Functional Autoreactive Anti-ß2 Adrenergic Antibodies May Contribute to Insulin Resistance Profile in Patients with Chronic Chagas Disease.

Potential activation of ß2 adrenergic receptors (ß2AR) by specific autoreactive antibodies (Abs) that arise during the host reaction to Trypanosoma cruzi, could contribute to the elevated prevalence of metabolic disturbances described in patients with chronic Chagas disease (CCD). This study aimed to determine the prevalence of anti-ß2AR Abs in patients with CCD, as well as the correlation of these Abs with the presence of glucose and lipid metabolism disturbances, in order to explore their association with an insulin resistance profile. Additionally, we tested the functional effects of anti-ß2AR Abs employing an in vitro bioassay with neuroendocrine cells expressing ß2AR. A clinical and metabolic evaluation including an OGTT was performed in 80 CCD patients and 40 controls. Anti-ß2AR Abs were measured by an in-house-developed ELISA, and the ß2 adrenergic activity of affinity-purified IgG fractions from patient' sera were assayed in CRE-Luc and POMCLuc transfected AtT-20 cells. A higher proportion of dysglycemia (72.5% vs. 37.5%; p = 0.001) was observed in the CCD group, accompanied by increased HOMA2-IR (p = 0.019), especially in subjects with Abs (+). Anti-ß2AR Abs reactivity (7.01 (2.39-20.5); p = 0.0004) and age >50 years (3.83 (1.30-11.25); p = 0.014) resulted as relevant for IR prediction (AUC: 0.786). Concordantly, Abs (+) CCD patients showed elevated metabolic risk scores and an increased prevalence of atherogenic dyslipidemia (p = 0.040), as compared to Abs (-) patients and controls. On functional bioassays, Abs exerted specific and dose-dependent ß2-agonist effects. Our findings suggest that anti-ß2AR Abs may induce the activation of ß2AR in other tissues besides the heart; furthermore, we show that in patients with CCD these Abs are associated with an insulin resistance profile and atherogenic dyslipidemia, providing biological plausibility to the hypothesis that adrenergic activation by anti-ß2AR Abs could contribute to the pathogenesis of metabolic disturbances described in CCD patients, increasing their cardiovascular risk.

KSHV G-protein coupled receptor vGPCR oncogenic signaling upregulation of Cyclooxygenase-2 expression mediates angiogenesis and tumorigenesis in Kaposi's sarcoma.

Kaposi's sarcoma-associated herpesvirus (KSHV) vGPCR is a constitutively active G protein-coupled receptor that subverts proliferative and inflammatory signaling pathways to induce cell transformation in Kaposi's sarcoma. Cyclooxygenase-2 (COX-2) is an inflammatory mediator that plays a key regulatory role in the activation of tumor angiogenesis. Using two different transformed mouse models and tumorigenic full KSHV genome-bearing cells, including KSHV-Bac16 based mutant system with a vGPCR deletion, we demostrate that vGPCR upregulates COX-2 expression and activity, signaling through selective MAPK cascades. We show that vGPCR expression triggers signaling pathways that upregulate COX-2 levels due to a dual effect upon both its gene promoter region and, in mature mRNA, the 3'UTR region that control mRNA stability. Both events are mediated by signaling through ERK1/2 MAPK pathway. Inhibition of COX-2 in vGPCR-transformed cells impairs vGPCR-driven angiogenesis and treatment with the COX-2-selective inhibitory drug Celecoxib produces a significant decrease in tumor growth, pointing to COX-2 activity as critical for vGPCR oncogenicity in vivo and indicating that COX-2-mediated angiogenesis could play a role in KS tumorigenesis. These results, along with the overexpression of COX-2 in KS lesions, define COX-2 as a potential target for the prevention and treatment of KSHV-oncogenesis.

Efectos del tratamiento antioxidante en la activación del eje hipotálamo-hipófiso-adrenal inducida por el consumo de dietas ricas en sacarosa / Effects of antioxidant treatment on the activation of the hipotalamo-hipofiso-adrenal axis induced by the consumption of sucrose rich diets

