Effect of minocycline on ischemic/reperfusion injury of isolated heart of hypertensive and diabetic rats

Uvod: Koronarna bolest arterija je jedna od najčešćih bolesti srca i glavni je uzrok obolevanja i smrtnosti širom sveta. Oštećenje tkiva miokarda u akutnom infarktu miokarda nastaje upravo zbog arterijske okluzije koja uzrokuje ishemiju dok naknadno uspostavljanje ponovnog protoka krvi može da rezultira reperfuzijskom povredom. U farmakološkoj terapiji i prevenciji ishemijsko/reperfuzione povrede tokom prethodne dve decenije učinjeno je mnogo napora kako bi se pronašao što efikasniji agens koji bi mogao da umanji morfološka i funkcionalna oštećenja miokarda nakon ishemije i reperfuzije. Pozitivni plejotropni efekti minociklina pripisuju se različitim mehanizmima uključujući antiinflamacijsko, antioksidaciono i antiapoptotsko dejstvo, kao i inhibicija metaloproteinaza. Cilj: Ispitivanje efekata prekondicioniranja i postkondicioniranja minociklinom na funkcionalni i morfološki oporavak srca pacova nakon ishemijsko/reperfuzione povrede miokarda sa posebnim osvrtom na uslove dijabetesa tipa 2 i hipertenzije. Metode: Istraživanje je obuhvatilo 72 pacova muškog pola (Wistar albino soj, telesne mase 250±20 g, starosti 8 nedelja). Pacovi su svrstani u grupe na osnovu prisustva dijebetesa tipa 2 ili hipertenzije kao i na osnovu nekog od tipa kondicioniranja minociklinom: prekondicioniranje minociklinom u dozi od 1µM ili postkondicioniranje minociklinom u istoj dozi. Dijabetes tip 2 indukovan je primenom ishrane bogate mastima i streptozotocina u dozi od 25 mg/kg telesne mase. Za eksperimentalni model hipertenzije koristili su se sponatno-hipertenzivni pacovi. Izolovana srca su perfundovana metodom retrogradne perfuzije po Langendorfu. Za ishemiju je upotrebljen model globalne ishemije u trajanju od 20 minuta kojoj sledi reperfuzija u trajanju od 30 minuta. Vrednosti koronarnog protoka su određivane floumetrijski, a parametri funkcije leve komore (dp/dt max, dp/dt min, SLVP, DLVP i HR) su kontinuirano praćeni. U uzorcima koronarnog venskog efluenta srca pacova spektrofotometrijskim metodama su određivani parametri oksidacionog stresa, a standardnom histološkom analizom ispitivane su promene na srcu. Rezultati: Rezultati ovog istraživanja ukazuju na nesumnjive protektivne efekte minociklina u uslovima eksperimentalno indukovane ishemije i reperfuzije kako na srcima pacova sa indukovanim dijabetesom tipa 2, tako i na srcima spontano hipertenzivnih pacova. Analizom dobijenih rezultata koji se odnose na dinamiku produkcije biomarkera oksidacionog stresa izvodi se zaključak da antioksidacioni potencijal minociklina i redukcija oksidacionog oštećenja svakako čini važan, ako ne i ključni mehanizam protektivnog dejstva minociklina. Ključne reči: minociklin, ishemija, reperfuzija, dijabetes tip 2, hipertenzija, oksidacioni stresntroduction: Coronary artery disease is one of the most common heart diseases and is the leading cause of morbidity and mortality worldwide. Myocardial damage in acute myocardial infarction occurs due to arterial occlusion that causes ischemia, while subsequent reestablishment of blood flow can result in reperfusion injury. Much effort has been made in pharmacological therapy and prevention of ischemic/reperfusion injury over the past two decades to find the most effective agent that could reduce morphological and functional myocardial damage after ischemia and reperfusion. The positive pleiotropic effects of minocycline are attributed to various mechanisms including anti-inflammatory, antioxidant and antiapoptotic effects, as well as inhibition of metalloproteinases. Objective: Investigation of the effects of preconditioning and postconditioning with minocycline on functional and morphological recovery of rat heart after ischemic/reperfusion myocardial injury with special attention to conditions of type 2 diabetes and hypertension. Methods: The study included 72 male rats (Wistar albino strain, body weight 250 ± 20 g, age 8 weeks). Rats were classified into groups based on the presence of type 2 diabetes or hypertension as well as on one of the types of minocycline conditioning: preconditioning with minocycline at a dose of 1µM or postconditioning with minocycline at the same dose. Type 2 diabetes was induced by a high-fat diet and streptozotocin at a dose of 25 mg/kg body weight. Spontaneously-hypertensive rats were used for the experimental model of hypertension. Isolated hearts were perfused by retrograde Langendorf perfusion. For ischemia, a 20-minute model of global ischemia was used, followed by a 30-minute reperfusion. Coronary flow values were determined fluometrically, and left ventricular function parameters (dp/dt max, dp/dt min, SLVP, DLVP and HR) were continuously monitored. In the coronary venous effluent samples of rat heart, oxidative stress parameters were determined by spectrophotometric methods, and changes in the heart were examined by standard histological analysis. Results: The results of this study indicate the undoubted protective effects of minocycline in conditions of experimentally induced ischemia and reperfusion in the hearts of rats with induced type 2 diabetes and in the hearts of spontaneously hypertensive rats. The analysis of the obtained results related to the dynamics of production of biomarkers of oxidative stress leads to the conclusion that the antioxidant potential of minocycline and reduction of oxidative damage certainly makes important, if not the key mechanism of protective action of minocycline