Combined administration of membrane-permeable and impermeable iron-chelating drugs attenuates ischemia/reperfusion-induced hepatic injury.

BACKGROUND: The underlying pathophysiological mechanisms of hepatic ischemia-reperfusion (I/R) injury have not been completely elucidated. However, it is well known that oxidative stress, caused by a burst of reactive oxygen species (ROS) production during the reperfusion phase, plays a crucial role. A growing body of evidence indicates that the intracellular availability of free iron represents a requirement for ROS-induced adverse effects, as iron catalyzes the generation of highly reactive free radicals. The aim of this study was to examine whether a combination of iron chelators with varying lipophilicity could offer enhanced protection against I/R by diminishing the conversion of weak oxidants, like H2O2, to extremely reactive ones such as hydroxyl radicals (HO.). METHODS: HepG2 cells (hepatocellular carcinoma cell line) were exposed to oxidative stress conditions after pre-treatment with the iron chelators desferrioxamine (DFO) and deferiprone (DFP) alone or in combination. Labile iron pool was estimated using the calcein-acetoxymethyl ester (calcein-AM) method and DNA damage with the comet assay. We subsequently used a rabbit model (male New Zealand white rabbits) of hepatic I/R-induced injury to investigate, by measuring biochemical (ALT, ALT, ALP, γGT) and histological parameters, whether this may be true for in vivo conditions. RESULTS: The combination of a membrane-permeable iron chelator (DFP) with a strong membrane-impermeable one (DFO) raises the level of protection in both hepatic cell lines exposed to oxidative stress conditions and hepatic I/R rabbit model. CONCLUSIONS: Our results show that combinations of iron chelators with selected lipophilicity and iron-binding properties may represent a valuable strategy to protect against tissue damage during reperfusion after a period of ischemia.

Flow cytometric estimation of 'labile iron pool' in human white blood cells reveals a positive association with ageing.

A small part of cellular iron, usually called 'labile iron pool' (LIP), is not securely stored and has the potential to catalyse the formation of highly reactive oxygen species. The present work estimated LIP levels in human white cells by using the analytical power of flow cytometry. The method relies essentially on already established principles but has the added value of monitoring LIP in different subpopulations of human blood cells concurrently in a single sample. Examination of 41 apparently healthy individuals revealed a positive correlation between LIP levels and the age of the donors (r=0.656, 0.572 and 0.702 for granulocytes, lymphocytes and monocytes, respectively, p<0.0001), indicating that cells of older individuals are prone to oxidations in conditions of oxidative stress. It is suggested that LIP estimation may represent a valuable tool in examinations searching for links between iron and a variety of oxidative stress-related pathological conditions.

Leukocyte labile iron pool in patients with systolic heart failure.

INTRODUCTION: Data regarding sources of oxidative stress in the failing myocardium are sparse. Leukocytes actively participate in the oxidative damage observed in human heart failure (HF). The intracellular labile iron pool (LIP) represents a source of toxic reactive oxygen species. METHODS: We studied patients with chronic systolic HF who had a left ventricular ejection fraction (LVEF) 45%. We examined the LIP status in different populations of leukocytes in HF patients and we investigated its association with clinical and laboratory parameters, including conventional inflammatory markers. RESULTS: Sixty patients were finally included in the analysis (mean age: 67 ± 11 years, 54 men, 42 with ischemic cardiomyopathy). The multivariate logistic regression analysis showed that only LIP in granulocytes (OR: 0.73; 95% CI: 0.55-0.98; p=0.039) and right ventricular systolic pressure (RVSP) (OR: 0.95; 95% CI: 0.92-0.99; p=0.027) were independently associated with severe LV systolic dysfunction (LVEF30%). The correlation analysis revealed that LVEF was inversely associated with LIP in granulocytes (Spearman's rho: -0.39, p=0.002), LIP in monocytes (Spearman's rho: -0.35, p=0.007), and RVSP (Spearman's rho: -0.43, p=0.003). No significant correlation between LVEF and inflammatory indexes was noted. CONCLUSIONS: LIP in granulocytes is independently associated with the severity of LV dysfunction in patients with systolic HF. Intracellular redox active iron may represent a source of leukocyte reactive oxygen species in this setting.