Depressed calcium-handling proteins due to endoplasmic reticulum stress and apoptosis in the diabetic heart are attenuated by argirein

Diabetic cardiomyopathy (DC) is a unique disease frequently complicated to diabetes mellitus, manifesting endoplasmic reticulum (ER) stress and depressed calcium-handling proteins. We hypothesized that the abnormal FKBP12.6, SERCA2a, and CASQ2 are consequent to ER stress and apoptosis that are likely due to an entity of inflammation. These abnormalities may be attributed to reactive oxygen species genesis from activated NADPH oxidase which could respond to argirein (AR) through its anti-inflammatory activity. Sprague Dawley rats were randomly divided into six groups. Except the normal group, rats were injected with streptozotocin (STZ; 60 mg/kg, i.p.) once. During weeks 5 to 8 following STZ injection, rats were treated (in milligrams per kilogram per day, i.g.) with aminoguanidine (AMG, 100; an inducible nitric oxide synthase and AGEs inhibitor) or three doses of AR (50, 100, and 200). FKBP12.6, SERCA2a, and CASQ2 and ER stress chaperones Bip and PERK and apoptotic molecules were monitored in vivo and in vitro. Impaired cardiac performance and downregulated FKBP12.6, SERCA2a, and CASQ2 were significant in DC in vivo, and abnormal calcium-handling proteins were also found in high-glucose-incubated myocytes in vitro. ER stress manifested by upregulated Bip and PERK was predominant in association with DNA ladder and upregulated Bax and downregulated BCL-2 in vivo and in vitro. AR is effective to attenuate these abnormalities compared to AMG. Diabetic myocardium has inflammatory entity expressed as ER stress contributing to downregulated calcium-handling proteins. AR has potential in managing DC through attenuating depressed calcium-handling proteins, activated ER stress, and apoptosis in the myocardium.     

Effects of aldose reductase inhibition on responses of the corpus cavernosum and mesenteric vascular bed of diabetic rats

We examined the effects of 2 months of streptozotocin-induced diabetes mellitus in rats on relaxation and contraction of corpus cavernosum and the mesenteric vascular bed in vitro. A further diabetic group was treated from diabetes induction with 10 mg/kg/day of the aldose reductase inhibitor, WAY121509. For corpus cavernosum, maximal acetylcholine-induced relaxation was 35.5% reduced (p < 0.001) by diabetes, and this deficit was completely prevented by WAY121509 treatment. Neither diabetes nor treatment affected contractile responses to field stimulation of noradrenergic nerves; however, nonadrenergic noncholinergic nerve relaxation responses were 32.9% decreased by diabetes and WAY 121509 attenuated this by 84% (p < 0.001). For the mesenteric vascular bed, diabetes depressed maximal endothelium-dependent vasodilation to acetylcholine by 25.2% (p < 0.001), and this was partially (50.6%; p < 0.01) prevented by WAY121509. Nitric oxide synthase blockade revealed endothelium-derived hyperpolarising factor-mediated vasodilation to acetylcholine that was 73.5% (p < 0.001) depressed by diabetes; WAY121509 provided partial (43.4%; p < 0.001) protection. Neither diabetes nor treatment affected endothelium-independent vasorelaxation to the nitric oxide donor, sodium nitroprusside, in corpus cavernosum or mesenteric vessels. Thus the data show protective effects of WAY121509 on nitric oxide-mediated cavernosal vasorelaxation responses and on mesenteric endothelium-derived hyperpolarising factor responses. Together these findings could account for the beneficial effects of aldose reductase inhibition on diabetic complications in experimental models.     

