Itaconic acid derivatives: structure, function, biosynthesis, and perspectives

Metabolomic profiling of Medicago sativa-derived fungal endophytes and evaluation of their biological activities

This study aimed to discover the potential of Medicago sativa-derived fungal endophytes as a prospective source of bioactive metabolites. In the present study, three different strains of fungal endophyte Aspergillus terreus were isolated from leaves L, roots T and stems St of Medicago sativa to explore their biological and chemical diversity. These isolated fungi were exposed to different fermentation conditions by adding various chemical elicitors to their solid fermentation media. According to LC-HRESIMS-based metabolomics and multivariate analysis, each chemical treatment had a different effect on the chemical profiles of the fungi. Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) proposed several compounds with anticancer action against MCF-7 (a human breast cancer cell line) and MDA-MB-231 (a human epithelial breast cancer cell line).

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.

High-altitude and low-altitude adapted chicken gut-microbes have different functional diversity

Recently, there has been considerable interest in the functions of gut microbiota in broiler chickens in relation to their use as feed additives. However, the gut-microbiota of chickens reared at different altitudes are not well documented for their potential role in adapting to prevailing conditions and functional changes. In this context, the present study investigates the functional diversity of gut-microbes in high-altitude (HACh) and low-altitude adapted chickens (LACh), assessing their substrate utilization profile through Biolog Ecoplates technology. This will help in the identification of potential microbes or their synthesized metabolites, which could be beneficial for the host or industrial applications. Results revealed that among the 31 different types of studied substrates, only polymers, carbohydrates, carboxylic acids, and amine-based substrates utilization varied significantly (p < 0.05) among the chickens reared at two different altitudes where gut-microbes of LACh utilized a broad range of substrates than the HACh. Further, diversity indices (Shannon and MacIntosh) analysis in LACh samples showed significant (p < 0.05) higher richness and evenness of microbes as compared to the HACh samples. However, no significant difference was observed in the Simpson diversity index in gut microbes of lowversus high-altitude chickens. In addition, the Principal Component Analysis elucidated variation in substrate preferences of gut-microbes, where 13 and 8 carbon substrates were found to constitute PC1 and PC2, respectively, where γ-aminobutyric acid, D-glucosaminic acid, i-erythritol and tween 40 were the most relevant substrates that had a major effect on PC1, however, alpha-ketobutyric acid and glycyl-L-glutamic acid affected PC2. Hence, this study concludes that the gut-microbes of high and low-altitudes adapted chickens use different carbon substrates so that they could play a vital role in the health and immunity of an animal host based on their geographical location. Consequently, this study substantiates the difference in the substrate utilization and functional diversity of the microbial flora in chickens reared at high and low altitudes due to altitudinal changes.

From Poly(glycerol itaconate) Gels to Novel Nonwoven Materials for Biomedical Applications

Electrospinning is a process that has attracted significant interest in recent years. It provides the opportunity to produce nanofibers that mimic the extracellular matrix. As a result, it is possible to use the nonwovens as scaffolds characterized by high cellular adhesion. This work focused on the synthesis of poly(glycerol itaconate) (PGItc) and preparation of nonwovens based on PGItc gels and polylactide. PGItc gels were synthesized by a reaction between itaconic anhydride and glycerol. The use of a mixture of PGItc and PLA allowed us to obtain a material with different properties than with stand-alone polymers. In this study, we present the influence of the chosen ratios of polymers and the OH/COOH ratio in the synthesized PGItc on the properties of the obtained materials. The addition of PGItc results in hydrophilization of the nonwovens' surface without disrupting the high porosity of the fibrous structure. Spectral and thermal analyzes are presented, along with SEM imagining. The preliminary cytotoxicity research showed that nonwovens were non-cytotoxic materials. It also helped to pre-determine the potential application of PGItc + PLA nonwovens as subcutaneous tissue fillers or drug delivery systems.

