Investigation of the metabolism of substance P at the blood–brain barrier using LC–MS/MS

Abstract: Substance P (SP) has been associated with pain and depression as well as neurodegenerative diseases. Many of these diverse actions of SP can potentially be attributed to SP metabolites generated at the blood–brain barrier (BBB). In this study, the metabolism of SP was investigated using an in vitro model of the BBB and LC–MS/MS. Substance P metabolism was found to be non-saturable in the concentration range of 100nM to 10μM, with approximately 70% of the peptide remaining intact after 5h. The major metabolites of SP were identified by MS as 3-11 and 5-11. Two previously unreported metabolites, 5-11 and 6-11, were also found in our studies. Several additional minor SP metabolites, including 1-9 and 2-11, were also identified. A profile of the SP metabolites generated by the BBB over time was obtained. The results from the present study provide a better understanding of the role of the blood–brain barrier in the pharmacology of SP. [Copyright &y& Elsevier]