Native LDL-induced oxidative stress in human proximal tubular cells: multiple players involved.

Abstract

Dyslipidemia is a well-established condition proved to accelerate the progression of chronic kidney disease leading to tubulo-interstitial injury. However, the molecular aspects of the dyslipidemia-induced renal damage have not been fully clarified and in particular the role played by low-density lipoproteins (LDLs). This study aimed to examine the effects of native non-oxidized LDL on cellular oxidative metabolism in cultured human proximal tubular cells. By means of confocal microscopy imaging combined to respirometric and enzymatic assays it is shown that purified native LDL caused a marked increase of cellular reactive oxygen species (ROS) production, which was mediated by activation of NADPH oxidase(s) and by mitochondrial dysfunction by means of a ROS-induced ROS release mechanism. 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. This involves first oxidants production via the plasmamembrane NADPH oxidase and then propagates downstream to mitochondria eliciting redox- and Ca(2+) -dependent dysfunctions leading to cell-harming conditions. These findings may help to clarify the mechanism of dyslipidemia-induced renal damage and suggest new potential targets for specific therapeutic strategies to prevent oxidative stress implicated in kidney diseases.

• Authors: Claudia Piccoli, Giovanni Quarato, Annamaria D'Aprile, Eustacchio Montemurno, Rosella Scrima, Maria Ripoli, Monica Gomaraschi, Pietro Cirillo, Domenico Boffoli, Laura Calabresi, Loreto Gesualdo, Nazzareno Capitanio
• Journal: Journal of cellular and molecular medicine (J Cell Mol Med) Vol. 15 Issue 2 Pg. 375-95 (Feb 2011) ISSN: 1582-4934 [Electronic] England
• PMID: 19863698 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.

Chemical References

• Lipoproteins, LDL
• Phospholipase A2 Inhibitors
• Reactive Oxygen Species
• Cytochromes c
• NADPH Oxidases
• Phospholipases A2
• Calcium

Topics

• Calcium (metabolism)
• Calcium Signaling
• Cell Line
• Cytochromes c (metabolism)
• Dyslipidemias (metabolism)
• Humans
• Kidney Tubules, Proximal (metabolism)
• Lipoproteins, LDL (metabolism)
• Mitochondria (pathology)
• NADPH Oxidases (antagonists & inhibitors, biosynthesis, metabolism)
• Oxidative Stress
• Phospholipase A2 Inhibitors
• Phospholipases A2 (metabolism)
• Reactive Oxygen Species (metabolism)
• Signal Transduction