The Histamine H4 Receptor Participates in the Neuropathic Pain-Relieving Activity of the Histamine H3 Receptor Antagonist GSK189254.

Growing evidence points to the histamine system as a promising target for the management of neuropathic pain. Preclinical studies reported the efficacy of H3R antagonists in reducing pain hypersensitivity in models of neuropathic pain through an increase of histamine release within the CNS. Recently, a promising efficacy of H4R agonists as anti-neuropathic agents has been postulated. Since H3R and H4R are both localized in neuronal areas devoted to pain processing, the aim of the study is to investigate the role of H4R in the mechanism of anti-hyperalgesic action of the H3R antagonist GSK189254 in the spared nerve injury (SNI) model in mice. Oral (6 mg/kg), intrathecal (6 µg/mouse), or intra locus coeruleus (LC) (10 µg/µL) administration of GSK189254 reversed mechanical and thermal allodynia in the ipsilateral side of SNI mice. This effect was completely prevented by pretreatment with the H4R antagonist JNJ 10191584 (6 µg/mouse i.t.; (10 µg/µL intraLC). Furthermore, GSK189254 was devoid of any anti-hyperalgesic effect in H4R deficient mice, compared with wild type mice. Conversely, pretreatment with JNJ 10191584 was not able to prevent the hypophagic activity of GSK189254. In conclusion, we demonstrated the selective contribution of H4R to the H3R antagonist-induced attenuation of hypernociceptive behavior in SNI mice. These results might help identify innovative therapeutic interventions for neuropathic pain.

The Interplay between Histamine H4 Receptor and the Kidney Function: The Lesson from H4 Receptor Knockout Mice.

Previous studies implicated the histamine H4 receptor in renal pathophysiology. The aim here is to elucidate the role of this receptor on renal function using H4 receptor knockout mice (H4R-/-). Healthy and diabetic H4R-/- mice compared to their C57BL/6J wild-type counterpart for renal function and the expression of crucial tubular proteins. H4R-/- and wild-type mice, matched for ages, showed comparable weight gain curves reaching similar median weight at the end of the study. However, H4R-/- mice displayed a higher basal glycemia. H4R-/- mice showed a lower urine 24 h outflow, and albumin-to-creatinine ratio (ACR) compared to wild-type mice. Consistently, H4R-/- mice presented a higher expression of megalin and a lower basal expression of the sodium-hydrogen exchanger (NHE)3 and aquaporin (AQP)2. According to these basal differences, diabetic H4R-/- mice developed more severe hyperglycemia and a higher 24 h urine volume, but a lower increase in ACR and decrease in urine pH were observed. These events were paralleled by a reduced NHE3 over-expression and megalin loss in diabetic H4R-/- mice. The AQP1 and AQP7 patterns were also different between H4R-/- and wild-type diabetic mice. The collected results highlight the role of the histamine H4 receptor in the control of renal reabsorption processes, particularly albumin uptake.

Effects of PARP-1 Deficiency and Histamine H4 Receptor Inhibition in an Inflammatory Model of Lung Fibrosis in Mice.

Pulmonary fibrosis is the most frequent form of interstitial lung disease. Effective therapies are not yet available; novel therapeutic approaches are needed for counteracting fibrosis. Poly(ADP-ribose) polymerases are enzymes, involved in DNA repair and cell apoptosis. PARP-1 deficient mice exhibited reduced lung fibrosis in response to bleomycin treatment compared to wild-type controls. Histamine H4 receptors (H4Rs) have been recognized as a new target for inflammatory and immune diseases, and H4R ligands reduced inflammation and oxidative stress in lung tissue. The aim of the study was to evaluate the cross-talk between PARP-1 and H4R in a model of bleomycin-induced lung fibrosis in PARP-1-/- and WT mice. Animals were treated with bleomycin or saline by intra-tracheal injection. JNJ7777120, an H4R antagonist, or VUF8430, an H4R agonist, were administered i.p for 21 days. Airway resistance to inflation was evaluated, and lung tissues were processed for PARylated protein content, oxidative stress evaluation, and histology of small bronchi. The levels of pro-inflammatory (IL-1ß and TNF-α), regulatory (IL-10), and pro-fibrotic (TGF-ß) cytokines were evaluated. The deposition of αSMA was determined by immunofluorescence analysis. The results indicate that JNJ7777120 reduces PARylated protein production, decreases oxidative stress damage, and MPO, a marker for leukocyte tissue infiltration, in PARP-1-/- mice. A significant decrease in the production of both IL-1ß and TNF-α and a significant increase in IL-10 levels are observed in mice treated with H4R antagonist, suggesting a crucial anti-inflammatory activity of JNJ7777120. The smooth muscle layer thickness, the goblet cell relative number, and collagen deposition decreased following JNJ7777120 administration. The H4R antagonist treatment also reduces TGF-ß production and αSMA deposition, suggesting an important role of JNJ7777120 in airway remodeling. Our results show that PARylation is essential for the pathogenesis of pulmonary fibrosis and propose that PARP-1 and H4Rs are both involved in inflammatory and fibrotic responses. JNJ7777120 treatment, in a condition of PARP-1 inhibition, exerts anti-inflammatory and anti-fibrotic effects, reducing airway remodeling and bronchoconstriction. Therefore, selective inhibition of H4Rs together with non-toxic doses of selective PARP-1 inhibitors could have clinical relevance for the treatment of idiopathic pulmonary fibrosis.

