The hydrophilic bile salt ursodeoxycholic acid (UDCA) protects against the membrane-damaging effects associated with hydrophobic bile acids. This study was undertaken to (a) determine if UDCA inhibits apoptosis from deoxycholic acid (DCA), as well as from ethanol, TGF-␤1, Fas ligand, and okadaic acid; and to (b) determine whether mitochondrial membrane perturbation is modulated by UDCA. DCA induced significant hepatocyte apoptosis in vivo and in isolated hepatocytes determined by terminal transferase-mediated dUTP-digoxigenin nick end-labeling assay and nuclear staining, respectively (P Ͻ 0.001). Apoptosis in isolated rat hepatocytes increased 12-fold after incubation with 0.5% ethanol (P Ͻ 0.001). HuH-7 cells exhibited increased apoptosis with 1 nM TGF-␤1 (P Ͻ 0.001) or DCA at Ն 100 M (P Ͻ 0.001), as did Hep G2 cells after incubation with anti-Fas antibody (P Ͻ 0.001). Finally, incubation with okadaic acid induced significant apoptosis in HuH-7, Saos-2, Cos-7, and HeLa cells. Coadministration of UDCA with each of the apoptosis-inducing agents was associated with a 50-100% inhibition of apoptotic changes (P Ͻ 0.001) in all the cell types. Also, UDCA reduced the mitochondrial membrane permeability transition (MPT) in isolated mitochondria associated with both DCA and phenylarsine oxide by Ͼ 40 and 50%, respectively (P Ͻ 0.001). FACS ® analysis revealed that the apoptosis-inducing agents decreased the mitochondrial transmembrane potential and increased reactive oxygen species production (P Ͻ 0.05). Coadministration of UDCA was associated with significant prevention of mitochondrial membrane alterations in all cell types. The results suggest that UDCA plays a central role in modulating the apoptotic threshold in both hepatocytes and nonliver cells, and inhibition of MPT is at least one pathway by which UDCA protects against apoptosis.

Non-apoptotic ferroptosis is of clinical importance because it offers a solution to the inevitable biocarriers of traditional apoptotic therapeutic means. Inspired by industrial electro-Fenton technology featured with electrochemical iron cycling, we construct ferrous-supply-regeneration nanoengineering to intervene tumorous iron metabolism for enhanced ferroptosis. Fe 3+ ion and naturally derived tannic acid (TA) spontaneously form a network-like corona onto sorafenib (SRF) nanocores. The formed SRF@Fe III TA nanoparticles can respond to a lysosomal acid environment with corona dissociation, permitting SRF release to inhibit GPX4 enzyme for ferroptosis initiation. TA is arranged to chemically reduce the liberated and the ferroptosis-generated Fe 3+ to Fe 2+ , offering iron redox cycling to, thus, effectively produce lipid peroxide required in ferroptosis. Sustained Fe 2+ supply leads to long-term cytotoxicity, which is identified to be specific to H 2 O 2 -overloaded cancer cells but minimal in normal cells. SRF@Fe III TA-mediated cell death proves to follow the ferroptosis pathway and strongly inhibits tumor proliferation. Moreover, SRF@Fe III TA provides a powerful platform capable of versatile integration between apoptosis and non-apoptosis means. Typically, photosensitizer-adsorbed SRF@Fe III TA demonstrates rapid tumor imaging owing to the acid-responsive fluorescence recovery. Together with ferroptosis, imaging-guided photodynamic therapy induces complete tumor elimination. This study offers ideas about how to advance anticancer ferroptosis through rational material design.

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Background: The hydrophilic bile salt ursodeoxycholate (UDCA) inhibits injury by hydrophobic bile acids and is used to treat cholestatic liver diseases. Interestingly, hepatocyte cell death from bile acid-induced toxicity occurs more frequently from apoptosis than from necrosis. However, both processes appear to involve the mitochondrial membrane permeability transition (MPT). In this study, we determined the inhibitory effect of UDCA on deoxycholic acid (DCA)-induced MPT in isolated mitochondria by measuring changes in transmembrane potential (APm) and production of reactive oxygen species (ROS). In addition, we examined the expression of apoptosis-associated proteins in mitochondria isolated from livers of bile acid-fed animals. Materials and Methods: Adult male rats were maintained on standard diet supplemented with DCA and/or UDCA for 10 days. Mitochondria were isolated from livers by sucrose/percoll gradient centrifugation and MPT was measured using spectrophotometric and fluorimetric assays. APm and ROS generation were determined by FACScan analysis. Cytoplasmic and mitochondrial protein abundance were determined by Western blot analysis.Results: DCA increased mitochondrial swelling 25-fold over controls (p < 0.001); UDCA reduced the swelling by >40% (p < 0.001). Similarly, UDCA inhibited DCAmediated release of calcein-loaded mitochondria by 50% (p < 0.001). APm was significantly decreased in mitochondria incubated with DCA but not with UDCA. ATm disruption was followed closely by increased superoxide anion and peroxides production (p < 0.01). Coincubation of mitochondria with UDCA significantly inhibited the changes associated with DCA (p < 0.05). In vivo, DCA feeding was associated with a 4.5-fold increase in mitochondria-associated Bax protein levels (p < 0.001); combination feeding with UDCA almost totally inhibited this increase (p < 0.001). Conclusion: UDCA significantly reduces DCA-induced disruption of ATm, ROS production, and Bax protein abundance in mitochondria, suggesting both shortand long-term mechanisms in preventing MPT. The results suggest a possible role for UDCA as a therapeutic agent in the treatment of both hepatic and nonhepatic diseases associated with high levels of apoptosis.

The hydrophilic bile salt ursodeoxycholic acid (UDCA) is a potent inhibitor of apoptosis. In this paper, we further characterize the mechanism by which UDCA inhibits apoptosis induced by deoxycholic acid, okadaic acid and transforming growth factor b1 in primary rat hepatocytes. Our data indicate that coincubation of cells with UDCA and each of the apoptosis-inducing agents was associated with an approximately 80% inhibition of nuclear fragmentation (P50.001). Moreover, UDCA prevented mitochondrial release of cytochrome c into the cytoplasm by 70 ± 75% (P50.001), thereby, inhibiting subsequent activation of DEVD-specific caspases and cleavage of poly(ADP-ribose) polymerase. Each of the apoptosis-inducing agents decreased mitochondrial transmembrane potential and increased mitochondrial-associated Bax protein levels. Coincubation with UDCA was associated with significant inhibition of these mitochondrial membrane alterations. The results suggest that the mechanism by which UDCA inhibits apoptosis involves an interplay of events in which both depolarization and channel-forming activity of the mitochondrial membrane are inhibited.