Increased nitric oxide activity compensates for increased oxidative stress to maintain endothelial function in rat aorta in early type 1 diabetes

Nilotinib-induced alterations in endothelial cell function recapitulate clinical vascular phenotypes independent of ABL1

Nilotinib is a highly effective treatment for chronic myeloid leukemia but has been consistently associated with the development of nilotinib-induced arterial disease (NAD) in a subset of patients. To date, which cell types mediate this effect and whether NAD results from on-target mechanisms is unknown. We utilized human induced pluripotent stem cells (hiPSCs) to generate endothelial cells and vascular smooth muscle cells for in vitro study of NAD. We found that nilotinib adversely affects endothelial proliferation and migration, in addition to increasing intracellular nitric oxide. Nilotinib did not alter endothelial barrier function or lipid uptake. No effect of nilotinib was observed in vascular smooth muscle cells, suggesting that NAD is primarily mediated through endothelial cells. To evaluate whether NAD results from enhanced inhibition of ABL1, we generated multiple ABL1 knockout lines. The effects of nilotinib remained unchanged in the absence of ABL1, suggesting that NAD results from off- rather than on-target signaling. The model established in the present study can be applied to future mechanistic and patient-specific pharmacogenomic studies.

Effect of tocilizumab, an interleukin-6 inhibitor, on early stage streptozotocin-induced diabetic nephropathy in rats

The aim of this study was to examine the effect of tocilizumab, an interleukin-6 (IL-6) inhibitor on streptozotocin-induced diabetic nephropathy. Male Sprague-Dawley rats (n = 36) were distributed into six groups and treated for 4 weeks. Groups 1, 3, 5 received either saline, tocilizumab (2 mg/kg), or tocilizumab (8 mg/kg) injection intraperitoneally (i.p.), every 2 weeks, respectively. Groups 2, 4, 6 were rendered diabetic by a single i.p. injection of streptozotocin (65 mg/kg) and were treated as in groups 1, 3, 5, respectively. Biochemical parameters were measured in plasma, urine, and kidneys. In the untreated diabetic group, there was a significant decrease in body weight, polyuria, and increased kidney weight. There was increased urinary albumin/creatinine ratio (UACR) and N-acetyl-β-D-glucosaminidase (NAG)/creatinine ratio (UNCR). Streptozotocin also induced a significant increase in creatinine clearance. In addition, diabetes was associated with increased oxidative stress [reduced renal glutathione reductase (GR), superoxide dismutase (SOD), catalase activities, and increased malondialdhyde (MDA)] and increased plasma tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and nitric oxide (NO) concentrations. Kidneys from streptozotocin-treated rats showed marked vacuolation of the proximal tubular epithelium with focal tubular necrosis and the glomeruli showing increase in mesangial cells. Tocilizumab significantly mitigated the increase in UACR and UNCR, renal MDA, plasma TNF-α, IL-6 and NO levels, and the decrease in renal SOD and catalase activities in diabetic rats. Tocilizumab did not significantly improve creatinine clearance; however, it attenuated the histopathological changes induced by streptozotocin. This study shows that tocilizumab was able to ameliorate some of the changes seen in streptozotocin-induced early diabetic nephropathy in rats. This is mainly due to its anti-inflammatory and antioxidative effects.

Tocomin Restores Endothelium-Dependent Relaxation in the Diabetic Rat Aorta by Increasing NO Bioavailability and Improving the Expression of eNOS

