GABA promotes elastin synthesis and elastin fiber formation in normal human dermal fibroblasts (HDFs).

The multiple physiological effects of γ-aminobutyric acid (GABA) as a functional food component have been recently reported. We previously reported that GABA upregulated the expression of type I collagen in human dermal fibroblasts (HDFs), and that oral administration of GABA significantly increased skin elasticity. However, details of the regulatory mechanism still remain unknown. In this study, we further examined the effects of GABA on elastin synthesis and elastin fiber formation in HDFs. Real-time PCR indicated that GABA significantly increased the expression of tropoelastin transcript in a dose-dependent manner. Additionally, the expression of fibrillin-1, fibrillin-2, and fibulin-5/DANCE, but not lysyl oxidase and latent transforming factor-ß-binding protein 4, were also significantly increased in HDFs. Finally, immunohistochemical analysis confirmed that treatment with GABA dramatically increased the formation of elastic fibers in HDFs. Taken together, our results showed that GABA improves skin elasticity in HDFs by upregulating elastin synthesis and elastin fiber formation.

Inhibition of Receptor-Interacting Protein Kinase 1 with Necrostatin-1s ameliorates disease progression in elastase-induced mouse abdominal aortic aneurysm model.

Abdominal aortic aneurysm (AAA) is a common aortic disease with a progressive nature. There is no approved pharmacological treatment to effectively slow aneurysm growth or prevent rupture. Necroptosis is a form of programmed necrosis that is regulated by receptor-interacting protein kinases (RIPs). We have recently demonstrated that the lack of RIP3 in mice prevented aneurysm formation. The goal of the current study is to test whether perturbing necroptosis affects progression of existing aneurysm using the RIP1 inhibitors Necrostatin-1 (Nec-1) and an optimized form of Nec-1, 7-Cl-O-Nec-1 (Nec-1s). Seven days after aneurysm induction by elastase perfusion, mice were randomly administered DMSO, Nec-1 (3.2 mg/kg/day) and Nec-1s (1.6 mg/kg/day) via intraperitoneal injection. Upon sacrifice on day 14 postaneurysm induction, the aortic expansion in the Nec-1s group (64.12 ± 4.80%) was significantly smaller than that of the DMSO group (172.80 ± 13.68%) (P < 0.05). The mean aortic diameter of Nec-1 treated mice appeared to be smaller (121.60 ± 10.40%) than the DMSO group, though the difference was not statistically significant (P = 0.1). Histologically, the aortic structure of Nec-1s-treated mice appeared normal, with continuous and organized elastin laminae and abundant αActin-expressing SMCs. Moreover, Nect-1s treatment diminished macrophage infiltration and MMP9 accumulation and increased aortic levels of tropoelastin and lysyl oxidase. Together, our data suggest that pharmacological inhibition of necroptosis with Nec-1s stabilizes pre-existing aneurysms by diminishing inflammation and promoting connective tissue repair.

Effect of L-fucose and fucose-rich polysaccharides on elastin biosynthesis, in vivo and in vitro.

With increasing age elastic fibres in human skin are progressively lysed and skin elasticity is also decreasing. Still there is an age-dependent increase of elastic fibre surface density, mostly due to an alteration of the fibres. The present experiments were undertaken to explore if L-fucose and fucose-rich polysaccharides (FROP-s) could influence elastin biosynthesis. We show here, that topical application of a fucose-containing preparation to the skin of hairless rats increased after 4 weeks the elastic fibre surface density by about 40%, shown by quantitative morphology. Using human skin fibroblasts in explant cultures, the addition of L-fucose or of FROP-3 increased the biosynthesis of immunoprecipitable tropoelastin by about 40%. No increase was found however of desmosine-isodesmosine in skin explant cultures after 72 h of incubation. The effect of L-fucose and FROP-3 on the biosynthesis of collagen and non-collagen proteins excreted by the skin explant cultures was also investigated. L-fucose, but not FROP-3, decreased collagen biosynthesis but both increased non-collagen protein biosynthesis. These results show that L-fucose and FROP-3 stimulate tropoelastin biosynthesis in vitro, and elastic fibre formation in vivo. This stimulation concerns also several non-collagen proteins secreted by skin explant cultures. Elastic fibre formation necessitates the simultaneous synthesis of several microfibrillar glycoproteins as well as of tropoelastin. The increased elastic fibre density in the in vivo experiments suggests that this is indeed achieved by L-fucose and FROP-3, further demonstrating their efficiency in the control of age-dependent modifications of connective tissues in general and of skin in particular.