Correction: Eid et al. Interference with TGFß1-Mediated Inflammation and Fibrosis Underlies Reno-Protective Effects of the CB1 Receptor Neutral Antagonists AM6545 and AM4113 in a Rat Model of Metabolic Syndrome. Molecules 2021, 26, 866.

The authors wish to make the following changes to the paper [...].

Development of depot PLGA-based in-situ implant of Linagliptin: Sustained release and glycemic control.

High percentage of diabetic people are diagnosed as type 2 who require daily dosing of an antidiabetic drug such as Linagliptin (Lina) to manage their blood glucose levels. This study aimed to develop injectable Lina-loaded biodegradable poly (lactic-co-glycolic acid) (PLGA) in-situ implants (ISIs) to deliver a desired burst effect of Lina followed by a sustained release over several days for controlling the blood glucose levels over prolonged time periods. The morphological, pharmacokinetic, and pharmacodynamic assessments of the Lina-loaded ISIs were performed. Scanning electron microscopy (SEM) study revealed the rapid exchange between the water miscible solvent (N-methyl-2-pyrrolidone; NMP) and water during the ISI preparation, hence enhancing the initial burst Lina release. While, triacetin of lower water affinity could lead to formation of more compact and dense ISI structure with slower drug release. By comparing various ISI formulations containing different solvents and different PLGA concentrations, the ISI containing 40 % PLGA and triacetin was selected for its sustained release of Lina (93.06 ± 1.50 %) after 21 days. The pharmacokinetic results showed prolonged half life (t1/2) and higher area under the curve (AUC) values of the selected Lina-loaded ISI when compared to those of oral Lina preparation. The single Lina-ISI injection produced a hypoglycemic control in the diabetic rats very similar to the daily oral administration of Lina after 7 and 14 days. In conclusion, PLGA-based ISIs confirmed their suitability for prolonging Lina release in patients receiving long-term antidiabetic therapy, thereby achieving more enhanced patient compliance and reduced dosing frequency.

Rp-HPLC Determination of Quercetin in a Novel D-α-Tocopherol Polyethylene Glycol 1000 Succinate Based SNEDDS Formulation: Pharmacokinetics in Rat Plasma.

Despite its proven efficacy in diverse metabolic disorders, quercetin (QU) for clinical use is still limited because of its low bioavailability. D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) is approved as a safe pharmaceutical adjuvant with marked antioxidant and anti-inflammatory activities. In the current study, several QU-loaded self-nanoemulsifying drug delivery systems (SNEDDS) were investigated to improve QU bioavailability. A reversed phase high performance liquid chromatography (RP-HPLC) method was developed, for the first time, as a simple and sensitive technique for pharmacokinetic studies of QU in the presence of TPGS SNEDDS formula in rat plasma. The analyses were performed on a Xterra C18 column (4.6 × 100 mm, 5 µm) and UV detection at 280 nm. The analytes were separated by a gradient system of methanol and phosphate buffer of pH 3. The developed RP-HPLC method showed low limit of detection (LODs) of 7.65 and 22.09 ng/mL and LOQs of 23.19 and 66.96 ng/mL for QU and TPGS, respectively, which allowed their determination in real rat plasma samples. The method was linear over a wide range, (30-10,000) and (100-10,000) ng/mL for QU and TPGS, respectively. The selected SNEDDS formula, containing 50% w/w TPGS, 30% polyethylene glycol 200 (PEG 200), and 20% w/w pumpkin seed oil (PSO), showed a globule size of 320 nm and -28.6 mV zeta potential. Results of the pharmacokinetic studies showed 149.8% improvement in bioavailability of QU in SNEDDS relative to its suspension. The developed HPLC method proved to be simple and sensitive for QU and TPGS simultaneous determination in rat plasma after oral administration of the new SNEDDS formula.

