Blockage of testicular connexins induced apoptosis in rat seminiferous epithelium

LncRNA SNHG5/IGF2BP1/Occludin axis regulates Nd2O3 induced blood-testis barrier disruption

Neodymium oxide (Nd2O3) is a rare earth element that can lead to various type of tissue and organ damage with prolonged exposure. The long noncoding RNA small nucleolar ribonucleic acid host gene 5 (lncRNA SNHG5) plays a role in disease progressiong. However, its connection with Nd2O3 induced reproductive harm in males has not been thoroughly investigated. Our research discovered that exposure to Nd2O3 increases the expression of SNHG5 in the testes of mice, which in turn binds directly to and reduces in the protein levels of insulin like growth factor 2 mRNA-binding protein 1 (IGF2BP1) both in vivo and in vitro. This process disrupts the cytoskeleton of blood-testis barrier(BTB) by impacting the stability of the tight junction protein Occludin (Ocln) mRNA structure and the permeability of the BTB. In summary, our study elucidates the regulatory mechanism of SNHG5/IGF2BP1/Occludin axis in Nd2O3-induced BTB injury, providing valuable insights for the treatment of male infertility.

Inositol hexakisphosphate kinase 1 is essential for cell junction integrity in the mouse seminiferous epithelium

Inositol hexakisphosphate kinases (IP6Ks) are enzymes that catalyse the synthesis of the inositol pyrophosphate 5-IP7 which is involved in the regulation of many physiological processes in mammals. The IP6K paralog IP6K1 is expressed at high levels in the mammalian testis, and its deletion leads to sterility in male mice. Here, we show that the loss of IP6K1 in mice causes a delay in the first wave of spermatogenesis. Testes from juvenile Ip6k1 knockout mice show downregulation of transcripts that are involved in cell adhesion and formation of the testis-specific inter-Sertoli cell impermeable junction complex known as the blood-testis barrier (BTB). We demonstrate that loss of IP6K1 in the mouse testis causes BTB disruption associated with transcriptional misregulation of the tight junction protein claudin 3, and subcellular mislocalization of the gap junction protein connexin 43. In addition to BTB disruption, we also observe a loss of germ cell adhesion in the seminiferous epithelium of Ip6k1 knockout mice, ultimately resulting in premature sloughing of round spermatids into the epididymis. Mechanistically, we show that loss of IP6K1 in the testis enhances cofilin dephosphorylation in conjunction with increased AKT/ERK and integrin signalling, resulting in destabilization of the actin-based cytoskeleton in Sertoli cells and germ cell loss.

Bisphenols as promoters of the dysregulation of cellular junction proteins of the blood-testis barrier in experimental animals: A systematic review of the literature

Daily, people are exposed to chemicals and environmental compounds such as bisphenols (BPs). These substances are present in more than 80% of human fluids. Human exposure to BPs is associated with male reproductive health disorders. Some of the main targets of BPs are intercellular junction proteins of the blood-testis barrier (BTB) in Sertoli cells because BPs alter the expression or induce aberrant localization of these proteins. In this systematic review, we explore the effects of BP exposure on the expression of BTB junction proteins and the characteristics of in vivo studies to identify potential gaps and priorities for future research. To this end, we conducted a systematic review of articles. Thirteen studies met our inclusion criteria. In most studies, animals treated with bisphenol-A (BPA) showed decreased occludin expression at all tested doses. However, bisphenol-AF treatment did not alter occludin expression. Cx43, ZO-1, β-catenin, nectin-3, cortactin, paladin, and claudin-11 expression also decreased in some tested doses of BP, while N-cadherin and FAK expression increased. BP treatment did not alter the expression of α and γ catenin, E-cadherin, JAM-A, and Arp 3. However, the expression of all these proteins was altered when BPA was administered to neonatal rodents in microgram doses. The results show significant heterogeneity between studies. Thus, it is necessary to perform more research to characterize the changes in BTB protein expression induced by BPs in animals to highlight future research directions that can inform the evaluation of risk of toxicity in humans.

Apoptosis and blood-testis barrier disruption during male reproductive dysfunction induced by PAHs of different molecular weights

The association between polycyclic aromatic hydrocarbons (PAHs) and male reproductive dysfunction has attracted increasing attention. The purpose of this study was to compare the male reproductive toxicity of multiple PAHs and to investigate the underlying molecular mechanisms. TM4 cells (mouse testicular Sertoli cells, SCs) were treated with benzo(a)pyrene (BaP), pyrene (Py), fluoranthene (Fl) and phenanthrene (Phe) (0, 0.1, 1, 10, 50, or 100 μM) for varying time points (4, 12, 24, or 48 h), and male C57BL/6 mice were administered BaP and Py (0, 10, 50, or 100 mg/kg body weight) for 14 days based on the cell experimental results. Histopathological examination, western blotting, ELISA, biochemical assays, RT-PCR, flow cytometry, JC-1 staining and trans-epithelium electrical resistance (TEER) measurements were used to assess apoptosis, blood-testis barrier (BTB) integrity, intracellular calcium ([Ca²⁺]_i) concentrations and oxidative stress (OS). The results revealed that the mRNA levels and enzymatic activities of CYP450 and GST family members; levels of ROS, MDA, cleaved caspase 3 (c-caspase 3), caspase 9, Bax, and cytochrome C (CytC); and numbers of TUNEL-positive cells were significantly increased by BaP and Py, while levels of AhR, GSH, SOD, CAT, Bcl-2 and ΔΨm were decreased. Additionally, BaP and Py notably interfered with tight junctions (TJs) and adherens junctions (AJs) in the BTB. Intriguingly, BaP, but not Py, induced [Ca²⁺]_i overload and gap junction (GJ) destruction. There was no dramatic effect of Fl and/or Phe on any of the above parameters except that slight cytotoxicity was observed with higher doses of Fl. Collectively, these findings showed that BaP and Py elicited SC apoptosis and BTB disruption involving mitochondrial dysfunction and OS, but [Ca²⁺]_i fluctuation and GJ injury were only observed with BaP-induced reproductive toxicity. The male reproductive toxicity of the selected PAHs was ranked in the order of BaP > Py > Fl > Phe.

Connexin 43 expression in the testes during postnatal development of finasteride-treated male rat offspring

INTRODUCTION

Hormone-dependent events that occur throughout the first wave of spermatogenesis, such as cellular communication within seminiferous epithelium during early postnatal testis maturation, are important for adult male fertility. Any changes in the T/DHT ratio in male progeny born from females fertilized by finasteride-treated male rats can result in impairment of testicular physiology. The aim of the study was to verify whether finasteride has a transgenerational effect on the expression of connexin 43 (Cx43), a gap junction protein in testes of the F1 generation.

MATERIAL AND METHODS

The subjects of the study were 7, 14, 21/22, 28, and 90-day-old Wistar male rats born by females fertilized by finasteride-treated rats (F1:Fin). The offspring born by untreated rats were used as controls (F1:Control). Connexin 43 was evaluated in the seminiferous epithelium by immunohistochemistry, and in the testis homogenates by Western blot and qRT-PCR. The Cx43 mRNA and protein expression was correlated with intratesticular levels of T and DHT by Spearman's rank correlation coefficient.

