Recombinant human erythropoietin suppresses endothelial cell apoptosis and reduces the ratio of Bax to Bcl-2 proteins in the aortas of apolipoprotein E-deficient mice

Improving Fat Graft Survival Using Soluble Molecule Preconditioning

Fat grafting is widely used in plastic surgery to correct soft tissue deformities. A major limitation of this technique is the poor long-term volume retention of the injected fat due to tissue remodeling and adipocyte death. To address this issue, various optimizations of the grafting process have been proposed. This scoping review focuses on preclinical and clinical studies that investigated the impact of various classes of soluble molecules on fat grafting outcomes. Globally, we describe that these molecules can be classified as acting through three main mechanisms to improve graft retention: supporting adipogenesis, improving vascularization, and reducing oxidative stress. A variety of 18 molecules are discussed, including insulin, VEGF, deferoxamine, botulinum toxin A, apocynin, N-acetylcysteine, and melatonin. Many biomolecules have shown the potential to improve long-term outcomes of fat grafts through enhanced cell survival and higher volume retention. However, the variability between experimental protocols, as well as the scarcity of clinical studies, remain obstacles to clinical translation. In order to determine the best preconditioning method for fat grafts, future studies should focus on dosage optimization, more sustained delivery of the molecules, and the design of homogenous experimental protocols and specific clinical trials.

Role of Erythropoiesis-Stimulating Agents in Cardiovascular Protection in CKD Patients: Reappraisal of Their Impact and Mechanisms

Erythropoiesis-stimulating agents (ESAs) have markedly reduced the need for blood transfusion for renal anemia and are included in standard therapies for patients with chronic kidney disease (CKD). Various protective effects of ESAs on the cardiovascular system have been discovered through basic research, and the effects have received much attention because the rates of cardiovascular events and mortality are high in CKD patients. However, randomized clinical trials did not provide strong evidence that ESAs exert cardioprotection in humans, including CKD patients. It is difficult to assess the cardioprotective effects of ESAs in CKD patients through the clinical data that has been reported to date because the relationship between hemoglobin level rather than ESA dose and cardiovascular event rates was examined in most studies. Interestingly, recent studies using a rat model of CKD showed that the infarct size-limiting effect of an ESA was lost when its dose was increased to a level that normalized blood hemoglobin levels, suggesting that the optimal dose of an ESA for myocardial protection is less than the dose required to normalize hemoglobin levels. Furthermore, animal models of traditional coronary risk factors or comorbidities were resistant to the cardioprotective effects of ESAs because of interruptions in signal-mediated mechanisms downstream of erythropoietin receptors. In this review, we briefly discuss basic and clinical data on the impact of anemia on coronary and systemic circulation, the effects of CKD on the cardiovascular system, and the multiple pharmacological actions of ESAs to examine whether the ESAs that are prescribed for renal anemia exert any cardioprotection in patients with CKD.

STUDY OF THE PHARMACOLOGICAL ACTIVITY OF NOVEL EPOR/CD131 HETERORECEPTOR AGONISTS IN MICE WITH ENDOTHELIAL-SPECIFIC EXPRESSION OF MUTANT POLG GENE

The aim of the research was to study antiatherosclerotic and endothelial kinds of a protective activity of peptides mimicking an erythropoietin a-helix B tertiary structure with laboratory codes EP-11-1 (UEHLERALNSS), EP-11-2. (UEQLERALNCS), EP-11-3 (UEQLERALNTS).

Materials and methods. The study was conducted on 96 C57Bl/6J male double transgenic Polgmut/mut/Cdh5-CRE mice. Atherosclerosis was induced by a balloon injury accompanied by Western diet. Then, for 27 days, the drugs under study were administered once per 3 days at the dose of 20 μg/kg. On the 28th day, the animals were euthanized and the area of atherosclerotic plaques was collected for an assessment. The expression of genes associated with the processes of inflammation, apoptosis, and angiogenesis was determined in the tissues of the aorta. In addition, the endothelial protective effect of peptides in isolated segments of the thoracic aorta of wild and transgenic ransgenic Polgmut/mut mice was studied.

