Morphological and biochemical effects of immunosuppressive drugs in a capillary tube assay for endothelial dysfunction

Pediatric Acute Toxic Leukoencephalopathy: Prediction of the Clinical Outcome by FLAIR and DWI for Various Etiologies

BACKGROUND AND PURPOSE

Pediatric acute toxic leukoencephalopathy is a clinicoradiologic entity comprising various etiologies. This study aimed to identify the MR imaging appearance of pediatric acute toxic leukoencephalopathy from various etiologies and determine whether the etiology correlates with clinical outcome.

MATERIALS AND METHODS

We retrospectively reviewed the electronic records of patients with pediatric acute toxic leukoencephalopathy younger than 19 years of age who had MR imaging within <2 weeks of presentation, including DWI and FLAIR sequences. Two neuroradiologists scored the DWI and FLAIR severity and measured the percentage ADC reduction within the visibly affected regions and normal-appearing WM. The percentage ADC reduction and DWI and FLAIR severity were correlated with clinical outcome using the Spearman correlation.

RESULTS

Of 22 children, 3 were excluded due to a nontoxic cause or incomplete examination. Regarding the included 19 children (mean age, 13 years), the etiologies of pediatric acute toxic leukoencephalopathy were the following: methotrexate (n = 6), bone marrow transplantation (n = 4), fludarabine (n = 3), cytarabine (n = 1), carboplatin (n = 1), vincristine (n = 1), cyclosporine (n = 1), uremia (n = 1), and bevacizumab (n = 1). Three subgroups were analyzed (chemotherapy, n = 12; immunosuppression, n = 5; others, n = 2). There was a strong correlation of FLAIR (r  = 0.773, P < .001) and DWI (r = 0.851, P < .001) severity with clinical outcome, and patients treated with fludarabine had the worst outcomes. High percentage ADC reduction values were associated with adverse outcomes, and lower percentage ADC reduction values were associated with favorable outcomes (r = 0.570, P = .011).

CONCLUSIONS

The DWI and FLAIR severity scores appear highly prognostic, whereas percentage ADC reduction is moderately prognostic for clinical outcomes in pediatric acute toxic leukoencephalopathy. Immunosuppressive pediatric acute toxic leukoencephalopathy tends toward favorable outcomes, and fludarabine tends toward worse outcomes.

FK506 regulates Ca2+ release evoked by inositol 1,4,5-trisphosphate independently of FK-binding protein in endothelial cells

Background and Purpose

FK506 and rapamycin are modulators of FK‐binding proteins (FKBP) that are used to suppress immune function after organ and hematopoietic stem cell transplantations. The drugs share the unwanted side‐effect of evoking hypertension that is associated with reduced endothelial function and nitric oxide production. The underlying mechanisms are not understood. FKBP may regulate IP₃ receptors (IP₃R) and ryanodine receptors (RyR) to alter Ca²⁺ signalling in endothelial cells.

Experimental Approach

We investigated the effects of FK506 and rapamycin on Ca²⁺ release via IP₃R and RyR in hundreds of endothelial cells, using the indicator Cal‐520, in intact mesenteric arteries from male Sprague‐Dawley rats. IP₃Rs were activated by acetylcholine or localised photo‐uncaging of IP₃, and RyR by caffeine.

Key Results

While FKBPs were present, FKBP modulation with rapamycin did not alter IP₃‐evoked Ca²⁺ release. Conversely, FK506, which modulates FKBP and blocks calcineurin, increased IP₃‐evoked Ca²⁺ release. Inhibition of calcineurin (okadiac acid or cypermethrin) also increased IP₃‐evoked Ca²⁺ release and blocked FK506 effects. When calcineurin was inhibited, FK506 reduced IP₃‐evoked Ca²⁺ release. These findings suggest that IP₃‐evoked Ca²⁺ release is not modulated by FKBP, but by FK506‐mediated calcineurin inhibition. The RyR modulators caffeine and ryanodine failed to alter Ca²⁺ signalling suggesting that RyR is not functional in native endothelium.

Conclusion and Implications

The hypertensive effects of the immunosuppressant drugs FK506 and rapamycin, while mediated by endothelial cells, do not appear to be exerted at the documented cellular targets of Ca²⁺ release and altered FKBP binding to IP₃ and RyR.

Acute Toxic Leukoencephalopathy: Etiologies, Imaging Findings, and Outcomes in 101 Patients

BACKGROUND AND PURPOSE

Prior studies regarding acute toxic leukoencephalopathy (ATL) are either small, or preliminary. Our aim was to evaluate etiologies of and differences in imaging severity and outcomes among various etiologies of ATL.

MATERIALS AND METHODS

MRIs of patients with suspected ATL over 15 years were retrospectively reviewed; inclusion criteria were: MRI <3 weeks of presentation with both DWI and FLAIR. These were jointly graded by two neuroradiologists via a previously described score of severity. Clinical outcome was evaluated via both modified Rankin (mRS) and ATL outcome (ATLOS) scores, each being correlated with the DWI and FLAIR scores. Etiologic subgroups of n > 6 patients were statistically compared.

RESULTS

Of 101 included patients, the 4 subgroups of n > 6 were the following: chemotherapy (n = 35), opiates (n = 19), acute hepatic encephalopathy (n = 14), and immunosuppressants (n = 11). Other causes (n = 22 total) notably included carbon monoxide (n = 3) metronidazole (n = 2), and uremia (n = 1). The mean DWI/FLAIR severity scores were 2.6/2.3, 3.3/3.3, 2.1/2.1 and 2.0/2.5 for chemotherapeutics, opiates, AHE and immunosuppressants, respectively, with significant differences in both imaging severity and outcome (P = .003-.032) among subgroups, particularly immunosuppressant versus chemotherapy-related ATL and immunosuppressants versus opiates (P = .004-.032) related ATL. DWI and FLAIR severity weakly correlated with outcome (ρ = 0.289-.349, P < .005) but correlated stronger in the chemotherapy (ρ = 0.460-.586, P < .010) and opiate (ρ =.472-.608, P < .05) subgroups, which had the worst outcomes. ATL clinically resolved in 36%, with severe outcomes in 23% (coma or death, 9/16 deaths from fludarabine). Notable laboratory results were elevated CSF myelin basic protein levels in 8/9 patients and serum blood urea nitrogen levels in 24/91.

