Reactive oxygen species contribute to dysfunction of bone marrow hematopoietic stem cells in aged C57BL/6 J mice

SDHAF1 confers metabolic resilience to aging hematopoietic stem cells by promoting mitochondrial ATP production

Aging generally predisposes stem cells to functional decline, impairing tissue homeostasis. Here, we report that hematopoietic stem cells (HSCs) acquire metabolic resilience that promotes cell survival. High-resolution real-time ATP analysis with glucose tracing and metabolic flux analysis revealed that old HSCs reprogram their metabolism to activate the pentose phosphate pathway (PPP), becoming more resistant to oxidative stress and less dependent on glycolytic ATP production at steady state. As a result, old HSCs can survive without glycolysis, adapting to the physiological cytokine environment in bone marrow. Mechanistically, old HSCs enhance mitochondrial complex II metabolism during stress to promote ATP production. Furthermore, increased succinate dehydrogenase assembly factor 1 (SDHAF1) in old HSCs, induced by physiological low-concentration thrombopoietin (TPO) exposure, enables rapid mitochondrial ATP production upon metabolic stress, thereby improving survival. This study provides insight into the acquisition of resilience through metabolic reprogramming in old HSCs and its molecular basis to ameliorate age-related hematopoietic abnormalities.

Neutral sphingomyelinase blockade enhances hematopoietic stem cell fitness through an integrated stress response

Hematopoietic stem and progenitor cell (HSPC) transplantation serves as a curative therapy for many benign and malignant hematopoietic disorders and as a platform for gene therapy. However, growing needs for ex vivo manipulation of HSPC-graft products are limited by barriers in maintaining critical self-renewal and quiescence properties. The role of sphingolipid metabolism in safeguarding these essential cellular properties has been recently recognized, but not yet widely explored. Here, we demonstrate that pharmacologic and genetic inhibition of neutral sphingomyelinase 2 (nSMase-2) leads to sustained improvements in long-term competitive transplantation efficiency after ex vivo culture. Mechanistically, nSMase-2 blockade activates a canonical integrated stress response (ISR) and promotes metabolic quiescence in human and murine HSPCs. These adaptations result in part from disruption in sphingolipid metabolism that impairs the release of nSMase-2-dependent extracellular vesicles (EVs). The aggregate findings link EV trafficking and the ISR as a regulatory dyad guarding HSPC homeostasis and long-term fitness. Translationally, transient nSMase-2 inhibition enables ex vivo graft manipulation with enhanced HSPC potency.

Infrared laser therapy decreases systemic oxidative stress and inflammation in hypercholesterolemic mice with periodontitis

BACKGROUND

Near-infrared irradiation photobiomodulation (NIR-PBM) has been successfully used in periodontal treatment as an adjuvant tool to locally improve cell function and regeneration. Although the relationship between periodontitis and systemic disease constitutes an important aspect of periodontal clinical research, the systemic effects of NIR-PBM in periodontitis are not well known. In this study, we aimed to investigate the effects of NIR-PBM on systemic oxidative stress and inflammation in an apolipoprotein E (ApoE) knockout mouse model of periodontal disease (PD).

METHODS

We evaluated alveolar bone loss by measuring the distance from the cementoenamel junction (CEJ) to the alveolar bone crest (ABC), reactive oxygen species (ROS) production in blood cells, inflammatory activity, plasma cholesterol levels, and lipid peroxidation levels in three experimental groups: (1) ApoEC, control group without intervention; (2) ApoEP, first molar ligation-induced periodontitis for 4 weeks; and (3) ApoEP + PBM, exposed to 808 nm continuous wave, ø ~ 3 mm2, 100 mW, 60 s of NIR-PBM for 7 consecutive days after 4 weeks of periodontitis. At the end of the experimental protocols, ApoEP mice presented significantly increased alveolar bone loss, ROS production, inflammatory activity, plasma cholesterol, and lipid peroxidation levels compared to the ApoEC group (P < 0.05). NIR-PBM for 7 days in the ApoEP + PBM mice significantly decreased systemic ROS production, inflammatory response, plasma cholesterol, and lipid peroxidation levels, similar to those found in the ApoEC group (P > 0.05). However, it was not capable of preventing alveolar bone loss (P > 0.05 compared to ApoEP mice).

CONCLUSION

A 7-day treatment with NIR-PBM effectively reduces systemic oxidative stress and inflammatory parameters in hypercholesterolemic mice with PD. However, more studies with longer evaluation times are needed to confirm the systemic effects of locally applied NIR-PBM on PD associated with hypercholesterolemia.

Hematopoietic stem cell aging and leukemia transformation

With aging, hematopoietic stem cells (HSCs) have an impaired ability to regenerate, differentiate, and produce an entire repertoire of mature blood and immune cells. Owing to dysfunctional hematopoiesis, the incidence of hematologic malignancies increases among elderly individuals. Here, we provide an update on HSC-intrinsic and -extrinsic factors and processes that were recently discovered to contribute to the functional decline of HSCs during aging. In addition, we discuss the targets and timing of intervention approaches to maintain HSC function during aging and the extent to which these same targets may prevent or delay transformation to hematologic malignancies.

Field-Deployable Treatments For Leishmaniasis: Intrinsic Challenges, Recent Developments and Next Steps

Leishmaniasis is a neglected tropical disease endemic primarily to low- and middle-income countries, for which there has been inadequate development of affordable, safe, and efficacious therapies. Clinical manifestations of leishmaniasis range from self-healing skin lesions to lethal visceral infection with chances of relapse. Although treatments are available, secondary effects limit their use outside the clinic and negatively impact the quality of life of patients in endemic areas. Other non-medicinal treatments, such as thermotherapies, are limited to use in patients with cutaneous leishmaniasis but not with visceral infection. Recent studies shed light to mechanisms through which Leishmania can persist by hiding in cellular safe havens, even after chemotherapies. This review focuses on exploring the cellular niches that Leishmania parasites may be leveraging to persist within the host. Also, the cellular, metabolic, and molecular implications of Leishmania infection and how those could be targeted for therapeutic purposes are discussed. Other therapies, such as those developed against cancer or for manipulation of the ferroptosis pathway, are proposed as possible treatments against leishmaniasis due to their mechanisms of action. In particular, treatments that target hematopoietic stem cells and monocytes, which have recently been found to be necessary components to sustain the infection and provide a safe niche for the parasites are discussed in this review as potential field-deployable treatments against leishmaniasis.

A single approach to targeting transferrin receptor 2 corrects iron and erythropoietic defects in murine models of anemia of inflammation and chronic kidney disease

Anemia is a common complication of systemic inflammation. Proinflammatory cytokines both decrease erythroblast sensitivity to erythropoietin (EPO) and increase the levels of the hepatic hormone hepcidin, sequestering iron in stores and causing functional iron deficiency. Anemia of chronic kidney disease (CKD) is a peculiar form of anemia of inflammation, characterized by impaired EPO production paralleling progressive kidney damage. Traditional therapy based on increased EPO (often in combination with iron) may have off-target effects due to EPO interaction with its non-erythroid receptors. Transferrin Receptor 2 (Tfr2) is a mediator of the iron-erythropoiesis crosstalk. Its deletion in the liver hampers hepcidin production, increasing iron absorption, whereas its deletion in the hematopoietic compartment increases erythroid EPO sensitivity and red blood cell production. Here, we show that selective hematopoietic Tfr2 deletion ameliorates anemia in mice with sterile inflammation in the presence of normal kidney function, promoting EPO responsiveness and erythropoiesis without increasing serum EPO levels. In mice with CKD, characterized by absolute rather than functional iron deficiency, Tfr2 hematopoietic deletion had a similar effect on erythropoiesis but anemia improvement was transient because of limited iron availability. Also, increasing iron levels by downregulating only hepatic Tfr2 had a minor effect on anemia. However, simultaneous deletion of hematopoietic and hepatic Tfr2, stimulating erythropoiesis and increased iron supply, was sufficient to ameliorate anemia for the entire protocol. Thus, our results suggest that combined targeting of hematopoietic and hepatic Tfr2 may be a therapeutic option to balance erythropoiesis stimulation and iron increase, without affecting EPO levels.

