Calcineurin mediates bladder wall remodeling secondary to partial outlet obstruction

Abstract

We hypothesized that the calcineurin-nuclear factor of activated T-cells (NFAT) pathway is activated following partial bladder outlet obstruction (pBOO), which would allow for pharmacologic treatment to prevent the ensuing bladder wall hypertrophy. Using a model of pBOO in male mice, we were able to demonstrate increased nuclear importation of the transcription factors NFAT and myocyte enhanching factor 2 both of which are under control of calcineurin in both the whole bladder wall as well as the urothelium. We further confirmed that this pathway was activated using transgenic mice containing an NFAT-luciferase reporter construct. Mice were randomized following pBOO to treatment with or without cyclosporine A (CsA), a known inhibitor of calcineurin. The bladder-to-body mass ratio (mg bladder wt/g body wt) of 0.95 ± 0.03 in shams increased to 3.1 ± 0.35 following pBOO, and it dropped back to 1.7 ± 0.22 in the CsA+ group (P < 0.001). Luciferase values (RLU) of 1,130 ± 133 in shams increased to 2,010 ± 474 following pBOO and were suppressed to 562 ± 177 in the CsA+ group (P < 0.05). The myosin heavy chain mRNA (A/B) isoform ratio of 0.07 ± 0.03 in shams increased to 1.04 ± 0.19 following pBOO but it diminished to 0.24 ± 0.1 in the CsA+ group (P < 0.001). In vitro whole organ physiology studies demonstrated improved responses in those bladders from mice treated with CsA. The mRNAs for all four known calcineurin-responsive NFAT isoforms are expressed in the bladder wall, although NFATc(3) and NFATc(4) predominate. Both NFATc3 and NFATc4 are expressed in urothelial as well as smooth muscle cells. We conclude that pBOO activates the calcineurin-NFAT pathway and that CsA treatment decreased bladder hypertrophy, shifted the pattern of myosin isoform mRNA expression back toward that seen in normal controls, and resulted in improved in vitro whole organ performance.

Water avoidance stress results in an altered voiding phenotype in male mice

“…An increase in the nuclear translocation of NFAT was observed in bladders following WAS which was consistent with the small degree of bladder hypertrophy that took place and was comparable to the NFAT translocation observed with mild hypertrophy following pBOO. The highest increases of NFAT translocation were observed in those bladders following pBOO that develop the greatest degree of hypertrophy which is similar to what we have reported previously 11, 12. These findings would suggest that swim stress does induce some of the molecular changes that are observed in moderate hypertrophy following surgically induced pBOO.…”

“…The highest increases of NFAT translocation were observed in those bladders following pBOO that develop the greatest degree of hypertrophy which is similar to what we have reported previously. 11,12 These findings would suggest that swim stress does induce some of the molecular changes that are observed in moderate hypertrophy following surgically induced pBOO.…”

Characterization of miRNA-regulated networks, hubs of signaling, and biomarkers in obstruction-induced bladder dysfunction

“…These miRNAs control hypertrophy in the heart, and their synthesis is activated by calcineurin/NFAT signaling (43)(44)(45). The miR-212/132 cluster was upregulated in animals with pBOO (6), concomitant with activation of the calcineurin/NFAT pathway (46).…”

Persistent myopathy despite release of partial obstruction: in vivo reversal of dysfunction and transcriptional responses using rapamycin

“…Rapamycin-resistant hypertrophy during both PBO and REL may be dependent on other growth pathways of bladder smooth muscle, such as NFATc/calcineurin, STAT3, IL1β, PDGF, FGF2, and TGFβ. 9,[60][61][62][63][64][65][66][67][68] Consequently, to understand persistent hypertrophy in future, it may be of interest to further delve into the gene expression patterns and transcriptional pathways induced despite rapamycin treatment, which correlate with the mTOR-independent gross hypertrophy. Nevertheless, while reducing hypertrophy remains an empiric therapeutic goal, it is not clear if mitigating ongoing gross hypertrophy post-REL is of additional functional benefit.…”