Indian Journal of Dermatopathology and Diagnostic Dermatology

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 7  |  Issue : 2  |  Page : 70--73

Loss of expression of claudin-1 in psoriasis is associated with proliferative state of keratinocytes


Manoj Gopal Madakshira, Bishan Dass Radotra, Uma Nahar Saikia 
 Department of Histopathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India

Correspondence Address:
Prof. Uma Nahar Saikia
Department of Histopathology, Post Graduate Institute of Medical Education and Research, Chandigarh - 160 012
India

Abstract

Background: Psoriasis is a chronic remitting and relapsing inflammatory disease, with a prevalence of 0.44%–2.5% and is characterized by T-cell-mediated rapid turnover of epithelial cells. Claudin-1 protein is an integral part of the keratinocyte tight junction and has a role in proliferation, differentiation, and cell adhesion. Aim: The aim of the study was to investigate the role of claudin-1 expression in relation to keratinocyte proliferation in psoriasis. Materials and Methods: Fifty cases of psoriasis were included in the study. Skin biopsies were subjected to claudin-1 and Ki67 immunohistochemistry. Claudin-1 expression in the basal and spinous layers was scored. Ki67 proliferation index was assessed. Seven cases of normal skin biopsies were also included as controls. Fisher's exact test was applied for statistical analysis. Results: The cases had a wide age range (14–78 years), with a mean of 46 years with a male preponderance (4:1). The basal cell layer showed a complete loss of expression for claudin-1 in 82% (n = 42). The spinous layer showed a decrescendo pattern of loss of claudin-1 expression in 96% (n = 48). The association of loss of expression of claudin-1 between the basal layer and spinous layer was statistically significant (P = 0.0229). The association of loss of expression of claudin-1 and high Ki67 proliferative index was also statistically significant (P < 0.00001). Conclusion: Our study showed consistent loss of expression of claudin-1 in the lower layers of the epidermis in psoriasis, which is also the site of intense proliferative activity. The cytokine soup released by the T-cells may be responsible for downregulation of claudin-1, which is one of the triggers for proliferation.



How to cite this article:
Madakshira MG, Radotra BD, Saikia UN. Loss of expression of claudin-1 in psoriasis is associated with proliferative state of keratinocytes.Indian J Dermatopathol Diagn Dermatol 2020;7:70-73


How to cite this URL:
Madakshira MG, Radotra BD, Saikia UN. Loss of expression of claudin-1 in psoriasis is associated with proliferative state of keratinocytes. Indian J Dermatopathol Diagn Dermatol [serial online] 2020 [cited 2022 Sep 26 ];7:70-73
Available from: https://www.ijdpdd.com/text.asp?2020/7/2/70/304341


Full Text



 Introduction



Psoriasis vulgaris is a chronic relapsing and remitting disease predominantly affecting the skin as erythematous papulosquamous dermatitis.[1] Over the years, keratinocytes have also been considered to play an adjunct role in cutaneous immune response.[2] The skin lesions are characterized by a dominant epidermal component in the form of T-cell-mediated abnormal hyperproliferation of keratinocytes.[3] Tight junction proteins have a proven role in barrier function and maintaining polarity of keratinocytes.[4] Of the various tight junctions, Claudin-1 is seen to be expressed in all the layers of keratinocytes.[4] Claudin-1 deficient mice experience transepidermal water loss and die within a day due to dehydration, indicating a principal role in barrier function.[5] Tokumasu et al. have demonstrated in mouse lines that reduced doses of claudin-1 regulate epidermal function in vivo, resulting in acanthosis, indicating a role in proliferation, and differentiation, other than cell adhesion.[6] We analyzed the altered expression of claudin-1 in psoriasis and revealed its association with keratinocyte proliferation.

 Materials and Methods



Fifty consecutive cases of clinically and histologically proven plaque psoriasis in the year 2019 were included in the study, retrieved retrospectively and assessed by two dermatopathologists [Figure 1]a and [Figure 1]b. The paraffin blocks were retrieved from the archives, and 4 μ sections were cut for poly L-lysine-coated glass slides. Immunohistochemistry was carried out on Ventana benchmark XT autostainer following heat retrieval using antibodies against Claudin-1 (Polyclonal, Abcam, 1:500 dilution) and Ki67 (Clone MIB-1, Dako, 1:100 dilution). Skin biopsies with normal histology (skin biopsies of noninvolved skin in cases of vitiligo) were included as controls and were run with each batch. The usual pattern of claudin-1 expression is membranous, while it is nuclear for Ki67. The claudin-1 expression in the basal and spinous layers of the epidermis was scored as: “2” if there was a complete loss of expression; “1” if there was a partial or decrescendo pattern of loss of expression; and '0' if there was retained expression [Figure 1]c. The Ki67 proliferative index was scored as a percentage of basal keratinocytes showing nuclear expression [Figure 1]d. The results were analyzed in SPSS (IBM Inc, Chicago, USA) software version 25 using Fisher's exact test.{Figure 1}

