Epidermal growth factor regulates connexin 43 in the human epididymis: role of gap junctions in azoospermia

The multifaceted role of extracellular ATP in sperm function: From spermatogenesis to fertilization

Extracellular adenosine 5'-triphosphate (ATP) is a vital signaling molecule involved in various physiological processes within the body. In recent years, studies have revealed its significant role in male reproduction, particularly in sperm function. This review explores the multifaceted role of extracellular ATP in sperm function, from spermatogenesis to fertilization. We discuss the impact of extracellular ATP on spermatogenesis, sperm maturation and sperm-egg fusion, highlighting the complex regulatory mechanisms and potential clinical applications in the context of male infertility. By examining the latest research, we emphasize the crucial role of extracellular ATP in sperm function and propose future research directions to further.

Connexin43 is associated with the progression of clear cell renal carcinoma and is regulated by tangeretin to sygergize with tyrosine kinase inhibitors

BACKGROUND

The roles of Connexin43 (Cx43) in clear cell renal cell carcinoma (ccRCC) microenviroment remains to be poorly defined.

METHODS

The expression profile, prognosis and immune analysis of Cx43 in various cancers, particularly in ccRCC were performed using TCGA database, and various biological function assays were applied to explore the physiological role of Cx43 and tangeretin in ccRCC. Western blot were applied to examine the protein expression and Kunming mice were used to evaluate preliminary safety or anti-tumor activity of tangeretin and sunitinib.

RESULTS

Compared with the normal group, higher expression levels of Cx43 in ccRCC, and distinct associations between Cx43 expression and ccRCC prognosis or immune infiltration, were found. Notably, the expression of Cx43 was found to be highly correlated with that of receptor tyrosine kinases (RTKs), particularly with VEGFR1, VEGFR2 and VEGFR3. The expression of Cx43 and EGFR was also found to be higher in ccRCC than that in the para-cancerous specimens. Knocking down Cx43 expression decreased RCC cell viability, cell migration, p-EGFR, MMP-9 and survivin expression. Using 14 Chinese medicine monomers, tangeretin was screened and found to inhibit tumor cell viability and Cx43 expression. Tangeretin also enhanced the sensitivity of RCC cells to tyrosine kinase inhibitors (TKIs) sunitinib and sorafenib. However, the same concentration of tangeretin exerted a less prominent effect on normal renal cell viability.

CONCLUSIONS

Cx43 is strongly associated with RTK expression and ccRCC progression, while tangeretin can inhibit RCC cell malignancy by inhibiting Cx43 expression and enhance the sensitivity of RCC cells to TKIs.

Venlafaxine increases aromatization, reduces apical V-ATPase in clear cells and induces increased number of mast cells and smooth muscle cells death in rat cauda epididymis

Depressive disorders (DD) have affected millions of people worldwide. Venlafaxine, antidepressant of the class of serotonin and norepinephrine reuptake inhibitors, has been prescribed for the treatment of DD. In rat testes, venlafaxine induces testosterone (T) aromatization and increases estrogen levels. Aromatase is a key enzyme for the formation of estrogen in the epididymis, an essential organ for male fertility. We investigated the impact of serotonergic/noradrenergic venlafaxine effect on the epididymal cauda region, focusing on aromatase, V-ATPase and EGF epithelial immunoexpression, smooth muscle (SM) integrity and mast cells number (MCN). Male rats were distributed into control (CG; n = 10) and venlafaxine (VFG, n = 10) groups. VFG received 30 mg/kg b.w. of venlafaxine for 35 days. The epididymal cauda was processed for light and transmission electron microscopy (TEM). The expression of connexin 43 (Cx43) and estrogen alpha (Esr1), adrenergic (Adra1a) and serotonergic (Htr1b) receptors were analyzed. Clear cells (CCs) area, SM thickness, viable spermatozoa (VS) and MCN were evaluated. Apoptosis was confirmed by TUNEL and TEM. The following immunoreactions were performed: T, aromatase, T/aromatase co-localization, V-ATPase, EGF, Cx43 and PCNA. The increased Adra1a and reduced Htr1b expressions confirmed the noradrenergic and serotonergic venlafaxine effects, respectively, corroborating the increased MCN, apoptosis and atrophy of SM. In VFG, the epithelial EGF increased, explaining Cx43 overexpression and basal cells mitotic activity. T aromatization and Esr1 downregulation indicate high estrogen levels, explaining CCs hypertrophy and changes in the V-ATPase localization, corroborating VS reduction. Thus, in addition to serotonergic/noradrenergic effects, T/estrogen imbalance, induced by venlafaxine, impairs epididymal structure and function.

Mechanisms of SARS-CoV-2 and Male Infertility: Could Connexin and Pannexin Play a Role?

