Cx26 Gene Expression Research Articles

Alteration of connexins gene expression by silibinin during hepatic warm ischemia-reperfusion injury in the rat model

Background: Ischemia-reperfusion injury (IRI) is an injurious phenomenon that is the primary determinant of liver dysfunction after surgery and transplantation. The present evidence demonstrated that connexin 43 (Cx43), Cx32, and Cx26 are the essential gap junction proteins involved in the liver IRI. This study aimed to characterize the beneficial effects of silibinin on Cx43, Cx32, and Cx26 gene expression during warm hepatic ischemia-reperfusion (IR). Materials and Methods: A total of 32 male Wistar rats weighing 250-300 g were randomly divided into four equal groups of eight animals in each group as follows: 1) control group (laparotomy+normal saline), 2) laparotomy+silibinin (30 mg/kg) (SILI), 3) liver IR procedure+normal saline (IR), and 4) liver IR procedure+silibinin (30 mg/kg) (IR+SILI). After 1 h of ischemia followed by 3 h of reperfusion, blood samples and tissue sections were gathered to assess the serum liver markers and evaluate the liver histological changes as well as gene expression, respectively. Results: The obtained data proved no considerable differences between control and SILI groups in all experiments. Furthermore, the gene expression of Cx26, Cx32, and Cx43 was significantly induced in the IR group, compared to the control group. Silibinin markedly reduced Cx26 and Cx32 mRNA expression, whereas increased Cx43 mRNA expression. Moreover, serum alanine aminotransferase and aspartate aminotransferase levels were markedly elevated in the IR group (P<0.001), compared to the control group. However, in the IR+SILI group, silibinin could significantly decline these elevations, compared to the IR group. In addition, silibinin diminished hepatic tissue damages during IR. Conclusion: Silibinin could attenuate liver injury through better cell-to-cell communication via lowering Cx32 and Cx26, as well as increasing Cx43 gene expression, respectively.

Nanoscale bubble delivered YCD-TK/Cx26 gene therapeutic system suppresses tumor growth by inducing necrosis of tumor tissues in mouse Xenograft bladder cancer models.

Bladder cancer is considered as the fifth most common cancer in the whole world. This study aimed to investigate the anti-tumor effects of Nanoscale bubbles delivered yeast cytosine deaminase thymidine kinase/connexin 26 (YCD-TK/Cx26) on tumor cell proliferation and tumor growth. Nanoscale bubble was prepared using thin-film hydration-sonication method. Nanoscale bubble-LV5-YCD-TK+PCD-Cx26 was generated and transfected into BIU-87 cells. MTT assay was employed to detect cell viability. Apoptosis was determined using a flow cytometry assay. YCD-TK and Cx26 expressions were detected using Western blot and Real Time-PCR (RT-PCR). BIU-87 cells were transplanted into mice to establish Xenograft models. The tumor volume was recorded. HE staining was used to examine necrosis areas in tumor tissues. Nanoscale bubble (Nanoscale bubble-LV5-YCD-TK+PCD-Cx26) successfully mediated YCD-TK and Cx26 gene expression in BIU-87 cells. Nanoscale bubble delivered YCD-TK/Cx26 expression significantly inhibited cell viability and induced apoptosis compared to Nanoscale bubble-LV5-YCD-TK and Nanoscale bubble group (p<0.05). Nanoscale bubble delivered YCD-TK/Cx26 expression triggered significantly higher levels of bystander effect compared to single YCD-TK or single Cx26 gene (p<0.05). Nanoscale bubble delivered YCD-TK/Cx26 expression significantly reduced tumor volume in mouse Xenograft bladder cancer model compared to LV5-YCD-TK and 5-FC+GCV group (p<0.05). Nanoscale bubble delivered YCD-TK/Cx26 expression significantly reduced the necrosis of tumor tissues in mouse Xenograft bladder cancer model compared to LV5-YCD-TK group and 5-FC+GCV group (p<0.05). Nanoscale bubble delivered YCD-TK/Cx26 gene therapeutic system efficiently reduced BIU-87 cell proliferation in vitro, and suppressed tumor growth by inducing necrosis of tumor tissues in mouse Xenograft bladder cancer models.