Comparison of sildenafil with strontium fructose diphosphate in improving erectile dysfunction against upregulated cavernosal NADPH oxidase, protein kinase Cε, and endothelin system in diabetic rats

Objectives Phosphodiesterase type 5 inhibitors are potent in relieving erectile dysfunction (ED), however, they are less satisfactory in diabetic patients, probably due to the pro‐inflammatory biomarkers caused by diabetes. Therefore, it was interesting to compare the effects of sildenafil with strontium fructose 1,6‐diphosphate (FDP‐Sr) on cavernosal vascular activity and expressions of pro‐inflammatory biomarkers in diabetic rats. Methods Male Sprague‐Dawley rats were injected with streptozocin (60 mg/kg, i.p.) to develop diabetes. The animals were diabetic for eight weeks with sildenafil (12 mg/kg per day) or FDP‐Sr (200 mg/kg per day) being administered for the last four of those eight weeks. Key findings Sildenafil was more effective in relieving reduced vascular dilatation (relevant to ED), but less in attenuating over‐expressions of NADPH oxidase p22, p47 and p67 subunits, and ET_A/BR (endothelin receptor type A and type B) in the diabetic cavernosum. In contrast, FDP‐Sr was less effective in improving ED, but more effective in normalizing the abnormal NADPH oxidase and ET_A/BR. Conclusions The activated NADPH oxidase and upregulated ET_AR and ET_BR due to diabetic lesions played a minor or moderate role in ED. By offering extra ATP, FPD‐Sr suppressed these abnormalities, however, sildenafil did not. A combined therapy of sildenafil with FDP‐Sr may be more effective in relieving ED in diabetic patients through normalizing pro‐inflammatory cytokines and improving the nitric oxide/cGMP pathway in the cavernosum.     

1,6-二磷酸果糖对糖尿病大鼠心肌超微结构及氧化应激的影响

目的 观察1,6-二磷酸果糖（FBP）对糖尿病大鼠心肌超微结构、氧化应激的影响.方法 将25只8周龄SPF级健康雄性SD大鼠按抽签法选择19只建立SD大鼠糖尿病模型,余下6只作为正常组.将造模成功的大鼠完全随机分成糖尿病组和FBP干预组（干预组,FBP 500 mg/kg·d腹腔注射）,糖尿病组及正常组给予等量生理盐水腹腔注射.1个月后处死大鼠,取心肌组织进行透射电镜（TEM）观察,并测定心肌组织内氧化应激指标后进行比较.结果 与正常组相比,糖尿病组大鼠心肌肌原纤维断裂,线粒体增多、空泡变性,毛细血管基底膜电子密度增加;丙二醛（MDA）含量、一氧化氮合成酶（NOS）及诱导性一氧化氮合成酶（iNOS）活性增加[（26.65±7.09）nmol/mg比（8.65±2.81）nmol/mg,（651.50±221.10）U/mg比（162.69±70.50）U/mg,（20.22±7.91）U/mg比（5.56±2.06）U/mg,P＜0.05].而干预组NOS及iNOS较糖尿病组降低（P＜0.05）.结论 FBP可以通过减轻氧化应激,减轻线粒体损伤,保护糖尿病大鼠心肌.     

氨基胍对糖尿病大鼠肾损害的治疗作用

目的通过探讨氨基胍（AG）对早期糖尿病（DM）大鼠一氧化氮（NO）、一氧化氮合酶（ni-tric oxi desynthase,NOS）活性及24h尿蛋白排泄量（24hUPE）的影响,了解氨基胍对糖尿病肾病的治疗作用。方法健康清洁级Wistar大鼠40只,检测24hUPE、血清NO水平、总一氧化氮合酶（total nitric oxide synthase,tNOS）和诱导型一氧化氮合酶（inducible nitric oxide synthase,iNOS）及结构型一氧化氮合酶（constructive nitric oxide synthase,cNOS）活性等5项指标后,用链脲佐菌素（Streptozotocin,STZ）60mg/kg制备成糖尿病大鼠模型,将糖尿病鼠随机分为糖尿病对照组、氨基胍组（AG组）。于8周末时再检测大鼠的上述5项指标并进行统计分析。结果①与造模前比较,DM对照组在8周末时24hUPE、NO和iNOS升高（P〈0.01,P〈0.05）;AG组24hUPE增加（P〈0.01）,tNOS、iNOS、cNOS降低（P〈0.01,P〈0.05）。②与DM对照组比较,8周末时AG组5项指标均下降（P〈0.05）。结论在糖尿病肾病（DN）的发展进程中,早期阶段应用AG可通过降低血NOS活性、NO生成量及其他机制,使24hUPE减少,减轻肾脏的损害。     

