Haem oxygenase-1 induction protects against tumour necrosis factor alpha impairment of endothelial-dependent relaxation in rat isolated pulmonary artery

The effects of pentoxifylline and caffeic acid phenethyl ester on TNF-α and lung histopathology in D-galactosamine-induced pulmonary injury in rats

In this study, we aimed to investigate the effects of pentoxifylline [PTX] and caffeic acid phenethyl ester [CAPE] in D-galactosamine [D-GAL]-induced pulmonary injury in rats. The rats were randomly divided into six groups: control, D-GAL, D-GAL+PTX, D-GAL+CAPE, PTX and CAPE. Each group included eight animals. Lung sections from the control, PTX and CAPE groups had a normal histological appearance. The D-GAL group showed histopathological changes in lung tissue, including haemorrhage, oedema, inter-alveolar septal thickening and widespread infiltration of inflammatory lymphocytes and macrophages. Administration of PTX and CAPE significantly reduced histopathological damage scores in the D-GAL+PTX and D-GAL+CAPE groups compared with the D-GAL group. PTX and CAPE treatment also significantly decreased malondialdehyde levels, increased levels of reduced GSH and increased catalase and superoxide dismutase activity in lung tissue samples. These results indicate that the destructive effects of D-GAL-induced inflammation in the rat lung are significantly reduced following administration of PTX and CAPE.

A Nano-Pharmaceutical Formula of Quercetin Protects from Cardiovascular Complications Associated with Metabolic Syndrome

Metabolic syndrome (MetS) is closely associated with the development of cardiovascular diseases. We recently developed a nano-preparation of the flavonoid quercetin (QU) in a self-nanoemulsifying drug delivery system (SNEDDS). The latter comprised a mixture composed of pumpkin seed oil, D-α-Tocopherol polyethylene glycol 1,000 succinate and polyethylene glycol. The QU SNEDDS preparations exhibited a considerably higher bioavailability compared with the standard quercetin suspension. Here, we investigated whether the quercetin loaded SNEDDS could offer better protection compared with the standard formulation against cardiovascular complications of MetS in rats. MetS was induced by high fructose, high salt and high fat diet for 12 weeks while the nano-preparation or the standard suspension of quercetin was orally administered for the last 6 weeks. Compared to little effect for the standard quercetin suspension (MQ), the treatment of MetS rats with the quercetin loaded SNEDDS (MNQ) virtually abolished the depressant effect of MetS on contractility index (control, 114 ± 4; MetS, 92 ± 3; MQ, 100 ± 2; MNQ, 114 ± 6 1/s) and rate of rise in left ventricular pressure (dP/dtmax) (control, 8,171 ± 274; MetS, 6,664 ± 135; MQ, 6,776 ± 108; MNQ, 7,498 ± 303 mmHg/s). Likewise, the prolongation by MetS of electrocardiographic markers of arrhythmogenesis (QTc, JT, and Tpeak-to-Tend intervals) and concomitant rises in dicrotic notch pressure were preferentially reversed by quercetin nano-preparation. On the other hand, the rises in the isovolumic relaxation constant (Tau, denotes diastolic dysfunction), blood pressure, pulse pressure, and difference between systolic and dicrotic pressure (SDP difference) were equally improved by the two preparations of quercetin. Additionally, no differences were noted in the ability of the two quercetin preparations in abrogating the elevated oxidative (MDA) and inflammatory (TNFα) markers in cardiac tissues of MetS rats. Histopathological, microscopical signs of necrosis, inflammatory cell infiltration, and vascular congestion in MetS hearts were more markedly inhibited by the nano-preparation, compared with the standard preparation of quercetin. In conclusion, the quercetin loaded SNEDDS is evidently more advantageous than the standard preparation of the drug in alleviating functional and histopathological manifestations of cardiac damage incited by MetS.

