Biomedical subjects

Sang Soo Kang

Publications and source records attributed to Sang Soo Kang.

At least 19 recordsLinked to original sources

PubMed2006

Hyperactivity and alteration of the midbrain dopaminergic system in maternally stressed male mice offspring.

We recently demonstrated that prolonged maternal stress produces profound and long-lasting deficits in brain functions by programming a subset of target genes. We have now examined the possible effects of prenatal stress on the motility of adult offspring and dopamine (DA)-related gene expression in their midbrains, one of the target brain regions of stress hormones. Maternally stressed adult male mice showed impaired response habituation to novelty, and increased wheel-running activity associated with altered responses to DA receptor and DA transporter (DAT) blockers. Along with the behavioral changes, the expression profiles of several genes of the midbrain DAergic system appeared to be altered. Expression of DAT was reduced and expression of DA receptors and striatal DA-regulated neuropeptide genes was also affected. Taken together, the present findings indicate that maternal stress can cause hyperactivity in adult offspring associated with alterations in the midbrain DAergic system suggestive of a functional hyperdopaminergic state.

Adaptation, Physiological↗

PubMed2006

Altered gene expression of caspase-10, death receptor-3 and IGFBP-3 in preeclamptic placentas.

Enhanced apoptosis has been observed in the placentas of women with preeclampsia, but few studies have examined changes at the molecular level. This study was designed to detect genes specifically expressed in full-term preeclamptic placentas. Tissue samples were collected immediately after cesarean delivery from 11 normal and 8 preeclamptic placentas at 35-40 weeks of gestation. Total RNAs were extracted and hybridized to a cDNA microarray. Results were confirmed by reverse-transcription polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry. Hematoxylin and eosin and TUNEL staining were also performed to confirm apoptosis in preeclamptic placentas. Among 205 genes, three were up- or down-regulated in preeclamptic placentas. The expression of caspase-10 and death receptor 3 (DR-3) was significantly increased, whereas insulin-like growth factor binding protein-3 (IGFBP-3) was strongly down-regulated. RT-PCR analysis and Western blotting confirmed these effects. Immunohistochemical analysis showed that the DR-3, caspase-10 and IGFBP-3 proteins were localized in the syncytial membrane. Apoptosis in the trophoblast was also increased in term placentas from women with pregnancies complicated by preeclampsia. These results suggest that caspase-10, DR-3 and IGFBP-3 are involved in apoptosis in the preeclamptic placenta.

Apoptosis↗

PubMed2006

Acute ethanol administration decreases GAP-43 and phosphorylated-GAP-43 in the rat hippocampus.

Acute alcohol ingestion is well known to have deleterious effects on memory and also known to inhibit long-term potentiation, a putative cellular substrate of memory. In this study, we for the first time revealed that growth-associated protein 43 (GAP-43), which is well known as a presynaptic substrate of protein kinase C and one of the major synaptic plasticity-related genes, was down regulated by single ethanol administration (2.5 g/kg, 15% in saline, i.p.) in the rat hippocampus. Using real-time PCR, we confirmed that GAP-43 mRNA level is significantly decreased 2 h after ethanol administration. GAP-43 and p-GAP-43 (Ser41) immunoreactivities in the hippocampus were also reduced 4 h after ethanol administration. Immunohistochemical study showed that the reduction of GAP-43 and p-GAP-43 expression was associated with the perforant and mossy fibers pathways. These results suggest that the reduction of GAP-43 in the hippocampus might be, at least in part, a cause of memory impairment after acute ethanol ingestion.

Analysis of Variance↗

PubMed2006

Heme oxygenase protects hippocampal neurons from ethanol-induced neurotoxicity.

Ethanol has deleterious effects on neuronal cells both in vivo and in vitro, but the mechanisms are unknown. Here, treatment with increasing doses of ethanol (from 20 up to 600mM) decreased the viability of a mouse hippocampal neuroblastoma cell line, HT22. The glutathione concentration decreased and intracellular reactive oxygen species (ROS) increased in a dose-and time-dependent manner, suggesting that the neurotoxicity was due to oxidative stress. Expression of heme oxygenase (HO)-1, a redox regulator and heat shock protein, increased with time after ethanol treatment, but HO-2 was expressed constitutively. The addition of 5microM zinc protoporphyrin IX (ZnPP IX), a competitive HO inhibitor, with the ethanol further reduced cell viability and increased intracellular ROS, but these effects were reversed by co-treatment with 50nM bilirubin, a well-known antioxidant and a product of HO catalysis. These results suggest that HO has a protective role in hippocampal neurons as an intrinsic factor against ethanol-induced oxidative stress and the protection depends on the degree of oxidative stress.

