The CXCR4/CXCR7/SDF-1 pathway contributes to the pathogenesis of Shiga toxin-associated hemolytic uremic syndrome in humans and mice.

Hemolytic uremic syndrome (HUS) is a potentially life-threatening condition. It often occurs after gastrointestinal infection with E. coli O157:H7, which produces Shiga toxins (Stx) that cause hemolytic anemia, thrombocytopenia, and renal injury. Stx-mediated changes in endothelial phenotype have been linked to the pathogenesis of HUS. Here we report our studies investigating Stx-induced changes in gene expression and their contribution to the pathogenesis of HUS. Stx function by inactivating host ribosomes but can also alter gene expression at concentrations that minimally affect global protein synthesis. Gene expression profiling of human microvascular endothelium treated with Stx implicated a role for activation of CXCR4 and CXCR7 by their shared cognate chemokine ligand (stromal cell-derived factor-1 [SDF-1]) in Stx-mediated pathophysiology. The changes in gene expression required a catalytically active Stx A subunit and were mediated by enhanced transcription and mRNA stability. Stx also enhanced the association of CXCR4, CXCR7, and SDF1 mRNAs with ribosomes. In a mouse model of Stx-mediated pathology, we noted changes in plasma and tissue content of CXCR4, CXCR7, and SDF-1 after Stx exposure. Furthermore, inhibition of the CXCR4/SDF-1 interaction decreased endothelial activation and organ injury and improved animal survival. Finally, in children infected with E. coli O157:H7, plasma SDF-1 levels were elevated in individuals who progressed to HUS. Collectively, these data implicate the CXCR4/CXCR7/SDF-1 pathway in Stx-mediated pathogenesis and suggest novel therapeutic strategies for prevention and/or treatment of complications associated with E. coli O157:H7 infection.

Co-regulation of transcellular and paracellular leak across microvascular endothelium by dynamin and Rac.

Increased permeability of the microvascular endothelium to fluids and proteins is the hallmark of inflammatory conditions such as sepsis. Leakage can occur between (paracellular) or through (transcytosis) endothelial cells, yet little is known about whether these pathways are linked. Understanding the regulation of microvascular permeability is essential for the identification of novel therapies to combat inflammation. We investigated whether transcytosis and paracellular leakage are co-regulated. Using molecular and pharmacologic approaches, we inhibited transcytosis of albumin in primary human microvascular endothelium and measured paracellular permeability. Blockade of transcytosis induced a rapid increase in paracellular leakage that was not explained by decreases in caveolin-1 or increases in activity of nitric oxide synthase. The effect required caveolin-1 but was observed in cells depleted of clathrin, indicating that it was not due to the general inhibition of endocytosis. Inhibiting transcytosis by dynamin blockade increased paracellular leakage concomitantly with the loss of cortical actin from the plasma membrane and the displacement of active Rac from the plasmalemma. Importantly, inhibition of paracellular leakage by sphingosine-1-phosphate, which activates Rac and induces cortical actin, caused a significant increase in transcytosis of albumin in vitro and in an ex vivo whole-lung model. In addition, dominant-negative Rac significantly diminished albumin uptake by endothelia. Our findings indicate that transcytosis and paracellular permeability are co-regulated through a signaling pathway linking dynamin, Rac, and actin.

Tissue inhibitor of metalloproteinase 2 and coronary artery lesions in Kawasaki disease.

OBJECTIVE: To identify cytokine genes uniquely expressed in peripheral blood mononuclear cells (PBMNCs) in the acute phase of Kawasaki disease (KD) with coronary artery lesions (CALs). STUDY DESIGN: We screened the mRNA expression levels of PBMNCs from 4 pairs of KD patients with and without CAL using DNA microarray. The result was confirmed by real-time polymerase chain reaction (RT-PCR). The genetic association study was performed to analyze the significance of single nucleotide polymorphisms in the identified gene for the development of CAL in KD patients (184 controls, 144 KD patients with CAL, 64 KD patients without CAL). RESULTS: The microarray analysis showed that tissue inhibitor of metalloproteinases 2 (TIMP2) was expressed at higher levels in PBMNCs of KD patients with CAL than in KD patients without CAL. Quantitative RT-PCR confirmed that the expression levels were significantly higher in the KD patients with CAL than in those without CAL (P < .05). Among KD patients, TIMP2 promoter polymorphisms were significantly associated with a risk of CAL (P < .01). There was a significant difference in the transcriptional activities between the haplotypes of the TIMP2 promoter polymorphisms by reporter assay using U-937. CONCLUSIONS: TIMP2 overexpression and the promoter polymorphisms might play a role in the development of CALs.

A novel transfection method for mammalian cells using gas plasma.

Introduction of foreign genes into target cells is a crucial step for achievement of gene therapy. We have recently developed a novel transfection system for eukaryotic cells, namely the electric pulse-activated gas plasma generator. To measure the transfection efficiency and mortality by flow-cytometry, we employed enhanced green fluorescent protein and propidium iodide staining, respectively. One day after the 1-3s plasma exposures with DNA concentration at 0.5 microg/microl, favorable transfection efficiencies (17.8-21.6%) and mortalities (0.65-2.86%) were obtained for HeLa-S3, HT-1080 and MCF-7 cells. The recipient cells became transiently permeable for plasmid DNA during the plasma exposure, suggesting that plasma-mediated transfection may involve similar mechanisms that accounts for electroporation. The relatively low mortality rates are encouraging in our attempt to apply this system to the various cell lines including the primary cell cultures.

