Diabetes-induced Vascular Complications Research Articles

STING-mediated DNA damage response in diabetes-induced vascular complications

Abstract Background Hyperglycemia drives endothelial dysfunction, a key factor in the development of diabetes vascular complications. The stimulator of interferon genes (STING) signal, plays a crucial role in the immune system and is implicated in the pathogenesis of inflammatory diseases. Therefore we investigated the role of STING in endothelial dysfunction in streptozotocin (STZ)-induced diabetic mice. Methods and Results Diabetes was induced by single-dose administration of STZ in 8-week-old C57BL/6 and Sting-/- mice. STZ injection promoted the expression of STING and DNA damage markers in the aorta of C57BL/6 mice. Genetic deletion of STING ameliorated endothelial dysfunction as determined by vascular reactivity assay (P < 0.001) and increased aortic eNOS phosphorylation (P < 0.05) in STZ-injected mice. Stimulation of STING agonist (cGAMP), or mtDNA increased inflammatory molecules expression (e.g., VCAM1 and IFNB) and decreased eNOS phosphorylation in HUVECs. In ex-vivo experiments, cGAMP significantly impaired endothelial function which was ameliorated in the presence of an STING inhibitor or a neutralizing IFN-β antibody. Furthermore, the administration of STING inhibitor ameliorated endothelial dysfunction in STZ-induced diabetic mice (P < 0.01). Conclusion The DNA damage response regulated by STING aggravated diabetes-induced endothelial dysfunction. STING signaling may be a potential therapeutic target for diabetic vascular complications.

Effect of Type-2 Diabetes Mellitus on the Expression and Function of Smooth Muscle ATP-Sensitive Potassium Channels in Human Internal Mammary Artery Grafts.

Here we have shown for the first time altered expression of the vascular smooth muscle (VSM) KATP channel subunits in segments of the human internal mammary artery (HIMA) in patients with type-2 diabetes mellitus (T2DM). Functional properties of vascular KATP channels in the presence of T2DM, and the interaction between its subunits and endogenous ligands known to relax this vessel, were tested using the potassium (K) channels opener, pinacidil. HIMA is the most commonly used vascular graft in cardiac surgery. Previously it was shown that pinacidil relaxes HIMA segments through interaction with KATP (SUR2B/Kir6.1) vascular channels, but it is unknown whether pinacidil sensitivity is changed in the presence of T2DM, considering diabetes-induced vascular complications commonly seen in patients undergoing coronary artery bypass graft surgery (CABG). KATP subunits were detected in HIMA segments using Western blot and immunohistochemistry analyses. An organ bath system was used to interrogate endothelium-independent vasorelaxation caused by pinacidil. In pharmacological experiments, pinacidil was able to relax HIMA from patients with T2DM, with sensitivity comparable to our previous results. All three KATP subunits (SUR2B, Kir6.1 and Kir6.2) were observed in HIMA from patients with and without T2DM. There were no differences in the expression of the SUR2B subunit. The expression of the Kir6.1 subunit was lower in HIMA from T2DM patients. In the same group, the expression of the Kir6.2 subunit was higher. Therefore, KATP channels might not be the only method of pinacidil-induced dilatation of T2DM HIMA. T2DM may decrease the level of Kir6.1, a dominant subunit in VSM of HIMA, altering the interaction between pinacidil and those channels.

Traditional Chinese medicine and its active substances reduce vascular injury in diabetes via regulating autophagic activity.

Due to its high prevalence, poor prognosis, and heavy burden on healthcare costs, diabetic vascular complications have become a significant public health issue. Currently, the molecular and pathophysiological mechanisms underlying diabetes-induced vascular complications remain incompletely understood. Autophagy, a highly conserved process of lysosomal degradation, maintains intracellular homeostasis and energy balance via removing protein aggregates, damaged organelles, and exogenous pathogens. Increasing evidence suggests that dysregulated autophagy may contribute to vascular abnormalities in various types of blood vessels, including both microvessels and large vessels, under diabetic conditions. Traditional Chinese medicine (TCM) possesses the characteristics of "multiple components, multiple targets and multiple pathways," and its safety has been demonstrated, particularly with minimal toxicity in liver and kidney. Thus, TCM has gained increasing attention from researchers. Moreover, recent studies have indicated that Chinese herbal medicine and its active compounds can improve vascular damage in diabetes by regulating autophagy. Based on this background, this review summarizes the classification, occurrence process, and related molecular mechanisms of autophagy, with a focus on discussing the role of autophagy in diabetic vascular damage and the protective effects of TCM and its active compounds through the regulation of autophagy in diabetes. Moreover, we systematically elucidate the autophagic mechanisms by which TCM formulations, individual herbal extracts, and active compounds regulate diabetic vascular damage, thereby providing new candidate drugs for clinical treatment of vascular complications in diabetes. Therefore, further exploration of TCM and its active compounds with autophagy-regulating effects holds significant research value for achieving targeted therapeutic approaches for diabetic vascular complications.

