Immunologic activation in an experimental brain death liver donor model
Alexandre Chagas Santana1,3,8, Wellington Andraus2, Dan Zimelewicz Oberman7, Nícollas Nunes Rabelo3, Filipe Miranda Oliveira Silva4, Humberto Dellê4, Rafael Pepineli4, Edvaldo Leal de Moraes1, Cristoforo Scavone5, Larissa de Sá Lima5, Sergio Brasil3, Liliane Moreira Ruiz6, Karina Andrighetti de Oliveira-Braga6, Natalia Aparecida Nepomuceno6, Paulo Manuel Pêgo-Fernandes6, Marcelo José Dos Santos8, Eberval Gadelha Figueiredo3.
1Organ Procurement Organization Department, University of São Paulo, São Paulo, Brazil; 2Gastroenterology Department, University of São Paulo, SAO PAULO, Brazil; 3Neurological Surgery Department, University of São Paulo, SAO PAULO, Brazil; 4Medical Science Department, Nove de Julho University, SAO PAULO, Brazil; 5Molecular Neuropharmacology Laboratory, University of São Paulo, SAO PAULO, Brazil; 6Cardiopneumology Department, University of São Paulo, SAO PAULO, Brazil; 7Department of Neurosurgery, Hospital de Forca Aerea do Galeão, SAO PAULO, Brazil; 8School of Nursing, University of São Paulo, SAO PAULO, Brazil
Introduction: Brain death (BD) is characterized by a complex inflammatory response, resulting in dysfunction of potentially transplantable organs. This process is modulated by cytokines, which results in an augmnented inflammation and, consequently, increases the expression of major histocompatibility complex (MHC) in donor cells, amplifying graft immunogenicity. The inflammatory mechanisms in BD are not fully understood, but there several pathways are reported. In this context, the nuclear factor kappa B (NF-κB) has a remarkable role in coordinating the expression of variety of genes, especially those that participate in inflammation and alloimmunity.
Objective: The purpose of this study is to analyse and characterize the local and systemic participation of immunologic response in an experimental model of BD, though evaluation of inflammatory cytokines and NF-κB activity in hepatic tissue, as well as evaluate biochemical parameters of liver function.
Methods: The study was developed with 2 experimental groups (n=8 per group) as follows: Control: Lewis rats submitted to trephination without Fogarty catheter insertion (sham-operated). BD: Lewis rats submitted to BD through ICP increase by Fogarty catheter. Color transcranial ultrasound was utilized to subsidiary examination for brain death determination diagnosis. After 6 h, serum levels of aspartate aminotransferase (AST), and alanine aminotransferese (ALT), as well as systemic and hepatic levels of TNF-α, and IL1-β were analysed. In addition, Class I MHC, Class II MHC and NF-κB activity in liver tissue were analised.
Results: 6h after BD, serum levels of ALT and AST were significantly elevated compared to the Control group. Signs of immunologic activation was demonstrated in the BD model, by the detection of significantly higher levels of serum and mRNA cytokines (TNF-α and IL1-β), as well as NFκB activation in the liver tissue, compared with the control group. Moreover, Class I MHC and Class II MHC molecules were increased significantly in the BD group compared to the controls, suggesting that the immunogenicity of the hepatic allograft increased following brain death. The results are shown in the attached figures.
Conclusion: The current study found that BD is a multifaceted process that elicits both a systemic immune response and a local inflammatory response in liver tissue. Our findings strongly suggested that the immunogenicity of plasma and liver increased with time following brain death. These findings, taken combined, shed light on the immunological response in brain-dead organ donors. Future research should focus on gaining a better knowledge of the pathophysiology of BD in order to identify new and effective therapy targets.
