Histamine beyond its effects on allergy: Potential therapeutic benefits for the treatment of Amyotrophic Lateral Sclerosis (ALS)

Pan-neuronal expression of human mutant SOD1 in Drosophila impairs survival and motor performance, induces early neuroinflammation and chromosome aberrations

Several mutations in the SOD1 gene encoding for the antioxidant enzyme Superoxide Dismutase 1, are associated with amyotrophic lateral sclerosis, a rare and devastating disease characterized by motor neuron degeneration and patients' death within 2-5 years from diagnosis. Motor neuron loss and related symptomatology manifest mostly in adult life and, to date, there is still a gap of knowledge on the precise cellular and molecular events preceding neurodegeneration. To deepen our awareness of the early phases of the disease, we leveraged two Drosophila melanogaster models pan-neuronally expressing either the mutation A4V or G85R of the human gene SOD1 (hSOD1A4V or hSOD1G85R). We demonstrate that pan-neuronal expression of the hSOD1A4V or hSOD1G85R pathogenic construct impairs survival and motor performance in transgenic flies. Moreover, protein and transcript analysis on fly heads indicates that mutant hSOD1 induction stimulates the glial marker Repo, up-regulates the IMD/Toll immune pathways through antimicrobial peptides and interferes with oxidative metabolism. Finally, cytological analysis of larval brains demonstrates hSOD1-induced chromosome aberrations. Of note, these parameters are found modulated in a timeframe when neurodegeneration is not detected. The novelty of our work is twofold: we have expressed for the first time hSOD1 mutations in all neurons of Drosophila and confirmed some ALS-related pathological phenotypes in these flies, confirming the power of SOD1 mutations in generating ALS-like phenotypes. Moreover, we have related SOD1 pathogenesis to chromosome aberrations and antimicrobial peptides up-regulation. These findings were unexplored in the SOD1-ALS field.

A Closer Look at Histamine in Drosophila

The present work intends to provide a closer look at histamine in Drosophila. This choice is motivated firstly because Drosophila has proven over the years to be a very simple, but powerful, model organism abundantly assisting scientists in explaining not only normal functions, but also derangements that occur in higher organisms, not excluding humans. Secondly, because histamine has been demonstrated to be a pleiotropic master molecule in pharmacology and immunology, with increasingly recognized roles also in the nervous system. Indeed, it interacts with various neurotransmitters and controls functions such as learning, memory, circadian rhythm, satiety, energy balance, nociception, and motor circuits, not excluding several pathological conditions. In view of this, our review is focused on the knowledge that the use of Drosophila has added to the already vast histaminergic field. In particular, we have described histamine's actions on photoreceptors sustaining the visual system and synchronizing circadian rhythms, but also on temperature preference, courtship behavior, and mechanosensory transmission. In addition, we have highlighted the pathophysiological consequences of mutations on genes involved in histamine metabolism and signaling. By promoting critical discussion and further research, our aim is to emphasize and renew the importance of histaminergic research in biomedicine through the exploitation of Drosophila, hopefully extending the scientific debate to the academic, industry, and general public audiences.

Revisiting Preclinical Observations of Several Histamine H3 Receptor Antagonists/Inverse Agonists in Cognitive Impairment, Anxiety, Depression, and Sleep-Wake Cycle Disorder

A relationship appears to exist between dysfunction of brain histamine (HA) and various neuropsychiatric brain disorders. The possible involvement of brain HA in neuropathology has gained attention recently, and its role in many (patho)physiological brain functions including memory, cognition, and sleep-wake cycle paved the way for further research on the etiology of several brain disorders. Histamine H3 receptor (H3R) evidenced in the brains of rodents and humans remains of special interest, given its unique position as a pre- and postsynaptic receptor, controlling the synthesis and release of HA as well as different other neurotransmitters in different brain regions, respectively. Despite several disappointing outcomes for several H3R antagonists/inverse agonists in clinical studies addressing their effectiveness in Alzheimer's disease (AD), Parkinson's disease (PD), and schizophrenia (SCH), numerous H3R antagonists/inverse agonists showed great potentials in modulating memory and cognition, mood, and sleep-wake cycle, thus suggesting its potential role in neurocognitive and neurodegenerative diseases such as AD, PD, SCH, narcolepsy, and major depression in preclinical rodent models. In this review, we present preclinical applications of selected H3R antagonists/inverse agonists and their pharmacological effects on cognitive impairment, anxiety, depression, and sleep-wake cycle disorders. Collectively, the current review highlights the behavioral impact of developments of H3R antagonists/inverse agonists, aiming to further encourage researchers in the preclinical drug development field to profile the potential therapeutic role of novel antagonists/inverse agonists targeting histamine H3Rs.

