A novel bronchial ring bioassay for the evaluation of small airway smooth muscle function in mice

Investigation of antinociceptive, antipyretic, antiasthmatic, and spasmolytic activities of Brazilian Cannabis sativa L. roots in rodents

ETHNOPHARMACOLOGICAL RELEVANCE

Many studies are performed with the aerial parts of Cannabis sativa L. (Cannabaceae). However, roots remain poorly studied, despite citations in the scientific literature. The C. sativa roots are indicated for the treatment of pain, inflammation, fever, among other health problems.

AIM OF THE STUDY

This study aimed to evaluate the antinociceptive, antipyretic, antiasthmatic, and spasmolytic activities of C. sativa roots in experimental models using mice and rats.

MATERIAL AND METHODS

The chemical composition of the aqueous extract of C. sativa roots (AECsR) was evaluated by LC-MS. The antinociceptive activity was assessed in mice by the induction of writhing with acetic acid, paw licking with formalin, and reactivity in the hot plate test. Fever was induced by the administration of a suspension of Saccharomyces cerevisiae in young rats. The asthmatic activity was performed with ovalbumin (OVA)-immunized mice with cellular and histological analysis. Finally, the spasmolytic activity was performed using mice isolated trachea. For in vivo studies, the doses were 12.5, 25, or 50 mg/kg whereas for in vitro, the concentration of AECsR was 729 μg/mL.

RESULTS

From the LC-MS data, we identified p-coumaroyltyramine, feruloyltyramine canabissativine in AECsR. The extract promoted a reduction of writhing in all tested doses (12.5, 25, or 50 mg/kg). Similarly, it reduced the pain in the formalin test at doses of 12.5 and 50 mg/kg (first phase) and 12.5 and 25 mg/kg (second phase). In the hot plate test, the doses of 12.5, 25, and 50 mg/kg promoted antinociceptive effect at different times, and the lowest dose maintained its action in the analyzes performed at 60, 90, and 120 min after administration. The anti-inflammatory activity of AECsR was observed in the mouse model of asthma, reducing the total leukocyte count in the bronchoalveolar fluid (BALF) at a dose of 25 mg/kg, as well as reducing eosinophilia in all tested doses (12.5, 25, and 50 mg/kg). Histological analysis of lungs stained with H&E and PAS showed a reduction in the number of inflammatory cells in the perivascular and peribronchial region, as well as reduced mucus production.

CONCLUSION

The results suggest that AECsR promotes pain control, either by a central or inflammatory mechanism, and has antiasthmatic activity. However, there was no antipyretic or spasmolytic effect.

Small-Airway Dysfunction is Involved in the Pathogenesis of Asthma: Evidence from Two Mouse Models

Background

There has been growing evidence of small-airway dysfunction in patients with asthma. Few studies have evaluated the mechanism of small-airway dysfunction in mouse models of asthma.

Purpose

We explored the correlation between small-airway spirometric variables and large-airway function or inflammation in different endotypes of asthma.

Methods

Ovalbumin (OVA) sensitization/challenge was used to produce a type 2 (T2)-high asthma model, and OVA combined with ozone exposure (OVA + ozone) was used for the T2-low asthma model with increased neutrophils. Spirometry, airway responsiveness, cytokine levels in bronchoalveolar lavage fluid (BALF), and pathological analyses of lung slices stained with hematoxylin-eosin, periodic acid–Schiff, and Masson’s trichrome stain were all determined. Muc5ac expression in lung tissue was evaluated by the reverse transcription-polymerase chain reaction (RT-PCR), and alpha-smooth muscle actin was measured by immunohistochemistry.

Results

Inflammatory cells infiltrated the lung tissue and inflammatory cytokines were increased in the BALF of both the OVA and OVA + ozone groups, compared with the control group. Peribronchial hypersecretion and collagen deposition were evident in the models. The OVA + ozone group showed greater neutrophilic infiltration and peribronchial smooth muscle proliferation than the OVA group. Large-airway obstruction, small-airway dysfunction, and airway hyperresponsiveness were confirmed in both models. Small-airway functional variables, such as MMEF (mean midexpiratory flow, average flow from 25 to 75% forced vital capacity [FVC]) and FEF50 (forced expiratory flow at 50% of FVC), were positively correlated with large-airway function and had a stronger negative correlation with airway inflammation, mucus secretion, and responsiveness than large-airway function.

