Alternate and Additional Functions of Erythrocyte Hemoglobin

Formation of Supplementary Metal-Binding Centers in Proteins under Stress Conditions

In many proteins, supplementary metal-binding centers appear under stress conditions. They are known as aberrant or atypical sites. Physico-chemical properties of proteins are significantly changed after such metal binding, and very stable protein aggregates are formed, in which metals act as "cross-linking" agents. Supplementary metal-binding centers in proteins often arise as a result of posttranslational modifications caused by reactive oxygen and nitrogen species and reactive carbonyl compounds. New chemical groups formed as a result of these modifications can act as ligands for binding metal ions. Special attention is paid to the role of cysteine SH-groups in the formation of supplementary metal-binding centers, since these groups are the main target for the action of reactive species. Supplementary metal binding centers may also appear due to unmasking of amino acid residues when protein conformation changing. Appearance of such centers is usually considered as a pathological process. Such unilateral approach does not allow to obtain an integral view of the phenomenon, ignoring cases when formation of metal complexes with altered proteins is a way to adjust protein properties, activity, and stability under the changed redox conditions. The role of metals in protein aggregation is being studied actively, since it leads to formation of non-membranous organelles, liquid condensates, and solid conglomerates. Some proteins found in such aggregates are typical for various diseases, such as Alzheimer's and Huntington's diseases, amyotrophic lateral sclerosis, and some types of cancer.

The low hemoglobin levels were associated with mortality in post-cardiotomy patients undergoing venoarterial extracorporeal membrane oxygenation

BACKGROUND

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is used as a rescue strategy for patients with refractory post-cardiotomy cardiogenic shock (PCS). These patients often have varying degrees of reduced hemoglobin levels, and there are few detailed investigations about the impact of hemoglobin level on their mortality. The objective of this study was to evaluate whether hemoglobin levels at day 1 from VA-ECMO initiation were associated with in-hospital mortality.

METHODS

We performed a retrospective analysis of adult VA-ECMO patients over approximately a 2-year period. We divided patients into survival and death groups based on their clinical outcomes and compared the differences in parameters between the two groups. Multivariate logistic regression analyses were performed to estimate whether hemoglobin level was related to the mortality.

RESULTS

One hundred and sixteen patients were included in final analysis. There were 52 patients in the survival group and 64 in the death group. The patients were younger in the survival group than the death group (58 vs 63, p = .023). The median (IQR) hemoglobin level at day 1 was 80 (73-89) × g/L, and the median (IQR) RelΔ hemoglobin was 41% (32-48%). Survival patients had a higher hemoglobin level at day 1 and a lower RelΔ hemoglobin than the death patients (91 vs 76 g/L, p < .001; 35% vs 45%, p < .001). The multivariable logistic regression analyses showed that the low hemoglobin levels at day 1 were independently associated with in-hospital mortality (OR 0.808; 95% CI, 0.747-0.874; p < .001). The AUROC for hemoglobin level was 0.89 (95% CI, 0.83-0.95) which was better than that of RelΔ hemoglobin (0.77, 95% CI, 0.68-0.86).

CONCLUSIONS

In patients receiving VA-ECMO for PCS, the low hemoglobin levels at day 1 were independently associated with in-hospital mortality.

Artificial Base-Directed In Vivo Assembly of an Albumin-siRNA Complex for Tumor-Targeting Delivery

