Downregulation of ferritin heavy chain increases labile iron pool, oxidative stress and cell death in cardiomyocytes.
Ferritin heavy chain (FHC) protein was significantly reduced in murine failing hearts following left coronary ligation or thoracic transverse aortic constriction. The mRNA expression of FHC was not significantly altered in failing hearts, compared to that in control sham-operated hearts. Prussian blue staining revealed spotty iron depositions in myocardial infarct failing hearts. Oxidative stress was enhanced in the myocardial infarct failing hearts, as evidenced by increases in 4-hydroxy-2-nonenal and 8-hydroxy-2'-deoxyguanosine immunoreactivity. To clarify the functional significance of FHC downregulation in hearts, we infected rat neonatal cardiomyocytes with adenoviral vector expressing short hairpin RNA targeted to FHC (Ad-FHC-RNAi). The downregulation of FHC induced a reduction in the viability of cardiomyocytes. The relative number of iron deposition-, 4-hydroxy-2-nonenal- or 8-hydroxy-2'-deoxyguanosine-positive cardiomyocytes was significantly higher in Ad-FHC-RNAi-infected cardiomyocytes than in control vector-infected cardiomyocytes. Treatment of Ad-FHC-RNAi-infected cardiomyocytes with desferrioxamine, an iron chelator, significantly reduced the number of iron, 4-hydroxy-2-nonenal or 8-hydroxy-2'-deoxyguanosine-positive cells, and increased viability. In addition, treatment with N-acetyl cysteine, an antioxidant, significantly reduced the number of 4-hydroxy-2-nonenal- or 8-hydroxy-2'-deoxyguanosine-positive cells. Reduced viability in Ad-FHC-RNAi-infected cardiomyocytes was significantly improved with N-acetyl cysteine treatment. These findings indicate that excessive free iron and the resultant enhanced oxidative stress caused by downregulation of FHC lead to cardiomyocyte death. The decrease in FHC expression in failing hearts may play an important role in the pathogenesis of heart failure.
Omiya
Shigemiki
S
Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Hikoso
Shungo
S
Imanishi
Yukiko
Y
Saito
Atsuhiro
A
Yamaguchi
Osamu
O
Takeda
Toshihiro
T
Mizote
Isamu
I
Oka
Takafumi
T
Taneike
Manabu
M
Nakano
Yuko
Y
Matsumura
Yasushi
Y
Nishida
Kazuhiko
K
Sawa
Yoshiki
Y
Hori
Masatsugu
M
Otsu
Kinya
K
D000818:Animals; D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism; D001011:Aorta / Q000473:pathology; D001052:Apoferritins / Q000737:chemistry / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D015536:Down-Regulation; D005295:Ferrocyanides / Q000494:pharmacology; D006333:Heart Failure / Q000378:metabolism; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018384:Oxidative Stress; D034622:RNA Interference
D000975:Antioxidants; D002614:Chelating Agents; D005295:Ferrocyanides; D001052:Apoferritins; D007501:Iron; D003676:Deferoxamine; C000170:ferric ferrocyanide