Hydroxyurea Scavenges Free Radicals and Induces the Expression of Antioxidant Genes in Human Cell Cultures Treated With Hemin

Characteristic effect of hydroxyurea on the higher-order structure of DNA and gene expression

Hydroxyurea (HU; hydroxycarbamide) is a chemotherapy medication used to treat various types of cancer and other diseases such as sickle cell anemia. HU inhibits DNA synthesis by targeting ribonucleotide reductase (RNR). Recent studies have suggested that HU also causes oxidative stress in living systems. In the present study, we investigated if HU could directly affect the activity and/or conformation of DNA. We measured in vitro gene expression in the presence of HU by adapting a cell-free luciferase assay. HU exhibited a bimodal effect on gene expression, where promotion or inhibition were observed at lower or higher concentrations (mM range), respectively. Using atomic force microscopy (AFM), the higher-order structure of DNA was revealed to be partially-thick with kinked-branching structures after HU was added. An elongated coil conformation was observed by AFM in the absence of HU. Single DNA molecules in bulk aqueous solution under fluctuating Brownian motion were imaged by fluorescence microscopy (FM). Both spring and damping constants, mechanical properties of DNA, increased when HU was added. These experimental investigations indicate that HU directly interacts with DNA and provide new insights into how HU acts as a chemotherapeutic agent and targets other diseases.

Oxidation of hemoproteins by Streptococcus pneumoniae collapses the cell cytoskeleton and disrupts mitochondrial respiration leading to the cytotoxicity of human lung cells

IMPORTANCE

Streptococcus pneumoniae (Spn) colonizes the lungs, killing millions every year. During its metabolism, Spn produces abundant amounts of hydrogen peroxide. When produced in the lung parenchyma, Spn-hydrogen peroxide (H2O2) causes the death of lung cells, and details of the mechanism are studied here. We found that Spn-H2O2 targets intracellular proteins, resulting in the contraction of the cell cytoskeleton and disruption of mitochondrial function, ultimately contributing to cell death. Intracellular proteins targeted by Spn-H2O2 included cytochrome c and, surprisingly, a protein of the cell cytoskeleton, beta-tubulin. To study the details of oxidative reactions, we used, as a surrogate model, the oxidation of another hemoprotein, hemoglobin. Using the surrogate model, we specifically identified a highly reactive radical whose creation was catalyzed by Spn-H2O2. In sum, we demonstrated that the oxidation of intracellular targets by Spn-H2O2 plays an important role in the cytotoxicity caused by Spn, thus providing new targets for interventions.

Irisin: A Potentially Fresh Insight into the Molecular Mechanisms Underlying Vascular Aging

Aging is a natural process that affects all living organisms, including humans. Aging is a complex process that involves the gradual deterioration of various biological processes and systems, including the cardiovascular system. Vascular aging refers to age-related changes in blood vessels. These changes can increase the risk of developing cardiovascular diseases, such as hypertension, atherosclerosis, and stroke. Recently, an exercise-induced muscle factor, irisin, was found to directly improve metabolism and regulate the balance of glucolipid metabolism, thereby counteracting obesity and insulin resistance. Based on a growing body of evidence, irisin modulates vascular aging. Adenosine monophosphate-activated protein kinase (AMPK) serves as a pivotal cellular energy sensor and metabolic modulator, acting as a central signaling cascade to coordinate various cellular processes necessary for maintaining vascular homeostasis. The vascular regulatory effects of irisin are closely intertwined with its interaction with the AMPK pathway. In conclusion, understanding the molecular processes used by irisin to regulate changes in vascular diseases caused by aging may inspire the development of techniques that promote healthy vascular aging. This review sought to describe the impact of irisin on the molecular mechanisms of vascular aging, including inflammation, oxidative stress, and epigenetics, from the perspective of endothelial cell function and vascular macroregulation, and summarize the multiple signaling pathways used by irisin to regulate vascular aging.

From Stress to Sick(le) and Back Again-Oxidative/Antioxidant Mechanisms, Genetic Modulation, and Cerebrovascular Disease in Children with Sickle Cell Anemia

Sickle cell anemia (SCA) is a genetic disease caused by the homozygosity of the HBB:c.20A>T mutation, which results in the production of hemoglobin S (HbS). In hypoxic conditions, HbS suffers autoxidation and polymerizes inside red blood cells, altering their morphology into a sickle shape, with increased rigidity and fragility. This triggers complex pathophysiological mechanisms, including inflammation, cell adhesion, oxidative stress, and vaso-occlusion, along with metabolic alterations and endocrine complications. SCA is phenotypically heterogeneous due to the modulation of both environmental and genetic factors. Pediatric cerebrovascular disease (CVD), namely ischemic stroke and silent cerebral infarctions, is one of the most impactful manifestations. In this review, we highlight the role of oxidative stress in the pathophysiology of pediatric CVD. Since oxidative stress is an interdependent mechanism in vasculopathy, occurring alongside (or as result of) endothelial dysfunction, cell adhesion, inflammation, chronic hemolysis, ischemia-reperfusion injury, and vaso-occlusion, a brief overview of the main mechanisms involved is included. Moreover, the genetic modulation of CVD in SCA is discussed. The knowledge of the intricate network of altered mechanisms in SCA, and how it is affected by different genetic factors, is fundamental for the identification of potential therapeutic targets, drug development, and patient-specific treatment alternatives.

