Publications by Author: Seth L Alper

Lower urinary tract symptoms (LUTS) affect approximately 50% of the population over 40 years of age and are strongly associated with obesity and metabolic syndrome. Adipose tissue plays a key role in obesity/metabolic syndrome by releasing adipokines that regulate systemic energy/lipid metabolism, insulin resistance, and inflammation. Adiponectin (ADPN), the most abundant adipokine, modulates energy/metabolism homeostasis through its insulin-sensitizing and antiinflammatory effects. Human plasma ADPN levels are inversely associated with obesity and diabetes. To the best of our knowledge, the role of adipokines such as ADPN in the LUTS associated with obesity/metabolic syndrome remains unknown. We have tested such a possible role in a global ADPN-knockout (Adpn-/-) mouse model. Adpn-/- mice exhibited increased voiding frequency, small voids, and reduced bladder smooth muscle (BSM) contractility, with absence of purinergic contraction. Molecular examination indicated significantly altered metabolic and purinergic pathways. The ADPN receptor agonist AdipoRon was found to abolish acute BSM contraction. Intriguingly, both AMPK activators and inhibitors also abolished BSM purinergic contraction. These data indicate the important contribution of what we believe is a novel ADPN signaling pathway to the regulation of BSM contractility. Dysregulation of this ADPN signaling pathway might be an important mechanism leading to LUTS associated with obesity/metabolic syndrome.

The general anesthetic ketamine has been repurposed by physicians as an anti-depressant and by the public as a recreational drug. However, ketamine use can cause extensive pathological changes, including ketamine cystitis. The mechanisms of ketamine's anti-depressant and adverse effects remain poorly understood. Here we present evidence that ketamine is an effective L-type Ca2+ channel (Cav1.2) antagonist that directly inhibits calcium influx and smooth muscle contractility, leading to voiding dysfunction. Ketamine prevents Cav1.2-mediated induction of immediate early genes and transcription factors, and inactivation of Cav1.2 in smooth muscle mimics the ketamine cystitis phenotype. Our results demonstrate that ketamine inhibition of Cav1.2 signaling is an important pathway mediating ketamine cystitis. In contrast, Cav1.2 agonist Bay k8644 abrogates ketamine-induced smooth muscle dysfunction. Indeed, Cav1.2 activation by Bay k8644 decreases voiding frequency while increasing void volume, indicating Cav1.2 agonists might be effective drugs for treatment of bladder dysfunction.

Purinergic signaling plays an important role in regulating bladder contractility and voiding. Abnormal purinergic signaling is associated with lower urinary tract symptoms (LUTS). Ecto-5'-nucleotidase (NT5E) catalyzes dephosphorylation of extracellular AMP to adenosine, which in turn promotes adenosine-A2b receptor signaling to relax bladder smooth muscle (BSM). The functional importance of this mechanism was investigated using Nt5e knockout (Nt5eKO) mice. Increased voiding frequency of small voids revealed by voiding spot assay was corroborated by urodynamic studies showing shortened voiding intervals and decreased bladder compliance. Myography indicated reduced contractility of Nt5eKO BSM. These data support a role for NT5E in regulating bladder function through modulation of BSM contraction and relaxation. However, the abnormal bladder phenotype of Nt5eKO mice is much milder than we previously reported in A2b receptor knockout (A2bKO) mice, suggesting compensatory response(s) in Nt5eKO mouse bladder. To better understand this compensatory mechanism, we analyzed changes in purinergic and other receptors controlling BSM contraction and relaxation in the Nt5eKO bladder. We found that the relative abundance of muscarinic CHRM3 (cholinergic receptor muscarinic 3), purinergic P2X1, and A2b receptors was unchanged, whereas P2Y12 receptor was significantly downregulated, suggesting a negative feedback response to elevated ADP signaling. Further studies of additional ecto-nucleotidases indicated significant upregulation of the nonspecific urothelial alkaline phosphatase ALPL, which might mitigate the degree of voiding dysfunction by compensating for Nt5e deletion. These data suggest a mechanistic complexity of the purinergic signaling network in bladder and imply a paracrine mechanism in which urothelium-released ATP and its rapidly produced metabolites coordinately regulate BSM contraction and relaxation.