Effects of sildenafil on nanostructural and nanomechanical changes in mitochondria in an ischaemia‐reperfusion rat model

Abstract

Sildenafil exerts cardioprotective effects by activating the opening of mitochondrial ATP-sensitive potassium channels to attenuate ischaemia-reperfusion (IR) injury. In the present study, we used atomic force microscopy (AFM) to investigate changes in mitochondrial morphology and properties to assess sildenafil-mediated cardioprotection in a rat myocardial infarction model. To investigate the cardioprotective effects of sildenafil, we used an in vivo Sprague-Dawley rat model of IR. Rats were randomly divided into three groups: (i) sham-operated rats (control; n = 5); (ii) IR-injured rats treated with vehicle (normal saline; IR; n = 10); and (iii) IR-injured rats treated with 0.75 mg/kg, i.p., sildenafil (IR + Sil; n = 10). Morphological and mechanical changes to mitochondria were analysed by AFM. Infarct areas were significantly reduced in sildenafil-treated rats (7.8 ± 3.9% vs 20.4 ± 7.0% in the sildenafil-treated and untreated IR groups, respectively; relative reduction 62%; P < 0.001). Analysis of mitochondria by AFM showed that IR injury significantly increased the areas of isolated mitochondria compared with control (24 150 ± 18 289 vs 1495 ± 1139 nm(2) , respectively; P < 0.001), indicative of mitochondrial swelling. Pretreatment with sildenafil before IR injury reduced the mitochondrial areas (7428 ± 3682 nm(2) ; P < 0.001; relative reduction 69.2% compared with the IR group) and ameliorated the adhesion force of mitochondrial surfaces. Together, these results suggest that sildenafil has cardioprotective effects against IR injury in a rat model by improving the morphological and mechanical characteristics of mitochondria.

Impact of Mitochondrial Ca2+-Sensitive Potassium (mBKCa) Channels in Sildenafil-Induced Cardioprotection in Rats

“…The present study shows that the phoshphodiesterase-5-inhibitor sildenafil has a powerful acute cardioprotective effect by reducing ischemia-reperfusion injury of the isolated perfused rat heart subjected to 30 minutes of global ischemia and 60 minutes of reperfusion in the Langendorff model, which is in line with previous studies, e.g. [ 7 , 12 , 13 ]. With regard to the clinical situation this finding might be of particular interest: first, sildenafil is a drug with a desirable side effect profile that is widely used for the treatment of erectile dysfunction and pulmonary arterial hypertension [ 14 ].…”

“…Because in cardiomyocytes BK Ca channels are located on the inner mitochondrial membrane and not in other subcellular structures [ 19 ], this finding suggests that opening of mitochondrial BK Ca (mBK Ca ) channels is essential in the early cardioprotective effect of sildenafil. As described previously, mitochondria play a pivotal role in controlling cell life and death by ATP synthesis and Ca 2+ homeostasis, and thus in ischemia-reperfusion injury [ 7 ]. We and others previously found mBK Ca channels to be a critical downstream target in the signalling pathway of several cardioprotective interventions [ 17 – 22 ].…”

“…The vasodilating effect is mediated by inhibitition of the breakdown of cyclic guanosine monophosphate (cGMP), which relaxes smooth muscle cells [ 5 ], whereas the anti-proliferative effect involves protein kinase A and protein kinase G (PKG) activated pathways [ 6 ]. Several animal studies suggest that sildenafil also protects against myocardial ischemia-reperfusion injury and thereby reduces infarct size by about 35–75% relative to untreated conditions [ 5 , 7 – 13 ]. The cardioprotective effects of sildenafil are thought to be mediated by opening of mitochondrial ATP-sensitive potassium (mito-K ATP ) channels [ 14 ], enhanced expression of endothelial nitric oxide synthase (NOS) and inducible NOS [ 5 ], and activation of protein kinase C and PKG [ 15 ].…”

Novel porcine model of acute myocardial infarction using polyethylene terephthalate

“…Previous studies have used open chest surgery (amyloid constructor and surgical ligation) and cardiac intervention procedure (ethanol infusion, coil embolization, and balloon occlusion) to induce a porcine AMI [7,[21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Our new model used interventional devices that are readily available and frequently used in clinical settings, and allows a simple and direct method to induce an ischemic lesion in the left ventricular myocardium without the need for non-biocompatible beads or invasive thoracotomy with coronary ligation [35,36].…”

Regulación de la actividad del intercambiador Na<SUP>+</SUP>/H<SUP>+</SUP> miocárdico por proteína quinasa G

“…Por último, es sabido que la mayor fuente de EROs es la mitocondria, en la que se generan como bioproducto de la respiración (Murphy 2009). Evidencias previas muestran que SIL es capaz de proteger de la injuria por isquemia-reperfusión en rata mediante un mecanismo que involucra mejoramiento de la función y morfología mitocondrial (Garciarena, Fantinelli et al 2011, Lee, Kwon et al 2014). También en ratas, otro estudio muestra que la apertura PKG-dependiente de los canales de mBKCa (canales de potasio sensibles a calcio) juega un papel fundamental en la cardioprotección inducida por SIL (Behmenburg, Dorsch et al 2015).…”