COVID-19 is an atypical respiratory disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has triggered a global pandemic and caused significant loss of life and property (1). Globally, as of 21 January, there were 774,395,593 confirmed cases of COVID-19, including 7,023,271 deaths, reported by the World Health Organization (WHO) (https://covid19.who.int/). Although more than 80% of patients with COVID-19 present with asymptomatic infection or mild to moderate self-resolving symptoms, more than 15% of patients still develop into severe cases, manifested as severe pneumonia or acute respiratory distress syndrome, and even multiple organ failure (2, 3). In addition to respiratory diseases, cardiovascular complications have gradually become a major threat for patients with COVID-19. Pericarditis is the most common pericardial disease worldwide; the pericardium provides fixation and physical protection for the heart, such as slowing down the impact of heart contraction on the surrounding blood vessels and preventing the spread of pulmonary and thoracic infections (4). The etiology of pericarditis may be infectious (bacterial or viral) or noninfectious (systemic inflammatory disease or post-cardiac injury syndrome) (5). Viral infection is an important cause of pericarditis and studies have shown that it can be an early complication of COVID-19. Notably, the incidence rate of pericarditis has increased by at least 15 times after SARS-CoV-2 infection than before COVID-19, and estimates of excess cases associated with vaccination also indicate a burden associated with pericarditis (6, 7). Over 13 billion doses of COVID-19 vaccines have been administered; furthermore, several passive surveillance systems have indicated that the risk of pericarditis increased after COVID-19 vaccination, especially in young men, but authoritative research claimed that the incidence was rare (8). Considering benefits and risks, vaccination should be firmly supported, but strengthening the surveillance of adverse events following vaccination and continuing to study the mechanistic relationship between COVID-19 and pericarditis are still essential.

Increasing evidence suggests that immune responses and potential immune markers may be associated with COVID-19 severity. Differences in innate immune system components lead to heterogeneity in the COVID-19 disease spectrum (9). An imbalanced immune response during viral invasion is an important immunopathological mechanism in severe diseases (10). After SARS-CoV-2 infection, immune effector cells release a large number of pro-inflammatory cytokines, triggering a cytokine storm that causes important immunopathological events, such as ARDS and multiple organ failure (11). In recent years, immune checkpoints have led to breakthroughs and progress in cancer treatment; however, their application is still limited due to immune-related adverse events, such as cardiotoxicity. The onset and progression of pericarditis in the cardiotoxicity brought on by immunotherapy are intimately tied to the unrestricted regulation of the immune system (12). The predisposing factors and pathogenesis of pericarditis remain unclear, and may be related to viral infections or autoimmune-inflammatory diseases. Under the influence of exogenous triggers, infections may lead to an autoimmune response in susceptible hosts by activating innate immunity (13, 14). Therefore, gaining a comprehensive and in-depth understanding of interactions between viruses and the human immune system is necessary. Furthermore, studying the impact and mechanism of the clinical outcomes of COVID-19 and pericarditis is crucial to promote the research and development of vaccines with reduced side effects.

In recent years, with the rapid development of high-throughput biotechnology, the use of gene interaction networks in bioinformatics research has become increasingly convenient. The construction of gene interaction network not only helps to further understand various biological processes from the perspective of systems, but also can be widely applied to explore the pathogenesis of diseases. However, massive data cannot be verified one by one to explain the mechanism, so gene enrichment studies are needed to classify differential genes, so as to filter redundant data and screen out more valuable functional information (15). Based on data sources and algorithms, methods for gene functional enrichment analysis can be roughly divided into four categories: over-representative analysis (ORA), function set scoring (FCS), pathway topology (PT), and network topology (NT). Enrichment analyses commonly used include GO enrichment analysis, KEGG enrichment analysis and gene set enrichment analysis (GSEA). GSEA consists of three key elements: calculating enrichment scores, evaluating significance, and adjusting for multiple hypothesis tests. Weighted Kolmogorov Smirnov (WKS) test was used in GSEA to obtain the statistical value of the functional set of the tested gene, and there are other statistical algorithms, such as χ2-test, Mean test, Median test, Wilcoxon rank sum test, etc. (16, 17). The schematic overview for GSEA can be found in Supplementary Figure 1 (https://www.gsea-msigdb.org/gsea/) (16).

