High concentration of glucose induces filaggrin-1 expression through AP-1 in skin keratinocytes

Interplay between diabetes mellitus and atopic dermatitis

Inflammatory dermatoses such as atopic dermatitis (AD) have long been linked to the pathogenesis of diabetes mellitus. Indeed, numerous studies show an increased risk of diabetes mellitus in individuals with AD although lower prevalence of diabetes mellitus is also observed in few studies. Though the underlying mechanisms accounting for the reciprocal influence between these two conditions are still unclear, the complex interplay between diabetes mellitus and AD is attributable, in part, to genetic and environmental factors, cytokines, epidermal dysfunction, as well as drugs used for the treatment of AD. Proper management of one condition can mitigate the other condition. In this review, we summarize the evidence of the interaction between diabetes mellitus and AD, and discuss the possible underlying mechanisms by which these two conditions influence each other.

A modified protocol for studying filaggrin degradation using a reconstructed human epidermis model under low and high humidity

BACKGROUND

Filaggrin (FLG) is an essential protein that plays a vital role in maintaining skin barrier function and moisture levels, allowing the skin to adapt to dry environments. However, the precise temporal dynamics of FLG metabolism in the human epidermis remain poorly understood, and suitable tools to study these time-dependent effects are currently lacking.

OBJECTIVE

To investigate the molecular mechanisms and time course of FLG metabolism and skin barrier function under high- and low-humidity conditions, utilizing a reconstructed epidermis model.

METHODS

EpiSkin specimens cultured under humid or dry conditions for varying durations (2-48 h) were compared by assessing FLG degradation and skin barrier formation using immunofluorescence staining and western blotting.

RESULTS

Under conditions of low humidity, the proteolysis of FLG in EpiSkin increased between 4 and 12 h and was accompanied by elevated levels of cysteine-aspartic protease (caspase)-14. The expression of peptidyl arginine deiminase 1 and calpain 1 also increased at 4 h. However, after 24 h, the expression of these three FLG-degrading proteins significantly decreased. Conversely, the levels of pyrrolidone-5-carboxylic acid and urocanic acid initially decreased at 2 h and then increased between 12 and 24 h. Additionally, the expression of skin barrier proteins, such as FLG, transglutaminase 5, loricrin and zonula occludens-1, decreased starting from 12 h. Notably, epidermal cell viability and activity were also inhibited.

CONCLUSION

We propose a reliable and ethical model to study the temporal dynamics of FLG metabolism and its role in skin barrier function. Using a commercially reconstructed epidermis to mimic dry skin formation obviates the need for animal and human testing.

Connexins and Glucose Metabolism in Cancer

Connexins are a family of transmembrane proteins that regulate diverse cellular functions. Originally characterized for their ability to mediate direct intercellular communication through the formation of highly regulated membrane channels, their functions have been extended to the exchange of molecules with the extracellular environment, and the ability to modulate numerous channel-independent effects on processes such as motility and survival. Notably, connexins have been implicated in cancer biology for their context-dependent roles that can both promote or suppress cancer cell function. Moreover, connexins are able to mediate many aspects of cellular metabolism including the intercellular coupling of nutrients and signaling molecules. During cancer progression, changes to substrate utilization occur to support energy production and biomass accumulation. This results in metabolic plasticity that promotes cell survival and proliferation, and can impact therapeutic resistance. Significant progress has been made in our understanding of connexin and cancer biology, however, delineating the roles these multi-faceted proteins play in metabolic adaptation of cancer cells is just beginning. Glucose represents a major carbon substrate for energy production, nucleotide synthesis, carbohydrate modifications and generation of biosynthetic intermediates. While cancer cells often exhibit a dependence on glycolytic metabolism for survival, cellular reprogramming of metabolic pathways is common when blood perfusion is limited in growing tumors. These metabolic changes drive aggressive phenotypes through the acquisition of functional traits. Connections between glucose metabolism and connexin function in cancer cells and the surrounding stroma are now apparent, however much remains to be discovered regarding these relationships. This review discusses the existing evidence in this area and highlights directions for continued investigation.

Camu-Camu Fruit Extract Inhibits Oxidative Stress and Inflammatory Responses by Regulating NFAT and Nrf2 Signaling Pathways in High Glucose-Induced Human Keratinocytes

Myrciaria dubia (HBK) McVaugh (camu-camu) belongs to the family Myrtaceae. Although camu-camu has received a great deal of attention for its potential pharmacological activities, there is little information on the anti-oxidative stress and anti-inflammatory effects of camu-camu fruit in skin diseases. In the present study, we investigated the preventative effect of 70% ethanol camu-camu fruit extract against high glucose-induced human keratinocytes. High glucose-induced overproduction of reactive oxygen species (ROS) was inhibited by camu-camu fruit treatment. In response to ROS reduction, camu-camu fruit modulated the mitogen-activated protein kinases (MAPK)/activator protein-1 (AP-1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and nuclear factor of activated T cells (NFAT) signaling pathways related to inflammation by downregulating the expression of proinflammatory cytokines and chemokines. Furthermore, camu-camu fruit treatment activated the expression of nuclear factor E2-related factor 2 (Nrf2) and subsequently increased the NAD(P)H:quinone oxidoreductase1 (NQO1) expression to protect keratinocytes against high-glucose-induced oxidative stress. These results indicate that camu-camu fruit is a promising material for preventing oxidative stress and skin inflammation induced by high glucose level.