• Tuberculosis and Respiratory Diseases
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• v.44 no.1
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• pp.162-174
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• 1997

Background : Metabolic cooperation via gap junctional intercellular communication (GJIC) is an important mechanism of the bystander effect in gene therapy using the Herpes Simplex Virus thymidine kinase/ganciclovir (HSVtk) "prodrug" system. Since retinoids have been reported to increase GJIC by induction of connexin 43 expression, we hyporthesized that treatment of tumor cells with retinoic acid could augment the bystander effect of the HSVtk/GCV system and result in improved tumor cell killing by enhancing GJIC. Methods : We transferred HSVtk gene to SKHep-J cell line that does not express connexin43, and also transferred the gene to human and murine mesothelioma cell lines that express connexin43. We verified that retinoic acid enhanced GJIC utilizing a functional double-dye transfer study and evaluated the effects of retinoic acid on the growth rate of tumor cells. We then tested the effects of retinoic acid on bystander-mediated cell killing. Results : Addition of all-trans retinoic acid (RA) increased GJIC in cell lines expressing connexin 43 and was asspciated with more efficient in vitro bystander killing in cells transduced with HSVtk via adenoviral and retroviral vectors. In contrast, there was no increase in the efficiency of the bystander effect after exposure to RA in a cell line which had no delectable connexin 43. Conclusion : These results provide evidence that retinoids can augment the efficiency of cell killing with the HSVtk/GCV system by enhancing bystander effect and may thus be a promising new approach to improve responses in gene therapy utilizing the HSVtk system to treat tumors.

• The Korean Journal of Physiology and Pharmacology
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• v.24 no.1
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• pp.11-18
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• 2020

The present study was aimed to explore the neuroprotective role of imatinib in global ischemia-reperfusion-induced cerebral injury along with possible mechanisms. Global ischemia was induced in mice by bilateral carotid artery occlusion for 20 min, which was followed by reperfusion for 24 h by restoring the blood flow to the brain. The extent of cerebral injury was assessed after 24 h of global ischemia by measuring the locomotor activity (actophotometer test), motor coordination (inclined beam walking test), neurological severity score, learning and memory (object recognition test) and cerebral infarction (triphenyl tetrazolium chloride stain). Ischemia-reperfusion injury produced significant cerebral infarction, impaired the behavioral parameters and decreased the expression of connexin 43 and phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in the brain. A single dose administration of imatinib (20 and 40 mg/kg) attenuated ischemia-reperfusion-induced behavioral deficits and the extent of cerebral infarction along with the restoration of connexin 43 and p-STAT3 levels. However, administration of AG490, a selective Janus-activated kinase 2 (JAK2)/STAT3 inhibitor, abolished the neuroprotective actions of imatinib and decreased the expression of connexin 43 and p-STAT3. It is concluded that imatinib has the potential of attenuating global ischemia-reperfusion-induced cerebral injury, which may be possibly attributed to activation of JAK2/STAT3 signaling pathway along with the increase in the expression of connexin 43.

• Journal of Life Science
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• v.17 no.11
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• pp.1517-1522
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• 2007

Gap junction channels formed by two adjacent cells allow the passage of small molecules up to ${\sim}\;1\;kDa$ between them. Hemichannel (connexon or half of gap junction) also behaves as a membrane channel like sodium or potassium channels in a single cell membrane. Among 26 types of connexin (Cx), $Cx32^*43E1$ (a chimera in which the first extracellular loop of Cx32 has been replaced with that of Cx43), Cx38, Cx46, and Cx50 form functional hemichannels as well as gap junction channels. Although it is known that Xenopus oocytes express endogenous connexin 38 (Cx38), its biophysical characteristics at single channel level are poorly understood. In this study, we performed single channel recordings from single Xenopus oocytes to acquire the biophysical properties of Cx38 including voltage-dependent gating and permeation (conductance and selectivity). The voltage-dependent fast and slow gatings of Cx38 hemichannel are distinct. Fast gating events occur at positive potentials and their open probabilities are low. In contrast, slow gatings dominate at negative potentials with high open probabilites. Based on hi-ionic experiments, Cx38 hemichannel is anion-selective. It will be interesting to test whether charged amino acid residues in the amino terminus of Cx38 are responsible for voltage gatings and permeation.

