Development and Evaluation of Phytosomes Containing Callistemon citrinus Leaf Extract: A Preclinical Approach for the Treatment of Obesity in a Rodent Model.

Callistemon citrinus has several biological effects; it is anti-inflammatory, anti-obesogenic, antioxidant, hepatoprotection, and chemoprotective. Its bioactive compounds include terpenoids, phenolic acids, and flavonoids which have low oral bioavailability and absorption. This study aimed at developing phytosomes of C. citrinus to improve oral bioavailability and absorption. Phytosomes were formulated with soybean phosphatidylcholine and C. citrinus leaf extract using the thin layer sonication method. Phytosomes were evaluated by scanning electron microscopy (SEM), entrapment efficiency, solubility, and particle size determination. Antioxidant capacity and total phenolic, flavonoid, and terpenoid contents were also measured. The in vivo anti-obesogenic activity was evaluated. Phytosomes loaded with C. citrinus (P C.c) extract had small spherical shapes. The average particle size was 129.98 ± 18.30 nm, encapsulation efficiency 80.49 ± 0.07%, and solubility 90.00%; the stability study presented no significant changes in the average particle size at 20 °C. P C.c presented high antioxidant capacity. For the first time, ellagic acid is reported in this plant. The in vivo obesity study showed a strong anti-obesogenic activity of phytosomes with C. citrinus to reduce 40% body weight as well as morphometric and biochemical parameters.

Evaluation of the toxicology, anti-lipase, and antioxidant effects of Callistemon citrinus in rats fed with a high fat-fructose diet.

CONTEXT: Callistemon citrinus Skeels (Myrtaceae) exhibits many biological activities. OBJECTIVE: This study analyzes for the first time, the toxicity, obesogenic, and antioxidant effects of C. citrinus in rats fed with a high fat-fructose diet (HFFD). MATERIALS AND METHODS: Four studies using male Wistar rats were conducted: (a) 7 groups (n = 3): control (corn oil) and ethanol extract of C. citrinus leaf (single oral dose at 100-4000 mg/kg) for acute toxicity; (b) 2 groups (n = 8): control (corn oil) and C. citrinus (1000 mg/kg/day) for 28 days for subacute toxicity; (c) 3 groups (n = 4) with single oral dose of lipid emulsion: control (lipid emulsion), C. citrinus and orlistat (250 and 50 mg/kg, respectively) for lipid absorption; (d) 4 groups (n = 6): control (normal diet) and 3 groups fed with HFFD: HFFD only, C. citrinus and simvastatin (oral dose 250 and 3 mg/kg, respectively) for 13 weeks. Antioxidant enzymes and biomarkers were evaluated and inhibition of pancreatic lipase was determined in vitro. RESULTS: Toxicological studies of C. citrinus showed no differences in biochemical parameters and lethal dose (LD50) was higher than 4000 mg/kg. C. citrinus inhibited pancreatic lipase activity, with IC50 of 392.00 µg/mL, and decreased lipid absorption by 70%. Additionally, it reduced the body weight 22%, restored the activities of antioxidant enzymes, and reduced the biomarkers of oxidative stress. CONCLUSIONS: Callistemon citrinus showed an effect against oxidative stress by reducing biomarkers and induced antioxidant system, without toxic effects.

Chemopreventive effect of Callistemon citrinus (Curtis) Skeels against colon cancer induced by 1,2-dimethylhydrazine in rats.

PURPOSE: Callistemon citrinus (Curtis) Skeels is a shrub native of Australia. In spite of containing an important number of bioactive compounds (1,8-cineole, limonene and α-terpineol) recognized as a potential chemotherapeutic agents, it is only used as an ornamental plant in Mexico. This study investigated the chemopreventive effect of C. citrinus leaves extract on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in rats. METHODS: Twenty-four rats were divided into 3 groups of eight rats. Group 1 served as negative control, groups 2 and 3 were given subcutaneous injections of DMH (65 mg/kg b.w.) twice a week the first 2 weeks, and then one the third week. In addition, group 3 was administrated with leaves extracts (250 mg/kg b.w., orally daily) during the 22 weeks of the experiment. Animals were killed and the presence of colon tumors and aberrant crypt foci (ACF) were scored for number and distribution pattern along the colon. The activity of two-phase II enzymes quinone reductase (QR) and glutathione S-transferase (GST) was determined in the liver and three segments of the colon: proximal, middle and distal. RESULTS: The results show that rats feed with C. citrinus leaves extract significantly reduced the size of tumors, the number of ACF and the crypt multiplicity. Additionally, C. citrinus leaves extract increased or maintained the activity of QR and GST in the different tissues as compared with DHM-treated group (p > 0.05). CONCLUSION: This study demonstrates that Callistemon citrinus extract could have a chemopreventive effect against colon carcinogenesis.