Protective effect of heme chloride on hypoxia-induced tissue injury in mice

OBJECTIVES

Heme chloride (Hemin) is an in vitro purified form of natural heme and an important raw material for anti-anemia and antitumor drugs. This study aims to analyze the protective effect of Hemin on tissue damage in low-pressure oxygen chamber simulated plateau hypoxic mice, and explore its role in anti-plateau hypoxia.

METHODS

Thirty male BALB/c mice were randomly divided into a blank group, a positive drug group (acetazolomide, 200 mg/kg), a Hemin low-dose group (15 mg/kg), a Hemin medium-dose group (30 mg/kg), and a Hemin high-dose group (60 mg/kg) with intraperitoneal injection. The anti-hypoxic activity of Hemin was explored by atmospheric closed hypoxia experiment and the optimal dose was screened. Thirty-six male BALB/c mice were randomly divided into a blank group, a hypoxia group, a positive drug group, and a Hemin high-dose group. The plasma inflammatory factor levels and oxidative stress indicators malondialdehyde (MDA), glutataione (GSH), and superoxide dismutase (SOD) levels of myocardium, brain, lung, and liver tissues were measured in different groups with hypoxia for 24 h. The degree of histopathological damage of mice was observed with HE staining. The degree of protection of Hemin against tissue hypoxia injury was detected with the hypoxia probe piperidazole.

RESULTS

Compared with the blank group, the survival time of mice in the positive drug group, the Hemin medium-dose group, and high-dose group was significantly extended (all P<0.05), with the highest prolongation rate in the Hemin high-dose group. Compared with the hypoxia group, mice in the Hemin high-dose group showed a significant increase in SOD level and GSH content of brain tissue, and a significant decrease in MDA content of lung tissue (all P<0.05). The results of HE staining and hypoxia probe showed that Hemin had a significant protective effect on the damage of liver, heart, brain and lung tissues of mice with hypoxia, and the most obvious effect on that of the brain tissue.

CONCLUSIONS

Hemin has an effect of improvement on oxidative stress and inflammatory response caused by hypoxia, and has obvious protective effect on tissue damage caused by hypoxia.

Microsomal glutathione transferase 1 in cancer and the regulation of ferroptosis

Microsomal glutathione transferase 1 (MGST1) is a member of the MAPEG family (membrane associated proteins in eicosanoid and glutathione metabolism), defined according to enzymatic activities, sequence motifs, and structural properties. MGST1 is a homotrimer which can bind three molecules of glutathione (GSH), with one modified to a thiolate anion displaying one-third-of-sites-reactivity. MGST1 has both glutathione transferase and peroxidase activities. Each is based on stabilizing the GSH thiolate in the same active site. MGST1 is abundant in the liver and displays a broad subcellular distribution with high levels in endoplasmic reticulum and mitochondrial membranes, consistent with a physiological role in protection from reactive electrophilic intermediates and oxidative stress. In this review paper, we particularly focus on recent advances made in understanding MGST1 activation, induction, broad subcellular distribution, and the role of MGST1 in apoptosis, ferroptosis, cancer progression, and therapeutic responses.

Oxidation of hemoproteins by Streptococcus pneumoniae collapses the cell cytoskeleton and disrupts mitochondrial respiration leading to cytotoxicity of human lung cells

