Reprogramming alternative macrophage polarization by GATM-mediated endogenous creatine synthesis: A potential target for HDM-induced asthma treatment

Mitochondrial dynamics at the intersection of macrophage polarization and metabolism

Macrophages are vital sentinels in innate immunity, and their functions cannot be performed without internal metabolic reprogramming. Mitochondrial dynamics, especially mitochondrial fusion and fission, contributes to the maintenance of mitochondrial homeostasis. The link between mitochondrial dynamics and macrophages in the past has focused on the immune function of macrophages. We innovatively summarize and propose a link between mitochondrial dynamics and macrophage metabolism. Among them, fusion-related FAM73b, MTCH2, SLP-2 (Stomatin-like protein 2), and mtSIRT, and fission-related Fis1 and MTP18 may be the link between mitochondrial dynamics and macrophage metabolism association. Furthermore, post-translational modifications (PTMs) of mtSIRT play prominent roles in mitochondrial dynamics-macrophage metabolism connection, such as deacetylates and hypersuccinylation. MicroRNAs such as miR-150, miR-15b, and miR-125b are also possible entry points. The metabolic reprogramming of macrophages through the regulation of mitochondrial dynamics helps improve their adaptability and resistance to adverse environments and provides therapeutic possibilities for various diseases.

A creatine efflux transporter in oligodendrocytes

Creatine is essential for ATP regeneration in energy-demanding cells. Creatine deficiency results in severe neurodevelopmental impairments. In the brain, creatine is synthesized locally by oligodendrocytes to supply neighboring neurons. Neuronal uptake is mediated by SLC6A8. However, it is still unknown how creatine is released from the producing cells. Here, we investigated the function of the transporter SLC22A15, which exhibits strikingly high amino acid sequence conservation. The release of substrates from 293 cells via heterologously expressed human and rat SLC22A15 was analyzed by mass spectrometry. A number of zwitterions were identified as substrates, with similar efflux transport efficiencies. However, in absolute numbers, the efflux of creatine far outweighed all other substrates. In contrast to the permanent creatine efflux mediated by SLC16A12 and SLC16A9, SLC22A15 was, by default, completely inactive, thereby preventing continuous creatine loss from producing cells. External substrates such as guanidinoacetic acid, GABA, or MPP+ trigger creatine release through a one-to-one exchange. Human and mouse mRNA profiles indicate that SLC22A15 expression is highest in oligodendrocytes and bone marrow. Single-cell RNA sequencing data substantiate the hypothesis that SLC22A15 depends on high intracellular creatine concentrations: high SLC22A15 counts, as in oligodendrocytes and macrophages, correlate with high counts of the creatine synthesis enzymes AGAT and GAMT in both humans and mice, whereas in proximal tubular cells and hepatocytes, AGAT counts are high, but SLC22A15 is absent. Our findings establish SLC22A15 as the pivotal transporter for controlled creatine release from oligodendrocytes, filling a critical gap in understanding creatine metabolism in the brain.

Assessing Creatine-Related Gene Expression in Kidney Disease: Can Available Data Give Insights into an Old Discussion?

The impact of creatine supplementation on individuals with kidney disease or pathological conditions with an increased risk of developing kidney dysfunction remains an active discussion. However, the literature on gene expression related to cellular creatine uptake and metabolism under altered renal function is scarce. Therefore, the present study utilized comprehensive bioinformatics analysis to evaluate the expression of creatine-related genes and to establish their relationships to normal and disturbed renal conditions. We identified 44 genes modulated explicitly in response to creatine exposure from a gene enrichment analysis, including IGF1, SLC2A4, and various creatine kinase genes. The analysis revealed associations with metabolic processes such as amino acid metabolism, indicating a connection between creatine and tissue physiology. Using the Genotype-Tissue Expression Portal, we evaluated their basal tissue-specific expression patterns in kidney and pancreas tissues. Then, we selected several pieces of Gene Expression Omnibus (GEO) transcriptomic data, estimated their expression values, and established relationships to the creatine metabolism pathways and regulation, shedding light on the potential regulatory roles of creatine in cellular processes during kidney diseases. These observations also highlight the connection between creatine and tissue physiology, emphasizing the importance of understanding the balance between endogenous creatine synthesis and creatine uptake, particularly the roles of genes such as GATM, GAMT, SLC6A8, and IGF1, under several kidney dysfunction conditions. Overall, the available data in the biological databases can provide new insights and directions into creatine's effects and role in renal function.

