Adrenoceptor Research Articles

Interaction effects of intracerebroventricular injection of crocin with the α2-adrenoceptors on memory deficit and hippocampal synaptic plasticity following chronic pain in rat

Patients with chronic pain exhibit anxiety and deficits in memory. Additionally, α2-adrenoceptors that are wildly expressed in the brain have an important role in modulating both pain and memory formation. In the present study, we investigated the interaction effects of crocin with central α2-adrenoceptors on pain comorbidity and hippocampal synaptic plasticity changes following chronic constriction injury (CCI) of the sciatic nerve in rats. All the drugs (crocin, an antagonist (yohimbine) and agonist (clonidine) of α2-adrenergic receptors) were injected (via intracerebroventricular injection) from the day of CCI operation (day 0) and continued daily (once per day) until the 14th day post-CCI. The effects of drugs on the cold allodynia (using acetone test) and anxiety-like behaviors (using elevated plus maze, EPM and open field tests) were assessed. Spatial memory (using Barnes maze) was assessed on day 14 post-CCI operation. Hippocampal synaptic plasticity (using in-vivo extracellular field potential recording) was performed on day 14 post-CCI operation. We observed that crocin induced analgesic, anxiolytic and memory enhancer action following CCI surgery. Furthermore, crocin significantly increased long-term potentiation (LTP) (increased fEPSP slope and population spike amplitude). Furthermore, the co-injection of yohimbine effectively decreased analgesic, anxiolytic and enhancer action of crocin on the LTP parameters (fEPSP slope and population spike amplitude). Our study provided information that protective effects of crocin on pain/anxiety responses and synaptic plasticity were possibly mediated by central α2-adrenoceptor in the rats with chronic pain.

INFLUENCE OF OBESITY ON VASCULAR DYSFUNCTION AFTER TRAUMATIC HEMORRHAGE.

Background: Obesity increases the risk for morbidity and mortality after trauma. These complications are associated with profound vascular damage. Traumatic hemorrhage acutely attenuates vascular responsiveness, but the impact of obesity on this dysfunction is not known. The local inflammatory response in vascular cells is also unknown. We hypothesized that obesity potentiates trauma-induced vascular inflammation and dysfunction. Methods: Male Sprague-Dawley rats (~250 g) were fed normal chow (NC; 13.5% kcal fat, n = 20) or high-fat (HF; 60% kcal fat, n = 20) diets for 6 to 8 weeks. Under anesthesia, hemorrhage was induced by a mesenteric artery laceration, a Grade V splenic injury, and hypotension (MAP = 30-40 mm Hg) for 30 minutes. Vascular responsiveness was assessed ex vivo in isolated mesenteric arteries prehemorrhage and posthemorrhage. Gene expression for IL-1β, and IL-6, prooxidant nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2), and α-adrenergic receptor were assessed in carotid artery endothelial cells (ECs) and non-ECs (media + adventitia). Results: In NC rats, hemorrhage attenuated norepinephrine-induced vasoconstriction and endothelium-dependent vasodilation to acetylcholine. In HF rats, baseline norepinephrine-induced vasoconstriction was attenuated compared with NC, but vasoconstriction and endothelium-dependent vasodilation did not change prehemorrhage to posthemorrhage. Hemorrhage led to elevated IL-1β gene expression in ECs and elevated IL1β, IL-6, NOX2, and α-adrenergic receptor gene expression in the media + adventitia compared with sham. HF rats had greater EC IL-1 β and NOX2 gene expression compared with NC rats. The hemorrhage-induced elevation of IL-1β in the media + adventitia was greatest in HF rats. Conclusion: Traumatic hemorrhage attenuates vascular responsiveness and induces vascular inflammation. The attenuated vascular responsiveness after hemorrhage is absent in obese rats, while the elevated vascular inflammation persists. A HF diet amplifies the arterial inflammation after hemorrhage. Altered vascular responsiveness and vascular inflammation may contribute to worse outcomes in obese trauma patients.

Associations of GPCR autoantibodies with clinical, histological, metabolic and hemodynamic features in non-ischemic heart failure patients

