Reactive Oxygen Species Depletion by Silibinin Stimulates Apoptosis-Like Death in Escherichia coli

Abstract

Silibinin is the major active component of silymarin, extracted from the medicinal plant . Silibinin has potent antibacterial activity; however, the exact mechanism underlying its activity has not been elucidated. Here, we investigated the novel mechanism of silibinin against Escherichia coli. Time-kill kinetic assay showed that silibinin possess a bactericidal effect at minimal inhibitory concentration (MIC) and higher concentrations (2- and 4-fold MIC). At the membrane, depolarization and increased intracellular Ca²⁺ levels were observed, considered as characteristics of bacterial apoptosis. Additionally, cells treated with MIC and higher concentrations showed apoptotic features like DNA fragmentation, phosphatidylserine exposure, and caspase-like protein expression. Generally, apoptotic death is closely related with ROS generation; however, silibinin did not induce ROS generation but acted as a scavenger of intracellular ROS. These results indicate that silibinin dosedependently induces bacterial apoptosis-like death, which was affected by ROS depletion, suggesting that silibinin is a potential candidate for controlling bacteria.

<p>Silibinin restores the sensitivity of cisplatin and taxol in A2780-resistant cell and reduces drug-induced hepatotoxicity</p>

“…Silibinin could take effect on both. Firstly, silibinin is a scavenger of intracellular ROS 34. It’s significantly reduced drug-induced hepatocyte line LO2 cell death and even rescued the LO2 cell proliferative ability (Figure 5).…”

Beetroot (Beta vulgaris) Extract against Salmonella Typhimurium via Apoptosis-Like Death and Its Potential for Application in Cooked Pork

“…PS, a phospholipid component, is present in the inner lobules of the plasma membrane. When cells undergo apoptosis, PS is no longer limited to the cytoplasmic side, resulting in PS externalization [ 21 ]. Therefore, we evaluated whether beetroot extract can cause PS translocation of S. Typhimurium.…”

“…Some studies reported that the depletion of ROS can affect signalling pathways and even lead to cell death [ 35 , 36 ]. In addition, one study has suggested that ROS consumption could induce ALD in E. coli [ 21 ]. To verify that the ALD of S. Typhimurium induced by beetroot extract is caused by ROS consumption, we treated S. Typhimurium with beetroot extract and hydrogen peroxide (H 2 O 2 ).…”

“…A cell death mechanism similar to cell apoptosis has been discovered in bacteria and named apoptosis-like death (ALD) [ 15 ]. As far as we know, natural products such as curcumin, chlorogenic acid, coprisin, apigenin, indole-3-carbinol, silibinin, naringin, isoquercitrin, pterostilbene, Sonchus brachyotus DC, Hypericum extract, and Portulaca oleracea L. flavonoid extract can cause bacterial ALD [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. The antibacterial mechanism of these substances through ALD are concentrated in E. coli , Staphylococcus aureus , Micrococcus luteus , and B. cereus .…”

Contribution of SOS genes to H2O2-induced apoptosis-like death in Escherichia coli

“…Bacterial cells were incubated for 2 h at 37 ℃ with H 2 O 2 , H 2 O 2 pretreated with 10 mM sodium pyruvate, H 2 O 2 pretreated with thiourea, or nor oxacin. Following incubation, DNA was extracted in an extraction solution (containing 100 mM NaCl, 10 mM Tris-Cl , 1 mM EDTA, 1 % SDS, 2 % Triton X-100, and 10 mg/mL proteinase K) as described in our previous study (Lee and Lee 2017). The 8-OHdG levels were estimated by competitive enzyme immunoassay method, using an Oxiselect Oxidative DNA Damage ELISA Kit (Cell Biolabs Inc., San Diego, CA, USA), according to the manufacturer's instructions.…”