Introducción: dados los efectos pleiotrópicos de los glucocorticoides (GCs) sobre el metabolismo, los niveles excesivos y sostenidos de GCs circulantes tienen efectos deletéreos e incrementan la morbilidad y mortalidad cardiovascular. Objetivos: estudiar el efecto de la terapia antioxidante (con ácido lipoico o melatonina) sobre la hiperactivación del eje hipotálamo-hipófiso-adrenal (HHA) en animales alimentados con dieta rica en sacarosa (DRS). Materiales y métodos: se evaluó la actividad del eje HHA y se determinaron parámetros hormonales, de estrés oxidativo y de inflamación en la adenohipófisis de animales tratados con DRS durante tres semanas. Resultados: los animales del grupo DRS mostraron mayores niveles circulantes de hormona adrenocorticotropa (ACTH, por sus siglas en inglés) y corticosterona. En paralelo se detectó un aumento en la expresión del polipéptido precursor (proopiomelanocortina, POMC) y de ACTH en la adenohipófisis, donde también se observó un aumento de lipoperóxidos y proteínas nitradas en tirosina (daño oxidativo), un mayor número de macrófagos tisulares y un incremento en la producción de IL-1beta. El tratamiento antioxidante previno los cambios en estos parámetros. En particular la melatonina también normalizó la actividad del eje HHA y la expresión hipofisaria de POMC. Conclusiones: la sobrecarga metabólica inducida por la administración de DRS genera daño oxidativo e inflamación en la adenohipófisis. La activación de los macrófagos tisulares producida en consecuencia podría impactar sobre los corticotropos hipofisarios e inducir su hiperfunción. La melatonina podría utilizarse como herramienta terapéutica para normalizar la actividad del eje HHA en modelos de obesidad por dieta.

Introduction: given the pleiotropic effects of glucocorticoids (GCs) on metabolism, excessive and sustained levels of circulating GCs, have deleterious effects and increase cardiovascular morbidity and mortality. Objectives: to study the effect of antioxidant therapy on hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis in animals fed a sucrose-rich diet (SRD). Materials and methods: the activity of the HPA axis was evaluated and hormonal, oxidative stress and inflammation parameters were determined in the adenohypophysis of animals treated with SRD for trhee weeks. Results: animals from the SRD group showed higher circulating levels of adrenocorticotropic hormone (ACTH) and corticosterone. In parallel, an increase in the expression of the polypeptide precursors, POMC and ACTH were detected in the adenohypophysis. We also observed an increase in lipoperoxides and proteins nitrated in tyrosine (oxidative damage), a greater number of tissue macrophages and an increase in the production of IL-1beta. Antioxidant treatment prevented all these changes. In particular, melatonin also normalized the activity of the HPA axis and pituitary expression of POMC. Conclusions: the metabolic overload induced by the administration of SRD generates oxidative damage and inflammation in the adenohypophysis. Activation of tissue macrophages could affect, in turn, pituitary corticotrophs inducing their activation. Melatonin could be used as a therapeutic tool to normalize the activity of the HPA axis in diet obesity models.

The enrichment of maternal environment prevents pre-term birth in a mice model.

Maternal lifestyle affects both mother health and pregnancy outcome in humans. Several studies have demonstrated that interventions oriented toward reducing stress and anxiety have positive effects on pregnancy complications such as preeclampsia, excessive gestational weight, gestational diabetes and preterm birth. In this work, we showed that the environmental enrichment (EE), defined as a noninvasive and biologically significant stimulus of the sensory pathway combined with voluntary physical activity, prevented preterm birth (PTB) rate by 40% in an inflammatory mouse model induced by the systemic administration of bacterial lipopolysaccharide (LPS). Furthermore, we found that EE modulates maternal metabolism and produces an anti-inflammatory environment that contributes to pregnancy maintenance. In pregnant mice uterus, EE reduces the expression of TLR4 and CD14 (the LPS receptor and its coactivator protein), preventing the LPS-induced increase in PGE2 and PGF2α release and nitric oxide synthase (NOS) activity. In cervical tissue, EE inhibits cervical ripening events, such as PGE2 release, matrix metalloproteinase (MMP)-9 increased activity and neutrophil recruitment, therefore conserving cervical function. It seems that EE exposure could mimic the stress and anxiety-reducing techniques mentioned above, explaining, at least partially, the beneficial effects of having a healthy lifestyle before and during gestation. Furthermore, we propose that designing an EE protocol for humans could be a noninvasive and preventive therapy for pregnancy complications, averting pre-term birth occurrence and dreaded sequelae that are present in the offspring born too soon.

Impaired HPA axis function in diabetes involves adrenal apoptosis and phagocytosis.

