Basic/Translational Development of Forthcoming Opioid- and Nonopioid-Targeted Pain Therapeutics

Puerarin alleviates oxaliplatin-induced neuropathic pain by promoting Nrf2/GPX4-mediated antioxidative response

Oxaliplatin (OXA) as the platinum-based agent induces the cumulative neuropathy including functional impairment and neuropathic pain. OXA treatment triggered oxidative stress and inflammatory reaction in the spinal cord. Puerarin as a natural product has the neuroprotective effect on neuropathic pain. Hence, the roles and mechanisms of Pue on OXA induced neuropathic pain were studied. In this study, OXA-induced neuropathic pain mouse model was constructed by oxaliplatin injection for 5 consecutive days and two cycles. Pue (10 mg/kg) was administered intraperitoneally for seven consecutive days. The changes of behavior, morphology and levels of related proteins were detected. As a result, OXA-induced mice exhibited as the increased pain hypersensitivity, the impaired motor coordination, the activated NLRP3 inflammasome mediated inflammation and the suppressed nuclear factor erythroid 2-related factor 2 (Nrf2) mediated antioxidative reaction in the spinal cord (P<0.05 vs Control). After Pue administration, the mechanical pain threshold, thermal pain latency, spontaneous pain number and motor latency were improved (P<0.05 vs OXA). In the spinal cord, Pue administration reduced the levels of inflammatory elements, increased the levels of antioxidative elements and decreased the levels of oxidative factors (P<0.05 vs OXA). Furthermore, Pue also bind with Nrf2 and increased the association of Nrf2 to glutathione peroxidase 4 (GPX4). In summary, Pue alleviates oxaliplatin induced neuropathic pain by enhancing Nrf2/GPX4-mediated antioxidant response and suppressing inflammatory reaction in the spinal cord.

Discovery of a Small Molecule Activator of Slack (Kcnt1) Potassium Channels That Significantly Reduces Scratching in Mouse Models of Histamine-Independent and Chronic Itch

Various disorders are accompanied by histamine-independent itching, which is often resistant to the currently available therapies. Here, it is reported that the pharmacological activation of Slack (Kcnt1, KNa1.1), a potassium channel highly expressed in itch-sensitive sensory neurons, has therapeutic potential for the treatment of itching. Based on the Slack-activating antipsychotic drug, loxapine, a series of new derivatives with improved pharmacodynamic and pharmacokinetic profiles is designed that enables to validate Slack as a pharmacological target in vivo. One of these new Slack activators, compound 6, exhibits negligible dopamine D2 and D3 receptor binding, unlike loxapine. Notably, compound 6 displays potent on-target antipruritic activity in multiple mouse models of acute histamine-independent and chronic itch without motor side effects. These properties make compound 6 a lead molecule for the development of new antipruritic therapies targeting Slack.

Subjects suffering from bipolar disorder taking lithium are less likely to report physical pain: a FACE-BD study

BACKGROUND

Physical pain is a common issue in people with bipolar disorder (BD). It worsens mental health and quality of life, negatively impacts treatment response, and increases the risk of suicide. Lithium, which is prescribed in BD as a mood stabilizer, has shown promising effects on pain.

METHODS

This naturalistic study included 760 subjects with BD ( FACE-BD cohort) divided in two groups: with and without self-reported pain (evaluated with the EQ-5D-5L questionnaire). In this sample, 176 subjects were treated with lithium salts. The objectives of the study were to determine whether patients receiving lithium reported less pain, and whether this effect was associated with the recommended mood-stabilizing blood concentration of lithium.

RESULTS

Subjects with lithium intake were less likely to report pain (odds ratio [OR] = 0.59, 95% confidence interval [CI], 0.35-0.95; p = 0.036) after controlling for sociodemographic variables, BD type, lifetime history of psychiatric disorders, suicide attempt, personality traits, current depression and anxiety levels, sleep quality, and psychomotor activity. Subjects taking lithium were even less likely to report pain when lithium concentration in blood was ≥0.5 mmol/l (OR = 0.45, 95% CI, 0.24-0.79; p = 0.008).

