Role of E-selectin in cell apoptosis induced by allogeneic blood perfusion in isolated mouse lung

In a model of mouse isolated lung, we have recently demonstrated that E-selectin is involved in the activation of endothelial cells induced by allogeneic blood perfusion. In the present study, we explored the signaling pathway of apoptosis induced by E-selectin triggering.

Lungs were perfused for 3 hours with fresh blood in the absence or presence of an anti-E-selectin monoclonal antibody, or a protein kinase C (PKC), protein tyrosine phosphatase (PTP), or protein tyrosine kinase (PTK) inhibitor. The number of apoptotic cells in lung sections was determined by a TUNEL method. mRNAs for Fas, FasL and caspase-8, and for Bad, Bax, Bcl-w, Bcl-xL and caspase-9, for the FasL and the mitochondrial cytochrome-c pathways of apoptosis, respectively, and mRNA for the effector caspase-3 were quantified in lung tissues by RT-PCR. PTP and Src-PTK activities were also measured.

After 3 hours of allogeneic perfusion, we observed a significant increase in: 1) the number of apoptotic cells in lung sections, 2) mRNA levels of FasL, Bcl-xL, caspase-8 and caspase-3, and 3) PTP activity (P < 0.05 compared with isogeneic perfusion). Surprisingly, mRNA levels of the proapoptotic genes Bad and Bax were significantly decreased (P < 0.05). PTK activity and caspase-9 mRNA level were not affected. Blocking anti-E-selectin mAbs and inhibitors for PKC, PTP, and PTK resulted in a significant reduction of apoptosis.

In our model, the engagement of E-selectin induced by endothelial cell allogeneic activation appeared to be a prerequisite for lung apoptosis, which involved FasL and increase of PTP activity. Blockade of apoptosis with selective inhibitors may be a promising approach to the treatment/prevention of lung graft injury.