Search Results (279)

Diabetic sensorimotor polyneuropathy (DSPN) is the most prevalent complication of diabetes, affecting nearly half of all persons with diabetes. It is characterized by nerve degeneration, progressive sensory loss and pain, with increased risk of ulceration and amputation. Despite its high prevalence, disease-modifying treatments for DSPN do not exist. Mitochondrial dysfunction and Ca²⁺ dyshomeostasis are key contributors to the pathophysiology of DSPN, disrupting neuronal energy homeostasis and initiating axonal degeneration. Recent findings have demonstrated that antagonism of the muscarinic acetylcholine type 1 receptor (M₁R) promotes restoration of mitochondrial function and axon repair in various neuropathies, including DSPN, chemotherapy-induced peripheral neuropathy (CIPN) and HIV-associated neuropathy. Pirenzepine, a selective M₁R antagonist with a well-established safety profile, is currently under clinical investigation for its potential to reverse neuropathy. The transient receptor potential melastatin-3 (TRPM3) channel, a Ca²⁺-permeable ion channel, has recently emerged as a downstream effector of G protein-coupled receptor (GPCR) pathways, including M₁R. TRPM3 activation enhanced mitochondrial Ca²⁺ uptake and bioenergetics, promoting axonal sprouting. This review highlights mitochondrial and Ca²⁺ signaling imbalances in DSPN and presents M₁R antagonism and TRPM3 activation as promising neuro-regenerative strategies that shift treatment from symptom control to nerve restoration in diabetic and other peripheral neuropathies. Full article

Diabetic neuropathy (DN) remains a major clinical burden, characterized by progressive sensory dysfunction, pain, and impaired quality of life. Despite the available symptomatic treatments, there is a pressing need for disease-modifying therapies. In recent years, preclinical research has highlighted the potential of repurposed pharmacological agents, originally developed for other indications, to target key mechanisms of DN. This narrative review examines the main pathophysiological pathways involved in DN, including metabolic imbalance, oxidative stress, neuroinflammation, ion channel dysfunction, and mitochondrial impairment. A wide array of repurposed drugs—including antidiabetics (metformin, empagliflozin, gliclazide, semaglutide, and pioglitazone), antihypertensives (amlodipine, telmisartan, aliskiren, and rilmenidine), lipid-lowering agents (atorvastatin and alirocumab), anticonvulsants (topiramate and retigabine), antioxidant and neuroprotective agents (melatonin), and muscarinic receptor antagonists (pirenzepine, oxybutynin, and atropine)—have shown promising results in rodent models, reducing neuropathic pain behaviors and modulating underlying disease mechanisms. By bridging basic mechanistic insights with pharmacological interventions, this review aims to support translational progress toward mechanism-based therapies for DN. Full article

α7 nAChRs are known to modulate several physiological and pathological functions in glial cells, and their selective activation might have anti-inflammatory effects in the central and peripheral nervous system. OL progenitors (OPCs) respond to cholinergic stimuli via muscarinic receptors that are mainly involved in the modulation of their proliferation. Conversely, the role of nicotinic receptors, particularly α7 nAChRs, has been poorly investigated. In this study, we evaluated the expression of α7 nAChRs in a model of OPCs (Oli neu) and the potential effects mediated by their selective activation. Methods: Oli neu cells were used as a murine immortalized OPCs model. The effects of α7 nAChRs stimulation on cell proliferation and survival were assessed by the MTT assay. RT-PCR and Western blot analysis were used to analyze the expression of α7 nAChRs and proliferative and differentiative markers (PCNA, MBP). LPS exposure was used to induce the environment in which the antioxidant and anti-inflammatory properties of α7 nAChRs were analyzed, evaluating NFR2 and TNF-α expression, ROS levels through DCFDA staining while Oil Red O staining was used for the analysis of lipid droplet content as a marker of cellular inflammation response. Results: The α7 nAChR is expressed both in OPCs and OLs, and its stimulation by the selective agonist ICH3 increases cell proliferation without modifying the OLs’ differentiation capability. Moreover, ICH3 showed anti-inflammatory and antioxidant effects against LPS exposure. Conclusions: The results herein obtained confirm the role of α7 nAChR in the modulation of neuroinflammatory processes as well as their protective effects on OLs. Full article

