H-ferritin ferroxidase induces cytoprotective pathways and inhibits microvascular stasis in transgenic sickle mice

Hemolysis, oxidative stress, inflammation, vaso-occlusion, and organ infarction are hallmarks of sickle cell disease (SCD). We have previously shown that increases in heme oxygenase-1 (HO-1) activity detoxify heme and inhibit vaso-occlusion in transgenic mouse models of SCD. HO-1 releases Fe(2+) from heme, and the ferritin heavy chain (FHC) ferroxidase oxidizes Fe(2+) to catalytically inactive Fe(3+) inside ferritin. FHC overexpression has been shown to be cytoprotective. In this study, we hypothesized that overexpression of FHC and its ferroxidase activity will inhibit inflammation and microvascular stasis in transgenic SCD mice in response to plasma hemoglobin. We utilized a Sleeping Beauty (SB) transposase plasmid to deliver a human wild-type-ferritin heavy chain (wt-hFHC) transposable element by hydrodynamic tail vein injections into NY1DD SCD mice. Control SCD mice were infused with the same volume of lactated Ringer's solution (LRS) or a human triple missense FHC (ms-hFHC) plasmid with no ferroxidase activity. 8 weeks later, LRS-injected mice had ~40% microvascular stasis (% non-flowing venules) 1 h after infusion of stroma-free hemoglobin, while mice overexpressing wt-hFHC had only 5% stasis (p < 0.05), and ms-hFHC mice had 33% stasis suggesting vascular protection by ferroxidase active wt-hFHC. The wt-hFHC SCD mice had marked increases in splenic hFHC mRNA and hepatic hFHC protein, ferritin light chain (FLC), 5-aminolevulinic acid synthase (ALAS), heme content, ferroportin, nuclear factor erythroid 2-related factor 2 (Nrf2), and HO-1 activity and protein. There was also a decrease in hepatic activated nuclear factor-kappa B (NF-κB) phospho-p65 and vascular cell adhesion molecule-1 (VCAM-1). Inhibition of HO-1 activity with tin protoporphyrin demonstrated HO-1 was not essential for the protection by wt-hFHC. We conclude that wt-hFHC ferroxidase activity enhances cytoprotective Nrf2-regulated proteins including HO-1, thereby resulting in decreased NF-κB-activation, adhesion molecules, and microvascular stasis in transgenic SCD mice.

Pilot study of vascular health in survivors of osteosarcoma

BACKGROUND

Cardiovascular-related toxicities have been reported among survivors of osteosarcoma.

METHODS

Fasting blood samples from 24 osteosarcoma survivors were analyzed for high-sensitivity C-reactive protein (hsCRP), triglycerides, total cholesterol, high-density lipoprotein (HDL), apolipoprotein-ß, lipoprotein (a), fibrinogen, circulating endothelial cells (CECs), and surface expression of vascular cell adhesion molecule-1 (VCAM-1). Values were compared to subjects in the natural history Coronary Artery Risk Development in Young Adults (CARDIA) cohort study except for CECs and VCAM-1 expression, which were compared to controls studied at the University of Minnesota Lillehei clinical trials unit.

PROCEDURE

Survivors (54.2% male), median age 18 years (9-32) at diagnosis, 36.5 years (20-56) at evaluation were treated with a variety of chemotherapeutic exposures, all but one were exposed to doxorubicin (median dose 450 mg/m(2) ; range: 90-645 mg/m(2)), 14 (58.3%) received cisplatin, and 3 (12.5%) were exposed to carboplatin. Two survivors (8.3%) received radiation therapy for disease relapse. Compared to CARDIA subjects, mean hsCRP (3.0 mg/L ± 2.0 vs. 1.6 ± 2.3), triglycerides (151 mg/dl ± 81.7 vs. 95.4 ± 101.3), lipoprotein (a) (34.9 mg/dl ± 17.7 vs. 13.8 ± 22.0), and fibrinogen (315.0 mg/dl ± 49.3 vs. 252.4 ± 61.7) were significantly elevated. The number of CECs (0.47 cells/ml ± 2.5 vs. 0.92 ± 2.5) did not differ while surface expression of VCAM-1 (86.4% ± 34.0 vs. 42.1 ± 33.8) was significantly elevated compared to controls.

CONCLUSIONS

Among survivors of osteosarcoma, assessed a median of 14 years from diagnosis, there is evidence of vascular inflammation, dyslipidemia, and early atherogenesis.