Interference with AGEs formation and AGEs-induced vascular injury mediates curcumin vascular protection in metabolic syndrome

Vascular dysfunction predisposes to cardiovascular complications of metabolic syndrome (MetS). The current study investigated the mechanism(s) of curcumin's (CUR) protective effect against vascular reactivity irregularities in MetS. MetS was induced by feeding rats on high fructose high salt diet. Tension studies were undertaken in aortic rings to assess the influence of CUR on vasoconstrictor or vasorelaxant responses. The effect on advanced glycation endproducts (AGEs) was studied by incubating aortic tissues with methylglyoxal, the AGEs precursor, in the absence and presence of CUR. In addition, CUR effects on in-vitro generation of AGEs and diphenyl-2-picrylhydrazyl (DPPH) free radicals were studied. The incubation with CUR for 1 hr produced significant and concentration-dependent alleviation of the exaggerated vasoconstriction observed in aortas isolated from MetS, however failed to improve the concomitant attenuation of vasodilatory responses to ACh in PE-precontracted aortas. By contrast, CUR caused direct concentration-dependent vasodilations of precontracted aortas, effects that were blunted after nitric oxide synthase inhibition by L-NAME. Similar to its effects in MetS aortas, CUR alleviated exaggerated PE vasoconstriction but did not affect impaired ACh vasodilations in AGEs-exposed aortas. In addition, CUR showed significant dose-dependent DPPH free radicals scavenging activity and inhibited both MG and fructose induced AGEs formation at the level of protein oxidation step as evident from the effect on dityrosine and N-formylkyramine. CUR alleviates exaggerated vasoconstriction in MetS through interfering with AGEs formation and AGEs-induced vascular injury. Free radical scavenging and direct vasodilatory activities could also participate in the advantageous vascular actions of CUR.

Curcumin and Heme Oxygenase: Neuroprotection and Beyond

Curcumin is a natural polyphenol component of Curcuma longa Linn, which is currently considered one of the most effective nutritional antioxidants for counteracting free radical-related diseases. Several experimental data have highlighted the pleiotropic neuroprotective effects of curcumin, due to its activity in multiple antioxidant and anti-inflammatory pathways involved in neurodegeneration. Although its poor systemic bioavailability after oral administration and low plasma concentrations represent restrictive factors for curcumin therapeutic efficacy, innovative delivery formulations have been developed in order to overwhelm these limitations. This review provides a summary of the main findings involving the heme oxygenase/biliverdin reductase system as a valid target in mediating the potential neuroprotective properties of curcumin. Furthermore, pharmacokinetic properties and concerns about curcumin's safety profile have been addressed.

Arginase overexpression and NADPH oxidase stimulation underlie impaired vasodilation induced by advanced glycation end products

BACKGROUND

Advanced glycation endproducts (AGEs) play a major role in the development of many vascular complications that are mediated by endothelial dysfunction. The present work aimed to investigate the mechanism by which AGEs impair vasodilation.

METHODS

The effect of AGEs on vasodilation induced by acetylcholine or D NONOate was examined by incubating isolated rat aortae with different AGEs concentrations. ACh-induced nitric oxide generation was assessed using the fluorescent probe diaminofluorecein (DAF-FM). The effect of AGEs on expression of mRNA for arginase 2, NADPH oxidase and endothelial nitric oxide synthase (eNOS) were determined by real-time PCR.

RESULTS

One-hour in vitro incubation of rat aortae with AGEs impaired endothelial-dependent vasodilation produced by ACh, while increasing D NONOate-induced vasodilation. Preincubation of aortae with l-ornithine, an arginase 2-inhibitor, prevented the impairment effect induced by AGEs on endothelial-dependent vasodilation. Superoxide scavenging by tempol or NADPH oxidase inhibition by apocynin also blocked the effect of AGEs. AGEs decreased ACh-induced NO production and this was inhibited by both l-ornithine and apocynin. Furthermore, AGEs exposure increased arginase mRNA expression but decreased mRNA expression for eNOS in isolated rat aortae.

CONCLUSION

The present results indicate that AGEs impairs endothelial-dependent vasodilation, and this effect is mediated via arginase overexpression and NADPH oxidase stimulation.

Inhibition of miR-92a Suppresses Oxidative Stress and Improves Endothelial Function by Upregulating Heme Oxygenase-1 in db/db Mice

AIMS

Inhibition of microRNA-92a (miR-92a) is reported to suppress endothelial inflammation and delay atherogenesis. We hypothesize that miR-92a inhibition protects endothelial function through suppressing oxidative stress in diabetic db/db mice.

