koumine and Neuralgia

New remedies are required for the treatment of diabetic neuropathic pain (DNP) due to insufficient efficacy of available therapies. Here, we used chemogenetic approaches combined with in vivo pharmacology to elucidate the role of basolateral amygdala (BLA) astrocytes in DNP pathogenesis and provide new insights into therapeutic strategies for DNP.. A streptozotocin-induced DNP model was established. Designer receptors exclusively activated by designer drugs (DREADDs) were used to regulate astrocyte activity. Mechanical hyperalgesia was assessed using the electronic von Frey test. Anxiety-like behaviours were detected using open field and elevated plus maze tests. Astrocytic activity was detected by immunofluorescence, and cytokine content was determined by ELISA.. BLA astrocytes were regulated by DREADDs, and inhibition of BLA astrocytes attenuated mechanical allodynia and pain-related negative emotions in DNP rats. In contrast, temporary activation of BLA astrocytes induced allodynia without anxious behaviours in naive rats. In addition, koumine (KM) alleviated mechanical allodynia and anxiety-like behaviours in DNP rats, inhibited the activation of BLA astrocytes and suppressed the inflammatory response. Furthermore, persistent activation of BLA astrocytes through chemogenetics mimicked chronic pain, and KM alleviated the pain hypersensitivity and anxiety-like behaviours.. DREADDs bidirectionally regulate the activity of BLA astrocytes, which proves for the first time the role of BLA astrocyte activation in the pathogenesis of DNP and represents a novel therapeutic strategy for DNP. KM ameliorates DNP, perhaps by inhibiting the activation of BLA astrocytes and reveal KM as a potential candidate for treating DNP.

Topics: Animals; Astrocytes; Basolateral Nuclear Complex; Diabetes Mellitus; Hyperalgesia; Neuralgia; Rats

Diabetic neuropathic pain (DNP), a complication of diabetes, has serious impacts on human health. As the pathogenesis of DNP is very complex, clinical treatments for DNP is limited. Koumine (KM) is an active ingredient extracted from Gelsemium elegans Benth. that exerts an inhibitory effect on neuropathic pain (NP) in several animal models.. To clarify the anti-NP effect of KM on rats with DNP and the molecular mechanisms involving the Notch- Jκ recombination signal binding protein (RBP-Jκ) signaling pathway.. Male Sprague-Dawley rats were administered streptozocin (STZ) by intraperitoneal injection to induce DNP. The effect of KM on mechanical hyperalgesia in rats with DNP was evaluated using the Von Frey test. Microglial polarization in the spinal cord was examined using western blotting and quantitative real-time PCR. The Notch-RBP-Jκ signaling pathway was analysed using western blotting.. KM attenuated DNP during the observation period. In addition, KM alleviated M1 microglial polarization in STZ-induced rats. Subsequent experiments revealed that Notch-RBP-Jκ signaling pathway was activated in the spinal cord of rats with DNP, and the activation of this pathways was decreased by KM. Additionally, KM-mediated analgesia and deactivation of the Notch-RBP-Jκ signaling pathway were inhibited by the Notch signaling agonist jagged 1, indicating that the anti-DNP effect of KM may be regulated by the Notch-RBP-Jκ signaling pathway.. KM is a potentially desirable candidate treatment for DNP that may inhibit microglial M1 polarization through the Notch-RBP-Jκ signaling pathway.

Topics: Animals; Cell Polarity; Diabetes Mellitus; Immunoglobulin J Recombination Signal Sequence-Binding Protein; Indole Alkaloids; Male; Microglia; Neuralgia; Rats; Rats, Sprague-Dawley; Receptors, Notch; Signal Transduction

Despite decades of studies, the currently available drugs largely fail to control neuropathic pain. Koumine-an alkaloidal constituent derived from the medicinal plant

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Astrocytes; Carrier Proteins; Cell Line; Indole Alkaloids; Inflammation; Male; Microglia; Neuralgia; Rats, Sprague-Dawley; Receptors, GABA-A; Sciatic Nerve; Spinal Cord

Koumine is an alkaloid monomer found abundantly in Gelsemium plants. It has been shown to reverse thermal hyperalgesia and mechanical allodynia induced by sciatic nerve chronic constriction injury (CCI) in rats in a dose-dependent manner. Interestingly, this effect is mediated by elevated allopregnanolone levels in the spinal cord (SC). Since 3α-hydroxysteroid oxidoreductase (3α-HSOR), the key synthetase of allopregnanolone, is responsible for allopregnanolone upregulation in the SC, the objective of the present study was to investigate the role of its expression in the SC in koumine-induced analgesia using a rat model of neuropathic pain following peripheral nerve injury.. Time-course investigations of immunohistochemistry and real-time polymerase chain reaction revealed that the immunoreactivity and mRNA expression of 3α-HSOR markedly increased in a time-dependent manner in the SC of koumine-treated CCI rats. Furthermore, 3α-HSOR activity in the SC of koumine-treated CCI rats increased by 15.8% compared to the activity in untreated CCI rats. Intrathecal injection of medroxyprogesterone acetate, a selective 3α-HSOR inhibitor, reversed the analgesic effect of koumine on CCI-induced mechanical pain perception. Our results confirm that koumine alleviates neuropathic pain in rats with CCI by enhancing 3α-HSOR mRNA expression and bioactivity in the SC.. This study demonstrates that 3α-HSOR is an important molecular target of koumine for alleviating neuropathic pain. Koumine may prove a promising compound for the development of novel analgesic agents effective against intractable neuropathic pain.

