Intrahepatic interleukin-10 synthesis during hypothermic cardioplumonary bypass inhibits TNFα synthesis throughout the STAT-3 pathway

Abstract

Background and aim Hypothermic cardiopulmonary bypass stimulates the synthesis of the anti-inflammatory cytokine IL10 and decreases that of TNFα in the organs. This study was intended to analyze the signaling pathways involved in the suppressive effects of IL10 on intra-hepatic TNFα gene expression Methods Twelve young pigs were assigned to a temperature (T°) regimen during standardized CPB: normothermia (T° 37°C; n = 6) and moderate hypothermia (T° 28°C; n = 6). Six hours after termination of CPB, liver tissue was sampled. Intra-hepatic gene expression and synthesis of TNFα IL10, and of the suppressor of cytokine signalling SOCS-3 were detected and quantified by competitive RT-PCR and by Western blot. DNA binding activity of the transcription factors NF-κB and STAT-3 was detected by eletrophoretic-mobility-shift assay (EMSA) and super shift, and phosphorylation of IκB-α and STAT-3 by Western blot. Cellular origin of TNFα and IL10 was assessed by immunohistochemical staining. Results Synthesis of IL10 and SOCS-3 were significantly higher, while that of TNFα was significantly lower, in pigs that were in moderate hypothermia during cardiac surgery than in the others. Hepatocytes themselves produced IL10 but not TNFα after cardiac surgery with CPB. Pigs under moderate hypothermia also showed significantly higher phosphorylation of STAT-3 and DNA binding activity of STAT-3 6 hours after CPB but no lower phos-phorylation of IκB-α and DNA binding activity of NF-κB than animals operated on in normothermia. Conclusion Suppression of TNFα synthesis during moderate hypothermic CPB by IL10 is dependent on the activation of the transcription factor STAT3- and of the activity of the regulatory SOCS-3, but not on the suppression of the activity of NF-κB.