The effect of phototherapy on the expression of innate immunity genes in patients with psoriasis

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BACKGROUND

Psoriasis is a chronic systemic inflammatory skin disease mediated by genetic and immunologic alterations, as well as environmental factors. Its estimated prevalence is 2%–4% worldwide [1]. Recent studies have confirmed the important role of the microbiota in the development and exacerbation of the disease [2].

The immunopathogenesis of psoriasis involves the interaction between innate and adaptive immunity, primarily through T-helper 17 (Th17) immune responses and reactions in resident skin cells [3]. Dendritic cell–derived interleukins (IL), particularly IL-12 and IL-23, especially when stimulated by antimicrobial peptides, enhance Th17 cell differentiation [4]. Th17 cells produce proinflammatory mediators, including IL-17A, IL-17F, IL-22, tumor necrosis factor alpha (TNF-α), and interferon alpha (IFN-α), leading to keratinocyte hyperproliferation and immune cell infiltration, which amplifies inflammation [5]. Over time, a vicious cycle develops in psoriasis, in which hyperproliferating keratinocytes release increased amounts of antimicrobial peptides and cytokines, such as IL-1, IL-24, chemokine CC motif ligand 20 (CCL20), and CXC motif ligands 1–3 (CXCL1-3). These mediators act as chemoattractants for leukocytes, promoting angiogenesis and further keratinocyte proliferation [6]. IL-9 also induces angiogenesis and sustains Th17-mediated inflammation by stimulating angiogenic markers, including vascular endothelial growth factor (VEGF) and glycoprotein 31 (CD31), and promoting the secretion of IL-17, IL-13, IFN-γ, and TNF-α [7]. Overall, psoriatic lesions are triggered by either exogenous or endogenous factors. Skin innate immunity factors play a key role in the adhesion of pathogenic microorganisms to the skin in psoriasis. Pathogen-recognition receptors, including toll-like receptors (TLR), are activated in response to triggers, initiating immune responses [8]. As previously mentioned, pathogens are counteracted by antimicrobial peptides such as cathelicidin, human β-defensins, and S100A7, which also contribute to chemotaxis, angiogenesis, and keratinocyte proliferation.

Phototherapy, particularly narrowband ultraviolet B (UVB) 311 nm, is one of the most effective treatment modalities for psoriasis; however, its mechanism of action on innate immunity has been minimally studied.

The study aimed to investigate the local expression profile of innate immunity factors in patients with psoriasis during phototherapy.

MATERIALS AND METHODS

Study Design

A multicenter, prospective, non-randomized study was conducted.

Eligibility Criteria

Inclusion criteria: patients older than 18 years, diagnosis of psoriasis vulgaris for the main group, and signed informed consent.

Study Setting

The study was conducted at the Rakhmanov Clinic of Skin and Venereal Diseases and the Mechnikov Research Institute of Vaccines and Sera.

Study Duration

The study was performed from 2023 to 2024.

Intervention

The study included patients with psoriasis vulgaris in the inpatient-stage aged 19 to 73 years and healthy volunteers who formed the control group. Patients with psoriasis vulgaris received narrowband UVB 311 nm phototherapy using a Valdmann UV7002 cabin, four sessions per week, without prior determination of the minimal erythema dose. The initial dose (0.05–0.1 J/cm²) was gradually increased by 0.1 J/cm² every two sessions. The course of narrowband UVB 311 nm phototherapy lasted 5 to 7 weeks, with a total cumulative dose of 35.2–44.6 J/cm².

