Arginine depletion as a therapeutic approach for patients with COVID-19.

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a source of significant morbidity and death worldwide, and effective treatments are urgently needed. Clinical trials have focused largely on direct antiviral therapies or on immunomodulation in patients with severe manifestations of COVID-19. One therapeutic approach that remains to be clinically investigated is disruption of the host-virus relationship through amino acid restriction, a strategy used successfully in the setting of cancer treatment. Arginine is an amino acid that has been shown in nonclinical studies to be essential in the life cycle of many viruses. Therefore, arginine depletion may be an effective therapeutic approach against SARS-CoV-2. Several arginine-metabolizing enzymes in clinical development may be a viable approach to induce a low arginine environment to treat COVID-19 and other viral diseases. Herein, we explore the rationale for arginine depletion as a therapeutic approach for COVID-19.

"Contrecoup" Paravalvular Leak Closure.

Paravalvular aortic regurgitation affects some patients after surgically implanted prosthesis. The number of patients affected is likely to increase with increased utilization of nonsurgical valve replacement techniques. These patients are at increased risk of persistent clinical symptoms often requiring repair. Clinical and procedural outcomes are of importance when performing these procedures and managing these patients. We describe a case where two different leaks around an aortic prosthesis improved with closure of one defect.

High-density lipoprotein cholesterol levels in middle-school children: association with cardiovascular risk factors and lifestyle behaviors.

To examine factors associated with low high-density lipoprotein cholesterol (HDL-C) levels among middle school children. HDL-C levels were the primary outcome of interest. A total of 1,104 middle-school children (mean age 11.6 years, 51.2% female) were included in this analysis, of whom 177 (16%) had an HDL-C level ≤40 mg/dL. More than half of those with low HDL-C were overweight or obese (62.2%) and had greater systolic and diastolic blood pressure, triglyceride (TRG) levels, and low-density lipoprotein cholesterol levels compared with children with an HDL-C level >40 mg/dL. Among those with an HDL-C ≤ 40 mg/dL, 35% also had body mass index ≥85% and TRG levels ≥150 mg/dL. Exercise habits were significantly associated with HDL-C level, whereas sedentary behaviors, such as screen time, were not significantly associated with HDL-C level. Fruit and vegetable intake was also not significantly associated with HDL-C level. Children with low HDL-C levels are more likely to be overweight and to have other physiological indicators of increased cardiovascular risk. Further research is needed to determine if school-based interventions can result in long-term improvements in HDL-C.

Endothelial-dependent mechanisms of leukocyte recruitment to the vascular wall.

Inflammation is a fundamental process that protects organisms by removing or neutralizing injurious agents. A key event in the inflammatory response is the localized recruitment of various leukocyte subsets. Here we address the cellular and regulatory mechanisms of leukocyte recruitment to the vessel wall in cardiovascular disease and discuss our evolving understanding of the role of the vascular endothelium in this process. The vascular endothelium is the continuous single-cell lining of the cardiovascular system that forms a critical interface between the blood and its components on one side and the tissues and organs on the other. It is heterogeneous and has many synthetic and metabolic functions including secretion of platelet-derived growth factor, von Willebrand factor, prostacyclin, NO, endothelin-1, and chemokines and the expression of adhesion molecules. It also acts as a nonthrombogenic and selective permeable barrier. Endothelial cells also interact closely with the extracellular matrix and with adjacent cells including pericytes and smooth muscle cells within the vessel wall. A central question in vascular biology is the role of the endothelium in the initiation of inflammatory response, the extent of its "molecular conversations" with recruited leukocytes, and its influence on the extent and/or outcome of this response.

Meckel's cave tuberculoma with unusual infratemporal extension.

The authors describe a rare case of intracranial tuberculoma of the Meckel's cave and cavernous sinus with extension into the infratemporal fossa causing widening of the foramen ovale and adjacent bone destruction. The rarity of the lesion and the unusual extension of the lesion are presented with a brief review of literature.

T-bet is required for optimal proinflammatory CD4+ T-cell trafficking.

