The comparative effects of Resveratrol and Curcumin in combination with photodynamic therapy.

Background and aim: Photodynamic therapy, PDT, is a promising option among the local treatments with oncolytic potential. Although the basic principle is simple, its intricate mechanisms allow for a broad range of optimization methods. The purpose of this study was to assess the effects of Resveratrol and Curcumin as adjuvants of PDT on experimental tumors. Methods: Sixty-six Wistar male rats were divided into 11 groups: control, Curcumin (CUR), Resveratrol (RES) alone or followed by irradiation (IR) (CUR+IR and RES+IR, respectively), 5,10,15,20-tetra-sulphonato-phenyl-porphyrin (TSPP), TSPP+IR (PDT), and CUR or RES administered prior to or after PDT (CUR+TSPP+IR, RES+TSPP+IR, TSPP+IR+CUR, TSPP+IR+RES). Results: Both CUR and RES significantly decreased lipid peroxidation, while RES also showed an increase in glutathione (GSH) levels, especially when it was administered before PDT (p<0.01). Both antioxidants decreased cyclooxygenase (COX)2 expression, to a minimum when they administered prior to PDT (p<0.001 and p<0.01) while nitric oxide synthase (NOS)2 expression diminished in the combined regimen, particularly in RES associated with PDT. CUR and RES induced similar changes in terms of cell death, but CUR seemed to be more efficient on tumor necrosis and showed a higher apoptotic index when was administered after PDT (p<0.001). Conclusion: Both RES and CUR in association with PDT decreased oxidative stress, diminished the COX2 and NOS2 expressions and increased cell death by positively influencing the necrotic rate and apoptotic index, particularly when CUR was administered after PDT. The results show that CUR is a promising class to study in PDT optimization and further invites to exploit its promises.