Morphine stimulates platelet-derived growth factor receptor-β signalling in mesangial cells in vitro and transgenic sickle mouse kidney in vivo

BACKGROUND

Pain and renal dysfunction occur in sickle cell disease. Morphine used to treat pain also co-activates platelet-derived growth factor receptor-β (PDGFR-β), which can adversely affect renal disease. We examined the influence of morphine in mesangial cells in vitro and in mouse kidneys in vivo.

METHODS

> Mouse mesangial cells treated with 1 μM morphine in vitro or kidneys of transgenic homozygous or hemizygous sickle or control mice (n=3 for each), treated with morphine (0.75, 1.4, 2.14, 2.8, 3.6, and 4.3 mg kg(-1) day(-1) in two divided doses during the first, second, third, fourth, fifth, and sixth weeks, respectively), were used. Western blotting, bromylated deoxy uridine incorporation-based cell proliferation assay, reverse transcriptase-polymerase chain reaction, immunofluorescent microscopy, and blood/urine chemistry were used to analyse signalling, cell proliferation, opioid receptor (OP) expression, and renal function.

RESULTS

Morphine stimulated phosphorylation of PDGFR-β and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) to the same extent as induced by platelet-derived growth factor-BB (PDGF-BB) and promoted a two-fold increase in mesangial cell proliferation. The PDGFR-β inhibitor, AG1296, OP antagonists, and silencing of μ- and κ-OP abrogated morphine-induced MAPK/ERK phosphorylation and proliferation by ~100%. Morphine treatment of transgenic mice resulted in phosphorylation of PDGFR-β, MAPK/ERK, and signal transducer and activator of transcription 3 (Stat3) in the kidneys. Morphine inhibited micturition and blood urea nitrogen (BUN) clearance and increased BUN and urinary protein in sickle mice.

CONCLUSION

Morphine stimulates mitogenic signalling leading to mesangial cell proliferation and promotes renal dysfunction in sickle mice.

Age sensitizes the kidney to heme protein-induced acute kidney injury

Age increases the risk for ischemic acute kidney injury (AKI). We questioned whether a similar age-dependent injury occurs following exposure to hemoglobin, a known nephrotoxin. Old mice (~16 mo old), but not young mice (~6 mo old), when administered hemoglobin, exhibited marked elevation in blood urea nitrogen (BUN) and serum creatinine, and acute tubular necrosis with prominent tubular cast formation. The aged kidney exhibited induction of heme oxygenase-1 (HO-1) and other genes/proteins that may protect against heme-mediated renal injury, including ferritin, ferroportin, haptoglobin, and hemopexin. Old mice did not evince induction of HO-2 mRNA by hemoglobin, whereas a modest induction of HO-2 mRNA was observed in young mice. To determine the functional significance of HO-2 in heme protein-induced AKI, we administered hemoglobin to relatively young HO-2(+/+) and HO-2(-/-) mice: HO-2(-/-) mice, compared with HO-2(+/+) mice, exhibited greater renal dysfunction and histologic injury when administered hemoglobin. In addition to failing to elicit a protective system such as HO-2 in response to hemoglobin, old mice exhibited an exaggerated maladaptive response typified by markedly greater induction of the nephrotoxic cytokine IL-6 (130-fold increase vs. 10-fold increase in mRNA in young mice). We conclude that aged mice, unlike relatively younger mice, are exquisitely sensitive to the nephrotoxicity of hemoglobin, an effect attended by a failure to induce HO-2 mRNA and a fulminant upregulation of IL-6. Age thus markedly augments the sensitivity of the kidney to heme proteins, and HO-2 confers resistance to such insults.

Pilot study of vascular health in survivors of Hodgkin lymphoma

BACKGROUND

Vascular-related toxicities have been reported among survivors of Hodgkin lymphoma (HL), but their genesis is not well understood.

PROCEDURE

Fasting blood samples from 25 previously irradiated HL survivors were analyzed for biomarkers that can reveal underlying inflammation and/or endothelial cell activation: high-sensitivity C-reactive protein (hsCRP), triglycerides, total cholesterol, high-density lipoprotein (HDL), apolipoprotein ß, lipoprotein (a), fibrinogen, circulating endothelial cells (CECs), and vascular cell adhesion molecule-1 (VCAM-1) expression. Values were compared to subjects in the Coronary Artery Risk Development in Young Adults (CARDIA) study. CECs and VCAM-1 were compared to healthy controls.

