Role of Nitric Oxide as Mediator of Nerve Injury in Inflammatory Neuropathies

Mechanisms behind diffuse idiopathic peripheral neuropathy in humans - a systematic review

Introduction: Diffuse peripheral neuropathy is a well-known complication of several conditions, whereas many patients have peripheral neuropathy of unknown etiology and pathophyisology. Increased knowledge of mechanisms may provide insight into enteric neuropathy with gastrointestinal dysmotility. The aim of the present systematic review was to identify mechanisms behind diffuse idiopathic peripheral neuropathies in humans.Methods: Searches were performed in PubMed, Embase, and Web of Science. Human original and review articles, written in English, describing mechanisms behind diffuse peripheral neuropathy verified by objective examinations were intended to be studied. Articles that described animal models, well-described hereditary diseases, drug-induced neuropathy, pain syndromes, malnutrition, and local neuropathy were excluded.Results: In total, 4712 articles were identified. After scrutinizing titles and abstracts, 633 remained and were studied in full text. After the removal of articles not fulfilling inclusion or exclusion criteria, 52 were finally included in this review. The most frequently described neuropathy was diabetic neuropathy, with a wide range of mechanisms involving mitochondrial dysfunction such as oxidative stress and inflammation. Microvascular changes in diabetes and vasculitis lead to ischemia and secondary oxidative stress with inflammation. Structural changes in neurons and glial cells are observed, with abnormalities in different neurotrophic factors. Neuropathy induced by autoantibodies or immunological mechanisms is described in infectious and systemic inflammatory diseases. Several ion channels may be involved in painful neuropathy. No study identified why some patients mainly develop large fiber neuropathy and others small fiber neuropathy.Conclusion: Metabolic and immunological factors and channelopathy may be considered in diffuse idiopathic peripheral neuropathy.

NO-Dependent Mechanisms of p53 Expression and Cell Death in Rat’s Dorsal Root Ganglia after Sciatic-Nerve Transection

Peripheral-nerve injury is a frequent cause of disability. Presently, no clinically effective neuroprotectors have been found. We have studied the NO-dependent expression of p53 in the neurons and glial cells of the dorsal root ganglia (DRG) of a rat’s spinal cord, as well as the role of NO in the death of these cells under the conditions of axonal stress, using sciatic-nerve axotomy as a model. It was found out that axotomy led to the nuclear–cytoplasmic redistribution of p53 in neurons, 24 h after trauma. The NO donor led to a considerable increase in the level of p53 in nuclei and, to a smaller degree, in the cytoplasm of neurons and karyoplasm of glial cells 4 and 24 h after axotomy. Application of a selective inhibitor of inducible NO-synthase (iNOS) provided the opposite effect. Introduction of the NO donor resulted in a significant increase in cell death in the injured ipsilateral DRG, 24 h and 7 days after trauma. The selective inhibitor of iNOS demonstrated a neuroprotective effect. Axotomy was shown to upregulate the iNOS in nuclei and cytoplasm of DRG cells. The NO-dependent expression of p53, which is particularly achieved through iNOS activation, is believed to be a putative signaling mechanism of neural and glial-cell death after axotomy.

SARS-CoV-2 and Guillain-Barré Syndrome: Lessons from Viral Infections

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the COVID-19 pandemic. COVID-19 has a broad clinical spectrum from asymptomatic patients to multiorgan dysfunction and septic shock. Most of the common symptoms of COVID-19 are classified as respiratory disorders, but some reports show neurological involvements. During the COVID-19 pandemic, a case series of neurological complications, such as Guillain-Barré syndrome (GBS), were reported. GBS is a neuroimmune disorder with acute inflammatory radicular polyneuropathy in different parts of the peripheral nerve. Some studies have reported GBS as an inflammatory neuropathy related to various viral infections, such as cytomegalovirus (CMV), Epstein-Barr Virus (EBV), herpes simplex virus (HSV), human immunodeficiency virus (HIV), influenza, and Zika virus. There are some immunomodulation approaches for the management of GBS. Studies have evaluated the effects of the various therapeutic approaches, including intravenous immunoglobulin (IVIG), plasma exchange (PE), complement inhibitors, and corticosteroids to regulate overactivation of immune responses during GBS in experimental and clinical studies. In this regard, the possible association between GBS and SARS-CoV-2 infection during the outbreak of the current pandemic and also the mentioned therapeutic approaches were reviewed.

