Ameliorative effect of gallic acid in paclitaxel-induced neuropathic pain in mice

Dietary gallic acid as an antioxidant: A review of its food industry applications, health benefits, bioavailability, nano-delivery systems, and drug interactions

Gallic acid (GA), a dietary phenolic acid with potent antioxidant activity, is widely distributed in edible plants. GA has been applied in the food industry as an antimicrobial agent, food fresh-keeping agent, oil stabilizer, active food wrap material, and food processing stabilizer. GA is a potential dietary supplement due to its health benefits on various functional disorders associated with oxidative stress, including renal, neurological, hepatic, pulmonary, reproductive, and cardiovascular diseases. GA is rapidly absorbed and metabolized after oral administration, resulting in low bioavailability, which is susceptible to various factors, such as intestinal microbiota, transporters, and metabolism of galloyl derivatives. GA exhibits a tendency to distribute primarily to the kidney, liver, heart, and brain. A total of 37 metabolites of GA has been identified, and decarboxylation and dihydroxylation in phase I metabolism and sulfation, glucuronidation, and methylation in phase Ⅱ metabolism are considered the main in vivo biotransformation pathways of GA. Different types of nanocarriers, such as polymeric nanoparticles, dendrimers, and nanodots, have been successfully developed to enhance the health-promoting function of GA by increasing bioavailability. GA may induce drug interactions with conventional drugs, such as hydroxyurea, linagliptin, and diltiazem, due to its inhibitory effects on metabolic enzymes, including cytochrome P450 3A4 and 2D6, and transporters, including P-glycoprotein, breast cancer resistance protein, and organic anion-transporting polypeptide 1B3. In conclusion, in-depth studies of GA on food industry applications, health benefits, bioavailability, nano-delivery systems, and drug interactions have laid the foundation for its comprehensive application as a food additive and dietary supplement.

Tinospora cordifolia ameliorates paclitaxel-induced neuropathic pain in albino rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tinospora cordifolia (T. cordifolia) (Willd.) Miers, a member of the Menispermaceae, family documented in the ancient textbooks of the Ayurveda System of Medicine, has been used in the management of sciatica pain and diabetic neuropathy.

AIM

The study has been designed to evaluate the antinociceptive potential of various extracts of T. cordifolia stem in Paclitaxel (PT)-generated neuropathic pain model in albino rats and explore its possible mechanism employing molecular docking studies.

METHODS

Stems of T. cordifolia were shade dried, grinded in fine powder, and extracted separately with different solvents viz. ethanol, water & hydro-alcoholic and characterized using LCMS/MS. The antinociceptive property of T. cordifolia stem (200 and 400 mg/kg) was examined in albino rats using a PT-induced neuropathic pain model. Further, the effect of these extracts was also observed using different behavioral assays viz. cold allodynia, mechanical hyperalgesia (pin-prick test), locomotor activity test, walking track test, and Sciatic Functional Index (SFI) in rats. Tissue lysate of the sciatic nerve was used to determine various biochemical markers such as GSH, SOD, TBARS, tissue protein, and nitrite. Further to explore the possible mechanism of action, the most abundant and therapeutically active compounds available in aqueous extract were analyzed for binding affinity towards soluble epoxide hydrolase (sEH) enzyme (PDB ID: 3wk4) employing molecular docking studies.

RESULTS

The results of the LCMS/MS study of different extracts of T. cordifolia indicated presence of alkaloids, glycosides, terpenoids, sterols and sugars such as amritoside A, tinocordin, magnoflorine, N-methylcoclaurine, coridine, 20β-hydroxyecdysone and menaquinone-7 palmatin, cordifolioside A and tinosporine etc. Among all the three extracts, the hydroalcoholic extract (400 mg/kg) showed the highest response followed by aqueous and ethanolic extracts as evident in in vivo behavioral and biochemical evaluations. Furthermore, docking studies also exposed that these compounds viz. N-methylcoclaurine tinosporin, palmatine, tinocordin, 20β-hydroxyecdysone, and coridine exhibited well to excellent affinity towards target sEH protein.

