Chemical analysis of C. majus extract
C. majus extract was analyzed by UPLC-Q-Excutive (Fig. 1B). 19 compounds were identified under positive ion mode, including Magnocurarine, Magnoflorine, Chelamine, Protopine, Allocryptopine, Chelidonine, (S)-N-Methylstylopine, Tetrahydrocoptisine, Coptisine, Homochelidonine, Norchelidonine, Sanguinarine, Berberine, Chelerythrine, Chelilutine, Oxysanguinarine, 6-Methoxydihydrosanguinarine, Dihydrochelerythrine, Corysamine. Supplementary Table S1 showed the detailed information with retention time, molecular formula, MS fragment of these compounds.
Roles of C. majus exposure in OVA-mediated changes of body weight and relative lung weight in rats.
There was no obvious variation of initial body weight or relative lung weight among the rats of 6 groups. Compared to Control group rats, OVA challenge lead to an evident reduction (p < 0.01) of body weight whereas a remarkable increase (p < 0.01) of relative lung weight in Model group rats. Administration with dexamethasone, medium and high dose of C. majus displayed a remarkable elevation in body weight (p < 0.05) whereas suppression (p < 0.01, p < 0.05, p < 0.01) in relative lung weight when compared to Model group rats (Fig. 1C, D).
Figure 1 (A) Experimental scheme. (B) Total ion chromatograms (+) of C. majus extract. (C, D) Body weights and relative lung weights of diverse groups after administration.
C. majus reduced inflammation, collagen deposition and mucus hypersecretion in OVA-induced asthmatic rats
Control group did not show abnormal findings of the structure in the bronchial and alveolar. Nevertheless, model rats showed an obviously increased thickness in the alveolar septum, and tremendous inflammatory cell infiltrations in bronchi and perivascular. Intragastric administration of Dex, medium and high dose of C. majus all apparently alleviated the severity of pulmonary lesion compared with Model group (p < 0.01, p < 0.05, p < 0.01). (Fig. 2A, D). As revealed by Masson staining, the collagen deposition of Model group was severe. Administration with Dex and high dose of C. majus both markedly alleviated the collagen deposition in OVA-induced rats (p < 0.01) (Fig. 2B, E). Based on PAS staining, there was no visible edema on the airway mucosa in Control group, and few goblet cells, little mucus secretion can be seen. On the contrary, lungs tissue structure of Model group were irregular with obvious edema on the airway mucous membrane, and massive goblet cells proliferate on airway epithelium, and the mucus hypersecretion can be seen in the inner wall of airway. And the goblet cell proliferation and mucus secretion were attenuated in Dex, CH groups rats (p < 0.01). (Fig. 2C, F). The results indicated that high dose of C. majus obviously attenuated the pulmonary histopathology of asthmatic rats.
C. majus regulate inflammatory cytokines production within asthmatic rats
According to statistical analyses, Model group had evidently increased IL-4, IL-6, and IL-17 levels (p < 0.01) relative to Control group. Inversely, in comparison with Model group, IL-17 and IL-4 expression reduced obviously (p < 0.01), IL-6 expression reduced obviously (p < 0.01, p < 0.05) in Dex and CH groups, administration with medium dose of C. majus showed a remarkable decrease in the level of IL-17, IL-4 (p < 0.05). (Fig. 2G-I). These findings demonstrated that C. majus exhibited good performance in anti-inflammatory effect, and the high dose was more effective than medium dose.
Figure 2 Pulmonary histopathology analysis. (A) H&E analysis (×200), blue arrows indicate inflammatory cell infiltration. (B) Masson analysis (×200). (C) PAS analysis of pulmonary sections (×200), red arrows indicate goblet cell proliferation. (D) inflammation score. (E) Masson score. (F) PAS score. The data are represented by mean ± SEM (n = 3). ##p < 0.01 versus Control group; *p < 0.05, **p < 0.01 versus Model group. (G-I) Inflammatory cytokines assay. The data are represented by mean ± SEM (n = 8). ##p < 0.01 versus Control group; *p < 0.05, **p < 0.01 versus Model group.
Metabolomic analysis
Control group was significantly separated from Model group, CH group was basically separated from Model group and approached Control group, based on PCA score plots (Fig. 3A). According to these results, there were significant differences in metabolite profiles of CH groups relative to Model group, and CH group manifested a better performance of the recovery from OVA-induced metabolic disturbance. The parameters R2Y, Q2 values of OPLS-DA were approached to 1 (0.99 and 0.91), which implied the presence of less unrelated variables of OPLS-DA models. For checking reliability of OPLS-DA model, replacement tests were carried out. R2 and Q2 values remarkably decreased compared with original points, which was indicative of the asthma model being well built (Fig. 3B-E). According to the multivariate analysis of OPLS-DA with the parameters settings of FC > 1, VIP > 1 and p < 0.05, we detected 46 candidate serum metabolites to be metabolic biomarkers that mainly associated with lipid, organic acid, fatty acid, and amino acid. Compared with Control group, 15 metabolites in Model group showed up-regulated, whereas 31 showed down-regulated. When compared with Model group, 12 metabolites of CH group were down-regulated, 18 metabolites were up-regulated (Supplementary Table S2). The metabolite heatmap is shown in Fig. 3F.
