Tryptophan metabolism as a common therapeutic target in cancer, neurodegeneration and beyond

Role of tumor-derived exosomes mediated immune cell reprograming in cancer

Tumor-derived exosomes (TDEs), as topologies of tumor cells, not only carry biological information from the mother, but also act as messengers for cellular communication. It has been demonstrated that TDEs play a key role in inducing an immunosuppressive tumor microenvironment (TME). They can reprogram immune cells indirectly or directly by delivering inhibitory proteins, cytokines, RNA and other substances. They not only inhibit the maturation and function of dendritic cells (DCs) and natural killer (NK) cells, but also remodel M2 macrophages and inhibit T cell infiltration to promote immunosuppression and create a favorable ecological niche for tumor growth, invasion and metastasis. Based on the specificity of TDEs, targeting TDEs has become a new strategy to monitor tumor progression and enhance treatment efficacy. This paper reviews the intricate molecular mechanisms underlying the immunosuppressive effects induced by TDEs to establish a theoretical foundation for cancer therapy. Additionally, the challenges of TDEs as a novel approach to tumor treatment are discussed.

Inhibition of kynurenine production by N,O-substituted hydroxylamine derivatives

The inhibition of kynurenine production is considered a promising target for cancer immunotherapy. In this study, an amino acid derivative, compound 1 was discovered using a cell-based assay with our screening library. Compound 1 suppressed kynurenine production without inhibiting indoleamine 2,3-dioxygenase 1 (IDO1) activity. The activity of 1 was derived from the inhibition of IDO1 by a metabolite of 1, O-benzylhydroxylamine (OBHA, 2a). A series of N-substituted 2a derivatives that exhibit potent activity in cell-based assays may represent effective prodrugs. Therefore, we synthesized and evaluated novel N,O-substituted hydroxylamine derivatives. The structure-activity relationships revealed that N,O-substituted hydroxylamine 2c inhibits kynurenine production in a cell-based assay. We conducted an in vivo experiment with 2c, although the effectiveness of O-substituted hydroxylamine derivatives in vivo has not been previously reported. The results indicate that N,O-substituted hydroxylamine derivatives are promising IDO1 inhibitors.

Recent contributions of single-cell and spatial profiling to the understanding of bladder cancer

PURPOSE OF REVIEW

Current risk stratification and treatment decision-making for bladder cancer informed by histopathology as well as molecular diagnostics face limitations. This review summarizes recent advancements in single-cell and spatial omics methodologies for understanding bladder cancer biology and their potential impact on development of novel therapeutic strategies.

RECENT FINDINGS

Single-cell RNA sequencing and spatial omics techniques offer unprecedented insights into various aspects of tumor microenvironment (TME), bladder cancer heterogeneity, cancer stemness, and cellular plasticity. Studies have identified multiple malignant cell subpopulations within tumors, revealing diverse transcriptional states and clonal evolution. Additionally, intratumor heterogeneity has been linked to tumor progression and therapeutic response. Immune cell composition analysis has revealed immunosuppressive features in the TME, impacting treatment response. Furthermore, studies have elucidated the role of cancer-associated fibroblasts and endothelial cells in shaping the tumor immune landscape and response to therapy.

SUMMARY

Single-cell and spatial omics technologies have revolutionized our understanding of bladder cancer biology, uncovering previously unseen complexities. These methodologies provide valuable insights into tumor heterogeneity and microenvironmental interactions, with implications for therapeutic development. However, challenges remain in translating research findings into clinical practice and implementing personalized treatment strategies. Continued interdisciplinary collaboration and innovation are essential for overcoming these challenges and leveraging the full potential of single-cell and spatial omics in improving bladder cancer diagnosis and treatment.

Tryptophan intake and pancreatic cancer: findings from a case-control study

BACKGROUND

Pancreatic cancer is a leading cause of cancer-related death worldwide. Tryptophan plays a vital role in cell growth and maintenance as a building block of protein and coordination of organismal responses to environmental and dietary cues. Animal model study showed that dietary tryptophan improved treatment response in those who received chemotherapy or immune checkpoint inhibitors. Limited data are available assessing the association between tryptophan intake and risk of pancreatic cancer. We aimed to evaluate this association in a case-control study in Vietnam.

METHODS

We analyzed data from a case-control study, including 3759 cancer cases and 2995 control subjects of whom 37 with pancreatic cancer cases. Tryptophan intake was derived from food frequency questionnaire. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for different levels of tryptophan intake with pancreatic cancer risk.

RESULTS

Overall, tryptophan intake was inversely associated with pancreatic cancer risk in a dose-dependent manner. The ORs and 95% CIs of pancreatic cancer were 0.51 (0.29-0.92) for continuous scale, 0.27 (0.10-0.73) for tertile 2 and 0.34 (0.11-1.06) for tertile 3, compared with tertile 1 (the lowest intake) ( Ptrend = 0.02). In stratified analysis, this inverse association pattern was present among those with BMI < 23 kg/m 2 and ever drinkers.

CONCLUSION

A diet with a higher intake of tryptophan was significantly associated with a lower incidence of pancreatic cancer among Vietnamese population. These suggest that dietary modification may be an effective strategy for primary prevention of pancreatic cancer development.

Coprococcus eutactus screened from healthy adolescent attenuates chronic restraint stress-induced depression-like changes in adolescent mice: Potential roles in the microbiome and neurotransmitter modulation

The onset of depression commonly occurs in adolescence; therefore, depressive prevention and intervention are pivotal during this period. It is becoming evident that neurotransmitter imbalance and gut microbiota dysbiosis are prominent causes of depression. However, the underlying links and mechanisms remain poorly understood. In this study, with 16S ribosomal RNA gene sequencing, genus Coprococcus markedly differentiated between the healthy and unmedicated depressive adolescents. Based on this, transplantation of Coprococcus eutactus (C.e.) was found to dramatically ameliorate the chronic restraint stress (CRS) induced depression-like changes and prevent synaptic loss and glial-stimulated neuroinflammation in mice. The Ultra-high performance liquid chromatography tandem mass spectrometry analysis (UHPLC-MS/MS) further showed that neurotoxic neurotransmitters in kynurenine pathway (KP) such as 3-hydroxykynurenine (3-HK) and 3-hydroxyanthranilic acid (3-HAA) decreased in mouse brains, mechanistically deciphering the transfer of the tryptophan metabolic pathway to serotonin metabolic signaling in the brain after C.e. treatment, which was also verified in the colon. Molecularly, blockage of KP activities mediated by C.e. was ascribed to the restraint of the limit-step enzymes responsible for kynurenine, 3-HK, and quinolinic acid generation. In the colon, C.e. treatment significantly recovered goblet cells and mucus secretion in CRS mice which may ascribe to the rebalance of the disordered gut microbiota, especially Akkermansia, Roseburia, Rikenella, Blautia, and Alloprevotella. Taken together, the current study reveals for the first time the beneficial effects and potential mechanisms of C.e. in ameliorating CRS-induced depression, unraveling the direct links between C.e. treatment and neurotransmitter rebalance, which may provide efficacious therapeutic avenues for adolescent depressive intervention.

Impaired tryptophan metabolism by type 2 inflammation in epithelium worsening asthma

Previous researches indicate that tryptophan metabolism is critical to allergic inflammation and that indoleamine 2,3-dioxygenase 1 (IDO1), as a key enzyme, is known for its immunosuppressive properties. Therefore, we are aimed to explore whether tryptophan metabolism, especially IDO1, influences allergic asthma and clarify specific mechanism. With the analysis of clinical data, exploration in cell experiments, and verifying in HDM-induced asthma mice models, we finally found that in allergic asthma, low level of T1 cytokines along with high level of T2 cytokines inhibited the expression of IDO1 in airway epithelium, hampering the kynurenine pathway in tryptophan metabolism and decreasing the level of intracellular kynurenine (Kyn). As an endogenous ligand of aryl hydrocarbon receptor, Kyn regulated the expression of cystathionine-γ-lyase (CTH). Notably, in asthma models, enhancing either IDO1 or H2S relieved asthma, while inhibiting the activity of CTH exacerbated it. IDO1-Kyn-CTH pathway could be a potential target for treatment for allergic asthma.