Comparative effects of avocado oil and losartan on blood pressure, renal vascular function, and mitochondrial oxidative stress in hypertensive rats.

OBJECTIVE: Angiotensin II (Ang-II) antagonism alleviates hypertensive kidney damage by improving mitochondrial function and decreasing oxidative stress. This condition also is associated with altered renal vascular tone due to enhanced constriction by Ang-II. Thus, approaches ameliorating these events are desirable to alleviate kidney damage. Avocado oil, a source of antioxidants and oleic acid, is known to improve mitochondrial function, while oleic acid has antihypertensive effects. Therefore, the aim of this study was to test whether avocado oil counteracts, to a similar degree as the Ang-II blocker losartan, the deleterious effects of hypertension on blood pressure, renal vascular performance, kidney mitochondrial function, and oxidative stress. METHODS: Hypertensive rats induced with Nω-nitro-l-arginine methyl ester (L-NAME) were supplemented during 45 d with avocado oil or losartan. Vascular responses were analyzed in perfused kidney. Membrane potential, reactive oxygen species levels, and glutathione were analyzed in isolated kidney mitochondria. RESULTS: In hypertensive rats, avocado oil decreased 21.2% and 15.5% diastolic and systolic blood pressures, respectively, and alleviated impaired renal vasodilation. Hypertension decreased membrane potential by 83.7% and augmented reactive oxygen species levels by 51% in mitochondria fueled with a complex I substrate, whereas it augmented the levels of oxidized glutathione in 48%. These alterations were normalized by avocado oil at a comparable degree to losartan. CONCLUSIONS: Because avocado oil mimicked the effects of losartan, we propose that the effects of avocado oil might be mediated by decreasing the actions of Ang-II on mitochondria. These results suggest that avocado oil intake might be a nutritional approach to attenuate the deleterious effects of hypertension on kidney.

Von Willebrand Factor: Multimeric Structure and Functional Activity in Patients With Atrial Fibrillation With and Without Oral Anticoagulation.

von Willebrand factor (vWF) is a multimeric glycoprotein present in blood plasma. It is synthesized in megakaryocytes and endothelial cells, secreted into circulation in the form of high-molecular-weight multimers (HMWMs), and cleaved into shorter, less active multimers by ADAMTS13. It is essential for platelet adhesion and aggregation. Previous studies have investigated the relationship between vWF levels and thromboembolic events with little regard to vWF multimeric structure. Patients with atrial fibrillation (AF) exhibit higher plasma vWF and lower ADAMTS13 levels. One hundred seven patients with AF, 51 anticoagulated and 56 nonanticoagulated, were eligible for the study. Plasma samples were analyzed for vWF antigen, vWF activity, and ADAMTS13; vWF multimers were analyzed by Western blot in 1% to 1.3% sodium dodecyl sulfate agarose gel electrophoresis. Patients with AF without oral anticoagulation (OAC) had significantly higher vWF plasma levels (154.00 [75-201] UI/dL) and vWF activity (60.00% [20%-210%]) compared to patients with OAC (133.50 [90-192] UI/dL, P = <.001; 50.00% [20%-160%], P = .02). Both were specially decreased in patients treated with acenocumarin. Patients without OAC also showed lower ADAMTS13 levels and presence of vWF HMWMs. Patients with AF show higher plasma levels and vWF activity. Moreover, treatment with traditional OAC (acenocumarin) significantly reduced vWF levels. Patients without OAC might have an increased risk of thrombotic events showing lower ADAMTS13 and higher vWF levels. Patients with stroke had higher plasma levels, vWF activity, and HMWMs. Our study suggests that increased vWF levels and presence of HMWMs could be related to cerebrovascular disease and may represent useful biomarkers for stroke in AF.

Toluene exposure enhances acute and chronic formalin-induced nociception in rats: Participation of 5-HT3 receptors.

