Dual strategy to improve the oral bioavailability of efavirenz employing nanomicelles and curcumin as a bio-enhancer

The present investigation was focused on the development of Soluplus®-based nanomicelles (NMs) (10 % w/v) loaded with Efavirenz (EFV) (5 mg/mL) and Curcumin (natural bio-enhancer) (CUR) (5, 10 and 15 mg/mL) to improve the oral bioavalability of EFV. Micellar formulations were obtained employing an acetone-diffusion technique. Apparent aqueous solubility was increased up to ∼1250-fold and 25,000-fold for EFV and CUR, respectively. Drug-loaded nanoformulations showed an excellent colloidal stability with unimodal size distribution and PDI values < 0.30. In vitro drug release was 41.5 % (EFV) and 2.6 % (CUR) from EFV-CUR-NMs over 6 h in simulated gastrointestinal fluids. EFV-CUR-loaded NMs resulted as safe nanoformulations according to the in vitro cytocompatibility assays in Caco-2 cells. Furthermore, CUR bio-enhancer activity was demonstrated for those nanoformulations. A CUR concentration of 15 mg/mL produced a significant (p < 0.05) increment (2.64-fold) of relative EFV oral bioavailability. Finally, the active role of the lymphatic system in the absorption process of EFV, after its oral administration was assessed in a comparative pharmacokinetic study in presence and absence of cycloheximide, a lymphatic transport inhibitor. Overall our EFV-CUR-NMs denoted their potential as a novel nanotechnological platform, representing a step towards an optimized "nano-sized" therapy for AIDS patients.

Formulation and Characterization of Ursodeoxycholic Acid Nanosuspension Based on Bottom-Up Technology and Box-Behnken Design Optimization

BACKGROUND

Ursodeoxycholic acid (UDCA) is a therapeutic agent used for the treatment of cholestatic hepatobiliary diseases in pediatric patients. It is a bile acid that presents high lipophilicity, and it belongs to Class II of the Biopharmaceutical Classification System (BCS), which exhibits low water solubility and high intestinal permeability, which leads to poor oral absorption. The objective of this work was to design and optimize UDCA nanosuspensions by means of the precipitation-ultrasonication method to improve the solubility, dissolution, and oral bioavailability of UDCA.

METHODS

A three-level, three-factor Box-Behnken design was used to optimize formulation variables and obtain uniform, small-particle-size UDCA nanosuspensions. The independent variables were: stabilizer percentage (X1), amplitude (X2), and sonication time (X3), and the dependent variable was the particle size (Y1). In the precipitation-ultrasonication method, UDCA was dissolved in acetone:PEG 400 (1:1 v/v) and quickly incorporated into the antisolvent (pre-cooled aqueous dispersion of HPMC E-15 0.3%), by means of intense sonication at 50 W for 5 min, controlling temperature through an ice water bath. The lyophilization efficacy was evaluated by means of a cryoprotective efficacy test, working with 10% maltose at -80 °C. The nanosuspensions were characterized by dynamic light scattering (DLS), X-ray diffraction, and scanning electron microscopy (SEM). The physicochemical stability was determined at 25 °C and 4 °C at 7, 14, 30, and 60 days, and the UDCA content was analyzed via HPLC-UV. An in vitro dissolution assay and an oral bioavailability study were performed in male Wistar rats.

RESULTS

A significant impact was achieved in the optimized nanosuspension with 0.3% (stabilizer), 50 W (amplitude), and 5 min (sonication time), with a particle size of 352.4 nm, PDI of 0.11, and zeta potential of -4.30 mV. It presented adequate physicochemical stability throughout the study and the UDCA content was between 90% and 110%. In total, 86% of UDCA was dissolved in the in vitro dissolution test. The relative oral bioavailability was similar without significant statistical differences when comparing the lyophilized nanosuspension and the commercial tablet, the latter presenting a more erratic behavior. The pharmacokinetic parameters of the nanosuspension and the commercial tablet were Tmax (1.0 ± 0.9 h vs. 2.0 ± 0.8 h, respectively), Cmax (0.558 ± 0.118 vs. 0.366 ± 0.113 µM, respectively), ΔCmax (0.309 ± 0.099 vs. 0.232 ± 0.056, respectively), AUC (4.326 ± 0.471 vs. 2.188 ± 0.353 µg/mL.h, respectively, p < 0.02), and IAUC0-24h (2.261 ± 0.187 µg/mL.h vs. 1.924 ± 0.440 µg/mL.h, respectively).

CONCLUSIONS

The developed nanosuspension presents an appropriate dosage and administration for pediatric patients. On the other hand, it exhibits an adequate absorption and UDCA oral bioavailability.

Characterization and bioavailability of a novel coenzyme Q10 nanoemulsion used as an infant formula supplement

Supplementation with Coenzyme Q₁₀ (CoQ₁₀), in patients with its deficiency, has greater odds of success if the treatment is carried out early with an appropriate formulation. For neonatal CoQ₁₀ deficiency, infant formula supplementation could be an attractive option. However, solid CoQ₁₀ cannot be solubilized or dispersed in milk matrix leading to an inefficient CoQ₁₀ dosage and poor intestinal absorption. We developed and characterized a high-dose CoQ₁₀ oil-in-water (O/W) nanoemulsion suitable to supplement infant formula without modifying its organoleptic characteristics. CoQ₁₀ powder and soy lecithin were solubilized in an oil phase consisted of Labrasol® and Labrafac^TM. The aqueous phase was Tween 80, TPGS, methylparaben and propylparaben. O/W nanoemulsion was prepared by adding dropwise the oil phase to the aqueous phase under stirring to a final concentration of CoQ₁₀ 9.5 % w/w followed by ultrasonic homogenization. Pharmacotechnical parameters were determined. This formulation resulted to be easily to be dispersed in milk matrix, stable for at least 90 days, with no cytotoxicity in in vitro assays, and higher bioavailability than CoQ₁₀ powder. CoQ₁₀ nanoemulsion supplementation in the infant formula facilitates the individualized administration for the child with accurate dosage, overcome swallowing difficulties and in turn could increase the treatment adherence and efficacy.

New and developing pharmacotherapies for hypertension

INTRODUCTION

Despite the significant contribution of hypertension to the global burden of disease, disease control remains poor worldwide. Considering this unmet clinical need, several new antihypertensive drugs with novel mechanisms of action are under development.

AREAS COVERED

The present review summarizes the recent advances in the development of emerging pharmacological agents for the management of hypertension. The latest technological innovations in the design of optimized formulations of available antihypertensive drugs and the potential role of the modification of intestinal microbiota to improve blood pressure (BP) control are also covered.

