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Abstract Alkaloid analgesics have been associated with adverse effects on the central nervous system (CNS). Therefore, it is crucial to characterize the effects of alkaloid analgesics. Plants rich in lycorine, an alkaloid, have shown promise as analgesics. However, the exploration of their CNS side effects, and analgesic effectiveness remains incomplete. The aim of the present study was to investigate the CNS safety profiles of lycorine and its potential analgesic efficacy. Lycorine (3, 10, and 30 mg/kg, intraperitoneal) did not affect motor coordination, and doses of 3 and 10 mg/kg of lycorine did not lead to any impairment in spontaneous locomotor activity. However, the highest dose (30 mg/kg) demonstrated a significant impairment in rearing behavior and an increase in immobility. The safety doses were subsequently used to assess the analgesic efficacy of lycorine in a mouse model of inflammatory pain. Lycorine (1, 3, and 10 mg/kg, intraperitoneal) demonstrated a dose-dependent reduction in pain-like behaviors in formalin-induced mice. In the in vitro study, lycorine regulated immune cells, suggesting its involvement as a cellular mechanism underlying the suppression of pain-like behaviors observed in the formalin model. Overall, our findings delineate the CNS safety range of lycorine in mice and suggest its potential use as an analgesic.

IntroductionBenign prostatic hyperplasia (BPH) is the enlargement of the prostate gland, primarily occurring in aging men, in which transforming growth factor-beta (TGF-β) plays a critical role in prostate cell hyperproliferation and leads to uncomfortable urinary symptoms in BPH patients. Pterocarpus indicus Willd. is well known for its ethnopharmacological applications for treating ailments such as diuresis and bladder stones.MethodsThis study aimed to examine the effect of P. indicus extract (PI extract) on TGF-β-induced WPMY-1 cell proliferation, followed by bioassay-guided fractionation to isolate the active metabolites. Angolensin (Ang) and maackiain (Mac) were isolated from bioassay-guided fractionation. Network analysis was performed to investigate the potential mechanisms. Furthermore, network analysis of the Ang-Mac combination in BPH highlighted the potential top ten pathways, including PI3K/AKT signaling pathway. Accordingly, subsequent investigation focused on evaluating the effect of PI extract, Ang, Mac, and Ang-Mac combination on the expression of PCNA, p53, and PI3K/AKT protein localization and expression.Results and discussionResults revealed inhibition of cell proliferation in TGF-β-induced WPMY-1 cells, correlating with downregulated PCNA expression. While PI extract and Mac induced apoptosis via p53 upregulation, Ang and Ang-Mac combination did not significantly affect apoptosis through the p53 pathway. Additionally, both metabolites exhibited potent inhibition of p-PI3K and p-AKT protein localization and expression in the nucleus of TGF-β-induced WPMY-1 cells. This study suggests that PI extract, Ang, and Mac are promising compounds for treating BPH, as evidenced by in silico and in vitro studies. Additionally, Ang and Mac could be used to standardize PI extract in future investigations.

Neurodegenerative diseases (NDDs) are marked by progressive degeneration of neurons within the central nervous system. A notable rise in the prevalence of NDDs has been noticed in the recent past. There is an undeniable requirement for the discovery of innovative therapies aimed at treating NDDs, as current medications predominantly address symptoms rather than provide cures. Approved therapies often experience a decline in therapeutic efficacy over time and are associated with significant side effects. The current investigation explores the potential of spilanthol, the major bioactive compound isolated from Acmella paniculata, in attenuating NDDs through a multi-faceted approach combining in silico, and in vitro methodologies. In silico pharmacokinetic and toxicity screening of spilanthol indicated favorable characteristics for oral delivery, blood–brain barrier permeability, and minimal toxicity. Network pharmacology predicts that spilanthol attenuates neuroinflammation in NDDs by suppressing the toll-like receptor signaling pathway. Molecular docking and dynamics simulations demonstrate robust binding affinities between spilanthol and key proteins in the TLR4 pathway. In vitro experiments conducted using BV-2 microglial cells demonstrate the potential of spilanthol to reduce the production of proinflammatory cytokines and mediators such as NO, TNF-α, and IL-6 induced by lipopolysaccharide. The cumulative findings of the present study indicate that spilanthol mitigates neurodegeneration by alleviating neuroinflammation.