Kombucha ameliorates experimental autoimmune encephalomyelitis through activation of Treg and Th2 cells

Multiple sclerosis (MS) is the most common inflammatory disorder of the central nervous system (CNS). Kombucha is produced by the fermentation of sugared tea with a symbiotic culture of bacteria and yeasts. This research was designed to reveal the therapeutic impact and the molecular and cellular processes determining the effect of kombucha on MS alleviation in an experimental autoimmune encephalomyelitis (EAE). The EAE was induced using myelin oligodendrocyte glycoprotein (MOG35-55) peptide emulsified in CFA and injected subcutaneously over two flank areas in C57BL/6 mice. In addition, pertussis toxin was injected intraperitoneally and repeated 48 h later. Treatment groups were received three different doses of kombucha (K1: low dose, K2: medium dose and K3: high dose) to obtain a maximum protection. Clinical scores and other criteria were followed daily for the 25 days. At the end of the course, T-helper-related cytokines (IFN-γ, IL-17, IL-4, and TGF-β) were measured through ELISA. Moreover, nitric oxide (NO) concentration in spinal cord tissue was detected. The severity of disease on the peak of disease in K1, K2, and K3 groups were 3.4 ± 0.18 and 2.6 ± 0.18 and 2 ± 0.14 respectively, compared to the CTRL group with 4.5 ± 0.19 (p < 0.001). Kombucha increased production of interleukin IL-4 (K1 = 95 ± 5, K2 = 110 ± 10, K3 = 115 ± 5 and CTRL = 65 ± 5; p < 0.05) and TGF-β (K1 = 1750 ± 80, K2 = 2050 ± 65, K3 = 2200 ± 75 and CTRL = 850 ± 85; p < 0.001) but concurrently resulted in a remarkable reduction in the production of IFN-γ (K1 = 950 ± 70, K2 = 890 ± 65, K3 = 850 ± 85 and CTRL = 3850 ± 115; p < 0.001) and IL-17 (K1 = 1250 ± 75, K2 = 1050 ± 90, K3 = 970 ± 80 and CTRL = 6450 ± 125; p < 0.001). Moreover, NO concentration in spinal cord tissue in the treatment groups was significantly less than the control group (K1: 35.42 ± 2.1, K2 = 31.21 ± 2.2, K3 = 28.24 ± 2.6 and CTRL = 45.25 ± 2.7; p < 0.05). These results supported that kombucha could reduce the severity of disease in an EAE model through motivating polarization of CD4+ T cells by induction of IL-4 and TGF-β as well as inhibition of IFN-γ and IL-17.

Assessment of Expression of SOCS Genes in Acquired Immune-Mediated Polyneuropathies

Acquired immune-mediated polyneuropathies are classified to some subtypes among them are acute and chronic inflammatory demyelinating polyradiculoneuropathies (AIDP and CIDP). These two conditions share some common signs and underlying mechanisms. Based on the roles of Suppressor of cytokine signaling (SOCS) genes in the modulation of immune system reactions, these genes might be involved in the pathogenesis of these conditions. We evaluated expression of SOCS1-3 and SOCS5 genes in the leukocytes of 32 cases of CIDP, 19 cases of AIDP and 40 age- and sex-matched controls using real time PCR method. The Bayesian regression model was used to estimate differences in mean values of genes expressions between cases and control group. Expression levels of SOCS1 and SOCS2 were significantly lower in male patients compared with controls. This sex-specific pattern was also observed for SOCS3 down-regulation. Based on the area under curve values in Receiver Operating Characteristics (ROC) curve, diagnostic powers of SOCS1, SOCS2, SOCS3 and SOCS5 genes in the mentioned disorder were 0.61, 0.73, 0.68 and 0.58, respectively. Expression of none of genes was correlated with age of enrolled cases. The current study shows evidences for participation of SOCS genes in the pathophysiology of acquired immune-mediated polyneuropathies.

Does Compression Sensory Axonopathy in the Proximal Tibia Contribute to Noncontact Anterior Cruciate Ligament Injury in a Causative Way?-A New Theory for the Injury Mechanism

Anterior cruciate ligament injury occurs when the ligament fibers are stretched, partially torn, or completely torn. The authors propose a new injury mechanism for non-contact anterior cruciate ligament injury of the knee. Accordingly, non-contact anterior cruciate ligament injury could not happen without the acute compression microinjury of the entrapped peripheral proprioceptive sensory axons of the proximal tibia. This would occur under an acute stress response when concomitant microcracks-fractures in the proximal tibia evolve due to the same excessive and repetitive compression forces. The primary damage may occur during eccentric contractions of the acceleration and deceleration moments of strenuous or unaccustomed fatiguing exercise bouts. This primary damage is suggested to be an acute compression/crush axonopathy of the proprioceptive sensory neurons in the proximal tibia. As a result, impaired proprioception could lead to injury of the anterior cruciate ligament as a secondary damage, which is suggested to occur during the deceleration phase. Elevated prostaglandin E2, nitric oxide and glutamate may have a critical neuro-modulatory role in the damage signaling in this dichotomous neuronal injury hypothesis that could lead to mechano-energetic failure, lesion and a cascade of inflammatory events. The presynaptic modulation of the primary sensory axons by the fatigued and microdamaged proprioceptive sensory fibers in the proximal tibia induces the activation of N-methyl-D-aspartate receptors in the dorsal horn of the spinal cord, through a process that could have long term relevance due to its contribution to synaptic plasticity. Luteinizing hormone, through interleukin-1β, stimulates the nerve growth factor-tropomyosin receptor kinase A axis in the ovarian cells and promotes tropomyosin receptor kinase A and nerve growth factor gene expression and prostaglandin E2 release. This luteinizing hormone induced mechanism could further elevate prostaglandin E2 in excess of the levels generated by osteocytes, due to mechanical stress during strenuous athletic moments in the pre-ovulatory phase. This may explain why non-contact anterior cruciate ligament injury is at least three-times more prevalent among female athletes.

