Señalización de la angiotensina II, a través de la producción de radicales libres en estructuras del sistema nervioso: papel en el estres agudo y crónico / Angiotensin II signaling, through the production of free radicals in structures of the nervous system: role in acute and chronic stress

Existen evidencias que apoyan la participación de las especies reactivas de oxígeno en las cascadas de señalización y transducción intracelular de la angiotensina II. La ANG II es importante en el mantenimiento de la homeostasis corporal, regulando la presión arterial y el metabolismo de fluidos y electrolitos. Se sabe que en la periferia, la ANG II es capaz de estimular a la NAD(P)H oxidasa con la subsiguiente producción de ERO. El anión superóxido es metabolizado secuencialmente por las enzimas antioxidantes como la superóxido dismutasa, la catalasa y la glutatión peroxidasa. A su vez, las especies reactivas de oxígeno son capaces de activar a las proteínas kinasas activadas por mitógenos, las cuales se encuentran asociadas al crecimiento y la diferenciación celular. Se evaluó la posible participación de las especies reactivas de oxígeno en el mecanismo de señalización intracelular mediado por el receptorAT1en el hipotálamo, el órgano subfornicaly médula suprarrenal de la rata. Nuestros resultados demostraron que la estimulación del tejido nervioso con ANG II in vitroincrementó la actividad de la enzimas antioxidante. Al evaluar el papel del receptor AT1, la NAD(P)H oxidasa, el anión superóxido y la proteína kinasa C; así como la activación de las ERK1/2 en la señalización de la ANG II en el hipotálamo, OSF y MSR, demostramos que el bloqueo del receptor AT1con losartán, la interferencia del ensamblaje de la NAD(P)H oxidasa con apocinina, el secuestro de anión superóxido empleando un mimético de la SOD, tempol,y la inhibición de la PKC con cheleritrina, bloquearon completamente el efecto que produce la ANG II sobre las enzimas antioxidantes in vitro.Igualmente, la activación de la ERK1/2 inducida por la ANG II fue reducida por APO y LOS a nivel hipotalámico. Adicionalmente, el bloqueo del receptor AT2hipotalámico con PD123319, no bloqueo sino que mas bien potenció la respuesta de las enzimas antioxidantes y la activación de las ERK1/2 inducida por la ANG II, lo que desenmascaró el efecto contra regulatorio del receptor AT2sobre la acción de la ANG II mediada por el receptor AT1. Se sabe que durante el estrés el sistema renina angiotensina circulante y cerebral se encuentra estimulado, por lo tanto el incremento de la ANG II endógena debería desencadenar vías de señalización similares a las reportadas in vitro. Efectivamente, nuestros hallazgos demostraron que tanto,el estrés agudo inducido por la inmovilización forzada,como el estrés crónico en ratas espontáneamente hipertensas incrementaron la actividad de las enzimas antioxidantes en las tres estructuras cerebrales estudiadas. Este efecto es mediado por la vía del receptor AT1, la estimulación de la NAD(P)H oxidasa y la producción de anión superóxido ya que el tratamiento in vivo con LOS, APO y TEM fue capaz de bloquear completamente el incremento de la actividad de las enzimas antioxidantes inducidas por el estrés y por ende por la ANG II endógena.A nivel de la MSR demostramos, por primera vez, que la estimulación del receptor AT2 esta asociada a la estimulación de la NAD(P)H oxidasa, ya que la APOy el PD 123319 fueron capaces de bloquear el incremento de la actividad de las enzimas antioxidantes inducida por la ANG II. Demostrando así, que el receptor AT1en la MSR contrarregula la acción de la ANG II a través del receptor AT2.En conclusión, nuestros resultados indican que a nivel del sistema nervioso las especies reactivas de oxígeno participan en la cascada de señalización intracelular de la ANG II, y ejercen un importante papel en la respuesta al estrés y la hipertensión.

