Immunomodulatory actions of a kynurenine-derived endogenous electrophile

L-Kynurenine regulates immune response in ICIs-associated myocarditis via JAK/STAT pathway

BACKGROUND

Immune checkpoint inhibitors associated drug-induced myocarditis (ICIAM) is a - myocarditis characterized by the infiltration of immune cells into cardiac. However, the mechanisms are unknown and effective drug therapies are lacking in clinical practice. This study aims to explore the relationship between plasma metabolites and the treatment of ICIAM.

METHODS

Human plasma metabolites were analyzed using untargeted metabolomics for characteristic metabolites. For in vivo experiments, Male Balb/c mice were divided into six groups: PBS, L-Kynurenine, cTNI+PD-1 inhibitor (ICIs), ICIs+L-Kynurenine, ICIs+RO8191, ICIs+RO8191+L-Kynurenine. On day 21 post-modeling, echocardiography, ELISA and histopathology were employed to evaluate the therapeutic effect of L-Kynurenine. Flow cytometry was used to determine the proportion of immune cells in the heart and spleen. Bulk-RNAseq was conducted to analyze differential genes, and q-PCR, immunofluorescence and western blot were performed for validation experiments.

RESULTS

Untargeted metabolomics verified that indoleamine 2,3 dioxygenase-1 (IDO1)-derived L-Kynurenine level was higher in the serum of ICIAM compared to non-ICIAM patients. Meanwhile, in vitro and in vivo experiments showed that L-Kynurenine exhibited a therapeutic ability in ICIAM by inhibiting the pro-inflammatory polarization of immune cells and the secretion of pro-inflammatory cytokines. Mechanistically, L-Kynurenine improved cardiac functions majorly by the inhibition of the JAK1/STAT3 signaling pathway.

CONCLUSION

L-Kynurenine exhibits significant therapeutic potential in ICIAM. The multi-roles of L-Kynurenine in regulating immune responses make it possible to be used as a targeted drug for ICIAM therapy.

Regulating Nrf2 activity: ubiquitin ligases and signaling molecules in redox homeostasis

Transcription factor NF-E2 p45-related factor 2 (Nrf2) orchestrates defenses against oxidants and thiol-reactive electrophiles. It is controlled at the protein stability level by several E3 ubiquitin ligases (CRL3Keap1, CRL4DCAF11, SCFβ-TrCP, and Hrd1). CRL3Keap1 is of the greatest importance because it constitutively targets Nrf2 for proteasomal degradation under homeostatic conditions but is prevented from doing so by oxidative stressors. Repression of Nrf2 by CRL3Keap1 is attenuated by SQSTM1/p62, and this is reinforced by phosphorylation of SQSTM1/p62. Repression by SCFβ-TrCP requires phosphorylation of Nrf2 by GSK3, the activity of which is inhibited by PKB/Akt and other kinases. We discuss how Nrf2 activity is controlled by the ubiquitin ligases under different circumstances. We also describe endogenous signaling molecules that inactivate CRL3Keap1 to alleviate stress and restore homeostasis.

N-formylkynurenine but not kynurenine enters a nucleophile-scavenging branch of the immune-regulatory kynurenine pathway

Tryptophan catabolism along the kynurenine pathway (KP) mediates key physiological functions ranging from immune tolerance to lens UV protection, but the contributory roles and chemical fates of individual KP metabolites are incompletely understood. This particularly concerns the first KP metabolite, N-formylkynurenine (NFK), canonically viewed as a transient precursor to the downstream kynurenine (KYN). Here, we challenge that canon and show that hydrolytic enzymes act as a rheostat switching NFK's fate between the canonical KP and a novel non-enzymatic branch of tryptophan catabolism. In the physiological environment (37 °C, pH 7.4), NFK deaminated into electrophilic NFK-carboxyketoalkene (NFK-CKA), which rapidly (<2 min) formed adducts with nucleophiles such as cysteine and glutathione, the key intracellular antioxidants. Serum hydrolases suppressed NFK deamination as they hydrolysed NFK to KYN ∼3 times faster than NFK deaminates. Whilst KYN did not deaminate, its deaminated product (KYN-CKA) rapidly reacted with cysteine but not glutathione. The new NFK transformations of a yet to be discovered function highlight NFK's significance beyond hydrolysis to KYN and suggests the dominance of its chemical transformations over those of KYN. Enzyme compartmentalisation and abundance offer insights into the regulation of non-enzymatic KP metabolite transformations such as KYN involved in immune regulation, protein modification, lens aging or neuropathology.

