Intranasally delivered TGF-β1 enters brain and regulates gene expressions of its receptors in rats

This study is aimed to evaluate the brain distribution of transforming growth factor-β1 (TGF-β1) following intranasal administration and the subsequent biological effects of TGF-β1. Adult rats were given recombinant human TGF-β1 (rhTGF-β1) or vehicle solution intranasally. TGF-β1 concentrations were significantly raised in several brain regions and the trigeminal nerve following intranasal delivery. The elevation appeared within 30 min and was sustained for at least 6 h, reaching its greatest level at 60 min. A concentration gradient in the central nervous system (CNS) regions was produced during the first 2 h after intranasal administration, with the OB presenting a significantly higher concentration than any other CNS regions. The nasally administered TGF-β1 subsequently regulated gene expressions of its two receptors (TGF-β receptor types I and II) in vivo, but did not affect mRNA level of TGF-β1 itself. Our results suggest that TGF-β1 can be transported into the CNS via the olfactory and trigeminal pathways, and may consequently exert its biological effects by regulating gene expressions of its receptors. Intranasal administration of neurotrophic factors may offer a potential strategy for treating some CNS disorders.