Regulation of extracellular signal-regulated kinases (ERKs) by naloxone-induced morphine withdrawal in the brain stress system.

Our previous studies have shown that morphine withdrawal increases the hypothalamic-pituitary-adrenocortical axis activity, which is dependent on a hyperactivity of noradrenergic pathways (nucleus tractus solitarius-A(2)) innervating the hypothalamic paraventricular nucleus. The extracellular signal-regulated kinase has been implicated in drug addiction, but its role in activation of paraventricular nucleus and nucleus tractus solitarius during morphine dependence remain poorly understood. We have determined the activation of extracellular signal-regulated kinase during morphine dependence and withdrawal as well as its involvement in morphine withdrawal-induced gene expression. We show that naloxone-induced morphine withdrawal activates extracellular signal-regulated kinases(1/2) and increases c-Fos expression in rat paraventricular nucleus and nucleus tractus solitarius-A(2) neurons. Activated extracellular signal-regulated kinases(1/2) was colocalized with c-Fos in both nuclei, and this response was blocked by SL327, a drug that prevents extracellular signal-regulated kinase activation. In the paraventricular nucleus from morphine-withdrawn rats, the number of neurons expressing CRF was increased. Immunohistochemical study showed a dramatic increase in c-Fos immunoreactivity within CRF-positive cells. These results suggest that extracellular signal-regulated kinases1/2 signaling pathway is necessary for morphine withdrawal-induced activation of brain areas associated with the stress system.

Efecto de la atorvastatina sobre la progresión y regresión de los depósitos grasos renales en un modelo experimental / Effect of atorvastatin on progression/regression of renal lipid accumulation in an experimental model

Introducción. Hay evidencias de la relación entre la arteriosclerosis y la enfermedad renal progresiva. Sin embargo, son escasos los estudios en humanos o animales en que se utilicen estatinas para valorar sus efectos sobre la lesión renal. Objetivos. El objetivo de este trabajo es estudiar a escala histológica el efecto de la atorvastatina sobre los fenómenos de progresión y regresión de los depósitos grasos en el riñón en un modelo experimental. Material y método. Para la realización de los protocolos experimentales se utilizaron 100 pollos White-Leghorn, sometidos a una dieta hiperlipémica en la fase de inducción y a diversos protocolos de dieta normal/dieta hiperlipémica y tratamiento o no con atorvastatina en la fase de intervención. Se realizó la valoración de la grasa renal mediante técnicas histológicas y análisis de imagen. Resultados. En el grupo control sano no se observó la existencia de depósitos grasos, mientras que el grupo aterogénico presentó grandes depósitos grasos. El grupo de regresión e intervención con atorvastatina presentó una menor presencia de grasa, lo que supuso una diferencia significativa con todos los grupos. También en el caso de este grupo, se encontró que el diámetro de la acumulación grasa es significativamente menor respecto al resto de los grupos. Conclusiones. Nuestro modelo experimental es, para el estudio del riñón graso, un modelo homogéneo y de fácil manejo. La retirada de la dieta grasa y la administración simultánea de atorvastatina da lugar a los índices más bajos de depósitos grasos renales. La retirada por sí sola de la dieta no produce efectos tan marcados. Del estudio de diferentes parámetros se deduce que la atorvastatina acelera la regresión y frena la progresión de las acumulaciones grasas renales (AU)

Introduction. There is evidence of a relationship between atherosclerosis and progressive kidney disease. However, information on the role of statins on kidney disease in humans and animal models is lacking. Objectives. To analyze the effect of atorvastatin on progression/regression of renal lipid accumulation in an experimental model using histological analysis. Material and method. We used 100 White-Leghorn chickens fed with a hyperlipemic diet (induction stage), followed by an interventional stage, in which the animals were fed a normal or hyperlipemic diet and administered atorvastatin or placebo. Assessment of renal lipid accumulation was made by histologic and imaging analyses. Results. In the healthy control group, no intracellular renal fat deposits or accumulations were found. The atherogenic group showed substantial lipid accumulations. The intervention group with suspension of the hyperlipemic diet and atorvastatin administration showed significant differences with the remaining groups, presenting the lowest fat accumulation. This group also showed significantly lower fat accumulation diameter with respect to the remaining groups. Conclusions. Our experimental model was useful and suitable for the study of renal fat accumulation. Hyperlipemic diet suspension and simultaneous atorvastatin therapy led to the lowest renal fat accumulation. Hyperlipemic diet suspension alone produced less pronounced results. The parameters studied indicate that atorvastatin was effective in accelerating regression of renal fat accumulation and in decreasing its progression (AU)

Increased p53 gene dosage reduces neointimal thickening induced by mechanical injury but has no effect on native atherosclerosis.

OBJECTIVE: The tumor suppressor p53 regulates cell proliferation and apoptosis, two key processes in the pathogenesis of occlusive vascular disease. Here, we examined the consequences of heightening p53 function on neointimal lesion formation in the setting of atherosclerosis and mechanical injury. METHODS: For this study we employed immunohistopathological characterization of neointimal lesions in atherosclerosis-prone apolipoprotein E-null mice with normal p53 gene dosage (apoE-KO) and carrying a p53 transgene (Super-p53/apoE-KO). We also carried out molecular studies in macrophages and smooth muscle cells (SMCs) obtained from these mice. RESULTS: The p53 transgene conferred p53 gain-of-function in cultured cells and mice. In vitro, survival of irradiated Super-p53 macrophages and femoral SMCs was reduced, but only Super-p53 SMCs exhibited attenuated proliferation. In vivo, whereas the size of spontaneously formed and diet-induced aortic atheromas was indistinguishable in apoE-KO and Super-p53/apoE-KO mice, the latter exhibited attenuated neointimal thickening in mechanically injured femoral artery. In both models, neither apoptosis nor cell proliferation were affected by additional p53 gene dosage when examined in established neointimal lesions. However, at 2 days after mechanical injury when neointimal lesions were not yet formed, cell proliferation was significantly attenuated within medial SMCs of Super-p53/apoE-KO mice. CONCLUSION: Heightening p53 function has differential effects on in vitro proliferation of macrophages (unaffected) versus SMCs (reduced), and on native atherosclerosis (unaffected) versus mechanically induced neointimal thickening (reduced) in apoE-KO mice. The protective effect of p53 in mechanically injured femoral artery coincided with limited medial SMC proliferation at early time points preceding neointima formation, but neither medial nor neointimal cell proliferation was affected in vessels with established occlusive lesions. These findings corroborate p53 gain-of-function as a promising therapeutic strategy to limit post-angioplasty restenosis but not native atherosclerosis.