CONCLUSIONS

Clinical outcomes of ATL vary on the basis of etiology, being worse in chemotherapeutic- and opiate-related ATL. Uremia may be a predisposing or exacerbating factor.

Concomitant Acute Toxic Leukoencephalopathy and Posterior Reversible Encephalopathy Syndrome

BACKGROUND AND PURPOSE

Posterior reversible encephalopathy syndrome (PRES) and acute toxic leukoencephalopathy (ATL) are both potentially reversible clinicoradiologic entities. Although their magnetic resonance imaging (MRI) findings differ, rarely both may occur simultaneously in acutely encephalopathic patients. Our aim was to determine the incidence and causes of concomitant "ATL-PRES."

METHODS

Retrospective search of suspected acutely encephalopathic adults since 1998 throughout our picture archiving and communication system revealed 167 patients with PRES and 106 patients with ATL. Images of these patients were retrospectively evaluated by two neuroradiologists and a fellow to identify the cases which carry both features of PRES and ATL. Imaging findings were scored based on previously reported scoring system as mild, moderate, and severe. The clinical outcome of the patients was determined according to the modified Rankin scale.

RESULTS

Our search revealed a series of 6 patients (%2.2) in 273 patients who presented acutely with either encephalopathy or seizures, caused by various etiologies, including immunosuppression following transplantation (n = 2), hypertensive crisis (n = 2), chemotherapy (n = 1), and sepsis (n = 1). MRI demonstrated findings consistent with both PRES and ATL simultaneously on FLAIR and diffusion weighted imaging. Severity of imaging findings of concomitant "ATL-PRES" was concordant with each other (rho ≈ 1.0, P < .00001), and each patient eventually returned to clinical baseline. This finding, along with their similar etiologies, raises the possibility of an underlying common pathophysiologic thread, perhaps being endothelial toxicity.

CONCLUSIONS

Concomitant "ATL-PRES" was found in 2.2% of the patients in a large cohort of ATL and PRES. Etiologies varied. Clinical symptoms and MRI findings were potentially reversible.

Determination of the mitigating effect of colon-specific bioreversible codrugs of mycophenolic acid and aminosugars in an experimental colitis model in Wistar rats

AIM

To design colon-targeted codrugs of mycophenolic acid (MPA) and aminosugars as a safer option to mycophenolate mofetil (MMF) in the management of inflammatory bowel disease.

METHODS

Codrugs were synthesized by coupling MPA with aminosugars (D-glucosamine and D-galactosamine) using EDCI coupling. The structures were confirmed by infrared radiation, nuclear magnetic resonance, mass spectroscopy and elemental analysis. The release profile of codrugs was extensively studied in aqueous buffers, upper gastrointestinal homogenates, faecal matter and caecal homogenates (in vitro) and rat blood (in vitro). Anti-colitic activity was assessed in 2,4,6-trinitrobezenesulfonic acid-induced colitis in Wistar rats by the estimation of various demarcating parameters. Statistical evaluation was performed by applying one-way and two-way ANOVA when compared with the disease control.

RESULTS

The prodrugs resisted activation in HCl buffer (pH 1.2) and stomach homogenates of rats with negligible hydrolysis in phosphate buffer (pH 7.4) and intestinal homogenates. Incubation with colon homogenates (in vitro) produced 76% to 89% release of MPA emphasizing colon-specific activation of codrugs and the release of MPA and aminosugars at the site of action. In the in vitro studies, the prodrug of MPA with D-glucosamine (MGLS) was selected which resulted in 68% release of MPA in blood. in vitro studies on MGLS revealed its colon-specific activation after a lag time of 8 h which could be ascribed to the hydrolytic action of N-acyl amidases found in the colon. The synthesized codrugs markedly diminished disease activity score and revived the disrupted architecture of the colon that was comparable to MMF but superior to MPA.

CONCLUSION

The significant attenuating effect of prodrugs and individual aminosugars on colonic inflammation proved that the rationale of the codrug approach is valid.

Controversy of posterior reversible encephalopathy syndrome: what have we learnt in the last 20 years?

Over two decades have passed since posterior reversible encephalopathy syndrome (PRES) was first described in 1996. It has becoming increasingly recognised because of improved and more readily available imaging modality. The exact pathophysiological mechanism is not completely understood and remains controversial at present. Precise diagnosis is essential to guide prompt, proper management. Our ability of differentiating it from other acute neurological disorders is likely to improve as we learnt more about the spectrum of this entity in the last 20 years. We emphasise the importance of recognising its diagnostic criteria and biomarker, which would be of great relevance to either outcome evaluation or study design. PRES has a favourable prognosis generally, but neurological sequelae and even fatalities can occur, especially in severe forms that might cause substantial morbidity and even mortality, particularly when the syndrome is complicated by intracranial haemorrhage or brain infarction. In this review, the pathophysiology, approach to diagnosis, some controversies as to the prognosis, as well as the future research direction of PRES are described.

Engineered phage nanofibers induce angiogenesis

Herein, we exploited a bioinspired M13 bacteriophage as an angiogenic nanofiber for soft tissue engineering applications. We demonstrated that engineered phage nanofibers induce angiogenesis with specific biochemical and topological cues. Specifically, nanofibrous phage structures provided a novel therapeutic platform for stem cell technologies in ischemic diseases.

[Bilateral ciliary body oedema under treatment with ciclosporine]

We present the case of a 27-year-old female patient who developed bilateral ciliary body edema with secondary glaucoma and myopic shift during systemic treatment with cyclosporine for aplastic anemia. After application of topical atropine and prednisolone acetate and conversion from cyclosporine to tacrolimus, the ophthalmologic symptoms resolved completely. Since an infectious etiology was not evident, we hypothesize that ciliary body edema was caused by impairment of microvascular integrity by cyclosporine.

Mycophenolate mofetil as an immunomodulatory silver bullet in atherogenesis?

