Increase of HO-1 Expression in Critically Ill COVID-19 Patients Is Associated with Poor Prognosis and Outcome

Abstract

Heme-oxygenase (HO)-1 is a cytoprotective enzyme with strong antioxidant and anti-apoptotic properties and previous reports have also emphasized the antiviral properties of HO-1, either directly or via induction of interferons. To investigate the potential role of HO-1 in patients with coronavirus disease 2019 (COVID-19), the present study assessed changes in HO-1 expression in whole blood and tissue samples. Upregulation of HO-1 protein was observed in lung, liver, and skin tissue independently of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presence. A significant increase of blood HO-1 mRNA levels was observed in critically ill COVID-19 patients compared to those in severe COVID-19 patients and healthy controls. This increase was accompanied by significantly elevated levels of serum ferritin and bilirubin in critically ill compared to patients with severe disease. Further grouping of patients in survivors and non-survivors revealed a significant increase of blood HO-1 mRNA levels in the later. Receiver operating characteristic (ROC) analysis for prediction of ICU admission and mortality yielded an AUC of 0.705 (p = 0.016) and 0.789 (p = 0.007) respectively indicating that HO-1 increase is associated with poor COVID-19 progression and outcome. The increase in HO-1 expression observed in critically ill COVID-19 patients could serve as a mechanism to counteract increased heme levels driving coagulation and thrombosis or as an induced protective mechanism.

Keywords: COVID-19; heme-oxygenase (HO-1); immune response.

Figure 1

HO-1 upregulation and hemosiderin deposition in tissues of critical COVID-19 patients. Representative images from lung, kidney, liver, heart, and skin tissue sections obtained from critical COVID-19 patients autopsy samples and stained for HO-1 protein (and their respective controls) and Prussian blue. Magnification at ×400.

Figure 2

SARS-CoV-2 detection in tissue tissues from critical COVID-19 patients. Post-mortem tissue samples were obtained and directly processed for detection of SARS-CoV-2 by immunohistochemistry. Representative images of SARS-CoV-2 (G2 mab) staining in liver and kidney tissue sections and their respective negative controls. Magnification at ×400.

Figure 3

HO-1 is upregulated in critical COVID-19 patients with concomitant increase in ferritin and bilirubin. Whole blood samples were obtained on admission from patients with either severe or critical disease and processed directly. (a) HO-1 mRNA upregulation determined in critical patients versus severe and healthy controls from whole blood samples. Increase of ferritin (b), bilirubin (c) and iron levels (d) in critical versus severe COVID-19 patients. Data are expressed as means ± SD. Statistical analysis was performed by one-way ANOVA in three group comparisons and Mann–Whitney U test in two group comparisons. * p < 0.05, ** p < 0.01. Analysis of variance and post hoc analysis was performed by Uncorrected Fisher’s least significant difference test.

Figure 4

Unaltered levels of haemoglobin, gamma glutamyl transferase (GGT) and alkaline phosphatase (ALP) levels in critical versus severe COVID-19 patients. Levels of (a) haemoglobin (b) gamma glutamyl transferase (GGT) and (c) alkaline phosphatase (ALP) in blood samples obtained on admission from COVID-19 patients by routine in-hospital blood analysis. Data are expressed as means ± SD. Statistical analysis was performed by Mann–Whitney U test. No statistically significant changes were observed.

Figure 5

HO-1 mRNA levels are associated with COVID-19 progression and outcome. HO-1 mRNA upregulation in whole blood samples from (a) critical versus severe patients (b) survivors versus non-survivors. Receiver operating characteristic (ROC) curves of HO-1 mRNA levels for prediction of need for intensive care (c) and mortality (d). The corresponding areas under the curve (AUC), p, sensitivity and specificity, odd ratio and cut off values are represented in (e). Statistical analysis was performed by Mann–Whitney U test. * p < 0.05.