4-Octyl itaconate alleviates dextran sulfate sodium-induced ulcerative colitis in mice via activating the KEAP1-NRF2 pathway

Ulcerative colitis (UC) is a chronic idiopathic inflammatory bowel disease with a relapsing-remitting course. Although its etiology remains unknown, excessive oxidative stress in colon is a major intermediate factor that can promote the progression of UC. In the present study, we investigated the effect and the underlying mechanisms of 4-Octyl itaconate (OI) on dextran sulfate sodium (DSS)-induced UC in mice. Our work identified that OI alleviated the colitis by reducing the oxidative stress and the apoptosis in colon tissue, then increasing the tight junction proteins expression and in turn enhancing the intestinal barrier function, thereby creating less severe inflammatory responses. Moreover, our results demonstrated that OI reduced the Kelch-like ECH-associated protein 1 (KEAP1) expression and subsequent upregulated nuclear factor E2-related factor (NRF2) expression and its nuclear translocation which in turn induced the expression of glutathione S-transferase (GST) and NAD(P)H: quinone oxidoreductase 1 (NQO1). In addition, ML385, a NRF2 antagonist, can inhibit the protective effects of OI on UC, indicating that the role of OI in this colitis model could be dependent on the activation of KEAP1-NRF2 pathway. Notably, OI co-administration significantly enhanced the therapeutic effects of mesalazine or 1400W on UC. Collectively, itaconate may have a great potential for use in the treatment of IBD.

4-Octyl Itaconate Attenuates Neuroinflammation in Experimental Autoimmune Encephalomyelitis Via Regulating Microglia

Abnormal activation of microglia, the resident macrophages in the central nervous system, plays an important role in the pathogenesis of multiple sclerosis (MS). The immune responsive gene 1(IRG1)/itaconate axis is involved in regulating microglia-mediated neuroinflammation. 4-Octyl itaconate (4-OI), a derivative of itaconate, plays a crucial immunomodulatory role in macrophages. This study investigated the effects and mechanisms of action of 4-OI on experimental autoimmune encephalomyelitis (EAE) and inflammatory BV2 microglia. In an EAE mouse model, clinical evaluation was conducted during the disease course. Hematoxylin and eosin staining was performed to assess inflammatory infiltration and Luxol Fast Blue was used to visualize pathological damage. Quantitative real-time polymerase chain reaction, western blotting and immunofluorescence were used to evaluate inflammatory response and microglial function status in EAE mice. BV2 microglia were used to further investigate the effects and mechanisms of action of 4-OI in vitro. 4-OI significantly alleviated the clinical symptoms of EAE, the inflammatory infiltration, and demyelination; reduced the levels of inflammatory factors; and inhibited the classical activation of microglia in the spinal cord. 4-OI successfully suppressed the classical activation of BV2 microglia and decreased the levels of inflammatory factors by activating the Nrf2/HO-1 signaling pathway. Furthermore, 4-OI downregulated IRG1 expression in both EAE mice and inflammatory BV2 microglia. 4-OI attenuates the microglia-mediated neuroinflammation and has promising therapeutic effects in MS.

Inhibition of Alzheimer's disease by 4-octyl itaconate revealed by RNA-seq transcriptome analysis

AIMS

This study aimed to examine the therapeutic effects and response mechanisms of 4-OI in Alzheimer's disease (AD).

METHODS

In this study, network pharmacology was employed to analyze potential targets for AD drug therapy. Immunofluorescence and quantitative reverse transcription polymerase chain reaction (qRT-PCR) techniques were utilized to detect inflammatory phenotypes in a 4-OI-resistant mouse microglia cell line (BV2). We conducted four classical behavioral experiments, namely the open field test, new object recognition test, Y maze test, and Morris water maze, to assess the emotional state and cognitive level of APPswe/PS1dE9 (referred to as APP/PS1) mice after 4-OI treatment. Hematoxylin and eosin (HE) staining, along with immunofluorescence staining, were performed to detect amyloid (Aβ) deposition in mouse brain tissue. To explore the potential molecular mechanisms regulating the effects of 4-OI treatment, we performed RNA-SEQ and transcription factor prediction analyses. Additionally, mouse BV2 cells underwent Western blotting analysis to elucidate potential molecular mechanisms underlying the observed effects.

RESULTS

We discovered that 4-OI exerts an inhibitory effect on neuroinflammation by promoting autophagy. This effect is attributed to the activation of the AMPK/mTOR/ULK1 pathway, achieved through enhanced phosphorylation of AMPK and ULK1, coupled with a reduction in mTOR phosphorylation. Furthermore, 4-OI significantly enhances neuronal recovery in the hippocampus and diminishes Aβ plaque deposition in APP/PS1 mice, improved anxiety in mice, and ultimately led to improved cognitive function.

