Sciatic nerve transection increases gluthatione antioxidant system activity and neuronal nitric oxide synthase expression in the spinal cord

Evaluated periodontal tissues and oxidative stress in rats with neuropathic pain-like behavior

BACKGROUND

Oxidative stress has a critical effect on both persistent pain states and periodontal disease. Voltage-gated sodium NaV1.7 (SCN9A), and transient receptor potential ankyrin 1 (TRPA1) are pain genes. The goal of this study was to investigate oxidative stress markers, periodontal status, SCN9A, and TRPA1 channel expression in periodontal tissues of rats with paclitaxel-induced neuropathic pain-like behavior (NPLB).

METHODS AND RESULTS

Totally 16 male Sprague Dawley rats were used: control (n = 8) and paclitaxel-induced pain (PTX) (n = 8). The alveolar bone loss and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels were analyzed histometrically and immunohistochemically. Gingival superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities (spectrophotometric assay) were measured. The relative TRPA1 and SCN9A genes expression levels were evaluated using quantitative real-time PCR (qPCR) in the tissues of gingiva and brain. The PTX group had significantly higher alveolar bone loss and 8-OHdG compared to the control. The PTX group had significantly lower gingival SOD, GPx and CAT activity than the control groups. The PTX group had significantly higher relative gene expression of SCN9A (p = 0.0002) and TRPA1 (p = 0.0002) than the control in gingival tissues. Increased nociceptive susceptibility may affect the increase in oxidative stress and periodontal destruction.

CONCLUSIONS

Chronic pain conditions may increase TRPA1 and SCN9A gene expression in the periodontium. The data of the current study may help develop novel approaches both to maintain periodontal health and alleviate pain in patients suffering from orofacial pain.

SUMOylation Modulates Reactive Oxygen Species (ROS) Levels and Acts as a Protective Mechanism in the Type 2 Model of Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is the prevalent type of peripheral neuropathy; it primarily impacts extremity nerves. Its multifaceted nature makes the molecular mechanisms of diabetic neuropathy intricate and incompletely elucidated. Several types of post-translational modifications (PTMs) have been implicated in the development and progression of DPN, including phosphorylation, glycation, acetylation and SUMOylation. SUMOylation involves the covalent attachment of small ubiquitin-like modifier (SUMO) proteins to target proteins, and it plays a role in various cellular processes, including protein localization, stability, and function. While the specific relationship between high blood glucose and SUMOylation is not extensively studied, recent evidence implies its involvement in the development of DPN in type 1 diabetes. In this study, we investigated the impact of SUMOylation on the onset and progression of DPN in a type 2 diabetes model using genetically modified mutant mice lacking SUMOylation, specifically in peripheral sensory neurons (SNS-Ubc9-/-). Behavioural measurement for evoked pain, morphological analyses of nerve fibre loss in the epidermis, measurement of reactive oxygen species (ROS) levels, and antioxidant molecules were analysed over several months in SUMOylation-deficient and control mice. Our longitudinal analysis at 30 weeks post-high-fat diet revealed that SNS-Ubc9-/- mice exhibited earlier and more pronounced thermal and mechanical sensation loss and accelerated intraepidermal nerve fibre loss compared to control mice. Mechanistically, these changes are associated with increased levels of ROS both in sensory neuronal soma and in peripheral axonal nerve endings in SNS-Ubc9-/- mice. In addition, we observed compromised detoxifying potential, impaired respiratory chain complexes, and reduced levels of protective lipids in sensory neurons upon deletion of SUMOylation in diabetic mice. Importantly, we also identified mitochondrial malate dehydrogenase (MDH2) as a SUMOylation target, the activity of which is negatively regulated by SUMOylation. Our results indicate that SUMOylation is an essential neuroprotective mechanism in sensory neurons in type 2 diabetes, the deletion of which causes oxidative stress and an impaired respiratory chain, resulting in energy depletion and subsequent damage to sensory neurons.

