Anti-psoriatic therapy recovers high-density lipoprotein composition and function

Abstract

Psoriasis is a chronic inflammatory disorder associated with increased cardiovascular mortality. Psoriasis affects high-density lipoprotein (HDL) composition, generating dysfunctional HDL particles. However, data regarding the impact of anti-psoriatic therapy on HDL composition and function are not available. HDL was isolated from 15 psoriatic patients at baseline and after effective topical and/or systemic anti-psoriatic therapy and from 15 age- and sex-matched healthy controls. HDL from psoriatic patients showed a significantly impaired capability to mobilize cholesterol from macrophages (6.4 vs. 8.0% [(3)H]cholesterol efflux, P<0.001), low paraoxonase (217 vs. 350 μM(-1) minute(-1) mg(-1) protein, P=0.011) and increased Lp-PLA2 activities (19.9 vs. 12.1 nM(-1) minute(-1) mg(-1) protein, P=0.028). Of particular interest, the anti-psoriatic therapy significantly improved serum lecithin-cholesterol acyltransferase activity and decreased total serum lipolytic activity but did not affect serum levels of HDL-cholesterol. Most importantly, these changes were associated with a significantly improved HDL-cholesterol efflux capability. Our results provide evidence that effective anti-psoriatic therapy recovers HDL composition and function, independent of serum HDL-cholesterol levels, and support to the emerging concept that HDL function may be a better marker of cardiovascular risk than HDL-cholesterol levels.

Figure 1. Psoriasis impairs cholesterol efflux capability of HDL

(a) Psoriasis area and severity index (PASI) score at baseline and after anti-psoriatic therapy. (b) HDL (50 μg/ml protein) from 15 control subjects and 15 psoriatic patients at baseline and after anti-psoriatic therapy were examined for its ability to induce [³H]cholesterol efflux from RAW264.7 macrophages. Cholesterol efflux is expressed as radioactivity in the supernatant relative to total radioactivity. Values shown represent means of two individual experiments performed in duplicate. (c) ApoB-depleted serum (2.8%) was examined for its ability to induce [³H]cholesterol efflux from cAMP-stimulated RAW264.7 macrophages. Values shown represent means of two individual experiments performed in duplicate. The Spearman correlation coefficient is noted. (d) HDL-mediated [³H]cholesterol efflux from RAW264.7 macrophages at baseline and after anti-psoriatic therapy. (e) Correlation between PASI and [³H]cholesterol efflux induced by HDL. (f) Correlation between PASI and apoB-mediated [³H]cholesterol efflux. The Spearman correlation coefficients are noted with its significance level.

Figure 2. HDL-phospholipid correlates with the cholesterol efflux capability of HDL

(a) Quantification of phospholipid content in isolated HDL from healthy controls and psoriasis patients at baseline and after anti-psoriatic therapy. Results represent duplicate measurements of three independent experiments. (b) Correlation between HDL-mediated [³H]-cholesterol efflux from macrophages and the HDL-phospholipid content (HDL-PL) Spearman correlation coefficients are noted for each plot.

Figure 3. Anti-psoriatic therapy reduces serum lipase activity

Quantification of (a) phospholipid transfer protein (PLTP) and (b) cholesteryl-ester transfer protein (CETP) (c) lipase and (d) lecithin-cholesterol acyltransferase (LCAT) activity. Enzymatic activities where measured in serum of psoriasis patients at baseline and after anti-psoriatic therapy with commercial available kits as described in the method section. Results represent measurements of three independent experiments. (e) Pooled HDL samples were separated by native gel electrophoresis and stained with Coomassie Brillant Blue G-250. A gel image was analyzed with ImageJ software to obtain an intensity plot. Standard proteins are indicated as dotted lines with their size in nm.

Figure 4. Anti-psoriatic therapy increases paraoxonase activity and reduced Lp-PLA2 activity on isolated HDL

(a, b) Activity of HDL-associated paraoxonase was measured using paraoxon as substrate. (c, d) Lipoprotein associated phospholipase A2 (Lp-PLA2) activity of HDL was measured using 2-thio PAF as substrate. Paraoxonase and Lp-PLA2 activities of HDL were calculated from the slopes of the kinetic chart of three independent experiments. (e, f) The anti-oxidative activity of HDL was determined by inhibition of AAPH-initiated oxidation of the fluorescent dye dihydrorhodamine (DHR). Incubation of DHR in presence of HDL from healthy subjects (control) or psoriasis patients (psoriasis) led to a reduction in the oxidation of DHR. Results represent measurements of three independent experiments.