To the Future: The Role of Exosome-Derived microRNAs as Markers, Mediators, and Therapies for Endothelial Dysfunction in Type 2 Diabetes Mellitus.

The prevalence of diabetes mellitus (DM) is increasing at a staggering rate around the world. In the United States, more than 30.3 million Americans have DM. Type 2 diabetes mellitus (T2DM) accounts for 91.2% of diabetic cases and disproportionately affects African Americans and Hispanics. T2DM is a major risk factor for cardiovascular disease (CVD) and is the leading cause of morbidity and mortality among diabetic patients. While significant advances in T2DM treatment have been made, intensive glucose control has failed to reduce the development of macro and microvascular related deaths in this group. This highlights the need to further elucidate the underlying molecular mechanisms contributing to CVD in the setting of T2DM. Endothelial dysfunction (ED) plays an important role in the development of diabetes-induced vascular complications, including CVD and diabetic nephropathy (DN). Thus, the endothelium provides a lucrative means to investigate the molecular events involved in the development of vascular complications associated with T2DM. microRNAs (miRNA) participate in numerous cellular responses, including mediating messages in vascular homeostasis. Exosomes are small extracellular vesicles (40-160 nanometers) that are abundant in circulation and can deliver various molecules, including miRNAs, from donor to recipient cells to facilitate cell-to-cell communication. Endothelial cells are in constant contact with exosomes (and exosomal content) that can induce a functional response. This review discusses the modulatory role of exosomal miRNAs and proteins in diabetes-induced endothelial dysfunction, highlighting the significance of miRNAs as markers, mediators, and potential therapeutic interventions to ameliorate ED in this patient group.

Synergistic effect of Ocimum Sanctum and Andrographis Paniculata against Diabetic Complications

The present study explored the effect of Ocimum sanctum, Andrographis paniculata and their combination for the management of experimental diabetic vascular complications. Diabetes associated dyslipidemia and free radical generation have been connected to the pathogenesis of diabetes-induced vascular complications. Ocimum sanctum, Andrographis paniculata, possess hypolipidemic and antioxidant property, thus we evaluated their vaso-protective potential. Hydroalcoholic extract of Ocimum sanctum (200 mg/kg p.o) and hydroalcoholic extract of Andrographis paniculata (400 mg/kg p.o) were noted to possess vascular protective potential in experimental chronic diabetes. Experimental diabetes mellitus was induced by Streptozotocin (55 mg/kg i.p., once) to Wistar rats. The induction of diabetes and its associated vascular complications were assessed biochemically. Diabetes-associated dyslipidemia and tissue oxidative stress were also assessed. Treatment of combination of Ocimum sanctum + Andrographis paniculata (300mg/kg p.o) was noted to be more efficient against the diabetes-induced vascular endothelial dysfunction and renal impairment as compared to either treatment with Ocimum sanctum (400mg/kg p.o) or Andrographis paniculata (200mg/kg p.o) or Lisinopril (1 mg/kg/day p.o.) (a reference agent). To conclude, diabetes associate oxidative stress and dyslipidemia are majorly accountable for the induction of vascular and renal impairment. The combination of Ocimum sanctum + Andrographis paniculata (300mg/kg p.o) shown the synergistic effect and may have prevented the progression of diabetes-induced vascular endothelial dysfunction and nephropathy by preventing the alteration lipid profile, restoring the serum nitrate/nitrite concentration, and decreasing the renal oxidative stress.

Endothelium-restricted endothelin-1 overexpression in type 1 diabetes worsens atherosclerosis and immune cell infiltration via NOX1.

NADPH oxidase (NOX) 1 but not NOX4-dependent oxidative stress plays a role in diabetic vascular disease, including atherosclerosis. Endothelin (ET)-1 has been implicated in diabetes-induced vascular complications. We showed that crossing mice overexpressing human ET-1 selectively in endothelium (eET-1) with apolipoprotein E knockout (Apoe-/-) mice enhanced high-fat diet-induced atherosclerosis in part by increasing oxidative stress. We tested the hypothesis that ET-1 overexpression in the endothelium would worsen atherosclerosis in type 1 diabetes through a mechanism involving NOX1 but not NOX4. Six-week-old male Apoe-/- and eET-1/Apoe-/- mice with or without Nox1 (Nox1-/y) or Nox4 knockout (Nox4-/-) were injected intraperitoneally with either vehicle or streptozotocin (55 mg/kg/day) for 5 days to induce type 1 diabetes and were studied 14 weeks later. ET-1 overexpression increased 2.5-fold and five-fold the atherosclerotic lesion area in the aortic sinus and arch of diabetic Apoe-/- mice, respectively. Deletion of Nox1 reduced aortic arch plaque size by 60%; in contrast, Nox4 knockout increased lesion size by 1.5-fold. ET-1 overexpression decreased aortic sinus and arch plaque alpha smooth muscle cell content by ∼35% and ∼50%, respectively, which was blunted by Nox1 but not Nox4 knockout. Reactive oxygen species production was increased two-fold in aortic arch perivascular fat of diabetic eET-1/Apoe-/- and eET-1/Apoe-/-/Nox4-/- mice but not eET-1/Apoe-/-/Nox1y/- mice. ET-1 overexpression enhanced monocyte/macrophage and CD3+ T-cell infiltration ∼2.7-fold in the aortic arch perivascular fat of diabetic Apoe-/- mice. Both Nox1 and Nox4 knockout blunted CD3+ T-cell infiltration whereas only Nox1 knockout prevented the monocyte/macrophage infiltration in diabetic eET-1/Apoe-/- mice. Endothelium ET-1 overexpression enhances the progression of atherosclerosis in type 1 diabetes, perivascular oxidative stress, and inflammation through NOX1.