Microglia-dependent neuroprotective effects of 4-octyl itaconate against rotenone-and MPP+-induced neurotoxicity in Parkinson's disease

Chronic neuroinflammation is implicated in the pathogenesis of Parkinson's disease (PD), one of the most common neurodegenerative diseases. Itaconate, an endogenous metabolite derived from the tricarboxylic acid cycle via immune-responsive gene 1 activity, may mediate anti-inflammatory responses by activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant pathway. This study investigates the neuroprotective potential of 4-octyl itaconate (OI), a cell-permeable derivative of itaconate, in cellular models of PD. OI not only suppressed lipopolysaccharide-induced proinflammatory cascades of inducible nitric oxide synthase, cyclooxygenase-2, and cytokines release in mouse BV2 microglial cells but also activated the Nrf2 signaling pathway and its downstream targets in these cells. Conditioned medium derived from OI-treated BV2 cells protected against rotenone- and MPP+-induced neurotoxicity in Neuro 2A cells. Overall, our findings support the anti-inflammatory neuroprotective potential of OI in PD.

Photoclick reaction for rapid and simple fluorescence detection of itaconic acid and its derivatives in fungal cultures

Itaconic acid (IA) and its derivatives produced by fungi have significant potential as industrial feedstocks. We recently developed a method for the detection of these compounds based on their terminal C-C double bonds. However, the presence of reducing agents, such as glucose and other fungal metabolites, leads to undesirable side reactions, and consequently, deteriorates the detection specificity. Therefore, we developed a fluorescence detection method for IA and its derivatives underpinned by a photoclick reaction. The photoclick reaction between conjugated IA and 5-(4-methoxyphenyl)-2-phenyl-2H-tetrazole under UV irradiation affords a fluorescent product. No fluorescence was detected when succinic acid was subjected to the reaction, indicating that a terminal C-C double bond is required to induce fluorescence. Optimal reaction conditions were determined to be a combination of 80% final dimethyl sulfoxide concentration, 30-s UV irradiation, and a pH of 2. Two weeks after the reaction at 4 °C, 89.0% of the initial intensity was retained, indicating that the reaction product was relatively stable. Glucose and kojic acid did not induce fluorescence after the reaction, indicating that these reducing agents did not affect fluorescence. IA was detected in a culture of Aspergillus terreus, and its quantification using the photoclick reaction was in agreement with the results obtained using high-performance liquid chromatography analysis. Interestingly, the IA derivative avenaciolide present in submillimolar quantities was also detectable in a culture of Aspergillus avenaceus using this method. The established method will enable the development of high-throughput screening methods to identify fungi that produce IA and its derivatives.

Skeletal myotube-derived extracellular vesicles enhance itaconate production and attenuate inflammatory responses of macrophages

Introduction

Macrophages play an important role in the innate immunity. While macrophage inflammation is necessary for biological defense, it must be appropriately controlled. Extracellular vesicles (EVs) are small vesicles released from all types of cells and play a central role in intercellular communication. Skeletal muscle has been suggested to release anti-inflammatory factors, but the effect of myotube-derived EVs on macrophages is unknown. As an anti-inflammatory mechanism of macrophages, the immune responsive gene 1 (IRG1)-itaconate pathway is essential. In this study, we show that skeletal muscle-derived EVs suppress macrophage inflammatory responses, upregulating the IRG1-itaconate pathway.

Methods

C2C12 myoblasts were differentiated into myotubes and EVs were extracted by ultracentrifugation. Skeletal myotube-derived EVs were administered to mouse bone marrow-derived macrophages, then lipopolysaccharide (LPS) stimulation was performed and inflammatory cytokine expression was measured by RT-qPCR. Metabolite abundance in macrophages after addition of EVs was measured by CE/MS, and IRG1 expression was measured by RT-PCR. Furthermore, RNA-seq analysis was performed on macrophages after EV treatment.

Results

EVs attenuated the expression of LPS-induced pro-inflammatory factors in macrophages. Itaconate abundance and IRG1 expression were significantly increased in the EV-treated group. RNA-seq analysis revealed activation of the PI3K-Akt and JAK-STAT pathways in macrophages after EV treatment. The most abundant miRNA in myotube EVs was miR-206-3p, followed by miR-378a-3p, miR-30d-5p, and miR-21a-5p.

