CD57(+) CD4 T Cells Underlie Belatacept-Resistant Allograft Rejection.

Belatacept is a B7-specific fusion protein used to prevent allograft rejection by blocking T cell costimulation. Generally efficacious, it fails to prevent acute rejection in a sizable minority of patients. In experimental models, memory T cells mediate costimulation blockade-resistant rejection (CoBRR), but this remains undefined in humans. To explore relationships between individual patients' immune cell phenotypes and CoBRR, we studied patients receiving belatacept or conventional calcineurin inhibitor-based immunosuppression. We identified a population of CD57(+) PD1(-) CD4 T cells present prior to transplantation that correlated with CoBRR. Contrary to data recognizing CD57 as a marker of senescence on CD8 T cells, we discovered a nonsenescent, cytolytic phenotype associated with CD57 on CD4 T cells. Moreover, CD57(+) CD4 T cells expressed high levels of adhesion molecules implicated in experimental CoBRR, were CD28(-) , expressed a transcriptional phenotype broadly defining allograft rejection and were shown to be present in rejecting human kidney allografts. These data implicate CD57(+) CD4 T cells in clinical CoBRR. If prospectively validated, this characteristic could identify patients at higher risk for acute rejection on belatacept-based therapy.

Expression patterns of Notch receptors and their ligands Jagged and Delta in human placenta.

The establishment of an appropriate fetomaternal vessel system is a prerequisite for prevention of pregnancy associated pathologies. Notch receptors and ligands are manifoldly involved in vascular development and angiogenesis. To further characterize the process of human placental vasculo- and angiogenesis we investigated the expression pattern of Notch receptors and their ligands during pregnancy. Real time RT-PCR, immunohistochemistry and flow cytometry analysis were performed in early (6-12) weeks of gestation (w.o.g.) and late placenta (37-41 w.o.g.). To specify the exact cellular localization immunofluorescent labelling of epithelial and endothelial cells (EC), respectively, with cytokeratin-7 and vonWillebrand factor (vWF) was done. One placenta from a patient with Alagille syndrome (AGS) was examined with real time RT-PCR and immunohistochemistry. The receptors Notch2, -3, -4 and their ligands Jagged1, -2 and Delta1, -4 were detected at both the mRNA and protein level in early and late placenta. Notch1 was only detected at protein level. The expression was found mainly in the stromal compartment: placental EC expressed Notch1, Delta4, Jagged1 and Delta1. A strong Jagged1 expression was found in the endothelium of arteries and veins supporting a role in differentiation of capillaries. Hofbauer cells (HC) primarily displayed the receptors Notch2, -3 and -4. Placental stromal cells (SC) were positive for Jagged2. The syncytiotrophoblast (ST) and cytotrophoblast (CT) cells revealed a weak but detectable co-localization with cytokeratin-7 and Notch1, -3 and Delta1. These results were verified by flow cytometry of freshly isolated placental cells of placental tissue. Interestingly Jagged1 expression was absent in endothelial cells from an AGS placenta. The Notch receptors and their ligands are expressed in human placental ST, CT, EC, SC and HC. The distribution pattern of Notch receptors and their ligands suggests their involvement in the process of placental vasculo- and angiogenesis via cell-cell communication between trophoblast, -stroma and endothelial cells.

How to study placental vascular development?

Both exogenous and endogenous factors during pregnancy may impact placental vascular development and cause different malformations of placental vessels. In humans, consequences of abnormal vascular development have been associated with different pregnancy-related pathologies ranging from miscarriage to intrauterine growth restriction or preeclampsia. Pregnancy-associated exposure to bacterial or viral infections or pharmacologic or toxic agents may also influence vascular development of the placenta and lead to preterm labor and delivery. Several steps of vascular adaptation on both the fetal and maternal side are necessary and include such events as uterine vasodilation, remodeling by extravillous trophoblast, as well as vasculogenesis and angiogenesis within the placenta. Ubiquitous as well as pregnancy-specific angiogenic factors are involved. Morphologic and stereologic approaches, as well as experiments in established laboratory animals, cannot be applied to large domestic animals or humans without hesitation. Thus, further studies into the different aspects of this process will require an appropriate in vitro model of placental vascular development. Reflecting the core of placental vascular development, the in vitro model should facilitate the interactions between trophoblast and stromal cells with endothelial progenitor cells. The effects of viral or bacterial infection as well as pharmacologic or toxic agents may be studied more closely in the process. This report reviews major aspects of vascular development in the placenta and describes the establishment of a three-dimensional in vitro model of human placental vascular development.

