Cyclooxygenase-2 inhibition restores ultraviolet B-induced downregulation of ATP2A2/SERCA2 in keratinocytes: possible therapeutic approach of cyclooxygenase-2 inhibition for treatment of Darier disease

Impaired Calcium Signaling and Neuropsychiatric Disorders in Darier Disease: An Exploratory Review

Darier (Darier-White) disease (DD) is an autosomal dominant skin disorder caused by pathogenic mutations in the ATP2A2 gene which encodes a calcium ATPase in the sarco-endoplasmic reticulum (SERCA2). Defects in the SERCA2 protein leads to an impairment of cellular calcium homeostasis, which in turn, triggers cell death pathways. There is a high prevalence of neuropsychiatric disorders in patients affected by this condition, namely intellectual disability, bipolar disorder, schizophrenia, and suicidality. Though these associations have been well-documented over the years, little has been discussed or investigated regarding the pathophysiological mechanisms. The goal of this article is to review the literature related to the most commonly associated neuropsychiatric disorders found in patients with DD, highlight the pathophysiological mechanisms underlying each condition, and examine potential interventions that may be of interest for future development. A literature search was performed using PubMed to access and review relevant articles published in the last 40 years. Keywords searched included Darier disease neuropsychiatric, Darier disease pathophysiology, SERCA2 central nervous system, SERCA 2 skin, ATP2A2 central nervous system, ATP2A2 skin, sphingosine-1-phosphate signaling skin, sphingosine-1-phosphate signaling central nervous system, P2X7 receptor skin, and P2X7 receptor central nervous system. Our search resulted in 2,692 articles, of which 61 articles were ultimately included in this review.

A review on mPGES-1 inhibitors: From preclinical studies to clinical applications

Prostaglandin E₂ (PGE₂) is a lipid mediator of inflammation and cancer progression. It is mainly formed via metabolism of arachidonic acid by cyclooxygenases (COX) and the terminal enzyme microsomal prostaglandin E synthase-1 (mPGES-1). Widely used non-steroidal anti-inflammatory drugs (NSAIDs) inhibit COX activity, resulting in decreased PGE₂ production and symptomatic relief. However, NSAIDs block the production of many other lipid mediators that have important physiological and resolving actions, and these drugs cause gastrointestinal bleeding and/or increase the risk for severe cardiovascular events. Selective inhibition of downstream mPGES-1 for reduction in only PGE₂ biosynthesis is suggested as a safer therapeutic strategy. This review covers the recent advances in characterization of new mPGES-1 inhibitors in preclinical models and their future clinical applications.

A molecular systems approach to modelling human skin pigmentation: identifying underlying pathways and critical components

BACKGROUND

Ultraviolet radiations (UV) serve as an environmental stress for human skin, and result in melanogenesis, with the pigment melanin having protective effects against UV induced damage. This involves a dynamic and complex regulation of various biological processes that results in the expression of melanin in the outer most layers of the epidermis, where it can exert its protective effect. A comprehensive understanding of the underlying cross talk among different signalling molecules and cell types is only possible through a systems perspective. Increasing incidences of both melanoma and non-melanoma skin cancers necessitate the need to better comprehend UV mediated effects on skin pigmentation at a systems level, so as to ultimately evolve knowledge-based strategies for efficient protection and prevention of skin diseases.

METHODS

A network model for UV-mediated skin pigmentation in the epidermis was constructed and subjected to shortest path analysis. Virtual knock-outs were carried out to identify essential signalling components.

RESULTS

We describe a network model for UV-mediated skin pigmentation in the epidermis. The model consists of 265 components (nodes) and 429 directed interactions among them, capturing the manner in which one component influences the other and channels information. Through shortest path analysis, we identify novel signalling pathways relevant to pigmentation. Virtual knock-outs or perturbations of specific nodes in the network have led to the identification of alternate modes of signalling as well as enabled determining essential nodes in the process.

CONCLUSIONS

The model presented provides a comprehensive picture of UV mediated signalling manifesting in human skin pigmentation. A systems perspective helps provide a holistic purview of interconnections and complexity in the processes leading to pigmentation. The model described here is extensive yet amenable to expansion as new data is gathered. Through this study, we provide a list of important proteins essential for pigmentation which can be further explored to better understand normal pigmentation as well as its pathologies including vitiligo and melanoma, and enable therapeutic intervention.

Protective effects of resveratrol against UVA-induced damage in ARPE19 cells

Ultraviolet radiation, especially UVA, can penetrate the lens, reach the retina, and induce oxidative stress to retinal pigment epithelial (RPE) cells. Even though it is weakly absorbed by protein and DNA, it may trigger the production of reactive oxygen species (ROS) and generate oxidative injury; oxidative injury to the retinal pigment epithelium has been implicated to play a contributory role in age-related macular degeneration (AMD). Studies showed that resveratrol, an abundant and active component of red grapes, can protect several cell types from oxidative stress. In this study, adult RPE cells being treated with different concentrations of resveratrol were used to evaluate the protective effect of resveratrol on RPE cells against UVA-induced damage. Cell viability assay showed that resveratrol reduced the UVA-induced decrease in RPE cell viability. Through flow cytometry analysis, we found that the generation of intracellular H₂O₂ induced by UVA irradiation in RPE cells could be suppressed by resveratrol in a concentration-dependent manner. Results of Western blot analysis demonstrated that resveratrol lowered the activation of UVA-induced extracellular signal-regulated kinase, c-jun-NH₂ terminal kinase and p38 kinase in RPE cells. In addition, there was also a reduction in UVA-induced cyclooxygenase-2 (COX-2) expression in RPE cells pretreated with resveratrol. Our observations suggest that resveratrol is effective in preventing RPE cells from being damaged by UVA radiation, and is worth considering for further development as a chemoprotective agent for the prevention of early AMD.

[Darier disease]

Darier disease (Darier-White disease, dyskeratosis follicularis) is a rare autosomal dominant genodermatosis with regional differences in prevalence. The responsible mutations have been identified on chromosome 12q23-24.1. The gene encodes a calcium-ATPase type 2 in the sarco-/endoplasmic reticulum (SERCA2), which belongs to the large family of P-type cation pumps. This pump couples ATP hydrolysis to the transport of cations across membranes and thus plays a significant role in intracellular calcium signaling. Neuropsychiatric disorders are often associated with Darier disease. However, these diseases are not due to mutations in the gene ATP2A2 but to a susceptibility locus in a 6.5 Mb region near this gene. Currently, the treatment is strictly limited to the relief of symptoms. In severe cases, oral retinoids (acitretin: initial 10-20 mg/Tag and isotretinoin: 0.5-1 mg/kg/day) lead to a response in 90% of cases. However, side effects often prevent long-term use of vitamin A derivatives.