Dietary sodium modulates mTORC1-dependent trained immunity in macrophages to accelerate CKD development

Chronic Kidney Disease (CKD) is a significant global health issue linked to dietary habits, especially high salt intake. However, the precise mechanisms driving this progression remain incompletely understood. This study reveals that a high-salt diet intensifies macrophage trained immunity, leading to a marked pro-inflammatory response upon repeated pathogenic exposures, as evidenced by increased renal damage and fibrosis. Under high-salt conditions, there was an induction of CD45+F4/80+ macrophage infiltration into the renal tissue, accompanied by heightened production of inflammatory cytokines. Distinct responses were observed between circulating and resident renal macrophages to a high-salt diet, with a notable upsurge in the migration of pro-inflammatory macrophages, driven by CCL2-CCR2 signaling and aberrant mTORC1 pathway activation. Treatment with rapamycin-liposome effectively reduced this inflammatory cascade by mitigating mTORC1 signaling. Transplantation of monocytes from CKD mice with a high-salt diet significantly exacerbates renal inflammatory damage in the host mice, showing increased migratory tendency and inflammatory activity. The cell co-culture experiment further confirmed that macrophages derived from CKD mice, particularly those under conditions of high salt exposure, significantly induced apoptosis and inflammatory responses in renal tubular cells. Taken together, recurrent exposure to LPS elicits the activation of trained immunity, consequently augmenting inflammatory response of monocytes/macrophages in the involved kidneys. The high-salt diet exacerbates this phenomenon, attributable at least in part to the overactivation of the mTORC1 pathway. This research emphasizes the importance of dietary modulation and targeted immunological interventions in slowing CKD progression, providing new insights into mTORC1-mediated pathophysiological mechanisms and potential management strategies for CKD.

Lymphocytes and innate immune cells in acute kidney injury and repair

Acute kidney injury (AKI) is a common and serious disease entity that affects native kidneys and allografts but for which no specific treatments exist. Complex intrarenal inflammatory processes driven by lymphocytes and innate immune cells have key roles in the development and progression of AKI. Many studies have focused on prevention of early injury in AKI. However, most patients with AKI present after injury is already established. Increasing research is therefore focusing on mechanisms of renal repair following AKI and prevention of progression from AKI to chronic kidney disease. CD4+ and CD8+ T cells, B cells and neutrophils are probably involved in the development and progression of AKI, whereas regulatory T cells, double-negative T cells and type 2 innate lymphoid cells have protective roles. Several immune cells, such as macrophages and natural killer T cells, can have both deleterious and protective effects, depending on their subtype and/or the stage of AKI. The immune system not only participates in injury and repair processes during AKI but also has a role in mediating AKI-induced distant organ dysfunction. Targeted manipulation of immune cells is a promising therapeutic strategy to improve AKI outcomes.

A novel bacterium-like particles platform displaying antigens by new anchoring proteins induces efficacious immune responses

Bacterium-like particles (BLP) are the peptidoglycan skeleton particles of lactic acid bacteria, which have high safety, mucosal delivery efficiency, and adjuvant effect. It has been widely used in recent years in the development of vaccines. Existing anchoring proteins for BLP surfaces are few in number, so screening and characterization of new anchoring proteins are necessary. In this research, we created the OACD (C-terminal domain of Escherichia coli outer membrane protein A) to serve as an anchoring protein on the surface of BLP produced by the immunomodulatory bacteria Levilactobacillus brevis 23017. We used red fluorescent protein (RFP) to demonstrate the novel surface display system's effectiveness, stability, and ability to be adapted to a wide range of lactic acid bacteria. Furthermore, this study employed this surface display method to develop a novel vaccine (called COB17) by using the multi-epitope antigen of Clostridium perfringens as the model antigen. The vaccine can induce more than 50% protection rate against C. perfringens type A challenge in mice immunized with a single dose and has been tested through three routes. The vaccine yields protection rates of 75% for subcutaneous, 50% for intranasal, and 75% for oral immunization. Additionally, it elicits a strong mucosal immune response, markedly increasing levels of specific IgG, high-affinity IgG, specific IgA, and SIgA antibodies. Additionally, we used protein anchors (PA) and OACD simultaneous to show several antigens on the BLP surface. The discovery of novel BLP anchoring proteins may expand the possibilities for creating mucosal immunity subunit vaccines. Additionally, it may work in concert with PA to provide concepts for the creation of multivalent or multiple vaccines that may be used in clinical practice to treat complex illnesses.

Enhanced STAT3/PIK3R1/mTOR signaling triggers tubular cell inflammation and apoptosis in septic-induced acute kidney injury: implications for therapeutic intervention

