Compounds and predicted targets in JHF
JHF contains 12 herb materials that include Renshen (Ginseng Radix et Rhizoma ,GRR), Maidong (radix ophiopogonis, RO), Dihuang (Radix Rehmanniae, RR), Gualou (Fructus et Semen Trichosanthis, FST), Zhebeimu (Bulbus Fritillariae Thunbergii, BFT), Mudanpi (Cortex Moutan Radicis, CMR), Yinyanghuo (Herba Epimedii Brevicornus, HEB), Baiguo (Semen Ginkgo, SG), Baitouweng (Radix Pulsatillae,RP), Yiyiren (Semen Coicis, SC), Chenpi (Pericarpium Citri Reticulatae, PCR), Gouqizi(inLycii Fructus, LF). We collected compounds from the TCMSP and TCMID databases by oral bioavailability and drug-likeness, including 162 compounds in GRR, 22 compounds in RO, 10 compounds in RR, 41 compounds in FST, 27 compounds in BFT, 28 compounds in CMR, 50 compounds in HEB, 53 compounds in SG, 25 compounds in RP, 11 compounds in SC, 40 compounds in PCR and 79 compounds in LF. Of the 548 compounds, 54 were duplicated and therefore removed, resulting in 494 compounds.
We used the STITCH database to predict the targets of the selected compounds. The compounds were predicted to interact with 1304 distinct protein targets with high confidence level (Additional file 1: Table S1). Figure 2 showed the JHF drug-target network, describing its multi-component and multi-target therapy. Notably, there were different numbers of mutual putative targets among the compounds in JHF, proposing that these herbs might have several interactions in the course of treatment.
Identification Of JHF's Important Targets By Intersection Analysis
We collected two sets of disease genes and two sets of drug targets associated with IPF as reference. We first looked at the overlap between these gene sets. As shown in Fig. 3A, among the IPF patients participating in the GSE2052 dataset experiment, 25 of the 378 disease genes were differentially expressed, accounting for 6.6% of all disease genes. On the other hand, there were 4 drug target genes for anti-IPF drugs in KEGG and DrugBank databases, accounting for 30.8% of the target genes in KEGG database.
In Fig. 3B we showed the overlaps of JHF’ target genes with IPF disease genes and target genes for anti-IPF drugs in KEGG database. Among the 1305 target genes of JHF, 99 were IPF disease genes, accounting for 7.59% of all disease genes. Among them, 4 were anti-IPF drug target genes. The four common genes in the three data sets were TNF (Tumor necrosis factor), CCL2 (C-C motif chemokine 2), IL6 (Interleukin-6), and IL10 (Interleukin-10), indicating their important role in the treatment of IPF. From the predictions, TNF was targeted by 13 compounds of JHF, i.e., kaempferol, quercetin, ruscogenin, luteolin, epicatechin, palmitic acid, methyl palmitate, adenosine, adenosine triphosphate, choline, ginsenoside rg1, hexadecanoic acid, spermine; CCL2 was targeted by 6 compounds of JHF (i.e., naringenin, quercetin, rutin, palmitic acid, adenosine triphosphate, hexadecanoic acid); IL6 was targeted by 8 compounds of JHF (i.e., quercetin, luteolin, palmitic acid, adenosine, adenosine triphosphate, dibutyl phthalate, hexadecanoic acid, spermine); IL10 was targeted by 3 compounds of JHF (i.e., quercetin, luteolin, adenosine) (See Additional file 1: Table S1). The four target genes were all target genes of PFD, and PFD have been approved for the treatment of IPF[20]. Therefore, in the following study, we used pirfenidone as a positive control drug.
Identification Of The Pathways And Diseases Regulated By JHF
We used Cytoscape software to construct the drug-target-pathway network of KEGG’s anti-IPF drugs (Fig. 4A). At present, pirfenidone, a drug commonly used in treatment of pulmonary fibrosis, is mainly involved in TNF signaling pathway, TGF-β signaling pathway, cytokine-cytokine receptor interaction and cellular senescence, etc. We used ClueGO, a Cytoscape plugin[21], to analyze the biological processes involved in KEGG’s anti-IPF drug targets. The biological processes mainly included transmembrane receptor protein kinase activity, regulation of phosphatidylinositol 3-kinase activity, vascular endothelial cell proliferation and regulation of vascular endothelial growth factor production (Fig. 4B).
As shown in Fig. 4C, a target gene participated in multiple pathways. To elucidate the biological pathways that JHF might regulate, we analyzed the important pathways involved by JHF targets through DAVID analysis, and constructed a target-pathway network of putative JHF targets. Considering that disease is an advanced biological process caused by the dysfunction of basic biological processes, we only focused on the relevant signaling pathways involved in biological processes. The targets were significantly enriched in 16 pathways (p < 0.01) (Fig. 4D). To uncover the therapeutic potential of the putative targets, disease ontology enrichment was conducted. Through "high" strict classification and enrichment score, a total of 59 clusters of diseases were related to JHF targets, including inflammation, bronchiolitis, coronary artery disease, etc (Additional file 6: Table S6).
Target, pathway and gene ontology analysis of IPF differential expression genes targeted in JHF
In order to further improve the reliability of the analysis, we mapped the predicted targets of JHF to the network of IPF disease genes, and obtained the target information that JHF could directly regulate IPF differential expression genes (Fig. 5A). By analyzing these targets with DAVID-KEGG, it was found that 72 targets (such as Transforming growth factor β1 (TGF-β1), SMAD3) were screened and participated in 18 pathways, including ErbB signaling pathway, Thyroid hormone signaling pathway, TGF-β signaling pathway and so on (Additional file 7: Table S7) (Fig. 5B). Through the analysis of ClueGO plug-in in the software of Cytoscape, the molecular functions of these targets mainly included regulation of oxidoreductase activity, kinase regulator activity, phosphotransferase activity and transmembrane receptor protein kinase activity (Fig. 5C). The biological processes mainly included tube development (Fig. 5D).
Experimental Validation
To confirm our predictions and the therapeutic effects of JHF, we used a well-characterized animal model of pulmonary fibrosis. JHF or PFD was administrated to PF rats. Previous studies have shown that compared with the model group, JHF and pirfenidone could significantly inhibit the decreases of FVC (Forced Vital Capacity) and the increases of lung coefficient[19]. Histological examination showed structural changes in the alveoli of the model group, including collapsed alveolar spaces, thickening of the alveolar walls, presence of inflammatory cells and excessive collagen fiber deposition. However, JHF and PFD could alleviate the alveolar damage described above due to bleomycin (Fig. 6A). The epithelial-mesenchymal transition (EMT) plays an important role in the pathogenesis of pulmonary fibrosis, which is an important pathological process of pulmonary fibrosis[22]. TGF-β is an important inducer of EMT and the strongest inducer of extracellular matrix deposition. Therefore, we detected the role of EMT involved in TGF-β signaling pathway in the development of pulmonary fibrosis. The occurrence of pulmonary fibrosis caused the increase of Vimentin and N-cadherin expression, and the decrease of E-cadherin expression. However, JHF could reverse the expression of these proteins (Fig. 6B). The expression of TGF-β and SMAD3 were increased in PF model group compared to normal control, while in the JHF group, the protein expression returned to the normal level (Fig. 6B).