MetaboAnalyst 5.0 was used to analyze pathways of all metabolic biomarkers with the filter Criteria of -log P > 1 and Impact > 0. 11 main metabolic pathways were determined in Control and Model group, included Arginine and proline metabolism, Citrate cycle, Pyruvate metabolism, Purine metabolism, Arachidonic acid metabolism, Arginine biosynthesis, Tyrosine metabolism, Sphingolipid metabolism, beta-Alanine metabolism, Phenylalanine, Tyrosine and tryptophan biosynthesis and Alanine, aspartate and glutamate metabolism. 6 major metabolic pathways could be detected from CH and Model group, included Arginine and proline metabolism, Arginine biosynthesis, Purine metabolism, beta-Alanine metabolism, Glycerophospholipid metabolism, and Phenylalanine, tyrosine and tryptophan biosynthesis (Fig. 3G, H).
To sum up, asthma induction disturbed these metabolic biomarkers as well as the associated metabolic pathways. The alteration was mainly associated with lipid, amino acid, and fatty acids metabolic disorders. Following intervention with high dose of C. majus, the disorder was restored to some extent.
Figure 3 Metabolomic results. (A) PCA score plots. (B-E) OPLS-DA score plots. (F) Heatmap visualization for metabolic biomarkers in Control, Model and CH groups (n = 6). (G, H) Metabolic pathway analysis of Model-vs-Control group, Model-vs-Control group and CH-vs-Model groups.
Transcriptomics analysis
KEGG enrichment analysis
There were altogether 754 DEGs detected when comparing Model-vs-Control group, including 454 with up-regulation while 300 with down-regulation. After treatment, there were 260 DEGs regulated in CH group, including 165 showing up-regulation whereas 95 showing down-regulation relative to Model group (Fig. 4A). Heatmap was obtained by clustering the DEGs (Fig. 4B). Supplementary Table S3 displays details for the DEGs. After high dose of C. majus intervention, gene levels within lung tissue showed a similarity to Control group, indicating the role of C. majus in regulating DEGs levels in Model group. In order to investigate DEGs-regulated biological pathways, we carried out KEGG analysis. Figure 4C, D displayed the 20 most significant pathways. Those pathways enriched were chiefly related to inflammatory pathways (Cytokine-cytokine receptor interaction, Chemokine pathway, IL-17 pathway, TNF pathway, PI3K-Akt pathway, T17 cell differentiation pathway), immune pathways (Intestinal immune network for IgA production pathway, Hematopoietic cell lineage pathway), airway remodeling related signaling pathway (ECM-receptor interaction pathway), energy metabolism pathway (Purine metabolism pathway) and Asthma pathway of Model-vs-Control group. The enrichment pathways were mostly related to inflammation signaling pathways (IL-17 pathway, Cytokine-cytokine receptor interaction, NF-κB pathways, PI3K-Akt pathway, TNF pathway, Chemokine pathway, NOD-like receptor pathway, Arachidonic acid metabolism), energy metabolism pathways (Purine metabolism), airway remodeling related signaling pathway (ECM-receptor interaction pathway) and Pertussis of Model-vs-Control and CH-vs-Model groups.
Figure 4 Transcriptomics results (n = 3). (A) Venn diagram showing DEGs in different groups. (B) Heatmap showing DEGs in Control, Model and CH groups. (C, D) KEGG pathway enrichment on DEGs-Bubble chart of Model-vs-Control group and Model-vs-Control and CH-vs-Model groups respectively.
We selected PI3K-Akt and NF-κB pathways for verifying the roles of C. majus in resisting inflammation when treating asthma. Compared with Control group, PI3K, Akt, NF-κB p65, p-NF-κB p65 levels had up-regulated significantly (p < 0.01, p < 0.01, p < 0.05, p < 0.01), while IKB-α level had down-regulated significantly (p < 0.05) of Model group. After high dose of C. majus administration, PI3K, Akt, NF-κB p65, p-NF-κB p65 levels had down-regulated dramatically (p < 0.05), IKB-α level had up-regulated evidently (p < 0.05) relative to Model group (Fig. 5A, B).
PPI network establishment and hub gene analyses
Based on these findings, 260 shared DEGs of Model-vs-Control and CH-vs-Model groups were obtained. PPI networks were built through STRING database, followed by visualization with Cytoscape 3.9.1 platform (Fig. 5C). And then according to degree centrality, 6 genes showing the greatest degree values were acquired, including Il-6 (degree = 60), Il-10 (degree = 48), H3f3c (degree = 30), Cdk1 (degree = 28), Cxcl2 (degree = 26) and Aurkb (degree = 26) of Model-vs-Control and CH-vs-Model groups.
For validating functions of C. majus in asthma by those potential hub genes, Il-6, IL-10, H3f3c, Cdk1, Cxcl2 and Aurkb mRNA expression was detected through qRT-PCR. According to Fig. 5D, OVA-induced asthma caused an obvious upregulation of Il-6, H3f3c, Cdk1, Cxcl2 and Aurkb (p < 0.05, p < 0.01, p < 0.05, p < 0.01, p < 0.01) relative to Control group. Administration with high dose of C. majus induced a significant down-regulation of Il-6, Cdk1, H3f3c, Cxcl2, Aurkb (p < 0.05). Unluckily, IL-10 was not detected.
