Early activation of the inflammatory response in the liver of brain-dead non-human primates

Association of Procurement Time With Pancreas Transplant Outcomes in Brain-Dead Donors

A brain-death-induced cytokine storm damages organs in an organ donor. However, a longer time period between declaration of brain death and organ procurement (procurement interval) is associated with improved outcomes in kidney, liver, heart, and lung transplantation. The aim of this study was to find the optimal procurement interval for pancreas transplantation. Association of procurement interval with pancreas graft outcomes was analyzed using multivariable models adjusted for variables possibly affecting procurement interval and outcomes. Altogether 10,119 pancreas transplantations were included from the Scientific Registry of Transplant Recipients. The median follow-up was 3.2 (IQR 1.01-6.50) years. During the first year, 832 (9.0%) grafts were lost, including 555 (6.0%) within the first 30 days. Longer procurement interval was associated with increased death-censored graft survival in a multivariable model (HR 0.944 95% CI 0.917-0.972, per 10-h increase, p < 0.001). A decreasing hazard of graft loss was observed also with 1-year, but not with 30-day graft survival. During 1-year follow-up, 953 (12.1%) patients had an acute rejection, and longer procurement interval was also associated with less acute rejections (OR 0.937 95% CI 0.900-0.976, per 10-h increase, p = 0.002) in the multivariable model. In conclusion, longer procurement interval is associated with improved long-term outcomes in pancreas transplantation.

Effects of donor source on transcriptomic profiles of human kidney tissue

Normal human tissue is a critical reference control in biomedical research. However, the type of tissue donor can significantly affect the underlying biology of the samples. We investigated the impact of tissue donor source type by performing transcriptomic analysis on healthy kidney tissue from three donor source types: cadavers, organ donors, and normal-adjacent tissue from surgical resections of clear cell renal cell carcinomas, and we compared the gene expression profiles to those of clear cell renal cell carcinoma samples. Comparisons among the normal samples revealed general similarity, with notable differences in gene expression pathways involving immune system and inflammatory processes, response to extracellular stimuli, ion transport, and metabolism. When compared to tumors, the transcriptomic profiles of the normal adjacent tissue were highly similar to the profiles from cadaveric and organ donor tissue samples, arguing against the presence of a field cancerization effect in clear cell renal cell carcinoma. We conclude that all three normal source types are suitable for reference kidney control samples, but important differences must be noted for particular research areas and tissue banking strategies.

Timing of Organ Procurement From Brain-Dead Donors Associates With Short- and Long-Term Outcomes After Liver Transplantation

Brain death-induced cytokine storm is thought to harm transplantable organs. However, longer procurement times have been associated with non-inferior or better outcomes in kidney, heart, and lung transplants, while optimal procurement time for liver allografts is unknown. Our aim was to analyze the association of time interval from brain death to organ procurement with liver allograft outcomes in two nationwide cohorts. The association of procurement interval with graft survival and short-term complications was analysed in multivariable models. Altogether 643 and 58,017 orthotopic liver transplantations from brain-dead donors were included from Finland between June 2004 and December 2017 and the US between January 2008 and August 2018, respectively. Median time from brain death to organ procurement was 10.5 h in Finland and 34.6 h in the US. Longer interval associated with better graft survival (non-linearly, p = 0.016) and less acute rejections (OR 0.935 95% CI 0.894–0.978) in the US cohort, and better early allograft function (p = 0.005; Beta −0.048 95% CI −0.085 −(−0.011)) in the Finnish cohort, in multivariable models adjusted with Donor Risk Index, recipient age, Model for End-Stage Liver Disease and indication for transplantation. Progressive liver injury after brain death is unlikely. Rushing to recover seems unnecessary; rest and repair might prove beneficial.

