Heart–lung transplantation is an acceptable therapy for patients with end-stage heart–lung or lung disease. Although the surgical techniques and the immunosuppressive drug regimen have improved, long-term survival is still hampered by the development of chronic rejection. Indeed, obliterative bronchiolitis or bronchiolitis obliterans syndrome (BOS), the clinical correlate of obliterative bronchiolitis, is now regarded as a manifestation of chronic rejection and remains the leading cause of morbidity and late mortality after lung transplantation (1). Treatment of BOS remains difficult and has primarily been performed by augmenting or switching the current immunosuppressive therapy, resulting, at best, in a temporary stabilization of the forced expiratory volume in 1 sec (FEV1) (2). It has been shown that BOS is characterized by a neutrophilic infiltration of the airways and a high interleukin (IL)-8 level in the bronchoalveolar lavage fluid, which may even precede the diagnosis of BOS for several months (3). Recently, azithromycin (AZI) maintenance therapy has been demonstrated to possess beneficial effects in patients with cystic fibrosis, improving the FEV1 and decreasing the exacerbation frequency (4). Because AZI is known to inhibit IL-8 release by human alveolar macrophages (5) and to increase apoptosis of neutrophils (6), we started AZI therapy in eight lung transplant recipients with BOS to investigate whether this might have an effect on the course of their disease.
Eight lung transplant recipients, who all demonstrated a significant decrease in their FEV1 attributed to BOS, were enrolled in this open-label study, which was approved by the local hospital’s ethics committee. Their mean age at transplantation was 36 years (range 5–61 years), and they all received AZI (250 mg every day for 5 days and then 250 mg every other day) in addition to their regular immunosuppressive therapy, consisting of corticosteroids and tacrolimus in all eight patients. In addition, five patients received mofetil mycophenolate, one patient received azathioprine, and one patient received sirolimus. Two patients underwent a single lung transplantation for emphysema, three patients underwent a sequential single lung transplantation (two for cystic fibrosis and one for emphysema), and two patients with congenital heart disease and one patient with primary pulmonary hypertension underwent a heart–lung transplantation. AZI was started on postoperative day 1,410±1,287 (range 172–4,095 days) and was continued until the preparation of this article. All eight patients were followed for at least 12 weeks (six patients were followed for 24 weeks, and three patients were followed for 36 weeks). At the time of adding AZI, four patients were in BOS stage 1, two patients were in stage 2, and two patients were in stage 3, according to the recent review of the BOS diagnostic criteria (7). Before AZI was added, all patients had been treated by classic augmentation or switching of the immunosuppressive drugs, without obvious effect on the course of their disease. Acute rejection was excluded by means of transbronchial biopsies in all patients. Five patients were colonized with Pseudomonas, with no signs of acute infection (no fever, no new pulmonary symptoms, and no new onset of symptoms). Data are represented as mean ± standard deviation. Repeated-measures analysis of variance with post hoc Scheffe F-test was used to identify a significance of less than 0.05. Where appropriate, a Student t test for unpaired data was used. The StatView 512+ (Abacus Concept, Berkeley, CA) statistical software package for Apple Macintosh was used.
Table 1 illustrates the changes in FEV1 before and during AZI treatment for different follow-up periods, for example, 12 weeks (eight patients), 24 weeks (six patients), and 36 weeks (three patients).
There was a significant difference in the FEV1 values (P <0.0001, analysis of variance) with a significant decrease until time 0 (when AZI was started) and then a significant increase of the FEV1 in all follow-up groups (12 weeks, 24 weeks, and 36 weeks). For all eight patients, the decrease in FEV1 from their postoperative best value until time 0 was 34.4%±14.7%. The increase in FEV1 after 12 weeks from time 0 was 18.3%±14.6%, representing an absolute value of 328±305 mL. In the six patients with a follow-up of 24 weeks, the increase in FEV1 was 22.0%±15.2%, representing 353±358 mL. In the three patients with a follow-up of 36 weeks, the increase in FEV1 was 33.3%±14.0%, or 533±300 mL.
