CD146/MCAM links doxorubicin-induced epigenetic dysregulation to the impaired fatty acid transportation in H9c2 cardiomyoblasts

CD146/MCAM has garnered significant attention for its potential contribution to cardiovascular disease; however, the transcriptional regulation and functions remain unclear. To explore these processes regarding cardiomyopathy, we employed doxorubicin, a widely used stressor for cardiomyocytes. Our in vitro study on H9c2 cardiomyoblasts highlights that, besides impairing the fatty acid uptake in the cells, doxorubicin suppressed the expression of fatty acid binding protein 4 (Fabp4) along with the histone deacetylase 9 (Hdac9), bromodomain and extra-terminal domain proteins (BETs: Brd2 and Brd4), while augmented the production of CD146/MCAM. Silencing and chemical inhibition of Hdac9 further augmented CD146/MCAM and deteriorated fatty acid uptake. In contrast, chemical inhibition of BETs as well as silencing of MCAM/CD146 ameliorated fatty acid uptake. Moreover, protein kinase C (PKC) inhibition abrogated CD146/MCAM, particularly in the nucleus. Taken together, our results suggest that epigenetic dysregulation of Hdac9, Brd2, and Brd4 alters CD146/MCAM expression, deteriorating fatty acid uptake by downregulating Fabp4. This process depends on the PKC-mediated nuclear translocation of CD146. Thus, this study highlights a pivotal role of CD146/MCAM in doxorubicin-induced cardiomyopathy.

Relationship between Ca2+ and cAMP as second messengers in ACTH-induced cortisol production in bovine adrenal fasciculata cells

In adrenal fasciculata cells stimulated by ACTH, Ca2+ and cAMP play indispensable roles as second messengers in cortisol production. However, whether their second messengers cooperatively or independently participate in steroid production remains unclear. We focused on the roles of Ca2+ and cAMP in cortisol production in bovine adrenal fasciculata cells stimulated by ACTH for a relatively short period (1 h). Incubation of the cells with 100 pM ACTH in Ca2+-containing (normal) medium for 1 h increased cortisol production without affecting cAMP content. In contrast, treatment of the cells with the peptide at a higher concentration (1 nM) significantly augmented both cortisol production and cAMP content. However, ACTH did not increase either of them in the Ca2+-free medium. ACTH rapidly increased the intracellular free Ca2+ concentration ([Ca2+]i) in the normal medium, but did not influence [Ca2+]i in the Ca2+-free medium, indicating that ACTH caused Ca2+ influx into the cells. ACTH-induced Ca2+ influx and cortisol production were suppressed by a voltage-sensitive L-type Ca2+ channel blocker but not by a T-type, N-type, or P-type Ca2+ channel blocker. In contrast, dibutyryl cAMP, a cell-permeable cAMP analog, greatly enhanced cortisol production in the normal or Ca2+-free medium and slowly caused Ca2+ influx into the cells. These results strongly suggest that Ca2+, as a second messenger, is more critical than cAMP for cortisol production. However, both second messengers jointly participate in the production in adrenal fasciculata cells stimulated by ACTH.

Mizagliflozin, a selective SGLT1 inhibitor, improves vascular cognitive impairment in a mouse model of small vessel disease

Previously, we showed that sodium/glucose cotransporter 1 (SGLT1) participates in vascular cognitive impairment in small vessel disease. We hypothesized that SGLT1 inhibitors can improve the small vessel disease induced-vascular cognitive impairment. We examined the effects of mizagliflozin, a selective SGLT1 inhibitor, and phlorizin, a non-selective SGLT inhibitor, on vascular cognitive impairment in a mouse model of small vessel disease. Small vessel disease was created using a mouse model of asymmetric common carotid artery surgery (ACAS). Two and/or 4 weeks after ACAS, all experiments were performed. Cerebral blood flow (CBF) was decreased in ACAS compared with sham-operated mice. Phlorizin but not mizagliflozin reversed the decreased CBF of ACAS mice. Both mizagliflozin and phlorizin reversed the ACAS-induced decrease in the latency to fall in a wire hang test of ACAS mice. Moreover, they reversed the ACAS-induced longer escape latencies in the Morris water maze test of ACAS mice. ACAS increased SGLT1 and proinflammatory cytokine gene expressions in mouse brains and phlorizin but not mizagliflozin normalized all gene expressions in ACAS mice. Hematoxylin/eosin staining demonstrated that they inhibited pyknotic cell death in the ACAS mouse hippocampus. In PC12HS cells, IL-1β increased SGLT1 expression and decreased survival rates of cells. Both mizagliflozin and phlorizin increased the survival rates of IL-1β-treated PC12HS cells. These results suggest that mizagliflozin and phlorizin can improve vascular cognitive impairment through the inhibition of neural SGLT1 and phlorizin also does so through the improvement of CBF in a mouse model of small vessel disease.

Chronic HDAC6 Activation Induces Atrial Fibrillation Through Atrial Electrical and Structural Remodeling in Transgenic Mice

Atrial fibrillation (AF) is a relatively common complication of hypertension. Chronic hypertension induces cardiac HDAC6 catalytic activity. However, whether HDAC6 activation contributes to hypertension-induced AF is still uncertain. We examined whether chronic cardiac HDAC6 activation-induced atrial remodeling, leading to AF induction.The HDAC6 constitutively active transgenic (TG) (HDAC6 active TG) mouse overexpressing the active HDAC6 protein, specifically in cardiomyocytes, was created to examine the effects of chronic HDAC6 activation on atrial electrical and structural remodeling and AF induction in HDAC6 active TG and non-transgenic (NTG) mice. Left atrial burst pacing (S₁S₁ = 30 msec) for 15-30 sec significantly increased the frequency of sustained AF in HDAC6 active-TG mice compared with NTG mice. Left steady-state atrial pacing (S₁S₁ = 80 msec) decreased the atrial conduction velocity in isolated HDAC6 active TG compared with NTG mouse atria. The atrial size was similar between HDAC6 active TG and NTG mice. In contrast, atrial interstitial fibrosis increased in HDAC6 active TG compared with that of NTG mouse atria. While protein expression levels of both CX40 and CX43 were similar between HDAC6 active TG and NTG mouse atria, a heterogeneous distribution of CX40 and CX43 occurred in HDAC6 active-TG mouse atria but not in NTG mouse atria. Gene expression of interleukin 6 increased in HDAC6 active TG compared with NTG mouse atria.Chronic cardiac HDAC6 activation induced atrial electrical and structural remodeling, and sustained AF. Hypertension-induced cardiac HDAC6 catalytic activity may play important roles in the development of AF.