Injury-Induced Effectors of Neuropathic Pain

Injuries typically result in the development of neuropathic pain, which decreases in parallel with wound healing. However, the pain may remain after the injury appears to have healed, which is generally associated with an ongoing underlying pro-inflammatory state. Injury induces many cells to release factors that contribute to the development of a pro-inflammatory state, which is considered an essential first step towards wound healing. However, pain elimination requires a transition of the injury site from pro- to anti-inflammatory. Therefore, developing techniques that eliminate chronic pain require an understanding of the cells resident at and recruited to injury sites, the factors they release, that promote a pro-inflammatory state, and promote the subsequent transition of that site to be anti-inflammatory. Although a relatively large number of cells, factors, and gene expression changes are involved in these processes, it may be possible to control a relatively small number of them leading to the reduction and elimination of chronic neuropathic pain. This first of two papers examines the roles of the most salient cells and mediators associated with the development and maintenance of chronic neuropathic pain. The following paper examines the cells and mediators involved in reducing and eliminating chronic neuropathic pain.

Nitric Oxide Donor DETA/NO Inhibits the Growth of Endometrial Cancer Cells by Upregulating the Expression of RASSF1 and CDKN1A

Nitric oxide (NO) is implicated in several biological processes, including cancer progression. At low concentrations, it promotes cell survival and tumor progression, and at high concentrations it causes apoptosis and cell death. Until now, the impact of NO donors has not been investigated on human endometrial tumors. Four cancer cell lines were exposed to different concentrations of DETA/NO for 24 to 120 h. The effects of DETA/NO on cell proliferation and invasion were determined utilizing MTS and Boyden chamber assays, respectively. The DETA/NO induced a dose and time-dependent reduction in cell viability by the activation of caspase-3 and cell cycle arrest at the G0/G1 phase that was associated with the attenuated expression of cyclin-D1 and D3. Furthermore, the reduction in the amount of CD133-expressing cancer stem-like cell subpopulation was observed following DETA/NO treatment of cells, which was associated with a decreased expression of stem cell markers and attenuation of cell invasiveness. To understand the mechanisms by which DETA/NO elicits anti-cancer effects, RNA sequencing (RNA-seq) was used to ascertain alterations in the transcriptomes of human endometrial cancer cells. RNA-seq analysis revealed that 14 of the top 21 differentially expressed genes were upregulated and seven were downregulated in endometrial cancer cells with DETA/NO. The genes that were upregulated in all four cell lines with DETA/NO were the tumor suppressors Ras association domain family 1 isoform A (RASSF1) and Cyclin-dependent kinase inhibitor 1A (CDKN1A). The expression patterns of these genes were confirmed by Western blotting. Taken together, the results provide the first evidence in support of the anti-cancer effects of DETA/NO in endometrial cancer.

Nitrosative damage during retrovirus infection-induced neuropathic pain

BACKGROUND

Peripheral neuropathy is currently the most common neurological complication in HIV-infected individuals, occurring in 35-50% of patients undergoing combination anti-retroviral therapy. Data have shown that distal symmetric polyneuropathy develops in mice by 6 weeks following infection with the LP-BM5 retrovirus mixture. Previous work from our laboratory has demonstrated that glial cells modulate antiviral T-cell effector responses through the programmed death (PD)-1: PD-L1 pathway, thereby limiting the deleterious consequences of unrestrained neuroinflammation.

METHODS

Using the MouseMet electronic von Frey system, we assessed hind-paw mechanical hypersensitivity in LP-BM5-infected wild-type (WT) and PD-1 KO animals. Using multi-color flow cytometry, we quantitatively assessed cellular infiltration and microglial activation. Using real-time RT-PCR, we assessed viral load, expression of IFN-γ, iNOS, and MHC class II. Using western blotting, we measured protein nitrosylation within the lumbar spinal cord (LSC) and dorsal root ganglion (DRG). Histochemical staining was performed to analyze the presence of CD3, ionized calcium binding adaptor molecule (Iba)-1, MHCII, nitrotyrosine, isolectin B4 (IB4) binding, and neurofilament 200 (NF200). Statistical analyses were carried out using graphpad prism.