455-P: Pan-ErbB Inhibition Attenuates Diabetes-Induced Vascular Dysfunction in an Experimental Model of Diabetes

The underlying mechanisms leading to diabetes-induced vascular complications are not fully understood. We have previously shown that epidermal growth factor receptor (EGFR), which is part of the four membered family of EGFR/ErbB receptor tyrosine kinases, appears to play a detrimental role. However, the role of the other ErbB family members (ErbB2, ErbB3, and ErbB4)- that regulate cell growth, proliferation, differentiation and apoptosis- is not fully known and was further evaluated in this study. In a streptozotocin-rat model of type 1 diabetes, 4-weeks of diabetes induced significant vascular dysfunction, as assessed by abnormally high vasoconstrictor responses to norepinephrine in the mesenteric vascular bed (MVB). Diabetes also led to increased phosphorylation of all ErbB receptors with subsequent increased phosphorylation of downstream ERK1/2 in the MVB. Chronic 4-week in vivo administration of a novel pan-ErbB inhibitor, generation 7 polyamidoamine dendrimer (G7PAMAM; 20mg/kg daily i.p), or the well-established pan-ErbB inhibitor, Genistein (1mg/kg i.p. alt diem) to diabetic rats led to a marked attenuation in the hyperphosphorylation of all ErbBs, ERK1/2 and to a significant correction in NE-mediated hyper-responsiveness of the diabetic MVB. Furthermore, pan-ErbB inhibitors attenuated high glucose-induced ErbBs-ERK1/2 signaling in primary vascular smooth muscle cells grown in high (25mM) glucose. These data show for the first time that pan-ErbB inhibition attenuates diabetes-induced vascular dysfunction in an experimental model of diabetes. Therefore, pan-ErbB inhibition might represent a novel strategy for the treatment of diabetes-induced vascular complications. Disclosure S. Akhtar: None. B. Chandrasekhar: None. I. Benter: None. Funding Qatar University (QUCG-CMED-19/20-3)

Mild Hypercaloric Intake is Associated with an Impaired Vascular Smooth Muscle Phenotype in Absence of Hyperglycemia: Potential Modulation by Anti‐diabetic Drugs

Cardiovascular disease is the leading cause of mortality and morbidity in diabetes. Diabetes‐induced vascular complications are associated with the contractile‐to‐synthetic phenotypic switch of the vascular smooth muscle cells (VSMCs). Emerging experimental and clinical data have shown that functionally impaired VSMCs contribute to the high incidence rates of macrovascular complications in diabetes. Moreover, a significant proportion of diabetic patients show signs of vascular impairment at initial presentation before prolonged exposure to hyperglycemia. The underlying mechanisms leading to VSMC deterioration, particularly in early stages of metabolic dysfunction, remain largely unknown. In this study, we have investigated VSMC phenotypic alterations in a model of early metabolic derangements. Rats fed a mild hypercaloric (MHC) diet were used at time points prior to the development of hyperglycemia. Aortic VSMCs were isolated from control rats, from MHC fed rats sacrificed after 4, 8, or 12 weeks of exposure. At twelve weeks, MHC‐fed rats did not show increased fasting or random blood glucose, impaired glucose tolerance, increased weight, or hypertension. The effect of a two‐week treatment with metformin and pioglitazone prior to sacrifice at the 12‐week time point was examined. A gradual reduction in VSMC activity in MTS assays was observed as a function of MHC‐feeding duration, with the sharpest decrease observed at 12 weeks. Cell cycle assays revealed no changes in cell proliferation indicating that the changes in MTS assays were rather a reduction in metabolic activity. Moreover, expression of VSMC contractile phenotype markers, a‐smooth muscle actin and calponin, decreased progressively with MHC feeding. Interestingly, in vivo treatment with non‐hypoglycemic doses of either metformin and pioglitazone, known to have positive vascular pleiotropic effects, restored VSMCs metabolic activity and contractile marker expression to control levels. Significantly, no changes were detected VSMC metabolic activity and contractile marker expression following in vitro exposure to either a range of concentrations of free fatty acids, to simulate the MHC diet effect, or to metformin or pioglitazone. The contrast between in vitro and in vivo results suggests a direct effect of lipids on VSMC phenotype and function is unlikely; however, the changes observed might be a result of a more complex interaction with more than one tissue type. We hypothesize that the observed effect of MHC diet is mediated by the induction of perivascular adipose inflammation. Studies are underway to verify this claim.Support or Funding InformationSupported by AUB MPP fund #320148This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Chronic administration of nano-sized PAMAM dendrimers in vivo inhibits EGFR-ERK1/2-ROCK signaling pathway and attenuates diabetes-induced vascular remodeling and dysfunction

