A critical time window for the analgesic effect of central histamine in the partial sciatic ligation model of neuropathic pain

Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating side effect of many common anti-cancer agents that can lead to dose reduction or treatment discontinuation, which decrease chemotherapy efficacy. Long-term CIPN can interfere with activities of daily living and diminish the quality of life. The mechanism of CIPN is not yet fully understood, and biomarkers are needed to identify patients at high risk and potential treatment targets. Metabolomics can capture the complex behavioral and pathophysiological processes involved in CIPN. This chapter is to review the CIPN metabolomics studies to find metabolic pathways potentially involved in CIPN. These potential CIPN metabolites are then investigated to determine whether there is evidence from studies of other neuropathy etiologies such as diabetic neuropathy and Leber hereditary optic neuropathy to support the importance of these pathways in peripheral neuropathy. Six potential biomarkers and their putative mechanisms in peripheral neuropathy were reviewed. Among these biomarkers, histidine and phenylalanine have clear roles in neurotransmission or neuroinflammation in peripheral neuropathy. Further research is needed to discover and validate CIPN metabolomics biomarkers in large clinical studies.

Decreased amino acids in the brain might contribute to the progression of diabetic neuropathic pain

AIMS

The pathophysiological alteration of diabetic neuropathic pain (DNP) in brain is unclear. Here we aimed to explore the metabolomic characteristics of brain in rats over the progression of DNP through metabolomic analysis.

METHODS

Adult rats were randomly divided into control group and DNP group. Body weight, blood glucose and behavioral assessment of neuropathic pain were measured every week after streptozotocin (STZ) injection. Finally, the brains of 2 rats from control group and 6 rats from DNP group were removed every 4 weeks after STZ injection for metabolomics analysis.

RESULTS

After 4 weeks of STZ-injection, the rats with diabetes developed DNP, which was characterized as mechanical allodynia and thermal nociception. As for metabolomic analysis, differentially expressed metabolites (DE metabolites) showed a dynamic alteration over the development of DNP and affected several KEGG pathways associated with amino acid metabolism. Furthermore, the expression of l-Threonine, l-Methionine, d-Proline, l-Lysine and N-Acetyl-l-alanine were significantly decreased at all time points of DNP group. The amino acids which were precursor of analgesic neurotransmitters were downregulated over the progression of DNP, including l-tryptophan, l-histidine and l-tyrosine.

CONCLUSIONS

The impairment of amino acid metabolism in brain might contribute to the progression of DNP through decreasing analgesic neurotransmitters.

Alterations in the gut microbiota and metabolite profiles in the context of neuropathic pain

The aim of this study was to explore the relationships among gut microbiota disturbances and serum and spinal cord metabolic disorders in neuropathic pain. 16S rDNA amplicon sequencing and serum and spinal cord metabolomics were used to identify alterations in the microbiota and metabolite profiles in the sham rats and the chronic constriction injury (CCI) model rats. Correlations between the abundances of gut microbiota components at the genus level, the levels of serum metabolites, and pain-related behavioural parameters were analysed. Ingenuity pathway analysis (IPA) was applied to analyse the interaction networks of the differentially expressed serum metabolites. First, we found that the composition of the gut microbiota was different between rats with CCI-induced neuropathic pain and sham controls. At the genus level, the abundances of Helicobacter, Phascolarctobacterium, Christensenella, Blautia, Streptococcus, Rothia and Lactobacillus were significantly increased, whereas the abundances of Ignatzschineria, Butyricimonas, Escherichia, AF12, and Corynebacterium were significantly decreased. Additionally, 72 significantly differentially expressed serum metabolites and 17 significantly differentially expressed spinal cord metabolites were identified between the CCI rats and the sham rats. Finally, correlation analysis showed that changes in the gut microbiota was significantly correlated with changes in serum metabolite levels, suggesting that dysbiosis of the gut microbiota is an important factor in modulating metabolic disturbances in the context of neuropathic pain. In conclusion, our research provides a novel perspective on the potential roles of the gut microbiota and related metabolites in neuropathic pain.