Septic acute kidney injury (AKI) is a severe form of renal dysfunction associated with high morbidity and mortality rates. However, the pathophysiological mechanisms underlying septic AKI remain incompletely understood. Herein, we investigated the signaling pathways involved in septic AKI using the mouse models of lipopolysaccharide (LPS) treatment and cecal ligation and puncture (CLP). In these models, renal inflammation and tubular cell apoptosis were accompanied by the aberrant activation of the mechanistic target of rapamycin (mTOR) and the signal transducer and activator of transcription 3 (STAT3) signaling pathways. Pharmacological inhibition of either mTOR or STAT3 significantly improved renal function and reduced apoptosis and inflammation. Interestingly, inhibition of STAT3 with pharmacological inhibitors or small interfering RNA blocked LPS-induced mTOR activation in renal tubular cells, indicating a role of STAT3 in mTOR activation. Moreover, knockdown of STAT3 reduced the expression of the phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1/p85α), a key subunit of the phosphatidylinositol 3-kinase for AKT and mTOR activation. Chromatin immunoprecipitation assay also proved the binding of STAT3 to PIK3R1 gene promoter in LPS-treated kidney tubular cells. In addition, knockdown of PIK3R1 suppressed mTOR activation during LPS treatment. These findings highlight the dysregulation of mTOR and STAT3 pathways as critical mechanisms underlying the inflammatory and apoptotic phenotypes observed in renal tubular cells during septic AKI, suggesting the STAT3/ PIK3R1/mTOR pathway as a therapeutic target of septic AKI.

Renal function at 12 months of kidney transplantation comparing tacrolimus and mycophenolate with tacrolimus and mTORi in donors with different KDPI ranges. A multicenter cohort study using propensity scoring

Introduction

The combination of tacrolimus/mTORi compared to tacrolimus/mycophenolate (MMF) was shown to be safe in the TRANSFORM trial. For donors with a high KDPI (Kidney Donor Profile Index), however, there are no data to support the effectiveness of this regimen. The main objective of this study was to explore the influence of the KDPI on 12-month renal function (eGFR) in patients receiving mTORi or MMF.

Methods

Multicenter cohort study of four Brazilian services that use the tacrolimus with mTORi as a protocol. Data from 2008 to 2018 of the tacrolimus/mycophenolate (MMF) and tacrolimus/mTORi (mTORi) regimens in renal transplant recipients over 18 years old were collected. For better homogeneity, the propensity score was used. Afterward, the method used for group selection ("match") was the K-nearest neighbor (KNN) method. New analyses were performed on this new balanced sample, and two different subsamples were constituted based on the median KDPI.

Results

The global analysis (n = 870) showed that the major determinant of worse kidney function was high KDPI. Afterward, the three strata were analyzed. In the first stratum (KDPI up to 50), 242 patients were evaluated, with 121 in each group. The eGFR was 64 ml/min/1.73 m2 in the mTORi group compared to 63 in the MMF group, p = 0.4, and when imputed eGFR was evaluated, 61 in the mTORi and 53 in the MMF, p = 0.065. In the second stratum (KDPI from 50 to 85), 282 patients were evaluated, with 141 in each group. eGFR was 46 ml/min/1.73 m2 in mTORi compared to 48 in MMF, p = 0.4, and when imputed eGFR was evaluated, 40 mTORi and 41 MMF, p = 0.8. In the last stratum (KDPI higher than 85) with n = 126 and 63 cases per group, eGFR was 36 ml/min/1.73 m2 in mTORi compared to 39 in MMF, p = 0.2, and when imputed eGFR was evaluated, 30 mTORi and 34 MMF, p = 0.2.

Discussion

The regimen using mTOR inhibitor is an effective and safe regimen when compared to the standard regimen. In addition, the scheme seems to offer additional protection against infections and may be an important ally in cases of high risk for these pathologies.

The kinetics of mTORC1 activation associates with FOXP3 expression pattern of CD4+ T cells and outcome of steroid-sensitive minimal change disease

Minimal change disease (MCD) usually responds to glucocorticoids (GCs) but relapses in most cases. Relapse pathogenesis after complete remission (CR) remains unclear. We hypothesized that FOXP3+ T regulatory cell (Treg) dysregulation may drive early relapses (ER). In this study, a cohort of 23 MCD patients were treated with a conventional GC regimen for the initial onset of nephrotic syndrome. Upon GC withdrawal, seven patients suffered from ER, while 16 patients sustained remission (SR) during the 12-month follow-up. Patients with ER had reduced FOXP3+ Treg proportions compared with healthy controls. Treg reduction, accompanied by IL-10 impairment, was ascribed to a proportional decline of FOXP3medium rather than FOXP3high cells. GC-induced CR was marked by a rise in the proportions of FOXP3+ and FOXP3medium cells compared to baseline levels. These increases declined in patients with ER. The expression level of phosphorylated ribosomal protein S6 was used to track the dynamic shifts in mTORC1 activity within CD4+ T cells of MCD patients at various stages of treatment. Baseline mTORC1 activity was inversely correlated with FOXP3+ and FOXP3medium Treg proportion. The mTORC1 activity in CD4+ T cells served as a reliable indicator for ER and demonstrated improved performance when paired with FOXP3 expression. Mechanically, targeting mTORC1 intervention by siRNAs sufficiently altered the conversion pattern of CD4+ T cell to FOXP3+ Treg. Taken together, the activity of mTORC1 in CD4+ T cells can act as a credible predictor for ER in MCD, especially when combined with FOXP3 expression, and may offer a potential therapeutic avenue for the treatment of podocytopathies.

Glucocorticoid regulation of the mTORC1 pathway modulates CD4+ T cell responses during infection

Objectives

Conventional glucocorticoid (GC) treatment poses significant risks for opportunistic infections due to its suppressive impact on CD4+ T cells. This study aimed to explore the mechanisms by which GCs modulate the functionality of CD4+ T cells during infection.