SGLT1 participates in the development of vascular cognitive impairment in a mouse model of small vessel disease

Sodium/glucose cotransporter 1 (SGLT1) participates in ischemia-reperfusion-induced cerebral injury. However, whether SGLT1 participates in the development of small vessel disease induced-vascular cognitive impairment is unknown. We examined the roles of SGLT1 in the development of vascular cognitive impairment in a mouse model of small vessel disease. Small vessel disease was created by placement of an ameroid constrictor around the right common carotid artery (CCA) and placement of a microcoil around the left CCA (ACAS) in wild-type (WT) and SGLT1-knock out (KO) mice. Two and/or 4 weeks after ACAS, all experiments were performed. Hematoxylin/eosin staining demonstrated that the number of pyknotic cell deaths was greater in the ACAS WT than ACAS SGLT1-KO hippocampus. The latency to fall in a wire hang test was significantly shorter in ACAS than sham-operated WT mice, whereas it was similar between ACAS and sham-operated SGLT1-KO mice. The Morris water maze test revealed that ACAS WT mice exhibited longer escape latencies than ACAS SGLT1-KO mice. ACAS significantly increased SGLT1 gene expression in WT mouse brains. Gene expressions of MCP-1, IL-1β, TNF-α, and IL-6 were increased in ACAS WT compared with sham-operated WT mouse brains. Their increased gene expressions were significantly decreased in ACAS SGLT1-KO compared with ACAS WT mice. These results suggest that SGLT1 plays important roles in the development of small vessel dementia.

Phlorizin prevents electrically-induced ventricular tachyarrhythmia during ischemia in langendorff-perfused guinea-pig hearts

Phlorizin is a type of flavonoids and has a peroxynitrite scavenging effect. This study aimed to elucidate the effects of phlorizin on ischemia-induced ventricular tachyarrhythmia (VT). Optical signals from the epicardial surface of the ventricle or left ventricular end diastolic pressure (LVEDP) were recorded during acute global ischemia in 42 Langendorff-perfused guinea pig hearts. Experiments were performed in the control condition and in the presence of phlorizin or N-2-mercaptopropionylglycine (2-MPG), a peroxynitrite scavenger, respectively. Mean action potential duration at 20 min of ischemia did not differ among the three interventions. Impulse conduction time-dependently slowed during 20 min of ischemia in the control. Phlorizin but not 2-MPG improved the ischemic conduction slowing at 15 and 20 min of ischemia. Programmed stimulation induced VT at 20 min of ischemia in the control and in the presence of 2-MPG but not in the presence of phlorizin (p<0.05). LVEDP was increased during 30 min of ischemia in the control and in the presence of 2-MPG but not in the presence of phlorizin. These results indicate that phlorizin prevents VT through the improvement of impulse conduction slowing during ischemia. Phlorizin may be more useful for ischemia-induced VT than 2-MPG.

Nicorandil improves electrical remodelling, leading to the prevention of electrically induced ventricular tachyarrhythmia in a mouse model of desmin-related cardiomyopathy

1. Transgenic (TG) mice overexpressing an arg120gly missense mutation in heat shock protein B5 (HSPB5; i.e. R120G TG mice) exhibit desmin-related cardiomyopathy. Recently, the cardioprotective effect of nicorandil has been shown to prolong the survival of R120G TG mice. However, whether the TG mice exhibit ventricular arrhythmias and whether nicorandil can inhibit these arrhythmias remain unknown. In the present study we examined the effects of chronic nicorandil administration on ventricular electrical remodelling and arrhythmias in R120G TG mice. 2. Mice were administered nicorandil (15 mg/kg per day) or vehicle (water) orally from 5 to 30 weeks of age. Electrocardiograms (ECG) and optical action potentials were recorded from R120G TG mouse hearts. In addition, the expression of ventricular connexin 43 and the cardiac Na(+) channel Nav1.5 was examined in TG mice. 3. All ECG parameters tested were prolonged in R120G TG compared with non-transgenic (NTG) mice. Nicorandil improved the prolonged P, PQ and QRS intervals in R120G TG mice. Interestingly, impulse conduction slowing and increases in the expression of total and phosphorylated connexin 43 and Nav1.5 were observed in ventricles from R120G TG compared with NTG mice. Nicorandil improved ventricular impulse conduction slowing and normalized the increased protein expression levels of total and phosphorylated connexin 43, but not of Nav1.5, in R120G TG mouse hearts. Electrical rapid pacing at the ventricle induced ventricular tachyarrhythmias (VT) in six of eight R120G TG mouse hearts, but not in any of the eight nicorandil-treated R120G TG mouse hearts (P < 0.05). 4. These findings demonstrate that nicorandil inhibits cardiac electrical remodelling and that the prevention of VT by nicorandil is associated with normalization of connexin 43 expression in this model.

Abstract 037: Transient Cardiac Expression Of Constitutively Active G alpha Q Activates Renin-angiotensin System, Leading To Progressive Heart Failure And Ventricular Arrhythmias In Transgenic Mice

Introduction: Transgenic mice with transient cardiac expression of constitutively active Galpha q (Gαq-TG) caused progressive heart failure and ventricular arrhythmias after the initiating stimulus becomes undetectable. However, the mechanisms are still unknown. Renin-angiotensin system plays a critical role in the development of cardiac hypertrophy and heart failure. We examined the effects of chronic administration of olmesartan on ventricular function, the number of premature ventricular contractions (PVC), and ventricular remodeling in Gαq-TG mice.

