Ethanolic extract of Aloe vera ameliorates sciatic nerve ligation induced neuropathic pain

Formulation of Phytosomes Containing Rubia cordifolia Extract for Neuropathic Pain: In Vitro and In Vivo Evaluation

This study aimed to develop a delivery system for the dried aqueous extract of Rubia cordifolia leaves (RCE) that could improve the neuroprotective potential of RCE by improving the bioavailability of the chief chemical constituent rubiadin. Rubiadin, an anthraquinone chemically, is a biomarker phytoconstituent of RCE. Rubiadin is reported to have strong antioxidant and neuroprotective activity but demonstrates poor bioavailability. In order to resolve the problem related to bioavailability, RCE and phospholipids were reacted in disparate ratios of 1:1, 1:2, and 1:3 to prepare phytosome formulations PC1, PC2, and PC3, respectively. The formulation PC2 showed particle size of 289.1 ± 0.21 nm, ζ potential of -6.92 ± 0.10 mV, entrapment efficiency of 72.12%, and in vitro release of rubiadin of 89.42% at pH 7.4 for a period up to 48 h. The oral bioavailability and neuroprotective potential of PC2 and RCE were assessed to evaluate the benefit of PC2 formulation over the crude extract RCE. Formulation PC2 showed a relative bioavailability of 134.14% with a higher neuroprotective potential and significantly (p < 0.05) augmented the nociceptive threshold against neuropathic pain induced by partial sciatic nerve ligation method. Antioxidant enzyme levels and histopathological studies of the sciatic nerves in various treatment groups significantly divulged that PC2 has enough potential to reverse the damaged nerves into a normal state. Finally, it was concluded that encapsulated RCE as a phytosome is a potential carrier system for enhancing the delivery of RCE for the efficient treatment of neuropathic pain.

Mitigation of sciatica injury-induced neuropathic pain through active metabolites derived from medicinal plants

Sciatica characterized by irritation, inflammation, and compression of the lower back nerve, is considered one of the most common back ailments globally. Currently, the therapeutic regimens for sciatica are experiencing a paradigm shift from the conventional pharmacological approach toward exploring potent phytochemicals from medicinal plants. There is a dire need to identify novel phytochemicals with anti-neuropathic potential. This review aimed to identify the potent phytochemicals from diverse medicinal plants capable of alleviating neuropathic pain associated with sciatica. This review describes the pathophysiology of sciatic nerve pain, its cellular mechanisms, and the pharmacological potential of various plants and phytochemicals using animal-based models of sciatic nerve injury-induced pain. Extensive searches across databases such as Medline, PubMed, Web of Science, Scopus, ScienceDirect, and Google Scholar were conducted. The findings highlights 39 families including Lamiaceae, Asteraceae, Fabaceae, and Apocyanaceae and Cucurbitaceae, effectively treating sciatic nerve injury-induced pain. Flavonoids made up 53% constituents, phenols and terpenoids made up 15%, alkaloids made up 13%, and glycosides made up 6% to be used in neuorpathic pain. Phytochemicals derived from various medicinal plants can serve as potential therapeutic targets for both acute and chronic sciatic injury-induced neuropathic pain.

Adenosine A2A Receptor Agonist, Polydeoxyribonucleotide Treatment Improves Locomotor Function and Thermal Hyperalgesia Following Neuropathic Pain in Rats

PURPOSE

Lithotomy position has been widely used in the various urologic surgery. Occasionally sensory and motor problems of the lower extremities are occurred due to the lithotomy position and these deficits may be related with sciatic nerve injury (SNI). Inflammatory process is a factor to induce functional impairment after SNI. Therefore, we evaluated the role of adenosine A2A receptor agonists, polydeoxyribonucleotide (PDRN) showing anti-inflammatory effect on locomotor function following SNI in rats.

METHODS

Sciatic nerve was compressed with surgical clips for 1 minute after exposing of right sciatic nerve. After 3 days of SNI, PDRN (2, 4, and 8 mg/kg) was applied to the damaged area of sciatic nerve once daily for 10 days. Walking track analysis was conducted for locomotor function and plantar test was performed for thermal pain sensitivity. Level of cyclic adenosine-3´,5´-monophosphate (cAMP) were measured using enzyme-linked immunosorbent assay. Western blot analysis was performed for tumor necrosis factor (TNF)-α, interleukin (IL)-1β, cAMP response element binding protein (CREP), vascular endothelial growth factor (VEGF). Immunofluorescence for neurofilament was also conducted.

