Development of microRNA biomarkers for predicting toxicities of selective COX-2 NSAIDs using Daphnia model

Non-steroidal anti-inflammatory drugs (NSAIDs) target the cyclooxygenase (COX) isoforms including COX-1, COX-2 or COX-3 in human and reduce pain, fever, and inflammation by inhibiting prostaglandin formation. Although NSAIDs... [ view full abstract ]

Non-steroidal anti-inflammatory drugs (NSAIDs) target the cyclooxygenase (COX) isoforms including COX-1, COX-2 or COX-3 in human and reduce pain, fever, and inflammation by inhibiting prostaglandin formation. Although NSAIDs have been extensively prescribed all over the world, NSAIDs in overdose were reported to induce various side effects on non-target tissues. Especially, many COX-2 inhibition drugs have been withdrawn from the markets due to their safety concerns. Therefore, it is important to understand toxicological mechanisms modulated by selective COX-2 inhibitors for prediction of their adverse effects. In this study, we used daphnia as test organism because they have been widely used in research fields such as toxicology and genomics, and their eicosanoids biosynthesis pathway regulated by COX was recently identified. Daphnia has only one isoform of COX while some genes such as prostaglandin D₂ (PGD₂) synthase and thromboxane A₂ (TXA₂) synthase exist in two isoforms unlike those in human. To compare molecular responses changed by non-selective inhibitors, preferential COX-2 inhibitors, and selective COX-2 inhibitor, we analyzed transcriptional levels of several genes involved in eicosanoids biosynthesis pathway triggered by COX in daphnia exposed to 7 different NSAIDs. As a result, Celecoxib (selective COX-2 inhibitor) induced most genes while ibuprofen (non-selective inhibitor) and Nimesulide (preferential COX-2 inhibitor) activated specific genes in a dose- and time-dependent manner, indicating selective COX-2 inhibitor strongly modulates eicosanoids biosynthesis pathway compared to other NSAIDs although we haven’t yet confirmed whether it inhibits COX enzyme activity in daphnia. And also we found that Diclofenac (non-selective inhibitor) shows similar expression patterns to Celecoxib. So we carried out microRNA sequencing using small RNA extracted from daphnia exposed to Celecoxib and Diclofenac. In fact, microRNAs are associated with various molecular mechanisms and regarded as promising biomarkers for a range of diseases. After analyzing microRNA sequencing data, we will elucidate toxicological mechanisms and find novel biomarkers for predicting toxicity by selective COX-2 inhibitor.