Epigenetics in critical illness: a new frontier

Mineralocorticoid Receptors in Vascular Smooth Muscle: Blood Pressure and Beyond

After half a century of evidence suggesting the existence of mineralocorticoid receptors (MR) in the vasculature, the advent of technology to specifically knockout the MR from smooth muscle cells (SMCs) in mice has elucidated contributions of SMC-MR to cardiovascular function and disease, independent of the kidney. This review summarizes the latest understanding of the molecular mechanisms by which SMC-MR contributes to (1) regulation of vasomotor function and blood pressure to contribute to systemic and pulmonary hypertension; (2) vascular remodeling in response to hypertension, vascular injury, obesity, and aging, and the impact on vascular calcification; and (3) cardiovascular pathologies including aortic aneurysm, heart valve dysfunction, and heart failure. Data are reviewed from in vitro studies using SMCs and in vivo findings from SMC-specific MR-knockout mice that implicate target genes and signaling pathways downstream of SMC-MR. By regulating expression of the L-type calcium channel subunit Cav1.2 and angiotensin II type-1 receptor, SMC-MR contributes to myogenic tone and vasoconstriction, thereby contributing to systemic blood pressure. MR activation also promotes SMC proliferation, migration, production and degradation of extracellular matrix, and osteogenic differentiation by regulating target genes including connective tissue growth factor, osteopontin, bone morphogenetic protein 2, galectin-3, and matrix metallopeptidase-2. By these mechanisms, SMC-MR promotes disease progression in models of aging-associated vascular stiffness, vascular calcification, mitral and aortic valve disease, pulmonary hypertension, and heart failure. While rarely tested, when sexes were compared, the mechanisms of SMC-MR-mediated disease were sexually dimorphic. These advances support targeting SMC-MR-mediated mechanisms to prevent and treat diverse cardiovascular disorders.

Methylation Profiling of Multiple Tumor Suppressor Genes in Hepatocellular Carcinoma and the Epigenetic Mechanism of 3OST2 Regulation

DNA methylation is considered as a significant mechanism that silences tumor suppressor genes (TSGs) and could be used in the early diagnosis of cancer. Histone modifications often work together with DNA methylation; however, how these epigenetic alterations regulate TSGs remains unclear. Here, we determined the methylation status of ten TSGs (3OST2, ppENK, CHFR, LKB1, THBS1, HIC1, SLIT2, EDNRB, COX2, and CLDN7) in hepatocellular carcinoma (HCC) and corresponding noncancerous tissues. Methylation profiling revealed that four genes had very high frequencies of methylation in HCCs, but interestingly, similar high frequencies were also detected in corresponding noncancerous tissues (97.9% vs 95.8% for SLIT2, 93.8% vs 81.3% for EDNRB, 66.7% vs 85.4% for HIC1, and 56.3% vs 56.3% for ppENK, P > 0.05). Only the 3OST2 gene was frequently methylated in HCCs and there was significant difference between HCCs and corresponding noncancerous tissues (68.8% vs 37.5%, P < 0.05). 5-aza-2'-deoxycytidine (5-Aza-CdR) or trichostatin A (TSA) alone could partially reverse 3OST2 methylation, and their combination resulted in complete reversal. UHRF1 and histone H3R8me2s were both enriched on the hypermethylated 3OST2 promoter, but H3R8me2a was not. After 5-Aza-CdR or TSA treatment, the UHRF1 and H3R8me2s enrichment was decreased, while H3R8me2a enrichment increased. We demonstrated that 3OST2 methylation may play a critical role in the earliest steps of hepatocarcinogenesis and is directly regulated by UHRF1. Furthermore, H3R8me2s acted as a repressive mark, while H3R8me2a was correlated with 3OST2 transcriptional activity.

Soluble adhesion molecules as markers for sepsis and the potential pathophysiological discrepancy in neonates, children and adults

Sepsis is a severe and life-threatening systemic inflammatory response to infection that affects all populations and age groups. The pathophysiology of sepsis is associated with aberrant interaction between leukocytes and the vascular endothelium. As inflammation progresses, the adhesion molecules that mediate these interactions become shed from cell surfaces and accumulate in the blood as soluble isoforms that are being explored as potential prognostic disease biomarkers. We critically review the studies that have tested the predictive value of soluble adhesion molecules in sepsis pathophysiology with emphasis on age, as well as the underlying mechanisms and potential roles for inflammatory shedding. Five soluble adhesion molecules are associated with sepsis, specifically, E-selectin, L-selectin and P-selectin, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. While increased levels of these soluble adhesion molecules generally correlate well with the presence of sepsis, their degree of elevation is still poorly predictive of sepsis severity scores, outcome and mortality. Separate analyses of neonates, children and adults demonstrate significant age-dependent discrepancies in both basal and septic levels of circulating soluble adhesion molecules. Additionally, a range of both clinical and experimental studies suggests protective roles for adhesion molecule shedding that raise important questions about whether these should positively or negatively correlate with mortality. In conclusion, while predictive properties of soluble adhesion molecules have been researched intensively, their levels are still poorly predictive of sepsis outcome and mortality. We propose two novel directions for improving clinical utility of soluble adhesion molecules: the combined simultaneous analysis of levels of adhesion molecules and their sheddases; and taking age-related discrepancies into account. Further attention to these issues may provide better understanding of sepsis pathophysiology and increase the usefulness of soluble adhesion molecules as diagnostic and predictive biomarkers.