Suprabasal expression of epidermal alpha 2 beta 1 and alpha 3 beta 1 integrins in skin treated with topical retinoic acid

Koebner phenomenon leading to the formation of new psoriatic lesions: evidences and mechanisms

Koebner phenomenon refers to the emergence of new psoriatic lesions in the healthy skin regions following an injury/trauma to psoriatic patients. The occurrence of psoriatic lesions at unusual areas of the body regions such as on penis, around eyes and on keloids suggest that the Koebner phenomenon may be responsible for these lesions. A number of agents/triggers have been reported to induce the development of new psoriatic lesions in healthy skin areas and these include, tattooing skin, radiations, skin incision, viral infections and striae etc. The different mechanisms that contribute in inducing the development of new psoriatic lesions as Koebernization include the involvement of mast cell-derived inflammatory mediators such as tryptase, IL-6, IL-8, IL-17, and IL-36γ. Moreover, an increased expression of nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) also contribute in Koebernization. Apart from these, there is a critical role of α 2 β1 integrins, S100A7 (psoriasin) and S100A15 (koebnerisin), change in the ratio of CD4+/CD8+ T cells, down-regulation of mechanosensitive polycystin 1 protein, decrease in inflammation controlling atypical chemokine receptor 2 (ACKR2), reduced expression of N-methyl-d-aspartate (NMDA) receptors (NMDARs) on the keratinocytes and increase in levels of chemokines (CXCL8 and CCL20) in inducing formation of new psoriatic lesions. The present review discusses the role of Koebner phenomenon in the development of new psoriatic lesions. Moreover, it also describes the mechanisms involved in Koebernization in the form of discussion of different key targets that may be potentially modulated pharmacologically to attenuate/halt the development of new psoriatic lesions.

Long non-coding RNA PICSAR decreases adhesion and promotes migration of squamous carcinoma cells by downregulating α2β1 and α5β1 integrin expression

Long non-coding RNAs (lncRNAs) regulate various cellular processes, and they have emerged as potential biomarkers and therapeutic targets in cancer. We have previously characterized the oncogenic role of lncRNA PICSAR (p38 inhibited cutaneous squamous cell carcinoma associated lincRNA) in cutaneous squamous cell carcinoma (cSCC), the most common metastatic skin cancer. In this study, we show that knockdown of PICSAR in cSCC cells upregulates expression of α2, α5 and β1 integrins, resulting in increased cell adhesion and decreased cell migration on collagen I and fibronectin. In contrast, overexpression of PICSAR in cSCC cells downregulates expression of α2, α5 and β1 integrins on cell surface, resulting in decreased cell adhesion on collagen I and fibronectin and increased cell migration. These results demonstrate a novel mechanism for regulation of the expression of collagen and fibronectin binding integrins by lncRNA PICSAR, leading to altered adhesion and migration of cSCC cells.

This article has an associated First Person interview with the first author of the paper.

Summary: Long non-coding RNA PICSAR decreases adhesion and promotes migration of cutaneous squamous cell carcinoma cells by regulating the expression of collagen and fibronectin binding α2β1 and α5β1 integrins.

Differential regulation of surface receptor expression, proliferation, and apoptosis in HaCaT cells stimulated with interferon-γ, interleukin-4, tumor necrosis factor-α, or muramyl dipeptide