Discussion

Skeletal myotube EVs are supposed to increase the production of itaconate via upregulation of IRG1 expression and exhibited an anti-inflammatory effect in macrophages. This anti-inflammatory effect was suggested to involve the PI3K-Akt and JAK-STAT pathways. The miRNA profiles within EVs implied that miR-206-3p, miR-378a-3p, miR-30d-5p, and miR-21a-5p may be responsible for the anti-inflammatory effects of the EVs. In summary, in this study we showed that myotube-derived EVs prevent macrophage inflammatory responses by activating the IRG1-itaconate pathway.

Recent advances and perspectives on production of value-added organic acids through metabolic engineering

Organic acids are important consumable materials with a wide range of applications in the food, biopolymer and chemical industries. The global consumer organic acids market is estimated to increase to $36.86 billion by 2026. Conventionally, organic acids are produced from the chemical catalysis process with petrochemicals as raw materials, which posts severe environmental concerns and conflicts with our sustainable development goals. Most of the commonly used organic acids can be produced from various organisms. As a state-of-the-art technology, large-scale fermentative production of important organic acids with genetically-modified microbes has become an alternative to the chemical route to meet the market demand. Despite the fact that bio-based organic acid production from renewable cheap feedstock provides a viable solution, low productivity has impeded their industrial-scale application. With our deeper understanding of strain genetics, physiology and the availability of strain engineering tools, new technologies including synthetic biology, various metabolic engineering strategies, omics-based system biology tools, and high throughput screening methods are gradually established to bridge our knowledge gap. And they were further applied to modify the cellular reaction networks of potential microbial hosts and improve the strain performance, which facilitated the commercialization of consumable organic acids. Here we present the recent advances of metabolic engineering strategies to improve the production of important organic acids including fumaric acid, citric acid, itaconic acid, adipic acid, muconic acid, and we also discuss the current challenges and future perspectives on how we can develop a cost-efficient, green and sustainable process to produce these important chemicals from low-cost feedstocks.

Optimisation of Glycerol and Itaconic Anhydride Polycondensation

Glycerol polyesters have recently become objects of interest in tissue engineering. Barely known so far is poly(glycerol itaconate) (PGItc), a biocompatible, biodegradable polyester. Due to the presence of a C=C electron-acceptor moiety, it is possible to post-modify the product by Michael additions to change the properties of PGItc. Thus, using PGItc as one of the elements of cellular scaffold crosslinked in situ for bone tissue regeneration seems to be a very attractive yet unexplored solution. This work aims to optimize the synthesis of PGItc to obtain derivatives with a double bond in the side chain with the highest conversion rates. The experiments were performed with itaconic anhydride and glycerol using mathematical planning of experiments according to the Box-Behnken plan without solvent and catalyst. The input variables of the process were the ratio of the OH/COOH, temperature, and reaction time. The optimised output variables were: the degree of esterification (EDtitr), the degree of esterification calculated from the analysis of 1H NMR spectra (EDNMR), and the degree of itaconic anhydride conversion—calculation based on 13C NMR spectra (%X13CNMR). In each of statistical models, the significance of the changed synthesis parameters was determined. Optimal conditions are when OH/COOH ratio is equal to 1.5, temperature is 140 °C and time of reaction is 5 h. The higher OH/COOH ratio, temperature and longer the experiment time, the higher the value of the degree of esterification and the degree of anhydride conversion.

Pulsed-Ultrasound Irradiation Induces the Production of Itaconate and Attenuates Inflammatory Responses in Macrophages

Background

Itaconate is a key metabolite in the innate immune system and exerts strong anti-inflammatory effects in macrophages. For the production of itaconate in macrophages, immune-responsive gene 1 (IRG1) is an imperative enzyme, and activating the IRG1-itaconate pathway is reported to alleviate inflammatory diseases by upregulating nuclear factor-erythroid 2-related factor 2 (NRF2). However, there are very few reports on strategies to increase itaconate production. Ultrasound therapy is a widely used intervention for anti-inflammatory and soft-tissue regeneration purposes. Here we show the effect of ultrasound irradiation on the production of itaconate in macrophages.