RESULTS

We observed a difference in the Cx43 expression in the testis of male rats born by female rats fertilized by finasteride-treated male rats, as compared to the control on following PND (7, 22 and 28 PND, p < 0.001; 14 PND, p < 0.01); and a strong, positive correlation between Cx43 with DHT was only in the F1:Fin group (mRNA: rs = +0.51, p = 0.004; protein: rs = +0.54, p = 0.002).

CONCLUSIONS

Finasteride treatment of male adult rats may cause changes in the communication between the testicular cells of their offspring, leading to a defective course of spermatogenesis.

Loss of connexin 43 in Sertoli cells provokes postnatal spermatogonial arrest, reduced germ cell numbers and impaired spermatogenesis

For the reason that adult Sertoli cell specific connexin 43 knockout (SCCx43KO) mice show arrested spermatogenesis at spermatogonial level or Sertoli cell only tubules and significantly reduced germ cell (GC) numbers, the aims of the present study were (1) to characterize the remaining GC population and (2) to elucidate possible mechanisms of their fading. Apoptosis was analyzed in both, KO and wild type (WT) male littermates during postnatal development and in adulthood using TUNEL. Although GC numbers were significantly reduced in KO at 2 and 8 days postpartum (dpp) when compared to WT, no differences were found concerning apoptotic incidence between genotypes. From 10 dpp, the substantial GC deficiency became more obvious. However, significantly higher apoptotic GC numbers were seen in WT during this period, possibly related to the first wave of spermatogenesis, a known phenomenon in normal pubertal testes associated with increased apoptosis. Characterization of residual spermatogonia in postnatal to adult KO and WT mice was performed by immunohistochemical reaction against VASA (marker of GCs in general), Lin28 and Fox01 (markers for undifferentiated spermatogonia) and Stra8 (marker for differentiating spermatogonia and early spermatocytes). During puberty, the GC component in SCCx43KO mice consisted likely of undifferentiated spermatogonia, few differentiating spermatogonia and very few early spermatocytes, which seemed to be rapidly cleared by apoptosis. In adult KOs, spermatogenesis was arrested at the level of undifferentiated spermatogonia. Overall, our data indicate that Cx43 gap junctions in SCs influence male GC development and differentiation rather than their survival.

Serine peptidase inhibitor Kazal type 1 (SPINK1) as novel downstream effector of the cadherin-17/β-catenin axis in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the most common type of liver cancer worldwide. Previously, we reported that cadherin-17 (CDH17) and its related CDH17/β-catenin axis may be responsible for inducing HCC in a subset of patients exhibiting CDH17 over-expression. Here we aimed at obtaining a better understanding of the CDH17-related HCC biology and to obtain further indications for the design of targeted therapies in CDH17 over-expressing HCC patients.

RESULTS

We found that SPINK1 acts as a downstream effector of the CDH17/β-catenin axis in HCC. In addition, we found that SPINK1 expression exhibited a positive correlation with CDH17 expression in human HCCs and was over-expressed in up to 70% of the tumors. We identified SPINK1 as a downstream effector of the CDH17/β-catenin axis using a spectrum of in vitro assays, including gene expression modulation and inhibitor assays, bioinformatics analyses and luciferase reporter assays. These in vitro results were validated in primary human HCCs, including the observation that alteration in β-catenin expression (a core component of the CDH17/β-catenin axis) in tumors affects SPINK1 serum levels in HCC patients. Similar to CDH17, SPINK1 expression in HCC cells was found to be associated with specific tumor-related properties via activating the c-Raf/MEK/ERK pathway.

CONCLUSIONS

Our current data substantiate our knowledge on the role of CDH17 in the biology of HCC and suggest that components of the CDH17/β-catenin axis may serve as therapeutic targets in CDH17 over-expressing HCC patients.

Multiple and complex influences of connexins and pannexins on cell death

Cell death is a fundamental process for organogenesis, immunity and cell renewal. During the last decades a broad range of molecular tools were identified as important players for several different cell death pathways (apoptosis, pyroptosis, necrosis, autosis…). Aside from these direct regulators of cell death programs, several lines of evidence proposed connexins and pannexins as potent effectors of cell death. In the present review we discussed the potential roles played by connexins, pannexins and innexins in the different cell death programs at different scales from gap junction intercellular communication to protein-protein interactions. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.

Inhibition of gap junction intercellular communication is involved in silica nanoparticles-induced H9c2 cardiomyocytes apoptosis via the mitochondrial pathway

Gap junction intercellular communication (GJIC) between cardiomyocytes is essential for synchronous heart contraction and relies on connexin-containing channels. Connexin 43 (Cx43) is a major component involved in GJIC in heart tissue, and its abnormal expression is closely associated with various cardiac diseases. Silica nanoparticles (SNPs) are known to induce cardiovascular toxicity. However, the mechanisms through which GJIC plays a role in cardiomyocytes apoptosis induced by SNPs remain unknown. The aim of the present study is to determine whether SNPs-decreased GJIC promotes apoptosis in rat cardiomyocytes cell line (H9c2 cells) via the mitochondrial pathway using CCK-8 Kit, scrape-loading dye transfer technique, Annexin V/PI double-staining assays, and Western blot analysis. The results showed that SNPs elicited cytotoxicity in H9c2 cells in a time- and concentration-dependent manner. SNPs also reduced GJIC in H9c2 cells in a concentration-dependent manner through downregulation of Cx43 and upregulation of P-Cx43. Inhibition of gap junctions by gap junction blocker carbenoxolone disodium resulted in decreased survival and increased apoptosis, whereas enhancement of the gap junctions by retinoic acid led to enhanced survival but decreased apoptosis. Furthermore, SNPs-induced apoptosis through the disrupted functional gap junction was correlated with abnormal expressions of the proteins involved in the mitochondrial pathway-related apoptosis such as Bcl-2/Bax, cytochrome C, Caspase-9, and Caspase-3. Taken together, our results provide the first evidence that SNPs-decreased GJIC promotes apoptosis in cardiomyocytes via the mitochondrial pathway. In addition, downregulation of GJIC by SNPs in cardiomyocytes is mediated through downregulation of Cx43 and upregulation of P-Cx43. These results suggest that in rat cardiomyocytes cell line, GJIC plays a protective role in SNPs-induced apoptosis and that GJIC may be one of the targets for SNPs-induced biological effects.

Chronic Intake of Green Propolis Negatively Affecting the Rat Testis

BACKGROUND

Human and animal evidence suggests that environmental toxicants may have an adverse impact on male reproductive health, reducing the population's reproductive output. Owing to the renewed attraction for natural products, some of them constitute effective alternatives to mitigate these effects. Propolis is a candidate for this use because of its intrinsic properties. In many situations, it improved the testicular damage and alleviated the toxic effects induced by environmental contaminant exposure.

OBJECTIVE

The aim of this study was to investigate possible alterations of testicular parameters and certify if its use is really advantageous to the testis, since this could affect rat reproductive function.

MATERIALS AND METHODS

Forty-eight adult male Wistar rats were divided into four groups (Co = control, T1 = 3 mg propolis/kg/day, T2 = 6 mg/kg/day, T3 = 10 mg/kg/day) and were exposed during 56 days. The testes were assessed with morphometrical, stereological, and ultrastructural analyses. Cell proliferation and death were diagnosed, respectively, by immunocytochemistry. Connexin 43 (Cx43) and N-cadherin transcript levels were determined by reverse transcription-polymerase chain reaction.

