Abnormal calcium homeostasis in peripheral neuropathies

Painful diabetic neuropathy: The role of ion channels

Painful diabetic neuropathy (PDN) is a common chronic complication of diabetes that causes neuropathic pain and negatively affects the quality of life. The management of PDN is far from satisfactory. At present, interventions are primarily focused on symptomatic treatment. Ion channel disorders are a major cause of PDN, and a complete understanding of their roles and mechanisms may provide better options for the clinical treatment of PDN. Therefore, this review summarizes the important role of ion channels in PDN and the current drug development targeting these ion channels.

Acerola (Malpighia emarginata) Anti-Inflammatory Activity-A Review

The manuscript provides an overview of recent scientific reports on the properties and range of health-promoting effects of acerola (Malpighia emarginata DC) fruits and leaves. Acerola is a natural raw material that, in its unprocessed form, is known to be a rich source of vitamin C and polyphenolic compounds. For this reason, the consumption of acerola may provide a number of health-promoting benefits, particularly related to its strong anti-free radical effects. The review discusses anti-inflammatory and anticancer effects of acerola fruit and leaves as well as its therapeutic effects on selected physiological processes in the human system. Their biochemical mechanisms are also explained. Recommendations for the consumption of acerola in the prevention of inflammatory and free radical diseases are presented. The part of the article devoted to anticancer effects of acerola describes the possibilities of using the edible parts of this raw material to obtain products and preparations of potential use in cancer prevention and therapy.

Resilience to Pain-Related Depression in σ1 Receptor Knockout Mice Is Associated with the Reversal of Pain-Induced Brain Changes in Affect-Related Genes

Mice lacking the σ1 receptor chaperone (σ1R-/-) are resilient to depressive-like behaviors secondary to neuropathic pain. Examining the resilience's brain mechanisms could help develop conceptually novel therapeutic strategies. We explored the diminished motivation for a natural reinforcer (white chocolate) in the partial sciatic nerve ligation (PSNL) model in wild-type (WT) and σ1R-/- mice. In the same mice, we performed a comprehensive reverse transcription quantitative PCR (qPCR) analysis across ten brain regions of seven genes implicated in pain regulation and associated affective disorders, such as anxiety and depression. PSNL induced anhedonic-like behavior in WT but not in σ1R-/- mice. In WT mice, PSNL up-regulated dopamine transporter (DAT) and its rate-limiting enzyme, tyrosine hydroxylase (Th), in the ventral tegmental area (VTA) and periaqueductal gray (PAG) as well as the serotonin transporters (SERT) and its rate-limiting enzyme tryptophan hydroxylase 2 (Tph2) in VTA. In addition, μ-opioid receptor (MOR) and σ1R were up-regulated in PAG, and MOR was also elevated in the somatosensory cortex (SS) but down-regulated in the striatum (STR). Finally, increased BDNF was found in the medial prefrontal cortex (mPFC) and hypothalamus (HPT). Sham surgery also produced PSNL-like expression changes in VTA, HPT, and STR. Genetic deletion of the σ1R in mice submitted to PSNL or sham surgery prevented changes in the expression of most of these genes. σ1R is critically involved in the supraspinal gene expression changes produced by PSNL and sham surgery. The changes in gene expression observed in WT mice may be related to pain-related depression, and the absence of these changes observed in σ1R-/- mice may be related to resilience.

Peripheral mechanisms of peripheral neuropathic pain

Peripheral neuropathic pain (PNP), neuropathic pain that arises from a damage or disease affecting the peripheral nervous system, is associated with an extremely large disease burden, and there is an increasing and urgent need for new therapies for treating this disorder. In this review we have highlighted therapeutic targets that may be translated into disease modifying therapies for PNP associated with peripheral neuropathy. We have also discussed how genetic studies and novel technologies, such as optogenetics, chemogenetics and single-cell RNA-sequencing, have been increasingly successful in revealing novel mechanisms underlying PNP. Additionally, consideration of the role of non-neuronal cells and communication between the skin and sensory afferents is presented to highlight the potential use of drug treatment that could be applied topically, bypassing drug side effects. We conclude by discussing the current difficulties to the development of effective new therapies and, most importantly, how we might improve the translation of targets for peripheral neuropathic pain identified from studies in animal models to the clinic.

An evaluation of the effect of lithium on taxane-induced neuropathy

PURPOSE

No medications are known to protect against chemotherapy-induced peripheral neuropathy (CIPN). Pre-clinical models suggest that lithium may lessen taxane-induced neuropathy. Our aim was to use clinical data to assess whether concurrent lithium usage decreased the frequency or severity of CIPN in patients receiving taxane chemotherapy.

METHODS

A retrospective analysis was performed using the electronic health record at Mayo Clinic to identify all patients prescribed concurrent lithium and paclitaxel. Four controls were matched to each case based on clinical variables. Neuropathy severity was graded from available patient and clinician reports. Rates of any neuropathy, dose reduction for CIPN, and treatment discontinuation for CIPN were compared. Conditional regression analysis was performed with propensity score matching.

RESULTS

Six patients, receiving concurrent lithium and paclitaxel, were included in the analysis, and compared to 24 control cases. A similar number of paclitaxel cycles were administered to both groups. Any neuropathy was experienced by 33% (2/6) of patients receiving lithium and 38% (9/24) patients who did not receive lithium (p = 1.000). There was no difference in neuropathy severity (p = 0.8565), rate of chemotherapy dose reduction (17% vs. 17%, p = 1.000), or treatment discontinuation (17% vs 4%, p = 0.3655) for CIPN. In the propensity score analysis, the odds ratio for developing any neuropathy was 0.63 (95% confidence interval, 0.06 to 6.96, p = 0.7079).

CONCLUSIONS

Lithium does not appear to significantly lessen the risk of neuropathy for patients receiving paclitaxel.

IMPLICATIONS FOR CANCER SURVIVORS

Targeted approaches for preventing CIPN are desperately needed. Despite sound scientific rationale, the current study did not identify neuroprotective properties of lithium.

Zinc homeostasis may reverse the synergistic neurotoxicity of heavy metal mixtures in Caenorhabditis elegans

Heavy metal mixtures can cause nerve damage. However, the combined effects of metal mixtures are extremely complex and rarely studied. Zinc (Zn) homeostasis plays an integral role in neural function, but the role of Zn homeostasis in the toxicity of metal mixtures is not well understood. Here, we investigated the combined effects of manganese (Mn), lead (Pb) and arsenic (As) on nerves and the effect of Zn homeostasis on metal toxicity. Caenorhabditis elegans (Maupas, 1900) were exposed to single and multiple metals for 8 days, their movement, behavior, neurons and metal concentration were detected to evaluate the combined effect of metal mixtures. After nematodes were co-treated with metal mixtures and Zn, the nerve function, Zn concentration and redox balance were detected to evaluate the effect of Zn homeostasis on metal toxicity. The results showed that Mn + Pb and Pb + As mixtures induced synergistic toxicity for nematode nerves, which damaged movement, behavior and neurons, and decreased Zn concentration. While Zn supplementation recovered Zn homeostasis and promoted redox balance on nematodes, and then improved the nerve function. Our study demonstrated the combined effects of metal mixtures and the neuroprotective effect of Zn homeostasis. Therefore, assessment of metal mixtures toxicity should consider their interaction and the impacts of essential metals homeostasis.

Does irisin has neuroprotective effect against diabetes induced neuropathy in male rats?

We aimed to investigate the contribution of irisin in the neuroprotective process of exercise training in diabetic rats. Serum irisin levels, thermal and mechanical pain thresholds and intracellular calcium ([Ca²⁺]_i) levels in sensory neurons were measured at different time intervals during the eight weeks of exercise sessions for the control, non-exercise diabetics (3 groups) and exercise performing (low and high intensity groups) diabetic rats (n = 7-10 for all groups). Non-exercise diabetic groups were treated with irisin in different doses (1, 10 and 20 µg/kg respectively). Recovered pain thresholds at the end of the exercise sessions (p < .05), higher serum irisin levels that compared to control and diabetics (p < .05) and insignificant mean [Ca2⁺]_i peak amplitudes in sensory neurons (p > .05) obtained from experiments. Furthermore, irisin injection decreased the thermal pain threshold of diabetics only at 60th minutes (p < .05). Irisin may have a role in the neuroprotective effect of exercise training.

