Inflammasome Signaling and Impaired Vascular Health in Psoriasis

Abstract

Objective- Psoriasis is an inflammatory skin disease which heightens the risk of cardiovascular disease. This study directly investigated vascular endothelial health and systemically altered pathways in psoriasis and matched controls. Approach and Results- Twenty patients (mean age, 40 years; 50% male) with active psoriasis and 10 age-, sex-matched controls were recruited. To investigate systemically alerted pathways, a deep sequencing omics approach was applied, including unbiased blood transcriptomic and targeted proteomic analysis. Vascular endothelial health was assessed by transcriptomic profiling of endothelial cells obtained from the brachial veins of recruited participants. Blood transcriptomic profiling identified inflammasome signaling as the highest differentially expressed canonical pathway ( Z score 1.6; P=1×10^-7) including upregulation of CASP5 and interleukin ( IL) -1β. Proteomic panels revealed IL-6 as a top differentially expressed cytokine in psoriasis with pathway analysis highlighting IL-1β ( Z score 3.7; P=1.02×10^-23) as an upstream activator of the observed upregulated proteins. Direct profiling of harvested brachial vein endothelial cells demonstrated inflammatory transcript (eg, IL-1β, CXCL10, VCAM-1, IL-8, CXCL1, Lymphotoxin beta, ICAM-1, COX-2, and CCL3) upregulation between psoriasis versus controls. A linear relationship was seen between differentially expressed endothelial inflammatory transcripts and psoriasis disease severity. IL-6 levels correlated with inflammatory endothelial cell transcripts and whole blood inflammasome-associated transcripts, including CASP5 and IL-1β. Conclusions- An unbiased sequencing approach demonstrated the inflammasome as the most differentially altered pathway in psoriasis versus controls. Inflammasome signaling correlated with psoriasis disease severity, circulating IL-6, and proinflammatory endothelial transcripts. These findings help better explain the heightened risk of cardiovascular disease in psoriasis. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT03228017.

Keywords: cardiovascular disease; endothelium; inflammasome; inflammation; psoriasis.

Figure 1.. Enrichment in inflammatory and atherosclerosis-associated pathways in the blood transcriptome of psoriasis patients.

(A) Heat map of 758 differentially expressed transcripts between 10 psoriasis and 10 age- sex-matched controls as determined by blood RNA sequencing (p<0.05). (B) Volcano plots of transcripts in whole blood from participants with psoriasis versus controls. The y-axis corresponds to the p value (-log₁₀), and the x-axis displays the log2 fold change. The red dots represent the significantly upregulated transcripts, and blue dots significantly downregulated transcripts (p<0.05). (C) Differential expression of IL-1β, TNF-α, and the top two upregulated transcripts (CASP5, SOCS3) in psoriasis patients compared to controls. (D) Pathway analysis (IPA) of differentially regulated transcripts highlights the inflammatory, immune response and cardiovascular disease biological process which are upregulated in psoriasis over control subjects p<0.05*, p<0.01**, p<0.001***. FPKM, fragments per kilobase of transcript per million mapped reads; IL, Interleukin; IPA, ingenuity pathway analysis; TNF, tumor necrosis factor.

Figure 2.. Endothelial cells from psoriasis patients reveal inflammatory activation.

(A) Differential transcript expression following in vitro human aortic endothelial cells stimulation with IL-17 versus PBS, IL-17+TNF-α versus PBS, IL-17+IFN-γ versus PBS (p<0.05 for all changes). (B) Direct analysis of venous endothelial cells harvested from psoriasis patients compared to controls show transcript upregulation in intracellular adhesion molecules (VCAM-1, ICAM-1), inflammation (COX-2) as well as chemokines (CXCL10, CXCL1, CX3CL1, CCL3, MCP-1) interleukins and tumor necrosis factors (IL-1β, IL-8, Lymphotoxin beta). (C) Differential endothelial transcript expression in psoriasis over controls stratified by psoriasis severity (control, PASI: ≤ 10, > 10). (D) Endothelial inflammatory activation in psoriatic patients, as assessed by nuclear p65 NFκB localization in the vascular endothelium of brachial vein endothelial cells. Direct immunofluorescence staining of harvested venous endothelial cells (VE-cadherin, green) of psoriasis patients compared to healthy controls show increased p65 NFκB (red) nuclear (DAPI - blue) co-localization (n=6). p<0.05*, p<0.01**. DAPI, 4’,6-diamidino-2-phenylinodle; IL, interleukin; NFκB, Nuclear factor kappa-light-chain-enhancer of activated B cells; PASI, psoriasis area and severity index; PSB, phosphate buffered-saline; TNF, tumor necrosis factor; VEGFA, vascular endothelial growth factor A; vWF, von willebrand factor.

Figure 3.. Representative regression plot showing a linear relationship between psoriasis disease severity (psoriasis area and severity index) and inflammatory transcript expression.

VCAM-1, r=0.81, p<0.001; CXCL10, r=0.89, p<0.001.

Figure 4.. Skin biopsies reveal vascular subcutaneous endothelial inflammation is present in psoriatic patients.

(A) Immunohistochemistry of p65 NFκB in lesional skin, non-lesional skin from a psoriasis patient and normal skin from a healthy control. (B) Immunofluorescence staining of skin biopsies show increased p65 NFκB (red) expression in the vascular endothelium (VE-cadherin, green) in both lesional skin and non-lesional skin of a psoriatic patient compared to normal healthy skin. Co-localization of p65 NFκB and VE-cadherin (yellow). (C) Increased magnification of images in B. NFκB, Nuclear factor kappa-light-chain-enhancer of activated B cells.