FK506 Donor Pretreatment Improves Intestinal Graft Microcirculation and Morphology by Concurrent Inhibition of Early NF-κB Activation and Augmented HSP72 Synthesis

Calcineurin Inhibition in Deceased Organ Donors: A Systematic Review and Meta-analysis of Preclinical Studies

Background

Preconditioning deceased organ donors with calcineurin inhibitors (CNIs) may reduce ischemia-reperfusion injury to improve transplant outcomes.

Methods

We searched MEDLINE, EMBASE, Cochrane Library, and conference proceedings for animal models of organ donation and transplantation, comparing donor treatment with CNIs with either placebo or no intervention, and evaluating outcomes for organ transplantation. Reviewers independently screened and selected studies, abstracted data, and assessed the risk of bias and clinical relevance of included studies. Where possible, we pooled results using meta-analysis; otherwise, we summarized findings descriptively.

Results

Eighteen studies used various animals and a range of CNI agents and doses and evaluated their effects on a variety of transplant outcomes. The risk of bias and clinical applicability were poorly reported. Pooled analyses suggested benefit of CNI treatment on early graft function in renal transplants (3 studies; serum creatinine: ratio of means [RoM] 0.54; 95% confidence interval [CI], 0.34-0.86) but not for liver transplants (2 studies; serum alanine transaminase: RoM 0.61; 95% CI, 0.30-1.26; and serum aspartate aminotransferase: RoM 0.58; 95% CI, 0.26-1.31). We found no reduction in graft loss at 7 d (2 studies; risk ratio 0.54; 95% CI, 0.08-3.42). CNI treatment was associated with reduced transplant recipient levels of interleukin-6 (4 studies; RoM 0.36; 95% CI, 0.19-0.70), tumor necrosis factor-alpha (5 studies; RoM 0.36; 95% CI, 0.12-1.03), and cellular apoptosis (4 studies; RoM 0.30; 95% CI, 0.19-0.47).

Conclusions

Although this compendium of animal experiments suggests that donor preconditioning with CNIs may improve early kidney graft function, the limited ability to reproduce a true clinical environment in animal experiments and to assess for risk of bias in these experiments is a serious weakness that precludes current clinical application.

Tacrolimus Prevents Mechanical and Humoral Alterations in Brain Death-Induced Lung Injury in Pigs

RATIONALE

Donor brain death-induced lung injury may compromise graft function after transplantation. Establishing strategies to attenuate lung damage remains a challenge because the underlying mechanisms remain uncertain.

OBJECTIVES

The effects of tacrolimus pretreatment were evaluated in an experimental model of brain death-induced lung injury.

METHODS

Brain death was induced by slow intracranial infusion of blood in anesthetized pigs after randomization to tacrolimus (orally administered at 0.25 mg. kg-1 BID the day before the experiment and intravenously at 0.05 mg. kg-1 one hour before the experiment; n=8) or placebo (n=9) pretreatment. Hemodynamic measurements were performed 1, 3, 5 and 7 hours after brain death. After euthanasia of the animals, lung tissue was sampled for pathobiological and histological analysis, including lung injury scoring (LIS).

MEASUREMENTS AND MAIN RESULTS

Tacrolimus pretreatment prevented increases in pulmonary artery pressure, pulmonary vascular resistance and pulmonary capillary pressure and decreases in systemic artery pressure and thermodilution cardiac output associated with brain death. After brain death, the ratio of the partial arterial O2 pressure to the inspired O2 fraction (PaO2/FiO2) decreased, which was prevented by tacrolimus. Tacrolimus pretreatment prevented increases in the interleukin (IL)-6-to-IL-10 ratio, vascular cell adhesion molecule-1, circulating levels of IL-1β, IL-6-to-IL-10 ratio and glycocalyx-derived molecules. Tacrolimus partially decreased apoptosis [Bax-to-Bcl2 ratio (p=0.07) and the number of apoptotic cells in the lungs (p<0.05)] but failed to improve LIS.

CONCLUSIONS

Immunomodulation through tacrolimus pretreatment prevented pulmonary capillary hypertension as well as the activation of inflammatory and apoptotic processes in the lungs after brain death; however, LIS did not improve.

Effect of intraportal infusion of tacrolimus on ischaemic reperfusion injury in orthotopic liver transplantation: a randomized controlled trial

The increased use of older and/or marginal donor organs in liver transplantation over the last decade calls for strategies to minimize ischaemic reperfusion (I/R) injury to prevent early graft failure. Tacrolimus, a very potent and effective calcineurin inhibitor, was selected because of its ability to ameliorate I/R injury. A randomized, blinded, controlled single-centre trial of 26 liver transplant recipients was performed between February 2008 and December 2009. Donor organs were randomized to be perfused intraportally during liver transplantation with 1.5 l 5% albumin infusion containing either 20 ng/ml tacrolimus or placebo. The primary end point was liver function as assessed by aspartate transaminase (AST) or alanine transaminase (ALT) levels 6 days after transplantation. Treatment effectiveness was tested by transcriptome-wide analysis of biopsies. There was no difference in the primary end point, i.e. AST (IU/l) and ALT (IU/l) at day 6 after transplantation between groups. Furthermore, choleastatic parameters as well as parameters of liver synthesis were not different between groups. However, tacrolimus treatment suppressed inflammation and immune response in the transplanted liver on a genome-wide basis. Intrahepatic administration of tacrolimus did not result in a reduction of AST and ALT within the first week after transplantation.

