Interplay of autophagy, apoptosis, and senescence in primary biliary cholangitis

Abstract

The pathogenesis of primary biliary cholangitis (PBC) is particularly complicated as both intrinsic and extrinsic factors are implicated. Several forms of cellular death, both programmable and non-programmable, operate leading biliary epithelial cells (BECs) to elimination. The precise role of critical pathways like autophagy, apoptosis, senescence, and their interplay has not been fully clarified. Therefore, in this review, data on these important mechanisms are presented and their implication in PBC is discussed. The interplay of the three mechanisms is examined and the factors that drive them are analyzed. Moreover, the upstream drivers of autophagy, apoptosis, and senescence are presented. They include the loss of the protective bicarbonate umbrella in BECs due to the reduction of activity of the anion exchanger 2 (AE2) with the resultant activation of the intracellular soluble adenylyl cyclase (sAC). The role of toxic bile acids is also presented. A sequence of events is proposed including involvement of the gut-liver axis and the possible role of ferroptosis. Finally, a brief account of the initial trigger of the disease is given.

Keywords

• primary biliary cholangitis
• autophagy
• apoptosis
• senescence
• mitophagy