Neuroprotective Effect of Natural Compounds in Paclitaxel-Induced Chronic Inflammatory Pain

The current study explored the effects of natural compounds, berbamine, bergapten, and carveol on paclitaxel-associated neuroinflammatory pain. Berbamine, an alkaloid obtained from BerberisamurensisRuprhas been previously researched for anticancer and anti-inflammatory potential. Bergapten is 5-methoxsalenpsoralen previously investigated in cancer, vitiligo, and psoriasis. Carveol obtained from caraway is a component of essential oil. The neuropathic pain model was induced by administering 2 mg/kg of paclitaxel (PTX) every other day for a week. After the final PTX injection, a behavioral analysis was conducted, and subsequently, tissue was collected for molecular analysis. Berbamine, bergapten, and carveol treatment attenuated thermal hypersensitivity, improved latency of falling, normalized the changes in body weight, and increased the threshold for pain sensation. The drugs increased the protective glutathione (GSH) and glutathione S-transferase (GST) levels in the sciatic nerve and spinal cord while lowering inducible nitric oxide synthase (iNOS) and lipid peroxidase (LPO). Hematoxylin and eosin (H and E) and immunohistochemistry (IHC) examinations confirmed that the medication reversed the abnormal alterations. The aforementioned natural substances inhibited cyclooxygenase-2 (COX-2), tumor necrosis factor-alpha (TNF-α), and nuclear factor kappa B (NF-κb) overexpression, as evidenced by enzyme-linked immunosorbant assay (ELISA) and Western blot and hence provide neuroprotection in chronic constriction damage.

Dietary proanthocyanidins alleviated ovarian fibrosis in letrozole-induced polycystic ovary syndrome in rats

This study investigated the effects of proanthocyanidins (PCs) on ovarian fibrosis in letrozole-induced polycystic ovary syndrome (PCOS) in rats. The administration of PCs effectively reduced the body weight (BW) and relative ovarian weight in PCOS rats. ELISA results revealed that PCs significantly reduced the level of serum T, LH, LH/FSH in the PCOS group. In addition, qRT-PCR results revealed that treatment with PCs significantly increased the main antioxidant enzymes (Cat, Sod2, Gpx3, Mgst1, Gsta4, Sod1 and Prdx3) in PCOS rats. Also, the expression analysis of proteins by Western blotting revealed that PCs significantly decreased the level of TGF-βR1, p-Smad3, p-Smad2 and Smad4 and reversed the downregulation of Smad7 in PCOS rats. The study suggested that PCs improved ovarian fibrosis in PCOS rats by regulating the serum hormone level, inhibiting oxidative stress and suppressing the activation of the TGF-β1/Smads signaling pathway. PRACTICAL APPLICATIONS: Currently, plant extracts are being widely used to treat female reproductive and metabolic disorders. Particularly, proanthocyanidins (PCs), the well-known natural polyphenolic compounds, which are a significant source of antioxidants present in many colored fruits, are consumed as fruits as well as a dietary supplement to prevent many disorders. Recent pharmacological studies have reported that PCs have many health beneficial properties, such as antioxidant activity, improving cholesterol homeostasis, blood lipid regulatory properties, microcirculation improvement effect, antitumor activity and anti-aging activity. Despite these properties of PCs, the antifibrosis effect of PCs has not been studied to date. The main purpose of this study was to research the role and the mechanisms of PCs in ovarian fibrosis in PCOS rats.

1,3,4-Oxadiazole Derivative Attenuates Chronic Constriction Injury Induced Neuropathic Pain: A Computational, Behavioral, and Molecular Approach

The production and up-regulation of inflammatory mediators are contributing factors for the development and maintenance of neuropathic pain. In the present study, the post-treatment of synthetic 1,3,4 oxadiazole derivative (B3) for its neuroprotective potential in chronic constriction injury-induced neuropathic pain was applied. In-silico studies were carried out through Auto Dock, PyRx, and DSV to obtain the possible binding and interactions of the ligands (B3) with COX-2, IL-6, and iNOS. The sciatic nerve of the anesthetized rat was constricted with sutures 3/0. Treatment with 1,3,4-oxadiazole derivative was started a day after surgery and continued until the 14th day. All behavioral studies were executed on day 0, 3rd, 7th, 10th, and 14th. The sciatic nerve and spinal cord were collected for further molecular analysis. The interactions in the form of hydrogen bonding stabilizes the ligand target complex. B3 showed three hydrogen bonds with IL-6. B3, in addition to correcting paw posture/deformation induced by CCI, attenuates hyperalgesia (p < 0.001) and allodynia (p < 0.001). B3 significantly raised the level of GST and GSH in both the sciatic nerve and spinal cord and reduced the LPO and iNOS (p < 0.001). B3 attenuates the pathological changes induced by nerve injury, which was confirmed by H&E staining and IHC examination. B3 down-regulates the over-expression of the inflammatory mediator IL-6 and hence provides neuroprotective effects in CCI-induced pain. The results demonstrate that B3 possess anti-nociceptive and anti-hyperalgesic effects and thus minimizes pain perception and inflammation. The possible underlying mechanism for the neuroprotective effect of B3 probably may be mediated through IL-6.

