Akihiro Yachie

Oxidative stress causes enhanced endothelial cell injury in human heme oxygenase-1 deficiency

The first known human case of heme oxygenase-1 (HO-1) deficiency is presented in this report. The patient is a six-year-old boy with severe growth retardation. He has been suffering from persistent hemolytic anemia characterized by marked erythrocyte fragmentation and intravascular hemolysis, with paradoxical increase of serum haptoglobin and low bilirubin. An abnormal coagulation/fibrinolysis system, associated with elevated thrombomodulin and von Willebrand factor, indicated the presence of severe, persistent endothelial damage. Electron microscopy of renal glomeruli revealed detachment of endothelium, with subendothelial deposition of an unidentified material. Iron deposition was noted in renal and hepatic tissue. Immunohistochemistry of hepatic tissue and immunoblotting of a cadmium-stimulated Epstein-Barr virus-transformed lymphoblastoid cell line (LCL) revealed complete absence of HO-1 production. An LCL derived from the patient was extremely sensitive to hemin-induced cell injury. Sequence analysis of the patients HO-1 gene revealed complete loss of exon-2 of the maternal allele and a two-nucleotide deletion within exon3 of the paternal allele. Growth retardation, anemia, iron deposition, and vulnerability to stressful injury are all characteristics observed in recently described HO-1 targeted mice. This study presents not only the first human case of HO-1 deficiency but may also provide clues to the key roles played by this important enzyme in vivo.

Prognostic Factors for Chronic Active Epstein-Barr Virus Infection

Chronic active Epstein-Barr virus infection (CAEBV) is a high-mortality and high-morbidity disease. To clarify the prognostic factors, a national survey was performed in Japan, and data for 82 patients who met the criteria for CAEBV were analyzed. Of these 82 patients, 47 were alive and 35 had already died. Multivariate analysis revealed that thromobocytopenia and age at disease onset were correlated with mortality. The probability of 5-year survival was 0.45 for older patients (onset age, > or = 8 years), 0.94 for younger patients (P<.001), 0.38 for patients with thrombocytopenia (platelet count < 12 x 10(4) platelets/microL at diagnosis), and 0.76 for patients without thrombocytopenia (P=.01). Furthermore, patients with T cell infection by EBV had shorter survival times than patients with natural killer cell infection (probability of 5-year survival, 0.59 vs. 0.87; P<.009). Patients with CAEBV with late onset of disease, thrombocytopenia, and T cell infection had significantly poorer outcomes.

Distinct cytokine profiles of systemic-onset juvenile idiopathic arthritis-associated macrophage activation syndrome with particular emphasis on the role of interleukin-18 in its pathogenesis

OBJECTIVES To compare the pro-inflammatory cytokine profiles and the cytokine kinetics in patients with secondary macrophage activation syndrome (MAS) due to systemic-onset juvenile idiopathic arthritis (s-JIA) and in both active and inactive disease states of s-JIA (but no MAS), with those demonstrated in EBV-induced haemophagocytic lymphohistiocytosis (HLH) and Kawasaki disease (KD), and to investigate the significance of IL-18 in the pathogenesis of s-JIA. METHODS Five patients with MAS complicating s-JIA (MAS/s-JIA), 10 with HLH due to EBV infection (EBV-HLH), 22 with KD and 28 healthy controls were analysed. Cytokine concentrations (IL-18, IL-6, neopterin and TNF-alpha receptor Types I and II) were quantified in serum by ELISA. Results were compared with clinical features of MAS/s-JIA, including ferritin concentrations. RESULTS Serum IL-18 concentrations in MAS/s-JIA patients were significantly higher than those in EBV-HLH or KD patients (P < 0.05). Serum IL-6 concentrations in KD patients were significantly higher than those in EBV-HLH or MAS/s-JIA patients. Serum neopterin concentrations in EBV-HLH patients were significantly higher than those in MAS/s-JIA or KD patients. Serum IL-18 correlated positively with the following measurements of disease activity: CRP, ferritin, lactate dehydrogenase and other cytokines (P < 0.05). Serum concentrations of IL-18 in s-JIA patients remained elevated in the inactive phase of disease, whereas clinical parameters and other cytokines normalized. CONCLUSIONS IL-18 may be an important mediator in s-JIA. Although serum Il-18 concentrations correlated with markers of the disease activity, IL-18 concentrations remained elevated even when other markers of disease activity normalized. Serum IL-18 concentration may be a promising indicator of the disease activity. The cytokine release pattern in MAS/HLH is different among patients with different aetiologies. Monitoring the cytokine profile, including IL-18, may be useful for differentiation of MAS/HLH and evaluation of disease activity in s-JIA.