Protein Susceptibility to Peroxidation by 4-Hydroxynonenal in Hereditary Hemochromatosis

Iron overload caused by hereditary hemochromatosis (HH) increases free reactive oxygen species that, in turn, induce lipid peroxidation. Its 4-hydroxynonenal (HNE) by-product is a well-established marker of lipid peroxidation since it reacts with accessible proteins with deleterious consequences. Indeed, elevated levels of HNE are often detected in a wide variety of human diseases related to oxidative stress. Here, we evaluated HNE-modified proteins in the membrane of erythrocytes from HH patients and in organs of Hfe^-/- male and female mice, a mouse model of HH. For this purpose, we used one- and two-dimensional gel electrophoresis, immunoblotting and MALDI-TOF/TOF analysis. We identified cytoskeletal membrane proteins and membrane receptors of erythrocytes bound to HNE exclusively in HH patients. Furthermore, kidney and brain of Hfe^-/- mice contained more HNE-adducted protein than healthy controls. Our results identified main HNE-modified proteins suggesting that HH favours preferred protein targets for oxidation by HNE.

Impact of exogenous hydrogen peroxide on osteogenic differentiation of broiler chicken compact bones derived mesenchymal stem cells

The effects of hydrogen peroxide (H₂O₂) on the osteogenic differentiation of primary chicken mesenchymal stem cells (MSCs) were investigated. MSCs were subjected to an osteogenic program and exposed to various concentrations of H₂O₂ for 14 days. Results showed that high concentrations of H₂O₂ (200 and 400 nM) significantly increased pro-apoptotic marker CASP8 expression and impaired osteogenic differentiation, as indicated by decreased mRNA expression levels of osteogenesis-related genes and reduced in vitro mineralization. In contrast, long-term H₂O₂ exposure promoted basal expression of adipogenic markers at the expense of osteogenesis in MSCs during osteogenic differentiation, and increased intracellular reactive oxygen species (ROS) production, as well as altered antioxidant enzyme gene expression. These findings suggest that long-term H₂O₂-induced ROS production impairs osteogenic differentiation in chicken MSCs under an osteogenic program.

DNA damage and repair on hematopoietic stem cells: impact of oxidative stress in renovascular hypertension

BACKGROUND

This study investigated oxidative damage to bone marrow cells in the pathogenesis of renovascular hypertension (RH).

METHODS

Male C57BL/6 J mice (10-week-old and ~23 g) were divided into two groups: Sham-operated and 2K1C, which has a stainless-steel clip placed around the left renal artery. After twenty-eight days, the animals were anesthetized for hemodynamic measurements and bone marrow cells isolation. The intracellular production of ROS, DNA damage, and DNA repair kinetics were evaluated.

RESULTS

Our results show that RH increases HSCs ROS production and that the 2K1C group showed a significant reduction of HSCs in the G0/G1 phase, increased p53 expression, DNA fragmentation, low DNA repair capacity, and a higher percentage of apoptotic cells when compared with the Sham group.

CONCLUSIONS

Our data imply that RH can compromise the hematopoiesis by increased oxidative stress leading to impaired DNA repair activity. Furthermore, this study provides new insights into the influence of hypertension on bone marrow homeostasis. This study showed for the first time that RH leads to oxidative damage, including genotoxic, to bone marrow cells. Thus, these findings provide new insights into the consequences of RH on bone marrow cells.

DNA damage and repair in the hematopoietic system

Although hematopoietic stem cells (HSCs) in the bone marrow are in a state of quiescence, they harbor the self-renewal capacity and the pluripotency to differentiate into mature blood cells when needed, which is key to maintain hematopoietic homeostasis. Importantly, HSCs are characterized by their long lifespan ( e. g., up to 60 months for mice), display characteristics of aging, and are vulnerable to various endogenous and exogenous genotoxic stresses. Generally, DNA damage in HSCs is endogenous, which is typically induced by reactive oxygen species (ROS), aldehydes, and replication stress. Mammalian cells have evolved a complex and efficient DNA repair system to cope with various DNA lesions to maintain genomic stability. The repair machinery for DNA damage in HSCs has its own characteristics. For instance, the Fanconi anemia (FA)/BRCA pathway is particularly important for the hematopoietic system, as it can limit the damage caused by DNA inter-strand crosslinks, oxidative stress, and replication stress to HSCs to prevent FA occurrence. In addition, HSCs prefer to utilize the classical non-homologous end-joining pathway, which is essential for the V(D)J rearrangement in developing lymphocytes and is involved in double-strand break repair to maintain genomic stability in the long-term quiescent state. In contrast, the base excision repair pathway is less involved in the hematopoietic system. In this review, we summarize the impact of various types of DNA damage on HSC function and review our knowledge of the corresponding repair mechanisms and related human genetic diseases.

Cellular and Molecular Mechanisms Involved in Hematopoietic Stem Cell Aging as a Clinical Prospect

There is a hot topic in stem cell research to investigate the process of hematopoietic stem cell (HSC) aging characterized by decreased self-renewal ability, myeloid-biased differentiation, impaired homing, and other abnormalities related to hematopoietic repair function. It is of crucial importance that HSCs preserve self-renewal and differentiation ability to maintain hematopoiesis under homeostatic states over time. Although HSC numbers increase with age in both mice and humans, this cannot compensate for functional defects of aged HSCs. The underlying mechanisms regarding HSC aging have been studied from various perspectives, but the exact molecular events remain unclear. Several cell-intrinsic and cell-extrinsic factors contribute to HSC aging including DNA damage responses, reactive oxygen species (ROS), altered epigenetic profiling, polarity, metabolic alterations, impaired autophagy, Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway, nuclear factor- (NF-) κB pathway, mTOR pathway, transforming growth factor-beta (TGF-β) pathway, and wingless-related integration site (Wnt) pathway. To determine how deficient HSCs develop during aging, we provide an overview of different hallmarks, age-related signaling pathways, and epigenetic modifications in young and aged HSCs. Knowing how such changes occur and progress will help researchers to develop medications and promote the quality of life for the elderly and possibly alleviate age-associated hematopoietic disorders. The present review is aimed at discussing the latest advancements of HSC aging and the role of HSC-intrinsic factors and related events of a bone marrow niche during HSC aging.

Upregulation of SIRT1 Contributes to dmPGE2-dependent Radioprotection of Hematopoietic Stem Cells

Exposure to potentially lethal high-dose ionizing radiation results in bone marrow suppression, known as the hematopoietic acute radiation syndrome (H-ARS), which can lead to pancytopenia and possible death from hemorrhage or infection. Medical countermeasures to protect from or mitigate the effects of radiation exposure are an ongoing medical need. We recently reported that 16,16 dimethyl prostaglandin E₂ (dmPGE₂) given prior to lethal irradiation protects hematopoietic stem (HSCs) and progenitor (HPCs) cells and accelerates hematopoietic recovery by attenuating mitochondrial compromise, DNA damage, apoptosis, and senescence. However, molecular mechanisms responsible for the radioprotective effects of dmPGE₂ on HSCs are not well understood. In this report, we identify a crucial role for the NAD⁺-dependent histone deacetylase Sirtuin 1 (Sirt1) downstream of PKA and CREB in dmPGE₂-dependent radioprotection of hematopoietic cells. We found that dmPGE₂ increases Sirt1 expression and activity in hematopoietic cells including HSCs and pharmacologic and genetic suppression of Sirt1 attenuates the radioprotective effects of dmPGE₂ on HSC and HPC function and its ability to reduce DNA damage, apoptosis, and senescence and stimulate autophagy in HSCs. DmPGE₂-mediated enhancement of Sirt1 activity in irradiated mice is accompanied by epigenetic downregulation of p53 activation and inhibition of H3K9 and H4K16 acetylation at the promoters of the genes involved in DNA repair, apoptosis, and autophagy, including p53, Ku70, Ku80, LC3b, ATG7, and NF-κB. These studies expand our understanding of intracellular events that are induced by IR but prevented/attenuated by dmPGE₂ and suggest that modulation of Sirt1 activity may facilitate hematopoietic recovery following hematopoietic stress. Graphical Abstract.

