beta-Adrenoceptor blockers protect against staurosporine-induced apoptosis in SH-SY5Y neuroblastoma cells

Selective Noradrenergic Activation of BDNF Translation by Mirtazapine

Antidepressants are known for their neurotrophic effects, particularly through the regulation of brain-derived neurotrophic factor (BDNF) expression. Mirtazapine, a tetracyclic noradrenergic and specific serotonergic antidepressant (NaSSA) has been observed to upregulate BDNF, though its underlying mechanism remains unclear. In this study, we used the human neuroblastoma SH-SY5Y cell line to investigate whether mirtazapine could enhance BDNF translation by modulating serotonin and/or norepinephrine and their receptors. A 1-h stimulation with 1 or 10 µM mirtazapine led to downregulation of serotonergic receptors 5HT1A, while increasing ADRA2A and ADRB2 receptors. Mirtazapine at 10 µM upregulated endogenous BDNF after 3h, but not 1h stimulation. To investigate the translation of major BDNF transcripts, we used chimeric BDNF-luciferase constructs with the untranslated 5'UTR exons I, IIc, IV, or VI, and the long version of the 3'UTR. Luciferase assays and Western blotting revealed that mirtazapine selectively enhanced exon-IIc-BDNF-long3'UTR-Luciferase translation. This increase was associated with norepinephrine release and was inhibited by blocking ADRA2A or ADRB2 adrenoceptors for the exon-IIc-BDNF-long3'UTR-Luciferase, and ADR2B for endogenous BDNF. These findings provide a new perspective on the critical role of the noradrenergic system in mediating mirtazapine's effects on BDNF translation. We propose a novel mechanism of action in which mirtazapine promotes norepinephrine release and noradrenergic responses by upregulating ADRA2A and ADRB2 while downregulating serotonergic receptors.

Implication of Central β2 Adrenergic Receptor for the Development of Novel Drugs Against Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a progressive onset of symptoms, including memory loss, accompanied by other neurological impairments. This progression is attributed to the deterioration of neuronal connections and a decrease in neurotransmission. Although this phenomenon has been extensively studied in the cholinergic system, it also affects other neurobiological pathways, particularly adrenergic transmission. In this context, the use of agonists, in particular, β2-adrenergic receptor (β2AR) agonists, may represent a promising therapeutic approach. After reviewing the main pharmacological aspects related to these receptors, we will first present the different existing modulators and their peripheral effects. We will then analyze the results of studies investigating their use in disease models. Finally, we will discuss the conditions and prospects for the development of a new treatment for Alzheimer's disease using a β2AR agonist.

Beta-Blocker Therapy Preserves Normal Splenic T-Lymphocyte Numbers Reduced in Proportion to Sepsis Severity in a Sepsis Model

Lymphocyte cell death contributes to sepsis-induced immunosuppression, leading to poor prognosis. This study examined whether sepsis severity and beta-blocker therapy could affect the degree of T-lymphocyte cell death in a mouse model of sepsis. In the first control study, 20 animals were allocated to 4 groups: control group with sham operation (group C, n = 5) and 3 groups with cecum ligation and puncture (CLP) performed at 3 different sites: proximal, middle, and distal cecum (groups CLP-P, CLP-M, and CLP-D, respectively; n = 5 in each group). Their spleens were resected under general anesthesia 24 hours after CLP, and the total number of normal splenic T lymphocytes per mouse and the percentage of apoptotic T lymphocytes were evaluated using flow cytometry. In the second experimental study, the effect of the beta-blocker esmolol was examined in CLP-P (group CLP-PE vs. CLP-P; n = 5 in each group). The total normal splenic T-lymphocyte numbers per mouse significantly decreased in proportion to CLP severity (group C, 18.6 × 10⁶ (15 × 10⁶–23.6 × 10⁶); CLP-D, 9.2 × 10⁶ (8.8 × 10⁶–9.8 × 10⁶); CLP-M, 6.7 × 10⁶ (6.3 × 10⁶–7.0 × 10⁶); and CLP-P, 5.3 × 10⁶ (5.1 × 10⁶–6.8 × 10⁶)). Beta-blocker therapy restored T-lymphocyte numbers (group CLP-PE vs. CLP-P; 6.94 ± 1.52 × 10⁶ vs. 4.18 ± 1.71 × 10⁶; p=0.027) without affecting apoptosis percentage. Beta-blocker therapy might improve sepsis-induced immunosuppression via normal splenic T-lymphocyte preservation.

