Transmembrane Delivery and Biological Effect of Human Growth Hormone Via a Phage Displayed Peptide In Vivo and In Vitro

Abstract

For a long time, people have been looking forward to being able to clinically deliver bio-drugs systemically by a noninvasive method. Here, we show that a synthetic peptide, TD (ACSSSPSKHCG) was efficient in transferring human growth hormone (GH) across various kinds of membranes and the blood-brain barrier (BBB) in vivo via rectal administration, resulting in elevation of GH level in serum, acetylcholine and O-choline acetyltransferase activities and GH /IGF-1 contents in brain tissues, manifesting great therapeutic effects on chronic age-related dementia in mice and ameliorating neuronal damage in the brain. Furthermore, the effects of Aβ and TD/GH on LDH release, apoptosis and its relevant gene expression, involving bcl-2 and bax/caspase-3, were observed in a human neuroblastoma cell line (SH-SY5Y). Results indicated that GH decreased LDH release, apoptosis, and bax/caspase-3 activity, and increased bcl-2 expression compared with Aβ treatment, moreover, TD/GH may enhance the effects due to existence of TD, which might be dependent on TD assisted cross-membrane delivery of GH. The transdermal/transmembrane-enhancing activity of the TD peptide was also manifested on porcine abdominal skin in vivo and the murine embryonic fibroblast cell line (3T3 cell) in vitro, which was further shown through interaction between TD and lecithin (one constituent of the cell membrane) by ESI-MS. In conclusion, TD/GH counteracted brain defects in aged mice in vivo and cell apoptosis induced by Aβ in vitro might explain several underlying mechanisms by which GH could ameliorate learning and memory deficits in aged mice. Mixed TD/GH transmembrane delivery might be a promising therapy of Alzheimer's disease.