Regulation of Connexin 43 by Basic Fibroblast Growth Factor in the Bladder: Transcriptional and Behavioral Implications

ArticleinThe Journal of urology 185(6):2398-404 · June 2011with2 Reads
DOI: 10.1016/j.juro.2011.02.018 · Source: PubMed
Abstract
Basic fibroblast growth factor is a candidate causative factor of detrusor overactivity in bladder outlet obstruction cases through up-regulation of the gap junction protein connexin 43. We addressed the transcriptional and behavioral implications of this axis. Cx43 and Cx45 mRNA expression was assessed by real-time reverse transcriptase-polymerase chain reaction in the bladder of a rat bladder outlet obstruction model and in cultured rat bladder smooth muscle cells with and without basic fibroblast growth factor treatment. Involvement of the extracellular signal regulated kinase 1/2-activator protein-1 pathway was evaluated by immunofluorescence study and a promoter-reporter assay in bladder smooth muscle cells. The effect of basic fibroblast growth factor on micturition behavior was measured in unrestrained rats under a 12-hour light/dark cycle using a controlled release system from gelatin hydrogels fixed on the bladder. The expression of extracellular signal regulated kinase 1/2 and connexin 43 protein was assessed by Western blotting of rat bladder protein. Cx43 but not Cx45 mRNA expression was increased in the bladder of the obstruction model and in bladder smooth muscle cells treated with basic fibroblast growth factor. The mitogen-activated and extracellular signal-regulated kinase kinase inhibitor PD98059 blocked the stimulatory effect of basic fibroblast growth factor on connexin 43 protein expression and promoter activity, which was also decreased by mutation or deletion of an activator protein-1 cis-element of the connexin 43 promoter. In vivo application of basic fibroblast growth factor on the bladder increased urinary frequency during the latter half of the dark phase, ie the late active phase of rats (F = 5.1, 2-way ANOVA p <0.05). The expression of phospho-extracellular signal regulated kinase 1/2 and connexin 43 protein was increased in the bladder. The extracellular signal regulated kinase 1/2-activator protein-1-connexin 43 axis could be a potential therapeutic target for increased urinary frequency.
    • "It has been known for some time that smooth muscle cells of the detrusor muscle are coupled by Cx43-based gap junctions [37]. Furthermore, an increase in Cx43 status in the bladder has been associated with overactive bladder and incontinence [25]. "
    [Show abstract] [Hide abstract] ABSTRACT: To date, over 65 mutations in the gene encoding Cx43 have been linked to the autosomal dominant disease, oculodentodigital dysplasia (ODDD). A subset of these patients experience bladder incontinence which could be due to underlying neurogenic deterioration or aberrant myogenic regulation. Bladder smooth muscle cells (BSMCs) from wild-type and two Cx43 mutant lines (Cx43G60s and Cx43I130T) that mimic ODDD exhibit a significant reduction in total Cx43. Dye transfer studies revealed that the G60S mutant was a potent dominant-negative inhibitor of co-expressed Cx43, a property not equally shared by the I130T mutant. BSMCs from both mutant mouse strains were defective in their ability to contract indicative of phenotype changes due to harboring the Cx43 mutants. Upon stretching, Cx43 levels were significantly elevated in control and mutant containing BSMCs but the nonmuscle- myosin heavy chain A levels were only reduced in cells from control mice. While the Cx43G60s mutant mice showed no difference in voided urine volume or frequency, the Cx43I130T mice voided less frequently. Thus, like the diversity of morbidities seen in ODDD patients, genetically-modified mice also display mutation specific changes in bladder function. Furthermore, while mutant mice have compromised smooth muscle contraction and response to stretch, overriding bladder defects in Cx43I130T mice are likely complemented by neurogenic changes.
    Full-text · Article · Nov 2013
    • "Because there is emerging evidence that Panx1 is related to various pathophysiological conditions, such as seizure31, death of enteric neurons during colitis27, nonalcoholic steatohepatitis32 and others, and because Cx43 has been reported to have important roles in bladder function1718242933, we focused our study on these two gap junction genes, Panx1 and Cx43. When comparing Panx1 and Cx43 expression in the bladder mucosa and detrusor compartments, we found that Panx1 mRNA was mainly expressed in mucosa while Cx43 mRNA was found in both mucosa and detrusor (Supplementary Fig. S5). "
    [Show abstract] [Hide abstract] ABSTRACT: Bladder dysfunction is common in Multiple Sclerosis (MS) but little is known of its pathophysiology. We show that mice with experimental autoimmune encephalomyelitis (EAE), a MS model, have micturition dysfunction and altered expression of genes associated with bladder mechanosensory, transduction and signaling systems including pannexin 1 (Panx1) and Gja1 (encoding connexin43, referred to here as Cx43). EAE mice with Panx1 depletion (Panx1(-/-)) displayed similar neurological deficits but lesser micturition dysfunction compared to Panx1(+/+) EAE. Cx43 and IL-1β upregulation in Panx1(+/+) EAE bladder mucosa was not observed in Panx1(-/-) EAE. In urothelial cells, IL-1β stimulation increased Cx43 expression, dye-coupling, and p38 MAPK phosphorylation but not ERK1/2 phosphorylation. SB203580 (p38 MAPK inhibitor) prevented IL-1β-induced Cx43 upregulation. IL-1β also increased IL-1β, IL-1R-1, PANX1 and CASP1 expression. Mefloquine (Panx1 blocker) reduced these IL-1β responses. We propose that Panx1 signaling provides a positive feedback loop for inflammatory responses involved in bladder dysfunction in MS.
    Full-text · Article · Jul 2013
    • "Peripheral neuropathy ↑Cx26, ↑Cx32 perineurium Animal diabetic STZ rat studies [62] Wound healing ↓Cx43, ↓Cx26 epidermis Animal diabetic STZ rat studies [70] [71] ↑Cx43 dermis, wound edge keratinocytes first 24 hours after injury ↑Cx43 wound edge keratinocytes Human studies [72] The in vivo effect of diabetes on the expression pattern of vascular Cxs within major large vessels is not fully understood . The effects of statins on connexin expression in the arterial wall have been observed by Sheu et al. [24], who observed reduced expression of Cx43 in diabetic rat aortic walls and an increase in Cx43 levels following simvastatin treatment. "
    [Show abstract] [Hide abstract] ABSTRACT: Cell-to-cell interactions via gap junctional communication and connexon hemichannels are involved in the pathogenesis of diabetes. Gap junctions are highly specialized transmembrane structures that are formed by connexon hemichannels, which are further assembled from proteins called "connexins." In this paper, we discuss current knowledge about connexins in diabetes. We also discuss mechanisms of connexin influence and the role of individual connexins in various tissues and how these are affected in diabetes. Connexins may be a future target by both genetic and pharmacological approaches to develop treatments for the treatment of diabetes and its complications.
    Full-text · Article · Mar 2012
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