Studies of placental vasculogenesis: a way to understand pregnancy pathology?

Undisturbed development and growth of the fetus depends on an adequate vascular development in the fetomaternal unit. Several steps of vascular adaptation both on fetal and maternal side are necessary and involve uterine vasodilation and remodelling by extravillous trophoblast as well as vasculo- and angiogenesis within the placenta. Ubiquitous (e. g. VEGF, bFGF) as well as pregnancy specific (PlGF, hCG, IGF-II, AFP) angiogenic factors are involved. Consequences of abnormal vascular development have been associated with different pregnancy-related pathologies ranging from miscarriage to intrauterine growth restriction or preeclampsia. Pregnancy-associated exposure to bacterial and viral infections or toxic agents (e. g. alcohol, nicotine or drugs) may also influence vascular development of the placenta and often lead to preterm labour and delivery. Different methods of study placental vascular development exist. Morphological and stereological approaches as well as animal models reveal significant limitations and can not be applied to in vivo human situation without hesitation. There is a need to design in vitro models of human placental vascular development allowing studies into the different aspects of this process including: trophoblast and stromal cells, interaction with endothelial progenitor cells, influence of viral or bacterial infection of trophoblast as well as influence of toxic agents. Our manuscript reviews major aspects of vascular development in the placenta and describes author's efforts to establish a three-dimensional model of this process in vitro.

HCG in the regulation of placental angiogenesis. Results of an in vitro study.

Placental vascular development is essential for fetal growth and development. Inadequate placental vascular development is associated with early pregnancy losses and other pregnancy related pathologies. In addition to the ubiquitous, well-characterized angiogenic factors like vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF), some pregnancy-specific factors (e.g. human chorionic gonadotropin (hCG), insulin-like growth factor-II (IGF-II) or alpha fetoprotein (AFP) were recently described to play a possible regulatory role in this process. In the present study we described an improved separation method for human placental microvascular endothelial cells (HPMVEC) and their functional characterization. Using the combination of enzymatic digestion and multistep immunomagnetic sorting with CD31 antibodies a model for villous vascularization was established. Isolated cells took up ac-dil-LDL, spontaneously formed capillary-like structures, and expressed common endothelial markers such as vascular endothelial growth factor receptor-2 (VEGFR-2), angiopoetin-1 and -2, Tie-2, CD144, thrombomodulin, and von Willebrand factor (vWF) as shown by RT-PCR, flow cytometry and Western blot analysis. The expression of the hCG/LH receptor in the placental vascular tree was verified both in vitro and in vivo. hCG stimulated proliferation of HPMVEC in a dose specific manner. While hCG alone had no significant effect on endothelial cell apoptosis, the combination of VEGF-A and hCG protected HPMVEC from staurosporine-induced apoptosis. hCG significantly stimulated sprout formation when compared to controls in a spheroid angiogenesis assay. Our results demonstrate a modified and reproducible method allowing studies of placental vascular development and provide new insights into the possible role of trophoblastic factors in this process.

HCG increases trophoblast migration in vitro via the insulin-like growth factor-II/mannose-6 phosphate receptor.