Biomimetic Hydrogel-Mediated Mechano-Immunometabolic Therapy for Inhibition of ccRCC Recurrence After Surgery

The unique physical tumor microenvironment (TME) and aberrant immune metabolic status are two obstacles that must be overcome in cancer immunotherapy to improve clinical outcomes. Here, an in situ mechano-immunometabolic therapy involving the injection of a biomimetic hydrogel is presented with sequential release of the anti-fibrotic agent pirfenidone, which softens the stiff extracellular matrix, and small interfering RNA IDO1, which disrupts kynurenine-mediated immunosuppressive metabolic pathways, together with the multi-kinase inhibitor sorafenib, which induces immunogenic cell death. This combination synergistically augmented tumor immunogenicity and induced anti-tumor immunity. In mouse models of clear cell renal cell carcinoma, a single-dose peritumoral injection of a biomimetic hydrogel facilitated the perioperative TME toward a more immunostimulatory landscape, which prevented tumor relapse post-surgery and prolonged mouse survival. Additionally, the systemic anti-tumor surveillance effect induced by local treatment decreased lung metastasis by inhibiting epithelial-mesenchymal transition conversion. The versatile localized mechano-immunometabolic therapy can serve as a universal strategy for conferring efficient tumoricidal immunity in "cold" tumor postoperative interventions.

Qingfei mixture mitigates immunosuppression of tumor microenvironment in non-small cell lung cancer by blocking stat1/Ido1-mediated tryptophan-kynurenine pathway

Programmed death-1 (PD-1) acts as a T cell checkpoint and is important in controlling T cell exhaustion. Blocking the intercommunication across PD-1 and PD-L1 is promising for advanced lung cancer treatment. However, the response rate requires being strengthened. This study aimed to determine whether the combination treatment of Qingfei mixture (QFM) and PD-1 inhibitor could improve the sensitivity of monoclonal antibody by regulating STAT1/IDO1-mediated tryptophan (Trp)-kynurenine (Kyn) pathway. The in vivo imaging system, immunofluorescence, hematoxylin-eosin staining, TUNEL, flow cytometry, HPLC, and ELISA were used to estimate the anti-tumor effects in LLC-luc tumor-bearing C57BL/6 mice treated with QFM, PD-1 inhibitor, 2-NP (enhancer of STAT1 transcription), and FICZ (AhR agonist) alone or in combination. IFN-γ-mediated A549 and LLC cells were treated with QFM-containing serum and fludarabine (FLU, STAT1 inhibitor), and cell viability, apoptosis, and Kyn content were then evaluated using CCK-8 assays, flow cytometry, and HPLC assays, respectively. Additionally, the expressions of STAT1, IDO1, AhR, NFATc1, TRIP12, PD-1, and PD-L1 were measured in vivo and in vitro. We found QFM increased the anti-cancer actions of PD-1 inhibitors by increasing the CD8+IFNγ+ T cells infiltration and decreasing the ratio of Kyn/Trp. Besides, QFM-containing serum suppressed the proliferation and promoted apoptosis in A549 and LLC cells, meanwhile, FLU boosted the effects of QFM-containing serum. Moreover, the suppression of tumor growth in the combination therapy was attenuated in the mice receiving 2-NP or FICZ. The occurrence of the above results was accompanied by a decrease in STAT1, IDO1, AhR, PD-1, and PD-L1 expressions. Collectively, the findings suggested that QFM may increase the influences of PD-1 inhibitors at least partially by blocking the STAT1/IDO1-mediated tryptophan-kynurenine pathway in lung cancer.

Developmental pyrethroid exposure in mouse leads to disrupted brain metabolism in adulthood

Environmental and genetic risk factors, and their interactions, contribute significantly to the etiology of neurodevelopmental disorders (NDDs). Recent epidemiology studies have implicated pyrethroid pesticides as an environmental risk factor for autism and developmental delay. Our previous research showed that low-dose developmental exposure to the pyrethroid pesticide deltamethrin in mice caused male-biased changes in the brain and in NDD-relevant behaviors in adulthood. Here, we used a metabolomics approach to determine the broadest possible set of metabolic changes in the adult male mouse brain caused by low-dose pyrethroid exposure during development. Using a litter-based design, we exposed mouse dams during pregnancy and lactation to deltamethrin (3 mg/kg or vehicle every 3 days) at a concentration well below the EPA-determined benchmark dose used for regulatory guidance. We raised male offspring to adulthood and collected whole brain samples for untargeted high-resolution metabolomics analysis. Developmentally exposed mice had disruptions in 116 metabolites which clustered into pathways for folate biosynthesis, retinol metabolism, and tryptophan metabolism. As a cross-validation, we integrated metabolomics and transcriptomics data from the same samples, which confirmed previous findings of altered dopamine signaling. These results suggest that pyrethroid exposure during development leads to disruptions in metabolism in the adult brain, which may inform both prevention and therapeutic strategies.

Clinical Challenges of Consensus Molecular Subtype CMS4 Colon Cancer in the Era of Precision Medicine

Over the past decade, our understanding of the diversity of colorectal cancer has expanded significantly, raising hopes of tailoring treatments more precisely for individual patients. A key achievement in this direction was the establishment of the consensus molecular classification, particularly identifying the challenging consensus molecular subtype (CMS) CMS4 associated with poor prognosis. Because of its aggressive nature, extensive research is dedicated to the CMS4 subgroup. Recent years have unveiled molecular and microenvironmental features at the tissue level specific to CMS4 colorectal cancer. This has paved the way for mechanistic studies and the development of preclinical models. Simultaneously, efforts have been made to easily identify patients with CMS4 colorectal cancer. Reassessing clinical trial results through the CMS classification lens has improved our understanding of the therapeutic challenges linked to this subtype. Exploration of the biology of CMS4 colorectal cancer is yielding potential biomarkers and novel treatment approaches. This overview aims to provide insights into the clinico-biological characteristics of the CMS4 subgroup, the molecular pathways driving this subtype, and available diagnostic options. We also emphasize the therapeutic challenges associated with this subtype, offering potential explanations. Finally, we summarize the current tailored treatments for CMS4 colorectal cancer emerging from fundamental and preclinical studies.

Tryptophan metabolism and piglet diarrhea: Where we stand and the challenges ahead

The intestinal architecture of piglets is vulnerable to disruption during weaning transition and leads to diarrhea, frequently accompanied by inflammation and metabolic disturbances (including amino acid metabolism). Tryptophan (Trp) plays an essential role in orchestrating intestinal immune tolerance through its metabolism via the kynurenine, 5-hydroxytryptamine, or indole pathways, which could be dictated by the gut microbiota either directly or indirectly. Emerging evidence suggests a strong association between piglet diarrhea and Trp metabolism. Here we aim to summarize the intricate balance of microbiota-host crosstalk by analyzing alterations in both the host and microbial pathways of Trp and discuss how Trp metabolism may affect piglet diarrhea. Overall, this review could provide valuable insights to explore effective strategies for managing piglet diarrhea and the related challenges.

Unveiling the hidden pathways: Exploring astrocytes as a key target for depression therapy

Depressive disorders are widely debilitating psychiatric disease. Despite the considerable progress in the field of depression therapy, extensive research spanning many decades has failed to uncover pathogenic pathways that might aid in the creation of long-acting and rapid-acting antidepressants. Consequently, it is imperative to reconsider existing approaches and explore other targets to improve this area of study. In contemporary times, several scholarly investigations have unveiled that persons who have received a diagnosis of depression, as well as animal models employed to study depression, demonstrate a decrease in both the quantity as well as density of astrocytes, accompanied by alterations in gene expression and morphological attributes. Astrocytes rely on a diverse array of channels and receptors to facilitate their neurotransmitter transmission inside tripartite synapses. This study aimed to investigate the potential processes behind the development of depression, specifically focusing on astrocyte-associated neuroinflammation and the involvement of several molecular components such as connexin 43, potassium channel Kir4.1, aquaporin 4, glutamatergic aspartic acid transporter protein, SLC1A2 or GLT-1, glucocorticoid receptors, 5-hydroxytryptamine receptor 2B, and autophagy, that localized on the surface of astrocytes. The study also explores novel approaches in the treatment of depression, with a focus on astrocytes, offering innovative perspectives on potential antidepressant medications.

Tryptophan catabolism via the kynurenine pathway regulates infection and inflammation: from mechanisms to biomarkers and therapies

BACKGROUND

L-Tryptophan (L-Trp), an essential amino acid, is the only amino acid whose level is regulated specifically by immune signals. Most proportions of Trp are catabolized via the kynurenine (Kyn) pathway (KP) which has evolved to align the food availability and environmental stimulation with the host pathophysiology and behavior. Especially, the KP plays an indispensable role in balancing the immune activation and tolerance in response to pathogens.