Protective effect of Liuwei Dihuang decoction on early diabetic nephropathy induced by streptozotocin via modulating ET-ROS axis and matrix metalloproteinase activity in rats

We aimed to investigate the effects of Liuwei Dihuang decoction (LW) on the endothelin-1-reactive oxidative species (ET-ROS) system and matrix metalloproteinases (MMPs) in the early diabetic nephropathy induced by streptozotocin (STZ) in rats. Rats were divided into six groups as follows: the control group, the untreated model group, the treated groups with the LW (5, 10 and 15 g kg(-1), p.o.) and the aminoguanidine-treated group (100 mg kg(-1), orally). The treatment was performed for 4 weeks, beginning on the fifth week after one intraperitoneal injection of STZ (65 mg kg(-1)). In the untreated model group, increased blood glucose, decreased plasma insulin level and an impaired renal function were observed. There was an altered redox system shown by an increased malondialdehyde and decreased activity of glutathione peroxidase and superoxide dismutase in the renal cortex. An enhanced inducible nitric oxide synthetase, total nitric oxide synthase and constitutive nitric oxide synthase and a declined nitric oxide were found. An increased extracellular matrix was indicated by an abnormality of MMP-2 and MMP-9 activities and an increase in hydroxyproline. An up-regulated ET-1 level and increased mRNA expression of endothelin-converting enzyme, preproET-1 and ET( A) receptor were presented in the affected renal cortex, but no change in ET(B) receptor mRNA. The LW was most effective in reversing these changes in diabetic rats and was as effective as aminoguanidine. The benefits of the extracts in relieving the abnormalities in early diabetic nephropathy are likely to be mediated by suppression of the renal ET-ROS system and escalating the activity of MMPs.     

ADM、NO及ADMR表达在糖尿病肾病中的变化及作用

目的探讨肾上腺髓质素（ADM）、一氧化氮（NO）及肾上腺髓质素受体（ADMR）在大鼠糖尿病肾病（DN）中的变化及作用。方法采用腹腔注射链脲佐菌素（STZ）制备糖尿病大鼠动物模型,随机分为对照组、糖尿病2周和4周组;采用RT-PCR和免疫组织化学方法检测肾皮质的AD-MRmRNA和蛋白的表达;同时检测大鼠的血糖、尿白蛋白排泄率（UAER）、尿量、肾重/体质量,以及肾皮质ADM与NO水平。结果注射STZ诱导糖尿病发生2周、4周后,与同批正常对照组比较,糖尿病组大鼠肾皮质的ADM、NO水平显著升高（P〈0.01）,肾皮质的ADMRmRNA和蛋白表达显著升高（P〈0.05）。结论糖尿病大鼠早期就有ADM、ADMR和NO的异常改变。提示ADM、ADMR以及NO可能参与糖尿病肾病的发生、发展过程。     

NaHS ameliorates diabetic vascular injury by correcting depressed connexin 43 and 40 in the vasculature in streptozotocin‐injected rats

