Sung-Vin Yim

Fluoxetine enhances cell proliferation and prevents apoptosis in dentate gyrus of maternally separated rats

The mother-infant relationship is an instinctive phenomenon, and loss of maternal care in early life influences neonatal development, behavior and physiologic responses.1,2 Furthermore, the early loss may affect the vulnerability of the infant to neuropsychiatric disorders, such as childhood anxiety disorders, personality disorders and depression, over its lifespan.3,4 Fluoxetine is prescribed worldwide for depression and is often used in the treatment of childhood mental problems related to maternal separation or loss of maternal care.5,6 In the present study, fluoxetine was administrated to rats with maternal separation to determine its effects on neuronal development, in particular with respect to cell proliferation and apoptosis in the dentate gyrus of the hippocampus. Rat pups were separated from their mothers and socially isolated on postnatal day 14 and were treated with fluoxetine (5 mg kg−1) and 5-bromo-2′-deoxyuridine (BrdU) (50 mg kg−1) for 7 days, after which immunohistochemistry and a terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining were carried out. In the pups with maternal separation treated with fluoxetine, the number of BrdU-positive cells was significantly increased and that of TUNEL-positive cells was significantly decreased in the dentate gyrus compared to pups with maternal separation that did not receive fluoxetine treatment. These findings indicate that fluoxetine affects new cell proliferation and apoptosis, and we propose that fluoxetine may be useful in the treatment of maternal separation-related diseases.

Estrogen receptor-α gene haplotype is associated with primary knee osteoarthritis in Korean population

Estrogen and estrogen receptors (ERs) are known to play important roles in the pathophysiology of osteoarthritis (OA). To investigate ER-α gene polymorphisms for its associations with primary knee OA, we conducted a case–control association study in patients with primary knee OA (n = 151) and healthy individuals (n = 397) in the Korean population. Haplotyping analysis was used to determine the relationship between three polymorphisms in the ER-α gene (intron 1 T/C, intron 1 A/G and exon 8 G/A) and primary knee OA. Genotypes of the ER-α gene polymorphism were determined by PCR followed by restriction enzyme digestion (PvuII for intron 1 T/C, XbaI for intron 1 A/G, and BtgI for exon 8 G/A polymorphism). There was no significant difference between primary knee OA patients and healthy control individuals in the distribution of any of the genotypes evaluated. However, we found that the allele frequency for the exon 8 G/A BtgI polymorphism (codon 594) was significantly different between primary knee OA patients and control individuals (odds ratio = 1.38, 95% confidence interval = 1.01–1.88; P = 0.044). In haplotype frequency estimation analysis, there was a significant difference between primary knee OA patients and control individuals (degrees of freedom = 7, χ2 = 21.48; P = 0.003). Although the number OA patients studied is small, the present study shows that ER-α gene haplotype may be associated with primary knee OA, and genetic variations in the ER-α gene may be involved in OA.

Melatonin suppresses NO-induced apoptosis via induction of Bcl-2 expression in PGT-β immortalized pineal cells

Abstract: In the present study, we investigated whether melatonin would prevent nitric oxide (NO)‐induced apoptotic death of PGT‐β immortalized pineal cells. To examine the protective effect of melatonin, cytotoxicity assay, DNA fragmentation analysis, caspase‐3 activity assay, and Western blotting for caspase‐3 and poly(ADP‐ribose) polymerase (PARP) were performed. Treatment of cells with S‐nitroso‐N‐acetylpenicillamine (SNAP), an NO donor, was shown to induce apoptotic cell death in a dose‐dependent manner, and pretreatment with melatonin (0.1 mm) attenuated the occurrence of NO‐induced apoptotic cell death. DNA fragmentation in response to NO was also arrested by melatonin. Caspase‐3 activity induced by NO was decreased with melatonin treatment. Furthermore, the active fragments of caspase‐3 and PARP were almost completely absent following exposure to melatonin. To elucidate the protective mechanisms of action of melatonin, Western blot analyses for Bcl‐2 expression and cytochrome c release were carried out. Pretreatment with melatonin (0.1 mm) induced the expression of Bcl‐2 and suppressed the release of cytochrome c into the cytosol, thereby arresting NO‐induced apoptotic cell death. These results suggest that the antiapoptotic effect of melatonin is associated with induction of Bcl‐2 expression in PGT‐β cells, which in turn blocks caspase‐3 activation and inhibits cytochrome c release into the cytosol.