SCOPE OF REVIEW

In this review, we elucidate the underlying immunological regulatory network of Trp and its KP-dependent catabolites in the pathophysiological conditions by participating in multiple signaling pathways. Furthermore, the KP-based regulatory roles, biomarkers, and therapeutic strategies in pathologically immune disorders are summarized covering from acute to chronic infection and inflammation.

MAJOR CONCLUSIONS

The immunosuppressive effects dominate the functions of KP induced-Trp depletion and KP-produced metabolites during infection and inflammation. However, the extending minor branches from the KP are not confined to the immune tolerance, instead they go forward to various functions according to the specific condition. Nevertheless, persistent efforts should be made before the clinical use of KP-based strategies to monitor and cure infectious and inflammatory diseases.

Anti-inflammatory and immunomodulatory effects of mesenchymal stem cell therapy on parasitic drug resistance

INTRODUCTION

The emergence of antiparasitic drug resistance poses a concerning threat to animals and humans. Mesenchymal Stem Cells (MSCs) have been widely used to treat infections in humans, pets, and livestock. Although this is an emerging field of study, the current review outlines possible mechanisms and examines potential synergism in combination therapies and the possible harmful effects of such an approach.

AREAS COVERED

The present study delved into the latest pre-clinical research on utilizing MSCs to treat parasitic infections. As per investigations, the introduction of MSCs to patients grappling with parasitic diseases like schistosomiasis, malaria, cystic echinococcosis, toxoplasmosis, leishmaniasis, and trypanosomiasis has shown a reduction in parasite prevalence. This intervention also alters the levels of both pro- and anti-inflammatory cytokines. Furthermore, the combined administration of MSCs and antiparasitic drugs has demonstrated enhanced efficacy in combating parasites and modulating the immune response.

EXPERT OPINION

Mesenchymal stem cells are a potential solution for addressing parasitic drug resistance. This is mainly because of their remarkable immunomodulatory abilities, which can potentially help combat parasites' resistance to drugs.

Magnetic natural lipid nanoparticles for oral treatment of colorectal cancer through potentiated antitumor immunity and microbiota metabolite regulation

The therapeutic efficacy of oral nanotherapeutics against colorectal cancer (CRC) is restricted by inadequate drug accumulation, immunosuppressive microenvironment, and intestinal microbiota imbalance. To overcome these challenges, we elaborately constructed 6-gingerol (Gin)-loaded magnetic mesoporous silicon nanoparticles and functionalized their surface with mulberry leaf-extracted lipids (MLLs) and Pluronic F127 (P127). In vitro experiments revealed that P127 functionalization and alternating magnetic fields (AMFs) promoted internalization of the obtained P127-MLL@Gins by colorectal tumor cells and induced their apoptosis/ferroptosis through Gin/ferrous ion-induced oxidative stress and magneto-thermal effect. After oral administration, P127-MLL@Gins safely passed to the colorectal lumen, infiltrated the mucus barrier, and penetrated into the deep tumors under the influence of AMFs. Subsequently, the P127-MLL@Gin (+ AMF) treatment activated antitumor immunity and suppressed tumor growth. We also found that this therapeutic modality significantly increased the abundance of beneficial bacteria (e.g., Bacillus and unclassified-c-Bacilli), reduced the proportions of harmful bacteria (e.g., Bacteroides and Alloprevotella), and increased lipid oxidation metabolites. Strikingly, checkpoint blockers synergistically improved the therapeutic outcomes of P127-MLL@Gins (+ AMF) against orthotopic and distant colorectal tumors and significantly prolonged mouse life spans. Overall, this oral therapeutic platform is a promising modality for synergistic treatment of CRC.

The role of metabolic reprogramming in kidney cancer

Metabolic reprogramming is a cellular process in which cells modify their metabolic patterns to meet energy requirements, promote proliferation, and enhance resistance to external stressors. This process also introduces new functionalities to the cells. The 'Warburg effect' is a well-studied example of metabolic reprogramming observed during tumorigenesis. Recent studies have shown that kidney cells undergo various forms of metabolic reprogramming following injury. Moreover, metabolic reprogramming plays a crucial role in the progression, prognosis, and treatment of kidney cancer. This review offers a comprehensive examination of renal cancer, metabolic reprogramming, and its implications in kidney cancer. It also discusses recent advancements in the diagnosis and treatment of renal cancer.

FLI1 promotes IFN-γ-induced kynurenine production to impair anti-tumor immunity

Nasopharyngeal carcinoma (NPC)-mediated immunosuppression within the tumor microenvironment (TME) frequently culminates in the failure of otherwise promising immunotherapies. In this study, we identify tumor-intrinsic FLI1 as a critical mediator in impairing T cell anti-tumor immunity. A mechanistic inquiry reveals that FLI1 orchestrates the expression of CBP and STAT1, facilitating chromatin accessibility and transcriptional activation of IDO1 in response to T cell-released IFN-γ. This regulatory cascade ultimately leads to augmented IDO1 expression, resulting in heightened synthesis of kynurenine (Kyn) in tumor cells. This, in turn, fosters CD8+ T cell exhaustion and regulatory T cell (Treg) differentiation. Intriguingly, we find that pharmacological inhibition of FLI1 effectively obstructs the CBP/STAT1-IDO1-Kyn axis, thereby invigorating both spontaneous and checkpoint therapy-induced immune responses, culminating in enhanced tumor eradication. In conclusion, our findings delineate FLI1-mediated Kyn metabolism as an immune evasion mechanism in NPC, furnishing valuable insights into potential therapeutic interventions.

Targeting metabolism to enhance immunotherapy within tumor microenvironment

Cancer metabolic reprogramming has been considered an emerging hallmark in tumorigenesis and the antitumor immune response. Like cancer cells, immune cells within the tumor microenvironment or premetastatic niche also undergo extensive metabolic reprogramming, which profoundly impacts anti-tumor immune responses. Numerous evidence has illuminated that immunosuppressive TME and the metabolites released by tumor cells, including lactic acid, Prostaglandin E2 (PGE2), fatty acids (FAs), cholesterol, D-2-Hydroxyglutaric acid (2-HG), adenosine (ADO), and kynurenine (KYN) can contribute to CD8+ T cell dysfunction. Dynamic alterations of these metabolites between tumor cells and immune cells can similarly initiate metabolic competition in the TME, leading to nutrient deprivation and subsequent microenvironmental acidosis, which impedes immune response. This review summarizes the new landscape beyond the classical metabolic pathways in tumor cells, highlighting the pivotal role of metabolic disturbance in the immunosuppressive microenvironment, especially how nutrient deprivation in TME leads to metabolic reprogramming of CD8+ T cells. Likewise, it emphasizes the current therapeutic targets or strategies related to tumor metabolism and immune response, providing therapeutic benefits for tumor immunotherapy and drug development in the future. Cancer metabolic reprogramming has been considered an emerging hallmark in tumorigenesis and the antitumor immune response. Dynamic alterations of metabolites between tumor cells and immune cells initiate metabolic competition in the TME, leading to nutrient deprivation and subsequent microenvironmental acidosis, which impedes immune response.

Unveiling the metabolic landscape of pulmonary hypertension: insights from metabolomics

Pulmonary hypertension (PH) is regarded as cardiovascular disease with an extremely poor prognosis, primarily due to irreversible vascular remodeling. Despite decades of research progress, the absence of definitive curative therapies remains a critical challenge, leading to high mortality rates. Recent studies have shown that serious metabolic disorders generally exist in PH animal models and patients of PH, which may be the cause or results of the disease. It is imperative for future research to identify critical biomarkers of metabolic dysfunction in PH pathophysiology and to uncover metabolic targets that could enhance diagnostic and therapeutic strategies. Metabolomics offers a powerful tool for the comprehensive qualitative and quantitative analysis of metabolites within specific organisms or cells. On the basis of the findings of the metabolomics research on PH, this review summarizes the latest research progress on metabolic pathways involved in processes such as amino acid metabolism, carbohydrate metabolism, lipid metabolism, and nucleotide metabolism in the context of PH.