• BMB Reports
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• v.36 no.1
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• pp.43-48
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• 2003

Understanding the process of carcinogenesis will involve both the accumulation of many scientific facts derived from molecular, biochemical, cellular, physiological, whole animal experiments and epidemiological studies, as well as from conceptual understanding as to how to order and integrate those facts. From decades of cancer research, a number of the "hallmarks of cancer" have been identified, as well as their attendant concepts, including oncogenes, tumor suppressor genes, cell cycle biochemistry, hypotheses of metastasis, angiogenesis, etc. While all these "hallmarks" are well known, two important concepts, with their associated scientific observations, have been generally ignored by many in the cancer research field. The objective of the short review is to highlight the concept of the role of human adult pluri-potent stem cells as "target cells" for the carcinogenic process and the concept of the role of gap junctional intercellular communication in the multi-stage, multi-mechanism process of carcinogenesis. With these two concepts, an attempt has been made to integrate the other well-known concepts, such as the multi-stage, multi-mechanisn or the "initiation/promotion/progression" hypothesis; the stem cell theory of carcinogenesis; the oncogene/tumor suppression theory and the mutation/epigenetic theories of carcinogenesis. This new "integrative" theory tries to explain the well-known "hallmarks" of cancers, including the observation that cancer cells lack either heterologous or homologous gap junctional intercellular communication whereas normal human adult stem cells do not have expressed or functional gap junctional intercellular communication. On the other hand, their normal differentiated, non-stem cell derivatives do express connexins and express gap junctional intercellular communication during their differentiation. Examination of the roles of chemical tumor promoters, oncogenes, connexin knock-out mice and roles of genetically-engineered tumor and normal cells with connexin and anti-sense connexin genes, respectively, seems to provide evidence which is consistent with the roles of both stem cells and gap junctional communication playing a major role in carcinogenesis. The integrative hypothesis provides new strategies for chemoprevention and chemotherapy which focuses on modulating connexin gene expression or gap junctional intercellular communication in the premalignant and malignant cells, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.565-571
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• 2000

Mixed primers based on the high sequence homology of selected regions of known connexins (Cxs) was used for PCR reaction. A full-length connexin cDNA of sweetfish (Plecoglossus altivelis) was cloned by rapid amplification of cDNA 5'and (5'RACE) and 3'RACE method. When compared to other known Cx sequences, homology of sweetfish Cx cDNA to Atlantic croaker, Mycropogonias undulatus Cx32.7, bovine, Bos taurus Cx44 and Atlantic croaker Cx32.2 were $63.8{\%},\;61.6{\%}\;and\;56.7{\%}$, respectively. This cDNA encoded 308 amino acids (35,028 dalton) and named as sweetfish Cx35. Hydropathicity analysis of predicted amino acid sequences indicated that sweetfish Cx35 have four major hydrophobic regions and four major hydrophilic regions, suggesting its topology is similar to that of known Cxs. The presence of a tfical Cx consensus sequences were identified in each of the extracellular loops (first loop and second loop).

• Clinical and Experimental Pediatrics
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• v.62 no.3
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• pp.95-101
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• 2019

Purpose: Increased apoptosis was recently found in the hypertrophied left ventricle of spontaneously hypertensive rats (SHRs). Although the available evidence suggests that apoptosis can be induced in cardiac cells by various insults including pressure overload, cardiac apoptosis appears to result from an exaggerated local production of angiotensin in adult SHRs. Altered expressions of Bcl associated X (Bax), Bcl-2, chemokine receptor (CCR)-2, monocyte chemoattractant protein (MCP)-1, transforming growth factor $(TGF)-{\beta}1$, phosphorylated extracellular signal-regulated kinases (PERK), and connexin 43 proteins, and kallikrein mRNA were investigated to explore the effects of losartan on the SHR model. Methods: Twelve-week-old male rats were grouped as follows: control (C), SHR (hypertension: H), and losartan (L; SHRs were treated with losartan [10 mg/kg/day] for 5 weeks). Western blot and reverse transcription polymerase chain reaction assays were performed. Results: Expression of Bax, CCR-2, MCP-1, $TGF-{\beta}1$, PERK, and connexin 43 proteins, and kallikrein mRNA was significantly increased in the H group compared to that in the C group at weeks 3 and 5. Expression of Bax, CCR-2, MCP-1, $TGF-{\beta}1$, and connexin 43 proteins and kallikrein mRNA was significantly decreased after losartan treatment at week 5. PERK protein expression was significantly decreased after losartan treatment at weeks 3 and 5. Bcl-2 protein expression was significantly decreased in the H group compared to that in the C group at weeks 3 and 5. Conclusion: Losartan treatment reduced expression of Bax, CCR-2, MCP-1, $TGF-{\beta}1$, PERK, and connexin 43 proteins, and kallikrein mRNA in SHRs, along with decreased inflammation and apoptosis.