Objectives Cardiovascular complication contributes an important role to morbidity and mortality in patients with diabetes. We hypothesized that these abnormalities are mainly mediated by oxidative stress, endothelial dysfunction and impaired intracellular communications. Thus, we examined vasoactivity and expression of connexin (Cx) 43 and 40, protein kinase C‐? (PKC?) and NADPH oxidase of the vasculature of thoracic aorta in streptozotocin (STZ)‐injected rats, and whether NaHS could reverse these abnormalities compared with aminoguanidine. Methods Male Sprague–Dawley rats were administered with STZ (60 mg/kg, i.p.) to induce diabetes. Diabetic rats were divided into untreated and treated groups in the 5th–8th week and intervention with either NaHS (5 mg/kg daily, s.c.) or aminoguanidine (100 mg/kg daily, p.o.) was made. Key findings In rats with untreated diabetes, hyperglycaemia, increased activity of inducible nitric oxide (NO) synthase, increased NO, mild vascular spasm, reduced NO bioavailability and diminished vasorelaxation were found. These findings were accompanied by downregulated Cx43 and Cx40, and upregulated PKC? and NADPH oxidase subunits p22^phox/p47^phox/p67^phox in the thoracic aorta. NaHS appears to be as effective as aminoguanidine in attenuating these abnormalities. Conclusions NaHS shows promise in relieving diabetic vascular abnormality by upregulating junctional connexin Cx40 and Cx43, via normalizing NADPH oxidase and PKC? in the vasculature.     

The effect of N-acetylcysteine on cardiac contractility to dobutamine in rats with streptozotocin-induced diabetes

We examined if myocardial depression at the acute phase of diabetes (3 weeks after injection of streptozotocin, 60 mg/kg i.v.) is due to activation of inducible nitric oxide synthase and production of peroxynitrite, and if treatment with N-acetylcysteine (1.2 g/day/kg for 3 weeks, antioxidant) improves cardiac function. Four groups of rats were used: control, N-acetylcysteine-treated control, diabetic and N-acetylcysteine-treated diabetic. Pentobarbital-anaesthetized diabetic rats, relative to the controls, had reduced left ventricular contractility to dobutamine (1-57 microg/min/kg). The diabetic rats also had increased myocardial levels of thiobarbituric acid reactive substances, immunostaining of inducible nitric oxide synthase and nitrotyrosine, and similar baseline 15-F2t-isoprostane. N-acetylcysteine did not affect responses in the control rats; but increased cardiac contractility to dobutamine, reduced myocardial immunostaining of inducible nitric oxide synthase and nitrotyrosine and level of 15-F2t-isoprostane, and increased cardiac contractility to dobutamine in the diabetic rats. Antioxidant supplementation in diabetes reduces oxidative stress and improves cardiac function.     

N-acetylcysteine prevents nitrosative stress-associated depression of blood pressure and heart rate in streptozotocin diabetic rats

Previous studies have indicated that cardiovascular abnormalities such as depressed blood pressure and heart rate occur in streptozotocin (STZ) diabetic rats. Chronic diabetes, which is associated with increased expression of inducible nitric oxide synthase (iNOS) and oxidative stress, may produce peroxynitrite/nitrotyrosine and cause nitrosative stress. We hypothesized that nitrosative stress causes cardiovascular depression in STZ diabetic rats and therefore can be corrected by reducing its formation. Control and STZ diabetic rats were treated orally for 9 weeks with N-acetylcysteine (NAC), an antioxidant and inhibitor of iNOS. At termination, the mean arterial blood pressure (MABP) and heart rate (HR) were measured in conscious rats. Nitrotyrosine and endothelial nitric oxide synthase (eNOS) and iNOS expression were assessed in the heart and mesenteric arteries by immunohistochemistry and Western blot experiments. Untreated diabetic rats showed depressed MABP and HR that was prevented by treatment with NAC. In untreated diabetic rats, levels of 15-F(2t)-isoprostane, an indicator of lipid peroxidation increased, whereas plasma nitric oxide and antioxidant concentrations decreased. Furthermore, decreased eNOS and increased iNOS expression were associated with elevated nitrosative stress in blood vessel and heart tissue of untreated diabetic rats. N-acetylcysteine treatment of diabetic rats not only restored the antioxidant capacity but also reduced the expression of iNOS and nitrotyrosine and normalized the expression of eNOS to that of control rats in heart and superior mesenteric arteries. The results suggest that nitrosative stress depress MABP and HR following diabetes. Further studies are required to elucidate the mechanisms involved in nitrosative stress mediated depression of blood pressure and heart rate.     