Keratinocytes are routinely subjected to both internal and external stimulation. This study investigates the effects of interferon gamma, interleukin-4, tumor necrosis factor alpha, and the synthetic immunomodulator muramyl dipeptide on the human keratinocyte cell line, HaCaT. Following HaCaT stimulation with cytokines or muramyl dipeptide for different time periods, changes in the expression of different cell surface receptors, cell proliferation, and cell apoptosis were evaluated by flow cytometry, tritiated thymidine uptake, and annexin-V staining, respectively. A significant decrease in the expression of CD49d was found upon treatment with interleukin-4. Interferon gamma and tumor necrosis factor alpha increased the expression of intercellular adhesion molecule 1 and major histocompatibility complex class I, whereas major histocompatibility complex class II and CD1b were only upregulated by interferon gamma. Interferon gamma and tumor necrosis factor alpha had opposite effects regarding CD119 expression, with the former downregulating, while the latter upregulating its expression. Of the stimuli tested, only interferon gamma and tumor necrosis factor alpha significantly inhibited proliferation of HaCaT cells, yet only interferon gamma played a significant role in inducing HaCaT cell apoptosis. Our data demonstrate differential effects of the three tested cytokines on keratinocytes and reveal that the absence of HaCaT cell responses to muramyl dipeptide is associated with undetectable levels of its cytoplasmic receptor, nucleotide-binding oligomerization domain-containing protein 2.

UV-mediated downregulation of the endocytic collagen receptor, Endo180, contributes to accumulation of extracellular collagen fragments in photoaged skin

BACKGROUND

Collagen is the most abundant protein in human skin and is responsible for its resilience. In particular during photoaging, collagen homeostasis is out of balance leading to a continuous loss of intact collagen and to the observed signs of aged skin such as diminished tensile strength and wrinkle development. The process of collagen turnover is very slow and the relevance of cellular uptake of damaged collagen, most likely mediated via Endo180 or integrin α2β1, still remains a matter of investigation.

OBJECTIVE

We investigated the role of different collagen receptors on dermal fibroblasts for collagen internalization and their impact on collagen homeostasis during photoaging.

METHODS

TaqMan Real-Time PCR, flow cytometry, UV irradiation, knockdown experiments and immunostaining.

RESULTS

We show that Endo180 and integrin α2 are regulated in photoaged skin and after acute UV stress in vivo and in vitro. Knockdown experiments revealed that Endo180 is essential for cellular uptake of collagen fragments by dermal fibroblasts, whereas integrin α2 is important for initial binding of collagen. UV irradiation decreases collagen endocytosis. This correlates with reduced Endo180 expression and pericellular accumulation of collagen fragments during photoaging.

CONCLUSION

Our findings correlate for the first time impaired collagen uptake via Endo180 with the pericellular accumulation of collagen fragments during photoaging. We assume an altered pericellular niche of fibroblasts in photoaged skin that has an impact on collagen homeostasis.

In vivo pharmacological disease models for psoriasis and atopic dermatitis in drug discovery

In order to perform relevant in vivo pharmacological investigations in drug discovery within dermatology it is fundamental to master or have access to relevant skin disease models that makes it possible to identify and validate targets and to screen and discover drugs in vivo. There is a strong need for highly predictive in vivo models in order to introduce the right drug candidates into the clinical phases of development. Recent advances in dermatological in vivo pharmacological disease models for psoriasis and atopic dermatitis are reviewed together with a discussion of the rationale for their application in drug discovery.

Immunopathogenesis of conjunctival remodelling in vernal keratoconjunctivitis

PURPOSE

To study the processes involved in mediating conjunctival remodelling in vernal keratoconjunctivitis (VKC) by investigating the expression of integrin receptors, epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), transforming growth factor-beta(TGF-beta), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), and Ki67 antigen, which is a marker for cell proliferation.

METHODS

Conjunctival biopsy specimens from 16 patients with active VKC and nine control subjects were studied by immunohistochemical techniques using monoclonal and polyclonal antibodies directed against the integrin alpha3 and alpha6 subunits, EGFR, VEGF, TGF-beta, bFGF, PDGF, and Ki67 antigen. The phenotype of inflammatory cells expressing growth factors was examined by double immunohistochemistry.