Stress and the "extended" autonomic system

This review updates three key concepts of autonomic neuroscience-stress, the autonomic nervous system (ANS), and homeostasis. Hans Selye popularized stress as a scientific idea. He defined stress variously as a stereotyped response pattern, a state that evokes this pattern, or a stimulus that evokes the state. According to the "homeostat" theory stress is a condition where a comparator senses a discrepancy between sensed afferent input and a response algorithm, the integrated error signal eliciting specific patterns of altered effector outflows. Scientific advances since Langley's definition of the ANS have incited the proposal here of the "extended autonomic system," or EAS, for three reasons. (1) Several neuroendocrine systems are bound inextricably to Langley's ANS. The first to be described, by Cannon in the early 1900s, involves the hormone adrenaline, the main effector chemical of the sympathetic adrenergic system. Other neuroendocrine systems are the hypothalamic-pituitary-adrenocortical system, the arginine vasopressin system, and the renin-angiotensin-aldosterone system. (2) An evolving body of research links the ANS complexly with inflammatory/immune systems, including vagal anti-inflammatory and catecholamine-related inflammasomal components. (3) A hierarchical network of brain centers (the central autonomic network, CAN) regulates ANS outflows. Embedded within the CAN is the central stress system conceptualized by Chrousos and Gold. According to the allostasis concept, homeostatic input-output curves can be altered in an anticipatory, feed-forward manner; and prolonged or inappropriate allostatic adjustments increase wear-and-tear (allostatic load), resulting in chronic, stress-related, multi-system disorders. This review concludes with sections on clinical and therapeutic implications of the updated concepts offered here.

Immunomodulatory effects of thalidomide in an experimental brain death liver donor model

Brain death is characterized by a generalized inflammatory response that results in multiorgan damage. This process is mainly mediated through cytokines, which amplify graft immunogenicity. We investigated the immunological response in a brain death liver donor model and analysed the effects of thalidomide, a drug with powerful immunomodulatory properties. Brain death was induced in male Lewis rats. We studied three groups: Control (sham-operated rats in which trepanation was performed without inserting the balloon catheter), BD (rats subjected to brain death by increasing intracranial pressure) and BD + Thalid (BD rats receiving thalidomide after brain death). After 6 h, serum levels of AST, ALT, LDH, and ALP as well as systemic and hepatic levels of TNF-α, IL1-β, IL-6, and IL-10 were analysed. We also determined the mRNA expression of MHC Class I and Class II, NF-κB, and macrophage infiltration. NF-κB was also examined by electrophoretic mobility shift assay. Thalidomide treatment significantly reduced serum levels of hepatic enzymes and TNF-α, IL-1-β, and IL-6. These cytokines were evaluated at either the mRNA expression or protein level in liver tissue. In addition, thalidomide administration resulted in a significant reduction in macrophages, MHC Class I and Class II, and NF-κB activation. This study reveals that thalidomide significantly inhibited the immunologic response and graft immunogenicity, possibly through suppression of NF-κB activation.

Effects of chitinase-3-like protein 1 on brain death-induced hepatocyte apoptosis via PAR2-JNK-caspase-3

Hepatocyte apoptosis is a crucial factor affecting liver quality in brain-dead donors. The identification of key molecular proteins involved in brain-death (BD)-induced hepatocyte apoptosis may help determine an effective method for improving the quality of livers from brain-dead donors. In this study, we used in vivo and in vitro models to investigate the role of chitinase-3-like protein 1 (CHI3L1) in promoting liver cell apoptosis after BD. Chitin was used to inhibit CHI3L1 in a rat model of BD. Macrophage polarization of THP-1 cells and hypoxia/reoxygenation (H/R) of LO-2 cells were used to mimic BD-induced cell stress in liver. We found that CHI3L1 played a vital role in promoting liver cell apoptosis. Six hours after BD, CHI3L1 expression was significantly upregulated in liver macrophages and was associated with BD-induced M1 polarization of these cells. In liver cells cultured under H/R conditions, recombinant CHI3L1 activated the protease-activated receptor 2 (PAR2)/c-June N-terminal kinase (JNK) apoptotic pathway and aggravated apoptosis. Compared with the control group, chitin particles inhibited the expression of CHI3L1 in the liver of brain dead rats, thereby reducing activation of the hepatocyte surface receptor, PAR2, and its downstream JNK/caspase-3 signaling pathway, ultimately reducing hepatocyte apoptosis. In conclusion, our results indicate that CHI3L1 relies on a PAR2/JNK-mediated mechanism to promote BD-induced hepatocyte apoptosis.