Topics: 3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); Analgesics; Animals; Biocatalysis; Chronic Disease; Constriction; Disease Models, Animal; Gene Expression Regulation, Enzymologic; Hyperalgesia; Immunohistochemistry; Indole Alkaloids; Injections, Subcutaneous; Male; Medroxyprogesterone Acetate; Neuralgia; Rats, Sprague-Dawley; RNA, Messenger; Sciatic Nerve; Spinal Cord; Spinal Cord Dorsal Horn

Diabetic neuropathy is characterized by progressive degeneration of nerve fibers associated with diabetes mellitus. Antidepressants and anticonvulsants are the mainstay of pharmacological treatment, but are often limited in effectiveness against the core clinical feature of pain. In the current study, we examined the potential effects of koumine, a Gelsemium elegans Benth alkaloid, using a rat model of diabetic neuropathy. Rats were administered intraperitoneally a single dose of streptozocin (60 mg/kg) to induce type 1 diabetes. Koumine was given at a dose range of 0.056-7 mg/kg subcutaneously for one week starting 3 weeks after streptozocin adminstration. Behavioral responses to mechanical stimuli were evaluated every day after streptozocin injection. At 4 weeks after streptozocin injection, sensory nerve conduction velocity (SNCV) and morphological alternation of sciatic nerves were assessed by electron microscopy. Diabetic rats developed mechanical hyperalgesia within 3 weeks after streptozocin injection and exhibited reduced SNCV and impaired myelin/axonal structure. Koumine treatment of diabetic rats decreased neuropathic pain behavior as early as after the first administration. At a dose of 7 mg/kg, koumine was more effective than gabapentin (100 mg/kg), and decreased mechanical sensitivity threshold to a level comparable to healthy control. Repeated treatment of koumine significantly reduced the damage to axon and myelin sheath of the sciatic nerve and increased SNCV, without affecting body weight and blood glucose. These findings encourage the use of koumine in the treatment of diabetic neuropathy.

Topics: Amines; Animals; Blood Glucose; Body Weight; Cyclohexanecarboxylic Acids; Diabetes Mellitus, Experimental; Diabetic Neuropathies; Dose-Response Relationship, Drug; Gabapentin; gamma-Aminobutyric Acid; Hyperalgesia; Indole Alkaloids; Male; Nerve Degeneration; Neural Conduction; Neuralgia; Neuroprotective Agents; Pain Measurement; Rats; Sciatic Nerve; Sensory Receptor Cells

Crude alkaloidal extraction from Gelsemium elegans Benth. produces analgesic property. However, its clinical utility has been obstructed by its narrow therapeutic index. Here, we investigated the potential of koumine, a monomer of Gelsemium alkaloids, to reduce both inflammatory and neuropathic pain. Interestingly, allopregnanolone, a neurosteroid, appeared to mediate the reduction of neuropathic pain. The potential anti-inflammatory pain effects of koumine were evaluated by acetic acid-, formalin- and complete Freund's adjuvant (CFA) -induced nociceptive behaviors in mice. Chronic constriction injury (CCI) and L5 spinal nerve ligation (L5 SNL), inducing thermal hyperalgesia and mechanical allodynia in rats, were used to test whether repeated treatment of koumine ameliorated neuropathic pain. Finally, we explored if koumine altered the level of neurosteroids in rat spinal cord of CCI neuropathy using liquid chromatography-tandem mass spectrometry. Koumine dose-dependently reduced the acetic acid-induced writhes and formalin-induced licking/biting time of Phase II in mice. Repeated administrations of koumine also dose-dependently reversed the CFA-, CCI- and L5 SNL-induced thermal hyperalgesia, as well as, CCI- and L5 SNL-induced mechanical allodynia in rats. The level of allopregnanolone, but not pregnenolone, in the L5-6 spinal cord was elevated by repeated treatment of koumine in CCI-induced neuropathic rats. These results demonstrate that koumine has a significant analgesic effect in rodent behavioral models of inflammatory and neuropathic pain, and that the reduction in neuropathic pain may be associated with the upregulation of allopregnanolone in the spinal cord.

Topics: Analgesics; Animals; Disease Models, Animal; Gelsemium; Hyperalgesia; Indole Alkaloids; Inflammation; Male; Mice; Mice, Inbred ICR; Neuralgia; Pain; Pain Measurement; Pregnanolone; Rats; Rats, Sprague-Dawley; Spinal Cord; Up-Regulation