RESULTS

Hind-paw mechanical hypersensitivity observed in LP-BM5-infected animals was associated with significantly increased lymphocyte infiltration into the spinal cord and DRG. We also observed elevated expression of IFN-γ (in LSC and DRG) and MHC II (on resident microglia in LSC). We detected elevated levels of 3-nitrotyrosine within the LSC and DRG of LP-BM5-infected animals, an indicator of nitric oxide (NO)-induced protein damage. Moreover, we observed 3-nitrotyrosine in both small (IB4+) and large (NF200+) DRG sensory neurons. Additionally, infected PD-1 KO animals displayed significantly greater mechanical hypersensitivity than WT or uninfected mice at 4 weeks post-infection (p.i.). Accelerated onset of hind-paw hypersensitivity in PD-1 KO animals was associated with significantly increased infiltration of CD4+ and CD8+ T lymphocytes, macrophages, and microglial activation at early time points. Importantly, we also observed elevated levels of 3-nitrotyrosine and iNOS in infected PD-1 KO animals when compared with WT animals.

CONCLUSIONS

Results reported here connect peripheral immune cell infiltration and reactive gliosis with nitrosative damage. These data may help elucidate how retroviral infection-induced neuroinflammatory networks contribute to nerve damage and neuropathic pain.

Nitric Oxide: Exploring the Contextual Link with Alzheimer's Disease

Neuronal inflammation is a systematically organized physiological step often triggered to counteract an invading pathogen or to rid the body of damaged and/or dead cellular debris. At the crux of this inflammatory response is the deployment of nonneuronal cells: microglia, astrocytes, and blood-derived macrophages. Glial cells secrete a host of bioactive molecules, which include proinflammatory factors and nitric oxide (NO). From immunomodulation to neuromodulation, NO is a renowned modulator of vast physiological systems. It essentially mediates these physiological effects by interacting with cyclic GMP (cGMP) leading to the regulation of intracellular calcium ions. NO regulates the release of proinflammatory molecules, interacts with ROS leading to the formation of reactive nitrogen species (RNS), and targets vital organelles such as mitochondria, ultimately causing cellular death, a hallmark of many neurodegenerative diseases. AD is an enervating neurodegenerative disorder with an obscure etiology. Because of accumulating experimental data continually highlighting the role of NO in neuroinflammation and AD progression, we explore the most recent data to highlight in detail newly investigated molecular mechanisms in which NO becomes relevant in neuronal inflammation and oxidative stress-associated neurodegeneration in the CNS as well as lay down up-to-date knowledge regarding therapeutic approaches targeting NO.

Erythropoietin Enhanced Recovery After Traumatic Nerve Injury: Myelination and Localized Effects

PURPOSE

We previously found that administration of erythropoietin (EPO) shortens the course of recovery after experimental crush injury to the mouse sciatic nerve. The course of recovery was more rapid than would be expected if EPO's effects were caused by axonal regeneration, which raised the question of whether recovery was instead the result of promoting remyelination and/or preserving myelin on injured neurons. This study tested the hypothesis that EPO has a direct and local effect on myelination in vivo and in vitro.

METHODS

Animals were treated with EPO after standard calibrated sciatic nerve crush injury; immunohistochemical analysis was performed to assay for myelinated axons. Combined in vitro neuron-Schwann cell co-cultures were performed to assess EPO-mediated effects directly on myelination and putative protective effects against oxidative stress. In vivo local administration of EPO in a fibrin glue carrier was used to demonstrate early local effects of EPO treatment well in advance of possible neuroregenerative effects.

RESULTS

Systemic Administration of EPO maintained more in vivo myelinated axons at the site of nerve crush injury. In vitro, EPO treatment promoted myelin formation and protected myelin from the effects of nitric oxide exposure in co-cultures of Schwann cells and dorsal root ganglion neurons. In a novel, surgically applicable local treatment using Food and Drug Administration-approved fibrin glue as a vehicle, EPO was as effective as systemic EPO administration at time points earlier than those explainable using standard models of neuroregeneration.

CONCLUSIONS

In nerve crush injury, EPO may be exerting a primary influence on myelin status to promote functional recovery.

CLINICAL RELEVANCE

Mixed injury to myelin and axons may allow the opportunity for the repurposing of EPO for use as a myeloprotective agent in which injuries spare a requisite number of axons to allow early functional recovery.

