Tissue-specific macrophage immunometabolism

Thiamine deficiency aggravates experimental colitis in mice by promoting glycolytic reprogramming in macrophages

BACKGROUND AND PURPOSE

Inflammatory bowel disease (IBD) is closely associated with immune dysfunction, where nutrient-mediated metabolic flux dictates immune cell fate and function. Thiamine is a central water-soluble vitamin involved in cellular energy metabolism, and its deficiency has been reported in IBD patients. However, whether thiamine deficiency is a cause or consequence of IBD pathogenesis remains unclear. The current study aimed to reveal the immunometabolic regulation of macrophages and underlying mechanism of thiamine deficiency in colitis development.

EXPERIMENTAL APPROACH

Thiamine deficiency was induced in C57BL/6 mice and bone marrow-derived macrophages (BMDMs), by administering a thiamine-deficient diet/medium together with pyrithiamine hydrobromide. The frequency of macrophage phenotypes and their intracellular metabolism were detected using flow cytometry and non-targeted metabolomics, respectively.

KEY RESULTS

Thiamine deficiency aggravated ulcerative colitis in mice and promoted the infiltration of proinflammatory M1 macrophages in colonic lamina propria. Our mechanistic study revealed that thiamine deficiency impaired pyruvate dehydrogenase (PDH) activity, thereby reprogramming cellular glucose metabolism to enhance glycolysis and lactic acid accumulation in M1 macrophages. Using a well-established PDH inhibitor (CPI-613) and lactic acid dehydrogenase inhibitor (galloflavin), we further demonstrated that PDH inhibition mimics, while lactate dehydrogenase inhibition partially rescues, thiamine deficiency-induced proinflammatory macrophage infiltration and experimental colitis in mice.

CONCLUSION AND IMPLICATIONS

Our study provides evidence linking thiamine deficiency with proinflammatory macrophage activation and colitis aggravation, suggesting that monitoring thiamine status and adjusting thiamine intake is necessary to protect against colitis.

Extracellular vesicles in tumor immunity: mechanisms and novel insights

Extracellular vesicles (EVs), nanoscale vesicles secreted by cells, have attracted considerable attention in recent years due to their role in tumor immunomodulation. These vesicles facilitate intercellular communication by transporting proteins, nucleic acids, and other biologically active substances, and they exhibit a dual role in tumor development and immune evasion mechanisms. Specifically, EVs can assist tumor cells in evading immune surveillance and attack by impairing immune cell function or modulating immunosuppressive pathways, thereby promoting tumor progression and metastasis. Conversely, they can also transport and release immunomodulatory factors that stimulate the activation and regulation of the immune system, enhancing the body's capacity to combat malignant diseases. This dual functionality of EVs presents promising avenues and targets for tumor immunotherapy. By examining the biological characteristics of EVs and their influence on tumor immunity, novel therapeutic strategies can be developed to improve the efficacy and relevance of cancer treatment. This review delineates the complex role of EVs in tumor immunomodulation and explores their potential implications for cancer therapeutic approaches, aiming to establish a theoretical foundation and provide practical insights for the advancement of future EVs-based cancer immunotherapy strategies.

Surface Molecularly Engineered Mitochondria Conduct Immunophenotype Repolarization of Tumor-Associated Macrophages to Potentiate Cancer Immunotherapy

Reprogramming tumor-associated macrophages (TAMs) to an inflammatory phenotype effectively increases the potential of immune checkpoint blockade (ICB) therapy. Artificial mitochondrial transplantation, an emerging and safe strategy, has made brilliant achievements in regulating the function of recipient cells in preclinic and clinic, but its performance in reprogramming the immunophenotype of TAMs has not been reported. Here, the metabolism of M2 TAMs is proposed resetting from oxidative phosphorylation (OXPHOS) to glycolysis for polarizing M1 TAMs through targeted transplantation of mannosylated mitochondria (mPEI/M1mt). Mitochondria isolated from M1 macrophages are coated with mannosylated polyethyleneimine (mPEI) through electrostatic interaction to form mPEI/M1mt, which can be targeted uptake by M2 macrophages expressed a high level of mannose receptors. Mechanistically, mPEI/M1mt accelerates phosphorylation of NF-κB p65, MAPK p38 and JNK by glycolysis-mediated elevation of intracellular ROS, thus prompting M1 macrophage polarization. In vivo, the transplantation of mPEI/M1mt excellently potentiates therapeutic effects of anti-PD-L1 by resetting an antitumor proinflammatory tumor microenvironment and stimulating CD8 and CD4 T cells dependent immune response. Altogether, this work provides a novel platform for improving cancer immunotherapy, meanwhile, broadens the scope of mitochondrial transplantation technology in clinics in the future.