CONCLUSIONS

This is the first naturalistic study to show lithium's promising effect on pain in subjects suffering from BD after controlling for many confounding variables. This analgesic effect seems independent of BD severity and comorbid conditions. Randomized controlled trials are needed to confirm the analgesic effect of lithium salts and to determine whether lithium decreases pain in other vulnerable populations.

SARS-CoV-2 airway infection results in the development of somatosensory abnormalities in a hamster model

Although largely confined to the airways, SARS-CoV-2 infection has been associated with sensory abnormalities that manifest in both acute and chronic phenotypes. To gain insight on the molecular basis of these sensory abnormalities, we used the golden hamster model to characterize and compare the effects of infection with SARS-CoV-2 and influenza A virus (IAV) on the sensory nervous system. We detected SARS-CoV-2 transcripts but no infectious material in the cervical and thoracic spinal cord and dorsal root ganglia (DRGs) within the first 24 hours of intranasal virus infection. SARS-CoV-2-infected hamsters exhibited mechanical hypersensitivity that was milder but prolonged compared with that observed in IAV-infected hamsters. RNA sequencing analysis of thoracic DRGs 1 to 4 days after infection suggested perturbations in predominantly neuronal signaling in SARS-CoV-2-infected animals as opposed to type I interferon signaling in IAV-infected animals. Later, 31 days after infection, a neuropathic transcriptome emerged in thoracic DRGs from SARS-CoV-2-infected animals, which coincided with SARS-CoV-2-specific mechanical hypersensitivity. These data revealed potential targets for pain management, including the RNA binding protein ILF3, which was validated in murine pain models. This work elucidates transcriptomic signatures in the DRGs triggered by SARS-CoV-2 that may underlie both short- and long-term sensory abnormalities.

Mechanisms of Transmission and Processing of Pain: A Narrative Review

Knowledge about the mechanisms of transmission and the processing of nociceptive information, both in healthy and pathological states, has greatly expanded in recent years. This rapid progress is due to a multidisciplinary approach involving the simultaneous use of different branches of study, such as systems neurobiology, behavioral analysis, genetics, and cell and molecular techniques. This narrative review aims to clarify the mechanisms of transmission and the processing of pain while also taking into account the characteristics and properties of nociceptors and how the immune system influences pain perception. Moreover, several important aspects of this crucial theme of human life will be discussed. Nociceptor neurons and the immune system play a key role in pain and inflammation. The interactions between the immune system and nociceptors occur within peripheral sites of injury and the central nervous system. The modulation of nociceptor activity or chemical mediators may provide promising novel approaches to the treatment of pain and chronic inflammatory disease. The sensory nervous system is fundamental in the modulation of the host's protective response, and understanding its interactions is pivotal in the process of revealing new strategies for the treatment of pain.

Opioid tolerance and opioid-induced hyperalgesia: Is TrkB modulation a potential pharmacological solution?

Opioids are widely prescribed for moderate to severe pain in patients with acute illness, cancer pain, and chronic noncancer pain. However, long-term opioid use can cause opioid tolerance and opioid-induced hyperalgesia (OIH), contributing to the opioid misuse and addiction crisis. Strategies to mitigate opioid tolerance and OIH are needed to reduce opioid use and its sequelae. Currently, there are few effective pharmacological strategies that reduce opioid tolerance and OIH. The intrinsic tyrosine kinase receptor B (TrkB) ligand, brain-derived neurotrophic factor (BDNF), has been shown to modulate pain. The BDNF-TrkB signaling plays a role in initiating and sustaining elevated pain sensitivity; however, increasing evidence has shown that BDNF and 7,8-dihydroxyflavone (7,8-DHF), a potent blood-brain barrier-permeable ligand to TrkB, exert neuroprotective, anti-inflammatory, and antioxidant effects that may protect against opioid tolerance and OIH. As such, TrkB signaling may be an important therapeutic avenue in opioid tolerance and OIH. Here, we review 1) the mechanisms of pain, opioid analgesia, opioid tolerance, and OIH; 2) the role of BDNF-TrkB in pain modulation; and 3) the neuroprotective effects of 7,8-DHF and their implications for opioid tolerance and OIH.

