An investigation of the effects of dithranol-induced apoptosis in a human keratinocyte cell line

Dithranol: An Insight into its Novel Delivery Cargos for Psoriasis Management

OBJECTIVE

Dithranol (DTH) is a well-known moiety that has long been used promisingly to impede and treat skin disorders, particularly psoriasis. Nowadays, a rekindled interest in the use of DTH for this disorder has been observed. Side effects associated with conventional topical formulations of this moiety have aroused the interest of the scientific community in investigating novel cargos of DTH for psoriasis management.

RESULTS

Previous research has evidenced the anti-inflammatory and anti-proliferating potential of DTH. Numerous studies have indicated that DTH inhibits polymorphonuclear (PMN) leucocyte, modulates epidermal cell receptors and promotes anti-psoriatic action. However, some deterrent factors like poor solubility, stability, toxicity, staining and skin irritation hamper its use as a potential therapeutic agent. With the adoption of novel drug delivery technologies, the above mentioned inherent limitations of DTH have been compensated to reestablish this drug moiety.

CONCLUSION

This article reviews novel drug delivery aspects, safety concerns, clinical evidence, current status, and future opportunities of DTH in the management of psoriasis. Further, it will update researchers on this promising drug moiety, which is free from systemic adverse responses in comparison to other therapeutic molecules like steroids, for psoriasis treatment.

Dithranol targets keratinocytes, their crosstalk with neutrophils and inhibits the IL-36 inflammatory loop in psoriasis

Despite the introduction of biologics, topical dithranol (anthralin) has remained one of the most effective anti-psoriatic agents. Serial biopsies from human psoriatic lesions and both the c-Jun/JunB and imiquimod psoriasis mouse model allowed us to study the therapeutic mechanism of this drug. Top differentially expressed genes in the early response to dithranol belonged to keratinocyte and epidermal differentiation pathways and IL-1 family members (i.e. IL36RN) but not elements of the IL-17/IL-23 axis. In human psoriatic response to dithranol, rapid decrease in expression of keratinocyte differentiation regulators (e.g. involucrin, SERPINB7 and SERPINB13), antimicrobial peptides (e.g. ß-defensins like DEFB4A, DEFB4B, DEFB103A, S100 proteins like S100A7, S100A12), chemotactic factors for neutrophils (e.g. CXCL5, CXCL8) and neutrophilic infiltration was followed with much delay by reduction in T cell infiltration. Targeting keratinocytes rather than immune cells may be an alternative approach in particular for topical anti-psoriatic treatment, an area with high need for new drugs.

Erianin Inhibits Proliferation and Induces Apoptosis of HaCaT Cells via ROS-Mediated JNK/c-Jun and AKT/mTOR Signaling Pathways

Psoriasis is a recurrent skin disease described as keratinocyte hyperproliferation and aberrant differentiation. Erianin, a bibenzyl compound extracted from Dendrobium chrysotoxum, has displayed antitumor and anti-angiogenesis effects. However, the effects of erianin on a human keratinocyte cell line (HaCaT) are not fully understood. In the present study, we explored the effect of erianin on proliferation and apoptosis in HaCaT cells. Our results indicated that treatment with erianin ranging from 12.5 nM to 50 nM inhibited proliferation and induced apoptosis of HaCaT cells. In addition, erianin-induced apoptosis was accompanied by elevated reactive oxygen species (ROS). The ROS scavenger N-acetyl-cysteine (NAC) attenuated this elevation. Moreover, treatment with erianin induced activation of the c-Jun N-terminal kinase (JNK)/c-Jun signaling pathway and suppressed the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway, while pretreatment with NAC also reversed these effects. Collectively, these data demonstrated that erianin inhibited proliferation and induced apoptosis of HaCaT cells through ROS-mediated JNK/c-Jun and AKT/mTOR signaling pathways. Erianin could be recognized as a potential anti-psoriasis drug.