Methods

We consistently measured FOXP3, inflammatory cytokines and phospho-S6 ribosomal protein levels in CD4+ T cells from patients undergoing conventional GC treatment. Using Foxp3EGFP animals, we investigated the dynamic activation of the mechanistic target of rapamycin complex 1 (mTORC1) pathway and its correlation with the immunoregulatory function of CD4+ T cells under the influence of GCs.

Results

GCs dynamically altered the expression pattern of FOXP3 in CD4+ T cells, promoting their acquisition of an active T regulatory (Treg) cell phenotype upon stimulation. Mechanistically, GCs undermined the kinetics of the mTORC1 pathway, which was closely correlated with phenotype conversion and functional properties of CD4+ T cells. Dynamic activation of the mTORC1 signaling modified the GC-dampened immunoregulatory capacity of CD4+ T cells by phenotypically and functionally bolstering the FOXP3+ Treg cells. Interventions targeting the mTORC1 pathway effectively modulated the GC-dampened immunoregulatory capacity of CD4+ T cells.

Conclusion

These findings highlight a novel mTORC1-mediated mechanism underlying CD4+ T cell immunity in the context of conventional GC treatment.

Immunometabolism changes in fibrosis: from mechanisms to therapeutic strategies

Immune cells are essential for initiating and developing the fibrotic process by releasing cytokines and growth factors that activate fibroblasts and promote extracellular matrix deposition. Immunometabolism describes how metabolic alterations affect the function of immune cells and how inflammation and immune responses regulate systemic metabolism. The disturbed immune cell function and their interactions with other cells in the tissue microenvironment lead to the origin and advancement of fibrosis. Understanding the dysregulated metabolic alterations and interactions between fibroblasts and the immune cells is critical for providing new therapeutic targets for fibrosis. This review provides an overview of recent advances in the pathophysiology of fibrosis from the immunometabolism aspect, highlighting the altered metabolic pathways in critical immune cell populations and the impact of inflammation on fibroblast metabolism during the development of fibrosis. We also discuss how this knowledge could be leveraged to develop novel therapeutic strategies for treating fibrotic diseases.

Activation of CD3+TIM3+ T Cells Contributes to Excessive Inflammatory Response During Glucocorticoid Treatment

Glucocorticoids (GCs) are widely used to treat autoimmune and inflammatory diseases, but recent research has challenged the notion that GCs are universally anti-inflammatory. In this study, we investigated the effects of long-term GC exposure on circulating T cells in a retrospective cohort of 5,476 patients with primary glomerular diseases. Our results revealed that GCs altered the composition pattern of circulating leukocytes and the correlation between circulating lymphocytes and serum cytokines in response to infections, as well as the subsets of CD4+ T cells. Specifically, GCs promoted the loss of CD4+ T cells and increased the proportions of CD3+TIM3+ T cells in response to infections, which correlated with the expression of serum inflammatory cytokines, such as IFNG and IL-10. Using animal models of cecal ligation and puncture, we demonstrated that long-term GC exposure exacerbated apoptosis of CD4+ T cells and cytokine storm during sepsis, which was mechanistically linked to the increase of CD3+TIM3+ T cells. Notably, we found that CD3+TIM3+ T cells expressed high levels of multiple cytokine genes during infections, suggesting a potent role of TIM3 in the regulation of T cell biology. In vitro studies further showed that engagement of anti-TIM3 treatment enhanced the inflammatory activity of CD3+ T cells. Our findings suggest a causal relationship between chronic exposure to GCs and an excessive inflammatory response mediated by T cells during infections, which is, at least partly, driven by dysregulation of CD3+TIM3+ T cells.

Long-term glucocorticoid exposure persistently impairs CD4+ T cell biology by epigenetically modulating the mTORC1 pathway

Conventional glucocorticoid (GC) treatment has a long-term influence on T-cell immunity, resulting in an increased risk of opportunistic infection after drug withdrawal. The underlying mechanisms remain ambiguous. This study demonstrated that long-term GC treatment induced persistent lymphopenia in patients with primary glomerular disease. GCs continuously suppressed the proportion of CD4+ T cells even after the daily dose was tapered down to the physiologic equivalences, leading to a significant decline of the CD4/CD8 ratio. Meanwhile, GCs impaired CD4+ T cell biology, leading to enhanced apoptotic cell death, reduced proliferative capacity, downregulated pro-inflammatory genes, and upregulated immunoregulatory genes. Specifically, GCs altered FOXP3 expression pattern in CD4+ T cells and favored their acquisition of an active T regulatory (Treg) cell phenotype with enhanced IL-10 production upon stimulation. Mechanistically, GCs tampered with the transcriptional regulation of mechanistic target of rapamycin complex 1 (mTORC1) pathway, resulting in an inhibitory impact on the signaling activity. Targeting mTORC1 signaling by siRNAs could sufficiently modify the viability of GC-exposed CD4+ T cells. By high-throughput sequencing of genome-wide DNA methylation and mRNA, we further uncovered a causal relationship between the altered DNA methylation level and transcription activity in a subset of mTORC1 pathway genes in long-term GC exposure. Taken together, this study reveals a novel regulation of mTORC1 signaling, which might dominate the long-term influence of GC on CD4+ T cell biology in a dose-independent manner.