In this study, we employed a wide range of bioinformatics techniques to identify the common genes of COVID-19 and pericarditis and analyzed their enrichment pathways and functions. Protein–protein interaction (PPI) networks were constructed to identify hub genes and further analyze the interaction networks of transcription factors (TFs), microRNAs (miRNAs), chemicals, and drugs. The immune response can serve as a resection point for studying the common pathogenesis of comorbidities. To uncover molecular regulatory networks and investigate the relationship between hub genes and immune cells, immune infiltration analysis was employed. This study provides new insights for exploring the pathophysiological connections and immune mechanisms and excavating the potential biomarkers and therapeutic targets for COVID-19 and pericarditis. The overall flowchart of the study is shown in Figure 1 .

Increasing evidence has linked cardiovascular disease to increased morbidity and mortality from COVID-19, and the burden is evident even among patients who are not hospitalized (38, 39). COVID-19 is a real-time global pandemic, and this virus infection is also a pathogenic factor of pericarditis. COVID-19 has significantly increased the risk of pericarditis, and because multiple monitoring reports suggest that the COVID-19 vaccine may also increase the likelihood of people suffering from pericarditis, many studies on vaccines and pericarditis have been conducted in different countries and regions (40, 41). Currently, most reports on COVID-19 and pericarditis focus on the epidemiology and vaccines; however, research on the potential mechanisms of comorbidity remains lacking. Therefore, our research aimed to reveal the etiology and mechanism of COVID-19 and pericarditis from the perspective of molecular regulation, based on network data mining and bioinformatics analysis.

GO is a bioinformatics resource that provides gene product functions and uses ontology to represent biological knowledge and it can identify the biological process of shared genes in this study (42). The enrichment results in the BP and CC were associated with immune cell proliferation, including that of white blood cells, lymphocytes, and monocytes, suggesting their involvement in regulating cytokine production and inflammatory responses. Lymphocyte count and cytokine levels are closely correlated with disease severity, which is of great significance for the early diagnosis, treatment, and prognosis of COVID-19 (43). Gerd et al. examined the immune cell spectrum in the cerebrospinal fluid with COVID-19 and the results indicated an expansion of dedifferentiated monocytes and interferon signature of leukocytes (44). Anti-inflammatory treatment can reduce the thickness of pericardial late gadolinium enhancement, alleviate pericardial and systemic inflammation, and improve the physiological status and symptoms of pericarditis (45). Studies have focused on the prognostic value of inflammatory markers in active pericarditis, suggesting that high-sensitivity C-reactive protein may affect the intensity and duration of pericarditis (46). MF results mainly involve the binding of proteases and chemokines as well as the activity of signaling and immune receptors. Assessing the chemokine status after SARS-CoV-2 infection and detecting the “immune signature” is crucial for individual risk stratification (47). Studying the extensive cytokine releasing syndrome in COVID-19 may be helpful for targeting chemokines and growth factors as therapeutic drugs; furthermore, autoantibodies targeting chemokines may inhibit the potentially harmful immune response observed in patients with COVID-19 (48, 49). KEGG connects genomic and higher-order functional information from the perspective of genes and molecular networks and annotates up-to-date gene catalogs and functions (50). The top 20 pathways in KEGG involved immune-related pathways such as COVID-19, influenza, hepatitis, rheumatoid arthritis, and inflammatory bowel disease, and involved in immune pathways such as Th17 cell differentiation, IL-17, TNF, and Toll-like receptors. TNF-α blockers have made important progress in the treatment of idiopathic recurrent pericarditis (51). Christian et al. found that after virus clearance, clonally expanded Th17 cells remained in the lungs, which was associated with the potentially pathogenic cytokine expression profile of IL-17, and interacted with cytotoxic CD8 T cells and macrophages (52). As key regulatory factors of the innate immune system, Toll-like receptors recognize viral particles and induce the secretion of pro-inflammatory cytokines, which may also be potential targets for vaccine production (53). In this study, we constructed the gene network to obtain the common differential genes of COVID-19 and pericarditis, so as to obtain the hub gene and explore the potential mechanism correlation between them. GO term functional enrichment and KEGG pathway enrichment were applied to identify functional changes caused by differential genes and their effects in the pathway. However, due to the need for a clear threshold for GO/KEGG enrichment of the common genes, it is possible to miss genes with significant biological significance. GSEA, which may not require the clear threshold and is based on overall trend analysis, can be implemented in the future. Meanwhile, Weighted correlation network analysis (WGCNA) can serve as a supplement to gene network studies and can analyze gene modules that coordinate expression.

