Precision engineered peptide targeting leukocyte extracellular traps mitigate acute kidney injury in Crush syndrome.

Crush syndrome induced by skeletal muscle compression causes fatal rhabdomyolysis-induced acute kidney injury (RIAKI) that requires intensive care, including hemodialysis. However, access to crucial medical supplies is highly limited while treating earthquake victims trapped under fallen buildings, lowering their chances of survival. Developing a compact, portable, and simple treatment method for RIAKI remains an important challenge. Based on our previous finding that RIAKI depends on leukocyte extracellular traps (ETs), we aimed to develop a novel medium-molecular-weight peptide to provide clinical treatment of Crush syndrome. We conducted a structure-activity relationship study to develop a new therapeutic peptide. Using human peripheral polymorphonuclear neutrophils, we identified a 12-amino acid peptide sequence (FK-12) that strongly inhibited neutrophil extracellular trap (NET) release in vitro and further modified it by alanine scanning to construct multiple peptide analogs that were screened for their NET inhibition ability. The clinical applicability and renal-protective effects of these analogs were evaluated in vivo using the rhabdomyolysis-induced AKI mouse model. One candidate drug [M10Hse(Me)], wherein the sulfur of Met10 is substituted by oxygen, exhibited excellent renal-protective effects and completely inhibited fatality in the RIAKI mouse model. Furthermore, we observed that both therapeutic and prophylactic administration of M10Hse(Me) markedly protected the renal function during the acute and chronic phases of RIAKI. In conclusion, we developed a novel medium-molecular-weight peptide that could potentially treat patients with rhabdomyolysis and protect their renal function, thereby increasing the survival rate of victims affected by Crush syndrome.

Macrophage extracellular trap formation promoted by platelet activation is a key mediator of rhabdomyolysis-induced acute kidney injury.

Rhabdomyolysis is a serious syndrome caused by skeletal muscle injury and the subsequent release of breakdown products from damaged muscle cells into systemic circulation. The muscle damage most often results from strenuous exercise, muscle hypoxia, medications, or drug abuse and can lead to life-threatening complications, such as acute kidney injury (AKI). Rhabdomyolysis and the AKI complication can also occur during crush syndrome, an emergency condition that commonly occurs in victims of natural disasters, such as earthquakes, and man-made disasters, such as wars and terrorism. Myoglobin released from damaged muscle is believed to trigger renal dysfunction in this form of AKI. Recently, macrophages were implicated in the disease pathogenesis of rhabdomyolysis-induced AKI, but the precise molecular mechanism remains unclear. In the present study, we show that macrophages released extracellular traps (ETs) comprising DNA fibers and granule proteins in a mouse model of rhabdomyolysis. Heme-activated platelets released from necrotic muscle cells during rhabdomyolysis enhanced the production of macrophage extracellular traps (METs) through increasing intracellular reactive oxygen species generation and histone citrullination. Here we report, for the first time to our knowledge, this unanticipated role for METs and platelets as a sensor of myoglobin-derived heme in rhabdomyolysis-induced AKI. This previously unknown mechanism might be targeted for treatment of the disease. Finally, we found a new therapeutic tool for prevention of AKI after rhabdomyolysis, which might rescue some sufferers of this pathology.