Developmental pyrethroid exposure in mouse leads to disrupted brain metabolism in adulthood

Environmental and genetic risk factors, and their interactions, contribute significantly to the etiology of neurodevelopmental disorders (NDDs). Recent epidemiology studies have implicated pyrethroid pesticides as an environmental risk factor for autism and developmental delay. Our previous research showed that low-dose developmental exposure to the pyrethroid pesticide deltamethrin in mice caused male-biased changes in the brain and in NDD-relevant behaviors in adulthood. Here, we used a metabolomics approach to determine the broadest possible set of metabolic changes in the adult male mouse brain caused by low-dose pyrethroid exposure during development. Using a litter-based design, we exposed mouse dams during pregnancy and lactation to deltamethrin (3 mg/kg or vehicle every 3 days) at a concentration well below the EPA-determined benchmark dose used for regulatory guidance. We raised male offspring to adulthood and collected whole brain samples for untargeted high-resolution metabolomics analysis. Developmentally exposed mice had disruptions in 116 metabolites which clustered into pathways for folate biosynthesis, retinol metabolism, and tryptophan metabolism. As a cross-validation, we integrated metabolomics and transcriptomics data from the same samples, which confirmed previous findings of altered dopamine signaling. These results suggest that pyrethroid exposure during development leads to disruptions in metabolism in the adult brain, which may inform both prevention and therapeutic strategies.

Dihydroartemisinin Protects Mice from CUMS-induced Depression-like Behaviors by Regulating Gut Microbes

Depression is one of the most common forms of psychopathology, which is associated with gut microbiota dysfunction. Dihydroartemisinin (DHA) has been shown to regulate gut microbiota and ameliorate neuropathies, but whether it can be used to treat depression remains unclear. Our study found that DHA treatment raised the preference for sugar water in chronic unpredictable mild stress (CUMS)-induced mice and reduced the immobility time in open field, forced swimming and tail suspension experiments, and promoted doublecortin expression. Additionally, DHA up-regulated the diversity and richness of intestinal microbiota in depression-like mice, and restored the abnormal abundance of microbiota induced by CUMS, such as Turicibacter, Lachnospiraceae, Erysipelotrichaceae, Erysipelatoclostridium, Eubacterium, Psychrobacter, Atopostipes, Ileibacterium, Coriobacteriacea, Alistipes, Roseburia, Rikenella, Eggerthellaceae, Ruminococcus, Tyzzerella, and Clostridia. Furthermore, KEGG pathway analysis revealed that gut microbiota involved in the process of depression may be related to glucose metabolism, energy absorption and transport, and AMPK signaling pathway. These results indicated that DHA may play a protective role in CUMS-induced depression by mediating gut-microbiome.

Double-duty isomerases: a case study of isomerization-coupled enzymatic catalysis

Enzymes can usually be unambiguously assigned to one of seven classes specifying the basic chemistry of their catalyzed reactions. Less frequently, two or more reaction classes are catalyzed by a single enzyme within one active site. Two examples are an isomerohydrolase and an isomero-oxygenase that catalyze isomerization-coupled reactions crucial for production of vision-supporting 11-cis-retinoids. In these enzymes, isomerization is obligately paired and mechanistically intertwined with a second reaction class. A handful of other enzymes carrying out similarly coupled isomerization reactions have been described, some of which have been subjected to detailed structure-function analyses. Herein we review these rarefied enzymes, focusing on the mechanistic and structural basis of their reaction coupling with the goal of revealing catalytic commonalities.

The Role of Coinhibitory Receptors in B Cell Dysregulation in SARS-CoV-2-Infected Individuals with Severe Disease

Severe SARS-CoV-2 infection is associated with significant immune dysregulation involving different immune cell subsets. In this study, when analyzing critically ill COVID-19 patients versus those with mild disease, we observed a significant reduction in total and memory B cell subsets but an increase in naive B cells. Moreover, B cells from COVID-19 patients displayed impaired effector functions, evidenced by diminished proliferative capacity, reduced cytokine, and Ab production. This functional impairment was accompanied by an increased apoptotic potential upon stimulation in B cells from severely ill COVID-19 patients. Our further studies revealed the expansion of B cells expressing coinhibitory molecules (PD-1, PD-L1, TIM-1, VISTA, CTLA-4, and Gal-9) in intensive care unit (ICU)-admitted patients but not in those with mild disease. The coinhibitory receptor expression was linked to altered IgA and IgG expression and increased the apoptotic capacity of B cells. Also, we found a reduced frequency of CD24hiCD38hi regulatory B cells with impaired IL-10 production. Our mechanistic studies revealed that the upregulation of PD-L1 was linked to elevated plasma IL-6 levels in COVID-19 patients. This implies a connection between the cytokine storm and altered B cell phenotype and function. Finally, our metabolomic analysis showed a significant reduction in tryptophan but elevation of kynurenine in ICU-admitted COVID-19 patients. We found that kynurenine promotes PD-L1 expression in B cells, correlating with increased IL-6R expression and STAT1/STAT3 activation. Our observations provide novel insights into the complex interplay of B cell dysregulation, implicating coinhibitory receptors, IL-6, and kynurenine in impaired B cell effector functions, potentially contributing to the pathogenesis of COVID-19.

An iridium(iii)-based photosensitizer disrupting the mitochondrial respiratory chain induces ferritinophagy-mediated immunogenic cell death

Cancer cells have a strategically optimized metabolism and tumor microenvironment for rapid proliferation and growth. Increasing research efforts have been focused on developing therapeutic agents that specifically target the metabolism of cancer cells. In this work, we prepared 1-methyl-4-phenylpyridinium-functionalized Ir(iii) complexes that selectively localize in the mitochondria and generate singlet oxygen and superoxide anion radicals upon two-photon irradiation. The generation of this oxidative stress leads to the disruption of the mitochondrial respiratory chain and therefore the disturbance of mitochondrial oxidative phosphorylation and glycolysis metabolisms, triggering cell death by combining immunogenic cell death and ferritinophagy. To the best of our knowledge, this latter is reported for the first time in the context of photodynamic therapy (PDT). To provide cancer selectivity, the best compound of this work was encapsulated within exosomes to form tumor-targeted nanoparticles. Treatment of the primary tumor of mice with two-photon irradiation (720 nm) 24 h after injection of the nanoparticles in the tail vein stops the primary tumor progression and almost completely inhibits the growth of distant tumors that were not irradiated. Our compound is a promising photosensitizer that efficiently disrupts the mitochondrial respiratory chain and induces ferritinophagy-mediated long-term immunotherapy.

Neuroimmune modulation by tryptophan derivatives in neurological and inflammatory disorders

The nervous and immune systems are highly developed, and each performs specialized physiological functions. However, they work together, and their dysfunction is associated with various diseases. Specialized molecules, such as neurotransmitters, cytokines, and more general metabolites, are essential for the appropriate regulation of both systems. Tryptophan, an essential amino acid, is converted into functional molecules such as serotonin and kynurenine, both of which play important roles in the nervous and immune systems. The role of kynurenine metabolites in neurodegenerative and psychiatric diseases has recently received particular attention. Recently, we found that hyperactivity of the kynurenine pathway is a critical risk factor for septic shock. In this review, we first outline neuroimmune interactions and tryptophan derivatives and then summarized the changes in tryptophan metabolism in neurological disorders. Finally, we discuss the potential of tryptophan derivatives as therapeutic targets for neuroimmune disorders.

Taking advantage of the interaction between the sulfoxide and heme cofactor to develop indoleamine 2, 3-dioxygenase 1 inhibitors

Taking advantage of key interactions between sulfoxide and heme cofactor, we used the sulfoxide as the anchor functional group to develop two series of indoleamine 2, 3-dioxygenase 1 (IDO1) inhibitors: 2-benzylsulfinylbenzoxazoles (series 1) and 2-phenylsulfinylbenzoxazoles (series 2). In vitro enzymatic screening shows that both series can inhibit the activity of IDO1 in low micromolar (series 1) or nanomolar (series 2) levels. They also show inhibitory selectivity between IDO1 and tryptophan 2, 3-dioxygenase 2. Interestingly, although series 1 is less potent IDO1 inhibitors of these two series, it exhibited stronger inhibitory activity toward kynurenine production in interferon-γ stimulated BxPC-3 cells. Enzyme kinetics and binding studies demonstrated that 2-sulfinylbenzoxazoles are non-competitive inhibitors of tryptophan, and they interact with the ferrous form of heme. These results demonstrated 2-sulfinylbenzoxazoles as type II IDO1 inhibitors. Furthermore, molecular docking studies supports the sulfoxide being of the key functional group that interacts with the heme cofactor. Compound 22 (series 1) can inhibit NO production in a concentration dependent manner in lipopolysaccharides (LPS) stimulated RAW264.7 cells, and can relieve pulmonary edema and lung injury in LPS induced mouse acute lung injury models.

