eISSN: 2299-0046
ISSN: 1642-395X
Advances in Dermatology and Allergology/Postępy Dermatologii i Alergologii
Current issue Archive Manuscripts accepted About the journal Abstracting and indexing Subscription Contact Instructions for authors
SCImago Journal & Country Rank
2/2019
vol. 36
 
Share:
Share:
more
 
 
Original paper

Analysis of circulating soluble programmed death 1 (PD-1), neuropilin 1 (NRP-1) and human leukocyte antigen-G (HLA-G) in psoriatic patients

Joanna Bartosińska, Anna Michalak-Stoma, Małgorzata Kowal, Dorota Raczkiewicz, Dorota Krasowska, Grażyna Chodorowska, Krzysztof Giannopoulos

Adv Dermatol Allergol 2019; XXXVI (2): 167-172
Online publish date: 2018/02/05
Article file
- Analysis.pdf  [0.14 MB]
Get citation
ENW
EndNote
BIB
JabRef, Mendeley
RIS
Papers, Reference Manager, RefWorks, Zotero
AMA
APA
Chicago
Harvard
MLA
Vancouver
 
 

Introduction

It has been established that in psoriasis, a systemic immune-mediated inflammatory disease of unknown origin, abnormal proliferation of keratinocytes, neoangiogenesis and activation of the immune system are the three fundamental processes responsible for the development of psoriatic skin manifestations. The presence and interactions of CD8+ T cells and neutrophils in the psoriatic epidermis as well as dendritic cells (DCs) and CD4+ T cells in the psoriatic dermis mediate the disruption of the immune tolerance. The imbalance between the regulatory T (Treg) cells, essential for maintaining immune homeostasis, and the effector T cells (i.e. Th1, Th17, Th22), accountable for activation of the immune response, has been observed not only in the skin of psoriatic patients but also in their blood, which appears to confirm the systemic nature of psoriasis [1–3]. Therefore, in order to shed more light on the molecular interactions in psoriasis pathogenesis, the immune mechanisms that fail to control both regulatory and effector T cells need to be thoroughly investigated and the role of such molecules as programmed death 1 (PD-1), neuropilin 1 (NRP-1) and human leukocyte antigen-G (HLA-G) should be carefully analysed.
In order to activate the T cells, which will subsequently trigger a cascade of immune responses, at least two signals are required. The first one involves interaction between the T cell receptor (TCR) and major histocompatibility complex (MHC) on the antigen-presenting cell (APC), while the other signal may be either stimulatory or inhibitory. Programmed death 1, a checkpoint inhibitor expressed on the T cells, B cells and macrophages, is engaged in the latter. However, any disturbance in the interaction between PD-1 and its ligands, i.e. PDL1 or PDL2, mainly expressed on the APC, as observed for example during anti-PD-1 treatment, will increase the T cell activation and pro-inflammatory cytokine production. Besides membrane-bound PD-1, a soluble form (sPD-1) which lacks the transmembrane domain is encoded. Soluble PD-1 is able to block the PD-1/PDL-1 pathway and promotes T cell responses toward pro-inflammatory Th1/Th17 [4, 5]. All this will be manifested in autoinflammatory or autoimmune diseases, e.g. in psoriasis.
Human leukocyte antigen-G (HLA-G) is another checkpoint molecule which plays a key role as an anti-inflammatory and tolerogenic protein [6]. It induces apoptosis in the T and NK cells and inhibits cytotoxic T-cell activity, therefore, all this can be considered a negative feedback signal that downregulates lymphoid reactions and inflammatory processes. Human leukocyte antigen-G is a non-classical major histocompatibility complex (MHC) class Ib molecule which consists of seven isoforms, i.e. membrane-bound (HLA-G1 to HLA-G4) and soluble (HLA-G5 to HLA-G7). The soluble HLA-G (sHLA-G) is mainly produced and secreted by the immune cells, including monocytes/macrophages and myeloid/plasmacytoid DCs [7]. Higher plasma levels of sHLA-G have been reported in various types of cancer and viral infections [6, 8–10]. Thus, it may be speculated that decreased HLA-G levels in psoriasis could favour the development of the disease.
Neuropilin-1 is a co-receptor for vascular endothelial growth factor (VEGF), a molecule responsible for the pro-angiogenic effect, and it also plays a role in T cell and DC immunoregulation [11, 12]. In psoriasis, elongated, tortuous capillaries in the dermis are the features of angiogenesis and progression of the disease [13]. NRP-1 is expressed on Tregs, myeloid cells, including DCs, as well as on neurons and blood vessel cells [11]. NRP-1 has been found to be involved in VEGF-mediated inhibition of DC maturation, an important immunosuppressive mechanism [11]. Since soluble NRP-1 (sNRP-1) isoforms lack the MAM/c, transmembrane and cytoplasmic domains, they can bind NRP-1 ligands, but are unable to transduce signals, and thus they may serve as decoy receptors/natural inhibitors to sequester the NRP-1 ligands [14, 15]. This will result in chronic activation of DCs and undesired immune response, e.g. in psoriasis.