Results. The assessment of the plaque size in the animals with the Polgmut/mut/Cdh5-CRE genotype against the background of the peptides under study did not reveal statistically significant differences in comparison to control. However, a quantitative PCR showed a statistically significant decreased expression of pro-apoptotic factors p-53 and Bax, and also increase the expression of anti-apoptotic factor Bcl-2 against the background of the peptides EP-11-1 and EP-11-2 administration. The administration of EP-11-1 and the original peptide pHBSP resulted in a statistically significant decrease in the Bax/Bcl-2 ratio. Compounds EP-11-1, EP-11-2, and EP-11-3 were more effective than the original peptide pHBSP, in reducing the increased expression of genes for inflammatory markers iNos, intercellular adhesion molecules Icam-1, Vcam-1 and E-selectin. The use of EP-11-1 led to a more efficient, in comparison with pHBSP, restoration of endothelial-dependent vasodilation of the aortic segments in mice with endothelial-specific overexpression of the mutant Polg gene.

Conclusion. The study carried out on a murine model of the endothelial-specific expression of mutant gamma polymerase has shown that derivatives of the pHBSP peptide with laboratory codes EP-11-1, EP-11-2, EP-11-3, obtained by BLAST-searching for groups of pHBSP related peptides, have atheroprotective and endothelial protective kinds of a protective activity, which is more pronounced in comparison with the original peptide pHBSP.

STUDY OF ANTIATHEROSCLEROTIC AND ENDOTHELIOPROTECTIVE ACTIVITY OF PEPTIDE AGONISTS OF EPOR/CD131 HETERORECEPTOR

Introduction. The drugs affecting a mitochondrial dysfunction, oxidative stresses, apoptosis and inflammation of the vascular wall, have a high potential for the prevention and treatment of atherosclerotic lesions. In this regard, the use of EPOR/CD131 heteroreceptor agonists which have a similar spectrum of pharmacological effects, is one of the promising strategies in the treatment of cardiovascular diseases.

Materials and Methods. The study was carried out on 68 C57Bl/6J male mice. Atherosclerosis was simulated in transgenic animals with an endotheliospecific knockdown of the Polg gene by simulating a balloon injury and keeping on a Western diet. Then, the studied drugs were injected once every 3 days at the dose of 20 μg/kg for 27 days. On the 28-th day, the animals were euthanized and the area of atherosclerotic plaques was assessed. The gene expression associated with the processes of inflammation, antioxidant protection, apoptosis, and angiogenesis was also determined in the aortic tissues. In addition, the endothelium protective effect of peptides on primary cultures of endothelial cells of wild and transgenic Polg-D257A mice was studied.

Results. No statistically significant effect of drugs on the area of lipid infiltration have been found. However, the studied peptides have significantly reduced the expression of proinflammatory genes (iNos, Icam1, Vcam1, Sele, Il6, Tnfa), the genes associated with angiogenesis (Vegfa, Kdr, and Hif1a), the expression of proapoptic factors; they decreased the Bax/Bcl-2 ratio by more than 1.5 times. In addition, when supplemented with H2 O2  in vitro, peptides dose-dependently increased endothelial cell survival.

Conclusion. The erythropoietin-based peptides can be used to improve the functional state of the vascular wall against the background of atherosclerotic lesions and have a depressing effect on pathobiological processes associated with a mitochondrial dysfunction. In addition, the studied peptides have a significant endothelial protective effect in the induction of oxidative stress in vitro.