Role of T cells in ischemic acute kidney injury and repair

Ischemic acute kidney injury (AKI) is a common medical problem with significant mortality and morbidity, affecting a large number of patients globally. Ischemic AKI is associated with intrarenal inflammation as well as systemic inflammation; thus, the innate and adaptive immune systems are implicated in the pathogenesis of ischemic AKI. Among various intrarenal immune cells, T cells play major roles in the injury process and in the repair mechanism affecting AKI to chronic kidney disease transition. Importantly, T cells also participate in distant organ crosstalk during AKI, which affects the overall outcomes. Therefore, targeting T cell-mediated pathways and T cell-based therapies have therapeutic promise for ischemic AKI. Here, we review the major populations of kidney T cells and their roles in ischemic AKI.

Lymphocytes: Versatile Participants in Acute Kidney Injury and Progression to Chronic Kidney Disease

Background: Acute kidney injury (AKI) remains a major global public health concern due to its high morbidity and mortality. The progression from AKI to chronic kidney disease (CKD) makes it a scientific problem to be solved. However, it is with lack of effective treatments. Summary: Both innate and adaptive immune systems participate in the inflammatory process during AKI, and excessive or dysregulated immune responses play a pathogenic role in renal fibrosis, which is an important hallmark of CKD. Studies on the pathogenesis of AKI and CKD have clarified that renal injury induces the production of various chemokines by renal parenchyma cells or resident immune cells, which recruits multiple-subtype lymphocytes in circulation. Some infiltrated lymphocytes exacerbate injury by proinflammatory cytokine production, cytotoxicity, and interaction with renal resident cells, which constructs the inflammatory environment and induces further injury, even death of renal parenchyma cells. Others promote tissue repair by producing protective cytokines. In this review, we outline the diversity of these lymphocytes and their mechanisms to regulate the whole pathogenic stages of AKI and CKD; discuss the chronological responses and the plasticity of lymphocytes related to AKI and CKD progression; and introduce the potential therapies targeting lymphocytes of AKI and CKD, including the interventions of chemokines, cytokines, and lymphocyte frequency regulation in vivo, adaptive transfer of ex-expanded lymphocytes, and the treatments of gut microbiota or metabolite regulations based on gut-kidney axis. Key Message: In the process of AKI and CKD, T helper (Th) cells, innate, and innate-like lymphocytes exert mainly pathogenic roles, while double-negative T (DNT) cells and regulatory T cells (Tregs) are confirmed to be protective. Understanding the mechanisms by which lymphocytes mediate renal injury and renal fibrosis is necessary to promote the development of specific therapeutic strategies to protect from AKI and prevent the progression of CKD.

Mesenchymal Stem Cell Protects Injured Renal Tubular Epithelial Cells by Regulating mTOR-Mediated Th17/Treg Axis

The increase in T helper 17 cell (Th17)-mediated pro-inflammatory response and decrease in regulatory T cell (Treg)-mediated anti-inflammatory effect aggravate renal tubular epithelial cell (RTEC) injury. However, increasing evidence indicated that mesenchymal stem cell (MSC) possessed the ability to control the imbalance between Th17 and Treg. Given that Th17 and Treg are derived from a common CD4⁺ T cell precursor, we summarize the current knowledge of MSC-mediated inhibition of the mammalian target of rapamycin (mTOR), which is a master regulator of CD4⁺ T cell polarization. During CD4⁺ T cell differentiation, mTOR signaling mediates Th17 and Treg differentiation via hypoxia-inducible factor-1α (HIF-1α)-dependent metabolic regulation and signaling pathway, as well as mTOR-mediated phosphorylation of signal transducer and activator of transcription (STAT) 3 and 5. Through interfering with mTOR signaling, MSC restrains CD4⁺ T cell differentiation into Th17, but in turn promotes Treg generation. Thus, this review indicates that MSC-mediated Th17-to-Treg polarization is expected to act as new immunotherapy for kidney injury.

Rapamycin Alternatively Modifies Mitochondrial Dynamics in Dendritic Cells to Reduce Kidney Ischemic Reperfusion Injury

Dendritic cells (DCs) are unique immune cells that can link innate and adaptive immune responses and Immunometabolism greatly impacts their phenotype. Rapamycin is a macrolide compound that has immunosuppressant functions and is used to prevent graft loss in kidney transplantation. The current study evaluated the therapeutic potential of ex-vivo rapamycin treated DCs to protect kidneys in a mouse model of acute kidney injury (AKI). For the rapamycin single (S) treatment (Rapa-S-DC), Veh-DCs were treated with rapamycin (10 ng/mL) for 1 h before LPS. In contrast, rapamycin multiple (M) treatment (Rapa-M-DC) were exposed to 3 treatments over 7 days. Only multiple ex-vivo rapamycin treatments of DCs induced a persistent reprogramming of mitochondrial metabolism. These DCs had 18-fold more mitochondria, had almost 4-fold higher oxygen consumption rates, and produced more ATP compared to Veh-DCs (Veh treated control DCs). Pathway analysis showed IL10 signaling as a major contributing pathway to the altered immunophenotype after Rapamycin treatment compared to vehicle with significantly lower cytokines Tnfa, Il1b, and Il6, while regulators of mitochondrial content Pgc1a, Tfam, and Ho1 remained elevated. Critically, adoptive transfer of rapamycin-treated DCs to WT recipients 24 h before bilateral kidney ischemia significantly protected the kidneys from injury with a significant 3-fold improvement in kidney function. Last, the infusion of DCs containing higher mitochondria numbers (treated ex-vivo with healthy isolated mitochondria (10 µg/mL) one day before) also partially protected the kidneys from IRI. These studies demonstrate that pre-emptive infusion of ex-vivo reprogrammed DCs that have higher mitochondria content has therapeutic capacity to induce an anti-inflammatory regulatory phenotype to protect kidneys from injury.