RESULTS

In this study, we found elevated expression of miR-92a in aortic endothelium from db/db mice and in renal arteries from diabetic subjects. Endothelial cells (ECs) exposed to advanced glycation end products (AGEs) and oxidized low-density lipoprotein express higher level of miR-92a. Overexpression of miR-92a impairs endothelium-dependent relaxations (EDRs) in C57BL/6 mouse aortas. Overexpression of miR-92a suppresses expression of heme oxygenase-1 (HO-1), a critical cytoprotective enzyme, whereas inhibition of miR-92a increases HO-1 expression in human umbilical vein ECs (HUVECs) and db/db mouse aortas. Importantly, miR-92a inhibition by Ad-anti-miR-92a improved EDRs and reduced reactive oxygen species (ROS) production in db/db mouse aortas. HO-1 inhibition by SnMP or HO-1 knockdown by shHO-1 reversed the suppressive effect of miR-92a inhibition on ROS production induced by AGE treatment in C57BL/6 mouse aortas. In addition, SnMP reversed miR-92a inhibition-induced improvement of EDRs in AGE-treated C57BL/6 mouse aortas and in db/db mouse aortas.

INNOVATION

Expression of miR-92a is increased in diabetic aortic endothelium and inhibition of miR-92a exerts vasoprotective effect in diabetic mice through HO-1 upregulation in ECs.

CONCLUSION

MiR-92a expression is elevated in diabetic ECs. MiR-92a overexpression impairs endothelial function and suppresses HO-1 expression in ECs. Inhibition of miR-92a attenuates oxidative stress and improves endothelial function through enhancing HO-1 expression and activity in db/db mouse aortas. Antioxid. Redox Signal. 28, 358-370.

Curcumin supplementation improves vascular endothelial function in healthy middle-aged and older adults by increasing nitric oxide bioavailability and reducing oxidative stress

We hypothesized that curcumin would improve resistance and conduit artery endothelial function and large elastic artery stiffness in healthy middle-aged and older adults. Thirty-nine healthy men and postmenopausal women (45-74 yrs) were randomized to 12 weeks of curcumin (2000 mg/day Longvida®; n=20) or placebo (n=19) supplementation. Forearm blood flow response to acetylcholine infusions (FBF_ACh; resistance artery endothelial function) increased 37% following curcumin supplementation (107±13 vs. 84±11 AUC at baseline, P=0.03), but not placebo (P=0.2). Curcumin treatment augmented the acute reduction in FBF_ACh induced by the nitric oxide synthase inhibitor NG monomethyl-L-arginine (L-NMMA; P=0.03), and reduced the acute increase in FBF_ACh to the antioxidant vitamin C (P=0.02), whereas placebo had no effect (both P>0.6). Similarly, brachial artery flow-mediated dilation (conduit artery endothelial function) increased 36% in the curcumin group (5.7±0.4 vs. 4.4±0.4% at baseline, P=0.001), with no change in placebo (P=0.1). Neither curcumin nor placebo influenced large elastic artery stiffness (aortic pulse wave velocity or carotid artery compliance) or circulating biomarkers of oxidative stress and inflammation (all P>0.1). In healthy middle-aged and older adults, 12 weeks of curcumin supplementation improves resistance artery endothelial function by increasing vascular nitric oxide bioavailability and reducing oxidative stress, while also improving conduit artery endothelial function.

Tissue heme oxygenase-1 exerts anti-inflammatory effects on LPS-induced pulmonary inflammation

Heme oxygenase-1 (HO-1) has been shown to display anti-inflammatory properties in models of acute pulmonary inflammation. For the first time, we investigated the role of leukocytic HO-1 using a model of HO-1(flox/flox) mice lacking leukocytic HO-1 that were subjected to lipopolysaccharide (LPS)-induced acute pulmonary inflammation. Immunohistology and flow cytometry demonstrated that activation of HO-1 using hemin decreased migration of polymorphonuclear leukocytes (PMNs) to the lung interstitium and bronchoalveolar lavage (BAL) in the wild-type and, surprisingly, also in HO-1(flox/flox) mice, emphasizing the anti-inflammatory potential of nonmyeloid HO-1. Nevertheless, hemin reduced the CXCL1, CXCL2/3, tumor necrosis factor-α (TNFα), and interleukin 6 (IL6) levels in both animal strains. Microvascular permeability was attenuated by hemin in wild-type and HO-1(flox/flox) mice, indicating a crucial role of non-myeloid HO-1 in endothelial integrity. The determination of the activity of HO-1 in mouse lungs revealed no compensatory increase in the HO-1(flox/flox) mice. Topical administration of hemin via inhalation reduced the dose required to attenuate PMN migration and microvascular permeability by a factor of 40, emphasizing its clinical potential. In addition, HO-1 stimulation was protective against pulmonary inflammation when initiated after the inflammatory stimulus. In conclusion, nonmyeloid HO-1 is crucial for the anti-inflammatory effect of this enzyme on PMN migration to different compartments of the lung and on microvascular permeability.