We aimed to determine whether tocomin, an extract from palm oil that has a high tocotrienol content, was able to prevent diabetes-induced endothelial dysfunction. To induce type 1 diabetes streptozotocin (50 mg/kg) was injected into the tail vein of Wistar rats. Six weeks later the diabetic rats, and normal rats injected with citrate buffer, commenced treatment with tocomin (40 mg/kg/day sc) or its vehicle (peanut oil) for a further 4 weeks. Aortae isolated from diabetic rats had impaired acetylcholine (ACh)-induced endothelium-dependent relaxation compared to normal rat aortae but there was no change in endothelium-independent relaxation in response to sodium nitroprusside. By contrast, responses to ACh in aortae from diabetic rats treated with tocomin were not different to normal rats. In addition to impaired endothelium-dependent relaxation the diabetic aortae had increased expression of the NADPH oxidase Nox2 subunit, increased generation of superoxide and decreased expression of eNOS and all of these effects were prevented by tocomin treatment. Tocomin did not affect plasma glucose levels. The impaired response to ACh in vitro was maintained in the presence of TRAM-34 and apamin, selective inhibitors of calcium-activated potassium (K Ca ) channels, indicating diabetes impaired the contribution of NO to endothelium-dependent relaxation. By contrast, neither diabetes nor tocomin treatment influenced EDH-type relaxation as, in the presence of L-NNA, an inhibitor of eNOS, and ODQ, to inhibit soluble guanylate cyclase, responses to ACh were similar in all treatment groups. Thus tocomin treatment improves NO mediated endothelium dependent relaxation in aortae from diabetic rats associated with a decrease in vascular oxidant stress but without affecting hyperglycaemia.

The role of potassium channels in the endothelial dysfunction induced by periodontitis

OBJECTIVE

Periodontitis is associated with endothelial dysfunction, which is clinically characterized by a reduction in endothelium-dependent relaxation. However, we have previously shown that impairment in endothelium-dependent relaxation is transient. Therefore, we evaluated which mediators are involved in endothelium-dependent relaxation recovery.

MATERIAL AND METHODS

Rats were subjected to ligature-induced experimental periodontitis. Twenty-one days after the procedure, the animals were prepared for blood pressure recording, and the responses to acetylcholine or sodium nitroprusside were obtained before and 30 minutes after injection of a nitric oxide synthase inhibitor (L-NAME), cyclooxygenase inhibitor (Indomethacin, SC-550 and NS- 398), or calcium-dependent potassium channel blockers (apamin plus TRAM- 34). The maxilla and mandible were removed for bone loss analysis. Blood and gingivae were obtained for C-reactive protein (CRP) and myeloperoxidase (MPO) measurement, respectively.

RESULTS

Experimental periodontitis induces bone loss and an increase in the gingival MPO and plasmatic CRP. Periodontitis also reduced endothelium-dependent vasodilation, a hallmark of endothelial dysfunction, 14 days after the procedure. However, the response was restored at day 21. We found that endothelium-dependent vasodilation at day 21 in ligature animals was mediated, at least in part, by the activation of endothelial calcium-activated potassium channels.

CONCLUSIONS

Periodontitis induces impairment in endothelial-dependent relaxation; this impairment recovers, even in the presence of periodontitis. The recovery is mediated by the activation of endothelial calcium-activated potassium channels in ligature animals. Although important for maintenance of vascular homeostasis, this effect could mask the lack of NO, which has other beneficial properties.

The crosstalk of gut microbiota and chronic kidney disease: role of inflammation, proteinuria, hypertension, and diabetes mellitus

Chronic kidney disease (CKD) has been shown to result in profound changes in the composition and functions of the gut microbial flora which by disrupting intestinal epithelial barrier and generating toxic by-products contributes to systemic inflammation and the associated complications. On the other hand, emerging evidence points to the role of the gut microbiota in the development and progression of CKD by provoking inflammation, proteinuria, hypertension, and diabetes. These observations demonstrate the causal interconnection between the gut microbial dysbiosis and CKD. The gut microbiota closely interacts with the inflammatory, renal, cardiovascular, and endocrine systems via metabolic, humoral, and neural signaling pathways, events which can lead to chronic systemic inflammation, proteinuria, hypertension, diabetes, and kidney disease. Given the established role of the gut microbiota in the development and progression of CKD and its complications, favorable modification of the composition and function of the gut microbiome represents an appealing therapeutic target for prevention and treatment of CKD. This review provides an overview of the role of the gut microbial dysbiosis in the pathogenesis of the common causes of CKD including hypertension, diabetes, and proteinuria as well as progression of CKD.

