A novel composition of endogenous metabolic modulators improves red blood cell properties in sickle cell disease

The most common forms of sickle cell disease (SCD) are sickle cell anemia (SCA; HbSS) and HbSC disease. In both, especially the more dense, dehydrated and adherent red blood cells (RBCs) with reduced deformability are prone to hemolysis and sickling, and thereby vaso-occlusion. Based on plasma amino acid profiling in SCD, a composition of 10 amino acids and derivatives (RCitNacQCarLKHVS; Axcella Therapeutics, USA), referred to as endogenous metabolic modulators (EMMs), was designed to target RBC metabolism. The effects of ex vivo treatment with the EMM composition on different RBC properties were studied in SCD (n = 9 SCA, n = 5 HbSC disease). Dose-dependent improvements were observed in RBC hydration assessed by hemocytometry (MCV, MCHC, dense RBCs) and osmotic gradient ektacytometry (Ohyper). Median (interquartile range [IQR]) increase in Ohyper compared to vehicle was 4.9% (4.0%-5.5%), 7.5% (6.9%-9.4%), and 12.8% (11.5%-14.0%) with increasing 20×, 40×, and 80X concentrations, respectively (all p < 0.0001). RBC deformability (EImax using oxygen gradient ektacytometry) increased by 8.1% (2.2%-12.1%; p = 0.0012), 9.6% (2.9%-15.1%; p = 0.0013), and 13.3% (5.7%-25.5%; p = 0.0007), respectively. Besides, RBC adhesion to subendothelial laminin decreased by 43% (6%-68%; p = 0.4324), 58% (48%-72%; p = 0.0185), and 71% (49%-82%; p = 0.0016), respectively. Together, these results provide a rationale for further studies with the EMM composition targeting multiple RBC properties in SCD.

COVID-19 PANDEMIC INDUCED DISRUPTIONS IN TROPONIN AND LOW-DENSITY LIPOPROTEIN CHOLESTEROL LABORATORY TEST VOLUMES ACROSS ALBERTA

BACKGROUND

Atherosclerotic cardiovascular disease (ASCVD) is a leading cause of morbidity and mortality in Canada and worldwide. Laboratory tests, including troponin and low-density lipoprotein cholesterol (LDL-C), are important biomarkers of ASCVD risk. The objective of this study was to investigate patterns of testing for troponin and LDL-C test volumes among Alberta residents during the coronavirus disease 2019 (COVID-19) pandemic.

METHODS AND RESULTS

A repeated cross-sectional study design captured population-level laboratory test volumes between March 15, 2019 and December 14, 2020. Three-month cross-sections were derived to report laboratory test volumes by different COVID-19 restriction periods during 2020-2021 and using 2019-2020 as a preceding control period. Percent change for troponin and LDL-C test volumes were calculated for both control and COVID-19 periods among adult (≥18 years of age) Alberta residents, and stratified by age (18-49, 50-65, 66-79, and ≥80 years), sex, and geographic zones (urban, rural). This preliminary data is part of an ongoing study for which further troponin and LDL-C test volumes will be available up until March 14, 2021 (representing one year of data throughout the COVID-19 pandemic). Among the Alberta population, 292,836 troponin and 794,789 LDL-C tests were captured between March 15, 2020 and December 14, 2020 (Figure 1). Testing patterns during the COVID-19 restriction period showed marked reduction in test volumes from the previous year. The initial cross-section of the COVID-19 period (March-June 2020) was characterized by the largest overall reduction with troponin test volumes decreasing 18% and LDL-C test volumes decreasing 63%, compared to the year prior. As restrictions eased in the summer months of 2020, testing volumes rebounded to near pre-pandemic volumes for both tests. However, in the fall of 2020, troponin tests decreased again (-15%). Within these drops in utilization, slightly larger relative declines were observed for troponin test volumes in women (-20%) and patients ≥80 years-old (-25%) and for LDL-C test volumes among urban residents (-64%), women (-67%) and patients aged 18-49 (-66%) and 50-65 (-65%) years (Table 1).

CONCLUSION

This study describes declines in troponin and LDL-C test volumes in the initial and second COVID-19 lockdown periods. Women had overall smaller total troponin and LDL-C test volumes and larger relative declines during the pandemic compared to men. The decrease in these ASCVD-related laboratory test volumes during the pandemic may have been accompanied by other important changes in indicators of healthcare utilization and associated clinical outcomes. Ongoing analyses will further explore the impact of the pandemic.

Analysis of Cysteine Redox Post-Translational Modifications in Cell Biology and Drug Pharmacology

Reversible cysteine oxidation is an emerging class of protein post-translational modification (PTM) that regulates catalytic activity, modulates conformation, impacts protein-protein interactions, and affects subcellular trafficking of numerous proteins. Redox PTMs encompass a broad array of cysteine oxidation reactions with different half-lives, topographies, and reactivities such as S-glutathionylation and sulfoxidation. Recent studies from our group underscore the lesser known effect of redox protein modifications on drug binding. To date, biological studies to understand mechanistic and functional aspects of redox regulation are technically challenging. A prominent issue is the lack of tools for labeling proteins oxidized to select chemotype/oxidant species in cells. Predictive computational tools and curated databases of oxidized proteins are facilitating structural and functional insights into regulation of the network of oxidized proteins or redox proteome. In this chapter, we discuss analytical platforms for studying protein oxidation, suggest computational tools currently available in the field to determine redox sensitive proteins, and begin to illuminate roles of cysteine redox PTMs in drug pharmacology.