Toxicological effects of air settled particles from the Vitoria Metropolitan Area mediated by oxidative stress, pro-inflammatory mediators and NFΚB pathway

Atmospheric pollution is a major environmental and public health risk due to its effect on global air quality and climate. Increase in pollutants concentrations, especially particulate matter (PM), are associated with increased respiratory diseases. The pathophysiology of respiratory diseases involves molecular and cellular mechanisms as inflammatory biomarkers and reactive oxygen species production. Thus, the present study aimed to investigate the in vitro cytotoxic and pro-inflammatory effects of particulate matter (PM) of six monitoring stations (1-6) from the Vitoria Metropolitan Area (VMA), Espirito Santo, Brazil in 2018. The PM was chemically characterized by inductively coupled plasma mass spectrometry. In vitro cytotoxic effects of PM (3.12-200.0 μg/mL) were analyzed in human lung epithelial cells (A549) and macrophage cells (RAW 264.7) by MTT assay (3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide). To investigate the pro-inflammatory effects of PM in RAW 264.7 cells, the levels of proinflammatory mediators such as nitric oxide (NO), superoxide anion (O₂^•-), tumor necrosis factor (TNF-α), interleukin 6 (IL-6), and the activation of nuclear factor kappa B (NF- κB) were measured. The comet assay evaluated genotoxicity. Cell cycle, oxidative stress (DCF and DHE), and apoptosis were analyzed by flow cytometry. Chemical analysis of PM revealed aluminum (Al) and Iron (Fe) as the major chemical elements in all studied monitoring stations. In addition, worrying concentrations of mercury (Hg) were detected in the PM. The in vitro results showed that PM presents a dose-dependent cytotoxic effect in macrophage and pulmonary epithelial cell lines. The PM increased the production of NO, O₂^•-, and pro-inflammatory cytokines TNF-α and IL-6. PM also promoted alterations in the cell cycle, increased apoptosis frequency, and DNA damage. Moreover, PM increased the expression NF-κB. In addition, a positive correlation between Al and Fe and ROS production was observed. Based on the results obtained during the study period, it was concluded that the sedimented particles from the VMA might have deleterious effects on human health, which was evidenced by the increase in oxidative stress, an increase in pro-inflammatory mediators, and genotoxic effects partially mediated by the NF-κB pathway. These results add aspects to elucidate the molecular mechanisms involved in the effects of sedimented particles in vivo and in vitro.

Use of kefir peptide (Kef-1) as an emerging approach for the treatment of oxidative stress and inflammation in 2K1C mice

The benefits of kefir consumption are partially due to the rich composition of bioactive molecules released from its fermentation. Angiotensin-converting enzyme (ACE) inhibitors are bioactive molecules with potential use in the treatment or prevention of hypertension, heart failure, and myocardial infarction. Here, the in vivo actions of the Kef-1 peptide, an ACE inhibitor derived from kefir, were evaluated in an angiotensin II-dependent hypertension model. The Kef-1 peptide showed a potential anti-hypertensive effect. Additionally, Kef-1 exhibited systemic antioxidant and anti-inflammatory activities. In smooth muscle cells (SMCs), the Kef-1 peptide decreased ROS production through the reduced participation of NADPH oxidase and mitochondria. The aorta of 2K1C mice treated with Kef-1 showed lesser wall-thickening and partial restoration of the endothelial structure. In conclusion, these novel findings highlight the in vivo biological potential of this peptide demonstrating that Kef-1 may be a relevant nutraceutical treatment for cardiovascular diseases.

DNA damage and aging on hematopoietic stem cells: Impact of oxidative stress in ApoE-/- mice

The effects of aging on ROS production and DNA damage were assessed in hematopoietic stem cells (HSCs) from apolipoprotein E-deficient (ApoE^-/^-) mice (2-, 12- and 24-month-old), a traditional experimental model of atherogenic dyslipidemia. HSCs from aged ApoE^-/- mice were associated with increased ROS levels, leading to loss quiescence, DNA damage, apoptosis and telomere shortening. The concurrence of lack of ApoE and aging result in exhaustion and senescence of HSCs accompanied by increased oxidative stress and inflammation. Therefore, our data open avenues to a better understanding of age-related changes and genetic factors, which may synergistically compromise the efficacy of aged HSC recovery and/or transplantation.

Hematopoiesis during Ontogenesis, Adult Life, and Aging

In the bone marrow of vertebrates, two types of stem cells coexist-hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). Hematopoiesis only occurs when these two stem cell types and their descendants interact. The descendants of HSCs supply the body with all the mature blood cells, while MSCs give rise to stromal cells that form a niche for HSCs and regulate the process of hematopoiesis. The studies of hematopoiesis were initially based on morphological observations, later extended by the use of physiological methods, and were subsequently augmented by massive application of sophisticated molecular techniques. The combination of these methods produced a wealth of new data on the organization and functional features of hematopoiesis in the ontogenesis of mammals and humans. This review summarizes the current views on hematopoiesis in mice and humans, discusses the development of blood elements and hematopoiesis in the embryo, and describes how the hematopoietic system works in the adult organism and how it changes during aging.

Deficiency of Antioxidative Paraoxonase 2 (Pon2) Leads to Increased Number of Phenotypic LT-HSCs and Disturbed Erythropoiesis

Background

Long-term hematopoietic stem cells (LT-HSCs) reside in bone marrow niches with tightly controlled reactive oxygen species (ROS) levels. ROS increase results into LT-HSC differentiation and stem cell exhaustion. Paraoxonase 2 (PON2) has been shown to be important for ROS control.

Objectives

We investigate the effects of inactivation of the PON2 gene on hematopoietic cell differentiation and activity.

Methods and Results

In young mice with inactivated Pon2 gene (Pon2^−/−, <3 months), we observed an increase of LT-HSCs and a reduced frequency of progenitor cells. In competitive transplantations, young Pon2^−/− BM outcompeted WT BM at early time points. ROS levels were significantly increased in Pon2^−/− whole BM, but not in Pon2^−/− LT-HSCs. In more differentiated stages of hematopoiesis, Pon2 deficiency led to a misbalanced erythropoiesis both in physiologic and stress conditions. In older mice (>9 months), Pon2 depletion caused an increase in LT-HSCs as well as increased levels of granulocyte/macrophage progenitors (GMPs) and myeloid skewing, indicating a premature aging phenotype. No significant changes in ROS levels in old Pon2^−/− LT- and short-term (ST-) HSCs were observed, but a significant reduction of spontaneous apoptotic cell death was measured. RNA-seq analysis in Pon2^−/− LT-HSCs identified overrepresentation of genes involved in the C-X-C chemokine receptor type 4 (Cxcr4) signaling, suggesting compensatory mechanisms to overcome ROS-mediated accelerated aging in hematopoietic progenitor cells.

Conclusions

In summary, our current data indicate that PON2 is involved in the regulation of HSC functions.

Tyrosine-Protein Phosphatase Non-receptor Type 9 (PTPN9) Negatively Regulates the Paracrine Vasoprotective Activity of Bone-Marrow Derived Pro-angiogenic Cells: Impact on Vascular Degeneration in Oxygen-Induced Retinopathy

Background and Aim

Insufficient post-ischemic neovascularization is an initial key step in the pathogenesis of Oxygen-Induced Retinopathy (OIR). During neovascularization, pro-angiogenic cells (PACs) are mobilized from the bone marrow and integrate into ischemic tissues to promote angiogenesis. However, the modulation of PAC paracrine activity during OIR and the specific mechanisms involved remain to be explored. Because Tyrosine-protein phosphatase non-receptor type 9 (PTPN9) is reported to be a negative regulator of stem cell differentiation and angiogenesis signaling, we investigated its effect on PAC activity in the context of OIR.

Methods and Results

In a rat model of OIR, higher levels of PTPN9 in the retina and in bone marrow derived PACs are associated with retinal avascular areas, lower levels of the mobilization factor SDF-1 and decreased number of CD34⁺/CD117⁺/CD133⁺ PACs. PACs exposed ex vivo to hyperoxia display increased PTPN9 expression, which is associated with impaired ability of PAC secretome to promote angiogenesis ex vivo (choroidal vascular sprouting) and in vitro (endothelial cell tubule formation) compared to the secretome of PACs maintained in normoxia. Suppression of PTPN9 (using siRNA) increases VEGF and SDF-1 expression to normalize PAC secretome during hyperoxia, leading to restored angiogenic ability of PAC secretome. Moreover, endothelial cells exposed to the secretome of siPTPN9-treated PACs expressed increased levels of activated form of VEGF receptor 2 (VEGFR2). In the rat model of OIR, intravitreal injection of secretome from siPTPN9-treated PACs significantly reduced retinal vaso-obliteration; this was associated with higher retinal levels of VEGF/SDF-1, and increased recruitment of PACs (CD34⁺ cells) to the retinal and choroidal vessels.

Conclusion

Our results suggest that hyperoxia alters the paracrine proangiogenic activity of BM-PACs by inducing PTPN9, which can contribute to impair post-ischemic revascularization in the context of OIR. Targeting PTPN9 restores PAC angiogenic properties, and provide a new target for vessel integrity in ischemic retinopathies.

