Activation of mitogen-activated protein kinases by lysophosphatidylcholine-induced mitochondrial reactive oxygen species generation in endothelial cells.

Lysophosphatidylcholine (lysoPC) evokes diverse biological responses in vascular cells including Ca(2+) mobilization, production of reactive oxygen species, and activation of the mitogen-activated protein kinases, but the mechanisms linking these events remain unclear. Here, we provide evidence that the response of mitochondria to the lysoPC-dependent increase in cytosolic Ca(2+) leads to activation of the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase through a redox signaling mechanism in human umbilical vein endothelial cells. ERK activation was attenuated by inhibitors of the electron transport chain proton pumps (rotenone and antimycin A) and an uncoupler (carbonyl cyanide p-trifluoromethoxyphenylhydrazone), suggesting that mitochondrial inner membrane potential plays a key role in the signaling pathway.

Interaction of electrophilic lipid oxidation products with mitochondria in endothelial cells and formation of reactive oxygen species.

Electrophilic lipids, such as 4-hydroxynonenal (HNE), and the cyclopentenones 15-deoxy-Delta12,14 -prostaglandin J2 (15d-PGJ2) and 15-J2-isoprostane induce both reactive oxygen species (ROS) formation and cellular antioxidant defenses, such as heme oxygenase-1 (HO-1) and glutathione (GSH). When we compared the ability of these distinct electrophiles to stimulate GSH and HO-1 production, the cyclopentenone electrophiles were somewhat more potent than HNE. Over the concentration range required to observe equivalent induction of GSH, dichlorofluorescein fluorescence was used to determine both the location and amounts of electrophilic lipid-dependent ROS formation in endothelial cells.

Oxidized LDL induces mitochondrially associated reactive oxygen/nitrogen species formation in endothelial cells.

Exposure of cells to complex mixtures of oxidized lipids such as those found in oxidized low-density lipoprotein (oxLDL) induce reactive oxygen and nitrogen species (ROS/RNS) formation. The source of the ROS/RNS within cells is unknown; it is thought they may be involved in redox cell signaling. Although this possibility was initially overlooked, it is becoming clear that mitochondria, which are a source of superoxide and hydrogen peroxide, may play a critical role in the response of cells on exposure to oxidized lipids.

Metabolic control of resistance of human epithelial cells to H2O2 and NO stresses.

The carbon flux through the oxidative branch of the pentose phosphate pathway (PPP) can be viewed as an integrator of the antioxidant mechanisms via the generation of NADPH. It could therefore be used as a control point of the cellular response to an oxidative stress. Replacement of glucose by galactose sensitized the human epithelial cell line HGT-1 to H2O2 stress.