Th17/Regulatory T-Cell Imbalance and Acute Kidney Injury in Patients with Sepsis

CIRP increases Foxp3+ regulatory T cells and inhibits development of Th17 cells by enhancing TLR4-IL-2 signaling in the late phase of sepsis

BACKGROUND

T helper (Th) cell imbalances have been associated with the pathophysiology of sepsis, including the Th1/Th2 and Th17/T regulatory cells (Treg) paradigms. Cold-inducible RNA-binding protein (CIRP), a novel damage-associated molecular pattern (DAMP) was reported that could induce T cell activation, and skew CD4+ T cells towards a Th1 profile. However, the effect and underlying mechanisms of CIRP on Th17/Treg differentiation in sepsis still remains unknown.

METHODS

A prospective exploratory study including patients with sepsis was conducted. Blood samples were collected from patients on days 0, 3 and 7 on admission. The serum CIRP and peripheral blood Treg/Th17 percentage was determined by ELISA and flow cytometry. CD4+ T cells from the spleen and lymph nodes of mice with experimental sepsis were collected after treatment with normal saline (NS), recombinant murine CIRP (rmCIRP) and C23 (an antagonist for CIRP-TLR4) at late stage of sepsis. RNA-seq was conducted to reveal the pivotal molecular mechanism of CIRP on Treg/Th17 differentiation. Naïve CD4+ T cell was isolated from the Tlr4 null and wildtype mice in the presence or absence rmCIRP and C23 to confirmed above findings.

RESULTS

A total of 19 patients with sepsis finally completed the study. Serum CIRP levels remained high in the majority of patients up to 1 week after admittance was closely associated with high Treg/Th17 ratio of peripheral blood and poor outcome. A univariate logistic analysis demonstrated that higher CIRP concentration at Day 7 is an independent risk factor for Treg/Th17 ratio increasing. CIRP promotes Treg development and suppresses Th17 differentiation was found both in vivo and in vitro. Pretreated with C23 not only alleviated the majority of negative effect of CIRP on Th17 differentiation, but also inhibited Treg differentiation, to some extent. Tlr4 deficiency could abolish almost all downstream effects of rmCIRP. Furthermore, IL-2 is proved a key downstream molecules of the effect CIRP, which also could amplify the activated CD4+ T lymphocytes.

CONCLUSIONS

Persistent high circulating CIRP level may lead to Treg/Th17 ratio elevated through TLR4 and subsequent active IL-2 signaling which contribute to immunosuppression during late phases of sepsis.

Th17/Treg balance: the bloom and wane in the pathophysiology of sepsis

Sepsis is a multi-organ dysfunction characterized by an unregulated host response to infection. It is associated with high morbidity, rapid disease progression, and high mortality. Current therapies mainly focus on symptomatic treatment, such as blood volume supplementation and antibiotic use, but their effectiveness is limited. Th17/Treg balance, based on its inflammatory property, plays a crucial role in determining the direction of the inflammatory response and the regression of organ damage in sepsis patients. This review provides a summary of the changes in T-helper (Th) 17 cell and regulatory T (Treg) cell differentiation and function during sepsis, the heterogeneity of Th17/Treg balance in the inflammatory response, and the relationship between Th17/Treg balance and organ damage. Th17/Treg balance exerts significant control over the bloom and wanes in host inflammatory response throughout sepsis.

The suppression of sepsis-induced kidney injury via the knockout of T lymphocytes

Patients with sepsis always have a high mortality rate, and acute kidney injury (AKI) is the main cause of death. It seems obvious that the immune response is involved in this process, but the specific mechanism is unknown, especially the pathogenic role of T cells and B cells needs to be further clarified. Acute kidney injury models induced by lipopolysaccharide were established using T-cell, B-cell, and T&B cell knockout mice to elucidate the role of immune cells in sepsis. Flow cytometry was used to validate the mouse models, and the pathology can confirm renal tubular injury. LPS-induced sepsis caused significant renal pathological damage, Second-generation gene sequencing showed T cells-associated pathway was enriched in sepsis. The renal tubular injury was significantly reduced in T cell and T&B cell knockout mice (BALB/c-nu, Rag1-/-), especially in BALB/c-nu mice, with a decrease in the secretion of inflammatory cytokines in the renal tissue after LPS injection. LPS injection did not produce the same effect after the knockout of B cells. We found that blocking T cells could alleviate inflammation and renal injury caused by sepsis, providing a promising strategy for controlling renal injury.

Identification of Cell-Cell Communications by Single-Cell RNA Sequencing in End Stage Renal Disease Provides New Insights into Immune Cell Heterogeneity

Objective

Impaired immune system characterized by low-grade inflammation is closely associated with kidney chronic kidney disease (CKD) progression. To reveal the alterations of the function, component, and intercellular communication of immune cells during the progression of CKD.

Patients and Methods

We conducted a case-control study enrolling regular hemodialysis patients and healthy controls. Clinical data, serum and peripheral blood mononuclear cell (PBMC) samples were collected. Flow cytometry and single-cell RNA sequencing were performed to quantitatively analyze the immune cell subsets and T-cell subsets of PBMCs. scRNA data of GSE140023 containing mouse unilateral ureteral obstruction (UUO) models were analyzed the heterogeneity of immune cells.

