Iron regulatory protein 2 contributes to antimicrobial immunity by preserving lysosomal function in macrophages.

Colorectal cancer and Crohn's disease patients develop pyogenic liver abscesses due to failures of immune cells to fight off bacterial infections. Here, we show that mice lacking iron regulatory protein 2 (Irp2), globally (Irp2-/-) or myeloid cell lineage (Lysozyme 2 promoter-driven, LysM)-specifically (Irp2ΔLysM), are highly susceptible to liver abscesses when the intestinal tissue was injured with dextran sodium sulfate treatment. Further studies demonstrated that Irp2 is required for lysosomal acidification and biogenesis, both of which are crucial for bacterial clearance. In Irp2-deficient liver tissue or macrophages, the nuclear location of transcription factor EB (Tfeb) was remarkably reduced, leading to the downregulation of Tfeb target genes that encode critical components for lysosomal biogenesis. Tfeb mislocalization was reversed by hypoxia-inducible factor 2 inhibitor PT2385 and, independently, through inhibition of lactic acid production. These experimental findings were confirmed clinically in patients with Crohn's disease and through bioinformatic searches in databases from Crohn's disease or ulcerative colitis biopsies showing loss of IRP2 and transcription factor EB (TFEB)-dependent lysosomal gene expression. Overall, our study highlights a mechanism whereby Irp2 supports nuclear translocation of Tfeb and lysosomal function, preserving macrophage antimicrobial activity and protecting the liver against invading bacteria during intestinal inflammation.

Lactic acid promotes nucleus pulposus cell senescence and corresponding intervertebral disc degeneration via interacting with Akt.

The accumulation of metabolites in the intervertebral disc is considered an important cause of intervertebral disc degeneration (IVDD). Lactic acid, which is a metabolite that is produced by cellular anaerobic glycolysis, has been proven to be closely associated with IVDD. However, little is known about the role of lactic acid in nucleus pulposus cells (NPCs) senescence and oxidative stress. The aim of this study was to investigate the effect of lactic acid on NPCs senescence and oxidative stress as well as the underlying mechanism. A puncture-induced disc degeneration (PIDD) model was established in rats. Metabolomics analysis revealed that lactic acid levels were significantly increased in degenerated intervertebral discs. Elimination of excessive lactic acid using a lactate oxidase (LOx)-overexpressing lentivirus alleviated the progression of IVDD. In vitro experiments showed that high concentrations of lactic acid could induce senescence and oxidative stress in NPCs. High-throughput RNA sequencing results and bioinformatic analysis demonstrated that the induction of NPCs senescence and oxidative stress by lactic acid may be related to the PI3K/Akt signaling pathway. Further study verified that high concentrations of lactic acid could induce NPCs senescence and oxidative stress by interacting with Akt and regulating its downstream Akt/p21/p27/cyclin D1 and Akt/Nrf2/HO-1 pathways. Utilizing molecular docking, site-directed mutation and microscale thermophoresis assays, we found that lactic acid could regulate Akt kinase activity by binding to the Lys39 and Leu52 residues in the PH domain of Akt. These results highlight the involvement of lactic acid in NPCs senescence and oxidative stress, and lactic acid may become a novel potential therapeutic target for the treatment of IVDD.

Metabolic Regulation-Mediated Reversion of the Tumor Immunosuppressive Microenvironment for Potentiating Cooperative Metabolic Therapy and Immunotherapy.

Tumor cells exhibit heightened glucose (Glu) consumption and increased lactic acid (LA) production, resulting in the formation of an immunosuppressive tumor microenvironment (TME) that facilitates malignant proliferation and metastasis. In this study, we meticulously engineer an antitumor nanoplatform, denoted as ZLGCR, by incorporating glucose oxidase, LA oxidase, and CpG oligodeoxynucleotide into zeolitic imidazolate framework-8 that is camouflaged with a red blood cell membrane. Significantly, ZLGCR-mediated consumption of Glu and LA not only amplifies the effectiveness of metabolic therapy but also reverses the immunosuppressive TME, thereby enhancing the therapeutic outcomes of CpG-mediated antitumor immunotherapy. It is particularly important that the synergistic effect of metabolic therapy and immunotherapy is further augmented when combined with immune checkpoint blockade therapy. Consequently, this engineered antitumor nanoplatform will achieve a cooperative tumor-suppressive outcome through the modulation of metabolism and immune responses within the TME.

Lactic acid regulates lipid droplet aggregation through a microglia-neuron axis in neuroinflammation.

