Effects of trombin in the regulation of rat's aortic smooth muscle cells proliferation

Kardiovaskularne bolesti predstavljaju najveći uzrok smrtnosti ljudske populacije, a njihova glavna i osnovna patološka komponenta je ateroskleroza. Proliferacija ili deoba glatkih mišićnih ćelija krvnog suda (VSMC) ključni je događaj u nastanku raznih vaskularnih oboljenja, uključujući aterosklerozu i hipertenziju. U procesu diferencijacije i abnormalne deobe VSMC povezanih sa hipertenzijom i aterosklerozom uključen je i trombin. Stimulisanje VSMC trombinom dovodi do aktivacije ekstracelularnim signalima regulisanih kinaza 1 i 2 (ERK1/2), preko transaktivacije receptora za epidermalni faktor rasta (EGFR). U ranijim studijama Isenović i saradnici potvrdili su na osnovu inhibicije ERK1/2 od strane PD9805 inhibitora, učešće ERK1/2 u regulaciji proliferacije VSMC izazvanoj trombinom. U nastavku, faktor rasta sličan epidermalnom faktoru rasta koji vezuje heparin (HB-EGF), protein kinaza C delta (PKCδ) i matriksne metaloproteinaze (MMP), nađene su u VSMC i pokazano je da je i njihova aktivnost regulisana trombinom. ADAM (engl. “A Disintegrin And Metalloproteinase”) transmembranske su metaloproteinaze koje pripadaju adamalizinskoj grupi i razlikuju se od matriksnih metaloproteinaza po tome što imaju vanćelijski dizintegrinski i citoplazmatski domen. C terminalni domen može da stupa u interakciju sa unutarćelijskim proteinima. Uvidom u literaturu, do sada ne postoji istraživanje koje ukazuje na prisustvo ADAM metaloproteinazne aktivnosti vezane za proliferaciju VSMC stimulisane trombinom. Predmet ove doktorske teze jeste proučavanje uloge EGFR, ERK1/2, HB-EGF, PKCδ, ukupnih metaloproteinaza, kao i specifičnih MMP-2 i ADAM 12, u posredovanju proliferativnog efekta trombina na VSMC pacova. Inkubacija VSMC pacova sa trombinom (1 U/ml) u periodu od 5 minuta rezultirala je u značajnom povećanju: fosforilacije ERK1/2 od 8.7 ± 0.9 puta (p<0.001), fosforilacije EGFR od 8.5 ± 1.3 puta (p<0.001) i sinteze DNK od 3.6 ± 0.4 puta (p<0.001). Prethodni pojedinačni tretmani ovih ćelija u trajanju od 30 minuta sa 10 μM PD169540 (PD), ireverzibilnim inhibitorom EGFR, i 20 μM antitelom protiv HB-EGF značajno su smanjili trombinom stimulisanu fosforilaciju EGFR za 81 % i 72 % i ERK1/2...ardiovascular disease is the largest single cause of mortality and its major underlying pathology is atherosclerosis. The proliferation of vascular smooth muscle cells (VSMC) is a key event in the pathogenesis of various vascular diseases, including atherosclerosis and hypertension. Thrombin is involved in the differentiation and abnormal proliferation of VSMC associated with atherosclerosis and hypertension. Thrombin stimulation results in extracellular signal-regulated kinase (ERK 1/2) activation through transactivation of the epidermal growth factor receptor (EGFR). Based on the studies in which PD98059 used to inhibit ERK1/2, we have shown previously that ERK1/2 was involved in the regulation by thrombin of VSMC’s proliferation. In addition, heparin-binding EGF-like growth factor (HB-EGF) and matrix metalloproteinases (MMPs) have also been detected in VSMC and shown to be regulated by thrombin. ADAMs (A Disintegrin And Metalloproteinase) are transmembrane metalloproteinases, belonging to adamalysin group, that are distinct from matrix metalloproteinases (MMPs) in that, they have an extracellular disintegrin domain and cytoplasmic domain that can associate with intracellular proteins. To the present knowledge there is no study that indicates the activation of an ADAM member in thrombin-induced VSMC proliferation. In this dissertation, the role of EGFR, ERK1/2, HB-EGF, general metalloproteinases, MMP-2 and ADAM 12, as well as PKCδ in mediating the mitogenic action of Thrombin in rat VSMC was investigated. Incubation of rat VSMC with Thrombin (1 U/ml) for 5 minutes resulted in significant increase of ERK1/2 phosphorylation by 8.7 ± 0.9 fold (p<0.001), EGFR phosphorylation by 8.5 ± 1.3 fold (p<0.001) and DNA synthesis by 3.6 ± 0.4 fold (p