AKAP150 involved in paclitaxel-induced neuropathic pain via inhibiting CN/NFAT2 pathway and downregulating IL-4

Desloratadine ameliorates paclitaxel-induced peripheral neuropathy and hypersensitivity reactions in mice

Paclitaxel (PTX) serves as a primary chemotherapy agent against diverse solid tumors including breast cancer, lung cancer, head and neck cancer and ovarian cancer, having severe adverse effects including PTX-induced peripheral neuropathy (PIPN) and hypersensitivity reactions (HSR). A recommended anti-allergic agent diphenhydramine (DIP) has been used to alleviate PTX-induced HSR. Desloratadine (DLT) is a third generation of histamine H1 receptor antagonist, but also acted as a selective antagonist of 5HTR2A. In this study we investigated whether DLT ameliorated PIPN-like symptoms in mice and the underlying mechanisms. PIPN was induced in male mice by injection of PTX (4 mg/kg, i.p.) every other day for 4 times. The mice exhibited 50% reduction in mechanical threshold, paw thermal response latency and paw cold response latency compared with control mice. PIPN mice were treated with DLT (10, 20 mg/kg, i.p.) 30 min before each PTX administration in the phase of establishing PIPN mice model and then administered daily for 4 weeks after the model was established. We showed that DLT administration dose-dependently elevated the mechanical, thermal and cold pain thresholds in PIPN mice, whereas administration of DIP (10 mg/kg, i.p.) had no ameliorative effects on PIPN-like symptoms. We found that the expression of 5HTR2A was selectively elevated in the activated spinal astrocytes of PIPN mice. Spinal cord-specific 5HTR2A knockdown by intrathecal injection of AAV9-5Htr2a-shRNA significantly alleviated the mechanical hyperalgesia, thermal and cold hypersensitivity in PIPN mice, while administration of DLT (20 mg/kg) did not further ameliorate PIPN-like symptoms. We demonstrated that DLT administration alleviated dorsal root ganglion neuronal damage and suppressed sciatic nerve destruction, spinal neuron apoptosis and neuroinflammation in the spinal cord of PIPN mice. Furthermore, we revealed that DLT administration suppressed astrocytic neuroinflammation via the 5HTR2A/c-Fos/NLRP3 pathway and blocked astrocyte-neuron crosstalk by targeting 5HTR2A. We conclude that spinal 5HTR2A inhibition holds promise as a therapeutic approach for PIPN and we emphasize the potential of DLT as a dual-functional agent in ameliorating PTX-induced both PIPN and HSR in chemotherapy. In summary, we determined that spinal 5HTR2A was selectively activated in PIPN mice and DLT could ameliorate the PTX-induced both PIPN- and HSR-like pathologies in mice. DLT alleviated the damages of DRG neurons and sciatic nerves, while restrained spinal neuronal apoptosis and CGRP release in PIPN mice. The underlying mechanisms were intensively investigated by assay against the PIPN mice with 5HTR2A-specific knockdown in the spinal cord by injection of adeno-associated virus 9 (AAV9)-5Htr2a-shRNA. DLT inhibited astrocytic NLRP3 inflammasome activation-mediated spinal neuronal damage through 5HTR2A/c-FOS pathway. Our findings have supported that spinal 5HTR2A inhibition shows promise as a therapeutic strategy for PIPN and highlighted the potential advantage of DLT as a dual-functional agent in preventing against PTX-induced both PIPN and HSR effects in anticancer chemotherapy.

NT-3 contributes to chemotherapy-induced neuropathic pain through TrkC-mediated CCL2 elevation in DRG neurons

Cancer patients undergoing treatment with antineoplastic drugs often experience chemotherapy-induced neuropathic pain (CINP), and the therapeutic options for managing CINP are limited. Here, we show that systemic paclitaxel administration upregulates the expression of neurotrophin-3 (Nt3) mRNA and NT3 protein in the neurons of dorsal root ganglia (DRG), but not in the spinal cord. Blocking NT3 upregulation attenuates paclitaxel-induced mechanical, heat, and cold nociceptive hypersensitivities and spontaneous pain without altering acute pain and locomotor activity in male and female mice. Conversely, mimicking this increase produces enhanced responses to mechanical, heat, and cold stimuli and spontaneous pain in naive male and female mice. Mechanistically, NT3 triggers tropomyosin receptor kinase C (TrkC) activation and participates in the paclitaxel-induced increases of C-C chemokine ligand 2 (Ccl2) mRNA and CCL2 protein in the DRG. Given that CCL2 is an endogenous initiator of CINP and that Nt3 mRNA co-expresses with TrkC and Ccl2 mRNAs in DRG neurons, NT3 likely contributes to CINP through TrkC-mediated activation of the Ccl2 gene in DRG neurons. NT3 may be thus a potential target for CINP treatment.

