Expression and clinical value of gastrin‐releasing peptide precursor in nephropathy and chronic kidney disease

Evaluation of a tumor marker gastrin-releasing peptide precursor in the patients with kidney injuries

Gastrin-releasing peptide precursor (ProGRP) is a bioactive precursor of GRP and might play an important role as an emerging tumor marker in early cancer diagnosis. It might also be abnormal in the nonmalignant disease and renal function abnormalities. The present study was undertaken to investigate the changes of ProGRP levels in patients with kidney injuries, especially with chronic kidney disease (CKD), determine the upper reference intervals and clinical diagnostic value of ProGRP in CKD, and thus help oncologists in interpreting ProGRP levels and making clinical judgments of malignances. 676 individuals were enrolled in this cross-sectional study and divided into five groups: healthy control (n=194), CKD (n=272), nephrotic syndrome (NS) (n=137), antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) (n=41), and urinary tract infection (UTI) (n=32). A total of 27 features including age, gender, and 25 laboratory markers were analyzed. Machine learning algorithms were built for the diagnostic models of CKD. Statistical analysis was performed by R software. It was shown that serum ProGRP level in CKD was significantly higher than that in healthy controls, UTI and NS (P < 0.01). The upper reference limit of ProGRP was 188.42 pg/ml for CKD, 245.40 pg/ml for CKD IV-V, and 97.25 pg/ml for NS. Compared with the healthy control, the level of serum ProGRP in CKD stages II, III, IV-V was significantly increased and elevated progressively with CKD grade (P < 0.01). Random Forest (RF) model works best among 4 building machine learning algorithms. 5 vital indicators, ProGRP, estimated glomerular filtration rate (eGFR), urea, albumin (ALB), and direct bilirubin (DBIL), were selected to establish RF model for diagnosing CKD with an area under the curve (AUC) of 0.96 (95% confidence interval [CI]: 0.94-0.97) and high sensitivity (0.89) and specificity (0.92). This study demonstrates that the level of ProGRP in patients with CKD, nephrotic syndrome or AAV, was significantly higher than that in the healthy population. The machine learning model of ProGRP with DBIL, eGFR, ALB, and urea, could provide good clinical value for CKD evaluation.

GRP/GRPR signaling pathway aggravates hyperuricemia-induced renal inflammation and fibrosis via ABCG2-dependent mechanisms

The gastrin-releasing peptide receptor (GRPR) binds to ligands such as gastrin-releasing peptide (GRP) and plays a variety of biological roles. In this study, we investigated the therapeutic effect of a novel gastrin-releasing peptide receptor antagonist RH-1402 in hyperuricemia-induced kidney fibrosis and its underlying mechanisms. We conducted enzyme linked immunosorbent assay (ELISA) and immunohistochemical analyses and found that proGRP and GRPR expression levels were significantly increased in patients with hyperuricemic nephropathy (HN) and HN mice. GRPR knockdown significantly attenuated inflammatory and fibrotic responses in adenosine-treated human proximal tubule epithelial cells. GRPR knockout or GRPR conditional knockout in renal tubular epithelial cells significantly alleviated the decline in renal function and fibrosis in HN mice in vivo. RNA-seq and String database analysis revealed that GRP/GRPR promoted HN by suppressing the ABCG2/PDZK1 and increasing TGF-β/Smad3 levels by activating the NF-κB pathway. Overexpression of GRPR increased TGF-β/Smad3 levels, where as it reduced ABCG2/PDZK1 levels in adenosine-treated HK2 cells, which was reversed by the NF-κB inhibitor. Furthermore, we evaluated the therapeutic effects of the novel GRPR inhibitor RH-1402 on hyperuricaemia-induced renal injury and evaluated the inflammatory and fibrosis responses in vivo and in vitro. Pre-treatment with RH-1402 attenuated hyperuricaemia-induced renal injury, restored renal function, and suppressed renal inflammation and fibrosis. Taken together, GRPR enhances hyperuricaemia-induced tubular injury, inflammation, and renal fibrosis via ABCG2-dependent mechanisms and may serve as a promising therapeutic target for HN treatment.

Genetic and pharmacological inhibition of GRPR protects against acute kidney injury via attenuating renal inflammation and necroptosis

Gastrin-releasing peptide (GRP) binds to its receptor (GRP receptor [GRPR]) to regulate multiple biological processes, but the function of GRP/GRPR axis in acute kidney injury (AKI) remains unknown. In the present study, GRPR is highly expressed by tubular epithelial cells (TECs) in patients or mice with AKI, while histone deacetylase 8 may lead to the transcriptional activation of GRPR. Functionally, we uncovered that GRPR was pathogenic in AKI, as genetic deletion of GRPR was able to protect mice from cisplatin- and ischemia-induced AKI. This was further confirmed by specifically deleting the GRPR gene from TECs in GRPRFlox/Flox//KspCre mice. Mechanistically, we uncovered that GRPR was able to interact with Toll-like receptor 4 to activate STAT1 that bound the promoter of MLKL and CCL2 to induce TEC necroptosis, necroinflammation, and macrophages recruitment. This was further confirmed by overexpressing STAT1 to restore renal injury in GRPRFlox/Flox/KspCre mice. Concurrently, STAT1 induced GRP synthesis to enforce the GRP/GRPR/STAT1 positive feedback loop. Importantly, targeting GRPR by lentivirus-packaged small hairpin RNA or by treatment with a novel GRPR antagonist RH-1402 was able to inhibit cisplatin-induced AKI. In conclusion, GRPR is pathogenic in AKI and mediates AKI via the STAT1-dependent mechanism. Thus, targeting GRPR may be a novel therapeutic strategy for AKI.