Interference with TGFß1-Mediated Inflammation and Fibrosis Underlies Reno-Protective Effects of the CB1 Receptor Neutral Antagonists AM6545 and AM4113 in a Rat Model of Metabolic Syndrome.

The role of cannabinoid receptors in nephropathy is gaining much attention. This study investigated the effects of two neutral CB1 receptor antagonists, AM6545 and AM4113, on nephropathy associated with metabolic syndrome (MetS). MetS was induced in rats by high-fructose high-salt feeding for 12 weeks. AM6545, the peripheral silent antagonist and AM4113, the central neutral antagonist were administered in the last 4 weeks. At the end of study, blood and urine samples were collected for biochemical analyses while the kidneys were excised for histopathological investigation and transforming growth factor beta 1 (TGFß1) measurement. MetS was associated with deteriorated kidney function as indicated by the elevated proteinuria and albumin excretion rate. Both compounds equally inhibited the elevated proteinuria and albumin excretion rate while having no effect on creatinine clearance and blood pressure. In addition, AM6545 and AM4113 alleviated the observed swelling and inflammatory cells infiltration in different kidney structures. Moreover, AM6545 and AM4113 alleviated the observed histopathological alterations in kidney structure of MetS rats. MetS was associated with a ten-fold increase in urine uric acid while both compounds blocked this increase. Furthermore, AM6545 and AM4113 completely prevented the collagen deposition and the elevated expression of the TGFß1 seen in MetS animals. In conclusion, AM6545 and AM4113, possess reno-protective effects by interfering with TGFß1-mediated renal inflammation and fibrosis, via peripheral action.

Effects of the CB1 Receptor Antagonists AM6545 and AM4113 on Insulin Resistance in a High-Fructose High-Salt Rat Model of Metabolic Syndrome.

Background and Objectives: Insulin resistance (IR) is a serious condition leading to development of diabetes and cardiovascular complications. Hyper-activation of cannabinoid receptors-1 (CB1) has been linked to the development of metabolic disorders such as IR. Therefore, the effect of blocking CB1 on the development of IR was investigated in the present study. Materials and Methods: A 12-week high-fructose/high-salt feeding model of metabolic syndrome was used to induce IR in male Wistar rats. For this purpose, two different CB1-antagonists were synthesized and administered to the rats during the final four weeks of the study, AM6545, the peripheral neutral antagonist and AM4113, the central neutral antagonist. Results: High-fructose/salt feeding for 12 weeks led to development of IR while both AM6545 and AM4113, administered in the last 4 weeks, significantly inhibited IR. This was correlated with increased animal body weight wherein both AM6545 and AM4113 decreased body weight in IR animals but with loss of IR/body weight correlation. While IR animals showed significant elevations in serum cholesterol and triglycerides with no direct correlation with IR, both AM6545 and AM4113 inhibited these elevations, with direct IR/cholesterol correlation in case of AM6545. IR animals had elevated serum uric acid, which was reduced by both AM6545 and AM4113. In addition, IR animals had decreased adiponectin levels and elevated liver TNFα content with strong IR/adiponectin and IR/TNFα correlations. AM6545 inhibited the decreased adiponectin and the increased TNFα levels and retained the strong IR/adiponectin correlation. However, AM4113 inhibited the decreased adiponectin and the increased TNFα levels, but with loss of IR/adiponectin and IR/TNFα correlations. Conclusions: Both CB1 neutral antagonists alleviated IR peripherally, and exerted similar effects on rats with metabolic syndrome. They also displayed anti-dyslipidemic, anti-hyperurecemic and anti-inflammatory effects. Overall, these results should assist in the development of CB1 neutral antagonists with improved safety profiles for managing metabolic disorders.

Cyclosporine A exhibits gender-specific nephrotoxicity in rats: Effect on renal tissue inflammation.

