Tigecycline Suppresses the Virulence Factors of Multidrug-Resistant Acinetobacter baumannii Allowing Human Neutrophils to Act

Purpose

To determine the ability of human neutrophils to kill multidrug-resistant Acinetobacter baumannii (MDRAB) in the presence of tigecycline (TGC).

Methods

Clinical isolates of MDRAB were cultured with human neutrophils and H₂O₂ in the presence of TGC. The numbers of viable bacteria, catalase activity, gene expression at the K locus of the MDRAB, reactive oxygen species (ROS) production, and granule exocytosis in human neutrophils were determined.

Results

There was a time-dependent increase in the numbers of MDRAB after co-culturing with human neutrophils, whereas there was a significant decrease in the MDRAB numbers when co-cultured with both, human neutrophils and TGC for 6 h. The presence or absence of TGC did not affect total ROS production or the expression of CD11b, CD15, and CD63 on human neutrophils occurred when co-cultured with MDRAB. TGC significantly suppressed catalase activity and gene expression at the K locus of MDRAB, and significantly reduced the thickness of the capsule. Additionally, the bacterial viability of TGC-treated MDRAB cultured with H₂O₂ was lower than that without H₂O₂ after 6 h of culture.

Conclusion

TGC significantly suppressed the expression of catalase and the capsule in MDRAB without adverse effects on neutrophil function, allowing human neutrophils to kill MDRAB. TGC is an effective antibiotic for treating MDRAB infections.

Histopathological Analysis of Acinetobacter baumannii Lung Infection in a Mouse Model

Acinetobacter baumannii is the main causative pathogen of nosocomial infections that causes severe infections in the lungs. In this study, we analyzed the histopathological characteristics of lung infection with two strains of A. baumannii (ATCC 19606 and the clinical isolate TK1090) and Pseudomonas aeruginosa PAO-1 in C3H/HeN mice to evaluate the virulence of A. baumannii. Survival was evaluated over 14 days. At 1, 2, 5, or 14 days postinfection, mice of C3H/HeN were sacrificed, and histopathological analysis of lung specimens was also performed. Histopathological changes and accumulation of neutrophils and macrophages in the lungs after infection with A. baumannii and P. aeruginosa were analyzed. Following intratracheal inoculation, the lethality of ATCC 19606- and TK1090-infected mice was lower than that of PAO-1-infected mice. However, when mice were inoculated with a sub-lethal dose of A. baumannii, the lung bacterial burden remained in the mice until 14 days post-infection. Additionally, histopathological analysis revealed that macrophages infiltrated the lung foci of ATCC 19606-, TK1090-, and PAO-1-infected mice. Although neutrophils infiltrated the lung foci of ATCC 19606- and TK1090-infected mice, they poorly infiltrated the lung foci of PAO-1-infected mice. Accumulation of these cells in the lung foci of ATCC 19606- and TK1090-infected mice, but not PAO-1-infected mice, was observed for 14 days post-infection. These results suggest that A. baumannii is not completely eliminated despite the infiltration of immune cells in the lungs and that inflammation lasts for prolonged periods in the lungs. Further studies are required to understand the mechanism of A. baumannii infection, and novel drugs and vaccines should be developed to prevent A. baumannii infection.

Effects of colistin and tigecycline on multidrug-resistant Acinetobacter baumannii biofilms: advantages and disadvantages of their combination

We investigated the antimicrobial effects of colistin (CST) and tigecycline (TGC), either alone or in combination, on biofilm-dispersed and biofilm-embedded multidrug-resistant Acinetobacter baumannii (MDRAB) strains R1 and R2. The bacterial growth of biofilm-dispersed MDRAB was inhibited by CST or TGC. However, the inhibitory effects were attenuated by a combination of CST and low concentrations of TGC. The bactericidal effects of CST, but not TGC, were observed on biofilm-dispersed MDRAB. Notably, the bactericidal effects increased with a combination of CST and high concentrations of TGC, whereas they were attenuated with the combination of CST and low concentrations of TGC. Although biofilm formation by MDRAB decreased with increasing concentrations of CST or TGC, there was no complete disruption of the biofilms. Additionally, the biofilms increased with a combination of 1–2 μg/mL CST and TGC at 2 μg/mL and 2–4 μg/mL for strains R1 and R2, respectively. Biofilm-embedded MDRAB was eradicated with CST, but not TGC. Notably, the eradication effects increased with a combination of CST and high concentrations of TGC, whereas attenuation happened with the combination of CST and low concentrations of TGC. These results provide information on the combined effects of CST and TGC in the treatment of biofilm-associated MDRAB infection.

Prevalence and Relatedness of mcr-1-Mediated Colistin-Resistant Escherichia coli Isolated From Livestock and Farmers in Japan

Colistin is used to treat infectious diseases in humans and livestock; it has also been used as a feed additive for livestock for approximately 50 years. Since the mcr-1 plasmid-mediated colistin resistance gene was discovered in China in 2015, it has been detected worldwide, mainly in livestock. In this study, we investigated the prevalence and characteristics of mcr-mediated colistin-resistant Escherichia coli in livestock and farmers in Japan. We collected fecal samples from 295 healthy livestock (202 cattle and 93 swine) and 62 healthy farmers from 72 livestock farms (58 cattle farms and 14 swine farms) between 2013 and 2015. Twenty-eight mcr-1-harboring E. coli strains were isolated from 25 livestock (six cattle and 19 swine) and three farmers (two cattle farmers and one swine farmer). The prevalence rates of mcr-1-harboring E. coli in livestock and farmers were 8.47 and 4.84%, respectively. Of the 28 strains, the resistance genes of three were transferable via the mcr-1-coding plasmids to E. coli J53 at low frequencies (10⁻⁷–10⁻⁸). Six strains coharbored mcr-1 with CTX-M β-lactamases (CTX-M-14, CTX-M-27, or CTX-M-156). Of the isolates obtained from livestock and farmers in four farms (farms C, I, N, and P), nine strains had the same genotypical characteristics (sequence types and pulsed-field gel electrophoresis band patterns), plasmid characteristics (incompatibility group and plasmid transferability), and minimum inhibitory concentrations. Thus, the findings suggested that clonal strains could spread among livestock and farmers within farms. To our knowledge, this is the first study to detect clonal relatedness of mcr-1-mediated colistin-resistant E. coli in livestock and farmers. It is suggested that farmers are at a higher risk of acquiring mcr-1-harboring strains, calling for our attention based on the One Health concept.

Immunomodulatory gene expression analysis in LPS-stimulated human polymorphonuclear leukocytes treated with antibiotics commonly used for multidrug-resistant strains

Conventional antibiotics used for the treatment of severe infections such as sepsis and septic shock confer immunomodulatory benefits. However, the growing problem of multidrug resistant infections has led to an increase in the administration of non-conventional last-resort antibiotics, including quinolones, aminoglycosides, and polypeptides, and the effects of these drugs on immunomodulatory gene expression in activated human polymorphonuclear leukocytes (PMNs) have not been reported. In this study, lipopolysaccharide-stimulated PMNs were incubated with piperacillin, rifampicin, fosfomycin (FOM), levofloxacin (LVFX), minocycline (MINO), colistin, tigecycline, or amikacin, and the mRNA expression levels of pattern recognition receptors (TLR2, TLR4, and CD14), inflammatory cytokines (TNFα and IL6), and chemokine receptors (IL8Rs and ITGAM) in these cells were quantitated using real-time qPCR. Many of the tested antibiotics altered the expression of the investigated cytokines. Notably, FOM, LVFX, and MINO significantly downregulated the expression of IL6, which is associated with pro- and anti-inflammatory defense mechanisms. Treatment of FOM and LVFX reduced IL-6 production as well as observed for IL6 gene expression. These findings indicated transcription and translation cooperation under the used experimental conditions. Therefore, our findings suggest that administration of these antibiotics suppresses the host anti-inflammatory response.