Recombinant human erythropoietin stimulates melanoma tumor growth through activation of initiation factor eIF4E

Recombinant human erythropoietin (EPO) is standard treatment for anemia in cancer patients. Recent clinical trials suggest that EPO may accelerate tumor progression and increase mortality. However, the evidence supporting a growth-promoting effect of EPO has remained controversial. Employing an in vivo model of B16 murine melanoma, we observed that administration of EPO to tumor bearing C57BL/6 mice resulted in pronounced acceleration of melanoma growth. Our in vitro studies demonstrate that B16 murine melanoma cells express EPOR, both at the protein and mRNA levels. Interestingly, expression of EPOR was retained in the established tumors. EPO stimulation of B16 cells enhanced proliferation and protein synthesis rates, and correlated with activation of the receptor associated Janus kinase 2 (Jak2) as well as phosphorylation of extracellular signal–regulated kinase (Erk) 1/2 and Akt kinases. Treatment with EPO and Jak-2 antagonists significantly inhibited EPO-mediated B16 cell proliferation. Moreover, EPO dose-dependently induced the phosphorylation and activation of the translation initiation factor eIF4E as well as the phosphorylation of its repressor, the eIF4E binding protein 4E-BP1. Finally, using eIF4E small interfering RNA (siRNA), we observed that EPO-mediated stimulation of B16 cell proliferation is eIF4E-dependent. Our results indicate that EPO exerts a powerful stimulatory effect on cell proliferation and de novo protein synthesis in melanoma cells through activation of the initiation factor eIF4E.

Possible Inhibitory Effect of Erythropoiesis-Stimulating Agents at the Predialysis Stage on Early-Phase Coronary Events after Hemodialysis Initiation

BACKGROUND

We examined whether the use of erythropoiesis-stimulating agents (ESAs) to correct anemia at the predialysis stage could inhibit early-phase coronary events after hemodialysis initiation.

METHODS

We enrolled 242 patients with chronic kidney disease who had received continued medical treatments and initiated maintenance hemodialysis from 1 September 2000 to 31 December 2014 at Toujinkai Hospital. Patients with a previous history of blood transfusion or any cardiovascular events or interventions were excluded. The coronary events were followed for 1 year after initiation of hemodialysis.

RESULTS

Coronary events occurred in 51 of 242 patients: 10 patients had acute coronary syndrome [9 with percutaneous coronary intervention (PCI), 1 without intervention], and 41 had elective coronary revascularization (38 PCI and 3 coronary artery bypass graft). ESA was administered in 118 of 242 patients (48.8%). In stepwise logistic analysis, coronary events were positively associated with nonuse of ESA at the predialysis stage (odds ratio 2.66, p = 0.005) and diabetes mellitus (odds ratio 5.33, p < 0.001). When dividing the patients into 4 subgroups by blood hemoglobin (Hb) level (8.5 g/dl) and the use/nonuse of ESA, coronary event-free survival rates were higher (p = 0.005) in those with Hb ≥8.5 g/dl, ESA+ (86.6%, n = 82) and tended to be higher (p = 0.055) in those with Hb <8.5 g/dl, ESA+ (86.1%, n = 36) than in patients with Hb <8.5 g/dl, ESA- (68.6%, n = 86) in a Kaplan-Meier analysis.

CONCLUSIONS

The use of ESA to correct anemia at the predialysis stage may inhibit early-phase coronary events after hemodialysis initiation.

Erythropoietin improves the accumulation and therapeutic effects of carboplatin by enhancing tumor vascularization and perfusion

Recombinant human erythropoietin (rhuEpo) is currently under debate for the treatment of chemotherapy-induced anemia due to clinical trials showing adverse effects in Epo-treated patients and the discovery of the erythropoietin-receptor (EpoR) in tumor and endothelial cells. Here, using Epo-Cy5.5 as theranostic near-infrared fluorescent probe we analyzed the effects of rhuEpo as co-medication to carboplatin in non-small-cell-lung-cancer (NSCLC)-xenografts with different tumor cell EpoR-expression (H838 ~8-fold higher than A549). Nude mice bearing subcutaneous A549 and H838 NSCLC-xenografts received either only carboplatin or carboplatin and co-medication of rhuEpo in two different doses. Tumor sizes and relative blood volumes (rBV) were longitudinally measured by 3D-contrast-enhanced ultrasound (3D-US). Tumoral EpoR-levels were determined by combined fluorescence molecular tomography (FMT)/ micro computed tomography (µCT) hybrid imaging. We found that rhuEpo predominantly acted on the tumor endothelium. In both xenografts, rhuEpo co-medication significantly increased vessel densities, diameters and the amount of perfused vessels. Accordingly, rhuEpo induced EpoR-phoshorylation and stimulated proliferation of endothelial cells. However, compared with solely carboplatin-treated tumors, tumor growth was significantly slower in the groups co-medicated with rhuEpo. This is explained by the Epo-mediated vascular remodeling leading to improved drug delivery as obvious by a more than 2-fold higher carboplatin accumulation and significantly enhanced tumor apoptosis. In addition, co-medication of rhuEpo reduced tumor hypoxia and diminished intratumoral EpoR-levels which continuously increased during carboplatin (Cp) -treatment. These findings suggest that co-medication of rhuEpo in well balanced doses can be used to improve the accumulation of anticancer drugs. Doses and indications may be personalized and refined using theranostic EpoR-probes.

