Paclitaxel Induces Sex-biased Behavioral Deficits and Changes in Gene Expression in Mouse Prefrontal Cortex

Naringenin relieves paclitaxel-induced pain by suppressing calcitonin gene-related peptide signalling and enhances the anti-tumour action of paclitaxel

BACKGROUND AND PURPOSE

Chemotherapy-induced peripheral neuropathy (CIPN) commonly causes neuropathic pain, but its pathogenesis remains unclear, and effective therapies are lacking. Naringenin, a natural dihydroflavonoid compound, has anti-inflammatory, anti-nociceptive and anti-tumour activities. However, the effects of naringenin on chemotherapy-induced pain and chemotherapy effectiveness remain unexplored.

EXPERIMENTAL APPROACH

Female and male mouse models of chemotherapy-induced pain were established using paclitaxel. Effects of naringenin were assessed on pain induced by paclitaxel or calcitonin gene-related peptide (CGRP) and on CGRP expression in dorsal root ganglia (DRG) and spinal cord tissue. Additionally, we examined peripheral macrophage infiltration, glial activation, c-fos expression, DRG neuron excitability, microglial M1/M2 polarization, and phosphorylation of spinal NF-κB. Furthermore, we investigated the synergic effect and related mechanisms of naringenin and paclitaxel on cell survival of cancer cells in vitro.

KEY RESULTS

Systemic administration of naringenin attenuated paclitaxel-induced pain in both sexes. Naringenin reduced paclitaxel-enhanced CGRP expression in DRGs and the spinal cord, and alleviated CGRP-induced pain in naïve mice of both sexes. Naringenin mitigated macrophage infiltration and reversed paclitaxel-elevated c-fos expression and DRG neuron excitability. Naringenin decreased spinal glial activation and NF-κB phosphorylation in both sexes but influenced microglial M1/M2 polarization only in females. Co-administration of naringenin with paclitaxel enhanced paclitaxel's anti-tumour effect, impeded by an apoptosis inhibitor.

CONCLUSION AND IMPLICATIONS

Naringenin's anti-nociceptive mechanism involves CGRP signalling and neuroimmunoregulation. Furthermore, naringenin facilitates paclitaxel's anti-tumour action, possibly involving apoptosis. This study demonstrates naringenin's potential as a supplementary treatment in cancer therapy by mitigating side effects and potentiating efficacy of chemotherapy.

Downregulation of lysine-specific histone demethylase 1A (KDM1A/LSD1) in medial prefrontal cortex facilitates chronic stress-induced pain and emotional dysfunction in female mice

Chronic primary pain, characterized by overlapping symptoms of chronic pain, anxiety, and depression, is strongly associated with stress and is particularly prevalent among females. Recent research has convincingly linked epigenetic modifications in the medial prefrontal cortex (mPFC) to chronic pain and chronic stress. However, our understanding of the role of histone demethylation in the mPFC in chronic stress-induced pain remains limited. In this study, we investigated the function of lysine-specific histone demethylase 1A (KDM1A/LSD1) in the context of chronic overlapping pain comorbid with anxiety and depression in female mice. We employed a chronic variable stress model to induce pain hypersensitivity in the face and hindpaws, as well as anxiety-like and depression-like behaviors, in female mice. Our findings revealed that chronic stress led to a downregulation of KDM1A mRNA and protein expression in the mPFC. Notably, overexpressing KDM1A in the mPFC alleviated the pain hypersensitivity, anxiety-like behaviors, and depression-like behaviors in female mice, without affecting basal pain responses or inducing emotional distress. Conversely, conditional knockout of KDM1A in the mPFC exacerbated pain sensitivity and emotional distress specifically in females. In summary, this study highlights the crucial role of KDM1A in the mPFC in modulating chronic stress-induced overlapping pain, anxiety, and depression in females. Our findings suggest that KDM1A may serve as a potential therapeutic target for treating chronic stress-related overlap pain and associated negative emotional disorders.

Paclitaxel-Associated Mechanical Sensitivity and Neuroinflammation Are Sex-, Time-, and Site-Specific and Prevented through Cannabigerol Administration in C57Bl/6 Mice