Hierarchical superstructure aerogels for in situ biofluid metabolomics

High-throughput biofluid metabolomics analysis for screening life-threatening diseases is urgently needed. However, the high salt content of biofluid samples, which introduces severe interference, can greatly limit the analysis throughput. Here, a new 3-D interconnected hierarchical superstructure, namely a "plasmonic gold-on-silica (Au/SiO2) double-layered aerogel", integrating distinctive features of an upper plasmonic gold aerogel with a lower inert silica aerogel was successfully developed to achieve in situ separation and storage of inorganic salts in the silica aerogel, parallel enrichment of metabolites on the surface of the functionalized gold aerogel, and direct desorption/ionization of enriched metabolites by the photo-excited gold aerogel for rapid, sensitive, and comprehensive metabolomics analysis of human serum/urine samples. By integrating all these unique advantages into the hierarchical aerogel, multifunctional properties were introduced in the SALDI substrate to enable its effective utilization in clinical metabolomics for the discovery of reliable metabolic biomarkers to achieve unambiguous differentiation of early and advanced-stage lung cancer patients from healthy individuals. This study provides insight into the design and application of superstructured nanomaterials for in situ separation, storage, and photoexcitation of multi-components in complex biofluid samples for sensitive analysis.

A Novel RP-UHPLC-MS/MS Approach for the Determination of Tryptophan Metabolites Derivatized with 2-Bromo-4'-Nitroacetophenone

Many biologically active metabolites of the essential amino acid L-tryptophan (Trp) are associated with different neurodegenerative diseases and neurological disorders. Precise and reliable methods for their determination are needed. Variability in their physicochemical properties makes the analytical process challenging. In this case, chemical modification of analyte derivatization could come into play. Here, we introduce a novel fast reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) coupled with tandem mass spectrometry (MS/MS) method for the determination of Trp and its ten metabolites in human plasma samples after derivatization with 2-bromo-4'-nitroacetophenone (BNAP). The derivatization procedure was optimized in terms of incubation time, temperature, concentration, and volume of the derivatization reagent. Method development comprises a choice of a suitable stationary phase, mobile phase composition, and gradient elution optimization. The developed method was validated according to the ICH guidelines. Results of all validation parameters were within the acceptance criteria of the guideline, i.e., intra- and inter-day precision (expressed as relative standard deviation; RSD) were in the range of 0.5-8.2% and 2.3-7.4%, accuracy was in the range of 93.3-109.7% and 94.7-110.1%, limits of detection (LODs) were in the range of 0.15-9.43 ng/mL, coefficients of determination (R2) were higher than 0.9906, and carryovers were, in all cases, less than 8.8%. The practicability of the method was evaluated using the blue applicability grade index (BAGI) with a score of 65. Finally, the developed method was used for the analysis of Alzheimer's disease and healthy control plasma to prove its applicability. Statistical analysis revealed significant changes in picolinic acid (PA), anthranilic acid (AA), 5 hydroxyindole-3-acetic acid (5-OH IAA), and quinolinic acid (QA) concentration levels. This could serve as the basis for future studies that will be conducted with a large cohort of patients.

Tryptophan metabolism and kynurenine metabolites in cancer: systemic nutritional and metabolic implications

PURPOSE OF REVIEW

To describe the role of Tryptophan (Trp) metabolism and Kynurenine (Kyn) metabolites in nutritional and metabolic changes in cancer.

RECENT FINDINGS

Trp is in part utilized for protein and neurotransmitters biosynthesis, but more than 95% is implicated in Kyn pathways. In this molecular cascade, metabolites are produced with distinct biological activities regulating the immune response and neurotransmission with potential implications in malnutrition/cachexia during cancer. Immune dysfunction is a phenomenon occurring during cancer and malnutrition. Kyn metabolites regulate lymphocytes activity and recent data in animals showed that the inhibition of indoleamine-2,3-dioxygenase (IDO) via 1-methyl-tryptophan determines partial amelioration of inflammation, but no positive effects on the preservation of muscularity were observed. Kynurenines seem to contribute to muscle catabolism via NAD+ biosynthesis and ROS generation. Trp metabolism via the serotonin biosynthesis is involved in appetite control in cancer. Moreover, kynurenines have a role in determining fatigue in conditions associated with inflammation.

SUMMARY

Trp metabolism has implications in immune and energy balance in cancer. The modulation of Trp and kynurenines have impact on central nervous system mechanisms, including appetite, fatigue, and muscle wasting/cachexia. Research focusing on these clinical implications will open new scenario for therapeutic interventions aimed at counteracting nutritional derangements in cancer.

Marked IDO2 expression and activity related to autophagy and apoptosis in brain tissue of fatal tuberculous meningitis

In about 1% of tuberculosis (TB) patients, Mycobacterium tuberculosis (M. tuberculosis) can disseminate to the meninges, causing tuberculous meningitis (TBM) with mortality rate up to 60%. Chronic granulomatous inflammation (non-necrotizing and necrotizing) in the brain is the histological hallmark of TBM. The tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase 1 (IDO1) and the generated kynurenine metabolites exert major effector functions relevant to TB granuloma functioning. Here we have assessed immunohistochemically IDO1 expression and activity and its effector function and that of its isoform, IDO2, in post-mortem brain tissue of patients that demised with neurotuberculosis. We also related these findings to brain tissue of fatal/severe COVID-19. In this study, IDO1 and IDO2 were abundantly expressed and active in tuberculoid granulomas and were associated with the presence of M. tuberculosis as well as markers of autophagy and apoptosis. Like in fatal/severe COVID-19, IDO2 was also prominent in specific brain regions, such as the inferior olivary nucleus of medulla oblongata and cerebellum, but not associated with granulomas or with M. tuberculosis. Spatially associated apoptosis was observed in TBM, whereas in fatal COVID-19 autophagy dominated. Together, our findings highlight IDO2 as a potentially relevant effector enzyme in TBM, which may relate to the symptomology of TBM.

Serum indoleamine 2, 3-dioxygenase and tryptophan-2, 3-dioxygenase: potential biomarkers for the diagnosis of major depressive disorder

OBJECTIVE

The objective of this study was to observe the changes in the levels of indoleamine 2, 3-dioxygenase (IDO) and tryptophan-2, 3-dioxygenase (TDO) in patients with major depressive disorder (MDD) and investigate their potential role as novel biomarkers for diagnosing MDD.

METHODS

A total of 55 MDD patients and 55 healthy controls (HC) were enrolled in the study. The severity of MDD was assessed using the 24-item Hamilton Depression Rating Scale (HAMD-24) before and after treatment. The serum concentrations of IDO and TDO were measured at baseline and after treatment. The correlations between the serum levels of IDO and TDO and HAMD-24 scores were evaluated using Pearson's correlation test. Receiver operating characteristic (ROC) curve analysis was used to evaluate the area under the curve (AUC) of serum levels of IDO and TDO for discriminating MDD patients from HC.

RESULTS

The serum IDO and TDO concentrations were significantly higher in patients with MDD at baseline than in healthy controls, and decreased significantly after 2 weeks or 1 month of treatment. The levels of IDO and TDO were significantly positively correlated with HAMD-24 scores. Furthermore, the AUC values for IDO and TDO were 0.999 and 0.966, respectively.

CONCLUSION

The study suggests that serum IDO and TDO may serve as novel biomarkers for diagnosing MDD. These findings may lead to a better understanding of the pathogenesis of MDD and the development of new therapeutic targets.