Arginase inhibition alleviates hypertension in the metabolic syndrome

BACKGROUND AND PURPOSE

We have previously shown that arginase inhibition alleviates hypertension associated with in a diabetic animal model. Here, we investigated the protective effect of arginase inhibition on hypertension in metabolic syndrome.

EXPERIMENTAL APPROACH

Metabolic syndrome was induced in rats by administration of fructose (10% in drinking water) for 12 weeks to induce vascular dysfunction. Three arginase inhibitors (citrulline, norvaline and ornithine) were administered daily in the last 6 weeks of study before and tail BP was recorded in conscious animals. Concentration response curves for phenylephrine (PE), KCl and ACh in addition to ACh-induced NO generation were obtained in thoracic aorta rings. Serum glucose, insulin, uric acid and lipid profile were determined as well as reactive oxygen species (ROS) and arginase activity.

KEY RESULTS

Arginase activity was elevated in metabolic syndrome while significantly inhibited by citrulline, norvaline or ornithine treatment. Metabolic syndrome was associated with elevations in systolic and diastolic BP, while arginase inhibition significantly reduced elevations in diastolic and systolic BP. Metabolic syndrome increased vasoconstriction responses of aorta to PE and KCl and decreased vasorelaxation to ACh, while arginase inhibition completely prevented impaired responses to ACh. In addition, arginase inhibition prevented impaired NO generation and exaggerated ROS formation in metabolic syndrome. Furthermore, arginase inhibition significantly reduced hyperinsulinaemia and hypertriglyceridaemia without affecting hyperuricaemia or hypercholesterolaemia associated with metabolic syndrome.

CONCLUSIONS AND IMPLICATIONS

Arginase inhibition alleviates hypertension in metabolic syndrome directly through endothelial-dependent relaxation/NO signalling protection and indirectly through inhibition of insulin resistance and hypertriglyceridaemia.

Chrysin and luteolin alleviate vascular complications associated with insulin resistance mainly through PPAR-γ activation

Chrysin and luteolin are two flavonoids with Peroxisome proliferators-activated receptor γ (PPAR-γ) stimulating activity. Here, we investigated the protective effect of chrysin and luteolin from vascular complications associated with insulin resistance (IR). IR was induced in rats by drinking fructose for 12 weeks while chrysin and luteolin were given for 6 weeks with or without PPAR-γ antagonist, bisphenol A diglycidyl ether (BADGE). Then, blood pressure (BP) was recorded and serum levels of glucose, insulin, advanced glycation end products (AGEs) and lipids were measured. Concentration response curves for phenylephrine (PE), KCl, and acetylcholine (ACh) were obtained in thoracic aorta rings. Aortic reactive oxygen species (ROS) and nitric oxide (NO) generation were also studied. Chrysin and luteolin significantly alleviated systolic BP elevations caused by IR, while the co-administration of BADGE prevented chrysin alleviation. Although, neither chrysin nor luteolin affected ACh impaired vasodilatation, they both alleviated exaggerated vasoconstrictions to PE and KCl in IR animals. In addition, incubation of the aorta from IR animals with chrysin or luteolin prevented exaggerated vasoconstrictions to PE and KCl. On the other hand, co-administration of BADGE or co-incubation with GW9662, the selective PPAR-γ antagonist, prevented chrysin alleviation. Both chrysin and luteolin inhibited the developed hyperinsulinemia and increases in serum AGEs, lipids while, BADGE reduced the effect of chrysin on hyperinsulinemia and dyslipidemia. Chrysin and luteolin markedly inhibited elevated NO and ROS in IR aortae while BADGE did not change their effect on NO and ROS. In conclusion, chrysin and luteolin alleviate vascular complications associated with IR mainly through PPAR-γ dependent pathways.

Curcumin attenuates fructose-induced vascular dysfunction of isolated rat thoracic aorta rings

CONTEXT

Consumption of high fructose is associated with metabolic abnormalities, insulin resistance, and hypertension. It is not known whether this hypertensive effect of fructose is related to metabolic abnormalities or due to the direct effect of fructose on blood vessels.