Nicotine-evoked cytosolic Ca2+ increase and cell depolarization in capillary endothelial cells of the bovine adrenal medulla

Endothelial cells are directly involved in many functions of the cardiovascular system by regulating blood flow and blood pressure through Ca2+ dependent exocitosis of vasoactive compounds. Using the Ca2+ indicator Fluo-3 and the patch-clamp technique, we show that bovine adrenal medulla capillary endothelial cells (B AMCECs) respond to acetylcholine (ACh) with a cytosolic Ca2+ increase and depolarization of the membrane potential (20.3±0.9 mV; n=23). The increase in cytosolic Ca2+ induced by 10µM ACh was mimicked by the same concentration of nicotine but not by muscarine and was blocked by 100 µM of hexamethonium. On the other hand, the increase in cytosolic Ca2+ could be depressed by nifedipine (0.01 -100 µM) or withdrawal of extracellular Ca2+. Taken together, these results give evidence for functional nicotinic receptors (nAChRs) in capillary endothelial cells of the adrenal medulla. It suggests that nAChRs in B AMCECs may be involved in the regulation of the adrenal gland's microcirculation by depolarizing the membrane potential, leading to the opening of voltage-activated Ca2+ channels, influx of external Ca2+ and liberation of vasoactive compounds.

effect of Methylcobalamin on the adrenal medulla

Methylcobalamin is one form of cobalamin that acts as a nerve growth factor. Since adrenal medulla is part of the nervous system, therefore, this study was designed to assess the effect of methylcobalamin on this gland in rats. Albino rats were injected with methylcobalamin for 14 days; adrenals were taken, fixed in Ortho's fixative, and embedded in paraffin. They were cut in thin sections and stained with H and E and Giemsa stain. They were studied under light microscope. The result showed that methylcobalamin has stimulated the adrenal medulla, which was expressed by dilated vessels, and increase in the granularity and size of chromaffin norepinephrine containing cells. Sympathetic ganglionic cells have also increased in number and size. Cortical zona reticularis was hypervascular and hypertrophied. This study suggests that, methylcobalamin might have acted directly through the sympathetic nerves on the adrenal medulla or indirectly on the medulla through the adrenal cortex resulting in an increase in number of norepinephrine containing cells and the ganglionic sympathetic cells

comparative study of the effect of Budesonide versus prednisolone on adrenal gland of the male rabbit

Although oral glucocorticoids are the treatment of choice for moderate to severe pancolitis, their systemic side effects and adrenal suppression account for considerable morbidity. Budesonide is a new intestinal topical active glucocorticoid which displays high therapeutic efficacy and high systemic tolerability. To deliver the active drug to ileal and ileocecal area, Budesonide has been formulated into enterocapsule preparation. Several studies compared the efficacy of Budesonide with that of Prednisolone. However, few determined the extent of adrenocortical suppression occurring with both drugs on histological basis. In this work, fifteen adult male New Zealand albino rabbits were used. They were classified into three equal groups. Group I served as control. Group II included animals that received intragastrically one tablet of 5 mg prednisolone daily for four weeks. Group III included animals that received orally one capsule of entocort containing 3 mg budesonide every other day for four weeks. The adrenals were processed for histological and immunohistochemical study. In the present comparative study, evidence of adrenal suppression was significantly greater in the prednisolone group than in budesonide treated animals. Light microscopic examination of H and E stained sections of prednisolone group, revealed an apparent decrease in the size of zona fasciulata cells which was proved significant by morphometric study. Moreover, Oil red stained sections of group II demonstrated a relative decrease in cytoplasmic lipid content of both zona glomerulosa and fasciculata. Using chromaffin reaction, it was noticed that there was a relative increase in the number of nor-epinephrine cells than in group III. Immunohistochemical study showed that most of the nuclei of cells in zona fasciculata in group II were negatively stained for proliferating cell nuclear antigen [PCNA] which was further proved significant morphometrically using the PCNA index. Thus it was concluded that, the budesonide preparation is associated with much less impairment of adrenal axis function. Therefore, budesonide offers a useful advance in treatment of inflammatory bowel disease

comparison between the effects of hypophysectomy and cyproterone acetate on the adrenal medulla chromaffin cells of the mouse

