Effect of oxidative stress and endotoxin on human serum albumin in brain-dead organ donors

Brain stem death induces pro-inflammatory cytokine production and cardiac dysfunction in sheep model

Introduction

Organs procured following brain stem death (BSD) are the main source of organ grafts for transplantation. However, BSD is associated with inflammatory responses that may damage the organ and affect both the quantity and quality of organs available for transplant. Therefore, we aimed to investigate plasma and bronchoalveolar lavage (BAL) pro-inflammatory cytokine profiles and cardiovascular physiology in a clinically relevant 6-h ovine model of BSD.

Methods

Twelve healthy female sheep (37–42 Kg) were anaesthetized and mechanically ventilated prior to undergoing BSD induction and then monitored for 6 h. Plasma and BAL endothelin-1 and cytokines (IL-1β, 6, 8 and tumour necrosis factor alpha (TNF-α)) were assessed by ELISA. Differential white blood cell counts were performed. Cardiac function during BSD was also examined using echocardiography, and cardiac biomarkers (A-type natriuretic peptide and troponin I were measured in plasma.

Results

Plasma concentrations big ET-1, IL-6, IL-8, TNF-α and BAL IL-8 were significantly (p < 0.01) increased over baseline at 6 h post-BSD. Increased numbers of neutrophils were observed in the whole blood (3.1 × 10⁹ cells/L [95% confidence interval (CI) 2.06–4.14] vs. 6 × 10⁹ cells/L [95%CI 3.92–7.97]; p < 0.01) and BAL (4.5 × 10⁹ cells/L [95%CI 0.41–9.41] vs. 26 [95%CI 12.29–39.80]; p = 0.03) after 6 h of BSD induction vs baseline. A significant increase in ANP production (20.28 pM [95%CI 16.18–24.37] vs. 78.68 pM [95%CI 53.16–104.21]; p < 0.0001) and cTnI release (0.039 ng/mL vs. 4.26 [95%CI 2.69–5.83] ng/mL; p < 0.0001), associated with a significant reduction in heart contractile function, were observed between baseline and 6 h.

Conclusions

BSD induced systemic pro-inflammatory responses, characterized by increased neutrophil infiltration and cytokine production in the circulation and BAL fluid, and associated with reduced heart contractile function in ovine model of BSD.

Pyroptosis in Kidney Disease

In the last several decades, apoptosis interference has been considered clinically irrelevant in the context of renal injury. Recent discovery of programmed necrotic cell death, including necroptosis, ferroptosis, and pyroptosis refreshed our understanding of the role of cell death in kidney disease. Pyroptosis is characterized by a lytic pro- inflammatory type of cell death resulting from gasdermin-induced membrane permeabilization via activation of inflammatory caspases and inflammasomes. The danger-associated molecular patterns (DAMPs), alarmins and pro-inflammatory cytokines are released from pyroptotic cells in an uncontrolled manner, which provoke inflammation, resulting in secondary organ or tissue injuries. The caspases and inflammasome activation-related proteins and pore-forming effector proteins known as GSDMD and GSDME have been implicated in a variety of acute and chronic microbial and non-microbial kidney diseases. Here, we review the recent advances in pathological mechanisms of pyroptosis in kidney disease and highlight the potential therapeutic strategies in future.

Direct peritoneal resuscitation reduces intestinal permeability after brain death

BACKGROUND

The profound inflammatory response associated with brain death is frequently cited as the reason organs procured from brain dead donors are associated with worse graft function. The intestine releases inflammatory mediators in other types of shock, but its role is brain death has not been well-studied. Direct peritoneal resuscitation (DPR) improves visceral organ blood flow and reduces inflammation after hemorrhagic shock. We hypothesized that use of DPR would maintain intestinal integrity and reduce circulating inflammatory mediators after brain death.

METHODS

Brain death was induced in male Sprague-Dawley rats by inserting a 4F Fogarty catheter into the epidural space and slowly inflating it. After herniation, rats were resuscitated with normal saline to maintain a mean arterial pressure of 80 mm Hg and killed with tissue collected immediately (time 0), or 2 hours, 4 hours, or 6 hours after brain death. Randomly selected animals received DPR via an intraperitoneal injection of 30-mL commercial peritoneal dialysis solution.

RESULTS

Levels of proinflammatory cytokines, including IL-1β and IL-6, as well as high-mobility group box 1 protein and heat shock protein 70, were all increased after brain death and decreased with DPR. Fatty acid binding protein and lipopolysaccharide, both markers of intestinal injury, were increased in the serum after brain death and decreased with DPR. Immunohistochemistry staining for zona occludin-1 showed decreased intestinal tight junction integrity after brain death, which improved with DPR.

CONCLUSIONS

Intestinal permeability increases after brain death, and this contributes to the increased inflammation seen throughout the body. Using DPR prevents intestinal ischemia and helps preserve intestinal integrity. This suggests that using this novel therapy as an adjunct to the resuscitation of brain dead donors has the potential to reduce inflammation and potentially improve the quality of transplanted organs.

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.