We investigated whether chronic administration of nano-sized polyamidoamine (PAMAM) dendrimers can have beneficial effects on diabetes-induced vascular dysfunction by inhibiting the epidermal growth factor receptor (EGFR)-ERK1/2-Rho kinase (ROCK)—a pathway known to be critical in the development of diabetic vascular complications. Daily administration of naked PAMAMs for up to 4 weeks to streptozotocin-induced diabetic male Wistar rats inhibited EGFR-ERK1/2-ROCK signaling and improved diabetes-induced vascular remodeling and dysfunction in a dose, generation (G6 > G5) and surface chemistry-dependent manner (cationic > anionic > neutral). PAMAMs, AG1478 (a selective EGFR inhibitor), or anti-EGFR siRNA also inhibited vascular EGFR-ERK1/2-ROCK signaling in vitro. These data showed that naked PAMAM dendrimers have the propensity to modulate key (e.g. EGFR) cell signaling cascades with associated pharmacological consequences in vivo that are dependent on their physicochemical properties. Thus, PAMAMs, alone or in combination with vasculoprotective agents, may have a beneficial role in the potential treatment of diabetes-induced vascular complications.

Prostaglandin E1 Inhibited Diabetes-Induced Phenotypic Switching of Vascular Smooth Muscle Cells Through Activating Autophagy

Background/Aims: The phenotype switching of vascular smooth muscle cells (VSMCs) was associated with the onset or progression of the atherogenic process in type 2 diabetes mellitus (T2DM). Alprostadil (Prostaglandin E1, PGE1) as a bioactive drug had a protective effect on vascular function. However, it is unknown whether PGE1 inhibited the phenotype switching in VSMCs via autophagy, which played a protective role in the vascular complications of diabetes. Methods: The phenotype switching was induced by high glucose (HG, 25mM) in VSMCs, the protein expression was measured by western blot analysis and immunofluorescent staining. In vivo study, vascular lesion and dysfunction were produced in the rats fed with high fat diet (HFD) combined with low dose streptozotocin (STZ) administration. Results: The decrease of α-SMA and the increase of vimentin, collagen I and proliferating cell nuclear antigen (PCNA) were found in HG-treated VSMCs. Along with more abundance of p62, autophagy markers LC3B and Beclin-1 significantly decreased in VSMCs exposed to HG. Such abnormal changes were significantly reversed by PGE1, which mimicked the role of autophagy activator rapamycin and was dramatically counteracted by 3-methyladenine, an autophagy inhibitor. Furthermore, PGE1 suppressed the phosphorylation of AKT and mTOR, which negatively regulated autophagy level in VSMCs. In vivo study, PGE1 remarkably improved the endothelium-independent contraction of thoracic aorta and restored the expression of α-SMA, osteopontin, LC3B, phosphorylated mTOR in the artery media of T2DM rats. Conclusion: These results demonstrated that PGE1 maintained the phenotype of VSMCs via the AKT/mTOR-dependent autophagy, which prevented diabetes-induced vascular complications.

Abstract 080: Endothelin-1 Exaggerates Type-1 Diabetes-Accelerated Atherosclerosis Through NADPH Oxidase 1