CONCLUSION

T. cordifolia stem could alleviate neuropathic pain via soluble epoxide hydrolase inhibitory activity.

From Plant to Chemistry: Sources of Antinociceptive Non-Opioid Active Principles for Medicinal Chemistry and Drug Design

Pain is associated with many health problems and a reduced quality of life and has been a common reason for seeking medical attention. Several therapeutics are available on the market, although side effects, physical dependence, and abuse limit their use. As the process of pain transmission and modulation is regulated by different peripheral and central mechanisms and neurotransmitters, medicinal chemistry continues to study novel ligands and innovative approaches. Among them, natural products are known to be a rich source of lead compounds for drug discovery due to their chemical structural variety and different analgesic mechanisms. Numerous studies suggested that some chemicals from medicinal plants could be alternative options for pain relief and management. Previously, we conducted a literature search aimed at identifying natural products interacting either directly or indirectly with opioid receptors. In this review, instead, we have made an excursus including active ingredients derived from plants whose mechanism of action appears from the literature to be other than the modulation of the opioid system. These substances could, either by themselves or through synthetic and/or semi-synthetic derivatives, be investigated in order to improve their pharmacokinetic characteristics and could represent a valid alternative to the opioid approach to pain therapy. They could also be the basis for the study of new mechanisms of action in the approach to this complex and disabling pathology.

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.

Chrysin attenuates paclitaxel-induced hepatorenal toxicity in rats by suppressing oxidative damage, inflammation, and apoptosis

AIMS

Paclitaxel (Pax) is a chemotherapeutic drug from the taxane family that is used in the treatment of human cancer, including ovarian, breast, and non-small cell lung carcinoma. Chrysin (CR) has antioxidant, anti-inflammatory, anti-apoptotic, anti-diabetic, and anti-carcinogenic properties, as well as hepatoprotective and renoprotective activities. In the present study, we evaluated the protective effect of CR against Pax-induced hepatorenal toxicity on inflammation, apoptosis, antioxidant levels, oxidative DNA damage, and histopathology in rats.

MATERIAL AND METHODS

Thirty-five male Sprague-Dawley rats were divided into five groups (n = 7): Group I (normal control), Group II (CR alone at a dose of 50 mg/kg), Group III (Pax at a dose of 2 mg/kg), Group IV (Pax+CR 25), and Group V (Pax+CR 50). The expressions of apoptotic (Bax and Bcl-2) and antioxidant genes (SOD1, CAT, GPx3, and GST) were evaluated using RT-PCR from paraffin sections. Caspase 3, KIM-1, NF-kB, COX-2, and 8-OHdG were also determined by immunohistochemical examination.

KEY FINDINGS

The results revealed that Pax exposure caused hepatic and renal damage in rats, which was indicated by a significant elevation of caspase 3, Bax, KIM-1, NF-kB, COX-2, and 8-OHdG. However, there was a marked downregulation in the expressions of the Bcl-2, SOD1, CAT, GPx3, and GST genes. In contrast, rats given CR in combination showed better gene expression, histological structure, and immunohistochemical staining results.

SIGNIFICANCE

Consequently, CR exhibited the ability to reduce oxidative DNA damage, exert anti-apoptotic and anti-inflammatory properties, and mitigate the toxic effects of Pax-induced hepatorenal toxicity.

Protective effect and mechanism research of Phyllanthus emblica Linn. fruit extract on UV-induced photodamage in keratinocytes

Ultraviolet (UV) irradiation causes acute and chronic cutaneous effects that may result in photodamage and photoaging. Epidermis keratinocytes, as the closest surface of skin, are susceptible to damage from UV rays. Phyllanthus emblica Linn. fruit (PE) extract, as a medicine and food dual-use plant, contains high levels of polyphenols and possesses multiple pharmacological properties. The present study investigated common and different molecular mechanisms and signaling pathway activations of UVA and UVB stimulated cell damage and photoprotective effect of PE extract against UVA and UVB by Methyl Thiazolyl Tetrazolium (MTT) method, Elisa assay, flow cytometry, differentially expressed genes analysis and western blot analysis. The results showed that UVA exposure (10 J/cm2) reduced HaCaT cell viability significantly, increased the apoptosis rate, elevated intracellular reactive oxygen species level and reduced antioxidant enzyme activities. And UVA irradiation could inhibit the ERK/TGF-β/Smad signaling pathway to downregulate collagen I, collagen III and elastin expressions, resulting in the photoaging of skin cells. We also found UVB exposure (30 mJ/cm2) caused HaCaT cell damage, promoted apoptosis, increased ROS production and induced the release of proinflammatory cytokines (IL-1α, IL-6 and PGE2). Further, in HaCaT cells, UVB ray was able to induce the activation of apoptosis markers (cleaved PARP1 and cleaved caspase3) through the MAPK/AP-1 signaling pathway using western blot analysis. Pre-treatment of PE extract prevented the UVA and UVB induced photoaging and injury in HaCaT cells through activation of ERK/TGF-β/Smad pathway and inhibition of MAPK/AP-1 pathway, respectively. Therefore, PE extract has the potential to be used as an oral and topical preparation against skin aging and injury induced by UVA and UVB.