Sterile inflammation in thoracic transplantation

The life-saving benefits of organ transplantation can be thwarted by allograft dysfunction due to both infectious and sterile inflammation post-surgery. Sterile inflammation can occur after necrotic cell death due to the release of endogenous ligands [such as damage-associated molecular patterns (DAMPs) and alarmins], which perpetuate inflammation and ongoing cellular injury via various signaling cascades. Ischemia-reperfusion injury (IRI) is a significant contributor to sterile inflammation after organ transplantation and is associated with detrimental short- and long-term outcomes. While the vicious cycle of sterile inflammation and cellular injury is remarkably consistent amongst different organs and even species, we have begun understanding its mechanistic basis only over the last few decades. This understanding has resulted in the developments of novel, yet non-specific therapies for mitigating IRI-induced graft damage, albeit with moderate results. Thus, further understanding of the mechanisms underlying sterile inflammation after transplantation is critical for identifying personalized therapies to prevent or interrupt this vicious cycle and mitigating allograft dysfunction. In this review, we identify common and distinct pathways of post-transplant sterile inflammation across both heart and lung transplantation that can potentially be targeted.

The extended autonomic system, dyshomeostasis, and COVID-19

The pandemic viral illness COVID-19 is especially life-threatening in the elderly and in those with any of a variety of chronic medical conditions. This essay explores the possibility that the heightened risk may involve activation of the “extended autonomic system” (EAS). Traditionally, the autonomic nervous system has been viewed as consisting of the sympathetic nervous system, the parasympathetic nervous system, and the enteric nervous system. Over the past century, however, neuroendocrine and neuroimmune systems have come to the fore, justifying expansion of the meaning of “autonomic.” Additional facets include the sympathetic adrenergic system, for which adrenaline is the key effector; the hypothalamic-pituitary-adrenocortical axis; arginine vasopressin (synonymous with anti-diuretic hormone); the renin-angiotensin-aldosterone system, with angiotensin II and aldosterone the main effectors; and cholinergic anti-inflammatory and sympathetic inflammasomal pathways. A hierarchical brain network—the “central autonomic network”—regulates these systems; embedded within it are components of the Chrousos/Gold “stress system.” Acute, coordinated alterations in homeostatic settings (allostasis) can be crucial for surviving stressors such as traumatic hemorrhage, asphyxiation, and sepsis, which throughout human evolution have threatened homeostasis; however, intense or long-term EAS activation may cause harm. While required for appropriate responses in emergencies, EAS activation in the setting of chronically decreased homeostatic efficiencies (dyshomeostasis) may reduce thresholds for induction of destabilizing, lethal vicious cycles. Testable hypotheses derived from these concepts are that biomarkers of EAS activation correlate with clinical and pathophysiologic data and predict outcome in COVID-19 and that treatments targeting specific abnormalities identified in individual patients may be beneficial.

Brain Death Enhances Activation of the Innate Immune System and Leads to Reduced Renal Metabolic Gene Expression

BACKGROUND

Brain death (BD)-associated inflammation has been implicated in decreased kidney allograft function and survival, but the underlying mechanisms have not been well distinguished from the conditions of critical care itself. We have developed a clinically translatable model to separate and investigate strategies to improve donor management and critical care.

METHODS

Brain-dead (n = 12) and sham (n = 5) rhesus macaques were maintained for 20 hours under intensive care unit-level conditions. Samples were collected for immunophenotyping, analysis of plasma proteins, coagulation studies, and gene analysis for changes in immune and metabolic profile with comparison to naive samples (n = 10).