SARS-CoV-2 Airway Infection Results in Time-dependent Sensory Abnormalities in a Hamster Model

Despite being largely confined to the airways, SARS-CoV-2 infection has been associated with sensory abnormalities that manifest in both acute and long-lasting phenotypes. To gain insight on the molecular basis of these sensory abnormalities, we used the golden hamster infection model to characterize the effects of SARS-CoV-2 versus Influenza A virus (IAV) infection on the sensory nervous system. Efforts to detect the presence of virus in the cervical/thoracic spinal cord and dorsal root ganglia (DRGs) demonstrated detectable levels of SARS-CoV-2 by quantitative PCR and RNAscope uniquely within the first 24 hours of infection. SARS-CoV-2-infected hamsters demonstrated mechanical hypersensitivity during acute infection; intriguingly, this hypersensitivity was milder, but prolonged when compared to IAV-infected hamsters. RNA sequencing (RNA-seq) of thoracic DRGs from acute infection revealed predominantly neuron-biased signaling perturbations in SARS-CoV-2-infected animals as opposed to type I interferon signaling in tissue derived from IAV-infected animals. RNA-seq of 31dpi thoracic DRGs from SARS-CoV-2-infected animals highlighted a uniquely neuropathic transcriptomic landscape, which was consistent with substantial SARS-CoV-2-specific mechanical hypersensitivity at 28dpi. Ontology analysis of 1, 4, and 30dpi RNA-seq revealed novel targets for pain management, such as ILF3. Meta-analysis of all SARS-CoV-2 RNA-seq timepoints against preclinical pain model datasets highlighted both conserved and unique pro-nociceptive gene expression changes following infection. Overall, this work elucidates novel transcriptomic signatures triggered by SARS-CoV-2 that may underlie both short- and long-term sensory abnormalities while also highlighting several therapeutic targets for alleviation of infection-induced hypersensitivity.

One Sentence Summary

SARS-CoV-2 infection results in an interferon-associated transcriptional response in sensory tissues underlying time-dependent hypersensitivity.

Opioid-free anesthesia for open radical cystectomy in morbid obesity

Opioid-free anaesthesia shows evidence about its efectivity and security, even though its risks and benefits are not well defined. Neither are the patient profile or sort of surgery where it could be superior to the conventional opioid-based anaesthetic technique. Aggressive and/or long-lasting surgeries set out several queries on this technique regarding sudden hemodynamic changes, as it does not produce sympatholysis through μ receptor and there is modest experience in this technique. A morbidly obese patient received open radical cystectomy with Bricker-type urinary diversion using infraumbilical incision under OFA protocol, maintaining an adequate hemodynamic stability and excellent analgesia in postoperatory care without using any intraoperative opioids. Opioid-free anaesthesia technique is developing its evidence. However, it is necessary to keep on researching its clinical applications, different drug combinations and solutions to its expected complications.

Comparison of bromazepam and ibuprofen influence on tooth pulp-evoked potentials in humans

Introduction/Objective Somatosensory evoked potentials are a neurophysiological tool for testing the effects of drugs in humans and animals. The aim of this study was to estimate the way that bromazepam and ibuprofen had on tooth pulp-evoked potentials (TPEPs) after non-painful stimuli, as well as to detect possible differences in this activity. Methods Sixty young healthy subjects were included in the study. They were arranged into three groups: ibuprofen, bromazepam and placebo. To record TPEPs response, dental pulp was electrically stimulated through intact enamel with non-painful stimuli. For stimulation and registration, we used Xltek Protektor 32 system, software EPWorks, version 5.0. The experiment consisted of two testing sessions. Five recordings were performed in each session. The first test session was before, and the second was 45 minutes after administration of a single dose of the ibuprofen (400 mg), bromazepam (1.5 mg) or placebo. Results The results of the present study exhibit that both ibuprofen and bromazepam significantly increased all the latencies; ibuprofen decreased amplitudes of all the waves except the first one (p < 0.05), and bromazepam decreased amplitudes of all the waves except the first one (p < 0.05); placebo did not modified TPEPs waves (p > 0.05). Additionally, there were no significant differences in influence on TPEPs between bromazepam and ibuprofen (p > 0.05). Conclusion Our study showed that both bromazepam and ibuprofen had the same influence on TPEPs after non-painful stimuli. That indicates that anxiolytic dose of bromazepam affects neurotransmission in the same manner as non-opioid analgesics ibuprofen.