Methods and Results: Olmesartan (1 mg/kg/day) or vehicle was chronically administered to Gαq-TG from 6 to 32 weeks of age, and all experiments were performed in mice at the age of 32 weeks. Chronic olmesartan treatment prevented the severe reduction of left ventricular fractional shortening and inhibited ventricular interstitial fibrosis and ventricular myocyte hypertrophy in Gαq-TG. Electrocardiogram demonstrated that premature ventricular contraction (PVC) was frequently (more than 20 beats/min) observed in 9 of 10 vehicle-treated Gαq-TG but in none of 10 olmesartan -treated Gαq-TG. The QT interval was significantly shorter in olmesartan-treated Gαq-TG than vehicle-treated Gαq-TG. CTGF, collagen type 1, ANP, BNP, and β-MHC gene expression was increased in vehicle-treated Gαq-TG. Olmesartan significantly decreased these gene expressions in Gαq-TG. Moreover, protein expressions of canonical transient receptor potential (TRPC) channels 3 and 6 increased in vehicle-treated Gαq-TG hearts. Olmesartan significantly decreased TRPC6 expressions in Gαq-TG. Angiotensin converting enzyme (ACE) 1 and 2 gene expressions were also increased in vehicle-treated Gαq-TG and was not decreased to the control level in olmesartan-treated Gαq-TG.

Conclusions: These findings suggest that renin-angiotensin system has an important role in the development of cardiac hypertrophy and heart failure even if the initiating stimulus is different from the activation of renin-angiotensin system.

Nicorandil prevents Gαq-induced progressive heart failure and ventricular arrhythmias in transgenic mice

BACKGROUND

Beneficial effects of nicorandil on the treatment of hypertensive heart failure (HF) and ischemic heart disease have been suggested. However, whether nicorandil has inhibitory effects on HF and ventricular arrhythmias caused by the activation of G protein alpha q (Gα(q)) -coupled receptor (GPCR) signaling still remains unknown. We investigated these inhibitory effects of nicorandil in transgenic mice with transient cardiac expression of activated Gα(q) (Gα(q)-TG).

METHODOLOGY/PRINCIPAL FINDINGS

Nicorandil (6 mg/kg/day) or vehicle was chronically administered to Gα(q)-TG from 8 to 32 weeks of age, and all experiments were performed in mice at the age of 32 weeks. Chronic nicorandil administration prevented the severe reduction of left ventricular fractional shortening and inhibited ventricular interstitial fibrosis in Gα(q)-TG. SUR-2B and SERCA2 gene expression was decreased in vehicle-treated Gα(q)-TG but not in nicorandil-treated Gα(q)-TG. eNOS gene expression was also increased in nicorandil-treated Gα(q)-TG compared with vehicle-treated Gα(q)-TG. Electrocardiogram demonstrated that premature ventricular contraction (PVC) was frequently (more than 20 beats/min) observed in 7 of 10 vehicle-treated Gα(q)-TG but in none of 10 nicorandil-treated Gα(q)-TG. The QT interval was significantly shorter in nicorandil-treated Gα(q)-TG than vehicle-treated Gα(q)-TG. Acute nicorandil administration shortened ventricular monophasic action potential duration and reduced the number of PVCs in Langendorff-perfused Gα(q)-TG mouse hearts. Moreover, HMR1098, a blocker of cardiac sarcolemmal K(ATP) channels, significantly attenuated the shortening of MAP duration induced by nicorandil in the Gα(q)-TG heart.

CONCLUSIONS/SIGNIFICANCE

These findings suggest that nicorandil can prevent the development of HF and ventricular arrhythmia caused by the activation of GPCR signaling through the shortening of the QT interval, action potential duration, the normalization of SERCA2 gene expression. Nicorandil may also improve the impaired coronary circulation during HF.

Involvement of gicerin, a cell adhesion molecule, in the portal metastasis of rat colorectal adenocarcinoma cells

Gicerin, an Ig-superfamily cell adhesion molecule, has homophilic adhesion activity, thus leading to the formation of gicerin aggregates. Gicerin is highly expressed in various embryonic tissues, and it contributes to development through its adhesive activities. In contrast, the expression of the protein is limited to the muscular tissues and endothelial cells in the mature animals. In the liver, gicerin is constitutively expressed in sinusoidal endothelial cells. Interestingly, an overexpression of gicerin is found in a variety of tumors and may play a role in tumorigenesis. Previously, up-regulated expression of the gicerin protein was found in some sporadic cases of chicken colorectal adenocarcinomas and their hepatic metastasized lesions. In the present study, gicerin cDNA was introduced into endogenous gicerin negative ACL-15 cells, a rat colon adenocarcinoma cell line. The cells were subsequently evaluated for changes in their metastatic potentials in order to elucidate the possible role of gicerin in the hepatic metastasis of colorectal adenocarcinomas. The stable overexpression of gicerin in the cells enhanced the self-aggregation and migratory activities on the protein compared with the mock-transfectants. In addition, the gicerin- transfectants had enhanced metastatic potential to the liver compared with mock-transfected cells after implantation into the ileocolic vein of the cognate rats. These results suggest that gicerin might promote the interaction of tumor cells with a hepatic endothelium, thus leading to the hepatic metastasis of colon adenocarcinomas.

Involvement of gicerin, a cell adhesion molecule, in a dermal autograft chicken model

Gicerin is a cell adhesion molecule in the immunoglobulin superfamily. This molecule has homophilic and heterophilic adhesive activities, binding to the neurite out-growth factor (NOF). We have previously reported that gicerin plays an important role in the development and regeneration as well as in the metastasis of tumors through its adhesive activities, mediating cell-cell and/or cell-extracellular matrix interactions. In this study, we investigated the involvement of gicerin in a dermal autograft chicken model. Gicerin and NOF were transiently present in the regenerating epithelia after the dermal graft transplantation. The treatment with an anti-gicerin polyclonal antibody, by placing drops onto the wounds, inhibited the adhesiveness of the grafts to the marginal skin. The chimeric protein of gicerin-IgG, gicerin-Fc, and NOF proteins promoted the regeneration of the grafts. These findings suggest the potential function of gicerin in dermal autografts, and gicerin and NOF proteins could help clinical improvement after transplantations.