CONCLUSIONS

Overall, the results of this study demonstrated that 4-OI improved cognitive deficits in AD mice, confirming the therapeutic effect of 4-OI on AD.

4-Octyl itaconate alleviates experimental autoimmune prostatitis by inhibiting the NLRP3 inflammasome-induced pyroptosis through activating Nrf2/HO-1 pathway

BACKGROUND

Chronic prostatitis demonstrates a prevalence rate of nearly 5%-10% among young and middle-aged individuals, significantly affecting their daily lives. Researchers have obtained significant outcomes investigating the anti-inflammatory properties of itaconic acid (IA) and its derivative, 4-Octyl itaconate (4-OI), against diverse chronic inflammatory disorders, such as osteoarthritis and airway inflammation. Nevertheless, whether IA can also exert anti-inflammatory effects in chronic prostatitis requires extensive research and validation.

METHODS

Human prostate tissues obtained through transurethral prostate resection (TURP) from individuals were divided into three groups based on different levels of inflammation using hematoxylin and eosin staining (H&E). Subsequently, immunohistochemistry (IHC) was employed to detect the expression of immune-responsive gene 1 (IRG-1) in these different groups. The animal experiment of this study induced experimental autoimmune prostatitis (EAP) in nonobese diabetic mice through intradermal prostate antigen injection and complete Freund's adjuvant. Then, the experimental group received intraperitoneal injections of different doses of 4-OI, while the control group received injections of saline. Western blot (WB), H&E staining, and TUNEL staining helped analyze the prostate tissues, while enzyme-linked immunosorbent assay (ELISA) helped evaluate serum inflammatory factors. Reactive oxygen species, superoxide dismutase (SOD), and malondialdehyde (MDA) were assessed for oxidative stress across experimental groups.

RESULTS

IHC analysis of human prostate tissue depicts that IRG-1 expression enhances as prostate inflammation worsens, highlighting the critical role of IA in human prostatitis. The application of 4-OI increased Nrf2/HO-1 expression while inhibited NLRP3 expression following the WB results, and its application resulted in a decrease in cell pyroptosis in prostate tissue, demonstrated by the results of TUNEL staining. Administering a Nrf2 inhibitor ML385 1 h before intraperitoneal injection of 50 mg/kg 4-OI reversed the previous conclusion, further confirming the above conclusion from another perspective. Meanwhile, the ELISA results of serum inflammatory factors (IL-1β, IL-6, and TNF-α), as well as the measurements of oxidative stress markers MDA and SOD, further confirmed the specific anti-inflammatory effects of 4-OI in EAP.

CONCLUSIONS

The present study indicates that 4-OI can alleviates EAP by inhibiting the NLRP3 inflammasome-induced pyroptosis through activating Nrf2/HO-1 pathway, which may facilitate a novel approach toward prostatitis treatment.

4-OI ameliorates bleomycin-induced pulmonary fibrosis by activating Nrf2 and suppressing macrophage-mediated epithelial-mesenchymal transition

OBJECTIVES

Pulmonary fibrosis (PF) is a chronic and refractory interstitial lung disease with limited therapeutic options. 4-octyl itaconate (4-OI), a cell-permeable derivative of itaconate, has been shown to have anti-oxidative and anti-inflammatory properties. However, the effect and the underlying mechanism of 4-OI on PF are still unknown.

METHODS

WT or Nrf2 knockout (Nrf2^-/-) mice were intratracheally injected with bleomycin (BLM) to establish PF model and then treated with 4-OI. The mechanism study was performed by using RAW264.7 cells, primary macrophages, and conditional medium-cultured MLE-12 cells.

RESULTS

4-OI significantly alleviated BLM-induced PF and EMT process. Mechanism studies have found that 4-OI can not only directly inhibit EMT process, but also can reduce the production of TGF-β1 by restraining macrophage M2 polarization, which in turn inhibits EMT process. Moreover, the effect of 4-OI on PF and EMT depends on Nrf2.

CONCLUSION

4-OI ameliorates BLM-induced PF in an Nrf2-dependent manner, and its role in alleviating PF is partly due to the direct inhibition on EMT, and partly through indirect inhibition of M2-mediated EMT. These findings suggested that 4-OI has great clinical potential to develop as a new anti-fibrotic agent for PF therapy.

