Inflammation is a natural protective process through which the immune system responds to injury, infection, or irritation. However, hyperinflammation or long-term inflammatory response can cause various inflammatory diseases. Although idebenone was initially developed for the treatment of cognitive impairment and dementia, it is currently used to treat various diseases. However, its anti-inflammatory effects and regulatory functions in inflammatory diseases is yet to be elucidated. Therefore, this study aimed to investigate the anti-inflammatory effects of idebenone in cecal ligation puncture-induced sepsis and lipopolysaccharide-induced systemic inflammation. Murine models of cecal ligation puncture-induced sepsis and lipopolysaccharide-induced systemic inflammation were generated, followed by treatment with various concentrations of idebenone. Additionally, lipopolysaccharide-stimulated macrophages were treated with idebenone to elucidate its anti-inflammatory effects at the cellular level. Idebenone treatment significantly improved survival rate, protected against tissue damage, and decreased the expression of inflammatory enzymes and cytokines in mice models of sepsis and systemic inflammation. Additionally, idebenone treatment suppressed inflammatory responses in macrophages, inhibited the NF-κB signaling pathway, reduced reactive oxygen species and lipid peroxidation, and normalized the activities of antioxidant enzyme. Idebenone possesses potential therapeutic application as a novel anti-inflammatory agent in systemic inflammatory diseases and sepsis.
Eukaryotic translation initiation factor 2α (eIF2α) phosphorylation, which regulates all three unfolded protein response pathways, helps maintain cellular homeostasis and overcome endoplasmic reticulum (ER) stress through transcriptional and translational reprogramming. However, transcriptional regulation of mitochondrial and redox homeostasis (especially glutathione (GSH) homeostasis) by eIF2α phosphorylation during ER stress is not fully understood. Here, we report that the eIF2α phosphorylation-activating transcription factor 4 (ATF4) axis is required for expression of multiple transcription factors (TFs) including nuclear factor erythroid 2-related factor 2 and their target genes responsible for mitochondrial and GSH homeostasis during ER stress. eIF2α phosphorylation-deficient (A/A) cells displayed dysregulated mitochondrial dynamics and mitochondrial DNA replication, decreased expression of oxidative phosphorylation complex proteins, and impaired mitochondrial function during ER stress. eIF2α phosphorylation deficiency also increased cellular (even mitochondrial) reactive oxygen species accumulation because expression of multiple antioxidant genes including GSH-synthesizing genes was decreased. Consequently, the ER stress-mediated decrease of the cellular (even mitochondrial) GSH level was aggravated in A/A cells. Moreover, the eIF2α phosphorylation-ATF4 axis was responsible for upregulation of ferroptosis-inhibiting genes and downregulation of ferroptosis-activating genes upon ER stress. Therefore, ER stress strongly induced ferroptosis of A/A cells, which was inhibited by the ferroptosis inhibitor ferrostatin-1. ATF4 overexpression suppressed impairment of mitochondrial and GSH homeostasis in A/A cells during ER stress by promoting expression of downstream TFs and their target genes. Consequently, ATF4 overexpression suppressed ferroptosis of A/A cells during ER stress. Our results indicate that eIF2α phosphorylation is essential for preservation of mitochondrial and GSH homeostasis to prevent cell death (particularly ferroptosis) via transcriptional reprogramming during ER stress.
