Identification of Key Genes and Pathways in Mouse Spinal Cord Involved in ddC-Induced Neuropathic Pain by Transcriptome Sequencing

Pathogenic mechanisms of human immunodeficiency virus (HIV)-associated pain

Chronic pain is a prevalent neurological complication among individuals living with human immunodeficiency virus (PLHIV) in the post-combination antiretroviral therapy (cART) era. These individuals experience malfunction in various cellular and molecular pathways involved in pain transmission and modulation, including the neuropathology of the peripheral sensory neurons and neurodegeneration and neuroinflammation in the spinal dorsal horn. However, the underlying etiologies and mechanisms leading to pain pathogenesis are complex and not fully understood. In this review, we aim to summarize recent progress in this field. Specifically, we will begin by examining neuropathology in the pain pathways identified in PLHIV and discussing potential causes, including those directly related to HIV-1 infection and comorbidities, such as antiretroviral drug use. We will also explore findings from animal models that may provide insights into the molecular and cellular processes contributing to neuropathology and chronic pain associated with HIV infection. Emerging evidence suggests that viral proteins and/or antiretroviral drugs trigger a complex pathological cascade involving neurons, glia, and potentially non-neural cells, and that interactions between these cells play a critical role in the pathogenesis of HIV-associated pain.

Long Non-Coding RNA and mRNA Profiles in the Spinal Cord of Rats with Resiniferatoxin-Induced Neuropathic Pain

Purpose

The ultrapotent transient receptor potential vanilloid 1 (TRPV1) agonist resiniferatoxin (RTX) induces small-fiber sensory neuropathy, which has been widely used model of postherpetic neuralgia to study mechanisms of neuropathic pain and new analgesics. The long non-coding RNA (lncRNA) and mRNA expression profiles in spinal dorsal horn tissues of rats six weeks after RTX injection to identify new RNAs related to neuropathic pain.

Methods

Microarray technology was applied to determine lncRNA expressions in spinal dorsal horn samples of adult rats 6 weeks after treatment with RTX or vehicle. The lncNA/mRNA co-expression network was constructed, and differential expression patterns of lncRNA and mRNA in RTX-treated rats were identified. Differential expressions of lncRNAs and mRNAs between RTX-treated samples and control samples were examined by RT-qPCR.

Results

Microarray analyses showed that 745 mRNA and 139 lncRNAs were upregulated, whereas 590 mRNA and 140 lncRNAs were downregulated in spinal dorsal horn tissues after RTX exposure. TargetScan was used to predict mRNA targets for these lncRNAs, which showed that the transcripts with multiple predicted target sites were related to neurologically important pathways. In addition, differential expressions of lncRNA (ENSRNOG00000022535, ENSRNOG00000042027, NR_027478, NR_030675) and Apobec3b mRNA in spinal cord tissue samples were validated, which confirmed the microarray data. The association between NR_030675 and Apobec3b levels was confirmed, which may be related to neuropathic pain.

Conclusion

Our study reveals lncRNA and mRNA of molecule targets that are enriched in the spinal cord dorsal horn and provides new information for further investigation on the mechanisms and therapeutics of neuropathic pain.

Neuroinflammation in HIV-Related Neuropathic Pain

In the management of human immunodeficiency virus (HIV) infection around the world, chronic complications are becoming a new problem along with the prolonged life expectancy. Chronic pain is widespread in HIV infected patients and even affects those with a low viral load undergoing long-term treatment with antiviral drugs, negatively influencing the adherence to disease management and quality of life. A large proportion of chronic pain is neuropathic pain, which defined as chronic pain caused by nervous system lesions or diseases, presenting a series of nervous system symptoms including both positive and negative signs. Injury caused by HIV protein, central and peripheral sensitization, and side effects of antiretroviral therapy lead to neuroinflammation, which is regarded as a maladaptive mechanism originally serving to promote regeneration and healing, constituting the main mechanism of HIV-related neuropathic pain. Gp120, as HIV envelope protein, has been found to be the major toxin that induces neuropathic pain. Particularly, the microglia, releasing numerous pro-inflammatory substances (such as TNFα, IL-1β, and IL-6), not only sensitize the neurons but also are the center part of the crosstalk bridging the astrocytes and oligodendrocytes together forming the central sensitization during HIV infection, which is not discussed detailly in recent reviews. In the meantime, some NRTIs and PIs exacerbate the neuroinflammation response. In this review, we highlight the importance of clarifying the mechanism of HIV-related neuropathic pain, and discuss about the limitation of the related studies as future research directions.