A mechanistic overview of spinal cord injury, oxidative DNA damage repair and neuroprotective therapies

Despite substantial development in medical treatment strategies scientists are struggling to find a cure against spinal cord injury (SCI) which causes long term disability and paralysis. The prime rationale behind it is the enlargement of primary lesion due to an initial trauma to the spinal cord which spreads to the neighbouring spinal tissues It begins from the time of traumatic event happened and extends to hours and even days. It further causes series of biological and functional alterations such as inflammation, excitotoxicity and ischemia, and promotes secondary lesion to the cord which worsens the life of individuals affected by SCI. Oxidative DNA damage is a stern consequence of oxidative stress linked with secondary injury causes oxidative base alterations and strand breaks, which provokes cell death in neurons. It is implausible to stop primary damage however it is credible to halt the secondary lesion and improve the quality of the patient's life to some extent. Therefore it is crucial to understand the hidden perspectives of cell and molecular biology affecting the pathophysiology of SCI. Thus the focus of the review is to connect the missing links and shed light on the oxidative DNA damages and the functional repair mechanisms, as a consequence of the injury in neurons. The review will also probe the significance of neuroprotective strategies in the present scenario. HIGHLIGHTSSpinal cord injury, a pernicious condition, causes excitotoxicity and ischemia, ultimately leading to cell death.Oxidative DNA damage is a consequence of oxidative stress linked with secondary injury, provoking cell death in neurons.Base excision repair (BER) is one of the major repair pathways that plays a crucial role in repairing oxidative DNA damages.Neuroprotective therapies curbing SCI and boosting BER include the usage of pharmacological drugs and other approaches.

Anti-hyperalgesic effects of photobiomodulation therapy (904 nm) on streptozotocin-induced diabetic neuropathy imply MAPK pathway and calcium dynamics modulation

Several recent studies have established the efficacy of photobiomodulation therapy (PBMT) in painful clinical conditions. Diabetic neuropathy (DN) can be related to activating mitogen-activated protein kinases (MAPK), such as p38, in the peripheral nerve. MAPK pathway is activated in response to extracellular stimuli, including interleukins TNF-α and IL-1β. We verified the pain relief potential of PBMT in streptozotocin (STZ)-induced diabetic neuropathic rats and its influence on the MAPK pathway regulation and calcium (Ca²⁺) dynamics. We then observed that PBMT applied to the L4-L5 dorsal root ganglion (DRG) region reduced the intensity of hyperalgesia, decreased TNF-α and IL-1β levels, and p38-MAPK mRNA expression in DRG of diabetic neuropathic rats. DN induced the activation of phosphorylated p38 (p-38) MAPK co-localized with TRPV1⁺ neurons; PBMT partially prevented p-38 activation. DN was related to an increase of p38-MAPK expression due to proinflammatory interleukins, and the PBMT (904 nm) treatment counteracted this condition. Also, the sensitization of DRG neurons by the hyperglycemic condition demonstrated during the Ca²⁺ dynamics was reduced by PBMT, contributing to its anti-hyperalgesic effects.

Obesity-Associated Neuropathy: Recent Preclinical Studies and Proposed Mechanisms

Significance: The prevalence of metabolic syndrome (MetS) and associated obesity has increased in recent years, affecting millions worldwide. One of the most common complications of obesity is damage to the peripheral nerve system, referred to as neuropathy. The lack of disease-modifying therapy for this complication is largely due to a poor understanding of the complex neurobiology underlying neuropathy. Recent preclinical studies suggest that in addition to glucotoxic events, other mechanisms, including lipid signaling, microbiome, or inflammation, may be viable targets to prevent nerve damage and neuropathic pain in obesity. Recent Advances: Clinical and preclinical studies using diet-induced obesity rodent models have identified novel interventions that improve neuropathy. Notably, mechanistic studies suggest that lipid, calcium signaling, and inflammation are converging pathways. Critical Issues: In this review, we focus on interventions and their mechanisms that are shown to ameliorate neuropathy in MetS obese models, including: (i) inhibition of a sensory neuron population, (ii), modification of dietary components, (iii) activation of nuclear and mitochondrial lipid pathways, (iv) exercise, and (v) modulation of gut microbiome composition and their metabolites. Future Directions: These past years, novel research increased our knowledge about neuropathy in obesity and discovered the involvement of nonglucose signaling. More studies are necessary to uncover the interplay between complex metabolic pathways in the peripheral nerve system of obese individuals. Further mechanistic studies in preclinical models and humans are crucial to create single- or multitarget interventions for this complex disease implying complex metabolic phenotyping. Antioxid. Redox Signal. 37, 597-612.

Can Photobiomodulation Support the Management of Temporomandibular Joint Pain? Molecular Mechanisms and a Systematic Review of Human Clinical Trials

This study aims to point out the correlation between photobiomodulation (PBM) targets and effects and management of temporomandibular disorders (TMDs) pain using diode lasers with infrared wavelengths ranging from 780 up to 980 nanometers (nm). A systematic search of multiple electronic databases was done to identify the clinical trials published between 1st January 2010 and 18th December 2021. The included studies were limited to human subjects who had TMD pain, involving two genders with age > 18 years, and were treated with PBM using a diode laser (780–980 nm) as a non-pharmacological therapy to decrease the intensity of the pain associated to TMDs. The risk of bias for included studies was assessed using the Cochrane RoB tool (for randomized studies). The methodologic quality was rated using the Delphi list. The findings suggest that PBM is an effective tool in alleviating TMDs’ pain and increasing the range of movement in patients with Axis 1 of TMDs. However, TMDs’ pain related to underlying pathology cannot be solely treated by PBM. The causative factors must be treated first. Studies displaying the highest quality Delphi score may represent a suggested PBM therapy protocol to follow for TMDs pain management.

Mitochondrial calcium uniporter deletion prevents painful diabetic neuropathy by restoring mitochondrial morphology and dynamics

ABSTRACT

Painful diabetic neuropathy (PDN) is an intractable complication affecting 25% of diabetic patients. Painful diabetic neuropathy is characterized by neuropathic pain accompanied by dorsal root ganglion (DRG) nociceptor hyperexcitability, resulting in calcium overload, axonal degeneration, and loss of cutaneous innervation. The molecular pathways underlying these effects are unknown. Using high-throughput and deep-proteome profiling, we found that mitochondrial fission proteins were elevated in DRG neurons from mice with PDN induced by a high-fat diet (HFD). In vivo calcium imaging revealed increased calcium signaling in DRG nociceptors from mice with PDN. Furthermore, using electron microscopy, we showed that mitochondria in DRG nociceptors had fragmented morphology as early as 2 weeks after starting HFD, preceding the onset of mechanical allodynia and small-fiber degeneration. Moreover, preventing calcium entry into the mitochondria, by selectively deleting the mitochondrial calcium uniporter from these neurons, restored normal mitochondrial morphology, prevented axonal degeneration, and reversed mechanical allodynia in the HFD mouse model of PDN. These studies suggest a molecular cascade linking neuropathic pain to axonal degeneration in PDN. In particular, nociceptor hyperexcitability and the associated increased intracellular calcium concentrations could lead to excessive calcium entry into mitochondria mediated by the mitochondrial calcium uniporter, resulting in increased calcium-dependent mitochondrial fission and ultimately contributing to small-fiber degeneration and neuropathic pain in PDN. Hence, we propose that targeting calcium entry into nociceptor mitochondria may represent a promising effective and disease-modifying therapeutic approach for this currently intractable and widespread affliction. Moreover, these results are likely to inform studies of other neurodegenerative disease involving similar underlying events.

Transcriptome of human neuroblastoma SH-SY5Y cells in response to 2B protein of enterovirus-A71

Infection with enterovirus-A71 (EV-A71) can cause hand-foot-mouth disease associated with fatal neurological complications. The host response to EV-A71 has not yet been fully elucidated, thus, hampering the development of a precise therapeutic approach. A nonstructural 2B protein of EV-A71 has been reported to involve with calcium dysregulation and apoptosis induction in human neuroblastoma SH-SY5Y cells. However, the molecular mechanism has not been delineated. To address this, comprehensive study of the gene expression from SH-SY5Y cells transfected with EV-A71 2B was carried out by RNA sequencing and transcriptomic analysis. It was found that the signature of the upregulated genes of SH-SY5Y cells expressing EV-A71 2B involved the Ca²⁺-related signaling pathways participating gene expression, inflammatory response, apoptosis, and long-term potentiation of the neuron. Protein-protein interaction network analysis revealed that the products encoded by CCL2, RELB, BIRC3, and TNFRSF9 were the most significant hub proteins in the network. It indicated that EV-A71 2B protein might play a role in immunopathogenesis of the central nervous system (CNS) which probably associated with the non-canonical NF-κB pathway. The data suggest that transcriptomic profiling can provide novel information source for studying the neuropathogenesis of EV-A71 infection leading to development of an effective therapeutic measure for CNS complications.

