Thioredoxin-1 is required for the cardioprotecive effect of sildenafil against ischemia/reperfusion injury and mitochondrial dysfunction in mice

Abstract

Sildenafil is a phosphodiesterase type 5 inhibitor which confers cardioprotection againstmyocardial ischemia/reperfusion (I/R) injury. The aim of this study was to determine if Trx1participates in cardioprotection exerted by sildenafil in an acute model of I/R, and to evaluatemitochondrial bioenergetics and cellular redox status. Langendorff-perfused hearts fromwild type mice (WT) and a dominant negative (DN-Trx1) mutant of Trx1 were assigned toplacebo or sildenafil (0.7 mg/kg i.p.) and subjected to 30 min of ischemia followed by 120min of reperfusion. WT + S showed a significantly reduction of infarct size (51.2±3.0% vs.30±3.0%, P<0.001), an effect not observed in DN-Trx. After I/R, sildenafil preserved state 3oxygen consumption from WT, but had a milder effect in DN-Trx1 only partially protectingstate 3 values. Treatment restored respiratory control (RC) after I/R, which resulted 8% (WT)and 24% (DN-Trx1) lower than in basal conditions. After I/R, a significant increase in H2O2production was observed both for WT and DN-Trx (WT: 1.17±0.13 nmol/mg protein and DNTrx: 1.38±0.12 nmol/min mg protein). With sildenafil, values were 21% lower only in WT I/R.Treatment decreased GSSG levels both in WT and DN-Trx1. In addition, GSSG/GSH2 ratio waspartially restored by sildenafil. Also, an increase in p-eNOS/eNOS even before the myocardialischemia was observed with sildenafil, both in WT (14%, P>0.05) and in DN-Trx (35%,P<0.05). Active Trx1 is required for the onset of the cardioprotective effects of sildenafil on I/Rinjury, together with the preservation of cellular redox balance and mitochondrial function.