Blockade of Endothelial Growth Factor, Angiopoietin-2, Reduces Indices of Ards and Mortality in Mice Resulting from the Dual-Insults of Hemorrhagic Shock and Sepsis

Abstract

We have demonstrated hemorrhagic shock “priming” for the development of indirect (i)ARDS in mice following subsequent septic challenge and show pathology characteristic of patients with iARDS, including increased lung micro-vascular permeability and arterial PO2/FI02 reduced to levels comparable to mild/moderate ARDS during the 48 hours following hemorrhage. Loss of endothelial cell (EC) barrier function is a major component in the development of iARDS. EC growth factors, Angiopoietin (Ang)-1 & 2, maintain vascular homeostasis via tightly regulated competitive interaction with tyrosine kinase receptor, Tie2, expressed on ECs. Ang-2/Tie2 binding, in contrast to Ang-1, is believed to produce vessel destabilization, pulmonary leakage and inflammation. Recent clinical findings from our trauma/surgical intensive care units and others have reported elevated Ang-2 in the plasma from patients that develop ARDS. We have previously described similarly elevated Ang-2 in plasma and lung tissue in our shock/sepsis model for the development of iARDS and demonstrated effective reduction in indices of inflammation and lung tissue injury following siRNA inhibition of Ang-2 protein synthesis. In this study we show that Ang-2 in lung tissue and plasma spikes following hemorrhage (priming) and remain elevated at sepsis induction. Also, that transient inhibition of Ang-2 function immediately following hemorrhage, suppressing priming, but not following sepsis, impacts the development of iARDS in our model. Our data demonstrates that selective temporal blockade of Ang-2 function following hemorrhagic shock priming, significantly improved PO2/FIO2, decreased lung protein leak and indices of inflammation, and improved 10-day survival in our murine model for the development iARDS.

Novel Role for PD-1:PD-L1 as Mediator of Pulmonary Vascular Endothelial Cell Functions in Pathogenesis of Indirect ARDS in Mice

“…A mouse model of hemorrhagic shock induced “priming” followed by the induction of sepsis for the development of iARDS [a model with which we have considerable experience and in which we have shown induces arterial PO 2 /FIO 2 , (mmHg) of ~150 mmHg by 24 h post-shock/sepsis along with evidence of protein leak and morphological changes (19)] was used here (15, 16, 20). Mortality associated with this model is typically 60–70% after 48 h post-sepsis (15, 20).…”

Circulating angiopoietin-2 and the risk of mortality in patients with acute respiratory distress syndrome: a systematic review and meta-analysis of 10 prospective cohort studies

“…[8][9][10] Notably, effects of endothelial receptors and changes in Ang-2 levels have been involved in the underlying mechanisms contributing to the link between circulating Ang-2 and the risk of mortality in patients with ARDS. 11,12 Indeed, an early prospective cohort study showed that increased plasma Ang-2 levels independently predicts mortality in over 900 patients with acute lung injury (ALI) or ARDS. 13 Subsequent studies showed that selective temporal blockade of Ang-2 function greatly improved PaO 2 /FiO 2 , decreased lung protein leak and indices of inflammation, and finally improved overall survival in murine models of ARDS.…”

A novel role for coinhibitory receptors/checkpoint proteins in the immunopathology of sepsis

“…Among wildtype mice after Hem-CLP, the P:F ratio (arterial P02:Fi02) decreases, suggesting loss of pulmonary compliance (99, 120). Among mice who were either PD-1 −/− or PD-L1 −/− , indices of lung inflammation (e.g.…”

“…decreases, suggesting loss of pulmonary compliance. 99,118 Among mice who were either PD-1 −/− or PD-L1 −/− , indices of lung inflammation (e.g., IL-6, MIP-2, myeloperoxidase) and injury (pulmonary edema, protein leak) were mitigated following the same Hem-CLP challenge. 99,119 Histologic analysis has also revealed increased leukocyte presence and cellular A o in lung tissue following Hem-CLP, a finding attenuated by PD-1 gene deletion.…”