Figure 5 (A, B) IHC detection of PI3K, Akt, IKB-α, NF-κB p65, p-NF-κB p65 protein levels within rats lung tissues. The data is represented by mean ± SEM (n = 3). #p < 0.05, ##p < 0.01 versus Control group; *p < 0.05 versus Model group. (C) PPI networks regarding DEGs in Model-vs-Control and CH-vs-Model groups. (D) hub genes verification. Results are represented by mean ± SEM (n = 3). #p < 0.05, ##p < 0.01 versus Control group; *p < 0.05, **p < 0.01 versus Model group.
Integration of metabolomics and transcriptomics analyses
The linked network of metabolic biomarkers and DEGs was displayed in Figure. 6A with the filter Criteria of -log P > 1, mainly included Arginine and proline metabolism, Arginine biosynthesis, Glycerophospholipid metabolism, Citrate cycle (TCA cycle), Pyruvate metabolism, Arachidonic acid metabolism, Purine metabolism, Tyrosine metabolism, Sphingolipid metabolism, beta-Alanine metabolism, Phenylalanine, tyrosine and tryptophan biosynthesis in Model-vs-Control group and Purine metabolism, Arachidonic acid metabolism, Retinol metabolism, Arginine and proline metabolism, Aminoacyl-tRNA biosynthesis, Glycerophospholipid metabolism, Linoleic acid metabolism, Ether lipid metabolism, Pyrimidine metabolism, Pyruvate metabolism in both Model-vs-Control and CH-vs-Model groups.
The metabolic biomarkers and DEGs were analyzed using spearman rank correlation (Fig. 6B and C). As was shown, there was noticeable correlation between some metabolites and DEGs. Pde3a, Adcy9 were negatively related with ADP, Inosine (p < 0.01), Xanthosine (p < 0.05), Hypoxanthine (p < 0.05, p < 0.01). Pde7b was negatively related with ADP, Inosine, Xanthosine (p < 0.01, p < 0.05, p < 0.05) and Entpd8 was positively related with ADP, Inosine, Xanthosine, Hypoxanthine (p < 0.01, p < 0.01, p < 0.05, p < 0.05). Rrm2b was positively related with ADP (p < 0.05), Xanthosine (p < 0.01), and negatively related with Inosine (p < 0.01). Nme1 was positively related with ADP and Inosine (p < 0.05). Pla2g16 was positively interrelated with PGE2 and phosphatidylserine (p < 0.05, p < 0.01) and negatively interrelated with LysoPC(10:0) (p < 0.05). Alox15 was negatively interrelated with PGF2a (p < 0.05). Ptgs2 was positively interrelated with PGF2a (p < 0.05). P4ha1 was negatively associated with Creatine (10:0) (p < 0.01). The results supplied a reference for the mechanism of alleviating asthma by C. majus.
Furthermore, to evaluate our results, qRT-PCR was carried out for verifying mRNA levels of those 10 genes (Fig. 6D). As a result, relative to Control group, Ptgs2, Entpd8, Pla2g16 and Nme1 levels within lung tissues in Model group rats had markedly elevated (p < 0.05, p < 0.01, p < 0.01, p < 0.05), Adcy9, Alox15, P4ha1, Pde3a and Pde7b levels were notably reduced (p < 0.05, p < 0.01, p < 0.05, p < 0.05, p < 0.05), but Rrm2b didn’t change. Relative to Model group, administration with high dose of C. majus suppressed Entpd8, Pla2g16 and Nme1 levels within lung tissues (p < 0.01), while facilitated Adcy9, Alox15 and P4ha1 levels (p < 0.01), but Pde7b and Ptgs2 levels remained unchanged.
The associated DEGs and metabolic biomarkers were displayed in Fig. 6E. 7 DEGs (Alox15, P4ha1, Pla2g16, Pde3a, Nme1, Entpd8 and Adcy9) were discovered related to the enrichment metabolic pathways. P4ha1 was related to Arginine and proline metabolism. Alox15 was associated with Arachidonic acid metabolism, Pla2g16 participated in Glycerophospholipid metabolism, Pde3a, Nme1, Entpd8 and Adcy9 were involved with Purine metabolism.
Figure 6 (A) Joint-Pathway analysis of Model-vs-Control and CH-vs-Model groups. (B, C) Correlation analysis between metabolic biomarkers and DEGs on the basis of spearman rank. (D) qRT-PCR validation of the 10 genes. Results are represented by mean ± SEM (n = 3). #p < 0.05, ##p < 0.01 versus Control group; *p < 0.05, **p < 0.01 versus Model group. (E) Changes in metabolites (blue squares) and differential genes (red circles) in the 4 metabolism on the basis of integrated analysis. The red arrow indicates the increase or decrease of Model group relative to Control group. The green arrow reveals the increase or decrease of CH relative to Model group.