Abstract Background Roughly one third of cases of chronic heart failure (HF) are caused by genetic predisposition, metabolic stress and cardiac inflammation. Animal studies suggest that heart-reactive autoantibodies, most notably those directed against G-protein-coupled receptors (GPCR), could also play a pathogenetic role in the disease. However, so far, a causal link between humoral GPCR-autoimmunity and human non-ischemic heart failure other than Chagas' cardiomyopathy remains unclear. Purpose Here, we investigated possible associations of GPCR autoantibodies with inflammatory, hemodynamic, metabolic and functional parameters in patients with chronic non-ischemic HF unrelated to Chagas' disease. Methods We prospectively included 95 patients with newly diagnosed non-ischemic heart failure of unknown origin. Basic cardiac characterization comprised transthoracic echocardiography, cardiac magnetic resonance imaging, coronary angiography and right heart catheterization with endomyocardial biopsy. Mitochondrial oxidative phosphorylation capacity and coupling was measured using high-resolution respirometry in permeabilized myocardial fibers. A panel of candidate GPCR-autoantibodies was determined by validated and certified immune-assays in peripheral venous blood of the HF-patients and 60 matched healthy individuals. Results were normalized to total IgG. Results Among 10 candidate GPCR-autoantibodies determined, only autoantibodies for α1-adrenergic receptor (α1AR), β1-adrenergic receptor (β1AR), muscarinic receptor M5 (M5AR), angiotensin II receptor type 1 (AT1R) and type 2 (AT2R) exhibited HF-associated alterations: Autoantibodies against β1AR, M5R and AT2R were increased. Autoantibodies against α1AR and AT1R were decreased (Figure). These alterations were significant (p<0.01), but not, or only weakly, correlated with markers of cardiac inflammation, cardiac damage, hemodynamics, endomyocardial histology or left ventricular inflammation judged by T2-mapping. However, in HF-patients, increased AT2R autoantibodies were associated with improved myocardial mitochondrial coupling (r=−0.27, p=0.021), and decreased AT2R autoantibodies were associated with insulin resistance (r=−0.24 p=0.027). Conclusion(s) Some previously postulated alterations of GPCR autoantibodies were confirmed in thoroughly characterized HF-patients. However, association of these alterations with cardiac function was not traceable, which argues against a specific pathogenic role. Our data are compatible with multifaceted interactions of GPCR-autoantibodies with the myocardium and potentially with glucose metabolism, possibly indicating a disease-modifying or compensatory role. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Research comission of the Heinrich-Heine University Duesseldorf

Dexmedetomidine protects cells from Angiotensin II-induced smooth muscle cell phenotype switch and endothelial cell dysfunction

ABSTRACT Abdominal aortic aneurysm (AAA) is a vascular disorder greatly threatening life of the elderly population. Dexmedetomidine (DEX), an α2-adrenergic receptor agonist, has been shown to suppress AAA development. Nevertheless, the signaling pathways that might be mediated by DEX in AAA has not been clarified. Vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) were treated with Angiotensin II (Ang II) to mimic AAA in vitro. BrdU, wound healing, and Transwell assays were utilized for measuring VSMC proliferation and migration. Western blotting was used for evaluating protein levels of contractile VSMC markers, collagens and matrix metalloproteinases (MMPs) in VSMCs as well as apoptosis- and HMGB1/TLR4/NF-κB signaling-related markers in ECs. Cell adhesion molecule expression and monocyte-endothelial adhesion were assessed by immunofluorescence staining and adhesion assays. Flow cytometry was implemented for analyzing EC apoptosis. Hematoxylin-eosin staining and ELISA were used to detect the effect of DEX in vivo. In this study, DEX inhibited Ang II-evoked VSMC phenotype switch and extracellular matrix degradation. DEX suppressed the inflammatory response and apoptosis of ECs induced by Ang II. DEX inhibited HMGB1/TLR4/NF-κB signaling pathway in Ang II-treated ECs. DEX attenuated Ang II-induced AAA and inflammation in mice. Overall, DEX ameliorates Ang II-induced VSMC phenotype switch, and inactivates HMGB1/TLR4/NF-κB signaling pathway to alleviate Ang II-induced EC dysfunction.

Connecting Aortic Stiffness to Vascular Contraction: Does Sex Matter?

This study was designed to connect aortic stiffness to vascular contraction in young male and female Wistar rats. We hypothesized that female animals display reduced intrinsic media-layer stiffness, which associates with improved vascular function. Atomic force microscopy (AFM)-based nanoindentation analysis was used to derive stiffness (Young’s modulus) in biaxially (i.e., longitudinal and circumferential) unloaded aortic rings. Reactivity studies compatible with uniaxial loading (i.e., circumferential) were used to assess vascular responses to a selective adrenergic receptor agonist in the presence or absence of extracellular calcium. Elastin and collagen levels were indirectly evaluated with fluorescence microscopy and a picrosirius red staining kit, respectively. We report that male and female Wistar rats display similar AFM-derived aortic media-layer stiffness, even though female animals withstand higher aortic intima-media thickness-to-diameter ratio than males. Female animals also present reduced phenylephrine-induced aortic force development in concentration-response and time-force curves. Specifically, we observed impaired force displacement in both parts of the contraction curve ( and ) in experiments conducted with and without extracellular calcium. Additionally, collagen levels were lower in female animals without significant elastin content and fragmentation changes. In summary, sex-related functional differences in isolated aortas appear to be related to dissimilarities in the dynamics of vascular reactivity and extracellular matrix composition rather than a direct response to a shift in intrinsic media-layer stiffness.