EXPERT OPINION

Significant efforts have been made to develop new antihypertensive agents with novel actions that target the main mechanisms involved in resistant hypertension. Sacubitril/valsartan may emerge as a potential first-line drug due to its superiority over renin angiotensin system inhibitors, and SGLT2 inhibitors can reduce BP in difficult-to-control hypertensive patients with type 2 diabetes. In addition, firibastat and aprocitentan may expand the therapeutic options for resistant hypertension by novel mechanism of actions. Since gut dysbiosis not only leads to hypertension but also causes direct target organ damage, prebiotics and probiotics could represent a potential strategy to prevent or reduce the development of hypertension and to contribute to BP control.

Plasma membrane calcium ATPase downregulation in dopaminergic neurons alters cellular physiology and motor behaviour in Drosophila melanogaster

The accumulation of Ca²⁺ and its subsequent increase in oxidative stress is proposed to be involved in selective dysfunctionality of dopaminergic neurons, the main cell type affected in Parkinson's disease. To test the in vivo impact of Ca²⁺ increment in dopaminergic neurons physiology, we downregulated the plasma membrane Ca²⁺ ATPase (PMCA), a pump that extrudes cytosolic Ca²⁺ , by expressing PMCA^RNAi in Drosophila melanogaster dopaminergic neurons. In these animals, we observed major locomotor alterations paralleled to higher cytosolic Ca²⁺ and increased levels of oxidative stress in mitochondria. Interestingly, although no overt degeneration of dopaminergic neurons was observed, evidences of neuronal dysfunctionality were detected such as increases in presynaptic vesicles in dopaminergic neurons and in the levels of dopamine in the brain, as well as presence of toxic effects when PMCA was downregulated in the eye. Moreover, reduced PMCA levels were found in a Drosophila model of Parkinson's disease, Parkin knock-out, expanding the functional relevance of PMCA reduction to other Parkinson's disease-related models. In all, we have generated a new model to study motor abnormalities caused by increments in Ca²⁺ that lead to augmented oxidative stress in a dopaminergic environment, added to a rise in synaptic vesicles and dopamine levels.

Nebivolol is more effective than atenolol for blood pressure variability attenuation and target organ damage prevention in L-NAME hypertensive rats

β-Adrenergic blockers are no longer recommended as first-line therapy due to the reduced cardioprotection of traditional β-blockers compared with other antihypertensive drugs. It is unknown whether third-generation β-blockers share the limitations of traditional β-blockers. The aim of the present study was to compare the effects of nebivolol or atenolol on central and peripheral systolic blood pressure (SBP) and its variability and target organ damage (TOD) in N-nitro-L-arginine methyl ester (L-NAME) hypertensive rats. Male Wistar rats were treated with L-NAME for 8 weeks together with oral administration of nebivolol 30 mg/kg (n = 8), atenolol 90 mg/kg (n = 8), or vehicle (n = 8). The control group was composed of vehicle-treated Wistar rats. SBP and its variability, as well as echocardiographic parameters, were assessed during the last 2 weeks of treatment. Tissue levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and transforming growth factor β (TGF-β), and histopathological parameters were evaluated in the left ventricle and aorta. Nebivolol had a greater ability than atenolol to decrease central SBP and mid-term and short-term blood pressure variability (BPV) in L-NAME rats. Echocardiographic analysis showed that nebivolol was more effective than atenolol on E/A wave ratio normalization. Compared with atenolol treatment, nebivolol had a greater protective effect on different TOD markers, inducing a decrease in collagen deposition and a reduction in the proinflammatory cytokines IL-6 and TNF-α in the left ventricle and aorta. Our findings suggest that the adverse hemodynamic profile and the reduced cardiovascular protection reported with traditional β-blockers must not be carried forward to third-generation β-blockers.

Neurochemical, Behavioral, and Neurogenic Validation of a Hyposerotonergic Animal Model by Voluntary Oral Consumption of para-Chlorophenylalanine

The inhibitor of tryptophan hydroxylase, para-chlorophenylalanine (PCPA), has been classically employed as a pharmacological tool to deplete serotonin (5-HT) in animal models and to evaluate whether this neurotransmitter is involved in the action of pharmacological compounds. PCPA is usually administrated by intraperitoneal (ip) injections, which are stressful and painful. To avoid ip injections, we designed and validated a protocol for PCPA oral administration. C57BL/6 elite male mice received PCPA during 7 days either ip or by giving the drug inside jelly cubes at an estimated dose of 500 mg/kg on days 1 and 2 and 250 mg/kg for the rest of the treatment. 5-HT levels decreased by 85% and 55% in the hippocampus of mice treated with oral or ip PCPA, respectively, whereas in the prefrontal cortex, 5-HT levels decreased by 65% (oral) and 50% (ip). Behavioral tests, like the forced swimming test (FST), the nestlet shredding test (NST), and the marble burying test (MBT), were performed. In the FST, mice received fluoxetine ip 30 min before the test. In mice with oral PCPA treatment, fluoxetine did not induce significant reductions of immobility, indicating that reduction of 5-HT levels was effective. No effect of ip or oral 5-HT depletion was observed in the NST nor in the MBT. In a second experiment, mice received oral PCPA for 8 weeks: again, serotonin levels were significantly decreased in both hippocampus and cortex, and effects on hippocampal neurogenesis replicated previous observations in hyposerotonergic mice. Therefore, neurochemical, behavioral, and neurogenic results allow us to validate this refined protocol for voluntary oral consumption of PCPA.

Dietary L-tryptophan modulates agonistic behavior and brain serotonin in male dyadic contests of a cichlid fish

Although some studies have investigated the effects of dietary L-tryptophan on agonistic behavior, research on adult fish specimens is still lacking. Moreover, submissive behaviors have been generally overlooked. We focused on agonistic behavior between males of the cichlid fish Cichlasoma dimerus, in dyadic encounters held in a novel context after being fed or not with an L-tryptophan enriched diet (TRP) for 2 weeks. We arranged three different dyads: control/control (control conditions: not TRP enriched), control/TRP, and TRP/TRP. We also registered the response of the brain serotonergic system in four brain regions. TRP/TRP dyads showed higher latencies to first attack, lower overall aggression, and lower proportions of bites and passive copings (submissive display) compared to control/control. TRP dominant males performed fewer bites with respect to controls, and subordinate males opposed to TRP males showed fewer passive copings. Higher serotonergic activities were found in subordinates' optic tectum and in the telencephalon and preoptic area/hypothalamus of TRP males. Altogether, results point out that dietary L-tryptophan reduced males' motivation to attack and dominant aggression, which consequently influenced subordinate agonistic repertory. In addition, males within TRP/TRP dyads showed a switch in their behavioral agonistic repertory. These behavioral outcomes were probably due to modifications at brain serotonergic functioning.