PURPOSE: The aim of the present study was to analyze the involvement of oxidative stress and inflammation in the modulation of glucocorticoid production in the adrenal cortex of diabetic rats. METHODS: Male Wistar rats were treated with or without streptozotocin (STZ, an insulinopenic model of diabetes) and either α-lipoic (90 mg/kg ip.), α-tocopherol (200 mg/kg po.) or with STZ and supplemented with insulin (STZ + INS: 2.5U/day) for 4 weeks. Oxidative/nitrosative stress parameters and antioxidant enzymes were determined in adrenocortical tissues. Apoptosis and macrophage activation were evaluated by immunohistochemistry (TUNEL and ED1+). Basal and ACTH-stimulated corticosterone production were assessed by RIA and plasma ACTH levels were determined by an immunometric assay. RESULTS: Diabetic rats showed a diminished response to exogenous ACTH stimulation along with higher basal corticosterone and lower plasma ACTH levels. In the adrenal cortex we determined an increase in the levels of lipoperoxides, S-nitrosothiols, nitric oxide synthase activity and nitro-tyrosine modified proteins while catalase activity and heme oxygenase-1 expression levels were also elevated. Antioxidant treatments were effective in the prevention of these effects, and in the increase in the number of apoptotic and phagocytic (ED1+) cells detected in diabetic rats. No changes were observed in the STZ + INS group. CONCLUSIONS: Generation of oxidative/nitrosative stress in the adrenal cortex of diabetic rats leads to the induction of apoptosis and the activation of adrenocortical macrophages and is associated with an elevated basal corticosteronemia and the loss of the functional capacity of the gland.

Melatonin prevents early pituitary dysfunction induced by sucrose-rich diets.

While physiological levels of glucocorticoids are required to ensure proper functions of the body, consistently high levels may engender several deleterious consequences. We have previously shown an increase in the activity of the hypothalamic-pituitary-adrenal (HPA) axis in rats fed sucrose-rich diets (SRD). The main goal of this study was to analyze the processes involved in the modulation of the pituitary production of ACTH by SRD, and to test melatonin as a possible therapeutic agent for the prevention of the HPA axis dysfunction. Male Wistar rats were fed standard chow and either SRD (30% sucrose in the drinking water) or plain water for three weeks. Melatonin was administered as subcutaneous pellets. Results showed that SRD treatment induced an increase in systemic ACTH and corticosterone levels and a decrease in melatonin levels. In the pituitary gland, we also detected an increase in the expression levels of proopiomelanocortin (POMC) that was accompanied by increased levels of: lipoperoxides, nitro-tyrosine modified proteins, catalase, heme oxygenase-1, interleukin-1ß mRNA, and by an increase in the tissue number of inflammatory cells (F4/80 and Iba-1 positive cells). Melatonin treatment prevented all these systemic and pituitary changes as well as the increase in POMC expression induced by incubation of AtT-20 corticotrophs with conditioned media obtained from stimulated macrophages. In conclusion, stimulation of POMC/ACTH production in rats fed a SRD could involve the generation of oxidative stress and inflammation in the pituitary gland. Melatonin treatment prevented these effects and normalized the activity of the HPA axis.

El ejercicio físico moderado evita la aparición de insulinorresistencia y de alteraciones morfofuncionales adrenocorticales en ratas tratadas con una dieta rica en sacarosa / Moderate exercise prevents insulin resistance and changes in adrenocortical morphology and function in rats fed a sucrose-enriched diet

Introducción: niveles elevados de glucocorticoides se asocian a las alteraciones somáticas y bioquímicas presentes en los pacientes y en animales con insulinorresistencia (IR). Hemos demostrado previamente que la IR inducida por una dieta rica en sacarosa (DRS) induce cambios morfológicos y funcionales a nivel adrenocortical y que estas alteraciones pueden evitarse mediante la administración simultánea de un agonista PPAR-γ. Objetivos: en el presente estudio evaluamos el impacto de un protocolo de ejercicio moderado sobre las alteraciones morfológicas y funcionales adrenocorticales asociadas con el desarrollo de IR inducida por una DRS administrada durante siete semanas. Metodología. Resultados: los animales (ratas Wistar macho adultas) tratados con la DRS (agregado de sacarosa al 30% en el agua de bebida) mostraron un incremento del peso corporal y de los panículos adiposos, así como de los niveles séricos de glucosa, insulina y triglicéridos. La respuesta glucémica a la administración de insulina i.p. se vio claramente menoscabada. Se observó una infiltración lipídica de la corteza adrenal, con aumento de la expresión de proteínas esteroidogénicas y marcadores de inflamación (IL-1ß, TNF-α, iNOS, COX-2) y un incremento marcado de la corticosteronemia basal. El protocolo de ejercicio consistió en correr en una cinta continua adaptada especialmente durante un máximo de 7 min/día. Este ejercicio moderado previno la aparición de los cambios somáticos y bioquímicos característicos del estado de IR y la infiltración lipídica adrenocortical, revirtiendo además los cambios inflamatorios y normalizando la corticosteronemia. Conclusiones: nuestros resultados subrayan el rol deletéreo del consumo exagerado de carbohidratos simples conteniendo fructosa y sugieren que el ejercicio moderado podría tener efectos adicionales cuando se emplea en el tratamiento de la IR

A role for the endocannabinoid system in premature luteal regression and progesterone withdrawal in lipopolysaccharide-induced early pregnancy loss model.