Atherosclerotic vascular disease is a chronic disorder of the vasculature with a substantial impact on society. Although the availability of statins has represented an unparalleled improvement in the treatment of patients with such cardiovascular disease, even more effective measures are required to reverse this disorder with a continuously growing incidence. The classification of atherosclerosis as an inflammatory disorder has prompted the hypothesis that immunomodulation could comprise a novel anti-atherosclerotic strategy. Mycophenolate mofetil (MMF) has various anti-atherogenic effects on major components of the atherosclerotic plaque such as T-lymphocytes, monocytes/macrophages and the endothelium. MMF can inhibit leukocyte recruitment to the subendothelium and the subsequent reduced activation of leukocytes will translate into attenuation of subendothelial crosstalk between T-cells and macrophages. This cascade of events will interrupt the self-perpetuating pro-inflammatory environment within the arterial wall, the hallmark of atherosclerotic vascular disease.

Colon cancer-derived myofibroblasts increase endothelial cell migration by glucocorticoid-sensitive secretion of a pro-migratory factor

Angiogenesis is important in cancer progression and can be influenced by tumor-associated myofibroblasts. We addressed the hypothesis that glucocorticoids indirectly affect angiogenesis by altering the release of pro-angiogenic factors from colon cancer-derived myofibroblasts. Our study shows that glucocorticoids reduced prostanoids, urokinase-type plasminogen activator (uPA) and angiopoietin-like protein-2 (ANGPTL2) levels, but increased angiogenin (ANG) in supernatant from human CT5.3hTERT colon cancer-derived myofibroblasts. Conditioned medium from solvent- (CMS) and dexamethasone (Dex)-treated (CMD) myofibroblasts increased human umbilical vein endothelial cell (HUVEC) proliferation, but did not affect expression of pro-angiogenic factors or tube-like structure formation (by HUVECs or human aortic ECs). In a HUVEC scratch assay CMS-induced acceleration of wound healing was blunted by CMD treatment. Moreover, CMS-induced neovessel growth in mouse aortic rings ex vivo was also blunted using CMD. The latter effect could be ascribed to both Dex-driven reduction of secreted factors and potential residual Dex present in CMD (indicated using a dexamethasone-spiked CMS control). A similar control in the scratch assay, however, revealed that altered levels of factors in the CMD, and not potential residual Dex, were responsible for decreased wound closure. In conclusion, our results suggest that glucocorticoids indirectly alter endothelial cell function during tumor development in vivo.

Utility and Significance of Gadolinium-Based Contrast Enhancement in Posterior Reversible Encephalopathy Syndrome

BACKGROUND AND PURPOSE

Posterior reversible encephalopathy syndrome is a clinicoradiologic syndrome. Literature regarding associated factors and the prognostic significance of contrast enhancement in posterior reversible encephalopathy syndrome is sparse. This study set out to evaluate an association between the presence of enhancement in posterior reversible encephalopathy syndrome and various clinical factors in a large series of patients with this syndrome.

MATERIALS AND METHODS

From an MR imaging report search that yielded 176 patients with clinically confirmed posterior reversible encephalopathy syndrome between 1997 and 2014, we identified 135 patients who had received gadolinium-based contrast. The presenting symptoms, etiology, clinical follow-up, and maximum systolic and diastolic blood pressures within 1 day of MR imaging were recorded. MRIs were reviewed for parenchymal hemorrhage, MR imaging severity, and the presence and pattern of contrast enhancement. Statistical analyses evaluated a correlation between any clinical features and the presence or pattern of enhancement.

RESULTS

Of 135 included patients (67.4% females; age range, 7-82 years), 59 (43.7%) had contrast enhancement on T1-weighted MR imaging, the most common pattern being leptomeningeal (n = 24, 17.8%) or leptomeningeal plus cortical (n = 21, 15.6%). Clinical outcomes were available in 96 patients. No significant association was found between the presence or pattern of enhancement and any of the variables, including sex, age, symptom, MR imaging severity, blood pressure, or outcome (all P > .05 after Bonferroni correction).

CONCLUSIONS

The presence or pattern of enhancement in posterior reversible encephalopathy syndrome is not associated with any of the tested variables. However, an association was found between MR imaging severity and clinical outcome.

Distinct deleterious effects of cyclosporine and tacrolimus and combined tacrolimus-sirolimus on endothelial cells: protective effect of defibrotide

Endothelial dysfunction seems to be a key factor in the development of several complications observed early after hematopoietic stem cell transplantation (HSCT). The conditioning regimen and many other factors associated with the procedure are responsible for this endothelial damage. The effects of immunosuppressive agents on endothelial function have not been explored in detail. We evaluated the effects of 3 drugs commonly used in HSCT: 2 calcineurin inhibitors, cyclosporine A (CSA) and tacrolimus (TAC), and an inhibitor of mTOR, sirolimus (SIR). We also evaluated the effect of the combination of TAC and SIR (TAC+SIR), which is used increasingly in clinical practice. Microvascular endothelial cells (HMEC-1) were exposed to these drugs to evaluate changes in (1) intercellular adhesion molecule (ICAM)-1 expression on the cell surface, assessed by immunofluorescence labeling and expressed as the mean gray value (MGV); (2) reactivity of the extracellular matrix (ECM) toward platelets, upon exposure of the ECM to circulating blood; and (3) whole-blood clot formation, assessed by thromboelastometry. Studies were conducted in the absence and presence of defibrotide (DF) to assess its possible protective effect. The exposure of HMEC-1 to CSA and TAC+SIR significantly increased the expression of ICAM-1 (157.5 ± 11.6 and 153.4 ± 9.5 MGV, respectively, versus 105.7 ± 6.5 MGV in controls [both P < .05]). TAC applied alone increased ICAM-1 slightly (120.3 ± 8.2 MGV), and SIR had no effect (108.9 ± 7.4 MGV). ECM reactivity increased significantly only in response to CSA (surface covered by platelets of 41.2% ± 5.4% versus 30.1% ± 2.0%, P < .05). DF attenuated all these changes. No significant changes in the viscoelastic properties of clot formation were observed in any condition with blood samples incubated in vitro. In conclusion, CSA and TAC+SIR had a proinflammatory effect, but only CSA exhibited an additional prothrombotic effect. Interestingly, DF exerted clear protective anti-inflammatory and antithrombotic effects on the endothelium.

Detection of microhemorrhage in posterior reversible encephalopathy syndrome using susceptibility-weighted imaging

BACKGROUND AND PURPOSE

PRES-related vasogenic edema is potentially reversible while hemorrhage occurs in only 15.2%-17.3% of patients. However, the true incidence of hemorrhage could be higher when SWI is considered. Thus, we set out to determine the incidence of MH, SAH, and IPH in PRES by using SWI and to particularly evaluate whether such MHs are reversible.

