Carvacrol nanoemulsion evokes cell cycle arrest, apoptosis induction and autophagy inhibition in doxorubicin resistant-A549 cell line.

Carvacrol is a monoterpenoid flavonoid found abundantly in thyme plants. Its physiochemical instability and partial solubility in water is the principal limitation for its industrial use. Hence, we made a carvacrol nanoemulsion (CANE) using ultrasonication method and characterized it by dynamic light scattering (DLS) technique which revealed a negative surface charge (-29.89 mV) with 99.1 nm average droplet size. CANE effectively induced apoptosis in doxorubicin-resistant A549 lung carcinoma cells (A549DR) evident by the elevated expression of apoptotic proteins such as Bax, Cytochrome C, and Cleaved caspase 3 and 9. Also, CANE displayed cell senescence leading to cell cycle arrest by reducing CDK2, CDK4, CDK6, Cyclin E, Cyclin D1 and enhancing p21 protein expression. In addition, a potential role of CANE in the inhibition of autophagy was noted by evaluating the reduced conversion of LC-3 I to II. Beside this, a down-regulation of important autophagy markers ATG5 and ATG7 and upregulation of p62 were detected in response to CANE. We conclude that the synthesized CANE has potential to cause cell senescence, cell cycle arrest, autophagy inhibition and apoptosis in A549DR cells and could be used as a potential candidate for lung cancer therapy.