S-nitrosoglutathione reductase deficiency-induced S-nitrosylation results in neuromuscular dysfunction

AIMS

Nitric oxide (NO) production is implicated in muscle contraction, growth and atrophy, and in the onset of neuropathy. However, many aspects of the mechanism of action of NO are not yet clarified, mainly regarding its role in muscle wasting. Notably, whether NO production-associated neuromuscular atrophy depends on tyrosine nitration or S-nitrosothiols (SNOs) formation is still a matter of debate. Here, we aim at assessing this issue by characterizing the neuromuscular phenotype of S-nitrosoglutathione reductase-null (GSNOR-KO) mice that maintain the capability to produce NO, but are unable to reduce SNOs.

RESULTS

We demonstrate that, without any sign of protein nitration, young GSNOR-KO mice show neuromuscular atrophy due to loss of muscle mass, reduced fiber size, and neuropathic behavior. In particular, GSNOR-KO mice show a significant decrease in nerve axon number, with the myelin sheath appearing disorganized and reduced, leading to a dramatic development of a neuropathic phenotype. Mitochondria appear fragmented and depolarized in GSNOR-KO myofibers and myotubes, conditions that are reverted by N-acetylcysteine treatment. Nevertheless, although atrogene transcription is induced, and bulk autophagy activated, no removal of damaged mitochondria is observed. These events, alongside basal increase of apoptotic markers, contribute to persistence of a neuropathic and myopathic state.

INNOVATION

Our study provides the first evidence that GSNOR deficiency, which affects exclusively SNOs reduction without altering nitrotyrosine levels, results in a clinically relevant neuromuscular phenotype.

CONCLUSION

These findings provide novel insights into the involvement of GSNOR and S-nitrosylation in neuromuscular atrophy and neuropathic pain that are associated with pathological states; for example, diabetes and cancer.

Mitochondrial dynamics in peripheral neuropathies

SIGNIFICANCE

Mitochondrial dynamics describes the continuous change in the position, size, and shape of mitochondria within cells. The morphological and functional complexity of neurons, the remarkable length of their processes, and the rapid changes in metabolic requirements arising from their intrinsic excitability render these cells particularly dependent on effective mitochondrial function and positioning. The rules that govern these changes and their functional significance are not fully understood, yet the dysfunction of mitochondrial dynamics has been implicated as a pathogenetic factor in a number of diseases, including disorders of the central and peripheral nervous systems.

RECENT ADVANCES

In recent years, a number of mutations of genes encoding proteins that play important roles in mitochondrial dynamics and function have been discovered in patients with Charcot-Marie-Tooth (CMT) disease, a hereditary peripheral neuropathy. These findings have directly linked mitochondrial pathology to the pathology of peripheral nerve and have identified certain aspects of mitochondrial dynamics as potential early events in the pathogenesis of CMT. In addition, mitochondrial dysfunction has now been implicated in the pathogenesis of noninherited neuropathies, including diabetic and inflammatory neuropathies.

CRITICAL ISSUES

The role of mitochondria in peripheral nerve diseases has been mostly examined in vitro, and less so in animal models.

FUTURE DIRECTIONS

This review examines available evidence for the role of mitochondrial dynamics in the pathogenesis of peripheral neuropathies, their relevance in human diseases, and future challenges for research in this field.

S-nitrosation and ubiquitin-proteasome system interplay in neuromuscular disorders

Protein S-nitrosation is deemed as a prototype of posttranslational modifications governing cell signaling. It takes place on specific cysteine residues that covalently incorporate a nitric oxide (NO) moiety to form S-nitrosothiol derivatives and depends on the ratio between NO produced by NO synthases and nitrosothiol removal catalyzed by denitrosating enzymes. A large number of cysteine-containing proteins are found to undergo S-nitrosation and, among them, the enzymes catalyzing ubiquitination, mainly the class of ubiquitin E3 ligases and the 20S component of the proteasome, have been reported to be redox modulated in their activity. In this review we will outline the processes regulating S-nitrosation and try to debate whether and how it affects protein ubiquitination and degradation via the proteasome. In particular, since muscle and neuronal health largely depends on the balance between protein synthesis and breakdown, here we will discuss the impact of S-nitrosation in the efficiency of protein quality control system, providing lines of evidence and speculating about its involvement in the onset and maintenance of neuromuscular dysfunctions.

Recent developments and future directions in Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) encompasses a spectrum of acquired neuropathic conditions characterized by inflammatory demyelinating or axonal peripheral neuropathy with acute onset. Clinical and experimental studies in the past years have led to substantial progress in epidemiology, pathogenesis of GBS variants, and identification of prognostic factors relevant to treatment. In this review we provide an overview and critical assessment of the most recent developments and future directions in GBS research.