Increased CSF Levels of Apolipoproteins and Complement Factors in Trigeminal Neuralgia Patients-In Depth Proteomic Analysis Using Mass Spectrometry

The main cause of trigeminal neuralgia (TN) is compression of a blood vessel at the root entry zone of the trigeminal nerve. However, a neurovascular conflict does not seem to be the only etiology and other mechanisms are implicated in the development of the disease. We hypothesized that TN patients may have distinct protein expression in the CSF. In this study, lumbar CSF from TN patients (n = 17), scheduled to undergo microvascular decompression, and from controls (n = 20) was analyzed and compared with in depth mass spectrometry TMTbased quantitative proteomics. We identified 2552 unique proteins, of which 46 were significantly altered (26 increased, and 20 decreased, q-value < .05) in TN patients compared with controls. An over-representation analysis showed proteins involved in high-density lipoprotein, such as Apolipoprotein A4, Apolipoprotein M, and Apolipoprotein A1, and the extracellular region, including proteins involved in the complement cascade to be over-represented. We conclude that TN patients have distinct protein expression in the CSF compared to controls. The pathophysiological background of the protein alterations found in this study warrants further investigation in future studies. PERSPECTIVE: In this article, cerebrospinal fluid from patients with trigeminal neuralgia was analyzed using in depth shotgun proteomics, revealing 46 differentially expressed proteins compared to controls. Among these, apolipoproteins and proteins involved in the complement system were elevated and significantly over-represented, implying an inflammatory component in the pathophysiology of the disease.

Effect of Gold Nanoparticle on 5-Fluorouracil-Induced Experimental Oral Mucositis in Hamsters

BACKGROUND

Oral mucositis (OM) is a severe inflammation of the oral mucosal cells associated with chemotherapy and/or radiotherapy-induced toxicity, resulting in epithelial ulcers and higher risk of death from sepsis. The aim of the present study was to evaluate the nanoparticle (AuNp) effect on OM induced in hamsters.

MATERIALS AND METHODS

5-fluorouracil (5FU) was used on the first and second day of the experimental model in Golden sirian hamsters, and on the fourth day, mechanical trauma was applied to induce OM. The animals were divided into groups, i.e., polyvinylpyrrolidone (PVP), mechanical trauma (MT), 5FU, and groups treated with gold nanoparticles (AuNps) (62.5, 125, and 250 μg/kg). On the 10th day, animals were euthanized for macroscopic, histopathological, immunohistochemical, western blot, quantitative polymerase chain reaction (qRT-PCR), and AuNp quantification.

RESULTS

AuNp (250 μg/kg) reduced TNF-α, IL-1β, COX-2, NF-κB, TGF-β, and SMAD 2/3; increased glutathione levels; decreased the expression of Kelch ECH-associated protein 1 (KEAP1); and induced heme oxygenase 1 (HMOX-1) and NAD (P) H quinone oxidoreductase 1 (NQO1) genes.

CONCLUSIONS

AuNp (250 μg/kg) prevented 5-FU-induced OM in hamsters and improved the parameters of inflammation and oxidative stress.