Repurposing Histaminergic Drugs in Multiple Sclerosis

Multiple sclerosis is an autoimmune disease with a strong neuroinflammatory component that contributes to severe demyelination, neurodegeneration and lesions formation in white and grey matter of the spinal cord and brain. Increasing attention is being paid to the signaling of the biogenic amine histamine in the context of several pathological conditions. In multiple sclerosis, histamine regulates the differentiation of oligodendrocyte precursors, reduces demyelination, and improves the remyelination process. However, the concomitant activation of histamine H1–H4 receptors can sustain either damaging or favorable effects, depending on the specifically activated receptor subtype/s, the timing of receptor engagement, and the central versus peripheral target district. Conventional drug development has failed so far to identify curative drugs for multiple sclerosis, thus causing a severe delay in therapeutic options available to patients. In this perspective, drug repurposing offers an exciting and complementary alternative for rapidly approving some medicines already approved for other indications. In the present work, we have adopted a new network-medicine-based algorithm for drug repurposing called SAveRUNNER, for quantifying the interplay between multiple sclerosis-associated genes and drug targets in the human interactome. We have identified new histamine drug-disease associations and predicted off-label novel use of the histaminergic drugs amodiaquine, rupatadine, and diphenhydramine among others, for multiple sclerosis. Our work suggests that selected histamine-related molecules might get to the root causes of multiple sclerosis and emerge as new potential therapeutic strategies for the disease.

The Multifaceted Role of GPCRs in Amyotrophic Lateral Sclerosis: A New Therapeutic Perspective?

Amyotrophic lateral sclerosis (ALS) is a degenerating disease involving the motor neurons, which causes a progressive loss of movement ability, usually leading to death within 2 to 5 years from the diagnosis. Much effort has been put into research for an effective therapy for its eradication, but still, no cure is available. The only two drugs approved for this pathology, Riluzole and Edaravone, are onlyable to slow down the inevitable disease progression. As assessed in the literature, drug targets such as protein kinases have already been extensively examined as potential drug targets for ALS, with some molecules already in clinical trials. Here, we focus on the involvement of another very important and studied class of biological entities, G protein-coupled receptors (GPCRs), in the onset and progression of ALS. This workaimsto give an overview of what has been already discovered on the topic, providing useful information and insights that can be used by scientists all around the world who are putting efforts into the fight against this very important neurodegenerating disease.

Histamine and Microglia

Microglia, a category of glial cells in the central nervous system (CNS), have attracted much attention because of their important role in neuroinflammation. Many translational studies are currently ongoing to discover novel drugs targeting microglia for the treatment of various CNS disorders, such as Alzheimer's disease, Parkinson's disease (PD), and depression. Recent studies have shown that brain histamine, a neurotransmitter essential for the regulation of diverse brain functions, controls glial cells and neurons. In vitro studies using primary microglia and microglial cell lines have reported that histamine receptors are expressed in microglia and control microglial functions, including chemotaxis, migration, cytokine secretion, and autophagy. In vivo studies have demonstrated that histamine-related reagents could ameliorate abnormal symptoms in animal models of human diseases, such as amyotrophic lateral sclerosis (ALS), PD, and brain ischemia. Several human studies have revealed alterations in histamine receptor levels in ALS and PD, emphasizing the importance of the CNS histamine system, including histamine-dependent microglial modulation, as a therapeutic target for these disorders. In this review article, we summarize histamine-related research focusing on microglial functions.

