Verapamil inhibits inflammation and promotes autophagy to alleviate ureteral scar by regulation of CaMK IIδ/STAT3 axis

Abstract

Background Ureteral stricture (US) is a pathological stenosis in the urinary tract characterized by increased collagen synthesis and inflammation. Autophagy activation has been shown to ameliorate tissue fibrosis and protect against fibrotic diseases. Verapamil has beneficial therapeutic benefits on fibrotic disorders. The pharmacological effects of verapamil on fibroblast autophagy in US and the underlying mechanism need to be investigated further.Methods US patients were recruited to isolate scar tissues, hematoxylin-eosin (HE) and Masson trichrome staining were performed to analyze histopathological changes. The US animal model was established and administered with verapamil (0.05 mg/kg) in the drinking water. Transforming growth factor (TGF)-β1 was adopted to facilitate collagen synthesis in fibroblasts. The mRNA and protein expressions were examined by qRT-PCR, western blot, immunofluorescence and immunohistochemistry. ELISA was adopted to measure interleukin (IL)-1β and IL-6 levels. Molecular interaction experiments like dual luciferase reporter and chromatin immunoprecipitation (ChIP) assays were performed to analyze the interaction between signal transducers and activators of transcription 3 (STAT3) and RNA polymerase II associated factor 1 (PAF1).Results Herein, our results revealed that verapamil activated TGF-β1-treated fibroblast autophagy and inhibited inflammation and fibrosis by repressing Ca2+⁄calmodulin-dependent protein kinase II (CaMK II) δ-mediated STAT3 activation. Our following tests revealed that STAT3 activated PAF1 transcription. PAF1 upregulation abrogated the regulatory effect of verapamil on fibroblast autophagy and fibrosis during US progression. Finally, verapamil mitigated US in vivo by activating fibroblast autophagy.Conclusion Taken together, verapamil activated TGF-β1-treated fibroblast autophagy and inhibited fibrosis by repressing the CaMK IIδ/STAT3/PAF1 axis.

Keywords

• Ureteral stricture
• verapamil
• autophagy
• CaMK IIδ
• PAF1