Aim

In order to better understand disturbed immune tolerance in psoriasis, this study investigates the levels of sNRP-1, sPD-1 and sHLA-G in the circulation of psoriatic patients.

Material and methods

Studied group

The study comprised 57 male psoriatic patients hospitalized in the Department of Dermatology, Venereology and Pediatric Dermatology, Medical University of Lublin, Poland and 29 male healthy controls. Fifteen patients (26.32%) suffering from PsA (Define!!! psoriatic arthritis???) met the Classification of Psoriatic Arthritis (CASPAR) criteria. After the demographic data and medical history had been gathered, the clinical examination of each studied patient was performed and blood specimens were collected.

Assessment of psoriasis severity

In all the studied patients the severity of psoriatic skin changes was assessed using the Psoriasis Area and Severity Index (PASI), body surface area (BSA), Physician Global Assessment (PGA) and Dermatology Life Quality Index (DLQI) scores.

Assessment of concentrations of selected immune tolerance mediators in plasma of studied psoriatic patients and controls

The blood specimens previously collected from the psoriatic patients and controls were centrifuged for 15 min at 1000 × g. Then, the plasma samples were subdivided into small aliquots and stored at –80°C to be subsequently tested for the selected immune tolerance mediators’ concentrations. All the concentrations were determined in compliance with the manufacturer’s instructions and using the Human Programmed cell death protein 1 ELISA Kit (EIAab), Human Neuropilin-1 (R&D Systems kits (R&D Systems, Minneapolis, MN, USA) and sHLA-G ELISA (BIOVendor).
The study was approved by the Local Ethic Committee at the Medical University of Lublin (KE-0254/81/2015). Informed consent was obtained from all the participants.
The study was supported by grant No. 164 of the Medical University of Lublin.

Statistical analysis

The data were statistically analyzed using Statistica 10.0 PL (StatSoft Inc., USA). The median values with the (min.–max.) range, and lower and upper quartiles, were calculated for the continuous variables, whereas the absolute (n) and relative numbers (%) were calculated for the categorical variables. The Mann-Whitney U test was used to compare age and the selected immune tolerance mediators plasma concentrations between psoriasis patients and the control group as well as between psoriatic patients with and without arthritis. Spearman’s correlation coefficient was used to assess correlations between the selected immune tolerance mediators’ plasma concentrations and clinical data in the psoriatic patients.
The value p < 0.05 was considered to indicate a significant difference.

Results

Socio-demographic characteristics and clinical data of the studied psoriatic patients are presented in Table 1.
The studied psoriatic patients’ median age was 46 years and did not significantly differ with respect to the control group’s age (p = 0.516). Duration of psoriasis ranged from 1 to 55 years with the median value of 19 years. Twenty (35.09%) patients had positive psoriatic family history.
The PASI value in the studied group ranged from 3 to 43; the median value was 12. The BSA value was in the range of 2–75%, median value 15%. The median value of the PGA was 3.

Comparing plasma concentrations of selected immune tolerance mediators between the studied psoriatic patients and controls

The serum concentrations of NRP-1 in the studied psoriatic patients was significantly higher than in the control group (p = 0.010) (Figure 1). However, no significant differences were found in the PD-1 and HLA-G concentrations between the psoriatic patients and the control group (p = 0.094 and p = 0.482, respectively) (Table 2).