MATERIALS AND METHODS

Thirty-one patients with PRES and SWI were included, 17 having follow-up SWI. Two neuroradiologists reviewed SWI, FLAIR, DWI, and CE-T1WI. The presence and number of MHs (<5 mm) on SWI, SAH, and IPH (>5 mm) were recorded at presentation and follow-up. We evaluated associations between the presence of MH on SWI and DWI lesions, SAH, IPH, contrast enhancement, and MR imaging severity.

RESULTS

Hemorrhage was present in 20/31 patients (64.5%), with MHs on SWI in 18/31 (58.1%) at presentation and in 11/17 (64.7%) at follow-up. SAH was present in 3/31 on SWI and 4/31 on FLAIR, while 2/31 had IPH. At follow-up, no patients had acquired new MHs; 2/5 MHs in 1 patient resolved. Four patients with available SWI before PRES developed MHs after PRES onset. No association was found between the presence of MHs on SWI and DWI, SAH, IPH, enhancement, and MR imaging severity (all P > .05).

CONCLUSIONS

SWI showed a higher rate of MH than previously described, underscoring the potential of SWI in evaluating PRES. Such MHs typically persist and may develop after PRES onset. However, the clinical relevance of MHs in PRES is yet to be determined. We propose that MHs in PRES relate to endothelial cell dysfunction.

The importance of neovascularization and its inhibition for allogeneic hematopoietic stem cell transplantation

GVHD and tumor relapse are fundamental problems in allogeneic HSCT. Recent research has linked neovascularization to GVHD, tumor growth, and graft-versus-tumor (GVT) activity. Damage of the endothelium by the conditioning regimen provides the initiation stimulus for recruitment of donor-derived endothelial cells and their progenitors. During the early inflammatory phase of GVHD there is considerable neovascularization facilitating migration of inflammatory cells to target organs. In the course of GVHD, however, the vasculature itself becomes a target of alloreactive donor T cells. As a consequence, later stages of GVHD are characterized by fibrosis and rarefaction of blood vessels. Importantly, the inhibition of tumor-neovascularization by activated donor T cells that release antiangiogenic substances contributes to GVT and may be enhanced by pharmacologic inhibition of neovascularization. Furthermore, the therapeutic inhibition of neovascularization may improve immunotherapy for cancer by enhancing leukocyte infiltration in tumor tissue because of normalization of tumor vessels and stimulation of leukocyte-vessel wall interactions. These insights identify important mechanisms underlining the importance of neovascularization for allogeneic immune responses and move therapeutic approaches targeting neovascularization into the spotlight. This perspective covers current knowledge of the role of neovascularization during GVHD as well as GVT and its implications for HSCT.

Glucocorticoid-mediated inhibition of angiogenic changes in human endothelial cells is not caused by reductions in cell proliferation or migration

Background

Glucocorticoid-mediated inhibition of angiogenesis is important in physiology, pathophysiology and therapy. However, the mechanisms through which glucocorticoids inhibit growth of new blood vessels have not been established. This study addresses the hypothesis that physiological levels of glucocorticoids inhibit angiogenesis by directly preventing tube formation by endothelial cells.

Methodology/Principal Findings

Cultured human umbilical vein (HUVEC) and aortic (HAoEC) endothelial cells were used to determine the influence of glucocorticoids on tube-like structure (TLS) formation, and on cellular proliferation (5-bromo-2′-deoxyuridine (BrdU) incorporation), viability (ATP production) and migration (Boyden chambers). Dexamethasone or cortisol (at physiological concentrations) inhibited both basal and prostaglandin F_2α (PGF_2α)-induced and vascular endothelial growth factor (VEGF) stimulated TLS formation in endothelial cells (ECs) cultured on Matrigel, effects which were blocked with the glucocorticoid receptor antagonist RU38486. Glucocorticoids had no effect on EC viability, migration or proliferation. Time-lapse imaging showed that cortisol blocked VEGF-stimulated cytoskeletal reorganisation and initialisation of tube formation. Real time PCR suggested that increased expression of thrombospodin-1 contributed to glucocorticoid-mediated inhibition of TLS formation.

Conclusions/Significance

We conclude that glucocorticoids interact directly with glucocorticoid receptors on vascular ECs to inhibit TLS formation. This action, which was conserved in ECs from two distinct vascular territories, was due to alterations in cell morphology rather than inhibition of EC viability, migration or proliferation and may be mediated in part by induction of thrombospodin-1. These findings provide important insights into the anti-angiogenic action of endogenous glucocorticoids in health and disease.

Clinical recommendations for the use of everolimus in heart transplantation

Proliferation signal inhibitors (PSIs), everolimus (EVL), and sirolimus are a group of immunosuppressor agents indicated for the prevention of acute rejection in adult heart transplant recipients. Proliferation signal inhibitors have a mechanism of action with both immunosuppressive and antiproliferative effects, representing an especially interesting treatment option for the prevention and management of some specific conditions in heart transplant population, such as graft vasculopathy or malignancies. Proliferation signal inhibitors have been observed to work synergistically with calcineurin inhibitors (CNIs). Data from clinical trials and from the growing clinical experience show that when administered concomitantly with CNIs, PSIs allow significant dose reductions of the latter without loss of efficacy, a fact that has been associated with stabilization or significant improvement in renal function in patients with CNI-induced nephrotoxicity. The purpose of this article was to review the current knowledge of the role of PSIs in heart transplantation to provide recommendations for the proper use of EVL in cardiac transplant recipients, including indications, treatment regimens, monitoring, and management of the adverse events.

Acute toxic leukoencephalopathy: potential for reversibility clinically and on MRI with diffusion-weighted and FLAIR imaging

OBJECTIVE

Toxic leukoencephalopathy may present acutely or subacutely with symmetrically reduced diffusion in the periventricular and supraventricular white matter, hereafter referred to as periventricular white matter. This entity may reverse both on imaging and clinically. However, a gathering together of the heterogeneous causes of this disorder as seen on MRI with diffusion-weighted imaging (DWI) and an analysis of their likelihood to reverse has not yet been performed. Our goals were to gather causes of acute or subacute toxic leukoencephalopathy that can present with reduced diffusion of periventricular white matter in order to promote recognition of this entity, to evaluate whether DWI with apparent diffusion coefficient (ADC) values can predict the extent of chronic FLAIR abnormality (imaging reversibility), and to evaluate whether DWI can predict the clinical outcome (clinical reversibility).