The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on male infertility has lately received significant attention. SARS-CoV-2, the virus that causes coronavirus disease (COVID-19) in humans, has been shown to impose adverse effects on both the structural components and function of the testis, which potentially impact spermatogenesis. These adverse effects are partially explained by fever, systemic inflammation, oxidative stress, and an increased immune response leading to impaired blood-testis barrier. It has been well established that efficient cellular communication via gap junctions or functional channels is required for tissue homeostasis. Connexins and pannexins are two protein families that mediate autocrine and paracrine signaling between the cells and the extracellular environment. These channel-forming proteins have been shown to play a role in coordinating cellular communication in the testis and epididymis. Despite their role in maintaining a proper male reproductive milieu, their function is disrupted under pathological conditions. The involvement of these channels has been well documented in several physiological and pathological conditions and their designated function in infectious diseases. However, their role in COVID-19 and their meaningful contribution to male infertility remains to be elucidated. Therefore, this review highlights the multivariate pathophysiological mechanisms of SARS-CoV-2 involvement in male reproduction. It also aims to shed light on the role of connexin and pannexin channels in disease progression, emphasizing their unexplored role and regulation of SARS-CoV-2 pathophysiology. Finally, we hypothesize the possible involvement of connexins and pannexins in SARS-CoV-2 inducing male infertility to assist future research ideas targeting therapeutic approaches.

The MAPK/ERK signaling pathway regulates the expression and localization of Cx43 in mouse proximal epididymis†

This study aimed to clarify the functional role of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK1/2)-signaling pathway in the expression and localization of connexin 43 (Cx43). Mice were treated with the mitogen-activated protein kinase kinase (MEK1/2) inhibitor, PD325901, which induced a progressive decrease in ERK1/2 phosphorylation (pERK) in the proximal epididymis of the mice, without affecting total ERK level. Cx43 staining with punctuated reactive sites was observed in the basolateral membranes in the initial segment (IS) of mouse epididymis. However, PD325901 induced a significant decrease in Cx43 labeling in the basolateral membranes. Interestingly, Cx43, which was undetectable in the apical region of epididymis under control conditions, showed a significant increase in the apical region after PD 325901 treatment. To confirm whether Cx43 was present in tight junctions (TJs) after PD 325901 treatment, PD325901-treated epididymis samples were double-labeled with Cx43 and zonula occludens (ZO)-1 (a TJ protein marker). Thereafter, confocal microscopy showed the colocalization of Cx43 and ZO-1 in the epididymis after PD325901 treatment. Collectively, our results indicated that PD325901 treatment induced a significant increase in Cx43 localization on TJs, where it was colocalized with ZO-1. Therefore, the study suggested that ERK phosphorylation is essential for the proper expression and localization of the gap junction (GJ) protein, and that the relationship between GJs and TJs could play an important role in establishing and maintaining microenvironmental homeostasis for sperm maturation in the IS of mouse epididymis.

Long noncoding RNAs regulated spermatogenesis in varicocele-induced spermatogenic dysfunction

Objectives

To evaluate the expression, potential functions and mechanisms of long noncoding RNAs (lncRNAs) in the pathogenesis of varicocele (VC)‐induced spermatogenic dysfunction.

Materials and Methods

We established a rat model with left experimental VC and divided rats into the sham group, the VC group, and the surgical treatment group (each group, n = 10). Haematoxylin and eosin (HE) staining and sperm quality were analysed to evaluate spermatogenesis function. LncRNA expression profiles were analysed using lncRNA‐Seq (each group n = 3) and validated using quantitative real‐time polymerase chain reaction (each group n = 10). Correlation analysis and gene target miRNA prediction were used to construct competing endogenous RNA network. The regulated signalling pathway and spermatogenic dysfunction of differentially expressed lncRNAs (DE lncRNAs) were validated by Western blot.

Results

HE detection and sperm quality analysis showed that VC could induce spermatogenic dysfunction. Eight lncRNAs were upregulated and three lncRNAs were downregulated in the VC group compared with the sham group and surgical treatment group. The lncRNA of NONRATG002949.2, NONRATG001060.2, NONRATG013271.2, NONRATG022879.2, NONRATG023424.2, NONRATG005667.2 and NONRATG010686.2 were significantly negatively related to sperm quality, while NONRATG027523.1, NONRATG017183.2 and NONRATG023747.2 were positively related to sperm quality. The lncRNAs promote spermatogenic cell apoptosis and inhibit spermatogonia and spermatocyte proliferation and meiotic spermatocytes by regulating the PI3K–Akt signalling pathway.

Conclusion

DE lncRNAs may be potential biomarkers for predicting the risk of spermatogenic dysfunction in VC and the effect of surgical repair. These DE lncRNAs promote spermatogenic dysfunction by regulating the PI3K–Akt signalling pathway.

Effects of prostaglandin E2 on gap junction protein alpha 1 in the rat epididymis

Gap junctions are responsible for intercellular communication. In the adult mammalian epididymis, gap junction protein alpha 1 (GJA1) is localized between basal and either principal or clear cells. GJA1 levels and localization change during the differentiation of basal cells. The present objective was to determine the role of basal cells and prostaglandin E2 (PGE2) on GJA1 in the rat epididymis. Prior to basal cell differentiation, GJA1 is colocalized with TJP1 at the apical lateral margins between adjacent epithelial cells. When basal cells are present, GJA1 becomes associated between basal and principal cells, where it is primarily immunolocalized until adulthood. Basal cells express TP63, differentiate from epithelial cells, and produce prostaglandin-endoperoxide synthase 1 by 21 days of age. Prior to day 21, GJA1and TP63 are not strongly associated at the apical region. However, by day 28, TP63-positive basal cells migrate to the base of the epithelium, and also express GJA1. To assess effects of PGE2 on GJA1, rat caput epididymal (RCE) cells were exposed to PGE2 (50 μM) for 3 h. PGE2 increased levels of Gja1 mRNA in RCE cells, while levels of Gjb1, Gjb2, Gjb4, and GjB5 were unaltered. Furthermore, PGE2 increased protein levels of GJA1, phospho-GJA1, phospho-AKT, CTNNB1, and phospho-CTNNB1. Total AKT and the tight junction protein claudin1 were also not altered by PGE2. Data suggest that development of the epididymal epithelium and differentiation of epididymal basal cells regulate the targeting of GJA1, and that this appears to be mediated by PGE2.