Targeting immune cell metabolism in kidney diseases

Insights into the relationship between immunometabolism and inflammation have enabled the targeting of several immunity-mediated inflammatory processes that underlie infectious diseases and cancer or drive transplant rejection, but this field remains largely unexplored in kidney diseases. The kidneys comprise heterogeneous cell populations, contain distinct microenvironments such as areas of hypoxia and hypersalinity, and are responsible for a functional triad of filtration, reabsorption and secretion. These distinctive features create myriad potential metabolic therapeutic targets in the kidney. Immune cells have crucial roles in the maintenance of kidney homeostasis and in the response to kidney injury, and their function is intricately connected to their metabolic properties. Changes in nutrient availability and biomolecules, such as cytokines, growth factors and hormones, initiate cellular signalling events that involve energy-sensing molecules and other metabolism-related proteins to coordinate immune cell differentiation, activation and function. Disruption of homeostasis promptly triggers the metabolic reorganization of kidney immune and non-immune cells, which can promote inflammation and tissue damage. The metabolic differences between kidney and immune cells offer an opportunity to specifically target immunometabolism in the kidney.

DNA Methylation Sustains "Inflamed" Memory of Peripheral Immune Cells Aggravating Kidney Inflammatory Response in Chronic Kidney Disease

The incidence of chronic kidney disease (CKD) has rapidly increased in the past decades. A progressive loss of kidney function characterizes a part of CKD even with intensive supportive treatment. Irrespective of its etiology, CKD progression is generally accompanied with the development of chronic kidney inflammation that is pathologically featured by the low-grade but chronic activation of recruited immune cells. Cumulative evidence support that aberrant DNA methylation pattern of diverse peripheral immune cells, including T cells and monocytes, is closely associated with CKD development in many chronic disease settings. The change of DNA methylation profile can sustain for a long time and affect the future genes expression in the circulating immune cells even after they migrate from the circulation into the involved kidney. It is of clinical interest to reveal the underlying mechanism of how altered DNA methylation regulates the intensity and the time length of the inflammatory response in the recruited effector cells. We and others recently demonstrated that altered DNA methylation occurs in peripheral immune cells and profoundly contributes to CKD development in systemic chronic diseases, such as diabetes and hypertension. This review will summarize the current findings about the influence of aberrant DNA methylation on circulating immune cells and how it potentially determines the outcome of CKD.

mTOR Signaling in Kidney Diseases

The mammalian target of rapamycin (mTOR), a serine/threonine protein kinase, is crucial in regulating cell growth, metabolism, proliferation, and survival. Under physiologic conditions, mTOR signaling maintains podocyte and tubular cell homeostasis. In AKI, activation of mTOR signaling in tubular cells and interstitial fibroblasts promotes renal regeneration and repair. However, constitutive activation of mTOR signaling in kidneys results in the initiation and progression of glomerular hypertrophy, interstitial fibrosis, polycystic kidney disease, and renal cell carcinoma. Here, we summarize the recent studies about mTOR signaling in renal physiology and injury, and discuss the possibility of its use as a therapeutic target for kidney diseases.

Autophagy and Inflammation Regulation in Acute Kidney Injury

Autophagy at an appropriate juncture in the cell cycle exerts protective effects in acute kidney injury (AKI), whereas abnormal autophagy may lead to cell death. Inflammatory response plays a pivotal role in the pathophysiological process of kidney injury and repair during AKI. Several studies have reported an interaction between autophagy and inflammation in the pathogenesis of AKI. This review outlines recent advances in the investigation of the role of autophagy in inflammatory response regulation based on the following aspects. (1) Autophagy inhibits inflammatory responses induced in AKI through the regulation of mTOR and AMPK pathways and the inhibition of inflammasomes activation. (2) Autophagy can also help in the regulation of inflammatory responses through the nuclear factor kappa B pathway, which is beneficial to the recovery of kidney tissues. These studies reviewed here provide better insight into the mechanisms underlying the protective effects of the autophagy-inflammatory pathway. Through this review, we suggest that the autophagy-inflammatory pathway may serve as an alternative target for the treatment of AKI.

Acute kidney injury during pregnancy leads to increased sFlt-1 and sEng and decreased renal T regulatory cells in pregnant rats with HELLP syndrome

BACKGROUND

The incidence of acute kidney injury (AKI) during pregnancy precedes a high maternal mortality rate of 20-40%. AKI during pregnancy has multiple etiologies; however, the more common are maternal hypertensive disorders, which include preeclampsia and HELLP (hemolysis, elevated liver enzyme, low platelet) syndrome. Therefore, we sought to assess the impact of AKI on blood pressure, kidney injury, and anti-angiogenic factors during pregnancies with and without HELLP syndrome.

