IL-17 aggravates renal injury by promoting podocyte injury in children with primary nephrotic syndrome

Swollen Feet: Considering the Paradoxical Roles of Interleukins in Nephrotic Syndrome

Interleukins are a family of 40 bioactive peptides that act through cell surface receptors to induce a variety of intracellular responses. While interleukins are most commonly associated with destructive, pro-inflammatory signaling in cells, some also play a role in promoting cellular resilience and survival. This review will highlight recent evidence of the cytoprotective actions of the interleukin 1 receptor (IL-1R)- and common gamma chain receptor (IL-Rγc)-signaling cytokines in nephrotic syndrome (NS). NS results from the injury or loss of glomerular visceral epithelial cells (i.e., podocytes). Although the causes of podocyte dysfunction vary, it is clear that pro-inflammatory cytokines play a significant role in regulating the propagation, duration and severity of disease. Pro-inflammatory cytokines signaling through IL-1R and IL-Rγc have been shown to exert anti-apoptotic effects in podocytes through the phosphoinositol-3-kinase (PI-3K)/AKT pathway, highlighting the potential utility of IL-1R- and IL-Rγc-signaling interleukins for the treatment of podocytopathy in NS. The paradoxical role of interleukins as drivers and mitigators of podocyte injury is complex and ill-defined. Emerging evidence of the cytoprotective role of some interleukins in NS highlights the urgent need for a nuanced understanding of their pro-survival benefits and reveals their potential as podocyte-sparing therapeutics for NS.

Th17 cells: A new target in kidney disease research

Type 17 T helper (Th17) cells, which are a subtype of CD4+ T helper cells, secrete pro-inflammatory cytokines such as IL-17A, IL-17F, IL-21, IL-22, and GM-CSF, which play crucial roles in immune defence and protection against fungal and extracellular pathogen invasion. However, dysfunction of Th17 cell immunity mediates inflammatory responses and exacerbates tissue damage. This pathological process initiated by Th17 cells is common in kidney diseases associated with renal injury, such as glomerulonephritis, lupus nephritis, IgA nephropathy, hypertensive nephropathy, diabetic kidney disease and acute kidney injury. Therefore, targeting Th17 cells to treat kidney diseases has been a hot topic in recent years. This article reviews the mechanisms of Th17 cell-mediated inflammation and autoimmune responses in kidney diseases and discusses the related clinical drugs that modulate Th17 cell fate in kidney disease treatment.

Understanding the podocyte immune responses in proteinuric kidney diseases: from pathogenesis to therapy

The glomerular filtration barrier, comprising the inner layer of capillary fenestrated endothelial cells, outermost podocytes, and the glomerular basement membrane between them, plays a pivotal role in kidney function. Podocytes, terminally differentiated epithelial cells, are challenging to regenerate once injured. They are essential for maintaining the integrity of the glomerular filtration barrier. Damage to podocytes, resulting from intrinsic or extrinsic factors, leads to proteinuria in the early stages and eventually progresses to chronic kidney disease (CKD). Immune-mediated podocyte injury is a primary pathogenic mechanism in proteinuric glomerular diseases, including minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and lupus nephritis with podocyte involvement. An extensive body of evidence indicates that podocytes not only contribute significantly to the maintenance of the glomerular filtration barrier and serve as targets of immune responses but also exhibit immune cell-like characteristics, participating in both innate and adaptive immunity. They play a pivotal role in mediating glomerular injury and represent potential therapeutic targets for CKD. This review aims to systematically elucidate the mechanisms of podocyte immune injury in various podocyte lesions and provide an overview of recent advances in podocyte immunotherapy. It offers valuable insights for a deeper understanding of the role of podocytes in proteinuric glomerular diseases, and the identification of new therapeutic targets, and has significant implications for the future clinical diagnosis and treatment of podocyte-related disorders.

Uric acid promotes interleukin-17 expression to cause kidney injury

Uric acid, an oxidation end-product of purine metabolism, is reportedly to be a risk factor for kidney injury. However, its underlying mechanism is still a mystery. This study aimed to reveal the detailed roles of uric acid in inducing kidney injury and the possible mechanisms. Injection of rats with uric acid significantly increased tubular injury score, and levels of blood urea nitrogen, serum creatinine, and urine kidney injury molecule-1. Uric acid increased the expression of collagen I, alpha-smooth muscle actin, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. Kyoto Encyclopedia of Genes and Genomes analysis result showed the IL-17 signaling pathway as the most significantly enriched pathway involved in hyperuricemia-related kidney injury. Long-term injection of uric acid induced significant production of IL-17 and recruitment of Th17 cells. Treating rats with the anti-IL-17 mAb attenuated uric acid-induced kidney injury, accompanied by the inactivation of nuclear factor-κB (NF-κB). In conclusion, uric acid was confirmed to be a risk factor for kidney injury via inducing IL-17 expression. Neutralization of IL-17 using the specific mAb relieved uric acid-induced kidney injury via inhibition of NF-κB signaling.