Association of vascular endothelial growth factor (VEGF) and VEGF receptor gene polymorphisms with coronary artery lesions of Kawasaki disease.

We analyzed the genetic polymorphisms of vascular endothelial growth factor (VEGF) and its receptors [Fms-related tyrosine kinase-1, kinase insert domain receptor (KDR)] in Japanese patients with Kawasaki disease (KD) and normal control subjects to examine whether these genes would contribute to the KD occurrence and/or the development of coronary artery lesion (CAL) in KD. We found that the frequency of G allele of VEGF g.-634 G>C single-nucleotide polymorphism in the promoter region was significantly higher in KD patients with CAL than in those without CAL (p = 0.012) or control subjects (p = 0.021) because of a significantly higher frequency of the GG genotype in KD patients with CAL. In addition, the frequency of the A1 allele with 11 AC repeats of KDR g.+4422(AC)11-14 dinucleotide repeat polymorphism in intron 2 was significantly higher in KD patients with CAL than in those without CAL (p = 0.013) or control subjects (p = 0.040) as a result of a significantly higher frequency of the A1A1 genotype in KD with CAL patients. The multivariate analysis of clinical features and genotypes of the two polymorphisms showed that the A1A1 genotype of KDR g.+4422(AC)11-14 polymorphism was an independent risk factor for the development of CAL with the highest odds ratio among several clinical parameters (odds ratio 6.76; 95% confidence interval 1.05-43.48). Dual luciferase assay demonstrated that the A1 allele with KDR g.+4422(AC)11 repeats showed a weaker silencer function than the A2 allele with 12 AC repeats. These findings suggested that VEGF and its receptor, KDR, genes contributed to the development of CAL in KD patients.

CD25+CD4+ regulatory T cells in patients with Kawasaki disease.

OBJECTIVE: To investigate whether the CD25 + CD4 + regulatory T-cell population, which plays important roles not only in maintaining immunologic self-tolerance but also in controlling the magnitude and character of antimicrobial immune responses, is related to the pathophysiology of Kawasaki disease (KD). STUDY DESIGN: The patient group consisted of 54 patients (median age, 30 months; 27 female and 27 male patients) fulfilling the criteria for KD. Age-matched control subjects included 17 patients with active infections and 24 healthy children. We analyzed CD25 + CD4 + cells and the mRNA expression of Foxp3, cytotoxic T lymphocyte-associated antigen 4 (CTLA4), glucocorticoid-induced tumor necrosis factor receptor (GITR), and transforming growth factor beta in peripheral blood mononuclear cells and purified CD4 + T cells. RESULTS: The proportions of CD25 + CD4 + cells in patients with acute-phase KD (median, 2.35% of total lymphocytes) were significantly lower than those in healthy control subjects (median, 3.14%) and control subjects with disease (median, 3.15%). The proportions returned to the normal level after intravenous gammaglobulin treatment (median, 3.86%). The mRNA expression of Foxp3, CTLA4, and GITR showed similar tendencies. CONCLUSIONS: The decrease of CD25 + CD4 + regulatory T cells in the acute phase might have a role in the development of KD.

Inducible and endothelial constitutive nitric oxide synthase gene polymorphisms in Kawasaki disease.

BACKGROUND: Nitric oxide (NO) is secreted by immune and vascular endothelial cells, and appears to play important roles in the pathophysiology of Kawasaki disease (KD). Thus, genetic variations in NO synthase (NOS) genes may be involved in the development of coronary artery lesions (CAL) in KD. METHODS: The present study investigated the association of endothelial constitutive NOS (ecNOS) and inducible NOS (iNOS) gene polymorphisms with the development of CAL in KD in a Japanese population. RESULTS: The genotype distributions of 27-bp tandem repeat polymorphism within intron 4 of ecNOS gene did not show any significant difference between controls and KD patients with or without CAL. In addition, there was no significant association between whole-allele distribution of iNOS gene promoter (penta-repeat CCTTT) polymorphism and KD with or without CAL. CONCLUSION: These results did not support any association of ecNOS and iNOS gene polymorphisms to the development of CAL in KD patients in a Japanese population.

Founder effect of the C9 R95X mutation in Orientals.

A nonsense mutation at codon 95 (R95X) in the C9 gene is responsible for most Japanese C9 deficiency (C9D) cases, with a carrier frequency of 6.7%. Upon analysis of microsatellite markers and newly identified dinucleotide repeat number polymorphisms in the 3' flanking region of the C9 gene, a founder effect was demonstrated for the R95X mutation of the C9 gene in Japanese. Screening for the R95X mutation in Korean and Chinese individuals showed that the R95X carrier frequencies in Koreans and Chinese were 2.0% and 1.0%, respectively. Although homozygotes for the R95X mutation were not found in Korea or China, the shared haplotype of the dinucleotide repeat number polymorphisms appeared to be associated with the R95X mutation in the heterozygotes in Korea and China. The founder effect found in East Asians (Japanese, Koreans and Chinese) but not in Caucasians, as well as the haplotype sharing in only a small chromosomal interval, suggested that the R95X mutation of C9 gene was ancient and had occurred after the divergence of East Asians and Caucasians, and before migration of the Yayoi people to Japan. Since the mortality of meningococcal infections in complement-deficient patients is lower than that in normal individuals, a founder effect and a selective advantage in isolation might be the main reasons for the high frequency of the R95X mutation in Japan.