Qu-Zhuo-Tong-Bi Decoction Alleviates Gouty Arthritis by Regulating Butyrate-Producing Bacteria in Mice

Qu-zhuo-tong-bi decoction (QZTBD) is a traditional Chinese medicine prescription used to treat hyperuricemia and gout with no obvious adverse effects. However, the mechanism by which QZTBD treats gout has not been fully explored. Here, we investigated the effects of QZTBD on gouty arthritis and its therapeutic mechanism from the perspective of the gut microbiome. Our results demonstrated that QZTBD was effective for reducing serum uric acid level and attenuating paw edema and mechanical allodynia. QZTBD promoted the abundance of butyrate-producing bacteria and the production of SCFAs. Further study revealed that QZTBD restored the intestinal barrier function, modulated the expression of GPR43 and ABCG2, suppressed the activity of key glycolysis-related enzymes, and inhibited the generation of intestinal inflammatory factors. These findings suggested that QZTBD is an effective therapeutic drug for gouty arthritis. Butyrate-producing bacteria and its metabolites SCFAs might act as a potential target of QZTBD.

A Traditional Clinic Chinese Medicine Prescription Qu-Zhuo-Tong-Bi (QZTB) Alleviates Gouty Arthritis in Model Rats

Qu-Zhuo-Tong-Bi (QZTB) is an empirical traditional Chinese medicine prescription for treating acute gouty arthritis clinically without serious adverse effects in mainland China. However, the biochemical mechanism underlying the therapeutic action produced by QZTB treatment against acute gouty arthritis and the effect on recurrent attack remain unknown. In this study, we investigated the anti-inflammatory and analgesic effects of QZTB on acute gouty arthritis and the recurrent attack in rats, as well as the underlying mechanisms. The gouty arthritis model was established by intra-articular injection of monosodium urate (MSU) crystal suspension (2 mg/50 μL) into the right ankle joint of Sprague Dawley (SD) male rats. QZTB (500 mg/kg) and the positive control drug meloxicam were administrated by gavages twice a day for 7 days before, or 3 days after, first MSU injection in different experiments, respectively. The analgesic effects were evaluated by pain-like behaviors and hind paw mechanical withdrawal threshold testing. The anti-inflammatory activities were evaluated by ankle swelling measurement, histologic examination, NLRP3 inflammasome, and inflammatory cytokine expression. Western blot and quantitative real-time PCR were used to detect the protein and mRNA expressions of NLRP3. IL-1β and TNF-α level in the blood serum were detected by enzyme-linked immunosorbent assay (ELISA). QZTB can suppress ankle swelling and synovial inflammation in the MSU-induced gouty arthritis rat model. QZTB alleviated the acute attack and prevented the recurrent attack of gouty arthritis. In addition, QZTB treatment significantly decreased both mRNA and protein levels of NLRP3, as well as the production of IL-1 and TNF-α in the ankle joint of model rats. Taken together, these results suggest that QZTB may be a promising herbal formula for the prevention and treatment of gouty arthritis in humans.

Histaminergic transmission slows progression of amyotrophic lateral sclerosis

BACKGROUND

Histamine is an immune modulator, neuroprotective, and remyelinating agent, beneficially acting on skeletal muscles and promoting anti-inflammatory features in amyotrophic lateral sclerosis (ALS) microglia. Drugs potentiating the endogenous release of histamine are in trial for neurological diseases, with a role not systematically investigated in ALS. Here, we examine histamine pathway associations in ALS patients and the efficacy of a histamine-mediated therapeutic strategy in ALS mice.

METHODS

We adopted an integrative multi-omics approach combining gene expression profiles, copy number variants, and single nucleotide polymorphisms of ALS patients. We treated superoxide dismutase 1 (SOD1)-G93A mice that recapitulate key ALS features, with the brain-permeable histamine precursor histidine in the symptomatic phase of the disease and analysed the rescue from disease pathological signs. We examined the action of histamine in cultured SOD1-G93A motor neuron-like cells.

RESULTS

We identified 13 histamine-related genes deregulated in the spinal cord of two ALS patient subgroups, among which genes involved in histamine metabolism, receptors, transport, and secretion. Some histamine-related genes overlapped with genomic regions disrupted by DNA copy number and with ALS-linked pathogenic variants. Histidine treatment in SOD1-G93A mice proved broad efficacy in ameliorating ALS features, among which most importantly lifespan, motor performance, microgliosis, muscle atrophy, and motor neurons survival in vivo and in vitro.

CONCLUSIONS

Our gene set/pathway enrichment analyses and preclinical studies started at the onset of symptoms establish that histamine-related genes are modifiers in ALS, supporting their role as candidate biomarkers and therapeutic targets. We disclose a novel important role for histamine in the characterization of the multi-gene network responsible for ALS and, furthermore, in the drug development process.