4-Octyl itaconate attenuates glycemic deterioration by regulating macrophage polarization in mouse models of type 1 diabetes

BACKGROUND

Pancreatic beta cell dysfunction and activated macrophage infiltration are early features in type 1 diabetes pathogenesis. A tricarboxylic acid cycle metabolite that can strongly activate NF-E2-related factor 2 (Nrf2) in macrophages, itaconate is important in a series of inflammatory-associated diseases via anti-inflammatory and antioxidant properties. However, its role in type 1 diabetes is unclear. We used 4-octyl itaconate (OI), the cell-permeable itaconate derivate, to explore its preventative and therapeutic effects in mouse models of type 1 diabetes and the potential mechanism of macrophage phenotype reprogramming.

METHODS

The mouse models of streptozotocin (STZ)-induced type 1 diabetes and spontaneous autoimmune diabetes were used to evaluate the preventative and therapeutic effects of OI, which were performed by measuring blood glucose, insulin level, pro- and anti-inflammatory cytokine secretion, histopathology examination, flow cytometry, and islet proteomics. The protective effect and mechanism of OI were examined via peritoneal macrophages isolated from STZ-induced diabetic mice and co-cultured MIN6 cells with OI-pre-treated inflammatory macrophages in vitro. Moreover, the inflammatory status of peripheral blood mononuclear cells (PBMCs) from type 1 diabetes patients was evaluated after OI treatment.

RESULTS

OI ameliorated glycemic deterioration, increased systemic insulin level, and improved glucose metabolism in STZ-induced diabetic mice and non-obese diabetic (NOD) mice. OI intervention significantly restored the islet insulitis and beta cell function. OI did not alter the macrophage count but significantly downregulated the proportion of M1 macrophages. Additionally, OI significantly inhibited MAPK activation in macrophages to attenuate the macrophage inflammatory response, eventually improving beta cell dysfunction in vitro. Furthermore, we detected higher IL-1β production upon lipopolysaccharide stimulation in the PBMCs from type 1 diabetes patients, which was attenuated by OI treatment.

CONCLUSIONS

These results provided the first evidence to date that OI can prevent the progression of glycemic deterioration, excessive inflammation, and beta cell dysfunction predominantly mediated by restricting macrophage M1 polarization in mouse models of type 1 diabetes.

4-Octyl itaconate inhibits aerobic glycolysis by targeting GAPDH to promote cuproptosis in colorectal cancer

Cuproptosis, a novel copper-induced cell death pathway, is linked to mitochondrial respiration and mediated by protein lipoylation. The discovery of cuproptosis unfolds new areas of investigation, particularly in cancers. The present study aimed to explore the role of cuproptosis in colorectal cancer progression. The genetic alterations of cuproptosis in colon cancer were evaluated using a database. MTT assays, colony formation, and flow cytometry were used to examine the effect of elesclomol-Cu and 4-Octyl itaconate (4-OI) on colorectal cancer cell and oxaliplatin-resistant cell viability. The anti-tumor effect of elesclomol with 4-OI was verified in vivo assay. The results showed that FDX1, SDHB, DLAT, and DLST genes were more highly expressed in normal tissues than those in primary tumor tissues. Patients with high expressions of these genes in tumor tissues had a better prognosis. Using MTT assay and colony formation analysis, elesclomol-Cu pulse treatment showed significant inhibition of cell viability in HCT116, LoVo, and HCT116-R cells. In addition, flow cytometry revealed elesclomol-Cu significantly promoted apoptosis. Tetrathiomolybdate, a copper chelator, markedly inhibited cuproptosis. Subsequently, we found 2-deoxy-D-glucose, a glucose metabolism inhibitor, sensitized cuproptosis. Furthermore, galactose further promoted cuproptosis. Interestingly, 4-OI significantly enhanced cuproptosis which was irrelevant to ROS production, apoptosis, necroptosis, or pyroptosis pathways. Aerobic glycolysis was inhibited by 4-OI through GAPDH, one of the key enzymes of glycolysis, sensitizing cuproptosis. Meanwhile, FDX1 knockdown weakened the ability of 4-OI to promote cuproptosis. In vivo experiments, 4-OI with elesclomol-Cu showed better anti-tumor effects. These results indicated that elesclomol-Cu rapidly halted cell growth in colorectal cancer cells and oxaliplatin-resistant cell line. Importantly, we revealed that 4-OI inhibited aerobic glycolysis by targeting GAPDH to promote cuproptosis.

