Connexin

Preterm birth (PTB) is a major public health problem, with a global prevalence of 9.6% and over a million annual neonatal deaths. In a mouse model of preterm labor (PTL) induced by intravaginal administration of a subclinical dose of lipopolysaccharide (LPS), we previously demonstrated that LPS ascends to the cervix, inducing complement activation, cervical remodeling and PTL. Here we show that complement activation also plays a role in myometrial contractions during PTL in this model. Increased levels of C5a were detected in the myometrium of LPS-treated mice but not in age-matched control or term myometrium. Human and mouse myometrium incubated with C5a showed increased frequency of contractions and expression of connexin 43, suggesting that C5a is an uterotonic molecule. Statins, which showed beneficial effects in preventing complement-mediated pregnancy complications, prevented cervical remodeling, myometrial contractions and PTL in the LPS model. The protective effects of stati...

Analysis of mice with genetically altered expression of cardiac connexins can provide insights into the role of individual gap junction channel proteins in cell-to-cell communication, impulse propagation, and arrhythmias. However, conflicting results have been reported regarding conduction velocity slowing in mice heterozygous for a null mutation in the gene encoding connexin43 (Cx43). Methods: High-resolution optical mapping was used to record

Rats chronically exposed to acrylonitrile (ACN) have shown a dose-dependent increase in the incidence of astrocytomas in the brain. The mechanism(s) by which ACN induces cancer in rodents has not been established. ACN does not appear to be directly genotoxic in the brain and thus a nongenotoxic mode of action has been proposed. Inhibition of gap junctional intercellular communication (GJIC) has been shown to be a property of many nongenotoxic carcinogens. The present study examined the effects of ACN on GJIC in a rat astrocyte transformed cell line, DI TNC1 cells (a target cell for ACN carcinogenicity) and primary cultured hepatocytes (a nontarget cell for ACN carcinogenicity). ACN inhibited GJIC in rat astrocytes in a dose-dependent manner. Inhibition of GJIC was observed following 2 h treatment with 0.10 mmol/L and 1.00 mmol/L ACN. However, in primary cultured hepatocytes, ACN exposed did not result in inhibition of GJIC even after 48 h of continued treatment. In the astrocytes, G...

Transient knock-down of the gap junction protein Cx43 by antisense and siRNA, or gap junction block with mimetic peptides, have been shown to enhance epidermal wound healing. However, patients with oculodentodigital dysplasia (ODDD) express mutant Cx43 that leads to a chronic reduction in gap junctional intercellular communication. To determine whether mutant Cx43 in keratinocytes would impact upon the wound healing process, we localized Cx43 in human and mouse skin tissue expressing mutant Cx43 and assessed the ability of primary keratinocytes derived from a mouse model of ODDD to proliferate, migrate and differentiate. In the epidermis from an ODDD patient and in the epidermis of mice expressing the G60S mutant or in keratinocytes obtained from mutant mice, Cx43 was frequently found within intracellular compartments and rarely localized to punctate sites of cell–cell apposition. Primary keratinocytes derived from G60S mutant mice proliferated faster but migrated similarly to keratinocytes derived from wild-type control mice. Keratinocytes derived from mutant mice expressed abundant Cx43 and higher levels of involucrin and loricrin under low calcium conditions. However, after calcium-induced differentiation, similar levels of Cx43, involucrin and loricrin were observed. Thus, we conclude that during wound healing, mutant Cx43 may enhance keratinocyte proliferation and promote early differentiation of keratinocytes.

Ubiquitously expressed connexins are tetra-spanning transmembrane proteins that form intercellular gap junction channels or cell surface hemichannels. Connexins share similar topology but no sequence homology with mammalian pannexins and CALHM1 (calcium homeostasis modulator 1), which are also large-pore transmembrane channels. Of these three channel types, clinical evidence and gene sequence analysis to date have revealed that inherited human diseases are only associated with mutations in the connexin gene family. Connexin-linked diseases often present at birth or early in life and range from mild developmental abnormalities to severe organ failure such as hearing loss. Inherited connexin gene mutations can manifest as a disease by causing anomalies or defects in connexin oligomerization, folding, ability to pass quality control mechanisms or unexpected gain- or loss-of-function. This review provides examples of the way that various connexin gene mutations can cause disease via a wide range of molecular mechanisms. We also reflect on exciting strategies being explored in the connexin field and beyond with a view of translating their findings into potential connexin-disease therapeutics.

Ageing processes play a major contributing role for the development of Osteoarthritis (OA). This prototypic degenerative condition of ageing is the most common form of arthritis and is accompanied by a general decline, chronic pain and mobility deficits. The disease is primarily characterized by articular cartilage degradation,
followed by subchondral bone thickening, osteophyte formation, synovial inflammation and joint degeneration.
In the early stages, osteoarthritic chondrocytes undergo phenotypic changes that increase cell proliferation and cluster formation and enhance the production of matrix-remodelling enzymes. In fact, chondrocytes exhibit differentiation plasticity and undergo phenotypic changes during the healing process. Current studies are focusing
on unravelling whether OA is a consequence of an abnormal wound healing response. Recent investigations suggest that alterations in different proteins, such as TGF-ß/BMPs, NF-Kß, Wnt, and Cx43, or SASP factors involved in signalling pathways in wound healing response, could be directly implicated in the initiation
of OA. Several findings suggest that osteoarthritic chondrocytes remain in an immature state expressing stemness-associated cell surface markers. In fact, the efficacy of new disease-modifying OA drugs that promote chondrogenic differentiation in animal models indicates that this may be a drug-sensible state. In this review, we highlight the current knowledge regarding cellular plasticity in chondrocytes and OA. A better comprehension of the mechanisms involved in these processes may enable us to understand the molecular pathways that promote
abnormal repair and cartilage degradation in OA. This understanding would be advantageous in identifying novel targets and designing therapies to promote effective cartilage repair and successful joint ageing by preventing functional limitations and disability.

