Mitochondria-targeted Uncouplers Decrease Inflammatory Reactions in Endothelial Cells by Enhancing Methylation of the ICAM1 Gene Promoter

INTRODUCTION

The study aimed to investigate the effects of low concentrations of mitochondrial uncouplers in endothelial cells on the CpG dinucleotide methylation of the ICAM1 gene promoter. The excessive inflammatory response in the endothelium is responsible for the development of many cardiovascular diseases. Mitochondria are important regulators of endothelial cell functions. Mild uncoupling of oxidative phosphorylation and respiration in endothelial mitochondria exerts a long lasting anti-inflammatory effect. However, the detailed mechanism of the anti-inflammatory activity of mitochondrial uncouplers remains unclear.We hypothesized that mild mitochondrial uncoupling leads to epigenetic changes in genomic DNA contributing to the anti-inflammatory response.

METHODS

We studied the long-term effects of mitochondria-targeted compounds with the uncoupler's activities: the antioxidant plastoquinonyl-decyltriphenylphosphonium (SkQ1), dodecyl-triphenylphosphonium (C12TPP), and 2,4-dinitrophenol (DNP). The mRNA expression of the intercellular adhesion molecule 1 (ICAM1), a marker of inflammatory activation of endothelial cells, was measured by RT-qPCR. Cytosine methylation in the CpG sites of the ICAM1 gene promoter was estimated by bisulfite sequencing of individual clones.

RESULTS

It was found that downregulation of ICAM1 expression caused by DNP and C12TPP was accompanied by an increase in the methylation of CpG sites in the ICAM1 gene promoter. None of the compounds affected intracellular or intramitochondrial ATP levels.

CONCLUSION

Low concentrations of mitochondrial oxidative phosphorylation uncouplers are able to increase methylation of ICAM1 gene promoter, which corresponds to the observed decrease in the levels of mRNA of this gene. Thus, the change in methylation of the ICAM1 gene promoter may underlie the mechanism of decreased ICAM1 expression caused by mild mitochondrial depolarization. Mitochondrial uncouplers may be exploited as possible therapeutic candidates to treat excessive inflammation in endothelium, by changing the methylation status of genomic DNA.

Ketogenic Diet and Ketone Bodies against Ischemic Injury: Targets, Mechanisms, and Therapeutic Potential

The ketogenic diet (KD) has been used as a treatment for epilepsy since the 1920s, and its role in the prevention of many other diseases is now being considered. In recent years, there has been an intensive investigation on using the KD as a therapeutic approach to treat acute pathologies, including ischemic ones. However, contradictory data are observed for the effects of the KD on various organs after ischemic injury. In this review, we provide the first systematic analysis of studies conducted from 1980 to 2022 investigating the effects and main mechanisms of the KD and its mimetics on ischemia-reperfusion injury of the brain, heart, kidneys, liver, gut, and eyes. Our analysis demonstrated a high diversity of both the composition of the used KD and the protocols for the treatment of animals, which could be the reason for contradictory effects in different studies. It can be concluded that a true KD or its mimetics, such as β-hydroxybutyrate, can be considered as positive exposure, protecting the organ from ischemia and its negative consequences, whereas the shift to a rather similar high-calorie or high-fat diet leads to the opposite effect.

Mitochondria-targeted triphenylphosphonium-based compounds inhibit FcεRI-dependent degranulation of mast cells by preventing mitochondrial dysfunction through Erk1/2

AIMS

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 C₁₂TPP on FcεRI-dependent mitochondrial dysfunction and signaling during MC degranulation.

MAIN METHODS

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.

KEY FINDINGS

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.

SIGNIFICANCE

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.