Curcumin restores the engraftment capacity of aged hematopoietic stem cells and also reduces PD-1 expression on cytotoxic T cells

Aging affects the functionality of hematopoietic stem cells (HSCs), and therefore, aged individuals are not preferred as donors in HSC transplantation. Such elimination leads to the restriction of donor cohort. Several efforts are being done to rejuvenate aged HSCs. Here, we show that treatment of aged mice with curcumin rejuvenates their HSCs by restoring the expression of autophagy-inducing messenger RNAs in them, and improves their engraftment capacity. Importantly, we show that curcumin is effective in rejuvenation of HSCs when administered via both, intraperitoneal as well as oral routes. Aging also affects the immune system. While elderly individuals are not immuno-deficient, they do not respond optimally to immunizations, and hence, a strategy needs to be developed to make them immunologically responsive. Programmed cell death 1 (PD-1), one of the inhibitory coreceptors, plays an important role in the regulation of autoimmunity, infectious immunity, and cancer immunity. Its expression on T cells is indicative of their exhaustion. Here, we show that curcumin reduces the frequency of PD1+ cytotoxic T cells in the spleens of aged mice. Curcumin has a proven safety profile, and hence, can be used to treat aged donors to boost the functionality of their HSCs and also to improve the immunological profile of aged individuals. These data could have implications in various other regenerative medicine protocols as well.

Protection of hematopoietic stem cells from stress-induced exhaustion and aging

PURPOSE OF REVIEW

Hematopoietic stem cells (HSCs) are defined by their ability to self-renew and differentiate to replenish all blood lineages throughout adult life. Under homeostasis, the majority of HSCs are quiescent, and few stem cells are cycling to sustain hematopoiesis. However, HSCs can be induced to proliferate and differentiate in response to stress signals produced during infection, inflammation, chemotherapy, radiation, bone marrow transplantation, and aging. Recent evidence suggests that acute and chronic stress impact the number and function of HSCs including their ability to repopulate and produce mature cells. This review will focus on how chronic stress affects HSC biology and methods to mitigate HSC loss during chronic hematopoietic stress.

RECENT FINDINGS

Quiescent HSCs exit dormancy, divide, and differentiate to maintain steady-state hematopoiesis. Under conditions of acute stress including infection or blood loss some HSCs are pushed into division by cytokines and proinflammatory stimuli to differentiate and provide needed myeloid and erythroid cells to protect and reconstitute the host; after which, hematopoiesis returns to steady-state with minimal loss of HSC function. However, under conditions of chronic stress including serial bone marrow transplantation (BMT), chronic inflammation, and genotoxic stress (chemotherapy) and aging, HSCs are continuously induced to proliferate and undergo accelerated exhaustion. Recent evidence demonstrates that ablation of inhibitor of DNA binding 1 (Id1) gene can protect HSCs from exhaustion during chronic proliferative stress by promoting HSC quiescence.

SUMMARY

Increasing our understanding of the molecular processes that protect HSCs from chronic proliferative stress could lead to therapeutic opportunities to prevent accelerated HSC exhaustion during physiological stress, genotoxic stress, BMT, and aging.

Azacitidine decreases reactive oxygen species production in peripheral white blood cells: A case report

BACKGROUND

In myelodysplastic syndrome (MDS), oxidative stress is closely related to iron overload and DNA damage. A recent study suggested the possibility that increased oxidative stress causes not only iron overload but also disease progression of MDS with DNA damage. We present a case of MDS with decreased reactive oxygen species (ROS) production in peripheral white blood cells (WBCs) and decreased diacron-reactive oxygen metabolites (d-ROMs) in serum after azacitidine therapy.

CASE SUMMARY

A 74-year-old man presented to the hematological department with the chief complaint of anemia. His vital signs were within normal limits at admission with a heart rate of 80 bpm and blood pressure of 135/60 mmHg. Laboratory tests indicated pancytopenia, a WBC count of 2190 cells/µL, a hemoglobin level of 6.2 g/dL and a platelet count of 7.4 × 10⁴/µL. The patient was diagnosed with MDS with fibrosis after a bone marrow examination. This case showed decreased ROS production in WBCs, d-ROMs in serum and Wilms’ tumor 1 after azacitidine therapy, after which his hematopoiesis recovered.

CONCLUSION

Azacitidine therapy can improve hematopoiesis and decrease ROS and d-ROM production.

Bone marrow oxidative stress and specific antioxidant signatures in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal stem cell disorders with an inherent tendency for transformation in secondary acute myeloid leukemia. This study focused on the redox metabolism of bone marrow (BM) cells from 97 patients compared with 25 healthy controls. The level of reactive oxygen species (ROS) was quantified by flow cytometry in BM cell subsets as well as the expression level of 28 transcripts encoding for major enzymes involved in the antioxidant cellular response. Our results highlight increased ROS levels in BM nonlymphoid cells and especially in primitive CD34posCD38low progenitor cells. Moreover, we identified a specific antioxidant signature, dubbed "antioxidogram," for the different MDS subgroups or secondary acute myeloblastic leukemia (sAML). Our results suggest that progression from MDS toward sAML could be characterized by 3 successive molecular steps: (1) overexpression of enzymes reducing proteic disulfide bonds (MDS with <5% BM blasts [GLRX family]); (2) increased expression of enzymes detoxifying H2O2 (MDS with 5% to 19% BM blasts [PRDX and GPX families]); and finally (3) decreased expression of these enzymes in sAML. The antioxidant score (AO-Score) defined by logistic regression from the expression levels of transcripts made it possible to stage disease progression and, interestingly, this AO-Score was independent of the revised International Scoring System. Altogether, this study demonstrates that MDS and sAML present an important disturbance of redox metabolism, especially in BM stem and progenitor cells and that the specific molecular antioxidant response parameters (antioxidogram, AO-Score) could be considered as useful biomarkers for disease diagnosis and follow-up.

Pro-Aging Effects of Xanthine Oxidoreductase Products

The senescence process is the result of a series of factors that start from the genetic constitution interacting with epigenetic modifications induced by endogenous and environmental causes and that lead to a progressive deterioration at the cellular and functional levels. One of the main causes of aging is oxidative stress deriving from the imbalance between the production of reactive oxygen (ROS) and nitrogen (RNS) species and their scavenging through antioxidants. Xanthine oxidoreductase (XOR) activities produce uric acid, as well as reactive oxygen and nitrogen species, which all may be relevant to such equilibrium. This review analyzes XOR activity through in vitro experiments, animal studies and clinical reports, which highlight the pro-aging effects of XOR products. However, XOR activity contributes to a regular level of ROS and RNS, which appears essential for the proper functioning of many physiological pathways. This discourages the use of therapies with XOR inhibitors, unless symptomatic hyperuricemia is present.

Premature synaptic mitochondrial dysfunction in the hippocampus during aging contributes to memory loss

Aging is a process characterized by cognitive impairment and mitochondrial dysfunction. In neurons, these organelles are classified as synaptic and non-synaptic mitochondria depending on their localization. Interestingly, synaptic mitochondria from the cerebral cortex accumulate more damage and are more sensitive to swelling than non-synaptic mitochondria. The hippocampus is fundamental for learning and memory, synaptic processes with high energy demand. However, it is unknown if functional differences are found in synaptic and non-synaptic hippocampal mitochondria; and whether this could contribute to memory loss during aging. In this study, we used 3, 6, 12 and 18 month-old (mo) mice to evaluate hippocampal memory and the function of both synaptic and non-synaptic mitochondria. Our results indicate that recognition memory is impaired from 12mo, whereas spatial memory is impaired at 18mo. This was accompanied by a differential function of synaptic and non-synaptic mitochondria. Interestingly, we observed premature dysfunction of synaptic mitochondria at 12mo, indicated by increased ROS generation, reduced ATP production and higher sensitivity to calcium overload, an effect that is not observed in non-synaptic mitochondria. In addition, at 18mo both mitochondrial populations showed bioenergetic defects, but synaptic mitochondria were prone to swelling than non-synaptic mitochondria. Finally, we treated 2, 11, and 17mo mice with MitoQ or Curcumin (Cc) for 5 weeks, to determine if the prevention of synaptic mitochondrial dysfunction could attenuate memory loss. Our results indicate that reducing synaptic mitochondrial dysfunction is sufficient to decrease age-associated cognitive impairment. In conclusion, our results indicate that age-related alterations in ATP produced by synaptic mitochondria are correlated with decreases in spatial and object recognition memory and propose that the maintenance of functional synaptic mitochondria is critical to prevent memory loss during aging.