Analysis of Immune Responses in Acinetobacter baumannii-Infected Klotho Knockout Mice: A Mouse Model of Acinetobacter baumannii Infection in Aged Hosts

Acinetobacter baumannii is an important opportunistic pathogen that primarily afflicts elderly people. To clarify the pathogenicity of A. baumannii in the elderly, we investigated immune responses to A. baumannii ATCC 19606 infection in klotho knockout (KO) mice, the mouse model of aging. Following intravenous inoculation, the mice seldom displayed severe symptoms. However, the survival rate was 56% at 7 days post-infection. Bacteria were detected in the lungs of klotho KO mice but not klotho wildtype (WT) mice at 7 days post-infection. Neutrophils, eosinophils, interstitial macrophages, and monocyte/dendritic cell subset in the lungs of klotho KO mice were transiently induced after infection with A. baumannii. The number of alveolar macrophages in klotho KO mice was lower than that in klotho WT mice, except for 1 day post-infection. CD11b expression on neutrophils and alveolar macrophages in the lungs of klotho KO mice was seldom upregulated by the infection. These results suggested that immune functions eliminating bacteria in the lungs of klotho KO mice were insufficient. CD11b^low conventional DC cells hardly increased in klotho KO mice infected with A. baumannii. Additionally, the production of interleukin (IL)-10 in the sera of klotho KO mice was significantly higher than that in klotho WT mice, whereas that production of interferon-gamma was not detected in the sera of klotho KO mice. These results suggested that acquired immune responses were hardly induced in klotho KO mice. IL-1β, CXCL1, CXCL2, and CCL2 expression was significantly higher in the lungs of klotho KO mice infected with A. baumannii than in those of klotho WT mice at 1 day post-infection. These results suggested that pulmonary inflammation was elicited in klotho KO mice during early infection. The expression levels of proinflammatory cytokines significantly correlated with TLR9 expression in the lungs of klotho KO mice. The collective results demonstrate an A. baumannii infection state in aged hosts and suggest that pulmonary inflammation and bacterial burden should be noted in aged hosts even in the absence of severe symptoms of A. baumannii infection.

Lipopolysaccharide-Deficient Acinetobacter baumannii Due to Colistin Resistance Is Killed by Neutrophil-Produced Lysozyme

Acinetobacter baumannii causes nosocomial infections due to its multidrug resistance and high environmental adaptability. Colistin is a polypeptide antibacterial agent that targets lipopolysaccharide (LPS) and is currently used to control serious multidrug-resistant Gram-negative bacterial infections, including those caused by A. baumannii. However, A. baumannii may acquire colistin resistance by losing their LPS. In mouse models, LPS-deficient A. baumannii have attenuated virulence. Nevertheless, the mechanism through which the pathogen is cleared by host immune cells is unknown. Here, we established colistin-resistant A. baumannii strains and analyzed possible mechanisms through which they are cleared by neutrophils. Colistin-resistant, LPS-deficient strains harbor mutations or insertion sequence (IS) in lpx genes, and introduction of intact lpx genes restored LPS deficiency. Analysis of interactions between these strains and neutrophils revealed that compared with wild type, LPS-deficient A. baumannii only weakly stimulated neutrophils, with consequent reduced levels of reactive oxygen species (ROS) and inflammatory cytokine production. Nonetheless, neutrophils preferentially killed LPS-deficient A. baumannii compared to wild-type strains. Moreover, LPS-deficient A. baumannii strains presented with increased sensitivities to antibacterial lysozyme and lactoferrin. We revealed that neutrophil-secreted lysozyme was the antimicrobial factor during clearance of LPS-deficient A. baumannii strains. These findings may inform the development of targeted therapeutics aimed to treat multidrug-resistant infections in immunocompromised patients who are unable to mount an appropriate cell-mediated immune response.

Resolvin E1, but not resolvins E2 and E3, promotes fMLF-induced ROS generation in human neutrophils

E-series resolvins are biosynthesized from eicosapentaenoic acid during the resolution phase of acute inflammation and enhance inflammation resolution. However, the role of E-series resolvins in inflammation resolution is not yet known. Herein, we show that in human polymorphonuclear neutrophils (PMNs), resolvin E1 (RvE1) selectively enhances reactive oxygen species (ROS) generation induced by N-formylmethionyl-leucyl-phenylalanine. The RvE1-mediated enhancement is eliminated by a pan-antagonist of leukotriene B4 (LTB4) receptors, LY255283, or an NADPH oxidase inhibitor, diphenyleneiodonium. Thus, RvE1 enhances NADPH oxidase-mediated ROS generation via LTB4 receptors. Unlike RvE1, resolvins E2 and E3 do not show such activation of PMNs. Our findings suggest that RvE1 contributes to regulation of ROS generation, in accordance with the inflammatory state of the host.

Pathogenic Bacterium Acinetobacter baumannii Inhibits the Formation of Neutrophil Extracellular Traps by Suppressing Neutrophil Adhesion

Hospital-acquired infections caused by Acinetobacter baumannii have become problematic because of high rates of drug resistance. A. baumannii is usually harmless, but it may cause infectious diseases in an immunocompromised host. Although neutrophils are the key players of the initial immune response against bacterial infection, their interactions with A. baumannii remain largely unknown. A new biological defense mechanism, termed neutrophil extracellular traps (NETs), has been attracting attention. NETs play a critical role in bacterial killing by bacterial trapping and inactivation. Many pathogenic bacteria have been reported to induce NET formation, while an inhibitory effect on NET formation is rarely reported. In the present study, to assess the inhibition of NET formation by A. baumannii, bacteria and human neutrophils were cocultured in the presence of phorbol 12-myristate 13-acetate (PMA), and NET formation was evaluated. NETs were rarely observed during the coculture despite neutrophil PMA stimulation. Furthermore, A. baumannii prolonged the lifespan of neutrophils by inhibiting NET formation. The inhibition of NET formation by other bacteria was also investigated. The inhibitory effect was only apparent with live A. baumannii cells. Finally, to elucidate the mechanism of this inhibition, neutrophil adhesion was examined. A. baumannii suppressed the adhesion ability of neutrophils, thereby inhibiting PMA-induced NET formation. This suppression of cell adhesion was partly due to suppression of the surface expression of CD11a in neutrophils. The current study constitutes the first report on the inhibition of NET formation by a pathogenic bacterium, A. baumannii, and prolonging the neutrophil lifespan. This novel pathogenicity to inhibit NET formation, thereby escaping host immune responses might contribute to a development of new treatment strategies for A. baumannii infections.