Rationale and Roadmap for Developing Panels of Hotspot Cancer Driver Gene Mutations as Biomarkers of Cancer Risk

Cancer driver mutations (CDMs) are necessary and causal for carcinogenesis and have advantages as reporters of carcinogenic risk. However, little progress has been made toward developing measurements of CDMs as biomarkers for use in cancer risk assessment. Impediments for using a CDM-based metric to inform cancer risk include the complexity and stochastic nature of carcinogenesis, technical difficulty in quantifying low-frequency CDMs, and lack of established relationships between cancer driver mutant fractions and tumor incidence. Through literature review and database analyses, this review identifies the most promising targets to investigate as biomarkers of cancer risk. Mutational hotspots were discerned within the 20 most mutated genes across the 10 deadliest cancers. Forty genes were identified that encompass 108 mutational hotspot codons overrepresented in the COSMIC database; 424 different mutations within these hotspot codons account for approximately 63,000 tumors and their prevalence across tumor types is described. The review summarizes literature on the prevalence of CDMs in normal tissues and suggests such mutations are direct and indirect substrates for chemical carcinogenesis, which occurs in a spatially stochastic manner. Evidence that hotspot CDMs (hCDMs) frequently occur as tumor subpopulations is presented, indicating COSMIC data may underestimate mutation prevalence. Analyses of online databases show that genes containing hCDMs are enriched in functions related to intercellular communication. In its totality, the review provides a roadmap for the development of tissue-specific, CDM-based biomarkers of carcinogenic potential, comprised of batteries of hCDMs and can be measured by error-correct next-generation sequencing. Environ. Mol. Mutagen. 61:152-175, 2020. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.

How does Helicobacter pylori cause gastric cancer through connexins: An opinion review

Helicobacter pylori (H. pylori) is a Gram-negative bacterium with a number of virulence factors, such as cytotoxin-associated gene A, vacuolating cytotoxin A, its pathogenicity island, and lipopolysaccharide, which cause gastrointestinal diseases. Connexins function in gap junctional homeostasis, and their downregulation is closely related to gastric carcinogenesis. Investigations into H. pylori infection and the fine-tuning of connexins in cells or tissues have been reported in previous studies. Therefore, in this review, the potential mechanisms of H. pylori-induced gastric cancer through connexins are summarized in detail.

GYY4137 a H2S donor, attenuates ipsilateral epididymis injury in experimentally varicocele-induced rats via activation of the PI3K/Akt pathway

OBJECTIVES

The current study was aimed to investigate the effect of morpholin-4-ium 4 methoxyphenyl (morpholino) phosphinodithioate (GYY4137) on ipsilateral epididymis injury in a rat model of experimental varicocele (VC).

MATERIALS AND METHODS

Sixty Wistar rats were randomly assigned to sham, sham plus GYY4137, VC and VC plus GYY4137 groups. Sperm quality parameters, including sperm count, motility and viability were evaluated after 4 weeks. Histological changes were measured by hematoxylin and eosin staining between the groups. The oxidative stress levels were estimated by determining epididymal superoxide dismutase (SOD) and malondialdehyde (MDA). The apoptosis status and the expression of phosphatidylinositol 3'-OH kinase (PI3K)/Akt were analyzed by immunohistochemical analysis, western blot and RT-qPCR.

RESULTS

VC resulted in the decrease of sperm parameters, significant histological damage and higher levels of oxidative stress and apoptosis. Compared to the VC group, GYY4137 markedly ameliorated these observed changes. In addition, treatment with GYY4137 obviously reduced the levels of caspase-3 and Bax and increased the levels of the phosphorylation of PI3K p85 and Akt.

CONCLUSION

Our data demonstrated that GYY4137 may alleviate the sperm damage and epididymis injury in experimentally VC-induced rats by activation of the PI3K/Akt pathway.

Tissue regeneration and the epididymal stem cell

BACKGROUND

In most pseudostratified epithelia, basal cells represent a multipotent adult stem cell population. These cells generally remain in a quiescent state, until they are stimulated to respond to tissue damage by initiating epithelial regeneration. In the epididymis, cell proliferation occurs at a relatively slow rate under normal physiological conditions. Epididymal basal cells have been shown to share common properties with multipotent adult stem cells. The development of organoids from stem cells represents a novel approach for understanding cellular differentiation and characterization of stem cells.

OBJECTIVE

To review the literature on tissue regeneration in the epididymis and demonstrate the presence of an epididymal stem cell population.

METHODS

PubMed database was searched for studies reporting on cell proliferation, regeneration, and stem cells in the epididymis. Three-dimensional cell culture of epididymal cells was used to determine whether these can develop into organoids in a similar fashion to stem cells from other tissues.