•

Hippocampus-dependent learning and memory are impaired with age, which correlated with synaptic mitochondrial dysfunction.

•

Synaptic mitochondria fail before non-synaptic mitochondria, indicating premature synaptic mitochondrial damage in aging.

•

Reducing synaptic mitochondrial dysfunction, with MitoQ or Curcumin, decrease age-associated hippocampal memory impairment.

•

Age-related changes in ATP production of synaptic mitochondria correlated with decreased hippocampal memory.

•

Maintenance of functional synaptic mitochondria is critical to prevent memory loss during aging.

Oxidative Stress and Dementia in Alzheimer's Patients: Effects of Synbiotic Supplementation

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia in elderly patients. Recently, several studies have shown that inflammation and oxidative stress precede the cardinal neuropathological manifestations of AD. In view of the proven antioxidant effects of probiotics, we proposed that continuous dietary supplementation with milk fermented with kefir grains might improve cognitive and metabolic and/or cellular disorders in the AD patients.

METHODS

This study was designed as an uncontrolled clinical investigation to test the effects of probiotic-fermented milk supplementation (2 mL/kg/daily) for 90 days in AD patients exhibiting cognitive deficit. Cognitive assessment, cytokine expression, systemic oxidative stress levels, and blood cell damage biomarkers were evaluated before (T0) and after (T90) kefir synbiotic supplementation.

RESULTS

When the patients were challenged to solve 8 classical tests, the majority exhibit a marked improvement in memory, visual-spatial/abstraction abilities, and executive/language functions. At the end of the treatment, the cytometric analysis showed an absolute/relative decrease in several cytokine markers of inflammation and oxidative stress markers (·O2 -, H2O2, and ONOO-, ~30%) accompanied by an increase in NO bioavailability (100%). In agreement with the above findings by using the same technique, we observed in a similar magnitude an improvement of serum protein oxidation, mitochondrial dysfunction, DNA damage/repair, and apoptosis.

CONCLUSION

In conclusion, we demonstrated that kefir improves cognitive deficits, which seems to be linked with three important factors of the AD-systemic inflammation, oxidative stress, and blood cell damage-and may be a promising adjuvant therapy against the AD progression.

NOX4 is the main NADPH oxidase involved in the early stages of hematopoietic differentiation from human induced pluripotent stem cells

Reactive oxygen species (ROS) produced in hematopoietic stem cells (HSCs) are involved in the balance between quiescence, self-renewal, proliferation and differentiation processes. However the role of NOX enzymes on the early stages of hematopoietic differentiation is poorly investigated. For that, we used induced pluripotent stem cells (iPSCs) derived from X-linked Chronic Granulomatous Disease (X⁰CGD) patients with deficiency in NOX2, and AR22⁰CGD patients with deficiency in p22^phox subunit which decreases NOX1, NOX2, NOX3 and NOX4 activities. CD34⁺ hematopoietic progenitors were obtained after 7, 10 and 13 days of iPS/OP9 co-culture differentiation system. Neither NOX expression nor activity was found in Wild-type (WT), X⁰CGD and AR22⁰CGD iPSCs. Although NOX2 and NOX4 mRNA were found in WT, X⁰CGD and AR22⁰CGD iPSC-derived CD34⁺ cells at day 10 and 13 of differentiation, NOX4 protein was the only NOX enzyme expressed in these cells. A NADPH oxidase activity was measured in WT and X⁰CGD iPSC-derived CD34⁺ cells but not in AR22⁰CGD iPSC-derived CD34⁺ cells because of the absence of p22^phox, which is essential for the NOX4 activity. The absence of NOX4 activity and the poor NOX-independent ROS production in AR22⁰CGD iPSC-derived CD34⁺ cells favored the CD34⁺ cells production but lowered their hematopoietic potential compared to WT and X⁰CGD iPSC-derived CD34⁺ cells. In addition we found a large production of primitive AR22⁰CGD iPSC-derived progenitors at day 7 compared to the WT and X⁰CGD cell types. In conclusion NOX4 is the major NOX enzyme involved in the early stages of hematopoietic differentiation from iPSCs and its activity can modulate the production, the hematopoietic potential and the phenotype of iPSC-derived CD34⁺.

Reactive Oxygen Species and Nrf2: Functional and Transcriptional Regulators of Hematopoiesis

Hematopoietic stem cells (HSCs) are characterized by self-renewal and multilineage differentiation potentials. Although they play a central role in hematopoietic homeostasis and bone marrow (BM) transplantation, they are affected by multiple environmental factors in the BM. Here, we review the effects of reactive oxygen species (ROS) and Nrf2 on HSC function and BM transplantation. HSCs reside in the hypoxic microenvironment of BM, and ROS play an important role in HSPC regulation. Recently, an extraphysiologic oxygen shock/stress phenomenon was identified in human cord blood HSCs collected under ambient air conditions. Moreover, Nrf2 has been recently recognized as a master transcriptional factor that regulates multiple antioxidant enzymes. Since several years, the role of Nrf2 in hematopoiesis has been extensively studied, which has functional similarities of cellular oxygen sensor hypoxia-inducible factor-1 as transcriptional factors. Increasing evidence has revealed that abnormally elevated ROS production due to factors such as genetic defects, aging, and ionizing radiation unexceptionally resulted in lethal impairment of HSC function and hematopoiesis. Both experimental and clinical studies have identified elevated ROS levels as a major culprit of ineffective BM transplantation. Lastly, we discuss the possibility of using small molecule antioxidants, such as N-acetyl cysteine, resveratrol, and curcumin, to augment HSC function and improve the therapeutic efficacy of BM transplantation. Further research on the function of ROS levels and improving the efficacy of BM transplantation may have a great potential for broad clinical applications of HSCs.

Psychological Stress and Cellular Aging in Cancer: A Meta-Analysis

BACKGROUND

Epidemiological evidence continues to accumulate on the effect of psychosocial and behavioral factors in relation to cancer risk, progression, and mortality.

MATERIAL AND METHODS

This article presents the current evidence on the relationship between psychological stress and the risk of cancer and cellular aging process. Ten databases were searched to identify publications up to September 2019. References from retrieved articles were also reviewed. We included nine review papers and 26 cohort or case-control studies based on inclusion/exclusion criteria.

RESULTS

Results of previously published review articles did not show consistent evidence for the association between cancer risk and psychological stress, while previous evidence is stronger regarding the role of chronic psychological stress on cancer growth and metastasis and aging. In seven observational studies, severe life events, anxiety, depression, insufficient social support perception, or avoiding coping strategy were significantly associated with breast cancer risk. For other specific types of cancer, 11 studies reported increased risk factors for stressful life events, and two others found increased mortality or a decline in treatment adherence.

CONCLUSIONS

Recent epidemiological evidence generally suggests psychosocial factors may be considered risk factors for specific types of cancer and play a key role in the cellular aging process. Understanding molecular mechanisms of the stress interaction is important in cancer management and prevention. The psychological stressors should be considered when developing or evaluating change in psychosocial practice.

DNA damage in aging, the stem cell perspective

DNA damage is one of the most consistent cellular process proposed to contribute to aging. The maintenance of genomic and epigenomic integrity is critical for proper function of cells and tissues throughout life, and this homeostasis is under constant strain from both extrinsic and intrinsic insults. Considering the relationship between lifespan and genotoxic burden, it is plausible that the longest-lived cellular populations would face an accumulation of DNA damage over time. Tissue-specific stem cells are multipotent populations residing in localized niches and are responsible for maintaining all lineages of their resident tissue/system throughout life. However, many of these stem cells are impacted by genotoxic stress. Several factors may dictate the specific stem cell population response to DNA damage, including the niche location, life history, and fate decisions after damage accrual. This leads to differential handling of DNA damage in different stem cell compartments. Given the importance of adult stem cells in preserving normal tissue function during an individual's lifetime, DNA damage sensitivity and accumulation in these compartments could have crucial implications for aging. Despite this, more support for direct functional effects driven by accumulated DNA damage in adult stem cell compartments is needed. This review will present current evidence for the accumulation and potential influence of DNA damage in adult tissue-specific stem cells and propose inquiry directions that could benefit individual healthspan.