The TNF-α of mast cells induces pro-inflammatory responses during infection with Acinetobacter baumannii

Mast cells serve important roles as sentinels against bacterial infection by secreting mediators stored in granules. Much of their effectiveness depends upon recruiting and/or modulating other immune cells. The location of mast cells implies that they recognize pathogens invading tissues or mucosal tissues. Acinetobacter baumannii is a gram-negative bacterium that is considered an emerging nosocomial pathogen and causes a wide range of infections associated with high morbidity and mortality. To date, the interaction of A. baumannii with mast cells remains unclear. In this study, we demonstrated an interaction between human LAD2 mast cells and A. baumannii in vitro. When LAD2 cells were co-cultured with live A. baumannii or Pseudomonas aeruginosa PAO1 in vitro for 4h, TNF-α and IL-8 were produced in the culture supernatant. These inflammatory cytokines were not detected in the supernatant after the cells were treated with live bacteria without serum. Gene expression analysis showed that TNF-α and IL-8 mRNA expression increased in A. baumannii- and P. aeruginosa-infected LAD2 cells. Scanning electron microscopy showed that A. baumannii was tightly attached to the surface of LAD2 cells and suggested that A. baumannii may bind to FcγRII (CD32) on LAD2 cells. TNF-α in the culture supernatant from A. baumannii-infected LAD2 cells, showed that PMN activation and migration increased in Boyden chamber assays. These results suggest that mast cells recognize and initiate immune responses toward A. baumannii by releasing the preformed mediator TNF-α to activate effector neutrophils.

Spontaneous formation of neutrophil extracellular traps in serum-free culture conditions

Neutrophils play a critical role in the innate immune response. Recently, a new neutrophilic biological defense mechanism, termed neutrophil extracellular traps (NETs), has been attracting attention. Neutrophils have been observed to release both lysosomal enzymes and their nuclear contents, including unfolded chromatin, which together trap and inactivate bacteria. The environment in tissues where neutrophils act is thought to be different from that of the blood serum. In this study, we assessed the effect of serum on NET formation. We found that neutrophils spontaneously form NETs in serum‐free cultivation conditions at early times. These NETs functioned properly to trap bacteria. Furthermore, we demonstrated that reactive oxygen species play a critical role in the spontaneous formation of NETs. These results suggest that the serum condition must be considered in studies on neutrophils, including the formation and mechanism of action of NETs.

Virulence characteristics of Acinetobacter baumannii clinical isolates vary with the expression levels of omps

PURPOSE

We investigated the expression levels of virulence factors (ompA, omp33-36 and carO) in five clinical isolates and in a standard ATCC 19606 strain of Acinetobacter baumannii to determine their effect on the virulence characteristics of the isolates.

METHODOLOGY

The mRNA levels of omps and proinflammatory cytokines were analyzed by quantitative real-time PCR. For adherence assay, after human lung epithelial cells (A549) were co-cultured with A. baumannii at 37 °C for 2 h, the cell-adherent bacteria was counted. Pearson correlation analysis was used to compare the omps mRNA levels, the proinflammatory cytokines and the number of adherent bacteria.

RESULTS

The mRNA levels of ompA in the clinical isolates were higher and similar compared with those in ATCC 19606, whereas the mRNA levels of omp33-36 in the clinical isolates were lower and similar compared with those in ATCC 19606. The mRNA levels of carO in the clinical isolates were significantly higher than those in ATCC 19606. The number of cell-adherent clinical isolates was higher than that of cell-adherent ATCC 19606. Furthermore, the number of cell-adherent clinical isolates was positively and significantly correlated with ompA mRNA level. The mRNA levels of TNF-α, IL-6 and IL-8 in A549 cells co-cultured with the clinical isolates were lower than those in A549 cells co-cultured with ATCC 19606. Moreover, the mRNA levels of TNF-α, IL-6 and IL-8 were negatively and significantly correlated with those of carO in the isolates.

CONCLUSION

These results provide insights into the renewed virulence characteristics of A. baumannii clinical isolates that depend on cell adherence capacity and the expression level of omp mRNAs.

A novel bacterial transport mechanism of Acinetobacter baumannii via activated human neutrophils through interleukin-8

Hospital-acquired infections as a result of Acinetobacter baumannii have become problematic because of high rates of drug resistance. Although neutrophils play a critical role in early protection against bacterial infection, their interactions with A. baumannii remain largely unknown. To elucidate the interactions between A. baumannii and human neutrophils, we cocultured these cells and analyzed them by microscopy and flow cytometry. We found that A. baumannii adhered to neutrophils. We next examined neutrophil and A. baumannii infiltration into Matrigel basement membranes by an in vitro transmigration assay. Neutrophils were activated by A. baumannii, and invasion was enhanced. More interestingly, A. baumannii was transported together by infiltrating neutrophils. Furthermore, we observed by live cell imaging that A. baumannii and neutrophils moved together. In addition, A. baumannii-activated neutrophils showed increased IL-8 production. The transport of A. baumannii was suppressed by inhibiting neutrophil infiltration by blocking the effect of IL-8. A. baumannii appears to use neutrophils for transport by activating these cells via IL-8. In this study, we revealed a novel bacterial transport mechanism that A. baumannii exploits human neutrophils by adhering to and inducing IL-8 release for bacterial portage. This mechanism might be a new treatment target.

Gene expression analysis in human polymorphonuclear leukocytes stimulated by LPSs from nosocomial opportunistic pathogens

Innate immunity coordinates LPS detection via TLR4 on polymorphonuclear leukocytes (PMNs) to elicit responses to many Gram-negative bacteria. In this study, we describe the effects of five subtypes of LPS [isolated from Escherichia coli B4, Pseudomonas aeruginosa PAO1, multidrug-resistant P. aeruginosa (MDRP), Acinetobacter baumannii and multidrug-resistant A. baumannii (MDRA)] on gene expression in PMNs. LPS isolated from B4, PAO1, and A. baumannii did not significantly alter TLR2 expression. However, LPS from MDRP and MDRA caused a 0.6-fold decrease and 2.7-fold increase, respectively, in TLR2 expression. Similarly, TLR4 expression was not significantly altered by LPS isolated from B4, PAO1 and A. baumannii but was down-regulated by LPS isolated from MDRP and MDRA by 0.1- and 0.6-fold, respectively. All LPS subtypes, excluding PAO1, down-regulated CD14 expression in PMNs. However, all five LPS subtypes up-regulated TNFA, IL1B, IL6, IL10 and TREM1 expression in a concentration-dependent manner, with the most substantial responses observed following exposure to LPS from MDRP and MDRA. These different effects on the gene expression in PMNs may depend on variation in LPS structural modifications related to acquired drug resistance, such as acylation and/or glycosylation.

Acinetobacter baumannii escape from neutrophil extracellular traps (NETs)

Acinetobacter baumannii and Pseudomonas aeruginosa are the same aerobic gram-negative bacillus and are usually harmless but cause infectious diseases in compromised hosts. Neutrophils play a critical role in infective protection against the extracellular growth of bacteria. Recently, a new biological defense mechanism called neutrophil extracellular traps (NETs) has been attracting attention. In present study, we investigated the responsiveness of neutrophils to A. baumannii and P. aeruginosa, focusing on NET formation. Neutrophils were co-cultured with A. baumannii or P. aeruginosa, and then DNA, histone and neutrophil elastase were stained, and the formation of NETs was evaluated. Neutrophils stimulated with A. baumannii had spread, but their shapes was maintained, and the nucleus was observed as clearly as that in non-stimulated neutrophils. However, neutrophils stimulated with P. aeruginosa did not maintain their cellular morphology, and the nucleus was disrupted with DNA, histones, and neutrophil elastase released into the extracellular space. These results suggest that A. baumannii does not induce NET formation, in contrast to P. aeruginosa. In addition, we measured expression of myeloperoxidase (MPO), reactive oxygen species (ROS) and superoxide in neutrophils, and we found that these expression in P. aeruginosa-stimulated neutrophils was stronger than that in A. baumannii-stimulated neutrophils. Furthermore, A. baumannii was not killed by neutrophils, in contrast to P. aeruginosa. In this study, we show that the reactivity of neutrophils and their biological defense mechanism are different between A. baumannii and P. aeruginosa, which is important for understanding the pathogenicity of these bacteria.

