Rat pineal alpha 1-adrenoceptor subtypes: studies using radioligand binding and reverse transcription-polymerase chain reaction analysis

Safety of Once-Daily Oxymetazoline HCl Ophthalmic Solution, 0.1% in Patients with Acquired Blepharoptosis: Results from Four Randomized, Double-Masked Clinical Trials

Purpose

An oxymetazoline 0.1% ophthalmic solution was recently approved for treatment of acquired blepharoptosis in adults. This study's objective was to evaluate the safety profile of oxymetazoline 0.1% when administered once daily for 14-84 days.

Patients and Methods

Pooled analysis examined safety outcomes from four randomized, double-masked, placebo-controlled clinical trials conducted at 6, 16, 27, and 35 sites, respectively, in the United States. In total, 568 participants with acquired blepharoptosis were evaluated. Median age was 66 years and 74.8% of participants were female. Overall, 375 participants self-administered oxymetazoline 0.1% to both eyes once/day and 193 self-administered placebo (vehicle) daily. Treatment-emergent adverse event (TEAE) rates, severity, and causality were evaluated in the overall population and within participant subgroups defined based on age, race, and ethnicity. Vital signs and ophthalmic findings were evaluated at predefined study visits. Patient-reported treatment tolerability was recorded at study end.

Results

TEAE incidence was similar among participants using oxymetazoline 0.1% (31.2%) or vehicle (30.6%). Nearly all TEAEs were mild-to-moderate, and most were not suspected of being treatment related. Serious TEAEs occurred in four participants receiving oxymetazoline 0.1% and one participant receiving vehicle. Nine and two participants in the oxymetazoline 0.1% and vehicle groups, respectively, discontinued due to a TEAE. Ocular TEAEs occurring in ≥2% of participants receiving oxymetazoline 0.1% were punctate keratitis, conjunctival hyperemia, dry eye, blurred vision, instillation site pain, and corneal vital dye staining, with none occurring in >3.5% of participants. TEAE rates were similar across subgroups based on age, race, and ethnicity. No clinically significant mean changes in vital signs or ophthalmologic findings occurred, and >98% of participants rated oxymetazoline 0.1% as causing no/mild discomfort.

Conclusion

Once-daily oxymetazoline 0.1% was safe and well tolerated in participants with acquired blepharoptosis when used for 14-84 days. Safety did not appear to differ based on age, race, or ethnicity.

A review of acquired blepharoptosis: prevalence, diagnosis, and current treatment options

Blepharoptosis (ptosis) is among the most common disorders of the upper eyelid encountered in both optometric and ophthalmic practice. The unilateral or bilateral drooping of the upper eyelid that characterises ptosis can affect appearance and impair visual function, both of which can negatively impact quality of life. While there are several known forms of congenital ptosis, acquired ptosis (appearing later in life, due to a variety of causes) is the predominant form of the condition. This review summarises the prevalence, causes, identification, differential diagnosis, and treatment of acquired ptosis. Particular attention is paid to the differential diagnosis of acquired ptosis and emerging treatment options, including surgical and pharmacologic approaches.

MicroRNA-7 inhibits melatonin synthesis by acting as a linking molecule between leptin and norepinephrine signaling pathways in pig pineal gland

MicroRNAs, including microRNA-7 (miR-7), are important modulators of numerous gene expressions and the related biological processes. Melatonin is a key hormone regulating daily and seasonal rhythms, in which a variety of positive and negative regulatory factors, such as norepinephrine (NE) and leptin, are involved. However, the interactions among these factors and the mechanisms remain to be elucidated. The aims of the present study were to identify the functions and the related mechanisms of miR-7 in regulating melatonin synthesis and secretion through in vitro and in vivo experiments in pineal gland of pigs, which is an important animal model for agricultural and biomedical studies. Our results firstly show that miR-7 is specifically expressed in porcine pinealocytes and negatively regulates melatonin synthesis. The further functional studies show that the dynamic expression levels of miR-7 are contrary to the melatonin levels throughout the day, and the forced inhibition of endogenous miR-7 in porcine pinealocytes sharply increases arylalkylamine N-acetyltransferase (AANAT) expression by 80.0% (P = 0.0031) and melatonin levels by 81.0% (P = 0.0421), whereas miR-7 over-expression down-regulates AANAT expression by 38.6% (P = 0.0004) and melatonin levels by 37.6% (P = 0.0212). In addition, the miR-7 expression is up-regulated by leptin through the JAK/STAT3 signaling pathway, and the in vivo intracerebroventricular injection of leptin increases miR-7 expression by 80.0% (P = 0.0044) in porcine pineal glands and reduces melatonin levels by 57.1% (P = 0.0060) compared with the controls. This functional inhibition of melatonin synthesis by miR-7 is accomplished by its binding to the 3'-UTR of Raf1. Further, our results demonstrate that the RAF1/MEK/ERK signaling pathway mediates NE-induced AANAT expression, whereas leptin attenuates NE's function through miR-7. Taken together, the results demonstrated that leptin activates the JAK/STAT3 signaling pathway to increase the expression of miR-7, which acts as a negative regulatory molecule inhibiting NE-activated RAF1/MEK/ERK signaling pathway by targeting Raf1, resulting in decreased AANAT expression and melatonin synthesis. These findings suggest that miR-7 is a novel negative regulator of melatonin synthesis and links leptin- and NE-mediated signaling pathways in porcine pineal glands, which will contribute to our understanding in the establishment of the biological rhythms resulting from melatonin.