Background: Glucocorticoid insensitivity is a problem for the therapy of chronic inflammatory lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD). Both are non-communicable chronic inflammatory lung diseases with worldwide increasing incidences. Only symptoms can be controlled by inhaled or systemic glucocorticoids, often combined with β2 agonists and/or muscarinic receptor antagonists. The therapeutic effect of glucocorticoids varies between individuals, and a significant number of patients do not respond well. It is believed that only protein-free circulating unbound glucocorticoids can enter cells by diffusion and achieve their therapeutic effect by binding to the intracellular glucocorticoid receptor (GR), encoded by the NR3C1 gene, for which over 3000 single-nucleotide polymorphisms have been described. In addition, various GR protein isoforms result from 11 transcription start sites, and differential mRNA splicing leads to further GR protein variants; each can be modified post-translational and alter steroid response. To add more variety, some GR isoforms are expressed cell-type specific or in a sub-cellular location. The GR only functions when it forms a complex with other intracellular proteins that regulate ligand binding, cytosol-to-nuclear transport, and nuclear and cytosolic action. Importantly, the timing of the GR activity can be cell type, time, and condition specific. These factors are rarely considered when assessing disease-specific loss or reduced GR response. Conclusions: Future studies should analyze the timing of the availability, activity, and interaction of all components of the glucocorticoid signaling cascade(s) and compare these factors between non-diseased and diseased probands, applying the combination of all omics methods (250). Full article

It has long been recognised that airway smooth muscle cells (ASMCs) possess an abundance of M2 muscarinic receptors (M2Rs). However, the contribution of postjunctional M2Rs to contractions of airway smooth muscle (ASM) induced by the release of acetylcholine (ACh) from parasympathetic nerves was thought to be minimal. Instead, it was believed that these responses were exclusively mediated by activation of M3Rs. However, evidence is emerging that postjunctional M2Rs may have a greater role than previously realised. In this review, we discuss ACh signalling in airways, highlighting the well-established autoinhibitory role of prejunctional M2Rs and the putative roles of postjunctional M2Rs to cholinergic contractions of ASM. The cellular mechanisms that underpin M2R-dependent contractions of ASM are reviewed, with a particular emphasis on the role of ion channels in these responses. The regulation of M2R signalling pathways by β-adrenoceptor activation is also considered, along with the potential involvement of postjunctional M2Rs in airway diseases such as asthma and chronic obstructive pulmonary disease (COPD). Full article

Background/Objectives: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating condition with not fully understood causes, though evidence points to immune system involvement and possible autoimmunity. ME/CFS could be triggered by various infectious pathogens, like SARS-CoV-2; furthermore, a subset of the post-COVID-19 condition (PCC) patients fulfill the diagnostic criteria of ME/CFS. According to the Canadian Consensus Criteria (CCC), the presence of specific symptoms such as fatigue, post-exertional malaise, sleep dysfunction, pain, neurological/cognitive manifestations, and symptoms from at least two of the following categories lead to the diagnosis of ME/CFS: autonomic, neuroendocrine, and immune manifestation. In this study, the patient selection was based on the identification of ME/CFS patients with elevated autoantibodies, regardless of the triggering factor of their condition. Methods: The aim of this study was to identify ME/CFS patients among long COVID patients with elevated autoantibodies. In seven cases, plasmapheresis (PE) and intravenous immunoglobulins (IVIGs) with repetitive autoantibody measurements were applied: four PE sessions on days 1, 5, 30, and 60, and a low-dose IVIG therapy after each treatment. Antibodies were measured before the first PE and two weeks after the last PE session. To monitor clinical outcomes, the following somatic and psychometric follow-up assessments were conducted before the first PE, 2 weeks after the second, and 2 weeks after the last PE: the Schellong test, ISI (insomnia), FSS (fatigue), HADS (depression and anxiety), and EQ-5D-5L (quality of life) questionnaires. Results: There was a negative association between both the β2-adrenergic and M3-muscarinic receptor autoantibody concentration and the quality of life measurements assessed with the EQ-5D-5L questionnaire. Per 1 U/mL increase in the concentration levels of β2-adrenergic receptor antibodies or M3-muscarinic acetylcholine receptor antibodies, the EQ-5D-5L index score [−0.59 to 1] decreased by 0.01 (0.63%) or 0.02 (1.26%), respectively. There were no significant associations between the ISI, HADS, and FSS questionnaires and the β1-adrenergic and M4-muscarinic receptor antibodies titers. Conclusions: After a thorough selection of patients with present autoantibodies, this pilot study found negative associations concerning autoantibody concentration and somatic, as well as psychological wellbeing. To validate these promising feasibility study results—indicating the potential therapeutic potential of antibody-lowering methods—further investigation with larger sample sizes is needed. Full article

