Thyroid hormone controls the gene expression of HSV-1 LAT and ICP0 in neuronal cells

Virus Infections and Host Metabolism-Can We Manage the Interactions?

When viruses infect cells, they almost invariably cause metabolic changes in the infected cell as well as in several host cell types that react to the infection. Such metabolic changes provide potential targets for therapeutic approaches that could reduce the impact of infection. Several examples are discussed in this review, which include effects on energy metabolism, glutaminolysis and fatty acid metabolism. The response of the immune system also involves metabolic changes and manipulating these may change the outcome of infection. This could include changing the status of herpesviruses infections from productive to latency. The consequences of viral infections which include coronavirus disease 2019 (COVID-19), may also differ in patients with metabolic problems, such as diabetes mellitus (DM), obesity, and endocrine diseases. Nutrition status may also affect the pattern of events following viral infection and examples that impact on the pattern of human and experimental animal viral diseases and the mechanisms involved are discussed. Finally, we discuss the so far few published reports that have manipulated metabolic events in-vivo to change the outcome of virus infection. The topic is expected to expand in relevance as an approach used alone or in combination with other therapies to shape the nature of virus induced diseases.

T3 Critically Affects the Mhrt/Brg1 Axis to Regulate the Cardiac MHC Switch: Role of an Epigenetic Cross-Talk

The LncRNA my-heart (Mhrt) and the chromatin remodeler Brg1 inhibit each other to respectively prevent or favor the maladaptive α-myosin-heavy-chain (Myh6) to β-myosin-heavy-chain (Myh7) switch, so their balance crucially guides the outcome of cardiac remodeling under stress conditions. Even though triiodothyronine (T3) has long been recognized as a critical regulator of the cardiac Myh isoform composition, its role as a modulator of the Mhrt/Brg1 axis is still unexplored. Here the effect of T3 on the Mhrt/Brg1 regulatory circuit has been analyzed in relation with chromatin remodeling and previously identified T3-dependent miRNAs. The expression levels of Mhrt, Brg1 and Myh6/Myh7 have been assessed in rat models of hyperthyroidism or acute myocardial ischemia/reperfusion (IR) treated with T3 replacement therapy. To gain mechanistic insights, in silico analyses and site-directed mutagenesis have been adopted in combination with gene reporter assays and loss or gain of function strategies in cultured cardiomyocytes. Our results indicate a pivotal role of Mhrt over-expression in the T3-dependent regulation of Myh switch. Mechanistically, T3 activates the Mhrt promoter at two putative thyroid hormone responsive elements (TRE) located in a crucial region that is necessary for both Mhrt activation and Brg1-dependent Mhrt repression. This newly identified T3 mode of action requires DNA chromatinization and is critically involved in mitigating the repressive function of the Brg1 protein on Mhrt promoter. In addition, T3 is also able to prevent the Brg1 over-expression observed in the post-IR setting through a pathway that might entail the T3-mediated up-regulation of miR-208a. Taken together, our data evidence a novel T3-responsive network of cross-talking epigenetic factors that dictates the cardiac Myh composition and could be of great translational relevance.

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.

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.

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.

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.

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

A global HSV-1 gene repression occurs during latency in sensory neurons where most viral gene transcriptions are suppressed. The molecular mechanisms of gene silencing and how stress factors trigger the reactivation are not well understood. Thyroid hormones are known to be altered due to stress, and with its nuclear receptor impart transcriptional repression or activation depending upon the hormone level. Therefore we hypothesized that triiodothyronine (T3) treatment of infected differentiated neuron like cells would reduce the ability of HSV-1 to produce viral progeny compared to untreated infected cells. Previously we identified putative thyroid hormone receptor elements (TREs) within the promoter regions of HSV-1 thymidine kinase (TK) and other key genes. Searching for a human cell line that can model neuronal HSV-1 infection, we performed HSV-1 infection experiments on differentiated human neuroendocrine cells, LNCaP. Upon androgen deprivation these cells undergo complete differentiation and exhibit neuronal-like morphology and physiology. These cells were readily infected by our HSV-1 recombinant virus, expressing GFP and maintaining many processes iconic of dendritic morphology. Our results demonstrated that differentiated LNCaP cells produced suppressive effects on HSV-1 gene expression and replication compared to its undifferentiated counterpart and T3 treatment has further decreased the viral plaque counts compared to untreated cells. Upon washout of the T3 viral plaque counts were restored, indicating an increase of viral replication. The qRT-PCR experiments using primers for TK showed reduced expression under T3 treatment. ChIP assays using a panel of antibodies for H3 lysine 9 epigenetic marks showed increased repressive marks on the promoter regions of TK. In conclusion we have demonstrated a T3 mediated quiescent infection in differentiated LNCaP cells that has potential to mimic latent infection. In this HSV-1 infection model thyroid hormone treatment caused decreased viral replication, repressed TK expression and increased repressive histone tail marks on the TK promoter.

