Ligands for peroxisome proliferator-activated receptor gamma, such as the thiazolidinedione class of antidiabetic drugs and 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), modulate various processes in atherogenesis. In search of cells that generate prostaglandin D(2) (PGD(2)), the metabolic precursor of 15d-PGJ(2), we identified PGD(2) from culture medium of endothelial cells. To study how PGD(2) production is regulated in endothelial cells, we investigated the role of fluid shear stress in the metabolism of PGD(2). Endothelial cells expressed the mRNA for the lipocalin-type PGD(2) synthase (L-PGDS) both in vitro and in vivo. Loading laminar shear stress using a parallel-plate flow chamber markedly enhanced the gene expression of L-PGDS, with the maximal effect being obtained at 15 to 30 dyne/cm(2). The expression began to increase within 6 hours after loading shear stress and reached the maximal level at 18 to 24 hours. In contrast, shear stress did not alter the expression levels of PGI(2) synthase and thromboxane A(2) synthase. In parallel with the increase in the expression level of L-PGDS, endothelial cells released PGD(2) and 15d-PGJ(2) into culture medium. These results demonstrate that shear stress promotes PGD(2) production by stimulating L-PGDS expression and suggest the possibility that a peroxisome proliferator-activated receptor gamma ligand is produced in vascular wall in response to blood flow.

During a survey of the prevalence of virulent Rhodococcus equi at horse-breeding farms by plasmid and protein profiles, cryptic plasmids of various sizes were found in 66 (3.8%) of 1,725 isolates from feces of horses and 129 (5.9%) of 2,200 isolates from soil. Twenty-two isolates, which contained cryptic plasmids of different sizes, were found by plasmid profiles, and their protein profiles and mouse pathogenicities were examined. Of the 22 isolates, 7 were virulent R. equi, contained both virulence and cryptic plasmids, and expressed 15-to 17-kDa antigens. The remaining 15 isolates were avirulent and did not express the antigens: 6 strains contained cryptic plasmids of two different sizes and 9 strains contained cryptic plasmids of various sizes. A PCR assay was developed for the rapid identification of virulence plasmids of R. equi. Oligonucleotide primers, derived from the sequence of a gene coding for the 15-to 17-kDa virulence-associated antigens of R. equi, amplified a 564-bp product from all the tested isolates harboring a virulence plasmid. This PCR product hybridized with virulence plasmid DNA in the Southern hybridization assay. Virulence plasmid-cured derivatives and all of the tested isolates harboring cryptic plasmids only were negative. The PCR is a rapid, sensitive, and specific test for the identification of virulent R. equi from environmental isolates compared with standard techniques, such as plasmid and protein profiles and the mouse pathogenicity test, and is considered to be a useful tool for epidemiological studies.

Twenty-three strains of Rhodococcus equi from independent clinical cases were analyzed for the presence of virulence plasmid DNA. Of the clinical isolates, 19 contained an 85-kb plasmid and the remaining 4 contained a 90-kb plasmid. All of the isolates expressed 15to 17-kDa antigens and were virulent in mice. Restriction enzyme and Southern blot analyses showed large regions of DNA homology between the 85-and 90-kb virulence plasmids. It was concluded tentatively that there are at least two virulence plasmids in R. equi and that they have a common origin.

To examine whether the bradykinin-nitric oxide (NO) pathway directly participates in the antihypertrophic property of angiotensin-converting enzyme (ACE) inhibitors in congestive heart failure, the effects of bradykinin were studied in rat cultured heart cells. Bradykinin (0.1, 1 nM) prevented the phenylephrine-induced increase in protein/DNA content, an index of hypertrophy of heart cells, and amplified the nitrite/nitrate content in the medium. Perindoprilat (1 μM), an ACE inhibitor, also restrained the progression of cardiac hypertrophy and augmented NO release. These effects of perindoprilat were abolished by HOE-140 (kinin B2 antagonist), N ω-nitro-l-arginine (NO synthase inhibitor), and methylene blue (guanylate cyclase inhibitor). Furthermore, there was a significant correlation between protein/DNA content and nitrite/nitrate content. These results indicate that bradykinin inhibits the progression of cardiac hypertrophy due to the increase in NO release and that perindoprilat produces beneficial effects on cardiac hypertrophy by stimulating the bradykinin-NO pathway.