Preclinical research in paclitaxel-induced neuropathic pain: a systematic review

Introduction

Chemotherapy-induced peripheral neuropathy (CIPN) is a common consequence of cancer treatment and pain is a frequent complaint of the patients. Paclitaxel, a cytostatic drug, generates a well-described peripheral nerve injury and neuroinflammation, which may be experimentally mimicked in animal models. We conducted a systematic review analyzing the experimental design, reporting and mechanisms underlying paclitaxel-induced neuropathy in the included studies to establish the perspectives of translation of the current literature in models of CIPN.

Methods

We elected studies published in Pubmed and Scopus between 1 January 2018 and 3 December 2022.

Results

According to a defined mesh of keywords searched, and after applying exclusion and inclusion criteria, 70 original studies were included and analyzed in detail. Most studies used male Sprague-Dawley rats to induce paclitaxel-induced neuropathy, used low doses of paclitaxel, and the analyzed studies mainly focused at 14-28 days of CIPN. Mechanical nociceptive tests were preferred in the behavioral evaluation. The mechanisms under study were mainly neuroinflammation of peripheral nerves. The overall methodological quality was considered moderate, and the risk of bias was unclear.

Discussion

Despite the ample preclinical research in paclitaxel-induced neuropathy, this systematic review alerts to some flaws in the experimental design along with limitations in reporting, e.g., lack of representation of both sexes in experimental work and the lack of reporting of the ARRIVE guidelines. This may limit the reproducibility of preclinical studies in CIPN. In addition, the clinical features of CIPN should be considered when designing animal experiments, such as sex and age of the CIPN patients. In this way the experimental studies aiming to establish the mechanisms of CIPN may allow the development of new drugs to treat CIPN and translation in the research of CIPN could be improved.

AKAP150 from nucleus accumbens dopamine D1 and D2 receptor-expressing medium spiny neurons regulates morphine withdrawal

Dopamine D1 receptor-expressing medium spiny neurons (D1R-MSNs) and dopamine D2 receptor-expressing MSNs (D2R-MSNs) in nucleus accumbens (NAc) have been demonstrated to show different effects on reward and memory of abstinence. A-kinase anchoring protein 150 (AKAP150) expression in NAc is significantly upregulated and contributes to the morphine withdrawal behavior. However, the underlying mechanism of AKAP150 under opioid withdrawal remains unclear. In this study, AKAP150 expression in NAc is upregulated in naloxone-precipitated morphine withdrawal model, and knockdown of AKAP150 alleviates morphine withdrawal somatic signs and improves the performance of conditioned place aversion (CPA) test. AKAP150 in NAc D1R-MSNs is related to modulation of the performance of morphine withdrawal CPA test, while AKAP150 in NAc D2R-MSNs is relevant to the severity of somatic responses. Our results suggest that AKAP150 from D1R-MSNs or D2R-MSNs in NAc contributes to the developmental process of morphine withdrawal but plays different roles in aspects of behavior or psychology.

Selective activation of AKAP150/TRPV1 in ventrolateral periaqueductal gray GABAergic neurons facilitates conditioned place aversion in male mice

Aversion refers to feelings of strong dislike or avoidance toward particular stimuli or situations. Aversion can be caused by pain stimuli and has a long-term negative impact on physical and mental health. Aversion can also be caused by drug abuse withdrawal, resulting in people with substance use disorder to relapse. However, the mechanisms underlying aversion remain unclear. The ventrolateral periaqueductal gray (vlPAG) is considered to play a key role in aversive behavior. Our study showed that inhibition of vlPAG GABAergic neurons significantly attenuated the conditioned place aversion (CPA) induced by hindpaw pain pinch or naloxone-precipitated morphine withdrawal. However, activating or inhibiting glutamatergic neurons, or activating GABAergic neurons cannot affect or alter CPA response. AKAP150 protein expression and phosphorylated TRPV1 (p-TRPV1) were significantly upregulated in these two CPA models. In AKAP150^flox/flox mice and C57/B6J wild-type mice, cell-type-selective inhibition of AKAP150 in GABAergic neurons in the vlPAG attenuated aversion. However, downregulating AKAP150 in glutamatergic neurons did not attenuate aversion. Knockdown of AKAP150 in GABAergic neurons effectively reversed the p-TRPV1 upregulation in these two CPA models utilized in our study. Collectively, inhibition of the AKAP150/p-TRPV1 pathway in GABAergic neurons in the vlPAG may be considered a potential therapeutic target for the CPA response.

NMDA Receptors at Primary Afferent-Excitatory Neuron Synapses Differentially Sustain Chemotherapy- and Nerve Trauma-Induced Chronic Pain

