Role of Micro-RNA for Pain After Surgery

miRNA packaging into small extracellular vesicles and implications in pain

Extracellular vesicles (EVs) are a heterogenous group of lipid bilayer bound particles naturally released by cells. These vesicles are classified based on their biogenesis pathway and diameter. The overlap in size of exosomes generated from the exosomal pathway and macrovesicles that are pinched off from the surface of the plasma membrane makes it challenging to isolate pure populations. Hence, isolated vesicles that are less than 200 nm are called small extracellular vesicles (sEVs). Extracellular vesicles transport a variety of cargo molecules, and multiple mechanisms govern the packaging of cargo into sEVs. Here, we discuss the current understanding of how miRNAs are targeted into sEVs, including the role of RNA binding proteins and EXOmotif sequences present in miRNAs in sEV loading. Several studies in human pain disorders and rodent models of pain have reported alterations in sEV cargo, including miRNAs. The sorting mechanisms and target regulation of miR-939, a miRNA altered in individuals with complex regional pain syndrome, is discussed in the context of inflammation. We also provide a broad overview of the therapeutic strategies being pursued to utilize sEVs in the clinic and the work needed to further our understanding of EVs to successfully deploy sEVs as a pain therapeutic.

Schwann cell-derived extracellular vesicles promote memory impairment associated with chronic neuropathic pain

BACKGROUND

The pathogenesis of memory impairment, a common complication of chronic neuropathic pain (CNP), has not been fully elucidated. Schwann cell (SC)-derived extracellular vesicles (EVs) contribute to remote organ injury. Here, we showed that SC-EVs may mediate pathological communication between SCs and hippocampal neurons in the context of CNP.

METHODS

We used an adeno-associated virus harboring the SC-specific promoter Mpz and expressing the CD63-GFP gene to track SC-EVs transport. microRNA (miRNA) expression profiles of EVs and gain-of-function and loss-of-function regulatory experiments revealed that miR-142-5p was the main cargo of SC-EVs. Next, luciferase reporter gene and phenotyping experiments confirmed the direct targets of miR-142-5p.

RESULTS

The contents and granule sizes of plasma EVs were significantly greater in rats with chronic sciatic nerve constriction injury (CCI)than in sham rats. Administration of the EV biogenesis inhibitor GW4869 ameliorated memory impairment in CCI rats and reversed CCI-associated dendritic spine damage. Notably, during CCI stress, SC-EVs could be transferred into the brain through the circulation and accumulate in the hippocampal CA1-CA3 regions. miR-142-5p was the main cargo wrapped in SC-EVs and mediated the development of CCI-associated memory impairment. Furthermore, α-actinin-4 (ACTN4), ELAV-like protein 4 (ELAVL4) and ubiquitin-specific peptidase 9 X-linked (USP9X) were demonstrated to be important downstream target genes for miR-142-5p-mediated regulation of dendritic spine damage in hippocampal neurons from CCI rats.

CONCLUSION

Together, these findings suggest that SCs-EVs and/or their cargo miR-142-5p may be potential therapeutic targets for memory impairment associated with CNP.

Cell-free therapy based on extracellular vesicles: a promising therapeutic strategy for peripheral nerve injury

Peripheral nerve injury (PNI) is one of the public health concerns that can result in a loss of sensory or motor function in the areas in which injured and non-injured nerves come together. Up until now, there has been no optimized therapy for complete nerve regeneration after PNI. Exosome-based therapies are an emerging and effective therapeutic strategy for promoting nerve regeneration and functional recovery. Exosomes, as natural extracellular vesicles, contain bioactive molecules for intracellular communications and nervous tissue function, which could overcome the challenges of cell-based therapies. Furthermore, the bioactivity and ability of exosomes to deliver various types of agents, such as proteins and microRNA, have made exosomes a potential approach for neurotherapeutics. However, the type of cell origin, dosage, and targeted delivery of exosomes still pose challenges for the clinical translation of exosome therapeutics. In this review, we have focused on Schwann cell and mesenchymal stem cell (MSC)-derived exosomes in nerve tissue regeneration. Also, we expressed the current understanding of MSC-derived exosomes related to nerve regeneration and provided insights for developing a cell-free MSC therapeutic strategy for nerve injury.

