P2X7 receptor antagonist BBG inhibits endoplasmic reticulum stress and pyroptosis to alleviate postherpetic neuralgia

Postherpetic neuralgia (PHN) is the most common complication of acute herpes zoster. The treatment of PHN remains a challenge for clinical pain management. The present study investigated the P2X7 receptor antagonist brilliant blue G (BBG) whether inhibits endoplasmic reticulum stress and pyroptosis (a necrotic form of cell death) and alleviates PHN. Varicella zoster virus (VZV)-infected CV-1 cells were used to induce PHN model. Mechanical paw withdrawal thresholds were measured using an ascending series of von Frey filaments. Immunohistochemistry was used to detect the expression of P2X7R in nerve tissues. Western blot was used to determine the expression of endoplasmic reticulum (ER) stress and pyroptosis-related molecules. The expression of IL-1β and IL-18 in tissue homogenate was detected by ELISA. The PHN rat has the lower paw withdrawal threshold, but higher expression of P2X7 in nerve tissues. And, endoplasmic reticulum stress was activated and pyroptosis was increased in PHN rats. BBG can decrease pain thresholds and reduce ER stress and pyroptosis in PHN rats. In addition, ER stress activator tunicamycin (TM) can reverse the effect of BBG on the paw withdrawal thresholds, endoplasmic reticulum stress, and pyroptosis. Therefore, P2X7 receptor antagonist BBG alleviates PHN by activating ER stress and reducing pyroptosis.

Electroacupuncture Inhibits Autophagy of Neuron Cells in Postherpetic Neuralgia by Increasing the Expression of miR-223-3p

Postherpetic neuralgia (PHN) is a complication of herpes zoster viral infection. Its main manifestations are continuous or intermittent burning-like and electroshock-like pain in the affected nerves. Electroacupuncture (EA) is widely used in clinical treatment and exerts effects in alleviating neuropathic pain. In this study, we investigated the effect and underlying mechanism of EA on PHN. Sprague-Dawley rats were treated with resiniferatoxin (RTX) to establish a PHN model and subjected to EA and/or miR-223-3p overexpression (OV) or interference. Mechanical withdrawal latency was measured as an indication of pain sensitivity. Hematoxylin-eosin staining and transmission electron microscopy were performed to observe neuron cell morphology and autophagic vacuoles, respectively. ELISA was performed to detect reactive oxygen species (ROS) production and the levels of tumor necrosis factor- (TNF-) α, inducible nitric oxide synthase (iNOS), interleukin- (IL-) 6, and IL-10. Changes in autophagy and apoptosis-related miRNAs were detected by immunofluorescence and qRT-PCR, respectively. In RTX-treated rats, OV and EA reduced pain sensitivity, decreased the number of eosinophils, and increased that of nerve cells. ROS generation and the levels of TNF-α and iNOS were significantly reduced, while those of IL-6 and IL-10 were increased. OV and EA induced fewer autophagic vacuoles than those in the model group. The expression of autophagy-related protein microtubule-associated protein 1 light chain 3-II, ATG9, and Rab1 was decreased by OV and EA, whereas that of P62 was increased. qRT-PCR revealed that miR-223-3p expression in the model group decreased but was increased by EA. EA inhibits neuron cell autophagy in PHN by increasing miR-223-3p expression.

Varicella-zoster reactivation after allogeneic stem cell transplantation without routine prophylaxis--the incidence remains high