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most prevalent and dose-limiting complications in chemotherapy patients. One identified mechanism underlying CIPN is neuroinflammation. Most of this research has been conducted in only male or female rodent models, making direct comparisons regarding the role of sex differences in the neuroimmune underpinnings of CIPN limited. Moreover, most measurements have focused on the dorsal root ganglia (DRG) and/or spinal cord, while relatively few studies have been aimed at characterizing neuroinflammation in the brain, for example the periaqueductal grey (PAG). The overall goals of the present study were to determine (1) paclitaxel-associated changes in markers of inflammation in the PAG and DRG in male and female C57Bl6 mice and (2) determine the effect of prophylactic administration of an anti-inflammatory cannabinoid, cannabigerol (CBG). In Experiment 1, male and female mice were treated with paclitaxel (8-32 mg/kg/injection, Days 1, 3, 5, and 7) and mechanical sensitivity was measured using Von Frey filaments on Day 7 (Cohort 1) and Day 14 (Cohort 2). Cohorts were euthanized on Day 8 or 15, respectively, and DRG and PAG were harvested for qPCR analysis of the gene expression of markers of pain and inflammation Aig1, Gfap, Ccl2, Cxcl9, Tlr4, Il6, and Calca. In Experiment 2, male and female mice were treated with vehicle or 10 mg/kg CBG i.p. 30 min prior to each paclitaxel injection. Mechanical sensitivity was measured on Day 14. Mice were euthanized on Day 15, and PAG were harvested for qPCR analysis of the gene expression of Aig1, Gfap, Ccl2, Cxcl9, Tlr4, Il6, and Calca. Paclitaxel produced a transient increase in potency to produce mechanical sensitivity in male versus female mice. Regarding neuroinflammation, more gene expression changes were apparent earlier in the DRG and at a later time point in the PAG. Also, more changes were observed in females in the PAG than males. Overall, sex differences were observed for most markers at both time points and regions. Importantly, in both the DRG and PAG, most increases in markers of neuroinflammation and pain occurred at paclitaxel doses higher than those associated with significant changes in the mechanical threshold. Two analytes that demonstrated the most compelling sexual dimorphism and that changed more in males were Cxcl9 and Ccl2, and Tlr4 in females. Lastly, prophylactic administration of CBG protected the male and female mice from increased mechanical sensitivity and female mice from neuroinflammation in the PAG. Future studies are warranted to explore how these sex differences may shed light on the mechanisms of CIPN and how non-psychoactive cannabinoids such as CBG may engage these targets to prevent or attenuate the effects of paclitaxel and other chemotherapeutic agents on the nervous system.

Translational PK-PD/TD modeling of antitumor effects and peripheral neuropathy in gemcitabine and nab-paclitaxel chemotherapy from xenograft mice to patients for optimal dose and schedule

PURPOSE

Gemcitabine and nab-paclitaxel (GnP) treatment, the standard first-line chemotherapy for unresectable pancreatic cancer, often causes peripheral neuropathy (PN). To develop alternative dosing strategies to avoid severe PN, understanding the relationship between pharmacokinetics (PK) and pharmacodynamics/toxicodynamics (PD/TD) is necessary. We established a PK-PD/TD model of GnP treatment to develop an optimal dose schedule.

METHODS

A mouse xenograft model of human pancreatic cancer was generated to measure drug concentrations in the plasma and tumor, antitumor effects, and PN after GnP treatment. The Simeoni tumor growth inhibition model with tumor concentrations and empirical indirect response models were used for the PD and TD models, respectively. Clinical outcomes were predicted with reported population estimates of PK parameters in cancer patients.

RESULTS

The PK-PD/TD model simultaneously described the observed tumor volume and paw withdrawal frequency in the von Frey test. For the standard GnP regimen, the model predicted clinical overall response (75.1%), which was overestimated compared to that in a recent phase II study (42.1%) but lower than the observed disease control rate (96.5%). Model simulation showed that dose reduction to less than 40% GnP dose was not effective; a change of dose schedule from every week for 3 weeks to every 2 weeks was a more favorable approach than dose reduction to 60% every week.

CONCLUSION

The PK-PD/TD model-based translational approach provides a guide for optimal dose determination to avoid severe PN while maintaining antitumor effects during GnP chemotherapy. Further research is needed to enhance its applicability and potential for combination chemotherapy regimens.

Spinal interleukin-16 mediates inflammatory pain via promoting glial activation

Proinflammatory cytokines are crucial contributors to neuroinflammation in the development of chronic pain. Here, we identified il16, which encodes interleukin-16 (IL-16), as a differentially expressed gene in spinal dorsal horn of a complete Freund's Adjuvant (CFA) inflammatory pain model in mice by RNA sequencing. We further investigated whether and how IL-16 regulates pain transmission in the spinal cord and contributes to the development of inflammatory pain hypersensitivity. RNA sequencing and bioinformatics analysis revealed elevated IL-16 transcript levels in the spinal dorsal horn after CFA injection. This increase was further confirmed by qPCR, immunofluorescence, and western blotting. Knockdown of IL-16 by intrathecal injection of IL-16 siRNA not only attenuated CFA-induced mechanical and thermal pain hypersensitivity, but also inhibited enhanced c-fos expression and glial activation in the spinal dorsal horn in male mice injected with CFA. Moreover, exogenous IL-16 induced nociceptive responses and increased c-fos expression and glial activation in spinal dorsal horn. This effect was largely impaired when CD4, the binding receptor for IL-16, was inhibited. In addition, CD4 expression was upregulated in the spinal dorsal horn after CFA injection and CD4 was present in microglia and in contact with astrocytes and activated spinal neurons. Taken together, these results suggest that enhanced IL-16-CD4 signaling triggers pain and activates microglia and astrocytes in the spinal dorsal horn, thus contributing to inflammatory pain. IL-16 may serve as a promising target for the treatment of inflammatory pain.