A novel 1-benzoazepine-derived Michael acceptor and its hetero-adducts active against MRSA

Multidrug-resistant bacterial infections continue to be a rising global health concern. Herein, we describe the development of a novel class of 3-substituted benzoazepinedione derivatives with promising antibacterial activity. The pivotal compound, benzoazepinedione carboxylate 9, represents a highly electrophilic Michael acceptor, enabling divergent access to a wide range of thia-, aza-, oxa-, and phospha-Michael adducts. Notably, most prepared compounds exhibited potent antibacterial activity against both drug-susceptible and drug-resistant strains of Staphylococcus aureus (MIC90 of up to 2 μg mL-1). The cytotoxicity assessment in the VERO6 cell line revealed that thia-adduct 10d (IC50 of 36.5 μg mL-1) exhibits lower toxicity compared to its parent electrophile 9 (IC50 of 14.3 μg mL-1), which is in agreement with the hypothesis of covalently modified prodrugs. Additionally, stability studies of the prepared compounds in CD3OD and a DMSO-PBS mixture confirmed that thia-Michael adducts 10 are stable under neutral conditions while dynamic under mildly basic conditions. Moreover, 3D reconstructed tissue models (human lung epithelial EpiAirway™ and a human small intestine model) did not exhibit a viability decrease below 80% of the untreated control at all concentrations tested, indicating tolerance to higher concentrations of potential drugs and prodrugs.

Revolutionizing our understanding of Parkinson's disease: Dr. Heinz Reichmann's pioneering research and future research direction

Millions of individuals around the world are afflicted with Parkinson's disease (PD), a prevalent and incapacitating neurodegenerative disorder. Dr. Reichmann, a distinguished professor and neurologist, has made substantial advancements in the domain of PD research, encompassing both fundamental scientific investigations and practical applications. His research has illuminated the etiology and treatment of PD, as well as the function of energy metabolism and premotor symptoms. As a precursor to a number of neurotransmitters and neuromodulators that are implicated in the pathophysiology of PD, he has also investigated the application of tryptophan (Trp) derivatives in the disease. His principal findings and insights are summarized and synthesized in this narrative review article, which also emphasizes the challenges and implications for future PD research. This narrative review aims to identify and analyze the key contributions of Reichmann to the field of PD research, with the ultimate goal of informing future research directions in the domain. By examining Reichmann's work, the study seeks to provide a comprehensive understanding of his major contributions and how they can be applied to advance the diagnosis and treatment of PD. This paper also explores the potential intersection of Reichmann's findings with emerging avenues, such as the investigation of Trp and its metabolites, particularly kynurenines, which could lead to new insights and potential therapeutic strategies for managing neurodegenerative disorders like PD.

The chemical biology of dinitrogen trioxide

Dinitrogen trioxide (N 2 O 3 ) mediates low-molecular weight and protein S- and N-nitrosation, with recent reports suggesting a role in the formation of nitrating intermediates as well as in nitrite-dependent hypoxic vasodilatation. However, the reactivity ofN 2 O 3 in biological systems results in an extremely short half-life that renders this molecule essentially undetectable by currently available technologies. As a result, evidence for in vivoN 2 O 3 formation derives from the detection of nitrosated products as well as from in vitro kinetic determinations, isotopic labeling studies, and spectroscopic analyses. This review will discuss mechanisms ofN 2 O 3 formation, reactivity and decomposition, as well as address the role of sub-cellular localization as a key determinant of its actions. Finally, evidence will be discussed supporting different roles forN 2 O 3 as a biologically relevant signaling molecule.

Electrophilic metabolites targeting the KEAP1/NRF2 partnership

Numerous electrophilic metabolites are formed during cellular activity, particularly under conditions of oxidative, inflammatory and metabolic stress. Among them are lipid oxidation and nitration products, and compounds derived from amino acid and central carbon metabolism. Here we focus on one cellular target of electrophiles, the Kelch-like ECH associated protein 1 (KEAP1)/nuclear factor erythroid 2 p45-related factor 2 (NRF2) partnership. Many of these reactive compounds modify C151, C273 and/or C288 within KEAP1. Other types of modifications include S-lactoylation of C273, N-succinylation of K131, and formation of methylimidazole intermolecular crosslink between two KEAP1 monomers. Modified KEAP1 relays the initial signal to transcription factor NRF2 and its downstream targets, the ultimate effectors that provide means for detoxification, adaptation and survival. Thus, by non-enzymatically covalently modifying KEAP1, the electrophilic metabolites discussed here serve as chemical signals connecting metabolism with stress responses.

