CD177+ Neutrophils Drive Lung Transplant Injury — and a Mitochondrial Drug Can Stop Them
Scientists pinpoint a hyperactivated neutrophil subtype fueling lung transplant damage and show a mitochondrial inhibitor can block it.
Summary
Lung transplant failure within the first 72 hours — called primary graft dysfunction (PGD) — kills thousands of patients yearly. Researchers used single-cell RNA sequencing and spatial transcriptomics in mouse models to identify CD177+ neutrophils as the key inflammatory culprit. These cells show abnormally high mitochondrial complex I activity driving oxidative phosphorylation, ROS production, and neutrophil extracellular trap (NET) formation. In human lung transplant recipients, a rise in blood CD177+ neutrophils within 4 hours post-transplant strongly predicted severe PGD (AUC=0.871). Blocking mitochondrial complex I with the drug IACS-010759 significantly reduced lung injury in both mouse and rat transplant models, opening a realistic path toward early diagnosis and targeted treatment of this devastating complication.
Detailed Summary
Primary graft dysfunction (PGD) complicates 15–25% of lung transplants and is the leading cause of early death, graft failure, and chronic rejection. Despite its clinical importance, the precise immune mechanisms driving PGD have remained poorly understood — particularly which neutrophil subpopulations are responsible and how they cause damage at the molecular level.
Using left hilar-clamp mouse ischemia-reperfusion injury (IRI) models alongside single-cell RNA sequencing (scRNA-seq) of 43,852 immune cells and spatial transcriptomics (Stereo-seq), the researchers mapped the full immune landscape of injured lungs. Among five transcriptionally distinct lung-associated neutrophil (LAN) subtypes identified, LAN3 — defined by high Cd177, Ltf, and Camp expression — was dramatically expanded in IRI lungs. LAN3 cells showed the highest degranulation scores, superoxide generation activity, and cell-killing capacity. CD177 expression was nearly exclusive to this neutrophil subpopulation and absent from other immune cells.
Mechanistically, CD177 was found to form a complex with MAC-1 (integrin αMβ2), engaging integrin-linked kinase (ILK) to activate the AKT/mTOR signaling pathway. This cascade upregulated mitochondrial complex I gene expression and elevated oxidative phosphorylation (OXPHOS), fueling ROS overproduction and NET formation — two major mechanisms of tissue destruction in IRI. Functional proteomics confirmed significantly increased mitochondrial complex I activity specifically in CD177+ neutrophils compared to CD177− counterparts.
In a prospective human cohort of lung transplant recipients, blood CD177+ neutrophil levels rose sharply within 4 hours post-transplantation. The delta between post- and pre-transplant CD177+ neutrophil proportions achieved an AUC of 0.871 for predicting grade 3 PGD — the most severe form — outperforming existing early biomarkers. This positions blood CD177+ neutrophil monitoring as a clinically actionable early warning tool.
Therapeutically, treatment with IACS-010759 (IACS), a selective mitochondrial complex I inhibitor administered at 1 mg/kg, significantly reduced CD177+ neutrophil activation, NET formation, and lung injury severity in both the mouse IRI model and a rat left lung transplant model. These findings validate mitochondrial complex I as a druggable target in post-transplant lung inflammation. Caveats include the reliance on animal models for therapeutic testing, the relatively small human cohort, and the need for further investigation into IACS-010759's safety profile in immunocompromised transplant patients.
Key Findings
- CD177+ neutrophils (LAN3) are the dominant pathogenic immune subset in lung ischemia-reperfusion injury.
- CD177/MAC-1 activates AKT/mTOR signaling, upregulating mitochondrial complex I and driving OXPHOS and ROS production.
- Blood CD177+ neutrophil rise at 4 hours post-transplant predicts severe PGD with AUC=0.871 in human recipients.
- Mitochondrial complex I inhibitor IACS-010759 reduces CD177+ neutrophil activation and alleviates lung injury in mouse and rat models.
- CD177+ neutrophils show the highest degranulation capacity and NET formation among all lung neutrophil subtypes.
Methodology
The study combined scRNA-seq (43,852 immune cells from mouse lung IRI and sham models) with spatial transcriptomics (Stereo-seq) to map neutrophil heterogeneity. Human validation used flow cytometry and a prospective cohort of lung transplant recipients, while therapeutic efficacy was tested in both mouse IRI and rat left lung transplant models using the mitochondrial complex I inhibitor IACS-010759.
Study Limitations
Human cohort for biomarker validation was relatively small, limiting generalizability of the AUC findings. Therapeutic experiments relied on animal models, and the safety, dosing, and systemic effects of IACS-010759 in immunosuppressed human transplant recipients have not yet been established. The study does not fully resolve whether CD177 expression is causal or consequential of neutrophil hyperactivation.
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