Histamine H4 receptor gene polymorphisms: a potential contributor to Meniere disease.

BACKGROUND: The immune system is likely involved in the pathophysiology of Meniere's disease (MD). However, its role of patients with MD has not been well studied. Given that histamine H4 receptors are highly expressed in immune system, we tested the hypothesis that histamine H4 receptor gene polymorphisms are a potential contributor to the risk of MD. METHODS: A group of patients was enrolled with a diagnosis of definite MD based on the American Academy of Otolaryngology-Head and Neck Surgery Committee on Hearing and Equilibrium guidelines and a control group of patients without any vestibular disease. We selected one SNP, rs77485247 in HRH4 and conducted an exploratory investigation of its correlations with the symptoms of vertigo and proinflammatory cytokines levels in MD patients. RESULTS: HRH4 rs77485247 polymorphism may be associated with the risk of MD. Furthermore, basal levels of proinflammatory cytokines, such as IL-1ß and TNF-α, in PBMCs are increased in patients with MD compared to control patients. This increased basal level of proinflammatory cytokines is prominent in MD patients with the A allele. CONCLUSIONS: These suggested that HRH4 rs77485247 polymorphism may be an important mediator in regulating proinflammatory cytokines, which are involved in the pathogenesis of MD.

Alkyl derivatives of 1,3,5-triazine as histamine H4 receptor ligands.

This study focuses on the design, synthesis, molecular modeling and biological evaluation of a novel group of alkyl-1,3,5-triazinyl-methylpiperazines. New compounds were synthesized and their affinities for human histamine H4 receptor (hH4R) were evaluated. Among them, 4-(cyclohexylmethyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (14) exhibited hH4R affinity with a Ki of 160 nM and behaved as antagonist in functional assays: the cellular aequorin-based assay (IC50 = 32 nM) and [35S]GTPγS binding assay (pKb = 6.67). In addition, antinociceptive activity of 14in vivo was observed in Formalin test (in mice) and in Carrageenan-induced acute inflammation test (in rats).

Differential effects of functionally different histamine H4 receptor ligands on acute irritant dermatitis in mice.

The anti-inflammatory effects of histamine H4 receptor (H4R) antagonists opened new therapeutic options for the treatment of inflammatory/allergic diseases, but the role of H4R in inflammation is far from being solved. Aim of the present study was to investigate the role of structurally related H4R ligands of the aminopyrimidine class with different efficacies and functionalities (neutral antagonist ST-994, partial agonist ST-1006, inverse agonist ST-1012, and partial inverse agonist ST-1124) on croton oil-induced ear edema and pruritus in mice. The H4R ligands were administered subcutaneously before topical application of croton oil. While ST-1006 and ST-1124 were ineffective at any dose tested (10-100 mg/kg), both ST-994 and ST-1012 (30 and 100 mg/kg) significantly reduced croton oil-induced ear edema. Moreover, ST-994, ST-1006, and ST-1124, but not ST-1012, significantly inhibited croton oil-induced ear pruritus at 30 mg/kg. In accordance with results obtained with the reference H4R antagonist JNJ7777120 (100 mg/kg), histological examination of inflamed ear tissue indicated that treatment with ST-994 (30 mg/kg) led to a significant reduction in the inflammatory severity score and in the number of eosinophils infiltrating the tissue, while the number of degranulated mast cells in inflamed tissues was increased in comparison with the number of intact mast cells. These data indicate that croton oil-induced ear inflammation and pruritus seem to be clearly, but variably, affected by the H4R ligands tested. The potential advantage of dual effect of the H4R neutral antagonist ST-994 has to be carefully considered as a new therapeutic approach to the treatment of inflammatory diseases.