Perioperative stress prolong post-surgical pain via miR-339-5p targeting oprm1 in the amygdala

Background

The decreased expression of mu-opioid receptors (MOR) in the amygdala may be a key molecular in chronic post-surgical pain (CPSP). It is known that miR-339-5p expression in the amygdala of a stressed rat model was increased. Analyzed by RNAhybrid, miR-339-5p could target opioid receptor mu 1 (oprm1) which codes MOR directly. So, the authors hypothesized that miR-339-5p could regulate the expression of MOR via targeting oprm1 and cause the effects to CPSP.

Methods

To simulate perioperative short-term stress, a perioperative stress prolongs incision-induced pain hypersensitivity without changing basal pain perception rat model was built. A pmiR-RB-REPORT™ dual luciferase assay was taken to verify whether miR-339-5p could act on oprm1 as a target. The serum glucocorticoid level of rats was test. Differential expressions of MOR, GFAP, and pERK1/2 in each group of the rats' amygdala were tested, and the expressions of miR-339-5p in each group of rats' amygdalas were also measured.

Results

Perioperative stress prolonged the recovery time of incision pain. The expression of MOR was down-regulated in the amygdala of rats in stress + incision (S + IN) group significantly compared with other groups (P < 0.050). miR-339-5p was up-regulated in the amygdala of rats in group S + IN significantly compared with other groups (P < 0.050). miR-339-5p acts on oprm1 3'UTR and take MOR mRNA as a target.

Conclusions

Perioperative stress could increase the expression of miR-339-5p, and miR-339-5p could cause the expression of MOR to decrease via targeting oprm1. This regulatory pathway maybe an important molecular mechanism of CPSP.

SARS-CoV-2 Infection: Host Response, Immunity, and Therapeutic Targets

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has resulted in a global pandemic with severe socioeconomic effects. Immunopathogenesis of COVID-19 leads to acute respiratory distress syndrome (ARDS) and organ failure. Binding of SARS-CoV-2 spike protein to human angiotensin-converting enzyme 2 (hACE2) on bronchiolar and alveolar epithelial cells triggers host inflammatory pathways that lead to pathophysiological changes. Proinflammatory cytokines and type I interferon (IFN) signaling in alveolar epithelial cells counter barrier disruption, modulate host innate immune response to induce chemotaxis, and initiate the resolution of inflammation. Here, we discuss experimental models to study SARS-CoV-2 infection, molecular pathways involved in SARS-CoV-2-induced inflammation, and viral hijacking of anti-inflammatory pathways, such as delayed type-I IFN response. Mechanisms of alveolar adaptation to hypoxia, adenosinergic signaling, and regulatory microRNAs are discussed as potential therapeutic targets for COVID-19.

Alternative adenosine Receptor activation: The netrin-Adora2b link

During hypoxia or inflammation, extracellular adenosine levels are elevated. Studies using pharmacologic approaches or genetic animal models pertinent to extracellular adenosine signaling implicate this pathway in attenuating hypoxia-associated inflammation. There are four distinct adenosine receptors. Of these, it is not surprising that the Adora2b adenosine receptor functions as an endogenous feedback loop to control hypoxia-associated inflammation. First, Adora2b activation requires higher adenosine concentrations compared to other adenosine receptors, similar to those achieved during hypoxic inflammation. Second, Adora2b is transcriptionally induced during hypoxia or inflammation by hypoxia-inducible transcription factor HIF1A. Studies seeking an alternative adenosine receptor activation mechanism have linked netrin-1 with Adora2b. Netrin-1 was originally discovered as a neuronal guidance molecule but also functions as an immune-modulatory signaling molecule. Similar to Adora2b, netrin-1 is induced by HIF1A, and has been shown to enhance Adora2b signaling. Studies of acute respiratory distress syndrome (ARDS), intestinal inflammation, myocardial or hepatic ischemia and reperfusion implicate the netrin-Adora2b link in tissue protection. In this review, we will discuss the potential molecular linkage between netrin-1 and Adora2b, and explore studies demonstrating interactions between netrin-1 and Adora2b in attenuating tissue inflammation.