Opioid-free anesthesia for open radical cystectomy in morbid obesity

Opioid-free anaesthesia shows evidence about its efectivity and security, even though its risks and benefits are not well defined. Neither are the patient profile or sort of surgery where it could be superior to the conventional opioid-based anaesthetic technique. Aggressive and/or long-lasting surgeries set out several queries on this technique regarding sudden hemodynamic changes, as it does not produce sympatholysis through μ receptor and there is modest experience in this technique. A morbidly obese patient received open radical cystectomy with Bricker-type urinary diversion using infraumbilical incision under OFA protocol, maintaining an adequate hemodynamic stability and excellent analgesia in postoperatory care without using any intraoperative opioids. Opioid-free anaesthesia technique is developing its evidence. However, it is necessary to keep on researching its clinical applications, different drug combinations and solutions to its expected complications.

Pancreas Cancer-Associated Pain Management

Pain is highly prevalent in patients with pancreas cancer and contributes to the morbidity of the disease. Pain may be due to pancreatic enzyme insufficiency, obstruction, and/or a direct mass effect on nerves in the celiac plexus. Proper supportive care to decrease pain is an important aspect of the overall management of these patients. There are limited data specific to the management of pain caused by pancreatic cancer. Here we review the literature and offer recommendations regarding multiple modalities available to treat pain in these patients. The dissemination and adoption of these best supportive care practices can improve quantity and quality of life for patients with pancreatic cancer. IMPLICATIONS FOR PRACTICE: Pain management is important to improve the quality of life and survival of a patient with cancer. The pathophysiology of pain in pancreas cancer is complex and multifactorial. Despite tumor response to chemotherapy, a sizeable percentage of patients are at risk for ongoing cancer-related pain and its comorbid consequences. Accordingly, the management of pain in patients with pancreas cancer can be challenging and often requires a multifaceted approach.

An approach to using pharmacokinetics and electroencephalography for propofol anesthesia for surgery in infants

Safe and effective techniques for propofol total intravenous anesthesia (TIVA) in infants are not well imbedded into clinical practice, resulting in practitioner unfamiliarity and potential for over- and under-dosing. In this education article, we describe our approach to TIVA dosing in infants and toddlers (birth to 36 months) which combines the use of pharmacokinetic models with EEG multi-parameter analysis. Pharmacokinetic models describe propofol and remifentanil effect site concentrations (Ce) over time in different age groups for a given dosing regimen. These models display substantial biological variability between individuals within age groups, impeding their application to clinical practice. Nevertheless, they reveal that younger infants require a higher propofol loading dose, a lower propofol maintenance dose, and a higher remifentanil dose compared with older infants. Proprietary EEG indices (eg, Bispectral Index) can serve as a biomarker of propofol Ce in adults and children to guide dosing to the individual patient; however, they are not recommended for infants as their validity remains uncertain this population. In our experience, EEG waveforms and processed parameters can reflect propofol Ce in infants, reflected by spectral edge frequency (SEF), density spectral array (DSA), and waveform patterns. In our practice, we use a "lookup table" of age-based dosing regimens or target-controlled infusion (TCI) based on the pharmacokinetic models to deliver a target propofol Ce and co-administer remifentanil and/or regional technique for analgesia. We analyze Electroencephalogram (EEG) waveforms, SEF, and DSA to adjust the propofol dose or TCI target concentration to the individual infant. EEG analysis mitigates against biological variability inherent in the pharmacokinetic models and has improved our experience with TIVA for infants.

