Role of Cannabinoid Receptors in Crocin-Induced Hypoalgesia in Neuropathic Pain in Rats

The effect of acute crocin on behavioral changes and BDNF expression level in socially isolated rats

Social isolation is a reliable method used for the induction of depression and psychiatric disorders in rodents. It has been suggested that social isolation can lead to hyperlocomotion, as a schizophrenic-like symptom in rodents. On the other hand, crocin (the major constituent of Crocus sativus) induces a wide-range of neuroprotective and mood enhancer effects. In the present study, we aimed to investigate the effect of acute crocin on social isolation-induced behavioral changes and BDNF expression in the hippocampus. Novelty-suppressed feeding test, open field test, marble burying test, hot plate, forced swim test, and the shuttle box were used to assess anxiety-like behavior, locomotor activity, obsessive-compulsive-like (OCD-like) behavior, pain threshold, depressive-like behavior, and passive avoidance memory, respectively. Real-time PCR was used to assess BDNF hippocampal expression level. The results showed that social isolation decreased anxiety- and depressive-like behavior, pain threshold, and BDNF expression, and induced OCD-like behavior and hyperlocomotion. Crocin dose-dependently restored the effect of social isolation on pain threshold, locomotor activity, depressive-like behavior, OCD-like behavior, and BDNF expression. Passive avoidance memory performance was also unaffected. In conclusion, we showed a hyperlocomotion profile and OCD-like behaviors, and a robust decrease in pain threshold in socially isolated rats. It can be suggested that social isolation from adolescence induces a "hyperlocomotion state" that affects all the behavioral functions of rats. Also, the function of BDNF can be related to a hyperlocomotion state and OCD-like symptom. It seems that BDNF expression level can be related to the therapeutic effect of crocin.

Mitochondrial DNA and Electron Transport Chain Protein Levels Are Altered in Peripheral Nerve Tissues from Donors with HIV Sensory Neuropathy: A Pilot Study

Distal sensory polyneuropathy (DSP) and distal neuropathic pain (DNP) remain significant challenges for older people with HIV (PWH), necessitating enhanced clinical attention. HIV and certain antiretroviral therapies (ARTs) can compromise mitochondrial function and impact mitochondrial DNA (mtDNA) replication, which is linked to DSP in ART-treated PWH. This study investigated mtDNA, mitochondrial fission and fusion proteins, and mitochondrial electron transport chain protein changes in the dorsal root ganglions (DRGs) and sural nerves (SuNs) of 11 autopsied PWH. In antemortem standardized assessments, six had no or one sign of DSP, while five exhibited two or more DSP signs. Digital droplet polymerase chain reaction was used to measure mtDNA quantity and the common deletions in isolated DNA. We found lower mtDNA copy numbers in DSP+ donors. SuNs exhibited a higher proportion of mtDNA common deletion than DRGs in both groups. Mitochondrial electron transport chain (ETC) proteins were altered in the DRGs of DSP+ compared to DSP- donors, particularly Complex I. These findings suggest that reduced mtDNA quantity and increased common deletion abundance may contribute to DSP in PWH, indicating diminished mitochondrial activity in the sensory neurons. Accumulated ETC proteins in the DRG imply impaired mitochondrial transport to the sensory neuron's distal portion. Identifying molecules to safeguard mitochondrial integrity could aid in treating or preventing HIV-associated peripheral neuropathy.

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.

The CB1 cannabinoid receptors involvement in anti-epileptic effect of safranal on penicillin-induced epileptiform activity in rats

