Peripherally induced Treg: mode, stability, and role in specific tolerance

Foxp3-expressing regulatory T cells (Treg) have an essential function of preventing autoimmune disease in man and mouse. Foxp3 binds to forkhead motifs of about 1,100 genes and the strength of binding increases upon phorbol 12-myristate 13-acetate/ionomycin stimulation. In Foxp3-expressing T cell hybridomas, Foxp3 promoter binding does not lead to activation or suppression of genes which becomes only visible after T cell activation. These findings are in line with observations by others that Foxp3 exerts important functions in collaboration with T cell receptor (TCR)-dependent transcription factors in a DNA-binding complex. Tregs can be generated when developing T cells encounter TCR agonist ligands in the thymus. This process apparently depends on costimulatory signals. In contrast, extrathymic conversion of naïve T cells into Tregs appears to depend on transforming growth factor (TGF)-beta and is inhibited by costimulation. In fact, dendritic cell-derived retinoic acid helps the conversion process by counteracting the negative impact of costimulation. Tregs induced by subimmunogenic antigen delivery in vivo are much more stable than Tregs induced by antigenic stimulation in the presence of TGF-beta in vitro which correlates with the extent of demethylation of the Foxp3 locus. Tregs can be induced by conversion of antigen-specific T cells that occur with a very low frequency in wt mice. Conversion of naïve cluster of differentiation (CD)4 T cells into Tregs by a single peptide of HY antigens results in complete antigen-specific tolerance to an entire set of HY epitopes recognized by CD4 as well as CD8 T cells when presented with male skin or hemopoietic grafts.

Epigenetic control of the foxp3 locus in regulatory T cells

Compelling evidence suggests that the transcription factor Foxp3 acts as a master switch governing the development and function of CD4(+) regulatory T cells (Tregs). However, whether transcriptional control of Foxp3 expression itself contributes to the development of a stable Treg lineage has thus far not been investigated. We here identified an evolutionarily conserved region within the foxp3 locus upstream of exon-1 possessing transcriptional activity. Bisulphite sequencing and chromatin immunoprecipitation revealed complete demethylation of CpG motifs as well as histone modifications within the conserved region in ex vivo isolated Foxp3(+)CD25(+)CD4(+) Tregs, but not in naïve CD25(-)CD4(+) T cells. Partial DNA demethylation is already found within developing Foxp3(+) thymocytes; however, Tregs induced by TGF-beta in vitro display only incomplete demethylation despite high Foxp3 expression. In contrast to natural Tregs, these TGF-beta-induced Foxp3(+) Tregs lose both Foxp3 expression and suppressive activity upon restimulation in the absence of TGF-beta. Our data suggest that expression of Foxp3 must be stabilized by epigenetic modification to allow the development of a permanent suppressor cell lineage, a finding of significant importance for therapeutic applications involving induction or transfer of Tregs and for the understanding of long-term cell lineage decisions.

Genetic screening in a large family with juvenile onset primary open angle glaucoma

AIMS

A number of genetic loci have been implicated in the pathogenesis of primary open angle glaucoma (POAG). The aim of this study was to identify the genetic cause of POAG in a large Scottish family and, if possible, offer genetic screening and advice to family members.

METHODS

Family members were examined to determine their disease status. Base excision sequence scanning was carried out in order to test for the presence of a POAG causing mutation at known genetic loci. Direct DNA sequencing was performed in order to determine the mutation sequence.

RESULTS

All family members of known affected disease status and two family members of unknown disease status were found to have a mutation in the TIGR gene. The mutation resulted in the substitution of a glycine residue with an arginine residue at codon 252 (Gly252Arg). No other sequence variations were present in any members of the family.

CONCLUSION

The Gly252Arg mutation in the TIGR gene results in the development of POAG in this family. It was possible to identify younger, currently unaffected, members of the family who carry the mutation and who are therefore at a very high risk of developing POAG themselves. This is the first demonstration that Gly252Arg can be a disease causing mutation rather than a benign polymorphism. The possible pathogenic mechanisms and wider implications of the mutation are considered.

