The lung as a target organ of graft-versus-host disease

Despite significant advances in critical care and transplantation medicine, non-infectious lung injury remains a major problem following allogeneic hematopoietic stem cell transplantation (HSCT) both in the immediate post-transplant period and in the months to years that follow. Historically, approximately 50% of all pneumonias seen after HSCT have been secondary to infection. Although non-infectious lung injury occasionally occurs following autologous transplants, the allogeneic setting greatly exacerbates toxicity acutely and chronically. Pulmonary injury is associated with significant morbidity and mortality and responds poorly to standard therapies. Insights generated using animal models suggest that the immunologic mechanisms contributing to lung inflammation after HSCT may be similar to those responsible for graft-versus-host disease (GVHD).     

Pulmonary endothelial permeability following lung transplantation.

During lung transplantation, a number of factors may cause endothelial injury to the donor organ, including ischemia, inadequate preservation, cardiopulmonary bypass, high potassium concentrations, and reperfusion. In this study, protein accumulation index (PAI) was used to assess pulmonary endothelial permeability (PEP) in ten patients immediately after lung transplantation. Six were studied sequentially every other day for ten days postoperatively. The PAI was also measured using the same technique in a group of 11 normal volunteers. Mean PAI x 10(-3)/min +/- (SEM) for ten patients measured within 36 h of transplantation was 1.27 (0.56) compared with 0.45 (0.08) for the normal group (p = 0.09). No correlation was found between preservation time and PAI following reperfusion. Three episodes of lung rejection were observed in two patients during the first ten postoperative days, during which PAI rose to 2.26 (0.26) compared with 0.73 (0.11) for all other studies in the group (p less than 0.01). We conclude that no increase in PEP could be demonstrated after graft reperfusion following lung transplantation as assessed by PAI in this small group of patients. However, further studies may show the technique to be useful in the detection of subsequent episodes of graft rejection.     

Addition of ATP and MgCl2 to the preservation solution attenuates lung reperfusion injury following cold ischemia.

BACKGROUND: In lung transplantation, reperfusion injury following cold ischemia is one of the crucial problems for recipients. OBJECTIVE: We evaluated the protective effect of adding a combination of ATP and MgCl2 to the preservation solution against lung reperfusion injury following cold ischemia. METHODS: Using an isolated rat lung perfusion model with fresh rat blood as the perfusate, the rats were divided into five groups (n = 6). In the fresh group, the study lungs were flushed with phosphate-buffered saline (PBS), then immediately reperfused for 120 min. In the control group, the study lungs were flushed with PBS, then cold ischemia was induced for 9 h (4 degrees C), after which reperfusion was performed. In the other three groups, the protocols were the same as for the control group except that ATP and/or MgCl2 were added to the PBS: ATP group (100 microM ATP), MgCl2 group (100 microM MgCl2) and ATP + MgCl2 group (100 microM ATP + 100 microM MgCl2). RESULTS: In the ATP + MgCl2 group, the intrapulmonary shunt fraction, peak airway pressure and wet to dry lung weight ratio were significantly lower than those in the control group. No improvement was observed in the ATP or MgCl2 groups. Histological examination supported these physiological results. In all groups, flush time and lipid peroxide levels in the lungs after cold ischemia did not show any significant differences. CONCLUSION: The addition of ATP and MgCl2 to the preservation solution attenuated reperfusion injury following cold ischemia in rat lungs.     

Ischemia/reperfusion injury of the liver: pathophysiologic hypotheses and potential relevance to human hypoxic hepatitis

For the last decade, numerous experimental studies have demonstrated that the main part of liver injury caused by low or no flow states does not occur at the time of hypoxia, but during reperfusion. These experimental studies have a crucial clinical impact, because ischemia/reperfusion injury is involved in situations such as temporary vascular exclusion during liver surgery for trauma or tumors, preservation injury before liver transplantation, and liver cell necrosis observed in hypoxic (ischemic) hepatitis. The aim of the present review is to clarify the sequence of pathophysiological events responsible for ischemia/reperfusion injury of the liver, and to examine the potential contribution of liver ischemia/reperfusion injury to the syndrome of human hypoxic hepatitis.     