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

ALS currently remains a challenge despite many efforts in performing successful clinical trials and formulating therapeutic solutions. By learning from current failures and striving for success, scientists and clinicians are checking every possibility to search for missing hints and efficacious treatments. Because the disease is very complex and heterogeneous and, moreover, targeting not only motor neurons but also several different cell types including muscle, glial, and immune cells, the right answer to ALS is conceivably a multidrug strategy or the use of broad-spectrum molecules. The aim of the present work is to gather evidence about novel perspectives on ALS pathogenesis and to present recent and innovative paradigms for therapy. In particular, we describe how an old molecule possessing immunomodulatory and neuroprotective functions beyond its recognized effects on allergy, histamine, might have a renewed and far-reaching momentum in ALS.

Microinjection of histamine and its H3 receptor agonist and antagonist into the agranular insular cortex influence sensory and affective components of neuropathic pain in rats

Many areas of the brain along with neurotransmitters involve in processing of nociceptive, emotional and cognitive dimensions of neuropathic pain. Brian neuronal histamine through H₁, H₂, H₃ and H₄ receptors mediates many physiological functions such as cognition, emotion and pain. In the present study we investigated the effects of intra-agranular insular cortex microinjection of histamine and its H₃ receptor agonist and antagonist on sensory and affective aspects of neuropathic pain. Spared nerve injury model of neuropathic pain was used. Two guide cannulas were surgically implanted in the right and left sides of agranular insular cortex. Sensory component (mechanical hyperalgesia) was recorded by application of von Frey filaments onto the plantar surface of the hind paw. Area under curve of mechanical hyperalgesia was calculated. Affective aspect (place escape avoidance paradigm) was recorded using an inverse white/black chamber. Histamine (0.5, 1 and 2 μg/site) and thioperamide (a histamine H₃ receptor antagonist, 4 μg/site) decreased, whereas immepip (a histamine H₃ receptor agonist, 2 μg/site) increased the percentages of paw withdrawal frequency and time spent in white side of white/black box. Prior administration of thioperamide (4 μg/site) increased the suppressive effects induced by histamine and inhibited immepip (2 μg/site)-induced hyperalgesia and aversion. Based on the present results, it is concluded that histamine and its H₃ receptor at the agranular insular cortex level may involve in modulation of sensory and affective components of neuropathic pain.

Histamine, histamine receptors, and neuropathic pain relief

Histamine, acting via distinct histamine H₁, H₂, H₃, and H₄ receptors, regulates various physiological and pathological processes, including pain. In the last two decades, there has been a particular increase in evidence to support the involvement of H₃ receptor and H₄ receptor in the modulation of neuropathic pain, which remains challenging in terms of management. However, recent data show contrasting effects on neuropathic pain due to multiple factors that determine the pharmacological responses of histamine receptors and their underlying signal transduction properties (e.g., localization on either the presynaptic or postsynaptic neuronal membranes). This review summarizes the most recent findings on the role of histamine and the effects mediated by the four histamine receptors in response to the various stimuli associated with and promoting neuropathic pain. We particularly focus on mechanisms underlying histamine‐mediated analgesia, as we aim to clarify the analgesic potential of histamine receptor ligands in neuropathic pain.

Linked Articles

This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc

Functional microglia neurotransmitters in amyotrophic lateral sclerosis

Today neuroscience is dominated by the perspective that microglia are essential elements in any integrated view of the nervous system. A number of different neuroinflammatory conditions affect the CNS where microglia involvement, and particularly microgliosis, is not only a prominent feature, but also a pathogenic key mechanism of disease. On the other side, microglia can also constitute an important trigger of neuronal protection during neurodegenerative disorders. For instance in ALS and other motor neuron diseases, available evidence suggests the coexistence of quite different roles for microglia, characterized by neuroprotective functions at early stages, and neurotoxic actions during disease progression. The scope of this review is a brief discussion about microglia being activated and functioning during ALS, and particularly about neurotransmitters participating to the pathological signature of ALS microglia. We will discuss that ALS microglia can express a variety of classical neurotransmitter receptors comprising those for extracellular ATP, glutamate and histamine. We will review data indicating that the modulation of these transmitter receptors may induce beneficial effects in ALS models, so that the protective properties of microglia can be emphasized at the expenses of their toxicity.

