GS-KG9 ameliorates diabetic neuropathic pain induced by streptozotocin in rats

Electroacupuncture may alleviate diabetic neuropathic pain by inhibiting the microglia P2X4R and neuroinflammation

Diabetic neuropathic pain (DNP) is a common and destructive complication of diabetes mellitus. The discovery of effective therapeutic methods for DNP is vitally imperative because of the lack of effective treatments. Although 2 Hz electroacupuncture (EA) was a successful approach for relieving DNP, the mechanism underlying the effect of EA on DNP is still poorly understood. Here, we established a rat model of DNP that was induced by streptozotocin (STZ) injection. P2X4R was upregulated in the spinal cord after STZ-injection. The upregulation of P2X4R was mainly expressed on activated microglia. Intrathecal injection of a P2X4R antagonist or microglia inhibitor attenuated STZ-induced nociceptive thermal hyperalgesia and reduced the overexpression of brain-derived neurotrophic factor (BDNF), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the spinal cord. We also assessed the effects of EA treatment on the pain hypersensitivities of DNP rats, and further investigated the possible mechanism underlying the analgesic effect of EA. EA relieved the hyperalgesia of DNP. In terms of mechanism, EA reduced the upregulation of P2X4R on activated microglia and decreased BDNF, IL-1β and TNF-α in the spinal cord. Mechanistic research of EA's analgesic impact would be beneficial in ensuring its prospective therapeutic effect on DNP as well as in extending EA's applicability.

Withametelin, a steroidal lactone, isolated from datura innoxa attenuates STZ-induced diabetic neuropathic pain in rats through inhibition of NF-kB/MAPK signaling

Diabetic neuropathic pain is one of the microvascular complications of diabetes mellitus characterized by symmetrical pain and sensory abnormalities. A steroidal lactone isolated from the datura innoxa plant, withametelin (WMT), exhibited significant neuroprotective, anti-inflammatory, antioxidant, and anticancer properties. The current study aimed to investigate anti-neuropathic pain activity and the molecular mechanism of WMT against streptozotocin (STZ)-induced diabetic neuropathy. Rats were given a single injection of STZ (60 mg/kg, intraperitoneally (i.p.)) for induction of diabetes on the first day of the study. After the onset of diabetic neuropathy, pregabalin (10 mg/kg, i.p.) and WMT (0.1 and 1 mg/kg, i.p.) treatments were started from day 14 up to day 42. It was found that STZ-induced neuropathic pain behaviors were markedly reduced by WMT. It inhibited the STZ-associated histopathological changes and genotoxicity in the sciatic nerve and spinal cord. Additionally, Fourier transforms infrared (FTIR) spectroscopy results revealed that STZ-induced alterations in the biochemical components of the sciatic nerve's myelin sheath were inhibited by WMT. In the spinal cord, it markedly reduced the immunoreactivity of mitogen-activated protein kinases (MAPKs) signaling components such as p38-MAPK, c-Jun N-terminal kinase (JNK), extracellular-signal-regulated-kinase (ERK), and activator-protein 1 (AP-1). It also reduced the expression levels of nuclear factor-kappa-B (NF-κB), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS). The production of inflammatory cytokines was considerably reduced by WMT. This study provides convincing evidence that WMT treatment attenuated STZ-induced diabetic neuropathic pain by inhibition of MAPK/NF-κB signaling.

Comparative Efficacy of East Asian Herbal Formulae Containing Astragali Radix-Cinnamomi Ramulus Herb-Pair against Diabetic Peripheral Neuropathy and Mechanism Prediction: A Bayesian Network Meta-Analysis Integrated with Network Pharmacology

The Astragali Radix-Cinnamomi Ramulus herb-pair (ACP) has been widely used in the treatment of diabetic peripheral neuropathy (DPN) as part of East Asian herbal medicine (EAHM). Eligible randomized controlled trials (RCTs) were identified by searching 10 databases. The outcomes investigated were response rate, sensory nerve conduction velocity (SNCV), and motor nerve conduction velocity (MNCV) in four regions of the body. The compounds in the ACP and their targets of action, disease targets, common targets, and other relevant information were filtered using network pharmacology. Forty-eight RCTs, with 4308 participants, and 16 different interventions were identified. Significant differences were observed in the response rate, MNCV, and SNCV, as all EAHM interventions were superior to conventional medicine or lifestyle modification. The EAHM formula containing the ACP ranked highest in more than half of the assessed outcomes. Furthermore, major compounds, such as quercetin, kaempferol, isorhamnetin, formononetin, and beta-sitosterol, were found to suppress the symptoms of DPN. The results of this study suggest that EAHM may increase therapeutic efficacy in DPN management, and EAHM formulations containing the ACP may be more suitable for improving treatment response rates to NCV and DPN therapy.

