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FcεRI-dependent activation and degranulation of mast cells (MC) play an important role in allergic diseases. We have previously demonstrated that triphenylphosphonium (TPP)-based antioxidant SkQ1 inhibits mast cell degranulation, but the exact mechanism of this inhibition is still unknown. This study focused on investigating the influence of TPP-based compounds SkQ1 and C 12 TPP on FcεRI-dependent mitochondrial dysfunction and signaling during MC degranulation. MC were sensitized by anti-dinitrophenyl IgE and stimulated by BSA-conjugated dinitrophenyl. The degranulation of MC was estimated by β-hexosaminidase release. The effect of TPP-based compounds on FcεRI-dependent signaling was determined by Western blot analysis for adapter molecule LAT, kinases Syk, PI3K, Erk1/2, and p38. Fluorescent microscopy was used to evaluate mitochondrial parameters such as morphology, membrane potential, reactive oxygen species and ATP level. Pretreatment with TPP-based compounds significantly decreased FcεRI-dependent degranulation of MC. TPP-based compounds also prevented mitochondrial dysfunction (drop in mitochondrial ATP level and mitochondrial fission), and decreased Erk1/2 kinase phosphorylation. Selective Erk1/2 inhibition by U0126 also reduced β-hexosaminidase release and prevented mitochondrial fragmentation during FcεRI-dependent degranulation of MC. These findings expand the fundamental understanding of the role of mitochondria in the activation of MC. It also contributes to the rationale for the development of mitochondrial-targeted drugs for the treatment of allergic diseases. Mast cell degranulation is accompanied by mitochondrial fragmentation mediated by Erk1/2 activity. Mitochondria-targeted TPP-based compounds SkQ1 and C12TPP accumulate in mitochondria and decrease mast cell degranulation by preventing Erk1/2-dependent mitochondrial dysfunction. [Display omitted] • FcεRI-dependent degranulation of RBL-2H3 cells is accompanied by mitochondrial fragmentation and dysfunction. • The mitochondrial fission is mediated by Erk1/2 activity. • TPP-based compounds inhibit FcεRI-dependent degranulation of mast cells. • TPP-based compounds decrease Erk1/2 phosphorylation during mast cell FcεRI-dependent degranulation. • TPP-based compounds prevent mitochondrial dysfunction during mast cell FcεRI-dependent degranulation. [ABSTRACT FROM AUTHOR]

Activation of neutrophils is accompanied by the oxidative burst, exocytosis of various granule types (degranulation) and a delay in spontaneous apoptosis. The major source of reactive oxygen species (ROS) in human neutrophils is NADPH oxidase (NOX2), however, other sources of ROS also exist. Although the function of ROS is mainly defensive, they can also play a regulatory role in cell signaling. However, the contribution of various sources of ROS in these processes is not clear. We investigated a possible role of mitochondria-derived ROS (mtROS) in the regulation of neutrophil activation induced by chemoattractant fMLP in vitro . Using the mitochondria-targeted antioxidant SkQ1, we demonstrated that mtROS are implicated in the oxidative burst caused by NOX2 activation as well as in the exocytosis of primary (azurophil) and secondary (specific) granules. Scavenging of mtROS with SkQ1 slightly accelerated spontaneous apoptosis and significantly stimulated apoptosis of fMLP-activated neutrophils. These data indicate that mtROS play a critical role in signal transduction that mediates the major neutrophil functional responses in the process of activation. [ABSTRACT FROM AUTHOR]

Mitochondrial dysfunctions occur in many diseases linked to the systemic inflammatory response syndrome (SIRS). Mild uncoupling of oxidative phosphorylation is known to rescue model animals from pathologies related to mitochondrial dysfunctions and overproduction of reactive oxygen species (ROS). To study the potential of SIRS therapy by uncoupling, we tested protonophore dinitrophenol (DNP) and a free fatty acid (FFA) anion carrier, lipophilic cation dodecyltriphenylphosphonium (C 12 TPP) in mice and in vitro models of SIRS. DNP and C 12 TPP prevented the body temperature drop and lethality in mice injected with high doses of a SIRS inducer, tumor necrosis factor (TNF). The mitochondria-targeted antioxidant plastoquinonyl decyltriphenylphosphonium (SkQ1) which also catalyzes FFA-dependent uncoupling revealed similar protective effects and downregulated expression of the NFκB-regulated genes (VCAM1, ICAM1, MCP1, and IL-6) involved in the inflammatory response of endothelium in aortas of the TNF-treated mice. In vitro mild uncoupling rescued from TNF-induced endothelial permeability, disassembly of cell contacts and VE-cadherin cleavage by the matrix metalloprotease 9 (ММР9). The uncouplers prevented TNF-induced expression of MMP9 via inhibition of NFκB signaling. Water-soluble antioxidant Trolox also prevented TNF-induced activation and permeability of endothelium in vitro via inhibition of NFκB signaling, suggesting that the protective action of the uncouplers is linked to their antioxidant potential. [ABSTRACT FROM AUTHOR]

The receptor for advanced glycation end products (RAGE) is considered to contribute to the pathogenesis of Alzheimer's disease (AD), mediating amyloid beta (Aβ) accumulation, mitochondrial damage, and neuroinflammation. Previously, we have synthesized small peptides corresponding to the fragments (60–76) (P1) and (60–62) (P2) of the RAGE extracellular domain, and have shown that administration of P1 fragment but not P2 results in restoration of the spatial memory and decreases the brain Aβ (1–40) level in olfactory bulbectomized (OBX) mice demonstrating main features of Alzheimer's type neurodegeneration. In the present study, we have investigated the supposed mechanism of the therapeutic efficacy of P1 RAGE fragment and compared it to P2 short fragment. We have found that P1 restored activities of the respiratory chain in the Complexes I and IV in both cortical and hippocampal mitochondria of the OBX mice while P2 had no effect. Besides, fluorescein-labeled analog Flu-P1 bound to Aβ (1–40) and Aβ (1–42) with high affinity (K d in the nanomolar range) whereas Flu-P2 revealed low affinity with tenfold higher K d value for Aβ (1–40) and did not bind to Aβ (1–42). However, neither of the peptides had a notable impact on inflammation, estimated as mRNA expression of proinflammatory cytokines in the brain tissues of OBX mice. Taken together, our results suggest that direct Aβ-P1 interaction is one of the molecular events mediating the protection of the mitochondria in OBX animals from Aβ toxic effect. The RAGE fragment P1 would be the soluble decoy for Aβs and serve as a promising therapeutic agent against neurodegeneration accompanied by mitochondrial dysfunction. • Peptide fragment (60–76) of RAGE restored activities of the respiratory chain Complexes I and IV in -mitochondria of OBX mice. • Fluorescein-labeled analog Flu-(60–76) bound to Aβ peptides (1–40)/(1–42) with a high affinity, K d is in the nanomolar range. • The RAGE fragment (60–76) would be the soluble decoy for Aβs and serve as a promising therapeutic agent. [ABSTRACT FROM AUTHOR]