Neurobiological effects of gallic acid: current perspectives

Gallic acid (GA) is a phenolic molecule found naturally in a wide range of fruits as well as in medicinal plants. It has many health benefits due to its antioxidant properties. This study focused on finding out the neurobiological effects and mechanisms of GA using published data from reputed databases. For this, data were collected from various sources, such as PubMed/Medline, Science Direct, Scopus, Google Scholar, SpringerLink, and Web of Science. The findings suggest that GA can be used to manage several neurological diseases and disorders, such as Alzheimer's disease, Parkinson's disease, strokes, sedation, depression, psychosis, neuropathic pain, anxiety, and memory loss, as well as neuroinflammation. According to database reports and this current literature-based study, GA may be considered one of the potential lead compounds to treat neurological diseases and disorders. More preclinical and clinical studies are required to establish GA as a neuroprotective drug.

Ameliorative effect of gallic acid on cisplatin-induced ovarian toxicity in rats

The aim of the present study was to evaluate the protective effect of gallic acid (GA) against cisplatin (CDDP)-induced ovarian toxicity, for the first time. The ovarian damage was generated with CDDP (5 mg/kg) intraperitoneally (i.p.) administration in rats. GA (2.5 and 5 mg/kg) were administered i.p. for 3 consecutive days. The study was carried out in 5 main groups containing 6 rats in each group: control, GA (5 mg/kg), CDDP, CDDP + GA (2.5 mg/kg) and CDDP + GA (5 mg/kg). The levels of ovarian malondialdehyde (MDA), total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), catalase (CAT), 8-hydroxy-2'-deoxyguanosine (8-OHdG), caspase-3 and tumor necrosis factor-alpha (TNF-α) were determined. Hematoxylin and eosin staining method was employed for the histopathological examination. In the CDDP group, it is determined that statistically significant decreasing in the levels of TAS and CAT, and increasing in the levels of MDA, TOS, OSI, 8-OHdG, caspase-3 and TNF-α (p < 0.05) compared with control group. GA administrations statistically significantly restored this damage (p < 0.05). Although vascular congestion, edema, hemorrhage, follicular degeneration and leukocyte infiltration were significantly higher in the CDDP group than in the control group, GA administrations statistically significantly restored these damages (p < 0.05). In conclusion, this study showed that GA prevented CDDP-induced ovarian damage with its antioxidant, anti-apoptotic and anti-inflammatory activities. More comprehensive studies are needed to see the underlying mechanisms.

Pharmacological Evidence of the Important Roles of CCR1 and CCR3 and Their Endogenous Ligands CCL2/7/8 in Hypersensitivity Based on a Murine Model of Neuropathic Pain

Neuropathic pain treatment remains a challenging issue because the therapies currently used in the clinic are not sufficiently effective. Moreover, the mechanism of neuropathy is still not entirely understood; however, much evidence indicates that chemokines are important factors in the initial and late phases of neuropathic pain. To date, the roles of CCR1, CCR3 and their endogenous ligands have not been extensively studied; therefore, they have become the subject of our research. In the present comprehensive behavioral and biochemical study, we detected significant time-dependent and long-lasting increases in the mRNA levels of CCR1 and/or CCR3 ligands, such as CCL2/3/4/5/6/7/8/9, in the murine spinal cord after chronic constriction injury of the sciatic nerve, and these increases were accompanied by changes in the levels of microglial/macrophage, astrocyte and neutrophil cell markers. ELISA results suggested that endogenous ligands of CCR1 and CCR3 are involved in the development (CCL2/3/5/7/8/9) and persistence (CCL2/7/8) of neuropathic pain. Moreover, intrathecal injection of CCL2/3/5/7/8/9 confirmed their possible strong influence on mechanical and thermal hypersensitivity development. Importantly, inhibition of CCL2/7/8 production and CCR1 and CCR3 blockade by selective/dual antagonists effectively reduced neuropathic pain-like behavior. The obtained data suggest that CCL2/7/8/CCR1 and CCL7/8/CCR3 signaling are important in the modulation of neuropathic pain in mice and that these chemokines and their receptors may be interesting targets for future investigations.