A reliable in vitro model for studying peripheral nerve myelination in mouse

The rat dorsal root ganglia (DRG) model is a long-standing in vitro model for analysis of myelination in the peripheral nervous system. For performing systematic, high throughput analysis with transgenic animals, a simplified BL6 mouse protocol is indispensable. Here we present a stable and reliable protocol for myelinating co-cultures producing a high myelin ratio using cells from C57BL/6 mice. As an easy accessible and operable method, Sudan staining proved to be efficient in myelin detection for fixed cultures. Green fatty acid stain turned out to be highly reliable for analysis of the dynamic biological processes of myelination in vital cultures. Once myelinated we were able to induce demyelination by the addition of forskolin into the model system. In addition, we provide an optimised rat DRG protocol with significantly improved myelin ratio and a comparison of the protocols presented. Our results strengthen the value of ex vivo myelination models in neurobiology.

The brain-derived neurotrophic factor, nerve growth factor, neurotrophin-3, and induced nitric oxide synthase expressions after low-level laser therapy in an axonotmesis experimental model

BACKGROUND DATA

A robust body of evidence has shown that low-level laser therapy (LLLT) improves peripheral nerve regeneration. However, the biochemical background triggered in this process is not yet fully understood.

OBJECTIVE

The purpose of this study was to evaluate the mRNA expression of neurotrophic factors (brain-derived neurotrophic factor [BDNF], nerve growth factor [NGF], and neurotrophin-3, [NT-3]) and also an inflammatory marker (induced nitric oxide synthase [iNOS]) in an axonotmesis experimental model after low-level laser therapy.

METHODS

Thirty-six adult male Wistar rats (250-350 g) were subjected to right sciatic nerve crush injury, and 24 h later, the animals in the three different experimental groups (n=18) were irradiated on a daily basis with helium-neon laser (collimated HeNe laser, continuous emission, wavelength: 632.8 nm, power density: 0.5 mW/cm(2), irradiation time: 20 sec, energy density: 10 J/cm(2)) during 7, 14, and 21 consecutive days, respectively. The control group (n=18) underwent the same procedures, but with the equipment turned off. At the end of the experiments, animals were killed with an overdose of anesthesia to remove samples from the sciatic nerve lesion epicenter to determine the mRNA expression of BDNF, NGF, NT-3 and iNOS enzyme.

RESULTS

Comparisons between groups showed that HeNe laser increased the mRNA expression of both BDNF and NGF factors after 14 days of LLLT, with peak expression at the 21st day. Increase in NT-3 mRNA expression was not observed. In addition, HeNe laser produced iNOS expression reduction, which played an important role in the inflammatory process.

CONCLUSIONS

The reported data could have a relevant practical value because LLLT is a noninvasive procedure, and have revealed significant increase in neurotrophic factor expressions and inflammatory process reduction, opening the possibility of using LLLT as an important aid to nerve regeneration process.

Levetiracetam exhibits protective properties on rat Schwann cells in vitro

Oxidative stress and inflammation represent pathways causing substantial damage to the peripheral nervous system. Levetiracetam (LEV) is a commonly used antiepileptic drug targeting high-voltage activated N-type calcium channels. Recent evidence suggests that LEV may also act as a histone deacetylase inhibitor, suggesting that this drug exhibits both anti-inflammatory and anti-oxidative effects, and as such may represent an interesting candidate for treating inflammatory diseases affecting the peripheral nerve. Therefore, we analysed the influence of LEV ex vivo on purified Schwann cells from neonatal P3 rats as well as on dorsal root ganglia prepared from E15 rat embryos. LEV diminished a lipopolysaccharide (LPS)-induced increase of the pro-inflammatory signature molecules tumour necrosis factor alpha, matrix metalloproteinase 9 (MMP-9), and caspase 6. Furthermore, LEV decreased LPS-induced cell death and protected cells against oxidative stress in a glutamate-based oxidative stress model. MMP-2 activity, usually elevated during myelination and repair, was also found to be up-regulated following LEV, while LEV exhibited no negative effects on myelination. Intracellular sodium or calcium concentrations were unaltered by LEV. Thus, LEV may be a promising, well-tolerated drug that - besides its antiepileptic potential - mediates anti-inflammatory, anti-oxidative, and anti-apoptotic properties that may potentially be useful in treating diseases of the peripheral nerve.

Pathogenesis and treatment of immune-mediated neuropathies

Immune-mediated neuropathies represent a heterogeneous spectrum of peripheral nerve disorders that can be classified according to time course, predominant involvement of motor/sensory fibers, distribution of deficits and paraclinical parameters such as electrophysiology and serum antibodies. In the last few years, significant advances have been achieved in elucidating underlying pathomechanisms, which made it possible to identify potential therapeutic targets. In this review, we discuss the latest development in pathogenesis and treatment of immune-mediated neuropathies.