Methods

Murine bone marrow-derived macrophages (BMDMs) were exposed to pulsed ultrasound (3.0 W/cm²) for 5 minutes. Three hours after irradiation, the intracellular levels of metabolites and mRNA expression levels of Irg1 and Nrf2 were measured using CE/MS and qPCR, respectively. To evaluate macrophage inflammation status, 3 h after irradiation, the cells were stimulated with 100 ng/mL lipopolysaccharide (LPS) for 1.5 h and the mRNA expression levels of pro-inflammatory factors (Il-1β, Il-6, and Tnf-α) were measured. Student’s t-test, one-way ANOVA and Tukey’s multiple comparison test were used for statistical processing, and the significance level was set to less than 5%.

Results

Ultrasound irradiation significantly increased the intracellular itaconate level and the expression levels of Irg1 and Nrf2 in BMDMs. Upregulation of Il-1β, Il-6, and Tnf-α by LPS was significantly suppressed in BMDMs treated with ultrasound. Ultrasound irradiation did not affect cell viability and apoptosis.

Conclusion

Ultrasound irradiation induces the production of itaconate by upregulating Irg1 expression and attenuates inflammatory responses in macrophages via Nrf2. These results suggest that ultrasound is a potentially useful method to increase itaconate production in macrophages.

Itaconate and leptin affecting PPARγ in M2 macrophages: A potential link to early-onset colorectal cancer

BACKGROUND

Along with the rising incidence of obesity, there has been an increase in patients diagnosed with early-onset colorectal cancer (<50 years old). In colorectal cancer, worse patient survival is associated with certain cytokine expression and downregulation of peroxisome proliferator activated receptor gamma expression. The effects of the obesity hormone leptin and macrophage-specific metabolite itaconate on these mechanisms are poorly understood. We investigated their impact on peroxisome proliferator activated receptor gamma and macrophage cytokine expression in vitro.

METHODS

M2-like macrophages were treated with either leptin, 4-octyl itaconate, or dimethyl itaconate in a dose- and time-dependent manner. Gene expression after treatment with 4 doses (D1-4) of each compound was analyzed at 4 time points (3, 6, 18, and 24 hours).

RESULTS

Peroxisome proliferator activated receptor gamma was downregulated after 4-octyl itaconate treatment at 18 hours (FC -32.67, P ≤ .001). Interleukin-8 was upregulated after leptin and dimethyl itaconate treatment at 6 hours (FC 26.35 at D4, P ≤ .001, and FC 23.26 at D3, P = .006). Dimethyl itaconate upregulated IL-1β at 24 hours (FC 18.00 at D4, P ≤ .001). Tumor necrosis factor-α showed maximum downregulation after 4-octyl itaconate at 18 hours (FC -103.25 at D4, P ≤ .001).

CONCLUSIONS

Itaconate downregulates peroxisome proliferator activated receptor gamma as a tumor-suppressing factor and upregulates anti-inflammatory cytokines in M2-like macrophages. Itaconate provides a link between obesity and colorectal cancer and may be a key regulator in early-onset colorectal cancer.

: conjugation with a CO-releasing unit greatly enhances the anti-inflammatory activity of itaconates

Endogenous itaconate as well as the gasotransmitter CO have recently been described as powerful anti-inflammatory and immunomodulating agents. However, each of the two agents comes along with a major drawback: Whereas itaconates only exert beneficial effects at high concentrations above 100 μM, the uncontrolled application of CO has strong toxic effects. To solve these problems, we designed hybrid prodrugs, i.e. itaconates that are conjugated with an esterase-triggered CO-releasing acyloxycyclohexadiene-Fe(CO)₃ unit (ItaCORMs). Here, we describe the synthesis of different ItaCORMs and demonstrate their anti-inflammatory potency in cellular assays of primary murine immune cells in the low μmolar range (<10 μM). Thus, ItaCORMs represent a promising new class of hybrid compounds with high clinical potential as anti-inflammatory agents.