Role of indoleamine 2,3-dioxygenase in testicular immune-privilege

Male meiotic germ cell including the spermatozoa represent a great challenge to the immune system, as they appear long after the establishment of normal immune tolerance mechanisms. The capacity of the testes to tolerate autoantigenic germ cells as well as survival of allogeneic organ engrafted in the testicular interstitium have led to consider the testis an immunologically privileged site. Disruption of this immune privilege following trauma, tumor, or autoimmune orchitis often results in male infertility. Strong evidence indicates that indoleamine 2,3-dioxygenase (IDO) has been implicated in fetal and allograft tolerance, tumor immune resistance, and regulation of autoimmune diseases. IDO and tryptophan 2,3-dioxygenase (TDO) catalyze the same rate-limiting step of tryptophan metabolism along a common pathway, which leads to tryptophan starvation and generation of catabolites collectively known as kynurenines. However, the relevance of tryptophan metabolism in testis pathophysiology has not yet been explored. Here we assessed the in vivo role of IDO/TDO in experimental autoimmune orchitis (EAO), a model of autoimmune testicular inflammation and immunologically impaired spermatogenesis. EAO was induced in adult Wistar rats with testicular homogenate and adjuvants. Control (C) rats injected with saline and adjuvants and normal untreated rats (N) were also studied. mRNA expression of IDO decreased in whole testes and in isolated Sertoli cells during EAO. TDO and IDO localization and level of expression in the testis were analyzed by immunostaining and Western blot. TDO is expressed in granulomas from EAO rats, and similar protein levels were observed in N, C, and EAO groups. IDO was detected in mononuclear and endothelial cells and reduced IDO expression was detected in EAO group compared to N and C rats. This phenomenon was concomitant with a significant reduction of IDO activity in EAO testis measured by tryptophan and kynurenine concentrations (HPLC). Finally, in vivo inhibition of IDO with 1-methyl-tryptophan increased severity of the disease, demonstrating down regulation of IDO-based tolerance when testicular immune regulation was disrupted. We present evidence that an IDO-based mechanism is involved in testicular immune privilege.

Adenosine A1 receptors and mitochondria: targets of remote ischemic preconditioning

Adenosine is involved in classic preconditioning in most species and acts especially through adenosine A₁ and A₃ receptors. The aim of the present study was to evaluate whether remote ischemic preconditioning (rIPC) activates adenosine A₁ receptors and improves mitochondrial function, thereby reducing myocardial infarct size. Isolated rat hearts were subjected to 30 min of global ischemia and 60 min of reperfusion [ischemia-reperfusion (I/R)]. In a second group, before isolation of the heart, a rIPC protocol (3 cycles of hindlimb I/R) was performed. Infarct size was measured with tetrazolium staining, and Akt/endothelial nitric oxide (NO) synthase (eNOS) expression/phosphorylation and mitochondrial function were evaluated after ischemia at 10 and 60 min of reperfusion. As expected, rIPC significantly decreased infarct size. This beneficial effect was abolished only when 8-cyclopentyl-1,3-dipropylxanthine (adenosine A₁ receptor blocker) and N^G-nitro-l-arginine methyl ester (NO synthesis inhibitor) were administered during the reperfusion phase. At the early reperfusion phase, rIPC induced significant Akt and eNOS phosphorylation, which was abolished by the perfusion with an adenosine A₁ receptor blocker. I/R led to impaired mitochondrial function, which was attenuated by rIPC and mediated by adenosine A₁ receptors. In conclusion, we demonstrated that rIPC limits myocardial infarct by activation of adenosine A₁ receptors at early reperfusion in the isolated rat heart. Interestingly, rIPC appears to reduce myocardial infarct size by the Akt/eNOS pathway and improves mitochondrial function during myocardial reperfusion. NEW & NOTEWORTHY Adenosine is involved in classic preconditioning and acts especially through adenosine A₁ and A₃ receptors. However, its role in the mechanism of remote ischemic preconditioning is controversial. In this study, we demonstrated that remote ischemic preconditioning activates adenosine A₁ receptors during early reperfusion, inducing Akt/endothelial nitric oxide synthase phosphorylation and improving mitochondrial function, thereby reducing myocardial infarct size.

Sociability deficits after prenatal exposure to valproic acid are rescued by early social enrichment

Background

Autism spectrum disorder (ASD) is characterized by impaired social interactions and repetitive patterns of behavior. Symptoms appear in early life and persist throughout adulthood. Early social stimulation can help reverse some of the symptoms, but the biological mechanisms of these therapies are unknown. By analyzing the effects of early social stimulation on ASD-related behavior in the mouse, we aimed to identify brain structures that contribute to these behaviors.

Methods

We injected pregnant mice with 600-mg/kg valproic acid (VPA) or saline (SAL) at gestational day 12.5 and evaluated the effect of weaning their offspring in cages containing only VPA animals, only SAL animals, or mixed. We analyzed juvenile play at PD21 and performed a battery of behavioral tests in adulthood. We then used preclinical PET imaging for an unbiased analysis of the whole brain of these mice and studied the function of the piriform cortex by c-Fos immunoreactivity and HPLC.

Results

Compared to control animals, VPA-exposed animals play less as juveniles and exhibit a lower frequency of social interaction in adulthood when reared with other VPA mice. In addition, these animals were less likely to investigate social odors in the habituation/dishabituation olfactory test. However, when VPA animals were weaned with control animals, these behavioral alterations were not observed. Interestingly, repetitive behaviors and depression-related behaviors were not affected by social enrichment. We also found that VPA animals present high levels of glucose metabolism bilaterally in the piriform cortex (Pir), a region known to be involved in social behaviors. Moreover, we found alterations in the somatosensory, motor, and insular cortices. Remarkably, these effects were mostly reversed after social stimulation. To evaluate if changes in glucose metabolism in the Pir correlated with changes in neuronal activity, we measured c-Fos immunoreactivity in the Pir and found it increased in animals prenatally exposed to VPA. We further found increased dopamine turnover in the Pir. Both alterations were largely reversed by social enrichment.

Conclusions

We show that early social enrichment can specifically rescue social deficits in a mouse model of ASD. Our results identified the Pir as a structure affected by VPA-exposure and social enrichment, suggesting that it could be a key component of the social brain circuitry.

Electronic supplementary material

The online version of this article (10.1186/s13229-018-0221-9) contains supplementary material, which is available to authorized users.

Nicotine-induced molecular alterations are modulated by GABAB receptor activity

It has been demonstrated that GABAB receptors modulate nicotine (NIC) reward effect; nevertheless, the mechanism implicated is not well known. In this regard, we evaluated the involvement of GABAB receptors on the behavioral, neurochemical, biochemical and molecular alterations associated with the rewarding effects induced by NIC in mice, from a pharmacological and genetic approach. NIC-induced rewarding properties (0.5 mg/kg, subcutaneously, sc) were evaluated by conditioned place preference (CPP) paradigm. CPP has three phases: preconditioning, conditioning and postconditioning. GABAB receptor antagonist 2-hydroxysaclofen (0.25, 0.5 and 1 mg/kg; intraperitoneally, ip) or the GABAB receptor agonist baclofen (3 mg/kg; ip) was injected before NIC during the conditioning phase. GABAB1 knockout (GABAB1 KO) mice received NIC during the conditioning phase. Vehicle and wild-type controls were employed. Neurochemical (dopamine, serotonin and their metabolites), biochemical (nicotinic receptor α4β2, α4β2nAChRs) and molecular (c-Fos) alterations induced by NIC were analyzed after the postconditioning phase by high-performance liquid chromatography (HPLC), receptor-ligand binding assays and immunohistochemistry, respectively, in nucleus accumbens (Acb), prefrontal cortex (PFC) and ventral tegmental area (VTA). NIC induced rewarding effects in the CPP paradigm and increased dopamine levels in Acb and PFC, α4β2nAChRs density in VTA and c-Fos expression in Acb shell (AcbSh), VTA and PFC. We showed that behavioral, neurochemical, biochemical and molecular alterations induced by NIC were prevented by baclofen. However, in 2-hydroxysaclofen pretreated and GABAB1 KO mice, these alterations were potentiated, suggesting that GABAB receptor activity is necessary to control alterations induced by NIC-induced rewarding effects. Therefore, the present findings provided important contributions to the mechanisms implicated in NIC-induced rewarding effects.