Catecholaminergic and Cholinergic Systems Mediate Beneficial Effect of Vortioxetine on Diabetes-Induced Neuropathic Pain

The therapeutic potential of vortioxetine on mechanical hyperalgesia/allodynia was investigated in rats with streptozotocin-induced diabetes, and its possible mechanism of action was elucidated in this study. The obtained findings demonstrated that subacute vortioxetine treatment (5 and 10 mg/kg for 2 weeks) increased the reduced paw-withdrawal thresholds of diabetic rats both in the Randall-Selitto and Dynamic plantar tests. Moreover, the falling latencies of animals did not change in the Rota-rod assessments. These results suggest that vortioxetine administration significantly improved diabetes-induced hyperalgesia and allodynia responses in the rats without affecting their motor coordination. The vortioxetine (5 mg/kg)-induced antihyperalgesic and antiallodynic effects were reversed by AMPT, yohimbine, ICI 118,551, sulpiride and atropine pre-treatments, suggesting the involvement of the catecholaminergic system, α₂- and β₂-adrenoceptors, D_2/3 dopaminergic receptors and cholinergic muscarinic receptors in the exhibited pharmacological activity, respectively. Moreover, the data from the immunohistochemical studies indicated that the inhibition of c-Fos overexpression in dorsal horn neurons also mediates the beneficial effect of this drug. Vortioxetine induced no difference in plasma glucose levels in diabetic rats. If clinical studies confirm these findings, the concomitant beneficial effect of vortioxetine on mood disorders and its neutral activity profile on glycemic control may make it an alternative drug for the treatment of neuropathic pain.

The Effect of Yiqi Huoxue Tongluo Decoction on Spinal Cord Microglia Activation and ASK1-MKK3-p38 Signal Pathway in Rats with Diabetic Neuropathic Pain

Diabetic neuropathic pain (DNP) is one of the most common chronic peripheral neuropathies in diabetes mellitus (DM). Objective. To observe the underlying mechanism of the effects of Yiqi Huoxue Tongluo Decoction (YQHX) on DNP rats. Methods. SD rats were intraperitoneally injected with 35 mg/kg streptozotocin (STZ) to prepare DNP models and were treated with YQHX for 8 weeks. Results. Studies have shown that the drug restores some levels of MWT, TWL, and MNCV, downregulates the levels of inflammatory factors IL-6, IL-1β, and TNF-α, downregulates the levels of ASK1-MKK3-p38, and weakens the level of OX42 activation. Conclusion. Yiqi Huoxue Tongluo Decoction can relieve DNP by affecting the activity of spinal cord microglia and the ASK1-MKK3-p38 signaling pathway, thereby reducing the central sensitization caused by the inflammatory response of DNP rats.

Molecular Correlates of Early Onset of Diabetic Cardiomyopathy: Possible Therapeutic Targets

Diabetes mellitus (DM) is associated with mitochondrial dysfunction and oxidative stress that can lead to diabetic cardiomyopathy (DCM), which can often remain undetected until late stages of the disease. However, myocardial injury occurs before the onset of measurable cardiac dysfunction, although its molecular correlates are poorly understood. In this study, we made a DM rat induced by a high-fat diet combined with low and high doses of streptozotocin (STZ) to emulate pre and early DCM. RNA-sequencing analysis of ventricular tissue revealed a differential transcriptome profile and abnormal activation of pathways involved in fatty acid metabolism, oxidative phosphorylation, cardiac structure and function, insulin resistance, calcium signalling, apoptosis, and TNF signalling. Moreover, using high glucose-treated human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM), we recapitulated the cardiac cellular phenotype of DM and identified several molecular correlates that may promote the development of DCM. In conclusion, we have developed an experimental framework to target pathways underlying the progression of DCM.