OBJECTIVE

Here, we investigated the direct effect of fructose on rat isolated aorta and the possible protective effect of curcumin.

MATERIALS AND METHODS

The isolated rat thoracic aorta rings were used to measure the contractile responses to different concentrations of both phenylephrine and KCl, and the relaxant response to acetylcholine (Ach). The effect of curcumin (1 µM) alone or in combination with tempol (1 mM), a superoxide dismutase mimetic agent, and N-{[3(amino-methyl)-phenyl]-methyl} ethanimidamide dihydrochloride (1400 W), a specific inducible nitric oxide synthase (iNOS) inhibitor, (1 µM) on fructose-treated aorta was compared. The aortic rings were incubated with different treatments for 60 min before starting the experiment. Changes in the intracellular calcium in response to KCl and nitric oxide levels were also measured.

RESULTS AND DISCUSSION

Fructose strongly increased the contractile response of aortic rings to both phenylephrine and KCl (Emax was increased by 147.3% and 150.5%, respectively) but it did not affect the relaxant response to Ach. Curcumin significantly decreased the hyper responsiveness of arterial rings to both vasopressors (for phenylephrine, Emax decreased from 147.3% in fructose incubated aorta to 81%, and for KCl, Emax decreased from 150.5% in fructose-incubated aorta to 77.24% respectively). Curcumin also reduces the intracellular calcium level (85% reduction in intracellular calcium). A 1400 W was the only agent that potentiates the effect of curcumin.

CONCLUSION

Fructose has a direct deleterious effect on aortic vascular reactivity. Curcumin can partially protect against fructose-induced impairment in vascular contractility via an antioxidant effect and reduction of elevated intracellular calcium.

Vascular dysfunction associated with type 2 diabetes and Alzheimer's disease: a potential etiological linkage

The endothelium performs a crucial role in maintaining vascular integrity leading to whole organ metabolic homeostasis. Endothelial dysfunction represents a key etiological factor leading to moderate to severe vasculopathies observed in both Type 2 diabetic and Alzheimer’s Disease (AD) patients. Accordingly, evidence-based epidemiological factors support a compelling hypothesis stating that metabolic rundown encountered in Type 2 diabetes engenders severe cerebral vascular insufficiencies that are causally linked to long term neural degenerative processes in AD. Of mechanistic importance, Type 2 diabetes engenders an immunologically mediated chronic pro-inflammatory state involving interactive deleterious effects of leukocyte-derived cytokines and endothelial-derived chemotactic agents leading to vascular and whole organ dysfunction. The long term negative consequences of vascular pro-inflammatory processes on the integrity of CNS basal forebrain neuronal populations mediating complex cognitive functions establish a striking temporal comorbidity of AD with Type 2 diabetes. Extensive biomedical evidence supports the pivotal multi-functional role of constitutive nitric oxide (NO) production and release as a critical vasodilatory, anti-inflammatory, and anti-oxidant, mechanism within the vascular endothelium. Within this context, we currently review the functional contributions of dysregulated endothelial NO expression to the etiology and persistence of Type 2 diabetes-related and co morbid AD-related vasculopathies. Additionally, we provide up-to-date perspectives on critical areas of AD research with special reference to common NO-related etiological factors linking Type 2 diabetes to the pathogenesis of AD.

Aldose reductase inhibitors zopolrestat and ferulic acid alleviate hypertension associated with diabetes: effect on vascular reactivity

This study investigated the effect of aldose reductase (AR) inhibitors on hypertension in diabetes. Diabetes was induced with streptozotocin, while AR inhibitors zopolrestat and ferulic acid were administered at 2 weeks after streptozotocin treatment and for 6 weeks afterwards. Then, blood pressure (BP) and serum level of glucose were determined. Concentration–response curves for phenylephrine (PE), KCl, and acetylcholine (ACh) were obtained in isolated aorta. In addition, ACh-induced NO and reactive oxygen species (ROS) generation in aorta and histopathology were examined. Compared with the control animals, diabetes increased diastolic and systolic BP. AR inhibitors reduced diastolic BP elevation without affecting the developed hyperglycaemia. Diabetes increased the contractile response of aorta to KCl, and decreased the relaxation response to Ach, while administering AR inhibitors prevented an impaired response to ACh. Incubation of aorta isolated from diabetic animals with AR inhibitors did not affect the impaired relaxation response to ACh. In addition, AR inhibitors negated the impaired Ach-stimulated NO generation seen in aorta isolated from diabetic animals. Furthermore, diabetes was accompanied with marked infiltration of leukocytes in aortic adventitia, endothelial cell pyknosis, and increased ROS formation. AR inhibitors reduced leukocyte infiltration and inhibited endothelial pyknosis and ROS formation. In conclusion, AR inhibitors negate diabetes-evoked hypertension via ameliorating impaired endothelial relaxation and NO production.