Advances in therapy for the prevention of HIV transmission from mother to child

INTRODUCTION

Actually, ~17.8 million women and 1.8 million children (<15 years) are currently infected with the Human Immunodeficiency Virus (HIV)/Acquired Immunodeficiency Syndrome (AIDS). Particularly, the majority of pediatric infections (>90%) resulted from 'HIV mother-to-child transmission' (MTCT), both in pregnancy, labour, delivery and later by breastfeeding. Due to its high pediatric incidence, MTCT represents a public health concern. Areas covered: In this review, we focus on available treatments and antiretroviral drugs recommended by the World Health Organization, and the main clinical investigations in antiretroviral pharmacotherapy to prevent the MTCT. Expert opinion: The MTCT has been improved dramatically in the last few years mainly due to prophylactic perinatal antiretroviral therapy for pregnant women living with HIV. However, there is still a milestone to reach since HIV MTCT remains as a public health challenge associated with MTCT though breastfeeding (post-natal transmission). In this context, different strategies could be employed as an attempt to reduce pediatric HIV infections. One of them involves the improvement of patient adherence to the HIV therapy. One possible solution is the development of novel long-acting formulations for prophylaxis of mothers and children, and a second possible solution is increase the inclusion of mothers and infants in care programs to more effectively prevent the vertical transmission.

Fructose increases corticosterone production in association with NADPH metabolism alterations in rat epididymal white adipose tissue

Metabolic syndrome is an array of closely metabolic disorders that includes glucose intolerance/insulin resistance, central obesity, dyslipidemia, and hypertension. Fructose, a highly lipogenic sugar, has profound metabolic effects in adipose tissue, and has been associated with the etiopathology of many components of the metabolic syndrome. In adipocytes, the enzyme 11 β-HSD1 amplifies local glucocorticoid production, being a key player in the pathogenesis of central obesity and metabolic syndrome. 11 β-HSD1 reductase activity is dependent on NADPH, a cofactor generated by H6PD inside the endoplasmic reticulum. Our focus was to explore the effect of fructose overload on epididymal white adipose tissue (EWAT) machinery involved in glucocorticoid production and NADPH and oxidants metabolism. Male Sprague-Dawley rats fed with a fructose solution (10% (w/v) in tap water) during 9 weeks developed some characteristic features of metabolic syndrome, such as hypertriglyceridemia, and hypertension. In addition, high levels of plasma and EWAT corticosterone were detected. Activities and expressions of H6PD and 11 β-HSD1, NAPDH content, superoxide anion production, expression of NADPH oxidase 2 subunits, and indicators of oxidative metabolism were measured. Fructose overloaded rats showed an increased potential in oxidant production respect to control rats. In parallel, in EWAT from fructose overloaded rats we found higher expression/activity of H6PD and 11 β-HSD1, and NADPH/NADP⁺ ratio. Our in vivo results support that fructose overload installs in EWAT conditions favoring glucocorticoid production through higher H6PD expression/activity supplying NADPH for enhanced 11 β-HSD1 expression/activity, becoming this tissue a potential extra-adrenal source of corticosterone under these experimental conditions.

Effects of carvedilol or amlodipine on target organ damage in L-NAME hypertensive rats: their relationship with blood pressure variability

The aim of the study was to compare the effects of chronic oral treatment with carvedilol or amlodipine on blood pressure, blood pressure variability and target organ damage in N-nitro-l-arginine methyl ester (L-NAME) hypertensive rats. Wistar rats were treated with L-NAME administered in the drinking water for 8 weeks together with oral administration of carvedilol 30 mg/kg (n = 6), amlodipine 10 mg/kg (n = 6), or vehicle (n = 6). At the end of the treatment, echocardiographic evaluation, blood pressure, and short-term variability measurements were performed. Left ventricular and thoracic aortas were removed to assess activity of metalloproteinase 2 and 9 and expression levels of transforming growth factor β, tumor necrosis factor α, and interleukin 6. Histological samples were prepared from both tissues. Carvedilol and amlodipine induced a comparable reduction of systolic and mean arterial pressure and its short-term variability in L-NAME rats. The expression of transforming growth factor β, tumor necrosis factor α, and interleukin 6 decreased in both organs after carvedilol or amlodipine treatment and the activity of metalloproteinase was reduced in aortic tissue. Treatment with carvedilol or amlodipine completely prevented left ventricular collagen deposition and morphometric alterations in aorta. Oral chronic treatment with carvedilol or amlodipine significantly attenuates blood pressure variability and reduces target organ damage and biomarkers of tissue fibrosis and inflammation in L-NAME hypertensive rats.

The SSRI fluoxetine exhibits mild effects on the reproductive axis in the cichlid fish Cichlasoma dimerus (Teleostei, Cichliformes)

Among the wide variety of pharmaceuticals released into the environment, Fluoxetine (FLX), a selective serotonin reuptake inhibitor, is one of the most prescribed for the treatment of major depression. It inhibits serotonin (5-HT) reuptake at the presinaptic membrane, increasing serotonergic activity. In vertebrates, including fish, the serotonergic system is closely related to the Hypothalamic Pituitary Gonadal (HPG) axis which regulates reproduction. As FLX can act as an endocrine disrupting compound (EDC) by affecting several reproductive parameters in fish, the aim of this study was to provide an integral assessment of the potential effect of FLX on the reproductive axis of the Neotropical freshwater fish Cichlasoma dimerus. Adult fish were intraperitoneally injected with 2 μg g^-1 FLX or saline every third day for 15 days. No significant differences were found on serotonergic turnover (5-HIAA/5-HT ratio). Pituitary βLH content in FLX injected females was significantly higher than control females; no significant differences were seen for βFSH content. Sex steroids remained unaltered, both in males and females fish, after FLX treatment. No plasma vitellogenin was induced in treated males. Some alterations were seen in testes of FLX injected males, such as the presence of foam cells and an acidophilic PAS positive, Alcian-Blue negative secretion in the lobular lumen. Although there is no clear consensus about the effect of this drug on reproductive physiology, these results indicate that FLX is acting as a mild EDC in adults of C. dimerus.

