An in vitro and in vivo study of the brain-targeting effects of an epidermal growth factor-functionalized cholera toxin-like chimeric protein.

The development of neuroprotective drugs has proven to be extremely difficult because of the blood-brain barrier. Intranasal administration is thought to transport the drug from the nasal cavity along the olfactory and trigeminal nerves to the brain, thus bypassing the blood-brain barrier. However, macromolecular protein drugs have low delivery efficiency via this route in general. We hypothesized that an innocuous cholera toxin-like chimeric protein could better enhance the efficiency of protein delivery through the intranasal route. To test this hypothesis, we designed an enhanced green fluorescent protein (EGFP) chimera to evaluate the effect of the cholera toxin (CT) as a carrier for drug delivery into the brain. Then, the EGFP was replaced with epidermal growth factor (EGF) in the chimeric protein, and the therapeutic effect of the new chimeric protein was studied in an LPS-induced neuritis mouse model. The results suggest that the CT-like chimeric protein can bypass the blood-brain barrier and enter the brain in approximately 30 min. This EGF chimeric protein can effectively protect the spatial cognitive ability of and confer anti-anxiety protection to mice. The results indicate that cholera toxin-like chimeric proteins are potential tools for effectively delivering macromodecular drugs into the brain through intranasal administration.