Cathepsin S as an early biomarker for cardiovascular disease in chronic kidney disease patients

Identification of co-expressed central genes and transcription factors in acute myocardial infarction and diabetic nephropathy

BACKGROUND

Acute myocardial infarction (AMI) and diabetic nephropathy (DN) are common clinical co-morbidities, but they are challenging to manage and have poor prognoses. There is no research on the bioinformatics mechanisms of comorbidity, and this study aims to investigate such mechanisms.

METHODS

We downloaded the AMI data (GSE66360) and DN datasets (GSE30528 and GSE30529) from the Gene Expression Omnibus (GEO) platform. The GSE66360 dataset was divided into two parts: the training set and the validation set, and GSE30529 was used as the training set and GSE30528 as the validation set. After identifying the common differentially expressed genes (DEGs) in AMI and DN in the training set, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses and protein-protein interaction (PPI) network construction were performed. A sub-network graph was constructed by MCODE, and 15 hub genes were screened by the Cytohubba plugin. The screened hub genes were validated, and the 15 screened hub genes were subjected to GO, KEGG, Gene MANIA analysis, and transcription factor (TF) prediction. Finally, we performed TF differential analysis, enrichment analysis, and TF and gene regulatory network construction.

RESULTS

A total of 46 genes (43 up-regulated and 3 down-regulated) were identified for subsequent analysis. GO functional analysis emphasized the presence of genes mainly in the vesicle membrane and secretory granule membrane involved in antigen processing and presentation, lipopeptide binding, NAD + nucleosidase activity, and Toll-like receptor binding. The KEGG pathways analyzed were mainly in the phagosome, neutrophil extracellular trap formation, natural killer cell-mediated cytotoxicity, apoptosis, Fc gamma R-mediated phagocytosis, and Toll-like receptor signaling pathways. Eight co-expressed hub genes were identified and validated, namely TLR2, FCER1G, CD163, CTSS, CLEC4A, IGSF6, NCF2, and MS4A6A. Three transcription factors were identified and validated in AMI, namely NFKB1, HIF1A, and SPI1.

CONCLUSIONS

Our study reveals the common pathogenesis of AMI and DN. These common pathways and hub genes may provide new ideas for further mechanistic studies.

Dysregulation of kidney proteases in the pathogenesis of hypertension following unilateral nephrectomy in juvenile mice

BACKGROUND

Unliteral nephrectomy (UNX) results in the reduction of kidney mass. The remaining kidney undergoes compensatory renal growth via hypertrophy of the glomeruli and renal tubules to maintain a normal glomerular filtration rate (GFR). These compensatory mechanisms result in increased capillary pressure and glomerular hyperfiltration to increase single nephron GFR. Over time, hyperfiltration may lead to kidney scarring and the development of hypertension.

OBJECTIVES

The first objective of this study was to test the hypothesis that a 50% reduction in functioning nephrons in juvenile mice leads to increased blood pressure over a 24-hour phase. The second objective was to test the hypothesis that UNX leads to changes in the expression and activity of kidney proteases in juvenile mice.

METHODS

Eight male C57B6 juvenile wild-type mice were subject to UNX and an equal number of mice were subject to sham (SH) surgery. Metabolic cage studies were performed for 5 weeks to collect urine produced during the inactive and active phases. Blood pressure was measured using the tail cuff method twice weekly and tail blood was collected on different days during the inactive or active phase of each animal. The mice were euthanized at the age of 9 weeks. Western blotting and immunohistochemistry were performed to investigate changes in renal protein expression of various cathepsins and renal kallikrein 1 (KLK1) between the two groups. Protease activity assays were performed using kidney lysates and urine samples from each group.

RESULTS

Compared to the SH group, UNX mice showed a persistent increase in blood pressure at week 3 which progressed toward the end of the study at week 5 of age. Cathepsin B, D, and S expression and activity were up-regulated in kidney cortex lysates from UNX mice compared to the SH control group. KLK1 protein expression was down-regulated and urinary nitric oxide excretion was decreased in UNX mice compared to the SH control group.

CONCLUSION

UNX results in the development of persistent and progressive hypertension. Down-regulation of KLK1 and up-regulation of various cathepsins may contribute to the development of hypertension via multiple mechanisms including a decrease in nitric oxide (NO) production.

Serum Cathepsin S Levels Do Not Show Alterations in Different Clinical, Neuropathological, or Genetic Subtypes of Frontotemporal Dementia Patients nor in Comparison to Healthy Control Individuals

Frontotemporal dementia (FTD) can manifest as diverse clinical phenotypes and is frequently caused by mutations in different genes, complicating differential diagnosis. This underlines the urgent need for valid biomarkers. Altered lysosomal and immune functions proposedly contribute to FTD pathogenesis. Cathepsins, including cathepsin S, are enzymes preferentially expressed in brain in microglia, which influence lysosomal and immune function. Here, we examined whether alterations in serum cathepsin S levels associate with specific clinical, genetic, or neuropathological FTD subgroups, but no such alterations were observed. However, further research on other lysosomal proteins may reveal new biologically relevant biomarkers in FTD.

Cathepsin S Inhibition Suppresses Experimental Systemic Lupus Erythematosus-Associated Pulmonary Arterial Remodeling

Patients with systemic lupus erythematosus (SLE) associated with pulmonary arterial hypnertension (PAH) receive targeted therapy for PAH to decrease pulmonary arterial systolic pressure and significantly prolong their survival. Cysteine cathepsin proteases play critical roles in the progression of cardiovascular disease. Inhibition of cathepsin S (Cat S) has been shown to improve SLE and lupus nephritis. However, the effect of Cat S inhibitors on SLE-associated PAH (SLE-PAH) remains unclear, and there is no animal model for translational research on SLE-PAH. We hypothesized that the inhibition of Cat S may affect PAH development and arterial remodeling associated with SLE. A female animal model of SLE-PAH, female MRL/lpr (Lupus), was used to evaluate the role of pulmonary arterial remodeling in SLE. The key finding of the research work is the establishment of an animal model of SLE associated with PAH in female MRL/lpr mice that is able to evaluate pulmonary arterial remodeling starting from the age of 11 weeks to 15 weeks. Cat S protein level was identified as a marker of experimental SLE. Pulmonary hypertension in female MRL/lpr (Lupus) mice was treated by administering the selective Cat S inhibitor Millipore-219393, which stimulated peroxisome proliferator-activated receptor-gamma (PPARγ) in the lungs to inhibit Cat S expression and pulmonary arterial remodeling. Studies provide an animal model of female MRL/lpr (Lupus) associated with PAH and a deeper understanding of the pathogenesis of SLE-PAH. The results may define the role of cathepsin S in preventing progressive and fatal SLE-PAH and provide approaches for therapeutic interventions in SLE-PAH.