RESULTS

Survivors (76% male), median age 17.6 years (5-33) at diagnosis, 33.0 years (19-55) at follow-up, included stages IA (n = 6), IIA (n = 10), IIB (n = 2), IIIA (n = 4), and IVA (n = 3) patients. Twenty-four received at least chest radiation therapy (RT) (median dose 3,150 cGy; range: 175-4,650 cGy), one received neck only; 14 (56%) had a history of anthracycline exposure (median dose: 124 mg/m(2) range: 63-200 mg/m2). Compared to CARDIA subjects, mean hsCRP (3.0 mg/L ± 2.0 vs. 1.6 ± 1.9), total cholesterol (194.1 mg/dl ± 33.2 vs. 179.4 ± 32.9), lipoprotein (a) (34.2 mg/dl ± 17.5 vs. 13.8 ± 17.5), and fibrinogen (342.0 mg/dl ± 49.1 vs. 252.6 ± 48.4) were significantly elevated. CECs (2.3 cells/ml ± 1.5 vs. 0.34 ± 1.4) were significantly elevated compared to controls. No difference in VCAM-1 expression (51.1% ± 36.8 vs. 42.3 ± 35.6) was detected.

CONCLUSION

HL survivors exposed to RT have evidence of vascular inflammation, dyslipidemia, and injury suggestive of early atherogenesis.

Morphine promotes renal pathology in sickle mice

Patients with sickle cell disease (SCD) are often treated with opioids for severe pain. Although opioids are known to have renal-specific effects, their role in nephropathy in SCD remains unknown. Because a subset of patients receives opioids for long periods of time, we examined the influence of chronic morphine treatment on mice with pre-existing renal disease expressing varying amounts of sickle hemoglobin. Morphine treatment for 3–6 weeks resulted in a variety of defects in renal morphology observed using light and electron microscopy. Notably, morphine induced glomerular pathology, resulting in increased glomerular volume, mesangial expansion, mesangial cell proliferation, parietal cell metaplasia, podocyte effacement, and microvillus transformation. Cystic tubulopathy and hemeoxygenase-1 expression and activity were also increased in morphine-treated mice. Naloxone, a non-selective opioid receptor (OR) antagonist, ameliorated these effects. Functionally, the urine albumin to creatinine ratio was increased following acute as well as chronic morphine treatment. These results suggest that clinically relevant doses of morphine induce renal pathology and that OR antagonists may be effective for ameliorating morphine-induced renal disease.

Carbon-fiber microelectrode amperometry reveals sickle-cell-induced inflammation and chronic morphine effects on single mast cells

Sickle cell disease, caused by a mutation of hemoglobin, is characterized by a complex pathophysiology including an important inflammatory component. Mast cells are tissue-resident leukocytes known to influence a range of immune functions in a variety of different ways, largely through the secretion of biologically active mediators from preformed granules. However, it is not understood how mast cells influence the inflammatory environment in sickle cell disease. A notable consequence of sickle cell disease is severe pain. Therefore, morphine is often used to treat this disease. Because mast cells express opioid receptors, it is pertinent to understand how chronic morphine exposure influences mast cell function and inflammation in sickle cell disease. Herein, carbon-fiber microelectrode amperometry (CFMA) was used to monitor the secretion of immunoactive mediators from single mast cells. CFMA enabled the detection and quantification of discrete exocytotic events from single mast cells. Mast cells from two transgenic mouse models expressing human sickle hemoglobin (hBERK1 and BERK) and a control mouse expressing normal human hemoglobin (HbA-BERK) were monitored using CFMA to explore the impact of sickle-cell-induced inflammation and chronic morphine exposure on mast cell function. This work, utilizing the unique mechanistic perspective provided by CFMA, describes how mast cell function is significantly altered in hBERK1 and BERK mice, including decreased serotonin released compared to HbA-BERK controls. Furthermore, morphine was shown to significantly increase the serotonin released from HbA-BERK mast cells and demonstrated the capacity to reverse the observed sickle-cell-induced changes in mast cell function.

Erythroid-specific expression of β-globin from Sleeping Beauty-transduced human hematopoietic progenitor cells

Gene therapy for sickle cell disease will require efficient delivery of a tightly regulated and stably expressed gene product to provide an effective therapy. In this study we utilized the non-viral Sleeping Beauty (SB) transposon system using the SB100X hyperactive transposase to transduce human cord blood CD34(+) cells with DsRed and a hybrid IHK-β-globin transgene. IHK transduced cells were successfully differentiated into multiple lineages which all showed transgene integration. The mature erythroid cells had an increased β-globin to γ-globin ratio from 0.66±0.08 to 1.05±0.12 (p=0.05), indicating expression of β-globin from the integrated SB transgene. IHK-β-globin mRNA was found in non-erythroid cell types, similar to native β-globin mRNA that was also expressed at low levels. Additional studies in the hematopoietic K562 cell line confirmed the ability of cHS4 insulator elements to protect DsRed and IHK-β-globin transgenes from silencing in long-term culture studies. Insulated transgenes had statistically significant improvement in the maintenance of long term expression, while preserving transgene regulation. These results support the use of Sleeping Beauty vectors in carrying an insulated IHK-β-globin transgene for gene therapy of sickle cell disease.