The spinal dorsal horn contains vesicular glutamate transporter-2 (VGluT2)-expressing excitatory neurons and vesicular GABA transporter (VGAT)-expressing inhibitory neurons, which normally have different roles in nociceptive transmission. Spinal glutamate NMDAR hyperactivity is a crucial mechanism of chronic neuropathic pain. However, it is unclear how NMDARs regulate primary afferent input to spinal excitatory and inhibitory neurons in neuropathic pain. Also, the functional significance of presynaptic NMDARs in neuropathic pain has not been defined explicitly. Here we showed that paclitaxel treatment or spared nerve injury (SNI) similarly increased the NMDAR-mediated mEPSC frequency and dorsal root-evoked EPSCs in VGluT2 dorsal horn neurons in male and female mice. By contrast, neither paclitaxel nor SNI had any effect on mEPSCs or evoked EPSCs in VGAT neurons. In mice with conditional Grin1 (gene encoding GluN1) KO in primary sensory neurons (Grin1-cKO), paclitaxel treatment failed to induce pain hypersensitivity. Unexpectedly, SNI still caused long-lasting pain hypersensitivity in Grin1-cKO mice. SNI increased the amplitude of puff NMDA currents in VGluT2 neurons and caused similar depolarizing shifts in GABA reversal potentials in WT and Grin1-cKO mice. Concordantly, spinal Grin1 knockdown diminished SNI-induced pain hypersensitivity. Thus, presynaptic NMDARs preferentially amplify primary afferent input to spinal excitatory neurons in neuropathic pain. Although presynaptic NMDARs are required for chemotherapy-induced pain hypersensitivity, postsynaptic NMDARs in spinal excitatory neurons play a dominant role in traumatic nerve injury-induced chronic pain. Our findings reveal the divergent synaptic connectivity and functional significance of spinal presynaptic and postsynaptic NMDARs in regulating cell type-specific nociceptive input in neuropathic pain with different etiologies.SIGNIFICANCE STATEMENT Spinal excitatory neurons relay input from nociceptors, whereas inhibitory neurons repress spinal nociceptive transmission. Chronic nerve pain is associated with aberrant NMDAR activity in the spinal dorsal horn. This study demonstrates, for the first time, that chemotherapy and traumatic nerve injury preferentially enhance the NMDAR activity at primary afferent-excitatory neuron synapses but have no effect on primary afferent input to spinal inhibitory neurons. NMDARs in primary sensory neurons are essential for chemotherapy-induced chronic pain, whereas nerve trauma causes pain hypersensitivity predominantly via postsynaptic NMDARs in spinal excitatory neurons. Thus, presynaptic and postsynaptic NMDARs at primary afferent-excitatory neuron synapses are differentially engaged in chemotherapy- and nerve injury-induced chronic pain and could be targeted respectively for treating these painful conditions.

Daidzein attenuated paclitaxel-induced neuropathic pain via the down-regulation of TRPV1/P2Y and up-regulation of Nrf2/HO-1 signaling

Paclitaxel (PTX) is an anti-microtubule agent, used for the treatment of various types of cancers; however, it produces painful neuropathy which limits its use. Many neuroprotective agents have been introduced to mitigate PTX-induced neuropathic pain (PINP), but they pose many adverse effects. The purpose of this study was to evaluate the pharmacological characteristics of soy isoflavone, and daidzein (DZ) in attenuating PINP. At the beginning of the investigation, the effect of DZ was confirmed through behavioral analysis, as it reduced pain hypersensitivity. Moreover, changes in the histological parameters were reversed by DZ administration along with vascular permeability. PTX administration upregulated transient receptor potential vanilloid 1 (TRPV1) channels and purinergic receptors (P2Y), contributing to hyperalgesia; but administration of DZ downregulated the TRPV1 and P2Y, thus reducing hyperalgesia. DZ increased nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), playing a pivotal role in the activation of the antioxidant pathway. DZ also decreased neuronal apoptosis by decreasing caspase-3 and Bcl2-associated X-protein (Bax), while simultaneously, increasing Bcl-2. PTX administration produced severe DNA damage, which was mitigated by DZ. Similarly, DZ administration resulted in inhibition of neuroinflammation by increasing antioxidant enzymes and reducing oxidative stress markers. PTX caused increased in production of pro-inflammatory mediators such as the cytokines production, while DZ inhibited the pro-inflammatory mediators. Additionally, in silico pharmacokinetic and toxicodynamic study of DZ was also conducted. In summary, DZ demonstrated significant neuroprotective activity against PTX induced neuropathic pain.

Khellin as a selective monoamine oxidase B inhibitor ameliorated paclitaxel-induced peripheral neuropathy in mice

BACKGROUND

Treatment of paclitaxel (PTX)-induced peripheral neuropathy (PIPN) is full of challenges because of the unclear pathogenesis of PIPN. Herbal folk medicine Khellin (Khe) is a natural compound extracted from Ammi visnaga for treatment of renal colics and muscle spasms.

PURPOSE

Here, we aimed to assess the potential of Khe in ameliorating PIPN-like pathology in mice and investigate the underlying mechanisms.

METHODS

PIPN model mice were conducted by injection of PTX based on the published approach. The capability of Khe in ameliorating the PTX-induced neurological dysfunctions was assayed by detection of nociceptive hypersensitivities including mechanical hyperalgesia, thermal hypersensitivity, and cold allodynia in mice. The underlying mechanisms were investigated by assays against the PIPN mice with MAOB-specific knockdown in spinal cord and dorsal root ganglion (DRG) tissues by injection of adeno-associated virus (AAV)-MAOB-shRNA.