Outcomes Registration

Gene Expression Analysis. Ribonucleic acid (RNA) was isolated from keratinocyte scrapings according to the Extract RNA kit instructions (Eurogen, Russia). RNA quality was assessed using a Nanodrop 2000 spectrophotometer (Thermo Fisher, USA). Concentration values were used to calculate the amount of RNA required for reverse transcription (1 µg per reaction) according to the OT-1 kit protocol (Sintol, Russia). Complementary deoxyribonucleic acid (DNA) obtained from reverse transcription was used to determine the expression levels of selected genes (TLR2, TLR9, IL13, DEFB1, CAMP, TLR4) using real-time polymerase chain reaction (RT-PCR). SYBR Green I kit (Sintol, Russia) was used for PCR. RT-PCR was performed on the DT-96 instrument (DNA-Technology, Russia). The reaction was performed under the following conditions: (1) 95 °C for 5 minutes, 1 cycle; (2) 95 °C for 15 seconds and 60 °C (or 58 °C) for 50 seconds, 40 cycles; (3) melting curve analysis. Threshold cycle (Ct) values were processed using the 2^-ΔΔC(t) method relative to the expression level of the housekeeping gene β-actin (ACTB). Data are presented in relative units. Gene expression analysis was performed before treatment and at the end of the phototherapy course.

Statistical Analysis

Statistical analysis was performed in several steps using GraphPad Prism version 9.4.1. Medians of 2^-ΔΔC(t) values were calculated for each dataset. Based on these values, graphs of the median relative expression levels of each gene were plotted. Box-and-whisker plots were constructed to visually represent numerical data by quartiles. Medians and corresponding interquartile ranges are indicated in the text as Ме and [Q1; Q3]. Statistical significance between groups was assessed using the nonparametric Kruskal–Wallis H test. Results were considered statistically significant at p < 0.05.

RESULTS

Participants

The study included 31 patients with psoriasis vulgaris in the inpatient-stage, aged 19 to 73 years, including 5 women and 26 men. Several sample groups were formed during the study, with three keratinocyte scraping samples collected from each patient: (1) lesional skin before treatment; (2) non-lesional skin before treatment; and (3) lesional skin after therapy.

The control group consisted of 30 healthy volunteers, matched for sex and age (19 to 70 years).

Primary Results

TLR gene expression levels across the four study groups are shown in Fig. 1. A significant difference in TLR2 gene expression was observed between the groups of patients before treatment (lesional skin, non-lesional skin) and after treatment (lesional skin)—Me 0.05 [0.03; 0.13], Me 1.32 [1.04; 1.69], and Me 0.81 [0.16; 1.63], respectively. A similar pattern was observed for TLR9 expression: Me 0.08 [0.04; 0.18], Me 0.66 [0.56; 2.98], and Me 0.69 [0.17; 6.42], respectively. For TLR4 expression, the highest value was recorded in the group of patients before treatment (non-lesional skin)—Me 0.35 [0.23; 1.23], which was significantly higher than in the group before treatment (lesional skin) and in the control group—Me 0.03 [0.02; 0.12] and Me 0.09 [0.09; 0.10], respectively.

 

Fig. 1. TLR gene expression levels by groups: * p <0.05; ** p <0.01; *** p <0.005. Source: Olisova O.Yu. et al., 2025.

 

Fig. 2 shows antimicrobial peptide gene expression levels. Non-lesional skin and lesional skin after treatment demonstrated increased expression of the β-defensin 1 (DEFB1) gene. Median values for the groups before treatment (lesional skin, non-lesional skin), after treatment (lesional skin), and controls were 1.23 [0.56; 2.16], 388.0 [387.9; 388.1], 477.7 [2.0; 548.7], and 1.0 [0.95; 1.0], respectively. For the cathelicidin (CAMP) gene, differences were observed between the groups before treatment (lesional skin, non-lesional skin) and after treatment (lesional skin)―Me 0.007 [0.001; 0.05], Me 0.98 [0.105; 3.05], and Me 3.37 [2.42; 4.09], respectively.

 

Fig. 2. Antimicrobial peptide gene expression levels by groups: * p <0.05; ** p <0.01. Source: Olisova O.Yu. et al., 2025.

 

For the IL-13 gene, the highest median values were observed in both groups before treatment―Me 0.64 [0.15; 1.22] for lesional skin and Me 3.73 [1.87; 6.96] for non-lesional skin. A significant difference was found between the non-lesional skin group before treatment and the lesional skin group after treatment (Me 0.22 [0.15; 3.03]); Fig. 3.