Silymarin protects against radiocontrast-induced nephropathy in mice

Silymarin, an extract from Silybum marianum (milk thistle) containing a standardized mixture of flavonolignans that ameliorates some types of liver disease and, more recently, kidney damage, could be used for the ROS-scavenging effect of these antioxidants. Furthermore, contrast-induced nephropathy (CIN) is an iatrogenic impairment of renal function in patients subjected to angiographic procedures for which there is not yet a successful preventative treatment. Recent evidence has shown that this event is related to tubular/vascular injury activated mainly by oxidative stress. However, whether this bioavailable and pharmacologically safe extract protects against CIN is not clear. We proposed to evaluate the possible protective role of the antioxidant silymarin in an experimental model of CIN. Adult male Swiss mice were separated into 6 groups and pretreated orally with silymarin (50, 200 and 300 mg/kg), N-acetylcysteine (200 mg/kg) or vehicle for 5 days before the CIN and control groups. Renal function was analyzed by plasma creatinine, urea and cystatin C levels. Additionally, blood reactive oxygen species (ROS) were evaluated using ROS bioavailability, protein oxidation and DNA damage. Renal oxidative damage was evaluated using apoptosis/cell viability assays and histological analysis. We showed that silymarin preserved renal function and decreased systemic and renal oxidative damage (antigenotoxic and antiapoptotic properties, respectively) in a dose-dependent manner and was superior to conventional treatment with N-acetylcysteine. Histologically, silymarin treatment also had beneficial effects on renal glomerular and tubular injuries. Therefore, silymarin prophylaxis may be an interesting strategy for the prevention of CIN.

Worsening of Oxidative Stress, DNA Damage, and Atherosclerotic Lesions in Aged LDLr-/- Mice after Consumption of Guarana Soft Drinks

BACKGROUND

Excessive consumption of soft drinks (SD) has become a health problem worldwide due to its association with related cardiovascular diseases. We investigated the possible impacts associated with the consumption of Brazilian guarana (normal and zero) SD in dyslipidemic mice, thus mitigating potential clinical confounders such as poor-quality diet, lifestyle, body composition, and/or comorbidities.

METHODS

Sixteen-month-old LDLr-/- mice were divided into the following groups: (1) control; (2) GSD: normal guarana SD; and (3) Z-GSD: zero guarana SD. All were fed ad libitum, and blood pressure was measured noninvasively. After 8 weeks, aorta, blood, liver, and stomach samples were collected for histological and biochemical analyses.

RESULTS

Guarana soft drinks increased atherosclerosis (~60%) and were associated with hypercholesterolemia, hypertension, oxidative stress, DNA fragmentation, and apoptosis (~2-fold) of blood cells, besides presenting an increase in liver and gastric damage even in normoglycemia. Interestingly, Z-GSD did not cause the aforementioned changes, except in hemodynamic and renal parameters.

CONCLUSIONS

Chronic administration of GSD is prooxidative, compromising the cardiovascular, gastric, and hepatic systems; the effects are due at least in part to free sugar consumption but not to guarana extract per se.

Vascular Regenerative Cell Exhaustion in Diabetes: Translational Opportunities to Mitigate Cardiometabolic Risk

Ischemic cardiovascular complications remain a major cause of mortality in people with type 2 diabetes (T2D). Individuals with T2D may have a reduced ability to revascularize ischemic tissues due to abnormal production of circulating provascular progenitor cells. This 'regenerative cell exhaustion' process is intensified by increasing oxidative stress and inflammation and during T2D progression. Chronic exhaustion may be mediated by changes in the bone marrow microenvironment that dysregulate the wingless related integration site network, a central pathway maintaining the progenitor cell pool. Restoration of vascular regenerative cell production by reducing glucotoxicity with contemporary antihyperglycemic agents, by reducing systemic inflammation postbariatric surgery, or by modulating progenitor cell provascular functions using exosomal manipulation, may provide unique approaches for mitigating ischemic disease.

Antioxidant effect of sildenafil: Potential hepatoprotection via differential expression of mitochondrial proteins in apolipoprotein E knockout mice

BACKGROUND

High plasma cholesterol levels are able to trigger several pathophysiological events, including inflammation, cell damage and especially oxidative stress. Previously, studies have shown that sildenafil exhibited antioxidant effects in several experimental models. Here we evaluate the role of sildenafil in liver redox equilibrium of apolipoprotein E knockout (apoE-KO) mice.

METHODS

ApoE-KO mice were divided in two groups: one group received the PDE5 inhibitor sildenafil (40 mg/kg/day) for 3 weeks (apoE-KO + Sil) and was compared to a second group of apoE-KO mice, which received only the vehicle (water) for 3 weeks (apoE-KO). Control group (C57 mice) received only a standard chow diet. At the age of 18 weeks, mice livers were collected for the measurement of intracellular ROS levels and apoptotic cells by flow cytometry analysis, and mitochondria isolation for proteomic analysis.

RESULTS

Compared to the control group, liver cells from apoE-KO presented some typical redox imbalance features: higher levels of intracellular ROS (global oxidative stress ˜60%, superoxide anion ˜82%, and peroxynitrite/hydroxyl radical ˜53%), higher amounts of apoptotic cells (up to ˜19%) and higher mitochondrial intensity of catalase (+339%) and transferrin spots (+914%). After treatment with sildenafil, apoE-KO presented ROS levels and the number of apoptotic cells similar to those observed in C57. In addition, when compared to apoE-KO, apoE-KO + Sil showed lower spots volumes of catalase (-23%) and transferrin (-71%) and up-regulation of urate oxidase (+94%).

CONCLUSION

The treatment with sildenafil is able to induce beneficial changes in liver mitochondrial protein dynamics, which restores the redox homeostasis contributing to a potential hepatoprotection.

Causes and Mechanisms of Hematopoietic Stem Cell Aging

Many elderly people suffer from hematological diseases known to be highly age-dependent. Hematopoietic stem cells (HSCs) maintain the immune system by producing all blood cells throughout the lifetime of an organism. Recent reports have suggested that HSCs are susceptible to age-related stress and gradually lose their self-renewal and regeneration capacity with aging. HSC aging is driven by cell-intrinsic and -extrinsic factors that result in the disruption of the immune system. Thus, the study of HSC aging is important to our understanding of age-related immune diseases and can also provide potential strategies to improve quality of life in the elderly. In this review, we delineate our understanding of the phenotypes, causes, and molecular mechanisms involved in HSC aging.

Carcinogenesis and Reactive Oxygen Species Signaling: Interaction of the NADPH Oxidase NOX1-5 and Superoxide Dismutase 1-3 Signal Transduction Pathways

SIGNIFICANCE

Reduction/oxidation (redox) balance could be defined as an even distribution of reduction and oxidation complementary processes and their reaction end products. There is a consensus that aberrant levels of reactive oxygen species (ROS), commonly observed in cancer, stimulate primary cell immortalization and progression of carcinogenesis. However, the mechanism how different ROS regulate redox balance is not completely understood. Recent Advances: In the current review, we have summarized the main signaling cascades inducing NADPH oxidase NOX1-5 and superoxide dismutase (SOD) 1-3 expression and their connection to cell proliferation, immortalization, transformation, and CD34+ cell differentiation in thyroid, colon, lung, breast, and hematological cancers.

CRITICAL ISSUES

Interestingly, many of the signaling pathways activating redox enzymes or mediating the effect of ROS are common, such as pathways initiated from G protein-coupled receptors and tyrosine kinase receptors involving protein kinase A, phospholipase C, calcium, and small GTPase signaling molecules.

FUTURE DIRECTIONS

The clarification of interaction of signal transduction pathways could explain how cells regulate redox balance and may even provide means to inhibit the accumulation of harmful levels of ROS in human pathologies.

TP53INP1 deficiency maintains murine B lymphopoiesis in aged bone marrow through redox-controlled IL-7R/STAT5 signaling

Bone marrow (BM) produces all blood and immune cells deriving from hematopoietic stem cells (HSCs). The decrease of immune cell production during aging is one of the features of immunosenescence. The impact of redox dysregulation in BM aging is still poorly understood. Here we use TP53INP1-deficient (KO) mice endowed with chronic oxidative stress to assess the influence of aging-associated redox alterations in BM homeostasis. We show that TP53INP1 deletion has no impact on aging-related accumulation of HSCs. In contrast, the aging-related contraction of the lymphoid compartment is mitigated in TP53INP1 KO mice. B cells that accumulate in old KO BM are differentiating cells that can mature into functional B cells. Importantly, this phenotype results from B cell-intrinsic events associated with defective redox control. Finally, we show that oxidative stress in aged TP53INP1-deficient mice maintains STAT5 expression and activation in early B cells, driving high Pax5 expression, which provides a molecular mechanism for maintenance of B cell development upon aging.