RESULTS

The epididymal epithelium can rapidly regenerate following orchidectomy or efferent duct ligation, in order to maintain epithelial integrity. Studies have isolated a highly purified fraction of rat epididymal basal cells and reported that these cells displayed properties similar to those of multipotent adult stem cells. In two-dimensional cell culture conditions, these cells differentiated into cells which expressed connexin 26, a marker of columnar cells, and cytokeratin 8. Furthermore, three-dimensional cell culture of epididymal cells resulted in the formation of organoids, a phenomenon associated with the proliferation and differentiation of stem cells in vitro.

CONCLUSIONS

The rapid proliferation and tissue regeneration of the epididymal epithelium to preserve its integrity following tissue damage as well as the ability of cells to differentiate into organoids in vitro support the notion of a resident progenitor/stem cell population in the adult epididymis.

Influence of warming and reanimation conditions on seminiferous tubule morphology, mitochondrial activity, and cell composition of vitrified testicular tissues in the domestic cat model

Understanding critical roles of warming and reanimation is critical to improve the survival of vitrified testicular tissue in domestic cats. The objective was to study structural and functional properties of testicular tissues from prepubertal domestic cats after standard vitrification followed by two warming protocols (directly at 37°C or with a 5-second pre-exposure to 50°C) and three reanimation time points (immediately, 24 h and 5 days post-warming). In Experiment 1, tissues were evaluated for histo-morphology and mitochondrial activity immediately or 24 h after warming protocols. In Experiment 2, cell viability, DNA fragmentation, and germ cell composition were assessed immediately, 24 h, or 5 days after optimal warming. Preservation of seminiferous tubule structure was better using warming at 50°C for five seconds, and survival of somatic as well as germinal cells was higher compared to direct warming at 37°C for one minute. Short term in vitro culture (for reanimation) also proved that cellular composition and functionality were better preserved when warmed for a short time at 50°C. Collective data showed that short warming at 50°C led to better quality of seminiferous tubule structure and cell composition after vitrification and short-term culture. In addition, data suggest clear directions to further understand and optimize testicular tissue survival after fertility preservation procedures.

Cellular junctions in the epididymis, a critical parameter for understanding male reproductive toxicology

Epididymal sperm maturation is a critical aspect of male reproduction in which sperm acquire motility and the ability to fertilize an ovum. Sperm maturation is dependent on the creation of a specific environment that changes along the epididymis and which enables the maturation process. The blood-epididymis barrier creates a unique luminal micro-environment, different from blood, by limiting paracellular transport and forcing receptor-mediated transport of macromolecules across the epididymal epithelium. Direct cellular communication between cells allows coordinated function of the epithelium. A limited number of studies have directly examined the effects of toxicants on junctional proteins and barrier function in the epididymis. Effects on the integrity of the blood-epididymis barrier have resulted in decreased fertility and, in some cases, the development of sperm granulomas. Studies have shown that in addition to tight junctions, proteins implicated in the maintenance of adherens junctions and gap junctions alter epididymal functions. This review will provide an overview of the types and roles of cellular junctions in the epididymis, and how these are targeted by different toxicants.

Curative GnRHa treatment has an unexpected repressive effect on Sertoli cell specific genes

Background

Follicle stimulating hormone and testosterone stimulate Sertoli cells to support germ cell function and differentiation. During mini-puberty, when gonadotropin (GnRH) stimulates increases in plasma luteinizing hormone (LH) and testosterone levels, gonocytes are transformed into Ad spermatogonia. In cryptorchidism, impaired gonadotropin secretion during mini-puberty results in insufficient LH and testosterone secretion, impaired gonocyte transition to Ad spermatogonia, and perturbed Sertoli cell proliferation. Treatment with a gonadotropin-releasing hormone agonist (GnRHa/Buserelin) induced gonocytes to differentiate into Ad spermatogonia and rescued fertility. The present study evaluated the impact of low LH secretion on Sertoli cell function by comparing differential gene expression data between testes with low LH that lacked Ad spermatogonia (Ad-) and testes that completed mini-puberty (Ad+). Furthermore, we analyzed changes in the transcription of selected Sertoli cell specific genes in response to GnRHa treatment.

Results

Ad- testes showed reduced expression of nine out of 40 selected Sertoli cell specific genes compared to Ad+ testes. GnRHa treatment repressed most of the Sertoli cell specific genes, including the inhibins, but it increased the expression of genes that regulate apoptosis (FASLG) and proliferation (GDNF).

Conclusions

Impaired-minipuberty with decreased LH and testosterone levels affected Ad and Sertoli cell development through positive and negative regulation of morphoregulatory and apoptotic genes. GnRHa treatment had a repressive effect on most Sertoli cell specific genes, which suggested that Sertoli cells underwent a cellular rearrangement. We propose that gonadotropin-dependent increases in FASLG and GDNF expression drove Sertoli cell proliferation and germ cell self-renewal and supported the transition of gonocytes to Ad spermatogonia, independent of inhibins.