Effects of hypo- and hyperthyroid states on herpes simplex virus infectivity in the rat

OBJECTIVE

Available data from in vitro studies show that thyroid hormones (THs) regulate herpes simplex virus (HSV) gene expression and may modulate latency/reactivation of the virus. Whether infectivity of the virus is also affected by THs is not known. Using animal models (in vivo study) and Vero cell culture (in vitro study), we examined the effects of alterations in THs level on HSV-1 infectivity.

METHODS

Rats were rendered hypo- and hyperthyroid by daily addition of methimazole and l-thyroxine into their drinking water, respectively. Euthyroid animals served as control. All animals were given a single dose of HSV-1 (10(7)TCID50, ip) and sacrificed 3 d later. The spleen of the animals was then removed and viral particles were recovered from the tissue extract through aseptic procedures. Serial dilution of the extracts was prepared and added to Vero cell culture. For the in vitro study, the cultures were pretreated with l-thyroxine and the viral particles were then added. Virus titration was determined by Reed-Muench quantal assay.

RESULTS

The viral load of spleen in hyperthyroid rats was significantly lower (1000-fold) than that of the euthyroid rats. Similarly, in vitro presence of supraphysiologic levels of l-thyroxine in the culture media of Vero cells decreased virus infectivity. Interestingly, hypothyroid animals showed a significant increase (10-fold) in spleen viral load as compared to that of their euthyroid counterparts.

CONCLUSIONS

These data clearly show that the HSV-1 infectivity is affected by THs, and suggest that THs or their analogs may have a potential application in prevention and/or treatment of viral infections.

A Cohort Historical Analysis of the Relationship between Thyroid Hormone Malady and Alpha-Human Herpesvirus Activation

Background

A number of physiological factors have been suggested to participate in the alpha- Human Herpesvirus (αHHV) reactivation, such as hormonal aberration. Thyroid hormone (TH) was shown to play a suppressive role in Herpes Simplex Virus Type-1 (HSV-1) gene expression and replication in cell culture and animal models. We hypothesize that reactivation of αHHV in humans may be due to, at least in part, by TH status.

Methods

Prior to implementing a full-scale population-based prospective inquiry into this hypothesis, a pilot study using a medical claims data base and a case-controlled, retrospective cohort investigation was conducted to develop a hypothetical link between TH complication and αHHV reactivation. Using diagnostic codes for treating thyroid disorders and αHHV infections as proxies for biologic/clinic outcomes, we queried a large, comprehensive hospital data base to construct two patient cohorts: Cohort 1 was comprised of patients receiving TH diagnoses over a twelve-year period, and Cohort 2 was composed of patients not receiving TH diagnoses during this period. Diagnoses of αHHV were recorded for each cohort and the difference in the frequency was examined for statistical significance. Demographic analyses such as age, gender, etc were also performed.

Results

Using 2×2 contingency table analyses and Statistical Analysis Software (SAS), an Odds Ratio (OR) of 2.83 was observed for the total population of 21 years old and above with a chi-square of 61.55 and p < 0.001, confirming that a severe significant difference was found between these two cohorts. This result suggested that patients with αHHV diagnosis have higher chances to have TH disorders. Additional investigation revealed that female were at higher/significant probability to have both TH and αHHV diagnosis, indicating a link of αHHV reactivation to a complex hormonal profile difference between genders. Our observation indicated that female patients of 21 years of age and above exhibited a very high incidence (OR of 3.40, p < 0.001) compared to the male groups (OR of 1.91, p < 0.05), indicating the possibility that hormonal alteration in females maybe transient but robust and can lead to αHHV reactivation more often than the males.

