Lactate-Driven HMGB1 Modification and Exosomal Release in Sepsis

Study Background and Research Question

Sepsis represents a critical challenge in medicine, characterized by a dysregulated host response to infection leading to organ dysfunction and high mortality. Elevated serum lactate serves as both a prognostic biomarker and a diagnostic criterion for septic shock, as persistently high lactate levels correlate with poor outcomes. Parallel to this, high mobility group box 1 (HMGB1), a nuclear protein released by activated macrophages, has emerged as a key mediator of sepsis severity. Although clinical correlations between serum lactate and HMGB1 levels had been established, the mechanistic basis by which lactate might actively drive HMGB1 release during sepsis was unclear (reference paper).

Key Innovation from the Reference Study

The study by Yang et al. provides the first direct evidence that extracellular lactate, taken up by macrophages, catalyzes both lactylation and acetylation of HMGB1. These post-translational modifications facilitate HMGB1 translocation from the nucleus and its subsequent release in exosomes—a mechanism newly linked to increased endothelial permeability in sepsis. The work uncovers two converging molecular routes: one involving p300/CBP-dependent lactylation via monocarboxylate transporter (MCT) uptake of lactate, and another involving Hippo/YAP suppression of SIRT1 and β-arrestin2-facilitated nuclear recruitment of acetylases through GPR81 signaling. Collectively, these findings reposition lactate from a mere metabolic byproduct to a central signaling molecule in the inflammatory cascade (reference paper).

Methods and Experimental Design Insights

The research employed a spectrum of in vitro and in vivo models to dissect the molecular details of lactate-driven HMGB1 release. Key approaches included:

• Use of peritoneal macrophages from wild-type and genetically engineered mice (notably, macrophage-specific YAP knockout via Cre/LoxP system) to parse the role of Hippo/YAP signaling.
• Pharmacological manipulation of lactate production and GPR81-mediated signaling using small molecules and receptor antagonists.
• Quantification of HMGB1 post-translational modifications by immunoprecipitation and mass spectrometry, focusing on lysine lactylation and acetylation.
• Isolation and characterization of exosomes from murine serum and macrophage supernatants to measure exosomal HMGB1 content.
• Functional assays assessing endothelial permeability in response to exosome exposure.

The study also included correlative analyses between blood lactate and HMGB1 levels in both murine sepsis models and published clinical datasets, strengthening translational relevance (reference paper).

Core Findings and Why They Matter

• Lactate Uptake and HMGB1 Modification: Macrophages actively transport extracellular lactate via MCTs, which is then used by p300/CBP to lactylate HMGB1. This lactylation, alongside acetylation (driven by Hippo/YAP and GPR81/β-arrestin2 pathways), is crucial for nuclear export of HMGB1.
• Exosomal HMGB1 Release: The lactylated and acetylated forms of HMGB1 are preferentially packaged into exosomes and released into circulation, directly correlating with increased endothelial permeability—a hallmark of sepsis-induced organ dysfunction.
• Targetability: Pharmacological inhibition of lactate production or GPR81 signaling substantially reduced circulating exosomal HMGB1 and improved survival in septic mice, suggesting actionable intervention points (reference paper).

These findings clarify how metabolic signals (lactate) and immune pathways intersect to escalate inflammatory responses in sepsis, with HMGB1 acting as a critical effector. Understanding this crosstalk opens new research avenues for modulating cytokine release and vascular leakage.

Comparison with Existing Internal Articles

Several recent internal articles have addressed the molecular landscape of NLRP3 inflammasome activation, cytokine signaling, and their intersection with advanced research tools such as NBC19. For instance, the article "NBC19: Precision NLRP3 Inflammasome Inhibitor for Inflammation Research" details how NBC19 enables precise dissection of IL-1β release and inflammasome-driven cytokine cascades, including those relevant to lactate-induced HMGB1 release (internal article). Another synthesis, "Rewiring Inflammation Research: NBC19 and the Next Wave of Discovery," explicitly connects NBC19’s utility to workflows investigating lactate-driven mechanisms in sepsis models, offering experimental guidance for targeting inflammasome and downstream cytokine output (internal article). While these internal resources focus on the role of NLRP3 and its inhibition in experimental models, the reference paper expands the mechanistic map by linking metabolic (lactate) and immune (HMGB1) axes. The convergence of these insights supports the development of multi-modal approaches for studying and modulating inflammation.

Limitations and Transferability

The study’s primary strength lies in its mechanistic depth, but several limitations should be noted:

• Animal models, while informative, may not fully recapitulate complex human sepsis pathophysiology.
• Pharmacological inhibitors used in vivo may lack the specificity or pharmacokinetics required for clinical translation.
• The interplay between lactate-driven HMGB1 release and other inflammasome components (such as NLRP3) remains to be fully mapped in both acute and chronic inflammation settings.

Nevertheless, the experimental systems and molecular readouts described are transferable to a broad range of inflammation research protocols, especially those leveraging advanced small molecule tools.

Protocol Parameters

• HMGB1 lactylation assay | 1–5 mM lactate | validated in murine macrophages | recapitulates sepsis-relevant metabolic concentrations | reference_paper
• GPR81 inhibition | 10–50 μM specific antagonist | murine sepsis models | reduces exosomal HMGB1 and improves survival | reference_paper
• IL-1β release inhibition (NBC19) | 60–80 nM in THP1 cells | human macrophage models | robust suppression of nigericin/ATP-induced inflammasome activation | product_spec
• Endothelial permeability assay | 10–50 μg/mL exosomal HMGB1 | endothelial monolayer | models vascular leakage in sepsis | reference_paper
• NLRP3 inflammasome inhibition (NBC19) | 60 nM IC50 | applicable to inflammasome-driven cytokine studies | allows mechanistic dissection of IL-1β/IL-18 pathways | product_spec

Research Support Resources

Researchers investigating lactate/HMGB1 signaling, inflammasome activation, or exosome-mediated cytokine release can leverage specialized small molecules to enhance experimental precision. NBC19 (SKU BA6129) is a highly selective NLRP3 inflammasome inhibitor validated for robust IL-1β release inhibition in differentiated THP1 cells and compatible with protocols dissecting nigericin- and ATP-induced inflammasome activation (workflow_recommendation). For optimal results, solutions should be prepared fresh and stored as recommended by APExBIO to maintain compound activity. This tool is particularly valuable for studies seeking to parse the interplay between metabolic triggers and innate immune signaling in sepsis and related inflammatory contexts.