 Results



The demographics showed a male preponderance (male-to-female ratio of 4:1) with a mean age of 46 years (range 14–78 years). The claudin-1 expression in the basal cell layer was seen to be completely lost in 82% of cases (n = 42) and partially lost in 18% of cases (n = 8) [Figure 2]. Claudin-1 expression in the spinous layer saw a decrescendo pattern of loss in 96% of cases (n = 48), while only 4% of cases (n = 2) showed retained expression [Figure 3]. All the normal skin biopsies included showed retained membranous expression of claudin-1 in all the layers of the epidermis. The association of loss of expression of claudin-1 in the basal and spinous layers was statistically significant with P value of 0.0229 (<0.05). The mean Ki67 proliferative index was 76% in skin biopsies of psoriasis in contrast to a mean Ki67 proliferative index of 21% among the normal skin biopsies [Figure 4]. The association of loss of expression of Claudin-1 and Ki67 proliferative index was also statistically significant with P value of 0.00001 (<0.05).{Figure 2}{Figure 3}{Figure 4}

 Discussion



Tight junctions are an integral part of the diffusion barrier and regulate the passage of selective molecules.[4] Claudin-1 is an important component of tight junctions which is expressed in simple epithelia and all the layers of stratified epithelia.[4] Chronic inflammatory diseases such as Crohn's disease, ulcerative colitis, and asthma have been shown to have an altered expression of claudin.[7],[8] This suggests that claudin integrity is essential for health and the altered expression has a role in the pathogenesis of diseases of simple epithelia.[9] A similar association of altered claudin-1 expression has been seen in inflammatory diseases affecting the stratified epithelia such as skin.[10]

Psoriasis is a common remitting and relapsing chronic inflammatory skin disease.[1] It is characterized by a conspicuous T-cell-rich dermal infiltrate with consequent cytokine soup of interleukins -23, -12, and -1, interferons. and tumor necrosis factor-α in the milieu.[2] This cytokine soup triggers hyperproliferation of keratinocytes, resulting in erythematous scaly plaques.[2] Itoh et al. identified seven differentially expressed genes in cases of psoriasis by gene expression analysis, of which only gene whose protein product is part of the tight junction complex was claudin-1, which is located on 3q28-q29.[11] Lopardo et al. demonstrated that claudin-1 is linked to the transcription factor p63, which is integral for stem cell proliferation and stratification.[12] p63 binds to the promoter fragment of claudin-1, resulting in its activation.[12] In addition, reduced expression of claudin-1 has been seen to downregulate apoptosis and enhance the survival of cells.[13]

We observed a consistent loss of expression in the basal and a decrescendo type of loss of expression in spinous layers of epidermis in cases of psoriasis [Table 1]. The differential expression of tight junctions in psoriasis was first documented by Yoshida et al. in 2001 by immunelectron microscopy and hypothesized a possible role of claudins in the pathogenesis of psoriasis.[14] Peltonen et al. in a small study showed by a reverse transcriptase-polymerase chain reaction that there was retained expression of claudin-1 in skin samples of psoriasis but indicated an altered barrier function in the acanthotic spinous layer due to dysregulation of tight junction proteins.[15] However, we studied only protein expression of claudin-1 expression by immunohistochemistry and did not compare it with m-RNA expression by RT-PCR. Similarly, Watson et al. illustrated a reduced expression of claudin-1 at the m-RNA level by reverse transcriptase and at the protein level by Western blotting. Immunofluorescence demonstrated the lack of claudin-1 expression in the lower layers.[9] Their in vivo model showed downregulation of claudin-1 following intradermal injection of interleukin 1β in controls.[9] Similar results were seen in the study by Kirschner et al. indicating an important role of cytokines in the regulation of expression of tight junction proteins including claudin-1 in the pathogenesis of psoriasis.[16] Reduced expression of Vitamin D receptor, an antiproliferative and pro-differentiation driver in the keratinocytes correlates with downregulation of claudin-1 in cases of psoriasis by immunohistochemistry was shown by Visconti et al.[17] Pan et al. illustrated a negative correlation of interleukin-36γ with expression of claudin-1 in psoriasis by immunohistochemistry.[18] Loss of expression of claudin-1 was associated with high proliferative activity of keratinocytes, as enumerated by Ki67 expression in the index study. Kirschner et al. also showed an association of increased keratinocyte proliferation in psoriasis associated with reduced claudin-1 expression by Ki67 immunohistochemistry on biopsy samples and Quick Cell Proliferation Assay Kit on cultured cells.[16] Another tight junction protein claudin-7 has also shown to have a similar pattern of downregulation in early psoriasis by Kirschner et al.[16] While the same investigators showed that occludin, which is normally localized to the lateral membranes of granular cell layer showed enhanced expression in early psoriasis, both along the entire perimeter of the granular cells and also in the lower layers.[16] It is hypothesized that such an attempt at upregulation of occludin could be a desperate attempt by the body at maintaining the barrier function in a light of onslaught by the cytokine soup released by the intruding inflammatory cells.[16]{Table 1}

The present study demonstrated a consistent loss of claudin-1 expression in the basal and spinous layers in cases of psoriasis associated with intense proliferative activity. These findings indicate a definite role of claudin-1 in the pathogenesis of psoriasis secondary to the stimulus received from the cytokine soup released by the T-lymphocytes. Upregulation of claudin-1 can be a potential therapeutic target in psoriasis as shown by the promising role of a traditional medicine Indigo naturalis.[19]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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