RESULTS

Increased cell proliferation and Leydig cell volume were observed in T2, and in contrast, Cx43 upregulation and cell death were observed in T3. Both T2 and T3 showed ultrastructural abnormalities in testicular parenchyma.

CONCLUSION

We recommend a cautious intake of propolis to avoid deleterious effects.

SUMMARY

Chronic intake of Brazilian green propolis induced N.-cadherin downregulation and decreased on seminiferous tubule volumeIncrease on connexin 43 expression and cell death and decrease in Leydig cell.(LC) number/testis with the concentration of 10 mg/kg/day were observedIncrease on cell proliferation, cytoplasmic proportion, and volume of LC with the concentration of 6 mg/kg/day was detectedThe presence of empty spaces between spermatids and malformed spermatozoa in the lumen of seminiferous tubule was showedThis male reproductive disruption can be linked to phenolic compounds present in Brazilian green propolis. Abbreviation Used: AEC: 3-amino-9-ethylcarbazole; AJ: Adherens junction; AME: Aromadendrin-40-methyl ether; CAPE: Caffeic acid phenethyl ester; Co: Control group; C×43: Connexin 43; DAB: Diaminobenzidine; dNTP: Deoxyribonucleotide phosphate; DSP: Daily sperm production; FA: Ferulic acid; FSH: Follicle-stimulating hormone; GJ: Gap junction; GJIC: Gap junction intercellular communication; HPLC: High-performance liquid chromatography; LC: Leydig cell; LH: Luteinizing hormone; N-cad: N-cadherin; PCNA: Proliferating cell nuclear antigen; PCR: Polymerase chain reaction; RT-PCR: Reverse transcription-polymerase chain reaction; SDM: Standard deviation of mean; T1: Group exposed to 3 mg of propolis/kg/day; T2: Group exposed to 6 mg of propolis/kg/day; T3: Group exposed to 10 mg of propolis/kg/day; TUNEL: Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling; WB-ras 2 cells: Ras-transformed rat liver epithelial cell line.

Blood-testis barrier and Sertoli cell function: lessons from SCCx43KO mice

The gap junction protein connexin43 (CX43) plays a vital role in mammalian spermatogenesis by allowing for direct cytoplasmic communication between neighbouring testicular cells. In addition, different publications suggest that CX43 in Sertoli cells (SC) might be important for blood-testis barrier (BTB) formation and BTB homeostasis. Thus, through the use of the Cre-LoxP recombination system, a transgenic mouse line was developed in which only SC are deficient of the gap junction protein, alpha 1 (Gja1) gene. Gja1 codes for the protein CX43. This transgenic mouse line has been commonly defined as the SC specific CX43 knockout (SCCx43KO) mouse line. Within the seminiferous tubule, SC aid in spermatogenesis by nurturing germ cells and help them to proliferate and mature. Owing to the absence of CX43 within the SC, homozygous KO mice are infertile, have reduced testis size, and mainly exhibit spermatogenesis arrest at the level of spermatogonia, seminiferous tubules containing only SC (SC-only syndrome) and intratubular SC-clusters. Although the SC specific KO of CX43 does not seem to have an adverse effect on BTB integrity, CX43 influences BTB composition as the expression pattern of different BTB proteins (like OCCLUDIN, β-CATENIN, N-CADHERIN, and CLAUDIN11) is altered in mutant males. The supposed roles of CX43 in dynamic BTB regulation, BTB assembly and/or disassembly and its possible interaction with other junctional proteins composing this unique barrier are discussed. Data collectively indicate that CX43 might represent an important regulator of dynamic BTB formation, composition and function.

Physiological roles of connexins and pannexins in reproductive organs

Reproductive organs are complex and well-structured tissues essential to perpetuate the species. In mammals, the male and female reproductive organs vary on their organization, morphology and function. Connectivity between cells in such tissues plays pivotal roles in organogenesis and tissue functions through the regulation of cellular proliferation, migration, differentiation and apoptosis. Connexins and pannexins can be seen as major regulators of these physiological processes. In the present review, we assembled several lines of evidence demonstrating that these two families of proteins are essential for male and female reproduction.

Supplemental dietary phytosterin protects against 4-nitrophenol-induced oxidative stress and apoptosis in rat testes

4-Nitrophenol (PNP), is generally regarded as an environmental endocrine disruptor (EED). Phytosterin (PS), a new feed additive, possesses highly efficient antioxidant activities. The transcription factor, nuclear factor-erythroid 2-related factor 2 (Nrf2), is an important regulator of cellular oxidative stress. Using rats, this study examined PNP-induced testicular oxidative damage and PS-mediated protection against that damage. The generation of MDA and H₂O₂ upon PNP and PS treatment was milder than that upon treatment with PNP alone. This mitigation was accompanied by partially reversed changes in SOD, CAT, GSH and GSH-Px. Moreover, PNP significantly reduced the caudal epididymal sperm counts and serum testosterone levels. Typical morphological changes were also observed in the testes of PNP-treated animals. PNP reduced the transcriptional level of Nrf2, as evaluated by RT-PCR, but it promoted the dissociation from the Nrf2 complex, stabilization and translocation into the nucleus, as evaluated by immunohistochemistry and Western blotting. In addition, PNP enhanced the Nrf2-dependent gene expression of heme oxygenase-1 (HO-1) and glutamate–cysteine ligase catalytic subunit (GCLC). These results suggest that the Nrf2 pathway plays an important role in PNP-induced oxidative damage and that PS possesses modulatory effects on PNP-induced oxidative damage in rat testes.

Testis specific serine/threonine protein kinase 4 (TSSK4) leads to cell apoptosis relying on its kinase activity

Testis specific serine/threonine protein kinase 4 (TSSK4) belongs to the TSSK family, and its members play an important role in spermatogenesis and/or spermiogenesis. Mouse TSSK4 has been reported to be expressed exclusively in the testis and can maintain its kinase activity through autophosphorylation at Thr-197. However, its biological function remains poorly understood. Here we found that GFP-TSSK4-overexpressed HeLa cells showed apoptotic bodies, indicating TSSK4 can lead to apoptosis in vitro. Furthermore, TSSK4 induced apoptosis in different cell lines including HeLa, Cos-7 and H1299 tested by flow cytometry but not its kinase-dead mutant TSSK4-K54M. TSSK4 knockout mice showed increased testes weight and decreased apoptotic spermatogonia and spermatocytes at 21st day after birth tested by TUNEL technology. So TSSK4 was able to induce cell apoptosis in vitro depending on its kinase activity, which leads to abnormal testes weight and apoptosis, shedding light on its function in the process of spermatogenesis and/or spermiogenesis.