The 3-iodothyronamine (T1AM) and the 3-iodothyroacetic acid (TA1) indicate a novel connection with the histamine system for neuroprotection

The 3-iodothyronamine (T1AM) and 3-iodothryoacetic acid (TA1), are endogenous occurring compounds structurally related with thyroid hormones (THs, the pro-hormone T4 and the active hormone T3) initially proposed as possible mediators of the rapid effects of T3. However, after years from their identification, the physio-pathological meaning of T1AM and TA1 tissue levels remains an unsolved issue while pharmacological evidence indicates both compounds promote in rodents central and peripheral effects with mechanisms which remain mostly elusive. Pharmacodynamics of T1AM includes the recognition of G-coupled receptors, ion channels but also biotransformation into an active metabolite, i.e. the TA1. Furthermore, long term T1AM treatment associates with post-translational modifications of cell proteins. Such array of signaling may represent an added value, rather than a limit, equipping T1AM to play different functions depending on local expression of targets and enzymes involved in its biotransformation. Up to date, no information regarding TA1 mechanistic is available. We here review some of the main findings describing effects of T1AM (and TA1) which suggest these compounds interplay with the histaminergic system. These data reveal T1AM and TA1 are part of a network of signals involved in neuronal plasticity including neuroprotection and suggest T1AM and TA1 as lead compounds for a novel class of atypical psychoactive drugs.

Influence of GSTP1 rs1695 polymorphism on survival in male patients' amyotrophic lateral sclerosis: a genetic association study in Brazilian population

BACKGROUND

Glutathione S-transferase Pi (GSTP1) enzyme has a major antioxidant effect on the central nervous system (CNS), where it acts against oxidative damage, an established risk factor for amyotrophic lateral sclerosis (ALS). Hence, the purpose of this study was to evaluate a possible relationship between GSTP1 rs1695 polymorphism and the survival rate of male ALS patients, which is the gender more affected by the disease.

METHODS AND RESULTS

A case-control study was performed with 56 male ALS patients and 70 healthy male individuals from Midwestern Brazil, which were age-adjusted. GSTP1 rs1695 polymorphism molecular analysis was carried out with restriction fragment length polymorphism. The relationship between ALS patients and GSTP1 rs1695 polymorphism was analyzed using cumulative survival rate as the major outcome, where differences in survival were evaluated through the log-rank test. Our results revealed that mutant genotype (G/G) did not influence the cumulative survival rate of male ALS patients regarding the age of diagnosis (p = 0.5) and time from symptom to diagnosis (p = 0.3). On the other hand, mutant carriers exhibited a significant survival of fewer than 25 months compared to A/A and A/G genotypes that survive more than 100 months (p = 7-E10) in comparison with symptom onset to outcome (p = 0.00006).

CONCLUSIONS

In summary, our findings revealed that mutant genotype carriers' male patients had a reduced lifetime, which probably may be resulted from oxidative stress exposure in CNS.

Fly for ALS: Drosophila modeling on the route to amyotrophic lateral sclerosis modifiers

Amyotrophic lateral sclerosis (ALS) is a rare, devastating disease, causing movement impairment, respiratory failure and ultimate death. A plethora of genetic, cellular and molecular mechanisms are involved in ALS signature, although the initiating causes and progressive pathological events are far from being understood. Drosophila research has produced seminal discoveries for more than a century and has been successfully used in the past 25 years to untangle the process of ALS pathogenesis, and recognize potential markers and novel strategies for therapeutic solutions. This review will provide an updated view of several ALS modifiers validated in C9ORF72, SOD1, FUS, TDP-43 and Ataxin-2 Drosophila models. We will discuss basic and preclinical findings, illustrating recent developments and novel breakthroughs, also depicting unsettled challenges and limitations in the Drosophila-ALS field. We intend to stimulate a renewed debate on Drosophila as a screening route to identify more successful disease modifiers and neuroprotective agents.