Circulating Pro-Vascular Progenitor Cell Depletion During Type 2 Diabetes: Translational Insights Into the Prevention of Ischemic Complications in Diabetes

•

This study combined ALDH activity with cell surface marker expression to develop a multiparametric flow cytometry assay to assess proangiogenic progenitor and proinflammatory cell content in the peripheral blood of patients with T2D compared with age-matched control subjects.

•

Patients with T2D exhibited an increased frequency of proinflammatory ALDH^hi cells with granulocyte side scatter properties and a decreased frequency of circulating monocytes with an M2 phenotype that is associated with proangiogenic and anti-inflammatory functions.

•

Patients with T2D exhibited significant depletion of circulating provascular ALDH^hiCD34+ progenitor cells with primitive, migratory, endothelial, and pericyte phenotypes.

•

Subgroup analyses that stratified patients with T2D according to age, duration of T2D, insulin requirement, and glycosylated hemoglobin levels revealed that only the duration of T2D correlated with vascular progenitor cell depletion.

•

Flow cytometric assessment of circulating ALDH^hi cell subsets represents a promising translational approach for identifying patients with T2D at increased risk for cardiovascular comorbidities.

Detection of vascular regenerative cell exhaustion is required to combat ischemic complications during type 2 diabetes mellitus (T2D). We used high aldehyde dehydrogenase (ALDH) activity and surface marker co-expression to develop a high-throughput flow cytometry–based assay to quantify circulating proangiogenic and proinflammatory cell content in the peripheral blood of individuals with T2D. Circulating proangiogenic monocytes expressing anti-inflammatory M2 markers were decreased in patients with T2D. Individuals with longer duration of T2D exhibited reduced frequencies of circulating proangiogenic ALDH^hiCD34+ progenitor cells with primitive (CD133) and migratory (CXCR4) phenotypes. This approach consistently detected increased inflammatory cell burden and decreased provascular progenitor content in individuals with T2D.

Pharmacological Regulation of Oxidative Stress in Stem Cells

Oxidative stress results from an imbalance between reactive oxygen species (ROS) production and antioxidant defense mechanisms. The regulation of stem cell self-renewal and differentiation is crucial for early development and tissue homeostasis. Recent reports have suggested that the balance between self-renewal and differentiation is regulated by the cellular oxidation-reduction (redox) state; therefore, the study of ROS regulation in regenerative medicine has emerged to develop protocols for regulating appropriate stem cell differentiation and maintenance for clinical applications. In this review, we introduce the defined roles of oxidative stress in pluripotent stem cells (PSCs) and hematopoietic stem cells (HSCs) and discuss the potential applications of pharmacological approaches for regulating oxidative stress in regenerative medicine.

Increased ROS production and DNA damage in monocytes are biomarkers of aging and atherosclerosis

Background

New evidence demonstrates that aging and dyslipidemia are closely associated with oxidative stress, DNA damage and apoptosis in some cells and extravascular tissues. However, in monocytes, which are naturally involved in progression and/or resolution of plaque in atherosclerosis, this concurrence has not yet been fully investigated. In this study, we evaluated the influence of aging and hypercholesterolemia on serum pro-inflammatory cytokines, oxidative stress, DNA damage and apoptosis in monocytes from apolipoprotein E-deficient (apoE^−/−) mice compared with age-matched wild-type C57BL/6 (WT) mice. Experiments were performed in young (2-months) and in old (18-months) male wild-type (WT) and apoE^−/− mice.

Results

Besides the expected differences in serum lipid profile and plaque formation, we observed that atherosclerotic mice exhibited a significant increase in monocytosis and in serum levels of pro-inflammatory cytokines compared to WT mice. Moreover, it was observed that the overproduction of ROS, led to an increased DNA fragmentation and, consequently, apoptosis in monocytes from normocholesterolemic old mice, which was aggravated in age-matched atherosclerotic mice.

Conclusions

In this study, we demonstrate that a pro-inflammatory systemic status is associated with an impairment of functionality of monocytes during aging and that these parameters are fundamental extra-arterial contributors to the aggravation of atherosclerosis. The present data open new avenues for the development of future strategies with the purpose of treating atherosclerosis.

Updates on Old and Weary Haematopoiesis

Blood formation, or haematopoiesis, originates from haematopoietic stem cells (HSCs), whose functions and maintenance are regulated in both cell- and cell non-autonomous ways. The surroundings of HSCs in the bone marrow create a specific niche or microenvironment where HSCs nest that allows them to retain their unique characteristics and respond rapidly to external stimuli. Ageing is accompanied by reduced regenerative capacity of the organism affecting all systems, due to the progressive decline of stem cell functions. This includes blood and HSCs, which contributes to age-related haematological disorders, anaemia, and immunosenescence, among others. Furthermore, chronological ageing is characterised by myeloid and platelet HSC skewing, inflammageing, and expanded clonal haematopoiesis, which may be the result of the accumulation of preleukaemic lesions in HSCs. Intriguingly, haematological malignancies such as acute myeloid leukaemia have a high incidence among elderly patients, yet not all individuals with clonal haematopoiesis develop leukaemias. Here, we discuss recent work on these aspects, their potential underlying molecular mechanisms, and the first cues linking age-related changes in the HSC niche to poor HSC maintenance. Future work is needed for a better understanding of haematopoiesis during ageing. This field may open new avenues for HSC rejuvenation and therapeutic strategies in the elderly.

Sex Differences in Macrophage Functions in Middle-Aged Rats: Relevance of Estradiol Level and Macrophage Estrogen Receptor Expression

The aim of this study was to examine the influence of sex on age-related changes in phenotype and functional capacity of rat macrophages. The potential role of estradiol as a contributing factor to a sex difference in macrophage function with age was also examined. Thioglycollate-elicited peritoneal macrophages derived from the young (2 months old) and the naturally senescent intact middle-aged (16 months old) male and female rats were tested for cytokine secretion and antimicrobial activity (NO and H₂O₂ production and myeloperoxidase activity). Serum concentration of estradiol and the expression of estrogen receptor (ER)α and ERβ on freshly isolated peritoneal macrophages were also examined. Decreased secretion of IL-1β and IL-6 by macrophages from middle-aged compared to the young females was accompanied with the lesser density of macrophage ERα expression and the lower systemic level of estradiol, whereas the opposite was true for middle-aged male rats. Macrophages in the middle-aged females, even with the diminished circulating estradiol levels, produce increased amount of IL-6, and comparable amounts of IL-1β, TNF-α, and NO to that measured in macrophages from the middle-aged males. Age-related changes in macrophage phenotype and the antimicrobial activity were independent of macrophage ERα/ERβ expression and estradiol level in both male and female rats. Although our study suggests that the sex difference in the level of circulating estradiol may to some extent contribute to sex difference in macrophage function of middle-aged rats, it also points to more complex hormonal regulation of peritoneal macrophage activity in females.

Genomic and functional integrity of the hematopoietic system requires tolerance of oxidative DNA lesions

Endogenous DNA damage is causally associated with the functional decline and transformation of stem cells that characterize aging. DNA lesions that have escaped DNA repair can induce replication stress and genomic breaks that induce senescence and apoptosis. It is not clear how stem and proliferating cells cope with accumulating endogenous DNA lesions and how these ultimately affect the physiology of cells and tissues. Here we have addressed these questions by investigating the hematopoietic system of mice deficient for Rev1, a core factor in DNA translesion synthesis (TLS), the postreplicative bypass of damaged nucleotides. Rev1 hematopoietic stem and progenitor cells displayed compromised proliferation, and replication stress that could be rescued with an antioxidant. The additional disruption of Xpc, essential for global-genome nucleotide excision repair (ggNER) of helix-distorting nucleotide lesions, resulted in the perinatal loss of hematopoietic stem cells, progressive loss of bone marrow, and fatal aplastic anemia between 3 and 4 months of age. This was associated with replication stress, genomic breaks, DNA damage signaling, senescence, and apoptosis in bone marrow. Surprisingly, the collapse of the Rev1Xpc bone marrow was associated with progressive mitochondrial dysfunction and consequent exacerbation of oxidative stress. These data reveal that, to protect its genomic and functional integrity, the hematopoietic system critically depends on the combined activities of repair and replication of helix-distorting oxidative nucleotide lesions by ggNER and Rev1-dependent TLS, respectively. The error-prone nature of TLS may provide mechanistic understanding of the accumulation of mutations in the hematopoietic system upon aging.

