Neutrophil gelatinase-associated lipocalin (NGAL) is localised to the primary cilium in renal tubular epithelial cells - A novel source of urinary biomarkers of renal injury

Development of an In Vitro Model for Inflammation Mediated Renal Toxicity Using 3D Renal Tubules and Co-Cultured Human Immune Cells

BACKGROUND

The emergence of various infectious diseases and the toxic effects of hyperinflammation by biotherapeutics have highlighted the need for in vitro preclinical models mimicking the human immune system. In vitro models studying the relationship between hyperinflammation and acute renal injury mainly rely on 2D culture systems, which have shown limitations in recapitulating kidney function. Herein, we developed an in vitro kidney toxicity model by co-culturing 3D engineered kidney proximal tubules cells (RPTEC/TERT1) with human peripheral blood mononuclear cells (PBMC).

METHODS

RPTEC/TERT1 were sandwich cultured to form 3D renal tubules for 16 days. The tubules were then co-cultured with PBMC using transwell (0.4 μm pores) for 24 h. Hyperinflammation of PBMC was induced during co-culture using polyinosinic-polycytidylic acid (polyI:C) and lipopolysaccharide (LPS) to investigate the effects of the induced hyperinflammation on the renal tubules.

RESULTS

Encapsulated RPTEC/TERT1 cells in Matrigel exhibited elevated renal function markers compared to 2D culture. The coexistence of PBMC and polyI:C induced a strong inflammatory response in the kidney cells. This hyperinflammation significantly reduced primary cilia formation and upregulated kidney injury markers along the 3D tubules. Similarly, treating co-cultured PBMC with LPS to induce hyperinflammation resulted in comparable inflammatory responses and potential kidney injury.

CONCLUSION

The model demonstrated similar changes in kidney injury markers following polyI:C and LPS treatment, indicating its suitability for detecting immune-associated kidney damage resulting from infections and biopharmaceutical applications.

An exome-wide study of renal operational tolerance

Background

Renal operational tolerance is a rare and beneficial state of prolonged renal allograft function in the absence of immunosuppression. The underlying mechanisms are unknown. We hypothesized that tolerance might be driven by inherited protein coding genetic variants with large effect, at least in some patients.

Methods

We set up a European survey of over 218,000 renal transplant recipients and collected DNAs from 40 transplant recipients who maintained good allograft function without immunosuppression for at least 1 year. We performed an exome-wide association study comparing the distribution of moderate to high impact variants in 36 tolerant patients, selected for genetic homogeneity using principal component analysis, and 192 controls, using an optimal sequence-kernel association test adjusted for small samples.

Results

We identified rare variants of HOMER2 (3/36, FDR 0.0387), IQCH (5/36, FDR 0.0362), and LCN2 (3/36, FDR 0.102) in 10 tolerant patients vs. 0 controls. One patient carried a variant in both HOMER2 and LCN2. Furthermore, the three genes showed an identical variant in two patients each. The three genes are expressed at the primary cilium, a key structure in immune responses.

Conclusion

Rare protein coding variants are associated with operational tolerance in a sizable portion of patients. Our findings have important implications for a better understanding of immune tolerance in transplantation and other fields of medicine.ClinicalTrials.gov, identifier: NCT05124444.

Primary Cilia: A Cellular Regulator of Articular Cartilage Degeneration

Osteoarthritis (OA) is the most common joint disease that can cause pain and disability in adults. The main pathological characteristic of OA is cartilage degeneration, which is caused by chondrocyte apoptosis, cartilage matrix degradation, and inflammatory factor destruction. The current treatment for patients with OA focuses on delaying its progression, such as oral anti-inflammatory analgesics or injection of sodium gluconate into the joint cavity. Primary cilia are an important structure involved in cellular signal transduction. Thus, they are very sensitive to mechanical and physicochemical stimuli. It is reported that the primary cilia may play an important role in the development of OA. Here, we review the correlation between the morphology (location, length, incidence, and orientation) of chondrocyte primary cilia and OA and summarize the relevant signaling pathways in chondrocytes that could regulate the OA process through primary cilia, including Hedgehog, Wnt, and inflammation-related signaling pathways. These data provide new ideas for OA treatment.

Investigation on the Effect of Hemodialysis Combined with MDT Multimode Intervention on Renal Fibrosis Degree and Renal Function Improvement in Uremia Patients

The effect of hemodialysis combined with MDT intervention on the degree of renal fibrosis and renal function in uremia patients was studied. 118 patients with uremia admitted to the hospital were selected as the research object, and they were divided into two groups according to the random number table method, 59 cases in the control group and 59 cases in the experimental group. The control group was treated with hemodialysis, and the experimental group was treated with MDT multimode intervention on the basis of hemodialysis. The differences in renal fibrosis, renal function, and satisfaction after treatment were compared before treatment and at 1, 3, and 6 months after treatment. The experimental results showed that hemodialysis combined with MDT multimode intervention in uremia patients could reduce renal fibrosis and improve renal function and improve clinical satisfaction evaluation.

p66Shc signaling does not contribute to tubular damage induced by renal ischemia-reperfusion injury in rat