RESULTS

Locomotor function was decreased and thermal pain sensitivity was increased by SNI. SNI enhanced proinflammatory cytokines' production, such as TNF-α and IL-1β, while suppressed CREP phosphorylation and cAMP level. SNI also reduced the expression of VEGF and neurofilaments. However, treatment with PDRN inhibited proinflammatory cytokines' production and upregulated CREP phosphorylation and cAMP expression. PDRN also enhanced the expression of VEGF and neurofilaments. As a result, PDRN improved locomotor function and alleviated thermal hyperalgesia after SNI.

CONCLUSION

PDRN has shown potential to be used as an effective treatment for neuropathic pain.

Traditional Chinese medicine alleviating neuropathic pain targeting purinergic receptor P2 in purinergic signaling: A review

Past studies have suggested that Chinese herbal may alleviate neuropathic pain, and the mechanism might target the inhibition of purinergic receptor P2. This review discusses whether traditional Chinese medicine target P2 receptors in neuropathic pain and its mechanism in order to provide references for future clinical drug development. The related literatures were searched from Pubmed, Embase, Sinomed, and CNKI databases before June 2023. The search terms included"neuropathic pain", "purinergic receptor P2", "P2", "traditional Chinese medicine", "Chinese herbal medicine", and "herb". We described the traditional Chinese medicine alleviating neuropathic pain via purinergic receptor P2 signaling pathway including P2X2/3 R, P2X3R, P2X4R, P2X7R, P2Y1R. Inhibition of activating glial cells, changing synaptic transmission, increasing painful postsynaptic potential, and activating inflammatory signaling pathways maybe the mechanism. Purine receptor P2 can mediate the occurrence of neuropathic pain. And many of traditional Chinese medicines can target P2 receptors to relieve neuropathic pain, which provides reasonable evidences for the future development of drugs. Also, the safety and efficacy and mechanism need more in-depth experimental research.

Dexmedetomidine Improves Locomotor Function and Alleviates Thermal Hyperalgesia Following Sciatic Nerve Crush Injury in Rats

PURPOSE

The effects of dexmedetomidine on locomotor function and thermal hyperalgesia in sciatic nerve crush injury (SNCI) were investigated using rats.

METHODS

After exposing the right sciatic nerve, the sciatic nerve was crushed for 1 minute by a surgical clip. One day after nerve injury, dexmedetomidine (5, 25, and 50 µg/kg) was directly applied to the injured sciatic nerve once a day for 14 days. Walking track analysis was used to assess locomotor function and plantar test was conducted to assess thermal pain sensitivity. Immunohistochemistry was performed to determine the expression of c-Fos in the ventrolateral periaqueductal gray (vlPAG) and paraventricular nucleus (PVN). Western blot was used to evaluate the expression level of nerve growth factor (NGF) and myelin basic protein (MBP) in the sciatic nerve.

RESULTS

SNCI resulted in deterioration of locomotor function and increased thermal pain sensitivity. The level of c-Fos expression in the PVN and vlPAG was increased and the level of NGF and MBP expression in the sciatic nerve was enhanced by SNCI. Dexmedetomidine treatment improved locomotor function and upregulated expression of NGF and MBP in the sciatic nerve of SNCI. Dexmedetomidine treatment alleviated thermal hyperalgesia and downregulated expression of c-Fos in the vlPAG and PVN after SNCI.

CONCLUSION

Dexmedetomidine may be used as a potential new treatment drug for recovery of locomotion and control of pain in peripheral nerve injury.

Haematoxylon campechianum Extract Ameliorates Neuropathic Pain via Inhibition of NF-κB/TNF-α/NOX/iNOS Signalling Pathway in a Rat Model of Chronic Constriction Injury

: In this study, the phytochemical composition and the possible prophylactic effects of an aqueous ethanol extract of Haematoxylon campechianum flowers (HCF) on peripheral neuropathic pain in a chronic constriction injury (CCI) rat model are investigated. Rats with induced CCI were subjected to neuropathic pain behaviour tests and evaluated by chemical, thermal, and mechanical sensation tests and functional recovery of the brain stem and sciatic nerve at 7- and 14-day intervals. The effect of the extract on acute pain and inflammation is also investigated. The extract exerted both peripheral and central analgesic and anti-inflammatory properties in addition to antipyretic effects that are clear from targeting COX, LOX and PGE. It was found that CCI produced significant thermal and mechanical hyperalgesia, cold allodynia and deleterious structural changes in both sciatic nerve and brain stem. Treatments with HCF extract significantly improved cold and thermal withdrawal latency, mechanical sensibility and ameliorated deleterious changes of sciatic nerve and brain stem at different dose levels. The extract also ameliorated oxidative stress and inflammatory markers in brain stem and sciatic nerve. It suppressed the apoptotic marker, p53, and restored myelin sheath integrity. The effects of HCF extract were more potent than pregabalin. Fifteen secondary metabolites, mainly gallotannins and flavonoids, were characterized in the extract based on their retention times and MS/MS data. The identified phenolic constituents from the extract could be promising candidates to treat neuropathic pain due to their diverse biological activities, including antioxidant, anti-inflammatory and neuroprotective properties.