Low-Level Laser Effect on Peripheral Sciatic Regeneration Under the Systemic Inflammatory Condition of Periodontal Disease

Introduction: Periodontal disease (PD) is an inflammatory condition, which leads to tooth loss and promotes a systemic inflammatory state that can aggravate the nerve degeneration. As laser therapy may stimulate regeneration, this study aimed to evaluate the effect of the low-level laser (LLL) on peripheral nerve regeneration under the systemic inflammatory condition of PD. Methods: Thirry-two male rats were used, distributed in 4 groups: nerve injury (NIG); periodontal disease with nerve injury (PDNI); nerve injury and treatment (TNIG); periodontal disease with nerve injury and treatment (PDNIT). On the 7th day of the experiment, the animals had ligatures placed around the lower first molars. On the 22nd day, they underwent peripheral nerve damage, and on the 25th day, the LLL treatment was initiated, performed for two weeks. The sciatic functional index (SFI) was evaluated with subsequent euthanasia of all the animals on the 37th day of the experiment. The sciatic nerve was collected for morphological and oxidative stress analysis and the hemi jaws for radiographic analysis. Results: Regarding the SFI, there was no difference among the groups in the first evaluation (EV) pre-injury; as for theEV2, after injury, all the groups presented a decrease in these values, which remained in post-treatment. For the morphology of the PDNI, nerve tissue presented larger diameter fibers, whereas, for NIT and PDNIT, fibers had smaller diameters with endoneurial organization. When it comes to the antioxidant system, there was an increase in protein concentration, higher superoxide activity, and decreased glutathione transferase activity in the treated groups. Catalase and cholinesterase did not differ between the groups, and lipoperoxidation (LPO) increased in the PD groups. For the mandible radiographic analysis, it was possible to verify the induction of PD. Conclusion: As for the used parameters, the low-level laser was not effective in increasing the nociceptive threshold, but it contributed to the regeneration of nerve fibers, although the inflammation was still present in the site. However, the treatment was effective in protecting cells against oxidative damage due to increased SOD and increased protein, although the decrease in GST demonstrates the inhibition of this stage of the antioxidant system.

Spinal Reactive Oxygen Species and Oxidative Damage Mediate Chronic Pain in Lame Dairy Cows

Simple Summary

Chronic inflammatory diseases could impact central nervous system homeostasis, being oxidative damage of the dorsal horn, a relevant mechanism mediating central sensitization. Chronic inflammatory lameness in dairy cows is a painful condition that affects animal welfare, affecting dairy production worldwide. This study reveals increased levels of reactive oxygen species, malondialdehyde, and carbonyl groups, indicating lipid and protein damage in the spinal cord of cows with chronic lameness. Moreover, antioxidant system activity was similar between lame and non-lame cows which suggests that antioxidant dysregulation was not the cause of oxidative damage, as has been proposed previously. Based on the fact that nociceptive pathways are strongly conserved between species, there is no reason to neglect that chronic pain in cows promotes Central Nervous System (CNS) alterations, such as oxidative damage. Moreover, lame cows develop central sensitization, as allodynia and hyperalgesia are centrally and not peripherally mediated. Our results support the current assumption that chronic pain is a central nervous system disease and lameness in dairy cows is far beyond an inflammation of the hoof.

Abstract

Lameness in dairy cows is a worldwide prevalent disease with a negative impact on animal welfare and herd economy. Oxidative damage and antioxidant system dysfunction are common features of many CNS diseases, including chronic pain. The aim of this study was to evaluate the levels of reactive oxygen species (ROS) and oxidative damage markers in the spinal cord of dairy cows with chronic inflammatory lameness. Locomotion score was performed in order to select cows with chronic lameness. Dorsal horn spinal cord samples were obtained post mortem from lumbar segments (L2–L5), and ROS, malondialdehyde (MDA), and carbonyl groups were measured along with the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and total antioxidant response (TAR). Lame cows had increased levels of ROS, MDA, and carbonyl groups, while no differences were observed between lame and non-lame cows in SOD, GPx, CAT, and TAR activity. We conclude that painful chronic inflammatory lameness in dairy cows is associated with an increase in ROS, MDA, and carbonyl groups. Nonetheless, an association between ROS generation and dysfunction of the antioxidant system, as previously proposed, could not be established.