Gene expression analysis of TREM1 and GRK2 in polymorphonuclear leukocytes as the surrogate biomarkers of acute bacterial infections

OBJECTIVE

In the acute stage of infectious diseases such as pneumonia and sepsis, sequelae hypercytokinemia and cytokine storm are often observed simultaneously. During bacterial infections, activated polymorphonuclear leukocytes (PMNs) cause inflammation and organ dysfunction in severely ill patients. Gene expression of the triggering receptor on myeloid cells (TREM)-1 and G-coupled-protein receptor kinase (GRK)-2 in PMNs isolated from patients was analysed to identify genes correlated with the severity of pathophysiological conditions.

METHODS

mRNA levels of TREM1 and GRK2 in the PMNs from 26 patients (13 with pneumonia, 5 with severe sepsis, and 8 with septic shock) were analysed by using quantitative real-time PCR. The synthesised soluble form (s)TREM-1 was incubated with normal PMNs to investigate its biological functions in vitro.

RESULTS

Copies of TREM1 transcript were 0.7- to 2.1-fold higher in patients with pneumonia compared to those of normal subjects; the average fold-change was 1.1-fold. The mRNA levels of patients suffering from severe sepsis and septic shock were 0.34- and 0.33-fold lower compared to those of healthy subjects, respectively. TREM1 mRNA levels in 5 of 26 patients in convalescent stages recovered to normal levels. The mRNA levels of GRK2 in the PMNs of patients were also downregulated. The synthesised sTREM-1 upregulated the mRNA levels of TREM1 in normal PMNs.

CONCLUSIONS

TREM1 mRNA levels were inversely correlated with the severity of pathophysiological conditions in acute bacterial infections. The gene expression levels of TREM1 in PMNs isolated from patients with bacterial infections may be used as a surrogate biomarker for determining the severity.

Rapid assay for detecting gyrA and parC mutations associated with fluoroquinolone resistance in Enterobacteriaceae

We developed a PCR-RFLP assay to detect mutations in the quinolone-resistance determining regions of gyrA and parC associated with fluoroquinolone resistance in Enterobacteriaceae. The assay detected mutations associated with reduced susceptibility to fluoroquinolones and may therefore serve as a specific, rapid, inexpensive, and simple testing alternative.

Evaluation of TREM1 gene expression in circulating polymorphonuclear leukocytes and its inverse correlation with the severity of pathophysiological conditions in patients with acute bacterial infections

During bacterial infection, activated polymorphonuclear leukocytes (PMNs) often cause inflammation and organ dysfunction in severely ill patients. Gene expression was analyzed in circulating PMNs isolated from these patients to determine the distinct expression profile. We focused on immunomodulatory genes, such as those for pattern recognition receptors, inflammatory cytokines, PMN surface antigens, and myeloid cell receptors in PMNs. Gene expression in 23 patients (12 with pneumonia and 11 with sepsis) were analyzed using quantitative real-time polymerase chain reaction. The mRNA levels of TLR2 (20/23 cases) and CD14 (18/23 cases) were upregulated in the PMNs of patients when compared with healthy subjects. The mRNA expression levels of TLR4 (16/23 cases) and IL6 (16/23 cases) were downregulated in patients' PMNs, and of TNFA (16/23 cases) were upregulated in these cells. Although mRNA levels of IL8RA (15/23 cases) were downregulated in PMNs, MAC-1 mRNA levels (14/23 cases) were upregulated in the same cells. Copies of the TREM1 transcript were 0.7- to 2.1-fold higher in patients with moderate pneumonia than in the healthy subjects; the average fold change was 1.1. The mRNA levels were 0.3-fold lower in the patients with severe pneumonia and sepsis than in the healthy subjects. In conclusion, the downregulation of TREM1 expression in PMNs is associated with the severity of the pathophysiological conditions and may be used as a surrogate marker of acute bacterial infections.

Analysis of membrane antigens on neutrophils from patients with sepsis

The aim of the present study was to assess changes of cell membrane antigens on neutrophils in septic patients. Expression levels of neutrophil membrane antigens were measured employing a FACS calibur flow cytometer with several fluorescence-labeled monoclonal antibodies. Expression levels of the CD14 antigen were higher in patients with sepsis than in healthy individuals. In particular, the expression levels of CD14 increased in patients complicated by septic shock. Expression levels of TLR-4 were higher in patients with sepsis or septic shock than in healthy individuals. Expression levels of CD11b and CD16 were lower in patients with sepsis or septic shock than in healthy individuals and were even lower in those complicated by septic shock. Expression levels of neutrophil membrane antigens in patients with sepsis markedly changed in the acute phase. However, these levels tended to return to those of healthy individuals in the convalescing phase. Analyses of the surface antigens on neutrophils strongly involved in biological defense or tissue injury are informative for understanding the pathology of sepsis and for conducting therapy targeting neutrophils in the future.

Aflatoxin B1 modulates the insulin-like growth factor-2 dependent signaling axis

Although aflatoxin B(1) (AFB(1)) is known as a mycotoxin that induces hepatocellular carcinoma (HCC), its effects on HCC cells have not been sufficiently investigated. The HCC cell lines HepG2, Huh-6, Huh-7, and PLC were cultured (5 x 10(5)cells/ml) and various concentrations of AFB(1) were added. The expression levels of the alpha-fetoprotein (AFP), insulin-like growth factor-2 (IGF-2), and insulin-like growth factor-1 receptor (IGF-1R) genes in each sample were determined by real-time PCR, with the following results: (1) The level of AFP expression in HepG2 increased at 5-50 ng/ml of AFB(1) in a dose-dependent manner. The AFP expression level in Huh-6 increased at 0.01-5 ng/ml of AFB(1) in a dose-dependent manner and decreased to half controls level at 50 ng/ml of AFB(1). The AFP expression level in Huh-7 decreased to one-third the original level at 0.5-50 ng/ml of AFB(1). The AFP expression level in PLC decreased at 0-0.5 ng/ml of AFB(1) in a dose-dependent manner, and decreased to one-third at concentrations of AFB(1) between 0.5 and 50 ng/ml. (2) The IGF-2 and IGF-1R expression levels in Huh-6 increased more than 10-fold at 0.5-5 ng/ml of AFB(1), but decreased to half at 50 ng/ml of AFB(1). The IGF-2 and IGF-1R expression levels in other cell lines increased in a dose-dependent manner. AFB(1) induced translations of IGF-2 and IGF-1R and cell proliferation: When 50 ng/ml AFB(1) was administrated, cell numbers were 2.0-, 1.7-, and 1.5-fold higher than those of controls after 3 days of culture in HepG2, Huh-7, and PLC, respectively. Particularly, in Huh-6, it increased 2.5-fold higher than those of controls following 5 ng/ml AFB(1) administration. The ratio of fold-change phospho-IGF-1R in all cell lines that were treated with AFB(1), increased 1.1-1.5-fold. These results indicate that AFB(1) may enhance HCC cell proliferation through an IGF-2-dependent signal axis, although it remains to be investigated whether those effects are associated with human hepatocarcinogenesis resulting from AFB(1) exposure.