The Histamine and Multiple Sclerosis Alliance: Pleiotropic Actions and Functional Validation

Multiple sclerosis (MS) is a disease with a resilient inflammatory component caused by accumulation into the CNS of inflammatory infiltrates and macrophage/microglia contributing to severe demyelination and neurodegeneration. While the causes are still in part unclear, key pathogenic mechanisms are the direct loss of myelin-producing cells and/or their impairment caused by the immune system. Proposed etiology includes genetic and environmental factors triggered by viral infections. Although several diagnostic methods and new treatments are under development, there is no curative but only palliative care against the relapsing-remitting or progressive forms of MS. In recent times, there has been a boost of awareness on the role of histamine signaling in physiological and pathological functions of the nervous system. Particularly in MS, evidence is raising that histamine might be directly implicated in the disease by acting at different cellular and molecular levels. For instance, constitutively active histamine regulates the differentiation of oligodendrocyte precursors, thus playing a central role in the remyelination process; histamine reduces the ability of myelin-autoreactive T cells to adhere to inflamed brain vessels, a crucial step in the development of MS; histamine levels are found increased in the cerebrospinal fluid of MS patients. The aim of the present work is to present further proofs about the alliance of histamine with MS and to introduce the most recent and innovative histamine paradigms for therapy. We will report on how a long-standing molecule with previously recognized immunomodulatory and neuroprotective functions, histamine, might still provide a renewed and far-reaching role in MS.

Histamine-4 Receptor: Emerging Target for the Treatment of Neurological Diseases

A major challenge in the field of the biogenic amine histamine is the search for new-generation histamine receptor specific drugs. Daniel Bovet and Sir James Black received their Nobel Prizes for Medicine for their work on histamine-1 receptor (H₁R) and H₂R antagonists to treat allergies and gastrointestinal disorders. The first H₃R-targeting drug to reach the market was approved for the treatment of the neurological disorder narcolepsy in 2018. The antagonists for the most recently identified histamine receptor, H₄R, are currently under clinical evaluation for their potential therapeutic effects on inflammatory diseases such as atopic dermatitis and pruritus. In this chapter, we propose that H₄R antagonists are endowed with prominent anti-inflammatory and immune effects, including in the brain. To substantiate this proposition, we combine data from transcriptional analyses of postmortem human neurodegenerative disease brain samples, human genome-wide association studies (GWAS), and translational animal model studies. The results prompt us to suggest the potential involvement of the H₄R in various neurodegenerative diseases and how manipulating the H₄R may create new therapeutic opportunities in central nervous system diseases.

Drug Repurposing: A Network-based Approach to Amyotrophic Lateral Sclerosis

The continuous adherence to the conventional "one target, one drug" paradigm has failed so far to provide effective therapeutic solutions for heterogeneous and multifactorial diseases as amyotrophic lateral sclerosis (ALS), a rare progressive and chronic, debilitating neurological disease for which no cure is available. The present study is aimed at finding innovative solutions and paradigms for therapy in ALS pathogenesis, by exploiting new insights from Network Medicine and drug repurposing strategies. To identify new drug-ALS disease associations, we exploited SAveRUNNER, a recently developed network-based algorithm for drug repurposing, which quantifies the proximity of disease-associated genes to drug targets in the human interactome. We prioritized 403 SAveRUNNER-predicted drugs according to decreasing values of network similarity with ALS. Among catecholamine, dopamine, serotonin, histamine, and GABA receptor modulators, as well as angiotensin-converting enzymes, cyclooxygenase isozymes, and serotonin transporter inhibitors, we found some interesting no customary ALS drugs, including amoxapine, clomipramine, mianserin, and modafinil. Furthermore, we strengthened the SAveRUNNER predictions by a gene set enrichment analysis that confirmed modafinil as a drug with the highest score among the 121 identified drugs with a score > 0. Our results contribute to gathering further proofs of innovative solutions for therapy in ALS pathogenesis.

Where and Why Modeling Amyotrophic Lateral Sclerosis

Over the years, researchers have leveraged a host of different in vivo models in order to dissect amyotrophic lateral sclerosis (ALS), a neurodegenerative/neuroinflammatory disease that is heterogeneous in its clinical presentation and is multigenic, multifactorial and non-cell autonomous. These models include both vertebrates and invertebrates such as yeast, worms, flies, zebrafish, mice, rats, guinea pigs, dogs and, more recently, non-human primates. Despite their obvious differences and peculiarities, only the concurrent and comparative analysis of these various systems will allow the untangling of the causes and mechanisms of ALS for finally obtaining new efficacious therapeutics. However, harnessing these powerful organisms poses numerous challenges. In this context, we present here an updated and comprehensive review of how eukaryotic unicellular and multicellular organisms that reproduce a few of the main clinical features of the disease have helped in ALS research to dissect the pathological pathways of the disease insurgence and progression. We describe common features as well as discrepancies among these models, highlighting new insights and emerging roles for experimental organisms in ALS.