Bile acids (BAs) are synthesized in the liver from cholesterol and are subsequently conjugated with glycine and taurine. In the intestine, bile acids undergo various modifications, such as deconjugation, dehydrogenation, oxidation, and epimerization by the gut microbiota. These bile acids are absorbed in the intestine and transported to the liver as well as the systemic circulation. BAs can activate many types of receptors, including nuclear receptors and cell surface receptors. By activating these receptors, BAs can exert various effects on the metabolic, immune, and nervous systems. Recently, the detailed structure of TGR5, the major plasma membrane receptor for BAs, was elucidated, revealing a putative second BA binding site along with the orthosteric binding site. Furthermore, BAs act as ligands for bitter taste receptors and the Leukemia inhibitory factor receptor. In addition, the Mas-related, G-protein-coupled receptor X4 interacts with receptor activity-modifying proteins. Thus, a variety of cell surface receptors are associated with BAs, and BAs are thought to have very complex activities. This review focuses on recent advances regarding cell surface receptors for bile acids and the biological actions they mediate. Full article

We tried to synthesize the possibilities of predicting the response to clozapine treatment, which can significantly improve the efficacy of the active substance and reduce adverse reactions, and how the active substance acts at the D1 dopaminergic receptors D2, D3, D4, and D5, muscarinic M1, M2, M3, and M5, and the histamine and alpha 1 adrenergic receptor, as well as how it contributes to increased cerebral blood flow, the effect on ribosomal protein S6 function, or the effect on kynurenine 3-monooxygenase function. Clozapine is one of the most effective antipsychotics, and there is potential to improve performance by combining it with different compounds to limit adverse effects or by augmenting it with other antipsychotics (amisulpride, paliperidone), other active substances with different properties (minocycline, N-acetylcysteine, memantine), or alternative therapies (electroconvulsive therapy, repetitive transcranial magnetic stimulation). There are also significant steps in optimizing clozapine efficacy by predicting treatment response, which could be determined by testing the following: plasma levels of clozapine N-oxide and N-desmethylclozapine, serum levels of neurotrophins and glutamate, genetic testing, the polygenic risk score, morphometry, or even the identification and accurate determination of persistent negative symptoms. Full article

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating disorder characterized by serious physical and cognitive impairments. Recent research underscores the role of immune dysfunction, including the role of autoantibodies, in ME/CFS pathophysiology. Expanding on previous studies, we analyzed 7542 antibody–antigen interactions in ME/CFS patients using two advanced platforms: a 1134 autoantibody Luminex panel from Oncimmune and Augmenta Bioworks, along with Rapid Extracellular Antigen Profiling (REAP), a validated high-throughput method that measures autoantibody reactivity against 6183 extracellular human proteins and 225 human viral pathogen proteins. Unlike earlier reports, our analysis of 172 participants revealed no significant differences in autoantibody reactivities between ME/CFS patients and controls, including against GPCRs such as β-adrenergic receptors. However, subtle trends in autoantibody ratios between male and female ME/CFS subgroups, along with patterns of herpesvirus reactivation, suggest the need for broader and more detailed exploration. Full article

Glomerular podocytes act as a part of the filtration barrier in the kidney. The activity of this filter is regulated by ionotropic and metabotropic glutamate receptors. Adjacent podocytes can potentially release glutamate into the intercellular space; however, little is known about how podocytes release glutamate. Here, we demonstrated vesicular glutamate transporter 3 (VGLUT3)-dependent glutamate release from podocytes. Immunofluorescence analysis revealed that rat glomerular podocytes and an immortal mouse podocyte cell line (MPC) express VGLUT1 and VGLUT3. Consistent with this finding, quantitative RT-PCR revealed the expression of VGLUT1 and VGLUT3 mRNA in undifferentiated and differentiated MPCs. In addition, the exocytotic proteins vesicle-associated membrane protein 2, synapsin 1, and synaptophysin 1 were present in punctate patterns and colocalized with VGLUT3 in MPCs. Interestingly, approximately 30% of VGLUT3 colocalized with VGLUT1. By immunoelectron microscopy, VGLUT3 was often observed around clear vesicle-like structures in differentiated MPCs. Differentiated MPCs released glutamate following depolarization with high potassium levels and after stimulation with the muscarinic agonist pilocarpine. The depletion of VGLUT3 in MPCs by RNA interference reduced depolarization-dependent glutamate release. These results strongly suggest that VGLUT3 is involved in glutamatergic signalling in podocytes and may be a new drug target for various kidney diseases. Full article

