Effect of inducible expressed human cytomegalovirus immediate early 86 protein on cell apoptosis

Mechanism of curcumin resistance to human cytomegalovirus in HELF cells

BACKGROUND

We have previously shown that curcumin exhibited an outstanding anti-HCMV effect in vitro and in vivo. However, the underlying mechanism for the anti-HCMV effect remains unclear.

METHODS

Levels of IL-6 and TNF-α cytokine secretions in HELF cells were determined by enzyme-linked immunosorbent assay (ELISA); cell cycles were assessed by flow cytometry; ie and ul83 gene expressions were evaluated using reverse transcriptase real-time quantitative PCR; HCMV IE and UL83 antigen expressions were studied using immunofluorescence staining assay and western blot.

RESULTS

Curcumin reduced HCMV immediate early antigen (IEA) and UL83A expressions and IL-6, and TNF-α secretions and recovered cell proliferation to normal level in HCMV infected HELF cells.

CONCLUSIONS

Curcumin anti-HCMV effect may possibly be that curcumin concurrently alters host cell microenviroment and inhibits the HCMV antigen expressions. These findings may provide a basic understanding of the curcumin anti-HCMV effect and a novel strategy for further development of curcumin anti-HCMV treatment.

Human cytomegalovirus inhibits apoptosis by regulating the activating transcription factor 5 signaling pathway in human malignant glioma cells

The activating transcription factor 5 (ATF5), also termed ATFx, is a member of the ATF/cAMP response element-binding protein (CREB) family of basic zipper proteins. ATF5 is an anti-apoptotic protein that is highly expressed in malignant glioma and is essential for glioma cell survival. Accumulating evidence indicates that human malignant gliomas are universally infected with human cytomegalovirus (HCMV). Recent studies have shown that HCMV may be resistant to the induction of apoptosis by disrupting cellular pathways in glioblastoma. To investigate the potential anti-apoptotic function of HCMV in glioma, malignant U87 glioma cells were infected with HCMV. The present study showed that HCMV infection suppressed apoptosis in glioblastoma U87 cells by regulating the expression of ATF5. Furthermore, in glioblastoma U87 cells, HCMV infection induced cellular proliferation in parallel with an increase in the expression level of ATF5 and B-cell lymphoma/leukemia-2 to Bcl-2-associated X protein ratio. Loss of ATF5 function was achieved using a dominant-negative form of ATF5 in U87 cells, whereby cells appeared to grow marginally following HCMV infection when compared with the control. However, the anti-apoptotic ability was appeared to decline in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. These results indicate that ATF5 signaling pathways may be important in the anti-apoptotic activity of HCMV-infected glioblastoma cells; therefore, the anti-apoptotic molecular mechanisms of HCMV in human glioblastoma cells were investigated in the current study. Prevention of HCMV infection may present a potential and promising approach for the treatment of malignant gliomas.

The human cytomegalovirus major immediate-early proteins as antagonists of intrinsic and innate antiviral host responses

The major immediate-early (IE) gene of human cytomegalovirus (CMV) is believed to have a decisive role in acute infection and its activity is an important indicator of viral reactivation from latency. Although a variety of gene products are expressed from this region, the 72-kDa IE1 and the 86-kDa IE2 nuclear phosphoproteins are the most abundant and important. Both proteins have long been recognized as promiscuous transcriptional regulators. More recently, a critical role of the IE1 and IE2 proteins in counteracting non-adaptive host cell defense mechanisms has been revealed. In this review we will briefly summarize the available literature on IE1- and IE2-dependent mechanisms contributing to CMV evasion from intrinsic and innate immune responses.