Conclusion

These results indicated that TH dysfunction may have implication in αHHV pathogenesis and females exhibited much higher probability to suffer αHHV reactivation due to TH disruption. Although the results from this pilot study have limitations and require additional controlled clinical examination such as more detailed patient records, lab data, therapeutic outcome, etc, it provides a tool to assess the effects of hormone imbalance on virus reactivation by retrospective analyses using existing large scale data base.

A Novel Thyroid Hormone Mediated Regulation of HSV-1 Gene Expression and Replication is Specific to Neuronal Cells and Associated with Disruption of Chromatin Condensation

Previously we showed that thyroid hormone (T3) regulated the Herpes Simplex Virus Type -1 (HSV-1) gene expression and replication through its nuclear receptor TR via histone modification and chromatin remodeling in a neuroblastoma cell line neuro-2a cells (N2a). This observation suggested that T3 regulation may be neuron-specific and have implication in HSV-1 latency and reactivation. In this study, our in vitro latency/reactivation model demonstrated that removal of T3 can de-repress the HSV-1 replication and favor reactivation. Transfection studies and infection assays indicated that HSV-1 thymidine kinase (TK), a key viral gene during reactivation, was repressed by TR/T3 in cells with neuronal origin but not in non-neuronal cells. Additional studies showed that RCC1 (Regulator of Chromosome Condensation 1) was sequestered but efficiently detected upon viral infection in N2a cells. Western blot analyses indicated that addition of T3 repressed the RCC1 expression upon infection. It is likely that diminution of RCC1 upon infection in neuronal cells under the influence of TR/T3 may lead to repression of viral replication/gene expression thus promote latency. Together these results demonstrated that TR/T3 mediated regulation is specific to neuronal cells and differential chromosome condensation may play a critical role in this process.

An unhealthy relationship: viral manipulation of the nuclear receptor superfamily

The nuclear receptor (NR) superfamily is a diverse group of over 50 proteins whose function is to regulate the transcription of a vast array of cellular genes. These proteins are able to tune transcription over an extremely dynamic range due to the fact that they may act as either transcriptional activators or repressors depending on promoter context and ligand status. Due to these unique properties, diverse families of viruses have evolved strategies to exploit NRs in order to regulate expression of their own genes and to optimize the cellular milieu to facilitate the viral lifecycle. While the specific NRs targeted by these viruses vary, the strategies used to target them are common. This is accomplished at the cis-level by incorporation of nuclear receptor response elements into the viral genome and at the trans-level by viral proteins that target NRs directly or indirectly to modulate their function. The specific NR(s) targeted by a particular virus are likely to be reflective of the tissue tropism of the virus in question. Thus, the essential role played by NRs in the replication cycles of such diverse viruses underscores the importance of understanding their functions in the context of specific infections. This knowledge will allow appropriate considerations to be made when treating infected individuals with hormone-associated diseases and will potentially assist in the rational design of novel antiviral therapeutics.

Effects of thyroid hormone on HSV-1 gene regulation: implications in the control of viral latency and reactivation

Thyroid hormone (TH) is involved in many biological functions such as animal development, cell differentiation, etc. Variation and/or disruption of plasma TH level often led to abnormalities and physiological disorders. TH exerts the effects through its nuclear receptors (TR). Literature showed that procedures resulted in TH alteration also linked to reactivation of several viruses including Herpes Simplex Virus Type -1 (HSV-1). Bioinformatic analyses revealed a number of putative TH responsive elements (TRE) located in the critical regulatory regions of HSV-1 genes such as thymidine kinase (TK), latency associated transcript (LAT), etc. Studies using neuronal cell lines have provided evidences demonstrating that liganded TR regulated viral gene expression via chromatin modification and controlled viral replication. The removal of TH reversed the inhibition and induced the viral replication previously blocked by TH. These results suggest that TH may have implication to participate in the control of reactivation during HSV-1 latency.