Comparing plasma concentrations of selected immune tolerance mediators between the psoriatic patients with and without arthritis

No significant differences were found in the sPD-1, sNRP-1 and sHLA-G concentrations between the psoriatic patients with and without arthritis (p > 0.05) (Table 3).

Analysis of correlations between selected immune tolerance mediators’ concentrations and clinical data in the studied psoriatic patients

No significant correlations were found between the concentrations of the selected immune tolerance mediators and psoriasis duration, psoriatic arthritis duration, or psoriasis severity expressed by PASI, BSA, and PGA (p > 0.05) (Table 4).

Discussion

The mechanisms of development, function and stability of the immune system, which are known to rely on the cell-to-cell contact and/or participation of cytokines, have been confirmed to play a pivotal role in both human physiology and pathology [16]. Since it has been shown that the Treg cells are capable of suppressing both activation and functioning of the Th cells, B cells and DCs [17], their preventive role in the pathogenesis of autoimmune and autoinflammatory diseases is unquestionable. In psoriasis, an autoinflammatory disease, the down-regulation and defective functioning of Tregs have also been confirmed both in the peripheral blood and in skin lesions [3]. Thus, the long contact between Tregs and DCs, an essential mechanism of immune tolerance, in psoriasis may be compromised, leading to autoimmunity. There are a few cell-surface molecules responsible for induction and maintenance of immune tolerance, i.e. NRP-1, PD-1, and HLA-G, but their possible role in psoriasis still awaits further clarification.
It should be noted that the cytokines involved in triggering immune tolerance produced by Tregs, i.e. transforming growth factor  (TGF-) and interleukin 2 (IL-2), control the expression of PD-1 and NRP-1 on Tregs, as well as Treg cells’ development into follicular regulatory T (Tfr) cells [18]. Transforming growth factor  promotes conversion of CD4+ T cells into Treg cells, while a deficit of the cytokine favours the conversion of Treg cells into Th1 and Th17 cells [18, 19]. IL-2 induces Foxp3 (Forkhead box p3), a known transcription factor which controls Treg development and function. PD-1 is known to be expressed on the surface of activated lymphocytes and the interaction of PD-1 with its ligand PD-L1 leads to suppression of T cell receptor signalling and generation of Treg cells from naïve CD4+ T cells [1, 18]. The soluble form of PD-1, however, acts as a decoy receptor able to bind and neutralize PD-1/PDL1 [4, 5]. In our recent studies we have found that both the expression of PDCD1 mRNA in peripheral blood mononuclear cells [20] and the expression of PD-1 protein on CD4+ and CD8+ T cells were significantly decreased in psoriatic patients both with and without arthritis [21]. Thus, the compromised PD-1 function on CD4+ and CD8+ T cells might indicate inappropriate activation status and suggest dysregulation of the immune suppression mechanisms, which may lead to abnormal, persistent T cell activation and cytokine production in psoriasis. Since no significant difference has been found in the plasma concentration of sPD-1 between the psoriatic patients and the controls, it seems that this study may provide further evidence confirming the presence of some disturbed feedback within the PD-1/PDL1 pathway.
Interestingly, Liu et al. [22] reported that their rheumatoid arthritis (RA) patients presented high levels of serum and synovial concentrations of sPD-1, which is known to be able to neutralize PD-1 on T cells [22]. This may well explain the contribution of sPD-1 to the increased immune response observed in RA.
NRP-1 and sNRP-1 act in the opposite way to one another in angiogenesis and the immune response, two fundamental processes in psoriasis pathogenesis. sNRP-1 is a decoy receptor able to bind its ligand and prevent long-term interactions between Tregs and immature DCs, thereby promoting immunity [23].
In our present study, the circulating sNRP-1 was significantly higher in psoriatic patients in comparison to the controls, whereas in one of our earlier studies, the expression of NRP-1 mRNA in PBMCs (Define!!!) was significantly downregulated in psoriatic patients, both with and without arthritis [21]. Therefore, the increased sNRP-1 concentrations observed in our psoriatic patients could be regarded as a negative feedback mechanism in the process of neovascularization, on the one hand, but, on the other hand, they could also be seen as an immune tolerance compromising factor.
Soluble HLA-G is a molecule capable of suppressing the immune response and promoting the development of Tregs. Borghi et al. [24] observed significantly lower plasma levels of sHLA-G in psoriatic patients than in healthy volunteers. However, in our study no difference in the plasma levels of sHLA-G in the psoriatic patients in comparison to the control group was found. Since the sHLA-G level in our psoriatic patients was not different from the sHLA-G level in the controls, the molecule’s immune suppressive and protective functions against inflammation might be insufficient and unable to prevent the progress of psoriasis. Thus, the lack of difference in sHLA-G concentration between psoriatic patients and healthy volunteers might suggest an insufficient mechanism which could limit immune responses and suppress pathologic immunity. Interestingly, in our previous study we did not find any difference in the mRNA HLA-G expression between the psoriatic patients and controls [20]. Both Aractingi et al. [25] and Cardili et al. [26] observed enhanced HLA-G expression within the psoriatic lesions, which may be suggestive of some modulating role of HLA-G+ T cells at the site of inflammation. Sweeney C and Kirby B [27] suggested that in psoriasis HLA-G might promote the development of Tregs and prevent tissue destruction.
Verbruggen et al. [28] in their RA patients observed lower plasma levels of sHLA-G in comparison to the healthy individuals. Thus, the low levels of sHLA-G observed in those patients could indicate inability of the immune system to suppress the development of self-reactive cells, leading to the development of an autoimmune disease. Veit et al. [29], however, observed high sHLA-G levels in patients with continuous anti-RA treatment, which could reflect an attempt of the immune system to counterbalance the autoimmune process. The same authors [29] also noted that the circulating sHLA-G levels were increased in the late stage of RA.

