Elucidation of the mechanisms underlying neuropathic pain is expected to aid in the discovery and selection of effective therapeutic methods. Currently, microRNA (miRNA) is thought to play an important role in the development and maintenance of the nervous system. We, therefore, hypothesized that miRNAs are involved in neuropathic pain, and investigated this possibility by analyzing miRNA expression in the dorsal horn of the spinal cord in a chronic constriction injury (CCI) rat model using the TaqMan® Low Density Array (TLDA). Neuropathic pain model rats were produced by CCI induced by ligation of the sciatic nerve. The miRNA expression in the dorsal horn of the spinal cord was analyzed in Day 0 rats, with no sciatic nerve ligation or sham operation, Day 7 rats, examined 7 days after sciatic nerve ligation or sham operation, and Day 14 rats, examined 14 days after sciatic nerve ligation or sham operation using TLDA. In this study, 111 miRNAs were significantly regulated in CCI rats in both the Day 7 and Day 14 groups compared with sham rats in both groups. Of these 111, there were 75 miRNAs (67.6%) that had been analyzed in previous reports and 36 miRNAs (32.4%) related to the development of tumors of the nervous system and neurodegenerative diseases. Certain miRNAs were reported to be related to neuropathic pain; miR-500, -221 and -21. The expression levels of a large number of miRNAs in the dorsal horn of the spinal cord in CCI rats changed. These results provide a step toward elucidation of the mechanisms underlying neuropathic pain.

The results showed that anesthetics cause many miRNA expression changes, and the miRNA expression pattern was particular for each anesthetic. Further studies are needed to determine the functional consequence of miRNA modulation by anesthetics.

Our results showed that the peripheral nerve injury altered rat hippocampal miRNA.

Reportedly, a large number of microRNAs (miRNAs) play an important role in inflammatory lung diseases such as asthma, idiopathic pulmonary fibrosis (IPF), acute respiratory distress syndrome (ARDS), and pulmonary arterial hypertension (PAH). Sevoflurane is routinely used to various patients, and its safety has been confirmed by clinical outcomes; however, its effects to lungs at the miRNA level have not been elucidated. In our previous genomic studies, we showed that sevoflurane anesthesia affected the expression of many genes and mRNAs in rat lungs. In this study, we comprehensively investigated changes in miRNA expression caused by sevoflurane anesthesia (2.0% and 4.0%). Sevoflurane anesthesia resulted in apparent changes in miRNA expression in rat lungs, and the pattern of 2.0% sevoflurane-induced changes in miRNA expression was similar to that of 4.0% sevoflurane. Some of the differentially expressed miRNAs are known to be involved in asthma, IPF, and PAH. Especially, miR-146a, the most up-regulated miRNA, is known to attenuate the toxic effects associated with LPS stimulation. We showed, for the first time, dynamic changes in miRNA expression caused by sevoflurane anesthesia, and moreover, our results were important to understand the influence of sevoflurane anesthesia on any patients suffered from various lung diseases.