Inflammatory responses are controlled by T helper 1 (Th1) lymphocytes. An important function of this polarity is the ability of T cells to traffick appropriately in vivo. This differential trafficking is dependent upon the binding of P-selectin glycoprotein ligand-1 to P- and E-selectin on inflamed endothelium as well as the expression of specific chemokine receptors. Here we show that in the absence of T-box expressed in T cells (T-bet), selective migration of T cells in vivo is completely abrogated and that T-bet regulates the binding of CD4(+) T cells to P-selectin. T-bet is also required for the expression of the chemokine receptor CXCR3. Thus, T-bet controls Th1-cell migration to inflammatory sites, which has fundamental consequences for the control of immunologic disease.

Electro-clinical characteristics and postoperative outcome of medically refractory tumoral temporal lobe epilepsy.

BACKGROUND: Very few studies have specifically addressed surgical treatment and outcome of patients with tumor-related temporal lobe epilepsy (TLE). AIM: To define the postoperative seizure outcome and the factors that influenced the outcome of patients with tumor-related TLE. MATERIALS AND METHODS: We selected patients whose surgical pathology revealed a temporal lobe neoplasm and who had completed > 1 year of postoperative follow-up. We reviewed the clinical, EEG, radiological and pathological data, and the seizure outcome of these patients and assessed the factors that influenced the outcome. RESULTS: Out of the 409 patients who underwent surgery for refractory TLE during the 8-year study period, there were 34 (8.3%) patients with temporal lobe neoplasms. The median age at surgery was 20 years and the median duration of epilepsy prior to surgery was 9.0 years. MRI revealed tumor in the mesial location in 21 (61.8%) patients. Interictal and ictal epileptiform EEG abnormalities were localized to the side of th lesion in the majority. Mesial temporal lobe structures were included in the resection, if they were involved by the tumor; otherwise, lesionectomy alone was performed. During a median follow-up of 4 years, 27 (79%) patients were completely seizure-free. The only factor that predicted long-term seizure-free outcome was being seizure-free during the first two postoperative years. CONCLUSIONS: Our results emphasize the fact that in patients with tumoral TLE, when the seizures are medically refractory, surgery offers potential for cure of epilepsy in the majority.

Emerging topics in the regulation of leukocyte transendothelial migration.

This year marks the 50th Anniversary of the founding of the Microcirculatory Society. Since the formation of this society this field has witnessed tremendous progress in understanding the process of leukocyte recruitment during inflammation, injury, and immune reactions. This topic has been an important focus of many of the members of the Microcirculatory Society as well as our colleagues worldwide. The goal of this brief review is to bring attention to a few emerging topics in inflammation research. Here the focus is on one particular model of how one leukocyte type (PMN) can regulate the recruitment of a second different leukocyte type (T cell) and provide an outline of other aspects that bear on spatial and temporal behavior of specific leukocyte and endothelial cell adhesion molecules during leukocyte transmigration under dynamic shear flow in vitro.

Coordinated redistribution of leukocyte LFA-1 and endothelial cell ICAM-1 accompany neutrophil transmigration.

The leukocyte integrin lymphocyte function-associated antigen 1 (LFA-1) and its endothelial ligand intercellular adhesion molecule (ICAM)-1 play an important role in transmigration as demonstrated by in vivo and in vitro models of inflammation. Despite the prominent role, little is known concerning the distribution and dynamic behavior of these adhesion molecules during leukocyte transmigration. Therefore, we examined the spatial and temporal distribution of LFA-1 on neutrophils actively transmigrating tumor necrosis factor-alpha-activated human umbilical vein endothelial monolayers under shear flow. Upon neutrophil arrest, LFA-1 was evenly distributed. However, once neutrophils initiated transmigration, LFA-1 rapidly redistributed to form a ringlike cluster at the neutrophil-endothelial junctional interface through which transmigration occurred. As transmigration was completed, LFA-1 redistributed to the neutrophil uropod. Endothelial ICAM-1 and JAM-A both colocalized with the ringlike LFA-1 cluster. Further analysis of PMA-stimulated neutrophils, which increase mobility of LFA-1, showed a rapid redistribution of LFA-1 and ICAM-1, but not endothelial JAM-A. Thus, endothelial JAM-A does not appear to contribute to adhesion or transmigration in this system. This is the first demonstration that neutrophil LFA-1 rapidly redistributes to form a ringlike structure that coclusters with endothelial ICAM-1 as the neutrophil transmigrates.

Elastase release by transmigrating neutrophils deactivates endothelial-bound SDF-1alpha and attenuates subsequent T lymphocyte transendothelial migration.

