Remote ischaemic preconditioning does not modulate the systemic inflammatory response or renal tubular stress biomarkers after endotoxaemia in healthy human volunteers: a single-centre, mechanistic, randomised controlled trial

Abstract

Background: Remote ischaemic preconditioning (RIPC) consists of repeated cycles of limb ischaemia and reperfusion, which may reduce perioperative myocardial ischaemic damage and kidney injury. We hypothesised that RIPC may be beneficial by attenuating the systemic inflammatory response. We investigated whether RIPC affects the response in humans to bacterial endotoxin (lipopolysaccharide [LPS]) by measuring plasma cytokines and renal cell-cycle arrest mediators, which reflect renal tubular stress.

Methods: Healthy male volunteers were randomised to receive either daily RIPC for 6 consecutive days (RIPCmultiple, n=10) plus RIPC during the 40 min preceding i.v. LPS (2 ng kg-1), RIPC only during the 40 min before LPS (RIPCsingle, n=10), or no RIPC preceding LPS (control, n=10). As a surrogate marker of renal tubular stress, the product of urinary concentrations of two cell-cycle arrest markers was calculated (tissue inhibitor of metalloproteinases-2 [TIMP2]*insulin-like growth factor binding protein-7 [IGFBP7]). Data are presented as median (inter-quartile range).

Results: In both RIPC groups, RIPC alone increased [TIMP2]*[IGFBP7]. LPS administration resulted in fever, flu-like symptoms, and haemodynamic alterations. Plasma cytokine concentrations increased profoundly during endotoxaemia (control group: tumor necrosis factor alpha [TNF-α] from 14 [9-16] pg ml-1 at baseline to 480 [284-709] pg ml-1 at 1.5 h after LPS; interleukin-6 [IL-6] from 4 [4-4] pg ml-1 at baseline to 659 [505-1018] pg ml-1 at 2 h after LPS). LPS administration also increased urinary [TIMP2[*[IGFBP7]. RIPC had no effect on LPS-induced cytokine release or [TIMP2]*[IGFBP7].

Conclusions: RIPC neither modulated systemic cytokine release nor attenuated inflammation-induced tubular stress after LPS. However, RIPC alone induced renal markers of cell-cycle arrest.

Clinical trial registration: NCT02602977.

Keywords: cytokine; endotoxaemia; immunity; innate; ischaemic preconditioning; lipopolysaccharides; renal tubular stress; systemic inflammatory response.

Conflict of interest statement

JAK discloses grant support and consulting fees from Astute Medical. In addition, the University of Pittsburgh holds intellectual property on the use of TIMP2*IGFBP7 together with RIPC.

Copyright © 2019 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

Figures

Fig. 1

Schematic overview of the study procedures. LPS, lipopolysaccharide.

Fig. 2

Symptoms, temperature and haemodynamic parameters during experimental endotoxaemia. (a) Aggregated score of self-reported symptoms. (b) Temperature. (c) MAP. (d) HR. Data are presented as mean and standard error of mean (SEM). Within-group changes over time were significant for all parameters within all groups (P<0.0001, calculated using one-way analysis of variance [ANOVA]). All P-values depicted in the graphs represent the three-group comparison over time calculated using two-way ANOVA (interaction term). AU, arbitrary units; Bpm, beats min−1; LPS, lipopolysaccharide; RIPC: remote ischaemic preconditioning.

Fig. 3

Plasma concentrations of inflammatory cytokines during experimental endotoxaemia. (a) Tumor necrosis factor (TNF)-α. (b) Interleukin-6 (IL-6). (c) IL-8. (d) IL-10. Data are presented as median and inter-quartile range (IQR). Within-group changes over time were significant for all cytokines within all groups (P<0.0001, calculated using one-way analysis of variance [ANOVA] on log-transformed data). All P-values depicted in the graphs represent the three-group comparison over time calculated using two-way ANOVA (interaction term) on log-transformed data. LPS, lipopolysaccharide; RIPC, remote ischaemic preconditioning.

Fig. 4

Cytokine production of ex vivo stimulated whole blood pre- and post-RIPC. (a) Tumor necrosis factor (TNF)-α. (b) Interleukin-6 (IL-6). (c). IL-10. For the control group, RIPC was not applied, but blood samples were obtained at the same time points. Data are presented as mean and standard error of mean (SEM) ratio (compared with the respective pre-condition). Absolute values of the pre-condition measurements in pg ml−1: TNF-α: 1256 (172) (Control), 1478 (239) (single RIPC), 1823 (227) (multiple RIPC); IL-6: 12 510 (1547) (Control), 13 182 (2546) (single RIPC), 15 676 (2194) (multiple RIPC); IL-10: 273 (55) (Control), 290 (31) (single RIPC), 248 (38) (multiple RIPC). *Indicates P<0.05 compared with pre-RIPC (calculated using Student's t-tests). RIPC, remote ischaemic preconditioning.

Fig. 5

Urinary tissue inhibitor of metalloproteinase 2 (TIMP2)*insulin-like growth factor binding protein-7 (IGFBP7) concentrations. (a) Creatinine-corrected urinary concentrations of TIMP2*IGFBP7 before and after RIPC (both before LPS administration). For the control group, RIPC was not applied, but urine samples were obtained at the same time points. Data are presented as mean and standard error of mean (SEM). *Indicates P<0.05 compared with pre-RIPC (calculated using Student's t-tests). (b) Creatinine-corrected urinary concentrations of TIMP2*IGFBP7 during experimental endotoxaemia. Baseline-corrected data are presented as mean and SEM (baseline: T=0 [time of LPS administration]). Within-group changes over time were significant in all groups (P=0.003, P=0.045, and P=0.012 in the control, single RIPC, and multiple RIPC groups, respectively, calculated using one-way analysis of variance [ANOVA]). The P-value depicted in the graph represents the three-group comparison over time calculated using two-way ANOVA (interaction term). LPS, lipopolysaccharide; RIPC, remote ischaemic preconditioning.

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