Inflammatory cytokines decrease the expression of nicotinic acetylcholine receptor during the cell maturation

It is known that the nervous system significantly attenuates systemic inflammatory responses through the parasympathetic nervous system. Furthermore, it has been reported that the alpha 7 subunit of a nicotinic acetylcholine receptor is required for a cholinergic inhibition against cytokine synthesis in a macrophage. As antigen-presenting cells (APCs) play a central role in the generation of primary T cell responses and the maintenance of immunity, in this study, we investigated the expression level of nicotinic receptors of a p53-deficient APC cell line (JawsII) derived from a mouse bone marrow. We showed that stimulation of the JawsII cells with lipopolysaccharide (LPS) and tumor necrosis factor alpha (TNF-alpha) led increase of CD80 and CD86 expression while diminishment of the surface nicotinic receptor. On the other hand, stimulation of nicotinic receptor had no effect on these phenomena. Furthermore, we examined the ability of the cells to release cytokine when stimulated with both nicotine and LPS and showed that the stimulation with LPS augmented the secretion of IL-1a, IL-1b, IL-6, and TNF-alpha. These results suggested that nicotinic stimulation had no effect on the diminishment of alpha 7 nicotinic acetylcholine receptor on JawsII cells by LPS stimulation.

Involvement of transforming growth factor-beta in the expression of gicerin, a cell adhesion molecule, in the regeneration of hepatocytes

Gicerin, an Ig-superfamily cell adhesion molecule, appears transiently in embryonic tissues including those of the nervous, urogenital, respiratory and digestive systems, and it promotes neurite extension, cell migration and epithelialization through its cell adhesive activities. In addition, gicerin also reappears in regenerating tissue after suffering either a traumatic injury or a viral infection. In the present study, we examined the expression pattern of gicerin in the regeneration of hepatocytes. Immunohistochemically, gicerin protein appeared in the regenerating hepatocytes of carbon tetrachloride (CCl4)-induced acute hepatitis, while it was scarcely expressed in the hepatocytes of normal mouse liver. Real-time PCR revealed the up-regulation of gicerin transcription in the regenerating process of CCl4-induced hepatitis. The expression of transforming growth factor (TGF)-beta1 was also increased during the regeneration. Furthermore, the gicerin mRNA expression increased during the process of an in vitro hepatocyte regeneration model using mouse primary hepatocytes and hepa 1-6 cells. To note, the mRNA levels of gicerin in these cells were enhanced by the presence of TGF-beta1. Collectively, these findings suggest that TGF-beta1 may therefore regulate gicerin expression in hepatocytes leading to liver regeneration by cell-cell or cell-ECM interactions.

Ca2+ channel activating action of maitotoxin in cultured brainstem neurons

The actions of maitotoxin were studied using cultured brainstem cells and adrenal chromaffin cells. Maitotoxin induced a profound increase in the Ca2+ influx into cultured brainstem cells after a brief lag period. The maitotoxin-induced Ca2+ influx was suppressed by various voltage-dependent Ca2+ channel blockers such as Co2+, Mn2+, verapamil and diltiazem. Maitotoxin-catecholamine release in brainstem cells initiated to increase after a lag period of about 1 min and the increase continued even at 4 min after treatment, while in the adrenal chromaffin cells the release started after an about 1-min lag period to attain a maximum within first 2-min and gradually decrease thereafter. These results suggest that maitotoxin acts on Ca2+ channels to increase the Ca2+ influx, accompanied by enhancement of catecholamine release in the brainstem cells with a different temporal profile from that in the adrenal chromaffin cells.

Neurite extension of DRG neurons by gicerin expression is enhanced by nerve growth factor

Gicerin, a cell adhesion molecule, is expressed in dorsal root ganglion (DRG) and sciatic nerves during chick development. This molecule re-appears in these tissues after an injury to the sciatic nerve. In the present study, we investigated the expression of nerve growth factor (NGF) in the regenerating sciatic nerve of chicks and the effects of NGF on the expression and neurite activities of gicerin in DRG. In the sciatic nerve after a crush injury, the expression of NGF and gicerin increased in the Schwann cells and in the nerve fibers, respectively. NGF promoted the neurite projections from in vitro DRG on the gicerin ligands, which were inhibited by anti-NGF antibody. The gicerin mRNA expression increased in the DRG with NGF, which was inhibited by the co-incubation with anti-NGF antibody. These results indicate that NGF might therefore enhance the expression of gicerin in DRG, thereby promoting the gicerin-dependent neurite extension during sciatic nerve regeneration.

Molecular cloning and analysis of the mouse gicerin gene

Gicerin is a cell adhesion molecule, which has five immunoglobulin-like loop structures in an extracellular domain followed by a single transmembrane domain and a short cytoplasmic tail. We have reported that gicerin participates in neurite extension and structural organization of the nervous system, and its expression in the nervous system is high during the development and dramatically decreased after birth. To elucidate the mechanism how the expression of gicerin is regulated, we performed a genomic cloning of a mouse gicerin. A fragment of 16 kbp genomic clone contained 8 kbp gicerin gene composed of 16 exons with 6 kbp upstream region. Genomic cloning revealed that two isoforms of gicerin were generated by an alternative splicing of exon 15 results in cytoplasmic domains composed of either 63 or 21 amino acids. As for an expressional regulation of gicerin, we found that the mRNA content of gicerin in PC12 cells was regulated by cAMP. Quantitative-PCR analysis revealed that forskolin induced four-fold increase of gicerin mRNA. To characterize the involvement of its promoter region, we examined the promoter activity in PC12 cells by a luciferase-reporter assay. We found that a CRE site located at 60 bp upstream of gicerin gene was responsible for the increase of its mRNA induced by forskolin.