Leukocyte trafficking to sites of inflammation follows a defined temporal pattern, and evidence suggests that initial neutrophil transendothelial migration modifies endothelial cell phenotype. We tested the hypothesis that preconditioning of human umbilical vein endothelial cells (HUVEC) by neutrophils would also modify the subsequent transendothelial migration of T lymphocytes across cytokine-stimulated HUVEC in an in vitro flow assay. Using fluorescence microscopy, preconditioning of HUVEC by neutrophils was observed to significantly reduce the extent of subsequent stromal cell-derived factor-1alpha (SDF-1alpha [CXCL12])-mediated T lymphocyte transendothelial migration, without reducing accumulation. In contrast, recruitment of a second wave of neutrophils was unaltered. Conditioned medium harvested after transendothelial migration of neutrophils or supernatants from stimulated neutrophils mediated a similar blocking effect, which was negated using a specific neutrophil elastase inhibitor. Furthermore, T lymphocyte transendothelial migration was inhibited by treatment of HUVEC with purified neutrophil elastase, which selectively cleaved the amino terminus of HUVEC-bound SDF-1alpha, which is required for its chemotactic activity. The reduction in T lymphocyte transendothelial migration was not observed using a different chemokine, ELC (CCL19), and was not reversed by replenishment of SDF-1alpha, indicating endothelial retention of the inactivated chemokine. In summary, transmigrating neutrophils secrete localized elastase that is protected from plasma inhibitors, and thereby modulate trafficking of other leukocyte subsets by altering the endothelial-associated chemotactic activities.

KLF2 Is a novel transcriptional regulator of endothelial proinflammatory activation.

The vascular endothelium is a critical regulator of vascular function. Diverse stimuli such as proinflammatory cytokines and hemodynamic forces modulate endothelial phenotype and thereby impact on the development of vascular disease states. Therefore, identification of the regulatory factors that mediate the effects of these stimuli on endothelial function is of considerable interest. Transcriptional profiling studies identified the Kruppel-like factor (KLF)2 as being inhibited by the inflammatory cytokine interleukin-1beta and induced by laminar shear stress in cultured human umbilical vein endothelial cells. Overexpression of KLF2 in umbilical vein endothelial cells robustly induced endothelial nitric oxide synthase expression and total enzymatic activity. In addition, KLF2 overexpression potently inhibited the induction of vascular cell adhesion molecule-1 and endothelial adhesion molecule E-selectin in response to various proinflammatory cytokines. Consistent with these observations, in vitro flow assays demonstrate that T cell attachment and rolling are markedly attenuated in endothelial monolayers transduced with KLF2. Finally, our studies implicate recruitment by KLF2 of the transcriptional coactivator cyclic AMP response element-binding protein (CBP/p300) as a unifying mechanism for these various effects. These data implicate KLF2 as a novel regulator of endothelial activation in response to proinflammatory stimuli.

EWI-2 modulates lymphocyte integrin alpha4beta1 functions.

The most prominent cell-surface integrin alpha4beta1 partner, a 70-kDa protein, was isolated from MOLT-4 T leukemia cells, using anti-alpha4beta1 integrin antibody-coated beads. By mass spectrometry, this protein was identified as EWI-2, a previously described cell-surface partner for tetraspanin proteins CD9 and CD81. Wild-type EWI-2 overexpression had no effect on MOLT-4 cell tethering and adhesion strengthening on the alpha4beta1 ligand, vascular cell adhesion molecule-1 (VCAM-1), in shear flow assays. However, EWI-2 markedly impaired spreading and ruffling on VCAM-1. In contrast, a mutant EWI-2 molecule, with a different cytoplasmic tail, neither impaired cell spreading nor associated with alpha4beta1 and CD81. The endogenous wild-type EWI-2-CD81-alpha4beta1 complex was fully soluble, and highly specific as seen by the absence of other MOLT-4 cell-surface proteins. Also, it was relatively small in size (0.5 x 10(6) Da to 4 x 10(6) Da), as estimated by size exclusion chromatography. Overexpression of EWI-2 in MOLT-4 cells caused reorganization of cell-surface CD81, increased the extent of CD81-CD81, CD81-alpha4beta1, and alpha4beta1-alpha4beta1 associations, and increased the apparent size of CD81-alpha4beta1 complexes. We suggest that EWI-2-dependent reorganization of alpha4beta1-CD81 complexes on the cell surface is responsible for EWI-2 effects on integrin-dependent morphology and motility functions.