Animals↗

PubMed2006

Action of citicoline on rat retinal expression of extracellular-signal-regulated kinase (ERK1/2).

Citicoline is an essential endogenous intermediate in the biosynthesis of phosphatidylcholine, which acts as a therapeutic agent in models of central nervous system injury and neurodegenerative diseases. The present study investigated the effects of citicoline on extracellular-signal-regulated kinase 1/2 (ERK1/2) expression in the rat retina after kainic acid (KA) treatment. KA (6 nmol) was injected into the vitreous of the rat eyes. The animals were then injected intraperitoneally with citicoline (500 mg/kg) twice daily after the KA injection. The neuroprotective effects of citicoline were estimated by evaluating temporal changes in ERK1/2 using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL), immunoblotting and immunohistochemical techniques. The expression of phosphorylated ERK1/2 was slightly decreased after 6 h, and significantly reduced after 12 h, in the rats receiving the KA injection plus citicoline treatment. Our results demonstrated that citicoline decreased the activation of ERK1/2 due to the KA treatment, suggesting that it exerts its neuroprotective activity by reducing the concentrations of proteins involved in apoptosis.

Animals↗

PubMed2006

Increased nitric oxide caused by the ketogenic diet reduces the onset time of kainic acid-induced seizures in ICR mice.

Although the antiepileptic effects of the ketogenic diet (KD) are well documented, the mechanisms underlying this action remain obscure. Nitric oxide (NO) has long been thought to play a role in regulating seizures. However, the effects of the KD on endogenous NO production have not been characterized. Therefore, the present study was designed to examine the effect of the KD on endogenous NO production, as well as the precise role of NO in kainic acid (KA)-induced seizures, in male ICR mice. We first found that preadministration of the KD for 4 weeks increased endogenous NO generation in the hippocampus. We also demonstrated that the increase in NO induced by the KD resulted from increased neuronal NO synthase (nNOS) activity and exerted an antiepileptic effect on KA-induced seizures, based on the results of experiments using NOS-knockout mice and two NOS inhibitors, N-omega-nitro-L-arginine methyl ester (L-NAME) and 7-nitroindazole (7-NI). These data suggest that the antiepileptic effects of the KD might be mediated, at least in part, by increased NO levels in the hippocampus.

3-Hydroxybutyric Acid↗

PubMed2006

Suppression of survival kinases and activation of JNK mediate ethanol-induced cell death in the developing rat brain.

Administration of ethanol to immature rat pups during the period in which synaptogenesis occurs triggers extensive apoptotic cell death in the brain. This ethanol-induced cell death is known to be mediated by Bax activation, which is caused by mitochondrial dysfunction. However, little data is available regarding the regulation of survival signaling pathways and their downstream events that lead to Bax activation. Thus, in the present study, we aimed to investigate the effect of ethanol on survival signaling pathways and their downstream events that lead to cell death in the rat brain during the brain developmental period. Ethanol (3 g/kg, 20% in saline) was administered subcutaneously to post-natal 7-day-old rat pups twice at 2-h intervals and the pups were sacrificed at 4 h following the first ethanol injection. Ethanol treatment suppressed the activation of survival kinases, particularly Akt, Erk1/2 and PKAalpha, whereas it increased the activation of JNK. Moreover, dissociation of dephosphorylated Bad from 14-3-3 and the interaction of activated JNK with Bcl-2 were elevated by ethanol treatment. The present study demonstrated that ethanol treatment during the brain developmental period induced mitochondrial dysfunction, which led to cell death by the suppression of survival kinases, Bad release from 14-3-3 and inactivation of Bcl-2 by activated JNK.

14-3-3 Proteins↗

PubMed2006

Acetoacetate protects neuronal cells from oxidative glutamate toxicity.