Conclusion

Small-airway dysfunction was evident in the two endotypes of asthma and was correlated with severe airway inflammation, mucus hypersecretion, and airway hyperresponsiveness. The small airways may be an important target in asthma treatment, and further research in the role of small-airway variables in the pathogenesis of asthma is warranted.

Effect of VX‑765 on the transcriptome profile of mice spinal cords with acute injury

Previous studies have shown that caspase-1 plays an important role in the acute inflammatory response of spinal cord injury (SCI). VX‑765, a novel and irreversible caspase‑1 inhibitor, has been reported to effectively intervene in inflammation. However, the effect of VX‑765 on genome‑wide transcription in acutely injured spinal cords remains unknown. Therefore, in the present study, RNA‑sequencing (RNA‑Seq) was used to analyze the effect of VX‑765 on the local expression of gene transcription 8 h following injury. The differentially expressed genes (DEGs) underwent enrichment analysis of functions and pathways by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses, respectively. Parallel analysis of western blot confirmed that VX‑765 can effectively inhibit the expression and activation of caspase‑1. RNA‑Seq showed that VX‑765 treatment resulted in 1,137 upregulated and 1,762 downregulated DEGs. These downregulated DEGs and their associated signaling pathways, such as focal adhesion, cytokine‑cytokine receptor interaction, leukocyte transendothelial migration, extracellular matrix‑receptor interaction, phosphatidylinositol 3‑kinase‑protein kinase B, Rap1 and hypoxia inducible factor‑1 signaling pathway, are mainly associated with inflammatory response, local hypoxia, macrophage differentiation, adhesion migration and apoptosis of local cells. This suggests that the application of VX‑765 in the acute phase can improve the local microenvironment of SCI by inhibiting caspase‑1. However, whether VX‑765 can be used as a therapeutic drug for SCI requires further exploration. The sequence data have been deposited into the Sequence Read Archive (https://www.ncbi.nlm.nih.gov/sra/PRJNA548970).

Glucagon-Like Peptide 1 and Atrial Natriuretic Peptide in a Female Mouse Model of Obstructive Pulmonary Disease

Glucagon-like peptide-1 (GLP-1) is protective in lung disease models but the underlying mechanisms remain elusive. Because the hormone atrial natriuretic peptide (ANP) also has beneficial effects in lung disease, we hypothesized that GLP-1 effects may be mediated by ANP expression. To study this putative link, we used a mouse model of chronic obstructive pulmonary disease (COPD) and assessed lung function by unrestrained whole-body plethysmography. In 1 study, we investigated the role of endogenous GLP-1 by genetic GLP-1 receptor (GLP-1R) knockout (KO) and pharmaceutical blockade of the GLP-1R with the antagonist exendin-9 to -39 (EX-9). In another study the effects of exogenous GLP-1 were assessed. Lastly, we investigated the bronchodilatory properties of ANP and a GLP-1R agonist on isolated bronchial sections from healthy and COPD mice.

Lung function did not differ between mice receiving phosphate-buffered saline (PBS) and EX-9 or between GLP-1R KO mice and their wild-type littermates. The COPD mice receiving GLP-1R agonist improved pulmonary function (P < .01) with less inflammation, but no less emphysema compared to PBS-treated mice. Compared with the PBS-treated mice, treatment with GLP-1 agonist increased ANP (nppa) gene expression by 10-fold (P < .01) and decreased endothelin-1 (P < .01), a peptide associated with bronchoconstriction. ANP had moderate bronchodilatory effects in isolated bronchial sections and GLP-1R agonist also showed bronchodilatory properties but less than ANP. Responses to both peptides were significantly increased in COPD mice (P < .05, P < .01).

Taken together, our study suggests a link between GLP-1 and ANP in COPD.