Enhanced recruitment of Th2 and CLA-negative lymphocytes by the S128R polymorphism of E-selectin.

E-selectin is a cytokine-inducible endothelial cell adhesion molecule that binds a restricted population of T lymphocytes consisting of Th1 memory cells bearing the cutaneous lymphocyte Ag (CLA). A serine to arginine (S128R) polymorphism in E-selectin has been reported at increased frequency in patients with systemic lupus erythematosus and atherosclerosis. Here we tested the hypothesis that the S128R substitution may contribute to increased vascular disease by altering the number and/or phenotype of lymphocytes interacting with E-selectin under shear flow. We observed that CHO cell monolayers transfected with S128R recruited significantly greater numbers of unfractionated lymphocytes than monolayers expressing an equivalent density of wild-type (WT) E-selectin. Depletion of the CLA(+) subpopulation or generation of CLA(-) lymphoblasts abolished rolling and arrest on WT E-selectin, but left a residual population that interacted with S128R. Generation of Th subsets revealed preferential interaction of Th0 and Th2, but not Th1, cells with S128R compared with WT. However, only T cells of a memory phenotype interacted with S128R, since neither monolayer supported rolling of CD45RA(+) cells. Our results demonstrate that the S128R polymorphism extends the range of lymphocytes recruited by E-selectin, which may provide a mechanistic link between this polymorphism and vascular inflammatory disease.

The S128R polymorphism of E-selectin mediates neuraminidase-resistant tethering of myeloid cells under shear flow.

E-selectin mediates the rolling of circulating leukocytes on vascular endothelial cells. A polymorphism, in which serine is substituted for arginine at position 128 (S128R) in the EGF domain, has been associated with both early-onset atherosclerosis and SLE. We investigated whether the substitution alters the ligand-binding properties of E-selectin under shear flow by studying the capacity of Chinese hamster ovary cell transfectants expressing wild type (WT) or S128R E-selectin to support interactions of neutrophils, K562 cells or HL60 cells. We initially chose to study non-fucosylated K562 cells. No interactions were observed on WT E-selectin, whereas S128R supported a transient tethering interaction of K562 cells, which was resistant to digestion with either neuraminidase or O-sialoglycoprotein endopeptidase, and, in turn, could result in firm adhesion in the presence of a beta2-integrin. HL60 cells exhibited increased rolling on S128R E-selectin. Although neuraminidase treatment inhibited all HL60 interactions with WT E-selectin, it unmasked transient tethers on S128R. We further observed that S128R recruited significantly more neutrophils than WT E-selectin, without affecting neutrophil rolling velocity. This polymorphism may therefore amplify leukocyte-endothelial cell interactions and may be a factor linking the S128R polymorphism to vascular disease.

Conditional immortalization of growth factor-responsive cardiac endothelial cells from H-2K(b)-tsA58 mice.

Although mouse endothelial cells (EC) may advance our understanding of endothelial function, primary EC remain difficult to isolate. We have established a murine cardiac endothelial cell line (MCEC-1) from transgenic mice harboring a temperature-sensitive simian virus 40 large TAg gene (tsA58 TAg) under H-2K(b) class I promoter control. MCEC-1 cells were characterized by their ability to form tubes, Griffonia simplicifolia isolectin B4 binding, and CD31, intercellular adhesion molecule (ICAM)-2, and endoglin expression. MCEC-1 cells proliferated rapidly under permissive conditions [33 degrees C with interferon (IFN)-gamma], where the T antigen is active and transcription is activated by the presence of IFN-gamma, whereas under nonpermissive conditions (38 degrees C without IFN-gamma) proliferation was reduced by 30-fold and the EC showed enhanced proliferation in response to growth factors. Expression of E- and P-selectin, ICAM-1, and vascular cell adhesion molecule-1 was upregulated by tumor necrosis factor-alpha and interleukin-1 beta, and MCEC-1 cells, in contrast to primary EC, were amenable to transfection by lipofection. This novel line will allow further study of the role of the endothelium in cardiovascular disease. Moreover, this technique will allow EC to be readily obtained from genetically modified mice backcrossed with H-2K(b)-tsA58 mice.