Cyclosporine A (CSA) is a widely used immunosuppressant drug known to commonly cause cardio and nephrotoxicity. A study looking at the sex specificity of the cardiotoxicity of CSA revealed that sexual dimorphism existed when looking at the electrocardiographs and left ventricles of CSA-treated rats. We hypothesized that cyclosporine A exhibited gender-specific nephrotoxicity by testing various parameters of kidney function in male and female rats treated for 21 days with 15 mg/kg CSA versus control male and female rats that received a vehicle consisting of 18% kolliphore and 2% ethanol in sterile saline. It was found that male rats treated with CSA had significantly higher levels of serum creatinine and lower creatinine clearance than control males. However, serum creatinine and creatinine clearance were not affected by CSA treatment in females. Histopathological examination of kidney cross-sections revealed a heavy aggregation of inflammatory cells and significant vascular congestion in males treated with CSA, which was less prominent in female rats receiving CSA. In addition CSA treated male rats had higher levels of serum cholesterol compared with control while, CSA did not affect serum cholesterol in female rats. Kidney tumor necrosis factor alpha (TNF-α) levels were found to drop in female rats following CSA treatment, whereas no change was observed in male rats before and after treatment. These results suggest that CSA exhibits gender-related nephrotoxicity in rats that might be mediated by differences in the inflammatory response between males and females.

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.

Enhanced calcium entry via activation of NOX/PKC underlies increased vasoconstriction induced by methylglyoxal.

Advanced glycation end-products (AGEs) play a pivotal role in macro- and micro-vascular diabetic complications. We investigated the mechanism by which methylglyoxal (an endogenous generator of AGEs) affects vascular contractility using the isolated artery technique. Contractile responses to vasoconstrictors phenylephrine (PE), angiotensin II (Ang II), vasopressin (VP) and KCl were measured in the isolated rat aorta following one-our exposure to methylglyoxal (50-200 µM). The perfused rat kidney was employed to confirm the effect of methylglyoxal on microvessels. Methylglyoxal-induced changes in cytosolic calcium were measured in the smooth muscle layer of the aorta with the calcium-sensing fluorophore Fluo-4 AM. Methylglyoxal significantly increased maximal contraction of the rat aorta to PE, Ang II and VP. Similar results were seen in response to the depolarizing vasoconstrictor KCl in macro and micro vessels. The methylglyoxal-induced increases in aortic contraction mediated by the agonist and KCl were endothelium independent. Methylglyoxal-induced increases in KCl-dependent aortic contraction were abolished after the removal of extracellular calcium or in the presence of the calcium channel blocker nifedipine. Incubation with the antioxidant N-acetyl-l-cysteine (NAC), apocynin (a nonselective NADPH oxidase (NOX) inhibitor) or chelerythrine (a protein kinase C (PKC) inhibitor) prior to methylglyoxal pre-treatment reversed the methylglyoxal-induced increases in the rat aortic contractility. In conclusion, the formation of AGEs increases vasoconstriction of both macro- and micro-vessels by increasing the voltage-activated calcium entry in vascular smooth muscles in a NOX and PKC dependent manner.

Cardioprotection by 6-gingerol in diabetic rats.

The current study was conducted to evaluate the effect of 6-gingerol (6G) on cardiac complications in streptozotocin (STZ)-induced diabetic (DM) rats. STZ-induced DM rats (single 50 mg/kg i.p. injection, 15 days prior to drug treatment) or time-matched controls were treated with 6G (75 mg/day route orally). After a further 8 weeks, blood was collected for biochemical analysis and 8-isoprostenol was measured in urine. Cardiac hemodynamics and ECG was assessed. 6G significantly attenuated the increased level of blood glucose in diabetic rats and improved cardiac hemodynamics in including RR interval, max dP/dt, min dP/dt and Tau. In addition, 6G alleviated the elevated ST segment, T amplitude and R amplitude with no significant effect on disturbed levels of adiponectin, TGF-ß or 8-isoprostenol induced by diabetes. The results showed that treatment with 6G has an ameliorative effect on cardiac dysfunction induced by diabetes. Which may be not related to its potential antioxidant effect.

