Type d syndrome of inappropriate antidiuretic hormone secretion in a schizophrenia patient with polydipsia

A 55-year-old man with schizophrenia developed water intoxication due to primary polydipsia. His manner of antidiuretic hormone secretion was investigated by water loading and infusion of hypertonic saline to clarify the form of the syndrome of inappropriate antidiuretic hormone secretion. The plasma antidiuretic hormone level, which may be involved in the occurrence of water intoxication, was consistently low in this patient, and linked to type D syndrome of inappropriate antidiuretic hormone secretion, designated “hypovasopressinemic antidiuresis”. Although this type is not common, it should be considered as a pathophysiology for water intoxication in schizophrenia patients.

Adiponectin suppresses colorectal carcinogenesis under the high-fat diet condition

BACKGROUND AND AIMS

The effect of adiponectin on colorectal carcinogenesis has been proposed but not fully investigated. We investigated the effect of adiponectin deficiency on the development of colorectal cancer.

METHODS

We generated three types of gene-deficient mice (adiponectin-deficient, adiponectin receptor 1-deficient, and adiponectin receptor 2-deficient) and investigated chemical-induced colon polyp formation and cell proliferation in colon epithelium. Western blot analysis was performed to elucidate the mechanism which affected colorectal carcinogenesis by adiponectin deficiency.

RESULTS

The numbers of colon polyps were significantly increased in adiponectin-deficient mice compared with wild-type mice fed a high-fat diet. However, no difference was observed between wild-type and adiponectin-deficient mice fed a basal diet. A significant increase in cell proliferative activity was also observed in the colonic epithelium of the adiponectin-deficient mice when compared with wild-type mice fed a high-fat diet; however, no difference was observed between wild-type and adiponectin-deficient mice fed a basal diet. Similarly, an increase in epithelial cell proliferation was observed in adiponectin receptor 1-deficient mice, but not in adiponectin receptor 2-deficient mice. Western blot analysis revealed activation of mammalian target of rapamycin, p70 S6 kinase, S6 protein and inactivation of AMP-activated protein kinase in the colon epithelium of adiponectin-deficient mice fed with high-fat diet.

CONCLUSIONS

Adiponectin suppresses colonic epithelial proliferation via inhibition of the mammalian target of the rapamycin pathway under a high-fat diet, but not under a basal diet. These studies indicate a novel mechanism of suppression of colorectal carcinogenesis induced by a Western-style high-fat diet.

Maternal immune activation in mice delays myelination and axonal development in the hippocampus of the offspring

Epidemiological data suggest a relationship between maternal infection and a high incidence of schizophrenia in offspring. An animal model based on this hypothesis was made by injecting double-stranded RNA, polyinosinic-polycytidylic acid (poly-I:C), into early pregnant mice, and their offspring were examined for biochemical and histological abnormalities. Mouse brains were examined with special reference to oligodendrocytes, which have been implicated in several neurodevelopmental disorders. We detected a significant decrease of myelin basic protein (MBP) mRNA and protein at early postnatal periods in poly-I:C mice. MBP immunocytochemistry and electron microscopy revealed that the hippocampus of juvenile poly-I:C mice was less myelinated than in PBS mice, with no significant loss of oligodendrocytes. In addition, axonal diameters were significantly smaller in juvenile poly-I:C mice than in control mice. These abnormalities reverted to normal levels when the animals reached the adult stage. These findings suggest that retarded myelination and axonal abnormalities in early postnatal stages caused by maternal immune activation could be related to schizophrenia-related behaviors in adulthood.

Lysophosphatidylcholine induces delayed myelination in the juvenile ventral hippocampus and behavioral alterations in adulthood

