Human neuronal cells (NT2-N) express functional substance P and neurokinin-1 receptor coupled to MIP-1β expression

Substance P (SP), the most extensively studied and potent member of the tachykinin family, is a major modulator of inflammation and immunomodulatory activities within the central and peripheral nervous systems. We have examined the gene expression of SP and its receptor in a human neuronal cell line (NT2-N). Using reverse transcribed polymerase chain reaction (RT-PCR), the four isoforms of preprotachykinin-A gene transcripts (α, β, γ, and δ) were detected in the NT2-N. We also identified the presence of mRNA for neurokinin-1 receptor (NK-1R), a primary receptor for SP, in the NT2-N cells. Concomitant with NT2 cell differentiation into neurons, SP and NK-1R mRNA expression increased consistently. Intracellular SP and cell membrane NK-1R immunoreactivity were all observed in NT2-N cells. Most importantly, we demonstrated that SP and NK-1R presented in NT2-N cells are functionally involved in the regulation of macrophage inflammatory protein 1 beta (MIP-1β), an important β-chemokine participating in the activation and directional migration of immune cells to sites of central nervous systems (CNS) inflammation. Thus, SP and its receptor may play an important role in modulation of neuronal functions related to regulation of immune activities within the CNS. The NT2-N cell line is well suited for in vitro investigations of the SP-NK-1R pathway in immune responses and inflammation in the CNS.