Lessons for Better Pain Management in the Future: Learning from the Past

The treatment of noncancer pain in the United States and globally is met with significant challenges, resulting in profound physical, emotional, and societal costs. Based on this need, numerous modalities have been proposed to manage chronic pain, including opioid and nonopioid interventions as well as surgical approaches. Thus, the future of pain management continues to be mired in evolving concepts and constant debates. Consequently, it is crucial to understand the past as we move towards the future. The evolution of lessons for better pain management at present and for the future starting from the 1990s to the present date are reviewed and emphasized with a focus on learning from the past for the future. This review summarizes the evolution of multiple modalities of treatments, including multidisciplinary programs, multimodal therapy, interventional techniques, opioid therapy, other conservative modalities, and surgical interventions. This review emphasizes the individual, patient-centered development of an effective pain treatment plan after proper evaluation to establish a diagnosis. It includes measurable outcomes that focus on improvements in the quality of life and activities of daily living, as well as improvement in pain and function and, most importantly, return to productive citizenship. It is crucial that the knowledge of best practices be advanced, along with emphasis on lessons learned in the past to provide best practices for better pain management.

Dual-Acting Peripherally Restricted Delta/Kappa Opioid (CAV1001) Produces Antinociception in Animal Models of Sub-Acute and Chronic Pain

Background

The development of highly efficacious alternatives to mu-opioid analgesics represents an urgent unmet medical and public health need. In the presence of inflammation both delta- and kappa-opioid agonists, acting on peripheral sensory neurons, mediate analgesia. The dual-acting, peripherally restricted kappa/delta-opioid agonist, CAV1001, was tested in four rodent pain models.

Methods

Experiment 1 – Formalin testing in mice. Three doses (1–10 mg/kg) of CAV1001 or ICI204448 at 30 minutes were tested after formalin injection. Spontaneous nocifensive responses were video recorded. Experiment 2 – Complete Freund’s Adjuvant (CFA)-induced arthritis. CFA was injected into the ankle joint of rats. Joint compression thresholds (JCT) were measured. CAV1001 was compared to celecoxib. Experiment 3 – Spinal nerve ligation (SNL) in rats. Paw compression thresholds (PCT) were measured. CAV1001 was compared to gabapentin. Experiment 4 – MMRT-1 bone cancer implantation into the rat tibia. Weight-bearing was assessed. CAV1001 was compared to morphine.

Results

In Phase 2 of the formalin model, CAV1001 (1 mg/kg) significantly reduced pain behaviors to a degree comparable to the peripherally restricted kappa-opioid agonist, ICI204448 (10 mg/kg). CAV1001 (10 mg/kg) effectively eliminated pain behaviors associated with phase 2. In the CFA-induced arthritis model, a significant increase in JCTs, similar to the comparator celecoxib, was observed with CAV1001 at 1 mg/kg at 2 hours; CAV1001 (10 mg/kg) was effective at 1 hour. In the SNL model, both the comparator gabapentin and CAV1001 (5 mg/kg) significantly reduced PCT at 2 hours, but at 4 hours, the CAV1001 thresholds improved to baseline. CAV1001 10 mg/kg significantly improved weight bearing at 4-hour post-dosing compared to baseline following MMRT-1 implantation.

Conclusion

CAV1001 demonstrated efficacy in several different preclinical pain models. Time- and dose-dependent differences in the efficacy of CAV1001 amongst these rodent pain models parallel the degree of underlying inflammation.

TRPV1 Responses in the Cerebellum Lobules V, VIa and VII Using Electroacupuncture Treatment for Inflammatory Hyperalgesia in Murine Model

