Proteomics investigation of the changes in serum proteins after high- and low-flux hemodialysis

Comparative analyses of adsorbed circulating proteins in the PMMA and PES hemodiafilters in patients on predilution online hemodiafiltration

Acute and chronic inflammation are common in patients with end-stage kidney disease (ESKD). So, the adsorption of pro-inflammatory cytokines by the hollow fiber of the dialysis membrane has been expected to modify the inflammatory dysregulation in ESKD patients. However, it remains to be determined in detail what molecules of fiber materials can preferably adsorb proteins from the circulating circuit. We aimed this study to analyze directly the adsorbed proteins in the polymethyl methacrylate (PMMA) and polyethersulfone (PES) membranes in patients on predilution online hemodiafiltration (OL-HDF). To compare the adsorbed proteins in the PMMA and PES hemodiafilters membrane, we initially performed predilution OL-HDF using the PES (MFX-25Seco) membrane while then switched to the PMMA (PMF™-A) membrane under the same condition in three patients. We extracted proteins from the collected hemodiafilters by extraction, then SDS-PAGE of the extracted sample, protein isolation, in-gel tryptic digestion, and nano-LC MS/MS analyses. The concentrations of adsorbed proteins from the PMMA and PES membrane extracts were 35.6±7.9 μg/μL and 26.1±9.2 μg/μL. SDS-PAGE analysis revealed distinct variations of adsorbed proteins mainly in the molecular weight between 10 to 25 kDa. By tryptic gel digestion and mass spectrometric analysis, the PMMA membrane exhibited higher adsorptions of β2 microglobulin, dermcidin, retinol-binding protein-4, and lambda-1 light chain than those from the PES membrane. In contrast, amyloid A-1 protein was adsorbed more potently in the PES membrane. Western blot analyses revealed that the PMMA membrane adsorbed interleukin-6 (IL-6) approximately 5 to 118 times compared to the PES membrane. These findings suggest that PMMA-based OL-HDF therapy may be useful in controlling inflammatory status in ESKD patients.

Comparative analysis of therapeutic effects between medium cut-off and high flux dialyzers using metabolomics and proteomics: exploratory, prospective study in hemodialysis

In this single-center prospective study of 20 patients receiving maintenance hemodialysis (HD), we compared the therapeutic effects of medium cut-off (MCO) and high flux (HF) dialyzers using metabolomics and proteomics. A consecutive dialyzer membrane was used for 15-week study periods: 1st HF dialyzer, MCO dialyzer, 2nd HF dialyzer, for 5 weeks respectively. ¹H-nuclear magnetic resonance was used to identify the metabolites and liquid chromatography-tandem mass spectrometry (LC–MS/MS) analysis was used to identify proteins. To compare the effects of the HF and MCO dialyzers, orthogonal projection to latent structure discriminant analysis (OPLS-DA) was performed. OPLS-DA showed that metabolite characteristics could be significantly classified by 1st HF and MCO dialyzers. The Pre-HD metabolites with variable importance in projection scores ≥ 1.0 in both 1st HF versus MCO and MCO versus 2nd HF were succinate, glutamate, and histidine. The pre-HD levels of succinate and histidine were significantly lower, while those of glutamate were significantly higher in MCO period than in the HF period. OPLS-DA of the proteome also substantially separated 1st HF and MCO periods. Plasma pre-HD levels of fibronectin 1 were significantly higher, and those of complement component 4B and retinol-binding protein 4 were significantly lower in MCO than in the 1st HF period. Interestingly, as per Ingenuity Pathway Analysis, an increase in epithelial cell proliferation and a decrease in endothelial cell apoptosis occurred during the MCO period. Overall, our results suggest that the use of MCO dialyzers results in characteristic metabolomics and proteomics profiles during HD compared with HF dialyzers, which might be related to oxidative stress, insulin resistance, complement-coagulation axis, inflammation, and nutrition.