Mouse models for studying pain in sickle disease: effects of strain, age, and acuteness

The clinical management of severe pain associated with sickle cell disease (SCD) remains challenging. Development of an optimal therapy would be facilitated by use of murine model(s) with varying degrees of sickling and pain tests that are most sensitive to vaso-occlusion. We found that young (≤3 months old) NY1DD and S+S(Antilles) mice (having modest and moderate sickle phenotype, respectively) exhibited evidence of deep tissue/musculoskeletal pain. Deep tissue pain and cold sensitivity in S+S(Antilles) mice increased significantly with both age and incitement of hypoxia/reoxygenation (H/R). C57/BL6 mice (genetic background strain of NY1DD and S+S(Antilles) ) were hypersensitive to mechanical and heat stimuli, even without the sickle transgene. H/R treatment of HbSS-BERK mice with severe sickle phenotype resulted in significantly decreased withdrawal thresholds and enhanced mechanical, thermal and deep tissue hyperalgesia. Deep hyperalgesia incited by H/R in HbSS-BERK was ameliorated by CP 55940, a cannabinoid receptor agonist. Thus, assessment of deep tissue pain appears to be the most sensitive measure for studying pain mechanisms across mouse models of SCD, and HbSS-BERK mice may be the best model for vaso-occlusive and chronic pain of SCD.

A PRACTICAL QUESTION BASED ON CROSS-PLATFORM MICROARRAY DATA NORMALIZATION: ARE BOEC MORE LIKE LARGE VESSEL OR MICROVASCULAR ENDOTHELIAL CELLS OR NEITHER OF THEM?

Since the available microarray data of BOEC (human blood outgrowth endothelial cells), large vessel, and microvascular endothelial cells were from two different platforms, a working cross-platform normalization method was needed to make these data comparable. With six HUVEC (human umbilical vein endothelial cells) samples hybridized on two-channel cDNA arrays and six HUVEC samples on Affymetrix arrays, 64 possible combinations of a three-step normalization procedure were investigated to search for the best normalization method, which was selected, based on two criteria measuring the extent to which expression profiles of biological samples of the same cell type arrayed on two platforms were indistinguishable. Next, three discriminative gene lists between the large vessel and the microvascular endothelial cells were achieved by SAM (significant analysis of microarrays), PAM (prediction analysis for microarrays), and a combination of SAM and PAM lists. The final discriminative gene list was selected by SVM (support vector machine). Based on this discriminative gene list, SVM classification analysis with best tuning parameters and 10,000 times of validations showed that BOEC were far from large vessel cells, they either formed their own class, or fell into the microvascular class. Based on all the common genes between the two platforms, SVM analysis further confirmed this conclusion.

Shear stress responses of adult blood outgrowth endothelial cells seeded on bioartificial tissue

Human blood outgrowth endothelial cells (HBOECs) are expanded from circulating endothelial progenitor cells in peripheral blood and thus could provide a source of autologous endothelial cells for tissue-engineered vascular grafts. To examine the suitability of adult HBOECs for use in vascular tissue engineering, the shear stress responsiveness of these cells was examined on bioartificial tissue formed from dermal fibroblasts entrapped in tubular fibrin gels. HBOECs adhered to this surface, deposited collagen IV and laminin, and remained adherent when exposed to 15 dyn/cm(2) shear stress for 24 h. The shear stress responses of HBOECs were compared to human umbilical vein endothelial cells (HUVECs). As with HUVECs, HBOECs upregulated vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 when exposed to tumor necrosis factor (TNF)-α and shear stress decreased the expression of these adhesion molecules on TNF-α-activated monolayers. Nitric oxide production was elevated by shear stress, but did not vary between cell types. Both cell types decreased platelet adhesion to the bioartificial tissue, whereas pre-exposing the cells to flow decreased platelet adhesion further. These results illustrate the potential utility for HBOECs in vascular tissue engineering, as not only do the cells adhere to bioartificial tissue and remain adherent under physiological shear stress, they are also responsive to shear stress signaling.