Introduction: NADPH oxidase (NOX) 1 but not NOX4-dependent oxidative stress plays a role in diabetic vascular disease, including atherosclerosis. Endothelin (ET)-1 has been implicated in diabetes-induced vascular complications. We showed that crossing mice overexpressing ET-1 selectively in endothelium (eET-1) with apolipoprotein E knockout ( Apoe -/- ) mice exaggerated high-fat diet-induced atherosclerosis in part by increasing oxidative stress. We hypothesized that ET-1 overexpression in the endothelium would exaggerate diabetes-accelerated atherosclerosis through a mechanism involving NOX1 but not NOX4. Methods: Six-week-old male Apoe -/- mice, eET-1/ Apoe -/- and eET-1/ Apoe -/- mice deficient in Nox1 (eET-1/ Apoe -/- / Nox1 y/- ) or Nox4 (eET-1/ Apoe -/- / Nox4 -/- ) were rendered diabetic with 55 mg/kg/day streptozotocin (STZ) IP for 5 days and studied 14 weeks later. Aortic atherosclerotic lesions were quantified using Oil Red O staining. Monocyte/macrophage infiltration and alpha-smooth muscle actin area were determined by immunofluorescence in aortic atherosclerotic lesions. Plasma cholesterol, HDL and triglycerides were measured. Results: ET-1 overexpression exaggerated 2.5-fold the atherosclerotic lesion area of the aortic sinus in diabetic Apoe -/- mice (plaque area [x10 5 μm 2 ]: 5.3±0.2 vs 2.1±0.4, P <0.05), which was reduced ~35% by Nox1 (3.5±0.4 x10 5 μm 2 , P <0.05) but not Nox4 knockout (5.0±0.7 x10 5 μm 2 ). Monocyte/macrophage infiltration was reduced ~30% in diabetic eET-1/ Apoe -/- and eET-1/ Apoe -/- / Nox4 -/- mice (31±1 and 35±2 vs 48±5% of lesion area, P <0.05) but not eET-1/ Apoe -/- / Nox1 y/- mice (35±2%). ET-1 overexpression decreased alpha-smooth muscle actin content by ~35% (9±1 vs 14±2% of lesion area, P <0.05), which was blunted by Nox1 (15±2%, P <0.05) but not Nox4 knockout (9±1%). Plasma triglycerides were unaffected by ET-1 overexpression (3.4±0.3 vs 3.6±0.5 mmol/L) but reduced by Nox1 and Nox4 knockout (2.2±0.4 and 1.8±0.4 mmol/L, P <0.05). Plasma HDL and cholesterol were similar between groups. Conclusions: Endothelium ET-1 overexpression exaggerates diabetes-accelerated atherosclerosis and reduces plaque stability through NOX1.

PS 16-31 ENDOTHELIN-1 EXAGGERATES TYPE-1 DIABETES-ACCELERATED ATHEROSCLEROSIS THROUGH NADPH OXIDASES 1 AND 4

Objective: NADPH oxidase (NOX) 1 but not NOX4-dependent oxidative stress plays a role in diabetic vascular disease, including atherosclerosis. Endothelin (ET)-1 has been implicated in diabetes-induced vascular complications. We showed that crossing mice overexpressing ET-1 selectively in endothelium (eET-1) with apolipoprotein E knockout (Apoe−/−) mice exaggerated high-fat diet-induced atherosclerosis in part by increasing oxidative stress. We hypothesized that ET-1 overexpression in the endothelium would exaggerate diabetes-accelerated atherosclerosis through a mechanism involving NOX1 but not NOX4. Design and method: Six-week-old male Apoe−/− mice, eET-1/Apoe−/− and eET-1/Apoe−/− mice deficient in Nox1 (eET-1/Apoe−/−/Nox1y/−) or Nox4 (eET-1/Apoe−/−/Nox4−/−) were rendered diabetic with 55 mg/kg/day streptozotocin (STZ) IP for 5 days and studied 14 weeks later. Endothelial function and vascular remodeling were assessed in mesenteric arteries (MA) using pressurized myography. Aortic atherosclerotic lesions were quantified using Oil Red O staining. Results: Diabetic Apoe−/− mice presented an impaired maximal endothelium-dependent vasodilatory response to acetylcholine (21%), which was not observed in diabetic eET-1/Apoe−/−, eET-1/Apoe−/−/Nox1y/− or eET-1/Apoe−/−/Nox4−/− mice (99%). Endothelium-independent relaxation to the nitric oxide (NO) donor sodium nitroprusside was similar between groups. Blockade of NO synthase with L-NAME completely blunted endothelium-dependent relaxation to acetylcholine in diabetic eET-1/Apoe−/− mice, which was prevented by Nox1 but not by Nox4 knockout. ET-1 overexpression caused a 1.8-fold increase in MA media/lumen of diabetic Apoe−/− mice, which was further exaggerated 1.2-fold by Nox4 but not Nox1 knockout. ET-1 overexpression exaggerated > 2-fold the atherosclerotic lesion area in the aortic sinus in diabetic Apoe−/− mice, which was reduced ∼40% by Nox1 and Nox4 knockout. Conclusions: Increased levels of ET-1 exaggerate diabetes-accelerated atherosclerosis through NOX1 and NOX4, despite paradoxically improving endothelium-dependent relaxation in small arteries.