The effect of dexamethasone/cell-penetrating peptide nanoparticles on gene delivery for inner ear therapy.

Dexamethasone (Dex)-loaded PHEA-g-C18-Arg8 (PCA) nanoparticles (PCA/Dex) were developed for the delivery of genes to determine the synergistic effect of Dex on gene expression. The cationic PCA nanoparticles were self-assembled to create cationic micelles containing an octadecylamine (C18) core with Dex and an arginine 8 (Arg8) peptide shell for electrostatic complexation with nucleic acids (connexin 26 [Cx26] siRNA, green fluorescent protein [GFP] DNA or brain-derived neurotrophic factor [BDNF] pDNA). The PCA/Dex nanoparticles conjugated with Arg8, a cell-penetrating peptide that enhances permeability through a round window membrane in the inner ear for gene delivery, exhibited high uptake efficiency in HEI-OC1 cells. This potential carrier co-delivering Dex and the gene into inner ear cells has a diameter of 120–140 nm and a zeta potential of 20–25 mV. Different types of genes were complexed with the Dex-loaded PCA nanoparticle (PCA/Dex/gene) for gene expression to induce additional anti-inflammatory effects. PCA/Dex showed mildly increased expression of GFP and lower mRNA expression of inflammatory cytokines (IL1b, IL12, and INFr) than did Dex-free PCA nanoparticles and Lipofectamine® reagent in HEI-OC1 cells. In addition, after loading Cx26 siRNA onto the surface of PCA/Dex, Cx26 gene expression was downregulated according to real-time polymerase chain reaction for 24 h, compared with that using Lipofectamine reagent. After loading BDNF DNA into PCA/Dex, increased expression of BDNF was observed for 30 h, and its signaling pathway resulted in an increase in phosphorylation of Akt, observed by Western blotting. Thus, Dex within PCA/Dex/gene nanoparticles created an anti-inflammatory effect and enhanced gene expression.

Significance of Cx26 Gene Expressions and Mutation in Skin Scar and Skin Scar Squamous Cell Carcinoma

Objective To investigate the significance of Cx26 gene expression and mutation in skin scar and skin scar squamous cell carcinoma.Methods The expressions of Cx26 protein and its mRNA in 15 skin scar and 22 skin scar squamous cell carcinomas were detected by immunohistochemical method of SP and in situ hybridization.To analyze the characteristics of Cx26 gene mutations,DNA was extracted from 28 samples(14 skin scar and 14 skin scar squamous cell carcinoma tissues)of Paraffin embedded and screened for mutation by direct sequencing.Pictures were collected and analyzed,statistical analysis was performed by SPSS system.Results(1)Cx26 and its mRNA showed positive expression in normal skin epidermis and strong positive in pathological skin scar epithelium,weakly positive or negative expression in skin scar squamous cell carcinoma tissues.Each of two groups was statistically different(P0.05).(2)The Cx26 genes were not examined to have the mutation in skin scar squamous cell carcinoma tissues after sequencing.Conclusion The high expression of Cx26 protein and Cx26mRNA may be related to the hyperplasia of skin scar epithelium.The low expression may be related to the occurrence of skin scar squamous cell carcinoma.The genetic mutation suits need more explored.

Differential expression and localization of connexins 26 and 43 in the rat gingival epithelium

We investigated the expression and localization of connexins (CX) 26 and 43 in the rat gingival epithelium. RT-PCR analysis revealed CX26 gene expression in both the upper and lower layers of the gingival epithelium and in the total epithelial layer, whereas CX43 gene expression was limited to the lower layer and the total epithelial layer. Immunoreactivity for CX43 was observed in the membranes of adjacent cells from the basal layer to the middle of the prickle cell layer, while immunoreactivity for CX26 was observed in the granular cell layer and lower part of the squamous cell layer. Merged images revealed the co-localization of CX26 and CX43 in the middle of the prickle cell layer. By immuno-electron microscopy, gap junctions appeared curved, hemi-circular, or annular within the cytoplasm, and gold particles indicating the presence of CX43 were localized at the outer edges of these cytoplasmic formations. These results suggest that CX43 is associated with the regulation of cell proliferation and that increased CX26 expression is associated with differentiation of keratinocytes. Thus, degradation of CX43 is considered to play an essential role in differentiation of the rat gingival epithelium.