Regional and systemic hemodynamic responses following the creation of a murine arteriovenous fistula

The study of hemodynamic alterations following the creation of an arteriovenous fistula (AVF) is relevant to vascular adaptive responses and hemodialysis access dysfunction. This study examined such alterations in a murine AVF created by anastomosing the carotid artery to the jugular vein. AVF blood flow was markedly increased due to reduced AVF vascular resistance. Despite such markedly increased basal blood flow, AVF blood flow further increased in response to acetylcholine. This AVF model exhibited increased cardiac output and decreased systemic vascular resistance; the kidney, in contrast, exhibited decreased blood flow and increased vascular resistance. Augmentation in AVF blood flow was attended by increased arterial heme oxygenase-1 (HO-1) mRNA and protein expression, the latter localized to smooth muscle cells of the AVF artery; AVF blood flow was substantially reduced in HO-1(-/-) mice compared with HO-1(+/+) mice. Finally, in a murine model of a representative disease known to exhibit impaired hemodynamic responses (sickle cell disease), the creation of an AVF was attended by decreased AVF flow and impaired AVF function. We conclude that this AVF model exhibits markedly increased AVF blood flow, a vasodilatory reserve capacity, increased cardiac output, decreased renal blood flow, and a dependency on intact hemodynamic responses, in general, and HO-1 expression, in particular, in achieving and maintaining AVF blood flow. We suggest that these findings support the utility of this model in investigating the basis for and the consequences of hemodynamic stress, including shear stress, and the pathobiology of hemodialysis AVF dysfunction.

Reconstructing sickle cell disease: a data-based analysis of the "hyperhemolysis paradigm" for pulmonary hypertension from the perspective of evidence-based medicine

The "hyperhemolytic paradigm" (HHP) posits that hemolysis in sickle disease sequentially and causally establishes increased cell-free plasma Hb, consumption of NO, a state of NO biodeficiency, endothelial dysfunction, and a high prevalence of pulmonary hypertension. The basic science underpinning this concept has added an important facet to the complexity of vascular pathobiology in sickle disease, and clinical research has identified worrisome clinical issues. However, this critique identifies and explains a number of significant concerns about the various HHP component tenets. In addressing these issues, this report presents: a very brief history of the HHP, an integrated synthesis of mechanisms underlying sickle hemolysis, a review of the evidentiary value of hemolysis biomarkers, an examination of evidence bearing on existence of a hyperhemolytic subgroup, and a series of questions that should naturally be applied to the HHP if it is examined using critical thinking skills, the fundamental basis of evidence-based medicine. The veracity of different HHP tenets is found to vary from true, to weakly supported, to demonstrably false. The thesis is developed that the HHP has misidentified the mechanism and clinical significance of its findings. The extant research questions identified by these analyses are delineated, and a conservative, evidence-based approach is suggested for application in clinical medicine.

Differential endothelial cell gene expression by African Americans versus Caucasian Americans: a possible contribution to health disparity in vascular disease and cancer

BACKGROUND

Health disparities and the high prevalence of cardiovascular disease continue to be perplexing worldwide health challenges. This study addresses the possibility that genetic differences affecting the biology of the vascular endothelium could be a factor contributing to the increased burden of cardiovascular disease and cancer among African Americans (AA) compared to Caucasian Americans (CA).

METHODS

From self-identified, healthy, 20 to 29-year-old AA (n = 21) and CA (n = 17), we established cultures of blood outgrowth endothelial cells (BOEC) and applied microarray profiling. BOEC have never been exposed to in vivo influences, and their gene expression reflects culture conditions (meticulously controlled) and donor genetics. Significance Analysis of Microarray identified differential expression of single genes. Gene Set Enrichment Analysis examined expression of pre-determined gene sets that survey nine biological systems relevant to endothelial biology.

RESULTS

At the highly stringent threshold of False Discovery Rate (FDR) = 0, 31 single genes were differentially expressed in AA. PSPH exhibited the greatest fold-change (AA > CA), but this was entirely accounted for by a homolog (PSPHL) hidden within the PSPH probe set. Among other significantly different genes were: for AA > CA, SOS1, AMFR, FGFR3; and for AA < CA, ARVCF, BIN3, EIF4B. Many more (221 transcripts for 204 genes) were differentially expressed at the less stringent threshold of FDR <.05. Using the biological systems approach, we identified shear response biology as being significantly different for AA versus CA, showing an apparent tonic increase of expression (AA > CA) for 46/157 genes within that system.