Phenolics from Garcinia mangostana alleviate exaggerated vasoconstriction in metabolic syndrome through direct vasodilatation and nitric oxide generation.

BACKGROUND: Exaggerated vasoconstriction plays a very important role in the hypertension, a major component of metabolic syndrome (MetS). In the current work, the potential protective effect of methanol extract of fruit hulls of Garcinia mangostana L. on the exaggerated vasoconstriction in MetS has been investigated. In addition, the bioactive fraction and compounds as well as the possible mechanism of action have been illustrated. METHODS: The effect of methanol extract of G. mangostana (GMT) fruit hulls on the vascular reactivity of aorta isolated from animals with MetS was investigated through bioassay-guided fractionation procedures. GMT was partitioned with chloroform (I) and the remaining mother liquor was fractionated on a Diaion HP-20 with H2O, 50 and 100 % methanol to give fractions II, III, and IV, respectively. The effect of total extract (GMT), bioactive fraction and the bioactive compounds on the vasoconstriction were examined in aortae isolated from animals with MetS by incubation for 30 min before exposing aortae to cumulative concentrations of phenylephrine (PE). The direct relaxant effect was also examined by adding cumulative concentrations of the bioactive fraction and its bioactive compounds to PE precontracted vessels. In addition, aortic nitric oxide (NO) and reactive oxygen species (ROS) production was investigated. RESULTS: Bioassay-guided fractionation of GMT revealed isolation of garcimangosone D (1), aromadendrin-8-C-ß-D-glucopyranoside (2), 2,4,3'-trihydroxy benzophenone-6-O-ß-D-glucopyranoside (3), maclurin-6-O-ß-D-glucopyranoside (rhodanthenone) (4), epicatechin (5), and 2,3',4,5',6-pentahydroxy benzophenone (6). Only compounds 2, 4, and 5 significantly alleviated the exaggerated vasoconstriction of MetS aortae and in the same time showed significant vasodilation of PE pre-contracted aortae. To further illustrate the mechanism of action, the observed vasodilation was completely blocked by the nitric oxide (NO) synthase inhibitor, Nω-nitro-L-arginine methyl ester hydrochloride and inhibited by guanylate cyclase inhibitor, methylene blue. However, vasodilation was not affected by the potassium channel blocker, tetraethylammonium or the cyclooxygenase inhibitor, indomethacin. In addition, compounds 2, 4, and 5 stimulated NO generation from isolated aortae to levels comparable with acetylcholine. Furthermore, 4 and 5 inhibited reactive oxygen species generation in MetS aortae. CONCLUSION: The phenolic compounds 2, 4, and 5 ameliorated the exaggerated vasoconstriction in MetS aortae through vasodilatation-NO generation mechanism.

Gingerol Synergizes the Cytotoxic Effects of Doxorubicin against Liver Cancer Cells and Protects from Its Vascular Toxicity.

Hydroxyphenylalkanes and diarylheptanoids possess potential therapeutic value in different pathophysiological conditions, such as malignancy. In the current study, naturally isolated hydroxyphenylalkane and diarylheptanoid compounds were investigated for potential chemo-modulatory effects in addition to potential vascular protective roles with doxorubicin. Diarylheptanoids showed stronger antioxidant effects, in comparison to hydroxyphenylalkanes, as demonstrated by DPPH assay and amelioration of CCl4-induced disturbed intracellular GSH/GSSG balance. Shogaol and 4'-methoxygingerol showed considerable cytotoxic effects against HCT116, HeLa, HepG2 and MCF7 cells, with IC50 values ranging from 3.1 to 19.4 µM. Gingerol significantly enhanced the cytotoxic profile of doxorubicin against HepG2 and Huh7, cells decreasing its IC50s by 10- and 4-fold, respectively. Cell cycle distribution was studied using DNA cytometry. Doxorubicin alone induced cell accumulation at S-phase and G2/M-phase, while in combination with gingerol it significantly induced cell cycle arrest at the G2/M-phase. Additionally, the vascular protective effect of gingerol against doxorubicin (10 µM) was examined on isolated aortic rings. Co-incubation with 6-gingerol (30 µM) completely blocked the exaggerated vasoconstriction and impaired vascular relaxation induced by doxorubicin. In conclusion, despite its relatively weak antioxidant properties, gingerol protected from DOX-induced vascular damage, apparently not through a ROS scavenging mechanism. Besides, gingerol synergized the cytotoxic effects of DOX against liver cancer cells without influencing the cellular pharmacokinetics.