An Integrative Transcriptome-Wide Analysis of Amyotrophic Lateral Sclerosis for the Identification of Potential Genetic Markers and Drug Candidates

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative neuromuscular disease. Although genome-wide association studies (GWAS) have successfully identified many variants significantly associated with ALS, it is still difficult to characterize the underlying biological mechanisms inducing ALS. In this study, we performed a transcriptome-wide association study (TWAS) to identify disease-specific genes in ALS. Using the largest ALS GWAS summary statistic (n = 80,610), we identified seven novel genes using 19 tissue reference panels. We conducted a conditional analysis to verify the genes’ independence and to confirm that they are driven by genetically regulated expressions. Furthermore, we performed a TWAS-based enrichment analysis to highlight the association of important biological pathways, one in each of the four tissue reference panels. Finally, utilizing a connectivity map, a database of human cell expression profiles cultured with bioactive small molecules, we discovered functional associations between genes and drugs to identify 15 bioactive small molecules as potential drug candidates for ALS. We believe that, by integrating the largest ALS GWAS summary statistic with gene expression to identify new risk loci and causal genes, our study provides strong candidates for molecular basis experiments in ALS.

Omics-based exploration and functional validation of neurotrophic factors and histamine as therapeutic targets in ALS

A plethora of genetic and molecular mechanisms have been implicated in the pathophysiology of the heterogeneous and multifactorial amyotrophic lateral sclerosis (ALS) disease, and hence the conventional "one target-one drug" paradigm has failed so far to provide effective therapeutic solutions, precisely because of the complex nature of ALS. This review intends to highlight how the integration of emerging "omics" approaches may provide a rational foundation for the comprehensive exploration of molecular pathways and dynamic interactions involved in ALS, for the identification of candidate targets and biomarkers that will assist in the rapid diagnosis and prognosis, lastly for the stratification of patients into different subgroups with the aim of personalized therapeutic strategies. To this purpose, particular emphasis will be placed on some potential therapeutic targets, including neurotrophic factors and histamine signaling that both have emerged as dysregulated at different omics levels in specific subgroups of ALS patients, and have already shown promising results in in vitro and in vivo models of ALS. To conclude, we will discuss about the utility of using integrated omics coupled with network-based approaches to provide additional guidance for personalization of medicine applications in ALS.

In vivo effects of the association of the psychoactive phenotiazine thioridazine on antitumor activity and hind limb paralysis induced by the native polypeptide crotamine

Crotamine is a cationic polypeptide composed by 42 amino acid residues with several pharmacological and biological properties, including the selective ability to enter and kill actively proliferating tumour cells, which led us to propose its use as a theranostic agent for cancer therapy. At the moment, the improvement of crotamine antitumoral efficacy by association with chemotherapeutic adjuvants is envisioned. In the present work, we evaluated the association of crotamine with the antitumoral adjuvant phenotiazine thioridazine (THD). In spite of the clear efficacy of these both compounds as anticancer agents in long-term in vivo treatment of animal model bearing implanted xenograph melanoma tumor, the expected mutual potentiation of the antitumor effects was not observed here. Moreover, this association revealed for the first time the influence of THD on crotamine ability to trigger the hind limb paralysis in mice, and this discovery may represent the first report suggesting the potential involvement of the CNS in the action of this snake polypeptide on the skeletal muscle paralysis, which was classically believed to be essentially limited to a direct action in peripheral tissues as the skeletal muscle. This is also supported by the observed ability of crotamine to potentiate the sedative effects of THD which action was consistently demonstrated to be based on its central action. The better characterization of crotamine properties in CNS may certainly bring important insights for the knowledge needed to pave the way toward the use of this molecule as a theranostic compound in human diseases as cancer.