One-year prophylaxis with acyclovir has been shown to effectively prevent varicella-zoster virus (VZV) reactivation after allogeneic hematopoietic stem cell transplantation (HSCT) in a cohort that underwent transplantation in the beginning of the 2000s. Transplantation procedures have since changed considerably and reduced-intensity conditioning (RIC) is nowadays common. We investigated VZV reactivation without routine prophylaxis in a cohort of HSCT patients, 50% of whom had received RIC. The cumulative 2-year incidence of VZV reactivation was 20.7%. Risk factors in a multivariate analysis were treatment with mesenchymal stromal cells (relative hazard [RH], 1.65; confidence interval [CI], 1.07 to 2.54; P = .02), total body irradiation ≥6 Gy (RH, 1.55; CI, 1.14 to 2.13; P = .006), engraftment later than day 16 (RH, 1.46; CI, 1.07 to 2.00; P = .02), and age 0 to 19 years (RH, 1.68; CI, 1.21 to 2.35; P = .002). There was no difference in VZV reactivation between patients receiving myeloablative conditioning or RIC. VZV-related complications occurred in 29% of the patients with reactivation; most common were disseminated disease and postherpetic neuralgia. No single low-risk group for VZV reactivation could be identified. We conclude that VZV reactivation remains common after HSCT and carries a high complication rate, warranting prophylaxis.

Increased density of cutaneous nerve fibres in the affected dermatomes after herpes zoster therapy

Herpes zoster neural injury was assessed by determining cutaneous nerve density in skin biopsies from the affected dermatomes of 35 adult patients with herpes zoster in the acute phase and 3 months post-treatment, using protein gene product 9.5 immunohistochemistry. In contrast to the significant increase in subepidermal nerve fibre density (11.77 ± 4.88/mm vs. 13.29 ± 5.74/mm, p = 0.045) after 3 months, no differences were found in epidermal free nerve endings (2.43 ± 2.35/mm and 2.8 ± 2.86/mm, p = 0.168). Patients with post-herpetic neuralgia had significantly lower subepidermal nerve fibre densities (9.7 ± 2.05/mm vs. 14.72 ± 6.13/mm, p = 0.011) compared with non-post-herpetic neuralgia patients. No differences in cutaneous nerve density were found in relation to antiviral therapy. In conclusion, 3 months after acute infection, no sign of epidermal innervation recovery is observed, while the increased subepidermal nerve fibre density in the affected dermatomes probably reflects nerve regeneration that is not affected by antiviral agent type. Subepidermal nerve fibre density is decreased in patients with post-herpetic neuralgia 3-months post-acute herpes zoster infection.

Varicella-zoster viruses associated with post-herpetic neuralgia induce sodium current density increases in the ND7-23 Nav-1.8 neuroblastoma cell line

Post-herpetic neuralgia (PHN) is the most significant complication of herpes zoster caused by reactivation of latent Varicella-Zoster virus (VZV). We undertook a heterologous infection in vitro study to determine whether PHN-associated VZV isolates induce changes in sodium ion channel currents known to be associated with neuropathic pain. Twenty VZV isolates were studied blind from 11 PHN and 9 non-PHN subjects. Viruses were propagated in the MeWo cell line from which cell-free virus was harvested and applied to the ND7/23-Nav1.8 rat DRG x mouse neuroblastoma hybrid cell line which showed constitutive expression of the exogenous Nav 1.8, and endogenous expression of Nav 1.6 and Nav 1.7 genes all encoding sodium ion channels the dysregulation of which is associated with a range of neuropathic pain syndromes. After 72 hrs all three classes of VZV gene transcripts were detected in the absence of infectious virus. Single cell sodium ion channel recording was performed after 72 hr by voltage-clamping. PHN-associated VZV significantly increased sodium current amplitude in the cell line when compared with non-PHN VZV, wild-type (Dumas) or vaccine VZV strains ((POka, Merck and GSK). These sodium current increases were unaffected by acyclovir pre-treatment but were abolished by exposure to Tetrodotoxin (TTX) which blocks the TTX-sensitive fast Nav 1.6 and Nav 1.7 channels but not the TTX-resistant slow Nav 1.8 channel. PHN-associated VZV sodium current increases were therefore mediated in part by the Nav 1.6 and Nav 1.7 sodium ion channels. An additional observation was a modest increase in message levels of both Nav1.6 and Nav1.7 mRNA but not Nav 1.8 in PHN virally infected cells.