Modulation of mitochondrial activity in HaCaT keratinocytes by the cell penetrating peptide Z-Gly-RGD(DPhe)-mitoparan

OBJECTIVE

Biologically active cell penetrating peptides (CPPs) are an emerging class of therapeutic agent. The wasp venom peptide mastoparan is an established CPP that modulates mitochondrial activity and triggers caspase-dependent apoptosis in cancer cells, as does the mastoparan analogue mitoparan (mitP). Mitochondrial depolarisation and activation of the caspase cascade also underpins the action of dithranol, a topical agent for treatment of psoriasis. The effects of a potent mitP analogue on mitochondrial activity were therefore examined to assess its potential as a novel approach for targeting mitochondria for the treatment of psoriasis.

RESULTS

In HaCaT keratinocytes treated with the mitP analogue Z-Gly-RGD(DPhe)-mitP for 24 h, a dose-dependent loss of mitochondrial activity was observed using the methyl-thiazolyl-tetrazolium (MTT) assay. At 10 μmol L^-1, MTT activity was less than 30% that observed in untreated cells. Staining with the cationic dye JC-1 suggested that Z-Gly-RGD(DPhe)-mitP also dissipated the mitochondrial membrane potential, with a threefold increase in mitochondrial depolarisation levels. However, caspase activity appeared to be reduced by 24 h exposure to Z-Gly-RGD(DPhe)-mitP treatment. Furthermore, Z-Gly-RGD(DPhe)-mitP treatment had little effect on overall cell viability. Our findings suggest Z-Gly-RGD(DPhe)-mitP promotes the loss of mitochondrial activity but does not appear to evoke apoptosis in HaCaT keratinocytes.

Anthralin modulates the expression pattern of cytokeratins and antimicrobial peptides by psoriatic keratinocytes

BACKGROUND

Psoriasis is an inflammatory skin disease with aberrant keratinocyte proliferation, presumably as a result of immune cell activation. Th17 cytokines like IL-17A and IL-22 are critically implicated in epidermal thickening, altered keratinocyte differentiation and production of innate factors such as antimicrobial peptides. Psoriasis treatment options include modern targeted therapies using anti-cytokine antibodies and traditional non-targeted treatments like anthralin (dithranol). While the mode of action of anti-cytokine antibodies is defined, the effects of topical anthralin on psoriatic skin are not fully understood.

OBJECTIVE

This study aims to unravel the direct effects of anthralin on keratinocyte proliferation, differentiation and production of psoriasis-associated factors.

METHODS

We tested the effects of anthralin on cell proliferation, cytokeratin expression and changes in the expression of antimicrobial peptides using primary keratinocytes and 3D psoriasis tissue models with and without stimulation of the psoriasis-promoting cytokines IL-17A and IL-22. Moreover, we compared the findings derived from monolayer and multilayer cultures to data derived from lesional skin of patients with psoriasis before and under treatment with anthralin.

RESULTS

Our study shows that anthralin directly induces cell apoptosis in vitro in monolayer cultures but not in 3D psoriasis tissue models treated with IL-17A and IL-22. Yet, keratinocyte proliferation as determined by Ki-67 staining is impaired by anthralin in vivo. In lesional skin but not in 3D psoriasis tissue models anthralin rapidly normalizes cytokeratin (CK)16 expression. Furthermore, anthralin directly inhibits DEFB4 expression in vitro and in vivo, while other antimicrobial peptides and cytokines studied like IL-6 and IL-8 are regulated differently in vitro and in vivo.

CONCLUSIONS

Our results show that anthralin directly regulates DEFB4A expression. However, its beneficial effects on psoriasis cannot be explained by direct effects on keratinocyte differentiation or cytokine expression.

Dithranol treatment of plaque-type psoriasis increases serum TNF-like weak inducer of apoptosis (TWEAK)

PURPOSE

TNF-like weak inducer of apoptosis (TWEAK) mediates not only apoptosis, but also inflammation, cell growth and angiogenesis. The role of TWEAK in psoriasis remains unknown. The aim of the study was to assess serum levels of TWEAK in psoriatic patients before and after topical treatment with dithranol in relation to the clinical activity of the disease.

