Takao Kohsaka

Clinical role for a superantigen in Yersinia pseudotuberculosis infection.

Yersinia pseudotuberculosis is an enteric pathogen that causes a variety of clinical symptoms in the human. Recently, we reported the production of a superantigen (Y. pseudotuberculosis-derived mitogen, YPM) by this organism and characterized the gene structure of ypm. To further study the potential pathogenic role of YPM in Y. pseudotuberculosis infection, we assayed IgG anti-YPM antibodies and T cell antigen receptor-Vbeta expression of the T cells in peripheral blood and in mesenteric lymph node in patients acutely infected with Y. pseudotuberculosis. 20 out of 33 patients (61%) had an elevated antibody titer compared with healthy controls (P = 0.0001). Patients with systemic symptoms such as lymphadenopathy, transient renal dysfunction, and arthritis had significantly higher titers of anti-YPM than patients with gastrointestinal tract symptoms alone. T cells bearing the Vbeta3 gene segment were significantly increased (P = 0.009) among acute phase patients compared with healthy children. During the convalescence phase of the illness, there was a reduction in the abnormal level of Vbeta3 T cells. Moreover, in the mesenteric lymph node, an elevated level of Vbeta3 T cells compared with peripheral blood and a sequence diversity in the junctional region of the T cell antigen receptor beta-chain containing Vbeta3 element was observed in one patient. Together, these findings suggest that YPM was produced in vivo and played an important role in the pathogenesis of Y. pseudotuberculosis infection.

Localization of Tamm-Horsfall Protein and Osteopontin in a Rat Nephrolithiasis Model

The possibility of more than one urinary protein being simultaneously associated with calcium oxalate (CaOx) crystallization in vivo was investigated by examining the localization of Tamm-Horsfall protein (THP) and osteopontin (Opn) in a rat model of nephrolithiasis. CaOx crystal deposits were induced in male Sprague-Dawley rats by feeding 0.75% ethylene glycol in drinking water. THP and Opn were localized on kidney sections by immunoperoxidase technique, using specific polyclonal antibodies. When only occasional crystal deposits were seen in the kidney, THP showed a similar to normal pattern of distribution, with positive staining in the thick ascending limbs of the loop of Henle. Opn was localized in some nephrons in the thin limb of loop of Henle and on the papillary surface in the calyceal fornix. In contrast, in samples with a significantly increased number of deposits in the kidneys, the staining for both THP and Opn was strikingly enhanced and altered, with positive staining around the crystals as well as abnormal localization in the papilla. Interestingly, the occurrence of Opn was, however, more consistent than that of THP. This is a first study showing that in this nephrolithiasis model, normal localization of THP and Opn is altered and they are closely and concurrently associated with crystal deposits in vivo.

Exon 9 mutations in the WT1 gene, without influencing KTS splice isoforms, are also responsible for Frasier syndrome

We report new mutations in exon 9 of the WT1 gene that did not alter the ratio of +/– KTS splice isoforms in two unrelated patients with Frasier syndrome (FS). The mutation of intron 9 inducing defective alternative splicing was reported to be responsible for this syndrome. The mutations found in our cases occurred in the same exon of the WT1 gene as detected in Denys‐Drash syndrome (DDS) and could not be explained by the previously proposed mechanism. The results suggest that the two syndromes originate from the same WT1 gene abnormality. From a molecular biological point of view, we concluded that the two diseases were not separable, and that FS should be included as an atypical form of DDS. Hum Mutat 14:466–470, 1999.

Iron Absorption in Patients with Chronic Uremia on Maintenance Hemodialysis and in Healthy Volunteers Measured with a Simple Oral Iron Load Test

Gastrointestinal iron absorption was measured by an oral iron load test in patients with uremia on maintenance hemodialysis (n = 19), with iron overload (n = 9), iron deficiency (n = 10) and in healthy volunteers (n = 9). After an overnight fast, serum iron was measured before, and 1, 2, 4 and 6 h after administration of 100 mg ferrous chloride. Bone marrow iron was assessed after staining with Prussian blue. The study shows that iron absorption is impaired in uremic patients. Even uremic subjects with iron deficiency absorbed significantly less than normal subjects. Patients with iron overload and uremia absorbed even less, showing that the iron status of the patient influences absorption also in uremia.

β2-Adrenoceptor Activation Attenuates Endotoxin-Induced Acute Renal Failure

ABSTRACT. Abnormalities in the β 2 -adrenergic control of organ function have been implicated in the pathogenesis of several disease states, such as septic shock. The objectives of the present study were to define the contribution of β 2 -adrenoceptors (β 2 -AR) to normal renal physiology and to investigate whether overexpression of renal β 2 -AR might be potentially beneficial in preventing progressive renal damage associated with endotoxemia. Adenoviral transgenes containing the human β 2 -AR (Adeno-β 2 -AR) were constructed and delivered into the rat kidney by means of intraparenchymal injections. Administration of 10 9 total viral particles of Adeno-β 2 -AR induced an approximately threefold increase in β 2 -AR density in the renal tissue, which 2 wk after delivery, enhanced GFR and sodium reabsorption compared with control rats. The enhanced GFR was abolished by the addition of the β 2 -AR antagonist, ICI 118,551. Administration of lipopolysaccharide (LPS) caused a reduction in GFR, β 2 -AR density, and cAMP together with enhanced TNF-α mRNA in the kidney. In rats overexpressing β 2 -AR, the reduction in baseline GFR and elevation of TNF-α mRNA and leukocyte infiltration into the kidney associated with the endotoxin were blocked. These findings suggested the possibility that a renal-specific overexpression of β 2 -AR preserves basal renal function in response to a ligand-independent β 2 -AR activation and that the delivery of Adeno-β 2 -AR gene is a potential novel therapeutic strategy for treatment of acute renal failure associated with sepsis.