SND1, a component of RNA-induced silencing complex, is up-regulated in human colon cancers and implicated in early stage colon carcinogenesis

Colon cancers have been shown to develop after accumulation of multiple genetic and epigenetic alterations with changes in global gene expression profiles, contributing to the establishment of widely diverse phenotypes. Transcriptional and posttranscriptional regulation of gene expression by small RNA species, such as the small interfering RNA and microRNA and the RNA-induced silencing complex (RISC), is currently drawing major interest with regard to cancer development. SND1, also called Tudor-SN and p100 and recently reported to be a component of RISC, is among the list of highly expressed genes in human colon cancers. In the present study, we showed remarkable up-regulation of SND1 mRNA in human colon cancer tissues, even in early-stage lesions, and also in colon cancer cell lines. When mouse Snd1 was stably overexpressed in IEC6 rat intestinal epithelial cells, contact inhibition was lost and cell growth was promoted, even after the cells became confluent. Intriguingly, IEC6 cells with high levels of Snd1 also showed an altered distribution of E-cadherin from the cell membrane to the cytoplasm, suggesting loss of cellular polarity. Furthermore, the adenomatous polyposis coli (Apc) protein was coincidentally down-regulated, with no significant changes in the Apc mRNA level. Immunohistochemical analysis using chemically induced colonic lesions developed in rats revealed overexpression of Snd1 not only in colon cancers but also in aberrant crypt foci, putative precancerous lesions of the colon. Up-regulation of SND1 may thus occur at a very early stage in colon carcinogenesis and contribute to the posttranscriptional regulation of key players in colon cancer development, including APC and beta-catenin.

Gr-1highPolymorphonuclear Leukocytes and NK Cells Act via IL-15 to Clear IntracellularHaemophilus influenzaein Experimental Murine Peritonitis and Pneumonia

Polymorphonuclear leukocytes (PMNs) can be divided into Gr-1(high) and Gr-1(low) subpopulations, but the differences in the functions of these cells in the host are unknown. This study investigated the roles of these two cell populations in the clearance of an intracellular pathogen (Haemophilus influenzae) causing murine peritonitis and pneumonia. Microarray analysis and quantitative real-time PCR analysis of proteose peptone-elicited peritoneal murine PMNs showed that IL-15 mRNA levels were significantly higher in Gr-1(high) PMNs than in Gr-1(low) PMNs. In addition, IL-15 was produced only by Gr-1-positive PMNs, especially Gr-1(high) PMNs. IL-15 was required for efficient clearance of experimental murine H. influenzae pneumonia, as 4 days postinfection lungs from IL-15 knockout mice contained 50- to 100-fold more bacteria than did wild-type mouse lungs. Gr-1 PMN-depleted C57BL/6 mice were more susceptible to H. influenzae pneumonia than were Gr-1 PMN replete C57BL/6 mice or C57BL/6 nude mice, demonstrating that Gr-1 PMNs are important in the clearance of intracellular bacteria. IL-15-activated NK cells killed H. influenzae in PMNs. Flow cytometry confirmed the expression of CD69 on the cell membrane of IL-15-activated NK cells. Our results show that Gr-1(high) PMNs produce more IL-15 than Gr-1(low) PMNs, and that IL-15-activated NK cells protect against early infection by H. influenzae.

[Intralobar pulmonary sequestration with high level of serum CEA; report of a case]

We reported a case of intralobar pulmonary sequestration with a high level of the serum CEA. A 53-year-old woman whose chief complaint was cough was admitted to our hospital. Enhanced chest computed tomography (CT) revealed the mass in the left lower lung, lymph-nodes swelling, and the aberrant artery. Magnetic resonance angiography (MRA) conformed the aberrant artery from the descending aorta. The level of serum CEA elevated at 9.6 ng/ml. Left lower lobectomy was performed. A diagnosis of intralobar pulmonary sequestration (Pryce type II) was established in this case. Histopathologically, the peribronchial epithelial cells in pulmonary sequestration showed weak positive for anti-CEA monoclonal antibody. Postoperative course was uneventful and the serum CEA level was 3.5 ng/ml in the normal range at the postoperative 17th day.

Up-regulation of hnRNP A1 gene in sporadic human colorectal cancers

We have previously reported that the heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1), a major hnRNP, binds to G-rich repetitive sequences and quadruplex (G4') structures in DNA, including the 5'-TTAGGG-3' telomere repeat and 5'-GGCAG-3' short-tandem-repeat. DNA synthesis arrest at the (GGG) sites within these repeats in vitro was retrieved by the addition of the hnRNP A1 protein or its N-terminal proteolytic product, UP1, in a dose-dependent manner. Therefore, functional perturbation of hnRNP A1 may abrogate the genomic stability of telomere repeats and other G-rich sequences, independent of its major role in transcriptional and translational regulation. In the present study, we conducted genetic and expression analysis of the hnRNP A1 gene in sporadic human colorectal cancers to clarify its possible involvement in human carcinogenesis. Of 30 lesions, one harbored a mutation at the -11 position from the translation initiation site, but none in the coding region. A single nucleotide polymorphism, an A or G-allele, was found in the 5' upstream promoter region of the gene. Quantitative gene expression analysis revealed that 60% (18/30) of cases showed over-expression of hnRNP A1 in cancer tissues by 2-fold or greater, compared to their normal colon tissues, with values of 78, 64 and 40% for clinicopathological stages II, III and IV, respectively. Although the biological consequences of hnRNP A1 overexpression in colorectal cancers remain to be clarified, it could contribute to maintenance of telomere repeats in cancer cells with enhanced cell proliferation. Alternatively, since the variations in the stoichiometry of hnRNP family proteins are considered to affect cell-specific gene expression, quantitative alteration of hnRNP A1 could result in facilitation of transformation of colon epithelial cells as a consequence of transcriptional and translational perturbation.

[Chronic hemorrhagic pyothorax treated with preoperative internal thoracic and intercostal arterial embolization and perioperative non-invasive positive pressure ventilation]

We reported successful surgery for chronic hemorrhagic empyema with severe right heart insufficiency. The preoperative embolization of right internal thoracic artery and intercostals arteries was effective for the control of intraoperative bleeding. Non-invasive positive pressure ventilation (NIPPV) was useful for the perioperative respiratory management. A 62-year-old female with a history of right pneumonectomy and thoracoplasty for pulmonary tuberculosis was admitted because of dyspnea on effort on Dec 5th 2002. Her right heart insufficiency was worsened gradually. On May 20th 2003, we performed the transcatheter embolization of right internal thoracic and intercostals arteries for the control of intraoperative bleeding. The next day, the curettage and fenestration was performed for intraoperative cardiac dysfunction. The intraoperative bleeding was 1,596 ml and operative time was 2 hours 24 minutes. Due to CO2 narcosis, the ventilator under the intratracheal tube was needed for respiratory management in the postoperative course. The switching of the respiratory management with NIPPV from the intratracheal tube during 8 days, her respiratory and general conditions had been improved gradually. Because of methicillin-resistant Staphylococcus aureus (MRSA) infection of thoracic cavity, the radical thoracoplasty following the latissimus dorsi muscules flap and the omentopexy was performed. The operative course was uneventful and she needed overnight NIPPV without O2 inhalation and was discharged.