Exploration of circulating metabolic signature of erythrodermic psoriasis based on LC-MS metabolomics

Erythrodermic psoriasis (EP) is a rare and life-threatening disease, the pathogenesis of which remains to be largely unknown. Metabolomics analysis can provide global information on disease pathophysiology, candidate biomarkers, and potential intervention strategies. To gain a better understanding of the mechanisms of EP and explore the serum metabolic signature of EP, we conducted an untargeted metabolomics analysis from 20 EP patients and 20 healthy controls. Furthermore, targeted metabolomics for focused metabolites were identified in the serum samples of 30 EP patients and 30 psoriasis vulgaris (PsV) patients. In the untargeted analysis, a total of 2992 molecular features were extracted from each sample, and the peak intensity of each feature was obtained. Principal component analysis (PCA), orthogonal partial least squares-discriminant analysis (OPLS-DA) revealed significant difference between groups. After screening, 98 metabolites were found to be significantly dysregulated in EP, including 67 down-regulated and 31 up-regulated. EP patients had lower levels of L-tryptophan, L-isoleucine, retinol, lysophosphatidylcholine (LPC), and higher levels of betaine and uric acid. KEGG analysis showed differential metabolites were enriched in amino acid metabolism and glycerophospholipid metabolism. The targeted metabolomics showed lower L-tryptophan in EP than PsV with significant difference and L-tryptophan levels were negatively correlated with the PASI scores. The serum metabolic signature of EP was discovered. Amino acid and glycerophospholipid metabolism were dysregulated in EP. The metabolite differences provide clues for pathogenesis of EP and they may provide insights for therapeutic interventions.

Novel Clinical Trials and Approaches in the Management of Glioblastoma

PURPOSE OF REVIEW

The purpose of this review is to discuss a wide variety of novel therapies recently studied or actively undergoing study in patients with glioblastoma. This review also discusses current and future strategies for improving clinical trial design in patients with glioblastoma to maximize efficacy in discovering effective treatments.

RECENT FINDINGS

Over the years, there has been significant expansion in therapy modalities studied in patients with glioblastoma. These therapies include, but are not limited to, targeted molecular therapies, DNA repair pathway targeted therapies, immunotherapies, vaccine therapies, and surgically targeted radiotherapies. Glioblastoma is the most common malignant primary brain tumor in adults and unfortunately remains with poor overall survival following the current standard of care. Given the dismal prognosis, significant clinical and research efforts are ongoing with the goal of improving patient outcomes and enhancing quality and quantity of life utilizing a wide variety of novel therapies.

Cellular metabolism regulates the differentiation and function of T-cell subsets

T cells are an important component of adaptive immunity and protect the host from infectious diseases and cancers. However, uncontrolled T cell immunity may cause autoimmune disorders. In both situations, antigen-specific T cells undergo clonal expansion upon the engagement and activation of antigens. Cellular metabolism is reprogrammed to meet the increase in bioenergetic and biosynthetic demands associated with effector T cell expansion. Metabolites not only serve as building blocks or energy sources to fuel cell growth and expansion but also regulate a broad spectrum of cellular signals that instruct the differentiation of multiple T cell subsets. The realm of immunometabolism research is undergoing swift advancements. Encapsulating all the recent progress within this concise review in not possible. Instead, our objective is to provide a succinct introduction to this swiftly progressing research, concentrating on the metabolic intricacies of three pivotal nutrient classes-lipids, glucose, and amino acids-in T cells. We shed light on recent investigations elucidating the roles of these three groups of metabolites in mediating the metabolic and immune functions of T cells. Moreover, we delve into the prospect of "editing" metabolic pathways within T cells using pharmacological or genetic approaches, with the aim of synergizing this approach with existing immunotherapies and enhancing the efficacy of antitumor and antiinfection immune responses.

Analysis of the Protective Effects of Rosa roxburghii-Fermented Juice on Lipopolysaccharide-Induced Acute Lung Injury in Mice through Network Pharmacology and Metabolomics

Acute lung injury, a fatal condition characterized by a high mortality rate, necessitates urgent exploration of treatment modalities. Utilizing UHPLS-Q-Exactive Orbitrap/MS, our study scrutinized the active constituents present in Rosa roxburghii-fermented juice (RRFJ) while also assessing its protective efficacy against LPS-induced ALI in mice through lung histopathological analysis, cytokine profiling, and oxidative stress assessment. The protective mechanism of RRFJ against ALI in mice was elucidated utilizing metabolomics, network pharmacology, and molecular docking methodologies. Our experimental findings demonstrate that RRFJ markedly ameliorates pathological injuries in ALI-afflicted mice, mitigates systemic inflammation and oxidative stress, enhances energy metabolism, and restores dysregulated amino acid and arachidonic acid metabolic pathways. This study indicates that RRFJ can serve as a functional food for adjuvant treatment of ALI.

Implications of Kynurenine Pathway Metabolism for the Immune System, Hypothalamic-Pituitary-Adrenal Axis, and Neurotransmission in Alcohol Use Disorder

In recent years, there has been a marked increase in interest in the role of the kynurenine pathway (KP) in mechanisms associated with addictive behavior. Numerous reports implicate KP metabolism in influencing the immune system, hypothalamic-pituitary-adrenal (HPA) axis, and neurotransmission, which underlie the behavioral patterns characteristic of addiction. An in-depth analysis of the results of these new studies highlights interesting patterns of relationships, and approaching alcohol use disorder (AUD) from a broader neuroendocrine-immune system perspective may be crucial to better understanding this complex phenomenon. In this review, we provide an up-to-date summary of information indicating the relationship between AUD and the KP, both in terms of changes in the activity of this pathway and modulation of this pathway as a possible pharmacological approach for the treatment of AUD.

The role of the "gut microbiota-mitochondria" crosstalk in the pathogenesis of multiple sclerosis

Multiple Sclerosis (MS) is a neurologic autoimmune disease whose exact pathophysiologic mechanisms remain to be elucidated. Recent studies have shown that the onset and progression of MS are associated with dysbiosis of the gut microbiota. Similarly, a large body of evidence suggests that mitochondrial dysfunction may also have a significant impact on the development of MS. Endosymbiotic theory has found that human mitochondria are microbial in origin and share similar biological characteristics with the gut microbiota. Therefore, gut microbiota and mitochondrial function crosstalk are relevant in the development of MS. However, the relationship between gut microbiota and mitochondrial function in the development of MS is not fully understood. Therefore, by synthesizing previous relevant literature, this paper focuses on the changes in gut microbiota and metabolite composition in the development of MS and the possible mechanisms of the crosstalk between gut microbiota and mitochondrial function in the progression of MS, to provide new therapeutic approaches for the prevention or reduction of MS based on this crosstalk.

Gut Microbiota-Derived Tryptophan Metabolites Alleviate Allergic Asthma Inflammation in Ovalbumin-Induced Mice

Asthma is a prevalent respiratory disease. The present study is designed to determine whether gut microbiota-derived tryptophan metabolites alleviate allergic asthma inflammation in ovalbumin (OVA)-induced mice and explore the effect and potential mechanism therein. Asthma model mice were constructed by OVA treatment, and kynurenine (KYN), indole-3-lactic acid (ILA), in-dole-3-carbaldehyde (I3C), and indole acetic acid (IAA) were administered by intraperitoneal injection. The percent survival, weight and asthma symptom score of mice were recorded. The total immunoglobulin E and OVA-specific (s)IgE in the serum and the inflammatory cytokines in the bronchoalveolar lavage fluid (BALF) were detected by the corresponding ELISA kits. The composition of the gut microbiota and tryptophan-targeted metabolism in mouse feces were analyzed using 16S rRNA gene sequencing and targeted metabolomics, respectively. The four tryptophan metabolites improved the percent survival, weight and asthma symptoms of mice, and reduced the inflammatory cells in lung tissues, especially I3C. I3C and IAA significantly (p < 0.05) downregulated the levels of OVA-IgE and inflammatory cytokines. KYN was observed to help restore gut microbiota diversity. Additionally, I3C, KYN, and ILA increased the relative abundance of Anaeroplasma, Akkermansia, and Ruminococcus_1, respectively, which were connected with tryptophan metabolic pathways. IAA also enhanced capability of tryptophan metabolism by the gut microbiota, restoring tryptophan metabolism and increasing production of other tryptophan metabolites. These findings suggest that tryptophan metabolites may modulate asthma through the gut microbiota, offering potential benefits for clinical asthma management.