Gicerin/CD146 is involved in neurite extension of NGF-treated PC12 cells

Gicerin/CD146 is a cell adhesion molecule, which belongs to the immunoglobulin (Ig) superfamily. We have reported that it has a homophilic binding activity, which participates in the neurite extension from embryonic neurons. To elucidate how gicerin is involved in the neurite extension mechanism, we employed PC12 cells, which expresses gicerin/CD146. PC12 cells extend longer neurites by nerve growth factor (NGF) on gicerin substrate than on without gicerin substrate, which indicates that gicerin participates in neurite extension by NGF. We also found that the expression of gicerin in PC12 cells is induced by NGF. Over-expression of gicerin also promotes neurite extension by gicerin-gicerin homophilic interaction. These findings suggested that increase of gicerin expression by NGF promotes the gicerin-gicerin homophilic interaction resulting in the neurite extension.

Characterization of Gicerin/MUC18/CD146 in the rat nervous system

Gicerin is a cell adhesion molecule of an immunoglobulin (Ig) superfamily isolated from a chicken. It shows homophilic and heterophilic binding activities and has two isoforms. s-Gicerin which has small cytoplasmic domain and the same extracellular domain as l-gicerin shows stronger cell adhesion activity. In the chick nervous system, gicerin expression is only observed in the developmental stage when neurons extend neurites and migrate. In other tissues, gicerin participates in the tissue regeneration or oncogenesis. In this report, we identified two isoforms of rat gicerin corresponding to chicken and we concluded that gicerin is a homologue of human CD146/MUC18/MCAM. Next we generated antibody to characterize a rat gicerin in the nervous system. Gicerin is expressed in the hippocampal cells, Purkinje cells, and sensory neurons of a spinal chord of an adult rat, while expressed most abundantly in the lung. In addition to this, its expression in the hippocampus was increased by electroconvulsive shock, suggesting some role in the mature nervous system. And we also showed neurite promotion activity of gicerin from hippocampal neurons.

Reticulon3 expression in rat optic and olfactory systems

Reticulon3 (RTN3), which belongs to a reticulon family, is first isolated from the retina, but little is known about its function. We investigated the distribution of RTN3 in rat retina and olfactory bulb by immunohistochemistry. In the retina, Müller cells highly expressed RTN3. The expression level of RTN3 in the optic nerve was high in the embryo, but low in the adult. In the olfactory system, RTN3 was highly expressed in the olfactory nerve both in developmental and adult stages. Further, RTN3 was co-localized with synaptophysin in tubulovesicular structures in the developing axon of cultured cortical neurons. These results suggest that RTN3 may play an important role in the developing axons and also in some glial cells such as Müller cells.

Induction of gicerin/CD146 in the rat carotid artery after balloon injury

Gicerin is a cell adhesion molecule belonging to the immunoglobulin superfamily. It is reported that the human homologous molecule, CD146, is expressed in the endothelial cells. Here, we found that the expression of gicerin was increased in the rat carotid arteries after balloon injury. Immunohistochemical analysis demonstrated that the expression of gicerin protein was increased in the medial smooth muscle cells prior to the formation of neointima one week after the injury and was also increased in the luminal edge of the neointima after two weeks. We employed A10 cells, a cell line derived from rat aortic smooth muscle cell, and examined the effect of growth factors on the expression of gicerin, such as IGF-1, PDGF-BB, and bFGF. We found that IGF-1, but not PDGF-BB and bFGF, significantly increases the expression of gicerin protein in A10 cells. These suggest gicerin might be involved in the arteriosclerotic neointima formation in the artery.

Expression and involvement of gicerin, a cell adhesion molecule, in the development of chick optic tectum

Gicerin is a cell adhesion molecule belonging to the immunoglobulin superfamily. It has both a homophilic binding activity and a heterophilic binding activity to neurite outgrowth factor (NOF) a molecule belonging to the laminin family. We have reported many studies on the heterophilic activity of gicerin and NOF, but the function of its homophilic binding activity in vivo had been unclear. In the retina, gicerin is expressed in retinal ganglion cells only when they extend neurites to the optic tectum. In this report we have found that gicerin is also transiently expressed in the optic tectum during this time. First, cell aggregation assays were used to show that gicerin expressed in the optic tectum displays homophilic binding activity. Then, explant cultures of embryonic day 6 chick optic tectum on gicerin-Fc chimeric protein-coated dishes and NOF-coated dishes were carried out. It was found that gicerin-gicerin homophilic interactions promoted cell migration, whereas heterophilic interactions with NOF induced neurite formation. Furthermore, when anti-gicerin antibodies were injected in order to examine the effect of gicerin protein in the formation of the tectal layer in ovo, cell migration was strongly inhibited. These data suggest that homophilic interaction of gicerin participates in the migration of neural cells during the layer formation and plays a crucial role in the organization of the optic tectum.

Expression of gicerin enhances the invasive and metastatic activities of a mouse mammary carcinoma cell line

Gicerin, an immunoglobulin superfamily protein, is expressed abundantly in the embryonic tissues and plays an important role in development through its cell adhesive activity. Interestingly, re-expression of gicerin is found in a variety of tumors. In the present study, the possible role of gicerin in the progression of mammary carcinoma was investigated. The normal mammary glands of mice were negative for gicerin, but sporadic mammary carcinoma cells expressed gicerin strongly on their surface. A mouse mammary carcinoma cell line, JYG-B, which is gicerin-negative was employed for introducing gicerin cDNA and the resultant gicerin transfectants were subsequently analyzed. In vitro, self-aggregation activity of the gicerin-transfectants progressed. For an in vivo study, invasive and metastatic potential of the cells was examined by a subcutaneous implantation into nude mice. The invasion of gicerin transfectants into the surrounding tissue was enhanced and severe metastasis to the lungs occurred. These findings suggest that gicerin is an effector for the malignant progression of mammary carcinoma.

