Mitochondria-targeted antioxidant SkQ1 inhibits leukotriene synthesis in human neutrophils

Abstract

Leukotrienes are among the most potent mediators of inflammation, and inhibition of their biosynthesis, is becoming increasingly important in the treatment of many pathologies. In this work, we demonstrated that preincubation of human neutrophils with the mitochondria targeted antioxidant SkQ1 (100 nM) strongly inhibits leukotriene synthesis induced by three different stimuli: the Ca2+ ionophore A23187, the chemotactic formyl-peptide fMLP in combination with cytocholasin B, and opsonized zymosan. The SkQ1 analogue lacking the antioxidant quinone moiety (C12TPP) was ineffective, suggesting that mitochondrial production of reactive oxygen species (ROS) is critical for activating of leukotriene synthesis in human neutrophils. The uncoupler of oxidative phosphorylation FCCP also inhibits leukotriene synthesis, indicating that a high membrane potential is a prerequisite for stimulating leukotriene synthesis in neutrophils. Our data show that activation of mitogen-activated protein kinases p38 and ERK1/2, which is important for leukotriene synthesis in neutrophils is a target for SkQ1: 1) the selective p38 inhibitor SB203580 inhibited fMLP-induced leukotriene synthesis, while the ERK1/2 activation inhibitor U0126 suppressed leukotriene synthesis induced by any of the three stimuli; 2) SkQ1 effectively prevents p38 and ERK1/2 activation (accumulation of phosphorylated forms) induced by all three stimuli. This is the first study pointing to the involvement of mitochondrial reactive oxygen species in the activation of leukotriene synthesis in human neutrophils. The use of mitochondria-targeted antioxidants can be considered as a promising strategy for inhibiting leukotriene synthesis and treating various inflammatory pathologies.

Redox processes are major regulators of leukotriene synthesis in neutrophils exposed to bacteria Salmonella typhimurium; the way to manipulate neutrophil swarming

“…DPI stimulated the accumulation of LTB4 and total leukotrienes ( Figure 1D ). This effect was observed previously when leukotriene synthesis was induced by various stimuli and was attributed to inhibition of LTB4 omega-hydroxylation ( 22 ). In fact, the ratio of LTB4 to ω-LTB4 with DPI is higher, than in other treatments ( Figures 1 , 2 ).…”

“…We have shown that S. typhimurium stimulates 5LOX, but the mechanism of the enhancing effect of bacteria upon subsequent addition of fMLP remains unclear. We have recently shown that LTB4 synthesis induced by fMLP (as well as some other stimuli) is dependent on mtROS production ( 22 ). However, the effect of fMLP in this study was artificially stimulated by cytochalasin, which disrupts the actin cytoskeleton.…”

“…In the search for possible targets of mtROS-dependent regulation of leukotriene synthesis, we previously showed that activation of the MAP kinases Erk1/2 and p38 (associated with their phosphorylation) is prevented by SkQ1 ( 22 ). Erk1/2 and p38 kinases are known to phosphorylate 5-LOX and stimulate its translocation to the nuclear envelope, which is required for 5-lipoxygenase activity ( 46 ), so they may be critical targets of mtROS.…”

“…Our previous work ( 22 ) using the mitochondria-targeted antioxidant SkQ1 demonstrated the important role of mitochondrial ROS in leukotriene synthesis induced by the Ca 2+ ionophore A23187, the chemoattractant fMLP, and the opsonized yeast cell wall components zymosan. Here, we showed ( Figure 1 ) that mitochondria-targeted antioxidants suppress fMLP-induced leukotriene synthesis in neutrophils exposed to S. typhimurium .…”

“…Mitochondria are an important source of ROS in various cell types, but their role in ROS production in neutrophils has long been underestimated. Only our recent studies ( 20 – 22 ) using the mitochondria-targeted antioxidant SkQ1 [10-(6’-plastoquinonyl)decyltriphenylphosphonium bromide] ( 23 ) have demonstrated the important role of mitochondrial ROS (mtROS) in NADPH oxidase activation, degranulation, extracellular trap formation (NETosis), and leukotriene synthesis. These studies analyzed the activation of neutrophils by the Ca 2+ ionophore A23187 and the chemoattractant N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP), while the role of mtROS in the interaction of neutrophils with bacteria remains unknown.…”