Haruo Mizuno

Interleukin-1β induces the expression of lipocortin 1 mRNA in cultured rat cortical astrocytes

Lipocortin 1 (LC1) has been shown to increase in neuronal damage and act as a neuroprotectant and a neurotrophic factor. IL-1beta acts as a mediator of inflammation and has been reported as a potent inducer of various neurotrophic factors including nerve growth factor and fibroblast growth factor. In this study, we investigated the relationship between LC1 and IL-1beta in cultured rat astrocytes. Time-and dose-dependent experiments of IL-1beta on rat cortical astrocytes in culture revealed that the expression of LC1 mRNA was significantly augmented by IL-1beta at 8 h, 10 ng/ml. In addition, IL-1beta evoked an extracellular secretion of LC1 without its cytotoxic effects. The effect of IL-1beta was completely abolished when we treated cells with inhibitor of mitogen-activated protein kinases (MAPKs) (PD98059) (25 microM), phospholipase A(2) inhibitor mepacrine (30 microM) and protein synthesis inhibitor cycloheximide (CHX) (10 microg/ml). This suggests that induction of LC1 by IL-1beta is through a MAPKs and phospholipaseA(2) pathway and requires protein synthesis. These results indicate that IL-1beta released in the central nervous system (CNS) injury can stimulate the transcription of the LC1 gene. Subsequent synthesis and release of LC1 may provide trophic support to neurons and modulate the action of IL-1beta in brain damage.

Glucocorticoid induced the expression of mRNA and the secretion of lipocortin 1 in rat astrocytoma cells.

The lipocortins are a family of structurally related proteins that have been shown to be implicated in multiple aspects of cell biology. Subsequent research has shown that lipocortin 1 (LC1) participates in the physiological and pathological functioning of the CNS and neuroendocrine system. In the present study, the effects of 12-O-tetradecanoylphorbol 13-acetate (TPA), dibutyryl cyclic AMP (Bt2cAMP) or dexamethasone (DEX) on expression of LC1 were investigated by a sandwich enzyme immunoassay and reverse transcription polymerase chain reaction (RT-PCR) in rat astrocytoma (C6) cells. Time-dependent experiments revealed that the intracellular protein content and the mRNA of rat LC1 increased significantly 4 h after TPA (10 mM) or DEX (1 microM) addition. TPA and DEX elicited a prominent induction of LC1 at 10(-8) M and 10(-6) M, respectively. Bt2cAMP (0.5 mM) also appeared to induce, but the induction was not statistically significant. In addition, DEX increased the extracellular secretion of LC1 without cytotoxicity. These results suggest that LC1 synthesis is chemically induced and selectively released from C6 cells by dexamethasone.

Clinical significance of heterozygous carriers associated with compensated hypothyroidism in R450H, a common inactivating mutation of the thyrotropin receptor gene in Japanese.

Loss-of-function mutations in the thyrotropin receptor (TSHR) gene were described as a syndrome characterized by thyroid hyposensivity to biologically active TSH, ranging from euthyroid to severe hypothyroidism. In Japanese, a common mutation in the TSHR gene is R450H, which demonstrated moderately impaired receptor function. We studied six subjects of Japanese origin whose major abnormality was persistent hyperthyrotropinemia by genetic sequence analysis of the TSHR gene. Three subjects were homozygous for the R450H mutation, whereas the three remaining subjects were single heterozygous. Homozygous subjects displayed mild hypothyroidism confirmed by moderately elevated basal TSH levels and excessive TSH response to TRH administration. Heterozygous subjects also demonstrated fully or partially compensated hypothyroidism, but less severe than that of homozygous subjects. More frequent involvement of the R450H mutation in the TSHR gene in Japanese was identified. In addition, a good correlation between phenotype and genotype was demonstrated in respect to biochemical analysis and drug dosage. Our observations showed clinical significance of heterozygosity associated with compensated hypothyroidism in spite of only mildly impaired receptor function.

Longitudinal Evaluation of Patients with a Homozygous R450H Mutation of the TSH Receptor Gene

Background/Aim: The R450H mutation of the TSH receptor (TSHR) gene has been frequently observed in Japanese patients with resistance to TSH. The purpose of this study was to clarify the phenotype of patients with a homozygous R450H mutation of the TSHR gene; the mutant receptor has previously demonstrated moderately impaired function in vitro. Methods: We performed a clinical investigation of 5 Japanese patients who had hyperthyrotropinemia as neonates, in whom a homozygous R450H mutation of the TSHR gene had been demonstrated by genetic sequencing analysis. Results: The thyroid hormone levels of the patients were normal in early infancy, although their serum levels of TSH were mildly elevated. After supplemental treatment with levothyroxine sodium (L-T4) was started, we had to increase the dose to maintain the level of TSH within the normal range in all patients. Thyroid dysfunction became obvious in one patient at reexamination during adolescence when L-T4 treatment was stopped for 1 month. Four patients were examined for intelligence quotient and their scores were normal. Conclusions: Thyroid hormone replacement therapy should be considered based on biological data in patients with hyperthyrotropinemia who have a homozygous R450H mutation of the TSHR gene even if they do not exhibit obvious hypothyroidism in infancy.

