A New Intravenous Immune Globulin: Novel or Not?

OBJECTIVE: To assess the clinical use and determine the place in therapy for immune globulin intravenous (IV), human-slra, a recently approved IV immune globulin for the treatment of primary immune deficiency diseases (PIDD). DATA SOURCES: A PubMed and MEDLINE search (2010 to April 2020) was conducted for relevant articles. Data were also obtained from the package insert. STUDY SELECTION AND DATA EXTRACTION: English language publications regarding the clinical efficacy and safety of immune globulin-slra were analyzed. Publications focused on use of immune globulin products were also included. DATA SYNTHESIS: Immune globulin-slra is indicated for patients with PIDD and was specifically developed to include donor plasma with high respiratory syncytial virus (RSV) antibody titers. Efficacy was demonstrated through favorable incidence of infections and infection-related complications. Patients treated with immune globulin-slra had increases in anti-RSV neutralizing antibody titers compared with baseline. Adverse events occurred at rates similar to or less than other available immune globulin products. RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE: This review describes a new immune globulin product available for use in patients with PIDD. A novel approach to managing patients at risk of serious infections may be to utilize products with formulations proven to not only boost IgG levels, but also antibodies to specific pathogens. CONCLUSIONS: The choice of which immune globulin product to select for a patient or formulary is complex. Each product is unique, and differences between products should be taken into consideration, along with cost and availability.

Cyclic AMP-dependent, protein kinase A-independent activation of extracellular signal-regulated kinase 1/2 following adenosine receptor stimulation in human umbilical vein endothelial cells: role of exchange protein activated by cAMP 1 (Epac1).

A critical process in angiogenesis is endothelial cell proliferation, which requires activation of extracellular signal-regulated kinase (ERK)1/2. This study analyzed the pathway responsible for adenosine-induced ERK1/2 phosphorylation in human umbilical vein endothelial cells (HUVEC). Characterization with adenosine receptor (AR) agonists and antagonists and the AR mRNA profile demonstrated that stimulation of the A(2B)AR can mediate ERK1/2 phosphorylation in HUVEC. The lack of sensitivity of A(2B)AR-mediated ERK1/2 phosphorylation to 3-[1-[3-(dimethylaminopropyl]-1H-indol-3-yl]-4-(1H-indol-3-yl)-1H-pyrrole-2,5-dione monohydrochloride (GF109203X) and 3-[1-[3-(amidinothio)propyl]-1H-in-dol-3-yl]-3-(1-methyl-1H-indol-3-yl) maleimide (bisindolylmaleimide IX) (Ro31-8220) indicated that protein kinase C stimulation is not required. The response did not involve transactivation of receptors for epidermal growth factor or vascular endothelial growth factor (VEGF). The A(2B)AR-mediated response required functional G(alphas) and was mimicked by forskolin and 8-bromoadenosine 3',5'-cyclic monophosphate. However, ERK1/2 phosphorylation induced by A(2B)AR stimulation and forskolin was insensitive to protein kinase A inhibitors. It was hypothesized that the A(2B)AR-mediated ERK1/2 activation may involve exchange protein activated by cAMP (Epac), a cAMP-activated guanine nucleotide exchange factor for Rap GTPases. Reverse Transcription-polymerase chain reaction analysis detected Epac1 but not Epac2 in HUVEC. 8-(p-Chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8CPT-2Me-cAMP), an Epac activator, stimulated ERK1/2 phosphorylation. Overexpression of Epac1 enhanced A(2B)AR-mediated and forskolin-induced ERK1/2 phosphorylation, whereas response to VEGF was unaffected. Inhibition of Epac1 expression with small interfering RNA substantially reduced A(2B)AR-mediated and forskolin-induced ERK1/2 phosphorylation and abolished that by 8CPT-2Me-cAMP. A(2B)AR stimulation and forskolin activated Rap1. Expression of a dominant-negative Ras protein did not affect either forskolin-induced or A(2B)AR-mediated ERK1/2 phosphorylation. In summary, Epac1 activation in HUVEC results in ERK1/2 activation, and this protein, at least in part, mediates response to the physiologically relevant event of A(2B)AR stimulation.

Effect of simulated microgravity on oxidation-sensitive gene expression in PC12 cells.

Oxygen utilization by and oxygen dependence of cellular processes may be different in biological systems that are exposed to microgravity (micro-g). A baseline in which cellular changes in oxygen sensitive molecular processes occur during micro-g conditions would be important to pursue this question. The objective of this research is to analyze oxidation-sensitive gene expression in a model cell line [rat pheochromocytoma (PC12)] under simulated micro-g conditions. The PC12 cell line is well characterized in its response to oxygen, and is widely recognized as a sensitive model for studying the responses of oxygen-sensitive molecular and cellular processes. This study uses the rotating wall vessel bioreactor (RWV) designed at NASA to simulate micro-g. Gene expression in PC12 cells in response to micro-g was analyzed by DNA microarray technology. The microarray analysis of PC12 cells cultured for 4 days under simulated micro-g under standardized oxygen environment conditions revealed more than 100 genes whose expression levels were changed at least twofold (up-regulation of 65 genes and down-regulation of 39 genes) compared with those from cells in the unit gravity (unit-g) control. This study observed that genes involved in the oxidoreductase activity category were most significantly differentially expressed under micro-g conditions. Also, known oxidation-sensitive transcription factors such as hypoxia-inducible factor-2alpha, c-myc, and the peroxisome proliferator-activated receptor-gamma were changed significantly. Our initial results from the gene expression microarray studies may provide a context in which to evaluate the effect of varying oxygen environments on the background of differential gene regulation of biological processes under variable gravity conditions.