Renal ischemia-reperfusion (IR) injury is one of the major causes of acute kidney injury and represents a significant risk factor for renal transplantation. The level of renal damage is influenced by the ischemic duration and is caused by excessive amounts of produced reactive oxygen species (ROS). Adaptor protein p66Shc is known to regulate cellular and organ's sensitivity to oxidative stress and to contribute significantly to mitochondrial production of hydrogen peroxide in stress conditions. Studies carried out in cultured renal cells suggest that p66Shc-mediated mitochondrial dysfunction and ROS production are responsible for renal ischemic injury. We used our genetically modified rats, which either lack p66Shc expression, or express p66Shc variant, which constitutively generates increased quantities of hydrogen peroxide, to evaluate potential contribution of p66Shc signaling to renal damage in ischemia reperfusion rat model. Analysis of outer medulla tubule damage revealed the lack of contribution of either p66Shc expression or its constitutive signaling to IR injury in rat model.

Secreted Neutrophil Gelatinase-Associated Lipocalin Shows Stronger Ability to Inhibit Cyst Enlargement of ADPKD Cells Compared with Nonsecreted Form

Polycystic kidney disease (PKD) is one of the most common inherited diseases and is characterized by the development of fluid-filled cysts along multiple segments of the nephron. Autosomal dominant polycystic kidney disease (ADPKD) is the most common form of PKD, which is caused by mutations in either PKD1 or PKD2 genes that encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively. As ADPKD progresses, cysts enlarge and disrupt normal kidney architecture, eventually leading to kidney failure. Our previous study showed that overexpression of exogenous kidney-specific neutrophil gelatinase-associated lipocalin (NGAL) reduced cyst progression and prolonged the lifespan of ADPKD mice (Pkd1^L3/L3, 2L3 for short). In this study, we attempted to explore the underlying mechanism of reduced cyst progression in the presence of NGAL using immortalized 2L3 cells. The results of MTT and BrdU incorporation assays showed that recombinant mouse NGAL (mNGAL) protein significantly decreased the viability and proliferation of 2L3 cells. Flow cytometry and western blot analyses showed that mNGAL inhibited activation of the ERK and AKT pathways and induced apoptosis and autophagy in 2L3 cells. In addition, a 3D cell culture platform was established to identify cyst progression in 2L3 cells and showed that mNGAL significantly inhibited cyst enlargement in 2L3 cells. Overexpression of secreted mNGAL (pN + LS) and nonsecreted mNGAL (pN − LS) repressed cell proliferation and cyst enlargement in 2L3 cells and had effects on markers involved in proliferation, apoptosis, and autophagy. However, secreted mNGAL had a more pronounced and consistent effect than that of nonsecreted form. These results reveal that secreted mNGAL has stronger ability to inhibit cyst enlargement of ADPKD cells than that of nonsecreted form. These findings could help to identify strategies for the future clinical treatment of ADPKD.

Literature review of the mechanisms of acute kidney injury secondary to acute liver injury

People exposed to liver ischaemia reperfusion (IR) injury often develop acute kidney injury and the combination is associated with significant morbidity and mortality. Molecular mediators released by the liver in response to IR injury are the likely cause of acute kidney injury (AKI) in this setting, but the mediators have not yet been identified. Identifying the mechanism of injury will allow the identification of therapeutic targets which may modulate both liver IR injury and AKI following liver IR injury.

A peripheral neutrophil-related inflammatory factor predicts a decline in executive function in mild Alzheimer's disease

Background

Studies suggest a role of the innate immune system, including the activity of neutrophils, in neurodegeneration related to Alzheimer’s disease (AD), but prospective cognitive data remain lacking in humans. We aimed to investigate the predictive relationship between neutrophil-associated inflammatory proteins in peripheral blood and changes in memory and executive function over 1 year in patients with AD.

Methods

Participants with AD were identified from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Neutrophil gelatinase-associated lipocalin (NGAL), myeloperoxidase (MPO), interleukin-8 (IL-8), macrophage inflammatory protein-1 beta (MIP-1β), and tumor necrosis factor (TNF) were assayed by luminex immunofluorescence multiplex assay at baseline. Confirmatory factor analysis was used to test an underlying neutrophil associated plasma inflammatory factor. Composite z-scores for memory and executive function were generated from multiple tests at baseline and at 1 year. A multiple linear regression model was used to investigate the association of the baseline inflammatory factor with changes in memory and executive function over 1 year.

Results

Among AD patients (n = 109, age = 74.8 ± 8.1, 42% women, Mini Mental State Examination [MMSE] = 23.6 ± 1.9), the neutrophil-related inflammatory proteins NGAL (λ = 0.595, p < .001), MPO (λ = 0.575, p < .001), IL-8 (λ = 0.525, p < .001), MIP-1β (λ = 0.411, p = .008), and TNF (λ = 0.475, p < .001) were found to inform an underlying factor. Over 1 year, this inflammatory factor predicted a decline in executive function (β = − 0.152, p = 0.015) but not memory (β = 0.030, p = 0.577) in models controlling for demographics, brain atrophy, white matter hyperintensities, the ApoE ε4 allele, concomitant medications, and baseline cognitive performance.

Conclusions

An inflammatory factor constructed from five neutrophil-related markers in peripheral blood predicted a decline in executive function over 1 year in people with mild AD.