Angiotensin-(1-7) protects from brain damage induced by shiga toxin 2-producing enterohemorrhagic Escherichia coli

Shiga toxin 2 (Stx2)-producing enterohemorrhagic induced brain damage. Since a cerebroprotective action was reported for angiotensin (Ang)-(1-7), our aim was to investigate whether Ang-(1-7) protects from brain damage induced by Stx2-producing enterohemorrhagic Escherichia coli The anterior hypothalamic area of adult male Wistar rats was injected with saline solution or Stx2 or Stx2 plus Ang-(1-7) or Stx2 plus Ang-(1-7) plus A779. Rats received a single injection of Stx2 at the beginning of the experiment, and Ang-(1-7), A779, or saline was administered daily in a single injection for 8 days. Cellular ultrastructural changes were analyzed by transmission electron microscopy. Stx2 induced neurodegeneration, axonal demyelination, alterations in synapse, and oligodendrocyte and astrocyte damage, accompanied by edema. Ang-(1-7) prevented neuronal damage triggered by the toxin in 55.6 ± 9.5% of the neurons and the Stx2-induced synapse dysfunction was reversed. In addition, Ang-(1-7) blocked Stx2-induced demyelination in 92 ± 4% of the axons. Oligodendrocyte damage caused by Stx2 was prevented by Ang-(1-7) but astrocytes were only partially protected by the peptide (38 ± 5% of astrocytes were preserved). Ang-(1-7) treatment resulted in 50% reduction in the number of activated microglial cells induced by Stx2, suggesting an anti-inflammatory action. All these beneficial effects elicited by Ang-(1-7) were blocked by the Mas receptor antagonist and thus it was concluded that Ang-(1-7) protects mainly neurons and oligodendrocytes, and partially astrocytes, in the central nervous system through Mas receptor stimulation.

Relative bioavailability of coenzyme Q10 formulation for paediatric individualized therapy

OBJECTIVES

Conduct a preliminary comparison of the bioavailability between two formulations: commercial grade coenzyme Q10 (CoQ10) powder (solid formulation) and a new oil-in-water liquid emulsion and their effect on other antioxidants.

METHODS

Six healthy individuals participated in a randomized, crossover, open, consecutive design, with a 2-week washout period. Pharmacokinetic parameters were assessed after a single and multiple intakes of 250 mg CoQ10 given daily for 1 week.

KEY FINDINGS

The differences in the pharmacokinetic parameters of maximum plasma concentration, area under the curve between 0-360 and 0-4 h, elimination half-life were statistically significant with a relative bioavailability of 489% increase over solid CoQ10 formulation. A multiple dose supplementation increased plasma CoQ10 levels in both formulations, liquid emulsion performing better (2.4- vs 3.9-fold for solid and liquid formulation, respectively) without modifications on other antioxidants. Furthermore, the plasma CoQ10 at 7th day was statistically different between formulations (P < 0.05).

CONCLUSIONS

The results obtained showed that liquid emulsion improves the bioavailability of CoQ10 respect to solid form which not only facilitates the individualized administration for the child but in turn could increase the therapeutic efficacy, which should be confirmed by further studies.

Novel carvedilol paediatric nanomicelle formulation: in-vitro characterization and in-vivo evaluation

Objectives

Carvedilol (CAR) is a poorly water-soluble beta-blocker. Its encapsulation within nanomicelles (NMs) could improve drug solubility and its oral bioavailability, allowing the development of a paediatric liquid CAR formulation with commercially available copolymers: D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and poly(vinyl caprolactam)-poly(vinyl acetate)-poly(ethylene glycol) (Soluplus®).

Methods

Drug-loaded NMs were prepared by copolymer and CAR dispersion in distilled water. Micellar size and morphology were characterized by dynamic light scattering and transmission electron microscopy, respectively. In-vitro drug permeation studies were evaluated by conventional gut sac method. In-vivo CAR oral bioavailability from NMs dispersions and drug control solution was evaluated in Wistar rats.

Key findings

Carvedilol apparent aqueous solubility was increased (up to 60.4-folds) after its encapsulation within NMs. The micellar size was ranged between 10.9 and 81.9 nm with a monomodal size distribution. There was a significant enhancement of CAR relative oral bioavailability for both copolymers vs a micelle-free drug solution (P &lt; 0.05). This improvement was higher for TPGS-based micelles (4.95-fold) in accordance with the in-vitro CAR permeation results.

Conclusions

The present investigation demonstrates the development of highly concentrated CAR liquid micellar formulation. The improvement on drug oral bioavailability contributes to the potential of this NMs formulation to enhance CAR paediatric treatment.

Myocardial triggers involved in activation of remote ischaemic preconditioning

NEW FINDINGS

What is the central question of this study? Ischaemia-reperfusion of peripheral tissues protects the heart from subsequent myocardial ischaemia-reperfusion injury, a phenomenon referred to as remote ischaemic preconditioning (rIPC). This study evaluated the possible myocardial triggers of rIPC. What is the main finding and its importance? Remote ischaemic preconditioning reduces infarct size through a vagal pathway and a mechanism involving phosphorylation of Akt and endothelial nitric oxide synthase, opening of mitochondrial ATP-dependent K(+) channels and an increase in mitochondrial H2 O2 production. All these phenomena occur before the myocardial ischaemia; hence, they could act as 'triggers' of rIPC. It has been proposed that remote ischaemic preconditioning (rIPC) activates a parasympathetic neural pathway. However, the myocardial intracellular mechanism of rIPC remains unclear. Here, we characterized some of the intracellular signals participating as rIPC triggers. Isolated rat hearts were subjected to 30 min of global ischaemia and 120 min of reperfusion (Non-rIPC group). In a second group, before the isolation of the heart, an rIPC protocol (three cycles of hindlimb ischaemia-reperfusion) was performed. The infarct size was measured with tetrazolium staining. Expression/phosphorylation of Akt and endothelial nitric oxide synthase (eNOS) and mitochondrial H2 O2 production were evaluated at the end of the rIPC protocol, before myocardial ischaemia-reperfusion. The rIPC significantly decreased the infarct size and induced Akt and eNOS phosphorylation. The protective effect on infarct size was abolished by cervical vagal section, l-NAME (an NO synthesis inhibitor) and 5-hydroxydecanoate (a mitochondrial ATP-dependent K(+) channel blocker). Mitochondrial production of H2 O2 was increased by rIPC, whereas it was abolished by cervical vagal section, l-NAME and 5-hydroxydecanoate. We conclude that rIPC activates a parasympathetic vagal pathway and a mechanism involving the phosphorylation of Akt and eNOS, the opening of mitochondrial ATP-dependent K(+) channels and the release of H2 O2 by the mitochondria. All these phenomena occur before myocardial ischaemia and could act as triggers of rIPC.