Acute insulin-responsive hyperglycemia and hypocalcemia in Theileria spp. infected goat

Theileriosis can be manifested in appreciably variable clinical forms among domestic ruminants and may often become life-threatening. The present report narrates, the quick remarkable clinical recovery of a lactating goat infected with Theileria spp., exhibiting acute insulin-responsive hyperglycemia and hypocalcemia, by providing intensive therapy. A four year old doe was presented with the complaint of acute manifestation of weakness, ventroflexion of neck with flaccid muscles, recumbency, hypersalivation, severe abdominal breathing, anorexia and polyuria since last eighteen hours. The animal kidded three kids one month before, out of which one was mummified. Clinical examination revealed severe depression, dehydration, dyspnoea, congested mucous membrane, sluggish rumen motility and reduced pupillary light reflex. Laboratory investigation revealed severe granulocytopenia, thrombocytopenia, hypocalcemia, hyperglycemia and Theileria spp. infection. The animal showed significant improvement within a few minutes of initiating the evidence-based stabilization therapy to correct hydration status, cellular glucose uptake, calcium levels and Theileria spp. infection. This case indicates the significance of investigating the metabolic status of animals suffering from theileriosis for achieving better clinical responses. Also, future studies may focus on the endocrinological perspectives of metabolic impact of Theileria spp. infection in goats.

Loganin Ameliorates Painful Diabetic Neuropathy by Modulating Oxidative Stress, Inflammation and Insulin Sensitivity in Streptozotocin-Nicotinamide-Induced Diabetic Rats

Loganin is an iridoid glycoside with antioxidant, anti-inflammatory, glucose-lowering activities which may address the pathological mechanisms of painful diabetic neuropathy (PDN) related to inflammation, oxidative stress, and hyperglycemia. This study investigated the underlying mechanisms of action of loganin on PDN. The in vivo model of PDN was established by streptozotocin-nicotinamide (STZ-NA) induction in Sprague Dawley (SD) rats. Subsequently, loganin (5 mg/kg) was administered by daily intraperitoneal injection. High-glucose stimulated human SH-SY5Y cells co-incubated with loganin were used to mimic the in vitro model of PDN. Loganin improved PDN rats' associated pain behaviors (allodynia and hyperalgesia), insulin resistance index (HOMA-IR), and serum levels of superoxide dismutase (SOD), catalase and glutathione. Loganin also reduced pain-associated channel protein CaV3.2 and calcitonin gene-related peptide (CGRP) in the surficial spinal dorsal horn of PDN rats. Loganin inhibited oxidative stress and NF-κB activation and decreased the levels of mRNA and protein of proinflammatory factors IL-1β and TNF-α. Moreover, loganin attenuated insulin resistance by modulating the JNK-IRS-1 (insulin receptor substrate-1)-Akt-GSK3β signaling pathway in PDN rats. These results suggested that loganin improved PDN-mediated pain behaviors by inhibiting oxidative stress-provoked inflammation in the spinal cord, resulting in improved neuropathic pain.

Comparing the results of manual and automated quantitative corneal neuroanalysing modules for beginners

This study aimed to evaluate the reliability of in vivo confocal microscopic neuroanalysis by beginners using manual and automated modules. Images of sub-basal corneal nerve plexus (SCNP) from 108 images of 18 healthy participants were analyzed by 7 beginner observers using manual (CCMetrics, [CCM]) and automated (ACCMetrics, [ACCM]) module. SCNP parameters analyzed included corneal nerve fiber density (NFD), corneal nerve branch density (NBD), corneal nerve fiber length (NFL), and tortuosity coefficient (TC). The intra-observer repeatability, inter-observer reliability, inter-module agreement, and left–right eye symmetry level of SCNP parameters were examined. All observers showed good intra-observer repeatability using CCM (intraclass correlation coefficient [ICC] > 0.60 for all), except when measuring TC. Two observers demonstrated especially excellent repeatability in analyzing NFD, NBD, and NFL using manual mode, indicating the quality of interpretation may still be observer-dependent. Among all SCNP parameters, NFL had the best inter-observer reliability (Spearman’s rank-sum correlation coefficient [SpCC] and ICC > 0.85 for the 3 original observers) and left–right symmetry level (SpCC and ICC > 0.60). In the additional analysis of inter-observer reliability using results by all 7 observers, only NFL showed good inter-observer reliability (ICC = 0.79). Compared with CCM measurements, values of ACCM measurements were significantly lower, implying a poor inter-module agreement. Our result suggested that performance of quantitative corneal neuroanalysis by beginners maybe acceptable, with NFL being the most reliable parameter, and automated method cannot fully replace manual work.

Chondroitin sulfate produces antinociception and neuroprotection in chronic constriction injury-induced neuropathic pain in rats by increasing anti-inflammatory molecules and reducing oxidative stress

OBJECTIVES

Damage to the peripheral and central nervous system lead to Neuropathic pain (NP) which is a widespread and devitalizing condition. chondroitin sulfate (CS), has been used in managing joint pain and osteoarthritis. In this study, the effectiveness of CS on NP induced by chronic constriction injury (CCI) is examined.

METHODS

Thirty Wistar rats were distributed at random into six groups (n = 5). Sciatic nerve ligation was carried out by encircling the nerve with four loose ligatures to induce NP. Allodynia (cold and mechanical) and heat hyperalgesia were assessed using Acetone, von Frey filament and Hot plate tests. CCI induction resulted to NP, prominent from the 3rd day after surgery. Structural architecture of sciatic nerves was evaluated via histological examination of the transverse section of the nerves.

RESULTS

Oral administration of CS (600 mg/kg and 900 mg/kg for 21 days) resulted in significant (P < 0.05) inhibition of allodynia (cold and mechanical) and thermal hyperalgesia. Lipid peroxidation, tumor necrosis factor-α (TNF-α), calcitonin gene related peptide (CGRP), C reactive protein (CRP), and oxidative stress were attenuated by CS. CS also improved interleukin (IL)-6, nitric oxide (NO), total antioxidant capacity (TAC).

CONCLUSION

These findings suggest that CS attenuates allodynia, and thermal hyperalgesia induced by CCI by downregulating TNF-α, CRP, CGRP, oxidative enzymes, and upregulating IL-6, NO, and TAC. Nociceptive behavioral studies and histological findings showed significant improvement in the CS treated groups compared to CCI rats. These findings are responsible for the beneficial effect of CS in NP.

Calcineurin Activity Is Increased in Charcot-Marie-Tooth 1B Demyelinating Neuropathy

Schwann cells produce a considerable amount of lipids and proteins to form myelin in the PNS. For this reason, the quality control of myelin proteins is crucial to ensure proper myelin synthesis. Deletion of serine 63 from P0 (P0S63del) protein in myelin forming Schwann cells causes Charcot-Marie-Tooth type 1B neuropathy in humans and mice. Misfolded P0S63del accumulates in the ER of Schwann cells where it elicits the unfolded protein response (UPR). PERK is the UPR transducer that attenuates global translation and reduces ER stress by phosphorylating the translation initiation factor eIF2alpha. Paradoxically, Perk ablation in P0S63del Schwann cells (S63del/PerkSCKO ) reduced the level of P-eIF2alpha, leaving UPR markers upregulated, yet unexpectedly improved S63del myelin defects in vivo We therefore investigated the hypothesis that PERK may interfere with signals outside of the UPR and specifically with calcineurin/NFATc4 pro-myelinating pathway. Using mouse genetics including females and males in our experimental setting, we show that PERK and calcineurin interact in P0S63del nerves and that calcineurin activity and NFATc4 nuclear localization are increased in S63del Schwann cells, without altering EGR2/KROX20 expression. Moreover, genetic manipulation of the calcineurin subunits appears to be either protective or toxic in S63del in a context-dependent manner, suggesting that Schwann cells are highly sensitive to alterations of calcineurin activity.SIGNIFICANCE STATEMENT Our work shows a novel activity and function for calcineurin in Schwann cells in the context of ER stress. Schwann cells expressing the S63del mutation in P0 protein induce the unfolded protein response and upregulate calcineurin activity. Calcineurin interacts with the ER stress transducer PERK, but the relationship between the UPR and calcineurin in Schwann cells is unclear. Here we propose a protective role for calcineurin in S63del neuropathy, although Schwann cells appear to be very sensitive to its regulation. The paper uncovers a new important role for calcineurin in a demyelinating diseases.