Aberrant Expression of Cx Isoforms in the Adult Caput Epididymis exposed to Estradiol Benzoate or Flutamide at the Weaning

Connexin (Cx) involves in the regulation of various physiological functions of tissue by forming a channel, a gap junction which allows direct cell-cell communication, between adjacent cells. The effect of a single subcutaneous treatment of estradiol benzoate (EB) or flutamide (Flu) at the weaning age on the expression of Cx isoforms in the adult caput epididymis was evaluated in this research. Using quantitative real-time PCR analysis, a low-dose of EB [0.015 μg/kg body weight (BW)] caused significant decreases of Cx30.3, Cx32, Cx40, Cx43, and Cx45 mRNA levels and no change of Cx26, Cx31, Cx31.1, Cx37 transcript levels. The treatment of a high-dose EB (1.5 μg/kg BW) resulted in reduced expression of Cx30.3, Cx31, Cx43, and Cx45 but increased expression of Cx37 and Cx40. Expression of all Cx isoforms examined, except Cx31, was significantly increased by the treatment of a low-dose Flu (500 μg/kg BW). However, the treatment of a high-dose Flu (5 mg/kg BW) led significant expressional suppression of Cx30.3, Cx31, Cx31.1, Cx32, Cx40, Cx43, and Cx45 but an increase of Cx37 transcript level. With the comparison of previous findings, the expression of Cx isoforms in the adult epididymis after the exposure to EB or Flu is likely differentially regulated in regional-specific and/or exposed postnatal age-specific manner.

Busulfan administration produces toxic effects on epididymal morphology and inhibits the expression of ZO-1 and vimentin in the mouse epididymis

Busulfan is an alkane sulphonate currently used as an anticancer drug and to prepare azoospermic animal models, because it selectively destroys differentiated spermatogonia in the testes. However, few studies have focussed on the exact effects of busulfan treatment on the epididymis currently. The present study assessed the effect of busulfan on epididymal morphology and the blood-epididymis barrier in mice. We treated mice with a single injection of busulfan and detected the effect at different time points. We showed that busulfan was toxic to the morphological structure and function of the epididymis. Furthermore, busulfan treatment down-regulated the epididymal expression of vimentin and zonula occludens-1 (ZO-1) at the mRNA and protein levels. In addition, there was an increase in total androgen receptor (AR) levels, whereas the estrogen receptor-α (ER-α) levels were reduced, both in the caput and cauda regions after busulfan treatment, which may be secondary to the testicular damage. In conclusion, our study describes the effects of busulfan administration on the mouse epididymis and also provides a potential understanding of male infertility arising from chemotherapy-related defects in the epididymis.

Connexin 43 in the development and progression of breast cancer: What's the connection? (Review)

Connexin 43 is a prominent gap junction protein within normal human breast tissue. Thus far, there have been a number of research studies performed to determine the function of connexin 43 in breast tumor formation and progression. Within primary tumors, research suggests that the level of connexin 43 expression in breast tumors is altered when compared to normal human breast tissue. While some reports indicate that connexin 43 levels decrease, other evidence suggests that connexin 43 levels are increased and protein localization shifts from the plasma membrane to the cytoplasm. In either case, the prevailing theory is that breast tumor cells have reduced gap junction intercellular communication within primary tumors. The current consensus appears to be that the loss of connexin 43 gap junction intercellular communication is an early event in malignancy, with the possibility of gap junction restoration in the event of metastasis. However, additional evidence is needed to support the latter claim. The purpose of this report is to review the connexin 43 literature that describes studies using human tissue samples, in order to evaluate the function of connexin 43 protein in normal human breast tissue as well as the role of connexin 43 in human breast tumor formation and metastatic progression.

Analysis of Epidermal Growth Factor Receptor Related Gene Expression Changes in a Cellular and Animal Model of Parkinson's Disease

We employed transcriptome analysis of epidermal growth factor receptor related gene expression changes in cellular and animal models of Parkinson’s disease (PD). We used a well-known Parkinsonian toxin 1-methyl-4-phenylpyridine (MPP⁺) to induce neuronal apoptosis in the human neuroblastoma SH-SY5Y cell line. The MPP⁺-treatment of SH-SY5Y cells was capable of inducing neuro-apoptosis, but it remains unclear what kinds of transcriptional genes are affected by MPP⁺ toxicity. Therefore the pathways that were significantly perturbed in MPP⁺ treated human neuroblastoma SH-SY5Y cells were identified based on genome-wide gene expression data at two time points (24 and 48 h). We found that the Epidermal Growth Factor Receptor (EGFR) pathway-related genes showed significantly differential expression at all time points. The EGFR pathway has been linked to diverse cellular events such as proliferation, differentiation, and apoptosis. Further, to evaluate the functional significance of the altered EGFR related gene expression observed in MPP⁺-treated SH-SY5Y cells, the EGFR related GJB2 (Cx26) gene expression was analyzed in an MPP⁺-intoxicated animal PD model. Our findings identify that the EGFR signaling pathway and its related genes, such as Cx26, might play a significant role in dopaminergic (DAergic) neuronal cell death during the process of neuro-apoptosis and therefore can be focused on as potential targets for therapeutic intervention.