Effects and mechanism of recombinant human erythropoietin on the growth of human breast cancer MDA-MB-231 cells in nude mice

This study aimed to explore the effects of recombinant human erythropoietin (rhEPO) on the growth of human breast cancer MDA-MB-231 cells in nude mice, and investigate its functions in regulating tumor growth, angiogenesis and apoptosis. A tumor-bearing nude mice model was established by subcutaneous injection of human breast cancer MDA-MB-231 cells. Two weeks later, the mice were randomly divided into four groups (n=6 for each group): negative control group, rhEPO group, EPO antibody group and EPO+EPO antibody group. Drugs were administered to the corresponding mice once every 3 days for five times. The size and weight of tumors were measured after the mice were sacrificed by cervical dislocation. The expression levels of EPO/EPOR, TNF-α, IL-10, and Bcl-2 in the tumor tissues were determined using RT-PCR and Western blot. The microvessel density (MVD) and expression of VEGF in the tumors were detected using immunohistochemistry. TUNEL assay was used to determine apoptosis in tumors. Results show that rhEPO significantly promoted the growth of MDA-MB-231 cells in nude mice (P<0.05). Compared with the negative control group, the expression levels of EPO, EPOR, TNF-α, IL-10, and VEGF, as well as the MVD values, were significantly elevated in the rhEPO group. However, the apoptotic index was significantly reduced (P<0.05). The ability of rhEPO to promote tumor growth may be associated with its functions in promoting microvessel formation and inhibiting tumor cell apoptosis.

Recombinant human erythropoietin increases cerebral cortical width index and neurogenesis following ischemic stroke

The cerebral cortical expansion index refers to the ratio between left and right cortex width and is recognized as an indicator for cortical hyperplasia. Cerebral ischemia was established in CB-17 mice in the present study, and the mice were subsequently treated with recombinant human erythropoietin via subcutaneous injection. Results demonstrated that cerebral cortical width index significantly increased. Immunofluorescence detection showed that the number of nuclear antigen antibody/5-bromodeoxyuridine-positive cells at the infarction edge significantly increased. Correlation analysis revealed a negative correlation between neurological scores and cortical width indices in rats following ischemic stroke. These experimental findings suggested that recombinant human erythropoietin promoted cerebral cortical hyperplasia, increased cortical neurogenesis, and enhanced functional recovery following ischemic stroke.

Erythropoietin administration for prevention of cardiac surgery-associated acute kidney injury: a meta-analysis of randomized controlled trials

The effect of erythropoietin (EPO) on the prevention of cardiac surgery-associated acute kidney injury (CSA-AKI) is controversial. Therefore, we undertook the meta-analysis of randomized controlled trials (RCTs) to assess the efficacy and safety of EPO on the prevention of CSA-AKI in adult patients and to explore whether risk factors for AKI could explain the inconsistent effects. PubMed and EMbase databases were searched to identify eligible RCTs. The meta-analysis was performed with fixed- or random-effects models according to the heterogeneity, and the subgroup analysis stratified by risk factors for AKI was carried out. Five RCTs involving 423 patients were included. Overall, EPO administration was not associated with a reduced incidence of CSA-AKI [relative risk (RR): 0.64, 95% confidence interval (CI): 0.35-1.16], with a moderate heterogeneity (I(2) = 67.4%, heterogeneity P = 0.02). Subgroup analysis showed that, in patients without high risk factors for AKI, EPO administration could significantly reduce the incidence of CSA-AKI (RR: 0.38, 95% CI: 0.24-0.61), intensive care unit length of stay [standardized mean difference (SMD): -0.54, 95% CI: -1.05 to -0.04] and hospital length of stay (SMD: -0.48, 95% CI: -0.94 to -0.02). The test of heterogeneity was not significant in the two subgroups. EPO administration could significantly reduce the incidence of CSA-AKI, but not in patients with high risk factors for AKI. Substantial heterogeneity across trials could be attributed to high risk factors for AKI. However, our findings should be interpreted cautiously because of the limited studies included, and high-quality RCTs are warranted.