Inflammatory pain sensation is an important symptom which protects the body against additional tissue damage and promotes healing. Discovering long-term and effective treatments for pain remains crucial in providing efficient healthcare. Electroacupuncture (EA) is a successful therapy used for pain relief. We aimed to investigate effects and mechanisms of Complete Freund’s Adjuvant (CFA)-inducing inflammatory pain in the cerebellum, and the inhibition of this inflammatory hyperalgesia using EA at Zusanli acupoint (ST36). The results display a significant increase in mechanical and thermal sensitivities in the CFA and CFA + SHAM groups, which was significantly reduced in the CFA+EA and CFA + KO groups. This evidence was substantiated in the protein levels observed using immunoblotting, and presented with significant escalations after CFA inducing inflammatory hyperalgesia in CFA and CFA + SHAM groups. Then, they were significantly attenuated by EA in the CFA + EA group. Furthermore, the CFA + transient receptor vanilloid member 1 (TRPV1)^−/− group indicated similar significant decreases of protein expression. Additionally, a concomitant overexpression in lobule VIa was also observed in immunofluorescence. These consequences suggest that CFA-induced inflammatory pain provokes modifications in cerebellum lobules V, VIa and VII, which can subsequently be regulated by EA treatment at the ST36 through its action on TRPV1 and related molecular pathways.

Opioid-Sparing Pain Management in Upper Extremity Surgery: Part 2: Surgeon as Prescriber

A multimodal pain management strategy combines complementary medications and techniques, targeting unique pathways, to improve overall analgesic effect and reduce opioid requirements. In this 2-part review, we examine the literature identifying nonopioid analgesic modalities and their targets in the pain pathway as well as anesthetic techniques found to be opioid sparing in the practice of upper extremity surgery. Part 1 focused on operative anesthesia and analgesia. In part 2, we discuss the nonopioid options available after surgery and explore areas for future investigation specific to upper extremity surgery.

Loxapine for Treatment of Patients With Refractory, Chemotherapy-Induced Neuropathic Pain: A Prematurely Terminated Pilot Study Showing Efficacy But Limited Tolerability

Neuropathic pain is a debilitating and commonly treatment-refractory condition requiring novel therapeutic options. Accumulating preclinical studies indicate that the potassium channel Slack (K_Na1.1) contributes to the processing of neuropathic pain, and that Slack activators, when injected into mice, ameliorate pain-related hypersensitivity. However, whether Slack activation might reduce neuropathic pain in humans remains elusive. Here, we evaluated the tolerability and analgesic efficacy of loxapine, a first-generation antipsychotic drug and Slack activator, in neuropathic pain patients. We aimed to treat 12 patients with chronic chemotherapy-induced, treatment-refractory neuropathic pain (pain severity ≥ 4 units on an 11-point numerical rating scale) in a monocentric, open label, proof-of-principle study. Patients received loxapine orally as add-on analgesic in a dose-escalating manner (four treatment episodes for 14 days, daily dose: 20, 30, 40, or 60 mg loxapine) depending on tolerability and analgesic efficacy. Patient-reported outcomes of pain intensity and/or relief were recorded daily. After enrolling four patients, this study was prematurely terminated due to adverse events typically occurring with first-generation antipsychotic drugs that were reported by all patients. In two patients receiving loxapine for at least two treatment episodes, a clinically relevant analgesic effect was found at a daily dose of 20-30 mg of loxapine. Another two patients tolerated loxapine only for a few days. Together, our data further support the hypothesis that Slack activation might be a novel strategy for neuropathic pain therapy. However, loxapine is no valid treatment option for painful polyneuropathy due to profound dopamine and histamine receptor-related side effects. Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT02820519.

Nociceptive mechanisms involved in the acute and chronic phases of a complex regional pain syndrome type 1 model in mice

