The Phosphodiesterase Type 5 Inhibitor Sildenafil Improves DNA Stability and Redox Homeostasis in Systemic Sclerosis Fibroblasts Exposed to Reactive Oxygen Species.

Luigi Di Luigi,Ambra Antonioni,Daniela Caporossi,Ivan Dimauro,Guglielmo Duranti,Roberta Ceci,Paolo Sgrò,Cristina Antinozzi,Francesco Del Galdo,Andrea Lenzi,Stefania Sabatini,Clara Crescioli

doi:10.3390/antiox9090786

Abstract

Systemic sclerosis (SSc) is a multi-system connective tissue disease characterized by the increased deposition of extracellular matrix proteins such as collagen and fibronectin. Although the pathogenesis is not completely understood, a number of studies suggest that free radicals could be the major contributors to the disease. Indeed, different studies demonstrated how oxidative stress could contribute to the fibrotic process activation at the level of the skin and visceral organs. Emerging evidences highlight the beneficial effects of sildenafil, a phosphodiesterase type 5 inhibitor (PDE5i), which protects different cell lines from the cell damage induced by reactive oxygen species (ROS). These data make sildenafil a good candidate for therapeutic treatment aimed to protect biological macromolecules against oxidative damage, thus preserving cell viability. The purpose of this study was to evaluate the sensitivity of SSc dermal fibroblasts to an oxidative insult and the ability for sildenafil to prevent/reduce the DNA damage due to ROS action. Additionally, we evaluated the capacity for sildenafil to influence redox homeostasis and cytotoxicity, as well as cell proliferation and cell cycle progression. We demonstrated that SSc fibroblasts have an increased sensitivity to a pro-oxidant environment in comparison to healthy controls. The sildenafil treatment reduced ROS-induced DNA damage, counteracted the negative effects of ROS on cell viability and proliferation, and promoted the activity of specific enzymes involved in redox homeostasis maintenance. To our knowledge, in this report, we demonstrate, for the first time, that sildenafil administration prevents ROS-induced instability in human dermal fibroblasts isolated by SSc patients. These results expand the use of PDE5i as therapeutic agents in SSc by indicating a protective role in tissue damage induced by oxidative insult.

Highlights

When the same analysis was extended to RAD51, a protein involved in DNA repair mechanisms [37], we found that, at the basal condition, Systemic sclerosis (SSc) already showed a higher number of RAD51 foci per cell than healthy Human dermal fibroblasts (Hfbs) (Figure 2A)
The present study demonstrates for the first time that the phosphodiesterase type 5 (PDE5) inhibitor sildenafil reduces the sensitivity to DNA damage of human SSc fibroblasts exposed to a pro-oxidant environment, improving their genomic stability
For the first time, we successfully demonstrated that the presence of sildenafil ameliorates the management of redox imbalance in SSc fibroblasts exposed to a pro-oxidant environment, reducing reactive oxygen species (ROS) levels and improving the efficiency of the glutathione system, as well as increasing the level of Superoxide dismutase (SOD) and its activity

Summary

Introduction

Systemic sclerosis (SSc) is a multi-system connective tissue disorder characterized by the increased deposition of extracellular matrix proteins, where increased oxidative stress plays a role in the activation of the fibrotic process at the level of the skin and visceral organs [1,2,3].it is known that excessive oxidative stress contributes to vascular damage, jeopardizes the function of the endothelial system, leading to immune system involvement, and it participates in the establishment and maintenance of fibroblast activation [4,5].Several authors have shown that SSc patients have a reduced antioxidant capacity; the exact stage of the disease at which the increase in reactive oxygen species (ROS) occurs is still uncertain [6,7]. Patients with SSc have shown a high rate of chromosomal breakages, consistent with the known clastogenic activity of ROS, and increased levels of plasma markers of oxidative stress [8,9]. Several authors have demonstrated that the systemic oxidative imbalance occurring in SSc patients induces changes in different subcellular components and macromolecules, oxidative denaturation, and derangement, as well as the loss of lipid asymmetry in membranes and DNA damage [10,11]. These are considered cellular changes that can induce premature cell senescence or cell death

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