Native LDL-induced oxidative stress in human proximal tubular cells: multiple players involved.
Bottom Line: The LDL-dependent mitochondrial alterations comprised inhibition of the respiratory chain activity, enhanced ROS production, uncoupling of the oxidative phosphorylation efficiency, collapse of the mtΔΨ, increased Ca(2+) uptake and loss of cytochrome c.All the above LDL-induced effects were completely abrogated by chelating extracellular Ca(2+) as well as by inhibition of the Ca(2+) -activated cytoplasmic phospholipase A2, NADPH oxidase and mitochondrial permeability transition.We propose a mechanicistic model whereby the LDL-induced intracellular redox unbalance is triggered by a Ca(2+) inward flux-dependent commencement of cPLA2 followed by activation of a lipid- and ROS-based cross-talking signalling pathway.
Affiliation: Department of Biomedical Science, University of Foggia, Foggia, Italy.Show MeSH
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Mentions: Figure 1A illustrates the effect of nLDL-treatment of HK-2 on ROS production as assessed by confocal microscopy performed with ROS-specific fluorescent probes. It is shown that 100 μg/ml of nLDL-treatment for 24 hrs caused a large increase of the dichlorofluorescein (DCF)-related fluorescence signal over the basal level, diagnostic of intracellular production of H2O2. This was fully prevented by N-acetyl cysteine (NAC) and not observed following treatment of HK-2 with 15 mg/ml of albumin. MitoSox, a probe sensing intramitochondrial O2− production , failed to detect evidence of increased ROS-production. However, reassessment of the nLDL-induced DCF fluorescence under different instrumental settings resulted in brighter spotting in sub-cellular compartments clearly resembling the mitochondrial network morphology (Fig. 1B).
Affiliation: Department of Biomedical Science, University of Foggia, Foggia, Italy.