COVID-19 has brought a tremendous threat to public health, especially the elderly over 60 years old being more likely to die after infection [1]. The clinical symptoms of COVID-19 have been reportedly ranged from mild to severe, ultimately leading to death. The mild symptoms included fever, cough, shortness of breath and pneumonia after viral infection, while the severe cases would rapidly developed to acute respiratory distress syndrome, septic shock, metabolic acidosis, coagulation dysfunction and multiple organ failure that eventually brought about mortality [19, 20]. There has been no effective antiviral drug to treat COVID-19 until now, even though significant efforts are used to develop therapeutic interventions against coronavirus infection [2]. Fortunately, the application of TCM in the auxiliary treatment of COVID-19 has achieve satisfactory therapeutic effects in China [21, 22]. LHQW capsule has been recommended for the treatment of patients with mild symptoms in 7th edition of COVID-19 treatment guidelines and widely used in the clinical treatment of COVID-19 in China [23]. LHQW capsule has been demonstrated to have anti-infection or antiviral effects in vitro or in vivo [24–26]. In the present study, network pharmacological and molecular docking approaches were used to explore the mechanisms of LHQW capsule treating COVID-19.
According to the GO analysis, the LHQW capsule treating COVID-19 is widely involved in regulating inflammation, virus infection, endothelial barrier and cytokine storm via mediating these processes such as response to molecule of bacterial origin, response to oxidative stress, membrane raft, membrane microdomain, cytokine receptor binding and cytokine activity, which were significantly enriched in the GO analysis. Molecule of bacterial origin is involved in Toll-Like Receptor Signaling, which represents a largely evolutionarily conserved pathogen recognition machinery responsible for recognition of bacterial, fungal, protozoan, and viral pathogen associated microbial patterns and initiation of inflammatory response [27]. Oxidative stress is an imbalance between oxidants and antioxidants when the organism exposures to adverse stimuli, playing important roles in virus infection [28]. Membrane raft and membrane microdomain are not only closely associated with inter-endothelial junctions and adhesion of endothelium, but also involved in immune cell adhesion and migration across endothelium [29]. Cytokine storm, emerged from prolonged cytokine/chemokine responses during COVID-19, causes ARDS or multiple-organ dysfunction, ultimately leading to physiological deterioration and death [30]. Quercetin, a typical flavonoid, is one of the major compounds of FF, LIF, EH, HH, PCB, and LI in LHQW capsule and has been reported to have the effects of anti-inflammation, antiviral, strengthening the endothelial barrier integrity and inhibiting the expression of cytokines [31–34]. Kaempferol is flavonoid found in FF, LIF, EH, FBR, HH, and LI of LHQW capsule, and can protect against inflammation, virus infection, endothelial barrier dysfunction, and cytokines release [35–38]. Another important compounds, such as luteolin, naringenin, and beta-sitosterol, in LHQW capsule also have these protective effects [39–42]. Thus, the results of GO analysis indicated that the mechanisms of LHQW capsule treating COVID-19 might be related with suppressing inflammation, virus infection, endothelial barrier dysfunction and cytokine storm.
The internal regulation of the body involves a complex regulatory network rather than a single signaling pathway. Therefore, the therapeutic effects of drugs against diseases involve in many pathways. KEGG enrichment analysis showed that LHQW capsule treating COVID-19 included AGE − RAGE signaling pathway in diabetic complications, Kaposi sarcoma − associated herpesvirus infection (KSHV), TNF, IL − 17, and Toll − like receptor (TLR) signaling pathway, which were associated with inflammation, virus infection and immune response. Taking IL − 17 and TLR signaling pathways as examples to explore the mechanisms of LHQW capsule treating COVID-19. IL − 17 is a key T helper cell population and founding member of a novel family of inflammatory cytokines [43]. IL-17 signaling can not only activate downstream pathways that include NF-κB, MAPKs and C/EBPs to induce the expression of anti-microbial peptides, cytokines and chemokines, but also is critical for protection against a variety of fungal and bacterial infections [44, 45]. TLRs are a well-known family of pattern recognition receptors that play important roles in host immune system and inflammation [46]. TLR signaling activation can result in the production of cytokines, chemokines and interferons and transcription factor NF-κB [47, 48], thus inducing inflammatory and immune response. Previous studies have demonstrated that quercetin not only exerted the effect of anti-inflammation by regulating IL-17 signaling [49, 50], but also effectively promoted the immunoregulatory effect by activating the TLR-3 pathway and inhibiting downstream cytokines production [51, 52]. Similarly to quercetin, another important compound also have these effects. As a result, LHQW capsule treating COVID-19 may directly interfere with IL-17 and TLR signaling, and further regulate the downstream signaling pathways, such as the NF-κB signaling pathway, leading to the inhibition of cytokines production, including TNF-α, IL-1β, IL-8.
Based on gene-pathway network analysis, MAPK3, MAPK1, RELA, IL-6, and CASP8 are the more important genes in LHQW capsule treating COVID-19. Clinical and laboratory data of COVID-19 showed evidence of inflammatory and immune injury, confirming that cytokine storms could be a crucial factor linked to the severity and mortality of COVID-19. MAPK3 and MAPK1, belong to serine/threonine protein kinase family, and the activation of MAPK promotes virus infection and inflammatory response [53–55]. REL/NF-κB family of transcription factors plays a central role in initiation and resolution of inflammatory responses [56, 57]. IL-6, promptly and transiently produced in response to infections and tissue injuries, contributes to host defense through the stimulation of acute phase responses, hematopoiesis, inflammatory and immune reactions [58, 59]. Caspase-8 is the initiator caspase of extrinsic apoptosis and required for the activation of NF-κB and secretion of cytokines in response to activated antigen receptors [60]. Quercetin, kaempferol, luteolin and naringenin, all can inhibit the activation of MAPK and RELA, decrease the expression of IL-6 and CASP8 [61–65]. Moreover, the most critical targets had good binding activities to main compounds, which indicated that pharmacodynamic mechanisms of LHQW capsule had sufficient material basis through preliminary analysis.