Tryptophan metabolic pathway plays a key role in the stress-induced emotional eating

Chronic stress disrupts the emotional and energetic balance, which may lead to abnormal behaviors such as binge eating. This overeating behavior alleviating the negative emotions is called emotional eating, which may exacerbate emotional instability and lead to obesity. It is a complex and multifaceted process that has not yet been fully understood. In this study, we constructed an animal model of chronic mild stress (CMS)-induced emotional eating. The emotional eating mice were treated with tryptophan for 21 days to reveal the key role of tryptophan. Furthermore, serum-targeted metabolomics, immunohistochemical staining, qPCR and ELISA were performed. The results showed that CMS led to the binge eating behavior, accompanied by the disturbed intestinal tryptophan-derived serotonin (5-hydroxytryptamine; 5-HT) metabolic pathways. Then we found that tryptophan supplementation improved depression and anxiety-like behaviors as well as abnormal eating behaviors. Tryptophan supplementation improved the abnormal expression of appetite regulators (e.g., AgRP, OX1R, MC4R), and tryptophan supplementation also increased the tryptophan hydroxylase 2 (tph2) and 5-HT receptors in the hypothalamus of CMS mice, which indicates that the 5-HT metabolic pathway influences feeding behavior. In vitro experiments confirmed that 5-HT supplementation ameliorated corticosterone-induced aberrant expression of appetite regulators, such as AgRP and OX1R, in the hypothalamic cell line. In conclusion, our findings revealed that the tryptophan-derived 5-HT pathway plays an important role in emotional eating, especially in providing targeted therapy for stress-induced obesity.

Tumor Antigens beyond the Human Exome

With the advent of immunotherapeutics, a new era in the combat against cancer has begun. Particularly promising are neo-epitope-targeted therapies as the expression of neo-antigens is tumor-specific. In turn, this allows the selective targeting and killing of cancer cells whilst healthy cells remain largely unaffected. So far, many advances have been made in the development of treatment options which are tailored to the individual neo-epitope repertoire. The next big step is the achievement of efficacious "off-the-shelf" immunotherapies. For this, shared neo-epitopes propose an optimal target. Given the tremendous potential, a thorough understanding of the underlying mechanisms which lead to the formation of neo-antigens is of fundamental importance. Here, we review the various processes which result in the formation of neo-epitopes. Broadly, the origin of neo-epitopes can be categorized into three groups: canonical, noncanonical, and viral neo-epitopes. For the canonical neo-antigens that arise in direct consequence of somatic mutations, we summarize past and recent findings. Beyond that, our main focus is put on the discussion of noncanonical and viral neo-epitopes as we believe that targeting those provides an encouraging perspective to shape the future of cancer immunotherapeutics.

Shenling Baizhu San ameliorates non-alcoholic fatty liver disease in mice by modulating gut microbiota and metabolites

Purpose: The prevalence of non-alcoholic fatty liver disease (NAFLD) and its related mortality is increasing at an unprecedented rate. Traditional Chinese medicine (TCM) has been shown to offer potential for early prevention and treatment of NAFLD. The new mechanism of "Shenling Baizhu San" (SLBZS) is examined in this study for the prevention and treatment of NAFLD at the preclinical level. Methods: Male C57BL/6J mice were randomly divided into three groups: normal diet (ND), western diet + CCl4 injection (WDC), and SLBZS intervention (WDC + SLBZS). Body weights, energy intake, liver enzymes, pro-inflammatory factors, and steatosis were recorded in detail. Meanwhile, TPH1, 5-HT, HTR2A, and HTR2B were tested using qRT-PCR or ELISA. Dynamic changes in the gut microbiota and metabolites were further detected through the 16S rRNA gene and untargeted metabolomics. Results: SLBZS intervention for 6 weeks could reduce the serum and liver lipid profiles, glucose, and pro-inflammatory factors while improving insulin resistance and liver function indexes in the mice, thus alleviating NAFLD in mice. More importantly, significant changes were found in the intestinal TPH-1, 5-HT, liver 5-HT, and related receptors HTR2A and HTR2B. The 16S rRNA gene analysis suggested that SLBZS was able to modulate the disturbance of gut microbiota, remarkably increasing the relative abundance of probiotics (Bifidobacterium and Parvibacter) and inhibiting the growth of pro-inflammatory bacteria (Erysipelatoclostridium and Lachnoclostridium) in mice with NAFLD. Combined with metabolomics in positive- and negative-ion-mode analyses, approximately 50 common differential metabolites were selected via non-targeted metabolomics detection, which indicated that the targeting effect of SLBZS included lipid metabolites, bile acids (BAs), amino acids (AAs), and tryptophan metabolites. In particular, the lipid metabolites 15-OxEDE, vitamin D3, desoxycortone, and oleoyl ethanol amide were restored by SLBZS. Conclusion: Integrating the above results of multiple omics suggests that SLBZS ameliorates NAFLD via specific gut microbiota, gut-derived 5-HT, and related metabolites to decrease fat accumulation in the liver and inflammatory responses.

Kynurenine Metabolites in CSF and Plasma in Healthy Males

In recent years, kynurenine metabolites generated by tryptophan catabolism have gained increasing attention in the context of brain diseases. The question of importance is whether there is a relationship between peripheral and central levels of these metabolites. Some of these compounds do not cross the blood-brain barrier; in particular, kynurenic acid, and most analyses of kynurenines from psychiatric patients have been performed using plasma samples. In the present study, we recruited 30 healthy volunteers with no history of psychiatric or neurological diagnosis, to analyze tryptophan, kynurenine, kynurenic acid, and quinolinic acid levels in CSF and plasma. In addition, kynurenic acid was analyzed in urine. The most important finding of this study is that CSF kynurenic acid levels do not correlate with those in plasma or urine. However, we found a correlation between plasma kynurenine and CSF kynurenic acid. Further, plasma kynurenine and plasma quinolinic acid were correlated. Our findings clarify the distribution of tryptophan and its metabolites in various body compartments and may serve as a guide for the analysis of these metabolites in humans. The most significant finding of the present study is that a prediction of brain kynurenic acid by of the analysis of the compound in plasma cannot be made.

Influence of Dietary Polyunsaturated Fatty Acid Intake on Potential Lipid Metabolite Diagnostic Markers in Renal Cell Carcinoma: A Case-Control Study

Non-invasive diagnostics are crucial for the timely detection of renal cell carcinoma (RCC), significantly improving survival rates. Despite advancements, specific lipid markers for RCC remain unidentified. We aimed to discover and validate potent plasma markers and their association with dietary fats. Using lipid metabolite quantification, machine-learning algorithms, and marker validation, we identified RCC diagnostic markers in studies involving 60 RCC and 167 healthy controls (HC), as well as 27 RCC and 74 HC, by analyzing their correlation with dietary fats. RCC was associated with altered metabolism in amino acids, glycerophospholipids, and glutathione. We validated seven markers (l-tryptophan, various lysophosphatidylcholines [LysoPCs], decanoylcarnitine, and l-glutamic acid), achieving a 96.9% AUC, effectively distinguishing RCC from HC. Decreased decanoylcarnitine, due to reduced carnitine palmitoyltransferase 1 (CPT1) activity, was identified as affecting RCC risk. High intake of polyunsaturated fatty acids (PUFAs) was negatively correlated with LysoPC (18:1) and LysoPC (18:2), influencing RCC risk. We validated seven potential markers for RCC diagnosis, highlighting the influence of high PUFA intake on LysoPC levels and its impact on RCC occurrence via CPT1 downregulation. These insights support the efficient and accurate diagnosis of RCC, thereby facilitating risk mitigation and improving patient outcomes.

Cancer cell metabolism and antitumour immunity

Accumulating evidence suggests that metabolic rewiring in malignant cells supports tumour progression not only by providing cancer cells with increased proliferative potential and an improved ability to adapt to adverse microenvironmental conditions but also by favouring the evasion of natural and therapy-driven antitumour immune responses. Here, we review cancer cell-intrinsic and cancer cell-extrinsic mechanisms through which alterations of metabolism in malignant cells interfere with innate and adaptive immune functions in support of accelerated disease progression. Further, we discuss the potential of targeting such alterations to enhance anticancer immunity for therapeutic purposes.

Role of N-acetylkynurenine in mediating the effect of gut microbiota on urinary tract infection: a Mendelian randomization study

Introduction

This study explored the causal connections between gut microbiota (GM), urinary tract infection (UTI), and potential metabolite mediators using Mendelian randomization (MR).

Methods

We utilized summary statistics from the most comprehensive and extensive genome-wide association studies (GWAS) available to date, including 196 bacterial traits for GM, 1,091 blood metabolites, 309 metabolite ratios, alongside UTI data from ukb-b-8814 and ebi-a-GCST90013890. Bidirectional MR analyses were conducted to investigate the causal links between GM and UTI. Subsequently, two MR analyses were performed to identify the potential mediating metabolites, followed by a two-step MR analysis to quantify the mediation proportion.