Enhancing cardiac repair post-myocardial infarction: a study on GATM/Gel hydrogel therapeutics

BACKGROUND AND PURPOSE

Significant advancements in therapeutic approaches are imperative to address the prevalent impact of myocardial infarction (MI) on morbidity and mortality rates worldwide. This study explores the therapeutic potential of GATM/Gel hydrogel, focusing on its ability to enhance cardiac repair and functionality after MI through modulation of inflammatory and repair pathways.

EXPERIMENTAL APPROACH

The effects of GATM/Gel hydrogel on cardiac recovery were studied in a murine MI model. HA-CHO and gelatin solutions were mixed in situ using a dual syringe with a static mixing needle, and the resulting hydrogel was applied directly to the epicardium during MI modeling, followed by repositioning of the heart and closure of the thorax. Comprehensive in vivo assessments-including echocardiography, electrocardiography, and histopathological analysis-were combined with molecular techniques such as RT-qPCR, Western blotting, and immunofluorescence to elucidate the underlying mechanisms. Key cellular and molecular changes were tracked, focusing on macrophage polarization, angiogenesis, and modulation of the TNF/TNFR2 signaling pathway.

KEY RESULTS

Employing the GATM/Gel hydrogel led to a substantial improvement in heart function, shown through enhanced ejection fraction and fractional shortening, and reduced infarction size compared to control groups. Mechanistically, the hydrogel promoted the polarization of anti-inflammatory M2 macrophages and stimulated angiogenesis. Moreover, treatment with GATM/Gel hydrogel altered the TNF/TNFR2 pathway, pivotal in mediating inflammatory responses and facilitating myocardial repair. The discoveries highlight the possibility of GATM/Gel hydrogels as an innovative remedy for MI, providing a twofold role in regulating inflammation and fostering recovery.

Arginine metabolism in myeloid cells in health and disease

Metabolic flexibility is key for the function of myeloid cells. Arginine metabolism is integral to the regulation of myeloid cell responses. Nitric oxide (NO) production from arginine is vital for the antimicrobial and pro-inflammatory responses. Conversely, the arginase 1 (ARG1)-dependent switch between the branch of NO production and polyamine synthesis downregulates inflammation and promotes recovery of tissue homeostasis. Creatine metabolism is key for energy supply and proline metabolism is required for collagen synthesis. Myeloid ARG1 also regulates extracellular arginine availability and T cell responses in parasitic diseases and cancer. Cancer, surgery, sepsis and persistent inflammation in chronic inflammatory diseases, such as neuroinflammatory diseases or arthritis, are associated with dysregulation of arginine metabolism in myeloid cells. Here, we review current knowledge on arginine metabolism in different myeloid cell types, such as macrophages, neutrophils, microglia, osteoclasts, tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs) and myeloid-derived suppressor cells (MDSCs). A deeper understanding of the function of arginine metabolism in myeloid cells will improve our knowledge on the pathology of several diseases and may set the platform for novel therapeutic applications.

It Is Not Just About Storing Energy: The Multifaceted Role of Creatine Metabolism on Cancer Biology and Immunology

Creatine, a naturally occurring compound in mammals, is crucial in energy metabolism, particularly within muscle and brain tissues. While creatine metabolism in cancer has been studied for several decades, emerging studies are beginning to clarify the sometimes-contradictory role creatine has in either the promotion or inhibition of cancer. On one hand, creatine can directly enhance anti-tumor CD8+ T-cell activity and induce tumor apoptosis, contributing to antitumor immunity. Conversely, other studies have shown that creatine can facilitate cancer cell growth and migration by providing an energy source and activating several signaling pathways. This review will examine what is known about creatine in cancer biology, with a focus on understanding its roles across different cellular compartments. Lastly, we discuss the emerging roles of creatine metabolism, providing exciting new insights into this often-overlooked pathway. This review highlights the complex role of creatine in cancer development and treatment, offering insights into its potential as both a therapeutic target and a risk factor in oncogenesis.