Mitochondrial Dysfunction Triggers Synaptic Deficits via Activation of p38 MAP Kinase Signaling in Differentiated Alzheimer's Disease Trans-Mitochondrial Cybrid Cells

Loss of synapse and synaptic dysfunction contribute importantly to cognitive impairment in Alzheimer's disease (AD). Mitochondrial dysfunction and oxidative stress are early pathological features in AD-affected brain. However, the effect of AD mitochondria on synaptogenesis remains to be determined. Using human trans-mitochondrial "cybrid" (cytoplasmic hybrid) neuronal cells whose mitochondria were transferred from platelets of patients with sporadic AD or age-matched non-AD subjects with relatively normal cognition, we provide the first evidence of mitochondrial dysfunction compromises synaptic development and formation of synapse in AD cybrid cells in response to chemical-induced neuronal differentiation. Compared to non-AD control cybrids, AD cybrid cells showed synaptic loss which was evidenced by a significant reduction in expression of two synaptic marker proteins: synaptophysin (presynaptic marker) and postsynaptic density protein-95, and neuronal proteins (MAP-2 and NeuN) upon neuronal differentiation. In parallel, AD-mediated synaptic deficits correlate to mitochondrial dysfunction and oxidative stress as well as activation of p38 MAP kinase. Notably, inhibition of p38 MAP kinase by pharmacological specific p38 inhibitor significantly increased synaptic density, improved mitochondrial function, and reduced oxidative stress. These results suggest that activation of p38 MAP kinase signaling pathway contributes to AD-mediated impairment in neurogenesis, possibly by inhibiting the neuronal differentiation. Our results provide new insight into the crosstalk of dysfunctional AD mitochondria to synaptic formation and maturation via activation of p38 MAP kinase. Therefore, blockade of p38 MAP kinase signal transduction could be a potential therapeutic strategy for AD by alleviating loss of synapses.

The Beta Adrenergic Receptor Blocker Propranolol Counteracts Retinal Dysfunction in a Mouse Model of Oxygen Induced Retinopathy: Restoring the Balance between Apoptosis and Autophagy

In a mouse model of oxygen induced retinopathy (OIR), beta adrenergic receptor (BAR) blockade has been shown to recover hypoxia-associated retinal damages. Although the adrenergic signaling is an important regulator of apoptotic and autophagic processes, the role of BARs in retinal cell death remains to be elucidated. The present study was aimed at investigating whether ameliorative effects of BAR blockers may occur through their coordinated action on apoptosis and autophagy. To this aim, retinas from control and OIR mice untreated or treated with propranolol, a non-selective BAR1/2 blocker, were characterized in terms of expression and localization of apoptosis and autophagy markers. The effects of propranolol on autophagy signaling were also evaluated and specific autophagy modulators were used to get functional information on the autophagic effects of BAR antagonism. Finally, propranolol effects on neurodegenerative processes were associated to an electrophysiological investigation of retinal function by recording electroretinogram (ERG). We found that retinas of OIR mice are characterized by increased apoptosis and decreased autophagy, while propranolol reduces apoptosis and stimulates autophagy. In particular, propranolol triggers autophagosome formation in bipolar, amacrine and ganglion cells that are committed to die by apoptosis in response to hypoxia. Also our data argue that propranolol, through the inhibition of the Akt-mammalian target of rapamycin pathway, activates autophagy which decreases retinal cell death. At the functional level, propranolol recovers dysfunctional ERG by recovering the amplitude of a- and b-waves, and oscillatory potentials, thus indicating an efficient restoring of retinal transduction. Overall, our results demonstrate that BAR1/2 are key regulators of retinal apoptosis/autophagy, and that BAR1/2 blockade leads to autophagy-mediated neuroprotection. Reinstating the balance between apoptotic and autophagic machines may therefore be viewed as a future goal in the treatment of retinopathies.

