Antioxidant potential of all-trans retinoic acid (ATRA) and enhanced activity of liposome encapsulated ATRA against inflammation and tumor-directed angiogenesis.

The purpose of this study was to investigate whether all-trans retinoic acid (ATRA) has antioxidant property. The study was also focused on its inhibitory effect on the acute and chronic inflammation and tumor-associated capillary formation in terms of angiogenesis in C57BL/6 mice after incorporated in liposome composed of distearoylphosphatidylcholine (DSPC/cholesterol). ATRA possesses a number of important biologic activities including oncostatic, antioxidant and immunostimulatory actions. Our study was designed to evaluate the antioxidant activity of free ATRA by nitric oxide scavenging, superoxide radical scavenging, hydroxyl radical scavenging and lipid peroxide scavenging assays. The ATRA showed significant scavenging activities in all these antioxidant assays comparable to the standard antioxidant. We have also evaluated the activity of encapsulated ATRA against anti-inflammatory activity in C57BL/6 mice. The paw oedema inhibition was found in carrageenan model as 55.56% and 66.67% for free ATRA and encapsulated ATRA treatment respectively and for formaldehyde model it was found to be 60.87% and 69.57% respectively compared with saline treated control mice. Encapsulated ATRA inhibited the tumor-associated capillary formation in mice induced by highly metastatic B16F10 melanoma cells significantly than the free ATRA did. In this study the inhibition of tumor-directed capillary formation was found to be 56.25% and 62.50% for free ATRA and encapsulated ATRA treatment respectively. In conclusion, ATRA showed a significant antioxidant property in vitro. Free ATRA has anti-inflammatory activity as proved by us in animal model of acute and chronic inflammation and antiangiogenesis activity. Furthermore, its activity was boosted by encapsulation in liposome.