Serotonergic outcome, stress and sexual steroid hormones, and growth in a South American cichlid fish fed with an L-tryptophan enriched diet

Reared animals for edible or ornamental purposes are frequently exposed to high aggression and stressful situations. These factors generally arise from conspecifics in densely breeding conditions. In vertebrates, serotonin (5-HT) has been postulated as a key neuromodulator and neurotransmitter involved in aggression and stress. The essential amino acid L-tryptophan (trp) is crucial for the synthesis of 5-HT, and so, leaves a gateway for indirectly augmenting brain 5-HT levels by means of a trp-enriched diet. The cichlid fish Cichlasoma dimerus, locally known as chanchita, is an autochthonous, potentially ornamental species and a fruitful laboratory model which behavior and reproduction has been studied over the last 15years. It presents complex social hierarchies, and great asymmetries between subordinate and dominant animals in respect to aggression, stress, and reproductive chance. The first aim of this work was to perform a morphological description of chanchita's brain serotonergic system, in both males and females. Then, we evaluated the effects of a trp-supplemented diet, given during 4weeks, on brain serotonergic activity, stress and sexual steroid hormones, and growth in isolated specimens. Results showed that chanchita's brain serotonergic system is composed of several populations of neurons located in three main areas: pretectum, hypothalamus and raphe, with no clear differences between males and females at a morphological level. Animals fed with trp-enriched diets exhibited higher forebrain serotonergic activity and a significant reduction in their relative cortisol levels, with no effects on sexual steroid plasma levels or growth parameters. Thus, this study points to food trp enrichment as a "neurodietary'' method for elevating brain serotonergic activity and decreasing stress, without affecting growth or sex steroid hormone levels.

Involvement of endothelins in deoxycorticosterone acetate-salt hypertension through the modulation of noradrenergic transmission in the rat posterior hypothalamus

NEW FINDINGS

What is the central question of this study? Does ex vivo administration of endothelin-1 and endothelin-3 regulate noradrenergic transmission in the posterior hypothalamus of deoxycorticosterone acetate-salt hypertensive rats compared with normotensive rats? What is the main finding and its importance? Endothelin-1 and endothelin-3 enhanced diverse mechanisms leading to increased noradrenergic transmission in the posterior hypothalamus of deoxycorticosterone acetate-salt hypertensive rats. Unveiling the role of brain endothelins in hypertension would probably favour the development of new therapeutic targets for the treatment of essential hypertension, which still represents a challenging disease with high mortality. Brain catecholamines participate in diverse biological functions regulated by the hypothalamus. We have previously reported that endothelin-1 and endothelin-3 (ET-1 and ET-3) modulate catecholaminergic activity in the anterior and posterior hypothalamus of normotensive rats. The aim of the present study was to evaluate the interaction between endothelins and noradrenergic transmission in the posterior hypothalamus of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. We assessed the effects of ET-1 and ET-3 on tyrosine hydroxylase activity and expression, neuronal noradrenaline (NA) release, neuronal NA transporter (NAT) activity and expression, monoamine oxidase activity and NA endogenous content and utilization (as a marker of turnover) in the posterior hypothalamus of DOCA-salt hypertensive rats. In addition, levels of ETA and ETB receptors were assayed in normotensive and hypertensive rats. Results showed that tyrosine hydroxylase activity and total and phosphorylated levels, NAT activity and content, NA release, monoamine oxidase activity and NA utilization were increased in DOCA-salt rats. Both ET-1 and ET-3 further enhanced all noradrenergic parameters except for total tyrosine hydroxylase level and NA endogenous content and utilization. The expression of ETA receptors was increased in the posterior hypothalamus of DOCA-salt rats, but ETB receptors showed no changes. These results show that ET-1 and ET-3 upregulate noradrenergic activity in the posterior hypothalamus of DOCA-salt hypertensive rats. Our findings suggest that the interaction between noradrenergic transmission and the endothelinergic system in the posterior hypothalamus may be involved in the development and/or maintenance of hypertension in this animal model.

Didanosine-loaded poly(epsilon-caprolactone) microparticles by a coaxial electrohydrodynamic atomization (CEHDA) technique

The goal of this study was to investigate the electrohydrodynamic atomization (EHDA) technology to encapsulate the water-soluble antiretroviral didanosine (ddI) within poly(epsilon-caprolactone) (PCL) particles and stabilize it in the gastric medium where it undergoes fast degradation. A preliminary study employing a one-needle setup enabled the adjustment of the critical process parameters. Then, a configuration of two concentric needles named coaxial electrohydrodynamic atomization (CEHDA) led to the formation of ddI-loaded PCL microcapsules. Scanning electron microscopy analysis showed that the microparticles were spherical and with narrow size distribution. Attenuated total reflectance/Fourier transform infrared spectroscopy confirmed that most of the drug was efficiently encapsulated within the particles, whereas differential scanning calorimetry and X-ray powder diffraction revealed that the drug was preserved mainly in crystalline form. The loading capacity was relatively high (approximately 12% w/w), and the encapsulation efficiency was approximately 100%. In vitro release assays (PBS pH = 7.4) indicated that ddI was released almost completely within 2 h. Moreover, the delayed release was expected to isolate ddI from the biological fluids during the gastric transit. Finally, pharmacokinetics studies in rats showed that ddI-loaded particles lead to a statistically significant increase of the oral bioavailability of almost 4 times and a 2-fold prolongation of the half-life with respect to a ddI aqueous solution, supporting the use of CEHDA as a promising reproducible, scalable and cost-viable technology to encapsulate water-soluble drugs within polymeric particles.

Tempol-nebivolol therapy potentiates hypotensive effect increasing NO bioavailability and signaling pathway

Nebivolol is a third generation beta blocker with endothelial nitric oxide synthase (eNOS) agonist properties. Considering the role of reactive oxygen species (ROS) in the uncoupling of eNOS, we hypothesized that the preadministration of an antioxidant as tempol, could improve the hypotensive response of nebivolol in normotensive animals increasing the nitric oxide (NO) bioavailability by a reduction of superoxide (O2(•-)) basal level production in the vascular tissue. Male Sprague Dawley rats were given tap water to drink (control group) or tempol (an antioxidant scavenger of superoxide) for 1 week. After 1 week, Nebivolol, at a dose of 3 mg/kg, was injected intravenously to the control group or to the tempol-treated group. Mean arterial pressure, heart rate, and blood pressure variability were evaluated in the control, tempol, nebivolol, and tempol nebivolol groups, as well as, the effect of different inhibitor as Nβ-nitro-l-arginine methyl ester (L-NAME, a Nitric oxide synthase blocker) or glybenclamide, a KATP channel inhibitor. Also, the expression of α,β soluble guanylate cyclase (sGC), phospho-eNOS, and phospho-vasodilator-stimulated phosphoprotein (P-VASP) were evaluated by Western Blot and cyclic guanosine monophosphate (cGMP) levels by an enzyme-linked immunosorbent assay (ELISA) commercial kit assay. We showed that pretreatment with tempol in normotensive rats produces a hypotensive response after nebivolol administration through an increase in the NO bioavailability and sGC, improving the NO/cGMP/protein kinase G (PKG) pathway compared to that of the nebivolol group. We demonstrated that tempol preadministration beneficiates the response of a third-generation beta blocker with eNOS stimulation properties, decreasing the basal uncoupling of eNOS, and improving NO bioavailability. Our results clearly open a possible new strategy therapeutic for treating hypertension.

