Thyroid hormone-dependent epigenetic suppression of herpes simplex virus-1 gene expression and viral replication in differentiated neuroendocrine cells

Theory: Treatments for Prolonged ICU Patients May Provide New Therapeutic Avenues for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

We here provide an overview of treatment trials for prolonged intensive care unit (ICU) patients and theorize about their relevance for potential treatment of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Specifically, these treatment trials generally target: (a) the correction of suppressed endocrine axes, notably through a "reactivation" of the pituitary gland's pulsatile secretion of tropic hormones, or (b) the interruption of the "vicious circle" between inflammation, oxidative and nitrosative stress (O&NS), and low thyroid hormone function. There are significant parallels in the treatment trials for prolonged critical illness and ME/CFS; this is consistent with the hypothesis of an overlap in the mechanisms that prevent recovery in both conditions. Early successes in the simultaneous reactivation of pulsatile pituitary secretions in ICU patients-and the resulting positive metabolic effects-could indicate an avenue for treating ME/CFS. The therapeutic effects of thyroid hormones-including in mitigating O&NS and inflammation and in stimulating the adreno-cortical axis-also merit further studies. Collaborative research projects should further investigate the lessons from treatment trials for prolonged critical illness for solving ME/CFS.

Pilot Analyses of Interferon Subtype Expression Profiles in Patients with Herpes Zoster or Postherpetic Neuralgia

Postherpetic neuralgia (PHN) is a painful neuropathic complication resulting from herpes zoster (HZ). The pain manifests in peripheral nerves infected by herpesviruses, mostly from reactivation of latent varicella zoster virus. Mechanistic descriptions suggest that PHN develops because of disrupted immune system signaling and inflammation or peripheral nerve damage; however, the pathophysiology is not clear. It is difficult to predict/prevent PHN manifestations of HZ patients due to the lack of accurate diagnostics. In this study, sera from healthy controls, HZ patients, and PHN patients were subjected to an interferon (IFN) expression profile (IEP) study. The corresponding cDNAs were analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) using primer pairs against a panel of 21 different IFN subtypes. The results showed that distinct IEPs were observed among HZ and PHN cohorts in comparison to the healthy controls. Together, this pilot study suggested that the IEP study may be used as a molecular tool for diagnosis of PHN and assist in designing new PHN therapeutic protocols.

Disturbed Yin-Yang balance: stress increases the susceptibility to primary and recurrent infections of herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1), a neurotropic herpes virus, is able to establish a lifelong latent infection in the human host. Following primary replication in mucosal epithelial cells, the virus can enter sensory neurons innervating peripheral tissues via nerve termini. The viral genome is then transported to the nucleus where it can be maintained without producing infectious progeny, and thus latency is established in the cell. Yin–Yang balance is an essential concept in traditional Chinese medicine (TCM) theory. Yin represents stable and inhibitory factors, and Yang represents the active and aggressive factors. When the organism is exposed to stress, especially psychological stress caused by emotional stimulation, the Yin–Yang balance is disturbed and the virus can re-engage in productive replication, resulting in recurrent diseases. Therefore, a better understanding of the stress-induced susceptibility to HSV-1 primary infection and reactivation is needed and will provide helpful insights into the effective control and treatment of HSV-1. Here we reviewed the recent advances in the studies of HSV-1 susceptibility, latency and reactivation. We included mechanisms involved in primary infection and the regulation of latency and described how stress-induced changes increase the susceptibility to primary and recurrent infections.

Modulation of Voltage-Gated Sodium Channel Activity in Human Dorsal Root Ganglion Neurons by Herpesvirus Quiescent Infection