RNA interference (RNAi) mediated by short interfering RNA (siRNA) is a promising method for cancer treatment, but the clinical application is hampered by several limitations, including metabolic instability, lack of tumor specificity, and poor cellular uptake. To meet these challenges, we have explored the possibility of structure modification of siRNA with artificial bases for property optimization. A series of siRNAs functionalized with different numbers of hydrophobic base F are prepared for screening. The interactions of plasma proteins with F-base-modified siRNA (F-siRNA) are investigated, and it is identified that the interaction with serum albumin is dominant. Experiments revealed that the introduction of F bases conferred modified siRNA with improved tumor-specific accumulation, prolonged circulatory retention time, and better tissue permeability. Mechanistic studies indicated that the F base induces the formulation of a stable siRNA-albumin complex, which transports siRNA to tumor tissues selectively owing to an enhanced permeability and retention (EPR) effect of albumin. The F base also facilitates the binding of siRNA to transport-associated proteins on the cell membrane, enabling its cellular internalization. Together, these data demonstrate that F base modification confers siRNA-enhanced cellular uptake and biostability and specific accumulation in tumor tissue, which provides a new approach for the development of siRNA-based cancer therapeutics.

The gender-specific bidirectional relations between chronic diseases and total bilirubin/urea in the elderly population: A 3-year longitudinal study

Aging is accompanied by changes in physiology over time, which remains the largest risk of chronic diseases. The aim of this study was to explore the gender-specific bidirectional relations between the risk of chronic diseases and serum traits in a 3-year longitudinal study. A hierarchical non-linear model with random effects was used to assess the temporal patterns of anthropometric and serum traits from 2017 to 2019 among 2,338 participants. To assess the directional effect between the risk of chronic diseases and serum traits, a bivariate cross-lagged panel model (CLPM) was used to estimate the structural relations of repeatedly measured variables at three different time points. Candidate SNPs were analyzed and genotyped in MassARRAY Analyzer 4 platforms. In this study, metabolic syndrome (MS) score increased with aging in females, whereas the fatty liver disease (FLD) index decreased with aging in males; the MS score was negatively correlated with TB in females, and FLD index was positively related to urea in males; CLPM showed that the MS score predicted total bilirubin (TB) in females, and urea predicted the FLD index in males. Additionally, rs2292354 in G protein-coupled receptor kinase interactor 2 (GIT2) was associated with the MS score and TB in aged females. Our study suggests the potential gender-specific causal associations between development in MS and increase in TB level in females, and rise in urea level and improved FLD index in males. The SNP rs2292354 we investigated might be a biomarker for predicting MS in the elderly Chinese Han population.

Long-Term Prognostic Factors in Patients With Antineutrophil Cytoplasmic Antibody-Associated Vasculitis: A 15-Year Multicenter Retrospective Study

Background

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a multisystem autoimmune disease with small-vessel involvement. In AAV, microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) are major clinicopathologic variants. In addition, myeloperoxidase (MPO) and proteinase 3 (PR3) are major target antigens. The objective of the study was to explore the predictive factors for long-term survival in AAV patients.

Materials and Methods

A multicenter retrospective study was carried out on 407 patients between 2005 and 2020. Clinical parameters were obtained from laboratory tests including the ANCA types, antinuclear antibody (ANA), extractable nuclear antigen (ENA), anti-streptolysin O (ASO), glomerular filtration rate (GFR), and the laboratory examinations for the blood routine, liver function, renal function, and immunity, etc. The data for clinical parameters were collected from electronic medical records (EMRs), and the data for patient survival were acquired through regular follow-up. The association of clinical parameters with overall survival (OS) along with 3-year and 5-year survival rates was analyzed, and the nomogram as a predictive model was established according to the analysis results.

Results

In the present study, 336 (82.6%) patients and 46 (11.3%) patients were diagnosed with MPA and GPA, respectively. The mean and median OS for all the patients were 2,285 and 2,290 days, respectively. The 1-year, 3-year, 5-year, and 10-year cumulative survival rates for all the patients were 84.2%, 76.3%, 57.2%, and 32.4%, respectively. Univariate and multivariate survival analyses indicated that the independent prognostic factors included age, pathological categories (MPA, GPA, and other types), serum ANCA types (negative or positive for MPO and/or PR3), ANA, ASO, GFR, lymphocyte, neutrophil-to-lymphocyte ratio (NLR), and C-reactive protein (CRP), and these clinical parameters except for ASO were used to construct a nomogram. The nomogram for 3-year and 5-year survival rates had a C-index of 0.721 (95% CI 0.676–0.766). The calibration curves showed that the predicted values of the nomogram for 3-year and 5-year survival rates were generally consistent with practical observed values, and decision curve analysis (DCA) further demonstrated the practicability and accuracy of the predictive model.