Therapeutic Potential of Polyphenols in the Management of Diabetic Neuropathy

Diabetic neuropathy (DN) is a common and serious diabetes-associated complication that primarily takes place because of neuronal dysfunction in patients with diabetes. Use of current therapeutic agents in DN treatment is quite challenging because of their severe adverse effects. Therefore, there is an increased need of identifying new safe and effective therapeutic agents. DN complications are associated with poor glycemic control and metabolic imbalances, primarily oxidative stress (OS) and inflammation. Various mediators and signaling pathways such as glutamate pathway, activation of channels, trophic factors, inflammation, OS, advanced glycation end products, and polyol pathway have a significant contribution to the progression and pathogenesis of DN. It has been indicated that polyphenols have the potential to affect DN pathogenesis and could be used as potential alternative therapy. Several polyphenols including kolaviron, resveratrol, naringenin, quercetin, kaempferol, and curcumin have been administered in patients with DN. Furthermore, chlorogenic acid can provide protection against glutamate neurotoxicity via its hydrolysate, caffeoyl acid group, and caffeic acid through regulating the entry of calcium into neurons. Epigallocatechin-3-gallate treatment can protect motor neurons by regulating the glutamate level. It has been demonstrated that these polyphenols can be promising in combating DN-associated damaging pathways. In this article, we have summarized DN-associated metabolic pathways and clinical manifestations. Finally, we have also focused on the roles of polyphenols in the treatment of DN.

High Dietary Fat Consumption Impairs Axonal Mitochondrial Function In Vivo

Peripheral neuropathy (PN) is the most common complication of prediabetes and diabetes. PN causes severe morbidity for Type 2 diabetes (T2D) and prediabetes patients, including limb pain followed by numbness resulting from peripheral nerve damage. PN in T2D and prediabetes is associated with dyslipidemia and elevated circulating lipids; however, the molecular mechanisms underlying PN development in prediabetes and T2D are unknown. Peripheral nerve sensory neurons rely on axonal mitochondria to provide energy for nerve impulse conduction under homeostatic conditions. Models of dyslipidemia in vitro demonstrate mitochondrial dysfunction in sensory neurons exposed to elevated levels of exogenous fatty acids. Herein, we evaluated the effect of dyslipidemia on mitochondrial function and dynamics in sensory axons of the saphenous nerve of a male high-fat diet (HFD)-fed murine model of prediabetes to identify mitochondrial alterations that correlate with PN pathogenesis in vivo We found that the HFD decreased mitochondrial membrane potential (MMP) in axonal mitochondria and reduced the ability of sensory neurons to conduct at physiological frequencies. Unlike mitochondria in control axons, which dissipated their MMP in response to increased impulse frequency (from 1 to 50 Hz), HFD mitochondria dissipated less MMP in response to axonal energy demand, suggesting a lack of reserve capacity. The HFD also decreased sensory axonal Ca²⁺ levels and increased mitochondrial lengthening and expression of PGC1α, a master regulator of mitochondrial biogenesis. Together, these results suggest that mitochondrial dysfunction underlies an imbalance of axonal energy and Ca²⁺ levels and impairs impulse conduction within the saphenous nerve in prediabetic PN.SIGNIFICANCE STATEMENT Diabetes and prediabetes are leading causes of peripheral neuropathy (PN) worldwide. PN has no cure, but development in diabetes and prediabetes is associated with dyslipidemia, including elevated levels of saturated fatty acids. Saturated fatty acids impair mitochondrial dynamics and function in cultured neurons, indicating a role for mitochondrial dysfunction in PN progression; however, the effect of elevated circulating fatty acids on the peripheral nervous system in vivo is unknown. In this study, we identify early pathogenic events in sensory nerve axons of mice with high-fat diet-induced PN, including alterations in mitochondrial function, axonal conduction, and intra-axonal calcium, that provide important insight into potential PN mechanisms associated with prediabetes and dyslipidemia in vivo.

Cisplatin-induced activation and functional modulation of satellite glial cells lead to cytokine-mediated modulation of sensory neuron excitability

Cisplatin plays an essential role in the treatment of various cancers. Cisplatin exhibits high efficacy, but it often leads to severe neurotoxic side effects, such as chemotherapy-induced polyneuropathy (CIPN). The pathophysiology of CIPN is not fully understood. There is increasing evidence for damage to satellite glial cells (SGC) and dorsal root ganglion (DRG) neurons. We investigated the influence of cisplatin on the function of SGCs and the direct influence on DRGs. Satellite glial cells were isolated from DRG and exposed to 0.1, 1, 10, or 100 μM cisplatin for 2 h, 4 h, and 24 h. Using immunocytochemical staining and Western blot analysis, the expression of the glial fibrillary acid protein (GFAP), reactive oxygen species (ROS), and inward rectifier potassium channel 4.1 (K_ir4.1) was determined. An increase in the immune reactivity (IR) and protein levels of GFAP and ROS was measured, and a reduction of IR and protein level of K_ir4.1 was detected. A decrease in these channels' current density was observed using the whole-cell patch-clamp recording. The interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) release of SGCs increased after cisplatin exposure as measured using ELISA, and interleukin-1β (IL-1β) decreased. The SGC-secreted factors in the supernatant after cisplatin treatment led to a modulation of cultured DRG neurons' excitability. Taken together, the modulation and function of different SGC proteins could be linked to a direct impact of cisplatin. Further, SGC-secreted factors influenced the excitability of sensory neurons. Overall, SGCs could be a potential target in preventing and treating chemotherapy-induced neuropathic pain.

Resolvins: Potent Pain Inhibiting Lipid Mediators via Transient Receptor Potential Regulation

Chronic pain is a serious condition that occurs in the peripheral nervous system (PNS) and the central nervous system (CNS). It is caused by inflammation or nerve damage that induces the release of inflammatory mediators from immune cells and/or protein kinase activation in neuronal cells. Both nervous systems are closely linked; therefore, inflammation or nerve damage in the PNS can affect the CNS (central sensitization). In this process, nociceptive transient receptor potential (TRP) channel activation and expression are increased. As a result, nociceptive neurons are activated, and pain signals to the brain are amplified and prolonged. In other words, suppressing the onset of pain signals in the PNS can suppress pain signals to the CNS. Resolvins, endogenous lipid mediators generated during the resolution phase of acute inflammation, inhibit nociceptive TRP ion channels and alleviate chronic pain. This paper summarizes the effect of resolvins in chronic pain control and discusses future scientific perspectives. Further study on the effect of resolvins on neuropathic pain will expand the scope of pain research.

Fecal transplantation and butyrate improve neuropathic pain, modify immune cell profile, and gene expression in the PNS of obese mice

Obesity affects over 2 billion people worldwide and is accompanied by peripheral neuropathy (PN) and an associated poorer quality of life. Despite high prevalence, the molecular mechanisms underlying the painful manifestations of PN are poorly understood, and therapies are restricted to use of painkillers or other drugs that do not address the underlying disease. Studies have demonstrated that the gut microbiome is linked to metabolic health and its alteration is associated with many diseases, including obesity. Pathologic changes to the gut microbiome have recently been linked to somatosensory pain, but any relationships between gut microbiome and PN in obesity have yet to be explored. Our data show that mice fed a Western diet developed indices of PN that were attenuated by concurrent fecal microbiome transplantation (FMT). In addition, we observed changes in expression of genes involved in lipid metabolism and calcium handling in cells of the peripheral nerve system (PNS). FMT also induced changes in the immune cell populations of the PNS. There was a correlation between an increase in the circulating short-chain fatty acid butyrate and pain improvement following FMT. Additionally, butyrate modulated gene expression and immune cells in the PNS. Circulating butyrate was also negatively correlated with distal pain in 29 participants with varied body mass index. Our data suggest that the metabolite butyrate, secreted by the gut microbiome, underlies some of the effects of FMT. Targeting the gut microbiome, butyrate, and its consequences may represent novel viable approaches to prevent or relieve obesity-associated neuropathies.

Genome-wide profiling of DNA methylation and gene expression identifies candidate genes for human diabetic neuropathy

BACKGROUND

Diabetic peripheral neuropathy (DPN) is the most common complication of type 2 diabetes (T2D). Although the cellular and molecular mechanisms of DPN are poorly understood, we and others have shown that altered gene expression and DNA methylation are implicated in disease pathogenesis. However, how DNA methylation might functionally impact gene expression and contribute to nerve damage remains unclear. Here, we analyzed genome-wide transcriptomic and methylomic profiles of sural nerves from T2D patients with DPN.

RESULTS

Unbiased clustering of transcriptomics data separated samples into groups, which correlated with HbA1c levels. Accordingly, we found 998 differentially expressed genes (DEGs) and 929 differentially methylated genes (DMGs) between the groups with the highest and lowest HbA1c levels. Functional enrichment analysis revealed that DEGs and DMGs were enriched for pathways known to play a role in DPN, including those related to the immune system, extracellular matrix (ECM), and axon guidance. To understand the interaction between the transcriptome and methylome in DPN, we performed an integrated analysis of the overlapping genes between DEGs and DMGs. Integrated functional and network analysis identified genes and pathways modulating functions such as immune response, ECM regulation, and PI3K-Akt signaling.

CONCLUSION

These results suggest for the first time that DNA methylation is a mechanism regulating gene expression in DPN. Overall, DPN patients with high HbA1c have distinct alterations in sural nerve DNA methylome and transcriptome, suggesting that optimal glycemic control in DPN patients is an important factor in maintaining epigenetic homeostasis and nerve function.

