INTRODUCTION
Stroke is a major mortality and morbidity cause worldwide (Ding et al., 2020; Ma, Jiang, Xu, Liu, & Guo, 2021). Ischemic stroke, which is caused by thrombosis or embolism in blood vessels, is the most common stroke subtype(Mendelson & Prabhakaran, 2021). Currently, there remains no specific treatment for improving the prognosis in patients with ischemic stroke given the complex pathogenesis. A series of post-stroke inflammatory responses are crucially involved in functional recovery, which compromises the ischemic stroke prognosis.
Peripheral leukocytes significantly affect the clinical outcome of stroke and could be a therapeutic target for treating and preventing ischemic stroke (G. Li, Ma, et al., 2018). There have been several studies on non-coding RNA (ncRNA) expression in peripheral leukocytes in patients with ischemic stroke. ncRNAs in leukocytes regulate the release of inflammatory factors and promote inflammatory responses after cerebral ischemic injury(Liu et al., 2020). ncRNAs can be classified as short (≤ 200 base pairs) or long ncRNAs (lncRNAs; > 200 base pairs) (Palazzo & Koonin, 2020). MicroRNAs (miRNAs, miRs) are small ncRNAs with < 22 nucleotides that modulate protein expression at the posttranscriptional level (G. Li, Morris-Blanco, et al., 2018). Mature miRNAs prevent mRNA translation or promote mRNA degradation by binding to the consensus seed sequences in the 3’ untranslated regions (UTRs) of the target mRNAs(G. Li, Morris-Blanco, et al., 2018). Recent studies have demonstrated a mutual regulation between miRNAs and lncRNAs, including a direct interaction and an indirect role by binding to target genes in ischemic stroke(Ghafouri-Fard, Shoorei, & Taheri, 2020).
To identify leukocyte genes related to ischemic stroke, we previously detected mRNA expression in neutrophils using RNA-seq and compared it between patients with acute ischemic stroke and healthy controls. We found altered expression of C1q and tumour necrosis factor (C1QTNF)6 after ischemic stroke. C1QTNF6 was originally identified in the heart, brain, and peripheral inflammatory cells; further, it is involved in diverse processes, including apoptosis, metabolism, and release of inflammatory factors(Yan et al., 2021). C1QTNF6 can directly modulate pro-inflammatory cytokine gene expression in leukocytes(Lei et al., 2017). Our preliminary findings demonstrated that C1QTNF6 mRNA can be modulated by several miRNAs in neutrophils, including miR-29b. miR-29b expression in leukocytes is significantly decreased after ischemic injury; moreover, changes in miR-29b are correlated with the prognosis of ischemic stroke(Y. Wang et al., 2015). miR-29b overexpression alleviates brain injury and attenuates blood-brain barrier (BBB) damage (Y. Wang et al., 2015). Moreover, we predicted potential targeting lncRNAs related to miR-29b and identified the binding site of miR-29b in H19 using Starbase (http://starbase.sysu.edu.cn/index.php). Blood H19 levels are increased after ischemic stroke in circulating blood, which promotes the release of inflammatory factors. Therefore, we hypothesised that C1QTNF6 in leukocytes may be regulated by H19 and miR-29b, which could be involved in the pathogenesis of ischemic stroke.
This study aimed to elucidate the inflammatory mechanism of lncRNA H19-mediated regulation of C1QTNF6 by sponging miR-29b in leukocytes during ischemic stroke.