Shibani Pati

Plasma restoration of endothelial glycocalyx in a rodent model of hemorrhagic shock

BACKGROUND: The use of plasma-based resuscitation for trauma patients in hemorrhagic shock has been associated with a decrease in mortality. Although some have proposed a beneficial effect through replacement of coagulation proteins, the putative mechanisms of protection afforded by plasma are unknown. We have previously shown in a cell culture model that plasma decreases endothelial cell permeability in comparison with crystalloid. The endothelial glycocalyx consists of proteoglycans and glycoproteins attached to a syndecan backbone, which together protect the underlying endothelium. We hypothesize that endothelial cell protection by plasma is due, in part, to its restoration of the endothelial glycocalyx and preservation of syndecan-1 after hemorrhagic shock. METHODS: Rats were subjected to hemorrhagic shock to a mean arterial blood pressure of 30 mm Hg for 90 minutes followed by resuscitation with either lactated Ringers (LR) solution or fresh plasma to a mean arterial blood pressure of 80 mm Hg and compared with shams or shock alone. After 2 hours, lungs were harvested for syndecan mRNA, immunostained with antisyndecan-1, or stained with hematoxylin and eosin. To specifically examine the effect of plasma on the endothelium, we infused small bowel mesentery with a lanthanum-based solution, identified venules, and visualized the glycocalyx by electron microscopy. All data are presented as mean ± SEM. Results were analyzed by 1-way analysis of variance with Tukey post hoc tests. RESULTS: Electron microscopy revealed degradation of the glycocalyx after hemorrhagic shock, which was partially restored by plasma but not LR. Pulmonary syndecan-1 mRNA expression was higher in animals resuscitated with plasma (2.76 ± 0.03) in comparison with shock alone (1.39 ± 0.22) or LR (0.82 ± 0.03) and correlated with cell surface syndecan-1 immunostaining. Shock also resulted in significant lung injury by histopathology scoring (1.63 ± 0.26), which was mitigated by resuscitation with plasma (0.67 ± 0.17) but not LR (2.0 ± 0.25). CONCLUSION: The protective effects of plasma may be due in part to its ability to restore the endothelial glycocalyx and preserve syndecan-1 after hemorrhagic shock.

Activation of NF-κB by the Human Herpesvirus 8 Chemokine Receptor ORF74: Evidence for a Paracrine Model of Kaposi's Sarcoma Pathogenesis

ABSTRACT Infection with human herpesvirus 8 (HHV-8), also known as Kaposis sarcoma (KS)-associated herpesvirus, is necessary for the development of KS. The HHV-8 lytic-phase gene ORF74 is related to G protein-coupled receptors, particularly interleukin-8 (IL-8) receptors. ORF74 activates the inositol phosphate/phospholipase C pathway and the downstream mitogen-activated protein kinases, JNK/SAPK and p38. We show here that ORF74 also activates NF-κB independent of ligand when expressed in KS-derived HHV-8-negative endothelial cells or primary vascular endothelial cells. NF-κB activation was enhanced by the chemokine GROα, but not by IL-8. Mutation of Val to Asp in the ORF74 second cytoplasmic loop did not affect ligand-independent signaling activity, but it greatly increased the response to GROα. ORF74 upregulated the expression of NF-κB-dependent inflammatory cytokines (RANTES, IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor) and adhesion molecules (VCAM-1, ICAM-1, and E-selectin). Supernatants from transfected KS cells activated NF-κB signaling in untransfected cells and elicited the chemotaxis of monocytoid and T-lymphoid cells. Expression of ORF74 conferred on primary endothelial cells a morphology that was strikingly similar to that of spindle cells present in KS lesions. Taken together, these data, demonstrating that ORF74 activates NF-κB and induces the expression of proangiogenic and proinflammatory factors, suggest that expression of ORF74 in a minority of cells in KS lesions could influence uninfected cells or latently infected cells via autocrine and paracrine mechanisms, thereby contributing to KS pathogenesis.