The effects of reduction in the glucocorticoid secretion on the adrenomedullary chromaffin cells of the mouse were studied through hypophysectomy and cyproterone acetate [CA] administration. The latter drug is reported to have a pronounced ACTH suppressive effect and to interfere with steroid biosynthesis. There was no evidence of a change in the proportion of epinephrine - storing [E] and nonepinephrine storing [NE] cells in the adrenal medulla of hypophysectomized mice or CA-treated animals. In hypophysectomized animals, the norepinephrine [NE] showed a significant Increase in content and proportion. This was attributed - to a significant decrease in the epinephrine [E] content of these animals. The adrenal glands of CA-treated animals did not show any significant change in NE content, although a significant increase in the NE proportion of the total catecholamine was observed. This was again attributed to the significant decrease in the E content of CA animals. The ultrastructural changes showed the presence of both E and NE granules in the same cell. In addition, many cells showed marked reduction in their secretory granules and appear similar to sympathetic neurons. The reversibility of these changes following cessation of CA - treatment suggests that they represented temporary metabolic changes rather than a process of dedifferentiation of these cells

Altered gonodal hormone level and constant light-induced stress interfere with the response of the adrenal medulla to oxytocin

The effect of oxytocin (0.25 IU/100 g per day) on the adrenal medulla was examined in intact, intact estrogen-treated, castrated and castrated testosterone-treated adult male Wistar rats. Stereological analysis of the gland (N = 5 rats per group) revealed that in intact animals the number of chromaffin cells (x10(3)) was significantly increased after 3-day (saline: 467.6 +/- 27.4; oxytocin: 567.6 +/- 28.9) or 7-day (saline: 486.2 +/- 39.1; oxytocin: 618.7 +/- 36.8) oxytocin administration. During 7 days of recovery after the 7-day treatment, the chromaffin cell number returned to the control level (saline: 491.4 +/- 12.6; oxytocin: 554.4 +/- 28.7). The effect of oxytocin on chromaffin cell number was also observed in rats simultaneously injected with estradiol (0.3 microg/100 g per day) for 10 days (estradiol: 454.3 +/- 32.8; estradiol + oxytocin: 576.1 +/- 25.0), as well as in 10-day castrated rats (saline: 594.7 +/- 22.7; oxytocin: 765.3 +/- 33.1). Testosterone replacement (0.6 mg/100 g per day) abolished the medullary response to oxytocin (testosterone + saline: 528.5 +/- 24.7; testosterone + oxytocin: 620.8 +/- 56.0). There was a 20 percent rise in adrenal dopamine content (from 0.236 +/- 0.015 to 0.283 +/- 0.015 microg per pair of glands; N = 9-12) in intact rats injected with oxytocin for 3 days. Oxytocin had no effect on any of the catecholamine levels in adrenal glands of rats exposed to stress induced by constant lighting. The present data indicate that the proliferative response of chromaffin tissue to oxytocin depends on the gonadal hormone level and the basal activity of the adrenal medulla.

Dopaminergic receptor regulates catecholamine release from perfused adrenal medulla

Nicotinic drug is a potent secretogogues for catecholamine from bovine adrenal glands perfused with oxygenated Locke's buffer. However, apomorphine, I IIM, [the dopaminergic agonist] markedly inhibit this catecholamine release by about 40%. Haloperidol 0.5 muM, [the dopaminergic antagonist] reversed the inhibitory effects of apomorphine. These data strongly suggested that, as in the cat, the bovine adrenal modulates the catecholamine cell contains a dopaminergic receptor that modulates the catecholamine secretory process triggered by stimulation of the nicotinic cholinergic receptor. This dopaminergic receptor might be involved in a sympathoadrenal cooperative mechanism