Rapid confirmation of Southeast Asian and Filipino alpha-thalassemia genotypes from newborn screening specimens

Animal models have recently clarified the lung injury after allogeneic hematopoietic transplantation. These works have confirmed the role of donor T lymphocytes in immune-mediated inflammatory reactions in the lung. We report here a fatal case of a 3-year-old child who developed acute respiratory failure coinciding with the onset of hyper-acute graft versus host disease (aGVHD) after allogeneic peripheral stem cell transplantation. aGVHD was refractory to treatment and the patient died on day +28. Lung necropsy showed interstitial pneumonia and peribronchial and perivascular infiltration by mononuclear cells, with no viral inclusions. These findings are not specific but have been found by some authors in animal models with acute immune-mediated lung injury related with donor T lymphocytes. Immune-mediated lung injury, as defined by animal models, should be considered in patients with severe signs of systemic aGVHD while excluding other known etiologies of pulmonary disease.     

Therapeutic hypercapnia reduces pulmonary and systemic injury following in vivo lung reperfusion

Permissive hypercapnia, involving tolerance to elevated Pa(CO(2)), is associated with reduced acute lung injury (ALI), thought to result from reduced mechanical stretch, and improved outcome in ARDS. However, deliberately elevating inspired CO(2) concentration alone (therapeutic hypercapnia, TH) protects against ALI in ex vivo models. We investigated whether TH would protect against ALI in an in vivo model of lung ischemia-reperfusion (IR). Anesthetized open chest rabbits were ventilated (standard eucapnic settings), and were randomized to TH (FI(CO(2)) 0.12) versus control (FI(CO(2)) 0.00). Pa(CO(2)) and arterial pH values achieved in the TH versus CON groups were 101 +/- 3 versus 44.4 +/- 4 mm Hg and 7.10 +/- 0.03 versus 7.37 +/- 0.03, respectively. Following left lung ischemia and reperfusion, TH versus control was associated with preservation of lung mechanics, attenuation of protein leakage, reduction in pulmonary edema, and improved oxygenation. Indices of systemic protection included improved acid-base and lactate profile, in the absence of systemic hypoxemia. In the TH group, mean BALF TNF-alpha levels were 3.5% of CON levels (p < 0.01), and mean 8-isoprostane levels were 30% of CON levels (p = 0.02). Western blot analysis demonstrated reduced lung tissue nitrotyrosine in TH, indicating attenuation of tissue nitration. Finally, preliminary data suggest that TH may attenuate apoptosis following lung IR. We conclude that in the current model TH is protective versus IR lung injury and mechanisms of protection include preservation of lung mechanics, attenuation of pulmonary inflammation, and reduction of free radical mediated injury. If these findings are confirmed in additional models, TH may become a candidate for clinical testing in critical care.     

How to protect liver graft with nitric oxide

Organ preservation and ischemia reperfusion injury as- sociated with liver transplantation play an important role in the induction of graft injury. One of the earliest events associated with the reperfusion injury is en- dothelial cell dysfunction. It is generally accepted that endothelial nitric oxide synthase (e-NOS) is cell-pro- tective by mediating vasodilatation, whereas inducible nitric oxide synthase mediates liver graft injury after transplantation. We conducted a critical review of the literature e...     

Quantitative assessment of pulmonary edema by nuclear magnetic resonance methods

Considerable progress has been made in the application of nuclear magnetic resonance (NMR) imaging and nonimaging techniques to the quantitative assessment of pulmonary edema. NMR measurements offer the advantages of being noninvasive, relatively rapid, and easily repeatable. In addition, NMR imaging is suitable for the determination of lung water distribution. Studies of various animal models have shown that NMR techniques can adequately detect and quantify relative changes in lung water content and distribution in various types of experimental lung injury. Preliminary observations in humans suggest that NMR measurement of relative lung water changes in clinical pulmonary edema should be feasible. Although the application of NMR to the assessment of pulmonary edema appears to be very promising, it also poses significant problems that must be solved before it can be established as a standard experimental and clinical method.     

Hypothermia and prostaglandin E(1) produce synergistic attenuation of ischemia-reperfusion lung injury.

Current methods of preserving lung tissue for transplantation are inadequate. In this study, we tested whether the combination of hypothermia plus prostaglandin E(1) (PGE(1)) treatment would have synergistic attenuation on ischemia-reperfusion (I/R) lung injury. Isolated rat lung experiments with ischemia for 1 h then reperfusion for 1 h, were conducted using six different perfusates: (1) University of Wisconsin solution (UW) at 30 degrees C (n = 5), (2) UW at 22 degrees C (n = 5), (3) UW at 10 degrees C (n = 4), (4) UW+PGE(1) at 30 degrees C (n = 4), (5) UW+PGE(1) at 22 degrees C (n = 4), and (6) UW+PGE(1) at 10 degrees C (n = 4). Hemodynamic changes, lung weight gain, capillary filtration coefficients, and lung pathology were analyzed to evaluate the I/R injury. Compared with 30 degrees C UW, animals treated with 22 degrees C UW and 10 degrees C UW had less I/R lung injury, with the groups receiving 22 degrees C UW showing superior results to group receiving 10 degrees C UW. The addition of PGE(1) to UW solution produced more attenuation of I/R injury than did UW alone. Among the six groups, 10 degrees C UW+PGE(1) produced the most reduction of I/R injury. This study has shown that hypothermia can attenuate I/R injury with the optimal flushing temperature being near 22 degrees C. PGE(1) also has a protective effect on I/R. Furthermore, hypothermia and PGE(1) have synergistic attenuation of I/R lung injury. We propose that pulmonary artery flushed with cooling UW+PGE(1) might improve lung preservation and improve results in lung transplantation.     