Central insulin-angiotensin II interaction in blood pressure regulation in fructose overloaded rats

The aim of the present study was to determine if insulin is able to modulate the pressor response to intracerebroventricularly administered angiotensin II in insulin resistant fructose overloaded rats. Male Sprague-Dawley rats were divided into two groups: 1) Control group (C) with tap water to drink for 6 weeks (n=36); and 2) fructose treated (F), with fructose solution (10% w/v) to drink for 6 weeks (n=36). On the day of the experiment, anesthetized male C and F rats were intracerebroventricularly infused with insulin (12 mU/h, n=15) or Ringer's solution as vehicle (n=15) for 2h. Immediately, changes in mean arterial pressure (MAP) in response to an intracerebroventricular subpressor dose of angiotensin II (5 pmol, n=10) or vehicle (n=5) were measured for 10 min. Then, hypothalami were removed and Akt and ERK1/2 phosphorylation levels were determined. In a subset of C (n=10) and F (n=20) animals, PD98059 (p44/42 MAPK inhibitor) or vehicle was administered intracerebroventricularly at a flow rate of 5 μl/min for 1 min. Ten minutes later, insulin (12 mU/h, n=5 for each group) or vehicle (Ringer's solution, only in the F group, n=5) was perfused for 2h at a flow rate of 4 μl/h, and cardiovascular parameters were measured every 15 min. Immediately, changes in MAP and HR in response to a subpressor dose of Ang II (5 pmol/2 μl) were evaluated for 10 min (n=5 for each group). In other subset of animals (n=6 for each group), AT1 and AT2 hypothalamic receptor levels were measured by Western blotting. Intracerebroventricular insulin pre-treatment increased the pressor response to angiotensin II in C rats. In F rats (with or without insulin pretreatment), the pressor response to angiotensin II was higher than that in vehicle pre-treated C animals, but similar to that observed in C after insulin infusion. In C rats phospho-ERK 1/2 hypothalamic levels significantly increased after angiotensin II injection in insulin pretreated animals compared to vehicle pre-treated rats, suggesting that MAPK activation might be involved in insulin potentiation of blood pressure response to angiotensin II in the brain. Phospho-ERK 1/2 hypothalamic levels were significantly increased in vehicle treated F rats compared to C, suggesting that basal MAPK activation might play a role in the enhanced response to angiotensin II observed in these animals. Finally, in F rats, either after vehicle or insulin infusion, angiotensin II injection was associated with a similar increase in phospho-ERK 1/2 hypothalamic levels, comparable to that observed after angiotensin II injection in insulin pre-treated C animals. ERK 1/2 blockade significantly reduced MAP in F rats compared to C. Moreover, ERK 1/2 inhibition completely abolished the Ang II pressor response in F rats and in insulin pre-treated C animals. All these findings suggest that insulin-angiotensin II interaction at hypothalamic level might be involved in the increase in blood pressure observed in the insulin resistant state.

Blood Pressure Variability: Prognostic Value and Therapeutic Implications

Blood pressure variability (BPV) is considered nowadays a novel risk factor for cardiovascular disease. Early findings in sinoaortic denervated rats have clearly shown that enhanced fluctuation of blood pressure induced left ventricular hypertrophy, vascular stiffness, and renal lesion. A large number of clinical trials confirm that short-term and long-term blood pressure variability independently contributes to target organ damage, cardiovascular events, and mortality not only in hypertensive patients but also in subjects with diabetes mellitus and chronic kidney disease. Therefore, amelioration of BPV has been suggested as an additional target of the treatment of cardiovascular diseases. Preliminary evidence obtained from meta-analysis and controlled clinical trials has shown that antihypertensive classes differ in their ability to control excessive BP fluctuations with an impact in the prevention of cardiovascular events. Calcium channel blockers seem to be more effective than other blood pressure lowering drugs for the reduction of short-term and long-term BPV. In order to increase actual knowledge regarding the prognostic value and therapeutic significance of BPV in cardiovascular disease, there is a need for additional clinical studies specifically designed for the study of the relevance of short-term and long-term BPV control by antihypertensive drugs.

Heme oxygenase-1 overexpression fails to attenuate hypertension when the nitric oxide synthase system is not fully operative

Heme oxygenase (HO) is an enzyme that is involved in numerous secondary actions. One of its products, CO, seems to have an important but unclear role in blood pressure regulation. CO exhibits a vasodilator action through the activation of soluble guanylate cyclase and the subsequent production of cyclic guanosine monophosphate (cGMP). The aim of the present study was to determine whether pathological and pharmacological HO-1 overexpression has any regulatory role on blood pressure in a renovascular model of hypertension. We examined the effect of zinc protoporyphyrin IX (ZnPP-IX) administration, an inhibitor of HO activity, on mean arterial pressure (MAP) and heart rate in sham-operated and aorta-coarcted (AC) rats and its interaction with the nitric oxide synthase (NOS) pathway. Inhibition of HO increased MAP in normotensive rats with and without hemin pretreatment but not in hypertensive rats. Pretreatment with NG-nitro-L-arginine methyl ester blocked the pressor response to ZnPP-IX, suggesting a key role of NOS in the cardiovascular action of HO inhibition. In the same way, AC rats, an experimental model of hypertension with impaired function and low expression of endothelial NOS (eNOS), did not show any cardiovascular response to inhibition or induction of HO. This finding suggests that eNOS was necessary for modulating the CO response in the hypertensive group. In conclusion, the present study suggests that HO regulates blood pressure through CO only when the NOS pathway is fully operative. In addition, chronic HO induction fails to attenuate the hypertensive stage induced by coarctation as a consequence of the impairment of the NOS pathway.

Measurement of inverse agonism in β-adrenoceptors

Increasing numbers of compounds, previously classified as antagonists, were shown to inhibit this spontaneous or constitutive receptor activity, instead of leave it unaffected as expected for a formal antagonist. In addition, some other antagonists did not have any effect by themselves, but prevented the inhibition of constitutive activity induced by thought-to-be antagonists. These thought-to-be antagonists with negative efficacy are now known as "inverse agonists." Inverse agonism at βAR has been evidenced for both subtypes in wild-type GPCRs systems and in engineered systems with high constitutive activity. It is important to mention that native systems are of particular importance for analyzing the in vivo relevance of constitutive activity because these systems have physiological expression levels of target receptors. Studies of inverse agonism of β blockers in physiological setting have also evidenced that pathophysiological conditions can affect pharmacodynamic properties of these ligands. To date, hundreds of clinically well-known drugs have been tested and classified for this property. Prominent examples include the beta-blockers propranolol, alprenolol, pindolol, and timolol used for treating hypertension, angina pectoris, and arrhythmia that act on the β₂ARs, metoprolol, and bisoprolol used for treating hypertension, coronary heart disease, and arrhythmias by acting on β₁ARs. Inverse agonists seem to be useful in the treatment of chronic disease characterized by harmful effects resulting from β₁AR and β₂AR overactivation, such as heart failure and asthma, respectively.