We have previously shown that both HCG and insulin-like growth factor-II (IGF-II) stimulate trophoblastic invasion. Furthermore, the invasion-promoting function of IGF-II resulted from IGF-II mannose 6-phosphate receptor (IGF-II/M6PR) activation. Since HCG and IGF-II did not have an additive effect on cell migration of extravillous trophoblast (EVT) cell line, HTR-8 SVneo, we hypothesized that HCG actions are mediated via alterations in the expression and/or function of IGF-II axis. HCG treatment (50-50,000 mU/ml) of the HTR-8/SVneo cells did not alter the expression of either insulin-like growth factor-I or IGF-II mRNA or peptide synthesis, but caused (i) an increase in the (125)I-IGF-II binding to EVT cells, and (ii) an increase in the externalization rate of the IGF-II binding sites without affecting their internalization. This effect was due to the increase in the number of IGF-II binding sites in the plasma membrane without any change in the IGF-II binding affinity. Although HCG did not influence the abundance of IGF-II/M6PR mRNA or protein, anti-IGF-II/M6PR antibody decreased HCG-induced migration of EVT, supporting the hypothesis that HCG might stimulate EVT migration by increasing IGF-II binding to the plasma membrane and subsequently by increasing the IGF-II effect probably mediated via the IGF-II/M6PR.

A case of intracranial dural arteriovenous fistula draining into the spinal medullary veins.

Intracranial dural arteriovenous fistulas draining into the spinal medullary veins (ICDAVFMs) are exceedingly rare lesions. Their diagnosis is difficult and is often made late. About twenty well documented cases have been published. We report a case in a 55-year-old woman who presented with persistent interscapular pain and neurological evidence of ascending myelopathy after therapy for cervicobrachial neuralgia. ICDAVFM should be considered by rheumatologists in patients with clinical and radiological findings suggestive of spinal cord disease, particularly if these findings indicate involvement of the medulla oblongata or cervical spinal cord.

Differential mechanisms of retinoid transfer from cellular retinol binding proteins types I and II to phospholipid membranes.

Cellular retinol-binding proteins types I and II (CRBP-I and CRBP-II) are known to differentially facilitate retinoid metabolism by several membrane-associated enzymes. The mechanism of ligand transfer to phospholipid small unilamellar vesicles was compared in order to determine whether differences in ligand trafficking properties could underlie these functional differences. Unidirectional transfer of retinol from the CRBPs to membranes was monitored by following the increase in intrinsic protein fluorescence that occurs upon ligand dissociation. The results showed that ligand transfer of retinol from CRBP-I was >5-fold faster than transfer from CRBP-II. For both proteins, transfer of the other naturally occurring retinoid, retinaldehyde, was 4-5-fold faster than transfer of retinol. Rates of ligand transfer from CRBP-I to small unilamellar vesicles increased with increasing concentration of acceptor membrane and with the incorporation of the anionic lipids cardiolipin or phosphatidylserine into membranes. In contrast, transfer from CRBP-II was unaffected by either membrane concentration or composition. Preincubation of anionic vesicles with CRBP-I was able to prevent cytochrome c, a peripheral membrane protein, from binding, whereas CRBP-II was ineffective. In addition, monolayer exclusion experiments demonstrated differences in the rate and magnitude of the CRBP interactions with phospholipid membranes. These results suggest that the mechanisms of ligand transfer from CRBP-I and CRBP-II to membranes are markedly different as follows: transfer from CRBP-I may involve and require effective collisional interactions with membranes, whereas a diffusional process primarily mediates transfer from CRBP-II. These differences may help account for their distinct functional roles in the modulation of intracellular retinoid metabolism.

Role of portal region lysine residues in electrostatic interactions between heart fatty acid binding protein and phospholipid membranes.