Abstract 068: Endothelin-1 Exaggerates Type-1 Diabetes-accelerated Atherosclerosis Through NADPH Oxidases 1 and 4

Objective: NADPH oxidase (NOX) 1 but not NOX4-dependent oxidative stress plays a role in diabetic vascular disease, including atherosclerosis. Endothelin (ET)-1 has been implicated in diabetes-induced vascular complications. We showed that crossing mice overexpressing ET-1 selectively in endothelium (eET-1) with apolipoprotein E knockout ( Apoe -/- ) mice exaggerated high-fat diet-induced atherosclerosis in part by increasing oxidative stress. We hypothesized that ET-1 overexpression in the endothelium would exaggerate diabetes-accelerated atherosclerosis through a mechanism involving NOX1 but not NOX4. Methods: Six-week-old male Apoe -/- mice, eET-1/ Apoe -/- and eET-1/ Apoe -/- mice deficient in Nox1 (eET-1/ Apoe -/- / Nox1 y/- ) or Nox4 (eET-1/ Apoe -/- / Nox4 -/- ) were rendered diabetic with 55 mg/kg/day streptozotocin (STZ) IP injections for 5 days and studied 14 weeks later. Endothelial function and vascular remodeling were assessed in mesenteric arteries (MA) using pressurized myography. Aortic atherosclerotic lesions were quantified using Oil Red O staining. Plasma cholesterol, HDL and triglycerides were measured. Results: Diabetic Apoe -/- mice presented an impaired endothelium-dependent vasodilatory response to acetylcholine, which was not observed in diabetic eET-1/ Apoe -/- , eET-1/ Apoe -/- / Nox1 y/- or eET-1/ Apoe -/- / Nox4 -/- mice (E max : 20±6 vs 99±1, 98±1 and 100±0%). ET-1 overexpression caused a 1.8-fold increase in MA media/lumen of diabetic Apoe -/- mice (5.3±0.3 vs 2.9±0.2%), which was further increased 1.2-fold by Nox4 (6.4±0.3%) but not Nox1 knockout (5.5±0.3%). ET-1 overexpression exaggerated >2-fold the atherosclerotic lesion area in the aortic sinus in diabetic Apoe -/- mice (plaque area [x10 5 μm 2 ]: 5.3±0.5 vs 2.9±0.6), which was reduced ~40% by Nox1 and Nox4 knockout (plaque area [x10 5 μm 2 ]: 3.3±0.6 and 3.6±0.6). Plasma triglycerides were unaffected by ET-1 overexpression but reduced by Nox1 (2.2±0.4 vs 3.4±0.3 mmol/L) and Nox4 knockout (1.8±0.4 mmol/L). Plasma HDL and cholesterol were similar between groups. Conclusions: Increased levels of ET-1 exaggerate diabetes-accelerated atherosclerosis through NOX1 and NOX4, despite paradoxically improving endothelium-dependent relaxation in small arteries.

Transactivation of ErbB Family of Receptor Tyrosine Kinases Is Inhibited by Angiotensin-(1-7) via Its Mas Receptor.

Transactivation of the epidermal growth factor receptor (EGFR or ErbB) family members, namely EGFR and ErbB2, appears important in the development of diabetes-induced vascular dysfunction. Angiotensin-(1–7) [Ang-(1–7)] can prevent the development of hyperglycemia-induced vascular complications partly through inhibiting EGFR transactivation. Here, we investigated whether Ang-(1–7) can inhibit transactivation of ErbB2 as well as other ErbB receptors in vivo and in vitro. Streptozotocin-induced diabetic rats were chronically treated with Ang-(1–7) or AG825, a selective ErbB2 inhibitor, for 4 weeks and mechanistic studies performed in the isolated mesenteric vasculature bed as well as in cultured vascular smooth muscle cells (VSMCs). Ang-(1–7) or AG825 treatment inhibited diabetes-induced phosphorylation of ErbB2 receptor at tyrosine residues Y1221/22, Y1248, Y877, as well as downstream signaling via ERK1/2, p38 MAPK, ROCK, eNOS and IkB-α in the mesenteric vascular bed. In VSMCs cultured in high glucose (25 mM), Ang-(1–7) inhibited src-dependent ErbB2 transactivation that was opposed by the selective Mas receptor antagonist, D-Pro7-Ang-(1–7). Ang-(1–7) via Mas receptor also inhibited both Angiotensin II- and noradrenaline/norephinephrine-induced transactivation of ErbB2 and/or EGFR receptors. Further, hyperglycemia-induced transactivation of ErbB3 and ErbB4 receptors could be attenuated by Ang-(1–7) that could be prevented by D-Pro7-Ang-(1–7) in VSMC. These data suggest that Ang-(1–7) via its Mas receptor acts as a pan-ErbB inhibitor and might represent a novel general mechanism by which Ang-(1–7) exerts its beneficial effects in many disease states including diabetes-induced vascular complications.