Valproate Administered after Traumatic Brain Injury Provides Neuroprotection and Improves Cognitive Function in Rats

Background Traumatic brain injury (TBI) initiates a complex series of neurochemical and signaling changes that lead to pathological events including neuronal hyperactivity, excessive glutamate release, inflammation, increased blood-brain barrier (BBB) permeability and cerebral edema, altered gene expression, and neuronal dysfunction. It is believed that a drug combination, or a single drug acting on multiple targets, may be an effective strategy to treat TBI. Valproate, a widely used antiepileptic drug, has a number of targets including GABA transaminase, voltage-gated sodium channels, glycogen synthase kinase (GSK)-3, and histone deacetylases (HDACs), and therefore may attenuate a number of TBI-associated pathologies. Methodology/Principal Findings Using a rodent model of TBI, we tested if post-injury administration of valproate can decrease BBB permeability, reduce neural damage and improve cognitive outcome. Dose-response studies revealed that systemic administration of 400 mg/kg (i.p.), but not 15, 30, 60 or 100 mg/kg, increases histone H3 and H4 acetylation, and reduces GSK-3 activity, in the hippocampus. Thirty min post-injury administration of 400 mg/kg valproate improved BBB integrity as indicated by a reduction in Evans Blue dye extravasation. Consistent with its dose response to inhibit GSK-3 and HDACs, valproate at 400 mg/kg, but not 100 mg/kg, reduced TBI-associated hippocampal dendritic damage, lessened cortical contusion volume, and improved motor function and spatial memory. These behavioral improvements were not observed when SAHA (suberoylanilide hydroxamic acid), a selective HDAC inhibitor, was administered. Conclusion/Significance Our findings indicate that valproate given soon after TBI can be neuroprotective. As clinically proven interventions that can be used to minimize the damage following TBI are not currently available, the findings from this report support the further testing of valproate as an acute therapeutic strategy.

Cardiomyocyte PDGFR-β signaling is an essential component of the mouse cardiac response to load-induced stress

PDGFR is an important target for novel anticancer therapeutics because it is overexpressed in a wide variety of malignancies. Recently, however, several anticancer drugs that inhibit PDGFR signaling have been associated with clinical heart failure. Understanding this effect of PDGFR inhibitors has been difficult because the role of PDGFR signaling in the heart remains largely unexplored. As described herein, we have found that PDGFR-beta expression and activation increase dramatically in the hearts of mice exposed to load-induced cardiac stress. In mice in which Pdgfrb was knocked out in the heart in development or in adulthood, exposure to load-induced stress resulted in cardiac dysfunction and heart failure. Mechanistically, we showed that cardiomyocyte PDGFR-beta signaling plays a vital role in stress-induced cardiac angiogenesis. Specifically, we demonstrated that cardiomyocyte PDGFR-beta was an essential upstream regulator of the stress-induced paracrine angiogenic capacity (the angiogenic potential) of cardiomyocytes. These results demonstrate that cardiomyocyte PDGFR-beta is a regulator of the compensatory cardiac response to pressure overload-induced stress. Furthermore, our findings may provide insights into the mechanism of cardiotoxicity due to anticancer PDGFR inhibitors.

Increased platelet:RBC ratios are associated with improved survival after massive transfusion.

