Initial Assessment of the Role of CXC Chemokine Receptor 4 after Polytrauma

Abstract

CXC chemokine receptor (CXCR)-4 agonists have been shown to attenuate inflammation and organ injury in various disease models, including trauma/hemorrhage. The pathophysiological role of CXCR4 during the early response to tissue injury, however, remains unknown. Therefore, we investigated the effects of AMD3100, a drug that antagonizes binding of stromal cell-derived factor (SDF)-1α and ubiquitin to CXCR4 during the initial response to polytrauma in pigs. Fifteen minutes before polytrauma (femur fractures/lung contusion; control: sham), 350 nmol/kg AMD3100, equimolar AMD3100 and ubiquitin (350 nmol/kg each) or vehicle were administered intravenously. After a 60-min shock period, fluid resuscitation was performed for 360 min. Ubiquitin binding to peripheral blood mononuclear cells was significantly reduced after intravenous AMD3100. SDF-1α plasma levels increased transiently >10-fold with AMD3100 in all animals. In injured animals, AMD3100 increased fluid requirements to maintain hemodynamics and enhanced increases in peripheral blood granulocytes, lymphocytes and monocytes, compared with its effects in uninjured animals. Cytokine release from leukocytes in response to Toll-like receptor (TLR)-2 and TLR-4 activation was increased after in vitro AMD3100 treatment of normal whole blood and after in vivo AMD3100 administration in animals subjected to polytrauma. Coadministration of AMD3100/ubiquitin reduced lactate levels, prevented AMD3100-induced increases in fluid requirements and sensitization of the tumor necrosis factor (TNF)-α and interleukin (IL)-6 release upon TLR-2/4 activation, but did not attenuate increases in leukocyte counts and SDF-1α plasma levels. Our findings suggest that CXCR4 controls leukocyte mobilization after trauma, regulates leukocyte reactivity toward inflammatory stimuli and mediates protective effects during the early phase of trauma-induced inflammation.

Modulation of the CXC Chemokine Receptor 4 Agonist Activity of Ubiquitin through C-Terminal Protein Modification

“…26 The affinity of FITC-ubiquitin binding to BV-2 and BV2 shRNA IDE cells is consistent with the affinity of the binding of FITC-ubiquitin to various other cells, including THP-1 cells and primary leukocytes. 12–14,46,47 This suggests that cell surface IDE knockdown does not affect ubiquitin binding to CXCR4. We detected, however, that the potency of ubiquitin to reduce cAMP levels was higher after IDE knockdown in BV-2 cells and further confirmed this observation in THP-1 cells.…”

Pharmacological targeting of chemokine (C-X-C motif) receptor 4 in porcine polytrauma and hemorrhage models

“…After stable baseline conditions (at least 30 minutes after instrumentation) were achieved, animals were subjected to polytrauma ( t = 0 minute, bilateral open femur fractures plus lung contusion), as described previously. 11,17–19 …”

“…As confirmed by necropsy, this resulted in lung contusion covering approximately 20% to 30% of the right lung without producing hemothoraces/pneumothoraces or rib fractures, which is consistent with our previous observations in this injury model. 11,17,18 All injuries were produced within 5 minutes. Based on an Abbreviated Injury Scale (AIS) score of 3 for the extremity trauma and 3 to 4 for the chest trauma, the estimated Injury Severity Score (ISS) was 18 to 25.…”

“…The dosing of ubiquitin and AMD3100 was selected based on our previous studies. 7,11,15–17 The following experimental series were performed:…”

“…7,9–12 Treatment with a peptide analog of the cognate CXCR4 agonist CXCL12 (SDF-1α) and with the noncognate CXCR4 agonist ubiquitin stabilized hemodynamics and prolonged survival in sepsis models, 13,14 and ubiquitin treatment stabilized hemodynamics and reduced systemic fluid requirements in various models of nonlethal traumatic/hemorrhagic shock. 7,11,15–17 The effects of CXCR4 blockade after polytrauma in large animal models, however, are unknown, and information on the dose-effect relationship of exogenous ubiquitin is limited. Furthermore, it remains unknown whether the finding that ubiquitin treatment prolonged survival in lethal hemorrhagic shock in rats translates from rodent models to large animal polytrauma/hemorrhage models.…”