The important anti-apoptotic role and its regulation mechanism of PTTG1 in UV-induced apoptosis

PTTG1 alleviates acute alcoholic liver injury by inhibiting endoplasmic reticulum stress-induced hepatocyte pyroptosis

BACKGROUND & AIMS

Heavy drinking is a primary cause of alcoholic liver injury (ALI). Pituitary tumour transforming gene 1 (PTTG1) is involved in the occurrence and development of hepatocellular carcinoma (HCC), which is a well-known inflammation-related cancer with various aetiologies, including alcohol consumption. However, the role of PTTG1 in alcohol-induced liver injury and inflammation is not clear.

METHODS

Blood samples were collected from patients with acute alcohol intoxication (n = 20) and healthy controls (n = 20). PTTG1 knockout (KO) mice and PTTG1 transgenic (TG) mice were given a single gavage of alcohol (5 g/kg, 50%) to construct the alcohol-induced liver injury.

RESULTS

We found that serum PTTG1 levels were downregulated in acute ALI patients. In addition, acute alcohol administration significantly reduced PTTG1 levels in the serum and liver of mice. Compared to wild-type mice, PTTG1 KO mice had more serious liver injury, which was accompanied by worsened hepatic endoplasmic reticulum (ER) stress and hepatocyte pyroptosis induced by alcohol. Similarly, PTTG1 deficiency exacerbated alcohol-induced cell death in primary mouse hepatocytes and LO2 cells, by increasing hepatic ER stress and pyroptosis. Importantly, TUDCA, an ER stress inhibitor, could blocked alcohol-induced hepatic pyroptosis in PTTG1 knockdown LO2 cells. Finally, overexpression of PTTG1 substantially attenuated alcohol-induced liver injury by reducing ER stress and hepatic pyroptosis in mice.

CONCLUSIONS

We demonstrated that PTTG1 participates in ALI and has a protective effect against alcohol-induced hepatic ER stress and pyroptosis.

Global gene expression in granulosa cells of growing, plateau and atretic dominant follicles in cattle

BACKGROUND

The physiological state of the dominant follicle is important as it may be linked to the competence of the oocyte within. The objective of this study was to analyze, by transcriptomic analysis, the changes occurring in granulosa cells from dominant follicles at different phases of follicular growth.

METHODS

Granulosa cells were collected from slaughterhouse dairy cattle follicles with a diameter greater than 9 mm, and were classified at different phases of follicle growth based on flow cytometry profiles of DNA content after staining with propidium iodide. Three phases were identified based on the proportion of cells in -G1 (less than 2n DNA), G0-G1 (2n DNA) or S-M (more than 2n DNA) and follicles were thus allocated to the growing, plateau or atresia group. Between group analysis (BGA) showed clear segregation of the three groups, and the groups were contrasted against each other in a loop design to identify differently expressed genes. Ingenuity Pathway Analysis (IPA) was used to identify the functions and upstream regulators associated with the observed differently expressed genes.

RESULTS

Major differences were observed between the growth phases. Granulosa cells from follicles in the plateau phase had increased expression of TYRO3 and downregulation of JAM2 compared to growing follicles, supporting the idea of a shift from proliferation to differentiation. On the other hand, genes regulating the response to oxidative stress (VNN1) and angiogenesis (ANGPT2) were upregulated in granulosa cells from atretic follicles. While the predicted activated functions in cells at the plateau stage compared to cells at the growing stage included synthesis and transport of molecules, the predictions for atretic follicles relative to plateau ones included an increase in apoptosis and cell death.

CONCLUSION

Consistent with previous studies, these observations allowed us to match the presence of specific gene transcripts to a particular physiological status and consequently to classify follicles. The results also demonstrated that the plateau phase is not a simple 'in between' status between growth and atresia, as several characteristics are unique to this stage.

RNAi-mediated knockdown of pituitary tumor- transforming gene-1 (PTTG1) suppresses the proliferation and invasive potential of PC3 human prostate cancer cells

Pituitary tumor-transforming gene-1 (PTTG1) is a proto-oncogene that promotes tumorigenesis and metastasis in numerous cell types and is overexpressed in a variety of human tumors. We have demonstrated that PTTG1 expression was up-regulated in both human prostate cancer specimens and prostate cancer cell lines. For a more direct assessment of the function of PTTG1 in prostate tumorigenesis, RNAi-mediated knockdown was used to selectively decrease PTTG1 expression in PC3 human prostate tumor cells. After three weeks of selection, colonies stably transfected with PTTG1-targeted RNAi (the knockdown PC3 cell line) or empty vector (the control PC3 cell line) were selected and expanded to investigate the role of PTTG1 expression in PC3 cell growth and invasion. Cell proliferation rate was significantly slower (28%) in the PTTG1 knockdown line after 6 days of growth as indicated by an MTT cell viability assay (P < 0.05). Similarly, a soft agar colony formation assay revealed significantly fewer (66.7%) PTTG1 knockdown PC3 cell colonies than control colonies after three weeks of growth. In addition, PTTG1 knockdown resulted in cell cycle arrest at G1 as indicated by fluorescence-activated cell sorting. The PTTG1 knockdown PC3 cell line also exhibited significantly reduced migration through Matrigel in a transwell assay of invasive potential, and down-regulation of PTTG1 could lead to increased sensitivity of these prostate cancer cells to a commonly used anticancer drug, taxol. Thus, PTTG1 expression is crucial for PC3 cell proliferation and invasion, and could be a promising new target for prostate cancer therapy.

Lipopolysaccharide-induced apoptosis in transformed bovine brain endothelial cells and human dermal microvessel endothelial cells: the role of JNK

Stimulation of transformed bovine brain endothelial cells (TBBEC) with LPS leads to apoptosis while human microvessel endothelial cells (HMEC) need the presence of cycloheximide (CHX) with LPS to induce apoptosis. To investigate the molecular mechanism of LPS-induced apoptosis in HMEC or TBBEC, we analyzed the involvement of MAPK and PI3K in TBBEC and HMEC. LPS-induced apoptosis in TBBEC was hallmarked by the activation of caspase 3, caspase 6, and caspase 8 after the stimulation of LPS, followed by poly(ADP-ribose) polymerase cleavage and lactate dehydrogenase release. We also observed DNA cleavage determined by TUNEL staining in TBBEC treated with LPS. Herbimycin A, a tyrosine kinase inhibitor, and SP600125, a JNK inhibitor, suppressed the activation of caspases and lactate dehydrogenase release. Moreover, a PI3K inhibitor (LY294002) suppressed activation of caspases and combined treatment with both SP600125 and LY294002 completely inhibited the activation of caspases. These results suggest that the JNK signaling pathway through the tyrosine kinase and PI3K pathways is involved in the induction of apoptosis in LPS-treated TBBEC. On the other hand, we observed sustained JNK activation in HMEC treated with LPS and CHX, and neither ERK1/2 nor AKT were activated. The addition of SP600125 suppressed phosphorylation of JNK and the activation of caspase 3 in HMEC treated with LPS and CHX. These results suggest that JNK plays an important role in the induction of apoptosis in endothelial cells.