Melatonin stimulates glucose transport via insulin receptor substrate-1/phosphatidylinositol 3-kinase pathway in C2C12 murine skeletal muscle cells

Abstract:  The prevalence of diabetes has exponentially increased in recent decades due to environmental factors such as nocturnal lifestyle and aging, both of which influence the amount of melatonin produced in the pineal gland. The present study investigated the effect of melatonin on signaling pathways of glucose transport in C2C12 mouse skeletal muscle cells. Intriguingly, treatment of C2C12 cells with melatonin (1 nm) stimulated glucose uptake twofold increase. Melatonin‐stimulated glucose transport was inhibited with co‐treatment with the melatonin receptor antagonist luzindole. Furthermore, treatment of stably over‐expressed melatonin receptor type 2B containing C2C12 myotubes with melatonin amplified glucose transport c. 13‐fold. Melatonin also increased the phosphorylation level of insulin receptor substrate‐1 (IRS‐1) and the activity of phosphoinositide 3‐kinase (PI‐3‐kinase). However, 3′,5′‐cyclic adenosine monophosphate‐activated protein kinase (AMPK), another important glucose transport stimulatory mediator via an insulin‐independent pathway, was not influenced by melatonin treatment. Activity of p38 mitogen‐activated protein kinase (MAPK), a downstream mediator of AMPK, was also not changed by melatonin. In addition, melatonin increased the expression level of forkhead box A2, which was recently discovered to regulate fatty acid oxidation and to be inhibited by insulin. In summary, melatonin stimulates glucose transport to skeletal muscle cells via IRS‐1/PI‐3‐kinase pathway, which implies, at the molecular level, its role in glucose homeostasis and possibly in diabetes. Additionally, exposure to light at night and aging, both of which lower endogenous melatonin levels may contribute to the incidence and/or development of diabetes.

Effect of human umbilical cord blood-derived mesenchymal stem cells in a cirrhotic rat model.

Background/Aim: Cirrhosis is a long‐term consequence of chronic hepatic injury and no effective therapy is currently available for this disease. Recent reports have shown that the mesenchymal stem cells (MSCs) have the capacity to differentiate into hepatocytes, and umbilical cord blood is a rich source of MSCs. Hence, we investigated the effect of infusing of human umbilical cord blood‐derived MSCs (HMSCs) in carbon tetrachloride (CCl4)‐induced cirrhosis in a rat model.

Susceptibility for ischemic stroke in Korean population is associated with polymorphisms of the interleukin-1 receptor antagonist and tumor necrosis factor-α genes, but not the interleukin-1β gene

Enhanced release of proinflammatory cytokines may contribute to the pathogenesis of ischemic stroke. Interleukin-1 receptor antagonist (IL-1Ra) is an anti-inflammatory cytokine, and tumor necrosis factor (TNF)-alpha and IL-1beta are proinflammatory cytokine. To determine the role of cytokines in genetic susceptibility to ischemic stroke, we genotyped ischemic stroke patients (n = 152) and the healthy control subjects (n = 165) for IL-1Ra, TNF-alpha and IL-1beta polymorphism by polymerase chain reaction-restriction fragment length polymorphism methods. The analysis shown the association of IL1RN*1, IL1RN*2 allele (IL1RN*1, OR=0.44, P = 0.0206 IL1RN*2, OR=2.90, P = 0.0141) and TNF1, TNF2 allele (TNF1, OR=2.16, P = 0.0225; TNF2, OR=2.16, P = 0.0225) to ischemic stroke. However, the genetic polymorphism of IL-1beta was not associated with ischemic stroke. Our results suggest that IL-1Ra and TNF-alpha gene polymorphism is associated with the susceptibility to ischemic stroke.

Melatonin increases cell proliferation in the dentate gyrus of maternally separated rats.

Abstract:  Melatonin in mammals, produced by the pineal gland and elsewhere, has shown antioxidant and neuroprotective properties in neuronal cells. We investigated whether melatonin would increase newly born cells (cell proliferation) in the dentate gyrus of maternally separated rats. To examine the effect of melatonin on cell proliferation of the dentate gyrus in maternally separated rats, 5‐bromo‐2′‐deoxyuridine (BrdU) immunohistochemistry was performed. Rat pups were separated from their mothers and socially isolated on postnatal day 14. Melatonin (10 mg/kg, i.p.) and BrdU (50 mg/kg, i.p.) were given to them for 7 days. The number of BrdU‐positive cells was significantly increased in the dentate gyrus of maternally separated pups with melatonin administration (P < 0.001). In addition, the expression of glucocorticoid receptor was significantly decreased in the dentate gyrus compared with maternally separated pups not given melatonin (P < 0.001). This is the first report that melatonin increases cell proliferation in the dentate gyrus of maternally separated rats.