Amyloid β production is regulated by β2-adrenergic signaling-mediated post-translational modifications of the ryanodine receptor

Alteration of ryanodine receptor (RyR)-mediated calcium (Ca²⁺) signaling has been reported in Alzheimer disease (AD) models. However, the molecular mechanisms underlying altered RyR-mediated intracellular Ca²⁺ release in AD remain to be fully elucidated. We report here that RyR2 undergoes post-translational modifications (phosphorylation, oxidation, and nitrosylation) in SH-SY5Y neuroblastoma cells expressing the β-amyloid precursor protein (βAPP) harboring the familial double Swedish mutations (APPswe). RyR2 macromolecular complex remodeling, characterized by depletion of the regulatory protein calstabin2, resulted in increased cytosolic Ca²⁺ levels and mitochondrial oxidative stress. We also report a functional interplay between amyloid β (Aβ), β-adrenergic signaling, and altered Ca²⁺ signaling via leaky RyR2 channels. Thus, post-translational modifications of RyR occur downstream of Aβ through a β2-adrenergic signaling cascade that activates PKA. RyR2 remodeling in turn enhances βAPP processing. Importantly, pharmacological stabilization of the binding of calstabin2 to RyR2 channels, which prevents Ca²⁺ leakage, or blocking the β2-adrenergic signaling cascade reduced βAPP processing and the production of Aβ in APPswe-expressing SH-SY5Y cells. We conclude that targeting RyR-mediated Ca²⁺ leakage may be a therapeutic approach to treat AD.

The role of Beta-adrenergic receptor blockers in Alzheimer's disease: potential genetic and cellular signaling mechanisms

According to genetic studies, Alzheimer's disease (AD) is linked to beta-adrenergic receptor blockade through numerous factors, including human leukocyte antigen genes, the renin-angiotensin system, poly(adenosine diphosphate-ribose) polymerase 1, nerve growth factor, vascular endothelial growth factor, and the reduced form of nicotinamide adenine dinucleotide phosphate. Beta-adrenergic receptor blockade is also implicated in AD due to its effects on matrix metalloproteinases, mitogen-activated protein kinase pathways, prostaglandins, cyclooxygenase-2, and nitric oxide synthase. Beta-adrenergic receptor blockade may also have a significant role in AD, although the role is controversial. Behavioral symptoms, sex, or genetic factors, including Beta 2-adrenergic receptor variants, apolipoprotein E, and cytochrome P450 CYP2D6, may contribute to beta-adrenergic receptor blockade modulation in AD. Thus, the characterization of beta-adrenergic receptor blockade in patients with AD is needed.

The Role of Neurotransmitters in Protection against Amyloid- β Toxicity by KiSS-1 Overexpression in SH-SY5Y Neurons

Recent studies have suggested that the kisspeptin (KP) and kissorphin (KSO) peptides have neuroprotective actions against the Alzheimer's amyloid-β (Aβ) peptide. Overexpression of the human KiSS-1 gene that codes for KP and KSO peptides in SH-SY5Y neurons has also been shown to inhibit Aβ neurotoxicity. The in vivo actions of KP include activation of neuroendocrine and neurotransmitter systems. The present study used antagonists of KP, neuropeptide FF (NPFF), opioids, oxytocin, estrogen, adrenergic, cholinergic, dopaminergic, serotonergic, and γ-aminobutyric acid (GABA) receptors plus inhibitors of catalase, cyclooxygenase, nitric oxide synthase, and the mitogen activated protein kinase cascade to characterize the KiSS-1 gene overexpression neuroprotection against Aβ cell model. The results showed that KiSS-1 overexpression is neuroprotective against Aβ and the action appears to involve the KP or KSO peptide products of KiSS-1 processing. The mechanism of neuroprotection does not involve the activation of the KP or NPFF receptors. Opioids play a role in the toxicity of Aβ in the KiSS-1 overexpression system and opioid antagonists naloxone or naltrexone inhibited Aβ toxicity. The mechanism of KiSS-1 overexpression induced protection against Aβ appears to have an oxytocin plus a cyclooxygenase dependent component, with the oxytocin antagonist atosiban and the cyclooxygenase inhibitor SC-560 both enhancing the toxicity of Aβ.