MATERIALS AND METHODS

Two neuroradiologists retrospectively reviewed the MRI examinations of 39 patients with acute symptoms and reduced diffusion of periventricular white matter. The reviewers then scored the extent of abnormality on DWI and FLAIR. ADC ratios of affected white matter versus the unaffected periventricular white matter were obtained. Each patient's clinical records were reviewed to determine the cause and clinical outcome. Histology findings were available in three patients. Correlations were calculated between the initial MRI markers and both the clinical course and the follow-up extent on FLAIR using Spearman's correlation coefficient.

RESULTS

Of the initial 39 patients, seven were excluded because of a nontoxic cause (hypoxic-ischemic encephalopathy [HIE] or congenital genetic disorders) or because of technical errors. In the remaining 32 patients, no correlation was noted between any of the initial MRI markers (percentage of ADC reduction, DWI extent, or FLAIR extent) with the clinical outcome. Three patients had histologic correlation. However, moderate correlation was seen between the extent of abnormality on initial FLAIR and the extent on follow-up FLAIR (r = 0.441, p = 0.047). Of the 13 patients who underwent repeat MRI at 21 days or longer, the reduced diffusion resolved in all but one. Significant differences were noted between ADC values in affected white matter versus unaffected periventricular white matter on initial (p < 0.0001) but not on follow-up MRI (p = 0.13), and in affected white matter on initial versus follow-up (p = 0.0014) in those individuals who underwent repeat imaging on the same magnet (n = 9), confirming resolution of the DWI abnormalities.

CONCLUSION

Acute toxic leukoencephalopathy with reduced diffusion may be clinically reversible and radiologically reversible on DWI, and may also be reversible, but to a lesser degree, on FLAIR MRI. None of the imaging markers measured in this study appears to correlate with clinical outcome, which underscores the necessity for prompt recognition of this entity. Alerting the clinician to this potentially reversible syndrome can facilitate treatment and removal of the offending agent in the early stages.

Role of calcineurin in thrombin-mediated endothelial cell contraction

Barrier function and shape changes of endothelial cells (EC) are regulated by phosphorylation/dephosphorylation of key signaling and contractile elements. EC contraction results in intercellular gap formation and loss of the selective vascular barrier to circulating macromolecules. EC dysfunction elicited by thrombin was found to correlate with actin microfilament redistribution. It is known that calcineurin (Cn) is involved in thrombin-induced EC dysfunction because inhibition of Cn potentiates PKC activity and the phosphorylation state of EC myosin light chain is also affected by Cn activity. Immunofluorescent detection of Cn catalytic subunit (CnA) isoforms coexpressed with GFP was visualized on paraformaldehyde (PFA) fixed bovine pulmonary artery endothelial cells (BPAEC). Actin microfilaments were stained with Texas Red-phalloidin. Cytotoxic effects of transfections or treatments and the efficiency of transfections were assessed by flow cytometry. Treatment of BPAEC with Cn inhibitors (cyclosporin A and FK506) hindered recovery of the cells from thrombin-induced EC dysfunction. Inhibition of Cn in the absence of thrombin had no effect on cytoskeletal actin filaments. We detected attenuated thrombin-induced stress fiber formation and changes in cell shape only when cells were transfected with constitutively active CnA and not with various CnA isoforms. Flow cytometry (FCM) analysis has proved that cytotoxic effect of treatments is negligible. We observed that Cn is involved in the recovery from thrombin-induced EC dysfunction. Inhibition of Cn caused prolonged contractile effect, while overexpression of constitutively active CnA resulted in reduced thrombin-induced stress fiber formation.

Cyclosporine triggers endoplasmic reticulum stress in endothelial cells: a role for endothelial phenotypic changes and death

Calcineurin inhibitors cyclosporine and tacrolimus are effective immunosuppressants, but both substances have the same intrinsic nephrotoxic potential that adversely affects allograft survival in renal transplant patients and causes end-stage renal disease in other solid organ or bone marrow transplant recipients. Endothelial cells are the first biological interface between drugs and the kidney, and calcineurin inhibitors may influence endothelial function and viability in a number of ways. Notably, endothelial cells have recently been shown to contribute to the accumulation of interstitial fibroblasts in nonrenal models, through endothelial-to-mesenchymal transition. Here we demonstrate that cyclosporine, but not tacrolimus or its metabolites, induces morphological and phenotypic endothelial changes suggestive of a partial endothelial-to-mesenchymal transition in human umbilical arterial endothelial cells. We identify for the first time a contingent of interstitial myofibroblasts that coexpress endothelial markers in rat kidneys treated with cyclosporine, suggesting that endothelial-to-mesenchymal transition could occur in vivo. Finally, our findings suggest that endoplasmic reticulum stress triggered by cyclosporine induces endothelial cells to undergo endothelial phenotypic changes suggestive of a partial endothelial-to-mesenchymal transition, whereas salubrinal partially preserves the endothelial phenotype. Inversely, tacrolimus does not induce endothelial-to-mesenchymal transition or endoplasmic reticulum stress. In conclusion, this study demonstrates for the first time that cyclosporine, and not tacrolimus, induces endoplasmic reticulum stress in endothelial cells. Our findings also suggest that endoplasmic reticulum stress contributes to endothelial cell death and phenotypic changes similar to a partial endothelial-to-mesenchymal transition.

An interleukin-6-neutralizing antibody prevents cyclosporine-induced nephrotoxicity in mice

INTRODUCTION

Chronic use of cyclosporine A (CyA) induces nephrotoxicity primarily due to endothelial dysfunction. In our previous studies, potential mechanisms were identified in vitro and implicated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and interleukin-6 (IL-6) as key components in causing endothelial dysfunction. In this study, we tested the hypothesis that NADPH oxidase activity and IL-6 are key components in renal damage in an in vivo model.

