Targeted high-resolution quadrupole-Orbitrap mass spectrometry analyses reveal a significant reduction of tachykinin and opioid neuropeptides level in PC1 and PC2 mutant mouse spinal cords

Estrogenic impregnation alters pain expression: analysis through functional neuropeptidomics in a surgical rat model of osteoarthritis

PURPOSE

Several observational studies suggest that estrogens could bias pain perception. To evaluate the influence of estrogenic impregnation on pain expression, a prospective, randomized, controlled, blinded study was conducted in a Sprague-Dawley rat model of surgically induced osteoarthritis (OA).

METHODS

Female rats were ovariectomized and pre-emptive 17β-estradiol (0.025 mg, 90-day release time) or placebo pellets were installed subcutaneously during the OVX procedures. Thirty-five days after, OA was surgically induced on both 17β-estradiol (OA-E) and placebo (OA-P) groups. Mechanical hypersensitivity was assessed by static weight-bearing (SWB) and paw withdrawal threshold (PWT) tests. Mass spectrometry coupled with high-performance liquid chromatography (HPLC-MS) was performed to quantify the spinal pronociceptive neuropeptides substance P (SP), calcitonin gene-related peptide (CGRP), bradykinin (BK), somatostatin (SST), and dynorphin-A (Dyn-A).

RESULTS

Compared to control, ovariectomized rats presented higher SP (P = 0.009) and CGRP (P = 0.017) concentrations. OA induction increased the spinal level of SP (+ 33%, P < 0.020) and decreased the release of BK (- 20%, (P < 0.037)). The OA-E rats at functional assessment put more % body weight on the affected hind limb than OA-P rats at D7 (P = 0.027) and D56 (P = 0.033), and showed higher PWT at D56 (P = 0.009), suggesting an analgesic and anti-allodynic effect of 17β-estradiol. Interestingly, the 17β-estradiol treatment counteracted the increase of spinal concentration of Dyn-A (P < 0.016) and CGRP (P < 0.018).

CONCLUSION

These results clearly indicate that 17β-estradiol interfers with the development of central sensitization and confirm that gender dimorphism should be considered when looking at pain evaluation.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

EGL-3 and EGL-21 are required to trigger nocifensive response of Caenorhabditis elegans to noxious heat

Caenorhabditis elegans (C. elegans) is a widely used model organism to examine nocifensive response to noxious stimuli, including heat avoidance. Recently, comprehensive analysis of the genome sequence revealed several pro-neuropeptide genes, encoding a series of bioactive neuropeptides. C. elegans neuropeptides are involved in the modulation of essentially all behaviors including locomotion, mechanosensation, thermosensation and chemosensation. The maturation of pro-neuropeptide to neuropeptide is performed by ortholog pro-protein convertases and carboxypeptidase E (e.g. EGL-3 and EGL-21). We hypothesized that C. elegans egl-3 or egl-21 mutants will have a significant decrease in mature neuropeptides and they will display an impaired heat avoidance behavior. Our data has shown that thermal avoidance behavior of egl-3 and egl-21 mutants was significantly hampered compared to WT(N2) C. elegans. Moreover, flp-18, flp-21 and npr-1 mutant C. elegans displayed a similar phenotype. EGL-3 pro-protein convertase and EGL-21 carboxypeptidase E are essential enzymes for the maturation of pro-neuropeptides to active neuropeptides in C. elegans. Quantitative mass spectrometry analyses with egl-3 and egl-21 mutant C. elegans homogenates demonstrated that proteolysis of ProFLP-18 and ProFLP-21 are severely impeded, leading to a lack of mature bioactive neuropeptides. Not only FLP-21 but also FLP-18 related mature neuropeptides, both are ligands of NPR-1 and are needed to trigger nocifensive response of C. elegans to noxious heat.