Heme oxygenase-1 induction protects against hypertension associated with diabetes: effect on exaggerated vascular contractility

Disturbances in vascular reactivity are important components of diabetes-evoked hypertension. Heme oxygenase-1 (HO-1) is a homeostatic enzyme upregulated in stress. This study aims to investigate the protective effect of HO-1 against diabetes-evoked hypertension. Rats were left 8 weeks after diabetes induction with streptozotocin to induce vascular dysfunction in the diabetic groups. HO-1 inducers, hemin and curcumin, were daily administrated in the last 6 weeks in the treated groups after 2 weeks of induction. Then, at the end of the study (8 weeks), HO-1 protein level was assessed by immunofluorescence; blood pressure (BP) was recorded; isolated aorta reactivity to phenylephrine (PE) and KCl was studied; reactive oxygen species (ROS) generation was determined; and serum level of glucose, advanced glycation end products (AGEs), and tumor necrosis factor alpha (TNF-α) were determined. While not affected by diabetes, HO-1 protein expression was strongly induced by hemin or curcumin administration. Compared with control animals, diabetes increased systolic and pulse BP. Induction of HO-1 by hemin or curcumin significantly reduced elevated systolic BP and abolished elevated pulse BP without affecting the developed hyperglycemia or AGEs level. The possibility that alterations in vascular reactivity contributed to diabetes-HO-1 BP interaction was investigated. Diabetes increased contractile response of the aorta to PE and KCl, while HO-1 induction by curcumin or hemin prevented aorta-exaggerated response to PE and KCl. Furthermore, the competitive HO inhibitor, tin protoporphyrin, abolished the protective effect of hemin. Diabetes was accompanied with elevated level of TNF-α and ROS generation, while HO-1 induction abrogated increased TNF-α and ROS generation. Collectively, induction of HO-1 protects against hypertension associated with diabetes via ameliorating exaggerated vascular contractility by reducing TNF-α and aortic ROS levels.

Anti-inflammatory potential of curcumin and quercetin in rats

Flavonoids are group of compounds that have been shown to possess potent anti-inflammatory effects in both cellular and animal models of inflammation. In the current study, the single and combined effects of the two flavonoids, curcumin and quercetin, against carrageenan-induced acute inflammation in rats were evaluated with emphasis on the role of oxidative stress, anti-inflammatory enzyme, heme oxygenase-1 (HO-1) and proinflammatory cytokine, tumor necrosis factor-alpha (TNF-α). Curcumin (50 mg/kg), quercetin (50 mg/kg) and a combination of both were orally administered for 14 days before carrageenan injection in rats and compared with the reference nonsteroidal anti-inflammatory drug, indomethacin (10 mg/kg). The percentage increase in paw thickness was calculated. Frozen hind paws were used for the estimation of lipid peroxides (malondialdehyde, MDA), nitric oxide (NO), reduced glutathione (GSH), TNF-α level and HO-1 messenger RNA (mRNA) expression. Formalin-fixed hind paws were used for histopathological examination. Results showed that both curcumin and quercetin caused reduction in carrageenin-induced edema and lymphocytes infiltration along with the decrease is being even higher in case of their combination. Additionally, both flavonoids reduced MDA and NO formation, and restored GSH contents in the paw. Furthermore, both flavonoids increased HO-1 mRNA expression and decreased the elevated TNF-α level. Results showed that both flavonoids moderately lowered inflammation, while their combination was more effective. Accordingly, this study suggests that the reduction in oxidative stress and modulation of HO-1 mRNA expression and TNF-α release by curcumin and quercetin may contribute to the synergistic anti-inflammatory effects of these two flavonoids upon combination.

