Non-canonical nitric oxide signalling and DNA methylation: Inflammation induced epigenetic alterations and potential drug targets

Epigenetic age acceleration mediates the association between low-grade systemic inflammation and cardiovascular diseases: insight from the NHANES 1999-2002

BACKGROUND

Currently, with the global aging of the population, inflammation, recognized as a hallmark in age-related diseases, has been studied and linked to cardiovascular diseases (CVD). However, limited evidence on whether inflammation modifies epigenetic aging and affects CVD risk.

METHODS

This study included 404 CVD patients and 1941 non-CVD individuals from the 1999-2002 National Health and Nutrition Examination Survey cross-sectional data. Low-grade systemic inflammation was assessed using C-reactive protein (CRP), neutrophil-to-lymphocyte ratio (NLR), and systemic inflammation response index (SIRI). Epigenetic age accelerations (EAAs) were calculated as the residuals between chronological and epigenetic ages: Horvath age acceleration (AgeAccel), AgeAccelHannum, and AgeAccelPheno. Weighted linear and logistic regression analyzed the associations between exposures and outcomes, with mediating effects assessed using the Sobel test.

RESULTS

After adjusting confoundings, the log-transformed NLR and SIRI were positively associated with CVD risk, and the odds ratio (OR) ranges from 1.260 to 1.354 (all P < 0.05). Furthermore, the ln-transformed CRP was positively associated with AgeAccelHannum and AgeAccelPheno, and the coefficient (β) ranges from 0.505 to 1.304 (all P < 0.05); the ln-transformed NLR and SIRI were positively associated with all three EAAs, and the β ranges from 0.392 to 2.212 (all P < 0.005). Additionally, 1-unit increase in AgeAccelHannum and AgeAccelPheno was associated with 2.8% (OR: 1.028, 95% CI 1.007-1.049, P = 0.011) and 3.5% (OR: 1.035, 95% CI 1.014-1.056, P = 0.002) increase in CVD risk, respectively. After adjusting confoundings, mediation analysis showed that AgeAccelHannum mediates 10.44% (P = 0.046) of the association between NLR and CVD risk; and AgeAccelPheno mediates 24.03% (P = 0.009) and 18.16% (P = 0.015) of the NLR-CVD and SIRI-CVD risk associations, respectively.

CONCLUSION

Our results demonstrate that EAAs mediate the association between systemic inflammation and CVD risk, highlighting the potential of a multi-target approach to inflammation and epigenetic modifications for personalized management to reduce CVD risk.

Nitric oxide inhibits ten-eleven translocation DNA demethylases to regulate 5mC and 5hmC across the genome

DNA methylation at cytosine bases (5-methylcytosine, 5mC) is a heritable epigenetic mark regulating gene expression. While enzymes that metabolize 5mC are well-characterized, endogenous signaling molecules that regulate DNA methylation machinery have not been described. We report that physiological nitric oxide (NO) concentrations reversibly inhibit the DNA demethylases TET and ALKBH2 by binding to the mononuclear non-heme iron atom forming a dinitrosyliron complex (DNIC) and preventing cosubstrates from binding. In cancer cells treated with exogenous NO, or endogenously synthesizing NO, 5mC and 5-hydroxymethylcytosine (5hmC) increase, with no changes in DNA methyltransferase activity. 5mC is also significantly increased in NO-producing patient-derived xenograft tumors from mice. Genome-wide methylome analysis of cells chronically treated with NO (10 days) shows enrichment of 5mC and 5hmC at gene-regulatory loci, correlating with altered expression of NO-regulated tumor-associated genes. Regulation of DNA methylation is distinctly different from canonical NO signaling and represents a unique epigenetic role for NO.

Total Synthesis and Anti-Inflammatory Activity of Tectoridin and Related Isoflavone Glucosides

The first total syntheses of four isoflavone glucosides, tectoridin (1), tectoridin A (2), tectorigenin 7-O-β-d-glucopyranosyl-12-O-β-d-glucopyranoside (3), and isotectroigenin 7-O-β-d-glucopyranoside (4), have been accomplished. Key steps in our synthetic approach include a regioselective halogenation reaction, followed by methanolysis to introduce the -OCH3 group into isoflavone frameworks and a PTC-promoted stereoselective glycosidation to establish glycosidic bonds. The synthesized isoflavone glucosides (1-4) and their corresponding aglycones (32 and 34) were evaluated for anti-inflammatory activity against nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1 β (IL-1β) in lipopolysaccharide (LPS)-induced RAW264.7 cells. Aglycones 32 and 34 exhibited stronger anti-inflammatory activity in vitro compared to isoflavone glucosides 1-4.