Neuroinflammation, marked by the release of proinflammatory cytokines and resulting neuronal death, is a multifaceted process extending beyond traditional inflammatory pathways. Microglia, primary cells in the inflammatory response, rapidly activate during neuroinflammation and produce proinflammatory and cytotoxic factors that affect neuronal function. Recent evidence highlights the significant role of abnormal lipid droplet (LD) deposition in the pathogenesis of neuroinflammation. While microglia are known to influence LD aggregation during neuroinflammation, the regulatory mechanism within neurons is not well understood. Our study demonstrates that lipopolysaccharide-activated microglia induce the accumulation of LD in neurons, identifying microglial-derived lactic acid as a key mediator in this process. Excessive lipid accumulation threatens neuronal function, a phenomenon reversed by eliminating microglia. Our study demonstrates that lipopolysaccharide-activated microglia induce the accumulation of LD in neurons, identifying microglial-derived lactic acid as a key mediator in this process. Excessive lipid accumulation threatens neuronal function, a phenomenon reversed by eliminating microglia.

Acidity promotes the differentiation of immunosuppressive regulatory T cells.

The metabolic milieu is emerging as a major contributing factor in the maintenance of the immunosuppressive microenvironment within tumors. In particular, the presence of lactic acid produced by highly glycolytic cancer cells is known to suppress antitumor immune cell subsets while promoting immunosuppressive cell populations, such as regulatory T cells (Tregs). Unlike conventional T cells, Tregs have a unique, potent ability to take up lactic acid to fuel both mitochondrial metabolism and gluconeogenesis, thus supporting suppressive function and proliferation. In this issue of the European Journal of Immunology [Eur. J. Immunol. 2023.53:2250258], Rao et al. uncover a novel mechanism by which lactic acid can support Treg accumulation within tumors in mice. This study shows that lactic acid, through a pH-dependent mechanism rather than lactate itself, promotes TGFß-induced differentiation of Tregs from conventional CD4+ T cells. These findings build on the already multifaceted role of lactic acid in maintaining an immunosuppressive tumor microenvironment.

Acidity-mediated induction of FoxP3+ regulatory T cells.

Glucose limitation and increased lactic acid levels are consequences of the elevated glycolytic activity of tumor cells, and constitute a metabolic barrier for the function of tumor infiltrating effector immune cells. The immune-suppressive functions of regulatory T cells (Tregs) are unobstructed in lactic-acid rich environments. However, the impact of lactic acid on the induction of Tregs remains unknown. We observed increased TGFß-mediated induction of Forkhead box P3+ (FoxP3+ ) cells in the presence of extracellular lactic acid, in a glycolysis-independent, acidity-dependent manner. These CD4+ FoxP3+ cells expressed Treg-associated markers, including increased expression of CD39, and were capable of exerting suppressive functions. Corroborating these results in vivo, we observed that neutralizing the tumor pH by systemic administration of sodium bicarbonate (NaBi) decreased Treg abundance. We conclude that acidity augments Treg induction and propose that therapeutic targeting of acidity in the tumor microenvironment (TME) might reduce Treg-mediated immune suppression within tumors.

Effects of temperature and lactic acid Bacteria additives on the quality and microbial community of wilted alfalfa silage.

This study investigated the influence of different temperatures (35℃ High temperature and average indoor ambient temperature of 25℃) and lactic acid bacterial additives (Lactiplantibacillus plantarym, Lentilactobacillus buchneri, or a combination of Lactiplantibacillus plantarym and Lentilactobacillus buchneri) on the chemical composition, fermentation quality, and microbial community of alfalfa silage feed. After a 60-day ensiling period, a significant interaction between temperature and additives was observed, affecting the dry matter (DM), crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) of the silage feed (p < 0.05). Temperature had a highly significant impact on the pH value of the silage feed (p < 0.0001). However, the effect of temperature on lactic acid, acetic acid, propionic acid, and butyric acid was not significant (p > 0.05), while the inoculation of additives had a significant effect on lactic acid, acetic acid, and butyric acid (p > 0.05). As for the dynamic changes of microbial community after silage, the addition of three kinds of bacteria increased the abundance of lactobacillus. Among all treatment groups, the treatment group using complex bacteria had the best fermentation effect, indicating that the effect of complex lactic acid bacteria was better than that of single bacteria in high temperature fermentation. In summary, this study explained the effects of different temperatures and lactic acid bacterial additives on alfalfa fermentation quality and microbial community, and improved our understanding of the mechanism of alfalfa related silage at high temperatures.

Genomics-based analysis of four porcine-derived lactic acid bacteria strains and their evaluation as potential probiotics.