RESULTS

We observed an increase in circulating leukocytes and cytokines, activation of complement and coagulation pathways, and upregulation of genes associated with inflammation in both brain-dead and sham subjects relative to naïve controls. Sham demonstrated an intermediate phenotype of inflammation compared to BD. Analysis of gene expression in kidneys from BD kidneys revealed a similar upregulation of inflammatory profile in both BD and sham subjects, but BD presented a distinct reduction in metabolic and respiratory processes compared to sham and naïve kidneys.

CONCLUSION

BD is associated with activation of specific pathways of the innate immune system and changes to metabolic gene expression in renal tissue itself; however, sham donors presented an intermediate inflammatory response attributable to the critical care environment. The early onset and penetrating impact of this inflammatory response underscores the need for early intervention to prevent perioperative tissue injury to transplantable organs.

Targeted donor complement blockade after brain death prevents delayed graft function in a nonhuman primate model of kidney transplantation

Delayed graft function (DGF) in renal transplant is associated with reduced graft survival and increased immunogenicity. The complement-driven inflammatory response after brain death (BD) and posttransplant reperfusion injury play significant roles in the pathogenesis of DGF. In a nonhuman primate model, we tested complement-blockade in BD donors to prevent DGF and improve graft survival. BD donors were maintained for 20 hours; kidneys were procured and stored at 4°C for 43-48 hours prior to implantation into ABO-compatible, nonsensitized, MHC-mismatched recipients. Animals were divided into 3 donor-treatment groups: G1 - vehicle, G2 - rhC1INH+heparin, and G3 - heparin. G2 donors showed significant reduction in classical complement pathway activation and decreased levels of tumor necrosis factor α and monocyte chemoattractant protein 1. DGF was diagnosed in 4/6 (67%) G1 recipients, 3/3 (100%) G3 recipients, and 0/6 (0%) G2 recipients (P = .008). In addition, G2 recipients showed superior renal function, reduced sC5b-9, and reduced urinary neutrophil gelatinase-associated lipocalin in the first week posttransplant. We observed no differences in incidence or severity of graft rejection between groups. Collectively, the data indicate that donor-management targeting complement activation prevents the development of DGF. Our results suggest a pivotal role for complement activation in BD-induced renal injury and postulate complement blockade as a promising strategy for the prevention of DGF after transplantation.

The role of innate immunity in the long-term outcome of lung transplantation

Long-term survival after lung transplantation remains suboptimal due to chronic lung allograft dysfunction (CLAD), a progressive scarring process affecting the graft. Although anti-donor alloimmunity is central to the pathogenesis of CLAD, its underlying mechanisms are not fully elucidated and it is neither preventable nor treatable using currently available immunosuppression. Recent evidence has shown that innate immune stimuli are fundamental to the development of CLAD. Here, we examine long-standing assumptions and new concepts linking innate immune activation to late lung allograft fibrosis.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Complement inhibition attenuates acute kidney injury after ischemia-reperfusion and limits progression to renal fibrosis in mice

The complement system is an essential component of innate immunity and plays a major role in the pathogenesis of ischemia-reperfusion injury (IRI). In this study, we investigated the impact of human C1-inhibitor (C1INH) on the early inflammatory response to IRI and the subsequent progression to fibrosis in mice. We evaluated structural damage, renal function, acute inflammatory response, progression to fibrosis and overall survival at 90-days post-injury. Animals receiving C1INH prior to reperfusion had a significant improvement in survival rate along with superior renal function when compared to vehicle (PBS) treated counterparts. Pre-treatment with C1INH also prevented acute IL-6, CXCL1 and MCP-1 up-regulation, C5a release, C3b deposition and infiltration by neutrophils and macrophages into renal tissue. This anti-inflammatory effect correlated with a significant reduction in the expression of markers of fibrosis alpha smooth muscle actin, desmin and picrosirius red at 30 and 90 days post-IRI and reduced renal levels of TGF-β1 when compared to untreated controls. Our findings indicate that intravenous delivery of C1INH prior to ischemic injury protects kidneys from inflammatory injury and subsequent progression to fibrosis. We conclude that early complement blockade in the context of IRI constitutes an effective strategy in the prevention of fibrosis after ischemic acute kidney injury.