METHODS

On gestational day (GD) 12, mini-osmotic pumps were inserted into a subset of normal pregnant (NP) rats infusing 4.7 μg/kg soluble fms-like tyrosine kinase-1 (sFlt-1) and 7 μg/kg soluble endoglin (sEng) to induce HELLP syndrome. On GD18, the renal pedicles were occluded for 45 min to induce AKI via bilateral ischemia reperfusion in a subset of NP (n = 18) or HELLP (n = 20) rats. Control NP (n = 20) and HELLP (n = 20) rats underwent a SHAM surgery on GD18. Plasma, urine, and maternal organs were saved for further analysis. Renal injury was assessed via renal histopathology, glomerular filtration rate (GFR), T cell infiltration, and assessment of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). Data was measured via two-way analysis of variance with Tukey's test for post hoc analysis.

RESULTS

Blood pressures were increased in HELLP+AKI rats (p = 0.0001); both NP+AKI and HELLP+AKI rats had increased lactate dehydrogenase (p < 0.0001) and aspartate aminotransferase levels (p < 0.0001), and decreased platelet levels (p < 0.001) vs. NP rats. HELLP+AKI (p = 0.002) and HELLP rats (p = 0.0002) had evidence of renal fibrosis vs. NP rats. GFR was decreased in HELLP+AKI (p = 0.01) rats vs. NP rats. Urinary KIM-1 was increased in NP+AKI rats vs. NP (p = 0.003) and HELLP rats (p = 0.01). HELLP+AKI rats had increased urinary KIM-1 vs. NP (p = 0.0008) and HELLP rats (p = 0.004) and increased NGAL vs. HELLP rats (p = 0.002). HELLP+AKI rats had increased sFlt-1 (p = 0.009) vs. NP rats. NP+AKI (p = 0.02) and HELLP+AKI (p = 0.007) rats had increased sEng vs. NP rats. CD3+CD4+ T cells were significantly increased in HELLP+AKI rats vs. NP (p = 0.0002) and NP+AKI (p = 0.05) rats. T regulatory cells were significantly decreased in HELLP+AKI (p = 0.03) and NP+AKI (p = 0.02) rats vs. NP rats; there were no changes between groups in T helper 17 cells (p = 0.34).

CONCLUSION

The findings in this study suggest that AKI during pregnancy contributes to increased blood pressure and biochemical markers for HELLP syndrome, creates an anti-angiogenic imbalance, and exacerbates kidney injury as shown on histopathology, GFR, and kidney injury markers.

The Roles of Immune Cells in the Pathogenesis of Fibrosis

Tissue injury and inflammatory response trigger the development of fibrosis in various diseases. It has been recognized that both innate and adaptive immune cells are important players with multifaceted functions in fibrogenesis. The activated immune cells produce various cytokines, modulate the differentiation and functions of myofibroblasts via diverse molecular mechanisms, and regulate fibrotic development. The immune cells exhibit differential functions during different stages of fibrotic diseases. In this review, we summarized recent advances in understanding the roles of immune cells in regulating fibrotic development and immune-based therapies in different disorders and discuss the underlying molecular mechanisms with a focus on mTOR and JAK-STAT signaling pathways.

T Cells and Acute Kidney Injury: A Two-Way Relationship

Acute Kidney Injury (AKI) complicates up to 10% of hospital admissions substantially increasing patient morbidity and mortality. Experimental evidence supports that AKI initiation and maintenance results from immune-mediated damage. Exogenous injury sources directly damage renal cells which produce pro-inflammatory mediators recruiting immune cells and furthering kidney injury. Many AKI studies focus on activation of innate immunity; major components include complement pathways, neutrophils, and monocytes. Recently, growing evidence emphasizes T lymphocytes role in affecting AKI pathogenesis and magnitude. In particular, T helper 17 lymphocytes enhance tissue injury by recruiting neutrophils and other inflammatory cells, while regulatory T cells conversely reduce renal injury and facilitate repair. Intriguingly, evidence supports local parenchymal-T cell interactions as essential to producing T cell phenotypic changes affecting long-term kidney and patient survival. Herein, we review T cells effects on AKI and patient outcomes and discuss related new therapeutic approaches to improve outcomes of affected individuals.

Harnessing Endogenous T-Regulatory Cells in Acute Kidney Injury

Acute kidney injury (AKI) affects 20-50% of hospitalized and intensive care patients, with a sizable proportion progressing to ESRD or death (https://www.kidney.org/atoz/content/AcuteKidneyInjury). Since inflammation contributes to the pathogenesis of AKI, studies on T-regulatory cells (Tregs), which suppress inflammation are important. Here, we highlight advances that utilize Tregs for intervention in AKI and were presented at the 25th International Conference on Advances in Critical Care Nephrology and UAB/UCSD O'Brien Center AKI &amp; CRRT 2020.

