As a typical neuropathic pain, post-herpetic neuralgia (PHN) is a common complication of herpes zoster (HZ), which seriously affects the normal life and work of patients. The unclear pathogenesis and lack of effective drugs make the clinical efficacy of PHN unsatisfactory. Here, we obtained the transcriptome profile of neuroblastoma cells (SH-SY5Y) and DRG in rats infected with varicella zoster virus (VZV) by transcriptome sequencing (RNA-Seq) combined with publicly available gene array data sets. Next, the data processing of the transcriptome map was analyzed using bioinformatics methods, including the screening of differentially expressed genes (DEGs), Gene Ontology (GO), and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Finally, real-time fluorescent quantitative PCR (qRT-PCR) was used to detect the expression of calcium-related genes, and calcium fluorescent probes and calcium colorimetry were used to evaluate the distribution and content of calcium ions in cells after VZV infection. Transcriptome data analysis (GO and KEGG enrichment analysis) showed that calcium disorder played an important role in SH-SY5Y cells infected by VZV and dorsal root ganglion (DRG) of the PHN rat model. The results of qRT-PCR showed that the expression levels of calcium-related genes BHLHA15, CACNA1F, CACNG1, CHRNA9, and STC2 were significantly upregulated, while the expression levels of CHRNA10, HRC, and TNNT3 were significantly downregulated in SH-SY5Y cells infected with VZV. Our calcium fluorescent probe and calcium colorimetric test results showed that VZV could change the distribution of calcium ions in infected cells and significantly increase the intracellular calcium content. In conclusion, our results revealed that the persistence of calcium disorder caused by VZV in nerve cells might be a crucial cause of herpetic neuralgia, and a potential target for clinical diagnosis and treatment of PHN.

Pain, as the most prevalent neurological complication of herpes zoster (HZ), may occur before or during the rash onset or even after the rash has recovered. Particularly, postherpetic neuralgia (PHN) is a refractory chronic condition, usually defined as pain persisting for 3 months or longer from the onset of HZ. Pain evoked by HZ impairs the normal physical and emotional functions of the patients, severely reducing their quality of life. However, how zoster-associated pain occurs and develops into PHN are elusive, making PHN difficult to predict. Uncovering the pathogenesis of zoster-associated pain (or HN) helps us to better understand the onset of PHN and supports developing more effective treatments. In this study, we successfully constructed a model for zoster-associated pain through varicella-zoster virus (VZV) infections of mouse footpads and pain behavior assessments. Next, we used the Kyoto Encyclopedia of Genes and Genomes (KEGG) and the Gene Ontology (GO) to analyze PHN rodent dorsal root ganglion (DRG) gene microarray data and found that calcium signal disorder might be involved in the onset of PHN. By using reverse transcription real-time fluorescent quantitative PCR (RT-qPCR) and Western blotting, we confirmed that VZV infection could significantly upregulate the expression of T-type calcium channel Cav3.2 in DRG and spinal dorsal horn (SDH). Intrathecal administration of Cav3.2 blocker (2R/S)-6-prenylnaringenin (6-PNG) relieved mechanical and thermal hyperalgesia induced by VZV. Taken together, our data indicated that VZV might participate in the occurrence and development of HN by upregulating the expression of Cav3.2 in DRG and SDH. These findings will help to reveal the underlying mechanisms on long-lasting pain and PHN formation, providing a new insight that Cav3.2 can be the promising drug target for remitting PHN.

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BackgroundInduced by varicella zoster virus (VZV), postherpetic neuralgia (PHN) is one of the common complications of herpes zoster (HZ) with refractory pain. Animal models play pivotal roles in disclosing the pain mechanisms and developing effective treatments. However, only a few rodent models focus on the VZV-associated pain and PHN.ObjectiveTo summarize the establishment and characteristics of popular PHN rodent models, thus offer bases for the selection and improvement of PHN models.DesignIn this review, we retrospect two promising PHN rodent models, VZV-induced PHN model and HSV1-induced PHN model in terms of pain-related evaluations, their contributions to PHN pathogenesis and pharmacology.ResultsSignificant difference of two PHN models is the probability of virus proliferation; 2) Most commonly used pain evaluation of PHN model is mechanical allodynia, but pain-induced anxiety and other behaviours are worth noting; 3) From current PHN models, pain mechanisms involve changes in virus gene and host gene expression, neuroimmune–glia interactions and ion channels; 4) antiviral drugs and classical analgesics serve more on the acute stage of herpetic pain.ConclusionsDifferent PHN models assessed by various pain evaluations combine to fulfil more comprehensive understanding of PHN.