Gicerin, a cell adhesion molecule, promotes the metastasis of lymphoma cells of the chicken

Gicerin is an immunoglobulin superfamily cell adhesion molecule purified from chicken gizzards. This molecule displays an adhesive interaction with a laminin-like protein as well as with gicerin itself. Gicerin appears in embryonic tissues and plays a role in chick development through its cell adhesive properties. An increase in gicerin expression is found in some sporadic tumors of the chicken. To elucidate the possible role of gicerin in tumor progression in chickens, we introduced gicerin cDNA into an endogenous gicerin negative lymphoma MDCC-MSB1 cell line, and subsequently analyzed them for changes in their metastatic potentials. After intravenous implantation of the gicerin transfectants into chickens, the metastatic potential to the lung, liver and kidney was enhanced compared with parental MDCC-MSB1 cells. Self-aggregation activity was increased in gicerin transfectants. In addition, adhesive and migratory activities of the gicerin transfectants to the gicerin ligands were enhanced in vitro. These findings indicate that gicerin can contribute to the malignancy and metastatic properties of lymphoma.

Involvement of gicerin, a cell adhesion molecule, in development and regeneration of chick sciatic nerve

We have examined the role of gicerin, an immunoglobulin superfamily cell adhesion molecule, in chick sciatic nerves during development and regeneration. Gicerin was expressed in the spinal cord, dorsal root ganglion (DRG) and sciatic nerves in embryos, but declined after hatching. Neurite extensions from explant cultures of the DRG were promoted on gicerin's ligands, which were inhibited by an anti-gicerin antibody. Furthermore, gicerin expression was upregulated in the regenerating sciatic nerves, DRG and dorsal horn of the spinal cord after injury to the sciatic nerve. These results indicate that gicerin might participate in the development and regeneration of sciatic nerves.

Gicerin, an Ig-superfamily cell adhesion molecule, promotes the invasive and metastatic activities of a mouse fibroblast cell line

Gicerin is a cell adhesion molecule in the immunoglobulin (Ig) superfamily and plays an important role during development through its adhesive properties. Gicerin has two isoforms that differ in their cytoplasmic domains; s-gicerin is the shorter and l-gicerin the longer form of the protein. Gicerin is over-expressed in some sporadic tumors as well as in developing tissues. To provide direct evidence that gicerin has the potential to participate in malignant aspects of tumor cell behavior, a gicerin cDNA was introduced into L-929 cells, an endogenous gicerin-negative mouse fibroblast and subsequently analyzed for changes in their invasive and metastatic potential by implantation into nude mice and chick embryos. Compared with parental cells, both gicerin isoform transfectants showed an enhanced cell growth and invaded deeply into surrounding tissues from implanted sites in both animal models. Furthermore, l-gicerin transfectants markedly enhanced metastasis to the lung. These findings suggest that gicerin promotes the tumor growth and invasion, and the isoform bearing the longer cytoplasmic domain may play a role in metastasis.

Molecular cloning and characterization of rKAB1, which interacts with KARP-1, localizes in the nucleus and protects cells against oxidative death

The Ku autoantigen/KARP-1 (Ku86 autoantigen related protein-1) plays an important role in the double-strand break repair of mammalian DNA as a DNA-binding component of DNA-dependent protein kinase (DNA-PK) complex. KARP-1 is differently transcribed from the human Ku86 autoantigen gene locus and it is implicated in the control of DNA-dependent protein kinase activity. We cloned rKAB1, a rat homolog of KAB1 (KARP-1 binding protein 1 of human) from a rat hippocampal cDNA library. rKAB1 mRNA was specifically expressed in the brain and the thymus. EGFP-tagged rKAB1 protein localized in cell nucleus and in the condensed chromosome during the mitotic cell division. We found that rKAB1 works as a protective protein against cell damage by oxidative stress.

Arrest of cell cycle by amida which is phosphorylated by Cdc2 kinase

Amida was first isolated from a rat hippocampal cDNA library as an Arc-associated protein. Although previous studies have shown that Amida mRNA is predominantly expressed and developmentally regulated in rat testis and overexpression induces apoptosis, the function of Amida remains unclear. In this study, we found that overexpression of Amida inhibited cell growth. Flow cytometry analysis showed that Amida caused cell cycle inhibition in the S-phase and blocked cell cycle from entry into mitosis. Attempting to elucidate Amida effect on the cell cycle, we found that Amida was interacted with Cdc2 in mitosis and Amida's overexpression resulted in a decrease in Cdc2 kinase activity. In addition, Amida showed DNA-binding ability with DNA-affinity column chromatography. A region (aa, 76-189) between the two nuclear localization signals was found to be responsible for cell growth inhibition and DNA-binding activity, implying that DNA-binding activity may be necessary for Amida to repress cell cycle. Moreover, Amida was phosphorylated by Cdc2 kinase in vitro and Ser-180 of Amida was identified as the phosphorylation site. Furthermore, AmidaS180G (eliminate phosphorylation of Ser-180) showed stronger DNA-binding activity. Taken together, the data suggest that Amida may play an important role in cell cycle and may be partly regulated by Cdc2 kinase.

The accumulation of arc (an immediate early gene) mRNA by the inhibition of protein synthesis

Arc (activity-regulated cytoskeleton-associated protein) gene is one of the neuron-specific immediate early genes induced by neural activity. The regulation of Arc gene expression is unknown. We found that Arc mRNA is expressed constitutively in L929 cells, a mouse fibroblast cell line, and was, not transiently, increased by the calcium ionophore A23187. To address the induction of Arc mRNA by A23187, we isolated the mouse Arc gene and found that it consists of three exons, with the first exon including the whole coding region. We then constructed luciferase reporters fused with various 5' flanking regions of the mouse Arc gene. The reporter activities were not enhanced by A23187 in the tested regions up to about -9500 bp. As it is reported that protein synthesis is inhibited in by A23187, we treated L929 cells with a protein synthesis inhibitor, cycloheximide (CHX). The increase of Arc mRNA was induced by CHX alone in a calcium-independent manner and was comparable to that by A23187. No additive effect of A23187 was observed on the increase by CHX, whereas the additive effect was seen in PC12 cells. These results suggest that the inhibition of protein synthesis is a crucial factor for the accumulation of Arc mRNA in L929 cells.