Results

Overall reduction in peripheral blood lymphocyte subsets in patients with end-stage renal disease (ESRD) was observed. A higher ratio of Th17/Treg, Th1/Treg, and b-cell/Treg in the ESRD group was associated with a decrease in eGFR, PTH, and ferritin. Among T cell subsets identified by scRNA analysis, Th17 cells were significantly increased in the ESRD and UU0 group. TFH, Th1, and Th2 cells are located at the final stage in the developmental tree, while Treg and memory CD8+ T cells are at the beginning site. Early developmental differentiation of Th17, Th1, and Tfh cells was observed in the ESRD and UUO group. Analysis of intercellular communication between t-cell subpopulations identified two major input and output signaling pathways: the CD40 and macrophage inhibitory factor (MIF) pathways. The MIF signaling pathway primarily mediates intercellular communication among th17 effects, CD8+ t-cell, and Th17-Treg in the ESRD group, the serum level of MIF showed significant upregulation, which was closely related to Th17/Treg cells.

Conclusions

A global immune imbalance was closely associated with the deterioration in renal function and complication development. The MIF signaling pathway mediates Th17/Treg communication and promotes the trans-differentiation of Treg cells to Th17 cells in CKD progression.

Protective role of the novel cytokine Metrnl/ interleukin-41 in host immunity defense during sepsis by promoting macrophage recruitment and modulating Treg/Th17 immune cell balance

BACKGROUND

Metrnl play an immunocytokine-like role in several diseases, which is also known as meteorin-like because it is homologous to the neurotrophic factor meteorin (Metrn). Although the expression and function of Metrnl, including neurotrophic, immunomodulatory, and insulin resistance functions in different tissues have been extensively studied, its role in sepsis has remained largely limited.

METHODS

The present work analyzed the levels of Metrnl and cytokines in the circulation, such as tumor necrosis factor (TNF-α), interleukin (IL-1)β, IL-6, IL-8, together with IL-10 among septic adult patients. Clinical information was obtained from such patients, including sofa score, procalcitonin(PCT)count, and C-reactive count (CRP) within 24 h when entering the intensive care unit (ICU). We constructed a sepsis model in Metrnl-deficient or normal wild-type mice using cecal ligation and perforation to study its functions in bacterial burden, survival, cytokine/chemokine generation, peritoneal lavage fluid neutrophils, macrophage and lymphocyte recruitment, and Treg/Th17 immune cell balance after CLP-induced sepsis.

RESULTS

The expression of Metrnl was remarkably elevated in the early phase of sepsis clinically. Its serum content in patients dying of sepsis slightly decreased relative to that in survivors. Furthermore, the concentration of Metrnl in septic cases when entering the ICU independently predicted the 28-day mortality. For septic patients who had low serum Metrnl content (≤ 274.40 pg/mL), the death risk increased by 2.3 folds relative to those who had a high serum content. It is reported that Metrnl is probably insufficient among patients dying of sepsis. Additionally, the content of Metrnl in the serum of septic patients when entering the ICU is markedly and negatively related to the levels of TNF-α, IL-1β, IL-6, IL-8, IL-17, PCT, and Sofa score. Collectively, Metrnl could be a potential therapeutic target for sepsis. A low-lethality non-severe sepsis (NSS) model was constructed, which suggested that Metrnl insufficiency elevated the death rate and reduced bacterial clearance during sepsis. For Metrnl-deficient mice, impaired sepsis immunity defense might be related to decreased macrophage recruitment and Treg/Th17 lymphocyte imbalance. Recombinant Metrnl administered to Metrnl-deficient mice abolished the immunity defense impairment following NSS while protecting the high-lethality severe sepsis (SS) model in wild-type (WT) mice. In addition, Metrnl-induced sepsis prevention was intricately associated with the increased recruitment of peritoneal macrophages and modulation of the Treg/TH17 immune cell balance. Furthermore, CCL3 exposure in Metrnl-deficient mice reduced peritoneal bacterial loads while improving survival during sepsis partially by promoting the recruitment of peritoneal macrophages. Furthermore, Metrnl regulated the polarization of M1 macrophages through the ROS signaling pathway and promoted macrophage phagocytosis, thereby killing Escherichia coli.

CONCLUSIONS

The present proof-of-concept work suggests that Metrnl-mediated recruitment of macrophages significantly affects sepsis defense in the host and modulates the Treg/Th17 immune cell balance. Findings in this work shed more light on the development of host-directed treatments that can be used to manipulate host immunity to treat sepsis.

Fecal Microbiota Transplantation in Reducing Uremic Toxins Accumulation in Kidney Disease: Current Understanding and Future Perspectives

During the past decades, the gut microbiome emerged as a key player in kidney disease. Dysbiosis-related uremic toxins together with pro-inflammatory mediators are the main factors in a deteriorating kidney function. The toxicity of uremic compounds has been well-documented in a plethora of pathophysiological mechanisms in kidney disease, such as cardiovascular injury (CVI), metabolic dysfunction, and inflammation. Accumulating data on the detrimental effect of uremic solutes in kidney disease supported the development of many strategies to restore eubiosis. Fecal microbiota transplantation (FMT) spread as an encouraging treatment for different dysbiosis-associated disorders. In this scenario, flourishing studies indicate that fecal transplantation could represent a novel treatment to reduce the uremic toxins accumulation. Here, we present the state-of-the-art concerning the application of FMT on kidney disease to restore eubiosis and reverse the retention of uremic toxins.