Roles Of BNIPL-2in Hepatic Stellate Cells And Molecular Mechanism Of Apoptosis Promoted By BNIPL-2in Cancer Cells

Liver fibrosis is a kind of pathological changes as a result of chronic liver injury. In the progression of liver fibrosis, normal intrahepatic microenvironment is destroyed; the balance between hepatocytes and stromal cells is broken. Hepatic stellate cell, a kind of liver stromal cell, plays an important role in homeostasis maintaining and liver disease. Substantial evidence indicates that stellate cells may be key a element in liver fibrosis.Bcl-2/adenovirus E1B19kDa interacting protein2like2(BNIPL-2) is a novel gene identified by our laboratory. According to the previous results, BNIPL-2could promote tumor cell apoptosis and might participate in the remodeling of the cytoskeleton and cell movement. However, the biological functions of BNIPL are still unknown, and the role of BNIPL-2in human diseases has not been reported.In the present research, we compared expression levels of BNIPL-2between liver fibrosis specimens and normal liver tissues by immunohistochemical staining and real-time PCR assay. The results showed that the BNIPL-2expression was relatively high in liver fibrosis. Afterwards, we observed that the mRNA level of BNIPL-2in hepatic stellate cell (HSC) line LX-2increased in responding to a lysophosphatidic acid (LPA) treatment. To explore the biological functions of BNIPL-2in hepatic stellate cells, BNIPL-2was overexpressed in the LX-2cell line by lentiviral vector system. The In vitro experiments showed that BNIPL could induce filopodia formation and morphology changes in LX-2cells. The further study demonstrated that BNIPL was able to promote movement and contractility of LX-2cells, and its adhesion to Collagenl. Moreover, BNIPL-2overexpression lead to an enhanced sensitivity of LX-2cells to the stimulation of LPA.It has been reported that RhoA as a key regulator acts important role in actin organization, cell morphology, chemotaxis and contraction in a wide range of cells including HSCs. Our study also found that BNIPL overexpression was related to increase of RhoA activation in LX-2.In summary, our results indicate that BNIPL-2is likely to participate in the regulation of RhoA signaling pathway to influence the biological behaviorrs of hepatic Apoptosis takes place under the physiologic condition, as well as existes to a pathologic circumstance. In addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in an extensive variety of diseases, such as tumorigenesis. Apoptosis, which also named programmed cell death (PCD), is an active process that is controlled by a diverse range of cell signals. Mitochondria have also been reported to participate in apoptosis. Bcl-2family proteins as a series of important regulators of apoptosis are subdivided into two groups on the basis of their pro-or anti-apoptotic action. Bcl-2/adenovirus E1B19kDa interacting protein2like2(BNIPL-2) is one of its new members.Our results in this study discovered that the mRNA level of BNIPL-2was increased during apoptosis induced by Staurosporine (STS). Later on, BNIPL and Bcl-2were overexpressed in the HepG2cells and H460cells. After treated with STS, the apoptotic rate in BNIPL-2overexpressed cells was increased, in contrast with the reduced apoptotic rate in Bcl-2overexpressed cells.In conclusion, BNIPL-2can improve the sensitivity of tumor cells to the apoptosis inducement and it had a contrary function with Bcl-2in the process of apoptosis. Further study will be required to clarify the role of BNIPL-2in apoptosis promotion. stellate cells and provide a new clue to further elucidate the important roles of BNIPL-2involved in process of hepatic fibrosis.