Distinct protein kinase C isoforms mediate regulation of vascular endothelial growth factor expression by A2A adenosine receptor activation and phorbol esters in pheochromocytoma PC12 cells.

Vascular endothelial growth factor (VEGF) stimulates angiogenesis during development and in disease. In pheochromocytoma (PC12) cells, VEGF expression is regulated by A(2A) adenosine receptor (A(2A)AR) activation. The present work examines the underlying signaling pathway. The adenylyl cyclase-protein kinase A cascade has no role in the down-regulation of VEGF mRNA induced by the A(2A)AR agonist, 2-[4-[(2-carboxyethyl)phenyl]ethylamino]-5'-N-ethylcarboxamidoadenosine (CGS21680). Conversely, 6-h exposure of cells to either phorbol 12-myristate 13-acetate (PMA) or protein kinase C (PKC) inhibitors mimicked the CGS21680-induced down-regulation. PMA activated PKCalpha, PKCepsilon, and PKCzeta, and CGS21680 activated PKCepsilon and PKCzeta as assessed by cellular translocation. By 6 h, PMA but not CGS21680 decreased PKCalpha and PKCepsilon expression. Neither compound affected PKCzeta levels. Following prolonged PMA treatment to down-regulate susceptible PKC isoforms, CGS21680 but not PMA inhibited the cobalt chloride induction of VEGF mRNA. The proteasome inhibitor, MG-132, abolished PMA- but not CGS21680-induced down-regulation of VEGF mRNA. Phorbol 12,13-diacetate reduced VEGF mRNA levels while down-regulating PKCepsilon but not PKCalpha expression. In cells expressing a dominant negative PKCzeta construct, CGS21680 was unable to reduce VEGF mRNA. Together, the findings suggest that phorbol ester-induced down-regulation of VEGF mRNA occurs as a result of a reduction of PKCepsilon activity, whereas that mediated by the A(2A)AR occurs following deactivation of PKCzeta.

Adenosine receptors and mammalian toll-like receptors: synergism in macrophages.

Adenosine is known to participate in tissue protection subsequent to ischemic events. New evidence points to a role for adenosine in promoting neovascularization through a mechanism that requires interaction with the Toll-like receptor (TLR) signaling pathway. In macrophages, the adenosine receptor subtype 2A (A(2A)R) synergizes with some but not all of the Toll-like receptors, leading to increased expression of vascular endothelial growth factor (VEGF). Simultaneously, the expression of tumor necrosis factor-alpha (TNFalpha) is decreased; this phenomenon depends on the presence of AR agonists; however, the activation of transcription factor nuclear factor-kappaB (NF-kappaB) is not attenuated in the presence of A(2A)R agonists. It appears that the addition of adenosine or other A(2A)R agonists can mediate the "angiogenic switch," in macrophages, from TNFalpha protein expression to expression of components necessary for angiogenesis. Although these observations might have important implications for wound healing, it will be important to discern whether this interaction between ARs and TLRs is necessary for angiogenesis associated with tumor growth.

Coaggregation, cointernalization, and codesensitization of adenosine A2A receptors and dopamine D2 receptors.

Antagonistic and reciprocal interactions are known to exist between adenosine and dopamine receptors in the striatum. In the present study, double immunofluorescence experiments with confocal laser microscopy showed a high degree of colocalization of adenosine A(2A) receptors (A(2A)R) and dopamine D(2) receptors (D(2)R) in cell membranes of SH-SY5Y human neuroblastoma cells stably transfected with human D(2)R and in cultured striatal cells. A(2A)R/D(2)R heteromeric complexes were demonstrated in coimmunoprecipitation experiments in membrane preparations from D(2)R-transfected SH-SY5Y cells and from mouse fibroblast Ltk(-) cells stably transfected with human D(2)R (long form) and transiently cotransfected with the A(2A)R double-tagged with hemagglutinin. Long term exposure to A(2A)R and D(2)R agonists in D(2)R-cotransfected SH-SY5Y cells resulted in coaggregation, cointernalization and codesensitization of A(2A)R and D(2)R. These results give a molecular basis for adenosine-dopamine antagonism at the membrane level and have implications for treatment of Parkinson's disease and schizophrenia, in which D(2)R are involved.

A SURVEY OF NONXANTHINE DERIVATIVES AS ADENOSINE RECEPTOR LIGANDS.

