Serotonin induces parathyroid hormone-related protein in goat mammary gland

Abstract

During lactation, large amounts of calcium are exported from the mammary gland into milk to ensure skeletal growth of the offspring. Recent studies revealed that serotonin (5-HT) is essential to stimulate skeletal calcium resorption for milk synthesis. Our objective was to explore the correlation between circulating 5-HT and serum calcium and parathyroid hormone-related protein (PTHrP) concentrations around parturition in dairy goats. We also investigated the effect of 5-HT on PTHrP expression in cultured primary goat mammary epithelial cells (GMEC). Blood samples of multiparous Guanzhong dairy goats were collected on day -5 to 3 postpartum for analysis of serum concentrations of calcium, 5-HT, and PTHrP. Results revealed that from day -3 to 0 postpartum serum calcium and 5-HT concentrations decreased progressively, but serum PTHrP concentration only had a sharp drop in the postpartum period sampled. Correlation analysis of circulating 5-HT and serum calcium and PTHrP concentrations on day 1 and 2 postpartum revealed that low serum 5-HT concentration was positively correlated with serum total calcium or PTHrP concentration. By knocking down tryptophan hydroxylase-1 (TPH1) or adding 5-hydroxytryptophan (5-HTP) to decrease or increase the levels of 5-HT in GMEC, we observed that 5-HTP increased PTHrP expression in a dose-dependent manner and siTPH1 decreased PTHrP protein expression. Furthermore, 5-HT increased mRNA abundance of calcium-sensing receptor (CaSR) in a dose-dependent manner and decreased the expression of plasma membrane Ca2+ ATPase-1 (PMCA1). Taken together, 5-HT seems to induce PTHrP expression in goat mammary cells during and after parturition. These findings suggest that increasing 5-HT biosynthesis could be a potential therapeutic target for prevention of hypocalcemia in dairy goats.

CRISPR/Cas9-mediated tryptophan hydroxylase 1 knockout decreases calcium transportation in goat mammary epithelial cells

“…Supplementation of 5-HTP increased contents of circulating 5-HT, PTHrP and milk calcium around parturition in mice and cows [14,46,47]. 5-HT induced PTHrP expression in bovine and goat mammary epithelial cells, while knockout of TPH1 in mice reduces the expression of mammary PTHrP and the expression can be rescued by restoring 5-HT synthesis [14,15]. Similarly, knockout of TPH1 in GEMC decreased mRNA expression and protein abundance of PTHrP in the present study.…”

“…There was no in uence on the expression of endoplasmic reticulum calcium sequestration pump SERCA2 [42]. However, in our previous study, only the upregulation of PMCA1 was detected when TPH1 was knocked down by small interfering RNA [15]. The present study indicated a more realistic result that knockout TPH1 affected the expressions of those calcium transportation related genes, which led to the decrease in intracellular calcium content.…”

“…Western Blot Western blot was performed as described previously [15]. Cells were collected from different treatment groups, pelletedby centrifugation and lysedin RIPA buffer.…”

“…More importantly, 5-HT in the mammary gland could affect the synthesis of Parathyroid hormone-related peptide (PTHrP) which has been recognized as a regulator of calcium metabolism, and thus maintain calcium homeostasis during lactation [13] [14]. The previous studies showed that there was a positive correlation between the contents of 5-HT and PTHrP in goats and cows during pregnancy and lactation [15,16].…”

Short communication: Differences in distribution of serotonin receptor subtypes in the mammary gland of sheep, goats, and cows during lactation and involution

“…Immunocytochemical staining of 5-HTR7 in the monolayer cultures of human MEC, MCF10A, showed that it is located on the basolateral membranes (Pai et al, 2015), and mediates tight junction stability in the mouse mammary glands (Pai and Horseman, 2011). Receptor subtype 2 activation is related to the synthesis of parathyroid hormone-related protein (PTHrP) and its release into the blood; PTHrP induces bone resorption, resulting in increased calcium in serum (Hernandez et al, 2012;Horseman and Hernandez, 2014;Zang et al, 2018). In dairy cows, the 5-HTR1B genotype is related to the milk production traits (Zhang et al, 2008).…”