The structure of heart fatty acid binding protein (HFABP) is a flattened beta-barrel comprising 10 antiparallel beta-sheets capped by two alpha-helical segments. The helical cap region is hypothesized to behave as a portal "lid" for the entry and release of ligand from the binding pocket. The transfer of fatty acid from HFABP is thought to occur via effective collisional interactions with membranes, and these interactions are enhanced when transfer is to membranes of net negative charge, thus implying that specific basic residues on the surface of HFABP may govern the transfer process [Wootan, M. G., & Storch, J. (1994) J. Biol. Chem. 269, 10517-10523]. To directly examine the role of charged lysine residues on the HFABP surface in specific interactions with membranes, chemical modification and selective mutagenesis of HFABP were used. All surface lysine residues were neutralized by acetylation of recombinant HFABP with acetic anhydride. In addition, seven mutant HFABPs were generated that resulted in charge alterations in five distinct sites of HFABP. Modification of the protein did not significantly alter the structural or ligand binding properties of HFABP, as assessed by circular dichroism, fluorescence quantum yield, and ligand binding analyses. By using a resonance energy transfer assay, transfer of 2-(9-anthroyloxy)palmitate (2AP) from acetylated HFABP to membranes was significantly slower than transfer from native HFABP. In addition, in distinct contrast to transfer from native protein, the 2AP transfer rate from acetylated HFABP was not increased to acceptor membranes of increased negative charge. Transfer of 2AP from HFABP mutants involving K22, located on alpha-helix I (alpha-I) of the helical cap region, was 3-fold slower than transfer from wild-type protein, whereas rates from a mutant involving the K59 residue, located on the beta 2-turn of the barrel near the helical cap, were 2-fold faster than those of wild type. A double mutant involving K22 and K59 resulted in transfer rates identical to those of wild type, indicating that at least two domains are involved in determining the overall rate of ligand transfer. In addition, 2AP transfer rates from HFABP mutated at position 22 were totally unaffected by the charge characteristics of acceptor membranes, in marked contrast to wild type and other members of the mutant series. Further, by introducing a positive charge to alpha-helix II (alpha-II) of the helical cap region, 2AP transfer rates increased by 4-fold and properties of HFABP transfer began to approach those seen for AFABP, another member of the FABP family thought to transfer ligand via collisional interactions with membranes, which has a lysine residue in the alpha-II helix. These studies demonstrate that the helical cap region of HFABP may play an important role in governing ionic interactions between binding protein and membranes.

Surface lysine residues modulate the collisional transfer of fatty acid from adipocyte fatty acid binding protein to membranes.

The transfer of unesterified fatty acids (FA) from adipocyte fatty acid binding protein (A-FABP) to phospholipid membranes is proposed to occur via a collisional mechanism involving transient ionic and hydrophobic interactions [Wootan & Storch (1994) J. Biol. Chem. 269, 10517-10523]. In particular, it was suggested that membrane acidic phospholipids might specifically interact with basic residues on the surface of A-FABP. Here we addressed whether lysine residues on the surface of the protein are involved in this collisional transfer mechanism. Recombinant A-FABP was acetylated to neutralize all positively charged surface lysine residues. Protein fluorescence, CD spectra, and chemical denaturant data indicate that acetylation did not substantially alter the conformational integrity of the protein, and nearly identical affinities were obtained for binding of the fluorescently labeled FA [12-(9-anthroyloxy)oleate] to native and acetylated protein. Transfer of 2-(9-anthroyloxy)palmitate (2AP) from acetylated A-FABP to small unilamellar vesicles (SUV) was 35-fold slower than from native protein. In addition, whereas the 2AP transfer rate from native A-FABP was directly dependent on SUV concentration, 2AP transfer from acetylated protein was independent on the concentration of acceptor membranes. Factors which alter aqueous-phase solubility of FA, such as ionic strength and acyl chain length and saturation, affected the AOFA transfer rate from acetylated but not native A-FABP. Finally, an increase in the negative charge density of the acceptor SUV resulted in a marked increase in the rate of transfer from native A-FABP but did not increase the rate from acetylated A-FABP.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal vitamin A metabolism: coordinate distribution of enzymes and CRBP(II).