Interactive Effects of µ-Opioid and Adrenergic-α 2 Receptor Agonists in Rats: Pharmacological Investigation of the Primary Kratom Alkaloid Mitragynine and Its Metabolite 7-Hydroxymitragynine.

The primary kratom alkaloid mitragynine is proposed to act through multiple mechanisms, including actions at µ-opioid receptors (MORs) and adrenergic-α 2 receptors (Aα 2Rs), as well as conversion in vivo to a MOR agonist metabolite (i.e., 7-hydroxymitragynine). Aα 2R and MOR agonists can produce antinociceptive synergism. Here, contributions of both receptors to produce mitragynine-related effects were assessed by measuring receptor binding in cell membranes and, in rats, pharmacological behavioral effect antagonism studies. Mitragynine displayed binding affinity at both receptors, whereas 7-hydroxymitragynine only displayed MOR binding affinity. Compounds were tested for their capacity to decrease food-maintained responding and rectal temperature and to produce antinociception in a hotplate test. Prototypical MOR agonists and 7-hydroxymitragynine, but not mitragynine, produced antinociception. MOR agonist and 7-hydroxymitragynine rate-deceasing and antinociceptive effects were antagonized by the opioid antagonist naltrexone but not by the Aα 2R antagonist yohimbine. Hypothermia only resulted from reference Aα 2R agonists. The rate-deceasing and hypothermic effects of reference Aα 2R agonists were antagonized by yohimbine but not naltrexone. Neither naltrexone nor yohimbine antagonized the rate-decreasing effects of mitragynine. Mitragynine and 7-hydroxymitragynine increased the potency of the antinociceptive effects of Aα 2R but not MOR reference agonists. Only mitragynine produced hypothermic effects. Isobolographic analyses for the rate-decreasing effects of the reference Aα 2R and MOR agonists were also conducted. These results suggest mitragynine and 7-hydroxymitragynine may produce antinociceptive synergism with Aα 2R and MOR agonists. When combined with Aα 2R agonists, mitragynine could also produce hypothermic synergism. SIGNIFICANCE STATEMENT: Mitragynine is proposed to target the µ-opioid receptor (MOR) and adrenergic-α2 receptor (Aα2R) and to produce behavioral effects through conversion to its MOR agonist metabolite 7-hydroxymitragynine. Isobolographic analyses indicated supra-additivity in some dose ratio combinations. This study suggests mitragynine and 7-hydroxymitragynine may produce antinociceptive synergism with Aα2R and MOR agonists. When combined with Aα2R agonists, mitragynine could also produce hypothermic synergism.

The contribution of autonomic mechanisms to pain in temporomandibular disorders: A narrative review.

Temporomandibular disorders (TMD) are diagnosed based on symptom presentation and, like other functional pain disorders, often lack definitive pathology. There is a strong association between elevated stress levels and the severity of TMD-related pain, which suggests that alterations in autonomic tone may contribute to this pain condition. This narrative review examines the association between altered autonomic function and pain in TMD. Relevant articles were identified by searching PubMed and through the reference list of those studies. TMD sufferers report an increased incidence of orthostatic hypotension. As in other chronic musculoskeletal pain conditions, TMD is associated with increased sympathetic tone, diminished baroreceptor reflex sensitivity and decreased parasympathetic tone. It remains to be determined whether ongoing pain drives these autonomic changes and/or is exacerbated by them. To examine whether increased sympathetic tone contributes to TMD-related pain through β2 adrenergic receptor activation, clinical trials with the beta blocker propranolol have been undertaken. Although evidence from small studies suggested propranolol reduced TMD-related pain, a larger clinical trial did not find a significant effect of propranolol treatment. This is consistent with human experimental pain studies that were unable to demonstrate an effect of β2 adrenergic receptor activation or inhibition on masticatory muscle pain. In preclinical models of temporomandibular joint arthritis, β2 adrenergic receptor activation appears to contribute to inflammation and nociception, whereas in masticatory muscle, α1 adrenergic receptor activation has been found to induce mechanical sensitisation. Some agents used to treat TMD, such as botulinum neurotoxin A, antidepressants and α2 adrenergic receptor agonists, may interact with the autonomic nervous system as part of their analgesic mechanism. Even if dysautonomia turns out to be a consequence rather than a causative factor of painful TMD, the study of its role has opened up a greater understanding of the pathogenesis of this condition.