Polyphenolic grape stalk and coffee extracts attenuate spinal cord injury-induced neuropathic pain development in ICR-CD1 female mice

More than half of spinal cord injury (SCI) patients develop central neuropathic pain (CNP), which is largely refractory to current treatments. Considering the preclinical evidence showing that polyphenolic compounds may exert antinociceptive effects, the present work aimed to study preventive effects on SCI-induced CNP development by repeated administration of two vegetal polyphenolic extracts: grape stalk extract (GSE) and coffee extract (CE). Thermal hyperalgesia and mechanical allodynia were evaluated at 7, 14 and 21 days postinjury. Then, gliosis, ERK phosphorylation and the expression of CCL2 and CX3CL1 chemokines and their receptors, CCR2 and CX3CR1, were analyzed in the spinal cord. Gliosis and CX3CL1/CX3CR1 expression were also analyzed in the anterior cingulate cortex (ACC) and periaqueductal gray matter (PAG) since they are supraspinal structures involved in pain perception and modulation. GSE and CE treatments modulated pain behaviors accompanied by reduced gliosis in the spinal cord and both treatments modulated neuron-glia crosstalk-related biomolecules expression. Moreover, both extracts attenuated astrogliosis in the ACC and PAG as well as microgliosis in the ACC with an increased M2 subpopulation of microglial cells in the PAG. Finally, GSE and CE prevented CX3CL1/CX3CR1 upregulation in the PAG, and modulated their expression in ACC. These findings suggest that repeated administrations of either GSE or CE after SCI may be suitable pharmacologic strategies to attenuate SCI-induced CNP development by means of spinal and supraspinal neuroinflammation modulation.

Neuroprotective Effect of Natural Compounds in Paclitaxel-Induced Chronic Inflammatory Pain

The current study explored the effects of natural compounds, berbamine, bergapten, and carveol on paclitaxel-associated neuroinflammatory pain. Berbamine, an alkaloid obtained from BerberisamurensisRuprhas been previously researched for anticancer and anti-inflammatory potential. Bergapten is 5-methoxsalenpsoralen previously investigated in cancer, vitiligo, and psoriasis. Carveol obtained from caraway is a component of essential oil. The neuropathic pain model was induced by administering 2 mg/kg of paclitaxel (PTX) every other day for a week. After the final PTX injection, a behavioral analysis was conducted, and subsequently, tissue was collected for molecular analysis. Berbamine, bergapten, and carveol treatment attenuated thermal hypersensitivity, improved latency of falling, normalized the changes in body weight, and increased the threshold for pain sensation. The drugs increased the protective glutathione (GSH) and glutathione S-transferase (GST) levels in the sciatic nerve and spinal cord while lowering inducible nitric oxide synthase (iNOS) and lipid peroxidase (LPO). Hematoxylin and eosin (H and E) and immunohistochemistry (IHC) examinations confirmed that the medication reversed the abnormal alterations. The aforementioned natural substances inhibited cyclooxygenase-2 (COX-2), tumor necrosis factor-alpha (TNF-α), and nuclear factor kappa B (NF-κb) overexpression, as evidenced by enzyme-linked immunosorbant assay (ELISA) and Western blot and hence provide neuroprotection in chronic constriction damage.

Effect of Cliothosa aurivilli on Paclitaxel-induced Peripheral Neuropathy in Experimental Animals

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious complication leading to painful episodes of parasthesia and numbness in hands and feet. The present drugs that have been used for symptomatic treatment yield inconclusive results in trials and assorted side effects. Thus, there is a pressing demand for development of therapeutically efficacious strategy to combat CIPN. The present study investigates about the effect of a marine sponge; Cliothosa aurivilli (CA) on paclitaxel (PT)-induced peripheral neuropathy in mice. Peripheral neuropathy was induced by intoxication with chemotherapeutic drug PT (2 mg/kg; i.p.) for 5 days consequently. Subsequent treatment with aqueous extract of CA (100 and 200 mg/kg) and standard drug methylcobalamin (MCA) (5 mg/kg) was done and results compared statistically. Neuropathic pain sensations were assessed using various behavioural and locomotory models and evaluated on 0^th, 7^th and 14^th days. Kinovea software was used for video path-tracking of animals and total distance travelled calculated. The results indicated clear signs of improvement post 10 days of PT intoxication in CA-treated groups when compared PT challenged group. A significant reduction in pain behaviours in mechanical allodynia, cold chemical allodynia and thermal hyperalgesia models, improvement in sensory motor coordination, locomotor activity, and distance travelled in closed field model reveals that CA possesses potential ameliorating effect against PT-induced neuropathic pain symptoms. The extract notably improved the movement of the PT challenged animals which was shown by the video path-tracking software and total distance travelled by those animals.