The causal relationship between immune cells and different kidney diseases: A Mendelian randomization study

Studies have suggested that the progress of most kidney diseases from occurrence to course and subsequent related complications are closely related to inflammatory reaction. Increased common leukocytes count in the family (neutrophils, eosinophils, basophils, lymphocytes, etc.) are also involved in the tissue damage of kidney diseases. However, these studies are only traditional observational studies, which cannot prove whether there is a causal relationship between these four kinds of leukocytes count and kidney diseases. We aim to explore the causal relationship between these four kinds of leukocytes count and kidney diseases by Mendelian randomization (MR). Large sample size of the genome-wide association database of four cell traits (neutrophil, basophil, lymphocyte, and eosinophil cell counts) in the leukocyte family were used as exposure variables. The outcome variables were various renal diseases (including chronic renal failure, acute renal failure, hypertensive heart or/and kidney disease, hypertensive renal disease, disorders resulting from impaired renal tubular function, and type 1 diabetes with renal complications). The covariates used in multivariable MR are also four cell traits related to blood cells (neutrophil, basophil, lymphocyte, and eosinophil cell counts). Instrumental variables and single nucleotide polymorphic loci were identified (P < 5 × 10-8. Linkage disequilibrium R2 < 0.001). The causal relationships were studied by inverse variance weighted (IVW), weighted median, and MR-Egger regression. Sensitivity analysis was also performed. In our study, IVW analysis results showed that increased neutrophil cell count was a risk factor for chronic renal failure (OR = 2.0245861, 95% CI = 1.1231207-3.649606, P = 0.01896524), increased basophil cell count was a risk factor for chronic renal failure (OR = 3.975935, 95% CI = 1.4871198-10.62998, P = 0.005942755). Basophil cell count was not a risk factor for acute renal failure (OR = 1.160434, 95% CI = 0.9455132-1.424207, P = 0.15448828). Increased basophil cell count was a protective factor for hypertensive heart and/or renal disease (OR = 0.7716065, 95% CI = 0.6484979-0.9180856, P = 0.003458707). Increased basophil cell count was a risk factor for disorders resulting from impaired renal tubular function (OR = 1.648131, 95% CI = 1.010116-2.689133, P = 0.04546835). Increased lymphocyte cell count was a risk factor for hypertensive renal disease (OR = 1.372961, 95% CI = 1.0189772-1.849915, P = 0.03719874). Increased eosinophil cell count was a risk factor for type 1 diabetes with renal complications (OR = 1.516454, 95% CI = 1.1826453-1.944482, P = 0.001028964). Macrophage inflammatory protein 1b levels was a protective factor for renal failure (OR = 0.9381862, 95% CI = 0.8860402-0.9934013, P = 0.02874872). After multivariable MR was used to correct covariates (neutrophil, basophil, and lymphocyte cell counts), the correlation effect between increased eosinophil cell counts and type 1 diabetes with renal complications was still statistically significant (P = 0.02201152). After adjusting covariates (neutrophil, basophil, and eosinophil cell counts) with multivariable MR, the correlation effect between increased lymphocyte cell counts and hypertensive renal disease was still statistically significant (P = 0.02050226). This study shows that increased basophils can increase the relative risk of chronic renal failure and renal tubular dysfunction, and reduce the risk of hypertensive heart disease and/or hypertensive nephropathy, while increased basophil cell count will not increase the relative risk of acute renal failure, increased neutrophil cell count can increase the risk of chronic renal failure, increased lymphocyte cell count can increase the relative risk of hypertensive nephropathy, and increased eosinophil cell count can increase the relative risk of type 1 diabetes with renal complications. Macrophage inflammatory protein 1b levels was a protective factor for renal failure.

A cell transcriptomic profile provides insights into adipocytes of porcine mammary gland across development

BACKGROUND

Studying the composition and developmental mechanisms in mammary gland is crucial for healthy growth of newborns. The mammary gland is inherently heterogeneous, and its physiological function dependents on the gene expression of multiple cell types. Most studies focused on epithelial cells, disregarding the role of neighboring adipocytes.