Glucagon-like peptide-1 receptor agonist attenuates diabetic neuropathic pain via inhibition of NOD-like receptor protein 3 inflammasome in brain microglia

AIMS

We aimed to explore the evidence of brain microglia activation in diabetic neuropathic pain (DNP) and the effect and mechanism of glucagon-like peptide-1 receptor agonist (GLP-RA) on DNP via brain microglia.

METHODS

Brain microglia activation was observed in DNP rats by positron emission tomography/computed tomography. The behavior of neuropathic pain was assessed in DNP rats after intracerebroventricular administration of GLP-1RA or microglial inhibitor minocycline. RNA sequencing was performed to explore the target of GLP-1RA on brain microglia. NOD-like receptor protein 3 (NLRP3) expression in brain microglia was evaluated in mentioned-above DNP rats, and the activation of NLRP3 inflammasome was analyzed in microglia treated with GLP-1RA.

RESULTS

Microglia were activated in the cortex and thalamus of DNP rats. The thermal and mechanical allodynia were alleviated in DNP rats via intracerebroventricular administration of GLP-1RA or minocycline. And the activation of brain microglia was attenuated in DNP rats by intracerebroventricular administration of GLP-1RA. The expression of NLRP3 in brain microglia, which was found by RNA sequencing, was reduced in DNP rats by administration of GLP-1RA. Furthermore, GLP-1RA attenuated NLRP3 inflammasome activation in microglia triggered by LPS.

CONCLUSION

GLP-1RA could alleviate DNP, possibly mediated by the suppression of brain microglia NLRP3 inflammasome activation.

Progress on the Elucidation of the Antinociceptive Effect of Ginseng and Ginsenosides in Chronic Pain

Ginseng (Panax ginseng C.A. Meyer) is a traditional Oriental herbal drug widely used in East Asia. Its main active ingredients are ginsenosides whose constituents are known to have various pharmacological activities such as anticancer, antinociception, and neuroprotection. The analgesic effects of ginsenosides, such as Rg1, Rg2, and Rb1, as well as compound K, are well known and the analgesic mechanism of action in inflammatory pain models is thought to be the down regulation of pro-inflammatory cytokine expression (TNF-α IL-1β, and IL-6). Several studies have also demonstrated that ginsenosides regulate neuropathic pain through the modulation of estrogen receptors. Recently, an increasing number of pathways have emerged in relation to the antinociceptive effect of ginseng and ginsenosides. Therefore, this review presents our current understanding of the effectiveness of ginseng in chronic pain and how its active constituents regulate nociceptive responses and their mechanisms of action.

A comprehensive review on the phytochemistry, pharmacokinetics, and antidiabetic effect of Ginseng

BACKGROUND

Radix Ginseng, one of the well-known medicinal herbs, has been used in the management of diabetes and its complications for more than 1000 years.

PURPOSE

The aim of this review is devoted to summarize the phytochemistry and pharmacokinetics of Ginseng, and provide evidence for the antidiabetic effects of Ginseng and its ingredients as well as the underlying mechanisms involved.

METHODS

For the purpose of this review, the following databases were consulted: the PubMed Database (https://pubmed.ncbi.nlm.nih.gov), Chinese National Knowledge Infrastructure (http://www.cnki.net), National Science and Technology Library (http://www.nstl.gov.cn/), Wanfang Data (http://www.wanfangdata.com.cn/) and the Web of Science Database (http://apps.webofknowledge.com/).

RESULTS

Ginseng exhibits glucose-lowering effects in different diabetic animal models. In addition, Ginseng may prevent the development of diabetic complications, including liver, pancreas, adipose tissue, skeletal muscle, nephropathy, cardiomyopathy, retinopathy, atherosclerosis and others. The main ingredients of Ginseng include ginsenosides and polysaccharides. The underlying mechanisms whereby this herb exerts antidiabetic activities may be attributed to the regulation of multiple signaling pathways, including IRS1/PI3K/AKT, LKB1/AMPK/FoxO1, AGEs/RAGE, MAPK/ERK, NF-κB, PPARδ/STAT3, cAMP/PKA/CERB and HIF-1α/VEGF, etc. The pharmacokinetic profiles of ginsenosides provide valuable information on therapeutic efficacy of Ginseng in diabetes. Although Ginseng is well-tolerated, dietary consumption of this herb should follow the doctors' advice.

