Monocyte Adhesion and Transmigration Through Endothelium Following Cardiopulmonary Bypass Shearing is Mediated by IL-8 Signaling

Background

The use of cardiopulmonary bypass (CPB) can induce sterile systemic inflammation that contributes to morbidity and mortality, especially in children. Patients have been found to have increased expression of cytokines and transmigration of leukocytes during and after CPB. Previous work has demonstrated that the supraphysiologic shear stresses present during CPB are sufficient to induce proinflammatory behavior in non-adherent monocytes. The interactions between shear stimulated monocytes and vascular endothelial cells have not been well studied and have important translational implications.

Methods

To test the hypothesis that non-physiological shear stress experienced by monocytes during CPB affects the integrity and function of the endothelial monolayer via IL-8 signaling pathway, we have used an in vitro CPB model to study the interaction between THP-1 monocyte-like cells and human neonatal dermal microvascular endothelial cells (HNDMVECs). THP-1 cells were sheared in polyvinyl chloride (PVC) tubing at 2.1 Pa, twice of physiological shear stress, for 2 hours. Interactions between THP-1 cells and HNDMVECs were characterized after coculture.

Results

We found that sheared THP-1 cells adhered to and transmigrated through the HNDMVEC monolayer more readily than static controls. When co-culturing, sheared THP-1 cells also disrupted in the VE-cadherin and led to reorganization of cytoskeletal F-actin of HNDMVECs. Treating HNDMVECs with IL-8 resulted in upregulation of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) while also increasing the adherence of non-sheared THP-1 cells. Preincubating HNDMVECs with Reparixin, an inhibitor of CXCR2/IL-8 receptor inhibited sheared THP-1 cell adhesion to the HNDMVECs.

Conclusions

These results suggested that IL-8 not only increases the endothelium permeability during monocyte migration, but also affects the initial adhesion of monocytes in a CPB setup. This study revealed a novel mechanism of post-CPB inflammation and will contribute to the development of targeted therapeutics to prevent and repair the damage to neonatal patients.

Highlights

Shear stress in a CPB-like environment promoted the adhesion and transmigration of monocytes to and through endothelial monolayer.

Treating endothelial monolayer with sheared monocytes led to disruption of VE-cadherin and reorganization of F-actin.

Interaction between sheared monocytes resulted in a significant increase of IL-8 release.

Inhibiting IL-8 receptor prevented sheared monocyte adhesion, while IL-8 promoted naive monocyte adhesion.

Off-pump myocardial revascularization attenuates endothelin-1 expression in systemic, pulmonary, and coronary circulation

OBJECTIVE

The objective of this study was to evaluate the influence of cardiopulmonary bypass (CPB) on endothelin-1 (ET-1) expression in various circulation compartments in patients undergoing myocardial revascularization.

METHODS

A total of 30 patients were randomized to undergo myocardial revascularization with (CABG, n = 15) or without (OPCAB, n = 15) CPB. Samples were taken preoperatively, after establishing CPB and after CPB (CABG group), prior to and after revascularization (OPCAB group), and 6 and 24 h postoperatively. Values of ET-1 were compared between groups at all time points and correlated with postoperative cardioselective enzyme values and clinical parameters.

RESULTS

In OPCAB group, ET-1 levels did not significantly vary between time points. In CABG group, ET-1 levels were significantly elevated vs. baseline in arterial: ART-T2 vs. ART-T0 (1.83 ± 1.81 vs. 0.76 ± 1.07 fmol/mL, p = 0.05), pulmonary: SG-T2 vs. SG-T0 (2.70 ± 2.75 vs. 0.39 ± 0.28 fmol/mL, p < 0.001) and SG-T3 vs. SG-T0 (1.56 ± 0.28 vs. 0.39 ± 0.28 fmol/mL, p < 0.001), and coronary circulation CS-T2 vs. CS-T1 (1.12 ± 0.49 vs. 0.27 ± 0.09 fmol/mL, p = 0.01). ET-1 levels were significantly higher in CABG group in all vascular compartments: ART-T2 (1.83 ± 1.81 vs. 0.17 ± 0.16 fmol/mL, p = 0.02), ART-T4 (0.99 ± 0.56 vs. 0.24 ± 0.12 fmol/mL, p = 0.01), SG-T1 (0.59 ± 0.15 vs. 0.25 ± 0.13 fmol/mL, p = 0.01), SG-T2 (2.70 ± 2.75 vs. 0.30 ± 0.24 fmol/mL, p = 0.004), SG-T3 (1.56 ± 0.28 vs. 0.35 ± 0.31 fmol/mL, p < 0.001), SG-T4 (1.34 ± 0.11 vs. 0.34 ± 0.16 fmol/mL, p < 0.001), and CS-T2 (1.12 ± 0.49 vs. 0.12 ± 0.12 fmol/mL, p = 0.004). Coronary sinus ET-1 level after CPB (CS-T2) in CABG group correlated positively with troponin-I level 24 h postoperatively (r(2) = 0.802, p = 0.02) CONCLUSION: Off-pump myocardial revascularization attenuates ET-1 expression in all investigated vascular compartments. Elevated coronary ET-1 levels after CPB in CABG group correlate with troponin-I levels 24 h postoperatively.