Complex regional pain syndrome I (CRPS-I) is a chronic painful pathology still undertreated. CTK 01512-2 is a recombinant version of the spider peptide Phα1β, and it functions as a voltage-gated calcium channel blocker and a transient receptor potential ankyrin 1 (TRPA1) antagonist with antinociceptive effect in different pain models. Here, we investigate the mechanisms involved in the acute and chronic nociceptive phases of a model of CPRS-I in mice and assess the antinociceptive effect of CTK 01512-2 using this model. Adult male and female mice C57BL/6 (20-30 g) were used to determine mechanical (von Frey test) or cold (acetone test) allodynia induction. Inflammatory parameters (serum and tibial nerve lactate levels, hind paw temperature and edema, or tissue cell infiltration) were evaluated after chronic post-ischemia pain (CPIP, a model of CPRS-I) induction. Anti-inflammatory and anti-neuropathic drugs or CTK 01512-2 were tested. First, we detected that CPIP-induced mechanical and cold allodynia in male and female mice in a similar way. In the acute phase (1 day after CPIP), an increase in inflammatory parameters were observed, as well as the anti-allodynic effect of anti-inflammatory compounds. In the chronic phase (17 days after CPIP), mice exhibited mechanical and cold allodynia, and anti-neuropathic drugs induced antinociception, while no inflammatory alterations were found. CTK 01512-2 reversed the CPIP allodynic effect in both nociceptive phases. Thus, this CPRS-I model can be used to understand the mechanisms involved in CPRS-I induced pain and inflammation. Besides, we observed that CTK 01512-2 has a valuable antinociceptive effect in this pain model.

Reversal of Peripheral Neuropathic Pain by the Small-Molecule Natural Product Physalin F via Block of CaV2.3 (R-Type) and CaV2.2 (N-Type) Voltage-Gated Calcium Channels

No universally efficacious therapy exists for chronic pain, a disease affecting one-fifth of the global population. An overreliance on the prescription of opioids for chronic pain despite their poor ability to improve function has led to a national opioid crisis. In 2018, the NIH launched a Helping to End Addiction Long-term plan to spur discovery and validation of novel targets and mechanisms to develop alternative nonaddictive treatment options. Phytochemicals with medicinal properties have long been used for various treatments worldwide. The natural product physalin F, isolated from the Physalis acutifolia (family: Solanaceae) herb, demonstrated antinociceptive effects in models of inflammatory pain, consistent with earlier reports of its anti-inflammatory and immunomodulatory activities. However, the target of action of physalin F remained unknown. Here, using whole-cell and slice electrophysiology, competition binding assays, and experimental models of neuropathic pain, we uncovered a molecular target for physalin F's antinociceptive actions. We found that physalin F (i) blocks CaV2.3 (R-type) and CaV2.2 (N-type) voltage-gated calcium channels in dorsal root ganglion (DRG) neurons, (ii) does not affect CaV3 (T-type) voltage-gated calcium channels or voltage-gated sodium or potassium channels, (iii) does not bind G-protein coupled opioid receptors, (iv) inhibits the frequency of spontaneous excitatory postsynaptic currents (EPSCs) in spinal cord slices, and (v) reverses tactile hypersensitivity in models of paclitaxel-induced peripheral neuropathy and spinal nerve ligation. Identifying CaV2.2 as a molecular target of physalin F may spur its use as a tool for mechanistic studies and position it as a structural template for future synthetic compounds.

Characterization of Effect of Repeated Bolus or Continuous Intrathecal Infusion of Morphine on Spinal Mass Formation in the Dog

BACKGROUND

We determined whether intrathecally delivering the same daily dose of morphine (MS) at a fixed concentration of 25 mg/mL by periodic boluses versus continuous infusion would reduce intrathecal mass (IMs) formation in dogs.

METHODS

Adult dogs (hound cross, n = 32) were implanted with intrathecal catheters connected to SynchroMed II infusion pumps. Animals were randomly assigned to receive infusion of 0.48 mL/day of saline or MS dosing (12 mg/day at 25 mg/mL) as boluses: x1 (q24hour), x2 (q12hour), x4 (q6hour), or x8 (q3hour) given at the rate of 1000 μL/hour, or as a continuous infusion (25 mg/mL/20 μL/hour).

RESULTS

With IT saline, minimal pathology was noted. In contrast, animals receiving morphine displayed spinally compressing durally derived masses with the maximal cross-sectional area being greatest near the catheter tip. Histopathology showed that IMs consisted of fibroblasts in a collagen (type 1) matrix comprised of newly formed collagen near the catheter and mature collagen on the periphery of the mass. The rank order of median cross-sectional mass area (mm² ) was: Saline: 0.7 mm² ; x2: 1.8 mm² ; x4: 2.7 mm² ; x1: 2.7 mm² ; x8: 4.2 mm² ; Continuous: 8.1 mm² , with statistical difference from saline being seen with continuous (p < 0.0001) and x8 (p < 0.05). Bench studies with a 2D diffusion chamber confirmed an increase in dye distribution and lower peak concentrations after bolus delivery versus continuous infusion of dye.