Involvement of gicerin in the extension of microvilli

Gicerin is a cell adhesion molecule belonging to the immunoglobulin superfamily. To study the functional differences between l- and s-gicerin, we first examined the distribution of endogenous gicerin in B16 cells and found that l-gicerin was densely localized in microvilli. To clarify the relationship between gicerin and the microvilli, we established independent stable cell lines expressing l- and s-gicerin in L cells and found that l-gicerin localized to the microvilli. Scanning electron microscopic analysis revealed that the microvilli of l-gicerin-transfected cells were longer than those of s-gicerin and control transfectants. This suggested that l-gicerin might participate in the elongation of the microvilli. When cells were double-stained with antibodies to gicerin and moesin, a microvilli-specific protein, the staining of l-gicerin corresponded to that of moesin in the elongated microvilli. Moesin was coprecipitated with glutathione S-transferase-fusion proteins of the l-gicerin cytoplasmic domain but not with the s-gicerin cytoplasmic domain. To determine the region involved in the extension of microvilli, we generated transfectants of two truncated forms of l-gicerin cytoplasmic domain, and we found that only the transfectants of the longer mutant had the longer microvilli, while the shorter mutant exhibited short microvilli. These results suggested that l-gicerin-specific amino acid residues, especially amino acids 16-39, within the cytoplasmic domain of l-gicerin might be involved in the extension of microvilli.

Amida predominantly expressed and developmentally regulated in rat testis

Amida was first isolated from a rat hippocampal cDNA library as an Arc-associated protein. Previous studies showed that Amida is a nuclear protein and overexpression of Amida induces cell apoptosis. In this study, we found that Amida mRNA was expressed predominantly in rat testis by Northern blot analysis. During the development of testis, Amida mRNA was barely detectable until postnatal days 24 to 29 during which it increased to levels found in adults. However, Amida protein was not detected until postnatal day 32. Amida mRNA was found to be enriched in spermatocytes and less in round spermatids, but was undetectable in elongated spermatids by in situ hybridization. In addition, Amida protein was observed in the nucleus of spermatocytes and even in the elongated spermatids by immunohistochemistry. The development and cellular localization differences of Amida mRNA and protein implicates that Amida mRNA may undergo posttranscriptional regulation. Furthermore, Amida mRNA decreased significantly in the 8-day experimental cryptorchid testis when spermatogenesis was disrupted. Taken together, these data suggest that Amida is involved in spermatogenesis and may play an important role in development of testicular germ cells.

Expression and adhesive ability of gicerin, a cell adhesion molecule, in the pock lesions of chorioallantoic membranes infected with an avian poxvirus

The expression and adhesive activities of gicerin, a cell adhesion protein, in the pock lesions on chicken chorioallantoic membranes (CAM) infected with an avian poxvirus were studied. In normal CAMs, gicerin was found on the flattened epithelial cells, and neurite outgrowth factor (NOF) was in the basement membrane. However, in the pock lesions on infected CAMs, gicerin was overexpressed on the cell membranes of hyperplastic epithelial cells forming thick epithelial layers. Neurite outgrowth factor was also found mainly in the basement membrane, but occasionally showed aberrant expression among hyperplastic cells. In vitro analyses, using the dissociated cells from pock lesions, demonstrated that an anti-gicerin polyclonal antibody inhibit cell aggregation activity and cell adhesion to NOF. These results suggest that gicerin might promote the cell-cell and cell-extracellular matrix protein bindings of the hyperplastic epithelial cells by its homophilic and heterophilic adhesive activities, and contribute to pock formation on the infected CAMs.

The role of gicerin, a novel cell adhesion molecule, in development, regeneration and neoplasia

Neurite outgrowth factor (NOF) is an extracellular matrix (ECM) protein in the laminin family and its ligand, gicerin, is a novel cell adhesion molecule in the immunoglobulin superfamily. Gicerin has a homophilic adhesive activity as well as a heterotypic manner to NOF. In the nervous systems, gicerin is expressed during developmental stage when neurons migrate or extend neurites to form a neural network. Gicerin promotes neurite extension and migration of embryonic neurons in vitro by its homophilic and heterophilic adhesion activities. Introduction of antigicerin antibody into early developing eyes perturbs the layer formation of neural retina. These data suggest that gicerin participates in the formation of neural tissues. Gicerin is also expressed in other non-neural tissues; in epithelia of trachea, kidney and oviduct, gicerin expression is restricted in the developmental period. In contrast, muscular tissues and endothelial cells express gicerin continuously even after maturation. Interestingly, gicerin re-appears strongly in the regenerating epithelia of trachea, kidney and oviduct, and also anti-gicerin antibody disrupts the healing process of trachea. Furthermore, gicerin and NOF are overexpressed in the chicken nephroblastomas (Wilm's tumor) and oviductal adenocarcinomas. In vitro analyses show that gicerin adhesive activities can promote binding among tumor cells and adhesion of tumor cells to NOF. A polyclonal antibody against gicerin also perturbs the re-attachment of cancer cells onto metastasizing sites. It is clear from these studies that gicerin is a potential effector for pathological tissue formation as well as for normal development.

Kheper, a novel ZFH/deltaEF1 family member, regulates the development of the neuroectoderm of zebrafish (Danio rerio)

Kheper is a novel member of the ZFH (zinc-finger and homeodomain protein)/deltaEF1 family in zebrafish. kheper transcripts are first detected in the epiblast of the dorsal blastoderm margin at the early gastrula stage and kheper is expressed in nearly all the neuroectoderm at later stages. kheper expression was expanded in noggin RNA-injected embryos and also in swirl mutant embryos and was reduced in bmp4 RNA-injected embryos and chordino mutant embryos, suggesting that kheper acts downstream of the neural inducers Noggin and Chordino. Overexpression of Kheper elicited ectopic expansion of the neuroectoderm-specific genes fkd3, hoxa-1, and eng3, and the ectopic expression of hoxa-1 was not inhibited by BMP4 overexpression. Kheper interacted with the transcriptional corepressors CtBP1 and CtBP2. Overexpression of a Kheper mutant lacking the homeodomain or of a VP16-Kheper fusion protein disturbed the development of the neuroectoderm and head structures. These data underscore the role of Kheper in the development of the neuroectoderm and indicate that Kheper acts as a transcriptional repressor.

