Abstract
Oxidative stress in fatty livers is mainly generated by impaired mitochondrial β-oxidation, inducing tissue damages and disease progression. Under suitable excitation, light liver endogenous fluorophores can give rise to autofluorescence (AF) emission, the properties of which depend on the organ morphofunctional state. In this work, we characterized the AF properties of a rat liver model of lipid accumulation and oxidative stress, induced by a 1–9-week hypercaloric methionine-choline deficient (MCD) diet administration. The AF analysis (excitation at 366 nm) was performed in vivo, via fiber optic probe, or ex vivo. The contribution of endogenous fluorophores involved in redox reactions and in tissue organization was estimated through spectral curve fitting analysis, and AF results were validated by means of different histochemical and biochemical assays (lipids, collagen, vitamin A, ROS, peroxidised proteins, and lipid peroxidation -TBARS-, GSH, and ATP). In comparison with the control, AF spectra changes found already at 1 week of MCD diet reflect alterations both in tissue composition and organization (proteins, lipopigments, and vitamin A) and in oxidoreductive pathway engagement (NAD(P)H, flavins), with a subsequent attempt to recover redox homeostasis. These data confirm the AF analysis potential to provide a comprehensive diagnostic information on negative effects of oxidative metabolism alteration.
Highlights
Oxidative stress results from the imbalance between intracellular generation of reactive oxygen species (ROS) and scavengers, in terms of increased ROS production, decreased antioxidant protection, and failure to repair oxidative damage
The contribution of endogenous fluorophores involved in redox reactions and in tissue organization was estimated through spectral curve fitting analysis, and AF results were validated by means of different histochemical and biochemical assays
The AF spectra collected in vivo, via fiber optic probe directly from liver tissue, showed changes in the emission profile between control and methionine-choline deficient (MCD) diet rats and among rats administered with MCD diet for increasing times (Figure 1(a))
Summary
Oxidative stress results from the imbalance between intracellular generation of reactive oxygen species (ROS) and scavengers, in terms of increased ROS production, decreased antioxidant protection, and failure to repair oxidative damage. The ROS are able to cause structural damages and functional failure of macromolecules containing double bonds, like lipids, proteins, and nucleic acids [1]. ROS are hypergenerated under different altered conditions, such as ischemia, ethanol metabolism in alcoholic hepatitis, and impaired mitochondrial β-oxidation. This latter is the dominant oxidative pathway for the degradation of fatty acids under normal physiological conditions and the ROS major source in nonalcoholic fatty liver disorder (NAFLD) [2, 3]. The production of ROS associated with lipid accumulation is a cause of enhanced risk of damage and disease progression to necroinflammation, steatohepatitis, fibrosis, cirrhosis, and eventually hepatocellular carcinoma [4, 5] and of injuries during ischemia/reperfusion of donor organs for transplantation [6, 7]
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