Expression of P2X3 and TRPV1 receptors in primary sensory neurons from estrogen receptors-α and estrogen receptor-β knockout mice

Abstract

In women, pain symptoms and nociceptive thresholds vary with the reproductive cycle, suggesting the role of estrogen receptors (ERs) in modulating nociception. Our previous data strongly suggest an interaction between ERs and ATP-induced purinergic (P2X3) as well as ERs and capsaicin-induced vanilloid (TRPV1) receptors at the level of dorsal root ganglion (DRG) neurons. In this study, we investigated the expression of P2X3 and TRPV1 receptors by western blotting and immunohistochemistry in lumbosacral DRGs from wild type, ERα, and ERβ knockout mice. We found a significant decrease for both P2X3 and TRPV1 in ERαKO and ERβKO. This phenomenon was visualized in L1, L2, L4, and L6 levels for P2X3 receptors and in L1, L2, and S2 levels for TRPV1 receptors. This tan interaction between P2X3/TRPV1 and ERs expression in sensory neurons may represent a novel mechanism that can explain the sex differences in nociception observed in clinical practice. The DRG is an important site of visceral afferent convergence and cross-sensitization and a potential target for designing new anti-nociceptive therapies.

Figure 1

Western blot analysis of DRG lysates shows reduced expression of P2X3 and TRPV1 in both knock-out mice. Equal amounts of lysates (40 µg) generated from ERαKO and ERβKO DRG neurons, as well as from Wt mice, were electrophoresed under denaturing conditions and probed with a anti-P2X3/TRPV1 antibodies (n=4 per group). a) Expression of P2X3/TRPV1 in DRG neurons. b) Both DRG neurons of knock-out mice showed a significant reduction in band intensity, 2~3 fold changes of knock-out compared with neurons from Wt (control) DRGs. Quantification of signals from Western blots shows statistically significant difference between the intensity of the bands from both knock-out DRG neurons when compared with wild type animals. Values are expressed as mean ± SEM p<0.05, n=4. * indicate significant difference from control.

Figure 2

(a) Expression of P2X3 receptors in DRG neurons from Wt, ERαKO, and ERβKO mice using immunocytochemistry (b) Percentage distribution of P2X3-labeled DRG neurons in Wt, ERαKO and ERβKO mice in L1-S1 levels. * indicate statistically significant difference from control, p<0.05.

Figure 3

(a) Distribution of TRPV1 receptors in DRG neurons from Wt, ERαKO, and ERβKO by immunocytochemistry. DRG sections (L1 through S1 levels) were incubated in TRPV1 primary antibodies. (b) Distribution percentage of TRPV1-labeled DRG neurons in ERαKO, ERβKO and Wt mice in L1-S1 levels. * indicate statistically significant difference, p<0.05.