Role of Specificity Protein-1 and Activating Protein-2 Transcription Factors in the Regulation of the Gap Junction Protein Beta-2 Gene in the Epididymis of the Rat

In prepubertal rats, connexin 26 (GJB2) is expressed between adjacent columnar cells of the epididymis. At 28 days of age, when columnar cells differentiate into adult epithelial cell types, Gjb2 mRNA levels decrease to barely detectable levels. There is no information on the regulation of GJB2 in the epididymis. The present study characterized regulation of the Gjb2 gene promoter in the epididymis. A single transcription start site at position −3829 bp relative to the ATG was identified. Computational analysis revealed several TFAP2A, SP1, and KLF4 putative binding sites. A 1.5-kb fragment of the Gjb2 promoter was cloned into a vector containing a luciferase reporter gene. Transfection of the construct into immortalized rat caput epididymal (RCE-1) cells indicated that the promoter contained sufficient information to drive expression of the reporter gene. Deletion constructs showed that the basal activity of the promoter resides in the first −230 bp of the transcriptional start site. Two response elements necessary for GJB2 expression were identified: an overlapping TFAP2A/SP1 site (−136 to −126 bp) and an SP1 site (−50 bp). Chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assays confirmed that SP1 and TFAP2A were bound to the promoter. ChIP analysis of chromatin from young and pubertal rats indicated that TFAP2A and SP1 binding decreased with age. SP1 and TFAP2A knockdown indicated that SP1 is necessary for Gjb2 expression. DNA methylation did not appear to be involved in the regulation of Gjb2 expression. Results indicate that SP1 and TFAP2A regulate Gjb2 promoter activity during epididymal differentiation in rat.

Tyrosine kinase-mediated axial motility of basal cells revealed by intravital imaging

Epithelial cells are generally considered to be static relative to their neighbours. Basal cells in pseudostratified epithelia display a single long cytoplasmic process that can cross the tight junction barrier to reach the lumen. Using in vivo microscopy to visualize the epididymis, a model system for the study of pseudostratified epithelia, we report here the surprising discovery that these basal cell projections--which we call axiopodia--periodically extend and retract over time. We found that axiopodia extensions and retractions follow an oscillatory pattern. This movement, which we refer to as periodic axial motility (PAM), is controlled by c-Src and MEK1/2-ERK1/2. Therapeutic inhibition of tyrosine kinase activity induces a retraction of these projections. Such unexpected cell motility may reflect a novel mechanism by which specialized epithelial cells sample the luminal environment.

Roles of connexins in testis development and spermatogenesis

The development and differentiation of cells involved in spermatogenesis requires highly regulated and coordinated interactions between cells. Intercellular communication, particularly via connexin43 (Cx43) gap junctions, plays a critical role in the development of germ cells during fetal development and during spermatogenesis in the adult. Loss of Cx43 in the fetus results in a decreased number of germ cells, while the loss of Cx43 in the adult Sertoli cells results in complete inhibition of spermatogenesis. Connexins 26, 32, 33, 36, 45, 46 and 50 have also been localized to specific compartments of the testis in various mammals. Loss of Cx46 is associated with an increase in germ cell apoptosis and loss of the integrity of the blood-testis barrier, while loss of other connexins appears to have more subtle effects within the seminiferous tubule. Outside the seminiferous tubule, the interstitial Leydig cells express connexins 36 and 45 along with Cx43; deletion of the latter connexin did not reveal it to be crucial for steroidogenesis or for the development and differentiation of Leydig cells. In contrast, loss of Cx43 from Sertoli cells results in Leydig cell hyperplasia, suggesting important cross-talk between Sertoli and Leydig cells. In the epididymis connexins 26, 30.3, Cx31.1, 32, and 43 have been identified and differentiation of the epithelium is associated with dramatic changes in their expression. Decreased expression of Cx43 results in decreased sperm motility, a function acquired by spermatozoa during epididymal transit. Clearly, intercellular gap junctional communication within the testis and epididymis represents a critical aspect of male reproductive function and fertility. The implications of this mode of intercellular communication for male fertility remains a poorly understood but important facet of male reproduction.

Isolated Rat Epididymal Basal Cells Share Common Properties with Adult Stem Cells

There is little information on the function of epididymal basal cells. These cells secrete prostaglandins, can metabolize radical oxygen species, and have apical projections that are components of the blood-epididymis barrier. The objective of this study was to develop a reproducible protocol to isolate rat epididymal basal cells and to characterize their function by gene expression profiling. Integrin-alpha6 was used to isolate a highly purified population of basal cells. Microarray analysis indicated that expression levels of 552 genes were enriched in basal cells relative to other cell types. Among these genes, 45 were expressed at levels of 5-fold or greater. These highly expressed genes coded for proteins implicated in cell adhesion, cytoskeletal function, ion transport, cellular signaling, and epidermal function, and included proteases and antiproteases, signal transduction, and transcription factors. Several highly expressed genes have been reported in adult stem cells, suggesting that basal cells may represent an epididymal stem cell population. A basal cell culture was established that showed that these basal cells can differentiate in vitro from keratin (KRT) 5-positive cells to cells that express KRT8 and connexin 26, a marker of columnar cells. These data provide novel information on epididymal basal cell gene expression and suggest that these cells can act as adult stem cells.