CONCLUSIONS

Many of the genes implicated here have substantial roles in endothelial biology. Shear stress response, a critical regulator of endothelial function and vascular homeostasis, may be different between AA and CA. These results potentially have direct implications for the role of endothelial cells in vascular disease (hypertension, stroke) and cancer (via angiogenesis). Also, they are consistent with our over-arching hypothesis that genetic influences stemming from ancestral continent-of-origin could impact upon endothelial cell biology and thereby contribute to disparity of vascular-related disease burden among AA. The method used here could be productively employed to bridge the gap between information from structural genomics (for example, disease association) and cell function and pathophysiology.

Circulating activated endothelial cells in pediatric obesity

OBJECTIVE

We characterized the state of the vascular endothelium in pediatric obesity by comparing circulating endothelial cell (CEC) number and activation phenotype in severely obese children to that of normal weight, overweight, and obese children.

STUDY DESIGN

We used immunohistochemical examination of buffy-coat smears to enumerate CEC and immunofluorescence microscopy to quantify activated CEC in 107 children and adolescents. Normal weight (body mass index [BMI]<85th percentile; n=40), overweight (BMI 85th-<95th percentile; n=17), and obese (BMI 95th-<99th percentile; n=23) participants were recruited from a longitudinal study. Severely obese (BMI>or=99th percentile; n=27) participants were recruited from a pediatric obesity clinic. Group means (adiposity; systolic blood pressure [SBP] quartiles) were compared with general linear models, adjusted for sex, age, and race. With Pearson correlations, we characterized relations of CEC with cardiovascular risk factors.

RESULTS

Activated CEC increased across BMI groups (P<.002) and SBP quartiles (P<.05). CEC number and activated CEC were highest in the severely obese group. CEC number was significantly associated with SBP, diastolic blood pressure, and triglycerides level. Activated CEC were significantly associated with SBP and high-density lipoprotein cholesterol levels.

CONCLUSIONS

The vascular endothelium was activated in relation to excess adiposity, particularly in severely obese children, and to elevated SBP in children and adolescents.

The dynamic regulation of microcirculatory conduit function: features relevant to transfusion medicine

The microcirculation is not merely a passive conduit for red cell transport, nutrient and gas exchange, but is instead a dynamic participant contributing to the multiple processes involved in the maintenance of metabolic homeostasis and optimal end-organ function. The microcirculation's angioarchitechture and surface properties influence conduit function and flow dynamics over a wide spectrum of conditions, accommodating many different mechanical, pathological or organ-specific responses. The endothelium itself plays a critical role as the interface between tissues and blood components, participating in the regulation of coagulation, inflammation, vascular tone, and permeability. The complex nitric oxide pathways affect vasomotor tone and influence vascular conduit caliber and distribution density, alter thrombotic propensity, and modify adhesion molecule expression. Nitric oxide pathways also interact with red blood cells and free hemoglobin moieties in normal and pathological conditions. Red blood cells themselves may affect flow dynamics. Altered rheology and compromised NO bioavailability from medical storage or disease states impede microcirculatory flow and adversely modulate vasodilation. The integration of the microcirculation as a system with respect to flow modulation is delicately balanced, and can be readily disrupted in disease states such as sepsis. This review will provide a description of these varied and intricate functions of the microvasculature.

Nuclear factor-kappa B (NFkappaB) component p50 in blood mononuclear cells regulates endothelial tissue factor expression in sickle transgenic mice: implications for the coagulopathy of sickle cell disease

Sickle cell anemia is accompanied by the activation of coagulation and thrombosis. We have studied the abnormal expression of tissue factor (TF) by the pulmonary vein endothelium of the mild-phenotype NY1DD sickle transgenic. As detected by immunofluorescence microscopy, this occurs only after the NY1DD mouse is exposed to hypoxia/reoxygenation (H/R), which actually causes ischemia/reperfusion in the sickle cell disease-but not the normal-mouse model. We tested the hypothesis that the nuclear factor-kappa B (NFkappaB)-activating inflammation that develops in post-H/R NY1DD mice is responsible for this phenotype switch. Various NFkappaB inhibitors (including p50-specific andrographolide) demonstrated that endothelial TF positivity is NFkappaB dependent. Several systemic inflammatory stimulators (tumor necrosis factor [TNFalpha], lipopolysaccharide, thioglycollate, and carageenan) given to control mice showed that the inflammatory promotion of TF expression by only pulmonary vein endothelium is not specific to the sickle cell disease model. We bred the NFkappaB(p50)-/- state into the NY1DD mouse. Combined with marrow transplantation, this allowed the creation of NY1DD mice that were NFkappaB(p50)-/- only in peripheral blood cells (and marrow) versus only in vessel walls (and tissues). This process revealed that endothelial TF expression in the NY1DD mouse is highly dependent on NFkappaB(p50) in peripheral blood mononuclear cells-but not in the vessel wall. In confirmation, the infusion of post-H/R sickle mouse blood mononuclear cells into naïve NY1DD mice stimulated endothelial TF expression; the infusion of such cells from unstimulated sickle cell disease mice at ambient air did not stimulate TF expression. We conclude that peripheral blood mononuclear cells indirectly promote endothelial TF expression via a NFkappaB(p50)-dependent mechanism. This approach may be relevant to the role of coagulopathy in clinical sickle cell disease.