Glutamate cytotoxicity contributes to neuronal degeneration in many central nervous system (CNS) diseases, such as epilepsy and ischemia. We previously reported that a high-fat and low-carbohydrate diet, the ketogenic diet (KD), protects against kainic acid-induced hippocampal cell death in mice. We hypothesized based on these findings that ketosis resulting from KD might inhibit glutamate cytotoxicity, resulting in inhibition of hippocampal neuronal cell death. Therefore, we investigated the role of ketone bodies [acetoacetate (AA) and beta-hydroxybutyrate (beta-OHB)] both in a mouse hippocampal cell line (HT22) and in rat primary hippocampal neurons. As a result, we found that pretreatment with 5 mM lithium AA and 4 mM Na beta-OHB protected the HT22 hippocampal cell line and primary hippocampal neuronal culture against 5 mM glutamate toxicity and that up to 2 hr of pretreatment with 5 mM AA had a protective effect against 5 mM glutamate toxicity in the HT22 cell line. Pretreatment with 5 mM AA decreased ROS production of HT22 cell line at 2 and 8 hr exposure of glutamate, and it decreased the appearance of annexin V-positive HT22 cells, which are indicative of an early stage of apoptosis, and propidium iodide-positive HT22 cells, which are indicative of necrosis.

Acetoacetates↗

PubMed2006

Ketogenic diet protects the hippocampus from kainic acid toxicity by inhibiting the dissociation of bad from 14-3-3.

The ketogenic diet (KD) is often effective for intractable epilepsy, but its antiepileptic mechanisms remain largely unknown. Within the cell death/survival pathway, Akt and its downstream protein Bad play an important role in kainic acid (KA)-induced cell death. Therefore, we investigated the effects of a KD on KA-induced changes in the Akt/Bad/14-3-3 signaling pathway by evaluating Akt, Bad, 14-3-3, and cleaved caspase-3 expression levels as well as their relative interactions. Our results showed that a KD did not affect the expression levels of Akt, Bad, Bcl-xL, Bax, and 14-3-3 but increased phospho-Akt [serine 473; p-Akt (Ser473)] and phospho-Bad [serine 136; p-Bad (Ser136)] expression levels as well as decreased cleaved caspase-3 levels following a KA-induced seizure in the hippocampus. Furthermore, we found that a KD increased the protein-protein interaction between 14-3-3 and p-Bad (Ser136), which might be phosphorylated by p-Akt (Ser473), and decreased interaction of Bad and Bcl-xL. These results suggest that a KD might protect, at least partially, the hippocampus from KA-induced cell death via inhibiting the dissociation of Bad from 14-3-3.

14-3-3 Proteins↗

PubMed2006

Systemic administration of alcohol to adult rats inhibits leydig cell activity: Time course of effect and role of nitric oxide.

BACKGROUND: Alcohol has been shown to interfere with testosterone (T) release from Leydig cells. However, the mechanisms responsible for this phenomenon, which may include decreased activity of the luteinizing hormone-releasing hormone (LHRH)-LH axis, as well as a direct influence of the drug on the testes, are not fully understood. In this work, we investigated the influence of alcohol, administered intragastrically (i.g.) or delivered via vapors, on Leydig cell activity and T release. Leydig cell function was studied by measuring changes in the levels of the steroidogenic proteins steroidogenic acute regulatory (StAR), the peripheral-type benzodiazepine receptor (PBR), and the cytochrome P450 side-chain cleavage enzyme (P450scc). Testosterone release was studied under basal conditions or in response to human chorionic gonadotropin (hCG). Finally, to identify potential factors mediating the influence of alcohol, we measured the testicular variant of the neuronal nitric oxide (NO) synthase (NOS), TnNOS, in semipurified Leydig cells. METHODS: Adult male Sprague-Dawley rats were either injected with alcohol i.g. once or exposed to alcohol vapors (4 h/d) for 1 or 5 days. Controls received the vehicle (i.g. model) or were kept in boxes through which no vapors were circulated. Following these treatments, one series of experiments was devoted to investigate Leydig cell responsiveness by measuring plasma T levels before or after the intravenous injection of hCG (1 U/kg). In another series of experiments, we used semipurified Leydig cell preparations to measure StAR, PBR, P450scc, and TnNOS by Western blot analysis. RESULTS: In the i.g. model, the T response to hCG was blunted for 12 hours following alcohol injection, but showed a rebound at 48 hours. Levels of StAR protein and of PBR, but not of P450scc, were significantly decreased within 10 minutes of drug administration. While StAR then remained depressed for 24 hours, PBR values were variable over this time course. By 48 hours, StAR, PBR, and P450scc levels had increased above control values. Both StAR and PBR levels showed correlations with plasma T levels. In the alcohol vapor models, both regimens of the drug also significantly depressed StAR and PBR protein concentrations, blunted the T response to hCG, and did not alter P450scc. Finally, we observed that alcohol delivered i.g. or via vapors up-regulated TnNOS levels in Leydig cells, but that blockade of NO formation failed to restore a normal T response to hCG. CONCLUSIONS: Collectively, these results suggest that (a) the ability of Leydig cells to release T does not show a simple correlation with changes in StAR, PBR, and P450scc levels; (b) the time course of the alcohol-induced changes were protein-specific; and (c) despite the ability of alcohol to stimulate TnNOS expression, NO does not appear to mediate the inhibitory influence of this drug on testicular steroidogenesis in the models that we studied.