Mutations in C1orf194, encoding a calcium regulator, cause dominant Charcot-Marie-Tooth disease

Charcot-Marie-Tooth disease is a hereditary motor and sensory neuropathy exhibiting great clinical and genetic heterogeneity. Here, the identification of two heterozygous missense mutations in the C1orf194 gene at 1p21.2-p13.2 with Charcot-Marie-Tooth disease are reported. Specifically, the p.I122N mutation was the cause of an intermediate form of Charcot-Marie-Tooth disease, and the p.K28I missense mutation predominately led to the demyelinating form. Functional studies demonstrated that the p.K28I variant significantly reduced expression of the protein, but the p.I122N variant increased. In addition, the p.I122N mutant protein exhibited the aggregation in neuroblastoma cell lines and the patient's peroneal nerve. Either gain-of-function or partial loss-of-function mutations to C1ORF194 can specify different causal mechanisms responsible for Charcot-Marie-Tooth disease with a wide range of clinical severity. Moreover, a knock-in mouse model confirmed that the C1orf194 missense mutation p.I121N led to impairments in motor and neuromuscular functions, and aberrant myelination and axonal phenotypes. The loss of normal C1ORF194 protein altered intracellular Ca2+ homeostasis and upregulated Ca2+ handling regulatory proteins. These findings describe a novel protein with vital functions in peripheral nervous systems and broaden the causes of Charcot-Marie-Tooth disease, which open new avenues for the diagnosis and treatment of related neuropathies.

Activation and functional modulation of satellite glial cells by oxaliplatin lead to hyperexcitability of sensory neurons in vitro

Platinum-based chemotherapeutics still play an important role in cancer therapy, however, severe side effects, such as painful neuropathy, occur frequently. The pathophysiologic mechanisms depend on the applied chemotherapeutic agent and are still controversial. In addition to neuronal damage, disturbance of glial cell activity may contribute to neurotoxicity. Here, we focused on the effect of oxaliplatin on satellite glial cell (SGC) function and on the activity of the dorsal root ganglion (DRG) neurons. SGCs were isolated as high-purity cultures and treated with 1 and 10 μM oxaliplatin for 2, 4 and 24 h. Subsequently, glial fibrillary acid protein (GFAP), reactive oxygen species (ROS), Connexin-43 (Cx-43), and inward rectifier potassium channel 4.1 (K_ir4.1) expression was determined by immunocytochemical staining (ICC) and Western blot analyses. Immunochemical staining and Western blot analysis showed an increase in the immune reactivity (IR) and protein levels of ROS, GFAP, and Cx-43. Furthermore, reduction of the IR and protein levels and current density were demonstrated using patch-clamp measurements, of K_ir4.1 channels after oxaliplatin exposure. Cytokine release in SGCs was measured using enzyme-linked immunosorbent assays (ELISA) after oxaliplatin exposure and indicated an increased release of IL-6 and TNFα, while IL-1β was decreased. The direct influence of SGC-secreted factors in the supernatant after oxaliplatin treatment led to the hyperexcitability of cultured DRG neurons. In summary, oxaliplatin has a direct impact on the modulation and function of different SGC proteins. Furthermore, SGC-released factors influence the excitability of sensory neurons, qualifying SGCs as potential targets for the prevention and treatment of oxaliplatin-induced polyneuropathy.

Examination and characterisation of burst spinal cord stimulation on cerebrospinal fluid cellular and protein constituents in patient responders with chronic neuropathic pain - A Pilot Study

INTRODUCTION

Patients with neuropathic pain have altered proteomic and neuropeptide constituents in cerebrospinal fluid (CSF) compared to controls. Tonic spinal cord stimulation (SCS) has demonstrated differential expression of neuropeptides in CSF before and after treatment suggesting potential mechanisms of action. Burst-SCS is an evidence-based paraesthesia free waveform utilised for neuropathic pain with a potentially different mechanistic action to tonic SCS. This study examines the dynamic biological changes of CSF at a cellular and proteome level after Burst-SCS.

METHODS

Patients with neuropathic pain selected for SCS had CSF sampled prior to implant of SCS and following 8 weeks of continuous Burst-SCS. Baseline and 8-week pain scores with demographics were recorded. T cell frequencies were analysed by flow cytometry, proteome analysis was performed using mass spectrometry and secreted cytokines, chemokines and neurotrophins were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

4 patients (2 females, 2 males) with a mean age of 51 years (+/-SEM 2.74, SD 5.48) achieved a reduction in pain of >50% following 8 weeks of Burst-SCS. Analysis of the CSF proteome indicated a significant alteration in protein expression most related to synapse assembly and immune regulators. There was significantly lower expression of the proteins: growth hormone A1 (PRL), somatostatin (SST), nucleobindin-2 (NUCB2), Calbindin (CALB1), acyl-CoA binding protein (DBI), proSAAS (PCSK1N), endothelin-3 (END3) and cholecystokinin (CCK) after Burst-SCS. The concentrations of secreted chemokines and cytokines and the frequencies of T cells were not significantly changed following Burst-SCS.

CONCLUSION

This study characterised the alteration in the CSF proteome in response to burst SCS in vivo. Functional analysis indicated that the alterations in the CSF proteome is predominately linked to synapse assembly and immune effectors. Individual protein analysis also suggests potential supraspinal mechanisms.

Diabetes, Diabetic Complications, and Phosphate Toxicity: A Scoping Review

This article presents a scoping review and synthesis of research findings investigating the toxic cellular accumulation of dysregulated inorganic phosphate-phosphate toxicity-as a pathophysiological determinant of diabetes and diabetic complications. Phosphorus, an essential micronutrient, is closely linked to the cellular metabolism of glucose for energy production, and serum inorganic phosphate is often transported into cells along with glucose during insulin therapy. Mitochondrial dysfunction and apoptosis, endoplasmic reticulum stress, neuronal degeneration, and pancreatic cancer are associated with dysregulated levels of phosphate in diabetes. Ectopic calcification involving deposition of calcium-phosphate crystals is prevalent throughout diabetic complications, including vascular calcification, nephropathy, retinopathy, and bone disorders. A low-glycemic, low-phosphate dietary intervention is proposed for further investigations in the treatment and prevention of diabetes and related diabetic pathologies.

Endoplasmic reticulum-mitochondria interplay in chronic pain: The calcium connection

Chronic pain is a debilitating condition that affects roughly a third to a half of the world's population. Despite its substantial effect on society, treatment for chronic pain is modest, at best, notwithstanding its side effects. Hence, novel therapeutics are direly needed. Emerging evidence suggests that calcium plays an integral role in mediating neuronal plasticity that underlies sensitization observed in chronic pain states. The endoplasmic reticulum and the mitochondria are the largest calcium repositories in a cell. Here, we review how stressors, like accumulation of misfolded proteins and oxidative stress, influence endoplasmic reticulum and mitochondria function and contribute to chronic pain. We further examine the shuttling of calcium across the mitochondrial-associated membrane as a mechanism of cross-talk between the endoplasmic reticulum and the mitochondria. In addition, we discuss how endoplasmic reticulum stress, mitochondrial impairment, and calcium dyshomeostasis are implicated in various models of neuropathic pain. We propose a novel framework of endoplasmic reticulum-mitochondria signaling in mediating pain hypersensitivity. These observations require further investigation in order to develop novel therapies for chronic pain.

Phosphoproteomics reveals conserved exercise-stimulated signaling and AMPK regulation of store-operated calcium entry

Exercise stimulates cellular and physiological adaptations that are associated with widespread health benefits. To uncover conserved protein phosphorylation events underlying this adaptive response, we performed mass spectrometry-based phosphoproteomic analyses of skeletal muscle from two widely used rodent models: treadmill running in mice and in situ muscle contraction in rats. We overlaid these phosphoproteomic signatures with cycling in humans to identify common cross-species phosphosite responses, as well as unique model-specific regulation. We identified > 22,000 phosphosites, revealing orthologous protein phosphorylation and overlapping signaling pathways regulated by exercise. This included two conserved phosphosites on stromal interaction molecule 1 (STIM1), which we validate as AMPK substrates. Furthermore, we demonstrate that AMPK-mediated phosphorylation of STIM1 negatively regulates store-operated calcium entry, and this is beneficial for exercise in Drosophila. This integrated cross-species resource of exercise-regulated signaling in human, mouse, and rat skeletal muscle has uncovered conserved networks and unraveled crosstalk between AMPK and intracellular calcium flux.