Lamiaceae in Mexican Species, a Great but Scarcely Explored Source of Secondary Metabolites with Potential Pharmacological Effects in Pain Relief

The search for molecules that contribute to the relief of pain is a field of research in constant development. Lamiaceae is one of the most recognized families world-wide for its use in traditional medicine to treat diseases that include pain and inflammation. Mexico can be considered one of the most important centers of diversification, and due to the high endemism of this family, it is crucial for the in situ conservation of this family. Information about the most common genera and species found in this country and their uses in folk medicine are scarcely reported in the literature. After an extensive inspection in bibliographic databases, mainly Sciencedirect, Pubmed and Springer, almost 1200 articles describing aspects of Lamiaceae were found; however, 217 articles were selected because they recognize the Mexican genera and species with antinociceptive and/or anti-inflammatory potential to relieve pain, such as Salvia and Agastache. The bioactive constituents of these genera were mainly terpenes (volatile and non-volatile) and phenolic compounds such as flavonoids (glycosides and aglycone). The aim of this review is to analyze important aspects of Mexican genera of Lamiaceae, scarcely explored as a potential source of secondary metabolites responsible for the analgesic and anti-inflammatory properties of these species. In addition, we point out the possible mechanisms of action involved and the modulatory pathways investigated in different experimental models. As a result of this review, it is important to mention that scarce information has been reported regarding species of this family from Mexican genera. In fact, despite Calosphace being one of the largest subgenera of Salvia in the world, found mainly in Mexico, it has been barely investigated regarding its potential biological activities and recognized bioactive constituents. The scientific evidence regarding the different bioactive constituents found in species of Lamiaceae demonstrates that several species require further investigation in preclinical studies, and of course also in controlled clinical trials evaluating the efficacy and safety of these natural products to support their therapeutic potential in pain relief and/or inflammation, among other health conditions. Since Mexico is one of the most important centers of diversification, and due to the high endemism of species of this family, it is crucial their rescue, in situ conservation, and investigation of their health benefits.

The protective effects of hesperidin against paclitaxel-induced peripheral neuropathy in rats

Paclitaxel (PTX), which is widely used in the treatment of solid tumors, leads to dose limitation because it causes peripheral neuropathy. This study was conducted to evaluate the potential effects of hesperidin (HES), which has various biological and pharmacological properties, against PTX-induced sciatic nerve damage. For this purpose, Sprague Dawley rats were given PTX 2 mg/kg/b.w for 5 days, then 100 or 200 mg/kg/b.w HES for 10 days, and behavioral tests were conducted at the end of the experiment. The data obtained show that PTX-induced MDA, NF-κB, IL-1β, TNF-α, COX-2, nNOS, JAK2, STAT3, and GFAP levels decreased with HES administration. Moreover, it was observed that SOD, CAT, and GPx activities inhibited by PTX increased with HES administration. It was determined that PTX caused apoptosis in the sciatic nerve by increasing Caspase-3 and Bax levels and suppressing Bcl-2 levels. HES, on the other hand, showed an anti-apoptotic effect, increasing Bcl-2 levels and decreasing Caspase-3 and Bax levels. Also, it was observed that PTX could cause endoplasmic reticulum stress (ERS) by increasing PERK, IRE1, ATF-6, GRP78 and CHOP mRNA transcript levels, while HES could alleviate ERS by suppressing them. The results indicate that neuropathic pain associated with PTX-induced peripheral neuropathy can be alleviated by HES administration and that it is a promising compound for cancer patients. In addition, it is thought that the results of the present study contain information that will shed light for researchers regarding further studies to be conducted with HES.

β2-adrenoreceptor agonist ameliorates mechanical allodynia in paclitaxel-induced neuropathic pain via induction of mitochondrial biogenesis

Chemotherapy-induced neuropathic pain is a debilitating and common side effect of cancer treatment and so far no effective drug is available for treatment of the serious side effect. Previous studies have demonstrated β2-adrenoreceptor (ADRB2) agonists can attenuate neuropathic pain. However, the role of ADRB2 in paclitaxel -induced neuropathic pain (PINP) remains unclear. In this study, we investigated the effect of formoterol, a long-acting ADRB2 agonist, and related mechanisms in PINP. A rat model of PINP was established by intraperitoneal injection of paclitaxel (2 mg/kg) every other day with a final cumulative dose of 8 mg/kg. Hind paw withdrawal thresholds (PWTs) in response to von Frey filament stimuli were used to evaluate mechanical allodynia. Western blot was used to examine the expression of ADRB2, peroxisome proliferator-activated receptor coactivator-1α (PGC-1α), nuclear respiratory factors 1 (NRF1) and mitochondrial transcription factor A (TFAM) and the immunofluorescence was to detect the cellular localization of ADRB2 and PGC-1α in the spinal cord. Moreover, we measured mitochondrial DNA (mtDNA) copy number by qPCR. In our study, formoterol attenuated established PINP and delayed the onset of PINP. Formoterol restored ADRB2 expression as well as mtDNA copy number and PGC-1α, NRF1, and TFAM protein expression, which are major genes involved in mitochondrial biogenesis, in the spinal cord of PINP rats. Moreover, we found the analgesic effect of formoterol against PINP was partially abolished by PGC-1α inhibitor SR-18292. Collectively, these results demonstrated the activation of ADRB2 with formoterol ameliorates PINP at least partially through induction of mitochondrial biogenesis.