The purpose of this study was to evaluate the effect of acute toluene exposure on formalin (0.5% and 1%)-induced acute and long-lasting nociceptive hypersensitivity in rats. In addition, we sought to investigate the role of peripheral 5-HT3 receptors in the pronociceptive effect of toluene. Toluene exposure (6000ppm) for 30min enhanced 0.5% or 1% formalin-induced acute nociception and long-lasting secondary allodynia and hyperalgesia. In contrast, exposition to toluene for 30min in rats previously injected (six days before) with 1% formalin did not affect long-lasting hypersensitivy. Local peripheral pre-treatment with alosetron (5-HT3 receptor antagonist, 10-100 nmol) reduced the pronociceptive effect of toluene in acute nociception and long-lasting secondary allodynia and hyperalgesia. Alosetron (100nmol) was also able to reduce the nociceptive effects of 1% formalin in absence of toluene. Moreover, local peripheral injection of m-CPBG (5-HT3 receptor agonist, 300 nmol) enhanced 0.5% formalin-induced acute and long-lasting nociception in air- and toluene-exposed rats. Alosetron (10nmol) blocked the pronociceptive effects of m-CPBG (300nmol) on 0.5% formalin-induced acute and long-lasting hypersensitivity in rats exposed to toluene. Alosetron (at 10nmol) did not modify formalin-induced nociceptive behaviors. Finally, local peripheral pre-treatment with methiothepin (non-selective 5-HT receptor antagonist, 1.5nmol), did not affect the pronociceptive effect of toluene on 1% formalin-induced acute and long-lasting hypersensitivity. Our data demonstrate that acute exposure to toluene has pronociceptive effects in formalin-induced acute nociception and long-lasting hypersensitivity. Our data suggest that this pronociceptive effect depend on activation of peripheral 5-HT3, but not methiothepin-sensitive 5-HT, receptors.

The effects of 17ß-oestradiol on increased α(1)-adrenergic vascular reactivity induced by prolonged ovarian hormone deprivation: the role of voltage-dependent L-type Ca channels.

The present study investigated the hypothesis that the duration of ovarian hormone deprivation before reintroduction of oestrogen affects the role of oestrogen as a mediator of the contractile function of α(1)-adrenergic receptors. Rats underwent ovariectomy (OVX) or were sham-operated, and the OVX rats were treated with vehicle (corn oil) or 17ß-oestradiol (E(2)) for 5 days either 10, 28 or 60 days after OVX. The OVX increased phenylephrine- and Ca(2+)-induced contractions. Interestingly, the phenylephrine-induced contractions were increased at each of the three time points, whereas the Ca(2+)-induced contractions were only increased in the 60-day group. E(2) had biphasic effects on phenylephrine- and Ca(2+)-induced contractility. Indeed, E(2) increased contractions in the 10-day group and diminished contractions in the other groups (the increased contractions were avoided by verapamil). These results indicate that E(2) controls α(1)-adrenergic receptor-mediated contractility through effects on L-type Ca(2+) channels in a way that depends on the timing in which the treatment with E(2) is initiated.

Protective effects of resveratrol on calcium-induced oxidative stress in rat heart mitochondria.

Trans-resveratrol is a nutraceutical with known antioxidant, anti-inflammatory, cardioprotective, and anti-apoptotic properties. The aim of this study was to evaluate the effects of resveratrol on heart mitochondria. Resveratrol significantly decreased Fe(2+) + ascorbate oxidant system-induced lipid peroxide levels, preserved physiological levels of glutathione, and increased nitric oxide (NO) levels in mitochondria. Under calcium-mediated stress, there was a 2.7-fold increase in the NO levels, and a mild decoupling in the mitochondrial respiratory chain. These results provide a mechanism for and support the beneficial effects of resveratrol under pathological conditions induced by oxidative stress and calcium overload. In addition, these findings underscore the usefulness of resveratrol in the prevention of cardiovascular diseases.

Angiotensin-II-dependent changes in alpha-1 adrenoceptor vascular expression in pregnant rats.

Vessels from pregnant animals show a blunted response to adrenergic agonists. In this work, we explored if pregnancy reduces alpha(1)-adrenergic receptor (alpha(1)-AR)-mediated vascular smooth muscle protein expression as well as agonist-induced contraction in rat aorta, and if angiotensin II (Ang II) levels during pregnancy are related to these changes. Female Wistar rats were divided randomly into nonpregnant (NP) and pregnant groups (first week: P1, second week: P2, third week: P3). Subsets of animals were treated with captopril (5 mg kg(-1) day(-1) for 7 days; n = 6). Phenylephrine (PHE) concentration-response curves were constructed (1 x 10(-9) to 3.1 x 10(-5) mol/l) and alpha(1A)-, alpha(1B)- and alpha(1D)-AR were measured in the aorta by immunoblot. Captopril decreased alpha-AR expression in the NP group. In contrast, pregnancy decreased alpha(1A)-, alpha(1B)- and alpha(1D)-AR levels and captopril prevented this reduction. PHE sensitivity was decreased in the thoracic and abdominal aorta in the P2 group, with no changes in E(max ), and E(max) was decreased in the abdominal aorta in all experimental groups. Our results suggest that Ang II levels during pregnancy are related to a decrease in aortic alpha(1)-AR expression. The physiological meaning of this finding remains to be established.