Review: The neurobiology of varicella zoster virus infection

Varicella zoster virus (VZV) is a neurotropic herpesvirus that infects nearly all humans. Primary infection usually causes chickenpox (varicella), after which virus becomes latent in cranial nerve ganglia, dorsal root ganglia and autonomic ganglia along the entire neuraxis. Although VZV cannot be isolated from human ganglia, nucleic acid hybridization and, later, polymerase chain reaction proved that VZV is latent in ganglia. Declining VZV-specific host immunity decades after primary infection allows virus to reactivate spontaneously, resulting in shingles (zoster) characterized by pain and rash restricted to one to three dermatomes. Multiple other serious neurological and ocular disorders also result from VZV reactivation. This review summarizes the current state of knowledge of the clinical and pathological complications of neurological and ocular disease produced by VZV reactivation, molecular aspects of VZV latency, VZV virology and VZV-specific immunity, the role of apoptosis in VZV-induced cell death and the development of an animal model provided by simian varicella virus infection of monkeys.

The impact of varicella zoster virus: chronic pain

Herpes zoster (HZ) is a common condition that affects all age groups and both immunocompetent and immunocompromised individuals. However, it mainly impacts elderly and immunocompromised people and is associated with important and sometimes permanent detriment to quality of life and activities of daily living. Age-related decline in cell-mediated immunity (CMI) permits reactivation of varicella zoster virus (VZV) from latency. The risk of developing post-herpetic neuralgia (PHN) can be predicted using epidemiologically identified risk factors, thus indicating which patients may benefit most from protection by appropriate means, including vaccination. Despite increasing knowledge of the pathology causing PHN, the management modalities for acute HZ pain and PHN remain inadequate. Public, and probably physician, understanding of HZ and its complications is poor, potentially leading to low utilisation of HZ vaccination and delayed presentation for treatment.

Limited BDNF contributes to the failure of injury to skin afferents to produce a neuropathic pain condition

Although a large body of evidence has shown that peripheral nerve injury usually induces neuropathic pain, there are also clinical studies demonstrating that injury of the sural nerve, which almost only innervates skin, fails to do so. The underlying mechanism, however, is largely unknown. In the present work, we found that the transection of either the gastrocnemius-soleus (GS) nerve innervating skeletal muscle or tibial nerve supplying both muscle and skin, but not of the sural nerve produced a lasting mechanical allodynia and thermal hyperalgesia in adult rats. High-frequency stimulation (HFS) or injury of either the tibial nerve or the GS nerve induced late-phase long-term potentiation (L-LTP) of C-fiber-evoked field potentials in spinal dorsal horn, while HFS or injury of the sural nerve only induced early-phase LTP (E-LTP). Furthermore, HFS of the tibial nerve induced L-LTP of C-fiber responses evoked by the stimulation of the sural nerve and the heterotopic L-LTP was completely prevented by spinal application of TrkB-Fc (a BDNF scavenger). Spinal application of low dose BDNF (10pg/ml) enabled HFS of the sural nerve to produce homotopic L-LTP. Finally, we found that injury of the GS nerve but not that of the sural nerve up-regulated BDNF in DRG neurons, and that the up-regulation of BDNF occurred not only in injured neurons but also in many uninjured ones. Therefore, the sural nerve injury failing to produce neuropathic pain may be due to the nerve containing insufficient BDNF under both physiological and pathological conditions.

Tinnitus in postherpetic neuralgia

We describe a woman who developed postherpetic neuralgia (PHN) located on the skin areas of the left ophthalmic division of the fifth cranial nerve without ocular involvement. PHN was associated with tinnitus, which was located ipsilaterally to the painful side and increased in proportion to the intensity of pain. Tinnitus was responsive to treatment with duloxetine, 60 mg daily, and subsided when the PHN resolved. This is the first description of tinnitus in PHN.