A Sertoli cell-specific connexin43 knockout leads to altered interstitial connexin expression and increased Leydig cell numbers

The Sertoli cell (SC)-specific knockout (KO) of connexin43 (Cx43) results in spermatogenic arrest at the level of spermatogonia and/or SC-only syndrome. Histology of the interstitial compartment suggests Leydig cell (LC) hyperplasia. Our aim has been to investigate possible effects of the SC-specific KO of Cx43 (SCCx43KO) on interstitial LC. We therefore counted LC via the optical dissector method (per microliter of testicular tissue and per testis) and found LC to be significantly increased in SCCx43KO(-/-) compared with wild-type mice. Semiquantitative western blot together with Cx43 and 3β-hydroxysteroid dehydrogenase immunohistochemistry showed that Cx43 protein was significantly reduced and barely detectable in LC in adult SCCx43KO(-/-) mice. This reduction of Cx43 protein was accompanied by a reduction of Cx43 mRNA as analyzed by laser-assisted microdissection of interstitial cells and subsequent quantitative real-time polymerase chain reaction (PCR). Interestingly, Cx45, another recently detected connexin in LC, was also downregulated. Preliminary qualitative data of LC differentiation markers (Thb2, Hsd3b6) and a steroidogenic marker (Hsd17b3) obtained by reverse transcription plus PCR revealed no obvious differences. Thus, the loss of Cx43 in SC also provokes the downregulation of connexins in interstitial LC at the transcriptional and translational levels. Moreover, SCCx43KO leads to alterations in LC numbers. Despite these alterations, steroidogenesis seems not to be impaired. Further studies, including ultrastructural analysis of the tissue as well as quantitative examination of additional LC markers and testosterone, and functional in vitro experiments, should provide more information about LC differentiation and function in SCCx43KO(-/-) mice.

Gap junction-mediated death of retinal neurons is connexin and insult specific: a potential target for neuroprotection

Secondary cell death via gap junctions (GJs) plays a role in the propagation of neuronal loss under a number of degenerative disorders. Here, we examined the role of GJs in neuronal death in the retina, which has arguably the most diverse expression of GJs in the CNS. Initially, we induced apoptotic death by injecting single retinal ganglion cells and glia with cytochrome C and found that this resulted in the loss of neighboring cells to which they were coupled via GJs. We next found that pharmacological blockade of GJs eradicated nearly all amacrine cell loss and reduced retinal ganglion cell loss by ∼70% after induction of either excitotoxic or ischemic insult conditions. These data indicate that the GJ-mediated secondary cell death was responsible for the death of most cells. Whereas genetic deletion of the GJ subunit Cx36 increased cell survivability by ∼50% under excitotoxic condition, cell loss in Cx45 knock-out mouse retinas was similar to that seen in wild-type mice. In contrast, ablation of Cx45 reduced neuronal loss by ∼50% under ischemic insult, but ablation of Cx36 offered no protection. Immunolabeling of the connexins showed differential changes in protein expression consistent with their differing roles in propagating death signals under the two insults. These data indicate that secondary cell death is mediated by different cohorts of GJs dependent on the connexins they express and the type of initial insult. Our results suggest that targeting specific connexins offers a novel therapeutic strategy to reduce progressive cell loss under different neurodegenerative conditions.

Overexpression of transferrin receptor CD71 and its tumorigenic properties in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the predominant type of esophageal cancer in endemic Asian regions. In the present study, we investigated the clinical implication and role of transferrin receptor CD71 in ESCC. CD71 has a physiological role in cellular iron intake and is implicated in the carcinogenesis of various types of tumors. In our cohort, more than a 2-fold upregulation of the CD71 transcript was detected in 61.5% of patients using quantitative polymerase chain reaction. Immunohistochemical analysis also showed strong membranous and cytoplasmic localization of CD71 in paraffin-embedded tumors. Staining parallel tumor sections with the proliferative marker Ki-67 revealed that the pattern of Ki-67 staining was associated with CD71 expression. Analysis of clinicopathological data indicated that CD71 overexpression can be used as an indicator for advanced T4 stage (p=0.0307). These data suggested a strong link between CD71 and ESCC. Subsequent in vitro assays using short interfering RNA (siRNA) to suppress CD71 expression confirmed the tumorigenic properties of CD71 in ESCC; cell growth inhibition and cell cycle arrest at S phase were observed in CD71-suppressed cells. The underlying mechanism involved activation of the MEK/ERK pathway. In summary, the present study provides evidence showing the tumorigenic properties of CD71 in ESCC with clinical correlations and suggests targeting CD71 as a strategy for the treatment of ESCC.

Regulation of blood-testis barrier (BTB) dynamics during spermatogenesis via the "Yin" and "Yang" effects of mammalian target of rapamycin complex 1 (mTORC1) and mTORC2

In mammalian testes, haploid spermatozoa are formed from diploid spermatogonia during spermatogenesis, which is a complicated cellular process. While these cellular events were reported in the 1960s and 1970s, the underlying molecular mechanism(s) that regulates these events remained unexplored until the past ∼10 years. For instance, adhesion proteins were shown to be integrated components at the Sertoli cell-cell interface and/or the Sertoli-spermatid interface in the late 1980s. But only until recently, studies have demonstrated that some of the adhesion proteins serve as the platform for signal transduction that regulates cell adhesion. In this chapter, a brief summary and critical discussion are provided on the latest findings regarding these cell-adhesion proteins in the testis and their relationship to spermatogenesis. Moreover, antagonistic effects of two mammalian target of rapamycin (mTOR) complexes, known as mTORC1 and mTORC2, on cell-adhesion function in the testis are discussed. Finally, a hypothetic model is presented to depict how these two mTOR-signaling complexes having the "yin" and "yang" antagonistic effects on the Sertoli cell tight junction (TJ)-permeability barrier can maintain the blood-testis barrier (BTB) integrity during the epithelial cycle while preleptotene spermatocytes are crossing the BTB.

Anti-cadherin-17 antibody modulates beta-catenin signaling and tumorigenicity of hepatocellular carcinoma

Cadherin-17 (CDH17) is an oncofetal molecule associated with poor prognostic outcomes of hepatocellular carcinoma (HCC), for which the treatment options are very limited. The present study investigates the therapeutic potential of a monoclonal antibody (Lic5) that targets the CDH17 antigen in HCC. In vitro experiments showed Lic5 could markedly reduce CDH17 expression in a dose-dependent manner, suppress β-catenin signaling, and induce cleavages of apoptotic enzymes caspase-8 and -9 in HCC cells. Treatment of animals in subcutaneous HCC xenograft model similarly demonstrated significant tumor growth inhibition (TGI) using Lic5 antibody alone (5 mg/kg, i.p., t.i.w.; ca.60–65% TGI vs. vehicle at day 28), or in combination with conventional chemotherapy regimen (cisplatin 1 mg/kg; ca. 85–90% TGI). Strikingly, lung metastasis was markedly suppressed by Lic5 treatments. Immunohistochemical and western blot analyses of xenograft explants revealed inactivation of the Wnt pathway and suppression of Wnt signaling components in HCC tissues. Collectively, anti-CDH17 antibody promises as an effective biologic agent for treating malignant HCC.

iTRAQ-based quantitative proteomics reveals myoferlin as a novel prognostic predictor in pancreatic adenocarcinoma

Histological differentiation is a major pathological parameter associated with poor prognosis in patients with pancreatic adenocarcinoma (PAC) and the molecular signature underlying PAC differentiation may involve key proteins potentially affecting the malignant characters of PAC. We aimed to identify the proteins which could be implicated in PAC prognosis. We used isobaric tags for relative and absolute quantitation (iTRAQ) coupled with two-dimensional liquid chromatography-tandem mass spectrometry to compare protein expression in PAC tissues with different degrees of histological differentiation. A total of 1623 proteins were repeatedly identified by performing the iTRAQ-based experiments twice. Of these, 15 proteins were differentially expressed according to our defined criteria. Myoferlin (MYOF) was selected to validate the proteomic results by western blotting. Immunohistochemistry in a further 154 PAC cases revealed that myoferlin significantly correlated with the degree of histological differentiation (P=0.004), and univariate and multivariate analyses indicated that MYOF is an independent prognostic factor for survival (hazard ratio, 1.540; 95% confidence interval, 1.061-2.234; P=0.023) of patients with PAC after curative surgery. RNA interference-mediated knockdown of MYOF alleviated malignant phenotypes of both primary and metastatic PAC cell lines in vitro and in vivo. Thus, ITRAQ-based quantitative proteomics revealed the prognostic value of MYOF in PAC.

