In vitro dopamine biosynthesis in the median eminence of rat hypothalamic slices: involvement of voltage-dependent Ca2+ channels

Inhibition of allergic inflammation by supplementation with 5-hydroxytryptophan

Clinical reports indicate that patients with allergy/asthma commonly have associated symptoms of anxiety/depression. Anxiety/depression can be reduced by 5-hydroxytryptophan (5-HTP) supplementation. However, it is not known whether 5-HTP reduces allergic inflammation. Therefore, we determined whether 5-HTP supplementation reduces allergic inflammation. We also determined whether 5-HTP decreases passage of leukocytes through the endothelial barrier by regulating endothelial cell function. For these studies, C57BL/6 mice were supplemented with 5-HTP, treated with ovalbumin fraction V (OVA), house dust mite (HDM) extract, or IL-4, and examined for allergic lung inflammation and OVA-induced airway responsiveness. To determine whether 5-HTP reduces leukocyte or eosinophil transendothelial migration, endothelial cells were pretreated with 5-HTP, washed and then used in an in vitro transendothelial migration assay under laminar flow. Interestingly, 5-HTP reduced allergic lung inflammation by 70-90% and reduced antigen-induced airway responsiveness without affecting body weight, blood eosinophils, cytokines, or chemokines. 5-HTP reduced allergen-induced transglutaminase 2 (TG2) expression and serotonylation (serotonin conjugation to proteins) in lung endothelial cells. Consistent with the regulation of endothelial serotonylation in vivo, in vitro pretreatment of endothelial cells with 5-HTP reduced TNF-α-induced endothelial cell serotonylation and reduced leukocyte transendothelial migration. Furthermore, eosinophil and leukocyte transendothelial migration was reduced by inhibitors of transglutaminase and by inhibition of endothelial cell serotonin synthesis, suggesting that endothelial cell serotonylation is key for leukocyte transendothelial migration. In summary, 5-HTP supplementation inhibits endothelial serotonylation, leukocyte recruitment, and allergic inflammation. These data identify novel potential targets for intervention in allergy/asthma.

[Role of genetics in the etiology of synucleinopathies]

The protein family known as synucleins is composed of α-, β- and γ-synuclein. The most widely studied is the α-synuclein protein due to its participation in essential processes of the central nervous system. Neurotoxicity of this protein is related to the presence of multiplications (duplications and triplications) and point mutations in the gene sequence of the α-synuclein gene (SNCA), differential expression of its isoforms and variations in post-transductional modifications. Neurotoxicity is also related to cytoplasmic inclusions known as Lewy bodies (LBs) and Lewy neurites (LNs), which are also present in α-synucleinopathies. In general, the β-synuclein protein, codified by the SNCB gene, acts as a regulator of processes triggered by α-synuclein and its function is altered by variations in the gene sequence, while γ-synuclein, codified by the SNCG gene, seems to play a major role in certain tumoral processes.

Pharmacology of Brain Na+/Ca2+Exchanger: From Molecular Biology to Therapeutic Perspectives

In the last two decades, there has been a growing interest in unraveling the role that the Na+/Ca2+ exchanger (NCX) plays in the function and regulation of several cellular activities. Molecular biology, electrophysiology, genetically modified mice, and molecular pharmacology have helped to delve deeper and more successfully into the physiological and pathophysiological role of this exchanger. In fact, this nine-transmembrane protein, widely distributed in the brain and in the heart, works in a bidirectional way. Specifically, when it operates in the forward mode of operation, it couples the extrusion of one Ca2+ ion with the influx of three Na+ ions. In contrast, when it operates in the reverse mode of operation, while three Na+ ions are extruded, one Ca2+ enters into the cells. Different isoforms of NCX, named NCX1, NCX2, and NCX3, have been described in the brain, whereas only one, NCX1, has been found in the heart. The hypothesis that NCX can play a relevant role in several pathophysiological conditions, including hypoxia-anoxia, white matter degeneration after spinal cord injury, brain trauma and optical nerve injury, neuronal apoptosis, brain aging, and Alzheimer's disease, stems from the observation that NCX, in parallel with selective ion channels and ATP-dependent pumps, is efficient at maintaining intracellular Ca2+ and Na+ homeostasis. In conclusion, although studies concerning the involvement of NCX in the pathological mechanisms underlying brain injury during neurodegenerative diseases started later than those related to heart disease, the availability of pharmacological agents able to selectively modulate each NCX subtype activity and antiporter mode of operation will provide a better understanding of its pathophysiological role and, consequently, more promising approaches to treat these neurological disorders.