Blockade of CC Chemokine Receptor Type 3 Diminishes Pain and Enhances Opioid Analgesic Potency in a Model of Neuropathic Pain

Neuropathic pain is a serious clinical issue, and its treatment remains a challenge in contemporary medicine. Thus, dynamic development in the area of animal and clinical studies has been observed. The mechanisms of neuropathic pain are still not fully understood; therefore, studies investigating these mechanisms are extremely important. However, much evidence indicates that changes in the activation and infiltration of immune cells cause the release of pronociceptive cytokines and contribute to neuropathic pain development and maintenance. Moreover, these changes are associated with low efficacy of opioids used to treat neuropathy. To date, the role of CC chemokine receptor type 3 (CCR3) in nociception has not been studied. Similarly, little is known about its endogenous ligands (C-C motif ligand; CCL), namely, CCL5, CCL7, CCL11, CCL24, CCL26, and CCL28. Our research showed that the development of hypersensitivity in rats following chronic constriction injury (CCI) of the sciatic nerve is associated with upregulation of CCL7 and CCL11 in the spinal cord and dorsal root ganglia (DRG). Moreover, our results provide the first evidence that single and repeated intrathecal administration of the CCR3 antagonist SB328437 diminishes mechanical and thermal hypersensitivity. Additionally, repeated administration enhances the analgesic properties of morphine and buprenorphine following nerve injury. Simultaneously, the injection of SB328437 reduces the protein levels of some pronociceptive cytokines, such as IL-6, CCL7, and CCL11, in parallel with a reduction in the activation and influx of GFAP-, CD4- and MPO-positive cells in the spinal cord and/or DRG. Moreover, we have shown for the first time that an inhibitor of myeloperoxidase-4-aminobenzoic hydrazide may relieve pain and simultaneously enhance morphine and buprenorphine efficacy. The obtained results indicate the important role of CCR3 and its modulation in neuropathic pain treatment and suggest that it represents an interesting target for future investigations.

Neuro-immune interactions in paclitaxel-induced peripheral neuropathy

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

The Restorative Effect of Gallic Acid on the Experimental Sciatic Nerve Damage Model

Objective

Peripheral nerve injuries occur mostly as a result of mechanical trauma. Due to the microvascular deterioration in peripheral nerve damage, it becomes challenging to remove free oxygen radicals. Gallic acid is a powerful antioxidant with anti-inflammatory effects and a free radical scavenger. The purpose of the study is to show that gallic acid contributes to the restorative effect in mechanical nerve damage, considering its antioxidant and anti-inflammatory effects.

Methods

Thirty male Sprague Dawley albino mature rats were included in the study. Ten of them constituted the control group, 10 out of 20 rats for which sciatic nerve damage was caused, constituted the saline group, and 10 formed the gallic acid group. Post-treatment motor functions, histological, immunohistochemical, and biochemical parameters of the rats were evaluated.

Results

Compared to the surgery+saline group, lower compound muscle action potential (CMAP) latency, higher CMAP amplitude, and higher inclined plane test values were found in the surgery+gallic acid group. Similarly, a higher nerve growth factor (NGF) percentage, a higher number of axons, and a lower percentage of fibrosis scores were observed in the surgery+gallic acid group. Finally, lower tissue malondialdehyde (MDA) and higher heat shock protein-70 (HSP-70) values were determined in the surgery+gallic acid group.

Conclusion

Gallic acid positively affects peripheral nerve injury healing due to its anti-inflammatory and antioxidant effects. It has been thought that gallic acid can be used as a supportive treatment in peripheral nerve damage.