Transcription factors such as NF‐κB provide powerful targets for drugs to use in the treatment of cancer. In this report parthenolide (PT), a sesquiterpene lactone of herbal remedies such as feverfew ( Tanacetum parthenium ) with NF‐κB inhibitory activity, markedly increased the degree of human leukaemia HL‐60 cell differentiation when simultaneously combined with 5 n M 1α,25‐dihydroxyvitamin D 3 (1,25‐(OH) 2 D 3 ). PT by itself did not induce HL‐60 cell differentiation. Cytofluorometric analysis indicated that PT stimulated 1,25‐(OH) 2 D 3 ‐induced differentiation of HL‐60 cells predominantly into monocytes. Pretreatment of HL‐60 cells with PT before the 1,25‐(OH) 2 D 3 addition also potentiated the 1,25‐(OH) 2 D 3 ‐induced HL‐60 cell differentiation in both a dose‐ and a time‐dependent manner, in which the enhanced levels of cell differentiation closely correlated with the inhibitory levels of NF‐κB binding activity by PT. In contrast, santonin, a sesquiterpene lactone without an inhibitory activity of NF‐κB binding to the κB sites, did not enhance the 1,25‐(OH) 2 D 3 ‐induced HL‐60 cell differentiation. In transfection experiments, PT enhanced 1,25‐(OH) 2 D 3 ‐induced VDRE‐dependent promoter activity. Furthermore, PT restored 1,25‐(OH) 2 D 3 ‐induced VDRE‐dependent promoter activity inhibited by TNF‐α, an activator of NF‐κB signalling pathway. These results indicate that PT strongly potentiates the 1,25‐(OH) 2 D 3 ‐induced HL‐60 cell differentiation into monocytes via the inhibition of NF‐κB activity and provide evidence that inhibition of NF‐κB activation can be a pre‐requisite to the efficient entry of promyelocytic leukaemia cells into a differentiation pathway. British Journal of Pharmacology (2002) 135 , 1235–1244; doi: 10.1038/sj.bjp.0704573
MitoNEET, a mitochondrial outer membrane protein containing the Asn-Glu-Glu-Thr (NEET) sequence, controls the formation of intermitochondrial junctions and confers autophagy resistance. Moreover, mitoNEET as a mitochondrial substrate undergoes ubiquitination by activated Parkin during the initiation of mitophagy. Therefore, mitoNEET is linked to the regulation of autophagy and mitophagy. Mitophagy is the selective removal of the damaged or unnecessary mitochondria, which is crucial to sustaining mitochondrial quality control. In numerous human diseases, the accumulation of damaged mitochondria by impaired mitophagy has been observed. However, the therapeutic strategy targeting of mitoNEET as a mitophagy-enhancing mediator requires further research. Herein, we confirmed that mitophagy is indeed activated by mitoNEET inhibition. CCCP (carbonyl cyanide m-chlorophenyl hydrazone), which leads to mitochondrial depolarization, induces mitochondrial dysfunction and superoxide production. This, in turn, contributes to the induction of mitophagy; mitoNEET protein levels were initially increased before an increase in LC3-Ⅱ protein following CCCP treatment. Pharmacological inhibition of mitoNEET using mitoNEET Ligand-1 (NL-1) promoted accumulation of Pink1 and Parkin, which are mitophagy-associated proteins, and activation of mitochondria-lysosome crosstalk, in comparison to CCCP alone. Inhibition of mitoNEET using NL-1, or mitoNEET shRNA transfected into RAW264.7 cells, abrogated CCCP-induced ROS and mitochondrial cell death; additionally, it activated the expression of PGC-1α and SOD2, regulators of oxidative metabolism. In particular, the increase in PGC-1α, which is a major regulator of mitochondrial biogenesis, promotes mitochondrial quality control. These results indicated that mitoNEET is a potential therapeutic target in numerous human diseases to enhance mitophagy and protect cells by maintaining a network of healthy mitochondria. [BMB Reports 2022; 55(7): 354-359].