Xanthine oxidase inhibition alleviates the cardiac complications of insulin resistance: effect on low grade inflammation and the angiotensin system.

BACKGROUND: We have previously shown that hyperuricemia plays an important role in the vascular complications of insulin resistance (IR). Here we investigated the effect of xanthine oxidase (XO) inhibition on the cardiac complications of IR. METHODS: IR was induced in rats by a high fructose high fat diet for 12 weeks. Allopurinol, a standard XO inhibitor, was administered in the last 4 weeks before cardiac hemodynamics and electrocardiography, serum glucose, insulin, tumor necrosis factor alpha (TNFα), 8-isoprostane, uric acid, lactate dehydrogenase (LDH) and XO activity were measured. Expression of cardiac angiotensin II (AngII) and angiotensin receptor 1 (AT1) were assessed by immunofluorescence. RESULTS: IR animals had significant hyperuricemia which was inhibited by allopurinol administration. IR was associated with impaired ventricular relaxation (reflected by a decreased diastolic pressure increment and prolonged diastolic duration) and XO inhibition greatly attenuated impaired relaxation. IR was accompanied by cardiac ischemia (reflected by increased QTc and T peak trend intervals) while XO inhibition alleviated the ECG abnormalities. When subjected to isoproterenol-induced ischemia, IR hearts were less resistant (reflected by larger ST height depression and higher LDH level) while XO inhibition alleviated the accompanying ischemia. In addition, XO inhibition prevented the elevation of serum 8-isoprostane and TNFα, and blocked elevated AngII and AT1 receptor expression in the heart tissue of IR animals. However, XO inhibition did not affect the developed hyperinsulinemia or dyslipidemia. CONCLUSIONS: XO inhibition alleviates cardiac ischemia and impaired relaxation in IR through the inhibition of low grade inflammation and the angiotensin system.

Characterization of vascular complications in experimental model of fructose-induced metabolic syndrome.

Vascular dysfunction is an important complication associated with metabolic syndrome (MS). Here we fully characterized vascular complications in a rat model of fructose-induced MS. MS was induced by adding fructose (10%) to drinking water to male Wistar rats of 6 weeks age. Blood pressure (BP) and isolated aorta responses phenylephrine (PE), KCl, acetylcholine (ACh), and sodium nitroprusside (SNP) were recorded after 6, 9, and 12 weeks of fructose administration. In addition, serum levels of glucose, insulin, uric acid, tumor necrosis factor α (TNFα), lipids, advanced glycation end products (AGEs), and arginase activity were determined. Furthermore, aortic reactive oxygen species (ROS) generation, hemeoxygenase-1 expression, and collagen deposition were examined. Fructose administration resulted in a significant hyperinslinemia after 6 weeks which continued for 12 weeks. It was also associated with a significant increase in BP after 6 weeks which was stable for 12 weeks. Aorta isolated from MS animals showed exaggerated contractility to PE and KCl and impaired relaxation to ACh compared with control after 6 weeks which were clearer at 12 weeks of fructose administration. In addition, MS animals showed significant increases in serum levels of lipids, uric acid, AGEs, TNFα, and arginase enzyme activity after 12 weeks of fructose administration. Furthermore, aortae isolated from MS animals were characterized by increased ROS generation and collagen deposition. In conclusion, adding fructose (10%) to drinking water produces a model of MS with vascular complications after 12 weeks that are characterized by insulin resistance, hypertension, disturbed vascular reactivity and structure, hyperuricemia, dyslipidemia, and low-grade inflammation.

