Modulation of elastase-like activity in fibroblasts stimulated with elastin peptides

The Elastin Receptor Complex: A Unique Matricellular Receptor with High Anti-tumoral Potential

Elastin, one of the longest-lived proteins, confers elasticity to tissues with high mechanical constraints. During aging or pathophysiological conditions such as cancer progression, this insoluble polymer of tropoelastin undergoes an important degradation leading to the release of bioactive elastin-derived peptides (EDPs), named elastokines. EDP exhibit several biological functions able to drive tumor development by regulating cell proliferation, invasion, survival, angiogenesis, and matrix metalloproteinase expression in various tumor and stromal cells. Although, several receptors have been suggested to bind elastokines (α_vβ₃ and α_vβ₅ integrins, galectin-3), their main receptor remains the elastin receptor complex (ERC). This heterotrimer comprises a peripheral subunit, named elastin binding protein (EBP), associated to the protective protein/cathepsin A (PPCA). The latter is bound to a membrane-associated protein called Neuraminidase-1 (Neu-1). The pro-tumoral effects of elastokines have been linked to their binding onto EBP. Additionally, Neu-1 sialidase activity is essential for their signal transduction. Consistently, EDP-EBP interaction and Neu-1 activity emerge as original anti-tumoral targets. Interestingly, besides its direct involvement in cancer progression, the ERC also regulates diabetes outcome and thrombosis, an important risk factor for cancer development and a vascular process highly increased in patients suffering from cancer. In this review, we will describe ERC and elastokines involvement in cancer development suggesting that this unique receptor would be a promising therapeutic target. We will also discuss the pharmacological concepts aiming at blocking its pro-tumoral activities. Finally, its emerging role in cancer-associated complications and pathologies such as diabetes and thrombotic events will be also considered.

Proteolytic digest derived from bovine Ligamentum Nuchae stimulates deposition of new elastin-enriched matrix in cultures and transplants of human dermal fibroblasts

BACKGROUND

Diverse topical products and injectable fillers used for correcting facial wrinkles induce rather short-lived effects because they target replacement of dermal collagen and hyaluronan, matrix components of limited biologic durability.

OBJECTIVE

Present studies were aimed at stimulation of fully differentiated human dermal fibroblasts to resume deposition of new extracellular matrix rich of elastin, the most durable and metabolically inert component of dermal ECM.

METHODS

We have created a novel proteolytic digest of bovine ligamentum nuchae (ProK-60), and tested its potential biological effect on dermal fibroblasts derived from females of different ages. Northern blots, quantitative immunohistochemistry and metabolic assays were used to assess effects of ProK-60 on proliferation and matrix production in primary cultures of dermal fibroblasts, in cultures of skin explants and after implantation of stimulated fibroblasts into the skin of athymic nude mice.

RESULTS

ProK-60 increased proliferation (25-30%) of cultured dermal fibroblasts and significantly enhanced their production of new elastic fibers (>250%) and collagen fibers (100%). These effects were mostly mediated by stimulation of cellular elastin receptor. In contrast, ProK-60 inhibited production of fibronectin (-30%) and chondroitin sulfate proteoglycans (-50%). ProK-60 also activated proliferation of dermal fibroblasts, mostly derived from the stratum basale and induced deposition of elastic fibers in cultures of skin explants. Moreover, human fibroblasts pre-treated with ProK-60 produced abundant elastic fibers after their injection into the skin of athymic nude mice.

CONCLUSION

The described biological effects of ProK-60, including its unique elastogenic property, encourage use of this compound in cosmetic formulations stimulating rejuvenation of aged skin.

Living skin substitutes: survival and function of fibroblasts seeded in a dermal substitute in experimental wounds

The healing of full-thickness skin defects requires extensive synthesis and remodeling of dermal and epidermal components. Fibroblasts play an important role in this process and are being incorporated in the latest generation of artificial dermal substitutes. We studied the fate of fibroblasts seeded in our artificial elastin/collagen dermal substitute and the influence of the seeded fibroblasts on cell migration and dermal substitute degradation after transplantation to experimental full-thickness wounds in pigs. Wounds were treated with either dermal substitutes seeded with autologous fibroblasts or acellular substitutes. Seeded fibroblasts, labeled with a PKH-26 fluorescent cell marker, were detected in the wounds with fluorescence microscopy and quantitated with flow cytofluorometric analysis of single-cell suspensions of wound tissue. The cellular infiltrate was characterized for the presence of mesenchymal cells (vimentin), monocytes/macrophages, and vascular cells. Dermal substitute degradation was quantitated by image analysis of wound sections stained with Herovici's staining. In the wounds treated with the seeded dermal substitute, fluorescent PKH-26-labeled cells were detectable up to 6 d and were positive for vimentin but not for the macrophage antibody. After 5 d, flow cytofluorometry showed the presence of 3.1 (+/-0.9) x 10(6) (mean +/- SD, n = 7) PKH-26-positive cells in these wounds, whereas initially only 1 x 10(6) fluorescent fibroblasts had been seeded. In total, the percentage of mesenchymal cells minus the macrophages was similar after 5 d between wounds treated with the seeded and the acellular substitutes. In the wounds treated with the seeded substitute, however, 19.5% of the mesenchymal cells were of seeded origin. Furthermore, the rate of substitute degradation in the seeded wounds was significantly lower at 2-4 wk after wounding than in wounds treated with the acellular substitute. Vascular in-growth and the number of infiltrated macrophages were not different. In conclusion, cultured dermal fibroblasts seeded in an artificial dermal substitute and transplanted onto full-thickness wounds in pigs survived and proliferated. The observed effects of seeded fibroblasts on dermal regeneration appeared to be mediated by reducing subcutaneous fibroblastic cell migration and/or proliferation into the wounds without impairing migration of monocytes/macrophages and endothelial cells. Moreover, the degradation of the implanted dermal substitute was retarded, indicating a protective activity of the seeded fibroblasts.

Vitamin E attenuates induction of elastase-like activity by tumor necrosis factor-alpha, cholestan-3 beta,5 alpha,6 beta-triol and linoleic acid in cultured endothelial cells

Disturbances in arterial wall elastin metabolism appear to be important factors in atherosclerosis development. To evaluate this hypothesis, elastase-like activity was determined in cultured endothelial cells and their surrounding media after exposure to tumor necrosis factor-alpha (TNF), cholestan-3 beta,5 alpha,6 beta-triol (Triol) and linoleic acid (18:2). Significant increases in elastase-like activity both in the cells and in the media were observed when subconfluent endothelial cells were treated with 12 microM Triol, 500 U TNF/ml, or 90 microM 18:2, for 72 h in the presence of 5% calf serum. Even higher activities were measured when endothelial cells were seeded directly into media enriched with 18:2, TNF or Triol and treated for 72 h. Vitamin E supplementation (25 microM) attenuated elastase-like activity in cells and media, independent of treatment. These results suggest that elastase-like enzyme induction in endothelial cells may be involved in cellular perturbations induced by certain lipids and cytokines. Vitamin E may provide a protective function by preventing the induction of elastolytic enzymes. This may have implications in elastin metabolism and atherosclerosis.