"Spongy skin" as a robust strategy to deliver 4-octyl itaconate for conducting dual-regulation against in-stent restenosis

The valid management of inflammation and precise inhibition of smooth muscle cells (SMCs) is regarded as a promising strategy for regulating vascular responses after stent implantation, yet posing huge challenges to current coating constructions. Herein, we proposed a spongy cardiovascular stent for the protective delivery of 4-octyl itaconate (OI) based on a "spongy skin" approach, and revealed the dual-regulation effects of OI for improving vascular remolding. We first constructed a "spongy skin" onto poly-l-lactic acid (PLLA) substrates, and realized the protective loading of OI with the highest dosage of 47.9 μg/cm². Then, we verified the remarkable inflammation mediation of OI, and surprisingly revealed that the OI incorporation specifically inhibited SMC proliferation and phenotype switching, which contributed to the competitive growth of endothelial cells (EC/SMC ratio ∼ 5.1). We further demonstrated that OI at a concentration of 25 μg/mL showed significant suppression of the TGF-β/Smad pathway of SMCs, leading to the promotion of contractile phenotype and reduction of extracellular matrix. In vivo evaluation indicated that the successful delivery of OI fulfilled the inflammation regulation and SMCs inhibition, therefore suppressing the in-stent restenosis. This "spongy skin" based OI eluting system may serve as a new strategy for improving vascular remolding, and provides a potential concept for the treatment of cardiovascular diseases.

Activation of Nrf2 signaling by 4-octyl itaconate attenuates the cartilaginous endplate degeneration by inhibiting E3 ubiquitin ligase ZNF598

OBJECTIVE

Cartilaginous endplate (CEP) degeneration is the main early manifestations of intervertebral disc degeneration (IVDD), and is closely related to the oxidative stress. Nrf2 (nuclear factor E2-related factor 2, NFE2L2) is a vital transcriptional factor of cellular antioxidant and anti-inflammatory responses. We aimed to illustrate whether the Nrf2 which was increased in expression by 4-octyl itaconate (4OI) could attenuate intervertebral disc degeneration through suppressing macrophage associated inflammation and catabolism of cartilaginous endplate.

METHODS

Firstly, we detected the expression of Nrf2 in human degenerative CEPs. Then, we performed in vitro, ex vivo and in vivo (a rat-tail puncture model) experiments to explore the role of 4OI in IVDD. Also, by cell co-culture experiments, we demonstrated 4OI restrained the macrophage-associated inflammatory responses. Finally, through western blotting and immunoprecipitation (IP) assay, we clarified the ZNF598-mediated ubiquitination of Nrf2.

RESULTS

We found decreased expression of Nrf2 in human degenerative CEPs. Using a rat IVDD model(n = 6), 4OI significantly ameliorated the progression of IVDD by MR images and histological analysis. Immunofluorescence results reveal that catabolism of CEPs and macrophage-associated inflammation are suppressed by 4OI treatment. Mechanistically, the 4OI increases Nrf2 expression and inhibits the secretion of inflammatory factors (IL-1β) by Lipopolysaccharide (LPS)-induced macrophages, thus preventing the inflammatory-related CEP degeneration. Meanwhile, 4OI suppresses the reactive oxygen species (ROS) production and catabolism of LPS-induced rat CEP cells. In addition, 4OI inhibits the ZNF598-dependent ubiquitination of Nrf2 in LPS-induced rat CEP cells.

CONCLUSIONS

4OI may alleviate IVDD by suppressing CEP degeneration and macrophage-associated inflammation. 4OI may be an alternative therapy for degenerative CEPs/IVDs.

4-Octyl itaconate suppresses the osteogenic response in aortic valvular interstitial cells via the Nrf2 pathway and alleviates aortic stenosis in mice with direct wire injury

Calcific aortic valve disease (CAVD) is the most prevalent valvular heart disease in older individuals, but there is a lack of drug treatment. The cellular biological mechanisms of CAVD are still unclear. Oxidative stress and endoplasmic reticulum stress (ER stress) have been suggested to be involved in the progression of CAVD. Many studies have demonstrated that 4-octyl itaconate (OI) plays beneficial roles in limiting inflammation and oxidative injury. However, the potential role of OI in CAVD has not been thoroughly explored. Thus, we investigated OI-mediated modulation of ROS generation and endoplasmic reticulum stress to inhibit osteogenic differentiation in aortic valve interstitial cells (VICs). In our study, calcified aortic valves showed increased levels of ER stress and superoxide anion, as well as abnormal expression of Hmox1 and NQO1. In VICs, OI activated the Nrf2 signaling cascade and contributed to Nrf2 stabilization and nuclear translocation, thus augmenting the expression of genes downstream of Nrf2 (Hmox1 and NQO1). Moreover, OI ameliorated osteogenic medium (OM)-induced ROS production, mitochondrial ROS levels and the loss of mitochondrial membrane potential in VICs. Furthermore, OI attenuated the OM-induced upregulation of ER stress markers, osteogenic markers and calcium deposition, which were blocked by the Nrf2-specific inhibitor ML385. Interestingly, we found that OM-induced ER stress and osteogenic differentiation were ROS-dependent and that Hmox1 silencing triggered ROS production, ER stress and elevated osteogenic activity, which were inhibited by NAC. Overexpression of NQO1 mediated by adenovirus vectors significantly suppressed OM-induced ER stress and osteogenic markers. Collectively, these results showed the anti-osteogenic effects of OI on AVICs by regulating the generation of ROS and ER stress by activating the Nrf2 signaling pathway. Furthermore, OI alleviated aortic stenosis in a mouse model with direct wire injury. Due to its antioxidant properties, OI could be a potential drug for the prevention and/or treatment of CAVD.