Endothelial activation after coronary artery bypass surgery: comparison between on-pump and off-pump techniques

BACKGROUND

The effects of off-pump coronary artery bypass (OPCAB) surgery on endothelial cell activation are poorly understood. Endothelial cell adhesion molecules (CAMs) are expressed and released when the endothelium is activated. We compared plasma CAMs (E-selectin, ICAM-1 and VCAM-1) and HUVEC expression of the same CAMs when exposed to plasma taken before, during and after OPCAB or on-pump coronary surgery (CABG).

METHODS

Patients undergoing first time CABG (n=10) or OPCAB (n=10) had 6 blood samples taken before surgery and up to 24h post-operatively. Plasma samples were assayed for E-selectin, ICAM-1 and VCAM-1. The same plasma samples were exposed to HUVEC cultures and cell-surface expression of E-selectin, ICAM-1 and VCAM-1 measured. Data are expressed as mean+/-SEM of n subjects.

RESULTS

Plasma E-selectin was unchanged. Plasma ICAM-1 and VCAM-1 were elevated 24h post-operatively in both groups (P<0.01), with no differences between the groups. Twenty-four hours post-OPCAB plasma increased basal and IL-1beta induced expression of endothelial VCAM-1 by 133+/-16% and 140+/-27% (P<0.05), respectively. Plasma taken 3h post-CABG decreased endothelial VCAM-1 expression by 76+/-10% (P<0.05). Peri-operative plasma had no effect on endothelial expression of E-selectin or ICAM-1 in either group.

CONCLUSIONS

OPCAB and CABG with CPB appear to generate qualitatively different inflammatory responses with respect to endothelial activation, which may have clinical implications.

Endothelial expression of intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 is suppressed by postbypass plasma containing increased soluble intercellular adhesion molecule 1 and vascular cell adhesion molecule 1

OBJECTIVE

Endothelial cell dysfunction has been implicated in the inflammatory response to cardiopulmonary bypass, and the upregulation of endothelial cell expression of adhesion molecules might promote leukocyte extravasation in vivo. Soluble endothelial cell adhesion molecules are increased after bypass. The aim of this study was to investigate the relationship between endothelial cell-surface expression of adhesion molecules and their concentration in plasma after coronary artery bypass grafting.

METHODS

Ten patients undergoing coronary artery bypass with cardiopulmonary bypass had 5 plasma samples taken at defined intervals before, during, and after cardiopulmonary bypass. Plasma was incubated with human umbilical vein endothelial cell monolayers, and expression of E-selectin, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 on the surface of human umbilical vein endothelial cell monolayers was measured by means of enzyme-linked immunosorbent assay. Plasma soluble adhesion molecules, C-reactive protein, interleukin 8, interleukin 10, transforming growth factor beta1, and neutrophil counts were determined for each patient.

RESULTS

Markers typical of acute inflammation (ie, interleukin 8, neutrophils, and C-reactive protein) were all increased after bypass. Soluble plasma intercellular and vascular cell adhesion molecule 1 (but not E-selectin) were increased after bypass. However, endothelial cell expression of vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 (but not E-selectin) were significantly decreased by exposure to postbypass plasma. Additionally, postbypass plasma inhibited interleukin 1beta-stimulated endothelial cell expression of vascular cell and intercellular adhesion molecule 1. Interleukin 10 and transforming growth factor beta1, both of which are known to inhibit endothelial cell adhesion molecule expression, were respectively increased 10-fold and 3-fold (P <.05) after bypass.

CONCLUSIONS

Despite containing increased soluble intercellular and vascular cell adhesion molecule 1, postbypass plasma inhibits endothelial cell expression of intercellular and vascular cell adhesion molecule 1. Upregulated vascular expression of adhesion molecules might not be essential for endothelial activation after bypass.