BACKGROUND Several recent military and civilian trauma studies demonstrate that improved outcomes are associated with early and increased use of plasma-based resuscitation strategies. However, outcomes associated with platelet transfusions are poorly characterized. We hypothesized that increased platelet:red blood cells (RBC) ratios would decrease hemorrhagic death and improve survival after massive transfusion (MT). METHODS A transfusion database of patients transported from the scene to 22 Level I Trauma Centers over 12 months in 2005 to 2006 was reviewed. MT was defined as receiving ≥ 10 RBC units within 24 hours of admission. To mitigate survival bias, 25 patients who died within 60 minutes of arrival were excluded from analysis. Six random donor platelet units were considered equal to a single apheresis platelet unit. Admission and outcome data associated with the low (>1:20), medium (1:2), and high (1:1) platelet:RBC ratios were examined. These groups were based on the median value of the tertiles for the ratio of platelets:RBC units. RESULTS Two thousand three hundred twelve patients received at least one unit of blood and 643 received an MT. Admission vital signs, INR, temperature, pH, Glasgow Coma Scale, Injury Severity Score, and age were similar between platelet ratio groups. The average admission platelet counts were lower in the patients who received the high platelet:RBC ratio versus the low ratio (192 vs. 216, p = 0.03). Patients who received MT were severely injured, with a mean (± standard deviation) Injury Severity Score of 33 ± 16 and received 22 ± 15 RBCs and 11 ± 14 platelets within 24 hours of injury. Increased platelet ratios were associated with improved survival at 24 hours and 30 days (p < 0.001 for both). Truncal hemorrhage as a cause of death was decreased (low: 67%, medium: 60%, high: 47%, p = 0.04). Multiple organ failure mortality was increased (low: 7%, medium: 16%, high: 27%, p = 0.003), but overall 30-day survival was improved (low: 52%, medium: 57%, high: 70%) in the high ratio group (medium vs. high: p = 0.008; low vs. high: p = 0.007). CONCLUSION Similar to recently published military data, transfusion of platelet:RBC ratios of 1:1 was associated with improved early and late survival, decreased hemorrhagic death and a concomitant increase in multiple organ failure-related mortality. Based on this large retrospective study, increased and early use of platelets may be justified, pending the results of prospective randomized transfusion data.

Protective Effects of Fresh Frozen Plasma on Vascular Endothelial Permeability, Coagulation, and Resuscitation After Hemorrhagic Shock Are Time Dependent and Diminish Between Days 0 and 5 After Thaw

BACKGROUND Clinical studies have shown that resuscitation with fresh frozen plasma (FFP) is associated with improved outcome after severe hemorrhagic shock (HS). We hypothesized that in addition to its effects on hemostasis, FFP has protective and stabilizing effects on the endothelium that translate into diminished endothelial cell (EC) permeability and improved resuscitation in vivo after HS. We further hypothesized that the beneficial effects of FFP would diminish over 5 days of routine storage at 4 degrees C. METHODS EC permeability was induced by hypoxia and assessed by the passage of 70-kDa Dextran between monolayers. Thrombin generation time and coagulation factor levels or activity were assessed in FFP. An in vivo rat model of HS and resuscitation was used to determine the effects of FFP on hemodynamic stability. RESULTS Thawed FFP inhibits EC permeability in vitro by 10.2-fold. Protective effects diminish (to 2.5-fold) by day 5. Thrombin generation time is increased in plasma that has been stored between days 0 and 5. In vivo data show that day 0 FFP is superior to day 5 FFP in maintaining mean arterial pressure in rats undergoing HS with resuscitation. CONCLUSION Both in vitro and in vivo studies show that FFP has beneficial effects on endothelial permeability, vascular stability, and resuscitation in rats after HS. The benefits are independent of hemostasis and diminish between days 0 and 5 of storage.

Intravenous multipotent adult progenitor cell therapy for traumatic brain injury: preserving the blood brain barrier via an interaction with splenocytes.