Characterization of dysplastic aberrant crypt foci in the rat colon induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine

The multistage model of colon carcinogenesis is well established in both humans and experimental animals, and aberrant crypt foci (ACF) are generally assumed to be putative preneoplastic lesions of the colon. However, morphological analyses of ACF have suggested that they are highly heterogeneous in nature and their role in tumorigenesis is still controversial. To better understand the biological significance of ACF in carcinogenesis, morphological and genetic analyses were performed using a rat colon cancer model induced by a food-borne colon carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). ACF of different sizes were collected at weeks 6, 18, 25, and 32 after three cycles of 2-week PhIP feeding (400 ppm in diet) with 4-week intervals on a high-fat diet, and a total of 110 ACF, representing approximately three-quarters of the total ACF, were subjected to histological evaluation. Thirty (27%) were diagnosed as dysplastic ACF, based on cytological and structural abnormalities of crypts. Dysplastic ACF were detected even at week 6 (0.4 per rat), and the numbers increased slightly at later time points, being 0.8, 1.4, and 0.8 per rat at weeks 18, 25, and 32, respectively. The sizes of these dysplastic ACF varied widely from 1 to 16 crypts and 50% (15 of 30) were composed of less than 4 crypts. Immunohistochemical analysis revealed that 83% (25 of 30) of dysplastic ACF demonstrated beta-catenin accumulation; 22 only in the cytoplasm and 3 in both the cytoplasm and nucleus, the latter manifesting a higher grade of dysplasia as compared with the former. Seven dysplastic ACF harbored beta-catenin mutations at codon 32, 34, or 36 in exon 2, and one had an Apc mutation at the boundary of intron 10 and exon 11. Mutations at these sites were also commonly found in colon tumors induced by PhIP. The results of our present study indicate that dysplastic ACF, which accounted for approximately one-fourth of the total ACF, are preneoplastic lesions of colon cancers induced by PhIP in rats.

Differential gene expression profiles in colon epithelium of two rat strains with distinct susceptibility to colon carcinogenesis after exposure to PhIP in combination with dietary high fat

Colon cancers develop through accumulation of multiple genetic and epigenetic alterations in colon epithelial cells, and the environment of the genetically altered epithelial cells may also have a substantial impact on their further development to cancer. In the present study, groups of 6-week-old F344 and ACI male rats, the former strain being susceptible to colon carcinogenesis induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and the latter being relatively resistant, were subjected to a long-term carcinogenesis experiment using our intermittent feeding protocol of PhIP in combination with a high-fat diet, which serves as a relevant risk factor that promotes the development of colon cancers. Animals were sacrificed at 60 weeks, and global gene expression analyses of normal parts of colon epithelial tissues were conducted using a high-density oligonucleotide microarray to elucidate the differential gene expression profile (environment) in normal colonic regions between F344 and ACI strains. Of 8799 entries on the RatU34A array, 74 genes exhibited 3-fold or greater variation. A subset of genes encoding ribosomal RNAs and proteins were highly preferentially expressed in the F344 strain. In addition, genes encoding fatty acid binding proteins and the peroxisome membrane protein 70 appeared up-regulated in the susceptible F344 strain. In the ACI strain, a mismatch repair gene, Msh2, was preferentially expressed, at approximately 20-fold the F344 level, along with a gene encoding a detoxification enzyme, catechol-O-methyltransferase. The combined effects of the repertoire of these differentially expressed genes in normal colon epithelial tissues may account for the distinct susceptibilities of F344 and ACI strains to colon carcinogenesis.

A rat colon cancer model induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, PhIP

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is one of the most abundant heterocyclic amines contained in cooked meat and fish, and induces aberrant crypt foci (ACF), putative preneoplastic lesions of the colon, and colon cancers in male rats when administered orally. As has been reported previously, F344 rats are susceptible to induction of ACF by PhIP, while ACI rats being relatively resistant. Approximately one-fourth of ACF induced by PhIP in F344 rats are dysplastic; exhibiting lesions with structural distortion of the crypt, decrease of goblet cells, nuclear stratification and enlargement of nuclei. Dysplastic ACF demonstrate beta-catenin accumulation, mainly in the cytoplasm, and increased cell proliferation in crypts. These dysplastic ACF are, therefore, strongly considered to be putative preneoplastic lesions of the colon.A genetic trait affecting the susceptibility to colon carcinogenesis in F344 rats was mapped to chromosome 16, between D16Rat17 and D16Wox3, using the number of ACF as a surrogate biomarker for colon carcinogenesis. Since the number of dysplastic lesions is well correlated with the total number of ACF, being approximately one-fourth of the total ACF as described above in F344 rats and will be described elsewhere in ACI rats, the gene involved in the susceptibility to ACF induction may possibly be partly responsible for the susceptibility to colon carcinogenesis by PhIP. We, thus, tentatively referred the name of the candidate susceptibility gene on rat chromosome 16 as susceptibility to colon tumor (Sct). In the present study, the colonic lesions induced by PhIP were well refined histologically and genetically, and the multi-step profiles of colon cancer development by PhIP were well characterized and revealed to be similar to the multi-step model of colon carcinogenesis in humans. The PhIP-induced colon cancer model in rats, thus contributes as a relevant tool to elucidate genetic factors responsible for susceptibility to colon carcinogenesis in human. Other unknown genetic or epigenetic alterations, which are essential for the development of early lesions of colon carcinogenesis, could also be clarified using this system.

Frequent and multiple mutations at minisatellite loci in sporadic human colorectal and gastric cancers--possible mechanistic differences from microsatellite instability in cancer cells

Minisatellites (MNs), composed of 5 to 100 nucleotide repeat units, range from 0.5 to 30 kb in length, and have been reported to be mutated in various human malignancies. In this study, frequencies of MN mutations in sporadic human colorectal (34 cases) and gastric cancers (24 cases) at various clinicopathological stages were assessed by multilocus DNA fingerprint analysis with three MN probes, Pc-1, 33.6 and 33.15. MN mutations were observed in both colorectal and gastric cancers, but at a significantly higher frequency in the former (56%) than in the latter (25%). Multiplicities of MN mutations were 1.50 +/- 1.81 and 0.46 +/- 1.10 in colorectal and gastric cancers, respectively, and the difference was also significant. Neither the presence nor multiplicity of MN mutations in either colorectal or gastric cancer cases had any correlation with the pathological stage, histological grading or the presence of microsatellite instability (MSI). Although the biological relevance of MN mutations still remains to be clarified, a subset of colorectal and gastric cancers could feature a new type of genomic instability, distinct from MSI.

Efficient induction of rat large intestinal tumors with a new spectrum of mutations by intermittent administration of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in combination with a high fat diet

In the present study we have established novel intermittent protocols featuring a high fat (HF) diet for efficient induction of large intestinal tumors with a relatively small amount of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). In protocol 1, F344 male rats were first fed a diet containing 400 p.p.m. PhIP for 2 weeks, followed by continuous administration of a HF diet without PhIP for 108 weeks. In protocol 2, 2 week PhIP treatments were repeated three times with 4 week intervals on the HF diet alone, followed by continuous feeding of the HF diet for 42 weeks. At termination of the experiments, 16 (3 of 19) and 45% (9 of 20) of the rats had developed a total of three and 13 large intestinal tumors with protocols 1 and 2, respectively. The tumor incidence in protocol 2 was comparable with that observed with continuous feeding of 400 p.p.m. PhIP for 52 weeks, after exposure to only approximately 10% of the amount of carcinogen. Five of nine (55%) tumors harbored mutations in either the beta-catenin or Apc gene, while all demonstrated accumulation of beta-catenin protein in the cytoplasm and nucleus. This suggests that other unknown genetic alterations in the Wnt-Apc-beta-catenin signaling pathway could have been involved in the development of tumors. By further modifying this intermittent protocol with HF diet, one could expect more efficient induction of lesions with much smaller amounts of PhIP in a shorter period. In addition, this model could provide a means to elucidate genetic alterations in large intestinal tumors induced by relatively low levels of carcinogenic insult, mimicking the cases of human colon carcinogenesis induced by exposure to environmental carcinogens.