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.

Spinal apolipoprotein E is involved in inflammatory pain via regulating lipid metabolism and glial activation in the spinal dorsal horn

INTRODUCTION

Inflammation and nerve injury promote astrocyte activation, which regulates the development and resolution of pain, in the spinal dorsal horn. APOE regulates lipid metabolism and is predominantly expressed in the astrocytes. However, the effect of astrocytic APOE and lipid metabolism on spinal cellular function is unclear. This study aimed to investigate the effect of spinal Apoe on spinal cellular functions using the complete Freund's adjuvant (CFA)-induced inflammatory pain mouse model.

METHODS

After intraplantar injection of CFA, we assessed pain behaviors in C57BL6 and Apoe knockout (Apoe-/-) mice using von Frey and Hargreaves' tests and analyzed dorsal horn samples (L4-5) using western blotting, immunofluorescence, quantitative real-time polymerase chain reaction, and RNA sequencing.

RESULTS

The Apoe levels were markedly upregulated at 2 h and on days 1 and 3 post-CFA treatment. Apoe was exclusively expressed in the astrocytes. Apoe-/- mice exhibited decreased pain on day 1, but not at 2 h, post-CFA treatment. Apoe-/- mice also showed decreased spinal neuron excitability and paw edema on day 1 post-CFA treatment. Global transcriptomic analysis of the dorsal horn on day 1 post-CFA treatment revealed that the differentially expressed mRNAs in Apoe-/- mice were associated with lipid metabolism and the immune system. Astrocyte activation was impaired in Apoe-/- mice on day 1 post-CFA treatment. The intrathecal injection of Apoe antisense oligonucleotide mitigated CFA-induced pain hypersensitivity.

CONCLUSIONS

Apoe deficiency altered lipid metabolism in astrocytes, exerting regulatory effects on immune response, astrocyte activation, and neuronal activity and consequently disrupting the maintenance of inflammatory pain after peripheral inflammation. Targeting APOE is a potential anti-nociception and anti-inflammatory strategy.

Melatonin Relieves Paclitaxel-Induced Neuropathic Pain by Regulating pNEK2-Dependent Epigenetic Pathways in DRG Neurons

The neurohormone melatonin (MLT) demonstrates promising potential in ameliorating neuropathic pain induced by paclitaxel (PTX) chemotherapy. However, little is known about its protective effect on dorsal root ganglion (DRG) neurons in neuropathic pain resulting from the chemotherapeutic drug PTX. Here, PTX-treated rats revealed that intrathecal administration of MLT dose-dependently elevated hind paw withdrawal thresholds and latency, indicating that MLT significantly reversed PTX-induced neuropathic pain. Mechanistically, the analgesic effects of MLT were found to be mediated via melatonin receptor 2 (MT2), as pretreatment with an MT2 receptor antagonist inhibited these effects. Moreover, intrathecal MLT injection reversed the pNEK2-dependent epigenetic program induced by PTX. All of the effects caused by MLT were blocked by pretreatment with an MT2 receptor-selective antagonist, 4P-PDOT. Remarkably, multiple MLT administered during PTX treatment (PTX+MLTs) exhibited not only rapid but also lasting reversal of allodynia/hyperalgesia compared to single-bolus MLT administered after PTX treatment (PTX+MLT). In addition, PTX+MLTs exhibited greater efficacy in reversing PTX-induced alterations in pRSK2, pNEK2, JMJD3, H3K27me3, and TRPV1 expression and interaction in DRG neurons than PTX+MLT. These results indicated that MLT administered during PTX treatment reduced the incidence and/or severity of neuropathy and had a better inhibitory effect on the pNEK2-dependent epigenetic program compared to MLT administered after PTX treatment. In conclusion, MLT/MT2 is a promising therapy for the treatment of pNEK2-dependent painful neuropathy resulting from PTX treatment. MLT administered during PTX chemotherapy may be more effective in the prevention or reduction of PTX-induced neuropathy and maintaining quality.