Adrenoceptor sub-type involvement in Ca2+ current stimulation by noradrenaline in human and rabbit atrial myocytes

Atrial fibrillation (AF) from elevated adrenergic activity may involve increased atrial L-type Ca2+ current (ICaL) by noradrenaline (NA). However, the contribution of the adrenoceptor (AR) sub-types to such ICaL-increase is poorly understood, particularly in human. We therefore investigated effects of various broad-action and sub-type-specific α- and β-AR antagonists on NA-stimulated atrial ICaL. ICaL was recorded by whole-cell-patch clamp at 37 °C in myocytes isolated enzymatically from atrial tissues from consenting patients undergoing elective cardiac surgery and from rabbits. NA markedly increased human atrial ICaL, maximally by ~ 2.5-fold, with EC75 310 nM. Propranolol (β1 + β2-AR antagonist, 0.2 microM) substantially decreased NA (310 nM)-stimulated ICaL, in human and rabbit. Phentolamine (α1 + α2-AR antagonist, 1 microM) also decreased NA-stimulated ICaL. CGP20712A (β1-AR antagonist, 0.3 microM) and prazosin (α1-AR antagonist, 0.5 microM) each decreased NA-stimulated ICaL in both species. ICI118551 (β2-AR antagonist, 0.1 microM), in the presence of NA + CGP20712A, had no significant effect on ICaL in human atrial myocytes, but increased it in rabbit. Yohimbine (α2-AR antagonist, 10 microM), with NA + prazosin, had no significant effect on human or rabbit ICaL. Stimulation of atrial ICaL by NA is mediated, based on AR sub-type antagonist responses, mainly by activating β1- and α1-ARs in both human and rabbit, with a β2-inhibitory contribution evident in rabbit, and negligible α2 involvement in either species. This improved understanding of AR sub-type contributions to noradrenergic activation of atrial ICaL could help inform future potential optimisation of pharmacological AR-antagonism strategies for inhibiting adrenergic AF.

Dexmedetomidine reduces myocardial ischemia-reperfusion injury in young mice through MIF/AMPK/GLUT4 axis

BackgroundReperfusion of ischemic tissue has adverse impact on the myocardium. Dexmedetomidine (Dex) is a α2-adrenergic receptor (α2-AR) agonist with sedative and analgesic effects. Macrophage migration inhibition factor (MIF) is a pressure-regulating cytokine and is responsible for inflammatory and immune diseases. This study aims to reveal the consequences of Dex on myocardial ischemia-reperfusion injury (IRI) in young mice.MethodsFifty mice were raised and examined. At the end of the experiment, all mice were euthanized. The anterior descending department of the left coronary artery in mice was under ischemia for 60 min, then the ligation line was released and reperfused for 120 min to establish the IRI model. Mice were randomly divided into Sham, control, treatment using 4,5-dihydro-3-(4-hydroxyphenyl)-5-isoxazoleacetic acid (ISO-1), Dex treatment, and Dex combined ISO-1 treatment groups. Interleukin (IL)-6, IL-10 and tumor necrosis factor (TNF-α) were determined by enzyme-linked immunosorbent assay (ELISA). Reactive oxygen species (ROS) and ATP levels were recorded. The expressions of MIF, P-adenosine monophosphate-activated kinase α (AMPKα), glucose transporter (GLUT)4, Bax and Bcl-2 were detected by Western Blot (WB). Hematoxylin and Eosin (H&E) staining was used to study cell morphology. Apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay. Echocardiography was carried out at the end of reperfusion, and the infarct size was calculated by Electron microscopy.ResultsI/R + Dex group showed significantly increased IL-6 and TNF-α levels and reduced myocardial cell necrosis and apoptosis. H&E staining showed alleviated myocardial disorder, myocardial cell swelling, myocardial fiber fracture, and inflammatory cell infiltration in I/R + Dex group. Myocardial cell necrosis and apoptosis were significantly reduced in I/R + Dex group. ATP level in myocardial tissue of mice in I/R group was substantially decreased, while that in Dex group was increased. WB results showed that MIF, P-AMPK α, GLUT4 and Bcl-2 levels were increased and Bax levels were decreased in I/R + Dex group.ConclusionDex may exert myocardial protection in young mice through MIF/AMPK/GLUT4 axis.

Vasoconstrictor and hemodynamic effects of a methanolic extract from Rhinella marina toad poison