Human Schwann cells retain essential phenotype characteristics after immortalization

Schwann cells (SCs) play an important role in the pathogenesis of peripheral nerve diseases and represent a potential target for development of therapies. However, use of primary human SCs (hSCs) for in vitro models is limited because these cells are difficult to prepare and maintain in high yield and purity under common cell culture conditions. To circumvent this obstacle, we immortalized primary human fetal SCs using the SV40 large T-antigen and human telomerase reverse transcriptase expression vectors. After cloning, selection, and purification, we evaluated several immortalized SC lines for their ability to express extracellular matrix (ECM) molecules and myelinate embryonic rat sensory axons. In addition, we established a gene expression profile and explored their sensitivity to oxidative stress in a simple in vitro assay. Immortalized hSC clones expressed common glial markers and a broad variety of growth factors, receptors, and ECM molecules as determined by immunocytochemistry, microarray, and quantitative reverse transcription-polymerase chain reaction. In neuron-SC co-cultures, these cells were able to myelinate rat dorsal root ganglia neurons, although their effectiveness was lower in comparison to primary rat SCs. In toxicity assays, immortalized hSCs remain susceptible to oxidative stress induced by H(2)O(2). This study shows that, using specific immortalization techniques, it is possible to establish hSC lines that retain characteristics of typical primary hSCs. These cells are particularly useful for drug screening and studies aimed at disease mechanisms involving SCs.

Plasma exchange and intravenous immunoglobulins: mechanism of action in immune-mediated neuropathies

Immune-mediated neuropathies are a heterogeneous group of peripheral nerve disorders, which are classified by time course, clinical pattern, affected nerves and pathological features. Plasma exchange (PE) and intravenous immunoglobulins (IVIg) are mainstays in the treatment of immune-mediated neuropathies. Of all treatments currently used, IVIg has probably the widest application range in immune-mediated neuropathies and efficacy has been well documented in several randomized controlled trials for Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP). Beneficial effects of IVIg have also been proven for multifocal motor neuropathy (MMN). Likewise, PE is an established treatment for GBS and CIDP, whereas it is considered to be ineffective in MMN. Different mechanisms of action are sought to be responsible for the immunemodulatory effect of PE and IVIg in autoimmune disorders. Some of those might be important for immune-mediated neuropathies, while others are probably negligible. The aim of this review is to summarize the recent advances in elucidating disease-specific mechanisms of actions of PE and IVIg in the treatment of immune-mediated neuropathies.

Enhancement of fermentation process in Pu-erh tea by tea-leaf extract

Pu-erh tea is known as a fermented tea and longer storage enhances its flavor and taste. Recently, Aspergillus, Blastobotrys, and Streptomyces are found to play important roles in nutritional enhancement of Pu-erh tea by fermentation. Since water and temperature affect the microbial growth, we therefore explored the factors that might enhance the Pu-erh tea fermentation. The results showed that the addition of fresh tea-leaf extract (TLE) enhanced the withered tea fermentation (at 37 degrees C, 80 to 85% RH) as compared with the water only. Contents of statin, GABA, gallic acid, DPPH scavenging and polyphenol oxidase (PPO) activities were increased, whereas polyphenols and caffeine were decreased over 6 mo. TLE dose-dependently enhanced some of the qualities (that is, statin, PPO) of Pu-erh tea significantly as compared with the water only. The effect was related to the increase population of A. niger and A. carbonarius at 6 mo (from 7.6 +/- 1.2 x 10(1) and 3.2 +/- 1.3 x 10(1) to 3.1 +/- 1.2 x 10(6) and 2.4 +/- 1.1 x 10(5) colony forming units [CFU]/g, respectively). After drying process (90 degrees C, 30 min), the total microbial count from these samples returned to background level (3 +/- 0.5 x 10(2) CFU/g). None of ochratoxin and fumonisin, toxins from Aspergillus, was detected in the final products. The flavor and taste were also enhanced by treatment with TLE. The inoculation with S. cinereus Y11 with 2% TLE further enhanced these functional contents (about 2-fold increase of statin level) in the experimental Pu-erh tea. Therefore, this result may add a new process for Pu-erh tea manufacture.