Transplantation and Damage-Associated Molecular Patterns (DAMPs)

Upon solid organ transplantation and during cancer immunotherapy, cellular stress responses result in the release of damage-associated molecular patterns (DAMPs). The various cellular stresses have been characterized in detail over the last decades, but a unifying classification based on clinically important aspects is lacking. Here, we provide an in-depth review of the most recent literature along with a unifying concept of the danger/injury model, suggest a classification of DAMPs, and review the recently elaborated mechanisms that result in the emission of such factors. We further point out the differences in DAMP responses including the release following a heat shock pattern, endoplasmic reticulum stress, DNA damage-mediated DAMP release, and discuss the diverse pathways of regulated necrosis in this respect. The understanding of various forms of DAMPs and the consequences of their different release patterns are prerequisite to associate serum markers of cellular stresses with clinical outcomes.

Exendin-4 attenuates brain death-induced liver damage in the rat

The majority of liver grafts destined for transplantation originate from brain dead donors. However, significantly better posttransplantation outcomes are achieved when organs from living donors are used, suggesting that brain death (BD) causes irreversible damage to the liver tissue. Recently, glucagon-like peptide-1 (GLP1) analogues were shown to possess interesting hepatic protection effects in different liver disease models. We hypothesized that donor treatment with the GLP1 analogue exendin-4 (Ex-4) could alleviate BD-induced liver damage. A rat model of BD was employed in order to estimate BD-induced liver damage and Ex-4's potential protective effects. Liver damage was assessed by biochemical determination of circulating hepatic markers. Apoptosis in the hepatic tissue was assessed by immunoblot and immunohistochemistry using an antibody that only recognizes the active form of caspase-3. Gene expression changes in inflammation and stress response genes were monitored by quantitative real-time polymerase chain reaction. Here, we show that Ex-4 administration to the brain dead liver donors significantly reduces levels of circulating aspartate aminotransferase and lactate dehydrogenase. This was accompanied by a remarkable reduction in hepatocyte apoptosis. In this model, BD caused up-regulation of tumor necrosis factor and stress-related genes, confirming previous findings in clinical and animal studies. In conclusion, treatment of brain dead rats with Ex-4 reduced BD-induced liver damage. Further investigation is needed to determine the molecular basis of the observed liver protection. After testing in a randomized clinical trial, the inclusion of GLP1 analogues in organ donor management might help to improve organ quality, maximize organ donation, and possibly increase liver transplantation success rates.

Inflammatory triggers of acute rejection of organ allografts

Solid organ transplantation is a vital therapy for end stage diseases. Decades of research have established that components of the adaptive immune system are critical for transplant rejection, but the role of the innate immune system in organ transplantation is just emerging. Accumulating evidence indicates that the innate immune system is activated at the time of organ implantation by the release of endogenous inflammatory triggers. This review discusses the nature of these triggers in organ transplantation and also potential mediators that may enhance inflammation resolution after organ implantation.

The role of complement in the pathogenesis of renal ischemia-reperfusion injury and fibrosis

The complement system is a major component of innate immunity and has been commonly identified as a central element in host defense, clearance of immune complexes, and tissue homeostasis. After ischemia-reperfusion injury (IRI), the complement system is activated by endogenous ligands that trigger proteolytic cleavage of complement components via the classical, lectin and/or alternative pathway. The result is the formation of terminal complement components C3a, C5a, and the membrane attack complex (C5b-9 or MAC), all of which play pivotal roles in the amplification of the inflammatory response, chemotaxis, neutrophil/monocyte recruitment and activation, and direct tubular cell injury. However, recent evidence suggests that complement activity transcends innate host defense and there is increasing data suggesting complement as a regulator in processes such as allo-immunity, stem cell differentiation, tissue repair, and progression to fibrosis. In this review, we discuss recent advances addressing the role of complement as a regulator of IRI and renal fibrosis after organ donation for transplantation. We will also briefly discuss currently approved therapies that target complement activity in kidney ischemia-reperfusion and transplantation.