Rhinella marina toad is abundant in Brazil. Its poison contains cardiac glycosides called bufadienolides, which are extensively investigated for their bioactivity. Our aim was to characterize the vasoactivity of Rhinella marina poison (RmP) on the aorta of male Wistar rats. For this, the RmP was first collected and processed to obtain an alcoholic extract. To determine cardiovascular effects of RmP, we performed in vivo tests by administering RmP intravenously in doses of 0.1–0.8 mg/kg. Vascular reactivity was also performed through concentration-response curves to RmP (10 ng/mL to 200 μg/mL) in aortic segments with and without endothelium. RmP induced a concentration-dependent contraction in rat aorta which was partly endothelium-mediated. Nitric oxide contributes with this response in view that incubation with L-NAME increased the contractile response. Additionally, treatment with indomethacin [cyclooxygenase, (COX) inhibitor], nifedipine (L-type voltage-gated calcium channels blocker), and BQ-123 (ETA receptors antagonist) decreased maximum response, and ketanserin (5-HT2 receptors antagonist) decreased pEC50, suggesting active participation of these pathways in the contractile response. On the other hand, apocynin (NADPH oxidase inhibitor) did not alter contractility. Incubation with prazosin (α1-adrenergic receptor antagonist) abolished the contractile response, suggesting that the RmP-induced contraction is dependent on the adrenergic pathway. In the Na+/K+ ATPase protocol, a higher Emax was observed in the RmP experimental group, suggesting that RmP potentiated Na+/K+ATPase hyperpolarizing response. When this extract was injected (i.v.) in vivo, increase in blood pressure and decrease in heart rate were observed. The results were immediate and transitory, and occurred in a dose-dependent manner. Overall, these data suggest that the poison extract of R. marina toad has an important vasoconstrictor action and subsequent vasopressor effects, and its use can be investigated to some cardiovascular disorders.

Carvedilol ameliorates dexamethasone-induced myocardial injury in rats independent of its action on the α1-adrenergic receptor

The current study aimed to investigate the cardiotoxic effect of dexamethasone-high-dose in rats, the therapeutic effect of carvedilol and the role of α1-adrenergic receptor (α1AR). The experiment involved 6 groups: control, dexamethasone (10 mg/kg), carvedilol (10 mg/kg), phenylephrine (1 mg/kg), phenylephrine plus carvedilol and propranolol (30 mg/kg). Drugs and vehicles were given for 7 days. Dexamethasone was given with the drugs in the last 4 groups. On the 8th-day and after overnight fasting, serum and cardiac samples were collected. Serum levels of cardiac troponin I and creatine kinase–myoglobin as well as cardiac levels of diacylglycerol, malondialdehyde, kinase activity of Akt, transforming growth factor-β, Smad3 and alpha smooth muscle actin were measured. Cardiac samples were also used for histopathological examination using hematoxylin–eosin and Sirius red stains, in addition to immunohistochemical examination using β-arrestin2 antibody. Dexamethasone induced cardiac injury via increasing oxidative stress, apoptosis and profibrotic signals. Carvedilol significantly reduced the dexamethasone-induced cardiotoxicity. Using phenylephrine, a competitive α1-agonist, with carvedilol potentiated the cardioprotective actions of carvedilol. Propranolol, a β-blocker without activity on α1ARs, showed higher cardiac protection than carvedilol. Dexamethasone-high-dose upregulates cardiac oxidative stress, apoptotic and profibrotic signals and induces cardiac injury. Blocking the α1-adrenergic receptor by carvedilol attenuates its cardioprotective effects against dexamethasone-induced cardiotoxicity.

The Antiarrhythmic and Hypotensive Effects of S-61 and S-73, the Pyrrolidin-2-one Derivatives with α1-Adrenolytic Properties.

Heart rhythm abnormalities are a cause of many deaths worldwide. Unfortunately, the available antiarrhythmic drugs show limited efficacy and proarrhythmic potential. Thus, efforts should be made to search for new, more effective, and safer pharmacotherapies. Several studies suggested that blocking the α1-adrenoceptors could restore normal heart rhythm in arrhythmia. In this study, we aimed to assess the antiarrhythmic potential of S-61 and S-73, two novel pyrrolidin-2-one derivatives with high affinity for α1-adrenergic receptors. First, using radioligand binding studies, we demonstrated that S-61 and S-73 did not bind with β1-adrenoceptors. Next, we assessed whether S-61 and S-73 could protect rats against arrhythmia in adrenaline-, calcium chloride- and aconitine-induced arrhythmia models. Both compounds showed potent prophylactic antiarrhythmic properties in the adrenaline-induced arrhythmia model, but the effect of S-61 was more pronounced. None of the compounds displayed antiarrhythmic effects in calcium chloride- or aconitine-induced arrhythmia models. Interestingly, both derivatives revealed therapeutic antiarrhythmic activity in the adrenaline-induced arrhythmia, diminishing heart rhythm irregularities. Neither S-61 nor S-73 showed proarrhythmic potential in rats. Finally, the compounds decreased blood pressure in rodents. The hypotensive effects were not observed after coadministration with methoxamine, which suggests the α1-adrenolytic properties of both compounds. Our results confirm that pyrrolidin-2-one derivatives possess potent antiarrhythmic properties. Given the promising results of our experiments, further studies on pyrrolidin-2-one derivatives might result in the development of a new class of antiarrhythmic drugs.

Prostatic Therapeutic Efficacy of LENILUTS®, a Novel Formulation with Multi-Active Principles.

