2-Bromo-1,4-naphthoquinone: a potentially improved substitute of menadione in Apatone™ therapy

Apatone™, a combination of menadione (2-methyl-1,4-naphthoquinone, VK3) and ascorbic acid (vitamin C, VC) is a new strategy for cancer treatment. Part of its effect on tumor cells is related to the cellular pro-oxidative imbalance provoked by the generation of hydrogen peroxide (H2O2) through naphthoquinone redox cycling. In this study, we attempted to find new naphthoquinone derivatives that would increase the efficiency of H2O2 production, thereby potentially increasing its efficacy for cancer treatment. The presence of an electron-withdrawing group in the naphthoquinone moiety had a direct effect on the efficiency of H2O2 production. The compound 2-bromo-1,4-naphthoquinone (BrQ), in which the bromine atom substituted the methyl group in VK3, was approximately 10- and 19-fold more efficient than VK3 in terms of oxygen consumption and H2O2 production, respectively. The ratio [H2O2]produced / [naphthoquinone]consumed was 68 ± 11 and 5.8 ± 0.2 (µM/µM) for BrQ and VK3, respectively, indicating a higher efficacy of BrQ as a catalyst for the autoxidation of ascorbic acid. Both VK3 and BrQ reacted with glutathione (GSH), but BrQ was the more effective substrate. Part of GSH was incorporated into the naphthoquinone, producing a nucleophilic substitution product (Q-SG). The depletion of BrQ by GSH did not prevent its redox capacity since Q-SG was also able to catalyze the production of reactive oxygen species. VK3/VC has already been submitted to clinical trials for the treatment of prostate cancer and has demonstrated promising results. However, replacement of VK3 with BrQ will open new lines of investigation regarding this approach to cancer treatment.

Roles of estrogen and progesterone in modulating renal nerve function in the rat kidney

The maintenance of extracellular Na+ and Cl- concentrations in mammals depends, at least in part, on renal function. It has been shown that neural and endocrine mechanisms regulate extracellular fluid volume and transport of electrolytes along nephrons. Studies of sex hormones and renal nerves suggested that sex hormones modulate renal function, although this relationship is not well understood in the kidney. To better understand the role of these hormones on the effects that renal nerves have on Na+ and Cl- reabsorption, we studied the effects of renal denervation and oophorectomy in female rats. Oophorectomized (OVX) rats received 17β-estradiol benzoate (OVE, 2.0 mg·kg-1·day-1, sc) and progesterone (OVP, 1.7 mg·kg-1·day-1,sc). We assessed Na+ and Cl-fractional excretion (FENa+ and FECl-, respectively) and renal and plasma catecholamine release concentrations. FENa+, FECl-, water intake, urinary flow, and renal and plasma catecholamine release levels increased in OVX vs control rats. These effects were reversed by 17β-estradiol benzoate but not by progesterone. Renal denervation did not alter FENa+, FECl-, water intake, or urinary flow values vs controls. However, the renal catecholamine release level was decreased in the OVP (236.6±36.1 ng/g) and denervated rat groups (D: 102.1±15.7; ODE: 108.7±23.2; ODP: 101.1±22.1 ng/g). Furthermore, combining OVX + D (OD: 111.9±25.4) decreased renal catecholamine release levels compared to either treatment alone. OVE normalized and OVP reduced renal catecholamine release levels, and the effects on plasma catecholamine release levels were reversed by ODE and ODP replacement in OD. These data suggest that progesterone may influence catecholamine release levels by renal innervation and that there are complex interactions among renal nerves, estrogen, and progesterone in the modulation of renal function.

Gene expression of estrogen and oxytocin receptors in the uterus of pregnant and parturient bitches