METHODS

Male mice C57B/6 mice from Jackson Laboratory (Bar Harbor, ME) at 6-8 wks were subjected to a low-salt diet throughout the trial. After 1 week on a low-salt diet, the mice were injected daily with treatments in 50 muL vehicle composed of 75% cremaphor (Sigma, St. Louis, MO) and ethanol for 5 wks. A vehicle-alone group was also set aside. Mice were weighed and 25 mg/kg/day cyclosporine (Novartis Pharma, St. Louis, MO) was injected daily. Apocynin (Calbiochem, Gibbstown, NJ) 20 mg/kg were injected either alone or concomitantly with CyA. Another group of mice were administered IL-6 antibody (Cat no. MAB406; R&D Systems, Minneapolis, MN) at 2 mug/day along with CyA. The kidneys were removed en bloc immediately and submitted in formalin for paraffin sections. Trichrome stains were performed. Slides were blinded and 10 photographs of cortical areas per treatment group were taken, which covered an estimate of 10% surface area in random fashion. Areas of renal damage, which were determined by tubular necrosis, were identified and quantified by amount of necrosis per photograph. Each photograph was divided into 10 blocks, and the number of blocks that contained necrotic tubules per photo was recorded.

RESULTS

The two control mice (low salt only) had no damage. The four vehicle mice had trace amounts of tubular necrosis. CyA treatment group demonstrated the highest amount of damage (29/70; 41%). CyA with apocynin, a specific NADPH oxidase inhibitor, was found to have 36% (22/60) damage, whereas the CyA with IL-6 antibody only was observed to have 15% (6/40) damage. Comparing imaging analysis, there was no difference between mice treated with CyA alone and with CyA with apocynin. However, the amount of damage in mice treated with CyA and IL-6 antibody was found to be significantly lower than both CyA and CyA with apocynin.

CONCLUSIONS

CyA action as a calcineurin inhibitor has allowed prolongation of kidney transplants, but its chronic use has led to devastating consequences such as allograft nephropathy. Previously, we have identified potential mechanisms of CyA-induced endothelial dysfunction in vitro. The current study identifies increased IL-6 expression as a mechanism by which CyA induces renal damage and that the use of an IL-6-neutralizing antibody may be useful in reducing CyA-induced renal damage.

Cyclosporin A suppresses proliferation of endothelial progenitor cells: involvement of nitric oxide synthase inhibition

OBJECTIVE

To investigate the effects of the potent immunosuppressive agent cyclosporin A (CsA) on the proliferation of human endothelial progenitor cells (EPCs) and endothelial nitric oxide synthase (eNOS) expression in EPCs.

METHODS AND RESULTS

The EPCs were obtained from cultured mononuclear cells, which were isolated from the peripheral blood of healthy adults, and stimulated with CsA (10 microg/mL) in the presence or absence of either vascular endothelial growth factor (VEGF; 50 ng/mL) or L-arginine (1 mM). To explore the effect of different concentrations of CsA alone on EPC proliferation, some cells were treated with CsA in a series of final concentrations ranging from 0 to 10 microg/mL. Cell proliferation and apoptosis were determined, respectively, by the Cell Counting Kit-8 assay and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. The expression of eNOS was assayed by reverse transcription-polymerase chain reaction analysis while nitric oxide (NO) generation was detected using the Griess method. The effects of CsA on EPC proliferation, apoptosis, and eNOS/NO production were dose dependent in the concentration ranging from 0.1 microg/mL to 10 microg/mL. Treatment with VEGF (50 ng/mL) significantly promoted EPC proliferation and eNOS/NO production, which were completely abrogated by pre-incubation with CsA (10 microg/mL). The supplement of L-arginine (1 mM) promoted NO production that enhanced EPC proliferation and attenuated the effect of CsA on EPC proliferation and apoptosis.

CONCLUSION

CsA significantly inhibited proliferation, eNOS mRNA expression and NO production of human EPCs, in a dose-dependent manner.

Posterior reversible encephalopathy syndrome: incidence of atypical regions of involvement and imaging findings

OBJECTIVE

Posterior reversible encephalopathy syndrome (PRES) is classically characterized as symmetric parietooccipital edema but may occur in other distributions with varying imaging appearances. This study determines the incidence of atypical and typical regions of involvement and unusual imaging manifestations.

MATERIALS AND METHODS

Seventy-six patients were eventually included as having confirmed PRES from 111 initially suspected cases, per imaging and clinical follow-up. Two neuroradiologists retrospectively reviewed each MR image. Standard sequences were unenhanced FLAIR and T1- and T2-weighted images in all patients, with diffusion-weighted imaging (n = 75) and contrast-enhanced T1-weighted imaging (n = 69) in most. The regions involved were recorded on the basis of FLAIR findings, and the presence of atypical imaging findings (contrast enhancement, restricted diffusion, hemorrhage) was correlated with the severity (extent) of hyperintensity or mass effect on FLAIR.

RESULTS

The incidence of regions of involvement was parietooccipital, 98.7%; posterior frontal, 78.9%; temporal, 68.4%; thalamus, 30.3%; cerebellum, 34.2%; brainstem, 18.4%; and basal ganglia, 11.8%. The incidence of less common manifestations was enhancement, 37.7%; restricted diffusion, 17.3%; hemorrhage, 17.1%; and a newly described unilateral variant, 2.6%. Poor correlation was found between edema severity and enhancement (r = 0.072), restricted diffusion (r = 0.271), hemorrhage (r = 0.267), blood pressure (systolic, r = 0.13; diastolic, r = 0.02). Potentially new PRES causes included contrast-related anaphylaxis and alcohol withdrawal.

CONCLUSION

This large series of PRES cases shows that atypical distributions and imaging manifestations of PRES have a higher incidence than commonly perceived, and atypical manifestations do not correlate well with the edema severity.

Downregulated gene expression in human palate fibroblasts after cyclosporin A treatment

BACKGROUND

Cyclosporin A is a powerful immunosuppressive drug with considerable impact on transplants and is able to modify extracellular matrix (ECM) composition. It has recently been demonstrated that cyclosporin A stimulates the production of the cytokine family. Cytokines such as interleukin, transforming growth factor beta(1), and bone morphogenetic protein induce the deposition of glycosaminoglycans (GAGs), proteoglycans, and collagen fibers in the connective ECM. ECM composition is very important for normal tissue development and function. In this work, we examine the effects caused by cyclosporin A on cultures of normal human palate fibroblasts in order to evaluate interleukin, transforming growth factor beta II, and bone morphogenetic protein II membrane receptor induction and extracellular GAG changes such as hyaluronic acid, heparin sulfate, and chondroitin sulfate.

