Apparent suppression of MMP-9 activity by GD1a as determined by gelatin zymography

Effects of electromagnetic pulse exposure on gelatinase of blood-brain barrier in vitro

The biological effects of electromagnetic pulse (EMP) on the brain have been focused on for years. It was reported that gelatinase played an important role in maintaining brain function through regulating permeability in the blood-brain barrier (BBB). To investigate the effects of EMP on gelatinase of BBB, an in vitro BBB model was established using primary cultured rat brain microvascular endothelial cells (BMVEC), astrocytes and half-contact culture of these cells in a transwell chamber. Cultured supernatant and cells were collected at different time points after exposure to EMP (peak intensity 400 kV/m, rise time 10 ns, pulse width 350 ns, 0.5 pps and 200 pulses). Protein levels of cellular gelatinase MMP-2 and MMP-9, and endogenous inhibitor TIMP-1 and TIMP-2 were detected by Western blot. The activity of gelatinase in culture supernatant was detected by gelatin zymography. It was found that compared with the sham-exposed group, the protein level of MMP-2 was significantly increased at 6 h (p < 0.05), and the protein level of its endogenous inhibitor TIMP-2 did not change after EMP exposure. In addition, the protein levels of MMP-9 and its endogenous inhibitor TIMP-1 did not change after EMP exposure. Gelatin zymography results showed that the activity of MMP-2 in the inner pool and the outer pool of the transwell chamber was significantly increased at 6 h after EMP exposure compared with that of the sham group. These results suggested that EMP exposure could affect the expression and activity of MMP-2 in the BBB model.

Expression and large-scale production of human tissue plasminogen activator (t-PA) in transgenic tobacco plants using different signal peptides

An attempt was made to assess the expression level and targeting of a human protein entitled recombinant tissue plasminogen activator (rt-PA) through accumulation in three cellular compartments including the endoplasmic reticulum and cytosolic and apoplastic spaces in transgenic tobacco plants. In this context, three chimeric constructs pBI-SP-tPA, pBI-tPA-KDEL, and pBI-Ext-tPA were employed and transferred into the tobacco plants through a popular transformation-based system called Agrobacterium tumefaciens. As an initial screening system, the incorporation of the rt-PA gene in the genomic DNA of tobacco transgenic plants and the possible existence of the rt-PA-specific transcript in the total RNAs of transgenic plant leaves were confirmed via PCR and reverse transcription (RT)-PCR, respectively. Southern blot analysis, in addition, was used to determine the copy number of the corresponding gene (i.e., t-PA) transformed into the each transgenic plant; one or more copies were detected regarding transformants derived from all three abovementioned constructs. According to the enzyme-linked immunosorbent assay, the mean values of t-PA expression were calculated as 0.50, 0.68, and 0.69 μg/mg of the total soluble protein when a collection containing 30 transgenic plants transformed with pBI-SP-tPA, pBI-tPA-KDEL, and pBI-Ext-tPA was taken into account, respectively. The zymography assay was lastly performed and concluded the expression of the properly folded rt-PA in this expression system. Our results, altogether, revealed that tobacco plants could be utilized as a bioreactor system for the large-scale production of enzymatically active t-PA and presumably other therapeutic recombinant proteins in large quantities.

Ganglioside GD1a suppresses TNFalpha expression via Pkn1 at the transcriptional level in mouse osteosarcoma-derived FBJ cells

Ganglioside GD1a has been reported to suppress metastasis [S. Hyuga, S. Yamagata, Y. Takatsu, M. Hyuga, H. Nakanishi, K. Furukawa, T. Yamagata, Suppression of FBJ-LL cell adhesion to vitronectin by ganglioside GD1a and loss of metastatic capacity, International J. Cancer. 83 (1999) 685-691.] and MMP-9 production in mouse osteosarcoma FBJ cells [D. Hu, Z. Man, P. Wang, X. Tan, X. Wang, S. Takaku, S. Hyuga, T. Sato, X. Yao, S. Yamagata, T. Yamagata, Ganglioside GD1a negatively regulates MMP9 expression in mouse FBJ cell lines at the transcriptional level, Connect. Tissue Res. 48 (2007) 198-205.]. In the present study, TNFalpha increased cell motility and MMP-9 and TNFalpha expression at the transcriptional level. TNFalpha expression was found to be inversely proportional to GD1a content in the FBJ-cell variants. The addition of exogenous GD1a to FBJ-LL cells suppressed TNFalpha expression, and treatment of FBJ-S1 cells with D-PDMP (glucosylceramide synthesis inhibitor) led to an increase in TNFalpha, indicating that TNFalpha is negatively regulated by GD1a in FBJ cells. SiRNA of Pkn1, a Rho-GTPase effecter protein kinase, suppressed TNFalpha levels as well as Pkn1 expression, suggesting that Pkn1 is involved in TNFalpha signaling. Treatment of Pkn1-silenced FBJ-LL cells with GD1a failed to suppress TNFalpha expression, demonstrating that GD1a signals that lead to TNFalpha suppression are transduced through Pkn1.

Ganglioside GD1a negatively regulates matrix metalloproteinase-9 expression in mouse FBJ cell lines at the transcriptional level

Mouse FBJ virus-induced osteosarcoma FBJ-S1 cells rich in GD1a are not readily metastatic, whereas FBJ-LL cells with low levels of GD1a are highly metastatic. GD1a was previously shown to suppress metastasis of mouse FBJ cells and to upregulate caveolin-1 and stromal interaction molecule 1 expression. The present study demonstrates that matrix metalloproteinase-9 (MMP-9) expression renders FBJ-LL cells invasive. MMP-9 is inversely regulated by GD1a, based upon four observations: MMP-9 mRNA content was 5 times higher in FBJ-LL cells than FBJ-S1 cells; a GD1a-re-expressing FBJ-LL cell variant produced through beta1,4GalNAcT-1 cDNA transfection expressed lower levels of MMP-9; exogenous addition of GD1a to FBJ-LL cells decreased MMP-9 production in a dose- and time-dependent manner; and treatment of GD1a-rich cells with D-PDMP or siRNA targeting St3gal2 decreased GD1a expression, but augmented MMP-9 expression. This is the first report demonstrating that GD1a negatively regulates expression of MMP-9 at the transcriptional level.