Smyd3-mediated immuno-modulation in HPV-negative head and neck squamous cell carcinoma mouse models

SET and MYND-domain containing protein 3 (SMYD3) mediates epigenetic repression of type I IFN response genes in human papillomavirus (HPV)-negative HNSCC cells, and Smyd3 depletion using anti-sense oligonucleotides (ASOs) increases the sensitivity of syngeneic mouse oral carcinoma (MOC1) models to anti-PD-1 therapy. In this study, we utilized single-cell RNA-seq of MOC1 tumors treated with Smyd3 ASOs and found enrichment of type I IFN response pathways in cancer cells, a shift of CD8+ T-cells toward an activated/memory phenotype, and a shift of neutrophils toward an anti-tumorigenic phenotype. Mechanisms of resistance to the Smyd3 ASO and anti-PD-1 combination were derived from cancer cells, macrophages, and CD8+ T-cells, including neutrophil enrichment through the upregulation of Cxcl2, repression of Cxcl9, and defective antigen presentation. This study sheds light on the immunomodulatory functions of Smyd3 in vivo and provides insight into actionable mechanisms of resistance to improve the efficacy of Smyd3 ASOs and anti-PD-1 combination.

Integrative Analysis of Lactylome and Proteome of Hypertrophic Scar To Identify Pathways or Proteins Associated with Disease Development

Lactylation (Kla), a recently discovered post-translational modification derived from lactate, plays crucial roles in various cellular processes. However, the specific influence of lactylation on the biological processes underlying hypertrophic scar formation remains unclear. In this study, we present a comprehensive profiling of the lactylome and proteome in both hypertrophic scars and adjacent normal skin tissues. A total of 1023 Kla sites originating from 338 nonhistone proteins were identified based on lactylome analysis. Proteome analysis in hypertrophic scar and adjacent skin samples revealed the identification of 2008 proteins. It is worth noting that Kla exhibits a preference for genes associated with ribosome function as well as glycolysis/gluconeogenesis in both normal skin and hypertrophic scar tissues. Furthermore, the functional enrichment analysis demonstrated that differentially lactyled proteins are primarily involved in proteoglycans, HIF-1, and AMPK signaling pathways. The combined analysis of the lactylome and proteome data highlighted a significant upregulation of 14 lactylation sites in hypertrophic scar tissues. Overall, our investigation unveiled the significant involvement of protein lactylation in the regulation of ribosome function as well as glycolysis/gluconeogenesis, potentially contributing to the formation of hypertrophic scars.

Toxic effects of freshwater grouper (Acrossocheilus fasciatus) eggs on poultry: Morphological and transcriptomic insights into hepatic toxicity

Fish egg poisoning is a serious and neglected public menace that kills hundreds of people and numerous poultry each year. Freshwater groupers (Acrossocheilus fasciatus) are common food fish in the southeastern regions of China. Their toxic eggs are regarded as a significant public health concern. The molecular mechanisms of egg-toxin toxicity in freshwater grouper to poisoned organisms are elusive. In this study, black-boned chicks were exposed to toxic eggs from freshwater grouper at a lethal dose. The hepatic morphology of the intoxicated chick was assessed. An analysis of the liver gene expression profile was conducted by comparing samples exposed to toxic eggs with control samples using RNA-Seq. The result revealed that an increase in vacuolation and congestion was observed in chicks with toxic eggs exposure. The transcriptome analysis revealed 5421 genes with differential expression, comprising 2810 up-regulated and 2611 down-regulated genes. The genes were primarily linked to energy metabolism, cell apoptosis, cell adhesion, exogenous microbial infection, and cell junction. The most strongly upregulated genes were cholecystokinin (CCK), cholecystokinin A receptor (CCKAR), and unc-80 homolog, NALCN activator (UNC80), and the most downregulated genes were glycine amidinotransferase (GATM), fatty acid desaturase 2 (FADS2), and hexokinase 2 (HKDC1). GO term with the highest enrichment of DEGs is nucleosome assembly. According to KEGG pathways, the three most significant metabolic pathways in the liver are DNA replication, retinol metabolism, and steroid biosynthesis. The results could be crucial for comprehending the negative biological impacts of egg-toxin and its toxic mechanisms. The outcome could provide potential biomarkers of egg-toxin exposure in hepatic, which might be useful for manufacturing an antidote to egg-toxin and providing valuable insights for ecotoxicity studies.

