Understanding how neutrophil signaling pathways disrupt the human intestinal barrier

The intestinal mucosal barrier separates the host from the gut lumen and is essential for systemic homeostasis. Ischemia-reperfusion (IR) injury, common in severe shock, major surgery, and burns, rapidly damages this barrier, allowing bacterial translocation, systemic inflammation, and multiple organ dysfunction. Intestinal epithelial cells (IECs) are highly vulnerable to apoptosis, but how infiltrating immune cells directly trigger their death remains unclear. Neutrophils arrive early and can injure the mucosa through reactive oxygen species (ROS), cytokines, proteases, and neutrophil extracellular traps (NETs), yet direct ligand-receptor signals to IECs are poorly defined. Given these challenges, further investigation is needed into how neutrophils directly communicate with IECs during early IR injury.

Researchers at the Affiliated Huaihai Hospital of Xuzhou Medical University and the 71st Group Army Hospital of the People's Liberation Army (PLA), China, published (DOI: 10.1093/burnst/tkag059) the study in Burns & Trauma on 02 September 2026. Supported by the National Natural Science Foundation of China (82302798) and other grants, the team combined a mouse IR model, single-cell RNA sequencing (scRNA-seq), neutrophil-specific Thbs1 knockout mice, and inhibitors or agonists of CD36 (cluster of differentiation 36) and c-Jun N-terminal kinase (JNK) to test the thrombospondin-1 (THBS1)-CD36-JNK axis.

In mice subjected to 45 min ischemia and 3 h reperfusion, scRNA-seq and CellChat analysis identified Thbs1-Cd36 as a significantly upregulated neutrophil-to-IEC ligand-receptor pair. Immunofluorescence and co-immunoprecipitation (co-IP) confirmed that neutrophil THBS1 interacts with epithelial CD36. Neutrophil-specific Thbs1 deletion reduced epithelial apoptosis, preserved occludin, and lessened edema, mucosal damage, and inflammation. Purified THBS1 alone impaired IEC viability and barrier protein expression. CD36 inhibition with sulfosuccinimidyl oleate (SSO) was protective, while the CD36 agonist oxidized low-density lipoprotein (oxLDL) reversed protection in Thbs1 knockout mice.

Mechanistically, CD36 activation increased phosphorylated JNK (p-JNK), which appeared in IECs as early as 5 min after reperfusion, before terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive apoptosis at 30 min. The JNK inhibitor SP600125 also reduced epithelial death. CD36 or JNK inhibition produced comparable protection, and CD36 activation restored JNK phosphorylation and injury in the knockout background. The epithelial specificity of p-JNK and TUNEL signals was confirmed by co-staining with E-cadherin. Human data showed neutrophil enrichment, and MAFK (v-maf musculoaponeurotic fibrosarcoma oncogene homolog K) was predicted as a possible upstream regulator of Thbs1. These results support a model in which THBS1 is the neutrophil ligand, CD36 is the epithelial receptor, and JNK is the downstream mediator of IEC apoptosis.

The authors said the results help explain how neutrophils can affect epithelial cells through a specific ligand-receptor interaction, not only through broader inflammation. They said blocking CD36 or JNK reduced injury in the mouse model, while activating CD36 reversed the effect of Thbs1 deletion. They said the pathway may be worth testing as a target, but more work is needed to assess safety and timing in patients. They said future studies should also examine whether MAFK regulates Thbs1 in neutrophils.

In severe burns, shock, major surgery, and intestinal transplantation, barrier failure can trigger bacterial translocation, systemic inflammation, and multiple organ dysfunction. The findings suggest that neutralizing THBS1, inhibiting CD36, or blocking JNK could protect the mucosa during early IR injury. Future strategies should selectively target the neutrophil-epithelial axis while preserving THBS1 repair functions mediated by other receptors. Such approaches would need careful timing to avoid interfering with later mucosal repair. The authors also highlight MAFK as a possible upstream regulator of Thbs1, although this requires further validation.