Characterization and Distribution of a New Enterotoxin‐Related Superantigen Produced by Staphylococcus aureus

Staphylococcal enterotoxins (SEs) are a family of structurally related pyrogenic exotoxins consisting of the five prototypic SEs (types A to E) and three newly characterized SEs (types G to I) produced by Staphylococcus aureus (S. aureus). They also work as superantigens and cause food poisoning and shock symptoms in humans. In this study, we cloned a new variant gene of the seg and characterized its superantigenic properties and distribution among the clinical isolates of S. aureus. The gene encodes a 233 amino acid protein which is highly homologous to SEG (97.7%). The variant SEG (SEGv) expressed by the cloned gene exerted mitogenic activity on human peripheral blood mononuclear cells at the concentration of 100 pg/ml. T cells bearing Vβ3, 12, 13.1, 13.2, 14 and 15 were preferentially expanded after stimulation with the recombinant protein. The mRNA of the variant seg gene was detected in the total RNA of the organisms bearing this gene. By PCR, 27 out of 48 clinical isolates of S. aureus (56%) possessed either the seg or variant seg gene. These findings suggest that SEG, or SEGv, is one of the most frequently produced superantigen exotoxins by S. aureus and may participate in the inflammatory process of the host by activating a distinct set of Vβ families of T cells.

Complement 4 locus II gene deletion and DQA1*0301 gene : Genetic risk factors for IgA nephropathy and Henoch-Schönlein nephritis

There have been several reports suggesting that the deficiency of complement 4 (C4) and/or deletion of C4 genes are the genetic risk factors in patients with IgA nephropathy (IgAN) and Henoch-Schönlein nephritis (HSN). In the current study, we tried to clarify the genetic structure of deleted C4 genes as well as the isotype deficiency of the patients. Also, we investigated the DQB and DRB genes which are located near the C4 genes to identify a possible linkage and to find the associated allele. Our results showed that locus II deletion of C4, not the C4B sequence loss, is a risk factor for these diseases and the deleted gene can be either C4A or C4B. There was no specific isotype deficiency or specific allotype which was significantly increased or decreased in the patients. But, there was an increased frequency of DQA1*0301 gene in the patient group (corrected p = 0.04), which suggests that DQA1*0301 as well as C4 gene deletion could be genetic risk factors for these diseases.

Heat Shock Protein 72/73 in Normal and Diseased Kidneys

The induction of heat shock (stress) proteins (HSP) is a response by cells due to a variety of physical, chemical, and infectious agents. They have a significant role as cytoprotectants, in the regulation of cellular functions, and in the recovery after sublethal injury. Using antibody to mammalian HSP 72/73, we have performed an immunohistological study of human renal tissue in normal and diseased states, including idiopathic nephrotic syndrome, proliferative and crescentic glomerulonephritis, and interstitial nephritis. A significant increase of HSP expression was noted in certain segments of the tubule in acute interstitial nephritis and in glomerulonephritis accompanied by active interstitial inflammation. A possible role by the inflammatory mediators in the induction of HSP in those cases is suggested.

Genetic study on HLA class II and class III region in the disease associated with IgA nephropathy.

Increased frequency of C4 gene deletions in IgA nephropathy and Henoch-Schönlein purpura nephritis. To determine the frequency of complement 4 (C4) deficiency among the patients with IgA nephropathy (IgAN) and Henoch-Schönlein purpura nephritis (HSPN), C4 and factor B protein allotypes and the DNA restriction fragment length polymorphism (RFLP) of C4, steroid 21-hydroxylase (21OHase), HLA DQ beta and DR beta chain genes were studied. Genomic DNA from 32 patients with IgAN, 24 patients with HSPN and 143 controls was digested with restriction enzyme TaqI or BamHI and subjected to Southern analysis. The frequency of C4 gene deletions was significantly increased in the patients (16.1 vs. 2.8%, p = 0.002). The serum C4 concentration in patients with C4 gene deletion was significantly lower than in patients without gene deletion (11.4 +/- 2.4 vs. 19.7 +/- 5.2 mg/dl, p = 0.001). DNA-RFLP typing of DQB/BamHI and DRB/TaqI showed increased frequency of 10.26 kb of D-DQw4/8/9 (87.5 vs. 64.5%, p = 0.004) and 5.22 kb of D-DR4 (66.1 vs. 41.7%, p = 0.03) among the patients. Segregation analysis showed that the association of the D-DQw4/8/9 and D-DR4 with the diseases was not responsible for the increased frequency of C4 gene deletion in the patients. The decreased concentration of C4 in sera in C4 gene-deleted patients might be directly involved in the pathogenesis of IgAN and HSPN.

Hepatopulmonary syndrome can show spontaneous resolution: Possible mechanism of portopulmonary hypertension overlap?

Abstract:  Hepatopulmonary syndrome (HPS) (hypoxaemia due to intrapulmonary vasodilation and a right‐to‐left shunt associated with liver disease) resolves after liver transplantation. The authors describe a case of spontaneous resolution of HPS prior to liver transplantation. This patient was diagnosed with HPS associated with extra‐hepatic biliary atresia when she was 10 years old. She exhibited digital clubbing, facial vascular dilation, cyanosis, and suffered from dyspnoea during exercise. The patients PaO2 at rest was 53.8 mm Hg in room air and a Technetium‐99m macro‐aggregated albumin lung perfusion scan demonstrated a right‐to‐left shunt. Although her symptoms and laboratory data supported a diagnosis of HPS, she nevertheless showed spontaneous resolution within 2 years. When she was 14 years old, pulmonary hypertension was evident upon examination of her echocardiogram. HPS may be improved or masked by an accidental overlap with pulmonary hypertension in the terminal stage of liver disease.