The influence of silica nanoparticles on small mesenteric arterial function

Aim: To determine the influence of silica nanoparticles (SiNPs) on small arterial function; both ex vivo and in vivo. Methods: Mono-dispersed dye-encapsulated SiNPs (97.85 ± 2.26 nm) were fabricated and vasoconstrictor and vasodilator responses of mesenteric arteries assessed. Results: We show that while exposure to SiNPs under static conditions, attenuated endothelial dependent dilator responses ex vivo, attenuation was only evident at lower agonist concentrations, when exposed under flow conditions or after intravenous administration in vivo. Pharmacological inhibition studies suggest that SiNPs may interfere with the endothelial dependent hyperpolarizing factor vasodilator pathway. Conclusion: The dosage dependent influence of SiNPs on arterial function will help identify strategies for their safe clinical administration.

Reduced nitric oxide-mediated relaxation and endothelial nitric oxide synthase expression in the tail arteries of streptozotocin-induced diabetic rats

Diabetes is associated with endothelial dysfunction, which is characterized by impaired endothelium-dependent relaxations. The present study aimed to examine the role of nitric oxide (NO), prostacyclin and endothelium-dependent hyperpolarization (EDH), in the relaxation of ventral tail arteries of rats under diabetic conditions. Relaxations of tail arteries of control and diabetic rats were studied in wire myograph. Western blotting and immunostaining were used to determine the presence of proteins. Acetylcholine-induced relaxations were significantly smaller in arteries of diabetic compared to control rats (Rmax; 70.81 ± 2.48% versus 85.05 ± 3.15%). Incubation with the combination of non-selective cyclooxygenase (COX) inhibitor, indomethacin and potassium channel blockers, TRAM 34 and UCL 1684, demonstrated that NO-mediated relaxation was attenuated significantly in diabetic compared to control rats (Rmax; 48.47 ± 5.84% versus 68.39 ± 6.34%). EDH-type (in the presence of indomethacin and NO synthase inhibitor, LNAME) and prostacyclin-mediated (in the presence of LNAME plus TRAM 34 and UCL 1684) relaxations were not significantly reduced in arteries of diabetic compared to control rats [Rmax: (EDH; 17.81 ± 6.74% versus 34.16 ± 4.59%) (prostacyclin; 15.85 ± 3.27% versus 17.23 ± 3.75%)]. Endothelium-independent relaxations to sodium nitroprusside, salbutamol and prostacyclin were comparable in the two types of preparations. Western blotting and immunostaining indicated that diabetes diminished the expression of endothelial NO synthase (eNOS), while increasing those of COX-1 and COX-2. Thus, since acetylcholine-induced NO-mediated relaxation was impaired in diabetes because of reduced eNOS protein expression, pharmacological intervention improving NO bioavailability could be useful in the management of diabetic endothelial dysfunction.

Endothelial Dysfunction in Rheumatoid Arthritis: Mechanistic Insights and Correlation with Circulating Markers of Systemic Inflammation

Objectives

To determine mechanisms involved in endothelial dysfunction (ED) during the course of arthritis and to investigate the link between cytokines, chemokines and osteoprotegerin.

Approach and Results

Experiments were conducted on aortic rings at day 4 (preclinical), day 11 (onset of disease), day 33 (acute disease) and day 90 (chronic disease) after adjuvant-induced arthritis (AIA) in Lewis rats. At day 4, the unique vascular abnormality was a reduced norepinephrine-induced constriction. At day 11, endothelial function assessed by the relaxation to acetylcholine was normal despite increased cyclo-oxygenase-2 activity (COX-2) and overproduction of superoxide anions that was compensated by increased nitric oxide synthase (NOS) activity. At day 33, ED apparition coincides with the normalization of NOS activity. At day 90, ED was only observed in rats with a persisting imbalance between endothelial NOS and COX-2 pathways and higher plasma levels of IL-1β and TNFα. Plasma levels of IL-1β, TNFα and MIP-1α negatively correlated with Ach-induced relaxation throughout the course of AIA.