Gene delivery and expression in human retinal pigment epithelial cells: effects of synthetic carriers, serum, extracellular matrix and viral promoters

Non-viral gene therapy is a potential treatment to many incurable retinal diseases. To fulfill this promise, plasmid DNA must be delivered to the retinal target cells. We evaluated the efficacy of synthetic DNA complexing compounds in transfecting primary human retinal pigment epithelial (RPE) cells in vitro. Fetal human RPE cells were cultured with or without extracellular matrix (ECM), produced using calf corneal endothelial cells. Plasmids encoding nuclear localizing beta galactosidase or luciferase (pRSVLuc, pCLuc4, pSV2Luc) were complexed in water at various +/- charge ratios using cationic lipids (Lipofectin, DOTAP, DOGS), polyethylene imines (25 and 750 kDa), and with degraded 6th generation starburst polyamidoamine dendrimers. Luciferase was quantified using a luminometric assay and beta galactosidase with X-gal staining. Toxicities of transfections were evaluated with the MTT-assay. Using beta galactosidase as the reporter gene naked DNA did not transfect RPE cells at measurable levels whereas 1-5% of the cells expressed histochemically detectable amounts of the gene after transfection with cationic lipid DNA complexes. In RPE cells, Rous sarcoma virus and cytomegalovirus (CMV) were more efficient promoters than SV40 in driving luciferase expression, and CMV was chosen for further experiments. At optimal complex charge ratios, expression levels of luciferase were > 10(9) light units/mg protein after transfection using dendrimers and PEI25, while transfection mediated with the other carriers resulted in luciferase expression levels of 10(7)-10(9) light units/mg protein or less. In general, dendrimers and large molecular weight PEI were less toxic than cationic lipids or PEI25 to RPE cells. Serum and ECM decreased gene expression to the RPE cells with all carriers. Despite low percentage of transfected cells the transgene expression per RPE cell is high, important feature in the retinal tissue with small dimensions, in particular in the case of secreted gene products. Degraded dendrimers and high molecular weight PEI exhibited the best combination of high activity and low toxicity in RPE cell transfection.

GLC1A mutations point to regions of potential functional importance on the TIGR/MYOC protein

PURPOSE

The aim of this study was to screen affected members of glaucoma families for mutations in the Trabecular Meshwork Inducible Glucocorticoid Response (TIGR) gene also known by the name myocilin (MYOC) or by combined names such as TIGR/MYOC. Our primary objectives were (1) to identify mutations responsible for glaucoma in members of three families for which we have shown linkage between chromosome 1 GLC1A-region markers and the primary open angle glaucoma (POAG) phenotype, and (2) to determine the relationship of these and other mutations to key points of predicted function and structure of the TIGR/MYOC protein.

METHODS

DNA sequence determination was used to identify sequence changes in sections of the TIGR/MYOC gene that were PCR-amplified from genomic DNA from the probands of three previously-reported GLC1A juvenile-onset POAG families, UM:JG1, UM:JG3, UM:GL57, and unmapped family UM:JG5. Allele-specific oligonucleotide hybridization was used to screen for the identified mutations in PCR-amplified DNA from individual members of each pedigree and from a panel of 11 additional juvenile glaucoma family probands, 42 adult POAG family probands, and 43 normal individuals. Computerized algorithms were used to identify functional motifs and predict structures of normal and mutant forms of the protein.

RESULTS

Sequence changes were found that alter amino acids in the olfactomedin-like domain near the carboxy terminal end of the TIGR protein in affected members of families UM:JG1 (Pro370Leu), UM:JG3 (Val426Phe), UM:GL57 (Glu323Lys) and UM:JG5 (Gly252Arg). Co-segregation of glaucoma and Pro370Leu, Val426Phe, and Gly252Arg in known GLC1A families suggests that these are mutations. Although the Gly252Arg substitution observed in UM:JG5 is non-conservative, it was not possible to distinguish whether it is a mutation or a polymorphism. None of the sequence changes described in these families were observed in other juvenile glaucoma cases in this study, nor in any of the POAG or phenotypically normal individuals tested here. Analysis of amino acid sequence changes resulting from mutations described in this and other works demonstrate localization of many mutations in the vicinity of predicted functional motifs in the olfactomedin-like domain. Identification of rat latrophilin (LPH1/CIRL) as a new member of the olfactomedin-like protein family to which TIGR/MYOC belongs suggests that the region of olfactomedin homology is a protein domain that can occur in different protein contexts.

CONCLUSIONS

Location of mutations described in this and previous work suggests that some specific predicted protein motifs in the olfactomedin-like domain may be important to TIGR/MYOC function. In some cases, the role of TIGR/MYOC in the etiology of glaucoma may result from alteration of the sequences recognized by modifying enzymes such as casein kinase II. In other cases altered protein folding may affect access of enzymes to their target sequences on TIGR/MYOC. Although modifications and structures discussed here are predicted rather than proven, they provide a useful theoretical framework for design of subsequent experiments. Alterations to protein folding and predicted modification motifs cannot explain the pathogenic mechanisms of all of the known TIGR/MYOC glaucoma mutations.