STUDY QUESTION: What is the role of the endocannabinoid system (eCS) in the alterations of the endocrine system in a murine model of lipopolysaccharide (LPS)-induced miscarriage? SUMMARY ANSWER: In 7-days pregnant wild type, but not cannabinoid receptor type 1 knockout (CB1-KO) mice, LPS increased COX-2 expression and prostaglandin F2α (PGF2α) production in the uterus leading to lower expression of prolactin receptor in the ovary and a marked regression of corpora lutea (CL), suggesting that the eCS mediates the deleterious effects of LPS on reproductive events. WHAT IS KNOWN ALREADY: Appropriate systemic progesterone levels are critical for a successful pregnancy outcome. Precocious loss of luteal progesterone (P4) secretion leads to miscarriage in rodents. We have previously shown that LPS administration to pregnant mice induces embryonic resorption accompanied by a dramatic decrease in systemic progesterone levels in a murine model of inflammatory miscarriage, with the eCS mediating these LPS-induced deleterious effects. STUDY DESIGN SAMPLES/MATERIALS, METHODS: CD1 wild-type (WT) and CB1-KO mice were randomly allocated to Vehicle (saline; i.p.) or LPS (0.5 µg/g body weight; i.p.) treated groups: (WT-Vehicle; WT-LPS; CB1-KO-Vehicle and CB1-KO-LPS). A single injection was given on day 7 of pregnancy and tissues (blood, ovary, uterus) were collected 6, 12, 24 and 48 h later. P4 and PGF2α plasma levels were determined by radioimmunoassay. Cyclooxygenase-2 (COX-2) mRNA (RT-PCR) and protein (Western blot) content in uterus was assayed. COX-2 and prolactin receptor (PrlR) mRNA levels in the ovary were assayed by RT-PCR. Tissue morphology of the CL was assessed by haematoxylin-eosin staining. MAIN RESULTS AND THE ROLE OF CHANCE: Treatment of 7-day pregnant WT mice with LPS induced a P4 withdrawal (p < 0.05), increased in uterine COX-2 mRNA and protein expression (p < 0.05) as well as an increase in uterine PGF2α production (p < 0.05). These changes were absent in LPS-treated 7-day pregnant CB1-KO mice. In ovarian tissues, LPS treatment to 7-day pregnant WT mice induced a downregulation of PrlR mRNA expression (p < 0.05) together with an increase in COX-2 mRNA expression (p < 0.05) and PGF2α content (p < 0.05). These effects were absent in the CB1-KO mice. Collectively, our results suggest a role for the eCS mediating LPS-induced deleterious effects on reproductive tissues. LIMITATIONS, REASONS FOR CAUTION: An important caveat of this study is the endocrine differences between mice and humans during pregnancy (e.g. P4 is produced by the CL throughout pregnancy in mice, whereas this is not the case in humans), which limits the extrapolation of the results presented here. WIDER IMPLICATIONS OF THE FINDINGS: Our findings provide new insights in the role of the endocannabinoid system in the physiopathology of reproduction as well as the role of this endogenous system as a mediator of LPS deleterious effects on reproductive tissues. LARGE SCALE DATA: None. STUDY FUNDING AND COMPETING INTERESTS: Dr Ana María Franchi was funded by Agencia Nacional para la Promoción Científica y Tecnológica (PICT 2010/0813 and PICT 2013/0097) and by Consejo Nacional de Investigaciones Científicas y Técnicas (PIP 2012/0061). The authors have no competing interests.