A reporter allele for investigating connexin 26 gene expression in the mouse brain.

A variety of connexins are expressed in the diverse cell types of the central nervous system and are thought to regulate some of the functional properties exhibited by immature and mature cells. A proper understanding of the role of specific connexins in these processes requires an unambiguous characterization of their spatial and temporal pattern of expression. In order to define the cellular distribution of connexin 26 (Cx26) in the mouse we have generated a reporter allele (Cx26lacZ) by genetically manipulating the locus so that the beta-galactosidase (lacZ) gene is expressed from the endogenous Cx26 promoter. This modification decreased expression from the allele and resulted in embryonic lethality for the Cx26lacZ/lacZ genotype in accordance with previous studies on Cx26 knock-out animals indicating that Cx26-containing gap junctions are necessary for embryonic development. Despite the lower than expected transcript levels, the amount of lacZ protein produced in heterozygous mice was sufficient to label tissues known to contain Cx26, such as liver, kidney, skin, cochlea, small intestine, placenta and thyroid gland. In the embryonic and mature central nervous system, however, lacZ was restricted to meningeal cells and could not be detected in either neurons or glia. The absence of Cx26 mRNA in these cells could also be confirmed by reverse transcription-polymerase chain reaction and in situ hybridization. Our experiments indicate that the Cx26lacZ mouse line can be used as a reporter of Cx26 gene expression and suggest that Cx26, contrary to previous reports, is restricted to the meninges in both embryonic and adult brain.

Exocrine specific expression of Connexin32 is dependent on the basic helix-loop-helix transcription factor Mist1.

Gap junctions are intercellular channels that provide direct passage of small molecules between adjacent cells. In pancreatic acini, the connexin26 (Cx26) and connexin32 (Cx32) proteins form functional channels that coordinate the secretion of digestive enzymes. Although the function of Cx26/Cx32 gap junctions are well characterized, the regulatory circuits that control the spatial and temporal expression patterns of these connexin genes are not known. In an effort to identify the molecular pathways that regulate connexin gene expression, we examined Cx26 and Cx32 gene activities in mice lacking the basic helix-loop-helix transcription factor Mist1 (Mist1KO). Mist1, Cx26 and Cx32 are co-expressed in most exocrine cell types, and acinar cells from Mist1KO mice exhibit a highly disorganized cellular architecture and an altered pattern of expression for several genes involved in regulated exocytosis. Analysis of Mist1KO mice revealed a dramatic decrease in both connexin proteins, albeit through different molecular mechanisms. Cx32 gene transcription was greatly reduced in all Mist1KO exocrine cells, while Cx26 gene expression remained unaffected. However, in the absence of Cx32 protein, Cx26 did not participate in gap junction formation, leading to a complete lack of intercellular communication among Mist1KO acinar cells. Additional studies testing Mist1 gene constructs in pancreatic exocrine cells confirmed that Mist1 transcriptionally regulates expression of the Cx32 gene. We conclude that Mist1 functions as a positive regulator of Cx32 gene expression and, in its absence, acinar cell gap junctions and intercellular communication pathways become disrupted.

Variable promoter region CpG island methylation of the putative tumor suppressor gene Connexin 26 in breast cancer.