Proteomic analysis of differentially expressed proteins in kidneys of brain dead rabbits

A large number of previous clinical studies have reported a delayed graft function for brain dead donors, when compared with living relatives or cadaveric organ transplantations. However, there is no accurate method for the quality evaluation of kidneys from brain-dead donors. In the present study, two-dimensional gel electrophoresis and MALDI-TOF MS-based comparative proteomic analysis were conducted to profile the differentially-expressed proteins between brain death and the control group renal tissues. A total of 40 age- and sex-matched rabbits were randomly divided into donation following brain death (DBD) and control groups. Following the induction of brain death via intracranial progressive pressure, the renal function and the morphological alterations were measured 2, 6 and 8 h afterwards. The differentially expressed proteins were detected from renal histological evidence at 6 h following brain death. Although 904±19 protein spots in control groups and 916±25 in DBD groups were identified in the two-dimensional gel electrophoresis, >2-fold alterations were identified by MALDI-TOF MS and searched by NCBI database. The authors successfully acquired five downregulated proteins, these were: Prohibitin (isoform CRA_b), beta-1,3-N-acetylgalactosaminyltransferase 1, Annexin A5, superoxide dismutase (mitochondrial) and cytochrome b-c1 complex subunit 1 (mitochondrial precursor). Conversely, the other five upregulated proteins were: PRP38 pre-mRNA processing factor 38 (yeast) domain containing A, calcineurin subunit B type 1, V-type proton ATPase subunit G 1, NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 10 and peroxiredoxin-3 (mitochondrial). Immunohistochemical results revealed that the expressions of prohibitin (PHB) were gradually increased in a time-dependent manner. The results indicated that there were alterations in levels of several proteins in the kidneys of those with brain death, even if the primary function and the morphological changes were not obvious. PHB may therefore be a novel biomarker for primary quality evaluation of kidneys from brain-dead donors.

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.

Protein Oxidation in the Lungs of C57BL/6J Mice Following X-Irradiation

Damage to normal lung tissue is a limiting factor when ionizing radiation is used in clinical applications. In addition, radiation pneumonitis and fibrosis are a major cause of mortality following accidental radiation exposure in humans. Although clinical symptoms may not develop for months after radiation exposure, immediate events induced by radiation are believed to generate molecular and cellular cascades that proceed during a clinical latent period. Oxidative damage to DNA is considered a primary cause of radiation injury to cells. DNA can be repaired by highly efficient mechanisms while repair of oxidized proteins is limited. Oxidized proteins are often destined for degradation. We examined protein oxidation following 17 Gy (0.6 Gy/min) thoracic X-irradiation in C57BL/6J mice. Seventeen Gy thoracic irradiation resulted in 100% mortality of mice within 127-189 days postirradiation. Necropsy findings indicated that pneumonitis and pulmonary fibrosis were the leading cause of mortality. We investigated the oxidation of lung proteins at 24 h postirradiation following 17 Gy thoracic irradiation using 2-D gel electrophoresis and OxyBlot for the detection of protein carbonylation. Seven carbonylated proteins were identified using mass spectrometry: serum albumin, selenium binding protein-1, alpha antitrypsin, cytoplasmic actin-1, carbonic anhydrase-2, peroxiredoxin-6, and apolipoprotein A1. The carbonylation status of carbonic anhydrase-2, selenium binding protein, and peroxiredoxin-6 was higher in control lung tissue. Apolipoprotein A1 and serum albumin carbonylation were increased following X-irradiation, as confirmed by OxyBlot immunoprecipitation and Western blotting. Our findings indicate that the profile of specific protein oxidation in the lung is altered following radiation exposure.

The influence of probiotic supplementation on gut permeability in patients with metabolic syndrome: an open label, randomized pilot study

BACKGROUND/OBJECTIVES

Obesity and metabolic disorders are linked to inflammation via gut microbiota and/or gut permeability. Gut-derived endotoxin triggers inflammation leading to metabolic syndrome (MetS) and contributing to oxidative stress. We intended to investigate the effect of Lactobacillus casei Shirota on gut permeability, presence of endotoxin and neutrophil function in MetS.

SUBJECTS/METHODS

Patients with MetS were randomized to receive 3 × 6.5 × 10⁹ CFU L. casei Shirota (probiotic group) or not for 3 months. Gut permeability was assessed by a differential sugar absorption method and by determination of diaminooxidase serum levels, endotoxin by an adapted limulus amoebocyte lysate assay, neutrophil function and toll-like receptor (TLR) expression by flow cytometry and ELISA was used to detect lipopolysaccharide-binding protein (LBP) and soluble CD14 (sCD14) levels.

RESULTS

Twenty-eight patients and 10 healthy controls were included. Gut permeability was significantly increased in MetS compared with controls but did not differ between patient groups. None of the patients were positive for endotoxin. LBP and sCD14 levels were not significantly different from healthy controls. High-sensitive C-reactive protein and LBP levels slightly but significantly increased after 3 months within the probiotics group. Neutrophil function and TLR expression did not differ from healthy controls or within the patient groups.

CONCLUSIONS

Gut permeability of MetS patients was increased significantly compared with healthy controls. L. casei Shirota administration in the MetS patients did not have any influence on any parameter tested possibly due to too-short study duration or underdosing of L. casei Shirota.