Antinociceptive and neuroprotective effects of bromelain in chronic constriction injury-induced neuropathic pain in Wistar rats

Background

The continuous search for a novel neuropathic pain drug with few or no side effects has been a main focus of researchers for decades. This study investigated the antinociceptive and neuroprotective effects of bromelain in sciatic nerve ligation-induced neuropathic pain in Wistar rats.

Methods

Forty-eight Wistar rats randomly divided into eight groups comprised of six animals each were used for this study. Peripheral neuropathy was induced via chronic constriction of the common sciatic nerve. Thermal hyperalgesic and mechanical allodynia were assessed using a hotplate and von Frey filaments, respectively. The functional recovery and structural architecture of the ligated sciatic nerve were evaluated using the sciatic functional index test and a histological examination of the transverse section of the sciatic nerve. The neuroprotective effects of bromelain were investigated in the proximal sciatic nerve tissue after 21 days of treatment.

Results

Bromelain significantly (P < 0.05) attenuated both the thermal hyperalgesia and mechanical allodynic indices of neuropathic pain. There were improvements in sciatic function and structural integrity in rats treated with bromelain. These rats showed significant (P < 0.05) increases in sciatic nerve nuclear transcription factors (nuclear factor erythroid-derived-2-related factors-1 [NrF-1] and NrF-2), antioxidant enzymes (superoxide dismutase and glutathione), and reduced membrane-lipid peroxidation compared with the ligated control group.

Conclusions

This study suggest that bromelain mitigated neuropathic pain by enhancing the activities of nuclear transcription factors (NrF-1 and NrF-2) which increases the antioxidant defense system that abolish neuronal stress and structural disorganization.

Scolopendra subspinipes mutilans Extract Suppresses Inflammatory and Neuropathic Pain In Vitro and In Vivo

Background

Sciatic nerve injury develops from a variety of pathological causes, including traumatic injury and neuroinflammatory disorders, which are accompanied by pathological changes that have a critical impact on neuropathic pain and locomotor activity. Extracts of Scolopendra subspinipes mutilans (SSM) are used in traditional medicine for the treatment of a wide range of neuropathic diseases, including lower back pain, peripheral neuropathy, and sciatic nerve injury. Although SSM shows anti-inflammatory, antibacterial, and anticonvulsant activities, its diverse mechanisms of action remain unclear. Thus, the present study examined the effects of SSM in vitro and in vivo.

Methods

To estimate the anti-inflammatory effects of SSM, inflammatory conditions were induced using lipopolysaccharide (LPS) in RAW 264.7 cells, and inflammatory-related factors were evaluated by enzyme-linked immunosorbent assay (ELISA) and western blotting analyses. Sciatic nerve crush injury (SNCI) was induced in rats using a surgical clip instrument. The effects of SSM in the SNCI model were evaluated in behavioral tests by calculating the sciatic functional index (SFI) and measuring thermal hyperalgesia sensitivity and by monitoring inflammatory factors expression in western blotting analyses.

Results

We observed the anti-inflammatory effects of SSM treatment both in vitro and in vivo. The PGE₂ and NO production were suppressed by SSM. Protein analyses indicated that expression of NF-κB and degradation of IκBα were suppressed by SSM treatment. In addition, the levels of iNOS, TNF-α, IL-6, and COX-2 expression were reduced by SSM treatment in RAW 264.7 cells and in the SNCI-induced animals. In behavioral studies, SSM treatment enhanced the SFI and improved the thermal sensitivity test results.

Conclusions

Our results suggest that SSM suppresses the production of inflammatory factors via the NF-κB pathway and accelerates the morphological and functional recovery of the peripheral nervous system. Hence, SSM may be a useful therapeutic candidate for treatment of neuropathic pain diseases.