Modulation of synovial fibroblast plasminogen activator and plasminogen activator inhibitor production by protein kinase C

Effects of humic acid on the viability and coagulant properties of human umbilical vein endothelial cells

We have previously shown that humic acid (well-water humic acid, HA, and synthetic humic acid, SHA) enhances cell surface expression of tissue factor (TF). Here we report that incubation of human umbilical vein endothelial cells (HUVEC) for 2 hr with HA or SHA cause a rapid rise in TF mRNA levels, as shown by Northern blot analysis. To understand the cytotoxic and fibrinolytic effects of HA and SHA on cultured HUVEC, the cells treated with varying concentrations of HA and SHA for various periods of time. Both HA and SHA (10-200 micrograms/ml) inhibited the viability of subconfluent HUVEC, cultured in the presence or absence of 20% FBS (Fetal Bovine serum) in the culture medium, in a dose-dependent manner. Both HA and SHA induced surface changes in the HUVEC as revealed by scanning electron micrography (SEM). However, protocatechuic acid, the monomer of SHA, did not significantly inhibit cell growth, and showed a cytotoxic effect only at 200 micrograms/ml. Furthermore both HA and SHA stimulated HUVEC to produce plasminogen activator inhibitor (PAI-1) and tissue plasminogen activator (t-PA) in a dose and time dependent fashion; the amount of PAI-1 produced was found to exceed that of t-PA. The monomer of SHA did not have this stimulatory effect. These results distinctly suggest that in addition to the inhibition of viability HA is involved in TF induction and PAI-1 synthesis in HUVEC and these may be some of the plausible mechanisms underlying the thrombotic disorders in Blackfoot disease.

Potential mechanisms for sex ratio adjustment in mammals and birds

Sex ratio skews in relation to a variety of environmental or parental conditions have frequently been reported among mammals and, though less commonly, among birds. However, the adaptive significance of such sex ratio variation remains unclear. This has, in part, been attributed to the absence of a low-cost physiological mechanism for sex ratio manipulation by the parent. It is shown here that several recent findings in reproductive biology are suggestive of many potential pathways by which gonadotropins and steroid hormones could interfere with the sex ratio at birth. And these hormone levels are well-known to be influenced by many parameters which have been invoked in correlating with offspring sex ratios. Hence, it is argued that the significant, but inconsistent sex ratio biases reported in mammalian and avian populations are coherent with current knowledge on reproductive physiology in those species. However, whether such variations can be viewed at as a consequence of physiological constraint or as adaptive sex ratio adjustment, has still to be determined.

Localization of urokinase-type plasminogen activator, plasminogen activator inhibitor-1, 2 and plasminogen in colon cancer

We examined the localization of urokinase-type plasminogen activator (u-PA), plasminogen activator inhibitors (PAI-1 and PAI-2) and plasminogen (plg) in 26 cases of colon cancer by immunohistochemical staining. The u-PA antigen was detected in the cytoplasm of cancer cells (18/26) and stromal cells adjacent to cancer tissues (9/26). The localization of u-PA mRNA examined by in situ hybridization was consistent with that of u-PA antigen. The PAI-1 antigen was detected in fibroblasts and endothelial cells (22/26), while PAI-2 antigen was found in cancer cells (20/26). The plg antigen was seen in the extracellular matrix of the cancer stroma. The u-PA expression in cancer cells was significantly more frequently detected in cases with lymph node metastasis than in cases without metastasis. In either PAI-1- or PAI-2-expressing cases, lymph node metastasis seemed to be restrained. These findings indicate that cancer cells themselves produce u-PA, and suggest that u-PA converts plg into plasmin, which dissolves the extracellular matrix surrounding cancer cells, resulting in cancer invasion and metastasis. PAI-1 and PAI-2 may have inhibitory actions on cancer invasion and metastasis mediated by u-PA.

A common response element mediates differential effects of phorbol esters and forskolin on type-1 plasminogen activator inhibitor gene expression in human breast carcinoma cells

We have characterized regulation of type-1 plasminogen activator inhibitor (PAI-1) gene expression by phorbol 12-myristate 13-acetate (PMA) and the cAMP-inducing agent forskolin in the human breast carcinoma cell line MCF-7. PMA caused a strong induction of PAI-1, while forskolin suppressed the PMA response. Transfection experiments with fusion genes showed that sequences mediating PMA induction as well as forskolin suppression were present between base pairs -100 and -30 of the 5'-flanking region of the PAI-1 gene. The region was found to contain two Sp1 binding sites. A proximal sequence in the region, TGAGTTCA (P box), with sequence similarity to phorbol ester response elements (TRE) as well as to cAMP response elements (CRE), bound a low-abundance, as yet unidentified nuclear protein in MCF-7 cells. This sequence had a higher affinity to purified c-jun homodimer than to c-jun/c-fos heterodimer in MCF-7 nuclear extracts; it had no affinity to the proteins binding to CRE consensus sequences in these extracts. A distal TRE-like sequence, TGAGTGG (D box), had a weak affinity to c-jun/c-fos heterodimer and c-jun homodimer; binding of proteins to this sequence was facilitated by binding of proteins to the P box. Both the P box and the D box were necessary for PMA responsiveness, suggesting a cooperativity between the two binding sites. A mutation of the P box removing the CRE similarity abolished the forskolin suppression of the PMA response. We propose that the protein kinase C and the protein kinase A signal-transduction pathways, with opposite effects on PAI-1 gene expression converge by modulating differently P-box-binding proteins.