RESULTS

Here, we constructed the largest transcriptomic dataset of porcine mammary gland cells thus far. The dataset captured 126,829 high-quality nuclei from physiological mammary glands across five developmental stages (d 90 of gestation, G90; d 0 after lactation, L0; d 20 after lactation, L20; 2 d post natural involution, PI2; 7 d post natural involution, PI7). Seven cell types were identified, including epithelial cells, adipocytes, endothelial cells, fibroblasts cells, immune cells, myoepithelial cells and precursor cells. Our data indicate that mammary glands at different developmental stages have distinct phenotypic and transcriptional signatures. During late gestation (G90), the differentiation and proliferation of adipocytes were inhibited. Meanwhile, partly epithelial cells were completely differentiated. Pseudo-time analysis showed that epithelial cells undergo three stages to achieve lactation, including cellular differentiation, hormone sensing, and metabolic activation. During lactation (L0 and L20), adipocytes area accounts for less than 0.5% of mammary glands. To maintain their own survival, the adipocyte exhibited a poorly differentiated state and a proliferative capacity. Epithelial cells initiate lactation upon hormonal stimulation. After fulfilling lactation mission, their undergo physiological death under high intensity lactation. Interestingly, the physiological dead cells seem to be actively cleared by immune cells via CCL21-ACKR4 pathway. This biological process may be an important mechanism for maintaining homeostasis of the mammary gland. During natural involution (PI2 and PI7), epithelial cell populations dedifferentiate into mesenchymal stem cells to maintain the lactation potential of mammary glands for the next lactation cycle.

CONCLUSION

The molecular mechanisms of dedifferentiation, proliferation and redifferentiation of adipocytes and epithelial cells were revealed from late pregnancy to natural involution. This cell transcriptomic profile constitutes an essential reference for future studies in the development and remodeling of the mammary gland at different stages.

Chronic treatment with IL-25 increases renal M2 macrophages and reduces renal injury in obese Dahl salt-sensitive rats during the prepubescent stage

Recently, we have reported that the early progression of proteinuria in the obese Dahl salt-sensitive (SS) leptin receptor mutant (SSLepRmutant) strain was associated with increased renal macrophage infiltration before puberty. Macrophages can be divided into two distinct phenotypes: M1 (proinflammatory) and M2 (anti-inflammatory). Moreover, previous studies have demonstrated that interleukin (IL)-25 converts resting macrophages and M1 into M2. Therefore, the present study examined whether treatment with IL-25 would reduce the early progression of renal injury in SSLepRmutant rats by increasing renal M2. We also investigated the impact of IL-25 on M2 subtypes: M2a (wound healing/anti-inflammatory), M2b (immune mediated/proinflammatory), M2c (regulatory/anti-inflammatory), and M2d (tumor associated/proangiogenic). Four-wk-old SS and SSLepRmutant rats were treated with either control (IgG) or IL-25 (1 µg/day ip every other day) for 4 wk. The kidneys from SSLepRmutant rats displayed progressive proteinuria and renal histopathology versus SS rats. IL-25 treatment had no effect on these parameters in SS rats. However, in the SSLepRmutant strain, proteinuria was markedly reduced after IL-25 treatment. Chronic treatment with IL-25 significantly decreased glomerular and tubular injury and renal fibrosis in the SSLepRmutant strain. Although the administration of IL-25 did not change total renal macrophage infiltration in both SS and SSLepRmutant rats, IL-25 increased M2a by >50% and reduced M1 by 60% in the kidneys of SSLepRmutant rats. Overall, these data indicate that IL-25 reduces the early progression of renal injury in SSLepRmutant rats by inducing M2a and suppressing M1 and suggest that IL-25 may be a therapeutic target for renal disease associated with obesity. NEW & NOTEWORTHY For the past few decades, immune cells and inflammatory cytokines have been demonstrated to play an important role in the development of renal disease. The present study provides strong evidence that interleukin-25 slows the early progression of renal injury in obese Dahl salt-sensitive rats before puberty by increasing systemic anti-inflammatory cytokines and renal M2a macrophages.

Interrelation of T cell cytokines and autoantibodies in systemic lupus erythematosus: A cross-sectional study

T-helper cytokines interferon gamma (IFNɣ), interleukin 17 (IL-17) and IL-10 impact systemic lupus erythematosus (SLE) directly and indirectly via modulation of autoAb production. We determined the separate and combined effects on clinical manifestations of SLE (N = 62). IFNɣ, IL-17 but not IL-10 were significantly elevated in patients with SLE. IFNɣ positively correlated with anti-DNA and anti-SSA. IL-17 positively correlated with anti-SSA and was significantly higher in patients with discoid rash and class V LN. IL-10 did not correlate with circulating autoantibodies but was significantly elevated in patients with LN. Patients with LN had elevated plasma levels of anti-DNA and anti-Sm/ribonuclear protein (RNP). Anti-Sm/RNP levels were decreased in patients with acute mucocutaneous manifestations, including photosensitivity and/or malar rash. The study provides critical insights into pathological mechanisms of LN, which could help guide future diagnoses and therapies.

