SARS-CoV-2 susceptibility and COVID-19 disease severity are associated with genetic variants affecting gene expression in a variety of tissues

Variability in SARS-CoV-2 susceptibility and COVID-19 disease severity between individuals is partly due to genetic factors. Here, we identify 4 genomic loci with suggestive associations for SARS-CoV-2 susceptibility and 19 for COVID-19 disease severity. Four of these 23 loci likely have an ethnicity-specific component. Genome-wide association study (GWAS) signals in 11 loci colocalize with expression quantitative trait loci (eQTLs) associated with the expression of 20 genes in 62 tissues/cell types (range: 1:43 tissues/gene), including lung, brain, heart, muscle, and skin as well as the digestive system and immune system. We perform genetic fine mapping to compute 99% credible SNP sets, which identify 10 GWAS loci that have eight or fewer SNPs in the credible set, including three loci with one single likely causal SNP. Our study suggests that the diverse symptoms and disease severity of COVID-19 observed between individuals is associated with variants across the genome, affecting gene expression levels in a wide variety of tissue types

A first update on mapping the human genetic architecture of COVID-19

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Secoisolariciresinol diglucoside abrogates oxidative stress-induced damage in cardiac iron overload condition.

Cardiac iron overload is directly associated with cardiac dysfunction and can ultimately lead to heart failure. This study examined the effect of secoisolariciresinol diglucoside (SDG), a component of flaxseed, on iron overload induced cardiac damage by evaluating oxidative stress, inflammation and apoptosis in H9c2 cardiomyocytes. Cells were incubated with 50 μ5M iron for 24 hours and/or a 24 hour pre-treatment of 500 μ M SDG. Cardiac iron overload resulted in increased oxidative stress and gene expression of the inflammatory mediators tumor necrosis factor-α, interleukin-10 and interferon γ, as well as matrix metalloproteinases-2 and -9. Increased apoptosis was evident by increased active caspase 3/7 activity and increased protein expression of Forkhead box O3a, caspase 3 and Bax. Cardiac iron overload also resulted in increased protein expression of p70S6 Kinase 1 and decreased expression of AMP-activated protein kinase. Pre-treatment with SDG abrogated the iron-induced increases in oxidative stress, inflammation and apoptosis, as well as the increased p70S6 Kinase 1 and decreased AMP-activated protein kinase expression. The decrease in superoxide dismutase activity by iron treatment was prevented by pre-treatment with SDG in the presence of iron. Based on these findings we conclude that SDG was cytoprotective in an in vitro model of iron overload induced redox-inflammatory damage, suggesting a novel potential role for SDG in cardiac iron overload

SDG increases SOD concentration in iron treated H9c2 cells.

<p>SOD concentration in control, 50 μM iron-treated, 500 μM secoisolariciresinol diglucoside (SDG), and SDG pre-treatment + iron-treated H9c2 cells. SOD concentration was assessed via a colourimetric assay. Data is expressed as SOD concentration (U/mL). (** = p < 0.01 versus control; * = p < 0.05 versus control, <i>n</i> = 3).</p

SDG decreases iron-induced oxidative stress in H9c2 cells.

<p>Reactive oxygen species (ROS) in control, 50 μM iron-treated, 500 μM secoisolariciresinol diglucoside (SDG), and SDG pre-treatment + iron-treated H9c2 cells. ROS levels were assessed using the CM-H₂DCFDA assay and measured via flow cytometry (A). The representative histogram of cell count versus FL1 fluorescence (B). Data is expressed as mean fluorescence arbitrary units (a.u.) (* = p < 0.05 versus control, <i>n</i> = 3).</p

SDG decreases iron-induced MMP gene expression in H9c2 cells.

<p>Gene expression of matrix metalloproteinases in control, 50 μM iron-treated, 500 μM secoisolariciresinol diglucoside (SDG), and SDG pre-treatment + iron-treated H9c2 cells. mRNA levels of matrix metalloproteinase (MMP)-2 (A) and MMP-9 (B) were determined via quantitative real-time PCR and normalized to β2-microglobulin, with normal expression standardized to the control. (*** = p < 0.001 versus control; ** = p < 0.01 versus control, <i>n</i> = 3).</p

SDG decreases p70S6K1 and increases AMPK protein expression in iron treated H9c2 cells.

<p>p70S6 Kinase 1 (p70S6K1) (A) and AMP-activated protein kinase (AMPK) (B) protein levels in control, 50 μM iron-treated, 500 μM secoisolariciresinol diglucoside (SDG), and SDG pre-treatment + iron-treated H9c2 cells. Protein levels were measured via immunoblotting. Data is expressed as protein/β-actin arbitrary units (a.u) (* = p < 0.05 versus control, <i>n</i> = 3).</p

SDG decreases iron-induced caspase 3/7 activity in H9c2 cells.

<p>Active caspases 3/7 in control, 50 μM iron-treated, 500 μM secoisolariciresinol diglucoside (SDG), and SDG pre-treatment + iron-treated H9c2 cells. Caspase levels were determined via the CaspaTag 3/7 assay and measured via flow cytometry. Data is expressed as mean fluorescence arbitrary units (a.u.) (A). The representative histogram of cell count versus FL1 fluorescence (B). (** = p < 0.01 versus control, <i>n</i> = 3).</p

SDG decreases iron-induced apoptosis in H9c2 cells.

<p>Forkhead box O (FOXO)3a (A), Bax (B) Bcl2 (C) protein levels and Bcl2/Bax ratio (D) in control, 50 μM iron-treated, 500 μM secoisolariciresinol diglucoside (SDG), and SDG pre-treatment + iron-treated H9c2 cells. Protein levels were measured via immunoblotting. Data is expressed as protein/β-actin arbitrary units (a.u) (** = p < 0.01 versus control; * = p < 0.05 versus control, <i>n</i> = 4).</p

Pretreatment with SDG prevents iron induced decrease in H9c2 cell size.

<p>Cell surface area of control, 50 μM iron-treated, 500 μM secoisolariciresinol diglucoside (SDG), and SDG pre-treatment + iron-treated H9c2 cells. Cell surface area was assessed with ImageJ software. Data is expressed as mean cell area (mm²) (*** = p < 0.001 vs control; * = p < 0.05 vs control; ### = p < 0.001 vs iron, <i>n</i> = 10 images).</p