Sulfur quantum dots as a fluorescent sensor for N-acetyl-beta-D-glucosaminidase detection

N-acetyl-beta-D-glucosaminidase (NAG) is an important biomarker for early clinical diagnosis of renal disease, suggesting the necessity to develop a fast and sensitive method for its detection. In this paper, we developed a fluorescent sensor based on polyethylene glycol (400) (PEG-400)-modified and H2O2-assisted etched sulfur quantum dots (SQDs). According to the fluorescence inner filter effect (IFE), the fluorescence of SQDs can be quenched by the p-nitrophenol (PNP) generated by NAG-catalyzed hydrolysis of p-Nitrophenyl-N-acetyl-β-D-glucosaminide (PNP-NAG). We successfully used the SQDs as a nano-fluorescent probe to detect the NAG activity from 0.4 to 7.5 U·L-1, with a detection limit of 0.1 U·L-1. Furthermore, the method is highly selective and was successfully used in the detection of NAG activity in bovine serum samples, suggesting its great application prospect in clinical detection.

Diagnostic value of conventional tumor markers in young patients with pulmonary nodules

Background

Lung cancer is one of the most common malignancies, and there is a trend of increasing incidence in young patients. The preoperative diagnosis of pulmonary nodules is mainly based on the combination of imaging and tumor markers. There is no relevant report on the diagnostic value of tumor markers in young pulmonary nodules. Our study was designed to explore the value of five tumor markers in young patients with pulmonary nodules.

Methods

We reviewed the medical records of 390 young patients (age ≤45 years) with pulmonary nodules treated at two separate centers from January 1, 2015, to January 1, 2021. Malignant pulmonary nodules were confirmed in 318 patients, and the other 72 patients were diagnosed with benign pulmonary nodules. The gold standard for diagnosis of pulmonary nodules was surgical biopsy. The conventional serum biomarkers included cytokeratin 19 (CYFRA21‐1), pro‐gastrin‐releasing‐peptide (ProGRP), carcinoembryonic antigen (CEA), neuron‐specific enolase (NSE), and squamous cell carcinoma‐associated antigen (SCCA). The diagnostic values of five tumor markers were analyzed by receiver operating characteristic (ROC) curves.

Results

There were no significant differences in the expression of five tumor markers between the groups (p > 0.05). Single tumor marker (CYFRA21‐1, ProGRP, CEA, NSE, and SCCA) showed a limited value in the diagnosis of malignant pulmonary nodules, with the AUC of 0.506, 0.503 0.532, 0.548, and 0.562, respectively. The AUC of the combined examination was only 0.502~0.596, which did not improve the diagnostic value.

Conclusions

Five conventional tumor markers had a limited diagnostic value in young patients with pulmonary nodules.

Recent advances in the biology of bombesin-like peptides and their receptors

PURPOSE OF REVIEW

The current review aims to update the important findings about molecular and cellular biology of mammalian bombesin-like peptides (BLPs) and their receptors.

RECENT FINDINGS

Recent identification of synaptic communication between gastrin-releasing peptide (GRP) neurons and GRP receptor (GRPR) neurons in spinal itch relay provides us novel insights into physiology of itch sensation. Neuromedin B (NMB) neurons were found to form connections with subcortical areas associated with arousal, hippocampal theta oscillation, and premotor processing and project to multiple downstream stations to regulate locomotion and hippocampal theta power. In addition to researches regarding the roles of BLPs and their receptors in central nervous system, recent findings reveal that NMB receptor is expressed on helminth-induced type 2 innate lymphoid cells and is regulated by basophils, suggesting an important function of NMB in helminth-induced immune responses. Bombesin transactivates epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), and HER3 receptors on human nonsmall-cell lung cancer (NSCLC) cells and elicits downstream signaling cascades and induces formation of both human epidermal growthfactor receptor 3 (HER3)/EGFR and HER3/HER2 heterodimers. Several high-affinity ligands for bombesin receptors were characterized, providing useful tools in investigation of biological roles of those peptides and their receptors.

SUMMARY

The most exciting findings of BLPs and their receptors in the past year come from studies in central nervous system. In addition, more researches are still underway to probe the molecular mechanisms of those peptides in peripheral tissues and characterize novel synthetic ligands with high affinity for mammalian bombesin receptors.