Conclusions

Analysis of the circulating sPD-1, sNRP-1 and sHLA-G provides evidence confirming their compromising effect on building immune tolerance in psoriatic patients. However, it goes without saying that further elucidation of the role of these molecules in the modulation of immune tolerance will contribute to better understanding of the complex molecular mechanisms involved, inter alia, in psoriasis.

Conflict of interest

The authors declare no conflict of interest.

References

1. Brandt D, Sergon M, Abraham S, et al. TCR+CD3+CD4-CD8- effector T cells in psoriasis. Clin Immunol 2017; 181: 51-9.
2. Nedoszytko B, Lange M, Sokołowska-Wojdyło M, et al. The role of regulatory T cells and genes involved in their differentiation in pathogenesis of selected inflammatory and neoplastic skin diseases. Part I: Treg properties and functions. Adv Dermatol Allergol 2017; 34: 285-94.
3. Nedoszytko B, Lange M, Sokołowska-Wojdyło M, et al. The role of regulatory T cells and genes involved in their differentiation in pathogenesis of selected inflammatory and neoplastic skin diseases. Part II: The role of Treg in skin diseases pathogenesis. Adv Dermatol Allergol 2017; 34: 405-17.
4. Liu C, Jiang J, Gao L, et al. Soluble PD-1 aggravates progression of collagen-induced arthritis through Th1 and Th17 pathways. Arthritis Res Ther 2015; 17: 340.
5. Rusak M, Eliaszewicz Ł, Bołkun E, et al. Prognostic significance of PD-1 expression on peripheral blood CD4+ T cells in patients with newly diagnosed chronic lymphocytic leukemia. Pol Arch Intern Med 2015; 125: 553-9.
6. Pelá FP, Rustiguel JK, Rodrigues LC, et al. A soluble recombinant form of human leucocyte antigen-G 6 (srHLA-G6). Biochem Biophys Res Commun 2017; 487: 28-33.
7. Kirana C, Ruszkiewicz A, Stubbs RS, et al. Soluble HLA-G is a differential prognostic marker in sequential colorectal cancer disease stages. Int J Cancer 2017; 140: 2577-86.
8. Li JB, Ruan YY, Hu B, et al. Importance of the plasma soluble HLA-G levels for prognostic stratification with traditional prognosticators in colorectal cancer. Oncotarget 2017; 8: 48854-62.
9. Rizzo R, Gabrielli L, Bortolotti D, et al. Study of soluble HLA-G in congenital human Cytomegalovirus infection. J Immunol Res 2016; 2016: 3890306.
10. Pan YQ, Ruan YY, Peng JB, et al. Diagnostic significance of soluble human leukocyte antigen-G for gastric cancer. Hum Immunol 2016; 77: 317-24.
11. Oussa NA, Dahmani A, Gomis M, et al. VEGF requires the receptor NRP-1 to inhibit lipopolysaccharide-dependent dendritic cell maturation. J Immunol 2016; 197: 3927-35.
12. Staton CA, Kumar I, Reed MW, Brown NJ. Neuropilins in physiological and pathological angiogenesis. J Pathol 2007; 212: 237-48.
13. Bartosińska J, Chodorowska. Original proposal of capillaroscopic images’ classification in psoriasis vulgaris and psoriatic arthritis. Post Dermatol Alergol 2009; 26: 17-24.
14. Geretti E, Klagsbrun M. Neuropilins: novel targets for anti-angiogenesis therapies. Cell Adh Migr 2007; 1: 56-61.