Neuroprotective effects for natural products are supported by several studies. In this regard, safranal, a constitute of saffron, has the potential to exert beneficial effects in neuro-logical disorders such as Parkinson's disease, epilepsy, stroke, multiple sclerosis and Alzheimer's disease. Here, we investigated the effect of safranal on penicillin-induced epileptiform activity. Also, the effects of intracerebroventricular (ICV) microinjection of AM251 as a CB1-cannabinoid receptors antagonist to clarify the possible mechanism of safranal were evaluated. Epileptiform activity was induced by intra-cortical administration of penicillin (300 IU, 1.50 μL) in urethane-anesthetized rats. Electrocorticographic recordings were used to analyze the frequency and amplitude of spike waves. Intraperitoneal injections of safranal at doses of 1.00 and 4.00 mg kg-1 significantly reduced both the number and amplitude of spike waves. The ICV microinjection of AM251 (0.50 μg 2.00 μL-1) significantly increased the frequency and amplitude of spike waves. In addition, the anti-epileptic effect induced by administration of safranal at a dose of 4.00 mg kg-1 was partially prevented by ICV microinjection of 0.50 μg 2.00 μL-1 of AM251. The results showed anti-epileptiform activities for safranal. Central CB1 cannabinergic receptors might be involved in the anti-epileptiform activity of safranal.

Medicinal Plants for the Treatment of Neuropathic Pain: A Review of Randomized Controlled Trials

Neuropathic pain is a disabling condition caused by various diseases and can profoundly impact the quality of life. Unfortunately, current treatments often do not produce complete amelioration and can be associated with potential side effects. Recently, herbal drugs have garnered more attention as an alternative or a complementary treatment. In this article, we summarized the results of randomized clinical trials to evaluate the effects of various phytomedicines on neuropathic pain. In addition, we discussed their main bioactive components and potential mechanisms of action to provide a better view of the application of herbal drugs for treating neuropathic pain.

Exercise induced myelin protein zero improvement in neuropathic pain rats

PURPOSE

Aerobic exercise including swimming plays a suitable role in improving somatosensory injuries. Neuropathic pain is a debilitating condition that occurs following injury or diseases of somatosensory system. In the present study, we tried to investigate the effect of exercise on myelin protein zero of sciatic nerve injured rats.

MATERIALS AND METHODS

Forty male rats (180-220 g) were divided into five groups (intact, sham, sham + exercise, neuropathy, and neuropathy + exercise). Right Sciatic nerve of anesthetized rats was exposed and loosely ligated (four ligations with 1 mm apart) using catgut chromic sutures to induce neuropathy. After 3 days of recovery, swimming exercise began (20 min/day/5 days a week/4 weeks). Mechanical allodynia and thermal hyperalgesia were detected using Von Frey filaments and plantar test, respectively. Sciatic nerve at the place of injury was dissected out to measure the myelin protein zero by western blot analysis. In the intact and sham groups, sciatic nerve removed at the place similar to injured group.

RESULTS

We found that neuropathy significantly (p < 0.05) reduced paw withdrawal mechanical and thermal thresholds and swimming exercise significantly (p < 0.05) increased paw withdrawal mechanical and thermal thresholds compared to the neuropathy group. Moreover, we found that MPZ level significantly (p < 0.01) decreased in neuropathy group against that in sham group, and exercise prominently (p < 0.05) reversed MPZ level towards control level.

CONCLUSIONS

Swimming exercise improves myelin protein zero level in neuropathic rats along with attenuating neuropathic pain. This is a promising approach in improving neuropathological disorders including Charcot-Marie-Tooth and Dejerine-Sottas disease.

Saffron (Crocus sativus) and its constituents for pain management: A review of current evidence

Pain can become a chronic and deliberating experience with a significant burden. In preclinical and clinical studies, Saffron (Crocus sativus L.) has shown analgesic activities. Considering the unsatisfactory results of current therapeutic management for chronic pain conditions, we aimed to review saffron's analgesic activity and underlying mechanisms. Saffron showed antinociceptive activities in formalin-, carrageenan-, and capsaicin-induced experimental pain models. Saffron analgesic activities affected several targets, including ion channels of nociceptors; the adrenergic system and central histaminic system; inhibition of inflammatory pathways, apoptotic pathways, and oxidative stress; regulation of NO pathway, and the endocannabinoid system. Clinical studies showed analgesia of Saffron in rheumatoid arthritis, after-pain following childbirth, dysmenorrhea, and fibromyalgia. Our literature review showed that saffron can be beneficial as an adjunct therapy to commonly used analgesics in practice, particularly in chronic pain conditions.

Carotenoids in Palliative Care—Is There Any Benefit from Carotenoid Supplementation in the Adjuvant Treatment of Cancer-Related Symptoms?

