LRPPRC Induces Neutrophil Immune Tolerance in Sepsis Through Differential Regulation of mt-mRNAs

Introduction: Mitochondrial dysfunction is a pivotal mechanism driving the transition from acute inflammation to persistent organ injury and immune dysregulation in sepsis, with OXPHOS impairment being a primary cause. LRPPRC, a critical regulator of mt-mRNA levels and stability, has unknown kinetics and clinical significance in sepsis.


Methods: We performed RNA-seq on PBMCs from healthy volunteers (HVs), sepsis patients, and non-septic ICU patients on days 1, 3, and 7 of ICU admission, with 6-month survival follow-up. 4D-FastDIA proteomics analyzed mitochondrial protein expression. Purified ND6 protein was injected into mice to evaluate its impact on inflammation, immune tolerance, and resistance to secondary infection. LNP-encapsulated LRPPRC mRNA was administered intravenously to CLP mice to assess effects on cytokine storm, immune tolerance, and survival.


Results: Multiple mt-mRNAs were downregulated in sepsis PBMCs ≥1 week, correlating with mitochondrial dysfunction; subsequent upregulation signaled treatment response. mt-mRNA patterns better distinguished sepsis patients from HVs/non-septic ICU patients and predicted 6-month survival. ND6 was the sole upregulated mt-DNA-encoded protein in PBMCs and plasma, correlating with neutrophil exhaustion, secondary infections, and mortality. LPS-stimulated monocytes showed downregulation of all mt-proteins except ND6. LRPPRC downregulation (critical for mt-mRNA stability/translation) was proved as the primary causative factor. LRPPRC KO cells exhibited impairing OXPHOS complexes I/V assembly, causing mitochondrial damage (swelling, cristae loss), and triggering ND6 leakage, which inducing neutrophil ROS burst, FPR1 internalization, impaired migration, and formyl peptide tolerance. Mice receiving ND6 developed transient inflammation and profound neutrophil tolerance, exacerbating P. aeruginosa-induced lung injury/mortality. LNP-LRPPRC mRNA therapy restored mitochondrial function, reduced plasma ND6, prolonged survival, and attenuated lung injury/mortality post-secondary P. aeruginosa infection.


Conclusions: LRPPRC downregulation is a key driver of mitochondrial dysfunction in sepsis patient PBMCs. The consequent aberrant increase in plasma ND6 induces neutrophil immune tolerance, increasing susceptibility to secondary infections and reducing survival.