Abstract 344: Endothelin-1 Overexpression Exaggerates Diabetes-induced Endothelial Dysfunction

Objective: Vascular disease associated with endothelial dysfunction is a major cause of morbidity in patients with type-1 diabetes. Endothelin (ET)-1 plays a role in diabetes-induced vascular complications, since ET-1 type A receptor blockade reduces diabetes-induced vascular injury. However, whether ET-1 contributes to diabetes-induced endothelial dysfunction remains unproven. We hypothesized that vascular ET-1 overexpression will exaggerate diabetes-induced endothelial dysfunction. Methods: Diabetes was induced by streptozotocin treatment (STZ, 55 mg/kg/day, ip) for 5 days in 6-week-old male wild-type (WT) mice and in mice overexpressing ET-1 restricted to the endothelium (eET-1). Mice were studied 14 weeks later. Blood was collected to determine glucose. Mesenteric artery reactivity and remodeling were evaluated using pressurized myography and aortic fibronectin expression by immnunofluorescence. Results: STZ-induced diabetes was confirmed by a 3-fold increase in glycemia in WT and eET-1 ( P <0.001). Diabetes impaired endothelium-dependent relaxation (EDR) reponses to acetylcholine in WT (60.9±6.4% vs 83.9±3.4%, P <0.05) and eET-1 (48.6±5.1% vs 81.5±5.2%, P <0.001). EDR impairment was exaggerated in eET-1 compared to WT ( P <0.05). Meclofenamic acid, an inhibitor of cyclooxygenase, increased EDR in eET-1 compared to WT (78.4±9.4% vs 66.7±3.2%, P <0.01), which was not observed in diabetic mice. L-NAME, an inhibitor of nitric oxide (NO) synthase, completely blocked EDR in WT, eET-1 and diabetic WT, but not in diabetic eET-1 (4.1±1.6%, 6.4±5.7%, 2.2±4.6% and 26.6±4.6%, P <0.05). Apamin plus Tram34, inhibitors of endothelium-dependent hyperpolarization inhibited EDR in the four groups. Endothelium-independent relaxation to sodium nitroprusside, a NO donor, was similar in the four groups. Diabetes reduced media/lumen in WT (2.7±0.3 vs 3.6±0.3, P <0.05) and eET-1 (2.9±0.2 vs 3.8±0.3, P <0.05). Diabetes decreased aortic fibronectin expression in WT (94.0±11.0 vs. 151.9±21.8 RFU/μm 2 , P <0.05) and eET-1 (66.3±8.7 vs. 146.6±20.7 RFU/μm 2 , P <0.05). Conclusion: ET-1 contributes to alterations in several pathways mediating endothelium-dependent relaxation in type-1 diabetes, leading to exaggerated endothelial dysfunction.

Phenotypic Modulation of Mesenteric Vascular Smooth Muscle Cells from Type 2 Diabetic Rats is Associated with Decreased Caveolin-1 Expression

Aims: Diabetes-induced vascular complications are associated with vascular smooth muscle cell (VSMC) phenotypic modulation, switching from a contractile to a synthetic-proliferative phenotype. Loss of caveolin-1 is involved with proliferation of VSMCs. We tested the hypothesis that mesenteric VSMCs from type 2 diabetic Goto-Kakizaki (GK) rat undergo phenotypic modulation and it is linked to decreased caveolin-1 expression. Methods: VSMCs were isolated from mesenteric arteries from GK rats and age-matched control Wistar rats. Western blotting was used to determine expression of target proteins such as caveolin-1, calponin (marker of differentiation), and proliferating cell nuclear antigen (PCNA, marker of proliferation). In addition, we measured intracellular reactive oxygen species (ROS) production using H2DCF-DA and activation of extracellular signal-regulated kinase (ERK1/2) by western blotting in VSMCs from GK stimulated with lipopolysaccharide (LPS), an endotoxin upregulated in diabetes. Results: Mesenteric VSMCs from diabetic GK rats exhibited decreased caveolin-1 and calponin expression and increased PCNA expression compared to control. Increased levels of ROS and phospho-ERK1/2 expression were also found in GK VSMCs. LPS augmented ROS and phosphorylated ERK1/2 levels to a greater extent in GK VSMCs than in control. Likewise, high glucose decreased caveolin-1 and calponin expression, increased PCNA expression and augmented ROS production in control mesenteric VSMCs. Conclusion: These results suggest that mesenteric VSMCs from diabetic GK rats undergo phenotypic modulation and it is associated with decreased caveolin-1 expression. These alterations may be due to enhanced inflammatory stimuli and glucose levels present in diabetic milieu.

Activation of ErbB2 and Downstream Signalling via Rho Kinases and ERK1/2 Contributes to Diabetes-Induced Vascular Dysfunction.

