Hypoxia and ischemia cause inflammatory injury and critically participate in the pathogenesis of various diseases in various organs. However, the protective strategies against hypoxic and ischemic insults are very limited in clinical settings up to date. It is of utmost importance to improve our understanding of hypoxic/ischemic (H/I) inflammation and find novel therapies for better prevention/treatment of H/I injury. Recent studies provide strong evidence that the expression of microRNAs (miRNAs), which regulate gene expression and affect H/I inflammation through post-transcriptional mechanisms, are differentially altered in response to H/I stress, while δ-opioid receptors (DOR) play a protective role against H/I insults in different organs, including both H/I-sensitive organs (e.g., brain, kidney, and heart) and H/I-insensitive organs (e.g., liver and muscle). Indeed, many studies have demonstrated the crucial role of the DOR-mediated cyto-protection against H/I injury by several molecular pathways, including NLRP3 inflammasome modulated by miRNAs. In this review, we summarize our recent studies along with those of others worldwide, and compare the effects of DOR on H/I expression of miRNAs in H/I-sensitive and -insensitive organs. The alternation in miRNA expression profiles upon DOR activation and the potential impact on inflammatory injury in different organs under normoxic and hypoxic conditions are discussed at molecular and cellular levels. More in-depth investigations into this field may provide novel clues for new protective strategies against H/I inflammation in different types of organs.

<b><i>Background:</i></b> It has been widely recognized that exosomal miRNAs can participate in the pathogenesis of different renal disorders and serve as disease biomarkers. Although kidney biopsy is still the gold standard for diagnosing and monitoring immunoglobulin A nephropathy (IgAN), it is highly required to identify new and effective noninvasive biomarkers for IgAN, the most frequently detected primary glomerulonephritis worldwide. <b><i>Methods:</i></b> Plasma and urinary exosomes were extracted by PEG precipitation. Size and morphological characteristics of plasma and urinary exosomes were observed by transmission electron microscopy and nanoparticle tracking analysis. The levels of plasma and urinary exosomes were revealed by Western blotting. The expressions of target miRNAs were revealed by in situ hybridization and qRT-PCR. <b><i>Results:</i></b> The levels of plasma and urinary exosomes were remarkably enhanced in IgAN patients compared with healthy controls (HCs). The expressions of miR-4639 and miR-210 in IgAN patients were significantly higher in contrast to the individuals with membranous nephropathy, minimal change nephrosis, diabetic nephropathy, or HC. These also played a valuable role in assessing the kidney function and the level of proteinuria. Furthermore, plasma and urinary exosomal miR-4639 expression was associated with more serious and active histological activity (mesangial hypercellularity, crescent, and C3 complement deposition). With an average follow-up of 8 months, miR-4639 and miR-210 expressions in plasma and urinary exosomes were higher in patients with progressive IgAN. Plasma exosomal miR-4639 and miR-210 were better than proteinuria (g/24 h) to estimate renal outcomes. <b><i>Conclusion:</i></b> Exosomal miR-4639 and miR-210 could be used as valid biomarkers to assist in diagnosis, evaluate severity, and assess disease development of IgAN.