CONCLUSIONS

Using multiple bolus dosing, IMs were reduced as compared to continuous infusion, suggesting relevance of bolus delivery in yielding reduced intrathecal masses.

Music-Enhanced Analgesia and Antiseizure Activities in Animal Models of Pain and Epilepsy: Toward Preclinical Studies Supporting Development of Digital Therapeutics and Their Combinations With Pharmaceutical Drugs

Digital therapeutics (software as a medical device) and mobile health (mHealth) technologies offer a means to deliver behavioral, psychosocial, disease self-management and music-based interventions to improve therapy outcomes for chronic diseases, including pain and epilepsy. To explore new translational opportunities in developing digital therapeutics for neurological disorders, and their integration with pharmacotherapies, we examined analgesic and antiseizure effects of specific musical compositions in mouse models of pain and epilepsy. The music playlist was created based on the modular progression of Mozart compositions for which reduction of seizures and epileptiform discharges were previously reported in people with epilepsy. Our results indicated that music-treated mice exhibited significant analgesia and reduction of paw edema in the carrageenan model of inflammatory pain. Among analgesic drugs tested (ibuprofen, cannabidiol (CBD), levetiracetam, and the galanin analog NAX 5055), music intervention significantly decreased paw withdrawal latency difference in ibuprofen-treated mice and reduced paw edema in combination with CBD or NAX 5055. To the best of our knowledge, this is the first animal study on music-enhanced antinociceptive activity of analgesic drugs. In the plantar incision model of surgical pain, music-pretreated mice had significant reduction of mechanical allodynia. In the corneal kindling model of epilepsy, the cumulative seizure burden following kindling acquisition was lower in animals exposed to music. The music-treated group also exhibited significantly improved survival, warranting further research on music interventions for preventing Sudden Unexpected Death in Epilepsy (SUDEP). We propose a working model of how musical elements such as rhythm, sequences, phrases and punctuation found in K.448 and K.545 may exert responses via parasympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis. Based on our findings, we discuss: (1) how enriched environment (EE) can serve as a preclinical surrogate for testing combinations of non-pharmacological modalities and drugs for the treatment of pain and other chronic diseases, and (2) a new paradigm for preclinical and clinical development of therapies leading to drug-device combination products for neurological disorders, depression and cancer. In summary, our present results encourage translational research on integrating non-pharmacological and pharmacological interventions for pain and epilepsy using digital therapeutics.

Development of New Analgesics: An Answer to Opioid Epidemic

Management of pain is a fundamental imperative in medicine. Current analgesics suffer from limitations related to efficacy and adverse events of which abuse potential has assumed an important role. Here we highlight the factors that drive the development of novel analgesics and the advances made in the field.

Contribution of Nrf2 Modulation to the Mechanism of Action of Analgesic and Anti-inflammatory Drugs in Pre-clinical and Clinical Stages

Despite the progress that has occurred in recent years in the development of therapies to treat painful and inflammatory diseases, there is still a need for effective and potent analgesics and anti-inflammatory drugs. It has long been known that several types of antioxidants also possess analgesic and anti-inflammatory properties, indicating a strong relationship between inflammation and oxidative stress. Understanding the underlying mechanisms of action of anti-inflammatory and analgesic drugs, as well as essential targets in disease physiopathology, is essential to the development of novel therapeutic strategies. The Nuclear factor-2 erythroid related factor-2 (Nrf2) is a transcription factor that regulates cellular redox status through endogenous antioxidant systems with simultaneous anti-inflammatory activity. This review summarizes the molecular mechanisms and pharmacological actions screened that link analgesic, anti-inflammatory, natural products, and other therapies to Nrf2 as a regulatory system based on emerging evidences from experimental disease models and new clinical trial data.