Efecto de un herbicida a base de glifosato sobre la generación de alteraciones metabólicas sistémicas y cambios histológicos hepáticos en un modelo animal de insulinorresistencia / Effects of a glyphosate-based herbicide on systemic metabolic alterations and histologic hepatic changes present in an animal model of insulin resistance

Introducción: el estrés oxidativo y la inflamación asociados a la insulinorresistencia (IR) contribuyen a generar esteatohepatitis no alcohólica. También la exposición al glifosato, un herbicida ampliamente utilizado, incrementa la peroxidación lipídica hepática con aumento de radicales libres de O2. Objetivos: evaluar los efectos de la administración prolongada de un herbicida a base de glifosato sobre la generación de IR, estrés oxidativo y cambios histológicos hepáticos en animales tratados con una dieta rica en sacarosa (DRS). Metodología: ratas Wistar macho (~300 g) recibieron Credit® por vía intraperitoneal (~50 mg/kg de glifosato tres veces por semana; grupo G, n=6), sacarosa al 30% en el agua de bebida (grupo S, n=6), ambos tratamientos (grupo G+S, n=8), o ninguno de ellos (grupo C, n=7). Tras una exposición de 8-10 semanas se midieron glucemia e insulinemia basales y tras una carga de glucosa intraperitoneal. En la semana 13, tras la eutanasia, se extrajo el hígado (tinciones con hematoxilina-eosina y tricrómica de Masson, TBARS). Resultados: no hubo diferencias significativas en los niveles glucémicos basales o postcarga. Los tratamientos con G o S generaron incrementos leves de la IR evidenciados por el índice HOMA-IR, mientras que la combinación de G+S llevó a un aumento altamente significativo de este parámetro. También fue más marcado, en estos animales, el grado de lipoperoxidación (TBARS) medido en homogenatos hepáticos. La evaluación histológica mostró signos de esteatosis y fibrosis en los grupos G y G+S, e infiltrados inflamatorios en todos los grupos tratados. Conclusiones: aislado o en combinación con sacarosa, el herbicida a base de glifosato aumentó el grado de esteatosis y fibrosis a nivel hepático. Por otro lado, la administración del herbicida incrementó la magnitud de la insulinorresistencia inducida por la DRS generando un mayor estrés oxidativo a nivel hepático

Moderate Exercise Prevents Functional Remodeling of the Anterior Pituitary Gland in Diet-Induced Insulin Resistance in Rats: Role of Oxidative Stress and Autophagy.

A sustained elevation of glucocorticoid production, associated with the establishment of insulin resistance (IR) could add to the deleterious effects of the IR state. The aim of this study is to analyze the consequences of long-term feeding with a sucrose-rich diet (SRD) on Pomc/ACTH production, define the underlying cellular processes, and determine the effects of moderate exercise (ME) on these parameters. Animals fed a standard chow with or without 30% sucrose in the drinking water were subjected to ME. Circulating hormone levels were determined, and pituitary tissues were processed and analyzed by immunobloting and quantitative real-time PCR. Parameters of oxidative stress (OxS), endoplasmic reticulum stress, and autophagy were also determined. Rats fed SRD developed a decrease in pituitary Pomc/ACTH expression levels, increased expression of antioxidant enzymes, and induction of endoplasmic reticulum stress and autophagy. ME prevented pituitary dysfunction as well as induction of antioxidant enzymes and autophagy. Reporter assays were performed in AtT-20 corticotroph cells incubated in the presence of palmitic acid. Pomc transcription was inhibited by palmitic acid-dependent induction of OxS and autophagy, as judged by the effect of activators and inhibitors of both processes. Long-term feeding with SRD triggers the generation of OxS and autophagy in the pituitary gland, which could lead to a decline in Pomc/ACTH/glucocorticoid production. These effects could be attributed to an increase in fatty acids availability to the pituitary gland. ME was able to prevent these alterations, suggesting additional beneficial effects of ME as a therapeutic strategy in the management of IR.

Lipopolysaccharide-induced murine embryonic resorption involves changes in endocannabinoid profiling and alters progesterone secretion and inflammatory response by a CB1-mediated fashion.

Genital tract infections are a common complication of human pregnancy that can result in miscarriage. We have previously shown that a lipopolysaccharide (LPS) induces embryonic resorption in a murine model of inflammatory miscarriage. This is accompanied by a dramatic decrease in systemic progesterone levels associated with a robust pro-inflammatory response that results in embryo resorption. Here, we tested the hypothesis that the endogenous cannabinoid system (eCS), through cannabinoid receptor 1 (CB1), plays a role in regulating progesterone levels and, therefore, the pro-inflammatory response. We show that LPS treatment in pregnant mice causes significant changes in the eCS ligands, which are reversed by progesterone treatment. We further show the CB1-KO mice maintain higher plasma progesterone levels after LPS treatment, which is associated with a feebler uterine inflammatory response and a significant drop in embryo resorption. These data suggest that manipulation of CB1 receptors and/or ligands is a potential therapeutic avenue to decrease infection-induced miscarriage.

Crosstalk between nitric oxide synthases and cyclooxygenase 2 in the adrenal cortex of rats under lipopolysaccharide treatment.