Recent Advances in Biotechnological Itaconic Acid Production, and Application for a Sustainable Approach

Intense research has been conducted to produce environmentally friendly biopolymers obtained from renewable feedstock to substitute fossil-based materials. This is an essential aspect for implementing the circular bioeconomy strategy, expressly declared by the European Commission in 2018 in terms of "repair, reuse, and recycling". Competent carbon-neutral alternatives are renewable biomass waste for chemical element production, with proficient recyclability properties. Itaconic acid (IA) is a valuable platform chemical integrated into the first 12 building block compounds the achievement of which is feasible from renewable biomass or bio-wastes (agricultural, food by-products, or municipal organic waste) in conformity with the US Department of Energy. IA is primarily obtained through fermentation with Aspergillus terreus, but nowadays several microorganisms are genetically engineered to produce this organic acid in high quantities and on different substrates. Given its trifunctional structure, IA allows the synthesis of various novel biopolymers, such as drug carriers, intelligent food packaging, antimicrobial biopolymers, hydrogels in water treatment and analysis, and superabsorbent polymers binding agents. In addition, IA shows antimicrobial, anti-inflammatory, and antitumor activity. Moreover, this biopolymer retains qualities like environmental effectiveness, biocompatibility, and sustainability. This manuscript aims to address the production of IA from renewable sources to create a sustainable circular economy in the future. Moreover, being an essential monomer in polymer synthesis it possesses a continuous provocation in the biopolymer chemistry domain and technologies, as defined in the present review.

Dimethyl itaconate inhibits LPS‑induced microglia inflammation and inflammasome‑mediated pyroptosis via inducing autophagy and regulating the Nrf‑2/HO‑1 signaling pathway

The endogenous metabolite itaconate and its cell‑permeable derivative dimethyl itaconate (DI) have been identified as anti‑inflammatory regulators of macrophages; however, their contribution to inflammasome‑mediated pyroptosis remains unknown. The present study examined the molecular mechanism of DI on NLR family pyrin domain‑containing 3 (NLRP3) inflammasome assembly and NLRP3 inflammasome‑dependent pyroptosis in microglia. Lipopolysaccharide (LPS) and ATP were used to induce microglia pyroptosis in vitro; this process was confirmed by TUNEL assay, lactate dehydrogenase (LDH) detection and gasdermin D (GSDMD) expression analysis. The regulation of microglia polarization and inflammatory cytokine expression was assessed by immunofluorescence assays and ELISA. To investigate the associated mechanism of action, the expression levels of the nuclear factor erythroid 2‑related factor 2 (Nrf‑2)/heme oxygenase‑1 (HO‑1) pathway proteins were analyzed by western blotting. Finally, the regulatory effect of DI on autophagy and its association with inflammation was determined by western blotting. The present study demonstrated that DI administration inhibited NLRP3 assembly, LDH release and GSDMD cleavage. Cotreatment of DI with LPS and ATP facilitated the transition from M1 to M2, reduced inflammatory mediator expression and impeded NF‑κB phosphorylation. In addition, DI effectively reduced reactive oxygen species production through the Nrf‑2/HO‑1 pathway. Moreover, DI induced cellular autophagy, whereas inhibition of autophagy with 3‑methyladenine markedly reversed its inhibitory effect on NLRP3‑dependent pyroptosis. Taken together, the present study suggested that DI participated in the Nrf‑2/HO‑1 pathway and served a key role in microglia inflammation and NLRP3 inflammasome‑mediated pyroptosis via induction of autophagy.

The Emerging Application of Itaconate: Promising Molecular Targets and Therapeutic Opportunities

Metabolites have recently been found to be involved in significant biological regulation and changes. Itaconate, an important intermediate metabolite isolated from the tricarboxylic acid cycle, is derived from cis-aconitate decarboxylation mediated by immune response gene 1 in mitochondrial matrix. Itaconate has emerged as a key autocrine regulatory component involved in the development and progression of inflammation and immunity. It could directly modify cysteine sites on functional substrate proteins which related to inflammasome, signal transduction, transcription, and cell death. Itaconate can be a connector among immunity, metabolism, and inflammation, which is of great significance for further understanding the mechanism of cellular immune metabolism. And it could be the potential choice for the treatment of inflammation and immune-related diseases. This study is a systematic review of the potential mechanisms of metabolite associated with different pathology conditions. We briefly summarize the structural characteristics and classical pathways of itaconate and its derivatives, with special emphasis on its promising role in future clinical application, in order to provide theoretical basis for future research and treatment intervention.