The binding affinities at rat A1, A2a, and A3 adenosine receptors of a wide range of heterocyclic derivatives have been determined. Mono-, bi-, tricyclic and macrocyclic compounds were screened in binding assays, using either [3H]PIA or [3H]CGS 21680 in rat brain membranes or [125I]AB-MECA in CHO cells stably transfected with rat A3 receptors. Several new classes of adenosine antagonists (e.g. 5-oxoimidazopyrimidines and a pyrazoloquinazoline) were identified. Various sulfonylpiperazines, 11-hydroxytetrahydrocarbazolenine, 4H-pyrido[1,2-a]pyrimidinone, folic acid, and cytochalasin H and J bound to A3 receptors selectively. Moreover, cytochalasin A, which bound to A1 adenosine receptors with Ki value of 1.9 µM, inhibited adenylyl cyclase in rat adipocytes, but not via reversible A1 receptor binding.

Species Differences in Ligand Affinity at Central A3-Adenosine Receptors.

[Table: see text] Binding affinities of purine derivatives at A3 adenosine receptors in different species were compared. Binding was carried out using the novel high affinity agonist ligand [125I]AB-MECA (3-iodo-4-aminobenzyladenosine-5'-N-methyluronamide) in the presence of 1.0 µM XAC (8-[4-[[[[(2-aminoethyl)amino]carbonyl]methyl]oxy]phenyl]-1,3-dipropylxanthine), an A1- and A2a-adenosine antagonist. XAC was added to eliminate binding to non-A3 receptors. In rat brain membranes [125I]AB-MECA exhibited saturable, specific binding with a Kd of 2.28 nM and a Bmax of 43 fmol/mg protein. The affinity of [125I]AB-MECA at the gerbil and rabbit brain A3-receptors was similar to the rat, suggesting that the affinity of this agonist is not highly species dependent. The affinity of various xanthine derivatives was measured in [125I]AB-MECA competition binding assays. Gerbil and rabbit brain A3-receptors were similar in the affinity of antagonists whose potency order in both species was: BWA522 ≥ CPX > XCC, XAC, SPX, BWA1433 > theophylline. The affinities of 8-arylxanthines at the rat, rabbit, and gerbil brain A3 receptors were considerably less than the previously reported affinities at cloned sheep and human A3 receptors. Species differences in agonist affinity were assessed by comparing Ki values at cloned rat brain A3 receptors expressed in CHO cells with cloned sheep and human A3 receptors. Human and rat brain A3 receptors were highly similar in the relative affinities of agonists, and sheep brain A3 receptors were unlike either human or rat A3 receptors in agonist affinity.

Molecular Characterization of A(1) and A(2a) Adenosine Receptors.

Detailed amino acid sequence analyses of A(1) and A(2a) adenosine receptors were assembled by analogy to other G-protein-coupled receptors and correlated with pharmacological observations. Sites for phosphorylation, palmitoylation, and sodium binding have been proposed. Striatal A(2a) receptors from human and other species were photoaffinity-labeled using the selective, radioiodinated agonist PAPA-APEC. Selective chemical affinity labels for A(1) and A(2a) receptors have been introduced. For example, an isothiocyanate, p-DITC-APEC (100 nM), irreversibly diminished the B(max) for [(3)H]CGS 21680 (2-[4-[(2-carboxyethyl) phenyl] ethylamino]-5'-N-ethylcarboxamidoadenosine) binding in rabbit striatal membranes by 71% (K(d) unaffected), suggesting a direct modification of the ligand binding site. Novel trifunctional affinity labels have been designed. Rabbit and human A(2a) receptors were characterized using [(3)H]XAC binding in the presence of 50 or 25 nM CPX (8-cyclopentyl-l,3-dipropylxanthine), respectively. The inhibition of A(2) radioligand binding by the histidyl-modifying reagent diethylpyrocarbonate suggested the involvement of His residues in interactions with adenosine agonists and antagonists. Properties of transiently expressed mutants of bovine A(1) receptors in which either His(251) or His(278) residues have been substituted with Leu suggest that both histidines are important in binding.

TRIFUNCTIONAL LIGANDS: A RADIOIODINATED HIGH AFFINITY ACYLATING ANTAGONIST FOR THE A1 ADENOSINE RECEPTOR.

A new xanthine (adenosine antagonist) radioligand that binds covalently to A1-adenosine receptors was prepared and used as a receptor probe. BH-DITC-XAC was synthesized via a trifunctional aryl diisothiocyanate crosslinker. containing the p-hydroxyphenylpropionyl group for radioiodination. The xanthine competed against agonist or antagonist A1 receptor radioligands in bovine brain membranes with an IC50, of 40nM. 125I-BH-DITC-XAC, prepared directly by the chloramine T method and purified by HPLC. bound specifically to A1 receptors. This binding was inhibited in the presence of the adenosine agonists R-PIA, S-PIA. and NECA in a dose dependent manner and with the order of potency characteristic of bovine A1 receptors. Incubation of affinity purified bovine A1-receptors with 125I-BH-DITC-XAC (0.8 nM) for 2 hours resulted in the specific and clean labelling of a polypeptide band corresponding to MW 36,000, identical to that previously found for the A1 receptor.