RESULTS

We determined that MAOB not MAOA is highly overexpressed in the spinal cord and DRG tissues of PIPN mice and Khe as a selective MAOB inhibitor improved PIPN-like pathology in mice. Khe promoted neurite outgrowth, alleviated apoptosis, and improved mitochondrial dysfunction of DRG neurons by targeting MAOB. Moreover, Khe inhibited spinal astrocytes activation and suppressed neuroinflammation of spinal astrocytes via MAOB/NF-κB/NLRP3/ASC/Caspase1/IL-1β pathway.

CONCLUSION

Our work might be the first to report that MAOB not MAOA is selectively overexpressed in the spinal cord and DRG tissues of PIPN mice, and all findings have highly addressed the potency of selective MAOB inhibitor in the amelioration of PIPN-like pathology and highlighted the potential of Khe in treating PTX-induced side effects.

Calcineurin Regulates Synaptic Plasticity and Nociceptive Transmission at the Spinal Cord Level

Calcineurin, the predominant Ca2+/calmodulin-dependent serine/threonine protein phosphatase (also known as protein phosphatase 2B), is highly expressed in immune T cells and the nervous system, including the dorsal root ganglion and spinal cord. It controls synaptic transmission and plasticity by maintaining the appropriate phosphorylation status of many ion channels present at presynaptic and postsynaptic sites. As such, normal calcineurin activity in neurons and synapses is mainly involved in negative feedback regulation in response to increased neuronal activity and intracellular Ca2+ levels. Calcineurin inhibitors (e.g., cyclosporine and tacrolimus) are widely used as immunosuppressants in tissue and organ transplantation recipients and for treating autoimmune diseases but can cause severe pain in some patients. Furthermore, diminished calcineurin activity at the spinal cord level may play a major role in the transition from acute to chronic neuropathic pain after nerve injury. Restoring calcineurin activity at the spinal cord level produces long-lasting pain relief in animal models of neuropathic pain. In this article, we provide an overview of recent studies on the critical roles of calcineurin in regulating glutamate NMDA and AMPA receptors, voltage-gated Ca2+ channels, potassium channels, and transient receptor potential channels expressed in the spinal dorsal horn and primary sensory neurons.

Pregabalin for chemotherapy-induced neuropathy: background and rationale for further study

Chemotherapy-induced neuropathy is difficult to manage, and the pain associated with neuropathy is poorly responsive to gabapentin in a randomized trial. Duloxetine is the only drug that has been found to be effective in reducing pain from chemotherapy neuropathy. In this qualitative review, the use of pregabalin for chemotherapy-induced neuropathy is discussed including the rationale and pharmacological reasons why pregabalin should be considered in a large, randomized placebo-controlled trial.

Metoprolol Mitigates Ischemic Heart Remodeling and Fibrosis by Increasing the Expression of AKAP5 in Ischemic Heart

The harm of heart failure mainly causes patients to develop dyspnea, fatigue, fluid retention, and other symptoms, which impair patients' activity tolerance and lead to a dramatic decrease in patients' quality of life. The purpose of this study was to verify whether metoprolol regulates AKAP5 expression and test the role of AKAP5 postinjury in mitigating cardiac infarction-associated tissue remodeling and fibrosis. Sprague-Dawley (SD) rats underwent coronary artery ligation (CAL), which was followed immediately with metoprolol daily. And western blot and coimmunoprecipitation experiments were performed to detect the expression of related proteins in the sham-operated group, model group, and drug-treated group. HW/BW ratio and cardiac expression of COL1 and COL3 were increased in rats following CAL compared with shams. Treatment with metoprolol postinjury was associated with a decrease in HW/BW ratio and COL1/COL3 expression compared to uncontrolled rats. CAL resulted in decreased cardiac AKAP5 expression compared to the control group, while metoprolol treatment restored levels compared to baseline shams. Cardiac expression levels of NFATc3/p-NFATc3 and GATA4 were modest at baseline and increased with injury, whereas metoprolol suppressed gene expression to below injury-associated changes. Immunoprecipitation indicated that AKAP5 could bind and regulate PP2B. In summary, we know that metoprolol alleviates ischemic cardiac remodeling and fibrosis, and the mechanism of alleviating remodeling may improve cardiac AKAP5 expression and AKAP5-PP2B interaction.

Mechanisms underlying paclitaxel-induced neuropathic pain: Channels, inflammation and immune regulations

Paclitaxel is a chemotherapeutic agent widely used for many types of malignancies. However, when paclitaxel is used to treat tumors, patients commonly experience severe neuropathic pain that is difficult to manage. The mechanism underlying paclitaxel-induced neuropathic pain remains unclear. Evidence demonstrates correlations between mechanisms of paclitaxel-mediated pain and associated actions of ion channels, neuroinflammation, mitochondrial damage, and other factors. This review provides a comprehensive analysis of paclitaxel-induced neuropathic pain mechanisms and suggestions for effective interventions.