The Role of Endothelial Dysfunction in Peripheral Blood Nerve Barrier: Molecular Mechanisms and Pathophysiological Implications

The exchange of solutes between the blood and the nerve tissue is mediated by specific and high selective barriers in order to ensure the integrity of the different compartments of the nervous system. At peripheral level, this function is maintained by the Blood Nerve Barrier (BNB) that, in the presence, of specific stressor stimuli can be damaged causing the onset of neurodegenerative processes. An essential component of BNB is represented by the endothelial cells surrounding the sub-structures of peripheral nerves and increasing evidence suggests that endothelial dysfunction can be considered a leading cause of the nerve degeneration. The purpose of this review is to highlight the main mechanisms involved in the impairment of endothelial cells in specific diseases associated with peripheral nerve damage, such as diabetic neuropathy, erectile dysfunction and inflammation of the sciatic nerve.

Nitroxidative Signaling Mechanisms in Pathological Pain

Tissue injury can initiate bidirectional signaling between neurons, glia, and immune cells that creates and amplifies pain. While the ability for neurotransmitters, neuropeptides, and cytokines to initiate and maintain pain has been extensively studied, recent work has identified a key role for reactive oxygen and nitrogen species (ROS/RNS; nitroxidative species), including superoxide, peroxynitrite, and hydrogen peroxide. In this review we describe how nitroxidative species are generated after tissue injury and the mechanisms by which they enhance neuroexcitability in pain pathways. Finally, we discuss potential therapeutic strategies for normalizing nitroxidative signaling, which may also enhance opioid analgesia, to help to alleviate the enormous burden of pathological pain.

Quercetin Inhibits Peripheral and Spinal Cord Nociceptive Mechanisms to Reduce Intense Acute Swimming-Induced Muscle Pain in Mice

The present study aimed to evaluate the effects of the flavonoid quercetin (3,3´,4´,5,7-pentahydroxyflavone) in a mice model of intense acute swimming-induced muscle pain, which resembles delayed onset muscle soreness. Quercetin intraperitoneal (i.p.) treatment dose-dependently reduced muscle mechanical hyperalgesia. Quercetin inhibited myeloperoxidase (MPO) and N-acetyl-β-D- glucosaminidase (NAG) activities, cytokine production, oxidative stress, cyclooxygenase-2 (COX-2) and gp91^phox mRNA expression and muscle injury (creatinine kinase [CK] blood levels and myoblast determination protein [MyoD] mRNA expression) as well as inhibited NFκB activation and induced Nrf2 and HO-1 mRNA expression in the soleus muscle. Beyond inhibiting those peripheral effects, quercetin also inhibited spinal cord cytokine production, oxidative stress and glial cells activation (glial fibrillary acidic protein [GFAP] and ionized calcium-binding adapter molecule 1 [Iba-1] mRNA expression). Concluding, the present data demonstrate that quercetin is a potential molecule for the treatment of muscle pain conditions related to unaccustomed exercise.

Targeting interleukin-1β reduces intense acute swimming-induced muscle mechanical hyperalgesia in mice

Objectives

The role of interleukin (IL)-1β in intense acute swimming-induced muscle mechanical hyperalgesia was investigated in mice.

Methods

Untrained mice were submitted to one session of intense acute swimming for 120 min or were submitted to sham conditions (30 s exposure to water), and muscle mechanical hyperalgesia (before and 6–48 h after swimming session), IL-1β production (skeletal muscle and spinal cord), myeloperoxidase activity, reduced glutathione (GSH) levels (skeletal muscle and spinal cord), and cortisol, glucose, lactate and creatine kinase (CK) levels (plasma) were analysed.

Key findings

Intense acute swimming-induced muscle mechanical hyperalgesia was dose-dependently inhibited by IL-1ra treatment. IL-1β levels were increased in soleus, but not gastrocnemius muscle and spinal cord 2 and 4 h after the session, respectively. Intense acute swimming-induced increase of myeloperoxidase activity and reduced GSH levels in soleus muscle were reversed by IL-1ra treatment. In the spinal cord, exercise induced an increase of GSH levels, which was reduced by IL-1ra. Finally, IL-1ra treatment reduced plasma levels of CK, an indicator of myocyte damage.

Conclusions

IL-1β mediates intense acute swimming-induced muscle mechanical hyperalgesia by peripheral (soleus muscle) and spinal cord integrative mechanisms and could be considered a potential target to treat exercise-induced muscle pain.

