Crosstalk between nonclassical monocytes and alveolar macrophages mediates transplant ischemia-reperfusion injury through classical monocyte recruitment

Abstract

Primary Graft Dysfunction (PGD) is the predominant cause of early graft loss following lung transplantation. We recently demonstrated that donor pulmonary intravascular non-classical monocytes (NCM) initiate neutrophil recruitment. Simultaneously, host-origin classical monocytes (CM) permeabilize the vascular endothelium to allow neutrophil extravasation necessary for PGD. Here, we show that a CCL2-CCR2 axis is necessary for CM recruitment. Surprisingly, although intravital imaging and multichannel flowcytometry revealed that depletion of donor NCM abrogated CM recruitment, single-cell RNA-seq identified donor alveolar macrophages (AM) as predominant CCL2 secretors. Unbiased transcriptomic analysis of murine tissues combined with murine knockouts and chimeras indicated that IL1β production by donor NCM was responsible for the early activation of AM and CCL2 release. IL1β production by NCM was NLRP3 inflammasome-dependent and inhibited by treatment with a clinically approved sulphonylurea. Production of CCL2 in the donor AM occurred through IL1R-dependent activation of the PKC and NFκB-pathway. Accordingly, we show that IL1β-dependent paracrine interaction between donor NCM and AM leads to recruitment of recipient CM necessary for PGD. Since depletion of donor NCM, IL1β or IL1R antagonism, and inflammasome inhibition, abrogated recruitment of CM as well as PGD, and are feasible using FDA-approved compounds, our findings may have potential for clinical translation.

Reprogramming Alveolar Macrophage Responses to TGF-β Reveals CCR2+ Monocyte Activity that Promotes Bronchiolitis Obliterans Syndrome

“…We have recently reported that AM produce CCL2 after lung transplantation ( 25 ). TGF-β targets activation of AP-1 and EGR1, transcription factors that can promote CCL2 gene transcription ( 47, 48 ).…”

“…Several reports show that Mo-AM are derived from bone marrow-derived cells, but have not directly addressed whether this AM subset arises from CCR2 + monocytes ( 22, 23 ). CCR2 expression on monocytes is critical for trafficking into inflamed lungs in response to the chemokine CCL2 ( 24, 25 ). CCR2 expression and Mo-AM have been shown to drive bleomycin-induced pulmonary fibrosis raising the possibility that CCR2 + monocytes drive pulmonary fibrotic disease through differentiation into Mo-AM ( 21, 26 ).…”

Donor leukocyte trafficking during human ex vivo lung perfusion

“…16 Retained donor pulmonary intravascular nonclassical monocytes initiate recipient neutrophil recruitment to donor graft following transplantation, playing a central role in development of acute lung injury. 33,34 Furthermore, preimplantation classical donor monocyte numbers have been correlated…”

Integrative Analysis of Spatial Transcriptome with Single-cell Transcriptome and Single-cell Epigenome in Mouse Lungs after Immunization

“…As the development of single-cell sequencing technologies, scRNA-seq has been gradually applied to study immune cells and immune responses in mouse lungs (Ballesteros et al, 2020;Cohen et al, 2018;Kurihara et al, 2021;Wang et al, 2021). In many cases, T helper cells and cytotoxic T cells can be identified in these scRNA-seq studies, but not their subtypes.…”