The molecular mechanisms of pain associated with alphaherpesvirus latency are not clear. We hypothesize that the voltage-gated sodium channels (VGSC) on the dorsal root ganglion (DRG) neurons controlling electrical impulses may have abnormal activity during latent viral infection and reactivation. We used herpes simplex virus 1 (HSV-1) to infect the human DRG-derived neuronal cell line HD10.6 in order to study the establishment and maintenance of viral latency, viral reactivation, and changes in the functional expression of VGSCs. Differentiated cells exhibited robust tetrodotoxin (TTX)-sensitive sodium currents, and acute infection significantly reduced the functional expression of VGSCs within 24 h and completely abolished VGSC activity within 3 days. A quiescent state of infection mimicking latency can be achieved in the presence of acyclovir (ACV) for 7 days followed by 5 days of ACV washout, and then the viruses can remain dormant for another 3 weeks. It was noted that during the establishment of HSV-1 latency, the loss of VGSC activity caused by HSV-1 infection could not be blocked by ACV treatment. However, neurons with continued ACV treatment for another 4 days showed a gradual recovery of VGSC functional expression. Furthermore, the latently infected neurons exhibited higher VGSC activity than controls. The overall regulation of VGSCs by HSV-1 during quiescent infection was proved by increased transcription and possible translation of Nav1.7. Together, these observations demonstrated a very complex pattern of electrophysiological changes during HSV infection of DRG neurons, which may have implications for understanding of the mechanisms of virus-mediated pain linked to latency and reactivation.IMPORTANCE The reactivation of herpesviruses, most commonly varicella-zoster virus (VZV) and pseudorabies virus (PRV), may cause cranial nerve disorder and unbearable pain. Clinical studies have also reported that HSV-1 causes postherpetic neuralgia and chronic occipital neuralgia in humans. The current work meticulously studies the functional expression profile changes of VGSCs during the processes of HSV-1 latency establishment and reactivation using human dorsal root ganglion-derived neuronal HD10.6 cells as an in vitro model. Our results indicated that VGSC activity was eliminated upon infection but steadily recovered during latency establishment and that latent neurons exhibited even higher VGSC activity. This finding advances our knowledge of how ganglion neurons generate uncharacteristic electrical impulses due to abnormal VGSC functional expression influenced by the latent virus.

Reversing thyroid-hormone-mediated repression of a HSV-1 promoter via computationally guided mutagenesis

Thyroid hormones (THs) and their DNA-binding nuclear receptors (TRs) direct transcriptional regulation in diverse ways depending on the host cell environment and specific promoter characteristics of TH-sensitive genes. This study sought to elucidate the impact on transcriptional repression of nucleotide sequence or orientation within TR binding sites - the TH response elements (TREs) of TH-sensitive promoters - to better understand ligand-dependent transcriptional repression of wild-type promoters. Computational analysis of the HSV-1 thymidine kinase (TK) gene TRE bound by TR and retinoid X receptor (RXR) revealed a single TRE point mutation sufficient to reverse the TRE orientation. In vitro experiments showed that the TRE point mutation had distinct impacts on promoter activity, sufficient to reverse the TH-dependent negative regulation in neuroendocrine differentiated cells. This point mutation altered the promoter's regulatory mechanism by discrete changes in transcription factor TR occupancy and altered enrichment of the repressive chromatin modification of histone-3-lysine-9-trimethyl (H3K9Me3). Insights relating to this negative TRE (nTRE) mechanism aids our understanding of other nTREs and TRE mutations associated with TH and herpes diseases.

Regulation of T-type Ca2+ channel expression by herpes simplex virus-1 infection in sensory-like ND7 cells

Infection of sensory neurons by herpes simplex virus (HSV)-1 disrupts electrical excitability, altering pain sensory transmission. Because of their low threshold for activation, functional expression of T-type Ca²⁺ channels regulates various cell functions, including neuronal excitability and neuronal communication. In this study, we have tested the effect of HSV-1 infection on the functional expression of T-type Ca²⁺ channels in differentiated ND7-23 sensory-like neurons. Voltage-gated Ca²⁺ currents were measured using whole cell patch clamp recordings in differentiated ND7-23 neurons under various culture conditions. Differentiation of ND7-23 cells evokes a significant increase in T-type Ca²⁺ current densities. Increased T-type Ca²⁺ channel expression promotes the morphological differentiation of ND7-23 cells and triggers a rebound depolarization. HSV-1 infection of differentiated ND7-23 cells causes a significant loss of T-type Ca²⁺ channels from the membrane. HSV-1 evoked reduction in the functional expression of T-type Ca²⁺ channels is mediated by several factors, including decreased expression of Ca_v3.2 T-type Ca²⁺ channel subunits and disruption of endocytic transport. Decreased functional expression of T-type Ca²⁺ channels by HSV-1 infection requires protein synthesis and viral replication, but occurs independently of Egr-1 expression. These findings suggest that infection of neuron-like cells by HSV-1 causes a significant disruption in the expression of T-type Ca²⁺ channels, which can results in morphological and functional changes in electrical excitability.

Receipt of thyroid hormone deficiency treatment and risk of herpes zoster

OBJECTIVE

Thyroid hormone (TH) has been suggested to control herpes virus gene expression and replication in neurons via epigenetics through its nuclear receptors. It has previously been shown that patients with hypothyroidism are predisposed to herpes zoster (HZ), suggesting that the TH deficiency may be a risk factor for varicella zoster virus (VZV) reactivation. The aim of this study was to test the hypothesis that TH treatment will ameliorate the complication of HZ.