BIOLOGICAL SIGNIFICANCE

Our results provide the possibility of novel strategies for pancreatic adenocarcinoma management.

Connexin 43 a check-point component of cell proliferation implicated in a wide range of human testis diseases

Gap junction channels link cytoplasms of adjacent cells. Connexins, their constitutive proteins, are essential in cell homeostasis and are implicated in numerous physiological processes. Spermatogenesis is a sophisticated model of germ cell proliferation, differentiation, survival, and apoptosis, in which a connexin isotype, connexin 43, plays a crucial role as evidenced by genomic approaches based on gene deletion. The balance between cell proliferation/differentiation/apoptosis is a prerequisite for maintaining levels of spermatozoa essential for fertility and for limiting anarchic cell proliferation, a major risk of testis tumor. The present review highlights the emerging role of connexins in testis pathogenesis, focusing specifically on two intimately interconnected human testicular diseases (azoospermia with impaired spermatogenesis and testicular germ cell tumors), whose incidence increased during the last decades. This work proposes connexin 43 as a potential cancer diagnostic and prognostic marker, as well as a promising therapeutic target for testicular diseases.

Loss of occludin expression and impairment of blood-testis barrier permeability in rats with autoimmune orchitis: effect of interleukin 6 on Sertoli cell tight junctions

Inflammation of the male reproductive tract is accepted as being an important etiological factor of infertility. Experimental autoimmune orchitis (EAO) is characterized by interstitial lymphomononuclear cell infiltration and severe damage of seminiferous tubules with germ cells that undergo apoptosis and sloughing. Because the blood-testis barrier (BTB) is relevant for the protection of haploid germ cells against immune attack, the aim of this study was to analyze BTB permeability and the expression of tight junction proteins (occludin, claudin 11, and tight junction protein 1 [TJP1]) in rats during development of autoimmune orchitis. The role of IL6 as modulator of tight junction dynamics was also evaluated because intratesticular content of this cytokine is increased in EAO rats. Orchitis was induced in Sprague-Dawley adult rats by active immunization with testicular homogenate and adjuvants. Control rats (C) were injected with saline solution and adjuvants. Untreated (N) rats were also studied. Concomitant with early signs of germ cell sloughing, a reduced expression of occludin and delocalization of claudin 11 and TJP1 were detected in the testes of rats with EAO compared to C and N groups. The use of tracers showed increased BTB permeability in EAO rats. Intratesticular injection of IL6 induced focal testicular inflammation, which is associated with damaged seminiferous tubules. Rat Sertoli cells cultured in the presence of IL6 exhibited a redistribution of tight junction proteins and reduced transepithelial electrical resistance. These data indicate the possibility that IL6 might be involved in the downregulation of occludin expression and in the modulation of BTB permeability that occur in rats undergoing autoimmune orchitis.

Cytoplasmic Forkhead box M1 (FoxM1) in esophageal squamous cell carcinoma significantly correlates with pathological disease stage

Abstract

Esophageal cancer is a deadly cancer with esophageal squamous cell carcinoma (ESCC) as the major type. Until now there has been a lack of reliable prognostic markers for this malignancy. This study aims to investigate the clinical correlation between Forkhead box M1 (FoxM1) and patients’ parameters in ESCC.

Methods

Immunohistochemistry was performed to investigate the expression and localization of FoxM1 in 64 ESCC tissues and 10 nontumor esophageal tissues randomly selected from 64 patients before these data were used for clinical correlations.

Results

Cytoplasmic and nuclear expressions of FoxM1 were found in 63 and 16 of the 64 ESCC tissues, respectively. Low cytoplasmic expression of FoxM1 was correlated with early pathological stage in ESCC (P = 0.018), while patients with nuclear FoxM1 were younger in age than those without nuclear expression (P < 0.001). Upregulation of FoxM1 mRNA was found in five ESCC cell lines (HKESC-1, HKESC-2, HKESC-3, HKESC-4, and SLMT-1) when compared to non-neoplastic esophageal squamous cell line NE-1 using quantitative polymerase chain reaction (qPCR). Except for HKESC-3, all studied ESCC cell lines demonstrated a high expression of FoxM1 protein using immunoblot. A high mRNA level of FoxM1 was observed in all of the ESCC tissues examined when compared to their adjacent nontumor tissues using qPCR.

Conclusion

Cytoplasmic FoxM1 was correlated with pathological stage and might be a biomarker for advanced ESCC.

Biological role of connexin intercellular channels and hemichannels

Gap junctions (GJ) and hemichannels (HC) formed from the protein subunits called connexins are transmembrane conduits for the exchange of small molecules and ions. Connexins and another group of HC-forming proteins, pannexins comprise the two families of transmembrane proteins ubiquitously distributed in vertebrates. Most cell types express more than one connexin or pannexin. While connexin expression and channel activity may vary as a function of physiological and pathological states of the cell and tissue, only a few studies suggest the involvement of pannexin HC in acquired pathological conditions. Importantly, genetic mutations in connexin appear to interfere with GJ and HC function which results in several diseases. Thus connexins could serve as potential drug target for therapeutic intervention. Growing evidence suggests that diseases resulting from HC dysfunction might open a new direction for development of specific HC reagents. This review provides a comprehensive overview of the current studies of GJ and HC formed by connexins and pannexins in various tissue and organ systems including heart, central nervous system, kidney, mammary glands, ovary, testis, lens, retina, inner ear, bone, cartilage, lung and liver. In addition, present knowledge of the role of GJ and HC in cell cycle progression, carcinogenesis and stem cell development is also discussed.

Sertoli-cell-specific knockout of connexin 43 leads to multiple alterations in testicular gene expression in prepubertal mice

A significant decline in human male reproductive function has been reported for the past 20 years but the molecular mechanisms remain poorly understood. However, recent studies showed that the gap junction protein connexin-43 (CX43; also known as GJA1) might be involved. CX43 is the predominant testicular connexin (CX) in most species, including in humans. Alterations of its expression are associated with different forms of spermatogenic disorders and infertility. Men with impaired spermatogenesis often exhibit a reduction or loss of CX43 expression in germ cells (GCs) and Sertoli cells (SCs). Adult male transgenic mice with a conditional knockout (KO) of the Gja1 gene [referred to here as connexin-43 (Cx43)] in SCs (SCCx43KO) show a comparable testicular phenotype to humans and are infertile. To detect possible signaling pathways and molecular mechanisms leading to the testicular phenotype in adult SCCx43KO mice and to their failure to initiate spermatogenesis, the testicular gene expression of 8-day-old SCCx43KO and wild-type (WT) mice was compared. Microarray analysis revealed that 658 genes were significantly regulated in testes of SCCx43KO mice. Of these genes, 135 were upregulated, whereas 523 genes were downregulated. For selected genes the results of the microarray analysis were confirmed using quantitative real-time PCR and immunostaining. The majority of the downregulated genes are GC-specific and are essential for mitotic and meiotic progression of spermatogenesis, including Stra8, Dazl and members of the DM (dsx and map-3) gene family. Other altered genes can be associated with transcription, metabolism, cell migration and cytoskeleton organization. Our data show that deletion of Cx43 in SCs leads to multiple alterations of gene expression in prepubertal mice and primarily affects GCs. The candidate genes could represent helpful markers for investigators exploring human testicular biopsies from patients showing corresponding spermatogenic deficiencies and for studying the molecular mechanisms of human male sterility.