CoREST1 in primary sensory neurons regulates neuropathic pain in male mice

AIMS

Epigenetic regulation is implicated in the neurogenesis of neuropathic pain. The repressor element 1 (RE1) silencing transcription factor (REST) corepressor (CoREST) proteins function as corepressors in the REST complex and/or LSD1 epigenetic complex. In the current study, we aimed to find the expression profile of CoREST1 in the dorsal root ganglion (DRG) and investigate whether it plays a role in neuropathic pain.

MAIN METHODS

The evoked pain behaviors in mice were examined by the von Frey test and thermal test in a spinal nerve ligation (SNL)-induced neuropathic pain mice model. CoREST1 siRNA or virus was administered by DRG microinjection or intrathecal injection. The CoREST1 expression in DRGs was examined by immunofluorescence, quantitative PCR, Western blotting, and co-immunoprecipitation.

KEY FINDINGS

CoREST1 was non-selectively expressed in large, medium, and small DRG neurons, and it exclusively colocalized with LSD1. In neuropathic pain models, peripheral nerve injury induced the upregulation of CoREST1 and increased binding of CoREST1 with LSD1 in injured DRGs in male mice. Furthermore, CoREST1 siRNA prevented the development of SNL-induced pain hypersensitivity as well as led to the reduction of established pain hypersensitivity during the maintenance period in SNL mice. Conversely, the overexpression of CoREST1 in DRGs by in vivo transfection of virus-induced pain hypersensitivity in naive mice.

SIGNIFICANCE

Our study demonstrated that CoREST1, along with LSD1, was expressed in primary sensory neurons specifically in response to nerve injury, and promoted nociceptive pain hypersensitivity in mice. Thus, CoREST1 might serve as a potential target for treating neuropathic pain.

Nerve injury-induced upregulation of apolipoprotein E in dorsal root ganglion participates in neuropathic pain in male mice

Apolipoprotein E (ApoE) is an apolipoprotein involved in lipid metabolism and is primarily responsible for lipid transport and cholesterol homeostasis in the central nervous system (CNS). The aim of this study is to explore the role of ApoE in the pathological development of neuropathic pain. First, we examined the location of ApoE in the dorsal root ganglion (DRG) and spinal cord in male mice using immunohistochemistry, and found that ApoE was predominantly expressed in DRG satellite glial cells (SGCs) and macrophages and spinal cord astrocytes. Using a spinal nerve ligation (SNL)-induced neuropathic pain mouse model, we found that nerve injury caused an increase in ApoE expression in the injured DRGs, but not in the spinal cord after SNL surgery. Furthermore, we observed reduced SNL-induced pain hypersensitivity in ApoE knockout mice compared to wild-type mice. Moreover, an antisense oligonucleotide (ASO) targeting the Apoe gene sequence, which was microinjected into the DRG or administered intrathecally, not only reduced ApoE expression in DRG but also attenuated SNL-induced pain hypersensitivity. Finally, we found that a tyrosine kinase receptor AXL, which was previously demonstrated to contribute to neuropathic pain, may mediate ApoE function under neuropathic pain condition. In conclusion, our data suggest that ApoE in DRG promote pain hypersensitivity via the DRG membrane receptor AXL in neurons under neuropathic pain conditions. This study revealed a novel mechanism between lipid homeostasis and neuropathic pain.

New Treatment for the Cognitive and Emotional Deficits Linked with Paclitaxel-Induced Peripheral Neuropathy in Mice

Chemotherapy-provoked peripheral neuropathy and its linked comorbidities severely reduce the quality of a patient's life. Its therapy is not completely resolved and has become an important clinical challenge. The protective actions of molecular hydrogen (H₂) in many neurological disorders have been described, but its effects on memory and the emotional deficits accompanying neuropathic pain induced by chemotherapy remain unknown. In this study, using male mice injected with paclitaxel (PTX), we examined the effects of systemic treatment with hydrogen-rich water (HRW) in: (i) the mechanical and thermal allodynia provoked by PTX and the pathways involved; (ii) the memory deficits, anxiety- and depressive-like behaviors associated with PTX-induced peripheral neuropathy (PIPN); and (iii) the plasticity (p-extracellular signal-regulated protein kinase; p-ERK ½), nociceptive (p-protein kinase B, p-Akt), inflammatory (p-nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha; p-IKBα), and oxidative (4-hydroxynonenal: 4-HNE) alterations provoked by PIPN in the prefrontal cortex (PFC). The results revealed: (1) the antiallodynic actions of HRW administered at one or two times per day during 7 and 3 consecutive days; (2) the participation of Kv7 potassium channels and the Nrf2-heme oxygenase 1-NAD(P)H: quinone oxidoreductase 1 pathway in the painkiller effects of HRW; (3) the inhibition of memory deficits and the anxiodepressive-like behaviors related with PIPN induced by HRW; and (4) the normalization of p-ERK ½, p-Akt and 4-HNE up-regulation and the activation of antioxidant enzymes produced by this treatment in PFC. This study proposes HRW as a possible effective and safe therapy for PIPN and its associated cognitive and emotional deficits.