Nociceptin/Orphanin Fq in inflammation and remodeling of the small airways in experimental model of airway hyperresponsiveness

It is widely recognized that airway inflammation and remodeling play a key role not only in the central airway but also small airway pathology during asthma. Nociceptin/Orphanin FQ (N/OFQ), an endogenous peptide, and its receptor N/OFQ peptide (NOP) are involved in airway hyperresponsiveness (AHR). We studied a murine model of AHR in order to understand the role of N/OFQ in the inflammation and remodeling of the small airways. Balb/c mice were sensitized to ovalbumin (OVA). At days 0 and 7 (pre-OVA sensitization) or from day 21 to 23 (post-OVA sensitization), the mice were treated intraperitoneally with N/OFQ or saline solution. After the last OVA challenge, all OVA-sensitized mice were aerosol-challenged with 1% OVA in PBS for 48 h, and then euthanized. Small airway compliance (sCaw ) was measured and lung samples were collected for histological and molecular evaluations such as perimeter and diameter of small airway, total wall area, airway smooth muscle (ASM) thickness and number of alveolar attachments. Both pre- and post-OVA sensitization N/OFQ treatments induced: (1) increases in sCaw ; (2) reduction of the bronchial wall thickness; (3) attenuation of the hyperplastic phase of airway smooth muscle mass; and (4) protection against loss of alveolar attachments compared with saline solution treatments. These results suggest that N/OFQ protects against inflammation, and mechanical damage and remodeling of small airways caused by OVA sensitization, suggesting a new potential therapeutic target for asthma.

Calcium-sensing receptor antagonists abrogate airway hyperresponsiveness and inflammation in allergic asthma

Airway hyperresponsiveness and inflammation are fundamental hallmarks of allergic asthma that are accompanied by increases in certain polycations, such as eosinophil cationic protein. Levels of these cations in body fluids correlate with asthma severity. We show that polycations and elevated extracellular calcium activate the human recombinant and native calcium-sensing receptor (CaSR), leading to intracellular calcium mobilization, cyclic adenosine monophosphate breakdown, and p38 mitogen-activated protein kinase phosphorylation in airway smooth muscle (ASM) cells. These effects can be prevented by CaSR antagonists, termed calcilytics. Moreover, asthmatic patients and allergen-sensitized mice expressed more CaSR in ASMs than did their healthy counterparts. Indeed, polycations induced hyperreactivity in mouse bronchi, and this effect was prevented by calcilytics and absent in mice with CaSR ablation from ASM. Calcilytics also reduced airway hyperresponsiveness and inflammation in allergen-sensitized mice in vivo. These data show that a functional CaSR is up-regulated in asthmatic ASM and targeted by locally produced polycations to induce hyperresponsiveness and inflammation. Thus, calcilytics may represent effective asthma therapeutics.

The cellular and molecular basis of bitter tastant-induced bronchodilation

Bitter tastants can activate bitter taste receptors on constricted smooth muscle cells to inhibit L-type calcium channels and induce bronchodilation.

Bronchodilators are a standard medicine for treating airway obstructive diseases, and β2 adrenergic receptor agonists have been the most commonly used bronchodilators since their discovery. Strikingly, activation of G-protein-coupled bitter taste receptors (TAS2Rs) in airway smooth muscle (ASM) causes a stronger bronchodilation in vitro and in vivo than β2 agonists, implying that new and better bronchodilators could be developed. A critical step towards realizing this potential is to understand the mechanisms underlying this bronchodilation, which remain ill-defined. An influential hypothesis argues that bitter tastants generate localized Ca²⁺ signals, as revealed in cultured ASM cells, to activate large-conductance Ca²⁺-activated K⁺ channels, which in turn hyperpolarize the membrane, leading to relaxation. Here we report that in mouse primary ASM cells bitter tastants neither evoke localized Ca²⁺ events nor alter spontaneous local Ca²⁺ transients. Interestingly, they increase global intracellular [Ca²⁺]_i, although to a much lower level than bronchoconstrictors. We show that these Ca²⁺ changes in cells at rest are mediated via activation of the canonical bitter taste signaling cascade (i.e., TAS2R-gustducin-phospholipase Cβ [PLCβ]- inositol 1,4,5-triphosphate receptor [IP3R]), and are not sufficient to impact airway contractility. But activation of TAS2Rs fully reverses the increase in [Ca²⁺]_i induced by bronchoconstrictors, and this lowering of the [Ca²⁺]_i is necessary for bitter tastant-induced ASM cell relaxation. We further show that bitter tastants inhibit L-type voltage-dependent Ca²⁺ channels (VDCCs), resulting in reversal in [Ca²⁺]_i, and this inhibition can be prevented by pertussis toxin and G-protein βγ subunit inhibitors, but not by the blockers of PLCβ and IP3R. Together, we suggest that TAS2R stimulation activates two opposing Ca²⁺ signaling pathways via Gβγ to increase [Ca²⁺]_i at rest while blocking activated L-type VDCCs to induce bronchodilation of contracted ASM. We propose that the large decrease in [Ca²⁺]_i caused by effective tastant bronchodilators provides an efficient cell-based screening method for identifying potent dilators from among the many thousands of available bitter tastants.