Topiramate prevents oxaliplatin-related axonal hyperexcitability and oxaliplatin induced peripheral neurotoxicity

Oxaliplatin (OHP) Induced Peripheral Neurotoxicity (OIPN) is one of the dose-limiting toxicities of the drug and these adverse effects limit cancer therapy with L-OHP, used for colorectal cancer treatment. Acute neurotoxicity consists of symptoms that are the hallmarks of a transient axonal hyperexcitability; chronic neurotoxicity has a clinical picture compatible with a length-dependent sensory neuropathy. Acute OIPN pathogenesis has been linked to sodium voltage-operated channels (Na + VOC) dysfunction and it has been advocated as a possible predisposing factor to chronic neurotoxicity. We tested if topiramate (TPM), a well-known Na + VOC modulator, was able to modify acute as well as chronic OIPN. The project was divided into two parts. In Experiment 1 we tested by means of Nerve Excitability Testing (NET) a cohort of female Wistar rats to assess TPM effects after a single OHP administration (5 mg/kg, iv). In Experiment 2 we assessed TPM effects after chronic OHP treatment (5 mg/kg, 2qw4ws, iv) using NET, nerve conduction studies (NCS), behavioral tests and neuropathology (caudal nerve morphometry and morphology and Intraepidermal Nerve Fiber [IENF] density). In Experiment 1 TPM was able to prevent OHP effects on Na + VOC: OHP treatment induced a highly significant reduction of the sensory nerve's threshold, during the superexcitability period (p-value = 0.008), whereas TPM co-administration prevented this effect. In Experiment 2 we verified that TPM was able to prevent not only acute phenomena, but also to completely prevent chronic OIPN. This latter observation was supported by a multimodal approach: in fact, only OHP group showed altered findings compared to CTRL group at a neurophysiological (proximal caudal nerve sensory nerve action potential [SNAP] amplitude, p-value = 0.001; distal caudal nerve SNAP amplitude, p-value<0.001, distal caudal nerve sensory conduction velocity, p-value = 0.04), behavioral (mechanical threshold, p-value 0.003) and neuropathological levels (caudal nerve fibers density, p-value 0.001; IENF density, p-value <0.001). Our data show that TPM is a promising drug to prevent both acute and chronic OIPN. These findings have a high translational potential, since they were obtained using outcome measures that match clinical practice and TPM is already approved for clinical use being free from detrimental interaction with OHP anticancer properties.

Polyphenols for diabetes associated neuropathy: Pharmacological targets and clinical perspective

OBJECTIVES

Diabetic neuropathy (DNP) is a widespread and debilitating complication with complex pathophysiology that is caused by neuronal dysfunction in diabetic patients. Conventional therapeutics for DNP are quite challenging due to their serious adverse effects. Hence, there is a need to investigate novel effective and safe options. The novelty of the present study was to provide available therapeutic approaches, emerging molecular mechanisms, signaling pathways and future directions of DNP as well as polyphenols' effect, which accordingly, give new insights for paving the way for novel treatments in DNP.

EVIDENCE ACQUISITION

A comprehensive review was done in electronic databases including Medline, PubMed, Web of Science, Scopus, national database (Irandoc and SID), and related articles regarding metabolic pathways on the pathogenesis of DNP as well as the polyphenols' effect. The keywords "diabetic neuropathy" and "diabetes mellitus" in the title/abstract and "polyphenol" in the whole text were used. Data were collected from inception until May 2019.

RESULTS

DNP complications is mostly related to a poor glycemic control and metabolic imbalances mainly inflammation and oxidative stress. Several signaling and molecular pathways play key roles in the pathogenesis and progression of DNP. Among natural entities, polyphenols are suggested as multi-target alternatives affecting most of these pathogenesis mechanisms in DNP.

CONCLUSION

The findings revealed novel pathogenicity signaling pathways of DNP and affirmed the auspicious role of polyphenols to tackle these destructive pathways in order to prevent, manage, and treat various diseases. Graphical Abstract .

Dystonin-A3 upregulation is responsible for maintenance of tubulin acetylation in a less severe dystonia musculorum mouse model for hereditary sensory and autonomic neuropathy type VI

Hereditary sensory and autonomic neuropathy type VI (HSAN-VI) is a recessive human disease that arises from mutations in the dystonin gene (DST; also known as Bullous pemphigoid antigen 1 gene). A milder form of HSAN-VI was recently described, resulting from loss of a single dystonin isoform (DST-A2). Similarly, mutations in the mouse dystonin gene (Dst) result in severe sensory neuropathy, dystonia musculorum (Dstdt). Two Dstdt alleles, Dstdt-Tg4 and Dstdt-27J, differ in the severity of disease. The less severe Dstdt-Tg4 mice have disrupted expression of Dst-A1 and -A2 isoforms, while the more severe Dstdt-27J allele affects Dst-A1, -A2 and -A3 isoforms. As dystonin is a cytoskeletal-linker protein, we evaluated microtubule network integrity within sensory neurons from Dstdt-Tg4 and Dstdt-27J mice. There is a significant reduction in tubulin acetylation in Dstdt-27J indicative of microtubule instability and severe microtubule disorganization within sensory axons. However, Dstdt-Tg4 mice have no change in tubulin acetylation, and microtubule organization was only mildly impaired. Thus, microtubule instability is not central to initiation of Dstdt pathogenesis, though it may contribute to disease severity. Maintenance of microtubule stability in Dstdt-Tg4 dorsal root ganglia could be attributed to an upregulation in Dst-A3 expression as a compensation for the absence of Dst-A1 and -A2 in Dstdt-Tg4 sensory neurons. Indeed, knockdown of Dst-A3 in these neurons resulted in a decrease in tubulin acetylation. These findings shed light on the possible compensatory role of dystonin isoforms within HSAN-VI, which might explain the heterogeneity in symptoms within the reported forms of the disease.

Coping with Phantom Limb Pain

Phantom limb pain is a chronic neuropathic pain that develops in 45-85% of patients who undergo major amputations of the upper and lower extremities and appears predominantly during two time frames following an amputation: the first month and later about 1 year. Although in most patients the frequency and intensity of pain diminish over time, severe pain persists in about 5-10%. It has been proposed that factors in both the peripheral and central nervous systems play major roles in triggering the development and maintenance of pain associated with extremity amputations. Chronic pain is physically and mentally debilitating, affecting an individual's capacity for self-care, but also diminishing an individual's daily capacity for personal and economic independence. In addition, the pain may lead to depression and feelings of hopelessness. A National Center for Biotechnology Information study found that in the USA alone, the annual cost of dealing with neuropathic pain is more than $600 billion, with an estimated 20 million people in the USA suffering from this condition. Although the pain can be reduced by antiepileptic drugs and analgesics, they are frequently ineffective or their side effects preclude their use. The optimal approach for eliminating neuropathic pain and improving individuals' quality of life is the development of novel techniques that permanently prevent the development and maintenance of neuropathic pain, or that eliminate the pain once it has developed. What is still required is understanding when and where an effective novel technique must be applied, such as onto the nerve stump of the transected peripheral axons, dorsal root ganglion neurons, spinal cord, or cortex to induce the desired influences. This review, the second of two in this journal volume, examines the techniques that may be capable of reducing or eliminating chronic neuropathic pain once it has developed. Such an understanding will improve amputees' quality of life by blocking the mechanisms that trigger and/or maintain PLP and chronic neuropathic pain.

Metabotropic Glutamate Receptor 5 and 8 Modulate the Ameliorative Effect of Ultramicronized Palmitoylethanolamide on Cognitive Decline Associated with Neuropathic Pain

This study investigated whether metabotropic glutamate receptor (mGluR) 5 and 8 are involved in the effect of ultramicronizedpalmitoylethanolamide (um-PEA) on the cognitive behavior and long term potentiation (LTP) at entorhinal cortex (LEC)-dentate gyrus (DG) pathway in mice rendered neuropathic by the spare nerve injury (SNI). SNI reduced discriminative memory and LTP. Um-PEA treatment started after the development of neuropathic pain had no effects in sham mice, whereas it restored cognitive behavior and LTP in SNI mice. 2-Methyl-6-(phenylethynyl) pyridine (MPEP), a selective mGluR5 antagonist, improved cognition in SNI mice and produced a chemical long term depression of the field excitatory postsynaptic potentials (fEPSPs) in sham and SNI mice. After theta burst stimulation (TBS) MPEP restored LTP in SNI mice. In combination with PEA, MPEP antagonized the PEA effect on discriminative memory and decreased LTP in SNI mice. The (RS)-4-(1-amino-1-carboxyethyl)phthalic acid (MDCPG), a selective mGluR8 antagonist, did not affect discriminative memory, but it induced a chemical LTP and prevented the enhancement of fEPSPs after TBS in SNI mice which were treated or not treated with PEA. The effect of PEA on LTP and cognitive behavior was modulated by mGluR5 and mGluR8. In particular in the SNI conditions, the mGluR5 blockade facilitated memory and LTP, but prevented the beneficial effects of PEA on discriminative memory while the mGluR8 blockade, which was ineffective in itself, prevented the favorable action of the PEA on LTP. Thus, although their opposite roles (excitatory/inhibitory of the two receptor subtypes on the glutamatergic system), they appeared to be required for the neuroprotective effect of PEA in conditions of neuropathic pain.