• Journal of Animal Science and Technology
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• v.54 no.6
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• pp.419-425
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• 2012

The coordinated action of the detrusor muscle cells in the urinary bladder is governed by cell-cell communication through gap junction, consisted of connexin (Cx) molecules. Even though a number of researches have been mostly focused on expressional changes of a few Cx isoforms in clinically dysfunctional condition of the bladder, less attention has been paid for investigation of Cx isoforms present in the bladder. Using real-time PCR analysis, the present study examined Cx isoforms expressing in the male rat bladder during postnatal period. Also, expressional patterns of Cx isoforms were evaluated in the bladder at different postnatal ages. Of a total of 13 Cx isoforms tested in the present study, we were able to detect mRNAs of 6 Cx isoforms in the rat urinary bladder, including Cxs 31, 31.1, 32, 37, 40, and 45. The transcript levels of Cxs 31, 31.1, 37, 40, and 45 were gradually increased from 1 week of age until 25 days of age, followed by transient decreases at 45 days of age. However, abundance of Cx32 transcript was drastically increased at 15 days of age, followed by a sharp drop at 45 days of age. These results indicate that differential expression of Cx isoforms in the bladder during postnatal development would be necessary for maintaining proper function of the bladder. A question remains to be answered if significant decreases of transcript levels of some Cx isoforms at the elderly are associated with age-dependent dysfunction of the bladder.

• Korean Journal of Veterinary Research
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• v.45 no.4
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• pp.517-525
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• 2005

This study was performed to evaluate using wild-type (WT) and $C{\times}32$ knockout (KO) mice if lack of cell to cell communication by connexin 32 gap junction enhances the benzene-induced hematotoxicity and hemopoietic tumor development. The WT and $C{\times}32$ KO mice were exposed to 300 ppm of benzene for 6 hours/day, 5 days/week for a total of 26 weeks by inhalation, and then sacrificed to evaluate the toxicities of hemopoietic organs or allowed to live out their life span to evaluate the hemopoietic tumor incidence. The significant increase and decrease of organ weight were respectively noted in spleen and thymus of both WT and $C{\times}32$ KO mice without significant difference between the genotypes. Histopathologically, benzene exposure for 26 weeks induced the morphological changes in hemopoietic organs, characterized by fat cell accumulation in the bone marrow and extramedullary hemopoiesis in the spleen. The fat cell accumulation was, compared with that of WT mice, considerably exacerbated in the $C{\times}32$ KO mice. However, no significant difference was observed in the changes of hematological values and bone marrow cellularity as well as in the onset and incidence of hemopoietic tumors between WT and $C{\times}32$ KO mice. In conclusion, this study indicated little significant role of the cellular communication by $C{\times}32$ gap junction in the action mechanism of benzene hematotoxicity and leukemogenicity.

• 대한치과교정학회:학술대회논문집
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• 1998.10a
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• pp.78.1-78.1
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• 1998

• Archives of Pharmacal Research
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• v.19 no.4
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• pp.264-268
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• 1996

Panax-ginseng saponin has been known to exert various pharmacological effects on cellular metabolism. This study was performed to determine the effect of ginseng saponin on gap junction channel-mediated intercellular communication, using an established in vitro system of reconstituted gap junction channels. Gap junction channels are a specialized plasma membrane fraction, which are permeable to relatively large water-soluble molecules. The sucrose permeable property of reconstituted gap junction channels was completely inhibited with 0.1 % (w/v) of ginseng saponin. We also compared the effect of ginseng saponin with that of Triton X-100, a nonionic detergent, on the same system. Triton X-100 showed significantly different effect on sucrose-permeability of gap junction channel from that was affected by ginseng saponin. The structures of liposomes containing gap junction channels was significantly destroyed by Triton X-100.