The effect of partial outlet obstruction on calpain and phospholipase-2 activities: analyzed by severity and duration

Abstract

In an attempt to better understand the two pathways that lead to bladder decompensation following partial obstruction in rabbits one of which is caused by calcium-activated enzymes and the other by oxidative stress, calpain and phospholipase A2 (PLA2) biochemical assays were conducted to see how bladder decompensation is mediated by these two calcium-activated enzymes. Partial outlet obstructions of varying durations (4, 8, and 12 weeks plus controls) were performed on 32 New Zealand white rabbits. The rabbits were also grouped by severity: control, mild, intermediate, and severe. The activities of Calpain and PLA2 on the muscle tissue of the bladders were analyzed. A stronger correlation was seen between activities and severities as opposed to between activities and durations for both PLA2 and calpain. The activity for PLA2 increased dramatically from control to mild and then stayed constant for both intermediate and severe obstructions. Calpain activity increased steadily from control to mild to intermediate to severe. Based on the increase in levels of the calcium-dependent enzymes, it was clearly shown that calcium levels increased in all stages of bladder decompensation most notably with the mild obstructions. Based on previous studies in which nitrotyrosine and dinitrophenol levels did not increase in mildly obstructed rabbits, the calcium overload pathway may predominate in mild decompensation because cells in mildly obstructed bladders are better able to cope with oxidative stress than increased calcium levels.

The putative involvement of actin‐binding proteins and cytoskeleton proteins in pathological mechanisms of ketamine cystitis—Revealed by a prospective pilot study using proteomic approaches

“…reported that the levels of CAPN increased as decompensation level increased from mild to intermediate to severe in a rabbit model of partial bladder outlet obstruction . A similar study also showed the level of CAPN decreased during the recovery process when compared with that after 8 weeks of obstruction . The present study revealed that the expressions of CAPN, cleaved CASP3 and PARP‐1 were significantly elevated in KC samples compared with those in IC/BPS and control samples.…”

Benefits and limitations of animal models in partial bladder outlet obstruction for translational research

“…reported that in pBOO models, some bladders with detrusor hypertrophy function close to normal, whereas others were decompensated, showing high intravesical pressure and large residual urine volume . In view of these results, they classified the pBOO model not in terms of the degree of obstruction, but in terms of bladder weight . This is one way of solving the pBOO problem.…”

Effect of partial bladder outlet obstruction and reversal on rabbit bladder physiology and biochemistry: duration of recovery period and severity of function

“…The increased levels of calpain seen in the severely decompensated bladders shows that calpain (calcium dysregulation) may play an important role in severe decompensation of the bladder. In a previous study, the level of calpain decreased during the recovery process when compared with that after 8 weeks of obstruction . The 4‐week group still showed a high level of calpain as a result of the ischaemia and reperfusion induced by the obstruction.…”

“…Analysing the bladders for severity of decompensation as a group, independently of recovery duration, provided reasonable standard errors and statistics. The range of bladder weights for the severity categories was based on the functional responses after 8 weeks of obstruction in an earlier experiment that did not involve reversals . For each rabbit in each recovery group (4, 8 and 12 weeks) it was therefore possible to determine the magnitude of recovery (shift in severity group).…”

“…mediated by the bladder hypertrophy that is directly related to partial BOO [20,21]. These aetiologies are: 1) oxidative stress resulting in the generation of free radicals and oxidative damage; 2) calcium overload resulting from the inability to remove intracellular free calcium after a contraction in a partially obstructed bladder, causing the activation of calcium-activated degradative enzymes such as calpain and phospholipase A2 (PLA2), increased activity of which has been observed after partial BOO [22][23][24][25][26][27]; and 3) the shift from smooth muscle to collagen as smooth muscle damage increases [22,23,28]. Collagen levels can serve as a valuable marker to characterise the level of obstructive damage during partial BOO as well as after relief from BOO [29].…”