Sciatic nerve transection modulates oxidative parameters in spinal and supraspinal regions

Neuropathic pain is a very common dysfunction caused by several types of nerve injury. This condition leads to a variety of pathological changes in central nervous system regions related to pain transmission. It has been demonstrated that nociception is modulated by reactive oxidative species and treatments with antioxidant compounds produce antinociceptive effects. Thus, the aim of the present study was to investigate oxidative parameters in spinal and supraspinal regions following sciatic nerve transection (SNT). In behavioral assessments, animals showed mechanical allodynia and a significant functional impairment following SNT, measured by von Frey hairs test and sciatic functional index, respectively. Superoxide dismutase activity was increased 3 and 7 days following SNT in cerebral cortex and brainstem. Catalase activity was also increased in cerebral cortex 3 days after SNT. Ascorbic acid levels were decreased 7 days in the spinal cord only in SNT group. We also showed an increase in lipid peroxidation in cerebral cortex and brainstem 3 days after surgery in SNT and sham groups. These results showed that supraspinal regions also exhibit changes in antioxidant activity after SNT and demonstrate an intricate relationship among antioxidant defenses in different regions of the neuro axis related to pain transmission.

Deletion of Nrf2 impairs functional recovery, reduces clearance of myelin debris and decreases axonal remyelination after peripheral nerve injury

Oxidative stress is generated in several peripheral nerve injury models. In response to oxidative stress, the transcription factor Nrf2 is activated to induce expression of antioxidant responsive element (ARE) genes. The role of Nrf2 in peripheral nerve injury has not been studied to date. In this study, we used a sciatic nerve crush model to examine how deletion of Nrf2 affects peripheral nerve degeneration and regeneration. Our study demonstrated that functional recovery in the Nrf2(-/-) mice were impaired compared to the wild type mice after sciatic nerve crush. Larger myelin debris were present in the distal nerve stump of the Nrf2(-/-) mice than in the wild type mice. The presence of larger myelin debris in the Nrf2(-/-) mice coincides with less macrophages accumulation in the distal nerve stump. Less accumulation of macrophages may have contributed to slower clearance of myelin and thus resulted in the presence of larger myelin debris. Meanwhile, axonal regeneration is comparatively lower in the Nrf2(-/-) mice than in the wild type mice. Even after 3months post the injury, more thinly myelinated axon fibers were present in the Nrf2(-/-) mice than in the wild type mice. Taken collectively, these data support the concept of therapeutic intervention with Nrf2 activators following nerve injury.

Assessment of oxidative parameters in rat spinal cord after chronic constriction of the sciatic nerve

Although reactive oxygen species (ROS) are involved in neuropathic pain, the direct relationship between these species and chronic constriction of sciatic nerve (CCI) has not been studied in spinal cord. Thus, this study induced CCI in rats and these animals were sacrificed 3 and 10 days after the surgical procedure to determine the superoxide dismutase (SOD) and catalase activities, as well as ascorbic acid, hydrogen peroxide (H(2)O(2)) and lipid hydroperoxide levels in lumbosacral spinal cord. Von Frey Hair and hot plate tests were performed to assess the degree of mechanical and thermal hyperalgesia at days 0, 3 and 10. The results showed that CCI significantly induced mechanical and thermal hyperalgesia at days 3 and 10. Parallel there was increase in spinal cord lipid hydroperoxide at days 3 and 10 in rats submitted to CCI. In Sham rats a significant increase in this parameter occurred at day 10. H(2)O(2) decreased at day 10 only in CCI group. SOD activity was decreased in Sham and CCI groups at day 3, while catalase activity was increased in CCI rats at days 3 and 10. Ascorbic acid levels were reduced only in CCI rats at day 3. Although the role of such changes is unclear, many were not specific to neuropathic pain and the differences could be related to different degrees of central sensitization in Sham and CCI rats.

FK506 neuroprotection after cavernous nerve injury is mediated by thioredoxin and glutathione redox systems

INTRODUCTION

Immunophilin ligands such as FK506 (FK) preserve erectile function (EF) following cavernous nerve injury (CNI), although the precise mechanisms are unclear. We examined whether the thioredoxin (Trx) and glutathione (GSH) redox systems mediate this effect after CNI.

