CK2 blockade alleviates liver fibrosis by suppressing activation of hepatic stellate cells via the Hedgehog pathway

Background and Purpose Liver fibrosis is a serious cause of morbidity and mortality worldwide characterized by accumulation of extracellular matrix produced by hepatic stellate cells (HSCs). The protein kinase CK2 is a pro-survival kinase overexpressed in human tumours. However, the biological role of CK2 in liver fibrosis is largely unknown. We aimed to investigate the mechanism by which CK2 promotes liver fibrosis. Experimental Approach In vitro, LX-2 cells were stimulated with transforming growth factor-beta (TGF-beta). HSCs were also isolated for research. In vivo, the adeno-associated virus AAV-sh-csnk2a1 was used to knockdown CK2 alpha specifically in HSCs, and CX-4945 was used to pharmacologically inhibit the enzymatic activity of CK2 in murine models of fibrosis induced by carbon tetrachloride (CCl4) and a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet. Histological and biochemical analyses were performed to study the involvement of CK2 in regulation of fibrogenic and fibrolytic factors as well as activation properties of HSCs. Key Results HSC-specific genetic invalidation of CK2 alpha or pharmacological inhibition of CK2 protected mice treated with CCl4 or fed a DDC diet against liver fibrosis and HSC accumulation. Mechanistically, CK2 alpha, which bound to Smoothened (SMO), was a positive regulator of the Hedgehog signal transduction pathway. CK2 prevented ubiquitination and proteasomal degradation of SMO, which was abolished by knockdown of CK2 alpha or pharmacological inhibition of CK2. Conclusions and Implications CK2 activation is critical to sustain the activated and fibrogenic phenotype of HSCs via SMO stabilization. Therefore, inactivation of CK2 by CX-4945 may be of therapeutic interest for liver fibrotic diseases.