Ischemia-reperfusion-induced lung injury

Ischemia-reperfusion-induced lung injury is characterized by nonspecific alveolar damage, lung edema, and hypoxemia occurring within 72 hours after lung transplantation. The most severe form may lead to primary graft failure and remains a significant cause of morbidity and mortality after lung transplantation. Over the past decade, better understanding of the mechanisms of ischemia-reperfusion injury, improvements in the technique of lung preservation, and the development of a new preservation solution specifically for the lung have been associated with a reduction in the incidence of primary graft failure from approximately 30 to 15% or less. Several strategies have also been introduced into clinical practice for the prevention and treatment of ischemia-reperfusion-induced lung injury with various degrees of success. However, only three randomized, double-blinded, placebo-controlled trials on ischemia-reperfusion-induced lung injury have been reported in the literature. In the future, the development of new agents and their application in prospective clinical trials are to be expected to prevent the occurrence of this potentially devastating complication and to further improve the success of lung transplantation.     

The role of fibre-optic bronchoscopy in solid organ, transplant patients with pulmonary infections.

Organ transplantation is currently the standard therapy for patients with end-stage organ dysfunction. The immunosuppression caused by this therapy increases the rate of infection, particularly in the lungs. Early diagnosis is extremely important and fibre-optic bronchoscopy is a helpful tool in reaching diagnosis. Knowing the timing of various pathogens following transplantation, and the radiological picture as well as the prophylactic regimen, is helpful when specific pathogens are suspected. Bronchoscopy with bronchoalveolar lavage and transbronchial biopsies are particularly helpful in diagnosis of bacterial cytomegalovirus (CMV) and pneumocytosis carinii pneumocytosis, and is considered a safe procedure. Open lung biopsy is reserved for those who have negative bronchoscopy with a reasonable prognosis.     

Post-transplant bronchiolitis obliterans.

Over the last decade, improvements in surgical techniques, lung preservation, immunosuppression, and management of ischaemia/reperfusion injury and infections have made intermediate-term survival after lung transplantation an achievable goal. However, chronic allograft dysfunction in the form of bronchiolitis obliterans remains a major hurdle that threatens both the quality of life and long-term survival of the recipients. It affects up to 50-60% of patients who survive 5 yrs after surgery, and it accounts for >30% of all deaths occurring after the third postoperative year. This article discusses the alloimmune-dependent and -independent risk factors for bronchiolitis obliterans, the current understanding of the pathogenesis of bronchiolitis obliterans based on results of animal and human studies, the clinical staging of the complication, strategies that may contribute to the prevention and/or early detection of bronchiolitis obliterans, and suggestions for future research.     

Monophosphoryl lipid A: A novel agent for inducing pharmacologic myocardial preconditioning