Angiotensin II protects cortical neurons against oxygen-glucose deprivation-induced injury in vitro

Ischemic cerebrovascular disease is a common type of cerebrovascular disease and the leading cause of disability and mortality worldwide. Therefore, it is crucial to elucidate its pathogenesis and develop novel therapeutic strategies. This study was performed to investigate whether angiotensin (Ang) II exerts a protective effect against cerebral ischemia/reperfusion (I/R) injury in vitro. The primary cultured neurons were prepared and an I/R model was established by incubation of cortical neurons with Na₂S₂O₄, followed by culture in fresh medium. The protective effect of Ang II and its underlying mechanisms were investigated by morphology observation, MTT assay, flow cytometry analysis and reverse transcription-polymerase chain reaction (RT-PCR). The data demonstrated that Ang II significantly ameliorated the neuronal injury caused by oxygen-glucose deprivation. Furthermore, Ang II increased cell viability through inhibiting cell apoptosis. The RT-PCR results revealed that Ang II was able to reverse the increased bax mRNA and the decreased bcl2 mRNA expression. Of note, the protective activity of Ang II may be attenuated by co-treatment with Ang II type 2 (AT2) receptor blockade (PD123319), but not Ang II type 1 (AT1) receptor blockade (valsartan). These findings suggested that Ang II exerted a protective effect against neuronal injury induced by oxygen-glucose deprivation through decreasing cell apoptosis. Therefore, Ang II may be used as a potential therapeutic target in the future.

Darbepoetin alpha reduces oxidative stress and chronic inflammation in atherosclerotic lesions of apo E deficient mice in experimental renal failure

Background

Cardiovascular morbidity and mortality is very important in patients with chronic renal failure. This occurs even in mild impairment of renal function and may be related to oxidative stress and chronic inflammation. The nephrectomized apo E knockout mouse is an accepted model for evaluating atherosclerosis in renal dysfunction. Erythropoietin derivates showed anti-oxidative and anti-inflammatory effects. Therefore, this study evaluates the effects of Darbepoetin on markers of oxidative stress and chronic inflammation in atherosclerotic lesions in apo E knockout mice with renal dysfunction.

Methods

Apo E knockout mice underwent unilateral (Unx, n = 20) or subtotal (Snx, n = 26) nephrectomy or sham operation (Sham, n = 16). Mice of each group were either treated with Darbepoetin or saline solution, a part of Snx mice received a tenfold higher dose of Darbepoetin. The aortic plaques were measured and morphologically characterized. Additional immunhistochemical analyses were performed on tissue samples taken from the heart and the aorta.

Results

Both Unx and Snx mice showed increased expression of markers of oxidative stress and chronic inflammation. While aortic plaque size was not different, Snx mice showed advanced plaque stages when compared to Unx mice. Darbepoetin treatment elevated hematocrit and lowered Nitrotyrosin as one marker of oxidative stress, inflammation in heart and aorta, plaque stage and in the high dose even plaque cholesterol content. In contrast, there was no influence of Darbepoetin on aortic plaque size; high dose Darbepoetin treatment resulted in elevated renal serum parameters.