The cholinergic pathways in the central nervous system (CNS) play a pivotal role in different cognitive functions of the brain, such as memory and learning. This review takes a dive into the pharmacological side of this important part of CNS function, taking into consideration muscarinic receptors and cholinesterase enzymes. Targeting a specific subtype of five primary muscarinic receptor subtypes (M1-M5) through agonism or antagonism may benefit patients; thus, there is a great pharmaceutical research interest. Inhibition of AChE and BChE, orthosteric or allosteric, or partial agonism of M1 mAChR are correlated with Alzheimer’s disease (AD) symptoms improvement. Agonism or antagonism on different muscarinic receptor subunits may lessen schizophrenia symptoms (especially positive allosteric modulation of M4 mAChR). Selective antagonism of M4 mAChR is a promising treatment for Parkinson’s disease and dystonia, and the adverse effects are limited compared to inhibition of all five mAChR. Additionally, selective M5 antagonism plays a role in drug independence behavior. M3 mAChR overexpression is associated with malignancies, and M3R antagonists seem to have a therapeutic potential in cancer, while M1R and M2R inhibition leads to reduction of neoangiogenesis. Depending on the type of cancer, agonism of mAChR may promote cancer cell proliferation (as M3R agonism does) or protection against further tumor development (M1R agonism). Thus, there is an intense need to discover new potent compounds with specific action on muscarinic receptor subtypes. Chemical structures, chemical modification of function groups aiming at action enhancement, reduction of adverse effects, and optimization of Drug Metabolism and Pharmacokinetics (DMPK) will be further discussed, as well as protein–ligand docking. Full article

Endothelial dysfunction mediated by elevated levels of autoantibodies against vasoactive peptides occurring after COVID-19 infection is proposed as a possible pathomechanism for orthostatic intolerance in long COVID patients. This case-control study comprised 100 long COVID patients from our prospective POSTCOV registry and three control groups, each consisting of 20 individuals (Asymptomatic post-COVID group; Healthy group = pan-negative for antispike protein of SARS-CoV-2; Vaccinated healthy group = no history of COVID-19 and vaccinated). Autoantibodies towards muscarinic acetylcholine receptor M3, endothelin type A receptor (ETAR), beta-2 adrenergic receptor (Beta-2 AR), angiotensin II receptor 1 and angiotensin 1-7 (Ang1-7) concentrations were measured by enzyme-linked immunosorbent assay in long COVID patients and controls. Orthostatic intolerance was defined as inappropriate sinus tachycardia, postural tachycardia, orthostatic hypotonia and other dysautonomia symptoms, such as dizziness or blurred vision (n = 38 long COVID patients). Autoantibody concentrations were compared with routine laboratory parameters and quality of life questionnaires (EQ-5D). The concentration of ETAR autoantibodies were significantly higher in long COVID, Asymptomatic and Vaccinated groups compared to the antispike protein pan-negative Healthy group. A trend towards higher plasma levels of Beta-2 AR and Ang1-7 was measured in long COVID patients, not related to presence of orthostatic intolerance. ETAR autoantibody concentration showed significant positive correlation with the EQ-5D item “Problems in performing usual activities”. Full article

