Paclitaxel (PTX), a commonly used chemotherapeutic, frequently leads to chemotherapy-induced peripheral neuropathy (CIPN), characterized by persistent pain and neuronal hypersensitivity. While its effects on peripheral nerves are well-documented, paclitaxel also influences central nervous system pathways, particularly spinal synaptic transmission, through Toll-like receptor 4 (TLR4) activation and subsequent sensitization of transient receptor potential vanilloid 1 (TRPV1) receptors. In this study, we used an in vitro model of paclitaxel-induced neuropathic pain to investigate the role of glial activation in TRPV1 receptor function. Using whole-cell patch-clamp recordings from superficial dorsal horn neurons in acute spinal cord slices, we evaluated the effects of minocycline (MX), a glial cell inhibitor, and ISO-1, a macrophage migration inhibitory factor (MIF) antagonist, on paclitaxel-induced synaptic changes. Our results demonstrate that acute paclitaxel application enhances nociceptive signaling and impairs capsaicin-induced TRPV1 receptor tachyphylaxis, leading to sustained hyperactivity. Minocycline preincubation effectively mitigated paclitaxel-induced sensitization, restoring normal nociceptive signaling, whereas acute minocycline treatment failed to prevent these changes. ISO-1 in vitro co-incubation with paclitaxel did not affect the paclitaxel-induced changes. These findings offer novel insight into the intricate interactions among neuroinflammatory mediators, glial cell activation, and TRPV1 receptor sensitization in paclitaxel-induced neuropathic pain. The differential effects of acute versus prolonged pre-incubation minocycline application suggest the importance of sustained glial inhibition for effective outcomes and neuropathic pain management.

• MeSH
• Antineoplastic Agents, Phytogenic toxicity   MeSH
• TRPV Cation Channels * metabolism   MeSH
• Rats MeSH
• Spinal Cord * metabolism   drug effects   MeSH
• Disease Models, Animal MeSH
• Neuralgia * chemically induced   metabolism   MeSH
• Neuroglia * metabolism   drug effects   MeSH
• Paclitaxel * toxicity   MeSH
• Rats, Sprague-Dawley MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Antineoplastic Agents, Phytogenic MeSH
• TRPV Cation Channels * MeSH
• Paclitaxel * MeSH
• Trpv1 protein, rat MeSH Browser
• TRPV1 receptor MeSH Browser

Transient receptor potential ion channel, vanilloid subfamily, type 1 (TRPV1) cation channel, and cannabinoid receptor 1 (CB1) are essential in the modulation of nociceptive signaling in the spinal cord dorsal horn that underlies different pathological pain states. TRPV1 and CB1 receptors share the endogenous agonist anandamide (AEA), produced from N-arachidonoylphosphatidylethanolamine (20:4-NAPE). We investigated the effect of the anandamide precursor 20:4-NAPE on synaptic activity in naive and inflammatory conditions. Patch-clamp recordings of miniature excitatory postsynaptic currents (mEPSCs) from superficial dorsal horn neurons in rat acute spinal cord slices were used. Peripheral inflammation was induced by subcutaneous injection of carrageenan. Under naive conditions, mEPSCs frequency (0.96 ± 0.11 Hz) was significantly decreased after 20 μM 20:4-NAPE application (55.3 ± 7.4%). This 20:4-NAPE-induced inhibition was blocked by anandamide-synthesizing enzyme N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD) inhibitor LEI-401. In addition, the inhibition was prevented by the CB1 receptor antagonist PF 514273 (0.2 μM) but not by the TRPV1 receptor antagonist SB 366791 (10 μM). Under inflammatory conditions, 20:4-NAPE (20 μM) also exhibited a significant inhibitory effect (74.5 ± 8.9%) on the mEPSCs frequency that was prevented by the TRPV1 receptor antagonist SB 366791 but not by PF 514273 application. Our results show that 20:4-NAPE application has a significant modulatory effect on spinal cord nociceptive signaling that is mediated by both TRPV1 and CB1 presynaptic receptors, whereas peripheral inflammation changes the underlying mechanism. The switch between TRPV1 and CB1 receptor activation by the AEA precursor 20:4-NAPE during inflammation may play an important role in nociceptive processing, hence the development of pathological pain.

• Keywords
• 20:4-NAPE, CB1, NAPE-PLD, TRPV1, anandamide, inflammation, spinal cord,
• Publication type
• Journal Article MeSH

The development of painful paclitaxel-induced peripheral neuropathy (PIPN) represents a major dose-limiting side effect of paclitaxel chemotherapy. Here we report a promising effect of duvelisib (Copiktra), a novel FDA-approved PI3Kδ/γ isoform-specific inhibitor, in preventing paclitaxel-induced pain-like behavior and pronociceptive signaling in DRGs and spinal cord dorsal horn (SCDH) in rat and mouse model of PIPN. Duvelisib blocked the development of mechanical hyperalgesia in both males and females. Moreover, duvelisib prevented paclitaxel-induced sensitization of TRPV1 receptors, and increased PI3K/Akt signaling in small-diameter DRG neurons and an increase of CD68+ cells within DRGs. Specific optogenetic stimulation of inhibitory neurons combined with patch-clamp recording revealed that duvelisib inhibited paclitaxel-induced weakening of inhibitory, mainly glycinergic control on SCDH excitatory neurons. Enhanced excitatory and reduced inhibitory neurotransmission in the SCDH following PIPN was also alleviated by duvelisib application. In summary, duvelisib showed a promising ability to prevent neuropathic pain in PIPN. The potential use of our findings in human medicine may be augmented by the fact that duvelisib is an FDA-approved drug with known side effects.SIGNIFICANCE STATEMENT We show that duvelisib, a novel FDA-approved PI3Kδ/γ isoform-specific inhibitor, prevents the development of paclitaxel-induced pain-like behavior in males and females and prevents pronociceptive signaling in DRGs and spinal cord dorsal horn in rat and mouse model of paclitaxel-induced peripheral neuropathy.