Conclusion

Darbepoetin showed some protective cardiovascular effects irrespective of renal function, i.e. it improved plaque structure and reduced some signs of oxidative stress and chronic inflammation without affecting plaque size. Nevertheless, the dose dependent adverse effects must be considered as high Darbepoetin treatment elevated serum urea. Elevation of hematocrit might be a favorable effect in anemic Snx animals but a thrombogenic risk in Sham animals.

The influence of the pleiotropic action of erythropoietin and its derivatives on nephroprotection

Erythropoietin (EPO) is traditionally described as a hematopoietic cytokine or growth hormone regulating proliferation, differentiation, and survival of erythroid progenitors. The use of EPO in patients with chronic kidney disease (CKD) was a milestone achievement in the treatment of anemia. However, EPO involves some degree of risk, which increases with increasing hemoglobin levels. A growing number of studies have assessed the renoprotective effects of EPO in acute kidney injury (AKI) or CKD. Analysis of the biological effects of erythropoietin and pathophysiology of CKD in these studies suggests that treatment with erythropoiesis-stimulating agents (ESAs) may exert renoprotection by pleiotropic actions on several targets and directly or indirectly slow the progression of CKD. By reducing ischemia and oxidative stress or strengthening anti-apoptotic processes, EPO may prevent the development of interstitial fibrosis and the destruction of tubular cells. Furthermore, it could have a direct protective impact on the integrity of the interstitial capillary network through its effects on endothelial cells and promotion of vascular repair, or modulate inflammation response. Thus, it is biologically plausible to suggest that correcting anemia with ESAs could slow the progression of CKD.                         The aim of this article is to discuss these possible renoprotection mechanisms and provide a comprehensive overview of erythropoietin and its derivatives.

Erythropoietin: new directions for the nervous system

New treatment strategies with erythropoietin (EPO) offer exciting opportunities to prevent the onset and progression of neurodegenerative disorders that currently lack effective therapy and can progress to devastating disability in patients. EPO and its receptor are present in multiple systems of the body and can impact disease progression in the nervous, vascular, and immune systems that ultimately affect disorders such as Alzheimer's disease, Parkinson's disease, retinal injury, stroke, and demyelinating disease. EPO relies upon wingless signaling with Wnt1 and an intimate relationship with the pathways of phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), and mammalian target of rapamycin (mTOR). Modulation of these pathways by EPO can govern the apoptotic cascade to control β-catenin, glycogen synthase kinase-3β, mitochondrial permeability, cytochrome c release, and caspase activation. Yet, EPO and each of these downstream pathways require precise biological modulation to avert complications associated with the vascular system, tumorigenesis, and progression of nervous system disorders. Further understanding of the intimate and complex relationship of EPO and the signaling pathways of Wnt, PI 3-K, Akt, and mTOR are critical for the effective clinical translation of these cell pathways into robust treatments for neurodegenerative disorders.

Erythropoietin improves long-term outcomes in patients with acute kidney injury after coronary artery bypass grafting

Previous studies reported the beneficial effect of erythropoietin (EPO) in acute injuries. We followed patients with and without acute kidney injury (AKI) after coronary artery bypass grafting (CABG) and evaluated the effect of EPO on long-term outcome. We also assessed the efficacy of urinary neutrophil gelatinase-associated lipocalin (uNGAL) as a predictive marker of AKI. Seventy-one patients scheduled for elective CABG were randomly given either 300 U/kg of EPO or saline before CABG. The primary outcome was AKI, and the secondary outcome was the all-cause-mortality and composite of all-cause-mortality and end stage renal disease (ESRD). Twenty-one patients had AKI, 14 (66.7%) in the placebo group and 7 (33.3%) in the EPO group (P = 0.05). Also, uNGAL was higher in the patients with AKI than in those without AKI at baseline, 2, 4, 24, and 72 hr after CABG (P = 0.011). Among patients with AKI, 2-week creatinine (Cr) was not different from baseline Cr in the EPO group, but 2-week Cr was significantly higher than baseline Cr in the placebo group (P = 0.009). All-cause-mortality (P = 0.022) and the composite of all-cause-mortality and ESRD (P = 0.003) were reduced by EPO. EPO reduces all-cause-mortality and ESRD in patients with AKI, largely due to the beneficial effect of EPO on recovery after AKI.