Mechanisms involved in the long-term modulation of tyrosine hydroxylase by endothelins in the olfactory bulb of normotensive rats

The olfactory bulbs play a relevant role in the interaction between the animal and its environment. The existence of endothelin-1 and -3 in the rat olfactory bulbs suggests their role in the control of diverse functions regulated at this level. Tyrosine hydroxylase, a crucial enzyme in catecholamine biosynthesis, is tightly regulated by short- and long-term mechanisms. We have previously reported that in the olfactory bulbs endothelins participate in the short-term tyrosine hydroxylase regulation involving complex mechanisms. In the present work we studied the effect of long-term stimulation by endothelins on tyrosine hydroxylase in the rat olfactory bulbs. Our findings show that endothelin-1 and -3 modulated catecholaminergic transmission by increasing enzymatic activity. However, these peptides acted through different receptors and intracellular pathways. Endothelin-1 enhanced tyrosine hydroxylase activity through a super high affinity ET(A) receptor and cAMP/PKA and CaMK-II pathways, whereas, endothelin-3 through a super high affinity atypical receptor coupled to cAMP/PKA, PLC/PKC and CaMK-II pathways. Endothelins also increased tyrosine hydroxylase mRNA and the enzyme total level as well as the phosphorylation of Ser 19, 31 and 40 sites. Furthermore, both peptides stimulated dopamine turnover and reduced its endogenous content. These findings support that endothelins are involved in the long-term regulation of tyrosine hydroxylase, leading to an increase in the catecholaminergic activity which might be implicated in the development and/or maintenance of diverse pathologies involving the olfactory bulbs.

Cardiovascular drugs inducing QT prolongation: facts and evidence

Acquired QT syndrome is mainly caused by the administration of drugs that prolong ventricular repolarization. On the other hand, the risk of drug-induced torsades de pointes is increased by numerous predisposing factors, such as genetic predisposition, female sex, hypokalemia and cardiac dysfunction. This adverse reaction is induced by different chemical compounds used for the treatment of a variety of pathologies, including arrhythmias. As it is known, antiarrhythmic agents and other cardiovascular drugs can prolong the QT interval, causing this adverse reaction. Of the 20 most commonly reported drugs, 10 were cardiovascular agents and these appeared in 348 of the reports (46%). Class Ia antiarrhythmic agents have frequently been linked to inducing arrhythmia, including torsades de pointes. Sotalol and amiodarone, class III antiarrhythmics, are known to prolong the QT interval by blocking I(Kr). Due to the severity of events caused by the therapeutic use of these drugs, in this work of revision the cardiovascular drugs that present this property and the factors and evidence will be mentioned.

Novel long-term anticonvulsant treatment with gabapentin without causing memory impairment in mice

We previously reported that administration of a single dose of gabapentin (GBP) immediately after training improves memory of mice in an inhibitory avoidance task (IA), whereas GBP administered repeatedly for 7 days impairs memory. This is in accordance with the observation that long-term clinical treatment with GBP may be associated with adverse cognitive side effects. In the present work we used a GBP-loaded poly(epsilon-caprolactone) implant, allowing controlled release of the drug and maintenance of constant plasma levels over 1 week. When GBP-loaded implants were inserted subcutaneously into mice, immediately after training in the IA task, memory consolidation was enhanced. Moreover, GBP released from implants had an anticonvulsant action against pentylenetetrazole-induced seizures. These results suggest that maintenance of stable GBP plasma levels could protect against seizures without causing memory impairment. Hence, the adverse cognitive effects might be avoided by stabilizing plasma levels of the drug.

Increased sensitivity to diltiazem hypotensive effect in an experimental model of high-renin hypertension

Objectives

The aim of this work was to evaluate the pharmacokinetic–pharmacodynamic properties of diltiazem in an experimental model of high-renin hypertension, such as the aortic coarctated (ACo) rat, to further characterize the responsiveness of this model to calcium channel blockers.

Methods

A ‘shunt’ microdialysis probe was inserted in a carotid artery of anaesthetized ACo and control sham-operated (SO) rats for simultaneous determination of diltiazem plasma concentrations and their effects on mean arterial pressure and heart rate after the intravenous application of 3 and 6 mg/kg of the drug. Correlation between plasma levels and cardiovascular effects was established by fitting the data to a modified Emax model.

Key findings

Volume of distribution was greater in ACo than in SO rats. Diltiazem plasma clearance (Cl) was significantly greater in ACo rats than in normotensive SO rats after administration of diltiazem (6 mg/kg). Moreover, Cl increased with dose in ACo but not in SO rats. No differences were observed in the maximal bradycardic effect comparing both experimental groups, and sensitivity (S0) to diltiazem chronotropic effect was similar comparing SO and ACo rats. Differences were not found in the maximal response of the hypotensive effect comparing SO and ACo rats, but the S0 to diltiazem hypotensive effect was greater in ACo rats than in SO rats.

Conclusions

ACo induced profound changes in diltiazem pharmacokinetic behaviour. In addition, our results suggested an increased sensitivity to diltiazem blood pressure lowering effect in experimental renovascular hypertension with high-renin levels.

Relationship between P-glycoprotein activity measured in peripheral blood mononuclear cells and indinavir bioavailability in healthy volunteers

Indinavir, a HIV-1 protease inhibitor, showed large inter-individual pharmacokinetic variability. It has been proposed as a substrate of P-glycoprotein (P-gp), an efflux transporter, that may contribute to limit indinavir bioavailability. A liquid formulation of indinavir was developed from indinavir capsules in order to study indinavir pharmacokinetics in healthy volunteers. Compartmental and noncompartmental analysis of indinavir plasma concentrations showed high inter-individual variability in terms of area under the curve (AUC) and maximal plasma concentration (C(max)). A significant negative association between AUC normalized to body weight (AUC x weight) and lymphocyte P-gp activity, using Rh123 efflux assay, was observed (p = 0.008; r = -0.75). AUC normalized to elimination rate constant (AUC x beta) also showed a significant negative relationship with lymphocyte P-gp activity (p = 0.03, r = -0.64). Apparent clearance (CL/[F x weight]) and volume of distribution (VD/[F x weight]) showed a positive correlation with P-gp activity. Conversely, elimination rate constant did not correlate with P-gp activity. Although there is not enough evidence of a correlation between lymphocitary and intestinal function of P-gp, our results suggest a relationship between a P-gp phenotype marker, Rh123 efflux assay in lymphocytes, and indinavir bioavailability.