AMPK Suppresses Connexin43 Expression in the Bladder and Ameliorates Voiding Dysfunction in Cyclophosphamide-induced Mouse Cystitis

• DOI: 10.1038/srep19708
• Publication Date: 2016-01-25T12:19:10Z
• Authors: Xiling Zhang; Jian Yao; Kun Gao; Yuan Chi; Takahiko Mitsui; Tatsuya Ihara; Norifumi Sawada; Manabu Kamiyama; Jianglin Fan; Masayuki Takeda
• Keywords: Mice, Knockout; 0303 health sciences; Gene Expression; AMP-Activated Protein Kinases; Article; Rats; Disease Models, Animal; Mice; 03 medical and health sciences; Connexin 43; Protein Biosynthesis; Cystitis; Animals; Cytokines; Female; Inflammation Mediators; Phosphorylation; Cyclic AMP Response Element-Binding Protein; Cyclophosphamide

AbstractBladder voiding dysfunction is closely related to local oxidation, inflammation and enhanced channel activities. Given that the AMP-activated protein kinase (AMPK) has anti-oxidative, anti-inflammatory and channel-inhibiting properties, we examined whether and how AMPK affected bladder activity. AMPK activation in rat bladder smooth muscle cells (BSMCs) using three different AMPK agonists resulted in a decrease in connexin43 (Cx43) expression and function, which was associated with reduced CREB phosphorylation, Cx43 promoter activity and mRNA expression, but not Cx43 degradation. Downregulation of CREB with siRNA increased Cx43 expression. A functional analysis revealed that AMPK weakened BSMC contraction and bladder capacity. AMPK also counteracted the IL-1β- and TNFα-induced increase in Cx43 in BSMCs. In vivo administration of the AMPK agonist AICAR attenuated cyclophosphamide-initiated bladder oxidation, inflammation, Cx43 expression and voiding dysfunction. Further analysis comparing the responses of the wild-type (Cx43+/+) and heterozygous (Cx43+/−) Cx43 mice to cyclophosphamide revealed that the Cx43+/− mice retained a relatively normal micturition pattern compared to the Cx43+/+ mice. Taken together, our results indicate that AMPK inhibits Cx43 in BSMCs and improves bladder activity under pathological conditions. We propose that strategies that target AMPK can be developed as novel therapeutic approaches for treating bladder dysfunction.