Increased Expression of Heat Shock Protein 20 and Decreased Contractile Stress in Obstructed Rat Bladder

Abstract

We noted that partially obstructed rat bladders 1) express higher levels of heat shock protein 20 and 2) generate less stress than sham operated bladders. These data suggest the possibility that heat shock protein 20 over expression could at least partially mediate the decreased contractile activity observed with partial bladder outlet obstruction. The mechanism for increased heat shock protein 20 expression is unknown but it may involve increased mechanical stress or hypoxia from urethral obstruction. Human bladder expressed immunoreactive heat shock protein 20, suggesting that a similar mechanism could potentially occur in humans. If confirmed in humans, patients with clinical conditions that result in detrusor hypocontractility could potentially benefit from pharmacological interventions aimed at inhibiting heat shock protein 20.

Expression and localization of the Xenopus laevis small heat shock protein, HSPB6 (HSP20), in A6 kidney epithelial cells

“…For example, in a mouse model of glomerulonephritis, renal cortices of diseased mice demonstrated an enhanced accumulation of HSPB6 without an increase in HSP70, suggesting a lack of a generalized stress response (Guess et al, 2013). Also, increased levels of HSPB6 were reported in dog and rat heart due to congestive heart failure or exercise and also in rat bladder in response to partial urethral ligation (Batts et al, 2006;Boluyt et al, 2006;Dohke et al, 2006). While the mechanism(s) associated with the increase in X. laevis HSPB6 levels in response to cadmium or MG132 is unclear, it is likely that their enhanced levels may be due, at least in part, to a reduction in HSPB6 degradation since both cadmium and MG132 were found to inhibit the ubiquitin-proteasome system in Xenopus A6 cells (Young and Heikkila, 2010;Brunt et al, 2012;Khan et al, 2012;Khamis and Heikkila, 2013;Khan et al, 2015).…”

Morphological changes in the small intestinal smooth muscle layers of horses suffering from small intestinal strangulation. Is there a basis for predisposition for reduced contractility?

“…The HSP20‐OD was significantly upregulated in colic tissue compared to control samples but was not related to lesion score. Severe distension of bladder smooth muscle has been reported to upregulate HSP20 causing relaxation of the muscle layer (Batts et al . 2006).…”

“…The mechanisms upregulating HSP20 are not yet elucidated but stress situations, e.g. hypoxia or mechanical stress due to obstruction can trigger its expression (Batts et al . 2006).…”

“…2006). HSP20 has been reported to decrease the contractile activity in the distended smooth muscle of the bladder (Batts et al . 2006).…”

Spinal Cord Injury Markedly Altered Protein Expression Patterns in the Affected Rat Urinary Bladder during Healing Stages

“…Hsp20 expression in smooth muscles is variable. Low levels of Hsp20 expression in the normal bladder are converted to substantial expression when the bladder is obstructed (28). Low or no expression of Hsp20 is associated with diminished cyclic nucleotide-induced relaxation, suggesting phosphorylation of Hsp20 can be a dominant mechanism of smooth muscle relaxation (29).…”