Background: Clerodendrum petasites, an herbal plant in Thailand, has been used for many years in folk medicine. However, scientific evidence regarding CNS safety pharmacology and antinociceptive activity of C. petasites (CP) has not yet been well characterized. Purpose: The present study aimed to assess the CNS safety pharmacology and antinociceptive and antiinflammatory effects of CP extract. Methods: The effect of CP extract on CNS safety pharmacology was assessed using LABORAS automated home cage monitoring and rotarod test. Its pharmacological activity was evaluated both in-vitro, and in-vivo using hot-plate, acetic acid-induced writhing, formalin, and carrageenan-induced paw edema models. Results and conclusion: CP extract significantly improved thermal and chemical nociceptive behaviors and acute inflammatory pain at all doses: 300, 600, and 1200 mg/kg, p.o. The antiinflammatory effect of CP extract in inflammatory pain models was comparable to the effect of positive control: indomethacin 10 mg/kg at all dose levels tested. Further, the CP extract at 600 mg/kg dose significantly inhibited 82.3% of carrageenan-induced total edema. In-vitro, CP extract at 12.5, 25, and 50 μg/mL concentrations significantly reduced the expression of LPS-induced nitric oxide, IL-6, and TNF-α expression in both RAW 264.7 macrophage and BV-2 microglial cell lines. In addition, CP extract did not show any potential effects on the CNS, indicated by no significant effects on motor coordination, spontaneous locomotor activity, general behaviors, and well-being compared to vehicle-treated mice (p > 0.05). Overall, the present study evidences the potential antinociceptive, antiinflammatory efficacies of CP extract with a favorable CNS safety profile.

Abstract Background Curcumin and piperine are major bioactive compounds of Curcuma longa and Piper nigrum, widely consumed as spices and flock medicine. The combinational use of these plants is a common practice in Southeast Asia. Synergism between curcumin and piperine has been found in several animal models but not in periodontal disease and diabetes, and the antinociceptive interaction is still unknown. Hence, the present study aimed to assess the interaction between curcumin and piperine in pain and its potential CNS side effect profile. Methods Formalin test and in vitro LPS-stimulated RAW 264.7 macrophage cells were used to assess the synergistic interaction of curcumin and piperine in a mouse model of inflammatory pain. Tail-flick and cold plate tests were applied to determine the antinociceptive synergism between piperine and curcumin. The interaction was determined by applying isobolographic analysis. The potential CNS-side effects of the curcumin and piperine combination were also assessed using LABORAS automated home-cage behavioral analysis. Results Curcumin alone dose-dependently improved pain-like behaviors in the formalin, tail-flick, and cold plate tests with the ED50 of 71.4, 34.4, and 31.9 mg/kg, respectively. Additionally, piperine exhibited efficacy in the formalin, tail-flick, and cold plate tests with the ED50 of 18.4, 8.1, and 28.1 mg/kg, respectively. The combination of curcumin and piperine (1:1 ED50 ratio) produced synergistic interaction in the formalin, tail-flick, and cold plate tests as assessed significantly lower experimental ED50 values (5.9, 5.2, and 5.5 mg/kg) compared to theoretical ED50 values (44.9, 21.3, and 30.0 mg/kg), isobologram analysis, and interaction index values of 0.13, 0.24 and 0.18, respectively. The synergistic interaction of curcumin and piperine was further confirmed by the efficacy of the combination in LPS-stimulated RAW 264.7 macrophage cells. Curcumin and piperine interacted synergistically, reducing proinflammatory mediators. The combination also demonstrated better compatibility profiles with neuronal cells. Furthermore, the curcumin-piperine combination had no effects on mouse spontaneous locomotor behaviors in LABORAS automated home cage monitoring. Conclusion Overall, the present study demonstrates strong antinociceptive synergism between curcumin and piperine in mouse models with no potential CNS side effects, suggesting its possible use in clinical trials.

Abstract Metformin is a well-tolerated antidiabetic drug and has recently been repurposed for numerous diseases, including pain. However, a higher dose of metformin is required for effective analgesia, which can potentiate its dose-dependent gastrointestinal side effects. Curcumin is a natural polyphenol and has beneficial therapeutic effects on pain. Curcumin has been used as an analgesic adjuvant with several analgesic drugs, allowing synergistic antinociceptive effects. Nevertheless, whether curcumin can exert synergistic analgesia with metformin is still unknown. In the present study, the nature of curcumin-metformin anti-inflammatory interaction was evaluated in in vitro using lipopolysaccharide-induced RAW 264.7 macrophage and BV-2 microglia cells. In both macrophage and microglia, curcumin effectively potentiates the anti-inflammatory effects of metformin, indicating potential synergistic effects in both peripheral and central pathways of pain. The nature of the interaction between curcumin and metformin was further recapitulated using a mouse model of formalin-induced pain. Coadministration of curcumin and metformin at a 1:1 fixed ratio of their ED50 doses significantly reduced the dose required to produce a 50% effect compared to the theoretically required dose in phase II of the formalin test with a combination index value of 0.24. Besides, the synergistic interaction does not appear to involve severe CNS side effects indicated by no motor alterations, no alterations in short-term and long-term locomotive behaviors, and the general well-being of mice. Our findings suggest that curcumin exerts synergistic anti-inflammation with metformin with no potential CNS adverse effects.