The effect of lipopolysaccharide on the modulation of steroid production by adrenal cells has been recently acknowledged. The purpose of this study was to determine the in vivo effects of LPS on adrenal cyclooxygenase 2 (COX-2) expression, analyze its crosstalk with the nitric oxide synthase (NOS) system, and assess its involvement on the modulation of glucocorticoid production. Male Wistar rats were injected with LPS and with specific inhibitors for NOS and COX activities. PGE2 and corticosterone levels were determined by RIA. Protein levels were analyzed by immunoprecipitation and western blotting. Transfection assays were performed in murine adrenocortical Y1 cells. Results show that LPS treatment increases PGE2 production and COX-2 protein levels in the rat adrenal cortex. Systemic inhibition of COX-2 blunted the glucocorticoid response to ACTH, as well as the increase in NOS activity and the NOS-2 expression levels induced by LPS. Conversely, NOS inhibition prevented the LPS-dependent increase in PGE2 production, COX-2 protein levels, and the nitrotyrosine modification of COX-2 protein. Treatment of adrenocortical cells with a NO-donor significantly potentiated the LPS-dependent increase in NFκB activity and COX-2 expression levels. In conclusion, our results show a significant crosstalk between COX-2 and NOS in the adrenal cortex upon LPS stimulation, in which each activity has a positive impact on the other. In particular, as both the activities differently affect adrenal steroid production, we hypothesize that this kind of fine modulation enables the gland to adjust steroidogenesis to prevent either an excessive or an insufficient response to the endotoxin challenge.

Insulin sensitization with a peroxisome proliferator-activated receptor γ agonist prevents adrenocortical lipid infiltration and secretory changes induced by a high-sucrose diet.

It has been hypothesized that deviations in glucocorticoid secretion and/or action may contribute to somatic and biochemical changes observed in patients with and animal models of insulin resistance (IR). In this study, we analyzed changes in rat adrenocortical function and morphology associated with the development of IR, generated in male adult rats by the addition of 30% sucrose to the drinking water. Caloric intake, body and adipose tissue weights, and biochemical parameters associated with IR were determined. Expression levels of Star, Cyp11A1, Mc2r, Pparγ (Pparg), and Cd36 were evaluated by real-time PCR, histochemical analysis of the adrenal cortex was performed using Masson's trichrome and Sudan III staining, and corticosterone levels were measured by RIA. After 7 weeks of sucrose administration, higher serum glucose, insulin, and triglyceride levels and an altered glycemic response to an i.p. insulin test were detected. Adrenal glands showed a neutral lipid infiltration. An increase in Star, Cyp11A1, Mc2r, Pparg and Cd36 and a decrease in Mc2r levels were also found. Furthermore, sucrose-treated animals exhibited higher basal corticosterone levels and a blunted response to ACTH injection. Noteworthy, the adrenocortical (functional and histological) abnormalities were prevented in sucrose-treated rats by the simultaneous administration of an insulin-sensitizing PPARγ agonist. In conclusion, sucrose-induced IR affects adrenocortical morphology and function possibly via the generation of adipokines or lipid metabolites within the adrenal gland. These abnormalities are prevented by the administration of a PPARγ agonist by mechanisms involving both extra- and intra-adrenal effects.

Effects of GABAB receptor agonists and antagonists on glycemia regulation in mice.

γ-Aminobutyric acid (GABA) inhibits insulin secretion through GABA(B) receptors in pancreatic ß-cells. We investigated whether GABA(B) receptors participated in the regulation of glucose homeostasis in vivo. BALB/c mice acutely pre-injected with the GABA(B) receptor agonist baclofen (7.5mg/kg, i.p.) presented glucose intolerance and diminished insulin secretion during a glucose tolerance test (GTT, 2g/kg body weight, i.p.). The GABA(B) receptor antagonist 2-hydroxysaclofen (15 mg/kg, i.p.) improved the GTT and reversed the baclofen effect. Also a slight increase in insulin secretion was observed with 2-hydroxysaclofen. In incubated islets 1.10(-5)M baclofen inhibited 20mM glucose-induced insulin secretion and this effect was reversed by coincubation with 1.10(-5)M 2-hydroxysaclofen. In chronically-treated animals (18 days) both the receptor agonist (5mg/kg/day i.p.) and the receptor antagonist (10mg/kg/day i.p.) induced impaired GTTs; the receptor antagonist, but not the agonist, also induced a decrease in insulin secretion. No alterations in insulin tolerance tests, body weight and food intake were observed with the treatments. In addition glucagon, insulin-like growth factor I, prolactin, corticosterone and growth hormone, other hormones involved in glucose metabolism regulation, were not affected by chronic baclofen or 2-hydroxysaclofen. In islets obtained from chronically injected animals with baclofen, 2-hydroxysaclofen or saline (as above), GABA(B2) mRNA expression was not altered. Results demonstrate that GABA(B) receptors are involved in the regulation of glucose homeostasis in vivo. Treatment with receptor agonists or antagonists, given acutely or chronically, altered glucose homeostasis and insulin secretion alerting to the need to evaluate glucose metabolism during the clinical use of these drugs.

