Interactions of NADPH oxidase, renin–angiotensin–aldosterone system and reactive oxygen species in mequindox-mediated aldosterone secretion in Wistar rats
Introduction
Mequindox (MEQ), a synthetic quinoxaline 1,4-dioxides (QdNOs) derivative (Fig. 1) which can effectively improve growth and feed efficiency in animals, was found to induce adrenal gland damage and reduce the output of aldosterone, thus cause the changes of Na+, K+ in Wistar rats. We previously reported that the induction of oxidative stress due to the reduction metabolism of MEQ could result in a membrane damage and dysfunction of adrenal mitochondrion, leading to the deregulation of steroid hormone secretion and imbalance of ion concentration (Huang et al., 2009). However, how oxidative species are generated via chemical metabolism and interact with other target tissues remains unclear.
Aldosterone, the main mineralocorticoid produced by the zona glomerulosa of the adrenal gland, plays a major role in water and electrolyte homeostasis (Lisurek and Bernhardt, 2004). Numerous investigations clearly showed a major role for the renin–angiotensin–aldosterone system (RAAS) in regulating aldosterone secretion in animal and man (Laragh et al., 1960, Davis et al., 1961, Mulrow, 1999). All the components, including angiotensin (ANG), have been demonstrated in several extra renal sites such as the brain, liver, lungs, heart, and kidneys (Lumbers, 1999, Wolf, 2002a, Wolf, 2002b, Liebau et al., 2006, Nguyen, 2007). The kidney is the principal target organ for aldosterone regulation of whole body electrolyte balance (Harvey et al., 2008). Local RAAS may be particularly important in kidney injury and dysfunction through the activation of multiple intracellular signaling pathways (Paul et al., 2006). For example, RAAS activation leads to the activation of reactive oxigen species (ROS)-generating enzyme systems that include metabolic oxygenases such as NADPH oxidase (Sachse and Wolf, 2007).
NADPH is a major source of ROS generation in both physiologic and pathophysiologic situations (Abid et al., 2007, Cave et al., 2006). ROS derived from NADPH oxidase play a signaling function by inducing specific biochemical changes in their molecular targets. Numerous studies have demonstrated that NADPH oxidase regulate a number of important reactions/processes. For example, several NADPH subunits are involved in ANG II as well as aldosterone functions in different tissues (Garrido and Griendling, 2009, Fan et al., 2008).
Taken together these information prompted us to hypothesize that RAAS and NADPH oxidase may play a key role in MEQ-induced oxidative stress and hypoaldosteronism, which would in turn, influence the function of other physiological system. Oxidative stress may affect some pathological procedure of the tissue dysfunction via responsible enzymes correlated to ROS generation or the metabolism of MEQ. However, no attempt has been made to discuss the interaction with intra- or extra-adrenal regulators on aldosterone secretion induced by MEQ. More studies need to be done in order to clarify the exact nature of the MEQ stimulatory effect upon responsible enzymes and aldosterone secretion. We decided to perform further studies to elucidate the pathways involved in RAAS-mediated aldosterone secretion and action. In addition, our study attempted to find the crosstalk among RAAS, NADPH and aldosterone action after exposure to long term of MEQ diets. Male Wistar rats were fed with MEQ for 180 days at five different doses (0, 25, 55, 110 and 275 mg/kg). Morphological changes and oxidative stress indices in kidney were examined. Real-time reverse transcriptional polymerase chain reaction (RT-PCR) was used to detect the dose–response interaction of gene expression. Components of renal and adrenal RAAS as well as mineralocorticoid receptor (MR) and Na+/K+-ATPase (NAKA) activation were detected. Meanwhile, five NADPH enzymes in kidney and adrenal gland were monitored to further explore the linkage among oxidative damage, RAAS and aldosterone release.
Section snippets
Materials
Mequindox (C11H10N2O3, mol. wt. 218.21, purity 98%) was purchased from Beijing Zhongnongfa Pharmaceutical Co. Ltd. (Huanggang, PR China). All the chemicals were purchased from Sigma (St. Louis, MO) unless otherwise it was specified.
Animals and diets
The study was approved by the local experimental animal committee. The animals were cared in accordance with the Regulation of Experimental Animal Administration issued by the State Committee of Science and Technology of the People's Republic of China on November 14,
Effect of MEQ on pathological changes in kidney
The toxicity of adrenal glands induced by long term of MEQ exposure has been described and investigated in our lab previously (Huang et al., 2009). In order to see whether MEQ diet cause any direct pathological alterations in the kidney of rats, H & E was used to stain the kidney tissue of rats as described in Section 2. Groups of 25 and 55 mg/kg showed no obvious damage in the kidney. As shown in Fig. 2, marked morphological changes were observed in 110 and 275 mg/kg groups as compared to
Discussion
The main findings in this report are that: (1) The dose-dependent long term toxicity of MEQ on kidney in male rats, raised further awareness of its toxic effects to animals and consumers. (2) Higher dose of MEQ may regulate aldosterone secretion via inhibition of both intra- and extra-adrenal RAAS pathway. (3) The imbalance of Na+/K+ homeostasis induced by aldosterone decrease in rat blood after MEQ exposure may be mediated by MR and NAKA, the downstream of aldosterone effect, further
Conflict of interest
The authors declare that there are no conflicts of interest.