Sex differences in the renal changes elicited by angiotensin II blockade during the nephrogenic period.

The renin-angiotensin system plays an important role in renal development. However, it is unknown whether reduction in angiotensin II effects during the nephrogenic period leads to different renal alterations in males and females during the adult age. The aim of this study was to evaluate whether the role of angiotensin II on renal development is sex dependent and whether there are sex differences in blood pressure, renal hemodynamics, and severity of renal damage during adult life when nephrogenesis is altered by blocking angiotensin II effects. Newborn Sprague-Dawley rats were treated with an angiotensin II type 1 receptor antagonist (L-158.809; 7 mg/kg per day) during the first 2 weeks of life. At 3 months of age, changes in blood pressure, albuminuria, and renal hemodynamics were assessed, and stereological and histopathologic studies were performed. Blood pressure increased (127+/-0.5 versus 115+/-0.7 mm Hg in control rats; P<0.05) and nephron number decreased (37%; P<0.05) similarly in treated males and females. However, only males had an elevation in albuminuria (5.92+/-1.65 versus 0.33+/-0.09 mg per day in control rats; P<0.05), a fall in glomerular filtration rate (12.6%; P<0.05), and a significant decrease in papillary volume (42%; P<0.05). Mean glomerular volume, glomerulosclerosis, arteriolar hypertrophy, and tubulointerstitial damage in cortex and medulla were also higher (P<0.05) in angiotensin II type 1 receptor antagonist-treated males than in treated females. The results of this study suggest that females seem to be more protected than males to the renal consequences of reducing angiotensin II effects during renal development.

Morphine withdrawal-induced c-fos expression in the heart: a peripheral mechanism.

We previously demonstrated that hyperactivity of cardiac noradrenergic pathways observed during morphine withdrawal is mediated by peripheral mechanisms. In the present study, naloxone methiodide (quaternary derivative of naloxone that does not cross the blood-brain barrier) and naloxone were administered to morphine-dependent rats and Fos immunostaining was used as a reflection of neuronal activity. Dependence on morphine was induced by 7-day chronic subcutaneous (s.c.) implantation of six morphine pellets (75 mg). Morphine withdrawal was precipitated by administration of naloxone methiodide (5 mg/kg, s.c.) or naloxone (5 mg/kg, s.c.) on day 8. Using immunohistochemical staining of Fos, present results indicate that the administration of naloxone methiodide or naloxone to morphine-dependent rats induced marked Fos immunoreactivity within the cardiomyocyte nuclei. Moreover, Western blot analysis revealed a peak expression of c-fos in the right and left ventricles after naloxone methiodide- or naloxone-precipitated withdrawal. In addition, in the hypothalamic paraventricular nucleus (PVN), Fos expression was increased after naloxone-but not after naloxone methiodide-administration to morphine-dependent rats. These results suggest that the activation of c-fos expression observed during morphine withdrawal in the heart is due to intrinsic mechanisms outside the central nervous system (CNS).

Activation of c-fos expression in the heart after morphine but not U-50,488H withdrawal.

1. In the present work we have studied in the heart the expression of Fos, the protein product of the c-fos proto-oncogene and the adaptive changes in noradrenergic neurons after naloxone or nor-binaltorphimine (nor-BNI) administration to morphine or U-50,488H pretreated rats. 2. Male rats were implanted with placebo (naïve) or morphine (tolerant/dependent) pellets for 7 days. On day 8 rats received saline s.c., naloxone (5 mg kg(-1) s.c.) or nor-BNI (5 mg kg(-1) i.p.). Other groups of rats were rendered tolerant/dependent on U-50,488H by injecting the drug twice daily (15 mg kg(-1) i.p.) for 4 days. Control animals received saline. On day 5 the animals were injected with vehicle i.p. or nor-BNI (5 mg kg(-1) i.p.). 3. Using immunohistochemical staining of Fos, present results indicate that morphine withdrawal induced marked Fos immunoreactivity (Fos-IR) within the cardiomyocyte nuclei. Moreover, Western blots analysis revealed a peak expression of c-fos in right and left ventricle after naloxone induced withdrawal in parallel with an increase in noradrenaline (NA) turnover. 4. However, after nor-BNI administration to rats chronically treated with U-50,488H, we found a decrease in the NA turnover. In addition, the administration of nor-BNI to rats chronically treated with U-50,488H or morphine did not induce modifications in the Fos-IR, in the heart. 5. These results demonstrated that morphine withdrawal induces the expression of Fos protein, as well as an enhancement of noradrenergic activity in the heart. In contrast to morphine U-50,488 withdrawal produces no changes in Fos-IR in parallel with a decrease in NA turnover, indicating that the kappa-opioid receptors are not involved in the molecular adaptive mechanisms responsible for the development of opioid dependence in the heart.