Recent investigation has shown an interaction between transplanted progenitor cells and resident splenocytes leading to the modulation of the immunologic response in neurological injury. We hypothesize that the intravenous injection of multipotent adult progenitor cells (MAPC) confers neurovascular protection after traumatic brain injury through an interaction with resident splenocytes, subsequently leading to preservation of the blood brain barrier. Four groups of rats underwent controlled cortical impact injury (3 groups) or sham injury (1 group). MAPC were injected via the tail vein at two doses (2*10(6) MAPC/kg or 10*10(6) MAPC/kg) 2 and 24h after injury. Blood brain barrier permeability was assessed by measuring Evans blue dye extravasation (n=6/group). Additionally, splenic mass was measured (n=12/group) followed by splenocyte characterization (n=9/group) including: cell cycle analysis (n=6/group), apoptosis index (n=6/group), cell proliferation (n=6/group), and inflammatory cytokine measurements (n=6/group). Vascular architecture was determined by immunohistochemistry (n=3/group). Traumatic brain injury results in a decrease in splenic mass and increased blood brain barrier permeability. Intravenous infusion of MAPC preserved splenic mass and returned blood brain barrier permeability towards control sham injured levels. Splenocyte characterization indicated an increase in the number and proliferative rate of CD4+ T cells as well as an increase in IL-4 and IL-10 production in stimulated splenocytes isolated from the MAPC treatment groups. Immunohistochemistry demonstrated stabilization of the vascular architecture in the peri-lesion area. Traumatic brain injury causes a reduction in splenic mass that correlates with an increase in circulating immune cells leading to increased blood brain barrier permeability. The intravenous injection of MAPC preserves splenic mass and the integrity of the blood brain barrier. Furthermore, the co-localization of transplanted MAPC and resident CD4+ splenocytes is associated with a global increase in IL-4 and IL-10 production and stabilization of the cerebral microvasculature tight junction proteins.

Coronary Microvascular Pericytes Are the Cellular Target of Sunitinib Malate–Induced Cardiotoxicity

Sunitinib-induced cardiotoxicity is caused by depletion of coronary pericytes due to loss of PDGFR signaling; this side effect can be prevented by thalidomide. Saving Pericytes to Prevent a Broken Heart In the world of targeted cancer therapies, sunitinib is a versatile one, targeting a variety of tyrosine kinase receptors. The breadth of its activity allows it to be effective in multiple different types of cancer but also increases the chances of unintended adverse effects. One such side effect is cardiotoxicity, with frequent reports of left ventricular dysfunction and heart failure in patients treated with sunitinib. Chintalgattu and co-workers have now uncovered the mechanism for this toxicity and demonstrated a way to protect the heart from treatment-induced damage in a mouse model. Pericytes are contractile cells that wrap around small blood vessels and are essential to their function. After sunitinib treatment, pericytes were no longer coating the coronary microvasculature in a mouse model. The blood vessels depleted of pericytes were unusually leaky, and the hearts of treated animals showed clear evidence of cardiac dysfunction. The depletion of pericytes was caused by the inhibition of signaling through platelet-derived growth factor receptor (PDGFR), a known target of sunitinib. The authors also discovered that thalidomide, a small-molecule drug that is already used in humans for the treatment of some cancers, could protect pericytes and prevent sunitinib-induced cardiotoxicity without affecting the antitumor effects of sunitinib. Future studies will be needed to uncover additional mechanism explaining why coronary pericytes in particular are so sensitive to inhibition of PDGFR and how thalidomide can protect these cells from toxicity. Eventually, this research could enable the creation of more specific targeted drugs that inhibit the kinases driving cancer cell proliferation without injuring pericytes and other healthy cells. In the meantime, the current findings of Chintalgattu et al. provide a rationale for testing the combination of thalidomide and sunitinib in human cancer patients to protect the patients’ hearts from injury while continuing to effectively target cancer cells. Sunitinib malate is a multitargeted receptor tyrosine kinase inhibitor used in the treatment of human malignancies. A substantial number of sunitinib-treated patients develop cardiac dysfunction, but the mechanism of sunitinib-induced cardiotoxicity is poorly understood. We show that mice treated with sunitinib develop cardiac and coronary microvascular dysfunction and exhibit an impaired cardiac response to stress. The physiological changes caused by treatment with sunitinib are accompanied by a substantial depletion of coronary microvascular pericytes. Pericytes are a cell type that is dependent on intact platelet-derived growth factor receptor (PDGFR) signaling but whose role in the heart is poorly defined. Sunitinib-induced pericyte depletion and coronary microvascular dysfunction are recapitulated by CP-673451, a structurally distinct PDGFR inhibitor, confirming the role of PDGFR in pericyte survival. Thalidomide, an anticancer agent that is known to exert beneficial effects on pericyte survival and function, prevents sunitinib-induced pericyte cell death in vitro and prevents sunitinib-induced cardiotoxicity in vivo in a mouse model. Our findings suggest that pericytes are the primary cellular target of sunitinib-induced cardiotoxicity and reveal the pericyte as a cell type of concern in the regulation of coronary microvascular function. Furthermore, our data provide preliminary evidence that thalidomide may prevent cardiotoxicity in sunitinib-treated cancer patients.