• Keywords
• PI3K, TRPV1, dorsal horn, glycine, neuropathy, pain,
• MeSH
• Pain MeSH
• Phosphatidylinositol 3-Kinases MeSH
• Antineoplastic Agents, Phytogenic * pharmacology   MeSH
• Hyperalgesia chemically induced   drug therapy   prevention & control   MeSH
• Isoquinolines MeSH
• Rats MeSH
• Mice MeSH
• Peripheral Nervous System Diseases MeSH
• Neuralgia * chemically induced   drug therapy   prevention & control   MeSH
• Paclitaxel adverse effects   MeSH
• Purines MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• duvelisib MeSH Browser
• Antineoplastic Agents, Phytogenic * MeSH
• Isoquinolines MeSH
• Paclitaxel MeSH
• Purines MeSH

Transient receptor potential vanilloid 1 (TRPV1) channels contribute to the development of several chronic pain states and represent a possible therapeutic target in many painful disease treatment. Proinflammatory mediator bradykinin (BK) sensitizes TRPV1, whereas noxious peripheral stimulation increases BK level in the spinal cord. Here, we investigated the involvement of spinal TRPV1 in thermal and mechanical hypersensitivity, evoked by intrathecal (i.t.) administration of BK and an endogenous agonist of TRPV1, N-oleoyldopamine (OLDA), using behavioral tests and i.t. catheter implantation, and administration of BK-induced transient thermal and mechanical hyperalgesia and mechanical allodynia. All these hypersensitive states were enhanced by co-administration of a low dose of OLDA (0.42 µg i.t.), which was ineffective only under the control conditions. Intrathecal pretreatment with TRPV1 selective antagonist SB366791 prevented hypersensitivity induced by i.t. co-administration of BK and OLDA. Our results demonstrate that both thermal and mechanical hypersensitivity evoked by co-administration of BK and OLDA is mediated by the activation of spinal TRPV1 channels.

• Keywords
• OLDA, TRPV1, allodynia, bradykinin, hyperalgesia, spinal cord,
• MeSH
• Bradykinin MeSH
• Dopamine analogs & derivatives   MeSH
• Hyperalgesia metabolism   MeSH
• TRPV Cation Channels agonists   metabolism   MeSH
• Rats MeSH
• Spinal Cord metabolism   MeSH
• Rats, Wistar MeSH
• Injections, Spinal MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Bradykinin MeSH
• Dopamine MeSH
• TRPV Cation Channels MeSH
• N-oleoyldopamine MeSH Browser
• TRPV1 protein, mouse MeSH Browser

Paclitaxel-induced peripheral neuropathy (PIPN) is often associated with neuropathic pain and neuroinflammation in the central and peripheral nervous system. Antihypertensive drug losartan, an angiotensin II receptor type 1 (AT1R) blocker, was shown to have anti-inflammatory and neuroprotective effects in disease models, predominantly via activation of peroxisome proliferator-activated receptor gamma (PPARγ). Here, the effect of systemic losartan treatment (100 mg/kg/d) on mechanical allodynia and neuroinflammation was evaluated in rat PIPN model. The expression of pro-inflammatory markers protein and mRNA levels in dorsal root ganglia (DRGs) and spinal cord dorsal horn (SCDH) were measured with Western blot, ELISA and qPCR 10 and 21 days after PIPN induction. Losartan treatment attenuated mechanical allodynia significantly. Paclitaxel induced overexpression of C-C motif chemokine ligand 2 (CCL2), tumour necrosis alpha (TNFα) and interleukin-6 (IL-6) in DRGs, where the presence of macrophages was demonstrated. Neuroinflammatory changes in DRGs were accompanied with glial activation and pro-nociceptive modulators production in SCDH. Losartan significantly attenuated paclitaxel-induced neuroinflammatory changes and induced expression of pro-resolving markers (Arginase 1 and IL-10) indicating a possible shift in macrophage polarization. Considering the safety profile of losartan, acting also as partial PPARγ agonist, it may be considered as a novel treatment strategy for PIPN patients.

• Keywords
• losartan, macrophage, neuroinflammation, neuropathic pain, paclitaxel,
• MeSH
• Biomarkers MeSH
• Enzyme-Linked Immunosorbent Assay MeSH
• Antineoplastic Agents, Phytogenic adverse effects   MeSH
• Rats MeSH
• Losartan pharmacology   MeSH
• Macrophages drug effects   metabolism   MeSH
• Pain Management MeSH
• Disease Models, Animal MeSH
• Neuralgia diagnosis   drug therapy   etiology   metabolism   MeSH
• Paclitaxel adverse effects   MeSH
• Ganglia, Spinal drug effects   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Biomarkers MeSH
• Antineoplastic Agents, Phytogenic MeSH
• Losartan MeSH
• Paclitaxel MeSH