Acknowledgements
This work was supported by grants from National Basic Research Program of China (2009CB118800), China Postdoctoral Science Foundation (nos. 20080440949 and 200902441) and Chinese Fundamental Research Funds for the Central Universities (no. 2009QC001).
References (43)
- et al.
NADPH oxidase activity selectively modulates vascular endothelial growth factor signaling pathways
J. Biol. Chem.
(2007) - et al.
Assessment of the renal toxicity of novel anti-inflammatory compounds using cynomolgus monkey and human kidney cells
Toxicology
(2009) - et al.
The kidney androgen-regulated protein promoter confers renal proximal tubule cell specific and highly androgen-responsive expression on the human angiotensinogen gene in transgenic mice
J. Biol. Chem.
(1997) - et al.
Synergy of aldosterone and high salt induces vascular smooth muscle hypertrophy through up-regulation of NOX1
J. Steroid Biochem. Mol. Biol.
(2008) - et al.
NADPH oxidases and angiotensin II receptor signaling
Mol. Cell. Endocrinol.
(2009) - et al.
Rapid responses to aldosterone in the kidney and colon
J. Steroid Biochem. Mol. Biol.
(2008) - et al.
High dietary potassium chloride intake augments rat renal mineralocorticoid receptor selectivity via 11β-hydroxysteroid dehydrogenase
Biochim. Biophys. Acta
(1999) - et al.
Long-term dose-dependent response of mequindox on aldosterone, corticosterone and five steroidogenic enzyme mRNAs in the adrenal of male rats
Toxicol. Lett.
(2009) - et al.
Nitric oxide inhibits human aldosteronogenesis without guanylyl cyclase stimulation
Mol. Cell. Endocrinol.
(1999) NOx enzymes, ROS, and chronic disease: an example of antagonistic pleiotropy
Free Radic. Biol. Med.
(2007)
Modulation of aldosterone and cortisol synthesis on the molecular level
Mol. Cell. Endocrinol.
Angiotensin and aldosterone
Regul. Pept.
Angiotensin II and aldosterone regulation
Regul Pept.
The role of nitric oxide in the regulation of aldosterone synthesis by adrenal glomerulosa cells
J. Steroid Biochem. Mol. Biol.
Regulation of water movement across vertebrate renal tubules
Comp. Biochem. Physiol., Part A: Mol. Integr. Physiol.
Renin–angiotensin–aldosterone system-mediated redox effects in chronic kidney disease
Transl. Res.
NAD(P)H oxidase inhibitor prevents blood pressure elevation and cardiovascular hypertrophy in aldosterone-infused rats
Biochem. Biophys. Res. Commun.
A novel superoxide-producing NAD(P)H oxidase in kidney
J. Biol. Chem.
Carbadox-induced inhibition of aldosterone production in porcine adrenals in vitro
Toxicol. In Vitro
Comparative study of the effect of carbadox, olaquindox and cyadox on aldosterone, sodium and potassium plasma levels in weaned pigs
Res. Vet. Sci.
Quinoxaline 1,4-dioxide: aversatile scaffold endowed with manifold activities
Curr. Med. Chem.
Cited by (34)
Mequindox induces apoptosis, DNA damage, and carcinogenicity in Wistar rats
2019, Food and Chemical ToxicologyAn insight into medicinal chemistry of anticancer quinoxalines
2019, Bioorganic and Medicinal ChemistryA two-year dietary carcinogenicity study of cyadox in Sprague-Dawley rats
2017, Regulatory Toxicology and PharmacologyGenomic and proteomic analysis of the inhibition of synthesis and secretion of aldosterone hormone induced by quinocetone in NCI-H295R cells
2016, ToxicologyCitation Excerpt :Studies have indicated that renin-angiotensin-aldosterone system (RAAS) showed important effects on the regulation of synthesis and secretion of aldosterone hormone (Cartledge and Lawson 2000). It was revealed that higher doses of MEQ (110 and 275 mg/kg diet) might regulate aldosterone secretion through inhibition of both the intra- and extra-adrenal RAAS pathway (Huang et al., 2010a), and ROS was a key mediator of QdNOs-induced adrenal toxicity via the mitochondria-dependent pathway in adrenocortical cells (Huang et al., 2010b). Moreover, presence of some dysregulated subunits of NADPH oxidase in the kidney and adrenal gland suggest that ROS generated by NADPH oxidase may be involved in the process of regulating the secretion of aldosterone by RAAS (Huang et al., 2010a).
- 1
These authors contributed equally to this paper.