The role of β-adrenergic blockers in Parkinson's disease: possible genetic and cell-signaling mechanisms

Genetic studies have identified numerous factors linking β-adrenergic blockade to Parkinson's disease (PD), including human leukocyte antigen genes, the renin-angiotensin system, poly(adenosine diphosphate-ribose) polymerase 1, nerve growth factor, vascular endothelial growth factor, and the reduced form of nicotinamide adenine dinucleotide phosphate. β-Adrenergic blockade has also been implicated in PD via its effects on matrix metalloproteinases, mitogen-activated protein kinase pathways, prostaglandins, cyclooxygenase 2, and nitric oxide synthase. β-Adrenergic blockade may have a significant role in PD; therefore, the characterization of β-adrenergic blockade in patients with PD is needed.

Effect of chronic restraint stress on human colorectal carcinoma growth in mice

Stress alters immunological and neuroendocrinological functions. An increasing number of studies indicate that chronic stress can accelerate tumor growth, but its role in colorectal carcinoma (CRC) progression is not well understood. The aim of this study is to investigate the effects of chronic restraint stress (CRS) on CRC cell growth in nude mice and the possible underlying mechanisms. In this study, we showed that CRS increased the levels of plasma catecholamines including epinephrine (E) and norepinephrine (NE), and stimulated the growth of CRC cell-derived tumors in vivo. Treatment with the adrenoceptor (AR) antagonists phentolamine (PHE, α-AR antagonist) and propranolol (PRO, β-AR antagonist) significantly inhibited the CRS-enhanced CRC cell growth in nude mice. In addition, the stress hormones E and NE remarkably enhanced CRC cell proliferation and viability in culture, as well as tumor growth in vivo. These effects were antagonized by the AR antagonists PHE and PRO, indicating that the stress hormone-induced CRC cell proliferation is AR dependent. We also observed that the β-AR antagonists atenolol (ATE, β1- AR antagonist) and ICI 118,551 (ICI, β2- AR antagonist) inhibited tumor cell proliferation and decreased the stress hormone-induced phosphorylation of extracellular signal-regulated kinases-1/2 (ERK1/2) in vitro and in vivo. The ERK1/2 inhibitor U0126 also blocked the function of the stress hormone, suggesting the involvement of ERK1/2 in the tumor-promoting effect of CRS. We conclude that CRS promotes CRC xenograft tumor growth in nude mice by stimulating CRC cell proliferation through the AR signaling-dependent activation of ERK1/2.

The roles of beta-adrenergic receptors in tumorigenesis and the possible use of beta-adrenergic blockers for cancer treatment: possible genetic and cell-signaling mechanisms

Cancer is the leading cause of death in the USA, and the incidence of cancer increases dramatically with age. Beta-adrenergic blockers appear to have a beneficial clinical effect in cancer patients. In this paper, we review the evidence of an association between β-adrenergic blockade and cancer. Genetic studies have provided the opportunity to determine which proteins link β-adrenergic blockade to cancer pathology. In particular, this link involves the major histocompatibility complex class II molecules, the renin-angiotensin system, transcription factor nuclear factor-kappa-light-chain-enhancer of activated B cells, poly(ADP-ribose) polymerase-1, vascular endothelial growth factor, and the reduced form of nicotinamide adenine dinucleotide phosphate oxidase. Beta-adrenergic blockers also exert anticancer effects through non-genomic factors, including matrix metalloproteinase, mitogen-activated protein kinase pathways, prostaglandins, cyclooxygenase-2, oxidative stress, and nitric oxide synthase. In conclusion, β-adrenergic blockade may play a beneficial role in cancer treatment. Additional investigations that examine β-adrenergic blockers as cancer therapeutics are required to further elucidate this role.