Varicella zoster virus: natural history and current therapies of varicella and herpes zoster

The natural history of varicella zoster virus (VZV) infection and the molecular mechanisms of viral pathogenesis are incompletely understood. Although no animal model yet reproduces all aspects of VZV infection, recently developed models of VZV infection, and the creation of genetically altered VZV recombinants, are yielding new information about primary viraemia and latency. During viraemia, T-cells transport VZV to the skin, where cell-free viral replication facilitates person-to-person spread and transmission to the neurons where latency is established. The alternate viral pathways of lytic infection or latency appear to be cell-type determined and involve both host and viral components. Antiviral therapy for varicella is safe and efficacious, and as varicella in children is usually mild, treatment is generally recommended only for adolescents and adults with varicella. Treatment is recommended for all individuals with herpes zoster, especially those aged over 50 years. For some varicella and zoster cases, aciclovir, the original standard, is being replaced by valaciclovir and famciclovir as preferred therapies. For herpes zoster, bromovinyl deoxyuridine (brivudin) has been added to the list of treatment options for immunocompetent individuals, but is contraindicated in patients with cancer. Antiviral therapy will still have a role in the treatment of disease caused by VZV even after the widespread implementation of vaccination programmes for both chickenpox and herpes zoster.

Broad-band ultraviolet B phototherapy in zoster patients may reduce the incidence and severity of postherpetic neuralgia

BACKGROUND

Postherpetic neuralgia (PHN) is one of the common complications of herpes zoster infection, particularly in the elderly. Current therapeutic measures are only partially effective in the affected patients. As inflammatory mediators released by different cells play an important role in the pathogenesis of this neuropathic pain and with regard to the immunomodulatory effects of ultraviolet B (UVB) spectrum, we presumed that UVB phototherapy might be effective in the prevention of PHN.

METHOD

This study was performed in two phases. Phase I was a prospective open controlled trial. Twenty-five patients with severe pain in the first 7 days of zoster rash were divided into two groups: the prevention group (n=12) received oral acyclovir (800 mg five times a day for 10 days) plus broad-band UVB to the affected dermatomes, starting with 20 mJ/cm(2) and gradually increasing the dose by 10 mJ/cm(2) each session to a maximum dose of 100 mJ/cm(2). Treatment sessions were repeated three times a week until pain relief or to a maximum of 15 sessions. The control group (n=13), who had disease characteristics similar to the prevention group, received only oral acyclovir with the same dose. All patients reported their severity of pain on a verbal rating scale (VRS, score 0-4) before treatment and at 1 and 3 months' follow-up. In phase II of the study, five patients with established PHN (more than 3 months after rash onset) received UVB with the above-mentioned protocol.

RESULTS

A total of 17 patients older than 40 (10 females, seven males; mean age, 65.5 years; range: 47-82 years) who had intractable pain due to zoster infection received UVB in two phases of the study. In patients who received phototherapy in the first 7 days of rash, 58.33% and 83.33% were completely pain free at 1-and 3-month follow-up, respectively. The corresponding figure in the control group was significantly lower (38.46% at 1 month and 53.85% at 3 months). The severity of pain was also lower in the phototherapy group than the control group (mean VRS 2.50 vs. 3.28 at 3 months). None of the patients who were treated more than 3 months after rash onset (established PHN) experienced significant (more than 50%) pain relief.

CONCLUSION

UVB phototherapy in the acute stage of zoster rash might reduce the incidence and severity of PHN. Treatment after 3 months does not seem to have a significant beneficial effect.

Post-herpetic trigeminal neuralgia treated with deep brain stimulation

Post-herpetic neuralgic affects up to 20% of patients after an attack of trigeminal Herpes Zoster infection. Past medical and surgical treatments have been unrewarding. We report the successful treatment of such a case with deep brain stimulation into the region of the contralateral periventricular grey area (PVG) and ventral posterior lateral thalamic nucleus (VPL).