The development of new analgesics endowed with mu/delta opioid receptors (MOR/DOR) activity represents a promising alternative to MOR selective compounds as their better therapeutic and tolerability profile. Recently, we synthetized the dual-target MOR/DOR agonist LP2 that showed a long lasting antinociceptive activity in the tail flick test. Notably LP2 also resulted effective in the mouse formalin test, a model of inflammatory pain: LP2 (0.25-1.00 mg/kg, i.p.) exhibited dose-dependently efficacy in counteracting both first and, above all, the second phase of formalin test where spinal cord neuronal sensitization occurs. This prompted us to investigate the pharmacological profile of LP2 in a neuropathic pain model the chronic constriction injury (CCI). Results showed that LP2 significantly ameliorated mechanical allodynia from the early phase of treatment up to 21 days post-ligatures. We additionally showed that LP2 prevented CCI-induced upregulation of connexin 43 (Cx43), the core glial gap junction-mediated cell coupling, which plays a role in the pathogenesis of neuropathy. The pathogenic role of neuroinflammation in neuropathic pain development has recently gained more attention. Pro-inflammatory cytokines, such as TNF and IL-6, are considered key modulators in the crosstalk among immune cells, neurons, and glia. We showed that LP2 was able to significantly downregulate the mRNA expression level of both CCI-induced TNF and IL-6. Notably, our data showed that neither NLX nor NTD were able to reverse LP2-mediated TNF reduction in CCI rats, indicating that concomitant MOR and DOR agonism was important to reduce the cytokine increase. To investigate the pivotal role of the stereocenter at the N-substituent of the 6,7-benzomorphan scaffold, 2R- and 2S-diastereoisomers of LP2 were synthesized and their pharmacological profile was evaluated. 2S-LP2 showed an improved pharmacological profile in comparison to LP2 and 2R-LP2. In vivo effect of 2S-LP2 was consistent with the improved MOR/DOR efficacy profile assessed by radioligand binding assay and BRET assay, to evaluate the capability to promote receptor/G-protein and receptor/β-arrestin 2 interaction. 2S-LP2 was able to activate G-protein pathway over β-arrestin 2-mediated signaling, with a biased agonist profile at MOR and mainly at DOR. We examined also the correlation between anti-allodynic effect of 2S-LP2, and TGF-β1 signaling in neuropathic CCI model. We detected a significant decrease of active TGF-β1 and its type II receptor TGFβ-R2 levels in the spinal cord from CCI rats and a selective deficit of TGF-β1 in microglia cells both at days 11 and 21 post-ligature, as assessed by immunofluorescence analysis. 2S-LP2, administered from day 11 to 21post-ligature, was able to reduce CCI-induced mechanical allodynia by rescue of TGF-β1 and TGFβ-R2 levels. Thus, the dual-target approach could represent a novel pharmacological approach to increase the analgesic efficacy of MOR agonists
Dual-target ligands and pain: our experience
Carmela Parenti;Simona Denaro;Nunzio Vicario;Rosalba Parenti;Rita Turnaturi;Annamaria Fidilio;Margherita Grasso;Lorella Pasquinucci
2024-01-01
Abstract
The development of new analgesics endowed with mu/delta opioid receptors (MOR/DOR) activity represents a promising alternative to MOR selective compounds as their better therapeutic and tolerability profile. Recently, we synthetized the dual-target MOR/DOR agonist LP2 that showed a long lasting antinociceptive activity in the tail flick test. Notably LP2 also resulted effective in the mouse formalin test, a model of inflammatory pain: LP2 (0.25-1.00 mg/kg, i.p.) exhibited dose-dependently efficacy in counteracting both first and, above all, the second phase of formalin test where spinal cord neuronal sensitization occurs. This prompted us to investigate the pharmacological profile of LP2 in a neuropathic pain model the chronic constriction injury (CCI). Results showed that LP2 significantly ameliorated mechanical allodynia from the early phase of treatment up to 21 days post-ligatures. We additionally showed that LP2 prevented CCI-induced upregulation of connexin 43 (Cx43), the core glial gap junction-mediated cell coupling, which plays a role in the pathogenesis of neuropathy. The pathogenic role of neuroinflammation in neuropathic pain development has recently gained more attention. Pro-inflammatory cytokines, such as TNF and IL-6, are considered key modulators in the crosstalk among immune cells, neurons, and glia. We showed that LP2 was able to significantly downregulate the mRNA expression level of both CCI-induced TNF and IL-6. Notably, our data showed that neither NLX nor NTD were able to reverse LP2-mediated TNF reduction in CCI rats, indicating that concomitant MOR and DOR agonism was important to reduce the cytokine increase. To investigate the pivotal role of the stereocenter at the N-substituent of the 6,7-benzomorphan scaffold, 2R- and 2S-diastereoisomers of LP2 were synthesized and their pharmacological profile was evaluated. 2S-LP2 showed an improved pharmacological profile in comparison to LP2 and 2R-LP2. In vivo effect of 2S-LP2 was consistent with the improved MOR/DOR efficacy profile assessed by radioligand binding assay and BRET assay, to evaluate the capability to promote receptor/G-protein and receptor/β-arrestin 2 interaction. 2S-LP2 was able to activate G-protein pathway over β-arrestin 2-mediated signaling, with a biased agonist profile at MOR and mainly at DOR. We examined also the correlation between anti-allodynic effect of 2S-LP2, and TGF-β1 signaling in neuropathic CCI model. We detected a significant decrease of active TGF-β1 and its type II receptor TGFβ-R2 levels in the spinal cord from CCI rats and a selective deficit of TGF-β1 in microglia cells both at days 11 and 21 post-ligature, as assessed by immunofluorescence analysis. 2S-LP2, administered from day 11 to 21post-ligature, was able to reduce CCI-induced mechanical allodynia by rescue of TGF-β1 and TGFβ-R2 levels. Thus, the dual-target approach could represent a novel pharmacological approach to increase the analgesic efficacy of MOR agonistsFile | Dimensione | Formato | |
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