15. Panigrahy D, Adini I, Mamluk R, et al. Regulation of soluble neuropilin 1, an endogenous angiogenesis inhibitor, in liver development and regeneration. Pathology 2014; 46: 416-23.
16. Mizui M, Kikutani H. Neuropilin-1: the glue between regulatory T cells and dendritic cells? Immunity 2008; 28: 302-3.
17. Miyara M, Sakaguchi S. Natural regulatory T cells: mechanisms of suppression. Trends Mol Med 2007; 13: 108-16.
18. Li L, Yang SH, Yao Y, et al. Block of both TGF-beta and IL-2 signaling impedes neurophilin-1+ regulatory T cell and follicular regulatory T cell development. Cell Death Dis 2016; 7: e2439.
19. Smilek DE, Ehlers MR, Nepom GT. Restoring the balance: immunotherapeutic combinations for autoimmune disease. Dis Model Mech 2014; 7: 503-13.
20. Bartosińska J, Purkot J, Kowal M, et al. Expression of selected molecular markers of immune tolerance in psoriatic patients. Adv Clin Exp Med 2018; 27. doi: 10.17219/acem/78020.
21. Bartosińska J, Zakrzewska E, Purkot J, et al. Decreased blood CD4+PD-1+ and CD8+PD-1+ T cells in psoriatic patients with and without arthritis. Adv Dermatol Alergol 2018; 35 (4).
22. Liu C, Jiang J, Gao L, et al. Soluble PD-1 aggravates progression of collagen-induced arthritis through Th1 and Th17 pathways. Arthritis Res Ther 2015; 17: 340.
23. Sarris M, Andersen KG, Randow F, et al. Neuropilin-1 expression on regulatory T cells enhances their interactions with dendritic cells during antigen recognition. Immunity 2008; 28: 402-13.
24. Borghi A, Fogli E, Stignani M, et al. Soluble human leukocyte antigen-G and interleukin-10 levels in plasma of psoriatic patients: preliminary study on a possible correlation between generalized immune status, treatments and disease. Arch Dermatol Res 2008; 300: 551-9.
25. Aractingi S, Briand N, Le Danff C, et al. HLA-G and NK receptor are expressed in psoriatic skin: a possible pathway for regulating infiltrating T cells? Am J Pathol 2001; 159: 71-7.
26. Cardili RN, Alves TG, Freitas JC, et al. Expression of human leucocyte antigen-G primarily targets affected skin of patients with psoriasis. Br J Dermatol 2010; 163: 769-75.
27. Sweeney C, Kirby B. Does HLA-G prevent tissue destruction in psoriasis? Br J Dermatol 2011; 164: 1118-9.
28. Verbruggen LA, Rebmann V, Demanet C, et al. Soluble HLA-G in rheumatoid arthritis. Circulating soluble neuropilin-1 in patients with early cervical cancer and cervical
29. intraepithelial neoplasia can be used as a valuable diagnostic biomarker. Hum Immunol 2006; 67: 561-7.
30. Veit TD, Chies JA, Switala M, et al. The paradox of high availability and low recognition of soluble HLA-G by LILRB1 receptor in rheumatoid arthritis patients. PLoS One 2015; 10: e0123838.
Copyright: © 2018 Termedia Sp. z o. o. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) License (http://creativecommons.org/licenses/by-nc-sa/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material, provided the original work is properly cited and states its license.
Quick links
© 2019 Termedia Sp. z o.o. All rights reserved.
Developed by Bentus.
PayU - płatności internetowe