The search for probiotics and exploration of their functions are crucial for livestock farming. Recently, porcine-derived lactic acid bacteria (LAB) have shown great potential as probiotics. However, research on the evaluation of porcine-derived LAB as potential probiotics through genomics-based analysis is relatively limited. The present study analyzed four porcine-derived LAB strains (Lactobacillus johnsonii L16, Latilactobacillus curvatus ZHA1, Ligilactobacillus salivarius ZSA5 and Ligilactobacillus animalis ZSB1) using genomic techniques and combined with in vitro tests to evaluate their potential as probiotics. The genome sizes of the four strains ranged from 1,897,301 bp to 2,318,470 bp with the GC contents from 33.03 to 41.97%. Pan-genomic analysis and collinearity analysis indicated differences among the genomes of four strains. Carbohydrate active enzymes analysis revealed that L. johnsonii L16 encoded more carbohydrate active enzymes than other strains. KEGG pathway analysis and in vitro tests confirmed that L. johnsonii L16 could utilize a wide range of carbohydrates and had good utilization capacity for each carbohydrate. The four strains had genes related to acid tolerance and were tolerant to low pH, with L. johnsonii L16 showing the greatest tolerance. The four strains contained genes related to bile salt tolerance and were able to tolerate 0.1% bile salt. Four strains had antioxidant related genes and exhibited antioxidant activity in in vitro tests. They contained the genes linked with organic acid biosynthesis and exhibited antibacterial activity against enterotoxigenic Escherichia coli K88 (ETEC K88) and Salmonella 6,7:c:1,5, wherein, L. johnsonii L16 and L. salivarius ZSA5 had gene clusters encoding bacteriocin. Results suggest that genome analysis combined with in vitro tests is an effective approach for evaluating different strains as probiotics. The findings of this study indicate that L. johnsonii L16 has the potential as a probiotic strain among the four strains and provide theoretical basis for the development of probiotics in swine production.

Comparative genomics of four lactic acid bacteria identified with Vitek MS (MALDI-TOF) and whole-genome sequencing.

Lactic acid bacteria (LAB) can be used as a probiotic or starter culture in dairy, meat, and vegetable fermentation. Therefore, their isolation and identification are essential. Recent advances in omics technologies and high-throughput sequencing have made the identification and characterization of bacteria. This study firstly aimed to demonstrate the sensitivity of the Vitek MS (MALDI-TOF) system in the identification of lactic acid bacteria and, secondly, to characterize bacteria using various bioinformatics approaches. Probiotic potency-related genes and secondary metabolite biosynthesis gene clusters were examined. The Vitek MS (MALDI-TOF) system was able to identify all of the bacteria at the genus level. According to whole genome sequencing, the bacteria were confirmed to be Lentilactobacillus buchneri, Levilactobacillus brevis, Lactiplantibacillus plantarum, Levilactobacillus namurensis. Bacteria had most of the probiotic potency-related genes, and different toxin-antitoxin systems such as PemIK/MazEF, Hig A/B, YdcE/YdcD, YefM/YoeB. Also, some of the secondary metabolite biosynthesis gene clusters, some toxic metabolite-related genes, and antibiotic resistance-related genes were detected. In addition, Lentilactobacillus buchneri Egmn17 had a type II-A CRISPR/Cas system. Lactiplantibacillus plantarum Gmze16 had a bacteriocin, plantaricin E/F.

Selective Electrooxidation of Crude Glycerol to Lactic Acid Coupled With Hydrogen Production at Industrially-Relevant Current Density.

Transforming glycerol (GLY, biodiesel by-product) into lactic acid (LA, biodegradable polymer monomer) through sustainable electrocatalysis presents an effective strategy to reduce biodiesel production costs and consequently enhance its applications. However, current research faces a trade-off between achieving industrially-relevant current density (>300 mA cm-2) and high LA selectivity (>80%), limiting technological advancement. Herein, a Au3Ag1 alloy electrocatalyst is developed that demonstrates exceptional LA selectivity (85%) under high current density (>400 mA cm-2). The current density can further reach 1022 mA cm-2 at 1.2 V versus RHE, superior to most previous reports for GLY electrooxidation. It is revealed that the Au3Ag1 alloy can enhance GLY adsorption and reactive oxygen species (OH*) generation, thereby significantly boosting activity. As a proof of concept, a homemade flow electrolyzer is constructed, achieving remarkable LA productivity of 68.9 mmol h-1 at the anode, coupled with efficient H2 production of 3.5 L h-1 at the cathode. To further unveil the practical possibilities of this technology, crude GLY extracted from peanut oil into LA is successfully transformed, while simultaneously producing H2 at the cathode. This work showcases a sustainable method for converting biodiesel waste into high-value products and hydrogen fuel, promoting the broader application of biodiesel.