CXCL8 and systemic sclerosis: The concomitant presence of sildenafil in the culture medium reduced the effects of H2O2 on the gene expression of IL-8 in both experimental groups, healthy (H2O2 + S: 0.2 ± 0.2, p > 0.05) and SSc fibroblasts (H2O2 + S: 0.2 ± 0.1, p < 0.05).