Early and prominent alterations in hemodynamics, signaling, and gene expression following renal ischemia in sickle cell disease

Acute ischemic insults to the kidney are recognized complications of human sickle cell disease (SCD). The present study analyzed in a transgenic SCD murine model the early renal response to acute ischemia. Renal hemodynamics were profoundly impaired following ischemia in sickle mice compared with wild-type mice: glomerular filtration rate, along with renal plasma flow and blood flow rates, were markedly reduced, while renal vascular resistances were increased more than threefold in sickle mice following ischemia. In addition to these changes in renal hemodynamics, there were profound disturbances in renal signaling processes: phosphorylation of members of the MAPK and Akt signaling proteins occurred in the kidney in wild-type mice after ischemia, whereas such phosphorylation did not occur in the kidney in sickle mice after ischemia. ATP content in the postischemic kidney in sickle mice was less than half that observed in wild-type mice. Examination of the expression of candidate genes uncovered changes that may predispose to increased sensitivity of the kidney in sickle mice to ischemia: increased expression of inducible nitric oxide synthase and decreased expression of endothelial nitric oxide synthase, and increased expression of TNF-alpha. Inducibility of anti-inflammatory, cytoprotective genes, such as heme oxygenase-1 and IL-10, was not impaired in sickle mice after ischemia. We conclude that the kidney in SCD is remarkably vulnerable to acute ischemic insults. We speculate that such sensitivity of the kidney to ischemia in SCD may underlie the occurrence of acute kidney injury in patients with SCD and may set the stage for the emergence of chronic kidney disease in SCD.

Proinflammatory phenotype with imbalance of KLF2 and RelA: risk of childhood stroke with sickle cell anemia

Altered inflammation signaling within the cerebral vasculature may be an important risk factor for stroke in children with sickle cell anemia (SCA). This study examines how differential expression of NFkappaB/p65 (RelA), KLF2, and other transcription factors may act as switches in inflammation signaling leading to observed differences between non-SCA (NS) African Americans and African Americans with SCA who are either at risk (AR) or not at risk (NAR) of childhood stroke based on occurrence of Circle of Willis disease. Clover/Transfac analysis was used to identify overrepresented transcription factor binding motifs on genes associated with inflammation. Transcription factor binding motifs for the NFkappaB family and RFX1 were overrepresented on inflammation signaling gene set analysis. Variations in protein expression were determined by flow cytometry of blood outgrowth endothelial cells (BOECs) from NS, AR, and NAR donors and Western blots of protein extracts from both unstimulated and TNFalpha/IL1beta-stimulated BOECs. BOECs from patients with SCA had more cytoplasmic-derived RelA compared with NS BOECs. Sickle BOECs also had heightened responses to inflammatory stimuli compared with NS BOECs, as shown by increased nuclear RelA, and intracellular adhesion molecule (ICAM) response to TNFalpha/IL1beta stimulation. Multiple control points in RelA signaling were associated with risk of childhood stroke. The ratio of proinflammatory factor RelA to anti-inflammatory factor KLF2 was greater in BOECs from AR donors than NS donors. Group risk of childhood stroke with SCA was greatest among individuals who exhibited increased expression of proinflammatory transcription factors and decreased expression of transcription factors that suppress inflammation.