Clinical correlation of nuclear survivin in esophageal squamous cell carcinoma

To examine the correlation of survivin (both total and nuclear survivin) with clinicopathological parameters of esophageal squamous cell carcinoma (ESCC) patients. Tumors and non-tumor tissues near the proximal resection margins were resected from ESCC patients undergone esophagectomy. Quantitative polymerase chain reaction (qPCR) was performed to detect survivin mRNA expression level in the 10 paired tumor and adjacent non-tumor tissues. To confirm with the clinical situation, survivin mRNA and protein expression were measured by qPCR and immunoblot, respectively, in 5 ESCC cell lines and a non-neoplastic esophageal epithelial cell line. Immunohistochemistry was employed to reveal the cellular localization of survivin in tumor tissues isolated from the 64 ESCC patients undergone surgery alone. Up-regulation of survivin mRNA and protein was found in 5 ESCC lines (HKESC-1, HKESC-2, HKESC-3, HKESC-4, and SLMT-1) when compared to a non-neoplastic esophageal epithelial cell line NE-1. In particular, HKESC-3, HKESC-4, and SLMT-1 cells demonstrated ~50-fold increase in survivin mRNA. High level of survivin mRNA in tumor tissues when compared to non-tumor tissues was found in 70 % (7 of 10) of clinical cases. The increase in expression ranged from ~twofold to ~16-fold. Immunohistochemistry results showed that survivin was found at the cell nuclei in all specimens examined. Nuclear expression of survivin was inversely associated with the likelihood of developing nodal metastasis (p = 0.021) and significantly associated with early-stage ESCC (p = 0.039). Nuclear survivin could serve as a marker for indicating disease status in ESCC patients.

Testicular connexin 43, a precocious molecular target for the effect of environmental toxicants on male fertility

Many recent epidemiological, clinical and experimental findings support the hypothesis that environmental toxicants are responsible for the increasing male reproductive disorders (congenital malformations, declining sperm counts and testicular cancer) over the past 20 years. It has also been reported that exposure to these toxicants, during critical periods of development (fetal and neonatal), represents a more considerable risk for animals and humans than exposure during adulthood. However, the molecular targets for these chemicals have not been clearly identified. Recent studies showed that a family of transmembranous proteins, named connexins, regulates numerous physiological processes involved in testicular development and function, such as Sertoli and germ cell proliferation, differentiation, germ cell migration and apoptosis. In the testis, knockout strategy revealed that connexin 43, the predominant connexin in this organ, is essential for spermatogenesis. In addition, there is evidence that many environmental toxicants could alter testicular connexin 43 by dysregulation of numerous mechanisms controlling its function. In the present work, we propose first to give an overview of connexin expression and intercellular gap junction coupling in the developing fetal and neonatal testes. Second, we underline the impact of maternally chemical exposure on connexin 43 expression in the perinatal developing testis. Lastly, we attempt to link this precocious effect to male offspring fertility.

Impaired expression and distribution of adherens and gap junction proteins in the seminiferous tubules of rats undergoing autoimmune orchitis

Experimental autoimmune orchitis (EAO) is characterized by an interstitial lymphomononuclear cell infiltration and a severe lesion of seminiferous tubules (ST) with germ cells that undergo apoptosis and sloughing. The aim of this study was to analyse the expression and localization of adherens junction (AJ) proteins: N-cadherin, α-, β- and p120 catenins and gap junction protein, connexin 43 (Cx43), to explore some aspects of germ-cell sloughing during the development of orchitis. EAO was induced in Sprague-Dawley adult rats by active immunization with testicular homogenate and adjuvants. Control rats (C) were injected with saline solution and adjuvants. Concomitant with early signs of germ-cell sloughing, we observed by immunofluorescence and Western blot, a delocalization and a significant increase in N-cadherin and α-catenin expression in the ST of EAO compared with C rats. In spite of this increased AJ protein expression, a severe germ-cell sloughing occurred. This is probably due to the impairment of the AJ complex function, as shown by the loss of N-cadherin/β-catenin colocalization (confocal microscopy) and increased pY654 β-catenin expression, suggesting lower affinity of these two proteins and increased pERK1/2 expression in the testis of EAO rats. The significant decrease in Cx43 expression detected in EAO rats suggests a gap junction function impairment also contributing to germ-cell sloughing.

Nitric oxide and cyclic nucleotides: their roles in junction dynamics and spermatogenesis

Spermatogenesis is a highly complicated process in which functional spermatozoa (haploid, 1n) are generated from primitive mitotic spermatogonia (diploid, 2n). This process involves the differentiation and transformation of several types of germ cells as spermatocytes and spermatids undergo meiosis and differentiation. Due to its sophistication and complexity, testis possesses intrinsic mechanisms to modulate and regulate different stages of germ cell development under the intimate and indirect cooperation with Sertoli and Leydig cells, respectively. Furthermore, developing germ cells must translocate from the basal to the apical (adluminal) compartment of the seminiferous epithelium. Thus, extensive junction restructuring must occur to assist germ cell movement. Within the seminiferous tubules, three principal types of junctions are found namely anchoring junctions, tight junctions, and gap junctions. Other less studied junctions are desmosome-like junctions and hemidesmosome junctions. With these varieties of junction types, testes are using different regulators to monitor junction turnover. Among the uncountable junction modulators, nitric oxide (NO) is a prominent candidate due to its versatility and extensive downstream network. NO is synthesized by nitric oxide synthase (NOS). Three traditional NOS, specified as endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS), and one testis-specific nNOS (TnNOS) are found in the testis. For these, eNOS and iNOS were recently shown to have putative junction regulation properties. More important, these two NOSs likely rely on the downstream soluble guanylyl cyclase/cGMP/protein kinase G signaling pathway to regulate the structural components at the tight junctions and adherens junctions in the testes. Apart from the involvement in junction regulation, NOS/NO also participates in controlling the levels of cytokines and hormones in the testes. On the other hand, NO is playing a unique role in modulating germ cell viability and development, and indirectly acting on some aspects of male infertility and testicular pathological conditions. Thus, NOS/NO bears an irreplaceable role in maintaining the homeostasis of the microenvironment in the seminiferous epithelium via its different downstream signaling pathways.