Myocardial tissue appears to possess an endogenous protective mechanism whereby brief ischemic periods precondition cells to better withstand both reversible and irreversible injury associated with prolonged subsequent ischemic events. Protection develops within minutes of transient ischemia, dissipates within 1–2 hours, and then reappears 12–24 hours following the preconditioning ischemic event. This phenomena, known as ischemic preconditioning (IP), is associated with limitation of infarct size, contractile stunning, and ventricular arrhythmias in postischemic/reperfused hearts. Preconditioned myocardium displays reduced anerobic metabolism, ATPase function, and, hence, improved ATP preservation during ischemia, reduced cytosolic calcium concentrations during reperfusion, and preservation of ultrastructural and myofilament integrity. Efforts to dissect the intracellular signal transduction pathway operative in IP have met with some success. Ischemic preconditioning is associated with activation of myocyte G_i protein-coupled receptors such as adenosine and acetylcholine, activation of PKC, production of nitric oxide, and, eventually, opening of ATP-sensitive potassium (K_ATP) channels. Preconditioning can also be elicited by pharmacologic means using adenosine receptor agonists, activators of PKC, nitric oxide inducers, and K_ATP openers, among other strategies. Monophosphoryl lipid A (MLA), a nontoxic derivative of the endotoxin pharmacophore lipid A, has been evaluated for cardioprotective activity in numerous preclinical models of cardiac ischemia/ reperfusion injury. MLA, when given as a single dose pre-treatment in various canine and rabbit models 12–24 hours prior to ischemia, limits infarct size and reduces regional and global contractile dysfunction. Cardioprotection in various models is associated with preservation of ATP during ischemia, enhanced 5-nucleotidase and adenosine kinase function during reperfusion, and in these aspects mimics ischemic preconditioning. Priming of K_ATP channel for enhanced opening during ischemia may be a prerequisite for the cardioprotective activity of MLA and is another feature establishing a similarity between MLA and ischemia induced preconditioning. Efforts continue to further our understanding regarding how MLA may regulate K_ATP channel and thereby precondition myocardium. Ongoing studies include evaluation of a possible direct effect on the K_ATP channel, investigation of the ability of MLA to induce a secondary mediator of potassium channel modulation, and evaluation of MLA's ability to phosphorylate the K_ATP channel as a consequence of kinase activation. Pretreatment with MLA represents a novel method of pharmacologically preconditioning myocardium, displaying a time course for development similar to that of the second window of ischemic preconditioning. Prior clinical experience with MLA indicates that intravenous doses of up to at least 20 g/kg may be given safely to humans. The drug is currently being evaluated in patients undergoing coronary artery bypass engraftment surgery and may prove to be a useful way to protect myocardium from anticipated ischemic events.     

Acute and chronic rejection after lung transplantation

Over the last decade, improvements in surgical techniques, lung preservation, immunosuppression, and management of ischemia-reperfusion injury and infections have contributed to increase the 1 year patient survival after lung transplantation to 70 to 80%. However, the incidence of acute rejection remains higher than after other types of solid organ transplantation, and long-term survival is threatened by bronchiolitis obliterans, which is thought to be a form of chronic allograft rejection. This article reviews major aspects of clinical presentation, risk factors, diagnosis, and management of acute and chronic rejection after lung transplantation.     

肺组织细胞凋亡与血清细胞因子变化的关系

目的 探讨大鼠肾缺血再灌注后肺组织细胞凋亡及血清细胞因子的的变化,分析其在肾缺血再灌注后肺损伤发病机制中的作用.方法 用无损伤动脉夹钳夹大鼠双侧肾蒂45 min制成肾缺血再灌注损伤模型.观察缺血再灌注后2 h、6 h、12 h、24 h、72 h血清白介素1β(IL-1β)和一氧化氮(NO)的浓度,病理切片观察肺组织病...     

Liver and kidney preservation by perfusion

The clinical boundaries of transplantation have been set in an era of simple cold storage. Research in organ preservation has led to the development of flush solutions that buffer the harsh molecular conditions which develop during ischaemia, and provide stored organs that are fit to sustain life after transplantation. Although simple and efficient, this method might be reaching its limit with respect to the duration, preservation, and the quality of organs that can be preserved. In addition, flush preservation does not allow for adequate viability assessment. There is good evidence that preservation times will be extended by the provision of continuous cellular substrate. Stimulation of in-vivo conditions by ex-vivo perfusion could also mean that marginal organs will be salvaged for transplantation. Perfusion will also allow for assessing the viability of organs before transplantation in a continuous fashion. The cumulative effect of these benefits would include expansion of the donor pool, less risk of primary non-function, and extension of the safe preservation period. Use of non-heart-beating donors, international organ sharing, and precise calculation of the risk of primary organ failure could become standard.     

Failure to express the P-selectin gene or P-selectin blockade confers early pulmonary protection after lung ischemia or transplantation