Background: Nowadays, exotoxic substance intake is among the most frequently employed methods of suicide. Self-poisoning is quite common among psychiatric patients treated in hospitals. Psychotropic drugs used for suicide include phenothiazines. Promazine hydrochloride (Talofen©) is an alpha-lytic phenothiazine neuroleptic with a high affinity for histaminergic H1 receptors and a low affinity for dopaminergic D2, serotoninergic 5-HT, alpha1-adrenergic, and muscarinic receptors, which may explain its potent sedative effect. The most common adverse effects include extrapyramidal syndromes, weight gain, orthostatic hypotension, QTc prolongation, convulsions, delirium, and psychosis. Rare adverse events include the potential occurrence of autoimmune syndromes and vasculitis. Methods: We report herein the delayed death of a 59-year-old woman due to cardiocirculatory arrest on an arrhythmic basis in the context of vasculitis of the small pulmonary vessels and prolongation of the QTc interval secondary to voluntary acute intoxication with promazine hydrochloride. Results: The incident occurred in a psychiatric patient with a history of prior self-harming acts. Histological investigations revealed wavy fibers in the heart, a lymphocytic granulocyte infiltrate in the walls of small- and medium-caliber vessels, and spotty perivascular deposition of histiocyte-macrophage cells in the lungs. Immunophenotypic investigations showed the prevalence of CD15+ and T-CD3+ elements, thus identifying a small vessel vasculitis. These findings were consistent with the literature regarding adverse events following the intake of promazine hydrochloride, although vasculitis is rare. Conclusions: Thus, while QTc lengthening and arrhythmic incidents are widely reported events associated with promazine hydrochloride use, the development of a rare condition such as pulmonary vasculitis undoubtedly played a synergistic and decisive stressogenic role in the genesis of the cardiac event, leading to irreversible functional arrest. Full article

The antioxidant properties of resveratrol (RES) against oxidative toxicity induced by testicular toxicants are well documented. The current study aimed to investigate the probable beneficial role of RES on male reproduction in adult rats following prepubertal exposure to perfluorooctanoic acid (PFOA). Healthy rats of the Wistar strain (23 days old) were allocated into four groups. Rats in group I did not receive any treatment, while rats in groups II, III, and IV received RES, PFOA, and RES + PFOA, respectively, between days 23 and 56 and were monitored for up to 90 days. Exposure to PFOA resulted in a significant reduction in spermiogram parameters, testicular 3β- and 17β-HSD activity levels, and circulatory levels of testosterone. A significant elevation in LPx, PCs, H₂O₂, and O₂⁻, associated with a concomitant reduction in SOD, CAT, GPx, GR, and GSH, was noticed in the testes, as well as region-specific changes in pro- and antioxidants in the epididymides of exposed rats compared to controls. A significant increase in serum FSH and LH, testicular cholesterol levels, and caspase-3 activity was observed in PFOA-exposed rats compared to controls. Histological analysis revealed that the integrity of the testes was deteriorated in PFOA-exposed rats. Transcriptomic profiling of the testes and epididymides revealed 98 and 611 altered genes, respectively. In the testes, apoptosis and glutathione pathways were disrupted, while in the epididymides, glutathione and bile secretion pathways were altered in PFOA-exposed rats. PFOA exposure resulted in the down-regulation in the testes of 17β-HSD, StAR, nfe2l2, ar, Lhcgr, and mRNA levels, associated with the up-regulation of casp3 mRNA, and down-regulation of alpha 1 adrenoceptor, muscarinic choline receptor 3, and androgen receptor in the epididymides of exposed rats compared to the controls. These events might lead to male infertility in PFOA-exposed rats. In contrast, restoration of selected reproductive variables was observed in RES plus PFOA-exposed rats compared to rats exposed to PFOA alone. Taken together, we postulate that prepubertal exposure to PFOA triggered oxidative damage and altered genes in the testes and epididymides, leading to suppressed male reproductive health in adult rats, while RES, with its steroidogenic, antiapoptotic, and antioxidant effects, restored PFOA-induced fertility potential in rats. Full article

G protein-coupled receptors (GPCRs) regulate multiple cellular functions and represent important drug targets. More than 20 years ago, it was noted that GPCR activation (agonist binding) and signaling (G protein activation) are dependent on the membrane potential (V_M). While it is now proven that many GPCRs display an intrinsic voltage dependence, the molecular mechanisms of how GPCRs sense depolarization of the plasma membrane are less well defined. This review summarizes the current knowledge of voltage-dependent signaling in GPCRs. We describe how voltage dependence was discovered in muscarinic receptors, present an overview of GPCRs that are regulated by voltage, and show how biophysical properties of GPCRs led to the discovery of voltage-sensing mechanisms in those receptors. Furthermore, we summarize physiological functions that have been shown to be regulated by voltage-dependent GPCR signaling of endogenous receptors in excitable tissues, such as the nervous system or the heart. Finally, we discuss challenges that remain in analyzing voltage-dependent signaling of GPCRs in vivo and present an outlook on experimental applications of the interesting concept of GPCR signaling. Full article