https://escholarship.org/content/qt3307p0k9/qt3307p0k9.pdf?t=q9i8ea

The Science and Translation of Lactate Shuttle Theory

Regulating the tumor microenvironment (TME) has been a promising strategy to improve antitumor therapy. Here, a red blood cell membrane (mRBC)-camouflaged hollow MnO2 (HMnO2 ) catalytic nanosystem embedded with lactate oxidase (LOX) and a glycolysis inhibitor (denoted as PMLR) is constructed for intra/extracellular lactic acid exhaustion as well as synergistic metabolic therapy and immunotherapy of tumor. Benefiting from the long-circulation property of the mRBC, the nanosystem can gradually accumulate in a tumor site through the enhanced permeability and retention (EPR) effect. The extracellular nanosystem consumes lactic acid in the TME by catalyzing its oxidation reaction via LOX. Meanwhile, the intracellular nanosystem releases the glycolysis inhibitor to cut off the source of lactic acid, as well as achieve antitumor metabolic therapy through the blockade of the adenosine triphosphate (ATP) supply. Both the extracellular and intracellular processes can be sensitized by O2 , which can be produced during the decomposition of endogenous H2 O2 catalyzed by the PMLR nanosystem. The results show that the PMLR nanosystem can ceaselessly remove lactic acid, and then lead to an immunocompetent TME. Moreover, this TME regulation strategy can effectively improve the antitumor effect of anti-PDL1 therapy without the employment of any immune agonists to avoid the autoimmunity.

Intra/Extracellular Lactic Acid Exhaustion for Synergistic Metabolic Therapy and Immunotherapy of Tumors

Cytokine-like Roles for Metabolites in Immunity

As an increased product of high-rate aerobic glycolysis in tumors, lactate could regulate the immunosuppressive tumor microenvironment (TME). A PEG-CDM surface modified, GSH-dependent responsive hollow mesoporous organosilica nanoplatform loaded with hydroxycamptothecin (HCPT) and siMCT-4 was administrated for synergistic tumor chemo-immunotherapy. The nanoplatform cascaded responded to the weak acid TME and the high level of GSH in tumor cells. HCPT and siMCT-4 were continuously released from the nanoplatform for chemotherapy and inhibiting intracellular lactate efflux. The increased intracellular lactate and HCPT effectively induced tumor cell apoptosis. Moreover, the decreased extracellular lactate polarized tumor-associated macrophages (TAMs) phenotype from M2 type to M1 type and restored CD8+ T cell activity in vivo. The results demonstrated that the nanoplatform effectively removed the immunosuppressive TME, inhibited tumor growth, and suppressed lung metastasis of B16F10 cells and 4T1 cells via the combination of inhibiting lactate efflux and chemotherapy. Accordingly, it suggested a strategy to transform immunosuppressive tumors into "hot" tumors and inhibit the tumor growth with high efficiency in vivo.

Engineering of Cascade-Responsive Nanoplatform to Inhibit Lactate Efflux for Enhanced Tumor Chemo-Immunotherapy.

Effective removal of pathogenic bacteria is key to improving the prognosis of sepsis. Polymorphonuclear neutrophils (PMNs) are the most important components of innate cellular immunity and play vital roles in clearing pathogenic bacteria. However, the metabolic characteristics and immunomodulatory pathways of PMNs during sepsis have not been investigated. In the present study, we explored the immune metabolism characteristics of PMNs and the mechanism by which neutrophilic glycolysis is regulated during sepsis.Metabolomics analysis was performed on PMNs isolated from 14 septic patients, 26 patients with acute appendicitis, and 19 healthy volunteers. Transcriptome analysis was performed on the PMNs isolated from the healthy volunteers and the patients with sepsis to assess glycolysis and investigate its mechanism. Lipopolysaccharide (LPS) was used to stimulate the neutrophils isolated from the healthy volunteers at different time intervals to build an LPS-tolerant model. Chemotaxis, phagocytosis, lactate production, oxygen consumption rate (OCR), and extracellular acidification rate (ECAR) were evaluated.Transcriptomics showed significant changes in glycolysis and the mTOR/HIF-1α signaling pathway during sepsis. Metabolomics revealed that the Warburg effect was significantly altered in the patients with sepsis. We discovered that glycolysis regulated PMNs' chemotaxis and phagocytosis functions during sepsis. Lactate dehydrogenase A (LDHA) downregulation was a key factor in the inhibition of glycolysis in PMNs. This study confirmed that the PI3K/Akt-HIF-1α pathway was involved in the LDHA expression level and also influenced PMNs' chemotaxis and phagocytosis functions.The inhibition of glycolysis contributed to neutrophil immunosuppression during sepsis and might be controlled by PI3K/Akt-HIF-1α pathway-mediated LDHA downregulation. Our study provides a scientific theoretical basis for the management and treatment of patients with sepsis and promotes to identify therapeutic target for the improvement of immune function in sepsis. 

/pdf/immune-effects-of-pi3k-akt-hif-1a-regulated-glycolysis-in-3lcsb3ch.pdf

Immune effects of PI3K/Akt/HIF-1α-regulated glycolysis in polymorphonuclear neutrophils during sepsis

Serum lactate levels are traditionally interpreted as a marker of tissue hypoxia and often used clinically as an indicator of severity and outcome of sepsis/septic shock. Interestingly, recent studies involving the effects of tumor-derived lactate suggest that lactate itself may have an immunosuppressive effect in its local environment. This finding adds to the recent advances in immunometabolism that shed light on the importance of metabolism and metabolic intermediates in the regulation of innate immune and inflammatory responses in sepsis. In this article, we summarize recent studies, showing that the activation of immune cells requires aerobic glycolytic metabolism and that lactate produced by aerobic glycolysis may play an immunosuppressive role in sepsis.

Lactate and Immunosuppression in Sepsis.

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Lactate and Immunosuppression in Sepsis.