Effect Of HSP27on Rat Detrusor Contractile Dysfunction After Acute Urinary Retention

Background and Objectives:Clinically, acute urinary retention (AUR) is the most common urologic emergency, andis serious complication of the lower urinary obstruction, neurogenic bladder, postsurgery ofepidural anesthesia, and using some drugs. AUR can cause to the damage of bladdercontractile function, and recovery function to be delayed, severely loss the bladdercontractile function. AUR leads to the detrusor underactivity (DU), and the effectivetreatment of the disease is not good, and the pathogenesis is still unknown.It is an important role of the detrusor smooth muscle cell (DSMC) for normal storingand voiding function. DSMC is a special smooth muscle cell, relaxation and contraction ofit accord with the classical sliding filament theory. Smooth muscle contraction depends onsliding displacement between the thick myofilament and thin myofilament, which cause tomuscle cell length changes. The process can be carried out by the neurotransmitters andreceptors, many associated proteins of contraction and some enzymes. The integratedcytoskeleton maintains smooth muscle contractile function, and the damage of thecytoskeleton can lead to contractile dysfunction. The regulation mechanism of DSMC isvery similar with skeletal muscle, and the precision and stability of the myofilament ensurethe normal contraction. Traditionally, prolonged bladder over-distension has been deemed toinduce stretch damage of the detrusor, alter bladder microstructures and reduce contractility.Heat shock protein27(HSP27) is a member of the small heat shock protein family,which is an important chaperone protein. It is a pivotal role of HSP27for smooth musclecontractile function. Previous studies of vascular, uterine and tracheal smooth musclesuggest a role for HSP27in response to physical and chemical stressors, and the expressingand activated state of HSP27can maintain and rebuild the smooth muscle contractilefunction. The phosphorylation status of HSP27is thought to regulate the mode. The p38MAPK and its protein kinases and protein kinase C (PKC) is the upper stream path of the phosphorylation of HSP27. HSP27is phosphorylated on three serine residues, Ser15,78and82causing the protein to be reorganised from large oligomers to smaller tetramericunits, which stabilize the smooth muscle cytoskeleton and enhance the smooth musclecontractile function. But the regulation of this process in the detrusor muscle after AUR isunknown.In this study, we established the AUR animal models, observed bladder morphosis byusing HE and transmission electron microscopy (TEM), estimated the bladder contractilefunction by bladder cystometry, measurement of contractile force of the bladder strip;studied the expressing of HSP27in rat bladder after AUR by immunofluorescencemicroscopy analysis, RT-PCR and Western blot. To explore the relationship between HSP27and phosphorylation with the detrusor contraction in rats after acute urinary retention.Constucted the lentivirus vectors of HSP27over-expression and interference, andtransfected to the human bladder smooth muscle cells, to observe the effect of HSP27in thecontractility of the human bladder smooth muscle cells. To provide the new ways forprotection and treatment of detrusor contractile function.Method:Female rats were randomized either to AUR by urethral ligation or to sham operation.Bladder and smooth muscle strip contraction at time points (0h,1h,6h,12h,24h,3d,7d）after AUR were estimated by cystometric and organ bath studies. Bladder morphosis wasobserved by HE. Smooth muscle ultrastructure was observed by transmission electronmicroscopy. HSP27expression in bladder tissue at each time point was detected byimmunofluorescence, Western blots, and real-time PCR. Expression of the3phosphorylatedforms of HSP27was detected by Western blots. Constucted the lentivirus vectors of HSP27over-expression and interference, and transfected to the human bladder smooth muscle cells,to observe the effect of HSP27in the contractility of the human bladder smooth musclecells.Results:1AUR can lead to the damage of the bladder structure, and impairment of the mucosaand submucosa was very obvious. The damage of the structure was the most serious at6hafter AUR, and then lessened gradually until by7d.2Smooth muscle ultrastructure damage was highest at6h after AUR, and then lessened gradually until by7d, ultrastructure was close to normal.3Maximum detrusor pressure and both carbachol-induced and spontaneous detrusorstrip contractile amplitude decreased gradually from0h to6h, and then increased graduallyto near normal values at7d.4HSP27mRNA and protein increased at0h, decreased to a low at6h, and thengradually increased.5Compared with the AUR0h group, the3phosphorylated forms of HSP27were theminimum at6h, and then the3phosphorylated forms of HSP27gradually increased.6Successfully Constucted the lentivirus vectors of HSP27over-expression andinterference, and transfected to the human bladder smooth muscle cells, respectivelypromoted and inhibited the expression of HSP27.7Compared with the bladder smooth muscle cell group, the artificial strip contractileforce of HSP27over-expression group increased, and the HSP27interference groupdecreased.Conclusions:1The damage of the bladder structure and smooth muscle ultrastructure was highest at6h after AUR, and then lessened gradually until by7d.2Rat bladder contractile function after AUR worsens for6h, and then graduallyrecovers.3HSP27modulates bladder smooth muscle contraction after AUR and thatphosphorylation of HSP27may be an important pathway modulating actin cytoskeletondynamics in bladder smooth muscle contraction and reconstruction after injury.4Successfully constructed the lentivirus vectors of HSP27over-expression andinterference, and transfected to the human bladder smooth muscle cells, respectivelypromoted and inhibited the expression of HSP27.5Successfully manufactured the artificial strip of bladder smooth muscle cells; and theexpression of HSP27correlated with the contraction of bladder smooth muscle.