Dorsal Root Ganglia Sensory Neuronal Cultures: a tool for drug discovery for peripheral neuropathies

BACKGROUND: Peripheral neuropathies affect many people worldwide and are caused by or associated with a wide range of conditions, both genetic and acquired. Current therapies are directed at symptomatic control because no effective regenerative treatment exists. Primary challenge is that mechanisms that lead to distal axonal degeneration, a common feature of all peripheral neuropathies, are largely unknown. OBJECTIVE/METHODS: To address the role and specific characteristics of dorsal root ganglia (DRG) derived sensory neuron culture system as a useful model in evaluating the pathogenic mechanisms of peripheral neuropathies and examination and validation of potential therapeutic compounds. A thorough review of the recent literature was completed and select examples of the use of DRG neurons in different peripheral neuropathy models were chosen to highlight the utility of these cultures. CONCLUSION: Many useful models of different peripheral neuropathies have been developed using DRG neuronal culture and potential therapeutic targets have been examined, but so far none of the potential therapeutic compounds have succeeded in clinical trials. In recent years, focus has changed to evaluation of axon degeneration as the primary outcome measure advocating a drug development strategy starting with phenotypic drug screening, followed by validation in primary complex co-cultures and animal models.

Lipopolysaccharide-induced inflammatory cytokine production by Schwann's cells dependent upon TLR4 expression

Signaling of Toll-like receptor-4 (TLR4) through its cognate ligand endotoxin appears critical in tissue inflammation associated with bacterial infection. We found that anti-GM1 antibody (Ab) enhances TLR4 expression in Schwann's cells (SCs) in vivo and in vitro. The anti-GM1 Ab-treated SC also showed increased release of pro-inflammation cytokines IL-1beta and TNF-alpha after incubation with lipopolysaccharide (LPS). Furthermore, down-regulation of TLR4 expression using antisense oligonucleotides targeted to TLR4 mRNA suppressed cytokine production in LPS stimulated cultures. These findings suggest that elevation of TLR4 expression increases sensitivity of SC to LPS and production of inflammatory mediators that may be responsible for peripheral nerve dysfunction.

Matrix metalloproteinase-2 is involved in myelination of dorsal root ganglia neurons

Matrix metalloproteinases (MMPs) comprise a large family of endopeptidases that are capable of degrading all extracellular matrix components. There is increasing evidence that MMPs are not only involved in tissue destruction but may also exert beneficial effects during axonal regeneration and nerve remyelination. Here, we provide evidence that MMP-2 (gelatinase A) is associated with the physiological process of myelination in the peripheral nervous system (PNS). In a myelinating co-culture model of Schwann cells and dorsal root ganglia neurons, MMP-2 expression correlated with the degree of myelination as determined by immunocytochemistry, zymography, and immunosorbent assay. Modulation of MMP-2 activity by chemical inhibitors led to incomplete and aberrant myelin formation. In vivo MMP-2 expression was detected in the cerebrospinal fluid (CSF) of patients with Guillain-Barré syndrome as well as in CSF and sural nerve biopsies of patients with chronic inflammatory demyelinating polyneuropathy. Our findings suggest an important, previously unrecognized role for MMP-2 during myelination in the PNS. Endogenous or exogenous modulation of MMP-2 activity may be a relevant target to enhance regeneration in demyelinating diseases of the PNS.

Effect of microbial fermentation on content of statin, GABA, and polyphenols in Pu-Erh tea

Besides cancer prevention, the hypolipidemic effects of tea have been well studied in animals and humans. Recently, statin has been identified in Pu-erh tea extract. Clinical trials have confirmed that statin decreases the incidence of major coronary and cerebrovascular events and this may be due to its hypolipidemic and antiinflammatory effects. Since a good Pu-erh tea needs longer storage (10 years or more) of fermentation to enhance the flavor and fragrance, we screened microorganisms from two Pu-erh teas, 20 and 25 years old. Species of fungi and bacteria strains that contributed to a good taste of Pu-erh tea were isolated. The effect of fermentation was investigated by inoculating fresh tea leaves with individual strains of isolated microorganisms. Results showed that statin, total polyphenol content, and the scavenging activities of alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radicals increased during fermentation. Tea leaves inoculated with Streptomyces bacillaris strain R9 had the highest polyphenol content (3.3 mg/100 g) and scavenging ability to DPPH radicals (92%). Streptomyces cinereus strain Y11 was equally good for polyphenol content but yielded the highest amount of statin (1012 ng/g) after 42 days of fermentation. Interestingly, the statin content of fresh tea leaves fermented with strain R9 or Y11 after 180 days was much higher (4- and 8-fold, respectively) than that of the 25-year-old Pu-erh tea (513 ng/g) as measured by the HPLC method. Similarly, these two strains also increased the content of gamma-aminobutyric acid (GABA) 5.7- and 4.7-fold in tea fermented for 180 days as compared with the fresh leaves (1270 microg/g) and that were higher than that of the Pu-erh tea (4900 microg/g). Taken together, the present results indicate that tea short-term fermented with S. bacillaris or S. cinereus enhances the color and content of statin, GABA, and polyphenols.