Substance P-Induced Increase In Brain Derived Neurotrophic Factor Expression And Secretion By Intestinal Smooth Muscle Is Mediated By A Rise In Intracellular Ca2+

Background We have previously shown that intestinal longitudinal smooth muscle cells express and secrete brain derived neurotrophic factor (BDNF) and addition of substance P (SP) to cultured smooth muscle cells induces further expression and secretion of BDNF above basal levels. It is not known, however, what cellular signaling pathways mediate SP‐induced expression and secretion of BDNF. Aim To identify the signaling pathways involved in BDNF synthesis and secretion by smooth muscle in response to SP. Method Cultured intestinal smooth muscle cells were treated with 10–100 nM SP for 24 hours in the presence and absence of 1,2 bis (o‐aminophenoxy)ethane‐N,N,N’,N’‐tetraacetic acid (BAPTA) to chelate intracellular Ca2+. BDNF protein expression and secretion were measured by in‐cell western and ELISA, and BDNF mRNA expression was measured by qRT‐PCR. Results The expression of BDNF protein was increased by 10–121% and BDNF secretion was increased by 50% by SP. Consistent with this, BDNF mRNA expression was increased by 161% by SP. Both BDNF protein and mRNA responses to SP were blocked by BAPTA. Conclusion SP stimulation of BDNF expression and secretion requires increased in intracellular Ca2+. The source of the intracellular Ca2+ increased remains to be determined. Supported by grants DK15564 and DK34153 from the National Institutes of Health.