To describe the effects of epididymal and vasal ligation, in an experimental rat model, by using connexin 43 and occludin immunohistochemistry as well as transmission electron microscopy.Comparative and controlled experimental research study.University animal research and histology laboratories in Turkey.Wistar male rats in experimental and control groups.The control group underwent sham operation (n = 7). The first experimental group (n = 7) underwent unilateral epididymal ligation, whereas the second experimental group (n = 7) underwent unilateral vasal ligation to induce experimental epididymal and vasal obstruction models, respectively. All animals were then killed at 90 days.Immunohistochemical expression of connexin 43 and occludin for testicular tissues was determined after epididymal and vasal obstruction models. Ultrastructural morphological changes were examined by electron microscopy.Results of the semiquantitative analysis revealed that expressions of both occludin and connexin 43 in the rat testis were decreased in the experimental groups compared with in the sham-operated group. However, changes after vasal ligation were more prominent. Ultrastructural examination confirmed decreased intercellular communication as well as increased cellular degeneration among the ipsilateral and contralateral testicular tissues.Immunohistochemical expression of occludin and connexin 43 were decreased in the testis after vasal and epididymal ligation when compared with the sham-operated group. Ultrastructural changes indicating cell degeneration were more prominent after vasal ligation.

Although a plethora of signaling pathways are known to drive the activation of hepatic stellate cells in liver fibrosis, the involvement of connexin-based communication in this process remains elusive. Connexin43 expression is enhanced in activated hepatic stellate cells and constitutes the molecular building stone of hemichannels and gap junctions. While gap junctions support intercellular communication, and hence the maintenance of liver homeostasis, hemichannels provide a circuit for extracellular communication and are typically opened by pathological stimuli, such as oxidative stress and inflammation. The present study was set up to investigate the effects of inhibition of connexin43-based hemichannels and gap junctions on liver fibrosis in mice. Liver fibrosis was induced by administration of thioacetamide to Balb/c mice for eight weeks. Thereafter, mice were treated for two weeks with TAT-Gap19, a specific connexin43 hemichannel inhibitor, or carbenoxolone, a general hemichann...

Excessive cardiac interstitial fibrosis impairs normal cardiac function. We have shown that the α11β1 (α11) integrin mediates fibrotic responses to glycated collagen in rat myocardium by a pathway involving transforming growth factor-β. Little is known of the role of the α11 integrin in the developing mammalian heart. Therefore, we examined the impact of deletion of the α11 integrin in wild type mice, and in mice treated with streptozotocin (STZ), to elucidate the role of the α11 integrin in normal cardiac homeostasis and in the pathogenesis of diabetes related fibrosis. As anticipated, cardiac fibrosis was reduced in α11 integrin knockout mice (α11(-/-); C57BL/6 background) treated with STZ compared with STZ-treated wild type mice (P < 0.05). Unexpectedly, diastolic function was impaired in both vehicle and STZ-treated α11(-/-) mice as shown by decreased dP/dtmin and prolonged Tau, in association with increased end-diastolic pressure (all P < 0.05 c/w wild type mice). Accordi...

Cardiac gap junctions have been implicated in maintaining intercellular electrical and metabolic couplings. The abnormalities in connexin-43 (Cx43) lead to conduction defects and contractile dysfunction. We have evaluated the expression and phoshorylation status of Cx43 in the left ventricular myocardium of male and female 16-month-old rats submitted to 14-week L-thyroxine (T4) treatment. Western blot analysis revealed the presence of fully or intermediately phosphorylated and unphosphorylated forms of Cx43. We have found no significant differences in Cx43 expression and phosphorylation between T4-treated and control untreated animals. However, expression of Cx43 was significantly higher in female compared to male rats. We conclude that T4 administration has no effect on Cx43 expression, but there are sex-dependent differences in Cx43 expression in the left ventricles between aging male and female rats.

Smooth muscle cells (SMC) of the human urinary bladder are believed to be electrically coupled. However, it has not been successfully demonstrated the nature of the underlying cell-cell communication. Here, we used Western blot technique to demonstrate the gap junction protein connexin 43 (Cx 43) in human bladder musculature and in smooth muscle cell cultures. We found expression of Cx 43 in all samples of the detrusor (Mdv, n=6) and in five of six samples of the internal sphincter (Mv). Cx 43 expression was less in cell cultures, 60% showing Cx 43 expression. Iontophoretic application of the gap junction permeable fluorescent dye lucifer yellow revealed a mean of 2.6±2.2 (mean±SD, n=8) coupled cells in cultured smooth muscle cells. Our findings support the notion that Cx 43 is constitutively expressed in human bladder SMC in vivo. Thus, the function of the bladder is likely to be influenced by the organisation of smooth muscle cells into functional syncytia.