MATERIAL AND METHODS

Serum samples were collected from 40 patients with plaque type psoriasis before and after topical treatment with dithranol. The concentrations of serum TWEAK were measured by ELISA and next compared with 16 healthy controls. The data were analyzed with respect to Psoriasis Area and Severity Index (PASI).

RESULTS

Baseline serum TWEAK concentrations of psoriatic patients (685±166pg/ml) were significantly greater compared to healthy controls (565±110pg/ml). Topical treatment resulted in further increase in serum TWEAK (749±179pg/ml; p<0.01). In case of patients with initial serum TWEAK concentrations above the median, PASI after topical treatment was lower compared to the individuals with initial TWEAK below the median.

CONCLUSION

According to the study, serum Tweak was increased in psoriasis patients compared with controls. Moreover, dithranol topical treatment caused further increase in serum TWEAK. Also, a higher effectiveness of topical treatment was observed in case of patients with higher initial TWEAK concentrations. The results suggest a potential role of TWEAK in psoriasis therapy.

Exploring the mode of action of dithranol therapy for psoriasis: a metabolomic analysis using HaCaT cells

Psoriasis is a common, immune-mediated inflammatory skin disease characterized by red, heavily scaled plaques. The disease affects over one million people in the UK and causes significant physical, psychological and societal impact. There is limited understanding regarding the exact pathogenesis of the disease although it is believed to be a consequence of genetic predisposition and environmental triggers. Treatments vary from topical therapies, such as dithranol, for disease of limited extent (<5% body surface area) to the new immune-targeted biologic therapies for severe psoriasis. Dithranol (also known as anthralin) is a topical therapy for psoriasis believed to work by inhibiting keratinocyte proliferation. To date there have been no metabolomic-based investigations into psoriasis. The HaCaT cell line is a model system for the epidermal keratinocyte proliferation characteristic of psoriasis and was thus chosen for study. Dithranol was applied at therapeutically relevant doses to HaCaT cells. Following the optimisation of enzyme inactivation and metabolite extraction, gas chromatography-mass spectrometry was employed for metabolomics as this addresses central metabolism. Cells were challenged with 0-0.5 μg mL(-1) in 0.1 μg mL(-1) steps and this quantitative perturbation generated data that were highly amenable to correlation analysis. Thus, we used a combination of traditional principal components analysis, hierarchical cluster analysis, along with correlation networks. All methods highlighted distinct metabolite groups, which had different metabolite trajectories with respect to drug concentration and the interpretation of these data established that cellular metabolism had been altered significantly and provided further clarification of the proposed mechanism of action of the drug.

In silico database screening of potential targets and pathways of compounds contained in plants used for psoriasis vulgaris

Reviews and meta-analyses of clinical trials identified plants used as traditional medicines (TMs) that show promise for psoriasis. These include Rehmannia glutinosa, Camptotheca acuminata, Indigo naturalis and Salvia miltiorrhiza. Compounds contained in these TMs have shown activities of relevance to psoriasis in experimental models. To further investigate the likely mechanisms of action of the multiple compounds in these TMs, we undertook a computer-based in silico investigation of the proteins known to be regulated by these compounds and their associated biological pathways. The proteins reportedly regulated by compounds in these four TMs were identified using the HIT (Herbal Ingredients' Targets) database. The resultant data were entered into the PANTHER (Protein ANnotation THrough Evolutionary Relationship) database to identify the pathways in which the proteins could be involved. The study identified 237 compounds in the TMs and these retrieved 287 proteins from HIT. These proteins identified 59 pathways in PANTHER with most proteins being located in the Apoptosis, Angiogenesis, Inflammation mediated by chemokine and cytokine, Gonadotropin releasing hormone receptor, and/or Interleukin signaling pathways. All four TMs contained compounds that had regulating effects on Apoptosis regulator BAX, Apoptosis regulator Bcl-2, Caspase-3, Tumor necrosis factor (TNF) or Prostaglandin G/H synthase 2 (COX2). The main proteins and pathways are primarily related to inflammation, proliferation and angiogenesis which are all processes involved in psoriasis. Experimental studies have reported that certain compounds from these TMs can regulate the expression of proteins involved in each of these pathways.

