Down-regulation of DDAH2 and eNOS induces endothelial dysfunction in sinoaortic-denervated rats

Nobiletin Regulates ROS/ADMA/DDAHII/eNOS/NO Pathway and Alleviates Vascular Endothelium Injury by Iron Overload

Iron overload is harmful to health and associates with intracellular excessive reactive oxygen species (ROS) generation. Nobiletin (Nob) is known to be antioxidant and anti-inflammatory. However, whether Nob can protect endothelial cells against iron overload has not been studied, and the specific mechanism has not yet been elucidated. In this study, we have identified the protective effects of Nob, and its underlying molecular mechanism in human umbilical vein endothelial cells (HUVECs) suffered from iron overload via ROS/ADMA/DDAHII/eNOS/NO pathway. We found that compared with 50 μM iron dextran treatment, co-treatment with 20 μM Nob increased cell viability and decreased lactate dehydrogenase activity. Besides, Nob could upregulate DDAHII expression and activity, promote eNOS phosphorylation to produce more NO, reduce ADMA content, and therefore increase superoxide dismutase, catalase, and glutathione peroxidase activities, and decrease malondialdehyde level and ROS generation. Nob also inhibited mitochondrial permeability transition pore (mPTP) openness and cleaved caspase-3 expression, and decreased apoptosis induced by iron overload. These results were consistent when Nob was replaced by the positive control reagents L-arginine (a competitive substrate of ADMA), cyclosporin A (an mPTP closing agent), or edaravone (a free radical scavenger). The addition of pAD/DDAHII-shRNA adenovirus reversed the above effects of Nob. These data suggested that the protective mechanism of Nob was to inhibit ROS burst, upregulate DDAHII expression and activity, promote eNOS phosphorylation, produce NO, reduce ADMA content, and ultimately alleviate iron overload damage in vascular endothelium.

Effects of losartan on vasomotor function and canonical transient receptor potential channels in the aortas of sinoaortic denervation rats

Increased short-term blood pressure variability (BPV) is strongly correlated with target organ damage. However, the molecular mechanisms underlying abnormal BPV-induced organ damage and effective therapeutic targets are poorly understood. The purpose of this study was to investigate the effects of losartan on vasomotor function and canonical transient receptor potential (TRPC) channels in the aortas of rats with arterial pressure lability induced by sinoaortic denervation (SAD). SAD was performed in male Sprague-Dawley rats at the age of 10 weeks. The experiment included sham-operated (Sham), SAD, and losartan-treated SAD (SAD+Los) groups. After 8 weeks of treatment, hemodynamic parameters were measured via catheterization, thoracic aortic vasomotor functions were evaluated using a physiological vascular ring tension recording system, and TRPC1 and 6 mRNA and protein expression levels in the endothelial cells (ECs) and smooth muscle cells (SMCs) of the thoracic aorta were determined via reverse transcription polymerase chain reaction (RT-PCR) and Western-blotting, respectively. Compared with Sham rats, SAD rats exhibited significantly increased BPV, enhanced norepinephrine-induced aortic contraction, and attenuated acetylcholine-induced aortic relaxation. Both the mRNA and the protein expression levels of TRPC1 and 6 were significantly downregulated in the ECs and upregulated in the SMCs of the thoracic aortas of SAD rats. Losartan treatment prevented these SAD-induced changes. In conclusion, losartan efficiently prevented vasomotor function impairment in SAD rats by reducing BPV and regulating TRPC1 and 6 expression levels.

Increased Blood Pressure Variability Prior to Chronic Kidney Disease Exacerbates Renal Dysfunction in Rats

Increased blood pressure variability (BPV), which can be experimentally induced by sinoaortic denervation (SAD), has emerged as a new marker of the prognosis of cardiovascular and renal outcomes. Considering that increased BPV can lead to organ-damage, the goal of the present study was to evaluate the effects of SAD on renal function in an experimental model of chronic kidney disease (CKD). SAD was performed in male Wistar rats 2 weeks before 5/6 nephrectomy and the animals were evaluated 4 weeks after the induction of CKD. Our data demonstrated that BPV was increased in SAD and CKD animals and that the combination of both conditions (SAD+CKD) exacerbated BPV. The baroreflex sensitivity index was diminished in the SAD and CKD groups; this reduction was more pronounced when SAD and CKD were performed together. 5/6 nephrectomy led to hypertension, which was higher in SAD+CKD animals. Regarding renal function, the combination of SAD and CKD resulted in reduced renal plasma and blood flow, increased renal vascular resistance and augmented uraemia when compared to CKD animals. Glomerular filtration rate and BPV were negatively correlated in SAD, CKD, and SAD+CKD animals. Moreover, SAD+CKD animals presented a higher level of glomerulosclerosis when compared to all other groups. Cardiac and renal hypertrophy, as well as oxidative stress, was also further increased when SAD and CKD were combined. These results show that SAD prior to 5/6 nephrectomy exacerbates renal dysfunction, suggesting that previous augmented BPV should be considered as an important factor to the progression of renal diseases.

