Substance P enhances the local activation of NK(1)R-expressing c-kit(+) cardiac progenitor cells in right atrium of ischemia/reperfusion-injured heart

BACKGROUND: Localization of neurokinin 1 receptor (NK(1)R), the endogenous receptor for neuropeptide substance P (SP), has already been described for the right atrium (RA) of the heart. However, the biological role of SP/NK(1)R signal pathways in the RA remains unclear. Sprague-Dawley rats were randomly divided into 4 groups (n = 22 each); subjected to sham, ischemia/reperfusion-injury (I/R), I/R with 5 nmole/kg SP injection (SP + I/R), and SP + I/R with 1 mg/kg RP67580 injection (RP, a selective non-peptide tachykinin NK(1)R antagonist) (RP/SP + I/R). The left anterior descending coronary artery was occluded for 40 min followed by 1 day reperfusion with SP or SP + RP or without either. After 1 day, both atria and ventricles as well as the heart apexes were collected. RESULTS: SP promoted the expression of c-Kit, GATA4, Oct4, Nanog, and Sox2 in only the RA of the SP + I/R rats via NK(1)R activation. In agreement with these observations, NK(1)R-expressing c-Kit(+) Nkx2.5(+)GATA4(+) cardiac progenitor cells (CPCs) in the ex vivo RA explant outgrowth assay markedly migrated out from RA(1 day SP + I/R) approximately 2-fold increase more than RA(1 day I/R). Treatment of SP promoted proliferation, migration, cardiosphere formation, and potential to differentiate into cardiomyocytes. Using RP inhibitor, NK(1)R antagonist not only inhibited cell proliferation and migration but also reduced the formation of cardiosphere and differentiation of c-Kit(+) CPCs. CONCLUSION: SP/NK(1)R might play a role as a key mediator involved in the cellular response to c-Kit(+) CPC expansion in RA of the heart within 24 h after I/R.