High susceptibility of Scid mice to colon carcinogenesis induced by azoxymethane indicates a possible caretaker role for DNA-dependent protein kinase

Severe combined immunodeficiency (Scid) mice have defects in V(D)J recombination and DNA double-strand breaks repair caused by an inherited genetic defect in the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs). Scid mice are highly susceptible to development of T-cell lymphomas, and because of the nature of its association with DNA repair and recombination, DNA-PKcs is considered to belong to the caretaker class of tumor suppressor genes. In the present study, the susceptibility of Scid mice to colon carcinogenesis due to administration of azoxymethane (AOM) was investigated. Significantly higher susceptibility in terms of induction of both aberrant crypt foci (ACFs), putative pre-cancerous lesions of the colon and colon cancers was observed as compared with the isogenic strain, C.B-17 mice. The incidences of colon tumors, either adenomas or adenocarcinomas, in Scid and C.B-17 mice after administration of AOM (10 mg/kg body weight/week) for 6 weeks were 87% (26 of 30) and 50% (15 of 30), respectively, by experimental week 22 (P < 0.01). The multiplicity of colon tumors in Scid mice was also significantly higher than in C.B-17 mice, being 2.2 +/- 1.5 and 0.9 +/- 1.2, respectively (P < 0.001). The present study clearly demonstrated high susceptibility of Scid mice to colon carcinogenesis, which might be attributable to disruption of the caretaker role of DNA-PK in colonic epithelial cells.

Comparative genomic hybridization analysis suggests a gain of chromosome 7p associated with lymph node metastasis in non-small cell lung cancer

We analyzed the chromosomal gains and losses that occur in 30 non-small cell lung carcinomas by comparative genomic hybridization. Their chromosomal imbalances showed histological type-specific patterns in adenocarcinomas and in squamous cell carcinomas. The genetic changes in non-small cell lung carcinoma were also strongly dependent on metastasis to lymph node. The average numbers of chromosomal alterations were increased from 6.2 to 9.1 along with the presence of metastasis, and it gave rise to the increased copy number in specific chromosomes. In particular, a novel imbalance at 7p12-21 was recognized in a half of carcinoma with metastasis, although no genetic alteration was observed in 15 non-metastasizing lung carcinoma tested here.

Methionine adenosyltransferase I/III deficiency: novel mutations and clinical variations

Methionine adenosyltransferase (MAT) I/III deficiency, caused by mutations in the MAT1A gene, is characterized by persistent hypermethioninemia without elevated homocysteine or tyrosine. Clinical manifestations are variable and poorly understood, although a number of individuals with homozygous null mutations in MAT1A have neurological problems, including brain demyelination. We analyzed MAT1A in seven hypermethioninemic individuals, to provide insight into the relationship between genotype and phenotype. We identified six novel mutations and demonstrated that mutations resulting in high plasma methionines may signal clinical difficulties. Two patients-a compound heterozygote for truncating and severely inactivating missense mutations and a homozygote for an aberrant splicing MAT1A mutation-have plasma methionine in the 1,226-1,870 microM range (normal 5-35 microM) and manifest abnormalities of the brain gray matter or signs of brain demyelination. Another compound heterozygote for truncating and inactivating missense mutations has 770-1,240 microM plasma methionine and mild cognitive impairment. Four individuals carrying either two inactivating missense mutations or the single-allelic R264H mutation have 105-467 microM plasma methionine and are clinically unaffected. Our data underscore the necessity of further studies to firmly establish the relationship between genotypes in MAT I/III deficiency and clinical phenotypes, to elucidate the molecular bases of variability in manifestations of MAT1A mutations.

Structural requirements for catalysis and dimerization of human methionine adenosyltransferase I/III

We have used site-directed mutagenesis to probe the structural requirements for catalysis and dimerization of human hepatic methionine adenosyltransferase (hMAT). We built a homology model of the dimeric hMAT III inferred by the crystal structure of the highly homologous Escherichia coli MAT dimer. The active sites of both enzymes comprise the same amino acids and are located in the inter-subunit interface. All of the amino acids predicted to be in the hMAT III active site were mutated, as well as residues in a conserved ATP binding region. All of the mutations except one severely affected catalytic activity. On the other hand, dimerization was affected only by single mutations of three different residues, all on one monomer. The homology model suggested that the side chains of these residues stabilized the monomer and participated in a bridge between subunits consisting of a network of metal and phosphate ions. In agreement with this observation, we demonstrated that dimerization cannot occur in the absence of phosphate.

The gene for glycogen-storage disease type 1b maps to chromosome 11q23

Glycogen-storage disease type 1 (GSD-1), also known as "von Gierke disease," is caused by a deficiency in microsomal glucose-6-phosphatase (G6Pase) activity. There are four distinct subgroups of this autosomal recessive disorder: 1a, 1b, 1c, and 1d. All share the same clinical manifestations, which are caused by abnormalities in the metabolism of glucose-6-phosphate (G6P). However, only GSD-1b patients suffer infectious complications, which are due to both the heritable neutropenia and the functional deficiencies of neutrophils and monocytes. Whereas G6Pase deficiency in GSD-1a patients arises from mutations in the G6Pase gene, this gene is normal in GSD-1b patients, indicating a separate locus for the disorder in the 1b subgroup. We now report the linkage of the GSD-1b locus to genetic markers spanning a 3-cM region on chromosome 11q23. Eventual molecular characterization of this disease will provide new insights into the genetic bases of G6P metabolism and neutrophil-monocyte dysfunction.

Dominant inheritance of isolated hypermethioninemia is associated with a mutation in the human methionine adenosyltransferase 1A gene

Methionine adenosyltransferase (MAT) I/III deficiency, characterized by isolated persistent hypermethioninemia, is caused by mutations in the MAT1A gene encoding MAT(alpha)1, the subunit of major hepatic enzymes MAT I ([alpha1]4) and III([alpha1]2). We have characterized 10 MAT1A mutations in MAT I/III-deficient individuals and shown that the associated hypermethioninemic phenotype was inherited as an autosomal recessive trait. However, dominant inheritance of hypermethioninemia, also hypothesized to be caused by MAT I/III deficiency, has been reported in two families. Here we show that the only mutation uncovered in one of these families, G, is a G-->A transition at nt 791 in exon VII of one MAT1A allele that converts an arginine at position 264 to a histidine (R264H). This single allelic R264H mutation was subsequently identified in two hypermethioninemic individuals in an additional family, C. Family C members were also found to inherit hypermethioninemia in a dominant fashion, and the available affected members analyzed carried the single allelic R264H mutation. Substitution of R-264 with histidine (R264H, the naturally occurring mutant), leucine (R264L), aspartic acid (R264D), or glutamic acid (R264E) greatly reduced MAT activity and severely impaired the ability of the MAT(alpha)1 subunits to form homodimers essential for optimal catalytic activity. On the other hand, when lysine was substituted for R-264 (R264K), the mutant alpha1 subunit was able to form dimers that retain significant MAT activity, suggesting that amino acid 264 is involved in intersubunit salt-bridge formation. Cotransfection studies show that R264/R264H MAT(alpha)1 heterodimers are enzymatically inactive, thus providing an explanation for the R264H-mediated dominant inheritance of hypermethioninemia.

