Effect of HMG CoA reductase inhibitors on the development of chronic lung allograft dysfunction

Impact of Angiotensin Blockade on Development of Chronic Lung Allograft Dysfunction

Background: The renin-angiotensin-aldosterone system (RAAS) is responsible for a multitude of physiological functions, including immunological effects such as promotion of TGF-β and upregulation of IL-6 and IL-8 which are also implicated in the development of chronic lung allograft dysfunction (CLAD). Blockade of the RAAS pathway in pre-clinical models has demonstrated a decrease in these cytokines and pulmonary neutrophil recruitment. Objective: This study sought to evaluate whether use of RAAS inhibitor (RAASi) in lung transplant recipients impacted CLAD-free survival. Methods: In this retrospective, single-center study, 35 lung transplant recipients who received a RAASi post-transplant were compared to 70 lung transplant recipients not exposed to a RAASi and were followed for up to 5 years post-transplant. Results: The incidence of CLAD did not differ based on RAASi treatment (34.3% in RAASi vs 38.6%, P-value .668). This was confirmed with a multivariable Cox proportional hazards model with RAASi initiation as a time-varying covariate (RAASi hazard ratio of 1.01, P-value .986). Incidence of hyperkalemia and acute kidney injury were low in the RAASi group. Conclusions: This study demonstrated no association between post-transplant RAASi use and decreased risk of CLAD development. RAASi were also well tolerated in this patient population.

Impact of statin treatment and exposure on the risk of chronic allograft dysfunction in Chinese lung transplant recipients

PURPOSE

Chronic lung allograft dysfunction (CLAD) was a common complication following lung transplantation that contributed to long-term morbidity and mortality. Statin therapy had been suggested to attenuate recipient inflammation and immune response, potentially reducing the risk and severity of CLAD. This study aimed to evaluate the impact of statin use and in vivo exposure on the incidence of CLAD in lung transplant recipients (LTRs), as well as their effects on immune cells and inflammatory factors.

METHODS

A retrospective cohort study was conducted on patients who underwent lung transplantation between January 2017 and December 2020. The incidence of CLAD, as per the 2019 ISHLT criteria, was assessed as the clinical outcome. The plasma concentrations of statin were measured using a validated UPLC-MS/MS method, while inflammation marker levels were determined using ELISA kits.

RESULTS

The statin group exhibited a significantly lower rate of CLAD (P = 0.002). Patients receiving statin therapy showed lower CD4+ T-cell counts, total T-lymphocyte counts, and IL-6 levels (P = 0.017, P = 0.048, and P = 0.038, respectively). Among the CLAD groups, the atorvastatin level (2.51 ± 1.31 ng/ml) was significantly lower than that in the non-CLAD group (OR = 1.438, 95%CI (1.007-2.053), P = 0.046).

CONCLUSION

Statin therapy significantly reduced the incidence of CLAD, as well as immune cell counts and inflammatory cytokine levels in LTRs. Although the statin exposure was significantly lower in CLAD patients, it was not associated with the incidence of CLAD.

Conventional and Novel Approaches to Immunosuppression in Lung Transplantation

Most therapeutic advances in immunosuppression have occurred over the past few decades. Although modern strategies have been effective in reducing acute cellular rejection, excess immunosuppression comes at the price of toxicity, opportunistic infection, and malignancy. As our understanding of the immune system and allograft rejection becomes more nuanced, there is an opportunity to evolve immunosuppression protocols to optimize longer term outcomes while mitigating the deleterious effects of traditional protocols.

Pharmacotherapy of chronic lung allograft dysfunction post lung transplantation

Chronic lung allograft dysfunction (CLAD) remains the primary cause of death in lung transplant recipients (LTRs) in spite of improvements in immunosuppression management. Despite advances in knowledge regarding the pathogenesis of CLAD, treatments that are currently available are usually ineffective and delay progression of disease at best. There are currently no evidence-based guidelines for the optimal treatment of CLAD, and management varies widely across transplant centers. Additionally, there are minimal publications available to summarize data for currently available therapies and outcomes in LTRs. We identified the major domains of the medical management of CLAD and conducted a comprehensive search of PubMed and Embase databases to identify articles published from inception to December 2021 related to CLAD in LTRs. Studies published in English pertaining to the pharmacologic prevention and treatment of CLAD were included; highest priority was given to prospective, randomized, controlled trials if available. Prospective observational and retrospective controlled trials were prioritized next, followed by retrospective uncontrolled studies, case series, and finally case reports if the information was deemed to be pertinent. Reference lists of qualified publications were also reviewed to find any other publications of interest that were not found on initial search. In the absence of literature published in the aforementioned databases, additional articles were identified by reviewing abstracts presented at the International Society for Heart and Lung Transplantation and American Transplant Congress annual meetings between 2010-2021. This document serves to provide a comprehensive review of the literature and considerations for the prevention and medical management of CLAD. This article is protected by copyright. All rights reserved.

An update on current treatment strategies for managing bronchiolitis obliterans syndrome after lung transplantation

INTRODUCTION

Bronchiolitis obliterans syndrome (BOS), a subtype of chronic lung allograft dysfunction, is quite common, with up to half of all lung recipients developing BOS within 5 years of transplantation. Preventive efforts are aimed at alleviating known risk factors of BOS development, while the primary goal of treatment is to delay the irreversible, fibrotic airway changes, and progressive loss of lung function.

AREAS COVERED

This narrative review will briefly discuss the updated definition, clinical presentation, pathogenesis, risk factors, and survival after BOS while paying particular attention to the salient evidence for optimal preventive strategies and treatments based on investigations in the modern era.

EXPERT OPINION

Future translational research focused on further characterizing the complex interplay between immune and nonimmune mechanisms mediating chronic lung rejection is the first step toward mitigating risk of allograft injury, improving early disease detection with noninvasive biomarkers, and ultimately, developing an effective, targeted therapy that can extend the life of the lung allograft.

The role of HIF-1α-VEGF pathway in bronchiolitis obliterans after lung transplantation

Background

Graft function may be affected if the organ is exposed to hypoxia. We hypothesized that bronchiolitis obliterans (BO) after lung transplantation is associated with hypoxia-inducible factor-1α (HIF-1α). This study compares the expression of HIF-1α and its downstream proteins in allograft and isograft to explore the relationship between this pathway and BO in rats.

Material and methods

We performed an orthotopic left pulmonary transplant model using the tri-cuff vascular anastomosis method and evaluated the histopathology, including the severity of fibrosis (SF). The expression of HIF-1α, VEGF-A, and VEGFR-2 was accessed by immunohistochemistry.

Results

The imageology and pathology showed that the allogenic model developed BO 90 days after the operation. The percentages of a high expression of HIF-1α, VEGF-A, and VEGFR-2 in the allogeneic group were 77.27, 63.64, and 68.18% higher than in the isogeneic group, respectively. The SF score was highest in the allograft and was positively correlated with the expression of the proteins.

Conclusion

This model can simulate human BO after lung transplantation. The expression of HIF-1α and its downstream proteins in post-transplantation was up-regulated, suggesting that activation of the HIF-1α-VEGF pathway might be involved in the occurrence and prognosis of BO.