Effects of heme oxygenase isozymes on Leydig cells steroidogenesis.

In the present study, we demonstrate the expression of heme oxygenase (HO) isozymes, HO-1 and HO-2 (listed as HMOX1 and HMOX2 in the MGI Database), in MA-10 Leydig tumor cells and its effect on steroidogenesis. The well-known HO inducer, hemin, increased both HO-1 and HO-2 protein levels and HO-specific activity. Induction of HO by hemin inhibited basal, hCG-, and dibutyryl cAMP (db-cAMP)-induced steroidogenesis in a reversible way. When we studied the effect of HO isozymes along the steroid synthesis, we found that steroidogenic acute regulatory protein levels were decreased, and the conversion of cholesterol to pregnenolone was inhibited by hemin treatment, with no changes in the content of cholesterol side-chain cleavage enzyme (P450scc). hCG and db-cAMP also stimulated the expression of HO-1 and HO-2, and HO enzymatic activity in MA-10 cells. Basal and hCG-stimulated testosterone synthesis was also inhibited by hemin in rat normal Leydig cells. Taken together, these results suggest that: i) at least one of HO products (presumably carbon monoxide) inhibits cholesterol transport to the inner mitochondrial membrane and Leydig cell steroidogenesis by binding to the heme group of the cytochrome P450 enzymes, in a similar way as we described for nitric oxide, and ii) hCG stimulation results in the induction of an antioxidant enzymatic system (HO) acting as a cytoprotective mechanism in Leydig cells, as already demonstrated in the adrenal gland.

Involvement of nitric oxide synthase in the mechanism of histamine-induced inhibition of Leydig cell steroidogenesis via histamine receptor subtypes in Sprague-Dawley rats.

This study was conducted to shed light on the so far unexplored intracellular mechanisms underlying negative modulation of Leydig cell steroidogenesis by histamine (HA). Using the MA-10 cell line and highly purified rat Leydig cells as experimental models, we examined the effect of the amine on biochemical steps known to be modulated by HA or involved in LH/hCG action. In agreement with previous findings, HA at 10 microM showed a potent inhibitory effect on hCG-stimulated steroid synthesis, regardless of the gonadotropin concentration used. Moreover, HA decreased not only LH/hCG-induced cAMP production but also steroid synthesis stimulated by the permeable cAMP analog dibutyryl cAMP (db-cAMP). Considering the post-cAMP sites of HA action, it is shown herein that HA markedly inhibited db-cAMP-stimulated steroidogenic acute regulatory (STAR) protein expression, as well as steps catalyzed by P450-dependent enzymes, mainly the conversion of cholesterol to pregnenolone by cholesterol side-chain cleavage enzyme (CYP11A). The antisteroidogenic action of HA was blocked by addition of the phospholipase C (PLC) inhibitor U73122, and HA significantly augmented inositol triphosphate (IP3) production, suggesting a major role for the PLC/IP3 pathway in HA-induced inhibition of Leydig cell function. Finally, HA increased nitric oxide synthase (NOS) activity, and the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) markedly attenuated the effect of the amine on steroid synthesis. On the basis of our findings, HA antagonizes the gonadotropin action in Leydig cells at steps before and after cAMP formation. NOS activation is the main intracellular mechanism by which HA exerts its antisteroidogenic effects.

Endogenous glucocorticoids participate in retinal degeneration during continuous illumination.

Continuous illumination (CI) induces an oxidative stress of the retina which is involved in light-induced retinal degeneration (LIRD). As the increase of glucocorticoids (GC) could also collaborate in the damage, adrenalectomized (ADX) and sham-operated rats (control, CTL) were submitted to CI, and their eyes were studied at light and electron microscopic levels. After CI, ADX retinas were significantly thicker than CTL retinas. Retinal alterations appeared earlier and were severer in CTL than in ADX retinas. Corticosterone levels increased gradually in the sera of CTL rats along CI. These results suggest that adrenalectomy attenuates LIRD, supporting the hypothesis.