Traumatic Spinal Cord Injury: An Overview of Pathophysiology, Models and Acute Injury Mechanisms

Traumatic spinal cord injury (SCI) is a life changing neurological condition with substantial socioeconomic implications for patients and their care-givers. Recent advances in medical management of SCI has significantly improved diagnosis, stabilization, survival rate and well-being of SCI patients. However, there has been small progress on treatment options for improving the neurological outcomes of SCI patients. This incremental success mainly reflects the complexity of SCI pathophysiology and the diverse biochemical and physiological changes that occur in the injured spinal cord. Therefore, in the past few decades, considerable efforts have been made by SCI researchers to elucidate the pathophysiology of SCI and unravel the underlying cellular and molecular mechanisms of tissue degeneration and repair in the injured spinal cord. To this end, a number of preclinical animal and injury models have been developed to more closely recapitulate the primary and secondary injury processes of SCI. In this review, we will provide a comprehensive overview of the recent advances in our understanding of the pathophysiology of SCI. We will also discuss the neurological outcomes of human SCI and the available experimental model systems that have been employed to identify SCI mechanisms and develop therapeutic strategies for this condition.

Neurons and Microglia; A Sickly-Sweet Duo in Diabetic Pain Neuropathy

Diabetes is a common condition characterized by persistent hyperglycemia. High blood sugar primarily affects cells that have a limited capacity to regulate their glucose intake. These cells include capillary endothelial cells in the retina, mesangial cells in the renal glomerulus, Schwann cells, and neurons of the peripheral and central nervous systems. As a result, hyperglycemia leads to largely intractable complications such as retinopathy, nephropathy, hypertension, and neuropathy. Diabetic pain neuropathy is a complex and multifactorial disease that has been associated with poor glycemic control, longer diabetes duration, hypertension, advanced age, smoking status, hypoinsulinemia, and dyslipidemia. While many of the driving factors involved in diabetic pain are still being investigated, they can be broadly classified as either neuron -intrinsic or -extrinsic. In neurons, hyperglycemia impairs the polyol pathway, leading to an overproduction of reactive oxygen species and reactive nitrogen species, an enhanced formation of advanced glycation end products, and a disruption in Na⁺/K⁺ ATPase pump function. In terms of the extrinsic pathway, hyperglycemia leads to the generation of both overactive microglia and microangiopathy. The former incites a feed-forward inflammatory loop that hypersensitizes nociceptor neurons, as observed at the onset of diabetic pain neuropathy. The latter reduces neurons' access to oxygen, glucose and nutrients, prompting reductions in nociceptor terminal expression and losses in sensation, as observed in the later stages of diabetic pain neuropathy. Overall, microglia can be seen as potent and long-lasting amplifiers of nociceptor neuron activity, and may therefore constitute a potential therapeutic target in the treatment of diabetic pain neuropathy.

A classification framework for exploiting sparse multi-variate temporal features with application to adverse drug event detection in medical records

BACKGROUND

Adverse drug events (ADEs) as well as other preventable adverse events in the hospital setting incur a yearly monetary cost of approximately $3.5 billion, in the United States alone. Therefore, it is of paramount importance to reduce the impact and prevalence of ADEs within the healthcare sector, not only since it will result in reducing human suffering, but also as a means to substantially reduce economical strains on the healthcare system. One approach to mitigate this problem is to employ predictive models. While existing methods have been focusing on the exploitation of static features, limited attention has been given to temporal features.

METHODS

In this paper, we present a novel classification framework for detecting ADEs in complex Electronic health records (EHRs) by exploiting the temporality and sparsity of the underlying features. The proposed framework consists of three phases for transforming sparse and multi-variate time series features into a single-valued feature representation, which can then be used by any classifier. Moreover, we propose and evaluate three different strategies for leveraging feature sparsity by incorporating it into the new representation.

RESULTS

A large-scale evaluation on 15 ADE datasets extracted from a real-world EHR system shows that the proposed framework achieves significantly improved predictive performance compared to state-of-the-art. Moreover, our framework can reveal features that are clinically consistent with medical findings on ADE detection.

CONCLUSIONS

Our study and experimental findings demonstrate that temporal multi-variate features of variable length and with high sparsity can be effectively utilized to predict ADEs from EHRs. Two key advantages of our framework are that it is method agnostic, i.e., versatile, and of low computational cost, i.e., fast; hence providing an important building block for future exploitation within the domain of machine learning from EHRs.

Hyperglycemia potentiates the effect of ionic calcium in photoreceptor ellipsoid zone disruption in diabetic retinopathy

PURPOSE

To study the association of serum ionic calcium and glycated hemoglobin (HbA1c) with retinal photoreceptor ellipsoid zone (EZ) disruption in diabetic retinopathy (DR).

METHODS

This is a tertiary care center-based observational cross-sectional study. Sixty-three consecutive cases, divided into 21 cases each with no diabetic retinopathy, non-proliferative diabetic retinopathy and proliferative diabetic retinopathy were included. Twenty-one healthy controls were also included. Ellipsoid zone disruption was assessed using spectral-domain optical coherence tomography. Serum ionic calcium and HbA1c were measured using standard protocol. Patient data from cases were divided into two groups according to their HbA1c levels: group 1 (HbA1c < 7, n = 26) and group 2 (HbA1c > 7, n = 37). Data were analyzed statistically.

RESULTS

Mean ionic calcium levels in group 1 and group 2 were 1.131 ± 0.073 mmol/dL and 1.170 ± 0.070 mmol/dL, respectively. In group 1, 11 out of 26 had EZ disruption (42.3%). Similarly, in group 2, 29 out of 37 had EZ disruption (78.4%). On logistic regression analysis, as compared to group 1, ellipsoid zone disruption was found to be positively associated with serum ionic calcium (p = 0.01) in group 2 cases.

CONCLUSION

Increased levels of serum ionic calcium are associated with increased EZ disruption in patients with HbA1c > 7 in DR.

Diabetic neuropathy research: from mouse models to targets for treatment

Diabetic neuropathy is one of the most serious complications of diabetes, and its increase shows no sign of stopping. Furthermore, current clinical treatments do not yet approach the best effectiveness. Thus, the development of better strategies for treating diabetic neuropathy is an urgent matter. In this review, we first discuss the advantages and disadvantages of some major mouse models of diabetic neuropathy and then address the targets for mechanism-based treatment that have been studied. We also introduce our studies on each part. Using stem cells as a source of neurotrophic factors to target extrinsic factors of diabetic neuropathy, we found that they present a promising treatment.

TRPA1 Antagonists for Pain Relief

Here, we review the literature assessing the role of transient receptor potential ankyrin 1 (TRPA1), a calcium-permeable non-selective cation channel, in various types of pain conditions. In the nervous system, TRPA1 is expressed in a subpopulation of nociceptive primary sensory neurons, astroglia, oligodendrocytes and Schwann cells. In peripheral terminals of nociceptive primary sensory neurons, it is involved in the transduction of potentially harmful stimuli and in their central terminals it is involved in amplification of nociceptive transmission. TRPA1 is a final common pathway for a large number of chemically diverse pronociceptive agonists generated in various pathophysiological pain conditions. Thereby, pain therapy using TRPA1 antagonists can be expected to be a superior approach when compared with many other drugs targeting single nociceptive signaling pathways. In experimental animal studies, pharmacological or genetic blocking of TRPA1 has effectively attenuated mechanical and cold pain hypersensitivity in various experimental models of pathophysiological pain, with only minor side effects, if any. TRPA1 antagonists acting peripherally are likely to be optimal for attenuating primary hyperalgesia (such as inflammation-induced sensitization of peripheral nerve terminals), while centrally acting TRPA1 antagonists are expected to be optimal for attenuating pain conditions in which central amplification of transmission plays a role (such as secondary hyperalgesia and tactile allodynia caused by various types of peripheral injuries). In an experimental model of peripheral diabetic neuropathy, prolonged blocking of TRPA1 has delayed the loss of nociceptive nerve endings and their function, thereby promising to provide a disease-modifying treatment.