 

Fig. 3. IL-13 gene expression levels by groups: * p <0.05. Source: Olisova O.Yu. et al., 2025.

 

DISCUSSION

In the work by Curry et al. [9], the expression of TLR1, TLR2, TLR4, and TLR9 genes in cutaneous immunocytes and keratinocytes obtained from patients with psoriasis was analyzed in comparison with healthy volunteers. Immunohistochemistry, performed with consideration of cell type and characteristics, demonstrated that TLR1 levels were elevated in dendritic cells and keratinocytes of both lesional and non-lesional skin in psoriasis and in cells from the control group. TLR2 expression was observed only in dermal dendritic cells, whereas TLR4 expression was detected in keratinocytes; TLR9 expression was not registered in any of the studied cell types. In cultured keratinocytes derived from patients, increased expression of TLR2, TLR4, or TLR9 was not demonstrated either, which partially agrees with the findings of the present study. Other works have shown the expression of TLR2, TLR4 and TLR9 genes in peripheral blood mononuclear cells but not locally in the skin [10–12]. In the investigation by Prignano et al. [13], increased expression of the intracellular receptor TLR9 was observed only in the spinous layer of the epidermis in lesional skin. An experimental study in mice demonstrated that activation of the TLR2 signaling pathway directly enhanced the proliferation of regulatory T cells and their IL-10 production, as well as IL-10 production by dendritic cells, thereby suppressing imiquimod-induced psoriasis-like skin inflammation [14]. In our study, we observed a significant decrease in the expression of innate immunity receptors in lesional skin before treatment, with a tendency toward an increase after treatment and higher expression of TLR in keratinocytes of non-lesional skin, which may indirectly indicate normalization of these parameters outside the lesion and beyond exacerbation of the disease.

Regarding antimicrobial peptides, the data are inconsistent. In our investigation, lesional skin exhibited decreased expression levels of these peptides, whereas after therapy and in non-lesional skin, expression was increased for β-defensin 1 and normalized for cathelicidin.

It is known that LL-37 production is elevated in psoriasis; this antimicrobial peptide forms complexes with self-DNA, which are detected by dermal plasmacytoid dendritic cells via TLR9 [15], subsequently inducing IFN-α production that mediates downstream T cell–related immune responses. One work reported that LL-37 activated TLR8 in keratinocytes, initiating IL-17C action through IL-36γ [16], whereas another work showed increased levels of this antimicrobial peptide in the serum of patients with psoriasis [17].

It has also been shown that IL-23 upregulates β-defensin 2 (DEFB2) gene expression, promoting keratinocyte proliferation and cytokine production along with enhanced Th17 cell differentiation [18]. Data on the role of DEFB1 in psoriasis are limited; for example, Uzuncakmak et al. [19] evaluated changes in the expression of HBD1 and HBD2, finding significantly higher levels in patients with psoriasis compared with controls, yet these levels did not change after phototherapy. In contrast, our study demonstrated changes after treatment indicative of increased antimicrobial peptide production by keratinocytes. It should be noted that heterogeneous factors influencing cutaneous antimicrobial peptide levels and individual variations in patient response to therapy, cannot be excluded.

Finally, our findings regarding IL-13 are consistent with previous studies. This interleukin participates in the Th2 immune response, which occurs in various inflammatory conditions, including atopic dermatitis. Bodoor et al. [20] assessed the production of several interleukins using enzyme immunoassay in patient groups with psoriasis and atopic dermatitis. Although IL-13 levels were higher in the group of patients with psoriasis compared with healthy controls, they remained lower than in the group with atopic dermatitis. The effects of IL-13 on keratinocyte growth or suppression under normal conditions or in psoriasis have not been studied [21].