Abstract The failure to develop analgesic drugs is attributed not only to the complex and diverse pathophysiology of pain in humans but also to the poor experimental design and poor preclinical assessment of pain. Although considerable efforts have been devoted to overcoming the relevant problems, many features of the behavioral pain assessment remain to be characterized. For example, a decreased locomotor activity as a common presentation of pain-like behavior has yet to be described. Studies on mice experimentally induced with carrageenan have provided opportunities to explore pain-related behaviors in automated home-cage monitoring. Through this approach, the locomotor activities of mice with carrageenan-induced inflammatory pain can be precisely and objectively captured. Here, we found that the mobile behaviors of mice reduced, and their immobility increased, indicating that carrageenan induction in mice caused a significant decrease in locomotor activity. These non-reflexive pain behaviors were strongly correlated with the reflexive pain behaviors measured via von Frey and plantar tests. Furthermore, the pharmacological intervention using indomethacin improved the locomotor activity of mice with carrageenan-induced pain. Thus, the analysis of the locomotor activity in automated home-cage monitoring is useful for studying the behavioral analgesia and the pharmacological screening of analgesic drugs. The combined evaluation of reflexive and non-reflexive pain behaviors enhances the translational utility of preclinical pain research in rodents.

Bacterial meningitis remains one of the most prevalent infectious diseases worldwide. Although advances in medical care have improved mortality and morbidity, neurological complications remain high. Therefore, aside from antibiotics, therapeutic adjuvants targeting neuroinflammation are essential to combat the long-term neuronal sequelae of bacterial meningitis. In the present study, we propose (−)-dendroparishiol as a potential add-on therapy to improve neuroinflammation associated with bacterial meningitis. The biological activity of (−)-dendroparishiol was first predicted by computational analysis and further confirmed in vitro using a cell-based assay with LPS-induced BV-2 microglial cells. Biological pathways involved with (−)-dendroparishiol were identified by applying network pharmacology. Computational predictions of biological activity indicated possible attenuation of several inflammatory processes by (−)-dendroparishiol. In LPS-induced BV-2 microglial cells, (−)-dendroparishiol significantly reduced the expression of inflammatory mediators: iNOS, NO, COX-2, IL-6, and TNF-α. Molecular docking results demonstrated the potential iNOS and COX-2 inhibitory activity of (−)-dendroparishiol. Network pharmacological analysis indicated the plausible role of (−)-dendroparishiol in biological processes involved in oxidative stress and neuroinflammation with enrichment in neuroinflammatory pathways. Overall, this study provides scientific evidence for the potential application of (−)-dendroparishiol in the management of bacterial meningitis-associated neuroinflammation.

The use of endotoxin, such as lipopolysaccharide (LPS) as a model of sickness behavior, has attracted recent attention. To objectively investigate sickness behavior along with its pain-like behaviors in LPS-treated mice, the behavioral measurement requires accurate methods, which reflects clinical relevance. While reflexive pain response tests have been used for decades for pain assessment, its accuracy and clinical relevance remain problematic. Hence, we used automated home-cage monitoring LABORAS to evaluate spontaneous locomotive behaviors in LPS-induced mice. LPS-treated mice displayed sickness behaviors including pain-like behaviors in automated home-cage monitoring characterized by decreased mobile behaviors (climbing, locomotion, rearing) and increased immobility compared to that of the control group in both short- and long-term locomotive assessments. Here, in short-term measurement, both in the open-field test and automated home-cage monitoring, mice demonstrated impaired locomotive behaviors. We also assessed 24 h long-term locomotor activity in the home-cage system, which profiled the diurnal behaviors of LPS-stimulated mice. The results demonstrated significant behavioral impairment in LPS-stimulated mice compared to the control mice in both light and dark phases. However, the difference is more evident in the dark phase compared to the light phase owing to the nocturnal activity of mice. In addition, the administration of indomethacin as a pharmacological intervention improved sickness behaviors in the open-field test as well as automated home-cage monitoring, confirming that automated home-cage monitoring could be potentially useful in pharmacological screening. Together, our results demonstrate that automated home-cage monitoring could be a feasible alternative to conventional methods, such as the open-field test and combining several behavioral assessments may provide a better understanding of sickness behavior and pain-like behaviors in LPS-treated mice.

