Resumen de Molecular mechanisms involved in the interactions between Chromatin-derived macromolecules and endothelial cells: potential for the Development of sepsis biomarkers
Sepsis is a prevalent global syndrome characterized by an exaggerated immune response to infection, resulting in hyperinflammation followed by immunosuppression. Pro-inflammatory molecules, including HMGB1 and histones, are released into the bloodstream during the hyperinflammatory phase, leading to significant physiological changes. Histones, known for their pro-inflammatory and procoagulant effects, particularly impact the endothelium of blood vessels, exacerbating sepsis symptoms. The aim of the study was to elucidate the role of histones in cellular processes and their potential implications in sepsis. The work presents key findings on the cytotoxic effects and cellular localization of extracellular histones, as well as their interactions with autophagy and miRNA expression in various experimental models.
The results demonstrate that high doses of core histones induce cytotoxicity in HeLa, Hep3B, HUVEC cells, and blood vessel organoids. An image analysis tool was developed to quantify the overlap between extracellular histones and fluorescently labeled lysosomes, revealing their predominant localization on lysosomes in HeLa and Hep3B cells. Modulation of autophagy did not significantly affect cell survival or the relative localization of histones and lysosomes in HeLa and Hep3B cells. However, in HUVEC cells and blood vessel organoids, treatment with extracellular histones led to a dose and time-dependent increase in colocalization between histones and the autophagy-associated protein LC3B. Blocking endocytosis reduced the entry of extracellular histones into the cells, resulting in decreased cytotoxicity in HUVEC cells and blood vessel organoids. Inhibition of autophagy in HUVEC cells reduced colocalization between histones and LC3B, while its activation had an impact. In blood vessel organoids, autophagy modulation did not significantly affect histone fluorescence intensity but altered histone localization. Furthermore, core histone treatment influenced miRNA expression, with downregulation of miR-155 observed in HeLa, Hep3B, and HUVEC cells, while its upregulation was found in blood vessel organoids. Additionally, miR-146 was downregulated in HeLa and Hep3B cells, while miR122 was not expressed in any experimental model. Treatment with core histones also induced the secretion of HMGB1 in blood vessel organoids, and plasma levels of HMGB1 were significantly higher in patients with sepsis and septic shock compared to an ICU control group. Plasma levels of HMGB1, measured using ELISA, demonstrated strong predictive power for prolonged ICU stays and exhibited significant correlations with clinical indicators in sepsis, such as D-dimer, ICU length of stay, and NtProBNP.
In conclusion, this study provides insights into the cytotoxicity, cellular localization, autophagy interactions, miRNA expression, and HMGB1 secretion induced by core histones in different experimental models. These findings contribute to a better understanding of the role of histones in cellular processes and their potential implications in sepsis.