Protective Effects of Curcumin Against Paclitaxel-Induced Spinal Cord and Sciatic Nerve Injuries in Rats

Paclitaxel (PTX) is an antineoplastic agent commonly used in the treatment of solid tumors and is known to cause dose-limiting peripheral neurotoxicity. This study was performed to evaluate the protective effect of curcumin (CUR) against PTX-induced spinal cord and sciatic nerve injuries in rats. The rats were administered PTX (2 mg/kg, BW) intraperitoneally for the first 5 consecutive days followed by administration of CUR (100 and 200 mg/kg, BW daily in corn oil) orally for 10 days. Our results showed that CUR significantly reduced mRNA expression levels of NF-κB, TNF-α, IL-6, iNOS and GFAP whereas caused an increase in levels of Nrf2, HO-1 and NQO1 in the spinal cord and sciatic nerve of PTX-induced rats. In addition, CUR suppressed the activation of apoptotic and autophagic pathways by increasing Bcl-2 and Bcl-xL, and decreasing p53, caspase-3, Apaf-1, LC3A, LC3B and beclin-1 mRNA expression levels. The results showed that CUR also maintained the spinal cord and sciatic nerve histological architecture and integrity by both LFB staining and H&E staining. Immunohistochemical expressions of 8-OHdG, caspase-3 and LC3B in the PTX-induced spinal cord tissue were decreased after administration of CUR. Taken together, our findings demonstrated that CUR has protective effects on PTX-induced spinal cord and sciatic nerve injuries in rats.

An Investigation of the Molecular Mechanisms Underlying the Analgesic Effect of Jakyak-Gamcho Decoction: A Network Pharmacology Study

Herbal drugs have drawn substantial interest as effective analgesic agents; however, their therapeutic mechanisms remain to be fully understood. To address this question, we performed a network pharmacology study to explore the system-level mechanisms that underlie the analgesic activity of Jakyak-Gamcho decoction (JGd; Shaoyao-Gancao-Tang in Chinese and Shakuyaku-Kanzo-To in Japanese), an herbal prescription consisting of Paeonia lactiflora Pallas and Glycyrrhiza uralensis Fischer. Based on comprehensive information regarding the pharmacological and chemical properties of the herbal constituents of JGd, we identified 57 active chemical compounds and their 70 pain-associated targets. The JGd targets were determined to be involved in the regulation of diverse biological activities as follows: calcium- and cytokine-mediated signalings, calcium ion concentration and homeostasis, cellular behaviors of muscle and neuronal cells, inflammatory response, and response to chemical, cytokine, drug, and oxidative stress. The targets were further enriched in various pain-associated signalings, including the PI3K-Akt, estrogen, ErbB, neurotrophin, neuroactive ligand-receptor interaction, HIF-1, serotonergic synapse, JAK-STAT, and cAMP pathways. Thus, these data provide a systematic basis to understand the molecular mechanisms underlying the analgesic activity of herbal drugs.

Herbal Decoction Divya-Peedantak-Kwath Alleviates Allodynia and Hyperalgesia in Mice Model of Chemotherapy-Induced Peripheral Neuropathy via Modulation in Cytokine Response

The widely used cancer treatment, chemotherapy, causes severe long-term neuropathic pain in 30–40% cases, the condition clinically known as chemotherapy-induced peripheral neuropathy (CIPN). Approved conventional analgesics are sometimes ineffective, while others like opioids have undesirable side effects like addiction, seizures, and respiratory malfunctioning. Tricyclic antidepressants and anticonvulsants, although exhibit anti-allodynic effects in neuropathy, also have unpleasant side effects. Thus, alternative medicines are being explored for CIPN treatment. Despite scattered reports on different extracts from different plants having potential anti-allodynic effects against CIPN, no established medicine or formulation of herbal origin exists. In this study, efficacy of an herbal decoction, formulated based on ancient medicinal principles and protocols for treating neuropathic pain, Divya-Peedantak-Kwath (DPK), has been evaluated in a paclitaxel (PTX)-induced peripheral neuropathic mouse model. We observed that DPK has prominent anti-allodynic and anti-hyperalgesic effects and acts as a nociceptive modulator for CIPN. With exhibited antioxidative effects, DPK restored the redox potential of the sciatic nerves to the normal. On histopathological evaluation, DPK prevented the PTX-induced lesions in the sciatic nerve, in a dose-dependent manner. It also prevented inflammation by modulating the levels of pro-inflammatory cytokines involved in CIPN pathogenesis. Our observations evinced that DPK can alleviate CIPN by attenuating oxidative stress and concomitant neuroinflammation through immune modulation.