CONCLUSION

Ginseng may offer an alternative strategy in protection against diabetes and its complications through the regulations of the multi-targets via various signaling pathways. Efforts to understand the underlying mechanisms with strictly-controlled animal models, combined with well-designed clinical trials and pharmacokinetic evaluation, will be important subjects of the further investigations and weigh in translational value of this herb in diabetes management.

The Modulatory Effect of Motor Cortex Astrocytes on Diabetic Neuropathic Pain

Diabetic neuropathic pain (DNP) is a common complication of diabetes characterized by persistent pain. Emerging evidence links astrocytes to mechanical nociceptive processing, and the motor cortex (MCx) is a cerebral cortex region that is known to play a key role in pain regulation. However, the association between MCx astrocytes and DNP pathogenesis remains largely unexplored. Here, we studied this association using designer receptors exclusively activated by designer drugs to specifically manipulate MCx astrocytes. We proved that the selective inhibition of MCx astrocytes reduced DNP in streptozocin (STZ)-induced DNP models and discovered a potential mechanism by which astrocytes release cytokines, including TNF-α and IL-1β, to increase neuronal activation in the MCx, thereby regulating pain. Together, these results demonstrate a pivotal role for MCx astrocytes in DNP pathogenesis and provide new insight into DNP treatment strategies.

Ginseng Extracts, GS-KG9 and GS-E3D, Prevent Blood-Brain Barrier Disruption and Thereby Inhibit Apoptotic Cell Death of Hippocampal Neurons in Streptozotocin-Induced Diabetic Rats

Type 1 diabetes mellitus is known to be linked to the impairment of blood–brain barrier (BBB) integrity following neuronal cell death. Here, we investigated whether GS-KG9 and GS-E3D, bioactive ginseng extracts from Korean ginseng (Panax ginseng Meyer), inhibit BBB disruption following neuronal death in the hippocampus in streptozotocin-induced diabetic rats showing type 1-like diabetes mellitus. GS-KG9 and GS-E3D (50, 150, or 300 mg/kg, twice a day for 4 weeks) administered orally showed antihyperglycemic activity in a dose-dependent manner and significantly attenuated the increase in BBB permeability and loss of tight junction proteins. GS-KG9 and GS-E3D also inhibited the expression and activation of matrix metalloproteinase-9 and the infiltration of macrophages into the brain parenchyma, especially into the hippocampal region. In addition, microglia and astrocyte activation in the hippocampus and the expression of proinflammatory mediators such as tnf-α, Il-1β, IL-6, cox-2, and inos were markedly alleviated in GS-KG9 and GS-E3D-treated group. Furthermore, apoptotic cell death of hippocampal neurons, especially in CA1 region, was significantly reduced in GS-KG9 and GS-E3D-treated groups as compared to vehicle control. These results suggest that GS-KG9 and GS-E3D effectively prevent apoptotic cell death of hippocampal neurons by inhibiting BBB disruption and may be a potential therapy for the treatment of diabetic patients.

Effect of aerobic exercise on innate immune responses and inflammatory mediators in the spinal cord of diabetic rats