Upregulation of the sFas/sFasL system in psoriatic patients

PURPOSE

Psoriasis is a chronic, recurrent, inflammatory disease. Recent investigations indicate its autoimmune pathogenesis. Apoptosis plays an important role in the development of many autoimmune diseases. The aim of this study was to evaluate the influence of topical treatment of psoriasis on soluble Fas (sFas) and soluble Fas-ligand (sFasL).

MATERIAL/METHODS

Serum concentrations of sFas and sFasL were measured using ELISA in 40 psoriatic patients before and after topical treatment with dithranol and compared to the values obtained from 16 healthy subjects. Data were analyzed with respect to severity of psoriasis, duration of the disease and coexisting obesity, diabetes and hypertension.

RESULTS

We found that serum levels of sFas before (11.9±2.4ng/mL) and after treatment (12.2±2.5ng/mL) were significantly higher in patients with psoriasis as compared to the control group (6.4±1.8ng/mL). Concentrations of sFasL did not differ significantly from healthy subjects, but increased after treatment. The sFas/sFasL ratio was significantly higher in psoriasis (128±47) than in the control group and, even though it tended to decrease after treatment, it still remained higher than in the control group (65±22). Additionally we observed a positive correlation of sFas/sFasL ratio with the age of patients and duration of the disease. Psoriatic patients suffering from hypertension and overweight had significantly higher sFas/sFasL ratio than other psoriatic patients.

CONCLUSIONS

Our data indicate upregulation of the sFas/sFasL system in psoriatic patients. We demonstrate association of sFas/sFasL with commorbidities - components of metabolic syndrome.

Making colourful sense of Raman images of single cells

We demonstrate how changes in the application of colour shading can dramatically alter Raman images of single human keratinocytes cells.

Cytotoxic effects of betaxolol on healthy corneal endothelial cells both in vitro and in vivo

AIM

To demonstrate the cytotoxic effect of betaxolol and its underlying mechanism on human corneal endothelial cells (HCE cells) in vitro and cat corneal endothelial cells (CCE cells) in vivo, providing experimental basis for safety anti-glaucoma drug usage in clinic of ophthalmology.

METHODS

In vivo and in vitro experiments were conducted to explore whether and how betaxolol participates in corneal endothelial cell injury. The in vitro morphology, growth status, plasma membrane permeability, DNA fragmentation, and ultrastructure of HCE cells treated with 0.021875-0.28g/L betaxolol were examined by light microscope, 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay, acridine orange (AO)/ethidium bromide (EB) double-fluorescent staining, DNA agarose gel electrophoresis, and transmission electron microscope (TEM). The in vivo density, morphology, and ultrastructure of CCE cells, corneal thickness, and eye pressure of cat eyes treated with 0.28g/L betaxolol were investigated by specular microscopy, applanation tonometer, alizarin red staining, scanning electron microscope (SEM), and TEM.

RESULTS

Exposure to betaxolol at doses from 0.0875g/L to 2.8g/L induced morphological and ultrastructural changes of in vitro cultured HCE cells such as cytoplasmic vacuolation, cellular shrinkage, structural disorganization, chromatin condensation, and apoptotic body appearance. Simultaneously, betaxolol elevated plasma membrane permeability and induced DNA fragmentation of these cells in a dose-dependent manner in AO/EB staining. Furthermore, betaxolol at a dose of 2.8g/L also induced decrease of density of CCE cells in vivo, and non-hexagonal and shrunk apoptotic cells were also found in betaxolol-treated cat corneal endothelia.

CONCLUSION

Betaxolol has significant cytotoxicity on HCE cells in vitro by inducing apoptosis of these cells, and induced apoptosis of CCE cells in vivo as well. The findings help provide new insight into the apoptosis-inducing effect of anti-glaucoma drugs in eye clinic.