Age related changes from youth to adulthood in rat brain cortex: nitric oxide synthase and mitochondrial respiratory function.

Age related changes in brain cortex NO metabolism were investigated in mitochondria and cytosolic extracts from youth to adulthood. Decreases of 19%, 40% and 71% in NO production were observed in mitochondrial fractions from 3, 7, and 14 months old rats, respectively, as compared with 1-month-old rats. Decreased nNOS protein expression in 14 months old rats was also observed in mitochondria as compared with the nNOS protein expression in 1-month-old rats. Low levels of eNOS protein expression close to the detection limits and no iNOS protein expression were significantly detected in mitochondrial fraction for both groups of age. NO production in the cytosolic extracts also showed a marked decreasing tendency, showing higher levels than those observed in mitochondrial fractions for all groups of age. In the cytosolic extracts, however, the levels were stabilized in adult animals from 7 to 14 months. nNOS protein expression showed a similar age-pattern in cytosolic extracts for both groups of age, while the protein expression pattern for eNOS was higher expressed in adult rats (14 months) than in young animals. As well as in mitochondrial extracts iNOS protein expression was not significantly detected in cytosolic extracts at any age. RT-PCR assays indicated increased levels of nNOS mRNA in 1-month-old rats as compared with 14 months old rats, showing a similar pattern to that one observed for protein nNOS expression. A different aged pattern was observed for eNOS mRNA expression, being lower in 1-month-old rats as compared with 14 months old animals. iNOS mRNA was very low expressed in both groups of age, showing a residual iNOS mRNA that was not significantly detected. State 3 respiration rates were 78% and 85% higher when succinate and malate-glutamate were used as substrates, respectively, in 14 months rats as compared with 1-month-old rats. No changes were observed in state 4 respiration rates. These results could indicate 1 that nNOS and eNOS mRNA and protein expression can be age-dependent, and confirmed the nNOS origin for the mitochondrial NOS. During rat growth, the respiratory function seems to be modulated by NO produced by the different NOS enzymes: nNOS, eNOS and mtNOS present in the cytosol and in the mitochondria.

Effect of ocular hypertension on retinal nitridergic pathway activity.

PURPOSE: Understanding the mechanisms of neuronal cell death in glaucoma is important for devising new treatments. Excitatory amino acids, excessive Ca(2+) influx, and formation of nitric oxide (NO) via NO synthase (NOS)-1 could be involved in glaucomatous neuropathy. The purpose of the present study was to examine the retinal nitridergic pathway activity in rats exposed to experimentally elevated intraocular pressure. METHODS: Weekly injections of HA were performed unilaterally in the rat anterior chamber, whereas the contralateral eye was injected with saline solution. At 3 or 6 weeks of treatment, retinal NOS activity was assessed through the conversion of (3)H-L-arginine to (3)H-L-citrulline, whereas NOS-1, -2, and -3 levels were assessed by Western blotting. L-Arginine uptake was measured using (3)H-l-arginine, whereas mRNA levels of L-arginine transporters were determined by semiquantitative RT-PCR. In addition, cyclic guanosine monophosphate (cGMP) levels were quantified by radioimmunoassay. RESULTS: At both 3 and 6 weeks of treatment, NOS activity significantly increased in HA-injected eyes although no changes in retinal NOS-1, -2, or -3 levels were observed in eyes injected with HA. L-Arginine influx and mRNA levels of cationic amino acid transporter type (CAT)-1 and -2 significantly increased in retinas from hypertensive eyes. Retinal cGMP levels significantly increased in eyes injected with HA for 3 but not 6 weeks. CONCLUSIONS: These results suggest a significant activation of the retinal nitridergic pathway in hypertensive eyes.

Characterization of L-arginine transport in adrenal cells: effect of ACTH.

Nitric oxide synthesis depends on the availability of its precursor L-arginine, which could be regulated by the presence of a specific uptake system. In the present report, the characterization of the L-arginine transport system in mouse adrenal Y1 cells was performed. L-arginine transport was mediated by the cationic/neutral amino acid transport system y+L and the cationic amino acid transporter (CAT) y+ in Y1 cells. These Na+-independent transporters were identified by their selectivity for neutral amino acids in both the presence and absence of Na+ and by the effect of N-ethylmaleimide. Transport data correlated to expression of genes encoding for CAT-1, CAT-2, CD-98, and y+LAT-2. A similar expression profile was detected in rat adrenal zona fasciculata. In addition, cationic amino acid uptake in Y1 cells was upregulated by ACTH and/or cAMP with a concomitant increase in nitric oxide (NO) production.