AIM

To investigate the roles of Trx reductase 2 (TrxR2) and S-Nitrosoglutathione reductase (GSNOR) as antioxidative/nitrosative and antiapoptotic mediators of the neuroprotective effect of FK in the penis after CNI.

METHODS

Adult male rats, wild-type (WT) mice, and GSNOR deficient (GSNOR -/-) mice were divided into four groups: sham surgery (CN [cavernous nerves] exposure only) + vehicle; sham surgery + FK (5 mg/kg/day/rat or 2 mg/kg/day/mouse, for 2 days, subcutaneous); CNI + vehicle; and CNI + FK. At day 4 after injury, electrically stimulated changes in intracavernosal pressure (ICP) were measured. Penises were collected for Western blot analysis of TrxR2, GSNOR, and Bcl-2, and for immunolocalization of TrxR2 and GSNOR.

MAIN OUTCOME MEASURES

EF assessment represented by maximal ICP and total ICP in response to electrical stimulation. Evaluation of protein expression levels and distribution patterns of antioxidative/nitrosative and antiapoptotic factors in penile tissue.

RESULTS

EF decreased after CNI compared with sham surgery values in both rats (P < 0.01) and WT and GSNOR -/- mice (P < 0.05). FK treatment preserved EF after CNI compared with vehicle treatment in rats (P < 0.01) and WT mice (P < 0.05) but not in GSNOR -/- mice. In rats, GSNOR (P < 0.01) and Bcl-2 (P < 0.05) expressions were significantly decreased after CNI. FK treatment in CN-injured rats restored expression of GSNOR and upregulated TrxR2 (P < 0.001) and Bcl-2 (P < 0.001) expressions compared with vehicle treatment. Localizations of proteins in the penis were observed for TrxR2 (endothelium, smooth muscle) and for GSNOR (nerves, endothelium, smooth muscle).

CONCLUSIONS

The neuroprotective effect of FK in preserving EF after CNI involves antioxidative/nitrosative and antiapoptotic mechanisms mediated, to some extent, by Trx and GSH systems.

Effect of emodin on neuropathic pain transmission mediated by P2X2/3 receptor of primary sensory neurons

Neuropathic pain is the most difficult type of pain to cure. The P2X(2/3) receptors play a crucial role in facilitating the transmission of pain at neuropathic pain states. Emodin is a natural anthraquinone in rhubarb. The present research investigated the effects of emodin on the pain transmission in neuropathic pain states that was mediated by P2X(2/3) receptor in primary sensory neurons. Chronic constriction injury (CCI) model was used as neuropathic pain model. Emodin was dissolved in 0.5% sodium carboxymethyl cellulose (CMC) as vehicle. Sprague-Dawley male rats had been randomly divided into Sham+vehicle group, CCI+emodin group, and CCI+vehicle group. Mechanical withdrawal threshold and thermal withdrawal latency were measured. P2X(2/3) expression in L4/L5 dorsal root ganglion (DRG) was detected by immunohistochemistry, in situ hybridization (ISH) and RT-PCR. The mechanical withdrawal threshold and thermal withdrawal latency in CCI+vehicle group were lower than those in Sham+vehicle group and CCI+emodin group (p<0.05), while P2X(2) and P2X(3) receptor expression of L4/L5 DRG in CCI+vehicle group was higher than those in the other two groups (p<0.05). The co-local staining of P2X(2) and P2X(3) in the DRG of CCI group appeared to be more intense than that in the DRG of the other two groups with double-label fluorescence immunohistochemistry. The results showed that the application of emodin alleviated the hyperalgesia of CCI rats and significantly decreased the P2X(2/3) expression of L4/L5 DRG in CCI+emodin group compared with that in CCI+vehicle group (p<0.05). The data of ISH and RT-PCR in P2X(2) and P2X(3) mRNA expression suggest that the pharmacologic mechanism of emodin is involved in the nucleic acid level. The results showed that emodin can inhibit the transmission of neuropathic pain mediated by P2X(2/3) receptor of primary sensory neurons to alleviate chronic neuropathic pain.