the blood–brain barrier

“…Recent reports have shown that statins have an attenuating role in CNS inflammation as demonstrated in the mouse EAE model [37] and by immunomodulatory effects on MS patient immune cells [38]. Interestingly, both pravastatin [39] and lovastatin [40] treatment leads to increased CD73 expression with tissue-protective effects. We speculate that increased CD73 expression and adenosine production might also be one mechanism whereby statin treatment leads to beneficial anti-inflammatory effects also seen in the treatment of autoimmune diseases.…”

Upregulation of Ecto-5′-Nucleotidase by Rosuvastatin Increases the Vasodilator Response to Ischemia

“…This was demonstrated for lovastatin in rat endothelial cells, 10 pitavastatin in canine in vivo, 11 and atorvastatin in human vascular endothelial cells. 23 Our results support these previous findings and are the first to demonstrate this effect in a human in vivo setting.…”

“…Inhibition of Rho may result in reduced endocytosis of CD73 and subsequently increased expression of CD73 on the cell membrane. 10 It has also been demonstrated that phosphatidylinositol 3-kinase and protein kinase C may influence CD73 activity by influencing its phosphorylation state and may thereby form an alternative route for statin-induced enhancement of CD73 activity. 11,24 Regardless of the underlying mechanism, activation of CD73 by statins is likely to contribute to the clinical efficacy of statins in a setting of cardiac infarction, because inhibition of CD73 attenuates the limiting effect of statins on infarct size in animals.…”

Atorvastatin does not Affect Ischaemia-Induced Phosphatidylserine Exposition in Humans in-vivo

“…We have previously shown in humans that activation of ecto-5'-nucleotidase mediates prevention of PS exposure by rosuvastatin after IR. The effect of statins on ecto-5'-nucleotidase appears to occur rapidly 6,7) . For example Sanada et al found a significant increase of ecto-5'-nucleotidase activity in dogs for different statins (pravastatin, pitavastatin and cerivastatin) already 10 minutes after treatment 7) .…”

“…Traditionally, this beneficial effect of statins has been explained by lowering of plasma cholesterol and sub-sequent reduced progression of atherosclerosis. Apart from its cholesterol lowering properties, statins have other ("pleiotropic") actions, such as up-regulation of ecto-5'-nucleotidase [5][6][7] , activation of the phosphatidylinositol 3-kinase-Akt pathway 8) and up-regulation of NO synthase 9,10) which all may increase tolerance against ischaemia and reperfusion (IR) [11][12][13] . Several animal studies have shown reduction of IR-injury as a result of statin treatment in both the heart and the kidney [14][15][16][17] .…”