Optimization of CaMKII inhibitory peptide with N-terminal fatty acid chain modification and its study on anti-kidney fibrosis.

Renal fibrosis, as the ultimate common pathway for the development of various kidney diseases, is characterized by abnormal accumulation of extracellular matrix (ECM) and destruction of renal structure, resulting in progressive, irreversible loss of renal functional units and eventually leading to end-stage renal disease. This poses a serious threat to patients' quality of life and imposes a heavy medical burden. To overcome the clinical treatment bottleneck of the core pathological process of kidney fibrosis, this study is based on bioinformatics analysis and discovers that the CaMKIIδ subtype (CaMK2D) is specifically highly expressed in chronic kidney disease (CKD), and its expression level is closely related to the degree of fibrosis, suggesting its significant potential as an intervention target. To address the intracellular delivery bottleneck for these inhibitory peptides, autocamtide-3-derived inhibitory peptide (AC3-I) and autocamtide-2-related inhibitory peptide (AIP), we proposed an optimization strategy that involves modifying the N-terminal fatty acid chain. This study has confirmed that the modification with tetradecanoic acid (C14) enhances the membrane penetration ability and in vitro activity of the peptide, and its effect is superior to that of the unmodified form and the similar compounds reported in the literature that are modified with myristoylation. Mechanistically, the C14-modified peptides inhibit calcium/calmodulin-dependent protein kinase II (CaMKII) phosphorylation, thereby regulating fibrosis-related pathways, including the TGF-β/AKT/β-catenin pathways. Animal experiments have shown that C14-AC3-I and C14-AIP can effectively improve renal function in the unilateral ureteral obstruction (UUO) model mice and inhibit ECM deposition. The above results have verified the potential of CaMK2D as an anti-renal fibrosis target and have highlighted the advantages of N-terminal C14 modification in enhancing the druggability of the peptide, providing new candidate molecules and a theoretical basis for the treatment of renal fibrosis.