Effects of chronic administration of the novel endothelin antagonist J-104132 on endothelial dysfunction in streptozotocin-induced diabetic rat

1. The biosynthesis of endothelin-1 is increased in the diabetic state. So this peptide may cause diabetic vascular complications. We tested this possibility by chronically administering J-104132, a potent orally active mixed antagonist of endothelin A and B (ET(A)/ET(B)) receptors to streptozotocin (STZ)-induced diabetic rats and focusing on changes in endothelial function. 2. The acetylcholine (ACh)-induced endothelium-dependent relaxation was impaired in diabetic rats and this impairment was significantly attenuated following chronic administration of J-104132 (10 mg kg(-1), p.o., daily for 4 weeks). 3. In an in vitro experiment using aortae from diabetic rats, the ACh-induced relaxation was not changed by the presence of J-104132 (3 x 10(-9) M). 4. The expression levels of the mRNA for endothelial nitric oxide synthase was comparable among aortae from the three groups (control, diabetic and chronically J-104132-treated diabetic). 5. The amount of superoxide anion was significantly greater in aortae from diabetic rats than in controls. Chronic J-104132 treatment significantly decreased the level of superoxide anion in diabetic rats. 6. The expression of the p22phox mRNA for the NADH/NADPH oxidase subunit was significantly increased in STZ-induced diabetic rats and this increase was completely prevented by chronic administration of J-104132. 7. These results suggest that in STZ-induced diabetic rats, ET-1 may be directly involved in impairing endothelium-dependent relaxation via increased superoxide-anion production.     

去肾交感神经对2型糖尿病大鼠血管内皮细胞自噬及NLRP3活化的影响

目的 探讨去肾交感神经（RDN）对2型糖尿病（T2DM）大鼠血管内皮细胞自噬及核苷酸结合寡聚化结构域受体蛋白3（NLRP3）炎症小体活化的影响。方法 采用高脂饮食联合小剂量链脲佐菌素（STZ）腹腔注射制备T2DM大鼠模型。采用随机数字表法分为对照组（CON组）、糖尿病对照组（T2DM组）、双侧假手术组（Sham组）、双...     

Effects of telmisartan or amlodipine monotherapy versus telmisartan/amlodipine combination therapy on vascular dysfunction and oxidative stress in diabetic rats

Our previous studies identified potent antioxidant effects and improvement of vascular function by telmisartan therapy in experimental diabetes and nitrate tolerance. The present study compared the beneficial effects of single telmisartan or amlodipine versus telmisartan/amlodipine combination therapy (T+A) in streptozotocin (STZ)-induced type 1 diabetic rats. Male Wistar rats were injected once with STZ (60 mg/kg, i.v.) and 1 week later the drugs (telmisartan, amlodipine, or T+A) were administrated orally by a special diet (2.5–5 mg?kg^?1?day^?1) for another 7 weeks. We only observed a marginal beneficial on-top effect of T+A therapy over the single drug regimen that was most evident in the improvement of endothelial function (acetylcholine response) and less pronounced in the reduction of whole blood, vascular and cardiac oxidative stress (blood leukocyte oxidative burst, aortic dihydroethidine and 3-nitrotyrosine staining, as well as cardiac NADPH oxidase activity and uncoupling of endothelial nitric oxide synthase) in diabetic rats. These effects on oxidative stress parameters were paralleled by those on the expression pattern of NADPH oxidase and nitric oxide synthase isoforms. In addition, development of mild hypotension in the T+A-treated rats was observed. Reasons for this moderate synergistic effect of T+A therapy may be related to the potent beneficial effects of telmisartan alone and the fact that amlodipine and telmisartan share similar pathways to improve endothelial function. Moreover, hypotension in the T+A-treated rats could partially antagonize the beneficial additive effects by counter-regulatory mechanisms (e.g., activation of the renin–angiotensin–aldosterone system).     