Lower Urinary Tract Symptoms (LUTs) in men are usually associated to benign prostatic hyperplasia (BPH), a non-malignant prostate enlargement. Unfortunately, BPH etiology is still unclear. Recent works highlighted a relevant inflammation role in BPH onset and development. Consequently, to complement the 5-α reductase (and α-adrenergic receptor agonists-based therapy, an anti-inflammatory therapy should be devised. To reduce potential adverse effects of multi-drug treatment, plant extract-based therapies are becoming increasingly common. Serenoa repens, the main phytotherapic treatment for BPH, is not sufficient to front the multi-faceted etiology of BPH. In response to this, a novel, multiple phytotherapic agents-based formulation, LENILUTS®, was developed. In the present work, we compared, using an in vitro approach, the prostatic safety and efficacy of LENILUTS® with a commercial formulation, based only on Serenoa repens, and a 5αR inhibitor, Dutasteride. Furthermore, preliminary in vitro experiments to investigate the active principles, bioaccessibility and bioavailability of LENILUTS® were performed. Our results showed a better prostatic safety and therapeutic efficacy of LENILUTS® compared to the commercial formulation and Dutasteride, with increased anti-inflammatory, and pro-apoptotic activity, and a stronger inhibitory effect on the release of the key enzyme 5αR and Prostatic-Specific Antigen (PSA). The limited bioaccessibility and bioavailability of the active principles of LENILUTS® were highlighted. Considering the results obtained, the LENILUTS® formulation is more promising for BPH and LUTs therapy compared to formulations based on Serenoa repens only, but further efforts should be made to improve the bioaccessibility and bioavailability of the active principles.

Therapeutic effects of silodosin and urapidil on underactive bladder associated with diabetic cystopathy.

Pharmacological treatment options for underactive bladder (UAB) syndrome are limited. Urapidil is the only alpha1 -adrenoceptor (AR) antagonist that can be used for urinary disorders in women in some countries. However, no studies have directly verified the effects of alpha1 -AR antagonists on the female urethra and UAB-like dysfunctions. We investigated the effects of silodosin (alpha1A -AR antagonist) and urapidil (nonselective alpha1 -AR antagonist) on the voiding function in female rats with diabetes mellitus (DM). Changes in intraurethral pressure (IUP) induced by midodrine (alpha1 -AR agonist) and mean blood pressure (MBP) were continuously measured in normal female rats to verify the pharmacological profiles of the drugs. To establish a DM model, rats were administered streptozotocin (STZ; 50 mg/kg, intravenous). Eight weeks after STZ administration, drugs were subcutaneously delivered through an osmotic pump. Four weeks after drug administration, emptied bladder blood flow (BBF), intravesical pressure, and the micturition volume were measured. Both silodosin and urapidil inhibited the midodrine-induced increase in IUP and decreased MBP in a dose-dependent manner. Silodosin had a more substantial effect on the lower urinary tract than on MBP. Twelve weeks after STZ administration, DM rats exhibited UAB-like dysfunction (increased bladder capacity/bladder weight and residual volume and decreased bladder voided efficiency) and decreased BBF. Both drug treatments controlled this dysfunction. Alpha1 -AR antagonists induced dose-dependent urethral relaxation in female rats. These drugs ameliorated UAB-like dysfunction in STZ-induced DM rats. In addition, alpha1A -AR antagonists such as silodosin, which have limited effects on blood pressure, appear to be useful for treating UAB.

Dopamine activates astrocytes in prefrontal cortex via α1-adrenergic receptors.

SUMMARYThe prefrontal cortex (PFC) is a hub for cognitive control, and dopamine profoundly influences its functions. In other brain regions, astrocytes sense diverse neurotransmitters and neuromodulators and, in turn, orchestrate regulation of neuroactive substances. However, basic physiology of PFC astrocytes, including which neuromodulatory signals they respond to and how they contribute to PFC function, is unclear. Here, we characterize divergent signaling signatures in mouse astrocytes of the PFC and primary sensory cortex, which show differential responsiveness to locomotion. We find that PFC astrocytes express receptors for dopamine but are unresponsive through the Gs/Gi-cAMP pathway. Instead, fast calcium signals in PFC astrocytes are time locked to dopamine release and are mediated by α1-adrenergic receptors both ex vivo and in vivo. Further, we describe dopamine-triggered regulation of extracellular ATP at PFC astrocyte territories. Thus, we identify astrocytes as active players in dopaminergic signaling in the PFC, contributing to PFC function though neuromodulator receptor crosstalk.

Kratom alkaloid mitragynine: Inhibition of chemotherapy-induced peripheral neuropathy in mice is dependent on sex and active adrenergic and opioid receptors.