The role of complement in the pathogenesis of renal ischemia-reperfusion injury and fibrosis

The complement system is a major component of innate immunity and has been commonly identified as a central element in host defense, clearance of immune complexes, and tissue homeostasis. After ischemia-reperfusion injury (IRI), the complement system is activated by endogenous ligands that trigger proteolytic cleavage of complement components via the classical, lectin and/or alternative pathway. The result is the formation of terminal complement components C3a, C5a, and the membrane attack complex (C5b-9 or MAC), all of which play pivotal roles in the amplification of the inflammatory response, chemotaxis, neutrophil/monocyte recruitment and activation, and direct tubular cell injury. However, recent evidence suggests that complement activity transcends innate host defense and there is increasing data suggesting complement as a regulator in processes such as allo-immunity, stem cell differentiation, tissue repair, and progression to fibrosis. In this review, we discuss recent advances addressing the role of complement as a regulator of IRI and renal fibrosis after organ donation for transplantation. We will also briefly discuss currently approved therapies that target complement activity in kidney ischemia-reperfusion and transplantation.

Treating the donor

PURPOSE OF REVIEW

Current pressures of organ supply and demand require maximization of potential for organ donation. The donor population is older and has more significant comorbidity than in the past.Optimal management of the donor after brain death (DBD) is essential to ensure that the greatest number of organs can be transplanted per donor. Defining evidence-based drugs and techniques to assist this has never been more important.

RECENT FINDINGS

Care of patients with catastrophic brain injury incorporating supportive therapy targeted at specific goals and delivered by experienced specialists provides the best donation outcomes. Such pathways represent best practice critical care applied to this population. In this context, the value of some previously recommended therapies appears questionable and warrants reassessment. Prolonged (>24 h) incorporeal organ conditioning may have significant benefits.Extracorporeal support in the resuscitation arena is emerging and, in patients who fail to respond, may yield a new source of donors.

SUMMARY

Early identification of potential DBD, best practice critical care, and achieving defined treatment goals are associated with more transplantable organs. Study of a complex intervention like donor management presents significant problems of organization, ethics and consent. This situation is recognized internationally and progress is being made.

Donor Pretreatment With IL-1 Receptor Antagonist Attenuates Inflammation and Improves Functional Potency in Islets From Brain-Dead Nonhuman Primates

Most pancreas and islet grafts are recovered from brain-dead (BD) donors. In this study we characterized the early inflammatory response induced by brain death in pancreata and islets from nonhuman primate donors and evaluated the effect of targeted anti-inflammatory intervention in the protection of pancreatic islets prior to transplantation. BD donors were monitored for 6 h and assigned to three experimental groups: group 1: BD-untreated donors (BD-UT) (n = 7), group 2: BD + donor pretreatment with IL-1ra (n = 6), and group 3: non-BD animals serving as controls (n = 7). We observed an IL-1ra-dependent reduction in the mobilization and activation of neutrophils from bone marrow and a significantly reduced accumulation of CD68(+) leukocytes in the pancreas and islets after brain death induction. Donor treatment with IL-1ra significantly decreased chemokine mRNA expression (MCP-1, IL-8, and MIP-1a) and attenuated the activation of circulating neutrophils and intraislet macrophages as demonstrated by a reduction in intracellular IL-1β, IL-6, MCP-1, and MIP-1α expression. As a result, IL-1ra dramatically improved viability, mitochondrial membrane polarity, and islet engraftment in mice transplanted using a minimal islet mass. These results suggest that early immunomodulation targeting inflammation in the BD donor may represent an effective therapeutic strategy to improve islet quality and function prior to transplantation.