Hydroxynonenal, a lipid peroxidation end product, stimulates uncoupling protein activity in Acanthamoeba castellanii mitochondria; the sensitivity of the inducible activity to purine nucleotides depends on the membranous ubiquinone redox state

Abstract

We studied the influence of exogenously generated superoxide and exogenous 4-hydroxy-2-nonenal (HNE), a lipid peroxidation end product, on the activity of the Acanthamoeba castellanii uncoupling protein (AcUCP). The superoxide-generating xanthine/xanthine oxidase system was insufficient to induce mitochondrial uncoupling. In contrast, exogenously added HNE induced GTP-sensitive AcUCP-mediated mitochondrial uncoupling. In nonphosphorylating mitochondria, AcUCP activation by HNE was demonstrated by increased oxygen consumption accompanied by a decreased membrane potential and ubiquinone (Q) reduction level. The HNE-induced GTP-sensitive proton conductance was similar to that observed with linoleic acid. In phosphorylating mitochondria, the HNEinduced AcUCP-mediated uncoupling decreased the yield of oxidative phosphorylation. We demonstrated that the efficiency of GTP to inhibit HNE-induced AcUCPmediated uncoupling was regulated by the endogenous Q redox state. A high Q reduction level activated AcUCP by relieving the inhibition caused by GTP while a low Q reduction level favoured the inhibition. We propose that the regulation of UCP activity involves a rapid response through the endogenous Q redox state that modulates the inhibition of UCP by purine nucleotides, followed by a late response through lipid peroxidation products resulting from an increase in the formation of reactive oxygen species that modulate the UCP activation.

Fatty Acids are Key in 4-Hydroxy-2-Nonenal-Mediated Activation of Uncoupling Proteins 1 and 2

“…The discussion was recently extended to the uncoupling protein of unicellular eukaryotes. Woyda-Ploszczyca and Jarmuszkiewicz demonstrated that HNE activates UCP in Acanthamoeba castellanii mitochondria during non-phosphorylating respiration [24].…”

Hydroxynonenal-stimulated activity of the uncoupling protein in Acanthamoeba castellanii mitochondria under phosphorylating conditions

“…This explanation does not exclude HNE-induced UCP-mediated uncoupling effect after the drop of Δ Ψ during oxidative phosphorylation. Moreover, in mammalian, plant, and amoeba mitochondria Smith et al , 2004 ;Woyda -Ploszczyca and Jarmuszkiewicz, 2012 ), the HNE-induced UCP-mediated proton leak is still observed at Δ Ψ values close to those of phosphorylating conditions in flux-force relationships.…”

“…Because the effect of HNE is highly sensitive to GTP, as confirmed in the present work for the UCP of a unicellular organism, HNE may bind reversibly to UCP in a PN-dependent manner. When A. castellanii and mammalian mitochondria have been incubated with HNE and PNs, the stimulation of UCP by HNE could be almost fully prevented Woyda -Ploszczyca and Jarmuszkiewicz, 2012 ). Moreover, in A. castellanii mitochondria, the inhibitory effect of GTP on the HNE-induced AcUCP-mediated uncoupling can be only observed when Q is sufficiently oxidized.…”

“…The activation of UCP1 from thermogenic mammalian brown adipose tissue by HNE remains controversial (Esteves et al , 2006 ;Shabalina et al , 2006 ). Recently, we have shown that HNE induces PN-sensitive uncoupling in the mitochondria of the amoeba Acanthamoeba castellanii (AcUCP) (Woyda -Ploszczyca and Jarmuszkiewicz, 2012 ). Therefore, mammalian UCP2 and UCP3, plant UCPs, and protozoan UCPs can be considered to be activated by lipid peroxidation products (such as HNE) to induce proton leak, thus providing a negative feedback regulation of mitochondrial ROS formation.…”

“…In parasite protist Plasmodium , it has been proposed that UCP may prevent mitochondrial ROS formation to minimize the risk of oxidative damage during infection cycle (Uyemura et al , 2000 ). In A. castellanii mitochondria, the action of AcUCP has been shown to mediate the free fatty acid-and HNE-activated PN-inhibited proton leak, resulting in mitochondrial uncoupling (Jarmuszkiewicz et al , 1999 ;Woyda -Ploszczyca and Jarmuszkiewicz, 2012 ). In the phosphorylating and nonphosphorylating mitochondria of A. castellanii , PNs have been observed to inhibit the free fatty acid-induced AcUCP activity in a manner dependent upon the redox state of membranous ubiquinone (coenzyme Q, Q) Swida et al , 2008 ).…”