Maternal virus infection or maternal polyinosinic-polycytidilic acid injection confers behavioral alterations including deficit in prepulse inhibition on the offspring. We previously found delayed myelination specifically in the early postnatal hippocampus in the polyinosinic-polycytidilic acid-injection model. To test whether the transient delay in myelination in the juvenile hippocampus leads to abnormal behaviors after adolescence, we injected lysophosphatidylcholine, a potent demyelinating agent, into the ventral hippocampus of the 10-day-old rat. The lysophosphatidylcholine treatment yielded hypomyelination at postnatal day 16, but myelination reverted to normal level in the adult rat. Neuronal arrays and morphology were not disturbed in this model. We then performed a battery of behavioral tests on the lysophosphatidylcholine-treated and control PBS-injected rats. The lysophosphatidylcholine-treated rats showed deficit in prepulse inhibition, motor hyperactivity in response to methamphetamine and anxiety-related behaviors, all of which are typical behaviors observed in the maternal infection models. These findings suggest that the timing of myelination in the early postnatal hippocampus is crucial for the proper development of sensorimotor and emotional functions. The lysophosphatidylcholine-treated rat without a gross anatomical defect is useful as a model for psychotic disorders.

Immunosuppressive effect of ER-38925, a retinoic acid receptor subtype α-selective agonist, in mouse models of human graft-vs-host disease

Graft-vs-host disease (GVHD) is a devastating disorder that determines the prognosis of patients who receive a bone marrow transplant. GVHD is caused by donor cells responding to host disparate MHC alleles. In this report, we demonstrate that ER-38925, a newly discovered retinoid agonist with selectivity to retinoic acid receptor subtype α (RAR-α), is a potent immunosuppressive agent in mouse models of human GVHD. In a mouse model of lethal acute GVHD (aGVHD), ER-38925 prolonged the lifespan of the recipient mice in a dose-dependent manner. Its effect at 1 mg/kg was almost comparable to that of cyclosporin A at 30 mg/kg. ER-38925 profoundly prevented the development of antiallogeneic cytotoxic T lymphocyte (CTL) response in the mouse model of aGVHD at 0.1 and 0.3 mg/kg. It strongly inhibited in vitro proliferation of alloantigenstimulated donor T lymphocytes, and RAR-α seemed to play an exclusive role in this effect since inhibition by all-trans retinoic acid, which can activate all subtypes of RAR, was completely reversed by an RAR-α selective antagonist. Moreover, it significantly inhibited the elevation of serum IL-12 and IFN-γ and LPS-induced serum TNF-α elevation, all of which are known to be crucial disease-exacerbating factors in this model and human GVHD, in the mouse model of aGVHD. These results suggest that ER-38925 prevents the development of aGVHD through substantial inhibition of anti-allogeneic responses of donor T lymphocytes. In addition, in vivo administration of ER-38925 also blocked serum anti-DNA autoantibody production in a mouse model of human chronic GVHD. This is the first report to clearly show the remarkable immunosuppressive effects of an RAR-α selective agonist in mouse models of human GVHD. These findings may allow an RAR-αselective agonist like ER-38925 to serve as a novel therapy to prevent both acute and chronic types of human GVHD.

Knockdown of the L3/Lhx8 gene suppresses cholinergic differentiation of murine embryonic stem cell-derived spheres

L3/Lhx8, a member of the Lim-homeobox gene family, is selectively and specifically expressed in the murine embryonic medial ganglionic eminence (MGE). Our previous study demonstrated that L3/Lhx8-deficient mice specifically lack cholinergic neurons in the basal forebrain. In this manuscript, we report the in vitro effects of reduced L3/Lhx8 gene expression on cholinergic differentiation in murine embryonic stem (ES) cell-derived spheres without dissociation. The knockdown of L3/Lhx8 gene expression dramatically decreased the cholinergic phenotype of spheres without altering other known phenotypes (TuJ1, GABA and GFAP). These results strongly suggest that L3/Lhx8 is a key factor for cholinergic differentiation of murine ES cell-derived spheres and is involved in basal forebrain development.

A novel role for Fyn: Change in sphere formation ability in murine embryonic stem cells

Fyn, a member of the Src-family protein tyrosine kinase (PTK), is an essential factor in myelination in the CNS and is involved in murine embryonic stem (ES) cell growth and differentiation. Although dysfunctions of Fyn have been comparatively studied, the gain of function by ectopic expression, especially using ES cells, has seldom been investigated. In this article, we give the first report of the involvement of Fyn alteration in the sphere formation ability of murine ES cells. First, transient transfection of Fyn hardly affected multiplication and specialization. Then, we investigated Fyn overexpression using ES cells, which stably express Fyn. As a result, altered sphere formation capability was observed in all clones stably expressing Fyn. These results may provide important information for reproduction medical treatment using ES cells.

