Transcriptome modulation by hydrocortisone in severe burn shock: ancillary analysis of a prospective randomized trial

Abstract

Background: Despite shortening vasopressor use in shock, hydrocortisone administration remains controversial, with potential harm to the immune system. Few studies have assessed the impact of hydrocortisone on the transcriptional response in shock, and we are lacking data on burn shock. Our objective was to assess the hydrocortisone-induced transcriptional modulation in severe burn shock, particularly modulation of the immune response.

Methods: We collected whole blood samples during a randomized controlled trial assessing the efficacy of hydrocortisone administration in burn shock. Using whole genome microarrays, we first compared burn patients (n = 32) from the placebo group to healthy volunteers to describe the transcriptional modulation induced by burn shock over the first week. Then we compared burn patients randomized for either hydrocortisone administration or placebo, to assess hydrocortisone-induced modulation.

Results: Study groups were similar in terms of severity and major outcomes, but shock duration was significantly reduced in the hydrocortisone group. Many genes (n = 1687) were differentially expressed between burn patients and healthy volunteers, with 85% of them exhibiting a profound and persistent modulation over seven days. Interestingly, we showed that hydrocortisone enhanced the shock-associated repression of adaptive, but also innate immunity.

Conclusions: We found that the initial host response to burn shock encompasses wide and persistent modulation of gene expression, with profound modulation of pathways associated with metabolism and immunity. Importantly, hydrocortisone administration may worsen the immunosuppression associated with severe injury. These data should be taken into account in the risk ratio of hydrocortisone administration in patients with inflammatory shock.

Trial registration: ClinicalTrials.gov, NCT00149123 . Registered on 6 September 2005.

Keywords: Burns; Host response; Hydrocortisone; Immunosuppression; Shock; Transcriptome modulation.

Fig. 1

Modulation of gene expression after burn shock. a Heatmap representation of expression in genes modulated by burn injury over time. Gene expression (rows) is color-coded from blue to orange. Individual values were averaged according to sample time (columns), and the associated number of samples is presented above each column. Although this analysis was performed only in patients on placebo, we included the representation of the identified gene modulation in hydrocortisone-treated patients alongside. Five (1 to 5) clusters were identified by unsupervised analysis, according to a similar longitudinal profile of expression, and are illustrated as boxplots (b-f). Hydrocortisone-treated patients are in purple and placebo-treated patients are in green. S1 to S4 sample times day 0, day 1, day 5 and day 7, respectively, HV healthy volunteers

Fig. 2

Modulation of the glucocorticoid receptor and nitric oxide signaling pathways. a Graphical representation of the glucocorticoid receptor (GR) pathway was performed through Ingenuity Pathway Analysis. The relative modulation of gene expression between burn patients and healthy volunteers (HV) is color coded from green (the gene is less expressed in patients with burns) to red (the gene is more expressed in patients with burns). b, c To focus on the effect of hydrocortisone administration, a zoom was performed on the targets of the glucocorticoid receptor, according to analysis 1 (placebo-treated burn patients vs. HV (b)) or analysis 2 (hydrocortisone-treated patients vs. placebo-treated patients (c)). d Summary of the effect of hydrocortisone administration on the gene expression for the nitric oxide mediated signal transduction pathway [GO:0007263] in HV (green), hydrocortisone-treated patients (red) or placebo-treated patients (blue). Statistical significance of the observed differences was assessed using repeated measures analysis of variance taking into account treatment, time and gene (probes) effects. We observed significant modulation over time (p value < 10 ^-6), and according to hydrocortisone administration (p value < 10 ^-6). S1 to S4 sample times day 0, day 1, day 5 and day 7, respectively

Fig. 3

Modulation of gene expression induced by hydrocortisone administration after burn shock. a Heatmap representation of expression in genes specifically modulated by hydrocortisone. Gene expression (rows) is color-coded from blue to orange. Individual values were averaged according to sampling time (columns), and the associated number of patients is presented above each column. Four (1 to 4) clusters were identified by unsupervised analysis, according to a similar longitudinal profile of expression, and illustrated as boxplots (b-e). Hydrocortisone-treated patients are in purple while placebo-treated patients are in green. S1 to S4 sample times day 0, day 1, day 5 and day 7, respectively, HV healthy volunteers

Fig. 4

Modulation of the immune response by hydrocortisone. Summary of the effect of hydrocortisone administration on gene expression in healthy volunteers (green), hydrocortisone-treated patients (red) or placebo-treated patients (blue) for various components of the immune response. a. Negative regulation of IL-6 production [GO:0032715]. c Antigen receptor-mediated signaling pathway [GO:0050851]. d Positive T cell selection [GO:0043368]. e Positive regulation of the T cell receptor signaling pathway [GO:0050862]. The statistical significance of the observed differences was assessed using repeated measures analysis of variance, taking into account treatment, time and gene (probes) effects. b Ingenuity Pathway Analysis® representation of the antigen presentation pathway, where components are color coded according to relative gene expression between hydrocortisone-treated patients and placebo-treated patients at S4. S1 to S4 sample times day 0, day 1, day 5 and day 7, respectively, HV healthy volunteers, ns not significant