Rosuvastatin, but not atorvastatin, enhances the antihypertensive effect of cilostazol in an acute model of hypertension.

PURPOSE: Hypertensive emergency, a sudden and severe increase in blood pressure, necessitates immediate intervention to avoid end-organ damage. Cilostazol, a selective phosphodiesterase-III inhibitor, has vasodilator effect. Here, we investigated the effect of two commonly used statins, atorvastatin or rosuvastatin, on cilostazol antihypertensive activity in acute model of hypertension. METHODS: Hypertensive emergency was induced via angiotensin II intravenous infusion (120 ng.kg-1.min-1). Rats were subjected to real-time arterial hemodynamics and electrocardiogram recording while investigated drugs were injected slowly at cumulative doses 0.5, 1, and 2 mg.kg-1, individually or in combination, followed by baroreflex sensitivity (BRS) analysis and serum electrolytes (Na+ and K+) and vasomodulators (norepinephrine (NE), and nitric oxide (NO)) assessment. RESULTS: Cilostazol reduced systolic blood pressure (SBP), while co-injection with rosuvastatin augmented cilostazol SBP-reduction up to 30 mmHg. Compared to atorvastatin, rosuvastatin boosted the cilostazol-associated reduction in peripheral resistance, as evidenced by further decrease in diastolic, pulse, and dicrotic-notch pressures. Rosuvastatin co-injection prevented cilostazol-induced changes of ejection and non-ejection durations. Additionally, rosuvastatin coadministration produced better restoration of BRS, with an observed augmented increase in BRS indexes from spectral analysis. Greater reduction in sympathetic/parasympathetic ratio and serum NE upon rosuvastatin coadministration indicates further shift in sympathovagal balance towards parasympathetic dominance. Additionally, rosuvastatin coinjection caused a greater decrease in serum sodium, while more increase in NO indicating augmented reduction of extracellular volume and endothelial dysfunction. CONCLUSION: Rosuvastatin boosted cilostazol's antihypertensive actions through effects on peripheral resistance, BRS, sympathovagal balance, endothelial dysfunction, and electrolytes balance, while atorvastatin did not demonstrate a comparable impact.

Vitamin B1 and calcitriol enhance glibenclamide suppression of diabetic nephropathy: Role of HMGB1/TLR4/NF-κB/TNF-α/Nrf2/α-SMA trajectories.

Glibenclamide is one of the most prescribed insulin secretagogues in diabetes due to its low cost, but its efficacy on suppressing diabetic complications is limited. Here, we examine whether addition of either vitamin B1 or calcitriol to glibenclamide could produce more suppression of diabetic nephropathy. Type 2 diabetes was induced by high fructose (10 % in drinking water), high salt (3 % in diet), and high fat diet (25 % in diet) for 3 weeks, followed by single dose of STZ (40 mg/kg, i.p.). Diabetic rats were treated with either glibenclamide (0.6 mg/kg), vitamin B1 (70 mg/kg), glibenclamide/vitamin B1, calcitriol (0.1 µg/kg), or glibenclamide/calcitriol. Addition of either vitamin B1 or calcitriol to glibenclamide therapy enabled more suppression of diabetic nephropathy development as evidenced by more preserved creatinine clearance and less renal damage scores. Combination therapy resulted in mild enhancement in the effect of glibenclamide on glucose tolerance without affecting the area under the curve. Combination therapy was associated with more suppression of inflammatory cascades as evidenced by reducing the expression of high mobility group box-1 (HMGB1), toll-like receptor-4 (TLR4), nuclear factor-kappa B (NF-κB), and tumor necrosis factor-α (TNF-α). In addition, combination therapy enhanced the antioxidant mechanisms as evidenced by increased expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and glutathione content and reducing malondialdehyde and nitric oxide levels. Furthermore, combination therapy provided more suppression of fibrotic pathways as appear from reducing collagen deposition and the expression of α- smooth muscle actin (α-SMA). In conclusion, addition of vitamin B1 or calcitriol to glibenclamide therapy can enhance the therapeutic efficiency of glibenclamide in suppressing diabetic nephropathy progression to the same extend, the protective effect is mediated through modulating HMGB1/TLR4/NF-κB/TNF-α/Nrf2/α-SMA trajectories.