Carotenoids are organic, liposoluble pigments found in nature, which are responsible for the characteristic colors of ripe tomatoes, carrots, peppers, and crustaceans, among others. Palliative care provided to patients with an incurable disease is aimed at improving the patient’s quality of life through appropriate treatment of symptoms accompanying the disease. Palliative care patients with burdensome symptoms related to advanced-stage cancers are especially interested in the use of natural dietary supplements and herbal remedies to reduce symptoms’ intensity and ameliorate the quality of life. Carotenoids seem to be a group of natural compounds with particularly promising properties in relieving symptoms, mainly due to their strong antioxidant, anti-inflammatory, and neuroprotective properties. Moreover, carotenoids have been used in folk medicine to treat various diseases and alleviate the accompanying symptoms. In this narrative review, the authors decided to determine whether there is any scientific evidence supporting the rationale for carotenoid supplementation in advanced-stage cancer patients, with particular emphasis on the adjuvant treatment of cancer-related symptoms, such as neuropathic pain and cancer-related cachexia.

Effectiveness of crocin of saffron (Crocus sativus L.) against chemotherapy-induced peripheral neuropathy: A randomized, double-blind, placebo-controlled clinical trial

ETHNOPHARMACOLOGICAL RELEVANCE

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the complications vexes patients treated with anti-cancer agents. Saffron has been demonstrated to attenuate symptoms of peripheral neuropathy in animal models. Also, there is a published clinical trial that investigated the pain relieving effect of saffron following nationally accepted rules and concluded that saffron was successful in alleviating pain symptoms in patients suffering from fibromyalgia.

AIM OF THE STUDY

We aimed to determine the efficacy of crocin as a constituent of saffron in CIPN as the first report.

MATERIALS AND METHODS

One hundred and seventy-seven enrolled eligible patients (between December 2018 and March 2020) for study entry were cases demonstrating mild to severe symptomatic CIPN for at least a month. These cases were randomly assigned to two main groups including 15 mg crocin tablet, bid (30 mg total daily target dose) and placebo tablet for 8 weeks. A crossover study was performed with a 2-week washout period. Patient outcomes were measured once a week for 8 consecutive weeks.

RESULTS

Grade of sensory, motor and neuropathic pain decreased considerably and significantly in the crocin group compared with placebo (P < 0.05). Observed toxicities were mild and adverse effects had no significant differences between the two groups (P > 0.05).

CONCLUSIONS

Crocin considerably seems to be effective for relieving symptoms of CIPN in cancer patients receiving chemotherapy agents. However, further studies are needed about crocin with its beneficial neuropharmacological effects and lower adverse effects than the chemical agents such as antidepressants, lamotrigine, and gabapentin.

Effects of varying degrees of ligation in a neuropathic pain model induced by chronic constriction injury

AIM

Ligature tightness of chronic constriction injury (CCI) model remains inconsistent and controversial, presenting barriers for researchers.

METHODS

We summarized the different ligation criteria in literature and attempted to clarify their effects. To assess constriction under different criteria, we calculated the radial strain (ε_R) of ligated nerves from digital photographs. The mechanical withdrawal thresholds (MWT), thermal withdrawal latency (TWL) and sciatic functional index (SFI) were observed in rats of different groups to assess the state of model. Changes of myelin sheath were detected by pathological staining and immunohistochemistry.

RESULTS

The median ε_R values in the Loose, Medium and Tight groups were 13.6%, 15.2% and 21.7%, respectively. Ligated groups had lower MWT than Sham group and the TWL of rats in the Loose approached to rats with sham operation, while that of the Tight group was higher than Medium group 14 days after surgery. Medium and Tight groups showed more abnormal in SFI, compared with the other two groups 14 days. Pathological staining revealed demyelination in three CCI groups, especially in the sciatic nerves. Myelin protein zero levels decreased in the sciatic nerves as the degree of constriction increased, but myelin basic protein of the Medium group was lowest abundant in the spinal cords of all rats.

CONCLUSIONS

Our study demonstrated that the surrounding muscles briefly twitched when the diameter of the sciatic nerves was constricted by approximately 14-15%, which may provide a reference for other researchers for establishing CCI models.