Mitragynine (MG) is an alkaloid found in Mitragyna speciosa (kratom) that is used as an herbal remedy for pain relief and opioid withdrawal. MG acts at μ-opioid and α-adrenergic receptors in vitro, but the physiological relevance of this activity in the context of neuropathic pain remains unknown. The purpose of the present study was to characterize the effects of MG in a mouse model of chemotherapy-induced peripheral neuropathy (CIPN), and to investigate the potential impact of sex on MG’s therapeutic efficacy. Inhibition of oxaliplatin-induced mechanical hypersensitivity was measured following intraperitoneal administration of MG. Both male and female C57BL/6J mice were used to characterize potential sex-differences in MG’s therapeutic efficacy. Pharmacological mechanisms of MG were characterized through pretreatment with the opioid and adrenergic antagonists naltrexone, prazosin, yohimbine, and propranolol (1, 2.5, 5 mg/kg). Oxaliplatin produced significant mechanical allodynia of equal magnitude in both male and females, which was dose-dependently attenuated by repeated MG exposure. MG was more potent in males vs females, and the highest dose of MG (10 mg/kg) exhibited greater anti-allodynic efficacy in males. Mechanistically, activity at µ-opioid, α1- and α2-adrenergic receptors, but not β-adrenergic receptors contributed to the effects of MG against oxaliplatin-induced mechanical hypersensitivity. Repeated MG exposure significantly attenuated oxaliplatin-induced mechanical hypersensitivity with greater potency and efficacy in males, which has crucial implications in the context of individualized pain management. The opioid and adrenergic components of MG indicate that it shares pharmacological properties with clinical neuropathic pain treatments.

Proteomic Analysis of the Sphincter in a Neurogenic Bladder Caused by T10 Spinal Cord Injury.

This study aimed to conduct proteomic analysis of the sphincter in a neurogenic bladder caused by T10 spinal cord injury. The differentially expressed proteins (DEPs) of the sphincters (internal urethral sphincter) in the neurogenic bladders (NBs) of rats after complete transection of the T10 spinal cord segment were screened using tandem mass tag (TMT)-based quantitative labeling, and their biological information was analyzed. Twelve adult Sprague Dawley rats out of 40 were randomly assigned to the blank group (n = 12), while the remaining 28 were placed in the T10 spinal cord injury model via modified Hassan Shaker spinal cord transection; 12 of these rats were then randomly selected as the model group. The rats in both groups underwent urodynamics detection and hematoxylin and eosin (H&E) staining. The proteins expressed in the bladder sphincter were detected using TMT-based quantitative proteomics. DEPs were defined as proteins with fold change >1.5 or <1/1.5, p < 0.05, and unique peptide ≥2. The DEPs were subjected to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis using KOBAS 3.0., and gene ontology functional annotation analysis was performed using the Cytoscape 3.7.1. BiNGO plug-in. The protein-protein interaction network was then constructed using the interactive gene-retrieval tool STRING and Cytoscape software. The leak-point pressure and maximum cystometric volume in the model group were significantly higher than those in the blank group (p < 0.01), and H&E staining showed continuous interruption of the bladder sphincter fibers in the model group. A total of 250 DEPs were screened in the bladder sphincter, 83 of which were up-regulated and 167 of which were down-regulated. KEGG analysis of the DEPs was used to screen 15 pathways, including metabolic pathways, extracellular matrix (ECM)-receptor interaction, adhesion spots, the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway, the cytochalasin signaling pathway, and the advanced glycation end-products (AGE)/receptor for AGEs (RAGE) signaling pathway in diabetic complications and vascular smooth muscle contraction. It is of great significance to explore the pathological mechanism of non-inhibitory contraction of the bladder sphincter caused by spinal cord injury above the T10 segment from the perspective of ECM-receptor interaction, focal adhesion-activated PI3K/Akt signaling pathway, and cell relaxation signaling pathways. Synaptic vesicle glycoprotein (Sv2A) involved in the release of neurotransmitters from synaptic vesicles, arrestin β2 inhibitory proteins involved in α-adrenergic receptors and G-protein-coupled receptor internalization, and calmodulin and calmodulin binding protein involved in calcium-sensitive signaling pathways may be potential targets for developing new ways to treat bladder sphincter overactivity caused by T10 spinal cord injury.

Effects of α2-adrenoceptor stimulation on luminal alkalinisation and net fluid flux in rat duodenum.