Protein redox chemistry: post-translational cysteine modifications that regulate signal transduction and drug pharmacology

The perception of reactive oxygen species has evolved over the past decade from agents of cellular damage to secondary messengers which modify signaling proteins in physiology and the disease state (e.g., cancer). New protein targets of specific oxidation are rapidly being identified. One emerging class of redox modification occurs to the thiol side chain of cysteine residues which can produce multiple chemically distinct alterations to the protein (e.g., sulfenic/sulfinic/sulfonic acid, disulfides). These post-translational modifications (PTM) are shown to affect the protein structure and function. Because redox-sensitive proteins can traffic between subcellular compartments that have different redox environments, cysteine oxidation enables a spatio-temporal control to signaling. Understanding ramifications of these oxidative modifications to the functions of signaling proteins is crucial for understanding cellular regulation as well as for informed-drug discovery process. The effects of EGFR oxidation of Cys₇₉₇ on inhibitor pharmacology are presented to illustrate the principle. Taken together, cysteine redox PTM can impact both cell biology and drug pharmacology.

Broad phenotypic changes associated with gain of radiation resistance in head and neck squamous cell cancer

AIMS

The central issue of resistance to radiation remains a significant challenge in the treatment of cancer despite improvements in treatment modality and emergence of new therapies. To facilitate the identification of molecular factors that elicit protection against ionizing radiation, we developed a matched model of radiation resistance for head and neck squamous cell cancer (HNSCC) and characterized its properties using quantitative mass spectrometry and complementary assays.

RESULTS

Functional network analysis of proteomics data identified DNA replication and base excision repair, extracellular matrix-receptor interaction, cell cycle, focal adhesion, and regulation of actin cytoskeleton as significantly up- or downregulated networks in resistant (rSCC-61) HNSCC cells. Upregulated proteins in rSCC-61 included a number of cytokeratins, fatty acid synthase, and antioxidant proteins. In addition, the rSCC-61 cells displayed two unexpected features compared with parental radiation-sensitive SCC-61 cells: (i) rSCC-61 had increased sensitivity to Erlotinib, a small-molecule inhibitor of epidermal growth factor receptor; and (ii) there was evidence of mesenchymal-to-epithelial transition in rSCC-61, confirmed by the expression of protein markers and functional assays (e.g., Vimentin, migration).

INNOVATION

The matched model of radiation resistance presented here shows that multiple signaling and metabolic pathways converge to produce the rSCC-61 phenotype, and this points to the function of the antioxidant system as a major regulator of resistance to ionizing radiation in rSCC-61, a phenomenon further confirmed by analysis of HNSCC tumor samples.

CONCLUSION

The rSCC-61/SCC-61 model provides the opportunity for future investigations of the redox-regulated mechanisms of response to combined radiation and Erlotinib in a preclinical setting.

A simple and effective strategy for labeling cysteine sulfenic acid in proteins by utilization of β-ketoesters as cleavable probes

β-ketoesters are robust probes for labeling sulfenic acid (-SOH) proteins allowing quantitative cleavage of the tag for improved analysis of the labeled peptides by MS.

Oxidation of Akt2 kinase promotes cell migration and regulates G1-S transition in the cell cycle

Phosphorylation has long been recognized as the key mediator of protein signaling. New modes of signaling regulation are emerging with the development of specific chemical probes and application of high-throughput mass spectrometry technologies. Using biotin-tagged chemical probes for protein oxidation, mass spectrometry and functional assays, our group has recently reported isoform-specific oxidation of Akt2 in response to PDGF signaling. The studies included here investigate the functional consequence of oxidation on Akt2-mediated cell migration and cell cycle. Akt2-KO MEFs transduced with WT and Cys124Ser Akt2 were used as the model system for these studies. The implications of these findings on disease pathology are discussed.

Collapsing glomerulopathy in an HIV-positive patient in a low-incidence belt

Human immunodeficiency virus (HIV) involves glomerular, tubulointerstitial, and vascular compartments of the kidney. The most common glomerular lesion is HIV-associated focal segmental glomerulosclerosis (FSGS) and related mesangiopathies collectively termed HIV-associated nephropathy (HIVAN). A variety of immune-complex mediated glomerular diseases such as membranoproliferative glomerulonephritis (MPGN), IgA nephropathy, and lupus-like glomerulonephritis also occur. HIVAN is restricted to patients presenting with proteinuria and progressive reduction of renal function and with distinctive but not pathognomonic pathology (FSGS often coexisting with glomerular collapse and tubular microcystic dilatations). The worldwide incidence of collapsing glomerulopathy (CG) in HIV-positive patients is high in Americans. But in India and other Asian countries, other forms of kidney diseases are more commonly seen. We report the first case of CG in the state of Jammu and Kashmir which also happens to be a very low incidence belt for HIV.

Chromate reduction by Burkholderia cepacia MCMB-821,isolated from the pristine habitat of alkaline crater lake

The Cr(VI)-reducing bacterial strain MCMB-821 was isolated from the alkaline crater lake of Lonar and was identified as Burkholderia cepacia. MCMB-821 was resistant to 1,000-ppm Cr(VI) and reduced 98% of the 75 ppm Cr(VI) within 36 h at pH 9.0 in the presence of 2% salt and lactose as the electron donor. The chromate-reducing efficiency of MCMB-821 was comparable under both aerobic as well as anaerobic conditions. Electron paramagnetic resonance spectroscopy data suggested that MCMB-821 reduced Cr(VI) to Cr(III) via the formation of transient Cr(V) intermediate. The chromate-reducing ability of MCMB-821 was suppressed in the presence of membrane inhibitors and enhanced in the presence of 2,4-dinitrophenol, suggesting the involvement of electron transport chain in the Cr(VI) bioreduction.