Klotho Pathways, Myelination Disorders, Neurodegenerative Diseases, and Epigenetic Drugs

In this review we outline a rationale for identifying neuroprotectants aimed at inducing endogenous Klotho activity and expression, which is epigenetic action, by definition. Such an approach should promote remyelination and/or stimulate myelin repair by acting on mitochondrial function, thereby heralding a life-saving path forward for patients suffering from neuroinflammatory diseases. Disorders of myelin in the nervous system damage the transmission of signals, resulting in loss of vision, motion, sensation, and other functions depending on the affected nerves, currently with no effective treatment. Klotho genes and their single-pass transmembrane Klotho proteins are powerful governors of the threads of life and death, true to the origin of their name, Fates, in Greek mythology. Among its many important functions, Klotho is an obligatory co-receptor that binds, activates, and/or potentiates critical fibroblast growth factor activity. Since the discovery of Klotho a little over two decades ago, it has become ever more apparent that when Klotho pathways go awry, oxidative stress and mitochondrial dysfunction take over, and age-related chronic disorders are likely to follow. The physiological consequences can be wide ranging, potentially wreaking havoc on the brain, eye, kidney, muscle, and more. Central nervous system disorders, neurodegenerative in nature, and especially those affecting the myelin sheath, represent worthy targets for advancing therapies that act upon Klotho pathways. Current drugs for these diseases, even therapeutics that are disease modifying rather than treating only the symptoms, leave much room for improvement. It is thus no wonder that this topic has caught the attention of biomedical researchers around the world.

Advances in nanotechnology-based strategies for the treatments of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND), is a progressive neurodegenerative disease that affects both upper and lower motor neurons, which results in loss of muscle control and eventual paralysis [1]. Currently, there are as yet unresolved challenges regarding efficient drug delivery into the central nervous system (CNS). These challenges can be attributed to multiple factors including the presence of the blood-brain barrier (BBB), blood-spinal cord barrier (BSCB), as well as the inherent characteristics of the drugs themselves (e.g. low solubility, insufficient bioavailability/bio-stability, 'off-target' effects) etc. As a result, conventional drug delivery systems may not facilitate adequate dosage of the required drugs for functional recovery in ALS patients. Nanotechnology-based strategies, however, employ engineered nanostructures that show great potential in delivering single or combined therapeutic agents to overcome the biological barriers, enhance interaction with targeted sites, improve drug bioavailability/bio-stability and achieve real-time tracking while minimizing the systemic side-effects. This review provides a concise discussion of recent advances in nanotechnology-based strategies in relation to combating specific pathophysiology relevant to ALS disease progression and investigates the future scope of using nanotechnology to develop innovative treatments for ALS patients.

Histamine Is an Inducer of the Heat Shock Response in SOD1-G93A Models of ALS

(1) Background: Amyotrophic lateral sclerosis (ALS) is a multifactorial non-cell autonomous disease where activation of microglia and astrocytes largely contributes to motor neurons death. Heat shock proteins have been demonstrated to promote neuronal survival and exert a strong anti-inflammatory action in glia. Having previously shown that the pharmacological increase of the histamine content in the central nervous system (CNS) of SOD1-G93A mice decreases neuroinflammation, reduces motor neuron death, and increases mice life span, here we examined whether this effect could be mediated by an enhancement of the heat shock response. (2) Methods: Heat shock protein expression was analyzed in vitro and in vivo. Histamine was provided to primary microglia and NSC-34 motor neurons expressing the SOD1-G93A mutation. The brain permeable histamine precursor histidine was chronically administered to symptomatic SOD1-G93A mice. Spine density was measured by Golgi-staining in motor cortex of histidine-treated SOD1-G93A mice. (3) Results: We demonstrate that histamine activates the heat shock response in cultured SOD1-G93A microglia and motor neurons. In SOD1-G93A mice, histidine augments the protein content of GRP78 and Hsp70 in spinal cord and cortex, where the treatment also rescues type I motor neuron dendritic spine loss. (4) Conclusion: Besides the established histaminergic neuroprotective and anti-inflammatory effects, the induction of the heat shock response in the SOD1-G93A model by histamine confirms the importance of this pathway in the search for successful therapeutic solutions to treat ALS.