Orally delivered 2D covalent organic frameworks releasing kynurenine generate anti-inflammatory T cell responses in collagen induced arthritis mouse model

Covalent organic framework (COF) crystalline biomaterials have great potential for drug delivery since they can load large amounts of small molecules (e.g. metabolites) and release them in a controlled manner, as compared to their amorphous counterparts. Herein, we screened different metabolites for their ability to modulate T cell responses in vitro and identified Kynurenine (KyH) as a key metabolite that not only decreases frequency of pro-inflammatory RORgt + T cells but also supports frequency of anti-inflammatory GATA3+ T cells. Moreover, we developed a methodology to generate imine-based TAPB-PDA COF at room temperature and loaded these COFs with KyH. KyH loaded COFs (COF-KyH) were able to then release KyH in a controlled manner for 5 days in vitro. Notably, COF-KyH when delivered orally in mice induced with collagen-induced rheumatoid arthritis (CIA) were able to increase frequency of anti-inflammatory GATA3+CD8+ T cells in the lymph nodes and decrease antibody titers in the serum as compared to the controls. Overall, these data demonstrate that COFs can be an excellent drug delivery vehicle for delivering immune modulating small molecule metabolites.

Nrf2 in TIME: The Emerging Role of Nuclear Factor Erythroid 2-Related Factor 2 in the Tumor Immune Microenvironment

Nuclear factor erythroid 2-related factor 2 (Nrf2) mediates the cellular antioxidant response, allowing adaptation and survival under conditions of oxidative, electrophilic and inflammatory stress, and has a role in metabolism, inflammation and immunity. Activation of Nrf2 provides broad and long-lasting cytoprotection, and is often hijacked by cancer cells, allowing their survival under unfavorable conditions. Moreover, Nrf2 activation in established human tumors is associated with resistance to chemo-, radio-, and immunotherapies. In addition to cancer cells, Nrf2 activation can also occur in tumor-associated macrophages (TAMs) and facilitate an anti-inflammatory, immunosuppressive tumor immune microenvironment (TIME). Several cancer cell-derived metabolites, such as itaconate, L-kynurenine, lactic acid and hyaluronic acid, play an important role in modulating the TIME and tumor-TAMs crosstalk, and have been shown to activate Nrf2. The effects of Nrf2 in TIME are context-depended, and involve multiple mechanisms, including suppression of pro-inflammatory cytokines, increased expression of programmed cell death ligand 1 (PD-L1), macrophage colony-stimulating factor (M-CSF) and kynureninase, accelerated catabolism of cytotoxic labile heme, and facilitating the metabolic adaptation of TAMs. This understanding presents both challenges and opportunities for strategic targeting of Nrf2 in cancer.

Extracellular Vesicle Size Reveals Cargo Specific to Coagulation and Inflammation in Pediatric and Adult Sickle Cell Disease

Aberrant coagulation in sickle cell disease (SCD) is linked to extracellular vesicle (EV) exposure. However, there is no consensus on the contributions of small EVs (SEVs) and large EVs (LEVs) toward underlying coagulopathy or on their molecular cargo. The present observational study compared the thrombin potential of SEVs and LEVs isolated from the plasma of stable pediatric and adult SCD patients. Further, EV lipid and protein contents were analyzed to define markers consistent with activation of thrombin and markers of underlying coagulopathy. Results suggested that LEVs-but not SEVs-from pediatrics and adults similarly enhanced phosphatidylserine (PS)-dependent thrombin generation, and cell membrane procoagulant PS (18:0;20:4 and 18:0;18:1) were the most abundant lipids found in LEVs. Further, LEVs showed activated coagulation in protein pathway analyses, while SEVs demonstrated high levels of cholesterol esters and a protein pathway analysis that identified complement factors and inflammation. We suggest that thrombin potential of EVs from both stable pediatric and adult SCD patients is similarly dependent on size and show lipid and protein contents that identify underlying markers of coagulation and inflammation.