L3/Lhx8 is a pivotal factor for cholinergic differentiation of murine embryonic stem cells

L3/Lhx8 is a member of the LIM-homeobox gene family. Previously, we demonstrated that L3/Lhx8-null mice specifically lacked cholinergic neurons in the basal forebrain. In the present study, we conditionally suppressed L3/Lhx8 function during retinoic acid-induced neural differentiation of a murine embryonic stem (ES) cell line using an L3/Lhx8-targeted small interfering RNA (siRNA) produced by an H1.2 promoter-driven vector. Our culture conditions induced efficient differentiation of the ES cells into neurons and astrocytes, but far less efficient differentiation into oligodendrocytes. Suppression of L3/Lhx8 expression by siRNA led to a dramatic decrease in the number of cells positive for the cholinergic marker ChAT, and overexpression of L3/Lhx8 recovered this effect. However, no significant changes were observed in the number of Tuj1+ neurons and GABA+ cells. These results strongly suggest that L3/Lhx8 is a key factor in the cholinergic differentiation of murine ES cells and is involved in basal forebrain development.

Pharmacological evidence of cholinergic involvement in adult hippocampal neurogenesis in rats

In adult hippocampus, neural progenitor cells give rise to neurons throughout life, and the neurogenesis is modulated by various intrinsic and extrinsic factors. Recent reports showed that lesion of septal cholinergic nuclei projecting to hippocampus suppressed the survival of newborn cells in the dentate gyrus (DG) of hippocampus. Here, we studied whether pharmacological treatment to activate or inhibit the cholinergic system could modulate adult hippocampal neurogenesis. 5'-Bromo-2'-deoxyuridine (BrdU) was injected to label dividing cells before the drug treatment. Immunohistochemical analysis was performed in normal rats chronically treated with an acetylcholinesterase inhibitor donepezil or a muscarinic acetylcholine receptor blocker scopolamine for four weeks. Donepezil increased, but scopolamine decreased, the number of BrdU-positive cells in the DG as compared with the control. Neither drug altered the percentage of BrdU-positive cells that were also positive for a neuronal marker neuronal nuclei, nor net population of proliferative cells labeled with proliferating cell nuclear antigen. We also found that donepezil enhanced, and scopolamine suppressed, the expression level of phosphorylated cAMP response element binding protein (CREB), which is related to cell survival, in the DG. These results indicate that donepezil enhances and scopolamine suppresses the survival of newborn cells in the DG via CREB signaling without affecting neural progenitor cell proliferation and the neuronal differentiation. This is the first evidence that pharmacological manipulation of the cholinergic system can modulate adult hippocampal neurogenesis.

Absence of an association between the polymorphisms in the genes encoding adiponectin receptors and type 2 diabetes

AIMS/HYPOTHESIS

Secreted by adipocytes, adiponectin is a hormone that acts as an antidiabetic and anti-atherogenic adipokine. We recently cloned the genes encoding two adiponectin receptors (ADIPOR1 and ADIPOR2). The aim of this study was to examine whether ADIPOR1 and/or ADIPOR2 play a major role in genetic susceptibility to insulin resistance or type 2 diabetes in the Japanese population.

METHODS

By direct sequencing and a search of public databases, we identified single nucleotide polymorphisms (SNPs) in ADIPOR1 and ADIPOR2, and investigated whether these SNPs are associated with insulin resistance and type 2 diabetes in the Japanese population.

RESULTS

The linkage disequilibrium (LD) in the chromosomal region of ADIPOR1 was almost completely preserved, whereas the LD in ADIPOR2 was less well preserved. None of the SNPs in ADIPOR1 or ADIPOR2 were significantly associated with insulin resistance or type 2 diabetes. No differences in ADIPOR1 or ADIPOR2 haplotype frequencies were observed between type 2 diabetic and non-diabetic subjects.

CONCLUSIONS/INTERPRETATION

Genetic variations in ADIPOR1 or ADIPOR2 are unlikely to lead to a common genetic predisposition to insulin resistance or type 2 diabetes in the Japanese population.