Increased alpha-1 adrenoceptor expression in pregnant rats with subrenal aortic coarctation.

UNLABELLED: The progression of pregnancy is associated with attenuation in vasopressor response to adrenergic agonists. In pregnancy-induced hypertension this attenuation is reverted. It is not known if this reversion involves alpha-1 adrenoceptor expression. OBJECTIVE: In this work we propose that in pregnant rats with subrenal aortic coarctation there are changes in the expression of alpha-1 adrenergic receptors in the thoracic and abdominal aorta during pregnancy. METHODS: We used non-pregnant, normal pregnant and pregnant with subrenal aortic coarctation female Wistar rats. Pregnancy-induced hypertension indicators, systolic blood pressure, 24 hours proteinuria, pup weight and maternal weight were measured. Dose response curves to phenylephrine were carried out to determine vascular reactivity along pregnancy. Alpha 1-adrenoceptors were detected from thoracic and abdominal aorta using immunoblot. RESULTS: Results show significant increases in arterial pressure and proteinuria in pregnant rats with SRAC at the end of the third week. Pregnancy reduces alpha-(1-A, -B) and (-D) adrenoceptor expression and this event is reverted by subrenal aortic coarctation. This phenomenon is more apparent in the abdominal segment of the aorta. CONCLUSIONS: These findings suggest that subrenal aortic coarctation is a good animal model of pregnancy-induced hypertension and that alpha1-adrenoceptors participate in its physiopathology increasing their expression in a segment-dependent manner.

Angiotensin II augments renal vasoconstriction via AT1 receptors in L-NAME-induced hypertensive rats.

The renal renin angiotensin system modulates blood pressure via the action of angiotensin II at type 1 (AT1) and type 2 (AT2) angiotensin receptors. It has been proposed that there is an increased pressor response to angiotensin II (ANG II) in the hypertensive rat kidney. We determined the role of the AT1 receptor in L-NAME-induced hypertension. Male Wistar rats (250-300 g) were divided into control (tap water) and L-NAME (50 mg/kg/day/2 weeks) treated groups. Concentration-response curves to ANG II were constructed in isolated perfused kidneys and AT1 receptor expression was determined by Western blot in the renal cortex, medulla and papilla. ANG II evoked an increase in perfusion pressure in kidneys of both control and L-NAME-treated rats in a concentration-related manner. In L-NAME-treated rats, a greater maximal effect was observed compared to control rats (160 +/- 13 vs. 138 +/- 8 mmHg; p<0.05, respectively), suggesting that L-NAME promoted ANG II hypersensitivity. In both, control and L-NAME groups, the response to ANG II was blocked by the selective AT1 receptor antagonist losartan (1 x 10(-8) and 3.16 x 10(-8) M). AT1 receptor expression in kidney cortex, medulla and papilla did not show significant differences between groups. Our results demonstrate that AT1 receptor stimulation is related to renal vasculature hypersensitivity in L-NAME-induced hypertension.

Angiotensin II pressor response in the L-NAME-induced hypertensive pithed rat: role of the AT1 receptor.

The blockade of renin-angiotensin system by pharmacological interventions with angiotensin converting-enzyme (ACE) inhibitors or AT1 receptor antagonists in the juvenile critical age may attenuate or even prevent the development of hypertension. In this work, we determined the Ang II type 1 (AT1) receptor role in L-NAME-induced hypertension in pithed rats. Male Wistar rats (250-300 g) were used. Rats were divided into the following groups: Control (tap water) and N(omega)-Nitro-L-arginine methyl ester (L-NAME, 60 mg/kg/day/2 weeks). Dose-response curves to Ang II were constructed in the pithed rat. The results show that Ang II evoked blood pressure increase in pithed rats in a dose-related manner. In L-NAME-treated rats a greater maximal effect was observed, indicating that L-NAME promotes Ang II hypersensitivity. In L-NAME-treated rats, Ang II response was blocked by losartan (1 and 3 mg/kg), a selective AT1 receptor antagonist, indicating that AT1 receptor influence L-NAME hypertensive mechanism. Our results suggest that Ang II hypersensitivity in L-NAME-induced hypertension can be due to increased AT1 receptor expression or sensitivity changes.