The role of molecular chaperonins in warm ischemia and reperfusion injury in the steatotic liver: a proteomic study.

BACKGROUND: The molecular basis of the increased susceptibility of steatotic livers to warm ischemia/reperfusion (I/R) injury during transplantation remains undefined. Animal model for warm I/R injury was induced in obese Zucker rats. Lean Zucker rats provided controls. Two dimensional differential gel electrophoresis was performed with liver protein extracts. Protein features with significant abundance ratios (p < 0.01) between the two cohorts were selected and analyzed with HPLC/MS. Proteins were identified by Uniprot database. Interactive protein networks were generated using Ingenuity Pathway Analysis and GRANITE software. RESULTS: The relative abundance of 105 proteins was observed in warm I/R injury. Functional grouping revealed four categories of importance: molecular chaperones/endoplasmic reticulum (ER) stress, oxidative stress, metabolism, and cell structure. Hypoxia up-regulated 1, calcium binding protein 1, calreticulin, heat shock protein (HSP) 60, HSP-90, and protein disulfide isomerase 3 were chaperonins significantly (p < 0.01) down-regulated and only one chaperonin, HSP-1 was significantly upregulated in steatotic liver following I/R. CONCLUSION: Down-regulation of the chaperones identified in this analysis may contribute to the increased ER stress and, consequently, apoptosis and necrosis. This study provides an initial platform for future investigation of the role of chaperones and therapeutic targets for increasing the viability of steatotic liver allografts.

Ischemia-reperfusion injury in rat steatotic liver is dependent on NFκB P65 activation.

BACKGROUND: Steatotic liver grafts tolerate ischemia-reperfusion (I/R) injury poorly, contributing to increased primary graft nonfunction following transplantation. Activation of nuclear factor kappa-B (NFκB) following I/R injury plays a crucial role in activation of pro-inflammatory responses leading to injury. METHODS: We evaluated the role of NFκB in steatotic liver injury by using an orthotopic liver transplant (OLT) model in Zucker rats (lean to lean or obese to lean) to define the mechanisms of steatotic liver injury. Obese donors were treated with bortezomib to assess the role of NF-κB in steatotic liver I/R injury. Hepatic levels of NF-κB and pro-inflammatory cytokines were analyzed by ELISA. Serum transaminase levels and histopathological analysis were performed to assess associated graft injury. RESULTS: I/R injury in steatotic liver results in significant increases in activation of NF-κB (40%, p<0.003), specifically the p65 subunit following transplantation. Steatotic donor pretreatment with proteasome inhibitor bortezomib (0.1mg/kg) resulted in significant reduction in levels of activated NF-κB (0.58±0.18 vs. 1.37±0.06O.D./min/10 µg protein, p<0.003). Bortezomib treatment also reduced expression of pro-inflammatory cytokines MIP-2 compared with control treated steatotic and lean liver transplants respectively (106±17.5 vs. 443.3±49.9 vs. 176±10.6 pg/mL, p=0.02), TNF-α (223.8±29.9 vs. 518.5±66.5 vs. 264.5±30.1 pg/2 µg protein, p=0.003) and IL-1ß (6.0±0.91 vs. 19.8±5.2 vs. 5±1.7 pg/10 µg protein, p=0.02) along with a significant reduction in ALT levels (715±71 vs. 3712.5±437.5 vs. 606±286 U/L, p=0.01). CONCLUSION: These results suggest that I/R injury in steatotic liver transplantation are associated with exaggerated activation of NFκB subunit p65, leading to an inflammatory mechanism of reperfusion injury and necrosis. Proteasome inhibition in steatotic liver donor reduces NFκB p65 activation and inflammatory I/R injury, improving transplant outcomes of steatotic grafts in a rat model.

Interleukin-1beta is prominent in the early pulmonary inflammatory response after hepatic injury.

BACKGROUND: Acute lung injury and inflammation can occur after hepatic ischemia/reperfusion or cryoablation. The etiology of this response is uncertain although it involves NF-kappaB-mediated cytokine release from the liver. METHODS: Inflammation-specific complementary DNA microarrays were utilized to evaluate cytokine upregulation in mouse lung at 4 hours after partial-volume hepatic cryoablation with a recirculating liquid N(2) probe. Hierarchical cluster analysis was performed to identify candidate genes. On the basis of these results, an enzyme-linked immunosorbent assay for interleukin-1beta (IL-1beta) was conducted on serum and pulmonary parenchymal specimens. The time course of IL-1beta transcriptional upregulation in the liver and lungs was evaluated by quantitative reverse transcription/real-time polymerase chain reaction. RESULTS: Starting with a pool of 35 genes generated from normalization and variation filtration, unsupervised hierarchical clustering clearly distinguished lungs of hepatic cryo-injured mice from controls. Genes from the IL-1-family were prominent in the signature. IL-1beta was demonstrable in serum within 2 hours postinjury (218 +/- 89 pg/mL vs 0 at baseline, P = .01). In the lung, IL-1beta was more than 4-fold greater at 4 hours than at baseline. Real-time polymerase chain reaction showed a transcription peak of IL-1beta at 30 minutes in the liver, whereas expression in the lungs remained low until 60 minutes, then continued to increase through 4 hours. CONCLUSIONS: Microarray analysis identified cytokines of the IL-1 family as central components of acute lung injury after hepatic cryoablation. IL-1beta levels increased in both serum and lung tissue over 4 hours after liver injury. Expression of IL-1beta peaked early in the injured liver remnant, followed by subsequent increases in the lungs. Targeted intervention against IL-1beta may ameliorate liver-mediated lung injury.