Genomics of neonatal sepsis: has-miR-150 targeting BCL11B functions in disease progression

As a kind of inflammatory systemic syndrome that is determined by a serious infection (bacterial or viral sepsis), neonatal sepsis is composed of early-onset sepsis (EOS) and late-onset sepsis (LOS) [1]. The leading risk factors of the disease are prematurity, prolonged rupture of membranes, and low birth weight [2]. Besides, neonatal sepsis is a main reason for morbidity and mortality in premature infants [3]. Therefore, investigating the molecular mechanisms of neonatal sepsis is urgent and important for developing novel therapies.

The key genes and miRNAs involved in the mechanisms of neonatal sepsis have been reported by several studies. For instance, interleukin (IL)-17A is recognized as a effector of IL-18–mediated injury and the outcomes of neonatal sepsis can be improved by disrupting the IL-18/IL-1/IL-17A axis [4]. Previous studies explore pancreatic stone protein (PSP) in neonatal sepsis, finding that PSP is a potential biomarker in combination with procalcitonin in EOS [5, 6]. The overexpression of CD64 is demonstrated to be a highly specific indicator for patients with neonatal sepsis, and CD64 index can be utilized to determine LOS before infants show signs of infection [7, 8]. MiR-15a/16 is a miRNA that may have a critical role in the regulation of gene expression at the post-transcriptional level, which is declared to be useful for the diagnosis and prognosis of neonatal sepsis [9]. In spite of the above studies, the genes and miRNAs acting in neonatal sepsis have not been fully revealed.

In 2014, Cernada et al. [10] used genome-wide expression profiles to assess the expression differences between infants with and without neonatal sepsis, finding that the expression profiles have differences in the early days of neonatal period. However, they have not performed comprehensive bioinformatics analysis to reveal the mechanisms of neonatal sepsis. Using the data deposited by Cernada et al. [10], we further conducted differential expression analysis, enrichment analysis, protein-protein interaction (PPI) network analysis and regulatory network analysis to better or to further investigate the structure and expression of some of the genes that seemed to influence the genesis of neonatal sepsis.

In this study, there were 275 DEGs (including 180 up-regulated genes and 95 down-regulated genes) in the sepsis samples compared with normal samples. A PPI network for the DEGs was constructed, in which TSPO, MAPK14, and ZAP70 were hub nodes according to the DC, BC and CC scores. Besides, a total of 5 modules were screened from the PPI network. Furthermore, CEBPB-DEG regulatory network and has-miR-150-DEG regulatory network separately were constructed.

TSPO (also named the peripheral benzodiazepine receptor) functions in the regulation of inflammation and immune function, and its antagonist PK-11195 can relief cigarette smoke extract-induced inflammation [30]. Santoro et al. demonstrate that TSPO ligands can lower pro-inflammatory enzymes and oxidative stress in glial cells via the biosynthesis of neurosteroids, thus these compounds may be used for treating inflammatory-based neuropathologies [31]. The MAPK14/p38α signaling is considered as a central pathway for integrating useful signals in dendritic cells for inflammation and TH17 differentiation [32]. The p38 kinase plays roles in responses of T cells and inflammation, which mediates the production of crucial inflammatory regulators (including IL-1β; TNFα; and cyclooxygenase-2, COX-2) through cells of the innate immune system [33]. The p38 MAP kinase signal transduction pathway plays an essential role in regulating inflammation and proinflammatory cytokine production, and inhibiting p38α isoform is sufficient and necessary for anti-inflammatory effect [34]. Enrichment analysis showed that ZAP70 was enriched in the function of T cell receptor complex and the T cell receptor signaling pathway. The function deletion of the ZAP70 tyrosine kinase in humans can lead to a serious immunodeficiency, characterized by non-functional CD4+ T cells and lacking mature CD8+ T cells [35]. In ZAP70-deficient patients, circulating T cells are under inadequate supervision, no longer differentiate into TH2 T cells, are short of inhibitory growth controls, and show decreased apoptosis, finally developing into inflammation and autoimmunity [36]. These declared that TSPO, MAPK14, and ZAP70 might play critical roles in neonatal sepsis.

Through inducing the CEBP family, endoplasmic reticulum (ER) stress results in inflammatory responses in response to palmitic acid stimulation in pancreatic acinar cells, wherein CEBPB activation induces CEBPA activation [37]. As a key transcription factor affecting metabolic disturbances, CEBPB is critical for the maturation and differentiation of adipocytes and is overexpressed during proinflammatory conditions and ER stress [38]. Pathway enrichment analysis indicated that CEBPB and MAPK14 were enriched in TNF signaling pathway. In the TF-DEG regulatory network, MAPK14 was targeted by CEBPB, indicating that CEBPB targeting MAPK14 might function in neonatal sepsis through TNF signaling pathway.

Vasilescu et al. demonstrate that the levels of miR-150 in both plasma and leukocytes are associated with sepsis aggressiveness and thus can act as a biomarker of early sepsis [39]. Decreased miR-150 serum levels correlate with an adverse outcome in patients with sepsis and critical illness, and circulating miR-150 serum concentrations may be used as a potential prognostic marker in patients with critical illness [40]. Previous studies reported that BCL11B is not only a transcription factor specific in T-cell, but also contributes to the lineage fidelity and the genetic and functional programs of mature type 2 innate lymphoid cell (ILC2) [41, 42]. In the miRNA-DEG regulatory network, BCL11B was targeted by has-miR-150, suggesting that has-miR-150 might be involved in the pathogenesis of neonatal sepsis by targeting BCL11B.

In conclusion, a total of 275 DEGs were identified from the sepsis samples. Besides, TSPO, ZAP70, CEBPB targeting MAPK14, has-miR-150 targeting BCL11B might act in the pathogenesis of neonatal sepsis. However, further experimental researches are needed to confirm these results obtained from bioinformatics analysis.