Juvenile open angle glaucoma: fine mapping of the TIGR gene to 1q24.3-q25.2 and mutation analysis

Autosomal dominant juvenile open angle glaucoma (JOAG) is an early-onset form of primary open angle glaucoma (POAG), which has been linked to chromosome 1q21-q31. Recently, mutations in the trabecular meshwork inducible glucocorticoid response gene (TIGR), one of the candidate genes mapped in this region, were identified in glaucoma patients of several families. We screened for mutations of the TIGR gene in two German families with JOAG and in 100 unselected sporadic cases of POAG. In the first family we identified a Pro370Leu mutation and in the second family a Gly367Arg mutation cosegregating with the glaucoma phenotype. No pathogenic mutation was found in 100 sporadic cases but a Tyr347Tyr polymorphism was found in two patients. Furthermore, fluorescence in situ hybridization (FISH) analysis was used to map a TIGR-specific yeast artificial chromosome to 1q24.3-q25.2.

Hospital waste--the current and future treatment and disposal trends

Hospital wastes pose a serious public health problem. This is primarily caused by the diversity of the individual components of the waste which constitute a risk to health if inadequately handled. It is evident that economic and technical conditions for both a safe disposal, including environmentally sound manner incineration as well as efficient stem or microwave disinfection and a safe management practice based on legal regulations consequently will contribute to protections of both human health and the environment. There is no reason to assume there may be any universal, standard regulations to be used and accepted unianimously and consistently valid for all countries. It is necessary to honor the specific, social and economic background of every country. Nevertheless the European Community principles of hospital waste treatment and disposal will be eventually accepted by this country in principal, in the framework of a general economic and political integration of European countries.

Increased proliferation of skin cells by sublethal doses of sodium lauryl sulfate

Most quantitative in vitro approaches to determine irritancy have examined the potential of compounds to decrease biological functions or inhibit growth of cells. Irritants, however, are known to generally have the opposite effect in vivo, i.e. to stimulate cell division. This property has not been directly studied in vitro. We examined the ability of sublethal concentrations of sodium lauryl sulfate (SLS) to stimulate cultured keratinocyte and fibroblast proliferation in vitro. The growth of keratinocytes, without added growth factors, continuously exposed to SLS for 4 days was stimulated approximately 89% compared to control. Keratinocytes exposed to SLS for 1 or 18 h were stimulated 36 and 12%, respectively, over the next 4 days of growth. Subconfluent fibroblasts were also stimulated approximately 38%. Confluent fibroblasts were stimulated 40%. All stimulations were maximal between 10(-8) and 10(-5) M added SLS. Media conditioned by keratinocytes exposed to 10(-8) M SLS were able to increase the growth of naive keratinocytes by 117%. In all experiments doses of SLS > 10(-5) M inhibited cell growth. We conclude that sublethal doses of SLS can stimulate the growth of cultured keratinocytes and fibroblasts. The stimulation of growth seen may be related to the stimulation observed in in vivo irritation.

Effects of betaxolol/timolol on epinephrine stimulated cyclic-AMP levels in human trabecular meshwork cells

The effects of timolol and betaxolol were compared for blocking beta agonist stimulation of cyclic-AMP in cultured human trabecular meshwork cells. Epinephrine (10(-5) M) produced a large and rapid increase in HTM cyclic-AMP; timolol (10(-6) M), at concentrations readily achieved in the aqueous humor after 0.5% eyedrops, completely blocked this effect. Recovery from timolol treatment appeared to be relatively slow, with only a 30-40% recovery observed by 9 hours. In comparison, betaxolol (10(-6) M) produced a smaller blockade of the epinephrine effects; a rapid recovery from the betaxolol effects was observed, with a greater than half-maximal response to epinephrine observed 15 minutes after removal of this beta blocker. These findings may help to explain the clinical observations of an outflow facility effect of epinephrine when used in combination protocols with betaxolol, but not with timolol.

Characterization of beta-adrenergic receptors in cultured human trabecular cells and in human trabecular meshwork

The characterization of beta-adrenergic receptors on cultured human trabecular cells and trabecular meshwork from human autopsy eyes was carried out by radioligand binding utilizing (125I)-iodopindolol. In cultured cells, the observed binding of (125I)-iodopindolol was of high affinity (Kd = 43 pM) and saturable. Scatchard plots were linear and revealed a Bmax of 33 +/- 7 fmol/mg of protein. Competition studies with a series of agonists and antagonists revealed that human trabecular cells contain a single class of beta-adrenergic receptors of the beta 2 subtype. Similarly, the IC50 of ICI 89,406 (176 nM) in human trabecular meshwork from autopsy eyes supports the presence of beta 2-adrenergic receptors in this tissue.

