The central role of adenosine in statin-induced ERK1/2, Akt, and eNOS phosphorylation

Statins activate phosphatidylinositol-3-kinase, which activates ecto-5′-nucleotidase and phosphorylates 3-phosphoinositide-dependent kinase-1 (PDK-1). Phosphorylated (P-)PDK-1 phosphorylates Akt, which phosphorylates endothelial nitric oxide synthase (eNOS). We asked if the blockade of adenosine receptors (A₁, A_2A, A_2B, or A₃ receptors) could attenuate the induction of Akt and eNOS by atorvastatin (ATV) and whether ERK1/2 is involved in the ATV regulation of Akt and eNOS. In protocol 1, mice received intraperitoneal ATV, theophylline (TH), ATV + TH, or vehicle. In protocol 2, mice received intraperitoneal injections of ATV, U0126 (an ERK1/2 inhibitor), ATV + U0126, or vehicle; 8 h later, hearts were assessed by immunoblot analysis. In protocol 3, mice received intraperitoneal ATV alone or with 8-sulfophenyltheophylline (SPT); 1, 3, and 6 h after injection, hearts were assessed by immunoblot analysis. In protocol 4, mice received intraperitoneal ATV alone or with SPT, 1,3-dipropyl-8- cyclopentylxanthine (DPCPX), 1,3,7-trimethyl-8-(3-chlorostyryl)xanthine (CSC), alloxazine, or MRS-1523; 3 h after injection, hearts were assessed by immunoblot analysis. ATV increased P-ERK, P-PDK-1, Ser⁴⁷³ P-Akt, Thr ³⁰⁸ P-Akt, and P-eNOS levels. TH blocked ATV-induced increases in P-ERK, Ser⁴⁷³ P-Akt, Thr³⁰⁸ P-Akt, and P-eNOS levels without affecting the induction of P-PDK-1 by ATV. U0126 blocked the ATV induction of Ser⁴⁷³ P-Akt and Thr³⁰⁸ P-Akt while attenuating the induction of P-eNOS. A detectable increase in P-ERK, Ser ⁴⁷³ P-Akt and P-eNOS was seen 3 and 6 h after injection but not at 1 h. DPCPX, CSC, and alloxazine partially blocked the ATV induction of P-ERK, Ser⁴⁷³ P-Akt, and P-eNOS. In conclusion, blockade of adenosine A ₁, A_2A, and A_2B receptors but not A₃ receptors inhibited the induction of Akt and eNOS by statins. Adenosine was required for ERK1/2 activation by statins, which resulted in Akt and eNOS phosphorylation.