Neuroprotective Effects of Curcumin-Loaded Emulsomes on Laser Axotomy-Induced CNS Injury Model

Abstract

Background Curcumin, a polyphenol isolated from the rhizomes of turmeric, holds a great potential as a neuroprotective agent along with its anti-inflammatory and antioxidant characteristics. Its poor bioavailability and low stability in water lie as foremost restraints against the clinical use. This study aims at investigating the neuroprotective effect of curcumin on axonal injury by delivering the lipophilic polyphenol to primary hippocampal neuron by means of a lipid-based drug delivery system, named emulsomes. Methods To study the neuroregeneration on ex vivo, an injury model was established through single-cell laser axotomy on hippocampal neurites. Upon treatment with curcumin-loaded emulsomes (CurcuEmulsomes), curcumin and CurcuEmulsome uptake into neurons were verified by 3-dimensional z-stack images acquired with confocal microscopy. Neuron survival after axonal injury were tracked by PI and Hoechst staining. Alterations in expression levels of physiological markers such as anti-apoptotic marker Bcl-2, apoptotic marker cleaved caspase 3, neuroprotective marker Wnt3a and the neuronal survival marker mTOR were investigated by immunocytochemistry analyses. Results Results indicated significant improvement in the survival rates of injured neurons upon CurcuEmulsome treatment. Bcl-2 expression became significantly higher for injured neurons treated with curcumin or CurcuEmulsome. Caspase 3 expressions decreased in both curcumin- and CurcuEmulsome-treatments, whereas Wnt3a and mTOR expressions did not alter significantly. Conclusions The established laser-axotomy model was exposed as a reliable methodology to study neurodegenerative models ex vivo. CurcuEmulsomes delivered curcumin to primary hippocampal neurons successfully. Treated with CurcuEmulsomes, injured hippocampal neurons benefit from neuroprotective effects of curcumin in terms of higher survival rate and increased anti-apoptotic marker levels.