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.

Transcriptome analysis of microRNAs, circRNAs, and mRNAs in the dorsal root ganglia of paclitaxel-induced mice with neuropathic pain

The microtubule-stabilizing drug paclitaxel (PTX) is a chemotherapeutic agent widely prescribed for the treatment of various tumor types. The main adverse effect of PTX-mediated therapy is chemotherapy-induced peripheral neuropathy (CIPN) and neuropathic pain, which are similar to the adverse effects associated with other chemotherapeutic agents. Dorsal root ganglia (DRG) contain primary sensory neurons; any damage to these neurons or their axons may lead to neuropathic pain. To gain molecular and neurobiological insights into the peripheral sensory system under conditions of PTX-induced neuropathic pain, we used transcriptomic analysis to profile mRNA and non-coding RNA expression in the DRGs of adult male C57BL/6 mice treated using PTX. RNA sequencing and in-depth gene expression analysis were used to analyze the expression levels of 67,228 genes. We identified 372 differentially expressed genes (DEGs) in the DRGs of vehicle- and PTX-treated mice. Among the 372 DEGs, there were 8 mRNAs, 3 long non-coding RNAs (lncRNAs), 16 circular RNAs (circRNAs), and 345 microRNAs (miRNAs). Moreover, the changes in the expression levels of several miRNAs and circRNAs induced by PTX have been confirmed using the quantitative polymerase chain reaction method. In addition, we compared the expression levels of differentially expressed miRNAs and mRNA in the DRGs of mice with PTX-induced neuropathic pain against those evaluated in other models of neuropathic pain induced by other chemotherapeutic agents, nerve injury, or diabetes. There are dozens of shared differentially expressed miRNAs between PTX and diabetes, but only a few shared miRNAs between PTX and nerve injury. Meanwhile, there is no shared differentially expressed mRNA between PTX and nerve injury. In conclusion, herein, we show that treatment with PTX induced numerous changes in miRNA expression in DRGs. Comparison with other neuropathic pain models indicates that DEGs in DRGs vary greatly among different models of neuropathic pain.

Sex Differences in Taxane Toxicities

Simple Summary

Clinically observed sex differences in acute and long-term taxane chemotherapy-induced normal tissue toxicity are routinely documented but remain poorly understood despite the significant impact such toxicities have on treatment tolerance and quality of life outcomes in cancer survivors. This review draws from pre-clinical and clinical literature to highlight sex-specific mechanisms of action in taxane drug toxicity and proposes hypotheses for sex-specific clinical discrepancies in taxane-induced acute and long-term toxicities. To our knowledge, this is the first review exploring how sex as a biological variable impacts taxane-mediated mechanisms of action and clinical outcomes. In doing so, we have provided a novel framework to investigate and understand common sex differences observed in clinical and pre-clinical research.

Abstract

The taxane family of microtubule poisons and chemotherapeutics have been studied for over 50 years and are among the most frequently used antineoplastic agents today. Still, limited research exists characterizing taxane-induced sex-specific mechanisms of action and toxicities in cancer and non-cancerous tissue. Such research is important to advance cancer treatment outcomes as well as to address clinically observed sex-differences in short- and long-term taxane-induced toxicities that have disproportionate effects on female and male cancer patients. To gain more insight into these underlying differences between the sexes, the following review draws from pre-clinical and clinical paclitaxel and taxane oncology literature, examines sex-discrepancies, and highlights uncharacterized sex-dependent mechanisms of action and clinical outcomes. To our knowledge, this is the first literature review to provide a current overview of the basic and clinical sex dimorphisms of taxane-induced effects. Most importantly, we hope to provide a starting point for improving and advancing sex-specific personalized chemotherapy and cancer treatment strategies as well as to present a novel approach to review sex as a biological variable in basic and clinical biology.

The Beneficial Effects of Heme Oxygenase 1 and Hydrogen Sulfide Activation in the Management of Neuropathic Pain, Anxiety- and Depressive-like Effects of Paclitaxel in Mice