Streptococcus pneumoniae (Spn) causes pneumonia that kills millions through acute toxicity and invasion of the lung parenchyma. During aerobic respiration, Spn releases hydrogen peroxide (Spn-H 2 O 2 ), as a by-product of enzymes SpxB and LctO, and causes cell death with signs of both apoptosis and pyroptosis by oxidizing unknown cell targets. Hemoproteins are molecules essential for life and prone to oxidation by H 2 O 2 . We recently demonstrated that during infection-mimicking conditions, Spn-H 2 O 2 oxidizes the hemoprotein hemoglobin (Hb), releasing toxic heme. In this study, we investigated details of the molecular mechanism(s) by which the oxidation of hemoproteins by Spn-H 2 O 2 causes human lung cell death. Spn strains, but not H 2 O 2 -deficient SpnΔ spxB Δ lctO strains caused time-dependent cell cytotoxicity characterized by the rearrangement of the actin, the loss of the microtubule cytoskeleton and nuclear contraction. Disruption of the cell cytoskeleton correlated with the presence of invasive pneumococci and an increase of intracellular reactive oxygen species. In cell culture, the oxidation of Hb or cytochrome c (Cyt c ) caused DNA degradation and mitochondrial dysfunction from inhibition of complex I-driven respiration, which was cytotoxic to human alveolar cells. Oxidation of hemoproteins resulted in the creation of a radical, which was identified as a protein derived side chain tyrosyl radical by using electron paramagnetic resonance (EPR). Thus, we demonstrate that Spn invades lung cells, releasing H 2 O 2 that oxidizes hemoproteins, including Cyt c , catalyzing the formation of a tyrosyl side chain radical on Hb and causing mitochondrial disruption, that ultimately leads to the collapse of the cell cytoskeleton.

Pulmonary hypertension is associated with poor cardiovascular and hematologic outcomes in patients with myeloproliferative neoplasms and cardiovascular disease

Cardiovascular events and hematologic progression to myelofibrosis or leukemia are leading causes of morbidity and mortality among patients with myeloproliferative neoplasms (MPN). Pulmonary hypertension (PH) is also associated with MPN and cardiovascular disease (CVD), though its prognostic significance in MPN is not well characterized. Our primary objective was to investigate the effect of PH, defined as right-ventricular systolic pressure (RVSP) ≥ 50 mmHg on echocardiogram or mean pulmonary artery pressure (mPAP) ≥ 20 on right heart catheterization, on cardiovascular and all-cause mortality and hematologic progression in patients with MPN and CVD (atrial fibrillation, heart failure hospitalization, and myocardial infarction after MPN diagnosis). Of the 197 patients included (86 ET, 80 PV, 31 PMF), 92 (47%) had PH and 98 (50%) were male. All-cause mortality (58 vs 37%, p = 0.004), cardiovascular death (35 vs 9%, p < 0.0001), and hematologic progression (23 vs 11%, p = 0.037) occurred more frequently in patients with PH. Multivariable competing-risk and proportional hazards regression showed that PH was associated with increased risk of all-cause death (adjusted hazard ratio [HR], 1.80, 95% CI 1.10-2.93), CV death (adjusted subdistribution HR 3.71, 95% CI 1.58-8.73), and hematologic progression (adjusted subdistribution HR 1.99, 95% CI 1.21-3.27).

In-Depth Immunological Typization of Children with Sickle Cell Disease: A Preliminary Insight into Its Plausible Correlation with Clinical Course and Hydroxyurea Therapy

Sickle cell disease (SCD) is a condition of functional hypo-/a-splenism in which predisposition to bacterial infections is only a facet of a wide spectrum of immune-dysregulation disorders forming the clinical expression of a peculiar immunophenotype. The objective of this study was to perform an in-depth immunophenotypical characterization of SCD pediatric patients, looking for plausible correlations between immunological biomarkers, the impact of hydroxyurea (HU) treatment and clinical course. This was an observational case−control study including 43 patients. The cohort was divided into two main groups, SCD subjects (19/43) and controls (24/43), differing in the presence/absence of an SCD diagnosis. The SCD group was split up into HU+ (12/19) and HU− (7/19) subgroups, respectively receiving or not a concomitant HU treatment. The principal outcomes measured were differences in the immunophenotyping between SCD patients and controls through chi-squared tests, t-tests, and Pearson’s correlation analysis between clinical and immunological parameters. Leukocyte and neutrophil increase, T-cell depletion with prevalence of memory T-cell compartment, NK and B-naïve subset elevation with memory and CD21low B subset reduction, and IgG expansion, significantly distinguished the SCD HU− subgroup from controls, with naïve T cells, switched-memory B cells and IgG maintaining differences between the SCD HU+ group and controls (p-value of <0.05). The mean CD4+ central-memory T-cell% count was the single independent variable showing a positive correlation with vaso-occlusive crisis score in the SCD group (Pearson’s R = 0.039). We report preliminary data assessing plausible clinical implications of baseline and HU-related SCD immunophenotypical alterations, which need to be validated in larger samples, but potentially affecting hypo-/a-splenism immuno-chemoprophylactic recommendations.