Monoamines as Drug Targets in Chronic Pain: Focusing on Neuropathic Pain

Monoamines are involved in regulating the endogenous pain system and indeed, peripheral and central monoaminergic dysfunction has been demonstrated in certain types of pain, particularly in neuropathic pain. Accordingly, drugs that modulate the monaminergic system and that were originally designed to treat depression are now considered to be first line treatments for certain types of neuropathic pain (e.g., serotonin and noradrenaline (and also dopamine) reuptake inhibitors). The analgesia induced by these drugs seems to be mediated by inhibiting the reuptake of these monoamines, thereby reinforcing the descending inhibitory pain pathways. Hence, it is of particular interest to study the monoaminergic mechanisms involved in the development and maintenance of chronic pain. Other analgesic drugs may also be used in combination with monoamines to facilitate descending pain inhibition (e.g., gabapentinoids and opioids) and such combinations are often also used to alleviate certain types of chronic pain. By contrast, while NSAIDs are thought to influence the monoaminergic system, they just produce consistent analgesia in inflammatory pain. Thus, in this review we will provide preclinical and clinical evidence of the role of monoamines in the modulation of chronic pain, reviewing how this system is implicated in the analgesic mechanism of action of antidepressants, gabapentinoids, atypical opioids, NSAIDs and histaminergic drugs.

Conditioned Medium of Bone Marrow-Derived Mesenchymal Stromal Cells as a Therapeutic Approach to Neuropathic Pain: A Preclinical Evaluation

Neuropathic pain is a type of chronic pain caused by injury or dysfunction of the nervous system, without effective therapeutic approaches. Mesenchymal stromal cells (MSCs), through their paracrine action, have great potential in the treatment of this syndrome. In the present study, the therapeutic potential of MSC-derived conditioned medium (CM) was investigated in a mouse model of neuropathic pain induced by partial sciatic nerve ligation (PSL). PSL mice were treated by endovenous route with bone marrow-derived MSCs (1 × 10⁶), CM, or vehicle. Gabapentin was the reference drug. Twelve hours after administration, neuropathic mice treated with CM exhibited an antinociceptive effect that was maintained throughout the evaluation period. MSCs also induced nonreversed antinociception, while gabapentin induced short-lasting antinociception. The levels of IL-1β, TNF-α, and IL-6 were reduced, while IL-10 was enhanced on sciatic nerve and spinal cord by treatment with CM and MSCs. Preliminary analysis of the CM secretome revealed the presence of growth factors and cytokines likely involved in the antinociception. In conclusion, the CM, similar to injection of live cells, produces a powerful and long-lasting antinociceptive effect on neuropathic pain, which is related with modulatory properties on peripheral and central levels of cytokines involved with the maintenance of this syndrome.

Histamine Regulates the Inflammatory Profile of SOD1-G93A Microglia and the Histaminergic System Is Dysregulated in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a late-onset motor neuron disease where activated glia release pro-inflammatory cytokines that trigger a vicious cycle of neurodegeneration in the absence of resolution of inflammation. Given the well-established role of histamine as a neuron-to-glia alarm signal implicated in brain disorders, the aim of this study was to investigate the expression and regulation of the histaminergic pathway in microglial activation in ALS mouse model and in humans. By examining the contribution of the histaminergic system to ALS, we found that particularly via H1 and H4 receptors, histamine promoted an anti-inflammatory profile in microglia from SOD1-G93A mice by modulating their activation state. A decrease in NF-κB and NADPH oxidase 2 with an increase in arginase 1 and P2Y12 receptor was induced by histamine only in the ALS inflammatory environment, but not in the healthy microglia, together with an increase in IL-6, IL-10, CD163, and CD206 phenotypic markers in SOD1-G93A cells. Moreover, histaminergic H1, H2, H3, and H4 receptors, and histamine metabolizing enzymes histidine decarboxylase, histamine N-methyltransferase, and diamine oxidase were found deregulated in spinal cord, cortex, and hypothalamus of SOD1-G93A mice during disease progression. Finally, by performing a meta-analysis study, we found a modulated expression of histamine-related genes in cortex and spinal cord from sporadic ALS patients. Our findings disclose that histamine acts as anti-inflammatory agent in ALS microglia and suggest a dysregulation of the histaminergic signaling in ALS.