Interleukin‐12 (IL‐12) plays a central role in the immune system by driving the immune response towards T helper 1 (Th1) type responses characterized by high IFN‐γ and low IL‐4 production. In this study we investigated whether retinoid‐mediated inhibition of interleukin‐12 production in mouse macrophages could regulate cytokine profile of antigen (Ag)‐primed CD4 + Th cells. Pretreatment with retinoids (9‐ cis ‐RA, all‐ trans ‐RA, TTNPB) significantly inhibited IL‐12 production by mouse macrophages stimulated with lipopolysaccharide (LPS) or heated‐killed Listeria monocytogenes (HKL). Retinoid‐pretreated macrophages reduced their ability to induce IFN‐γ and increased the ability to induce IL‐4 in Ag‐primed CD4 + T cells. Addition of recombinant IL‐12 to cultures of retinoid‐pretreated macrophages and CD4 + T cells restored IFN‐γ production in CD4 + T cells. The in vivo administration of 9‐ cis ‐RA resulted in the inhibition of IL‐12 production by macrophages stimulated in vitro with either LPS or HKL, leading to the inhibition of Th1 cytokine profile (decreased IFN‐γ and increased IL‐4 production) in CD4 + T cells. These findings may explain some known effects of retinoids including the inhibition of encephalitogenicity, and point to a possible therapeutic use of retinoids in the Th1‐mediated immune diseases such as autoimmune diseases. British Journal of Pharmacology (2000) 130 , 581–586; doi: 10.1038/sj.bjp.0703345
Haem oxygenase (HO)-1 is a cytoprotective enzyme that plays a critical role in defending the body against oxidant-induced injury during inflammatory processes. HO catalydes the degradation of haem to carbon monoxide (CO), biliverdin and ferrous iron. Biliverdin is converted to bilirubin, a potent endogenous antioxidant. CO has a number of biological functions, including anti-inflammatory properties. In various models of disease, HO-1 is known to play a critical role by ameliorating the pathological consequences of injury. In many of these models, the beneficial effects of HO-1 and its products of haem catabolism are by suppressing an inflammatory response. However, when investigating diseases due to microbial infections, inhibition of the inflammatory response could disrupt the ability of the immune system to eradicate an invading pathogen. Thus, questions remain regarding the role of HO-1 in microbial host defence. This microreview will address our present understanding of HO-1 and its functional significance in a variety of microbial infections.
<i>Background:</i> Diethylhexyl phthalate (DEHP) and diisononyl phthalate (DINP), two commonly used plasticizers in flexible polyvinylchloride formulations, have potentially adverse effects on human health. However, the influence of these diphthalates on allergic responses remains unclear. In this study we examined the effects of DEHP and DINP on IL-4 production in CD4+ T cells and the level of IgE in sera, critical hallmarks associated with allergic diseases. <i>Methods:</i> Mouse T cells were exposed to two diphthalates in vitro and in vivo. The levels of IL-4 and IgE were determined by ELISA, and the degree of NF-AT activation was determined by IL-4 gene promoter assay and electrophoretic mobility shift assay. <i>Results and Discussion:</i> Both DEHP and DINP significantly enhanced IL-4 production in activated CD4+ T cells in a concentration-dependent manner. Treatment with DEHP or DINP in vivo resulted in a significant increase of IL-4 production in CD4+ T cells and of IgE levels in sera. Furthermore, DEHP and DINP enhanced the activation of IL-4 gene promoter in EL4 T cells and the enhancing effect mapped to a region in the IL-4 promoter containing binding sites for a transcription factor, NF-AT. The activation of T cells resulted in markedly enhanced binding activities to the NF-AT site, which significantly increased upon addition of DEHP or DINP, indicating that NF-AT was involved in the enhancing effect of DEHP and DINP on IL-4 production. These findings suggest that both DEHP and DINP enhance allergic responses by enhancement of IL-4 production in CD4+ T cells via stimulation of NF-AT-binding activity.
Endoplasmic reticulum (ER) stress-induced cell death of vascular smooth muscle cells (VSMCs) is extensively involved in atherosclerotic plaque stabilization. We previously reported that nucleotide-binding oligomerization domain protein 2 (NOD2) participated in vascular homeostasis and tissue injury. However, the role and underlying mechanisms of NOD2 remain unknown in ER stress-induced cell death of VSMC during vascular diseases, including advanced atherosclerosis. Here, we report that NOD2 specifically interacted with ER stress sensor activating transcription factor 6 (ATF6) and suppressed the expression of proapoptotic transcription factor CHOP (C/EBP homologous protein) during ER stress. CHOP-positive cells were increased in neointimal lesions after femoral artery injury in NOD2-deficient mice. In particular, a NOD2 ligand, MDP, and overexpression of NOD2 decreased CHOP expression in wild-type VSMCs. NOD2 interacted with an ER stress sensor molecule, ATF6, and acted as a negative regulator for ATF6 activation and its downstream target molecule, CHOP, that regulates ER stress-induced apoptosis. Moreover, NOD2 deficiency promoted disruption of advanced atherosclerotic lesions and CHOP expression in NOD2-/- ApoE-/- mice. Our findings indicate an unsuspected critical role for NOD2 in ER stress-induced cell death.
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