Pparγ Expression in T Cells as a Prognostic Marker of Sepsis

Integrative bioinformatics analysis reveals CGAS as a ferroptosis-related signature gene in sepsis and screens the potential natural inhibitors of CGAS

Sepsis is a fatal organ dysfunction characterized by the simultaneous hyperinflammation and immunosuppression. Nowadays, the early precision intervention of sepsis is challenging. Ferroptosis is involved in the development of sepsis. The current study aimed to find out the signature genes of sepsis with network topology analysis and machine learning, and further provide the potential natural compounds for sepsis with virtual screening and in vitro validation. In this study, five genes namely CGAS, DPP4, MAPK14, PPARG and TXN were identified as ferroptosis-related signature genes for sepsis by network topological analysis, machine learning algorithms, and external datasets verification. The results of immune infiltration analysis confirmed these genes were significantly associated with the infiltration abundance of some immune cells including neutrophil, macrophage, plasmacytoid dendritic cell and activated dendritic cell. Moreover, coniferin, 5-O-caffeoylshikimic acid, and psoralenoside were initially identified as the natural inhibitors of CGAS by virtual screening. However, further in vitro study on macrophages revealed coniferin and psoralenoside had better inhibitory activities on CGAS. In summary, the present study pointed out the importance of CGAS in sepsis, and discovered novel natural inhibitors of CGAS.

Identification of CRTH2 as a New PPARγ-Target Gene in T Cells Suggested CRTH2 Dependent Conversion of Th2 Cells as Therapeutic Concept in COVID-19 Infection

Background

COVID-19 is a serious viral infection, which is often associated with a lethal outcome. Therefore, understanding mechanisms, which affect the immune response during SARS-CoV2 infection, are important.

Methods

To address this, we determined the number of T cells in peripheral blood derived from intensive care COVID-19 patients. Based on our previous studies, evaluating PPARγ-dependent T cell apoptosis in sepsis patients, we monitored PPARγ expression. We performed a next generation sequencing approach to identify putative PPARγ-target genes in Jurkat T cells and used a PPARγ transactivation assay in HEK293T cells. Finally, we translated these data to primary T cells derived from healthy donors.

Results

A significantly reduced count of total CD3+ T lymphocytes and the CD4+ and CD8+ subpopulations was observed. Also, the numbers of anti-inflammatory, resolutive Th2 cells and FoxP3-positive regulatory T cells (Treg) were decreased. We observed an augmented PPARγ expression in CD4+ T cells of intensive care COVID-19 patients. Adapted from a next generation sequencing approach in Jurkat T cells, we found the chemoattractant receptor-homologous molecule expressed on T helper type 2 cells (CRTH2) as one gene regulated by PPARγ in T cells. This Th2 marker is a receptor for prostaglandin D and its metabolic degradation product 15-deoxy-∆12,14-prostaglandin J2 (15d-PGJ2), an established endogenous PPARγ agonist. In line, we observed an increased PPARγ transactivation in response to 15d-PGJ2 treatment in HEK293T cells overexpressing CRTH2. Translating these data to primary T cells, we found that Th2 differentiation was associated with an increased expression of CRTH2. Interestingly, these CRTH2+ T cells were prone to apoptosis.

Conclusion

These mechanistic data suggest an involvement of PPARγ in Th2 differentiation and T cell depletion in COVID-19 patients.

Association of Leukocyte Subpopulations Identified by Flow Cytometry with Outcomes of Sepsis in a Respiratory Intensive Care Unit: An Observational Study

INTRODUCTION

The dysregulated host immune response in sepsis is orchestrated by peripheral blood leukocytes. This study explored the associations of the peripheral blood leukocyte subpopulations with early clinical deterioration and mortality in sepsis.

METHODS

We performed a prospective observational single-center study enrolling adult subjects with sepsis within 48 h of hospital admission. Peripheral blood flow cytometry was performed for the patients at enrolment and after 5 days. The primary outcome was to explore the association between various leukocyte subpopulations at enrolment and early clinical deterioration [defined as an increase in the sequential organ failure assessment (SOFA) score between enrolment and day 5, or death before day 5]. Other pre-specified outcomes explored associations of leukocyte subpopulations at enrolment and on day 5 with in-hospital mortality.

