Fulvene-5 inhibition of Nadph oxidases attenuate activation of epitehlial sodium channels in A6 distal nephron cells.
ABSTRACT Nadph oxidase 4 is an important cellular source of reactive oxygen species (ROS) generation in the kidney. Novel anti-oxidant drugs, such as Nox4-inhibitor compounds, are being developed. There is however, very little experimental evidence for the biological role and regulation of Nadph oxidase isoforms in the kidney. Herein, we show that Fulvene-5 is an effective inhibitor of Nox-generated ROS and report the role of Nox isoforms in activating epithelial sodium channels (ENaC) in A6 distal nephron cells via oxidant signaling and cell stretch activation. Using single channel patch clamp analysis, we report that Fulvene-5 blocked the increase in ENaC activity that is typically observed with H2O2 treatment of A6 cells: average ENaC NPo values decreased from a baseline level of 1.04±0.18 (mean±SE) to 0.25±0.08 following Fulvene-5 treatment. H2O2 treatment failed to increase ENaC activity in the presence of Fulvene-5. Moreover, Fulvene-5 treatment of A6 cells blocked the osmotic-cell stretch response of A6 cells; indicating that stretch activation of Nox-derived ROS plays an important role in ENaC regulation. Together, these findings indicate that Fulvene-5, and perhaps other classes of antioxidant inhibitors, may represent a novel class of compounds useful for the treatment of pathological disorders stemming from inappropriate ion channel activity, such as hypertention.
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ABSTRACT: The physiological evidence linking the production of superoxide, hydrogen peroxide,and nitric oxide in the renal medullary thick ascending limb of Henle to regulation of medullary blood flow, sodium homeostasis, and long term control of blood pressure is summarized in this review. Data obtained largely from rats indicate that experimentally induced elevations of either superoxide or hydrogen peroxide in the renal medulla result in reduction of medullary blood flow, enhanced Na+ reabsorption and hypertension. A shift in the redox balance between nitric oxide and reactive oxygen species (ROS) is found to occur naturally in the Dahl salt-sensitive (SS) rat model where selective reduction of ROS production in the renal medulla reduces salt-induced hypertension. Excess medullary production of ROS in SS rats emanates from the medullary thick ascending limbs of Henle (both from the mitochondria and membrane NAD(P)H-oxidases) in response to increased delivery and reabsorption of excess sodium and water. There is evidence that ROS and perhaps other mediators such as ATP diffuse from the mTAL to surrounding vasa recta capillaries resulting in medullary ischemia which thereby contributes to the hypertension.American journal of physiology. Renal physiology 10/2014; 308(3):ajprenal.00455.2014. DOI:10.1152/ajprenal.00455.2014 · 3.30 Impact Factor
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ABSTRACT: Ion channels perform a variety of cellular functions in lung epithelia. Oxidant- and antioxidant-mediated mechanisms (that is--redox regulation) of ion channels are areas of intense research. Significant progress has been made in our understanding of redox regulation of ion channels since the last Experimental Biology report in 2003. Advancements include: 1) identification of non-phagocytic NADPH oxidases as sources of regulated reactive species (RS) production in epithelia, 2) an understanding that excessive treatment with antioxidants can result in greater oxidative stress, and 3) characterization of novel RS signaling pathways that converge upon ion channel regulation. These advancements, as discussed at the 2013 Experimental Biology Meeting in Boston, MA, impact our understanding of oxidative stress in the lung, and in particular, illustrate that the redox state has profound effects on ion channel and cellular function.AJP Lung Cellular and Molecular Physiology 09/2013; 305(9). DOI:10.1152/ajplung.00212.2013 · 4.04 Impact Factor