METHODS

This study investigated the hypothesis by enquiring into a comprehensive medical database at Kaiser Permanente Southern California (KPSC) to verify whether patients taking TH medication experience a reduction in HZ occurrence.

RESULTS

It was shown by Kaplan-Meier analysis that hypothyroidism patients taking TH medicines had a lower risk of HZ. The fully adjusted analysis indicated that patients receiving medication for the treatment of TH deficiency exhibited a reduced risk of HZ (hazard ratio 0.60, 95% confidence interval 0.51-0.71). This lower risk of HZ was significant in all age groups except the 18-39 years cohort. In addition, female patients taking TH treatment exhibited a lower risk than their male counterparts.

CONCLUSIONS

Together these findings support the hypothesis that a constant level of TH will provide a degree of protection from contracting HZ. More studies are underway to evaluate the laboratory data for an analysis of hormonal effects on individuals.

New insights on thyroid hormone mediated regulation of herpesvirus infections

Thyroid hormone (T₃) has been suggested to participate in the regulation of herpesvirus replication during reactivation. Clinical observations and in vivo experiments suggest that T₃ are involved in the suppression of herpes virus replication. In vitro, differentiated LNCaP cells, a human neuron-like cells, further resisted HSV-1 replication upon addition of T₃. Previous studies indicate that T₃ controlled the expression of several key viral genes via its nuclear receptors in differentiated LNCaP cells. Additional observation showed that differentiated LNCaP cells have active PI3K signaling and inhibitor LY294002 can reverse T₃-mediated repression of viral replication. Active PI3K signaling has been linked to HSV-1 latency in neurons. The hypothesis is that, in addition to repressing viral gene transcription at the nuclear level, T₃ may influence PI3K signaling to control HSV-1 replication in human neuron-like cells. We review the genomic and non-genomic regulatory roles of T₃ by examining the phosphoinositide 3-kinase (PI3K) pathway gene expression profile changes in differentiated LNCaP cells under the influence of hormone. The results indicated that 15 genes were down-regulated and 22 genes were up-regulated in T₃-treated differentiated LNCaP cells in comparison to undifferentiated state. Of all these genes, casein kinase 2 (CK2), a key component to enhance PI3K signaling pathway, was significantly increased upon T₃ treatment only while the cells were differentiated. Further studies revealed that CK2 inhibitors tetrabrominated cinnamic acid (TBCA) and 4, 5, 6, 7-tetrabromo-2H-benzotriazole (TBB) both reversed the T₃-mediated repression of viral replication. Together these observations suggested a new approach to understanding the roles of T₃ in the complicated regulation of HSV-1 replication during latency and reactivation.

Volatile Organic Compound Gamma-Butyrolactone Released upon Herpes Simplex Virus Type -1 Acute Infection Modulated Membrane Potential and Repressed Viral Infection in Human Neuron-Like Cells

Herpes Simplex Virus Type -1 (HSV-1) infections can cause serious complications such as keratitis and encephalitis. The goal of this study was to identify any changes in the concentrations of volatile organic compounds (VOCs) produced during HSV-1 infection of epithelial cells that could potentially be used as an indicator of a response to stress. An additional objective was to study if any VOCs released from acute epithelial infection may influence subsequent neuronal infection to facilitate latency. To investigate these hypotheses, Vero cells were infected with HSV-1 and the emission of VOCs was analyzed using two-dimensional gas chromatograph/mass spectrometry (2D GC/MS). It was observed that the concentrations of gamma-butyrolactone (GBL) in particular changed significantly after a 24-hour infection. Since HSV-1 may establish latency in neurons after the acute infection, GBL was tested to determine if it exerts neuronal regulation of infection. The results indicated that GBL altered the resting membrane potential of differentiated LNCaP cells and promoted a non-permissive state of HSV-1 infection by repressing viral replication. These observations may provide useful clues towards understanding the complex signaling pathways that occur during the HSV-1 primary infection and establishment of viral latency.