In the mucosal layer of the small intestine, we found nearly identical gradients of CRBP(II), retinal reductase, and LRAT levels down the duodenal-ileal axis, suggesting coordinate regulation of these three proteins. In all cases the level of binding protein or enzyme activity was greatest in the proximal intestine and then decreased sharply in the distal half. This pattern fits with the known capacity of the intestine to absorb vitamin A. In addition, the retinal reductase activity was found predominantly in the intestinal mucosa, while LRAT activity was found in both the intestinal mucosa and muscle. An even distribution of LRAT activity along the longitudinal axis of the intestinal muscle was consistent with an even distribution of CRBP in that tissue. In conjunction with LRAT activity and CRBP, we found endogenous retinyl ester stores in the intestinal muscle layer. The patterns of retinyl ester produced by LRAT in vitro and found in vivo were similar, with retinyl palmitate predominating and a high percentage comprised of retinyl stearate. We also observed a bile salt-independent retinyl ester hydrolase activity in intestinal muscle whose distribution paralleled the retinyl ester stores and LRAT levels. This hydrolase appears to be distinct from retinyl ester hydrolases described from other organs as its activity was insensitive to retinyl ester chain length, the presence of bile salts, or the addition of apo-CRBP. This activity was inhibited by diethyl-p-nitrophenyl-phosphate (IC50 100 microM) and diethylpyrocarbonate (IC50 10 microM), demonstrating a requirement for active serine and histidine residues. In addition, we describe an activity present in some intestinal microsomal preparations that can perturb determinations of reductase and LRAT activity and must be avoided.

Differential interaction of lecithin-retinol acyltransferase with cellular retinol binding proteins.

Esterification of retinol (vitamin A alcohol) with long-chain fatty acids by lecithin-retinol acyltransferase (LRAT) is an important step in both the absorption and storage of vitamin A. Retinol in cells is bound by either cellular retinol binding protein (CRBP), present in most tissues including liver, or cellular retinol binding protein type II [CRBP(II)], present in the absorptive cell of the small intestine. Here we investigated whether retinol must dissociate from these carrier proteins in order to serve as a substrate for LRAT by comparing Michaelis constants for esterification of retinol presented either free or bound. Esterification of free retinol by both liver and intestinal LRAT resulted in Km values (0.63 and 0.44 microM, respectively) similar to those obtained for esterification of retinol-CRBP (0.20 and 0.78 microM, respectively) and esterification of retinol-CRBP(II) (0.24 and 0.32 microM, respectively). Because Kd values for retinol-CRBP and retinol-CRBP(II) are 10(-8)-10-(-10) M, these similar Km values indicated prior dissociation is not required and that direct binding protein-enzyme interaction must occur. Evidence for such interaction was obtained when apo-CRBP proved to be a potent competitive inhibitor of LRAT, with a KI (0.21 microM) lower than the Km for CRBP-retinol (0.78 microM). Apo-CRBP(II), in contrast, was a poor competitor for esterification of retinol bound to CRBP(II). Apo-CRBP reacted with 4 mM p-(chloromercuri)benzenesulfonic acid lost retinol binding ability but retained the ability to inhibit LRAT, confirming that the inhibition could not be explained by a reduction in the concentration of free retinol.(ABSTRACT TRUNCATED AT 250 WORDS)

The behavioral pharmacology of butaclamol hydrochloride (AY-23,028), a new potent neuroleptic drug.

Butaclamol hydrochloride (AY-23,028) is a member of a new chemical class for which antipsychotic activity in humans has recently been demonstrated. The compound antagonized amphetamine-induced stereotyped behavior in rats, amphetamine toxicity in aggregated mice and apomorphine-induced emesis in dogs. It depressed both discriminated avoidance and continuous lever-pressing behavior in rats and inhibited ambulation and rearing in the open field. At higher doses, AY-23,028 induced catalepsy. Adrenergic blocking activity, measured by the antagonism of epinephrine-induced mortality, was weak. These pharmacological actions are characteristic of neuroleptic drugs. In the dose range where the aforementioned effects were observed AY-23,028 did not antagonize either the tetrabenazine-induced ptosis or the tremorine syndrome and did not cause either hypothermia or ataxia. The potency and onset of action of AY-23,028 were comparable to those of fluphenazine but AY-23,028 was of longer duration. The results are discussed in relation to current concepts of neuroleptic mechanisms.