Immune response gene 1 deficiency impairs Nrf2 activation and aggravates liver fibrosis in mice

A growing body of evidence suggests that metabolic events play essential roles in the development of liver fibrosis. Immune response gene 1 (IRG1) catalyzes the generation of itaconate, which function as a metabolic checkpoint under several pathological circumstances. In the present study, the hepatic level of IRG1 was determined in mice with carbon tetrachloride (CCl₄)-induced liver fibrosis. And then the pathological significance of IRG1 and the pharmacological potential of 4-octyl itaconate (4-OI), a cell-permeable derivate of itaconate, in liver fibrosis were investigated in mice. The results indicated that the hepatic level of IRG1 was upregulated in mice with liver fibrosis. CCl₄-induced formation of fibrotic septa and deposition of collagen was aggravated in IRG1 KO mice. IRG1 deletion also resulted in increased expression of transforming growth factor beta 1 (TGF-β1), enhanced phosphorylation of Smad3, elevated level of alpha smooth muscle actin (α-SMA) and hydroxyproline, which were associated with compromised activation of nuclear erythroid 2-related factor 2 (Nrf2)-mediated antioxidant system and exacerbated oxidative stress. Interestingly, supplementation with 4-OI activated Nrf2 pathway, suppressed TGF-β1 signaling and attenuated fibrogenesis. Our data indicated that upregulation of IRG1 might function as a protective response during the development of liver fibrosis, and 4-OI might have potential value for the pharmacological intervention of liver fibrosis.

Protective effects of 4-octyl itaconate against inflammatory response in angiotensin II-induced oxidative stress in human primary retinal pigment epithelium

4-octyl itaconate (OI) is one kind of cell-permeable derivative of itaconate to regulate inflammation and oxidative stress. However, its effects on the angiotensin II (Ang II)-induced inflammatory response and oxidative stress in human primary retinal pigment epithelium (hRPE) cells as well as its underlying mechanisms were unclear. In this study, we found that OI suppressed changes in pro-inflammatory cytokines (MCP-1, IL-8, and IL-6) and reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) via activation of Nrf2 signaling in Ang II-treated hRPE cells. A total of 645 differentially expressed long non-coding RNAs (lncRNAs) and 455 mRNAs were identified by microarray analysis. Ten lncRNAs were analyzed using the Coding-non-coding gene co-expression (CNC) network and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, revealing that many differentially expressed lncRNAs were enriched in immune response-related pathways, such as IL-17, TNF, and NOD-like receptor signaling. This finding suggested that OI inhibits Ang II-induced inflammatory response and oxidative stress by activating Nrf2 signaling in hRPE cells. We also provided a novel perspective on the role of lncRNAs in the protective effects of OI.

4-Octyl itaconate protects against renal fibrosis via inhibiting TGF-β/Smad pathway, autophagy and reducing generation of reactive oxygen species

Renal fibrosis is an inevitable course of all kinds of progressive chronic kidney disease (CKD). Itaconic acid is an endogenous metabolite that has shown anti-inflammatory and antioxidant effects. 4-octyl itaconate (OI), a derivative of itaconic acid with higher fat solubility, can penetrate the cell membranes and be metabolized into itaconic acid in vitro. However, whether OI has an anti-renal fibrotic effect is still unclear. The current study purposed to investigate the anti-fibrotic effect in renal and the underlying mechanisms of OI. The unilateral ureteral occlusion (UUO) model and adenine-induced fibrosis model in Sprague-Dawley (SD) rats and Transforming growth factor-β1 (TGF-β1) induced HK-2 cells were applied to investigate the renoprotective effects of OI. This study reports for the first time that OI ameliorated renal fibrosis by suppressing the activation of TGF-β/Smad and nuclear factor kappa B (NF-κB) pathways, reducing generation of reactive oxygen species and inhibiting autophagy. These results clearly suggest that OI has great clinical potential for managing renal fibrosis.