Bitter taste receptors (TAS2Rs), a G-protein-coupled receptor family long thought to be solely expressed in taste buds on the tongue, have recently been detected in airways. Bitter substances can activate TAS2Rs in airway smooth muscle to cause greater bronchodilation than β2 adrenergic receptor agonists, the most commonly used bronchodilators. However, the mechanisms underlying this bronchodilation remain elusive. Here we show that, in resting primary airway smooth muscle cells, bitter tastants activate a TAS2R-dependent signaling pathway that results in an increase in intracellular calcium levels, albeit to a level much lower than that produced by bronchoconstrictors. In bronchoconstricted cells, however, bitter tastants reverse the bronchoconstrictor-induced increase in calcium levels, which leads to the relaxation of smooth muscle cells. We find that this reversal is due to inhibition of L-type calcium channels. Our results suggest that under normal conditions, bitter tastants can activate TAS2Rs to modestly increase calcium levels, but that when smooth muscle cells are constricted, they can block L-type calcium channels to induce bronchodilation. We postulate that this novel mechanism could operate in other extraoral cells expressing TAS2Rs.

Influence of influenza A infection on capsaicin-induced responses in murine airways

The principal aim of the study was to determine the influence of influenza A virus infection on capsaicin-induced relaxation responses in mouse isolated tracheal segments and clarify the underlying mechanisms. Anesthetized mice were intranasally inoculated with influenza A/PR-8/34 virus (VIRUS) or vehicle (SHAM), and 4 days later tracheal segments were harvested for isometric tension recording and biochemical and histologic analyses. Capsaicin induced dose-dependent relaxation responses in carbachol-contracted SHAM trachea (e.g., 10 μM capsaicin produced 66 ± 4% relaxation; n = 11), which were significantly inhibited by capsazepine [transient receptor potential vanilloid type 1 (TRPV1) antagonist], (2S,3S)-3-{[3,5-bis(trifluoromethyl)phenyl]methoxy}-2-phenylpiperidine hydrochloride (L-733,060) [neurokinin 1 (NK₁) receptor antagonist], indomethacin [cyclooxygenase (COX) inhibitor], and the combination of 6-isopropoxy-9-oxoxanthene-2-carboxylic acid (AH6809) and 7-[5α-([1S,1α(Z)-biphenyl]-4-ylmethoxy)-2β-(4-morpholinyl)-3-oxocyclopentyl]-4-heptenoic acid, calcium salt, hydrate (AH23848) [E-prostanoid (EP)₂ and EP₄ receptor antagonists, respectively], indicating that capsaicin-induced relaxation involved the TRPV1-mediated release of substance P (SP), activation of epithelial NK₁ receptors, and production of COX products capable of activating relaxant EP₂/EP₄ receptors. Consistent with this postulate, capsaicin-induced relaxation was associated with the significant release of SP and prostaglandin E₂ (PGE₂) from mouse tracheal segments. As expected, influenza A virus infection was associated with widespread disruption of the tracheal epithelium. Tracheal segments from VIRUS mice responded weakly to capsaicin (7 ± 3% relaxation) and were 25-fold less responsive to SP than tracheas from SHAM mice. In contrast, relaxation responses to exogenous PGE₂ and the β-adrenoceptor agonist isoprenaline were not inhibited in VIRUS trachea. Virus infection was associated with impaired capsaicin-induced release of PGE₂, but the release of SP was not affected. In summary, influenza A virus infection profoundly inhibits capsaicin- and SP-induced relaxation responses, most likely by inhibiting the production of PGE₂.