Large-Scale Generation of Human Allospecific Induced Tregs With Functional Stability for Use in Immunotherapy in Transplantation

Regulatory T cells play an important role in the control of autoimmune diseases and maintenance of tolerance. In the context of transplantation, regulatory T cells (Tregs) have been proposed as new therapeutic tools that may induce allospecific tolerance toward the graft, avoiding the side effects induced by generalized immunosuppressors. Although most clinical trials are based on the use of thymic Tregs in adoptive therapy, some reports suggest the potential use of in vitro induced Tregs (iTregs), based on their functional stability under inflammatory conditions, indicating an advantage in a setting of allograft rejection. The aim of this work was to generate and expand large numbers of allospecific Tregs that maintain stable suppressive function in the presence of pro-inflammatory cytokines. Dendritic cells were derived from monocytes isolated from healthy donors and were co-cultured with CTV-labeled naïve T cells from unrelated individuals, in the presence of TGF-β1, IL-2, and retinoic acid. After 7 days of co-culture, proliferating CD4⁺CD25⁺⁺CTV⁻ cells (allospecific iTregs) were sorted and polyclonally expanded for 6 weeks in the presence of TGF-β1, IL-2, and rapamycin. After 6 weeks of polyclonal activation, iTregs were expanded 230,000 times, giving rise to 4,600 million allospecific iTregs. Allospecific iTregs were able to specifically suppress the proliferation of autologous CD4⁺ and CD8⁺ T cells in response to the allo-MoDCs used for iTreg generation, but not to third-party allo-MoDCs. Importantly, 88.5% of the expanded cells were CD4⁺CD25⁺FOXP3⁺, expressed high levels of CCR4 and CXCR3, and maintained their phenotype and suppressive function in the presence of TNF-α and IL-6. Finally, analysis of the methylation status of the FOXP3 TSDR locus demonstrated a 40% demethylation in the purified allospecific iTreg, prior to the polyclonal expansion. Interestingly, the phenotype and suppressive activity of expanded allospecific iTregs were maintained after 6 weeks of expansion, despite an increase in the methylation status of the FOXP3 TSDR. In conclusion, this is the first report that demonstrates a large-scale generation of allospecific iTregs that preserve a stable phenotype and suppressor function in the presence of pro-inflammatory cytokines and pave the way for adoptive cell therapy with iTregs in transplanted patients.

Protective Role of mTOR in Liver Ischemia/Reperfusion Injury: Involvement of Inflammation and Autophagy

Liver ischemia/reperfusion (IR) injury is a common phenomenon after liver resection and transplantation, which often results in liver graft dysfunction such as delayed graft function and primary nonfunction. The mammalian target of rapamycin (mTOR) is an evolutionarily highly conserved serine/threonine protein kinase, which coordinates cell growth and metabolism through sensing environmental inputs under physiological or pathological conditions, involved in the pathophysiological process of IR injury. In this review, we mainly present current evidence of the beneficial role of mTOR in modulating inflammation and autophagy under liver IR to provide some evidence for the potential therapies for liver IR injury.

Aldosterone promotes renal interstitial fibrosis via the AIF‑1/AKT/mTOR signaling pathway

A number of studies have shown that aldosterone serves an important role in promoting renal interstitial fibrosis, although the specific mechanism remains to be elucidated. A previous study revealed that the fibrotic effect of aldosterone was associated with the expression of allograft inflammatory factor 1 (AIF‑1) in RAW264.7 macrophage cells, in a time‑ and concentration‑dependent manner. However, the exact mechanism through which aldosterone promotes renal interstitial fibrosis remains unknown. In the present study, the effects of aldosterone on renal inflammatory cell infiltration, collagen deposition and the expression levels of AIF‑1, phosphatidylinositol 3‑kinase (PI3K), AKT serine/threonine kinase (AKT), mammalian target of rapamycin (mTOR), the oxidative stress factor NADPH oxidase 2 (NOX2) and nuclear transcription factor erythroid‑related factor 2 (Nrf2) were assessed in normal rats, rats treated with aldosterone, rats treated with aldosterone and spironolactone and those treated with spironolactone only (used as the control). The effect of aldosterone on these factors was also investigated in the renal interstitium of unilateral ureteral obstruction (UUO) rats. Additionally, the AIF‑1 gene was overexpressed and knocked down in macrophage RAW264.7 cells, and the effects of aldosterone on PI3K, AKT, mTOR, NOX2 and Nrf2 were subsequently investigated. The results showed that aldosterone promoted inflammatory cell infiltration, collagen deposition and the expression of AIF‑1, PI3K, AKT, mTOR and NOX2, but inhibited the expression of Nrf2. In the UUO rats, aldosterone also promoted renal interstitial inflammatory cell infiltration, collagen deposition and the expression of AIF‑1, NOX2, PI3K, AKT and mTOR, whereas the expression of Nrf2 was downregulated by aldosterone compared with that in the UUO‑only group; the influence of aldosterone was counteracted by spironolactone in the normal and UUO rats. In vitro, aldosterone upregulated the expression levels of AKT, mTOR, NOX2 and Nrf2 in RAW264.7 cells compared with those in untreated cells. Suppressing the expression of AIF‑1 inhibited the effects of aldosterone, whereas the overexpression of AIF‑1 enhanced these effects in RAW264.7 cells. These findings indicated that aldosterone promoted renal interstitial fibrosis by upregulating the expression of AIF‑1 and that the specific mechanism may involve AKT/mTOR and oxidative stress signaling.