Clinical characteristics of eight patients with congenital nephrogenic diabetes insipidus

Congenital nephrogenic diabetes insipidus (NDI) is characterized by the insensitivity of the distal nephron to arginine vasopressin. Clinical knowledge of this disease is based largely on case reports. For this study, we investigated the clinical findings of eight patients in terms of age at onset, age at diagnosis, main complaint, results of physical examination, the diagnosis, the effect of treatment, kidney function, and presence or absence of gene defects. The main complaints of all eight cases at initial examination were unknown fever, failure to thrive, and short stature. Polyuria and polydipsia are not always the chief complaints with congenital NDI. In one case, diabetes insipidus could be diagnosed based only on the results of a 5% hypertonic saline test. In six cases, we found abnormalities in the V2 receptor gene. Initially, trichlormethiazide therapy was shown to have a significant effect on polyuria; however, this effect decreased over time. In one patient with partial NDI, the addition of trichlormethiazide twice a day to 1-desamino-8-d-arginine vasopression increased urine osmolality in the morning and caused nocturia to disappear. Results of 99mTc-diethylenetriamine pentaacetic acid kidney scintigraphy revealed a slight decrease in glomerular filtration rate in three patients. No patient experienced serious renal dysfunction.

Successful Treatment of Partial Nephrogenic Diabetes insipidus with Thiazide and Desmopressin

Objective: To clarify whether combination treatment with desmopressin (DDAVP) and thiazide was clinically effective in a patient with congenital nephrogenic diabetes insipidus (CNDI), we evaluated the treatment in a 7-year-old boy with CNDI who had demonstrated a partial response to DDAVP. Method: Both volume of urine and the presence of nocturia were determined during treatment. Result: Neither the usual therapy of a low-salt diet and a thiazide nor intranasal therapy with a large dose of DDAVP was effective. However, combination treatment resulted in a decrease in urinary volume and the disappearance of nocturia. Conclusion: DDAVP coupled with thiazide may be useful for CNDI in patients who have shown a partial response to DDAVP.

Elevated aldosterone in amniotic fluid and maternal blood has diagnostic potential in pregnancies complicated with a fetus of Bartter syndrome.

Pregnancies with fetuses affected with the Bartter syndrome, an autosomal recessive disorder of hyperreninism and hyperaldosteronism, are complicated by early onset of polyhydramnios which results in preterm deliveries. We have assessed biochemical changes in amniotic fluid and the mother’s blood with a view to early diagnosis. Aldosterone levels of both amniotic fluid and the mother’s blood were found to be increased at 27 weeks of gestation, while electrolyte levels did not differ significantly from those reported earlier for controls. After birth the baby suffered from polyuria with hyponatremia, hypomagnesemia and hypercalciuria which could be controlled by treatment with sodium chloride and magnesium. Elevated aldosterone thus might be a useful marker for early diagnostic purposes.

Neurotrophic action of lipocortin 1 derived from astrocytes on cultured rat cortical neurons

The lipocortins are a family of structurally related proteins, namely an annexin family, that exerts a variety of cellular functions through Ca2+-dependent binding to phospholipase A2 [EC 3.1. 1.4], including a crucial role in the central nervous system (CNS) such as antipyrogenic, thermoregulatory and neuroprotective agents in vivo. To elucidate the paradigm of lipocortin 1 functions in the CNS, we have first demonstrated (1) the induction and subsequent extracellular secretion of LC1 by glucocorticoid in cultured rat astrocytes, and (2) neurotrophic activities (survival-promoting, neuritogenic and synaptogenic actions on rat cortical neurons) of recombinant LC1. Time-and dose-dependent experiments of a synthetic glucocorticoid, dexamethasone (DEX), on rat cortical astrocytes in culture revealed that the expression of the intracellular LC1 mRNA and protein were significantly augmented by DEX (1 microM). In addition, DEX evoked an extracellular secretion of LC1 without its cytotoxic effects. Furthermore, the recombinant LC1 appeared to promote not only the survival and neurite outgrowth but also the synaptogenesis of embryonal rat cortical neurons. These results suggest that LC1 induced and selectively released from astrocytes by either endogenously or exogenously introduced glucocorticoids may play a specific and essential role on development and regeneration of the central nervous system.

Clinical and genetic analyses of presumed shwachman-diamond syndrome in Japan

Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disorder characterized by exocrine pancreatic insufficiency, bone marrow dysfunction, and skeletal abnormalities. SBDS was identified as a causative gene for SDS in 2003, and genetic analyses of SDS have been performed.We performed genetic analysis of 13 Japanese patients with presumed SDS and found that 10 of them had SBDS mutations. Most patients had recurrent mutations (181-184TA→CT and 258+2T→C); however, 2 patients had unique mutations (259-1G→A and 428C→G). Although genetic analysis is useful for definitive diagnosis and for genetic counseling of SDS patients and families, SDS appears to be a genetically heterogeneous disorder. In addition, presumed SDS patients without SBDS mutations may be included in other disorders.

Guidelines for Mass Screening of Congenital Hypothyroidism (2014 revision)

Purpose of developing the guidelines: Mass screening for congenital hypothyroidism started in 1979 in Japan, and the prognosis for intelligence has been improved by early diagnosis and treatment. The incidence was about 1/4000 of the birth population, but it has increased due to diagnosis of subclinical congenital hypothyroidism. The disease requires continuous treatment, and specialized medical facilities should make a differential diagnosis and treat subjects who are positive in mass screening to avoid unnecessary treatment. The Guidelines for Mass Screening of Congenital Hypothyroidism (1998 version) were developed by the Mass Screening Committee of the Japanese Society for Pediatric Endocrinology in 1998. Subsequently, new findings on prognosis and problems in the adult phase have emerged. Based on these new findings, the 1998 guidelines were revised in the current document (hereinafter referred to as the Guidelines). Target disease/conditions: Primary congenital hypothyroidism. Users of the Guidelines: Physician specialists in pediatric endocrinology, pediatric specialists, physicians referring patients to pediatric practitioners, general physicians, laboratory technicians in charge of mass screening, and patients.