Epigenetic Alterations in Prescription Opioid Misuse: New Strategies for Precision Pain Management

Prescription opioids are used for some chronic pain conditions. However, generally, long-term therapy has unwanted side effects which may trigger addiction, overdose, and eventually cause deaths. Opioid addiction and chronic pain conditions have both been associated with evidence of genetic and epigenetic alterations. Despite intense research interest, many questions about the contribution of epigenetic changes to this typology of addiction vulnerability and development remain unanswered. The aim of this review was to summarize the epigenetic modifications detected in specific tissues or brain areas and associated with opioid prescription and misuse in patients who have initiated prescribed opioid management for chronic non-cancer pain. The review considers the effects of opioid exposure on the epigenome in central and peripheral tissues in animal models and human subjects and highlights the mechanisms in which opioid epigenetics may be involved. This will improve our current understanding, provide the basis for targeted, personalized pain management, and thus balance opioid risks and benefits in managing chronic pain.

Characterization of a Murine Model System to Study MicroRNA-147 During Inflammatory Organ Injury

Inflammatory organ injury and sepsis have profound impacts on the morbidity and mortality of surgical and critical care patients. MicroRNAs are small RNAs composed of 20-25 nucleotides that have a significant contribution to gene regulation. MicroRNA-147 (miR-147), in particular, has been shown to have an emerging role in different physiological functions such as cell cycle regulation and inflammatory responses. However, animal model systems to study tissue-specific functions of miR-147 during inflammatory conditions in vivo are lacking. In the present study, we characterize miR-147 expression in different organs and cell types. Next, we generated a transgenic mouse line with a floxed miR-147 gene. Subsequently, we used this mouse line to generate mice with whole-body deletion of miR-147 (miR-147 -/-) by crossing "floxed" miR-147 mice with transgenic mice expressing Cre recombinase in all tissues (CMVcre mice). Systematic analysis of miR-147 -/- mice demonstrates normal growth, development, and off-spring. In addition, deletion of the target gene in different organs was successful at baseline or during inflammation, including the heart, intestine, stomach, liver, spleen, bone marrow, lungs, kidneys, or stomach. Moreover, miR-147 -/- mice have identical baseline inflammatory gene expression compared to C57BL/6 mice, except elevated IL-6 expression in the spleen (7.5 fold, p < 0.05). Taken together, our data show the successful development of a transgenic animal model for tissue and cell-specific deletion of miR-147 that can be used to study the functional roles of miR-147 during inflammatory organ injury.

Nociception and Pain: New Roles for Exosomes

The interchange of information from one cell to another relies on the release of hundreds of different molecules including small peptides, amino acids, nucleotides, RNA, steroids, retinoids, or fatty acid metabolites. Many of them are released to the extracellular matrix as free molecules and others can be part of the cargo of cellular vesicles. Small extracellular vesicles (30-150 nm), also known as exosomes, are a known mechanism of cell-to-cell communication in the nervous system. Exosomes participate in the pathogenesis of several neurological conditions including Alzheimer's and Parkinson's disease. However, exciting emerging evidence demonstrates that exosomes also regulate mechanisms of the sensory process including nociception. The goal of this review is to summarize the literature on exosome biogenesis, methods of small vesicle isolation and purification, and their role in nociception. We also provide insights on the potential applications of exosomes as pain biomarkers or as novel therapeutics.