Exogenous exposure to estradiol benzoate or flutamide at the weaning age alters expression of connexin isoforms in the initial segment of male rat

Connexin (Cx) is a complex which allows direct communication between neighboring cells via exchange of signaling molecules and eventually leads to functional harmony of cells in a tissue. The initial segment (IS) is an excurrent duct of male reproductive tract and expression of numerous genes in the IS are controlled by andevrepogens and estrogens. The effects of these steroid hormones on gene expression in the IS during postnatal development have not extensively examined. The present research investigated expressional modulation of Cx isoforms in the IS by exogenous exposure to estrogen agonist, estradiol benzoate (EB), or andevrepogen antagonist, flutamide (Flu), at weaning age. Two different doses of EB or Flu were subcutaneously administrated in 21-day old of male rats, and expressional changes of Cx isoforms in the adult IS were analyzed by quantitative real-time PCR. Treatment of a low-dose EB (0.015 μg/kg body weight) resulted in an increased expression of Cx31 gene and a decreased expression of Cx37 gene. A high-dose EB (1.5 μg/kg body weight) treatment caused an increase of Cx31 gene expression. Increased levels of Cx30.3 and Cx40 transcripts were observed with a low-dose Flu (500 μg/kg body weight) treatment. Treatment of high-dose Flu (50 mg/kg body weight) led to expressional increases of Cx30.3, 40, and 43 genes. Our previous and present findings suggest differential responsiveness on gene expression of Cx isoforms in the IS by andevrepogens and estrogens at different postnatal ages.

Exogenous exposure to estradiol benzoate or flutamide at the weaning age alters expression of connexin isoforms in the initial segment of male rat

Connexin (Cx) is a complex which allows direct communication between neighboring cells via exchange of signaling molecules and eventually leads to functional harmony of cells in a tissue. The initial segment (IS) is an excurrent duct of male reproductive tract and expression of numerous genes in the IS are controlled by androgens and estrogens. The effects of these steroid hormones on gene expression in the IS during postnatal development have not extensively examined. The present research investigated expressional modulation of Cx isoforms in the IS by exogenous exposure to estrogen agonist, estradiol benzoate (EB), or androgen antagonist, flutamide (Flu), at weaning age. Two different doses of EB or Flu were subcutaneously administrated in 21-day old of male rats, and expressional changes of Cx isoforms in the adult IS were analyzed by quantitative real-time PCR. Treatment of a low-dose EB (0.015 μg/kg body weight) resulted in an increased expression of Cx31 gene and a decreased expression of Cx37 gene. A high-dose EB (1.5 μg/kg body weight) treatment caused an increase of Cx31 gene expression. Increased levels of Cx30.3 and Cx40 transcripts were observed with a low-dose Flu (500 μg/kg body weight) treatment. Treatment of high-dose Flu (50 mg/kg body weight) led to expressional increases of Cx30.3, 40, and 43 genes. Our previous and present findings suggest differential responsiveness on gene expression of Cx isoforms in the IS by androgens and estrogens at different postnatal ages.

Expressional Modulation of Connexin Isoforms in the Initial Segment of Male Rat treated with Estradiol Benzoate or Flutamide

Direct cell-cell communication through connexin (Cx) complexes is a way to achieve functional accordance of cells within a tissue or an organ. The initial segment (IS), a part of the epididymis, plays important roles in sperm maturation. Steroid hormones influence on expression of a number of genes in the IS of adult animals. However, developmental effect of sex hormones on the gene expression in the IS has not been examined. In this study, estradiol benzoate (EB, an estrogen agonist) or flutamide (Flu, an andevrepogen antagonist) was exogenously administrated at 1 week of postnatal age, and expressional changes of Cx genes in the IS were determined at 4 months of age by a quantitative real-time PCR analysis. Treatment of EB at 0.015 μg/kg body weight (BW) increased expression of Cx30.3, 31.1, and 43 genes. However, treatment of 1.5 μg EB/kg BW resulted in expressional decreases of Cx31, 32, and 45 genes and caused increases of Cx30.3 and 43 gene expression. Significant decreases of Cx31, 31.1, 32, 37, and 45 gene expression were detected with a treatment of 500 μg Flu/kg BW, while expression of Cx43 gene was significantly increased with a treatment of 500 μg Flu/kg BW. A treatment of 50 mg Flu/kg BW led to significant increases of Cx30.3, 32, 37, 40, and 43 gene expression. These findings imply that exogenous exposure of steroidal hormones during the early developmental period would result in aberrant expression of Cx genes in the adult IS.

Expressional Modulation of Connexin Isoforms in the Initial Segment of Male Rat treated with Estradiol Benzoate or Flutamide

Direct cell-cell communication through connexin (Cx) complexes is a way to achieve functional accordance of cells within a tissue or an organ. The initial segment (IS), a part of the epididymis, plays important roles in sperm maturation. Steroid hormones influence on expression of a number of genes in the IS of adult animals. However, developmental effect of sex hormones on the gene expression in the IS has not been examined. In this study, estradiol benzoate (EB, an estrogen agonist) or flutamide (Flu, an andevrepogen antagonist) was exogenously administrated at 1 week of postnatal age, and expressional changes of Cx genes in the IS were determined at 4 months of age by a quantitative real-time PCR analysis. Treatment of EB at 0.015 μg/kg body weight (BW) increased expression of Cx30.3, 31.1, and 43 genes. However, treatment of 1.5 μg EB/kg BW resulted in expressional decreases of Cx31, 32, and 45 genes and caused increases of Cx30.3 and 43 gene expression. Significant decreases of Cx31, 31.1, 32, 37, and 45 gene expression were detected with a treatment of 500 μg Flu/kg BW, while expression of Cx43 gene was significantly increased with a treatment of 500 μg Flu/kg BW. A treatment of 50 mg Flu/kg BW led to significant increases of Cx30.3, 32, 37, 40, and 43 gene expression. These findings imply that exogenous exposure of steroidal hormones during the early developmental period would result in aberrant expression of Cx genes in the adult IS.