Immune cell infiltration showed that patients with COVID-19 had significantly higher levels of plasma cells, resting memory CD4 rest cells, monocytes, M0 macrophages, resting mast cells, and neutrophils than the healthy population. Persistent antibody protection, produced by memory B cells and long-lived plasma cells, is the pillar of the “arms race” between vaccines immunity and the constantly mutating SARS-CoV-2 virus infection, and long-lived plasma cells in bone marrow tissue are the source of these persistent “memory” antibodies during acute infection (54). Some studies have evaluated whether pre-existing cross-reactive memory T cells affect vaccine immunity, and the results displayed that subjects with memory CD4 T cells have stronger antibody responses to vaccines (55). Notably, long-lasting memory T cells responded to SARS-CoV-2 and exhibited substantial cross-reactivity with the N protein of SARS-CoV-2 in patients recovering from SARS-CoV-2 in 2003 (56). Excessive infiltration of macrophages and monocytes into organs is a critical driver of severe COVID-19, and the activation of pulmonary macrophages from infiltrating monocytes results in the recruitment of cytotoxic effector cells and the release of pro-inflammatory cytokines (57). Macrophages activate inflammasomes, which oppose host infection and promote tissue repair by releasing interleukin and inducing pyroptosis; however, it should be noted that macrophage activation syndrome induced by macrophage dysfunction may cause damage to the host (58, 59). The high density of mast cells is related to the activation and release of proteases, which are affected by soluble factors released by T cells with the help of stem cell factors. The proliferation and activation of mast cells are manifestations of inflammatory cell changes in severe and lethal SARS-CoV-2 infection; thus, regulating mast cells and their pro-inflammatory mediators may be a potentially effective treatment for COVID-19 (60, 61). The characteristics of neutrophils in severe COVID-19 include the formation and degradation of neutrophil extracellular traps, expansion and infiltration of neutrophils into the lungs, and activation and immune suppression of neutrophil subsets in the circulatory system (62). The abnormal response of neutrophils after infection with SARS-CoV-2 may be related to uncontrolled viral replication and exacerbated inflammation. Assessing the number, function, and status of neutrophils are crucial for distinguishing the disease severity and identifying the clinical deterioration risk (63). Many studies have been conducted on the progression of immune cells in pericarditis. Neutrophils and macrophages produce a large number of cytokines through the activation of inflammasomes, which contribute to the immune pathogenesis of recurrent pericarditis (64). Interference with neutrophil chemotaxis and adhesion, reduction of recruitment to damaged tissues, and superoxide production are effective strategies and mechanisms for the anti-inflammatory treatment of pericarditis (65). The pericardial interstitial cells of patients with pericarditis exhibit senescent features that induce structural remodeling of the pericardium, such as increased collagen matrix secretion and calcium deposition, promotion of chemotaxis of monocytes/lymphocytes, and recruitment of inflammatory factors (66). Moreover, many clinical samples have been collected from patients with pericarditis. Pleural biopsy revealed pleural pericarditis accompanied by lymphoplasmacytic inflammation, such as IgG4-positive plasma cells, and detection of pericardial fluid indicated that the histamine receptor depended on mast cells to infiltrate the pericardial tissue and was involved in the inflammatory reaction (67, 68). Notably, this study analyzed the difference of immune infiltration in COVID-19 and identified the types of immune cells associated with hub gene. With the accumulation of research data related to pericarditis, immune infiltration analysis of pericarditis can be carried out in this study.

Based on the PPI network and topological analysis, IL-1β, CD8A, IL-10, CD4, IL-6, TLR4, CCL2, and PTPRC were identified as hub genes. Since the COVID-19 pandemic, many trials have found that the COVID-19 group had higher levels of IL-1, IL-6, and IL-10 than the control group. Logistic regression and ROC analyses have revealed that these cytokines have a predictive effect on disease severity (69, 70). A genome-wide association study showed that patients with critical COVID-19 had significantly greater blood IL-6 expression levels than patients without symptoms and that an allele change at the rs2069837 site can reduce IL-6 levels to prevent critical conditions (71). Anti-interleukin (IL)-1 drugs have been developed and used to treat autoimmune and rheumatic immune diseases. As one of the family members with the strongest pro-inflammatory effects, IL-1β is considered the therapeutic target for recurrent idiopathic pericarditis (72). Research has been conducted on the etiology, immune mechanisms, and treatment of tuberculous pericarditis, and showed that IL-10 levels are elevated in the pericardium and blood (73). Myocardial fibrosis is considered a non-negligible feature of constrictive pericarditis. IL-6 mediates abnormal Ca²⁺ handling and induces atrial fibrosis in sterile pericarditis rats (74). Patients with severe COVID-19 exhibit less pronounced increases in TLR4 expression on CD14 monocytes than those with mild COVID-19, which is related to activation of TLR4/NF-κB axis after lipopolysaccharide stimulation (75). TLR4 signaling pathway also regulates myocardial fibrosis by inhibiting its target genes (76). The detection of specific chemokines in the plasma at the mRNA and protein levels suggests that higher concentrations of CCL2 are associated with the severity of COVID-19, which has potential as a prognostic factor (77). The immunopathological changes in the spleen of patients with COVID-19 are also worthy of attention as they involve the functions of plasma cells and monocytes/macrophages and a decrease in CD8A abundance (78). Through the analysis of transcriptome data, PTPRC was shown to be an important inflammatory and immunomodulatory signature in COVID-19, and that it has high binding efficiency with related drugs in clinical transformation research (79). There have been some studies on CCL2, CD8A, and PTPRC in cardiovascular diseases; however, their roles in pericarditis require further research. Overall, these hub genes may be potential immune regulatory pivots in COVID-19 and pericarditis. In addition, there is a very interesting issue worth discussing. The expression of pro-inflammatory cytokines such as IL-1β and IL-6 may change over time, and their dynamics may be potential predictors of disease (80). Currently, database-based research considers gene expression at different time points as a whole, and more in-depth studies in the future will focus on dynamic changes in gene expression to achieve precise intervention for diseases.