The HRH4 rs11662595 mutation is associated with histamine H4 receptor dysfunction and with increased epithelial-to-mesenchymal transition progress in non-small cell lung cancer.

We previously demonstrated that histamine H4 receptor (HRH4) played important roles to suppress epithelial-to-mesenchymal transition (EMT) progress in non-small cell lung cancer (NSCLC). Furthermore, recent investigations suggested that genetic variations in HRH4 gene affected HRH4 function and eventually contributed to certain HRH4-related diseases. However, the relations between polymorphisms in HRH4 gene and NSCLC as well as their underlying mechanisms remain largely uninvestigated. This study aims to investigate the genetic effect of a nonsynonymous HRH4 polymorphism (rs11662595) on HRH4 function and its association with NSCLC both basically and clinically. For basic experiments, A549 cells were transfected with either wild type or rs11662595 mutated HRH4 clone and subjected to both in vitro and in vivo experiments. We showed that rs11662595 significantly decreased the ability of HRH4 to activate Gi protein, which resulted in facilitation of EMT progress, cell proliferation, and invasion behavior in vitro. Moreover, in vivo experiments also showed that rs11662595 attenuated the anti-EMT effects of HRH4 agonist in inoculated nu/nu mice. For clinical experiments, we performed a prospective cohort study among 624 NSCLC patients and further proved that rs11662595 was responsible for the prognosis, degree of malignancy and metastasis of NSCLC. In conclusion, these findings reveal that rs11662595 is a loss-of-function polymorphism that results in dysfunction of HRH4 and attenuates the anti-EMT function of HRH4 in NSCLC, which provides a promising biomarker for prognosis and therapy of NSCLC.

Behavioural phenotype of histamine H4 receptor knockout mice: Focus on central neuronal functions.

The functional expression of H4 receptors (H4R) within neurons of the central nervous system has been recently reported, but their role is poorly understood. The present study aims to elucidate the role of neuronal H4R by providing the first description of the behavioural phenotype of H4R-deficient (H4R knockout, H4R-KO) mice. Mice lacking H4R underwent behavioural studies to evaluate locomotor activity, pain perception, anxiety, depression, memory and feeding behaviour. H4R-KO mice showed a significant increase in ambulation in an open field as well as in exploratory activity in the absence of any modification of motor coordination. The sensitivity of mutant mice to a thermal or a mechanical stimulus was identical to that of the wild type mice, but H4R-KO showed sensory hypersensitivity toward a condition of neuropathic pain. The lack of H4R is associated with the promotion of anxiety in the light-dark box test. H4R-KO mice showed an increased immobility time in the tail suspension test, experimental procedure used to evaluate the response of H4R deficient mice to a behavioural despair paradigm. Cognitive function parameters of H4R deficient mice, examined using the passive avoidance and the novel object recognition tests, were unaltered showing the lack of influence of H4R on working and recognition memory. Finally, H4R-deficient mice showed an orectic phenotype. These results illustrate that H4R modulates various neurophysiological functions such as locomotor activity, anxiety, nociception and feeding behaviour, confirming the importance of the integrity and functionality of neuronal H4R in the histaminergic regulation of neuronal functions.

Role of histamine H4 receptor ligands in bleomycin-induced pulmonary fibrosis.

Fibrosis of lung tissue is a disease where a chronic inflammatory process determines a pathological remodelling of lung parenchyma. The animal model obtained by intra-tracheal administration of bleomycin in C57BL/6 mice is one of the most validated murine model. Bleomycin stimulates oxidative stress and the production of pro-inflammatory mediators. Histamine H4R have recently been implicated in inflammation and immune diseases. This study was focused to investigate the effects of H4R ligands in the modulation of inflammation and in the reduction of lung fibrosis in C57BL/6 mice treated with bleomycin. C57BL/6 mice were treated with vehicle, JNJ7777120 (JNJ, selective H4R antagonist) or ST-1006 (partial H4R agonist), ST-994 (H4R neutral antagonist) and ST-1012 (inverse H4R agonist) at equimolar doses, released by micro-osmotic pumps for 21days. Airway resistance to inflation was assayed and lung samples were processed to measure malondialdehyde (TBARS); 8-hydroxy-2'-deoxyguanosine (8OHdG); myeloperoxidase (MPO); COX-2 expression and activity as markers of oxidative stress and inflammation. Fibrosis and airway remodelling were evaluated throughout transforming growth factor-ß (TGF-ß), percentage of positive Goblet cells, smooth muscle layer thickness determination. Our results indicated that JNJ, ST-994 and ST-1012 decreased inflammation and oxidative stress markers, i.e. the number of infiltrating leukocytes evaluated as lung tissue MPO, COX-2 expression and activity, TBARS and 8OHdG production. They also reduced the level of TGF-ß, a pro-fibrotic cytokine, collagen deposition, thickness of smooth muscle layer, Goblet cells hyperplasia; resulting in a decrease of airway functional impairment. The results here reported clearly demonstrated that H4R ligands have a beneficial effect in a model of lung fibrosis in the mouse, thus indicating that H4R antagonists or inverse agonists could be a novel therapeutic strategy for lung inflammatory diseases.