Overexpression of thyroid hormone receptor β1 altered thyroid hormone-mediated regulation of herpes simplex virus-1 replication in differentiated cells

Thyroid hormone (T₃) has been suggested to play a role in herpes simplex virus 1 (HSV-1) replication. It was previously reported that HSV-1 replication was suppressed by T₃ in mouse neuroblastoma cells overexpressing thyroid hormone receptor β1 (TRβ1). Using a human neuro-endocrine cells LNCaP differentiated by androgen deprivation, HSV-1 replication was active but decreased by T₃ at very low moi, probably due to low copy of TRβ1. In this study, a recombinant HSV-1 was constructed expressing TRβ1 (HSV-1/TRβ1). Infection of Vero cells (very little TRβ1 expression) with HSV-1/TRβ1 exhibited increased replication in the presence of T₃ compared to the counterpart without TRβ1 overexpression. Interestingly, HSV-1/TRβ1 infection of differentiated LNCaP cells showed strong suppression of viral replication by T₃ and the removal of hormone did not fully reversed the suppression as was observed in parent virus. Quantitative analyses indicated that ICP0 expression was blocked using HSV-1/TRβ1 for infection during T₃ washout, suggesting that overexpression of TRβ1 is likely to delay its inhibitory effect on viral gene expression. Together these results emphasized the importance of TRβ1 in the regulation of HSV-1 replication in differentiated environment with neuronal phenotype.

Occupancy of RNA Polymerase II Phosphorylated on Serine 5 (RNAP S5P) and RNAP S2P on Varicella-Zoster Virus Genes 9, 51, and 66 Is Independent of Transcript Abundance and Polymerase Location within the Gene

Regulation of gene transcription in varicella-zoster virus (VZV), a ubiquitous human neurotropic alphaherpesvirus, requires coordinated binding of multiple host and virus proteins onto specific regions of the virus genome. Chromatin immunoprecipitation (ChIP) is widely used to determine the location of specific proteins along a genomic region. Since the size range of sheared virus DNA fragments governs the limit of accurate protein localization, particularly for compact herpesvirus genomes, we used a quantitative PCR (qPCR)-based assay to determine the efficiency of VZV DNA shearing before ChIP, after which the assay was used to determine the relationship between transcript abundance and the occupancy of phosphorylated RNA polymerase II (RNAP) on the gene promoter, body, and terminus of VZV genes 9, 51, and 66. The abundance of VZV gene 9, 51, and 66 transcripts in VZV-infected human fetal lung fibroblasts was determined by reverse transcription-linked quantitative PCR. Our results showed that the C-terminal domain of RNAP is hyperphosphorylated at serine 5 (S5(P)) on VZV genes 9, 51, and 66 independently of transcript abundance and the location within the virus gene at both 1 and 3 days postinfection (dpi). In contrast, phosphorylated serine 2 (S2(P))-modified RNAP was not detected at any virus gene location at 3 dpi and was detected at levels only slightly above background levels at 1 dpi.

IMPORTANCE

Regulation of herpesvirus gene transcription is an elaborate choreography between proteins and DNA that is revealed by chromatin immunoprecipitation (ChIP). We used a quantitative PCR-based assay to determine fragment size after DNA shearing, a critical parameter in ChIP assays, and exposed a basic difference in the mechanism of transcription between mammalian cells and VZV. We found that hyperphosphorylation at serine 5 of the C-terminal domain of RNAP along the lengths of VZV genes (the promoter, body, and transcription termination site) was independent of mRNA abundance. In contrast, little to no enrichment of serine 3 phosphorylation of RNAP was detected at these virus gene regions. This is distinct from the findings for RNAP at highly regulated host genes, where RNAP S5(P) occupancy decreased and S2(P) levels increased as the polymerase transited through the gene. Overall, these results suggest that RNAP associates with human and virus transcriptional units through different mechanisms.

Influence of thyroid hormone disruption on the incidence of shingles

The reactivation of dormant alpha-human herpesvirus (αHHV) has been attributed to various causes often referred to as stressors. However, no clinical study investigating the relationship between stressors and reactivation exists in humans at this time. Herpes simplex virus type-1 (HSV-1), an important αHHV, was shown to have its gene expression and replication regulated by thyroid hormone (TH) using molecular biology approaches. Varicella zoster virus (VZV) is categorized in αHHV superfamily and shares similar homology with HSV-1. We hypothesize that a history of TH imbalance may be associated with the incidence of shingles (VZV reactivation). This current pilot study, based on a hospital medical claims database, was conducted as a retrospective case-controlled investigation to determine if a putative link between TH imbalance and incidence of shingles is present. An odds ratio of 2·95 with a χ 2 value of 51·74 was calculated for the total population diagnosed with TH disruption and shingles. Further analyses indicated that African American males exhibited a much higher chance of simultaneous diagnoses. These results show that a TH imbalance history may affect VZV reactivation at different incidence rates in different races and age groups.