Physiological and physiopathological aspects of connexins and communicating gap junctions in spermatogenesis

Spermatogenesis is a highly regulated process of germ cell proliferation and differentiation, starting from spermatogonia to spermatocytes and giving rise to spermatids, the future spermatozoa. In addition to endocrine regulation, testicular cell-cell interactions are essential for spermatogenesis. This precise control is mediated through paracrine/autocrine pathways, direct intercellular contacts and through intercellular communication channels, consisting of gap junctions and their constitutive proteins, the connexins. Gap junctions are localized between adjacent Leydig cells, between Sertoli cells and between Sertoli cells and specific germ cells. This review focuses on the distribution of connexins within the seminiferous epithelium, their participation in gap junction channel formation, the control of their expression and the physiological relevance of these junctions in both the Sertoli-Sertoli cell functional synchronization and the Sertoli-germ cell dialogue. In this review, we also discuss the potential implication of disrupted connexin in testis cancer, since impaired expression of connexin has been described as a typical feature of tumoral proliferation.

Major involvement of connexin 43 in seminiferous epithelial junction dynamics and male fertility

In different epithelia, cell membranes contacting one another form intercellular junctional complexes including tight, adherens and gap junctions, which could mutually influence the expression of each other. We have here investigated the role of Cx43 in the control of adherens and tight junction proteins (N-cadherin, beta-catenin, occludin and ZO-1) by using conditional Sertoli cell knockout Cx43 (SCCx43KO(-/-)) transgenic mice and specific anti-Cx43 siRNA. Gap junction coupling and Cx43 levels were reduced in SCCx43KO(-/-) as compared to Wild-type testes. Ultrastructural analysis revealed disappearance of gap junctions, the presence of tight and adherens junctions and persistent integrity of the blood-testis barrier in SCCx43KO(-/-) testis. Occludin, N-cadherin and beta-catenin levels were enhanced in SCCx43KO(-/-) mice as compared to Wild-type animals whereas ZO-1 levels were reduced. Cx43 siRNA blocked gap junction functionality in Sertoli cells and altered tight and adherens protein levels. The Cx43 control of tight and adherens junctions appeared channel-dependent since gap junction blockers (glycyrrhetinic acid and oleamide) led to similar results. These data suggest that the control of spermatogenesis by Cx43 may be mediated through Sertoli cell Cx43 channels, which are required, not only in cell/cell communication between Sertoli and germ cells, but also in the regulation of other junctional proteins essential for the blood-testis barrier.

Prophylactic uses of integrin CD18-βA peptide in a murine polymicrobial peritonitis model

AIM: To evaluate the prophylactic properties of integrin CD18-βA peptide in a murine model of abdominal polymicrobial peritonitis and sepsis.

METHODS: Bacterial sepsis was induced in Institute of Cancer Research (ICR) mice by cecal ligation and puncture (CLP) surgery. Inflicted mice were then injected with either sterile saline or CD18-βA peptide intraperitoneally at 2 h after surgery, and were sacrificed at 12 and 24 h after surgery. Blood samples were immediately collected, and analyzed for endotoxin activity and tumor necrosis factor (TNF)-α and interleukin (IL)-6. Lungs and liver were studied for CD45+ leukocyte and CD3 mRNA content. Pulmonary expression of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM) and E-selectin was also determined.

RESULTS: Intraperitoneal injection of CD18-βA peptide significantly suppressed circulating endotoxin activity (P < 0.01) at 24 h, as well as serum levels of TNF-α (P < 0.05 at 12 and 24 h) and IL-6 (P < 0.01 at 12 h, P < 0.05 at 24 h) in CLP-inflicted mice. CD18-βA peptide also abrogated leukocyte infiltration into liver and lungs as unveiled by reduced CD45+ leukocyte and CD3 mRNA contents. Furthermore, the peptide significantly reduced pulmonary expression of VCAM (P < 0.01 at 12 h, P < 0.001 at 24 h), E-selectin (P < 0.01 at 12 and 24 h), and ICAM-1 (P < 0.01 at 12 h, P < 0.001 at 24 h). These actions of CD18-βA peptide collectively protected septic mice against lethality (P < 0.01).

CONCLUSION: CD18-βA peptide is a potent endotoxin antagonist that can protect surgical patients against sepsis-associated lethality.

Spermatocyte apoptosis, which involves both intrinsic and extrinsic pathways, explains the sterility of Graomys griseoflavus x Graomys centralis male hybrids

Spermatogenic impairment and the apoptotic pathways involved in establishing sterility of male hybrids obtained from crossing Graomys griseoflavus females with Graomys centralis males were studied. Testes from G. centralis, G. griseoflavus and hybrids were compared at different ages. Terminal transferase-mediated dUTP nick-end labelling assay (TUNEL), Fas, Bax and cytochrome c labelling were used for apoptosis evaluation, and calbindin D(28k) staining as an anti-apoptotic molecule. In 1-month-old animals, spermatocytes were positive for all apoptotic markers, but moderate TUNEL (+) spermatocyte frequency was only found in G. centralis. At subsequent ages, the apoptotic markers were downregulated in testes from parental cytotypes, but not in hybrid testes. TUNEL (+) spermatocytes were present at 78% and 44% per tubule cross-section in 2- and 3-month-old hybrid animals, respectively. Pachytene spermatocyte death in adult hybrids occurs via apoptosis, as revealed by high caspase-3 expression. Calbindin was highly expressed in spermatocytes of adult hybrids, in which massive cell death occurs via apoptosis. Calbindin co-localisation with TUNEL or Fas, Bax and cytochrome c was very limited, suggesting an inverse regulation of calbindin and apoptotic markers. Hybrid sterility is due to breakdown of spermatogenesis at the pachytene spermatocyte stage. Both extrinsic and intrinsic pathways are involved in apoptosis of spermatocytes, which are the most sensitive cell type to apoptotic stimuli.

Hepatic tight junctions: From viral entry to cancer metastasis

The tight junction (TJ) is a critical cellular component for maintenance of tissue integrity, cellular interactions and cell-cell communications, and physiologically functions as the “great wall” against external agents and the surrounding hostile environment. During the host-pathogen evolution, viruses somehow found the key to unlock the gate for their entry into cells and to exploit and exhaust the host cells. In the liver, an array of TJ molecules is localized along the bile canaliculi forming the blood-biliary barrier, where they play pivotal roles in paracellular permeability, bile secretion, and cell polarity. In pathology, certain hepatic TJ molecules mediate virus entry causing hepatitis infection; deregulation and functional abnormality of the TJ have also been implicated in triggering liver cancer development and metastasis. All these findings shed new insights on the understanding of hepatic TJs in the development of liver disease and provide new clues for potential intervention.

Targeting cadherin-17 inactivates Wnt signaling and inhibits tumor growth in liver carcinoma

Hepatocellular carcinoma (HCC) is a lethal malignancy for which there are no effective therapies. To develop rational therapeutic approaches for treating this disease, we are performing proof-of-principle studies targeting molecules crucial for the development of HCC. Here, we show that cadherin-17 (CDH17) adhesion molecule is up-regulated in human liver cancers and can transform premalignant liver progenitor cells to produce liver carcinomas in mice. RNA interference-mediated knockdown of CDH17 inhibited proliferation of both primary and highly metastatic HCC cell lines in vitro and in vivo. The antitumor mechanisms underlying CDH17 inhibition involve inactivation of Wnt signaling, because growth inhibition and cell death were accompanied by relocalization of beta-catenin to the cytoplasm and a concomitant reduction in cyclin D1 and an increase in retinoblastoma.

