Neurogenic-derived 6-nitrodopamine is the most potent endogenous modulator of the mouse urinary bladder relaxation

6-Nitrodopamine (6-ND) modulates vas deferens, seminal vesicles, and corpus cavernosum contractility; however, its role on the lower urinary tract organs has not been evaluated. Investigations of isolated urinary bladders from wild-type (WT) mice revealed 6-ND release was comparable to that of dopamine and adrenaline, whereas noradrenaline was hardly detected, as assessed by liquid chromatography coupled to tandem mass spectrometry. In vitro, 6-ND induced concentration-dependent relaxations in carbachol pre-contracted bladders with high potency (pEC50: 8.04 ± 0.86), independently of eNOS/sGC activity. Co-incubation of 6-ND (1-10 μM) antagonizes the contractile effects of acetylcholine (p < 0.05). Experiments using nitric oxide synthase (NOS) knockout mice demonstrated that 6-ND release from isolated urinary bladder was significantly reduced by neuronal NOS (nNOS-/-) deletion and abolished by triple NOSs deletion (n/i/eNOS-/-), while no significant changes were observed in endothelial (eNOS-/-) or inducible (iNOS-/-) knockout mice. Incubation with tetrodotoxin resulted in a significant decrease in 6-ND release in bladders obtained from WT, but not in nNOS-/- mice. The bladders from nNOS-/- and n/i/eNOS-/- mice exhibited significantly higher contractile responses to electric field stimulation (EFS), compared to eNOS-/-, iNOS-/-, or WT bladders. The hyperreactivity observed in triple NOS knockouts was reversed by the incubation with bladder mucosal layer obtained from a donor WT mice, but not with the muscular layer. These findings clearly demonstrate 6-ND is the most potent endogenous relaxing agent of urinary bladder, and inhibition of its release is associated with bladder hyperreactivity.

Ethanol and cyclophosphamide induce similar nephrotoxic effects: possible role for Nox4 and superoxide

We tested the hypothesis that ethanol consumption would aggravate the renal damage induced by cyclophosphamide (CYP). Male C57BL/6 J mice from control (n = 8) and CYP (n = 12) groups had free access to filtered water and standard rodent chow for 12 weeks. Then, 24 h before euthanasia mice received an intraperitoneal injection of saline or CYP (300 mg/kg). Mice from ethanol (n = 8) and CYP + ethanol (n = 12) groups had free access to increasing doses of ethanol for 12 weeks. Twenty-four hours before euthanasia, mice from ethanol and CYP + ethanol groups received an intraperitoneal injection of saline or CYP, respectively. Ethanol, CYP, or the association of both drugs augmented serum levels of creatinine and increased the levels of superoxide ([Formula: see text]) generation and thiobarbituric acid reactive substances in the renal cortex. Upregulation of Nox4 and increased activity of superoxide dismutase were detected in the renal cortex of mice treated with ethanol, CYP, or the combination of these drugs; however, these molecular alterations induced by CYP were not potentiated by ethanol consumption. Our findings revealed that chronic ethanol consumption had no potentiating effect on the nephrotoxic effects displayed by CYP. It is possible that the combination of these drugs showed no synergistic effect because they share the same molecular mechanisms of renal toxicity.