Induced tauopathy in a novel 3D-culture model mediates neurodegenerative processes: a real-time study on biochips

Tauopathies including Alzheimer's disease represent one of the major health problems of aging population worldwide. Therefore, a better understanding of tau-dependent pathologies and consequently, tau-related intervention strategies is highly demanded. In recent years, several tau-focused therapies have been proposed with the aim to stop disease progression. However, to develop efficient active pharmaceutical ingredients for the broad treatment of Alzheimer's disease patients, further improvements are necessary for understanding the detailed neurodegenerative processes as well as the mechanism and side effects of potential active pharmaceutical ingredients (API) in the neuronal system. In this context, there is a lack of suitable complex in vitro cell culture models recapitulating major aspects of taupathological degenerative processes in sufficient time and reproducible manner.Herewith, we describe a novel 3D SH-SY5Y cell-based, tauopathy model that shows advanced characteristics of matured neurons in comparison to monolayer cultures without the need of artificial differentiation promoting agents. Moreover, the recombinant expression of a novel highly pathologic fourfold mutated human tau variant lead to a fast and emphasized degeneration of neuritic processes. The neurodegenerative effects could be analyzed in real time and with high sensitivity using our unique microcavity array-based impedance spectroscopy measurement system. We were able to quantify a time- and concentration-dependent relative impedance decrease when Alzheimer's disease-like tau pathology was induced in the neuronal 3D cell culture model. In combination with the collected optical information, the degenerative processes within each 3D-culture could be monitored and analyzed. More strikingly, tau-specific regenerative effects caused by tau-focused active pharmaceutical ingredients could be quantitatively monitored by impedance spectroscopy.Bringing together our novel complex 3D cell culture taupathology model and our microcavity array-based impedimetric measurement system, we provide a powerful tool for the label-free investigation of tau-related pathology processes as well as the high content analysis of potential active pharmaceutical ingredient candidates.

The design, synthesis and pharmacological characterization of novel β₂-adrenoceptor antagonists

BACKGROUND AND PURPOSE

Selective and potent antagonists for the β(2) -adrenoceptor are potentially interesting as experimental and clinical tools, and we sought to identify novel ligands with this pharmacology.

EXPERIMENTAL APPROACH

A range of pharmacological assays was used to assess potency, affinity, selectivity (β(2) -adrenoceptor vs. β(1) -adrenoceptor) and efficacy.

KEY RESULTS

Ten novel compounds were identified but none had as high affinity as the prototypical β(2) -adrenoceptor blocker ICI-118,551, although one of the novel compounds was more selective for β(2) -adrenoceptors. Most of the ligands were inverse agonists for β(2) -adrenoceptor-cAMP signalling, although one (5217377) was a partial agonist and another a neutral antagonist (7929193). None of the ligands were efficacious with regard to β(2) -adrenoceptor-β-arrestin signalling. The (2S,3S) enantiomers were identified as the most active, although unusually the racemates were the most selective for the β(2) -adrenoceptors. This was taken as evidence for some unusual enantiospecific behaviour.

CONCLUSIONS AND IMPLICATIONS

In terms of improving on the pharmacology of the ligand ICI-118,551, one of the compounds was more selective (racemic JB-175), while one was a neutral antagonist (7929193), although none had as high an affinity. The results substantiate the notion that β-blockers do more than simply inhibit receptor activation, and differences between the ligands could provide useful tools to investigate receptor biology.

Isoflurane protects human kidney proximal tubule cells against necrosis via sphingosine kinase and sphingosine-1-phosphate generation

BACKGROUND/AIMS

We previously showed that the inhalational anesthetic isoflurane protects against renal ischemia reperfusion injury in part via sphingosine kinase (SK)-mediated synthesis of sphingosine-1-phosphate (S1P). In this study, we tested the hypothesis that isoflurane directly targets renal proximal tubule cells via SK activation, S1P synthesis and activation of S1P receptors to initiate cytoprotective signaling.