Fluoxetine increases the nitric oxide production via nuclear factor kappa B-mediated pathway in BV2 murine microglial cells

A body of recent evidence implicates that antidepressants affect the inflammatory response and immune system. The present study is focused on the effects of the most widely used antidepressant agent, fluoxetine on the production of nitric oxide (NO) in BV2 microglial cells. In this study, we observed interesting result that NO production was increased by fluoxetine. The mRNA level of nitric oxide synthase (iNos, Nos2) by RT-PCR was also stimulated by fluoxetine. We next conducted electophoretic mobility shift assay (EMSA) to determine the DNA binding activity of nuclear factor kappa B (Nfkappab), an important upstream modulator for Nos2 expression, to find that fluoxetine increased DNA binding activity of Nfkappab. By Western blot analysis, phosphorylation levels of p38 mitogen-activated protein kinase (p38 Mapk, Mapk14) and extracellular signal-related kinase (Erk)1/2 Mapk, upstream signaling mediators of Nfkappab were found to be increased by fluoxetine. In addition, the mRNA expressions of other proinflammatory cytokines, interleukin 6 (Il6) and tumor necrosis factor alpha (Tnfalpha) were examined. The expressions of both Il6 and Tnfalpha by fluoxetine treatment were similar to those of Nos2 and Nfkappab. Taken together, our results show that fluoxetine stimulates NO production via Nfkappab-mediated pathway in BV2 cells.

Extracts from Citrus unshiu promote immune-mediated inhibition of tumor growth in a murine renal cell carcinoma model.

AIM OF THIS STUDY Citrus unshiu (Satsuma mandarin, SM) is a citrus fruit the peel of which has been used as a traditional Chinese medicine to treat common cold, relieve exhaustion, and cancer. In this study, we examined how effectively the content and peel extracts of SM can suppress cancer growth. The mechanism underlying cancer-suppressing properties of SM was investigated in tumor-bearing mice with renal carcinoma cell, Renca. MATERIALS AND METHODS Effectiveness of SM in tumor suppression was evaluated by measuring size of tumor mass in tumor-bearing mice treated with various doses of SM content and peel extracts. Proliferation of tumor cells and splenocytes was determined by MTT assay and [³H]TdR uptake, respectively. Relevant immunological mechanisms were chased by assaying cytokines including TGF-β, IL-6, IFN-γ, and TNF-α by ELISA. RESULTS The content and peel extracts of SM inhibited the growth of tumor cells in tumor-bearing mice. Especially, average tumor volume of two groups treated with 3 and 30 mg peel extracts per mouse weight (kg) were significantly decreased to 52.32% (p<0.05) and 68.72% (p<0.01), respectively. To identify tumor regression mechanism, anti-tumor cytokines measured in Con A-activated splenocytes from tumor-bearing mice. IFN-γ was increased in both of the peel extract-treated groups, while TNF-α, which had been decreased by tumor growth, was rescued to the normal level in SM content and peel extracts-treated groups. However, SM content and peel extracts did not inhibit proliferation and tumor-proliferative cytokines including TGF-β and IL-6 production of tumor cells. CONCLUSION These results indicate that SM content and peel extracts have anti-tumor properties in the tumor-bearing murine model. The mechanism underlying the anti-tumor effects of SM extracts is strongly suggested to be via boosting cytokines such as IFN-γ and TNF-α, enhancing immune-mediated anti-tumor properties.

Association of Polymorphism in the Promoter of the Melatonin Receptor 1A Gene with Schizophrenia and with Insomnia Symptoms in Schizophrenia Patients

Schizophrenia patients commonly have sleep disturbances. In this study, we investigated whether single nucleotide polymorphisms (SNPs) in the promoter region of the melatonin receptor genes (MTNR1A and MTNR1B) were associated with schizophrenia and with sleep problems such as insomnia and hypersomnia in schizophrenia patients. We genotyped two promoter SNPs [rs2119882 (−184T/C) of MTNR1A and rs4753426 (−1193C/T) of MTNR1B] using direct sequencing in 289 schizophrenia patients and 505 control subjects. We found that rs2119882 of MTNR1A was associated with schizophrenia in recessive model [CC vs. TT/TC, p = 0.013, odds ratio (OR) = 1.69, 95% confidence interval (CI) = 1.12–2.55]. Interestingly, in an analysis of clinical phenotypes, we found that rs2119882 of MTNR1A was also associated with insomnia symptoms of schizophrenia (recessive model, p = 0.010, OR = 2.24, 95% CI = 1.21–4.14), but not with hypersomnia symptoms as determined using the Operational Criteria checklist. However, rs4753426 of MTNR1B was not associated with either schizophrenia or clinical phenotypes. Our results suggest that MTNR1A may be a susceptibility gene for schizophrenia and may be associated with insomnia symptoms exhibited in schizophrenia patients.