Direct vasodilative effect of FK506 on porcine mesenteric artery in small bowel transplantation

BACKGROUND

Tacrolimus (FK506) is widely used as an immunosuppressive drug in small bowel transplantation. However, its precise effects on the vascular tone of the transplanted organ have not been studied. This study aimed to clarify the effects of FK506 on the porcine mesenteric artery.

METHODS

The effects of FK506 on the changes in cytosolic Ca(2+) concentration ([Ca(2+)]i) and force using fura-2 fluorometry were investigated in mesenteric arterial strips of the porcine small intestine. The effects of FK506 on the activity of voltage-dependent Ca(2+) channels and receptor-operated Ca(2+) channels using high K(+) (118 mmol/L K(+)) depolarization and thromboxane A(2) analog (U46619) stimulation were also examined.

RESULTS

FK506 inhibited the force development induced by 118 mmol/L K(+) depolarization and 1 micromol/L U46619 stimulation in a concentration-dependent manner. The extent of inhibition of this contraction was greater than that of the K(+)-induced contraction, and its inhibitory potency was about 10-fold. FK506 (10 micromol/L) inhibited the increases in [Ca(2+)]i (24.9% +/- 7.4%) and the force development (52.0% +/- 5.6%) induced by 1 micromol/L U46619, respectively.

CONCLUSIONS

FK506 induces arterial relaxation by decreasing [Ca(2+)]i. Pretreatment of a graft with FK506 may reduce the risk of vasospasm, ischemia-reperfusion injury, and thrombosis in small bowel transplantation.

Induction of heat shock proteins for protection against oxidative stress

Heat shock proteins (Hsps) have been studied for many years and there is now a large body of evidence that demonstrates the role of Hsp upregulation in tissue and cell protection in a wide variety of stress conditions. Oxidative stress is known to be involved in a number of pathological conditions, including neurodegeneration, cardiovascular disease and stroke, and even plays a role in natural aging. In this review we summarize the current understanding of the role of Hsps and the heat shock response (HSR) in these pathological conditions and discuss the therapeutic potential of an Hsp therapy for these disorders. However, although an Hsp based therapy appears to be a promising approach for the treatment of diseases that involve oxidative damage, there are some significant hurdles that must be overcome before this approach can be successful. For example, to be effective an Hsp based therapy will need to ensure that the upregulation of Hsps occurs in the right place (i.e. be cell specific), at the right time and to a level and specificity that ensures that all the important binding partners, namely the co-chaperones, are also present at the appropriate levels. It is therefore unlikely that strategies that involve genetic modifications that result in overexpression of specific Hsps will achieve such sophisticated and coordinated effects. Similarly, it is likely that some pharmaceutical inducers of Hsps may be too generic to achieve the desired specific effects on Hsp expression, or may simply fail to reach their target cells due to delivery problems. However, if these difficulties can be overcome, it is clear that an effective Hsp based therapy would be of great benefit to the wide range of depilating conditions in which oxidative stress plays a critical role.

Transplantation of preconditioned intestinal grafts is associated with lower inflammatory activation and remote organ injury in rats

Reperfused grafts--particularly the intestine--release free radicals and cytokines into the systemic circulation. The type of discharge, which is greatly dependent on the local injury, may also induce inflammatory activation in distant organs and leading to multiple system and organ failure. It has been suggested that intestinal grafts from tacrolimus (TRL)-pretreated donors show improved morphology and microcirculation. We studied whether transplantation of intestines from TRL-pretreated donors influenced inflammatory response and remote organ injury posttransplantation. Donor Sprague Dawley rats received TRL or saline (controls) intravenously at 6 hours prior to graft harvest. The intestinal grafts were preserved in saline for 3 hours before transplantation. At 6 and 12 hours postreperfusion hepatic and renal cortical microcirculation were assessed using laser-Doppler flowmetry (n = 8-12 per group). Blood pressure was measured; liver, kidney, and serum samples were obtained. We analyzed hepatic and renal ICAM-1 expression and caspase-3-like activity as well as plasma content of tumor necrosis factor-alpha and interleukin-6. Pretreated graft recipients had higher mean arterial pressure (82 +/- 10 vs 51 +/- 17 mm Hg, P < .05) and renal perfusion at 6 hours whereas liver perfusion was similar at both 6 and 12 hours. Liver and renal functions were also superior among recipients of pretreated grafts. Both caspase-3-like activity and ICAM-1 expression in liver and kidney were lower in pretreated graft recipients. Plasma IL-6 levels were lower in animals receiving pretreated grafts. Transplantation of intestines from TRL-pretreated donors was followed by a lower systemic inflammatory response, improved organ function and decreased remote injury early posttransplantation compared with animals receiving grafts from untreated donors.