Endothelial P-selectin expression contributes to the first wave of neutrophil (polymorphonuclear leukocyte; PMN) influx in several inflammatory conditions. Although remote tissue ischemia, such as a crush injury to the hindlimb, may result in P-selectin-mediated pulmonary leukosequestration, it is not known whether the lungs exhibit a similar response after hypothermic preservation or when subjected to a direct ischemic insult. To determine if P-selectin may mediate early primary graft failure, left lungs harvested from male Lewis rats were preserved for 6 hr at 4°C and transplanted orthotopically into isogeneic recipients. Recipients immunodepleted of PMNs before transplantation demonstrated improved graft function; pulmonary vascular resistance was reduced ≈6-fold, arterial oxygenation was increased ≈3-fold, and recipient survival was increased ≈4-fold (P < 0.05, 0.05, and 0.005, respectively). Administration of a blocking anti-P-selectin IgG 10 min before reperfusion diminished graft PMN infiltration and resulted in improved graft function and recipient survival compared with controls. To establish the role of P-selectin in normothermic pulmonary ischemia, mice were subjected to temporary left pulmonary artery ligation. After functional removal of the nonischemic right lung, mice deletionally mutant for the P-selectin gene (P-selectin −/−) exhibited reduced PMN infiltration (≈2-fold), improved arterial oxygenation (≈2-fold), and improved survival (≈3-fold) compared with P-selectin +/+ control mice (P < 0.05, 0.01, and 0.05, respectively). These studies isolate and identify the central role of a single gene product (P-selectin) in early PMN recruitment and tissue injury after frank pulmonary ischemia and in the setting of lung transplantation after hypothermic preservation.     

Ischemic post-conditioning to counteract intestinal ischemia/reperfusion injury

Intestinal ischemia is a severe disorder with a variety of causes. Reperfusion is a common occurrence during treatment of acute intestinal ischemia but the injury resulting from ischemia/reperfusion (IR) may lead to even more serious complications from intestinal atrophy to multiple organ failure and death. The susceptibility of the intestine to IR-induced injury (IRI) appears from various experimental studies and clinical settings such as cardiac and major vascular surgery and organ transplantation. Whereas oxygen free radicals, activation of leukocytes, failure of microvascular perfusion, cellular acidosis and disturbance of intracellular homeostasis have been implicated as important factors in the pathogenesis of intestinal IRI, the mechanisms underlying this disorder are not well known. To date, increasing attention is being paid in animal studies to potential pre- and post-ischemia treatments that protect against intestinal IRI such as drug interference with IR-induced apoptosis and inflammation processes and ischemic pre-conditioning. However, better insight is needed into the molecular and cellular events associated with reperfusion-induced damage to develop effective clinical protection protocols to combat this disorder. In this respect, the use of ischemic post-conditioning in combination with experimentally prolonged acidosis blocking deleterious reperfusion actions may turn out to have particular clinical relevance.     

Ex vivo lung perfusion

Lung transplantation is a life-saving treatment for patients with end stage lung disease. The imbalance between lung graft supply and recipients has been a serious issue and barrier to successful lung transplantation. Ex vivo lung perfusion is a strategy wherein lungs are perfused and ventilated outside of the body. This technology has emerged as a safe preservation method that also enables the reassessment and reconditioning of marginal lung grafts. Ex vivo lung perfusion has successfully expanded the donor pool and led to greater lung transplant activity worldwide. Furthermore, ex vivo lung perfusion can be used as a platform for advanced diagnostics that enable specific targeted or personalized treatments that can be developed along a bench to bedside pathway leading to safe ex vivo intervention. Recent findings have shown that ex vivo lung perfusion could significantly and safely extend the preservation period, which enables transplant programs further optimization of the logistics around transplantation surgeries, and create a new paradigm whereby donor lungs are assessed at a centralized ex vivo lung perfusion center prior to delivery to a transplant clinic in need. The introduction of ex vivo lung perfusion to clinical lung transplantation has been a major step in the evolution and practice of lung transplantation.     

New concepts in reactive oxygen species and cardiovascular reperfusion physiology

Increasingly complex behavior of free radicals and reactive oxygen species (ROS) are noted within biological systems. Classically free radicals and ROS were considered injurious, however current mechanisms describe both protective and deleterious effects. A burst of ROS has been well described with the first moments of reperfusion and is associated with injury. However ROS can also be protective as signal preconditioning protection and induce stress responses that lead to survival. ROS generation is appreciated to occur during ischemia despite the low oxygen tension, from a likely mitochondria source, and ROS-induced ROS release may amplify its signal. The burst of ROS seen during reperfusion may originate from a different cellular source than during ischemia and is not yet fully identified. ROS and cellular redox conditions regulate a large number of vital pathways (energy metabolism, survival/stress responses, apoptosis, inflammatory response, oxygen sensing, etc). While cellular systems may demonstrate reperfusion injury, whole organ and animal models continue to report contradictory results on reperfusion injury and the role of antioxidants as a therapy. Collectively, these data may offer insight into why clinical trials of antioxidants have had such mixed and mostly negative results. Future antioxidant therapies are likely to be effective but they must become: more specific for site of action, not have deleterious effects on other signaling pathways, be targeted to a specific reactive oxygen species or cellular compartment, and be "time sensitive" so they deliver the correct therapy at precisely the correct time in ischemia and reperfusion.