Metabotropic glutamate receptor 2/3 (mGluR2/3) activation suppresses TRPV1 sensitization in mouse, but not human sensory neurons

AbstractThe use of human tissue to validate putative analgesic targets identified in rodents is a promising strategy for improving the historically poor translational record of preclinical pain research. We recently demonstrated that in mouse and human sensory neurons, agonists for metabotropic glutamate receptors 2 and 3 (mGluR2/3) reduce membrane hyperexcitability produced by the inflammatory mediator prostaglandin E2(PGE2). Previous rodent studies indicate that mGluR2/3 can also reduce peripheral sensitization by suppressing inflammation-induced sensitization of TRPV1. Whether this observation similarly translates to human sensory neurons has not yet been tested. We found that activation of mGluR2/3 with the agonist APDC suppressed PGE2-induced sensitization of TRPV1 in mouse, but not human, sensory neurons. We also evaluated sensory neuron expression of the gene transcripts for mGluR2 (Grm2), mGluR3 (Grm3), and TRPV1 (Trpv1). The majority ofTrpv1+mouse and human sensory neurons expressedGrm2and/orGrm3, and in both mice and humans,Grm2was expressed in a greater percentage of sensory neurons thanGrm3. Although we demonstrated a functional difference in the modulation of TRPV1 sensitization by mGluR2/3 activation between mouse and human, there were no species differences in the gene transcript colocalization of mGluR2 or mGluR3 with TRPV1 that might explain this functional difference. Taken together with our previous work, these results suggest that mGluR2/3 activation suppresses only some aspects of human sensory neuron sensitization caused by PGE2. These differences have implications for potential healthy human voluntary studies or clinical trials evaluating the analgesic efficacy of mGluR2/3 agonists or positive allosteric modulators.</jats:p

Small RNAs, but sizable itch: TRPA1 activation by an extracellular microRNA

No abstract available

Figure s2

Sheahan_2023_figureS2_stats.pzfx -Graphpad Prism file with data for the graphs and statistics presented in Figure S2 Sheahan_2023_figureS2_data.xlsx -Excel spreadsheet of all the raw data used to build Figure S

Figure 3

Sheahan_2023_7.23.10_Western.pdf - Acrobat file containing the original scanned image of the Western blot used for Figure 3 as well as a description of the samples in each lane

Figure 7

Acrobat files containing the original scanned images of the Western blot used for Figure 7 and additional confirmatory Western blots as well as descriptions of the samples in each lane. The file containing the blot used in the figure is Sheahan_2023_05.22.12_Western.pdf

Figure 6

Sheahan_2023_figure6_stats.pzfx -Graphpad Prism file with data for the graphs and statistics presented in Figure 6 Sheahan_2023_figure6_data.xlsx - Excel spreadsheet of all the raw data used to build Figure

The Drosophila drop-dead gene is required for eggshell integrity.

The eggshell of the fruit fly Drosophila melanogaster is a useful model for understanding the synthesis of a complex extracellular matrix. The eggshell is synthesized during mid-to-late oogenesis by the somatic follicle cells that surround the developing oocyte. We previously reported that female flies mutant for the gene drop-dead (drd) are sterile, but the underlying cause of the sterility remained unknown. In this study, we examined the role of drd in eggshell synthesis. We show that eggs laid by drd mutant females are fertilized but arrest early in embryogenesis, and that the innermost layer of the eggshell, the vitelline membrane, is abnormally permeable to dye in these eggs. In addition, the major vitelline membrane proteins fail to become crosslinked by nonreducible bonds, a process that normally occurs during egg activation following ovulation, as evidenced by their solubility and detection by Western blot in laid eggs. In contrast, the Cp36 protein, which is found in the outer chorion layers of the eggshell, becomes crosslinked normally. To link the drd expression pattern with these phenotypes, we show that drd is expressed in the ovarian follicle cells beginning in mid-oogenesis, and, importantly, that all drd mutant eggshell phenotypes could be recapitulated by selective knockdown of drd expression in the follicle cells. To determine whether drd expression was required for the crosslinking itself, we performed in vitro activation and crosslinking experiments. The vitelline membranes of control egg chambers could become crosslinked either by incubation in hyperosmotic medium, which activates the egg chambers, or by exogenous peroxidase and hydrogen peroxide. In contrast, neither treatment resulted in the crosslinking of the vitelline membrane in drd mutant egg chambers. These results indicate that drd expression in the follicle cells is necessary for vitelline membrane proteins to serve as substrates for peroxidase-mediated cross-linking at the end of oogenesis

Table 2

Sheahan_2023_table2_stats.pzfx - Graphpad Prism file with data for the graphs and statistics presented in Table 2 Sheahan_2023_table2_data.xlsx - Excel spreadsheet of all the raw data used to build Table

Figure 4

Acrobat files containing the original scanned images of the Western blots used for Figures 4A and 4B and additional confirmatory Western blots as well as descriptions of the samples in each lane. The files containing the blots used in the figures are Sheahan_2023_7.23.10a_Western.pdf (figure 4A) and Sheahan_2023_6.12.12_Western.pdf (figure 4B)