Somatodendritic localization of Translin, a component of the Translin/Trax RNA binding complex

Recent studies implicating dendritic protein synthesis in synaptic plasticity have focused attention on identifying components of the molecular machinery involved in processing dendritic RNA. Although Translin was originally identified as a protein capable of binding single-stranded DNA, subsequent studies have demonstrated that it also binds RNA in vitro. Because previous studies indicated that Translin-containing RNA/single-stranded DNA binding complexes are highly enriched in brain, we and others have proposed that it may be involved in dendritic RNA processing. To assess this possibility, we have conducted studies aimed at defining the localization of Translin and its partner protein, Trax, in brain. In situ hybridization studies demonstrated that both Translin and Trax are expressed in neurons with prominent staining apparent in cerebellar Purkinje cells and neuronal layers of the hippocampus. Subcellular fractionation studies demonstrated that both Translin and Trax are highly enriched in the cytoplasmic fraction compared with nuclear extracts. Furthermore, immunohistochemical studies with Translin antibodies revealed prominent staining in Purkinje neuron cell bodies that extends into proximal and distal dendrites. A similar pattern of somatodendritic localization was observed in hippocampal and neocortical pyramidal neurons. These findings demonstrate that Translin is expressed in neuronal dendrites and therefore support the hypothesis that the Translin/Trax complex may be involved in dendritic RNA processing.

Molecular cloning and characterization of Amida, a novel protein which interacts with a neuron-specific immediate early gene product arc, contains novel nuclear localization signals, and causes cell death in cultured cells

Amida was isolated by the yeast two-hybrid system as a novel protein which associated with Arc, a non-transcriptional immediate early gene specific to the brain. Amida was confirmed to be associated with Arc in vitro and in vivo. Amida shows no homology to known proteins. Amida is ubiquitously expressed, although it is abundant in the brain. A transfection study revealed that Amida was localized in the nucleus and after 72 h the transfected cells underwent apoptosis. Furthermore, we found two nuclear localization signals and a domain needed for interacting with Arc was encompassed by two nuclear localization signals. Co-transfection experiment with Amida and Arc suggested that Amida transported Arc into the nucleus and negatively regulated Amida-induced cell death. These results indicate that Arc together with Amida may modulate cell death in the brain.

Inhibition by naloxone of promoter activity of the neurofilament gene in SK-N-SH cells

Chronic administration of morphine is known to decrease the levels of neurofilaments (NFs) in the ventral tegmental area. We ligated a promoter region of the mouse 68-KDa neurofilament (NF-68) gene to the pGL3-enhancer vector containing a luciferase gene, transfected it into SK-N-SH cells and then analyzed transcriptional activity in the cells treated with agonists or antagonists of opiate receptors. The activity of the NF-68 promoter was suppressed by naloxone about 55% at 10(-5) M and 30% at 10(-7) M at 48 h, but suppressed not by morphine. Naltrexone at 10(-5) M suppressed the promoter activity about 20%, but levallorphan, DAMGO, DPDPE and U50488 did not. The inhibition by naloxone was dose-dependent and not reversed by morphine. The inhibitory effect of naloxone was not observed in N18TG-2 cells and PC12 cells. Experiments with various deletion mutants revealed that a region responsible for naloxone suppression spans from -328 to -101 in the gene. These results suggest that naloxone has the ability to suppress transcriptional activity in some neurons.

Cytoplasmic domain is not essential for the cell adhesion activities of gicerin, an Ig-superfamily molecule

Gicerin is a cell adhesion molecule in the immunoglobulin (Ig) superfamily and is expressed abundantly during development in the nervous system. It has homophilic cell adhesion activity and also has heterophilic binding activity with NOF (neurite outgrowth factor) and mediates neurite extension. There are two isoforms of gicerin, one with a short (s-gicerin) and the other with a longer cytoplasmic domain (l-gicerin). We have reported that s-gicerin possesses stronger activities than l-gicerin during cell aggregation, in NOF-binding, and in neurite extension. In this study, we established cell lines which expressed a mutant-gicerin whose cytoplasmic domain was deleted and we compared the above three biological activities of the mutant-gicerin with those of s- and l-gicerin. We found that the mutant-gicerin retained all these activities, but the activities were weaker than those of s-gicerin and almost the same as those of l-gicerin. We concluded that the cytoplasmic domain of gicerin is not essential for optimal adhesive activities of gicerin, but might be involved in the regulation of its activities.

Expression of gicerin, a cell adhesion molecule, in the abnormal retina in silver plumage color mutation of Japanese quail (Coturnix japonica)

Silver plumage color mutant (B/B) quail has an abnormal retina characterizing the transdifferentiation of retinal pigment epithelium (RPE) following the retinal separation in the early developmental stage. In the present study; (i) the expression of gicerin, an immunoglobulin-superfamily cell adhesion molecule, was examined in the retina of B/B quail. In the wild-type quail, gicerin protein was enriched in the apical membrane (facing the neural retina, NR) of RPE cells on embryonic day (E) 4 and then appeared also in NR cells from E5. However, in the B/B retina, no gicerin expression was found in the transdifferentiation area of RPE prior to the retinal separation. (ii) In addition to this, microinjection of anti-gicerin polyclonal antibody into the eyeball of wild-type quail on E3 caused the retinal separation and induced the transdifferentiation of RPE into new NR. These observations suggest that the decrease of gicerin expression might participate in the retinal separation and RPE-transdifferentiation in B/B quail.