PubMed · 9741213
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P Rivera, J V López Mut, J R García Novales, S Pamos, M Luján. 1998. [Acute ischemic proctocolitis].. https://pubmed.ncbi.nlm.nih.gov/9741213/
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Matrix metalloproteinase-19 (MMP-19), originally isolated as an autoantigen from the synovium of a patient suffering from rheumatoid arthritis (RA), is expressed in smooth muscle cells of the tunica media of large blood vessels of an RA patient, but not in the endothelial cell layer. By contrast, in acutely inflamed tissue, synovial capillaries strongly express MMP-19 in the cytoplasm, as shown by immunofluorescence of cryostat sections. In MMP-19-producing capillaries the beta3 integrin chain was found at the endothelial cell surface, as was the vascular endothelial cell growth factor receptor-2 (KDR). The specific tissue inhibitor of metalloproteinases TIMP-1 was absent or faintly stained in MMP-19-expressing capillaries, whereas TIMP-1, but not TIMP-2, was strongly expressed in large vessels and in MMP-19-negative capillaries of RA synovia. In the spontaneously transformed human umbilical vein endothelial cell line ECV304 neither MMP-19 transcripts nor protein could be detected. By contrast, primary cultures of human endothelial cells of either dermal or adipose tissue origin produced MMP-19 mRNA and protein. The results strongly suggest the regulated induction of matrix metalloproteinase-19 in capillary endothelial cells during acute inflammation and hint at a role of MMP-19 in angiogenesis.
Before de novo synthesized von Willebrand factor (vWF) leaves the endothelial cell, it undergoes endoproteolytic cleavage of its propeptide (vW antigen II). The processed vWF and propeptide are either released constitutively or, following activation of the endothelium, released through the regulated pathway. In a recent study (Borchiellini et al, Blood 88:2951, 1996), we showed that the half-life of mature vWF and of its propeptide differ fourfold to fivefold. We postulated that the molar ratio of the propeptide to mature vWF could serve as a tool to assess the extent of endothelial cell activation under physiologic and clinical conditions. To test this hypothesis, we measured mature vWF and propeptide in patients with documented acute and chronic vascular disease, including patients with thrombotic thrombocytopenic purpura (TTP), acute septicemia, and diabetes mellitus. These data were compared with experimental conditions in healthy subjects in which perturbation of the endothelium was simulated by physical exercise or by administration of 1-deamino-8-D-arginine vasopressin (DDAVP) or endotoxin. In all individuals of the latter study group, both vWF and propeptide levels were elevated during the acute phase of the experimentally induced vascular perturbation; at later time points after stimulation, only vWF levels remained elevated. In patients with sepsis and TTP, both vWF and propeptide were elevated several-fold. Thus, this pattern can readily be explained in terms of acute perturbation of the endothelium. In contrast, in patients with diabetes mellitus propeptide levels were only slightly elevated, whereas vWF levels were elevated twofold to threefold. This pattern is a typical feature of chronic, low-grade activation of the endothelium. These observations support our hypothesis that measurement of both propeptide and vWF levels allows to discriminate between chronic and acute phases of endothelial cell activation in vivo. Measurement of only vWF is less indicative in this respect.
Rearrangements involving the MLL gene at chromosome 11q23 are associated with leukemia and are present in up to 70% of infant leukemias. Loss of heterozygosity (LOH) has been shown for anonymous polymorphic markers at 11q23 in adult leukemias. To study LOH at the MLL locus, we have identified two new polymorphic microsatellite markers: a GAA repeat (mllGAAn) in intron 6 of the MLL gene and a GA (mllGAn) repeat in the 5' flanking region of the gene, approximately 2 kb upstream of the translation initiation codon. The heterozygosity index of mllGAAn is 0.54, which renders it useful for analyzing LOH. We screened two groups of leukemia patients to study LOH at the mllGAAn marker. Group A (n = 18) was selected on the basis of presentation before 18 months. Cytogenetic and reverse transcription-polymerase chain reaction analysis showed that 9 of these 18 children had translocations involving MLL. No LOH was observed. Group B (n = 36) were randomly selected children who had presented with leukemia between 1993 and 1994. Cytogenetic analysis of this group showed a variety of different chromosomal abnormalities. LOH was shown in 9 of 20 individuals (45%) who were informative. Microsatellite instability (MSI) was demonstrated in 1 of 18 individuals in group A and 5 of 36 individuals (13.9%) in group B. MSI and LOH were observed simultaneously in three individuals. Loss of an allele was confirmed in one individual by fluorescence in situ hybridization. Individuals with MSI or LOH at mllGAAn were selected for analysis at anonymous polymorphic markers D11S1364 and D11S1356, which flank the MLL gene. No LOH or MSI was observed at these markers in those individuals who were informative. These results show that LOH at the MLL gene locus is a common event during leukemogenesis. Furthermore, the presence of MSI at this locus suggests that the region is a hotspot for genetic instability.