A novel tRNA‑derived small RNA, 5'tiRNA‑Gln‑TTG‑001, aggravates cardiomyocyte inflammatory injury through upregulation of CLIC4

Acute myocarditis encompasses a spectrum of diseases characterized by ongoing inflammation and cardiomyocyte injury, lacking specific diagnostic biomarkers and effective therapies. Transfer RNA (tRNA)‑derived small RNAs (tsRNAs), formed by specific cleavage of tRNAs in response to certain stimuli, participate in diverse diseases; however, their involvement in myocarditis remains unclear. The present study aimed to investigate the role and mechanism of a novel tsRNA, 5'tRNA‑derived stress‑induced RNA (tiRNA)‑Gln‑TTG‑001, in myocarditis. Plasma samples were obtained from patients with acute myocarditis to examine the clinical significance of 5'tiRNA‑Gln‑TTG‑001. AC16 human cardiomyocytes treated with lipopolysaccharide to induce inflammatory responses were utilized to explore the function and mechanism of 5'tiRNA‑Gln‑TTG‑001. Cell viability, apoptosis rates, and levels of factors associated with inflammation (IL‑1β, IL‑6 and IL‑18), myocardial injury (creatine kinase MB and high‑sensitivity cardiac troponin) and myocardial dysfunction (N‑terminal pro‑B‑type natriuretic peptide) were quantified to assess the degree of cardiomyocyte inflammatory injury. RNA fluorescence <i>in situ</i> hybridization (RNA‑FISH), cell transfection, dual‑luciferase reporter assays and functional experiments, including gain‑of‑function and loss‑of‑function assays and rescue experiments, were carried out to further explore the underlying mechanisms. The results revealed that 5'tiRNA‑Gln‑TTG‑001 was upregulated in acute myocarditis and positively correlated with high‑sensitivity cardiac troponin T and T2 ratio. <i>In vitro</i> experiments demonstrated that 5'tiRNA‑Gln‑TTG‑001 aggravated cardiomyocyte inflammatory injury. RNA‑FISH revealed co‑localization of 5'tiRNA‑Gln‑TTG‑001 and chloride intracellular channel 4 (CLIC4) in the nucleus and cytoplasm. Gain‑of‑function and loss‑of‑function experiments revealed that 5'tiRNA‑Gln‑TTG‑001 promoted CLIC4 expression. Dual‑luciferase reporter assays indicated that 5'tiRNA‑Gln‑TTG‑001 activated CLIC4 by binding to its 3'untranslated region. Furthermore, downregulation of CLIC4 rescued cardiomyocyte inflammatory injury aggravated by 5'tiRNA‑Gln‑TTG‑001. Meanwhile, the knockdown of 5'tiRNA‑Gln‑TTG‑001 reduced cardiomyocyte inflammatory injury and the effect was reversed by the upregulation of CLIC4. Overall, the present study demonstrated that 5'tiRNA‑Gln‑TTG‑001 may aggravate cardiomyocyte inflammatory injury via CLIC4 upregulation. Moreover, 5'tiRNA‑Gln‑TTG‑001 could offer a promising option for the diagnosis of myocarditis and serve as a potential therapeutic target.