Activation of histamine H4 receptors decreases epithelial-to-mesenchymal transition progress by inhibiting transforming growth factor-ß1 signalling pathway in non-small cell lung cancer.

Previous investigations found that epithelial-to-mesenchymal transition (EMT) was an important character of non-small cell lung cancer (NSCLC) and it was also suggested that histamine H4 receptors may have a role in preventing EMT progress in certain kind of tumours. However, the effect of H4 receptor activation on EMT progress of NSCLC and its potential mechanisms remain unclear. Therefore, we performed both in vitro and in vivo experiments to explore the effects of specific H4 receptor agonist 4-methylhistamine and antagonist JNJ7777120 on EMT progress. We showed the expression of H4 receptors in NSCLC and found that 4-methylhistamine increased the expression of the epithelial marker E-cadherin and decreased the expression of Vimentin, the mesenchymal marker, in both NSCLC cell lines and xenograft NSCLC tumours. Pretreatment with JNJ7777120 or H4 receptor gene silencing decreased while overexpression of H4 receptors facilitated this effect of 4-methylhistamine. Furthermore, we showed that down-regulation of cyclic adenosine monophosphate (cAMP) was the secondary signalling after H4 receptor activation, which in turn resulted in inactivation of transforming growth factor-ß1 (TGF-ß1) pathway and down-regulation of several important EMT inducing factors such as ZEB1, Snail and Slug. In conclusion, these findings revealed the anti-EMT effect of histamine H4 receptor activation in NSCLC, which provide novel insight into the development mechanism of NSCLC; and H4 receptors may be a new therapeutic target for NSCLC treatment.

A selective antagonist of histamine H4 receptors prevents antigen-induced airway inflammation and bronchoconstriction in guinea pigs: involvement of lipocortin-1.

BACKGROUND AND PURPOSE: Among the pathogenic mechanisms of asthma, a role for oxidative/nitrosative stress has been well documented. Recent evidence suggests that histamine H4 receptors play a modulatory role in allergic inflammation. Here we report the effects of compound JNJ 7777120 (JNJ), a selective H4 receptor antagonist, on antigen-induced airway inflammation, paying special attention to its effects on lipocortin-1 (LC-1/annexin-A1), a 37 kDA anti-inflammatory protein that plays a key role in the production of inflammatory mediators. EXPERIMENTAL APPROACH: Ovalbumin (OA)-sensitized guinea pigs placed in a respiratory chamber were challenged with antigen. JNJ (5, 7.5 and 10 mg.kg⁻¹) was given i.p. for 4 days before antigen challenge. Respiratory parameters were recorded. Bronchoalveolar lavage (BAL) fluid was collected and lung specimens taken for further analyses 1 h after antigen challenge. In BAL fluid, levels of LC-1, PGD2 , LTB4 and TNF-α were measured. In lung tissue samples, myeloperoxidase, caspase-3 and Mn-superoxide dismutase activities and 8-hydroxy-2-deoxyguanosine levels were measured. KEY RESULTS: OA challenge decreased LC-1 levels in BAL fluid, induced cough, dyspnoea and bronchoconstriction and increased PGD2 , LTB4 and TNF-α levels in lung tissue. Treatment with JNJ dose-dependently increased levels of LC-1, reduced respiratory abnormalities and lowered levels of PGD2 , LTB4 and TNF-α in BAL fluid. CONCLUSIONS AND IMPLICATIONS: Antigen-induced asthma-like reactions in guinea pigs decreased levels of LC-1 and increased TNF-α and eicosanoid production. JNJ pretreatment reduced allergic asthmatic responses and airway inflammation, an effect associated with LC-1 up-regulation.