Using the Nrf2 activator Oltipraz we observed an enhancement of PSMB5 expression in pterygium fibroblasts, which is in agreement with previous studies showing that the expression of catalytic core subunit of proteasome PSMB5 bearing chemotrypsin-like activity is increased by Nrf2 through the ARE-located on the proximal promoter region of this gene [29]. This evidence concerns the gene PSMB5 and pterygium.