We constructed TF-gene and gene-miRNA interaction networks to better understand the molecular regulation between COVID-19 and pericarditis. CREB1, YY1, FOXC1, and NR3C1 were the TFs having the strongest correlation to the hub genes. We analyzed the transcriptome RNA-seq data related to COVID-19 and used bioinformatics to decode the molecular tags and pathways of the host cell response to SARS CoV-2. The genes YY1 and CREB1 may co-regulate autophagy to affect severe conditions. FOXC1 and YY1 may have good binding affinities to candidate drugs. The NR3C1-CXCL8-neutrophil axis may determine the severity of COVID-19 (81–83). The miRNAs that strongly interacted with the hub genes were hsa-mir-335-5p, hsa-mir-1-3p, hsa-mir-106a-5p, and hsa-mir-98-5p. In different studies, peripheral blood mononuclear cells, serum samples, and bronchial aspirates from patents with COVID-19 and healthy individuals were collected. Sequencing analysis has shown that miR-1-3p is involved in the regulation of autophagy and has high specificity and sensitivity for predicting mortality (84, 85). MiR-335-5p is regulated by angiotensin-converting enzyme and histone deacetylase and is involved in drug development to interfere with host-virus interactions (86). TMPRSS2 is a potential therapeutic target for COVID-19, and miR-98-5p is a regulatory factor of TMPRSS2 that originates from two types of endothelial cells in the lungs and umbilical vein (87). Due to the lack of transcriptome sequencing and network information analysis of pericarditis, the regulatory roles of these TFs and miRNAs in pericarditis need to be further elucidated.

According to the gene-disease interaction network, COVID-19 combined with pericarditis can damage the heart, liver, kidney, and other organs; trigger inflammation and rheumatism; and cause neurological and psychiatric diseases. Several cases have reported that simultaneous onset of glomerulonephritis and pericarditis in patients with rheumatic immunity and viral infection (88, 89), and many studies have focused on COVID-19 vaccine that may increase the risk of glomerulonephritis similar to pericarditis (90, 91). The humoral immune response of patients with liver cirrhosis after COVID-19 vaccination is being explored, and case suggest that constrictive pericarditis may appear as a comorbidity in patients with liver cirrhosis (92, 93). The increased incidence of rheumatoid arthritis in patients with COVID-19 may be due to the impaired function of the autoimmune system and the iatrogenic effect of immunosuppressants, and genome-wide cross-trait analysis shows that higher genetic susceptibility to rheumatoid arthritis also increases the risk of COVID-19 (94, 95). A similar mechanism reveals the possibility of antirheumatic drugs as a potential treatment for COVID-19. The effects of drugs on pericardial contractions secondary to rheumatoid arthritis have also been studied in patients with pericarditis (96, 97). Globally, major depressive disorder and anxiety disorder cases have increased by 27.6% and 25.6%, respectively, as a result of the COVID-19 pandemic, resulting in 49.4 million and 44.5 million DALYs (disability-adjusted life years) (98). Immune dysfunction caused by infection can aggravate mental sequelae, and studies on the influence of COVID-19 on mental health have found that the levels of inflammatory markers are directly proportional to depression severity of depression (99). Tryptophan metabolism may be correlated with the potential susceptibility to depression, and tryptophan supplementation may improve depressive symptoms in patients with COVID-19 treated with drugs that can affect tryptophan metabolism (100). Numerous investigations have shown that COVID-19 increases the risk of schizophrenia, and willingness to be vaccinated is related to the severity of psychiatric symptoms (101, 102). A case report of clozapine-related pericarditis in a patient with refractory schizophrenia during the drug titration phase suggested that great attention should be paid to the side effects of antipsychotics and antidepressants in patients with COVID-19 and pericarditis (103).