Diabetes mellitus leads to vascular complications but the underlying signalling mechanisms are not fully understood. Here, we examined the role of ErbB2 (HER2/Neu), a transmembrane receptor tyrosine kinase of the ErbB/EGFR (epidermal growth factor receptor) family, in mediating diabetes-induced vascular dysfunction in an experimental model of type 1 diabetes. Chronic treatment of streptozotocin-induced diabetic rats (1 mg/kg/alt diem) or acute, ex-vivo (10−6, 10−5 M) administration of AG825, a specific inhibitor of ErbB2, significantly corrected the diabetes-induced hyper-reactivity of the perfused mesenteric vascular bed (MVB) to the vasoconstrictor, norephinephrine (NE) and the attenuated responsiveness to the vasodilator, carbachol. Diabetes led to enhanced phosphorylation of ErbB2 at multiple tyrosine (Y) residues (Y1221/1222, Y1248 and Y877) in the MVB that could be attenuated by chronic AG825 treatment. Diabetes- or high glucose-mediated upregulation of ErbB2 phosphorylation was coupled with activation of Rho kinases (ROCKs) and ERK1/2 in MVB and in cultured vascular smooth muscle cells (VSMC) that were attenuated upon treatment with either chronic or acute AG825 or with anti-ErbB2 siRNA. ErbB2 likley heterodimerizes with EGFR, as evidenced by increased co-association in diabetic MVB, and further supported by our finding that ERK1/2 and ROCKs are common downstream effectors since their activation could also be blocked by AG1478. Our results show for the first time that ErbB2 is an upstream effector of ROCKs and ERK1/2 in mediating diabetes-induced vascular dysfunction. Thus, potential strategies aimed at modifying actions of signal transduction pathways involving ErbB2 pathway may prove to be beneficial in treatment of diabetes-induced vascular complications.

Mechanisms Underlying Sesamolin-Induced Attenuation of Vascular Dysfunction in Rats With Streptozotocin-Induced Diabetes

: Background: Cardiovascular disorders constitute the major causes of morbidity and mortality among diabetic patients.Objectives: The effect of chronic sesamolin administration was studied on aortic reactivity of rats with streptozotocin (STZ)-induced diabetesMaterials and Methods: One week after induction of diabetes, male rats received sesamolin for 7 weeks. The contractile responses to KCl and phenylephrine (PE) and the relaxation response to acetylcholine (ACh) were measured in aortic rings.Results: The maximum contractile response to PE of endothelium-intact aortic rings was significantly lower in sesamolin-treated diabetic rats than in untreated diabetic rats. Removal of the endothelium from the aortic rings abolished this difference. The endothelium-dependent relaxation response to ACh was significantly higher in sesamolin-treated diabetic rats than in untreated diabetic rats. Pretreatment of aortic rings with the nitric oxide synthase inhibitor N(G) -nitro-L-arginine methyl ester (L-NAME) significantly attenuated the observed response. A 2-month course of diabetes also resulted in elevated malondialdehyde (MDA) and decreased superoxide dismutase (SOD) activity; sesamolin treatment reversed the increased MDA level and reversed the reduced SOD activityConclusions: We conclude that chronic treatment of diabetic rats with sesamolin can prevent abnormal changes in vascular reactivity via nitric oxide regulation and attenuation of oxidative stress in aortic tissue. Furthermore, endothelial integrity is necessary for sesamolin’s beneficial effect. Implication for health policy/practice/research/medical education:This study has potential application in development of new treatment strategies for attenuation of diabetes-induced vascular complications. Please cite this paper as:Mechanisms Underlying Sesamolin-Induced Attenuation of Vascular Dysfunction in Rats With Streptozotocin-Induced Diabetes. Int J Endocriol Metab.2011;9(2):311-6. DOI: 10.5812/kowsar.1726913X.2380 Copyright © 2011, Kowsar M.P.Co. All rights reserved.

Sphingosine-1-phosphate induced vasoconstriction is increased in the isolated perfused kidneys of diabetic rats

We observed that in isolated perfused rat kidneys, sphingosine-1-phosphate produces S1P 2 receptor-mediated vasoconstriction, and this response increased in kidneys of diabetic rats. These results suggest that the antagonists of S1P 2 receptor may have potential as drugs to control diabetes-induced vascular complications.

Section-illumination photoacoustic microscopy for dynamic 3D imaging of microcirculation in vivo

We developed section-illumination photoacoustic microscopy capable of dynamic in vivo imaging of microvessels as small as 30 microm in diameter. The section illumination improved the elevational resolution while an ultrasound array provided the in-plane axial and lateral resolutions. Using the imaging system, we monitored the wash-in dynamics of Evans Blue in the microcirculation of mouse ears at 249 Hz 2D and 0.5 Hz 3D image acquisition rates. Such observation allowed us to differentiate the arterioles from the venules. In the future, the technology may be used to study angiogenesis, diabetes-induced vascular complications, and pharmacokinetics.