METHODS

Palate fibroblasts were maintained for 24 h in serum-free 199 medium containing 5 microg/mL (3)H glucosamine hydrochloride. After this time, TGF II and BMP II receptors were determined by microarray analysis and GAG classes by the biochemical method.

RESULTS

The results show that TGFbeta(1) II and BMP II membrane receptors are significantly inhibited in cyclosporin A-treated cultures as compared to controls, whereas IL-1R2 membrane receptors are stimulated. The behavior of total intra- and extracellular GAGs is significantly increased in cyclosporin A-treated cultures, whereas the ratio between non-sulfated/sulfated GAGs decreases (p <or=0.01) vis-à-vis controls.

CONCLUSIONS

Because they form a highly complicated macromolecular network in the ECM, which provides an indication of cell function and gene expression and modulates growth factor activities, GAG changes are related to modification of ECM functions. Our data show that cyclosporin A causes biochemical changes to ECM through alterations in cytokines and respective membrane receptor linkages.

Differential effects of immunosuppressive drugs on T-cell motility

The best-characterized mechanism of the action of immunosuppressive drugs is to prevent T-cell clonal expansion, thus containing the magnitude of the ensuing immune response. As T-cell recruitment to the inflammatory site is another key step in the development of T-cell-mediated inflammation, we analyzed and compared the effects of two commonly used immunosuppressants, cyclosporin A (CsA) and the rapamycin-related compound SDZ-RAD, on the motility of human CD4+ T cells. We show that CsA, but not SDZ-RAD, inhibits T-cell transendothelial migration in vitro. CsA selectively impaired chemokine-induced T-cell chemotaxis while integrin-mediated migration was unaffected. The inhibition of T-cell chemotaxis correlated with reduced AKT/PKB but not ERK activation following exposure to the chemokine CXCL-12/SDF-1. In addition, CsA, but not SDZ-RAD, prevents some T-cell receptor-mediated effects on T-cell motility. Finally, we show that CsA, but not SDZ-RAD inhibits tissue infiltration by T cells in vivo. Our data suggest a prominent antiinflammatory role for CsA in T-cell-mediated tissue damage, by inhibiting T-cell trafficking into tissues in addition to containing clonal expansion.

Drugs modulating endothelial function after transplantation

Endothelial cells play a vital role in the success or failure of a transplant procedure. The procedure itself can be viewed as a series of insults that damages the endothelium thereby triggering an inflammatory cascade that may, if uncontrolled, drive the proliferative and fibrotic processes characteristic of chronic graft vasculopathy. Unfortunately, many immunosuppressant agents contribute to this process. Glucocorticoids and the calcineurin inhibitor cyclosporine induce endothelial dysfunction, and although tacrolimus may not have the same disruptive effects on endothelial function as cyclosporine, its endothelial activity is still being established. In contrast, antiproliferative agents slow the proliferation and migration of endothelial cells and so help protect against graft vasculopathy. Researchers agree that endothelial cell dysfunction is a potentially treatable stage in the multifactorial process of graft vasculopathy and rejection. A number of cardiovascular agents (statins, angiotensin converting enzyme inhibitors, calcium channel blockers), immunoregulatory drugs, and dietary compounds have been shown to have beneficial effects on endothelial function. We briefly review the evidence supporting their use as protection for endothelial cells in transplant recipients.

Coronary endothelial vasomotor function and vascular remodeling in heart transplant recipients randomized for tacrolimus or cyclosporine immunosuppression

OBJECTIVES

This study aimed to compare changes in coronary endothelial function, systemic endothelin-1 (ET-1) levels, and vascular remodeling in heart transplant recipients randomized to cyclosporin A (CyA) or tacrolimus (Tac) immunosuppression.

BACKGROUND

Functional endothelial abnormalities and intimal thickening are sensitive measures of early cardiac allograft vasculopathy (CAV).

METHODS

The randomized, prospective study was performed in two groups of 22 patients, maintained on Tac or CyA and mycophenolate mofetil immunosuppression, 1 and 12 months after heart transplantation. We investigated epicardial luminal diameter, coronary blood flow velocity, and ET-1 plasma levels at 1 and 12 months after transplantation. Structural coronary alterations were determined using intravascular ultrasound.

RESULTS

Epicardial vasomotor function at baseline and during follow-up was comparable between the groups. Deterioration of microvascular endothelial function during follow-up was significantly enhanced in the CyA versus Tac group (p < 0.05). Circulating ET-1 concentration increased in the CyA group but significantly decreased over time in the Tac group (CyA +17% vs. Tac -25%; p < 0.05). The time-dependent increase in mean intimal area was significantly enhanced in the CyA versus Tac group, whereas the vessel area significantly increased during follow-up in the Tac compared with the CyA group.

CONCLUSIONS

Epicardial endothelial function is comparable between CyA- and Tac-treated patients. Microvascular endothelial function deteriorates more in CyA-treated patients, a finding that correlates with enhanced ET-1 concentration and an increased intimal area during follow-up. The mean vessel area in the Tac group increased over time, indicating positive vascular remodeling. Tac is superior to CyA with respect to microvascular endothelial function, intimal thickening, and vascular remodeling.