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.

Chrysin and luteolin attenuate diabetes-induced impairment in endothelial-dependent relaxation: effect on lipid profile, AGEs and NO generation.

Chrysin and luteolin are two important plant flavonoids. In the present study, we hypothesized that they protect against deleterious vascular effects of diabetes. Diabetes was induced in rats by streptozotocin (STZ) injection, while chrysin and luteolin were administered two weeks after STZ administration for 6 weeks. Then, blood pressure (BP) and serum levels of glucose, advanced glycation end products (AGEs), triglycerides (TGs), total cholesterol and low density lipoprotein-cholesterol (LDL-C) were determined. Concentration response curves for KCl, phenylephrine (PE), acetylcholine (ACh) and ACh-induced NO generation were obtained in isolated aorta. Compared with control, diabetes increased diastolic and systolic BP, while chrysin and luteolin attenuated diastolic BP elevation without affecting the developed hyperglycemia. Diabetes increased contractile response of aorta to KCl, PE, decreased relaxation response to ACh, while chrysin and luteolin prevented the impaired response to ACh. In addition, diabetes was accompanied by elevated levels of TGs, total and LDL cholesterol, while both chrysin and luteolin prevented this dyslipidemia. Furthermore, chrysin decreased the elevated AGEs level in serum of diabetic animals, while luteolin abrogated the impaired NO generation in diabetic aorta. Collectively, chrysin and luteolin attenuate diabetes-evoked impairment in endothelial-dependent relaxation possibly via ameliorating detrimental changes in lipid profile, AGEs and NO generation.

Hinokitiol for hypertensive emergencies: effects on peripheral resistance, cardiac load, baroreflex sensitivity, and electrolytes balance.

Hinokitiol, a natural monoterpenoid, has been shown previously to possess a potent vasodilating activity in vitro in both control and hypertensive aortae. Here, the antihypertensive and cardioprotective effects of an intravenous hinokitiol injection were fully investigated in angiotensin II-induced hypertensive emergency in rats. Hinokitiol intravenous injection was prepared in the form of self-nanoemulsifying drug delivery system. Rat's arterial and ventricular hemodynamics were measured in real-time recordings in addition to surface electrocardiogram while slow injection of cumulative doses of hinokitiol or vehicle as well as time control. Hinokitiol at dose 10 mg/kg showed a considerable reduction in the raised systolic blood pressure (30 mmHg) within only 30 min. The decrease in blood pressure seems to be mediated through a reduction in peripheral resistance, as appears from the decreases in diastolic pressure, dicrotic notch pressure, and pulse pressure. In addition, hinokitiol injection reduced heart load due to the decrease in heart rate, increases in cycle duration (particularly the non-ejection duration) and diastolic duration, and decreases in end-diastolic pressure. An effect most likely mediated via prolongation of ventricular repolarization as appears from the increases in PR, QTc, and JT intervals. However, acute intravenous injection of hinokitiol neither affected the baroreflex sensitivity nor sodium/potassium balance. In conclusion, acute hinokitiol intravenous injection markedly reduced severe hypertension in rats. This effect seems to be mediated through decreasing peripheral resistance and decreasing cardiac load, suggesting that it is an effective treatment in hypertensive emergencies after clinical evaluation.

Effects of the CB1 receptor antagonists AM6545 and AM4113 on metabolic syndrome-induced prostatic hyperplasia in rats.