Conclusions

Our data identified increased endothelial NOS activity as an important compensatory response that opposes the ED in the early arthritis. Thereafter, a cross-talk between endothelial COX-2/NOS pathways appears as an important element for the occurrence of ED. Our results encourage determining the clinical value of IL-1β, TNFα and MIP-1α as biomarkers of ED in RA.

Antisense versus proopiomelanocortin mRNA reduces vascular risk in a murine model of type-2 diabetes following stress exposure in early post-natal life

Mechanisms of vascular complications in type-2 diabetes patients and animal models are matter of debate. We previously demonstrated that a double-stress model applied to male mice during nursing period produces enduring hyperfunction of endogenous opioid and adrenocorticotropin (ACTH)-corticosteroid systems, accompanied by type-2 diabetes-like alterations in adult animals. Administration of the opioid receptor antagonist naloxone, or of an antisense oligodeoxynucleotide versus proopiomelanocortin mRNA, capable to block the pro-opiomelanocortin-derived peptides β-endorphin and ACTH, selectively prevent these alterations. Here, we investigated alterations produced by our stress model on aorta endothelium-dependent relaxation and contractile responses. Mice, stressed during nursing period, showed in the adulthood hormonal and metabolic type-2 diabetes-like alterations, including hyperglycemia, increased body weight and increased plasma ACTH and corticosterone levels. Ex vivo isolated aorta rings, gathered from stressed mice, were less sensitive to noradrenaline-induced contractions versus controls. This effect was blocked by nitric-oxide synthase-inhibitor l-N(G)-nitroarginine added to bath organ solution. Aorta rings relaxation caused by acetylcholine was enhanced in stressed mice versus controls, but following treatment with the nitric-oxide donor sodium nitroprusside, concentration-relaxation curves in aorta from stressed groups were similar to controls. Therefore, vascular response alterations to physiologic-pharmacologic stimuli were apparently due to nitric-oxide hyperfunction-dependent mechanisms. Aorta functional alterations, and plasma stress hormones enhancement, were prevented in mice stressed and treated with antisense oligodeoxinucleotide, addressed to reduce ACTH- and corticosteroid-mediated hyperfunction. This study demonstrates the key role of ACTH-corticosteroid axis hyperfunction for the triggering of vascular conditions in male adult rodents following postnatal stress in a type-2 diabetes model.

Prolonged AMP-activated protein kinase induction impairs vascular functions

AMP-activated protein kinase (AMPK) is a regulator of cellular metabolism and is involved in the pathogenesis of several diseases, including type 2 diabetes and cardiovascular diseases. Data showing the effects of AMPK on vasculature are controversial. Therefore, the aim of this study was to determine the impact of prolonged AMPK activation on vascular functions. For this purpose we have examined the role of AMPK in endothelium-dependent and -independent relaxation and vascular contractions. For this, we incubated thoracic aortic rings, from rats, with AMPK activator 5-aminoimidazole-4-carboxamide-1-4-ribofuranoside (AICAR, 500 μmol/L or 2 mmol/L) in the presence or absence of AMPK inhibitor compound C (10 μmol/L). Next, cumulative dose–response curves to acetylcholine (ACh) (10−9−10−4 mol/L), nitroglycerine (NG) (10−9–3 × 10−5 mol/L), and noradrenaline (NA) (10−9−10−4 mol/L) were obtained. Endothelial nitric oxide synthase (eNOS) protein expression was determined. Our results show that endothelium-dependent relaxation was inhibited after AICAR treatment, and that this effect was reversed by AMPK inhibition. Moreover, AICAR enhanced the contractile response to NA and caused a decrease in eNOS protein expression. In conclusion, prolonged AMPK induction causes endothelial impairment, possibly via increased degradation and (or) reduced expression of eNOS.