Chemotherapy-induced peripheral neuropathy constitutes an unresolved clinical problem that severely decreases the quality of the patient’s life. It is characterized by somatosensory alterations, including chronic pain, and a high risk of suffering mental disorders such as depression and anxiety. Unfortunately, an effective treatment for this neuropathology is yet to be found. We investigated the therapeutic potential of cobalt protoporphyrin IX (CoPP), a heme oxygenase 1 inducer, and morpholin-4-ium 4-methoxyphenyl(morpholino) phosphinodithioate dichloromethane complex (GYY4137), a slow hydrogen sulfide (H₂S) donor, in a preclinical model of paclitaxel (PTX)-induced peripheral neuropathy (PIPN) in mice. At three weeks after PTX injection, we evaluated the effects of the repetitive administration of 5 mg/kg of CoPP and 35 mg/kg of GYY4137 on PTX-induced nociceptive symptoms (mechanical and cold allodynia) and on the associated emotional disturbances (anxiety- and depressive-like behaviors). We also studied the mechanisms that could mediate their therapeutic properties by evaluating the expression of key proteins implicated in the development of nociception, oxidative stress, microglial activation, and apoptosis in prefrontal cortex (PFC) and dorsal root ganglia (DRG) of mice with PIPN. Results demonstrate that CoPP and GYY4137 treatments inhibited both the nociceptive symptomatology and the derived emotional alterations. These actions were mainly mediated through potentiation of antioxidant responses and inhibiting oxidative stress in the DRG and/or PFC of mice with PIPN. Both treatments normalized some plasticity changes and apoptotic reactions, and GYY4137 blocked microglial activation induced by PTX in PFC. In conclusion, this study proposes CoPP and GYY4137 as good candidates for treating neuropathic pain, anxiety- and depressive-like effects of PTX.

Glutamatergic Neurons in the Amygdala Are Involved in Paclitaxel-Induced Pain and Anxiety

Paclitaxel is widely used as a first-line chemotherapy agent to treat malignant tumors. However, paclitaxel causes peripheral nerve fiber damage and neuropathic pain in some patients. In addition, patients received paclitaxel chemotherapy are often accompanied by negative emotions such as anxiety. The amygdala is critically involved in regulating pain signals, as well as anxiety. The purpose of this study is to clarify the role of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII)-positive glutamatergic neurons in the amygdala in paclitaxel-induced pain and negative affective symptoms. Intraperitoneal injection of paclitaxel into mice caused mechanical and thermal allodynia, as measured by Von Frey test and Hargreaves test, and anxiety, as measured by open field test and elevated plus maze test. Immunofluorescence staining revealed that c-fos-positive neurons were significantly more in the basolateral amygdala (BLA) and central amygdala (CeA) in paclitaxel-treated mice than untreated mice. Furthermore, part of c-fos-positive neurons in the BLA were immunoreactive of CaMKII. Engineered Designer receptors exclusively activated by designer drugs (DREADD) receptor hM4Di or hM3Dq was selectively expressed on CaMKII neurons by injection of adeno-associated virus (AAV) vectors containing CaMKII and hM4Di or hM3Dq. Administration of DREADD agonist CNO to selectively inhibit the CaMKII neurons in the BLA significantly increased the paw withdrawal thresholds and paw withdrawal latencies. In addition, selectively inhibition of CaMKII neurons in the BLA alleviated anxiety behavior without affecting the motor activity. In summary, our findings suggest that CaMKII neurons in the amygdala are critical for neuropathic pain and anxiety behaviors induced by paclitaxel chemotherapy.

Sex differences in the behavioral and immune responses of mice to tumor growth and cancer therapy

There is significant variability in the expression of cancer-related fatigue. Understanding the factors that account for this variation provide insight into the underlying mechanisms. One important, but often overlooked, variable is biological sex. While a few clinical studies have indicated that female patients report higher levels of fatigue, these studies are subject to potential socio-culture reporting biases. Only a limited number of preclinical studies have considered sex differences in animal model of fatigue and few have simultaneously considered both disease- and treatment-related factors. The present series of studies was initiated to address the current knowledge gap on the importance of sex differences in cancer-related fatigue. We selected a murine model of human papilloma virus-positive head and neck cancer based on heterotypic injection of the mEERL95 cell line that grows in both male and female mice and responds to a regimen of cisplatin plus irradiation. We also tested the impact of immunotherapy treatment targeting PD1. Voluntary wheel running was used to evaluate fatigue-like behavior. Male mice grew larger tumors than did female mice and showed more severe fatigue-like behavior. We confirmed that the tumor increased the expression of inflammatory cytokines in the liver, but no sex differences were observed. As a trend toward elevated Cd3 mRNA was observed in female mice, we tested the importance of T cells using female Rag2-/- mice. The Rag2-/- female mice had accelerated tumor growth and more severe fatigue-like behavior. In response to cisplatin alone non-tumor-bearing female mice showed a slower recovery of wheel running activity compared to males. However, in response to chemoradiation and anti-PD1 neutralizing antibody, tumor-bearing female mice showed a better tumor response to therapy than male mice, but no significant sex differences were observed for wheel running. These findings point to different mechanisms underlying tumor- and treatment-induced behavioral fatigue and indicate that the sex factor can intervene to modulate the expression of fatigue-like behavior in particular circumstances.