Cinnamaldehyde protects from the hypertension associated with diabetes

Here we investigated cinnamaldehyde (CA) effect on diabetes-induced hypertension. Insulin deficiency was induced by streptozotocin while, insulin resistance by fructose. Rats were left 8 weeks or 12 weeks after STZ or fructose administration respectively. CA (20 mg kg(-1)day(-1)) was daily administered in the last 6 weeks. Then, blood pressure (BP) was recorded. Isolated Aorta reactivity to phenylephrine (PE), KCl, acetylcholine (ACh) was studied as well as nitric oxide (NO) generation plus Ca(2+) influx. Insulin deficiency was associated with elevated BP, increased response to PE and KCl, decreased response to ACh and impaired NO generation. CA treatment prevented hyperglycemia and its associated impaired vascular reactivity. Insulin resistance was associated with elevated BP while, CA prevented this elevation. Insulin resistance increased response to PE and KCl, decreased response to ACh, while CA treatment normalized response to KCl and PE but not to ACh. Insulin resistance was accompanied with reduced NO generation but exaggerated Ca(2+) influx while CA restored normal Ca(2+) influx but did not affect NO generation. In conclusion, CA prevents development of hypertension in insulin deficiency and insulin resistance through normalization of vascular contractility in addition to its insulinotropic effect in insulin deficiency.

Pentoxifylline alleviates vascular impairment in insulin resistance via TNF-α inhibition

Deterioration of vascular reactivity plays a pivotal role in vascular complications. Pentoxifylline (PTX) is a well-tolerated drug used to treat vascular insufficiency. We investigated the protective effect of PTX against vascular impairment in insulin resistance. Insulin resistance was induced by fructose (10%) in drinking water while PTX was concurrently administered (50 mg/kg(-1)) for 8 weeks. Serum levels of glucose, insulin, tumor necrosis factor alpha (TNF-α) were determined. Isolated aorta reactivity to phenylephrine (PE), potassium chloride (KCl), and acetylcholine (ACh) was studied, as was nitric oxide (NO) generation and histopathology. Insulin resistance was accompanied with a significant elevation in serum TNF-α level, marked leukocytes infiltration, and endothelial pyknosis. PTX inhibited insulin resistance and prevented TNF-α elevation, leukocyte infiltration and endothelial pyknosis. Vascular dysfunction was evident in insulin resistance as increased vascular contractility to PE and decreased relaxation to ACh, whereas PTX protected against this dysfunction. Notably, in vitro incubation with TNF-α (1 ng/ml(-1)) increased contractility to PE and decreased relaxation to ACh while concomitant PTX (1 mM) incubation partially restored response to ACh but not to PE. Furthermore, TNF-α reduced ACh-induced NO generation, whereeas PTX restored it. In conclusion, PTX protects from the impairment in vascular reactivity in insulin resistance, by a mechanism involving TNF-α inhibition.

Peroxisome proliferator-activated receptor-γ as a potential therapeutic target in the treatment of preeclampsia

Preeclampsia is a multisystemic disorder of pregnancy characterized by hypertension, proteinuria, and maternal endothelial dysfunction. It is a major cause of maternal and perinatal morbidity and mortality and is thought to be attributable, in part, to inadequate trophoblast invasion. Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a ligand-activated transcription factor expressed in trophoblasts, and the vasculature of which activation has been shown to improve endothelium-dependent vasodilatation in hypertensive conditions. We investigated the effects of the administration of a PPAR-γ agonist using the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. The selective PPAR-γ agonist, rosiglitazone, was administered to pregnant rats that had undergone RUPP surgery. To investigate whether any observed beneficial effects of PPAR-γ activation were mediated by the antioxidant enzyme, heme oxygenase 1, rosiglitazone was administered in combination with the heme oxygenase 1 inhibitor tin-protoporphyrin IX. RUPP rats were characterized by hypertension, endothelial dysfunction, and elevated microalbumin:creatinine ratios. Rosiglitazone administration ameliorated hypertension, improved vascular function, and reduced the elevated microalbumin:creatinine ratio in RUPP rats. With the exception of microalbumin:creatinine ratio, these beneficial effects were abrogated in the presence of the heme oxygenase 1 inhibitor. Administration of a PPAR-γ agonist prevented the development of several of the pathophysiological characteristics associated with the RUPP model of preeclampsia, via a heme oxygenase 1-dependent pathway. The findings from this study provide further insight into the underlying etiology of preeclampsia and a potential therapeutic target for the treatment of preeclampsia.