Reduced Neutrophil Extracellular Trap Formation During Ischemia Reperfusion Injury in C3 KO Mice: C3 Requirement for NETs Release

Abstract

Complement C3 plays a prominent role in inflammatory processes, and its increase exacerbates ischemia reperfusion injury (IRI)-induced acute kidney injury (AKI). Infiltrated neutrophils can be stimulated to form neutrophil extracellular traps (NETs), leading to renal injury. However, the relationship between the increase of C3 and the release of NETs in AKI was not clear. Here we found that IRI in the mouse kidney leads to increased neutrophils infiltration and NET formation. Furthermore, neutrophils depletion by anti-Ly6G IgG (1A8) did not reduce C3 activation but reduced kidney injury and inflammation, indicating a link between neutrophils infiltration and renal tissue damage. Pretreatment with 1A8 suppressed ischemia-induced NET formation, proving that extracellular traps (ETs) in renal tissue were mainly derived from neutrophils. Renal ischemia injury also leads to increased expression of C3. Moreover, C3 KO mice (C3 KO) with IRI exhibited attenuated kidney damage and decreased neutrophils and NETs. In vitro, C3a primed neutrophils to form NETs, reflected by amorphous extracellular DNA structures that colocalized with CitH3 and MPO. These data reveal that C3 deficiency can ameliorate AKI by reducing the infiltration of neutrophils and the formation of NETs. Targeting C3 activation may be a new therapeutic strategy for alleviating the necroinflammation of NETs in AKI.

The role of extracellular traps in ischemia reperfusion injury

“…In addition, the oral administration of Candida albicans to mice prior to renal I/R increased systemic inflammation and NETs through the activation of TLR-4 and dectin-1, exacerbating renal IRI ( 62 ). In line with these findings, Complement C3 KO mice with renal I/R showed attenuated renal injury when neutrophil infiltration and NET formation were reduced ( 106 ).…”

“…Nevertheless, most current studies have focused on the NETs promoting renal IRI. Pretreatment with anti-Ly6G IgG can deplete neutrophils in mice with renal I/R, significantly reducing renal NET production and renal injury at 24 h post-reperfusion ( 106 ). This depletion experiment demonstrated that neutrophils and their ETs play an important role in promoting renal IRI.…”

“…Among the many approaches used to target intracellular signaling molecules, the drugs rTM and HCQ inhibit NET formation by inhibiting the TLR pathway ( 95 , 99 ). The inhibition of genes such as IL-33, ST2, IL-36R, P2RX1, PKM2, and complement C3 via gene knockout technology or drugs can reduce NET formation and attenuate IRI ( 50 , 105 , 106 , 118 , 129 ). In addition, the interaction of platelets and mast cells with neutrophils can promote the formation of NETs.…”

Neutrophils activated by membrane attack complexes increase the permeability of melanoma blood vessels

“…Thus, the enrichment of biologically active complement C3 fragments and C5a along the vasculature is a sound explanation for the observed recruitment of neutrophils around tumor blood vessels and is in line with reduced neutrophil numbers in tumors of C5-def mice. Next to their attraction, C3a and C5a can also promote neutrophil activation ( 57 , 58 ). C5a can induce the swelling of neutrophils, which might represent the reorganization of the cytoskeleton necessary for chemotaxis ( 59 ).…”

Neutrophil Extracellular Traps (NETs) im Gefäßsystem

“…Diese sekundären Gewebeschäden nach IRS werden maßgeblich durch die übermäßige lokale und systemische Immunantwort vorangetrieben. Im Rahmen von IRS kommt es zum Anfall reaktiver Sauerstoffspezies, welche die schnelle und effektive Aktivierung von NG und der Komplementkaskade bewirken [ 19 ]. Geschädigte Zellen produzieren weiterhin sogenannte Damage Associated Molecular Pattern (DAMP), welche wiederum zu einer Aktivierung von TLR führen.…”