Role of testicular luminal factors on Basal cell elongation and proliferation in the mouse epididymis

A subset of basal cells (BCs) in the initial segment (IS) of the mouse epididymis has a slender body projection between adjacent epithelial cells. We show here that these projections occasionally cross the apical tight junctions and are in contact with the luminal environment. Luminal testicular factors are critical for the establishment of the IS epithelium, and we investigated their role in the regulation of this luminal sensing property. Efferent duct ligation (EDL) was performed to block luminal flow from the testis without affecting blood flow. Cytokeratin 5 (KRT5) labeling showed a time-dependent reduction of the percentage of BCs with intercellular projections from 1 to 5 days after EDL, compared to controls. Double labeling for caspase-3 and KRT5 showed that a subset of BCs undergoes apoptosis 1 day after EDL. Ki67/KRT5 double labeling showed a low rate of BC proliferation under basal conditions. However, EDL induced a marked increase in the proliferation rate of a subset of BCs 2 days after EDL. A 2-wk treatment with the androgen receptor antagonist flutamide did not affect the number of BCs with intercellular projections, but reduced BC proliferation. Flutamide treatment also reduced the increase in BC proliferation induced 2 days after EDL. We conclude that, in the adult mouse IS, 1) luminal testicular factors play an important role in the ability of BCs to extend their body projection towards the lumen, and are essential for the survival of a subset of BCs; 2) androgens play an important role in the proliferation of some of the BCs that survive the initial insult induced by EDL; and 3) the formation and elongation of BC intercellular projections do not depend on androgens.

Gap junction modulation and its implications for heart function

Gap junction communication (GJC) mediated by connexins is critical for heart function. To gain insight into the causal relationship of molecular mechanisms of disease pathology, it is important to understand which mechanisms contribute to impairment of gap junctional communication. Here, we present an update on the known modulators of connexins, including various interaction partners, kinases, and signaling cascades. This gap junction network (GJN) can serve as a blueprint for data mining approaches exploring the growing number of publicly available data sets from experimental and clinical studies.

Plasticity of basal cells during postnatal development in the rat epididymis

Our previous study has shown that basal cells sense luminal factors by forming a narrow body projection that can cross epithelial tight junctions. As a first step toward characterizing the structural plasticity of basal cells, in this study, we followed their appearance and morphology in the rat epididymis and vas deferens (VD) during postnatal development and examined their modulation by androgens in adulthood. Immunofluorescence labeling for cytokeratin 5 showed that basal cells are absent at birth. They progressively appear in a retrograde manner from the VD and cauda epididymis to the initial segments during the postnatal weeks PNW1-3. At the onset of differentiation, basal cells are in contact with the lumen and their nucleus is located at the same level as that of adjacent epithelial cells. Basal cells then position their nucleus to the base of the epithelium, and while some are still in contact with the lumen, others have a 'dome-shaped' appearance. At PNW5-6, basal cells form a loose network at the base of the epithelium, and luminal-reaching basal cells are rarely detected. The arrival of spermatozoa during PNW7-8 did not trigger the development of projections in basal cells. However, cells with a narrow luminal-reaching projection began to reappear between PNW8 and PNW12 in the corpus and the cauda. Treatment with flutamide from PNW10 to PNW12 significantly reduced the number of luminal-reaching basal cell projections. In summary, basal cells exhibit significant structural plasticity during differentiation. Fewer apical-reaching projections were detected after flutamide treatment in adulthood, indicating the role of androgens in the luminal-sensing function of basal cells.

Endogenous EGF maintains Sertoli germ cell anchoring junction integrity and is required for early recovery from acute testicular ischemia/reperfusion injury

Administration of exogenous epidermal growth factor (EGF) improves testicular injury after acute ischemia–reperfusion (IR) stress, but the molecular basis is poorly understood. The role of endogenous EGF in testicular recovery and the underlying intracellular signaling pathways involved were herein investigated. In mice, testicular IR injury significantly enhanced the expression level of endogenousEgfat the very beginning of reperfusion. Expression of EGF receptor (Egfr(ErbB1)) was accordingly upregulated 3 h after reperfusion. Deprivation of majority of circulated EGF by sialoadenectomy aggravated testicular detriment (especially in pachytene spermatocytes), enhanced germ cell apoptosis, and thereafter resulted in impaired meiotic differentiation after IR insult. Mechanistically, endogenous EGF signaling appeared to be indispensable for the proper maintenance of Sertoli germ cells anchoring junction dynamics during the early testicular recovery. We also provided thein vitroevidences in a well-established rat Sertoli germ cell co-cultures model that the pro-survival effect of endogenous EGF on germ cells in response to testicular IR insult is mediated, at least in part, via the phosphatidylinositol 3-kinase/pAkt pathway. Collectively, our results suggest that the augment of endogenous EGF during the early testicular recovery may act on top of an endocrinous cascade orchestrating the intimate interactions between Sertoli cells and germ cells and may operate as indispensable defensive mechanism in response to testicular IR stress. Future studies in this field would shed light on this complicated pathogenesis.