Night/day changes in pineal expression of >600 genes: central role of adrenergic/cAMP signaling

The pineal gland plays an essential role in vertebrate chronobiology by converting time into a hormonal signal, melatonin, which is always elevated at night. Here we have analyzed the rodent pineal transcriptome using Affymetrix GeneChip(R) technology to obtain a more complete description of pineal cell biology. The effort revealed that 604 genes (1,268 probe sets) with Entrez Gene identifiers are differentially expressed greater than 2-fold between midnight and mid-day (false discovery rate <0.20). Expression is greater at night in approximately 70%. These findings were supported by the results of radiochemical in situ hybridization histology and quantitative real time-PCR studies. We also found that the regulatory mechanism controlling the night/day changes in the expression of most genes involves norepinephrine-cyclic AMP signaling. Comparison of the pineal gene expression profile with that in other tissues identified 334 genes (496 probe sets) that are expressed greater than 8-fold higher in the pineal gland relative to other tissues. Of these genes, 17% are expressed at similar levels in the retina, consistent with a common evolutionary origin of these tissues. Functional categorization of the highly expressed and/or night/day differentially expressed genes identified clusters that are markers of specialized functions, including the immune/inflammation response, melatonin synthesis, photodetection, thyroid hormone signaling, and diverse aspects of cellular signaling and cell biology. These studies produce a paradigm shift in our understanding of the 24-h dynamics of the pineal gland from one focused on melatonin synthesis to one including many cellular processes.

Generation of the melatonin endocrine message in mammals: a review of the complex regulation of melatonin synthesis by norepinephrine, peptides, and other pineal transmitters

Melatonin, the major hormone produced by the pineal gland, displays characteristic daily and seasonal patterns of secretion. These robust and predictable rhythms in circulating melatonin are strong synchronizers for the expression of numerous physiological processes in photoperiodic species. In mammals, the nighttime production of melatonin is mainly driven by the circadian clock, situated in the suprachiasmatic nucleus of the hypothalamus, which controls the release of norepinephrine from the dense pineal sympathetic afferents. The pivotal role of norepinephrine in the nocturnal stimulation of melatonin synthesis has been extensively dissected at the cellular and molecular levels. Besides the noradrenergic input, the presence of numerous other transmitters originating from various sources has been reported in the pineal gland. Many of these are neuropeptides and appear to contribute to the regulation of melatonin synthesis by modulating the effects of norepinephrine on pineal biochemistry. The aim of this review is firstly to update our knowledge of the cellular and molecular events underlying the noradrenergic control of melatonin synthesis; and secondly to gather together early and recent data on the effects of the nonadrenergic transmitters on modulation of melatonin synthesis. This information reveals the variety of inputs that can be integrated by the pineal gland; what elements are crucial to deliver the very precise timing information to the organism. This also clarifies the role of these various inputs in the seasonal variation of melatonin synthesis and their subsequent physiological function.

Dopamine induces intracellular Ca2+ signals mediated by alpha1B-adrenoceptors in rat pineal cells

We have studied the functional interaction of dopamine with alpha1-adrenoceptor subtypes by measuring intracellular Ca2+ levels in pineal cells, a cell type where adrenoceptors are well characterized. We show that dopamine induces transient intracellular Ca2+ signals in only 70% of cells responding to phenylephrine. Dopamine-induced Ca2+ signals desensitise faster than Ca2+ transients elicited with phenylephrine and are selectively blocked by desipramine, imipramine, and alpha1B-adrenoceptor antagonists. These results suggest that dopamine induced Ca2+ signals are mainly due to the activation of one subtype of alpha-adrenoceptor, the alpha1B.