Wnt3a/YTHDF1 Regulated Oxaliplatin-Induced Neuropathic Pain Via TNF-α/IL-18 Expression in the Spinal Cord

Oxaliplatin is widely used in cancer treatment, however, many patients will suffer from neuropathic pain (NP) induced by it at the same time. Therefore exploring the mechanism and founding novel target for this problem are needed. In this study, YTHDF1 showed upregulation in oxaliplatin treated mice. As m6A is known as conserved and it widely functions in numerous physiological and pathological processes. Therefore, we focused on exploring the molecular mechanism of whether and how YTHDF1 functions in NP induced by oxaliplatin. IHC and western blotting were conducted to measure proteins. Intrathecal injection for corresponding siRNAs in C57/BL6 mice or spinal microinjection for virus in YTHDF1^flox/flox mice were applied to specially knockdown the expression of molecular. Von Frey, acetone test and ethyl chloride (EC) test were applied to evaluate NP behavior. YTHDF1, Wnt3a, TNF-α and IL-18 were increased in oxaliplatin treated mice, restricted the molecular mentioned above respectively can significantly attenuate oxaliplatin-induced NP, including the mechanical allodynia and cold allodynia. Silencing YTHDF1 and inhibiting Wnt3a and Wnt signaling pathways can reduce the enhancement of TNF-α and IL-18, and the decreasing of the upregulation of YTHDF1 can be found when inhibiting Wnt3a and Wnts signaling pathways in oxaliplatin treated mice. Our study indicated a novel pathway that can contribute to oxaliplatin-induced NP, the Wnt3a/YTHDF1 to cytokine pathway, which upregulating YTHDF1 functioned as the downstream of Wnt3a signal and promoted the translation of TNF-α and IL-18 in oxaliplatin treated mice.

A synthetic prostaglandin E1 analogue, misoprostol, ameliorates paclitaxel-induced oxidative damage in rat brain

The main objective of our study was to examine the protection of misoprostol (MP) on paclitaxel (PAX) side effects in rat brains. Twenty-eight female Sprague-Dawley rats were provided to form 4 groups, each containing seven rats: the control group was given 1 mL of 0.9% NaCl intraperitoneally (i.p.) and 1 mL of 0.9% NaCl orally for six days. In treatment groups, each rat was injected with 2 mg/kg PAX i.p. on days 0, 2, 4, and 6 of the study, and 0.2 mg/kg/day MP was given by oral gavage for six days. Levels of malondialdehyde (MDA) and glutathione (GSH), activities of superoxide dismutase (SOD), and catalase (CAT) of tissue samples were measured. In immunohistochemical analyzes, it was observed that tumor necrosis factor-alpha (TNF-α) and cleaved caspase-3 expression in the cerebellum hippocampus and cerebral cortex were increased in the PAX group compared to the other groups. The increase in TNF-α and cleaved caspase-3 expression detected in PAX group rats were significantly decreased in the PAX + MP group. The results obtained in this study confirm the hypotheses that PAX can increase apoptosis in brain tissue both directly and through cytokines such as TNF-α. It also shows that MP can be used as a protective and therapeutic pharmacological agent against the harmful effects of PAX on brain tissue. In addition, it seems that the use of MP can improve PAX-induced brain damage by preventing oxidative damage.

Neuro-immune interactions in paclitaxel-induced peripheral neuropathy

BACKGROUND

Paclitaxel is a taxane-based chemotherapeutic agent used as a treatment in breast cancer. There is no effective prevention or treatment strategy for the most common side effect of peripheral neuropathy. In this manuscript, we reviewed the molecular mechanisms that contribute to paclitaxel-induced peripheral neuropathy (PIPN) with an emphasis on immune-related processes.

METHODS

A systematic search of the literature was conducted in PubMed, EMBASE and Cochrane Library. The SYRCLE's risk of bias tool was used to assess internal validity.

RESULTS

156 studies conducted with rodent models were included. The risk of bias was high due to unclear methodology. Paclitaxel induces changes in myelinated axons, mitochondrial dysfunction, and mechanical hypersensitivity by affecting ion channels expression and function and facilitating spinal transmission. Paclitaxel-induced inflammatory responses are important contributors to PIPN.

CONCLUSION

Immune-related processes are an important mechanism contributing to PIPN. Studies in humans that validate these mechanistic data are highly needed to facilitate the development of therapeutic strategies.

Review of the Role of the Brain in Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a common, debilitating, and dose-limiting side effect of many chemotherapy regimens yet has limited treatments due to incomplete knowledge of its pathophysiology. Research on the pathophysiology of CIPN has focused on peripheral nerves because CIPN symptoms are felt in the hands and feet. However, better understanding the role of the brain in CIPN may accelerate understanding, diagnosing, and treating CIPN. The goals of this review are to (1) investigate the role of the brain in CIPN, and (2) use this knowledge to inform future research and treatment of CIPN. We identified 16 papers using brain interventions in animal models of CIPN and five papers using brain imaging in humans or monkeys with CIPN. These studies suggest that CIPN is partly caused by (1) brain hyperactivity, (2) reduced GABAergic inhibition, (3) neuroinflammation, and (4) overactivation of GPCR/MAPK pathways. These four features were observed in several brain regions including the thalamus, periaqueductal gray, anterior cingulate cortex, somatosensory cortex, and insula. We discuss how to leverage this knowledge for future preclinical research, clinical research, and brain-based treatments for CIPN.