Arterial baroreflex dysfunction impairs ischemia-induced angiogenesis

Background

Endothelium‐derived acetylcholine (eACh) plays an important role in the regulation of vascular actions in response to hypoxia, whereas arterial baroreflex (ABR) dysfunction impairs the eACh system. We investigated the effects of ABR dysfunction on ischemia‐induced angiogenesis in animal models of hindlimb ischemia with a special focus on eACh/nicotinic ACh receptor (nAChR) signaling activation.

Methods and Results

Male Sprague‐Dawley rats were randomly assigned to 1 of 3 groups that received (1) sham operation (control group), (2) sinoaortic denervation (SAD)‐induced ABR dysfunction (SAD group), or (3) SAD rats on diet with an acetylcholinesterase inhibitor pyridostigmine (30 mg/kg per day, SAD+Pyr group). After 4 weeks of the SAD intervention, unilateral limb ischemia was surgically induced in all animals. At postoperative day 14, SAD rats exhibited impaired angiogenic action (skin temperature and capillary density) and decreased angiogenic factor expressions (vascular endothelial growth factor [VEGF] and hypoxic inducible factor [HIF]‐1α) in ischemic muscles. These changes were restored by acetylcholinesterase inhibition. Rats with ABR dysfunction had lower eACh levels than did control rats, and this effect was recovered in SAD+Pyr rats. In α7‐nAChR knockout mice, pyridostigmine improved ischemia‐induced angiogenic responses and increased the levels of VEGF and HIF‐1α. Moreover, nicotinic receptor blocker inhibited VEGF expression and VEGF receptor 2 phosphorylation (p‐VEGFR2) induced by ACh analog.

Conclusions

Thus, ABR dysfunction appears to impair ischemia‐induced angiogenesis through the reduction of eACh/α7‐nAChR‐dependent and ‐independent HIF‐1α/VEGF‐VEGFR2 signaling activation.

Activation of receptor for advanced glycation end products contributes to aortic remodeling and endothelial dysfunction in sinoaortic denervated rats

OBJECTIVE

The aim of present study was to test the hypothesis that activation of receptor for advanced glycation end products (RAGE) pathway contributes to aortic remodeling and endothelial dysfunction in sinoaortic denervated (SAD) rats.

METHODS AND RESULTS

Experiment 1: 8 weeks after sinoaortic denervation, aortas were removed for measurement of AGE/RAGE pathway. Sinoaortic denervation in rats resulted in enhanced activity of aldose reductase, reduced activity of glyoxalase 1, accumulation of methylglyoxal and AGE, and upregulated expression of RAGE in aortas. Experiment 2: 5 weeks after sinoaortic denervation, the rats received intraperitoneal injections of 500 μg soluble RAGE (sRAGE) daily for 3 weeks. Treatment of SAD rats with sRAGE attenuated aortic remodeling, marked by reduction in AW/length, wall thickness, proliferation of SMC, and collagen deposition, and improvement of endothelial function. Treatment of SAD rats with sRAGE abated aortic oxidative stress, marked by reduction in formation of malondialdehyde, reactive oxygen species, superoxide, peroxynitrite and 3-nitrotyrosine, and enhancement of ratio of GSH/GSSG. Treatment of SAD rats with sRAGE attenuated aortic mitochondrial dysfunction. Treatment of SAD rats with sRAGE suppressed aortic NFκB nuclear translocation and inflammation. Treatment of SAD rats with sRAGE restored aortic NO formation through upregulating eNOS and dimethylarginine dimethylaminohydrolase-2 and downregulating protein arginine methyltransferase-1.

CONCLUSION

Activated RAGE contributed to aortic remodeling and endothelial dysfunction in SAD rats, possibly via induction of oxidative stress and inflammation, impairment of mitochondrial function, and reduction in NO bioavailability.