Breaking the psoriasis pathological signaling cycle: A novel nanomedicine strategy targeting metabolism and oxidative stress

Abstract

Psoriasis is a chronic skin disorder characterized by dysregulation of immune and epithelial cells, resulting in persistent symptoms such as erythema, scaling, and induration. The abnormal metabolism and increased oxidative stress in psoriasis lesions have been identified as key drivers in the pathogenesis of psoriasis, forming a positive feedback loop within psoriatic skin. Therefore, targeting this feedback loop through modulation of local metabolism and alleviation of oxidative stress could be a rational and promising therapeutic strategy for addressing psoriasis. Herein, we designed a carrier-free nanomedicine (BTN) incorporating bilirubin (BR) and triptolide (TPL) to specifically target two key pathological features of psoriasis: inflammation induced by enhanced reactive oxygen species (ROS) and aberrant proliferation/immune activation driven by heightened nutrient metabolism. In vitro studies demonstrated that BTN effectively improved the water solubility of BR and TPL while facilitating efficient drug delivery to inflammatory keratinocytes. Mechanistically, BTN was found to alleviate the inflammatory cascade caused by oxidative stress and inhibit the IL-23/IL-17 axis. Importantly, downregulation of HIF-1α in keratinocytes resulted in blocking glucose transportation via GLUT-1 as well as amino acid transportation via LAT1, ultimately impeding excessive proliferation by disrupting nutritional requirements. In an imiquimod-induced psoriasis model, BTN effectively permeated inflamed skin epithelium with long-term retention effect. As a multifunctional nanomedicine combining ROS scavenging properties with regulation of nutrition metabolism, BTN shows great promise for reducing inflammatory cell infiltration and suppressing keratinocyte proliferation. Our findings demonstrated the great potential of BTN in ameliorating psoriasis symptoms by restoring the metabolic imbalance and mitigating oxidative stress between the epithelial and immune compartments.

Keywords: Bilirubin; HIF-1α; Nanomedicine; Psoriasis; Triptolide.

Graphical abstract

Scheme 1

Schematic illustration of Bilirubin/Triptolide self-assembled nanoparticle hydrogel (BTN-G) for the treatment of psoriasis.

Fig. 1

Characterization of bilirubin/triptolide nanoparticles (BTN). (A) Particle size distribution and Zeta potential of BTN. (B) TEM image of BTN. Scale bar: 50 nm. (C) The UV–vis–NIR spectra analysis. (D) The mode of binding between Bilirubin (green) and Triptolide (blue). (E) The electrostatic surface characteristics of both Bilirubin and Triptolide. (F) The stability analysis of BTN by monitoring changes in particle size and polydispersity index (PDI), under pH 7.4 PBS at 4 °C. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 2

Uptake assay of BTN in normal and IL-6- and CoCl₂-stimulated HaCaT cells. The uptake in normal HaCaT cells and inflammatory HaCaT cells after treated with coumarin 6 (C6)-labeled BTN or C6 for 0.5 h (A), 1 h (B), 3 h (C) were monitored by fluorescence microscopy. (Scale bar = 100 μm). Quantification of uptake in 0.5 h (D), 1 h (E), 3 h (F) by flow cytometry.

Fig. 3

The anti-proliferation effect and ROS-scavenging property of BTN in inflammatory HaCaT cells. (A) Colony formation assay indicated that BTN inhibited IL-6-induced HaCaT hyperplasia. (B) Viability of HaCaT cells following treatment with different concentrations (1–100 nM) of BTN for 24 h. (C) Quantitative analysis of colony formation assay (n = 3). (D) Intracellular ROS measurements of HaCaT cells following treatment with BR (B), TPL (T), mixture of BR and TPL (BT), and BTN for 24 h. Scale bar: 100 μm. (E) Quantification of the fluorescence intensity of images (n = 3). Data was presented as mean ± SD. ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, indicating significant difference between groups or compared to the blank group.