RESULTS

In the normal conjunctiva, very weak immunoreactivity was observed for EGFR and VEGF in epithelial cells, and for alpha3 and alpha6 integrin subunits on basal epithelial cells, and on vascular endothelial cells in the upper substantia propria. There was no immunoreactivity for the other antibodies. In VKC specimens, strong staining for alpha3 and alpha6 integrin subunits was observed on the membranes of basal and suprabasal epithelial cells, and all vascular endothelial cells. Immunoreactivity for Ki67 antigen was observed in the nuclei of the basal and suprabasal epithelial cells. Strong immunoreactivity was observed for EGFR in the deeper layers of the epithelium, and for VEGF in all epithelial cells. Inflammatory cells expressing EGFR, VEGF, TGF-beta, bFGF, and PDGF were noted in 8, 9, 11, 10, and 10 specimens, respectively. The majority of inflammatory cells expressing growth factors were eosinophils (45+/-4%) and monocytes/macrophages (35+/-4%).

CONCLUSIONS

Chronic conjunctival inflammation in VKC is associated with increased staining of alpha3, and alpha6 integrin subunits, EGFR, VEGF, TGF-beta, bFGF, and PDGF that might mediate conjunctival remodelling.

Influence of anti-CD49f and anti-CD29 monoclonal antibodies on mitotic activity of epithelial cells (HaCaT) and gingival fibroblasts in vitro

A major complication in the treatment of periodontitis marginalis is the reepithelization of periodontal defects inhibiting collagen fiber attachment and periodontal regeneration. In this study we investigated the possibility of a molecular blockade of epithelial mitosis in vitro. Monoclonal antibodies against the VLA-6 laminin receptor subunit alpha6 interrupted interactions between epithelial cells (HaCaT cells) and their extracellular matrix and thus resulted in reduction of proliferation rates by more than 50%. The same effect was observed with anti alpha1-antibodies. In contrast, collagen-producing and -secreting gingival fibroblasts, which play an important role in periodontal regeneration, remained unaffected by the applied anti alpha6 antibodies. Correspondingly, these cells were found to lack VLA-6 laminin receptors. Selective molecular inhibition of epithelial proliferation and apical migration by monoclonal anti alpha6 antibody application may provide an adjuvant periodontitis therapy resulting in an enhanced periodontal regeneration.

Retinoic Acid Upregulates the Plasminogen Activator System in Human Epidermal Keratinocytes

The activation of the proteolytic plasminogen activator system is important for the re-epithelialization of skin wounds. Keratinocytes synthesize and secrete the urokinase-type plasminogen activator, which binds to its specific receptor on keratinocytes. Receptor-bound urokinase-type plasminogen activator efficiently activates cell surface bound plasminogen. This results in pericellular proteolysis, which facilitates keratinocyte migration. Urokinase-type plasminogen activator activity is specifically controlled by plasminogen activator inhibitor-1 and -2. As retinoids have been reported to accelerate epithelialization of skin wounds in animal studies and clinical settings, we investigated the effects of all-trans retinoic acid on the plasminogen activator system in human epidermal keratinocytes. As tested in a chromogenic plasminogen activation assay, incubation with 10 microM all-trans retinoic acid caused a marked induction of cell-associated plasminogen activity after 24 h, and this induction was blocked by neutralizing anti-urokinase-type plasminogen activator antibodies, but not anti-tissue-type plasminogen activator antibodies. All-trans retinoic acid lead to a strong increase in urokinase-type plasminogen activator (enzyme-linked immunosorbent assay) and urokinase-type plasminogen activator receptor cell surface expression (flow cytometry) after 24 h. At this time-point, tissue-type plasminogen activator and plasminogen activator inhibitor-1 and -2 proteins were not or only slightly increased. Northern blot analyses revealed that all-trans retinoic acid caused an early and short-lived increase of plasminogen activator inhibitor-1, but a prolonged induction of urokinase-type plasminogen activator and urokinase-type plasminogen activator receptor mRNA levels. Collectively, these data suggest that all-trans retinoic acid activates the plasminogen activator system in human epidermal keratinocytes by differentially regulating activating and inhibiting components. The activation of the plasminogen activator system may be one mechanism by which all-trans retinoic acid exerts beneficial effects in cutaneous wound healing.