The skin is constantly exposed to exogenous and endogenous sources of reactive oxygen species (ROS). An adequate balance between ROS levels and antioxidant defenses is necessary for the optimal cell and tissue functions, especially for the skin, since it must face additional ROS sources that do not affect other tissues, including UV radiation. Melanocytes are more exposed to oxidative stress than other cells, also due to the melanin production process, which itself contributes to generating ROS. There is an increasing amount of evidence that oxidative stress may play a role in many skin diseases, including melanoma, being the primary cause or being a cofactor that aggravates the primary condition. Indeed, oxidative stress is emerging as another major force involved in all the phases of melanoma development, not only in the arising of the malignancy but also in the progression toward the metastatic phenotype. Furthermore, oxidative stress seems to play a role also in chemoresistance and thus has become a target for therapy. In this review, we discuss the existing knowledge on oxidative stress in the skin, examining sources and defenses, giving particular consideration to melanocytes. Therefore, we focus on the significance of oxidative stress in melanoma, thus analyzing the possibility to exploit the induction of oxidative stress as a therapeutic strategy to improve the effectiveness of therapeutic management of melanoma.

Vitiligo is an acquired hypopigmentation of the skin due to a progressive selective loss of melanocytes; it has a prevalence of 1–2% and appears as rounded, well-demarcated white macules. The etiopathology of the disease has not been well defined, but multiple factors contribute to melanocyte loss: metabolic abnormalities, oxidative stress, inflammation, and autoimmunity. Therefore, a convergence theory was proposed that combines all existing theories into a comprehensive one in which several mechanisms contribute to the reduction of melanocyte viability. In addition, increasingly in-depth knowledge about the disease’s pathogenetic processes has enabled the development of increasingly targeted therapeutic strategies with high efficacy and fewer side effects. The aim of this paper is, by conducting a narrative review of the literature, to analyze the pathogenesis of vitiligo and the most recent treatments available for this condition.

Psoriasis is a chronic skin disease, characterized by epidermal hyperplasia, inflammation, angiogenesis and vascular remodelling. An immunohistochemical study on fifteen cryosections of psoriatic skin was performed using antibodies against VEGF, HIF1-α, CD34, Factor VIII, MMP-2, MMP-9, TIMP-1 and TIMP-2. Psoriatic skin showed a diffuse VEGF positive staining (13.15± 6.6), while no expression was observed in normal epidermis. No or faint HIF-1α immunostaining was detected in healthy skin, while in psoriatic skin HIF-1α was diffusely expressed. A positive correlation between HIF-1α and VEGF was reported in psoriatic skin (r= 0.644; p=0.010). In psoriatic sections CD34 expression was significantly higher in respect to control skin (19.15 ± 12.61 vs 3.0 ± 0.23; p= 0.04), factor VIII immunostaining also demonstrated a significant increased development of the microvasculature in comparison with healthy skin (18.39 ± 8.16 vs 7.4 ± 0.20; p= 0.033). Total MMP-2 expression of healthy skin (30± 2.26) was significantly lower in respect to the MMP-2 psoriatic skin (71.5±4.13; p= 0.0001) and a positive correlation was observed between VEGF and MMP-2 in psoriatic patients (r= 0.688; p= 0.046). In psoriatic skin MMP-9 expression was significantly increased in comparison to control skin (31±3.3 vs 8±6.1; p=0.007). All cases of psoriatic skin tissue showed that TIMP-2 and TIMP-1 expression statistically decreased in psoriatic skin (respectively 11±1.2 and 12±1.5) in comparison with healthy skin (respectively 15±3.2 and 53±3.8; p=0.0001). In conclusion, we observed that VEGF overexpression correlated with HIF-1α and MMP-2 expression, underlining the role of VEGF in psoriasis as a key factor in the link between inflammation and angiogenesis.

Quorum sensing is a mechanism through which a bacterial population receives input from neighboring cells and elicits an appropriate response to enable survival within the host. Inhibiting quorum sensing by RNAIII-inhibiting peptide (RIP) has been demonstrated as a very effective mode of prevention and therapy for device-associated staphylococcal infections and was tested here for healing of wounds that are otherwise resistant to conventional antibiotics. Wounds, established through the panniculus carnosus of BALB/c mice, were inoculated with 5 × 10 ⁷ CFU of methicillin-resistant Staphylococcus aureus . Mice were treated with Allevyn, RIP-soaked Allevyn (containing 20 μg RIP), daily intraperitoneal teicoplanin (7 mg/kg of body weight), Allevyn and teicoplanin, and RIP-soaked Allevyn and daily intraperitoneal teicoplanin. The main outcome measures were quantitative bacterial culture and histological examination with assessment of microvessel density and of vascular endothelial growth factor (VEGF) expression in tissue sections. Treatment with RIP-soaked Allevyn together with teicoplanin injection greatly reduced the bacterial load to 13 CFU/g (control untreated animals had 10 ⁸ CFU/g bacteria). All other treatments were also significantly effective but only reduced the bacterial load to about 10 ³ CFU/ml. Histological examination indicated that only treatment with RIP-soaked Allevyn with teicoplanin injection restored epithelial, granulation, and collagen scores, as well as microvessel density and VEGF expression, to the levels found with uninfected mice. In conclusion, we observed that RIP may be useful for the management of infected wounds and that it could represent an exciting and future alternative to the conventional antibiotics, at present considered the gold-standard treatments for methicillin-resistant S. aureus infections.