Circulating "Neutrophils extra-cellular traps" during the early post-renal transplant period and correlation with graft dysfunction and rejection

Background: Neutrophil extracellular traps (NETs) have a role in infection, autoimmunity, autoinflammation, thrombosis, ischemia-reperfusion injury (IRI), epithelial-mesenchymal transition, vasculitis, and metabolic diseases. However, its role in early graft injury and graft outcome has not been elucidated till now. We evaluated the circulating NETs during early post-transplant periods and their correlation with graft outcome and IRI.

Methods: Prospectively, thirty kidney transplants recipient (KTR) were recruited and grouped into non-dysfunction (Group-A) and dysfunction groups (Group-B). Serum levels of circulating NETs were estimated by measuring myeloperoxidase-DNA complex at three-time points: pre-transplant, 8 h post-transplant, and 18 h post-transplant; and correlated with early graft outcome. Malondialdehyde (MDA), a marker of oxidative stress or IRI, was also measured to assess its relation with NETs and early graft outcome.

Results: Circulating NETs were significantly increased in both non-dysfunctional [Median OD: 0.11 (0.01-0.19) to 0.51 (0.22-0.91); p = 0.001] and dysfunctional [Median OD: 0.16 (0.12-0.27) to 0.38 (0.19-0.68); p = 0.047] KTR during first 8 h of transplant followed by fall at 18 h post-transplant [0.25 (0.18-0.72) and 0.35 (0.26-0.36) respectively]; however, no significant difference were observed between two groups at any time points. Isolated biopsy-proven graft rejection KTR also had higher circulating NETs during the early post-transplant period [Median OD: 0.16 (0.13-0.31) to 0.38 (0.28-1.5); p > 0.05] but no significant difference compared to non-dysfunctional KTR. MDA also displayed similar trends with an early significant rise [9.30 (7.74-12.56) μM to 17.37 (9.11-22.25) μM; p = 0.03 in group-A, and 8.7 (6.04-10.30) μM to 14.66 (13.39-21.63) μM; p = 0.01in group-B] followed by fall at 18 h in both groups [10.21 (7.64-13.90) μM and 11.11 (9.15-17.54) μM respectively]. Despite similar trends of both NETs and MDA, there was no significant correlation between these; however, creatinine exhibits a significant inverse correlation with NETs and MDA both.

Conclusion: Circulating NETs are significantly increased during the early post-transplant period in KTR irrespective of early graft outcome. Similar dynamics of MDA indicate that the early rise of NETs might be a part of IRI. However, molecular studies with large sample sizes and longer follow up are required to reach more defined conclusions.