Cytokine receptor clustering in sensory neurons with an engineered cytokine fusion protein triggers unique pain resolution pathways

New therapeutic approaches to resolve persistent pain are highly needed. We tested the hypothesis that manipulation of cytokine receptors on sensory neurons by clustering regulatory cytokine receptor pairs with a fusion protein of interleukin (IL)-4 and IL-10 (IL4-10 FP) would redirect signaling pathways to optimally boost pain-resolution pathways. We demonstrate that a population of mouse sensory neurons express both receptors for the regulatory cytokines IL-4 and IL-10. This population increases during persistent inflammatory pain. Triggering these receptors with IL4-10 FP has unheralded biological effects, because it resolves inflammatory pain in both male and female mice. Knockdown of both IL4 and IL10 receptors in sensory neurons in vivo ablated the IL4-10 FP-mediated inhibition of inflammatory pain. Knockdown of either one of the receptors prevented the analgesic gain-of-function of IL4-10 FP. In vitro, IL4-10 FP inhibited inflammatory mediator-induced neuronal sensitization more effectively than the combination of cytokines, confirming its superior activity. The IL4-10 FP, contrary to the combination of IL-4 and IL-10, promoted clustering of IL-4 and IL-10 receptors in sensory neurons, leading to unique signaling, that is exemplified by activation of shifts in the cellular kinome and transcriptome. Interrogation of the potentially involved signal pathways led us to identify JAK1 as a key downstream signaling element that mediates the superior analgesic effects of IL4-10 FP. Thus, IL4-10 FP constitutes an immune-biologic that clusters regulatory cytokine receptors in sensory neurons to transduce unique signaling pathways required for full resolution of persistent inflammatory pain.

[Escin alleviates chemotherapy-induced peripheral neuropathic pain by inducing autophagy in the spinal cord of rats]

OBJECTIVE

To investigate the effect of escin in relieving chemotherapy-induced peripheral neuropathic pain in rats and explore and the underlying mechanism.

METHODS

Eighteen SD rats were randomly divided into 3 groups (n=6), including an escin preconditioning group (treated with 4 mg/kg escin on days 1-7 and then with 2 mg/kg taxol on days 8, 10, 12, and 14), an escin postconditioning group (treated with 2 mg/kg taxol on days 1, 3, 5, and 7 and then with 4 mg/mg escin on days 8-14) and control group (treated with 2 mg/kg taxol on days 1, 3, 5, and 7 and then with saline on days 8-14). Mechanical allodynia and thermal hyperalgesia of the mice were tested on days 4, 7, 10 and 14, and the expression levels of LC3II and p62 in the spinal cord of the rats were detected using Western blotting.

RESULTS

The rats in both the escin preconditioning group and escin postconditioning group showed obviously increased thresholds of mechanical allodynia and thermal hyperalgesia as compared with those in the control group (P < 0.01). Western blotting showed that the expression level of LC3II was significantly increased while p62 expression was lowered in escin preconditioning group as compared with those in the control group (P < 0.05). The escin postconditioning group also showed significantly higher LC3II expression and lower p62 expression levels than the control group (P < 0.05).

CONCLUSIONS

Escin can alleviate chemotherapy-induced peripheral neuropathic pain in rats possibly by upregulating the expressions of autophagy-related proteins in the spinal cord.

Co-administration of paclitaxel and 2-methoxyestradiol using folate-conjugated human serum albumin nanoparticles for improving drug resistance and antitumor efficacy

The use of chemotherapeutic drug paclitaxel (PTX) for the treatment of tumors has several limitations, including multidrug resistance (MDR) and serious adverse reactions. This research aims to co-encapsulate PTX and the chemosensitizer 2-methoxyestradiol (2-ME) into folate-conjugated human serum albumin nanoparticles (FA-HSANPs) to reduce multiple drug resistance and improve antitumor efficiency. The results show PTX/2-ME@FA-HSANPs had uniform particle size (180 ± 12.31 nm) and high encapsulation efficacy. It also exhibited highly potent cytotoxicity and apoptosis-inducing activities in the G2/M phase of PTX-resistant EC109/Taxol cells. Moreover, PTX/2-ME@FA-HSANPs not only displayed better inhibition of tumor growth in S-180 tumor-bearing mice than PTX alone but also reduced pathological damage to normal tissues. In summary, PTX/2-ME@FA-HSANPs could be a promising vehicle for tumor therapy and reducing drug resistance. This research will also provide references for other MDR treatment.

