Abstract
BackgroundCapillary leakage is a key contributor to the pathological host response to infections. The underlying mechanisms remain incompletely understood, and the role of microRNAs (MIR) has not been investigated in detail. We hypothesized that specific MIRs might be regulated directly in the endothelium thereby contributing to vascular leakage.MethodsSmallRNA sequencing of endotoxemic murine pulmonary endothelial cells (ECs) was done to detect regulated vascular MIRs. In vivo models: transgenic zebrafish (flk1:mCherry/l-fabp:eGFP-DPB), knockout/wildtype mouse (B6.Cg-Mir155tm1.1Rsky/J); disease models: LPS 17.5 mg/kgBW and cecal ligation and puncture (CLP); in vitro models: stimulated human umbilical vein EC (HUVECs), transendothelial electrical resistance.ResultsEndothelial MIR155 was identified as a promising candidate in endotoxemic murine pulmonary ECs (25 × upregulation). Experimental overexpression in a transgenic zebrafish line and in HUVECs was sufficient to induce spontaneous vascular leakage. To the contrary, genetic MIR155 reduction protects against permeability both in vitro and in endotoxemia in vivo in MIR155 heterozygote knockout mice thereby improving survival by 40%. A tight junction protein, Claudin-1, was down-regulated both in endotoxemia and by experimental MIR155 overexpression. Translationally, MIR155 was detectable at high levels in bronchoalveolar fluid of patients with ARDS compared to healthy human subjects.ConclusionsWe found that MIR155 is upregulated in the endothelium in mouse and men as part of a systemic inflammatory response and might contribute to the pathophysiology of vascular leakage in a Claudin-1-dependent manner. Future studies have to clarify whether MIR155 could be a potential therapeutic target.
Highlights
Capillary leakage is a key contributor to the pathological host response to infections
Identification of MIRs that are regulated in the endothelium in systemic inflammation Mice were challenged intraperitoneally with a high dosage of LPS (17.5 mg/kg bodyweight, n = 3) or vehicle (n = 3) to induce a systemic inflammatory response that regularly leads to severe pulmonary capillary leakage
Mice were killed after 24 h, and lungs were harvested for endothelial cell (EC) separation with a magnetic CD146 antibody strategy followed by isolation of MIRs
Summary
Capillary leakage is a key contributor to the pathological host response to infections. Etzrodt et al Crit Care (2021) 25:76 basis for maintenance of cell–cell contacts is the so-called adherens and tight junctions, transmembrane proteins that dynamically link adjacent cells to one another [4]. MicroRNAs (MIR)—small non-coding RNAs that have the ability to simultaneously regulate a variety of proteins—have not been investigated in detail in modulating the endothelial junctional apparatus controlling permeability [6]. In this context, one could hypothesize, that MIRs could trigger mechanisms that affect endothelial barrier function by targeting both essential proteins of the junctional apparatus or of the cytoskeleton either in a beneficial or harmful nature
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