Resveratrol, curcumin and gallic acid attenuate glyoxal-induced damage to rat renal cells

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RES, CUR and GA protected renal cells from GO–induced cells death.

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RES, CUR and GA reduced formation of ROS.

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RES, CUR and GA diminished lipid peroxidation products.

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RES, CUR and GA repressed GO-induced mitochondrial membrane potential collapse.

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RES, CUR and GA decreased lysosomal membrane leakage in GO-treated cells.

Glyoxal (GO), a by-product of glucose auto-oxidation, is involved in the glycation of proteins/ lipids and formation of advanced glycation (AGE) and lipoxidation (ALE) end products. AGE/ALE were shown to contribute to diabetic complications development/progression such as nephropathy. Diabetic nephropathy progression has an oxidative nature. Given the antioxidant effects of polyphenols, potential protective effects of resveratrol, curcumin and gallic acid, in rat renal cells treated with GO, were evaluated in the present work. According to our results, incubation of GO with the cells reduced their viability and led to membrane lysis, reactive oxygen species (ROS) formation, lipid peroxidation, mitochondrial membrane potential collapse, and lysosomal membrane leakage. These findings were prevented by pre-treatment with resveratrol, curcumin and gallic acid. Mitochondrial and lysosomal toxic interactions appear to worsen oxidative stress/cytotoxicity produced by GO. Resveratrol, curcumin and gallic acid inhibited ROS formation and attenuated GO-induced renal cell death.

Evaluation of the protective effects of quercetin and gallic acid against oxidative toxicity in rat's kidney and HEK-293 cells

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Gallic acid has better antioxidant protective effect than quercetin in vivo.

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Quercetin has better antioxidant protective effect than gallic acid in vitro.

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The antioxidant effect of quercetin was at the least concentration tested.

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The antioxidant effect of gallic acid was at a higher concentrated tested.

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The in vivo dosage for the antioxidant effects of quercetin in the kidney is low.

Quercetin and gallic acid are phytochemicals with interesting pharmacological properties. We herein investigated the protective effect of quercetin (QUE) in comparison with gallic acid (GAL) against exogenously-induced oxidative damage in rats’ kidney and human embryonic kidney (HEK-293) cell lines. Adult Wistar rats were treated with QUE and GAL (50 mg/kg) separately or in combination with di-n-butylphthalate (DnBP) for 14 days; and HEK-293 cells were treated with different concentrations of GAL (25−294 μM) or QUE (2−17 μM or 28−165.43 μM) singly or in combination with H₂O₂ (200 μM). After treatment, the kidney and cell extracts were processed for biochemical analysis and histopathology. We found that GAL but not QUE prevented DnBP-induced increase in lipid peroxidation (2.603 ± 0.25 vs. 3.65 ± 0.21 μmol/mL). Treatment with QUE but not GAL was associated with increased plasma creatinine (729.09 ± 55.68 vs. 344.25 ± 50.78 μmol/l) and tissue malondialdehyde (3.72 ± 0.62 vs. 1.67 ± 0.47 μmol/mL) concentrations, along with histo-pathological changes such as glomerular and tubular degenerations. However, QUE exhibited wider therapeutic concentration ranges than GAL at which it inhibits lipid peroxidation in HEK-293 cells, and was found to inhibit H₂O₂-induced lipid peroxidation even at the lowest concentration (2 μM) that was tested (0.607 ± 0.074 vs. 0.927 ± 0.106 μmol/l). These suggest that the in vivo dosages required for the antioxidant protective effects of QUE in renal tissues are low.

Methods for in vivo studies in rodents of chemotherapy induced peripheral neuropathy

Peripheral neuropathy is one of the most common, dose limiting, and long-lasting disabling adverse events of chemotherapy treatment. Unfortunately, no treatment has proven efficacy to prevent this adverse effect in patients or improve the nerve regeneration, once it is established. Experimental models, particularly using rats and mice, are useful to investigate the mechanisms related to axonal or neuronal degeneration and target loss of function induced by neurotoxic drugs, as well as to test new strategies to prevent the development of neuropathy and to improve functional restitution. Therefore, objective and reliable methods should be applied for the assessment of function and innervation in adequately designed in vivo studies of CIPN, taking into account the impact of age, sex and species/strains features. This review gives an overview of the most useful methods to assess sensory, motor and autonomic functions, electrophysiological and morphological tests in rodent models of peripheral neuropathy, focused on CIPN. We include as well a proposal of protocols that may improve the quality and comparability of studies undertaken in different laboratories. It is recommended to apply more than one functional method for each type of function, and to perform parallel morphological studies in the same targets and models.