Conclusion

The pathogenesis of psoriasis is mediated by immunologic responses and environmental factors. Recently, mechanisms of innate immunity in psoriasis have been actively investigated. In our study, innate immunity receptors (TLR2, TLR4, TLR9), antimicrobial peptides, and other effector molecules were found to be differentially expressed in lesional and non-lesional skin. The observed local imbalance of innate immunity factors may contribute to a more severe course of the disease. A course of phototherapy led to normalization of the expression profile of receptor and effector molecules of innate immunity, resulting in a stable positive clinical effect.

Future studies should evaluate the effects of phototherapy on genetic and protein profiles of immunity, which would help clarify the immunopathogenesis of psoriasis and support the rationale for the applied therapy.

ADDITIONAL INFORMATION

Authors' contributions. O.Yu. Olisova ― concept development, critical analysis of the study, observation of patients with psoriasis, analysis of the study groups, article editing; O.S. Yazkova ― analysis of the study, observation of patients with psoriasis, article editing; writing the article; E.P. Bystritskaya ― conducting the experimental (laboratory) part of the stud, statistical data analysis, writing the article; T.I. Radchenko ― conducting the experimental (laboratory) part of the stud, statistical data analysis; E.I. Zhgelskaya ― observation of patients with psoriasis, analysis of the study groups, writing the article; O.A. Svitich ― concept development, critical analysis of the study, analysis of the study groups, article editing. Thereby, all authors provided approval of the version to be published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Ethics approval. The study was conducted in compliance with the principles of clinical practice (Good Clinical Practice) and the ethical standards of the Helsinki Declaration of the World Medical Association (recommendations for physicians on conducting biomedical research on humans) with informed consent to participate in the study. The study was approved by the local ethics committee of I.M. Sechenov First Moscow State Medical University (protocol No. 120 dated 03/15/2023).

Funding sources. No funding.

Disclosure of interests. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Statement of originality. When conducting the research and creating this work, the authors did not use previously published information (text, illustrations, data).

Data availability statement. Access to the data obtained in this study is closed due to data confidentiality.

Generative AI. Generative AI technologies were not used for this article creation.

Provenance and peer-review. This paper was submitted to the journal on an unsolicited basis and reviewed according to the usual procedure. Two external reviewers and the scientific editor of the publication participated in the review.

About the authors

Olga Yu. Olisova

I.M. Sechenov First Moscow State Medical University (Sechenov University)

Author for correspondence.
Email: olisovaolga@mail.ru
ORCID iD: 0000-0003-2482-1754
SPIN-code: 2500-7989

д-р мед. наук, профессор, чл.-корр. РАН

Russian Federation, Moscow

Olga S. Yazkova

Central polyclinic

Email: olesha230808@mail.ru
ORCID iD: 0000-0002-9644-4778
SPIN-code: 9548-9076

MD, Cand. Sci. (Medicine)

Russian Federation, Moscow

Elizaveta P. Bystritskaya

I. Mechnikov Research Institute of Vaccines and Sera

Email: lisabystritskaya@gmail.com
ORCID iD: 0000-0001-8430-1975
SPIN-code: 6769-2534
Russian Federation, Moscow

Tatiana I. Radchenko

Lomonosov Moscow State University

Email: tati.radchenko2004@gmail.com
ORCID iD: 0009-0007-2575-4158
Russian Federation, Moscow

Elizaveta I. Zhgelskaya

I.M. Sechenov First Moscow State Medical University (Sechenov University)

Email: lizaderm@yandex.ru
ORCID iD: 0009-0003-9228-0686
Russian Federation, Moscow

Oxana A. Svitich

I.M. Sechenov First Moscow State Medical University (Sechenov University); I. Mechnikov Research Institute of Vaccines and Sera

Email: svitichoa@yandex.ru
ORCID iD: 0000-0003-1757-8389
SPIN-code: 8802-5569

MD, Dr. Sci. (Medicine), corresponding member of the Russian Academy of Sciences

Russian Federation, Moscow; Moscow

References

Supplementary files