Macrophage activation via the NTPDase1-adenosine pathway and associated injury in acute antibody-mediated rejection.

Background: Nucleoside triphosphate diphosphohydrolase 1 (NTPDase1) is a calcium- and magnesium-dependent nucleoside triphosphate diphosphohydrolase. NTPDase1, expressed in mature immune cells to hydrolyze ATP and ADP into adenosine. The NTPDase1and its function in an adenosine pathway plays an important role in suppressing inflammation, immune responses, cell proliferation, and other processes. We investigated the effects and mechanisms of macrophage activation through the NTPDase1-adenosine pathway and the resulting damage from acute antibody-mediated rejection (AMR).

Methods: We established an acute AMR skin-graft model by transplanting MHC-mismatched B10.A ear skin onto BALB/c nude mice and inducing rejection with 100 μg anti-H-2Kk IgG. Mice were grouped as wild-type, NTPDase1-knockout, and NTPDase1-overexpression, with isotype-IgG controls. Outcomes were compared across groups, and statistical analyses were performed using SPSS 16.0.

Results: After the onset of acute AMR, higher NTPDase1 expression in B cells and grafted skin was associated with lower concentration of extracellular ADP, a reduced proportion of CD68+ macrophages, and milder pathological injury in nude mice, and each parameter showing a negative correlation. At 30 min after AMR onset, CD68 + TNF-α + M1 macrophages predominated, whereas CD68 + CD163+ M2 macrophage numbers did not change significantly. Over time, M1 macrophages progressively decreased, and M2 macrophages became increasingly prominent. By day 7 after AMR onset, compared with controls, CD163+ M2 macrophages and the expression of TGF-β1, vimentin, and α-SMA were significantly increased, whereas the epithelial marker E-cadherin was significantly decreased.

Conclusion: NTPDase1 constrains acute AMR by limiting extracellular ADP, curbing macrophage expansion, and reducing graft injury. Transgenic overexpression sustained expression, moderated M1-to-M2 dynamics, and attenuated C4d and fibrotic markers, whereas knockout intensified purinergic signaling, inflammation, and fibrosis. Findings position NTPDase1 as a protective regulator and therapeutic target in AMR.