Neuronal inflammation is one of the pathophysiological causes of diabetes neuropathic pain. The purpose of this research was to determine the effect of aerobic exercise on innate immune responses and inflammatory mediators in the spinal dorsal horn in rats with diabetic neuropathic pain. 40 eight-week-old male Wistar rats (weight range 220±10.2 g) were randomly divided into four groups of (1) sedentary diabetic neuropathy (SDN), (2) training diabetic neuropathy (TDN), (3) training control (TC), and (4) sedentary control (SC). Diabetes was induced by injection of streptozocin (50 mg/kg). Following confirmation of behavioural tests for diabetes neuropathy, the training groups performed 6 weeks of moderate-intensity aerobic exercise on the treadmill. The expression of Toll like receptor (TLR)4, TLR2, tumour necrosis factor (TNF)-α, interleukin (IL)-1β and IL-10 genes in L4-L6 spinal cord sensory neurons was measured by Real Time PCR. Two-way ANOVA and Bonferroni’s post hoc tests were used for statistical analysis. After performing aerobic exercise protocol, the TDN compared to the SDN showed a significant decrease in the mean score of pain in the formalin test and a significant increase in the latency in Tail-Flick test was observed. The expression of TLR4, TLR2, TNF-α and IL-1β genes was significantly higher in the SDN than in the SC group (P<0.05). The expression of the above genes in the TDN was significantly lower than the SDN group (P<0.05). Also, the expression level of IL-10 gene was significantly higher in the TDN than the SDN group (P<0.05). Aerobic exercise improved sensitivity of nociceptors to pain-inducing agents in diabetic neuropathy due to inhibition of inflammatory receptors and increased levels of anti-inflammatory agents in the nervous system. Thus, aerobic exercise should be used as a non-pharmacological intervention for diabetic patients to reduce neuropathic pain.

Pim1 kinase provides protection against high glucose-induced stress and apoptosis in cultured dorsal root ganglion neurons

The pathogenesis of diabetic peripheral neuropathy (DPN) is complex and not well understood. Recently, oxidative stress and endoplasmic reticulum (ER) stress induced by hyperglycemia have been demonstrated to play a critical role in neuronal apoptosis, which then contributing to DPN. However, the specific molecular mechanism that underlies the hyperglycemia-induced neuronal stresses and apoptosis remains largely unknown. In this study, we demonstrated for the first time that Pim1 kinase is a positive modulator of dorsal root ganglion (DRG) neuron survival in vitro. Hyperglycemia causes compensatory upregulation of Pim1 kinase in the DRG neurons, which provides protection against high glucose-induced oxidative stress and ER stress. Pharmacological inhibition of Pim1 not only sensitizes the stress response to high glucose in the DRG neurons, but also accelerates the apoptosis of DRG neurons in vitro. Therefore, our work provides experimental evidence for the prevention of high glucose-induced neuronal stress and apoptosis by targeting Pim1 kinase.

The neuroprotective effects of micronized PEA (PEA-m) formulation on diabetic peripheral neuropathy in mice

Diabetic peripheral neuropathy (DPN) is a complication of diabetes connected with morbidity and mortality. DPN presents deterioration of peripheral nerves with pain, feebleness, and loss of sensation. Particular medications might display their remedial potential by controlling neuroinflammation. Palmitoylethanolamide (PEA) is an autacoid local injury antagonist distinguished for its neuroprotective, analgesic, and anti-inflammatory properties in numerous experimental models of neuroinflammation. Based on these findings, the goal of this work was to better test the neuroprotective effects of a formulation of micronized PEA (PEA-m) and the probable mechanism of action in a mouse model of DPN induced by streptozotocin (STZ) injection. Diabetic and control animals received PEA-m (10 mg/kg) by oral gavage daily starting 2 wk from STZ injection. After 16 wk, the animals were euthanized, and blood, urine, spinal cord, and sciatic nerve tissues were collected. Our results demonstrated that after diabetes induction, PEA-m was able to reduce mechanical, thermal hyperalgesia, and motor alterations as well as reduce mast cell activation and nerve growth factor expression. In addition, PEA-m decreased neural histologic damage, oxidative and nitrosative stress, cytokine release, angiogenesis, and apoptosis. Moreover, spinal microglia activation (IBA-1), phospho-P38 MAPK, and nuclear factor NF-κB inflammatory pathways were also inhibited. The protective effects of PEA-m could be correlated at least in part to peroxisome proliferator-activated receptor-α activation. In summary, we demonstrated that PEA-m represents a new therapeutic strategy for neuroinflammation pain associated with mixed neuropathies.-Impellizzeri, D., Peritore, A. F., Cordaro, M., Gugliandolo, E., Siracusa, R., Crupi, R., D'Amico, R., Fusco, R., Evangelista, M., Cuzzocrea, S., Di Paola, R. The neuroprotective effects of micronized PEA (PEA-m) formulation on diabetic peripheral neuropathy in mice.