Sex-Specific Differences in Toxicity Following Systemic Paclitaxel Treatment and Localized Cardiac Radiotherapy

Simple Summary

The objective of the present study was to investigate the impact of sex in the development of long-term toxicities affecting quality of life in cancer survivors after systemic paclitaxel treatment and cardiac irradiation. Sex-specific differences may affect tumor biology, drug pharmacokinetics and dynamics, and response to local treatment such as radiation therapy (RT). However, sex is rarely taken into consideration when administering cancer therapies. Interestingly, female mice are protected from paclitaxel-induced neurotoxicity as well as from radiotherapy-induced cardiotoxicity, and deficiency in the small GTPase RhoB reversed the protection in females but not in males. In conclusion, our results are the first to identify sex- and organ-specific responses to systemic paclitaxel administration and localized RT. These results may have important implications for the management of cancer patients and implementation of personalized medicine in oncology.

Abstract

The impact of sex in the development of long-term toxicities affecting the quality of life of cancer survivors has not been investigated experimentally. To address this issue, a series of neurologic and cardiologic endpoints were used to investigate sex-based differences triggered by paclitaxel treatment and radiotherapy exposure. Male and female wild-type (WT) mice were treated with paclitaxel (150 and 300 mg/kg) administered weekly over 6 weeks or exposed to 19 Gy cardiac irradiation. Cohorts were analyzed for behavioral and neurobiologic endpoints to assess systemic toxicity of paclitaxel or cardiovascular endpoints to assess radiotherapy toxicity. Interestingly, female WT mice exhibited enhanced tolerance compared to male WT mice regardless of the treatment regimen. To provide insight into the possible sex-specific protective mechanisms, rhoB-deficient animals and elderly mice (22 months) were used with a focus on the possible contribution of sex hormones, including estrogen. In females, RhoB deficiency and advanced age had no impact on neurocognitive impairment induced by paclitaxel but enhanced cardiac sensitivity to radiotherapy. Conversely, rhoB-deficiency protected males from radiation toxicity. In sum, RhoB was identified as a molecular determinant driving estrogen-dependent cardioprotection in female mice, whereas neuroprotection was not sex hormone dependent. To our knowledge, this study revealed for the first time sex- and organ-specific responses to paclitaxel and radiotherapy.

Effects of chemotherapy on operant responding for palatable food in male and female mice

Patients treated with cancer chemotherapeutics frequently report chemotherapy-induced peripheral neuropathy (CIPN), changes in mood (depression and anxiety) and functional impairments. Rodent models of CIPN elicit limited alterations in functional behaviors, which pose challenges in developing preclinical models of chemotherapy-induced behavioral depression. The study examined the consequences of chemotherapy-induced mechanical hypersensitivity (paclitaxel: 32 or 64 mg/kg, cumulative; oxaliplatin: 30 mg/kg, cumulative) on behavioral depression, as measured with operant responding for palatable food during periods of food restriction and ad libitum chow, consumption of noncontingently available palatable food in the presence of ad libitum chow, and voluntary wheel running. The study employed two inbred mouse strains (C57BL/6J and Balb/cJ) and examined potential sex differences. All chemotherapeutic regimens caused profound mechanical hypersensitivity for the duration of the observation periods (up to 7 months), but no treatments changed voluntary wheel running or consumption of noncontingent palatable food. The high dose of paclitaxel temporarily reduced operant responding for palatable food in male C57BL/6J mice undergoing food restriction or maintained on ad libitum chow. However, paclitaxel failed to decrease operant responding for palatable food in free-feeding female C57BL/6J mice or Balb/cJ mice of either sex. Moreover, oxaliplatin did not significantly alter operant responding for palatable food in male or female C57BL/6J mice maintained on ad libitum chow. These findings demonstrate a dissociation between chemotherapy-induced mechanical hypersensitivity and behavioral depression. The transient effects of paclitaxel on operant responding in male C57BL/6J mice may represent a fleeting behavioral correlate of chemotherapy-associated pain-like behaviors.

Nicotinamide riboside relieves paclitaxel-induced peripheral neuropathy and enhances suppression of tumor growth in tumor-bearing rats