Saline ingestion stimulates the in situ molar activity of tyrosine hydroxylase in the median eminence and superior cervical ganglion

The effects of drinking saline for 7 days on the mass and in situ activity of tyrosine hydroxylase (TH) in the median eminence (ME) and superior cervical ganglion (SCG) of rats were investigated. TH mass was quantified by immunoblot assay. In situ TH activity was calculated from the rate of intracellular accumulation of L-dihydroxyphenylalanine (DOPA). In rats that drank 10 mM, 30 mM, and 100 mM NaCl for 7 days, TH activity in the ME was 34 +/- 4, 36 +/- 5, and 45 +/- 3 (mean and S.E.M.) mol of DOPA.h-1.mol of TH-1, respectively, compared to 30 +/- 2 for rats that drank water. The activity of TH in the SCG of animals that drank 10 mM, 30 mM, and 100 mM NaCl was 143 +/- 24, 167 +/- 12, and 272 +/- 13 mol DOPA.h-1.mol TH-1, respectively, compared to 119 +/- 10 for animals that drank water. The mass of TH in the ME and SCG decreased as a function of the concentration of NaCl in the drinking water. In animals that drank water, 10 mM, 30 mM, and 100 mM NaCl, the amounts (pmol) of TH were, respectively, 0.28 +/- 0.03, 0.31 +/- 0.04, 0.23 +/- 0.02, and 0.21 +/- 0.01 per ME and 0.67 +/- 0.06, 0.72 +/- 0.11, 0.37 +/- 0.01, and 0.34 +/- 0.02 per SCG. TH activity in the ME or SCG was unaffected by treatment for 7 days with arginine vasopressin.(ABSTRACT TRUNCATED AT 250 WORDS)

Hormonal modulation of the quantity and in situ activity of tyrosine hydroxylase in neurites of the median eminence

The role of ovarian hormones in the control of the quantity and activity of tyrosine hydroxylase (TyrOHase) in neurites of the median eminence of the rat was investigated. TyrOHase was quantified by an immunoblot assay using purified rat TyrOHase as the standard. Treatment of ovariectomized animals with progesterone, but not estradiol, resulted in a significant reduction in the amount of TyrOHase in the median eminence. The in situ activity of the enzyme was assayed by measuring the rate of synthesis of L-3,4-dihydroxyphenylalanine (dopa), and the results were expressed as mol of dopa per hr per mol of TyrOHase. In animals treated with both estradiol and progesterone for 3 days, the in situ activity of TyrOHase in the median eminence was 114 +/- 13.5 (mean +/- SEM) compared to 26 +/- 4.7 for the controls. Estradiol or progesterone alone was much less effective than was the combination of estradiol and progesterone. To ascertain whether the effect of estradiol and progesterone on TyrOHase activity was reflected in the secretion of dopamine into hypophyseal portal blood, ovariectomized rats were treated for 3 days with both estradiol and progesterone or with the solvent vehicle. The concentration of dopamine in portal plasma of the hormone-treated animals was 1.93 +/- 0.533 ng/ml compared to 0.34 +/- 0.094 ng/ml in vehicle-treated animals. We conclude that the quantity and in situ molar activity of TyrOHase in neurites of the median eminence as well as the secretion of dopamine from these neurites are modulated by the combined action of estradiol and progesterone.

Adenosine 3',5'-cyclic monophosphate stimulates dopamine biosynthesis in the median eminence of rat hypothalamic slices

The regulation of dopamine biosynthesis in tuberoinfundibular dopaminergic (TIDA) neurons by adenosine 3',5'-cyclic monophosphate (cAMP) was investigated in the present study. Dopamine biosynthesis in TIDA neurons was estimated by the rate of in vitro dihydroxyphenylalanine (DOPA) accumulation in the median eminence of rat hypothalamic slices after incubation with a DOPA decarboxylase inhibitor. Addition of dibutyryl cAMP (db-cAMP) into medium caused an increase in the rate of DOPA accumulation in the median eminence in a dose- and time-dependent manner. 8-Bromo-cAMP also increased the rate of DOPA accumulation in the median eminence and cAMP was less effective than db-cAMP whereas neither adenosine nor sodium butyrate altered the rate of DOPA accumulation. An increase in the concentration of endogenous cAMP achieved by addition into medium of isobutylmethylxanthine, a phosphodiesterase inhibitor, or forskolin, an adenylate cyclase activator, was associated with an increase in the rate of DOPA accumulation in the medium eminence. db-cAMP, however, had an almost negligible effect on the secretion of dopamine from the median eminence. The stimulatory effect of db-cAMP on DOPA accumulation in the median eminence was not dependent upon the presence of extracellular Ca2+ and was not blocked by tetrodotoxin. Furthermore, the stimulation of DOPA accumulation in the median eminence induced by db-cAMP was additive with that induced by high potassium depolarization, which was Ca2+ -dependent. These results suggest that dopamine biosynthesis in TIDA neurons is regulated by two distinct mechanisms, one of which involves cAMP, and another of which involves Ca2+.

Effect of aging on in vitro dopamine biosynthesis in the median eminence of rat hypothalamic slices

The rates of basal and cyclic AMP-dependent DOPA accumulation in the median eminence of hypothalamic slices were not different between ovariectomized young and aged rats. However, the rate of Ca2+-dependent, depolarization-induced DOPA accumulation was smaller in aged rats, suggesting that the Ca2+ system in the regulation of dopamine biosynthesis in tuberoinfundibular dopaminergic neurons is altered by aging.