Conclusion

Laboratory tests at diagnosis have great significance in the prediction of long-term survival in AAV patients.

Posthepatectomy jaundice induced by paroxysmal nocturnal hemoglobinuria: A case report

BACKGROUND

Jaundice is a major manifestation of posthepatectomy liver failure, a feared complication after hepatic resection. Herein, we report a case of posthepatectomy jaundice that was not caused by liver failure but by paroxysmal nocturnal hemoglobinuria (PNH)-induced hemolysis.

CASE SUMMARY

A 56-year-old woman underwent right hepatectomy and biliary tract exploration surgery due to hepatic duct stones. Prior to surgery, the patient was mildly anemic. The direct antiglobulin test was negative. A bone marrow biopsy showed mild histiocyte hyperplasia. After surgery, the patient suffered a progressive increase in serum bilirubin. Meanwhile, the patient developed hemolytic symptoms after blood transfusion. She was ultimately diagnosed with PNH. PNH is a rare bone marrow failure disorder that manifests as complement-dependent intravascular hemolysis with varying severity. After steroid treatment, the patient’s jaundice gradually decreased, and the patient was discharged on the 35^th postoperative day.

CONCLUSION

PNH-induced hemolysis is a rare cause of posthepatectomy jaundice. It should be suspected in patients having posthepatectomy hyperbilirubinemia without other signs of liver failure. Steroid therapy can be considered for the treatment of PNH in such cases.

The influence of anaemia on pressure ulcer healing in elderly patients

Anaemia is a common and multifactorial blood disorder in elderly individuals. This condition may be a significant barrier to pressure ulcers healing as it is associated with a decreased level of oxygen being supplied to body tissues. Some nutritional deficiencies such as iron, vitamin B12 and folate may also cause anaemia and have a negative impact on pressure ulcer healing. An increased iron demand in hard-to-heal pressure ulcers is a significant factor associated with the risk of anaemia of chronic disease in elderly patients. Anaemia screening and correction may need to be considered as well as iron supplementation if required in pressure ulcer prevention and management.

RNA-Seq analysis of knocking out the neuroprotective proton-sensitive GPR68 on basal and acute ischemia-induced transcriptome changes and signaling in mouse brain

Brain acid signaling plays important roles in both physiological and disease conditions. One key neuronal metabotropic proton receptor in the brain is GPR68, which contributes to hippocampal long-term potentiation (LTP) and mediates neuroprotection in acidotic and ischemic conditions. Here, to gain greater understanding of GPR68 function in the brain, we performed mRNA-Seq analysis in mice. First, we studied sham-operated animals to determine baseline expression. Compared to wild type (WT), GPR68-/- (KO) brain downregulated genes that are enriched in Gene Ontology (GO) terms of misfolding protein binding, response to organic cyclic compounds, and endoplasmic reticulum chaperone complex. Next, we examined the expression profile following transient middle cerebral artery occlusion (tMCAO). tMCAO-upregulated genes cluster to cytokine/chemokine-related functions and immune responses, while tMCAO-downregulated genes cluster to channel activities and synaptic signaling. For proton-sensitive receptors, tMCAO downregulated ASIC1a and upregulated GPR4 and GPR65, but had no effect on ASIC2, PAC, or GPR68. GPR68 deletion did not alter the expression of these proton receptors, either at baseline or after ischemia. Lastly, we performed GeneVenn analysis of differential genes at baseline and post-tMCAO. Ischemia upregulated the expression of three hemoglobin genes, along with H2-Aa, Ppbp, Siglece, and Tagln, in WT but not in KO. Immunostaining showed that tMCAO-induced hemoglobin localized to neurons. Western blot analysis further showed that hemoglobin induction is GPR68-dependent. Together, these data suggest that GPR68 deletion at baseline disrupts chaperone functions and cellular signaling responses and imply a contribution of hemoglobin-mediated antioxidant mechanism to GPR68-dependent neuroprotection in ischemia.