Demyelination of the brain is associated with methionine adenosyltransferase I/III deficiency

Individuals deficient in hepatic methionine adenosyltransferase (MAT) activity (MAT I/III deficiency) have been demonstrated to contain mutations in the gene (MATA1) that encodes the major hepatic forms, MAT I and III. MAT I/III deficiency is characterized by isolated persistent hypermethioninemia and, in some cases, unusual breath odor. Most individuals with isolated hypermethioninemia have been free of major clinical difficulties. Therefore a definitive diagnosis of MAT I/III deficiency, which requires hepatic biopsy, is not routinely made. However, two individuals with isolated hypermethioninemia have developed abnormal neurological problems, including brain demyelination, suggesting that MAT I/III deficiency can be deleterious. In the present study we have examined the MATA1 gene of eight hypermethioninemic individuals, including the two with demyelination of the brain. Mutations that abolish or reduce the MAT activity were detected in the MATA1 gene of all eight individuals. Both patients with demyelination are homozygous for mutations that alter the reading frame of the encoded protein such that the predicted MATalpha1 subunits are truncated and enzymatically inactive. The product of MAT, S-adenosylmethionine (AdoMet), is the major methyl donor for a large number of biologically important compounds including the two major myelin phospholipids, phosphatidylcholine and sphingomyelin. Both are synthesized primarily in the liver. Our findings demonstrate that isolated persistent hypermethioninemia is a marker of MAT I/III deficiency, and that complete lack of MAT I/III activity can lead to neurological abnormalities. Therefore, a DNA-based diagnosis should be performed for individuals with isolated hypermethioninemia to assess if therapy aimed at the prevention of neurological manifestations is warranted.

Molecular mechanisms of an inborn error of methionine pathway. Methionine adenosyltransferase deficiency

Methionine adenosyltransferase (MAT) is a key enzyme in transmethylation, transsulfuration, and the biosynthesis of polyamines. Genetic deficiency of alpha/beta-MAT causes isolated persistent hypermethioninemia and, in some cases, unusual breath odor or neural demyelination. However, the molecular mechanism(s) underlying this deficiency has not been clearly defined. In this study, we characterized the human alpha/beta-MAT transcription unit and identified several mutations in the gene of patients with enzymatically confirmed diagnosis of MAT deficiency. Site-directed mutagenesis and transient expression assays demonstrated that these mutations partially inactivate MAT activity. These results establish the molecular basis of this disorder and allow for the development of DNA-based methodologies to investigate and diagnose hypermethioninemic individuals suspected of having abnormalities at this locus.

Prenatal diagnosis of Duchenne muscular dystrophy by polymerase chain reaction analysis

The efficacy of the polymerase chain reaction (PCR) in the first-trimester prenatal diagnosis of Duchenne muscular dystrophy (DMD) was examined. Twenty-seven fetuses from 26 Japanese pedigrees at risk for DMD were analyzed. PCR-restriction fragment length polymorphism analysis, multiplex PCR, and dinucleotide repeat polymorphism analysis were used. Of 16 males, 11 were determined to be unaffected, 4 were affected, and the remaining 1 was undetermined. Of the 11 female fetuses, 1 was diagnosed as a noncarrier, 4 were carriers, and the carrier status of the remaining 6 was not determined at the option of the patients, although DNA polymorphisms could be detected in those patients. Prenatal diagnosis by PCR analysis was possible in 96% of the fetuses tested (26 of 27).

Deletion detection for diagnosis of Duchenne muscular dystrophy in the Japanese population--comparison between the polymerase chain reaction and the Southern blot analysis

We compared the efficacy of the multiplex PCR with that of the cDNA analysis for detection of deletions of the DMD gene in the Japanese patients. Thirty males with DMD from 27 Japanese families were studied by the multiplex PCR, and 24 of them were also investigated by Southern blot analysis. We used five dystrophin cDNA probes for deletion analysis. A total of 19 regions were amplified by the PCR to detect deletions, 9 regions by the method of Chamberlain et al. and another 10 regions by the method of Beggs et al. Deletions were detected in 14 (52%) out of 27 DMD families by the PCR. Southern blot analysis detected deletions in 14 (64%) out of 22 families. Thirteen (93%) of the 14 DMD families with deletions detected by Southern blotting were also confirmed by the multiplex PCR. Provided care is taken in cases where the deletion is limited to a single exon, the multiplex PCR appears to be an efficient and useful alternative to conventional Southern blot analysis for detecting deletions during the prenatal and postnatal diagnosis of DMD.

DNA analysis of Duchenne and Becker muscular dystrophy using pERT87 genomic probes and dystrophin cDNA probes--establishing the optimum strategy for carrier diagnosis in the Japanese population

DNA analysis was performed on 19 unrelated Duchenne muscular dystrophy (DMD) families and one Becker muscular dystrophy (BMD) family in Japan to determine their carrier status. The intragenic genomic probe pERT87 with its subclones 87-1, 87-8, and 87-15 were used together with five cDNA probes from the 5' end of the dystrophin gene. The tests with both a high polymorphism information content (P.I.C.) and a high observed P.I.C. were most effective, i.e., pERT87-1/XmnI, pERT87-15/XmnI, pERT87-8/TaqI, and pERT87-8/BstXI. These test combinations were useful in the Japanese population but pERT87-15/TaqI was not, although it was effective in Caucasians. Two additional test combinations of pERT87-1/MspI and pERT87-15/BamHI were highly useful in detecting restriction fragment length polymorphisms (RFLPs) when other tests were not informative. Carrier status could be determined in 18 out of 20 clients who were at risk for DMD/BMD carrier status from 20 families, similar to the rate of detection in Caucasians. The total detection rate of deletions was 74% with the five cDNA probes. Deletions were concentrated on two hot spots where 92% of all deletions were detected by only two probes, 1-2a and 8. Deletions were detected in two males with DMD who had none of the eight RFLPs tested. Our results emphasize the usefulness of DNA analysis with pERT87 genomic probes and cDNA probes. In addition, an optimum strategy for carrier detection in Japanese DMD/BMD families was proposed.

Prenatal diagnosis of Duchenne muscular dystrophy by restriction fragment length polymorphism analysis with pERT 87 intragenomic deoxyribonucleic acid probes

Prenatal diagnosis of DMD was performed with three intragenic genomic probes and chorionic villus sampling. A total of 8 unrelated families with at least one DMD were analysed. DNA was extracted from peripheral white blood cells for carrier testings (50 individuals). For prenatal detection, it was extracted from chorionic villi obtained by chorionic villus sampling at 9 menstrual weeks. DNA was digested with an appropriate restriction enzyme followed by overnight electrophoresis in 1% agarose gels. DNA was transferred from the gel to nylon membrane according to the protocol of an alkaline transfer method. The pERT 87 probes were labeled by nick translation. The membranes were hybridized overnight after prehybridization. After washing, the membranes were exposed to X-ray films to make autoradiograms for restriction fragment length polymorphism analysis. Fetal sex was determined by a rapid screening test with a Y chromosome-specific repeat sequence. Out of 8 fetuses, 4 were males and 4 were females. All of 4 male fetuses were determined to be unaffected. Out of 4 female fetuses, 3 were diagnosed as non-carriers, and the carrier status of the remaining one was not able to be determined because her mother was not informative for all testings.