Tubular Injury as a Cardinal Pathologic Feature in Human Heme Oxygenase-1 Deficiency

Heme oxygenase (HO) catalyzes degradation of heme to biliverdin, iron, and carbon monoxide. It consists of three isoforms: an inducible form (HO-1), a constitutive form (HO-2), and the third isoform (HO-3), with properties similar to HO-2. There is limited evidence to suggest that the induction of HO-1 may have anti-inflammatory effects in an in vivo model of oxidative stress-mediated renal injury. We experienced the first human case of HO-1 deficiency. The patient had persistent proteinuria and hematuria, with biochemical evidence of renal tubular injury. We obtained three consecutive renal specimens: two from renal biopsies at 2 and 5 years of age and the third from autopsy at 6 years of age. The patient had systemic vascular endothelial-cell injury with massive intravascular hemolysis. The serum was loaded with heme and a large amount of heme-conjugated haptoglobin. A high concentration of haptoglobin was also detectable in urine. Mesangial proliferation or change in glomerular capillary-wall thickness was relatively mild to moderate in all specimens. Electron microscopic examination showed widespread endothelial detachment and subendothelial deposits of an unidentifiable material. It was striking that tubulointerstitial injury, with tubular dilatation and/or atrophy, interstitial fibrosis, and inflammatory cell infiltration, advanced progressively. Tubular epithelial cells were injured, and massive deposition of iron and haptoglobin was detectable. Bowmans capsules were dilated significantly, probably secondary to the collapse of atrophic tubuli. This is the first report to show that HO-1 has critical roles in vivo in protecting renal tubuli, in addition to vascular endothelium, from oxidative injury.

Human heme oxygenase-1 deficiency presenting with hemolysis, nephritis, and asplenia.

Heme oxygenase-1 (HO-1) is a stress-induced enzyme that catalyses the oxidation of heme to biliverdin. The primary deficiency of this enzyme has been shown in HO-1 knockout mice, and is characterized by intrauterine death and chronic inflammation. The first case of human HO-1 deficiency was reported in 1999. Human HO-1 deficiency has been observed to involve the endothelial cells more severely, resulting in hemolysis and disseminated intravascular coagulation. We report another case of human HO-1 deficiency in a young girl with congenital asplenia, who presented with severe hemolysis, inflammation, nephritis, which was refractory to therapy with corticosteroids, cyclophosphamide, and rituximab.

Gene Transfection of H25A Mutant Heme Oxygenase-1 Protects Cells against Hydroperoxide-induced Cytotoxicity

Heme oxygenase (HO)-1 is a stress-inducible enzyme protecting cells against oxidative stress, and mechanisms have been considered to depend exclusively on its enzyme activity. This study aimed to examine if the protein lacking catalytic activities could also display such resistance against oxidative stress. Stable transfectants of rat wild type HO-1 cDNA (HO-1-U937) and those of its H25A mutant gene (mHO-1-U937) were established using human monoblastic lymphoma cell U937. HO-1-U937 and mHO-1-U937 used in the study exhibited similar levels of the protein expression, while only the former increased enzyme activities. HO-1- and mHO-1 U937 cells became more and less sensitive to H2O2than mock transfectants, respectively; such distinct susceptibility between the cells was ascribable to differences in the capacity to scavenge H2O2 through catalase and to execute iron-mediated oxidant propagation. On the other hand, both cell lines exhibited greater resistance to tert-butyl hydroperoxide than mock transfectants. The resistance of HO-1-U937 to hydroperoxides appeared to result from antioxidant properties of bilirubin, an HO-derived product, while that of mHO-1-U937 was ascribable to increased contents of catalase and glutathione. These results provided evidence that gene transfection of the activity-lacking mutant HO-1 protects cells against oxidative stress through multiple mechanisms involving up-regulation of catalase and glutathione contents.