Nrf2 activation ameliorates mechanical allodynia in paclitaxel-induced neuropathic pain

Paclitaxel-induced neuropathic pain (PINP) is refractory to currently used analgesics. Previous studies show a pivotal role of oxidative stress in PINP. Because the nuclear factor erythroid-2-related factor 2 (Nrf2) has been considered as the critical regulator of endogenous antioxidant defense, we here explored whether activation of Nrf2 could attenuate PINP. A rat model of PINP was established by intraperitoneal injection of paclitaxel (2 mg/kg) every other day with a final cumulative dose of 8 mg/kg. Hind paw withdrawal thresholds (PWTs) in response to von Frey filament stimuli were used to assess mechanical allodynia. We showed that a single dose of Nrf2 activator, oltipraz (10, 50, and 100 mg/kg), dose-dependently attenuated established mechanical allodynia, whereas repeated injection of oltipraz (100 mg· kg-1· d-1, i.p. from d 14 to d 18) almost abolished the mechanical allodynia in PINP rats. The antinociceptive effect of oltipraz was blocked by pre-injection of Nrf2 inhibitor trigonelline (20 mg/kg, i.p.). Early treatment with oltipraz (100 mg· kg-1· d-1, i.p. from d 0 to d 6) failed to prevent the development of the PINP, but delayed its onset. Western blot and immunofluorescence analysis revealed that the expression levels of Nrf2 and HO-1 were significantly upregulated in the spinal cord of PINP rats. Repeated injection of oltipraz caused further elevation of the expression levels of Nrf2 and HO-1 in the spinal cord of PINP rats, which was reversed by pre-injection of trigonelline. These results demonstrate that oltipraz ameliorates PINP via activating Nrf2/HO-1-signaling pathway in the spinal cord.

Psychoneuroimmunology goes East: Development of the PNIRSChina affiliate and its expansion into PNIRSAsia-Pacific

The Psychoneuroimmunology Research Society (PNIRS) created an official Chinese regional affiliate in 2012, designated PNIRS_China. Now, just eight years later, the program has been so successful in advancing the science of psychoneuroimmunology that it has expanded to the whole of Asia-Oceania. In 2017, PNIRS_China became PNIRS_Asia-Pacific. Between 2012 and 2019, this outreach affiliate of PNIRS organized seven symposia at major scientific meetings in China as well as nine others in Taiwan, Japan, South Korea, Australia and New Zealand. This paper summarizes the remarkable growth of PNIRS_Asia-Pacific. Here, regional experts who have been instrumental in organizing these PNIRS_Asia-Pacific symposia briefly review and share their views about the past, present and future state of psychoneuroimmunology research in China, Taiwan, Australia and Japan. The newest initiative of PNIRS_Asia-Pacific is connecting Asia-Pacific laboratories with those in Western countries through a simple web-based registration system. These efforts not only contribute to the efforts of PNIRS to serve a truly global scientific society but also to answer the imperative call of increasing diversity in our science.

JTC-801 alleviates mechanical allodynia in paclitaxel-induced neuropathic pain through the PI3K/Akt pathway

Chemotherapy-induced peripheral neuropathy is a serious adverse effect of chemotherapeutic agents such as paclitaxel. JTC-801, a nociceptin/orphanin FQ opioid peptide (NOP) receptor antagonist, has been reported to attenuate neuropathic pain in several pain models. However, the therapeutic significance and function of JTC-801 in chemotherapy-induced peripheral neuropathy remain unclear. In this study, we determined the effect of JTC-801 on neuropathic pain induced by paclitaxel, and we explored the potential mechanism in the dorsal root ganglion (DRG). The behavioral test showed that single or multiple systemic administrations of JTC-801 significantly alleviated mechanical allodynia in paclitaxel-treated rats. Using Western blot analysis and immunohistochemistry, we found that paclitaxel increased the expression of phosphatidylinositol 3-kinase (PI3K) and phospho-Akt (p-Akt) in the DRG. Double immunofluorescence staining indicated that p-Akt was expressed in neurons in the DRG. Multiple injections of JTC-801 significantly inhibited the activation of Akt and decreased the expression of inflammatory cytokines. The data suggest that JTC-801 alleviates mechanical allodynia associated with paclitaxel-induced neuropathic pain via the PI3K/Akt pathway.

Cortical Binding Potential of Opioid Receptors in Patients With Fibromyalgia Syndrome and Reduced Systemic Interleukin-4 Levels - A Pilot Study

Objective: We investigated cerebral opioid receptor binding potential in patients with fibromyalgia syndrome (FMS) using positron-emission-tomography (PET) and correlated our results with patients’ systemic interleukin-4 (IL-4) gene expression.

Methods: In this pilot study, seven FMS patients (1 man, 6 women) agreed to participate in experimental PET scans. All patients underwent neurological examination, were investigated with questionnaires for pain, depression, and FMS symptoms. Additionally, blood for IL-4 gene expression analysis was withdrawn at two time points with a median latency of 1.3 years. Patients were investigated in a PET scanner using the opioid receptor ligand F-18-fluoro-ethyl-diprenorphine ([18F]FEDPN) and results were compared with laboratory normative values.