Endothelial nitric oxide synthase and nitric oxide regulate endothelial tissue factor expression in vivo in the sickle transgenic mouse

Activation of the coagulation system is a characteristic feature of sickle cell anemia, which also includes clinical thrombosis. The sickle transgenic mouse abnormally expresses tissue factor (TF) on the pulmonary vein endothelium. Knowing that this aberrancy is stimulated by inflammation, we sought to determine whether nitric oxide (NO) contributes to regulation of endothelial TF expression in the sickle mouse model. We used the NY1DD sickle mouse, which exhibits a low-TF to high-TF phenotype switch on exposure to hypoxia/reoxygenation. Manipulations of NO biology, such as breathing NO or addition of arginine or L-NAME (N-nitro-L-arginine-methyl-ester) to the diet, caused significant modulations of TF expression. This was also seen in hBERK1 sickle mice, which have a different genetic background and already have high-TF even at ambient air. Study of NY1DD animals bred to overexpress endothelial nitric oxide synthase (eNOS; eNOS-Tg) or to have an eNOS knockout state (one eNOS(-/-) animal and several eNOS(+/-) animals) demonstrated that eNOS modulates endothelial TF expression in vivo by down-regulating it. Thus, the biodeficiency of NO characteristic of patients with sickle cell anemia may heighten risk for activation of the coagulation system.

A systems biology consideration of the vasculopathy of sickle cell anemia: the need for multi-modality chemo-prophylaxsis

Much of the morbidity and mortality of sickle cell anemia is accounted for by a chronic vasculopathy syndrome. There is currently no identified therapy, interventional or prophylactic, for this problem. For two reasons, development of an effective therapeutic approach will require a systems biology level perspective on the vascular pathobiology of sickle disease. In the first place, multiple biological processes contribute to the pathogenesis of vasculopathy: red cell sickling, inflammation and adhesion biology, coagulation activation, stasis, deficient bioavailability and excessive consumption of NO, excessive oxidation, and reperfusion injury physiology. The probable hierarchy of involvement of these disparate sub-biologies places inflammation caused by reperfusion injury physiology as the likely, proximate, linking pathophysiological factor. In the second place, most of these sub-biologies overlap with each other and, in any case, have multiple points of potential interaction and transactivation. Consequently, an approach modeled upon chemotherapy for cancer is needed. This would be a truly multi-modality approach that hopefully could be achieved via employment of relatively few drugs. It is proposed here that the specific combination of a statin with suberoylanilide hydroxamic acid would provide a suitable, broad, multi-modality approach to chemo-prophylaxis for sickle vasculopathy.

Cell adhesion molecule 1: a novel risk factor for venous thrombosis

Protein C (PC) deficiency increases the risk of venous thrombosis (VT) among members of Kindred Vermont II but fails to fully account for the inheritance pattern. A genome scan of the pedigree supported the presence of a prothrombotic gene on chromosome 11q23 (nominal P < .0001), with weaker support on chromosomes 10p12 (P < .0003) and 18p11.2-q11 (P < .0007). Resequencing of 109 genes in the linkage regions identified 5030 variants in a sample of 20 kindred members. Of 16 single nucleotide polymorphisms in 6 genes tested in the larger family set, only single nucleotide polymorphisms in cell adhesion molecule 1 (CADM1) associated with VT. Among the 8 CADM1 single nucleotide polymorphisms genotyped in the complete sample, rs6589488 was most strongly supported (P < .000007), but the association was limited to the PC-deficient subset of the sample (P < .000001). Haplotype analysis narrowed the region containing the causative variant to the coding region of the CADM1 gene. CADM1 gene expression analyzed in blood outgrowth endothelial cells cultured from family members was decreased compared with control subjects, lending phenotypic support to this conclusion. Finally, we have for the first time demonstrated CADM1 in endothelial cells, where it appears to be selectively involved in endothelial cell migration, suggesting a role in endothelial barrier repair.

Vasculopathy in sickle cell disease: Biology, pathophysiology, genetics, translational medicine, and new research directions

Sickle cell disease has been very well characterized as a single amino acid molecular disorder of hemoglobin leading to its pathological polymerization, with resulting red cell rigidity that causes poor microvascular blood flow, with consequent tissue ischemia and infarction. More recently, an independent spectrum of pathophysiology of blood vessel function has been demonstrated, involving abnormal vascular tone and activated, adhesive endothelium. These vasculopathic abnormalities are attributable to pathways involving hemolysis-associated defects in nitric oxide bioavailability, oxidative stress, ischemia-reperfusion injury, hemostatic activation, leukocytes and platelets. Vasculopathy of sickle cell disease has been implicated in the development of pulmonary hypertension, stroke, leg ulceration and priapism, particularly associated with hemolytic severity, and reported also in other severe hemolytic disorders. This vasculopathy might also play a role in other chronic organ dysfunction in patients with sickle cell disease. These pathways present novel targets for pharmacologic intervention, and several clinical trials are already under way. The authors present their perspectives of a workshop held at the National Institutes of Health in August 2008 on vasculopathy in sickle cell disease, along with meritorious future scientific questions on the topic of vascular complications of sickle cell disease.