Kupffer cells (KCs), as residents and sentinels of the liver, are involved in the formation of hepatic fibrosis (HF). However, the biological functions of circular RNAs (circRNAs) in KCs to HF have not been determined. In this study, the expression levels of circRNAs, microRNAs, and messenger RNAs (mRNAs) in KCs from a mouse model of HF mice were investigated using microarray and circRNA-Seq analyses. circDcbld2 was identified as a candidate circRNA in HF, as evidenced by its up-regulation in KCs. Silver staining and mass spectrometry showed that Wtap and Igf2bp2 bind to cirDcbld2. The suppression of circDcbld2 expression decreased the KC inflammatory response and oxidative stress and inhibited hepatic stellate cell (HSCs) activation, attenuating mouse liver fibrogenesis. Mechanistically, Wtap mediated the N ⁶-methyladenosine (m6A) methylation of circDcbld2, and Igf2bp2 recognized m6A-modified circDcbld2 and increased its stability. circDcbld2 contributes to the occurrence of HF by binding miR-144-3p/Et-1 to regulate the inflammatory response and oxidative stress. These findings indicate that circDcbld2 functions via the m6A/circDcbld2/miR-144-3p/Et-1 axis and may act as a potential biomarker for HF treatment.

Poly(ADP-ribosyl)ation (PARylation) is a specific form of post-translational modification (PTM) predominantly triggered by the activation of poly-ADP-ribose polymerase 1 (PARP1). However, the role and mechanism of PARylation in the advancement of acute kidney injury (AKI) remain undetermined. Here, we demonstrated the significant upregulation of PARP1 and its associated PARylation in murine models of AKI, consistent with renal biopsy findings in patients with AKI. This elevation in PARP1 expression might be attributed to trimethylation of histone H3 lysine 4 (H3K4me3). Furthermore, a reduction in PARylation levels mitigated renal dysfunction in the AKI mouse models. Mechanistically, liquid chromatography-mass spectrometry indicated that PARylation mainly occurred in receptor for activated C kinase 1 (RACK1), thereby facilitating its subsequent phosphorylation. Moreover, the phosphorylation of RACK1 enhanced its dimerization and accelerated the ubiquitination-mediated hypoxia inducible factor-1α (HIF-1α) degradation, thereby exacerbating kidney injury. Additionally, we identified a PARP1 proteolysis-targeting chimera (PROTAC), A19, as a PARP1 degrader that demonstrated superior protective effects against renal injury compared with PJ34, a previously identified PARP1 inhibitor. Collectively, both genetic and drug-based inhibition of PARylation mitigated kidney injury, indicating that the PARylated RACK1/HIF-1α axis could be a promising therapeutic target for AKI treatment.