Inhibition of p38 MAPK-dependent bronchial contraction after ozone by corticosteroids

We determined the role of p38 mitogen-activated protein kinase (MAPK) in the increased airway smooth muscle (ASM) contractile responses following ozone and modulation by corticosteroids. Mice were exposed to air or ozone (3 ppm for 3 h) and isometric contractile responses of bronchial rings to acetylcholine (ACh) were measured using a myograph in the presence of p38 MAPK inhibitor, SB239063 (10⁻⁶ M) or dexamethasone (10⁻⁶ M). Because MAPK phosphatase (MKP)-1 is a negative regulator of p38 MAPK, we also studied these effects in MKP-1(-/-) mice. Bronchial rings from ozone-exposed wild-type and MKP-1(-/-) mice showed increased contractile responses, with a leftward shift of the dose-response curve in MKP-1(-/-) mice. SB239063 inhibited bronchial contraction equally in air- and ozone-exposed C57/BL6 and MKP-1(-/-) mice. Dexamethasone inhibited ACh-induced bronchial contraction in both air- and ozone-exposed C57/BL6 mice, but not in air- or ozone-exposed MKP-1(-/-) mice. ACh-stimulated p38 MAPK and heat shock protein (HSP)27 phosphorylation, as measured by Western blotting, and this effect was suppressed by SB239063 in C57/BL6 and MKP-1(-/-) mice, but not by dexamethasone in either air- or ozone-exposed MKP-1(-/-) mice. p38 MAPK plays a role in maximal ACh-induced isometric contractile responses and increased contractility induced by ozone. Dexamethasone inhibits ACh-induced ASM contraction through phosphorylation of p38 MAPK and HSP27.

Myosin light chain kinase is necessary for tonic airway smooth muscle contraction

Different interacting signaling modules involving Ca(2+)/calmodulin-dependent myosin light chain kinase, Ca(2+)-independent regulatory light chain phosphorylation, myosin phosphatase inhibition, and actin filament-based proteins are proposed as specific cellular mechanisms involved in the regulation of smooth muscle contraction. However, the relative importance of specific modules is not well defined. By using tamoxifen-activated and smooth muscle-specific knock-out of myosin light chain kinase in mice, we analyzed its role in tonic airway smooth muscle contraction. Knock-out of the kinase in both tracheal and bronchial smooth muscle significantly reduced contraction and myosin phosphorylation responses to K(+)-depolarization and acetylcholine. Kinase-deficient mice lacked bronchial constrictions in normal and asthmatic airways, whereas the asthmatic inflammation response was not affected. These results indicate that myosin light chain kinase acts as a central participant in the contractile signaling module of tonic smooth muscle. Importantly, contractile airway smooth muscles are necessary for physiological and asthmatic airway resistance.

Severe asthma in adults: what are the important questions?

The term severe refractory asthma (SRA) in adults applies to patients who remain difficult to control despite extensive re-evaluation of diagnosis and management following an observational period of at least 6 months by a specialist. Factors that influence asthma control should be recognized and adequately addressed prior to confirming the diagnosis of SRA. This report presents statements according to the literature defining SRA in order address the important questions. Phenotyping SRA will improve our understanding of mechanisms, natural history, and prognosis. Female gender, obesity, and smoking are associated with SRA. Atopy is less frequent in SRA, but occupational sensitizers are common inducers of new-onset SRA. Viruses contribute to severe exacerbations and can persist in the airways for long periods. Inflammatory cells are in the airways of the majority of patients with SRA and persist despite steroid therapy. The T(H)2 immune process alone is inadequate to explain SRA. Reduced responsiveness to corticosteroids is common, and epithelial cell and smooth muscle abnormalities are found, contributing to airway narrowing. Large and small airway wall thickening is observed, but parenchymal abnormalities may influence airway limitation. Inhaled corticosteroids and bronchodilators are the mainstay of treatment, but patients with SRA remain uncontrolled, indicating a need for new therapies.