A time-resolved proteomic and prognostic map of COVID-19

COVID-19 is highly variable in its clinical presentation, ranging from asymptomatic infection to severe organ damage and death. We characterized the time-dependent progression of the disease in 139 COVID-19 inpatients by measuring 86 accredited diagnostic parameters, such as blood cell counts and enzyme activities, as well as untargeted plasma proteomes at 687 sampling points. We report an initial spike in a systemic inflammatory response, which is gradually alleviated and followed by a protein signature indicative of tissue repair, metabolic reconstitution, and immunomodulation. We identify prognostic marker signatures for devising risk-adapted treatment strategies and use machine learning to classify therapeutic needs. We show that the machine learning models based on the proteome are transferable to an independent cohort. Our study presents a map linking routinely used clinical diagnostic parameters to plasma proteomes and their dynamics in an infectious disease.

Proteomic analysis of plasma proteins of high-flux haemodialysis and on-line haemodiafiltration patients reveals differences in transthyretin levels related with anaemia

A large proportion of end-stage renal disease (ESRD) patients under long-term haemodialysis, have persistent anaemia and require high doses of recombinant human erythropoietin (rhEPO). However, the underlying mechanisms of renal anaemia have not been fully elucidated in these patients. In this study, we will be focusing on anaemia and plasma proteins in ESRD patients on high-flux haemodialysis (HF) and on-line haemodiafiltration (HDF), to investigate using two proteomic approaches if patients undergoing these treatments develop differences in their plasma protein composition and how this could be related to their anaemia. The demographic and biochemical data revealed that HDF patients had lower anaemia and much lower rhEPO requirements than HF patients. Regarding their plasma proteomes, HDF patients had increased levels of a protein highly similar to serotransferrin, trypsin-1 and immunoglobulin heavy constant chain alpha-1, and lower levels of alpha-1 antitrypsin, transthyretin, apolipoproteins E and C-III, and haptoglobin-related protein. Lower transthyretin levels in HDF patients were further confirmed by transthyretin-peptide quantification and western blot detection. Since ESRD patients have increased transthyretin, a protein that can aggregate and inhibit transferrin endocytosis and erythropoiesis, our finding that HDF patients have lower transthyretin and lower anaemia suggests that the decrease in transthyretin plasma levels would allow an increase in transferrin endocytosis, contributing to erythropoiesis. Thus, transthyretin could be a critical actor for anaemia in ESRD patients and a novel player for haemodialysis adequacy.

Shrunken pore syndrome - a common kidney disorder with high mortality. Diagnosis, prevalence, pathophysiology and treatment options

Invasive studies show that the glomerular sieving coefficients for 5-30 kDa plasma proteins in the human kidney may be selectively reduced compared to those for small molecules < 0.9 kDa, commonly used to measure glomerular filtration rate (GFR). Identification of this pathophysiological state, called shrunken pore syndrome (SPS), can easily and non-invasively be done by comparing estimations of GFR using cystatin C (13.3 kDa) and creatinine (0.113 kDa). SPS is present if the estimate of GFR using cystatin C is lower than 60 or 70% of the estimate using creatinine in the absence of non-renal influences on cystatin C or creatinine. All studies of SPS show that the 3- or 5-year mortality is strongly increased and high hazard ratios for mortality associated with SPS have been observed for many different patient cohorts, including cohorts with normal measured GFR, no albuminuria and no diagnosis. The prevalence of SPS in the cohorts so far investigated is between 0.2 and 36%. Proteome studies of SPS demonstrate that the high mortality associated with the syndrome might be caused by the accumulation of 10-30 kDa signalling proteins promoting development of atherosclerosis and thus suggesting use of monoclonal antibodies to reduce the levels of the most detrimental signalling proteins as a treatment option. The KDIGO recommendations for classification of chronic kidney disease (CKD) comprise determination, or estimation, of GFR and analysis of albuminuria and therefore cannot identify a large fraction of the patients with SPS. The high prevalence and mortality of SPS and the possible treatment options strongly suggest that the KDIGO recommendations should be expanded to include determination of cystatin C to be able to identify all patients with SPS.