BackgroundThe majority of the critically ill patients may have critical illness-related corticosteroid insufficiency (CIRCI). The therapeutic effect of dexamethasone may be related to its ability to improve cortical function. Recent study showed that dexamethasone can reduce COVID-19 deaths by up to one third in critically ill patients. The aim of this article is to investigate whether SARS-CoV-2 can attack the adrenal cortex to aggravate the relative adrenal insufficiency.MethodsWe summarized the clinical features of COVID-19 reported in currently available observational studies. ACE2 and TMPRSS2 expression was examined in human adrenal glands by immunohistochemical staining. We retrospectively analyzed serum cortisol levels in critically ill patients with or without COVID-19.ResultsHigh percentage of critically ill patients with SARS-COV-2 infection in the study were treated with vasopressors. ACE2 receptor and TMPRSS2 serine protease were colocalized in adrenocortical cells in zona fasciculata and zona reticularis. We collected plasma cortisol concentrations in nine critically ill patients with COVID-19. The cortisol levels of critically ill patients with COVID-19 were lower than those in non-COVID-19 critically ill group. Six of the nine COVID-19 critically ill patients had random plasma cortisol concentrations below 10 µg/dl, which met the criteria for the diagnosis of CIRCI.ConclusionWe demonstrate that ACE2 and TMPRSS2 are colocalized in adrenocortical cells, and that the cortisol levels are lower in critically ill patients with COVID-19 as compared to those of non-COVID-19 critically ill patients. Based on our findings, we recommend measuring plasma cortisol level to guide hormonal therapy.

Dysregulation of matrix metalloproteinase- (MMP-) 9 is implicated in the pathogenesis of acute lung injury (ALI). However, it remains controversial whether MMP-9 improves or deteriorates acute lung injury of different etiologies. The receptor for advanced glycation end products (RAGE) plays a critical role in the pathogenesis of acute lung injury. MMPs are known to mediate RAGE shedding and release of soluble RAGE (sRAGE), which can act as a decoy receptor by competitively inhibiting the binding of RAGE ligands to RAGE. Therefore, this study is aimed at clarifying whether and how pulmonary knockdown of MMP-9 affected sepsis-induced acute lung injury as well as the release of sRAGE in a murine cecal ligation and puncture (CLP) model. The analysis of GEO mouse sepsis datasets GSE15379, GSE52474, and GSE60088 revealed that the mRNA expression of MMP-9 was significantly upregulated in septic mouse lung tissues. Elevation of pulmonary MMP-9 mRNA and protein expressions was confirmed in CLP-induced mouse sepsis model. Intratracheal injection of MMP-9 siRNA resulted in an approximately 60% decrease in pulmonary MMP-9 expression. It was found that pulmonary knockdown of MMP-9 significantly increased mortality of sepsis and exacerbated sepsis-associated acute lung injury. Pulmonary MMP-9 knockdown also decreased sRAGE release and enhanced sepsis-induced activation of the RAGE/nuclear factor-κB (NF-κB) signaling pathway, meanwhile aggravating sepsis-induced oxidative stress and inflammation in lung tissues. In addition, administration of recombinant sRAGE protein suppressed the activation of the RAGE/NF-κB signaling pathway and ameliorated pulmonary oxidative stress, inflammation, and lung injury in CLP-induced septic mice. In conclusion, our data indicate that MMP-9-mediated RAGE shedding limits the severity of sepsis-associated pulmonary edema, inflammation, oxidative stress, and lung injury by suppressing the RAGE/NF-κB signaling pathway via the decoy receptor activities of sRAGE. MMP-9-mediated sRAGE production may serve as a self-limiting mechanism to control and resolve excessive inflammation and oxidative stress in the lung during sepsis.

Ventilator-associated lung injury (VALI) remains a significant medical problem in intensive care units. The present study aimed to investigate the role of sphingosine kinase 1 (SPHK1) in VALI using a two-hit model and explore the potential underlying molecular mechanism. Mice were divided into five groups: i) Non-ventilated group; ii) non-ventilated + lipopolysaccharide (LPS) group; iii) ventilated group; iv) ventilated + LPS group; and v) ventilated + LPS + SPHK1 inhibitor group. Mice were administered LPS (1 mg/kg) via an intraperitoneal injection. After 12 h, the mice were anesthetized and connected to a ventilator (10 ml/kg at 150 breaths/min) for 4 h. SPHK1 inhibitor (50 mg/kg) was injected intraperitoneally 1 h prior to ventilation. Mouse lung vascular endothelial cells were treated with LPS and SPHK1 inhibitor, and then subjected to cyclic stretch for 4 h. The present results suggested that the expression of SPHK1 and sphingosine 1 phosphate was upregulated in the two-hit model of VALI; SPHK1 inhibitor could attenuate VALI in the two-hit model as observed by hematoxylin and eosin staining, and affected the cell count and the protein content levels in the bronchoalveolar lavage fluid. In addition, treatment with SPHK1 inhibitor reduced the wet-to-dry ratio of the lungs and suppressed Evans blue dye leakage into the lung tissue. Furthermore, SPHK1 inhibitor exhibited protective effects on the two-hit model of VALI by inhibiting the Ras homolog family member a-mediated phosphorylation of myosin phosphatase target subunit 1 (MYPT-1) and endothelial hyperpermeability. Additionally, mice were divided into five additional groups: i) Non-ventilated group; ii) non-ventilated + LPS group; iii) ventilated group; iv) ventilated + LPS group; and v) ventilated + LPS + Rho-associated coiled-coil forming protein kinase (ROCK)1 inhibitor group. ROCK1 inhibitor (10 mg/kg) was injected intraperitoneally 1 h prior to ventilation. The present results suggested that ROCK1 inhibitor could attenuate mechanical stretch-induced lung endothelial injury and the phosphorylation of MYPT-1 in vivo and in vitro. Collectively, the present findings indicated that upregulation of SPHK1 may contribute to VALI in a two-hit model.

Thrombocytopenia is independently related with increased mortality in severe septic patients. Renin‐angiotensin system (RAS) is elevated in septic subjects; accumulating studies show that angiotensin II (Ang II) stimulate the intrinsic apoptosis pathway by promoting reactive oxygen species (ROS) production. However, the mechanisms underlying the relationship of platelet apoptosis and RAS system in sepsis have not been fully elucidated. The present study aimed to elucidate whether the RAS was involved in the pathogenesis of sepsis‐associated thrombocytopenia and explore the underlying mechanisms. We found that elevated plasma Ang II was associated with decreased platelet count in both patients with sepsis and experimental animals exposed to lipopolysaccharide (LPS). Besides, Ang II treatment induced platelet apoptosis in a concentration‐dependent manner in primary isolated platelets, which was blocked by angiotensin II type 1 receptor (AT1R) antagonist losartan, but not by angiotensin II type 2 receptor (AT2R) antagonist PD123319. Moreover, inhibiting AT1R by losartan attenuated LPS‐induced platelet apoptosis and alleviated sepsis‐associated thrombocytopenia. Furthermore, Ang II treatment induced oxidative stress level in a concentration‐dependent manner in primary isolated platelets, which was partially reversed by the AT1R antagonist losartan. The present study demonstrated that elevated Ang II directly stimulated platelet apoptosis through promoting oxidative stress in an AT1R‐dependent manner in sepsis‐associated thrombocytopenia. The results would helpful for understanding the role of RAS system in sepsis‐associated thrombocytopenia.