Association of plasma neutrophil gelatinase-associated lipocalin with parameters of CKD-MBD in maintenance hemodialysis patients

Lipocalin-2 promotes CKD vascular calcification by aggravating VSMCs ferroptosis through NCOA4/FTH1-mediated ferritinophagy

Vascular calcification (VC) is a common complication of chronic kidney disease (CKD), for which no effective therapies are available. Hyperphosphatemia, a feature of CKD, is a well-known inducer of VC. High phosphate (HP)-induced ferroptosis plays a crucial role in CKD-related VC (CKD-VC), but the mechanisms remain unclear. Lipocalin-2 (LCN2), an iron-trafficking protein, has been implicated in ferroptosis regulation. In the present study, the role of LCN2 as a potential mediator of CKD-VC was investigated. HP-induced LCN2 expression in the arteries of CKD-VC patients, animal models and vascular smooth muscle cells (VSMCs). LCN2 knockout (LCN2KO) mice and wild-type (WT) mice fed with a high adenine and phosphate (AP) diet were studied to explore CKD-VC. Compared with WT mice, LCN2KO mice showed an amelioration of the CKD-VC induced by the AP diet. The inhibition of LCN2 also alleviated HP-induced calcium deposition and phenotypic transition in VSMCs. Conversely, VSMCs-targeted LCN2 overexpression or recombinant LCN2 treatment exacerbated CKD-VC in vivo and in vitro. Mechanistically, nuclear receptor coactivator 4 (NCOA4)/ferritin heavy chain 1 (FTH1)-mediated ferritinophagy-dependent ferroptosis was involved in LCN2-mediated CKD-VC. Under HP conditions, LCN2 interacted with NCOA4, potentially accelerating the degradation of FTH1 and inducing ferroptosis. The inhibition of LCN2 may rescue the degradation of FTH1 and thus ameliorate ferroptosis, significantly suppressing VSMCs calcification. In summary, our study revealed a novel role for LCN2 induced ferritinophagy-dependent ferroptosis in CKD-VC, and targeting LCN2 might be a promising treatment for CKD-VC.

The Review of Current Knowledge on Neutrophil Gelatinase-Associated Lipocalin (NGAL)

Neutrophil gelatinase-associated lipocalin (NGAL) is a 25-kDa protein that is secreted mostly by immune cells such as neutrophils, macrophages, and dendritic cells. Its production is stimulated in response to inflammation. The concentrations of NGAL can be measured in plasma, urine, and biological fluids such as peritoneal effluent. NGAL is known mainly as a biomarker of acute kidney injury and is released after tubular damage and during renal regeneration processes. NGAL is also elevated in chronic kidney disease and dialysis patients. It may play a role as a predictor of the progression of renal function decreases with complications and mortality due to kidney failure. NGAL is also useful in the diagnostic processes of cardiovascular diseases. It is highly expressed in injured heart tissue and atherosclerostic plaque; its serum concentrations correlate with the severity of heart failure and coronary artery disease. NGAL increases inflammatory states and its levels rise in arterial hypertension, obesity, diabetes, and metabolic complications such as insulin resistance, and is also involved in carcinogenesis. In this review, we present the current knowledge on NGAL and its involvement in different pathologies, especially its role in renal and cardiovascular diseases.

Aging-suppressor Klotho: Prospects in diagnostics and therapeutics

INTRODUCTION

The protein Klotho (KL) was first discovered in KL-deficient mice, which developed a syndrome similar to premature aging in humans. Since then, KL has been implicated in multiple molecular signaling pathways and diseases. KL has been shown to have anti-aging, healthspan and lifespan extending, cognitive enhancing, anti-oxidative, anti-inflammatory, and anti-tumor properties. KL levels decrease with age and in many diseases. Therefore, it has been of great interest to develop a KL-boosting or restoring drug, or to supplement endogenous Klotho with exogenous Klotho genetic material or recombinant Klotho protein, and to use KL levels in the body as a marker for the efficacy of such drugs and as a biomarker for the diagnosis and management of diseases.

OBJECTIVE

The goal of this study was to provide a comprehensive review of KL levels across age groups in individuals who are healthy or have certain health conditions, using four sources: blood, cerebrospinal fluid, urine, and whole biopsy/necropsy tissue. By doing so, baseline KL levels can be identified across the lifespan, in the absence or presence of disease. In turn, these findings can be used to guide the development of future KL-based therapeutics and biomarkers, which will heavily rely on an individual's baseline KL range to be efficacious.

METHODS

A total of 65 studies were collected primarily using the PubMed database. Research articles that were published up to April 2022 were included. Statistical analysis was conducted using RStudio.

RESULTS

Mean and median blood KL levels in healthy individuals, mean blood KL levels in individuals with renal conditions, and mean blood KL levels in individuals with metabolic or endocrine conditions were shown to decrease with age. Similarly, CSF KL levels in patients with AD also declined compared with age-matched controls.

CONCLUSIONS

The present study confirms the trend that KL levels in blood decrease with age in humans, among those who are healthy, and even further among those with renal and endocrine/metabolic illnesses. Further, by drawing this trend from multiple published works, we were able to provide a general idea of baseline KL ranges, specifically in blood in these populations. These data add to the current knowledge on normal KL levels in the body and how they change with time and in disease, and can potentially support efforts to create KL-based treatments and screening tools to better manage aging, renal, and metabolic/endocrine diseases.

Association of plasma neutrophil gelatinase-associated lipocalin and thoracic aorta calcification in maintenance hemodialysis patients with and without diabetes

Background

Neutrophil gelatinase-associated lipocalin (NGAL) is not only a bone-derived factor involved in metabolism, but also a biomarker of kidney disease and cardiovascular pathophysiology. We conducted this cross-sectional observational study to explore relationships between plasma NGAL and thoracic aorta calcification (TAC) in maintenance hemodialysis (MHD) patients with and without diabetes.

Methods

Plasma NGAL was measured by ELISA, TAC was evaluated via computed tomography scan using a 3D quantification method or chest radiography aortic arch calcification score. Spearman correlation, Logistic regression and Partial correlation analysis were used to describe the correlations between NGAL and TAC.

Results

Plasma NGAL levels were lower in MHD patients with diabetes compared to those without diabetes (49.33(42.37, 55.48) vs 56.78(44.37, 674.13) ng/mL, P = 0.026). In MHD patients without diabetes, lg (NGAL) was positively correlated with ARC value(R = 0.612, P = 0.003) analyzed by Spearman correlation; for partial correlation analysis, lg (NGAL) was positively correlated with ARC value, after adjusting for age and sex (R = 0.550, P = 0.015), adjusting for age, sex and CHD (R = 0.565, P = 0.015), adjusting for age, sex, CHD and Alb (R = 0.536, P = 0.027), or adjusting for age, sex, CHD, Alb, and dialyzer membrane (polysulfone) (R = 0.590, P = 0.016); however, when adjusting for age, sex, CHD, Alb and Ca, the correlation between lg (NGAL) and ARC value disappeared. Positive correlation were found between NGAL and Ca (R = 0.644, P < 0.001), Ca and ACR (R = 0.534, P = 0.013) in Spearman coefficient analysis.

Conclusion

There were positive correlations among plasma NGAL, serum Ca and ARC in MHD patients without diabetes; which suggests that NGAL is possibly a participant in cardiovascular calcification, in non-diabetic MHD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02773-z.