Shear stress associated with cardiopulmonary bypass induces expression of inflammatory cytokines and necroptosis in monocytes
Lan N. Tu, … , Peter Pastuzsko, Vishal Nigam
Lan N. Tu, … , Peter Pastuzsko, Vishal Nigam
Published November 24, 2020
Citation Information: JCI Insight. 2021;6(1):e141341. https://doi.org/10.1172/jci.insight.141341.
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Research Article Cardiology Inflammation

Shear stress associated with cardiopulmonary bypass induces expression of inflammatory cytokines and necroptosis in monocytes

Abstract

Cardiopulmonary bypass (CPB) is required during most cardiac surgeries. CBP drives systemic inflammation and multiorgan dysfunction that is especially severe in neonatal patients. Limited understanding of molecular mechanisms underlying CPB-associated inflammation presents a significant barrier to improve clinical outcomes. To better understand these clinical issues, we performed mRNA sequencing on total circulating leukocytes from neonatal patients undergoing CPB. Our data identify myeloid cells, particularly monocytes, as the major cell type driving transcriptional responses to CPB. Furthermore, IL-8 and TNF-α were inflammatory cytokines robustly upregulated in leukocytes from both patients and piglets exposed to CPB. To delineate the molecular mechanism, we exposed THP-1 human monocytic cells to CPB-like conditions, including artificial surfaces, high shear stress, and cooling/rewarming. Shear stress was found to drive cytokine upregulation via calcium-dependent signaling pathways. We also observed that a subpopulation of THP-1 cells died via TNF-α–mediated necroptosis, which we hypothesize contributes to post-CPB inflammation. Our study identifies a shear stress–modulated molecular mechanism that drives systemic inflammation in pediatric CPB patients. These are also the first data to our knowledge to demonstrate that shear stress causes necroptosis. Finally, we observe that calcium and TNF-α signaling are potentially novel targets to ameliorate post-CPB inflammation.

Authors

Lan N. Tu, Lance Hsieh, Masaki Kajimoto, Kevin Charette, Nataliya Kibiryeva, Adriana Forero, Sarah Hampson, Jennifer A. Marshall, James O’Brien, Marta Scatena, Michael A. Portman, Ram Savan, Chris Benner, Alberto Aliseda, Muhammad Nuri, Douglas Bittel, Peter Pastuzsko, Vishal Nigam

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Figure 3

In vitro CPB conditions upregulate IL-8 and TNF-α in THP-1 cells.

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In vitro CPB conditions upregulate IL-8 and TNF-α in THP-1 cells. (A) Th...
(A) The design of in vitro CPB system. THP-1 cells at a density of 2 million cells/mL were pumped by a roller pump through PVC tubing at an average shear stress of 2.1 Pa. The majority of the tubing was kept in the water bath that maintained the temperature at 30°C. Cells were warmed up to 37°C for recovery. (B and C) The CPB conditions of high shear stress, low temperature (High S_Low T) significantly upregulated the mRNA and protein levels of IL-8 (B) and TNF-α (C) in the sheared THP-1 cells compared with static cells (n = 3 replicates/group). *P < 0.05, 1-way ANOVA and post hoc Tukey’s test. (D) Static THP-1 cells incubated with PVC tubing for 2 hours significantly upregulated IL8 by approximately 5-fold. Level of TNFA was not changed (n = 3 replicates/group). *P < 0.05, 2-tailed Student’s t test. (E and F) When THP-1 cells were sheared at 37°C (High S_High T) or at low shear stress of 0.67 Pa (Low S_Low T and Low S_High T), upregulation of mRNA and protein levels of IL-8 (E) and TNF-α (F) were significantly reduced compared with when cells were sheared at CPB conditions (High S_Low T) (n = 3–5 replicates/group). *P < 0.05, 1-way ANOVA and post hoc Dunnett’s test.