Receptor GPR91 contributes to voiding function and detrusor relaxation mediated by succinate

Succinate as a New Actor in Pluripotency and Early Development?

Pluripotent cells have been stabilized from pre- and post-implantation blastocysts, representing respectively naïve and primed stages of embryonic stem cells (ESCs) with distinct epigenetic, metabolic and transcriptomic features. Beside these two well characterized pluripotent stages, several intermediate states have been reported, as well as a small subpopulation of cells that have reacquired features of the 2C-embryo (2C-like cells) in naïve mouse ESC culture. Altogether, these represent a continuum of distinct pluripotency stages, characterized by metabolic transitions, for which we propose a new role for a long-known metabolite: succinate. Mostly seen as the metabolite of the TCA, succinate is also at the crossroad of several mitochondrial biochemical pathways. Its role also extends far beyond the mitochondrion, as it can be secreted, modify proteins by lysine succinylation and inhibit the activity of alpha-ketoglutarate-dependent dioxygenases, such as prolyl hydroxylase (PHDs) or histone and DNA demethylases. When released in the extracellular compartment, succinate can trigger several key transduction pathways after binding to SUCNR1, a G-Protein Coupled Receptor. In this review, we highlight the different intra- and extracellular roles that succinate might play in the fields of early pluripotency and embryo development.

Adaptation to partial urethral obstruction in healthy aging LOU rats and the role of nerve growth factor signaling pathway in the bladder

AIM

Aging is associated with poor ability to adapt to stress and abnormal nerve growth factor (NGF) profile. Lower urinary tract symptoms frequently disturb the quality of life of the aging population with no optimal treatment for both genders. The aim of the study was to compare the bladder response to bladder outflow obstruction in young and old LOU rats, a model of healthy aging that does not develop insulin resistance, and its relation to proNGF/NGF imbalance.

METHODS

6- and 36-month-old female LOU rats were subjected to partial bladder urethral obstruction (PUO) for 2 weeks. Morphometric parameters (body and bladder weight) and glycemia were evaluated. Cystometry was carried out to measure functional parameters followed by ex vivo assessment of muscle strip contractile characteristics. Tissue proteins were examined by immunoblotting and morphology was examined by microscopy.

RESULTS

Body weight and glycaemia were not affected by surgery. PUO increases significantly bladder weight with increased thickness and fibrosis of the bladder wall as revealed by histological examination in both age groups. Cystometry showed that old PUO rats had a significant reduction in the intercontraction interval and the bladder capacity, a pattern opposite to young rats with PUO. Contractile properties of bladder strip were not affected by age or PUO. On the molecular level, the old rats had lower abundance of the mature NGF relative to proNGF, with signs of p75^NTR activation suggested by the higher expression of TNF-α and JNK phosphorylation in the bladder tissue.

CONCLUSION

Bladder adaptation to PUO occurs only in young LOU rats to maintain efficient bladder contractility. Old LOU rats display proNGF/NGF imbalance and the associated p75^NTR activation. This can further induce tissue damage and degeneration through activation of JNK pathway and release of TNF-α which in turn interferes with the necessary bladder adaptation.