The Identification Distinct Antiviral Factors Regulated Influenza Pandemic H1N1 Infection

Influenza pandemic with H1N1 (H1N1pdms) causes severe lung damage and "cytokine storm," leading to higher mortality and global health emergencies in humans and animals. Explaining host antiviral molecular mechanisms in response to H1N1pdms is important for the development of novel therapies. In this study, we organised and analysed multimicroarray data for mouse lungs infected with different H1N1pdm and nonpandemic H1N1 strains. We found that H1N1pdms infection resulted in a large proportion of differentially expressed genes (DEGs) in the infected lungs compared with normal lungs, and the number of DEGs increased markedly with the time of infection. In addition, we found that different H1N1pdm strains induced similarly innate immune responses and the identified DEGs during H1N1pdms infection were functionally concentrated in defence response to virus, cytokine-mediated signalling pathway, regulation of innate immune response, and response to interferon. Moreover, comparing with nonpandemic H1N1, we identified ten distinct DEGs (AREG, CXCL13, GATM, GPR171, IFI35, IFI47, IFIT3, ORM1, RETNLA, and UBD), which were enriched in immune response and cell surface receptor signalling pathway as well as interacted with immune response-related dysregulated genes during H1N1pdms. Our discoveries will provide comprehensive insights into host responding to pandemic with influenza H1N1 and find broad-spectrum effective treatment.

Lactobacillus paracasei L9 affects disease progression in experimental autoimmune neuritis by regulating intestinal flora structure and arginine metabolism

BACKGROUND

Autoimmune neuropathies are common peripheral nervous system (PNS) disorders. Environmental influences and dietary components are known to affect the course of autoimmune diseases. Intestinal microorganisms can be dynamically regulated through diet, and this study combines intestinal microorganisms with diseases to open up new therapeutic ideas.

METHODS

In Lewis rats, a model of EAN was established with P0 peptide, Lactobacillus were used as treatment, serum T-cell ratio, inflammatory factors, sciatic neuropathological changes, and pathological inflammatory effects on intestinal mucosa were detected, and fecal metabolomics and 16 s microbiome analysis were performed to further explore the mechanism.

RESULTS

In the EAN rat model, Lactobacillus paracasei L9 (LP) could dynamically regulate the CD4⁺/CD8⁺T balance in serum, reduce serum IL-1, IL-6 and TNF-α expression levels, improve sciatic nerve demyelination and inflammatory infiltration, and reduce nervous system score. In the rat model of EAN, intestinal mucosa was damaged. Occludin and ZO-1 were downregulated. IL-1, TNF-α and Reg3γ were upregulated. LP gavage induced intestinal mucosa recovery; occludin and ZO-1 upregulation; IL-1, TNF-α and Reg3γ downregulation. Finally, metabolomics and 16 s microbiome analysis were performed, and differential metabolites were enriched with an important metabolic pathway, arginine and proline metabolism.

CONCLUSION

LP improved EAN in rats by influencing intestinal community and the lysine and proline metabolism.

Metabolism in type 2 immune responses

The immune response is tailored to the environment in which it takes place. Immune cells sense and adapt to changes in their surroundings, and it is now appreciated that in addition to cytokines made by stromal and epithelial cells, metabolic cues provide key adaptation signals. Changes in immune cell activation states are linked to changes in cellular metabolism that support function. Furthermore, metabolites themselves can signal between as well as within cells. Here, we discuss recent progress in our understanding of how metabolic regulation relates to type 2 immunity firstly by considering specifics of metabolism within type 2 immune cells and secondly by stressing how type 2 immune cells are integrated more broadly into the metabolism of the organism as a whole.