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
Related in: MedlinePlus
Mentions: Stimulation of the Ca2+-dependent cytoplasmic phospholipase A2 (cPLA2) with release of arachidonic acid (AA) is a process known to activate NOX [13, 21]. Therefore, we tested the effect of arachidonyl trifluoromethyl ketone (AACOCF3), an inhibitor of cPLA2, on the nLDL-induced ROS overproduction. Figure 6A clearly shows that AACOCF3 abrogated completely the DCF-fluorescence in nLDL-treated HK-2. Moreover, either chelation of the external Ca2+ by EGTA and treatment with the Ca2+-channel blocker vera-pamil caused, similarly, a depression of the nLDL-induced ROS production. Importantly AACOCF3 prevented the nLDL-dependent extra-cellular production of superoxide (Fig. 6B) supporting the occurrence of NOX activation. These results indicated that the pro-oxidant effect of nLDL on HK-2 was largely mediated by the reaction products of the cPLA2 whose activation was likely linked to stimulation of the inward current of external Ca2+ into the cell.
Affiliation: Department of Biomedical Science, University of Foggia, Foggia, Italy.