CONCLUSION

Our results identify CDH17 as a novel oncogene in HCC and suggest that CDH17 is a biomarker and attractive therapeutic target for this aggressive malignancy.

Testicular cell junction: a novel target for male contraception

Even though various contraceptive methods are widely available, the number of unwanted pregnancies is still on the rise in developing countries, pressurizing the already resource limited nations. One of the major underlying reasons is the lack of effective, low cost, and safe contraceptives for couples. During the past decade, some studies were performed using animal models to decipher if the Sertoli-germ cell junction in the testis is a target for male fertility regulation. Some of these study models were based on the use of hormones and/or chemicals to disrupt the hypothalamic-pituitary-testicular axis (e.g., androgen-based implants or pills) and others utilized a panel of chemical entities or synthetic peptides to perturb spermatogenesis either reversibly or non-reversibly. Among them, adjudin, a potential male contraceptive, is one of the compounds exerting its action on the unique adherens junctions, known as ectoplasmic specializations, in the testis. Since the testis is equipped with inter-connected cell junctions, an initial targeting of one junction type may affect the others and these accumulative effects could lead to spermatogenic arrest. This review attempts to cover an innovative theme on how male infertility can be achieved by inducing junction instability and defects in the testis, opening a new window of research for male contraceptive development. While it will still take much time and effort of intensive investigation before a product can reach the consumable market, these findings have provided hope for better family planning involving men.

Proteomic expression signature distinguishes cancerous and nonmalignant tissues in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an aggressive liver cancer but clinically validated biomarkers that can predict natural history of malignant progression are lacking. The present study explored the proteome-wide patterns of HCC to identify biomarker signature that could distinguish cancerous and nonmalignant liver tissues. A retrospective cohort of 80 HBV-associated HCC was included and both the tumor and adjacent nontumor tissues were subjected to proteome-wide expression profiling by 2-DE method. The subjects were randomly divided into the training (n = 55) and validation (n = 25) subsets, and the data analyzed by classification-and-regression tree algorithm. Protein markers were characterized by MALDI-ToF/MS and confirmed by immunohistochemistry, Western blotting and qPCR assays. Proteomic expression signature composed of six biomarkers (haptoglobin, cytochrome b5, progesterone receptor membrane component 1, heat shock 27 kDa protein 1, lysosomal proteinase cathepsin B, keratin I) was developed as a classifier model for predicting HCC. We further evaluated the model using both leave-one-out procedure and independent validation, and the overall sensitivity and specificity for HCC both are 92.5%, respectively. Clinical correlation analysis revealed that these biomarkers were significantly associated with serum AFP, total protein levels and the Ishak's score. The described model using biomarker signatures could accurately distinguish HCC from nonmalignant tissues, which may also provide hints on how normal hepatocytes are transformed to malignant state during tumor progression.

Connexin 33 impairs gap junction functionality by accelerating connexin 43 gap junction plaque endocytosis

Connexin 33 (Cx33) is a testis-specific gap junction protein. We previously reported that Cx33 exerts dominant-negative effect on gap junction intercellular communication by sequestering Cx43 within early endosomes in Sertoli cells. However, the molecular mechanisms that drive this process are unknown. The present study analyzed: (i) the trafficking of Cx33 and Cx43 in wild-type Sertoli cells transfected with Cx33-DsRed2 and Cx43-green fluorescent protein vectors; (ii) the formation of heteromeric Cx33/Cx43 hemi-channels and their incorporation into gap junction plaques. Fluorescence lifetime imaging microscopy-fluorescence resonance energy transfer and videomicroscopy studies demonstrated that Cx33 and Cx43 associated to form heteromeric oligomers that trafficked along microtubules to the plasma membrane. However, the plaques containing Cx33 were not functional. Immunoprecipitation experiments revealed that zonula occludens-1 (ZO-1), a scaffold protein proposed to secure Cx in gap junction plaques at the cell-cell boundary, associated with Cx33 in testis extracts. In cells expressing Cx33, Cx33 and ZO-1 specifically interacted with P(1) phosphorylated and P(0) unphosphorylated isoforms of Cx43, and the ZO-1 membranous signal level was reduced. It is suggested that alteration of Cx43/ZO-1 association by Cx33 could be one mechanism by which Cx33 exerts its dominant-negative effect on gap junction plaque.

Connexin-related signaling in cell death: to live or let die?

Evidence is accumulating that some forms of cell death, like apoptosis, are not only governed by the complex interplay between extracellular and intracellular signals but are also strongly influenced by intercellular communicative networks. The latter is provided by arrays of channels consisting of connexin proteins, with gap junctions directly connecting the cytoplasm of neighboring cells and hemichannels positioned as pores that link the cytoplasm to the extracellular environment. The role of gap junctions in cell death communication has received considerable interest and recently hemichannels have joined in as potentially toxic pores adding their part to the cell death process. However, despite a large body of existing evidence, especially for gap junctions, the exact contribution of the connexin channel family still remains controversial, as both gap junctions and hemichannels may furnish cell death as well as cell survival signals. An additional layer of complexity is formed by the fact that connexin proteins as such, beyond their channel function, may influence the cell death process. We here review the current knowledge on connexins and their channels in cell death and specifically address the molecular mechanisms that underlie connexin-related signaling. We also briefly focus on pannexins, a novel set of connexin-like proteins that have been implicated in cellular responses to pathological insults.

Nitric oxide and cyclic nucleotides: their roles in junction dynamics and spermatogenesis

Spermatogenesis is a highly complicated process in which functional spermatozoa (haploid, 1n) are generated from primitive mitotic spermatogonia (diploid, 2n). This process involves the differentiation and transformation of several types of germ cells as spermatocytes and spermatids undergo meiosis and differentiation. Due to its sophistication and complexity, testis possesses intrinsic mechanisms to modulate and regulate different stages of germ cell development under the intimate and indirect cooperation with Sertoli and Leydig cells, respectively. Furthermore, developing germ cells must translocate from the basal to the apical (adluminal) compartment of the seminiferous epithelium. Thus, extensive junction restructuring must occur to assist germ cell movement. Within the seminiferous tubules, three principal types of junctions are found namely anchoring junctions, tight junctions, and gap junctions. Other less studied junctions are desmosome-like junctions and hemidesmosome junctions. With these varieties of junction types, testes are using different regulators to monitor junction turnover. Among the uncountable junction modulators, nitric oxide (NO) is a prominent candidate due to its versatility and extensive downstream network. NO is synthesized by nitric oxide synthase (NOS). Three traditional NOS, specified as endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS), and one testis-specific nNOS (TnNOS) are found in the testis. For these, eNOS and iNOS were recently shown to have putative junction regulation properties. More important, these two NOSs likely rely on the downstream soluble guanylyl cyclase/cGMP/protein kinase G signaling pathway to regulate the structural components at the tight junctions and adherens junctions in the testes. Apart from the involvement in junction regulation, NOS/NO also participates in controlling the levels of cytokines and hormones in the testes. On the other hand, NO is playing a unique role in modulating germ cell viability and development, and indirectly acting on some aspects of male infertility and testicular pathological conditions. Thus, NOS/NO bears an irreplaceable role in maintaining the homeostasis of the microenvironment in the seminiferous epithelium via its different downstream signaling pathways.