Chronic administration of antioxidant resin from Virola oleifera attenuates atherogenesis in LDLr -/- mice

ETHNOPHARMACOLOGICAL RELEVANCE

Virola oleifera (Schott) A. C. Smith, Myristicaceae has been largely used in traditional folk medicine in Brazil as an anti-inflammatory agent and our previous data indicated the antioxidant properties in other oxidative stress-related models. However, its effects on atherosclerosis (AT) are not yet investigated.

AIMS OF THE STUDY

To evaluate the influence of resin from Virola oleifera (RV) on progression of AT in LDLr^-/- mice.

MATERIALS AND METHODS

LDLr^-/- mice were divided into 4 groups: 1) The ND group received a normal diet without treatment. 2) The HD group received a high-fat diet without treatment. 3) The HD-V50 received a high-fat diet and was orally treated with RV at 50mg/Kg. 4) The HD-V300 received a high-fat diet and was orally treated with RV at 300mg/Kg. After 4 weeks, blood was collected to quantify biochemical parameters and ROS total and the aorta was removed to measure the lipid deposition by en face analysis. The liver was also collected to determine total lipids and lipid and protein oxidation. In order to investigate in more detail the contributions of RV in the vascular structure, we carried out the in vitro tests using four cellular types: macrophages, fibroblasts, vascular smooth muscle and endothelial cells.

RESULTS

We showed that the chronic treatment of RV at both doses reduced vascular lipid accumulation (~50%, p<0.05), probably through systemic and hepatic antioxidant effects, independent of dyslipidemia. Moreover, the in vitro assay results demonstrated that RV develops antioxidant properties on the vascular smooth muscle and endothelial cells, reinforcing the protective role of RV in progression of AT. LPS-stimulated macrophages treated with RV resulted in a significant reduction of NO production in a concentration-dependent manner.

CONCLUSIONS

Chronic treatment with RV diminishes lipid deposition in atherosclerotic mice, which may be justified, at least in part, by antioxidant systemic and local mechanisms, reinforcing the protective role this resin in the setting of vascular lipid deposition, independent of hypercholesterolemia.

Metabolic Syndrome as a Multifaceted Risk Factor for Oxidative Stress

SIGNIFICANCE

Metabolic syndrome (MetS) is associated with a greater risk of diabetes and cardiovascular diseases. It is estimated that this multifactorial condition affects 20%-30% of the world's population. A detailed understanding of MetS mechanisms is crucial for the development of effective prevention strategies and adequate intervention tools that could curb its increasing prevalence and limit its comorbidities, particularly in younger age groups. With advances in basic redox biology, oxidative stress (OxS) involvement in the complex pathophysiology of MetS has become widely accepted. Nevertheless, its clear association with and causative effects on MetS require further elucidation. Recent Advances: Although a better understanding of the causes, risks, and effects of MetS is essential, studies suggest that oxidant/antioxidant imbalance is a key contributor to this condition. OxS is now understood to be a major underlying mechanism for mitochondrial dysfunction, ectopic lipid accumulation, and gut microbiota impairment.

CRITICAL ISSUES

Further studies, particularly in the field of translational research, are clearly required to understand and control the production of reactive oxygen species (ROS) levels, especially in the mitochondria, since the various therapeutic trials conducted to date have not targeted this major ROS-generating system, aimed to delay MetS onset, or prevent its progression.

FUTURE DIRECTIONS

Multiple relevant markers need to be identified to clarify the role of ROS in the etiology of MetS. Future clinical trials should provide important proof of concept for the effectiveness of antioxidants as useful therapeutic approaches to simultaneously counteract mitochondrial OxS, alleviate MetS symptoms, and prevent complications. Antioxid. Redox Signal. 26, 445-461.

Impaired haematopoietic stem cell differentiation and enhanced skewing towards myeloid progenitors in aged caspase-2-deficient mice

The apoptotic cysteine protease caspase-2 has been shown to suppress tumourigenesis in mice and its reduced expression correlates with poor prognosis in some human malignancies. Caspase-2-deficient mice develop normally but show ageing-related traits and, when challenged by oncogenic stimuli or certain stress, show enhanced tumour development, often accompanied by extensive aneuploidy. As stem cells are susceptible to acquiring age-related functional defects because of their self-renewal and proliferative capacity, we examined whether loss of caspase-2 promotes such defects with age. Using young and aged Casp2^−/− mice, we demonstrate that deficiency of caspase-2 results in enhanced aneuploidy and DNA damage in bone marrow (BM) cells with ageing. Furthermore, we demonstrate for the first time that caspase-2 loss results in significant increase in immunophenotypically defined short-term haematopoietic stem cells (HSCs) and multipotent progenitors fractions in BM with a skewed differentiation towards myeloid progenitors with ageing. Caspase-2 deficiency leads to enhanced granulocyte macrophage and erythroid progenitors in aged mice. Colony-forming assays and long-term culture-initiating assay further recapitulated these results. Our results provide the first evidence of caspase-2 in regulating HSC and progenitor differentiation, as well as aneuploidy, in vivo.

Accumulation of DNA damage in the aged hematopoietic stem cell compartment

Aging is associated with loss of functional potential of multiple tissue systems, and there has been significant interest in understanding how tissue-specific cells contribute to this decline. DNA damage accumulation has been widely associated with aging in differentiated cell types. However, tissue-specific stem cells were once thought to be a geno-protected population, as damage accrued in a stem cell population has the potential to be inherited by differentiated progeny, as well as propagated within the stem cell compartment through self-renewal divisions. This review will discuss the evidence for DNA damage accumulation in the aged HSC compartment, potential drivers, and finally the consequences of the acquired damage.

Long-term genotoxic effects in the hematopoietic system of prenatally X-irradiated mice

PURPOSE

To investigate the genotoxic effects of prenatal X-irradiation in mice and the possible presence of late genomic instability.

MATERIALS AND METHODS

Pregnant mice were exposed to 0, 1 or 2 Gy at embryonic day 11.5. Blood smears were obtained from pups at birth and on post-natal day 11, 21, 42 and 140. Hematological data (diameter of erythrocytes, percentage of reticulocytes and Granulocyte-to-Lymphocyte ratio [GLR]) and genotoxicity (micronucleated erythrocytes, micronucleated reticulocytes, CREST-positive and negative micronuclei) were assessed.

RESULTS

Prenatal irradiation caused perinatal reticulocytosis (which ended on postnatal day 11) and a dose-dependent increase of GLR (indicative of myeloid skewing) on postnatal days 42 and 140. Two temporally distinct genotoxic effects were observed: an early, acute damage (still detectable at birth and soon after) and a late, long-term damage.

CONCLUSIONS

Increases in micronuclei frequencies and GLR observed from day 42 on are both ascribable to DNA damage. Time of appearance of this late effect may be linked to the shift of hematopoiesis from spleen to bone marrow and to cell-extrinsic factor such as the microenvironment. This study confirms that ionizing radiation can induce long-term genotoxic effects in the hematopoietic system and shows that prenatal irradiation determines genomic instability in blood-forming tissues of adult mice.

Therapeutic Strategies for Oxidative Stress-Related Cardiovascular Diseases: Removal of Excess Reactive Oxygen Species in Adult Stem Cells

Accumulating evidence indicates that acute and chronic uncontrolled overproduction of oxidative stress-related factors including reactive oxygen species (ROS) causes cardiovascular diseases (CVDs), atherosclerosis, and diabetes. Moreover ROS mediate various signaling pathways underlying vascular inflammation in ischemic tissues. With respect to stem cell-based therapy, several studies clearly indicate that modulating antioxidant production at cellular levels enhances stem/progenitor cell functionalities, including proliferation, long-term survival in ischemic tissues, and complete differentiation of transplanted cells into mature vascular cells. Recently emerging therapeutic strategies involving adult stem cells, including endothelial progenitor cells (EPCs), for treating ischemic CVDs have highlighted the need to control intracellular ROS production, because it critically affects the replicative senescence of ex vivo expanded therapeutic cells. Better understanding of the complexity of cellular ROS in stem cell biology might improve cell survival in ischemic tissues and enhance the regenerative potentials of transplanted stem/progenitor cells. In this review, we will discuss the nature and sources of ROS, drug-based therapeutic strategies for scavenging ROS, and EPC based therapeutic strategies for treating oxidative stress-related CVDs. Furthermore, we will discuss whether primed EPCs pretreated with natural ROS-scavenging compounds are crucial and promising therapeutic strategies for vascular repair.