Administration, Inhalation↗

PubMed2005

Ketogenic diet decreases the level of proenkephalin mRNA induced by kainic acid in the mouse hippocampus.

The ketogenic diet (KD) has been used to control medically refractory epilepsy in children for more than 80 years. Despite the clinical efficacy of the KD, its underlying bases are still obscure. Previous work from our laboratory has established that the KD has an antiepileptic and neuroprotective effect in the kainic acid (KA)-induced seizure model. The neuronal excitation caused by KA leads to increases in the expression of a variety of genes, including immediate-early genes and opioid peptides derived from proenkephalin (PENK) and prodynorphin (PDYN). In particular, the up-regulated PENK gene that is induced by KA in the hippocampal dentate granule cells has proconvulsant properties. PENK is regulated by the c-jun amino-terminal kinase (JNK) signaling pathway, the crucial role of which is involved in the regulation of transcription factors, such as Jun and Fos. In the present study, we examined the effect of the KD on the increase of PENK, Fos, Jun, AP-1 DNA-binding activity and JNK gene expression induced by KA in the mouse hippocampus. Using in situ hybridization and northern blot analysis, we found that the KD significantly decreases the level of PENK gene expression induced by KA of the granular cells in the hippocampus. In addition, we have also found that KD diminished KA-induced AP-1 DNA-binding activity, Fos and Jun expression, and phoshorylated form of the three types of JNKs. These results suggest that the KD suppresses KA-induced activation of JNK signaling pathways, followed by a decrease of PENK gene expression in the hippocampus, thereby resulting in antiepileptic effects.

Animals↗

PubMed2005

Ethanol induces cell death by activating caspase-3 in the rat cerebral cortex.

Ethanol has long been implicated in triggering apoptotic neurodegeneration. We examined the effects of ethanol on the rat brain during synaptogenesis when a spurt in brain growth occurs. This period corresponds to the first 2 postnatal weeks in rats and is very sensitive to ethanol exposure. Ethanol was administered subcutaneously to 7-day- postnatal rat pups by a dosing regimen of 3 g/kg at 0 h and again at 2 h. Blood ethanol levels peaked (677+/-16.4 mg/dl) at 4 h after the first ethanol administration. The cerebral cortexes of the ethanol-treated group showed several typical symptoms of apoptosis such as chromosome condensation and disintegration of cell bodies. Activated caspase-3 positive cells were found in the cortex within 2 h of the first injection, and reached a peak at 12 h. In addition, TUNEL staining revealed DNA fragmentation in the same regions. These results demonstrate that acute ethanol administration causes neuronal cell death via a caspase-3-dependent pathway within 24 h, suggesting that activation of caspase-3 is a marker of the developmental neurotoxicity of ethanol.

Animals↗

PubMed2005

Estradiol prevents the injury-induced decrease of Akt activation and Bad phosphorylation.

Estradiol prevents neuronal cell death through the inhibition of apoptotic signals and the activation of cell survival signals. This study investigated whether estradiol modulates the anti-apoptotic signal through the activation of Akt and its downstream targets, including Bad, Bcl-x(L), and 14-3-3. Adult female rats were ovariectomied and treated with estradiol prior to middle cerebral artery occlusion (MCAO). Brains were collected 24 h after MCAO and infarct volumes were analyzed. We confirmed that estradiol significantly reduces infarct volume and decreases the positive cells of TUNEL staining in the cerebral cortex. Potential activation was measured by phosphorylation of Akt at Ser473 and Bad at Ser136 using Western blot analysis. Estradiol prevents the injury-induced decrease of pAkt, pBad, and Bcl-x(L). Further, in the presence of estradiol, the interaction of pBad and 14-3-3 increased, compared to that of oil-treated animals. Our findings suggest that estradiol prevents cell death due to brain injury and that Akt activation and Bad phosphorylation by estradiol mediated these protective effects.