Results

Our findings revealed that out of the total 15 bacterial traits, significant associations with UTI risk were observed across both datasets. Particularly, taxon g_Ruminococcaceae UCG010 displayed a causal link with a diminished UTI risk in both datasets (ukb-b-8814: odds ratio [OR] = 0.9964, 95% confidence interval [CI] = 0.9930-0.9997, P = 0.036; GCST90013890: OR = 0.8252, 95% CI = 0.7217-0.9436, P = 0.005). However, no substantial changes in g_Ruminococcaceae UCG010 due to UTI were noted (ukb-b-8814: β = 0.51, P = 0.87; ebi-a-GCST90013890: β = -0.02, P = 0.77). Additionally, variations in 56 specific metabolites were induced by g_Ruminococcaceae UCG010, with N-acetylkynurenine (NAK) exhibiting a causal correlation with UTI. A negative association was found between g_Ruminococcaceae UCG010 and NAK (OR: 0.8128, 95% CI: 0.6647-0.9941, P = 0.044), while NAK was positively associated with UTI risk (OR: 1.0009; 95% CI: 1.0002-1.0016; P = 0.0173). Mediation analysis revealed that the association between g_Ruminococcaceae UCG010 and UTI was mediated by NAK with a mediation proportion of 5.07%.

Discussion

This MR study provides compelling evidence supporting the existence of causal relationships between specific GM taxa and UTI, along with potential mediating metabolites.

High indoleamine 2,3-dioxygenase transcript levels predict better outcome after front-line cancer immunotherapy

Indoleamine 2,3-dioxygenase 1 (IDO1), which catabolizes tryptophan, is a potential target to unlock the immunosuppressive tumor microenvironment. Correlations between IDO1 and immune checkpoint inhibitor (ICI) efficacy remain unclear. Herein, we investigated IDO1 transcript expression across cancers and clinical outcome correlations. High IDO1 transcripts were more frequent in uterine (54.2%) and ovarian cancer (37.2%) but varied between and within malignancies. High IDO1 RNA expression was associated with high expression of PD-L1 (immune checkpoint ligand), CXCL10 (an effector T cell recruitment chemokine), and STAT1 (a component of the JAK-STAT pathway) (all multivariable p < 0.05). PIK3CA and CTCF alterations were more frequent in the high IDO1 group. High IDO1 expression was an independent predictor of progression-free survival (adjusted HR = 0.44, 95% CI 0.20-0.99, p = 0.049) and overall survival (adjusted HR = 0.31, 95% CI 0.11-0.87, p = 0.026) after front-line ICIs. IDO1 expression warrants further exploration as a predictive biomarker for immunotherapy. Moreover, co-expressed immunoregulatory molecules merit exploration for co-targeting.

Integrated physiological, intestinal microbiota, and metabolomic responses of adult zebrafish (Danio rerio) to subacute exposure to antimony at environmentally relevant concentrations

The available information regarding the impact of antimony (Sb), a novel environmental pollutant, on the intestinal microbiota and host health is limited. In this study, we conducted physiological characterizations to investigate the response of adult zebrafish to different environmental concentrations (0, 30, 300, and 3000 µg/L) of Sb over a period of 14 days. Biochemical and pathological changes demonstrated that Sb effectively compromised the integrity of the intestinal physical barrier and induced inflammatory responses as well as oxidative stress. Analysis of both intestinal microbial community and metabolome revealed that exposure to 0 and 30 µg/L of Sb resulted in similar microbiota structures; however, exposure to 300 µg/L altered microbial communities' composition (e.g., a decline in genus Cetobacterium and an increase in Vibrio). Furthermore, exposure to 300 µg/L significantly decreased levels of bile acids and glycerophospholipids while triggering intestinal inflammation but activating self-protective mechanisms such as antibiotic presence. Notably, even exposure to 30 µg/L of Sb can trigger dysbiosis of intestinal microbiota and metabolites, potentially impacting fish health through the "microbiota-intestine-brain axis" and contributing to disease initiation. This study provides valuable insights into toxicity-related information concerning environmental impacts of Sb on aquatic organisms with significant implications for developing management strategies.

Spatiotemporally Controlled T-Cell Combination Therapy for Solid Tumor

Due to multidimensional complexity of solid tumor, development of rational T-cell combinations and corresponding formulations is still challenging. Herein, a triple combination of T cells are developed with Indoleamine 2,3-dioxygenase inhibitors (IDOi) and Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i). To maximize synergism, a spatiotemporally controlled T-cell engineering technology to formulate triple drugs into one cell therapeutic, is established. Specifically, a sequentially responsive core-shell nanoparticle (SRN) encapsulating IDOi and CDK4/6i is anchored onto T cells. The yielded SRN-T cells migrated into solid tumor, and achieved a 1st release of IDOi in acidic tumor microenvironment (TME). Released IDOi restored tryptophan supply in TME, which activated effector T cells and inhibited Tregs. Meanwhile, 1st released core is internalized by tumor cells and degraded by glutathione (GSH), to realize a 2nd release of CDK4/6i, which induced up-regulated expression of C-X-C motif chemokine ligand 10 (CXCL10) and C-C motif chemokine ligand 5 (CCL5), and thus significantly increased tumor infiltration of T cells. Together, with an enhanced recruitment and activation, T cells significantly suppressed tumor growth, and prolonged survival of tumor-bearing mice. This study demonstrated rationality and superiority of a tri-drug combination mediated by spatiotemporally controlled cell-engineering technology, which provides a new treatment regimen for solid tumor.

Altered neopterin and IDO in kynurenine metabolism based on LC-MS/MS metabolomics study: Novel therapeutic checkpoints for type 2 diabetes mellitus

BACKGROUND

This study assessed the alternations of kynurenine pathway (KP) and neopterin in type 2 diabetes mellitus (T2DM) and explored possible differential metabolites.

METHODS

A fresh residual sera panel was collected from 80 healthy control (HC) individuals and 72 T2DM patients. Metabolites/ratios of interest including tryptophan (TRP), kynurenine (KYN), 5-hydroxytryptamine (5HT), kynurenic acid (KA), xanthurenic acid (XA), neopterin (NEO), KA/KYN ratio and KYN/TRP ratio were determined using a targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) metabolomics approach, and the difference between groups was assessed. Supervised orthogonal partial least squares-discriminant analysis and differential metabolite screening with fold change (FC) were performed to identify distinct biomarkers. The diagnostic performance of KP metabolites in T2DM was evaluated.

RESULTS

Significant decreases of TRP, 5HT, KA, XA, and KA/KYN and increases of KYN/TRP and NEO in T2DM compared to HC group were observed (P < 0.05). The KP metabolites panel significantly changed between T2DM and HC groups (Q2: 0.925, P < 0.005). 5HT (FC: 0.63, P < 0.01) and NEO (FC: 3.27, P < 0.01) were proven to be distinct differential metabolites. A combined testing of fasting plasma glucose and KYN/TRP showed good value in the prediction of T2DM (AUC: 0.904, 95% CI 0.843-0.947).

CONCLUSIONS

The targeted LC-MS/MS metabolomics study is a powerful tool for evaluating the status of T2DM. This study facilitated the application of KP metabolomics into future clinical practice. 5HT and NEO are promising biomarkers in T2DM. KYN/TRP was highly associated with the development of T2DM and may serve as a potential treatment target.

Targeting metabolism of breast cancer and its implications in T cell immunotherapy

Breast cancer is a prominent health issue amongst women around the world. Immunotherapies including tumor targeted antibodies, adoptive T cell therapy, vaccines, and immune checkpoint blockers have rejuvenated the clinical management of breast cancer, but the prognosis of patients remains dismal. Metabolic reprogramming and immune escape are two important mechanisms supporting the progression of breast cancer. The deprivation uptake of nutrients (such as glucose, amino acid, and lipid) by breast cancer cells has a significant impact on tumor growth and microenvironment remodeling. In recent years, in-depth researches on the mechanism of metabolic reprogramming and immune escape have been extensively conducted, and targeting metabolic reprogramming has been proposed as a new therapeutic strategy for breast cancer. This article reviews the abnormal metabolism of breast cancer cells and its impact on the anti-tumor activity of T cells, and further explores the possibility of targeting metabolism as a therapeutic strategy for breast cancer.