Mechanisms of action of mycophenolate mofetil in preventing acute and chronic allograft rejection

Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), an inhibitor of inosine-5'-monophosphate dehydrogenase, has several immunosuppressant actions. MPA depletes guanosine and deoxyguanosine nucleotides preferentially in T and B lymphocytes, inhibiting proliferation and suppressing cell-mediated immune responses and antibody formation, major factors in acute and chronic rejection. MPA also can induce T-lymphocyte apoptosis. MPA suppresses dendritic cell maturation and can induce human monocyte-macrophage cell line differentiation, decreasing the expression of interleukin (IL)-1 and enhancing expression of the IL-1 receptor antagonist. In addition, MPA inhibits adhesion molecule glycosylation and expression and lymphocyte and monocyte recruitment. Activated macrophages produce nitric oxide (NO) and superoxide, which combine to generate tissue-damaging peroxynitrite. MPA depletes tetrahydrobiopterin and decreases NO production by inducible NO synthase without affecting constitutive NO synthase activity. By these mechanisms, MMF exerts anti-inflammatory activity, which could attenuate both acute and chronic rejection. Unlike calcineurin inhibitors, MMF is nonnephrotoxic and does not induce transforming growth factor-beta production, which is fibrogenic. MMF inhibits arterial smooth muscle cell proliferation, a contributor to graft proliferative arteriopathy, and does not increase blood pressure, cholesterol, or triglyceride levels. By decreasing high-density lipoprotein oxidation and macrophage recruitment, MMF also may delay onset/progression of graft atherosclerosis. Thus, MMF may prevent chronic rejection by several mechanisms. MMF activity is synergistic with that of other agents such as valganciclovir for treating cytomegalovirus infection. MMF also has synergistic activity with angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists in the treatment of some nephropathies in experimental animals. This combination may prevent progression toward end-stage renal disease in humans with chronic allograft, lupus, and diabetic nephropathies.

Effects of mycophenolic acid on endothelial cells

Mycophenolate mofetil (MMF) is a potent immunosuppressant that inhibits the activity of inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in de novo synthesis of guanosine nucleotides. MMF has been used widely in solid-organ transplantation. Increased evidence indicated that MMF exhibited beneficial effects on various types of vasculitis, for reasons that were not fully understood. Endothelial cells play a pivotal role in the pathogenesis of vasculitis. Endothelium may not only be the main target for injury, but also be able to amplify the inflammatory response by adhesion molecule expression, leukocyte adhesion, cytokine production and angiogenesis. In the present study, the effect of mycophenolic acid (MPA), the active metabolite of MMF, on human umbilical vein endothelial cells (HUVECs) was investigated. MPA markedly inhibited tumor necrosis factor-alpha (TNFalpha)-induced intercellular adhesion molecule-1 (ICAM-1) mRNA and surface expression, suppressed TNFalpha-induced neutrophils adhesion to endothelial cells, and reduced TNFalpha-induced interleukin-6 (IL-6) secretion. The inhibitory effects of MPA on ICAM-1 surface expression and IL-6 secretion were not attenuated by addition of guanosine, implying that inhibition of these processes were not due to intracellular guanosine nucleotides depletion. MPA also decreased angiogenesis of endothelial cells in three-dimensional collagen gel culture system, reduced the migration in a wounded monolayer of endothelial cells, and inhibited the proliferation of endothelial cells. In conclusion, MPA exhibited multifarious effects on endothelial cells including inhibition of ICAM-1 expression, neutrophil attachment, IL-6 secretion, and the process of angiogenesis, which might contribute to the efficacy of MMF in the treatment of vasculitis.

Effect of immunosuppressive agents on long-term survival of renal transplant recipients: focus on the cardiovascular risk

In the control of acute rejection, attention is being focused more and more on the long-term adverse effects of the immunosuppressive agents used. Since cardiovascular disease is the main cause of death in renal transplant recipients, optimal control of cardiovascular risk factors is essential in the long-term management of these patients. Unfortunately, several commonly used immunosuppressive drugs interfere with the cardiovascular system. In this review, the cardiovascular adverse effects of the immunosuppressive agents currently used for maintenance immunosuppression are thoroughly discussed. Optimising immunosuppression means finding a balance between efficacy and safety. Corticosteroids induce endothelial dysfunction, hypertension, hyperlipidaemia and diabetes mellitus, and impair fibrinolysis. The use of corticosteroids in transplant recipients is undesirable, not only because of their cardiovascular effects, but also because they induce such adverse effects as osteoporosis, obesity, and atrophy of the skin and vessel wall. Calcineurin inhibitors are the most powerful agents for maintenance immunosuppression. The calcineurin inhibitor ciclosporin (cyclosporine) not only induces these same adverse effects as corticosteroids but is also nephrotoxic. Tacrolimus has a more favourable cardiovascular risk profile than ciclosporin and is also less nephrotoxic. It has little or no effect on blood pressure and serum lipids; however, its diabetogenic effect is more prominent in the period immediately following transplantation, although at maintenance dosages, the diabetogenic effect appears to be comparable to that of ciclosporin. The diabetogenic effect of tacrolimus can be managed by reducing the dose of tacrolimus and early corticosteroid withdrawal. The effect of tacrolimus on endothelial function has not been completely elucidated. The proliferation inhibitors azathioprine and mycophenolate mofetil (MMF) have little effect on the cardiovascular system. Yet, indirectly, by inducing anaemia, they may lead to left ventricular hypertrophy. MMF is an attractive alternative to azathioprine because of its higher potency and possibly lower risk of malignancies. Sirolimus also induces anaemia, but may be promising because of its antiproliferative features. Whether the hyperlipidaemia induced by sirolimus counteracts its beneficial effects is, as yet, unknown. It may be combined with MMF, however, initial attempts resulted in severe mouth ulcers.

Augmentation of Ischemia/Reperfusion Injury to Endothelial Cells by Cyclosporin A

Ischemia/reperfusion (I/R) carries significant injury to endothelial cells in transplanted organs and is an important factor in chronic rejection. Immunosuppressive drugs, notably cyclosporin A (CyA) and FK506, can potentially augment this injury. Here, our goal was to determine the combined effects of I/R and CyA or FK506 on endothelial cells. Transformed mouse endothelial cells (SVEC 4–10) were subjected to ischemia or I/R for 2–24 hours by incubating cells in 100 per cent N2 (ischemia) followed by 5 per cent CO2 and 95 per cent O2 (reperfusion) for 24 hours. In separate experiments, CyA or FK506 was added to cells subjected to ischemia or I/R. Nonviable cells were determined by Trypan blue exclusion assay. All experiments (done in triplicate) were analyzed by Student's t test. Increasing ischemia times resulted in a greater number of nonviable cells (2% nonviable cells at 0 hours and 57% at 24 hours of I/R). Addition of CyA significantly increased the number of nonviable cells when compared with the control (I/R only) group ( P = 0.014). Interestingly, FK506 did not increase the percentage of nonviable cells compared with the control group ( P = 0.2). Unlike FK506, CyA augments I/R injury to endothelial cells in vitro. These findings could be relevant in chronic rejection and transplantation.