Intercellular communication via gap junctions is a mechanism for tumor suppression. Connexin 26 (Cx26) is a structural component of gap junctions expressed by breast epithelial cells. Expression levels of Cx26 are reduced in many breast tumors. Methylation-sensitive single-stranded conformation analysis showed variable methylation in the promoter region CpG island in 11 out of 20 (55%) breast cancer patients. Heterogeneity in methylation patterns was observed both between and within tumors. The degree of methylation ranged from a few CpG dinucleotides to almost all the CpG dinucleotides in the analyzed region. The most frequently methylated CpG was in an Sp1 site known to be important for Cx26 gene expression. One of eight breast cancer cell lines (MD-MBA-453) was methylated in the promoter region and did not express Cx26. Treatment of MDA-MB-453 with 5-aza-2'-deoxycytidine resulted in the re-expression of Cx26 mRNA. Methylation of the promoter region is likely to be an important mechanism in modulating the expression of Cx26 in breast cancer.

Gap Junction Connexin Genes cx26 and cx43 Are Differentially Regulated by Ovarian Steroid Hormones in Rat Endometrium

In rat endometrium, expression of gap junction connexin-26 (cx26) in the epithelium and cx43 in the uterine stroma is suppressed by progesterone before implantation. For further study of connexin gene regulation we analyzed expression of cx26, cx43, and cx32 in the endometrium of ovariectomized rats treated with different ratios of 17beta-estradiol (E2) and progesterone (P). A hormonal ratio of E2 to P that mimics conditions during pregnancy (0.1 microg E2 and 4 mg P) suppressed expression of cx26 and cx43. By changing the ratio to higher E2 levels (1 microg E2), cx26, in contrast to cx43, was not suppressed even by application of a high P concentration (10 mg). Time-course experiments supplying E2 alone led to an early gene response of cx26 within 3 h, whereas induction of cx43 transcripts was not detected until 14 h after E2 treatment. Simultaneous application of the antiestrogen ICI 182780 abolished E2-mediated induction of both connexins. No hormonal regulation of cx32 could be detected. As already shown for cx43 gene induction in the myometrium, E2-mediated induction of cx26 expression in the endometrium also required newly synthesized transcription factors. It can be concluded that only a hormonal ratio resembling conditions during pregnancy is able to suppress the expression of both cx26 and cx43 and that cx26 gene expression is induced earlier by E2 and is likely to be more sensitive to a shift in the E2 to P ratio than cx43.

Mapping and characterization of the basal promoter of the human connexin26 gene

Connexin26 (Cx26) is a major gap junction protein expressed in mammary and endometrial epithelial cells. Previously, we have cloned the genomic upstream sequence of the human connexin26 gene. In this paper, we studied the structure and function of its basal promoter. Various 5′-flanking regions of the human Cx26 gene were inserted upstream of the bacterial chloramphenicol acetyltransferase (CAT) reporter gene and transfected into human immortalized mammary MCF-10A and MCF-12A cell lines and endometrial RL95-2 cancer cell line. Through CAT reporter gene analysis, we identified the basal promoter of human Cx26 gene in the proximal 5′-flanking region from −128 to +2 (relative to the transcription initiation site). Further deletion analyses suggested that the critical regulatory area was located within a 29 bp region (from −97 to −69), where two GC consensus boxes (CCGCCC) resided, one at −93 and the other at −81. Labeled oligonucleotides encompassing these two GC box DNA sequences could bind the nuclear extracts from MCF-12A and RL95-2 cells in the electrophoretic mobility shift assay. These binding complexes could be competitively reduced by non-labeled self or Sp1 consensus oligonucleotide, and supershifted by antibodies against either Sp1 or Sp3. Mutations in the core sequence of these two GC boxes from CCGCCC to CCG AA C caused a loss of competitive ability and also produced a drastic reduction of basal promoter activity when integrated into promoter/reporter constructs. Furthermore, co-transfection of Sp1 and/or Sp3 expressing plasmids could trans-activate the expression of human Cx26 promoter/reporter constructs in Drosophila Schneider line 2 (SL2) cells. Taken together, these data indicated that the two GC boxes in the proximal promoter region play an important role in the control of human Cx26 gene expression.