Argirein alleviates diabetic nephropathy through attenuating NADPH oxidase,Cx43, and PERK in renal tissue

Diabetic nephropathy (DN) due to microvascular complication is a serious status characterized by continuously progressive until occurrence of the end stage of renal disease. It is attractive to investigate further mechanisms underlying the entity of DN and new drug discovery. We hypothesized that the entity of DN is inflammatory and is characterized by upregulated inflammatory/pro-inflammatory factors such as peroxisome proliferator-activated receptor alpha, NADPH oxidase, endoplasmic reticulum stress (ER stress), and endothelin receptor A (ET_A) and downregulated connexin 43 (Cx43) in the kidney. Aminoguanidine is a special blocker to advanced glycation end products and argirein, a new compound contains a molecule of rhein linked to l-arginine by a hydrogen bond. Rhein possesses anti-inflammatory activity and has been chemically modified to produce a new compound diacerein launched in European market for treating osteoarthritis. Argirein with two active molecules rhein and l-arginine may be effective in suppressing the inflammatory cytokines contributing to the pathogenesis of DN. With a single injection of streptozotocin 65 mg/kg, ip in rats, early diabetic nephropathy was produced and revealed as an increased microalbuminuria, elevated creatinine and urea in serum, associated with upregulation of mRNA and protein of NADPH oxidase p22phox, p47phox, and p67phox and ET_A, upregulated PKR-like eukaryotic initiation factor 2α kinase (PERK), and downregulated Cx43 in the renal tissue. Upregulation of PERK suggested that there is an ER stress involved in the diabetic kidney, along with an increase in inflammatory/pro-inflammatory factors indicating an entity of chronic inflammation. Abnormalities of biomarkers were blunted by either aminoguanidine or argirein significantly. The new compound argirein is potential in alleviating and retarding microvascular complications of diabetes such as DN in clinical settings.     

New 1,4‐Dihydropyridines Down‐regulate Nitric Oxide in Animals with Streptozotocin‐induced Diabetes Mellitus and Protect Deoxyribonucleic Acid against Peroxynitrite Action

Diabetes mellitus (DM) and its complications cause numerous health and social problems throughout the world. Pathogenic actions of nitric oxide (NO) are responsible to a large extent for development of complications of DM. Search for compounds regulating NO production in patients with DM is thus important for the development of pharmacological drugs. Dihydropyridines (1,4‐DHPs) are prospective compounds from this point of view. The goals of this study were to study the in vivo effects of new DHPs on NO and reactive nitrogen and oxygen species production in a streptozotocin (STZ)‐induced model of DM in rats and to study their ability to protect DNA against nocive action of peroxynitrite. STZ‐induced diabetes caused an increase in NO production in the liver, kidneys, blood and muscles, but a decrease in NO in adipose tissue of STZ‐treated animals. Cerebrocrast treatment was followed by normalization of NO production in the liver, kidneys and blood. Two other DHPs, etaftorone and fenoftorone, were effective in decreasing NO production in kidneys, blood and muscles of diabetic animals. Furthermore, inhibitors of nitric oxide synthase (NOS) and an inhibitor of xanthine oxidoreductase (XOR) decreased NO production in kidneys of diabetic animals. Treatment with etaftorone decreased expression of inducible NOS and XOR in kidneys, whereas it increased the expression of endothelial NOS. In vitro, the studied DHPs did not significantly inhibit the activities of NOS and XOR but affected the reactivity of peroxynitrite with DNA. These new DHPs thus appear of strong interest for treatment of DM complications.