14-3-3 Proteins↗

PubMed2005

Prepubertal chronic ethanol administration alters TTF-1 and Oct-2 expression in the hypothalamus of female rats.

We found that prolonged administration of ethanol (3 g/kg i.p. at 08:00, once per day) to young female rats starting on postnatal day 24 caused delayed puberty. We further found that prolonged ethanol administration changed the typical hypothalamic expression patterns of TTF-1 and Oct-2 and reduced GnRH mRNA expression. We suggest that these changes may cause the ethanol-induced disturbances in the regulation of GnRH in the hypothalamus and may be responsible for the ethanol-induced reduction in GnRH and LH associated with delayed puberty.

Aging↗

PubMed2005

Ketogenic diet prevents clusterin accumulation induced by kainic acid in the hippocampus of male ICR mice.

We investigated the effect of ketogenic diet (KD) on clusterin accumulation in the kainic acid (KA)-induced seizure model. Two days after KA administration, strong clusterin-like immunoreactivity (IR) was detected in the hippocampus in the normal diet (ND)-fed mice. But in the KD-fed mice, few clusterin-like IR was detected. These results indicate that KD has neuroprotective effects throughout diminishing nuclear clusterin accumulation that is involved in caspase-3 independent cell death mechanism.

Animal Nutritional Physiological Phenomena↗

PubMed2005

Ketogenic diet increases calbindin-D28k in the hippocampi of male ICR mice with kainic acid seizures.

The ketogenic diet (KD) increased the expression of calbindin-D(28k) (CB) in the interneurons of the hippocampus compared with the normal diet (ND)-fed mice. Also, 2 days after kainic acid (KA) administration, numerous CB-expressing astrocytes were found in the KD-fed mice compared with those of the ND-fed mice. These results suggest that the neuroprotective effect of the KD on the KA-induced toxicity may be, in part, mediated via an increased expression of CB.

Animals↗

PubMed2005

Changes in rhodopsin kinase and transducin in the rat retina in early-stage diabetes.

To establish changes in phototransduction in diabetes, the effects of high glucose on rhodopsin kinase (RK) and transducin (G(t)), as well as recoverin, were examined in the retina of STZ-induced diabetic rats. Diabetes was induced by single intraperitoneal injection of STZ (50mg/kg) to Sprague-Dawley (SD) rats and the animals were sacrificed after 6 weeks. Immunohistochemistry (IHC) and Western blot analysis were carried out using antibodies against RK and G(talpha) (alpha subunit of G(t)) in the STZ-induced diabetic retina and the control retina. The expression level of recoverin protein was also analysed. In the diabetic retina, while the expression of RK protein increased, that of G(talpha) and recoverin proteins decreased. RK immunoreactivity (IR) appeared generally in the retina, and its signal increased in the outer limiting membrane (OLM), some rod cells in the outer segment layer (OSL) and at the tip of the outer plexiform layer (OPL) in the diabetic retina. G(talpha)-IR also appeared in the OPL and in photoreceptor layer. In the diabetic retina, G(talpha)-IR significantly decreased in the OPL, indicating RK-IR increase. This study illustrates the alterations in RK, G(talpha) and recoverin in the diabetic retina that may induce dysfunctions in phototransduction even in early-stage diabetes.

Animals↗

PubMed2005

Effect of ethanol on the regulation of corticotropin-releasing factor (CRF) gene expression.

Ethanol stimulates hypothalamic-pituitary-adrenal axis activity in vivo. To determine the cellular and molecular mechanisms through which ethanol regulates corticotropin-releasing factor (CRF) gene expression, we compared the effect of ethanol and forskolin on CRF peptide secretion and messenger RNA levels in hypothalamic primary cell cultures, and on CRF promoter activity in the NG108-15 cell line. CRF secretion, mRNA levels, and gene transcription significantly increased in response to ethanol or forskolin. Mutation of the cAMP-response element (CRE) reduced luciferase activity under basal conditions as well as in response to forskolin or ethanol. On the other hand, plasmid with five CRE repeats yielded dramatically elevated basal luciferase activity and significantly increased upregulation by ethanol. Inclusion of adenosine deaminase reduced the promoter response to ethanol. Finally a PKA inhibitor and a cAMP antagonist both decreased ethanol-induced CRF peptide secretion, gene expression, and transcription. These results suggest that ethanol upregulates CRF expression through cAMP/PKA-dependent pathways.

Animals↗