Protein–chemical interaction networks indicated that methotrexate, antirheumatic agents, nickel, tretinoin, arsenic, benzo(a)pyrene, cadmium, and dexamethasone have a high correlation with hub genes. As a specific immunosuppressive drug, methotrexate impairs immunogenicity and raises the risk of infection and poor prognosis (104). Interruption of methotrexate for two weeks enhances antibody responses in patients with immune-mediated inflammatory diseases after vaccination (105). IL-6 and IL-1β are pivotal targets of antirheumatic agents, and there is evidence that blocking the IL-6 receptor can reduce lung involvement and acute cardiovascular complications in patients with COVID-19 by inhibiting the systemic inflammatory response (106). Several clinical trials have been conducted to evaluate the long-term prognosis of COVID-19 with different doses of dexamethasone and whether the clinical benefits are related to different respiratory support modes (107, 108). Methotrexate has previously been used for the treatment of purulent pericarditis in rheumatoid arthritis; however, methotrexate-induced pericarditis and pericardial effusion should be considered (109, 110). In addition, clinical guidelines indicate that non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin are recommended as effective drugs for the first-line treatment of pericarditis (111). Notably, when the screening scope of the interaction network is expanded, NSAIDs such as aspirin and ibuprofen can also be searched. Protein–drug interaction networks revealed that some drugs, such as AV411, minocycline, rilonacept, canakinumab, XOMA 052, and VX-765, exert therapeutic effects by targeting hub genes. AV411 reduces opioid withdrawal by inhibiting glial pro-inflammatory responses, whereas minocycline prevents potentially fatal arrhythmias by inhibiting pro-inflammatory cytokines and poly (ADP-ribose) polymerase-1 associated with SARS-CoV-2 replication (112, 113). Rilonacept is a trap for IL-1β and has been shown in clinical trials to inhibit recurrent pericarditis episodes and prevent the recurrence of pericarditis (114). Canakinumab, a human monoclonal antibody targeting IL-1β, is associated with the reduction of serum C-reactive protein level and the improvement of overall mortality in COVID-19; case reports showed that canakinumab can reduce the risk of recurrence of systemic disease-related pericarditis (115, 116). As the neutralizing antibody to IL-1β, XOMA 052 has a rapid onset and sustained control of intraocular inflammation, and VX-765 ameliorates myocardial reperfusion injury by inhibiting caspase-1 activity and reducing lactate dehydrogenase release (117, 118). In summary, some chemicals and drugs predicted based on hub genes have been proven in clinical trials and experimental studies of COVID-19 and pericarditis, whereas others deserve further exploration.

This study had several limitations. There are currently no suitable microarray or RNA sequencing data for pericarditis, resulting in a lack of available datasets that may prevent the acquisition and identification of sufficient DEGs. In addition, our study was purely based on bioinformatics analysis and requires subsequent in vivo and in vitro to confirm the validity of the results, as well as to fully evaluate the biological function of the hub gene and the clinical value of the drug.

In recent years, the topic of increased risk of pericarditis caused by COVID-19 has triggered a large number of studies and heated discussions, but there is still a lack of exploration and research on the mechanism of COVID-19 and pericarditis. The immunological mechanisms and common genes linked to COVID-19 and pericarditis were identified in this investigation. The eight hub genes (IL-1β, CD8A, IL-10, CD4, IL-6, TLR4, CCL2, and PTPRC) are relatively mature and have been extensively studied in immune regulation, and some also have the potential to affect immune functions. Thus, COVID-19 and pericarditis exhibit complex interactions. The enrichment analysis and various interaction networks constructed and analyzed in this study revealed the molecular mechanisms of COVID-19 and pericarditis from multiple perspectives. Based on the analysis, some potential compounds and drugs were predicted. However, further research on their functions and mechanisms is required to provide new ideas for identify potential biomarkers and explore appropriate treatment methods.

The original contributions presented in the study are included in the article/ Supplementary Materials , further inquiries can be directed to the corresponding authors.

DL: Formal Analysis, Investigation, Resources, Validation, Visualization, Writing – original draft, Writing – review & editing. RC: Visualization, Writing – review & editing. CH: Writing – review & editing. GZ: Writing – review & editing. ZL: Writing – review & editing. XX: Writing – review & editing. BW: Writing – review & editing. BL: Writing – review & editing, Writing – original draft. XC: Writing – review & editing, Writing – original draft.