RESULTS

A total of 100 patients, including 47 with septic shock were enrolled. The mean (SD) age of the patients was 53.99 (14.93) years. Among them, 26 patients had early clinical deterioration, whereas 41 died during hospitalization. There was no significant association between the leukocyte subpopulations at enrolment and early clinical deterioration on day 5. On multivariate logistic regression, a reduced percentage of CD8 + CD25+ T-cells at enrolment was associated with in-hospital mortality [odds ratio (OR), 0.82 (0.70-0.97); p-value = 0.02]. A reduced lymphocyte percentage on day 5 was associated with in-hospital mortality [OR, 0.28 (0.11-0.69); p-value = 0.01]. In a post-hoc analysis, patients with "very early" deterioration within 48 h had an increased granulocyte CD64 median fluorescent intensity (MFI) [OR, 1.07 (1.01-1.14); p-value = 0.02] and a reduced granulocyte CD16 MFI [OR, 0.97 (0.95-1.00); p-value = 0.04] at enrolment.

CONCLUSIONS

None of the leukocyte subpopulations showed an association with early clinical deterioration at day 5. Impaired lymphocyte activation and lymphocytopenia indicative of adaptive immune dysfunction may be associated with in-hospital mortality.

The protective effect of PPARγ in sepsis-induced acute lung injury via inhibiting PTEN/β-catenin pathway

The present study aims to reveal the molecular mechanism of peroxisome proliferator-activated receptor γ (PPARγ) on sepsis-induced acute lung injury (ALI). To do that, the rat injury model was established using cecal ligation and perforation (CLP) method, followed by different treatments, and the rats were divided into Sham group, CLP group, CLP + rosiglitazone (PPARγ agonist) group, CLP + GW9662 (PPARγ inhibitor) group, CLP + bpV (phosphatase and tensin homolog (PTEN) inhibitor) group, CLP + GW9662 + bpV group. Compared with Sham group, the mRNA and protein expression levels of PPARγ were down-regulated, the inflammation levels were elevated, and the apoptosis was increased in CLP group. After treatment with rosiglitazone, the protein expression level of PPARγ was significantly up-regulated, the phosphorylation level of PTEN/β-catenin pathway was decreased, the PTEN/β-catenin pathway was inhibited, the lung injury, inflammation and apoptosis were reduced. The opposite effect was observed after treatment with GW9662. Besides, bpV inhibited PTEN/β-catenin pathway, and relieved the lung tissue injury. The overexpression of PPARγ reduced inflammatory response and inhibited apoptosis in sepsis-induced ALI. Furthermore, PPARγ relieved the sepsis-induced ALI by inhibiting the PTEN/β-catenin pathway.

Apoptotic Diminution of Immature Single and Double Positive Thymocyte Subpopulations Contributes to Thymus Involution During Murine Polymicrobial Sepsis

To generate and maintain functional T-cell receptor diversity, thymocyte development is tightly organized. Errors in this process may have dramatic consequences, provoking, for example, autoimmune diseases. Probably for this reason, the thymus reacts to septic stress with involution, decreasing the numbers of thymocytes. Because it is still unclear which thymocyte subpopulation contributes to thymus involution and whether thymocyte emigration is altered, we were interested to clarify this question in detail. Here, we show, using the cecal ligation and puncture (CLP) mouse model of polymicrobial sepsis, that predominantly immature thymocytes are reduced. The number of immature single positive thymocytes was most marked diminished (CLP: 6.54 × 10 ± 3.79 × 10 vs. sham: 4.54 × 10 ± 7.66 × 10 cells/thymus [24 h], CLP: 2.60 × 10 ± 2.14 × 10 vs. sham: 2.17 × 10 ± 1.90 × 10 cells/thymus [48 h]), and was consequently associated with the highest rate of apoptosis (8.4 [CLP] vs. 2.2% [sham]), the reduction in double positive thymocytes being associated with a smaller apoptotic response (number, CLP: 2.33 × 10 ± 1.38 × 10 vs. sham: 1.07 × 10 ± 2.72 × 10 cells/thymus [24 h], CLP: 2.34 × 10 ± 9.08 × 10 vs. sham: 3.5 × 10 ± 9.62 × 10 cells/thymus [48 h]; apoptosis: 2.5% [CLP] vs. 0.7% [sham]). Analysis of T-cell receptor excision circles revealed that the emigration of mature thymocytes was not inhibited. Real-time qPCR analysis revealed upregulation of pro-apoptotic Bim expression and suggested interference between Notch receptor expression on thymocytes and the respective ligands on thymic stromal cells during CLP-dependent sepsis, which might be responsible for the altered thymocyte viability in CLP-dependent sepsis.