Fig. 4

BTN inhibited nutrient uptake-related transporters and inflammation cytokines in keratinocytes. (A) HIF-1α, LAT1 and GLUT1 expression following various treatments for 24 h. Quantification of (C) LAT1, (D) GLUT1, (E) HIF-1α in Western Blot assay (n = 3). (B) Inflammatory cytokine expression following various treatments for 24 h. The mRNA levels of (F) LAT1, (G) GLUT1, and (H) HIF-1α following various treatments for 24 h. Data are presented as mean ± SD. ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, indicating significant difference between groups or compared to the Blank group.

Fig. 5

Improved permeation and accumulation of BTN-G in the skin of mice with psoriasis. (A) Sequential fluorescence confocal images depicting ear skin tissues (groups without disease and groups induced with psoriasis) treated topically with C6@BTN-G or fC6-G. Images were captured at 5-μm intervals beneath the surface of lateral ear skin. (Scale bars = 200 μm). (B) Orthogonal x-z images illustrating the treatment of fC6-G or C6@BJN-G on disease-free or psoriatic ear skin. Horizontal image length, 180 μm; vertical image length, 45 μm. (C) Permeation and retention of fDiR-G or DiR@BTN-G drugs in back skin tissue (disease-free group and psoriasis group).

Fig. 6

Reversal of psoriasis symptoms through the application of topical BTN-G was investigated. (A) The experimental design involved inducing psoriasiform dermatitis in mice by topically applying IMQ on one side of the ear for 7 consecutive days (days 0–6) (n = 6). (B) The appearance of the ears and histological analysis using H&E staining were assessed on day 7 (Scale bars = 100 μm). (C) Ear thickness and (D) epidermal thickness were quantified, with data presented as mean ± SD (n = 4). (E) Measurement of ROS in isolated cells from ear tissue was performed by using flow cytometry. Statistical analysis revealed significant differences compared to the IMQ group, indicated by ∗∗∗P < 0.001 and ∗∗∗∗P < 0.0001. Flow cytometry was used to measure ROS levels in isolated cells from ear tissue.

Fig. 7

Systemic therapeutic efficacy of BTN-G against psoriasis. (A) Representative gross images of mouse back on day 0 and day 7 after various treatments and H&E staining. (B) Quantitative analysis of thickness of back skin. (C) Day 7 measurements of the overall PASI scores in distinct mouse groups with psoriasis lesions on their dorsal area. (D) Body weight of mice in different treatment groups. Erythema score (E), Desquamation score (F), Induration score (G) in PASI. Data are presented as mean ± SD. (n = 7) ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001 and ∗∗∗∗P < 0.0001, indicating the significant difference compared to the IMQ group.

Fig. 8

Inhibition of nutrient uptake and inflammation-related proteins by BTN in psoriasis skin. (A) Immunohistochemical images of Ki67, IL-17A, and LAT 1 (Scale bars = 100 μm). Quantification of Ki67 (B), IL-17A (C) and LAT1 (D). (E) Western blot analysis of HIF-1α, LAT1, GLUT 1, and β-Tublin. (F) Western blot analysis of inflammatory factors IL-17A, IL-6, TNF- α, IL-1 β, and GAPDH. Data are presented as mean ± SD. (n = 3). ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, indicating statistically significant differences when compared to the IMQ group.

Fig. 9

BTN-G demonstrated an enhancement in the overall immune status and a reduction in T cell maturation and activation of Th17 cells. (A) Images of spleen from different experimental groups. (n = 5) (B) H&E staining of spleen sections from different experimental groups (scale bar = 100 μm). (C) Analysis of CD69+/IL-17+ cell population within the CD4⁺ splenocyte subset. (D) Percentage of CD69+/IL-17+ cells across various experimental groups. Data was presented as mean ± SD. (E) Ratio of spleen weight to mouse body weight. Splenocytes were isolated from mouse spleens for flow cytometry analysis. Data was presented as mean ± SD (n = 3). ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, ∗∗∗∗P < 0.0001, indicating statistically significant differences compared to the IMQ group.