Elastin microfibril interface‐located protein 1 and its catabolic enzyme, cathepsin K, regulate the age‐related structure of elastic fibers in the skin

Thioredoxin promotes the regeneration and binding of elastic fibre and basement membrane

OBJECTIVE

Thioredoxin (TRX), a ubiquitous protein with strong antioxidant activity, decreases in the skin with age. A decrease in TRX is expected to induce cellular senescence, chronic inflammation, and degeneration and loss of extracellular matrix (ECM), such as collagen and elastin within the skin. In this study, we investigated the effects of TRX addition to excised skin or skin models to understand the role of TRX on cells and ECM within the skin.

METHODS

To evaluate its effect on skin cells, we cultured a three-dimensional (3D) skin model in a medium containing TRX. The mRNA expression levels of proteins related to elastic and collagen fibres and the basement membrane were determined. Furthermore, 3D imaging and computational analysis were performed to evaluate the effect of TRX on the elastic fibres and extending COL VII structures in excised human skin after coculturing with TRX for 1, 4, 5 and 6 days.

RESULTS

Thioredoxin application to a 3D skin model upregulated elastin, COLI and COLVII mRNA expression. Applying TRX to the excised skin increased the number of linear elastic fibres. This effect of TRX demonstrated a daily increment in a dose-dependent manner. Thioredoxin extended the fibrous structure of COL VII into the dermis, expanding its colocalization region with elastic fibres. These structural effects were confirmed using 3D imaging and computational methods.

CONCLUSION

Thioredoxin elongates elastic fibres from the dermis to the basement membrane and extends the COL VII structure from the basement membrane to the dermis in excised human skin. These findings suggest the potential of TRX to protect the skin against age-related alterations such as wrinkles and sagging.

Elastin microfibril interface-located protein 1 in fibroblasts is regulated by amphiregulin and interleukin-1α produced by keratinocytes

OBJECTIVE

The structure of elastic fibres changes with ageing. Elastin microfibril interface-located protein 1 (EMILIN-1) is known to contribute to structural changes in elastic fibres. EMILIN-1 is one of the components of elastic fibres and also colocalizes with oxytalan fibres near the epidermis. Therefore, EMILIN-1 may be affected by epidermal-dermal interactions. The purpose of this study is to identify the key factors involved in epidermal-dermal interactions during the structural degeneration of elastic fibres.

METHODS

Keratinocytes and fibroblasts were co-cultured, and changes in elastic fibre-related proteins were evaluated. Additionally, cytokine arrays were used to identify the factors involved in epidermal-dermal interactions.

RESULTS

EMILIN-1 expression in fibroblasts was increased in the presence of keratinocytes, and its expression decreased when keratinocytes were stressed. Amphiregulin (AREG) and interleukin-1α (IL-1α) were identified as the keratinocyte-derived cytokines that influence the production of EMILIN-1, which is secreted by the fibroblasts. EMILIN-1 expression was promoted by AREG and decreased by IL-1α via an increase in cathepsin K (a catabolic enzyme). AREG and IL-1α were associated with changes in EMILIN-1 levels in fibroblasts.

CONCLUSION

The findings suggest that the suppression of IL-1α expression and promotion of AREG expression in the epidermis could be a new approach that prevents the wrinkles and sagging caused by the structural changes in elastic fibres.

Cathepsins in the extracellular space: Focusing on non-lysosomal proteolytic functions with clinical implications

Cathepsins can be found in the extracellular space, cytoplasm, and nucleus. It was initially suspected that the primary physiological function of the cathepsins was to break down intracellular protein, and that they also had a role in pathological processes including inflammation and apoptosis. However, the many actions of cathepsins outside the cell and their complicated biological impacts have garnered much interest. Cathepsins play significant roles in a number of illnesses by regulating parenchymal cell proliferation, cell migration, viral invasion, inflammation, and immunological responses through extracellular matrix remodeling, signaling disruption, leukocyte recruitment, and cell adhesion. In this review, we outline the physiological roles of cathepsins in the extracellular space, the crucial pathological functions performed by cathepsins in illnesses, and the recent breakthroughs in the detection and therapy of specific inhibitors and fluorescent probes in associated dysfunction.