Giardia duodenalis Induces Apoptosis in Intestinal Epithelial Cells via Reactive Oxygen Species-Mediated Mitochondrial Pathway In Vitro

Abstract

The intestinal protozoan parasite, Giardia duodenalis, infects a large number of people in the world annually. Giardia infection has been considered a negative effect on intestinal epithelial cell growth, while the underlying mechanisms remain to be explored. Here we evaluated reactive oxygen species (ROS) production and apoptotic events in Giardia trophozoites-stimulated Caco-2 cells via fluorescence microscopy, transmission electron microscopy, flow cytometry, western blot, and cell counting kit-8 analyses. The results showed that Giardia trophozoite treatment could induce lactate dehydrogenase release and Caco-2 cell apoptosis. The ROS levels were increased post treatment. The observed typical characteristics of mitochondria damage include significant swelling and degeneration of matrix and cristae. After trophozoite treatment, the level of Bax protein expression was increased, while Bcl-2 protein decreased. Trophozoite stimulation also led to reduction of mitochondrial membrane potential and release of cytochrome c from the mitochondria to the cytoplasm, and this process was accompanied by activation of caspase-9 and caspase-3 and poly (ADP-ribose) polymerase 1 cleavage. Pretreatment with N-acetyl-L-cysteine, a ROS inhibitor, reversed G. duodenalis-induced Caco-2 cell apoptosis. Taken together, we indicated that G. duodenalis could induce Caco-2 cell apoptosis through a ROS- and mitochondria-mediated caspase-dependent pathway. This study furthers our understanding of the cellular mechanism of the interaction between Giardia trophozoites and host cells.

Uncovering the Genetic Diversity of Giardia Isolates from Outbreaks in New Zealand

“…As stated in the introduction, the clinical manifestation of giardiasis can differ between individuals. Further work needs to be done to ascertain if there is a link between (sub)assemblage and clinical presentation, however recent advances in the in vitro culture of Giardia (Liu et al, 2020) have the potential to address this. So, the ability to capture the genetic diversity within samples from cases of giardiasis and link them to the symptoms displayed by the patient could greatly advance our understanding of the disease mechanisms of this parasite.…”

Mucosal Defense Against Giardia at the Intestinal Epithelial Cell Interface

“…It was shown that the NF and S2 strains of G. duodenalis , but not WB or PB, were able to induce apoptosis in IECs, and these effects were abolished by pre-treating human duodenal epithelial monolayers with a caspase-3 inhibitor, Z-DEVD-FMK ( 50 ). Further studies have indicated the importance of caspases, including caspase 3 ( 50 , 52 , 70 , 71 ) and caspase 9 ( 72 ) in mediating Giardia -induced apoptosis in IECs. Giardia infections facilitate apoptosis in IECs by the downregulation of anti-apoptotic proteins, including Bcl-2, and the up-regulation of the pro-apoptotic proteins, including Bax, suggesting a potential contribution of caspase-dependent apoptosis signaling pathways in the induction of pathogenesis during giardiasis ( 51 , 70 , 73 ).…”

Mitochondrial Voltage-Dependent Anion Channel 1–Hexokinase-II Complex-Targeted Strategy for Melanoma Inhibition Using Designed Multiblock Peptide Amphiphiles

“…[6][7][8][9][10] Mitochondria-mediated apoptosis can be activated also via targeting the B-cell lymphoma-2 (Bcl-2) family proteins using small molecules or peptidomimetic-based strategies, [11][12][13] hexokinase (HK) inhibitors, 14 VDAC1 targeting drugs, [15][16][17][18][19] growth factor withdrawal, increased production of reactive oxygen species (ROS), hypoxia or DNA damage. [20][21] VDAC1, located at the outer mitochondrial membrane (OMM), is a multi-functional barrel protein. 17,22 It regulates mitochondrial energy metabolism by transporting various ions, active substances, and metabolites into and out of the mitochondria.…”