Abstract
BackgroundRho kinase (ROCK) and myosin-light chain kinase (MLCK) are key enzymes in smooth muscle contraction. Previous data have suggested that ROCK contribution to human detrusor contraction is increasing with age. Here, we have analyzed the transcriptional expression of Rho kinase isoforms (ROCK1 and ROCK2) as well as MLCK in the aging human detrusor smooth muscle obtained from resected tissue.MethodsSmall pieces of macroscopically healthy human detrusor smooth muscle (urothelium-free) were prepared for quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR). Transcript expression (mRNA level) of the target genes ROCK1, ROCK2 and MLCK was normalized to three common reference genes (glyceraldehyde-3-phosphate dehydrogenase, β-actin, phosphoglycerate kinase 1).ResultsWe found that across all ages the expression level of ROCK (i.e. ROCK1 and ROCK2 together) was almost equal to that of MLCK in the human bladder. Further, ROCK2 showed a significantly higher expression level than ROCK1. Among all subjects, there was no significant correlation of any single target gene to age, but expression levels of ROCK and MLCK were inversely correlated. Moreover, the within-subject analysis revealed that the ROCK-to-MLCK ratio showed a significantly negative correlation to age. Thus, within a given subject, there is a relative ROCK down-regulation and concomitant MLCK up-regulation.ConclusionsTogether with previous data in human detrusor specimens showing increased ROCK contribution to detrusor contraction, we speculate that the drop of the ROCK-to-MLCK ratio may occur as an attempt to compensate for the increased Rho kinase activity.
Highlights
Rho kinase (ROCK) and myosin-light chain kinase (MLCK) are key enzymes in smooth muscle contraction
We have recently addressed the key enzymes Rho kinase (ROCK) and myosin-light chain kinase (MLCK) in the aging human bladder and could demonstrate that ROCK contribution to detrusor contractility was positively correlated with age, while MLCK contribution was not altered during aging [5]
We performed quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR) in order to determine the mRNA expression levels of the two isoforms of Rho kinase (ROCK1 and ROCK2) and MLCK in detrusor smooth muscle tissue obtained from patients undergoing cystectomy
Summary
Rho kinase (ROCK) and myosin-light chain kinase (MLCK) are key enzymes in smooth muscle contraction. We have analyzed the transcriptional expression of Rho kinase isoforms (ROCK1 and ROCK2) as well as MLCK in the aging human detrusor smooth muscle obtained from resected tissue. Age-related changes in urinary bladder contractility are believed to contribute to dysfunctional micturition such as overactive bladder syndrome (OAB) This is a common urological condition associated with urgency, with or without urge incontinence, and increased micturition frequency and nocturia [1]. We hypothesized that transcriptional up-regulation of Rho kinase could be responsible for this age-related effect To this end, we performed quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR) in order to determine the mRNA expression levels of the two isoforms of Rho kinase (ROCK1 and ROCK2) and MLCK in detrusor smooth muscle tissue obtained from patients undergoing cystectomy
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