Expression of calcineurin activity after lung transplantation: a 2-year follow-up

Abstract

The objective of this pharmacodynamic study was to longitudinally assess the activity of calcineurin during the first 2 years after lung transplantation. From March 2004 to October 2008, 107 patients were prospectively enrolled and their follow-up was performed until 2009. Calcineurin activity was measured in peripheral blood mononuclear cells. We report that calcineurin activity was linked to both acute and chronic rejection. An optimal activity for calcineurin with two thresholds was defined, and we found that the risk of rejection was higher when the enzyme activity was above the upper threshold of 102 pmol/mg/min or below the lower threshold of 12 pmol/mg/min. In addition, we report that the occurrence of malignancies and viral infections was significantly higher in patients displaying very low levels of calcineurin activity. Taken together, these findings suggest that the measurement of calcineurin activity may provide useful information for the management of the prevention therapy of patients receiving lung transplantation.

Figure 1. Calcineurin activity and acute rejection.

(A) Calcineurin activity (CN-a) was measured before lung transplantation in 52 of the 107 patients enrolled in the participating center. The results are presented as box plots and 10–90 percentile whiskers. We compared CN-a expression prior to transplantation in patients with or without cystic fibrosis (CF) since it is the main initial end-stage lung disease that led to lung transplantation in this cohort of patients and a similar dispersion of the CN-a values was found in CF+ and CF- patients (p = 0.77, Mann-Whitney test). Subsequently, a relationship between extreme values of calcineurin activity and acute rejection was investigated. (B) Comparison across time of the median CN-a levels in patients displaying or not acute rejection: Kernel smoothing curves were generated. The 2 groups of patients displayed similar profiles of CN-a which consist of a phase of enzyme inhibition within the first 10 weeks after transplantation followed by a phase in which enzyme activity is restored. The phase of CN-a inhibition tended to be faster and more marked in patients who had developed acute rejection as compared to patients who were free of acute rejection. Similarly, the increase of enzyme activity to baseline levels tended to be faster and more pronounced in patients who had developed acute rejection.

Figure 2. Calcineurin activity and adverse events related to over-immunosuppression.

The onset of events known to be related to over-immunosuppression, such as malignancies and infections, was compared between patients displaying or not low CN-a levels by the Kaplan and Meier method. (A) CN-a and malignancies: the occurrence of malignancies was significantly higher in patients displaying at least one CN-a value below 12 pmol/mg/min during the first 24 months after transplantation as compared to patients with higher CN-a values (28% vs 6%, p = 0.0218, Log-rank test). The examination of the relationship between CN-a and infections was performed by separating the infections of bacterial, viral and fungal origin. (B) CN-a and bacterial infections: the occurrence of 3 episodes of bacterial infections was similar in the 2 groups of patients (18% vs 25%, p = 0.85, Log-rank test). (C) CN-a and fungal infections: the occurrence of 3 episodes of fungal infections was similar in the 2 groups of patients (3.5% vs 0%, p = 0.21, Log-rank test). (D) CN-a and viral infections: the occurrence of 3 episodes of viral infections was significantly higher in patients displaying at least one CN-a value below 12 pmol/mg/min during the first 24 months after transplantation compared to patients with higher CN-a values (15% vs 0%, p = 0.01, Log-rank test).

Figure 3. Calcineurin activity, BOS and overall survival.

BOS-free survival was estimated at 5 years after transplantation by the Kaplan and Meier method. (A) Calcineurin activity (CN-a) monitoring during the first 24 months after transplantation: although not statistically significant, the survival without BOS was higher in patients who displayed CN-a levels within the range of 12–102 pmol/mg/min as compared to patients who exhibited at least one CN-a value outside this range of 12–102 pmol/mg/min during the first 24 months following transplantation (76% vs 43%, p = 0.4717, Log-rank test). (B) CN-a monitoring from the 6^th month to the 24^th month after transplantation: the survival without BOS was significantly higher in patients who displayed CN-a levels within the range of 12–102 pmol/mg/min as compared to that of patients who exhibited at least one CN-a value outside this range from the 6^th month to the 24^th months following transplantation (80% vs 40%, p = 0.0118, Log-rank test). (C) CN-a monitoring from the 6^th to the 24^th month after transplantation: the threshold values were further separated in 2 groups : <12 pmol/mg/min, >102 pmol/mg/min. The BOS-free survival in patients from each of these groups was compared to that from patients who displayed CN-a levels within the range of 12–102 pmol/mg/min. A significant reduction of the survival without BOS was found in patients who displayed CN-a levels higher than 102 pmol/mg/min (40% vs 80%, p = 0.037, Log-rank test), whereas a reduction in BOS-free survival in the limit of statistical significance was found in patients who displayed CN-a levels lower than 12 pmol/mg/min (49% vs 80%, p = 0.0574, Log-rank test). (D) Calcineurin activity and overall survival: no significant difference was found in the overall survival between the 2 groups of patients exhibiting calcineurin activity levels within or outside of the range of 12–102 pmol/mg/min.

Figure 4. Calcineurin activity and cyclosporine blood levels.

The relationship between calcineurin activity (CN-a) and the levels of cyclosporine (CsA) in blood was investigated. No correlation was found between CN-a and the level of CsA in blood.