Erythropoietin and Wnt1 govern pathways of mTOR, Apaf-1, and XIAP in inflammatory microglia

Inflammatory microglia modulate a host of cellular processes in the central nervous system that include neuronal survival, metabolic fluxes, foreign body exclusion, and cellular regeneration. Elucidation of the pathways that oversee microglial survival and integrity may offer new avenues for the treatment of neurodegenerative disorders. Here we demonstrate that erythropoietin (EPO), an emerging strategy for immune system modulation, prevents microglial early and late apoptotic injury during oxidant stress through Wnt1, a cysteine-rich glycosylated protein that modulates cellular development and survival. Loss of Wnt1 through blockade of Wnt1 signaling or through the gene silencing of Wnt1 eliminates the protective capacity of EPO. Furthermore, endogenous Wnt1 in microglia is vital to preserve microglial survival since loss of Wnt1 alone increases microglial injury during oxidative stress. Cellular protection by EPO and Wnt1 intersects at the level of protein kinase B (Akt1), the mammalian target of rapamycin (mTOR), and p70S6K, which are necessary to foster cytoprotection for microglia. Downstream from these pathways, EPO and Wnt1 control "anti-apoptotic" pathways of microglia through the modulation of mitochondrial membrane permeability, the release of cytochrome c, and the expression of apoptotic protease activating factor-1 (Apaf-1) and X-linked inhibitor of apoptosis protein (XIAP). These studies offer new insights for the development of innovative therapeutic strategies for neurodegenerative disorders that focus upon inflammatory microglia and novel signal transduction pathways.

Erythropoietin employs cell longevity pathways of SIRT1 to foster endothelial vascular integrity during oxidant stress

Given the cytoprotective ability of erythropoietin (EPO) in cerebral microvascular endothelial cells (ECs) and the invaluable role of ECs in the central nervous system, it is imperative to elucidate the cellular pathways for EPO to protect ECs against brain injury. Here we illustrate that EPO relies upon the modulation of SIRT1 (silent mating type information regulator 2 homolog 1) in cerebral microvascular ECs to foster cytoprotection during oxygen-glucose deprivation (OGD). SIRT1 activation which results in the inhibition of apoptotic early membrane phosphatidylserine (PS) externalization and subsequent DNA degradation during OGD becomes a necessary component for EPO protection in ECs, since inhibition of SIRT1 activity or diminishing its expression by gene silencing abrogates cell survival supported by EPO during OGD. Furthermore, EPO promotes the subcellular trafficking of SIRT1 to the nucleus which is necessary for EPO to foster vascular protection. EPO through SIRT1 averts apoptosis through activation of protein kinase B (Akt1) and the phosphorylation and cytoplasmic retention of the forkhead transcription factor FoxO3a. SIRT1 through EPO activation also utilizes mitochondrial pathways to prevent mitochondrial depolarization, cytochrome c release, and Bad, caspase 1, and caspase 3 activation. Our work identifies novel pathways for EPO in the vascular system that can govern the activity of SIRT1 to prevent apoptotic injury through Akt1, FoxO3a phosphorylation and trafficking, mitochondrial membrane permeability, Bad activation, and caspase 1 and 3 activities in ECs during oxidant stress.

Translating cell survival and cell longevity into treatment strategies with SIRT1

The sirtuin SIRT1, a class III NAD(+)-dependent protein histone deacetylase, is present throughout the body that involves cells of the central nervous system, immune system, cardiovascular system, and the musculoskeletal system. SIRT1 has broad biological effects that affect cellular metabolism as well as cellular survival and longevity that can impact both acute and chronic disease processes that involve neurodegenerative disease, diabetes mellitus, cardiovascular disease, and cancer. Given the intricate relationship SIRT1 holds with a host of signal transduction pathways ranging from transcription factors, such as forkhead, to cytokines and growth factors, such as erythropoietin, it becomes critical to elucidate the cellular pathways of SIRT1 to safely and effectively develop and translate novel avenues of treatment for multiple disease entities.