Inhibition of Vascular Endothelial Growth Factor Receptors 1 and 2 Attenuates Natural Killer Cell and Innate Immune Responses in an Experimental Model for Obliterative Bronchiolitis

Funding Information: Supported by the Helsinki University Hospital , the Sigrid Juselius Foundation , the Academy of Finland , Finska Läkaresällskapet , the Research and Science Foundation of Farmos , The Paulo Foundation , Jalmari and Rauha Ahokas Foundation , Aarne Koskelo Foundation , Päivi and Sakari Sohlberg Foundation , Finnish Pulmonary Association , Biomedicum Helsinki Foundation , Jane and Aatos Erkko Foundation , and the University of Helsinki . Funding Information: Supported by the Helsinki University Hospital, the Sigrid Juselius Foundation, the Academy of Finland, Finska L?kares?llskapet, the Research and Science Foundation of Farmos, The Paulo Foundation, Jalmari and Rauha Ahokas Foundation, Aarne Koskelo Foundation, P?ivi and Sakari Sohlberg Foundation, Finnish Pulmonary Association, Biomedicum Helsinki Foundation, Jane and Aatos Erkko Foundation, and the University of Helsinki. Publisher Copyright: © 2022 American Society for Investigative PathologyObliterative bronchiolitis (OB) after lung transplantation is a nonreversible, life-threatening complication. Herein, the role of vascular endothelial growth factor receptor (Vegfr)-1 and -2 was investigated in the development of obliterative airway disease (OAD), an experimental model for OB. The nonimmunosuppressed recipients underwent transplantation with fully major histocompatibility complex mismatched heterotopic tracheal allografts and received Vegfr1 and -2-specific monoclonal antibodies either alone or in combination, or rat IgG as a control. The treatment with Vegfr1- or -2-blocking antibody significantly decreased intragraft mRNA expression of natural killer cell activation markers early after transplantation. This was followed by reduced infiltration of Cd11b thorn cells and Cd4 thorn T cells as well as down-regulated mRNA expression of proinflammatory chemokines and profibrotic growth factors. However, blocking of both Vegfr1 and -2 was necessary to reduce luminal occlusion. Furthermore, concomitant inhibition of the calcineurin activation pathway almost totally abolished the development of OAD. This study proposes that blocking of Vegf receptors blunted natural killer cell and innate immune responses early after transplantation and attenuated the development of OAD. The results of this study suggest that further studies on the role of Vegfr1 and -2 blocking in development of obliterative airway lesions might be rewarding. (Am J Pathol 2022, 192: 254-269; https://doi.org/10.1016/ j.ajpath.2021.10.018)Peer reviewe

Increased myeloid cell hypoxia-inducible factor-1 delays obliterative airway disease in the mouse

BACKGROUND: Obliterative bronchiolitis after lung transplantation is characterized by chronic airway inflammation leading to the obliteration of small airways. Hypoxia-inducible factor-1 (HIF-1) is a master regulator of cellular responses to hypoxia and inflammation. The Von Hippel-Lindau protein (pVHL) drives the degradation of oxygen-sensitive subunit HIF-1 alpha that controls the activity of HIF-1. We investigated the effect of myeloid cell targeted gene deletion of HIF-1 alpha or its negative regulator pVHL on the development of obliterative airway disease (OAD) in the recipients of tracheal allografts, a mouse model for obliterative bronchiolitis after lung transplantation. METHODS: Tracheal allografts were heterotopically transplanted from BALB/c donor mice to fully major histocompatibility complex mismatched recipient mice with HIF-1 alpha or VHL gene deletion in myeloid cells. The recipients were left non-immunosuppressed or received tacrolimus daily. Histologic, immunohistochemical, and real-time reverse transcription polymerase chain reaction analyses were performed at 3, 10, and 30 days. RESULTS: In the absence of immunosuppression, myeloid cell-specific VHL deficiency of the recipient mice improved epithelial recovery, decreased inflammatory cell infiltration and expression of pro-inflammatory cytokines, increased regulatory forkhead box P3 messenger RNA expression, and reduced OAD development in tracheal allografts. In the presence of tacrolimus immunosuppression, loss of HIF-1 alpha activity in myeloid cells of the recipient by HIF-1 alpha gene deletion accelerated OAD development in mouse tracheal allografts. CONCLUSIONS: Activity of the HIF-pathway affects the development of allograft rejection, and our results suggest that myeloid cell-specific VHL-deficiency that potentially increases HIF-activity decreases allograft inflammation and the subsequent development of OAD in mouse tracheal allografts. (C) 2016 International Society for Heart and Lung Transplantation. All rights reserved.Peer reviewe

Simvastatin pretreatment reduces caspase-9 and RIPK1 protein activity in rat cardiac allograft ischemia-reperfusion

Background: In transplantation-associated ischemia/reperfusion injury (Tx-IRI), tumor necrosis factor alpha and damage-associated molecular patterns promote caspase-8 and -9 apoptotic and receptor-interacting protein kinase-1 and-3 (RIPK1/3) necroptotic pathway activation. The extent of cell death and the counterbalance between apoptosis and regulated necrosis eventually determine the immune response of the allograft. Although simvastatin prevents Tx-IRI, its role in apoptotic and necroptotic activity remains unsolved. Methods: Rat allograft donors and recipients were treated with a single-dose of simvastatin 2 h prior to allograft procurement and reperfusion, respectively. Intragraft caspase-3, -8, and -9 and RIPK1 and-3 mRNA expression was analysed by quantitative RT-PCR and protein activity measured by immunohistochemistry and luminescent assays 6 h after reperfusion. Lactate and lactate dehydrogenase (LDH) levels were analysed from allograft recipient and from hypoxic endothelial cell cultures having treated with activated simvastatin. Results: When compared to without cold ischemia, prolonged 4-hour cold ischemia significantly enhanced intragraft mRNA expression of caspase-3 and-9, and RIPK1 and -3, and elevated protein activity of caspase-9 and RIPK1 in the allografts. Simvastatin pretreatment decreased mRNA expression of caspase-3 and -9, and RIPK1 and-3 and protein activity of caspase-9 and RIPK1 in the allografts. Intragraft caspase-8 mRNA expression remained constant regardless of cold ischemia or simvastatin pretreatment. Simvastatin pretreatment attenuated lactate and LDH levels, both in the allograft recipients and in hypoxic endothelial cell cultures. Conclusions: The beneficial effects of simvastatin pretreatment in cardiac allograft IRI may involve prevention of apoptosis and necroptosis. (C) 2016 Elsevier B.V. All rights reserved.Peer reviewe