Immunophenotype characterization of rat mesenchymal stromal cells

BACKGROUND Mesenchymal stromal cells (MSC) have shown diverse therapeutic potential. While characterization of human and mouse MSC has seen significant advances, rat bone marrow-derived MSC (rBM-MSC) remain under-characterized. We detail the isolation, expansion, differentiation, and detailed immunocharacterization of rBM-MSC. METHODS Rat MSC were isolated and expanded in multipotent adult progenitor cell (MAPC) media, and cell-surface marker expression through 10 passages was used to characterize the population and multipotency was confirmed via differentiation. RESULTS By passage 3, rBM-MSC were found to be CD11b-, CD45-, CD29+, CD49e+, CD73+, CD90+, CD105+ and Stro-1+, without the use of cell sorting. Media selection was responsible for the isolation of a nearly homogeneous population of rBM-MSC. The rBM-MSC immunophenotype changed by passage 10, showing decreases in CD73, CD105 and Stro-1 expression. DISCUSSION Detailed characterization of cell populations facilitates accurate and reproducible cell therapy investigation. Given the expanding body of research involving rBM-MSC, these results advance our ability to compare rBM-MSC populations.

Bone marrow derived mesenchymal stem cells inhibit inflammation and preserve vascular endothelial integrity in the lungs after hemorrhagic shock.

Hemorrhagic shock (HS) and trauma is currently the leading cause of death in young adults worldwide. Morbidity and mortality after HS and trauma is often the result of multi-organ failure such as acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), conditions with few therapeutic options. Bone marrow derived mesenchymal stem cells (MSCs) are a multipotent stem cell population that has shown therapeutic promise in numerous pre-clinical and clinical models of disease. In this paper, in vitro studies with pulmonary endothelial cells (PECs) reveal that conditioned media (CM) from MSCs and MSC-PEC co-cultures inhibits PEC permeability by preserving adherens junctions (VE-cadherin and β-catenin). Leukocyte adhesion and adhesion molecule expression (VCAM-1 and ICAM-1) are inhibited in PECs treated with CM from MSC-PEC co-cultures. Further support for the modulatory effects of MSCs on pulmonary endothelial function and inflammation is demonstrated in our in vivo studies on HS in the rat. In a rat “fixed volume” model of mild HS, we show that MSCs administered IV potently inhibit systemic levels of inflammatory cytokines and chemokines in the serum of treated animals. In vivo MSCs also inhibit pulmonary endothelial permeability and lung edema with concurrent preservation of the vascular endothelial barrier proteins: VE-cadherin, Claudin-1, and Occludin-1. Leukocyte infiltrates (CD68 and MPO positive cells) are also decreased in lungs with MSC treatment. Taken together, these data suggest that MSCs, acting directly and through soluble factors, are potent stabilizers of the vascular endothelium and inflammation. These data are the first to demonstrate the therapeutic potential of MSCs in HS and have implications for the potential use of MSCs as a cellular therapy in HS-induced lung injury.