Carbonyl Stress in Red Blood Cells and Hemoglobin

The paper overviews the peculiarities of carbonyl stress in nucleus-free mammal red blood cells (RBCs). Some functional features of RBCs make them exceptionally susceptible to reactive carbonyl compounds (RCC) from both blood plasma and the intracellular environment. In the first case, these compounds arise from the increased concentrations of glucose or ketone bodies in blood plasma, and in the second-from a misbalance in the glycolysis regulation. RBCs are normally exposed to RCC-methylglyoxal (MG), triglycerides-in blood plasma of diabetes patients. MG modifies lipoproteins and membrane proteins of RBCs and endothelial cells both on its own and with reactive oxygen species (ROS). Together, these phenomena may lead to arterial hypertension, atherosclerosis, hemolytic anemia, vascular occlusion, local ischemia, and hypercoagulation phenotype formation. ROS, reactive nitrogen species (RNS), and RCC might also damage hemoglobin (Hb), the most common protein in the RBC cytoplasm. It was Hb with which non-enzymatic glycation was first shown in living systems under physiological conditions. Glycated HbA1c is used as a very reliable and useful diagnostic marker. Studying the impacts of MG, ROS, and RNS on the physiological state of RBCs and Hb is of undisputed importance for basic and applied science.

Hemoglobin: Structure, Function and Allostery

This chapter reviews how allosteric (heterotrophic) effectors and natural mutations impact hemoglobin (Hb) primary physiological function of oxygen binding and transport. First, an introduction about the structure of Hb is provided, including the ensemble of tense and relaxed Hb states and the dynamic equilibrium of Hb multistate. This is followed by a brief review of Hb variants with altered Hb structure and oxygen binding properties. Finally, a review of different endogenous and exogenous allosteric effectors of Hb is presented with particular emphasis on the atomic interactions of synthetic ligands with altered allosteric function of Hb that could potentially be harnessed for the treatment of diseases.

Phase III, placebo-controlled, randomized, double-blind trial of tableted, therapeutic TB vaccine (V7) containing heat-killed M. vaccae administered daily for one month

Objective

Immunotherapy of tuberculosis (TB) to shorten treatment duration represents an unmet medical need. Orally delivered, tableted TB vaccine (V7) containing heat-killed Mycobacterium vaccae (NCTC 11659) has been demonstrated in prior clinical studies to be safe and fast-acting immune adjunct.

Methods

The outcome of Phase III trial of V7 containing 10 µg of hydrolyzed M. vaccae was evaluated in 152 patients randomized at 2:1 ratio: V7 (N = 100), placebo (N = 52). Both arms received conventional 1st or 2nd line TB drugs co-administered with daily pill of V7 or placebo.

Results

After one month mycobacterial clearance was observed in 68% (P < 0.0001) and 23.1% (P = 0.04) of patients on V7 and placebo. Stratified conversion rates in V7 recipients with drug-sensitive and multidrug-resistant TB were 86.7% and 55.6% vs 27.2% and 15% in placebo. Patients on V7 gained on average 2.4 kg (P < 0.0001) vs 0.3 kg (P = 0.18) in placebo. Improvements in hemoglobin levels, erythrocyte sedimentation rate and leukocyte counts were significantly better than in controls. Liver function tests revealed that V7 can prevent chemotherapy-induced hepatic damage.

Conclusion

Oral M. vaccae is safe, can overcome TB-associated weight loss and inflammation, reduce hepatotoxicity of TB drugs, improve sputum conversion three-fold OR 3.15; 95%CI (2.3,4.6), and cut treatment length by at least six-fold. Longer follow-up studies might be needed to further substantiate our findings (Clinicaltrials.gov: NCT01977768).