Defining a significant response as an increase in the FEV1 of 15% or greater, there were four responders with a mean increase in FEV1 of 26.6%±11.5% or an absolute increase of 482±285 mL. Figure 1 demonstrates the individual changes in FEV1 from the best postoperative value until the last moment of follow-up in responders (Fig. 1A) and nonresponders (Fig. 1B). Two patients (both nonresponders) died because of progression of BOS 19 and 30 weeks after the addition of AZI. There were no significant differences in the changes of the FEV1 between the patients who were colonized with Pseudomonas and those who were not (18.6%±15.1% and 17.7%±17.0%, respectively, P =0.94). There were no significant changes in the tacrolimus trough levels between time 0 and 2 and 4 weeks after adding AZI in all patients.
We treated eight lung transplant recipients with progressive chronic allograft dysfunction with AZI, four of whom demonstrated a significant increase in the FEV1. This open, prospective study further corroborates the recent data by Gerhardt et al. (8). They treated six lung transplant recipients with BOS with AZI and demonstrated a significant improvement of the FEV1 (+17.1%, or an absolute increase of 0.5 L) after a mean follow-up of 13.7 weeks, which is comparable to the improvement of the FEV1 in our patients after 12 weeks (+18.3%). In their series, five of the six patients demonstrated a significant response, whereas in our series four of the eight patients significantly improved their FEV1. However, two nonresponders in our study experienced at least a temporary stabilization of their pulmonary function parameters. Three of our patients were followed up during 36 weeks, and it was demonstrated that the improvement in their FEV1 persisted during the entire time period.
The study of Gerhardt et al. (8) was the first to show a significant improvement of the FEV1 in patients with BOS. Until the time of their study, only a stabilization of the FEV1 had been achieved in such patients (2). The mechanisms of action of AZI in lung transplant recipients is not clear at the present time. On the basis of the improvement of the FEV1 in patients with cystic fibrosis and diffuse panbronchiolitis when they were treated with macrolide antibiotics (4), it was assumed that colonization with Pseudomonas might be a prerequisite for an improvement in the FEV1. It is accepted now that macrolide antibiotics have several in vitro and in vivo effects on Pseudomonas without having an effect on the bacterial growth itself. For example, erythromycin inhibits Pseudomonas aeruginosa adherence to collagen in vitro, and clarithromycin inhibits overproduction of muc5ac core protein in a Pseudomonas-infected murine model of diffuse panbronchiolitis. In addition, AZI inhibits the transcription of quorum-sensing genes, which may prevent production of tissue-damaging proteins. In fact, quorum-sensing signals have been recently detected in clinically stable lung transplant recipients without signs of infection (9). However, because the improvement in the FEV1 in our series was comparable in patients who were or were not colonized with Pseudomonas, we doubt whether this mechanism of action might explain the effect on the pulmonary function. Another possible explanation could be an antibacterial effect on other bacteria, especially Mycoplasma and Chlamydia pneumoniae. Up to now, however, there is no evidence indicating that these bacteria might be involved in the process of chronic allograft dysfunction in lung transplant recipients. Gastroesophageal reflux is also known as a cause for reversible chronic allograft dysfunction in lung transplant recipients. Immunosuppressive agents may indeed influence gastric emptying, for instance, cyclosporin A causes a slower solid emptying pattern, whereas tacrolimus produces a significantly faster solid emptying (10). None of our patients showed any clinical symptoms of gastroesophageal reflux, and they were all being treated with tacrolimus as part of their immunosuppressive drug regimen. Therefore, we do not assume that this factor may have influenced the present results. Chronic allograft dysfunction after lung transplantation is characterized by a neutrophilic infiltration of the airways and by the presence of high amounts of IL-8 in the bronchoalveolar lavage fluid (3); moreover, macrolide antibiotics have an effect on neutrophils and IL-8 (5, 6). At the present time, however, there are no data available demonstrating that macrolide antibiotics reduce the airway neutrophilia or the IL-8 secretion in patients with BOS.
Our data further corroborate the data of Gerhardt et al. (8). Both show a substantial increase of the FEV1 in patients with chronic allograft dysfunction after lung transplantation by additional treatment with AZI. This improvement is maintained for at least 9 months. The mechanism of action of AZI remains unknown at the present time, but an attractive hypothesis is its potential anti-inflammatory effect on neutrophils and IL-8. Further studies are warranted to unravel the exact mechanisms of action.
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