In the canine species, the precise mechanisms of pregnancy maintenance and the initiation of parturition are not completely understood. The expression of genes encoding the receptors for estrogen (ERα mRNA) and oxytocin (OTR mRNA) was studied in the endometrium and myometrium during pregnancy and parturition in dogs. Real-time PCR was performed to quantify the levels of ERα mRNA and OTR mRNA in the uterus of bitches during early (up to 20 days of gestation), mid (20 to 40 days) and late pregnancy (41 to 60 days), and parturition (first stage of labor). All tissues expressed ERα and OTR mRNA, and are thus possibly able to respond to eventual estrogen and oxytocin hormonal stimuli. No statistically significant differences in the expression of ERα mRNA were verified in the endometrium and myometrium throughout pregnancy and parturition, but expression of OTR mRNA increased at both parturition and late pregnancy. We concluded that the increase of endometrial and myometrial OTR mRNA expression in dogs is not an event dependent on estrogenic stimulation. Moreover, the contractility response of the canine uterus to oxytocin begins during pregnancy and maintains myometrial activity. The expression of OTR mRNA in canine uterine tissues varied over time, which supports an interpretation that the sensitivity and response to hormone therapy varies during the course of pregnancy and labor. Further studies are needed to elucidate the factors underlying the synthesis of uterine oxytocin receptors and the possible role of ERβ rather than ERα in the uterine tissues during pregnancy and parturition in dogs.

Development of the endocrine pancreas and novel strategies for β-cell mass restoration and diabetes therapy

Diabetes mellitus represents a serious public health problem owing to its global prevalence in the last decade. The causes of this metabolic disease include dysfunction and/or insufficient number of β cells. Existing diabetes mellitus treatments do not reverse or control the disease. Therefore, β-cell mass restoration might be a promising treatment. Several restoration approaches have been developed: inducing the proliferation of remaining insulin-producing cells, de novo islet formation from pancreatic progenitor cells (neogenesis), and converting non-β cells within the pancreas to β cells (transdifferentiation) are the most direct, simple, and least invasive ways to increase β-cell mass. However, their clinical significance is yet to be determined. Hypothetically, β cells or islet transplantation methods might be curative strategies for diabetes mellitus; however, the scarcity of donors limits the clinical application of these approaches. Thus, alternative cell sources for β-cell replacement could include embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells. However, most differentiated cells obtained using these techniques are functionally immature and show poor glucose-stimulated insulin secretion compared with native β cells. Currently, their clinical use is still hampered by ethical issues and the risk of tumor development post transplantation. In this review, we briefly summarize the current knowledge of mouse pancreas organogenesis, morphogenesis, and maturation, including the molecular mechanisms involved. We then discuss two possible approaches of β-cell mass restoration for diabetes mellitus therapy: β-cell regeneration and β-cell replacement. We critically analyze each strategy with respect to the accessibility of the cells, potential risk to patients, and possible clinical outcomes.

Hormonal therapy with estradiol and drospirenone improves endothelium-dependent vasodilation in the coronary bed of ovariectomized spontaneously hypertensive rats

Drospirenone (DRSP) is a progestin with anti-aldosterone properties and it reduces blood pressure in hypertensive women. However, the effects of DRSP on endothelium-dependent coronary vasodilation have not been evaluated. This study investigated the effects of combined therapy with estrogen (E2) and DRSP on endothelium-dependent vasodilation of the coronary bed of ovariectomized (OVX) spontaneously hypertensive rats. Female spontaneously hypertensive rats (n=87) at 12 weeks of age were randomly divided into sham operated (Sham), OVX, OVX treated with E2 (E2), and OVX treated with E2 and DRSP (E2+DRSP) groups. Hemodynamic parameters were directly evaluated by catheter insertion into the femoral artery. Endothelium-dependent vasodilation in response to bradykinin in the coronary arterial bed was assessed using isolated hearts according to a modified Langendorff method. Coronary protein expression of endothelial nitric oxide synthase and estrogen receptor alpha (ER-α) was assessed by Western blotting. Histological slices of coronary arteries were stained with hematoxylin and eosin, and morphometric parameters were analyzed. Oxidative stress was assessed in situ by dihydroethidium fluorescence. Ovariectomy increased systolic blood pressure, which was only prevented by E2+DRSP treatment. Estrogen deficiency caused endothelial dysfunction, which was prevented by both treatments. However, the vasodilator response in the E2+DRSP group was significantly higher at the three highest concentrations compared with the OVX group. Reduced ER-α expression in OVX rats was restored by both treatments. Morphometric parameters and oxidative stress were augmented by OVX and reduced by E2 and E2+DRSP treatments. Hormonal therapy with E2 and DRSP may be an important therapeutic option in the prevention of coronary heart disease in hypertensive post-menopausal women.