The Immune System and Idiopathic Nephrotic Syndrome

Idiopathic nephrotic syndrome often responds to immunosuppressive treatment. Nevertheless, this syndrome-and the drugs used to treat it-remain important causes of patient morbidity. Idiopathic nephrotic syndrome is usually caused by minimal change disease or FSGS, diseases that primarily affect the podocytes. In spite of decades of research, the underlying causes of both diseases remain incompletely understood. There is, however, a large body of observational and experimental data linking the immune system with both minimal change disease and FSGS, including associations with systemic infections and hematologic malignancies. Perhaps most compellingly, many different immunomodulatory drugs are effective for treating idiopathic nephrotic syndrome, including biologic agents that have well-defined immune targets. In fact, the unexpected efficacy of targeted therapeutic agents has provided important new insights into the pathogenesis of these diseases. Given the large number of drugs that are available to deplete or block specific cells and molecules within the immune system, a better understanding of the immunologic causes of idiopathic nephrotic syndrome may lead to better diagnostic and therapeutic approaches.

LncRNA Snhg5 Attenuates Status Epilepticus Induced Inflammation through Regulating NF-κΒ Signaling Pathway

Status epilepticus (SE) induced inflammation plays an important role in the pathogenesis of SE. Long non-coding RNA small nucleolar RNA host gene 5 (lncRNA Snhg5) has been reported in various inflammatory diseases. However, the mechanism of Snhg5 regulated inflammation in SE remains unclear. Therefore, this study aimed to clarify the role and mechanism of Snhg5 in SE-induced inflammation in vitro and vivo. In vitro, lipopolysaccharide (LPS)-induced inflammation in microglia was used to mimic the inflammation after SE. In vivo, SE model was induced by lithium chloride and pilocarpine. The level of Snhg5, p65, p-p65, p-inhibitor of kappaB (IκB)α, IκBα and inflammatory factors (tumor necrosis factor (TNF)-α, interleukin (IL)-1β) were measured via quantitative real-time PCR or Western blot. The Nissl stain and immunohistochemical stain were performed to observe hippocampal damage and microglia proliferation. The results showed Snhg5 was up-regulated in the rat and microglia. Knockdown of Snhg5 inhibited LPS-induced inflammation and relative expression of p-65/p65, p-IκBα/IκBα. Moreover, down-regulation of Snhg5 attenuated SE-induced inflammation and reduced the number of microglia in hippocampus. These findings indicated that Snhg5 modulates the inflammation via nuclear factor-kappaB (NF-κB) signaling pathway in SE rats.

The Th17/IL-17 Axis and Kidney Diseases, With Focus on Lupus Nephritis

Systemic lupus erythematosus (SLE) is a disease characterized by dysregulation and hyperreactivity of the immune response at various levels, including hyperactivation of effector cell subtypes, autoantibodies production, immune complex formation, and deposition in tissues. The consequences of hyperreactivity to the self are systemic and local inflammation and tissue damage in multiple organs. Lupus nephritis (LN) is one of the most worrying manifestations of SLE, and most patients have this involvement at some point in the course of the disease. Among the effector cells involved, the Th17, a subtype of T helper cells (CD4+), has shown significant hyperactivation and participates in kidney damage and many other organs. Th17 cells have IL-17A and IL-17F as main cytokines with receptors expressed in most renal cells, being involved in the activation of many proinflammatory and profibrotic pathways. The Th17/IL-17 axis promotes and maintains repetitive tissue damage and maladaptive repair; leading to fibrosis, loss of organ architecture and function. In the podocytes, the Th17/IL-17 axis effects include changes of the cytoskeleton with increased motility, decreased expression of health proteins, increased oxidative stress, and activation of the inflammasome and caspases resulting in podocytes apoptosis. In renal tubular epithelial cells, the Th17/IL-17 axis promotes the activation of profibrotic pathways such as increased TGF-β expression and epithelial-mesenchymal transition (EMT) with consequent increase of extracellular matrix proteins. In addition, the IL-17 promotes a proinflammatory environment by stimulating the synthesis of inflammatory cytokines by intrinsic renal cells and immune cells, and the synthesis of growth factors and chemokines, which together result in granulopoiesis/myelopoiesis, and further recruitment of immune cells to the kidney. The purpose of this work is to present the prognostic and immunopathologic role of the Th17/IL-17 axis in Kidney diseases, with a special focus on LN, including its exploration as a potential immunotherapeutic target in this complication.

Immune-mediated entities of (primary) focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) represents a glomerular scar formation downstream of various different mechanisms leading to podocytopathy and podocyte loss. Recently, significant advances were made in understanding genetic factors, podocyte intrinsic mechanisms, and adaptive mechanisms causing FSGS. However, while most cases of nephrotic FSGS are being treated with immunosuppressants, the underlying immune dysregulation, involved immune cells, and soluble factors are only incompletely understood. Thus, we here summarize the current knowledge of proposed immune effector cells, secreted soluble factors, and podocyte response in immune-mediated (primary) FSGS.