Results: Neurological examination was normal in all FMS patients. Reduced opioid receptor binding was found in mid cingulate cortex compared to healthy controls (p < 0.005). Interestingly, three patients with high systemic IL-4 gene expression had increased opioid receptor binding in the fronto-basal cortex compared to those with low IL-4 gene expression (p < 0.005).

Conclusion: Our data give further evidence for a reduction in cortical opioid receptor availability in FMS patients as another potential central nervous system contributor to pain in FMS.

Upregulation of TRPC6 Mediated by PAX6 Hypomethylation Is Involved in the Mechanical Allodynia Induced by Chemotherapeutics in Dorsal Root Ganglion

BACKGROUND

Although the action mechanism of antineoplastic agents is different, oxaliplatin, paclitaxel, or bortezomib as first-line antineoplastic drugs can induce painful neuropathy. In rodents, mechanical allodynia is a common phenotype of painful neuropathy for 3 chemotherapeutics. However, whether there is a common molecular involved in the different chemotherapeutics-induced painful peripheral neuropathy remains unclear.

METHODS

Mechanical allodynia was tested by von Frey hairs following i.p. injection of vehicle, oxaliplatin, paclitaxel, or bortezomib in Sprague-Dawley rats. Reduced representation bisulfite sequencing and methylated DNA immunoprecipitation were used to detect the change of DNA methylation. Western blot, quantitative polymerase chain reaction, chromatin immunoprecipitation, and immunohistochemistry were employed to explore the molecular mechanisms.

RESULTS

In 3 chemotherapeutic models, oxaliplatin, paclitaxel, or bortezomib accordantly upregulated the expression of transient receptor potential cation channel, subfamily C6 (TRPC6) mRNA and protein without affecting the DNA methylation level of TRPC6 gene in DRG. Inhibition of TRPC6 by using TRPC6 siRNA (i.t., 10 consecutive days) relieved mechanical allodynia significantly following application of chemotherapeutics. Furthermore, the downregulated recruitment of DNA methyltransferase 3 beta (DNMT3b) at paired box protein 6 (PAX6) gene led to the hypomethylation of PAX6 gene and increased PAX6 expression. Finally, the increased PAX6 via binding to the TPRC6 promoter contributes to the TRPC6 increase and mechanical allodynia following chemotherapeutics treatment.

CONCLUSIONS

The TRPC6 upregulation through DNMT3b-mediated PAX6 gene hypomethylation participated in mechanical allodynia following application of different chemotherapeutic drugs.

FK506 (tacrolimus) causes pain sensation through the activation of transient receptor potential ankyrin 1 (TRPA1) channels

FK506 (tacrolimus) is an immunosuppressant widely used as an ointment in the treatment of atopic dermatitis. However, local application of FK506 can evoke burning sensations in atopic dermatitis patients, and its mechanisms are unknown. In this study, we found that FK506 activates transient receptor potential ankyrin 1 (TRPA1) channels. In Ca2+-imaging experiments, increases in intracellular Ca2+ concentrations ([Ca2+]i) by FK506 were observed in HEK293T cells expressing hTRPA1 or hTRPM8. FK506-induced currents were observed in HEK293T cells expressing hTRPA1 or mTRPA1, but less or not at all in cells expressing hTRPV1 or hTRPM8 using a patch-clamp technique. FK506 also evoked single-channel opening of hTRPA1 in an inside-out configuration. FK506-induced [Ca2+]i increases were also observed in TRPA1-expressing mouse primary sensory neurons. Furthermore, injection of FK506 evoked licking or biting behaviors and these behaviors were almost abolished in TRPA1 knockout mice. These results indicate that FK506 might cause pain sensations through TRPA1 activation.

DNMT3a-triggered downregulation of K2p 1.1 gene in primary sensory neurons contributes to paclitaxel-induced neuropathic pain

Antineoplastic drugs induce dramatic transcriptional changes in dorsal root ganglion (DRG) neurons, which may contribute to chemotherapy-induced neuropathic pain. K_2p 1.1 controls neuronal excitability by setting the resting membrane potential. Here, we report that systemic injection of the chemotherapy agent paclitaxel time-dependently downregulates the expression of K _2p 1.1 mRNA and its coding K_2p 1.1 protein in the DRG neurons. Rescuing this downregulation mitigates the development and maintenance of paclitaxel-induced mechanical allodynia and heat hyperalgesia. Conversely, in the absence of paclitaxel administration, mimicking this downregulation decreases outward potassium current and increases excitability in the DRG neurons, leading to the enhanced responses to mechanical and heat stimuli. Mechanically, the downregulation of DRG K _2p 1.1 mRNA is attributed to paclitaxel-induced increase in DRG DNMT3a, as blocking this increase reverses the paclitaxel-induced the decrease of DRG K_2p 1.1 and mimicking this increase reduces DRG K_2p 1.1 expression. In addition, paclitaxel injection increases the binding of DNMT3a to the K _2p 1.1 gene promoter region and elevates the level of DNA methylation within this region in the DRG. These findings suggest that DNMT3a-triggered downregulation of DRG K_2p 1.1 may contribute to chemotherapy-induced neuropathic pain.