Inflammatory Mediators and Renal Fibrosis

Renal inflammation is the initial, healthy response to renal injury. However, prolonged inflammation promotes the fibrosis process, which leads to chronic pathology and eventually end-stage kidney disease. There are two major sources of inflammatory cells: first, bone marrow-derived leukocytes that include neutrophils, macrophages, fibrocytes and mast cells, and second, locally activated kidney cells such as mesangial cells, podocytes, tubular epithelial cells, endothelial cells and fibroblasts. These activated cells produce many profibrotic cytokines and growth factors that cause accumulation and activation of myofibroblasts, and enhance the production of the extracellular matrix. In particular, activated macrophages are key mediators that drive acute inflammation into chronic kidney disease. They produce large amounts of profibrotic factors and modify the microenvironment via a paracrine effect, and they also transdifferentiate to myofibroblasts directly, although the origin of myofibroblasts in the fibrosing kidney remains controversial. Collectively, understanding inflammatory cell functions and mechanisms during renal fibrosis is paramount to improving diagnosis and treatment of chronic kidney disease.

Low-dose IL-2 expands CD4+ regulatory T cells with a suppressive function in vitro via the STAT5-dependent pathway in patients with chronic kidney diseases

BACKGROUND

Patients with chronic kidney disease (CKD) often have CD4+ regulatory T cells (Tregs) dysfunction and chronic inflammation. We aim to investigate the effect, function, and related mechanism of low-dose IL-2 on CD4+ regulatory T cells expansion in vitro from patients with CKD.

METHODS

A total of 148 newly diagnosed patients with CKD at Stage III and 35 healthy volunteer subjects were recruited into our studies. The number of peripheral Tregs in peripheral blood mononuclear cells isolated from CKD patients, which were characterized by FACS as CD4+CD25hi and CD4+CD25+FoxP3+. The effect of low-dose IL-2 on expansion of Tregs, and the suppressive function of expanded Tregs were also analyzed by FACS. The levels of FoxP3 mRNA were detected by qRT-PCR. The activation of IL-2 induced Stat5 and blocking experiments were assessed by Western Blotting and FACS.

RESULTS

We found that the frequency of peripheral Tregs from CKD patients was significantly lower than that in healthy volunteer subjects. We also showed that IL-2 selectively expanded CD4+CD25hi and CD4+CD25+FoxP3+ regulatory T cells, and also upregulated the expression of FoxP3 mRNA. Our in vitro studies demonstrated that expanded CD4+ regulatory T cells from CKD patients suppressed proinflammatory Th1 and Th17 cell response. Furthermore, STAT5 activation is required for IL-2-induced expansion of regulatory T cells and expression of FoxP3 mRNA from CKD patients.

CONCLUSIONS

Our findings support the clinical Treg defects in CKD patients with glomerular diseases, and the rationale of evaluating low-dose IL-2 treatment for selectively modulating CD4+ Tregs.

Comparison of acute kidney injury of different etiology reveals in-common mechanisms of tissue damage

Acute kidney injury (AKI) is a syndrome of reduced glomerular filtration rate and urine production caused by a number of different diseases. It is associated with renal tissue damage. This tissue damage can cause tubular atrophy and interstitial fibrosis that leads to nephron loss and progression of chronic kidney disease (CKD). This review describes the in-common mechanisms behind tissue damage in AKI caused by different underlying diseases. Comparing six high-quality microarray studies of renal gene expression after AKI in disease models (gram-negative sepsis, gram-positive sepsis, ischemia-reperfusion, malignant hypertension, rhabdomyolysis, and cisplatin toxicity) identified 5,254 differentially expressed genes in at least one of the AKI models; 66% of genes were found only in one model, showing that there are unique features to AKI depending on the underlying disease. There were in-common features in the form of four genes that were differentially expressed in all six models, 49 in at least five, and 215 were found in common between at least four models. Gene ontology enrichment analysis could be broadly categorized into the injurious processes hypoxia, oxidative stress, and inflammation, as well as the cellular outcomes of cell death and tissue remodeling in the form of epithelial-to-mesenchymal transition. Pathway analysis showed that MYC is a central connection in the network of activated genes in-common to AKI, which suggests that it may be a central regulator of renal gene expression in tissue injury during AKI. The outlining of this molecular network may be useful for understanding progression from AKI to CKD.

Rapamycin Enhances Repressed Autophagy and Attenuates Aggressive Progression in a Rat Model of IgA Nephropathy

BACKGROUND

IgA nephropathy (IgAN) has been considered to be the most frequent form of primary glomerulonephritis that occurs worldwide with a variety of factors involved in its occurrence and development. The impact of autophagy in IgAN, however, remains partially unclear. This study was designed to investigate the effects of rapamycin in an IgAN model.

METHOD

After establishing an IgAN rat model, SD rats were divided into 4 groups: control, control + rapamycin, IgAN, IgAN + rapamycin. Proteinuria and the pathological changes and the level of autophagy of kidney were texted. Identify the expression of phosphorylation and total mammalian target of rapamycin (mTOR) and s6k1 as well as cyclin D1 in the kidney of rats through Western blot and immunohistochemistry.

RESULTS

With rapamycin treatment, we observed a significant reduction in the progression of proteinuria as well as alleviation of pathological lesions in IgAN rats. Besides, autophagy was inhibited, while the mTOR/S6k1 pathway was activated and expression of cyclin D1 was increased in IgAN. Rapamycin treatment increased autophagy and decreased the expression of cyclin D1.

CONCLUSION

These results may suggest that mTOR-mediated autophagy inhibition may result in mesangial cell proliferation in IgAN.