Chronic pain is a persistent and unremitting condition that has immense effects on patients’ quality of life. Studies have shown that neuroinflammation is associated with the induction and progression of chronic pain. The activation of microglia and astrocytes is the major hallmark of spinal neuroinflammation leading to neuronal excitability in the projection neurons. Excessive activation of microglia and astrocytes is one of the major contributing factors to the exacerbation of pain. However, the current chronic pain treatments, mainly by targeting the neuronal cells, remain ineffective and unable to meet the patients’ needs. Curcumin, a natural plant product found in the Curcuma genus, improves chronic pain by diminishing the release of inflammatory mediators from the spinal glia. This review details the role of curcumin in microglia and astrocytes both in vitro and in vivo and how it improves pain. We also describe the mechanism of curcumin by highlighting the major glia-mediated cascades in pain. Moreover, the role of curcumin on inflammasome and epigenetic regulation is discussed. Furthermore, we discuss the strategies used to improve the efficacy of curcumin. This review illustrates that curcumin modulating microglia and astrocytes could assure the treatment of chronic pain by suppressing spinal neuroinflammation.

Analgesic drugs in a combination-form can achieve greater efficacy with lesser side effects compared to either drug alone. The combination of drugs acting at different targets or mechanisms of action has been recognized as an alternative approach for achieving optimal analgesia. In this study, the analgesic effects of pregabalin (30, 60, 100, 200 mg/kg), curcumin (15, 30, 60, 100, 120 mg/kg), and 1:1 fixed-dose ratio of the pregabalin-curcumin combination were assessed using two acute nociceptive pain models, the acetic acid-induced writhing and tail-flick tests in mice. The pregabalin-curcumin combination produced a dose-dependent decrease in mean of writhes and an increase in the percentage of antinociception by the acetic acid-induced writhing test. In the tail-flick test, the combination also showed an improvement in antinociception indicated by the tail-flick latency, % antinociception, and area under the curve (AUC). Isobolographic analysis of interactions demonstrated a significant synergistic interaction effect between pregabalin and curcumin in both acute nociceptive pain models with the experimental ED50 below the predicted additive line and the combination index < 1. These findings demonstrate that the combination of pregabalin and curcumin exhibits a synergistic interaction in mouse models of acute nociceptive pain.

Curcumin diglutaric acid (CurDG), an ester prodrug of curcumin, has the potential to be developed as an anti-inflammatory agent due to its improved solubility and stability. In this study, the anti-inflammatory effects of CurDG were evaluated. The effects of CurDG on inflammatory mediators were evaluated in LPS-stimulated RAW 264.7 macrophage cells. CurDG reduced the increased levels of NO, IL-6, and TNF- α, as well as iNOS and COX-2 expression in cells to a greater extent than those of curcumin, along with the potent inhibition of MAPK (ERK1/2, JNK, and p38) activity. The anti-inflammatory effects were assessed in vivo by employing a carrageenan-induced mouse paw edema model. Oral administration of CurDG demonstrated significant anti-inflammatory effects in a dose-dependent manner in mice. The effects were significantly higher compared to those of curcumin at the corresponding doses (p < 0.05). Moreover, 25 mg/kg curcumin did not exert a significant anti-inflammatory effect for the overall time course as indicated by the area under the curve data, while the equimolar dose of CurDG produced significant anti-inflammatory effects comparable with 50, 100, and 200 mg/kg curcumin (p < 0.05). Similarly, CurDG significantly reduced the proinflammatory cytokine expression in paw edema tissues compared to curcumin (p < 0.05). These results provide the first experimental evidence for CurDG as a promising anti-inflammatory agent.

The drug treatment for neuropathic pain remains a challenge due to poor efficacy and patient satisfaction. Curcumin has been reported to alleviate neuropathic pain, but its clinical application is hindered by its low solubility and poor oral bioavailability. Curcumin diglutaric acid (CurDG) is a curcumin prodrug with improved water solubility and in vivo antinociceptive effects. In this study, we investigated the anti-inflammatory mechanisms underlying the analgesic effect of CurDG in the chronic constriction injury (CCI)-induced neuropathy mouse model. Repeated oral administration of CurDG at a low dose equivalent to 25 mg/kg/day produced a significant analgesic effect in this model, both anti-allodynic activity and anti-hyperalgesic activity appearing at day 3 and persisting until day 14 post-CCI surgery (p < 0.001) while having no significant effect on the motor performance. Moreover, the repeated administration of CurDG diminished the increased levels of the pro-inflammatory cytokines: TNF-α and IL-6 in the sciatic nerve and the spinal cord at the lowest tested dose (equimolar to 25 mg/kg curcumin). This study provided pre-clinical evidence to substantiate the potential of pursuing the development of CurDG as an analgesic agent for the treatment of neuropathic pain.