Hypoxia-Reoxygenation Induced Cardiac Mitochondrial Dysfunction

Abstract

Objectives: Cellular response to low oxygen tension is altered by severity and duration of hypoxia. Although the subject has been studied extensively, mechanisms leading to hypoxia-reoxygenation damage remain undefined. Here, we investigated the effect of long term continuous hypoxia (48 hours) on cardiac derived HL-1 cells, mainly the role of mitochondria in cellular energy and reactive oxygen species homeostasis. Materials and Methods: In this study, mammalian atrium derived HL-1 cells were cultured either in long term hypoxia (48 hours, 1% O2) or in normoxia (48 hours, 21% O2) conditions. Mitochondrial membrane potential and reactive oxygen species (ROS) level was measured using florescent dyes in a confocal microscope. GAPDH protein levels were detected by western blotting in normoxic control and hypoxic cells. Results: Present results demonstrate that, 48 hours of hypoxia did not alter baseline mitochondrial membrane potential and its oxidative respiration capacity in cardiac HL-1 cells. The mitochondrial depolarization response to in reoxygenation period of oxygen deprived cells was slower in hypoxic cells. In hypoxic cells, basal ROS levels were higher whereas hydrogen peroxide response was smaller when compared with the normoxic control group. GAPDH protein levels were unaltered between groups. Conclusion: Present results indicate that, persistent mitochondrial oxidation phosphorylation uncoupling may lead to an over production of ROS.

Keywords

• HL-1 Cells
• Hypoxia
• Mitochondrial Membrane Potential
• Reactive Oxygen Species

Hipoksi-Reoksijenasyon ile İndüklenen Kardiyak Mitokondriyal Disfonksiyon

Abstract

Amaç: Hücrelerin azalan oksijen konsantrasyonuna verdikleri yanıt hipoksinin şiddeti ve süresine göre değişiklik göstermektedir. Bu konuda oldukça fazla çalışma yapılmış olmasına karşın, hipoksi ile indüklenen fonksiyonel yanıtların altında yatan mekanizmalar büyük ölçüde aydınlatılamamıştır. Bu çalışmada, kardiyak kökenli HL-1 hücrelerinin, uzun süreli (48 saat) kesintisiz hipoksiye verdikleri yanıtta mitokondrinin hücresel enerji ve reaktif oksijen türevleri (ROS) dengesindeki rolü araştırılmıştır. Gereç ve Yöntem: Bu çalışmada memeli atriyum kökenli hücre serisi HL-1 hücrelerinde uzun süreli hipokside (48 saat, %1 O2) ve normoksik (48 saat, %21 O2) şartlarda kültür edilmiştir. Normoksik kontrol ve hipoksik hücrelerden mitokondri membran potansiyeli ve ROS miktarı floresan boyalar ile konfokal mikroskopta ölçülmüş, GAPDH protein seviyeleri western blot yöntemi ile belirlenmiştir. Bulgular: Sonuçlarımıza göre, kardiyak HL-1 hücrelerinde 48 saat hipoksi bazal mitokondri membran potansiyeli ve oksijenli solunum kapasitesini değiştirmedi. Bununla birlikte hipoksik hücrelerin reoksijenasyon sırasında ortamdan tekrar oksijen uzaklaştırılmasına olan mitokondriyal depolarizasyon yanıtları normoksik kontrol hücrelere göre yavaştı. Hipoksik hücrelerde bazal ROS miktarında artış gözlenirken, hidrojen peroksite olan yanıtlar normoksik kontrol grubuna göre azaldı. GAPDH protein seviyesinde gruplar arası bir fark saptanmadı. Sonuç: Bu sonuçlar, uzun süreli hipoksi ile indüklenen mitokondriyal oksidatif fosforilasyon kenetindeki kalıcı disfonksiyonun hücresel ROS artışından sorumlu olabileceğini düşündürmektedir.

Keywords

• HL-1 Hücreleri
• Hipoksi
• Mitokondri Membran Potansiyeli
• Reaktif Oksijen Türevleri

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