Fluoxetine pretreatment enhances neurogenic, angiogenic and immunomodulatory effects of MSCs on experimentally induced diabetic neuropathy

Being one of the most debilitating complications among diabetic patients, diabetic polyneuropathy (DPN) is a paramount point of continuous research. Stem cell therapies have shown promising results. However, limited cell survival and paracrine activities hinder its transfer from bench to bedside. We designed this study to evaluate fluoxetine-pretreatment technique of mesenchymal stem cells (MSCs) as an approach to enhance their paracrine and immunomodulatory properties in DPN. Effects of fluoxetine treatment of MSCs were tested in vitro. Forty-two adult Wistar male albino rats were utilized, further subdivided into control, diabetic, MSC-treated and fluoxetine-pretreated MSC groups. Sciatic nerve sections were prepared for light and electron microscope examination and immunohistochemical detection of neurofilament (NF) protein. Also, we assessed in vitro survival and paracrine properties of fluoxetine-pretreated MSCs. Real time PCR of BDNF, VEGF, IL-1β, and IL-10 expression in tissue homogenate was performed. Our results showed restoration of normal neuronal histomorphology and ultrastructure, moreover, immunohistochemical expression of anti-neurofilament protein was significantly elevated in MSC-treated groups compared to the diabetic one. Fluoxetine enhanced the MSC survival and their paracrine properties of MSCs in vitro. Furthermore, the fluoxetine-pretreated MSC group revealed a significant elevation of mRNA expression of BDNF (neurotrophic factor) and VEGF (angiogenic factor), denoting ameliorated MSC paracrine properties. Similarly, improved immunomodulatory functions were evident by a significant reduction of interleukin-1β mRNA expression (pro-inflammatory) and a reciprocal significant increase of interleukin-10 (anti-inflammatory). We concluded that fluoxetine-pretreatment of MSCs boosts their survival, paracrine, and immunomodulatory traits and directly influenced neuronal histomorphology. Hence, it presents a promising intervention of diabetic polyneuropathy. Graphical Abstract.

Comprehensive analysis of differentially expressed microRNAs and mRNAs in dorsal root ganglia from streptozotocin-induced diabetic rats

Diabetic peripheral neuropathy is a common complication associated with diabetes mellitus with a pathogenesis that is incompletely understood. By regulating RNA silencing and post-transcriptional gene expression, microRNAs participate in various biological processes and human diseases. However, the relationship between microRNAs and the progress of diabetic peripheral neuropathy still lacks a thorough exploration. Here we used microarray microRNA and mRNA expression profiling to analyze the microRNAs and mRNAs which are aberrantly expressed in dorsal root ganglia from streptozotocin-induced diabetic rats. We found that 37 microRNAs and 1357 mRNAs were differentially expressed in comparison to non-diabetic samples. Bioinformatics analysis indicated that 399 gene ontology terms and 29 Kyoto Encyclopedia of Genes and Genomes pathways were significantly enriched in diabetic rats. Additionally, a microRNA-gene network evaluation identified rno-miR-330-5p, rno-miR-17-1-3p and rno-miR-346 as important players for network regulation. Finally, quantitative real-time polymerase chain reaction analysis was used to confirm the microarray results. In conclusion, this study provides a systematic perspective of microRNA and mRNA expression in dorsal root ganglia from diabetic rats, and suggests that dysregulated microRNAs and mRNAs may be important promotors of peripheral neuropathy. Our results may be the underlying framework of future studies regarding the effect of the aberrantly expressed genes on the pathophysiology of diabetic peripheral neuropathy.

Erythropoietin: A potential drug in the management of diabetic neuropathy

Erythropoietin (EPO) is required for promoting the progress of erythroid differentiation. However, the discovery of EPO and the EPO receptor (EPOR) in the nervous system may contribute to new treatment strategies for the use of EPO in neurodegenerative disorders. Diabetic neuropathy is a neurodegenerative disease that affects a large proportion of diabetic patients and results in alterations in functionality, mood and sleep. The pathogenic mechanisms generating diabetic neuropathy involve: Schwannopathy, polyol pathway activity, advanced glycation end-products (AGEs) accumulation, protein kinase C (PKC) activity, increased hexosamine pathway flux, oxidative stress, nitric oxide and inflammation. In this sense, evidence from both clinical and experimental studies indicates that EPO may reverse diabetic neuropathy through an antioxidant action by decreasing pro-inflammatory cytokines, restoring Na+/K+-ATPase activity, and blocking the generation of pro-apoptotic proteins. The aim of this review is to discuss the neuroprotector effect of EPO on pathogenic mechanisms of diabetic neuropathy.

Cisplatin alters the function and expression of N-type voltage-gated calcium channels in the absence of morphological damage of sensory neurons

Platinum-based chemotherapeutic agents, such as cisplatin, are still frequently used for treating various types of cancer. Besides its high effectiveness, cisplatin has several serious side effects. One of the most common side effects is dorsal root ganglion (DRG) neurotoxicity. However, the mechanisms underlying this neurotoxicity are still unclear and controversially discussed. Cisplatin-mediated modulation of voltage-gated calcium channels (VGCCs) in the DRG neurons has been shown to alter intracellular calcium homeostasis, a process critical for the induction of neurotoxicity. Using the whole-cell patch-clamp technique, immunostaining, behavioural experiments and electron microscopy (EM) of rat DRGs, we here demonstrate that cisplatin-induced neurotoxicity is due to functional alteration of VGCC, but not due to morphological damage. In vitro application of cisplatin (0.5 µM) increased N-type VGCC currents (I_Ca(V)) in small DRG neurons. Repetitive in vivo administration of cisplatin (1.5 mg/kg, cumulative 12 mg/kg) increased the protein level of N-type VGCC over 26 days, with the protein level being increased for at least 14 days after the final cisplatin administration. Behavioural studies revealed that N-type VGCCs are crucial for inducing symptoms of cisplatin-related neuropathic pain, such as thermal and mechanical hyperalgesia. EM and histology showed no evidence of any structural damage, apoptosis or necrosis in DRG cells after cisplatin exposure for 26 days. Furthermore, no nuclear DNA damage in sensory neurons was observed. Here, we provide evidence for a mainly functionally driven induction of neuropathic pain by cisplatin.

MSCs ameliorates DPN induced cellular pathology via [Ca2+ ]i homeostasis and scavenging the pro-inflammatory cytokines

The MSCs of various origins are known to ameliorate or modulate cell survival strategies. We investigated, whether UCB MSCs could improve the survival of the human neuronal cells and/or fibroblast assaulted with DPN sera. The results showed, the co-culture of UCB MSCs with human neuronal cells and/or fibroblasts could effectively scavenge the pro-inflammatory cytokines TNF-α, IL-1β, IFN-ɤ and IL - 12 and control the pro-apoptotic expression of p53/Bax. Further co-culture of UCB MSCs have shown to induce anti-inflammatory cytokines like IL-4, IL-10 and TGF-β and anti-apoptotic Bclxl/Bcl2 expression in the DPN sera stressed cells. Amelioration of elevated [Ca²⁺ ]_i and cROS, the portent behind the NFκB/Caspase-3 mediated inflammation in DPN rescued the cells from apoptosis. The results of systemic administration of BM MSCs improved DPN pathology in rat as extrapolated from human cell model. The BM MSCs ameliorated prolonged distal motor latency (control: 0.70 ± 0.06, DPN: 1.29 ± 0.13 m/s DPN + BM MSCs: 0.89 ± 0.02 m/s, p < 0.05) and lowered high amplitude of compound muscle action potentials (CMAPs) (control: 12.36 ± 0.41, DPN: 7.52 ± 0.61 mV, DPN + MSCs: 8.79 ± 0.53 mV, p < 0.05), while slowly restoring the plasma glucose levels. Together, all these results showed that administration of BM or UCB MSCs improved the DPN via ameliorating pro-inflammatory cytokine signaling and [Ca²⁺ ]_i homeostasis.

Aberrant plasticity of peripheral sensory axons in a painful neuropathy

Neuronal cells express considerable plasticity responding to environmental cues, in part, through subcellular mRNA regulation. Here we report on the extensive changes in distribution of mRNAs in the cell body and axon compartments of peripheral sensory neurons and the 3' untranslated region (3'UTR) landscapes after unilateral sciatic nerve entrapment (SNE) injury in rats. Neuronal cells dissociated from SNE-injured and contralateral L4 and L5 dorsal root ganglia were cultured in a compartmentalized system. Axonal and cell body RNA samples were separately subjected to high throughput RNA sequencing (RNA-Seq). The injured axons exhibited enrichment of mRNAs related to protein synthesis and nerve regeneration. Lengthening of 3'UTRs was more prevalent in the injured axons, including the newly discovered alternative cleavage and polyadenylation of NaV1.8 mRNA. Alternative polyadenylation was largely independent from the relative abundance of axonal mRNAs; but they were highly clustered in functional pathways related to RNA granule formation in the injured axons. These RNA-Seq data analyses indicate that peripheral nerve injury may result in highly selective mRNA enrichment in the affected axons with 3'UTR alterations potentially contributing to the mechanism of neuropathic pain.