Use of immunotoxin to inhibit proliferating human corneal endothelium

Transferrin plays a central role in cellular proliferation and proliferating cells have been shown to express transferrin receptors with increased density. We examined the effect of an immunotoxin consisting of anti-transferrin receptor monoclonal antibody (454A12) conjugated to recombinant ricin A chain (rRTA) on the proliferation of human corneal endothelium (HCE) in vitro. In proliferating cultures an immunotoxin (454A12-rRTA) concentration of 50 ng/mL reduced cell counts at day 7 by at least 89%, with no effect observed at 0.01 ng/ml. In contrast, cell counts were only minimally reduced in confluent cultures, even after 7 days' exposure to high concentrations of immunotoxin. These data suggest that 454A12-rRTA may be used to prevent growth of human corneal endothelium in pathological conditions such as the iridocorneal endothelial (ICE) syndrome.

The cytoskeleton of the cultured human trabecular cell. Characterization and drug responses

To determine the organization of the three major cytoskeletal elements of cultured human trabecular meshwork cells (actin filaments, microtubules and intermediate filaments), we employed fluorescence microscopy and stereo-transmission electron microscopy of extracted, S-1 labeled and critical-point dried cells. Morphologic changes resulting from treatment with cytochalasin B, colchicine, taxol and nocodozole were also characterized. Compared with the cynomolgus monkey trabecular cell, morphologic differences in overall cell shape and orientation of both actin filaments and microtubules were noted. However, the responses to cytoskeletal active drugs were quite similar. Taxol, nocodozole and colchicine had a marked effect on microtubule organization, while nocodozole and colchicine had a marked effect on vimentin filament organization. None of these drugs produced marked changes in human trabecular cell shape. In contrast, treatment with the anti-actin drug cytochalasin B resulted in both a marked change in cell shape associated with organizational changes in all three cytoskeletal elements. These studies suggest a central role of actin filaments in determining overall cell shape and cytoskeletal organization in the cultured human trabecular cell.

Cellular sensitivity to glucocorticoids in patients with POAG. Steroid receptors and responses in cultured skin fibroblasts

The question of a generalized hypersensitivity to corticosteroids in primary open-angle glaucoma (POAG) was investigated using cultured skin fibroblasts from patients with POAG and age-matched controls. Nuclear binding of (3H)-dexamethasone was performed to evaluate possible changes in the glucocorticoid receptors. Cortisol effects on (3H)-thymidine uptake into the cells were investigated as a measure of the cellular sensitivity to corticosteroids. When POAG and control groups were compared, no significant differences (P less than 0.05) were found for either the number or affinity of glucocorticoid receptors (POAG: Kd = 6.1 +/- 1.0 nM, Rt = 94 +/- 13 sites/cell X 10(3); control: Kd = 5.5 +/- 1.6 nM, Rt = 124 +/- 20 X 10(3) sites/cell) or for cortisol effects on thymidine uptake (POAG: C50 = 83 +/- 38 nM; control: C50 = 80 +/- 34 nM). Use of epidermal growth factor (EGF) resulted in an increased steroid sensitivity in some cell lines, but again no differences between POAG and control groups were detected. These results suggest that a generalized cellular hypersensitivity to glucocorticoids is not intrinsic to POAG. It is possible that environmental alterations and/or endogenous factors may influence the steroid responses observed in these patients.

Age-related changes in trabecular meshwork cellularity

To investigate whether alterations in the cellular component of the trabecular meshwork occur with age, we evaluated trabecular meshwork cellularity and absolute cell number, using specimens obtained from patients ranging in age from newborn to 81 years. We obtained reproducible, quantitative measurements of these parameters, using montages of 1 micrometer meridional sections. A progressive decrease in cellularity (58%) and absolute cell number (47%) in the trabecular meshwork occurred over the 81-year period studied. Regression analysis suggested that the decrease in cellularity and cell number is linear function of age, resulting from a loss of approximately 0.58% of all cells per year. This change in cellularity parallels that seen in the corneal endothelium. implying that trabecular cells, like corneal endothelial cells, may have a limited reparative capacity.

Combination vasodilator therapy for severe chronic congestive heart failure

A patient with severe, chronic congestive heart failure was unresponsive not only to conventional therapy, but also to nonparenteral nitroglycerin and isosorbide dinitrate; he became nitroprusside dependent. Oral minoxidil therapy produced a significant decrease in systemic vascular resistance and an increase in cardiac output, with no tachycardia, hypotension, or decrease in systemic and pulmonary venous pressures. The addition of sublingual isosorbide dinitrate decreased venous pressures and produced a further increase in cardiac output. The combination of oral minoxidil and sublingual isosorbide dinitrate maintained clinical and hemodynamic improvements, and the patient could be weaned off nitroprusside. Deterioration in hemodynamics occurred with the withdrawal of minoxidil. Therapy with oral hydralazine produced hemodynamic effects comparable to those of oral minoxidil. These observations suggest that chronic reduction of impedance to left ventricular ejection with minoxidil or hydralazine is possible in patients with severe intractable heart failure and deserves further clinical trial.