Characterization of alpha1-adrenoceptor subtypes mediating noradrenaline-induced contraction of rat epididymal vas deferens in calcium-free medium

The alpha1-adrenoceptor subtype mediating noradrenaline (NA)-induced contractions of rat epididymal vas deferens in Ca2+-free/EGTA (1 mM) medium was studied using competitive antagonists. The effects of chloroethylclonidine (CEC) was investigated in Ca2+-free and normal Krebs' medium and RT-PCR was used to identify alpha1-adrenoceptor specific mRNA in epididymal vas deferens. In Ca2+-free medium, NA evoked sustained contractions but was less potent (pD2, 5.9) than in normal Krebs' medium (pD2, 7.3). The contractions in Ca2+-free medium were inhibited by prazosin (pA2, 9.3), 5-methylurapidil (pA2, 8.4), spiperone (pA2, 7.6) and BMY 7378 (pK(B), 6.8) consistent with activation of alpha1A-subtype. Repeated pretreatment with CEC (100 microM) reduced the potency of NA and maximum contractions in normal and Ca2+-free media. CEC-sensitivity in normal Krebs' medium was enhanced by prior treatment with phenoxybenzamine. mRNA for alpha1a- and alpha1d- but not alpha1b-adrenoceptors were detected in epididymal vas deferens. These results suggest that NA contracts the tissue in Ca2+-free medium by the stimulation of alpha1A-adrenoceptors. Two factors affecting CEC-sensitivity of NA-induced contractions in this tissue are discussed.

Analysis of alpha 1L-adrenoceptor pharmacology in rat small mesenteric artery

1. To illuminate the controversy on alpha 1A- or alpha 1L-adrenoceptor involvement in noradrenaline-mediated contractions of rat small mesenteric artery (SMA), we have studied the effects of subtype-selective alpha 1-adrenoceptor agonists and antagonists under different experimental conditions. 2. The agonist potency order in rat SMA was: A61603 >> SKF89748-A > cirazoline > noradrenaline > ST-587 > methoxamine. Prazosin antagonized all agonists with a low potency (pA2: 8.29-8.80) indicating the involvement of alpha 1L-rather than alpha 1A-adrenoceptors. 3. The putative alpha 1L-adrenoceptor antagonist JTH-601, but not the alpha 1B-adrenoceptor antagonist chloroethylclonidine (10 microM) antagonized noradrenaline-induced contractions of SMA. The potency of the selective alpha 1D-adrenoceptor antagonist BMY 7378 against noradrenaline (pA2 = 6.16 +/- 0.13) and of the selective alpha 1A-adrenoceptor antagonist RS-17053 against noradrenaline (pKB = 8.35 +/- 0.10) and against the selective alpha 1A-adrenoceptor agonist A-61603 (pKB = 8.40 +/- 0.09) were too low to account for alpha 1D- and alpha 1A-adrenoceptor involvement. 4. The potency of RS-17053 (pKB/pA2's = 7.72-8.46) was not affected by lowering temperature, changing experimental protocol or inducing myogenic tone via KCl or U46619. 5. Selective protection of a putative alpha 1A-adrenoceptor population against the irreversible action of phenoxybenzamine also failed to increase the potency of RS-17053 (pA2 = 8.25 +/- 0.06 against A61603). 6. Combined concentration-ratio analysis demonstrated that tamsulosin, which does not discriminate between alpha 1A- and alpha 1L-adrenoceptors, and RS-17053 competed for binding at the same site in the SMA. 7. In summary, data obtained in our experiments in rat SMA indicate that the alpha 1-adrenoceptor mediating noradrenaline-induced contraction displays a distinct alpha 1L-adrenoceptor pharmacology. This study does not provide evidence for the hypothesis that alpha 1L-adrenoceptors represent an affinity state of the alpha 1A-adrenoceptor in functional assays. Furthermore, there is no co-existing alpha 1A-adrenoceptor in the SMA.

Reversal of endothelin-1 release by stimulation of endothelial alpha2-adrenoceptor contributes to cerebral vasorelaxation

Agonists acting on the vascular endothelium can modulate the release of a number of factors that interact with the surrounding smooth muscle cells and influence their tone. One such factor is the vasoconstricting agent endothelin-1 (ET-1), which has been implicated in several disease states, including stroke. However, very little is known about the physiological role of ET-1 in the cerebral circulation. We demonstrate that activation of alpha2-adrenoceptors in human pial artery endothelial cells reduces both constitutive and agonist-stimulated release of immunoreactive ET-1. That this has physiological relevance is supported by our demonstration that in segments of rabbit middle cerebral arteries, alpha2-adrenoceptor activation reduces the release of endothelium-derived ET-1 and causes an endothelium-dependent relaxation. The adrenoceptor-dependent relaxation was not blocked by combined addition of indomethacin and N omega-nitro-L-arginine in 25 mmol/L KCl-depolarizing physiological solution but was selectively antagonized by a subthreshold concentration of exogenous ET-1. Our data suggest that activation of endothelial alpha2-adrenoceptor would favor a decrease in ET-1 production and possibly promote vascular relaxation.