Proteomic analysis of descending thoracic aorta identifies unique and universal signatures of aneurysm and dissection.

Objective: Very few clinical predictors of descending thoracic aorta dissection have been determined. Although aneurysms can dissect in a size-dependent process, most descending dissections will occur without prior enlargement. We compared the proteomic profiles of normal, dissected, aneurysm, and both aneurysm and dissected descending thoracic aortas to identify novel biomarkers and further understand the molecular pathways that lead to tissue at risk of dissection. Methods: We performed proteomic profiling of descending thoracic aortas with four phenotypes: normal (n = 46), aneurysm (n = 22), dissected (n = 12), and combined aneurysm and dissection (n = 8). Pairwise differential protein expression analyses using a Bayesian approach were then performed to identify common proteins that were dysregulated between each diseased tissue type and control aorta and to uncover unique proteins between aneurysmal and dissected aortas. Network and Markov cluster algorithms of differentially expressed proteins were used to find enriched ontology processes. A convex analysis of mixtures was also performed to identify the molecular subtypes within the different tissue types. Results: The diseased aortas had 71 common differentially expressed proteins compared with the control, including higher amounts of the protein thrombospondin 1. We found 42 differentially expressed proteins between the aneurysm and dissected tissue, with an abundance of apolipoproteins in the former and higher quantities of extracellular matrix proteins in the latter. The convex analysis of mixtures showed enhancement of a molecular subtype enriched in contractile proteins within the control tissue compared with the diseased tissue, in addition to increased proportions of molecular subtypes enriched in inflammation and red blood cell expression in the aneurysmal compared with the dissected tissue. Conclusions: We found some overlapping differentially expressed proteins in aneurysmal and nonaneurysmal descending thoracic aortas at risk of dissection compared with normal aortas. However, we also found uniquely altered molecular pathways that might uncover mechanisms for dissection.

Transcriptome and Functions of Granulocytic Myeloid-Derived Suppressor Cells Determine their Association with Disease Severity of COVID-19.

COVID-19 ranges from asymptomatic in 35% of cases to severe in 20% of patients. Differences in the type and degree of inflammation appear to determine the severity of the disease. Recent reports show an increase in circulating monocytic-myeloid-derived suppressor cells (M-MDSC) in severe COVID 19, that deplete arginine but are not associated with respiratory complications. Our data shows that differences in the type, function and transcriptome of Granulocytic-MDSC (G-MDSC) may in part explain the severity COVID-19, in particular the association with pulmonary complications. Large infiltrates by Arginase 1 + G-MDSC (Arg + G-MDSC), expressing NOX-1 and NOX-2 (important for production of reactive oxygen species) were found in the lungs of patients who died from COVID-19 complications. Increased circulating Arg + G-MDSC depleted arginine, which impaired T cell receptor and endothelial cell function. Transcriptomic signatures of G-MDSC from patients with different stages of COVID-19, revealed that asymptomatic patients had increased expression of pathways and genes associated with type I interferon (IFN), while patients with severe COVID-19 had increased expression of genes associated with arginase production, and granulocyte degranulation and function. These results suggest that asymptomatic patients develop a protective type I IFN response, while patients with severe COVID-19 have an increased inflammatory response that depletes arginine, impairs T cell and endothelial cell function, and causes extensive pulmonary damage. Therefore, inhibition of arginase-1 and/or replenishment of arginine may be important in preventing/treating severe COVID-19.

DNA damage is an early event in doxorubicin-induced cardiac myocyte death.

Anthracyclines are antitumor agents the main clinical limitation of which is cardiac toxicity. The mechanism of this cardiotoxicity is thought to be related to generation of oxidative stress, causing lethal injury to cardiac myocytes. Although protein and lipid oxidation have been documented in anthracycline-treated cardiac myocytes, DNA damage has not been directly demonstrated. This study was undertaken to determine whether anthracyclines induce cardiac myocyte DNA damage and whether this damage is linked to a signaling pathway culminating in cell death. H9c2 cardiac myocytes were treated with the anthracycline doxorubicin at clinically relevant concentrations, and DNA damage was assessed using the alkaline comet assay. Doxorubicin induced DNA damage, as shown by a significant increase in the mean tail moment above control, an effect ameliorated by inclusion of a free radical scavenger. Repair of DNA damage was incomplete after doxorubicin treatment in contrast to the complete repair observed in H2O2-treated myocytes after removal of the agent. Immunoblot analysis revealed that p53 activation occurred subsequent in time to DNA damage. By a fluorescent assay, doxorubicin induced loss of mitochondrial membrane potential after p53 activation. Chemical inhibition of p53 prevented doxorubicin-induced cell death and loss of mitochondrial membrane potential without preventing DNA damage, indicating that DNA damage was proximal in the events leading from doxorubicin treatment to cardiac myocyte death. Specific doxorubicin-induced DNA lesions included oxidized pyrimidines and 8-hydroxyguanine. DNA damage therefore appears to play an important early role in anthracycline-induced lethal cardiac myocyte injury through a pathway involving p53 and the mitochondria.