METHODS AND RESULTS

Isoflurane-mediated phosphorylation of extracellular signal-regulated kinase (ERK) and Akt and induction of HSP70 in human kidney proximal tubule (HK-2) cells were inhibited by dimethylsphingosine (DMS), an SK inhibitor, and VPC23019, an S1P(1/3) receptor selective antagonist, in HK-2 cells. A selective S1P(1) receptor agonist, SEW2781, mimicked isoflurane-induced phosphorylation of ERK and Akt and induction of HSP70. Moreover, isoflurane-mediated protection against H(2)O(2)-induced necrosis of HK-2 cells was significantly attenuated by an S1P(1/3) receptor antagonist, VPC23019, and by SK inhibitors DMS or 4-[[4- (4-chlorophenyl)-2-thiazolyl]amino]phenol. Finally, overexpression of the SK1 enzyme in HK-2 cells protected against H(2)O(2)-induced necrosis.

CONCLUSIONS

Collectively, our study demonstrates that S1P released via isoflurane-mediated SK1 stimulation produces direct anti-necrotic effects probably via S1P(1) receptor-mediated cytoprotective signaling (ERK/Akt phosphorylation and HSP70 induction) in HK-2 cells. Our findings may help to unravel the cellular signaling pathways of volatile anesthetic-mediated renal protection and lead to new therapeutic applications of volatile anesthetics during the perioperative period.

Isoflurane via TGF-beta1 release increases caveolae formation and organizes sphingosine kinase signaling in renal proximal tubules

We previously showed that the inhalational anesthetic isoflurane protects against renal proximal tubule necrosis via isoflurane-mediated stimulation and translocation of sphingosine kinase-1 (SK1) with subsequent synthesis of sphingosine-1-phosphate (S1P) in renal proximal tubule cells (Kim M, Kim M, Kim N, D'Agati VD, Emala CW Sr, Lee HT. Am J Physiol Renal Physiol 293: F1827-F1835, 2007). We also demonstrated that the anti-necrotic and anti-inflammatory effect of isoflurane is due in part to phosphatidylserine (PS) externalization and subsequent release of transforming growth factor-beta1 (TGF-beta1) (Lee HT, Kim M, Kim J, Kim N, Emala CW. Am J Nephrol 27: 416-424, 2007). In this study, we tested the hypothesis that isoflurane, via TGF-beta1 release, increases caveolae formation in the buoyant fraction of the cell membrane of human renal proximal tubule (HK-2) cells to organize SK1 and S1P signaling. To detect SK1 protein in the caveolae/caveolin fractions, we overexpressed human SK1 in HK-2 cells (SK1-HK-2). SK1-HK-2 cells exposed to isoflurane increased caveolae/caveolin formation in the buoyant membrane fractions which contained key signaling intermediates involved in isoflurane-mediated renal tubule protection, including S1P, SK1, ERK MAPK, and TGF-beta1 receptors. Furthermore, treating SK1-HK-2 cells with recombinant TGF-beta1 or PS liposome mixture increased caveolae formation, mimicking the effects of isoflurane. Conversely, TGF-beta1-neutralizing antibody blocked the increase in caveolae formation induced by isoflurane in SK1-HK-2 cells. The increase in SK1 activity in the caveolae-enriched fractions from isoflurane-treated nonlentivirus-infected HK-2 cells, while smaller in magnitude, was qualitatively similar to that found in the SK1-HK-2 cell line. Finally, isoflurane also increased caveolae formation in the kidneys of TGF-beta1 +/+ mice but not in TGF-beta1 +/- mice (mice with reduced levels of TGF-beta1). Our study demonstrates that isoflurane organizes several key cytoprotective signaling intermediates including TGF-beta1 receptors, SK1 and ERK, within the caveolae fraction of the plasma membrane. Our findings may help to unravel the cellular signaling pathways of volatile anesthetic-mediated renal protection and lead to new therapeutic applications of inhalational anesthetics during the perioperative period.