Metabolic syndrome (MetS) is a combination of metabolic disorders that can predispose individuals to benign prostatic hyperplasia (BPH). The inhibition of the cannabinoid 1 (CB1) receptor has been used to treat metabolic disorders in animal models. This study reports the use of a peripherally restricted CB1 antagonist (AM6545) and a neutral CB1 antagonist (AM4113) to improve MetS-related BPH in rats. Animals were divided into three control groups to receive either a normal rodent diet, AM6545, or AM4113. MetS was induced in the fourth, fifth, and sixth groups using a concentrated fructose solution and high-salt diet delivered as food pellets for eight weeks. The fifth and sixth groups were further given AM6545 or AM4113 for additional four weeks. Body and prostate weights were measured and prostate sections were stained with hematoxylin eosin. Cyclin D1, markers of oxidative stress and inflammation, and levels of the endocannabinoids were recorded. BPH in rats with MetS was confirmed through increased prostate weight and index, as well as histopathology. Treatment with either AM6545 or AM4113 significantly decreased prostate weight, improved prostate histology, and reduced cyclin D1 expression compared with the MetS group. Groups treated with CB1 antagonists experienced reduced lipid peroxidation, recovered glutathione depletion, restored catalase activity, and had lower inflammatory markers interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α). MetS rats treated with either AM6545 or AM4113 showed reduced concentrations of anandamide (AEA) and 2-arachidonoylglycerol (2-AG) in the prostate compared with the MetS group. In conclusion, the CB1 antagonists AM6545 and AM4113 protect against MetS-induced BPH through their anti-proliferative, antioxidant, and anti-inflammatory effects.

Rosiglitazone, a peroxisome proliferator-activated receptor γ stimulant, abrogates diabetes-evoked hypertension by rectifying abnormalities in vascular reactivity.

In addition to insulin sensitization, rosiglitazone exhibits favourable circulatory effects. In the present study, we tested the hypothesis that rosiglitazone protects against hypertension and vascular derangements caused by diabetes. Diabetes was induced by a single bolus injection of streptozotocin (50 mg/kg, i.p.). After 2 weeks, rats were started on a treatment regimen of 5 mg/kg rosiglitazone daily for a period of 6 weeks. The control group consisted of rats treated with vehicle (distilled water) for the same period of time. After 6 weeks treatment, blood pressure (BP) was recorded and serum levels of glucose, advanced glycation end-products (AGE), triglycerides, total cholesterol and low-density lipoprotein-cholesterol (LDL-C) were determined. In in vitro experiments, concentration-response curves were constructed to phenylephrine (PE), KCl and acetylcholine (ACh) in thoracic aorta rings. In addition, ACh-induced nitric oxide (NO) generation and KCl-induced intracellular Ca accumulation were determined in the aorta. Compared with values in control rats, both diastolic and systolic BP were increased in diabetic rats. Rosiglitazone treatment of diabetic rats abolished the increase in diastolic BP and significantly reduced the increased systolic BP without affecting the development of hyperglycaemia. The possibility that changes in vascular reactivity and/or lipid profile contributed to the effects of rosiglitazone on BP in diabetic rats was investigated. In aortic rings from diabetic rats, contractile responses to KCl were increased, whereas the relaxant responses to ACh were decreased. In rings from diabetic rosiglitazone-treated rats, the exaggerated response to KCl and the impaired response to ACh were abolished. Furthermore, rosiglitazone abrogated impaired ACh-stimulated NO generation in aortas isolated from diabetic rats. Diabetes in rats was accompanied by elevated levels of triglycerides, total cholesterol, LDL-C and AGE. Rosiglitazone treatment abrogated the increased levels of triglycerides, total cholesterol and LDL-C, but only partially reduced AGE levels. Collectively, these observations indicate that rosiglitazone abrogates diabetes-evoked hypertension by ameliorating detrimental changes in vascular reactivity and lipid profiles.