VCAM1, HMOX1 and NOS3 differential endothelial expression may impact sickle cell anemia vasculopathy

Endothelial dysfunction plays a major role in sickle cell anemia (SCA) systemic vasculopathy, with upregulation of adhesion molecules (e.g., VCAM-1), decreased nitric oxide bioavailability, and oxidative stress. We aimed to assess the modulation role of pro-inflammatory and pro-oxidative stimuli on endothelial VCAM1, NOS3, and HMOX1 expression. We also evaluated the effect of the main SCA therapeutic agent, hydroxyurea, on that modulation. Our results showed that two VCAM1 promoter haplotypes, we previously associated with pediatric cerebral vasculopathy and severe hemolysis in SCA, increased promoter activity in TNF-α-stimulated transfected EA.hy926 and HBEC cell lines, consistent with a higher VCAM1 expression in macro and microvascular settings. In non-transfected cells, we also observed TNF-α-induced VCAM1 overexpression as well as heme-induced overexpression of HMOX1 in both cell models. Heme did not affect VCAM1 nor NOS3 expression and the latter was also not affected by TNF-α stimulus. Hydroxyurea treatment lowered TNF-induced VCAM1 and NOS3 expression but did not affect heme-induced HMOX1 expression. These data further indicate that VCAM1 haplotypes we studied lead to higher VCAM1 expression affecting not only cerebral but also systemic vasculopathy risk. The differential endothelial expression of VCAM1, NOS3, and HMOX1 also confirms their genetic modulation role in SCA systemic vasculopathy.

Irisin rescues diabetic cardiac microvascular injury via ERK1/2/Nrf2/HO-1 mediated inhibition of oxidative stress

AIMS

Cardiac microvascular dysfunction is a common feature across cardiovascular complications in diabetes, while effective therapy remains elusive. This study was designed to evaluate the effect of irisin on cardiac microvascular injury in type 2 diabetes mellitus (T2DM).

METHODS

T2DM was induced in C57BL/6J mice. A cohort diabetic mice received a 12-week treatment of irisin. Cardiac function and microvessel density were evaluated. Whether irisin directly regulates cardiac microvascular endothelial cells (CMECs) function was determined in vitro. Discovery-drive approaches followed by cause-effect analysis were used to uncover the molecular mechanisms.

RESULTS

Irisin improved cardiac function in diabetic mice, and increased microvessel density. In vitro study revealed that irisin promoted CMECs proliferation and reduced high glucose and high lipid (HGHL)-induced apoptosis. Mechanistically, irisin increased mRNA and protein levels of heme oxygenase 1 (HO-1), superoxide dismutase 1 and superoxide dismutase 2, among which HO-1 ranked top. Irisin stimulated the phosphorylation of extracellular regulated protein kinases (ERK) 1/2 and nuclear factor erythroid-derived 2-like 2 (Nrf2) nuclear translocation, while U0126 (the inhibitor of ERK1/2) inhibited irisin-induced Nrf2 nuclear translocation and HO-1 expression. Nrf2 siRNA inhibited irisin's antioxidative effects.

CONCLUSION

Irisin could rescue cardiac microvessels against oxidative stress and apoptosis in diabetes via ERK1/2/Nrf2/HO-1 pathway.

Toxic effects of cell-free hemoglobin on the microvascular endothelium: implications for pulmonary and nonpulmonary organ dysfunction

Levels of circulating cell-free hemoglobin are elevated during hemolytic and inflammatory diseases and contribute to organ dysfunction and severity of illness. Though several studies have investigated the contribution of hemoglobin to tissue injury, the precise signaling mechanisms of hemoglobin-mediated endothelial dysfunction in the lung and other organs are not yet completely understood. The purpose of this review is to highlight the knowledge gained thus far and the need for further investigation regarding hemoglobin-mediated endothelial inflammation and injury to develop novel therapeutic strategies targeting the damaging effects of cell-free hemoglobin.

Hydroxyurea treatment is associated with reduced degree of oxidative perturbation in children and adolescents with sickle cell anemia

Sickle cell anemia (SCA) is the most common inherited hemolytic anemia worldwide. Here, we performed an exploratory study to investigate the systemic oxidative stress in children and adolescents with SCA. Additionally, we evaluated the potential impact of hydroxyurea therapy on the status of oxidative stress in a case–control study from Brazil. To do so, a panel containing 9 oxidative stress markers was measured in plasma samples from a cohort of 47 SCA cases and 40 healthy children and adolescents. Among the SCA patients, 42.5% were undertaking hydroxyurea. Multidimensional analysis was employed to describe disease phenotypes. Our results demonstrated that SCA is associated with increased levels of oxidative stress markers, suggesting the existence of an unbalanced inflammatory response in peripheral blood. Subsequent analyses revealed that hydroxyurea therapy was associated with diminished oxidative imbalance in SCA patients. Our findings reinforce the idea that SCA is associated with a substantial dysregulation of oxidative responses which may be dampened by treatment with hydroxyurea. If validated by larger prospective studies, our observations argue that reduction of oxidative stress may be a main mechanism through which hydroxyurea therapy attenuates the tissue damage and can contribute to improved clinical outcomes in SCA.