Hydrogen sulfide impairs keratinocyte cell growth and adhesion inhibiting mitogen-activated protein kinase signaling

Abstract

The effects of exogenous hydrogen sulfide (H 2 S) on normal skin-derived immortalized human keratinocytes have been investigated in detail. We show in vitro that exogenous hydrogen sulfide reduces clonal growth, cell proliferation and cell adhesion of human keratinocytes. H 2 S, in fact, decreases the frequency of the putative keratinocyte stem cell subpopulation in culture, consequently affecting clonal growth, and impairs cell proliferation and adhesion of mature cells. As a mechanistic explanation of these effects, we show at the molecular level that (i) H 2 S reduces the Raf/MAPK kinase/ERK signaling pathway; (ii) the reduced adhesion of sulfur-treated cells is associated to the downregulation of the expression of b4, a2 and a6 integrins that are necessary to promote cell adhesion as well as anti-apoptotic and proliferative signaling in normal keratinocytes. One specific interest of the effects of sulfurs on keratinocytes derives from the potential applications of the results, as sulfur is able to penetrate the skin and a sulfur-rich balneotherapy has been known for long to be effective in the treatment of psoriasis. Thus, the relevance of our findings to the pathophysiology of psoriasis was tested in vivo by treating psoriatic lesions with sulfurs at a concentration comparable to that most commonly found in sulfurous natural springs. In agreement with the in vitro observations, the immunohistochemical analysis of patient biopsies showed a specific downregulation of ERK activation levels, the key molecular event in the sulfur-induced effects on keratinocytes.

Hydrogen sulfide inhibits IL-8 expression in human keratinocytes via MAP kinase signaling

“…Accordingly, we observed a strong expression of IL-8 in the untreated skin of the psoriatic patient, where a diffuse immunostaining was observed in the keratinocytes present in the lesions (Figure 4c). As we previously reported, 22 NaHS reduces ERK activation levels in psoriatic lesions, where total pERK expression is downregulated, with a dramatic decrease of its nuclear localization (Figure 3d). Of note, the treatment of the lesions with NaHS significantly reduced IL-8 expression as well (Figure 4d as compared with negative control, Figure 4a).…”

“…Filters were finally washed and incubated for 1 h at room temperature with anti-rabbit (1:2000) or anti-mouse (1:2000) peroxidase-conjugated secondary antibodies, and revealed by Enhanced Chemiluminescence Western blotting detection reagent (Amersham Biosciences, Buckinghamshire, UK). 22,27,28 The membranes were then stripped and reprobed with b-actin for protein loading control. Chemiluminescence was quantified by the KODAK Molecular Imaging Software 4.0 using the KODAK Image Station 4000 MM (Carestream Health, Rochester, NY, USA).…”

“…20 It has been reported that the activity of the p38 and extracellular signalregulated kinase (ERK)1/2 MAPKs is increased in lesional psoriatic skin as compared with non-lesional skin. 21,22 Many studies have been published on the involvement of hydrogen sulfide in inflammation, and evidence has been shown for both pro-or anti-inflammatory roles of H 2 S. 23,24 Recently, we have demonstrated that hydrogen sulfide can impair human keratinocytes adhesion and proliferation by impairing the activation of Raf-MEK-ERK pathway. 22 The specific interest to hydrogen sulfide derives from the potential applications of the results, as sulfur is able to penetrate the skin and a sulfur-rich balneotherapy, known to be effective in the treatment of psoriasis, 25 might turn useful in this disease.…”

“…21,22 Many studies have been published on the involvement of hydrogen sulfide in inflammation, and evidence has been shown for both pro-or anti-inflammatory roles of H 2 S. 23,24 Recently, we have demonstrated that hydrogen sulfide can impair human keratinocytes adhesion and proliferation by impairing the activation of Raf-MEK-ERK pathway. 22 The specific interest to hydrogen sulfide derives from the potential applications of the results, as sulfur is able to penetrate the skin and a sulfur-rich balneotherapy, known to be effective in the treatment of psoriasis, 25 might turn useful in this disease. In this context, we have also demonstrated that H 2 S can exert a subset-specific toxicity on peripheral blood lymphocytes, which die by a caspase-independent mechanism of necrosis after a rapid loss of mitochondrial membrane potential, and not by apoptosis.…”

Skin, Inflammation and Sulfurous Waters: What is Known, What is Believed

“…Recently, we demonstrated that NaHS is able to inhibit the expression of a6p4 in keratinocytes and can be considered relevant in the control ofkeratinocyte growth and adhesion. In fact, NaHS-induced reduction of p4-integrin expression in the NCTC cell line can explain sulfur-induced cell death as well as sulfur-mediated inhibition of keratinocyte clonal growth and cell adhesion (29). The NaHS-mediated interference with the Ras/ ERK-1/2 kinase, with the consequent down-regulation of ERKs phosporylation observed after sulfur treatment is responsible for a6p4 inhibition.…”