Nicotinamide riboside (NR) is a vitamin B3 precursor of NAD that blunts diabetic and chemotherapy-induced peripheral neuropathy in preclinical models. This study examined whether NR also blunts the loss of intraepidermal nerve fibers induced by paclitaxel, which is associated with peripheral neuropathy. The work was conducted in female rats with N-methyl-nitrosourea (MNU)-induced tumors of the mammary gland to increase its translational relevance, and to assess the interaction of NR with paclitaxel and NR's effect on tumor growth. Once daily oral administration of 200 mg/kg NR p.o. beginning with the first of 3 i.v. injections of 6.6 mg/kg paclitaxel to tumor-bearing rats significantly decreased paclitaxel-induced hypersensitivity to tactile and cool stimuli, as well as place-escape avoidance behaviors. It also blunted the loss of intraepidermal nerve fibers in tumor-bearing rats, as well as a separate cohort of tumor-naive rats. Unexpectedly, concomitant administration of NR during paclitaxel treatment further decreased tumor growth; thereafter, tumor growth resumed at the same rate as vehicle-treated controls. Administration of NR also decreased the percentage of Ki67-positive tumor cells in these rats. Once daily administration of NR did not seem to alter tumor growth or the percentage of Ki67-positive tumor cells in rats that were not treated with paclitaxel and followed for 3 months. These results further support the ability of NR to play a protective role after nerve injury. They also suggest that NR may not only alleviate peripheral neuropathy in patients receiving taxane chemotherapy, but also offer an added benefit by possibly enhancing its tumor-suppressing effects.

Metformin: A Prospective Alternative for the Treatment of Chronic Pain

Metformin (biguanide) is a drug widely used for the treatment of type 2 diabetes. This drug has been used for 60 years as a highly effective antihyperglycemic agent. The search for the mechanism of action of metformin has produced an enormous amount of research to explain its effects on gluconeogenesis, protein metabolism, fatty acid oxidation, oxidative stress, glucose uptake, autophagy and pain, among others. It was only up the end of the 1990s and beginning of this century that some of its mechanisms were revealed. Metformin induces its beneficial effects in diabetes through the activation of a master switch kinase named AMP-activated protein kinase (AMPK). Two upstream kinases account for the physiological activation of AMPK: liver kinase B1 and calcium/calmodulin-dependent protein kinase kinase 2. Once activated, AMPK inhibits the mechanistic target of rapamycin complex 1 (mTORC1), which in turn avoids the phosphorylation of p70 ribosomal protein S6 kinase 1 and phosphatidylinositol 3-kinase/protein kinase B signaling pathways and reduces cap-dependent translation initiation. Since metformin is a disease-modifying drug in type 2 diabetes, which reduces the mTORC1 signaling to induce its effects on neuronal plasticity, it was proposed that these mechanisms could also explain the antinociceptive effect of this drug in several models of chronic pain. These studies have highlighted the efficacy of this drug in chronic pain, such as that from neuropathy, insulin resistance, diabetic neuropathy, and fibromyalgia-type pain. Mounting evidence indicates that chronic pain may induce anxiety, depression and cognitive impairment in rodents and humans. Interestingly, metformin is able to reverse some of these consequences of pathological pain in rodents. The purpose of this review was to analyze the current evidence about the effects of metformin in chronic pain and three of its comorbidities (anxiety, depression and cognitive impairment).

Kappa opioid receptors mediate an initial aversive component of paclitaxel-induced neuropathy

RATIONALE

Cancer patients receiving the antineoplastic drug paclitaxel report higher incidences and longer duration of treatment-resistant depression than patients receiving other classes of chemotherapeutics. Rodents treated with paclitaxel exhibit a suite of changes in affect-like behaviors. Further, paclitaxel causes chemotherapy-induced peripheral neuropathy (CIPN) in humans and rodents. Kappa opioid receptors (KOR) have a well-established role in depression and neuropathy. The contributions of KOR signaling to paclitaxel-induced aversive-like state and CIPN in rodents remain to be explored.

OBJECTIVES

We aimed to investigate whether dysregulation of the KOR/dynorphin system is associated with paclitaxel-mediated pain-like behavior and depression-like behavior.

METHODS

Cancer-free male C57BL/6J mice were treated with four injections of vehicle or paclitaxel (32 mg/kg cumulative). The effects of the selective KOR antagonist norbinaltorphimine (norBNI) on paclitaxel-induced sucrose preference deficits and mechanical hypersensitivity were measured. Prodynorphin mRNA and receptor-mediated G protein activation were measured at two time points following the last paclitaxel injection using quantitative real-time polymerase chain reaction and agonist-stimulated [³⁵S]guanosine-5'-O'-(γ-thio)-triphosphate ([³⁵S]GTPγS) binding, respectively, in the nucleus accumbens (NAc), caudate-putamen, amygdala, and spinal cord.

RESULTS

Paclitaxel produced a norBNI-reversible sucrose preference deficit, whereas mechanical hypersensitivity was not reversed by norBNI. Paclitaxel treatment increased the levels of mRNA for prodynorphin, a precursor for endogenous KOR agonists, in the NAc. Paclitaxel also had time-dependent effects on KOR-mediated G protein activation in the NAc.

CONCLUSIONS

These results suggest that KOR signaling mediates an initial aversive component of paclitaxel, but not necessarily paclitaxel-induced mechanical hypersensitivity.