The sympathetic nervous system is highly involved in the regulation of gastrointestinal functions such as luminal alkalinisation and fluid absorption. However, the exact mechanisms are not clear. This study aimed to delineate how α2-adrenergic receptor stimulation reduces duodenal luminal alkalinisation and induces net fluid absorption. This was tested by perfusing the duodenum of anesthetized rats with isotonic solutions devoid of Cl- and/or Na+, in the absence and presence of the α2-adrenoceptor agonist clonidine. The clonidine was also studied in rats treated with dimethylamiloride (a Na+/H+ exchange inhibitor), vasoactive intestinal peptide, and the nicotinic receptor antagonist hexamethonium. Clonidine reduced luminal alkalinisation and induced net fluid absorption. The Cl--free solution decreased luminal alkalinisation and abolished net fluid absorption, but did not prevent clonidine from doing so. Both the Na+-free solution and luminal dimethylamiloride increased luminal alkalinisation and abolished net fluid absorption, effects counteracted by clonidine. The NaCl-free solution (D-mannitol) did not affect luminal alkalinisation, but reduced net fluid absorption. Clonidine reduced luminal alkalinisation and induced net fluid absorption in rats perfused luminally with mannitol. However, clonidine did not affect the vasoactive intestinal peptide-induced increase in luminal alkalinisation or fluid secretion. Pre-treatment with hexamethonium abolished the effects of clonidine on luminal alkalinisation and net fluid flux. In summary, our in vivo experiments showed that clonidine-induced reduction in luminal alkalinisation and induction of net fluid absorption was unrelated to luminal Na+ and Cl-, or to apical Na+/H+ or Cl-/HCO3- exchangers. Instead, clonidine seems to exert its effects via suppression of nicotinic receptor-activated acetylcholine secretomotor neurons.

PEX1 is a mediator of α1-adrenergic signaling attenuating doxorubicin-induced cardiotoxicity.

Doxorubicin (DOX) is a potent chemotherapeutic agent used for cancer treatment, however, DOX-induced cardiotoxicity is a serious clinical problem because it causes acute and chronic heart dysfunction. Many studies have indicated that the α1-adrenergic receptor protects the heart from pathologic stress through activation survival signaling, however, the mechanism remains largely unknown. Previous studies have detected that the phenylephrine-induced complex-1 (PEX1) transcription factor, also known as zinc-finger protein 260 (Zfp260), is an effector of α1-adrenergic signaling in cardiac hypertrophy. Our present study aimed to investigate the role and underlying mechanism of PEX1 in cardiomyocyte survival during DOX-induced cardiotoxicity. Mice were exposed to a single intraperitoneal injection of DOX (15 mg/kg) to generate DOX-induced cardiotoxicity. We found that PEX1 expression was downregulated in DOX-treated murine hearts. PEX1 deficiency resulted in increased apoptosis, and conversely, PEX1 overexpression alleviated apoptosis induced by DOX in primary cardiomyocytes, as well as upregulated antiapoptotic genes such as BCL-2 and BCL-XL. Mechanistically, we identified that PEX1 might exert its antiapoptosis effect by playing a pivotal role in the action of α1-adrenergic signaling activation, which depends on the presence of GATA-4. Based on these findings, we supposed that PEX1may be a novel transcription factor involved in cardiac cell survival and a promising candidate target for DOX-induced cardiotoxicity.

Novel Smooth Muscle Ca2+-Signaling Nanodomains in Blood Pressure Regulation.

Ca2+ signals in smooth muscle cells (SMCs) contribute to vascular resistance and control blood pressure. Increased vascular resistance in hypertension has been attributed to impaired SMC Ca2+ signaling mechanisms. In this regard, transient receptor potential vanilloid 4 (TRPV4SMC) ion channels are a crucial Ca2+ entry pathway in SMCs. However, their role in blood pressure regulation has not been identified. We used SMC-specific TRPV4-/- (TRPV4SMC-/-) mice to assess the role of TRPV4SMC channels in blood pressure regulation. We determined the contribution of TRPV4SMC channels to the constrictor effect of α1 adrenergic receptor (α1AR) stimulation and elevated intraluminal pressure: 2 main physiologic stimuli that constrict resistance-sized arteries. The contribution of spatially separated TRPV4SMC channel subpopulations to elevated blood pressure in hypertension was evaluated in angiotensin II-infused mice and patients with hypertension. We provide first evidence that TRPV4SMC channel activity elevates resting blood pressure in normal mice. α1AR stimulation activated TRPV4SMC channels through PKCα (protein kinase Cα) signaling, which contributed significantly to vasoconstriction and blood pressure elevation. Intraluminal pressure-induced TRPV4SMC channel activity opposed vasoconstriction through activation of Ca2+-sensitive K+ (BK) channels, indicating functionally opposite pools of TRPV4SMC channels. Superresolution imaging of SMCs revealed spatially separated α1AR:TRPV4 and TRPV4:BK nanodomains in SMCs. These data suggest that spatially separated α1AR-TRPV4SMC and intraluminal pressure-TRPV4SMC-BK channel signaling have opposite effects on blood pressure, with α1AR-TRPV4SMC signaling dominating under resting conditions. Furthermore, in patients with hypertension and a mouse model of hypertension, constrictor α1AR-PKCα-TRPV4 signaling was upregulated, whereas dilator pressure-TRPV4-BK channel signaling was disrupted, thereby increasing vasoconstriction and elevating blood pressure. Our data identify novel smooth muscle Ca2+-signaling nanodomains that regulate blood pressure and demonstrate their impairment in hypertension.