Mechanism Of Epidermal Growth Factor Receptor Regulate Endotoxemia

Background:endotoxemia is a clinical syndrome characterized by a multisystem response to a pathogenic assault due to underlying infection that involves a combination of interconnected biochemical,cellular and organ-organ interactive networks.Despite many advances in mechanism and treatments,sepsis is still one of the main causes of death in critical patients.Lipopolysaccharide(LPS),a component of the outer membrane of Gram-negative bacteria,can induce endotoxemia and sepsis,by triggering a cascade of pro-inflammatory cytokines,such as tumor necrosis factor-a(TNF-α),interleukin(IL)-1β,IL-6,and IL-8.Recently,researchers found that epithelial growth factor receptor(EGFR)play a critical role in LPS-induced endotoxemia.EGFR belongs to tyrosine kinase receptor family,which is expressed in various cells and plays a key role in cell survival,proliferation,and metastasis.Mitogen-inducible gene 6(Mig6),an endogenous feedback inhibitor of EGFR signal,plays an important role in many pathophysiological states.EGFR activation can increase Mig6 transcription,leading to accumulation of the Mig6 protein.In turn,Mig6 directly binds to the tyrosine kinase domain of the ligand-occupied EGFRs,causing their catalytic inactivation and directing their internalization and degradation.Nevertheless,the role of Mig6 in endotoxemia has not been investigated although EGFR activation is required for LPS induced inflammatory cytokines generation.Parthanatos is a new form of programmed cell death.Poly(ADP-ribose)(PAR)polymerase-1(PARP-1)is an important nuclear enzyme that responds to DNA damage and facilitates DNA repair.Excessive activation of PARP-1 leads to cellular NAD+and ATP depletion,accumulates Poly(ADP-ribose)(PAR)polymers,causes translocation of apoptosis-inducing factor(AIF)from mitochondria to the nucleus,which is a caspase-independent cell death program.But,it is unclear that parthanatos in endotoxemia whether or not.And,it is not clear that EGFR can play a critical role in LPS-induced parthanatos.Method:1.We inhibited the activity of EGFR by EGFR inhibitor erlotinib,and then tested the transcription and expression of Mig6;we silenced or overexpressed Mig6,and then tested the activity of EGFR,the transcription and production of inflammatory mediators(TNF-α,il-1β),the activity of MAPKs(ERK1/2,p-38).2.We inhibited the activity of EGFR by EGFR inhibitor erlotinib,and then tested the parthanatos-related proteins(PAR formation,AIF translocation into nuclear);We tested the production of ROS.Results:1.LPS treatment increased the expression of Mig6 and this effect could be inhibited by EGFR inhibitor,PD168393 or erlotinib.Furthermore,knocking down of Mig6 expression led to increased EGFR activation and inflammatory mediators(TNF-α,il-1β)production in response to LPS treatment.On the other hand,the increased EGFR activation and TNF-α or il-lb production in LPS treatment could be inhibited by Mig6 overexpression.Besides,in LPS induced endotoxemia,ERK1/2 and p-38 activation required Mig6.2.Parthanatos can be induced by LPS,which can be inhibited by erlotinib.Erlotinib inhibited parthanatos through inhibiting ROS overproduction.Conclusion:1.Mig6 regulates the production of inflammatory mediators(TNF-α,il-1β)through inhibiting the over activation of EGFR,which in turn inhibit MAPKs signaling(ERK1/2,p-38)2.EGFR inhibits LPS-induced parthanatos through reducing the over production of ROS.