Expression of L‐selectin (CD62L) discriminates Th1‐ and Th2‐like cytokine‐producing memory CD4+ T cells

Human memory (CD45RO+) CD4+ T cells can be distinguished into two subpopulations on the basis of expression of the lymph node homing receptor, L‐selectin (CD62L). In a prior study we showed that human L‐selectin‐positive memory T‐helper (Th) cells promote the maturation of IgG‐ and IgA‐producing cells by naive B cells. To further elucidate the contribution of memory CD4+ T cells to B‐cell differentiation, human memory CD4+ T cells with or without L‐selectin expression were evaluated for production of cytokines that participate in regulation of immunoglobulin production. It was found that L‐selectin‐positive human memory CD4+ T cells produce mainly interleukin (IL)‐4 and IL‐5, whereas L‐selectin‐negative CD4+ T cells produce mainly interferon‐γ (IFN‐γ). This profile of cytokine expression coincides with the profile that distinguishes Th1 and Th2 subsets. In contrast to the murine system, IL‐10 production was similarly contributed by human L‐selectin‐positive and ‐negative memory CD4+ T‐cell subpopulations. These results suggest that the human L‐selectin‐negative and ‐positive subpopulations of human memory CD4+ T cells contain Th1‐like and Th2‐like cytokine‐producing cells, respectively.

Tocilizumab masks the clinical symptoms of systemic juvenile idiopathic arthritis-associated macrophage activation syndrome: the diagnostic significance of interleukin-18 and interleukin-6.

Macrophage-activation syndrome (MAS) is a potentially life-threatening complication of systemic juvenile idiopathic arthritis (s-JIA). Tocilizumab (TCZ), a humanized anti-IL-6 receptor monoclonal antibody, is an effective cytokine inhibitor for the treatment of s-JIA. We described the clinical courses of five cases of MAS during TCZ therapy and demonstrated the need for monitoring serum interleukin (IL)-18 and IL-6 concentrations. Clinical symptoms of patients with s-JIA receiving TCZ were apparently mild compared to those not receiving TCZ. Furthermore, serum CRP concentrations never increased during TCZ therapy, even in MAS. Serum IL-6 concentrations increased during s-JIA flare-up and with the complication of infection. Serum IL-18 concentrations increased persistently before the other measures of disease activity. The clinical symptoms of MAS and s-JIA could be masked during TCZ therapy; hence, monitoring serum concentrations of IL-18 and IL-6 is recommended for the evaluation of disease activity in s-JIA and to detect the complication of infection.

Cell type specific infection of Epstein/Barr virus (EBV) in EBV- associated hemophagocytic lymphohistiocytosis and chronic active EBV infection

While Epstein-Barr virus (EBV) tropism in B cells and nasopharygeal epithelial cells in the normal host has been demonstrated, recently the role of its infection into non-B cell populations has been suggested to play a pivotal role in the pathogenesis of several EBV-related hematological as well as non-hematological diseases. Ectopic EBV infection in T cells or natural killer (NK) cells has been reported in EBV-associated hematological diseases, such as acute fulminant EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) and chronic active EBV infection (CAEBV). Recent advances in the analysis of EBV infection in lymphocyte subpopulations have clarified the differential virus-cell interaction within these EBV-related disorders. EBV infection was predominantly found in CD8(+) T-cells from EBV-HLH, and in CD4(+) T-cells or NK cells from CAEBV, while the majority of EBV infected cells were found in B cells from acute infectious mononucleosis (IM). Different virus-cell interactions between acute EBV-HLH and CAEBV have indicated different pathogenic mechanisms against EBV infection between the two EBV-associated diseases, accounting for the difference in clinical manifestations between the two diseases.

Heme Oxygenase-1 Production by Peripheral Blood Monocytes During Acute Inflammatory Illnesses of Children

Monocytes play key roles both in innate and adaptive antigen-specific immunity and they constitute critical components of the immune responses. Although most of the monocyte-derived cytokines exhibit proinflammatory functions in vivo, heme oxygenase-1 (HO-1), an inducible heme-degrading enzyme, exerts potent anti-inflammatory effect through production of carbon monoxide and bilirubin. We compared HO-1 production by monocytes in vivo in various acute inflammatory illnesses and in normal controls. Freshly isolated monocytes produced little HO-1 as detected by immunohistochemistry, but it was rapidly induced in vitro upon stimulation. HO-1 production by monocytes was selective because it was not induced in other leukocyte populations, including granulocytes and lymphocytes. Monocytes from acute inflammatory illnesses, such as Kawasaki disease and acute infectious diseases, viral or bacterial, produced significant levels of HO-1, as detected by flow cytometry, immunohistochemistry, and reverse transcription polymerase chain reaction. Quantitative analysis of HO-1 mRNA expression by real-time polymerase chain reaction revealed that monocytes from controls exhibited low, but significant levels of HO-1 mRNA, indicating that circulating monocytes produce HO-1 constantly, in response to basal level of oxidative stress encountered daily. Significantly elevated HO-1 mRNA levels seen in acute inflammatory illnesses suggest that monocyte HO-1 production serve as potent anti-inflammatory agent to control excessive cell or tissue injury in the presence of oxidative stress and cytokinemia.