Disruption of 5-HT2A Receptor-PDZ Protein Interactions Alleviates Mechanical Hypersensitivity in Carrageenan-Induced Inflammation in Rats

Abstract

Despite common pathophysiological mechanisms, inflammatory and neuropathic pain do not respond equally to the analgesic effect of antidepressants, except for selective serotonin reuptake inhibitors (SSRIs), which show a limited efficacy in both conditions. We previously demonstrated that an interfering peptide (TAT-2ASCV) disrupting the interaction between 5-HT2A receptors and its associated PDZ proteins (e.g. PSD-95) reveals a 5-HT2A receptor-mediated anti-hyperalgesic effect and enhances the efficacy of fluoxetine (a SSRI) in diabetic neuropathic pain conditions in rats. Here, we have examined whether the same strategy would be useful to treat inflammatory pain. Sub-chronic inflammatory pain was induced by injecting λ-carrageenan (100 µl, 2%) into the left hind paw of the rat. Mechanical hyperalgesia was assessed after acute treatment with TAT-2ASCV or/and fluoxetine (SSRI) 2.5 h after λ-carrageenan injection. Possible changes in the level of 5-HT2A receptors and its associated PDZ protein PSD-95 upon inflammation induction were quantified by Western blotting in dorsal horn spinal cord. Administration of TAT-2ASCV peptide (100 ng/rat, intrathecally) but not fluoxetine (10 mg/kg, intraperitoneally) relieves mechanical hyperalgesia (paw pressure test) in inflamed rats. This anti-hyperalgesic effect involves spinal 5-HT2A receptors and GABAergic interneurons as it is abolished by a 5-HT2A antagonist (M100907, 150 ng/rat, intrathecally) and a GABAA antagonist, (bicuculline, 3 µg/rat, intrathecally). We also found a decreased expression of 5-HT2A receptors in the dorsal spinal cord of inflamed animals which could not be rescued by TAT-2ASCV injection, while the amount of PSD-95 was not affected by inflammatory pain. Finally, the coadministration of fluoxetine does not further enhance the anti-hyperalgesic effect of TAT-2ASCV peptide. This study reveals a role of the interactions between 5-HT2A receptors and PDZ proteins in the pathophysiological pathways of inflammatory pain and opens new perspectives in its control thanks to molecules disrupting 5-HT2A receptor/PDZ protein interactions.

Mechanisms of imidazoline I2 receptor agonist‐induced antinociception in rats: involvement of monoaminergic neurotransmission

“…5-HT 1A , 5-HT 2A and α 1 -adrenoceptors) which then produces anti-nociception, presumably through their downstream mechanisms (Figure 9). The involvement of the three receptors implicated in antinociception in this study has previously been demonstrated (Tasker et al, 1992;Bardin, 2011;Valhondo et al, 2013;Wattiez et al, 2013;Sun et al, 2014). Interestingly,…”

The Role of Descending Pain Modulation in Chronic Primary Pain: Potential Application of Drugs Targeting Serotonergic System

“…Also, TAT-2ASCV enhanced SSRI-induced anti-hyperalgesia [99]. Recent studies identified this process in traumatic neuropathic pain and inflammatory pain models [100,101], as well as the evidence that spinal GABA release and GABA A receptor activation are involved in this process [101,102]. Presently, a final conclusion of the facilitatory or inhibitory role of 5-HT 2A/2C receptors in painrelated circuits in the descending pain system is still not clear.…”

Role of SAP97 in the Regulation of 5-HT2AR Endocytosis and Signaling

“…In particular, pharmacological studies and knockout mice have demonstrated that 5-HT 2A R and 5-HT 2C R contribute to anxiety and are pharmacological targets for the treatment of anxiety (Weisstaub et al, 2006). Although many studies have investigated the pharmacological regulation of 5-HT 2A R and 5-HT 2C R in psychiatric disorders, a limited number of studies have focused on the contribution of C-terminal 5-HT 2A R and 5-HT 2C R PSD-95/disc large/zona occludens (PDZ)-binding motif interactions with PDZ domain-containing proteins to 5-HT 2 R-related disorders (Abbas et al, 2009;Jones et al, 2009;Magalhaes et al, 2010;Pichon et al, 2010;Wattiez et al, 2013). For example, PSD-95 regulates the actions of atypical antipsychotics on 5-HT 2 Rs and kalirin-7 mediates 5-HT 2 R-dependent modulation of spine morphology (Abbas et al, 2009;Jones et al, 2009).…”

“…For example, PSD-95 regulates the actions of atypical antipsychotics on 5-HT 2 Rs and kalirin-7 mediates 5-HT 2 R-dependent modulation of spine morphology (Abbas et al, 2009;Jones et al, 2009). In addition, disruption of 5-HT 2A R PDZ protein interactions enhances selective serotonin reuptake inhibitor (SSRI) efficacy in neuropathic pain and alleviates mechanical sensitivity to inflammation (Pichon et al, 2010;Wattiez et al, 2013). Thus, the emerging understanding of the importance of PDZ domaincontaining proteins in the regulation of 5-HT 2A R activity will be essential for understanding how the intracellular trafficking of 5-HT 2A R may contribute to the regulation of agonist-stimulated 5-HT 2A R cellular responses (Backstrom et al, 2000;Xia et al, 2003a;Xia et al, 2003b;Gavarini et al, 2006;Jones et al, 2009;Magalhaes et al, 2010;Pichon et al, 2010;Wattiez et al, 2013).…”